Patent Application
20240349603
One embodiment of the present invention relates to an organic compound, a light-emitting device, a light-emitting apparatus, a light-emitting and light-receiving apparatus, a display apparatus, an electronic appliance, a lighting device, and an electronic device. Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a driving method, or a manufacturing method. One embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display apparatus, a liquid crystal display apparatus, a light-emitting apparatus, a lighting device, a power storage device, a memory device, an image capturing device, a driving method thereof, and a manufacturing method thereof.
Light-emitting devices (organic EL devices) that include organic compounds and utilize electroluminescence (EL) have been put to practical use. In the basic structure of such light-emitting devices, an organic compound layer containing a light-emitting material (an EL layer) is held between a pair of electrodes. Carriers are injected by application of voltage to the device, and recombination energy of the carriers is used, whereby light emission can be obtained from the light-emitting material.
Such light-emitting devices are of self-luminous type and thus have advantages over liquid crystal devices, such as high visibility and no need for backlight when used in pixels of a display, and are suitable as flat panel display devices. Displays that include such light-emitting devices are also highly advantageous in that they can be thin and lightweight. Another feature of such light-emitting devices is that they have an extremely fast response speed.
Since light-emitting layers of such light-emitting devices can be formed two-dimensionally and continuously, planar light emission can be achieved. This feature is difficult to realize with point light sources typified by incandescent lamps and LEDs or linear light sources typified by fluorescent lamps; thus, the light-emitting devices also have great potential as planar light sources, which can be used for lighting devices and the like.
Displays or lighting devices that include light-emitting devices can be used suitably in a variety of electronic appliances as described above, and research and development of light-emitting devices have progressed for more favorable characteristics.
A variety of methods for manufacturing light-emitting devices are known. As a method of manufacturing a high-resolution light-emitting device, a method in which a light-emitting layer is formed without using a fine metal mask is known. An example of the method is a method of manufacturing an organic EL display described in Patent Document 1. The method includes a step of forming a first light-emitting layer as a continuous film crossing a display region including an electrode array by deposition of a first luminescent organic material containing a mixture of a host material and a dopant material over the electrode array that is formed over an insulating substrate and includes a first pixel electrode and a second pixel electrode; a step of irradiating part of the first light-emitting layer positioned over the second pixel electrode with ultraviolet light while part of the first light-emitting layer positioned over the first pixel electrode is not irradiated with ultraviolet light; a step of forming a second light-emitting layer as a continuous film crossing the display region by deposition of a second luminescent organic material, which contains a mixture of a host material and a dopant material but differs from the first luminescent organic material, over the first light-emitting layer; and a step of forming a counter electrode over the second light-emitting layer.
Non-Patent Document 1 discloses a method employing standard UV photolithography for manufacturing an organic optoelectronic device, which is one of organic EL devices (Non-Patent Document 1).
In general, an alkali metal with a low work function, such as lithium (Li), or a compound of such an alkali metal is used in an electron-injection layer of a light-emitting device. By using the alkali metal or the compound of the alkali metal, an excellent electron-injection property can be ensured. Interaction of the alkali metal or the compound of the alkali metal with an electron-transport material ensures charge-generation capability and enables electron injection to an electron-transport layer. In this manner, the use of the alkali metal or the compound of the alkali metal in the electron-injection layer lowers the voltage of the device.
However, the alkali metal or the compound of the alkali metal is easily oxidized and is an unstable material. Thus, any reaction of the alkali metal or the compound of the alkali metal with, for example, an atmospheric component such as water or oxygen in the manufacturing process of the light-emitting device causes a problem such as a significant driving voltage increase or a significant emission efficiency decrease in the light-emitting device. For this reason, an organic EL device needs to be manufactured in a vacuum or an atmosphere of an inert gas such as nitrogen.
In a tandem light-emitting device, specifically, a plurality of light-emitting layers are stacked in series with an intermediate layer therebetween, and the intermediate layer also has a structure that includes a layer containing an alkali metal or a compound of an alkali metal so that electrons can be injected to a light-emitting unit that is in contact with the anode side of the intermediate layer. Meanwhile, in a light-emitting device with a single structure, a structure that includes a layer containing an alkali metal or a compound of an alkali metal can be formed after an organic compound layer is processed into a predetermined shape. Thus, the probability that the layer containing the alkali metal or the compound of the alkali metal will react with an atmospheric component such as water or oxygen is higher in the tandem light-emitting device than in the light-emitting device with the single structure.
A vacuum evaporation method using a metal mask (mask vapor deposition) has been widely used as one of methods for forming an organic compound layer in a predetermined shape in recent years. However, in these days of higher density and higher resolution, mask vapor deposition has come close to the limit of increasing the resolution for various reasons such as the alignment accuracy and the distance between the mask and the substrate. Meanwhile, when a lithography method (e.g., a photolithography method or an electron beam lithography method) is used to process the shape of an organic compound film, a finer pattern can be formed. Moreover, because of the easiness of large-area processing, the processing of an organic compound film by a photolithography method is being researched.
During a processing step in manufacture of a tandem light-emitting device by a photolithography method, the intermediate layer is exposed to the air, a resist resin, water, a chemical solution, or the like. This step causes deterioration of an n-type layer that contains an alkali metal or a compound of an alkali metal and is included in the intermediate layer, resulting in significant deterioration of device characteristics. That is, the layer containing the alkali metal or the compound of the alkali metal in the intermediate layer subjected to the photolithography process causes a significant increase in driving voltage and a significant decrease in emission efficiency.
An object of one embodiment of the present invention is to provide a novel organic compound that is highly convenient, useful, or reliable. Another object of one embodiment of the present invention is to provide a semiconductor device with high design flexibility. Another object of one embodiment of the present invention is to provide a light-emitting device with high design flexibility in a manufacturing process. Another object of one embodiment of the present invention is to provide a highly reliable light-emitting device. Another object of one embodiment of the present invention is to provide a light-emitting device, a light-emitting apparatus, an electronic appliance, a display apparatus, and an electronic device each having low power consumption. Another object of one embodiment of the present invention is to provide a light-emitting device, a light-emitting apparatus, an electronic appliance, a display apparatus, and an electronic device each having low power consumption and high reliability.
Note that the description of these objects does not preclude the existence of other objects. In one embodiment of the present invention, there is no need to achieve all these objects. Other objects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
One embodiment of the present invention is a light-emitting device including an organic compound layer between a first electrode and a second electrode. The organic compound layer includes a first light-emitting unit, a second light-emitting unit, and an intermediate layer. The intermediate layer is positioned between the first light-emitting unit and the second light-emitting unit. The intermediate layer includes an organic compound. A peak current of electron oxidation is detected and a peak current of electron reduction is not detected in the case where the organic compound is measured by the cyclic voltammetry (CV) at a scan rate greater than or equal to 1 V/s and less than or equal to 100 V/s.
One embodiment of the present invention is a light-emitting device including an organic compound layer between a first electrode and a second electrode. The organic compound layer includes a first light-emitting unit, a second light-emitting unit, and an intermediate layer. The intermediate layer is positioned between the first light-emitting unit and the second light-emitting unit. The intermediate layer includes an organic compound. In the case where the organic compound is measured by CV at a scan rate greater than or equal to 1 V/s and less than or equal to 100 V/s, when the potential is swept in the positive direction from the initial potential, a current of an extremum in the negative direction is detected, and then when the potential is swept in the negative direction to the initial potential, a current of an extremum in the positive direction is not detected.
One embodiment of the present invention is a light-emitting device including an organic compound layer between a first electrode and a second electrode. The organic compound layer includes a first light-emitting unit, a second light-emitting unit, and an intermediate layer. The intermediate layer is positioned between the first light-emitting unit and the second light-emitting unit. The intermediate layer includes an organic compound. In the case where the organic compound is measured by CV at a scan rate greater than or equal to 1 V/s and less than or equal to 100 V/s, when the potential is swept in the positive direction from the initial potential, a current of an extremum in the negative direction (a current value |Ipa−Ia0|) is detected, and then when the potential is swept in the negative direction to the initial potential, a current of an extremum in the positive direction (a current value |Ipc−Ic0|) is less than or equal to 1/20 of the current value |Ipa−Ia0|.
One embodiment of the present invention is a light-emitting device including an organic compound layer between a first electrode and a second electrode. The organic compound layer includes a first light-emitting unit, a second light-emitting unit, and an intermediate layer. The intermediate layer is positioned between the first light-emitting unit and the second light-emitting unit. The intermediate layer includes an organic compound whose m/z value is Xm. In the case where the light-emitting device is driven with a luminance greater than or equal to 500 cd/m2 for five minutes or longer and then the organic compound layer is measured by LC-MS, a signal whose m/z value is Xm−2 or Xm−4 is detected.
Note that the m/z value is a dimensionless quantity obtained by dividing the mass of an ion by the unified atomic mass unit and dividing it by the charge number of the ion.
One embodiment of the present invention is a light-emitting device including an organic compound layer between a first electrode and a second electrode. The organic compound layer includes a first light-emitting unit, a second light-emitting unit, and an intermediate layer. The intermediate layer is positioned between the first light-emitting unit and the second light-emitting unit. The intermediate layer includes an organic compound whose m/z value is Xm. In the case where the organic compound is measured by CV at a scan rate greater than or equal to 1 V/s and less than or equal to 100 V/s, when the potential is swept in the positive direction, a current of an extremum in the negative direction is detected, and then when the potential is swept in the negative direction to the initial potential, a current of an extremum in the positive direction is not detected. In the case where the light-emitting device is driven with a luminance greater than or equal to 500 cd/m2 for five minutes or longer and then the organic compound layer is measured by LC-MS, a signal whose m/z value is Xm−2 or Xm−4 is detected.
In any of the above light-emitting devices, the first electrode functions as an anode and the second electrode functions as a cathode, the first light-emitting unit is placed on the first electrode side, the second light-emitting unit is placed on the second electrode side, and the organic compound is placed in a region in contact with at least the first light-emitting unit.
In any of the above light-emitting devices, the organic compound includes a guanidine skeleton.
In any of the above light-emitting devices, the organic compound includes a guanidine skeleton, and a hydrogen atom is released from each of a first carbon bonded to the guanidine skeleton and a second carbon bonded to the first carbon.
In any of the above light-emitting devices, the organic compound has a ring structure including a guanidine skeleton, and a hydrogen atom is released from each of a first carbon bonded to the guanidine skeleton and a second carbon bonded to the first carbon.
One embodiment of the present invention is a light-emitting device including an organic compound layer between a first electrode and a second electrode. The organic compound layer includes a first light-emitting unit, a second light-emitting unit, and an intermediate layer. The intermediate layer is positioned between the first light-emitting unit and the second light-emitting unit. The intermediate layer includes an organic compound whose m/z value is Xm. The ion intensity of a signal whose m/z value is Xm−2 or Xm−4 according to results of LC-MS measurement of the intermediate layer of the light-emitting device after being driven with a luminance greater than or equal to 500 cd/m2 for five minutes or longer is high as compared with the ion intensity of a signal whose m/z value is Xm−2 or Xm−4 according to results of LC-MS measurement of the intermediate layer of the light-emitting device before being driven.
One embodiment of the present invention is a light-emitting apparatus that includes the light-emitting device having any of the above-described structures, and a transistor or a substrate.
One embodiment of the present invention can provide a light-emitting device having a novel tandem structure. One embodiment of the present invention can provide a highly efficient light-emitting device having a novel tandem structure. One embodiment of the present invention can provide a highly reliable light-emitting device having a novel tandem structure. One embodiment of the present invention can provide a highly reliable and efficient light-emitting device having a novel tandem structure.
One embodiment of the present invention can provide a semiconductor device with high design flexibility. One embodiment of the present invention can provide a light-emitting device with high design flexibility in a manufacturing process. One embodiment of the present invention can provide a highly reliable light-emitting device. One embodiment of the present invention can provide a light-emitting device, a light-emitting apparatus, an electronic appliance, a display apparatus, and an electronic device each having low power consumption. One embodiment of the present invention can provide a light-emitting device, a light-emitting apparatus, an electronic appliance, a display apparatus, an electronic device, and a lighting device each having low power consumption and high reliability.
Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all these effects. Other effects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
Embodiments will be described in detail with reference to the drawings. Note that the embodiments of the present invention are not limited to the following description, and it will be readily appreciated by those skilled in the art that modes and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description in the following embodiments.
Note that in structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and the description thereof is not repeated. The same hatching pattern is used for portions having similar functions, and the portions are not denoted by specific reference numerals in some cases.
The position, size, range, or the like of each component illustrated in drawings does not represent the actual position, size, range, or the like in some cases for easy understanding. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings.
In this specification and the like, a light-emitting device (also referred to as a light-emitting element) includes an EL layer between a pair of electrodes. The EL layer includes at least a light-emitting layer. In this specification and the like, a light-receiving device (also referred to as a light-receiving element) includes at least an active layer functioning as a photoelectric conversion layer between a pair of electrodes. In this specification and the like, one of the pair of electrodes may be referred to as a pixel electrode and the other may be referred to as a common electrode.
Note that the light-emitting apparatus in this specification includes, in its category, an image display device that uses an organic EL device. The light-emitting apparatus may also include a module in which an organic EL device is provided with a connector such as an anisotropic conductive film or a tape carrier package (TCP), a module in which a printed wiring board is provided at the end of a TCP, and a module in which an integrated circuit (IC) is directly mounted on an organic EL device by a chip on glass (COG) method. Furthermore, a lighting device or the like may include the light-emitting apparatus.
A light-emitting device includes an organic compound layer containing a light-emitting substance between electrodes (a first electrode and a second electrode), and energy generated by recombination of carriers (holes and electrons) injected to the organic compound layer from the electrodes causes light emission.
Although the light-emitting device includes one intermediate layer 116 and two light-emitting units in
For example, the light-emitting device 130 illustrated in
The color gamut of light emitted by a light-emitting layer in one light-emitting unit may be the same as or different from that of light emitted by a light-emitting layer in another light-emitting unit. In addition, the light-emitting layer may have either a single-layer structure or a stacked-layer structure. For example, white light emission can be achieved with a structure in which the first light-emitting unit and the third light-emitting unit emit light in a blue region and light-emitting layers in a stacked-layer structure of the second light-emitting unit emit light in a red region and light in a green region.
Here, an organic compound whose electron oxidation is irreversible is used for at least the electron-injection buffer region 119 of the intermediate layer. In general, for an organic light-emitting device (OLED) typified by a light-emitting device, an organic compound whose electron oxidation or electron reduction is reversible has been used. This is because in the case where an organic compound whose electron oxidation or electron reduction is irreversible is used, a degradation material (a substance generated by an irreversible reaction) adversely affects the reliability. However, a light-emitting device in which the organic compound of one embodiment of the present invention is used for the electron-injection buffer region 119 of the intermediate layer can be driven favorably despite electron oxidation of the organic compound being irreversible. Conversely, use of the organic compound whose electron oxidation is irreversible for the electron-injection buffer region 119 of the intermediate layer allows the tandem light-emitting device to function favorably.
Alternatively, the electron-injection buffer region 119 may be a mixed layer containing one or more kinds of different organic compounds in addition to the above-described organic compound whose electron oxidation is irreversible. In the following description, the organic compound whose electron oxidation is irreversible is called a first organic compound and an organic compound that is contained in the electron-injection buffer region 119 and other than the first organic compound is called a second organic compound. Depending on the kinds of organic compounds contained in the mixed layer, ordinal numbers are given as appropriate to the organic compounds in some cases.
As the first organic compound whose electron oxidation is irreversible which can be used for the device of one embodiment of the present invention, an alkylamine skeleton having 1 to 20 carbon atoms, a cycloalkylamine skeleton having 3 to 20 carbon atoms, and a heterocyclic skeleton having 1 to 20 carbon atoms and including a nitrogen atom whose an unshared electron pair is in a sp3 hybrid orbital can be used. Specifically, organic compounds having a basic skeleton, such as an acetamidine skeleton, a guanidine skeleton, a pyrrolidine skeleton, and a piperidine skeleton represented by Structural Formulae (120) to (123) below, are given as examples. In particular, Structural Formulae (122) and (123) including a guanidine skeleton are preferable because their basicity is high. The first organic compound including the alkylamine skeleton, the cycloalkylamine skeleton, or the heterocyclic skeleton including a nitrogen atom whose an unshared electron pair is in a sp3 hybrid orbital preferably includes a substituent having an electron-transport property, and preferably includes any one of an aromatic hydrocarbon skeleton, a π-electron deficient heteroaromatic ring skeleton, and a nitrogen-containing heteroaromatic ring skeleton. Specific examples include a benzene skeleton, a fluorene skeleton, a naphthalene skeleton, an anthracene skeleton, a phenanthrene skeleton, a triphenylene skeleton, a pyrene skeleton, a polyazole skeleton, a pyridine skeleton, a pyrimidine skeleton, a pyrazine skeleton, a diazine skeleton, a triazine skeleton, a quinoline skeleton, a quinazoline skeleton, a quinoxaline skeleton, a phenanthroline skeleton, and a dibenzoquinoxaline skeleton.
It is preferable that the first organic compound be specifically an organic compound that includes a bicyclo ring structure having 2 or more nitrogen atoms in the bicyclo ring and a heteroaromatic ring having 2 to 30 carbon atoms in the ring or an aromatic hydrocarbon ring having 6 to 30 carbon atoms in the ring, and more specifically be an organic compound that includes a 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine skeleton and a heteroaromatic ring having 2 to 30 carbon atoms in the ring or an aromatic hydrocarbon ring having 6 to 30 carbon atoms in the ring. It is preferable that the first organic compound be an organic compound that includes a bicyclo ring structure having 2 or more nitrogen atoms in the bicyclo ring and a heteroaromatic ring having 2 to 30 carbon atoms in the ring, and more specifically be an organic compound that includes a 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine skeleton and a heteroaromatic ring having 2 to 30 carbon atoms in the ring. It is preferable that the first organic compound be an organic compound including a guanidine skeleton, and further preferable that the first organic compound be an organic compound that includes a bicyclo ring structure having 2 or more nitrogen atoms in the bicyclo ring and being a molecular structure including a guanidine skeleton is further preferable.
Further specifically, the first organic compound is preferably an organic compound represented by General Formula (G1) below.
In the organic compound represented by General Formula (G1) above, X represents a group represented by General Formula (G1-1) below, and Y represents a group represented by General Formula (G1-2) below. R1 and R2 each independently represent hydrogen (including deuterium), h represents an integer of 1 to 6, and Ar represents a substituted or unsubstituted heteroaromatic ring having 2 to 30 carbon atoms in the ring or a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 30 carbon atoms in the ring. Ar is preferably the substituted or unsubstituted heteroaromatic ring having 2 to 30 carbon atoms in the ring.
Furthermore, the organic compound can have a high sublimation property when h is an integer of 1 or 2.
Ar preferably includes one or more of an aromatic ring skeleton, a π-electron deficient heteroaromatic ring skeleton, and a nitrogen-containing heteroaromatic skeleton. Specifically, a benzene skeleton, a naphthalene skeleton, an anthracene skeleton, a phenanthrene skeleton, a polyazole skeleton, a pyridine skeleton, a pyrimidine skeleton, a pyrazine skeleton, a diazine skeleton, a triazine skeleton, a quinoline skeleton, a quinazoline skeleton, a quinoxaline skeleton, a phenanthroline skeleton, or a dibenzo quinoxaline skeleton is preferable.
In General Formulae (G1-1) and (G1-2) above, R3 to R6 each independently represent hydrogen (including deuterium), m represents an integer of 0 to 4, n represents an integer of 1 to 5, and m+1≥n is satisfied. In the case where m or n is 2 or more, R3s may be the same as or different from each other, and the same applies to R4s, R5s, and R6s. In the case where m is 0, carbon (C) and nitrogen (N) are preferably bonded to each other in General Formula (G1) above.
The organic compound represented by General Formula (G1) above is preferably any one of compounds represented by General Formulae (G2-1) to (G2-6) below.
R11 to R26 each independently represent hydrogen (including deuterium), h represents an integer of 1 to 6, and Ar represents a substituted or unsubstituted heteroaromatic ring having 2 to 30 carbon atoms in the ring or a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 30 carbon atoms in the ring. Ar is preferably the substituted or unsubstituted heteroaromatic ring having 2 to 30 carbon atoms in the ring.
In General Formula (G1) and General Formulae (G2-1) to (G2-6) above, the substituted or unsubstituted heteroaromatic ring having 2 to 30 carbon atoms in the ring or the substituted or unsubstituted aromatic hydrocarbon ring having 6 to 30 carbon atoms in the ring that is represented by Ar is specifically a pyridine ring, a bipyridine ring, a pyrimidine ring, a bipyrimidine ring, a pyrazine ring, a bipyrazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a benzoquinoline ring, a phenanthroline ring, a quinoxaline ring, a benzoquinoxaline ring, a dibenzoquinoxaline ring, an azafluorene ring, a diazofluorene ring, a carbazole ring, a benzocarbazole ring, a dibenzocarbazole ring, a dibenzofuran ring, a benzonaphthofuran ring, a dinaphthofuran ring, a dibenzothiophene ring, a benzonaphthothiophene ring, a dinaphthothiophene ring, a benzofuropyridine ring, a benzofuropyrimidine ring, a benzothiopyridine ring, a benzothiopyrimidine ring, a naphthofuropyridine ring, a naphthofuropyrimidine ring, a naphthothiopyridine ring, a naphthothiopyrimidine ring, an acridine ring, a xanthene ring, a phenothiazine ring, a phenoxazine ring, a phenazine ring, a triazole ring, an oxazole ring, an oxadiazole ring, a thiazole ring, a thiadiazole ring, an imidazole ring, a benzimidazole ring, a pyrazole ring, a pyrrole ring, a benzene ring, a naphthalene ring, a fluorene ring, a dimethylfluorene ring, a diphenylfluorene ring, a spirofluorene ring, an anthracene ring, a phenanthrene ring, a triphenylene ring, a pyrene ring, a tetracene ring, a chrysene ring, a benzo[a]anthracene ring, or the like. Ar is especially preferably the ring represented by any one of Structural Formulae (Ar-1) to (Ar-27) below.
Note that Ar preferably has a nitrogen atom in its ring and is preferably bonded to the skeleton within parentheses in General Formula (G1) above by a bond of the nitrogen atom or a bond of a carbon atom adjacent to the nitrogen atom.
As specific examples of the organic compounds represented by General Formula (G1) and General Formulae (G2-1) to (G2-6) above, organic compounds represented by Structural Formulae (100) to (119) below, including 1,1′-(9,9′-spirobi[9H-fluorene]-2,7-diyl)bis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) (abbreviation: 2,7hpp2SF) (Structural Formula (112)) and 1-(9,9′-spirobi[9H-fluoren]-2-yl)-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (abbreviation: 2hppSF) (Structural Formula (113)), can be given.
The first organic compound is an organic compound that exhibits an irreversible reaction to electron oxidation. Whether electron oxidation is reversible can be determined by the electrochemical characteristics (a reduction potential and an oxidation potential) of the first organic compound measured by the cyclic voltammetry (CV), or by a change in the MS value (m/z value) detected before and after the energization of the first organic compound by the LC-MS measurement using the high-speed liquid chromatography mass spectrometry. Electron oxidation being irreversible means that the first organic compound in a hole (radical cation) state does not return to its original neutral state even when receiving an electron again, so that a light-emitting device including the first organic compound has a significantly low hole-transport property.
Here, determining whether electron oxidation of the first organic compound is irreversible by CV measurement is described. A current value at an oxidation current peak potential (Ipa) and a current value at a reduction current peak potential (Ipc) are measured by CV measurement in which a potential of a working electrode is changed with respect to a reference electrode, whereby whether electron oxidation of the first organic compound is irreversible can be determined.
Specifically, in CV measurement conducted on an organic compound at a scan rate greater than or equal to 1 V/s and less than or equal to 100 V/s, if a current of an extremum in the negative direction (a negative current peak) is detected when the potential is swept from the initial potential in the positive direction, and a current of an extremum in the positive direction (a positive current peak) is not detected when the potential is swept in the negative direction to the initial potential, electron oxidation of the organic compound is determined to be irreversible.
Note that the initial potential is a value obtained by open circuit potential measurement, that is, a potential difference between the working electrode and the reference electrode before the measurement in a state where a voltage or a potential is not applied to the first organic compound.
The CV measurement is preferably performed in the following procedure. First, scanning from the vicinity of the initial potential to the positive potential side (outward scanning) is performed and after a negative current peak (specifically, an oxidation current peak or a peak in outward scanning), which is an electron oxidation peak, is observed, the scanning is continued toward a higher potential side by approximately 0.1 V to 0.5 V, and the potential at this point is regarded as a turn-back potential. Subsequently, the scan direction is reversed to the negative potential direction, and scanning is performed to the vicinity of the initial potential that is the final potential (return scanning), and whether a positive current peak (specifically, a reduction current peak or a peak in return scanning), which is a peak observed when the organic compound returns to the neutral state, exists is determined.
Note that in the CV measurement, first, two or more cycles of measurement are performed from the initial potential, and the data of any of the second to tenth cycles, and any of the reproducible data of the second to tenth cycles is preferably employed. One of the reasons is that a peak potential derived from the electrodes is likely to be observed in the data of the first cycle.
In the case where a negative current peak (an extremum in the negative direction) is difficult to read from the CV measurement results obtained through the above procedure and a current value obtained by secondary differentiation has a projecting peak on the positive side, a value of raw data of the current value can be obtained. As for existence of the peak in return scanning (in this case, an extremum in the positive direction), in the case where x in Formula (1) below is greater than or equal to 20, preferably greater than or equal to 50, it can be determined that a peak does not exist in return scanning and electron reduction is not detected, that is, electron oxidation is irreversible. Note that in the following formula, the current value at the peak potential of oxidation current is Ipa, the current value at the initial potential in outward scanning is Ia0, the maximum value of the reduction current is Ipc, and the current value at the initial potential when the potential is returned to the initial potential in return scanning is Ic0. x is a variable. Note that in the case where the peak potential of reduction current can be read, the current value may be Ipc. In contrast, when x is less than 20, the material is determined to be a material whose electron oxidation is reversible.
Specifically, in the CV measurement results of the first organic compound, in the case where an absolute value (|Ipa−Ia0|) of a difference between the current value Ipa at the peak potential of oxidation current and the current value Ia0 at the initial potential in outward scanning is larger than or equal to 20 times, preferably larger than or equal to 50 times, an absolute value (|Ipc−Ic0|) of a difference between the maximum value (or the current value at the peak potential) Ipc of reduction current and the current value Ic0 at the initial potential when the potential is returned to the initial potential in return scanning, the first organic compound can be determined as a material whose electron oxidation is irreversible. In this manner, even when a hole is injected to a material whose electron oxidation is irreversible, the material does not release the injected hole; accordingly, the hole-transport property is probably inhibited.
As a solvent that can be used for the CV measurement, a solvent in which the first organic compound and an electrolyte are dissolved is selected. For example, N,N-dimethylformamide (DMF) or acetonitrile is given.
Whether electron oxidation of the first organic compound is irreversible can also be determined by LC-MS measurement using high-speed liquid chromatography mass spectrometry. Specifically, it can be determined by a change in the MS value (m/z) between the first organic compound detected before being energized and the first organic compound detected after being energized.
Note that “after energization” in this specification refers to a state after a light-emitting device including the first organic compound is driven with a luminance greater than or equal to 500 cd/m2 for five minutes or longer. In the light-emitting device, the luminance greater than or equal to 500 cd/m2 refers to the luminance of only the light-emitting region, and may be the luminance measured through a color filter and a polarizing plate. Note that in the case where the display apparatus emits light, the luminance of the display apparatus and the current density required for driving it with the luminance vary depending on aperture ratios of a pixel and a subpixel. Thus, the luminance of the pixel and the subpixel may be calculated by dividing the luminance of the display apparatus by the aperture ratio of the pixel and the subpixel. For example, in the case where the display apparatus with a pixel aperture ratio of 10% is driven with a luminance of 1,000 cd/m2, the luminance of the pixel corresponds to 10,000 cd/m2.
In the case where electron oxidation of the first organic compound is irreversible, when LC-MS measurement results of the first organic compound before being energized and those of the first organic compound after being energized are compared, an MS value decreased from the MS value corresponding to the first organic compound by 2 or 4, which is not detected before the energization, is detected after the energization. Alternatively, after the energization, the detection intensity of the MS value decreased from the MS value corresponding to the first organic compound by 2 or 4 is increased.
Specifically, two or four hydrogen atoms are dissociated from one molecule of the first organic compound when the first organic compound is energized, leading to the increase in detection intensity of the MS value decreased from the MS value corresponding to the first organic compound by 2 or 4. Accordingly, the detection of the MS value decreased from the MS value corresponding to the first organic compound by 2 or 4 or the increase in the detection intensity caused by energization is an index of confirming dissociation of hydrogen from the first organic compound by energization. It is considered that the first organic compound from which two or four hydrogen atoms are dissociated forms a double bond and becomes chemically stable and dissociated hydrogen atoms are less likely to return to the original positions.
Here, calculation results of an activation barrier at the time when a proton (a hydrogen cation) is transferred to bring 1-(9,9′-spirobi[9H-fluoren]-2-yl)-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (abbreviation: 2hppSF) including an hpp skeleton from a radical cation state to a neutral state are described.
Note that Gaussian 16 is used as a quantum chemistry computational program. A high performance computer (SGI8600 produced by Hewlett Packard Enterprise) is used for the calculation.
Description is given with reference to
Specifically, as for the proton translocation reaction of 2hppSF in a radical cation state, stable structures of 2hppSF in an initial state, a transition state, and a final state are calculated by density functional theory (DFT).
In the DFT, the total energy is represented as the sum of potential energy, electrostatic energy between electrons, electronic kinetic energy, and exchange-correlation energy including all the interactions between electrons. In the DFT, an exchange-correlation interaction is approximated by a functional (a function of a function) of one electron potential represented in terms of electron density. Here, B3LYP which is a hybrid functional is used to specify the weight of each energy related to exchange-correlation energy. As a basis function, 6-311G (d,p) is used.
As a calculation model, proton translocation between 2hppSF in a radical cation state and 2hppSF in a neutral state is used. On the assumption that the total energy of 2hppSF in a radical cation state and 2hppSF in a neutral state illustrated in
According to the results of calculating proton translocation reaction energy of the calculation model using 2hppSF in a radical cation state and 2hppSF in a neutral state, the activation barrier is as small as 0.11 eV and stabilization energy is stabilized at −0.72 eV. Accordingly, the proton translocation reaction is likely to occur.
As for the energy of the proton translocation reaction of the first organic compound calculated by the above calculation method, the activation barrier is preferably less than or equal to 0.5 eV, and further preferably less than or equal to 0.2 eV. In addition, the stabilization energy is preferably less than or equal to 0.0 eV, and further preferably less than or equal to −0.2 eV.
The proton-added cation of the produced 2hppSF molecule is stable in a cation state. For this reason, 2hppSF that can be used as the first organic compound is likely to accumulate protons (hydrogen cations) when holes are injected and 2hppSF is in a radical cation state.
When 2hppSF is in a radical cation state, a proton (a hydrogen cation) tends to be added to a nitrogen atom having a π electron as illustrated in
<<Calculation Results of Portion where Hydrogen is Released from Dehydrogenated Radical>>
Here, calculation results of energy at the time when a proton (a hydrogen cation) is released from a dehydrogenated radical of 1-(9,9′-spirobi[9H-fluoren]-2-yl)-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (abbreviation: 2hppSF) including an hpp skeleton is described.
Note that Gaussian 16 is used as a quantum chemistry computational program. A high performance computer (SGI8600 produced by Hewlett Packard Enterprise) is used for the calculation.
Specifically, in a 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine portion (an hpp group) of 2hppSF illustrated in
As for the hydrogen release reaction in a neutral state, stable structures in an initial state and a final state are calculated by density functional theory (DFT).
In the DFT, the total energy is represented as the sum of potential energy, electrostatic energy between electrons, electronic kinetic energy, and exchange-correlation energy including all the interactions between electrons. In the DFT, an exchange-correlation interaction is approximated by a functional (a function of a function) of one electron potential represented in terms of electron density. Here, B3LYP which is a hybrid functional is used to specify the weight of each energy related to exchange-correlation energy. As a basis function, 6-311G (d,p) is used.
On the assumption that the energy of the hpp group included in the 2hppSF molecule in a dehydrogenated radical state illustrated in
In
As a result, the stabilization energy of the case where a hydrogen radical in the position indicated by the arrow 7 (the 7-position of the hpp group) is released from the dehydrogenated radical of 2hppSF represented by the structural formula in
Accordingly, in 2hppSF in a two-electron oxidation state, a hydrogen atom tends to be released from each of a first carbon bonded to the guanidine skeleton and a second carbon bonded to the first carbon and these carbon atoms tend to form a double bond. That is, it is suggested that when holes are injected to 2hppSF, holes are consumed in an irreversible chemical reaction and transport of holes is inhibited.
Note that a proton (a hydrogen cation) released from the first organic compound in a radical cation state is added to another first organic compound in a neutral state, whereby a positive electric charge can be retained. Furthermore, a proton-added cation illustrated in
The LUMO level of the first organic compound is preferably higher than or equal to −2.50 eV and lower than or equal to −1.00 eV. Note that the LUMO level can be obtained by CV measurement.
The first organic compound is preferably a strongly basic organic compound with an acid dissociation constant pKa higher than or equal to 8. The first organic compound which is a strongly basic organic compound with an acid dissociation constant pKa higher than or equal to 8 can accumulate positive electric charges because a hydrogen cation (a proton) is dissociated by electron (hole) oxidation and a cation is formed by adding a proton.
The acid dissociation constant pKa of the first organic compound is preferably higher than or equal to 8, further preferably higher than 10. The acid dissociation constant pKa of the first organic compound is still further preferably higher than or equal to 12, yet still further preferably higher than 13.
As the acid dissociation constant pKa of a basic skeleton, the acid dissociation constant value of the organic compound formed by substituting hydrogen for part of the skeleton can be used. As an indicator of acidity of an organic compound having a basic skeleton, the acid dissociation constant pKa of the basic skeleton can be used. As for an organic compound having a plurality of basic skeletons, the acid dissociation constant pKa of the basic skeleton having the highest acid dissociation constant pKa can be used as the indicator of acidity of the organic compound.
Alternatively, the acid dissociation constant pKa of an organic compound may be calculated in the following manner.
First, the initial structure of a molecule serving as a calculation model is the most stable structure (a singlet ground state) obtained from first-principles calculation.
For the first-principles calculation, Jaguar, which is the quantum chemical computational software produced by Schrödinger, Inc., is used, and the most stable structure in the singlet ground state is calculated by the density functional theory (DFT). As a basis function, 6-31G** is used, and as a functional, B3LYP-D3 is used. The structure subjected to quantum chemical calculation is sampled by conformational analysis in mixed torsional/low-mode sampling with Maestro GUI produced by Schrödinger, Inc.
In calculation of pKa, one or more atoms of the molecule is designated as a basic site, Macro Model is used for searching for a structure that allows the protonated molecule to be stable in water, conformation is searched for with the use of the OPLS 2005 force field, and the lowest-energy conformational isomer thereby obtained is used. Structure optimization is performed by B3LYP/6-31G* using the pKa calculation module of Jaguar; then, single point calculation is performed with cc-pVTZ(+) to obtain a pKa value through empirical correction for a functional group. In the case where one or more atoms are designated as basic sites in a molecule, the largest of obtained values is used as a pKa value.
A mixed layer of the first organic compound, which is one embodiment of the present invention, and the second organic compound whose lowest unoccupied molecular orbital (LUMO) level is lower than that of the first organic compound is preferably used for the electron-injection buffer region 119. That is, the LUMO level of the strongly basic first organic compound is preferably higher than the LUMO level of the second organic compound. The use of this mixed layer for a device can reduce emergence of the problems due to an alkali metal or a compound of an alkali metal, which has been conventionally used.
The first organic compound preferably has a LUMO level higher than that of the second organic compound by greater than or equal to 0.05 eV. Alternatively, the first organic compound preferably has a LUMO level higher than that of the second organic compound by, preferably, greater than or equal to 0.1 eV, further preferably, greater than or equal to 0.2 eV. Such a difference in LUMO level makes it less likely that the first organic compound accepts electrons owing to the energy of room temperature or the influence of an electric field or the like.
As the second organic compound, an organic compound having an electron-transport property can be used. In a substance with a high electron-transport property, electron mobility is higher than hole mobility. Specifically, the electron mobility is preferably higher than or equal to 1×10−7 cm2/Vs, further preferably higher than or equal to 1×10−6 cm2/Vs in the case where the square root of the electric field strength [V/cm] is 600.
As the organic compound having a high electron-transport property, a heteroaromatic compound can be used, for example. The heteroaromatic compound refers to a cyclic compound containing at least two different kinds of elements in a ring. Examples of cyclic structures include a three-membered ring, a four-membered ring, a five-membered ring, and a six-membered ring, among which a five-membered ring and a six-membered ring are particularly preferable. The elements contained in the heteroaromatic compound are preferably one or more of nitrogen, oxygen, sulfur, and the like, in addition to carbon. In particular, a heteroaromatic compound containing nitrogen (a nitrogen-containing heteroaromatic compound) is preferable, and any of materials having a high electron-transport property (electron-transport materials), such as a nitrogen-containing heteroaromatic compound and an organic compound having a π-electron deficient heteroaromatic ring including the nitrogen-containing heteroaromatic compound, is preferably used.
It is preferable that the second organic compound not have a hole-transport skeleton. The second organic compound is, for example, an organic compound without an amine skeleton or an organic compound without a carbazole skeleton.
The LUMO level of the second organic compound is preferably higher than or equal to −3.25 eV and lower than or equal to −2.50 eV. The HOMO level of the second organic compound is preferably higher than or equal to −6.5 eV and lower than or equal to −5.7 eV.
The acid dissociation constant pKa of the second organic compound is preferably higher than or equal to 3 and lower than or equal to 8, further preferably higher than or equal to 4 and lower than or equal to 6.
The second organic compound preferably has a skeleton with an electron-transport property. As a material having an electron-transport property, for example, a metal complex such as bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BA1q), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), or bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); or an organic compound having a π-electron deficient heteroaromatic ring is preferably used. Examples of the organic compound having a π-electron deficient heteroaromatic ring include an organic compound that includes a heteroaromatic ring having a polyazole skeleton, an organic compound that includes a heteroaromatic ring having a pyridine skeleton, an organic compound that includes a heteroaromatic ring having a diazine skeleton, and an organic compound that includes a heteroaromatic ring having a triazine skeleton.
Among the above materials, the organic compound that includes a heteroaromatic ring having a diazine skeleton (a pyrimidine skeleton, a pyrazine skeleton, or a pyridazine skeleton), the organic compound that includes a heteroaromatic ring having a pyridine skeleton, and the organic compound that includes a heteroaromatic ring having a triazine skeleton have high reliability and thus are preferable. In particular, the organic compound that includes a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and the organic compound that includes a heteroaromatic ring having a triazine skeleton have a high electron-transport property to contribute to a reduction in driving voltage. A benzofuropyrimidine skeleton, a benzothienopyrimidine skeleton, a benzofuropyrazine skeleton, and a benzothienopyrazine skeleton are preferable because of their high reliability.
As the organic compound having a π-electron deficient heteroaromatic ring skeleton, it is possible to use any of materials given as examples of an electron-transport organic compound for the later-described first electron-transport layer. Among the materials, the organic compound that includes a heteroaromatic ring having a diazine skeleton, the organic compound that includes a heteroaromatic ring having a pyridine skeleton, and the organic compound that includes a heteroaromatic ring having a triazine skeleton have high reliability and thus are preferable. In particular, the organic compound that includes a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and the organic compound that includes a heteroaromatic ring having a triazine skeleton have a high electron-transport property to contribute to a reduction in driving voltage. Specifically, 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), 2-[3-(2-triphenylenyl)phenyl]-1,10-phenanthroline (abbreviation: mpPPhen), 2-[4-(9-phenanthrenyl)-1-naphthalenyl]-1,10-phenanthroline (abbreviation: PnNPhen), or any other organic compound having a phenanthroline skeleton is preferably used; it is further preferable to use mPPhen2P or any other organic compound having a phenanthroline dimer structure because such an organic compound enables excellently stable film quality. A material with a bipyridine skeleton, a material with a triazine skeleton, and a material with a phenanthroline skeleton are preferable because of having a high electron-transport property; in particular, any of these materials is particularly preferable as the electron-transport material that is used as the second organic compound in the light-emitting device of one embodiment of the present invention. A molecule having a larger number of pyridine skeletons, pyrimidine skeletons, triazine skeletons, or phenanthroline skeletons has a lower hole-transport property and thus is particularly preferable as the electron-transport material that is used as the second organic compound in the light-emitting device of one embodiment of the present invention.
A mixed layer of any of the organic compounds described in <First organic compound> and any of the organic compounds described in <Second organic compound> can be formed by co-evaporation thereof. Using the mixed layer as the electron-injection buffer region of the intermediate layer increases the reliability of the light-emitting device.
Here, the mechanism of the tandem light-emitting device of one embodiment of the present invention is described in detail with reference to
In a typical tandem light-emitting device, charge separation occurs to make a Li compound in an n-type layer of an intermediate layer act as a donor and transport carriers to an electron-transport material. By contrast, no charge separation occurs and neither carriers nor electric charge is generated in the electron-injection buffer region 119 (layer 1) in one embodiment of the present invention.
In the charge-generation region 117 (layer 3), carriers (holes and electrons) are generated by voltage application, despite the electron-injection buffer region 119 (layer 1) generating no electric charge. However, injection of the elections generated in the charge-generation region 117 to the electron-injection buffer region 119 is hindered by a large potential gap between the LUMO level (LUMOAC) of an acceptor material in the charge-generation region 117 and the LUMO level (LUMOETM) of the electron-transport material in the electron-injection buffer region 119, because the difference between the LUMO level of an electron-transport material and that of an acceptor material is usually large (
Thus, the electrons generated in the charge-generation region 117 are hardly injected to a first electron-transport layer 114_1 of the light-emitting unit (the first light-emitting unit 501) on the anode side since no electric charge is generated in the electron-injection buffer region 119, inhibiting the first light-emitting layer 113_1 of the first light-emitting unit 501 from emitting light. Note that the holes generated in the charge-generation region 117 can be injected to the second light-emitting unit 502 without difficulty, because the HOMO level (HOMOHTM) of a hole-transport material in the charge-generation region 117 and that of a hole-transport material in a second hole-transport layer 112_2 in the second light-emitting unit 502 can be equal or close to each other.
Despite the electron-injection buffer region 119 not serving as a charge-generation layer, the tandem light-emitting device of one embodiment of the present invention was found to work successfully. This can be explained referring to the driving mechanism of the tandem light-emitting device, which involves electric dipole generation due to electric charge accumulation and a resultant shift of the vacuum level.
First of all, no carriers are generated from the electron-injection buffer region 119 of the tandem light-emitting device of one embodiment of the present invention by voltage application, as described above. Meanwhile, a slight amount of holes injected from the anode to the first light-emitting unit 501 are transported by the electron-transport layer and injected to the first electron-transport layer 114_1 side in the electron-injection buffer region 119 (400 in
Holes and electrons are generated in the charge-generation region 117; however, the electrons generated in the charge-generation region 117 are not injected to the electron-injection buffer region 119 but are accumulated on the electron-injection buffer region 119 side of the charge-generation region 117 (a region 401 in
Accordingly, the vacuum level shifts (a region 403 in
An unstable element such as an alkali metal or an alkaline earth metal or a compound of such an element (e.g., Li or Li oxide) acts as a donor. In a light-emitting device that includes an intermediate layer containing the element or the compound, the amount of carriers generated is decreased due to the air exposure. By contrast, a light-emitting device that includes the first organic compound of one embodiment of the present invention in the electron-injection buffer region 119 is unlikely to suffer from air-exposure-induced degradation, and functions as a tandem light-emitting device by accumulating positive electric charges by driving after the fabrication of the light-emitting device. Thus, the light-emitting device of one embodiment of the present invention is unlikely to suffer from air-exposure-induced degradation even after passing through a processing step using a photolithography method, which involves air exposure, thereby having favorable characteristics.
The light-emitting device of one embodiment of the present invention with the above-described structure has high current efficiency and high reliability and is less likely to suffer from an increase in driving voltage.
One embodiment of the present invention, which is particularly suitable for a light-emitting device manufactured using a photolithography step, also contributes to cost reduction in a light-emitting device manufactured without using a photolithography step since one embodiment of the present invention enables the light-emitting device to be stable toward the air and accordingly have increased yield and eliminates the need for strict control of an atmosphere during a manufacturing process.
Structures of the light-emitting device 130 that includes the above-described organic compound other than the above-described structures are specifically described below.
The first light-emitting unit 501 and the second light-emitting unit 502 may include a functional layer in addition to the light-emitting layer. Although
Since the intermediate layer 116 includes the electron-injection buffer region 119, the electron-injection buffer region 119 serves as an electron-injection layer for the light-emitting unit on the anode side. Therefore, an electron-injection layer may be provided as necessary in the light-emitting unit on the anode side (the first light-emitting unit 501 in
The structure of the intermediate layer 116 in the light-emitting device 130 is described below.
The electron-injection buffer region 119 is a layer containing the first organic compound and the second organic compound with an electron-transport property as described above. In this layer, one or more of a metal, a metal compound, a metal complex, and a metal oxide may be mixed.
The first organic compound in the electron-injection buffer region 119 preferably has basicity. The first organic compound preferably has a low hole-transport property. Electron oxidation of the first organic compound is preferably irreversible. This can suppress a hole-transport property. It is preferable that hydrogen be easily dissociated from the first organic compound by electron oxidation. It is preferable that hydrogen be easily added to the first organic compound. In the first organic compound, hydrogen is easily dissociated by electron oxidation and a hydrogen cation (a proton) is easily added to another first organic compound, so that positive electric charges (cations) can be accumulated; thus, the first organic compound can serve as an intermediate layer of a tandem light-emitting device. Accordingly, the intermediate layer and the tandem light-emitting device can be stable toward an atmospheric component such as water or oxygen.
The charge-generation region 117 that is a charge-generation layer is preferably formed using a composite material containing an acceptor material and a hole-transport organic compound.
The acceptor material in the charge-generation region 117 preferably has an electron-accepting property. The acceptor material preferably has an electron-accepting property with respect to the hole-transport organic compound. The acceptor material having an electron-accepting property causes charge separation in the charge-generation region 117, so that the charge-generation region 117 can function as a charge-generation layer and can thus function as an intermediate layer of a tandem light-emitting device. A signal is preferably observed by electron spin resonance in the charge-generation region 117. For example, spin density derived from the signal observed at a g-factor of around 2.00 is preferably higher than or equal to 1×1016 spins/cm3, further preferably higher than or equal to 1×1017 spins/cm3, still further preferably higher than or equal to 1×1018 spins/cm3, yet still further preferably higher than or equal to 1×1019 spins/cm3.
As the hole-transport organic compound used in the composite material, any of a variety of organic compounds such as aromatic amine compounds, heteroaromatic compounds, aromatic hydrocarbons, and high molecular compounds (e.g., oligomers, dendrimers, and polymers) can be used. Note that the hole-transport organic compound used in the composite material preferably has a hole mobility higher than or equal to 1×10−6 cm2/Vs. The hole-transport organic compound used in the composite material is preferably a compound having a condensed aromatic hydrocarbon ring or a π-electron rich heteroaromatic ring. As the condensed aromatic hydrocarbon ring, an anthracene ring, a naphthalene ring, or the like is preferable. As the π-electron rich heteroaromatic ring, a condensed aromatic ring having at least one of a pyrrole skeleton, a furan skeleton, and a thiophene skeleton is preferable; specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further condensed to the carbazole ring or the dibenzothiophene ring is preferable.
Such a hole-transport organic compound further preferably has any of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, an aromatic amine having a substituent that includes a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine that has a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to the nitrogen of the amine through an arylene group may be used. Note that the hole-transport organic compound preferably has an N,N-bis(4-biphenyl)amino group to enable fabricating a light-emitting device having a long lifetime.
Specific examples of the hole-transport organic compound include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), 4,4′-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4″-phenyltriphenylamine (abbreviation: BnfBB1BP), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl-4-biphenylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4′,4″-diphenyltriphenylamine (abbreviation: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4′,4″-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4′-diphenyl-4″-(6; 1′-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4′-diphenyl-4″-(7; 1′-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB-03), 4,4′-diphenyl-4″-(7-phenyl)naphthyl-2-yl)triphenylamine (abbreviation: BBAPβNB-03), 4,4′-diphenyl-4″-(6; 2′-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B), 4,4′-diphenyl-4″-(7; 2′-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B-03), 4,4′-diphenyl-4″-(4; 2′-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB), 4,4′-diphenyl-4″-(5; 2′-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenylyl)-4′-(2-naphthyl)-4″-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenylyl)-4′-[4-(2-naphthyl)phenyl]-4″-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenylyl)-4′-[4-(2-naphthyl)phenyl]-4″-phenyltriphenylamine (abbreviation: TPBiAβNBi), 4-phenyl-4′-(1-naphthyl)triphenylamine (abbreviation: αNBA1BP), 4,4′-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4′-diphenyl-4″-[4′-(carbazol-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4′-[4-(3-phenyl-9H-carbazol-9-yl)phenyl]tris(biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-[4′-(carbazol-9-yl)biphenyl-4-yl]-4′-(2-naphthyl)-4″-phenyltriphenylamine (abbreviation: YGTBiβNB), N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBNBSF), N,N-bis(biphenyl-4-yl)-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: BBASF), N,N-bis(biphenyl-4-yl)-9,9′-spirobi[9H-fluoren]-4-amine (abbreviation: BBASF(4)), N-(biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi[9H-fluoren]-4-amine (abbreviation: oFBiSF), N-(biphenyl-4-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)dibenzofuran-4-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4′-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF), N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi[9H-fluoren]-4-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi[9H-fluoren]-3-amine, and N,N-bis(9,9-dimethyl-9H[fluoren]-2-yl)-9,9′-spirobi[9H-fluoren]-2-amine.
As the hole-transport organic compound, any of the following aromatic amine compounds can also be used: N,N-di(p-tolyl)-N,N-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4′-bis(N-{4-[N-(3-methylphenyl)-N-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B).
Examples of the acceptor material contained in the charge-generation region 117 include an organic compound having an electron-withdrawing group (e.g., a halogen group or a cyano group), such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), or 2-(7-dicyanomethylen-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile. A compound in which electron-withdrawing groups are bonded to a condensed aromatic ring having a plurality of heteroatoms, such as HAT-CN, is particularly preferable because it is thermally stable. A [3]radialene derivative having an electron-withdrawing group (in particular, a cyano group or a halogen group such as a fluoro group) has a very high electron-accepting property and thus is preferable. Specific examples include α,α′,α″-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile]. As the acceptor material, a transition metal oxide such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, or manganese oxide can also be used, other than the above-described organic compounds.
The electron-relay region 118 contains a substance having an electron-transport property and has a function of preventing an interaction between the electron-injection buffer region 119 and the charge-generation region 117 and smoothly transferring electrons. The LUMO level of the substance having an electron-transport property in the electron-relay region 118 is preferably between the LUMO level of the acceptor material in the charge-generation region 117 and the LUMO level of an organic compound contained in a layer that is included in the light-emitting unit on the first electrode 101 side and is in contact with the intermediate layer 116 (the first electron-transport layer 114_1 in the first light-emitting unit 501 in
Specifically, it is possible to use a perylenetetracarboxylic acid derivative such as diquinoxalino[2,3-a:2′,3′-c]phenazine (abbreviation: HATNA), 2,3,8,9,14,15-hexafluorodiquinoxalino[2,3-a:2′,3′-c]phenazine (abbreviation: HATNA-F6), 3,4,9,10-perylenetetracarboxylic diimide (abbreviation: PTCDI), or 3,4,9,10-perylenetetracarboxyl-bis-benzimidazole (abbreviation: PTCBI), (C60-Ih)[5,6]fullerene (abbreviation: C60), (C70-D5h)[5,6]fullerene (abbreviation: C70), or phthalocyanine (abbreviation: H2Pc). Alternatively, it is possible to use a metal phthalocyanine containing copper, zinc, cobalt, iron, chromium, nickel, or the like or a derivative thereof, such as copper phthalocyanine (abbreviation: CuPc), zinc phthalocyanine (abbreviation: ZnPc), cobalt phthalocyanine (abbreviation: CoPc), iron phthalocyanine (abbreviation: FePc), tin phthalocyanine (abbreviation: SnPc), tin oxide phthalocyanine (abbreviation: SnOPc), titanium oxide phthalocyanine (abbreviation: TiOPc), or vanadium oxide phthalocyanine (abbreviation: VOPc). It is particularly preferable to use a phthalocyanine-based metal complex such as copper phthalocyanine or zinc phthalocyanine or 2,3,8,9,14,15-hexafluorodiquinoxalino[2,3-a:2′,3′-c]phenazine. Among these materials, CuPc and ZnPc are preferable because they are inexpensive and have favorable characteristics. Using ZnPc, which has a low diffusion coefficient with respect to silicon, reduces the probability that metal diffusion to a semiconductor adversely affects the semiconductor characteristics; accordingly, ZnPc is particularly suitable for a display apparatus fabricated using a silicon semiconductor.
The thickness of the electron-relay region 118 is preferably greater than or equal to 1 nm and less than or equal to 10 nm, further preferably greater than or equal to 2 nm and less than or equal to 5 nm.
A tandem light-emitting device including the intermediate layer 116 does not suffer from a significant increase in driving voltage and a significant decrease in emission efficiency even when the organic compound layer 103 is processed by a photolithography method and thus has favorable characteristics.
The structures of the first electrode 101 and the second electrode 102 in the light-emitting device 130 are described below.
The first electrode 101 includes an anode. The first electrode 101 may have a stacked-layer structure; in that case, a layer in contact with the organic compound layer 103 functions as an anode. The anode is preferably formed using any of metals, alloys, and conductive compounds with a high work function (specifically, higher than or equal to 4.0 eV), mixtures thereof, and the like. Specific examples include indium oxide-tin oxide (ITO: indium tin oxide), indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). Such conductive metal oxide films are usually formed by a sputtering method, but may be formed by application of a sol-gel method or the like. In an example of the formation method, indium oxide-zinc oxide is deposited by a sputtering method using a target obtained by adding 1 wt % to 20 wt % zinc oxide to indium oxide. Furthermore, indium oxide containing tungsten oxide and zinc oxide (IWZO) can be deposited by a sputtering method using a target in which tungsten oxide and zinc oxide are added to indium oxide at 0.5 wt % to 5 wt % and 0.1 wt % to 1 wt %, respectively. Alternatively, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), a nitride of a metal material (e.g., titanium nitride), or the like can be used as a material of the anode. Graphene can also be used as a material of the anode. Note that when a composite material contained in the charge-generation region 117 in the intermediate layer 116 is used for a layer that is in contact with the anode (the layer is typically a hole-injection layer), an electrode material can be selected regardless of the work function.
The second electrode 102 includes a cathode. The second electrode 102 may have a stacked-layer structure; in that case, a layer in contact with the organic compound layer 103 functions as a cathode. As a substance of the cathode, any of metals, alloys, and electrically conductive compounds with a low work function (specifically, lower than or equal to 3.8 eV), mixtures thereof, and the like can be used. Specific examples of such a cathode material include elements belonging to Group 1 and Group 2 of the periodic table, such as alkali metals (e.g., lithium (Li) or cesium (Cs)), magnesium (Mg), calcium (Ca), and strontium (Sr), alloys containing any of these elements (e.g., MgAg and AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing any of these rare earth metals. However, when an electron-injection layer is provided between the second electrode 102 and the electron-transport layer, any of a variety of conductive materials such as Al, Ag, ITO, or indium oxide-tin oxide containing silicon or silicon oxide can be used for the cathode regardless of the work function.
When the second electrode 102 is formed using a material that transmits visible light, the light-emitting device can emit light from the second electrode 102 side.
Films of these conductive materials can be formed by a dry process such as a vacuum evaporation method or a sputtering method, an ink-jet method, a spin coating method, or the like. Alternatively, a wet process using a sol-gel method or a wet process using a paste of a metal material may be employed.
The structures of the first light-emitting unit 501 and the second light-emitting unit 502 in the light-emitting device 130 are described below.
The organic compound layer 103 has a stacked-layer structure. As the stacked-layer structure,
The hole-injection layer 111 is provided in contact with the anode and has a function of facilitating injection of holes into the organic compound layer 103 (the first light-emitting unit 501). The hole-injection layer 111 can be formed using a porphyrin-based compound such as phthalocyanine (abbreviation: H2Pc), a phthalocyanine-based complex compound such as copper phthalocyanine (abbreviation: CuPc), an aromatic amine compound such as 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB) or 4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), or a high molecular compound such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (abbreviation: PEDOT/PSS).
The hole-injection layer 111 may be formed using a substance having an electron-accepting property. As the substance having an acceptor property, any of substances described as examples of the acceptor material that is used in the composite material contained in the charge-generation region 117 in the intermediate layer 116 can similarly be used.
Furthermore, the hole-injection layer 111 may be formed using the same composite material contained in the charge-generation region 117 in the intermediate layer 116.
Further preferably, in the hole-injection layer 111, the organic compound with a hole-transport property that is used in the composite material has a relatively low HOMO level higher than or equal to −5.7 eV and lower than or equal to −5.4 eV. When the organic compound with a hole-transport property that is used in the composite material has a relatively low HOMO level, holes can be easily injected into the hole-transport layer to easily provide a light-emitting device having a long lifetime. In addition, when the organic compound with a hole-transport property that is used in the composite material has a relatively low HOMO level, degradation of the organic compound having a hole-transport property can be inhibited, so that the light-emitting device can have a longer lifetime.
The formation of the hole-injection layer 111 can improve the hole-injection property, offering the light-emitting device with a low driving voltage.
Among substances having an acceptor property, an organic compound having an acceptor property is easy to use because it is easily deposited by evaporation.
Since the charge-generation region 117 in the intermediate layer 116 functions as a hole-injection layer, a hole-injection layer is not provided in the second light-emitting unit 502. However, a hole-injection layer may be provided in the second light-emitting unit 502.
The hole-transport layers (the first hole-transport layer 112_1 and the second hole-transport layer 112_2) each contain an organic compound having a hole-transport property. The organic compound having a hole-transport property preferably has a hole mobility higher than or equal to 1×10−6 cm2/Vs.
Examples of the organic compound having a hole-transport property include compounds having an aromatic amine skeleton, such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N-diphenyl-N,N-bis(3-methylphenyl)-4,4′-diaminobiphenyl (abbreviation: TPD), N,N-bis(9,9′-spirobi[9H-fluoren]-2-yl)-N,N-diphenyl-4,4′-diaminobiphenyl (abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF); compounds having a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 9,9′-bis(biphenyl-4-yl)-3,3′-bi-9H-carbazole (abbreviation: BisBPCz), 9,9′-bis(biphenyl-3-yl)-3,3′-bi-9H-carbazole (abbreviation: BismBPCz), and 9-(biphenyl-3-yl)-9′-(biphenyl-4-yl)-9H,9′H-3,3′-bicarbazole (abbreviation: mBPCCBP), 9-(2-naphthyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: βNCCP), 9-(3-biphenyl)-9′-(2-naphthyl)-3,3′-bi-9H-carbazole (abbreviation: βNCCmBP), 9-(4-biphenyl)-9′-(2-naphthyl)-3,3′-bi-9H-carbazole (abbreviation: βNCCBP), 9,9′-di-2-naphthyl-3,3′-9H,9′H-bicarbazole (abbreviation: BisNCz), 9-(2-naphthyl)-9′-[1,1′:4′,1″-terphenyl]-3-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-3-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-5′-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:4′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-phenyl-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole (abbreviation: PCCzTp), 9,9′-bis(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-(4-biphenyl)-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, and 9-(triphenylen-2-yl)-9′-[1,1′:3′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole; compounds having a thiophene skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV); and compounds having a furan skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above materials, the compound having an aromatic amine skeleton and the compound having a carbazole skeleton are preferable because these compounds are highly reliable and have high hole-transport properties to contribute to a reduction in driving voltage. Note that any of the substances given as examples of the organic compound with a hole-transport property used in the composite material for the hole-injection layer 111 can also be suitably used as the material contained in the hole-transport layer 112.
The light-emitting layers (the first light-emitting layer 113_1 and the second light-emitting layer 1132) each preferably include a light-emitting substance and a host material. The light-emitting layer may additionally contain other materials. Alternatively, the light-emitting layer may be a stack of two layers with different compositions.
As the light-emitting substance, a fluorescent substance, a phosphorescent substance, a substance exhibiting thermally activated delayed fluorescence (TADF), or any of other light-emitting substances may be used.
Examples of the material that can be used as a fluorescent substance in the light-emitting layer are as follows. Other fluorescent substances can also be used.
The examples include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine (abbreviation: PAPP2BPy), N,N-diphenyl-N,N-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N-bis(3-methylphenyl)-N,N-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N-bis[4-(9H-carbazol-9-yl)phenyl]-N,N-diphenylstilbene-4,4′-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis(N,N′,N-triphenyl-1,4-phenylenediamine) (abbreviation: DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N,N-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N′,N′,N″,N′″,N″″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N′,N-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthryl]-N,N,N-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), coumarin 545T, N,N-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-bis(biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N,N-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N′,N-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N′-diphenyl-N,N′-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b; 6,7-b′]bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), and 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b; 6,7-b′]bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02). Condensed aromatic diamine compounds typified by pyrenediamine compounds such as 1,6FLPAPrn, 1,6mMemFLPAPm, and 1,6BnfAPrn-03 are particularly preferable because of their high hole-trapping properties and high emission efficiency or reliability.
Examples of the material that can be used when a phosphorescent substance is used as the light-emitting substance in the light-emitting layer are as follows.
The examples include an organometallic iridium complex having a 4H-triazole skeleton, such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp)3]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz)3]), or tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b)3]); an organometallic iridium complex having a 1H-triazole skeleton, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Mptz1-mp)3]) or tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me)3]); an organometallic iridium complex having an imidazole skeleton, such as fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpim)3]) or tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me)3]); and an organometallic iridium complex in which a phenylpyridine derivative having an electron-withdrawing group is a ligand, such as bis[2-(4′,6′-difluorophenyl)pyridinato-N,C2′]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4′,6′-difluorophenyl)pyridinato-N,C2′]iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C2′}iridium(III) picolinate (abbreviation: [Ir(CF3ppy)2(pic)]), or bis[2-(4′,6′-difluorophenyl)pyridinato-N,C2′]iridium(III) acetylacetonate (abbreviation: FIracac). These compounds exhibit blue phosphorescence and have an emission peak in the wavelength range from 450 nm to 520 nm.
Other examples include an organometallic iridium complex having a pyrimidine skeleton, such as tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)3]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)3]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)2(acac)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]), (acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm)2(acac)]), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm)2(acac)]), or (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm)2(acac)]); an organometallic iridium complex having a pyrazine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-Me)2(acac)]) or (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-iPr)2(acac)]); an organometallic iridium complex having a pyridine skeleton, such as tris(2-phenylpyridinato-N,C2′)iridium(III) (abbreviation: [Ir(ppy)3]), bis(2-phenylpyridinato-N,C2′)iridium(III) acetylacetonate (abbreviation: [Ir(ppy)2(acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: [Ir(bzq)2(acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq)3]), tris(2-phenylquinolinato-N,C2)iridium(III) (abbreviation: [Ir(pq)3]), bis(2-phenylquinolinato-N,C2)iridium(III) acetylacetonate (abbreviation: [Ir(pq)2(acac)]), [2-d3-methyl-8-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-KC]bis[2-(5-d3-methyl-2-pyridinyl-κN2)phenyl-KC]iridium(III) (abbreviation: Ir(5mppy-d3)2(mbfpypy-d3)), {2-(methyl-d3)-8-[4-(1-methylethyl-1-d)-2-pyridinyl-κN]benzofuro[2,3-b]pyridin-7-yl-κC}bis{5-(methyl-d3)-2-[5-(methyl-d3)-2-pyridinyl-N]phenyl-KC}iridium(III) (abbreviation: Ir(5mtpy-d6)2(mbfpypy-iPr-d4)), [2-d3-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-KC]bis[2-(2-pyridinyl-κN)phenyl-KC]iridium(III) (abbreviation: Ir(ppy)2(mbfpypy-d3)), or [2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-KC]bis[2-(2-pyridinyl-κN)phenyl-KC]iridium(III) (abbreviation: Ir(ppy)2(mdppy)); and a rare earth metal complex such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)3(Phen)]). These are mainly compounds that exhibit green phosphorescence and have an emission peak in the wavelength range from 500 nm to 600 nm. Note that organometallic iridium complexes having a pyrimidine skeleton have distinctively high reliability or emission efficiency and thus are particularly preferable.
Other examples include an organometallic iridium complex having a pyrimidine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm)2(dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm)2(dpm)]), or bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm)2(dpm)]); an organometallic iridium complex having a pyrazine skeleton, such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)2(dpm)]), or (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq)2(acac)]); an organometallic iridium complex having a pyridine skeleton, such as tris(1-phenylisoquinolinato-N,C2′)iridium(III) (abbreviation: [Ir(piq)3]) or bis(1-phenylisoquinolinato-N,C″)iridium(III) acetylacetonate (abbreviation: [Ir(piq)2(acac)]); a platinum complex such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (abbreviation: PtOEP); and a rare earth metal complex such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM)3(Phen)]) or tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA)3(Phen)]). These compounds exhibit red phosphorescence and have an emission peak in the wavelength range from 600 nm to 700 nm. Organometallic iridium complexes having a pyrazine skeleton can provide red light emission with favorable chromaticity.
Besides the above phosphorescent compounds, known phosphorescent compounds may be selected and used.
Examples of the TADF material include a fullerene, a derivative thereof, an acridine, a derivative thereof, and an eosin derivative. Furthermore, a metal-containing porphyrin, such as a porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd), can be given. Examples of the metal-containing porphyrin include a protoporphyrin-tin fluoride complex (SnF2(Proto IX)), a mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), a hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), a coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), an octaethylporphyrin-tin fluoride complex (SnF2(OEP)), an etioporphyrin-tin fluoride complex (SnF2(Etio I)), and an octaethylporphyrin-platinum chloride complex (PtCl2OEP), which are represented by the following structural formulae.
Alternatively, a heterocyclic compound having one or both of a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring and represented by the following structural formulae, such as 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PCCzTzn), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), or 10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation: ACRSA) can be used. Such a heterocyclic compound is preferable because of having excellent electron-transport and hole-transport properties owing to a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring. Among skeletons having the π-electron deficient heteroaromatic ring, a pyridine skeleton, a diazine skeleton (a pyrimidine skeleton, a pyrazine skeleton, and a pyridazine skeleton), and a triazine skeleton are preferable because of their high stability and reliability. In particular, a benzofuropyrimidine skeleton, a benzothienopyrimidine skeleton, a benzofuropyrazine skeleton, and a benzothienopyrazine skeleton are preferable because of their high acceptor properties and high reliability. Among skeletons having the π-electron rich heteroaromatic ring, an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton have high stability and reliability; thus, at least one of these skeletons is preferably included. A dibenzofuran skeleton is preferable as a furan skeleton, and a dibenzothiophene skeleton is preferable as a thiophene skeleton. As a pyrrole skeleton, an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, and a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton are particularly preferable. Note that a substance in which the π-electron rich heteroaromatic ring is directly bonded to the π-electron deficient heteroaromatic ring is particularly preferable because the electron-donating property of the π-electron rich heteroaromatic ring and the electron-accepting property of the π-electron deficient heteroaromatic ring are both improved, the energy difference between the S1 level and the T1 level becomes small, and thus thermally activated delayed fluorescence can be obtained with high efficiency. Note that an aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used instead of the π-electron deficient heteroaromatic ring. As a π-electron rich skeleton, an aromatic amine skeleton, a phenazine skeleton, or the like can be used. As a π-electron deficient skeleton, a xanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a skeleton containing boron such as phenylborane or boranthrene, an aromatic ring or a heteroaromatic ring having a cyano group or a nitrile group such as benzonitrile or cyanobenzene, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, or the like can be used. As described above, a π-electron deficient skeleton and a π-electron rich skeleton can be used instead of at least one of the π-electron deficient heteroaromatic ring and the π-electron rich heteroaromatic ring.
Alternatively, a TADF material whose singlet excited state and triplet excited state are in a thermal equilibrium state may be used. Such a TADF material has a short emission lifetime (excitation lifetime), which allows inhibition of a decrease in efficiency in a high-luminance region of a light-emitting device. Specifically, a material having the following molecular structure can be used.
Note that a TADF material is a material having a small difference between the S1 level and the T1 level and a function of converting triplet excitation energy into singlet excitation energy by reverse intersystem crossing. Thus, a TADF material can upconvert triplet excitation energy into singlet excitation energy (i.e., reverse intersystem crossing) using a small amount of thermal energy and efficiently generate a singlet excited state. In addition, the triplet excitation energy can be converted into light.
An exciplex whose excited state is formed of two kinds of substances has an extremely small difference between the S1 level and the T1 level and functions as a TADF material capable of converting triplet excitation energy into singlet excitation energy.
A phosphorescence spectrum observed at a low temperature (e.g., 77 K to 10 K) is used for an index of the T1 level. When the level of energy with a wavelength of the line obtained by extrapolating a tangent to the fluorescence spectrum at a tail on the short wavelength side is the S1 level and the level of energy with a wavelength of the line obtained by extrapolating a tangent to the phosphorescence spectrum at a tail on the short wavelength side is the T1 level, the difference between the S1 level and the T1 level of the TADF material is preferably smaller than or equal to 0.3 eV, further preferably smaller than or equal to 0.2 eV.
When a TADF material is used as the light-emitting substance, the S1 level of the host material is preferably higher than that of the TADF material. In addition, the T1 level of the host material is preferably higher than that of the TADF material.
As the host material in the light-emitting layer, any of various carrier-transport materials such as materials having an electron-transport property and/or materials having a hole-transport property, and the TADF materials can be used.
The material having a hole-transport property is preferably an organic compound having an amine skeleton or a π-electron rich heteroaromatic ring skeleton, for example. Examples of the material include compounds having an aromatic amine skeleton, such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N-diphenyl-N,N-bis(3-methylphenyl)-4,4′-diaminobiphenyl (abbreviation: TPD), N,N-bis(9,9′-spirobi[9H-fluoren]-2-yl)-N,N-diphenyl-4,4′-diaminobiphenyl (abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF); compounds having a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and 3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP); compounds having a thiophene skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV); and compounds having a furan skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above materials, the compound having an aromatic amine skeleton and the compound having a carbazole skeleton are preferable because these compounds are highly reliable and have high hole-transport properties to contribute to a reduction in driving voltage. In addition, the organic compounds given as examples of the material with a hole-transport property that can be used for the hole-transport layer can also be used.
As the material having an electron-transport property, for example, a metal complex such as bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BA1q), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), or bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); or an organic compound having a π-electron deficient heteroaromatic ring is preferably used. Examples of the organic compound having a π-electron deficient heteroaromatic ring include an organic compound having an azole skeleton, such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), or 4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs); an organic compound that includes a heteroaromatic ring having a pyridine skeleton, such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP), 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), or 2,2′-biphenyl-4,4′-diylbis(1,10-phenanthroline) (abbreviation: Phen2BP), an organic compound having a diazine skeleton, such as 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3-(3′-dibenzothiophen-4-yl)biphenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4′-(9-phenyl-9H-carbazol-3-yl)-3,1′-biphenyl-1-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mpPCBPDBq), 2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 9-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), 9-[3′-(dibenzothiophen-4-yl)biphenyl-4-yl]naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9pmDBtBPNfpr), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), 9,9′-[pyrimidine-4,6-diylbis(biphenyl-3,3′-diyl)]bis(9H-carbazole) (abbreviation: 4,6mCzBP2Pm), 8-(biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), 3,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzofuro[2,3-b]pyrazine (abbreviation: 3,8mDBtP2Bfpr), 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 8-[3′-(dibenzothiophen-4-yl)(biphenyl-3-yl)]naphtho[1′,2′:4,5]furo[3,2-d]pyrimidine (abbreviation: 8mDBtBPNfpm), 8-[(2,2′-binaphthalen)-6-yl)]-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8(PN2)-4mDBtPBfpm), 2,2′-(pyridine-2,6-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 2,6(P-Bqn)2Py), 2,2′-(pyridine-2,6-diyl)bis{4-[4-(2-naphthyl)phenyl]-6-phenylpyrimidine} (abbreviation: 2,6(NP-PPm)2Py), 6-(biphenyl-3-yl)-4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenylpyrimidine (abbreviation: 6mBP-4Cz2PPm), 2,6-bis(4-naphthalen-1-ylphenyl)-4-[4-(3-pyridyl)phenyl]pyrimidine (abbreviation: 2,4NP-6PyPPm), 4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenyl-6-(biphenyl-4-yl)pyrimidine (abbreviation: 6BP-4Cz2PPm), or 7-[4-(9-phenyl-9H-carbazol-2-yl)quinazolin-2-yl]-7H-dibenzo[c,g]carbazole (abbreviation: PC-cgDBCzQz); and an organic compound that includes a heteroaromatic ring having a triazine skeleton, such as 2-(biphenyl-4-yl)-4-phenyl-6-(9,9′-spirobi[9H-fluoren]-2-yl)-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-2,3′-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 2-[3′-(9,9-dimethyl-9H-fluoren-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 5-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-7,7-dimethyl-5H,7H-indeno[2,1-b]carbazole (abbreviation: mINc(II)PTzn), 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTzn), 2,4,6-tris[3′-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-phenylindolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), 2-[3′-(triphenylen-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTpBPTzn), 3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]-9-phenyl-9H-carbazole (abbreviation: PCDBfTzn), or 2-(biphenyl-3-yl)-4-phenyl-6-{8-[(1,1′:4′,1″-terphenyl)-4-yl]-1-dibenzofuranyl}-1,3,5-triazine (abbreviation: mBP-TPDBfTzn). Among the above materials, the organic compound that includes a heteroaromatic ring having a diazine skeleton, the organic compound that includes a heteroaromatic ring having a pyridine skeleton, and the organic compound that includes a heteroaromatic ring having a triazine skeleton have high reliability and thus are preferable. In particular, the organic compound that includes a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and the organic compound that includes a heteroaromatic ring having a triazine skeleton have a high electron-transport property to contribute to a reduction in driving voltage.
As the TADF material that can be used as the host material, the above materials mentioned as the TADF material can also be used. When the TADF material is used as the host material, triplet excitation energy generated in the TADF material is converted into singlet excitation energy by reverse intersystem crossing and transferred to the light-emitting substance, whereby the emission efficiency of the light-emitting device can be increased. Here, the TADF material functions as an energy donor, and the light-emitting substance functions as an energy acceptor.
This is very effective in the case where the light-emitting substance is a fluorescent substance. In that case, the S1 level of the TADF material is preferably higher than that of the fluorescent substance in order that high emission efficiency can be achieved. Furthermore, the T1 level of the TADF material is preferably higher than the S1 level of the fluorescent substance. Therefore, the T1 level of the TADF material is preferably higher than that of the fluorescent substance.
It is also preferable to use a TADF material that emits light whose wavelength overlaps with the wavelength of a lowest-energy-side absorption band of the fluorescent substance, in which case excitation energy is transferred smoothly from the TADF material to the fluorescent substance and light emission can be obtained efficiently.
In addition, in order to efficiently generate singlet excitation energy from the triplet excitation energy by reverse intersystem crossing, carrier recombination preferably occurs in the TADF material. It is also preferable that the triplet excitation energy generated in the TADF material not be transferred to the triplet excitation energy of the fluorescent substance. For that reason, the fluorescent substance preferably has a protective group around a luminophore (a skeleton which causes light emission) of the fluorescent substance. As the protective group, a substituent having no π bond and a saturated hydrocarbon are preferably used. Specific examples include an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 12 carbon atoms, and a trialkylsilyl group having 3 to 10 carbon atoms. It is further preferable that the fluorescent substance have a plurality of protective groups. The substituents having no π bond are poor in carrier transport performance, whereby the TADF material and the luminophore of the fluorescent substance can be made away from each other with little influence on carrier transport or carrier recombination. Here, the luminophore refers to an atomic group (skeleton) that causes light emission in a fluorescent substance. The luminophore is preferably a skeleton having a π bond, further preferably includes an aromatic ring, and still further preferably includes a condensed aromatic ring or a condensed heteroaromatic ring. Examples of such a luminophore include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, and a naphthobisbenzofuran skeleton. Specifically, a fluorescent substance having any of a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, and a naphthobisbenzofuran skeleton is preferable because of its high fluorescence quantum yield.
In the case where a fluorescent substance is used as the light-emitting substance, a material having an anthracene skeleton is suitably used as the host material. The use of a substance having an anthracene skeleton as the host material for the fluorescent substance makes it possible to obtain a light-emitting layer with high emission efficiency and high durability. Among the substances having an anthracene skeleton, a substance having a diphenylanthracene skeleton, in particular, a substance having a 9,10-diphenylanthracene skeleton, is chemically stable and thus is preferably used as the host material. The host material preferably has a carbazole skeleton to have higher hole-injection and hole-transport properties; further preferably, the host material has a benzocarbazole skeleton in which a benzene ring is further condensed to a carbazole skeleton, because the HOMO level of the host material having a benzocarbazole skeleton is higher than that of the host material having a carbazole skeleton by approximately 0.1 eV and the host material having a benzocarbazole skeleton is thus easier for holes to enter than the host material having a carbazole skeleton. In particular, the host material preferably has a dibenzocarbazole skeleton, because the HOMO level of the host material having a dibenzocarbazole skeleton is higher than that of the host material having a carbazole skeleton by approximately 0.1 eV, the host material having a dibenzocarbazole skeleton is thus easier for holes to enter than the host material having a carbazole skeleton, and the host material having a dibenzocarbazole skeleton has a higher hole-transport property and higher heat resistance than the host material having a carbazole skeleton. Accordingly, a substance that has both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole or dibenzocarbazole skeleton) is further preferable as the host material. Note that in terms of the hole-injection and hole-transport properties described above, instead of a carbazole skeleton, a benzofluorene skeleton or a dibenzofluorene skeleton may be used. Examples of such a substance include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-[4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl]anthracene (abbreviation: FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), 9-(1-naphthyl)-10-(2-naphthyl)anthracene (abbreviation: α,βADN), 2-(10-phenylanthracen-9-yl)dibenzofuran, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA), 9-(2-naphthyl)-10-[3-(2-naphthyl)phenyl]anthracene (abbreviation: βN-mβNPAnth), and 1-[4-(10-biphenyl-4-yl-9-anthracenyl)phenyl]-2-ethyl-1H-benzimidazole (abbreviation: EtBImPBPhA). In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA exhibit excellent properties and thus are preferably selected.
Note that the host material may be a mixture of a plurality of kinds of substances; in the case of using a mixed host material, it is preferable to mix a material having an electron-transport property with a material having a hole-transport property. By mixing the material having an electron-transport property with the material having a hole-transport property, the transport property of the light-emitting layer 113 can be easily adjusted and a recombination region can be easily controlled. The weight ratio of the content of the material having a hole-transport property to the content of the material having an electron-transport property may be 1:19 to 19:1.
Note that a phosphorescent substance can be used as part of the mixed material. When a fluorescent substance is used as the light-emitting substance, a phosphorescent substance can be used as an energy donor for supplying excitation energy to the fluorescent substance.
An exciplex may be formed by these mixed materials. These mixed materials are preferably selected so as to form an exciplex that exhibits light emission whose wavelength overlaps with the wavelength of a lowest-energy-side absorption band of the light-emitting substance, in which case energy can be transferred smoothly and light emission can be obtained efficiently. Such a structure is preferably used to reduce the driving voltage.
Note that at least one of the materials forming an exciplex may be a phosphorescent substance. In this case, triplet excitation energy can be efficiently converted into singlet excitation energy by reverse intersystem crossing.
Combination of a material having an electron-transport property and a material having a hole-transport property whose HOMO level is higher than or equal to that of the material having an electron-transport property is preferable for forming an exciplex efficiently. In addition, the LUMO level of the material having a hole-transport property is preferably higher than or equal to that of the material having an electron-transport property. Note that the LUMO levels and the HOMO levels of the materials can be derived from the electrochemical characteristics (the reduction potentials and the oxidation potentials) of the materials that are measured by cyclic voltammetry (CV).
The formation of an exciplex can be confirmed by a phenomenon in which the electroluminescence spectrum of the mixed film in which the material having a hole-transport property and the material having an electron-transport property are mixed is shifted to the longer wavelength side than the electroluminescence spectrum of each of the materials (or has another peak on the longer wavelength side) observed by comparison of the electroluminescence spectra of the material having a hole-transport property, the material having an electron-transport property, and the mixed film of these materials, for example. Alternatively, the formation of an exciplex can be confirmed by a difference in transient response, such as a phenomenon in which the transient photoluminescence (PL) lifetime of the mixed film has longer lifetime components or has a larger proportion of delayed components than that of each of the materials, observed by comparison of transient PL of the material having a hole-transport property, the material having an electron-transport property, and the mixed film of these materials. The transient PL can be rephrased as transient electroluminescence (EL). That is, the formation of an exciplex can also be confirmed by a difference in transient response observed by comparison of the transient EL of the material having a hole-transport property, the material having an electron-transport property, and the mixed film of these materials.
The electron-transport layers (the first electron-transport layer 114_1 and the second electron-transport layer 114_2) each contain a substance having an electron-transport property. The electron mobility of the substance having an electron-transport property is preferably higher than or equal to 1×10−7 cm2/Vs, further preferably higher than or equal to 1×10−6 cm2/Vs in the case where the square root of the electric field strength [V/cm] is 600. Note that any other substance can also be used as long as the substance has an electron-transport property higher than a hole-transport property. An organic compound having a π-electron deficient heteroaromatic ring is preferable as the above organic compound. The organic compound having a π-electron deficient heteroaromatic ring is preferably one or more of an organic compound that includes a heteroaromatic ring having a polyazole skeleton, an organic compound that includes a heteroaromatic ring having a pyridine skeleton, an organic compound that includes a heteroaromatic ring having a diazine skeleton, and an organic compound that includes a heteroaromatic ring having a triazine skeleton.
As the organic compound with an electron-transport property that can be used in the electron-transport layer, any of the above-described materials with an electron-transport property and the organic compounds that can be used as the organic compound having an electron-transport property in the electron-injection buffer region of the intermediate layer 116 can be similarly used. Among the materials, the organic compound that includes a heteroaromatic ring having a diazine skeleton, the organic compound that includes a heteroaromatic ring having a pyridine skeleton, and the organic compound that includes a heteroaromatic ring having a triazine skeleton have high reliability and thus are preferable. In particular, the organic compound that includes a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and the organic compound that includes a heteroaromatic ring having a triazine skeleton have a high electron-transport property to contribute to a reduction in driving voltage.
The electron mobility of the electron-transport layer in the case where the square root of the electric field strength [V/cm] is 600 is preferably higher than or equal to 1×10−7 cm2/Vs and lower than or equal to 5×10−5 cm2/Vs. The amount of electrons injected into the light-emitting layer can be controlled by the reduction in the electron-transport property of the electron-transport layer 114, whereby the light-emitting layer can be prevented from having excess electrons. It is particularly preferable to employ this structure when the hole-injection layer is formed using a composite material that includes a material having a hole-transport property with a relatively low HOMO level higher than or equal to −5.7 eV and lower than or equal to −5.4 eV, in which case a long lifetime can be achieved. In this case, the material having an electron-transport property preferably has a HOMO level higher than or equal to −6.0 eV.
As the electron-injection layer 115, a layer containing an alkali metal, an alkaline earth metal, a rare earth metal, a compound thereof, or a complex thereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), 8-hydroxyquinolinato-lithium (abbreviation: Liq), or ytterbium (Yb) in addition to the above-described organic compound having a basic skeleton, can be used. An electride or a layer that is formed using a substance having an electron-transport property and that contains an alkali metal, an alkaline earth metal, or a compound thereof can be used as the electron-injection layer 115. Examples of the electride include a substance in which electrons are added at high concentration to calcium oxide-aluminum oxide.
Note that as the electron-injection layer 115, it is possible to use a layer including a substance that has an electron-transport property (preferably an organic compound having a bipyridine skeleton) and includes a fluoride of the alkali metal or the alkaline earth metal at a concentration higher than or equal to that at which the electron-injection layer 115 becomes in a microcrystalline state (50 wt % or higher). Since the layer has a low refractive index, a light-emitting device including the layer can have high external quantum efficiency.
The organic compound layer 103 can be formed by any of a variety of methods, including a dry process and a wet process. For example, a vacuum evaporation method, a gravure printing method, an offset printing method, a screen printing method, an ink-jet method, a spin coating method, or the like may be used.
Different methods may be used to form the electrodes or the layers described above.
The light-emitting device 130a includes an organic compound layer 103a between a first electrode 101a and the second electrode 102 over an insulating layer 175. The organic compound layer 103a has a structure in which a first light-emitting unit 501a and a second light-emitting unit 502a are stacked with an intermediate layer 116a therebetween. Although
The light-emitting device 130b includes an organic compound layer 103b between a first electrode 101b and the second electrode 102 over the insulating layer 175. The organic compound layer 103b has a structure in which a first light-emitting unit 501b and a second light-emitting unit 502b are stacked with an intermediate layer 116b therebetween. Although
The electron-injection layer 115 and the second electrode 102 are each preferably one layer shared by the light-emitting device 130a and the light-emitting device 130b. The organic compound layer 103a and the organic compound layer 103b, except for the electron-injection layer 115, are processed by a photolithography method after the layer to be the second electron-transport layer 114a_2 is formed and after the layer to be the second electron-transport layer 114b_2 is formed and thus are independent of each other. Since the edge (contour) of the organic compound layer 103a except for the electron-injection layer 115 is processed by a photolithography method, the edges of the layers in the organic compound layer 103a except for the electron-injection layer 115 are substantially aligned in the direction perpendicular to the substrate surface. Furthermore, since the edge (contour) of the organic compound layer 103b except for the electron-injection layer 115 is processed by a photolithography method, the edges of the layers in the organic compound layer 103b except for the electron-injection layer 115 are substantially aligned in the direction perpendicular to the substrate surface.
Since the organic compound layers are processed by a photolithography method, a distance d between the first electrode 101a and the first electrode 101b can be smaller than that of the case where the light-emitting devices are formed by mask vapor deposition. The distance d can be more than or equal to 2 μm and less than or equal to 5 μm.
The structure of this embodiment can be used in combination with any of the other structures as appropriate.
As illustrated as an example in
A light-emitting apparatus 1000 includes a pixel portion 177 in which a plurality of pixels 178 are arranged in matrix. The pixel 178 includes a subpixel 110R, a subpixel 110G, and a subpixel 110B.
In this specification and the like, for example, matters common to the subpixels 110R, 110G, and 110B are sometimes described using the collective term “subpixel 110”. As for components that are distinguished from each other using letters of the alphabet, matters common to the components are sometimes described using reference numerals excluding the letters of the alphabet.
The subpixel 110R emits red light, the subpixel 110G emits green light, and the subpixel 110B emits blue light. Thus, an image can be displayed on the pixel portion 177. Note that in this embodiment, three colors of red (R), green (G), and blue (B) are given as examples of colors of light emitted by subpixels; however, the structure of the present invention is not limited to this structure. That is, subpixels of a different combination of colors may be employed. The number of subpixels is not limited to three, and four or more subpixels may be used, for example. Examples of four subpixels include subpixels emitting light of four colors of R, G, B, and white (W), subpixels emitting light of four colors of R, G, B, and yellow (Y), and four subpixels emitting light of R, G, and B and infrared light (IR).
In this specification and the like, the row direction and the column direction are sometimes referred to as the X direction and the Y direction, respectively. The X direction and the Y direction intersect with each other and are perpendicular to each other, for example.
A connection portion 140 and a region 141 may be provided outside the pixel portion 177. The region 141 is preferably positioned between the pixel portion 177 and the connection portion 140, for example. The organic compound layer 103 is provided in the region 141. A conductive layer 151C is provided in the connection portion 140.
Although
In the pixel portion 177, the light-emitting device 130 is provided over the insulating layer 175 and the plug 176. A protective layer 131 is provided to cover the light-emitting device 130. A substrate 120 is bonded to the protective layer 131 with a resin layer 122. An inorganic insulating layer 125 and an insulating layer 127 over the inorganic insulating layer 125 may be provided between adjacent light-emitting devices 130.
Although
In
Note that the organic compound layer 103 at least includes a light-emitting layer and can include other functional layers (a hole-injection layer, a hole-transport layer, a hole-blocking layer, an electron-blocking layer, an electron-transport layer, an electron-injection layer, and the like). A combination of the organic compound layer 103 and a common layer 104 may constitute functional layers (a hole-injection layer, a hole-transport layer, a hole-blocking layer, a light-emitting layer, an electron-blocking layer, an electron-transport layer, an electron-injection layer, and the like) of the light-emitting device.
The light-emitting apparatus of one embodiment of the present invention can be, for example, a top-emission light-emitting apparatus where light is emitted in the direction opposite to a substrate over which light-emitting devices are formed. Note that the light-emitting apparatus of one embodiment of the present invention may be of a bottom-emission type.
The light-emitting device 130 (130R, 130G, or 130B) has a structure as described in Embodiment 1. The light-emitting device 130 (130R, 130G, or 130B) includes the first electrode (pixel electrode) including a conductive layer 151 (151R, 151G, or 151B) and a conductive layer 152 (152R, 152G, or 152B), the organic compound layer 103 (103R, 103G, or 103B) over the first electrode, the common layer 104 over the organic compound layer 103 (103R, 103G, or 103B), and the second electrode (common electrode) 102 over the common layer 104.
Note that the common layer 104 is not necessarily provided. The common layer 104 can reduce damage to the organic compound layer 103R caused in a later step. In the case where the common layer 104 is provided, the common layer 104 may function as an electron-injection layer. In the case where the common layer 104 functions as an electron-injection layer, a stack of the organic compound layer 103R and the common layer 104 corresponds to the organic compound layer 103 in Embodiment 1.
In the light-emitting device, one of the pixel electrode and the common electrode functions as an anode and the other functions as a cathode. Hereinafter, description is made on the assumption that the pixel electrode functions as the anode and the common electrode functions as the cathode unless otherwise specified.
The organic compound layer 103R, the organic compound layer 103G, and the organic compound layer 103B are island-shaped layers that are independent of one another. Alternatively, an organic compound layer of the light-emitting devices of one emission color may be independent of an organic compound layer of the light-emitting devices of another emission color. Providing the island-shaped organic compound layer 103 in each of the light-emitting devices 130 can suppress leakage current between the adjacent light-emitting devices 130 even in a high-resolution light-emitting apparatus. This can prevent crosstalk, so that a light-emitting apparatus with extremely high contrast can be obtained. Specifically, a light-emitting apparatus having high current efficiency at low luminance can be obtained.
The organic compound layer 103 may be provided to cover the top and side surfaces of the first electrode (pixel electrode) of the light-emitting device 130. In that case, the aperture ratio of the light-emitting apparatus 1000 can be easily increased as compared to the structure where an edge portion of the organic compound layer 103 is positioned inward from an edge portion of the pixel electrode. Covering the side surface of the pixel electrode of the light-emitting device 130 with the organic compound layer 103 can inhibit the pixel electrode from being in contact with the second electrode 102; hence, a short circuit of the light-emitting device 130 can be inhibited. Furthermore, the distance between a light-emitting region (i.e., a region overlapping with the pixel electrode) in the organic compound layer 103 and the edge portion of the organic compound layer 103 can be increased. Since the edge portion of the organic compound layer 103 might be damaged by processing, using a region that is away from the edge portion of the organic compound layer 103 as the light-emitting region can increase the reliability of the light-emitting device 130.
In the light-emitting apparatus of one embodiment of the present invention, the first electrode (pixel electrode) of the light-emitting device may have a stacked-layer structure. For example, in the example illustrated in
In the case where the light-emitting apparatus 1000 is a top-emission light-emitting apparatus, for example, in the pixel electrode of the light-emitting device 130, the conductive layer 151 preferably has high visible light reflectance and the conductive layer 152 preferably has a visible-light-transmitting property and a high work function. The higher the visible light reflectance of the pixel electrode is, the higher the efficiency of extraction of the light emitted by the organic compound layer 103 is. In the case where the pixel electrode functions as an anode, the higher the work function of the pixel electrode is, the easier it is to inject holes into the organic compound layer 103. Accordingly, when the pixel electrode of the light-emitting device 130 is a stack of the conductive layer 151 with high visible light reflectance and the conductive layer 152 with a high work function, the light-emitting device 130 can have high light extraction efficiency and a low driving voltage.
Specifically, the visible light reflectance of the conductive layer 151 is preferably higher than or equal to 40% and lower than or equal to 100%, further preferably higher than or equal to 70% and lower than or equal to 100%, for example. When the conductive layer 152 is used as an electrode having a visible-light-transmitting property, the visible light transmittance is preferably higher than or equal to 40%, for example.
In the case where a film formed after the formation of the pixel electrode having a stacked-layer structure is removed by a wet etching method, for example, the stack might be impregnated with a chemical solution used for the etching. When the chemical solution reaches the pixel electrode, galvanic corrosion between a plurality of layers constituting the pixel electrode might occur, leading to deterioration of the pixel electrode.
In view of the above, the conductive layer 152 is preferably formed to cover the top and side surfaces of the conductive layer 151. When the conductive layer 151 is covered with the conductive layer 152, the chemical solution does not reach the conductive layer 151; thus, occurrence of galvanic corrosion in the pixel electrode can be inhibited. This allows the light-emitting apparatus 1000 to be fabricated by a high-yield method and to be accordingly inexpensive. In addition, generation of a defect in the light-emitting apparatus 1000 can be inhibited, which makes the light-emitting apparatus 1000 highly reliable.
A metal material can be used for the conductive layer 151, for example. Specifically, it is possible to use a metal such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing an appropriate combination of any of these metals, for example.
For the conductive layer 152, an oxide containing one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon can be used. For example, it is preferable to use a conductive oxide containing one or more of indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide containing gallium, titanium oxide, indium zinc oxide containing gallium, indium zinc oxide containing aluminum, indium tin oxide containing silicon, indium zinc oxide containing silicon, and the like. In particular, indium tin oxide containing silicon can be suitably used for the conductive layer 152 because of having a high work function, for example, a work function higher than or equal to 4.0 eV.
The conductive layer 151 and the conductive layer 152 may each be a stack of a plurality of layers containing different materials. In that case, the conductive layer 151 may include a layer formed using a material that can be used for the conductive layer 152, such as a conductive oxide. Furthermore, the conductive layer 152 may include a layer formed using a material that can be used for the conductive layer 151, such as a metal material. In the case where the conductive layer 151 is a stack of two or more layers, for example, a layer in contact with the conductive layer 152 can contain the same material as a layer of the conductive layer 152 that is in contact with the conductive layer 151.
The conductive layer 151 preferably has an edge portion with a tapered shape. Specifically, the edge portion of the conductive layer 151 preferably has a tapered shape with a taper angle less than 90°. In that case, the conductive layer 152 provided along the side surface of the conductive layer 151 also has a tapered shape. When an edge portion of the conductive layer 152 has a tapered shape, coverage with the organic compound layer 103 provided along the side surface of the conductive layer 152 can be improved.
In the case where the conductive layer 151 or the conductive layer 152 has a stacked-layer structure, at least one of the stacked layers preferably has a tapered side surface. The stacked layers of the conductive layer(s) may have different tapered shapes.
In the example illustrated in
In this manner, the structure in which the conductive layer 151_2 is interposed between the conductive layers 151_1 and 151_3 can expand the range of choices for the material for the conductive layer 151_2. The conductive layer 151_2, for example, can thus have higher visible light reflectance than at least one of the conductive layers 151_1 and 151_3. For example, aluminum can be used for the conductive layer 151_2. The conductive layer 151_2 may be formed using an alloy containing aluminum. The conductive layer 151_1 can be formed using titanium; titanium has lower visible light reflectance than aluminum but is less likely to migrate by contact with the insulating layer 175 than aluminum. Furthermore, the conductive layer 151_3 can be formed using titanium; titanium is less likely to be oxidized than aluminum and an oxide of titanium has lower electrical resistivity than aluminum oxide, although titanium has lower visible light reflectance than aluminum.
The conductive layer 151_3 may be formed using silver or an alloy containing silver. Silver is characterized by its visible light reflectance higher than that of titanium. In addition, silver is characterized by being less likely to be oxidized than aluminum, and silver oxide is characterized by its electrical resistivity lower than that of aluminum oxide. Thus, the conductive layer 151_3 formed using silver or an alloy containing silver can favorably increase the visible light reflectance of the conductive layer 151 and inhibit an increase in the electric resistance of the pixel electrode due to oxidation of the conductive layer 151_2. Here, as the alloy containing silver, an alloy of silver, palladium, and copper (Ag—Pd—Cu, also referred to as APC) can be used, for example. When the conductive layer 151_3 is formed using silver or an alloy containing silver and the conductive layer 151_2 is formed using aluminum, the visible light reflectance of the conductive layer 151_3 can be higher than that of the conductive layer 1512. Here, the conductive layer 151_2 may be formed using silver or an alloy containing silver. The conductive layer 151_1 may be formed using silver or an alloy containing silver.
Meanwhile, a film formed using titanium has better processability in etching than a film formed using silver. Thus, use of titanium for the conductive layer 151_3 can facilitate formation of the conductive layer 151_3. Note that a film formed using aluminum also has better processability in etching than a film formed using silver.
The conductive layer 151 having a stacked-layer structure of a plurality of layers as described above can improve the characteristics of the light-emitting apparatus. For example, the light-emitting apparatus 1000 can have high light extraction efficiency and high reliability.
Here, in the case where the light-emitting device 130 has a microcavity structure, use of silver or an alloy containing silver, i.e., a material with high visible light reflectance, for the conductive layer 151_3 can favorably increase the light extraction efficiency of the light-emitting apparatus 1000.
Depending on the selected material or the processing method of the conductive layer 151, the side surface of the conductive layer 151_2 is positioned inward from the side surfaces of the conductive layer 151_1 and the conductive layer 151_3 and a protruding portion might be formed as illustrated in
Thus, an insulating layer 156 is preferably provided as illustrated in
Although
The insulating layer 156 preferably has a curved surface as illustrated in
Note that one embodiment of the present invention is not limited thereto.
A conductive layer 152_1 has higher adhesion to a conductive layer 152_2 than the insulating layer 175 does, for example. For the conductive layer 152_1, an oxide containing one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon, for example, can be used. For example, it is preferable to use a conductive oxide containing one or more of indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide containing gallium, titanium oxide, indium titanium oxide, zinc titanate, aluminum zinc oxide, indium zinc oxide containing gallium, indium zinc oxide containing aluminum, indium tin oxide containing silicon, indium zinc oxide containing silicon, and the like. Accordingly, peeling of the conductive layer 152_2 can be inhibited. The conductive layer 152_2 is not in contact with the insulating layer 175.
The conductive layer 152_2 is a layer whose visible light reflectance (e.g., reflectance with respect to light with a predetermined wavelength longer than or equal to 400 nm and shorter than 750 nm) is higher than that of the conductive layers 151, 152_1, and 152_3. The visible light reflectance of the conductive layer 152_2 can be, for example, higher than or equal to 70% and lower than or equal to 100%, and is preferably higher than or equal to 80% and lower than or equal to 100%, further preferably higher than or equal to 90% and lower than or equal to 100%. For the conductive layer 152_2, silver or an alloy containing silver can be used, for example. An example of the alloy containing silver is an alloy of silver, palladium, and copper (APC). In the above manner, the light-emitting apparatus 1000 can have high light extraction efficiency. Note that a metal other than silver may be used for the conductive layer 152_2.
When the conductive layers 151 and 152 serve as the anode, a layer having a high work function is preferably used as the conductive layer 1523. The conductive layer 152_3 has a higher work function than the conductive layer 152_2, for example. For the conductive layer 1523, a material similar to the material usable for the conductive layer 152_1 can be used, for example. For example, the conductive layers 152_1 and 152_3 can be formed using the same kind of material.
When the conductive layers 151 and 152 serve as the cathode, a layer having a low work function is preferably used as the conductive layer 1523. The conductive layer 152_3 has a lower work function than the conductive layer 1522, for example.
The conductive layer 152_3 is preferably a layer having high visible light transmittance (e.g., transmittance with respect to light with a predetermined wavelength longer than or equal to 400 nm and shorter than 750 nm). For example, the visible light transmittance of the conductive layer 152_3 is preferably higher than that of the conductive layers 151 and 152_2. The visible light transmittance of the conductive layer 152_3 can be, for example, higher than or equal to 60% and lower than or equal to 100%, and is preferably higher than or equal to 70% and lower than or equal to 100%, further preferably higher than or equal to 80% and lower than or equal to 100%. Accordingly, the amount of light absorbed by the conductive layer 152_3 among light emitted from the organic compound layer 103 can be reduced. As described above, the conductive layer 152_2 under the conductive layer 152_3 can be a layer having high visible light reflectance. Thus, the light-emitting apparatus 1000 can have high light extraction efficiency.
Next, an example method of fabricating the light-emitting apparatus 1000 having the structure illustrated in
Thin films included in the light-emitting apparatus (e.g., insulating films, semiconductor films, and conductive films) can be formed by a sputtering method, a chemical vapor deposition (CVD) method, a vacuum evaporation method, a pulsed laser deposition (PLD) method, an ALD method, or the like. Examples of a CVD method include a plasma-enhanced CVD (PECVD) method and a thermal CVD method. An example of a thermal CVD method is a metal organic CVD (MOCVD) method.
Thin films included in the light-emitting apparatus (e.g., insulating films, semiconductor films, and conductive films) can also be formed by a wet process such as spin coating, dipping, spray coating, ink-jetting, dispensing, screen printing, offset printing, doctor blade coating, slit coating, roll coating, curtain coating, or knife coating.
Specifically, for fabrication of the light-emitting device, a vacuum process such as an evaporation method and a solution process such as a spin coating method or an ink-jet method can be used. Examples of an evaporation method include physical vapor deposition methods (PVD methods) such as a sputtering method, an ion plating method, an ion beam evaporation method, a molecular beam evaporation method, and a vacuum evaporation method, and a chemical vapor deposition method (CVD method). Specifically, the functional layers (e.g., the hole-injection layer, the hole-transport layer, the hole-blocking layer, the light-emitting layer, the electron-blocking layer, the electron-transport layer, and the electron-injection layer) included in the organic compound layer can be formed by an evaporation method (e.g., a vacuum evaporation method), a coating method (e.g., a dip coating method, a die coating method, a bar coating method, a spin coating method, or a spray coating method), a printing method (e.g., ink-jetting, screen printing (stencil), offset printing (planography), flexography (relief printing), gravure printing, or micro-contact printing), or the like.
Thin films included in the light-emitting apparatus can be processed by a photolithography method, for example. Alternatively, a nanoimprinting method, a sandblasting method, a lift-off method, or the like may be used to process thin films. Alternatively, island-shaped thin films may be directly formed by a film formation method using a shielding mask such as a metal mask.
There are two typical examples of photolithography methods. In one of the methods, a resist mask is formed over a thin film that is to be processed, the thin film is processed by etching, for example, and then the resist mask is removed. In the other method, a photosensitive thin film is formed and then processed into a desired shape by light exposure and development.
For etching of thin films, a dry etching method, a wet etching method, a sandblast method, or the like can be used.
First, as illustrated in
As the substrate, a substrate that has heat resistance high enough to withstand at least heat treatment performed later can be used. When an insulating substrate is used, it is possible to use a glass substrate, a quartz substrate, a sapphire substrate, a ceramic substrate, an organic resin substrate, or the like. Alternatively, it is possible to use a semiconductor substrate such as a single crystal semiconductor substrate or a polycrystalline semiconductor substrate of silicon, silicon carbide, or the like, a compound semiconductor substrate of silicon germanium or the like, or an SOI substrate.
Next, as illustrated in
Next, as illustrated in
Subsequently, a resist mask 191 is formed over the conductive film 151f, for example, as illustrated in
Subsequently, as illustrated in
Next, the resist mask 191 is removed as illustrated in
Then, as illustrated in
For the insulating film 156f, an inorganic material can be used. As the insulating film 156f, an inorganic insulating film such as an oxide insulating film, a nitride insulating film, an oxynitride insulating film, or a nitride oxide insulating film can be used, for example. For example, an oxide insulating film containing silicon, a nitride insulating film containing silicon, an oxynitride insulating film containing silicon, a nitride oxide insulating film containing silicon, or the like can be used as the insulating film 156f. For the insulating film 156f, silicon oxynitride can be used, for example.
Subsequently, as illustrated in
Then, as illustrated in
The conductive film 152f can be formed by a sputtering method or a vacuum evaporation method, for example. The conductive film 152f can be formed by an ALD method. A conductive oxide can be used for the conductive film 152f, for example. The conductive film 152f can be a stack of a film formed using a metal material and a film formed thereover using a conductive oxide. For example, the conductive film 152f can be a stack of a film formed using titanium, silver, or an alloy containing silver and a film formed thereover using a conductive oxide.
Then, as illustrated in
Next, hydrophobization treatment is preferably performed on the conductive layer 152. The hydrophobization treatment can change the hydrophilic properties of the subject surface to hydrophobic properties or increase the hydrophobic properties of the subject surface. The hydrophobization treatment for the conductive layer 152 can increase the adhesion between the conductive layer 152 and the organic compound layer 103 formed in a later step and inhibit film peeling. Note that the hydrophobization treatment is not necessarily performed.
Next, as illustrated in
Note that in the present invention, the organic compound film 103Bf includes a plurality of organic compound layers including at least one light-emitting layer. The structure of the light-emitting device 130 described in Embodiment 1 can be referred to for the specific structure. The plurality of organic compound layers including at least one light-emitting layer may be stacked with an intermediate layer positioned therebetween.
As illustrated in
The organic compound film 103Bf can be formed by an evaporation method, specifically a vacuum evaporation method, for example. The organic compound film 103Bf may be formed by a transfer method, a printing method, an ink-jet method, a coating method, or the like.
Next, as illustrated in
The sacrificial film 158Bf and the mask film 159Bf can be formed by a sputtering method, an ALD method (including a thermal ALD method and a PEALD method), a CVD method, or a vacuum evaporation method, for example. Alternatively, the sacrificial film 158Bf and the mask film 159Bf may be formed by the above-described wet process.
The sacrificial film 158Bf and the mask film 159Bf are formed at a temperature lower than the upper temperature limit of the organic compound film 103Bf. The typical substrate temperatures in formation of the sacrificial film 158Bf and the mask film 159Bf are each lower than or equal to 200° C., preferably lower than or equal to 150° C., further preferably lower than or equal to 120° C., still further preferably lower than or equal to 100° C., yet still further preferably lower than or equal to 80° C.
Although this embodiment shows an example where a mask film having a two-layer structure of the sacrificial film 158Bf and the mask film 159Bf is formed, a mask film may have a single-layer structure or a stacked-layer structure of three or more layers.
Providing the sacrificial layer over the organic compound film 103Bf can reduce damage to the organic compound film 103Bf in the fabrication process of the light-emitting apparatus, resulting in an increase in reliability of the light-emitting device.
As the sacrificial film 158Bf, a film that is highly resistant to the process conditions for the organic compound film 103Bf, specifically, a film having high etching selectivity with respect to the organic compound film 103Bf is used. For the mask film 159Bf, a film having high etching selectivity with respect to the sacrificial film 158Bf is used.
The sacrificial film 158Bf and the mask film 159Bf are preferably films that can be removed by a wet etching method. The use of a wet etching method can reduce damage to the organic compound film 103Bf in processing of the sacrificial film 158Bf and the mask film 159Bf, as compared to the case of using a dry etching method.
In the case where a wet etching method is used, a water-soluble chemical solution is preferably used, in which case the organic compound is unlikely to elute. In particular, an acidic chemical solution can be used. As an acidic chemical solution, a chemical solution containing one of phosphoric acid, hydrofluoric acid, nitric acid, acetic acid, oxalic acid, sulfuric acid, and the like or a mixed chemical solution (also referred to as a mixed acid) that contains two or more of these acids is preferably used. An alkaline chemical solution can also be used. As an alkaline chemical solution, quaternary ammonium such as tetramethylammonium hydroxide or tetraethyl tetraethylammonium hydroxide can be used.
As each of the sacrificial film 158Bf and the mask film 159Bf, one or more of a metal film, an alloy film, a metal oxide film, a semiconductor film, an organic insulating film, and an inorganic insulating film, for example, can be used.
When a film containing a material having a property of blocking ultraviolet rays is used as each of the sacrificial film 158Bf and the mask film 159Bf, the organic compound layer can be inhibited from being irradiated with ultraviolet rays in a light exposure step, for example. When the organic compound layer is inhibited from being damaged by ultraviolet rays, the reliability of the light-emitting device can be improved.
Note that the same effect is obtained when a film containing a material having a property of blocking ultraviolet rays is used for an inorganic insulating film 125f described later.
For each of the sacrificial film 158Bf and the mask film 159Bf, it is possible to use a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, titanium, aluminum, yttrium, zirconium, or tantalum or an alloy material containing any of the metal materials, for example. It is particularly preferable to use a low-melting-point material such as aluminum or silver.
The sacrificial film 158Bf and the mask film 159Bf can each be formed using a metal oxide such as In—Ga—Zn oxide, indium oxide, In—Zn oxide, In—Sn oxide, indium titanium oxide (In—Ti oxide), indium tin zinc oxide (In—Sn—Zn oxide), indium titanium zinc oxide (In—Ti—Zn oxide), indium gallium tin zinc oxide (In—Ga—Sn—Zn oxide), or indium tin oxide containing silicon.
In place of gallium described above, an element M (M is one or more of aluminum, silicon, boron, yttrium, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium) may be used.
The sacrificial film 158Bf and the mask film 159Bf are preferably formed using a semiconductor material such as silicon or germanium, for example, for excellent compatibility with a semiconductor manufacturing process. An oxide or a nitride of the semiconductor material can be used. A non-metallic material such as carbon or a compound thereof can be used. A metal such as titanium, tantalum, tungsten, chromium, or aluminum or an alloy containing at least one of these metals can be used. Alternatively, an oxide containing the above-described metal, such as titanium oxide or chromium oxide, or a nitride such as titanium nitride, chromium nitride, or tantalum nitride can be used.
As each of the sacrificial film 158Bf and the mask film 159Bf, any of a variety of inorganic insulating films can be used. In particular, an oxide insulating film is preferable because its adhesion to the organic compound film 103Bf is higher than that of a nitride insulating film. For example, an inorganic insulating material such as aluminum oxide, hafnium oxide, or silicon oxide can be used for the sacrificial film 158Bf and the mask film 159Bf. As the sacrificial film 158Bf and the mask film 159Bf, aluminum oxide films can be formed by an ALD method, for example. An ALD method is preferably used, in which case damage to a base (in particular, the organic compound layer) can be reduced.
One or both of the sacrificial film 158Bf and the mask film 159Bf may be formed using an organic material. For example, as the organic material, a material that can be dissolved in a solvent chemically stable with respect to at least the uppermost film of the organic compound film 103Bf may be used. Specifically, a material that will be dissolved in water or an alcohol can be suitably used. In forming a film of such a material, it is preferable to apply the material dissolved in a solvent such as water or an alcohol by a wet process and then perform heat treatment for evaporating the solvent. At this time, the heat treatment is preferably performed in a reduced-pressure atmosphere, in which case the solvent can be removed at a low temperature in a short time and thermal damage to the organic compound film 103Bf can be reduced accordingly.
The sacrificial film 158Bf and the mask film 159Bf may be formed using an organic resin such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, an alcohol-soluble polyamide resin, or a fluorine resin like perfluoropolymer.
For example, an organic film (e.g., a PVA film) formed by an evaporation method or the above wet process can be used as the sacrificial film 158Bf, and an inorganic film (e.g., a silicon nitride film) formed by a sputtering method can be used as the mask film 159Bf.
Subsequently, a resist mask 190B is formed over the mask film 159Bf as illustrated in
The resist mask 190B may be formed using either a positive resist material or a negative resist material.
The resist mask 190B is provided at a position overlapping with the conductive layer 152B. The resist mask 190B is preferably provided also at a position overlapping with the conductive layer 152C. This can inhibit the conductive layer 152C from being damaged during the fabrication process of the light-emitting apparatus. Note that the resist mask 190B is not necessarily provided over the conductive layer 152C. The resist mask 190B is preferably provided to cover the area from the edge portion of the organic compound film 103Bf to the edge portion of the conductive layer 152C (the edge portion closer to the organic compound film 103Bf), as illustrated in the cross-sectional view along the line B1-B2 in
Next, as illustrated in
Each of the sacrificial film 158Bf and the mask film 159Bf can be processed by a wet etching method or a dry etching method. The sacrificial film 158Bf and the mask film 159Bf are preferably processed by wet etching.
The use of a wet etching method can reduce damage to the organic compound film 103Bf in processing of the sacrificial film 158Bf and the mask film 159Bf, as compared to the case of using a dry etching method. In the case of using a wet etching method, it is preferable to use a developer, an aqueous solution of tetramethylammonium hydroxide (TMAH), dilute hydrofluoric acid, oxalic acid, phosphoric acid, acetic acid, nitric acid, or a chemical solution containing a mixed solution of any of these acids, for example.
Since the organic compound film 103Bf is not exposed in the processing of the mask film 159Bf, the range of choice for a processing method for the mask film 159Bf is wider than that for the sacrificial film 158Bf. Specifically, even in the case where a gas containing oxygen is used as the etching gas in the processing of the mask film 159Bf, deterioration of the organic compound film 103Bf can be suppressed.
In the case where a wet etching method is employed, it is particularly preferable to use an acidic chemical solution. As an acidic chemical solution, a chemical solution containing one of phosphoric acid, hydrofluoric acid, nitric acid, acetic acid, oxalic acid, sulfuric acid, and the like or a mixed chemical solution (also referred to as a mixed acid) that contains two or more of these acids is preferably used.
In the case of using a dry etching method to process the sacrificial film 158Bf, deterioration of the organic compound film 103Bf can be suppressed by not using a gas containing oxygen as the etching gas. In the case of using a dry etching method, it is preferable to use a gas containing CF4, C4F8, SF6, CHF3, C12, H2O, BCl3, or a Group 18 element such as He, for example, as the etching gas.
The resist mask 190B can be removed by a method similar to that for the resist mask 191. At this time, the sacrificial film 158Bf is positioned on the outermost surface, and the organic compound film 103Bf is not exposed; thus, the organic compound film 103Bf can be inhibited from being damaged in the step of removing the resist mask 190B. In addition, the range of choice of the method of removing the resist mask 190B can be widened.
Next, as illustrated in
Accordingly, as illustrated in
The organic compound film 103Bf can be processed by dry etching or wet etching. In the case where the processing is performed by a dry etching method, for example, an etching gas containing oxygen can be used. When the etching gas contains oxygen, the etching rate can be increased. Thus, the etching can be performed under a low-power condition while an adequately high etching rate is maintained. Accordingly, damage to the organic compound film 103Bf can be inhibited. Furthermore, a defect such as attachment of a reaction product generated during the etching can be inhibited.
An etching gas that does not contain oxygen may be used. In that case, deterioration of the organic compound film 103Bf can be inhibited, for example.
As described above, in one embodiment of the present invention, the mask layer 159B is formed in the following manner: the resist mask 190B is formed over the mask film 159Bf and part of the mask film 159Bf is removed using the resist mask 190B. After that, part of the organic compound film 103Bf is removed using the mask layer 159B as a hard mask, so that the organic compound layer 103B is formed. In other words, the organic compound layer 103B is formed by processing the organic compound film 103Bf by a photolithography method. Note that part of the organic compound film 103Bf may be removed using the resist mask 190B. Then, the resist mask 190B may be removed.
Here, hydrophobization treatment for the conductive layer 152G may be performed as necessary. At the time of processing the organic compound film 103Bf, the properties of a surface of the conductive layer 152G change to hydrophilic properties in some cases, for example. The hydrophobization treatment for the conductive layer 152G, for example, can increase the adhesion between the conductive layer 152G and a layer to be formed in a later step (which is the organic compound layer 103G here) and inhibit film peeling.
Next, as illustrated in
The organic compound film 103Gf can be formed by a method similar to that for forming the organic compound film 103Bf. The organic compound film 103Gf can have a structure similar to that of the organic compound film 103Bf.
Then, as illustrated in
The resist mask 190G is provided at a position overlapping with the conductive layer 152G.
Subsequently, as illustrated in
Accordingly, as illustrated in
Hydrophobization treatment for the conductive layer 152R may be performed, for example.
Next, as illustrated in
The organic compound film 103Rf can be formed by a method similar to that for forming the organic compound film 103Gf. The organic compound film 103Rf can have a structure similar to that of the organic compound film 103Gf.
Subsequently, as illustrated in
Note that the side surfaces of the organic compound layers 103B, 103G, and 103R are preferably perpendicular or substantially perpendicular to their formation surfaces. For example, the angle between the formation surfaces and these side surfaces is preferably greater than or equal to 60° and less than or equal to 90°.
The distance between two adjacent layers among the organic compound layers 103B, 103G, and 103R, which are formed by a photolithography method as described above, can be reduced to less than or equal to 8 μm, less than or equal to 5 μm, less than or equal to 3 μm, less than or equal to 2 μm, or less than or equal to 1 μm. Here, the distance can be determined, for example, by the distance between opposite edge portions of two adjacent layers among the organic compound layers 103B, 103G, and 103R. Reducing the distance between the island-shaped organic compound layers can provide a light-emitting apparatus having high resolution and a high aperture ratio. In addition, the distance between the first electrodes of adjacent light-emitting devices can also be shortened to be, for example, less than or equal to 10 μm, less than or equal to 8 μm, less than or equal to 5 μm, less than or equal to 3 μm, or less than or equal to 2 μm. Note that the distance between the first electrodes of adjacent light-emitting devices is preferably greater than or equal to 2 μm and less than or equal to 5 μm.
Next, as illustrated in
This embodiment describes an example where the mask layers 159B, 159G, and 159R are removed; however, the mask layers 159B, 159G, and 159R are not necessarily removed. For example, in the case where the mask layers 159B, 159G, and 159R contain the above-described material having a property of blocking ultraviolet rays, the procedure preferably proceeds to the next step without removing the mask layers 159B, 159G, and 159R, in which case the organic compound layers can be protected from light irradiation (including lighting).
The step of removing the mask layers can be performed by a method similar to that for the step of processing the mask layers. Specifically, by using a wet etching method, damage applied to the organic compound layers 103B, 103G, and 103R at the time of removing the mask layers can be reduced as compared to the case of using a dry etching method.
The mask layers may be removed by being dissolved in a solvent such as water or an alcohol. Examples of an alcohol include ethyl alcohol, methyl alcohol, isopropyl alcohol (IPA), and glycerin.
After the mask layers are removed, drying treatment may be performed in order to remove water included in the organic compound layers 103B, 103G, and 103R and water adsorbed on surfaces of the organic compound layers 103B, 103G, and 103R. For example, heat treatment in an inert atmosphere or a reduced-pressure atmosphere can be performed. The heat treatment can be performed at a substrate temperature higher than or equal to 50° C. and lower than or equal to 200° C., preferably higher than or equal to 60° C. and lower than or equal to 150° C., further preferably higher than or equal to 70° C. and lower than or equal to 120° C. The heat treatment is preferably performed in a reduced-pressure atmosphere, in which case drying at a lower temperature is possible.
Next, as illustrated in
As described later, an insulating film to be the insulating layer 127 is formed in contact with the top surface of the inorganic insulating film 125f. Thus, the top surface of the inorganic insulating film 125f preferably has a high affinity for the material used for the insulating film to be the insulating layer 127 (e.g., a photosensitive resin composition containing an acrylic resin). To improve the affinity, surface treatment may be performed on the top surface of the inorganic insulating film 125f. Specifically, a surface of the inorganic insulating film 125f is preferably made hydrophobic (or its hydrophobic property is preferably improved). For example, it is preferable to perform the treatment using a silylation agent such as hexamethyldisilazane (HMDS). By making the top surface of the inorganic insulating film 125f hydrophobic in such a manner, an insulating film 127f can be formed with favorable adhesion.
Then, as illustrated in
The inorganic insulating film 125f and the insulating film 127f are preferably formed by a formation method by which the organic compound layers 103B, 103G, and 103R are less damaged. The inorganic insulating film 125f, which is formed in contact with the side surfaces of the organic compound layers 103B, 103G, and 103R, is particularly preferably formed by a formation method that causes less damage to the organic compound layers 103B, 103G, and 103R than the method of forming the insulating film 127f.
Each of the inorganic insulating film 125f and the insulating film 127f is formed at a temperature lower than the upper temperature limit of the organic compound layers 103B, 103G, and 103R. When the inorganic insulating film 125f is formed at a high substrate temperature, the formed inorganic insulating film 125f, even with a small thickness, can have a low impurity concentration and a high barrier property against at least one of water and oxygen.
The substrate temperature at the time of forming the inorganic insulating film 125f and the insulating film 127f is preferably higher than or equal to 60° C., higher than or equal to 80° C., higher than or equal to 100° C., or higher than or equal to 120° C. and lower than or equal to 200° C., lower than or equal to 180° C., lower than or equal to 160° C., lower than or equal to 150° C., or lower than or equal to 140° C.
As the inorganic insulating film 125f, an insulating film having a thickness greater than or equal to 3 nm, greater than or equal to 5 nm, or greater than or equal to 10 nm and less than or equal to 200 nm, less than or equal to 150 nm, less than or equal to 100 nm, or less than or equal to 50 nm is preferably formed in the above-described range of the substrate temperature.
The inorganic insulating film 125f is preferably formed by an ALD method, for example. An ALD method is preferably used, in which case damage due to film formation is reduced and a film with good coverage can be formed. As the inorganic insulating film 125f, an aluminum oxide film is preferably formed by an ALD method, for example.
Alternatively, the inorganic insulating film 125f may be formed by a sputtering method, a CVD method, or a PECVD method, each of which has a higher deposition rate than an ALD method. In that case, a highly reliable light-emitting apparatus can be fabricated with high productivity.
The insulating film 127f is preferably formed by the aforementioned wet process. The insulating film 127f is preferably formed by spin coating using a photosensitive material, for example, and specifically preferably formed using a photosensitive resin composition containing an acrylic resin.
The insulating film 127f is preferably formed using a resin composition containing a polymer, an acid-generating agent, and a solvent, for example. The polymer is formed using one or more kinds of monomers and has a structure where one or more kinds of structural units (also referred to as building blocks) are repeated regularly or irregularly. As the acid-generating agent, one or both of a compound that generates an acid by light irradiation and a compound that generates an acid by heating can be used. The resin composition may also include one or more of a photosensitizing agent, a sensitizer, a catalyst, an adhesive aid, a surface-active agent, and an antioxidant.
Heat treatment (also referred to as prebaking) is preferably performed after the insulating film 127f is formed. The heat treatment is performed at a temperature lower than the upper temperature limit of the organic compound layers 103B, 103G, and 103R. The substrate temperature in the heat treatment is preferably higher than or equal to 50° C. and lower than or equal to 200° C., further preferably higher than or equal to 60° C. and lower than or equal to 150° C., still further preferably higher than or equal to 70° C. and lower than or equal to 120° C. Accordingly, the solvent contained in the insulating film 127f can be removed.
Then, part of the insulating film 127f is exposed to visible light or ultraviolet rays. Here, when a positive photosensitive resin composition containing an acrylic resin is used for the insulating film 127f, a region where the insulating layer 127 is not formed in a later step is irradiated with visible light or ultraviolet rays. The insulating layer 127 is formed in regions that are sandwiched between any two of the conductive layers 152B, 152G, and 152R and around the conductive layer 152C. Thus, the top surfaces of the conductive layers 152B, 152G, 152R, and 152C are irradiated with visible light or ultraviolet rays. Note that when a negative photosensitive material is used for the insulating film 127f, the region where the insulating layer 127 is to be formed is irradiated with visible light or ultraviolet rays.
The width of the insulating layer 127 formed later can be controlled in accordance with the exposed region of the insulating film 127f. In this embodiment, processing is performed such that the insulating layer 127 includes a portion overlapping with the top surface of the conductive layer 151.
Here, when a barrier insulating layer against oxygen (e.g., an aluminum oxide film) is provided as one or both of the sacrificial layer 158 (the sacrificial layers 158B, 158G, and 158R) and the inorganic insulating film 125f, diffusion of oxygen to the organic compound layers 103B, 103G, and 103R can be suppressed. When the organic compound layer is irradiated with light (visible light or ultraviolet rays), the organic compound contained in the organic compound layer is brought into an excited state and a reaction between the organic compound and oxygen in the atmosphere is promoted in some cases. Specifically, when the organic compound layer is irradiated with light (visible light or ultraviolet rays) in an atmosphere containing oxygen, oxygen might be bonded to the organic compound contained in the organic compound layer. By providing the sacrificial layer 158 and the inorganic insulating film 125f over the island-shaped organic compound layer, bonding of oxygen in the atmosphere to the organic compound contained in the organic compound layer can be inhibited.
Next, as illustrated in
Next, as illustrated in
In other words, the sacrificial layers 158B, 158G, and 158R are not removed completely by the first etching treatment, and the etching treatment is stopped when the thicknesses of the sacrificial layers 158B, 158G, and 158R are reduced. The sacrificial layers 158B, 158G, and 158R remain over the corresponding organic compound layers 103B, 103G, and 103R in this manner, whereby the organic compound layers 103B, 103G, and 103R can be prevented from being damaged by treatment in a later step.
The first etching treatment can be performed by dry etching or wet etching. Note that the inorganic insulating film 125f is preferably formed using a material similar to that of the sacrificial layers 158B, 158G, and 158R, in which case the processing of the inorganic insulating film 125f and thinning of the exposed part of the sacrificial layer 158 can be concurrently performed by the first etching treatment.
By etching using the insulating layer 127a with a tapered side surface as a mask, the side surface of the inorganic insulating layer 125 and upper edge portions of the side surfaces of the sacrificial layers 158B, 158G, and 158R can be made to have a tapered shape relatively easily.
In the case where the first etching treatment is performed by dry etching, for example, a chlorine-based gas can be used. As the chlorine-based gas, one of C12, BCl3, SiCl4, CCl4, and the like or a mixture of two or more of them can be used. Moreover, one of an oxygen gas, a hydrogen gas, a helium gas, an argon gas, and the like or a mixture of two or more of them can be added as appropriate to the chlorine-based gas. By the dry etching, the thin regions of the sacrificial layers 158B, 158G, and 158R can be formed with favorable in-plane uniformity.
The first etching treatment can be performed by wet etching, for example. The use of wet etching can reduce damage to the organic compound layers 103B, 103G, and 103R, as compared to the case of using dry etching.
The wet etching is preferably performed using an acidic chemical solution. As an acidic chemical solution, a chemical solution containing one of phosphoric acid, hydrofluoric acid, nitric acid, acetic acid, oxalic acid, sulfuric acid, and the like or a mixed chemical solution (also referred to as a mixed acid) that contains two or more of these acids is preferably used.
The wet etching can be performed using an alkaline solution. For instance, TMAH, which is an alkaline solution, can be used for the wet etching of an aluminum oxide film. In that case, puddle wet etching can be performed.
Then, heat treatment (also referred to as post-baking) is performed. The heat treatment can change the insulating layer 127a into the insulating layer 127 having a tapered side surface (
The heat treatment can improve adhesion between the insulating layer 127 and the inorganic insulating layer 125 and increase corrosion resistance of the insulating layer 127. Furthermore, owing to the change in shape of the insulating layer 127a, an edge portion of the inorganic insulating layer 125 can be covered with the insulating layer 127.
When the sacrificial layers 158B, 158G, and 158R are not completely removed by the first etching treatment and the thinned sacrificial layers 158B, 158G, and 158R are left, the organic compound layers 103B, 103G, and 103R can be prevented from being damaged and deteriorating in the heat treatment. This increases the reliability of the light-emitting device.
Next, as illustrated in
The second etching treatment is performed by wet etching. The use of wet etching can reduce damage to the organic compound layers 103B, 103G, and 103R, as compared to the case of using dry etching. The wet etching can be performed using an acidic chemical solution or an alkaline solution as in the first etching treatment.
Heat treatment may be performed after the organic compound layers 103B, 103G, and 103R are partly exposed. By the heat treatment, water included in the organic compound layer and water adsorbed on a surface of the organic compound layer, for example, can be removed. The shape of the insulating layer 127 may be changed by the heat treatment. Specifically, the insulating layer 127 may be widened to cover at least one of the edge portion of the inorganic insulating layer 125, the edge portions of the sacrificial layers 158B, 158G, and 158R, and the top surfaces of the organic compound layers 103B, 103G, and 103R.
The insulating layer 127 may cover the entire edge portion of the sacrificial layer 158G. For example, an edge portion of the insulating layer 127 may droop to cover the edge portion of the sacrificial layer 158G. For another example, the edge portion of the insulating layer 127 may be in contact with the top surface of at least one of the organic compound layers 103B, 103G, and 103R.
Next, as illustrated in
Next, as illustrated in
Then, the substrate 120 is bonded over the protective layer 131 using the resin layer 122, so that the light-emitting apparatus can be fabricated. In the method of fabricating the light-emitting apparatus of one embodiment of the present invention, the insulating layer 156 is formed to include a region overlapping with the side surface of the conductive layer 151 and the conductive layer 152 is formed to cover the conductive layer 151 and the insulating layer 156 as described above. This can increase the yield of the light-emitting apparatus and inhibit generation of defects.
As described above, in the method of fabricating the light-emitting apparatus of one embodiment of the present invention, the island-shaped organic compound layers 103B, 103G, and 103R are formed not by using a fine metal mask but by processing a film formed on the entire surface; thus, the island-shaped layers can be formed to have a uniform thickness. Consequently, a high-resolution light-emitting apparatus or a light-emitting apparatus with a high aperture ratio can be obtained. Furthermore, even when the resolution or the aperture ratio is high and the distance between the subpixels is extremely short, the organic compound layers 103B, 103G, and 103R can be inhibited from being in contact with each other in the adjacent subpixels. As a result, generation of a leakage current between the subpixels can be inhibited. This can prevent crosstalk, so that a light-emitting apparatus with extremely high contrast can be obtained. Moreover, even a light-emitting apparatus that includes tandem light-emitting devices formed by a photolithography method can have favorable characteristics.
In this embodiment, the light-emitting apparatus of one embodiment of the present invention will be described with reference to
In this embodiment, pixel layouts different from that in
In this embodiment, the top surface shapes of the subpixels shown in the diagrams correspond to top surface shapes of light-emitting regions.
Examples of a top surface shape of the subpixel include polygons such as a triangle, a tetragon (including a rectangle and a square), and a pentagon; these polygons with rounded corners; an ellipse; and a circle.
The circuit constituting the subpixel is not necessarily placed within the dimensions of the subpixel illustrated in the diagrams and may be placed outside the subpixel.
The pixel 178 illustrated in
The pixel 178 illustrated in
Pixels 124a and 124b illustrated in
The pixels 124a and 124b illustrated in
In
In the pixels illustrated in
In a photolithography method, as a pattern to be formed by processing becomes finer, the influence of light diffraction becomes more difficult to ignore; therefore, the fidelity in transferring a photomask pattern by light exposure is degraded, and it becomes difficult to process a resist mask into a desired shape. Thus, a pattern with rounded corners is likely to be formed even with a rectangular photomask pattern. Consequently, the top surface of a subpixel may have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like.
Furthermore, in the method of fabricating the light-emitting apparatus of one embodiment of the present invention, the organic compound layer is processed into an island shape with the use of a resist mask. A resist film formed over the organic compound layer needs to be cured at a temperature lower than the upper temperature limit of the organic compound layer. Therefore, the resist film is insufficiently cured in some cases depending on the upper temperature limit of the material of the organic compound layer and the curing temperature of the resist material. An insufficiently cured resist film may have a shape different from a desired shape by processing. As a result, the top surface of the organic compound layer may have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like. For example, when a resist mask with a square top surface is intended to be formed, a resist mask with a circular top surface may be formed, and the top surface of the organic compound layer may be circular.
To obtain a desired top surface shape of the organic compound layer, a technique of correcting a mask pattern in advance so that a transferred pattern agrees with a design pattern (an optical proximity correction (OPC) technique) may be used. Specifically, with the OPC technique, a pattern for correction is added to a corner portion of a figure on a mask pattern, for example.
As illustrated in
The pixels 178 illustrated in
The pixels 178 illustrated in
The pixel 178 illustrated in
The pixel 178 illustrated in
In the pixel 178 illustrated in
The pixel 178 illustrated in
In the pixel 178 illustrated in
The pixel 178 illustrated in each of
As described above, the pixel composed of the subpixels each including the light-emitting device can employ any of a variety of layouts in the light-emitting apparatus of one embodiment of the present invention.
This embodiment can be combined as appropriate with the other embodiments or examples. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.
In this embodiment, a light-emitting apparatus of one embodiment of the present invention will be described.
The light-emitting apparatus in this embodiment can be a high-resolution light-emitting apparatus. Thus, the light-emitting apparatus in this embodiment can be used for display portions of information terminals (wearable devices) such as watch-type and bracelet-type information terminals and display portions of wearable devices capable of being worn on a head, such as a VR device like a head mounted display (HMD) and a glasses-type AR device.
The light-emitting apparatus in this embodiment can be a high-definition light-emitting apparatus or a large-sized light-emitting apparatus. Accordingly, the light-emitting apparatus in this embodiment can be used for display portions of a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, and an audio reproducing device, in addition to display portions of electronic appliances with a relatively large screen, such as a television device, desktop and notebook personal computers, a monitor of a computer and the like, digital signage, and a large game machine such as a pachinko machine.
The display module 280 includes a substrate 291 and a substrate 292. The display module 280 includes a display portion 281. The display portion 281 is a region of the display module 280 where an image is displayed, and is a region where light emitted from pixels provided in a pixel portion 284 described later can be seen.
The pixel portion 284 includes a plurality of pixels 284a arranged periodically. An enlarged view of one pixel 284a is illustrated on the right side in
The pixel circuit portion 283 includes a plurality of pixel circuits 283a arranged periodically.
One pixel circuit 283a is a circuit that controls driving of a plurality of elements included in one pixel 284a. One pixel circuit 283a can be provided with three circuits each of which controls light emission of one light-emitting device. For example, the pixel circuit 283a can include at least one selection transistor, one current control transistor (driving transistor), and a capacitor for one light-emitting device. A gate signal is input to a gate of the selection transistor, and a video signal is input to a source or a drain of the selection transistor. With such a structure, an active-matrix light-emitting apparatus is obtained.
The circuit portion 282 includes a circuit for driving the pixel circuits 283a in the pixel circuit portion 283. For example, the circuit portion 282 preferably includes one or both of a gate line driver circuit and a source line driver circuit. The circuit portion 282 may also include at least one of an arithmetic circuit, a memory circuit, a power supply circuit, and the like.
The FPC 290 functions as a wiring for supplying a video signal, a power supply potential, or the like to the circuit portion 282 from the outside. An IC may be mounted on the FPC 290.
The display module 280 can have a structure in which one or both of the pixel circuit portion 283 and the circuit portion 282 are stacked below the pixel portion 284; hence, the aperture ratio (effective display area ratio) of the display portion 281 can be significantly high. For example, the aperture ratio of the display portion 281 can be higher than or equal to 40% and lower than 100%, preferably higher than or equal to 50% and lower than or equal to 95%, further preferably higher than or equal to 60% and lower than or equal to 95%. Furthermore, the pixels 284a can be arranged extremely densely and thus the display portion 281 can have significantly high resolution. For example, the pixels 284a are preferably arranged in the display portion 281 with a resolution higher than or equal to 2,000 ppi, further preferably higher than or equal to 3,000 ppi, still further preferably higher than or equal to 5,000 ppi, yet still further preferably higher than or equal to 6,000 ppi, and lower than or equal to 20,000 ppi or lower than or equal to 30,000 ppi.
Such a display module 280 has extremely high resolution, and thus can be suitably used for a VR device such as an HMD or a glasses-type AR device. For example, even in the case of a structure in which the display portion of the display module 280 is seen through a lens, pixels of the extremely-high-resolution display portion 281 included in the display module 280 are prevented from being recognized when the display portion is enlarged by the lens, so that display providing a high sense of immersion can be performed. Without being limited thereto, the display module 280 can be suitably used for electronic appliances including a relatively small display portion. For example, the display module 280 can be favorably used in a display portion of a wearable electronic appliance, such as a wrist watch.
The light-emitting apparatus 100A illustrated in
The substrate 301 corresponds to the substrate 291 in
An element isolation layer 315 is provided between two adjacent transistors 310 to be embedded in the substrate 301.
An insulating layer 261 is provided to cover the transistor 310, and the capacitor 240 is provided over the insulating layer 261.
The capacitor 240 includes a conductive layer 241, a conductive layer 245, and an insulating layer 243 between the conductive layers 241 and 245. The conductive layer 241 functions as one electrode of the capacitor 240, the conductive layer 245 functions as the other electrode of the capacitor 240, and the insulating layer 243 functions as a dielectric of the capacitor 240.
The conductive layer 241 is provided over the insulating layer 261 and is embedded in an insulating layer 254. The conductive layer 241 is electrically connected to one of the source and the drain of the transistor 310 through a plug 271 embedded in the insulating layer 261. The insulating layer 243 is provided to cover the conductive layer 241. The conductive layer 245 is provided in a region overlapping with the conductive layer 241 with the insulating layer 243 therebetween.
An insulating layer 255 is provided to cover the capacitor 240. The insulating layer 174 is provided over the insulating layer 255. The insulating layer 175 is provided over the insulating layer 174. The light-emitting devices 130R, 130G, and 130B are provided over the insulating layer 175.
The insulating layer 156R is provided to include a region overlapping with the side surface of the conductive layer 151R of the light-emitting device 130R. The insulating layer 156G is provided to include a region overlapping with the side surface of the conductive layer 151G of the light-emitting device 130G. The insulating layer 156B is provided to include a region overlapping with the side surface of the conductive layer 151B of the light-emitting device 130B. The conductive layer 152R is provided to cover the conductive layer 151R and the insulating layer 156R. The conductive layer 152G is provided to cover the conductive layer 151G and the insulating layer 156G. The conductive layer 152B is provided to cover the conductive layer 151B and the insulating layer 156B. The sacrificial layer 158R is positioned over the organic compound layer 103R of the light-emitting device 130R. The sacrificial layer 158G is positioned over the organic compound layer 103G of the light-emitting device 130G. The sacrificial layer 158B is positioned over the organic compound layer 103B of the light-emitting device 130B.
Each of the conductive layers 151R, 151G, and 151B is electrically connected to one of the source and the drain of the corresponding transistor 310 through a plug 256 embedded in the insulating layers 243, 255, 174, and 175, the conductive layer 241 embedded in the insulating layer 254, and the plug 271 embedded in the insulating layer 261. The top surface of the insulating layer 175 and the top surface of the plug 256 are level with or substantially level with each other. Any of a variety of conductive materials can be used for the plugs.
The protective layer 131 is provided over the light-emitting devices 130R, 130G, and 130B. The substrate 120 is bonded to the protective layer 131 with the resin layer 122. Embodiment 2 can be referred to for the details of the light-emitting device 130 and the components thereover up to the substrate 120. The substrate 120 corresponds to the substrate 292 in
In the light-emitting apparatus 100B, a substrate 352 and a substrate 351 are bonded to each other. In
The light-emitting apparatus 100B includes the pixel portion 177, the connection portion 140, a circuit 356, a wiring 355, and the like.
The connection portion 140 is provided outside the pixel portion 177. The connection portion 140 can be provided along one side or a plurality of sides of the pixel portion 177. The number of connection portions 140 may be one or more.
As the circuit 356, a scan line driver circuit can be used, for example.
The wiring 355 has a function of supplying a signal and power to the pixel portion 177 and the circuit 356. The signal and power are input to the wiring 355 from the outside through the FPC 353 or from the IC 354.
The light-emitting apparatus 100B illustrated in
The stacked-layer structure of each of the light-emitting devices 130R, 130G, and 130B is the same as any of the stacked-layer structures illustrated in
The light-emitting device 130R includes a conductive layer 224R, the conductive layer 151R over the conductive layer 224R, and the conductive layer 152R over the conductive layer 151R. The light-emitting device 130G includes a conductive layer 224G, the conductive layer 151G over the conductive layer 224G, and the conductive layer 152G over the conductive layer 151G. The light-emitting device 130B includes a conductive layer 224B, the conductive layer 151B over the conductive layer 224B, and the conductive layer 152B over the conductive layer 151B. Here, the conductive layers 224R, 151R, and 152R can be collectively referred to as the pixel electrode of the light-emitting device 130R; the conductive layers 151R and 152R excluding the conductive layer 224R can also be referred to as the pixel electrode of the light-emitting device 130R. Similarly, the conductive layers 224G, 151G, and 152G can be collectively referred to as the pixel electrode of the light-emitting device 130G; the conductive layers 151G and 152G excluding the conductive layer 224G can also be referred to as the pixel electrode of the light-emitting device 130G. The conductive layers 224B, 151B, and 152B can be collectively referred to as the pixel electrode of the light-emitting device 130B; the conductive layers 151B and 152B excluding the conductive layer 224B can also be referred to as the pixel electrode of the light-emitting device 130B.
The conductive layer 224R is connected to a conductive layer 222b included in the transistor 205 through the opening provided in an insulating layer 214. The edge portion of the conductive layer 151R is positioned outward from an edge portion of the conductive layer 224R. The insulating layer 156R is provided to include a region that is in contact with the side surface of the conductive layer 151R, and the conductive layer 152R is provided to cover the conductive layer 151R and the insulating layer 156R.
The conductive layers 224G, 151G, and 152G and the insulating layer 156G in the light-emitting device 130G are not described in detail because they are respectively similar to the conductive layers 224R, 151R, and 152R and the insulating layer 156R in the light-emitting device 130R; the same applies to the conductive layers 224B, 151B, and 152B and the insulating layer 156B in the light-emitting device 130B.
The conductive layers 224R, 224G, and 224B each have a depression portion covering an opening provided in the insulating layer 214. A layer 128 is embedded in the depression portion.
The layer 128 has a function of filling the depression portions of the conductive layers 224R, 224G, and 224B to enable planarity. Over the conductive layers 224R, 224G, and 224B and the layer 128, the conductive layers 151R, 151G, and 151B that are respectively electrically connected to the conductive layers 224R, 224G, and 224B are provided. Thus, the regions overlapping with the depression portions of the conductive layers 224R, 224G, and 224B can also be used as light-emitting regions, whereby the aperture ratio of the pixel can be increased.
The layer 128 may be an insulating layer or a conductive layer. Any of a variety of inorganic insulating materials, organic insulating materials, and conductive materials can be used for the layer 128 as appropriate. Specifically, the layer 128 is preferably formed using an insulating material and is particularly preferably formed using an organic insulating material. The layer 128 can be formed using an organic insulating material usable for the insulating layer 127, for example.
The protective layer 131 is provided over the light-emitting devices 130R, 130G, and 130B. The protective layer 131 and the substrate 352 are bonded to each other with an adhesive layer 142. The substrate 352 is provided with a light-blocking layer 157. A solid sealing structure, a hollow sealing structure, or the like can be employed to seal the light-emitting device 130. In
The light-emitting apparatus 100B has a top-emission structure. Light from the light-emitting device is emitted toward the substrate 352. For the substrate 352, a material having a high visible-light-transmitting property is preferably used. The pixel electrode contains a material that reflects visible light, and the counter electrode (the common electrode 155) contains a material that transmits visible light.
The transistor 201 and the transistor 205 are formed over the substrate 351. These transistors can be fabricated using the same materials in the same steps.
An insulating layer 211, an insulating layer 213, an insulating layer 215, and the insulating layer 214 are provided in this order over the substrate 351. Part of the insulating layer 211 functions as a gate insulating layer of each transistor. Part of the insulating layer 213 functions as a gate insulating layer of each transistor. The insulating layer 215 is provided to cover the transistors. The insulating layer 214 is provided to cover the transistors and has a function of a planarization layer. Note that the number of gate insulating layers and the number of insulating layers covering the transistors are not limited and may each be one or more.
A material through which impurities such as water and hydrogen do not easily diffuse is preferably used for at least one of the insulating layers covering the transistors. This is because such an insulating layer can function as a barrier layer. Such a structure can effectively inhibit diffusion of impurities to the transistors from the outside and increase the reliability of the light-emitting apparatus.
An inorganic insulating film is preferably used as each of the insulating layers 211, 213, and 215. As the inorganic insulating film, a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, or an aluminum nitride film can be used, for example. A hafnium oxide film, an yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, a neodymium oxide film, or the like may be used. A stack including two or more of the above insulating films may also be used.
An organic insulating layer is suitable for the insulating layer 214 functioning as a planarization layer. Examples of materials that can be used for the organic insulating layer include an acrylic resin, a polyimide resin, an epoxy resin, a polyamide resin, a polyimide-amide resin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin, and precursors of these resins. The insulating layer 214 may have a stacked-layer structure of an organic insulating layer and an inorganic insulating layer. The outermost layer of the insulating layer 214 preferably functions as an etching protective layer. This can inhibit formation of a recessed portion in the insulating layer 214 at the time of processing of the conductive layer 224R, 151R, or 152R or the like. Alternatively, a recessed portion may be provided in the insulating layer 214 at the time of processing of the conductive layer 224R, 151R, or 152R or the like.
Each of the transistors 201 and 205 includes a conductive layer 221 functioning as a gate, the insulating layer 211 functioning as a gate insulating layer, a conductive layer 222a and a conductive layer 222b functioning as a source and a drain, a semiconductor layer 231, the insulating layer 213 functioning as a gate insulating layer, and a conductive layer 223 functioning as a gate. Here, a plurality of layers obtained by processing the same conductive film are shown with the same hatching pattern. The insulating layer 211 is positioned between the conductive layer 221 and the semiconductor layer 231. The insulating layer 213 is positioned between the conductive layer 223 and the semiconductor layer 231.
There is no particular limitation on the structure of the transistors included in the light-emitting apparatus of this embodiment. For example, a planar transistor, a staggered transistor, or an inverted staggered transistor can be used. A top-gate transistor or a bottom-gate transistor can be used. Alternatively, gates may be provided above and below a semiconductor layer where a channel is formed.
The structure in which the semiconductor layer where a channel is formed is provided between two gates is used for the transistors 201 and 205. The two gates may be connected to each other and supplied with the same signal to operate the transistor. Alternatively, the threshold voltage of the transistor may be controlled by applying a potential for controlling the threshold voltage to one of the two gates and a potential for driving to the other of the two gates.
There is no particular limitation on the crystallinity of a semiconductor material used for the transistors, and either an amorphous semiconductor or a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor partly including crystal regions) can be used. A semiconductor having crystallinity is preferably used, in which case deterioration of transistor characteristics can be suppressed.
The semiconductor layer of the transistor preferably includes a metal oxide. That is, a transistor including a metal oxide in its channel formation region (hereinafter, also referred to as an OS transistor) is preferably used in the light-emitting apparatus of this embodiment.
Examples of an oxide semiconductor having crystallinity include a c-axis-aligned crystalline oxide semiconductor (CAAC-OS) and a nanocrystalline oxide semiconductor (nc-OS).
Alternatively, a transistor including silicon in its channel formation region (a Si transistor) may be used. Examples of silicon include single crystal silicon, polycrystalline silicon, and amorphous silicon. In particular, a transistor containing low-temperature polysilicon (LTPS) in its semiconductor layer (hereinafter also referred to as an LTPS transistor) can be used. The LTPS transistor has high field-effect mobility and excellent frequency characteristics.
With the use of Si transistors such as LTPS transistors, a circuit required to be driven at a high frequency (e.g., a source driver circuit) can be formed on the same substrate as the display portion. This allows for simplification of an external circuit mounted on the light-emitting apparatus and a reduction in costs of parts and mounting costs.
An OS transistor has much higher field-effect mobility than a transistor containing amorphous silicon. In addition, the OS transistor has an extremely low leakage current between a source and a drain in an off state (hereinafter also referred to as an off-state current), and electric charge accumulated in a capacitor that is connected in series to the transistor can be held for a long period. Furthermore, the power consumption of the light-emitting apparatus can be reduced with the OS transistor.
To increase the luminance of the light-emitting device included in the pixel circuit, the amount of current fed through the light-emitting device needs to be increased. To increase the current amount, the source-drain voltage of a driving transistor included in the pixel circuit needs to be increased. An OS transistor has a higher breakdown voltage between a source and a drain than a Si transistor; hence, a high voltage can be applied between the source and the drain of the OS transistor. Therefore, when an OS transistor is used as the driving transistor in the pixel circuit, the amount of current flowing through the light-emitting device can be increased, so that the luminance of the light-emitting device can be increased.
When transistors operate in a saturation region, a change in a source-drain current relative to a change in a gate-source voltage can be smaller in an OS transistor than in a Si transistor. Accordingly, when an OS transistor is used as the driving transistor in the pixel circuit, a current flowing between the source and the drain can be set minutely by a change in a gate-source voltage; hence, the amount of current flowing through the light-emitting device can be controlled. Consequently, the number of gray levels in the pixel circuit can be increased.
Regarding saturation characteristics of a current flowing when transistors operate in a saturation region, even in the case where the source-drain voltage of an OS transistor increases gradually, a more stable current (saturation current) can be fed through the OS transistor than through a Si transistor. Thus, by using an OS transistor as the driving transistor, a stable current can be fed through light-emitting devices even when the current-voltage characteristics of the light-emitting devices vary, for example. In other words, when the OS transistor operates in the saturation region, the source-drain current hardly changes with an increase in the source-drain voltage; hence, the luminance of the light-emitting device can be stable.
As described above, by using OS transistors as the driving transistors included in the pixel circuits, it is possible to inhibit black-level degradation, increase the luminance, increase the number of gray levels, and suppress variations in light-emitting devices, for example.
The semiconductor layer preferably contains indium, M (M is one or more of gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium), and zinc, for example. Specifically, M is preferably one or more of aluminum, gallium, yttrium, and tin.
It is particularly preferable that an oxide containing indium (In), gallium (Ga), and zinc (Zn) (also referred to as IGZO) be used for the semiconductor layer. It is preferable to use an oxide containing indium, tin, and zinc. It is preferable to use an oxide containing indium, gallium, tin, and zinc. It is preferable to use an oxide containing indium (In), aluminum (Al), and zinc (Zn) (also referred to as IAZO). It is preferable to use an oxide containing indium (In), aluminum (Al), gallium (Ga), and zinc (Zn) (also referred to as IAGZO).
When the semiconductor layer is an In-M-Zn oxide, the atomic proportion of In is preferably higher than or equal to the atomic proportion of M in the In-M-Zn oxide. Examples of the atomic ratio of the metal elements in such an In-M-Zn oxide are In:M:Zn=1:1:1, 1:1:1.2, 2:1:3, 3:1:2, 4:2:3, 4:2:4.1, 5:1:3, 5:1:6, 5:1:7, 5:1:8, 6:1:6, and 5:2:5 and a composition in the neighborhood of any of the above atomic ratios. Note that the neighborhood of the atomic ratio includes ±30% of an intended atomic ratio.
For example, in the case of describing an atomic ratio of In:Ga:Zn=4:2:3 or a composition in the vicinity thereof, the case is included in which, the atomic proportion of Ga is greater than or equal to 1 and less than or equal to 3 and the atomic proportion of Zn is greater than or equal to 2 and less than or equal to 4 with the atomic proportion of In being 4. In the case of describing an atomic ratio of In:Ga:Zn=5:1:6 or a composition in the vicinity thereof, the case is included in which the atomic proportion of Ga is greater than 0.1 and less than or equal to 2 and the atomic proportion of Zn is greater than or equal to 5 and less than or equal to 7 with the atomic proportion of In being 5. In the case of describing an atomic ratio of In:Ga:Zn=1:1:1 or a composition in the vicinity thereof, the case is included in which the atomic proportion of Ga is greater than 0.1 and less than or equal to 2 and the atomic proportion of Zn is greater than 0.1 and less than or equal to 2 with the atomic proportion of In being 1.
The transistors included in the circuit 356 and the transistors included in the pixel portion 177 may have the same structure or different structures. One structure or two or more kinds of structures may be employed for a plurality of transistors included in the circuit 356. Similarly, one structure or two or more kinds of structures may be employed for a plurality of transistors included in the pixel portion 177.
All transistors included in the pixel portion 177 may be OS transistors, or all transistors included in the pixel portion 177 may be Si transistors. Alternatively, some of the transistors included in the pixel portion 177 may be OS transistors and the others may be Si transistors.
For example, when both an LTPS transistor and an OS transistor are used in the pixel portion 177, the light-emitting apparatus can have low power consumption and high driving capability. Note that a structure in which an LTPS transistor and an OS transistor are used in combination is referred to as LTPO in some cases. For example, it is preferable that an OS transistor be used as a transistor functioning as a switch for controlling electrical continuity between wirings and an LTPS transistor be used as a transistor for controlling a current.
For example, one transistor included in the pixel portion 177 functions as a transistor for controlling a current flowing through the light-emitting device and can be referred to as a driving transistor. One of a source and a drain of the driving transistor is electrically connected to the pixel electrode of the light-emitting device. An LTPS transistor is preferably used as the driving transistor. In that case, the amount of current flowing through the light-emitting device can be increased in the pixel circuit.
Another transistor included in the pixel portion 177 functions as a switch for controlling selection or non-selection of a pixel and can be referred to as a selection transistor. A gate of the selection transistor is electrically connected to a gate line, and one of a source and a drain thereof is electrically connected to a source line (signal line). An OS transistor is preferably used as the selection transistor. In that case, the gray level of the pixel can be maintained even with an extremely low frame frequency (e.g., lower than or equal to 1 fps); thus, power consumption can be reduced by stopping the driver in displaying a still image.
As described above, the light-emitting apparatus of one embodiment of the present invention can have all of a high aperture ratio, high resolution, high display quality, and low power consumption.
Note that the light-emitting apparatus of one embodiment of the present invention has a structure including the OS transistor and the light-emitting device having a metal maskless (MML) structure. This structure can significantly reduce a leakage current that would flow through a transistor and a leakage current that would flow between adjacent light-emitting devices (sometimes referred to as a horizontal leakage current or a lateral leakage current). Displaying images on the light-emitting apparatus having this structure can bring one or more of image crispness, image sharpness, high color saturation, and a high contrast ratio to the viewer. When a leakage current that would flow through the transistor and a lateral leakage current that would flow between the light-emitting devices are extremely low, leakage of light at the time of black display (black-level degradation) or the like can be minimized.
In particular, in the case where a light-emitting device having an MML structure employs a side-by-side (SBS) structure, which is the above-described structure for separately forming or coloring light-emitting layers, a layer provided between light-emitting devices (for example, also referred to as an organic layer or a common layer which is shared by the light-emitting devices) is disconnected; accordingly, side leakage can be prevented or be made extremely low.
Transistors 209 and 210 each include the conductive layer 221 functioning as a gate, the insulating layer 211 functioning as a gate insulating layer, the semiconductor layer 231 including a channel formation region 231i and a pair of low-resistance regions 231n, the conductive layer 222a connected to one of the pair of low-resistance regions 231n, the conductive layer 222b connected to the other of the pair of low-resistance regions 231n, an insulating layer 225 functioning as a gate insulating layer, the conductive layer 223 functioning as a gate, and the insulating layer 215 covering the conductive layer 223. The insulating layer 211 is positioned between the conductive layer 221 and the channel formation region 231i. The insulating layer 225 is positioned at least between the conductive layer 223 and the channel formation region 231i. Furthermore, an insulating layer 218 covering the transistor may be provided.
In the transistor 210 illustrated in
A connection portion 204 is provided in a region of the substrate 351 where the substrate 352 does not overlap. In the connection portion 204, the wiring 355 is electrically connected to the FPC 353 through a conductive layer 166 and a connection layer 242. An example is described in which the conductive layer 166 has a stacked-layer structure of a conductive film obtained by processing the same conductive film as the conductive layers 224R, 224G, and 224B; a conductive film obtained by processing the same conductive film as the conductive layers 151R, 151G, and 151B; and a conductive film obtained by processing the same conductive film as the conductive layers 152R, 152G, and 152B. On the top surface of the connection portion 204, the conductive layer 166 is exposed. Thus, the connection portion 204 and the FPC 353 can be electrically connected to each other through the connection layer 242.
The light-blocking layer 157 is preferably provided on the surface of the substrate 352 on the substrate 351 side. The light-blocking layer 157 can be provided over a region between adjacent light-emitting devices, in the connection portion 140, in the circuit 356, and the like. A variety of optical members can be arranged on the outer surface of the substrate 352.
A material that can be used for the substrate 120 can be used for each of the substrates 351 and 352.
A material that can be used for the resin layer 122 can be used for the adhesive layer 142.
As the connection layer 242, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like can be used.
A light-emitting apparatus 100H illustrated in
Light from the light-emitting device is emitted toward the substrate 351. For the substrate 351, a material having a high visible-light-transmitting property is preferably used. By contrast, there is no limitation on the light-transmitting property of a material used for the substrate 352.
The light-blocking layer 157 is preferably formed between the substrate 351 and the transistor 201 and between the substrate 351 and the transistor 205.
The light-emitting device 130R includes a conductive layer 112R, a conductive layer 126R over the conductive layer 112R, and a conductive layer 129R over the conductive layer 126R.
The light-emitting device 130B includes a conductive layer 112B, a conductive layer 126B over the conductive layer 112B, and a conductive layer 129B over the conductive layer 126B.
A material having a high visible-light-transmitting property is used for each of the conductive layers 112R, 112B, 126R, 126B, 129R, and 129B. A material that reflects visible light is preferably used for the common electrode 155.
Although not illustrated in
Although
The light-emitting apparatus 100C illustrated in
In the light-emitting apparatus 100C, the light-emitting device 130 includes a region overlapping with one of the coloring layers 132R, 132G, and 132B. The coloring layers 132R, 132G, and 132B can be provided on the surface of the substrate 352 on the substrate 351 side. Edge portions of the coloring layers 132R, 132G, and 132B can overlap with the light-blocking layer 157.
In the light-emitting apparatus 100C, the light-emitting device 130 can emit white light, for example. The coloring layer 132R, the coloring layer 132G, and the coloring layer 132B can transmit red light, green light, and blue light, respectively, for example. Note that in the light-emitting apparatus 100C, the coloring layers 132R, 132G, and 132B may be provided between the protective layer 131 and the adhesive layer 142.
Although
As illustrated in
As illustrated in
The top surface of the layer 128 may include one or both of a convex surface and a concave surface. The number of convex surfaces and the number of concave surfaces included in the top surface of the layer 128 are not limited and can each be one or more.
The level of the top surface of the layer 128 and the level of the top surface of the conductive layer 224R may be the same or substantially the same, or may be different from each other. For example, the level of the top surface of the layer 128 may be either lower or higher than the level of the top surface of the conductive layer 224R.
This embodiment can be combined as appropriate with the other embodiments or examples. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.
In this embodiment, electronic appliances of embodiments of the present invention will be described.
Electronic appliances of this embodiment include the light-emitting apparatus of one embodiment of the present invention in their display portions. The light-emitting apparatus of one embodiment of the present invention is highly reliable and can be easily increased in resolution and definition. Thus, the light-emitting apparatus of one embodiment of the present invention can be used for display portions of a variety of electronic appliances.
Examples of the electronic appliances include a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, and an audio reproducing device, in addition to electronic appliances with a relatively large screen, such as a television device, desktop and notebook personal computers, a monitor of a computer and the like, digital signage, and a large game machine such as a pachinko machine.
In particular, the light-emitting apparatus of one embodiment of the present invention can have high resolution, and thus can be favorably used for an electronic appliance having a relatively small display portion. Examples of such an electronic appliance include watch-type and bracelet-type information terminal devices (wearable devices) and wearable devices capable of being worn on a head, such as a VR device like a head-mounted display, a glasses-type AR device, and an MR device.
The definition of the light-emitting apparatus of one embodiment of the present invention is preferably as high as HD (number of pixels: 1280×720), FHD (number of pixels: 1920×1080), WQHD (number of pixels: 2560×1440), WQXGA (number of pixels: 2560×1600), 4K (number of pixels: 3840×2160), or 8K (number of pixels: 7680×4320). In particular, definition of 4K, 8K, or higher is preferable. The pixel density (resolution) of the light-emitting apparatus of one embodiment of the present invention is preferably higher than or equal to 100 ppi, further preferably higher than or equal to 300 ppi, further preferably higher than or equal to 500 ppi, further preferably higher than or equal to 1,000 ppi, still further preferably higher than or equal to 2,000 ppi, still further preferably higher than or equal to 3,000 ppi, still further preferably higher than or equal to 5,000 ppi, yet further preferably higher than or equal to 7,000 ppi. With such a light-emitting apparatus having one or both of high definition and high resolution, the electronic appliance can provide higher realistic sensation, sense of depth, and the like in personal use such as portable use or home use. There is no particular limitation on the screen ratio (aspect ratio) of the light-emitting apparatus of one embodiment of the present invention. For example, the light-emitting apparatus is compatible with a variety of screen ratios such as 1:1 (a square), 4:3, 16:9, and 16:10.
The electronic appliance in this embodiment may include a sensor (a sensor having a function of measuring force, displacement, position, speed, acceleration, angular velocity, rotational frequency, distance, light, liquid, magnetism, temperature, a chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, oscillation, odor, or infrared rays).
The electronic appliance in this embodiment can have a variety of functions. For example, the electronic appliance in this embodiment can have a function of displaying a variety of information (e.g., a still image, a moving image, and a text image) on the display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of executing a variety of software (programs), a wireless communication function, and a function of reading out a program or data stored in a recording medium.
Examples of head-mounted wearable devices are described with reference to
An electronic appliance 700A illustrated in
The light-emitting apparatus of one embodiment of the present invention can be used for the display panels 751. Thus, a highly reliable electronic appliance is obtained.
The electronic appliances 700A and 700B can each project images displayed on the display panels 751 onto display regions 756 of the optical members 753. Since the optical members 753 have a light-transmitting property, the user can see images displayed on the display regions, which are superimposed on transmission images seen through the optical members 753. Accordingly, the electronic appliances 700A and 700B are electronic appliances capable of AR display.
In the electronic appliances 700A and 700B, a camera capable of capturing images of the front side may be provided as the image capturing portion. Furthermore, when the electronic appliances 700A and 700B are provided with an acceleration sensor such as a gyroscope sensor, the orientation of the user's head can be sensed and an image corresponding to the orientation can be displayed on the display regions 756.
The communication portion includes a wireless communication device, and a video signal, for example, can be supplied by the wireless communication device. Instead of or in addition to the wireless communication device, a connector that can be connected to a cable for supplying a video signal and a power supply potential may be provided.
The electronic appliances 700A and 700B are provided with a battery, so that they can be charged wirelessly and/or by wire.
A touch sensor module may be provided in the housing 721. The touch sensor module has a function of detecting a touch on the outer surface of the housing 721. Detecting a tap operation, a slide operation, or the like by the user with the touch sensor module enables various types of processing. For example, a moving image can be paused or restarted by a tap operation, and can be fast-forwarded or fast-reversed by a slide operation. When the touch sensor module is provided in each of the two housings 721, the range of the operation can be increased.
Various touch sensors can be applied to the touch sensor module. For example, any of touch sensors of the following types can be used: a capacitive type, a resistive type, an infrared type, an electromagnetic induction type, a surface acoustic wave type, and an optical type. In particular, a capacitive sensor or an optical sensor is preferably used for the touch sensor module.
In the case of using an optical touch sensor, a photoelectric conversion device (also referred to as a photoelectric conversion element) can be used as a light-receiving element. One or both of an inorganic semiconductor and an organic semiconductor can be used for an active layer of the photoelectric conversion device.
Note that the device of one embodiment of the present invention can be used for a photoelectric conversion element such as an organic thin film solar cell (OPV) having a tandem structure with two or more units or an organic photodiode (OPD) having a tandem structure with two or more units. Specifically, the first organic compound whose electron oxidation is irreversible can be used for a charge-generation region in an intermediate layer sandwiched between two photoelectric conversion layers. Alternatively, for example, the first organic compound may be used for a charge-generation region in an intermediate layer sandwiched between a light-emitting layer and a photoelectric conversion layer. At this time, it is preferable that a light-emitting element be located on the transparent electrode side and a photoelectric conversion element be located on the reflective electrode side, in which case the light absorption loss of the photoelectric conversion layer with respect to the light-emitting layer can be reduced.
An electronic appliance 800A illustrated in
The light-emitting apparatus of one embodiment of the present invention can be used in the display portions 820. Thus, a highly reliable electronic appliance is obtained.
The display portions 820 are positioned inside the housing 821 so as to be seen through the lenses 832. When the pair of display portions 820 display different images, three-dimensional display using parallax can be performed.
The electronic appliances 800A and 800B can be regarded as electronic appliances for VR. The user who wears the electronic appliance 800A or the electronic appliance 800B can see images displayed on the display portions 820 through the lenses 832.
The electronic appliances 800A and 800B preferably include a mechanism for adjusting the lateral positions of the lenses 832 and the display portions 820 so that the lenses 832 and the display portions 820 are positioned optimally in accordance with the positions of the user's eyes. Moreover, the electronic appliances 800A and 800B preferably include a mechanism for adjusting focus by changing the distance between the lenses 832 and the display portions 820.
The electronic appliance 800A or the electronic appliance 800B can be mounted on the user's head with the wearing portions 823.
The image capturing portion 825 has a function of obtaining information on the external environment. Data obtained by the image capturing portion 825 can be output to the display portion 820. An image sensor can be used for the image capturing portion 825. Moreover, a plurality of cameras may be provided so as to cover a plurality of fields of view, such as a telescope field of view and a wide field of view.
Although an example where the image capturing portions 825 are provided is described here, a range sensor (hereinafter also referred to as a sensing portion) capable of measuring the distance between the user and an object just needs to be provided. In other words, the image capturing portion 825 is one embodiment of the sensing portion. As the sensing portion, an image sensor or a range image sensor such as a light detection and ranging (LiDAR) sensor can be used, for example. By using images obtained by the camera and images obtained by the range image sensor, more information can be obtained and a gesture operation with higher accuracy is possible.
The electronic appliance 800A may include a vibration mechanism that functions as bone-conduction earphones. For example, at least one of the display portion 820, the housing 821, and the wearing portion 823 can include the vibration mechanism. Thus, without additionally requiring an audio device such as headphones, earphones, or a speaker, the user can enjoy video and sound only by wearing the electronic appliance 800A.
The electronic appliances 800A and 800B may each include an input terminal. To the input terminal, a cable for supplying a video signal from a video output device or the like, power for charging a battery provided in the electronic appliance, and the like can be connected.
The electronic appliance of one embodiment of the present invention may have a function of performing wireless communication with earphones 750. The earphones 750 include a communication portion (not illustrated) and have a wireless communication function. The earphones 750 can receive information (e.g., audio data) from the electronic appliance with the wireless communication function. For example, the electronic appliance 700A in
The electronic appliance may include an earphone portion. The electronic appliance 700B in
Similarly, the electronic appliance 800B in
The electronic appliance may include an audio output terminal to which earphones, headphones, or the like can be connected. The electronic appliance may include one or both of an audio input terminal and an audio input mechanism. As the audio input mechanism, a sound collecting device such as a microphone can be used, for example. The electronic appliance may have a function of a headset by including the audio input mechanism.
As described above, both the glasses-type device (e.g., the electronic appliances 700A and 700B) and the goggles-type device (e.g., the electronic appliances 800A and 800B) are preferable as the electronic appliance of one embodiment of the present invention.
The electronic appliance of one embodiment of the present invention can transmit information to earphones by wire or wirelessly.
An electronic appliance 6500 illustrated in
The electronic appliance 6500 includes a housing 6501, a display portion 6502, a power button 6503, buttons 6504, a speaker 6505, a microphone 6506, a camera 6507, a light source 6508, and the like. The display portion 6502 has a touch panel function.
The light-emitting apparatus of one embodiment of the present invention can be used in the display portion 6502. Thus, a highly reliable electronic appliance is obtained.
A protection member 6510 having a light-transmitting property is provided on the display surface side of the housing 6501. A display panel 6511, an optical member 6512, a touch sensor panel 6513, a printed circuit board 6517, a battery 6518, and the like are provided in a space surrounded by the housing 6501 and the protection member 6510.
The display panel 6511, the optical member 6512, and the touch sensor panel 6513 are fixed to the protection member 6510 with an adhesive layer (not illustrated).
Part of the display panel 6511 is folded back in a region outside the display portion 6502, and an FPC 6515 is connected to the part that is folded back. An IC 6516 is mounted on the FPC 6515. The FPC 6515 is connected to a terminal provided on the printed circuit board 6517.
The light-emitting apparatus of one embodiment of the present invention can be used in the display panel 6511. Thus, an extremely lightweight electronic appliance can be obtained. Since the display panel 6511 is extremely thin, the battery 6518 with high capacity can be mounted without an increase in the thickness of the electronic appliance. An electronic appliance with a narrow bezel can be obtained when part of the display panel 6511 is folded back so that the portion connected to the FPC 6515 is provided on the back side of a pixel portion.
The light-emitting apparatus of one embodiment of the present invention can be used in the display portion 7000. Thus, a highly reliable electronic appliance is obtained.
Operation of the television device 7100 illustrated in
Note that the television device 7100 includes a receiver, a modem, and the like. A general television broadcast can be received with the receiver. When the television device is connected to a communication network with or without wires via the modem, one-way (from a transmitter to a receiver) or two-way (e.g., between a transmitter and a receiver or between receivers) information communication can be performed.
The light-emitting apparatus of one embodiment of the present invention can be used in the display portion 7000. Thus, a highly reliable electronic appliance is obtained.
Digital signage 7300 illustrated in
In
A larger area of the display portion 7000 can increase the amount of information that can be provided at a time. The display portion 7000 having a larger area attracts more attention, so that the effectiveness of the advertisement can be increased, for example.
The touch panel is preferably used in the display portion 7000, in which case in addition to display of still or moving images on the display portion 7000, intuitive operation by a user is possible. Moreover, in the case of an application for providing information such as route information or traffic information, usability can be enhanced by intuitive operation.
As illustrated in
It is possible to make the digital signage 7300 or the digital signage 7400 execute a game with the use of the screen of the information terminal 7311 or the information terminal 7411 as an operation means (controller). Thus, an unspecified number of users can join in and enjoy the game concurrently.
Electronic appliances illustrated in
The electronic appliances illustrated in
The electronic appliances in
This embodiment can be combined as appropriate with the other embodiments or examples. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.
In this example, light-emitting devices of one embodiment of the present invention were fabricated and their characteristics were evaluated, and the evaluation results will be described. Furthermore, the evaluation results of electrochemical characteristics (oxidation reaction characteristics) of the organic compounds whose electron oxidation is irreversible which were used for the light-emitting devices will be described.
As the organic compounds whose electron oxidation is irreversible, 1-(2′,7′-di-tert-butyl-9,9′-spirobi[9H-fluoren]-2-yl)-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (abbreviation: 2′,7′tBu-2hppSF), 8,8′-pyridine-2,6-diyl-bis(5,6,7,8-tetrahydroimidazo[1,2-a]pyrimidine) (abbreviation: 2,6tip2Py), and 2-(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidin-1-yl)-9-phenyl-1,10-phenanthroline (abbreviation: 9Ph-2hppPhen) were selected, and light-emitting devices were fabricated. Structural formulae of the organic compounds are shown below.
As a comparative example, a structural formula of an organic compound whose electron oxidation is reversible, 2-[4-(1,3-dimethyl-2H-benzimidazol-2-yl)phenyl]-1,3-dimethyl-2H-benzimidazole (abbreviation: Dhbi2P) is also shown below.
<Light-Emitting Device 1A: Device Including 2′,7′tBu-2hppSF>
In a light-emitting device 1A, 1-(2′,7′-di-tert-butyl-9,9′-spirobi[9H-fluoren]-2-yl)-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (abbreviation: 2′,7′tBu-2hppSF) was used for an intermediate layer.
Structural formulae of organic compounds used for the light-emitting device 1A are shown below.
As illustrated in
The first EL layer 903 has a structure in which a hole-injection layer 910, a first hole-transport layer 911, a first light-emitting layer 912, and a first electron-transport layer 913 are stacked in this order. The intermediate layer 905 includes an electron-injection buffer region 914 and a layer 915 including an electron-relay region and a charge-generation region. The second EL layer 904 has a structure in which a second hole-transport layer 916, a second light-emitting layer 917, a second electron-transport layer 918, and an electron-injection layer 919 are stacked in this order.
First, as a reflective electrode, silver (Ag) was deposited over the substrate 900 that is a glass substrate to a thickness of 100 nm by a sputtering method, and then, as a transparent electrode, indium tin oxide containing silicon oxide (ITSO) was deposited to a thickness of 10 nm by a sputtering method, so that the first electrode 901 was formed. The electrode area was set to 4 mm2 (2 mm×2 mm).
Next, the first EL layer 903 was provided. First, in pretreatment for forming the light-emitting device 1A over the substrate, a surface of the substrate was washed with water and baking was performed at 200° C. for 1 hour. Then, the substrate was transferred into a vacuum evaporation apparatus where the pressure was reduced to approximately 1×10−4 Pa, and vacuum baking was performed at 170° C. for 30 minutes in a heating chamber of the vacuum evaporation apparatus. After that, natural cooling was performed for approximately 30 minutes.
Then, the substrate provided with the first electrode 901 was fixed to a substrate holder provided in the vacuum evaporation apparatus such that the surface on which the first electrode 901 was formed faced downward. Over the first electrode 901, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited by co-evaporation using resistance heating to a thickness of 10 nm such that the weight ratio of PCBBiF to OCHD-003 was 1:0.03, whereby the hole-injection layer 910 was formed.
Next, PCBBiF was deposited by evaporation to a thickness of 20 nm over the hole-injection layer 910, so that the first hole-transport layer 911 was formed.
Next, the first light-emitting layer 912 was formed over the first hole-transport layer 911. Using a resistance-heating method, 8-(1,1′:4′,1″-terphenyl-3-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8mpTP-4mDBtPBfpm), 9-(2-naphthyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PNCCP), and [2-d3-methyl-8-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-KC]bis[2-(5-d3-methyl-2-pyridinyl-κN2)phenyl-KC]iridium(III) (abbreviation: Ir(5mppy-d3)2(mbfpypy-d3)) were deposited to a thickness of 40 nm by co-evaporation such that the weight ratio of 8mpTP-4mDBtPBfpm to PNCCP and Ir(5mppy-d3)2(mbfpypy-d3) was 5:5:1, whereby the first light-emitting layer 912 was formed.
Next, 3,6-bis(diphenylamino)-9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9H-carbazole (abbreviation: DACT-II) was deposited to a thickness of 10 nm by evaporation over the first light-emitting layer 912, whereby the first electron-transport layer 913 was formed.
Next, the intermediate layer 905 was provided. First, over the first electron-transport layer 913, 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) and 1-(2′,7′-di-tert-butyl-9,9′-spirobi[9H-fluoren]-2-yl)-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (abbreviation: 2′,7′tBu-2hppSF) were deposited to a thickness of 5 nm by co-evaporation using a resistance-heating method such that the weight ratio of mPPhen2P to 2′,7′tBu-2hppSF was 1:1, whereby a layer serving as the electron-injection buffer region 914 was formed.
Then, as the electron-relay region, copper phthalocyanine (abbreviation: CuPc) was deposited to a thickness of 2 nm. Next, as the charge-generation region, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited by co-evaporation using resistance heating to a thickness of 10 nm such that the weight ratio of PCBBiF to OCHD-003 was 1:0.15, whereby the layer 915 including the charge-generation region was formed.
Next, the second EL layer 904 was provided. First, PCBBiF was deposited by evaporation to a thickness of 55 nm, so that the second hole-transport layer 916 was formed.
Next, using a resistance-heating method, 8-(1,1′:4′,1″-terphenyl-3-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8mpTP-4mDBtPBfpm), 9-(2-naphthyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PNCCP), and [2-d3-methyl-8-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-KC]bis[2-(5-d3-methyl-2-pyridinyl-κN2)phenyl-C]iridium(III) (abbreviation: Ir(5mppy-d3)2(mbfpypy-d3)) were deposited to a thickness of 40 nm by co-evaporation such that the weight ratio of 8mpTP-4mDBtPBfpm to PNCCP and Ir(5mppy-d3)2(mbfpypy-d3) was 5:5:1, whereby the second light-emitting layer 917 was formed.
Next, over the second light-emitting layer 917, 2-{3-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq) was deposited by evaporation to a thickness of 20 nm, and then 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) was deposited by evaporation to a thickness of 20 nm, so that the second electron-transport layer 918 was formed.
Next, over the second electron-transport layer 918, lithium fluoride (LiF) and ytterbium (Yb) were deposited by co-evaporation to a thickness of 1.5 nm such that the volume ratio of LiF to Yb was 2:1, whereby the electron-injection layer 919 was formed.
Next, over the electron-injection layer 919, Ag and Mg were deposited by co-evaporation to a thickness of 15 nm such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode 902 was formed. Note that the second electrode 902 is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.
Then, as a cap layer, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II) was deposited by evaporation to a thickness of 70 nm.
Through the above process, the light-emitting device 1A was fabricated. The structure of the light-emitting device 1A is shown in the following table.
The light-emitting device 1A was sealed using a glass substrate in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (a sealing material was applied to surround the device, and at the time of sealing, UV treatment was performed and then heat treatment was performed at 80° C. for an hour). Then, the characteristics of the light-emitting device 1A were measured.
Furthermore, as shown in
A reliability test was performed on the light-emitting device 1A.
In
Therefore, the light-emitting device 1A was found to be a highly reliable device.
<LC-MS Measurement Results of 2′,7′tBu-2hppSF>
Here, the light-emitting device 1A which has been energized for five minutes and the light-emitting device 1A which has been energized for 500 hours with a current density of 50 mA/cm2 were analyzed by liquid chromatography mass spectrometry (abbreviation: LC-MS analysis). Note that the luminance at a current density of 50 mA/cm2 was approximately 65000 cd/m2.
A sample of the light-emitting device 1A used for the LC-MS analysis was formed in the following manner: the light-emitting devices were each cut into a region of approximately 4 mm×24 mm including a light-emitting region (2 mm×2 mm) over the first electrode; the light-emitting device 1A which have been energized for five minutes and the light-emitting device 1A which have been energized for 500 hours are mixed; the mixture and 0.1 ml of a mixed solution of acetonitrile: chloroform=8:2 were put into a brown bottle; ultrasonic treatment was performed for ten minutes; and the solution was filtrated with a porous filter with a pore size of 0.2 μm.
A single film of 2′,7′tBu-2hppSF was formed as a reference sample. The evaporation film of 2′,7′tBu-2hppSF was cut into approximately 2 cm×2 cm. The evaporation film and a mixed solution of acetonitrile: chloroform=8:2 were put into a brown bottle, and ultrasonic treatment was performed for ten minutes. The solution was diluted with acetonitrile 45 times to have the same concentration as 2′,7′tBu-2hppSF in the light-emitting device 1A after being energized, and then the solution was filtrated with a porous filter with a pore size of 0.2 μm.
The liquid chromatography mass spectrometer is constructed of ACQUITY H-Class (produced by Waters Corporation) and ACQUITY UPLC HSS T3 Column (1.8 μm, 2.1 mm×100 mm) (produced by Waters Corporation, hereinafter referred to as Column) was used as a column.
The column temperature was set to 40° C. Acetonitrile was used for Mobile Phase A and a 0.1% formic acid aqueous solution was used for Mobile Phase B. The injection amount was set to 5 μL for each of the sample of the light-emitting device A and the single film of 2′,7′tBu-2hppSF for comparison after being energized.
In LC separation, a gradient method in which the composition of mobile phases is changed was employed. The ratio of Mobile Phase A to Mobile Phase B was 50:50 for 0 to 1 minute after the start of the measurement, and then the composition was changed such that the ratio of Mobile Phase A to Mobile Phase B after 70 minutes was 99:1. The composition was changed linearly.
m/z 566 is a value obtained by adding 1, which is a mass number of a proton, to the mass number of 2′,7′tBu-2hppSF. This proton includes a proton derived from a formic acid of the mobile phase. As compared with the single evaporation film of 2′,7′tBu-2hppSF, ion intensity of a signal with m/z 562 and ion intensity of a signal with m/z 564 are increased in the light-emitting device 1A after being energized. m/z 562 is a value obtained by adding 1, which is a mass number of a proton, to a substance obtained by releasing four hydrogen atoms from 2′,7′tBu-2hppSF. m/z 564 is a value obtained by adding 1, which is a mass number of a proton, to a substance obtained by releasing two hydrogen atoms from 2′,7′tBu-2hppSF. This proton includes a proton derived from a formic acid of the mobile phase.
Accordingly, 2′,7′tBu-2hppSF probably releases two or four hydrogen atoms from one compound when being energized. A similar increase in m/z is observed in the electron oxidation reaction to be described later; thus, while the device is driven, holes are probably injected to 2′,7′tBu-2hppSF and electron oxidation occurs.
It was found that in the organic compound whose electron oxidation is irreversible, the m/z value tends to decrease by 2 or 4. This is probably because when two hydrogen atoms or four hydrogen atoms dissociate from each molecule in the organic compound, the organic compound becomes stable by forming a double bond and hydrogen is unlikely to return. The dissociated hydrogen cation (proton) probably retains and accumulates positive electric charges by being added to another organic compound whose electron oxidation is irreversible. In addition, a high HOMO level is formed and a hole-transport property is inhibited. These facts indicate that the organic compound whose electron oxidation is irreversible functions as an intermediate layer of a tandem light-emitting device.
<Evaluation of Electrochemical Characteristics (Oxidation Reaction Characteristics) of 2′,7′tBu-2Hppsf>
Here, the electrochemical characteristics of 2′,7′tBu-2hppSF used for the light-emitting device 1A were measured. Specifically, a peak current of the oxidation current (Ipa) and a peak current of the reduction current (Ipc), which are obtained by changing potential of the working electrode with respect to the reference electrode, were measured by cyclic voltammetry (CV).
<<Fabrication of Sample of 2′,7′tBu-2hppSF>>
A first sample was fabricated in the following manner: with use of a dehydrated solvent N,N-dimethylformamide (DMF) (produced by FUJIFILM Wako Pure Chemical Corporation, product number: 043-32361) as a solvent, tetra-n-butylammonium perchlorate (n-Bu4NClO4) (produced by Tokyo Chemical Industry Co., Ltd., product number: T0836), which is a supporting electrolyte, was dissolved to have a concentration of 100 mmol/L; 2′,7′tBu-2hppSF, which is a measurement target, was dissolved to have a concentration of 2 mmol/L; and the resulting solution was subjected to bubbling with argon (Ar) for 30 minutes.
A second sample was fabricated in the following manner: with use of a super-dehydrated solvent, acetonitrile (produced by FUJIFILM Wako Pure Chemical Corporation, product number: 018-22901) as a solvent, tetra-n-butylammonium perchlorate (n-Bu4NClO4) (produced by Tokyo Chemical Industry Co., Ltd., product number: T0836), which is a supporting electrolyte, was dissolved to have a concentration of 100 mmol/L; 2′,7′tBu-2hppSF, which is a measurement target, was dissolved to have a concentration of 2 mmol/L; and the resulting solution was subjected to bubbling with argon (Ar) for 30 minutes.
The electrochemical characteristics (oxidation reaction characteristics) were measured by cyclic voltammetry (CV). For the measurement, an electrochemical analyzer (ALS model 600, produced by BAS Inc.) was used.
A platinum electrode (PTE platinum electrode, produced by BAS Inc.) was used as a working electrode, another platinum electrode (Pt counter electrode (5 cm), produced by BAS Inc.) was used as an auxiliary electrode, and an Ag/Ag+ electrode (RE7 reference electrode for a nonaqueous solvent, produced by BAS Inc.) was used as a reference electrode. Note that the measurement was performed at room temperature under an argon stream.
As a scanning measurement condition, the scan rate was set to 1.0 V/s. Scanning was performed from an initial potential to 0.6 V (outward scanning), then the scan direction was reversed to the negative potential side and scanning was performed to a final potential (the above-described initial potential) (return scanning). Whether a positive current peak (a reduction current peak or a peak in return scanning) exists or not was observed. The initial potential was set to a voltage value obtained by an open circuit potential measurement (a potential difference between the working electrode and the reference electrode in a state where the working electrode and the counter electrode are electrically disconnected). Note that two or more cycles were measured, and data in the second cycle was used.
<<Measurement Results of Oxidation Reaction Characteristics of 2′,7′tBu-2hppSF>>
As for measurement results of oxidation reaction characteristics of 2′,7′tBu-2hppSF,
According to the results in
According to
According to
As for existence of a peak (an extremum), in the case where x in Formula (1) below is greater than or equal to 20, it was determined that a peak in return scanning does not exist and the oxidation reaction generated by outward scanning is irreversible. Note that in Formula (1) below, a peak current value in outward scanning (the oxidation side) or a peak current value read from a potential value which is obtained by secondary differentiation and which has a peak on the positive side is Ipa, a current value at the initial potential in outward scanning (the oxidation side) is Ia0, the maximum current value in return scanning (the reduction side) is Ipc, and the current value at the initial potential when the potential is returned to the initial potential in return scanning is Ic0. x is a variable.
According to
According to
Accordingly, in the oxidation potential measurement of 2′,7′tBu-2hppSF in the case of using acetonitrile as a solvent, a peak potential in return scanning was not observed by CV measurement at a scan rate of 1.0 V/s. Therefore, 2′,7′tBu-2hppSF, which is an organic compound of one embodiment of the present invention, is a material whose electron oxidation is irreversible.
Furthermore, a 2′,7′tBu-2hppSF solution using DMF as a solvent was subjected to an electron oxidation reaction at around 0.6 V, and then LC-MS measurement was performed in a manner similar to that of LC-MS measurement performed on the light-emitting device 1A. The results are described later in Example 2. According to the results in Example 2, an increase in ion intensity of a signal with m/z 564 was observed in the 2′,7′tBu-2hppSF solution subjected to the electron oxidation reaction as in the light-emitting device 1A subjected to energization, compared with the solution before the electron oxidation reaction. Since an oxidation reaction of the DMF solution of 2′,7′tBu-2hppSF is irreversible as described in Example 2, a hydrogen dissociation reaction occurs, leading to an increase in m/z 564. Also in the above-described light-emitting device 1A, a reaction similar to the oxidation reaction at the time of CV measurement is generated by oxidation (hole injection) of 2′,7′tBu-2hppSF by driving, hydrogen dissociation occurs and ion intensity of a signal with m/z 564 increases.
A structural formula of 8,8′-pyridine-2,6-diyl-bis(5,6,7,8-tetrahydroimidazo[1,2-a]pyrimidine) (abbreviation: 2,6tip2Py), which is an organic compound used for a light-emitting device 1B, is shown below.
As illustrated in
The first EL layer 903 has a structure in which the hole-injection layer 910, the first hole-transport layer 911, the first light-emitting layer 912, and the first electron-transport layer 913 are stacked in this order. The intermediate layer 905 includes the electron-injection buffer region 914 and the layer 915 including an electron-relay region and a charge-generation region. The second EL layer 904 has a structure in which the second hole-transport layer 916, the second light-emitting layer 917, the second electron-transport layer 918, and the electron-injection layer 919 are stacked in this order.
First, as a reflective electrode, an alloy containing silver (Ag), palladium (Pd), and copper (Cu) was deposited over the substrate 900 that is a glass substrate to a thickness of 100 nm by a sputtering method, and then, as a transparent electrode, indium tin oxide containing silicon oxide (ITSO) was deposited to a thickness of 100 nm by a sputtering method, so that the first electrode 901 was formed. The electrode area was set to 4 mm2 (2 mm×2 mm).
Next, the first EL layer 903 was provided. First, in pretreatment for forming the light-emitting device 1B over the substrate, a surface of the substrate was washed with water and baking was performed at 200° C. for 1 hour. Then, the substrate was transferred into a vacuum evaporation apparatus where the pressure was reduced to approximately 1×10−4 Pa, and vacuum baking was performed at 170° C. for 30 minutes in a heating chamber of the vacuum evaporation apparatus. After that, natural cooling was performed for approximately 30 minutes.
Then, the substrate provided with the first electrode 901 was fixed to a substrate holder provided in the vacuum evaporation apparatus such that the surface on which the first electrode 901 was formed faced downward. Over the first electrode 901, PCBBiF and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited by co-evaporation using resistance heating to a thickness of 10 nm such that the weight ratio of PCBBiF to OCHD-003 was 1:0.03, whereby the hole-injection layer 910 was formed.
Next, PCBBiF was deposited by evaporation to a thickness of 60 nm over the hole-injection layer 910, so that the first hole-transport layer 911 was formed.
Next, the first light-emitting layer 912 was formed over the first hole-transport layer 911. Using a resistance-heating method, 4, 8mDBtP2Bfpm, PNCCP, and Ir(ppy)2(mbfpypy-d3) were deposited to a thickness of 40 nm by co-evaporation such that the weight ratio of 4,8mDBtP2Bfpm to βNCCP and Ir(ppy)2(mbfpypy-d3) was 5:5:1, whereby the first light-emitting layer 912 was formed.
Next, over the first light-emitting layer 912, 2mPCCzPDBq was deposited to a thickness of 10 nm by evaporation, and then mPPhen2P was deposited to a thickness of 15 nm by evaporation, whereby the first electron-transport layer 913 was formed.
Next, the intermediate layer 905 was provided. First, over the first electron-transport layer 913, mPPhen2P and 2,6tip2Py were deposited to a thickness of 5 nm by co-evaporation using a resistance-heating method such that the weight ratio of mPPhen2P to 2,6tip2Py was 1:0.5, whereby a layer serving as the electron-injection buffer region 914 was formed.
Then, as the electron-relay region, copper phthalocyanine (abbreviation: CuPc) was deposited to a thickness of 2 nm. Next, as the charge-generation region, PCBBiF and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited by co-evaporation using resistance heating to a thickness of 10 nm such that the weight ratio of PCBBiF to OCHD-003 was 1:0.15, whereby the layer 915 including the charge-generation region was formed.
Next, the second EL layer 904 was provided. First, PCBBiF was deposited by evaporation to a thickness of 40 nm, so that the second hole-transport layer 916 was formed.
Next, using a resistance-heating method, 4, 8mDBtP2Bfpm, PNCCP, and Ir(ppy)2(mbfpypy-d3) were deposited to a thickness of 40 nm by co-evaporation such that the weight ratio of 4,8mDBtP2Bfpm to PNCCP and Ir(ppy)2(mbfpypy-d3) was 5:5:1, whereby the second light-emitting layer 917 was formed.
Next, over the second light-emitting layer 917, 2mPCCzPDBq was deposited to a thickness of 20 nm by evaporation, and then mPPhen2P was deposited to a thickness of 20 nm by evaporation, whereby the second electron-transport layer 918 was formed.
Here, after the light-emitting device 1B was exposed to the air, an aluminum oxide (AlOx) film with a thickness of 30 nm was formed by an ALD method, and an oxide containing indium, gallium, and zinc (abbreviation: IGZO) was deposited to a thickness of 50 nm by a sputtering method. After that, a resist was formed using a photoresist, and the IGZO was processed into a predetermined shape by a lithography method (dry etching). Specifically, a slit with a width of 3 μm was formed in a position 3.5 μm away from the end portion of the first electrode 901.
Next, using the IGZO as a mask, the stacked-layer structure formed of the aluminum oxide film, the first EL layer 903, the intermediate layer 905, the second hole-transport layer 916, the second light-emitting layer 917, and the second electron-transport layer 918 was processed into a predetermined shape, and then the IGZO and the aluminum oxide film were removed. The IGZO and the aluminum oxide film were removed by wet etching using a basic chemical solution.
Next, heat treatment was performed in vacuum at 110° C. for one hour. The heat treatment can remove moisture or the like attached by the above-described processing, the exposure to the air, or the like.
Next, over the second electron-transport layer 918, lithium fluoride (LiF) and ytterbium (Yb) were deposited by co-evaporation to a thickness of 1.5 nm such that the volume ratio of LiF to Yb was 2:1, whereby the electron-injection layer 919 was formed.
Next, over the electron-injection layer 919, Ag and Mg were deposited by co-evaporation to a thickness of 15 nm such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode 902 was formed. Note that the second electrode 902 is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.
Then, DBT3P-II was deposited by evaporation to a thickness of 70 nm as a cap layer.
Through the above process, the light-emitting device 1B was fabricated in an MML process accompanied with exposure to the air. The structure of the light-emitting device 1B is listed in the following table.
The light-emitting device 1B was sealed using a glass substrate in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (a sealing material was applied to surround the device, and at the time of sealing, UV treatment was performed and then heat treatment was performed at 80° C. for an hour). Then, the light-emitting device 1B was driven with a current density of 50 mA/cm2 for 20 hours. After that, the emission characteristics of the light-emitting device 1B were measured.
Furthermore, as shown in
The light-emitting device 1B was subjected to processing of end surfaces of the first hole-transport layer 911 to the second electron-transport layer 918 by a lithography method and processing of a surface of the second electron-transport layer 918 and the end surfaces of the first hole-transport layer 911 to the second electron-transport layer 918 by wet etching. Nevertheless, it was confirmed that the light-emitting region of 2 mm×2 mm emits light uniformly without a noticeable shrinkage. Therefore, the light-emitting device of one embodiment of the present invention can be suitably used in a patterning process.
As described later, 2,6tip2Py is an organic compound whose electron oxidation is irreversible. In this manner, a film containing 2,6tip2Py that is an organic compound whose electron oxidation is irreversible functions as an intermediate layer of a tandem light-emitting device and has favorable characteristics though passing through the air exposure, the lithography process, or wet etching process.
<<Measurement Results of Oxidation Reaction Characteristics of 2,6tip2Py>>
The electrochemical characteristics of 2,6tip2Py used for the light-emitting device 1B were measured. Note that for the measurement method, <<Measurement method of electrochemical characteristics (oxidation reaction characteristics)>> described above can be referred to.
<<Fabrication of Sample of 2,6tip2Py>>
A sample was fabricated in the following manner: with use of a dehydrated solvent N,N-dimethylformamide (DMF) (produced by Sigma-Aldrich Co., Ltd., 99.8%) as a solvent, tetra-n-butylammonium perchlorate (n-Bu4NClO4) (produced by Tokyo Chemical Industry Co., Ltd.), which is a supporting electrolyte, was dissolved to have a concentration of 100 mmol/L; 2,6tip2Py, which is a measurement target, was dissolved to have a concentration of 2 mmol/L; and the resulting solution was subjected to bubbling with argon (Ar) for 30 minutes.
<<Measurement Results of Oxidation Reaction Characteristics of 2,6tip2Py>>
As the measurement results, an oxidation peak derived from 2,6tip2Py was observed at around 0.47 V in outward scanning. Meanwhile, in return scanning, an obvious reduction peak derived from 2,6tip2Py was not detected.
As for existence of a peak in return scanning, in the case where Formula (1) above is satisfied, it was determined that the peak in return scanning does not exist and the oxidation reaction generated by outward scanning is irreversible.
According to
A structural formula of 2-[4-(1,3-dimethyl-2H-benzimidazol-2-yl)phenyl]-1,3-dimethyl-2H-benzimidazole (abbreviation: Dhbi2P), which is an organic compound used for a light-emitting device 1C and a light-emitting device 1C-S which are comparative examples, is shown below.
As illustrated in
The first EL layer 903 has a structure in which the hole-injection layer 910, the first hole-transport layer 911, the first light-emitting layer 912, and the first electron-transport layer 913 are stacked in this order. The intermediate layer 905 includes the electron-injection buffer region 914 and the layer 915 including an electron-relay region and a charge-generation region. The second EL layer 904 has a structure in which the second hole-transport layer 916, the second light-emitting layer 917, the second electron-transport layer 918, and the electron-injection layer 919 are stacked in this order.
The light-emitting device 1C-S has a single structure of the light-emitting device 1C and thus has a structure in which part of the intermediate layer and the second EL layer 904 are removed from the light-emitting device 1C. That is, the light-emitting device 1C-S has a structure in which a first electrode, a first EL layer over the first electrode, an electron-injection layer corresponding to the electron-injection buffer region 914 over the first EL layer, and a second electrode over the electron-injection layer are sequentially stacked.
First, as a reflective electrode, an alloy containing silver (Ag), palladium (Pd), and copper (Cu) was deposited over the substrate 900 that is a glass substrate to a thickness of 100 nm by a sputtering method, and then, as a transparent electrode, indium tin oxide containing silicon oxide (ITSO) was deposited to a thickness of 85 nm by a sputtering method, so that the first electrode 901 was formed. The electrode area was set to 4 mm2 (2 mm×2 mm).
Next, the first EL layer 903 was provided. First, in pretreatment for forming the light-emitting device 1C over the substrate, a surface of the substrate was washed with water and baking was performed at 200° C. for 1 hour. Then, the substrate was transferred into a vacuum evaporation apparatus where the pressure was reduced to approximately 1×10−4 Pa, and vacuum baking was performed at 170° C. for 30 minutes in a heating chamber of the vacuum evaporation apparatus. After that, natural cooling was performed for approximately 30 minutes.
Then, the substrate provided with the first electrode 901 was fixed to a substrate holder provided in the vacuum evaporation apparatus such that the surface on which the first electrode 901 was formed faced downward. Over the first electrode 901, PCBBiF and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited by co-evaporation using resistance heating to a thickness of 10 nm such that the weight ratio of PCBBiF to OCHD-003 was 1:0.03, whereby the hole-injection layer 910 was formed.
Next, PCBBiF was deposited by evaporation to a thickness of 70 nm over the hole-injection layer 910, so that the first hole-transport layer 911 was formed.
Next, the first light-emitting layer 912 was formed over the first hole-transport layer 911. The first light-emitting layer 912 was formed by depositing 2-[4′-(9-phenyl-9H-carbazol-3-yl)-3,1′-biphenyl-1-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mpPCBPDBq), PCBBiF, and tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: Ir(tBuppm)3) to a thickness of 40 nm by co-evaporation using resistance heating such that the weight ratio of 2mpPCBPDBq to PCBBiF and Ir(tBuppm)3 was 0.8:0.2:0.06.
Next, over the first light-emitting layer 912, 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen) was deposited by evaporation to a thickness of 10 nm, whereby the first electron-transport layer 913 was formed.
Next, the intermediate layer 905 was provided. First, over the first electron-transport layer 913, NBPhen and Dhbi2P were deposited to a thickness of 10 nm by co-evaporation using a resistance-heating method such that the weight ratio of NBPhen to Dhbi2P was 0.5:0.5, whereby a layer serving as the electron-injection buffer region 914 was formed.
Then, as the electron-relay region, copper phthalocyanine (abbreviation: CuPc) was deposited to a thickness of 2 nm. Next, as the charge-generation region, PCBBiF and a fluorine-containing electron acceptor material with a molecular weight of 672 (OCHD-003) were deposited by co-evaporation using resistance heating to a thickness of 10 nm such that the weight ratio of PCBBiF to OCHD-003 was 1:0.15, whereby the layer 915 including the charge-generation region was formed.
Next, the second EL layer 904 was provided. First, PCBBiF was deposited by evaporation to a thickness of 40 nm, so that the second hole-transport layer 916 was formed.
Next, 2mpPCBPDBq, PCBBiF, and Ir(tBuppm)3 were deposited by co-evaporation using resistance heating to a thickness of 40 nm such that the weight ratio of 2mpPCBPDBq to PCBBiF and Ir(tBuppm)3 was 0.8:0.2:0.06, whereby the second light-emitting layer 917 was formed.
Next, over the second light-emitting layer 917, 2mPCCzPDBq was deposited to a thickness of 10 nm by evaporation, and then NBPhen was deposited to a thickness of 10 nm by evaporation, whereby the second electron-transport layer 918 was formed.
Here, after the light-emitting device 1C was exposed to the air, an aluminum oxide (AlOx) film with a thickness of 30 nm was formed by an ALD method, and an oxide containing indium, gallium, and zinc (abbreviation: IGZO) was deposited to a thickness of 50 nm by a sputtering method. After that, a resist was formed using a photoresist, and the IGZO was processed into a predetermined shape by a lithography method. Specifically, a slit with a width of 3 μm was formed in a position 3.5 μm away from the end portion of the first electrode 901.
Next, using the IGZO as a mask, the stacked-layer structure formed of the aluminum oxide film, the first EL layer 903, the intermediate layer 905, the second hole-transport layer 916, the second light-emitting layer 917, and the second electron-transport layer 918 was processed into a predetermined shape, and then the IGZO and the aluminum oxide film were removed. The IGZO and the aluminum oxide film were removed by wet etching using a basic chemical solution.
Next, heat treatment was performed in vacuum at 110° C. for one hour. The heat treatment can remove moisture or the like attached by the above-described processing, the exposure to the air, or the like.
Next, lithium fluoride (LiF) was deposited by evaporation to a thickness of 1.0 nm over the second electron-transport layer 918, whereby the electron-injection layer 919 was formed.
Next, over the electron-injection layer 919, Ag and Mg were deposited by co-evaporation to a thickness of 15 nm such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode 902 was formed. Note that the second electrode 902 is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.
Then, DBT3P-II was deposited by evaporation to a thickness of 70 nm as a cap layer.
Through the above process, the light-emitting device C was fabricated in an MML process accompanied with exposure to the air. The structure of the light-emitting device C is listed in the following table.
The light-emitting device 1C-S has a single structure that includes the same first EL layer as the light-emitting device 1C and does not include the second EL layer. Thus, the light-emitting device 1C-S was fabricated in a manner similar to that of the light-emitting device 1C up to the electron-injection buffer region 914 corresponding to the electron-injection layer.
Over the electron-injection buffer region 914 (the electron-injection layer), Ag and Mg were deposited by co-evaporation to a thickness of 15 nm such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode 902 was formed. Note that the second electrode 902 is a semi-transmissive and semi-reflective electrode having functions of transmitting light and reflecting light.
Then, DBT3P-II was deposited by evaporation to a thickness of 70 nm as a cap layer.
Through the above process, the light-emitting device 1C-S was fabricated in an MML process accompanied with exposure to the air. The structure of the light-emitting device 1C-S is listed in the following table.
The light-emitting device 1C was sealed using a glass substrate in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (a sealing material was applied to surround the device, and at the time of sealing, UV treatment was performed and then heat treatment was performed at 80° C. for an hour). Then, the light-emitting device 1C was driven with a current density of 50 mA/cm2 for 20 hours. After that, the emission characteristics of the light-emitting device 1C were measured.
According to
Furthermore, as shown in
The electrochemical characteristics of Dhbi2P used for the light-emitting device 1C were measured. For fabrication of a sample, DMF was used as a solvent as in 2′,7′tBu-2hppSF or 2,6tip2Py. Note that for the measurement method, <<Measurement method of electrochemical characteristics (oxidation reaction characteristics)>> described above can be referred to.
According to
The electrochemical characteristics of 2-(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidin-1-yl)-9-phenyl-1,10-phenanthroline (abbreviation: 9Ph-2hppPhen), which is an organic compound that can be used for the light-emitting device of one embodiment of the present invention, and 1-(9,9′-spirobi[9H-fluoren]-2-yl)-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (abbreviation: 2hppSF) were measured. Specifically, a peak current of the oxidation current (Ipa) and a peak current of the reduction current (Ipc), which are obtained by changing potential of the working electrode with respect to the reference electrode, were measured by cyclic voltammetry (CV). Note that for the measurement method, <<Measurement method of electrochemical characteristics (oxidation reaction characteristics)>> described above can be referred to.
As a reference, the measurement results shown in
Samples of 9Ph-2hppPhen, which is an organic compound that can be used for the light-emitting device of one embodiment of the present invention, and 2hppSF were fabricated using a dehydrated solvent N,N-dimethylformamide (DMF) (produced by Sigma-Aldrich Co., Ltd., 99.8%). Specifically, each sample was fabricated in the following manner: with use of a dehydrated solvent N,N-dimethylformamide (DMF) (produced by Sigma-Aldrich Co., Ltd., 99.8%) as a solvent, tetra-n-butylammonium perchlorate (n-Bu4NClO4) (produced by Tokyo Chemical Industry Co., Ltd.), which is a supporting electrolyte, was dissolved to have a concentration of 100 mmol/L; any of 9Ph-2hppPhen, 2hppSF, and Dhbi2P, which is a measurement target, was dissolved to have a concentration of 2 mmol/L; and the resulting solution was subjected to bubbling with argon (Ar) for 30 minutes.
In addition to the sample of 2hppSF using the DMF as the solvent, a sample of 2hppSF using acetonitrile as a solvent was fabricated. Specifically, with use of acetonitrile as a solvent, tetra-n-butylammonium perchlorate (n-Bu4NClO4) (produced by Tokyo Chemical Industry Co., Ltd.), which is a supporting electrolyte, was dissolved to have a concentration of 100 mmol/L; 2′,7′tBu-2hppSF, which is a measurement target, was dissolved to have a concentration of 2 mmol/L; and the resulting solution was subjected to bubbling with argon (Ar) for 30 minutes.
According to
<<Measurement Results of Oxidation Reaction Characteristics of 2hppSF>>
As for measurement results of 2hppSF,
As shown in
According to
As shown in
According to
Therefore, it was found from
According to
As for the measurement results of the samples of 2′,7′tBu-2hppSF and 2hppSF each using acetonitrile as a solvent, an absolute value of a difference between the current value Ipa at the peak potential in outward scanning and the current value Ia0 at the initial potential in outward scanning and an absolute value of a difference between the peak potential Ipc in return scanning and the current value Ic0 at the initial potential when the potential is returned to the initial potential in return scanning are listed in the following table. The unit is μA. It was confirmed that when each of these organic compounds that can be used for the light-emitting device of one embodiment of the present invention is applied to Formula (1) above, the value of x in Formula (1) above becomes greater than or equal to 20, preferably greater than or equal to 50. In this manner, when the solvent is changed, irreversible reactions to electron oxidation remained, and thus similar results were obtained.
In general, for an OLED typified by a light-emitting device, an organic compound whose electron oxidation or electron reduction is reversible is used. This is because in the case where an organic compound whose electron oxidation or electron reduction is irreversible is used, a degradation material (a substance generated by an irreversible reaction) is thought to adversely affect the reliability. Meanwhile, the organic compounds used for the light-emitting devices of one embodiment of the present invention exhibited an irreversible reaction to electron oxidation.
Furthermore, 2′,7′tBu-2hppSF was measured by LC-MS after the electron oxidation reaction, so that the detection intensities of m/z 562 and m/z 564 were increased. That is, it is considered that in the organic compound used for the light-emitting device of one embodiment of the present invention, a hydrogen cation (a proton) is easily dissociated by electron oxidation.
Furthermore, in the case where each of 2′,7′tBu-2hppSF, 2,6tip2Py, and 9Ph-2hppPhen was used for an intermediate layer of a light-emitting device, the light-emitting device was driven as appropriate.
As described above, when 2′,7′tBu-2hppSF, 2,6tip2Py, and 9Ph-2hppPhen whose peak potential cannot be observed in return scanning of CV measurement of oxidation potential at a scan rate of 1.0 V/s are used for intermediate layers of light-emitting devices, the favorable light-emitting devices can be provided.
In this example, a change of 1-(2′,7′-di-tert-butyl-9,9′-spirobi[9H-fluoren]-2-yl)-1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (abbreviation: 2′,7′tBu-2hppSF), which is an organic compound that can be used for the light-emitting device of one embodiment of the present invention, due to energization was analyzed by ultra-high-performance liquid chromatography mass spectroscopy (UHPLC). The structural formula of 2′,7′tBu-2hppSF is shown below.
<LC-MS Measurement of 2′,7′tBu-2hppSF>
A solvent used for the measurement was N,N-dimethylformamide (DMF), which is a polar solvent. As the DMF, a super-dehydrated solvent (produced by FUJIFILM Wako Pure Chemical Corporation, product number: 043-32361) was used because of its high moisture absorbency. An electrolyte was tetra-n-butylammonium perchlorate (produced by Tokyo Chemical Industry Co., Ltd., product number: T0836).
The measurement apparatus was an electrochemistry measurement apparatus ALS600A produced by BAS Inc., and a three-electrode method where a reference electrode is a silver-silver ion reference electrode, a working electrode is a platinum electrode, and an auxiliary electrode is a platinum electrode was used for the measurement. The diameter of the platinum (Pt) electrode as the working electrode was 3.0 mmΦ.
The solution was adjusted such that the concentration of 2′,7′tBu-2hppSF, which is a material to be measured, was 2 mmol/L as in the first sample. In the adjusted solution, 1 mL was stored in a light-blocking bottle in advance and was used as a reference solution (a sample 2A). In the adjusted solution, 4 mL was put into a CV measurement cell as a solution to be measured, the three electrodes were set, bubbling treatment in an inert gas (Ar gas) was performed for 30 minutes, and then CV measurement was started.
In the CV oxidation potential measurement, first, measurement was performed in a wide range from the initial potential to 1.5 V. Four segments (two cycles) measurement were performed, and the data of the third and fourth segments (the second cycle) was employed because, for example, a peak potential derived from the electrodes is likely to be observed in the first and second segments (the first cycle). As the CV oxidation potential measurement results, although a peak potential in outward scanning was observed at 0.4 V (vs. Ag/Ag+), a peak potential in return scanning was not observed; thus, a waveform indicating that electron oxidation of 2′,7′tBu-2hppSF is irreversible was obtained.
Next, 4 mL of the above solution to be measured was stirred under an inert gas (an Ar gas) stream while being applied with a predetermined potential, so that electrolytic oxidation was performed. Cycle scanning was performed in a range of electrolytic oxidation potential of 0.5 V to 0.6 V (vs. Ag/Ag+), which is slightly higher (+0.05 V to +0.15 V) than the peak potential in outward scanning according to the above CV oxidation potential measurement results. The scan rate at this time was set to 0.1 V/sec.
During the above energization, the solution to be measured was sampled several times. At the time of sampling, the cycle scanning was stopped temporarily and after the sampling was finished, the cycle scanning was restarted. The details of the sampling are described below. 0.05 mL of the solution taken out and stored in light-blocking bottles after 1.5 hours, 3.0 hours, and 20.5 hours from the start of energization, and was called a sample 2B, a sample 2C, and a sample 2D, respectively. The following table lists the samples.
Four samples, which were sampled before and after the energization, were diluted with acetonitrile by ten times and filtrated with a filter. Then, the samples were measured with a liquid chromatography mass spectrometer (LC-MS). The spectrometer is constructed of ACQUITY H-Class (produced by Waters Corporation) and ACQUITY UPLC HSS T3 Column (1.8 μm, 2.1 mm×100 mm) (produced by Waters Corporation, hereinafter referred to as Column) was used as a column.
The column temperature was set to 40° C. Acetonitrile was used for Mobile Phase A and a 0.1% formic acid aqueous solution was used for Mobile Phase B. The injection amount was set to 5 μL for each of the sample of the light-emitting device A and the single film of 2′,7′tBu-2hppSF for comparison after being energized.
In LC separation, a gradient method in which the composition of mobile phases is changed was employed. The ratio of Mobile Phase A to Mobile Phase B was 50:50 for 0 to 1 minute after the start of the measurement, and then the composition was changed such that the ratio of Mobile Phase A to Mobile Phase B after 25 minutes was 67:23. The composition was changed linearly.
The wavelength of a photodiode array (PDA) for the analysis was set to 254 nm.
<LC-MS Measurement Results of 2′,7′tBu-2hppSF>
As shown in
(Reference synthesis example 1) In this reference synthesis example, a specific method of synthesizing 2-(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidin-1-yl)-9-phenyl-1,10-phenanthroline (abbreviation: 9Ph-2hppPhen) represented by Structural Formula (102) below is described. The structure of 9Ph-2hppPhen is shown below.
Into a 200 mL three-neck flask, 6.1 g (21 mmol) of 2-chloro-9-phenyl-1,10-phenanthroline, 6.7 g (48 mmol) of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, and 100 mL of toluene were put, and stirring was performed at 100° C. for 11 hours under a nitrogen atmosphere. After a predetermined time, the reaction solution was concentrated, methanol was added to the solid, and an insoluble matter was removed by suction filtration. After the obtained filtrate was concentrated, toluene was added and heating was performed. The heated solution was subjected to hot filtration, whereby an insoluble matter was removed. The obtained filtrate was concentrated to give a solid. Ethyl acetate was added to the obtained solid, and suction filtration was carried out, whereby 5.3 g of a yellowish white solid was obtained in a yield of 64%. By a train sublimation method, 5.0 g of the obtained solid was purified. The purification by sublimation was performed by heating at 220° C. under a pressure of 3.0 Pa with an argon flow rate of 12 mL/min for 18 hours. After the purification by sublimation, 2.54 g of a yellowish white solid was obtained at a collection rate of 51%. Synthesis scheme (s1-1) is shown below.
The protons (1H) of the yellowish white solid of 9Ph-2hppPhen obtained by Synthesis scheme (s3-1) above were measured by nuclear magnetic resonance (NMR) spectroscopy. The obtained values are shown below.
1H NMR. δ (CDCl3, 500 MHz): 1.92-1.96 (m, 2H), 2.16-2.21 (m, 2H), 3.28-3.32 (m, 4H), 3.49 (t, J=5.73 Hz, 2H), 4.34 (t, J=5.73 Hz, 2H), 7.46 (t, J=7.45 Hz, 1H), 7.55 (d, J=7.45 Hz, 2H), 7.61 (d, J=8.59 Hz, 1H), 7.68 (d, J=8.59 Hz, 1H), 7.97 (d, J=9.16 Hz, 1H), 8.06 (d, J=8.02 Hz, 1H), 8.17 (d, J=9.16 Hz, 1H), 8.25 (d, J=8.02 Hz, 1H), 8.39 (d, J=6.87 Hz, 2H).
This application is based on Japanese Patent Application Serial No. 2023-066480 filed with Japan Patent Office on Apr. 14, 2023, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-066480 | Apr 2023 | JP | national |
