Patent Application
20250204248
One embodiment of the present invention relates to an organic compound, an organic semiconductor element, a light-emitting device, a photodiode sensor, a display module, a lighting module, a display device, 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 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 device, a liquid crystal display device, a lighting device, a power storage device, a memory device, an image capturing device, a driving method thereof, and a manufacturing method thereof.
A light-emitting device (also referred to as an organic EL element) including an organic compound that is a light-emitting substance between a pair of electrodes has characteristics such as being thin and light in weight, high-speed response, and low voltage driving. Thus, displays including such light-emitting devices have been developed. When a voltage is applied to this light-emitting device, electrons and holes injected from the electrodes recombine to put the light-emitting substance into an excited state. Light is emitted when the light-emitting substance returns to a ground state from the excited state. The excited state can be a singlet excited state (S*) and a triplet excited state (T*). Light emission from a singlet excited state is referred to as fluorescence, and light emission from a triplet excited state is referred to as phosphorescence. The formation ratio in the light-emitting device is considered to be S*:T*=1:3 according to the spin statistics.
As the above light-emitting substance, a compound capable of converting singlet excitation energy into light emission is called a fluorescent compound (fluorescent material), and a compound capable of converting triplet excitation energy into light emission is called a phosphorescent compound (phosphorescent material).
Accordingly, on the basis of the above generation ratio, the internal quantum efficiency (the ratio of the number of generated photons to the number of injected carriers) of a light-emitting device including a fluorescent material is thought to have a theoretical limit of 25%, while the internal quantum efficiency of a light-emitting device including a phosphorescent material is thought to have a theoretical limit of 75%.
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 achieve 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.
To improve device characteristics of the light-emitting devices, development of a substance, improvement of a device structure, and the like have been carried out. For example, Patent Document 1 discloses a light-emitting device or the like in which a novel anthracene derivative is used as a host material to obtain a light-emitting element with high emission efficiency.
An object of one embodiment of the present invention is to provide a novel organic compound. Another object of one embodiment of the present invention is to provide an organic compound that can be used for a light-emitting device. Another object of one embodiment of the present invention is to provide a light-emitting device having high emission efficiency. Another object of one embodiment of the present invention is to provide a high-color-purity light-emitting device. 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 any of low-power-consumption display device, electronic appliance, and lighting device. Another object of one embodiment of the present invention is to provide any of highly reliable display device, electronic appliance, and lighting device. Another object of one embodiment of the present invention is to provide any of high-color-purity display device, electronic appliance, and lighting device.
It is only necessary that at least one of the above-described objects be achieved in the present invention.
One embodiment of the present invention is an organic compound that includes a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton, a first substituent, and a second substituent. The first substituent represents a carbazole skeleton. The second substituent represents any of a carbazole skeleton, a dibenzofuran skeleton, a tetraphenylsilane skeleton, and a triphenylene skeleton. The first substituent is bonded to a pyrimidine ring included in the benzofuropyrimidine skeleton or the benzothienopyrimidine skeleton. The second substituent is bonded to a benzene ring included in the benzofuropyrimidine skeleton or the benzothienopyrimidine skeleton.
Another embodiment of the present invention is an organic compound that includes a benzofuro[3,2-d]pyrimidine skeleton or a benzothieno[3,2-d]pyrimidine skeleton, a first substituent, and a second substituent. The first substituent represents a carbazole skeleton. The second substituent represents any of a carbazole skeleton, a dibenzofuran skeleton, a tetraphenylsilane skeleton, and a triphenylene skeleton. The first substituent is bonded to a 4-position of the benzofuro[3,2-d]pyrimidine skeleton or a 4-position of the benzothieno[3,2-d]pyrimidine skeleton. The second substituent is bonded to an 8-position of the benzofuro[3,2-d]pyrimidine skeleton or an 8-position of the benzothieno[3,2-d]pyrimidine skeleton.
Another embodiment of the present invention is an organic compound represented by General Formula (G1).
In the above formula, R1 to R8 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms. R9 to R11 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group having 1 to 30 carbon atoms. X represents an oxygen atom or a sulfur atom. A1 represents any of substituents represented by General Formulae (A-1) to (A-5) below.
In the above formulae, R12 to R57 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group having 1 to 30 carbon atoms.
In the above organic compound, a lowest triplet excitation energy (T1) level is lower than or equal to 2.95 eV and higher than or equal to 2.75 eV.
Another embodiment of the present invention is an organic compound represented by Structural Formula (100), Structural Formula (101), Structural Formula (102), or Structural Formula (103).
Another embodiment of the present invention is a light-emitting device including a first electrode, a second electrode, and a light-emitting layer between the first electrode and the second electrode. The light-emitting layer includes a first organic compound, a second organic compound, and a light-emitting substance emitting blue light. The second organic compound includes a benzofuro[3,2-d]pyrimidine skeleton or a benzothieno[3,2-d]pyrimidine skeleton, a first substituent, and a second substituent. The first substituent represents a carbazole skeleton. The second substituent represents any of a carbazole skeleton, a dibenzofuran skeleton, a tetraphenylsilane skeleton, and a triphenylene skeleton. The first substituent is bonded to a 4-position of the benzofuro[3,2-d]pyrimidine skeleton or a 4-position of the benzothieno[3,2-d]pyrimidine skeleton. The second substituent is bonded to an 8-position of the benzofuro[3,2-d]pyrimidine skeleton or an 8-position of the benzothieno[3,2-d]pyrimidine skeleton. An absolute value of a difference between a HOMO level of the first organic compound and a LUMO level of the second organic compound is greater than or equal to 2.78 eV and less than or equal to 2.85 eV.
Another embodiment of the present invention is a light-emitting device including a first electrode, a second electrode, and a light-emitting layer between the first electrode and the second electrode. The light-emitting layer includes a first organic compound, a second organic compound that is represented by General Formula (G1), and a light-emitting substance emitting blue light. An absolute value of a difference between a HOMO level of the first organic compound and a LUMO level of the second organic compound is greater than or equal to 2.78 eV and less than or equal to 2.85 eV.
In the above formula, R1 to R8 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms. X represents an oxygen atom or a sulfur atom. A1 represents any of substituents represented by General Formulae (A-1) to (A-5) below.
In the above formulae, R12 to R57 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group having 1 to 30 carbon atoms.
Another embodiment of the present invention is a light-emitting device including an organic compound represented by Structural Formula (100), Structural Formula (101), Structural Formula (102), or Structural Formula (103).
In the above light-emitting device, a combination of the first organic compound and the second organic compound can form an exciplex.
In the above light-emitting device, an emission spectrum of the light-emitting substance is greater than or equal to 400 nm and less than 490 nm.
In the above light-emitting device, the light-emitting substance can emit phosphorescent light.
In the above light-emitting device, the light-emitting layer includes a fluorescent sensitizer.
Another embodiment of the present invention is a display device including any of the above light-emitting devices.
Another embodiment of the present invention is an electronic device that includes any of the above light-emitting devices and a sensor, an operation button, a speaker, or a microphone.
Another embodiment of the present invention is a lighting device that includes any of the above light-emitting devices and a housing.
According to one embodiment of the present invention, a novel organic compound can be provided. According to another embodiment of the present invention, an organic compound that can be used for a light-emitting device. According to another embodiment of the present invention, a light-emitting device having high emission efficiency can be provided. According to another embodiment of the present invention, a high-color-purity light-emitting device can be provided. According to another embodiment of the present invention, a highly reliable light-emitting device can be provided. According to another embodiment of the present invention, any of low-power-consumption display device, electronic appliance, and lighting device can be provided. According to another embodiment of the present invention, any of highly reliable display device, electronic appliance, and lighting device can be provided. According to another embodiment of the present invention, any of high-color-purity display device, electronic appliance, and lighting device can be provided.
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 of 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.
In the accompanying drawings:
Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the present invention is 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. Thus, the present invention should not be construed as being limited to the description in the following embodiments.
In this specification and the like, a device manufactured using a metal mask or a fine metal mask (FMM) is sometimes referred to as a device having a metal mask (MM) structure. In this specification and the like, a device manufactured without using a metal mask or an FMM is sometimes referred to as a device having a metal maskless (MML) structure.
In this embodiment, an organic compound of one embodiment of the present invention will be described.
One embodiment of the present invention is an organic compound that includes a benzofuropyrimidine skeleton or a benzothienopyrimidine skeleton, a first substituent, and a second substituent. The first substituent represents a carbazole skeleton. The second substituent represents any of a carbazole skeleton, a dibenzofuran skeleton, a tetraphenylsilane skeleton, and a triphenylene skeleton. The first substituent is bonded to a pyrimidine ring included in the benzofuropyrimidine skeleton or the benzothienopyrimidine skeleton. The second substituent is bonded to a benzene ring included in the benzofuropyrimidine skeleton or the benzothienopyrimidine skeleton.
In particular, the benzofuropyrimidine skeleton is preferably a benzofuro[3,2-d]pyrimidine skeleton, and the benzothienopyrimidine skeleton is preferably a benzothieno[3,2-d]pyrimidine skeleton. Each of the skeletons has a high triplet excitation energy level (T1 level) and a high electron-transport property and thus is most suitable for the material used for a light-emitting device that emits light in a blue region.
Another embodiment of the present invention is an organic compound that includes a benzofuro[3,2-d]pyrimidine skeleton or a benzothieno[3,2-d]pyrimidine skeleton, a first substituent, and a second substituent. The first substituent represents a carbazole skeleton. The second substituent represents any of a carbazole skeleton, a dibenzofuran skeleton, a tetraphenylsilane skeleton, and a triphenylene skeleton. The first substituent is bonded to the 4-position of the benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton. The second substituent is bonded to the 8-position of the benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton.
When a carbazole skeleton is at the 4-position of the benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton, expansion of conjugation can be inhibited, and an appropriate LUMO (Lowest Unoccupied Molecular Orbital) level can be maintained. In addition, the thermophysical property and the stability of a molecule can be improved while a high triplet excitation energy level (T1 level) is maintained.
When a substituent is at the 8-position of the benzofuro[3,2-d]pyrimidine skeleton or the 8-position of the benzothieno[3,2-d]pyrimidine skeleton, the thermophysical property and the stability of a molecule can be improved while a high triplet excitation energy level (T1 level) is maintained.
In the organic compound of one embodiment of the present invention, the lowest triplet excitation energy (T1) level is lower than or equal to 2.95 eV and higher than or equal to 2.75 eV.
The lowest triplet excitation energy (T1) of an organic compound can be energy of the intersection of the horizontal axis (wavelength) or the base line and a tangent to the phosphorescent spectrum at a point where the slope of the phosphorescent spectrum at a peak on the shorter wavelength side has a maximum value (see Daisaku TANAKA et al., “Ultra High Efficiency Green Organic Light-Emitting Devices”, Japanese Journal of Applied Physics, Vol. 46, No. 1, 2007, pp. L10-L12, for example). As another method, when the v=0→v=0 transition (0→0 band) between vibrational levels of the ground state and the excited state is clearly observed from a phosphorescent spectrum, the T1 level can also be calculated using the 0→0 band (Nicholas J. Turro, V. Ramamurthy, J. C. Scaiano, “MODERN MOLECULAR PHOTOCHEMISTRY OF ORGANIC MOLECULES”, UNIVERSITY SCIENCE BOOKS, 2010 Feb. 10, pp. 204-208). In the case where the levels are compared with each other, those calculated by the same method are used.
Note that in this specification, for calculation of the lowest triplet excitation energy level (T1 level), an emission spectrum (a phosphorescence spectrum) is measured at a measurement temperature of 10 K using a 50-nm-thick thin film of a sample formed over a quartz substrate. The measurement is preferably performed with a PL microscope (LabRAM HR-PL, produced by HORIBA, Ltd.) and a He—Cd laser (325 nm) as excitation light. Note that the emission edge is determined as the intersection of a tangent and the horizontal axis (representing wavelength) or the baseline. The tangent is drawn to have the maximum slope at a point on a shorter wavelength side of the shortest-wavelength peak (or the shortest-wavelength shoulder peak) of the emission spectrum (phosphorescence spectrum).
One embodiment of the present invention is an organic compound represented by General Formula (G1).
R1 to R8 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms. R9 to R11 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group having 1 to 30 carbon atoms. X represents an oxygen atom or a sulfur atom. A1 represents any of substituents represented by General Formulae (A-1) to (A-5) below.
Note that R12 to R57 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group having 1 to 30 carbon atoms.
Specific examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, a hexyl group, an isohexyl group, a 3-methylpentyl group, a 2-methylpentyl group, a 2-ethylbutyl group, a 1,2-dimethylbutyl group, and a 2,3-dimethylbutyl group.
Specific examples of the substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononanyl group, a cyclodecyl group, and a cyclododecyl group. Examples of the cycloalkyl group having 4 to 10 carbon atoms and having a bridged structure include a bicyclobutyl group, a noradamantyl group, an adamantyl group, a norbornanyl group, and a tetrahydrodicyclopentadienyl group.
Specific examples of the aryl group having 6 to 30 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, an indenyl group, a naphthyl group, a fluorenyl group, a spirofluorenyl group, a phenanthrenyl group, and a triphenylenyl group.
Specific examples of the heteroaryl group having 1 to 30 carbon atoms include a group including a triazine ring, a group including a pyrimidine ring, a group including a pyridine ring, a group including a phenanthroline ring, a group including a carbazole ring, a group including a dibenzofuran ring, a group including a dibenzothiophene ring, a group including a benzonaphthofuran ring, a group including a benzonaphthothiophene ring, a group including an indolocarbazole ring, a group including a benzofurocarbazole ring, a group including a benzothienocarbazole ring, a group including an indenocarbazole ring, and a group including a dibenzocarbazole ring.
In General Formulae (G1) and (A-1) to (A-5), hydrogen may be replaced with deuterium as appropriate.
The following are specific examples of the organic compound of one embodiment of the present invention having the structure represented by General Formula (G1) above.
The organic compounds represented by Structural Formulae (100) to (114) and (200) to (214) above are examples of the organic compound represented by General Formula (G1); however, the organic compound of one embodiment of the present invention is not limited to the examples.
A synthesis method of the organic compound represented by the general formula (G1) is described below. A variety of reactions can be applied to the synthesis method of the organic compound.
As shown in Synthesis Scheme (S-1) below, the organic compound represented by General Formula (G1) above can be obtained in the following manner: a dihalogen compound (B1) having a benzofuro[3,2-d]pyrimidine skeleton or a benzothieno[3,2-d]pyrimidine skeleton is reacted with a carbazole compound (B2), and an intermediate (B3) is reacted with a boronic acid compound (B4) of A1.
In General Formula (B1) above, X represents an oxygen atom or a sulfur atom, and Y1 and Y2 represent halogen. Moreover, R1 to R8 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms; R9 to R11 each independently represent hydrogen (including deuterium), an alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group having 1 to 30 carbon atoms; and A1 represents any of substituents represented by General Formulae (A-1) to (A-5). Furthermore, Q represents a boronic acid, a boronic ester, a cyclic-triolborate salt, or the like. As the cyclic-triolborate salt, a lithium salt, a potassium salt, or a sodium salt may be used.
Examples of a palladium catalyst that can be used in the coupling reaction represented by Synthesis Scheme (S-1) above include palladium(II) acetate, tetrakis(triphenylphosphine)palladium(0), bis(triphenylphosphine)palladium(II) dichloride, and allylpalladium(II) chloride dimer.
Examples of a ligand of the above palladium catalyst include di(1-adamantyl)-n-butylphosphine, (±)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl, tri(ortho-tolyl)phosphine, triphenylphosphine, tricyclohexylphosphine, and di-tert-butyl(2,2-diphenyl-1-methyl-1-cyclopropyl)phosphine.
Examples of a base that can be used in the coupling reaction represented by Synthesis Scheme (S-1) above include an organic base such as potassium tert-butoxide and an inorganic base such as potassium carbonate, sodium carbonate, or tripotassium phosphate.
Examples of a solvent that can be used in the coupling reaction represented by Synthesis Scheme (S-1) above include toluene, xylene, mesitylene, benzene, tetrahydrofuran, dioxane, and diethylene glycol dimethyl ether. However, the solvent that can be used is not limited to these solvents.
The reaction employed in Synthesis Scheme (S-1) is not limited to a Suzuki-Miyaura reaction or a Buchwald-Hartwig reaction. A Migita-Kosugi-Stille coupling reaction using an organotin compound, a coupling reaction using a Grignard reagent, an Ullmann reaction using copper or a copper compound, a nucleophilic substitution reaction, or the like can be used.
The compounds (B1), (B2), and (B4) above can be of various kinds and can be used for the synthesis.
The organic compound of one embodiment of the present invention can be synthesized in the above manner, but the present invention is not limited to this and other synthesis methods may be employed.
This embodiment can be freely combined with any of the other embodiments and the examples.
In this embodiment, structures of a light-emitting device including the organic compound described in Embodiment 1 will be described.
It is a long time since displays (organic EL displays) that include organic EL elements (hereinafter also referred to as light-emitting devices) as display elements were put into practical use. These displays are usually provided with pixels emitting light with at least three colors of red, green, and blue to achieve full-color display.
The pixels are provided with light-emitting devices for the respective emission colors. In a display fabricated by a side-by-side method, or what is called a separate coloring method, light-emitting devices include light-emitting substances corresponding to the respective emission colors of the pixels.
It is known that in current-excitation type organic EL devices, the theoretical limit of the internal quantum efficiency of a light-emitting device using a fluorescent material, which can utilize only a singlet excited state for light emission, is 25% since the generation probability ratio of a singlet excited state to that of a triplet excited state is 1:3. By contrast, a phosphorescent material can convert a singlet excited state into a triplet excited state through intersystem crossing and thus enables a light-emitting device with an internal quantum efficiency of 100% theoretically, which allows the light-emitting device to have higher emission efficiency than the case of using the fluorescent material.
In the case where an organic compound (also referred to as a host material) to disperse a light-emitting substance is used in a light-emitting layer, the host material is preferably a substance having a triplet excitation energy level and a single excitation energy level that are higher than the triplet excitation energy level and the single excitation energy level of the light-emitting substance (also referred to as a guest material). In addition, blue light emission energy is higher than red or green light emission energy, and thus, a host material to disperse a blue-light-emitting substance preferably has a triplet excitation energy level and a singlet excitation energy level that are higher than those of a red- or green-light-emitting substance. Accordingly, the choice of the material is limited and it is difficult to obtain a material having high performance.
One embodiment of the present invention provides a light-emitting device using a phosphorescent material as a light-emitting substance and the organic compound described in Embodiment 1 as a host material. A structure of the light-emitting device of one embodiment of the present invention is described below.
The organic compound layer 103 illustrated in
Although description is given in this embodiment assuming that the first electrode 101 and the second electrode 102 of the pair of electrodes serve as an anode and a cathode, respectively, the structure of the light-emitting device 10 is not limited thereto. That is, the first electrode 101 may be a cathode, the second electrode 102 may be an anode, and the stacking order of the layers between the electrodes may be reversed. In other words, the hole-injection layer 111, the hole-transport layer 112, the light-emitting layer 113, the electron-transport layer 114, and the electron-injection layer 115 may be stacked in this order from the anode side.
The structure of the organic compound layer 103 is not limited to the structure illustrated in
The guest material 119 may be a light-emitting organic compound, and the light-emitting organic compound is preferably a substance capable of emitting phosphorescent light (hereinafter also referred to as a phosphorescent compound).
In the light-emitting layer 113, the host materials 118 are present in the largest proportion by weight, and the guest material 119 is dispersed in the host materials 118. As described above, the lowest triplet excitation energy level (T1 level) of the host materials 118 (the organic compound 118_1 and the organic compound 118_2) in the light-emitting layer 113 are preferably higher than the T1 level of the guest material 119 in the light-emitting layer 113.
Specifically, for example, in the case where a phosphorescent compound emitting blue light is used as the guest material 119, the lowest triplet excitation energy level (T1 level) of at least the organic compound 118_1 is preferably higher than or equal to 2.75 eV and lower than or equal to 2.95 eV.
The host materials 118 (the organic compound 118_1 and the organic compound 118_2) in the light-emitting layer 113 preferably form an exciplex. Note that an exciplex is an excited state formed by two or more kinds of substances. In photoexcitation, the exciplex is formed by interaction between one substance in an excited state and another substance in a ground state.
Specifically, for example, in the case where a phosphorescent compound emitting blue light is used as the guest material 119, it is difficult to form an exciplex whose emission (PL) spectrum overlaps with the absorption spectrum of the guest material 119 when the absolute value of the difference between the LUMO level of the organic compound 118_1 and the HOMO level of the organic compound 1182 is lower than or equal to 2.70 eV. In the case where the LUMO level of the organic compound 118_1 is too low, an exciplex having low energy is formed between the HOMO level of the guest material 119 and the LUMO level of the organic compound 118_1, and the emission spectrum might be broadened.
In view of this, the intermolecular interaction between the organic compound 118_1 and the guest material 119 is made small, so that a sharp emission spectrum can be obtained.
Thus, a light-emitting device that exhibits a favorable blue color can be provided by employing the following structure: the lowest triplet excitation energy level (T1 level) of the organic compound 118_1 is greater than or equal to 2.75 eV and less than or equal to 2.95 eV, and the absolute value of the difference between the LUMO level of the organic compound 118_1 and the HOMO level of the organic compound 118_2 is greater than or equal to 2.75 eV and less than or equal to 2.85 eV, preferably greater than or equal to 2.78 eV and less than or equal to 2.85 eV
The organic compound of one embodiment of the present invention, which is described in Embodiment 1, can be used as the organic compound 118_1. The organic compound includes a benzofuro[3,2-d]pyrimidine skeleton or a benzothieno[3,2-d]pyrimidine skeleton, a first substituent, and a second substituent. The first substituent represents a carbazole skeleton. The second substituent represents any of a carbazole skeleton, a dibenzofuran skeleton, a tetraphenylsilane skeleton, and a triphenylene skeleton. The first substituent is bonded to the 4-position of the benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton. The second substituent is bonded to the 8-position of the benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton.
In particular, in the organic compound represented by General Formula (G1), when hydrogen is bonded to the 2-position of the benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton, the organic compound can be inhibited from becoming bulky. This facilitates interaction with the organic compound 118_2 and formation of an exciplex.
In the organic compound represented by General Formula (G1), when a substituent is bonded to the 8-position of the benzofuro[3,2-d]pyrimidine skeleton or the benzothieno[3,2-d]pyrimidine skeleton, stability of the molecule and the thermophysical property can be improved while a high triplet excitation energy level (T1 level) is maintained, and thus, the reliability of the light-emitting device can be improved.
Basic structures of the light-emitting device will be described in more detail with reference to
The charge-generation layer 106 has a function of injecting electrons into one of the organic compound layers 103a and 103b and injecting holes into the other of the organic compound layers 103a and 103b when a potential difference is caused between the first electrode 101 and the second electrode 102. Thus, when voltage is applied in
Note that in terms of light extraction efficiency, the charge-generation layer 106 preferably has a property of transmitting visible light (specifically, the charge-generation layer 106 preferably has a visible light transmittance higher than or equal to 40%). The charge-generation layer 106 functions even if it has lower conductivity than the first electrode 101 and the second electrode 102.
The light-emitting layer 113 included in the organic compound layers (103, 103a, and 103b) includes an appropriate combination of a light-emitting substance and a plurality of substances, so that fluorescent light of a desired color or phosphorescent light of a desired color can be obtained. The light-emitting layer 113 may have a stacked-layer structure having different emission colors. In that case, a light-emitting substance and other substances are different between the stacked light-emitting layers. Alternatively, the plurality of organic compound layers (103a and 103b) in
The light-emitting device of one embodiment of the present invention can have a micro optical resonator (microcavity) structure when, for example, the first electrode 101 is a reflective electrode and the second electrode 102 is a transflective electrode in
Note that when the first electrode 101 of the light-emitting device is a reflective electrode having a stacked-layer structure of a reflective conductive material and a light-transmitting conductive material (transparent conductive film), optical adjustment can be performed by adjusting the thickness of the transparent conductive film. Specifically, when the wavelength of light obtained from the light-emitting layer 113 is λ, the optical path length between the first electrode 101 and the second electrode 102 (the product of the thickness and the refractive index) is preferably adjusted to be mλ/2 (m is an integer greater than or equal to 1) or close to mλ/2.
To amplify desired light (wavelength: λ) obtained from the light-emitting layer 113, it is preferable to adjust each of the optical path length from the first electrode 101 to a region where the desired light is obtained in the light-emitting layer 113 (light-emitting region) and the optical path length from the second electrode 102 to the region where the desired light is obtained in the light-emitting layer 113 (light-emitting region) to be (2m′+1) λ/4 (m′ is an integer greater than or equal to 1) or close to (2m′+1) λ/4. Here, the light-emitting region means a region where holes and electrons are recombined in the light-emitting layer 113.
By such optical adjustment, the spectrum of specific monochromatic light obtained from the light-emitting layer 113 can be narrowed and light emission with high color purity can be obtained.
In the above case, the optical path length between the first electrode 101 and the second electrode 102 is, to be exact, the total thickness from a reflective region in the first electrode 101 to a reflective region in the second electrode 102. However, it is difficult to precisely determine the reflective regions in the first electrode 101 and the second electrode 102; thus, it is assumed that the above effect can be sufficiently obtained wherever the reflective regions may be set in the first electrode 101 and the second electrode 102. Furthermore, the optical path length between the first electrode 101 and the light-emitting layer that emits the desired light is, to be exact, the optical path length between the reflective region in the first electrode 101 and the light-emitting region in the light-emitting layer that emits the desired light. However, it is difficult to precisely determine the reflective region in the first electrode 101 and the light-emitting region in the light-emitting layer that emits the desired light; thus, it is assumed that the above effect can be sufficiently obtained wherever the reflective region and the light-emitting region may be set in the first electrode 101 and the light-emitting layer that emits the desired light, respectively.
The light-emitting device illustrated in
The light-emitting device illustrated in
In the above light-emitting device of one embodiment of the present invention, at least one of the first electrode 101 and the second electrode 102 is a light-transmitting electrode (e.g., a transparent electrode or a transflective electrode). In the case where the light-transmitting electrode is a transparent electrode, the transparent electrode has a visible light transmittance higher than or equal to 40%. In the case where the light-transmitting electrode is a transflective electrode, the transflective electrode has a visible light reflectance higher than or equal to 20% and lower than or equal to 80%, preferably higher than or equal to 40% and lower than or equal to 70%. These electrodes preferably have a resistivity lower than or equal to 1×10−2 Qcm.
When one of the first electrode 101 and the second electrode 102 is a reflective electrode in the above light-emitting device of one embodiment of the present invention, the visible light reflectance of the reflective electrode is higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 70% and lower than or equal to 100%. This electrode preferably has a resistivity lower than or equal to 1×10−2 Ωcm.
Next, a specific structure of the light-emitting device of one embodiment of the present invention will be described. Here, the description is made using
The light-emitting layers (113, 113a, and 113b) include a light-emitting substance. Note that as a light-emitting substance that can be used in the light-emitting layers (113, 113a, and 113b), a substance whose emission color is blue, violet, bluish violet, green, yellowish green, yellow, orange, red, or the like can be used as appropriate. When a plurality of light-emitting layers are provided, the use of different light-emitting substances for the light-emitting layers enables exhibiting different emission colors (e.g., white light emission obtained by a combination of complementary emission colors). Furthermore, one light-emitting layer may have a stacked-layer structure including different light-emitting substances.
The light-emitting layers (113, 113a, and 113b) may each include one or more kinds of organic compounds (e.g., a host material) in addition to a light-emitting substance (a guest material).
Specifically, the light-emitting layer 113 can have the structure that is described in Embodiment 1 with reference to
As the organic compound 118_1, a material having an electron-transport property higher than a hole-transport property can be used, and a material having an electron mobility higher than or equal to 1×10−6 cm2/Vs is preferable. A compound having a π-electron deficient heteroaromatic ring skeleton such as a nitrogen-containing heteroaromatic compound, or a zinc- or aluminum-based metal complex can be used, for example, as a material which easily accepts electrons (a material having an electron-transport property). Examples of the compound having a π-electron deficient heteroaromatic ring skeleton include compounds such as an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, and a triazine derivative. Examples of the zinc- or aluminum-based metal complex include a metal complex having a quinoline ligand, a metal complex having a benzoquinoline ligand, a metal complex having an oxazole ligand, and a metal complex having a thiazole ligand.
Specific examples thereof include metal complexes having a quinoline or benzoquinoline skeleton, such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato) (4-phenylphenolato)aluminum(III) (abbreviation: BAlq), and bis(8-quinolinolato)zinc(II) (abbreviation: Znq). Alternatively, a metal complex having an oxazole-based or thiazole-based ligand, such as bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) or bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), can be used. Other than such organometallic complexes, any of the following can be used: heterocyclic compounds such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 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: COil), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 9-[4-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)phenyl]-9H-carbazole (abbreviation: CzTAZ1), 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), bathophenanthroline (abbreviation: BPhen), and bathocuproine (abbreviation: BCP); heterocyclic compounds having a diazine skeleton such as 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 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), 2-[3-(3,9′-bi-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzCzPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(dibenzothiophen-4-yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), and 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm); heterocyclic compounds having a triazine skeleton such as 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn); heterocyclic compounds having a pyridine skeleton such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB); and heteroaromatic compounds such as 4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs). Among the heterocyclic compounds, the heterocyclic compounds having a triazine skeleton, a diazine (pyrimidine, pyrazine, or pyridazine) skeleton, or a pyridine skeleton are highly reliable and stable and are thus preferably used. In addition, the heterocyclic compounds having any of these skeletons have a high electron-transport property to contribute to a reduction in driving voltage. Further alternatively, a high-molecular compound such as poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), or poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can be used. The substances described here are mainly substances having an electron mobility higher than or equal to 1×10−6 cm2/Vs. Note that other substances may also be used as long as their electron-transport properties are higher than their hole-transport properties.
As the organic compound 118_1, any of the organic compounds represented by Structural Formulae (400) to (415) can be used, for example.
As the organic compound 118_2, a substance which can form an exciplex together with the organic compound 1181 is preferably used. Specifically, the organic compound 118_2 preferably includes a skeleton having a high donor property, such as a π-electron rich heteroaromatic ring skeleton or an aromatic amine skeleton. Examples of the compound having a π-electron rich heteroaromatic ring skeleton include heteroaromatic compounds such as a dibenzothiophene derivative, a dibenzofuran derivative, and a carbazole derivative. In that case, it is preferable that the organic compound 118_1, the organic compound 118_2, and the guest material 119 (phosphorescent compound) be selected such that the emission peak of the exciplex formed by the organic compounds 118_1 and 118_2 overlaps with an absorption band, specifically the longest-wavelength absorption band, of a triplet metal to ligand charge transfer (MLCT) transition of the guest material 119 (phosphorescent compound). This makes it possible to provide a light-emitting device with drastically improved emission efficiency. Note that in the case where a thermally activated delayed fluorescence material is used instead of the phosphorescent compound, it is preferable that the longest-wavelength absorption band be a singlet absorption band.
As the organic compound 118_2, any of the hole-transport materials given below can be used.
A material having a hole-transport property higher than an electron-transport property can be used as a hole-transport material, and a material having a hole mobility higher than or equal to 1×10−6 cm2/Vs is preferably used. Specifically, an aromatic amine, a carbazole derivative, an aromatic hydrocarbon, a stilbene derivative, or the like can be used. Furthermore, the hole-transport material may be a high molecular compound.
Examples of the aromatic amine compounds that can be used as the material having a high hole-transport property are N,N-di(p-tolyl)-N,N-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N-bis[4-bis(3-methylphenyl)aminophenyl]-N,N-diphenyl-4,4′-diaminobiphenyl (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B), and the like.
Specific examples of the carbazole derivative include 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), and 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1).
Other examples of the carbazole derivative are 4,4′-di(9H-carbazol-9-yl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), and 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene.
Examples of the aromatic hydrocarbon include 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA), 2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9′-bianthryl, 10,10′-diphenyl-9,9′-bianthryl, 10,10′-bis(2-phenylphenyl)-9,9′-bianthryl, 10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl, anthracene, tetracene, rubrene, perylene, and 2,5,8,11-tetra(tert-butyl)perylene. Other examples include pentacene and coronene. The aromatic hydrocarbon having a hole mobility higher than or equal to 1×10−6 cm2/Vs and having 14 to 42 carbon atoms is particularly preferable.
The aromatic hydrocarbon may have a vinyl skeleton. Examples of the aromatic hydrocarbon having a vinyl skeleton include 4,4′-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi) and 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA).
A high molecular compound such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N-[4-(4-diphenylamino)phenyl]phenyl-N-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), or poly[N,N-bis(4-butylphenyl)-N,N-bis(phenyl)benzidine](abbreviation: Poly-TPD) can also be used.
Examples of the material having a high hole-transport property include aromatic amine compounds such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or a-NPD), N,N-diphenyl-N,N-bis(3-methylphenyl)-4,4′-diaminobiphenyl (abbreviation: TPD), 4,4′,4″-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), 4,4′,4″-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1′-TNATA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: m-MTDATA), 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), N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N-phenyl-N-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine (abbreviation: DFLADFL), N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation: DPNF), N-(9,9-spirobi[9H-fluoren]-2-yl)-N,N,N-triphenyl-1,4-phenylenediamine (abbreviation: DPASF), 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), 4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation: PCA1BP), N,N-bis(9-phenylcarbazol-3-yl)-N,N-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N,N,N″-triphenyl-N,N,N″-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), N-(9,9-diphenyl-9H-fluoren-2-yl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: PCAFLP(2)), N-(9,9-diphenyl-9H-fluoren-2-yl)-N,9-diphenyl-9H-carbazol-2-amine (abbreviation: PCAFLP(2)-02), N-(biphenyl-4-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF), N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF), N-(9,9-spirobi[9H-fluoren]-2-yl)-N,9-diphenylcarbazol-3-amine (abbreviation: PCASF), N,N-diphenyl-N,N-bis(4-diphenylaminophenyl)spirobi[9H-fluorene]-2,7-diamine (abbreviation: DPA2SF), N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP), and N,N-bis[4-(carbazol-9-yl)phenyl]-N,N-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F). Other examples are amine compounds, carbazole compounds, thiophene compounds, furan compounds, fluorene compounds, triphenylene compounds, phenanthrene compounds, and the like such as 3-[4-(1-naphthyl)phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]phenanthrene (abbreviation: PCPPn), 3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 9′-phenyl-9′H-9,3′:6′,9″-tercarbazole (abbreviation: PhCzGI), 2,8-di(9H-carbazol-9-yl)dibenzothiophene (abbreviation: Cz2DBT), 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II), 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 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), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and 4-[3-(triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPTp-II). Among the above compounds, compounds having a pyrrole skeleton, a furan skeleton, a thiophene skeleton, or an aromatic amine skeleton are preferable because of their high stability and high reliability. In addition, the compounds having any of these skeletons have a high hole-transport property to contribute to a reduction in driving voltage.
The guest material 119 (phosphorescent compound) can be an iridium-, rhodium-, or platinum-based organometallic complex or metal complex. Other examples include a platinum complex having a nitrogen-containing heterocyclic carbene. An organoiridium complex such as an iridium-based orthometalated complex may be used. As an orthometalated ligand, a 4H-triazole ligand, a 1H-triazole ligand, an imidazole ligand, a pyridine ligand, a pyrimidine ligand, a pyrazine ligand, an isoquinoline ligand, or the like can be used.
The organic compound 118_1, the organic compound 118_2, and the guest material 119 (phosphorescent compound) are preferably selected such that the LUMO (Lowest Unoccupied Molecular Orbital) level of the guest material 119 (phosphorescent compound) is higher than that of the organic compound 118_1 and the HOMO (Highest Occupied Molecular Orbital) level of the guest material 119 is lower than that of the organic compound 118_2. With this structure, a light-emitting device with high emission efficiency and low driving voltage can be obtained.
The organic compound 118_1, the organic compound 118_2, and the guest material 119 (phosphorescent compound) are preferably selected such that the LUMO level of the guest material 119 (phosphorescent compound) is higher than that of the organic compound 118_1 and the HOMO level of the guest material 119 is higher than that of the organic compound 118_2. With this structure, a light-emitting device with high emission efficiency and low driving voltage can be obtained.
The organic compound 118_1 and the guest material 119 (phosphorescent compound) are preferably selected such that the energy difference between the LUMO level of the organic compound 118_1 and the HOMO level of the guest material 119 (phosphorescent compound) is greater than or equal to the energy that is calculated from the longest-wavelength absorption edge in the absorption spectrum of the guest material 119 (phosphorescent compound). With this structure, a light-emitting device with high emission efficiency and low driving voltage can be obtained.
The longest-wavelength absorption edge in an absorption spectrum can be determined from a Tauc plot, with an assumption of direct transition, of a measured absorption spectrum of a target substance in the form of a thin film or a thin film in which a matrix material is doped with the target substance. Alternatively, an absorption spectrum of the target substance in a solution may be measured and an absorption edge may be calculated from the intersection of the horizontal axis (wavelength) or the base line and a tangent drawn at the half of a peak value on the longer wavelength side in the longest-wavelength peak or shoulder peak in the absorption spectrum. There is no particular limitation on a solvent of the solution; a solvent with relatively low polarity, such as toluene or chloroform, is preferable.
The values of HOMO and LUMO levels used in this specification can be obtained by electrochemical measurement. Typical examples of the electrochemical measurement include cyclic voltammetry (CV) measurement and differential pulse voltammetry (DPV) measurement.
In the cyclic voltammetry (CV) measurement, the values (E) of HOMO and LUMO levels can be calculated on the basis of an oxidation peak potential (Epa) and a reduction peak potential (Epc), which are obtained by changing the potential of a working electrode with respect to a reference electrode. In the measurement, a HOMO level and a LUMO level are obtained by potential scanning in positive direction and potential scanning in negative direction, respectively. The scanning speed in the measurement is 0.1 V/s.
Calculation steps of the HOMO level and the LUMO level are described in detail. A standard oxidation-reduction potential (Eo) (=Epa+Epc)/2) is calculated from an oxidation peak potential (Epa) and a reduction peak potential (Epc), which are obtained by the cyclic voltammogram of a material. Then, the standard oxidation-reduction potential (Eo) is subtracted from the potential energy (Ex) of the reference electrode with respect to a vacuum level, whereby each of the values (E) (=Ex−Eo) of HOMO and LUMO levels can be obtained.
Note that the reversible oxidation-reduction wave is obtained in the above case; in the case where an irreversible oxidation-reduction wave is obtained, the HOMO level is calculated as follows: a value obtained by subtracting a predetermined value (0.1 eV) from an oxidation peak potential (Epa) is assumed to be a reduction peak potential (Epc), and a standard oxidation-reduction potential (Eo) is calculated to one decimal place. To calculate the LUMO level, a value obtained by adding a predetermined value (0.1 eV) to a reduction peak potential (Epc) is assumed to be an oxidation peak potential (Epa), and a standard oxidation-reduction potential (Eo) is calculated to one decimal place.
Examples of a substance that has an emission peak in the blue or green wavelength range include organometallic complexes having a 4H-triazole skeleton, such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-kN2]phenyl-kC}iridium(III) (abbreviation: Ir(mpptz-dmp)3), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Mptz)3), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPrptz-3b)3), and tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPr5btz)3); organometallic complexes having a 1H-triazole skeleton, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(Mptzl-mp)3) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptzl-Me)3); organometallic complexes having an imidazole skeleton, such as fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: Ir(iPrpim)3) and tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: Ir(dmpimpt-Me)3); organometallic complexes 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)), bis[2-(4′,6′-difluorophenyl)pyridinato-N,C2′]iridium(III) acetylacetonate (abbreviation: Flr(acac)); and organoplatinum complexes such as (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-kC2]phenoxy-kC2}-9-(4-tert-butyl-2-pyridinyl-kN)carbazole-2,1-diyl-kC1)platinum(II) (abbreviation: PtON-TBBI). Among the materials given above, the organometallic iridium complexes or organoplatinum complexes having a nitrogen-containing five-membered heterocyclic skeleton, such as a 4H-triazole skeleton, a 1H-triazole skeleton, or an imidazole skeleton have high triplet excitation energy as well as high reliability or high emission efficiency and are thus particularly preferable.
Examples of a substance that has an emission peak in the green or yellow wavelength range include organometallic iridium complexes 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[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III) (abbreviation: Ir(nbppm)2(acac)), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: Ir(mpmppm)2(acac)), (acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-kN3]phenyl-kC}iridium(III) (abbreviation: Ir(dmppm-dmp)2(acac)), and (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: Ir(dppm)2(acac)); organometallic iridium complexes having a pyrazine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-Me)2(acac)) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: Ir(mppr-iPr)2(acac)); organometallic iridium complexes 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), and bis(2-phenylquinolinato-N,C2′)iridium(III) acetylacetonate (abbreviation: Ir(pq)2(acac)); organometallic iridium complexes such as bis(2,4-diphenyl-1,3-oxazolato-N,C2′)iridium(III) acetylacetonate (abbreviation: Ir(dpo)2(acac)), bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C2′}iridium(III) acetylacetonate (abbreviation: Ir(p-PF-ph)2(acac)), and bis(2-phenylbenzothiazolato-N,C2′)iridium(III) acetylacetonate (abbreviation: Ir(bt)2(acac)); and a rare earth metal complex such as tris(acetylacetonato) (monophenanthroline)terbium(III) (abbreviation: Tb(acac)3(Phen)). Among the materials given above, the organometallic iridium complexes having a pyrimidine skeleton have distinctively high reliability or emission efficiency and are thus particularly preferable.
Examples of a substance that has an emission peak in the yellow or red wavelength range include organometallic iridium complexes 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)), and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: Ir(d1npm)2(dpm)); organometallic iridium complexes 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)), and (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: Ir(Fdpq)2(acac)); organometallic iridium complexes having a pyridine skeleton, such as tris(1-phenylisoquinolinato-N,C2′)iridium(III) (abbreviation: Ir(piq)3) and bis(1-phenylisoquinolinato-N,C2′)iridium(III) acetylacetonate (abbreviation: Ir(piq)2(acac)); a platinum complex such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviation: PtOEP); and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: Eu(DBM)3(Phen)) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: Eu(TTA)3(Phen)). Among the materials given above, the organometallic iridium complexes having a pyrimidine skeleton have distinctively high reliability or emission efficiency and are thus particularly preferable. Furthermore, the organometallic iridium complexes having a pyrazine skeleton can provide red light emission with favorable chromaticity.
The light-emitting substance included in the light-emitting layer 113 is a material that can convert the triplet excitation energy into light emission. As an example of the material that can convert the triplet excitation energy into light emission, a thermally activated delayed fluorescence (TADF) material can be given in addition to phosphorescent compounds. Thus, it is acceptable that the “phosphorescent compound” in the description is replaced with the “thermally activated delayed fluorescence material”. Note that the thermally activated delayed fluorescence material has a small difference between the triplet excitation energy level and the singlet excitation energy level and a function of converting triplet excitation energy into singlet excitation energy by reverse intersystem crossing. Thus, the thermally activated delayed fluorescence material can up-convert a triplet excited state into a singlet excited state (i.e., reverse intersystem crossing is possible) using a little thermal energy and efficiently exhibit light emission (fluorescence) from the singlet excited state. The thermally activated delayed fluorescence is efficiently obtained under the condition where the difference in energy between the triplet excitation energy level and the singlet excitation energy level is preferably larger than 0 eV and smaller than or equal to 0.2 eV, further preferably larger than 0 eV and smaller than or equal to 0.1 eV.
In the case where the thermally activated delayed fluorescence material is composed of one kind of material, any of the following materials can be used, for example.
First, a derivative of a fullerene or the like, an acridine derivative such as proflavine, eosin, and the like can be given as examples. Other examples thereof include a metal-containing porphyrin such as a porphyrin including magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). 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).
As the thermally activated delayed fluorescence material composed of one kind of material, a heterocyclic compound having a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring can also be used. Specific examples include 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 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), and 10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation: ACRSA). The heterocyclic compound is preferable because of its high electron-transport and hole-transport properties due to the π-electron rich heteroaromatic ring and the π-electron deficient heteroaromatic ring included therein. Among skeletons having the π-electron deficient heteroaromatic ring, a diazine skeleton (a pyrimidine skeleton, a pyrazine skeleton, or a pyridazine skeleton) and a triazine skeleton are particularly preferable because of their high stability and high reliability. Among skeletons having the π-electron rich heteroaromatic ring, an acridine skeleton, a phenoxazine skeleton, a thiophene skeleton, a furan skeleton, and a pyrrole skeleton have high stability and high reliability; thus, one or more of these skeletons are preferably included. As the pyrrole skeleton, an indole skeleton, a carbazole skeleton, or a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton is particularly preferable. It is particularly preferable that the π-electron rich heteroaromatic ring be directly bonded to the π-electron deficient heteroaromatic ring, in which case the donor property of the π-electron rich heteroaromatic ring and the acceptor property of the π-electron deficient heteroaromatic ring are both increased and the difference between the singlet excitation energy level and the triplet excitation energy level becomes small.
As a light-emitting substance, for example, any of the organic compounds represented by Structural Formulae (500) to (511) below can be used.
The light-emitting layer 113 can include two or more layers. For example, in the case where the light-emitting layer 113 is formed by stacking a first light-emitting layer and a second light-emitting layer in this order from the hole-transport layer side, the first light-emitting layer is formed using a substance having a hole-transport property as the host material and the second light-emitting layer is formed using a substance having an electron-transport property as the host material. A light-emitting substance included in the first light-emitting layer may be the same as or different from a light-emitting substance included in the second light-emitting layer. In addition, the materials may have functions of emitting light of the same color or light of different colors. When light-emitting substances having functions of emitting light of different colors are used for the two light-emitting layers, light of a plurality of emission colors can be obtained at the same time. It is particularly preferable to select light-emitting substances of the light-emitting layers so that white light can be obtained by combining light emission from the two light-emitting layers.
The light-emitting layer 113 may include a material other than the host material 118 and the guest material 119.
A substance which emits fluorescent light (fluorescent substance) can also be used in the light-emitting layer, for example. In that case, light is emitted when excitation energy of a phosphorescent substance is transferred to the fluorescent substance in the light-emitting layer. A fluorescent substance, in which transition from a singlet excited state to a singlet ground state is allowed, has a shorter excitation lifetime (emission lifetime) than a phosphorescent substance. Accordingly, using a fluorescent substance in the light-emitting layer allows the light-emitting device to be stable and highly reliable.
Examples of the fluorescent substance include a pyrene derivative, an anthracene derivative, a triphenylene derivative, a fluorene derivative, a carbazole derivative, a dibenzothiophene derivative, a dibenzofuran derivative, a dibenzoquinoxaline derivative, a quinoxaline derivative, a pyridine derivative, a pyrimidine derivative, a phenanthrene derivative, and a naphthalene derivative. A fluorescent substance whose singlet excitation energy level and triplet excitation energy level are lower than the triplet excitation energy level of a phosphorescent substance can be used.
Specific 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,N,N,N,N″,N″,N″,N″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N,N-diphenyl-N,N′-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03), N,N-diphenyl-N,N′-bis(9-phenyl-9H-carbazol-2-yl)naphtho[2,3-b;6,7-b′]bisbenzofuran-3,10-diamine (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).
A fused heteroaromatic compound including nitrogen and boron, especially a compound having a diaza-boranaphtho-anthracene skeleton, exhibits a narrow emission spectrum, emits blue light with high color purity, and can thus be used suitably. Examples of the compound include 5,9-diphenyl-5,9-diaza-13b-boranaphtho[3,2,1-de]anthracene (abbreviation: DABNA1), 9-[(1,1′-diphenyl)-3-yl]-N,N,5,11-tetraphenyl-5,9-dihydro-5,9-diaza-13b-boranaphtho[3,2,1-de]anthracene-3-amine (abbreviation: DABNA2), 2,12-di(tert-butyl)-5,9-di(4-tert-butylphenyl)-N,N-diphenyl-5H,9H-[1,4]benzazaborino[2,3,4-kl]phenazaborin-7-amine (abbreviation: DPhA-tBu4DABNA), 2,12-di(tert-butyl)-N,N,5,9-tetra(4-tert-butylphenyl)-5H,9H-[1,4]benzazaborino[2,3,4-kl]phenazaborin-7-amine (abbreviation: tBuDPhA-tBu4DABNA), 2,12-di(tert-butyl)-5,9-di(4-tert-butylphenyl)-7-methyl-5H,9H-[1,4]benzazaborino[2,3,4-kl]phenazaborine (abbreviation: Me-tBu4DABNA), N7,N7,N13,N13,5,9,11,15-octaphenyl-5H,9H,11H,15H-[1,4]benzazaborino[2,3,4-kl][1,4]benzazaborino[4′,3′,2′:4,5][1,4]benzazaborino[3,2-b]phenazaborine-7,13-diamine (abbreviation: n-DABNA), and 2-(4-tert-butylphenyl)benz[5,6]indolo[3,2,1-jk]benzo[b]carbazole (abbreviation: tBuPBibc).
Besides the above compounds, 9,10,11-tris[3,6-bis(1,1-dimethylethyl)-9H-carbazol-9-yl]-2,5,15,18-tetrakis(1,1-dimethylethyl)indolo[3,2,1-de]indolo[3′,2′,1′:8,1][1,4]benzazaborino[2,3,4-kl]phenazaborine (abbreviation: BBCz-G), 9,11-bis[3,6-bis(1,1-dimethylethyl)-9H-carbazol-9-yl]-2,5,15,18-tetrakis(1,1-dimethylethyl)indolo[3,2,1-de]indolo[3′,2′,1′:8,1][1,4]benzazaborino[2,3,4-kl]phenazaborine (abbreviation: BBCz-Y), or the like can be suitably used.
As the light-emitting material included in the light-emitting layer, a thermally activated delayed fluorescence (TADF) material can be used. As a thermally activated delayed fluorescence material, a heterocyclic compound having a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring can be used. Specific examples include 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 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), and 10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation: ACRSA). The heterocyclic compound is preferable because of its high electron-transport and hole-transport properties due to the π-electron rich heteroaromatic ring and the π-electron deficient heteroaromatic ring included therein. Among skeletons having the π-electron deficient heteroaromatic ring, a diazine skeleton (a pyrimidine skeleton, a pyrazine skeleton, or a pyridazine skeleton) and a triazine skeleton are particularly preferable because of their high stability and high reliability. Among skeletons having the π-electron rich heteroaromatic ring, an acridine skeleton, a phenoxazine skeleton, a thiophene skeleton, a furan skeleton, and a pyrrole skeleton have high stability and high reliability; thus, one or more of these skeletons are preferably included. As the pyrrole skeleton, an indole skeleton, a carbazole skeleton, or a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton is particularly preferable. It is particularly preferable that the π-electron rich heteroaromatic ring be directly bonded to the π-electron deficient heteroaromatic ring, in which case the donor property of the π-electron rich heteroaromatic ring and the acceptor property of the π-electron deficient heteroaromatic ring are both increased and the difference between the singlet excitation energy level and the triplet excitation energy level becomes small. The aforementioned compound having a diaza-boranaphtho-anthracene skeleton is suitable because this compound has a function of a thermally activated delayed fluorescence material and emits blue light with high color purity.
A thermally activated delayed fluorescence material may be used instead of a phosphorescent substance. The thermally activated delayed fluorescence material has a small difference between the triplet excitation energy level and the singlet excitation energy level and a function of converting triplet excitation energy into singlet excitation energy by reverse intersystem crossing. Thus, the thermally activated delayed fluorescence material can up-convert a triplet excited state into a singlet excited state (i.e., reverse intersystem crossing is possible) using a little thermal energy and efficiently exhibit light emission (fluorescence) from the singlet excited state. The thermally activated delayed fluorescence is efficiently obtained under the condition where the difference in energy between the triplet excitation energy level and the singlet excitation energy level is preferably larger than 0 eV and smaller than or equal to 0.2 eV, further preferably larger than 0 eV and smaller than or equal to 0.1 eV.
Note that the light-emitting layer 113 can be formed by an evaporation method (including a vacuum evaporation method), an ink-jet method, a coating method, gravure printing, or the like. Besides the above-mentioned materials, an inorganic compound such as a quantum dot or a high molecular compound (e.g., an oligomer, a dendrimer, or a polymer) may be used.
The hole-injection layers (111, 111a, and 111b) inject holes from the first electrode 101 serving as the anode and the charge-generation layers (106, 106a, and 106b) to the organic compound layers (103, 103a, and 103b) and include an organic acceptor material and a material having a high hole-injection property.
The hole-injection layers (111, 111a, and 111b) have a function of lowering a barrier for hole injection from one of the pair of electrodes (the first electrode 101 or the second electrode 102) to promote hole injection and is formed using a transition metal oxide, a phthalocyanine derivative, or an aromatic amine, for example. As examples of the transition metal oxide, molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide can be given. As examples of the phthalocyanine derivative, phthalocyanine and metal phthalocyanine can be given. As examples of the aromatic amine, a benzidine derivative and a phenylenediamine derivative can be given. It is also possible to use a high molecular compound such as polythiophene or polyaniline; a typical example thereof is poly(ethylenedioxythiophene)/poly(styrenesulfonic acid), which is self-doped polythiophene.
As each of the hole-injection layers (111, 111a, and 111b), a layer including a composite material of a hole-transport material and a material having a property of accepting electrons from the hole-transport material can also be used. Alternatively, a stack of a layer including a material having an electron-accepting property and a layer including a hole-transport material may also be used. In a steady state or in the presence of an electric field, electric charge can be transferred between these materials. As examples of the material having an electron-accepting property, organic acceptors such as a quinodimethane derivative, a chloranil derivative, and a hexaazatriphenylene derivative can be given. A specific example is a compound having an electron-withdrawing group (a halogen group or a cyano group), such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, or 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN). Alternatively, a transition metal oxide such as an oxide of a metal from Group 4 to Group 8 can be used. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, or the like can be used. In particular, molybdenum oxide is preferable because it is stable in the air, has a low hygroscopic property, and is easily handled.
A material having a hole-transport property higher than an electron-transport property can be used as a hole-transport material, and a material having a hole mobility higher than or equal to 1×10−6 cm2/Vs is preferably used. Specifically, any of the aromatic amine, carbazole derivative, aromatic hydrocarbon, stilbene derivative, and the like described as examples of the hole-transport material that can be used in the light-emitting layer 113 can be used. Furthermore, the hole-transport material may be a high molecular compound.
The hole-transport layers (112, 112a, and 112b) include a hole-transport material and can be formed using any of the hole-transport materials given as examples of the material of the hole-injection layers (111, 111a, and 111b). In order that the hole-transport layers (112, 112a, and 112b) can have a function of transporting holes injected into the hole-injection layers (111, 111a, and 111b) to the light-emitting layers (113, 113a, and 113b), the HOMO level of the hole-transport layers (112, 112a, and 112b) is preferably equal or close to the HOMO level of the hole-injection layers (111, 111a, and 111b).
As the hole-transport material, a substance having a hole mobility higher than or equal to 1×10−6 cm2/Vs is preferably used. Note that other substances may also be used as long as their hole-transport properties are higher than their electron-transport properties. The layer including a substance having a high hole-transport property is not limited to a single layer and may be a stack of two or more layers each including any of the above substances.
The electron-transport layers (114, 114a, and 114b) have a function of transporting, to the light-emitting layer 113, electrons injected from the other of the pair of electrodes (the first electrode 101 or the second electrode 102) through the electron-injection layers (115, 115a, and 115b). As the electron-transport material, a material having an electron-transport property higher than a hole-transport property can be used, and a material having an electron mobility higher than or equal to 1×10−6 cm2/Vs is preferable. A compound having a π-electron deficient heteroaromatic ring skeleton such as a nitrogen-containing heteroaromatic compound or a metal complex can be used, for example, as a compound which easily accepts electrons (a material having an electron-transport property). Specific examples include a metal complex having a quinoline ligand, a benzoquinoline ligand, an oxazole ligand, or a thiazole ligand, which is described as the electron-transport material usable for the light-emitting layer 113. In addition, an oxadiazole derivative, a triazole derivative, a benzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a phenanthroline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, a triazine derivative, or the like can be used. As the electron-transport material, a substance having an electron mobility higher than or equal to 1×106 cm2/Vs is preferably used. Note that other substances may also be used for the electron-transport layer as long as their electron-transport properties are higher than their hole-transport properties. Each of the electron-transport layers (114, 114a, and 114b) is not limited to a single layer and may be a stack of two or more layers each including any of the above substances.
Between the electron-transport layer (114, 114a, or 114b) and the light-emitting layer (113, 113a, or 113b), a layer that controls transfer of electron carriers may be provided. This is a layer formed by addition of a small amount of a substance having a high electron-trapping property to a material having a high electron-transport property as described above, and the layer is capable of adjusting carrier balance by suppressing transport of electron carriers. Such a structure is very effective in inhibiting a problem (such as a reduction in element lifetime) caused when electrons pass through the light-emitting layer.
The electron-injection layers (115, 115a, and 115b) have a function of reducing a barrier for electron injection from the second electrode 102 to promote electron injection and can be formed using a Group 1 metal or a Group 2 metal, or an oxide, a halide, or a carbonate of any of these metals, for example. Alternatively, a composite material including an electron-transport material described above and a material having a property of donating electrons to the electron-transport material can also be used. As examples of the material having an electron-donating property, a Group 1 metal, a Group 2 metal, an oxide of any of these metals, and the like can be given. Specifically, an alkali metal, an alkaline earth metal, or a compound thereof, such as lithium fluoride (LiF), sodium fluoride (NaF), cesium fluoride (CsF), calcium fluoride (CaF2), or lithium oxide (LiOx), can be used. Alternatively, a rare earth metal compound like erbium fluoride (ErF3) can be used. Electride may also be used for 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. The electron-injection layers (115, 115a, and 115b) can be formed using the substance that can be used for the electron-transport layers (114, 114a, and 114b).
A composite material in which an organic compound and an electron donor (donor) are mixed may also be used for the electron-injection layers (115, 115a, and 115b). Such a composite material is excellent in an electron-injection property and an electron-transport property because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material that is excellent in transporting the generated electrons. Specifically, the above-described substances for forming the electron-transport layer 114 (e.g., a metal complex or a heteroaromatic compound) can be used, for example. As the electron donor, a substance showing an electron-donating property with respect to an organic compound can be used. Specifically, it is preferable to use an alkali metal, an alkaline earth metal, or a rare earth metal, such as lithium, sodium, cesium, magnesium, calcium, erbium, or ytterbium. It is also preferable to use an alkali metal oxide or an alkaline earth metal oxide, such as lithium oxide, calcium oxide, or barium oxide. Alternatively, a Lewis base such as magnesium oxide can be used. Further alternatively, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can be used.
Note that the light-emitting layer, the hole-injection layer, the hole-transport layer, the electron-transport layer, and the electron-injection layer described above can each be formed by an evaporation method (including a vacuum evaporation method), an ink-jet method, a coating method, a gravure printing method, or the like. Besides the above-mentioned materials, an inorganic compound such as a quantum dot or a high molecular compound (e.g., an oligomer, a dendrimer, or a polymer) may be used in the light-emitting layer, the hole-injection layer, the hole-transport layer, the electron-transport layer, and the electron-injection layer.
The quantum dot may be a colloidal quantum dot, an alloyed quantum dot, a core-shell quantum dot, or a core quantum dot, for example. The quantum dot including elements belonging to Groups 2 and 16, elements belonging to Groups 13 and 15, elements belonging to Groups 13 and 17, elements belonging to Groups 11 and 17, or elements belonging to Groups 14 and 15 may be used. Alternatively, the quantum dot including an element such as cadmium (Cd), selenium (Se), zinc (Zn), sulfur (S), phosphorus (P), indium (In), tellurium (Te), lead (Pb), gallium (Ga), arsenic (As), or aluminum (Al) may be used.
The first electrode 101 and the second electrode 102 function as an anode and a cathode of the light-emitting device. The first electrode 101 and the second electrode 102 can be formed using a metal, an alloy, or a conductive compound, a mixture or a stack thereof, or the like.
One of the first electrode 101 and the second electrode 102 is preferably formed using a conductive material having a function of reflecting light. Examples of the conductive material include aluminum (Al), an alloy including Al, and the like. Examples of the alloy including Al include an alloy including Al and L (L represents one or more of titanium (Ti), neodymium (Nd), nickel (Ni), and lanthanum (La)), such as an alloy including Al and Ti and an alloy including Al, Ni, and La. Aluminum has low resistance and high light reflectivity. Aluminum is included in earth's crust in large amount and is inexpensive; thus, it is possible to reduce costs for manufacturing a light-emitting device with aluminum. Alternatively, silver (Ag), an alloy of Ag and N (N represents one or more of yttrium (Y), Nd, magnesium (Mg), ytterbium (Yb), Al, Ti, gallium (Ga), zinc (Zn), indium (In), tungsten (W), manganese (Mn), tin (Sn), iron (Fe), Ni, copper (Cu), palladium (Pd), iridium (Ir), and gold (Au)), or the like may be used. Examples of the alloy including silver include an alloy including silver, palladium, and copper, an alloy including silver and copper, an alloy including silver and magnesium, an alloy including silver and nickel, an alloy including silver and gold, an alloy including silver and ytterbium, and the like. Besides, a transition metal such as tungsten, chromium (Cr), molybdenum (Mo), copper, or titanium can be used.
Light emitted from the light-emitting layer is extracted through the first electrode 101 and/or the second electrode 102. Thus, at least one of the first electrode 101 and the second electrode 102 is preferably formed using a conductive material having a function of transmitting light. As the conductive material, a conductive material having a visible light transmittance higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 60% and lower than or equal to 100%, and a resistivity lower than or equal to 1×10−2 Ω·cm can be used.
The first electrode 101 and the second electrode 102 may each be formed using a conductive material having functions of transmitting light and reflecting light. As the conductive material, a conductive material having a visible light reflectivity higher than or equal to 20% and lower than or equal to 80%, preferably higher than or equal to 40% and lower than or equal to 70%, and a resistivity lower than or equal to 1×10−2 Ω·cm can be used. For example, one or more kinds of conductive metals and alloys, conductive compounds, and the like can be used. Specifically, a metal oxide such as indium tin oxide (hereinafter, referred to as ITO), indium tin oxide including silicon or silicon oxide (ITSO), indium oxide-zinc oxide (indium zinc oxide), indium oxide-tin oxide including titanium, indium titanium oxide, or indium oxide including tungsten oxide and zinc oxide can be used. A metal thin film having a thickness that allows transmission of light (preferably, a thickness greater than or equal to 1 nm and less than or equal to 30 nm) can also be used. As the metal, Ag can be used, for example. An alloy of Ag and Al, an alloy of Ag and Mg, an alloy of Ag and Au, an alloy of Ag and Yb, or the like can be used.
In this specification and the like, as the material having a function of transmitting light, a material having a function of transmitting visible light and having conductivity is used. Examples of the material include, in addition to the above-described oxide conductor typified by ITO, an oxide semiconductor and an organic conductor including an organic substance. Examples of the organic conductor including an organic substance include a composite material in which an organic compound and an electron donor (donor) are mixed and a composite material in which an organic compound and an electron acceptor (acceptor) are mixed. Alternatively, an inorganic carbon-based material such as graphene may be used. The resistivity of the material is preferably lower than or equal to 1×105 Ω·cm, further preferably lower than or equal to 1×104 Ω·cm.
The first electrode 101 and/or the second electrode 102 may be formed by stacking two or more of the materials described above.
In order to improve the light extraction efficiency, a material whose refractive index is higher than that of an electrode having a function of transmitting light may be formed in contact with the electrode. The material may be electrically conductive or non-conductive as long as it has a function of transmitting visible light. In addition to the oxide conductors described above, an oxide semiconductor and an organic substance are given as the examples of the material. Examples of the organic substance include the materials for the light-emitting layer, the hole-injection layer, the hole-transport layer, the electron-transport layer, and the electron-injection layer. Alternatively, an inorganic carbon-based material or a metal film thin enough to transmit light can be used. Further alternatively, stacked layers with a thickness of several nanometers to several tens of nanometers may be used.
In the case where the first electrode 101 or the second electrode 102 functions as the cathode, the electrode preferably includes a material having a low work function (lower than or equal to 3.8 eV). For example, it is possible to use an element belonging to Group 1 or 2 of the periodic table (e.g., an alkali metal such as lithium, sodium, or cesium, an alkaline earth metal such as calcium or strontium, or magnesium), an alloy including any of these elements (e.g., Ag—Mg or Al—Li), a rare earth metal such as europium (Eu) or Yb, an alloy including any of these rare earth metals, an alloy including aluminum or silver, or the like.
When the first electrode 101 or the second electrode 102 is used as an anode, a material with a high work function (4.0 eV or higher) is preferably used.
The first electrode 101 and the second electrode 102 may be a stacked layer of a conductive material having a function of reflecting light and a conductive material having a function of transmitting light. This structure is preferably employed, in which case the first electrode 101 and the second electrode 102 can have a function of adjusting the optical path length so that light of a desired wavelength emitted from each light-emitting layer resonates and is intensified.
As the method for forming the first electrode 101 and the second electrode 102, a sputtering method, an evaporation method, a printing method, a coating method, a molecular beam epitaxy (MBE) method, a CVD method, a pulsed laser deposition method, an atomic layer deposition (ALD) method, or the like can be used as appropriate.
The charge-generation layer 106 has a function of injecting electrons into the organic compound layer 103a and injecting holes into the organic compound layer 103b when a voltage is applied between the first electrode (anode) 101 and the second electrode (cathode) 102. The charge-generation layer 106 may be either a p-type layer in which an electron acceptor (acceptor) is added to a hole-transport material or an electron-injection buffer layer in which an electron donor (donor) is added to an electron-transport material. Alternatively, both of these structures may be stacked. Furthermore, an electron-relay layer may be provided between the p-type layer and the electron-injection buffer layer. Note that forming the charge-generation layer 106 with the use of any of the above materials can inhibit an increase in driving voltage caused by the stack of the organic compound layers including light-emitting layers.
In the case where the charge-generation layer 106 is a p-type layer in which an electron acceptor is added to a hole-transport material, which is an organic compound, any of the materials described in this embodiment can be used as the hole-transport material. Examples of the electron acceptor include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ) and chloranil. Other examples include oxides of metals that belong to Group 4 to Group 8 of the periodic table. Specific examples include vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide. Any of the above-described acceptor materials may be used. Furthermore, a mixed film obtained by mixing materials of a p-type layer or a stack of films including the respective materials may be used.
In the case where the charge-generation layer 106 is an electron-injection buffer layer in which an electron donor is added to an electron-transport material, any of the materials described in this embodiment can be used as the electron-transport material. As the electron donor, it is possible to use an alkali metal, an alkaline earth metal, a rare earth metal, a metal belonging to Group 2 or Group 13 of the periodic table, or an oxide or a carbonate thereof. Specifically, lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide (Li2O), cesium carbonate, or the like is preferably used. An organic compound such as tetrathianaphthacene may be used as the electron donor.
When an electron-relay layer is provided between a p-type layer and an electron-injection buffer layer in the charge-generation layer 106, the electron-relay layer includes at least a substance having an electron-transport property and has a function of preventing an interaction between the electron-injection buffer layer and the p-type layer and transferring electrons smoothly. The LUMO level of the substance having an electron-transport property in the electron-relay layer is preferably between the LUMO level of the acceptor substance in the p-type layer and the LUMO level of the substance having an electron-transport property in the electron-transport layer in contact with the charge-generation layer 106. Specifically, the LUMO level of the substance having an electron-transport property in the electron-relay layer is preferably higher than or equal to −5.0 eV, further preferably higher than or equal to −5.0 eV and lower than or equal to −3.0 eV. Note that as the substance having an electron-transport property in the electron-relay layer, a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand is preferably used.
Although
Although not illustrated in
Specific examples of a material that can be used for the cap layer include 5,5′-diphenyl-2,2′-di-5H-[1]benzothieno[3,2-c]carbazole (abbreviation: BisBTc) and 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II). In addition, the organic compound described in Embodiment 1 can be used.
A light-emitting device of one embodiment of the present invention may be formed over a substrate of glass, plastic, or the like. As the way of stacking layers over the substrate, layers may be sequentially stacked from the first electrode 101 side or sequentially stacked from the second electrode 102 side.
For the substrate over which the light-emitting device of one embodiment of the present invention can be formed, glass, quartz, plastic, or the like can be used, for example. Alternatively, a flexible substrate may be used. The flexible substrate means a substrate that can be bent, such as a plastic substrate made of polycarbonate or polyarylate, for example. Alternatively, a film, an inorganic vapor deposition film, or the like can be used. Another material may be used as long as the substrate functions as a support in a manufacturing process of the light-emitting devices or the optical elements. Another material having a function of protecting the light-emitting devices or the optical elements may be used.
In this specification and the like, a light-emitting device can be formed using any of a variety of substrates, for example. There is no particular limitation on the type of the substrate. Examples of the substrate include a semiconductor substrate (e.g., a single crystal substrate such as a silicon substrate); an SOI substrate; a glass substrate; a quartz substrate; a plastic substrate; a metal substrate; a stainless steel substrate; a substrate including stainless steel foil; a tungsten substrate; a substrate including tungsten foil; a flexible substrate; an attachment film; and cellulose nanofiber (CNF), paper, and a base material film that include a fibrous material. Examples of a glass substrate include a barium borosilicate glass substrate, an aluminoborosilicate glass substrate, and a soda lime glass substrate. Examples of the flexible substrate, the attachment film, the base material film, and the like are substrates of plastics typified by polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), and polytetrafluoroethylene (PTFE). Another example is an acrylic resin. Furthermore, polypropylene, polyester, polyvinyl fluoride, and polyvinyl chloride can be given as examples. Other examples include a resin such as a polyamide resin, a polyimide resin, an aramid resin, or an epoxy resin, an inorganic vapor deposition film, and paper.
Alternatively, a flexible substrate may be used as the substrate, and a light-emitting device may be provided directly on the flexible substrate. Further alternatively, a separation layer may be provided between the substrate and the light-emitting device. The separation layer can be used to separate part or the whole of the light-emitting device, which is formed over the separation layer, from the substrate and transfer the separated component onto another substrate. In that case, the light-emitting device can be transferred to a substrate having low heat resistance or a flexible substrate as well. For the above separation layer, a stack including inorganic films, which are a tungsten film and a silicon oxide film, or a structure in which a resin film of polyimide or the like is formed over a substrate can be used, for example.
In other words, after the light-emitting device is formed using a substrate, the light-emitting device may be transferred to another substrate. Examples of the substrate to which the light-emitting device is transferred are, in addition to the above substrates, a cellophane substrate, a stone substrate, a wood substrate, a cloth substrate (including a natural fiber (e.g., silk, cotton, or hemp), a synthetic fiber (e.g., nylon, polyurethane, or polyester), a regenerated fiber (e.g., acetate, cupro, rayon, or regenerated polyester), and the like), a leather substrate, a rubber substrate, and the like. When such a substrate is used, a light-emitting device with high durability, high heat resistance, reduced weight, or reduced thickness can be formed.
The light-emitting device may be formed over an electrode electrically connected to a field-effect transistor (FET), for example, that is formed over any of the above-described substrates. Accordingly, an active matrix display apparatus in which the FET controls the driving of the light-emitting device can be manufactured.
In this embodiment, one embodiment of the present invention has been described. Other embodiments of the present invention are described in other embodiments. Note that one embodiment of the present invention is not limited thereto. In other words, various embodiments of the invention are described in this embodiment and the other embodiments, and one embodiment of the present invention is not limited to a particular embodiment. For example, although the example in which one embodiment of the present invention is applied to a light-emitting device is described, one embodiment of the present invention is not limited thereto. For example, depending on circumstances or conditions, one embodiment of the present invention is not necessarily used in a light-emitting device. One embodiment of the present invention shows, but is not limited to, an example of including a first organic compound, a second organic compound, and a guest material capable of converting triplet excitation energy into light emission, in which the LUMO level of the first organic compound is lower than that of the second organic compound and the HOMO level of the first organic compound is lower than that of the second organic compound. Depending on circumstances or conditions, in one embodiment of the present invention, for example, the LUMO level of the first organic compound is not necessarily lower than that of the second organic compound. Alternatively, the HOMO level of the first organic compound is not necessarily lower than that of the second organic compound. One embodiment of the present invention shows, but is not limited to, an example in which the first organic compound and the second organic compound form an exciplex. Depending on circumstances or conditions, in one embodiment of the present invention, for example, the first organic compound and the second organic compound do not necessarily form an exciplex. One embodiment of the present invention shows, but is not limited to, an example in which the LUMO level of the guest material is higher than that of the first organic compound and the HOMO level of the guest material is lower than that of the second organic compound. Depending on circumstances or conditions, in one embodiment of the present invention, for example, the LUMO level of the guest material is not necessarily higher than that of the first organic compound. Alternatively, the HOMO level of the guest material is not necessarily lower than that of the second organic compound.
The structure described above in this embodiment can be used in combination with any of the structures described in the other embodiments as appropriate.
As illustrated in
The display device 100 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, description common to the subpixels 110R, 110G, and 110B is sometimes made using the collective term “subpixel 110”. As for other 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 the subpixels; however, subpixels of a different combination of colors may be employed. The number of subpixels is not limited to three, and may be four or more. 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 Y, and four subpixels emitting light of R, G, and B and infrared (IR) light.
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.
Outside the pixel portion 177, a connection portion 140 is provided and a region 141 may also be provided. The region 141 is provided between the pixel portion 177 and the connection portion 140. 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, a 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 attached 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 are preferably provided between the adjacent light-emitting devices 130.
Although each of the inorganic insulating layer 125 and the insulating layer 127 looks like a plurality of layers in the cross-sectional view in
In
The display apparatus of one embodiment of the present invention can be, for example, a top-emission display apparatus where light is emitted in the direction opposite to a substrate over which light-emitting devices are formed. Note that the display apparatus of one embodiment of the present invention may be of a bottom-emission type.
Examples of a light-emitting substance included in the light-emitting device 130 include an organometallic complex and organic compounds such as a substance emitting fluorescent light (a fluorescent material), a substance emitting phosphorescent light (a phosphorescent material), and a substance exhibiting thermally activated delayed fluorescence (a thermally activated delayed fluorescent (TADF) material). Other examples include inorganic compounds (e.g., a quantum dot material).
The light-emitting device 130R has a structure as described in Embodiment 1. The light-emitting device 130R includes the first electrode (pixel electrode) including a conductive layer 151R and a conductive layer 152R, an organic compound layer 103R over the first electrode, a common layer 104 over the organic compound layer 103R, and a second electrode (common electrode) 102 over the common layer 104. Although the common layer 104 is not necessarily provided, it is preferable to provide the common layer 104 to reduce damage to the organic compound layer 103R during processing. In the case where the common layer 104 is provided, the common layer 104 is preferably an electron-injection layer. Furthermore, in the case where the common layer 104 is provided, a stacked of the organic compound layer 103R and the common layer 104 corresponds to the organic compound layer 103 described in Embodiment 2.
The light-emitting device 130G has a structure as described in Embodiment 1. The light-emitting device 130G includes the first electrode (pixel electrode) including a conductive layer 151G and a conductive layer 152G, an organic compound layer 103G over the first electrode, the common layer 104 over the organic compound layer 103G, and the second electrode (common electrode) 102 over the common layer. Although the common layer 104 is not necessarily provided, it is preferable to provide the common layer 104 to reduce damage to the organic compound layer 103G during processing. In the case where the common layer 104 is provided, the common layer 104 is preferably an electron-injection layer. Furthermore, in the case where the common layer 104 is provided, a stacked of the organic compound layer 103G and the common layer 104 corresponds to the organic compound layer 103 described in Embodiment 2.
The light-emitting device 130B has a structure as described in Embodiment 1. The light-emitting device 130B includes the first electrode (pixel electrode) including a conductive layer 151B and a conductive layer 152B, an organic compound layer 103B over the first electrode, the common layer 104 over the organic compound layer 103B, and the second electrode (common electrode) 102 over the common layer 104. Although the common layer 104 is not necessarily provided, it is preferable to provide the common layer 104 to reduce damage to the organic compound layer 103B during processing. In the case where the common layer 104 is provided, the common layer 104 is preferably an electron-injection layer. Furthermore, in the case where the common layer 104 is provided, a stacked of the organic compound layer 103B and the common layer 104 corresponds to the organic compound layer 103 described in Embodiment 2.
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 layers 103R, 103G, and 103B are island-shaped layers that are independent of each other on a subpixel basis or on an emission color basis. Providing the island-shaped organic compound layer 103 in each of the light-emitting devices 130 can inhibit leakage current between the adjacent light-emitting devices 130 even in a high-resolution display device. This can prevent crosstalk, so that a display device with extremely high contrast can be obtained. Specifically, a display device having high current efficiency at low luminance can be obtained.
The island-shaped organic compound layer 103 is formed by forming an EL film and processing the EL film by a lithography method.
In the display device of one embodiment of the present invention, the first electrode (pixel electrode) of the light-emitting device preferably has a stacked-layer structure. For example, in the example illustrated in
In the case where the conductive layer 151 has high visible light reflectance, the visible light reflectance of the conductive layer 151 is higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 70% and lower than or equal to 100%, for example. When used as an electrode having a visible-light-transmitting property, the conductive layer 152 preferably has a visible light transmittance higher than or equal to 40%, for example.
Here, such a pixel electrode being a stack composed of a plurality of layers might change in quality as a result of, for example, a reaction between the plurality of layers. For example, when a film formed after the formation of the pixel electrode is removed by a wet etching method, contact of a chemical solution with the pixel electrode might cause galvanic corrosion.
In view of the above, an insulating layer 156 is formed on the side surfaces of the conductive layers 151 and 152 in the display device 100 of this embodiment. This can inhibit a chemical solution from coming into contact with the conductive layer 151 when a film that is formed after formation of the pixel electrode including the conductive layer 151 and the conductive layer 152 is removed by a wet etching method, for example. Accordingly, occurrence of galvanic corrosion in the pixel electrode can be inhibited, for example. This allows the display device 100 to be manufactured by a high-yield method and to be accordingly inexpensive. In addition, generation of a defect in the display device 100 can be inhibited, which makes the display device 100 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 including an appropriate combination of any of these metals, for example.
For the conductive layer 152, an oxide including 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 including one or more of indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide including gallium, titanium oxide, indium zinc oxide including gallium, indium zinc oxide including aluminum, indium tin oxide including silicon, indium zinc oxide including silicon, and the like. In particular, indium tin oxide including 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 that include 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 be formed using a material that can be used for the conductive layer 152.
Note that an end portion of the insulating layer 156 may have a tapered shape. Specifically, when the end portion of the insulating layer 156 has a tapered shape with a taper angle less than 90°, coverage with a component provided along the side surface of the insulating layer 156 can be improved.
In the example illustrated in
In this manner, the structure where the conductive layer 151b is sandwiched between the conductive layers 151a and 151c can expand the range of choices for the material for the conductive layer 151b. The conductive layer 151b, for example, can thus have higher visible light reflectance than at least one of the conductive layers 151a and 151c. For example, aluminum can be used for the conductive layer 151b. The conductive layer 151b may be formed using an alloy including aluminum. The conductive layer 151a can be formed using titanium; titanium has lower visible light reflectance than aluminum but is less likely to migrate owing to contact with the insulating layer 175 than aluminum. Furthermore, the conductive layer 151c 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 151c may be formed using silver or an alloy including 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 having electrical resistivity lower than that of aluminum oxide. Thus, the conductive layer 151c formed using silver or an alloy including silver can favorably increase the visible light reflectance of the conductive layer 151 and inhibit an increase in the electrical resistance of the pixel electrode due to oxidation of the conductive layer 151b. Here, as the alloy including silver, an alloy of silver, palladium, and copper (also referred to as Ag—Pd—Cu or APC) can be used, for example. When the conductive layer 151c is formed using silver or an alloy including silver and the conductive layer 151b is formed using aluminum, the visible light reflectance of the conductive layer 151c can be higher than that of the conductive layer 151b. Here, the conductive layer 151b may be formed using silver or an alloy including silver. The conductive layer 151a may be formed using silver or an alloy including 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 151c can facilitate formation of the conductive layer 151c. 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 display device. For example, the display device 100 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 including silver, i.e., a material with high visible light reflectance, for the conductive layer 151c can favorably increase the light extraction efficiency of the display device 100.
As already described above, the conductive layer 151 preferably has a side surface with a tapered shape. Specifically, the side surface of the conductive layer 151 preferably has a tapered shape with a taper angle less than 90°. For example, in the conductive layer 151 illustrated in
The conductive layer 151 illustrated in
Here, when the conductive film is processed under conditions where the resist mask is easily recessed (reduced in size), the conductive film might be easily processed in the horizontal direction. That is, the etching sometimes might become isotropic as compared to the case where the conductive layer 151 is formed to have a perpendicular side surface.
In the case where the conductive layer 151 is a stack of a plurality of layers formed of different materials, the plurality of layers sometimes differ in processability in the horizontal direction. For example, the conductive layer 151a, the conductive layer 151b, and the conductive layer 151c sometimes differ in processability in the horizontal direction.
In that case, after the processing of the conductive film, the side surface of the conductive layer 151b may be positioned inward from the side surfaces of the conductive layers 151a and 151c and a protruding portion may be formed as illustrated in
In view of this, the insulating layer 156 is preferably provided as illustrated in
Although
In the case where the conductive layer 151 has the structure illustrated in
Here, the insulating layer 156 preferably has a curved surface as illustrated in
A conductive layer 152a has higher adhesion to a conductive layer 152b than the insulating layer 175 does, for example. For the conductive layer 152a, an oxide including 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 including one or more of indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide including gallium, titanium oxide, indium titanium oxide, zinc titanate, aluminum zinc oxide, indium zinc oxide including gallium, indium zinc oxide including aluminum, indium tin oxide including silicon, indium zinc oxide including silicon, and the like. Accordingly, peeling of the conductive layer 152b can be inhibited. The conductive layer 152b is not in contact with the insulating layer 175.
The conductive layer 152b 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 layer 151, the conductive layer 152a, and the conductive layer 152c. The visible light reflectance of the conductive layer 152b 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 152b, a material having higher visible light reflectance than aluminum can be used, for example. Specifically, for the conductive layer 152b, silver or an alloy including silver can be used, for example. As the alloy including silver, an alloy including silver, palladium, and copper (APC), for example, can be used. Consequently, the display device 100 can be a display device with high light extraction efficiency. Note that a metal other than silver may be used for the conductive layer 152b.
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 152c. The conductive layer 152c has a higher work function than the conductive layer 152b, for example. For the conductive layer 152c, a material similar to the material usable for the conductive layer 152a can be used, for example. For example, the conductive layers 152a and 152c can be formed using the same kind of material. For example, in the case where indium tin oxide is used for the conductive layer 152a, indium tin oxide can also be used for the conductive layer 152c.
When the conductive layers 151 and 152 serve as the cathode, the conductive layer 152c is preferably a layer having a low work function. The conductive layer 152c has a lower work function than the conductive layer 152b, for example.
The conductive layer 152c 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 152c is preferably higher than that of the conductive layers 151 and 152b. The visible light transmittance of the conductive layer 152c 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%. In that case, the amount of light that is absorbed by the conductive layer 152c after being emitted from the organic compound layer 103 can be reduced. As described above, the conductive layer 152b under the conductive layer 152c can be a layer having high visible light reflectance. Thus, the display device 100 can have high light extraction efficiency.
Next, a method for manufacturing the display device 100 having the structure illustrated in
Thin films included in the display device (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 display device (e.g., insulating films, semiconductor films, and conductive films) can also be formed by a wet film-formation method 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 display device can be processed by a lithography 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.
As a lithography method, for example, a photolithography method can be used. 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.
As light used for exposure in the photolithography method, for example, light with an i-line (wavelength: 365 nm), light with a g-line (wavelength: 436 nm), light with an h-line (wavelength: 405 nm), or light in which the i-line, the g-line, and the h-line are mixed can be used. Alternatively, ultraviolet rays, KrF laser light, ArF laser light, or the like can be used. Exposure may be performed by liquid immersion exposure technique. As the light for exposure, extreme ultraviolet (EUV) light or X-rays may also be used. Furthermore, instead of the light used for exposure, an electron beam can be used. It is preferable to use EUV light, X-rays, or an electron beam to perform extremely minute processing. Note that when exposure is performed by scanning of a beam such as an electron beam, a photomask is not needed.
For etching of thin films, a dry etching method, a wet etching method, a sandblasting method, or the like can be used.
First, as illustrated in
As the substrate, a substrate having 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
Next, as illustrated in
The conductive film 152f can be formed by an ALD method. In this case, for the conductive film 152f, an oxide including one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon can be used. In this case, the conductive film 152f can be formed by repeating a cycle of introduction of a precursor (generally referred to as a metal precursor or the like in some cases), purge of the precursor, introduction of an oxidizer (generally referred to as a reactant, a non-metal precursor, or the like in some cases), and purge of the oxidizer. Here, in the case where an oxide film including a plurality of kinds of metals (e.g., an indium tin oxide film) is formed as the conductive film 152f, the composition of the metals can be controlled by varying the number of cycles for different kinds of precursors.
For example, in the case where an indium tin oxide film is formed as the conductive film 152f, after a precursor including indium is introduced, the precursor is purged, and an oxidizer is introduced to form an In—O film, and then a precursor including tin is introduced, the precursor is purged, and an oxidizer is introduced to form a Sn—O film. Here, when the number of cycles of forming an In—O film is larger than the number of cycles of forming a Sn—O film, the number of In atoms included in the conductive film 152f can be larger than the number of Sn atoms included therein.
For example, to form a zinc oxide film as the conductive film 152f, a Zn—O film is formed in the above procedure. For another example, to form an aluminum zinc oxide film as the conductive film 152f, a Zn—O film and an Al—O film are formed in the above procedure. For another example, to form a titanium oxide film as the conductive film 152f, a Ti—O film is formed in the above procedure. For another example, to form an indium tin oxide film including silicon as the conductive film 152f, an In—O film, a Sn—O film, and a Si—O film are formed in the above procedure. For another example, to form a zinc oxide film including gallium, a Ga—O film and a Zn—O film are formed in the above procedure.
As a precursor including indium, it is possible to use, for example, triethylindium, trimethylindium, or [1,1,1-trimethyl-N-(trimethylsilyl)amide]-indium. As a precursor including tin, it is possible to use, for example, tin chloride or tetrakis(dimethylamido)tin. As a precursor including zinc, it is possible to use, for example, diethylzinc or dimethylzinc. As a precursor including gallium, it is possible to use, for example, triethylgallium. As a precursor including titanium, it is possible to use, for example, titanium chloride, tetrakis(dimethylamido)titanium, or tetraisopropyl titanate. As a precursor including aluminum, it is possible to use, for example, aluminum chloride or trimethylaluminum. As a precursor including silicon, it is possible to use, for example, trisilylamine, bis(diethylamino)silane, tris(dimethylamino)silane, bis(tert-butylamino)silane, or bis(ethylmethylamino)silane. As the oxidizer, water vapor, oxygen plasma, or an ozone gas can be used.
Subsequently, a resist mask 191 is formed over the conductive films 151f and 152f as illustrated in
Subsequently, as illustrated in
Note that the following process may be employed: the conductive film 152f is processed by a lithography method to form the conductive layers 152R, 152G, 152B, and 152C, and then, the conductive film 151f is processed using the conductive layers 152R, 152G, 152B, and 152C as masks. Specifically, after a resist mask is formed, part of the conductive film 152f is removed by an etching method, for example. The conductive film 152f can be removed by a wet etching method, for example. The conductive film 152f may be removed by a dry etching method. After that, the conductive film 151f is preferably removed by a wet etching method.
Here, 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, 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 including silicon, a nitride insulating film including silicon, an oxynitride insulating film including silicon, a nitride oxide insulating film including 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
Next, as illustrated in
As illustrated in
The organic compound film 103Rf can be formed by an evaporation method, specifically a vacuum evaporation method, for example. The organic compound film 103Rf may be formed by a transfer method, a printing method, an ink-jet method, a coating method, or the like.
Next, as illustrated in
Although this embodiment shows an example where a mask film having a two-layer structure of the sacrificial film 158Rf and the mask film 159Rf 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 103Rf can reduce damage to the organic compound film 103Rf in the manufacturing process of the display device, resulting in an increase in reliability of the light-emitting device.
As the sacrificial film 158Rf, a film that is highly resistant to the process conditions for the organic compound film 103Rf, specifically, a film having high etching selectivity with respect to the organic compound film 103Rf is used. For the mask film 159Rf, a film having high etching selectivity with respect to the sacrificial film 158Rf is used.
The sacrificial film 158Rf and the mask film 159Rf are formed at a temperature lower than the upper temperature limit of the organic compound film 103Rf. The typical substrate temperatures in formation of the sacrificial film 158Rf and the mask film 159Rf 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.
The sacrificial film 158Rf and the mask film 159Rf 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 103Rf in processing of the sacrificial film 158Rf and the mask film 159Rf, as compared to the case of using a dry etching method.
The sacrificial film 158Rf and the mask film 159Rf 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 158Rf and the mask film 159Rf may be formed by the above-described wet film-formation method.
Note that the sacrificial film 158Rf that is formed over and in contact with the organic compound film 103Rf is preferably formed by a formation method that is less likely to damage the organic compound film 103Rf than a formation method of the mask film 159Rf. For example, the sacrificial film 158Rf is preferably formed by an ALD method or a vacuum evaporation method rather than a sputtering method.
As each of the sacrificial film 158Rf and the mask film 159Rf, 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.
For each of the sacrificial film 158Rf and the mask film 159Rf, 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 including any of the metal materials, for example. It is particularly preferable to use a low-melting-point material such as aluminum or silver. A metal material that can block ultraviolet rays is preferably used for one or both of the sacrificial film 158Rf and the mask film 159Rf, in which case the organic compound film 103Rf can be inhibited from being irradiated with ultraviolet rays and deteriorating.
The sacrificial film 158Rf and the mask film 159Rf 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 including 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.
As each of the sacrificial film and the mask film, a film including a material having a light-blocking property, particularly with respect to ultraviolet rays, is preferably used. Although a variety of materials such as a metal, an insulator, a semiconductor, and a metalloid that have a property of blocking ultraviolet rays can be used as a light-blocking material, each of the sacrificial film and the mask film is preferably a film capable of being processed by etching and is particularly preferably a film having good processability because part or the whole of each of the sacrificial film and the mask film is removed in a later step.
For the sacrificial film and the mask film, a semiconductor material such as silicon or germanium, for example, is preferable for its excellent compatibility with a semiconductor manufacturing process. Alternatively, 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 including at least one of these metals can be used. Alternatively, an oxide including 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.
When a film including a material having a property of blocking ultraviolet rays is used as each of the sacrificial film and the mask film, the organic compound layer can be inhibited from being irradiated with ultraviolet rays in a light exposure step, for example. The organic compound layer is inhibited from being damaged by ultraviolet rays, so that the reliability of the light-emitting device can be improved.
Note that the same effect is obtained when a film including a material having a property of blocking ultraviolet rays is used for an after-mentioned inorganic insulating film 125f.
As each of the sacrificial film 158Rf and the mask film 159Rf, 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 103Rf 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 158Rf and the mask film 159Rf. As the sacrificial film 158Rf and the mask film 159Rf, 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.
For example, an inorganic insulating film (e.g., an aluminum oxide film) formed by an ALD method can be used as the sacrificial film 158Rf, and an inorganic film (e.g., an In—Ga—Zn oxide film, an aluminum film, or a tungsten film) formed by a sputtering method can be used as the mask film 159Rf.
Note that the same inorganic insulating film can be used for both the sacrificial film 158Rf and the inorganic insulating layer 125 that is to be formed later. For example, an aluminum oxide film formed by an ALD method can be used for both the sacrificial film 158Rf and the inorganic insulating layer 125. For the sacrificial film 158Rf and the inorganic insulating layer 125, the same film formation conditions may be used or different film formation conditions may be used. For example, when the sacrificial film 158Rf is formed under conditions similar to those of the inorganic insulating layer 125, the sacrificial film 158Rf can be an insulating layer having a high barrier property against at least one of water and oxygen. Meanwhile, since the sacrificial film 158Rf is a layer a large part or the whole of which is to be removed in a later step, it is preferable that the processing of the sacrificial film 158Rf be easy. Thus, the sacrificial film 158Rf is preferably formed with a substrate temperature lower than that for formation of the inorganic insulating layer 125.
One or both of the sacrificial film 158Rf and the mask film 159Rf 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 103Rf 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 film-formation method 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 103Rf can be reduced accordingly.
The sacrificial film 158Rf and the mask film 159Rf 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 any of the above wet film-formation methods can be used as the sacrificial film 158Rf, and an inorganic film (e.g., a silicon nitride film) formed by a sputtering method can be used as the mask film 159Rf.
Subsequently, a resist mask 190R is formed over the mask film 159Rf as illustrated in
The resist mask 190R may be formed using either a positive resist material or a negative resist material.
The resist mask 190R is provided at a position overlapping with the conductive layer 152R. The resist mask 190R 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 process of manufacturing the display device. Note that the resist mask 190R is not necessarily provided over the conductive layer 152C. The resist mask 190R is preferably provided to cover the area from an end portion of the organic compound film 103Rf to an end portion of the conductive layer 152C (the end portion closer to the organic compound film 103Rf), as illustrated in the cross-sectional view along the line B1-B2 in
Next, as illustrated in
Each of the sacrificial film 158Rf and the mask film 159Rf can be processed by a wet etching method or a dry etching method. The sacrificial film 158Rf and the mask film 159Rf are preferably processed by isotropic etching.
The use of a wet etching method can reduce damage to the organic compound film 103Rf in processing of the sacrificial film 158Rf and the mask film 159Rf, 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 including a mixed solution of any of these acids, for example.
Since the organic compound film 103Rf is not exposed in the processing of the mask film 159Rf, the range of choice for a processing method for the mask film 159Rf is wider than that for the sacrificial film 158Rf. Specifically, even in the case where a gas including oxygen is used as the etching gas in the processing of the mask film 159Rf, deterioration of the organic compound film 103Rf can be inhibited.
In the case of using a dry etching method to process the sacrificial film 158Rf, deterioration of the organic compound film 103Rf can be inhibited by not using a gas including oxygen as the etching gas. In the case of using a dry etching method, it is preferable to use a gas including CF4, C4F8, SF6, CHF3, Cl2, H2O, BCl3, or a Group 18 element such as He, for example, as the etching gas.
For example, in the case where an aluminum oxide film formed by an ALD method is used as the sacrificial film 158Rf, part of the sacrificial film 158Rf can be removed by a dry etching method using CHF3 and He or a combination of CHF3, He, and CH4. In the case where an In—Ga—Zn oxide film formed by a sputtering method is used as the mask film 159Rf, part of the mask film 159Rf can be removed by a wet etching method using diluted phosphoric acid. Alternatively, part of the mask film 159Rf may be removed by a dry etching method using CH4 and Ar. Alternatively, part of the mask film 159Rf can be removed by a wet etching method using diluted phosphoric acid. In the case where a tungsten film formed by a sputtering method is used as the mask film 159Rf, part of the mask film 159Rf can be removed by a dry etching method using a combination of SF6, CF4, and O2 or a combination of CF4, Cl2, and O2.
The resist mask 190R can be removed by a method similar to that for the resist mask 191. For example, the resist mask 190R can be removed by ashing using oxygen plasma. Alternatively, an oxygen gas and any of CF4, C4F8, SF6, CHF3, Cl2, H2O, BCl3, and a Group 18 element such as He may be used. Alternatively, the resist mask 190R may be removed by wet etching. At this time, the sacrificial film 158Rf is located on the outermost surface, and the organic compound film 103Rf is not exposed; thus, the organic compound film 103Rf can be inhibited from being damaged in the step of removing the resist mask 190R. In addition, the range of choice for the method for removing the resist mask 190R can be widened.
Next, as illustrated in
Accordingly, as illustrated in
In the example illustrated in
As described above, the resist mask 190R is preferably provided to cover the area from the end portion of the organic compound layer 103R to the end portion of the conductive layer 152C (the end portion closer to the organic compound layer 103R) in the cross section along the dashed-dotted line B1-B2. In that case, as illustrated in
The organic compound film 103Rf is preferably processed by anisotropic etching. Anisotropic dry etching is particularly preferable. Alternatively, wet etching may be used.
In the case of using a dry etching method, deterioration of the organic compound film 103Rf can be inhibited by not using a gas including oxygen as the etching gas.
A gas including oxygen may be used as the etching gas. When the etching gas includes 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 103Rf can be reduced. Furthermore, a defect such as attachment of a reaction product generated in the etching can be inhibited.
In the case of using a dry etching method, it is preferable to use a gas including at least one of H2, CF4, C4F8, SF6, CHF3, Cl2, H2O, BCl3, and a Group 18 element such as He or Ar as the etching gas, for example. Alternatively, a gas including oxygen and at least one of the above is preferably used as the etching gas. Alternatively, an oxygen gas may be used as the etching gas. Specifically, for example, a gas including H2 and Ar or a gas including CF4 and He can be used as the etching gas. For another example, a gas including CF4, He, and oxygen can be used as the etching gas. For another example, a gas including H2 and Ar and a gas including oxygen can be used as the etching gas.
As described above, in one embodiment of the present invention, the mask layer 159R is formed in the following manner: the resist mask 190R is formed over the mask film 159Rf and part of the mask film 159Rf is removed using the resist mask 190R. After that, part of the organic compound film 103Rf is removed using the mask layer 159R as a hard mask, so that the organic compound layer 103R is formed. In other words, the organic compound layer 103R is formed by processing the organic compound film 103Rf by a lithography method. Note that part of the organic compound film 103Rf may be removed using the resist mask 190R. Then, the resist mask 190R may be removed.
Next, hydrophobization treatment for the conductive layer 152G, for example, is preferably performed. At the time of processing the organic compound film 103Rf, 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. Note that the hydrophobization treatment is not necessarily performed.
Next, as illustrated in
The organic compound film 103Gf can be formed by a method similar to that for forming the organic compound film 103Rf. The organic compound film 103Gf can have a structure similar to that of the organic compound film 103Rf.
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
Next, hydrophobization treatment for the conductive layer 152B, for example, is preferably performed. At the time of processing the organic compound film 103Gf, the properties of a surface of the conductive layer 152B change to hydrophilic properties in some cases, for example. The hydrophobization treatment for the conductive layer 152B, for example, can increase the adhesion between the conductive layer 152B and a layer to be formed in a later step (which is the organic compound layer 103B here) and inhibit film peeling. Note that the hydrophobization treatment is not necessarily performed.
Next, as illustrated in
The organic compound film 103Bf can be formed by a method similar to that for forming the organic compound film 103Rf. The organic compound film 103Bf can have a structure similar to that of the organic compound film 103Rf.
Then, as illustrated in
The resist mask 190B is provided at a position overlapping with the conductive layer 152B.
Subsequently, as illustrated in
Accordingly, as illustrated in
Note that the side surfaces of the organic compound layers 103R, 103G, and 103B 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 103R, 103G, and 103B, which are formed by a lithography method as described above, can be shortened 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 specified, for example, by the distance between opposite end portions of two adjacent layers among the organic compound layers 103R, 103G, and 103B. Shortening the distance between the island-shaped organic compound layers can provide a display device 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 159R, 159G, and 159B are removed; however, the mask layers 159R, 159G, and 159B are not necessarily removed. For example, in the case where the mask layers 159R, 159G, and 159B include the above-described material having a property of blocking ultraviolet rays, the procedure preferably proceeds to the next step without removing the mask layers 159R, 159G, and 159B, in which case the organic compound layers can be protected from ultraviolet rays.
The step of removing the mask layers can be performed by a method similar to that for the step of processing the mask films. Specifically, by using a wet etching method, damage applied to the organic compound layers 103R, 103G, and 103B 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 103R, 103G, and 103B and water adsorbed onto the surfaces of the organic compound layers 103R, 103G, and 103B. For example, heat treatment in an inert gas 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 127f 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 (e.g., a photosensitive resin composition including an acrylic resin). To improve the affinity, surface treatment is preferably performed so that the top surface of the inorganic insulating film 125f is made hydrophobic or its hydrophobic properties are 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, the insulating film 127f can be formed with favorable adhesion. Note that the above-described hydrophobization treatment may be performed as the surface treatment.
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 103R, 103G, and 103B are less damaged. The inorganic insulating film 125f, which is formed in contact with the side surfaces of the organic compound layers 103R, 103G, and 103B, is particularly preferably formed by a formation method that causes less damage to the organic compound layers 103R, 103G, and 103B than the formation method of 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 limits of the organic compound layers 103R, 103G, and 103B. 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 film formation rate than an ALD method. In that case, a highly reliable display device can be manufactured with high productivity.
The insulating film 127f is preferably formed by the aforementioned wet film-formation method. 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 including an acrylic resin.
The insulating film 127f is preferably formed using a resin composition including 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 limits of the organic compound layers 103R, 103G, and 103B. 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 included 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 including 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 152R, 152G, and 152B and around the conductive layer 152C. Thus, the top surfaces of the conductive layers 152R, 152G, 152B, 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 that is to be 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.
The light used for the exposure preferably includes the i-line (wavelength: 365 nm). Furthermore, the light used for the exposure may include at least one of the g-line (wavelength: 436 nm) and the h-line (wavelength: 405 nm).
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 158R, 158G, and 158B) and the inorganic insulating film 125f, diffusion of oxygen into the organic compound layers 103R, 103G, and 103B can be inhibited. When the organic compound layer is irradiated with light (visible light or ultraviolet rays), the organic compound included 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 including oxygen, oxygen might be bonded to the organic compound included 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 included in the organic compound layer can be inhibited.
Next, as illustrated in
Then, a residue (scum) due to the development may be removed. For example, the residue can be removed by ashing using oxygen plasma.
Etching may be performed to adjust the surface level of the insulating layer 127a. The insulating layer 127a may be processed by ashing using oxygen plasma, for example. In the case where a non-photosensitive material is used for the insulating film 127f, the surface level of the insulating film 127f can be adjusted by the ashing, for example.
Next, as illustrated in
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 158R, 158G, and 158B, in which case the first etching treatment can be performed collectively.
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 end portions of the side surfaces of the sacrificial layers 158R, 158G, and 158B can be made to have a tapered shape relatively easily.
In the case of performing dry etching, a chlorine-based gas is preferably used. As the chlorine-based gas, one of Cl2, 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 158R, 158G, and 158B can be formed with favorable in-plane uniformity.
As a dry etching apparatus, a dry etching apparatus including a high-density plasma source can be used. As the dry etching apparatus including a high-density plasma source, an inductively coupled plasma (ICP) etching apparatus can be used, for example. Alternatively, a capacitively coupled plasma (CCP) etching apparatus including parallel plate electrodes can be used. The capacitively coupled plasma etching apparatus including parallel plate electrodes may have a structure where a high-frequency voltage is applied to one of the parallel plate electrodes. Alternatively, the capacitively coupled plasma etching apparatus may have a structure where different high-frequency voltages are applied to one of the parallel-plate electrodes. Alternatively, the capacitively coupled plasma etching apparatus may have a structure where high-frequency voltages with the same frequency are applied to the parallel-plate electrodes. Alternatively, the capacitively coupled plasma etching apparatus may have a structure where high-frequency voltages with different frequencies are applied to the parallel-plate electrodes.
In the case of performing dry etching, a by-product or the like generated by the dry etching might be deposited on the top surface and the side surface of the insulating layer 127a, for example. Accordingly, a component of the etching gas, a component of the inorganic insulating film 125f, a component of the sacrificial layers 158R, 158G, and 158B, and the like might be included in the insulating layer 127 in the completed display device.
The first etching treatment is preferably performed by wet etching. The use of a wet etching method can reduce damage to the organic compound layers 103R, 103G, and 103B, as compared to the case of using a dry etching method. For example, 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 this case, puddle wet etching can be performed. Note that the inorganic insulating film 125f is preferably formed using a material similar to that of the sacrificial layers 158R, 158G, and 158B, in which case the above etching treatment can be performed collectively.
The sacrificial layers 158R, 158G, and 158B are not removed completely by the first etching treatment, and the etching treatment is stopped when the thicknesses of the sacrificial layers 158R, 158G, and 158B are reduced. The sacrificial layers 158R, 158G, and 158B remain over the corresponding organic compound layers 103R, 103G, and 103B in this manner, whereby the organic compound layers 103R, 103G, and 103B can be prevented from being damaged by treatment in a later step.
Next, the insulating layer 127a is preferably irradiated with visible light or ultraviolet rays by performing light exposure on the entire substrate. The energy density for the light exposure is preferably greater than 0 mJ/cm2 and less than or equal to 800 mJ/cm2, further preferably greater than 0 mJ/cm2 and less than or equal to 500 mJ/cm2. Performing such light exposure after the development can sometimes increase the degree of transparency of the insulating layer 127a. In addition, it is sometimes possible to lower the substrate temperature required for subsequent heat treatment for changing the shape of the insulating layer 127a to a tapered shape.
Here, when a barrier insulating layer against oxygen (e.g., an aluminum oxide film) is present as each of the sacrificial layers 158R, 158G, and 158B, diffusion of oxygen into the organic compound layers 103R, 103G, and 103B can be inhibited. When the organic compound layer is irradiated with light (visible light or ultraviolet rays), the organic compound included 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 including oxygen, oxygen might be bonded to the organic compound included in the organic compound layer. By providing the sacrificial layers 158R, 158G, and 158B over the island-shaped organic compound layers, bonding of oxygen in the atmosphere to the organic compounds included in the organic compound layers can be inhibited.
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 (
When the sacrificial layers 158R, 158G, and 158B are not completely removed by the first etching treatment and the thinned sacrificial layers 158R, 158G, and 158B are left, the organic compound layers 103R, 103G, and 103B can be prevented from being damaged and deteriorating in the heat treatment. This increases the reliability of the light-emitting devices.
Note that the side surface of the insulating layer 127 may have a concave shape depending on the material of the insulating layer 127 and the temperature, time, and atmosphere of the post-baking. For example, when the temperature of the post-baking is higher or the duration of the post-baking is longer, the insulating layer 127 is more likely to change in shape and thus the concave shape may be more likely to be formed.
Next, as illustrated in
An end portion of the inorganic insulating layer 125 is covered with the insulating layer 127.
If the first etching treatment is not performed and the inorganic insulating layer 125 and the mask layer are collectively etched after the post-baking, the inorganic insulating layer 125 and the mask layer under an end portion of the insulating layer 127 may disappear because of side etching and a void may be formed. The void causes unevenness on the formation surface of the common electrode 155, so that step disconnection is more likely to be caused in the common electrode 155. Even when a void is formed owing to side etching of the inorganic insulating layer 125 and the mask layer by the first etching treatment, the post-baking performed subsequently can make the insulating layer 127 fill the void. After that, the thinned mask layer is etched by the second etching treatment; thus, the amount of side etching decreases, a void is less likely to be formed, and even if a void is formed, it can be extremely small. Consequently, the formation surface of the common electrode 155 can be made flatter.
Note that the insulating layer 127 may cover the entire end portion of the sacrificial layer 158G. For example, the end portion of the insulating layer 127 may droop to cover the end portion of the sacrificial layer 158G. For another example, the end portion of the insulating layer 127 may be in contact with the top surface of at least one of the organic compound layers 103R, 103G, and 103B. As described above, when light exposure is not performed on the insulating layer 127a after the development, the shape of the insulating layer 127 may be likely to change.
The second etching treatment is performed by wet etching. The use of a wet etching method can reduce damage to the organic compound layers 103R, 103G, and 103B, as compared to the case of using a dry etching method. The wet etching can be performed using an alkaline solution such as TMAH, for example.
Meanwhile, in the case where the second etching treatment is performed by a wet etching method and gaps due to, for example, poor adhesion between the organic compound layer 103 and another layer exist at the interface between the organic compound layer 103 and the sacrificial layer 158, the interface between the organic compound layer 103 and the inorganic insulating layer 125, and the interface between the organic compound layer 103 and the insulating layer 175, the chemical solution used in the second etching treatment sometimes enters the gaps to come into contact with the pixel electrode. Here, when the chemical solution comes into contact with both the conductive layer 151 and the conductive layer 152, one of the conductive layers 151 and 152 that has a lower spontaneous potential than the other suffers from galvanic corrosion in some cases. For example, when the conductive layer 151 is formed using aluminum and the conductive layer 152 is formed using indium tin oxide, the conductive layer 152 sometimes corrodes. As a result, the yield of the display device decreases in some cases. Moreover, the reliability of the display device decreases in some cases.
When the insulating layer 156 is formed to have a region overlapping with the side surface of the conductive layer 151 and the insulating layer 156 is formed to cover the side surfaces of the conductive layers 151 and 152 as described above, step disconnection in the inorganic insulating layer 125 can be prevented, whereby the chemical solution can be prevented from coming into contact with a lower-layer structure such as the conductive layer 151 in the second etching treatment, for example. Thus, corrosion of the pixel electrode can be prevented.
As described above, by providing the insulating layer 127, the inorganic insulating layer 125, and the sacrificial layers 158R, 158G, and 158B, poor connection due to a disconnected portion and an increase in electrical resistance due to a locally thinned portion can be inhibited from occurring in the common electrode 155 between the light-emitting devices. Thus, the display device of one embodiment of the present invention can have improved display quality.
Heat treatment is performed after the organic compound layers 103R, 103G, and 103B are partly exposed. By the heat treatment, water included in the organic compound layers and water adsorbed onto the surfaces of the organic compound layers, 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 end portion of the inorganic insulating layer 125, the end portions of the sacrificial layers 158R, 158G, and 158B, and the top surfaces of the organic compound layers 103R, 103G, and 103B.
If the temperature of the heat treatment is too low, water included in the organic compound layers and water adsorbed onto the surfaces of the organic compound layers, for example, cannot be sufficiently removed. If the temperature of the heat treatment is too high, the organic compound layer 103 might deteriorate and the insulating layer 127 might change in shape excessively. Thus, the temperature of the heat treatment is preferably higher than the temperature at which water is released from the organic compound layer 103 and lower than the glass transition temperature of the organic compound included in the organic compound layer 103, further preferably lower than the glass transition temperature of the organic compound included in the upper surface of the organic compound layer 103. Specifically, the substrate temperature is preferably higher than or equal to 80° C. and lower than or equal to 130° C., further preferably higher than or equal to 90° C. and lower than or equal to 120° C., still further preferably higher than or equal to 100° C. and lower than or equal to 120° C., yet still further preferably higher than or equal to 100° C. and lower than or equal to 110° C. The heating atmosphere may be an air atmosphere or an inert gas atmosphere. Although the heating atmosphere may be an atmospheric-pressure atmosphere or a reduced-pressure atmosphere, a reduced-pressure atmosphere is preferably employed to prevent re-adsorption of water released from the organic compound layer 103.
By the heat treatment, water included in the organic compound layers and water adsorbed onto the surfaces of the organic compound layers, for example, can be sufficiently removed without deterioration of the organic compound layers 103R, 103G, and 103B and an excessive change in the shape of the insulating layer 127. Thus, degradation of the characteristics of the light-emitting devices can be prevented.
Next, as illustrated in
Next, as illustrated in
Then, the substrate 120 is attached to the protective layer 131 using the resin layer 122, so that the display device can be manufactured. In the method for manufacturing the display device of one embodiment of the present invention, the insulating layer 156 is provided on the side surfaces of the conductive layer 151 and the conductive layer 152 as described above. This can increase the yield of the display device and inhibit generation of defects.
As described above, in the method for manufacturing the display device of one embodiment of the present invention, the island-shaped organic compound layers 103R, 103G, and 103B are each 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 display device or a display device 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 103R, 103G, and 103B 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 display device with extremely high contrast can be obtained. Moreover, even a display device that includes tandem light-emitting devices formed by a lithography method can have favorable characteristics.
The structure described in this embodiment can be used in combination with any of the structures described in other embodiments as appropriate.
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; thus, 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 for 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. Thus, 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 display device of one embodiment of the present invention will be described.
The display device in this embodiment can be a high-resolution display device. Thus, the display device 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 display device in this embodiment can be a high-definition display device or a large-sized display device. Accordingly, the display device 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 devices 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.
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 ofa 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.
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.
The display device 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. An insulator is provided in regions between adjacent light-emitting devices.
The insulating layer 156R is provided to include a region overlapping with the side surface of the conductive layer 151R. The insulating layer 156G is provided to include a region overlapping with the side surface of the conductive layer 151G. The insulating layer 156B is provided to include a region overlapping with the side surface of the conductive layer 151B. 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. The sacrificial layer 158G is positioned over the organic compound layer 103G. The sacrificial layer 158B is positioned over the organic compound layer 103B.
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. 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. A substrate 120 is bonded to the protective layer 131 with a resin layer 122. Embodiment 4 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 display device 100B, a substrate 352 and a substrate 351 are bonded to each other. In
The display device 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 number of connection portions 140 may be one or more. In the connection portion 140, a common electrode of a light-emitting device is electrically connected to a conductive layer, so that a potential can be supplied to the common electrode.
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 display device 100C illustrated in
Embodiment 4 can be referred to for the details of the light-emitting devices 130R, 130G, and 130B.
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.
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. An end portion of the conductive layer 151R is positioned outward from an end 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 display device 100C 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 includes a material that reflects visible light, and the counter electrode (the common electrode 155) includes a material that transmits visible light.
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.
An inorganic insulating film is preferably used as each of the insulating layers 211, 213, and 215.
An organic insulating layer is suitable as the insulating layer 214 functioning as a planarization layer.
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 the 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.
A connection portion 204 is provided in a region of the substrate 351 not overlapping with the substrate 352. In the connection portion 204, the source electrode or the drain electrode of the transistor 201 is electrically connected to the FPC 353 through a conductive layer 166 and a connection layer 242. As an example, 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.
The display device 100D 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 317 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 second electrode 102.
Although not illustrated in
Although
The display device 100D2 illustrated in
As illustrated in
A plurality of the depressed portions 181 may be formed in a matrix. The depressed portion 181a and the depressed portion 181b may be provided in contact with each other or may have a flat surface therebetween.
Although the top surface shape and the cross-sectional shape of the depressed portion are hexagonal (
As the organic resin layer 180, an insulating layer including an organic material can be used. For the organic resin layer 180, an acrylic resin, a polyimide resin, an epoxy resin, an imide resin, a polyamide resin, a polyimide-amide resin, a silicone resin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin, or a precursor of any of these resins can be used, for example. Alternatively, an organic material such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or an alcohol-soluble polyamide resin may be used for the organic resin layer 180.
Further alternatively, a photosensitive resin can be used for the organic resin layer 180. A photoresist may be used as the photosensitive resin. As the photosensitive resin, a positive photosensitive material or a negative photosensitive material can be used.
The organic resin layer 180 may include a material absorbing visible light. For example, the organic resin layer 180 itself may be made of a material absorbing visible light, or the organic resin layer 180 may include a pigment absorbing visible light. For the organic resin layer 180, for example, a resin that can be used as a color filter transmitting red, blue, or green light and absorbing light of the other colors or a resin that includes carbon black as a pigment and functions as a black matrix can be used.
The first electrodes 101 (a first electrode 101R and a first electrode 101W) are provided over the organic resin layer 180, and the organic compound layer 103 is provided over the first electrodes 101. End portions of the first electrode 101 and the organic compound layer 103 may be covered with the insulating layer 127.
The first electrode 101 formed over the organic resin layer 180 has a depressed portion along the depressed portion of the organic resin layer 180. Furthermore, the organic compound layer 103 formed over the first electrode 101 has a depressed portion along the depressed portion of the first electrode 101. Furthermore, the common layer 104 formed over the organic compound layer 103 has a depressed portion along the depressed portion of the organic compound layer 103. Furthermore, the second electrode 102 formed over the common layer 104 has a depressed portion along the depressed portion of the common layer 104. That is, the depressed portions of the organic resin layer 180, the first electrode 101, the organic compound layer 103, the common layer 104, and the second electrode 102 overlap with each other.
The common layer 104 is provided over the organic compound layer 103 and the insulating layer 127, and the second electrode 102 is provided over the common layer 104. The protective layer 131 is provided over the second electrode 102, and the substrate 352 is bonded with the use of the adhesive layer 142.
Although not shown in
In the light-emitting apparatus of one embodiment of the present invention including the above-described organic resin layer 180, the organic compound layer 103 includes the organic compound represented by General Formula (G1) as described in Embodiment 1, in which case an organic semiconductor device with high emission efficiency can be provided owing to an indivisible effect of the organic resin layer 180 and the organic semiconductor device using the organic compound of the present invention. Thus, an organic semiconductor device with high reliability, low driving voltage, and low power consumption can be provided.
The display device 100E illustrated in
In the display device 100E, 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 a surface of the substrate 352 on the substrate 351 side. End portions of the coloring layers 132R, 132G, and 132B can overlap with the light-block layer 157.
In the display device 100E, 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 display device 100E, the coloring layers 132R, 132G, and 132B may be provided between the protective layer 131 and the adhesive layer 142.
A display device 100E2 illustrated in
In the display device 100E2 illustrated in
Note that as illustrated in
Although the top surface shape of the microlens 182 is illustrated as a hexagon in
The microlens 182 can be formed using a material similar to that for the organic resin layer 180.
In the light-emitting apparatus of one embodiment of the present invention including the above-described microlens 182, the organic compound layer 103 includes the organic compound represented by General Formula (G1) as described in Embodiment 1, in which case an organic semiconductor device with high emission efficiency can be provided owing to an indivisible effect of the microlens 182 and the organic semiconductor device using the organic compounds of the present invention. Thus, an organic semiconductor device with high reliability, low driving voltage, and low power consumption can be provided.
This embodiment can be combined as appropriate with the other embodiments or the 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 a mixed reality (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, still further preferably higher than or equal to 500 ppi, yet still further preferably higher than or equal to 1000 ppi, yet still further preferably higher than or equal to 2000 ppi, yet still further preferably higher than or equal to 3000 ppi, yet still further preferably higher than or equal to 5000 ppi, yet still further preferably higher than or equal to 7000 ppi. The use of the light-emitting apparatus having one or both of such high definition and high resolution can further increase realistic sensation, sense of depth, and the like. 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 performing 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.
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 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 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 synthesis example, a method for synthesizing 4,8-di(9H-carbazol-9-yl)-benzofuro[3,2-d]pyrimidine (abbreviation: 4,8Cz2Bfpm), which is an organic compound represented by Structural Formula (100), is specifically described.
First, into a 200-mL three-neck flask were put 2.4 g (10 mmol) of 4,8-dichloro[1]benzofuro[3,2-d]pyrimidine, 3.7 g (22 mmol) of 9H-carbazole, 1.9 g (20 mmol) of sodium tert-butoxide (abbreviation: tBuONa), and 0.14 g (0.34 mmol) of di-tert-butyl(2,2-diphenyl-1-methyl-1-cyclopropyl)phosphine (abbreviation: cBRIDP). To the mixture was added 100 mL of mesitylene, and the mixture was degassed by being stirred while the pressure was reduced. Then, to the mixture was added 62 mg (0.17 mmol) of allylpalladium(II) chloride (dimer), and the mixture was stirred while being heated under a nitrogen stream at 140° C. for 31.5 hours. After the stirring, toluene was added to this mixture, and the mixture was subjected to suction-filtration through Celite to give a filtrate. The obtained filtrate was concentrated to give a solid. The obtained solid was purified by silica gel column chromatography (developing solvent: toluene). The obtained solid was recrystallized from toluene/ethanol to give 2.8 g of a light-yellow solid in a yield of 56%. By a train sublimation method, 2.7 g of the obtained solid was purified. The purification by sublimation was performed by heating at 260° C. under a pressure of 3.3 Pa with an argon flow rate of 15 mL/min. After the sublimation purification, 2.5 g of a light-yellow solid was obtained at a collection rate of 91%. The synthesis scheme of Step 1 is shown in (a-1) below.
Analysis results by nuclear magnetic resonance spectroscopy (1H NMR) of a deuterated chloroform (abbreviation: CDCl3) solution of the light-yellow solid obtained in Step 1 are shown below.
1H NMR (CDCl3, 300 MHz): δ=7.31-7.55 (m, 10H), 7.86-7.94 (m, 4H), 8.17-8.21 (m, 4H), 8.56 (d, J1=1.2 Hz, 1H), 9.31 (s, 1H).
Next,
The solid thin film was formed over a quartz substrate by a vacuum evaporation method. The absorption spectrum of the toluene solution was measured with an ultraviolet-visible light spectrophotometer (V-770DS, JASCO Corporation), and the spectrum of toluene alone in a quartz cell was subtracted. The absorption spectrum of the thin film was measured with a spectrophotometer (U-4100 Spectrophotometer, manufactured by Hitachi High-Technologies Corporation). The emission spectrum was measured with a fluorescence spectrophotometer (FP-8600, manufactured by JASCO Corporation).
As shown in
In this synthesis example, a method for synthesizing 4-(9H-carbazol-9-yl)-8-[3-(triphenylsilyl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8PSi-4CzBfpm), which is an organic compound represented by Structural Formula (101), is specifically described.
First, in Step 1, 4-(9H-carbazol-9-yl)-8-chloro-[1]benzofuro[3,2-d]pyrimidine was synthesized. Step 1 was performed in the following procedure.
Into a 300-mL three-neck flask were put 6.4 g (27 mmol) of 4,8-dichloro-benzofuro[3,2-d]pyrimidine, 4.5 g (27 mmol) of 9H-carbazole, and 5.7 g (27 mmol) of tripotassium phosphate. To the mixture was added 135 mL of dimethylsulfoxide (abbreviation: DMSO), and the mixture was stirred while being heated under a nitrogen stream at 90° C. for 6 hours. After the stirring, water was added to the mixture, and the solid was collected by suction filtration. Toluene was added to the resulting solid, heating and stirring were performed, and a solid was collected to give 7.5 g of a light-brown solid in a yield of 75%. The synthesis scheme of Step 1 is shown in (b-1) below.
Analysis results by nuclear magnetic resonance spectroscopy (1H NMR) of a deuterated chloroform (abbreviation: CDCl3) solution of the light-brown solid obtained in Step 1 are shown below.
1H NMR (CDCl3, 300 MHz): δ=7.39-7.52 (m, 4H), 7.59 (d, J1=8.7 Hz, 1H), 7.68 (dd, J1=8.7 Hz, J2=1.8 Hz, 1H), 7.81 (d, J1=8.1 Hz, 2H), 8.15 (d, J1=7.5 Hz, 2H), 8.31 (d, J1=2.1 Hz, 1H), 9.28 (s, 1H).
Next, 8PSi-4CzBfpm was synthesized using 4-(9H-carbazol-9-yl)-8-chloro-benzofuro[3,2-d]pyrimidine obtained in Step 1. Step 2 was performed in the following procedure.
Into a 200-mL three-neck flask were put 1.7 g (4.5 mmol) of 4-(9H-carbazol-9-yl)-8-chloro-[1]benzofuro[3,2-d]pyrimidine obtained in Step 1, 2.3 g (4.9 mmol) of 2-[3-(triphenylsilyl)phenyl]-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 96 mg (0.27 mmol) of di(1-adamantyl)-n-butylphosphine, 2.9 g (13 mmol) of tripotassium phosphate, and 1.0 g (13 mmol) of tert-butanol (abbreviation: tBuOH). To this mixture was added 40 mL of diethylene glycol dimethyl ether (abbreviation: Diglyme). The mixture was degassed by being stirred while the pressure was reduced. To this mixture was added 30 mg (0.13 mmol) of palladium(II) acetate, and the mixture was stirred under a nitrogen stream at 120° C. for 6 hours. After the stirring, water was added to the mixture, and the solid was collected by suction filtration. This solid was purified by silica gel column chromatography (developing solvent: toluene and then toluene and ethyl acetate in a 50:1 ratio). The obtained solid was recrystallized from ethyl acetate to give 2.3 g of a white solid in a yield of 77%. By a train sublimation method, 2.3 g of the obtained solid was purified. The purification by sublimation was performed by heating at 290° C. under a pressure of 3.6 Pa with an argon flow rate of 15 mL/min. After the sublimation purification, 2.2 g of a white solid was obtained at a collection rate of 94%. The synthesis scheme of Step 2 is shown in (b-2) below.
Analysis results by nuclear magnetic resonance spectroscopy (1H NMR) of a deuterated chloroform (abbreviation: CDCl3) solution of the white solid obtained in Step 2 are shown below.
1H NMR (CDCl3, 300 MHz): δ=7.39-7.68 (m, 22H), 7.76-7.90 (m, 5H), 8.15 (d, J1=7.5 Hz, 2H), 8.47 (d, J1=1.5 Hz, 1H), 9.27 (s, 1H).
Next,
The absorption spectrum of the toluene solution was measured with an ultraviolet-visible light spectrophotometer (V-770DS, JASCO Corporation), and the spectrum of toluene alone in a quartz cell was subtracted. The absorption spectrum of the thin film was measured with a spectrophotometer (U-4100 Spectrophotometer, manufactured by Hitachi High-Technologies Corporation). The emission spectrum was measured with a fluorescence spectrophotometer (FP-8600, manufactured by JASCO Corporation).
As shown in
In this synthesis example, a method for synthesizing 4-(9H-carbazol-9-yl)-8-(dibenzofuran-2-yl)-[1]benzofuro-[3,2-d]pyrimidine (abbreviation: 8DBf-4CzBfpm), which is an organic compound represented by Structural Formula (102), is specifically described.
In this step, 8DBf-4CzBfpm was synthesized using 4-(9H-carbazol-9-yl)-8-chloro-benzofuro[3,2-d]pyrimidine obtained in Step 1 of Synthesis Example 2. Step 1 was performed in the following procedure.
Into a 200-mL three-neck flask were put 1.7 g (4.5 mmol) of 4-(9H-carbazol-9-yl)-8-chloro-[1]benzofuro[3,2-d]pyrimidine obtained in Step 1 of Synthesis Example 2, 2.3 g (4.9 mmol) of 2-[3-(triphenylsilyl)phenyl]-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 96 mg (0.27 mmol) of di(1-adamantyl)-n-butylphosphine, 2.9 g (13 mmol) of tripotassium phosphate, and 1.0 g (13 mmol) of tert-butanol (abbreviation: tBuOH). To this mixture was added 40 mL of diethylene glycol dimethyl ether (abbreviation: Diglyme). The mixture was degassed by being stirred while the pressure was reduced. To this mixture was added 30 mg (0.13 mmol) of palladium(II) acetate, and the mixture was stirred under a nitrogen stream at 120° C. for 6 hours. After the stirring, water was added to the mixture, and the solid was collected by suction filtration. This solid was purified by silica gel column chromatography (developing solvent: hexane and then toluene and ethyl acetate in a 50:1 ratio). The obtained solid was recrystallized from ethyl acetate to give 2.3 g of a white solid in a yield of 77%. By a train sublimation method, 2.3 g of the obtained solid was purified. The purification by sublimation was performed by heating at 290° C. under a pressure of 3.6 Pa with an argon flow rate of 15 mL/min. After the sublimation purification, 2.2 g of a white solid was obtained at a collection rate of 94%. The synthesis scheme of Step 1 is shown in (c-1) below.
Analysis results by nuclear magnetic resonance spectroscopy (1H NMR) of a deuterated chloroform (abbreviation: CDCl3) solution of the white solid obtained in Step 2 are shown below.
1H NMR (CDCl3, 300 MHz): δ=7.38-7.54 (m, 6H), 7.62-7.82 (m, 4H), 7.86 (d, J1=7.8 Hz, 2H), 8.03-8.07 (m, 2H), 8.17 (d, J1=7.2 Hz, 2H), 8.28 (d, J1=1.5 Hz, 1H), 8.63 (d, J1=1.5 Hz, 1H), 9.31 (s, 1H).
Next,
The absorption spectrum of the toluene solution was measured with an ultraviolet-visible light spectrophotometer (V-770DS, JASCO Corporation), and the spectrum of toluene alone in a quartz cell was subtracted. The absorption spectrum of the thin film was measured with a spectrophotometer (U-4100 Spectrophotometer, manufactured by Hitachi High-Technologies Corporation). The emission spectrum was measured with a fluorescence spectrophotometer (FP-8600, manufactured by JASCO Corporation).
As shown in
In this example, the lowest triplet excitation energy level (T1 level) of the following materials were calculated by measuring the emission spectra (phosphorescence spectra) thereof: 4,8-di(9H-carbazol-9-yl)-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8Cz2Bfpm) which is an organic compound represented by Structural Formula (100); 4-(9H-carbazol-9-yl)-8-[3-(triphenylsilyl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8PSi-4CzBfpm) which is an organic compound represented by Structural Formula (101); and 4-(9H-carbazol-9-yl)-8-(dibenzofuran-2-yl)-[1]benzofuro-[3,2-d]pyrimidine (abbreviation: 8DBf-4CzBfpm) which is an organic compound represented by Structural Formula (102).
As a comparative example, the lowest triplet excitation energy level (T1 level) was calculated by measuring the emission spectrum (phosphorescence spectrum) of 4,8-bis[3-(9H-carbazol-9-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mCzP2Bfpm).
Structural Formulae of organic compounds used in this example are shown below.
For calculation of the lowest triplet excitation energy level (T1 level), an emission spectrum (a phosphorescence spectrum) was measured at a measurement temperature of 10 K using a 50-nm-thick thin film of a sample formed over a quartz substrate. The measurement was performed with a PL microscope (LabRAM HR-PL, produced by HORIBA, Ltd.) and a He—Cd laser (325 nm) as excitation light. Note that the emission edge was determined as the intersection of a tangent and the horizontal axis (representing wavelength) or the baseline. The tangent is drawn to have the maximum slope at a point on a shorter wavelength side of the shortest-wavelength peak (or the shortest-wavelength shoulder peak) of the emission spectrum (phosphorescence spectrum).
The calculated T1 levels of 4,8Cz2Bfpm, 8PSi-4CzBfpm, 8DBf-4CzBfpm, and 4,8mCzP2Bfpm were 2.82 eV, 2.90 eV, 2.88 eV, and 2.71 eV, respectively. The calculated Ti levels of the organic compounds are listed in the following table.
From the above table, it was found that the T1 levels of 4,8Cz2Bfpm, 8PSi-4CzBfpm, and 8DBf-4CzBfpm, which are the organic compounds of embodiments of the present invention, were each lower than 2.95 eV and higher than 2.75 eV. Meanwhile, it was found that the T1 level of 4,8mCzP2Bfpm, which is a comparative example, was lower than 2.75 eV.
Thus, the organic compound of one embodiment of the present invention has a high triplet excitation energy level (T1 level); accordingly, in the case where the organic compound is used as a host material in a light-emitting device that emits light in a blue region, the degree of freedom in selecting the guest material can be increased.
In this example, a light-emitting device 5A, a light-emitting device 5B, and a light-emitting device 5C each including the organic compound of one embodiment of the present invention and a comparative light-emitting device 5D including the organic compound for comparison were fabricated, and the characteristics thereof were measured.
Structural Formulae of organic compounds used for the light-emitting devices 5A to 5D are shown below.
In each of the devices, as illustrated in
As the first electrode 901 serving as a transparent electrode, a film of indium tin oxide including silicon oxide (ITSO) was formed to a thickness of 70 nm over the glass substrate 900 by a sputtering method. The electrode area was set to 4 mm2 (2 mm×2 mm).
Next, in pretreatment for forming the light-emitting device over a substrate, the surface of the substrate was washed with water, and baking was performed at 200° C. for one hour. Then, the substrate was transferred into a vacuum evaporation apparatus where the internal 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 to lower than or equal to 30° C.
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, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and an electron acceptor material including fluorine and having a molecular weight of 672 (OCHD-003) were deposited by co-evaporation 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 911 was formed.
Next, over the hole-injection layer 911, PCBBiF was deposited by evaporation to a thickness of 30 nm and then, 9-[3-(triphenylsilyl)phenyl]-3,9′-bi-9H-carbazole (abbreviation: PSiCzCz) was deposited by evaporation to a thickness of 5 nm, so that the hole-transport layer 912 was formed.
Subsequently, over the hole-transport layer 912, 4,8-di(9H-carbazol-9-yl)-benzofuro[3,2-d]pyrimidine (abbreviation: 4,8Cz2Bfpm), PSiCzCz, and (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-kC2]phenoxy-kC2}-9-(4-tert-butyl-2-pyridinyl-kN)carbazole-2,1-diyl-kC1)platinum(II) (abbreviation: PtON-TBBI) were deposited by co-evaporation to a thickness of 35 nm using resistance heating such that the weight ratio between 4,8Cz2Bfpm, PSiCzCz, and PtON-TBBI was 0.45:0.45:0.10, whereby the light-emitting layer 913 was formed.
Then, over the light-emitting layer 913, 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviation: mSiTrz) was deposited by evaporation to a thickness of 5 nm and then, 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) was deposited by co-evaporation to a thickness of 20 nm, whereby the electron-transport layer 914 was formed.
Next, lithium fluoride (LiF) was deposited by evaporation to a thickness of 1 nm over the electron-transport layer 914, whereby the electron-injection layer 915 was formed.
Then, aluminum (Al) was deposited by evaporation to a thickness of 200 nm over the electron-injection layer, whereby the second electrode was formed.
Next, a method for fabricating the light-emitting device 5B is described.
The light-emitting device 5B is different from the light-emitting device 5A in the structure of the light-emitting layer 913. That is, in the light-emitting device 5B, 4-(9H-carbazol-9-yl)-8-[3-(triphenylsilyl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8PSi-4CzBfpm), PSiCzCz, and PtON-TBBI were deposited by co-evaporation to a thickness of 35 nm using resistance heating such that the weight ratio between 8PSi-4CzBfpm, PSiCzCz, and PtON-TBBI was 0.60:0.30:0.10, whereby the light-emitting layer 913 was formed.
Other components were fabricated in a manner similar to that for the light-emitting device 5A.
Next, a method for fabricating the light-emitting device 5C is described.
The light-emitting device 5C is different from the light-emitting device 5A in the structure of the light-emitting layer 913. That is, in the light-emitting device 5C, 4-(9H-carbazol-9-yl)-8-(dibenzofuran-2-yl)-[1]benzofuro-[3,2-d]pyrimidine (abbreviation: 8DBf-4CzBfpm), PSiCzCz, and PtON-TBBI were deposited by co-evaporation to a thickness of 35 nm using resistance heating such that the weight ratio between 8DBf-4CzBfpm, PSiCzCz, and PtON-TBBI was 0.45:0.45:0.10, whereby the light-emitting layer 913 was formed.
Other components were fabricated in a manner similar to that for the light-emitting device 5A.
Next, a method for fabricating the light-emitting device 5D is described.
The light-emitting device 5D is different from the light-emitting device 5A in the structure of the light-emitting layer 913. That is, in the light-emitting device 5D, 9,9′-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviation: SiTrzCz2), PSiCzCz, and PtON-TBBI were deposited by co-evaporation to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2, PSiCzCz, and PtON-TBBI was 0.45:0.45:0.10, whereby the light-emitting layer 913 was formed.
Other components were fabricated in a manner similar to that for the light-emitting device 5A.
The structures of the light-emitting devices 5A to 5D are listed in the following table. Note that the structure of the light-emitting layer indicated by 5X in the table is shown in a separate table.
The light-emitting devices were sealed using a glass substrate in a glove box including a nitrogen atmosphere so as not to be exposed to the air (a sealing material was applied to surround the devices, and UV treatment and heat treatment at 80° C. for 1 hour were performed at the time of sealing). Then, the characteristics of the devices were measured.
Note that the blue index (BI) is a value obtained by dividing current efficiency (cd/A) by the y value of CIE chromaticity (x, y), and is one of the indicators of characteristics of blue light emission. As the y chromaticity value of blue light emission becomes smaller, the color purity thereof tends to be higher. Blue light emission having a small y chromaticity value and high color purity enables expression of blue colors with a wide range of chromaticity in a display. Using blue light emission with high color purity reduces the luminance of blue light emission necessary for a display to express white, leading to lower power consumption of the display. Thus, BI, which is current efficiency based on a y chromaticity value as one of the indicators of color purity of blue, is suitably used as a means for showing efficiency of blue light emission in some cases. The light-emitting device with higher BI can be regarded as a blue-light-emitting device having higher efficiency for a display.
The table below shows the main characteristics of the light-emitting devices at a luminance of 1000 cd/m2. The luminance, CIE chromaticity, and emission spectra were measured with a spectroradiometer (SR-UL1R, manufactured by TOPCON TECHNOHOUSE CORPORATION). The external quantum efficiency (EQE) was calculated from the luminance and the emission spectra measured with the spectroradiometer, on the assumption that the devices had Lambertian light-distribution characteristics.
From
Here, PL spectra of the thin films of 4,8Cz2Bfpm, 8PSi-4CzBfpm, 8DBf-4CzBfpm, and PSiCzCz used in the light-emitting layers of the light-emitting devices 5A to 5C were measured at room temperature. The PL spectra of mixed films in each of which 4,8Cz2Bfpm, 8PSi-4CzBfpm, or 8DBf-4CzBfpm, and PSiCzCz were mixed were measured at room temperature.
Note that the PL spectrum at room temperature (e.g., approximately 290 K to 300 K (17° C. to 27° C.), preferably at or around 298 K (e.g., 25° C.)) was obtained by measuring light emitted when photoexcited molecules returned from the singlet excited state to the ground state and thus corresponds to a fluorescent spectrum.
A spectrofluorometer FP-8600DS produced by JASCO Corporation was used for the measurement of the fluorescent spectrum.
The PL spectrum of each of the mixed films was measured using a 50-nm-thick thin film formed over a quartz substrate. Note that the mixed films were formed by co-evaporation at the respective mixing ratios in the following table.
In
It was found from
In
It was found from
In
It was found from
From the above results, it was found that in the light-emitting layers of the light-emitting devices 5A, 5B, and 5C, PSiCzCz and each of 4,8Cz2Bfpm, 8PSi-4CzBfpm, and 8DBf-4CzBfpm form an exciplex in combination. The photoluminescence (PL) spectra of the exciplex shown in
Here, the HOMO level of PSiCzCz and the LUMO levels of 4,8Cz2Bfpm, 8PSi-4CzBfpm, 8DBf-4CzBfpm, and SiTrzCz2 were calculated by cyclic voltammetry (CV) measurement.
An electrochemical analyzer (ALS model 600A or 600C, BAS Inc.) was used for the measurement. Dehydrated dimethylformamide (DMF) was used as a solvent of the solutions of the organic compounds used in the measurement. In the measurement, the potential of a working electrode with respect to a reference electrode was changed within an appropriate range, so that the oxidation peak potential and the reduction peak potential were obtained. A platinum electrode (PTE platinum electrode, BAS Inc.) was used as a working electrode, a platinum electrode (Pt counter electrode for VC-3 (5 cm), BAS Inc.) was used as an auxiliary electrode, and an Ag/Ag+ electrode (RE-7 nonaqueous reference electrode, BAS Inc.) was used as a reference electrode. The HOMO and LUMO levels of the organic compounds were calculated from the estimated redox potential of the reference electrode of −4.94 eV and the obtained peak potentials.
As a result, the LUMO levels of 4,8Cz2Bfpm, 8PSi-4CzBfpm, 8DBf-4CzBfpm, and SiTrzCz2 were −2.94 eV, −2.87 eV, −2.87 eV, and −2.98 eV, respectively. The HOMO level of PSiCzCz was −5.7 eV. The absolute value of the difference (JAEJ) between the HOMO level of PSiCzCz and the LUMO level of 4,8Cz2Bfpm, 8PSi-4CzBfpm, 8DBf-4CzBfpm, or SiTrzCz2 was calculated. The results were listed in the table below.
When the difference between the HOMO level of a second host material and the LUMO level of a first host material is less than or equal to 2.70 eV, the emission spectrum of the exciplex does not overlap with the absorption spectrum of the blue dopant in some cases even when the exciplex is formed.
Thus, a light-emitting device that exhibits a favorable blue color can be provided with the following structure because energy can be efficiently transferred from the exciplex to the light-emitting substance: the absolute value of the difference between the HOMO level of the second host material such as PSiCzCz and the LUMO level of the organic compound of one embodiment of the present invention, which is used as the first host material, is greater than or equal to 2.75 eV and less than or equal to 2.85 eV, preferably greater than or equal to 2.78 eV and less than or equal to 2.85 eV, and the T1 levels of the host materials are higher than the T1 level of the guest material such as PtON-TBBI.
That is, it was confirmed that a light-emitting device with high efficiency can be provided with the use of the organic compound of one embodiment of the present invention.
Furthermore, each of the light-emitting device 5A, the light-emitting device 5B, and the light-emitting device 5C was able to obtain a sharp emission spectrum with a full width at half maximum of less than or equal to 44 nm as compared with the comparative light-emitting device 5D because intermolecular interaction between the organic compound of one embodiment of the present invention (4,8Cz2Bfpm, 8PSi-4CzBfpm, or 8DBf-4CzBfpm) which is used as the host material and PtON-TBBI used as the guest material was small. This is ascribed to that the LUMO level of SiTrzCz2, which is a comparative host material, is low. That is, the emission spectrum was broadened due to the formation of an exciplex having small energy difference between the HOMO level of PtON-TBBI and the LUMO level of SiTrzCz2.
Thus, with the structure of a light-emitting device in which the LUMO level of the organic compound of one embodiment of the present invention is lower than or equal to −2.80 eV and higher than or equal to −2.97 eV, preferably lower than or equal to −2.80 eV and higher than or equal to −2.87 eV, a light-emitting device exhibiting favorable blue color can be provided.
Accordingly, when the organic compound of one embodiment of the present invention is used in a light-emitting device, the emission spectrum can be narrowed and blue light emission with high color purity can be obtained. Blue light emission with high color purity allows expression of a wide range of blue and reduces the luminance needed for expressing blue, whereby power consumption can be lowered.
It is thus found that the use of the organic compound of one embodiment of the present invention enables a light-emitting device to have favorable characteristics.
In this synthesis example, a method for synthesizing 4-(9H-carbazol-9-yl)-8-(triphenylen-2-yl)-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8Tp-4CzBfpm), which is an organic compound represented by Structural Formula (103), is specifically described.
First, into a 200-mL three-neck flask were put 2.0 g (5.3 mmol) of 4-(9H-carbazol-9-yl)-8-chloro-[1]benzofuro[3,2-d]pyrimidine, 2.2 g (8.0 mmol) of 2-triphenyleneboronic acid, 0.12 g (0.32 mmol) of di(1-adamantyl)-n-butylphosphine, 3.4 g (16 mmol) of tripotassium phosphate, and 1.2 g (16 mmol) of tert-butanol (abbreviation: tBuOH). To this mixture was added 55 mL of diethylene glycol dimethyl ether (abbreviation: Diglyme). The mixture was degassed by being stirred while the pressure was reduced. To this mixture was added 57 mg (0.16 mmol) of palladium(II) acetate, and the mixture was stirred under a nitrogen stream at 120° C. for 11 hours. After the stirring, water was added to the mixture, and the solid was collected by suction filtration. This solid was purified by silica gel column chromatography (developing solvent: toluene and hexane in a 1:3 ratio and then toluene). The obtained solid was recrystallized from toluene to give 1.9 g of a light-yellow solid in a yield of 62%. By a train sublimation method, 1.8 g of the obtained solid was purified. The purification by sublimation was performed by heating at 300° C. under a pressure of 3.7 Pa with a flow rate of argon gas of 15 mL/min. After the sublimation purification, 1.6 g of a light-yellow solid was obtained at a collection rate of 90%. A synthesis scheme of Step 1 is shown in (d-1) below.
Analysis results by nuclear magnetic resonance spectroscopy (1H NMR) of a deuterated chloroform (abbreviation: CDCl3) solution of the light-yellow solid obtained in Step 1 are shown below.
1H NMR (CDCl3, 300 MHz): δ=7.43 (td, J1=7.8 Hz, J2=1.2 Hz, 2H), 7.52 (td, J1=6.9 Hz, J2=1.2 Hz, 2H), 7.67-7.75 (m, 4H), 7.79 (d, J1=8.4 Hz, 1H), 7.88 (d, J1=8.1 Hz, 2H), 8.00 (dd, J1=8.7 Hz, J2=1.8 Hz, 1H), 8.15-8.19 (m, 3H), 8.67-8.82 (m, 6H), 8.97 (d, J1=1.8 Hz, 1H), 9.32 (s, 1H).
This application is based on Japanese Patent Application Serial No. 2023-212446 filed with Japan Patent Office on Dec. 15, 2023, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-212446 | Dec 2023 | JP | national |
