Patent Application
20250176421
One embodiment of the present invention relates to an organometallic complex, an organic compound, a light-emitting device, a light-receiving device, a light-emitting and light-receiving device, a light-emitting apparatus, a light-emitting and light-receiving apparatus, a display apparatus, an electronic appliance, a lighting device, and an electronic device. Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. One embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display apparatus, a liquid crystal display apparatus, a light-emitting apparatus, a lighting device, a power storage device, a memory device, an image capturing device, a driving method thereof, and a manufacturing method thereof.
Organic electroluminescence (EL) devices (organic EL elements) typified by light-emitting devices, light-receiving devices, and light-emitting and light-receiving devices, which utilize EL with an organic compound, are being put to practical use.
In the basic structure of the light-emitting devices, for example, an organic compound layer containing a light-emitting material (an EL layer) is located between a pair of electrodes. Carriers are injected by application of a voltage to the device, and light emission can be obtained from the light-emitting material by using the recombination energy of the carriers.
In the basic structure of the light-receiving devices, an organic compound layer containing a photoelectric conversion material (an active layer) is located between a pair of electrodes. This device absorbs light energy to generate carriers, whereby electrons from the photoelectric conversion material can be obtained.
For example, a functional panel in which a pixel provided in a display region includes a light-emitting element (light-emitting device) and a photoelectric conversion element (light-receiving device) is known (Patent Document 1).
Displays or lighting devices that include organic EL devices can be suitably used for a variety of electronic appliances as described above, and research and development of organic EL devices have progressed for higher efficiency or a longer lifetime.
Although the characteristics of organic EL devices have been improved considerably, advanced requirements for various characteristics including efficiency and durability are not yet satisfied. In particular, to solve a problem such as burn-in, which is an issue peculiar to organic EL devices, it is preferable to inhibit a reduction in efficiency due to deterioration as much as possible.
Deterioration largely depends on an emission center substance and its surrounding materials; therefore, organic compound materials having good characteristics, such as an organometallic complex, have been actively developed.
An object of one embodiment of the present invention is to provide a novel organometallic complex. Another object of one embodiment of the present invention is to provide an organometallic complex that is stable in an excited state. Another object of one embodiment of the present invention is to provide an organometallic complex that can be used as a light-emitting material. Another object of one embodiment of the present invention is to provide an organometallic complex that is easy to synthesize. Another object of one embodiment of the present invention is to provide a light-emitting device with along driving lifetime. Another object of one embodiment of the present invention is to provide a light-emitting device in which a voltage change during driving is small. Another object of one embodiment of the present invention is to provide a novel light-emitting device. Another object of one embodiment of the present invention is to reduce manufacturing costs of a light-emitting device. Another object of one embodiment of the present invention is to provide a light-emitting apparatus, an electronic appliance, or a lighting device having low power consumption.
Another object of one embodiment of the present invention is to provide an organometallic complex in which a partial structure is selectively deuterated. Another object of one embodiment of the present invention is to perform a molecular design with which the degree of complexity of a synthesis pathway can be reduced and increases in the temperature, pressure, and the like for synthesis can be inhibited, and to synthesize an organometallic complex with such a molecular design.
Note that the description of these objects does not preclude the existence of other objects. One embodiment of the present invention does not need to achieve all these objects. Other objects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
One embodiment of the present invention is an organometallic complex represented by General Formula (G1) below.
In General Formula (G1) above, each of R2 and R8 represents a deuterated alkyl group having 1 to 10 carbon atoms, each of R1, R3 to R7, and R9 to R26 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, at least one of R4 to R6 represents an alkyl group having 1 to 10 carbon atoms, and at least one of R22 to R26 represents an alkyl group having 3 to 10 carbon atoms.
In the organometallic complex having the above structure, it is preferable that each of R23 and R25 represent an alkyl group having 3 to 10 carbon atoms.
Another embodiment of the present invention is an organometallic complex represented by General Formula (G1) below.
In General Formula (G1) above, each of R2 and R8 represents a deuterated alkyl group having 1 to 10 carbon atoms, R5 represents an alkyl group having 1 to 10 carbon atoms, each of R1, R3, R4, R6, R7, and R9 to R26 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, and at least one of R22 to R26 represents an alkyl group having 3 to 10 carbon atoms.
Another embodiment of the present invention is an organometallic complex represented by General Formula (G1) below.
In General Formula (G1) above, R5 represents an alkyl group having 1 to 10 carbon atoms, each of R2 and R8 represents a deuterated alkyl group having 1 to 10 carbon atoms, each of R23 and R25 represents an alkyl group having 3 to 10 carbon atoms, and each of R1, R3, R4, R6, R7, R9 to R22, R24, and R26 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms.
Another embodiment of the present invention is an organometallic complex represented by General Formula (G2) below.
In General Formula (G2) above, each of R1, R3, R4, R6, R7, R9 to R22, R24, and R26 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms.
Another embodiment of the present invention is an organometallic complex represented by Structural Formula (100) below.
Another embodiment of the present invention is a light-emitting device fabricated using any of the above organometallic complexes. Another embodiment of the present invention is a light-emitting device that includes a light-emitting layer including any of the above organometallic complexes. Another embodiment of the present invention is a light-emitting apparatus that includes a light-emitting device fabricated using any of the above organometallic complexes, and a light-receiving device.
Another embodiment of the present invention is a light-emitting apparatus that includes the light-emitting device with any of the above structures, and a transistor or a substrate.
Another embodiment of the present invention is an electronic appliance that includes the light-emitting apparatus with any of the above structures, and a sensing portion, an input portion, or a communication portion.
Another embodiment of the present invention is a lighting device that includes the light-emitting apparatus with any of the above structures and a housing.
One embodiment of the present invention can provide a novel organometallic complex. Another embodiment of the present invention can provide an organometallic complex that is stable in an excited state. Another embodiment of the present invention can provide an organometallic complex that can be used as a light-emitting material. Another embodiment of the present invention can provide an organometallic complex that is easy to synthesize. Another embodiment of the present invention can provide a novel light-emitting device. Another embodiment of the present invention can provide a light-emitting device with a long driving lifetime. Another embodiment of the present invention can provide a light-emitting device in which a voltage change during driving is small. Another embodiment of the present invention can reduce manufacturing costs of a light-emitting device. Another embodiment of the present invention can provide a light-emitting apparatus, an electronic appliance, or a lighting device having low power consumption.
Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all these effects. Other effects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
In this embodiment, an organometallic complex of one embodiment of the present invention and a light-emitting device that includes the organometallic complex are described.
First, a structure of a light-emitting device of one embodiment of the present invention is described with reference to
The light-emitting device 10 includes a pair of electrodes (a first electrode 101 and a second electrode 102) and an organic compound layer 103 between the pair of electrodes. The organic compound layer 103 includes at least a light-emitting layer 113.
The organic compound layer 103 illustrated in
Although description in this embodiment is made 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 organometallic complex, and the light-emitting organometallic complex is preferably a substance capable of emitting phosphorescent light (hereinafter also referred to as a phosphorescent compound). In the description below, an organometallic complex is used as the guest material 119.
According to the present invention, the guest material 119 is an organometallic complex that contains platinum (Pt) as a central metal. Note that in the organometallic complex used in one embodiment of the present invention, a pyridine ring is coordinated to the central metal, and a deuterated alkyl group is bonded to each of the 3- and 5-positions of the pyridine ring. A phenyl group is bonded to the 4-position of the pyridine ring, and the phenyl group further has an alkyl group.
In this specification and the like, “hydrogen” includes protium and deuterium. Deuterium is a stable hydrogen isotope having a mass number of 2. Protium is a stable hydrogen isotope having a mass number of 1. The dissociation energy of a carbon-deuterium bond is higher than the dissociation energy of a carbon-protium bond; thus, in the organometallic complex having the pyridine ring, the introduction of the deuterated alkyl group to each of the carbon atoms at the 3- and 5-positions of the pyridine ring, which have a high spin density in a triplet excited state, can increase the stability of the molecule. The introduction also inhibits bond dissociation in an excited state to increase the stability of the organometallic complex. In addition, the introduction of the deuterated alkyl group to each of the carbon atoms at the 3- and 5-positions of the pyridine ring, where the lowest unoccupied molecular orbital (LUMO) distribution is concentrated, can increase the stability of the organometallic complex in a state where the LUMO has received electrons, i.e., a reduction state.
The introduction of the deuterated alkyl group in the organometallic complex having the pyridine ring produces an effect of steric hindrance on the phenyl group bonded to the 4-position of the pyridine ring. Rotation of the phenyl group can be suppressed and the thermophysical property, e.g., the sublimation property, of the organometallic complex can be improved. Vibration of the organometallic complex can be suppressed and thermal deactivation from the excited state can be suppressed.
The introduction of the phenyl group to the carbon atom at the 4-position between the carbon atoms at the 3- and 5-positions of the pyridine ring, where the LUMO distribution is concentrated, can expand the LUMO distribution. Moreover, the LUMO level is stabilized and the stability of the organometallic complex in a reduction state can be improved.
In the organometallic complex having the pyridine ring, the introduction of the phenyl group to the carbon atom at the 4-position of the pyridine ring can increase the planarity of the organometallic complex. Accordingly, in the case where the organometallic complex is used as a guest material in a light-emitting layer of a light-emitting device, higher molecular orientation is induced and the orientation is likely to be parallel to a substrate plane. Light from the organometallic complex is emitted in the direction perpendicular to the transition dipole moment involved in the light emission of the organometallic complex; thus, when the transition dipole moment of the organometallic complex is parallel to the substrate plane, a larger proportion of the light from the organometallic complex is emitted in the direction perpendicular to the substrate plane, leading to higher light extraction efficiency of the light-emitting device. Thus, the organometallic complex preferably has orientation such that the transition dipole moment involved in light emission of the organometallic complex is parallel to the substrate plane.
The phenyl group bonded to the 4-position of the pyridine ring and having the alkyl group can inhibit intermolecular interaction. For example, when the organometallic complex of one embodiment of the present invention is used as the guest material 119 in the light-emitting layer 113 illustrated in
Accordingly, for example, the organometallic complex of one embodiment of the present invention can be suitably used for a light-emitting layer of a light-emitting device. For another example, the organometallic complex of one embodiment of the present invention can be suitably used for a layer in contact with a light-emitting layer of a light-emitting device.
One embodiment of the present invention is an organometallic complex containing platinum (Pt) as a central metal and represented by the general formula below. An organometallic complex containing platinum (Pt) is extremely suitable for a light-emitting device.
One embodiment of the present invention is an organometallic complex represented by General Formula (G1) below.
In General Formula (G1) above, each of R2 and R8 represents a deuterated alkyl group having 1 to 10 carbon atoms, each of R1, R3 to R7, and R9 to R26 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, at least one of R4 to R6 represents an alkyl group having 1 to 10 carbon atoms, and at least one of R22 to R26 represents an alkyl group having 3 to 10 carbon atoms. It is preferable that each of R23 and R25 represent an alkyl group having 3 to 10 carbon atoms.
In General Formula (G1) above, the phenyl group bonded to the 4-position of the pyridine ring, where the LUMO distribution is concentrated, can stabilize the LUMO level. In General Formula (G1) above, the introduction of a deuterated alkyl group as each of R2 and R8 allows the phenyl group bonded to the 4-position of the pyridine ring, where the LUMO distribution is concentrated, to be easily twisted with respect to the pyridine ring; thus, the LUMO level can be adjusted to an appropriate value, and the organometallic complex can emit light with a shorter wavelength. In particular, when R2 and R8 are each a deuterated alkyl group having 1 to 10 carbon atoms in General Formula (G1) above, dissociation of a carbon-deuterium bond is less likely to occur. In addition, the introduction of the deuterated alkyl group to each of the carbon atoms at the 3- and 5-positions of the pyridine ring, where the LUMO distribution is concentrated, can increase the stability of the organometallic complex in a state where the LUMO has received electrons, i.e., a reduction state.
The introduction of an alkyl group having 1 to 10 carbon atoms as at least one of R4 to R6 in General Formula (G1) above can inhibit intermolecular interaction and increase the emission efficiency of the light-emitting device. Specifically, it is preferable that an alkyl group having 1 to 10 carbon atoms be introduced as R5 in General Formula (G1) above to enhance the effect of inhibiting intermolecular interaction and to increase the planarity of the organometallic complex.
The introduction of an alkyl group having 1 to 10 carbon atoms as at least one of R23 to R25 in General Formula (G1) above can inhibit intermolecular interaction. Specifically, it is preferable that an alkyl group having 1 to 10 carbon atoms be introduced as each of R23 and R25 in General Formula (G1) above. In that case, rotation of the phenyl group to which R23 and R25 are bonded can be suppressed and the thermophysical property, e.g., the sublimation property, of the organometallic complex can be improved. Moreover, thermal deactivation of the molecule is suppressed, increasing the quantum efficiency. The effect of inhibiting intermolecular interaction can be enhanced, so that the emission efficiency of the light-emitting device can be improved.
Another embodiment of the present invention is an organometallic complex represented by General Formula (G2) below.
In General Formula (G2) above, each of R1, R3, R4, R6, R7, R9 to R22, R24, and R26 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms.
General Formula (G2) is different from General Formula (G1) in that R2 and R8 are limited to methyl-d3 groups, R5 is limited to a tert-butyl group, and R23 and R25 are limited to tert-butyl groups.
The limitation of R2 and R8 in General Formula (G2) above to methyl-d3 groups increases the stability of the organometallic complex. Moreover, the limitation makes the cost of synthesizing the organometallic complex lower than that in the case where R2 and R8 are each a deuterated alkyl group having 2 or more carbon atoms.
The limitation of R5 in General Formula (G2) above to a bulky tert-butyl group further enhances the effect of steric hindrance on a surrounding material.
The limitation of R23 and R21 in General Formula (G2) above to bulky tert-butyl groups further enhances the effect of steric hindrance on a surrounding material. Rotation of the phenyl group to which R23 and R25 are bonded can be suppressed and the thermophysical property, e.g., the sublimation property, of the organometallic complex can be improved. Moreover, thermal deactivation of the molecule is suppressed, increasing the quantum efficiency. The effect of inhibiting intermolecular interaction can be enhanced, so that the emission efficiency of the light-emitting device can be improved.
Next, specific examples of substituents that can be applied to the organometallic complexes represented by General Formulae (G1) and (G2) are described. Note that in the specific examples described below, some or all of hydrogen atoms may be deuterium atoms unless otherwise specified. The groups that can be used in the above general formulae are not limited to the following specific examples.
Specific examples of the alkyl group having 1 to 10 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, a 2,3-dimethylbutyl group, and a 1-ethylhexyl group. A tert-butyl group is particularly preferable because it is bulky and has a high effect of inhibiting intermolecular interaction.
Specific examples of the deuterated alkyl group having 1 to 10 carbon atoms include a methyl-d3 group, an ethyl-d5 group, a propyl-d7 group, a 2-propyl-2-d group, an isopropyl-d7 group, a butyl-d9 group, a 2-methyl-1-propyl-1,1-d2 group, an isobutyl-d9 group, a sec-butyl-d9 group, a tert-butyl-d9 group, a pentyl-dii group, an isopentyl-dii group, a hexyl-d13 group, and a 1-ethylhexyl-1-d group. Other examples include the groups which are given above as specific examples of the alkyl group having 1 to 10 carbon atoms and in which one or more hydrogen atoms are substituted by deuterium atoms. It is particularly preferable to use a methyl-d3 group or any other group in which all hydrogen atoms are substituted by deuterium atoms, to further increase the stability of the organometallic complex. An organometallic complex to which a methyl-d3 group is introduced is preferable because the organometallic complex can be synthesized at lower cost than an organometallic complex to which a deuterated alkyl group having 2 or more carbon atoms is introduced.
Specific examples of the aryl group having 6 to 18 carbon atoms include a phenyl group, a biphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthryl group, a tetracenyl group, a benzanthracenyl group, a triphenylenyl group, a pyrenyl group, and a spirobi[9H-fluoren]yl group. In the case where the aryl group having 6 to 18 carbon atoms has a substituent, specific examples of the substituent include an alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, and an aryl group having 6 to 13 carbon atoms.
Next, specific examples of the organometallic complex of one embodiment of the present invention having the structure represented by General Formula (G1) or (G2) above are shown below.
Although the organometallic complexes represented by Structural Formulae (100) to (116) above are examples of the organometallic complex represented by General Formula (G1) or (G2) above, the organometallic complex of one embodiment of the present invention is not limited to these examples.
A synthesis method of the organometallic complex represented by General Formula (G1) is described below. A variety of reactions can be applied to the synthesis method of the organometallic complex. For example, the organometallic complex represented by General Formula (G1) can be synthesized by a simple synthesis scheme shown below.
First, a pyridyl carbazole derivative (A1) as a starting material of the organometallic complex represented by General Formula (G1) can be synthesized by Scheme (s1-1) below. The pyridyl carbazole derivative (A1) can be obtained when a pyridyl carbazole derivative to which phenyl benzimidazole is bonded through ether-bridge (A′1) reacts with a hypervalent iodine reagent (A′2).
In Synthesis Scheme (s1-1) above, each of R2 and R8 represents a deuterated alkyl group having 1 to 10 carbon atoms, each of R1, R3 to R7, and R9 to R26 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, at least one of R4 to R6 represents an alkyl group having 1 to 10 carbon atoms, and at least one of R22 to R26 represents an alkyl group having 3 to 10 carbon atoms.
Then, the organometallic complex represented by General Formula (G1) can be obtained when the pyridyl carbazole derivative (A1) obtained by Scheme (s1-1) above reacts with a halogen-containing platinum compound (e.g., dichloro(1,5-cyclooctadiene)platinum(II)) as shown in Synthesis Scheme (s1-2).
In Synthesis Scheme (s1-2) above, each of R2 and R8 represents a deuterated alkyl group having 1 to 10 carbon atoms, each of R1, R3 to R7, and R9 to R26 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, at least one of R4 to R6 represents an alkyl group having 1 to 10 carbon atoms, and at least one of R22 to R26 represents an alkyl group having 3 to 10 carbon atoms.
For another example, the organometallic complex represented by General Formula (G1) can be synthesized by a simple synthesis scheme shown below.
First, a pyridyl carbazole derivative (B1) as a starting material of the organometallic complex represented by General Formula (G1) can be synthesized by Scheme (s2-1) below. The pyridyl carbazole derivative (B1) can be obtained when a pyridyl carbazole derivative to which a diamine compound is bonded through ether-bridge (B′1) reacts with triethyl orthoformate to cause cyclization and produce a compound represented by (B′2) and ion exchange is then caused using ammonium hexafluorophosphate.
In Synthesis Scheme (s2-1) above, each of R2 and R8 represents a deuterated alkyl group having 1 to 10 carbon atoms, each of R1, R3 to R7, and R9 to R216 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, at least one of R4 to R6 represents an alkyl group having 1 to 10 carbon atoms, and at least one of R22 to R26 represents an alkyl group having 3 to 10 carbon atoms.
Then, the organometallic complex represented by General Formula (G1) can be obtained when the pyridyl carbazole derivative (B1) obtained by Scheme (s2-1) above reacts with a halogen-containing platinum compound (e.g., dichloro(1,5-cyclooctadiene)platinum(II)) as shown in Synthesis Scheme (s2-2).
In Synthesis Scheme (s2-2) above, each of R2 and R8 represents a deuterated alkyl group having 1 to 10 carbon atoms, each of R1, R3 to R7, and R9 to R26 independently represents hydrogen (including deuterium), an alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 18 carbon atoms, at least one of R4 to R6 represents an alkyl group having 1 to 10 carbon atoms, and at least one of R22 to R26 represents an alkyl group having 3 to 10 carbon atoms.
Since a wide variety of the compounds (A′1), (A′2), (B13), and (B′2) are commercially available or their synthesis is feasible, a great variety of the organometallic complexes represented by General Formula (G1) can be synthesized. That is, the organometallic complex of one embodiment of the present invention is characterized by having numerous variations.
The above is the description on examples of a method for synthesizing the organometallic complex of one embodiment of the present invention; however, the present invention is not limited thereto and any other synthesis method may be employed.
Note that the organometallic complexes described in this embodiment can be used in combination with any of the structures described in the other embodiments as appropriate.
In this embodiment, structures of the light-emitting device including any of the organometallic complexes described in Embodiment 1 will be described with reference to
A basic structure of the light-emitting device is described.
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 or the second electrode 102.
The light-emitting layer 113 included in the organic compound layers (103, 103a, and 103b) contains 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, light-emitting substances 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 in the case where the first electrode 101 of the light-emitting device is a reflective electrode that has a stacked-layer structure of a reflective conductive material and a light-transmitting conductive material (transparent conductive film) located closer to the organic compound layer 103 than the reflective conductive material is, 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 of 1 or more) or close to mλ/2.
To amplify desired light (wavelength: λ) obtained from the light-emitting layer 113 in the above case, 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) is preferably adjusted to (2m′+1)λ/4 (m′ is an integer of 1 or more) 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 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% and lower than or equal to 100%, preferably higher than or equal to 60% and lower than or equal to 100%. 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 Ωcm.
When one of the first electrode 101 and the second electrode 102 is a reflective electrode in the 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) contain 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 a structure that exhibits 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 contain 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 metal 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: CO11), 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_2, a substance which can form an exciplex together with the organic compound 118_1 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 preferable. Specifically, an aromatic amine, a carbazole derivative, an aromatic hydrocarbon, a stilbene derivative, or the like can be used. 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(N-carbazolyl)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), 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, and the like.
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 α-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), 3,6-di(9H-carbazol-9-yl)-9-phenyl-9H-carbazole (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.
A substance which emits fluorescent light (fluorescent substance) can also be used in the light-emitting layer. 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), 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b′]bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), and 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b′]bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02).
A fused heteroaromatic compound containing 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]anthracen-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: v-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 contained 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 contained 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; therefore, 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.
The guest material 119 (phosphorescent compound) can be an iridium-, rhodium-, or platinum-based organometallic complex or metal complex. A particularly preferable example of the metal complex is a platinum 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 level of the guest material 119 (phosphorescent compound) is higher than that of the organic compound 118_1 and the highest occupied molecular orbital (HOMO) 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 1182. 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 iridium complexes having a 4H-triazole skeleton, such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: Ir(mpptz-dmp)3), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Mptz)3), 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 iridium 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(Mptz1-mp)3) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: Ir(Prptz1-Me)3); organometallic iridium 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); and organometallic iridium 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)), and bis[2-(4′,6′-difluorophenyl)pyridinato-N,C2′]iridium(III) acetylacetonate (abbreviation: FIr(acac)). Among the materials given above, the organometallic iridium 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-κN3]phenyl-κC}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 the 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 material 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. Therefore, 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 include a metal-containing porphyrin, such as a porphyrin containing 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 (PtCl2(OEP)).
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 contained 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; therefore, 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 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 material included in the first light-emitting layer may be the same as or different from a light-emitting material 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 materials 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 materials 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.
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 contain 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, manganese oxide, and the like can be given. As examples of the phthalocyanine derivative, phthalocyanine, metal phthalocyanine, and the like can be given. As examples of the aromatic amine, a benzidine derivative, a phenylenediamine derivative, and the like 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 containing 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 containing a material having an electron-accepting property and a layer containing 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 easy to handle.
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 preferable. 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) contain 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 containing 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 1×10−6 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 containing 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 containing 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 (Li2O), 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 having an electron-donating property with respect to the organic compound is 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 containing 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 containing 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 containing Al, and the like. Examples of the alloy containing Al include an alloy containing Al and L (L represents one or more of titanium (Ti), neodymium (Nd), nickel (Ni), and lanthanum (La)), such as an alloy containing Al and Ti and an alloy containing 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; therefore, 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 containing silver include an alloy containing silver, palladium, and copper, an alloy containing silver and copper, an alloy containing silver and magnesium, an alloy containing silver and nickel, an alloy containing silver and gold, an alloy containing 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.
One or both of the first electrode 101 and the second electrode 102 may be formed using a conductive material having functions of transmitting light and reflecting light. As the conductive material having a function of transmitting light, 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. 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 containing silicon or silicon oxide (ITSO), indium oxide-zinc oxide (indium zinc oxide), indium oxide-tin oxide containing titanium, indium titanium oxide, or indium oxide containing 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, 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 containing an organic substance. Examples of the organic conductor containing 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.
Alternatively, the first electrode 101 and/or the second electrode 102 may be formed by stacking two or more of these materials.
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, a metal film thin enough to transmit light can be used. Further alternatively, a plurality of layers each having a thickness of 2 nm to 20 nm may be stacked.
In the case where the first electrode 101 or the second electrode 102 functions as the cathode, the electrode preferably contains 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 containing any of these elements (e.g., Ag—Mg or Al—Li), a rare earth metal such as europium (Eu) or Yb, an alloy containing any of these rare earth metals, an alloy containing 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 with 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 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 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 layers may be stacked. Furthermore, an electron-relay layer may be provided between the p-type layer and the electron-injection buffer layer. Forming the charge-generation layer 106 that includes the p-type layer and the electron-injection buffer layer can inhibit an increase in driving voltage caused by the stack of the organic compound 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 containing 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 contains 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).
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 device or an optical element or as long as it has a function of protecting the light-emitting device or an optical element.
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 or 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. As examples of a glass substrate, a barium borosilicate glass substrate, an aluminoborosilicate glass substrate, a soda lime glass substrate, and the like can be given. 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. In that case, an active matrix display apparatus in which the FET controls the driving of the light-emitting device can be manufactured.
In Embodiment 2, 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 combined as appropriate with any of the structures described in the other embodiments.
In this embodiment, a light-emitting apparatus 1000 of one embodiment of the present invention will be described in detail. Note that in this specification and the like, a light-emitting apparatus is sometimes referred to as a display apparatus.
As illustrated in
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 yellow (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 of one embodiment of the present invention 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 Embodiments 1 and 2. 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 not provided, the organic compound layer 103R corresponds to the organic compound layer 103 described in Embodiments 1 and 2. In the case where the common layer 104 is provided, a stack of the organic compound layer 103R and the common layer 104 corresponds to the organic compound layer 103 described in Embodiments 1 and 2.
The light-emitting device 130G has a structure as described in Embodiments 1 and 2. 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 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 103G during processing. Furthermore, in the case where the common layer 104 is not provided, the organic compound layer 103G corresponds to the organic compound layer 103 described in Embodiments 1 and 2. In the case where the common layer 104 is provided, a stack of the organic compound layer 103G and the common layer 104 corresponds to the organic compound layer 103 described in Embodiments 1 and 2.
The light-emitting device 130B has a structure as described in Embodiments 1 and 2. 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. Furthermore, in the case where the common layer 104 is not provided, the organic compound layer 103B corresponds to the organic compound layer 103 described in Embodiments 1 and 2. In the case where the common layer 104 is provided, a stack of the organic compound layer 103B and the common layer 104 corresponds to the organic compound layer 103 described in Embodiments 1 and 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 light-emitting device 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 light-emitting apparatus. This can prevent crosstalk, so that a light-emitting apparatus with extremely high contrast can be obtained. Specifically, a light-emitting apparatus having high current efficiency at low luminance can be obtained.
The island-shaped organic compound layer 103 is formed by forming an EL film and processing the EL film by a lithography method.
In the light-emitting apparatus 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 preferably higher than or equal to 40% and lower than or equal to 100%, further preferably higher than or equal to 70% and lower than or equal to 100%, for example. When 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, as illustrated in
A metal material can be used for the conductive layer 151, for example. Specifically, it is possible to use a metal such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing an appropriate combination of any of these metals, for example.
For the conductive layer 152, an oxide containing one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon can be used. For example, it is preferable to use a conductive oxide containing one or more of indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide containing gallium, titanium oxide, indium zinc oxide containing gallium, indium zinc oxide containing aluminum, indium tin oxide containing silicon, indium zinc oxide containing silicon, and the like. In particular, indium tin oxide containing silicon can be suitably used for the conductive layer 152 because of having a high work function, for example, a work function higher than or equal to 4.0 eV.
The conductive layer 151 and the conductive layer 152 may each be a stack of a plurality of layers 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 conductive layer 151 may have a tapered shape. Specifically, when the end portion of the conductive layer 151 has a tapered shape with a taper angle less than 90°, coverage with a component provided along the side surface of the conductive layer 151 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 containing 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 containing silver. Silver is characterized by its visible light reflectance higher than that of titanium. In addition, silver is characterized by being less likely to be oxidized than aluminum, and silver oxide is characterized by having electrical resistivity lower than that of aluminum oxide. Thus, the conductive layer 151c formed using silver or an alloy containing silver can favorably increase the visible light reflectance of the conductive layer 151 and inhibit an increase in the electrical resistance of the pixel electrode due to oxidation of the conductive layer 151b. Here, as the alloy containing 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 containing 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 containing silver. The conductive layer 151a may be formed using silver or an alloy containing silver.
Meanwhile, a film formed using titanium has better processability in etching than a film formed using silver. Thus, use of titanium for the conductive layer 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 light-emitting apparatus. For example, the light-emitting apparatus 1000 can have high light extraction efficiency and high reliability.
Here, in the case where the light-emitting device 130 has a microcavity structure, use of silver or an alloy containing silver, i.e., a material with high visible light reflectance, for the conductive layer 151c can favorably increase the light extraction efficiency of the light-emitting apparatus 1000.
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. This might impair coverage of the conductive layer 151 with the conductive layer 152 and cause step disconnection of the conductive layer 152.
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 containing one or more selected from indium, tin, zinc, gallium, titanium, aluminum, and silicon, for example, can be used. For example, it is preferable to use a conductive oxide containing one or more of indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide containing gallium, titanium oxide, indium titanium oxide, zinc titanate, aluminum zinc oxide, indium zinc oxide containing gallium, indium zinc oxide containing aluminum, indium tin oxide containing silicon, indium zinc oxide containing silicon, and the like. Accordingly, peeling of the conductive layer 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 layers 151, 152a, and 152c. The visible light reflectance of the conductive layer 152b can be, for example, 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 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 containing silver can be used, for example. An example of the alloy containing silver is an alloy of silver, palladium, and copper (APC). In the above manner, the light-emitting apparatus 1000 can have high light extraction efficiency. Note that a metal other than silver may be used for the conductive layer 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 40% and lower than or equal to 100%, preferably higher than or equal to 60% and lower than or equal to 100%, and is further preferably higher than or equal to 70% and lower than or equal to 100%, still 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 light-emitting apparatus 1000 can have high light extraction efficiency.
Next, a method for manufacturing the light-emitting apparatus 1000 having the structure illustrated in
Thin films included in the display apparatus (e.g., insulating films, semiconductor films, and conductive films) can be formed by a sputtering method, a chemical vapor deposition (CVD) method, a vacuum evaporation method, a pulsed laser deposition (PLD) method, an ALD method, or the like. Examples of a CVD method include a plasma-enhanced CVD (PECVD) method and a thermal CVD method. An example of a thermal CVD method is a metal organic CVD (MOCVD) method.
Thin films included in the display apparatus (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 apparatus 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 containing 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 containing indium is introduced, the precursor is purged, and an oxidizer is introduced to form an In—O film, and then a precursor containing 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 containing indium, it is possible to use, for example, triethylindium, trimethylindium, or [1,1,1-trimethyl-N-(trimethylsilyl)amide]-indium. As a precursor containing tin, it is possible to use, for example, tin chloride or tetrakis(dimethylamido)tin. As a precursor containing zinc, it is possible to use, for example, diethylzinc or dimethylzinc. As a precursor containing gallium, it is possible to use, for example, triethylgallium. As a precursor containing titanium, it is possible to use, for example, titanium chloride, tetrakis(dimethylamido)titanium, or tetraisopropyl titanate. As a precursor containing aluminum, it is possible to use, for example, aluminum chloride or trimethylaluminum. As a precursor containing 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. In this specification and the like, a mask layer may be referred to as a sacrificial layer.
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 apparatus, 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 containing 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 containing silicon.
In place of gallium described above, an element M (M is one or more of aluminum, silicon, boron, yttrium, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium) may be used.
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.
The sacrificial film and the mask film are preferably formed using a semiconductor material such as silicon or germanium, for example, for 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 containing at least one of these metals can be used. Alternatively, an oxide containing the above-described metal, such as titanium oxide or chromium oxide, or a nitride such as titanium nitride, chromium nitride, or tantalum nitride can be used.
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. Therefore, 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 apparatus. 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 containing 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 containing 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 containing oxygen as the etching gas. In the case of using a dry etching method, it is preferable to use a gas containing CF4, C4F8, SF6, CHF3, 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 containing oxygen as the etching gas.
A gas containing oxygen may be used as the etching gas. When the etching gas contains oxygen, the etching rate can be increased. Therefore, 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 containing 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 containing 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 containing H2 and Ar or a gas containing CF4 and He can be used as the etching gas. For another example, a gas containing CF4, He, and oxygen can be used as the etching gas. For another example, a gas containing H2 and Ar and a gas containing 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 600 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 apparatus having high resolution and a high aperture ratio. In addition, the distance between the first electrodes of adjacent light-emitting devices can also be shortened to be, for example, less than or equal to 10 μm, less than or equal to 8 μm, less than or equal to 5 μm, less than or equal to 3 μm, or less than or equal to 2 μm. Note that the distance between the first electrodes of adjacent light-emitting devices is preferably greater than or equal to 2 μm and less than or equal to 5 μm.
Next, as illustrated in
This embodiment describes an example where the mask layers 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. Therefore, 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 containing 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 apparatus 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 containing an acrylic resin.
The insulating film 127f is preferably formed using a resin composition containing a polymer, an acid-generating agent, and a solvent, for example. The polymer is formed using one or more kinds of monomers and has a structure where one or more kinds of structural units (also referred to as building blocks) are repeated regularly or irregularly. As the acid-generating agent, one or both of a compound that generates an acid by light irradiation and a compound that generates an acid by heating can be used. The resin composition may also include one or more of a photosensitizing agent, a sensitizer, a catalyst, an adhesive aid, a surface-active agent, and an antioxidant.
Heat treatment (also referred to as prebaking) is preferably performed after the insulating film 127f is formed. The heat treatment is performed at a temperature lower than the upper temperature 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 containing an acrylic resin is used for the insulating film 127f, a region where the insulating layer 127 is not formed in a later step is irradiated with visible light or ultraviolet rays. The insulating layer 127 is formed in regions that are sandwiched between any two of the conductive layers 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 containing 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 apparatus.
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 containing 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 sacrificial layer are collectively etched after the post-baking, the inorganic insulating layer 125 and the sacrificial 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 sacrificial layer by the first etching treatment, the post-baking performed subsequently can make the insulating layer 127 fill the void. After that, the thinned sacrificial 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 apparatus decreases in some cases. Moreover, the reliability of the display apparatus decreases in some cases.
As described above, when the insulating layer 156 is formed to cover the side surfaces of the conductive layers 151 and 152, the step disconnection of the inorganic insulating layer 125 can be prevented, whereby the chemical solution can be prevented from coming into contact with a lower component 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 apparatus 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. Therefore, 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 apparatus can be manufactured. In the method for manufacturing the display apparatus 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 apparatus and inhibit generation of defects.
As described above, in the method for manufacturing the display apparatus 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 apparatus or a display apparatus with a high aperture ratio can be obtained. Furthermore, even when the resolution or the aperture ratio is high and the distance between the subpixels is extremely short, the organic compound layers 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 apparatus with extremely high contrast can be obtained. Moreover, even a display apparatus 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; therefore, the fidelity in transferring a photomask pattern by light exposure is degraded, and it becomes difficult to process a resist mask into a desired shape. Thus, a pattern with rounded corners is likely to be formed even with a rectangular photomask pattern. Consequently, the top surface of a subpixel may have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like.
Furthermore, in the method 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. Therefore, the resist film is insufficiently cured in some cases depending on the upper temperature limit of the material of the organic compound layer and the curing temperature of the resist material. An insufficiently cured resist film may have a shape different from a desired shape by processing. As a result, the top surface of the organic compound layer may have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like. For example, when a resist mask with a square top surface is intended to be formed, a resist mask with a circular top surface may be formed, and the top surface of the organic compound layer may be circular.
To obtain a desired top surface shape of the organic compound layer, a technique of correcting a mask pattern in advance so that a transferred pattern agrees with a design pattern (an optical proximity correction (OPC) technique) may be used. Specifically, with the OPC technique, a pattern for correction is added to a corner portion of a figure on a mask pattern, for example.
As illustrated in
The pixels 178 illustrated in
The pixels 178 illustrated in
The pixel 178 illustrated in
The pixel 178 illustrated in
In the pixel 178 illustrated in
The pixel 178 illustrated in
In the pixel 178 illustrated in
The pixel 178 illustrated in each of
As described above, the pixel composed of the subpixels each including the light-emitting device can employ any of a variety of layouts in the light-emitting apparatus of one embodiment of the present invention.
This embodiment can be combined as appropriate with the other embodiments or examples. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.
In this embodiment, a light-emitting apparatus of one embodiment of the present invention will be described.
The light-emitting apparatus in this embodiment can be a high-resolution light-emitting apparatus. Thus, the light-emitting apparatus in this embodiment can be used for display portions of information terminals (wearable devices) such as watch-type and bracelet-type information terminals and display portions of wearable devices capable of being worn on a head, such as a VR device like a head mounted display (HMD) and a glasses-type AR device.
The light-emitting apparatus in this embodiment can be a high-definition light-emitting apparatus or a large-sized light-emitting apparatus. Accordingly, the light-emitting apparatus in this embodiment can be used for display portions of a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, and an audio reproducing device, in addition to display portions of electronic appliances with a relatively large screen, such as a television device, desktop and notebook personal computers, a monitor of a computer and the like, digital signage, and a large game machine such as a pachinko machine.
The display module 280 includes a substrate 291 and a substrate 292. The display module 280 includes a display portion 281. The display portion 281 is a region of the display module 280 where an image is displayed, and is a region where light emitted from pixels provided in a pixel portion 284 described later can be seen.
The pixel portion 284 includes a plurality of pixels 284a arranged periodically. An enlarged view of one pixel 284a is illustrated on the right side in
The pixel circuit portion 283 includes a plurality of pixel circuits 283a arranged periodically.
One pixel circuit 283a is a circuit that controls driving of a plurality of elements included in one pixel 284a. One pixel circuit 283a can be provided with three circuits each of which controls light emission of one light-emitting device. For example, the pixel circuit 283a can include at least one selection transistor, one current control transistor (driving transistor), and a capacitor for one light-emitting device. A gate signal is input to a gate of the selection transistor, and a video signal is input to a source or a drain of the selection transistor. With such a structure, an active-matrix light-emitting apparatus is obtained.
The circuit portion 282 includes a circuit for driving the pixel circuits 283a in the pixel circuit portion 283. For example, the circuit portion 282 preferably includes one or both of a gate line driver circuit and a source line driver circuit. The circuit portion 282 may also include at least one of an arithmetic circuit, a memory circuit, a power supply circuit, and the like.
The FPC 290 functions as a wiring for supplying a video signal, a power supply potential, or the like to the circuit portion 282 from the outside. An IC may be mounted on the FPC 290.
The display module 280 can have a structure in which one or both of the pixel circuit portion 283 and the circuit portion 282 are stacked below the pixel portion 284; hence, the aperture ratio (effective display area ratio) of the display portion 281 can be significantly high. For example, the aperture ratio of the display portion 281 can be higher than or equal to 40% and lower than 100%, preferably higher than or equal to 50% and lower than or equal to 95%, further preferably higher than or equal to 60% and lower than or equal to 95%. Furthermore, the pixels 284a can be arranged extremely densely and thus the display portion 281 can have significantly high resolution. For example, the pixels 284a are preferably arranged in the display portion 281 with a resolution higher than or equal to 2000 ppi, further preferably higher than or equal to 3000 ppi, still further preferably higher than or equal to 5000 ppi, yet still further preferably higher than or equal to 6000 ppi, and lower than or equal to 20000 ppi or lower than or equal to 30000 ppi.
Such a display module 280 has extremely high resolution, and thus can be suitably used for a VR device such as an HMD or a glasses-type AR device. For example, even in the case of a structure in which the display portion of the display module 280 is seen through a lens, pixels of the extremely-high-resolution display portion 281 included in the display module 280 are prevented from being recognized when the display portion is enlarged by the lens, so that display providing a high sense of immersion can be performed. Without being limited thereto, the display module 280 can be suitably used for electronic appliances including a relatively small display portion. For example, the display module 280 can be favorably used in a display portion of a wearable electronic appliance, such as a wrist watch.
The light-emitting apparatus 100A illustrated in
The substrate 301 corresponds to the substrate 291 in
An element isolation layer 315 is provided between two adjacent transistors 310 to be embedded in the substrate 301.
An insulating layer 261 is provided to cover the transistor 310, and the capacitor 240 is provided over the insulating layer 261.
The capacitor 240 includes a conductive layer 241, a conductive layer 245, and an insulating layer 243 between the conductive layers 241 and 245. The conductive layer 241 functions as one electrode of the capacitor 240, the conductive layer 245 functions as the other electrode of the capacitor 240, and the insulating layer 243 functions as a dielectric of the capacitor 240.
The conductive layer 241 is provided over the insulating layer 261 and is embedded in an insulating layer 254. The conductive layer 241 is electrically connected to one of the source and the drain of the transistor 310 through a plug 271 embedded in the insulating layer 261. The insulating layer 243 is provided to cover the conductive layer 241. The conductive layer 245 is provided in a region overlapping with the conductive layer 241 with the insulating layer 243 therebetween.
An insulating layer 255 is provided to cover the capacitor 240. The insulating layer 174 is provided over the insulating layer 255. The insulating layer 175 is provided over the insulating layer 174. The light-emitting devices 130R, 130G, and 130B are provided over the insulating layer 175.
The insulating layer 156R is provided to cover the side surfaces of the conductive layers 151R and 152R of the light-emitting device 130R. The insulating layer 156G is provided to cover the side surfaces of the conductive layers 151G and 152G of the light-emitting device 130G. The insulating layer 156B is provided to cover the side surfaces of the conductive layers 151B and 152B of the light-emitting device 130B. The sacrificial layer 158R is positioned over the organic compound layer 103R of the light-emitting device 130R. The sacrificial layer 158G is positioned over the organic compound layer 103G of the light-emitting device 130G. The sacrificial layer 158B is positioned over the organic compound layer 103B of the light-emitting device 130B.
Each of the conductive layers 151R, 151G, and 151B is electrically connected to one of the source and the drain of the corresponding transistor 310 through a plug 256 embedded in the insulating layers 243, 255, 174, and 175, the conductive layer 241 embedded in the insulating layer 254, and the plug 271 embedded in the insulating layer 261. The top surface of the insulating layer 175 and the top surface of the plug 256 are level with or substantially level with each other. Any of a variety of conductive materials can be used for the plugs.
The protective layer 131 is provided over the light-emitting devices 130R, 130G, and 130B. The substrate 120 is attached to the protective layer 131 with the resin layer 122. Embodiment 3 can be referred to for the details of the light-emitting device 130 and the components thereover up to the substrate 120. The substrate 120 corresponds to the substrate 292 in
In the light-emitting apparatus 100B, a substrate 352 and a substrate 351 are bonded to each other. In
The light-emitting apparatus 100B includes the pixel portion 177, the connection portion 140, a circuit 356, a wiring 355, and the like.
The connection portion 140 is provided outside the pixel portion 177. The connection portion 140 can be provided along one side or a plurality of sides of the pixel portion 177. The number of connection portions 140 may be one or more.
As the circuit 356, a scan line driver circuit can be used, for example.
The wiring 355 has a function of supplying a signal and power to the pixel portion 177 and the circuit 356. The signal and power are input to the wiring 355 from the outside through the FPC 353 or from the IC 354.
The light-emitting apparatus 100B illustrated in
The stacked-layer structure of each of the light-emitting devices 130R, 130G, and 130B is the same as that illustrated in
The light-emitting device 130R includes a conductive layer 224R, the conductive layer 151R over the conductive layer 224R, and the conductive layer 152R over the conductive layer 151R. The light-emitting device 130G includes a conductive layer 224G, the conductive layer 151G over the conductive layer 224G, and the conductive layer 152G over the conductive layer 151G. The light-emitting device 130B includes a conductive layer 224B, the conductive layer 151B over the conductive layer 224B, and the conductive layer 152B over the conductive layer 151B. Here, the conductive layers 224R, 151R, and 152R can be collectively referred to as the pixel electrode of the light-emitting device 130R; the conductive layers 151R and 152R excluding the conductive layer 224R can also be referred to as the pixel electrode of the light-emitting device 130R. Similarly, the conductive layers 224G, 151G, and 152G can be collectively referred to as the pixel electrode of the light-emitting device 130G; the conductive layers 151G and 152G excluding the conductive layer 224G can also be referred to as the pixel electrode of the light-emitting device 130G. The conductive layers 224B, 151B, and 152B can be collectively referred to as the pixel electrode of the light-emitting device 130B; the conductive layers 151B and 152B excluding the conductive layer 224B can also be referred to as the pixel electrode of the light-emitting device 130B.
The conductive layer 224R is connected to a conductive layer 222b included in the transistor 205 through the opening provided in an insulating layer 214. 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 light-emitting apparatus 100B has a top-emission structure. Light from the light-emitting device is emitted toward the substrate 352. For the substrate 352, a material having a high visible-light-transmitting property is preferably used. The pixel electrode contains a material that reflects visible light, and the counter electrode (the common electrode 155) contains a material that transmits visible light.
The transistor 201 and the transistor 205 are formed over the substrate 351. These transistors can be fabricated using the same materials in the same steps.
An insulating layer 211, an insulating layer 213, an insulating layer 215, and the insulating layer 214 are provided in this order over the substrate 351. Part of the insulating layer 211 functions as a gate insulating layer of each transistor. Part of the insulating layer 213 functions as a gate insulating layer of each transistor. The insulating layer 215 is provided to cover the transistors. The insulating layer 214 is provided to cover the transistors and has a function of a planarization layer. Note that the number of gate insulating layers and the number of insulating layers covering the transistors are not limited and may each be one or more.
A material through which impurities such as water and hydrogen do not easily diffuse is preferably used for at least one of the insulating layers covering the transistors. This is because such an insulating layer can function as a barrier layer. Such a structure can effectively inhibit diffusion of impurities to the transistors from the outside and increase the reliability of the light-emitting apparatus.
An inorganic insulating film is preferably used as each of the insulating layers 211, 213, and 215. As the inorganic insulating film, a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, or an aluminum nitride film can be used, for example. A hafnium oxide film, an yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, a neodymium oxide film, or the like may be used. A stack including two or more of the above insulating films may also be used.
An organic insulating layer is suitable for the insulating layer 214 functioning as a planarization layer. Examples of materials that can be used for the organic insulating layer include an acrylic resin, a polyimide resin, an epoxy resin, a polyamide resin, a polyimide-amide resin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin, and precursors of these resins. The insulating layer 214 may have a stacked-layer structure of an organic insulating layer and an inorganic insulating layer. The outermost layer of the insulating layer 214 preferably functions as an etching protective layer. This can inhibit formation of a recessed portion in the insulating layer 214 at the time of processing of the conductive layer 224R, 151R, or 152R or the like. Alternatively, a recessed portion may be provided in the insulating layer 214 at the time of processing of the conductive layer 224R, 151R, or 152R or the like.
Each of the transistors 201 and 205 includes a conductive layer 221 functioning as a gate, the insulating layer 211 functioning as a gate insulating layer, a conductive layer 222a and 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. Here, a plurality of layers obtained by processing the same conductive film are shown with the same hatching pattern. The insulating layer 211 is positioned between the conductive layer 221 and the semiconductor layer 231. The insulating layer 213 is positioned between the conductive layer 223 and the semiconductor layer 231.
There is no particular limitation on the structure of the transistors included in the light-emitting apparatus of this embodiment. For example, a planar transistor, a staggered transistor, or an inverted staggered transistor can be used. A top-gate transistor or a bottom-gate transistor can be used. Alternatively, gates may be provided above and below a semiconductor layer where a channel is formed.
The structure in which the semiconductor layer where a channel is formed is provided between two gates is used for the transistors 201 and 205. The two gates may be connected to each other and supplied with the same signal to operate the transistor. Alternatively, the threshold voltage of the transistor may be controlled by applying a potential for controlling the threshold voltage to one of the two gates and a potential for driving to the other of the two gates.
There is no particular limitation on the crystallinity of a semiconductor material used for the transistors, and either an amorphous semiconductor or a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor partly including crystal regions) can be used. A semiconductor having crystallinity is preferably used, in which case deterioration of transistor characteristics can be suppressed.
The semiconductor layer of the transistor preferably includes a metal oxide. That is, a transistor including a metal oxide in its channel formation region (hereinafter, also referred to as an OS transistor) is preferably used in the light-emitting apparatus of this embodiment.
Examples of an oxide semiconductor having crystallinity include a c-axis-aligned crystalline oxide semiconductor (CAAC-OS) and a nanocrystalline oxide semiconductor (nc-OS).
Alternatively, a transistor including silicon in its channel formation region (a Si transistor) may be used. Examples of silicon include single crystal silicon, polycrystalline silicon, and amorphous silicon. In particular, a transistor containing low-temperature polysilicon (LTPS) in its semiconductor layer (hereinafter also referred to as an LTPS transistor) can be used. The LTPS transistor has high field-effect mobility and excellent frequency characteristics.
With the use of Si transistors such as LTPS transistors, a circuit required to be driven at a high frequency (e.g., a source driver circuit) can be formed on the same substrate as the display portion. This enables simplification of an external circuit mounted on the light-emitting apparatus and a reduction in costs of parts and mounting costs.
An OS transistor has much higher field-effect mobility than a transistor containing amorphous silicon. In addition, the OS transistor has an extremely low leakage current between a source and a drain in an off state (hereinafter also referred to as an off-state current), and electric charge accumulated in a capacitor that is connected in series to the transistor can be held for a long period. Furthermore, the power consumption of the light-emitting apparatus can be reduced with the OS transistor.
To increase the luminance of the light-emitting device included in the pixel circuit, the amount of current fed through the light-emitting device needs to be increased. To increase the current amount, the source-drain voltage of a driving transistor included in the pixel circuit needs to be increased. An OS transistor has a higher breakdown voltage between a source and a drain than a Si transistor; hence, a high voltage can be applied between the source and the drain of the OS transistor. Therefore, when an OS transistor is used as the driving transistor in the pixel circuit, the amount of current flowing through the light-emitting device can be increased, so that the luminance of the light-emitting device can be increased.
Regarding saturation characteristics of a current flowing when transistors operate in a saturation region, even in the case where the source-drain voltage of an OS transistor increases gradually, a more stable current (saturation current) can be fed through the OS transistor than through a Si transistor. Thus, by using an OS transistor as the driving transistor, a stable current can be fed through light-emitting devices even when the current-voltage characteristics of the light-emitting devices vary, for example. In other words, when the OS transistor operates in the saturation region, the source-drain current hardly changes with an increase in the source-drain voltage; hence, the luminance of the light-emitting device can be stable.
As described above, by using OS transistors as the driving transistors included in the pixel circuits, it is possible to inhibit black-level degradation, increase the luminance, increase the number of gray levels, and suppress variations in light-emitting devices, for example.
The semiconductor layer preferably contains indium, M (M is one or more of gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium), and zinc, for example. Specifically, M is preferably one or more of aluminum, gallium, yttrium, and tin.
It is particularly preferable that an oxide containing indium (In), gallium (Ga), and zinc (Zn) (also referred to as IGZO) be used for the semiconductor layer. It is preferable to use an oxide containing indium, tin, and zinc. It is preferable to use an oxide containing indium, gallium, tin, and zinc. It is preferable to use an oxide containing indium (In), aluminum (Al), and zinc (Zn) (also referred to as IAZO). It is preferable to use an oxide containing indium (In), aluminum (Al), gallium (Ga), and zinc (Zn) (also referred to as IAGZO).
When the semiconductor layer is formed using an In-M-Zn oxide, the atomic proportion of In is preferably higher than or equal to the atomic proportion of M in the In-M-Zn oxide. Examples of the atomic ratio of the metal elements in such an In-M-Zn oxide are In:M:Zn=1:1:1, 1:1:1.2, 2:1:3, 3:1:2, 4:2:3, 4:2:4.1, 5:1:3, 5:1:6, 5:1:7, 5:1:8, 6:1:6, and 5:2:5 and a composition in the neighborhood of any of the above atomic ratios. Note that the neighborhood of the atomic ratio includes ±30% of an intended atomic ratio.
For example, in the case of describing an atomic ratio of In:Ga:Zn=4:2:3 or a composition in the neighborhood thereof, the case is included in which with the atomic proportion of In being 4, the atomic proportion of Ga is greater than or equal to 1 and less than or equal to 3 and the atomic proportion of Zn is greater than or equal to 2 and less than or equal to 4. In the case of describing an atomic ratio of In:Ga:Zn=5:1:6 or a composition in the neighborhood thereof, the case is included in which with the atomic proportion of In being 5, the atomic proportion of Ga is greater than 0.1 and less than or equal to 2 and the atomic proportion of Zn is greater than or equal to 5 and less than or equal to 7. In the case of describing an atomic ratio of In:Ga:Zn=1:1:1 or a composition in the neighborhood thereof, the case is included in which with the atomic proportion of In being 1, the atomic proportion of Ga is greater than 0.1 and less than or equal to 2 and the atomic proportion of Zn is greater than 0.1 and less than or equal to 2.
The transistors included in the circuit 356 and the transistors included in the pixel portion 177 may have the same structure or different structures. One structure or two or more kinds of structures may be employed for a plurality of transistors included in the circuit 356. Similarly, one structure or two or more kinds of structures may be employed for a plurality of transistors included in the pixel portion 177.
All transistors included in the pixel portion 177 may be OS transistors, or all transistors included in the pixel portion 177 may be Si transistors. Alternatively, some of the transistors included in the pixel portion 177 may be OS transistors and the others may be Si transistors.
For example, when both an LTPS transistor and an OS transistor are used in the pixel portion 177, the light-emitting apparatus can have low power consumption and high driving capability. Note that a structure in which an LTPS transistor and an OS transistor are used in combination is referred to as LTPO in some cases. For example, it is preferable that an OS transistor be used as a transistor functioning as a switch for controlling electrical continuity between wirings and an LTPS transistor be used as a transistor for controlling a current.
For example, one transistor included in the pixel portion 177 functions as a transistor for controlling a current flowing through the light-emitting device and can be referred to as a driving transistor. One of a source and a drain of the driving transistor is electrically connected to the pixel electrode of the light-emitting device. An LTPS transistor is preferably used as the driving transistor. In that case, the amount of current flowing through the light-emitting device can be increased in the pixel circuit.
Another transistor included in the pixel portion 177 functions as a switch for controlling selection or non-selection of a pixel and can be referred to as a selection transistor. A gate of the selection transistor is electrically connected to a gate line, and one of a source and a drain thereof is electrically connected to a source line (signal line). An OS transistor is preferably used as the selection transistor. In that case, the gray level of the pixel can be maintained even with an extremely low frame frequency (e.g., lower than or equal to 1 fps); thus, power consumption can be reduced by stopping the driver in displaying a still image.
As described above, the light-emitting apparatus of one embodiment of the present invention can have all of a high aperture ratio, high resolution, high display quality, and low power consumption.
Note that the light-emitting apparatus of one embodiment of the present invention has a structure including the OS transistor and the light-emitting device having a metal maskless (MML) structure. This structure can significantly reduce a leakage current that would flow through a transistor and a leakage current that would flow between adjacent light-emitting devices (sometimes referred to as a horizontal leakage current or a lateral leakage current). Displaying images on the light-emitting apparatus having this structure can bring one or more of image crispness, image sharpness, high color saturation, and a high contrast ratio to the viewer. When a leakage current that would flow through the transistor and a lateral leakage current that would flow between the light-emitting devices are extremely low, leakage of light at the time of black display (black-level degradation) or the like can be minimized.
In particular, in the case where a light-emitting device having an MML structure employs a side-by-side (SBS) structure, which is the above-described structure for separately forming or coloring light-emitting layers, a layer provided between light-emitting devices (for example, also referred to as an organic layer or a common layer which is shared by the light-emitting devices) is disconnected; accordingly, side leakage can be prevented or be made extremely low.
Transistors 209 and 210 each include the conductive layer 221 functioning as a gate, the insulating layer 211 functioning as a gate insulating layer, the semiconductor layer 231 including a channel formation region 231i and a pair of low-resistance regions 231n, the conductive layer 222a connected to one of the pair of low-resistance regions 231n, the conductive layer 222b connected to the other of the pair of low-resistance regions 231n, an insulating layer 225 functioning as a gate insulating layer, the conductive layer 223 functioning as a gate, and the insulating layer 215 covering the conductive layer 223. The insulating layer 211 is positioned between the conductive layer 221 and the channel formation region 231i. The insulating layer 225 is positioned at least between the conductive layer 223 and the channel formation region 231i. Furthermore, an insulating layer 218 covering the transistor may be provided.
In the transistor 210 illustrated in
A connection portion 204 is provided in a region of the substrate 351 where the substrate 352 does not overlap. In the connection portion 204, the wiring 355 is electrically connected to the FPC 353 through a conductive layer 166 and a connection layer 242. An example is described in which the conductive layer 166 has a stacked-layer structure of a conductive film obtained by processing the same conductive film as the conductive layers 224R, 224G, and 224B; a conductive film obtained by processing the same conductive film as the conductive layers 151R, 151G, and 151B; and a conductive film obtained by processing the same conductive film as the conductive layers 152R, 152G, and 152B. On the top surface of the connection portion 204, the conductive layer 166 is exposed. Thus, the connection portion 204 and the FPC 353 can be electrically connected to each other through the connection layer 242.
The light-blocking layer 157 is preferably provided on the surface of the substrate 352 on the substrate 351 side. The light-blocking layer 157 can be provided over a region between adjacent light-emitting devices, in the connection portion 140, in the circuit 356, and the like. A variety of optical members can be arranged on the outer surface of the substrate 352.
A material that can be used for the substrate 120 can be used for each of the substrates 351 and 352.
A material that can be used for the resin layer 122 can be used for the adhesive layer 142.
As the connection layer 242, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like can be used.
The light-emitting apparatus 100H illustrated in
Light from the light-emitting device is emitted toward the substrate 351. For the substrate 351, a material having a high visible-light-transmitting property is preferably used. By contrast, there is no limitation on the light-transmitting property of a material used for the substrate 352.
The light-blocking layer 157 is preferably formed between the substrate 351 and the transistor 201 and between the substrate 351 and the transistor 205.
The light-emitting device 130R includes a conductive layer 112R, a conductive layer 126R over the conductive layer 112R, and a conductive layer 129R over the conductive layer 126R.
The light-emitting device 130B includes a conductive layer 112B, a conductive layer 126B over the conductive layer 112B, and a conductive layer 129B over the conductive layer 126B.
A material having a high visible-light-transmitting property is used for each of the conductive layers 112R, 112B, 126R, 126B, 129R, and 129B. A material that reflects visible light is preferably used for the common electrode 155.
Although not illustrated in
Although
The light-emitting apparatus 100H2 with a bottom-emission structure 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 contain 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 contain 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 contains 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.
Along the depressed portion of the organic resin layer 180, the first electrode 101 formed over the organic resin layer 180 has a depressed portion in a manner similar to that of the organic resin layer 180. Furthermore, along the depressed portion of the first electrode 101, the organic compound layer 103 formed over the first electrode 101 has a depressed portion in a manner similar to that of the first electrode 101. Furthermore, along the depressed portion of the organic compound layer 103, the common layer 104 formed over the organic compound layer 103 has a depressed portion in a manner similar to that of the organic compound layer 103. Furthermore, along the depressed portion of the common layer 104, the second electrode 102 formed over the common layer 104 has a depressed portion in a manner similar to that 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
The light-emitting apparatus 100C illustrated in
In the light-emitting apparatus 100C, the light-emitting device 130 includes a region overlapping with one of the coloring layers 132R, 132G, and 132B. The coloring layers 132R, 132G, and 132B can be provided on the surface of the substrate 352 on the substrate 351 side. End portions of the coloring layers 132R, 132G, and 132B can overlap with the light-blocking layer 157.
In the light-emitting apparatus 100C, the light-emitting device 130 can emit white light, for example. 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. Note that in the light-emitting apparatus 100C, the coloring layers 132R, 132G, and 132B may be provided between the protective layer 131 and the adhesive layer 142.
Although
As illustrated in
As illustrated in
The top surface of the layer 128 may include one or both of a convex surface and a concave surface. The number of convex surfaces and the number of concave surfaces included in the top surface of the layer 128 are not limited and can each be one or more.
The level of the top surface of the layer 128 and the level of the top surface of the conductive layer 224R may be the same or substantially the same, or may be different from each other. For example, the level of the top surface of the layer 128 may be either lower or higher than the level of the top surface of the conductive layer 224R.
The light-emitting apparatus 100C2 illustrated in
In the light-emitting apparatus 100C2 illustrated in
Note that as illustrated in
Although the top surface shape of the microlens 182 is hexagonal in
The microlenses 182 can be formed using a material similar to that of the organic resin layer 180.
This embodiment can be combined as appropriate with the other embodiments or examples. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.
In this embodiment, electronic appliances of embodiments of the present invention will be described.
Electronic appliances of this embodiment include the light-emitting apparatus of one embodiment of the present invention in their display portions. The light-emitting apparatus of one embodiment of the present invention is highly reliable and can be easily increased in resolution and definition. Thus, the light-emitting apparatus of one embodiment of the present invention can be used for display portions of a variety of electronic appliances.
Examples of the electronic appliances include a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, and an audio reproducing device, in addition to electronic appliances with a relatively large screen, such as a television device, desktop and notebook personal computers, a monitor of a computer and the like, digital signage, and a large game machine such as a pachinko machine.
In particular, the light-emitting apparatus of one embodiment of the present invention can have high resolution, and thus can be favorably used for an electronic appliance having a relatively small display portion. Examples of such an electronic appliance include watch-type and bracelet-type information terminal devices (wearable devices) and wearable devices capable of being worn on a head, such as a VR device like a head-mounted display, a glasses-type AR device, and an MR device.
The definition of the light-emitting apparatus of one embodiment of the present invention is preferably as high as HD (number of pixels: 1280×720), FHD (number of pixels: 1920×1080), WQHD (number of pixels: 2560×1440), WQXGA (number of pixels: 2560×1600), 4K (number of pixels: 3840×2160), or 8K (number of pixels: 7680×4320). In particular, definition of 4K, 8K, or higher is preferable. The pixel density (resolution) of the light-emitting apparatus of one embodiment of the present invention is preferably higher than or equal to 100 ppi, further preferably higher than or equal to 300 ppi, 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. With such a light-emitting apparatus having one or both of high definition and high resolution, the electronic appliance can provide higher realistic sensation, sense of depth, and the like in personal use such as portable use or home use. There is no particular limitation on the screen ratio (aspect ratio) of the light-emitting apparatus of one embodiment of the present invention. For example, the light-emitting apparatus is compatible with a variety of screen ratios such as 1:1 (a square), 4:3, 16:9, and 16:10.
The electronic appliance in this embodiment may include a sensor (a sensor having a function of measuring force, displacement, position, speed, acceleration, angular velocity, rotational frequency, distance, light, liquid, magnetism, temperature, a chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, oscillation, odor, or infrared rays).
The electronic appliance in this embodiment can have a variety of functions. For example, the electronic appliance in this embodiment can have a function of displaying a variety of information (e.g., a still image, a moving image, and a text image) on the display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of executing a variety of software (programs), a wireless communication function, and a function of reading out a program or data stored in a recording medium.
Examples of head-mounted wearable devices are described with reference to
An electronic appliance 700A illustrated in
The light-emitting apparatus of one embodiment of the present invention can be used for the display panels 751. Thus, a highly reliable electronic appliance is obtained.
The electronic appliances 700A and 700B can each project images displayed on the display panels 751 onto display regions 756 of the optical members 753. Since the optical members 753 have a light-transmitting property, the user can see images displayed on the display regions, which are superimposed on transmission images seen through the optical members 753. Accordingly, the electronic appliances 700A and 700B are electronic appliances capable of 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 Synthesis Example 1, a synthesis example of (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[4-tert-butylphenyl-3,5-di(methyl-d3)-2-pyridinyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviation: Pt(mmtBubOcz35dm4tBuppy-d6)), which is an organometallic complex of one embodiment of the present invention represented by Structural Formula (100) in Embodiment 1, is specifically described.
First, 6.1 g of 4-tert-butylphenyl-2-fluoro-3,5-dimethylpyridine, 6.1 g of 2-bromocarbazole, 15 g of cesium carbonate, and 54 mL of N-methyl-2-pyrrolidone (abbreviation: NMP) were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. After that, the mixture was stirred at 140° C. for 8 hours to cause a reaction. After a predetermined time elapsed, extraction was performed with toluene. The resulting residue was purified by silica gel column chromatography using hexane and toluene in a ratio of 1:5 as a developing solvent, so that 8.5 g of a target white solid was obtained in a yield of 74%. The synthesis scheme of Step 1 is shown in Formula (a-1) below.
Then, 8.5 g of 2-bromo-9-(4-tert-butylphenyl-3,5-dimethylpyridin-2-yl)carbazole obtained in Step 1 above, 25 mL of dimethyl sulfoxide-d6 (abbreviation: DMSO-d6), and 1.0 g of sodium tert-butoxide were put into a recovery flask, and the air in the flask was replaced with nitrogen. After that, the mixture was stirred at 140° C. for 2.5 hours to cause a reaction. After a predetermined time elapsed, extraction was performed with toluene. The resulting residue was purified by silica gel column chromatography using hexane and toluene in a ratio of 1:5 as a developing solvent, so that 6.2 g of a target yellowish white solid was obtained in a yield of 72%. The synthesis scheme of Step 2 is shown in Formula (a-2) below.
Next, 6.2 g of 2-bromo-9-[4-tert-butylphenyl-3,5-di(methyl-d3)pyridin-2-yl]carbazole obtained in Step 2 above, 2.6 g of sodium tert-butoxide, 51 mL of dimethyl sulfoxide, and 13 mL of water were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure; then, 0.13 g of copper(I) chloride (abbreviation: CuCl) and 0.42 g of N1,N2-bis(4-hydroxy-2,6-dimethylphenyl)oxalamide were added and stirring was performed at 110° C. for 10.5 hours to cause a reaction. After a predetermined time elapsed, 300 mL of water was added, and the resulting mixture was suction-filtered. The resulting residue was purified by being recrystallized with toluene, so that 3.8 g of a target gray solid was obtained in a yield of 70%. The synthesis scheme of Step 3 is shown in Formula (a-3) below.
Then, 3.8 g of 2-hydroxy-9-[4-tert-butylphenyl-3,5-di(methyl-d3)pyridin-2-yl]carbazole obtained in Step 3 above, 2.6 g of 1-(3-bromophenyl)benzimidazole, 3.7 g of tripotassium phosphate, and 88 mL of dimethyl sulfoxide were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure; then, 0.17 g of copper(I) iodide (abbreviation: CuI) and 0.11 g of picolinic acid were added and stirring was performed at 160° C. for 3 hours to cause a reaction. After a predetermined time elapsed, extraction was performed with ethyl acetate. The resulting residue was purified by silica gel column chromatography using toluene and ethyl acetate in a ratio of 10:1 as a developing solvent, so that 5.6 g of a target brown solid was obtained in a yield of 100%. The synthesis scheme of Step 4 is shown in Formula (a-4) below.
Next, 5.6 g of 2-[3-(benzimidazol-1-yl)phenoxy]-9-[4-tert-butylphenyl-3,5-di(methyl-d3)pyridin-2-yl]carbazole obtained in Step 4 above and 25 mL of N,N-dimethylformamide (abbreviation: DMF) were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure; then, 0.25 g of copper(II) acetate (abbreviation: Cu(OAc)2) was added, and heating was performed at 100° C. To the resulting mixture, a solution obtained by dissolving 10 g of (3,5-di-tert-butylphenyl)(mesityl)iodonium trifluoromethanesulfonate in 100 mL of DMF was dropped, and stirring was performed at 100° C. for 3 hours to cause a reaction. After a predetermined time elapsed, the solvent was distilled off and the resulting residue was purified by silica gel column chromatography using dichloromethane and acetone in a ratio of 9:1 as a developing solvent, so that 8.0 g of a target brown solid was obtained in a yield of 92%. The synthesis scheme of Step 5 is shown in Formula (a-5) below.
Subsequently, 8.0 g of 1-(3,5-di-tert-butylphenyl)-3-[3-({9-[4-tert-butylphenyl-3,5-di(methyl-d3)pyridin-2-yl]carbazol-2-yl}oxy)phenyl]benzimidazolium-1,1,1-trifluoromethanesulfonate obtained in Step 5 above, 3.7 g of dichloro(1,5-cyclooctadiene)platinum(II), 2.1 g of sodium acetate, and 380 mL of DMF were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. After that, the mixture was stirred at 160° C. for 2 hours to cause a reaction. After a predetermined time elapsed, the solvent was distilled off, and extraction was performed with dichloromethane. The resulting residue was purified by silica gel column chromatography using toluene as a developing solvent, and then purification by recrystallization was performed using a mixed solvent of toluene and ethanol, so that 3.0 g of a target yellow solid was obtained in a yield of 36%.
By a train sublimation method, 1.9 g of the obtained yellow solid was purified by sublimation. In the purification by sublimation, the solid was heated at 325° C. under a pressure of 3.1 Pa. After the purification by sublimation, 1.4 g of a target yellow solid was obtained in a yield of 74%. The synthesis scheme of Step 6 is shown in Formula (a-6) below.
Results of nuclear magnetic resonance (1H-NMR) spectroscopy analysis of the yellow solid obtained in Step 6 above are described below. The 1H-NMR chart is shown in
1H-NMR. δ (CD2Cl2, 500 MHz): 1.08 (brs, 9H), 1.33 (s, 9H), 1.42 (brs, 9H), 6.86 (d, 1H, J=7.5 Hz), 7.03 (d, 1H, J=7.5 Hz), 7.10 (d, 1H, J=8.0 Hz), 7.20 (d, 1H, J=8.0 Hz), 7.29-7.42 (m, 6H), 7.48 (s, 1H), 7.51 (t, 2H, J=8.0 Hz), 7.58 (d, 1H, J=8.5 Hz), 7.70 (d, 1H, J=7.0 Hz), 7.78 (brs, 1H), 7.84 (d, 2H, J=8.0 Hz), 8.03 (d, 1H, J=6.5 Hz), 8.27 (d, 1H, J=8.0 Hz), 8.77 (s, 1H).
Next, an ultraviolet-visible absorption spectrum (hereinafter, simply referred to as absorption spectrum) and an emission spectrum of Pt(mmtBubOcz35dm4tBuppy-d6) in a dichloromethane solution were measured. The absorption spectrum was measured with an ultraviolet-visible spectrophotometer (V550 manufactured by JASCO Corporation). The emission spectrum was measured with a fluorescence spectrophotometer (FP-8600 manufactured by JASCO Corporation).
As shown in
In this example, a light-emitting device 1A and a light-emitting device 1B each including Pt(mmtBubOcz35dm4tBuppy-d6)) (100) of one embodiment of the present invention as a guest material, a reference light-emitting device 2 including a reference organometallic complex (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-[3,5-di(methyl-d3)-4-phenyl-2-pyridinyl-κN]carbazole-2,1-diyl-κC)platinum(II) (abbreviation: Pt(mmtBubOcz35dm4ppy-d6)) as a guest material, and a reference light-emitting device 3 including a reference organometallic complex (2-{3-[3-(3,5-di-tert-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-KN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviation: PtON-TBBI) as a guest material were fabricated. The results of measuring the element characteristics are described.
The structural formulae of the organic compounds used in the light-emitting devices 1A and 1B and the reference light-emitting devices 2 and 3 are shown below.
In each of the light-emitting devices, as illustrated in
Indium tin oxide containing silicon oxide (ITSO) was deposited by a sputtering method over the glass substrate 900 to a thickness of 70 nm, so that the first electrode 901 as a transparent electrode was formed. The electrode area was set to 4 mm2 (2 mm×2 mm).
Next, in pretreatment for forming the light-emitting device over the substrate, the substrate was washed with water and baking was performed at 200° C. for 1 hour. Then, the substrate was transferred into a vacuum evaporation apparatus where the pressure was reduced to approximately 1×10−4 Pa, and vacuum baking was performed at 170° C. for 30 minutes in a heating chamber of the vacuum evaporation apparatus. After that, natural cooling was performed.
Then, the substrate provided with the first electrode 901 was fixed to a substrate holder provided in the vacuum evaporation apparatus such that the surface on which the first electrode 901 was formed faced downward. Over the first electrode 901, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and an electron acceptor material containing 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 using resistance heating and then, 9-[3-(triphenylsilyl)phenyl]-3,9′-bi-9H-carbazole (abbreviation: PSiCzCz) was deposited by evaporation to a thickness of 5 nm using resistance heating, so that the hole-transport layer 912 was formed.
Subsequently, over the hole-transport layer 912, 9,9′-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviation: SiTrzCz2), PSiCzCz, and Pt(mmtBubOcz35dm4tBuppy-d6) were deposited by co-evaporation to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4tBuppy-d6 was 0.45:0.45:0.10, whereby the light-emitting layer 913 was formed. Note that SiTrzCz2 and PSiCzCz each function as a host material. A combination of SiTrzCz2 and PSiCzCz forms an exciplex.
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 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, so that the electron-injection layer 915 was formed.
Then, over the electron-injection layer 915, aluminum (Al) was deposited by evaporation to a thickness of 200 nm to form the second electrode 902.
The light-emitting device 1B is different from the light-emitting device 1A in the ratio between the host materials in the light-emitting layer 913. That is, the light-emitting layer 913 of the light-emitting device 1B was formed by co-evaporation of SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4tBuppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4tBuppy-d6) was 0.30:0.60:0.10. Other components were fabricated in a manner similar to that for the light-emitting device 1A.
The reference light-emitting device 2 is different from the light-emitting device 1A in that the light-emitting layer 913 was formed using Pt(mmtBubOcz35dm4ppy-d6) instead of Pt(mmtBubOcz35dm4tBuppy-d6), which was used in the light-emitting device 1A. That is, the light-emitting layer 913 of the reference light-emitting device 2 was formed by co-evaporation of SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4ppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4ppy-d6) was 0.45:0.45:0.10. Other components were fabricated in a manner similar to that for the light-emitting device 1A.
The reference light-emitting device 3 is different from the light-emitting device 1A in that the light-emitting layer 913 was formed using PtON-TBBI instead of Pt(mmtBubOcz35dm4tBuppy-d6), which was used in the light-emitting device 1A. That is, the light-emitting layer 913 of the reference light-emitting device 3 was formed by co-evaporation of SiTrzCz2, PSiCzCz, and PtON-TBBI 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. Other components were fabricated in a manner similar to that for the light-emitting device 1A.
The structures of the light-emitting devices 1A and 1B and the reference light-emitting devices 2 and 3 are listed in the following table.
The light-emitting devices were sealed using a glass substrate in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (a sealing material was applied to surround the 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 light-emitting 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 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. The light-emitting device with higher BI can be regarded as a blue-light-emitting device having higher efficiency for a display.
The following table shows the main characteristics of the light-emitting devices at a luminance of approximately 1000 cd/m2. The luminance, CIE chromaticity, and electroluminescence spectra were measured with a spectroradiometer (SR-UL1R manufactured by TOPCON TECHNOHOUSE CORPORATION). The external quantum efficiency was calculated from the luminance and the electroluminescence spectra measured with the spectroradiometer, on the assumption that the devices had Lambertian light-distribution characteristics.
From
As shown in
Next, the peak wavelengths and the half widths of the electroluminescence spectra of the light-emitting devices are shown in the table below. In this example, a full width at half maximum (FWHM) is shown as a half width.
The above table shows that the peak wavelength of each of the light-emitting devices 1A and 1B is equivalent to that of the reference light-emitting device 2. The above table also shows that the full width at half maximum of each of the light-emitting devices 1A and 1B is smaller than that of each of the reference light-emitting devices 2 and 3 and that the electroluminescence spectra of the light-emitting devices 1A and 1B are narrower than those of the reference light-emitting devices 2 and 3. It is thus found that a light-emitting device can have high color purity and high efficiency by including the organometallic complex of one embodiment of the present invention.
Here, the HOMO and LUMO levels of Pt(mmtBubOcz35dm4tBuppy-d6), which is the organometallic complex of one embodiment of the present invention used for the light-emitting devices 1A and 1B, Pt(mmtBubOcz35dm4ppy-d6), which is the reference organometallic complex used for the reference light-emitting device 2, and PtON-TBBI, which is the reference organometallic complex used for the reference light-emitting device 3, were calculated by cyclic voltammetry (CV) measurement. An electrochemical analyzer (ALS model 600A or 600C, manufactured by BAS Inc.) was used for the measurement. The solvent used in the measurement was dehydrated dimethylformamide (DMF). 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, manufactured by BAS Inc.) was used as a working electrode, another platinum electrode (Pt counter electrode for VC-3 (5 cm), manufactured by BAS Inc.) was used as an auxiliary electrode, and an Ag/Ag+ electrode (RE7 reference electrode for nonaqueous solvent, manufactured by BAS Inc.) was used as a reference electrode. The HOMO and LUMO levels of the compound were calculated from the estimated redox potential of the reference electrode of −4.94 eV and the obtained peak potentials. As a result, the HOMO and LUMO levels of Pt(mmtBubOcz35dm4tBuppy-d6) were found to be −5.4 eV and −2.45 eV, respectively. The HOMO and LUMO levels of Pt(mmtBubOcz35dm4ppy-d6) were found to be −5.5 eV and −2.47 eV, respectively. The HOMO and LUMO levels of PtON-TBBI were found to be −5.5 eV and −2.30 eV, respectively. The results show that the HOMO level of Pt(mmtBubOcz35dm4tBuppy-d6) is slightly higher than that of Pt(mmtBubOcz35dm4ppy-d6) and is equivalent to that of PtON-TBBI, and that the LUMO level of Pt(mmtBubOcz35dm4tBuppy-d6) is slightly higher than that of Pt(mmtBubOcz35dm4ppy-d6) and is lower than that of PtON-TBBI.
The LUMO level of SiTrzCz2 and the HOMO level of PSiCzCz were calculated by cyclic voltammetry (CV) measurement. As a result, the LUMO level of SiTrzCz2 was found to be −2.98 eV and the HOMO level of PSiCzCz was found to be −5.7 eV. The difference between the HOMO level of Pt(mmtBubOcz35dm4tBuppy-d6) and the LUMO level of SiTrzCz2 as a host material was 2.42 eV.
Next, to examine the emission characteristics of Pt(mmtBubOcz35dm4tBuppy-d6), which is the organometallic complex of one embodiment of the present invention used for the light-emitting devices 1A and 1B, and Pt(mmtBubOcz35dm4ppy-d6), which is the reference organometallic complex used for the reference light-emitting device 2, poly(methyl methacrylate) (PMMA) thin films into which the materials were dispersed were each formed in the following manner: a film of a solution in which deoxidized dichloromethane was used as a solvent and the material was dispersed at a concentration of 4.8 wt % with respect to PMMA was formed over a quartz substrate by a drop casting method, and drying was performed in a glove box at room temperature under a nitrogen stream for 30 minutes. The emission spectra and quantum yields of the obtained PMMA dispersion thin films were measured.
As shown in
Here, the phosphorescence lifetimes of Pt(mmtBubOcz35dm4tBuppy-d6) and Pt(mmtBubOcz35dm4ppy-d6) were measured. For the measurement, a picosecond fluorescence lifetime measurement system (manufactured by Hamamatsu Photonics K.K.) and PMMA thin films into which the materials were dispersed were used. In this measurement, the PMMA dispersion thin film was irradiated with pulsed laser, and light emission of the thin film which was attenuated from the laser irradiation underwent time-resolved measurement using a streak camera. A nitrogen gas laser (MNL 106-PD manufactured by LTB Lasertechnik Berlin GmbH) with a wavelength of 337 nm was used as the pulsed laser. The PMMA dispersion thin films were irradiated with the pulsed laser at a repetition rate of 10 Hz. By integrating data obtained by repeated measurements, data with a high S/N ratio was obtained. The measurement was performed at room temperature (in an atmosphere kept at 23° C. (296 K)). As shown in the example in
The following table lists the quantum yield Φ, the phosphorescence lifetime τ, the radiative rate constant kr, and the non-radiative rate constant knr of each material.
As shown in the above table, the comparison between Pt(mmtBubOcz35dm4tBuppy-d6) and Pt(mmtBubOcz35dm4ppy-d6) reveals that Pt(mmtBubOcz35dm4ppy-d6) has a larger radiative rate constant kr and a slightly smaller non-radiative rate constant knr, which probably made the quantum yield of Pt(mmtBubOcz35dm4ppy-d6) slightly higher than that of Pt(mmtBubOcz35dm4tBuppy-d6) as described above.
In general, a light-emitting device has higher emission efficiency when including a light-emitting material with a higher quantum yield. However, despite the quantum yield of Pt(mmtBubOcz35dm4tBuppy-d6) that is lower than that of Pt(mmtBubOcz35dm4ppy-d6) as described above, the light-emitting devices 1A and 1B using Pt(mmtBubOcz35dm4tBuppy-d6) have higher color purity and higher emission efficiency than the reference light-emitting device 2 using Pt(mmtBubOcz35dm4ppy-d6). The results show that the emission characteristics of the light-emitting devices are affected by a factor other than the emission characteristics of the light-emitting materials.
Here, Pt(mmtBubOcz35dm4tBuppy-d6), which is the organometallic complex of one embodiment of the present invention, has the structure where the bulky tert-butyl group is introduced to the phenyl group bonded to the pyridinyl group of Pt(mmtBubOcz35dm4ppy-d6), which is the reference organometallic complex. Thus, intermolecular interaction of Pt(mmtBubOcz35dm4tBuppy-d6), which is the organometallic complex of one embodiment of the present invention, is inhibited more than intermolecular interaction of Pt(mmtBubOcz35dm4ppy-d6), which is the reference organometallic complex. It can thus be said that the fact that the light-emitting devices 1A and 1B have higher color purity and higher emission efficiency than the reference light-emitting device 2 is associated with the ease of interaction between the light-emitting material and the host material(s) in the light-emitting layer of each light-emitting device.
In this example, a light-emitting device 5A, a light-emitting device 5B, a light-emitting device 5C, and a light-emitting device 5D each including Pt(mmtBubOcz35dm4tBuppy-d6)) (100) of one embodiment of the present invention and a reference light-emitting device 6A, a reference light-emitting device 6B, a reference light-emitting device 6C, and a reference light-emitting device 6D each including the reference organometallic complex Pt(mmtBubOcz35dm4ppy-d6) were fabricated. The results of measuring the element characteristics are described.
The structural formulae of the organic compounds used in the light-emitting devices 5A to 5D and the reference light-emitting devices 6A to 6D are shown below.
The light-emitting devices 5A to 5D and the reference light-emitting devices 6A to 6D are different from the light-emitting device 1A described in Example 2 in the structure of the electron-transport layer 914. The electron-transport layer 914 in each of the light-emitting devices 5A to 5D and the reference light-emitting devices 6A to 6D was formed in the following manner: 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) was deposited by evaporation to a thickness of 5 nm over the light-emitting layer 913, and then, 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB) was deposited by evaporation to a thickness of 20 nm. The light-emitting devices 5A to 5D and the reference light-emitting devices 6A to 6D are each different from the light-emitting device 1A described in Example 2 in the structure of the light-emitting layer 913. Other components were fabricated in a manner similar to that for the light-emitting device 1A.
The structures of the light-emitting layers of the light-emitting devices 5A to 5D and the reference light-emitting devices 6A to 6D are described below.
The light-emitting layer 913 was formed by co-evaporation of SiTrzCz2 and Pt(mmtBubOcz35dm4tBuppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2 and Pt(mmtBubOcz35dm4tBuppy-d6) was 0.90:0.10.
The light-emitting layer 913 was formed by co-evaporation of SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4tBuppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4tBuppy-d6) was 0.60:0.30:0.10.
The light-emitting layer 913 was formed by co-evaporation of SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4tBuppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4tBuppy-d6) was 0.30:0.60:0.10.
The light-emitting layer 913 was formed by co-evaporation of PSiCzCz and Pt(mmtBubOcz35dm4tBuppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between PSiCzCz and Pt(mmtBubOcz35dm4tBuppy-d6) was 0.90:0.10.
The light-emitting layer 913 was formed by co-evaporation of SiTrzCz2 and Pt(mmtBubOcz35dm4ppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2 and Pt(mmtBubOcz35dm4ppy-d6) was 0.90:0.10.
The light-emitting layer 913 was formed by co-evaporation of SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4ppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4ppy-d6) was 0.60:0.30:0.10.
The light-emitting layer 913 was formed by co-evaporation of SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4ppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between SiTrzCz2, PSiCzCz, and Pt(mmtBubOcz35dm4ppy-d6) was 0.30:0.60:0.10.
The light-emitting layer 913 was formed by co-evaporation of PSiCzCz and Pt(mmtBubOcz35dm4ppy-d6) to a thickness of 35 nm using resistance heating such that the weight ratio between PSiCzCz and Pt(mmtBubOcz35dm4ppy-d6) was 0.90:0.10.
The structures of the light-emitting devices 5A to 5D are listed in the following table. As shown in the following table, the light-emitting devices 5A to 5D differ in the ratio between SiTrzCz2 and PSiCzCz in the light-emitting layer 913.
The structures of the reference light-emitting devices 6A to 6D are listed in the following table. As shown in the following table, the reference light-emitting devices 6A to 6D differ in the ratio between SiTrzCz2 and PSiCzCz in the light-emitting layer 913.
The light-emitting devices were sealed using a glass substrate in a glove box containing a nitrogen atmosphere so as not to be exposed to the air (a sealing material was applied to surround the 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 light-emitting devices were measured.
The following table shows the main characteristics of the light-emitting devices at a luminance of approximately 1000 cd/m2. The luminance, CIE chromaticity, and electroluminescence spectra were measured with a spectroradiometer (SR-UL1R manufactured by TOPCON TECHNOHOUSE CORPORATION). The external quantum efficiency was calculated from the luminance and the electroluminescence spectra measured with the spectroradiometer, on the assumption that the devices had Lambertian light-distribution characteristics.
Next, the peak wavelengths and the half widths of the electroluminescence spectra of the light-emitting devices are shown in the table below. In this example, a full width at half maximum (FWHM) is shown as a half width.
Meanwhile,
From the above results, it can be said that the interaction between the light-emitting substance Pt(mmtBubOcz35dm4tBuppy-d6) and the host material(s) is weak in the light-emitting layers of the light-emitting devices 5A to 5D. By contrast, it can be said that the light-emitting substance Pt(mmtBubOcz35dm4ppy-d6) easily interacts with the host material SiTrzCz2 in the light-emitting layers of the reference light-emitting devices 6A to 6C.
As described in Example 2, Pt(mmtBubOcz35dm4tBuppy-d6), which is the organometallic complex of one embodiment of the present invention, has the structure where the bulky tert-butyl group is introduced to the phenyl group bonded to the pyridinyl group of Pt(mmtBubOcz35dm4ppy-d6), which is the reference organometallic complex. It can be said that the tert-butyl group makes Pt(mmtBubOcz35dm4tBuppy-d6) less likely to interact with SiTrzCz2 than Pt(mmtBubOcz35dm4ppy-d6). It is thus found that the organometallic complex of one embodiment of the present invention is a material whose intermolecular interaction is inhibited and which does not easily interact with a host material in a light-emitting layer.
In this reference synthesis example, a synthesis example of Pt(mmtBubOcz35dm4ppy-d6), which is the reference organometallic complex described in Examples 2 and 3, is described.
First, 4.9 g of 2-fluoro-4-iodo-3,5-dimethylpyridine, 2.7 g of phenylboronic acid, 8.3 g of potassium carbonate, 80 mL of 1,4-dioxane, and 20 mL of water were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure, and then 1.4 g of tetrakis(triphenylphosphine)palladium(0) (abbreviation: Pd(PPh3)4) was added thereto. The mixture was stirred at 85° C. for 23 hours to cause a reaction.
After a predetermined time elapsed, extraction was performed with toluene. The resulting residue was purified by silica gel column chromatography using toluene as a developing solvent, so that 3.6 g of a target pale yellow solid was obtained in a yield of 90%. The synthesis scheme of Step 1 is shown in Formula (c-1) below.
Next, 3.6 g of 2-fluoro-3,5-dimethyl-4-phenylpyridine obtained in Step 1 above, 4.6 g of 2-bromocarbazole, 12 g of cesium carbonate, and 40 mL of N-methyl-2-pyrrolidone (abbreviation: NMP) were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. After that, the mixture was stirred at 120° C. for 18.5 hours to cause a reaction.
After a predetermined time elapsed, extraction was performed with toluene. The resulting residue was purified by silica gel column chromatography using hexane and toluene in a ratio of 1:5 as a developing solvent, so that 6.9 g of a target colorless oil was obtained in a yield of 90%. The synthesis scheme of Step 2 is shown in Formula (c-2) below.
Then, 6.9 g of 2-bromo-9-(3,5-dimethyl-4-phenylpyridin-2-yl)carbazole obtained in Step 2 above, 23 mL of dimethyl sulfoxide-d6 (abbreviation: DMSO-d6), and 0.93 g of sodium tert-butoxide were put into a recovery flask, and the air in the flask was replaced with nitrogen. After that, the mixture was stirred at room temperature for 16 hours to cause a reaction.
After a predetermined time elapsed, extraction was performed with toluene. The resulting residue was purified by silica gel column chromatography using hexane and toluene in a ratio of 1:5 as a developing solvent, so that 5.8 g of a target white solid was obtained in a yield of 83%. The synthesis scheme of Step 3 is shown in Formula (c-3) below.
Subsequently, 5.8 g of 2-bromo-9-[3,5-di(methyl-d3)-4-phenylpyridin-2-yl]carbazole obtained in Step 3 above, 2.7 g of sodium tert-butoxide, 54 mL of dimethyl sulfoxide, and 13 mL of water were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure; then, 0.066 g of copper(I) chloride and 0.22 g of N1,N2-bis(4-hydroxy-2,6-dimethylphenyl)oxalamide were added and stirring was performed at 110° C. for 2 hours to cause a reaction.
After a predetermined time elapsed, extraction was performed with ethyl acetate. The resulting residue was purified by being recrystallized with toluene, so that 4.0 g of a target pale orange solid was obtained in a yield of 80%. The synthesis scheme of Step 4 is shown in Formula (c-4) below.
Next, 1.9 g of 2-hydroxy-9-[3,5-di(methyl-d3)-4-phenylpyridin-2-yl]carbazole obtained in Step 4 above, 1.5 g of 1-(3-bromophenyl)benzimidazole, 2.2 g of tripotassium phosphate, and 51 mL of dimethyl sulfoxide were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure, and then 0.098 g of copper(I) iodide (abbreviation: CuI) and 0.063 g of picolinic acid were added thereto. The mixture was stirred at 160° C. for 6.5 hours to cause a reaction.
After a predetermined time elapsed, extraction was performed with ethyl acetate. The resulting residue was purified by silica gel column chromatography using toluene and ethyl acetate in a ratio of 10:1 as a developing solvent, so that 2.7 g of a target brown solid was obtained in a yield of 94%. The synthesis scheme of Step 5 is shown in Formula (c-5) below.
Then, 2.7 g of 2-[3-(benzimidazol-1-yl)phenoxy]-9-[3,5-di(methyl-d3)-4-phenylpyridin-2-yl]carbazole obtained in Step 5 above, 5.7 g of (3,5-di-tert-butylphenyl)(mesityl)iodonium trifluoromethanesulfonate, and 25 mL of N,N-dimethylformamide (abbreviation: DMF) were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure, and then 0.13 g of copper(II) acetate was added thereto. The mixture was stirred at 100° C. for 6 hours to cause a reaction.
After a predetermined time elapsed, the solvent was distilled off and the obtained residue was purified by silica gel column chromatography using dichloromethane and acetone in a ratio of 9:1 as a developing solvent, so that 0.84 g of a target reddish brown solid was obtained in a yield of 19%. The synthesis scheme of Step 6 is shown in Formula (c-6) below.
Subsequently, 0.84 g of 1-(3,5-di-tert-butylphenyl)-3-[3-({9-[3,5-di(methyl-d3)-4-phenylpyridin-2-yl]carbazol-2-yl}oxy)phenyl]benzimidazolium-1,1,1-trifluoromethanesulfonate obtained in Step 6 above, 0.42 g of dichloro(1,5-cyclooctadiene)platinum(II), 0.23 g of sodium acetate, and 42 mL of N,N-dimethylformamide were put into a three-neck flask equipped with a reflux pipe, and the air in the flask was replaced with nitrogen. After that, the mixture was stirred at 160° C. for 3 hours to cause a reaction.
After a predetermined time elapsed, the solvent was distilled off, and extraction was performed with dichloromethane. The resulting residue was purified by silica gel column chromatography using toluene as a developing solvent, and then purification by recrystallization was performed using toluene, so that 0.19 g of a target yellow solid was obtained in a yield of 22%.
By a train sublimation method, 0.12 g of the obtained yellow solid was purified by sublimation. In the purification by sublimation, the solid was heated at 305° C. under a pressure of 2.5 Pa. After the purification by sublimation, 0.060 g of a target yellow solid was obtained in a yield of 50%. The synthesis scheme of Step 7 is shown in Formula (c-7) below.
Results of nuclear magnetic resonance (1H-NMR) spectroscopy analysis of the yellow solid obtained in Step 7 above are described below. The results show that Pt(mmtBubOcz35dm4ppy-d6) was obtained.
1H-NMR. δ (CDCl3): 1.08 (brs, 9H), 1.42 (brs, 9H), 6.93-6.94 (m, 1H), 7.10 (d, 2H), 7.19 (d, 1H), 7.29-7.42 (m, 7H), 7.48-7.53 (m, 3H), 7.58 (d, 1H), 7.71 (d, 1H), 7.77 (brs, 1H), 7.87 (d, 2H), 8.03 (d, 1H), 8.27 (d, 1H), 8.79 (s, 1H).
This application is based on Japanese Patent Application Serial No. 2023-195993 filed with Japan Patent Office on Nov. 17, 2023 and Japanese Patent Application Serial No. 2024-074863 filed with Japan Patent Office on May 2, 2024, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-195993 | Nov 2023 | JP | national |
| 2024-074863 | May 2024 | JP | national |
