Patent Application
20250221157
One embodiment of the present invention relates to an organic compound, an organic semiconductor element, a light-emitting device, a photodiode sensor, a display module, a lighting module, a display device, an electronic appliance, a lighting device, and an electronic device. Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. One embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a lighting device, a power storage device, a memory device, an image capturing device, a driving method thereof, and a manufacturing method thereof.
A light-emitting device (also referred to as organic EL element) including an organic compound and utilizing electroluminescence (EL) has been put into more practical use. In the basic structure of such a light-emitting device, an organic compound layer including an emission center substance is located between a pair of electrodes. Carriers are injected by application of a voltage to the device, and recombination energy of the carriers is used, whereby light emission can be obtained from the emission center substance.
Since such a light-emitting device is of self-luminous type, a display device in which the light-emitting device is used for a pixel has higher visibility than a liquid crystal display device and does not need a backlight. A display device including such a light-emitting device is also highly advantageous in that it can be thin and lightweight. Another feature of such a light-emitting device is that it has an extremely high response speed.
Since a continuous planar light-emitting layer can be formed for such light-emitting devices, planar light emission can be achieved. This feature is difficult to realize with a point light source typified by an incandescent lamp and an LED or a linear light source typified by a fluorescent lamp; thus, the light-emitting device also has great potential as a planar light source, which can be used for a lighting device and the like.
A display device or lighting device that include light-emitting devices are suitable for a variety of electronic appliances as described above, and research and development of light-emitting devices have progressed for better characteristics.
Tandem light-emitting devices have attracted particular attention because of their high current efficiency.
Patent Documents 1 and 2 disclose tandem light-emitting devices fabricated by a side-by-side patterning method.
An object of one embodiment of the present invention is to provide a light-emitting device having favorable characteristics. Another object of one embodiment of the present invention is to provide a light-emitting device having high emission efficiency. Another object of one embodiment of the present invention is to provide a light-emitting device having high reliability. Another object of one embodiment of the present invention is to provide a light-emitting device having a low driving voltage. Another object of one embodiment of the present invention is to provide a light-emitting device having high reliability and a low driving voltage.
Another object of one embodiment of the present invention is to provide a light-emitting device which enables a display device to have favorable characteristics. Another object of one embodiment of the present invention is to provide a light-emitting device which enables a display device to have high emission efficiency. Another object of one embodiment of the present invention is to provide a light-emitting device which enables a display device to have high reliability. Another object of one embodiment of the present invention is to provide a display device which enables a display device to have a low driving voltage. Another object of one embodiment of the present invention is to provide a light-emitting device which enables a display device to have high reliability and a low driving voltage.
Another object of one embodiment of the present invention is to provide any of an organic semiconductor device, a light-emitting device, a light-receiving device, a display device, an electronic appliance, and a lighting device each having low power consumption. Another object of one embodiment of the present invention is to provide an electronic appliance having high reliability or a lighting device having high reliability. Another object of one embodiment of the present invention is to provide any of a novel organic semiconductor device, a novel light-emitting device, a novel light-receiving device, a novel display device, a novel electronic appliance, and a novel lighting device.
It is only necessary that at least one of the above-described objects be achieved in the present invention. 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 a light-emitting device including a first electrode, a second electrode, an intermediate layer, a first light-emitting layer, a second light-emitting layer, a first electron-transport layer, and a second electron-transport layer. In the light-emitting device, the intermediate layer is positioned between the first electrode and the second electrode, the first light-emitting layer is positioned between the first electrode and the intermediate layer, the second light-emitting layer is positioned between the intermediate layer and the second electrode, the first electron-transport layer is positioned between the first light-emitting layer and the intermediate layer, the second electron-transport layer is positioned between the second light-emitting layer and the second electrode, the second electron-transport layer includes a first organic compound having a triazine skeleton, the intermediate layer includes a mixed layer of a second organic compound having a phenanthroline skeleton and one of lithium and a lithium compound, the first light-emitting layer includes a first emission center substance, the second light-emitting layer includes a second emission center substance, a difference between a maximum peak wavelength in an emission spectrum of the first emission center substance and a maximum peak wavelength in an emission spectrum of the second emission center substance is less than or equal to 30 nm, and the first light-emitting layer and the second light-emitting layer are each different from a light-emitting layer included in at least one of a plurality of light-emitting devices adjacent to the light-emitting device.
Another embodiment of the present invention is the light-emitting device having the above-described structure, in which the first electron-transport layer includes a third organic compound having a triazine skeleton.
Another embodiment of the present invention is the light-emitting device having the above-described structure, in which the first organic compound and the third organic compound are the same organic compound.
Another embodiment of the present invention is the light-emitting device having the above-described structure, in which the first electron-transport layer includes a fourth organic compound having no triazine skeleton.
Another embodiment of the present invention is the light-emitting device having the above-described structure, in which the first electron-transport layer includes a fourth organic compound having at least one of a pyrimidine skeleton, an imidazole skeleton, and an anthracene skeleton.
One embodiment of the present invention is a light-emitting device including a first electrode, a second electrode, an intermediate layer, a first light-emitting layer, a second light-emitting layer, a first electron-transport layer, and a second electron-transport layer. In the light-emitting device, the intermediate layer is positioned between the first electrode and the second electrode, the first light-emitting layer is positioned between the first electrode and the intermediate layer, the second light-emitting layer is positioned between the intermediate layer and the second electrode, the first electron-transport layer is positioned between the first light-emitting layer and the intermediate layer, the second electron-transport layer is positioned between the second light-emitting layer and the second electrode, the second electron-transport layer includes a first organic compound having a triazine skeleton, the intermediate layer includes a second organic compound having a phenanthroline skeleton, the first electron-transport layer includes a third organic compound having a triazine skeleton, the first light-emitting layer includes a first emission center substance, the second light-emitting layer includes a second emission center substance, a difference between a maximum peak wavelength in an emission spectrum of the first emission center substance and a maximum peak wavelength in an emission spectrum of the second emission center substance is less than or equal to 30 nm, and the first light-emitting layer and the second light-emitting layer are each different from a light-emitting layer included in at least one of a plurality of light-emitting devices adjacent to the light-emitting device.
Another embodiment of the present invention is the light-emitting device having the above-described structure, in which the first organic compound and the third organic compound are the same organic compound.
Another embodiment of the present invention is the light-emitting device having the above-described structure, in which the intermediate layer includes one of lithium and a lithium compound.
Another embodiment of the present invention is the light-emitting device having the above-described structure, in which the intermediate layer includes a mixed layer of the second organic compound and one of the lithium and the lithium compound.
Another embodiment of the present invention is the light-emitting device having the above-described structure, in which the second electron-transport layer includes lithium or a lithium compound.
Another embodiment of the present invention is the light-emitting device having the above-described structure, in which the first emission center substance and the second emission center substance are the same substance.
Another embodiment of the present invention is the light-emitting device having any of the above-described structures, in which the intermediate layer includes a first layer including the second organic compound.
Another embodiment of the present invention is the light-emitting device having any of the above-described structures, in which the first layer includes lithium or a lithium compound.
Another embodiment of the present invention is the light-emitting device having any of the above-described structures, in which the intermediate layer further includes a second layer and the second layer is positioned between the first layer and the second light-emitting layer.
Another embodiment of the present invention is the light-emitting device having any of the above-described structures, in which the second layer includes a fifth organic compound having a hole-transport property.
Another embodiment of the present invention is the light-emitting device having any of the above-described structures, in which the second layer includes an organic compound having at least one of a halogen group and a cyano group.
Another embodiment of the present invention is the light-emitting device having any of the above-described structures, in which the second layer includes an organic compound having at least one of fluorine and a cyano group.
Another embodiment of the present invention is the light-emitting device having any of the above-described structures, in which the second layer includes an organic compound having at least four halogen groups, at least four cyano groups, or a combination of halogen and cyano groups the number of which is four or more.
Another embodiment of the present invention is the light-emitting device having any of the above-described structures, in which the second layer includes an organic compound having at least four fluorines, at least four cyano groups, or a combination of fluorines and cyano groups the number of which is four or more.
Another embodiment of the present invention is a display device including any of the above-described light-emitting devices.
Another embodiment of the present invention is a display device including a light-emitting device A and a light-emitting device B. In the display device, the light-emitting device A and the light-emitting device B are adjacent to each other; the light-emitting device A includes a first electrode A, a second electrode A, an intermediate layer A, a first light-emitting layer A, a second light-emitting layer A, a first electron-transport layer A, and a second electron-transport layer A; the intermediate layer A is positioned between the first electrode A and the second electrode A; the first light-emitting layer A is positioned between the first electrode A and the intermediate layer A; the second light-emitting layer A is positioned between the intermediate layer A and the second electrode A; the first electron-transport layer A is positioned between the first light-emitting layer A and the intermediate layer A; the second electron-transport layer A is positioned between the second light-emitting layer A and the second electrode A; the light-emitting device B includes a first electrode B, a second electrode B, an intermediate layer B, a first light-emitting layer B, a second light-emitting layer B, a first electron-transport layer B, and a second electron-transport layer B; the intermediate layer B is positioned between the first electrode B and the second electrode B; the first light-emitting layer B is positioned between the first electrode B and the intermediate layer B; the second light-emitting layer B is positioned between the intermediate layer B and the second electrode B; the first electron-transport layer B is positioned between the first light-emitting layer B and the intermediate layer B; the second electron-transport layer B is positioned between the second light-emitting layer B and the second electrode B; the second electron-transport layer A and the second electron-transport layer B each include a first organic compound having a triazine skeleton; the second electron-transport layer A and the second electron-transport layer B are made of the same material; the intermediate layer A and the intermediate layer B each include a second organic compound having a phenanthroline skeleton and one of lithium and a lithium compound; the first light-emitting layer A includes a first emission center substance; the second light-emitting layer A includes a second emission center substance; the first light-emitting layer B includes a third emission center substance; the second light-emitting layer B includes a fourth emission center substance; a difference between a maximum peak wavelength in an emission spectrum of the first emission center substance and a maximum peak wavelength in an emission spectrum of the second emission center substance is less than or equal to 30 nm; a difference between a maximum peak wavelength in an emission spectrum of the third emission center substance and a maximum peak wavelength in an emission spectrum of the fourth emission center substance is less than or equal to 30 nm; the first light-emitting layer A and the first light-emitting layer B are different light-emitting layers from each other; and the second light-emitting layer A and the second light-emitting layer B are different light-emitting layers from each other.
Another embodiment of the present invention is a display device including a light-emitting device A and a light-emitting device B. In the display device, the light-emitting device A and the light-emitting device B are adjacent to each other; the light-emitting device A includes a first electrode A, a second electrode A, an intermediate layer A, a first light-emitting layer A, a second light-emitting layer A, a first electron-transport layer A, and a second electron-transport layer A; the intermediate layer A is positioned between the first electrode A and the second electrode A; the first light-emitting layer A is positioned between the first electrode A and the intermediate layer A; the second light-emitting layer A is positioned between the intermediate layer A and the second electrode A; the first electron-transport layer A is positioned between the first light-emitting layer A and the intermediate layer A; the second electron-transport layer A is positioned between the second light-emitting layer A and the second electrode A; the light-emitting device B includes a first electrode B, a second electrode B, an intermediate layer B, a first light-emitting layer B, a second light-emitting layer B, a first electron-transport layer B, and a second electron-transport layer B; the intermediate layer B is positioned between the first electrode B and the second electrode B; the first light-emitting layer B is positioned between the first electrode B and the intermediate layer B; the second light-emitting layer B is positioned between the intermediate layer B and the second electrode B; the first electron-transport layer B is positioned between the first light-emitting layer B and the intermediate layer B; the second electron-transport layer B is positioned between the second light-emitting layer B and the second electrode B; the second electron-transport layer A and the second electron-transport layer B each include a first organic compound having a triazine skeleton; the second electron-transport layer A and the second electron-transport layer B are one continuous layer; the intermediate layer A and the intermediate layer B each include a second organic compound having a phenanthroline skeleton and one of lithium and a lithium compound; the first light-emitting layer A includes a first emission center substance; the second light-emitting layer A includes a second emission center substance; the first light-emitting layer B includes a third emission center substance; the second light-emitting layer B includes a fourth emission center substance; a difference between a maximum peak wavelength in an emission spectrum of the first emission center substance and a maximum peak wavelength in an emission spectrum of the second emission center substance is less than or equal to 30 nm; a difference between a maximum peak wavelength in an emission spectrum of the third emission center substance and a maximum peak wavelength in an emission spectrum of the fourth emission center substance is less than or equal to 30 nm; the first light-emitting layer A and the first light-emitting layer B are different light-emitting layers from each other; and the second light-emitting layer A and the second light-emitting layer B are different light-emitting layers from each other.
Another embodiment of the present invention is an electronic appliance including any of the above-described light-emitting device and a sensor, an operation button, a speaker, or a microphone.
Another embodiment of the present invention is a lighting device including any of the above-described light-emitting devices and a housing.
The structures described above are embodiments of the present invention, and the present invention is not limited to the above-described structures.
One embodiment of the present invention can provide a light-emitting device having favorable characteristics. Another embodiment of the present invention can provide a light-emitting device having high emission efficiency. Another embodiment of the present invention can provide a light-emitting device having high reliability. Another embodiment of the present invention can provide a light-emitting device having a low driving voltage. Another embodiment of the present invention can provide a light-emitting device having high reliability and a low driving voltage.
Another embodiment of the present invention can provide a light-emitting device which enables a display device to have favorable characteristics. Another embodiment of the present invention can provide a light-emitting device which enables a display device to have high emission efficiency. Another embodiment of the present invention can provide a light-emitting device which enables a display device to have high reliability. Another object of one embodiment of the present invention can provide a light-emitting device which enables a display device to have a low driving voltage. Another embodiment of the present invention can provide a light-emitting device which enables a display device to have high reliability and a low driving voltage.
Another embodiment of the present invention can provide any of an organic semiconductor device, a light-emitting device, a light-receiving device, a display device, an electronic appliance, and a lighting device each having low power consumption. Another embodiment of the present invention can provide an electronic appliance having high reliability or a lighting device having high reliability.
In the accompanying drawings:
Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the following description, and it will be readily appreciated by those skilled in the art that modes and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Thus, the present invention should not be construed as being limited to the description in the following embodiments.
In this specification and the like, a device formed using a metal mask or a fine metal mask (FMM, a high-resolution metal mask) is sometimes referred to as a device having a metal mask (MM) structure. In this specification and the like, a device formed without using a metal mask or an FMM is sometimes referred to as a device having a metal maskless (MML) structure.
A tandem light-emitting device has a structure in which a plurality of light-emitting units are stacked between a pair of electrodes with an intermediate layer (a charge-generation layer) therebetween. The plurality of light-emitting units include their respective light-emitting layers, and each of the light-emitting layers can emit light with a flow of current therethrough. The tandem light-emitting device having such a structure has a much higher current efficiency than a non-tandem light-emitting device, and can thus be suitably used for a display device that requires high-luminance display or high reliability.
Since the tandem light-emitting device includes a plurality of light-emitting layers and can thus easily provide white light emission, many full-color display devices including the tandem light-emitting device employ a “white+color filter” method. A color conversion method is also in practical use in which light-emitting layers that emit blue light are stacked and a color conversion layer typified by quantum dots is used.
Meanwhile, some full-color display devices employing a side-by-side patterning method and the tandem light-emitting device have also been put into practical use. A light-emitting device fabricated by the side-by-side patterning method has little or no energy loss due to a color filter or a color conversion layer and can thus have a higher emission efficiency than light-emitting devices fabricated by the above-described two methods.
In a tandem light-emitting device of one embodiment of the present invention, an electron-transport layer included in a light-emitting unit on the cathode side includes a first organic compound having a triazine skeleton, and an intermediate layer includes a second organic compound having a phenanthroline skeleton.
A light-emitting layer included in the tandem light-emitting device is preferably separated from a light-emitting layer included in at least one adjacent light-emitting device.
Alternatively, the light-emitting layer included in the tandem light-emitting device is preferably a different light-emitting layer from a light-emitting layer included in at least one adjacent light-emitting device. Alternatively, the emission color of the tandem light-emitting device or a pixel including the tandem light-emitting device is preferably different from the emission color of at least one adjacent light-emitting device or pixel. Alternatively, an emission center substance included in the light-emitting layer of the tandem light-emitting device preferably has a different structure from an emission center substance included in a light-emitting layer of at least one adjacent light-emitting device.
The light-emitting device of one embodiment of the present invention that has such a structure can have high current efficiency, low energy loss, and favorable characteristics. A display device of one embodiment of the present invention that includes such a light-emitting device can achieve low power consumption, high reliability, high-luminance display, and high visibility.
The first organic compound having a triazine skeleton can be used as long as it has a property of transporting more electrons than holes. The first organic compound preferably has an electron mobility of 1×10−7 cm2/Vs or higher and further preferably has an electron mobility of 1×10−6 cm2/Vs or higher when the square root of electric field strength [V/cm] is 600.
The first organic compound having the triazine skeleton preferably has the triazine skeleton and an aromatic ring. The aromatic ring is preferably a monocyclic aromatic ring, a polycyclic aromatic ring, an aromatic ring having an alkyl group as a substituent, an aromatic ring having a fluoro group as a substituent, an aromatic ring having a cyano group as a substituent, or the like. The triazine skeleton may have a substituent other than the above-described aromatic ring, and the aromatic ring may have a substituent other than the above-described fluoro group, cyano group, or alkyl group. Note that the triazine skeleton is also referred to as a triazine ring, and other skeletons can also be rephrased as rings.
Examples of the monocyclic aromatic ring include aromatic hydrocarbon rings such as a benzene ring and heteroaromatic rings such as a pyrrole ring, a pyridine ring, a pyrimidine ring, and a triazine ring. Having the aromatic ring as a substituent has the effect of improving heat resistance, specifically, a glass transition temperature (Tg), and the effect of improving an electron-transport property, for example.
Examples of the polycyclic aromatic ring include aromatic hydrocarbon rings such as a naphthalene ring, a phenanthrene ring, a chrysene ring, a triphenylene ring, a fluorene ring, and a spirobifluorene ring and heteroaromatic rings such as a carbazole ring, a dibenzofuran ring, a dibenzothiophene ring, a xanthene ring, an indolocarbazole ring, and an indenocarbazole ring. A compound having the polycyclic aromatic ring as a substituent can improve heat resistance more than a compound having the monocyclic aromatic ring such as a benzene ring. A compound having as a substituent a ring in which an aromatic ring (e.g., a benzene ring, a naphthalene ring, or a pyridine ring) is further condensed to any of the above polycyclic aromatic rings can further improve heat resistance. Examples of the ring in which an aromatic ring is further condensed to the polycyclic aromatic ring include a benzofluorene ring, a benzonaphthofuran ring, a benzoxanthene ring, and a benzonaphthothiophene ring. Providing a layer including a compound having high heat resistance in the vicinity of the cathode can inhibit heat damage to the device when high-temperature treatment in a patterning step or the like is performed after the layer or the cathode is formed.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a tertiary butyl group, a cyclohexyl group, and an adamantyl group. The first organic compound having the alkyl group as a substituent can have a low refractive index, and a layer including the first organic compound can have a low refractive index. This can inhibit total reflection at the interface between the layer and another layer and improve the light extraction efficiency of the light-emitting device including the layer. An organic compound having an alkyl group having a plurality of carbon atoms, preferably three or more carbon atoms, further preferably four or more carbon atoms, still further preferably five or more carbon atoms, can enhance the effect of lowering the refractive index.
When such a compound having an alkyl group is used also for the hole-transport layer, the refractive index of the hole-transport layer can be lowered. In particular, when a compound having a triazine skeleton and an alkyl group is used for the electron-transport layer and a compound having an aromatic amine skeleton and an alkyl group is used for the hole-transport layer, the effect of improving the light extraction efficiency can be synergistically enhanced.
A layer including a compound having a fluoro group as a substituent is also preferable because it can lower the refractive index. In particular, an organic compound having a plurality of fluoro groups can enhance the effect of lowering the refractive index. It is also effective to use a compound having a fluoro group for both the electron-transport layer and the hole-transport layer.
A compound having a structure in which a plurality of alkyl groups or fluoro groups are bonded to one aromatic ring can further lower the refractive index of the layer. In one example, two or three or more tertiary butyl groups are bonded as substituents to one benzene ring. Without limitation to the benzene ring, the plurality of alkyl groups or fluoro groups may be bonded to another monocyclic aromatic ring such as a pyridine ring or a polycyclic aromatic ring such as a fluorene ring. In addition, the plurality of alkyl groups or fluoro groups are suitably bonded to one or more rings included in a polycyclic aromatic ring (e.g., a naphthalene ring, a fluorene ring, a carbazole ring, a quinoline ring, or a xanthene ring). In one example, a plurality of tertiary butyl groups are bonded to one benzene ring included in a fluorene ring.
The first organic compound having a cyano group as a substituent is preferable because it can improve the electron-transport property.
A combination of some of polycyclic aromatic rings, alkyl groups, fluoro groups, and cyano groups is also suitable for substituents of the first organic compound. Having a polycyclic aromatic ring and a cyano group as substituents, for example, can improve both the heat resistance and the electron-transport property. In addition, having a polycyclic aromatic ring and an alkyl group can improve both the heat resistance and the light extraction efficiency. In this manner, substituents can be combined in accordance with the required function.
The first organic compound having a plurality of polycyclic aromatic rings as substituents can further improve the heat resistance. In that case, the first organic compound preferably has the aromatic hydrocarbon ring and the heteroaromatic ring.
The first organic compound having the triazine skeleton can be specifically, for example, an organic compound that has a heteroaromatic ring having a triazine skeleton, such as 2-(biphenyl-4-yl)-4-phenyl-6-(9,9′-spirobi[9H-fluoren]-2-yl)-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)pbenyl]pbenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-2,3′-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 2-[3′-(9,9-dimethyl-9H-fluoren-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 5-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-7,7-dimethyl-5H,7H-indeno[2,1-b]carbazole (abbreviation: mINc(II)PTzn), 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTzn), 2,4,6-tris[3′-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-phenylindolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), 2-[3′-(triphenylen-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTpBPTzn), 3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]-9-phenyl-9H-carbazole (abbreviation: PCDBfTzn), 2-(biphenyl-3-yl)-4-phenyl-6-{8-[(1,1′:4′,1″-terphenyl)-4-yl]-1-dibenzofuranyl}-1,3,5-triazine (abbreviation: mBP-TPDBfTzn), 2-[4-(2-naphthalenyl)phenyl]-4-phenyl-6-spiro[9H-fluoren-9,9′-[9H]xanthen]-4-yl-1,3,5-triazine abbreviation: PNP-SFx(4)Tzn), 9,9′-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviation: SiTrzCz2), 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviation: mSiTrz), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-(biphenyl-3-yl)indolo[2,3-a]carbazole (abbreviation: BP-mBPIcz(II)Tzn), 3-{3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]phenyl}-9-phenyl-9H-carbazole (abbreviation: mPCPDBfTzn), 9,9′-[6-(biphenyl-4-yl)-2-phenyl-1,3,5-triazine-4,3″-diyl]bis(9H-carbazole) (abbreviation: Cz-pmCzBPTzn), 3-pheny-9-[4-phenyl-6-(9-phenyl-3-dibenzofuranyl-1,3,5-triazin-2-yl]-9N-carbazole (abbreviation: PDBf-PCzTzn), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzothienyl]-2-phenyl-9H-carbazole (abbreviation: PCzDBtTzn), 2,4-diphenyl-6-[3′-(spiro[7H-benzo[c]fluorene-7,9′-[9H]xanthen]-2′-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: mSbfxBPTzn), 3′-[4-phenyl-6-(spiro[9H-fluorene-9,9′-[9N]xanthen]-2′-yl)-1,3,5-triazin-2-yl]biphenyl-4-carbonitrile (abbreviation: mpCNBP-SFxTzn), or 2,2′-[1,2-naphthalenediyldi(4,1-phenylene)]bis(4,6-diphenyl-1,3,5-triazine) (abbreviation: TznP2N), and is particularly preferably TznP2N (100), mSbfxBPTzn (101), mpCNBP-SFxTzn (102), CNBPNPTzn (103), PNP-SFx(4)Tzn (104), mmtBuBP-mDMePyPTzn (105), or mBlnfBPTzn (106) represented by Structural Formulae (100) to (106) below or the like. Note that any of the above organic compounds deuterated as appropriate can also be used.
Note that an electron-transport layer included in a light-emitting unit on the anode side may include a third organic compound having a triazine skeleton, like the electron-transport layer included in the light-emitting unit on the cathode side, or may include a fourth organic compound not having a triazine skeleton.
The electron-transport layer included in the light-emitting unit on the anode side preferably includes the third organic compound having a triazine skeleton in order to reduce power consumption. It is particularly preferable for the electron-transport layer to include the same organic compound as the first organic compound in order to inhibit a manufacturing apparatus from becoming complex and offer a cost advantage in raw material procurement.
When the electron-transport layer included in the light-emitting unit on the anode side includes the fourth organic compound not having a triazine skeleton, the carrier-transport property can be easily controlled to provide a light-emitting device with better characteristics. The organic compound not having a triazine skeleton is preferably an organic compound that has a heteroaromatic ring having a pyridine skeleton or an organic compound that has a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton. Alternatively, the organic compound not having a triazine skeleton is preferably an organic compound having at least one of a pyrimidine skeleton, an imidazole skeleton, and an anthracene skeleton. For example, an organic compound having a pyrimidine skeleton and an anthracene skeleton or an organic compound having an imidazole skeleton and an anthracene skeleton is preferably used, in which case carrier transport can be controlled more easily.
The above-described second organic compound having a phenanthroline skeleton preferably has an electron mobility of 1×10−7 cm2/Vs or higher and further preferably has an electron mobility of 1×10−6 cm2/Vs or higher when the square root of electric field strength [V/cm] is 600. Note that any other substance can also be used as long as the substance has a property of transporting more electrons than holes.
The second organic compound having the phenanthroline skeleton preferably has the phenanthroline skeleton and an aromatic ring. The aromatic ring is preferably a monocyclic aromatic ring, a polycyclic aromatic ring, or the like.
Examples of the monocyclic aromatic ring include a benzene ring, a pyrrole ring, a pyridine ring, and a pyrimidine ring. Preferable examples of the polycyclic aromatic ring include heteroaromatic rings such as a phenanthroline ring and a pyrrole ring, as well as aromatic hydrocarbon rings such as a naphthalene ring, a phenanthrene ring, a chrysene ring, a triphenylene ring, and a fluorene ring. It is particularly preferable that the second organic compound have a plurality of such polycyclic aromatic rings to improve its heat resistance or electron-transport property.
The second organic compound having the phenanthroline skeleton can be, for example, an organic compound that has a heteroaromatic ring having a phenanthroline skeleton, such as bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP), 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), 2-[3-(2-triphenylenyl)phenyl]-1,10-phenanthroline (abbreviation: mTpPPhen), 2-phenyl-9-(2-triphenylenyl)-1,10-phenanthroline (abbreviation: Ph-TpPhen), 2-[4-(9-phenanthrenyl)-1-naphthalenyl]-1,10-phenanthroline (abbreviation: PnNPhen), or 2-[4-(2-triphenylenyl)phenyl]-1,10-phenanthroline (abbreviation: pTpPPhen), and is preferably PnNPhen (200) or mPPhen2P (201) represented by Structural Formula (200) or (201) below, or the like.
In the light-emitting device of one embodiment of the present invention, the intermediate layer can have any structure as long as it includes the second organic compound having a phenanthroline skeleton and can inject electrons and holes respectively into the light-emitting unit on the anode side and the light-emitting unit on the cathode side, which are in contact with the intermediate layer, by voltage application between a first electrode and a second electrode. Note that the intermediate layer preferably has a stacked-layer structure of a first layer including the second organic compound and a second layer positioned closer to the cathode than the first layer is.
The first layer preferably includes a metal or a metal compound in addition to the second organic compound. The metal or a metal of the metal compound is preferably an alkali metal (Group 1 element) such as Li, an alkaline earth metal (Group 2 element) such as Mg or Ca, a Group 3 element including Y and lanthanoids such as Eu and Yb, a Group 11 element such as Cu, Ag, or Au, a Group 12 element such as Zn, an earth metal (Group 13 element) such as Al or In.
Note that the first layer may have a stacked-layer structure of a layer including an organic compound and a layer including a metal or a metal compound and positioned closer to the cathode than the layer including an organic compound is, or may be a mixed layer of an organic compound and a metal or a metal compound. The first layer is preferably the mixed layer, in which case it requires a smaller number of film formation chambers and a lower manufacturing cost and contributes to an improvement in the stability of the light-emitting device.
In the case where the organic compound and the metal or the metal compound are mixed, the organic compound and the metal or the metal compound tend to show substantially the same distribution when the first layer is analyzed in the thickness direction. That is, when the organic compound is uniformly distributed, the metal or the metal compound is also substantially uniformly distributed. In the case of the stacked-layer structure of the layer including the organic compound and the layer including the metal or the metal compound, the metal or the metal compound is sometimes diffused from the layer including the metal or the metal compound and detected also in a region other than the layer but shows a different distribution from the organic compound; thus, the analysis results of diffusion and mixing can be distinguished from each other.
In the case where the metal or the metal compound is detected over a region having a thickness greater than or equal to 10 nm, preferably greater than or equal to 15 nm, further preferably greater than or equal to 20 nm when the first layer is analyzed in the thickness direction, the first layer can be regarded as including a mixed layer in which the organic compound and the metal or the metal compound are mixed.
The metal or a metal of the metal compound is preferably, among others, a substance exhibiting a donor property with respect to the second organic compound. Examples of the substance exhibiting a donor property with respect to the second organic compound include metals belonging to Groups 1 and 2; lithium or a lithium compound is particularly preferable. Specifically, Li, lithium fluoride (LiF), lithium oxide (Li2O), 8-hydroxyquinolinato-lithium (abbreviation: Liq), or the like is preferable. In the case where the first layer includes the second organic compound and the substance exhibiting a donor property with respect to the second organic compound, electrons are generated by charge separation, and the electrons are injected into the light-emitting unit on the anode side through the second organic compound when voltage is applied between the first electrode and the second electrode. Thus, the light-emitting device of one embodiment of the present invention can have a low driving voltage.
The second organic compound is preferably an organic compound having a phenanthroline skeleton having an electron-donating substituent, as well as the above-described organic compound. The phenanthroline skeleton is likely to interact with the metal or the like, and when the second organic compound having such a phenanthroline skeleton further has an electron-donating group, the phenanthroline skeleton can have a higher electron density and become more likely to interact with the metal or the metal compound. In particular, the use of a metal belonging to Group 3, 11, 12, or 13 as the metal or a metal of the metal compound makes it possible to provide a tandem light-emitting device which is inhibited from having an increase in driving voltage and which has favorable characteristics.
Specific examples of the electron-donating group include an alkyl group, an alkoxy group, an aryloxy group, an alkylamino group, an arylamino group, and a heterocyclic amino group. Note that examples of the electron-donating group that is preferably introduced to the phenanthroline ring are not limited to the above examples. The electron-donating group may be any group that can increase the electron density of the phenanthroline ring by being introduced to the phenanthroline ring. The electron-donating group may be introduced to the phenanthroline ring via an arylene group such as a phenylene group, and the arylene group is preferably a p-phenylene group.
Specific examples of the organic compound having the phenanthroline skeleton having the electron-donating substituent are shown in Structural Formulae (300) to (310).
Note that the first layer preferably includes a Group 1 or Group 2 element, especially lithium or a lithium compound, and the second organic compound having a phenanthroline skeleton having an electron-donating substituent, in which case the tandem light-emitting device can have a lower driving voltage and higher reliability. Moreover, the first layer preferably includes a Group 1 or Group 2 element, especially lithium or a lithium compound, and the second organic compound having a phenanthroline skeleton having an electron-donating substituent, in which case it is possible to inhibit an increase in driving voltage due to processing of the organic compound layer of the light-emitting device by a photolithography method.
In the intermediate layer having the above-described structure, the second organic compound is particularly preferably an organic compound having, among phenanthroline skeletons, a 1,10-phenanthroline skeleton, in which case the second organic compound is likely to interact with the metal or the metal compound because two nitrogen atoms of the organic compound can be coordinated to the metal.
In the case where an electron-donating group is introduced to a 1,10-phenanthroline skeleton, the electron-donating group is preferably substituted at the 4- and 7-positions of the 1,10-phenanthroline skeleton. Introducing an electron-donating group to the 4- and 7-positions of the 1,10-phenanthroline skeleton can increase the electron density of the nitrogen atoms at the 1- and 10-positions, thereby facilitating the interaction with the metal or the metal compound.
The first layer may further include an organic compound different from the second organic compound. Note that the different organic compound preferably has an electron-transport property. It is particularly preferable that the organic compound have two or more heteroaromatic rings bonded or condensed to each other and the two or more heteroaromatic rings have three or more heteroatoms in total. The first layer including such an organic compound can improve the heat resistance, the electron-transport property, and the like.
The second layer preferably includes a fifth organic compound having a hole-transport property. The second layer preferably further includes a substance exhibiting an acceptor property, and the substance exhibiting an acceptor property is preferably an organic compound exhibiting an acceptor property with respect to the fifth organic compound. The substance having an acceptor property is particularly preferably an organic compound having at least one of a halogen group and a cyano group, further preferably an organic compound having at least one of fluorine and a cyano group. Note that it is further preferable that the total number of halogen groups (fluorines) and cyano groups of the organic compound be four or more.
In the case where the second layer includes the fifth organic compound and the substance exhibiting an acceptor property with respect to the fifth organic compound, holes are generated by charge separation, and the holes are injected into the light-emitting unit on the cathode side through the fifth organic compound when voltage is applied between the first electrode and the second electrode. Thus, the light-emitting device of one embodiment of the present invention can have a low driving voltage.
The intermediate layer may include a third layer between the first layer and the second layer.
The third layer includes a substance having an electron-transport property and has functions of smoothly transferring and receiving electrons between the first layer and the second layer to reduce the driving voltage, and reducing the interaction between the first layer and the second layer to improve the reliability, for example.
The thickness of the third layer is preferably greater than or equal to 1 nm and less than or equal to 10 nm, further preferably greater than or equal to 2 nm and less than or equal to 5 nm, in which case an increase in driving voltage can be inhibited.
The light-emitting device of one embodiment of the present invention that has the above structure can have high current efficiency, low energy loss, and favorable characteristics. A display device of one embodiment of the present invention that includes such a light-emitting device can achieve low power consumption, high reliability, high-luminance display, and high visibility.
Next, light-emitting devices of one embodiment of the present invention will be described in detail with reference to the drawings.
In the light-emitting device 130, the second electron-transport layer 114_2 includes the first organic compound having a triazine skeleton, and the intermediate layer 116 includes the second organic compound having a phenanthroline skeleton. The second electron-transport layer 114_2 including the first organic compound having a triazine skeleton is preferably in contact with the second electrode 102 in order to reduce power consumption.
Although light-emitting devices each including one intermediate layer 116 and two light-emitting units are described as examples in this embodiment, a light-emitting device including n intermediate layer(s) (n is an integer greater than or equal to 1) and n+1 light-emitting units may be employed. For example, the light-emitting device 130 illustrated in
The first light-emitting unit 501 and the second light-emitting unit 502 may include a functional layer in addition to the above-described light-emitting and electron-transport layers. Although
The first electrode 101 includes the anode. The first electrode 101 may have a stacked-layer structure, in which case a layer in contact with the organic compound layer 103 functions as the anode. The anode is preferably formed using a metal, an alloy, a conductive compound, or a mixture thereof each having a high work function (specifically, higher than or equal to 4.0 eV), for example. Specific examples include indium oxide-tin oxide (ITO: indium tin oxide), indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). Films of such conductive metal oxides are usually formed by a sputtering method, but may be formed by a sol-gel method or the like. For example, a film of indium oxide-zinc oxide is formed by a sputtering method using a target in which 1 wt % to 20 wt % zinc oxide is added to indium oxide. Furthermore, a film of indium oxide containing tungsten oxide and zinc oxide (IWZO) can be formed by a sputtering method using a target in which 0.5 wt % to 5 wt % tungsten oxide and 0.1 wt % to 1 wt % zinc oxide are added to indium oxide. Alternatively, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), a nitride of a metal material (e.g., titanium nitride), or the like can be used for the anode. Graphene can also be used for the anode. Note that an electrode material can be selected regardless of the work function when the composite material forming the second layer 117 in the above intermediate layer 116 is used for the layer (typically the hole-injection layer) in contact with the anode.
The hole-injection layer 111 is provided in contact with the anode and has a function of facilitating injection of holes into the organic compound layer 103 (the first light-emitting unit 501). The hole-injection layer 111 can be formed using a phthalocyanine-based compound or complex compound such as phthalocyanine (abbreviation: H2Pc) or copper phthalocyanine (abbreviation: CuPc), an aromatic amine compound such as 4,4′-bis[V-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB) or 4,4′-bis(N-{4-[NA-(3-methylphenyl)-N-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), or a high molecular compound such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (abbreviation: PEDOT/PSS), for example.
The hole-injection layer 111 may be formed using a substance having an electron-acceptor property. Examples of the substance having an acceptor property include organic compounds having an electron-withdrawing group (e.g., a halogen group or a cyano group), such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile. A compound in which electron-withdrawing groups are bonded to a condensed aromatic ring having a plurality of heteroatoms, such as HAT-CN, is particularly preferable because it is thermally stable. A [3]radialene derivative having an electron-withdrawing group (in particular, a cyano group, a halogen group such as a fluoro group, or the like) has a significantly high electron-acceptor property and thus is preferable. Specific examples include, α,α′,α″-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile]. As the substance having an acceptor property, a transition metal oxide such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, or manganese oxide can be used, other than the above-described organic compounds. Alternatively, the hole-injection layer 111 can be formed using a phthalocyanine-based compound or complex compound such as phthalocyanine (abbreviation: H2Pc) of copper phthalocyanine (abbreviation: CuPc), an aromatic amine compound such as 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB) or 4,4′-bis(N-{4-[N-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), or a high molecular compound such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (abbreviation: PEDOT/PSS), for example. The substance having an acceptor property can extract electrons from an adjacent hole-transport layer (or hole-transport material) by application of an electric field.
The hole-injection layer 111 is preferably formed using a composite material containing any of the aforementioned materials having an acceptor property and a substance having a hole-transport property.
As the substance having a hole-transport property used in the composite material, any of a variety of organic compounds such as aromatic amine compounds, heteroaromatic compounds, aromatic hydrocarbons, and high molecular compounds (e.g., oligomers, dendrimers, and polymers) can be used. Note that the substance having a hole-transport property used for the composite material preferably has a hole mobility of 1×10−6 cm2/Vs or higher. The substance having a hole-transport property used in the composite material is preferably a compound having a condensed aromatic hydrocarbon ring or a π-electron rich heteroaromatic ring. As the condensed aromatic hydrocarbon ring, an anthracene ring, a naphthalene ring, or the like is preferable. As the π-electron rich heteroaromatic ring, a condensed aromatic ring having at least one of a pyrrole skeleton, a furan skeleton, and a thiophene skeleton in the ring is preferable; specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further condensed to a carbazole ring or a dibenzothiophene ring is preferable.
Such a substance having a hole-transport property further preferably has any of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, an aromatic amine having a substituent that has a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine that has a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to nitrogen of an amine through an arylene group may be used. Note that the substance having a hole-transport property preferably has an N,N-bis(4-biphenyl)amino group to enable fabricating a light-emitting device having a long lifetime.
Specific examples of the substance having a hole-transport property include N-(4-biphenyl)-6,A-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BnfABP), N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), 4,4′-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4″-phenyltriphenylamine (abbreviation: BnfBB1BP), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), NAV-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-NV-phenyl-4-biphenylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4′,4″-diphenyltriphenylamine (abbreviation: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4′,4″-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4′-diphenyl-4″-(6;1-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4′-diphenyl-4″-(7;1′-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB-03), 4,4′-diphenyl-4″-(7-phenyl)naphthyl-2-yl)triphenylamine (abbreviation: BBAPβNB-03), 4,4′-diphenyl-4″-(6;2′-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B), 4,4′-diphenyl-4″-(7;2′-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B-03), 4,4′-diphenyl-4″-(4;2′-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB), 4,4′-diphenyl-4″-(5;2′-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNaNB-02), 4-(4-biphenylyl)-4′-(2-naphthyl)-4″-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenylyl)-4′-[4-(2-naphthyl)phenyl]-4″-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenylyl)-4′-[4-(2-naphthyl)phenyl]-4″-phenyltriphenylamine (abbreviation: TPBiApβBi), 4-phenyl-4′-(1-naphthyl)triphenylamine (abbreviation: αNBA1BP), 4,4′-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4′-diphenyl-4″-[4′-(carbazol-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBiIBP), 4′-[4-(3-phenyl-9H-carbazol-9-yl)phenyl]tris(biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-[4′-(carbazol-9-yl)biphenyl-4-yl]-4′-(2-naphthyl)-4″-phenyltriphenylamine (abbreviation: YGTBiβNB), N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBNBSF), N,N-bis(biphenyl-4-yl)-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: BBASF), N,N-bis(biphenyl-4-yl)-9,9′-spirobi[9H-fluoren]-4-amine (abbreviation: BBASF(4)), N-(biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi[9H-fluoren]-4-amine (abbreviation: oFBiSF), N-(biphenyl-4-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)dibenzofuran-4-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylanine (abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4′-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF), N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9N-fluoren-2-amine (abbreviation: PCBBiF), N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-4-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-3-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-2-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-1-amine, 9-[3-(triphenylsilyl)phenyl]-3,9′-bi-9H-carbazole (abbreviation: PSiCzCz), and 9′-phenyl-9′H-9,3′:6′,9″-tercarbazole (abbreviation: PSiCzGI).
Examples of the aromatic amine compounds that can be used as the substance having a hole-transport property include N,N′-di(p-tolyl)-N,N′-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B).
The formation of the hole-injection layer 111 can improve the hole-injection property, which allows the light-emitting device to be driven at a low voltage.
Among substances having an acceptor property, an organic compound having an acceptor property is easy to use because the organic compound is easily deposited by evaporation as a film.
The hole-transport layer (the first hole-transport layer 112_1 or the second hole-transport layer 112_2) includes an organic compound having a hole-transport property. The organic compound having a hole-transport property preferably has a hole mobility of 1×10−6 cm2/Vs or higher.
Examples of the aforementioned substance having a hole-transport property include the following compounds: compounds having an aromatic amine skeleton, such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-4,4′-diaminobiphenyl (abbreviation: TPD), N,N′-bis(9,9′-spirobi[9H-fluoren]-2-yl)-N,N′-diphenyl-4,4′-diaminobiphenyl (abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASP); compounds having a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 9,9′-bis(biphenyl-4-yl)-3,3′-bi-9H-carbazole (abbreviation: BisBPCz), 9,9′-bis(biphenyl-3-yl)-3,3′-bi-9H-carbazole (abbreviation: BismBPCz), 9-(biphenyl-3-yl)-9′-(biphenyl-4-yl)-9H,9′H-3,3′-bicarbazole (abbreviation: mBPCCBP), 9-(2-naphthyl)-9′-phenyl-9,9′1-3,3′-bicarbazole (abbreviation: βNCCP), 9-(3-biphenyl)-9′-(2-naphthyl)-3,3′-bi-9H-carbazole (abbreviation: βNCCmBP), 9-(4-biphenyl)-9′-(2-naphthyl)-3,3′-bi-9H-carbazole (abbreviation: βNCCBP), 9,9′-di-2-naphthyl-3,3′-9H,9′H-bicarbazole (abbreviation: BisβNCz), 9-(2-naphthyl)-9′-[1,1′:4′,1″-terphenyl]-3-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-3-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-5′-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:4′,1′-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-phenyl-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole (abbreviation: PCCzTp), 9,9′-bis(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-(4-biphenyl)-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-(triphenylen-2-yl)-9′-[1,1′:3′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-1-amine, and 9-[3-(triphenylsilyl)phenyl]-3,9′-bi-9H-carbazole (abbreviation: PSiCzCz); compounds having a thiophene skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-JJJ), and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-JV); and compounds having a furan skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-IL). Among the above materials, the compound having an aromatic amine skeleton and the compound having a carbazole skeleton are preferable because these compounds are highly reliable and have a high hole-transport property to contribute to a reduction in driving voltage. Any of the organic compounds given as examples of the substance having a hole-transport property that is used for the composite material in the hole-injection layer 111 can also be suitably used as the material included in the hole-transport layer 112. Note that any of the above organic compounds deuterated as appropriate can also be used.
Note that the first hole-transport layer 112_1 and the second hole-transport layer 112_2 preferably include organic compounds having the same skeleton, and further preferably include the same compound.
The light-emitting layer (the first light-emitting layer 113_1 and the second light-emitting layer 1132) preferably includes an emission center substance and a host material. The light-emitting layer may additionally include another material.
The first light-emitting layer 113_1 and the second light-emitting layer 113_2 preferably emit light of similar colors. For example, red, green, and blue pixels are often used in a full-color display device. In a light-emitting device used in a red pixel, both the first light-emitting layer 113_1 and the second light-emitting layer 113_2 emit red light. In a green pixel, both of the two light-emitting layers emit green light. In a blue pixel, both of the two light-emitting layers emit blue light. In that case, the emission center substance included in the first light-emitting layer 113_1 and the emission center substance included in the second light-emitting layer 113_2 are preferably compounds whose emission spectra have a difference in maximum peak wavelength of less than or equal to 30 nm, further preferably less than or equal to 20 nm, still further preferably less than or equal to 10 nm. Note that it is further preferable that the first light-emitting layer 113_1 and the second light-emitting layer 113_2 include the same emission center substance.
The emission center substance may be a fluorescent substance, a phosphorescent substance, a substance exhibiting thermally activated delayed fluorescence (TADF), or any other light-emitting substance.
Examples of the fluorescent substance that can be used as the emission center substance in the light-emitting layer are as follows. Other fluorescent substances can also be used.
The examples include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine (abbreviation: PAPP2BPy), N,N′-diphenyl-N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(91H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9N-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N′-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis(N,N′,N′-triphenyl-1,4-phenylenediamine) (abbreviation: DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, 9,10-diphenyl-2-[N-phenyl-N-(9-phenyl-carbazol-3-yl)-amino]-anthracene (abbreviation: 2PCAPA), A-[9,10-bis(biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), coumarin 545T, N,N′-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-bis(biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[j]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N′-diphenyl-,N,N′-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03), N,N′-diphenyl-N,N-bis(9-phenyl-9H-carbazol-2-yl)naphtho[2,3-b;6,7-b′]bisbenzofuran-3,10-diamine (abbreviation: 3,10PCA2Nbf(IV)-02), and 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b′]bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02). Condensed aromatic diamine compounds typified by pyrenediamine compounds such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03 are particularly preferable because of their high hole-trapping properties, high emission efficiency, or high reliability.
Examples of the phosphorescent substance that can be used as the emission center substance in the light-emitting layer are as follows.
The examples 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]), and tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz)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(Mptzl-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]), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me)3]), and tris(2-{1-[2,6-bis(I-methylethyl)phenyl]-1H-imidazol-2-yl-}-4-cyanophenyl-κC)iridium(III) (abbreviation: CNImIr); organometallic complexes having a benzimizazolidene skeleton, such as tris[(6-tert-butyl-3-phenyl-2H-imidazo[4,5-b]pyrazin-1-yl-κC2)phenyl-xC]iridium(III) (abbreviation: [Ir(cb)3]); 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(I-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: FIracac); and platinum complexes such as (2-{3-[3-(3,5-di-teri-butylphenyl)benzimidazol-1-yl-2-ylidene-κC2]phenoxy-κC2}-9-(4-tert-butyl-2-pyridinyl-κN)carbazole-2,1-diyl-κC1)platinum(II) (abbreviation: PtON-TBBI). These compounds emit blue phosphorescent light and have an emission peak in the wavelength range from 450 nm to 520 nm. Alternatively, a compound obtained by substituting deuterium for part of hydrogen in any of these compounds can also be used.
Other examples 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[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm)2(acac)]), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm)2(acac)]), 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]), bis(2-phenylquinolinato-N,C2)iridium(III) acetylacetonate (abbreviation: [Ir(pq)2(acac)]), [2-d3-methyl-8-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(5-d3-methyl-2-pyridinyl-κN2)phenyl-κC]iridium(III) (abbreviation: [Ir(5mppy-d3)2(mbfpypy-d3)]), {2-(methyl-d3)-8-[4-(1-methylethyl-1-d)-2-pyridinyl-κN]benzofuro[2,3-b]pyridin-7-yl-κC}bis{5-(methyl-d3)-2-[5-(methyl-d3)-2-pyridinyl-κN]phenyl-κCC}iridium(III) (abbreviation: [Ir(5mtpy-d6)2(mbfpypy-iPr-d4)]), [2-d3-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(mbfpypy-d3)]), [2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(mdppy)]), [2-(4-d3-methyl-5-phenyl-2-pyridinyl-κN2)phenyl-κC]bis[2-(5-d3-methyl-2-pyridinyl-κN2)phenyl-κC]iridium(III) (abbreviation: [Ir(5mppy-d3)2(mdppy-d3)]), [2-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(mbfpypy)]), [2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium (abbreviation: [Ir(ppy)2(mdppy)]), and tris{2-[5-(methyl-d3)-4-phenyl-2-pyridinyl-κN]phenyl-κC}iridium(III) (abbreviation: [Ir(5m4dppy-d3)3]); and rare earth metal complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)3(Phen)]). These compounds mainly emit green phosphorescent light and have an emission peak in the wavelength range from 500 nm to 600 nm. Note that organometallic iridium complexes having a pyrimidine skeleton have distinctively high reliability or emission efficiency and thus are particularly preferable. Alternatively, a compound obtained by substituting deuterium for part of hydrogen in any of these compounds can also be used.
Other examples 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]), bis(I-phenylisoquinolinato-N,C2)iridium(III) acetylacetonate (abbreviation: [Ir(piq)2(acac)]), (3,7-diethyl-4,6-nonanedionato-κO4,κO6)bis[2,4-dimethyl-6-[7-(1-methylethyl)-1-isoquinolinyl-icN]phenyl-κC]iridium(III), and (3,7-diethyl-4,6-nonanedionato-κO4,κO6)bis[2,4-dimethyl-6-[5-(1-methylethyl)-2-quinolinyl-KJN]phenyl-κC]iridium(III); platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (abbreviation: PtOEP); and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europiunm(III) (abbreviation: [Eu(DBM)3(Phen)]) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA)3(Phen)]). These compounds emit red phosphorescent light and have an emission peak in the wavelength range from 600 nm to 700 nm. Furthermore, the organometallic iridium complexes having a pyrazine skeleton can provide red light emission with favorable chromaticity. Alternatively, a compound obtained by substituting deuterium for part of hydrogen in any of these compounds can also be used.
Note that in one embodiment of the present invention, the use of a deuterated compound as the emission center substance improves the emission efficiency. Thus, the emission center substance is preferably a deuterated material.
Besides the above phosphorescent compounds, known phosphorescent compounds may be selected and used.
Examples of the TADF material include a fullerene, a derivative thereof, an acridine, a derivative thereof, and an eosin derivative. Furthermore, a metal-containing porphyrin, such as a porphyrin containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd), can be given. Examples of the metal-containing porphyrin include a protoporphyrin-tin fluoride complex (SnF2(Proto IX)), a mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), a hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), a coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro ILJ-4Me)), an octaethylporphyrin-tin fluoride complex (SnF2(OEP)), an etioporphyrin-tin fluoride complex (SnF2(Etio I)), and an octaethylporphyrin-platinum chloride complex (PtCl2OEP), which are represented by the following structural formulae.
Alternatively, it is possible to use a heterocyclic compound having one or both of a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring that is represented by the following structural formulae, such as 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PCCzTzn), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), or 10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation: ACRSA). Such a heterocyclic compound is preferable because of having high electron-transport and hole-transport properties owing to a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring. Among skeletons having the π-electron deficient heteroaromatic ring, a pyridine skeleton, a diazine skeleton (a pyrirnidine skeleton, a pyrazine skeleton, and a pyridazine skeleton), and a triazine skeleton are preferable because of their high stability and reliability. In particular, a benzofuropyrimidine skeleton, a benzothienopyrinidine skeleton, a benzofuropyrazine skeleton, and a benzothienopyrazine skeleton are preferable because of their high acceptor properties and high reliability. Among skeletons having the π-electron rich heteroaromatic ring, an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton have high stability and reliability; thus, at least one of these skeletons is preferably included. A dibenzofuran skeleton is preferable as a furan skeleton, and a dibenzothiophene skeleton is preferable as a thiophene skeleton. As a pyrrole skeleton, an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, and a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton are particularly preferable. Note that a substance in which the π-electron rich heteroaromatic ring is directly bonded to the π-electron deficient heteroaromatic ring is particularly preferable because the electron-donating property of the n-electron rich heteroaromatic ring and the electron-acceptor property of the π-electron deficient heteroaromatic ring are both improved, the energy difference between the S1 level and the T1 level becomes small, and thus thermally activated delayed fluorescence can be obtained with high efficiency. Note that an aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used instead of the π-electron deficient heteroaromatic ring. As a n-electron rich skeleton, an aromatic amine skeleton, a phenazine skeleton, or the like can be used. As a π-electron deficient skeleton, a xanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a skeleton including boron such as phenylborane or boranthrene, an aromatic ring or a heteroaronatic ring having a cyano group or a nitrile group such as benzonitrile or cyanobenzene, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, or the like can be used. As described above, a π-electron deficient skeleton and a π-electron rich skeleton can be used instead of at least one of the π-electron deficient heteroaromatic ring and the π-electron rich heteroaromatic ring.
Alternatively, a TADF material whose singlet excited state and triplet excited state are in a thermal equilibrium state may be used. Since such a TADF material enables a short emission lifetime (excitation lifetime), the efficiency of a light-emitting device in a high-luminance region can be less likely to decrease. Specifically, a material having the following molecular structure can be used.
Note that a TADF material is a material having a small difference between the S1 level and the T1 level and a function of converting triplet excitation energy into singlet excitation energy by reverse intersystem crossing. Thus, a TADF material can upconvert triplet excitation energy into singlet excitation energy (i.e., reverse intersystem crossing) using a small amount of thermal energy and efficiently generate a singlet excited state. In addition, the triplet excitation energy can be converted into light emission.
An exciplex whose excited state is formed of two kinds of substances has an extremely small difference between the S1 level and the T1 level and functions as a TADF material capable of converting triplet excitation energy into singlet excitation energy.
A phosphorescent spectrum observed at a low temperature (e.g., 77 K to 10 K) is used for an index of the T1 level. When the level of energy with a wavelength of the line obtained by extrapolating a tangent to the fluorescent spectrum at a tail on the short wavelength side is the S1 level and the level of energy with a wavelength of the line obtained by extrapolating a tangent to the phosphorescent spectrum at a tail on the short wavelength side is the T1 level, the difference between the S1 level and the T1 level of the TADF material is preferably smaller than or equal to 0.3 eV, further preferably smaller than or equal to 0.2 eV.
When a TADF material is used as the light-emitting substance, the S1 level of the host material is preferably higher than that of the TADF material. In addition, the T1 level of the host material is preferably higher than that of the TADF material.
As the host material in the light-emitting layer, various carrier-transport materials such as materials having an electron-transport property and/or materials having a hole-transport property, and the TADF materials can be used.
The material having a hole-transport property is preferably an organic compound having an amine skeleton or a π-electron rich heteroaromatic ring skeleton, for example. As the π-electron rich heteroaromatic ring, a condensed aromatic ring having at least one of an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton is preferable; specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further condensed to a carbazole ring or a dibenzothiophene ring is preferable.
Such a substance having a hole-transport property further preferably has any of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, an aromatic amine having a substituent that has a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine that has a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to nitrogen of an amine through an arylene group may be used. Note that the substance having a hole-transport property is preferably an organic compound having an N,N-bis(4-biphenyl)amino group to enable fabricating a light-emitting device having a long lifetime.
Preferable examples of such organic compounds include the following organic compounds: compounds having an aromatic amine skeleton, such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-4,4′-diaminobiphenyl (abbreviation: TPD), N,N-bis(9,9′-spirobi[9H-fluoren]-2-yl)-N,N-diphenyl-4,4′-diaminobiphenyl (abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-V-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF); compounds having a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 3,9-bis(9-phenyl-9H-carbazol-3-yl)-9H-carbazole (abbreviation: PCCzPC), 9-(biphenyl-4-yl)-9′-phenyl-3,3′-bi-9H-carbazole (abbreviation: PCCzBP), 9,9′-bis(biphenyl-4-yl)-3,3′-bi-9H-carbazole (abbreviation: BisBPCz), 9,9′-bis(biphenyl-3-yl)-3,3′-bi-9H-carbazole (abbreviation: BismBPCz), 9-(biphenyl-3-yl)-9′-(biphenyl-4-yl)-9H,9′H-3,3′-bicarbazole (abbreviation: mBPCCBP), 9-(2-naphthyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PNCCP), 9-(3-biphenyl)-9′-(2-naphthyl)-3,3′-bi-9H-carbazole (abbreviation: P)NCCmBP), 9-(4-biphenyl)-9′-(2-naphthyl)-3,3′-bi-9H-carbazole (abbreviation: PNCCBP), 9,9′-di-2-naphthyl-3,3′-9H,9′H-bicarbazole (abbreviation: Bis3NCz), 9-(2-naphthyl)-9′-[1,1′:4′,1″-terphenyl]-3-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-3-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-5′-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:4′,9″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-phenyl-9′-(triphenylen-2-yl)-3,3′-9H,9′11-bicarbazole (abbreviation: PCCzTp), 9,9′-bis(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-(4-biphenyl)-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-(triphenylen-2-yl)-9′-[1,1′:3′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-1-amine, 9-[3-(triphenylsilyl)phenyl]-3,9′-bi-9H-carbazole (abbreviation: PSiCzCz), and 9′-phenyl-9′H-9,3′:6′,9″-tercarbazole (abbreviation: PSiCzGI); compounds having a thiophene skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV); and compounds having a furan skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above materials, the compound having an aromatic amine skeleton and the compound having a carbazole skeleton are preferable because these compounds are highly reliable and have a high hole-transport property to contribute to a reduction in driving voltage. In addition, the organic compounds given as examples of the material having a hole-transport property that can be used for the hole-transport layer can also be used.
The material having an electron-transport property is preferably an organic compound having a in-electron deficient heteroaromatic ring. Examples of the organic compound having a it-electron deficient heteroaromatic ring skeleton include an organic compound that has a heteroaromatic ring having a polyazole skeleton, an organic compound that has a heteroaromatic ring having a pyridine skeleton, an organic compound that has a heteroaromatic ring having a diazine skeleton, and an organic compound that has a heteroaromatic ring having a triazine skeleton.
Among the above organic compounds, the organic compound that has a heteroaromatic ring having a diazine skeleton (a pyrimidine skeleton, a pyrazine skeleton, or a pyridazine skeleton), the organic compound that has a heteroaromatic ring having a pyridine skeleton, and the organic compound that has a heteroaromatic ring having a triazine skeleton are preferable because of their high reliability. In particular, the organic compound that has a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and the organic compound that has a heteroaromatic ring having a triazine skeleton have a high electron-transport property to contribute to a reduction in driving voltage. A benzofuropyrimidine skeleton, a benzothienopyrimidine skeleton, a benzofuropyrazine skeleton, and a benzothienopyrazine skeleton are preferable because of their high acceptor properties and high reliability.
Preferable examples of the organic compound having a π-electron deficient heteroaromatic ring skeleton include the following organic compounds: organic compounds having an azole skeleton, such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-11), and 4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOS); organic compounds that have a heteroaromatic ring having a pyridine skeleton, such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP), 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), 2-[3-(2-triphenylenyl)phenyl]-1,10-phenanthroline (abbreviation: mTpPPhen), 2-phenyl-9-(2-triphenylenyl)-1,10-phenanthroline (abbreviation: Ph-TpPhen), 2-[4-(9-phenanthrenyl)-1-naphthalenyl]-1,10-phenanthroline (abbreviation: PnNPhen), and 2-[4-(2-triphenylenyl)phenyl]-1,10-phenanthroline (abbreviation: pTpPPhen); organic 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-11), 2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4′-(9-phenyl-9H-carbazol-3-yl)-3,1′-biphenyl-1-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mpPCBPDBq), 2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 9-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), 9-[3′-(dibenzothiophen-4-yl)biphenyl-4-yl]naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9pmDBtBPNfpr), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(dibenzothiophen-4-yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pn-II), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), 9,9′-[pyrimidine-4,6-diylbis(biphenyl-3,3′-diyl)]bis(9H-carbazole) (abbreviation: 4,6mCzBP2Pm), 8-(biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), 3,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzofuro[2,3-b]pyrazine (abbreviation: 3,8mDBtP2Bfpr), 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofturo[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 8-[3′-(dibenzothiophen-4-yl)(biphenyl-3-yl)]naphtho[1′,2′:4,5]furo[3,2-a]pyrimidine (abbreviation: 8mDBtBPNfpm), 8-[(2,2′-binaphthalen)-6-yl]-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8(βN2)-4mDBtPBfpm), 2,2′-(pyridine-2,6-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 2,6(P-Bqn)2Py), 2,2′-(pyridine-2,6-diyl)bis{4-[4-(2-naphthyl)phenyl]-6-phenylpyrimidine}(abbreviation: 2,6(NP-PPm)2Py), 6-(biphenyl-3-yl)-4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenylpyrimidine (abbreviation: 6mBP-4Cz2PPm), 2,6-bis(4-naphthalen-1-ylphenyl)-4-[4-(3-pyridyl)phenyl]pyrimidine (abbreviation: 2,4NP-6PyPPm), 4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenyl-6-(biphenyl-4-yl)pyrimidine (abbreviation: 6BP-4Cz2PPm), 7-[4-(9-phenyl-9H-carbazol-2-yl)quinazolin-2-yl]-7H-dibenzo[c,g]carbazole (abbreviation: PC-cgDBCzQz), and 8-(1,1′:4′,1″-terphenyl-3-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofturo[3,2-d]pyrimidine (abbreviation: 8mpTP-4mDBtPBfpm); organic compounds that have a heteroaromatic ring having a triazine skeleton, such as 2-(biphenyl-4-yl)-4-phenyl-6-(9,9′-spirobi[9H-fluoren]-2-yl)-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBntBPTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-2,3′-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 2-[3′-(9,9-dimethyl-9H-fluoren-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 5-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-7,7-dimethyl-5H,7H-indeno[2,1-b]carbazole (abbreviation: mINc(II)PTzn), 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTzn), 2,4,6-tris[3′-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-phenylindolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), 2-[3′-(triphenylen-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTpBPTzn), 3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]-9-phenyl-9H-carbazole (abbreviation: PCDBfTzn), 2-(biphenyl-3-yl)-4-phenyl-6-{8-[(1,1′:4′,1″-terphenyl)-4-yl]-1-dibenzofuranyl}-1,3,5-triazine (abbreviation: mBP-TPDBfTzn), 2-[4-(2-naphthalenyl)phenyl]-4-phenyl-6-spiro[9H-fluorene-9,9′-[9H]xanthen]-4-yl-1,3,5-triazine (abbreviation: βNP-SFx(4)Tzn), 9,9′-{6-[3-(triphenylsilyl)phenyl]-1,3,5-triazine-2,4-diyl}bis(9H-carbazole) (abbreviation: SiTrzCz2), 2-phenyl-4,6-bis[3-(triphenylsilyl)phenyl]-1,3,5-triazine (abbreviation: mSiTrz), 11-[4-(biphenyl-4-yl)-6-phenyl-1,3,5-triazin-2-yl]-11,12-dihydro-12-(biphenyl-3-yl)indolo[2,3-a]carbazole (abbreviation: BP-mBPIcz(II)Tzn), 3-{3-[9-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzofuranyl]phenyl}-9-phenyl-9H-carbazole (abbreviation: mPCPDBfTzn), 9,9′-[6-(biphenyl-4-yl)-2-phenyl-1,3,5-triazine-4,3″-diyl]bis(9H-carbazole) (abbreviation: Cz-pmCzBPTzn), 3-phenyl-9-[4-phenyl-6-(9-phenyl-3-dibenzofuranyl)-1,3,5-triazin-2-yl]-9H-carbazole (abbreviation: PDBf-PCzTzn), and 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzothienyl]-2-phenyl-9H-carbazole (abbreviation: PCzDBtTzn). The organic compound that has a heteroaromatic ring having a diazine skeleton, the organic compound that has a heteroaromatic ring having a pyridine skeleton, and the organic compound that has a heteroaromatic ring having a triazine skeleton are preferable because of their high reliability. In particular, the organic compound that has a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and the organic compound that has a heteroaromatic ring having a triazine skeleton have a high electron-transport property to contribute to a reduction in driving voltage.
As the TADF material that can be used as the host material, the above materials mentioned as the TADF material that can be used as the emission center substance can also be used. When the TADF material is used as the host material, triplet excitation energy generated in the TADF material is converted into singlet excitation energy by reverse intersystem crossing and transferred to the light-emitting substance, whereby the emission efficiency of the light-emitting device can be increased. Here, the TADF material functions as an energy donor, and the light-emitting substance functions as an energy acceptor.
This is very effective in the case where the light-emitting substance is a fluorescent substance. In that case, the S1 level of the TADF material is preferably higher than that of the fluorescent substance in order that high emission efficiency can be achieved. Furthermore, the T1 level of the TADF material is preferably higher than the S1 level of the fluorescent substance. Therefore, the T1 level of the TADF material is preferably higher than that of the fluorescent substance.
It is also preferable to use a TADF material that emits light whose wavelength overlaps with the wavelength on the lowest-energy-side absorption band of the fluorescent substance. This enables smooth transfer of excitation energy from the TADF material to the fluorescent substance and accordingly enables efficient light emission, which is preferable.
In order to efficiently generate singlet excitation energy from the triplet excitation energy by reverse intersystem crossing, carrier recombination preferably occurs in the TADF material. It is also preferable that the triplet excitation energy generated in the TADF material not be transferred to the triplet excitation energy of the fluorescent substance. For that reason, the fluorescent substance preferably has a protective group around a luminophore (a skeleton that brings about light emission) of the fluorescent substance. As the protective group, a substituent having no π bond and a saturated hydrocarbon are preferably used. Specific examples include an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 10 carbon atoms. It is further preferable that the fluorescent substance have a plurality of protective groups. The substituents having no zr bond are poor in carrier transport performance, whereby the TADF material and the luminophore of the fluorescent substance can be trade away from each other with little influence on carrier transportation or carrier recombination. Here, the luminophore refers to an atomic group (skeleton) that brings about light emission in a fluorescent substance. The luminophore is preferably a skeleton having a Tc bond, further preferably has an aromatic ring, and still further preferably has a condensed aromatic ring or a condensed heteroaromatic ring. Examples of the luminophore include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, and a naphthobisbenzofuran skeleton. Specifically, a fluorescent substance having any of a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, and a naphthobisbenzofuran skeleton is preferable because of its high fluorescence quantum yield.
In the case where a fluorescent substance is used as the emission center substance, a material having an anthracene skeleton is suitably used as the host material. The use of a substance having an anthracene skeleton as the host material for the fluorescent substance makes it possible to obtain a light-emitting layer with high emission efficiency and high durability. Among the substance having an anthracene skeleton that is used as the host material, a substance having a diphenylanthracene skeleton, in particular, a substance having a 9,10-diphenylanthracene skeleton, is chemically stable and thus is preferably used as the host material. The host material preferably has a carbazole skeleton because the hole-injection and hole-transport properties are improved; further preferably, the host material has a benzocarbazole skeleton in which a benzene ring is further condensed to a carbazole skeleton because the HOMO level thereof is shallower than that of the host material having a carbazole skeleton by approximately 0.1 eV and thus holes enter the host material easily. In particular, the host material preferably has a dibenzocarbazole skeleton because the HOMO level thereof is shallower than that of the host material having a carbazole skeleton by approximately 0.1 eV so that holes enter the host material easily, the hole-transport property is improved, and the heat resistance is increased. Accordingly, a substance that has both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole or dibenzocarbazole skeleton) is further preferable as the host material. Note that in terms of the hole-injection and hole-transport properties described above, instead of a carbazole skeleton, a benzofluorene skeleton or a dibenzofluorene skeleton may be used. Examples of such a substance include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)phenyl]-9-phenyl-91H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-[4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl]anthracene (abbreviation: FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), 9-(I-naphthyl)-10-(2-naphthyl)anthracene (abbreviation: α,βADN), 2-(10-phenylanthracen-9-yl)dibenzofuran, 2-(10-phenyl-9-anthracenyl)benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA), 9-(2-naphthyl)-10-[3-(2-naphthyl)phenyl]anthracene (abbreviation: β3N-mβNPAnth), and 1-{4-[10-(biphenyl-4-yl)-9-anthracenyl]phenyl}-2-ethyl-1H-benzimidazole (abbreviation: EtBImPBPhA). In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA exhibit excellent properties and thus are preferably selected.
Note that the host material may be a mixture of a plurality of kinds of substances; in the case of using a mixed host material, it is preferable to mix a material having an electron-transport property with a material having a hole-transport property. By mixing the material having an electron-transport property with the material having a hole-transport property, the transport property of the light-emitting layer 113 can be easily adjusted and a recombination region can be easily controlled. The weight ratio of the content of the material having a hole-transport property to the content of the material having an electron-transport property may be 1:19 to 19:1.
Note that a phosphorescent substance can be used as part of the mixed material. When a fluorescent substance is used as the light-emitting substance, a phosphorescent substance can be used as an energy donor for supplying excitation energy to the fluorescent substance.
These mixed materials may form an exciplex. These mixed materials are preferably selected so as to form an exciplex that exhibits light emission whose wavelength overlaps with the wavelength on the lowest-energy-side absorption band of the light-emitting substance, in which case energy can be transferred smoothly and light emission can be obtained efficiently. The use of such a structure is preferable because the driving voltage can also be reduced.
Note that at least one of the materials forming an exciplex may be a phosphorescent substance. In this case, triplet excitation energy can be efficiently converted into singlet excitation energy by reverse intersystem crossing.
In order to form an exciplex efficiently, a material having an electron-transport property is preferably combined with a material having a hole-transport property and a HOMO level higher than or equal to that of the material having an electron-transport property. In addition, the LUMO level of the material having a hole-transport property is preferably higher than or equal to that of the material having an electron-transport property. Note that the LUMO levels and the HOMO levels of the materials can be calculated from the electrochemical characteristics (the reduction potentials and the oxidation potentials) of the materials that are measured by cyclic voltammetry (CV).
The formation of an exciplex can be confirmed by a phenomenon in which the emission spectrum of the mixed film in which the material having a hole-transport property and the material having an electron-transport property are mixed is shifted to the longer wavelength side than the emission spectrum of each of the materials (or has another peak on the longer wavelength side) observed by comparison of the emission spectra of the material having a hole-transport property, the material having an electron-transport property, and the mixed film of these materials, for example. Alternatively, the formation of an exciplex can be confirmed by a difference in transient response, such as a phenomenon in which the transient photoluminescence (PL) lifetime of the mixed film has longer lifetime components or has a larger proportion of delayed components than that of each of the materials, observed by comparison of transient PL of the material having a hole-transport property, the material having an electron-transport property, and the mixed film of these materials. The transient PL can be rephrased as transient electroluminescence (EL). That is, the formation of an exciplex can also be confirmed by a difference in transient response observed by comparison of the transient EL of the material having a hole-transport property, the material having an electron-transport property, and the mixed film of these materials.
The first electron-transport layer 114_1 is a layer including a substance that has an electron-transport property. The material having an electron-transport property preferably has an electron mobility higher than or equal to 1×10−7 cm2/Vs, further preferably higher than or equal to 1×10−6 cm2/Vs when the square root of the electric field strength [V/cm] is 600. Note that any other substance can also be used as long as the substance has a property of transporting more electrons than holes. The above organic compound is preferably an organic compound that has a π-electron deficient heteroaromatic ring. The organic compound that has a π-electron deficient heteroaromatic ring is preferably one or more of an organic compound that has a heteroaromatic ring having a polyazole skeleton, an organic compound that has a heteroaromatic ring having a pyridine skeleton, an organic compound that has a heteroaromatic ring having a diazine skeleton, and an organic compound that has a heteroaromatic ring having a triazine skeleton, and is particularly preferably triazine.
As the organic compound having an electron-transport property that can be used in the first electron-transport layer 1141, any of the aforementioned organic compounds that can be used as the organic compound having an electron-transport property that servs as the host material in the first light-emitting layer 113_1 and the second light-emitting layer 113_2 can be used. Among the above organic compounds, the organic compound that has a heteroaromatic ring having a diazine skeleton, the organic compound that has a heteroaromatic ring having a pyridine skeleton, and the organic compound that has a heteroaromatic ring having a triazine skeleton are especially preferable because of having high reliability. In particular, the organic compound that has a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and the organic compound that has a heteroaromatic ring having a triazine skeleton have a high electron-transport property to contribute to a reduction in driving voltage.
The second electron-transport layer 114_2 is, as described above, a layer including the first organic compound having a triazine skeleton. Since the details have already been described, the description is omitted here.
Note that the first electron-transport layer 114_1 preferably includes the organic compound having a triazine skeleton to reduce power consumption. In particular, the first electron-transport layer 114_1 preferably includes the same organic compound having a triazine skeleton as the first organic compound having a triazine skeleton that is included in the second electron-transport layer 1142, which inhibits the complication of a manufacturing apparatus and is advantageous also in terms of source material procurement cost.
In the case where the first electron-transport layer 114_1 includes an organic compound not having a triazine skeleton, the light-emitting device can have favorable characteristics owing to easy control of carrier transport. The organic compound not having a triazine skeleton is preferably an organic compound that has a heteroaromatic ring having a pyridine skeleton or an organic compound that has a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton.
The intermediate layer 116 includes the second organic compound having a phenanthroline skeleton. As illustrated in
The details of the first layer are described above and not repeated here.
The first layer 119 may further include an organic compound having an electron-transport property. As the organic compound having an electron-transport property, any of the aforementioned organic compounds that can be used as the organic compound having an electron-transport property that serves as the host material in the first light-emitting layer 113_1 and the second light-emitting layer 113_2 can also be used. The organic compound having an electron-transport property is preferably an organic compound having two or more heteroaromatic rings that are bonded or condensed to each other and that have three or more heteroatoms in total, in which case the resistance to a photolithography method can be improved and an increase in driving voltage can be inhibited.
Note that the first layer 119 may have a stacked-layer structure of a layer including an organic compound and a layer including a metal or a metal compound and positioned closer to the cathode than the layer including an organic compound is, or may be a mixed layer of an organic compound and a metal or a metal compound. The first layer 119 is preferably the mixed layer because it requires a smaller number of film formation chambers and a lower manufacturing cost and contributes to an improvement in the stability of the light-emitting device.
In the case where the organic compound and the metal or the metal compound are mixed, the organic compound and the metal or the metal compound tend to show substantially the same distribution when the first layer 119 is analyzed in the thickness direction. That is, when the organic compound is uniformly distributed, the metal or the metal compound is also substantially uniformly distributed. In the case of the stacked-layer structure of the layer including the organic compound and the layer including the metal or the metal compound, the metal or the metal compound is sometimes diffused from the layer including the metal or the metal compound and detected also in a region other than the layer but shows a different distribution from the organic compound; thus, the analysis results of diffusion and mixing can be distinguished from each other.
The second layer 117 preferably includes the fifth organic compound having a hole-transport property. The second layer 117 preferably further includes a substance exhibiting an acceptor property, and the substance exhibiting an acceptor property is preferably an organic compound exhibiting an acceptor property with respect to the fifth organic compound.
In the case where the second layer 117 includes the fifth organic compound and the substance exhibiting an acceptor property with respect to the fifth organic compound, holes are generated by charge separation, and the holes are injected into the light-emitting unit on the cathode side through the fifth organic compound when voltage is applied between the first electrode 101 and the second electrode 102. Thus, the light-emitting device 130 of one embodiment of the present invention can have a low driving voltage.
As the fifth organic compound having a hole-transport property, any of a variety of organic compounds such as aromatic amine compounds, heteroaromatic compounds, aromatic hydrocarbons, and high molecular compounds (e.g., oligomers, dendrimers, and polymers) can be used. Note that the fifth organic compound preferably has a hole mobility of 1×10−6 cm2/Vs or higher. The fifth organic compound preferably has a condensed aromatic hydrocarbon ring or a π-electron rich heteroaromatic ring. As the condensed aromatic hydrocarbon ring, an anthracene ring, a naphthalene ring, or the like is preferable. As the π-electron rich heteroaromatic ring, a condensed aromatic ring having at least one of a pyrrole skeleton, a furan skeleton, and a thiophene skeleton is preferable; specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further condensed to a carbazole ring or a dibenzothiophene ring is preferable.
Such an organic compound having a hole-transport property further preferably has any of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, an aromatic amine having a substituent that has a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine that has a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to nitrogen of an amine through an arylene group may be used. Note that the organic compound having a hole-transport property preferably has an N,N-bis(4-biphenyl)amino group to enable fabricating a light-emitting device having a long lifetime.
The above-described organic compound having a hole-transport property can specifically be any of the organic compounds given as examples of the organic compound having a hole-transport property that can be used in the hole-injection layer 111.
The substance having an acceptor property can be, for example, any of the substances given as examples of the organic compound having an acceptor property that can be used in the hole-injection layer 111. An organic compound having at least one of a halogen group and a cyano group is particularly preferable, and an organic compound having at least one of fluorine and a cyano group is further preferable. Note that it is further preferable that the total number of halogen groups (fluorines) and cyano groups of the organic compound be four or more. Examples of the organic compound having at least one of a halogen group and a cyano group include α,α′,α″-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile].
Note that the material having an acceptor property preferably has an electron-accepting property with respect to the fifth organic compound having a hole-transport property. When the material having an acceptor property has an electron-accepting property with respect to the fifth organic compound, charge separation occurs and the second layer 117 can function as a charge-generation layer and functions as an intermediate layer of the tandem light-emitting device. A signal is preferably observed by electron spin resonance in the second layer 117. For example, the density of spins attributed to a signal observed at a g-factor of approximately 2.00 is preferably higher than or equal to 1×1017 spins/cm3, further preferably higher than or equal to 1×1018 spins/cm3, still further preferably higher than or equal to 1×1019 spins/cm3.
The third layer 118 includes a substance having an electron-transport property and has functions of preventing the interaction between the first layer 119 and the second layer 117 and smoothly transferring and receiving electrons therebetween to reduce the driving voltage, and reducing the interaction between the first layer 119 and the second layer 117 to improve the reliability, for example.
The LJMO level of the substance having an electron-transport property that is included in the third layer 118 is preferably between the LUMO level of the substance having an acceptor property in the second layer 117 and the LUMO level of the organic compound included in a layer (e.g., the first electron-transport layer 114_1 in the first light-emitting unit 501 in FIG. TA) which is in contact with the first layer 119 in the light-emitting unit on the anode side.
A specific energy level of the LUMO level of the substance having an electron-transport property that is used in the third layer 118 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, still further preferably higher than or equal to −4.30 eV and lower than or equal to −3.00 eV, yet further preferably higher than or equal to −4.30 eV and lower than or equal to −3.30 eV, in which case an increase in driving voltage can be inhibited. Note that the substance having an electron-transport property that is used in the third layer 118 is preferably a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand.
Specific examples of the substance having an electron-transport property that is used in the third layer 118 include perylenetetracarboxylic acid derivatives such as diquinoxalino[2,3-a:2′,3-c]phenazine (abbreviation: HATNA), 2,3,8,9,14,15-hexafluorodiquinoxalino[2,3-a:2′,3′-c]phenazine (abbreviation: HATNA-F6), 3,4,9,10-perylenetetracarboxylic diimide (abbreviation: PTCDI), and 3,4,9,10-perylenetetracarboxyl-bis-benzimidazole (abbreviation: PTCBI), (C60-Ih)[5,6]fullerene (abbreviation: C60), and (C70-D5h)[5,6]fullerene (abbreviation: C70). It is also possible to use a compound having a heterophane skeleton, which is a cyclophane skeleton having a hetero ring; for example, a phthalocyanine compound such as phthalocyanine (abbreviation: H2Pc) can be used as the compound. Alternatively, it is possible to use a metal phthalocyanine containing copper, zinc, cobalt, iron, chromium, nickel, or the like or a derivative thereof, such as copper phthalocyanine (abbreviation: CuPc), zinc phthalocyanine (abbreviation: ZnPc), cobalt phthalocyanine (abbreviation: CoPc), iron phthalocyanine (abbreviation: FePc), tin phthalocyanine (abbreviation: SnPc), tin oxide phthalocyanine (abbreviation: SnOPc), titanium oxide phthalocyanine (abbreviation: TiOPc), or vanadium oxide phthalocyanine (abbreviation: VOPc). It is particularly preferable to use a phthalocyanine-based metal complex such as copper phthalocyanine or zinc phthalocyanine or 2,3,8,9,14,15-hexafluorodiquinoxalino[2,3-a:2′,3′-c]phenazine.
The thickness of the third layer 118 is preferably greater than or equal to 1 nm and less than or equal to 10 nm, further preferably greater than or equal to 2 nm and less than or equal to 5 nm.
Note that the second light-emitting unit 502 includes no hole-injection layer because the second layer 117 in the intermediate layer 116 functions as a hole-injection layer; however, the second light-emitting unit 502 may include a hole-injection layer.
The second electrode 102 includes the cathode. The second electrode 102 may have a stacked-layer structure, in which case a layer in contact with the organic compound layer 103 functions as the cathode. The cathode is preferably formed using a metal, an alloy, an electrically conductive compound, or a mixture thereof each having a low work function (specifically, lower than or equal to 3.8 eV), for example. Specific examples of such a cathode material include elements belonging to Group 1 and Group 2 of the periodic table, such as alkali metals (e.g., lithium (Li) or cesium (Cs)), magnesium (Mg), calcium (Ca), and strontium (Sr), alloys containing any of these elements (e.g., MgAg and AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing any of these rare earth metals. Specifically, a layer including an alkali metal, an alkaline earth metal, a rare earth metal, a compound thereof, or a complex thereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), or 8-hydroxyquinolinato-lithium (abbreviation: Liq), can be used. Examples of an electride include substances in which electrons are added at high concentration to calcium oxide-aluminum oxide. Note that a mixture of two or more of these materials may be used as a cathode material. In the case where the second electrode 102 has a stacked-layer structure, a material having high conductivity can be used for the layer(s) other than the cathode, regardless of the work function.
Note that the second electron-transport layer 114_2 is preferably in contact with the second electrode 102. When the second electron-transport layer 114_2 is in contact with the second electrode 102, the light-emitting device can have excellent electron-injection and electron-transport properties, a low driving voltage, and low power consumption.
When the second electrode 102 is formed using a material that transmits visible light, the light-emitting device can emit light from the second electrode 102 side.
Films of these conductive materials can be formed by a dry process such as a vacuum evaporation method or a sputtering method, an ink-jet method, a spin coating method, or the like. Alternatively, a wet process using a sol-gel method or a wet process using a paste of a metal material may be employed.
The organic compound layer 103 can be formed by any of a variety of methods, including a dry process and a wet process. For example, a vacuum evaporation method, a gravure printing method, an offset printing method, a screen printing method, an ink-jet method, a spin coating method, or the like may be used.
Different film formation methods may be used to form the electrodes or the layers described above.
The light-emitting device 130a includes an organic compound layer 103a between a first electrode 101a and the second electrode 102 over an insulating layer 175. The organic compound layer 103a has a structure in which a first light-emitting unit 501a and a second light-emitting unit 502a are stacked with an intermediate layer 116a therebetween. Although
The light-emitting device 130b includes an organic compound layer 103b between a first electrode 101b and the second electrode 102 over the insulating layer 175. The organic compound layer 103b has a structure in which a first light-emitting unit 501b and a second light-emitting unit 502b are stacked with an intermediate layer 116b therebetween. Although
The second electron-transport layer 114a_2b and the second electron-transport layer 114b_2b preferably include the first organic compound having a triazine skeleton. The first layer 119a and the first layer 119b each include the second organic compound having a phenanthroline skeleton.
The first light-emitting layer 113a_1 and the second light-emitting layer 113a_2 preferably emit light of similar colors. The emission center substance included in the first light-emitting layer 113a_1 and the emission center substance included in the second light-emitting layer 113a_2 are preferably compounds whose emission spectra have a difference in maximum peak wavelength of less than or equal to 30 nm, further preferably less than or equal to 20 nm, still further preferably less than or equal to 10 nm. It is further preferable that the first light-emitting layer 113a_1 and the second light-emitting layer 113a_2 include the same emission center substance. The first light-emitting layer 113b_1 and the second light-emitting layer 113b_2 preferably emit light of similar colors. The emission center substance included in the first light-emitting layer 113b_1 and the emission center substance included in the second light-emitting layer 113b_2 are preferably compounds whose emission spectra have a difference in maximum peak wavelength of less than or equal to 30 nm, further preferably less than or equal to 20 nm, still further preferably less than or equal to 10 nm. It is further preferable that the first light-emitting layer 113b_1 and the second light-emitting layer 113b_2 include the same emission center substance.
It is preferable that the first light-emitting layer 113a_1 and the first light-emitting layer 113b_1 be separated from each other and the second light-emitting layer 113a_2 and the second light-emitting layer 113b_2 be separated from each other. It is preferable that the emission color(s) of the first light-emitting layer 113a_1 and the second light-emitting layer 113a_2 be different from the emission color(s) of the first light-emitting layer 113b_1 and the second light-emitting layer 113b_2. It is preferable that the emission center substance included in the first light-emitting layer 113a_1 and the emission center substance included in the first light-emitting layer 113b_1 be different substances from each other and the emission center substance included in the second light-emitting layer 113a_2 and the emission center substance included in the second light-emitting layer 113b_2 be different substances from each other.
Note that each of the pairs of the hole-injection layers 111a and 111b, the first hole-transport layers 112a_1 and 112b_1, the first electron-transport layers 114a_1 and 114b_1, the intermediate layers 116a and 116b (the second layers 117a and 117b, the third layers 118a and 118b, and the first layers 119a and 119b), the second hole-transport layers 112a_2 and 112b_2, and the second electron-transport layers 114a_2 and 114b_2 may be one continuous layer or may be separate layers independent of each other between the light-emitting device 130a and the light-emitting device 130b. When these layers are continuous layers, the light-emitting devices can be fabricated with high productivity at low cost. When the layers are separate layers between the light-emitting devices, the layers can be formed using materials suitable for their emission colors, thereby enabling the light-emitting devices or a display device to have favorable characteristics. In particular, the second electron-transport layer 114a_2 and the second electron-transport layer 114b_2 are preferably one continuous layer, in which case both the light-emitting device 130a and the light-emitting device 130b can have favorable characteristics.
The second electron-transport layer 114a_2 and the second electron-transport layer 114b_2 being one continuous layer means that the second electron-transport layer 114a_2 and the second electron-transport layer 114b_2 are made of the same material. That is, when the second electron-transport layer 114a_2 and the second electron-transport layer 114b_2 are made of the same material, both the light-emitting device 130a and the light-emitting device 130b can have favorable characteristics. It is further preferable that the second electron-transport layer 114a_2 and the second electron-transport layer 114b_2 have similar structures, and it is still further preferable that the second electron-transport layer 114a_2 and the second electron-transport layer 114b_2 have the same structure.
Furthermore, in the case where the emission center substances included in the first light-emitting layers 113a_1 and 113b_1 are different substances from each other and the emission center substances included in the second light-emitting layers 113a_2 and 113b_2 are different substances from each other (e.g., in the case where the first light-emitting layer 113a_1 and the second light-emitting layer 113a_2 are blue fluorescent layers and the first light-emitting layer 113b_1 and the second light-emitting layer 113b_2 are green phosphorescent layers, in the case where the first light-emitting layers 113a_1 and 113a2 are blue fluorescent layers and the first light-emitting layers 113b_1 and 113b_2 are red phosphorescent layers, or in the case where the first light-emitting layers 113a_1 and 113a_2 are green phosphorescent layers and the first light-emitting layers 113b_1 and 113b_2 are red phosphorescent layers), the light-emitting layers of the light-emitting devices 130a and 130b have different carrier balances. Therefore, in order to improve the performance of each of the light-emitting devices 130a and 130b, it is usually necessary to select and use an appropriate intermediate layer and an appropriate electron-transport layer for each light-emitting device. However, even when the second electron-transport layers 114a_2 and 114b_2 have the same structure, the use of the first organic compound having a triazine skeleton in the second electron-transport layers 114a_2 and 114b_2 and the use of the second organic compound having a phenanthroline skeleton in the first layers 119a and 119b can improve the performance of each of the light-emitting devices 130a and 130b. That is, both the productivity and the performance can be improved. Note that the first layers 119a and 119b may have the same structure.
Note that one continuous layer is so-called common layer formed across the light-emitting devices 130a and 130b.
The light-emitting device 130c includes an organic compound layer 103c between a first electrode 101c and the second electrode 102 over the insulating layer 175. The organic compound layer 103c has a structure where a first light-emitting unit 501c and a second light-emitting unit 502c are stacked with an intermediate layer 116c therebetween. Although
It is assumed here that the light-emitting device 130c emits light whose wavelength is shorter than those of light from the light-emitting devices 130a and 130b1. The distance between the electrodes in the light-emitting device 130c is adjusted by the thicknesses of the first light-emitting layer 113c_1 and the second light-emitting layer 113c_2, which are smaller than those of the light-emitting layers in the other two light-emitting devices.
The second electron-transport layer 114c2 includes the first organic compound having a triazine skeleton. The first layer 119c includes the second organic compound having a phenanthroline skeleton.
The first light-emitting layer 113c_1 and the second light-emitting layer 113c_2 preferably emit light of similar colors. The emission center substance included in the first light-emitting layer 113c_1 and the emission center substance included in the second light-emitting layer 113c_2 are preferably compounds whose emission spectra have a difference in maximum peak wavelength of less than or equal to 30 nm, further preferably less than or equal to 20 nm, still further preferably less than or equal to 10 nm. It is further preferable that the first light-emitting layer 113c_1 and the second light-emitting layer 113c_2 include the same emission center substance.
It is preferable that the first light-emitting layer 113a_1 and the first light-emitting layer 113c_1 be separated from each other and the second light-emitting layer 113a_2 and the second light-emitting layer 113c_2 be separated from each other. It is preferable that the emission color(s) of the first light-emitting layer 113a_1 and the second light-emitting layer 113a_2 be different from the emission color(s) of the first light-emitting layer 113c_1 and the second light-emitting layer 113c_2. It is preferable that the emission center substance included in the first light-emitting layer 113a_1 and the emission center substance included in the first light-emitting layer 113c_1 be different substances from each other and the emission center substance included in the second light-emitting layer 113a_2 and the emission center substance included in the second light-emitting layer 113c_2 be different substances from each other.
Note that each of the pairs of the hole-injection layers 111a and 111ic, the first hole-transport layers 112a_1 and 112c_1, the first electron-transport layers 114a_1 and 114c_1, the intermediate layers 116a and 116c (the second layers 117a and 117c, the third layers 118a and 118c, and the first layers 119a and 119c), and the second hole-transport layers 112a_2 and 112c_2 in this example are separate layers independent of each other between the light-emitting device 130a and the light-emitting device 130c, and the second electron-transport layers 114a_2 and 114c_2 in this example are a continuous layer. In this manner, one light-emitting device may include both continuous and separate layers. This allows the light-emitting device or the display device to balance productivity and characteristics. In particular, the second electron-transport layer 114a_2 and the second electron-transport layer 114c_2 are preferably one continuous layer, in which case both the light-emitting device 130a and the light-emitting device 130c can have favorable characteristics.
In the case where light-emitting devices exhibiting three colors consist of, for example, two light-emitting devices including fluorescent emission center substances and one light-emitting device including a phosphorescent emission center substance, the light-emitting devices including the fluorescent emission center substances preferably have one continuous carrier-transport layer, and the light-emitting device including the phosphorescent emission center substance preferably has a carrier-transport layer separated from that in the light-emitting devices exhibiting the other emission colors. Alternatively, in the case where light-emitting devices exhibiting three colors consist of two light-emitting devices including phosphorescent emission center substances and one light-emitting device including a fluorescent emission center substance, the light-emitting devices including the phosphorescent emission center substances preferably have one continuous carrier-transport layer, and the light-emitting device including the fluorescent emission center substance preferably has a carrier-transport layer separated from that in the light-emitting devices exhibiting the other emission colors.
The light-emitting device of one embodiment of the present invention that has such a structure can have high current efficiency, low energy loss, and favorable characteristics. The display device of one embodiment of the present invention that includes such a light-emitting device can achieve low power consumption, high reliability, high-luminance display, and high visibility. This embodiment can be freely combined with any of the other embodiments.
In this embodiment, the display device manufactured using the light-emitting device described in Embodiment 1 is described with reference to
Reference numeral 608 denotes a wiring for transmitting signals to be input to the source line driver circuit 601 and the gate line driver circuit 603 and receiving signals such as a video signal, a clock signal, a start signal, and a reset signal from a flexible printed circuit (FPC) 609 serving as an external input terminal. Although only the FPC is illustrated here, a printed wiring board (PWB) may be attached to the FPC. The display device in this specification includes, in its category, not only the display device itself but also the display device provided with the FPC or the PWB.
Next, a cross-sectional structure is described with reference to
The element substrate 610 may be a substrate formed of glass, quartz, an organic resin, a metal, an alloy, or a semiconductor or a plastic substrate formed of fiber reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester, or an acrylic resin.
The structure of transistors used in the pixels and the driver circuits is not particularly limited. For example, inverted staggered transistors may be used, or staggered transistors may be used. Furthermore, top-gate transistors or bottom-gate transistors may be used. A semiconductor material used for the transistors is not particularly limited, and for example, silicon, germanium, silicon carbide, gallium nitride, or the like can be used. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In—Ga—Zn-based metal oxide, may be used.
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. It is preferable to use a semiconductor having crystallinity, in which case degradation of transistor characteristics can be inhibited.
Here, an oxide semiconductor is preferably used for semiconductor devices such as the transistors provided in the pixels and the driver circuits and transistors used for touch sensors described later, and the like. In particular, an oxide semiconductor having a wider band gap than silicon is preferably used. When an oxide semiconductor having a wider band gap than silicon is used, off-state current of the transistors can be reduced.
The oxide semiconductor preferably contains at least indium (In) or zinc (Zn). Further preferably, the oxide semiconductor contains an oxide represented by an In—M—Zn-based oxide (M represents a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).
As a semiconductor layer, it is particularly preferable to use an oxide semiconductor film including a plurality of crystal parts whose c-axes are aligned perpendicular to a surface on which the semiconductor layer is formed or the top surface of the semiconductor layer and in which the adjacent crystal parts have no grain boundary.
The use of such materials for the semiconductor layer makes it possible to provide a highly reliable transistor in which a change in the electrical characteristics is suppressed.
Charge accumulated in a capacitor through a transistor including the above-described semiconductor layer can be held for a long time because of the low off-state current of the transistor. When such a transistor is used in a pixel, operation of a driver circuit can be stopped while a gray scale of an image in each display region is maintained. As a result, an electronic appliance with extremely low power consumption can be obtained.
For stable characteristics of the transistor and the like, a base film is preferably provided. The base film can be formed with a single-layer structure or a stacked-layer structure using an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film. The base film can be formed by a sputtering method, a chemical vapor deposition (CVD) method (e.g., a plasma CVD method, a thermal CVD method, or a metal organic CVD (MOCVD) method), an atomic layer deposition (ALD) method, a coating method, a printing method, or the like. Note that the base film is not necessarily provided.
Note that an FET 623 is illustrated as a transistor formed in the driver circuit portion 601. In addition, the driver circuit may be formed with any of a variety of circuits such as a CMOS circuit, a PMOS circuit, or an NMOS circuit. Although a driver integrated type in which the driver circuit is formed over the substrate is described in this embodiment, the driver circuit is not necessarily formed over the substrate, and can be formed outside.
The pixel portion 602 includes a plurality of pixels including a switching FET 611, a current controlling FET 612, and a first electrode 613 electrically connected to a drain of the current controlling FET 612. One embodiment of the present invention is not limited to the structure, and the pixel portion 602 may include three or more FETs and a capacitor in combination.
Note that an insulator 614 is formed to cover an end portion of the first electrode 613. Here, the insulator 614 can be formed using a positive photosensitive acrylic resin film.
In order to improve coverage with an organic compound layer or the like which is formed later, the insulator 614 is formed to have a curved surface with curvature at its upper or lower end portion. For example, in the case where a positive photosensitive acrylic resin is used as a material of the insulator 614, only the upper end portion of the insulator 614 preferably has a curved surface with a curvature radius (0.2 μm to 3 μm). For the insulator 614, either a negative photosensitive resin or a positive photosensitive resin can be used.
An organic compound layer 616 and a second electrode 617 are formed over the first electrode 613. Here, as a material used for the first electrode 613 functioning as an anode, a material having a high work function is preferably used. For example, a single-layer film of an ITO film, an indium tin oxide film including silicon, an indium oxide film including zinc oxide at 2 wt % to 20 wt %, a titanium nitride film, a chromium film, a tungsten film, a Zn film, a Pt film, or the like, a stack of a titanium nitride film and a film including aluminum as its main component, a stack of three layers of a titanium nitride film, a film including aluminum as its main component, and a titanium nitride film, or the like can be used. The stacked-layer structure enables low wiring resistance, favorable ohmic contact, and a function as an anode.
The organic compound layer 616 is formed by any of a variety of methods such as an evaporation method using an evaporation mask, an ink-jet method, and a spin coating method. The organic compound layer 616 has the structure described in Embodiment 1. As another material included in the organic compound layer 616, a low molecular compound or a high molecular compound (including an oligomer or a dendrimer) may be used.
As a material used for the second electrode 617, which is formed over the organic compound layer 616 and functions as a cathode, a material having a low work function (e.g., Al, Mg, Li, and Ca, or an alloy or a compound thereof, such as MgAg, MgIn, and AlLi) is preferably used. In the case where light generated in the organic compound layer 616 is transmitted through the second electrode 617, a stack of a thin metal film and a transparent conductive film (e.g., ITO, indium oxide containing zinc oxide at 2 wt % to 20 wt %, indium tin oxide containing silicon, or zinc oxide (ZnO)) is preferably used for the second electrode 617.
Note that the light-emitting device is formed with the first electrode 613, the organic compound layer 616, and the second electrode 617. The light-emitting device is the light-emitting device described in Embodiment 1. In the display device of this embodiment, the pixel portion, which includes a plurality of light-emitting devices, tray include both the light-emitting device described in Embodiment 1 and a light-emitting device having a different structure.
The sealing substrate 604 is attached to the element substrate 610 with the sealing material 605, so that a light-emitting device 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. The space 607 may be filled with a filler, or may be filled with an inert gas (such as nitrogen or argon), or the sealing material. The structure of the sealing substrate in which a recessed portion is formed and a desiccant is provided is preferable because deterioration due to the influence of moisture can be inhibited.
An epoxy-based resin or glass frit is preferably used for the sealing material 605. It is desirable that such a material not be permeable to moisture or oxygen as much as possible. As the sealing substrate 604, a glass substrate, a quartz substrate, or a plastic substrate formed of fiber reinforced plastic (FRP), polyvinyl fluoride (PVF), polyester, and acrylic resin can be used.
Although not illustrated in
The protective film can be formed using a material that is less likely to transmit an impurity such as water easily. Thus, diffusion of an impurity such as water from the outside into the inside can be effectively suppressed.
As a material for the protective film, an oxide, a nitride, a fluoride, a sulfide, a ternary compound, a metal, a polymer, or the like can be used. For example, the material may contain aluminum oxide, hafnium oxide, hafnium silicate, lanthanum oxide, silicon oxide, strontium titanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide, zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide, erbium oxide, vanadium oxide, indium oxide, aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, gallium nitride, a nitride containing titanium and aluminum, an oxide containing titanium and aluminum, an oxide containing aluminum and zinc, a sulfide containing manganese and zinc, a sulfide containing cerium and strontium, an oxide containing erbium and aluminum, an oxide containing yttrium and zirconium, or the like.
The protective film is preferably formed using a film formation method with favorable step coverage. One such method is an atomic layer deposition (ALD) method. A material that can be deposited by an ALD method is preferably used for the protective film. A dense protective film having reduced defects such as cracks or pinholes or a uniform thickness can be formed by an ALD method. Furthermore, damage caused to a process member in forming the protective film can be reduced.
By an ALD method, a uniform protective film with few defects can be formed even on, for example, a surface with a complex uneven shape or upper, side, and lower surfaces of a touch panel.
As described above, the display device manufactured using the light-emitting device described in Embodiment 1 can be obtained.
The display device in this embodiment is manufactured using the light-emitting device described in Embodiment 1 and thus can have favorable characteristics. Specifically, since the light-emitting device described in Embodiment 1 has high emission efficiency, the display device can achieve low power consumption. Since the light-emitting device described in Embodiment 1 has high reliability, the display device can be highly reliable. In addition, since the light-emitting device described in Embodiment 1 can have favorable chromaticity and high color purity, the display device can achieve high display quality.
This embodiment can be freely combined with any of the other embodiments.
As illustrated in
A display device 100 includes a pixel portion 177 in which a plurality of pixels 178 are arranged in a matrix. The pixel 178 includes a subpixel 11R, a subpixel 110G, and a subpixel 110B.
In this specification and the like, for example, description common to the subpixels 110R, 110G, and 110B is sometimes made using the collective term “subpixel 110”. As for other components that are distinguished from each other using letters of the alphabet, matters common to the components are sometimes described using reference numerals excluding the letters of the alphabet.
The subpixel 110R emits red light, the subpixel 110G emits green light, and the subpixel 110B emits blue light. Thus, an image can be displayed on the pixel portion 177. Note that in this embodiment, three colors of red (R), green (G), and blue (B) are given as examples of colors of light emitted by the subpixels; however, subpixels of a different combination of colors may be employed. The number of subpixels is not limited to three, and may be four or more. Examples of four subpixels include subpixels emitting light of four colors of R, G, B, and white (W), subpixels emitting light of four colors of R, G, B, and Y, and four subpixels emitting light of R, G, and B and infrared light (IR).
In this specification and the like, the row direction and the column direction are sometimes referred to as the X direction and the Y direction, respectively. The X direction and the Y direction intersect with each other and are perpendicular to each other, for example.
Outside the pixel portion 177, a connection portion 140 is provided and a region 141 may also be provided. In the case where the region 141 is provided, the region 141 is provided between the pixel portion 177 and the connection portion 140. In the case where the region 141 is provided, an organic compound layer is provided in the region 141. A conductive layer 151C is provided in the connection portion 140.
Although
In the pixel portion 177, the light-emitting device 130 is provided over the insulating layer 175 and the plug 176. A protective layer 131 is provided to cover the light-emitting device 130. A substrate 120 is bonded to the protective layer 131 with a resin layer 122. An inorganic insulating layer 125 and an insulating layer 127 over the inorganic insulating layer 125 are preferably provided between the adjacent light-emitting devices 130.
Although
In
The display device of one embodiment of the present invention can be, for example, a top-emission display device where light is emitted in the direction opposite to a substrate over which light-emitting devices are formed. Note that the display device of one embodiment of the present invention may be of a bottom emission type.
The light-emitting device 130R includes a first electrode 101R (pixel electrode) including a conductive layer 151R and a conductive layer 152R, an organic compound layer 103R over the first electrode, the common layer 104 over the organic compound layer 103R, and the second electrode 102 (common electrode) 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.
The light-emitting device 130G includes a first electrode 101G (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 102 (common electrode) 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.
The light-emitting device 130B has a structure described in Embodiment 1. The light-emitting device 130B includes a first electrode 101B (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 102 (common electrode) 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 provided, a stack of the organic compound layer 103B and the common layer 104 corresponds to the organic compound layer 103 described in Embodiment 1; 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 Embodiment 1.
Note that the common layer 104 is preferably an electron-transport layer.
The light-emitting devices 130R and 130G are manufactured through a photolithography process.
In the light-emitting device 130, 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 display device. This can prevent crosstalk, so that a display device with extremely high contrast can be obtained. Specifically, a display device having high current efficiency at low luminance can be obtained.
The island-shaped organic compound layer 103 is formed by forming an organic compound film and processing the organic compound film by a photolithography method.
The organic compound layer 103 is preferably provided to cover the top surface and the side surface of the first electrode (pixel electrode) of the light-emitting device 130. In this case, the aperture ratio of the display device 100 can be easily increased as compared to the structure where an end portion of the organic compound layer 103 is positioned inside an end portion of the pixel electrode. Covering the side surface of the pixel electrode of the light-emitting device 130 with the organic compound layer 103 can inhibit the pixel electrode from being in contact with the second electrode 102; hence, a short circuit of the light-emitting device 130 can be inhibited.
In the display device of one embodiment of the present invention, the first electrode (pixel electrode) of the light-emitting device preferably has a stacked-layer structure. For example, in the example illustrated in
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, an indium tin oxide containing silicon can be suitably used for the conductive layer 152 because of having a work function of higher than or equal to 4.0 eV, for example.
The conductive layer 151 and the conductive layer 152 may each be a stack of a plurality of layers including 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.
Next, an exemplary method for manufacturing the display device 100 having the structure illustrated in
Thin films included in the display device (e.g., insulating films, semiconductor films, and conductive films) can be formed by a sputtering method, a chemical vapor deposition (CVD) method, a vacuum evaporation method, a pulsed laser deposition (PLD) method, an ALD method, or the like.
Thin films included in the display device (e.g., insulating films, semiconductor films, and conductive films) can also be formed by a wet process such as spin coating, dipping, spray coating, ink-jetting, dispensing, screen printing, offset printing, doctor blade coating, slit coating, roll coating, curtain coating, or knife coating.
Thin films included in the display device can be processed by a photolithography method, for example.
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 the exposure, an electron beam can also be used.
For etching of thin films, a dry etching method, a wet etching method, a sandblast method, or the like can be used.
First, as illustrated in
As the substrate, a substrate that has heat resistance high enough to withstand at least heat treatment performed later can be used. For example, it is possible to use a glass substrate; a quartz substrate; a sapphire substrate; a ceramic substrate; an organic resin substrate; or 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
Subsequently, as illustrated in
Then, as illustrated in
Subsequently, as illustrated in
Next, the resist mask 191 is removed as illustrated in
Then, as illustrated in
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, e.g., silicon oxynitride, can be used.
Subsequently, as illustrated in
Next, as illustrated in
Then, as illustrated in
Providing the sacrificial film 158Rf over the organic compound film 103Rf can reduce damage to the organic compound film 103Rf in the manufacturing process of the display device, resulting in an increase in the 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 higher than or equal to 100° C. and lower than or equal to 200° C., preferably higher than or equal to 100° C. and lower than or equal to 150° C., further preferably higher than or equal to 100° C. and lower than or equal to 120° C. The light-emitting device of one embodiment of the present invention includes the first organic compound, and thus enables a display device with high display quality even when manufactured through a heating process at higher temperature.
The sacrificial film 158Rf and the mask film 159Rf are preferably films that can be removed by a wet etching method or a dry etching method.
Note that the sacrificial film 158Rf 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 103Rfthan 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, an inorganic insulating film, and the like can be used, for example.
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. It is preferable to use a metal material that can block ultraviolet rays 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 in light exposure for patterning and deterioration of the organic compound film 103Rf can be inhibited.
The sacrificial film 158Rf and the mask film 159Rf can each be formed using a metal oxide such as an In—Ga—Zn oxide, an indium oxide, an In—Zn oxide, an In—Sn oxide, an indium titanium oxide (In—Ti oxide), an indium tin zinc oxide (In—Sn—Zn oxide), an indium titanium zinc oxide (In—Ti—Zn oxide), an indium gallium tin zinc oxide (In—Ga—Sn—Zn oxide), or an indium tin oxide containing silicon.
In the above metal oxide, in place of gallium, an element M (M is one or more of aluminum, silicon, boron, yttrium, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium) may be used.
The sacrificial film 158Rf and the mask film 159Rf are preferably formed using a semiconductor material such as silicon or germanium for excellent compatibility with a semiconductor manufacturing process. Alternatively, a compound containing the above semiconductor material can be used.
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.
Subsequently, a resist mask 190R is formed as illustrated in
The resist mask 190R is provided at a position overlapping with the conductive layer 152R. The resist mask 190R is preferably provided also at a position overlapping with the conductive layer 152C. This can inhibit the conductive layer 152C from being damaged during the process of manufacturing the display device.
Next, as illustrated in
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 alkaline aqueous solution such as a tetramethylammonium hydroxide (TMAH) aqueous solution, or an acid aqueous solution such as 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.
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.
The resist mask 190R can be removed by a method similar to that for the resist mask 191.
Next, as illustrated in
Accordingly, 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. Thus, the etching can be performed under a low-power condition while an adequately high etching rate is maintained. Accordingly, damage to the organic compound film 103Rf can be reduced. Furthermore, a defect such as attachment of a reaction product generated during 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, C—F3, 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.
Then, 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.
Subsequently, a sacrificial film 158Gf and a mask film 159Gf are formed in this order as illustrated in
The resist mask 190G is provided at a position overlapping with the conductive layer 152G.
Subsequently, as illustrated in
Then, an organic compound film 103Bf is formed 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.
Subsequently, a sacrificial film 158Bf and a mask film 159Bf are formed in this order as illustrated in
The resist mask 190B is provided at a position overlapping with the conductive layer 152B.
Subsequently, as illustrated in
Accordingly, as illustrated in
Note that the side surfaces of the organic compound layers 103R, 103G, and 103B are preferably perpendicular or substantially perpendicular to their formation surfaces. For example, the angle between the formation surfaces and these side surfaces is preferably greater than or equal to 60° and less than or equal to 90°.
The distance between two adjacent layers among the organic compound layers 103R, 103G, and 103B, which are formed by a photolithography method as described above, can be reduced to less than or equal to 8 Lm, 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 pm. Here, the distance can be specified, for example, by a distance between facing end portions of two adjacent layers among the organic compound layers 103R, 103G, and 103B. Reducing the distance between the island-shaped organic compound layers makes it possible to provide a display device having high resolution and a high aperture ratio. In addition, the distance between the first electrodes of adjacent light-emitting devices can also be reduced to 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
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 to the organic compound layer 103 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 polar 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 adsorbed on surfaces. 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, an inorganic insulating film 125f is formed as illustrated in
Then, as illustrated in
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 deposition damage 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.
The insulating film 127f is preferably formed by the aforementioned wet process. The insulating film 127f is preferably formed by spin coating using a photosensitive material, for example, and specifically preferably formed using a photosensitive resin composition containing an acrylic resin.
Then, part of the insulating film 127f is exposed to visible light or ultraviolet rays. The insulating layer 127 is formed in regions that are interposed between any two of the conductive layers 152R, 152G, and 152B and around the conductive layer 152C.
The width of the insulating layer 127 formed later can be controlled 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.
Light used for the exposure preferably includes the i-line (wavelength: 365 nm). Furthermore, light used for the exposure may include at least one of the g-line (wavelength: 436 nm) and the h-line (wavelength: 405 nm).
Next, as illustrated in
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 for the sacrificial layers 158R, 158G, and 158B, in which case the first etching treatment can be performed concurrently.
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 first etching treatment is preferably performed by wet etching. The use of wet etching can reduce damage to the organic compound layers 103R, 103G, and 103B, as compared to the case of using dry etching. Wet etching can be performed using an alkaline solution, for example. For instance, TMAH, which is an alkaline solution, can be used for the wet etching of an aluminum oxide film. Alternatively, an acid solution containing fluoride can also be used. 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 for the sacrificial layers 158R, 158G, and 158B, in which case the first etching treatment can be performed concurrently.
The sacrificial layers 158R, 158G, and 158B are not removed completely by the first etching treatment, and the etching treatment is stopped when the thickness of the sacrificial layers 158R, 158G, and 158B is 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, light exposure is preferably performed on the entire substrate so that the insulating layer 127a is irradiated with visible light or ultraviolet rays. 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 into a tapered shape.
Here, when a barrier insulating layer against oxygen (e.g., an aluminum oxide film) exists as each of the sacrificial layers 158R, 158G, and 158B, diffusion of oxygen to the organic compound layers 103R, 103G, and 103B 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 can increase the reliability of the light-emitting device.
Next, as illustrated in
An end portion of the inorganic insulating layer 125 is covered with the insulating layer 127.
The second etching treatment is performed by wet etching. The use of wet etching can reduce damage to the organic compound layers 103R, 103G, and 103B, as compared to the case of using dry etching. Wet etching can be performed using an alkaline solution or an acid solution, for example. An aqueous solution is preferably used in order that the organic compound layer 103 is not dissolved.
Next, as illustrated in
Next, as illustrated in
Then, the substrate 120 is bonded to the protective layer 131 using the resin layer 122, so that the display device can be manufactured. In the method for manufacturing the display device of one embodiment of the present invention, the insulating layer 156 is formed to include a region overlapping with the side surface of the conductive layer 151 and the conductive layer 152 is formed to cover the conductive layer 151 and the insulating layer 156 as described above. This can increase the yield of the display device and inhibit generation of defects.
As described above, in the method for manufacturing the display device of one embodiment of the present invention, the island-shaped organic compound layers 103R, 103G, and 103B are 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. In addition, a high-resolution display device or a display device with a high aperture ratio can be obtained. Furthermore, even when the resolution or the aperture ratio is high and the distance between the subpixels is extremely short, the organic compound layers 103R, 103G, and 103B can be inhibited from being in contact with each other in the adjacent subpixels. As a result, generation of leakage current between the subpixels can be inhibited. This can prevent crosstalk, so that a display device with extremely high contrast can be obtained. Moreover, even a display device that includes tandem light-emitting devices formed by a photolithography method can have favorable characteristics.
In this embodiment, a display device of one embodiment of the present invention will be described.
The display device in this embodiment can be a high-resolution display device. Thus, the display device in this embodiment can be used for display portions of information terminals (wearable devices) such as watch-type and bracelet-type information terminals and display portions of wearable devices capable of being worn on a head, such as a VR device like a head mounted display (LMD) and a glasses-type AR device.
The display device in this embodiment can be a high-definition display device or a large-sized display device. Accordingly, the display device in this embodiment can be used for display portions of a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, and an audio reproducing device, in addition to display portions of electronic 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.
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.
Such a display module 280 has extremely high resolution, and thus can be suitably used for a VR device such as an HMD or a glasses-type AR device. For example, even in the case of a structure in which the display portion of the display module 280 is seen through a lens, pixels of the extremely-high-resolution display portion 281 included in the display module 280 are prevented from being recognized when the display portion is enlarged by the lens, so that display providing a high sense of immersion can be performed. Without being limited thereto, the display module 280 can be suitably used for electronic appliances including a relatively small display portion.
The display device 100A illustrated in
The substrate 301 corresponds to the substrate 291 in
An element isolation layer 315 is provided between two adjacent transistors 310 to be embedded in the substrate 301.
An insulating layer 261 is provided to cover the transistor 310, and the capacitor 240 is provided over the insulating layer 261.
The capacitor 240 includes a conductive layer 241, a conductive layer 245, and an insulating layer 243 between the conductive layers 241 and 245. The conductive layer 241 functions as one electrode of the capacitor 240, the conductive layer 245 functions as the other electrode of the capacitor 240, and the insulating layer 243 functions as a dielectric of the capacitor 240.
The conductive layer 241 is provided over the insulating layer 261 and is embedded in an insulating layer 254. The conductive layer 241 is electrically connected to one of the source and the drain of the transistor 310 through a plug 271 embedded in the insulating layer 261. The insulating layer 243 is provided to cover the conductive layer 241. The conductive layer 245 is provided in a region overlapping with the conductive layer 241 with the insulating layer 243 therebetween.
An insulating layer 255 is provided to cover the capacitor 240. The insulating layer 174 is provided over the insulating layer 255. The insulating layer 175 is provided over the insulating layer 174. The light-emitting devices 130R, 130G, and 130B are provided over the insulating layer 175. An insulator is provided in regions between adjacent light-emitting devices.
The insulating layer 156R is provided to include a region overlapping with the side surface of the conductive layer 151R. The insulating layer 156G is provided to include a region overlapping with the side surface of the conductive layer 151G. The insulating layer 156B is provided to include a region overlapping with the side surface of the conductive layer 151B. The conductive layer 152R is provided to cover the conductive layer 151R and the insulating layer 156R. The conductive layer 152G is provided to cover the conductive layer 151G and the insulating layer 156G. The conductive layer 152B is provided to cover the conductive layer 151B and the insulating layer 156B. The sacrificial layer 158R is positioned over the organic compound layer 103R. The sacrificial layer 158G is positioned over the organic compound layer 103G. The sacrificial layer 158B is positioned over the organic compound layer 103B.
Each of the conductive layers 151R, 151G, and 151B is electrically connected to one of the source and the drain of the corresponding transistor 310 through a plug 256 embedded in the insulating layers 243, 255, 174, and 175, the conductive layer 241 embedded in the insulating layer 254, and the plug 271 embedded in the insulating layer 261. Any of a variety of conductive materials can be used for the plugs.
The protective layer 131 is provided over the light-emitting devices 130R, 130G, and 130B. The substrate 120 is bonded 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 display device 100B, a substrate 352 and a substrate 351 are bonded to each other. In
The display device 100B includes the pixel portion 177, the connection portion 140, a circuit 356, a wiring 355, and the like.
The connection portion 140 is provided outside the pixel portion 177. The number of connection portions 140 may be one or more. In the connection portion 140, a common electrode of a light-emitting device is electrically connected to a conductive layer, so that a potential can be supplied to the common electrode.
As the circuit 356, a scan line driver circuit can be used, for example.
The wiring 355 has a function of supplying a signal and power to the pixel portion 177 and the circuit 356. The signal and power are input to the wiring 355 from the outside through the FPC 353 or from the IC 354.
The display device 100C illustrated in
Embodiment 3 can be referred to for the details of the light-emitting devices 130R, 130G, and 130B.
The light-emitting device 130R includes a conductive layer 224R, the conductive layer 151R over the conductive layer 224R, and the conductive layer 152R over the conductive layer 151R. The light-emitting device 130G includes a conductive layer 224G, the conductive layer 151G over the conductive layer 224G, and the conductive layer 152G over the conductive layer 151G. The light-emitting device 130B includes a conductive layer 224B, the conductive layer 151B over the conductive layer 224B, and the conductive layer 152B over the conductive layer 151B.
The conductive layer 224R is connected to a conductive layer 222b included in the transistor 205 through an opening provided in an insulating layer 214. An end portion of the conductive layer 151R is positioned outside 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 depressed portion covering the opening provided in the insulating layer 214. A layer 128 is embedded in the depressed portion.
The layer 128 has a function of filling the depressed portions of the conductive layers 224R, 224G, and 224B to obtain 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 depressed portions of the conductive layers 224R, 224G, and 224B can also be used as light-emitting regions, whereby the aperture ratio of the pixel can be increased.
The layer 128 may be an insulating layer or a conductive layer. Any of a variety of inorganic insulating materials, organic insulating materials, and conductive materials can be used for the layer 128 as appropriate. Specifically, the layer 128 is preferably formed using an insulating material and is particularly preferably formed using an organic insulating material. The layer 128 can be formed using an organic insulating material usable for the insulating layer 127, for example.
The protective layer 131 is provided over the light-emitting devices 130R, 130G, and 130B. The protective layer 131 and the substrate 352 are bonded to each other with an adhesive layer 142. The substrate 352 is provided with a light-blocking layer 157. A solid sealing structure, a hollow sealing structure, or the like can be employed to seal the light-emitting device 130. In
The display device 100C has a top-emission structure. Light from the light-emitting device is emitted toward the substrate 352. For the substrate 352, a material with a high visible-light-transmitting property is preferably used. The pixel electrode includes a material that reflects visible light, and the counter electrode (the common electrode 155) includes a material that transmits visible light.
An insulating layer 211, an insulating layer 213, an insulating layer 215, and the insulating layer 214 are provided in this order over the substrate 351. Part of the insulating layer 211 functions as a gate insulating layer of each transistor. Part of the insulating layer 213 functions as a gate insulating layer of each transistor. The insulating layer 215 is provided to cover the transistors. The insulating layer 214 is provided to cover the transistors and has a function of a planarization layer. Note that the number of gate insulating layers and the number of insulating layers covering the transistors are not limited and may each be one or more.
An inorganic insulating film is preferably used as each of the insulating layers 211, 213, and 215.
An organic insulating layer is suitable as the insulating layer 214 functioning as a planarization layer.
Each of the transistors 201 and 205 includes a conductive layer 221 functioning as a gate, the insulating layer 211 functioning as the 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 the gate insulating layer, and a conductive layer 223 functioning as a gate.
A connection portion 204 is provided in a region of the substrate 351 not overlapping with the substrate 352. In the connection portion 204, one of the source electrode and the drain electrode of the transistor 201 is electrically connected to the FPC 353 through a conductive layer 166 and a connection layer 242. As an example, the conductive layer 166 has a stacked-layer structure of a conductive film obtained by processing the same conductive film as the conductive layers 224R, 224G, and 224B; a conductive film obtained by processing the same conductive film as the conductive layers 151R, 151G, and 151B; and a conductive film obtained by processing the same conductive film as the conductive layers 152R, 152G, and 152B. On the top surface of the connection portion 204, the conductive layer 166 is exposed. Thus, the connection portion 204 and the FPC 353 can be electrically connected to each other through the connection layer 242.
The light-blocking layer 157 is preferably provided on the surface of the substrate 352 on the substrate 351 side. The light-blocking layer 157 can be provided over a region between adjacent light-emitting devices, in the connection portion 140, in the circuit 356, and the like. A variety of optical members can be arranged on the outer surface of the substrate 352.
A material that can be used for the substrate 120 can be used for each of the substrates 351 and 352.
A material that can be used for the resin layer 122 can be used for the adhesive layer 142.
As the connection layer 242, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like can be used.
The display device 100D illustrated in
Light from the light-emitting device is emitted toward the substrate 351. For the substrate 351, a material with 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.
A light-blocking layer 317 is preferably formed between the substrate 351 and the transistor 201 and between the substrate 351 and the transistor 205.
The light-emitting device 130R includes a conductive layer 112R, a conductive layer 126R over the conductive layer 112R, and a conductive layer 129R over the conductive layer 126R.
The light-emitting device 130B includes a conductive layer 112B, a conductive layer 126B over the conductive layer 112B, and a conductive layer 129B over the conductive layer 126B.
A material with a high visible-light-transmitting property is used for each of the conductive layers 112R, 112B, 126R, 126B, 129R, and 129B. A material that reflects visible light is preferably used for the second electrode 102.
Although not illustrated in
Although
The display device 100D2 illustrated in
As illustrated in
A plurality of depressed portions 181 may be formed in a matrix. The depressed portions 181a and 181b may be provided in contact with each other or may be provided to have a flat surface therebetween.
Although the top surface shape and the cross-sectional shape of the depressed portion are hexagonal (
An insulating layer including an organic material can be used as the organic resin layer 180. Examples of materials used for the organic resin layer 180 include 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, and precursors of these resins. The organic resin layer 180 may be formed using an organic material such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or an alcohol-soluble polyamide resin.
A photosensitive resin can also be used for the organic resin layer 180. A photoresist may be used for the photosensitive resin. As the photosensitive resin, a positive photosensitive material or a negative photosensitive material can be used.
The organic resin layer 180 may include a material absorbing visible light. For example, the organic resin layer 180 itself may be made of a material absorbing visible light, or the organic resin layer 180 may include a pigment absorbing visible light. For example, the organic resin layer 180 can be formed using 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.
The first electrode 101 (the first electrode 101R and a first electrode 101W) is over the organic resin layer 180 and the organic compound layer 103 is over the first electrode 101. End portions of the first electrode 101 and the organic compound layer 103 may be covered with the insulating layer 127.
The first electrode 101 formed over the organic resin layer 180 also has a depressed portion along the depressed portion of the organic resin layer 180. The organic compound layer 103 formed over the first electrode 101 also has a depressed portion along the depressed portion of the first electrode 101. The common layer 104 formed over the organic compound layer 103 also has a depressed portion along the depressed portion of the organic compound layer 103. The second electrode 102 formed over the common layer 104 also has a depressed portion along the depressed portion of the common layer 104. That is, the depressed portions of the organic resin layer 180, the first electrode 101, the organic compound layer 103, the common layer 104, and the second electrode 102 overlap with each other.
The common layer 104 is provided over the organic compound layer 103 and the insulating layer 127, and the second electrode 102 is provided over the common layer 104. The protective layer 131 is provided over the second electrode 102 and bonded to the substrate 352 with the adhesive layer 142 therebetween.
Although the light-emitting devices 130G and 130B are not illustrated in
The display device 100E illustrated in
In the display device 100E, the light-emitting device 130 includes a region overlapping with one of the coloring layers 132R, 132G, and 132B. The coloring layers 132R, 132G, and 132B can be provided on a surface of the substrate 352 on the substrate 351 side. End portions of the coloring layers 132R, 132G, and 132B can overlap with the light-blocking layer 157.
In the display device 100E, the light-emitting device 130 can emit white light, for example. The coloring layer 132R, the coloring layer 132G, and the coloring layer 132B can transmit red light, green light, and blue light, respectively, for example. Note that in the display device 100E, the coloring layers 132R, 132G, and 132B may be provided between the protective layer 131 and the adhesive layer 142.
A display device 100E2 illustrated in
In the display device 100E2 illustrated in
Note that as illustrated in
Although the top surface shape of the microlens 182 is illustrated as a hexagon in
The microlens 182 can be formed using a material similar to that for the organic resin layer 180.
This embodiment can be combined as appropriate with the other embodiments or the examples. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.
In this embodiment, electronic appliances of embodiments of the present invention will be described.
Electronic appliances in this embodiment each include the display device of one embodiment of the present invention in a display portion. The display device of one embodiment of the present invention has low power consumption and high reliability. Thus, the display device 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.
Examples of wearable devices capable of being worn on a head are described with reference to
An electronic appliance 700A illustrated in
The display device 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.
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.
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.
An electronic appliance 800A illustrated in
The display device 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 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.
The electronic appliance 800A or the electronic appliance 800B can be mounted on the user's head with the wearing portions 823.
The image capturing portion 825 has a function of obtaining information on the external environment. Data obtained by the image capturing portion 825 can be output to the display portion 820. An image sensor can be used for the image capturing portion 825. Moreover, a plurality of cameras may be provided so as to support a plurality of fields of view, such as a telescope field of view and a wide field of view.
The electronic appliance 800A may include a vibration mechanism that functions as bone-conduction earphones.
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 electronic appliance may include an earphone portion. The electronic appliance 700B illustrated in
Similarly, the electronic appliance 800B illustrated in
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.
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 display device 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 a bonding 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 display device of one embodiment of the present invention can be used in the display panel 6511. Thus, an extremely lightweight electronic appliance can be achieved. 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. Moreover, part of the display panel 6511 is folded back so that a connection portion with the FPC 6515 is provided on the back side of the pixel portion, whereby an electronic appliance with a narrow bezel can be achieved.
The display device 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
The display device 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 larger display portion 7000 attracts more attention, so that the effectiveness of the advertisement can be increased, for example.
As illustrated in
Electronic appliances illustrated in
The electronic appliances illustrated in
The electronic appliances illustrated in
This embodiment can be combined as appropriate with the other embodiments or the examples. In this specification, in the case where a plurality of structure examples are shown in one embodiment, the structure examples can be combined as appropriate.
Specific fabrication methods and characteristics of a light-emitting device R1, a light-emitting device G1, and a light-emitting device B1, which are light-emitting devices of one embodiment of the present invention, and a comparative light-emitting device R1, a comparative light-emitting device G1, and a comparative light-emitting device B1, which are comparative light-emitting devices, are described in this example. Structural formulae of main compounds used in this example are shown below.
First, 100-nm-thick silver (Ag) and 85-nm-thick indium tin oxide containing silicon oxide (ITSO) were stacked over a glass substrate sequentially from the substrate side by a sputtering method as a reflective electrode and a transparent electrode, respectively, whereby the first electrode 101 with a size of 2 mm×2 mm was formed. Note that the transparent electrode functions as an anode, and the transparent electrode and the reflective electrode are collectively regarded as the first electrode 101.
Next, in pretreatment for fabricating the light-emitting device over the substrate, the surface of the substrate was washed with water, and baking was performed at 200° C. for one hour.
After that, the substrate was transferred into a vacuum evaporation apparatus where the pressure was reduced to approximately 1×10−4 Pa, and was subjected to vacuum baking at 170° C. for 30 minutes in a heating chamber of the vacuum evaporation apparatus, and then the substrate was cooled down for approximately 30 minutes.
Next, the substrate provided with the first electrode 101 was fixed to a substrate holder provided in the vacuum evaporation apparatus such that the surface on which the first electrode 101 was formed faced downward. Then, N-(biphenyl-2-yl)-N-(9,9-dimethylfluoren-2-yl)-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: oFBiSF(2)) represented by Structural Formula (i) above and a fluorine-containing material having an electron-acceptor property with a molecular weight of 672 (OCHD-003) were deposited over the first electrode 101 to a thickness of 10 nm by co-evaporation such that the weight ratio of oFBiSF(2) to OCHD-003 was 1:0.03, whereby the hole-injection layer 111 was formed.
Over the hole-injection layer 111, oFBiSF(2) was deposited by evaporation to athickness of 150 nm, whereby the first hole-transport layer was formed.
Next, 11-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]phenanthro[9′,10′:4,5]furo[2,3-b]pyrazine (abbreviation: 11mDBtBPPnfpr) represented by Structural Formula (ii) above, N-(biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by Structural Formula (iii) above, and a red phosphorescent material OCPG-006 were deposited over the first hole-transport layer to a thickness of 40 nm by co-evaporation such that the weight ratio of 1ImDBtBPPnfpr to PCBBiF to OCPG-006 was 0.7:0.3:0.05, whereby the first light-emitting layer was formed.
Next, 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-2,3′-bi-9H-carbazole (abbreviation: mPCCzPTzn-02) represented by Structural Formula (iv) above was deposited by evaporation to a thickness of 10 nm, whereby the first electron-transport layer was formed.
After the first electron-transport layer was formed, 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P) represented by Structural Formula (v) above as the second organic compound having a phenanthroline skeleton and lithium oxide (Li2O) were deposited by co-evaporation to a thickness of 5 nm such that the weight ratio of mPPhen2P to Li2O was 1:0.02, whereby the first layer was formed. Then, copper phthalocyanine (abbreviation: CuPc) represented by Structural Formula (vii) above was deposited by evaporation to a thickness of 2 nm, whereby the third layer was formed. Furthermore, oFBiSF(2) and OCHD-003 were deposited by co-evaporation to a thickness of 10 nm such that the weight ratio of oFBiSF(2) to OCHD-003 was 1:0.15, whereby the second layer was formed. Thus, the intermediate layer was formed.
Over the intermediate layer, oFBiSF(2) was deposited by evaporation to a thickness of 75 nm, whereby the second hole-transport layer was formed.
Over the second hole-transport layer, ImDBtBPPnfpr, PCBBiF, and OCPG-006 were deposited by co-evaporation to a thickness of 40 nm such that the weight ratio of 11mDBtBPPnfpr to PCBBiF to OCPG-006 was 0.7:0.3:0.05, whereby the second light-emitting layer was formed.
Then, 2,2′-[1,2-naphthalendiyl di(4,1-phenylene)]bis(4,6-diphenyl-1,3,5-triazine) (abbreviation: TznP2N) represented by Structural Formula (viii) above and 8-hydroxyquinolinato-lithium (abbreviation: Liq) represented by Structural Formula (ix) above were deposited by co-evaporation to a thickness of 25 nm such that the weight ratio of TznP2N to Liq was 1:1, whereby the second electron-transport layer was formed.
Then, Liq was deposited by evaporation to a thickness of 1 nm and silver (Ag) and magnesium (Mg) were deposited by co-evaporation to a thickness of 15 nm such that the volume ratio of Ag to Mg was 1:0.1, whereby the second electrode 102 was formed. Over the second electrode 102, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II) represented by Structural Formula (x) above was deposited to a thickness of 70 nm as a cap layer to improve light extraction efficiency.
Next, the light-emitting device was sealed using a glass substrate in a glove box containing a nitrogen atmosphere so as not to be exposed to the air. Specifically, a UV curable sealing material was applied to surround the device, only the sealing material was irradiated with UV while the light-emitting device was not irradiated with the UV, and heat treatment was performed at 80° C. under an atmospheric pressure for one hour. In this manner, the light-emitting device R1 was fabricated.
The comparative light-emitting device R1 was fabricated in a manner similar to that of the light-emitting device R1 except that 4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenyl-6-(biphenyl-4-yl)pyrimidine (abbreviation: 6BP-4Cz2PPm) represented by Structural Formula (xi) above was used instead of TznP2N in the second electron-transport layer.
The light-emitting device G1 was fabricated in a manner similar to that of the light-emitting device R1 except that the thickness of the first hole-transport layer was changed to 80 nm, the thickness of the second hole-transport layer was changed to 60 nm, and the first light-emitting layer and the second light-emitting layer were each deposited by co-evaporation of 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA) represented by Structural Formula (xii) above and 9,10-diphenyl-2-[N-phenyl-N-(9-phenyl-carbazol-3-yl)-amino]-anthracene (abbreviation: 2PCAPA) represented by Structural Formula (xiii) above such that the weight ratio of cgDBCzPA to 2PCAPA was 1:0.05.
The comparative light-emitting device G1 was fabricated in a manner similar to that of the light-emitting device G1 except that 6BP-4Cz2PPm was used instead of TznP2N in the second electron-transport layer.
The light-emitting device B1 was fabricated in a manner similar to that of the light-emitting device R1 except that the thickness of the first hole-transport layer was changed to 45 nm, the thickness of the second hole-transport layer was changed to 55 nm, and the first light-emitting layer and the second light-emitting layer were each deposited to a thickness of 25 nm by co-evaporation of 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth) represented by Structural Formula (xiv) above and N,N′-diphenyl-N,N′-bis(9-phenyl-9H-carbazol-2-yl)naphtho[2,3-b;6,7-b′]bisbenzofuran-3,10-diamine (abbreviation: 3,10PCA2Nbf(IV)-02) represented by Structural Formula (xv) above such that the weight ratio of αN-βNPAnth to 3,10PCA2Nbf(IV)-02 was 1:0.015.
The comparative light-emitting device B1 was fabricated in a manner similar to that of the light-emitting device B1 except that 6BP-4Cz2PPm was used instead of TznP2N in the second electron-transport layer.
The device structures of the light-emitting device R1, the light-emitting device G1, the light-emitting device B1, the comparative light-emitting device R1, the comparative light-emitting device G1, and the comparative light-emitting device B1 are shown below.
Note that the blue index (BI) is a value obtained by dividing current efficiency (cd/A) by they value of CIE chromaticity (x, v), and is one of the indicators of characteristics of blue light emission. As the y chromaticity value of blue light emission becomes smaller, the color purity thereof tends to be higher. Blue light emission having a small y chromaticity value and high color purity enables expression of blue colors with a wide range of chromaticity in a display. Using blue light emission with high color purity reduces the luminance of blue light emission necessary for a display to express white, leading to lower power consumption of the display. Thus, BI, which is current efficiency based on a y chromaticity value as one of the indicators of color purity of blue, is suitably used as a means for showing efficiency of blue light emission in some cases. The light-emitting device with higher BI can be regarded as a blue-light-emitting device having higher efficiency for a display.
Table 4 shows the main characteristics of the light-emitting device R1 and the comparative light-emitting device R1 at approximately 1000 cd/m2. Table 5 shows those of the light-emitting device G1 and the comparative light-emitting device G1 at approximately 1000 cd/m2. Table 6 shows those of the light-emitting device B1 and the comparative light-emitting device B1 at approximately 1000 cd/m2. The luminance, CIE chromaticity, and electroluminescence spectra were measured at room temperature with a spectroradiometer (SR-ULIR, TOPCON TECHNOHOUSE CORPORATION).
Here, the second electron-transport layers of the light-emitting device R1, the light-emitting device G1, and the light-emitting device B1 include the same material (the first organic compound having a triazine skeleton). Thus, the light-emitting devices of different emission colors of one embodiment of the present invention can each have favorable characteristics even when the second electron-transport layers of the light-emitting devices are made of the same material.
Next, a display device of this example including the light-emitting device R1, the light-emitting device G1, and the light-emitting device B1 respectively in red, green, and blue subpixels and a display device of the comparative example including the comparative light-emitting device R1, the comparative light-emitting device G1, and the comparative light-emitting device B1 respectively in red, green, and blue subpixels were assumed, and the power consumption of their display portions (except for the power consumption of a driving transistor, a driving circuit, and the like) was tentatively calculated. Note that each of the light-emitting devices assumed to be used in both of the display devices is a tandem light-emitting device, and the same emission center substance is used in the plurality of light-emitting layers in each of the light-emitting devices. Thus, the display devices are side-by-side display devices.
The conditions of the display devices assumed for the tentative calculation are as follows.
First, in each of the display devices under the above-described conditions, the luminance (effective luminance) of the light-emitting devices of RGB to obtain 1000 cd/m2 emission of white light with CIE 1931 chromaticity coordinates (x,y)=(0.31, 0.33) when the display device is made to emit white light from the entire screen was calculated.
Next, the luminance (intrinsic luminance) required to obtain the calculated effective luminance of the light-emitting devices of RGB was calculated in consideration of the aperture ratios. The intrinsic luminance is the luminance at which each light-emitting device actually emits light in order to obtain the effective luminance of 1000 cd/m2 when the display device is made to emit white lightwith CIE 1931 chromaticity coordinates (x,y)=(0.31, 0.33) from the entire screen. Since the aperture ratio of the whole display device subjected to the tentative calculation is 30% and the aperture ratio per emission color is 10%, the intrinsic luminance is approximately ten times the effective luminance.
From the measurement results of the light-emitting devices described above and the intrinsic luminance, the current density and voltage for making each light-emitting device emit light at the intrinsic luminance can be obtained. In other words, in each of the display devices under the above-described conditions, the current density and voltage of each light-emitting device to obtain 1000 cd/m2 luminance emission of white light with CIE 1931 chromaticity coordinates (x, y)=(0.31, 0.33) when the display device is made to emit white light from the entire screen can be obtained.
The power consumption is calculated by multiplying the amount of current by the voltage. The amount of current is calculated by multiplying the current density, the panel area, and the aperture ratio. The display devices subjected to the tentative calculation each have a diagonal size of 5 inches, an aspect ratio of 16:9, a panel area of 68.9 cm2, and an aperture ratio of the light-emitting device of each color of 10%, and the amount of current can be calculated by multiplying the current density calculated in the previous paragraph by these values. Furthermore, power consumption of the light-emitting device of each emission color can be calculated by multiplying the amount of current by the voltage obtained in the previous paragraph. By calculating and summing up the power consumptions of the light-emitting devices of RGB, the total power consumption of the display portion of the display device (except for the power consumption of the driving transistor, the driving circuit, and the like) can be obtained.
Table 8 shows the calculated power consumption of the display device of this example assumed to use the light-emitting device R1, the light-emitting device G1, and the light-emitting device B1, and Table 9 shows the calculated power consumption of the display device of the comparative example assumed to use the comparative light-emitting device R1, the comparative light-emitting device G1, and the comparative light-emitting device B1.
Table 8 and Table 9 show that the display device of this example has higher current efficiency in white light emission and lower driving voltage than the display device of the comparative example. Moreover, the power consumption of the display device of this example is lower than that of the display device of the comparative example.
Thus, the display device including the tandem light-emitting devices each of which includes the second electron-transport layer including the first organic compound having a triazine skeleton, includes the intermediate layer including the mixed layer of the second organic compound having a phenanthroline skeleton and lithium or a lithium compound, and has a difference between maximum peak wavelengths in emission spectra of the plurality of light-emitting layers of less than or equal to 30 nm has favorable characteristics with low power consumption.
This application is based on Japanese Patent Application Serial No. 2023-223533 filed with Japan Patent Office on Dec. 28, 2023 and Japanese Patent Application Serial No. 2024-035811 filed with Japan Patent Office on Mar. 8, 2024, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-223533 | Dec 2023 | JP | national |
| 2024-035811 | Mar 2024 | JP | national |
