Light-emitting devices, light-emitting apparatus, electronic devices and lighting devices

Abstract

A novel light-emitting device is provided. In addition, a light-emitting device with high emission efficiency is provided. In addition, a light-emitting device with a long lifetime is provided. In addition, a light-emitting device with a low driving voltage is provided. One embodiment of the present application provides a light-emitting device including an anode, a cathode, and an EL layer between the anode and the cathode, in which the EL layer includes a hole-injection layer, a light-emitting layer, and an electron-transport layer, the hole-injection layer is between the anode and the light-emitting layer, the electron-transport layer is between the light-emitting layer and the cathode, the hole-injection layer contains a first substance and a second substance, the first substance is an organic compound having a hole-transport property and a HOMO level of -5.7 eV or more and -5.4 eV or less, the second substance is a substance that exhibits electron-accepting property with respect to the first substance, and the electron-transport layer is formed using a material whose resistance value decreases when current flows.

Description

TECHNICAL FIELD

[0001] One embodiment of the present application relates to a light-emitting device, a light-emitting apparatus, a display module, a lighting module, a display apparatus, an electronic device, and a lighting apparatus. Note that one embodiment of the present application is not limited to the above technical field. The technical field of one embodiment of the present application disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present application relates to a program, a machine, manufacture, or composition of matter. Specifically, according to one embodiment of the present application disclosed in this specification, a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a storage device, an imaging device, a method for driving any of them, or a method for manufacturing any of them can be given. BACKGROUND

[0002] In recent years, practical use of a light-emitting device (organic EL element) using an organic compound and utilizing electroluminescence (EL) has been actively developed. In a basic structure of such a light-emitting device, an organic compound layer (EL layer) containing a light-emitting substance is interposed between a pair of electrodes. By application of voltage to this device, carriers are injected and, by recombination energy of the carriers, light emission from the light-emitting substance can be obtained.

[0003] Since such a light-emitting device is a self-luminous light-emitting device, it has advantages of higher visibility than liquid crystals, no need for a backlight, and the like when used for a pixel of a display. Thus, the light-emitting device is suitable for a flat-panel display element. Furthermore, a display using such a light-emitting device can be manufactured to be thin and light, which is also a great advantage. Furthermore, very high-speed response is one of the features of the light-emitting device.

[0004] In addition, since the light-emitting layer of such a light-emitting device can be formed continuously in two dimensions, surface emission can be obtained. Since this is a feature that is difficult to obtain in a point light source typified by an incandescent lamp or an LED or a linear light source typified by a fluorescent lamp, the above light-emitting device is also high in utility value as a surface light source which can be applied to illumination or the like.

[0005] As described above, although a display or a lighting apparatus using a light-emitting device is suitable for a variety of electronic devices, research and development of a light-emitting device having more excellent efficiency and lifetime are increasingly active.

[0006] Patent Document 1 discloses a structure in which a hole-transport material whose HOMO level is between the HOMO level of a first hole-transport layer and the HOMO level of a host material is provided between the first hole-transport layer and a light-emitting layer in contact with the hole-injection layer.

[0007] The characteristics of the light emitting device are significantly improved, but are not yet sufficient to cope with high demands for various characteristics such as efficiency and durability.

[0008] [Patent Document 1] International Publication No. 2011 / 065136 pamphlet SUMMARY

[0009] Thus, an object of one embodiment of the present application is to provide a novel light emitting device. Another object of one embodiment of the present application is to provide a light emitting device with high luminance efficiency. Another object of one embodiment of the present application is to provide a light emitting device with long lifetime. Another object of one embodiment of the present application is to provide a light emitting device with low driving voltage.

[0010] Another object of one embodiment of the present application is to provide a light emitting device, an electronic device, and a display device with high reliability. Another object of one embodiment of the present application is to provide a light emitting device, an electronic device, and a display device with low power consumption.

[0011] One embodiment of the present application can achieve any of the above objects.

[0012] One embodiment of the present application is a light emitting device including an anode, a cathode, and an EL layer between the anode and the cathode, in which the EL layer includes a hole injecting layer, a light emitting layer, and an electron transporting layer, the hole injecting layer is positioned between the anode and the light emitting layer, the electron transporting layer is positioned between the light emitting layer and the cathode, the hole injecting layer includes a first substance and a second substance, the first substance is an organic compound having a hole transporting property and a HOMO level of -5.7 eV or more and -5.4 eV or less, the second substance is a substance that exhibits electron accepting property with respect to the first substance, and the electron transporting layer is formed using a material whose resistance value decreases when current flows therethrough.

[0013] In the above structure, another embodiment of the present application is a light emitting device in which the material whose resistance value decreases when current flows therethrough includes an organic metal complex of an alkali metal or an alkaline earth metal.

[0014] In the above structure, another embodiment of the present application is a light emitting device in which the material whose resistance value decreases when current flows therethrough includes an organic compound having an electron transporting property and an organic metal complex of an alkali metal or an alkaline earth metal.

[0015] In the above structure, another embodiment of the present application is a light emitting device in which the organic metal complex of an alkali metal or an alkaline earth metal forms a cluster.

[0016] In the above structure, another embodiment of the present application is a light-emitting device in which the organometallic complex of an alkali metal or an alkaline earth metal is a metal complex including a ligand including nitrogen and oxygen and an alkali metal or an alkaline earth metal.

[0017] In the above structure, another embodiment of the present application is a light-emitting device in which the organometallic complex of an alkali metal or an alkaline earth metal is a metal complex including a ligand having a 8-hydroxyquinoline structure and a monovalent metal ion.

[0018] In the above structure, another embodiment of the present application is a light-emitting device in which the organometallic complex of an alkali metal or an alkaline earth metal is a lithium complex including a ligand having a 8-hydroxyquinoline structure.

[0019] In the above structure, another embodiment of the present application is a light-emitting device in which the electron-transport layer includes a first layer and a second layer, the first layer is positioned between the light-emitting layer and the second layer, the second layer is positioned between the first layer and the cathode, and the concentration of the organometallic complex of an alkali metal or an alkaline earth metal contained in the first layer is different from that of the second layer.

[0020] In the above structure, another embodiment of the present application is a light-emitting device in which the concentration of the organometallic complex of an alkali metal or an alkaline earth metal in the first layer is higher than that in the second layer.

[0021] In the above structure, another embodiment of the present application is a light-emitting device in which the second substance is an organic compound.

[0022] In the above structure, another embodiment of the present application is a light-emitting device in which the light-emitting layer includes a host material and a light-emitting substance, and the light-emitting substance emits blue fluorescence.

[0023] In the above structure, another embodiment of the present application is an electronic device including a sensor, an operation button, a speaker, or a microphone.

[0024] In the above structure, another embodiment of the present application is a light-emitting device including a transistor or a substrate.

[0025] In the above structure, another embodiment of the present application is a lighting device including a housing.

[0026] In this specification, a light-emitting device includes an image display device using a light-emitting element. In addition, the light-emitting device also includes a module in which a light-emitting element is mounted with a connector such as an anisotropic conductive film or a TCP (Tape Carrier Package); a module in which a printed wiring board is provided at an end of a TCP; or a module in which an IC (Integrated Circuit) is directly mounted on a light-emitting element by a COG (Chip On Glass) method. Furthermore, a lighting device or the like includes a light-emitting device in some cases.

[0027] One embodiment of the present application can provide a novel light-emitting device. Another embodiment of the present application can provide a light-emitting device with a long lifetime. Another embodiment of the present application can provide a light-emitting device with high emission efficiency. Another embodiment of the present application can provide a light-emitting device with low driving voltage.

[0028] Another embodiment of the present application can provide a light-emitting device, an electronic device, and a display device with high reliability. Another embodiment of the present application can provide a light-emitting device, an electronic device, and a display device with low power consumption.

[0029] Note that the description of these effects does not preclude the presence of other effects. One embodiment of the present application does not necessarily achieve all the effects described above. Other effects will be apparent from the description of the specification, the attached drawings, the claims, and the like. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1A1 , Figure 1A2 , Figure 1B and Figure 1C are schematic diagrams of light-emitting devices;

[0031] Figure 2A and Figure 2B are diagrams illustrating a long lifetime;

[0032] Figure 3A and Figure 3B are diagrams illustrating an increase in luminance;

[0033] Figure 4A and Figure 4B are schematic diagrams of active matrix light-emitting devices;

[0034] Figure 5A and Figure 5B are schematic diagrams of active matrix light-emitting devices;

[0035] Figure 6 is a schematic diagram of an active matrix light-emitting device;

[0036] Figure 7A andFigure 7B is a schematic view of a passive matrix light-emitting device;

[0037] Figure 8A and Figure 8B is a view showing a lighting device;

[0038] Figure 9A , Figure 9B1 , Figure 9B2 and Figure 9C is a view showing an electronic device;

[0039] Figure 10A , Figure 10B and Figure 10C is a view showing an electronic device;

[0040] Figure 11 is a view showing a lighting device;

[0041] Figure 12 is a view showing a lighting device;

[0042] Figure 13 is a view showing an in-vehicle display device and a lighting device;

[0043] Figure 14A and Figure 14B is a view showing an electronic device;

[0044] Figure 15A , Figure 15B and Figure 15C is a view showing an electronic device;

[0045] Figure 16 is a view showing one example of Z plot of a light-emitting device of one embodiment of the present application;

[0046] Figure 17 is a view showing one example of M plot of a light-emitting device of one embodiment of the present application;

[0047] Figure 18 is a view showing one example of an equivalent circuit of a light-emitting device of one embodiment of the present application;

[0048] Figure 19 is a view showing changes in resistance values of each resistance component of a light-emitting device of one embodiment of the present application before and after driving;

[0049] Figure 20 is a graph showing changes in luminance with respect to driving time of the light-emitting device 1 and the comparative light-emitting device 1;

[0050] Figure 21A and Figure 21B is a view showing Z plots of the light-emitting device 1 and the comparative light-emitting device 1;

[0051] Figure 22 is a graph showing changes in voltage with respect to driving time of the light emitting device 1 and the comparative light emitting device 1;

[0052] Figure 23 is a graph showing M plots of the light emitting device 1;

[0053] Figure 24A is M plots of the light emitting devices 2 to 5, Figure 24B is a resistance value before and after driving of each resistance component;

[0054] Figure 25A is M plots of the light emitting devices 2, 6 and 7, Figure 25B is a resistance value before and after driving of each resistance component;

[0055] Figure 26A is M plots of the light emitting devices 2 and 8, Figure 26B is a resistance value before and after driving of each resistance component;

[0056] Figure 27 is a graph showing a stabilization energy of each molecule in a Liq polymer;

[0057] Figure 28 is a graph showing a structure of a measurement element;

[0058] Figure 29 shows a frequency characteristic of a calculated capacitance C of ZADN:Liq (1:1) of a direct current voltage 7.0 V;

[0059] Figure 30 shows a frequency characteristic of -ΔB of ZADN:Liq (1:1) of a direct current voltage 7.0 V;

[0060] Figure 31 shows an electric field strength dependency of an electron mobility of each organic compound;

[0061] Figure 32A1 、 Figure 32A2 、 Figure 32B1 and Figure 32B2 is a graph showing a concentration distribution of the eighth substance in an electron transport layer. DETAILED DESCRIPTION

[0062] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings. However, the present application is not limited to the embodiments described below, but can be easily understood by those skilled in the art that one fact is that the modes and details thereof can be changed into various forms without departing from the spirit and scope of the present application. Therefore, one embodiment of the present application should not be interpreted as being limited to the contents described in the following embodiments.

[0063] Embodiment 1

[0064] Figure 1A1 、 Figure 1A2 FIG. 1 is a diagram showing a light-emitting device of one embodiment of the present application. The light-emitting device of one embodiment of the present application includes an anode 101, a cathode 102, and an EL layer 103 including a hole-injection layer 111, a hole-transport layer 112, a light-emitting layer 113, and an electron-transport layer 114. Note that it is preferable that the hole-transport layer 112 include a first hole-transport layer 112-1 and a second hole-transport layer 112-2, and the electron-transport layer 114 include a first electron-transport layer 114-1 and a second electron-transport layer 114-2 as shown in FIG. 1. Figure 1A2

[0065] Note that although an electron-injection layer 115 is shown in the EL layer 103 in FIG. 1 in addition to the above, the structure of the light-emitting device is not limited thereto. As long as the above structure is included, a layer having another function can be included. Figure 1A1 、 Figure 1A2

[0066] The hole-injection layer 111 is a layer for easily injecting holes into the EL layer 103, and the hole-injection layer 111 is formed using a material with high hole-injection property. The hole-injection layer 111 includes a first substance and a second substance. The first substance is an organic compound having a hole-transport property and a deep HOMO level, i.e., -5.7 eV or more and -5.4 eV or less, and the second substance is a substance having electron-accepting property with respect to the first substance. By making the first substance have a deep HOMO level, the sensing of holes is appropriately suppressed, and the sensed holes can be easily injected into the hole-transport layer 112. By making the hole-injection layer 111 have such a structure, a light-emitting device in which the recombination region of carriers at the initial stage of driving is not only in the light-emitting layer but also expanded to the electron-transport layer can be manufactured.

[0067] ​​The second substance can be either an inorganic compound or an organic compound, but an organic compound having an electron-withdrawing group (especially a halogen group such as a fluorine group or a cyano group) or the like is preferred. As the second substance, a substance that exhibits electron-accepting properties with respect to the above-mentioned first substance can be appropriately selected from among such substances. As such a preferred organic compound, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviated as: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-l,4,5,8,9,12-hexaazatriphenylene (abbreviated as: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviated as: F6-TCNNQ), 2-(7-dicyanomethylene-l,3,4,5,6,8,9,10-octafluoro-7H-pyr-2-ylidene)malononitrile, and the like can be given. In particular, a compound in which an electron-withdrawing group is bonded to a fused aromatic ring having a plurality of hetero atoms such as HAT-CN and the like is thermally stable, and is therefore preferred. In addition, a [3]radialene derivative including an electron-withdrawing group (especially a halogen group such as a fluorine group or a cyano group) is particularly preferred because of its very high electron-accepting properties, and specifically, α,α',α"-l,2,3-cyclopropanetriyltris[4-cyano-2,3,5,6-tetrafluorobenzonitrile], α,α',α"-l,2,3-cyclopropanetriyltris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzonitrile], α,α',α"-l,2,3-cyclopropanetriyltris[2,3,4,5,6-pentafluorobenzonitrile], and the like can be given. When the second substance is an inorganic compound, a transition metal oxide can be used. In particular, a metal oxide belonging to Groups 4 to 8 of the periodic table is suitably used, and a high electron-accepting metal oxide such as vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, and the like is preferably used. Molybdenum oxide is particularly preferred because it is stable in the atmosphere, has low hygroscopicity, and is easy to handle.

[0068] The first substance is preferably an organic compound with hole-transporting capabilities, more preferably having any one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. Particularly preferred are aromatic amines having substituents including a dibenzofuran ring or a dibenzothiophene ring, aromatic monoamines including a naphthyl ring, or aromatic monoamines in which a 9-fluorene group is bonded to the nitrogen of the amine via an arylene group. Note that when these first substances are substances including N,N-bis(4-biphenyl)amino groups, light-emitting devices with good lifetimes can be manufactured, and therefore are preferred. Specifically, examples of the aforementioned first substance include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as: BBABnf), 4,4'-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4”-phenyltriphenylamine (abbreviated as: BnfBB1BP), and N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as: BnfBB1BP). -d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophene-4-yl)phenyl]-N-phenyl- 4-Benzidine (abbreviated as ThBA1BP), 4-(2-naphthyl)-4',4”-diphenyltriphenylamine (abbreviated as BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4”-diphenyltriphenylamine (abbreviated as BBAβNBi), 4-(2;1'-binathyl-6-yl)-4',4”-diphenyltriphenylamine (abbreviated as BBAαNβNB), 4,4'-diphenyl-4”-(7;1'-binathyl-2-yl)triphenylamine (abbreviated as BBAαNβNB-03), 4,4'-diphenyl 4"-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4-(6;2'-binaphthyl-2-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBA(βN2)B), 4-(2;2'-binaphthyl-7-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBA(βN2)B-03), 4-(1;2'-binaphthyl-4-yl)-4',4"-diphenyltriphenylamine (abbreviation: BBAβNαNB), 4-(1;2'-binaphthyl-5-yl)-4',4”-Diphenyltriphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenyl)-4'-(2-naphthyl)-4”-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenyl)-4'-[4-(2-naphthyl)phenyl]-4”-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenyl)-4'-[4-(2-naphthyl)phenyl]-4”-phenyltriphenylamine (abbreviation: TPBiAβNBi), 4-(1-naphthyl)-4'-phenyltriphenylamine (abbreviation: αNBA1BP), 4,4'-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4'-diphenyl-4”-[4' -(carbazole-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazole-9-yl)phenyl]tri(1,1'-biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-[4'-(carbazole-9-yl)biphenyl-4-yl]-4'-(2-naphthyl)-4”-phenyltriphenylamine (abbreviation: YGTBiβNB), N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9'-spirobis[9H-fluorene]-2-amine (abbreviation: PCBNBSF), N,N-bis([1,1'-biphenyl]-4-yl)-9,9'-spirobis[9H-fluorene]-2-amine (abbreviation: PCBNBSF), N,N-bis([1,1'-biphenyl]-4-yl)-9,9'-spirobis[9H-fluorene]-2-amine H-fluorene]-2-amine (abbreviation: BBASF), N,N-bis([1,1'-biphenyl]-4-yl)-9,9'-spirobis[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(1,1'-biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluorene-2-yl)-9,9'-spirobis(9H-fluorene)-4-amine (abbreviation: oFBiSF), N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluorene-2-yl)dibenzofuran-4-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN) 4-Phenylacetyl-4'-(9-phenylfluorene-9-yl)triphenylamine (abbreviation: BPAFLP), 4-Phenylacetyl-3'-(9-phenylfluorene-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-Phenylacetyl-4'-[4-(9-phenylfluorene-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-Phenylacetyl-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-Di(1-naphthyl)-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviated as: PCCNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]spiro-9,9'-bifluorene-2-amine (abbreviated as: PCBASF), N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]-9H-fluorene-2-amine (abbreviated as: PCBiF), etc.

[0069] The composition of the first substance and the second substance in the hole injection layer 111 is preferably 1:0.01 to 1:0.15 (weight ratio). Note that it is more preferably 1:0.01 to 1:0.1 (weight ratio).

[0070] The hole transport layer 112 can also be a single layer, but it preferably includes a first hole transport layer 112-1 and a second hole transport layer 112-2. The first hole transport layer 112-1 is located closer to the anode 101 than the second hole transport layer 112-2. Note that sometimes the second hole transport layer 112-2 also functions as an electron blocking layer.

[0071] The first hole transport layer 112-1 and the second hole transport layer 112-2 contain hole-transporting organic compounds. As these hole-transporting organic compounds, organic compounds that can also be used as the first substance described above can be used. Note that the hole-transporting organic compounds in the first hole transport layer 112-1 and the second hole transport layer 112-2 can be the same or different organic compounds. Furthermore, the hole-transporting organic compound contained in the first hole transport layer 112-1 and the first substance in the hole injection layer 111 can be the same or different organic compounds.

[0072] The materials are preferably selected such that the HOMO level of the first material contained in the hole injection layer 111 and the HOMO level of the hole-transporting organic compound contained in the first hole transport layer 112-1 are deeper than the latter and the difference is less than 0.2 eV.

[0073] Furthermore, the HOMO level of the hole-transporting organic compound contained in the second hole transport layer 112-2 is preferably deeper than the HOMO level of the hole-transporting organic compound contained in the first hole transport layer 112-1. Moreover, it is preferable to select materials such that the difference between them is less than 0.2 eV. By ensuring the HOMO levels of the hole-transporting organic compounds contained in the hole injection layer 111 to the second hole transport layer 112-2 have the aforementioned relationship, holes can be smoothly injected into each layer, thereby preventing the driving voltage from rising and the state of insufficient holes in the light-emitting layer.

[0074] Furthermore, the first material contained in the hole injection layer 111 and the hole-transporting organic compounds contained in the hole transport layers 112 (first hole transport layer 112-1 and second hole transport layer 112-2) preferably each have a hole-transporting framework. As this hole-transporting framework, carbazole, dibenzofuran, dibenzothiophene, and anthracene frameworks that do not cause the HOMO level of the aforementioned organic compounds to be too shallow are preferred. Additionally, when the materials contained in adjacent layers all have the aforementioned hole-transporting frameworks, hole injection can be performed smoothly, which is therefore preferable. A dibenzofuran framework is particularly preferred as the aforementioned hole-transporting framework.

[0075] Furthermore, it is preferable that hole injection can be smoothly performed by making the materials contained in adjacent layers the same organic compound. It is particularly preferable that the first material contained in the hole injection layer 111 and the hole-transporting organic compound contained in the first hole transport layer 112-1 are the same material.

[0076] The light-emitting layer 113 contains a light-emitting substance and a host material. Note that the light-emitting layer 113 may also contain other materials. Furthermore, it may be a stack of two different layers.

[0077] The luminescent material can be a fluorescent luminescent material, a phosphorescent luminescent material, a material exhibiting thermally activated delayed fluorescence (TADF), or other luminescent materials. In one embodiment of the invention, the luminescent layer 113 is preferably used as a layer exhibiting fluorescent luminescence, particularly a layer exhibiting blue fluorescent luminescence.

[0078] In the luminescent layer 113, materials that can be used as fluorescent luminescent substances include, for example, the following substances. Note that other fluorescent luminescent substances can also be used.

[0079] Examples include 5,6-bis[4-(10-phenyl-9-anthrayl)phenyl]-2,2'-bipyridine (abbreviated as PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthrayl)biphenyl-4-yl]-2,2'-bipyridine (abbreviated as PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviated as 1,6FLPAPrn), and N,N'-bis(3-methylphenyl)-N N'-bis[3-(9-phenyl-9H-fluorene-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazole-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazole-9-yl)-4'-(10-phenyl-9-anthrayl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazole-9-yl)-4'-(9,10-diphenyl-2-yl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazole-9-yl)-4'-(9,10-diphenyl-2-yl)triphenylamine -Anthracene)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole-3-amine (abbreviation: PCAPA), dinaphthalene, 2,5,8,11-tetra(tert-butyl)dinaphthalene (abbreviation: TBP), 4-(10-phenyl-9-anthrayl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCPAPA), N,N”-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene) )Bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviated as DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-9H-carbazole-3-amine (abbreviated as 2PCAPPA), N-[4-(9,10-diphenyl-2-anthrayl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviated as 2DPAPPA), N,N,N',N',N',N",N",N"',N"'-octaphenyldibenzo[g,p] (chrysene)-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, N-(9,10-diphenyl-2-anthrayl)-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthrayl]-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthrayl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthrayl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetraphenyl (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]vinyl}-6-methyl-4H-pyran-4-yl)malonitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-yl)-[4 ... -Tetrahydro-1H,5H-benzo[ij]quinazine-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviation: DCM2), N,N,N',N'-tetra(4-methylphenyl)tetraphenyl-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetra(4-methylphenyl)acenaphthene[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]quinazine-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviation: DCJTI), 2-{2- tert-Butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]vinyl}-4H-pyran-4-ylidene)malonium (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinazin-9-yl)vinyl]-4H-pyran-4-ylidene}malonium (abbreviation: BisDCJTM), N,N'-(pyrene-1,6-diyl)bis[(6,N-Diphenylbenzo[b]naphtho[1,2-d]furan-8-amine] (abbreviation: 1,6BnfAPrn-03), 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02), etc. In particular, fused aromatic diamine compounds, represented by pyrene diamine derivatives such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03, possess suitable hole-trapping properties and exhibit good luminescence efficiency and reliability, making them the preferred choice.

[0080] In the light-emitting layer 113, when a phosphorescent light-emitting material is used as the light-emitting material, the following materials can be used as examples.

[0081] For example, materials such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviated as [Ir(mpptz-dmp)3]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazole)iridium(III) (abbreviated as [Ir(Mptz)3]), and tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazole]iridium(III) (abbreviated as [Ir(iPrptz-3b)3]) with a 4H-triazole skeleton, such as organometallic iridium complexes; and tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazole]iridium(III) (abbreviated as: Organometallic iridium complexes with a 1H-triazole skeleton, such as [Ir(Mptz1-mp)3] and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazole)iridium(III) (abbreviated as [Ir(Prptz1-Me)3]); organometallic iridium complexes with an imidazole skeleton, such as fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazolium]iridium(III) (abbreviated as [Ir(iPrpmi)3]) and tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviated as [Ir(dmpimpt-Me)3]); and bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2 Iridium(III) tetrakis(1-pyrazolyl)borate (abbreviated as: FIr6), bis[2-(4',6'-difluorophenyl)pyridinium-N,C2 Iridium(III) pyridine carboxylate (abbreviated as FIRPIC), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinium-N,C 2 Iridium(III)pyridinecarboxylate (abbreviated as: [Ir(CF3ppy)2(pic)]), bis[2-(4',6'-difluorophenyl)pyridinium-N,C 2 Organometallic iridium complexes such as iridium(III) acetylacetone (abbreviated as FIr(acac)) with phenylpyridine derivatives having electron-withdrawing groups as ligands. These substances are compounds that emit blue phosphorescence and have an emission peak in the range of 440 nm to 520 nm.

[0082] Additionally, examples include: tris(4-methyl-6-phenylpyrimidine)iridium(III) (abbreviated as [Ir(mppm)3]), tris(4-tert-butyl-6-phenylpyrimidine)iridium(III) (abbreviated as [Ir(tBuppm)3]), (acetylacetonate)bis(6-methyl-4-phenylpyrimidine)iridium(III) (abbreviated as [Ir(mppm)2(acac)]), (acetylacetonate)bis(6-tert-butyl-4-phenylpyrimidine)iridium(III) (abbreviated as [Ir(tBuppm)2(acac)]), (acetylacetonate)bis[6-(2-norborneol)-4-phenylpyrimidine]iridium(III) (abbreviated as [Ir(nbppm)2(acac)]), (acetylacetonate)bis[5-methyl Organometallic iridium complexes with a pyrimidine skeleton, such as [Ir(mpmppm)2(acac)]((acetylacetonate)bis(4,6-diphenylpyrimidine)iridium(III)]([Ir(dppm)2(acac)]); organometallic iridium complexes with a pyrazine skeleton, such as [Ir(mppr-Me)2(acac)]((acetylacetonate)bis(5-isopropyl-3-methyl-2-phenylpyrazine)iridium(III)]([Ir(mppr-iPr)2(acac)]); and tris(2-phenylpyridinium-N,C 2 Iridium(III) (abbreviated as: [Ir(ppy)3]), bis(2-phenylpyridinium-N,C) 2 Iridium(III) acetylacetone (abbreviated as: [Ir(ppy)2(acac)]), bis(benzo[h]quinoline)iridium(III) acetylacetone (abbreviated as: [Ir(bzq)2(acac)]), tri(benzo[h]quinoline)iridium(III) (abbreviated as: [Ir(bzq)3]), tri(2-phenylquinoline-N,C 2Iridium(III) (abbreviated as: [Ir(pq)3]), bis(2-phenylquinoline-N,C) 2 Organometallic iridium complexes with a pyridine backbone, such as iridium(III)acetylacetone (abbreviated as [Ir(pq)2(acac)]), and rare earth metal complexes such as tri(acetylacetone)(monophenanthroline)terbium(III) (abbreviated as [Tb(acac)3(Phen)]), are preferred. These substances are primarily compounds that emit green phosphorescence and exhibit an emission peak in the 500 nm to 600 nm range. Furthermore, organometallic iridium complexes with a pyrimidine backbone are particularly preferred due to their exceptionally high reliability and luminescent efficiency.

[0083] In addition, examples of organogold compounds with pyrimidine skeletons include: (diisobutyrylmethane)bis[4,6-bis(3-methylphenyl)pyrimidinyl]iridium(III) (abbreviated as: [Ir(5mdppm)2(dibm)]), (bis[4,6-bis(3-methylphenyl)pyrimidinyl)(dineopentaylmethane)iridium(III) (abbreviated as: [Ir(5mdppm)2(dpm)]), and (bis[4,6-di(naphthyl-1-yl)pyrimidinyl](dineopentaylmethane)iridium(III) (abbreviated as: [Ir(d1npm)2(dpm)]). Organometallic iridium complexes with a pyrazine skeleton, such as (acetylacetonate)bis(2,3,5-triphenylpyrazine)iridium(III) (abbreviated as [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazine)(dinepentanoylmethane)iridium(III) (abbreviated as [Ir(tppr)2(dpm)]), and (acetylacetonate)bis[2,3-bis(4-fluorophenyl)quinoxaloline]iridium(III) (abbreviated as [Ir(Fdpq)2(acac)]); tris(1-phenylisoquinoline-N,C 2’ Iridium(III) (abbreviated as: [Ir(piq)3]), bis(1-phenylisoquinoline-N,C) 2’Organometallic iridium complexes with a pyridine skeleton, such as iridium(III)acetylacetone (abbreviated as [Ir(piq)2(acac)]); platinum complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviated as PtOEP); and rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenyline)eup(III) (abbreviated as [Eu(DBM)3(Phen)]) and tris[1-(2-thiophenecarboxyl)-3,3,3-trifluoroacetone](monophenyline)eup(III) (abbreviated as [Eu(TTA)3(Phen)]). These substances are compounds that emit red phosphorescence and have an emission peak in the 600 nm to 700 nm range. In addition, organometallic iridium complexes with pyrazine skeletons can obtain red luminescence with good colorimetry.

[0084] In addition to the phosphorescent compounds mentioned above, known phosphorescent materials can also be selected for use.

[0085] Fullerenes and their derivatives, acridines and their derivatives, and eosin derivatives can be used as TADF materials. Additionally, metal porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can also be used. Examples of metalloporphyrins include, for instance, protoporphyrin-tin fluoride complexes represented by the following structural formulas: protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesotoporphyrin-tin fluoride complex (SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), tetramethyl coprophyrin-tin fluoride complex (SnF2(Copro III-4Me), octaethylporphyrin-tin fluoride complex (SnF2(OEP)), protoporphyrin-tin fluoride complex (SnF2(Etio I)), and octaethylporphyrin-platinum chloride complex (PtCl2OEP).

[0086] [Chemical Formula 1]

[0087]

[0088] Alternatively, the following structural formulas can be used: 2-(biphenyl-4-yl)-4,6-bis(12-phenylindol[2,3-a]carbazole-11-yl)-1,3,5-triazine (abbreviated as: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviated as: PCCzTzn), 2-{4-[3-(N-phenyl-9H-carbazole-3-yl)-9H-carbazole-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as: PCCzPTzn), 2-[4-(10H-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3 Heterocyclic compounds such as 5-triazine (abbreviated as PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviated as PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-oxazanthracene-9-one (abbreviated as ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridin)phenyl]sulfone (abbreviated as DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviated as ACRSA) are heterocyclic compounds with one or both of π-electron-rich and π-electron-deficient heterocyclic rings. This heterocyclic compound possesses both π-electron-rich and π-electron-deficient heteroaromatic rings, exhibiting high electron and hole transport capabilities, and is therefore preferred. In particular, among the skeletons possessing π-electron-deficient heteroaromatic rings, pyridine, diazine (pyrimidine, pyrazine, pyridazine), and triazine skeletons are stable and reliable, and are therefore preferred. Especially, benzofuran-pyrimidine, benzothiophene-pyrimidine, benzofuran-pyrazine, and benzothiophene-pyrazine skeletons exhibit high electron acceptability and good reliability, and are therefore preferred. Furthermore, among the skeletons possessing π-electron-rich heteroaromatic rings, acridine, phenoxazine, phenothiazine, furan, thiophene, and pyrrole skeletons are stable and reliable, and it is preferred to have at least one of these skeletons. Additionally, dibenzofuran skeletons are preferred as furan skeletons, and dibenzothiophene skeletons are preferred as thiophene skeletons. As the pyrrole skeleton, indole, carbazole, indole-carbazole, bicarbazole, and 3-(9-phenyl-9H-carbazole-3-yl)-9H-carbazole skeletons are particularly preferred. In substances where π-electron-rich and π-electron-deficient aromatic heterocycles are directly bonded, the π-electron-rich aromatic heterocycle exhibits high electron-donating capacity and the π-electron-deficient aromatic heterocycle has high electron-accepting capacity, resulting in a smaller energy difference between the S1 and T1 energy levels. This allows for efficient acquisition of thermally activated delayed fluorescence, making it particularly preferred. Note that aromatic rings bonded with electron-withdrawing groups such as cyano groups can also be used instead of π-electron-deficient aromatic heterocycles. Furthermore, aromatic amine skeletons and phenazine skeletons can be used as π-electron-rich skeletons.Furthermore, as π-electron-deficient skeletons, the following can be used: oxanthracene skeleton, thioxanthene dioxide skeleton, oxadiazole skeleton, triazole skeleton, imidazole skeleton, anthraquinone skeleton, boron-containing skeletons such as phenylborane or boranthrene, aromatic or heteroaromatic rings with nitrile or cyanobenzene, carbonyl skeletons such as benzophenone, phosphine oxide skeleton, sulfone skeleton, etc. Thus, π-electron-deficient and π-electron-rich skeletons can be used to replace at least one of the π-electron-deficient and π-electron-rich heteroaromatic rings.

[0089] [Chemical Formula 2]

[0090]

[0091] TADF materials refer to materials with a small energy difference between the S1 and T1 levels and the ability to convert triple excitation energy into single excitation energy through antisystem crossing. Therefore, they can upconvert triple excitation energy into single excitation energy (antisystem crossing) with minimal thermal energy, efficiently generating singlet excited states. Furthermore, triple excitation energy can be converted into luminescence.

[0092] The exciplex formed by two substances in an excited state has the function of converting triple excitation energy into single excitation energy due to the extremely small difference between the S1 and T1 energy levels.

[0093] Note that the phosphorescence spectrum observed at low temperatures (e.g., 77K to 10K) can be used as an indicator of the T1 energy level. For TADF materials, it is preferable that the difference between S1 and T1 is 0.3 eV or less, more preferably 0.2 eV or less, when the wavelength energy of the extrapolated line obtained by drawing a tangent at the tail of the short-wavelength side of the fluorescence spectrum is taken as the S1 energy level and the wavelength energy of the extrapolated line obtained by drawing a tangent at the tail of the short-wavelength side of the phosphorescence spectrum is taken as the T1 energy level.

[0094] Furthermore, when using TADF material as the luminescent material, the S1 energy level of the host material is preferably higher than that of the TADF material. Additionally, the T1 energy level of the host material is preferably higher than that of the TADF material.

[0095] As the main material of the light-emitting layer, various carrier transport materials such as materials with electron transport properties, materials with hole transport properties, and the aforementioned TADF material can be used.

[0096] As a material with hole transport capabilities, it is preferable to have an amine backbone and a π-electron-rich heteroaryl ring backbone. Examples include: 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (TPD), 4,4'-bis[N-(spiro-9,9'-bifluorene-2-yl)-N-phenylamino]biphenyl (BSPB), 4-phenyl-4'-(9-phenylfluorene-9-yl)triphenylamine (BPAFLP), 4-phenyl-3'-(9-phenylfluorene-9-yl)triphenylamine (mBPAFLP), 4-phenyl-4'-(9-phenyl- 9H-carbazole-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4”-(9-phenyl-9H-carbazole-3-yl)triphenylamine (abbreviation: PCCNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazole-3-yl)phenyl]fluorene-2-amine (abbreviation: PCBAF), N-phenyl- Compounds with an aromatic amine skeleton, such as N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluorene-2-amine (abbreviated as PCBASF); compounds with a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviated as mCP), 4,4'-bis(N-carbazolyl)biphenyl (abbreviated as CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviated as CzTP), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviated as PCCP); and compounds with a carbazole skeleton, such as 4,4',4”-(benzene-1,3,5-triyl)tris(dibenzothiophene) (abbreviated as DBT3P-II). Compounds with a thiophene skeleton, such as 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviated as DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviated as DBTFLP-IV); and compounds with a furan skeleton, such as 4,4',4”-(phenyl-1,3,5-triyl)tris(dibenzofuran) (abbreviated as DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviated as mmDBFFLBi-II). Among these, compounds with an aromatic amine skeleton and compounds with a carbazole skeleton are preferred due to their good reliability, high hole transport properties, and ability to reduce driving voltage. Additionally, organic compounds exemplified as the first substance described above can also be used.

[0097] Materials with electron transport properties are preferably, for example, metal complexes of bis(10-hydroxybenzo[h]quinoline) beryllium(II) (abbreviated as BeBq2), bis(2-methyl-8-hydroxyquinoline)(4-phenylphenol) aluminum(III) (abbreviated as BAlq), bis(8-hydroxyquinoline) zinc(II) (abbreviated as Znq), bis[2-(2-benzoxazolyl)phenol] zinc(II) (abbreviated as ZnPBO), bis[2-(2-benzothiazolyl)phenol] zinc(II) (abbreviated as ZnBTZ) or organic compounds with π-electron-deficient aromatic heterocyclic skeletons. Organic compounds with π-electron-deficient aromatic heterocyclic skeletons include, for example, 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazole-2-yl)phenyl]-9H-carbazole (CO11), and 2,2',2”-(1,3,5-phenyltriyl)tris(1-phenyl-1H-benzimidazole) (TPBI). Heterocyclic compounds with polyazole skeletons, such as 2-[3-(dibenzothiophene-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviated as mDBTBIm-II); 2-[3-(dibenzothiophene-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviated as 2mDBTPDBq-II), 2-[3'-(dibenzothiophene-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviated as 2mDBTBPDBq-II), 2-[3'-(9H-carbazole-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviated as 2mCzBPDBq), 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviated as:

[0098] Heterocyclic compounds with a diazine skeleton, such as 4,6mPnP2Pm and 4,6-bis[3-(4-dibenzothiophene)phenyl]pyrimidine (abbreviated as: 4,6mDBTP2Pm-II); 2-[3'-(9,9-dimethyl-9H-fluorene-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviated as: mFBPTzn), 2-[(1,1'-biphenyl)-4-yl]-4-phenyl-6-[9,9'-spiro(9H-fluorene)-2-yl]-1,3,5-triazine (abbreviated as: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[ Heterocyclic compounds with a triazine skeleton, such as 1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mBnfBPTzn) and 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviated as mBnfBPTzn-02); and heterocyclic compounds with a pyridine skeleton, such as 3,5-bis[3-(9H-carbazole-9-yl)phenyl]pyridine (abbreviated as 35DCzPPy) and 1,3,5-tris[3-(3-pyridyl)phenyl]benzene (abbreviated as TmPyPB). Among these, heterocyclic compounds with a diazine skeleton, heterocyclic compounds with a triazine skeleton, or heterocyclic compounds with a pyridine skeleton are preferred due to their good reliability. In particular, heterocyclic compounds with a diazine (pyrimidine or pyrazine) skeleton and heterocyclic compounds with a triazine skeleton have high electron transport properties, which also help to reduce the driving voltage.

[0099] As a TADF material that can be used as the host material, the same material as the TADF material mentioned above can be used. When using a TADF material as the host material, the triple excitation energy generated by the TADF material is converted into a single excitation energy via antisystem crossing and further transferred to the luminescent material, thereby improving the luminous efficiency of the light-emitting device. In this case, the TADF material is used as the energy donor, and the luminescent material is used as the energy acceptor.

[0100] This is highly effective when the luminescent material is a fluorescent luminescent material. Furthermore, to obtain high luminescent efficiency, the S1 energy level of the TADF material is preferably higher than the S1 energy level of the fluorescent luminescent material. Additionally, the T1 energy level of the TADF material is preferably higher than the S1 energy level of the fluorescent luminescent material. Therefore, the T1 energy level of the TADF material is preferably higher than the T1 energy level of the fluorescent luminescent material.

[0101] Furthermore, it is preferable to use a TADF material that exhibits luminescence with a wavelength overlapping the absorption band on the lowest energy side of the fluorescent luminescent material. This allows for efficient transfer of excitation energy from the TADF material to the fluorescent luminescent material, resulting in highly efficient luminescence, and is therefore preferred.

[0102] To efficiently generate a singlet excitation energy from a triplet excitation energy via antisystem crossing, it is preferable to induce carrier recombination within the TADF material. Furthermore, it is preferable that the triplet excitation energy generated in the TADF material does not transfer to the fluorescent luminescent material. For this purpose, the fluorescent luminescent material preferably has a protecting group surrounding the luminescent body (the framework that causes luminescence). This protecting group is preferably a substituent without π bonds, preferably a saturated hydrocarbon; specifically, examples include alkyl groups with 3 or more but less than 10 carbon atoms, substituted or unsubstituted cycloalkyl groups with 3 or more but less than 10 carbon atoms, and trialkylsilyl groups with 3 or more but less than 10 carbon atoms; more preferably, multiple protecting groups are preferred. Substituents without π bonds have almost no function in transporting charge carriers, thus having little effect on carrier transport or recombination, allowing the TADF material and the luminescent body of the fluorescent luminescent material to be kept apart. Here, the luminescent body refers to the atomic group (backbone) in the fluorescent luminescent material that causes luminescence. The luminescent material preferably has a π-bonded framework, preferably containing an aromatic ring, and even more preferably having a fused aromatic ring or a fused heteroaromatic ring. Examples of fused aromatic rings or fused heteroaromatic rings include phenanthrene frameworks, stilbene frameworks, acridinone frameworks, phenoxazine frameworks, and phenothiazine frameworks. In particular, frameworks containing naphthalene, anthracene, or fluorene are preferred. Fluorescent materials with skeletons such as triphenylene skeleton, tetraphenylene skeleton, pyrene skeleton, perylene skeleton, coumarin skeleton, quinacridone skeleton, and naphthobisbenzofuran skeleton have high fluorescence quantum yields and are therefore preferred.

[0103] When using a fluorescent luminescent material as the luminescent material, a material with an anthracene framework is preferably used as the host material. By using a material with an anthracene framework as the host material of the fluorescent luminescent material, a luminescent layer with good luminescence efficiency and durability can be achieved. Among the anthracene framework materials used as host materials, those with a diphenylanthracene framework (especially 9,10-diphenylanthracene framework) are chemically stable and therefore preferred. Furthermore, when the host material has a carbazole framework, hole injection / transport is improved, which is also preferred. In particular, when a benzo[a]carbazole framework is included, containing a benzene ring fused to a carbazole, its HOMO level is about 0.1 eV shallower than that of carbazole, making hole injection easier and therefore more preferred. Especially when the host material has a dibenzo[a]carbazole framework, its HOMO level is about 0.1 eV shallower than that of carbazole, which not only facilitates hole injection but also improves hole transport and heat resistance, making it preferred. Therefore, substances further preferred for use as host materials are those having a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzo[a]carbazole skeleton or a dibenzo[a]carbazole skeleton). Note that from the viewpoint of hole injection / transportation described above, a benzo[a]fluorene skeleton or a dibenzo[a]fluorene skeleton can also be used instead of a carbazole skeleton. Examples of such substances include 9-phenyl-3-[4-(10-phenyl-9-anthrayl)phenyl]-9H-carbazole (abbreviated as PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviated as PCPN), 9-[4-(10-phenylanthracene-9-yl)phenyl]-9H-carbazole (abbreviated as CzPA), and 7-[4-(10-phenyl-9-anthrayl)phenyl]-7H-dibenzo[c,g] Carbazole (abbreviated as cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthrayl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviated as 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluorene-9-yl)-biphenyl-4'-yl}-anthracene (abbreviated as FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviated as αN-βNPAnth), etc. In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA exhibit very good properties and are therefore preferred.

[0104] Alternatively, the host material can be a mixture of multiple substances. When using a mixed host material, it is preferable to mix materials with electron transport properties and materials with hole transport properties. By mixing materials with electron transport properties and materials with hole transport properties, it is easier to adjust the transport properties of the light-emitting layer 113 and to control the composite region more easily. The weight ratio of the material with hole transport properties to the material with electron transport properties can be from 1:19 to 19:1.

[0105] Note that phosphorescent materials can be used as part of the above-described mixture. When phosphorescent materials are used as fluorescent materials, they can be used as energy donors to supply excitation energy to the fluorescent materials.

[0106] Alternatively, these mixed materials can be used to form excimer complexes. By selecting the mixed materials in a way that creates an excimer complex that emits light at a wavelength overlapping with the absorption band on the lowest energy side of the luminescent material, energy transfer can be facilitated, resulting in efficient luminescence, which is therefore preferred. Furthermore, this structure reduces the driving voltage, making it also preferred.

[0107] Note that at least one of the materials forming the excitocomplex can be a phosphorescent material. This allows for the efficient conversion of the triple excitation energy into a single excitation energy via an antisystem crosstalk.

[0108] Regarding the combination of materials for efficiently forming excitocomplexes, the HOMO energy level of the material with hole transport is preferably higher than or equal to the HOMO energy level of the material with electron transport. Furthermore, the LUMO energy level of the material with hole transport is preferably higher than or equal to the LUMO energy level of the material with electron transport. Note that the LUMO and HOMO energy levels of the material can be determined from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV).

[0109] Note that the formation of excitocomplexes can be confirmed, for example, by comparing the emission spectra of a hole-transporting material, the emission spectra of an electron-transporting material, and the emission spectra of a hybrid film formed by mixing these materials. When the emission spectrum of the hybrid film is observed to shift towards a longer wavelength (or to have a new peak at a longer wavelength) compared to the emission spectra of each material, it indicates the formation of an excitocomplex. Alternatively, by comparing the transient photoluminescence (PL) of a hole-transporting material, the transient PL of an electron-transporting material, and the transient PL of a hybrid film formed by mixing these materials, when a difference in transient response is observed, such as the mixed film having a longer lifetime component or a higher ratio of delayed components compared to the transient PL lifetimes of each material, it indicates the formation of an excitocomplex. Furthermore, the aforementioned transient PL can be referred to as transient electroluminescence (EL). In other words, by comparing the transient EL of a hole-transporting material, the transient EL of an electron-transporting material, and the transient EL of a hybrid film of these materials, and observing the differences in transient responses, the formation of an excitocomplex can be confirmed.

[0110] In one embodiment of the present invention, the electron transport layer 114 of the light-emitting device is constructed using a material whose resistance decreases when current flows through it. By using a material whose resistance decreases when current flows through it to construct the electron transport layer 114, a light-emitting device can be manufactured in which the resistance of the electron transport layer 114 decreases when the light-emitting device is driven by current flow. Here, by pre-designing the light-emitting device so that the recombination region of charge carriers extends not only in the light-emitting layer but also into the electron transport layer during the initial driving stage, a light-emitting device can be obtained in which the carrier balance changes as the transport capacity of the electron transport layer 114 increases over time, thereby causing the cathode-side end of the recombination region to move towards the light-emitting layer 113. Since the energy of the recombinated charge carriers in the electron transport layer 114 is hardly converted into light emission, the recombination region extending into the electron transport layer 114 returns to the light-emitting layer 113, thereby reducing the loss of recombination energy. As a result, a light-emitting device with increased luminous efficiency and brightness during driving can be obtained. The light-emitting device exhibiting this behavior can use the increase in brightness to offset the rapid degradation during the initial driving phase (i.e., the so-called initial degradation), thereby achieving a light-emitting device with small initial degradation and resulting in a very good driving lifetime. Such a light-emitting device is called a Recombination-Site Tailoring Injection (ReSTI) device.

[0111] In order to manufacture a light-emitting device in which the recombination region of charge carriers in the initial stage of driving extends not only in the light-emitting layer but also to the electron transport layer, the hole injection layer 111 may contain a first material having hole transport properties and a deep HOMO energy level, namely above -5.7 eV and below -5.4 eV, and a second material having electron accepting properties for the first material.

[0112] As a material that reduces resistance when current flows through it, it is preferable to use an organometallic complex containing an alkali metal or alkaline earth metal. This material can be formed solely of an organometallic complex of an alkali metal or alkaline earth metal, or it can be formed from an organometallic complex of an alkali metal or alkaline earth metal and other substances. When the material that reduces resistance when current flows through it contains substances other than organometallic complexes of alkali metals or alkaline earth metals, an organic compound with electron transport properties is preferably used as this substance.

[0113] When the material whose resistance decreases when current flows through it contains an organometallic complex of an alkali metal or alkaline earth metal, the organometallic complex of the alkali metal or alkaline earth metal is preferably a complex that forms clusters when current flows through it. When the complex forms clusters, the electron transport capacity increases, thereby obtaining a light-emitting device with a reduced resistance of the electron transport layer 114.

[0114] In particular, when the material is an organometallic complex containing alkali metals or alkaline earth metals and an organic compound with electron transport properties, the complex aggregates into clusters when current flows through it, and the individual organic compounds with electron transport properties inevitably move closer together. Therefore, the conductive paths of the individual organic compounds with electron transport properties become thicker, the electron transport properties of the electron transport layer 114 become higher, and a light-emitting device with a reduced resistance value of the electron transport layer 114 can be obtained.

[0115] The electron transport properties of this organic compound are superior to those of hole transport, and its electron mobility is preferably 1 × 10⁻⁶ when the square root of the electric field strength [V / cm] is 600. -7 cm 2 / Vs or more and 5×10 -5 cm 2 / Vs or less. By keeping the electron mobility in the electron transport layer within the above range, the amount of electrons injected into the light-emitting layer can be controlled, thereby preventing the light-emitting layer from becoming an electron-overloaded state.

[0116] The HOMO level of the electron-transporting organic compound is preferably -6.0 eV or higher. Furthermore, the electron-transporting organic compound preferably contains anthracene skeleton, and more preferably contains both anthracene skeleton and heterocyclic skeleton. The heterocyclic skeleton is preferably a nitrogen-containing five-membered ring skeleton, and this nitrogen-containing five-membered ring skeleton is particularly preferably containing two heteroatoms in a ring such as a pyrazole ring, imidazole ring, oxazole ring, or thiazole ring.

[0117] Organometallic complexes of alkali metals or alkaline earth metals are preferably metal complexes containing ligands with nitrogen and oxygen and alkali metals or alkaline earth metals. In particular, organometallic complexes of alkali metals or alkaline earth metals are preferably metal complexes containing ligands having an 8-hydroxyquinoline structure and monovalent metal ions, and more preferably lithium complexes containing ligands having an 8-hydroxyquinoline structure. Specifically, examples include 8-hydroxyquinoline-lithium (abbreviated as Liq) and 8-hydroxyquinoline-sodium (abbreviated as Naq). 8-hydroxyquinoline-lithium (abbreviated as Liq) is particularly preferred.

[0118] Note that the electron transport layer 114 may also have portions in its thickness direction where the mixing ratio of the electron-transporting organic compound and the organometallic complex of the alkali metal or alkaline earth metal differs. In this mixing ratio, the mixing ratio of the organometallic complex of the alkali metal or alkaline earth metal on the cathode side is preferably smaller. The magnitude of this mixing ratio can be estimated based on the detection quantity of atoms or molecules obtained from time-of-flight secondary ion mass spectrometry (ToF-SIMS). In the portions with different mixing ratios composed of the same two materials, the values ​​detected by ToF-SIMS analysis correspond to the magnitudes of the notable atoms, molecules, or ions. Therefore, the magnitude of the mixing ratio can also be estimated by comparing the detection quantities of substances derived from the electron-transporting organic compound or the organometallic complex of the alkali metal or alkaline earth metal.

[0119] In other words, preferably, the electron transport layer 114 contains a first electron transport layer 114-1 and a second electron transport layer 114-2. The first electron transport layer is closer to the anode side than the second electron transport layer. The concentration of the alkali metal or alkaline earth metal organometallic complex in the first electron transport layer is different from that in the second electron transport layer. Note that when the concentration of the alkali metal or alkaline earth metal organometallic complex in the first electron transport layer is higher than that in the second electron transport layer, a longer-life device can be obtained, which is therefore preferred.

[0120] The presence of organometallic complexes of alkali metals or alkaline earth metals in the electron transport layer 114, for example... Figure 1A1 When there is no clear layer boundary, such as Figure 32A1 , Figure 32A2 As shown, it can change continuously, such as Figure 1A2 As shown, it can be confirmed that when dividing into layers, such as Figure 32B1 , Figure 32B2 In this way, the changes can be phased. In the electron transport layer 114, it is preferable to have a region with a high concentration of alkali metal or alkaline earth metal organometallic complexes closer to the light-emitting layer 113 than a region with a low concentration of alkali metal or alkaline earth metal organometallic complexes that determine the rate of electron transport. In other words, in the electron transport layer 114, it is preferable to have a region where the amount (concentration) of alkali metal or alkaline earth metal organometallic complexes increases from the cathode side to the anode side. Furthermore, in the electron transport layer 114, the region with the highest amount (concentration) of alkali metal or alkaline earth metal organometallic complexes is preferably closer to the anode side than the region with the lowest concentration.

[0121] As the electron transport organic compound included in the electron transport layer 114, an electron transport organic compound that can be used in the host material or an organic compound that can be used in the host material of the fluorescent luminescent material can be used.

[0122] In the organic compound with electron transport properties contained in the electron transport layer 114, the electron mobility with the square root of the electric field strength [V / cm] of 600 is preferably smaller than that of the host material or the light-emitting layer 113.

[0123] When the luminescent layer becomes in a state with an excess of electrons, such as Figure 2A As shown, the recombination region 113-1 is confined to a partial region, increasing the burden on that portion and accelerating degradation. Furthermore, the inability of electrons to recombine and pass through the light-emitting layer also leads to a decrease in lifetime and luminous efficiency. In one aspect of the invention, by reducing the electron transport properties in the electron transport layer 114, such as... Figure 2B As shown, the composite region 113-1 can be widened to distribute the burden on the material constituting the light-emitting layer 113, thereby providing a light-emitting device with long life and good luminous efficiency.

[0124] Furthermore, in light-emitting devices with the above-described structure, the degradation curve of brightness obtained through driving tests under constant current density conditions sometimes exhibits a shape with a maximum value. That is, the degradation curve of a light-emitting device according to one aspect of the present invention sometimes exhibits a shape with a brightness increase over time. Light-emitting devices exhibiting this degradation behavior can utilize this brightness increase to offset the rapid degradation at the beginning of driving (i.e., the so-called initial degradation), thereby achieving a light-emitting device with small initial degradation and very good driving lifetime. Such a light-emitting device is called a Recombination-Site Tailoring Injection (ReSTI) element.

[0125] Note that when taking the derivative of the degradation curve with such a maximum value, there exists a portion where its value is 0. Thus, the light-emitting device of one aspect of the present invention, in which the derivative of the degradation curve has a portion of 0, has small initial degradation, and can therefore be considered a light-emitting device with excellent lifespan.

[0126] like Figure 3AAs shown, the degradation curve described above can be attributed to the following reason: In the initial driving phase, the electron mobility in the electron transport layer is low, thus hindering the formation of luminescent recombination in the non-luminescent recombination region 120. That is, in the light-emitting device of the present invention with the above structure, since the hole injection barrier is low (the HOMO level of the first material is deep) and the electron transport properties of the electron transport layer 114 are low in the initial driving phase, the recombination region 113-1 is formed extending from the luminescent layer 113 to the electron transport layer 114. Furthermore, when the HOMO level of the electron-transporting organic compound in the electron transport layer 114 is high, i.e., above -6.0 eV, holes easily reach the electron transport layer 114 and recombine within it, thus easily forming the non-luminescent recombination region 120, because the HOMO levels of alkali metal or alkaline earth metal organometallic complexes are located at the same position.

[0127] Here, in one embodiment of the light-emitting device of the present invention, the balance of charge carriers changes as the driving time progresses, such as... Figure 3B The cathode-side end of the recombination region 113-1 shown gradually moves towards the hole transport layer 112. As the non-luminescent recombination region 120 decreases, the energy of the recombinated carriers can be effectively used for luminescence, resulting in an increase in brightness compared to the initial driving state. This increase in brightness offsets the sharp decrease in brightness that occurs during the initial driving of the light-emitting device (so-called initial degradation), thereby providing a light-emitting device with low initial degradation and a long driving lifetime.

[0128] Here, the inventors have experimentally verified the following: the change in carrier balance in the light-emitting device of one aspect of the present invention is caused by the change in the resistance of the light-emitting device (in particular, the change in the resistance of the electron transport layer 114). The change in resistance was measured by impedance spectroscopy (IS).

[0129] In the measurement using the impedance spectroscopy method, a small sinusoidal voltage signal [V=V0exp(iωt)] is applied to the light-emitting device, and the impedance (Z=V / I) can be obtained from the phase difference between the current amplitude of its response current signal [I=I0exp{i(ωt+φ)}] and the input signal.

[0130] The plotting of the impedance on the complex plane using the frequency of the applied voltage signal as a parameter is called Nyquist plotting. By determining the impedance (Z), the admittance (Y), modulus (M), and dielectric constant (ε) of the fundamental transfer functions can be calculated. The relationships between the various transfer functions are shown below.

[0131] [Table 1]

[0132]

[0133] In this embodiment, the light-emitting device is analyzed using impedance (Z), which represents the resistive component, and modulus (M), which represents the reciprocal of the capacitance component. Table 2 shows the structure of the measured light-emitting device.

[0134] [Table 2]

[0135]

[0136] Figure 16 An example of a Z-plot of a light-emitting device according to one aspect of the present invention is shown. In the Z-plot, the resistance component is represented by the real axis, from which it can be seen that the resistance after driving is significantly lower than the resistance before driving. Therefore, it can be seen that the resistance of the light-emitting device according to one aspect of the present invention changes significantly before and after driving, and the resistance of the light-emitting device after driving is lower than that before driving.

[0137] then, Figure 17 The diagram shows the M-plot of the same light-emitting device. This diagram was generated using the equivalent circuit analysis software ZView (Scribner Associates / USA). The equivalent circuit of this light-emitting device can be represented as... Figure 18 The diagram shows four RC parallel circuits and one series resistor. Note that the values ​​in this plot indicate where the resistive components appear using the corresponding equivalent circuit obtained from the proposed diagram.

[0138] Figure 19 Show Figure 18 The equivalent circuit in the diagram shows the resistance values ​​of each resistor component before and after the drive. From this, we can see that only the resistance of resistor R2 decreases by more than one order of magnitude.

[0139] Therefore, by changing the thickness, it was determined which layer each resistance component corresponded to. The change in M ​​plotted and the increase in resistance when the thickness was large confirmed that the resistance component of R2 originated from the electron transport layer.

[0140] These results confirm that by driving the light-emitting device with current, the resistance of the electron transport layer 114 decreases, and the electron transport capacity of the electron transport layer 114 increases. As described above, when the electron transport capacity of the electron transport layer 114 increases, the carrier balance changes, the end of the recombination region extending into the electron transport layer moves towards the light-emitting layer, and the non-light-emitting recombination region 120 shrinks. As a result, recombination within the light-emitting layer increases, effectively enabling recombination energy to contribute to light emission. Therefore, a light-emitting device according to one aspect of the present invention exhibits a unique behavior of increasing its brightness compared to the initial driving stage.

[0141] Therefore, it can be seen that the resistance of the light-emitting device after driving is lower than the resistance before driving, and the resistance of the electron transport layer of the light-emitting device decreases during driving. This means that the electron transport layer is made of a material whose resistivity decreases even when current flows through it.

[0142] A light-emitting device of one embodiment of the present invention having the structure described above can be a light-emitting device with excellent lifespan. In particular, the lifespan of the region with minimal degradation of approximately 95% (LT95) of the initial brightness can be significantly extended.

[0143] In addition, since initial degradation can be suppressed, the burn-in problem, one of the major drawbacks of organic EL devices, can be significantly reduced, as well as the time and labor required for the aging process before shipment to reduce this problem.

[0144] Implementation Method 2

[0145] Next, examples of the detailed structure and materials of the above-mentioned light-emitting device will be described. As described above, one aspect of the light-emitting device of the present invention includes an EL layer 103 composed of multiple layers between a pair of electrodes, namely an anode 101 and a cathode 102, and the EL layer 103 includes a hole injection layer 111, a first hole transport layer 112-1, a second hole transport layer 112-2, a light-emitting layer 113, and an electron transport layer 114 from the anode 101 side.

[0146] There are no particular restrictions on the other layers in EL layer 103. Various layer structures can be adopted, such as hole injection layer, hole transport layer, electron transport layer, electron injection layer, carrier blocking layer, exciton blocking layer, and charge generation layer.

[0147] The anode 101 is preferably formed using a metal, alloy, conductive compound, or mixture thereof with a high work function (specifically 4.0 eV or higher). Specifically, examples include indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide, indium zinc oxide, and indium oxide (IWZO) containing tungsten oxide and zinc oxide. While these conductive metal oxide films are typically formed by sputtering, sol-gel methods can also be used. Examples of formation methods include sputtering an indium oxide-zinc oxide film using a target containing 1 wt% to 20 wt% zinc oxide. Alternatively, indium oxide (IWZO) containing tungsten oxide and zinc oxide can be formed by sputtering a target containing 0.5 wt% to 5 wt% tungsten oxide and 0.1 wt% to 1 wt% zinc oxide. Additionally, examples include nitrides of gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or metallic materials (e.g., titanium nitride). Graphene can also be used. Note that while materials with high work functions and typically used to form anodes are mentioned here, in one aspect of the invention, a composite material comprising an organic compound with hole transport properties and a substance exhibiting electron accepting properties to that organic compound is used as the hole injection layer 111, thus eliminating the need to consider the work function when selecting electrode materials.

[0148] In this embodiment, the following two structures will be described as the stacked structure of EL layer 103: (e.g.) Figure 1A1 , Figure 1A2 As shown, the structure includes a hole injection layer 111, a first hole transport layer 112-1, a second hole transport layer 112-2, a light-emitting layer 113, an electron transport layer 114 (first electron transport layer 114-1, second electron transport layer 114-2), and an electron injection layer 115; Figure 1B As shown, a structure is adopted in which a charge generation layer 116 is used instead of an electron injection layer 115. The materials constituting each layer are shown in detail below.

[0149] Since the hole injection layer 111, the hole transport layer 112 (first hole transport layer 112-1, second hole transport layer 112-2), the light emission layer 113, and the electron transport layer 114 (first electron transport layer 114-1, second electron transport layer 114-2) have been described in detail in Embodiment 1, repeated descriptions are omitted. Refer to the description in Embodiment 1.

[0150] An electron injection layer 115, formed of an alkali metal, alkaline earth metal, or compound thereof, such as lithium fluoride (LiF), cesium fluoride (CsF), or calcium fluoride (CaF2), can be provided between the electron transport layer 114 and the cathode 102. The electron injection layer 115 can be a layer or electron compound in which an alkali metal, alkaline earth metal, or compound thereof is contained within a layer made of a substance with electron transport properties. Examples of electron compounds include, for instance, substances that add electrons at a high concentration to a mixed oxide of calcium and aluminum.

[0151] Alternatively, a charge generation layer 116 can be provided between the electron transport layer 114 and the cathode 102, instead of the electron injection layer 115. Figure 1B The charge generation layer 116 is a layer that, by applying a potential, can inject holes into the layer in contact with the cathode side of the layer and inject electrons into the layer in contact with the anode side of the layer. The charge generation layer 116 includes at least a P-type layer 117. The P-type layer 117 is preferably formed using the composite material that constitutes the hole injection layer 111 described above. Alternatively, the P-type layer 117 can also be formed by laminating a film containing the electron-receiving material and a film containing a hole transport material as the constituent material of the composite material. By applying a potential to the P-type layer 117, electrons and holes are injected into the electron transport layer 114 and the cathode 102, which serves as the cathode, respectively, causing the light-emitting device to operate.

[0152] In addition to the P-type layer 117, the charge generation layer 116 preferably includes one or both of the electron relay layer 118 and the electron injection buffer layer 119.

[0153] The electron relay layer 118 contains at least an electron transport material and is capable of preventing the interaction between the electron injection buffer layer 119 and the p-type layer 117, while facilitating electron transfer. Preferably, the LUMO energy level of the electron transport material contained in the electron relay layer 118 is set between the LUMO energy level of the electron receiving material in the p-type layer 117 and the LUMO energy level of the material contained in the layer in the electron transport layer 114 that contacts the charge generation layer 116. Specifically, the LUMO energy level of the electron transport material in the electron relay layer 118 is preferably -5.0 eV or higher, more preferably -5.0 eV or higher and -3.0 eV or lower. Furthermore, phthalocyanine materials or metal complexes having metal-oxygen bonds and aromatic ligands are preferably used as the electron transport material in the electron relay layer 118.

[0154] The electron injection buffer layer 119 can use alkali metals, alkaline earth metals, rare earth metals and their compounds (alkali metal compounds (including oxides such as lithium oxide, halides, carbonates such as lithium carbonate or cesium carbonate), alkaline earth metal compounds (including oxides, halides, carbonates) or rare earth metal compounds (including oxides, halides, carbonates)) and other materials with high electron injection properties.

[0155] Furthermore, when the electron injection buffer layer 119 contains both electron transport and electron donor materials, the electron donor materials can be alkali metals, alkaline earth metals, rare earth metals, and compounds of these materials (alkali metal compounds (including oxides, halides, and carbonates such as lithium oxide or cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)). Organic compounds such as tetrathianaphthacene (TTN), nickel-cadmium, and decamethylnickel-cadmium can also be used. Additionally, the electron transport material can be formed using the same material described above for the electron transport layer 114.

[0156] As the material forming the cathode 102, metals, alloys, conductive compounds, and mixtures thereof with low work functions (specifically below 3.8 eV) can be used. Specific examples of such cathode materials include alkali metals such as lithium (Li) or cesium (Cs), elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), or strontium (Sr), alloys containing them (MgAg, AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing them. However, by providing an electron injection layer between the cathode 102 and the electron transport layer, various conductive materials such as Al, Ag, ITO, and indium oxide-tin oxide containing silicon or silicon oxide can be used as the cathode 102 regardless of the work function. These conductive materials can be formed by dry methods such as vacuum evaporation and sputtering, inkjet printing, spin coating, etc. Furthermore, the electrode can be formed by wet methods such as sol-gel or by wet methods using a paste of metallic materials.

[0157] Furthermore, various methods can be used to form the EL layer 103, whether dry or wet. For example, vacuum evaporation, gravure printing, photogravure printing, screen printing, inkjet printing, or spin coating can also be used.

[0158] Alternatively, the electrodes or layers described above can be formed by using different film-forming methods.

[0159] Note that the structure of the layer disposed between the anode 101 and the cathode 102 is not limited to the structure described above. However, it is preferable to adopt a structure in which a light-emitting region for hole-electron recombination is disposed in a portion far from the anode 101 and the cathode 102, so as to suppress quenching that occurs due to the proximity of the light-emitting region to the metal used for the electrode or carrier injection layer.

[0160] In addition, in order to suppress energy transfer from excitons generated in the light-emitting layer, the carrier transport layer, such as the hole transport layer and electron transport layer in contact with the light-emitting layer 113, especially the carrier transport layer near the recombination region in the light-emitting layer 113, is preferably made of a material having a band gap larger than that of the light-emitting material constituting the light-emitting layer or the light-emitting material contained in the light-emitting layer.

[0161] Next, refer to Figure 1C This describes a light-emitting device (hereinafter also referred to as a stacked element or series element) with a structure having multiple light-emitting units stacked together. This light-emitting device has multiple light-emitting units between the anode and cathode. Each light-emitting unit has a... Figure 1A1 or Figure 1A2 The structure is roughly the same as that of EL layer 103 shown. That is to say, it can be said that... Figure 1C The light-emitting device shown is a light-emitting device with multiple light-emitting units, while Figure 1A1 , Figure 1A2 , Figure 1B The light-emitting device shown is a light-emitting device with one light-emitting unit.

[0162] exist Figure 1C In this structure, a first light-emitting unit 511 and a second light-emitting unit 512 are stacked between the anode 501 and the cathode 502, and a charge-generating layer 513 is disposed between the first light-emitting unit 511 and the second light-emitting unit 512. The anode 501 and the cathode 502 respectively correspond to... Figure 1A1 The anode 101 and cathode 102 are in the middle, and can be applied to... Figure 1A1 The same material is used for the description. Furthermore, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same structure or different structures.

[0163] The charge generation layer 513 has the function of injecting electrons into one light-emitting unit and holes into another light-emitting unit when a voltage is applied to the anode 501 and the cathode 502. That is to say, in Figure 1C In the case where a voltage is applied such that the potential of the anode is higher than that of the cathode, the charge generation layer 513 can simply be a layer that injects electrons into the first light-emitting unit 511 and holes into the second light-emitting unit 512.

[0164] The charge generation layer 513 preferably has the same as Figure 1BThe charge generation layer 116 shown has the same structure. Because the composite material of organic compound and metal oxide has good carrier injection and carrier transport properties, low voltage drive and low current drive can be achieved. Note that when the surface of the anode side of the light-emitting unit is in contact with the charge generation layer 513, the charge generation layer 513 can function as the hole injection layer of the light-emitting unit, so the hole injection layer may not be provided in the light-emitting unit.

[0165] In addition, when an electron injection buffer layer 119 is provided in the charge generation layer 513, since the electron injection buffer layer 119 has the function of an electron injection layer in the light-emitting unit on the anode side, it is not necessary to provide an electron injection layer in the light-emitting unit on the anode side.

[0166] Although Figure 1C The description includes a light-emitting device with two light-emitting units, but similarly, light-emitting devices with three or more light-emitting units stacked can be applied. As in the light-emitting device according to this embodiment, by separating and arranging multiple light-emitting units between a pair of electrodes using a charge-generating layer 513, the device can achieve high brightness emission while maintaining low current density and can achieve a long lifespan. Furthermore, a light-emitting device capable of low-voltage driving and low power consumption can be realized.

[0167] Furthermore, by making each light-emitting unit emit a different color, the desired color of light emission can be obtained from the entire light-emitting device. For example, by obtaining red and green light emission colors from the first light-emitting unit and blue light emission color from the second light-emitting unit in a light-emitting device with two light-emitting units, a light-emitting device that emits white light throughout the entire device can be obtained. Additionally, as a structure for a light-emitting device with three or more stacked light-emitting units, for example, a series-connected device can be used where the first light-emitting unit includes a first blue light-emitting layer, the second light-emitting unit includes a yellow or yellow-green light-emitting layer and a red light-emitting layer, and the third light-emitting unit includes a second blue light-emitting layer. This series-connected device, like the aforementioned light-emitting device, can also produce white light emission.

[0168] Furthermore, the aforementioned EL layer 103, first light-emitting unit 511, second light-emitting unit 512, charge-generating layer, and electrodes can be formed using methods such as vapor deposition (including vacuum vapor deposition), droplet jetting (also known as inkjet printing), coating, and gravure printing. Additionally, they may contain low-molecular-weight materials, medium-molecular-weight materials (including oligomers and dendritic polymers), or high-molecular-weight materials.

[0169] Implementation Method 3

[0170] In this embodiment, a light-emitting device using the light-emitting devices shown in Embodiment 1 and Embodiment 2 will be described.

[0171] In this embodiment, refer to Figure 4A and Figure 4B A light-emitting device manufactured using the light-emitting devices shown in Embodiments 1 and 2 will be described. Note that... Figure 4A It is a top view showing the light-emitting device, and Figure 4B It is along Figure 4A The diagram shows a cross-sectional view of lines AB and CD cut off. This light-emitting device, as a unit for controlling the light emission of the light-emitting device, includes a driving circuit section (source line driving circuit) 601 (indicated by dashed lines), a pixel section 602, and a driving circuit section (gate line driving circuit) 603. Additionally, reference numeral 604 is a sealing substrate, reference numeral 605 is a sealing material, and the inner side surrounded by the sealing material 605 is a space 607.

[0172] Note that the guide wiring 608 is used to transmit signals input to the source line drive circuit 601 and the gate line drive circuit 603, and to receive video signals, clock signals, start signals, reset signals, etc., from the FPC (flexible printed circuit) 609, which serves as an external input terminal. Note that although only the FPC is shown here, it can also be mounted with a printed circuit board (PWB). The light-emitting device described in this specification includes not only the main body of the light-emitting device but also the light-emitting device mounted with an FPC or PWB.

[0173] Below, refer to Figure 4B Explanation of the cross-sectional structure. Although a driving circuit section and a pixel section are formed on the element substrate 610, only one pixel of the source line driving circuit 601 and pixel section 602 is shown here.

[0174] In addition to substrates made of glass, quartz, organic resin, metal, alloy, semiconductor, etc., plastic substrates made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester or acrylic resin, etc., can be used to manufacture the component substrate 610.

[0175] There are no particular restrictions on the structure of the transistors used in the pixel or driving circuitry. For example, de-interleaved or interleaved transistors can be used. Additionally, top-gate or bottom-gate transistors can also be used. There are no particular restrictions on the semiconductor materials used for the transistors; for example, silicon, germanium, silicon carbide, gallium nitride, etc., can be used. Alternatively, oxide semiconductors containing at least one of indium, gallium, and zinc, such as In-Ga-Zn metal oxides, can be used.

[0176] There are no particular restrictions on the crystallinity of the semiconductor material used in transistors; amorphous semiconductors or crystalline semiconductors (microcrystalline semiconductors, polycrystalline semiconductors, single-crystal semiconductors, or semiconductors with a portion of crystalline regions) can be used. When using crystalline semiconductors, the degradation of transistor characteristics can be suppressed, so they are preferred.

[0177] Here, oxide semiconductors are preferably used in semiconductor devices such as transistors disposed in the aforementioned pixels or driving circuits, and in transistors for touch sensors, etc., which will be described later. Oxide semiconductors with a wider bandgap than silicon are particularly preferred. By using oxide semiconductors with a wider bandgap than silicon, the off-state current of the transistors can be reduced.

[0178] The aforementioned oxide semiconductor preferably contains at least indium (In) or zinc (Zn). Furthermore, the aforementioned oxide semiconductor is more preferably an oxide semiconductor containing oxides represented by In-M-Zn type oxides (M being metals such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0179] Here, an oxide semiconductor that can be used in one aspect of the present invention will be described.

[0180] Oxide semiconductors are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include CAAC-OS (c-axis aligned crystalline oxide semiconductor), polycrystalline oxide semiconductors, nc-OS (nano crystalline oxide semiconductor), a-like OS (amorphous-like oxide semiconductor), and amorphous oxide semiconductors.

[0181] CAAC-OS exhibits c-axis orientation, with multiple nanocrystals linked along the ab-plane direction, resulting in a distorted crystal structure. Distortion refers to the change in the orientation of the lattice arrangement between regions with consistent lattice alignment and other regions with consistent lattice alignment within the linked nanocrystal region.

[0182] Nanocrystals are primarily hexagonal, but not limited to regular hexagons; sometimes they are non-regular hexagonal. Furthermore, nanocrystals sometimes exhibit pentagonal or heptagonal lattice arrangements during distortion. Additionally, in CAAC-OS, no distinct grain boundaries (also known as grain boundaries) are observed even near the distortion. That is, it can be seen that lattice distortion suppresses grain boundary formation. This is because CAAC-OS can contain distortion due to the low density of oxygen atoms along the ab plane or changes in interatomic bonding distance caused by the substitution of metal elements.

[0183] CAAC-OS tends to have a layered crystalline structure (also called a layered structure), in which layers containing indium and oxygen (hereinafter referred to as In layers) and layers containing elements M, zinc, and oxygen (hereinafter referred to as (M, Zn) layers) are stacked. Furthermore, indium and element M can substitute for each other; when element M in a (M, Zn) layer is replaced by indium, the layer can also be represented as an (In, M, Zn) layer. Similarly, when indium in an In layer is replaced by element M, the layer can also be represented as an (In, M) layer.

[0184] CAAC-OS is a highly crystalline oxide semiconductor. On the other hand, distinct grain boundaries are not easily observed in CAAC-OS, thus reducing the likelihood of decreased electron mobility due to grain boundaries. Furthermore, the crystallinity of oxide semiconductors can sometimes decrease due to the introduction of impurities or the formation of defects; therefore, CAAC-OS can be considered a semiconductor with high crystallinity due to impurities or defects (oxygen vacancies, also known as V0 vacancies). O Oxide semiconductors with low oxygen vacancy (CAAC-OS) exhibit stable physical properties. Therefore, oxide semiconductors containing CAAC-OS possess high heat resistance and high reliability.

[0185] In nc-OS, the atomic arrangement in tiny regions (e.g., regions above 1 nm and below 10 nm, particularly above 1 nm and below 3 nm) exhibits periodicity. Furthermore, no regularity in crystal orientation is observed between different nanocrystals in nc-OS. Therefore, no orientation is observed in the overall film. Thus, sometimes nc-OS is indistinguishable from a-like OS or amorphous oxide semiconductors in certain analytical methods.

[0186] Furthermore, indium gallium zinc oxide (IGZO), a type of oxide semiconductor containing indium, gallium, and zinc, sometimes exhibits a stable structure when composed of the aforementioned nanocrystals. In particular, IGZO tends to be difficult to grow in the atmosphere, so it is sometimes structurally more stable when formed from small crystals (e.g., the aforementioned nanocrystals) than when formed from large crystals (here, crystals a few millimeters or a few centimeters).

[0187] a-like OS is an oxide semiconductor with a structure intermediate between nc-OS and amorphous oxide semiconductors. A-like OS contains voids or low-density regions. In other words, a-like OS has lower crystallinity than nc-OS and CAAC-OS.

[0188] Oxide semiconductors possess various structures and properties. One embodiment of the present invention may also include two or more of amorphous oxide semiconductors, polycrystalline oxide semiconductors, a-like OS, nc-OS, and CAAC-OS.

[0189] In addition to the aforementioned oxide semiconductors, CAC (Cloud-Aligned Composite)-OS can also be used.

[0190] Furthermore, CAC-OS exhibits conductivity in one part of the material and insulation in another, thus functioning as a semiconductor as a whole. In addition, when CAC-OS is used as a semiconductor layer in a transistor, conductivity allows electrons (or holes) to flow, while insulation prevents them from flowing. Through the complementary interaction of conductivity and insulation, CAC-OS can perform switching (on / off) functions. By separating these functions within CAC-OS, each function can be maximized.

[0191] Furthermore, CAC-OS possesses both conductive and insulating regions. The conductive regions exhibit the aforementioned conductivity, and the insulating regions exhibit the aforementioned insulation. Moreover, in the material, the conductive and insulating regions are sometimes separated at the nanoparticle level. Additionally, the conductive and insulating regions are sometimes unevenly distributed within the material. Furthermore, conductive regions with blurred edges and cloud-like connections are sometimes observed.

[0192] Furthermore, in CAC-OS, conductive and insulating regions are sometimes dispersed in the material with a size of 0.5 nm or more and 10 nm or less, preferably 0.5 nm or more and 3 nm or less.

[0193] Furthermore, the CAC-OS is composed of components with different band gaps. For example, the CAC-OS is composed of a component with a wide gap originating from an insulating region and a component with a narrow gap originating from a conductive region. In this structure, when charge carriers flow through, they mainly flow in the component with the narrow gap. Moreover, the component with the narrow gap complements the component with the wide gap, and charge carriers flow in the component with the wide gap in conjunction with the component with the narrow gap. Therefore, when the above-mentioned CAC-OS is used in the channel formation region of a transistor, a high current driving force, i.e., a large on-state current and a high field-effect mobility, can be obtained in the transistor's on-state.

[0194] In other words, CAC-OS can also be referred to as a matrix composite or a metal matrix composite.

[0195] By using the aforementioned oxide semiconductor material as a semiconductor layer, highly reliable transistors with suppressed variations in electrical characteristics can be achieved.

[0196] Furthermore, because the transistors with the aforementioned semiconductor layer have low off-state currents, the charge stored in the capacitors through the transistors can be maintained for extended periods. By using such transistors in pixels, the driving circuit can be stopped while maintaining the grayscale of the image displayed in each display area. As a result, electronic devices with extremely low power consumption can be realized.

[0197] To stabilize transistor characteristics, a base film is preferably provided. As the base film, inorganic insulating films such as silicon oxide, silicon nitride, silicon oxynitride, and silicon oxynitride can be used and fabricated as a single layer or in stacks. The base film can be formed by sputtering, CVD (Chemical Vapor Deposition) methods (plasma CVD, thermal CVD, MOCVD (Metal Organic Chemical Vapor Deposition), etc.), ALD (Atomic Layer Deposition), coating, printing, etc. Note that a base film may be omitted if not required.

[0198] Note that FET623 represents one of the transistors formed in the drive circuit section 601. Alternatively, the drive circuit can be formed using various CMOS, PMOS, or NMOS circuits. Furthermore, although this embodiment shows an integrated driver type with the drive circuit formed on the substrate, this structure is not mandatory; the drive circuit can also be formed externally instead of on the substrate.

[0199] In addition, the pixel unit 602 is formed by multiple pixels, each of which includes a switching FET 611, a current control FET 612, and an anode 613 electrically connected to the drain of the current control FET 612. However, it is not limited to this and a pixel unit combining three or more FETs and capacitors can also be used.

[0200] Note that an insulating material 614 is formed to cover the end of the anode 613. Positive photosensitive acrylic acid can be used to form the insulating material 614.

[0201] Furthermore, the upper or lower end of the insulator 614 is formed as a curved surface to obtain good coverage for the subsequently formed EL layer, etc. For example, when using a positive photosensitive acrylic resin as the material of the insulator 614, it is preferable that only the upper end of the insulator 614 includes a curved surface with a radius of curvature (0.2 μm to 3 μm). Additionally, either a negative photosensitive resin or a positive photosensitive resin can be used as the insulator 614.

[0202] An EL layer 616 and a cathode 617 are formed on the anode 613. Here, a material with a high work function is preferably used as the material for the anode 613. For example, in addition to single-layer films such as ITO films, indium tin oxide films containing silicon, indium oxide films containing 2 wt% to 20 wt% zinc oxide, titanium nitride films, chromium films, tungsten films, Zn films, and Pt films, multilayer films composed of titanium nitride films and films with aluminum as the main component, as well as three-layer structures composed of titanium nitride films, films with aluminum as the main component, and titanium nitride films, can also be used. Note that if a multilayer structure is used here, good ohmic contact can be obtained due to the low resistance of the wiring, and it can also be used as an anode.

[0203] Furthermore, the EL layer 616 is formed using various methods such as vapor deposition using a vapor deposition mask, inkjet printing, and spin coating. The EL layer 616 includes the structures shown in Embodiments 1 and 2. Additionally, low-molecular-weight compounds or high-molecular-weight compounds (including oligomers and dendritic polymers) can be used as other materials constituting the EL layer 616.

[0204] Furthermore, as the material used for the cathode 617 formed on the EL layer 616, it is preferable to use a material with a low work function (Al, Mg, Li, Ca, or their alloys or compounds (MgAg, MgIn, AlLi, etc.)). Note that when light generated in the EL layer 616 is transmitted through the cathode 617, it is preferable to use a stack of a thinned metal film and a transparent conductive film (ITO, indium oxide containing 2 wt% to 20 wt% zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the cathode 617.

[0205] Furthermore, the light-emitting device is formed of an anode 613, an EL layer 616, and a cathode 617. This light-emitting device is the same as that shown in Embodiments 1 and 2. Additionally, the pixel portion is composed of multiple light-emitting devices, and the light-emitting device of this embodiment may also include both the light-emitting devices shown in Embodiments 1 and 2 and light-emitting devices with other structures.

[0206] Furthermore, by attaching the sealing substrate 604 to the element substrate 610 using a sealing material 605, the light-emitting device 618 is disposed within a space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filler; an inert gas (such as nitrogen or argon) or a sealant can be used as the filler. Forming a recess in the sealing substrate and placing a desiccant therein is preferred as it helps to suppress deterioration caused by moisture.

[0207] Furthermore, epoxy resin or glass powder is preferably used as the sealing material 605. These materials are preferably those that prevent water or oxygen from permeating as much as possible. In addition to glass or quartz substrates, plastic substrates made of FRP (fiber reinforced plastics), PVF (polyvinyl fluoride), polyester, acrylic resin, etc., can also be used as the material for the sealing substrate 604.

[0208] Although Figure 4A and Figure 4B Although not shown, a protective film can also be provided on the cathode. The protective film can be formed of an organic resin film or an inorganic insulating film. Alternatively, the protective film can be formed to cover the exposed portion of the sealing material 605. Furthermore, the protective film can be provided to cover the surface and side surfaces of a pair of substrates, the exposed sides of the sealing layer, the insulating layer, etc.

[0209] As a protective membrane, materials that are not easily permeable to water and other impurities can be used. Therefore, it is possible to effectively prevent water and other impurities from diffusing from the outside into the inside.

[0210] Materials constituting the protective film can include oxides, nitrides, fluorides, sulfides, ternary compounds, metals, or polymers. 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, nitrides containing titanium and aluminum, oxides containing titanium and aluminum, oxides containing aluminum and zinc, sulfides containing manganese and zinc, sulfides containing cerium and strontium, oxides containing erbium and aluminum, and oxides containing yttrium and zirconium.

[0211] The protective film is preferably formed using a film-forming method with good step coverage. One such method is atomic layer deposition (ALD). Materials that can be formed using ALD are preferably used for the protective film. ALD can form a dense protective film with reduced or uniform thickness, minimizing defects such as cracks or pinholes. Furthermore, it can reduce damage to the processed parts during the formation of the protective film.

[0212] For example, the ALD method can be used to form a uniform protective film with few defects on the surface with complex uneven shapes or on the top, sides and back of a touch screen.

[0213] As described above, a light-emitting device manufactured using the light-emitting devices shown in Embodiment 1 and Embodiment 2 can be obtained.

[0214] Because the light-emitting device in this embodiment uses the light-emitting devices shown in Embodiments 1 and 2, a light-emitting device with excellent characteristics can be obtained. Specifically, the light-emitting devices shown in Embodiments 1 and 2 are long-life light-emitting devices, thereby enabling a light-emitting device with good reliability. In addition, the light-emitting device using the light-emitting devices shown in Embodiments 1 and 2 has good luminous efficiency, thereby enabling a low-power light-emitting device.

[0215] Figure 5A and Figure 5B An example of a light-emitting device that achieves full-color illumination by setting a color layer (color filter) or the like to form a light-emitting device that emits white light is shown. Figure 5A The diagram shows a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, and 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a driving circuit portion 1041, an anode 1024W, 1024R, 1024G, and 1024B for a light-emitting device, a separator 1025, an EL layer 1028, a cathode 1029 for a light-emitting device, a sealing substrate 1031, and a sealing material 1032.

[0216] In addition, Figure 5A In this process, colored layers (red colored layer 1034R, green colored layer 1034G, and blue colored layer 1034B) are disposed on a transparent substrate 1033. Additionally, a black matrix 1035 may be disposed. The transparent substrate 1033, on which the colored layers and black matrix are disposed, is aligned and fixed to the substrate 1001. Furthermore, the colored layers and black matrix 1035 are covered by a protective layer 1036. Figure 5AIt shows a light-emitting layer that transmits light to the outside without passing through the color layer and a light-emitting layer that transmits light to the outside through the color layers of each color. The light that does not pass through the color layer becomes white light and the light that passes through the color layer becomes red light, green light, and blue light, so that an image can be presented with pixels of four colors.

[0217] Figure 5B An example is shown in which colored layers (red colored layer 1034R, green colored layer 1034G, and blue colored layer 1034B) are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. As described above, the colored layers may also be disposed between the substrate 1001 and the sealing substrate 1031.

[0218] In addition, although the light-emitting device described above is a light-emitting device with a structure that emits light from the side of the substrate 1001 on which the FET is formed (bottom-emitting type), a light-emitting device with a structure that emits light from the side of the sealing substrate 1031 (top-emitting type) may also be used. Figure 6 A cross-sectional view of the top-emitting light-emitting device is shown. In this case, the substrate 1001 can be a light-blocking substrate. The processes up to fabricating the connection electrode for connecting the FET to the anode of the light-emitting device are performed in the same manner as for the bottom-emitting light-emitting device. Then, a third interlayer insulating film 1037 is formed to cover the electrode 1022. This insulating film may also have a planarization function. The third interlayer insulating film 1037 can be formed using the same material as the second interlayer insulating film or other known materials.

[0219] Although the anodes 1024W, 1024R, 1024G, and 1024B in this light-emitting device are all anodes, they can also be formed as cathodes. Furthermore, when using... Figure 6 In the case of a top-emitting light-emitting device as shown, the anode is preferably a reflective electrode. The structure of the EL layer 1028 adopts the structure of the EL layer 103 shown in Embodiments 1 and 2, and adopts a device structure capable of obtaining white light emission.

[0220] In Adoption Figure 6In the case of the top-emitting structure shown, sealing can be achieved using a sealing substrate 1031 provided with color layers (red color layer 1034R, green color layer 1034G, and blue color layer 1034B). The sealing substrate 1031 may also have a black matrix 1035 located between pixels. The color layers (red color layer 1034R, green color layer 1034G, and blue color layer 1034B) and the black matrix may also be covered by a protective layer. Furthermore, a light-transmitting substrate is used as the sealing substrate 1031. Although an example of full-color display using four colors—red, green, blue, and white—is shown here, it is not limited to this; full-color display using four colors—red, yellow, green, and blue, or three colors—red, green, and blue, is also possible.

[0221] In top-emitting light-emitting devices, a microcavity structure is preferably applicable. By using a reflective electrode as the anode and a transflective electrode as the cathode, a light-emitting device with a microcavity structure can be obtained. At least an EL layer is present between the reflective electrode and the transflective electrode, and at least a light-emitting layer that forms the light-emitting region is also present.

[0222] Note that the reflective electrode has a visible light reflectance of 40% to 100%, preferably 70% to 100%, and a resistivity of 1 × 10⁻⁶. -2 A film with a resistivity of less than Ωcm. Furthermore, the transmissive electrode has a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1×10⁻⁶. -2 Membranes with a diameter of less than Ωcm.

[0223] Light emitted from the light-emitting layer contained in the EL layer is reflected by the reflective electrode and the transflective electrode, and resonates.

[0224] In this light-emitting device, the optical path between the reflective electrode and the transflective electrode can be changed by altering the thickness of the transparent conductive film, the aforementioned composite material, or the carrier transport material. This allows for the enhancement of resonant wavelengths of light between the reflective electrode and the transflective electrode while attenuating non-resonant wavelengths of light.

[0225] Note that the light reflected back by the reflective electrode (the first reflected light) will cause significant interference to the light directly incident from the light-emitting layer to the transmissive electrode (the first incident light). Therefore, it is preferable to adjust the optical path between the reflective electrode and the light-emitting layer to (2n-1)λ / 4 (note that n is a natural number greater than 1, and λ is the wavelength of the light to be amplified). By adjusting this optical path, the first reflected light can be made to be in phase with the first incident light, thereby further amplifying the light emitted from the light-emitting layer.

[0226] Furthermore, in the above structure, the EL layer may contain multiple light-emitting layers or only one light-emitting layer. For example, the following structure can also be adopted: combining the above-described series-type light-emitting device structure, multiple EL layers are disposed in a single light-emitting device with a charge-generating layer sandwiched between them, and one or more light-emitting layers are formed in each EL layer.

[0227] By employing a microcavity structure, the luminescence intensity in the front direction at a specified wavelength can be enhanced, thereby achieving low power consumption. Note that in the case of a light-emitting device that displays an image using sub-pixels of four colors—red, yellow, green, and blue—the increased brightness due to yellow emission can be obtained, and microcavity structures suitable for the wavelengths of each color can be used in all sub-pixels, thus enabling a light-emitting device with excellent characteristics.

[0228] Because the light-emitting device in this embodiment uses the light-emitting devices shown in Embodiments 1 and 2, a light-emitting device with excellent characteristics can be obtained. Specifically, the light-emitting devices shown in Embodiments 1 and 2 are long-life light-emitting devices, thereby enabling a light-emitting device with good reliability. In addition, the light-emitting device using the light-emitting devices shown in Embodiments 1 and 2 has good luminous efficiency, thereby enabling a low-power light-emitting device.

[0229] Although active matrix light-emitting devices have been described here, passive matrix light-emitting devices will be described below. Figure 7A and Figure 7B A passive matrix-type light-emitting device manufactured using the present invention is shown. Note that... Figure 7A It is a perspective view showing the light-emitting device, and Figure 7B It is along Figure 7A The cross-sectional view obtained by cutting along the XY line. Figure 7A and Figure 7B In this embodiment, an EL layer 955 is disposed between electrodes 952 and 956 on substrate 951. The end of electrode 952 is covered by an insulating layer 953. An isolation layer 954 is disposed on the insulating layer 953. The sidewalls of the isolation layer 954 have an inclination such that the gap between the two sidewalls is narrower the closer they are to the substrate surface. In other words, the cross-section of the isolation layer 954 in the short side direction is trapezoidal, and the bottom side (the side facing the same direction as the surface direction of the insulating layer 953 and in contact with the insulating layer 953) is shorter than the top side (the side facing the same direction as the surface direction of the insulating layer 953 and not in contact with the insulating layer 953). Thus, by providing the isolation layer 954, malfunctions of the light-emitting device caused by static electricity, etc., can be prevented. In addition, in the passive matrix type light-emitting device, by using the light-emitting devices shown in Embodiments 1 and 2, a light-emitting device with good reliability or a light-emitting device with low power consumption can also be obtained.

[0230] The light-emitting device described above can control each of a plurality of tiny light-emitting devices arranged in a matrix, so the light-emitting device is suitable for display devices that display images.

[0231] Furthermore, this embodiment can be freely combined with other embodiments.

[0232] Implementation Method 4

[0233] In this embodiment, refer to Figure 8A and Figure 8B An example of using the light-emitting device shown in Embodiment 1 and Embodiment 2 in a lighting device will be described. Figure 8B This is a top view of the lighting fixture. Figure 8A It is along Figure 8B The cross-sectional view of the line ef cut off.

[0234] In the lighting device of this embodiment, an anode 401 is formed on a light-transmitting substrate 400, which serves as a support. The anode 401 corresponds to the anode 101 in Embodiment 2. When light is extracted from the anode 401 side, the anode 401 is formed using a light-transmitting material.

[0235] A pad 412 for supplying voltage to the cathode 404 is formed on the substrate 400.

[0236] An EL layer 403 is formed on the anode 401. The EL layer 403 corresponds to the structure of the EL layer 103 in Embodiment 1 and Embodiment 2, or the structure of the light-emitting unit 511, the light-emitting unit 512, and the charge-generating layer 513, etc. Note that their structures are described in the respective descriptions.

[0237] A cathode 404 is formed by covering an EL layer 403. The cathode 404 corresponds to the cathode 102 in Embodiment 2. The cathode 404 is formed using a material with high reflectivity when light is extracted from the anode 401 side. Voltage is supplied to the cathode 404 by connecting it to a pad 412.

[0238] As described above, the lighting device shown in this embodiment includes a light-emitting device comprising an anode 401, an EL layer 403, and a cathode 404. Since this light-emitting device is a high-efficiency light-emitting device, the lighting device of this embodiment can provide a low-power lighting device.

[0239] The lighting device is manufactured by sealing the substrate 400, on which the light-emitting device with the above structure is formed, and the sealing substrate 407, using sealing materials 405 and 406 to fix and seal them. Only one of the sealing materials 405 and 406 may be used. Alternatively, the inner sealing material 406 (in...) Figure 8B(Not shown in the diagram) When mixed with a desiccant, it can absorb moisture from space 408, thereby improving reliability.

[0240] Furthermore, by providing a portion of the pad 412 and the anode 401 extending to the exterior of the sealing materials 405 and 406, they can be used as external input terminals. Additionally, an IC chip 420, on which a converter or similar device is mounted, can also be provided on the external input terminal.

[0241] In summary, the lighting device described in this embodiment uses the light-emitting devices shown in Embodiments 1 and 2 in the EL element, thus achieving a light-emitting device with high reliability. Furthermore, a low-power light-emitting device can be achieved.

[0242] Implementation Method 5

[0243] In this embodiment, an example of an electronic device that includes, in part, the light-emitting devices shown in Embodiments 1 and 2 will be described. The light-emitting devices shown in Embodiments 1 and 2 are light-emitting devices with good lifespan and high reliability. As a result, the electronic device described in this embodiment can realize an electronic device including a light-emitting part with high reliability.

[0244] Examples of electronic devices employing the aforementioned light-emitting devices include television sets (also called televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game consoles, portable information terminals, sound reproduction devices, and large game machines such as pinball machines. Specific examples of these electronic devices are shown below.

[0245] Figure 9A An example of a television device is shown. In the television device, a display unit 7103 is assembled in a housing 7101. Furthermore, a structure in which the housing 7101 is supported by a bracket 7105 is shown here. Images can be displayed using the display unit 7103, and the light-emitting devices shown in Embodiments 1 and 2 are arranged in a matrix to form the display unit 7103.

[0246] The television device can be operated using the operation switch provided in the housing 7101 or the separately provided remote control 7110. Using the operation keys 7109 provided in the remote control 7110, channels and volume can be controlled, thereby controlling the image displayed on the display unit 7103. Alternatively, a structure can be adopted in which a display unit 7107 for displaying information output from the remote control 7110 is provided in the remote control 7110.

[0247] Furthermore, the television device incorporates a receiver, modem, and other components. It can receive general television broadcasts via the receiver. Moreover, by connecting to a wired or wireless communication network via the modem, it can perform one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers, etc.) information communication.

[0248] Figure 9B1 The computer shown includes a main body 7201, a casing 7202, a display unit 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, etc. Furthermore, this computer is manufactured by arranging the light-emitting devices shown in Embodiments 1 and 2 in a matrix and using them in the display unit 7203. Figure 9B1 The computer in the middle can also be like Figure 9B2 As shown in the diagram. Figure 9B2 The computer shown has a second display unit 7210 replacing the keyboard 7204 and pointing device 7206. The second display unit 7210 is a touchscreen, allowing input to be performed by using a finger or a special stylus to operate the input display shown on the second display unit 7210. Furthermore, the second display unit 7210 can display not only the input display but also other images. Alternatively, the display unit 7203 can also be a touchscreen. Because the two screens are connected by a hinge, problems such as screen damage or breakage during storage or transport can be prevented.

[0249] Figure 9C An example of a portable terminal is shown. The mobile phone includes a display unit 7402, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc., all assembled in a housing 7401. Furthermore, the mobile phone includes a display unit 7402 manufactured by arranging the light-emitting devices shown in Embodiments 1 and 2 in a matrix configuration.

[0250] Figure 9C The portable terminal shown can also have a structure that allows information to be input using a touch display unit 7402 such as a finger. In this case, it is possible to make phone calls or compose emails using the touch display unit 7402 such as a finger.

[0251] The display unit 7402 has three main screen modes. The first is a display mode that primarily displays images, the second is an input mode that primarily inputs information such as text, and the third is a display-input mode that combines both display and input modes.

[0252] For example, when making a phone call or composing an email, the text displayed on the screen can be entered using a text input mode primarily used for inputting text on the display unit 7402. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display unit 7402.

[0253] In addition, by installing a detection device with sensors such as gyroscopes and accelerometers to detect tilt inside the portable terminal, the orientation (vertical or horizontal) of the portable terminal can be determined and the screen display of the display unit 7402 can be switched automatically.

[0254] Additionally, the screen mode can be switched by touching the display unit 7402 or by operating the operation button 7403 on the housing 7401. Furthermore, the screen mode can also be switched according to the type of image displayed on the display unit 7402. For example, when the image signal displayed on the display unit is moving image data, the screen mode is switched to display mode; when the image signal is text data, the screen mode is switched to input mode.

[0255] In addition, when it is known that there is no touch operation input on the display unit 7402 within a certain period of time by detecting the signal detected by the light sensor of the display unit 7402 in the input mode, the screen mode can also be switched from the input mode to the display mode.

[0256] The display unit 7402 can also be used as an image sensor. For example, by touching the display unit 7402 with the palm or fingers, palm prints, fingerprints, etc., can be captured for personal identification. In addition, by using a backlight that emits near-infrared light or a sensing light source that emits near-infrared light in the display unit, finger veins, palm veins, etc., can also be captured.

[0257] Furthermore, the structure shown in this embodiment can be used in appropriate combinations with the structures shown in Embodiments 1 to 4.

[0258] As described above, the light-emitting device equipped with the light-emitting device shown in Embodiments 1 and 2 has a very wide range of applications, and can be used in electronic devices in various fields. By using the light-emitting device shown in Embodiments 1 and 2, highly reliable electronic devices can be obtained.

[0259] Figure 10A This is a schematic diagram illustrating an example of a robotic vacuum cleaner.

[0260] The robotic vacuum cleaner 5100 includes a display 5101 on its top surface, multiple cameras 5102 on its sides, a brush 5103, and operation buttons 5104. Although not shown, the bottom of the robotic vacuum cleaner 5100 has tires and a suction inlet. Furthermore, the robotic vacuum cleaner 5100 includes various sensors such as infrared sensors, ultrasonic sensors, accelerometers, piezoelectric sensors, light sensors, and gyroscope sensors. Additionally, the robotic vacuum cleaner 5100 includes a wireless communication unit.

[0261] The 5100 robotic vacuum cleaner can walk automatically, and the 5120 can detect trash and suck it up from the suction port on the bottom.

[0262] In addition, the robotic vacuum cleaner 5100 analyzes the images captured by the camera 5102 to determine the presence or absence of obstacles such as walls, furniture, or steps. Furthermore, if it detects objects such as wiring that may get tangled in the brush 5103 through image analysis, it can stop the rotation of the brush 5103.

[0263] The display 5101 can show the remaining battery power and the amount of debris collected. The display 5101 can also show the robot vacuum cleaner's path. Additionally, the display 5101 can be a touch panel, displaying the operation buttons 5104.

[0264] The robotic vacuum cleaner 5100 can communicate with portable electronic devices 5140 such as smartphones. Images captured by the camera 5102 can be displayed on the portable electronic device 5140. Therefore, the owner of the robotic vacuum cleaner 5100 can know the condition of the room when leaving home. In addition, the content displayed on the monitor 5101 can be checked using a portable electronic device such as a smartphone.

[0265] The light-emitting device of one aspect of the present invention can be used in the display 5101.

[0266] Figure 10B The robot 2100 shown includes a computing device 2110, an illuminance sensor 2101, a microphone 2102, an upper camera 2103, a speaker 2104, a display 2105, a lower camera 2106, an obstacle sensor 2107, and a movement mechanism 2108.

[0267] The microphone 2102 has the function of detecting the user's voice and ambient sounds. Additionally, the speaker 2104 has the function of emitting sound. The robot 2100 can use the microphone 2102 and speaker 2104 to communicate with the user.

[0268] The display 2105 has the function of displaying various information. The robot 2100 can display the information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. The display 2105 can be a detachable information terminal, which can be charged and send and receive data by setting it at a designated position on the robot 2100.

[0269] The upper camera 2103 and the lower camera 2106 are capable of capturing images of the surrounding environment of the robot 2100. Additionally, the obstacle sensor 2107 can detect the presence or absence of obstacles in front of the robot 2100 when it moves using the mobility mechanism 2108. The robot 2100 can use the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107 to perceive its surrounding environment and move safely. The light-emitting device of one embodiment of the present invention can be used in the display 2105.

[0270] Figure 10C This diagram illustrates an example of a goggle-type display. A goggle-type display may include, for example, a housing 5000, a display unit 5001, a speaker 5003, an LED light 5004, a connection terminal 5006, a sensor 5007 (which has the function of measuring factors such as force, displacement, position, velocity, acceleration, angular velocity, rotational speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, electricity, radiation, flow rate, humidity, tilt, vibration, odor, or infrared radiation), a microphone 5008, a display unit 5002, a support unit 5012, and headphones 5013, etc.

[0271] The light-emitting device of one aspect of the present invention can be used in display unit 5001 and display unit 5002.

[0272] Figure 11 An example is shown of using the light-emitting device shown in Embodiment 1 and Embodiment 2 as a table lamp as a lighting device. Figure 11 The table lamp shown includes a housing 2001 and a light source 2002, and uses the lighting device described in Embodiment 3 as the light source 2002.

[0273] Figure 12 An example is shown of using the light-emitting devices shown in Embodiments 1 and 2 in an indoor lighting device 3001. The light-emitting devices shown in Embodiments 1 and 2 are highly reliable, thus enabling the realization of a highly reliable lighting device. Furthermore, because the light-emitting devices shown in Embodiments 1 and 2 can be made in large areas, they can be used in large-area lighting devices. Additionally, because the light-emitting devices shown in Embodiments 1 and 2 are thin, it is possible to manufacture a thinner lighting device.

[0274] The light-emitting devices shown in Embodiments 1 and 2 can also be installed on the windshield or dashboard of a car. Figure 13 This illustrates one method of using the light-emitting devices shown in Embodiments 1 and 2 on a car windshield or dashboard. Display areas 5200 to 5203 are display areas provided using the light-emitting devices shown in Embodiments 1 and 2.

[0275] Display areas 5200 and 5201 are display devices mounted on the windshield of an automobile and equipped with the light-emitting devices shown in Embodiments 1 and 2. By using electrodes with light transmittance to manufacture the anode and cathode of the light-emitting devices shown in Embodiments 1 and 2, a so-called see-through display device that allows the view of the opposite side can be obtained. With a see-through display, even when mounted on the windshield of an automobile, the view is not obstructed. Furthermore, when using transistors or the like for driving the device, it is preferable to use transistors with light transmittance, such as organic transistors using organic semiconductor materials or transistors using oxide semiconductors.

[0276] Display area 5202 is a display device installed on the pillar portion, in which light-emitting devices as shown in Embodiments 1 and 2 are mounted. By displaying images from the imaging unit installed on the vehicle body on display area 5202, the view obstructed by the pillar can be supplemented. Similarly, display area 5203 on the dashboard portion, by displaying images from the imaging unit installed on the exterior of the vehicle, can supplement blind spots obstructed by the vehicle body, thereby improving safety. By displaying images to supplement unseen areas, safety can be confirmed more naturally and simply.

[0277] Display area 5203 can provide various information. Users can appropriately change the display content and layout. Additionally, this information can also be displayed on display areas 5200 to 5202. Furthermore, display areas 5200 to 5203 can also be used as lighting devices.

[0278] Figure 14A and Figure 14B A foldable portable information terminal 5150 is shown. The foldable portable information terminal 5150 includes a housing 5151, a display area 5152, and a bending portion 5153. Figure 14A Portable information terminal 5150 is shown in its unfolded state. Figure 14B The portable information terminal 5150 is shown in its folded state. Although the portable information terminal 5150 has a large display area 5152, it becomes smaller and more portable by folding it.

[0279] The display area 5152 can be folded in half by the bending portion 5153. The bending portion 5153 is composed of a telescopic member and a plurality of support members. When folding, the telescopic member is stretched, and the bending portion 5153 is folded in such a way that it has a radius of curvature of 2 mm or more, preferably 3 mm or more.

[0280] Alternatively, the display area 5152 can also be a touch panel (input / output device) equipped with a touch sensor (input device). A light-emitting device according to one aspect of the present invention can be used in the display area 5152.

[0281] also, Figures 15A to 15C A foldable portable information terminal 9310 is shown. Figure 15A Portable information terminal 9310 is shown in its unfolded state. Figure 15B A portable information terminal 9310 shows the intermediate state between an unfolded state and a folded state. Figure 15C The portable information terminal 9310 is shown in its folded state. The portable information terminal 9310 is highly portable in its folded state, and offers excellent visibility when unfolded due to its large, seamlessly integrated display area.

[0282] The display panel 9311 is supported by three housings 9315 connected by a hinge portion 9313. Note that the display panel 9311 can also be a touch panel (input / output device) equipped with a touch sensor (input device). Furthermore, by bending the display panel 9311 at the hinge portion 9313 between two housings 9315, the portable information terminal 9310 can be reversibly changed from an unfolded state to a folded state. A light-emitting device according to one aspect of the present invention can be used in the display panel 9311.

[0283] Example 1

[0284] In this embodiment, a method for manufacturing a light-emitting device 1 according to one aspect of the present invention and a comparative light-emitting device 1, as well as impedance spectroscopy measurement results, will be described. The structural formulas of the organic compounds used in the light-emitting device 1 and the comparative light-emitting device 1 are shown below.

[0285] [Chemical Formula 3]

[0286]

[0287] (Manufacturing method of light-emitting device 1)

[0288] First, indium tin oxide (ITSO) containing silicon oxide is formed on a glass substrate by sputtering to form the anode 101. Note that its thickness is 70 nm and the electrode area is 2 mm × 2 mm.

[0289] Next, as a pretreatment for forming light-emitting devices on the substrate, the substrate surface is washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0290] Then, the substrate is placed inside and depressurized to 10. -4The substrate is placed in a vacuum evaporation apparatus with a pressure of approximately Pa and is vacuum baked at 170°C for 30 minutes in the heating chamber of the apparatus, followed by cooling for approximately 30 minutes.

[0291] Next, the substrate with the anode 101 formed thereon is fixed on a substrate support provided in a vacuum evaporation apparatus with the anode 101 facing downwards. A hole injection layer 111 is formed on the anode 101 by a resistance heating evaporation method using N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviated as BBABnf) and ALD-MP001Q (Analysis Atelier Corporation, material serial number: 1S20180314) in a weight ratio of 1:0.1 (=BBABnf:ALD-MP001Q) and a thickness of 10 nm. Note that ALD-MP001Q is a receiving organic compound.

[0292] Next, BBABnf is deposited on the hole injection layer 111 as the first hole transport layer 112-1 with a thickness of 20 nm, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviated as PCzN2) represented by the above structural formula (ii) is deposited as the second hole transport layer 112-2 with a thickness of 10 nm, thereby forming the hole transport layer 112. Note that the second hole transport layer 112-2 is also used as an electron blocking layer.

[0293] Next, a co-evaporation process is performed with 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviated as αN-βNPAnth) represented by the above structural formula (iii) and 3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviated as 3,10PCA2Nbf(IV)-02) represented by (iv) in a weight ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) and a thickness of 25 nm, thereby forming the luminescent layer 113.

[0294] Then, an electron transport layer 114 is formed on the light-emitting layer 113 by co-deposition of 2-{4-[9,10-bis(naphthyl-2-yl)-2-anthrayl]phenyl}-1-phenyl-1H-benzimidazole (ZADN) represented by the above structural formula (v) and 8-hydroxyquinoline lithium (Liq) (Chemipro Kasei Kaisha, Ltd., Material Serial No.: 181201) in a weight ratio of 0.7:1 (=ZADN:Liq) and a thickness of 12.5 nm. Then, an electron transport layer 114 is formed by co-deposition of 1:0.7 (=ZADN:Liq) in a weight ratio of 1:0.7 (=ZADN:Liq) and a thickness of 12.5 nm.

[0295] After forming the electron transport layer 114, an electron injection layer 115 is formed by evaporating Liq with a thickness of 1 nm. Then, a cathode 102 is formed by evaporating aluminum with a thickness of 200 nm, thereby manufacturing the light-emitting device 1 of this embodiment.

[0296] (Compare the manufacturing methods of light-emitting device 1)

[0297] The difference between Comparative Light-Emitting Device 1 and Light-Emitting Device 1 lies in the following: αN-βNPAnth in the light-emitting layer 113 is replaced with 7-[4-(10-phenyl-9-anthrayl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviated as cgDBCzPA) as represented by the above structural formula (vii); 15 nm of 2-[3'-(dibenzothiophene-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviated as 2mDBTBPDBq-II) as represented by the above structural formula (ix) is deposited, followed by 10 nm of 2,9-bis(2-naphthyl)-4,7-diphenyl-1,10-phenanthroline (abbreviated as NBPhen), thereby forming the electron transport layer 114. Otherwise, Comparative Light-Emitting Device 1 and Light-Emitting Device 1 are manufactured in the same manner.

[0298] The component structures of light-emitting device 1 and comparative light-emitting device 1 are shown in the table below.

[0299] [Table 3]

[0300] Light-emitting device 1

[0301]

[0302] Comparison of light-emitting devices 1

[0303]

[0304] Here, the following table shows the HOMO level, LUMO level, and electron mobility of the organic compounds used in this embodiment when the square root of the electric field strength [V / cm] is 600.

[0305] [Table 4]

[0306]

[0307] In a nitrogen-atmospheric glove box, the light-emitting devices were sealed using a glass substrate in a manner that prevented them from being exposed to the atmosphere (a sealing material was applied around the components, UV treatment was performed during sealing, and a heat treatment was carried out at 80°C for 1 hour). The initial characteristics and reliability of the light-emitting device were then measured. Note that the measurements were performed at room temperature. Table 5 shows the 1000 cd / m² characteristics of light-emitting device 1 and the comparative light-emitting device 1. 2 Key features of the vicinity.

[0308] [Table 5]

[0309]

[0310] As shown in Table 5, both the light-emitting device 1 of one embodiment of the present invention and the comparative light-emitting device 1 are blue light-emitting devices with good initial characteristics.

[0311] in addition, Figure 20 The current density is shown to be 50 mA / cm. 2 A graph showing the change in brightness relative to driving time under certain conditions. (e.g.) Figure 20 As shown, in one aspect of the present invention, the light-emitting device 1 experiences an increase in brightness after being driven, reaching a level higher than the initial brightness, and then gradually decreases. In other words, it exhibits a maximum point on the degradation curve. Consequently, the driving lifetime can be significantly improved based on fewer degradation states (especially degradation states where the brightness decreases by 2% to 5% from the initial brightness).

[0312] Next, impedance spectroscopy (IS) measurements were performed on both the light-emitting device 1 and the comparison light-emitting device 1. A small sinusoidal voltage signal [V = V0exp(iωt)] was applied to the light-emitting device, and the impedance (Z = V / I) was calculated from the phase difference between the current amplitude of its response current signal [I = I0exp{i(ωt+φ)}] and the input signal. By applying a voltage from a high frequency to a low frequency to the element, components with various relaxation times that contribute to impedance can be separated and measured.

[0313] The plotting of the impedance on the complex plane using the frequency of the applied voltage signal as a parameter is called Nyquist plotting. By determining the impedance (Z), the admittance (Y), modulus (M), and dielectric constant (ε) of the fundamental transfer functions can be calculated. The relationships between the various transfer functions are shown below.

[0314] In this embodiment, the light-emitting device is analyzed using impedance (Z) plotted from the real axis, which indicates the resistive component, and modulus (M) plotted from the reciprocal of the capacitance component.

[0315] The measurements were performed using the SP-300 supermodel of the high-performance electrochemical measurement system manufactured by Biologic and a cable for measuring minute current.

[0316] Figure 21A and Figure 21B The Z-axis plot of light-emitting device 1 and comparison light-emitting device 1 is shown. Figure 21A and Figure 21B The measurement conditions were as follows: frequency range of 1MHz to 3MHz, AC voltage of 100mV, and applied voltage of 2.5V. Furthermore, the light-emitting device 1 was subjected to an AC voltage of 50mA / cm². 2 Driven for 670 hours, compared to light-emitting device 1 at 50 mA / cm 2 Drive for 380 hours to obtain the driven components.

[0317] Depend on Figure 21A It can be seen that, in one embodiment of the present invention, the resistance of the light-emitting device 1 after driving is less than the resistance before driving. On the other hand, due to... Figure 21B It can be seen that the resistance of the existing light-emitting device 1 after driving is slightly greater than the resistance before driving.

[0318] Figure 22 The current density is shown to be 50 mA / cm². 2 The change in voltage relative to the driving time under constant conditions. (By...) Figure 22 It is understood that in the light-emitting device 1 of one embodiment of the present invention, the driving voltage decreases under the condition of constant current density, and this result does not contradict the IS measurement results showing the decrease in resistance during driving.

[0319] Note that the driving voltage of the existing comparative light-emitting device 1 increases during driving, a result that does not contradict the IS measurement results. Most existing light-emitting devices show a tendency for the driving voltage to increase with driving under constant current density conditions; the phenomenon of the driving voltage decreasing with driving is unique to the light-emitting device of one embodiment of the present invention.

[0320] then, Figure 23 The diagram shows the M-axis plot of the light-emitting device 1. The shape of the plot before and after driving is different, indicating that the module changes before and after driving.

[0321] Next, the equivalent circuit of this light-emitting device was determined using the equivalent circuit analysis software ZView (Scribner Associates / USA). Figure 18 The diagram shows four RC parallel circuits and one series resistor. Note that the values ​​in the M plot indicate where the resistive components of the proposed separate equivalent circuits appear.

[0322] then, Figure 19 The graph shows the values ​​of the separated resistive components before and after the drive. It can be seen that only the resistance of R2 after the drive decreases by more than one decimal place compared to the resistance before the drive.

[0323] Therefore, by manufacturing light-emitting devices (light-emitting devices 2 to 8) with varying thicknesses of each layer and performing IS measurements, it was determined which layer of each light-emitting device 1 these resistance components corresponded to. Note that these light-emitting devices have the same structure as light-emitting device 1, except for the structure of electron transport layer 114 and the thickness of the portions indicated in bold in the table below. The electron transport layer 114 of light-emitting device 1 has a stacked structure of a first electron transport layer 114-1 of 12.5 nm ZADN:Liq (=0.7:1) and a second electron transport layer 114-2 of 12.5 nm ZADN:Liq (=1:0.7), but the electron transport layer 114 of light-emitting devices 2 to 8 is formed by a single layer of 25 nm, 35 nm, 45 nm, and 55 nm ZADN:Liq (=1:1).

[0324] [Table 6]

[0325]

[0326] IS measurements were performed on light-emitting devices 2 to 8. Figures 24A to 26B The M-plot is shown using the obtained results. Figure 24A The diagram shows the M-plot of light-emitting devices 3 to 5 with varying thicknesses of the electron transport layer 114, and a reference light-emitting device 2. Figure 25A The diagram shows the M-plot of light-emitting devices 6 and 7 with varying thicknesses of the light-emitting layer 113, and a reference light-emitting device 2. Figure 26A The M-plots of the light-emitting device 8 with altered thickness of the first hole transport layer 112-1 and the reference light-emitting device 2 are shown.

[0327] according to Figure 24A , Figure 25A and Figure 26A It can be seen that by changing the thickness of each layer, the shape of the M-plot also changes. Note that in Figure 24B , Figure 25B and Figure 26BIn the diagram, the resistance of each light-emitting device is plotted according to the resistance components R1 to R5 corresponding to the equivalent circuit, which are calculated by ZView.

[0328] Depend on Figures 24A to 26B It can be seen that in the light-emitting device with a changed thickness of electron transport layer 114, the resistance component of R2 changes; in the light-emitting device with a changed thickness of light-emitting layer 113, the resistance component of R1 changes; and in the light-emitting device with a changed thickness of the first hole transport layer 112-1, the resistance component of R3 changes. Therefore, it can be seen that in... Figure 18 In the equivalent circuit of the light-emitting device of one embodiment of the present invention shown, R1 is the light-emitting layer, R2 is the electron transport layer, R3 is the first hole transport layer, and the remaining R4 is considered to be the second hole transport layer.

[0329] Therefore, it can be seen that the resistance component R2 that changes before and after the drive originates from the component of the electron transport layer 114.

[0330] As described above, the light-emitting device 1 of one embodiment of the present invention is a long-life light-emitting device, and the overall resistance of the light-emitting device after driving is smaller than the resistance before driving. Furthermore, this decrease in resistance originates from a decrease in the resistance of the electron transport layer 114.

[0331] As a result, when the light-emitting device 1 is driven, the resistance of the electron transport layer 114 decreases, making it easier for charge carriers (electrons) to flow through. The end of the recombination region, which extends to a portion of the electron transport layer 114, moves towards the light-emitting region. Therefore, it can be considered that recombination energy that is deactivated in the electron transport layer and does not contribute to light emission can be converted into light emission, thus achieving the desired effect. Figure 20 The brightness increases as shown.

[0332] Thus, the light-emitting device of one aspect of the present invention can be a light-emitting device with a very good lifespan.

[0333] Example 2

[0334] In this embodiment, an example of a material that can be used in the electron transport layer 114 to reduce the resistance value when current flows through it (driving the light-emitting device) is described.

[0335] As a material that reduces the resistance value when current flows through it, it is suitable to use monomers of organometallic complexes of alkali metals or alkaline earth metals, or mixtures of organometallic compounds with electron transport properties and organometallic complexes of alkali metals or alkaline earth metals. This embodiment shows the calculation results when 2-phenyl-3-{4-[10-(3-pyridyl)-9-anthrayl]phenyl}quinoxaline (abbreviated as PyAlPQ) is used as the organometallic compound with electron transport properties and Liq is used as the organometallic complex of alkali metals or alkaline earth metals.

[0336] First, the ease of Liq polymer formation was calculated in a film containing a 1:1 weight ratio of PyAlPQ and Liq. Classical molecular dynamics was used for the calculations. Specifically, corresponding to the 1:1 weight ratio, molecules were introduced into the unit cell at a molar ratio of 18:82 for PyAlPQ. The unit cell was then compressed under high temperature and pressure, the pressure was reduced to atmospheric pressure, and the temperature was lowered to room temperature to temper the cell, thus generating an amorphous state. The condensation state of the molecules within the unit cell confirmed the extraction of Liq dimers, trimers, and hexamers. This indicates that Liq polymers readily form even at room temperature and under atmospheric conditions.

[0337] Next, first-principles calculations were used to optimize the structure and evaluate the stabilization degree when Liq monomers were polymerized. The optimization conditions were as follows: calculations were performed under vacuum using Gaussian 09, Revision E.01, with RB3LYP / 6-311g(d,p) as the work function. In the evaluation, the energy of each polymer composed of Liq monomers was compared with the energy of each polymer composed of the same monomer to calculate the stabilization energy when polymerized. This energy value was then divided by the number of Liq monomers to obtain the stabilization energy for each Liq monomer. Note that calculations and evaluations were performed for Liq dimers, trimers, tetramers, hexamers, and octamers. Figure 27 The results are shown.

[0338] Depend on Figure 27 As shown in the chart, Liq is most stable in its hexamer form, with a stabilization energy of approximately 1.54 eV per Liq unit. This indicates that the hexamer structure is very stable in Liq and is preferentially formed. Note that the calculated stabilization energies for Liq from tetramer to octamer do not show a significant difference, suggesting that it is easy to form polymers of more than four tetramers.

[0339] Therefore, it can be assumed that the Liq used in the electron transport layer gradually forms polymers when driving the light-emitting device (allowing current to flow through it). That is, materials whose resistivity decreases when current flows through them improve electron mobility and reduce resistance when organometallic complexes of alkali metals or alkaline earth metals form polymers.

[0340] In one embodiment of the light-emitting device of the present invention, the carrier balance is adjusted such that the recombination region reaches the electron transport layer in the initial stage of driving. However, with continued driving, clusters of organometallic complexes of alkali metals or alkaline earth metals are formed in the electron transport layer, the electron mobility increases, and the carrier balance changes. As a result, the recombination region shrinks into the light-emitting layer, resulting in an increase in brightness, thereby obtaining a light-emitting device with small initial degradation and long lifetime.

[0341] <Reference Example 1>

[0342] In this reference example, the methods for calculating the HOMO level, LUMO level, and electron mobility of the organic compounds used in each embodiment are described.

[0343] The HOMO and LUMO energy levels can be calculated using cyclic voltammetry (CV).

[0344] An electrochemical analyzer (BAS Inc. ALS model 600A or 600C) was used as the measuring apparatus. The solution for the CV determination was prepared as follows: Dehydrated dimethylformamide (DMF) (Aldrich Co., Ltd., 99.8%, catalog number: 22705-6) was used as the solvent; tetrabutylammonium perchlorate (n-Bu4NClO4) (Tokyo Chemical Industry Co., Ltd., catalog number: T0836) was dissolved at a concentration of 100 mmol / L as the supporting electrolyte; and the analyte was dissolved at a concentration of 2 mmol / L. A platinum electrode (BAS Inc., PTE platinum electrode) was used as the working electrode; a platinum electrode (BAS Inc., Pt counter electrode for VC-3 (5 cm)) was used as the auxiliary electrode; and an Ag / Ag reference electrode was used. + Electrode (BAS Inc., RE7 non-aqueous solvent reference electrode). Note that measurements were performed at room temperature (20°C to 25°C). The scan rate during CV measurements was uniformly set to 0.1 V / sec, and the oxidation potential Ea [V] and reduction potential Ec [V] relative to the reference electrode were measured. Ea is the intermediate potential between the oxidation-reduction wave and Ec is the intermediate potential between the reduction-oxidation wave. Here, it is known that the potential energy of the reference electrode used in this embodiment relative to the vacuum level is -4.94 [eV]. Therefore, the HOMO level and LUMO level were obtained using the formulas HOMO level [eV] = -4.94 - Ea and LUMO level [eV] = -4.94 - Ec, respectively.

[0345] Electron mobility can be determined by impedance spectroscopy (IS method).

[0346] Methods for measuring carrier mobility in EL materials include the time-of-flight (TOF) method and the SCLC method, which determines it from the IV characteristics of the space-charge-limited current (SCLC). The TOF method requires a much thicker sample compared to actual organic EL devices. The SCLC method has drawbacks, such as not being able to obtain the electric field intensity dependence of carrier mobility. In the IS method, because the required organic film thickness is thin (around a few hundred nm), a smaller amount of EL material can be used to form the film. Mobility can be measured with a thickness close to that of actual EL devices, and the electric field intensity dependence of carrier mobility can be obtained.

[0347] In the IS method, a small sinusoidal voltage signal (V = V0[exp(jωt)]) is applied to the EL element, and the impedance of the EL element (Z = V / I) is determined from the phase difference between the current amplitude of its response current signal (I = I0exp[j(ωt+φ)]) and the input signal. By applying a voltage from a high frequency to a low frequency to the element, components with various relaxation times that contribute to impedance can be separated and measured.

[0348] Here, the admittance Y (=1 / Z), the reciprocal of the impedance, can be expressed by the conductance G and the susceptance B as shown in the following formula (1).

[0349] [Equation 1]

[0350]

[0351] Furthermore, using the single injection model, the following equations (2) and (3) can be calculated. Here, g (equation (4)) is the differential conductance. Note that in the equations, C represents the electrostatic capacitance (capacitance), θ represents the transit angle (ωt), and ω represents the angular frequency. t is the transit time. The analysis uses the current equation, Poisson equation, and current continuity equation, and ignores the existence of diffusion current and trapped states.

[0352] [Equation 2]

[0353]

[0354]

[0355]

[0356] The method for calculating mobility from the frequency characteristics of electrostatic capacitance is the -ΔB method. Alternatively, the method for calculating mobility from the frequency characteristics of conductivity is the ωΔG method.

[0357] In practice, firstly, a measuring element is manufactured using the material from which the electron mobility is to be calculated. This measuring element is designed so that only electrons flow as charge carriers. Figure 28 A schematic diagram of the measuring elements used is shown. This specification describes a method for calculating mobility from the frequency characteristics of electrostatic capacitance (-ΔB method).

[0358] This time, in order to measure the measuring elements manufactured, such as Figure 28 As shown, a first layer 210, a second layer 211, and a third layer 212 are included between the anode 201 and the cathode 202. The material for which the electron mobility needs to be determined is used as the material of the second layer 211. This explanation will use the measurement of the electron mobility of a co-evaporated film with a ZADN and Liq ratio of 0.5:0.5 (weight ratio) as an example. Specific structural examples are shown in the table below.

[0359] [Table 7]

[0360]

[0361] Impedance measurements were performed while applying a DC voltage of 5.0V to 9.0V, and simultaneously under AC voltage conditions of 70mV and frequency conditions of 1Hz to 3MHz. The capacitance was calculated from the admittance, which is the reciprocal of the impedance obtained here (equation (1) above). Figure 29 The frequency response of capacitor C is shown when a voltage of 7.0V is applied.

[0362] Since the space charge generated by the carriers injected by the small voltage signal cannot keep up with the small AC voltage, the frequency characteristics of capacitor C are obtained from the phase difference generated by the current. Here, the travel time of the carriers in the membrane is defined by the time T when the injected carriers reach the counter electrode, and is expressed by the following formula (5).

[0363] [Equation 3]

[0364]

[0365] The change in negative susceptance (-ΔB) corresponds to the change in electrostatic capacitance -ΔC multiplied by the angular frequency ω (-ωΔC). The peak frequency f' on the lowest frequency side is derived from equation (3). max (=ω max The relationship between ( / 2π) and travel time T is satisfied by the following formula (6).

[0366] [Equation 4]

[0367]

[0368] Figure 30 The frequency response of -ΔB calculated from the above measurements (i.e., at a DC voltage of 7.0V) is shown. Arrows in the attached figure indicate the frequency response from... Figure 30 The peak frequency f' of the lowest frequency side is obtained. max .

[0369] Because of the f' obtained from the above measurements and analyses max The travel time T is calculated (refer to the above formula (6)), so the electron mobility at a voltage of 7.0V can be calculated from the above formula (5). By performing the same measurement in the range of DC voltage from 5.0V to 9.0V, the electron mobility at each voltage (electric field strength) can be calculated, and thus the electric field strength dependence of the mobility can also be determined.

[0370] Figure 31 Table 9 shows the final electric field strength dependence of the electron mobility of each organic compound obtained by the above calculation method. Figure 31 The square root of the read electric field strength [V / cm] is 600 [V / cm]. 1 / 2 The value of electron mobility at that time.

[0371] [Table 8]

[0372]

[0373] Electron mobility can be calculated as described above. Note that for detailed measurement methods, refer to "Japanese Journal of Applied Physics" by Takayuki Okachi et al., Vol. 47, No. 12, 2008, pp. 8965-8972.

[0374] <Reference Example 2>

[0375] In this reference example, the synthesis method of 2-phenyl-3-{4-[10-(3-pyridyl)-9-anthrayl]phenyl}quinoxaline (abbreviated as PyA1PQ) used in Example 2 is described. The structure of PyA1PQ is shown below.

[0376] [Chemical Formula 4]

[0377]

[0378] 0.74 g (2.2 mmol) of 3-(10-bromo-9-anthrayl)pyridine, 0.26 g (0.85 mmol) of tris(o-tolyl)phosphine, 0.73 g (2.3 mmol) of 4-(3-phenylquinoxalo-2-yl)phenylboronic acid, 1.3 g (9.0 mmol) of potassium carbonate aqueous solution, 40 mL of dimethyl ethylene glycol (DME), and 4.4 mL of water were placed in a 50 mL three-necked flask. The mixture was degassed by stirring under reduced pressure to purge nitrogen from the flask.

[0379] 65 mg (0.29 mmol) of palladium(II) acetate was added to the mixture in the flask, and the mixture was stirred at 80 °C for 11 hours under a nitrogen stream. After stirring, water was added to the mixture, and extraction was performed using toluene. The resulting extract was washed with saturated brine and dried over magnesium sulfate. The extract was then gravity filtered and the filtrate was concentrated to give an oil. This oil was purified twice by silica gel column chromatography using chloroform and toluene:ethyl acetate in a 5:1 ratio, and recrystallized from toluene / hexane. 0.43 g of a yellow solid of the target compound was given in 36% yield. The synthetic route is shown below.

[0380] [Chemical Formula 5]

[0381]

[0382] The obtained yellow solid (0.44 g) was purified by gradient sublimation. The sublimation conditions were: pressure 10 Pa, argon flow rate 5.0 mL / min, and heating at 260 °C for 18 hours. After sublimation purification, 0.35 g of the target yellow solid was obtained with a recovery rate of 79%.

[0383] The following shows the nuclear magnetic resonance spectroscopy of the yellow solid obtained by the above reaction. 1 The analysis results (H-NMR) show that PyA1PQ with the above-described structural formula was obtained in this embodiment.

[0384] 1 H NMR (CDCl3, 300MHz): δ = 7.37-7.50 (m, 9H), 7.56-7.78 (m, 9H), 7.82-7.86 (m, 3H), 8.24-8.30 (m, 2H), 8.75 (dd, J=1.8Hz, 0.9Hz, 1H), 8.84 (dd, J=4.8Hz, 1.8Hz, 1H).

[0385] Symbol Explanation

[0386] 101 Anode

[0387] 102 Cathode

[0388] 103 EL layer

[0389] 111 Hole Injection Layer

[0390] 112 Hole Transport Layer

[0391] 112-1 First Hole Transport Layer

[0392] 112-2 Second Hole Transport Layer

[0393] 113 Emissive Layer

[0394] 113-1 Composite Region

[0395] 114 Electron Transport Layer

[0396] 114-1 First Electron Transport Layer

[0397] 114-2 Second Electron Transport Layer

[0398] 115 Electron Injection Layer

[0399] 116 Charge Generation Layer

[0400] 117 P-type layer

[0401] 118 Electronic Relay Layer

[0402] 119 Electron Injection Buffer Layer

[0403] 120 Non-luminescent composite area

[0404] 201 Anode

[0405] 202 Cathode

[0406] 210 First Floor

[0407] 211 Second Floor

[0408] 212 Third Floor

[0409] 400 substrate

[0410] 401 Anode

[0411] 403 EL layer

[0412] 404 cathode

[0413] 405 sealant

[0414] 406 sealant

[0415] 407 Sealed Substrate

[0416] 408 Space

[0417] 412 pads

[0418] 420 IC chip

[0419] 501 Anode

[0420] 502 cathode

[0421] 511 First Light-Emitting Unit

[0422] 512 Second Light-Emitting Unit

[0423] 513 Charge Generation Layer

[0424] 601 Drive Circuit Section (Source Line Drive Circuit)

[0425] 602 pixels

[0426] 603 Drive Circuit Section (Gate Line Drive Circuit)

[0427] 604 hermetically sealed substrate

[0428] 605 sealant

[0429] Space 607

[0430] 608 wiring

[0431] 609 FPC (Flexible Printed Circuit)

[0432] 610 Component Substrate

[0433] 611 Switching FET

[0434] 612 Current-Controlled FET

[0435] 613 Anode

[0436] 614 Insulator

[0437] 616 EL layer

[0438] 617 Cathode

[0439] 618 Light-emitting devices

[0440] 951 substrate

[0441] 952 electrode

[0442] 953 Insulation Layer

[0443] 954 partition wall layer

[0444] 955 EL layer

[0445] 956 electrode

[0446] 1001 substrate

[0447] 1002 substrate insulating film

[0448] 1003 gate insulating film

[0449] 1006 gate electrode

[0450] 1007 gate electrode

[0451] 1008 gate electrode

[0452] 1020 First interlayer insulating film

[0453] 1021 Second interlayer insulating film

[0454] 1022 electrode

[0455] 1024W anode

[0456] 1024R anode

[0457] 1024G anode

[0458] 1024B anode

[0459] 1025 partition wall

[0460] 1028 EL layer

[0461] 1029 Cathode

[0462] 1031 Sealed Substrate

[0463] 1032 sealant

[0464] 1033 Transparent Substrate

[0465] 1034R Red Coloring Layer

[0466] 1034G Green Coloring Layer

[0467] 1034B Blue Coloring Layer

[0468] 1035 Black Matrix

[0469] 1036 Protective Layer

[0470] 1037 Third interlayer insulating film

[0471] 1040 pixels

[0472] 1041 Drive Circuit Section

[0473] 1042 Peripheral Department

[0474] 2001 casing

[0475] 2002 Light Source

[0476] 2100 Robot

[0477] 2110 Computing Device

[0478] 2101 Illuminance Sensor

[0479] 2102 Microphone

[0480] 2103 Upper camera

[0481] 2104 Speaker

[0482] 2105 Monitor

[0483] 2106 Lower Camera

[0484] 2107 Obstacle Sensor

[0485] 2108 Mobile Agency

[0486] 3001 lighting fixtures

[0487] 5000 casing

[0488] 5001 Display Section

[0489] 5002 Second Display Unit

[0490] 5003 Speaker

[0491] 5004 LED lights

[0492] 5006 Connecting Terminal

[0493] 5007 sensor

[0494] 5008 microphone

[0495] 5012 Support Section

[0496] 5013 Headphones

[0497] 5100 Robotic Vacuum Cleaner

[0498] 5101 Monitor

[0499] 5102 Camera

[0500] 5103 brush

[0501] 5104 Operation Button

[0502] 5150 Portable Information Terminal

[0503] 5151 casing

[0504] 5152 Display Area

[0505] 5153 Bending section

[0506] 5120 Garbage

[0507] 5200 display area

[0508] 5201 Display Area

[0509] 5202 Display Area

[0510] 5203 Display Area

[0511] 7101 casing

[0512] 7103 Display Section

[0513] 7105 bracket

[0514] 7107 Display Section

[0515] 7109 Operation Keys

[0516] 7110 Remote Control Operator

[0517] 7201 Main Body

[0518] 7202 casing

[0519] 7203 Display Section

[0520] 7204 Keyboard

[0521] 7205 External Connection Port

[0522] 7206 Pointing Device

[0523] 7210 Second Display Unit

[0524] 7401 casing

[0525] 7402 Display Section

[0526] 7403 Operation Button

[0527] 7404 External Connection Port

[0528] 7405 speaker

[0529] 7406 Microphone

[0530] 9310 Portable Information Terminal

[0531] 9311 Display Panel

[0532] 9313 Hinge section

[0533] 9315 casing

Claims

1. A light-emitting device comprising: an anode; a cathode; and an EL layer between the anode and the cathode, wherein the EL layer comprises a hole-injection layer, a light-emitting layer, and an electron-transport layer, the hole-injection layer is between the anode and the light-emitting layer, the electron-transport layer is between the light-emitting layer and the cathode, the hole-injection layer contains a first substance and a second substance, the first substance is an organic compound having a hole-transport property and a HOMO level of -5.7 eV or more and -5.4 eV or less, the second substance exhibits electron-accepting property with respect to the first substance, and the electron-transport layer contains a material whose resistance value decreases when current flows therethrough.

2. The light-emitting device according to claim 1, wherein the material whose resistance value decreases when current flows therethrough contains an organic metal complex of an alkali metal or an alkaline earth metal.

3. The light-emitting device according to claim 1, wherein the material whose resistance value decreases when current flows therethrough contains an organic compound having an electron-transport property and an organic metal complex of an alkali metal or an alkaline earth metal.

4. The light-emitting device according to claim 2 or 3, wherein the organic metal complex of an alkali metal or an alkaline earth metal forms a cluster.

5. The light-emitting device according to claim 2 or 3, wherein the organic metal complex of an alkali metal or an alkaline earth metal is a metal complex containing a ligand having nitrogen and oxygen and an alkali metal or an alkaline earth metal.

6. The light-emitting device according to claim 2 or 3, wherein the organic metal complex of an alkali metal or an alkaline earth metal is a metal complex containing a monovalent metal ion and a ligand having a 8-hydroxyquinoline structure.

7. The light-emitting device according to claim 2 or 3, wherein the organic metal complex of an alkali metal or an alkaline earth metal is a lithium complex containing a ligand having a 8-hydroxyquinoline structure.

8. The light-emitting device according to claim 2 or 3, wherein the electron-transport layer includes a first layer and a second layer, the first layer is between the light-emitting layer and the second layer, the second layer is between the first layer and the cathode, and the concentration of the organic metal complex of an alkali metal or an alkaline earth metal in the first layer is different from that in the second layer.

9. The light-emitting device according to claim 8, wherein the concentration of the organic metal complex of an alkali metal or an alkaline earth metal in the first layer is higher than that in the second layer.

10. The light-emitting device according to claim 1, wherein the second substance is an organic compound.

11. The light-emitting device according to claim 1, wherein the light-emitting layer contains a host material and a light-emitting substance, and the light-emitting substance emits blue fluorescence.

12. An electronic appliance comprising: the light-emitting device according to claim 1; and a sensor, an operation button, a speaker, or a microphone.

13. A light-emitting apparatus comprising: the light-emitting device according to claim 1; and a transistor or a substrate.

14. An illumination apparatus comprising: the light-emitting device according to claim 1; and a housing. ​ ​ ​ ​

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