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

Abstract

To provide a novel light-emitting device, to provide a light-emitting device with high emission efficiency, to provide a light-emitting device with a favorable lifetime, or to provide a light-emitting device with low driving voltage.SOLUTION: There is provided a light-emitting device which includes an anode, a cathode, and an EL layer positioned between the anode and the cathode. The EL layer includes a hole-injection layer, a light-emitting layer, and an electron-transport layer. The hole-injection layer contains a hole-transport material and an electron-accepting material. The electron-transport layer contains: an electron-transport material; and an alkali metal itself, an alkaline earth metal itself, a compound of an alkali metal or an alkaline earth metal, or a complex thereof. The spin density of the hole-injection layer measured by an ESR method is lower than or equal to 1×1019 spins / cm3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An aspect of the present invention relates to a light-emitting device, a light-emitting element, a display module, a lighting module, a display device, a light-emitting device, an electronic device, and a lighting device. Note that an aspect of the present invention is not limited to the above technical field. The technical field of an aspect of the invention disclosed in the present specification and the like relates to an object, a method, or a manufacturing method. Alternatively, an aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of an aspect of the present invention disclosed in the present specification include 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 driving method thereof, or a manufacturing method thereof. [Background technology]

[0002] Light-emitting devices (organic EL elements) that utilize electroluminescence (EL) using organic compounds are becoming more and more practical. The basic structure of these light-emitting devices is a pair of electrodes sandwiching an organic compound layer (EL layer) containing a light-emitting material between them. By applying a voltage to this element, carriers are injected, and the recombination energy of the carriers is utilized to emit light from the light-emitting material.

[0003] Since such light-emitting devices are self-emitting, when used as display pixels, they have advantages such as higher visibility than liquid crystals and no need for backlighting, making them suitable as flat panel display elements. Another major advantage of displays using such light-emitting devices is that they can be made thin and lightweight. Another characteristic is that they have an extremely fast response speed.

[0004] In addition, these light-emitting devices can have light-emitting layers formed continuously in two dimensions, making it possible to obtain surface-like light emission. This is a feature that is difficult to obtain with point light sources such as incandescent light bulbs and LEDs, or linear light sources such as fluorescent lamps, making them highly valuable as surface light sources for lighting and other applications.

[0005] Displays and lighting devices using such light-emitting devices are suitable for use in a variety of electronic devices, and research and development is ongoing to develop light-emitting devices with better efficiency and life span.

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

[0007] Although the characteristics of light-emitting devices have improved remarkably, they are still insufficient to meet high demands for efficiency, durability, and all other characteristics. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2011 / 065136 Brochure Summary of the Invention [Problem to be solved by the invention]

[0009] In view of the above, an object of one embodiment of the present invention is to provide a novel light-emitting device, to provide a light-emitting device with high emission efficiency, to provide a light-emitting device with a long lifetime, or to provide a light-emitting device with a low driving voltage.

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

[0011] It is sufficient for the present invention to solve any one of the above problems. [Means for solving the problem]

[0012] One embodiment of the present invention is an organic EL device having an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer having a hole injection layer, a light emitting layer, and an electron transport layer, the hole injection layer containing a hole transport material and an electron accepting material, the electron transport layer containing an electron transport material and an element, compound, or complex of an alkali metal or an alkaline earth metal, and a spin density of the hole injection layer measured by an ESR method of 1×10 19 spins / cm 3 A light emitting device comprising:

[0013] Alternatively, another embodiment of the present invention is an organic EL device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer comprising a hole injection layer, a light emitting layer, and an electron transport layer, the hole injection layer comprising a hole transport material and an electron accepting material, the electron transport layer comprising an electron transport material, and a metal complex having a ligand including an 8-hydroxyquinolinato structure and a monovalent metal ion, the hole injection layer having a spin density of 1×10 measured by an ESR method. 19 spins / cm 3 A light emitting device comprising:

[0014] Alternatively, another embodiment of the present invention is an organic EL device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer comprising a hole injection layer, a light emitting layer, and an electron transport layer, the hole injection layer comprising a hole transport material and an electron accepting material, the electron transport layer comprising an electron transport material and a lithium complex having a ligand including an 8-hydroxyquinolinato structure, and the hole injection layer having a spin density of 1×10 measured by an ESR method. 19spins / cm 3 A light emitting device comprising:

[0015] Alternatively, another embodiment of the present invention includes an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer includes a hole injection layer, a light emitting layer, and an electron transport layer, the hole injection layer includes a hole transport material and an electron accepting material, the electron transport layer includes an electron transport material, the HOMO level of the electron transport material is −6.0 eV or higher, and the hole injection layer has a spin density of 1×10 measured by an ESR method. 19 spins / cm 3 A light emitting device comprising:

[0016] Alternatively, another embodiment of the present invention includes an electroluminescent device having an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer having a hole injection layer, a light emitting layer, and an electron transport layer, the hole injection layer includes a hole transport material and an electron accepting material, the electron transport layer includes an electron transport material, the electron transport material is an organic compound having an anthracene skeleton, and the hole injection layer has a spin density of 1×10 19 spins / cm 3 A light emitting device comprising:

[0017] Alternatively, another embodiment of the present invention is a light-emitting device comprising an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer having a hole injection layer, a light-emitting layer, and an electron transport layer, the hole injection layer containing a hole transport material and an electron accepting material, and the electron transport layer having an electron mobility of 1×10 when the square root of the electric field strength [V / cm] is 600. -7 cm 2 / Vs or more 5×10 -5 cm 2 / Vs or less, and the spin density of the hole injection layer measured by an ESR method is 1×10 19 spins / cm 3 A light emitting device comprising:

[0018] Alternatively, another embodiment of the present invention includes an anode, a cathode, and an EL layer located between the anode and the cathode, the EL layer includes a hole injection layer, a light emitting layer, and an electron transport layer, the hole injection layer includes a hole transport material and an electron accepting material, the electron transport layer includes an electron transport material and an element, compound, or complex of an alkali metal or an alkaline earth metal, the concentration of the element, compound, or complex of the alkali metal or alkaline earth metal being higher in a region of the electron transport layer on the light emitting layer side than in a region of the electron transport layer on the cathode side, the electron transport layer includes a first region and a second region, the first region is located between the light emitting layer and the second region, the concentrations of the element, compound, or complex of the alkali metal or alkaline earth metal being different from each other in the first region and the second region, and the spin density of the hole injection layer measured by an ESR method is 1×10 19 spins / cm 3 A light emitting device comprising:

[0019] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first region has a high concentration of the alkali metal or alkaline earth metal element, compound, or complex.

[0020] Alternatively, another embodiment of the present invention is a light-emitting device having the above structure, wherein the electron transport layer is composed of a plurality of layers, and the second region has a high concentration of the alkali metal or alkaline earth metal element, compound, or complex.

[0021] Another embodiment of the present invention is a light-emitting device having the above structure, wherein the concentration of the alkali metal or alkaline earth metal simple substance, compound, or complex in the first region or the second region is zero.

[0022] Alternatively, another embodiment of the present invention is a light-emitting device having the above-mentioned structure, wherein the electron-accepting material is a material that exhibits electron-accepting property to the hole-transporting material, and the hole-transporting material is an organic compound having a HOMO level of −5.7 eV or more and −5.4 eV or less.

[0023] Alternatively, in the above-mentioned structure, the hole transport material has a hole mobility of 1×10 -3 cm 2 / Vs or less.

[0024] Alternatively, in the above-described structure, the hole injection layer has a spin density of 1×10 16 spins / cm 3 The above is a light emitting device.

[0025] Alternatively, in another aspect of the present invention, in the above structure, the hole injection layer has a spin density of 1×10 17 spins / cm 3 The above is a light emitting device.

[0026] Alternatively, in another embodiment of the present invention, in the above structure, the hole injection layer has a spin density of 3×10 17 spins / cm 3 The above is a light emitting device.

[0027] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the EL layer has a hole-transport layer between the hole-injection layer and the light-emitting layer.

[0028] Alternatively, another embodiment of the present invention is a light-emitting device having the above-mentioned structure, wherein the hole transport layer has a two-layer structure of a first hole transport layer located on the hole injection layer side and a second hole transport layer located on the light-emitting layer side.

[0029] Another embodiment of the present invention is a light-emitting device having the above structure, in which the second hole-transporting layer also functions as an electron blocking layer.

[0030] Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the light-emitting layer includes a host material and a light-emitting center material, and the electron mobility of the electron transport material is smaller than that of the host material.

[0031] Another embodiment of the present invention is a light-emitting device having the above structure, in which the luminescence center material exhibits fluorescent emission.

[0032] Another embodiment of the present invention is a light-emitting device having the above structure, in which the luminescent center material emits blue fluorescent light.

[0033] Another embodiment of the present invention is an electronic device having the above-described structure, which includes at least one of a sensor, an operation button, a speaker, and a microphone.

[0034] Another embodiment of the present invention is a light-emitting device having the above structure, further including a transistor and a substrate.

[0035] Another embodiment of the present invention is a lighting device having the above structure and a housing.

[0036] In this specification, the term "light-emitting device" includes an image display device using a light-emitting device. The term "light-emitting device" may also include a module in which a connector, such as an anisotropic conductive film or TCP (Tape Carrier Package), is attached to a light-emitting device, a module in which a printed wiring board is provided at the end of a TCP, or a module in which an IC (integrated circuit) is directly mounted on a light-emitting device by a COG (Chip On Glass) method. Furthermore, lighting fixtures and the like may have a light-emitting device. Effect of the Invention

[0037] According to one embodiment of the present invention, a novel light-emitting device can be provided. Alternatively, a light-emitting device having a long lifetime can be provided. Alternatively, a light-emitting device having high luminous efficiency can be provided. Alternatively, a light-emitting device having a low driving voltage can be provided.

[0038] According to another embodiment of the present invention, a light-emitting device, an electronic device, and a display device each having high reliability can be provided. According to another embodiment of the present invention, a light-emitting device, an electronic device, and a display device each having low power consumption can be provided.

[0039] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract effects other than these from the description in the specification, drawings, claims, etc. [Brief description of the drawings]

[0040] [Figure 1] 1A1, 1A2, 1B, and 1C are schematic diagrams of light emitting devices. [Diagram 2] 2A1, 2A2, 2B1, and 2B2 are diagrams showing the concentration distribution of the eighth substance in the electron transport layer. [Diagram 3] 3A and 3B are diagrams illustrating the recombination region of a light-emitting device. [Figure 4] 4A and 4B are conceptual diagrams of an active matrix type light emitting device. [Diagram 5] 5A and 5B are conceptual diagrams of an active matrix type light emitting device. [Figure 6] FIG. 6 is a conceptual diagram of an active matrix type light emitting device. [Figure 7] 7A and 7B are diagrams illustrating a lighting device. [Figure 8] 8A, 8B1, 8B2 and 8C are diagrams showing electronic equipment. [Figure 9] 9A, 9B and 9C are diagrams showing electronic devices. [Figure 10] FIG. 10 is a diagram showing a lighting device. [Figure 11]FIG. 11 is a diagram showing a lighting device. [Figure 12] FIG. 12 is a diagram showing an in-vehicle display device. [Figure 13] 13A and 13B are diagrams illustrating an electronic device. [Figure 14] 14A, 14B and 14C are diagrams showing electronic devices. [Figure 15] FIG. 15 is a graph showing the luminance-current density characteristics of light-emitting devices 1-1, 1-2, 2-1, and 2-2, and the comparative light-emitting device. [Figure 16] FIG. 16 is a graph showing the current efficiency-luminance characteristics of the light-emitting devices 1-1, 1-2, 2-1, and 2-2 and the comparative light-emitting device. [Figure 17] FIG. 17 is a graph showing the luminance-voltage characteristics of the light-emitting devices 1-1, 1-2, 2-1, and 2-2 and the comparative light-emitting device. [Figure 18] FIG. 18 is a graph showing the current-voltage characteristics of the light-emitting devices 1-1, 1-2, 2-1, and 2-2 and the comparative light-emitting device. [Figure 19] FIG. 19 is a graph showing the external quantum efficiency-luminance characteristics of the light-emitting devices 1-1, 1-2, 2-1, and 2-2 and the comparative light-emitting device. [Figure 20] FIG. 20 shows the emission spectra of light-emitting devices 1-1, 1-2, 2-1, and 2-2 and the comparative light-emitting device. [Figure 21] FIG. 21 is a graph showing the normalized luminance-time change characteristics of the light-emitting devices 1-1, 1-2, 2-1, and 2-2 and the comparative light-emitting device. [Figure 22] FIG. 22 is a diagram showing the spin densities calculated by measuring the electron spin resonance spectra of samples 1-1, 1-2, 1-3, 2-1, 2-2, 3-1 and 3-2. [Diagram 23] FIG. 23 is a diagram showing the structure of a measuring element. [Figure 24] FIG. 24 shows the current density-voltage characteristics of the measurement element. [Diagram 25] Figure 25 shows the frequency characteristics of the calculated capacitance C of ZADN:Liq (1:1) at a DC power supply of 7.0 V. [Figure 26] Figure 26 shows the frequency characteristics of -ΔB of ZADN:Liq(1:1) at a DC voltage of 7.0V. [Figure 27] FIG. 27 shows the electric field strength dependence of electron mobility in each organic compound. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that the form and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0042] (Embodiment 1) 1A1 and 1A2 show a light-emitting device according to one embodiment of the present invention. The light-emitting device according to one embodiment of the present invention includes an anode 101, a cathode 102, and an EL layer 103. The EL layer includes a hole injection layer 111, a hole transport layer 112, an emitting layer 113, and an electron transport layer 114. It is preferable that the hole transport layer 112 includes a first hole transport layer 112-1 and a second hole transport layer 112-2, and that the electron transport layer 114 includes a first electron transport layer 114-1 and a second electron transport layer 114-2 as shown in FIG. 1A2.

[0043] 1A1 and 1A2, the EL layer 103 further includes an electron injection layer 115, but the configuration of the light-emitting device is not limited to this. As long as the device has the above-mentioned configuration, it may also include layers having other functions.

[0044] The hole-injection layer 111 is a layer for facilitating the injection of holes into the EL layer 103, and is formed using a material with high hole-injection properties. The hole-injection layer 111 may be formed of a single material, but is preferably formed of a material containing a first substance and a second substance. The first substance is an acceptor substance and exhibits electron-accepting properties toward the second substance. The second substance is a hole-transporting material and preferably has a relatively deep HOMO level of -5.7 eV or more and -5.4 eV or less. When the second substance has a relatively deep HOMO level, the induction of holes is appropriately suppressed, while the induced holes are easily injected into the hole-transporting layer 112.

[0045] In the light-emitting device according to one embodiment of the present invention, the material constituting the hole injection layer 111 has a spin density of 1×10 19 spins / cm 3 The light-emitting device has a good life span, and a light-emitting device using the light-emitting device can be a light-emitting device with good display quality in which crosstalk is suppressed. However, if the spin density is too small, it becomes difficult to inject holes from the anode. Therefore, the spin density is set to 1×10 16 spins / cm 3 More than 1×10 19 spins / cm 3 Preferably less than or equal to 1×10 17 spins / cm 3 More than 1×10 19 spins / cm 3 Less than 3×10, more preferably 16 spins / cm 3 More than 1×10 19 spins / cm 3 The following is the result.

[0046] The first substance can be either an inorganic compound or an organic compound, but it is preferable to use an organic compound having an electron-withdrawing group (particularly a halogen group such as a fluoro group or a cyano group). As the first substance, a substance that exhibits electron-accepting properties toward the second substance may be appropriately selected from such substances. Examples of such organic compounds include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile, etc. In particular, compounds in which an electron-withdrawing group is bonded to a condensed aromatic ring having a plurality of heteroatoms, such as HAT-CN, are thermally stable and preferable. Radialene derivatives having an electron-withdrawing group (especially a halogen group such as a fluoro group or a cyano group)[3] are preferred because of their extremely high electron-accepting properties. Specific examples include α,α',α''-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile]. When the first substance is an inorganic compound, a transition metal oxide can also be used. In particular, oxides of metals belonging to Groups 4 to 8 of the periodic table are suitable, and as oxides of metals belonging to Groups 4 to 8 of the periodic table, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, etc. are preferred due to their high electron-accepting properties. Among them, molybdenum oxide is preferred because it is stable in the air, has low hygroscopicity, and is easy to handle.

[0047] The second substance is a hole transport material, and is preferably an organic compound having hole transport properties, and more preferably has any one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, aromatic amines having a substituent containing a dibenzofuran ring or a dibenzothiophene ring, aromatic monoamines having a naphthalene ring, or aromatic monoamines in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group are preferred. Note that if these second substances have an N,N-bis(4-biphenyl)amino group, it is preferable because a light-emitting device with a long life can be fabricated. Specific examples of the second substance include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), 4,4'-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-in N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl-4-biphenylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4',4''-diphenyltriphenylamine (abbreviation: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4''-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4'-diphenyl-4''-(6;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4'-diphenyl-4''-(7;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB-03), 4,4'-Diphenyl-4''-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4,4'-Diphenyl-4''-(6;2'-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B), 4,4'-Diphenyl-4''-(7;2'-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B-03), 4,4'-Diphenyl-4''-(4;2'-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB), 4,4'-Diphenyl-4''-(5;2'- Binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenylyl)-4'-(2-naphthyl)-4''-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: TPBiAβNBi), 4-phenyl-4'-(1-naphthyl)triphenylamine 4,4'-Bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4'-diphenyl-4''-[4'-(carbazol-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazol-9-yl)phenyl]tris(1,1'-biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-diphenyl-4'-(2-naphthyl)-4''-{9-(4-biphenylyl)carbazole)}triphenylamine N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9'-spirobi(9H-fluorene)-2-amine (abbreviation: PCBNBSF), N,N-bis(4-biphenylyl)-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: BBASF), N,N-bis(1,1'-biphenyl-4-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(1,1'-biphenyl-2-yl)-N-(9,9-Dimethyl-9H-fluoren-2-yl)-9,9'-spirobi(9H-fluorene)-4-amine (abbreviation: oFBiSF), N-(4-biphenyl)-N-(dibenzofuran-4-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBf BNBN), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-phenyl-4'-(9-phenyl-9H-carbazole- 3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), Examples of such fluorenylamine include PCBNBB, N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (PCBASF), and N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine (PCBBiF).

[0048] In addition, the second material has a hole mobility of 1×10 when the square root of the electric field strength [V / cm] is 600. -3 cm 2 It is preferable that the value is equal to or less than / Vs.

[0049] The composition ratio of the first substance to the second substance in the hole-injection layer 111 is preferably 1:0.01 to 1:0.15 (weight ratio), and more preferably 1:0.01 to 1:0.1 (weight ratio).

[0050] The hole transport layer 112 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. The second hole transport layer 112-2 may also function as an electron block layer.

[0051] The first hole-transporting layer 112-1 includes a third material, and the second hole-transporting layer 112-2 includes a fourth material.

[0052] The third substance and the fourth substance are preferably organic compounds having a hole transporting property. The third substance and the fourth substance can be the same as those exemplified as the organic compounds that can be used as the second substance.

[0053] It is preferable to select the second and third materials so that the HOMO level of the third material is deeper than that of the second material, and the difference between the HOMO levels is 0.2 eV or less.

[0054] In addition, the HOMO level of the fourth material is preferably deeper than that of the third material. Furthermore, it is preferable to select each material so that the difference between the HOMO levels is 0.2 eV or less. When the HOMO levels of the second material to the fourth material are in the above-mentioned relationship, holes are smoothly injected into each layer, and an increase in driving voltage and a state of insufficient holes in the light-emitting layer can be prevented.

[0055] Each of the second to fourth substances preferably has a hole-transporting skeleton. As the hole-transporting skeleton, a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton are preferable because the HOMO level of these organic compounds is not too shallow. In addition, it is preferable that these hole-transporting skeletons are common to the materials of adjacent layers (for example, the second substance and the third substance, or the third substance and the fourth substance) because this facilitates the injection of holes. In particular, the dibenzofuran skeleton is preferable as these hole-transporting skeletons.

[0056] In addition, it is preferable that the materials contained in the adjacent layers (for example, the second substance and the third substance, or the third substance and the fourth substance) are the same material because this facilitates the injection of holes. In particular, it is preferable that the second substance and the third substance are the same material.

[0057] The light-emitting layer 113 contains a fifth substance and a sixth substance. The fifth substance is a light-emitting center substance, and the sixth substance is a host material for dispersing the fifth substance. The light-emitting layer 113 may simultaneously contain other materials different from the fifth substance and the sixth substance. The light-emitting layer 113 may also be a stack of two layers with different compositions.

[0058] The luminescent center material may be a fluorescent material, a phosphorescent material, a material exhibiting thermally activated delayed fluorescence (TADF), or other luminescent materials. The luminescent center material may be a single layer or may be composed of multiple layers. Note that one embodiment of the present invention is more preferably applicable to the case where the light-emitting layer 113 is a layer exhibiting fluorescent light, particularly a layer exhibiting blue fluorescent light.

[0059] Examples of materials that can be used as the fluorescent substance in the light-emitting layer 113 include the following: In addition, fluorescent substances other than these can also be used.

[0060] 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl )phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-( 10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9 -Diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N'',N'',N'''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,10-diphenyl-2-anthryl)-N,9-Diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAB PhA), 9,10-bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), Coumarin 545T, N,N'-diphenylquinacridone, (abbreviation: DPQd), rubrene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6 -methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine Amine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-Bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N'-diphenyl-N,N'-(1,6-pyrene-diyl)bis[(6-phenylbenzo[b ]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), 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, condensed aromatic diamine compounds such as pyrene diamine compounds such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03 are preferred because they have high hole trapping properties and excellent luminous efficiency and reliability.

[0061] When a phosphorescent material is used as the luminescent center material in the light-emitting layer 113, examples of materials that can be used include the following.

[0062] Organometallic iridium complexes with 4H-triazole skeletons such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp)3]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz)3]), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b)3]), and tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b)3]) are also available. Organometallic iridium complexes having a 1H-triazole skeleton, such as tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me)3]), fac-tris[(1-2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpmi)3]), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me)3]), and bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’ ]iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C 2’}Iridium(III) picolinate (abbreviation: [Ir(CF3ppy)2(pic)]), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’] Organometallic iridium complexes with phenylpyridine derivatives having electron-withdrawing groups as ligands, such as iridium(III) acetylacetonate (abbreviated as FIracac), are examples of such compounds that exhibit blue phosphorescence and have emission peaks at 440 nm to 520 nm.

[0063] In addition, tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)3]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)3]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)2(acac)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]), (acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm)2(acac)]), (acetylacetonato)bis[5-methyl-6-( Organometallic iridium complexes having a pyrimidine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-Me)2(acac)]) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-iPr)2(acac)]), and organometallic iridium complexes having a pyrazine skeleton, such as tris(2-phenylpyridinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(ppy)3]), bis(2-phenylpyridinato-N,C 2’)iridium(III) acetylacetonate (abbreviation: [Ir(ppy)2(acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: [Ir(bzq)2(acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq)3]), tris(2-phenylquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(pq)3]), bis(2-phenylquinolinato-N,C 2’ In addition to organometallic iridium complexes having a pyridine skeleton such as iridium(III) acetylacetonate (abbreviation: [Ir(pq)2(acac)]), rare earth metal complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)3(Phen)]) can be mentioned. These are compounds that mainly exhibit green phosphorescence, and have an emission peak at 500 nm to 600 nm. In addition, organometallic iridium complexes having a pyrimidine skeleton are particularly preferred because they are remarkably excellent in reliability and luminous efficiency.

[0064] In addition, organometallic iridium complexes having a pyrimidine skeleton, such as (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm)2(dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm)2(dpm)]), and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm)2(dpm)]), Organometallic iridium complexes with a pyrazine skeleton, such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)2(dpm)]), and (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq)2(acac)]), and tris(1-phenylisoquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(piq)3]), bis(1-phenylisoquinolinato-N,C 2’ In addition to organometallic iridium complexes with a pyridine skeleton such as iridium(III) acetylacetonate (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)(monophenanthroline)europium(III) (abbreviated as [Eu(DBM)3(Phen)]) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviated as [Eu(TTA)3(Phen)]) are examples of such compounds that exhibit red phosphorescence and have an emission peak at 600 nm to 700 nm. Furthermore, an organometallic iridium complex having a pyrazine skeleton can emit red light with good chromaticity.

[0065] In addition to the phosphorescent compounds described above, known phosphorescent light-emitting materials may be selected and used.

[0066] TADF materials include fullerene and its derivatives, acridine and its derivatives, eosin derivatives, etc. Also included are metal-containing porphyrins including magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), palladium (Pd), etc. Examples of the metal-containing porphyrin include protoporphyrin-tin fluoride complex (SnF2(Proto IX)), mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), octaethylporphyrin-tin fluoride complex (SnF2(OEP)), etioporphyrin-tin fluoride complex (SnF2(Etio I)), and octaethylporphyrin-platinum chloride complex (PtCl2OEP), which are shown in the following structural formulas.

[0067] [ka]

[0068] In addition, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ) shown in the following structural formula, 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: PCCzTzn), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: P Heterocyclic compounds having one or both of a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, such as 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), and 10-phenyl-10H,10'H-spiro[acridin-9,9'-anthracene]-10'-one (abbreviation: ACRSA), can also be used. The heterocyclic compound has a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, and therefore has high electron transport and hole transport properties, and is therefore preferred. Among the skeletons having a π-electron deficient heteroaromatic ring, the pyridine skeleton, the diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and the triazine skeleton are preferred because they are stable and reliable. In particular, the benzofuropyrimidine skeleton, the benzothienopyrimidine skeleton, the benzofuropyrazine skeleton, and the benzothienopyrazine skeleton are preferred because they have high acceptor properties and good reliability. In addition, among the skeletons having a π-electron rich heteroaromatic ring, the acridine skeleton, the phenoxazine skeleton, the phenothiazine skeleton, the furan skeleton, the thiophene skeleton, and the pyrrole skeleton are preferred because they are stable and reliable.In addition, the furan skeleton is preferably a dibenzofuran skeleton, and the thiophene skeleton is preferably a dibenzothiophene skeleton. In addition, the pyrrole skeleton is particularly preferably an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, or a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton. In addition, a substance in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded is particularly preferable because the electron donating property of the π-electron-rich heteroaromatic ring and the electron accepting property of the π-electron-deficient heteroaromatic ring are both strong, and the energy difference between the S1 level and the T1 level is small, so that thermally activated delayed fluorescence can be efficiently obtained. In addition, an aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used instead of the π-electron-deficient heteroaromatic ring. In addition, an aromatic amine skeleton, a phenazine skeleton, or the like can be used as the π-electron-rich skeleton. In addition, examples of the π-electron-deficient skeleton that can be used include a xanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a boron-containing skeleton such as phenylborane or boranthrene, an aromatic ring or a heteroaromatic ring having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, etc. In this way, a π-electron-deficient skeleton and a π-electron-rich skeleton can be used in place of at least one of a π-electron-deficient heteroaromatic ring and a π-electron-rich heteroaromatic ring.

[0069] [ka]

[0070] TADF materials are materials that have a small difference between the S1 and T1 levels and have the function of converting triplet excitation energy to singlet excitation energy by reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy by a small amount of thermal energy (reverse intersystem crossing), and singlet excitation states can be generated efficiently. In addition, triplet excitation energy can be converted into light emission.

[0071] In addition, exciplexes (also called exciplexes), which form an excited state with two types of substances, have an extremely small difference between the S1 level and the T1 level and function as TADF materials that can convert triplet excitation energy into singlet excitation energy.

[0072] As an index of the T1 level, a phosphorescence spectrum observed at low temperatures (for example, 77 K to 10 K) may be used. For a TADF material, when a tangent is drawn at the base of the short wavelength side of the fluorescence spectrum, and the energy of the wavelength of the extrapolated line is taken as the S1 level, and a tangent is drawn at the base of the short wavelength side of the phosphorescence spectrum, and the energy of the wavelength of the extrapolated line is taken as the T1 level, the difference between S1 and T1 is preferably 0.3 eV or less, and more preferably 0.2 eV or less.

[0073] In addition, when a TADF material is used as the emission center material, the S1 level of the host material is preferably higher than the S1 level of the TADF material, and the T1 level of the host material is preferably higher than the T1 level of the TADF material.

[0074] As the host material of the light-emitting layer, various carrier transporting materials such as a material having an electron transporting property, a material having a hole transporting property, or the above-mentioned TADF material can be used.

[0075] As a material having hole transport properties, an organic compound having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton is preferable. For example, 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP ... mBPAFLP, 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBANB) , 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF) and other aromatic amine skeletons. Compounds with a carbazole skeleton, such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), compounds with a carbazole skeleton, such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,Examples of the compound include compounds having a thiophene skeleton such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the above, compounds having an aromatic amine skeleton and compounds having a carbazole skeleton are preferable because they have good reliability, high hole transport properties, and contribute to reducing the driving voltage. In addition, the hole transport material given as an example of the second substance above can also be used.

[0076] Examples of materials having electron transport properties include metal complexes such as bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), as well as organic compounds having a π-electron-deficient heteroaromatic ring skeleton.Examples of organic compounds having a π-electron-deficient heteroaromatic ring skeleton include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), Heterocyclic compounds with polyazole skeletons such as 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), and 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II) are also available. 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]dibenzo[f,h]quinoxaline Examples of the heterocyclic compounds include heterocyclic compounds having a diazine skeleton such as 4,6mPnP2Pm, 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), and heterocyclic compounds having a pyridine skeleton such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB). Among the above, heterocyclic compounds having a diazine skeleton and heterocyclic compounds having a pyridine skeleton are preferred because of their good reliability. In particular, heterocyclic compounds having a diazine (pyrimidine or pyrazine) skeleton have high electron transport properties and contribute to reducing the driving voltage.

[0077] As a TADF material that can be used as a host material, the same TADF materials listed above can be used. When a TADF material is used as a host material, the triplet excitation energy generated in the TADF material is converted to singlet excitation energy by reverse intersystem crossing, and the energy is further transferred to the luminescent center substance, thereby increasing the luminous efficiency of the light-emitting device. In this case, the TADF material functions as an energy donor, and the luminescent center substance functions as an energy acceptor.

[0078] This is very effective when the luminescent center substance is a fluorescent substance. In this case, in order to obtain high luminous efficiency, the S1 level of the TADF material is preferably higher than the S1 level of the fluorescent substance. In addition, the T1 level of the TADF material is preferably higher than the S1 level of the fluorescent substance. Therefore, the T1 level of the TADF material is preferably higher than the T1 level of the fluorescent substance.

[0079] It is also preferable to use a TADF material that emits light that overlaps with the wavelength of the lowest energy absorption band of the fluorescent material, because this allows for smooth transfer of excitation energy from the TADF material to the fluorescent material, resulting in efficient emission.

[0080] In addition, in order to efficiently generate singlet excitation energy from triplet excitation energy by reverse intersystem crossing, it is preferable that carrier recombination occurs in the TADF material. In addition, it is preferable that the triplet excitation energy generated in the TADF material does not transfer to the triplet excitation energy of the fluorescent material. For this purpose, it is preferable that the fluorescent material has a protective group around the luminophore (skeleton causing light emission) of the fluorescent material. As the protective group, a substituent having no π bond is preferable, and a saturated hydrocarbon is preferable, specifically, an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 10 carbon atoms are mentioned, and it is more preferable that there are a plurality of protective groups. Since a substituent having no π bond has poor function of transporting carriers, the distance between the TADF material and the luminophore of the fluorescent material can be increased without affecting carrier transport or carrier recombination. Here, the luminophore refers to an atomic group (skeleton) causing light emission in the fluorescent material. The luminophore preferably has a skeleton having a π bond, preferably contains an aromatic ring, and preferably has a condensed aromatic ring or a condensed heteroaromatic ring. Examples of the condensed aromatic ring or the condensed heteroaromatic ring include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, and a phenothiazine skeleton. In particular, fluorescent substances having a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, or a naphthobisbenzofuran skeleton are preferred because they have a high fluorescence quantum yield.

[0081] When a fluorescent material is used as the luminescence center material, a material having an anthracene skeleton is suitable as the host material. When a material having an anthracene skeleton is used as the host material of a fluorescent material, it is possible to realize an emission layer having both good luminescence efficiency and durability. As a material having an anthracene skeleton to be used as a host material, a material having a diphenylanthracene skeleton, particularly a 9,10-diphenylanthracene skeleton, is preferable because it is chemically stable. In addition, when the host material has a carbazole skeleton, it is preferable because the injection and transport properties of holes are improved, but when the host material contains a benzocarbazole skeleton in which a benzene ring is further condensed to carbazole, the HOMO is shallower by about 0.1 eV than that of carbazole, making it easier for holes to enter, which is more preferable. In particular, when the host material contains a dibenzocarbazole skeleton, it is preferable because the HOMO is shallower by about 0.1 eV than that of carbazole, making it easier for holes to enter, and it also has excellent hole transport properties and high heat resistance. Therefore, a more preferable host material is a material having both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole skeleton or a dibenzocarbazole skeleton). From the viewpoint of the hole injection / transport property, a benzofluorene skeleton or a dibenzofluorene skeleton may be used instead of the carbazole skeleton. Examples of such a material include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: CzPA), and 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: CzPA). Examples of such compounds include carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4'-yl}anthracene (abbreviation: FLPPA), and 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth).In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA are preferred choices since they exhibit very good properties.

[0082] The host material may be a mixture of a plurality of substances, and when a mixture of host materials is used, it is preferable to mix a material having an electron transporting property with a material having a hole transporting property. By mixing a material having an electron transporting property with a material having a hole transporting property, the transporting property of the light-emitting layer 113 can be easily adjusted, and the recombination region can be easily controlled. The weight ratio of the content of the material having a hole transporting property to the material having an electron transporting property may be 1:19 to 19:1 (material having a hole transporting property:material having an electron transporting property).

[0083] A phosphorescent material can be used as a part of the mixed material. The phosphorescent material can be used as an energy donor that provides excitation energy to a fluorescent material when the fluorescent material is used as the luminescence center material.

[0084] In addition, these mixed materials may form an exciplex. As a combination of materials to be mixed, it is preferable to select a combination that forms an exciplex that emits light that overlaps with the wavelength of the lowest energy absorption band of the light-emitting material, because this makes energy transfer smooth and allows efficient emission. In addition, the use of this configuration is preferable because the driving voltage is also reduced.

[0085] At least one of the materials forming the exciplex may be a phosphorescent material, which allows the triplet excitation energy to be efficiently converted into singlet excitation energy by reverse intersystem crossing.

[0086] As a combination of materials that efficiently form an exciplex, it is preferable that the HOMO level of the material having hole transport properties is equal to or higher than the HOMO level of the material having electron transport properties. It is also preferable that the LUMO level of the material having hole transport properties is equal to or higher than the LUMO level of the material having electron transport properties. The LUMO level and HOMO level of the material can be derived from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV) measurement.

[0087] The formation of an exciplex can be confirmed, for example, by comparing the emission spectrum of a material having hole transport properties, the emission spectrum of a material having electron transport properties, and the emission spectrum of a mixed film obtained by mixing these materials, and observing the phenomenon that the emission spectrum of the mixed film shifts to a longer wavelength than the emission spectrum of each material (or has a new peak on the longer wavelength side). Alternatively, the formation of an exciplex can be confirmed by comparing the transient photoluminescence (PL) of a material having hole transport properties, the transient PL of a material having electron transport properties, and the transient PL of a mixed film obtained by mixing these materials, and observing the difference in transient response, such as the transient PL lifetime of the mixed film having a longer lifetime component than the transient PL lifetime of each material, or the proportion of delayed components becoming larger. The above-mentioned transient PL may also be read as transient electroluminescence (EL). That is, the formation of an exciplex can also be confirmed by comparing the transient EL of a material having hole transport properties, the transient EL of a material having electron transport properties, and the transient EL of a mixed film obtained by mixing these materials, and observing the difference in transient response.

[0088] The electron transport layer 114 is preferably provided in contact with the light-emitting layer 113 as shown in FIG. 1A1 and contains a seventh substance and an eighth substance. The seventh substance is an organic compound that has a dominant electron transport property over a hole transport property. The electron mobility of the electron transport layer 114 is 1×10 at a square root of an electric field strength [V / cm] of 600. -7 cm 2 / Vs or more 5×10 -5 cm 2 It is preferable that the value is equal to or less than / Vs.

[0089] The eighth substance is an alkali metal or an alkali metal simple substance, compound, or complex, and preferably contains an 8-hydroxyquinolinato structure. Specific examples include 8-hydroxyquinolinato-lithium (abbreviation: Liq) and 8-hydroxyquinolinato-sodium (abbreviation: Naq). In particular, a complex of a monovalent metal ion, particularly a lithium complex, is preferred, and Liq is more preferred. In addition, when the 8-hydroxyquinolinato structure is contained, its methyl-substituted product (for example, a 2-methyl-substituted product or a 5-methyl-substituted product) can also be used.

[0090] The eighth substance in the electron-transport layer 114 preferably has a concentration difference (including the case where the concentration of the eighth substance is 0) in the thickness direction. This enables the light-emitting device of one embodiment of the present invention to have a long life and high reliability.

[0091] There may be many configurations in which the concentration of the eighth substance in the electron transport layer 114 differs in the thickness direction. For example, the concentration of the eighth substance may have a concentration gradient in which the concentration decreases (including zero) from the light-emitting layer side to the cathode side in the electron transport layer 114; as shown in FIG. 1A2 , the electron transport layer 114 has multiple layers, such as a first electron transport layer 114-1 and a second electron transport layer 114-2 from the light-emitting layer 113 side, and the layer closer to the light-emitting layer among the multiple layers has a higher concentration of the eighth substance than the layer closer to the cathode; or the electron transport layer 114 has a first electron transport layer located on the light-emitting layer side and a second electron transport layer located on the cathode side, and the concentration of the eighth substance in the first electron transport layer is higher than the concentration of the eighth substance in the second electron transport layer. In another embodiment, the electron transport layer 114 may have a plurality of layers, and a layer having a higher concentration of the eighth substance than the concentration of the eighth substance in the layer closest to the cathode may be present in any of the remaining layers. It may also be said that the electron transport layer 114 has a first region located on the light-emitting layer side and a second region located on the cathode side, and a difference in concentration of the eighth substance exists between the first region and the second region. The concentration of the eighth substance may be high in the first region or high in the second region, but the embodiment in which the concentration of the eighth substance is high in the first region is more preferable because it is easier to obtain a light-emitting device with a long life. The electron transport layer 114 may have a region other than the first region and the second region.

[0092] In addition, the concentration of the eighth substance may change continuously as in Figures 2A1 and 2A2 when there is no clear layer boundary as in Figure 1A1, or may change stepwise as in Figures 2B1 and 2B2 when it is clear that the substance is separated into layers as in Figure 1A2.

[0093] Note that the seventh substance preferably has an electron transporting property and a HOMO level of −6.0 eV or higher.

[0094] Other examples of organic compounds having electron-transporting properties that can be used as the seventh substance include the organic compounds having electron-transporting properties that can be used as the host material described above, and the organic compounds that can be used as the host material for the fluorescent substance described above.

[0095] Moreover, the region where the concentration of the eighth substance is low includes a region where the concentration of the eighth substance is zero.

[0096] The region with a high concentration of the eighth material and the region with a low concentration of the eighth material can be formed by changing the mixing ratio of the seventh material and the eighth material. However, different substances may be used as the seventh material and the eighth material in the region with a high concentration of the eighth material and the region with a low concentration of the eighth material.

[0097] In addition, the seventh material preferably has a smaller electron mobility than the sixth material or the light-emitting layer 113 when the square root of the electric field strength [V / cm] is 600.

[0098] When the light-emitting layer has an excess of electrons, the light-emitting region 113-1 is limited to a certain area as shown in FIG. 3A, which places a large burden on that area and accelerates degradation. In addition, the lifetime and light-emitting efficiency are also reduced when electrons pass through the light-emitting layer without being able to recombine. In one embodiment of the present invention, the transportability of electrons in the electron transport layer 114 is reduced, thereby expanding the light-emitting region 113-1 as shown in FIG. 3B, and distributing the burden on the material constituting the light-emitting layer 113, thereby providing a light-emitting device with a long lifetime and good light-emitting efficiency.

[0099] In addition, in a light-emitting device having such a configuration, a deterioration curve of luminance obtained by a drive test under a constant current density condition may have a shape having a maximum value. That is, the deterioration curve of a light-emitting device according to one embodiment of the present invention may have a shape having a portion where the luminance increases with time. A light-emitting device exhibiting such deterioration behavior can offset the rapid deterioration at the beginning of driving, which is called initial deterioration, by the increase in luminance, and can be a light-emitting device with small initial deterioration and very good driving life. Such a light-emitting device is referred to as a Recombination-Site Tailoring Injection element (ReSTI element).

[0100] Note that when the differentiation of a deterioration curve having such a maximum value is taken, there is a portion where the value is 0. Therefore, it can be said that a light-emitting device according to one embodiment of the present invention, in which the differentiation of the deterioration curve has a portion where the value is 0, is a light-emitting device that has small initial deterioration and has a very long life.

[0101] The light-emitting device according to one embodiment of the present invention having the above-described structure can have an extremely long lifetime, particularly in a region where degradation up to about LT95 is extremely small.

[0102] Furthermore, by being able to suppress initial deterioration, it will be possible to significantly reduce the problem of burn-in, which is still discussed as one of the major weaknesses of OLED devices, and the effort required for aging before shipment to reduce this problem.

[0103] As described above, the hole injection layer in one embodiment of the light-emitting device of the present invention has a hole transport material with a deep HOMO level, so that induced holes are easily injected into the hole transport layer and the light-emitting layer. Therefore, in the initial stage of operation, it is easy to create a state in which holes, although only a small portion of them, pass through the light-emitting layer and reach the electron transport layer.

[0104] Here, since the electron transport layer of the light-emitting device in one embodiment of the present invention contains an electron transport material and an alkali metal or alkaline earth metal simple substance, compound, or complex (or contains an electron transport material and a metal complex having a ligand containing an 8-hydroxyquinolinato structure and a monovalent metal ion), when the light-emitting device is continuously lit, a phenomenon is observed in which the electron injection and transport properties of the electron transport layer are improved. On the other hand, as described above, the hole injection layer is adequately suppressed inducing holes, so that it is not possible to supply many holes to the electron transport layer. As a result, the number of holes that can reach the electron transport layer decreases over time, and the probability that holes will recombine with electrons in the light-emitting layer increases. In other words, a shift in the carrier balance occurs during continuous lighting such that recombination is more likely to occur in the light-emitting layer. This shift results in a light-emitting device with suppressed initial deterioration.

[0105] (Embodiment 2) Next, examples of the detailed structure and materials of the above-mentioned light-emitting device will be described. In this embodiment, an EL layer 103 consisting of a plurality of layers is provided between a pair of electrodes, an anode 101 and a cathode 102, and the EL layer 103 includes, from the anode 101 side, 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. However, various layer structures such as a hole injection layer, a hole transport layer, an electron injection layer, a carrier block layer, an exciton block layer, and a charge generation layer can be applied to the layers included in the EL layer 103.

[0106] The anode 101 is preferably formed using a metal, alloy, conductive compound, or mixture thereof having a large work function (specifically, 4.0 eV or more). Specific examples include indium oxide-tin oxide (ITO), indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). These conductive metal oxide films are usually formed by a sputtering method, but may be formed by applying a sol-gel method or the like. As an example of a method for forming the indium oxide-zinc oxide, there is a method for forming the indium oxide-zinc oxide by a sputtering method using a target containing 1 to 20 wt % zinc oxide added to indium oxide. In addition, indium oxide containing tungsten oxide and zinc oxide (IWZO) can also be formed by a sputtering method using a target containing 0.5 to 5 wt % tungsten oxide and 0.1 to 1 wt % zinc oxide relative to indium oxide. Other examples include gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), and nitrides of metal materials (for example, titanium nitride). Graphene can also be used. Note that here, typical substances having a large work function and used to form an anode are listed. However, in one embodiment of the present invention, a composite material containing an organic compound having a hole-transporting property and a substance showing an electron-accepting property with respect to the organic compound is used for the hole-injection layer 111, and therefore an electrode material can be selected regardless of the work function.

[0107] Regarding the laminated structure of the EL layer 103, two types of structures will be described in this embodiment: a structure having an electron injection layer 115 in addition to a hole injection layer 111, a hole transport layer 112 (first hole transport layer 112-1, second hole transport layer 112-2), a light emitting layer 113, and an electron transport layer 114 (first electron transport layer 114-1, second electron transport layer 114-2) as shown in Figures 1A1 and 1A2, and a structure having a charge generation layer 116 instead of the electron injection layer 115 as shown in Figure 1B. The materials constituting each layer are specifically described below.

[0108] The hole injection layer 111, the hole transport layer 112 (hole transport layer 112-1, hole transport layer 112-2), the light emitting layer 113, and the electron transport layer 114 (electron transport layer 114-1, electron transport layer 114-2) have been described in detail in the first embodiment, so that repeated description will be omitted. Please refer to the description in the first embodiment.

[0109] Between the electron transport layer 114 and the cathode 102, a layer containing an alkali metal or alkaline earth metal, such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), or a compound thereof may be provided as the electron injection layer 115. The electron injection layer 115 may be a layer made of a substance having electron transport properties containing an alkali metal or alkaline earth metal, or a compound thereof, or an electride. Examples of the electride include a substance in which electrons are added at a high concentration to a mixed oxide of calcium and aluminum.

[0110] Alternatively, a charge generation layer 116 may be provided between the electron transport layer 114 and the cathode 102 instead of the electron injection layer 115 (FIG. 1B). The charge generation layer 116 is a layer capable of injecting holes into a layer in contact with the cathode side of the layer and electrons into a layer in contact with the anode side of the layer by applying a potential. 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 listed above as a material capable of forming the hole injection layer 111. The P-type layer 117 may also be formed by laminating a film containing an electron accepting material and a film containing a hole transport material, both of which are materials that constitute the composite material. By applying a potential to the P-type layer 117, electrons are injected into the electron transport layer 114 and holes are injected into the cathode 102, and the light-emitting device operates.

[0111] It is preferable that the charge generating layer 116 is provided with either or both of an electron relay layer 118 and an electron injection buffer layer 119 in addition to the P-type layer 117 .

[0112] The electron relay layer 118 contains at least a substance having electron transport properties, and has a function of preventing interaction between the electron injection buffer layer 119 and the P-type layer 117 and smoothly transferring electrons. The LUMO level of the substance having electron transport properties contained in the electron relay layer 118 is preferably between the LUMO level of the electron accepting substance in the P-type layer 117 and the LUMO level of the substance contained in the layer in contact with the charge generation layer 116 in the electron transport layer 114. The specific energy level of the LUMO level of the substance having electron transport properties used in the electron relay layer 118 is -5.0 eV or more, preferably -5.0 eV or more and -3.0 eV or less. Note that the substance having electron transport properties used in the electron relay layer 118 is preferably a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand.

[0113] The electron injection buffer layer 119 can be made of a material with high electron injection properties, such as an alkali metal, an alkaline earth metal, a rare earth metal, or a compound thereof (an alkali metal compound (including an oxide such as lithium oxide, a halide, or a carbonate such as lithium carbonate or cesium carbonate), an alkaline earth metal compound (including an oxide, a halide, or a carbonate), or a rare earth metal compound (including an oxide, a halide, or a carbonate)).

[0114] In addition, when the electron-injection buffer layer 119 is formed containing a substance having an electron-transporting property and an electron-donating substance, as the electron-donating substance, alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates)) as well as organic compounds such as tetrathianaphthacene (abbreviation: TTN), nickelocene, and decamethylnickelocene can be used. Note that as the substance having an electron-transporting property, a material similar to the material constituting the electron-transporting layer 114 described above can be used.

[0115] As a material for forming the cathode 102, metals, alloys, electrically conductive compounds, and mixtures thereof having a small work function (specifically, 3.8 eV or less) can be used. Specific examples of such cathode materials include alkali metals such as lithium (Li) and cesium (Cs), elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), and strontium (Sr), and alloys containing these (MgAg, AlLi), rare earth metals such as europium (Eu), ytterbium (Yb), and alloys containing these. However, by providing an electron injection layer between the cathode 102 and the electron transport layer, various conductive materials such as Al, Ag, ITO, indium oxide-tin oxide containing silicon or silicon oxide can be used as the cathode 102 regardless of the magnitude of the work function. These conductive materials can be formed into films using dry methods such as vacuum deposition and sputtering, inkjet methods, spin coating methods, and the like. Also, it may be formed by a wet method using a sol-gel method, or may be formed by a wet method using a paste of a metal material.

[0116] In addition, various methods, whether dry or wet, can be used to form the EL layer 103. For example, a vacuum deposition method, a gravure printing method, an offset printing method, a screen printing method, an inkjet method, or a spin coating method may be used.

[0117] Moreover, the above-mentioned electrodes or layers may be formed using different film formation methods.

[0118] The configuration of the layer provided between the anode 101 and the cathode 102 is not limited to the above. However, a configuration in which a light-emitting region where holes and electrons recombine is provided at a position away from the anode 101 and the cathode 102 is preferable so as to suppress quenching caused by the proximity of the light-emitting region to metals used in the electrodes and the carrier injection layer.

[0119] In addition, the hole transport layer and electron transport layer in contact with the light-emitting layer 113, particularly the carrier transport layer close to the recombination region in the light-emitting layer 113, are preferably composed of a substance having a band gap larger than the band gap of the light-emitting material constituting the light-emitting layer or the light-emitting material contained in the light-emitting layer, in order to suppress energy transfer from excitons generated in the light-emitting layer.

[0120] Next, an embodiment of a light-emitting device having a configuration in which a plurality of light-emitting units are stacked (also called a stacked element or a tandem element) will be described with reference to FIG. 1C. This light-emitting device has a plurality of light-emitting units between an anode and a cathode. One light-emitting unit has a configuration almost similar to that of the EL layer 103 shown in FIG. 1A1 or 1A2. In other words, the light-emitting device shown in FIG. 1C is a light-emitting device having a plurality of light-emitting units, and the light-emitting devices shown in FIG. 1A1, FIG. 1A2, and FIG. 1B can be said to be light-emitting devices having one light-emitting unit.

[0121] 1C, a first light-emitting unit 511 and a second light-emitting unit 512 are laminated between an anode 501 and a cathode 502, and a charge generation layer 513 is provided between the first light-emitting unit 511 and the second light-emitting unit 512. The anode 501 and the cathode 502 correspond to the anode 101 and the cathode 102 in FIG. 1A1, respectively, and the same as those described in the description of FIG. 1A1 can be applied. In addition, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same configuration or different configurations.

[0122] Charge generation layer 513 has a function of injecting electrons into one light-emitting unit and injecting holes into the other light-emitting unit when a voltage is applied between anode 501 and cathode 502. That is, when a voltage is applied so that the potential of the anode is higher than the potential of the cathode in FIG. 1C, charge generation layer 513 only needs to inject electrons into first light-emitting unit 511 and inject holes into second light-emitting unit 512.

[0123] The charge generation layer 513 is preferably formed in the same structure as the charge generation layer 116 described in FIG. 1B. A composite material of an organic compound and a metal oxide has excellent carrier injection and carrier transport properties, and therefore can realize low-voltage driving and low-current driving. When the anode side surface of the light-emitting unit is in contact with the charge generation layer 513, the charge generation layer 513 can also play the role of the hole injection layer of the light-emitting unit, so that the light-emitting unit does not need to be provided with a hole injection layer.

[0124] Furthermore, when an electron injection buffer layer 119 is provided in the charge generation layer 513, the electron injection buffer layer 119 plays the role of an electron injection layer in the light-emitting unit on the anode side, so that it is not necessarily necessary to form an electron injection layer in the light-emitting unit on the anode side.

[0125] Although the light-emitting device having two light-emitting units has been described in Fig. 1C, the present invention can be applied to a light-emitting device having three or more light-emitting units stacked in the same manner. By disposing a plurality of light-emitting units between a pair of electrodes and separating them with a charge generating layer 513 as in the light-emitting device according to the present embodiment, it is possible to realize an element that can emit light with high brightness while keeping the current density low and has a long life. In addition, it is possible to realize a light-emitting device that can be driven at a low voltage and consumes low power.

[0126] Moreover, by making the emission colors of the respective light-emitting units different, it is possible to obtain light emission of a desired color as the whole light-emitting device. For example, in a light-emitting device having two light-emitting units, it is possible to obtain a light-emitting device that emits white light as the whole light-emitting device by obtaining red and green emission colors in the first light-emitting unit and blue emission color in the second light-emitting unit. In addition, as a configuration of a light-emitting device in which three or more light-emitting units are stacked, for example, a tandem type device can be used in which the first light-emitting unit has a first blue light-emitting layer, the second light-emitting unit has a yellow or yellow-green light-emitting layer and a red light-emitting layer, and the third light-emitting unit has a second blue light-emitting layer. The tandem type device can obtain white light emission like the above-mentioned light-emitting device.

[0127] In addition, each layer and electrode such as the above-mentioned EL layer 103, the first light-emitting unit 511, the second light-emitting unit 512, and the charge generation layer can be formed by using, for example, a deposition method (including a vacuum deposition method), a droplet discharge method (also called an ink-jet method), a coating method, a gravure printing method, etc. In addition, they may contain a low molecular weight material, a medium molecular weight material (including an oligomer and a dendrimer), or a polymer material.

[0128] (Embodiment 3) In this embodiment, a light emitting apparatus using the light emitting device described in the first and second embodiments will be described.

[0129] In this embodiment, a light-emitting device manufactured using the light-emitting device described in Embodiments 1 and 2 will be described with reference to FIG. 4. FIG. 4A is a top view showing the light-emitting device, and FIG. 4B is a cross-sectional view taken along the lines AB and CD in FIG. 4A. This light-emitting device includes a driver circuit section (source line driver circuit) 601, a pixel section 602, and a driver circuit section (gate line driver circuit) 603, all of which are shown by dotted lines, for controlling the light emission of the light-emitting device. Reference numeral 604 denotes a sealing substrate, 605 denotes a sealant, and the inside surrounded by the sealant 605 defines a space 607.

[0130] The lead wiring 608 is a wiring for transmitting signals input to the source line driving circuit 601 and the gate line driving circuit 603, and receives a video signal, a clock signal, a start signal, a reset signal, and the like from an FPC (flexible printed circuit) 609 serving as an external input terminal. Although only an FPC is shown here, a printed wiring board (PWB) may be attached to this FPC. In this specification, the light emitting device includes not only the light emitting device itself, but also a state in which an FPC or a PWB is attached to it.

[0131] Next, the cross-sectional structure will be described with reference to Fig. 4B. A driver circuit section and a pixel section are formed on an element substrate 610, but here, a source line driver circuit 601, which is the driver circuit section, and one pixel in a pixel section 602 are shown.

[0132] The element substrate 610 may be made of a substrate made of glass, quartz, organic resin, metal, alloy, semiconductor, or a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl fluoride), polyester, acrylic, or the like.

[0133] The structure of the transistor used in the pixel or the driver circuit is not particularly limited. For example, the transistor may be an inverted staggered type transistor or a staggered type transistor. In addition, the transistor may be a top-gate type transistor or a bottom-gate type transistor. The semiconductor material used for the transistor is not particularly limited, and for example, silicon, germanium, silicon carbide, gallium nitride, or the like may be used. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In-Ga-Zn-based metal oxide, may be used.

[0134] The crystallinity of a semiconductor material used for a transistor is not particularly limited, and any of an amorphous semiconductor and a crystalline semiconductor (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor having a crystalline region in a part) may be used. The use of a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0135] Here, in addition to the transistors provided in the pixels and driver circuits, an oxide semiconductor is preferably used for semiconductor devices such as transistors used in touch sensors, which will be described later. In particular, an oxide semiconductor having a wider band gap than silicon is preferably used. By using an oxide semiconductor having a wider band gap than silicon, the current in the off state of the transistor can be reduced.

[0136] The oxide semiconductor preferably contains at least indium (In) or zinc (Zn), and more preferably contains an oxide represented by In-M-Zn oxide (M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0137] Here, an oxide semiconductor that can be used in one embodiment of the present invention is described below.

[0138] Oxide semiconductors are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors other than those mentioned above. Examples of non-single-crystal oxide semiconductors include c-axis aligned crystalline oxide semiconductors (CAAC-OS), polycrystalline oxide semiconductors, nano crystalline oxide semiconductors (nc-OS), amorphous-like oxide semiconductors (a-like OS), and amorphous oxide semiconductors.

[0139] CAAC-OS has a c-axis orientation and a distorted crystal structure in which multiple nanocrystals are connected in the ab-plane direction. The distortion refers to a portion where the lattice orientation changes between a region with a uniform lattice arrangement and a region with a different uniform lattice arrangement in the region where multiple nanocrystals are connected.

[0140] Nanocrystals are basically hexagonal, but may be non-regular hexagonal. In addition, the lattice arrangement may be pentagonal or heptagonal due to the distortion. It is difficult to confirm clear grain boundaries in CAAC-OS even near the distortion. In other words, it is found that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is because CAAC-OS can tolerate distortion due to the lack of dense arrangement of oxygen atoms in the ab-plane direction and the change in the bond distance between atoms due to the substitution of metal elements.

[0141] CAAC-OS also tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium and oxygen (hereinafter, In layer) and a layer containing element M, zinc, and oxygen (hereinafter, (M, Zn) layer) are stacked. Note that indium and element M can be substituted for each other, and when element M in an (M, Zn) layer is substituted for indium, it can also be expressed as an (In, M, Zn) layer. When indium in an In layer is substituted for element M, it can also be expressed as an (In, M) layer.

[0142] CAAC-OS is an oxide semiconductor with high crystallinity. On the other hand, it is difficult to identify clear crystal boundaries in CAAC-OS, so it can be said that the decrease in electron mobility caused by crystal boundaries is unlikely to occur. In addition, the crystallinity of oxide semiconductors can be decreased by the introduction of impurities or the generation of defects. Therefore, CAAC-OS is not prone to impurities or defects (oxygen vacancies (V O The oxide semiconductor having the CAAC-OS has stable physical properties. Therefore, the oxide semiconductor having the CAAC-OS has high heat resistance and reliability.

[0143] The nc-OS has periodic atomic arrangement in a microscopic region (for example, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In addition, the nc-OS does not show regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is seen throughout the film. Therefore, depending on the analysis method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor.

[0144] Indium-gallium-zinc oxide (hereinafter, IGZO), a type of oxide semiconductor containing indium, gallium, and zinc, may have a stable structure when made into the above-mentioned nanocrystals. In particular, since IGZO tends to have difficulty in crystal growth in the air, it may be structurally more stable when made into small crystals (for example, the above-mentioned nanocrystals) rather than large crystals (here, crystals of several mm or several cm).

[0145] The a-like OS is an oxide semiconductor having a structure between the nc-OS and an amorphous oxide semiconductor. The a-like OS has a pore or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS.

[0146] Oxide semiconductors have a variety of structures and have different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, an nc-OS, and a CAAC-OS.

[0147] As an alternative to the oxide semiconductor, a cloud-aligned composite (CAC)-OS may be used.

[0148] CAC-OS is a material in which some of the material has a conductive function and some of the material has an insulating function, and the material as a whole functions as a semiconductor. When CAC-OS is used in the active layer of a transistor, the conductive function is a function of allowing electrons (or holes) to flow as carriers, and the insulating function is a function of not allowing electrons to flow as carriers. By making the conductive function and the insulating function act in a complementary manner, it is possible to give the CAC-OS a switching function (on / off function). By separating the respective functions in CAC-OS, it is possible to maximize both functions.

[0149] The CAC-OS has a conductive region and an insulating region. The conductive region has the above-mentioned conductive function, and the insulating region has the above-mentioned insulating function. In the material, the conductive region and the insulating region may be separated at the nanoparticle level. In addition, the conductive region and the insulating region may be unevenly distributed in the material. In addition, the conductive region may be observed to be connected in a cloud shape with a blurred periphery.

[0150] In addition, in the CAC-OS, the conductive regions and the insulating regions may each be 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.

[0151] In addition, the CAC-OS is composed of components having different band gaps. For example, the CAC-OS is composed of a component having a wide gap due to an insulating region and a component having a narrow gap due to a conductive region. In this configuration, when carriers are caused to flow, the carriers mainly flow in the component having the narrow gap. In addition, the component having the narrow gap acts complementarily to the component having the wide gap, and carriers also flow in the component having the wide gap in conjunction with the component having 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, that is, a large on-current and a high field effect mobility can be obtained in the on-state of the transistor.

[0152] That is, CAC-OS can also be called a matrix composite or a metal matrix composite.

[0153] By using the above-described oxide semiconductor material for the semiconductor layer, a change in electrical characteristics can be suppressed, and a highly reliable transistor can be realized.

[0154] In addition, the transistor having the above-mentioned semiconductor layer can hold charge accumulated in a capacitance through the transistor for a long period of time due to its low off-state current. By applying such a transistor to a pixel, it is possible to stop a driver circuit while maintaining the gray level of an image displayed in each display region. As a result, an electronic device with extremely low power consumption can be realized.

[0155] It is preferable to provide an undercoat film in order to stabilize the characteristics of the transistor. The undercoat film can be prepared as a single layer or a multilayer structure using an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film. The undercoat film can be formed by a sputtering method, a CVD (Chemical Vapor Deposition) method (such as a plasma CVD method, a thermal CVD method, or a MOCVD (Metal Organic CVD) method), an ALD (Atomic Layer Deposition) method, a coating method, a printing method, or the like. Note that the undercoat film need not be provided if it is not necessary.

[0156] The FET 623 indicates one of the transistors formed in the driving circuit section 601. The driving circuit may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. Although the present embodiment shows a driver-integrated type in which a driving circuit is formed on a substrate, this is not necessarily required, and the driving circuit may be formed externally instead of on the substrate.

[0157] In addition, the pixel section 602 is formed of a plurality of pixels including a switching FET 611, a current control FET 612, and an anode 613 electrically connected to the drain of the FET 612. However, the present invention is not limited to this, and the pixel section may be formed by combining three or more FETs and a capacitive element.

[0158] An insulator 614 is formed to cover the end of the anode 613. Here, the insulator 614 can be formed by using a positive type photosensitive acrylic.

[0159] In order to improve the covering ability of an EL layer or the like to be formed later, a curved surface having a curvature is formed at the upper end or lower end of the insulator 614. For example, when a positive type photosensitive acrylic is used as the material of the insulator 614, it is preferable that only the upper end of the insulator 614 has a curved surface having a radius of curvature (0.2 μm to 3 μm). In addition, either a negative type photosensitive resin or a positive type photosensitive resin can be used as the insulator 614.

[0160] An EL layer 616 and a cathode 617 are formed on the anode 613. Here, it is desirable to use a material with a large work function as the material used for the anode 613. For example, in addition to a single layer film such as an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing 2 to 20 wt % zinc oxide, a titanium nitride film, a chromium film, a tungsten film, a Zn film, or a Pt film, a laminated structure of a titanium nitride film and a film mainly composed of aluminum, or a three-layer structure of a titanium nitride film, a film mainly composed of aluminum, and a titanium nitride film, can be used. Note that the laminated structure has low resistance as wiring, provides good ohmic contact, and can further function as an anode.

[0161] The EL layer 616 is formed by various methods such as a deposition method using a deposition mask, an inkjet method, a spin coating method, etc. The EL layer 616 includes the configurations described in the first and second embodiments. Other materials constituting the EL layer 616 may be low molecular weight compounds or high molecular weight compounds (including oligomers and dendrimers).

[0162] Furthermore, it is preferable to use a material having a small work function (such as Al, Mg, Li, Ca, or alloys or compounds thereof (MgAg, MgIn, AlLi, etc.)) as a material used for the cathode 617 formed on the EL layer 616. When the light generated in the EL layer 616 is transmitted through the cathode 617, it is preferable to use a laminate of a thin metal thin film and a transparent conductive film (ITO, indium oxide containing 2 to 20 wt % zinc oxide, indium tin oxide containing silicon, zinc oxide (ZnO), etc.) as the cathode 617.

[0163] Note that a light-emitting device is formed with the anode 613, the EL layer 616, and the cathode 617. The light-emitting device is the light-emitting device described in Embodiments 1 and 2. Note that a pixel portion is formed with a plurality of light-emitting devices, but the light-emitting device in this embodiment may include both the light-emitting devices described in Embodiments 1 and 2 and light-emitting devices having other structures.

[0164] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with a sealant 605, a structure is formed in which a light emitting device 618 is provided in a space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealant 605. The space 607 is filled with a filler, and may be filled with an inert gas (nitrogen, argon, etc.) or a sealant. A recess is formed in the sealing substrate and a desiccant is provided therein to suppress deterioration due to the influence of moisture, which is a preferable configuration.

[0165] It is preferable to use epoxy resin or glass frit for the sealing material 605. It is also preferable that these materials are as moisture and oxygen impermeable as possible. In addition to glass and quartz substrates, materials that can be used for the sealing substrate 604 include plastic substrates made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic, etc.

[0166] Although not shown in Fig. 4, a protective film may be provided on the cathode. The protective film may be formed of an organic resin film or an inorganic insulating film. The protective film may be formed so as to cover the exposed portion of the sealant 605. The protective film may be provided so as to cover the surfaces and side surfaces of the pair of substrates, the exposed side surfaces of the sealing layer, the insulating layer, etc.

[0167] The protective film can be made of a material that is difficult for impurities such as water to permeate, and therefore can effectively prevent impurities such as water from diffusing from the outside to the inside.

[0168] The protective film may be made of an oxide, a nitride, a fluoride, a sulfide, a ternary compound, a metal, a polymer, or the like. For example, a material containing 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, or the like; a material containing aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, gallium nitride, or the like; a nitride containing titanium and aluminum; an oxide containing titanium and aluminum; an oxide containing aluminum and zinc; a sulfide containing manganese and zinc; a sulfide containing cerium and strontium; an oxide containing erbium and aluminum; an oxide containing yttrium and zirconium, or the like.

[0169] The protective film is preferably formed using a film formation method with good step coverage. One such method is the atomic layer deposition (ALD) method. It is preferable to use a material that can be formed using the ALD method for the protective film. By using the ALD method, it is possible to form a dense protective film with reduced defects such as cracks and pinholes, or with a uniform thickness. In addition, it is possible to reduce damage to the processed member when forming the protective film.

[0170] For example, by forming a protective film using the ALD method, it is possible to form a uniform protective film with few defects on surfaces with complex uneven shapes, as well as on the top, side, and back surfaces of a touch panel.

[0171] In the above manner, a light-emitting device manufactured using the light-emitting device described in Embodiments 1 and 2 can be obtained.

[0172] The light-emitting device in this embodiment uses the light-emitting device described in Embodiment 1 and Embodiment 2, and therefore a light-emitting device with good characteristics can be obtained. Specifically, the light-emitting device described in Embodiment 1 and Embodiment 2 has a long life, and therefore a light-emitting device with good reliability can be obtained. In addition, the light-emitting device using the light-emitting device described in Embodiment 1 and Embodiment 2 has good luminous efficiency, and therefore a light-emitting device with low power consumption can be obtained.

[0173] Fig. 5 shows an example of a full-color light-emitting device in which a light-emitting device that emits white light is formed and a colored layer (color filter) is provided, etc. Fig. 5A shows a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral section 1042, a pixel section 1040, a driving circuit section 1041, anodes 1024W, 1024R, 1024G, 1024B of the light-emitting device, a partition wall 1025, an EL layer 1028, a cathode 1029 of the light-emitting device, a sealing substrate 1031, a sealant 1032, etc.

[0174] In FIG. 5A, the colored layers (red colored layer 1034R, green colored layer 1034G, blue colored layer 1034B) are provided on a transparent base material 1033. A black matrix 1035 may be further provided. The transparent base material 1033 on which the colored layers and black matrix are provided is aligned and fixed to the substrate 1001. The colored layers and black matrix 1035 are covered with an overcoat layer 1036. In FIG. 5A, there are light-emitting layers from which light does not pass through the colored layers and goes out, and light-emitting layers from which light passes through the colored layers of each color and goes out. The light that does not pass through the colored layers is white, and the light that passes through the colored layers is red, green, and blue, so that an image can be expressed by four color pixels.

[0175] 5B shows an example in which the 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. In this manner, the colored layers may be provided between the substrate 1001 and the sealing substrate 1031.

[0176] In the light-emitting device described above, the light-emitting device has a structure (bottom emission type) in which light is extracted to the substrate 1001 side on which the FET is formed, but the light-emitting device may have a structure (top emission type) in which light is extracted to the sealing substrate 1031 side. A cross-sectional view of a top emission type light-emitting device is shown in FIG. 6. In this case, a substrate that does not transmit light can be used as the substrate 1001. The process is performed in the same manner as the bottom emission type light-emitting device until a connection electrode that connects the FET and the anode of the light-emitting device is formed. Then, a third interlayer insulating film 1037 is formed to cover the electrode 1022. This insulating film may play a role of planarization. The third interlayer insulating film 1037 can be formed using the same material as the second interlayer insulating film, as well as other known materials.

[0177] The anodes 1024W, 1024R, 1024G, and 1024B of the light-emitting device are anodes in this embodiment, but may be formed as cathodes. In addition, in the case of a top-emission type light-emitting device as shown in FIG. 6, it is preferable that the anodes are reflective electrodes. The EL layer 1028 has a structure as described for the EL layer 103 in the first and second embodiments, and has an element structure that can emit white light.

[0178] In the top emission structure as shown in FIG. 6, sealing can be performed with a sealing substrate 1031 provided with colored layers (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B). A black matrix 1035 may be provided on the sealing substrate 1031 so as to be located between pixels. The colored layers (the red colored layer 1034R, the green colored layer 1034G, and the blue colored layer 1034B) and the black matrix may be covered with an overcoat layer 1036. Note that a substrate having light transmissivity is used as the sealing substrate 1031. In addition, although an example of full color display using four colors, red, green, blue, and white, is shown here, the present invention is not particularly limited, and full color display using four colors, red, yellow, green, and blue, or three colors, red, green, and blue, may be used.

[0179] In top-emission type light-emitting devices, the application of a microcavity structure is suitable. A light-emitting device having a microcavity structure can be obtained by using a reflective electrode as the anode and a semi-transmissive / semi-reflective electrode as the cathode. At least an EL layer is present between the reflective electrode and the semi-transmissive / semi-reflective electrode, and at least a light-emitting layer that becomes the light-emitting region is present.

[0180] The reflectance of the reflective electrode to visible light is 40% to 100%, preferably 70% to 100%, and the resistivity is 1×10 -2 The semi-transmitting and semi-reflective electrode has a visible light reflectance of 20% to 80%, preferably 40% to 70%, and a resistivity of 1×10 -2 It is assumed that the film has a resistance of less than Ωcm.

[0181] Light emitted from a light-emitting layer included in the EL layer is reflected by the reflective electrode and the semi-transmissive and semi-reflective electrode, causing resonance.

[0182] In this light-emitting device, the optical distance between the reflective electrode and the semi-transmissive / semi-reflective electrode can be changed by changing the thickness of the transparent conductive film, the above-mentioned composite material, the carrier transport material, etc. This makes it possible to intensify the light of resonating wavelengths and attenuate the light of non-resonating wavelengths between the reflective electrode and the semi-transmissive / semi-reflective electrode.

[0183] In addition, since the light reflected by the reflective electrode and returned (first reflected light) causes significant interference with the light (first incident light) that is directly incident on the semi-transmissive and semi-reflective electrode from the light-emitting layer, it is preferable to adjust the optical distance between the reflective electrode and the light-emitting layer to (2n-1)λ / 4 (where n is a natural number equal to or greater than 1, and λ is the wavelength of the emitted light to be amplified). By adjusting the optical distance, the phase of the first reflected light and the first incident light can be aligned, thereby further amplifying the light emitted from the light-emitting layer.

[0184] In the above configuration, the EL layer may have a plurality of light-emitting layers or a single light-emitting layer. For example, the EL layer may be combined with the above-mentioned tandem light-emitting device configuration to provide a single light-emitting device with a plurality of EL layers sandwiched between charge generating layers, and each EL layer may have a single or multiple light-emitting layers.

[0185] The microcavity structure makes it possible to increase the emission intensity of a specific wavelength in the front direction, thereby reducing power consumption. In the case of a light-emitting device that displays images using four sub-pixels of red, yellow, green, and blue, in addition to the brightness improvement effect of yellow emission, the microcavity structure that matches the wavelength of each color can be applied to all sub-pixels, resulting in a light-emitting device with good characteristics.

[0186] The light-emitting device in this embodiment uses the light-emitting device described in Embodiment 1 and Embodiment 2, and therefore a light-emitting device with good characteristics can be obtained. Specifically, the light-emitting device described in Embodiment 1 and Embodiment 2 has a long life, and therefore a light-emitting device with good reliability can be obtained. In addition, the light-emitting device using the light-emitting device described in Embodiment 1 and Embodiment 2 has good luminous efficiency, and therefore a light-emitting device with low power consumption can be obtained.

[0187] (Embodiment 4) In this embodiment, an example in which the light-emitting device described in Embodiments 1 and 2 is used as a lighting device will be described with reference to Fig. 7. Fig. 7B is a top view of the lighting device, and Fig. 7A is a cross-sectional view taken along line ef in Fig. 7B.

[0188] In the lighting device of this embodiment, an anode 401 is formed on a light-transmitting substrate 400 serving as a support. The anode 401 corresponds to the anode 101 in the second embodiment. When light is extracted from the anode 401 side, the anode 401 is formed from a light-transmitting material.

[0189] A pad 412 for supplying a voltage to the cathode 404 is formed on the substrate 400 .

[0190] An EL layer 403 is formed on the anode 401. The EL layer 403 corresponds to the configuration of the EL layer 103 in the first and second embodiments, or a combination of the light-emitting units 511 and 512 and the charge generation layer 513. For details of these configurations, see the descriptions therein.

[0191] A cathode 404 is formed to cover the EL layer 403. The cathode 404 corresponds to the cathode 102 in the second embodiment. When light is extracted from the anode 401 side, the cathode 404 is formed of a material with high reflectivity. The cathode 404 is connected to a pad 412 to supply a voltage.

[0192] As described above, the lighting device described in this embodiment has a light-emitting device including the anode 401, the EL layer 403, and the cathode 404. Since the light-emitting device has high emission efficiency, the lighting device in this embodiment can consume little power.

[0193] The lighting device is completed by adhering and sealing the substrate 400 on which the light-emitting device having the above-mentioned configuration is formed and the sealing substrate 407 using the sealing materials 405 and 406. Either one of the sealing materials 405 and 406 may be used. Also, a desiccant may be mixed into the inner sealing material 406 (not shown in FIG. 7B), which allows it to adsorb moisture and improves reliability.

[0194] Moreover, the pad 412 and a part of the anode 401 can be extended outside the sealing materials 405 and 406 to serve as an external input terminal. Also, an IC chip 420 equipped with a converter or the like may be provided thereon.

[0195] As described above, the lighting device described in this embodiment uses the light-emitting device described in Embodiments 1 and 2 as an EL element, and can be a highly reliable light-emitting device. In addition, the lighting device can be a light-emitting device with low power consumption.

[0196] (Embodiment 5) In this embodiment, an example of an electronic device including the light-emitting device described in the first and second embodiments will be described. The light-emitting device described in the first and second embodiments has a long life and is a highly reliable light-emitting device. As a result, the electronic device described in this embodiment can be an electronic device having a highly reliable light-emitting part.

[0197] Examples of electronic devices to which the light-emitting devices are applied include television sets (also called televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game machines, personal digital assistants, audio playback devices, large game machines such as pachinko machines, etc. Specific examples of these electronic devices are shown below.

[0198] 8A illustrates an example of a television set. In the television set, a display portion 7103 is incorporated in a housing 7101. Here, the housing 7101 is supported by a stand 7105. Images can be displayed by the display portion 7103, and the display portion 7103 is configured in such a manner that the light-emitting devices described in Embodiments 1 and 2 are arranged in a matrix.

[0199] The television device can be operated using an operation switch provided on the housing 7101 or a separate remote control 7110. Using operation keys 7109 provided on the remote control 7110, the channel and volume can be controlled, and an image displayed on the display portion 7103 can be operated. The remote control 7110 may be provided with a display portion 7107 that displays information output from the remote control 7110.

[0200] The television device is configured to include a receiver, a modem, etc. The receiver can receive general television broadcasts, and by connecting to a wired or wireless communication network via the modem, it is also possible to perform one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers, etc.) information communication.

[0201] FIG. 8B1 shows a computer, which includes a main body 7201, a housing 7202, a display portion 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, and the like. Note that this computer is manufactured by arranging the light-emitting devices described in Embodiments 1 and 2 in a matrix and using them for the display portion 7203. The computer in FIG. 8B1 may have a form as shown in FIG. 8B2. The computer in FIG. 8B2 is provided with a second display portion 7210 instead of the keyboard 7204 and the pointing device 7206. The second display portion 7210 is a touch panel type, and input can be performed by operating the display for input displayed on the second display portion 7210 with a finger or a dedicated pen. The second display portion 7210 can display not only the display for input, but also other images. The display portion 7203 may also be a touch panel. The two screens are connected by a hinge, which can prevent trouble such as scratches or breakage of the screens during storage or transportation.

[0202] 8C shows an example of a mobile terminal. The mobile phone has a display portion 7402 in which the light-emitting devices described in Embodiments 1 and 2 are arranged in a matrix. Note that the mobile phone includes operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like in addition to the display portion 7402 incorporated in a housing 7401.

[0203] 8C can be configured so that information can be input by touching the display portion 7402 with a finger or the like. In this case, operations such as making a call or composing an e-mail can be performed by touching the display portion 7402 with a finger or the like.

[0204] The screen of the display unit 7402 has three main modes. The first is a display mode that is mainly for displaying images, the second is an input mode that is mainly for inputting information such as characters, and the third is a display + input mode that combines the display mode and the input mode.

[0205] For example, when making a call or composing an e-mail, the display portion 7402 may be set to a character input mode mainly for inputting characters, and the character input operation may be performed by inputting characters displayed on the screen. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display portion 7402.

[0206] In addition, by providing a detection device having a sensor for detecting tilt, such as a gyro or an acceleration sensor, inside the mobile terminal, the orientation of the mobile terminal (portrait or landscape) can be determined and the screen display of the display portion 7402 can be automatically switched.

[0207] The screen mode can be switched by touching the display portion 7402 or by operating operation buttons 7403 on the housing 7401. The mode can also be switched depending on the type of image displayed on the display portion 7402. For example, if the image signal to be displayed on the display portion is moving image data, the mode is switched to the display mode, and if it is text data, the mode is switched to the input mode.

[0208] In addition, in the input mode, a signal detected by an optical sensor of the display portion 7402 may be detected, and if there is no input by a touch operation on the display portion 7402 for a certain period of time, the screen mode may be controlled to be switched from the input mode to the display mode.

[0209] The display portion 7402 can also function as an image sensor. For example, personal authentication can be performed by touching the display portion 7402 with a palm or a finger to capture an image of a palm print, a fingerprint, or the like. In addition, finger veins, palm veins, or the like can be captured by using a backlight that emits near-infrared light or a sensing light source that emits near-infrared light for the display portion.

[0210] Note that the structure described in this embodiment mode can be used by appropriately combining the structures described in any of Embodiment Modes 1 to 4.

[0211] As described above, the light-emitting device having the light-emitting device described in the first and second embodiments has a very wide range of application, and the light-emitting device can be applied to electronic devices in a variety of fields. By using the light-emitting device described in the first and second embodiments, highly reliable electronic devices can be obtained.

[0212] FIG. 9A is a schematic diagram showing an example of a cleaning robot.

[0213] The cleaning robot 5100 has a display 5101 arranged on the top surface, a plurality of cameras 5102 arranged on the side surface, a brush 5103, and an operation button 5104. Although not shown, the bottom surface of the cleaning robot 5100 is provided with tires, a suction port, and the like. The cleaning robot 5100 also has various sensors such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezoelectric sensor, an optical sensor, and a gyro sensor. The cleaning robot 5100 also has wireless communication means.

[0214] The cleaning robot 5100 can move by itself, detect dirt 5120, and suck up the dirt from a suction port provided on the bottom surface.

[0215] In addition, the cleaning robot 5100 can analyze the image captured by the camera 5102 and determine the presence or absence of obstacles such as walls, furniture, steps, etc. Furthermore, when an object that may become entangled in the brush 5103, such as a wire, is detected by image analysis, the rotation of the brush 5103 can be stopped.

[0216] The remaining battery level, the amount of sucked up dirt, etc. can be displayed on the display 5101. The route traveled by the cleaning robot 5100 may be displayed on the display 5101. The display 5101 may be a touch panel, and an operation button 5104 may be provided on the display 5101.

[0217] The cleaning robot 5100 can communicate with a portable electronic device 5140 such as a smartphone. Images captured by the camera 5102 can be displayed on the portable electronic device 5140. Therefore, the owner of the cleaning robot 5100 can know the state of the room even when he or she is away from home. Also, the display on the display 5101 can be confirmed on a portable electronic device such as a smartphone.

[0218] The light-emitting device according to one embodiment of the present invention can be used for the display 5101 .

[0219] The robot 2100 shown in FIG. 9B 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.

[0220] The microphone 2102 has a function of detecting the user's voice, environmental sounds, etc. The speaker 2104 has a function of emitting sound. The robot 2100 can communicate with the user using the microphone 2102 and the speaker 2104.

[0221] The display 2105 has a function of displaying various information. The robot 2100 can display information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. The display 2105 may also be a removable information terminal, and by installing it in a fixed position on the robot 2100, charging and data transfer are possible.

[0222] The upper camera 2103 and the lower camera 2106 have a function of capturing images of the surroundings of the robot 2100. In addition, the obstacle sensor 2107 can detect the presence or absence of an obstacle in the moving direction when the robot 2100 moves forward using the moving mechanism 2108. The robot 2100 can recognize the surrounding environment and move safely using the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107. The light-emitting device of one embodiment of the present invention can be used for the display 2105.

[0223] 9C is a diagram showing an example of a goggle-type display. The goggle-type display includes, for example, a housing 5000, a display unit 5001, a speaker 5003, an LED lamp 5004, a connection terminal 5006, a sensor 5007 (including a function for measuring force, displacement, position, speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared), a microphone 5008, a display unit 5002, a support unit 5012, and an earphone 5013.

[0224] The light-emitting device of one embodiment of the present invention can be used for the display portion 5001 and the display portion 5002 .

[0225] 10 shows an example in which the light-emitting device described in Embodiments 1 and 2 is used in a desk lamp, which is a lighting device. The desk lamp shown in Fig. 10 has a housing 2001 and a light source 2002, and the lighting device described in Embodiment 3 may be used as the light source 2002.

[0226] FIG. 11 shows an example in which the light-emitting device according to the first and second embodiments is used as an indoor lighting device 3001. The light-emitting device according to the first and second embodiments is a highly reliable light-emitting device, and therefore can be used as a highly reliable lighting device. In addition, the light-emitting device according to the first and second embodiments can be made large in area, and therefore can be used as a large-area lighting device. In addition, the light-emitting device according to the first and second embodiments is thin, and therefore can be used as a thin lighting device.

[0227] The light-emitting devices described in Embodiments 1 and 2 can also be mounted on a windshield or dashboard of an automobile. FIG 12 shows an example in which the light-emitting devices described in Embodiments 1 and 2 are used on a windshield or dashboard of an automobile. Display regions 5200 to 5203 are provided using the light-emitting devices described in Embodiments 1 and 2.

[0228] A display region 5200 and a display region 5201 are display devices equipped with the light-emitting devices described in the first and second embodiments, which are provided on the windshield of an automobile. The light-emitting devices described in the first and second embodiments can be made into a so-called see-through display device, in which the opposite side can be seen through, by fabricating the anode and cathode with light-transmitting electrodes. If the display is in a see-through state, the display device can be installed on the windshield of an automobile without interfering with the view. When a transistor for driving is provided, a light-transmitting transistor such as an organic transistor made of an organic semiconductor material or a transistor using an oxide semiconductor is preferably used.

[0229] The display area 5202 is a display device provided on a pillar and equipped with the light-emitting device described in Embodiments 1 and 2. By displaying an image from an imaging means provided on the vehicle body in the display area 5202, the view blocked by the pillar can be complemented. Similarly, the display area 5203 provided on the dashboard can complement the view blocked by the vehicle body by displaying an image from an imaging means provided on the outside of the vehicle, thereby compensating for blind spots and improving safety. By displaying an image to complement the invisible parts, safety can be confirmed more naturally and without discomfort.

[0230] The display area 5203 can also provide various other information, such as navigation information, a speedometer, a tachometer, and the setting status of an air conditioner. The display items and layout can be changed as appropriate to suit the user's preferences. Note that this information can also be provided in the display areas 5200 to 5202. The display areas 5200 to 5203 can also be used as lighting devices.

[0231] 13A and 13B show a foldable mobile information terminal 5150. The foldable mobile information terminal 5150 has a housing 5151, a display area 5152, and a bending portion 5153. Fig. 13A shows the mobile information terminal 5150 in an unfolded state. Fig. 13B shows the mobile information terminal in a folded state. Although the mobile information terminal 5150 has a large display area 5152, it is compact and highly portable when folded.

[0232] Display area 5152 can be folded in half by bending portion 5153. Bending portion 5153 is composed of an expandable member and multiple support members, and when folding, the expandable member stretches and bending portion 5153 is folded with a radius of curvature of 2 mm or more, preferably 3 mm or more.

[0233] Note that the display region 5152 may be a touch panel (input / output device) equipped with a touch sensor (input device). The light-emitting device of one embodiment of the present invention can be used for the display region 5152.

[0234] 14A to 14C show a foldable portable information terminal 9310. Fig. 14A shows the portable information terminal 9310 in an unfolded state. Fig. 14B shows the portable information terminal 9310 in a state in the process of changing from one of the unfolded state and the folded state to the other. Fig. 14C shows the portable information terminal 9310 in a folded state. The portable information terminal 9310 has excellent portability in the folded state, and has excellent viewability of the display due to a seamless wide display area in the unfolded state.

[0235] The display panel 9311 is supported by three housings 9315 connected by hinges 9313. Note that the display panel 9311 may be a touch panel (input / output device) equipped with a touch sensor (input device). The display panel 9311 can be reversibly transformed from an unfolded state of the mobile information terminal 9310 to a folded state by bending the two housings 9315 via the hinges 9313. The light-emitting device of one embodiment of the present invention can be used for the display panel 9311. EXAMPLES

[0236] In this example, a light-emitting device 1 according to one embodiment of the present invention will be described. The structural formula of an organic compound used in the light-emitting device 1 is shown below.

[0237] [ka]

[0238] (Method of manufacturing light-emitting device 1-1) First, indium tin oxide containing silicon oxide (ITSO) was formed into a film on a glass substrate by sputtering to form the anode 101. The film thickness was 70 nm, and the electrode area was 2 mm×2 mm.

[0239] Next, as a pretreatment for forming a light-emitting device on the substrate, the substrate surface was washed with water, baked at 200° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0240] Then, 10 -4 The substrate was introduced into a vacuum deposition apparatus whose inside had been reduced in pressure to about Pa, and vacuum baking was carried out at 170° C. for 30 minutes in a heating chamber in the vacuum deposition apparatus, and then the substrate was allowed to cool for about 30 minutes.

[0241] Next, the substrate on which the anode 101 was formed was fixed to a substrate holder provided in a vacuum deposition apparatus so that the surface on which the anode 101 was formed faced downward. On the anode 101, N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf) represented by the above structural formula (i) and ALD-MP001Q (Bunseki Kobo Co., Ltd., material serial number: 1S20180314) were co-deposited to a thickness of 10 nm by a deposition method using resistance heating so as to have a weight ratio of 1:0.05 (=BBABnf:ALD-MP001Q) to form a hole injection layer 111.

[0242] Next, BBABnf was deposited on the hole injection layer 111 to a thickness of 20 nm as a first hole transport layer 112-1, and then 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole (abbreviation: PCzN2) represented by the above structural formula (ii) was deposited on the hole injection layer 111 to a thickness of 10 nm as a second hole transport layer 112-2 to form the hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0243] Next, 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth) represented by the above structural formula (iii) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by (iv) were co-deposited to a thickness of 25 nm in a weight ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form the light-emitting layer 113.

[0244] Thereafter, 2-{4-[9,10-di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN) represented by the above structural formula (v) and 8-hydroxyquinolinato-lithium (abbreviation: Liq) represented by the above structural formula (vi) were co-deposited on the light-emitting layer 113 to a thickness of 25 nm in a weight ratio of 1:1 (=ZADN:Liq) to form an electron-transporting layer 114.

[0245] After forming the electron transport layer 114, Liq was evaporated to a thickness of 1 nm to form the electron injection layer 115, and then aluminum was evaporated to a thickness of 200 nm to form the cathode 102, thereby producing the light-emitting device 1 of this embodiment.

[0246] (Method of manufacturing light-emitting device 1-2) Light-emitting device 1-2 was fabricated in the same manner as light-emitting device 1-1, except that hole-injection layer 111 was co-deposited to a thickness of 10 nm so as to have a weight ratio of BBABnf:ALD-MP001Q=1:0.1.

[0247] (Method of manufacturing light-emitting device 2-1) Light-emitting device 2-1 was prepared in the same manner as light-emitting device 1-1, except that BBABnf in light-emitting device 1-1 was replaced with 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-fluoren-9-yl)triphenylamine (abbreviation: FLPAPA) represented by the above structural formula (vii).

[0248] (Method of manufacturing light-emitting device 2-2) Light-emitting device 2-2 was fabricated in the same manner as light-emitting device 1-2, except that BBABnf in light-emitting device 1-2 was replaced with FLPAPA.

[0249] (Method of manufacturing comparative light-emitting device) The comparative light-emitting device was prepared in the same manner as light-emitting device 1-2, except that BBABnf in light-emitting device 1-2 was changed to N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine (abbreviation: PCBBiF) represented by the above structural formula (viii), and PCzN2 was changed to N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP) represented by the above structural formula (ix).

[0250] The device structures of light-emitting device 1-1, light-emitting device 1-2, light-emitting device 2-1, light-emitting device 2-2 and the comparative light-emitting device are summarized in the following table.

[0251] [Table 1]

[0252] Here, a table showing the HOMO level, LUMO level, and electron mobility at a square root of an electric field strength [V / cm] of 600 of the organic compounds used in this example is shown below.

[0253] [Table 2]

[0254] These light-emitting devices were sealed with a glass substrate in a nitrogen-atmosphere glove box to prevent exposure to the atmosphere (a sealant was applied around the elements, and UV treatment was performed during sealing, followed by heat treatment at 80°C for 1 hour), after which the initial characteristics and reliability of Light-emitting Device 1-1, Light-emitting Device 1-2, Light-emitting Device 2-1, Light-emitting Device 2-2, and the comparative light-emitting device were measured. The measurements were performed at room temperature.

[0255] The luminance-current density characteristics of the light-emitting device 1 are shown in Fig. 15, the current efficiency-luminance characteristics in Fig. 16, the luminance-voltage characteristics in Fig. 17, the current-voltage characteristics in Fig. 18, the external quantum efficiency-luminance characteristics in Fig. 19, and the emission spectrum in Fig. 20. 2 The main characteristics of the area are shown in Table 3.

[0256] [Table 3]

[0257] 15 to 20 and Table 3 show that light-emitting device 1 according to one embodiment of the present invention is a blue light-emitting device having favorable initial characteristics.

[0258] In addition, the current density is 50mA / cm 2 A graph showing the change in luminance with respect to drive time in the light-emitting devices 1-1 and 1-2 and the light-emitting devices 2-1 and 2-2 is shown in Fig. 21. As shown in Fig. 21, the luminance of the light-emitting devices 1-1 and 1-2 and the light-emitting devices 2-1 and 2-2 increases after drive, reaches a level higher than the initial luminance, and then gradually decreases. This shows that the drive life was significantly improved, especially when the degradation level was as low as 2 to 5%.

[0259] Next, the electron spin resonance spectrum was obtained by the ESR method for the material constituting the hole injection layer in each light-emitting device.

[0260] The samples used in the measurements are described below. All samples were formed on a quartz substrate measuring 3.0 mm×19 to 22 mm by co-evaporating an acceptor material (ALD-MP001Q in this example) as a first substance and a hole transport material (BBABnf for light-emitting devices 1-1 and 1-2, FLPAPA for light-emitting devices 2-1 and 2-2, and PCBBiF for the comparative light-emitting device) as a second substance.

[0261] The sample was fixed to a holder in a vacuum deposition apparatus so that the surface to be deposited faced downwards, and the vacuum apparatus was evacuated for 10 -4 After reducing the pressure to 10 Pa, the first and second substances were co-deposited. The film thickness of the sample was adjusted to the range of 100 nm to 1000 nm.

[0262] The molar ratio of the first and second substances in each sample was adjusted by the deposition rate. The weight ratio and molar ratio of the first and second substances in each sample are shown in Table 4 below. In the ESR measurement, two or four samples with the same organic compound type and molar ratio were stacked and measured. In this example, samples with a different mixture ratio from that used in the light-emitting device were also prepared and measured.

[0263] [Table 4]

[0264] The measurement of the electron spin resonance spectrum by the ESR method was carried out using an electron spin resonance measuring device JES FA300 type (manufactured by JEOL Ltd.). The above measurement was carried out at room temperature with a resonance frequency of about 9.2 GHz, output power of 1 mW, modulation magnetic field of 50 mT, modulation width of 0.5 mT, time constant of 0.03 sec, and sweep time of 1 min. 2+ The magnetic field was corrected based on the positions of the third and fourth signals, and the spin density was calculated from the peak area of ​​the electron spin resonance spectrum obtained by the measurement. The g value calculated from the peak of the electron spin resonance spectrum was about 2.00, which was consistent with the g value of free electrons.

[0265] Fig. 22 is a graph showing the relationship between the molar ratio of the first substance to the second substance in each sample and the spin density calculated by measuring the electron spin resonance spectrum. As shown in Fig. 22, the spin density of Samples 1-1, 1-2, Samples 2-1, 2-2, which have the same molar ratio as the materials constituting the hole injection layers of Light-emitting Devices 1-1, 1-2, Light-emitting Devices 2-1, 2-2, and Sample 1-3, which uses the same hole transport material, is 1 x 10 19 spins / cm 3 It was found that the following was true.

[0266] If the spin density is too low, the hole injection ability is impaired. Therefore, the spin density is set to 1×10 16 spins / cm 3 More preferably, 1×10 17 spins / cm 3 More preferably, 3×10 17 spins / cm 3 It was found that more than this is good.

[0267] <Reference example 1> In this reference example, a method for calculating the HOMO level, LUMO level, and electron mobility of the organic compounds used in each example will be described.

[0268] The HOMO level and the LUMO level can be calculated based on cyclic voltammetry (CV) measurements.

[0269] The measurement device used was an electrochemical analyzer (manufactured by BAS Co., Ltd., model number: ALS model 600A or 600C). The solution used for CV measurement was prepared by dissolving the supporting electrolyte tetra-n-butylammonium perchlorate (n-Bu4NClO4) (manufactured by Tokyo Chemical Industry Co., Ltd., catalog number: T0836) in dehydrated dimethylformamide (DMF) (manufactured by Aldrich Co., Ltd., 99.8%, catalog number: 22705-6) to a concentration of 100 mmol / L, and further dissolving the measurement target to a concentration of 2 mmol / L. A platinum electrode (PTE platinum electrode, BAS Co., Ltd.) was used as the working electrode, a platinum electrode (Pt counter electrode (5 cm) for VC-3, BAS Co., Ltd.) was used as the auxiliary electrode, and an Ag / Ag+ electrode (RE7 non-aqueous solvent reference electrode, BAS Co., Ltd.) was used as the reference electrode. The measurements were performed at room temperature (20-25°C). The scan rate during CV measurements was standardized to 0.1 V / sec, and the oxidation potential Ea [V] and reduction potential Ec [V] relative to the reference electrode were measured. Ea was the midpoint potential of the oxidation-reduction wave, and Ec was the midpoint potential of the reduction-oxidation wave. Here, since the potential energy of the reference electrode used in this example with respect to the vacuum level is known to be -4.94 [eV], the HOMO level and LUMO level can be calculated from the formulas HOMO level [eV] = -4.94-Ea and LUMO level [eV] = -4.94-Ec, respectively.

[0270] The electron mobility can be measured by impedance spectroscopy (IS method).

[0271] The carrier mobility of EL materials has long been measured using the time-of-flight (TOF) method and the space-charge-limited current (SCLC) method, which uses the I-V characteristics of the SCLC. The TOF method requires a sample with a significantly thicker film thickness than an actual organic EL element. The SCLC method has the disadvantage of not being able to obtain the electric field strength dependence of the carrier mobility. The IS method requires a thin organic film thickness of only a few hundred nm, so it is possible to form a film with a relatively small amount of EL material. This method is characterized by being able to measure the mobility at a film thickness close to that of an actual EL element, and also being able to obtain the electric field strength dependence of the carrier mobility.

[0272] In the IS method, a minute sine wave voltage signal (V=V0[exp(jωt)]) is applied to the EL element, and the impedance (Z=V / I) of the EL element is calculated from the phase difference between the input signal and the current amplitude of the response current signal (I=I0exp[j(ωt+φ)]). By applying a voltage varying from high frequency to low frequency to the element, it is possible to separate and measure the components with various relaxation times that contribute to the impedance.

[0273] Here, admittance Y (=1 / Z), which is the reciprocal of impedance, can be expressed by conductance G and susceptance B as shown in the following equation (1).

[0274]

number

[0275] Furthermore, the following equations (2) and (3) can be calculated using a single charge injection model. Here, g (equation (4)) is the differential conductance. In the equations, C is the capacitance, θ is ωt, which is the travel angle, and ω is the angular frequency. t is the travel time. The current equation, Poisson's equation, and current continuity equation are used in the analysis, and the existence of diffusion current and trap levels is ignored.

[0276]

number

[0277] The -ΔB method is a method for calculating mobility from the frequency characteristics of capacitance, and the ωΔG method is a method for calculating mobility from the frequency characteristics of conductance.

[0278] In practice, first, a measuring element for the material for which the electron mobility is to be determined is prepared. This measuring element is designed so that only electrons flow as carriers. In this specification, a method for calculating mobility from the frequency characteristics of capacitance (-ΔB method) is explained. A schematic diagram of the measuring element used is shown in Figure 23.

[0279] The structure of the measurement element prepared for this measurement has a first layer 210, a second layer 211, and a third layer 212 between an anode 201 and a cathode 202, as shown in Figure 23. The material for which the electron mobility is to be determined can be used as the material for the second layer 211. Here, an example will be described in which the electron mobility of a co-evaporated film of ZADN and Liq at a 1:1 (weight ratio) was measured. Specific configuration examples are summarized in the table below.

[0280] [Table 5]

[0281] FIG. 24 shows the current density-voltage characteristics of an electron-only element fabricated using a co-evaporation film of ZADN and Liq as the second layer 211.

[0282] The impedance measurement was performed under the conditions of an AC voltage of 70 mV and a frequency of 1 Hz to 3 MHz while applying a DC voltage in the range of 5.0 V to 9.0 V. The capacitance was calculated from the admittance (the above-mentioned formula (1)), which is the reciprocal of the impedance obtained here. The frequency characteristic of the calculated capacitance C at an applied voltage of 7.0 V is shown in FIG.

[0283] The frequency characteristic of capacitance C is obtained because the space charge caused by the carriers injected by the minute voltage signal cannot completely follow the minute AC voltage, and a phase difference occurs in the current. Here, the transit time of the carriers in the film is defined as the time T for the injected carriers to reach the opposing electrode, and is expressed by the following formula (5).

[0284]

number

[0285] The negative susceptance change (-ΔB) corresponds to the capacitance change -ΔC multiplied by the angular frequency ω (-ωΔC). The lowest frequency peak frequency f' max (=ω max From equation (3), the relationship between the distance (km) from the center of gravity (P) to the travel time T can be derived as shown in equation (6).

[0286]

number

[0287] The frequency characteristic of -ΔB calculated from the above measurement (i.e., when the DC voltage is 7.0 V) is shown in Figure 26. The lowest frequency peak frequency f' obtained from Figure 26 max is indicated by an arrow in the figure.

[0288] f' obtained from the above measurements and analysis max From this, the transit time T can be calculated (see formula (6) above), and from formula (5) above, the electron mobility at a voltage of 7.0 V in this case can be calculated. By performing similar measurements at DC voltages in the range of 5.0 V to 9.0 V, the electron mobility at each voltage (electric field strength) can be calculated, and the electric field strength dependence of the mobility can also be measured.

[0289] Using the above calculation method, the final electron mobility dependence of each organic compound on electric field strength is shown in Figure 27. The square root of the electric field strength [V / cm] read from the figure is 600 [V / cm]. 1 / 2 The electron mobility values ​​at these times are shown in Table 9.

[0290] [Table 6]

[0291] It is possible to calculate the electron mobility in this way. For details on the measurement method, please refer to Takayuki Okachi et al., "Japanese Journal of Applied Physics," Vol. 47, No. 12, 2008, pp. 8965-8972. [Explanation of symbols]

[0292] 101: anode, 102: cathode, 103: EL layer, 111: hole injection layer, 112: hole transport layer, 112-1: first hole transport layer, 112-2: second hole transport layer, 113: light emitting layer, 113-1: light emitting region, 114: electron transport layer, 114-1: first electron transport layer, 114-2: second electron transport layer, 115: electron injection layer, 116: charge generation layer, 117: P-type layer, 118: electron relay layer, 119: electron injection buffer layer, 201: anode, 202: cathode, 210: first layer, 211: second layer, 212: third layer, 400: substrate, 401: anode, 403: EL layer, 40 4: cathode, 405: sealant, 406: sealant, 407: sealing substrate, 412: pad, 420: IC chip, 501: anode, 502: cathode, 511: first light-emitting unit, 512: second light-emitting unit, 513: charge generation layer, 601: drive circuit section (source line drive circuit), 602: pixel section, 603: drive circuit section (gate line drive circuit), 604: sealing substrate, 605: sealant, 607: space, 608: wiring, 609: FPC (flexible printed circuit), 610: element substrate, 611: switching FET, 612: current control FET, 613: anode , 614: insulator, 616: EL layer, 617: cathode, 618: light emitting device, 1001: substrate, 1002: undercoat insulating film, 1003: gate insulating film, 1006: gate electrode, 1007: gate electrode, 1008: gate electrode, 1020: first interlayer insulating film, 1021: second interlayer insulating film, 1022: electrode, 1024W: anode, 1024R: anode, 1024G: anode, 1024B: anode, 1025: partition wall, 1028: EL layer, 1029: cathode, 1031: sealing substrate, 1032: sealing material, 1033: transparent base material, 1034R: red colored layer, 1034G: green colored layer Color layer, 1034B: blue coloring layer, 1035: black matrix, 1036: overcoat layer, 1037: third interlayer insulating film, 1040: pixel section, 1041: driving circuit section, 1042: peripheral section, 2001: housing, 2002: light source, 2100: robot, 2110: computing device, 2101: illuminance sensor, 2102: microphone, 2103: upper camera, 2104: speaker, 2105: display, 2106: lower camera, 2107: obstacle sensor, 2108: moving mechanism, 3001: lighting device, 5000: housing, 5001: display section, 5002: display section,5003: speaker, 5004: LED lamp, 5006: connection terminal, 5007: sensor, 5008: microphone, 5012: support, 5013: earphone, 5100: cleaning robot, 5101: display, 5102: camera, 5103: brush, 5104: operation button, 5150: mobile information terminal, 5151: housing, 5152: display area, 5153: bending part, 5120: dust, 5200: display area, 5201: display area, 5202: display area, 5203: display area, 7101: housing, 7103 : Display unit, 7105: Stand, 7107: Display unit, 7109: Operation keys, 7110: Remote control unit, 7201: Main body, 7202: Housing, 7203: Display unit, 7204: Keyboard, 7205: External connection port, 7206: Pointing device, 7210: Second display unit, 7401: Housing, 7402: Display unit, 7403: Operation buttons, 7404: External connection port, 7405: Speaker, 7406: Microphone, 9310: Portable information terminal, 9311: Display panel, 9313: Hinge, 9315: Housing,

Claims

1. An anode; A cathode; A hole injection layer, a light emitting layer, and an electron transport layer are provided between the anode and the cathode, the hole injection layer comprises a hole transport material and an electron accepting material; the electron transport layer has a region in contact with the light emitting layer, the electron transport layer includes an electron transport material and any one of an alkali metal, an alkali metal compound, an alkali metal complex, an alkaline earth metal, an alkaline earth metal compound, and an alkaline earth metal complex; the electron accepting material is a material that exhibits electron accepting properties to the hole transport material, the hole transport material is an organic compound having a HOMO level of −5.7 eV or more and −5.4 eV or less, The spin density of the material constituting the hole injection layer measured by the ESR method is 1×10 １９ spins / cm ３ 2. A light emitting device, comprising:

2. An anode; A cathode; A hole injection layer, a light emitting layer, and an electron transport layer are provided between the anode and the cathode, the hole injection layer comprises a hole transport material and an electron accepting material; the electron transport layer has a region in contact with the light emitting layer, the electron transport layer includes an electron transport material and a metal complex having a ligand including an 8-hydroxyquinolinato structure and a monovalent metal ion; the electron accepting material is a material that exhibits electron accepting properties to the hole transport material, the hole transport material is an organic compound having a HOMO level of −5.7 eV or more and −5.4 eV or less, The spin density of the material constituting the hole injection layer measured by the ESR method is 1×10 １９ spins / cm ３ 2. A light emitting device, comprising:

3. An anode; A cathode; A hole injection layer, a light emitting layer, and an electron transport layer are provided between the anode and the cathode, the hole injection layer comprises a hole transport material and an electron accepting material; the electron transport layer has a region in contact with the light emitting layer, the electron transport layer includes an electron transport material and a lithium complex having a ligand including an 8-hydroxyquinolinato structure, the electron accepting material is a material that exhibits electron accepting properties to the hole transport material, the hole transport material is an organic compound having a HOMO level of −5.7 eV or more and −5.4 eV or less, The spin density of the material constituting the hole injection layer measured by the ESR method is 1×10 １９ spins / cm ３ 2. A light emitting device, comprising:

4. An anode; A cathode; A hole injection layer, a light emitting layer, and an electron transport layer are provided between the anode and the cathode, the hole injection layer comprises a hole transport material and an electron accepting material; the electron transport layer has a region in contact with the light emitting layer, The electron transport layer comprises an electron transport material, The HOMO level of the electron transport material is −6.0 eV or more; the electron accepting material is a material that exhibits electron accepting properties to the hole transport material, the hole transport material is an organic compound having a HOMO level of −5.7 eV or more and −5.4 eV or less, The spin density of the material constituting the hole injection layer measured by an ESR method is 1×10 １９ spins / cm ３ 2. A light emitting device, comprising:

5. An anode; A cathode; A hole injection layer, a light emitting layer, and an electron transport layer are provided between the anode and the cathode, the hole injection layer comprises a hole transport material and an electron accepting material; the electron transport layer has a region in contact with the light emitting layer, The electron transport layer comprises an electron transport material, the electron transport material is an organic compound having an anthracene skeleton, the electron accepting material is a material that exhibits electron accepting properties to the hole transport material, the hole transport material is an organic compound having a HOMO level of −5.7 eV or more and −5.4 eV or less, The spin density of the material constituting the hole injection layer measured by an ESR method is 1×10 １９ spins / cm ３ 2. A light emitting device, comprising:

6. An anode; A cathode; A hole injection layer, a light emitting layer, and an electron transport layer are provided between the anode and the cathode, the hole injection layer comprises a hole transport material and an electron accepting material; the electron transport layer has a region in contact with the light emitting layer, The electron mobility of the material constituting the electron transport layer when the square root of the electric field strength [V / cm] is 600 is 1×10 －７ cm ２ / Vs or more 5×10 －５ cm ２ / Vs or less, the electron accepting material is a material that exhibits electron accepting properties to the hole transport material, the hole transport material is an organic compound having a HOMO level of −5.7 eV or more and −5.4 eV or less, The spin density of the material constituting the hole injection layer measured by an ESR method is 1×10 １９ spins / cm ３ 2. A light emitting device, comprising:

7. An anode; A cathode; A hole injection layer, a light emitting layer, and an electron transport layer are provided between the anode and the cathode, the hole injection layer comprises a hole transport material and an electron accepting material; the electron transport layer has a region in contact with the light emitting layer, the electron transport layer comprises an electron transport material and any one of an alkali metal, an alkali metal compound, an alkali metal complex, an alkaline earth metal, an alkaline earth metal compound, and an alkaline earth metal complex; the electron transport layer has a first region and a second region; the first region is located between the light emitting layer and the second region, the concentrations of the alkali metal, the alkali metal compound, the alkali metal complex, the alkaline earth metal, the alkaline earth metal compound, or the alkaline earth metal complex in the first region and the second region are different; the electron accepting material is a material that exhibits electron accepting properties to the hole transport material, the hole transport material is an organic compound having a HOMO level of −5.7 eV or more and −5.4 eV or less, The spin density of the material constituting the hole injection layer measured by an ESR method is 1×10 １９ spins / cm ３ 2. A light emitting device, comprising:

8. In claim 7, A light-emitting device, wherein the concentration of the alkali metal alone, the alkali metal compound, the alkali metal complex, the alkaline earth metal alone, the alkaline earth metal compound, or the alkaline earth metal complex in the first region is higher than the concentration of the alkali metal alone, the alkali metal compound, the alkali metal complex, the alkaline earth metal alone, the alkaline earth metal compound, or the alkaline earth metal complex in the second region.

9. In claim 7, A light-emitting device, wherein the concentration of the alkali metal alone, the alkali metal compound, the alkali metal complex, the alkaline earth metal alone, the alkaline earth metal compound, or the alkaline earth metal complex in the first region or the second region is 0.

10. In any one of claims 1 to 5 and claims 7 to 9, The light-emitting layer comprises a host material and a light-emitting center material, A light-emitting device, wherein the electron mobility of the electron transporting material is less than the electron mobility of the host material.

11. In claim 10, A light-emitting device in which the luminescent center material exhibits fluorescent emission.

12. In claim 10, The light-emitting device comprises a light-emitting center material that exhibits blue fluorescent emission.

13. In any one of claims 1 to 12, The hole transport material has a hole mobility of 1×10 when the square root of the electric field strength [V / cm] is 600. －３ cm ２ / Vs or less.

14. In any one of claims 1 to 13, a mixing ratio of the hole transport material to the electron acceptor material in the film whose spin density was measured is the same as a mixing ratio of the hole transport material to the electron acceptor material in the hole injection layer;

15. In any one of claims 1 to 14, A light emitting device comprising a hole transport layer between said hole injection layer and said light emitting layer.

16. In claim 15, The light-emitting device, wherein the hole transport layer has a two-layer structure including a first hole transport layer located on the hole injection layer side and a second hole transport layer located on the light-emitting layer side.

17. In claim 16, The light-emitting device wherein the second hole transport layer also functions as an electron blocking layer.

18. In claim 16 or 17, the first hole transport layer comprises a first organic compound; the second hole transport layer comprises a second organic compound; the HOMO level of the second organic compound is deeper than the HOMO level of the first organic compound; A light-emitting device, wherein a difference between a HOMO level of the first organic compound and a HOMO level of the second organic compound is 0.2 eV or less.

19. A light emitting device according to any one of claims 1 to 18; An electronic device having a sensor, an operation button, a speaker, or a microphone.

20. A light emitting device according to any one of claims 1 to 18; A light-emitting device having a transistor or a substrate.

21. A lighting device comprising: a light-emitting device according to claim 1; and a housing.

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