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

Abstract

To provide a light-emitting device having long life or a low drive voltage.SOLUTION: A light-emitting device is provided in which an electron transport layer includes an organic metal complex of an alkali metal and an organic compound having electron transportability. The organic metal complex and the organic compound are a combination that forms an excited complex. A value (eV) obtained by converting a peak wavelength of a light-emitting spectrum of the excited complex formed when the organic metal complex and the organic compound are in a mass ratio of 1:1 into energy is 0.1 eV or more smaller than difference (eV) between a HOMO level of the organic metal complex and a LUMO level of the organic compound.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One 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 one aspect of the present invention is not limited to the above technical field. The technical field of one aspect of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. Alternatively, one 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 one aspect of the invention disclosed in this 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 Art

[0002] The practical application of light-emitting devices (organic EL elements) using electroluminescence (EL) using organic compounds has been progressing. The basic configuration of these light-emitting devices is such that an organic compound layer (EL layer) containing a light-emitting material is sandwiched between a pair of electrodes. By applying a voltage to this element to inject carriers and utilizing the recombination energy of the carriers, light emission from the light-emitting material can be obtained.

[0003] Since such a light-emitting device is self-luminous, when used as a pixel of a display, it has advantages such as higher visibility than liquid crystals and the need for no backlight, and is suitable as a device for a flat panel display. In addition, a display using such a light-emitting device can be manufactured to be thin and lightweight, which is also a great advantage. Furthermore, it is also characterized by a very fast response speed.

[0004] In addition, since these light-emitting devices can form a light-emitting layer continuously in two dimensions, planar light emission can be obtained. This is a characteristic that is difficult to achieve with point light sources typified by incandescent bulbs and LEDs, or line light sources typified by fluorescent lamps. Therefore, it has high utility value as a surface light source that can be applied to lighting and the like.

[0005] As described above, displays and lighting devices using such light-emitting devices are suitable for various electronic devices, and research and development are being carried out to obtain light-emitting devices with better efficiency and longer lifespan.

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

[0007] Although the characteristics of light-emitting devices have improved remarkably, it still has to be said that they are still insufficient to meet the high demands for all characteristics, including efficiency and durability.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, in one aspect of the present invention, an object is to provide a novel light-emitting device. Or, an object is to provide a light-emitting device with good lifespan. Or, an object is to provide a light-emitting device with low driving voltage.

[0010] Or, in another aspect of the present invention, an object is to provide a highly reliable light-emitting device, electronic device, and display device, respectively.

[0011] One aspect of the present invention only needs to solve any one of the above-described problems.

Means for Solving the Problems

[0012] One aspect of the present invention has a first electrode, a second electrode, and an EL layer. The EL layer is located between the first electrode and the second electrode. The EL layer has a light-emitting layer and an electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. The electron transport layer has an organometallic complex of an alkali metal and an organic compound having electron-transporting properties. The organometallic complex and the organic compound are a combination that forms an exciplex. The value (eV) obtained by converting the peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound are in a mass ratio of 1:1 into energy is smaller than the difference (eV) between the HOMO level of the organometallic complex and the LUMO level of the organic compound by 0.1 eV or more. It is a light-emitting device.

[0013] Alternatively, another aspect of the present invention has a first electrode, a second electrode, and an EL layer. The EL layer is located between the first electrode and the second electrode. The EL layer has a light-emitting layer and an electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. The electron transport layer has an organometallic complex of an alkali metal and an organic compound having electron-transporting properties. The organometallic complex and the organic compound are a combination that forms an exciplex. The peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound are in a mass ratio of 1:1 is 570 nm or more. It is a light-emitting device.

[0014] Alternatively, another aspect of the present invention has a first electrode, a second electrode, and an EL layer. The EL layer is located between the first electrode and the second electrode. The EL layer has a light-emitting layer and an electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. The electron transport layer has an organometallic complex of an alkali metal and an organic compound having electron-transporting properties. The organometallic complex and the organic compound are a combination that forms an exciplex. The peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound are in a mass ratio of 1:1 is 570 nm or more and less than 610 nm. It is a light-emitting device.

[0015] Alternatively, another aspect of the present invention has a first electrode, a second electrode, and an EL layer. The EL layer is located between the first electrode and the second electrode. The EL layer has a light-emitting layer and an electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. The electron transport layer has an organometallic complex of an alkali metal and an organic compound having electron transporting properties. The organometallic complex and the organic compound form a combination that forms an exciplex, and the peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound are in a mass ratio of 1:1 is 610 nm or more. It is a light-emitting device.

[0016] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the organometallic complex of an alkali metal is a lithium organometallic complex.

[0017] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the organometallic complex of an alkali metal has a ligand having a quinolinol skeleton.

[0018] Alternatively, another aspect of the present invention is a light-emitting device in the above configuration, wherein the organometallic complex of an alkali metal is lithium 8-hydroxyquinolinate or a derivative thereof.

[0019] Alternatively, another aspect of the present invention has a first electrode, a second electrode, and an EL layer. The EL layer is located between the first electrode and the second electrode. The EL layer has a light-emitting layer and an electron transport layer. The electron transport layer is located between the light-emitting layer and the second electrode. The electron transport layer has an organometallic complex of an alkali metal and an organic compound having electron transporting properties. The difference between the HOMO level of the organometallic complex and the LUMO level of the organic compound is 2.9 eV or less. When the mixed film of the organometallic complex and the organic compound is analyzed by mass spectrometry, the value obtained by subtracting 2 from the sum of the molecular weight of the organometallic complex, the molecular weight of the organic compound, and the atomic weight of the alkaline earth metal contained in the organometallic complex is observed as m / z. It is a light-emitting device.

[0020] Alternatively, another aspect of the present invention is a light-emitting device in which the organometallic complex of an alkali metal is a lithium organometallic complex in the above configuration.

[0021] Alternatively, another aspect of the present invention is a light-emitting device in which the organometallic complex of an alkali metal is lithium 8-hydroxyquinolinate in the above configuration.

[0022] Alternatively, another aspect of the present invention is a light-emitting device in which an exciplex is formed between the organometallic complex and the organic compound in the above configuration.

[0023] Alternatively, another aspect of the present invention is a light-emitting device in which the value (eV) obtained by converting the peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound are in a mass ratio of 1:1 into energy is at least 0.1 eV smaller than the difference (eV) between the HOMO level of the organometallic complex and the LUMO level of the organic compound in the above configuration.

[0024] Alternatively, another aspect of the present invention is a light-emitting device in which the peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound are in a mass ratio of 1:1 is 570 nm or more in the above configuration.

[0025] Alternatively, another aspect of the present invention is a light-emitting device in which the peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound are in a mass ratio of 1:1 is 570 nm or more and less than 610 nm in the above configuration.

[0026] Alternatively, another aspect of the present invention is a light-emitting device in which the peak wavelength of the emission spectrum of the exciplex formed when the organometallic complex and the organic compound are in a mass ratio of 1:1 is 610 nm or more in the above configuration.

[0027] Alternatively, another aspect of the present invention is a light-emitting device in which the organic compound is an organic compound having a heteroaromatic ring in the above configuration.

[0028] Alternatively, in another aspect of the present invention, in the above configuration, the electron transport layer is a light-emitting device in contact with the light-emitting layer.

[0029] Alternatively, in another aspect of the present invention, the light-emitting layer has a host material and a light-emitting material, and the light-emitting material is a light-emitting device that emits blue fluorescence.

[0030] Alternatively, in another aspect of the present invention, an electronic device includes the above light-emitting device, a sensor, an operation button, a speaker, or a microphone.

[0031] Alternatively, in another aspect of the present invention, a light-emitting device includes the above light-emitting device, a transistor, or a substrate.

[0032] Alternatively, in another aspect of the present invention, a lighting device includes the above light-emitting device and a housing.

[0033] Note that the light-emitting device in this specification includes an image display device using a light-emitting device. In addition, a module in which a connector, for example, an anisotropic conductive film or a TCP (Tape Carrier Package), is attached to the light-emitting device, a module in which a printed wiring board is provided at the tip of the TCP, or a module in which an IC (integrated circuit) is directly mounted on the light-emitting device by a COG (Chip On Glass) method may also be included in the light-emitting device. Furthermore, lighting fixtures and the like may have a light-emitting device.

Advantages of the Invention

[0034] In one aspect of the present invention, a novel light-emitting device can be provided. Alternatively, a light-emitting device with good lifespan can be provided. Alternatively, a light-emitting device with good luminous efficiency can be provided.

[0035] Alternatively, in another aspect of the present invention, a highly reliable light-emitting device, electronic device, and display device can be provided respectively. Alternatively, in another aspect of the present invention, a light-emitting device, electronic device, and display device with low power consumption can be provided respectively.

[0036] Note that the description of these effects does not preclude the existence of other effects. Note that one aspect of the present invention does not necessarily have to have all of these effects. Note that other effects will be apparent from the description in the specification, drawings, claims, etc., and it is possible to extract these other effects from the description in the specification, drawings, claims, etc.

Brief Description of the Drawings

[0037]

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[0038] Hereinafter, 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 can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments shown below.

[0039] (Embodiment 1) FIG. 1A shows a diagram representing a light-emitting device according to an aspect of the present invention. A light-emitting device according to an aspect of the present invention includes an anode 101, a cathode 102, and an EL layer 103, and the EL layer has at least a light-emitting layer 113 and an electron transport layer 114.

[0040] In the EL layer 103 in FIG. 1A, in addition to the light-emitting layer 113 and the electron transport layer 114, a hole injection layer 111, a hole transport layer 112, and an electron injection layer 115 are shown, but the configuration of the EL layer 103 is not limited thereto. As shown in FIG. 1B, the hole transport layer 112 may have a first hole transport layer 112-1 and a second hole transport layer 112-2, and the electron transport layer 114 may have a first electron transport layer 114-1 and a second electron transport layer 114-2.

[0041] In the light-emitting device according to one aspect of the present invention, the electron transport layer 114 contains an organic compound having electron transporting properties and an organometallic complex of an alkali metal. The mixing ratio is preferably 3:7 to 7:3 (mass ratio).

[0042] The organic compound having electron transporting properties and the organometallic complex of an alkali metal are preferably a combination that forms an exciplex. At this time, the peak wavelength (λp Ex ) in the emission spectrum of the exciplex when the organic compound having electron transporting properties and the organometallic complex of an alkali metal are in a mass ratio of 1:1 is converted into energy (E Ex ), and the difference (ΔE LUMO-HOMO ) between the LUMO level of the organic compound having electron transporting properties and the HOMO level of Liq which is the organometallic complex of an alkali metal is preferably smaller by 0.1 eV or more. More preferably, it is smaller by 0.3 eV or more, and still more preferably, it is smaller by 0.5 eV or more.

[0043] To convert the peak wavelength into energy, using the energy formula (E = hν = hc / λ, where E: energy [J], h = Planck's constant (6.626×10 -34 [J·s]), ν: frequency, c: speed of light (2.998×10 8 [m / s]), λ: wavelength [m]) and elementary charge (1.602×10 -19 [J]), E [eV] = 1240 / λ [nm] can be obtained, and conversion can be performed using this formula.

[0044] It is suggested that in the light-emitting device according to one aspect of the present invention having such a configuration, the organic compound having electron transporting properties and the organometallic complex of an alkali metal form an exciplex, and further interactions other than exciplex formation occur. It is considered that in the light-emitting device according to one aspect of the present invention, this interaction affects the device characteristics, and as a result, it is possible to obtain a light-emitting device with a long lifespan.

[0045] In addition, when a light-emitting device according to an aspect of the present invention is measured by a mass spectrometry method such as time-of-flight secondary ion mass spectrometry (TOF-SIMS) or laser desorption ionization method (LDI-TOF) using a film formed by mixing an organic compound having electron transporting properties contained in an electron transport layer and an organometallic complex of an alkali metal at a mixing ratio equivalent to that of the electron transport layer, characteristic results were found. That is, when the molecular weight of the organic compound having electron transporting properties is M E , the molecular weight of the organometallic complex of an alkali metal is M ACom , and the molecular weight of the alkali metal is M A , as a result of the mass spectrometry, positive ions are detected at a mass-to-charge ratio m / z = M E + M ACom + M A - 2.

[0046] Normally, when performing positive ion measurement by the mass spectrometry method as described above, ions derived from molecules contained in the film or substituents desorbed from those molecules, molecules from which substituents have desorbed, and their aggregates are detected. Therefore, the sum of the molecular weights of the molecule, the substituents of the molecule, the molecule from which the substituents have detached, etc., M (corresponding to M = M E + M ACom + M A in a light-emitting device according to an aspect of the present invention) or M + 1 is detected as m / z, and the detection of ions corresponding to M - 2 is usually almost non-existent.

[0047] That is, the detection of ions of M - 2 in positive ion measurement is a characteristic result as an analysis result of a light-emitting device according to an aspect of the present invention. In such a light-emitting device as well, the organic compound having electron transporting properties contained in the electron transport layer and the organometallic complex of an alkali metal are preferably a combination that forms an exciplex. When the organometallic complex of an alkali metal is measured by ToF-SIMS, the mass-to-charge ratio m / z = M ACom + M Amay be detected. In that case, the aforementioned aggregate is considered to be an aggregate of M ACom +M A ions and an organic compound generated when an organometallic complex of an alkali metal is ionized.

[0048] In addition, a light-emitting device in which the above ΔE LUMO-HOMO (the difference between the LUMO level of the electron-transporting organic compound and the HOMO level of the organometallic complex of the alkali metal) is 2.90 eV or less is a preferred embodiment because the electron-transporting organic compound and the organometallic complex of the alkali metal contained in the electron transport layer are likely to form an exciplex.

[0049] In addition, a light-emitting device in which the peak wavelength (λp Ex ) in the emission spectrum of the exciplex composed of the electron-transporting organic compound and the organometallic complex of the alkali metal contained in the electron transport layer is 570 nm or more is a light-emitting device with a smaller inclination of long-term deterioration and less deterioration during long-term driving.

[0050] In addition, a light-emitting device in which the peak wavelength (λp Ex ) in the emission spectrum of the exciplex is 570 nm or more and less than 610 nm can cancel out the initial deterioration because the inclination of long-term deterioration is small and the luminance increases at the initial stage of driving, and can be a light-emitting device with better lifetime.

[0051] In addition, a light-emitting device in which the peak wavelength (λp Ex ) in the emission spectrum of the exciplex is 610 nm or more can be a light-emitting device with a small inclination of long-term deterioration and high luminous efficiency.

[0052] As the electron-transporting organic compound, an organic compound having a more dominant electron-transporting property than a hole-transporting property can be used. In addition, the electron mobility of the electron-transporting organic compound is 1×10 -7 cm 2 / Vs or more and 5×10 -5 cm2 It is preferably an organic compound with a voltage of / Vs or less. By reducing the electron transport property in the electron transport layer, the amount of electrons injected into the light-emitting layer can be controlled, and the light-emitting layer can be prevented from being in a state of excessive electrons.

[0053] In addition, the organic compound having the above electron transport property preferably has an electron transport property and its HOMO level is -6.0 eV or more.

[0054] Examples of organic compounds that can be used as the organic compound having the above-described electron transporting property include 2,9-di(2-naphthyl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), 2-phenyl-3-[10-(3-pyridyl)-9-anthryl]phenylquinoxaline (abbreviation: PyA1PQ), etc., and PyA1PQ is particularly preferred. Further, 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), bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), and organic compounds having a π-electron deficient heteroaromatic ring skeleton are preferred. Examples of the organic compound 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), 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), heterocyclic compounds having a polyazole skeleton such as 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3’-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3’-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,Heterocyclic compounds having a diazine skeleton such as quinoxaline (abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), and heterocyclic compounds having a triazine skeleton such as 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 2-[(1,1'-biphenyl)-4-yl]-4-phenyl-6-[9,9'-spirobi(9H-fluorene)-2-yl]-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), and heterocyclic compounds having a pyridine skeleton such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB). Also, 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,Anthracene derivatives such as 2-d] furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl) biphenyl-4'-yl} anthracene (abbreviation: FLPPA), etc. can be mentioned. From these, a material that forms an exciplex with the organometallic complex of an alkali metal planned to be used together, or the difference between the LUMO level of these and the HOMO level of the organometallic complex of the alkali metal is 2.90 eV or less can be selected and used. Among those described above, heterocyclic compounds having a diazine skeleton, heterocyclic compounds having a triazine skeleton, and heterocyclic compounds having a pyridine skeleton are preferable from the viewpoint of driving life because the energy when forming an exciplex with the organometallic complex of an alkali metal is likely to be stabilized (the emission wavelength of the exciplex is likely to be lengthened). In particular, heterocyclic compounds having a diazine skeleton and heterocyclic compounds having a triazine skeleton are suitable for the energy stabilization of the exciplex because they have a deep LUMO level.,

[0055] In addition, the organometallic complex of the alkali metal is preferably a lithium organometallic complex. Or, the organometallic complex of the alkali metal preferably has a ligand having a quinolinol skeleton. More preferably, the organometallic complex of the alkali metal is preferably lithium 8-hydroxyquinolinate or a derivative thereof.

[0056] In addition, in the light-emitting device according to one aspect of the present invention, the light-emitting layer 113 is a layer having a light-emitting material. The light-emitting layer 113 may further have a host material for dispersing the light-emitting material.

[0057] The light-emitting material may be a fluorescent substance, a phosphorescent substance, a substance showing thermally activated delayed fluorescence (TADF), or other light-emitting materials. It may be a single layer or may be composed of a plurality of layers. One aspect of the present invention is more suitable when the light-emitting layer 113 is a layer that exhibits fluorescent light emission, particularly a layer that exhibits blue fluorescent light emission. On the other hand, one aspect of the present invention can be used regardless of the emission color of the light-emitting device and can be used across different color light-emitting devices (light-emitting elements).

[0058] In the light-emitting layer 113, examples of materials that can be used as fluorescent light-emitting substances include 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-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-diyl-di-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-carbazole-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-carbazole-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazole-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: 2DPABPhA), 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 (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]quinolin-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]quinolin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM), N,N'-diphenyl-N,N'-(1,6-pyrenediyl)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. are mentioned. In particular, condensed aromatic diamine compounds typified by pyrene diamine compounds such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03 are preferable because they have high hole trapping properties and are excellent in luminous efficiency and reliability.,

[0059] In the light-emitting layer 113, when a phosphorescent substance is used as the light-emitting center material, examples of materials that can be used include organometallic iridium complexes having a 4H-triazole skeleton such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp)3]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz)3]), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b)3]), organometallic iridium complexes having a 1H-triazole skeleton such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Mptz1-mp)3]), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me)3]), organometallic iridium complexes having an imidazole skeleton such as fac-tris[(1-2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpmi)3]), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me)3]), 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’Examples of the organometallic iridium complex having a phenylpyridine derivative having an electron-withdrawing group such as iridium(III) acetylacetonate (abbreviation: FIracac) as a ligand. These are compounds that exhibit blue phosphorescent emission and have an emission peak in the range of 440 nm to 520 nm.

[0060] In addition, materials that can be used in the light-emitting layer 113 include tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)3]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)3]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)2(acac)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]), (acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm)2(acac)]), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm)2(acac)]), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm)2(acac)]) and other organometallic iridium complexes having a pyrimidine skeleton, (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-Me)2(acac)]), (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-iPr)2(acac)]) and other organometallic iridium complexes having a pyrazine skeleton, 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 mainly compounds that exhibit green phosphorescent emission and have an emission peak at 500 nm to 600 nm. In addition, organometallic iridium complexes having a pyrimidine skeleton are particularly preferable because they are also remarkably excellent in reliability and emission efficiency.

[0061] In addition, as materials that can be used in the light-emitting layer 113, 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)]), bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm)2(dpm)]), or organometallic iridium complexes having a pyrazine skeleton such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)2(dpm)]), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq)2(acac)]), or organometallic iridium complexes having a pyridine skeleton such as tris(1-phenylisoquinolinato-N,C 2 ’)iridium(III) (abbreviation: [Ir(piq)3]), bis(1-phenylisoquinolinato-N,C 2 ’)iridium(III) acetylacetonate (abbreviation: [Ir(piq)2(acac)]). In addition to these, platinum complexes such as platinum(II) 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin (abbreviation: PtOEP), or rare earth metal complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM)3(Phen)]), tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA)3(Phen)]) can be mentioned. These are compounds that exhibit red phosphorescent emission and have an emission peak in the range of 600 nm to 700 nm. In addition, organometallic iridium complexes having a pyrazine skeleton can obtain red emission with good chromaticity.

[0062] In addition to the phosphorescent compounds described above, known phosphorescent light-emitting materials may also be selected and used.

[0063] As the TADF material, fullerenes and their derivatives, acridine and its derivatives, eosin derivatives, etc. can be used. Also, metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd), etc. can be mentioned. 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)), octaethylporphyrin-platinum chloride complex (PtCl2OEP), etc. shown in the following structural formulas.

[0064] [Chemical formula]

[0065] In addition, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ) represented by 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: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracene]-10'-one (abbreviation: ACRSA), etc., heterocyclic compounds having one or both of a π-electron-excessive heteroaromatic ring and a π-electron-deficient heteroaromatic ring can also be used. Since the heterocyclic compound has a π-electron-excessive heteroaromatic ring and a π-electron-deficient heteroaromatic ring, it has both high electron transportability and hole transportability, which is preferable. Among them, among the skeletons having a π-electron-deficient heteroaromatic ring, a pyridine skeleton, a diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and a triazine skeleton are preferable because they are stable and have good reliability. In particular, a benzofuropyrimidine skeleton, a benzothienopyrimidine skeleton, a benzofuropyrazine skeleton, and a benzothienopyrazine skeleton are preferable because they have high acceptor properties and good reliability. Also, among the skeletons having a π-electron-excessive heteroaromatic ring, an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton are stable and have good reliability, so it is preferable to have at least one of these skeletons.Note that as the furan skeleton, a dibenzofuran skeleton is preferable, and as the thiophene skeleton, a dibenzothiophene skeleton is preferable. Further, as the pyrrole skeleton, an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, and a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton are particularly preferable. Note that a substance in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded has both the electron-donating property of the π-electron-rich heteroaromatic ring and the electron-accepting property of the π-electron-deficient heteroaromatic ring enhanced, and the energy difference between the S1 level and the T1 level is reduced. Therefore, it is particularly preferable because thermally activated delayed fluorescence can be efficiently obtained. Note that instead of the π-electron-deficient heteroaromatic ring, an aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used. Further, as the π-electron-rich skeleton, an aromatic amine skeleton, a phenazine skeleton, or the like can be used. Further, as the π-electron-deficient skeleton, 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 boranthene, an aromatic ring or 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, or the like can be used. Thus, a π-electron-deficient skeleton and a π-electron-rich skeleton can be used instead of at least one of the π-electron-deficient heteroaromatic ring and the π-electron-rich heteroaromatic ring.

[0066]

Chemical formula

[0067] Note that a TADF material is a material having a function capable of converting energy from triplet excitation energy to singlet excitation energy by reverse intersystem crossing with a small difference between the S1 level and the T1 level. Therefore, upconversion (reverse intersystem crossing) of triplet excitation energy to singlet excitation energy is possible with a small amount of thermal energy, and a singlet excited state can be efficiently generated. Further, triplet excitation energy can be converted into light emission.

[0068] In addition, an exciplex (also referred to as an exciplex, exiplex, or Exciplex) that forms an excited state with two types of substances has a very small difference between the S1 level and the T1 level and functions as a TADF material capable of converting triplet excitation energy into singlet excitation energy.

[0069] Note that as an index of the T1 level, a phosphorescence spectrum observed at a low temperature (for example, from 77K to 10K) may be used. For a TADF material, a tangent is drawn at the trailing edge on the short-wavelength side of its fluorescence spectrum, and the energy of the wavelength of the extrapolated line is taken as the S1 level. When a tangent is drawn at the trailing edge on the short-wavelength side of the phosphorescence spectrum and the energy of the wavelength of the extrapolated line is taken as the T1 level, it is preferable that the difference between S1 and T1 is 0.3 eV or less, and more preferably 0.2 eV or less.

[0070] When using a TADF material as a light-emitting center material, it is preferable that the S1 level of the host material is higher than the S1 level of the TADF material. Also, it is preferable that the T1 level of the host material is higher than the T1 level of the TADF material.

[0071] As the host material of the light-emitting layer 113, various carrier transport materials such as a material having electron-transporting properties, a material having hole-transporting properties, and the above-mentioned TADF material can be used.

[0072] As materials having hole-transporting properties that can be used as host materials, organic compounds having an amine skeleton or a π-electron-rich heteroaromatic ring skeleton are preferred. 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'-bifluorene-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluorene-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluorene-2-amine (abbreviation: PCBASF), N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-bis(9,9-dimethyl-9H-fluoren-2-yl)amine (abbreviation: PCBFF), and other compounds having an aromatic amine skeleton, 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), and other compounds having a carbazole skeleton, 4,4',4''-(benzene-1,3,Compounds having a thiophene skeleton such as 5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton such as 4,4’,4’’-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among those described above, compounds having an aromatic amine skeleton or a carbazole skeleton are preferable because they have good reliability, high hole transportability, and contribute to reducing the driving voltage. In addition, the organic compounds having hole transportability exemplified as the second substance can also be used. Among the compounds having a carbazole skeleton, compounds having a 3,3’-bi(9H-carbazole) skeleton are particularly preferable because they contribute greatly to reliability, transportability, and driving voltage reduction.,

[0073] Examples of materials having electron transporting properties that can be used as host materials 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), bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), and organic compounds having a π-electron deficient heteroaromatic ring skeleton. Examples of organic compounds having a π-electron deficient heteroaromatic ring skeleton include polyazole skeleton-containing heterocyclic compounds such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2’,2’’-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), and 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3’-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3’-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis〔3-(4-dibenzothienyl)phenyl〕pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 8-(1,(1'-Biphenyl-4-yl)-4-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtBPBfpm), 11-[(3'-dibenzothiophen-4-yl)biphenyl-3-yl]phenanthro[9',10':4,5]furo[2,3-b]pyrazine (abbreviation: 11mDBtBPPnfpr), 9-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), 9-phenyl-9'-(4-phenyl-2-quinazolinyl)-3,3'-bi-9H-carbazole (abbreviation: PCCzQz), and other heterocyclic compounds having a diazine skeleton, 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), and other heterocyclic compounds having a pyridine skeleton, 2-[3'-(triphenylene-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mTpBPTzn), 11-(4-[1,1'-biphenyl]-4-yl-6-phenyl-1,3,5-triazin-2-yl)-11,12-dihydro-12-phenyl-indolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), etc. Among the above, heterocyclic compounds having a triazine skeleton, 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 triazine skeleton or a diazine (pyrimidine or pyrazine) skeleton have high electron transport properties and also contribute to reducing the driving voltage.,

[0074] As the TADF material that can be used as the host material, those previously listed as TADF materials can be used in the same manner. When the TADF material is used as the host material, the triplet excitation energy generated by the TADF material is converted into singlet excitation energy by reverse intersystem crossing, and further energy transfer to the light-emitting center substance can increase the luminous efficiency of the light-emitting device. At this time, the TADF material functions as an energy donor, and the light-emitting center substance functions as an energy acceptor.

[0075] This is very effective when the above light-emitting center substance is a fluorescent light-emitting substance. Also, at this time, in order to obtain a high luminous efficiency, it is preferable that the S1 level of the TADF material is higher than the S1 level of the fluorescent light-emitting substance. Also, it is preferable that the T1 level of the TADF material is higher than the S1 level of the fluorescent light-emitting substance. Therefore, it is preferable that the T1 level of the TADF material is higher than the T1 level of the fluorescent light-emitting substance.

[0076] Also, it is preferable to use a TADF material that exhibits light emission overlapping with the wavelength of the absorption band on the lowest energy side of the fluorescent light-emitting substance. Thereby, the transfer of excitation energy from the TADF material to the fluorescent light-emitting substance becomes smooth, and light emission can be obtained efficiently.

[0077] In addition, in order to efficiently generate singlet excited energy from triplet excited energy by reverse intersystem crossing, it is preferable that carrier recombination occurs in the TADF material. Further, it is preferable that the triplet excited energy generated in the TADF material does not move to the triplet excited energy of the fluorescent substance. For this purpose, the fluorescent substance preferably has a protecting group around the lumophore (skeleton responsible for luminescence) of the fluorescent substance. As the protecting 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 can be mentioned, and it is more preferable that a plurality of protecting groups are substituted on the fluorescent substance. Since a substituent having no π bond has poor function of transporting carriers, it is possible to increase the distance between the TADF material and the lumophore of the fluorescent substance with little influence on carrier transport and carrier recombination. Here, the lumophore refers to an atomic group (skeleton) that is the origin of luminescence in the fluorescent substance. The lumophore 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, and a naphthobisbenzofuran skeleton are preferable because they have a high fluorescence quantum yield.

[0078] When using a fluorescent light-emitting substance as a light-emitting center substance, as the host material, a material having an anthracene skeleton is suitable. When a substance having an anthracene skeleton is used as the host material of the fluorescent light-emitting substance, it is possible to realize a light-emitting layer with both good luminous efficiency and durability. As the substance having an anthracene skeleton that can be used as the host material, a substance having a diphenylanthracene skeleton, particularly a substance having a 9,10-diphenylanthracene skeleton, is preferable because it is chemically stable. Further, when the host material has a carbazole skeleton, it is preferable because the hole injection and transport properties are enhanced. However, when it contains a benzocarbazole skeleton in which a benzene ring is further condensed with carbazole, the HOMO becomes about 0.1 eV shallower than that of carbazole, and holes can enter more easily, so it is more preferable. In particular, when the host material contains a dibenzocarbazole skeleton, the HOMO becomes about 0.1 eV shallower than that of carbazole, holes can enter more easily, the hole transport property is excellent, and the heat resistance is also high, so it is suitable. Therefore, a substance having both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole skeleton or a dibenzocarbazole skeleton) is more preferable as the host material. From the above viewpoints of hole injection and transport properties, a benzofluorene skeleton or a dibenzofluorene skeleton may be used instead of the carbazole skeleton. Examples of such substances 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: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4'-yl}anthracene (abbreviation: FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), and the like.In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA are preferred choices because they exhibit very good properties.

[0079] Note that the host material may be a material obtained by mixing multiple substances. When using a mixed host material, it is preferable to mix a material having electron-transporting properties and a material having hole-transporting properties. By mixing a material having electron-transporting properties and a material having hole-transporting properties, the transport properties of the light-emitting layer 113 can be easily adjusted, and the control of the recombination region can also be easily performed. The mass ratio of the content of the material having hole-transporting properties to the material having electron-transporting properties may be Hole-transporting material: Electron-transporting material = 1:19 to 19:1.

[0080] Note that a phosphorescent material can be used as part of the above-mentioned mixed material. The phosphorescent material can be used as an energy donor that supplies excitation energy to the fluorescent material when using the fluorescent material as the light-emitting center material.

[0081] In addition, an exciplex may be formed between these mixed materials. By selecting a combination that forms an exciplex that emits light overlapping with the wavelength of the absorption band on the lowest energy side of the light-emitting material, energy transfer becomes smooth and light emission can be efficiently obtained, which is preferable. Also, since the driving voltage is reduced by using this configuration, it is preferable.

[0082] Note that at least one of the materials forming the exciplex in the light-emitting layer may be a phosphorescent material. By doing so, triplet excitation energy can be efficiently converted into singlet excitation energy by reverse intersystem crossing.

[0083] As a combination of materials that efficiently form an exciplex, it is preferable that the HOMO level of the hole-transporting material is equal to or higher than the HOMO level of the electron-transporting material. Also, it is preferable that the LUMO level of the hole-transporting material is equal to or higher than the LUMO level of the electron-transporting material. Note that 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. Also, the HOMO level can be obtained from the ionization potential measurement (IP measurement) of the thin film. The LUMO level can also be calculated using the HOMO level obtained from the IP measurement and the optical bandgap (energy (eV) calculated from the absorption edge on the long-wavelength side of the absorption spectrum of the thin film). Specifically, the LUMO level is calculated by adding the energy (eV) calculated from the bandgap to the HOMO level.

[0084] Note that the formation of the exciplex can be confirmed by comparing the spectra of each of the mixed materials (e.g., the emission spectrum of the hole-transporting material, the emission spectrum of the electron-transporting material, the spectrum of the organometallic complex, etc.) with the emission spectrum of the mixed film formed by mixing these materials, and observing the phenomenon that the emission spectrum of the mixed film is shifted to a longer wavelength (or has a new peak on the long-wavelength side) compared to the emission spectra of the individual materials. Alternatively, the formation of the exciplex can be confirmed by comparing the transient photoluminescence (PL) of each of the mixed materials with the transient PL of the mixed film formed by mixing these materials, and observing differences in transient responses such as the transient PL lifetime of the mixed film having a longer-lived component or a larger proportion of the delayed component compared to the transient PL lifetimes of the individual materials. Also, the above-mentioned transient PL can be read as transient electroluminescence (EL). That is, the formation of the exciplex can also be confirmed by comparing the transient EL of each of the mixed materials with the transient EL of the mixed film of these materials and observing differences in transient responses.

[0085] Subsequently, other layers that can be used for the EL layer 103 will be described.

[0086] The positive hole injection layer 111 is a layer for facilitating the injection of positive holes into the EL layer 103 and is composed of a material with high positive hole injectability. The positive hole injection layer 111 may be composed of an acceptor substance alone, but is preferably composed of a composite material containing an acceptor substance and an organic compound having positive hole transportability.

[0087] The acceptor substance is a substance that exhibits electron-accepting properties with respect to the organic compound having positive hole transportability contained in the positive hole transport layer or the positive hole injection layer.

[0088] As the acceptor substance, either an inorganic compound or an organic compound can be used, but it is preferable to use an organic compound having an electron-withdrawing group (especially a halogen group such as a fluoro group or a cyano group). The acceptor substance may be appropriately selected from such substances as a substance that exhibits electron-accepting properties with respect to the organic compound having positive hole transportability contained in the positive hole transport layer or the positive hole injection layer.

[0089] Examples of such acceptor substances 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 - pyrene - 2 - ylidene) malononitrile, and the like. 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. Further, [3]radialene derivatives having an electron - withdrawing group (especially a halogen group such as a fluoro group or a cyano group) are preferable because of their very high electron - accepting properties. Specifically, organic compounds such as α,α’,α’’ - 1,2,3 - cyclopropanetriylidene tris[4 - cyano - 2,3,5,6 - tetrafluorobenzeneacetonitrile], α,α’,α’’ - 1,2,3 - cyclopropanetriylidene tris[2,6 - dichloro - 3,5 - difluoro - 4 - (trifluoromethyl)benzeneacetonitrile], α,α’,α’’ - 1,2,3 - cyclopropanetriylidene tris[2,3,4,5,6 - pentafluorobenzeneacetonitrile] can be mentioned. When the acceptor substance is an inorganic compound, transition metal oxides can also be used. In particular, oxides of metals belonging to Groups 4 to 8 in the periodic table are suitable. Examples of oxides of metals belonging to Groups 4 to 8 in the periodic table include vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide, etc., which are preferable due to their high electron - accepting properties. Among them, molybdenum oxide is preferable because it is stable in the atmosphere, has low hygroscopicity, and is easy to handle.

[0090] The organic compound having hole transporting property used in the composite material preferably has a relatively deep HOMO level with the HOMO level being -5.7 eV or more and -5.4 eV or less. By the organic compound having hole transporting property used in the composite material having a relatively deep HOMO level, the induction of holes is moderately suppressed, while on the other hand, the injection of the induced holes into the hole transport layer 112 becomes easy.

[0091] As the organic compound having hole transporting properties used in the composite material, it is more preferable to have any one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. In particular, an aromatic amine having a substituent containing a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine having a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group may be used. In addition, when these substances are substances having an N,N-bis(4-biphenyl)amino group, it is preferable because a light-emitting device with good lifespan can be fabricated. Specific examples of the substances as described above 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-yl-4''-phenyltriphenylamine (abbreviation: BnfBB1BP), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophene-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)naphthalen-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4,4'-diphenyl-4''-(6;2'-binaphthalen-2-yl)triphenylamine (abbreviation: BBA(βN2)B), 4,4'-diphenyl-4''-(7;2'-binaphthalen-2-yl)triphenylamine (abbreviation: BBA(βN2)B-03), 4,4'-diphenyl-4''-(4;2'-binaphthalen-1-yl)triphenylamine (abbreviation: BBAβNαNB), 4,4'-diphenyl-4''-(5;2'-binaphthalen-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 (abbreviation: αNBA1BP), 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 (abbreviation: YGTBiβNB), 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-fluorene-2-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN), 4-phenyl-4'-(9-phenylfluoren-9-yl)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-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluorene-2-amine (abbreviation: PCBASF), N-(1,1'-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluorene-2-amine (abbreviation: PCBBiF), etc. can be mentioned.,

[0092] In addition, for an organic compound having hole transporting properties, when the square root of the electric field strength [V / cm] is 600, its hole mobility is preferably 1×10 -3 cm 2 / Vs or less.,

[0093] The composition of the organic compound having hole transporting properties and the acceptor material in the composite material is preferably 1:0.01 to 1:0.15 (mass ratio). More preferably, it is 1:0.01 to 1:0.1 (mass ratio).

[0094] Also, at this time, when the square root of the electric field strength [V / cm] is 600, the electron mobility of the electron transport layer 114 is 1×10 -7 cm 2 / Vs or more and 5×10 -5 cm 2 / Vs or less is preferable.

[0095] Furthermore, at this time, the electron transport layer 114 preferably contains an organometallic complex of an alkali metal, and it is more preferable that the organometallic complex of the alkali metal contains an 8-hydroxyquinolinate structure. Among them, a complex of a monovalent metal ion is preferable. Specifically, for example, it preferably contains 8-hydroxyquinolinate-lithium (abbreviation: Liq), 8-hydroxyquinolinate-sodium (abbreviation: Naq), etc. In particular, a complex of lithium is preferable, and Liq is more preferable. When including an 8-hydroxyquinolinate structure, its methyl-substituted products (for example, 2-methyl-substituted product, 5-methyl-substituted product, etc.) can also be used.

[0096] Also, it is preferable that the organometallic complex of the alkali metal in the electron transport layer 114 has a concentration difference (including the case where the concentration is 0) in the thickness direction. Thereby, it becomes possible to obtain a light-emitting device having better lifespan and reliability.

[0097] In addition, the organic compound having electron transporting properties used for the electron transport layer 114 preferably has a HOMO level of -6.0 eV or more.

[0098] In a light-emitting device having such a configuration, in the luminance degradation curve obtained by a driving test under the condition of a constant current density, when it shows a shape having a maximum value, that is, when it has a portion where the luminance increases with the passage of time. A light-emitting device showing such degradation behavior can cancel out the rapid degradation at the initial stage of driving, so-called initial degradation, by the increase in luminance, and can be made into a light-emitting device with small initial degradation and a very good driving life. Such a light-emitting device shall be called a Recombination-Site Tailoring Injection element (ReSTI element).

[0099] Since the hole injection layer having the configuration as described above contains an organic compound having a hole transporting property with a deep HOMO level, the induced holes are easily injected into the hole transporting layer and the light-emitting layer. Therefore, at the initial stage of driving, it is easy to create a state where a very small part of the holes passes through the light-emitting layer and reaches the electron transporting layer.

[0100] Here, in a light-emitting device having an electron transporting layer containing an organic compound having electron transporting properties and an organometallic complex of an alkali metal, when the light-emitting device is continuously lit, a phenomenon is observed in which the electron injection / transporting property of the electron transporting layer is improved. On the other hand, as described above, since the hole injection layer has a moderately suppressed hole induction, a large number of holes cannot be supplied to the electron transporting layer. As a result, the holes that can reach the electron transporting layer over time decrease, and the probability of holes recombining with electrons in the light-emitting layer increases. That is, during continuous lighting, a carrier balance shift occurs such that recombination is more likely to occur in the light-emitting layer. Due to this shift, a light-emitting device with an initial degradation suppressed, whose degradation curve has a portion where the luminance increases with the passage of time, can be obtained.

[0101] The light-emitting device according to one embodiment of the present invention having the above-described configuration can be a light-emitting device with extremely good lifespan. In particular, it is possible to significantly extend the lifespan in the region where the degradation is extremely small up to about LT95. Furthermore, as the organic compound having electron-transporting properties, a compound having a first skeleton with a function of transporting electrons, a second skeleton with a function of accepting holes, and a third skeleton which is a monocyclic and π-electron-deficient heteroaromatic ring is used, the light-emitting device has very small long-term degradation and can be a light-emitting device with better lifespan.

[0102] Note that by being able to suppress the initial degradation, it is possible to greatly reduce the problem of burn-in, which is still regarded as one of the major weaknesses of the organic EL device, and the labor of pre-shipment aging performed to reduce it.

[0103] The hole transport layer 112 may be a single layer (FIG. 1A), but preferably has a first hole transport layer 112-1 and a second hole transport layer 112-2 (FIG. 1B). Further, it may have a plurality of hole transport layers.

[0104] The hole transport layer 112 can be formed using an organic compound having hole-transporting properties. As the organic compound having hole-transporting properties used for the hole transport layer 112, an organic compound having hole-transporting properties that can be used as the above-described host material and an organic compound having hole-transporting properties that can be used as a composite material can be used.

[0105] When the hole transport layer 112 is formed as a plurality of layers, the HOMO level of the organic compound having hole-transporting properties constituting the adjacent hole transport layers is preferably deeper for the organic compound used in the hole transport layer closer to the light-emitting layer 113 side, and the difference is within 0.2 V.

[0106] In addition, when the hole injection layer 111 is formed of a composite material, the HOMO level of the hole transporting organic compound used in the hole transport layer 112 in contact with the hole injection layer 111 is deeper than that of the hole transporting organic compound used in the composite material, and preferably the difference is within 0.2 eV.

[0107] When the HOMO levels are in the above relationship, holes can be smoothly injected into each layer, preventing an increase in driving voltage and a shortage of holes in the light emitting layer.

[0108] The hole transporting organic compound used in the hole transport layer 112 preferably has a skeleton having a function of transporting holes. As such skeletons having a function of transporting holes, a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton in which the HOMO level of the organic compound does not become too shallow are preferable, and a dibenzofuran skeleton is particularly preferable. Further, between adjacent layers in the hole injection layer 111 and the plurality of hole transport layers 112, it is preferable that these skeletons are common because hole injection becomes smooth. In addition, for the same reason, it is preferable to use the same hole transporting organic compound between adjacent layers in the hole injection layer 111 and the plurality of hole transport layers 112.

[0109] When laminating a plurality of hole transport layers, the first hole transport layer 112-1 is located closer to the anode 101 side than the second hole transport layer 112-2. Note that the second hole transport layer 112-2 may also simultaneously function as an electron blocking layer.

[0110] The light emitting device of one embodiment of the present invention having the above configuration can be a light emitting device with very good lifetime.

[0111] Next, examples of other structures and materials of the above-described light-emitting device will be described. As described above, the light-emitting device in the present embodiment has an EL layer 103 composed of a plurality of layers between a pair of electrodes, an anode 101 and a cathode 102, and the EL layer 103 includes at least a light-emitting layer 113 and an electron transport layer 114 from the anode 101 side. In addition to these, various layer structures such as a hole injection layer, a hole transport layer, an electron injection layer, a carrier blocking layer, an exciton blocking layer, and a charge generation layer can be applied to the layers included in the EL layer 103.

[0112] The anode 101 is preferably formed using a metal, an alloy, a conductive compound, or a mixture thereof having a large work function (specifically, 4.0 eV or more). Specifically, for example, indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide, indium zinc oxide, indium oxide containing tungsten oxide and zinc oxide (IWZO), etc. can be mentioned. These conductive metal oxide films are usually formed by a sputtering method, but may be produced by applying a sol-gel method or the like. As an example of the production method, indium zinc oxide can be formed by a sputtering method using a target obtained by adding 1 to 20 wt% of zinc oxide 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% of tungsten oxide and 0.1 to 1 wt% of zinc oxide with respect to indium oxide. In addition, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or nitrides of metal materials (for example, titanium nitride), etc. can be mentioned. Graphene can also be used. Here, substances having a large work function and representative as materials for forming the anode are listed, but in one aspect of the present invention, since a composite material containing an organic compound having hole transporting properties and a substance showing electron accepting properties with respect to the organic compound is used for the hole injection layer 111, the electrode material can be selected regardless of the work function.

[0113] Regarding the hole injection layer 111, the hole transport layer 112 (the first hole transport layer 112-1 and the second hole transport layer 112-2), the light-emitting layer 113, and the electron transport layer 114, since they have already been described in detail, repetitive descriptions are omitted.

[0114] Between the electron transport layer 114 and the cathode 102, as the electron injection layer 115, a layer containing an alkali metal or an alkaline earth metal or their compounds such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), etc. may be provided. The electron injection layer 115 may be a layer in which an alkali metal or an alkaline earth metal or their compounds are contained in a layer made of a substance having electron transport properties, or an electride may be used. Examples of electrides include substances in which electrons are added at a high concentration to a mixed oxide of calcium and aluminum.

[0115] Also, instead of the electron injection layer 115, a charge generation layer may be provided between the electron transport layer 114 and the cathode 102. The charge generation layer is a layer that can inject holes into the layer in contact with the cathode side of the layer and electrons into the layer in contact with the anode side by applying a potential. The charge generation layer includes at least a P-type layer. The P-type layer is preferably formed using the composite material mentioned as a material that can constitute the above-mentioned hole injection layer 111. Also, the P-type layer may be formed by laminating a film containing the acceptor material mentioned above as a material constituting the composite material and a film containing an organic compound having hole transport properties. By applying a potential to the P-type layer, electrons are injected into the electron transport layer and holes are injected into the cathode 102, which is the cathode, and the light-emitting device operates.

[0116] Note that it is preferable that either one or both of an electron relay layer and an electron injection buffer layer are provided in addition to the P-type layer in the charge generation layer.

[0117] The electron relay layer contains at least a substance having electron transporting properties, and has a function of preventing the interaction between the electron injection buffer layer and the P-type layer and smoothly transferring electrons. The LUMO level of the substance having electron transporting properties contained in the electron relay layer is preferably between the LUMO level of the electron accepting substance in the P-type layer and the LUMO level of the substance contained in the layer in contact with the charge generation layer in the electron transport layer 114. The specific energy level of the LUMO level in the substance having electron transporting properties used for the electron relay layer is preferably -5.0 eV or more, preferably -5.0 eV or more and -3.0 eV or less. In addition, as the substance having electron transporting properties used for the electron relay layer, it is preferable to use a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand.

[0118] For the electron injection buffer layer, it is possible to use substances with high electron injection properties such as alkali metals, alkaline earth metals, rare earth metals, and their compounds (alkali metal compounds (including oxides such as lithium oxide, halides, carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, carbonates), or rare earth metal compounds (including oxides, halides, carbonates)).

[0119] In addition, when the electron injection buffer layer is formed by including a substance having electron transporting properties and an electron donating substance, as the electron donating substance, in addition to alkali metals, alkaline earth metals, rare earth metals, and their compounds (alkali metal compounds (including oxides such as lithium oxide, halides, carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, carbonates), or rare earth metal compounds (including oxides, halides, carbonates)), organic compounds such as tetrathianaphthacene (abbreviation: TTN), nickelocene, and decamethylnickelocene can also be used. Note that as the substance having electron transporting properties, it can be formed using the same material as the material constituting the electron transport layer 114 described above.

[0120] As the 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) and 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 tin oxide containing silicon or silicon oxide, etc. can be used as the cathode 102 regardless of the work function value. These conductive materials can be formed into a film using dry methods such as vacuum evaporation and sputtering, inkjet methods, spin coating methods, etc. Further, it may be formed by a wet method using the sol-gel method, or may be formed by a wet method using a paste of a metal material.

[0121] Note that as the method for forming the EL layer 103, various methods can be used regardless of whether it is a dry method or a wet method. For example, vacuum evaporation, gravure printing, offset printing, screen printing, inkjet method, or spin coating method may be used.

[0122] Also, the above-described respective electrodes or respective layers may be formed using different film-forming methods.

[0123] Note that 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 site away from the anode 101 and the cathode 102 is preferred so as to suppress quenching caused by the proximity of the light-emitting region to the electrodes and the metals used in the carrier injection layer.

[0124] In addition, the hole transport layer or 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, is preferably composed of a material having a band gap larger than the band gap of the light-emitting material constituting the light-emitting layer or the band gap of the light-emitting material contained in the light-emitting layer in order to suppress energy transfer from the excitons generated in the light-emitting layer.

[0125] Subsequently, an embodiment of a light-emitting device having a structure in which a plurality of light-emitting units are stacked (also referred to as a stacked element or a tandem element) will be described with reference to FIG. 1C. This light-emitting device is a light-emitting device having a plurality of light-emitting units between an anode and a cathode. One light-emitting unit has substantially the same structure as the EL layer 103 shown in FIG. 1A or FIG. 1B. That is, it can be said that 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 FIGS. 1A and 1B are light-emitting devices having one light-emitting unit.

[0126] In FIG. 1C, a first light-emitting unit 511 and a second light-emitting unit 512 are stacked 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. 1A, respectively, and the same ones as those described in the description of FIG. 1A can be applied. Also, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same structure or different structures.

[0127] The charge generation layer 513 has a function of injecting electrons into one light-emitting unit and holes into the other light-emitting unit when a voltage is applied to the anode 501 and the cathode 502. That is, in FIG. 1C, when a voltage is applied so that the potential of the anode is higher than the potential of the cathode, the charge generation layer 513 may inject electrons into the first light-emitting unit 511 and holes into the second light-emitting unit 512.

[0128] The charge generation layer 513 is preferably formed with the same configuration as the charge generation layer described in FIG. 1B. Since the composite material of the organic compound and the metal oxide is excellent in carrier injection property and carrier transport property, low-voltage driving and low-current driving can be realized. When the surface on the anode side of the light-emitting unit is in contact with the charge generation layer 513, the charge generation layer 513 can also serve as the hole injection layer of the light-emitting unit, so that the light-emitting unit does not necessarily need to be provided with a hole injection layer.

[0129] In addition, when an electron injection buffer layer is provided in the charge generation layer 513, since the electron injection buffer layer serves as the electron injection layer in the light-emitting unit on the anode side, it is not always necessary to form an electron injection layer in the light-emitting unit on the anode side.

[0130] In FIG. 1C, a light-emitting device having two light-emitting units has been described, but the same can be similarly applied to a light-emitting device in which three or more light-emitting units are stacked. By arranging a plurality of light-emitting units between a pair of electrodes partitioned by the charge generation layer 513 as in the light-emitting device according to the present embodiment, high-brightness light emission can be enabled while keeping the current density low, and a longer-life element can be realized. In addition, a light-emitting device capable of low-voltage driving and having low power consumption can be realized.

[0131] In addition, by making the emission colors of the respective light-emitting units different, light emission of a desired color can be obtained for the entire light-emitting device. For example, in a light-emitting device having two light-emitting units, by obtaining red and green emission colors in the first light-emitting unit and a blue emission color in the second light-emitting unit, it is also possible to obtain a light-emitting device that emits white light as a whole. As a configuration of a light-emitting device in which three or more light-emitting units are stacked, for example, a tandem device 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 can be used. The tandem device can obtain white light emission in the same manner as the above-described light-emitting device.

[0132] In addition, each layer and electrode such as the above-described EL layer 103, the first light-emitting unit 511, the second light-emitting unit 512, and the charge generation layer can be formed, for example, by methods such as vapor deposition (including vacuum vapor deposition), droplet ejection method (also referred to as inkjet method), coating method, gravure printing method, etc. Further, they may contain low molecular weight materials, medium molecular weight materials (including oligomers and dendrimers), or high molecular weight materials.

[0133] (Embodiment 2) In this embodiment, a light-emitting device using the light-emitting device described in Embodiment 1 will be described.

[0134] In this embodiment, a light-emitting device manufactured using the light-emitting device described in Embodiment 1 will be described with reference to FIG. 2. Note that FIG. 2A is a top view showing the light-emitting device, and FIG. 2B is a cross-sectional view obtained by cutting FIG. 2A along A-B and C-D. This light-emitting device includes a driving circuit portion (source line driving circuit) 601, a pixel portion 602, and a driving circuit portion (gate line driving circuit) 603, which are indicated by dotted lines, as a means for controlling the light emission of the light-emitting device. Further, 604 is a sealing substrate, and 605 is a sealing material. The inside surrounded by the sealing material 605 is a space 607.

[0135] Note that the routing 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, etc. from an FPC (flexible printed circuit) 609 serving as an external input terminal. Although only the FPC is illustrated here, a printed wiring board (PWB) may be attached to this FPC. The light-emitting device in this specification includes not only the light-emitting device main body but also a state in which an FPC or a PWB is attached thereto.

[0136] Next, the cross-sectional structure will be described with reference to FIG. 2B. Although a driving circuit portion and a pixel portion are formed on the element substrate 610, here, the source line driving circuit 601, which is a driving circuit portion, and one pixel in the pixel portion 602 are shown.

[0137] The element substrate 610 may be made of a substrate such as glass, quartz, organic resin, metal, alloy, semiconductor, etc., or a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (polyvinyl fluoride), polyester, acrylic, or the like.

[0138] The structure of the transistor used in the pixel and the driving circuit is not particularly limited. For example, it may be an inverted staggered type transistor or a staggered type transistor. Also, it 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, etc. can be used. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In-Ga-Zn based metal oxide, may be used.

[0139] The crystallinity of the semiconductor material used for the transistor is not particularly limited either, and any of an amorphous semiconductor, a semiconductor having crystallinity (microcrystalline semiconductor, polycrystalline semiconductor, single crystal semiconductor, or a semiconductor having a crystal region in part) may be used. Using a semiconductor having crystallinity is preferable because deterioration of transistor characteristics can be suppressed.

[0140] Here, in addition to the transistors provided in the above-mentioned pixel and driving circuit, for semiconductor devices such as transistors used in a touch sensor and the like described later, it is preferable to apply an oxide semiconductor. In particular, it is preferable to apply an oxide semiconductor having a wider bandgap than silicon. By using an oxide semiconductor having a wider bandgap than silicon, the current in the off state of the transistor can be reduced.

[0141] The above oxide semiconductor preferably contains at least indium (In) or zinc (Zn). Moreover, it is more preferable that it is an oxide semiconductor containing an oxide represented by In-M-Zn based oxide (M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0142] Here, the oxide semiconductor that can be used in one aspect of the present invention will be described below.

[0143] Oxide semiconductors are classified into single-crystalline oxide semiconductors and other non-single-crystalline oxide semiconductors. Examples of non-single-crystalline oxide semiconductors include CAAC-OS (c-axis aligned crystalline oxide semiconductor), polycrystalline oxide semiconductors, nc-OS (nano crystalline oxide semiconductor), pseudo-amorphous oxide semiconductors (a-like OS: amorphous-like oxide semiconductor), and amorphous oxide semiconductors.

[0144] CAAC-OS has a c-axis orientation, and a plurality of nanocrystals are connected in the a-b plane direction, resulting in a crystal structure with strain. Note that the strain refers to a location where the orientation of the lattice arrangement changes between a region where the lattice arrangement is aligned and another region where the lattice arrangement is aligned in the region where the plurality of nanocrystals are connected.

[0145] Nanocrystals are based on hexagons, but are not limited to regular hexagons and may be non-regular hexagons. Also, in the strain, there may be lattice arrangements such as pentagons and heptagons. In CAAC-OS, it is difficult to confirm a clear grain boundary (also referred to as a grain boundary) even in the vicinity of the strain. That is, it can be seen that the formation of grain boundaries is suppressed by the strain of the lattice arrangement. This is because CAAC-OS can tolerate strain due to the fact that the arrangement of oxygen atoms is not dense in the a-b plane direction and the interatomic bond distance changes due to the substitution of metal elements.

[0146] In addition, CAAC-OS tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium and oxygen (hereinafter referred to as the In layer) and a layer containing element M, zinc, and oxygen (hereinafter referred to as the (M,Zn) layer) are laminated. Note that indium and element M are mutually substitutable, and when element M in the (M,Zn) layer is substituted with indium, it can also be expressed as an (In,M,Zn) layer. Further, when indium in the In layer is substituted with element M, it can also be expressed as an (In,M) layer.

[0147] CAAC-OS is a highly crystalline oxide semiconductor. On the other hand, since it is difficult to confirm clear grain boundaries in CAAC-OS, it can be said that a decrease in electron mobility due to grain boundaries is less likely to occur. In addition, since the crystallinity of an oxide semiconductor may decrease due to the incorporation of impurities or the generation of defects, CAAC-OS can also be said to be an oxide semiconductor with few impurities and defects (such as oxygen vacancies (also referred to as V O :oxygen vacancy)). Therefore, the physical properties of the oxide semiconductor having CAAC-OS are stable. For this reason, the oxide semiconductor having CAAC-OS is resistant to heat and has high reliability.

[0148] nc-OS has periodicity in the atomic arrangement in a minute region (for example, a region of 1 nm or more and 10 nm or less, particularly a region of 1 nm or more and 3 nm or less). Further, nc-OS does not show regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is observed in the entire film. Therefore, depending on the analysis method, nc-OS may not be distinguishable from a-like OS or an amorphous oxide semiconductor.

[0149] Note that indium-gallium-zinc oxide (hereinafter referred to as IGZO), which is a type of oxide semiconductor having indium, gallium, and zinc, may take a stable structure by using the above-described nanocrystals. In particular, since IGZO tends to be difficult to grow crystals in the air, a crystal smaller than a large crystal (here, a crystal of several mm or a crystal of several cm), for example, the above-described nanocrystal, may be structurally more stable.

[0150] The a-like OS is an oxide semiconductor having a structure between nc-OS and an amorphous oxide semiconductor. The a-like OS has a loose or low-density region. That is, the a-like OS has lower crystallinity compared to nc-OS and CAAC-OS.

[0151] Oxide semiconductors have various structures, each having different characteristics. The oxide semiconductor according to one aspect of the present invention may have two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, a-like OS, nc-OS, and CAAC-OS.

[0152] In addition to the above-described oxide semiconductors, CAC (Cloud-Aligned Composite)-OS may be used.

[0153] The CAC-OS has a conductive function in a part of the material and an insulating function in a part of the material, and has a function as a semiconductor in the whole material. When the CAC-OS is used for the active layer of a transistor, the conductive function is a function of flowing electrons (or holes) serving as carriers, and the insulating function is a function of not flowing electrons serving as carriers. By causing the conductive function and the insulating function to act complementarily, respectively, a switching function (On / Off function) can be imparted to the CAC-OS. In the CAC-OS, by separating the respective functions, both functions can be maximally enhanced.

[0154] In addition, the CAC-OS has a conductive region and an insulating region. The conductive region has the above-described conductive function, and the insulating region has the above-described insulating function. Also, in the material, the conductive region and the insulating region may be separated at the nanoparticle level. Also, the conductive region and the insulating region may be unevenly distributed in the material, respectively. Also, the conductive region may be observed to be blurred at the periphery and connected in a cloud shape.

[0155] In addition, in CAC-OS, the conductive regions and the insulating regions may be dispersed in the material with sizes of 0.5 nm or more and 10 nm or less, preferably 0.5 nm or more and 3 nm or less, respectively.

[0156] In addition, CAC-OS is composed of components having different band gaps. For example, CAC-OS is composed of a component having a wide band gap due to the insulating region and a component having a narrow band gap due to the conductive region. In such a configuration, when carriers flow, the carriers mainly flow in the component having the narrow band gap. In addition, the component having the narrow band gap acts complementarily to the component having the wide band gap, and carriers also flow in the component having the wide band gap in conjunction with the component having the narrow band gap. Therefore, when the above CAC-OS is used for 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.

[0157] That is, CAC-OS can also be referred to as a matrix composite or a metal matrix composite.

[0158] By using the above-described oxide semiconductor material as the semiconductor layer, fluctuations in electrical characteristics can be suppressed, and a highly reliable transistor can be realized.

[0159] In addition, due to its low off-current, the transistor having the above-described semiconductor layer can hold the charges accumulated in the capacitor through the transistor for a long period of time. By applying such a transistor to a pixel, it is also possible to stop the driving circuit while maintaining the gradation of the image displayed in each display region. As a result, an electronic device with extremely low power consumption can be realized.

[0160] For the purpose of stabilizing the characteristics of the transistor, etc., it is preferable to provide an underlayer film. As the underlayer film, an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film can be used, and it can be fabricated as a single layer or as a laminate. The underlayer film can be formed using 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, etc. Note that the underlayer film may not be provided if not necessary.

[0161] Note that FET623 indicates one of the transistors formed in the drive circuit section 601. Also, the drive circuit may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. In this embodiment, a driver integrated type in which the drive circuit is formed on the substrate is shown, but this is not necessarily required, and the drive circuit can also be formed externally rather than on the substrate.

[0162] Also, the pixel section 602 is formed by a plurality of pixels including a switching FET611, a current control FET612, and an anode 613 electrically connected to its drain, but is not limited thereto, and may be a pixel section combining three or more FETs and a capacitive element.

[0163] Note that an insulator 614 is formed covering the end portion of the anode 613. Here, it can be formed by using a positive-type photosensitive acrylic.

[0164] Also, in order to make the coating property of the EL layer, etc. formed later good, a curved surface having a curvature is formed at the upper end portion or the lower end portion of the insulator 614. For example, when a positive-type photosensitive acrylic is used as the material of the insulator 614, it is preferable to provide a curved surface having a curvature radius (0.2 μm to 3 μm) only at the upper end portion of the insulator 614. Also, either a negative-type photosensitive resin or a positive-type photosensitive resin can be used as the insulator 614.

[0165] On the anode 613, an EL layer 616 and a cathode 617 are respectively formed. Here, as the material used for the anode 613, it is desirable to use a material with a large work function. For example, in addition to single-layer films such as ITO films, indium tin oxide films containing silicon, indium oxide films containing 2 to 20 wt% zinc oxide, titanium nitride films, chromium films, tungsten films, Zn films, Pt films, etc., a laminate of a titanium nitride film and a film mainly composed of aluminum, a three-layer structure of a titanium nitride film, a film mainly composed of aluminum, and a titanium nitride film can be used. In addition, when a laminated structure is adopted, the resistance as a wiring is low, good ohmic contact can be achieved, and it can further function as an anode.

[0166] Also, the EL layer 616 is formed by various methods such as vapor deposition using a vapor deposition mask, inkjet method, spin coating method, etc. The EL layer 616 includes the configuration as described in Embodiment 1. In addition, as other materials constituting the EL layer 616, low molecular compounds or high molecular compounds (including oligomers and dendrimers) may be used.

[0167] Furthermore, as the material used for the cathode 617 formed on the EL layer 616, it is preferable to use a material with a small work function (Al, Mg, Li, Ca, or alloys or compounds thereof (MgAg, MgIn, AlLi, etc.)). 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 film with a reduced film thickness 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.

[0168] Note that a light-emitting device 618 is formed by the anode 613, the EL layer 616, and the cathode 617. The light-emitting device is the light-emitting device described in Embodiment 1. Note that a plurality of light-emitting devices are formed in the pixel portion, but in the light-emitting device of this embodiment, both the light-emitting device described in Embodiment 1 and a light-emitting device having other configurations may be included.

[0169] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with the sealing material 605, a structure is formed in which the light-emitting device 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. Note that the space 607 is filled with a filling material, and in addition to the case where an inert gas (such as nitrogen or argon) is filled, it may also be filled with a sealing material. It is a preferable configuration to form a recess in the sealing substrate and provide a drying material therein to suppress deterioration due to the influence of moisture.

[0170] Note that it is preferable to use an epoxy-based resin or glass frit for the sealing material 605. Moreover, these materials are desirably materials that hardly transmit moisture and oxygen. In addition to a glass substrate or a quartz substrate, a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (polyvinyl fluoride), polyester, acrylic, or the like can be used as the material for the sealing substrate 604.

[0171] Although not shown in FIG. 2B, 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. Further, the protective film may be formed so as to cover the exposed portion of the sealing material 605. Further, the protective film can be provided to cover the exposed side surfaces of the surfaces and side surfaces of the pair of substrates, the sealing layer, the insulating layer, and the like.

[0172] A material that hardly transmits impurities such as water can be used for the protective film. Therefore, it is possible to effectively suppress the diffusion of impurities such as water from the outside to the inside.

[0173] As materials for forming the protective film, oxides, nitrides, fluorides, sulfides, ternary compounds, metals, polymers, etc. can be used. For example, materials 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 or indium oxide, etc., materials containing aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride or gallium nitride, etc., nitrides containing titanium and aluminum, oxides containing titanium and aluminum, oxides containing aluminum and zinc, sulfides containing manganese and zinc, sulfides containing cerium and strontium, oxides containing erbium and aluminum, oxides containing yttrium and zirconium, etc. can be used.

[0174] The protective film is preferably formed using a film-forming method with good step coverage. One such method is the atomic layer deposition (ALD) method. It is preferable to use the materials that can be formed by the ALD method for the protective film. By using the ALD method, a protective film that is dense, has reduced defects such as cracks and pinholes, or has a uniform thickness can be formed. Also, the damage given to the processing member when forming the protective film can be reduced.

[0175] For example, by forming the protective film using the ALD method, a protective film that is uniform and has few defects can be formed on the surface with a complex uneven shape, and on the upper surface, side surface and back surface of the touch panel.

[0176] In the above manner, a light-emitting device manufactured using the light-emitting device described in Embodiment 1 can be obtained.

[0177] Since the light-emitting device in this embodiment uses the light-emitting device described in Embodiment 1, a light-emitting device with good characteristics can be obtained. Specifically, since the light-emitting device described in Embodiment 1 is a light-emitting device with a long lifespan, a highly reliable light-emitting device can be obtained. In addition, since the light-emitting device using the light-emitting device described in Embodiment 1 has good luminous efficiency, it is possible to obtain a light-emitting device with low power consumption.

[0178] FIGS. 3A and 3B show examples of a light-emitting device that forms a light-emitting device exhibiting white light emission and is colorized by providing a coloring layer (color filter) or the like. FIG. 3A shows a substrate 1001, an underlying 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 portion 1042, a pixel portion 1040, a driving circuit portion 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 sealing material 1032, etc.

[0179] In FIG. 3A, the coloring layers (red coloring layer 1034R, green coloring layer 1034G, blue coloring layer 1034B) are provided on a transparent base material 1033. A black matrix 1035 may be further provided. The transparent base material 1033 provided with the coloring layer and the black matrix is aligned and fixed to the substrate 1001. Note that the coloring layer and the black matrix 1035 are covered with an overcoat layer 1036. In FIG. 3A, there are a light-emitting layer where light does not pass through the coloring layer and exits to the outside, and a light-emitting layer where light passes through the coloring layers of each color and exits to the outside. Since the light that does not pass through the coloring layer is white, and the light that passes through the coloring layer is red, green, or blue, an image can be expressed with four-color pixels.

[0180] FIG. 3B shows an example in which the coloring layers (red coloring layer 1034R, green coloring layer 1034G, blue coloring layer 1034B) are formed between the gate insulating film 1003 and the first interlayer insulating film 1020. In this way, the coloring layer may be provided between the substrate 1001 and the sealing substrate 1031.

[0181] Also, in the light-emitting device described above, a light-emitting device having a structure for extracting light to the side of the substrate 1001 on which the FET is formed (bottom emission type) is used, but a light-emitting device having a structure for extracting light emission to the side of the sealing substrate 1031 (top emission type) may also be used. A cross-sectional view of the top emission type light-emitting device is shown in FIG. 4. In this case, a substrate that does not transmit light can be used for the substrate 1001. Until a connection electrode connecting the FET and the anode of the light-emitting device is formed, it is formed in the same manner as the bottom emission type light-emitting device. Then, a third interlayer insulating film 1037 is formed to cover the electrode 1022. This insulating film may serve as a planarization film. 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.

[0182] The anodes 1024W, 1024R, 1024G, 1024B of the light-emitting device are anodes here, but they may be formed as cathodes. Also, in the case of a top emission type light-emitting device as shown in FIG. 4, it is preferable to use the anode as a reflective electrode. The configuration of the EL layer 1028 is the same as the configuration described for the EL layer 103 in the first embodiment, and has an element structure capable of obtaining white light emission.

[0183] In the top emission structure as shown in FIG. 4, sealing can be performed with a sealing substrate 1031 provided with a coloring layer (red coloring layer 1034R, green coloring layer 1034G, blue coloring layer 1034B). A black matrix 1035 may be provided on the sealing substrate 1031 so as to be located between pixels. The coloring layer (red coloring layer 1034R, green coloring layer 1034G, blue coloring layer 1034B) and the black matrix may be covered by an overcoat layer 1036. Note that a substrate having translucency is used for the sealing substrate 1031. Also, here, an example of full-color display using four colors of red, green, blue, and white is shown, but it is not particularly limited, and full-color display may be performed using four colors of red, yellow, green, and blue or three colors of red, green, and blue.

[0184] In a top emission type light emitting device, the application of a microcavity structure can be preferably carried out. A light emitting device having a microcavity structure can be obtained by using a reflective electrode as the anode and a semi-transmissive and semi-reflective electrode as the cathode. Between the reflective electrode and the semi-transmissive and semi-reflective electrode, there is at least an EL layer, and at least a light emitting layer serving as a light emitting region.

[0185] Note that the reflective electrode has a visible light reflectance of 40% to 100%, preferably 70% to 100%, and its resistivity is 1×10 -2 Ωcm or less of a film. Also, the semi-transmissive and semi-reflective electrode has a visible light reflectance of 20% to 80%, preferably 40% to 70%, and its resistivity is 1×10 -2 Ωcm or less of a film.

[0186] The light emitted from the light emitting layer included in the EL layer is reflected and resonated by the reflective electrode and the semi-transmissive and semi-reflective electrode.

[0187] The optical distance between the reflective electrode and the semi-transmissive and semi-reflective electrode of the light emitting device can be changed by changing the thicknesses of a transparent conductive film, the above-mentioned composite material, a carrier transport material, etc. Thereby, between the reflective electrode and the semi-transmissive and semi-reflective electrode, light of a resonant wavelength can be enhanced and light of a non-resonant wavelength can be attenuated.

[0188] Note that since the light (first reflected light) reflected by the reflective electrode and returned causes a large interference with the light (first incident light) directly incident from the light emitting layer on the semi-transmissive and semi-reflective electrode, 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 of 1 or more and λ is the wavelength of the light to be amplified). By adjusting the optical distance, the phases of the first reflected light and the first incident light can be matched and the light emission from the light emitting layer can be further amplified.

[0189] In the above configuration, the EL layer may have a structure with a plurality of light-emitting layers or a structure with a single light-emitting layer. For example, in combination with the configuration of the tandem light-emitting device described above, it may be applied to a configuration in which a plurality of EL layers are provided with a charge generation layer interposed therebetween in one light-emitting device, and a single or a plurality of light-emitting layers are formed in each EL layer.

[0190] By having a microcavity structure, it becomes possible to enhance the forward emission intensity of a specific wavelength, so that power consumption can be reduced. In the case of a light-emitting device that displays an image with four sub-pixels of red, yellow, green, and blue, in addition to the luminance improvement effect by yellow light emission, a microcavity structure adapted to the wavelength of each color can be applied to all sub-pixels, so that a light-emitting device with good characteristics can be obtained.

[0191] Since the light-emitting device in the present embodiment uses the light-emitting device described in Embodiment 1, a light-emitting device having good characteristics can be obtained. Specifically, since the light-emitting device described in Embodiment 1 is a light-emitting device with a long lifespan, a light-emitting device with good reliability can be obtained. In addition, since the light-emitting device using the light-emitting device described in Embodiment 1 has good luminous efficiency, it is possible to obtain a light-emitting device with low power consumption.

[0192] (Embodiment 3) In the present embodiment, an example in which the light-emitting device described in Embodiment 1 is used as an illumination device will be described with reference to FIGS. 5A and 5B. FIG. 5B is a top view of the illumination device, and FIG. 5A is a cross-sectional view taken along the line e-f in FIG. 5B.

[0193] In the illumination device in the present embodiment, an anode 401 is formed on a light-transmissive substrate 400 that is a support. The anode 401 corresponds to the anode 101 in Embodiment 1. When extracting light emission from the anode 401 side, the anode 401 is formed of a light-transmissive material.

[0194] A pad 412 for supplying a voltage to the cathode 404 is formed on the substrate 400.

[0195] An EL layer 403 is formed on the anode 401. The EL layer 403 corresponds to the configuration of the EL layer 103 in Embodiment 1, or the configuration combining the light-emitting units 511, 512, and the charge generation layer 513. For these configurations, please refer to the relevant description.

[0196] A cathode 404 is formed to cover the EL layer 403. The cathode 404 corresponds to the cathode 102 in Embodiment 1. When extracting light from the anode 401 side, the cathode 404 is formed of a material with high reflectivity. The cathode 404 is connected to the pad 412 to supply voltage.

[0197] As described above, the lighting device in this embodiment has a light-emitting device having an anode 401, an EL layer 403, and a cathode 404. Since the light-emitting device has high luminous efficiency, the lighting device in this embodiment can be a lighting device with low power consumption.

[0198] The substrate 400 on which the light-emitting device having the above configuration is formed and the sealing substrate 407 are fixed and sealed using sealing materials 405, 406, thereby completing the lighting device. Either of the sealing materials 405, 406 can be used. Also, a desiccant can be mixed into the inner sealing material 406 (not shown in FIG. 5B), whereby moisture can be adsorbed, leading to an improvement in reliability.

[0199] Also, by extending a part of the pad 412 and the anode 401 outside the sealing materials 405, 406, it can be used as an external input terminal. Also, an IC chip 420 with a converter or the like mounted thereon can be provided.

[0200] As described above, the lighting device described in this embodiment uses the light-emitting device described in Embodiment 1 for the EL element, and can be a light-emitting device with good reliability. Also, it can be a light-emitting device with low power consumption.

[0201] (Embodiment 4) In this embodiment, an example of an electronic device including the light-emitting device described in Embodiment 1 in part will be described. The light-emitting device described in Embodiment 1 has a good lifespan 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 section.

[0202] Examples of electronic devices to which the above light-emitting device is applied include, for example, a television device (also referred to as a TV or a television receiver), a monitor for a computer, a digital camera, a digital video camera, a digital photo frame, a mobile phone (also referred to as a cellular phone or a mobile phone device), a portable game machine, a portable information terminal, an audio playback device, and a large game machine such as a pachinko machine. Specific examples of these electronic devices are shown below.

[0203] FIG. 6A shows an example of a television device. In the television device, a display section 7103 is incorporated in a housing 7101. Here, a configuration in which the housing 7101 is supported by a stand 7105 is shown. The display section 7103 can display an image, and the display section 7103 is configured by arranging the light-emitting devices described in Embodiment 1 in a matrix.

[0204] The operation of the television device can be performed by an operation switch provided in the housing 7101 or by a separate remote control operation unit 7110. Channel and volume operations can be performed by operation keys 7109 provided in the remote control operation unit 7110, and the image displayed on the display section 7103 can be operated. Further, the remote control operation unit 7110 may be configured to be provided with a display section 7107 for displaying information output from the remote control operation unit 7110.

[0205] 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, one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers) information communication can also be performed.

[0206] FIG. 6B1 is a computer, including a main body 7201, a housing 7202, a display unit 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, etc. Note that this computer is manufactured by arranging the light-emitting devices described in Embodiment 1 in a matrix and using them for the display unit 7203. The computer in FIG. 6B1 may be in the form shown in FIG. 6B2. In the computer of FIG. 6B2, a second display unit 7210 is provided instead of the keyboard 7204 and the pointing device 7206. The second display unit 7210 is a touch panel type, and input can be performed by operating the input display displayed on the second display unit 7210 with a finger or a dedicated pen. In addition, the second display unit 7210 can display not only input displays but also other images. Also, the display unit 7203 may be a touch panel. By connecting the two screens with a hinge, it is possible to prevent troubles such as damaging or breaking the screens during storage or transportation.

[0207] FIG. 6C shows an example of a mobile terminal. The mobile phone includes, in addition to a display unit 7402 incorporated in a housing 7401, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, etc. Note that the mobile phone 7400 has a display unit 7402 manufactured by arranging the light-emitting devices described in Embodiment 1 in a matrix.

[0208] The mobile terminal shown in FIG. 6C can also be configured such that information can be input by touching the display unit 7402 with a finger or the like. In this case, operations such as making a call or creating an email can be performed by touching the display unit 7402 with a finger or the like.

[0209] The screen of the display unit 7402 mainly has three modes. The first is a display mode mainly for displaying images, the second is an input mode mainly for inputting information such as characters, and the third is a display + input mode in which the two modes of the display mode and the input mode are mixed.

[0210] For example, when making a call or creating an email, the display unit 7402 can be set to a character input mode mainly for character input, and an input operation on the characters displayed on the screen can be performed. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display unit 7402.

[0211] In addition, by providing a detection device having sensors such as a gyro and an acceleration sensor inside the mobile terminal to detect the inclination, the orientation (portrait or landscape) of the mobile terminal can be determined, and the screen display of the display unit 7402 can be automatically switched.

[0212] In addition, the screen mode can be switched by touching the display unit 7402 or operating the operation button 7403 of the housing 7401. It can also be switched according to the type of image displayed on the display unit 7402. For example, if the image signal displayed on the display unit is video data, it is switched to the display mode, and if it is text data, it is switched to the input mode.

[0213] In addition, in the input mode, the signal detected by the optical sensor of the display unit 7402 can be detected, and when there is no input by touch operation on the display unit 7402 for a certain period, the screen mode can be controlled to be switched from the input mode to the display mode.

[0214] The display unit 7402 can also function as an image sensor. For example, by touching the display unit 7402 with a palm or finger and imaging palm prints, fingerprints, etc., personal authentication can be performed. In addition, if a backlight that emits near-infrared light or a sensing light source that emits near-infrared light is used for the display unit, finger veins, palm veins, etc. can also be imaged.

[0215] Note that the configurations shown in this embodiment can be used by appropriately combining the configurations shown in Embodiments 1 to 3.

[0216] As described above, the application range of the light-emitting device including the light-emitting device described in Embodiment 1 is extremely wide, and this light-emitting device can be applied to electronic devices in all fields. By using the light-emitting device described in Embodiment 1, a highly reliable electronic device can be obtained.

[0217] FIG. 7A is a schematic diagram showing an example of a cleaning robot.

[0218] The cleaning robot 5100 has a display 5101 disposed on the upper surface, a plurality of cameras 5102 disposed on the side surface, a brush 5103, and operation buttons 5104. Although not shown, the lower surface of the cleaning robot 5100 is provided with tires, a suction port, and the like. The cleaning robot 5100 is further provided with various sensors such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezo sensor, an optical sensor, and a gyro sensor. In addition, the cleaning robot 5100 is provided with wireless communication means.

[0219] The cleaning robot 5100 can travel automatically, detect dust 5120, and suck the dust from the suction port provided on the lower surface.

[0220] 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, or steps. Further, when an object that is likely to get caught in the brush 5103, such as wiring, is detected by image analysis, the rotation of the brush 5103 can be stopped.

[0221] The display 5101 can display the remaining amount of the battery, the amount of sucked dust, and the like. The path traveled by the cleaning robot 5100 may be displayed on the display 5101. Further, the display 5101 may be a touch panel, and the operation buttons 5104 may be provided on the display 5101.

[0222] The cleaning robot 5100 can communicate with a mobile electronic device 5140 such as a smartphone. The image captured by the camera 5102 can be displayed on the mobile electronic device 5140. Therefore, the owner of the cleaning robot 5100 can know the state of the room even when away from home. Also, the display on the display 5101 can be confirmed on a mobile electronic device such as a smartphone.

[0223] The light-emitting device according to one aspect of the present invention can be used for the display 5101.

[0224] The robot 2100 shown in FIG. 7B includes an arithmetic unit 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 moving mechanism 2108.

[0225] The microphone 2102 has a function of detecting the user's voice and environmental sounds, etc. Also, 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.

[0226] The display 2105 has a function of displaying various information. The robot 2100 can display the information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. Also, the display 2105 may be a removable information terminal, and by installing it in a fixed position of the robot 2100, charging and data transfer are made possible.

[0227] The upper camera 2103 and the lower camera 2106 have the function of imaging the surroundings of the robot 2100. Also, the obstacle sensor 2107 can detect the presence or absence of obstacles in the traveling 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 according to one aspect of the present invention can be used for the display 2105.

[0228] FIG. 7C 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 of 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 rays), a microphone 5008, a display unit 5002, a support unit 5012, earphones 5013, and the like.

[0229] The light-emitting device according to one aspect of the present invention can be used for the display unit 5001 and the second display unit 5002.

[0230] FIG. 8 is an example in which the light-emitting device described in Embodiment 1 is used for an electric stand which is a lighting device. The electric stand shown in FIG. 8 has a housing 2001 and a light source 2002, and as the light source 2002, the lighting device described in Embodiment 2 may be used.

[0231] FIG. 9 is an example in which the light-emitting device described in Embodiment 1 is used as an indoor lighting device 3001. Since the light-emitting device described in Embodiment 1 is a highly reliable light-emitting device, it can be made into a reliable lighting device. Also, since the light-emitting device described in Embodiment 1 can be made large in area, it can be used as a large-area lighting device. Further, since the light-emitting device described in Embodiment 1 is thin, it can be used as a thin lighting device.

[0232] The light-emitting device described in Embodiment 1 can also be mounted on the windshield or dashboard of an automobile. FIG. 10 shows an aspect in which the light-emitting device described in Embodiment 1 is used for the windshield or dashboard of an automobile. Display areas 5200 to 5203 are displays provided using the light-emitting device described in Embodiment 1.

[0233] Display area 5200 and display area 5201 are display devices equipped with the light-emitting device described in Embodiment 1 provided on the windshield of an automobile. The light-emitting device described in Embodiment 1 can be made into a so-called see-through display device in which the anode and cathode are made of a light-transmissive electrode and the opposite side can be seen through. For a see-through display, even if it is installed on the windshield of an automobile, it can be installed without obstructing the view. When providing a transistor or the like for driving, it is preferable to use a light-transmissive transistor such as an organic transistor made of an organic semiconductor material or a transistor using an oxide semiconductor.

[0234] Display area 5202 is a display device equipped with the light-emitting device described in Embodiment 1 provided on the pillar portion. By projecting an image from imaging means provided on the vehicle body onto display area 5202, the view blocked by the pillar can be supplemented. Similarly, display area 5203 provided on the dashboard portion can supplement the blind spot by projecting an image from imaging means provided outside the automobile to the view blocked by the vehicle body, thereby enhancing safety. By projecting an image so as to supplement the invisible part, safety confirmation can be performed more naturally without a sense of incongruity.

[0235] The display area 5203 can also provide various information by displaying navigation information, speedometers, tachometers, travel distances, fuel gauges, gear states, air conditioning settings, etc. The display can be appropriately changed in terms of its display items and layout according to the user's preferences. Note that this information can also be provided in the display areas 5200 to 5202. Also, the display areas 5200 to 5203 can be used as lighting devices.

[0236] Also, FIGS. 11A to 11C show a foldable portable information terminal 9310. FIG. 11A shows the portable information terminal 9310 in an unfolded state. FIG. 11B shows the portable information terminal 9310 in a state during the change from one of the unfolded state or the folded state to the other. FIG. 11C shows the portable information terminal 9310 in a folded state. The portable information terminal 9310 has excellent portability in the folded state and excellent display listability due to a seamless and wide display area in the unfolded state.

[0237] The display panel 9311 is supported by three housings 9315 connected by a hinge 9313. Note that the display panel 9311 may be a touch panel (input / output device) equipped with a touch sensor (input device). Also, the display panel 9311 can be reversibly deformed from the unfolded state to the folded state of the portable information terminal 9310 by bending between the two housings 9315 via the hinge 9313. The light-emitting device according to one aspect of the present invention can be used for the display panel 9311.

[0238] Also, FIGS. 12A and 12B show a foldable portable information terminal 5150. The foldable portable information terminal 5150 has a housing 5151, a display area 5152, and a bending portion 5153. FIG. 12A shows the portable information terminal 5150 in an unfolded state. FIG. 12B shows the portable information terminal in a folded state. Despite having a large display area 5152, the portable information terminal 5150 is compact and has excellent portability when folded.

[0239] The display area 5152 can be folded in half by the bending portion 5153. The bending portion 5153 is composed of an expandable member and a plurality of support members. When folding, the expandable member extends. The bending portion 5153 is folded with a radius of curvature of 2 mm or more, preferably 3 mm or more.

[0240] Note that the display area 5152 may be a touch panel (input / output device) equipped with a touch sensor (input device). The light-emitting device of one aspect of the present invention can be used for the display area 5152.

Example

[0241] In this example, a manufacturing method of a light-emitting device 1 which is a light-emitting device of one aspect of the present invention, a comparative light-emitting device 2, and a comparative light-emitting device 1 which is a comparative light-emitting device are shown. The structural formulas of the materials used in this example are shown below.

[0242]

Chemical formula

[0243] ≪Manufacturing method of light-emitting device 1≫ First, indium tin oxide (ITSO) containing silicon oxide was formed into a film by sputtering on a glass substrate to form an anode 101. The film thickness was 70 nm, and the electrode area was 4 mm 2 (2 mm × 2 mm).

[0244] 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 UV ozone treatment was performed for 370 seconds.

[0245] After that, the substrate was introduced into a vacuum evaporation apparatus whose internal pressure was reduced to about 10 -4 Pa, and vacuum baking was performed at 170 °C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then the substrate was allowed to cool for about 30 minutes.

[0246] Next, the substrate on which the anode 101 is formed is fixed to a substrate holder provided in a vacuum deposition apparatus so that the surface on which the anode 101 is formed faces 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 an electron acceptor material (OCHD-001) are co-evaporated at a mass ratio of 1:0.1 (=BBABnf:OCHD-001) to form a hole injection layer 111 with a thickness of 10 nm.

[0247] Next, on the hole injection layer 111, as the first hole transport layer 112-1, BBABnf is deposited to a thickness of 20 nm, and then, as the second hole transport layer 112-2, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (ii) is deposited to a thickness of 10 nm to form a hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0248] Subsequently, 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) are co-evaporated at a mass ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form a light-emitting layer 113 with a thickness of 25 nm.

[0249] Thereafter, on the light-emitting layer 113, OCET010 and lithium 8-hydroxyquinolinate (abbreviation: Liq) represented by the above structural formula (v) are co-evaporated at a mass ratio of 1:2 (=OCET010:Liq) to a thickness of 12.5 nm, and then co-evaporated at a mass ratio of 2:1 (=OCET010:Liq) to a thickness of 12.5 nm to form an electron transport layer 114. Note that OCET010 is an organic compound having electron transport properties.

[0250] After forming the electron transport layer 114, Liq was deposited to a film thickness of 1 nm to form the electron injection layer 115, and then aluminum was deposited as the cathode 102 to a film thickness of 200 nm to fabricate the light-emitting device 1 of this example.

[0251] <<Fabrication method of light-emitting device 2>> The light-emitting device 2 was fabricated in the same manner as the light-emitting device 1, except that OCET010 in the light-emitting device 1 was changed to 2,9-di(2-naphthyl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen) represented by the above structural formula (vi).

[0252] <<Fabrication method of comparative light-emitting device 1>> The comparative light-emitting device 1 was fabricated in the same manner as the light-emitting device 1, except that OCET010 in the light-emitting device 1 was changed to αN-βNPAnth represented by the above structural formula (iii).

[0253] The element structures of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1 are summarized in the following table.

[0254]

Table 1

[0255] After these light-emitting devices were sealed with a glass substrate in a glove box under a nitrogen atmosphere so that the light-emitting devices were not exposed to the atmosphere (a sealing material was applied around the elements, and UV treatment and heat treatment were performed at 80 °C for 1 hour during sealing), the initial characteristics and reliability of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1 were measured. The measurements were performed at room temperature.

[0256] The luminance-current density characteristics of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1 are shown in FIG. 13, the current efficiency-luminance characteristics are shown in FIG. 14, the luminance-voltage characteristics are shown in FIG. 15, the current-voltage characteristics are shown in FIG. 16, the external quantum efficiency-luminance characteristics are shown in FIG. 17, and the emission spectrum is shown in FIG. 18. Also, the main characteristics of the light-emitting device 1, the light-emitting device 2, and the comparative light-emitting device 1 near 1000 cd / m 2 are shown in Table 2.

[0257] [Table 2]

[0258] From FIGS. 13 to 18 and Table 2, it was found that all three devices are blue light-emitting devices having good initial characteristics.

[0259] Also, a graph showing the change in luminance with respect to the driving time at a current density of 50 mA / cm 2 is shown in FIG. 19. As shown in FIG. 19, it was found that the light-emitting device 1 and the light-emitting device 2, which are light-emitting devices according to one aspect of the present invention, are light-emitting devices with good lifetimes compared to the comparative light-emitting device 1. In particular, the light-emitting device 1 has a longer lifetime because the luminance increases at the initial stage of driving. Also, the light-emitting device 2 has a small slope of long-term degradation and is a light-emitting device resistant to long-term driving.

[0260] Here, the results of investigating the photoluminescence characteristics of the materials used for the electron transport layer in each device are shown. A fluorometer (FS920 manufactured by Hamamatsu Photonics K.K.) or a fluorometer (FP-8600 manufactured by JASCO Corporation) was used for the measurement. Figure 20 shows the emission spectra of the OCET010Q film, the Liq film, and the mixed film in which OCET010 and Liq were mixed at a ratio of 1:1 (mass ratio) used in the light-emitting device 1. Figure 21 shows the emission spectra of the NBPhen film, the Liq film, and the mixed film in which NBPhen and Liq were mixed at a ratio of 1:1 (mass ratio) used in the light-emitting device 2. Figure 22 shows the emission spectra of the αN-βNPAnth film, the Liq film, and the mixed film in which αN-βNPAnth and Liq were mixed at a ratio of 1:1 (mass ratio) used in the comparative light-emitting device 1.

[0261] From Figure 20, the emission spectrum of the mixed film in which OCET010 and Liq were mixed at a ratio of 1:1 (mass ratio) is significantly shifted to the longer wavelength side compared to the emission spectra of the OCET010 film and the Liq film, suggesting that OCET010 and Liq form an exciplex. Similarly, it is suggested from Figure 21 that NBPhen and Liq form an exciplex. On the other hand, in Figure 22, since the spectrum of the mixed film of αN-βNPAnth and Liq was somewhat broadened to the longer wavelength side but was almost the same as the spectrum of Liq, it is considered that no exciplex was formed.

[0262] An exciplex is formed by the interaction of the molecular orbits of two substances to form one exciplex. The exciplex exhibits luminescence having a peak at a wavelength corresponding to the difference between the shallower HOMO level and the deeper LUMO level among the levels of the two substances.

[0263] The HOMO level and the LUMO level can be calculated based on cyclic voltammetry (CV) measurements.

[0264] As the measuring device, an electrochemical analyzer (manufactured by BAS Inc., model number: ALS model 600A or 600C) was used. For the solution in CV measurement, dehydrated dimethylformamide (DMF) (manufactured by Aldrich Co., Ltd., 99.8%, catalog number: 22705-6) was used as the solvent, and tetra-n-butylammonium perchlorate (n-Bu4NClO4) (manufactured by Tokyo Chemical Industry Co., Ltd., catalog number: T0836), which is a supporting electrolyte, was dissolved to a concentration of 100 mmol / L, and further the measurement target was dissolved to a concentration of 2 mmol / L for preparation. As the working electrode, a platinum electrode (manufactured by BAS Inc., PTE platinum electrode) was used, as the auxiliary electrode, a platinum electrode (manufactured by BAS Inc., Pt counter electrode for VC-3 (5 cm)) was used, and as the reference electrode, an Ag / Ag+ electrode (manufactured by BAS Inc., RE7 non-aqueous solvent-based reference electrode) was used respectively. Note that the measurement was carried out at room temperature (20~25 °C). Also, the scan rate during CV measurement was unified to 0.1 V / sec, and the oxidation potential Ea [V] and reduction potential Ec [V] with respect to the reference electrode were measured. Ea was taken as the intermediate potential of the oxidation-reduction wave, and Ec was taken as the intermediate potential of the reduction-oxidation wave. Here, since it is known that the potential energy of the reference electrode used in this example with respect to the vacuum level is -4.94 [eV], the HOMO level [eV] = -4.94 - Ea and the LUMO level [eV] = -4.94 - Ec, and the HOMO level and LUMO level can be obtained respectively from these formulas (since Ea and Ec are the potentials of one-electron oxidation and one-electron reduction respectively, the values of the potentials can be directly converted to electron volts for calculation).

[0265] Figure 33 shows the oxidation-reduction wave of OCET010. The oxidation peak potential (Epa) in the oxidation-reduction wave of OCET010 was observed at 0.936 V, and the reduction peak potential (Epc) was observed at 0.822 V. From this, Ea could be determined to be 0.88 V, and the HOMO level of OCET010 could be calculated to be -5.82 eV.

[0266] Similarly, the reduction-oxidation wave of OCET010 was shown in Fig. 34. The reduction peak potential (Epc) in the reduction-oxidation wave of OCET010 was observed at -2.113 V, and the oxidation peak potential (Epa) was observed at -2.029 V. From this, Ec could be determined to be -2.07 V, and the LUMO level of OCET010 could be calculated to be -2.87 eV.

[0267] Fig. 35 shows the oxidation-reduction wave of NBPhen. The oxidation peak potential (Epa) in the oxidation-reduction wave of NBPhen was observed as a broad shoulder peak around approximately 1.3 V. On the other hand, since the reduction peak potential (Epc) was not observed, it was assumed that the difference between Epa and Epc was about 0.1 V (because in an ideal diffusion system where electron transfer is sufficiently fast, it is known that the difference between Epa and Epc is less than 60 mV). That is, here, Epc in the oxidation-reduction wave of NBPhen was set to 1.2 V. From this, the Ea of NPBhen could be determined to be 1.25 V. However, since the peak of Epa is broad and based on the above assumption, the calculation should be carried out with the first decimal place as the significant figure. Therefore, the HOMO level of NBPhen was calculated to be approximately -6.2 eV.

[0268] Similarly, Fig. 36 shows the reduction-oxidation wave of NBPhen. The reduction peak potential (Epc) in the reduction-oxidation wave of NBPhen was observed at -2.166 V, and the oxidation peak potential (Epa) was observed at -2.062 V. From this, Ec could be determined to be -2.12 V, and the LUMO level of NBPhen could be calculated to be -2.83 eV.

[0269] Figure 37 shows the oxidation-reduction wave of Liq. From this, the oxidation peak potential (Epa) in the oxidation-reduction wave of Liq was observed as a shoulder peak at around 0.77 eV. On the other hand, since the reduction peak potential (Epc) was not observed, the difference between Epa and Epc was assumed to be about 0.1 V (because in an ideal diffusion system where electron transfer is sufficiently fast, it is known that the difference between Epa and Epc is slightly less than 60 mV). That is, here, Epc in the oxidation-reduction wave of Liq was set to 0.67 V. As a result, the Ea of Liq can be calculated to be 0.72 eV, but since the first decimal place should be calculated as a significant figure based on the above assumption, the HOMO level of Liq is calculated to be about -5.7 eV.

[0270] Similarly, Figure 38 shows the reduction-oxidation wave of Liq. Note that Figure 38B is a graph showing an enlarged view of the range from -1.7 V to -2.8 V in Figure 38A. From this, the reduction peak potential (Epc) in the reduction-oxidation wave of Liq was observed as a shoulder peak at around -2.29 V. On the other hand, since the oxidation peak potential (Epa) was not observed, the difference between Epa and Epc was assumed to be about 0.1 V (because in an ideal diffusion system where electron transfer is sufficiently fast, it is known that the difference between Epa and Epc is slightly less than 60 mV). That is, here, Epc in the reduction-oxidation wave of Liq was assumed to be -2.19 V. As a result, the Ec of Liq can be obtained as -2.24 eV, but since the first decimal place should be calculated as a significant figure based on the above assumption, the LUMO level of Liq is calculated to be -2.7 eV.

[0271] Table 3 shows the HOMO level and LUMO level of the electron-transporting organic compounds OCET010 and NBPhen having electron-transporting properties used in the electron transport layers of the light-emitting devices 1 and 2 obtained as described above, and the difference (ΔE LUMO-HOMO ) between the LUMO level of these two materials and the HOMO level of Liq, which is an organometallic complex of an alkali metal, the peak wavelength (λp Ex ) of the emission spectrum of the exciplex with Liq, the value (E Ex ) obtained by converting the peak wavelength to energy, and the value obtained by subtracting E LUMO-HOMO from ΔEEx The value obtained by subtracting (ΔE HL -E Ex ) is shown. As described above, since the significant figure of the HOMO level of Liq is up to the first decimal place, ΔE LUMO-HOMO , ΔE HL -E Ex all have the first decimal place as the significant figure.

[0272]

Table 3

[0273] As can be seen from FIGS. 20 and 21, in the electron transport layers of the light-emitting device 1 and the light-emitting device 2, it is considered that OCET010 and NBPhen form an exciplex with Liq, which is an organometallic complex of an alkali metal (note that since no new absorption peak generated by mixing was observed in the absorption spectrum of the mixed film, it could not be identified as an exciplex). As described above, normally, the value obtained by converting the peak wavelength of the emission spectrum of the exciplex into energy should be close to the difference between the HOMO level of Liq and the LUMO level of OCET010, or the difference between the HOMO level of Liq and the LUMO level of NBPhen. However, as shown in Table 3, in the light-emitting device of the present application, the ΔE HL -E Ex shows relatively large values of 0.6 eV and 0.9 eV, respectively. The light-emitting device according to one aspect of the present invention is a light-emitting device in which ΔE HL -E Ex is 0.5 eV or more, and it has been found that the value obtained by converting the peak wavelength of the emission spectrum of the exciplex formed in the electron transport layer of the light-emitting device into energy is 0.5 eV or more smaller than the difference between the HOMO level of Liq and the LUMO level of OCET010 or NBPhen.

[0274] In addition, the light-emitting device 2 with the peak wavelength of the emission spectrum of the exciplex being 570 nm or more was a light-emitting device with a smaller long-term degradation slope compared to the light-emitting device 1 with a peak wavelength of 570 nm or less. Further, it was found that the light-emitting device 2 had a peak wavelength of the emission spectrum of the exciplex of 610 nm or more and was a light-emitting device with better luminous efficiency.

[0275] Subsequently, a part of the results of analyzing the film obtained by mixing NBPhen and Liq used in the electron transport layer 114 in the light-emitting device 2 by ToF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) is shown in FIG. 23. FIG. 23 shows the results in the range of m / z of positive ions (positive ions) from 730 to 760 in the ToF-SIMS analysis. In the figure, an ion is detected at m / z = 740, and this ion corresponds to an ion with the molecular weight of NBPhen + the molecular weight of Liq + the atomic weight of Li - 2. This is a characteristic result obtained when measuring a material having the structure of the electron transport layer in the light-emitting device of the present invention.

[0276] In a light-emitting device having an electron transport layer containing an organic compound having electron transporting properties and an organic compound of an alkali metal, when the molecular weight of the organic compound having electron transporting properties is M E , the molecular weight of the organometallic complex of the alkali metal is M ACom , and the molecular weight of the alkali metal is M A , when measuring the electron transport layer or a film equivalent to the electron transport layer by mass spectrometry, a positive ion is detected at the mass-to-charge ratio m / z = M E + M ACom + M A - 2, and the above ΔE LUMO-HOMO(Difference between the LUMO level of an organic compound having electron transporting properties and the HOMO level of an organometallic complex of an alkali metal) A light-emitting device with a difference of 2.9 eV or less can be a light-emitting device with good lifespan like the above-described light-emitting device 1 and light-emitting device 2. Note that in the electron transport layer of comparative light-emitting device 1, a mixed film of αN-βNPAnth and Liq is used, but the mixed film with αN-βNPAnth and Liq mixed at a ratio of 1:1 (mass ratio) not only does not form an exciplex, but its ΔE LUMO-HOMO is also 3.0 eV.

Example

[0277] In this example, a method for manufacturing a light-emitting device 3 which is a light-emitting device according to one aspect of the present invention is shown. The structural formulas of the materials used in this example are shown below.

[0278]

Chemical formula

[0279] ≪Method for manufacturing light-emitting device 3≫ First, indium tin oxide (ITSO) containing silicon oxide was formed into a film on a glass substrate by sputtering to form an anode 101. Note that the film thickness was 70 nm and the electrode area was 4 mm 2 (2 mm × 2 mm).

[0280] 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.

[0281] After that, the substrate was introduced into a vacuum evaporation apparatus whose internal pressure was reduced to about 10 -4 Pa, and in the heating chamber of the vacuum evaporation apparatus, vacuum baking was performed at 170 °C for 30 minutes, and then the substrate was allowed to cool for about 30 minutes.

[0282] Next, the substrate on which the anode 101 is formed is fixed to a substrate holder provided in a vacuum deposition apparatus so that the surface on which the anode 101 is formed faces 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 an electron acceptor material (OCHD-001) are co-evaporated at a mass ratio of 1:0.1 (= BBABnf:OCHD-001) to form a hole injection layer 111 with a thickness of 10 nm using a resistance heating evaporation method.

[0283] Next, on the hole injection layer 111, BBABnf is evaporated to a thickness of 20 nm as the 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) is evaporated to a thickness of 10 nm as the second hole transport layer 112-2 to form a hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0284] Subsequently, 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) are co-evaporated at a mass ratio of 1:0.015 (= αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form a light-emitting layer 113 with a thickness of 25 nm.

[0285] Thereafter, 2-phenyl-3-[10-(3-pyridyl)-9-anthryl]phenylquinoxaline (abbreviation: PyA1PQ) represented by the above structural formula (viii) and lithium 8-hydroxyquinolinate (abbreviation: Liq) represented by the above structural formula (vi) were co-evaporated at a mass ratio of 1:2 (= PyA1PQ:Liq) to a thickness of 12.5 nm, and then co-evaporated at a mass ratio of 2:1 (= PyA1PQ:Liq) to a thickness of 12.5 nm to form the electron transport layer 114.

[0286] 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 as the cathode 102 to fabricate the light-emitting device 3 of this example.

[0287] The device structure of the light-emitting device 3 is summarized in the following table.

[0288]

Table 4

[0289] After performing the operation of sealing this light-emitting device with a glass substrate so as not to be exposed to the atmosphere in a glove box under a nitrogen atmosphere (applying a sealing material around the device and performing UV treatment and heat treatment at 80 °C for 1 hour during sealing), the initial characteristics and reliability of the light-emitting device 3 were measured. The measurement was performed at room temperature.

[0290] The luminance-current density characteristics of the light-emitting device 3 are shown in FIG. 24, the current efficiency-luminance characteristics are shown in FIG. 25, the luminance-voltage characteristics are shown in FIG. 26, the current-voltage characteristics are shown in FIG. 27, the external quantum efficiency-luminance characteristics are shown in FIG. 28, and the emission spectrum is shown in FIG. 29. Also, the main characteristics of the light-emitting device 3 near 1000 cd / m 2 are shown in Table 5.

[0291]

Table 5

[0292] From FIGS. 24 to 29 and Table 5, it was found that the light-emitting device 3 is a blue light-emitting device having good initial characteristics.

[0293] Also, a graph showing the change in luminance with respect to the driving time at a current density of 50 mA / cm 2 is shown in FIG. 30. As shown in FIG. 30, the light-emitting device 3, which is a light-emitting device according to one aspect of the present invention, is a light-emitting device with a very long lifespan because initial deterioration is suppressed by an increase in luminance at the initial stage of driving, and furthermore, the slope of long-term deterioration is small.

[0294] Here, the results of investigating the photoluminescence characteristics of the material used for the electron transport layer of the light-emitting device 3 are shown. A fluorophotometer (FS920 manufactured by Hamamatsu Photonics K.K.) was used for the measurement. FIG. 31 shows the emission spectra of the PyA1PQ film, the Liq film, and the mixed film in which PyA1PQ and Liq are mixed at a ratio of 1:1 (mass ratio) used in the light-emitting device 3.

[0295] From FIG. 31, the emission spectrum of the mixed film in which PyA1PQ and Liq are mixed at a ratio of 1:1 (mass ratio) is shifted significantly to the longer wavelength side compared to the emission spectra of the PyA1PQ film and the Liq film, suggesting that PyA1PQ and Liq form an exciplex.

[0296] Note that an exciplex is formed by the interaction of the molecular orbitals of two substances to form one exciplex, and the exciplex exhibits emission having a peak at a wavelength corresponding to the difference between the shallower HOMO level and the deeper LUMO level among the levels of the two substances.

[0297] Table 6 shows the HOMO level and LUMO level of PyA1PQ, which is an organic compound having electron transport properties used for the electron transport layer of each light-emitting device 3, and the difference (ΔE LUMO-HOMO ) between the LUMO level of PyA1PQ and the HOMO level of Liq, which is an organometallic complex of an alkali metal, the peak wavelength (λp Ex ) of the emission spectrum of the exciplex with Liq, and the value (E Ex) and ΔE HOMO-LUMO from E Ex subtracted value (ΔE HL -E Ex ) is shown. Regarding the measurement method and calculation method of the HOMO level and LUMO level, since they are described in Example 1, they will be omitted. Please refer to the description of Example 1. Since the significant figures of the HOMO level of Liq are up to the first decimal place, ΔE LUMO-HOMO , ΔE HL -E Ex all have the first decimal place as significant figures, which is the same as in Example 1.

[0298] In addition, FIG. 39 shows the oxidation-reduction wave of PyA1PQ. The oxidation peak potential (Epa) in the oxidation-reduction wave of PyA1PQ was observed at 1.045 V, and the reduction peak potential (Epc) was observed at 0.885 V. From this, Ea can be determined to be 0.97 V, and the HOMO level of PyA1PQ could be calculated to be -5.91 eV.

[0299] Similarly, FIG. 40 shows the reduction-oxidation wave of PyA1PQ. The reduction peak potential (Epc) in the reduction-oxidation wave of PyA1PQ was observed at -1.984 V, and the oxidation peak potential (Epa) was observed at -1.904 V. From this, Ec can be determined to be -1.94 V, and the LUMO level of PyA1PQ could be calculated to be -3.00 eV.

[0300]

Table 6

[0301] As can be seen from FIG. 31, in the electron transport layer of the light-emitting device 3, it is considered that PyA1PQ forms an exciplex with Liq (note that since no new absorption peak generated by mixing was observed in the absorption spectrum of the mixed film, it could not be identified as an exciplex). As described above, normally, the value obtained by converting the peak wavelength of the emission spectrum of the exciplex into energy should be close to the difference between the HOMO level of Liq and the LUMO level of PyA1PQ, but in the light-emitting device 3 as shown in Table 6, ΔEHL -E Ex shows a large value of 0.6 eV. The light-emitting device according to one aspect of the present invention is a light-emitting device in which ΔE HL -E Ex is 0.5 eV or more, and the value obtained by converting the peak wavelength of the emission spectrum of the exciplex formed in the electron transport layer of the light-emitting device into energy is 0.5 eV or more smaller than the difference between the HOMO level of Liq and the LUMO level of PyA1PQ.

[0302] In addition, the light-emitting device 3 in which the peak wavelength of the emission spectrum of the exciplex is 570 nm or more has a small inclination of long-term deterioration. Further, the light-emitting device 3 has a peak wavelength of the emission spectrum of the exciplex of 570 nm or more and less than 610 nm, and has a very good lifetime having both an increase in luminance at the initial stage of driving and a small inclination of long-term deterioration.

[0303] Subsequently, a part of the result of analyzing the film obtained by mixing PyA1PQ and Liq used for the electron transport layer 114 in the light-emitting device 3 by ToF-SIMS is shown in FIG. 32. FIG. 32 shows the result in the range of m / z 685 to 710 of positive ions (cations) in the ToF-SIMS analysis. In the figure, an ion is detected at m / z 691, and this ion corresponds to an ion of PyA1PQ (molecular weight) + Liq (molecular weight) + Li (atomic weight) - 2. This is a characteristic result obtained when measuring a material having the configuration of the electron transport layer in the light-emitting device of the present invention.

[0304] When the molecular weight of the organic compound having electron transporting properties is M E , the molecular weight of the organometallic complex of the alkali metal is M ACom , and the molecular weight of the alkali metal is M A , when measuring the electron transport layer or a film equivalent to the electron transport layer by mass spectrometry, a positive ion is detected at the mass-to-charge ratio m / z = M E + M ACom + M A - 2, and the above ΔE LUMO-HOMOA light-emitting device with a difference (between the LUMO level of an organic compound having electron-transporting properties and the HOMO level of an organometallic complex of an alkali metal) of 2.9 eV or less can be a light-emitting device with good lifespan like the above-described light-emitting device 3.

Example

[0305] In this example, a method for manufacturing a light-emitting device 4 which is a light-emitting device according to one aspect of the present invention is shown. The structural formulas of the materials used in this example are shown below.

[0306]

Chemical formula

[0307] ≪Method for manufacturing the light-emitting device 4≫ First, indium tin oxide (ITSO) containing silicon oxide was formed into a film on a glass substrate by sputtering to form an anode 101. The film thickness was 70 nm, and the electrode area was 4 mm 2 (2 mm × 2 mm).

[0308] 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.

[0309] After that, the substrate was introduced into a vacuum evaporation apparatus whose internal pressure was reduced to about 10 -4 Pa, and in the heating chamber of the vacuum evaporation apparatus, vacuum baking was performed at 170 °C for 30 minutes, and then the substrate was allowed to cool for about 30 minutes.

[0310] Next, the substrate on which the anode 101 is formed is fixed to a substrate holder provided in a vacuum deposition apparatus so that the surface on which the anode 101 is formed faces 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 an electron acceptor material (OCHD-001) are co-evaporated in a mass ratio of 1:0.1 (=BBABnf:OCHD-001) to form a hole injection layer 111 with a thickness of 10 nm using a resistive heating evaporation method.

[0311] Next, on the hole injection layer 111, as the first hole transport layer 112-1, BBABnf is evaporated to a thickness of 20 nm, and then, as the second hole transport layer 112-2, 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (ii) is evaporated to a thickness of 10 nm to form a hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0312] Subsequently, 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) are co-evaporated in a mass ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form a light-emitting layer 113 with a thickness of 25 nm.

[0313] Thereafter, 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) represented by the above structural formula (viii) and lithium 8-hydroxyquinolinate (abbreviation: Liq) represented by the above structural formula (vi) were co-evaporated at 12.5 nm so that the mass ratio was 1:2 (= mPn-mDMePyPTzn:Liq), and then co-evaporated at 12.5 nm so that the mass ratio was 2:1 (= mPn-mDMePyPTzn:Liq) to form an electron transport layer 114.

[0314] After forming the electron transport layer 114, Liq was evaporated to a film thickness of 1 nm to form an electron injection layer 115, and then aluminum was evaporated to a film thickness of 200 nm as the cathode 102 to fabricate the light-emitting device 4 of this example.

[0315] The device structure of the light-emitting device 4 is summarized in a table.

[0316]

Table 7

[0317] After the operation of sealing this light-emitting device with a glass substrate so as not to be exposed to the atmosphere in a glove box under a nitrogen atmosphere (applying a sealing material around the device and performing UV treatment and heat treatment at 80 °C for 1 hour during sealing), measurements were made on the initial characteristics and reliability. The measurements were performed at room temperature.

[0318] The luminance-current density characteristics of the light-emitting device 4 are shown in FIG. 41, the luminance-voltage characteristics are shown in FIG. 42, the current efficiency-luminance characteristics are shown in FIG. 43, the current-voltage characteristics are shown in FIG. 44, the external quantum efficiency-luminance characteristics are shown in FIG. 45, and the emission spectrum is shown in FIG. 46. Also, the main characteristics of the light-emitting device 3 near 1000 cd / m 2 are shown in Table 8.

[0319]

Table 8

[0320] From FIGS. 41 to 46 and Table 8, it was found that the light-emitting device 4 is a blue light-emitting device having good initial characteristics.

[0321] Also, a graph showing the change in luminance with respect to the driving time at a current density of 50 mA / cm 2 is shown in FIG. 47. As shown in FIG. 47, the light-emitting device 4, which is a light-emitting device according to one aspect of the present invention, is a light-emitting device with a long lifespan.

[0322] Here, the results of investigating the photoluminescence characteristics of the material used in the electron transport layer of the light-emitting device 4 are shown. FIG. 48 shows the emission spectra of the mPn-mDMePyPTzn film, the Liq film, and a mixed film in which mPn-mDMePyPTzn and Liq are mixed at a ratio of 1:1 (mass ratio) used in the light-emitting device 4. For the measurement of the mPn-mDMePyPTzn film, a fluorescence photometer (FP-8600 manufactured by JASCO Corporation) was used, and for the measurement of the other films, a fluorescence photometer (FS920 manufactured by Hamamatsu Photonics K.K.) was used.

[0323] From FIG. 48, the emission spectrum of the mixed film in which mPn-mDMePyPTzn and Liq are mixed at a ratio of 1:1 (mass ratio) is shifted to the long wavelength side compared to the emission spectra of the mPn-mDMePyPTzn film and the Liq film, suggesting that mPn-mDMePyPTzn and Liq form an exciplex.

[0324] Note that an exciplex is formed by the interaction of the molecular orbitals of two substances to form one exciplex, and the exciplex exhibits emission having a peak at a wavelength corresponding to the difference between the shallower HOMO level and the deeper LUMO level among the levels of the two substances.

[0325] Table 9 shows the HOMO level and LUMO level of mPn-mDMePyPTzn, which is an organic compound having electron transporting properties used in the electron transport layer of the light-emitting device 4, and the difference (ΔE between the LUMO level of mPn-mDMePyPTzn and the HOMO level of Liq, which is an organometallic complex of an alkali metalLUMO-HOMO ) The peak wavelength (λp) of the emission spectrum of the exciplex with Liq Ex ) The value (E) obtained by converting the peak wavelength into energy Ex ), and ΔE HOMO-LUMO from E Ex The value obtained by subtracting E HL -E Ex )(ΔE LUMO-HOMO ), ΔE HL -E Ex ) are shown. Regarding the measurement method and calculation method of the HOMO level and LUMO level, since they are described in Example 1, they will be omitted. Please refer to the description of Example 1. Since the significant figures of the HOMO level of Liq are up to the first decimal place, the same as in Example 1 is also that both ΔE

[0326] Figure 49 shows the reduction-oxidation wave of mPn-mDMePyPTzn. The reduction peak potential (Epc) in the reduction-oxidation wave of mPn-mDMePyPTzn was observed at -2.001 V, and the oxidation peak potential (Epa) was observed at -1.917 V. From this, Ec can be determined to be -1.96 V, and the LUMO level of mPn-mDMePyPTzn could be calculated to be -2.98 eV.

[0327]

Table 9

[0328] As can be seen from Figure 49, in the electron transport layer of the light-emitting device 4, it is considered that mPn-mDMePyPTzn and Liq form an exciplex (note that since no new absorption peak generated by mixing was observed in the absorption spectrum of the mixed film, it could be identified as an exciplex). As described above, normally, the value obtained by converting the peak wavelength of the emission spectrum of the exciplex into energy should be close to the difference between the HOMO level of Liq and the LUMO level of mPn-mDMePyPTzn. However, as shown in Table 9, in the light-emitting device 4, ΔE HL -E Ex shows a large value of 0.3 eV. The light-emitting device of this example has such a ΔEHL -E Ex It is a light-emitting device in which HL is 0.3 eV or more, and the value obtained by converting the peak wavelength of the emission spectrum of the exciplex formed in the electron transport layer of the light-emitting device into energy is smaller than the difference between the HOMO level of Liq and the LUMO level of mPn-mDMePyPTzn by 0.3 eV or more.

Example

[0329] In this example, a method for manufacturing light-emitting devices 5 to 7, which are light-emitting devices according to one aspect of the present invention, is shown. The structural formulas of the organic compounds used in this example are shown below.

[0330]

Chemical formula

[0331] ≪Method for manufacturing light-emitting device 5≫ First, indium tin oxide (ITSO) containing silicon oxide was formed into a film on a glass substrate by a sputtering method to form an anode 101. The film thickness was 70 nm, and the electrode area was 4 mm 2 (2 mm × 2 mm).

[0332] 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.

[0333] Thereafter, the substrate was introduced into a vacuum evaporation apparatus whose internal pressure was reduced to about 10 -4 Pa, and vacuum baking was performed at 170 °C for 30 minutes in the heating chamber of the vacuum evaporation apparatus, and then the substrate was allowed to cool for about 30 minutes.

[0334] Next, the substrate on which the anode 101 is formed is fixed to a substrate holder provided in a vacuum deposition apparatus so that the surface on which the anode 101 is formed faces downward. Onto 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 an electron acceptor material (OCHD-001) are co-evaporated in a mass ratio of 1:0.1 (=BBABnf:OCHD-001) to form a hole injection layer 111 with a thickness of 10 nm by a deposition method using resistance heating.

[0335] Next, on the hole injection layer 111, as the first hole transport layer 112-1, BBABnf is deposited to a thickness of 20 nm, and then, as the second hole transport layer 112-2, 3,3’-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) represented by the above structural formula (ii) is deposited to a thickness of 10 nm to form a hole transport layer 112. Note that the second hole transport layer 112-2 also functions as an electron blocking layer.

[0336] Subsequently, 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) are co-evaporated in a mass ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to form a light-emitting layer 113 with a thickness of 25 nm.

[0337] Thereafter, on the light-emitting layer 113, αN-βNPAnth and lithium 4-methyl-8-quinolinolate (abbreviation: Li-4mq) represented by the above structural formula (ix) are co-evaporated in a mass ratio of 1:1 (=αN-βNPAnth:Li-4mq) to form an electron transport layer 114 with a thickness of 25 nm.

[0338] After forming the electron transport layer 114, 8-hydroxyquinolinato-lithium (abbreviation: Liq) represented by the above structural formula (vi) was deposited to a film thickness of 1 nm to form the electron injection layer 115, and then aluminum was deposited as the cathode 102 to a film thickness of 200 nm to fabricate the light-emitting device 5 of this example.

[0339] ≪Method for fabricating the light-emitting device 6≫ The light-emitting device 6 was fabricated in the same manner as the light-emitting device 5, except that αN-βNPAnth in the light-emitting device 5 was changed to 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) represented by the above structural formula (viii).

[0340] ≪Method for fabricating the light-emitting device 7≫ The light-emitting device 7 was fabricated in the same manner as the light-emitting device 5, except that αN-βNPAnth in the light-emitting device 5 was changed to 2-phenyl-3-[10-(3-pyridinyl)-9-anthryl]phenylquinoxaline (abbreviation: PyA1PQ) represented by the above structural formula (viii).

[0341] The device structures of the light-emitting devices 5 to 7 are summarized in a table.

[0342]

Table 10

[0343] After these light-emitting devices were sealed with a glass substrate in a nitrogen atmosphere glove box so that the light-emitting devices were not exposed to the atmosphere (a sealing material was applied around the device, and UV treatment and heat treatment were performed at 80 °C for 1 hour during sealing), the initial characteristics and reliability of the light-emitting devices 5 to 7 were measured. The measurement was performed at room temperature.

[0344] The luminance-current density characteristics of light-emitting devices 5 to 7 are shown in FIG. 50, the luminance-voltage characteristics are shown in FIG. 51, the current efficiency-luminance characteristics are shown in FIG. 52, the current-voltage characteristics are shown in FIG. 53, the external quantum efficiency-luminance characteristics are shown in FIG. 54, and the emission spectrum is shown in FIG. 55. Also, the main characteristics near 1000 cd / m 2 of light-emitting devices 5 to 7 are shown in Table 11.

[0345]

Table 11

[0346] From FIGS. 50 to 55 and Table 11, it was found that the blue light-emitting devices of all three devices have good initial characteristics.

[0347] Also, a graph showing the change in luminance with respect to the driving time at a current density of 50 mA / cm 2 is shown in FIG. 56. As shown in FIG. 56, it was found that light-emitting devices 5 to 7, which are light-emitting devices according to one aspect of the present invention, are light-emitting devices with good lifetimes.

[0348] Here, the results of investigating the photoluminescence characteristics of the materials used for the electron transport layer in each device are shown. The measurement was performed in the same manner as in Example 1. FIG. 57 shows the emission spectra of the αN-βNPAnth film, the Li-4mq film, and the mixed film in which αN-βNPAnth and Li-4mq are mixed at a ratio of 1:1 (mass ratio) used in light-emitting device 5, FIG. 58 shows the emission spectra of the mPn-mDMePyPTzn film, the Li-4mq film, and the mixed film in which mPn-mDMePyPTzn and Li-4mq are mixed at a ratio of 1:1 (mass ratio) used in light-emitting device 6, and FIG. 59 shows the emission spectra of the PyA1PQ film, the Li-4mq film, and the mixed film in which PyA1PQ and Li-4mq are mixed at a ratio of 1:1 (mass ratio) used in light-emitting device 7.

[0349] As shown in Fig. 57, the emission spectrum of the mixed film obtained by mixing αN-βNPAnth and Li-4mq at a mass ratio of 1:1 is significantly shifted towards the longer wavelength side compared to the emission spectra of the αN-βNPAnth film and the Li-4mq film, suggesting that αN-βNPAnth and Li-4mq form an exciplex. Similarly, as shown in Fig. 58, it is suggested that mPn-mDMePyPTzn and Li-4mq, and in Fig. 59, PyA1PQ and Li-4mq form exciplexes.

[0350] Note that an exciplex is formed by the interaction of the molecular orbitals of two substances to form one exciplex, and the exciplex exhibits emission with a peak at a wavelength corresponding to the difference between the shallower HOMO level and the deeper LUMO level among the levels of the two substances. Since the measurement and calculation methods of the HOMO level and the LUMO level are described in Example 1, they are omitted here. Please refer to the description of Example 1. Since the significant figures of the HOMO level of Liq are up to the first decimal place, ΔE LUMO-HOMO 、ΔE HL -E Ex All have significant figures up to the first decimal place, which is the same as in Example 1.

[0351] Fig. 60 shows the oxidation-reduction wave of αN-βNPAnth. The oxidation peak potential (Epa) in the oxidation-reduction wave of αN-βNPAnth was observed at 0.978 V, and the reduction peak potential (Epc) was observed at 0.840 V. From this, Ea could be determined to be 0.91 V, and the HOMO level of αN-βNPAnth could be calculated to be -5.85 eV.

[0352] Similarly, Fig. 61 shows the reduction-oxidation wave of αN-βNPAnth. The reduction peak potential (Epc) in the reduction-oxidation wave of αN-βNPAnth was observed at -2.248 V, and the oxidation peak potential (Epa) was observed at -2.161 V. From this, Ec could be determined to be -2.20 V, and the LUMO level of αN-βNPAnth could be calculated to be -2.74 eV.

[0353] Figure 49 shows the reduction-oxidation wave of mPn-mDMePyPTzn. The reduction peak potential (Epc) in the reduction-oxidation wave of mPn-mDMePyPTzn was observed at -2.001 V, and the oxidation peak potential (Epa) was observed at -1.917 V. From this, Ec could be determined to be -1.96 V, and the LUMO level of mPn-mDMePyPTzn could be calculated to be -2.98 eV.

[0354] Note that Figure 39 shows the oxidation-reduction wave of PyA1PQ. The oxidation peak potential (Epa) in the oxidation-reduction wave of PyA1PQ was observed at 1.045 V, and the reduction peak potential (Epc) was observed at 0.885 V. From this, Ea could be determined to be 0.97 V, and the HOMO level of PyA1PQ could be calculated to be -5.91 eV.

[0355] Similarly, Figure 40 shows the reduction-oxidation wave of PyA1PQ. The reduction peak potential (Epc) in the reduction-oxidation wave of PyA1PQ was observed at -1.984 V, and the oxidation peak potential (Epa) was observed at -1.904 V. From this, Ec could be determined to be -1.94 V, and the LUMO level of PyA1PQ could be calculated to be -3.00 eV.

[0356] Also, Figure 62 shows the oxidation-reduction wave of Li-4mq. From this, the oxidation peak potential (Epa) in the oxidation-reduction wave of Li-4mq was observed as a shoulder peak at around 0.70 eV. On the other hand, since the reduction peak potential (Epc) was not observed, it was assumed that the difference between Epa and Epc was about 0.1 V (because in an ideal diffusion system where electron transfer is sufficiently fast, it is known that the difference between Epa and Epc is slightly less than 60 mV). That is, here, Epc in the oxidation-reduction wave of Li-4mq was set to 0.60 V. As a result, Ea of Li-4mq could be calculated to be 0.65 eV, but since the first decimal place should be used as a significant figure based on the above assumption, the HOMO level of Li-4mq was calculated to be approximately -5.6 eV.

[0357] Similarly, the reduction-oxidation wave of Li-4mq was shown in Fig. 63. The reduction peak potential (Epc) in the reduction-oxidation wave of Li-4mq was observed at -2.437 V, and the oxidation peak potential (Epa) was observed at -2.325 V. From this, Ec could be determined to be -2.38 V, and the LUMO level of Li-4mq could be calculated to be -2.56 eV.

[0358] Table 12 shows the HOMO levels and LUMO levels of αN-βNPAnth, mPn-mDMePyPTzn, and PyA1PQ, which are organic compounds having electron-transporting properties and used in the electron transport layer of the light-emitting devices 5 to 7 obtained as described above, and the difference (ΔE LUMO-HOMO ) between the LUMO level of these three materials and the HOMO level of the organometallic complex of an alkali metal, Li-4mq, the peak wavelength (λp Ex ) of the emission spectrum of the exciplex with Liq, the value (E Ex ) obtained by converting the peak wavelength into energy, and the value obtained by subtracting E LUMO-HOMO from ΔE Ex (ΔE HL -E Ex ). As described above, since the significant figures of the HOMO level of Liq are up to the first decimal place, both ΔE LUMO-HOMO and ΔE HL -E Ex have the first decimal place as significant figures.

[0359]

Table 12

[0360] As can be seen from FIGS. 57 to 59, in the electron transport layers of light-emitting devices 5 to 7, αN-βNPAnth, mPn-mDMePyPTzn, and PyA1PQ are considered to form an exciplex with Li-4mq, which is an organometallic complex of an alkali metal (note that since no new absorption peak generated by mixing was observed in the absorption spectrum of the mixed film, it could not be identified as an exciplex). As described above, normally, the value obtained by converting the peak wavelength of the emission spectrum of the exciplex into energy should be close to the difference between the HOMO level of Li-4mq and the LUMO levels of αN-βNPAnth, mPn-mDMePyPTzn, and PyA1PQ respectively. However, as shown in Table 12, in the light-emitting device of the present application, the ΔE HL -E Ex shows a large value of 0.4 eV to 0.5 eV. The light-emitting device according to one aspect of the present invention is a light-emitting device in which ΔE HL -E Ex is 0.3 eV or 0.5 eV or more. The value obtained by converting the peak wavelength of the emission spectrum of the exciplex formed in the electron transport layer of the light-emitting device into energy is 0.3 eV or 0.5 eV or more smaller than the difference between the HOMO level of Li-4mq and the LUMO levels of αN-βNPAnth, mPn-mDMePyPTzn, and PyA1PQ.

[0361] (Reference Example 1) ≪Synthesis Example 1≫ In this reference example, the synthesis method of 2-phenyl-3-[10-(3-pyridyl)-9-anthryl]phenylquinoxaline (abbreviation: PyA1PQ) used in Example 2 will be described. The structure of PyA1PQ is shown below.

[0362]

Chemical Formula

[0363] To a 50 mL three-necked flask, 0.74 g (2.2 mmol) of 3-(10-bromo-9-anthryl)pyridine, 0.26 g (0.85 mmol) of tri(ortho-tolyl)phosphine, 0.73 g (2.3 mmol) of 4-(3-phenylquinoxalin-2-yl)phenylboronic acid, 1.3 g (9.0 mmol) of aqueous potassium carbonate solution, 40 mL of ethylene glycol dimethyl ether (DME), and 4.4 mL of water were added. This mixture was degassed by stirring under reduced pressure, and the inside of the flask was purged with nitrogen.

[0364] To the mixture in this flask, 65 mg (0.29 mmol) of palladium(II) acetate was added, and the mixture was stirred at 80 °C for 11 hours under a nitrogen stream. After stirring, water was added to the mixture in the flask, and the mixture was extracted with toluene. The obtained extraction solution was washed with saturated brine and dried over magnesium sulfate. This was filtered naturally, and the filtrate was concentrated to obtain an oily substance. The obtained oily substance was purified twice by silica gel column chromatography (chloroform and toluene:ethyl acetate = 5:1), and recrystallized from toluene / hexane to obtain 0.43 g of the target yellow solid in a yield of 36%. The synthetic scheme is shown in the following formula.

[0365]

Chemical formula

[0366] 0.44 g of the obtained yellow solid was purified by sublimation using the train sublimation method. The sublimation purification was carried out under the conditions of a pressure of 10 Pa, an argon flow rate of 5.0 mL / min, and a temperature of 260 °C for 18 hours of heating. After sublimation purification, 0.35 g of the target yellow solid was obtained with a recovery rate of 79%.

[0367] In addition, the analysis results of the yellow solid obtained in the above reaction by nuclear magnetic resonance spectroscopy ( 1 1H-NMR) are shown below. From these results, it was found that in this example, PyA1PQ represented by the above structural formula was obtained.

[0368] 11H NMR (CDCl3, 300 MHz): δ = 7.37 - 7.50 (m, 9H), 7.56 - 7.78 (m, 9H), 7.82 - 7.86 (m, 3H), 8.24 - 8.30 (m, 2H), 8.75 (dd, J = 1.8 Hz, 0.9 Hz, 1H), 8.84 (dd, J = 4.8 Hz, 1.8 Hz, 1H).

Explanation of symbols

[0369] 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, 114: Electron transport layer, 114-1: First electron transport layer, 114-2: Second electron transport layer, 115: Electron injection layer, 400: Substrate, 401: Anode, 403: EL layer, 404: Cathode, 405: Sealing material, 406: Sealing material, 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: Driving circuit section (source line driving circuit), 602: Pixel section, 603: Driving circuit section (gate line driving circuit), 604: Sealing substrate, 605: Sealing material, 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: Underlying 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 coloring layer, 1034G: Green coloring 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: Arithmetic unit, 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 section, 5013: Earphone, 5100: Cleaning robot, 5101: Display5102: Camera, 5103: Brush, 5104: Operation button, 5150: Portable 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 key, 7110: Remote control operation 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 button, 7404: External connection port, 7405: Speaker, 7406: Microphone, 7400: Mobile phone, 9310: Portable information terminal, 9311: Display panel, 9313: Hinge, 9315: Housing,

Claims

1. A light-emitting device having a first electrode, a second electrode, a light-emitting layer positioned between the first electrode and the second electrode, and an electron transport layer, wherein the electron transport layer is positioned between the light-emitting layer and the second electrode, the electron transport layer includes an organometallic complex of an alkali metal and an organic compound having electron transporting properties, the organometallic complex and the organic compound form a combination that forms an exciplex, and a peak wavelength of an emission spectrum of a mixed film in which the organometallic complex and the organic compound are mixed at a mass ratio of 1:1 is 570 nm or more.

2. A light-emitting device having a first electrode, a second electrode, a light-emitting layer positioned between the first electrode and the second electrode, and an electron transport layer, wherein the electron transport layer is positioned between the light-emitting layer and the second electrode, the electron transport layer includes an organometallic complex of an alkali metal and an organic compound having electron transporting properties, the organometallic complex and the organic compound form a combination that forms an exciplex, and a peak wavelength of an emission spectrum of a mixed film in which the organometallic complex and the organic compound are mixed at a mass ratio of 1:1 is 570 nm or more and less than 610 nm.

3. A light-emitting device having a first electrode, a second electrode, a light-emitting layer positioned between the first electrode and the second electrode, and an electron transport layer, wherein the electron transport layer is positioned between the light-emitting layer and the second electrode, the electron transport layer includes an organometallic complex of an alkali metal and an organic compound having electron transporting properties, the organometallic complex and the organic compound form a combination that forms an exciplex, and a peak wavelength of an emission spectrum of a mixed film in which the organometallic complex and the organic compound are mixed at a mass ratio of 1:1 is 610 nm or more.

4. The light-emitting device according to any one of Claims 1 to 3, wherein a value obtained by subtracting a value (eV) obtained by converting a peak wavelength of an emission spectrum of the mixed film into energy from a difference (eV) between a HOMO level of the organometallic complex and a LUMO level of the organic compound is 0.1 eV or more.

5. The light-emitting device according to any one of Claims 1 to 3, wherein a value obtained by subtracting a value (eV) obtained by converting a peak wavelength of an emission spectrum of the mixed film into energy from a difference (eV) between a HOMO level of the organometallic complex and a LUMO level of the organic compound is 0.3 eV or more.

6. The light-emitting device according to any one of Claims 1 to 3, A light-emitting device, wherein a value obtained by subtracting, from a difference (eV) between the HOMO level of the organometallic complex and the LUMO level of the organic compound, a value (eV) obtained by converting the peak wavelength of the emission spectrum of the mixed film into energy is 0.5 eV or more.

7. In any one of Claims 1 to 6, A light-emitting device, wherein the organometallic complex is an organometallic complex of lithium.

8. In any one of Claims 1 to 6, A light-emitting device, wherein the organometallic complex has a ligand having a quinolinol skeleton.

9. In any one of Claims 1 to 6, A light-emitting device, wherein the organometallic complex is 8-hydroxyquinolinato-lithium or a derivative thereof.

10. In any one of Claims 1 to 9, A light-emitting device, wherein the organic compound is an organic compound having a heteroaromatic ring.

11. In any one of Claims 1 to 10, A light-emitting device, wherein the electron transport layer is in contact with the light-emitting layer.

12. In any one of Claims 1 to 11, The light-emitting layer has a host material and a light-emitting material, A light-emitting device, wherein the light-emitting material emits blue fluorescence.

13. A light-emitting device according to any one of Claims 1 to 12, and At least one of a sensor, an operation button, a speaker, and a microphone, An electronic device having the same.

14. A light-emitting device according to any one of Claims 1 to 12, and At least one of a transistor and a substrate, a light-emitting device having the same.

15. A light-emitting device according to any one of Claims 1 to 12, and A housing, a lighting device having the same.

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