Organic thin-film solar cell, photoelectric conversion element, and power-

Abstract

To provide an organic thin film solar cell having higher power generation efficiency.SOLUTION: The organic thin film solar battery 1 includes a pair of electrodes 311, and a photoelectric conversion layer 8 located between them, wherein the photoelectric conversion layer 8 is composed of at least a donor material and an accepter material, and the difference between the HOMO energy level of the donor material and the LUMO energy level of the accepter material is 1. 8eV or more and 2. 5eV or less. The donor material and the accepter material preferably have a band gap of 3eV or more, or an optical gap of 2. 5eV.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an organic thin-film solar cell, a photoelectric conversion element, and a power-generating light-emitting element. [Background technology]

[0002] Compared to conventional inorganic solar cells, organic thin-film solar cells are lighter, thinner, more flexible, and easier to make transparent. As a result, they can be installed on walls, windows, etc., making it possible to generate electricity in places where conventional inorganic solar cells could not. In particular, lightweight, flexible, and transparent solar cells can be used in a variety of applications. For this reason, organic thin-film solar cells are expected to be used in a wider range of applications.

[0003] However, organic thin-film solar cells have lower power generation efficiency than conventional inorganic solar cells, and therefore there is a demand for improvements in power generation efficiency.

[0004] An organic thin-film solar cell is a laminate of a cathode, a photoelectric conversion layer, and an anode. The photoelectric conversion layer is generally composed of an electron donor (donor material) and an electron acceptor (acceptor material). When the donor material or acceptor material absorbs incident light, excitons are generated, and electrons are separated into the acceptor material and holes into the donor material, becoming free carriers. These flow to the cathode and anode, respectively, generating electric current, which enables electricity to be generated. Therefore, the combination of donor and acceptor materials is very important for the photoelectric conversion efficiency (power generation efficiency) of organic thin-film solar cells. In fact, the difference (energy gap) between the energy level of the highest occupied molecular orbital (HOMO) of the donor material and the energy level of the lowest unoccupied molecular orbital (LUMO) of the acceptor material is the open circuit voltage (V OC ) (see Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] MCScharber, D.Muhlbacher, M.Koppe,P.Denk, C.Waldauf, AJHeeger, CJBrabec, LS Hung, Advanced Materials 18, 789 (2006) Summary of the Invention [Problem to be solved by the invention]

[0006] However, the combination of donor and acceptor materials to maximize the power generation efficiency of organic thin-film solar cells has not been fully understood. In particular, the combination of energy levels that systematically improves power generation efficiency in various materials with different material frameworks has not been elucidated.

[0007] Furthermore, photoelectric conversion elements such as solar cells are also used in sensors (photodetectors) and the like, and from the viewpoint of sensor sensitivity, improvements in conversion efficiency are required. Furthermore, in order to enable display devices such as smartphones to function even in situations where there is no power source, such as during a disaster, there is a demand for power-generating light-emitting elements that can both generate electricity and emit light, and there is also a demand for improved power generation efficiency in these power-generating light-emitting elements.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic thin-film solar cell with higher power generation efficiency. Another object of the present invention is to provide a photoelectric conversion element with high conversion efficiency (that is, a highly sensitive sensor) and a power-generating light-emitting element that can efficiently generate both electricity and light. [Means for solving the problem]

[0009] To solve the above-mentioned problems, the present inventors have focused on combinations of donor and acceptor materials for improving power generation efficiency and have investigated the relationship between the magnitude of the energy gap, which is the difference between the HOMO energy level of the donor material and the LUMO energy level of the acceptor material, and power generation efficiency. As a result of extensive investigations, the present inventors have found that power generation efficiency is significantly increased by combining donor and acceptor materials with an energy gap between 1.8 eV and 2.5 eV. The present invention has been completed based on the above findings, and the gist of the present invention is as follows.

[0010] [1] An organic thin-film solar cell comprising a pair of electrodes and a photoelectric conversion layer located therebetween, the photoelectric conversion layer is composed of at least a donor material and an acceptor material, An organic thin-film solar cell, wherein a difference between a HOMO level of the donor material and a LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less.

[0011] [2] The organic thin-film solar cell according to [1], wherein the donor material and the acceptor material have a band gap of 3 eV or more.

[0012] [3] The organic thin-film solar cell according to [1] or [2], wherein the donor material and the acceptor material have an optical gap of 2.5 eV or more.

[0013] [4] The organic thin-film solar cell according to any one of [1] to [3], wherein the donor material and the acceptor material have a visible light transmittance of 50% or more.

[0014] [5] A photoelectric conversion element comprising a pair of electrodes and a photoelectric conversion layer located therebetween, the photoelectric conversion layer is composed of at least a donor material and an acceptor material, A photoelectric conversion element, characterized in that the difference between the HOMO level of the donor material and the LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less.

[0015] [6] A power-generating light-emitting element comprising a pair of electrodes and a photoelectric conversion layer and light-emitting layer positioned therebetween, the photoelectric conversion layer / light-emitting layer is composed of at least a donor material and an acceptor material, A power-generating light-emitting device, wherein the difference between the HOMO level of the donor material and the LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less. [Effects of the Invention]

[0016] The organic thin-film solar cell of the present invention can efficiently convert excitons generated by absorbing light into free carriers, and therefore, according to the present invention, an organic thin-film solar cell with higher power generation efficiency can be provided.

[0017] Furthermore, according to a preferred embodiment of the present invention, by forming the photoelectric conversion layer of an organic thin-film solar cell from a donor material and an acceptor material having a large band gap or optical gap, the absorption of visible light is reduced, and a transparent organic thin-film solar cell can be obtained.

[0018] Furthermore, the photoelectric conversion element of the present invention can efficiently convert excitons generated by absorbing light into free carriers, and therefore, according to the present invention, a photoelectric conversion element with high conversion efficiency (i.e., a highly sensitive sensor) can be provided.

[0019] Furthermore, the power-generating light-emitting element of the present invention can obtain visible exciplex emission between a donor material and an acceptor material, where the difference between the HOMO level of the donor material and the LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less. Therefore, the present invention can provide a power-generating light-emitting element that can efficiently generate both electricity and light. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of an organic thin-film solar cell of the present invention. [Figure 2] FIG. 1 is a schematic diagram for explaining the relationship between energy levels of an organic thin-film solar cell of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The organic thin-film solar cell, the photoelectric conversion element, and the power-generating light-emitting element of the present invention will be illustrated and described in detail below based on their embodiments.

[0022] <Organic thin film solar cell> The organic thin-film solar cell of the present invention comprises a pair of electrodes (anode and cathode) and a photoelectric conversion layer located therebetween. The organic thin-film solar cell of the present invention is characterized in that the photoelectric conversion layer is composed of at least a donor material and an acceptor material, and the difference between the HOMO level of the donor material and the LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less. In the organic thin-film solar cell of the present invention, the photoelectric conversion layer may be a pn heterojunction type in which an electron donor (donor) layer and an electron acceptor (acceptor) layer are stacked, or may be a bulk heterojunction type in which a donor material and an acceptor material are mixed.

[0023] In the organic thin-film solar cell of the present invention, the difference between the HOMO level of the donor material and the LUMO level of the acceptor material in the photoelectric conversion layer is 1.8 eV or more and 2.5 eV or less, and therefore excitons generated when the donor material or the acceptor material absorbs light can be efficiently converted into free carriers (electrons and holes), resulting in a significant improvement in power generation efficiency.

[0024] Next, the organic thin-film solar cell of the present invention will be described in detail with reference to examples. Fig. 1 is a schematic cross-sectional view illustrating an example of an organic thin-film solar cell of the present invention. The organic thin-film solar cell 1 of this embodiment shown in Fig. 1 has a photoelectric conversion layer 8 between an anode (electrode) 3 and a cathode (electrode) 11. The organic thin-film solar cell 1 of this embodiment has a laminated structure in which an anode 3, a hole collecting layer 4, a hole transport layer 5, a photoelectric conversion layer 8 consisting of an electron donor layer 6 and an electron acceptor layer 7, an electron transport layer 9, an electron collecting layer 10, and a cathode 11 are formed in this order on a substrate 2. The organic thin-film solar cell of the present invention may have an inverted structure in which the configuration from the cathode to the anode is inverted.

[0025] "substrate" The substrate 2 may be made of a resin material, a glass material, or the like. Examples of resin materials used for the substrate 2 include polyethylene terephthalate, polyethylene naphthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, and polyarylate. Examples of glass materials used for the substrate 2 include quartz glass and soda glass.

[0026] When the organic thin-film solar cell 1 receives light from the substrate side or is a transparent solar cell, the substrate 2 is made of a transparent substrate. When the organic thin-film solar cell 1 allows light to be incident from the opposite side of the substrate, not only a transparent substrate but also an opaque substrate may be used as the material for the substrate 2. Examples of opaque substrates include a substrate made of a ceramic material such as alumina, a substrate in which an oxide film (insulating film) is formed on the surface of a metal plate such as stainless steel, a substrate made of a resin material, a silicon substrate, etc.

[0027] The average thickness of the substrate 2 can be determined depending on the material of the substrate 2, and is preferably 0.1 to 30 mm, and more preferably 0.1 to 10 mm. The average thickness of the substrate 2 can be measured using a digital multimeter and vernier calipers.

[0028] "anode" The anode 3 shown in FIG. 1 is formed on the substrate 2 in direct contact therewith. Examples of materials for the anode 3 include conductive oxide materials such as ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorine tin oxide), In2O3, SnO2, Sb-containing SnO2, and Al-containing ZnO. Of these, it is preferable to use ITO, IZO, or FTO as the material for the anode 3. The average thickness of the anode 3 is not particularly limited, but is preferably 10 to 500 nm, and more preferably 30 to 200 nm. The average thickness of the anode 3 can be measured by a stylus profilometer or spectroscopic ellipsometry.

[0029] "Hole collection layer" The hole-collecting layer 4 may be made of an inorganic material or an organic material. The inorganic material is not particularly limited, but for example, one or more metal oxides such as vanadium oxide (V2O5), molybdenum oxide (MoO3), and ruthenium oxide (RuO2) can be used. Examples of organic materials that can be used include low molecular weight materials such as dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ), as well as poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT:PSS).

[0030] The average thickness of the hole-collecting layer 4 is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 5 to 50 nm. The average thickness of the hole-collecting layer 4 can be measured by, for example, a stylus profilometer or spectroscopic ellipsometry.

[0031] "Hole transport layer" The organic thin-film solar cell of the present invention may have a hole transport layer 5, as in the organic thin-film solar cell 1 shown in FIG. 1 . When the organic thin-film solar cell has a hole transport layer, any compound that can be typically used as a material for a hole transport layer may be used as the material for the hole transport layer, and these compounds may be mixed and used. A hole-transporting organic material can be suitably used for the hole-transporting layer 5. As the hole-transporting organic material, various p-type high molecular weight materials (organic polymers) and various p-type low molecular weight materials can be used alone or in combination. Furthermore, the hole-transporting layer 5 can also be made of a donor material (electron donor) of the photoelectric conversion layer 8 described below.

[0032] Specific examples of materials for the hole transport layer 5 include N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD), N4,N4'-bis(dibenzo[b,d]thiophen-4-yl)-N4,N4'-diphenylbiphenyl-4,4'-diamine (DBTPB), polyarylamine, fluorene-arylamine copolymer, fluorene-bithiophene copolymer, poly(N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, polyalkylthiophene, polyhexylthiophene, poly(p-phenylenevinylene), polythienylenevinylene, pyrene formaldehyde resin, ethylcarbazole formaldehyde resin, and derivatives thereof. These materials for the hole transport layer 5 can also be used as mixtures with other compounds. An example of a mixture containing polythiophene that can be used as a material for the hole transport layer 5 is poly(3,4-ethylenedioxythiophene / styrenesulfonic acid) (PEDOT / PSS).

[0033] The hole transport layer 5 may contain, as a dopant, any of the materials listed above for the hole collection layer 4. The content of the dopant in the hole transport layer 5 is preferably in the range of 1 to 20% by mass, more preferably in the range of 5 to 15% by mass.

[0034] The average thickness of the hole transport layer 5 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 20 to 100 nm. The average thickness of the hole transport layer 5 can be measured by, for example, a stylus profilometer or spectroscopic ellipsometry.

[0035] "Photoelectric conversion layer" The photoelectric conversion layer 8 is composed of at least a donor material (electron donor) and an acceptor material (electron acceptor). The photoelectric conversion layer 8 may be a pn heterojunction type in which an electron donor layer (donor layer) 6 containing a donor material and an electron acceptor layer (acceptor layer) 7 containing an acceptor material are stacked (see FIG. 1), or may be a bulk heterojunction type in which the donor material and the acceptor material are mixed. The material forming the photoelectric conversion layer 8 may be a low molecular weight compound or a high molecular weight compound. In the present invention, a low molecular weight material means a material that is not a high molecular weight material (polymer), and does not necessarily mean an organic compound with a low molecular weight.

[0036] FIG. 2 is a schematic diagram illustrating the relationship between energy levels in the organic thin-film solar cell of the present invention. As shown in FIG. 2, the HOMO level (energy level of the highest occupied molecular orbital) of the donor material corresponds to the ionization potential (IP) of the donor material, while the LUMO level (energy level of the lowest unoccupied molecular orbital) of the acceptor material corresponds to the electron affinity (EA) of the acceptor material. In the photoelectric conversion layer 8, the difference between the HOMO level of the donor material and the LUMO level of the acceptor material (energy gap (Eg)), in other words, the difference between the ionization potential (IP) of the donor material and the electron affinity (EA) of the acceptor material, is 1.8 eV to 2.5 eV. The energy gap (Eg) being within the range of 1.8 eV to 2.5 eV allows the donor material or the acceptor material to efficiently convert excitons generated by absorbing light into free carriers (electrons, holes), resulting in significantly improved power generation efficiency in the organic thin-film solar cell of the present invention. Here, in this specification, the HOMO level (i.e., ionization potential (IP)) of the donor material and the LUMO level (i.e., electron affinity (EA)) of the acceptor material are measured by the method described in the examples below.

[0037] -Donor material (electron donor)- Examples of the donor material include arylcycloalkane compounds such as N4,N4'-bis(dibenzo[b,d]thiophen-4-yl)-N4,N4'-diphenylbiphenyl-4,4'-diamine (DBTPB), 1,1-bis(4-di-para-triaminophenyl)cyclohexane, and 1,1'-bis(4-di-para-tolylaminophenyl)-4-phenyl-cyclohexane; 4,4',4''-trimethyltriphenylamine; N,N,N',N'-tetraphenyl-1,1'-biphenyl-4,4'-diamine; and N,N'-diphenyl Arylamine compounds such as -N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD1), N,N'-diphenyl-N,N'-bis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD2), N,N,N',N'-tetrakis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (TPD3), N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD), TPTE, N,N,N',N'- Phenylenediamine compounds such as tetraphenyl-para-phenylenediamine, N,N,N',N'-tetra(para-tolyl)-para-phenylenediamine, and N,N,N',N'-tetra(meta-tolyl)-meta-phenylenediamine (PDA); carbazole compounds such as carbazole, N-isopropylcarbazole, and N-phenylcarbazole; stilbene compounds such as stilbene and 4-di-para-tolylaminostilbene; oxazole compounds such as OxZ; and triphenylmethane compounds such as triphenylmethane and m-MTDATA. compounds, pyrazoline compounds such as 1-phenyl-3-(para-dimethylaminophenyl)pyrazoline, benzine (cyclohexadiene) compounds, triazole compounds such as triazole, imidazole compounds such as imidazole, oxadiazole compounds such as 1,3,4-oxadiazole and 2,5-di(4-dimethylaminophenyl)-1,3,4-oxadiazole, anthracene compounds such as 9-(4-diethylaminostyryl)anthracene, fluorenone, 2,4,7-trinitro-9-fluorenone, 2,Fluorenone compounds such as 7-bis(2-hydroxy-3-(2-chlorophenylcarbamoyl)-1-naphthylazo)fluorenone, aniline compounds such as polyaniline, silane compounds, pyrrole compounds such as 1,4-dithioketo-3,6-diphenyl-pyrrolo-(3,4-c)pyrrolopyrrole, fluorene compounds such as fluorene, porphyrin compounds such as metal tetraphenylporphyrin, quinacridone compounds such as quinacridone, and phthalocyanine compounds such as phthalocyanine. Examples of compounds that can be used include metallic or non-metallic phthalocyanine compounds such as cyanine, copper phthalocyanine, tetra(t-butyl)copper phthalocyanine, and iron phthalocyanine; metallic or non-metallic naphthalocyanine compounds such as copper naphthalocyanine, vanadyl naphthalocyanine, and monochlorogallium naphthalocyanine; and benzidine compounds such as N,N'-di(naphthalen-1-yl)-N,N'-diphenylbenzidine and N,N,N',N'-tetraphenylbenzidine.

[0038] -Acceptor materials (electron acceptors)- Examples of the acceptor material include bis[2-(o-hydroxyphenylbenzothiazole]zinc(II) (ZnBTZ2), boron-containing compounds, pyridine derivatives such as tris-1,3,5-(3'-(pyridin-3''-yl)phenyl)benzene (TmPyPhB), quinoline derivatives such as (2-(3-(9-carbazolyl)phenyl)quinoline (mCQ)), and pyridine derivatives such as 2-phenyl-4,6-bis(3,5-dipyridylphenyl)pyrimidine (BPyPPM). imidine derivatives, pyrazine derivatives, phenanthroline derivatives such as bathophenanthroline (BPhen), triazine derivatives such as 2,4-bis(4-biphenyl)-6-(4'-(2-pyridinyl)-4-biphenyl)-[1,3,5]triazine (MPT), triazole derivatives such as 3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), oxazole derivatives, 2-(4-biphenylyl)-5-(4-tert-butyl)- ... oxadiazole derivatives such as 2,2',2''-(1,3,5-benzotriyl)-tris(1-phenyl-1-H-benzimidazole) (PBD), imidazole derivatives such as 2,2',2''-(1,3,5-benzotriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), aromatic ring tetracarboxylic acid anhydrides such as naphthalene and perylene, bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ)2), tris(8-hydroxyquinolinato)aluminum (Alq3), etc. Various metal complexes represented by the formula (I) and (II), organosilane derivatives represented by silole derivatives such as 2,5-bis(6'-(2',2''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), and boron-containing compounds described in JP 2013-239691 A, WO 2014 / 133141 A, JP 2016-172728 A, JP 2016-199507 A, and JP 2016-199508 A can be used.

[0039] The donor material and the acceptor material preferably have a band gap of 3 eV or more. The band gap is the difference between the HOMO level and the LUMO level of each material, and corresponds to the difference between the ionization potential (IP) and the electron affinity (EA). When the band gap of the donor material and the band gap of the acceptor material are both 3 eV or more, the absorption of visible light in the photoelectric conversion layer 8 is reduced, and the visible light transmittance of the photoelectric conversion layer 8 is improved, resulting in a transparent organic thin-film solar cell. Such a transparent organic thin-film solar cell can not only generate electricity but also emit light, and can therefore be used as a power-generating light-emitting element, as described below. Herein, the HOMO level (i.e., ionization potential (IP)) and LUMO level (i.e., electron affinity (EA)) of the donor material, and the HOMO level (i.e., ionization potential (IP)) and LUMO level (i.e., electron affinity (EA)) of the acceptor material are measured by the method described in the examples below.

[0040] Furthermore, the donor material and the acceptor material preferably have an optical gap of 2.5 eV or more. The optical gap is a value obtained by converting the rising wavelength (long wavelength region) of the absorption spectrum of each material into energy, and generally, light with a wavelength longer than the rising wavelength is transmitted. When the optical gap of the donor material and the optical gap of the acceptor material are both 2.5 eV or more, the absorption of visible light in the photoelectric conversion layer 8 is reduced, and the visible light transmittance of the photoelectric conversion layer 8 is improved, resulting in a transparent organic thin-film solar cell. Such a transparent organic thin-film solar cell is capable of not only generating electricity but also emitting light, and can therefore be used as a power-generating light-emitting element, as described below. In this specification, the absorption spectra of the donor material and the acceptor material are measured by the method described in the examples below.

[0041] Furthermore, the donor material and the acceptor material preferably have a visible light transmittance of 50% or more. When the visible light transmittance of the donor material and the acceptor material is 50% or more, the visible light absorption of the photoelectric conversion layer 8 is reduced, and the visible light transmittance of the photoelectric conversion layer 8 is improved, resulting in a transparent organic thin-film solar cell. Such a transparent organic thin-film solar cell can not only generate electricity but also emit light, and can therefore be used as a power-generating light-emitting element, which will be described later. In this specification, the visible light transmittance of the donor material and the acceptor material is measured by the method described in the examples below.

[0042] When photoelectric conversion layer 8 is a pn heterojunction type in which electron donor layer 6 and electron acceptor layer 7 are stacked, the average thickness of electron donor layer 6 is preferably 2 to 30 nm, more preferably 4 to 20 nm, while the average thickness of electron acceptor layer 7 is preferably 8 to 120 nm, more preferably 16 to 80 nm. Furthermore, when the photoelectric conversion layer 8 is a bulk heterojunction type in which a donor material and an acceptor material are mixed, the mass ratio of the donor material to the acceptor material (donor material / acceptor material) is preferably in the range of 5 / 95 to 50 / 50, more preferably in the range of 10 / 90 to 30 / 70.

[0043] The average thickness of the photoelectric conversion layer 8 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 20 to 100 nm. The average thicknesses of the electron donor layer 6, electron acceptor layer 7, and photoelectric conversion layer 8 may be measured using a stylus profilometer or may be measured using a quartz crystal film thickness meter during the formation of the light-emitting layer 6.

[0044] "Electron transport layer" The organic thin-film solar cell of the present invention may have an electron transport layer 9, as in the organic thin-film solar cell 1 shown in FIG. 1 . When the organic thin-film solar cell has an electron transport layer, any compound that can be typically used as a material for an electron transport layer may be used as the material for the electron transport layer, and these compounds may be mixed and used. The electron transport layer 9 can be preferably made of an organic material having electron transport properties, and examples of the organic material having electron transport properties include various n-type polymeric materials (organic polymers) and various n-type low molecular weight materials, used alone or in combination. The electron transport layer 9 can also be made of the acceptor material of the photoelectric conversion layer 8 described above.

[0045] Examples of compounds that can be used as the material of the electron transport layer 9 include pyridine derivatives such as tris-1,3,5-(3'-(pyridin-3''-yl)phenyl)benzene (TmPyPhB), quinoline derivatives such as (2-(3-(9-carbazolyl)phenyl)quinoline (mCQ)), pyrimidine derivatives such as 2-phenyl-4,6-bis(3,5-dipyridylphenyl)pyrimidine (BPyPPM), pyrazine derivatives, phenanthroline derivatives such as bathophenanthroline (BPhen), triazine derivatives such as 2,4-bis(4-biphenyl)-6-(4'-(2-pyridinyl)-4-biphenyl)-[1,3,5]triazine (MPT), triazole derivatives such as 3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole (TAZ), oxazole derivatives, 2- Examples of the organic silane derivative include oxadiazole derivatives such as (4-biphenylyl)-5-(4-tert-butylphenyl-1,3,4-oxadiazole) (PBD), imidazole derivatives such as 2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBI), aromatic tetracarboxylic acid anhydrides such as naphthalene and perylene, various metal complexes such as bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ)2) and tris(8-hydroxyquinolinato)aluminum (Alq3), and organic silane derivatives such as silole derivatives such as 2,5-bis(6′-(2′,2″-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy). One or more of these can be used.

[0046] The average thickness of the electron transport layer 9 is not particularly limited, but is preferably 10 to 150 nm, and more preferably 20 to 100 nm. The average thickness of the electron transport layer 9 can be measured by a stylus profilometer or spectroscopic ellipsometry.

[0047] "Electron trapping layer" The electron collecting layer 10 improves the speed of electron injection and electron transport properties from the cathode 11 to the photoelectric conversion layer 8. The material of the electron collecting layer 10 may be an organic compound or an inorganic compound. When the electron collecting layer 10 is made of an inorganic compound, for example, alkali metals, alkaline earth metals, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, cesium carbonate, etc. can be used. When the electron collecting layer 10 is made of an organic compound, for example, 8-quinolinolatolithium (Liq), a hexahydropyrimidopyrimidine compound having a structure represented by the following general formula (I), or a compound having a structure represented by the following general formula (II) can be used.

[0048] [ka] (In general formula (I), R 1 represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent chain or cyclic hydrocarbon group which may have a substituent, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom. 1 is an integer between 1 and 4.)

[0049] [ka] (In general formula (II), X 1 , X 2 are the same or different and represent a nitrogen atom, an oxygen atom, a sulfur atom or a divalent linking group which may have a substituent. L represents a direct bond or a p-valent linking group. n 2 represents the number 0 or 1, and p represents the number 1 to 4. q represents the number 0 or 1, and when p is 1, q is 0. R 2 ~R 4 are the same or different and represent monovalent substituents.1 ~m 3 are the same or different and represent a number from 0 to 3. 2 ~R 4 is X 1 , X 2 may be bonded to form a ring structure. 2 If there are multiple R 2 may be bonded to form a ring structure. 3 If there are multiple R 3 may be bonded to form a ring structure. 4 If there are multiple R 4 may be bonded to form a ring structure.

[0050] R in the above general formula (I) 1 represents an aromatic hydrocarbon group, an aromatic heterocyclic group, an aryl alkylene group, a divalent to tetravalent chain or cyclic hydrocarbon group which may have a substituent, a group formed by combining two or more of these groups, or a group formed by combining one or more of these groups with a nitrogen atom. The aromatic hydrocarbon group and aromatic heterocyclic group preferably have 3 to 30 carbon atoms, more preferably 4 to 24 carbon atoms, and even more preferably 5 to 20 carbon atoms. Examples of aromatic hydrocarbon groups include compounds consisting of only one aromatic ring, such as benzene; compounds in which multiple aromatic rings, such as biphenyl and diphenylbenzene, are directly bonded to each other via one carbon atom; and groups formed by removing 1 to 4 hydrogen atoms from any of the aromatic rings of condensed ring aromatic hydrocarbon compounds, such as naphthalene, anthracene, phenanthrene, and pyrene. Examples of aromatic heterocyclic groups include compounds consisting of only one aromatic heterocycle, such as thiophene, furan, pyrrole, oxazole, oxadiazole, thiazole, thiadiazole, imidazole, pyridine, pyrimidine, pyrazine, and triazine; compounds in which a plurality of compounds consisting of only one aromatic heterocycle are directly bonded to each other via one carbon atom (e.g., bipyridine); and groups obtained by removing 1 to 4 hydrogen atoms from any aromatic heterocycle of fused-ring heteroaromatic hydrocarbon compounds, such as quinoline, quinoxaline, benzothiophene, benzothiazole, benzimidazole, benzoxazole, indole, carbazole, dibenzofuran, dibenzothiophene, acridine, and phenanthroline. Examples of the aryl alkylene group include groups formed by combining the above aromatic hydrocarbon groups with alkylene groups having 1 to 3 carbon atoms. The divalent to tetravalent chain or cyclic hydrocarbon group preferably has 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 carbon atoms. The chain hydrocarbon group may be linear or branched. Also, R 1 may be a group formed by combining two or more of the above aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent to tetravalent chain hydrocarbon groups. Furthermore, R 1 may be a group formed by combining one or more of the above aromatic hydrocarbon groups, aromatic heterocyclic groups, aryl alkylene groups, and divalent to tetravalent chain hydrocarbon groups with a nitrogen atom. Examples of such groups include groups formed by removing 1 to 4 hydrogen atoms from trialkylamines such as trimethylamine or triphenylamine.

[0051] The aromatic hydrocarbon group, aromatic heterocyclic group, or arylalkylene group may have one or more monovalent substituents. Examples of the monovalent substituent include a fluorine atom; a haloalkyl group such as a fluoromethyl group, a difluoromethyl group, or a trifluoromethyl group; a linear or branched alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, or a tert-butyl group; a cyclic alkyl group having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, or a cycloheptyl group; a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, or a methyloxy group. linear or branched alkoxy groups having 1 to 20 carbon atoms, such as a hydroxyl group or an octyloxy group; a nitro group; a cyano group; an alkylamino group having an alkyl group having 1 to 10 carbon atoms, such as a methylamino group, an ethylamino group, a dimethylamino group or a diethylamino group; a cyclic amino group, such as a pyrrolidino group, a piperidino group or a morpholino group; a diarylamino group, such as a diphenylamino group or a carbazolyl group; an acyl group, such as an acetyl group, a propionyl group or a butyryl group; an alkenyl group having 2 to 30 carbon atoms, such as a styryl group; a halogen atom, such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, or an aryl group having 1 to 20 carbon atoms; an aryl group having 5 to 20 carbon atoms which may be substituted with a silyl group, an amino group, or the like (specific examples of the aryl group are the same as those of the aromatic hydrocarbon group); a heterocyclic group having 4 to 40 carbon atoms which contains one or more of a nitrogen atom, a sulfur atom, or an oxygen atom which may be substituted with a halogen atom such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an amino group, or the like (the heterocyclic group may consist of only one ring, or may be a compound in which a plurality of compounds consisting of only one aromatic heterocycle are directly bonded together at one carbon atom, or may be a fused heterocyclic group. Specific examples of the heterocyclic group include: Specific examples of the aromatic heterocyclic group include a thiophene ring, a furan ring, a pyrrole ring, a benzothiophene ring, a benzofuran ring, an indole ring, a dibenzothiophene ring, a dibenzofuran ring, a carbazole ring, a thiazole ring, a benzothiazole ring, an oxazole ring, a benzoxazole ring, an imidazole ring, a benzimidazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a benzothiadiazole ring, and a phenanthridine ring; an ester group, a thioether group, and the like.These groups may be substituted with a halogen atom, a hetero element, an alkyl group, an aromatic ring, or the like.

[0052] In the above general formula (I), n 1 is an integer of 1 to 4, preferably 2 or 3.

[0053] The compound represented by the above general formula (I) can be synthesized by Ullmann coupling reaction, Buchwald-Hartwig amination reaction, nucleophilic substitution reaction, or the like using a halogen compound having iodine, bromine, chlorine, or fluorine and hexahydropyrimidopyrimidine as raw materials.

[0054] X in the above general formula (II) 1 , X 2 are the same or different and represent a nitrogen atom, an oxygen atom, a sulfur atom or a divalent linking group which may have a substituent. Examples of the divalent linking group include divalent hydrocarbon groups and groups in which some of the carbon atoms of a hydrocarbon group have been substituted with a heteroatom such as a nitrogen atom, an oxygen atom, or a sulfur atom. The hydrocarbon group preferably has 1 to 6 carbon atoms, and more preferably has 1, 2 or 6 carbon atoms. The hydrocarbon group may be linear, branched, cyclic, or a combination thereof. The divalent hydrocarbon group may be an alkylene group, which is a saturated hydrocarbon group, or an unsaturated hydrocarbon group such as an alkenylene group or an alkynylene group.

[0055] In the above general formula (II), L represents a direct bond or a p-valent linking group. Note that L becomes a direct bond only when p is 2. Examples of p-valent linking groups include nitrogen atoms, oxygen atoms, sulfur atoms, and carbon atoms, as well as groups obtained by removing p hydrogen atoms from hydrocarbon groups and groups in which some of the carbon atoms in a hydrocarbon group have been substituted with a heteroatom such as a nitrogen atom, an oxygen atom, or a sulfur atom. When the p-valent linking group has carbon atoms, it preferably has 1 to 30 carbon atoms, and more preferably has 1 to 20 carbon atoms. The hydrocarbon group may be linear, branched, cyclic, or a combination thereof. The hydrocarbon group may be any of a saturated hydrocarbon group, an unsaturated hydrocarbon group, and an aromatic hydrocarbon group. Examples of aromatic hydrocarbon groups include groups formed by removing a hydrogen atom from an aromatic compound such as a benzene ring, a naphthalene ring, an anthracene ring, a tetracene ring, a pentacene ring, a triphenylene ring, a pyrene ring, a fluorene ring, or an indene ring.

[0056] R in the above general formula (II) 2 ~R 4 are the same or different and represent monovalent substituents. 1 ~m 3 are the same or different and represent a number from 0 to 3. Examples of the monovalent substituent include a fluorine atom; a haloalkyl group such as a fluoromethyl group, a difluoromethyl group, or a trifluoromethyl group; a linear or branched alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, or a tert-butyl group; a cyclic alkyl group having 5 to 7 carbon atoms such as a cyclopentyl group, a cyclohexyl group, or a cycloheptyl group; a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, or a methyloxy group. linear or branched alkoxy groups having 1 to 20 carbon atoms, such as a hydroxyl group or an octyloxy group; a nitro group; a cyano group; an alkylamino group having an alkyl group having 1 to 10 carbon atoms, such as a methylamino group, an ethylamino group, a dimethylamino group or a diethylamino group; a cyclic amino group, such as a pyrrolidino group, a piperidino group or a morpholino group; a diarylamino group, such as a diphenylamino group or a carbazolyl group; an acyl group, such as an acetyl group, a propionyl group or a butyryl group; an alkenyl group having 2 to 30 carbon atoms, such as a styryl group; a halogen atom, such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, or an aryl group having 1 to 20 carbon atoms; an aryl group having 5 to 20 carbon atoms which may be substituted with a silyl group, an amino group, or the like (specific examples of the aryl group are the same as those of the aromatic hydrocarbon group); a heterocyclic group having 4 to 40 carbon atoms which contains one or more of a nitrogen atom, a sulfur atom, or an oxygen atom which may be substituted with a halogen atom such as a fluorine atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an amino group, or the like (the heterocyclic group may consist of only one ring, or may be a compound in which a plurality of compounds consisting of only one aromatic heterocycle are directly bonded together at one carbon atom, or may be a fused heterocyclic group. Specific examples of the heterocyclic group include: Specific examples of the aromatic heterocyclic group include a thiophene ring, a furan ring, a pyrrole ring, a benzothiophene ring, a benzofuran ring, an indole ring, a dibenzothiophene ring, a dibenzofuran ring, a carbazole ring, a thiazole ring, a benzothiazole ring, an oxazole ring, a benzoxazole ring, an imidazole ring, a benzimidazole ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, a benzothiadiazole ring, and a phenanthridine ring; an ester group, a thioether group, and the like.These groups may be substituted with a halogen atom, a hetero element, an alkyl group, an aromatic ring, or the like.

[0057] In the above general formula (II), p represents a number of 1 to 4, and is preferably a number of 1 to 3. In addition, n in the above general formula (II) 2 represents the number 0 or 1, but is preferably 0.

[0058] The average thickness of the electron-collecting layer 10 is preferably 0.5 to 100 nm, more preferably 1 to 50 nm. The electron-collecting layer 10 can be formed by applying a coating composition or by depositing it using a vacuum deposition method. The average thickness of the electron-collecting layer 10 can be measured by, for example, a stylus profilometer or spectroscopic ellipsometry.

[0059] "cathode" Examples of materials used for the cathode 11 include ITO, IZO, Au, Pt, Ag, Cu, Al, Mg, and alloys containing these. Among these, it is preferable to use ITO, IZO, Au, Ag, or Al as the material for the cathode 11. The average thickness of cathode 11 is not particularly limited, but is preferably 1 to 1000 nm, and more preferably 10 to 150 nm. Even when an opaque material is used as the material for cathode 11, by setting the average thickness to, for example, about 10 to 30 nm, it can be used as a transparent cathode in a transparent organic thin-film solar cell. The average thickness of the cathode 11 can be measured by a quartz crystal film thickness meter when the cathode 11 is formed.

[0060] "Sealing" The organic thin-film solar cell 1 shown in FIG. 1 may be sealed as needed. 1 may be sealed by a sealed container (not shown) having a recessed space for accommodating the organic thin-film solar cell 1, and an adhesive that bonds the edge of the sealed container to the substrate 2. Alternatively, the organic thin-film solar cell 1 may be housed in a sealed container and sealed by filling it with a sealant made of an ultraviolet (UV) curable resin or the like. Furthermore, for example, the organic thin-film solar cell 1 shown in FIG. 1 may be sealed using a sealing member made up of a plate member (not shown) placed on the cathode 11 and a frame member (not shown) placed along the edge of the plate member on the side facing the cathode 11, and an adhesive that bonds between the plate member and the frame member and between the frame member and the substrate 2.

[0061] When the organic thin-film solar cell 1 is sealed using a sealing container or a sealing member, a moisture-absorbing desiccant may be placed inside the sealing container or the sealing member. Furthermore, a moisture-absorbing material may be used for the sealing container or the sealing member. Furthermore, a space may be formed inside the sealed sealing container or the sealing member.

[0062] Resin materials, glass materials, etc. can be used as the material for the sealing container or sealing member used to seal the organic thin-film solar cell 1 shown in Fig. 1. Examples of the resin materials and glass materials used for the sealing container or sealing member include the same materials as those used for the substrate 2.

[0063] "Method of manufacturing organic thin-film solar cells" Next, as an example of a method for manufacturing an organic thin-film solar cell of the present invention, a method for manufacturing an organic thin-film solar cell 1 shown in FIG. 1 will be described. To manufacture the organic thin-film solar cell 1 shown in FIG. 1, first, an anode 3 is formed on a substrate 2 . The anode 3 can be formed by a sputtering method, a vacuum deposition method, a sol-gel method, a spray pyrolysis (SPD) method, an atomic layer deposition (ALD) method, a vapor phase film formation method, a liquid phase film formation method, etc. The anode 3 may also be formed by bonding a metal foil.

[0064] Next, on the anode 3, a hole collection layer 4, a hole transport layer 5, a photoelectric conversion layer 8 consisting of an electron donor layer 6 and an electron acceptor layer 7, an electron transport layer 9, and an electron collection layer 10 are formed in this order. The methods for forming the hole collecting layer 4, the hole transport layer 5, the photoelectric conversion layer 8 (electron donor layer 6, electron acceptor layer 7), the electron transport layer 9, and the electron collecting layer 10 are not particularly limited, and various conventionally known formation methods can be used as appropriate in accordance with the properties of the materials used for the hole collecting layer 4, the hole transport layer 5, the photoelectric conversion layer 8 (electron donor layer 6, electron acceptor layer 7), the electron transport layer 9, and the electron collecting layer 10, respectively.

[0065] Specifically, examples of methods for forming the hole collecting layer 4, the hole transport layer 5, the photoelectric conversion layer 8 (electron donor layer 6, electron acceptor layer 7), the electron transport layer 9, and the electron collecting layer 10 include a coating method in which an organic compound solution containing an organic compound that will become the hole collecting layer 4, the hole transport layer 5, the photoelectric conversion layer 8 (electron donor layer 6, electron acceptor layer 7), the electron transport layer 9, and the electron collecting layer 10 is applied; a vacuum deposition method; and an ESDUS (Evaporative Spray Deposition from Ultra-dilute Solution) method.

[0066] When the hole collecting layer 4, the hole transport layer 5, the photoelectric conversion layer 8 (electron donor layer 6, electron acceptor layer 7), the electron transport layer 9, and the electron collecting layer 10 are formed by using a coating method, organic compounds to be formed into the hole collecting layer 4, the hole transport layer 5, the photoelectric conversion layer 8 (electron donor layer 6, electron acceptor layer 7), the electron transport layer 9, and the electron collecting layer 10 are dissolved in a solvent, respectively, to form organic compound solutions containing the organic compounds to be formed into the hole collecting layer 4, the hole transport layer 5, the photoelectric conversion layer 8 (electron donor layer 6, electron acceptor layer 7), the electron transport layer 9, and the electron collecting layer 10, respectively.

[0067] Preferred solvents used to dissolve the organic compounds that form the hole collection layer 4, the hole transport layer 5, the photoelectric conversion layer 8 (electron donor layer 6, electron acceptor layer 7), the electron transport layer 9, and the electron collection layer 10 include aromatic hydrocarbon solvents such as xylene, toluene, cyclohexylbenzene, dihydrobenzofuran, trimethylbenzene, and tetramethylbenzene; aromatic heterocyclic compound solvents such as pyridine, pyrazine, furan, pyrrole, thiophene, and methylpyrrolidone; and aliphatic hydrocarbon solvents such as hexane, pentane, heptane, and cyclohexane, and these can be used alone or in combination.

[0068] Various coating methods such as spin coating, casting, microgravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, flexographic printing, offset printing, and inkjet printing can be used to apply an organic compound solution containing an organic compound that will become the hole collection layer 4, the hole transport layer 5, the photoelectric conversion layer 8 (electron donor layer 6, electron acceptor layer 7), the electron transport layer 9, and the electron collection layer 10. Among these coating methods, spin coating and slit coating are preferred because they allow easier control of the film thickness.

[0069] Next, the cathode 11 is formed. The cathode 11 can be formed, for example, in the same manner as the anode 3 . Through the above steps, the organic thin-film solar cell 1 shown in FIG. 1 is obtained.

[0070] "Other examples" The organic thin-film solar cell of the present invention is not limited to the above-described embodiment. For example, in the organic thin-film solar cell 1 shown in FIG. 1, the hole collection layer 4, the hole transport layer 5, the electron transport layer 9, and the electron collection layer 10 may be formed as needed, and may not be provided. Furthermore, each of the anode 3, the hole collection layer 4, the hole transport layer 5, the electron transport layer 9, the electron collection layer 10, and the cathode 11 may be formed as a single layer or may consist of two or more layers.

[0071] "Visible light transmittance" The organic thin-film solar cell of the present invention preferably has a visible light transmittance of 50% or more. If the visible light transmittance is 50% or more, the organic thin-film solar cell becomes transparent, and such a transparent organic thin-film solar cell is capable of not only generating electricity but also emitting light, and therefore can be suitably used as a power-generating light-emitting element described below.

[0072] <Photoelectric conversion element> The present invention is not limited to the above-described embodiment, and the organic thin-film solar cell of the present invention can be used as a photoelectric conversion element in a sensor or the like. That is, the photoelectric conversion element of the present invention comprises a pair of electrodes and a photoelectric conversion layer located therebetween, the photoelectric conversion layer being composed of at least a donor material and an acceptor material, and the difference between the HOMO level of the donor material and the LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less. The photoelectric conversion element of the present invention can efficiently convert excitons generated by absorbing light into free carriers, and therefore has high conversion efficiency and can be used as a highly sensitive sensor.

[0073] In the photoelectric conversion element of the present invention, the electrodes may be the same as those (anode and cathode) used in the organic thin-film solar cell described above. In the photoelectric conversion element of the present invention, the photoelectric conversion layer may be the same as that of the organic thin-film solar cell described above.

[0074] Furthermore, the photoelectric conversion element of the present invention may include, in addition to the electrodes and the photoelectric conversion layer, a substrate, a hole collection layer, a hole transport layer, an electron transport layer, an electron collection layer, etc., similar to the above-mentioned organic thin-film solar cell. The preferred embodiments of the photoelectric conversion element of the present invention are the same as the preferred embodiments of the organic thin-film solar cell described above.

[0075] The method for producing the photoelectric conversion element of the present invention is not particularly limited. For example, the photoelectric conversion element of the present invention can be produced by sequentially forming an electrode (anode), a photoelectric conversion layer, an electrode (cathode), and the like on a substrate, similar to the above-mentioned organic thin-film solar cell.

[0076] <Power-generating light-emitting element> Furthermore, the present invention is not limited to the above-described embodiments, and the organic thin-film solar cell of the present invention can be used as a power-generating light-emitting element that is also capable of emitting light. That is, the power-generating light-emitting element of the present invention comprises a pair of electrodes and a photoelectric conversion layer / light-emitting layer located therebetween, the photoelectric conversion layer / light-emitting layer being composed of at least a donor material and an acceptor material, and the difference between the HOMO level of the donor material and the LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less. The power-generating light-emitting element of the present invention can generate visible exciplex emission between a donor material and an acceptor material, the difference between the HOMO level of the donor material and the LUMO level of the acceptor material being 1.8 eV or more and 2.5 eV or less, and therefore can efficiently generate both electricity and light.

[0077] In the power-generating light-emitting device of the present invention, the electrodes may be the same as those (anode and cathode) used in the organic thin-film solar cell described above. In the power-generating light-emitting element of the present invention, the photoelectric conversion layer of the organic thin-film solar cell described above can be used as the photoelectric conversion layer / light-emitting layer. In this case, the photoelectric conversion layer may further contain a light-emitting material because it also serves as a power generation layer.

[0078] The luminescent material can include, for example, bis[2-(2-benzothiazolyl)phenolato]zinc(II) (Zn(BTZ)2) and tris[1-phenylisoquinoline]iridium(III) (Ir(piq)3). For example, three-coordinate iridium complexes with 2,2'-bipyridine-4,4'-dicarboxylic acid as the ligand include factoris(2-phenylpyridine)iridium (Ir(ppy)3), 8-hydroxyquinoline aluminum (Alq3), tris(4-methyl-8-quinolinolato)aluminum(III) (Almq3), 8-hydroxyquinoline zinc (Znq2), and (1,10-phenanthroline)-tris-(4,4,4-trifluoro-1-(2-thienyl)-butane-1,3-dionate)europium(III) (Eu(TTA)3(phen)). , 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum(II) and other metal complexes; benzene-based compounds such as distyrylbenzene (DSB) and diaminodistyrylbenzene (DADSB); naphthalene-based compounds such as naphthalene and Nile Red; phenanthrene-based compounds such as phenanthrene; chrysene-based compounds such as chrysene and 6-nitrochrysene; perylene-based compounds such as perylene and N,N'-bis(2,5-di-t-butylphenyl)-3,4,9,10-perylene-dicarboximide (BPPC); Coronene compounds such as anthracene; anthracene compounds such as anthracene and bisstyrylanthracene; pyrene compounds such as pyrene; pyran compounds such as 4-(dicyanomethylene)-2-methyl-6-(para-dimethylaminostyryl)-4H-pyran (DCM); acridine compounds such as acridine; stilbene compounds such as stilbene; thiophene compounds such as 2,5-dibenzoxazolethiophene; benzoxazole compounds such as benzoxazole; benzimidazole compounds such as benzimidazole; 2,2'-(para-phenylenediamine) Benzothiazole compounds such as (vinylene)-bisbenzothiazole; butadiene compounds such as bistyryl(1,4-diphenyl-1,3-butadiene) and tetraphenylbutadiene; naphthalimide compounds such as naphthalimide; coumarin compounds such as coumarin; perinone compounds such as perinone; oxadiazole compounds such as oxadiazole; aldazine compounds; cyclopentadiene compounds such as 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP); quinacridone compounds such as quinacridone and quinacridone red;Examples of suitable compounds include pyridine compounds such as pyrrolopyridine and thiadiazolopyridine; spiro compounds such as 2,2',7,7'-tetraphenyl-9,9'-spirobifluorene; metal or metal-free phthalocyanine compounds such as phthalocyanine (HPc) and copper phthalocyanine; and boron compound materials described in JP-A Nos. 2009-155325, 2011-184430, and 2012-151149.

[0079] Furthermore, the power-generating light-emitting element of the present invention may include, in addition to the electrodes and the photoelectric conversion layer / light-emitting layer, a substrate, a hole-collecting layer, a hole-transporting layer, an electron-transporting layer, an electron-collecting layer, and the like, similar to the above-mentioned organic thin-film solar cell. The preferred embodiments of the power-generating light-emitting element of the present invention are the same as those of the above-mentioned organic thin-film solar cell. For example, in the power-generating light-emitting element of the present invention, the donor material and the acceptor material preferably have a band gap of 3 eV or more, the donor material and the acceptor material preferably have an optical gap of 2.5 eV or more, and the donor material and the acceptor material preferably have a visible light transmittance of 50% or more. The power-generating light-emitting element of the present invention also preferably has a visible light transmittance of 50% or more.

[0080] The method for manufacturing the power-generating light-emitting element of the present invention is not particularly limited. For example, the power-generating light-emitting element of the present invention can be manufactured by sequentially forming an electrode (anode), a photoelectric conversion layer / light-emitting layer, an electrode (cathode), and the like on a substrate, similar to the above-mentioned organic thin-film solar cell. [Example]

[0081] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0082] (Examples 1 to 12 and Comparative Examples 1 to 22) An organic thin-film solar cell 1 shown in FIG. 1 was produced and evaluated by the method described below.

[0083] [Process 1] As the substrate 2, a commercially available transparent glass substrate having an average thickness of 0.7 mm and having an electrode (anode 3) patterned to a width of 3 mm and made of ITO with a thickness of 70 nm was prepared. The substrate 2 having the anode 3 was then subjected to ultrasonic cleaning in acetone and isopropanol for 10 minutes each, and boiled in isopropanol for 5 minutes. Thereafter, the substrate 2 having the anode 3 was taken out of the isopropanol, dried by nitrogen blowing, and subjected to UV ozone cleaning for 20 minutes.

[0084] [Process 2] The substrate 2 on which the anode 3 cleaned in [Step 1] was formed was set on a spin coater, and a hole-collecting layer 4 was formed using a hole-injection material "Clevios HIL1.3N" manufactured by Heraeus GmbH to a thickness of 20 nm. Thereafter, the layer was heated on a hot plate heated to 180°C for 1 hour.

[0085] [Process 3] Next, the substrate 2 on which the hole-collecting layer 4 had been formed was fixed to a substrate holder of a vacuum deposition device. In addition, Novaled's p-type dopant NDP-9 and A compound represented by the following structural formula (1), Compounds represented by the following structural formulas (2) to (25) which serve as donor materials and / or acceptor materials, Al were placed in alumina crucibles and set as evaporation sources.

[0086] [ka]

[0087] [ka]

[0088] [ka]

[0089] [ka]

[0090] [ka]

[0091] Then, the chamber of the vacuum deposition device was filled with 1×10 -5 The pressure was reduced to 1000 Pa, and a hole transport layer 5, an electron donor layer 6, an electron acceptor layer 7, an electron collection layer 10, and a cathode 11 were successively formed by vacuum deposition using resistance heating.

[0092] Specifically, first, the donor material was used as a host and NDP-9 was used as a dopant to form a hole transport layer 5 with a thickness of 30 nm by co-evaporation. At this time, the doping concentration of NDP-9 was set to 10 mass % with respect to the entire hole transport layer 5. Subsequently, an electron donor layer 6 made of a donor material was formed to a thickness of 10 nm. Next, an electron acceptor layer 7 made of an acceptor material was formed to a thickness of 40 nm. Next, a compound represented by structural formula (1) was deposited to a thickness of 3 nm to form the electron-collecting layer 10. Next, a cathode 11 made of aluminum and having a thickness of 100 nm was formed by vacuum deposition on the substrate 2 on which the electron-collecting layer 10 had been formed. The cathode 11 was formed using a stainless steel deposition mask so that the deposition surface would be a strip with a width of 3 mm, and the light-emitting area of ​​the fabricated organic thin-film solar cell was 9 mm2. 2 It was decided. In addition, the compounds used as donor materials and acceptor materials in each of the examples and comparative examples are as shown in Tables 1 to 3.

[0093] [Step 4] Next, the substrate 2 on which each layer up to the cathode 11 was formed was placed in a glass cap (sealing container) having a concave space, and sealed by filling it with a sealant made of ultraviolet (UV) curable resin, thereby obtaining each organic thin-film solar cell (element).

[0094] (Evaluation of power generation characteristics) The solar cell characteristics of each of the fabricated organic thin-film solar cells were measured using an "OTENTO-SUN III Solar Simulator" and an AM1.5G filter manufactured by Bunkoukeiki Co., Ltd. The results of the fill factor and conversion efficiency obtained in each example and comparative example are shown in Tables 1 to 3.

[0095] (Evaluation of the energy levels of materials) The ionization potential (IP) of each donor and acceptor material was measured using an AC-3 spectrometer manufactured by Riken Keiki Co., Ltd., and the electron affinity (EA) was measured using an LE-1 low-energy inverse photoelectron spectrometer manufactured by ALS Technology Co., Ltd. The samples used for the measurements were made by depositing a 5-nm film of each material on a glass substrate with an ITO film. Tables 1 to 3 show the IP, EA, and band gap values ​​of the donor and acceptor materials, as well as the energy gap (Eg), which is the difference between the IP of the donor material and the EA of the acceptor material (corresponding to the difference between the HOMO level of the donor material and the LUMO level of the acceptor material).

[0096] (Evaluation of material optical gap and visible light transmittance) The absorption spectra of each donor material and acceptor material were measured using a PerkinElmer spectrophotometer "LAMBDA950." The samples used for the measurements were 50 nm thick films of each material formed on a quartz glass substrate. The optical gap value was determined by converting the rising wavelength of the absorption spectrum into energy. The visible light transmittance is the average value obtained by calculating the transmittance at each wavelength (380 to 780 nm) from the absorption spectrum. The optical gap and visible light transmittance are shown in Tables 1 to 3.

[0097] (Evaluation of light-emitting properties) To evaluate the light-emitting properties of each organic thin-film solar cell fabricated, a voltage was applied using a Keithley 2400 Source Meter, and the brightness was measured using a Konica Minolta LS-100 to examine the relationship between applied voltage and brightness. The emission spectrum was also examined using a Konica Minolta CS-2000A. Table 1 shows the applied voltage and maximum external quantum efficiency at a brightness of 1 nit.

[0098] [Table 1]

[0099] [Table 2]

[0100] [Table 3]

[0101] As can be seen from Tables 1 to 3, in the organic thin-film solar cells shown in the examples in which the difference between the HOMO level of the donor material and the LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less, the conversion efficiency is 0.18% or more, which is higher than the conversion efficiency of the comparative examples. Furthermore, the organic thin-film solar cells of the examples have a relatively large fill factor, and it is clear that good power generation characteristics are obtained.

[0102] Furthermore, with regard to light-emitting characteristics, the elements of the examples required a low driving voltage for light emission and had high external quantum efficiency. In other words, it is clear that the organic thin-film solar cells of the examples according to the present invention have excellent characteristics in both power generation and light emission, and can also be used as power-generating light-emitting elements. [Industrial Applicability]

[0103] The organic thin-film solar cell of the present invention can be used in display devices, lighting devices, tandem solar cells, and the like. [Explanation of symbols]

[0104] 1:Organic thin film solar cell 2: Circuit board 3: Anode (electrode) 4: Hole collection layer 5: Hole transport layer 6: Electron donor layer 7: Electron acceptor layer 8: Photoelectric conversion layer 9: Electron transport layer 10: Electron collection layer 11: Cathode (electrode)

Claims

1. An organic thin-film solar cell comprising a pair of electrodes and a photoelectric conversion layer located therebetween, the photoelectric conversion layer is composed of at least a donor material and an acceptor material, An organic thin-film solar cell, wherein a difference between a HOMO level of the donor material and a LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less.

2. The organic thin film solar cell according to claim 1 , wherein the donor material and the acceptor material have a band gap of 3 eV or more.

3. 2. The organic thin film solar cell according to claim 1, wherein the donor material and the acceptor material have an optical gap of 2.5 eV or more.

4. The organic thin-film solar cell according to claim 1 , wherein the donor material and the acceptor material have a visible light transmittance of 50% or more.

5. A photoelectric conversion element comprising a pair of electrodes and a photoelectric conversion layer located therebetween, the photoelectric conversion layer is composed of at least a donor material and an acceptor material, A photoelectric conversion element, characterized in that the difference between the HOMO level of the donor material and the LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less.

6. A power-generating light-emitting element comprising a pair of electrodes and a photoelectric conversion layer / light-emitting layer positioned therebetween, the photoelectric conversion layer / light-emitting layer is composed of at least a donor material and an acceptor material, A power-generating light-emitting element, wherein a difference between a HOMO level of the donor material and a LUMO level of the acceptor material is 1.8 eV or more and 2.5 eV or less.

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