Transparent conductive laminate and photoelectric conversion element

Abstract

The present invention aims to provide a photoelectric conversion element that can achieve high output by using a transparent conductive laminate with excellent light transmittance as an electrode. [Solution] To achieve the above objective, the transparent conductive laminate of the present disclosure is a laminate composed of two or more transparent conductive films formed on a light-transmitting support, characterized in that the dope concentration (D1) of the first transparent conductive film on the side closer to the support and the dope concentration (D2) of the second transparent conductive film on the side further away are given by the following formula. D1 > D2 ... (1) The transparent conductive laminate of this disclosure provides a photoelectric conversion element capable of obtaining high output.

Description

[Technical Field]

[0001] This disclosure relates to a transparent conductive laminate and a photoelectric conversion element. [Background technology]

[0002] In recent years, solar power generation has attracted attention as a clean energy source, and the development of solar cells is progressing. As one example, solar cells that use perovskite materials as the light-absorbing layer are rapidly gaining attention as a next-generation solar cell that can be manufactured at low cost. For example, Non-Patent Document 1 reports on a solution-type solar cell that uses perovskite materials as the light-absorbing layer, and Non-Patent Document 2 reports that solid-state perovskite solar cells exhibit high efficiency. As for the basic structure of perovskite solar cells, a forward structure is known in which an electron transport layer, a light absorption layer (perovskite layer), a hole transport layer (also called a hole transport layer), and a back electrode are stacked on top of the electrode in that order, and an inverted structure is known in which a hole transport layer, a light absorption layer, an electron transport layer, and a back electrode are stacked on top of the electrode in that order. In both of these structures, a transparent conductive film is used for the electrode. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Journal of the American Chemical Society, 2009, 131, 6050-6051. [Non-Patent Document 2] Science, 2012, 388, 643-647. [Overview of the project] [Problems that the invention aims to solve]

[0004] Since a solar cell needs to capture a lot of light in the light absorption layer, at least one of the electrodes uses a transparent conductive film such as tin-doped indium oxide as the electrode, and by improving the light transmission performance of this transparent conductive film, the performance of the solar cell is improved.

[0005] Therefore, an object of the present disclosure is to provide a photoelectric conversion element capable of achieving high output by using a transparent conductive laminate having better light transmittance and the like as an electrode.

Means for Solving the Problems

[0006] In order to achieve the above object, the transparent conductive laminate of the present disclosure is a laminate composed of a transparent conductive film including two or more transparent films formed on a light-transmissive support, and the doping concentration (D1) of the first transparent film closer to the support and the doping concentration (D2) of the second transparent film farther away satisfy the following formula. D1>D2...(1) The transparent conductive laminate of the present disclosure is characterized in that the first and second transparent films are mainly composed of a metal oxide of indium (In), and the doping component is tin (Sn) or tungsten (W). The transparent conductive laminate of the present disclosure is a laminate composed of a transparent conductive film including two or more transparent films formed on a light-transmissive support, and the refractive index (N1) of the first transparent film closer to the support and the refractive index (N2) of the second transparent film farther away satisfy the following formula. N1<N2...(2) The transparent conductive laminate of the present disclosure is characterized in that the film thickness (T1) of the first transparent conductive film and the film thickness (T2) of the second transparent conductive film satisfy the following formula. T1>T2...(3) The transparent conductive laminate of the present disclosure is characterized in that the first transparent film is an optical adjustment film mainly composed of a metal oxide, and the second transparent film is a transparent conductive film mainly composed of a metal oxide of indium (In). The photoelectric conversion element of the present disclosure is characterized in that the transparent conductive film of the transparent conductive laminate is used as an electrode for the photoelectric conversion element. The photoelectric conversion element of the present disclosure is composed of the transparent conductive laminate, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a second electrode in that order, wherein the first electrode is a transparent conductive film of the laminate, and the hole transport layer is formed on the second transparent film of this transparent conductive film. The photoelectric conversion element of this disclosure is characterized in that the hole transport layer contains a compound represented by the following general formula (4). [ka] In the chemical formula (4) above, Ar is a structure containing an aromatic ring, and the atoms constituting the aromatic ring may or may not contain heteroatoms, Ar may or may not have substituents other than -LZ, -LZ may be one or more, and if there are multiple, each L and each Z may be the same or different from each other, each L is an atomic group bonding Ar and Z or a covalent bond, and each Z is a group that can form a chemical bond or hydrogen bond with a metal oxide. The photoelectric conversion element of the present disclosure is characterized in that the hole transport layer contains a compound represented by the general formula (4) and a p-type metal oxide. The photoelectric conversion element of the present disclosure is characterized in that the p-type metal oxide is selected from nickel oxide, copper oxide, aluminum copper oxide, and aluminum nickel oxide. The photoelectric conversion element of the present disclosure is characterized in that the photoelectric conversion layer is a perovskite layer containing a perovskite structure. The photoelectric conversion element of this disclosure includes insulating nanoparticles between the hole transport layer and the perovskite layer. The photoelectric conversion element of the present disclosure has a median particle size of the insulating nanoparticles in the range of 1 to 100 nm. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a transparent conductive laminate with excellent light transmittance, etc., or a photoelectric conversion element capable of obtaining high output. [Brief explanation of the drawing]

[0008] [Figure 1] It is a cross-sectional view showing an example of the transparent conductive laminate of the present disclosure. [Figure 2] It is a cross-sectional view showing an example of the normal structure of the photoelectric conversion element of the present disclosure. [Figure 3] It is a cross-sectional view showing an example of the inverted structure of the photoelectric conversion element of the present disclosure. [Figure 4] It is a measurement diagram of a spectroscopic ellipsometer of an ITO single film. [Figure 5] It is a measurement diagram of a spectroscopic ellipsometer of an indium oxide single film. [Figure 6] It is a measurement diagram of a spectroscopic ellipsometer of an IWO single film. [Figure 7] It is a graph showing the relationship between the average transmittance of the transparent conductive laminate of the present disclosure and the average refractive index of the optical adjustment film.

Embodiments for Carrying Out the Invention

[0009] The present disclosure will be described in more detail with examples. However, the present disclosure is not limited by the following description. In the present disclosure, unless otherwise specified, "mass%" and "weight%" may be read interchangeably, and "parts by mass" and "parts by weight" may be read interchangeably. In the present disclosure, "on" or "on the surface" may be in a state of direct contact on or on the surface, or in a state via other components or the like.

[0010] Hereinafter, the present disclosure will be specifically described with reference to the drawings. However, the present disclosure is not limited to the following examples. Also, each drawing is a schematic diagram shown for convenience of explanation, and the dimensional ratios and shapes are different from the cross-sectional structures of actual laminates and elements.

[0011] Figure 1 is a cross-sectional view showing an example of a transparent conductive laminate 1. The laminate 1 is composed of a light-transmitting support 11 and transparent conductive films 2a and 2b formed on the surface of the support 11 as transparent films. The support 11 is made of a light-transmitting material. The material is not particularly limited, and for example, a substrate commonly used for solar cells may be used as appropriate. Examples of the substrate include glass, a plastic plate including a plastic film, a plastic film, an inorganic crystal, etc. The thickness of the substrate is not particularly limited. If the substrate is glass, for example, the thickness of the substrate is preferably 0.3 to 1.1 mm. If the substrate is a plastic film, for example, the thickness of the substrate is preferably 25 to 125 μm. In addition, a substrate on which at least one of the following films is formed on part or all of the surface of the substrate is a metal film, a semiconductor film, a conductive film, and an insulating film, can also be suitably used as the support 11. The "light transmittance" required for the support 11 is best achieved by a material having light transmittance characteristics of 50% or more, preferably 80% or more, in the visible light region. Furthermore, the transparent conductive laminate 1 of this disclosure may be a laminate of three or more transparent films or transparent conductive films, as long as the characteristics of the laminate 1 are not impaired.

[0012] The transparent conductive film, as a transparent film, is laminated in two layers: a first transparent film (first transparent conductive film) 2a on the side closer to the support 11 and a second transparent film (second transparent conductive film 2b) on the side further from the support 11. The transparent conductive films 2a and 2b are mainly composed of metal oxides and contain doping components to enhance conductivity while maintaining light transmittance. However, if light transmittance and conductivity are not impaired, the transparent conductive film 2b does not need to contain doping components. The first transparent conductive film 2a may be formed directly on the surface of the support 11. The first and second transparent conductive films 2a and 2b must be transparent, as described above. The "transparency" required for a transparent conductive film is optimally achieved by having a visible light transmittance of 50% or more, preferably 80% or more. The material of the transparent conductive film as a transparent film is not particularly limited, but it is preferable from a manufacturing and economic standpoint to use tin-doped indium oxide (ITO), tungsten-doped indium oxide (IWO), or indium oxide. In addition, it may be a combination of or composed of metal oxides such as indium-doped zinc oxide (IZO), boron-doped zinc oxide (BZO), aluminum-doped zinc oxide (AZO), fluorine-doped tin dioxide (FTO), antimond-doped tin oxide (ATO), niobium-doped tin oxide, or niobium-doped titanium oxide.

[0013] The doping concentration (D1) of the first transparent conductive film 2a and the doping concentration (D2) of the second transparent conductive film 2b are stacked such that the following equation (1) is satisfied. D1 > D2 ... (1) Here, the dope concentration of each transparent conductive film refers to the ratio of the mass of the doped component to the total mass of each transparent conductive film. If there is variation in the dope concentration of each transparent conductive film, it is possible to convert it using the mass ratio of the entire film region that has the function of transmitting light. The typical concentration ranges for D1 and D2 are 0.1–30% (D1) and 0–15% (D2), respectively. The preferred concentration ranges are 0.5–25% (D1) and 0–13% (D2), respectively. Furthermore, the optimal concentration ranges are 1–20% (D1) and 0–10% (D2), respectively. The transparent conductive laminate 1 of this disclosure is laminated such that the doping concentration of the transparent conductive film decreases as it moves away from the support side, thereby making it possible to create a highly transparent conductive film.

[0014] In this disclosure, the transparent conductive films, the first and second transparent conductive films 2a and 2b, are mainly composed of indium (In) metal oxide, and the doping component consists of tin (Sn) or tungsten (W). Since the first and second transparent conductive films 2a and 2b are mainly composed of indium (In) metal oxide and the doping component is made of tin (Sn) or tungsten (W), the transparent conductive films are easy to manufacture and their durability and transparency can be stabilized. Furthermore, within limits that do not affect the durability or transparency of the transparent conductive film, the first and second transparent conductive films 2a and 2b may be combined with transparent conductive films in which the main component is a metal oxide of zinc (Zn), tin (Sn), or titanium (Ti), and the doping component is indium (In), boron (B), fluorine (F), niobium (Nb), or antimony (Sb).

[0015] The refractive index (N1) of the first transparent conductive film 2a and the refractive index (N2) of the second transparent conductive film 2b are stacked such that the relationship shown in equation (2) below is satisfied. N1 <N2 ...(2) Here, the refractive index of each transparent conductive film is defined as the value for light with a wavelength of 589.3 nm (sodium D line). The typical refractive indices for N1 and N2 are 1.0–1.4 (N1) and 1.41–3.0 (N2), respectively. Preferred refractive indices are 1.05–1.4 (N1) and 1.41–2.5 (N2), respectively. The optimal refractive indices are 1.1–1.4 (N1) and 1.41–2.0 (N2), respectively. The transparent conductive laminate 1 of this disclosure is laminated such that the refractive index increases as it moves away from the support 11. By laminating the laminates such that the refractive index increases as it moves away from the support, reflection due to optical interference is suppressed, making it possible to form a highly transparent conductive film.

[0016] The thickness of the first transparent conductive film 2a (T1) and the thickness of the second transparent conductive film 2b (T2) are stacked such that the relationship shown in equation (3) below is satisfied. T1 > T2 ... (3) In this disclosure, it is preferable that the transparent conductive film, which is composed of two or more laminated layers, is laminated such that the film thickness decreases as it moves away from the support 11. The typical film thickness ranges for T1 and T2 are 5–400 nm (T1) and 0.1–150 nm (T2), respectively. Preferred film thickness ranges are 10–300 nm (T1) and 1.0–100 nm (T2), respectively. The optimal film thickness ranges are 20–250 nm (T1) and 5–80 nm (T2), respectively. Furthermore, the ratio T2 / (T1+T2) of the total film thickness (T1+T2) to the film thickness (T2) preferably satisfies the following relationship (4), preferably relationship (5), and optimally relationship (6). 1.0% ≤ T2 / (T1+T2) ≤ 45%...(4) 5.0% ≤ T2 / (T1+T2) ≤ 25%...(5) 10% ≤ T2 / (T1+T2) ≤ 20%...(6) The transparent conductive laminate 1 of this disclosure is laminated such that the thickness of the transparent conductive film decreases as it moves away from the support 11. Because the thickness of the transparent conductive film on the support side is greater, it is possible to form a highly transparent conductive film without impairing the electrical conductivity or durability of the transparent conductive film.

[0017] The following describes a photoelectric conversion element in which the transparent conductive films 2a and 2b of the transparent conductive laminate 1 of this disclosure are used as electrodes for a photoelectric conversion element. Figure 2 is a cross-sectional view showing an example of a forward-facing structure of the photoelectric conversion element disclosed herein, and Figure 3 is a cross-sectional view showing an example of an inverted-facing structure of the same photoelectric conversion element. The support 11 and 21 are made of the transparent conductive laminate 1, specifically support 11. First electrodes 12 and 22, corresponding to the first and second transparent conductive films 2a and 2b, are formed on the surface of this support 11 and 21. The first electrodes 12 and 22 are layers that support, for example, the electron transport layer 13 and the hole transport layer 25, and also have the function of extracting electrons or holes from the photoelectric conversion layers 14 and 24. Furthermore, the first electrode 12 acts as the anode (negative electrode), and the first electrode 22 acts as the cathode (positive electrode). The first electrodes 12,22 in this disclosure are transparent. Transparency in this disclosure means that visible light does not interact with the first electrodes, and that absorption and scattering of visible light are unlikely to occur. Specifically, it is defined as an average transmittance of 60% or more, preferably 70% or more, and optimally 80% or more, of light in the visible light region. The first electrodes 12 and 22 may be formed directly on the supports 11 and 21. As mentioned above, the first electrodes 12 and 22 need to be transparent and are not particularly limited, but tin-doped indium oxide (ITO), tungsten-doped indium oxide (IWO), and indium oxide are preferred. In addition, they may be composed of metal oxides such as indium-doped zinc oxide (IZO), boron-doped zinc oxide (BZO), aluminum-doped zinc oxide (AZO), fluorine-doped tin dioxide (FTO), antimond-doped tin oxide (ATO), niobium-doped tin oxide, and niobium-doped titanium oxide. This disclosure uses a first electrode composed of two or more laminated layers to enhance transparency. When light is incident from the support side, it is possible to form a highly transparent conductive film by laminating the layers so that the doping concentration decreases from the support side. Furthermore, the second transparent conductive film 2b, which is close to the photoelectric conversion layers 14 and 24, is not affected by doped carriers and impurities formed by the doping components, or their concentration is reduced, so recombination with electrons or holes moving from the photoelectric conversion layers 14 and 24 is suppressed, and thus the photoelectric conversion efficiency is also expected to improve. In this disclosure, the first electrode, which is composed of two or more laminated layers, is preferably laminated such that the refractive index increases as it moves away from the support when light is incident from the support side. Furthermore, it is preferable that the thickness of the transparent conductive film decreases as it moves away from the support 11 and 21. The thickness of the first electrodes 12 and 22 is not particularly limited, but it is preferable to adjust it so that the sheet resistance is 5 to 15 Ω / □ (per unit area). The method for forming the first electrodes 12 and 22 is not particularly limited, but can be obtained by known film formation methods depending on the material to be formed. The method for forming the first electrodes 12 and 22 on the supports 11 and 21 is not particularly limited, but can be a known method, and vacuum deposition such as vacuum deposition or sputtering is preferred. The first electrodes 12 and 22 may also be patterned, for example. The patterning method is not particularly limited, but examples include immersion in a laser or etching solution, or patterning using a mask during vacuum deposition, and any of these methods may be used in this disclosure. The first electrodes 12 and 22 may also be used in combination with metal wiring, for example, to lower the electrical resistance. The material of the metal wiring (metal lead wire) is not particularly limited, but examples include aluminum, copper, silver, gold, platinum, and nickel. The aforementioned metal lead wires can be formed on a first substrate by, for example, vapor deposition, sputtering, and crimping, and then used in combination by providing a layer of ITO or FTO on top of them, or by providing them on top of ITO or FTO.

[0018] [Electron transport layer 13, 23] The materials used in the electron transport layers 13 and 23 are not particularly limited and can be appropriately selected according to the purpose, but semiconductor materials are preferred, for example. The semiconductor material is not particularly limited and known materials can be used, for example, elemental semiconductors, compound semiconductors, organic n-type semiconductors, etc.

[0019] The aforementioned single-element semiconductors are not particularly limited, but examples include silicon and germanium. The aforementioned compound semiconductors are not particularly limited, but examples include metal chalcogenides, specifically oxides of titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, tantalum, etc.; sulfides of cadmium, zinc, lead, silver, antimony, bismuth, etc.; selenides of cadmium, lead, etc.; tellurides of cadmium, etc. Other compound semiconductors include phosphides of zinc, gallium, indium, cadmium, etc., gallium arsenide, copper-indium-selenium, copper-indium-sulfide, etc.

[0020] The aforementioned organic n-type semiconductor is not particularly limited, but examples include perylenetetracarboxylic anhydride, perylenetetracarboxydiimide compounds, naphthalenediimide-bithiophene copolymer, benzobisimidazobenzophenanthroline polymer, C 60 , C 70 PCBM([6,6]-phenyl-C 61 Examples include fullerene compounds such as methyl butyrate, carbonyl bridge-bithiazole compounds, ALq3 (tris(8-quinolinolato)aluminum), triphenylene bipyridyl compounds, silole compounds, and oxadiazole compounds.

[0021] Among the aforementioned materials used in the electron transport layers 13 and 23, organic n-type semiconductors are particularly preferred.

[0022] The materials used to form the electron transport layers 13 and 23 may be, for example, one type alone or two or more types in combination. If the materials used to form the electron transport layers 13 and 23 are semiconductor materials, there are no particular restrictions on the crystal type of the semiconductor material, and it can be appropriately selected according to the purpose. For example, it may be a single crystal, a polycrystalline material, or an amorphous material.

[0023] The film thickness of the electron transport layers 13 and 23 is not particularly limited and can be appropriately selected depending on the purpose, but for example, 5 nm to 1000 nm is preferred, and 10 nm to 700 nm is more preferred.

[0024] The method for forming the electron transport layers 13 and 23 is not particularly limited and can be appropriately selected depending on the purpose. Examples of the formation method include forming a thin film in a vacuum (vacuum deposition method) and wet deposition methods. Examples of the vacuum deposition method include sputtering, pulsed laser deposition (PLD method), ion beam sputtering, ion-assisted method, ion plating, vacuum evaporation, atomic layer deposition (ALD method), and chemical vapor deposition (CVD method). Examples of the wet deposition method include forming by coating a solvent in which the electron transport material is dissolved, or, in the case where the material used to form the electron transport layers 13 and 23 is an oxide semiconductor, the sol-gel method. The sol-gel method is a method in which a gel is prepared from a solution through chemical reactions such as hydrolysis, polymerization, and condensation, and then densification is promoted by heat treatment. When using the sol-gel method described above, there are no particular restrictions on the method of applying the sol solution, and it can be appropriately selected according to the purpose. Examples include the dip method, spray method, wire bar method, spin coating method, roller coating method, blade coating method, and gravure coating method. Examples of wet printing methods include letterpress, offset, gravure, intaglio, rubber plate, and screen printing. The temperature during the heat treatment after applying the sol solution is preferably 80°C or higher, and more preferably 100°C or higher.

[0025] In the inverted structure shown in Figure 3, an electron injection layer (hole blocking layer) may be formed between the electron transport layer 23 and the second electrode 26 after the electron transport layer 23 has been formed. Examples of materials that can be used for the electron injection layer include metal oxides such as BCP (basocuproine) and tin oxide, and it may also be doped with cesium or the like. The film thickness of the electron injection layer is preferably, for example, 1 nm to 100 nm, and more preferably 3 nm to 20 nm.

[0026] [Hole transport layers 15, 25] The hole transport layers 15 and 25 are layers that have the function of transporting electric charge. For example, conductors, semiconductors, organic hole transport materials, etc., can be used for the hole transport layers 15 and 25. The organic hole transport material can function as a hole transport material that receives holes from the perovskite layers (photoelectric conversion layers) 14 and 24 and transports the holes. The conductor and semiconductor can be an inorganic hole transport material or an organic hole transport material. Examples of the inorganic hole transport material include compound semiconductors containing monovalent copper such as CuI, CuInSe2, and CuS; and compounds containing metals other than copper such as GaP, NiO, CuO, FeO, Bi2O3, MoO3, and Cr2O. From the viewpoint of more efficiently receiving only holes and obtaining higher hole mobility, a semiconductor containing monovalent copper is preferred as the inorganic hole transport material, and CuI or CuSCN is more preferred. Examples of the organic hole transport material include polythiophene derivatives such as poly-3-hexylthiophene (P3HT) and polyethylenedioxythiophene (PEDOT); fluorene derivatives such as 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD); carbazole derivatives such as polyvinylcarbazole; triphenylamine derivatives such as poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine](PTAA); diphenylamine derivatives; polysilane derivatives; and polyaniline derivatives. From the viewpoint of more efficiently receiving only holes and obtaining higher hole mobility, triphenylamine derivatives and fluorene derivatives are preferred, and PTAA and Spiro-OMeTAD are more preferred.

[0027] Furthermore, the aforementioned organic hole transport materials are further improved in order to enhance their hole transport properties, for example, by using lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), silver bis(trifluoromethylsulfonyl)imide, zinc bis(trifluoromethylsulfonyl)imide, ammonium bis(trifluoromethanesulfonyl)imide, lithium bis(nonafluorobutanesulfonyl)imide, sodium bis(nonafluorobutanesulfonyl)imide, lithium nonafluoro-N-[(trifluoromethane)sulfonyl]butanesulfonylamide, potassium nonafluoro The material may also contain oxidizing agents such as oro-N-[(trifluoromethane)sulfonyl]butanesulfonylamide, nonafluoro-N-[(trifluoromethane)sulfonyl]butanesulfonylamide, lithium N,N-hexafluoro-1,3-disulfonylimide, sodium N,N-hexafluoro-1,3-disulfonylimide, trifluoromethylsulfonyloxysilver, NOSbF6, SbCl5, SbF5, and tris(2-(1H-pyrazole-1-yl)-4-tert-butylpyridine)cobalt(III)tri[bis(trifluoromethane)sulfonimide]. Furthermore, the hole transport layers 15 and 25 may also contain basic compounds such as tert-butylpyridine (TBP), 2-picoline, and 2,6-lutidine. The content of the oxidizing agent and basic compounds can be, for example, amounts commonly used conventionally. From the viewpoint of more efficiently receiving only holes and obtaining higher hole mobility, the film thickness of the hole transport layers 15 and 25 is preferably 1 to 500 nm, and more preferably 2 to 300 nm. The method for forming the hole transport layers 15 and 25 is preferably carried out under a dry atmosphere. For example, it is preferable to coat (spin coat, etc.) a solution containing an organic hole transport material onto a perovskite layer (light absorption layer) under a dry atmosphere and heat it at 30 to 180°C, particularly 100 to 150°C.

[0028] Furthermore, as the hole transport layer 25 in the inverted structure, for example, a hole transport compound that forms a monolayer (hereinafter also referred to as "monolayer hole transport compound") can be used. The monolayer hole transport compound preferably has an anchor that chemically bonds with a transparent electrode such as ITO in the inverted structure. Examples of such anchors include phosphonic acid groups (-P=O(OH)2), carboxyl groups (-COOH), sulfo groups (-SO3H), boronic acid groups (-B(OH)2), trihalogenated silyl groups (-SiX3, where X is a halogen atom), or trialkoxysilyl groups (-Si(OR)3, where R is an alkyl group), and salts of these may also be formed. Examples of salts include salts with alkali metals such as potassium and sodium, and quaternary ammonium salts such as tetramethylamine and tetra-n-butylamine. Among these, phosphonic acid groups, trihalogenated silyl groups, and trialkoxysilyl groups are particularly preferred.

[0029] The single-molecule hole transport compound may contain the compound represented by the following chemical formula (4).

[0030] [ka]

[0031] In the chemical formula (4) above, Ar is a structure containing an aromatic ring, and the atoms constituting the aromatic ring may or may not contain heteroatoms, Ar may or may not have substituents other than -LZ, there may be one or more -LZ groups, and if there are multiple, each L and each Z may be the same or different from each other, each L is an atomic group bonding Ar and Z or a covalent bond, and each Z is a group capable of transferring charge to and from the first electrode. The number of -LZ groups is not particularly limited, but may be in the range of 1 to 4, for example.

[0032] In the photoelectric conversion element of the present disclosure, in the chemical formula (4), L may be a divalent substituent such as a divalent alkylene group such as a 1,1-methylene group or a 1,2-ethylene group, or a divalent alkoxy group such as diethoxyethane, and these substituents may or may not have substituents other than Z.

[0033] In the photoelectric conversion element of the present disclosure, each Z in the chemical formula (4) may be a phosphonic acid group (-P=O(OH)2), a carboxyl group (-COOH), a sulfo group (-SO3H), a boronic acid group (-B(OH)2), a trihalide silyl group (-SiX3, where X is a halo group), or a trialkoxysilyl group (-Si(OR)3, where R is an alkyl group).

[0034] Specific examples of single-molecule hole transport materials include, but are not limited to, the compounds shown in (A-01) to (A-30) below. [ka] [ka] [ka] [ka] [ka]

[0035] In the aforementioned single-molecule hole transport material, it is preferable that there are two or more substituent LZs, and more preferably three or more.

[0036] The method for forming the hole transport layer 25 using the monomolecule hole transport material is not particularly limited, but for example, the hole transport layer 25 can be formed by adsorbing the monomolecule hole transport compound onto the first electrode 22 to form a monomolecule layer. The method for adsorbing the monomolecule hole transport compound onto the first electrode 22 to form a monomolecule layer is not particularly limited, but for example, the monomolecule hole transport compound can be dissolved in a solvent and brought into contact with the first electrode 22 to form a bond. The bond between the monomolecule hole transport compound and the first electrode 22 is not particularly limited and may be a physical bond or a chemical bond. The type of bond is also not particularly limited and may be any of the following: hydrogen bond, ester bond, chelate bond, etc. The solvent for dissolving the monomolecule hole transport compound is also not particularly limited and may be either water and an organic solvent, or both. More specifically, examples of the aforementioned solvents include water; alcohols such as methanol, ethanol, and 2-propanol; ethers such as diethyl ether and diisopropyl ether; ketones such as acetone and methyl isobutyl ketone; esters such as ethyl acetate, isobutyl acetate, and γ-butyrolactone; heterocyclic compounds such as tetrahydrofuran and thiophene; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; sulfoxides such as dimethyl sulfoxide; sulfones such as diethyl sulfone and sulfolane; nitriles such as acetonitrile and 3-methoxypropionitrile; aromatic compounds such as benzene, toluene, and chlorobenzene; halogenated solvents such as dichloromethane and chloroform; and fluorinated solvents such as chlorofluorocarbon, hydrochlorofluorocarbon, and hydrofluorocarbon. These can be used individually or in mixtures of two or more.

[0037] The specific method for adsorbing the monomolecule hole transport compound onto the first electrode 22 to form a monolayer is not particularly limited, but known methods such as dipping, spraying, spin coating, and bar coating can be used. The temperature during adsorption is not particularly limited, but -20°C to 100°C is preferred, and 0°C to 50°C is more preferred. The adsorption time is also not particularly limited, but for example, 1 second to 48 hours is preferred, and 10 seconds to 1 hour is more preferred. Furthermore, after the adsorption treatment, washing may or may not be performed. The washing method is also not particularly limited, but for example, known methods may be used as appropriate.

[0038] After the adsorption treatment or cleaning, a heat treatment may or may not be performed. The temperature for the heat treatment is preferably 50°C to 150°C, and more preferably 70°C to 120°C. The heat treatment time is preferably 1 second to 48 hours, and more preferably 10 seconds to 1 hour. This heat treatment may be performed, for example, in the atmosphere or in a vacuum.

[0039] When adsorbing the monomolecule hole transport compound onto the first electrode 22, a co-adsorbent may or may not be used in combination. The co-adsorbent can be added, for example, when the monomolecule hole transport compound alone cannot completely coat the electrode surface, or to inhibit the interaction between the monomolecule hole transport compounds.

[0040] The co-adsorbent is not particularly limited, but examples include phosphonic acid compounds such as n-butylphosphonic acid, n-hexylphosphonic acid, n-decylphosphonic acid, n-octadecylphosphonic acid, 2-ethylhexylphosphonic acid, methoxymethylphosphonic acid, 3-acryloyloxypropylphosphonic acid, 11-hydroxyundecylphosphonic acid, and 1H,1H,2H,2H-perfluorophosphonic acid, as well as acetic acid, propionic acid, isobutyric acid, nonanoic acid, fluoroacetic acid, α-chloropropionic acid, glyoxylic acid, and chenodeoxycholic acid. These may be used individually or in mixtures of two or more types.

[0041] The method for adsorbing the co-adsorbent onto the first electrode 22 is not particularly limited, but, similar to the monomolar hole transport compound, it is preferable to dissolve it in a solvent before adsorption. The solvent is also not particularly limited, but may be the same as the solvents exemplified above for the monomolar hole transport compound. Furthermore, the co-adsorbent may be adsorbed by first adsorbing the monomolar hole transport compound onto the substrate and then immersing the first electrode 22 in a solvent in which the co-adsorbent is dissolved, or it may be used after mixing and dissolving it together with the monomolar hole transport compound in an organic solvent.

[0042] Furthermore, if a compound has isomers such as tautomers or stereoisomers (e.g., geometric isomers, conformational isomers, and optical isomers) in this disclosure, any isomer may be used in this disclosure unless otherwise specified. Also, if a compound can form a salt in this disclosure, such salt may be used in this disclosure unless otherwise specified. The salt may be an acid addition salt or a base addition salt. Furthermore, the acid forming the acid addition salt may be an inorganic acid or an organic acid, and the base forming the base addition salt may be an inorganic base or an organic base. The inorganic acid is not particularly limited, but examples include sulfuric acid, phosphoric acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypofluorite, hypochlorous acid, hypobromous acid, hypoiodic acid, hypofluorite, chlorous acid, bromous acid, iodic acid, fluorite, chloric acid, bromate, iodic acid, perfluorite, perchloric acid, perbromic acid, and periodic acid. The organic acid is not particularly limited, but examples include p-toluenesulfonic acid, methanesulfonic acid, oxalic acid, p-bromobenzenesulfonic acid, carbonic acid, succinic acid, citric acid, benzoic acid, and acetic acid. The inorganic base is not particularly limited, but examples include ammonium hydroxide, alkali metal hydroxide, alkaline earth metal hydroxide, carbonate, and bicarbonate. More specifically, examples include sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, calcium hydroxide, and calcium carbonate. The organic base is also not particularly limited, but examples include ethanolamine, triethylamine, and tris(hydroxymethyl)aminomethane. The method for producing these salts is not particularly limited, and they can be produced, for example, by adding the aforementioned acids or bases to the compounds using known methods.

[0043] Furthermore, the aforementioned organic hole transport materials are further improved in order to enhance their hole transport properties, for example, by using lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), silver bis(trifluoromethylsulfonyl)imide, zinc bis(trifluoromethylsulfonyl)imide, ammonium bis(trifluoromethanesulfonyl)imide, lithium bis(nonafluorobutanesulfonyl)imide, sodium bis(nonafluorobutanesulfonyl)imide, lithium nonafluoro-N-[(trifluoromethane)sulfonyl]butanesulfonylamide, potassium nonafluoro The material may also contain oxidizing agents such as ruolo-N-[(trifluoromethane)sulfonyl]butanesulfonylamide, nonafluoro-N-[(trifluoromethane)sulfonyl]butanesulfonylamide, lithium N,N-hexafluoro-1,3-disulfonylimide, sodium N,N-hexafluoro-1,3-disulfonylimide, trifluoromethylsulfonyloxysilver, NOSbF6, SbCl5, SbF5, and tris(2-(1H-pyrazole-1-yl)-4-tert-butylpyridine)cobalt(III)tri[bis(trifluoromethane)sulfonimide]. The hole transport layers 15 and 25 may also contain basic compounds such as tert-butylpyridine (TBP), 2-picoline, and 2,6-lutidine. The content of the oxidizing agent and the basic compound can be, for example, amounts that are conventionally used. From the viewpoint of more efficiently receiving only holes and obtaining higher hole mobility, the film thickness of the hole transport layers 15 and 25 is preferably 1 to 500 nm, and more preferably 2 to 300 nm. The method for forming the hole transport layers 15 and 25 is preferably carried out under a dry atmosphere. The method for forming the hole transport layers 15 and 25 is preferably, for example, to coat (spin coat, etc.) a solution containing an organic hole transport material onto a perovskite layer (light absorption layer) under a dry atmosphere, and to heat it at 30 to 180°C, particularly 100 to 150°C.

[0044] [Photoelectric conversion layers 14, 24] The photoelectric conversion layers 14 and 24 are not particularly limited and may be similar to those used in photoelectric conversion elements such as general solar cells. The photoelectric conversion layers 14 and 24 include, for example, a perovskite compound. The perovskite compound may be, for example, a compound represented by the following chemical formula (5). A α B β C γ (5)

[0045] In the chemical formula (5) above, the ratio of α:β:γ is, for example, 3:1:1, where A represents a halogen ion, B represents a monovalent cation, and C represents a divalent cation. The perovskite layer is preferably arranged adjacent to the electron transport layer. Note that the ratio of α:β:γ does not necessarily have to be 3:1:1, for example, 3:1.05:0.95 or 3:0.95:1.05. The ratio of α:β:γ is, for example, 3:(0.95~1.05):(0.95~1.05).

[0046] In the chemical formula (5) above, A is not particularly limited and can be appropriately selected depending on the purpose, for example, halogen ions such as chlorine, bromine, and iodine. The halogen ions may be used individually or in combination of two or more.

[0047] In the chemical formula (5) above, B is, for example, an alkylamine compound ion (an organic compound having an amino group) such as methylammonium cation, ethylammonium cation, n-butylammonium cation, or formamidinium cation, or, not limited to organic compounds, an alkali metal ion such as cesium cation, potassium cation, or rubidium cation. The alkylamine compound ion and the alkali metal ion may be used individually or in combination of two or more. Furthermore, an organic (alkylamine compound ion) and an inorganic (alkali metal ion) may be used in combination; for example, a cesium ion and formamidinium may be used in combination.

[0048] In the chemical formula (5) above, C is not particularly limited and can be appropriately selected depending on the purpose, and examples include divalent metal ions such as lead, indium, antimony, tin, copper, bismuth, and germanium. The divalent metal ion may be used alone or two or more may be used in combination. Lead is particularly preferred as the divalent metal ion, and a combination of lead and tin is particularly preferred.

[0049] As described above, the photoelectric conversion layers 14 and 24 may be formed from a perovskite compound. The method for forming the perovskite layer is not particularly limited and can be appropriately selected depending on the purpose. For example, a method may be used in which a solution of metal halide and alkylamine halide is dissolved or dispersed is applied and then dried.

[0050] Furthermore, methods for forming the perovskite layer include, for example, a two-step precipitation method in which a solution of dissolved or dispersed metal halide is applied, dried, and then immersed in a solution of dissolved alkylamine halide to form a perovskite compound.

[0051] Other methods for forming the perovskite layer include, for example, a method in which a solution containing dissolved or dispersed metal halides and alkylamine halides is applied while adding a poor solvent (solvent with low solubility) for the perovskite compound to precipitate crystals. Furthermore, other methods for forming the perovskite layer include, for example, a method of depositing metal halides in a gas filled with methylamine or the like.

[0052] A particularly preferred method for forming the perovskite layer is to coat a solution containing dissolved or dispersed metal halides and alkylamine halides while adding a poor solvent for the perovskite compound to precipitate the crystals. The method of coating the solution is not particularly limited and can be appropriately selected depending on the purpose, and examples include immersion, spin coating, spraying, dipping, roller, and air knife methods. Alternatively, the method of coating the solution may be, for example, a method of precipitation in a supercritical fluid using carbon dioxide. In the method of precipitating crystals by adding the poor solvent, the poor solvent can be, for example, hydrocarbons such as n-hexane and n-octane; alcohols such as methanol, ethanol, and 2-propanol; ethers such as diethyl ether and diisopropyl ether; ketones such as acetone and methyl isobutyl ketone; esters such as ethyl acetate, isobutyl acetate, and γ-butyrolactone; nitriles such as acetonitrile and 3-methoxypropionitrile; aromatic hydrocarbon compounds such as benzene, toluene, and chlorobenzene; halogenated solvents such as dichloromethane and chloroform; and fluorinated solvents such as chlorofluorocarbon, hydrochlorofluorocarbon, and hydrofluorocarbon.

[0053] The method for forming the perovskite layer may further include, for example, a step aimed at removing the solvent after the perovskite layer has been formed (solvent removal step), or a step aimed at arranging perovskite crystals (crystal arrangement step). The solvent removal step and the crystal arrangement step may be carried out by, for example, blowing dry air, heating with a hot plate or oven, or vacuum drying. In the solvent removal step and the crystal arrangement step, the heating temperature is preferably, for example, 50 to 200°C, and more preferably 70 to 180°C. In the solvent removal step and the crystal arrangement step, the heating time is preferably, for example, 1 to 150 minutes, and more preferably 5 to 60 minutes. Furthermore, the thickness of the photoelectric conversion layers 14 and 24 is not particularly limited, but from the viewpoint of further suppressing performance degradation due to defects and peeling, for example, 50 to 1500 nm is preferred, and 200 to 1000 nm is more preferred.

[0054] The method for forming the perovskite layer may include, for example, a surface treatment step (surface treatment step) using a salt formed from one or more cations and one or more anions. The cations are, for example, inorganic cations such as lithium, sodium, potassium, rubidium, cesium, magnesium, and calcium; ammonium cations, methylamine, ethylamine, n-butylamine, isopentylamine, neopentylamine, formamidine, acetamidine, benzylamine, 2-phenylethylamine, 2-(4-methoxyphenyl)ethylamine, 4-fluorobenzylamine, 2-(4-fluorophenyl)ethylamine, 1,4-phenylenediamine, 5-aminovaleric acid, metamine, ethylenediamine, p-xylylenediamine, m-xylylenediamine, and 1,2-adamantine. Examples of organic compounds having an amino group include tandiamine, 1,3-adamantanediamine, N,N-dimethylethylenediamine, 1,3-diaminopropane, 1,4-diazabicyclo[2.2.2]octane, guanidine, aniline, pyrrole, imidazole, 1-ethylimidazole, 2-ethylimidazole, benzmidazole, morpholin, pyrrolidine, pyrazole, triazole, and carbazole; and cations obtained from heterocycles containing nitrogen atoms such as pyridine, pyrazine, pyridazine, pyrimidine, quinoline, isoquinoline, phenanthroline, 2,2'-bipyridyl, and 4,4'-bipyridyl. Examples of anions include halogen ions such as fluoride ions, chloride ions, bromide ions, and iodide ions; carboxylate ions such as formate ions and acetate ions; isocyanate ions, thiocyanate ions, tetrafluoroborate ions, hexafluorophosphate ions; and trifluoromethanesulfonylimide ions.

[0055] The salt comprising the cation and the anion is preferably soluble in one or more solvents. Examples of such solvents include alcohols such as isopropanol (2-propanol), ethanol (EtOH), methanol (MeOH), and n-butanol; nitriles such as acetonitrile and propionitrile; and aromatic solvents such as toluene, chlorobenzene, and 1,2-dichlorobenzene. For example, one solvent may be used alone, or two or more solvents may be used in combination.

[0056] The surface treatment step is carried out by applying a solution containing the dissolved salt onto the formed perovskite layer and drying it. The method of applying the solution is not particularly limited and can be appropriately selected depending on the purpose, and examples include immersion, spin coating, spraying, dipping, roller coating, and air knife coating. In the surface treatment step, a heat treatment may be performed after application, and if heating is performed, the heating temperature is preferably, for example, 50 to 200°C, and more preferably 70 to 180°C. The heating time is preferably, for example, 1 to 150 minutes, and more preferably 5 to 60 minutes. The film thickness to which the solution is applied is not particularly limited.

[0057] [Second electrodes 16, 26] The second electrodes 16, 26 (which may be, for example, back electrodes) are layers that have the function of extracting holes or electrons from the photoelectric conversion layers 14, 24 via, for example, a hole transport layer or an electron transport layer.

[0058] The second electrodes 16 and 26 may be formed directly on the hole transport layer 15 in the case of the forward structure, or directly on the electron transport layer 23 in the case of the reverse structure. The material of the second electrodes 16 and 26 is not particularly limited, and for example, the same material as that of the first electrodes 12 and 22 can be used. The shape, structure, and size of the second electrodes 16 and 26 are not particularly limited and can be appropriately selected according to the purpose. Examples of materials for the second electrodes 16 and 26 include metals, carbon compounds, conductive metal oxides, and conductive polymers. Examples of metals include platinum, gold, silver, copper, and aluminum. Examples of carbon compounds include graphite, fullerene, carbon nanotubes, and graphene. Examples of conductive metal oxides include ITO, IZO, FTO, and ATO. Examples of conductive polymers include polythiophene and polyaniline. Furthermore, the materials used to form the second electrodes 16 and 26 may be, for example, one type alone or two or more types in combination.

[0059] The second electrodes 16 and 26 can be formed on the hole transport layer 15 or electron transport layer 23 by methods such as coating, laminating, vacuum deposition, CVD, sputtering, and bonding, depending on the type of material used and the type of hole transport layer 15 or electron transport layer 23.

[0060] Furthermore, the configuration of the photoelectric conversion element in this disclosure is not limited to the configuration in Figure 2 or Figure 3. For example, the support 11 may be positioned on the opposite side from Figure 2 (above the second electrode 16 in Figure 2), and the second electrode 16, electron transport layer 15, photoelectric conversion layer 14, hole transport layer 13, and first electrode 12 may be stacked on the support 11 in this order. Also, as mentioned above, other components may or may not exist between each layer of the support 11, first electrode 12, hole transport layer 13, photoelectric conversion layer 14, electron transport layer 15, and second electrode 16. In addition, although an example in which the first electrode 12 is a transparent electrode and the second electrode 16 is a back electrode has been described, the photoelectric conversion element in this disclosure is not limited to this. For example, in the photoelectric conversion element in this disclosure, conversely, the first electrode may be a back electrode and the second electrode may be a transparent electrode.

[0061] The total thickness of the photoelectric conversion element disclosed herein can be appropriately changed depending on the thickness of the support used.

[0062] [Sealed] The photoelectric conversion element (e.g., solar cell) of the present disclosure is preferably sealed to protect the device from water and oxygen. The sealing structure is not particularly limited, but may be the same as that of a general photoelectric conversion element (e.g., solar cell). Specifically, for example, the sealing material may be applied only to the outer periphery of the photoelectric conversion element of the present disclosure and covered with glass or film, the sealing material may be applied to the entire surface of the photoelectric conversion element of the present disclosure and covered with glass or film, or the sealing material may be applied to the entire surface of the photoelectric conversion element of the present disclosure alone.

[0063] The material of the sealing member is not particularly limited and can be appropriately selected depending on the purpose. For example, epoxy resin or acrylic resin is preferably used and cured, but it is also acceptable if it is not cured or if only a part of it is cured.

[0064] The epoxy resin is not particularly limited, but examples include water-dispersible, solvent-free, solid, heat-curable, curing agent-mixed, and UV-curable types. Among these, the heat-curable and UV-curable types are preferred, and the UV-curable type is more preferred. Even if the epoxy resin is UV-curable, heating is possible, and it is preferable to heat it even after UV curing. Specifically, the epoxy resin includes bisphenol A type, bisphenol F type, novolac type, cyclic aliphatic type, long-chain aliphatic type, glycidylamine type, glycidyl ether type, and glycidyl ester type, which may be used alone or in combination of two or more. Furthermore, it is preferable to mix the epoxy resin with a curing agent and various additives as needed. Existing epoxy resin compositions can be used in this disclosure. Examples of commercially available epoxy resin compositions include those developed and sold for solar cell and organic EL element applications, which can be used particularly effectively in this disclosure. Examples of the commercially available epoxy resin compositions mentioned above include TB3118, TB3114, TB3124, TB3125F (manufactured by ThreeBond Corporation), WorldRock5910, WorldRock5920, WorldRock8723 (manufactured by Kyōritsu Chemical Industry Co., Ltd.), WB90US(P), and WB90US-HV (manufactured by Moresco).

[0065] The acrylic resin is not particularly limited, but for example, those developed and commercially available for solar cells and organic EL elements can be effectively used. Examples of commercially available acrylic resin compositions include TB3035B and TB3035C (manufactured by ThreeBond Corporation).

[0066] The curing agent is not particularly limited and can be appropriately selected depending on the purpose, but examples include amine-based, acid anhydride-based, polyamide-based, and other curing agents. Examples of amine-based curing agents include aliphatic polyamines such as diethylenetriamine and triethylenetetramine; aromatic polyamines such as metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone. Examples of acid anhydride-based curing agents include phthalic anhydride, tetra and hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride, hetic anhydride, and dodecenyl succinic anhydride. Examples of other curing agents include imidazoles and polymer captans. The curing agents may be used individually or in combination of two or more.

[0067] The aforementioned additives are not particularly limited and can be appropriately selected depending on the purpose. Examples include fillers, gap fillers, polymerization initiators, desiccants (hygroscopic agents), curing accelerators, coupling agents, softening agents, colorants, flame retardant aids, antioxidants, and organic solvents. Fillers, gap fillers, curing accelerators, polymerization initiators, and desiccants (hygroscopic agents) are preferred, and fillers and polymerization initiators are more preferred. By including the aforementioned filler as an additive, it is possible to suppress the intrusion of moisture and oxygen, and furthermore, to obtain effects such as reduced volume shrinkage during curing, reduced outgassing during curing or heating, improved mechanical strength, and control of thermal conductivity and fluidity. Therefore, including the aforementioned filler as an additive is very effective in maintaining stable output in various environments.

[0068] Furthermore, regarding the output characteristics and durability of the photoelectric conversion element, the effects of outgassing generated during the curing or heating of the sealing member cannot be ignored, in addition to the effects of moisture and oxygen that enter. In particular, the effects of outgassing generated during heating have a significant impact on the output characteristics when stored in a high-temperature environment. By including the filler, gap agent, and desiccant in the sealing member, these materials themselves can suppress the intrusion of moisture and oxygen, and the amount of sealing member used can be reduced, thereby reducing outgassing. Including the filler, gap agent, and desiccant in the sealing member is effective not only during curing but also when storing the photoelectric conversion element in a high-temperature environment.

[0069] The filler material is not particularly limited and can be appropriately selected depending on the purpose. Examples include crystalline or amorphous silica, silicate minerals such as talc, inorganic fillers such as alumina, aluminum nitride, silicon nitride, calcium silicate, and calcium carbonate, with hydrotalcite being particularly preferred. The filler material may be used alone or in combination of two or more types.

[0070] The average primary particle size of the filler is not particularly limited, but is preferably 0.1 μm or more and 10 μm or less, and more preferably 1 μm or more and 5 μm or less. When the average primary particle size of the filler is within the above preferred range, the effect of suppressing the intrusion of moisture and oxygen can be sufficiently obtained, the viscosity becomes appropriate, adhesion to the substrate and degassing performance are improved, and it is also effective in controlling the width of the sealing part and workability.

[0071] The content of the filler is preferably 10 parts by mass or more and 90 parts by mass or less, and more preferably 20 parts by mass or more and 70 parts by mass or less, relative to the entire sealing member (100 parts by mass). By having the content of the filler within the above preferred range, sufficient effect in suppressing the penetration of moisture and oxygen is obtained, the viscosity becomes appropriate, and adhesion and workability are also good.

[0072] The gap agent is also called a gap control agent or spacer agent. By including the gap agent as an additive, it becomes possible to control the gap of the sealed portion. For example, when a sealing member is applied to a substrate or a first electrode, and a second substrate is placed on top of it to perform sealing, the gap of the sealed portion can be easily controlled because the sealing member contains a gap agent, causing the gap to match the size of the gap agent.

[0073] The gap filler is not particularly limited, but is preferably granular with a uniform particle size and high solvent resistance and heat resistance, and can be appropriately selected depending on the purpose. The gap filler is preferably highly compatible with epoxy resin and has a spherical particle shape. Specifically, the gap filler is preferably glass beads, silica fine particles, organic resin fine particles, etc. The gap filler may be used alone or two or more may be used in combination. The particle size of the gap filler can be selected according to the gap of the sealing part to be set, but is preferably 1 μm to 100 μm, and more preferably 5 μm to 50 μm.

[0074] The polymerization initiator is not particularly limited, but examples include polymerization initiators that initiate polymerization using heat or light, and can be appropriately selected depending on the purpose. Examples include thermal cation polymerization initiators and photocationic polymerization initiators. The thermal polymerization initiator is a compound that generates active species such as radicals and cations when heated, and examples include azo compounds such as 2,2'-azobisisobutyronitrile (AIBN) and peroxides such as benzoyl peroxide (BPO). Examples of thermal cationic polymerization initiators include benzenesulfonic acid esters and alkylsulfonium salts. For example, in the case of epoxy resins, photocationic polymerization initiators are preferably used. When a photocationic polymerization initiator is mixed with an epoxy resin and irradiated with light, the photocationic polymerization initiator decomposes, generating acid, which causes polymerization of the epoxy resin, and the curing reaction proceeds. The photocationic polymerization initiator has the effect of low volume shrinkage during curing, not being affected by oxygen inhibition, and having high storage stability.

[0075] Examples of the photocationic polymerization initiators include aromatic diazonium salts, aromatic iodonium salts, aromatic sulfonium salts, metacerone compounds, and silanol-aluminum complexes. As the polymerization initiator, a photoacid generator that generates acid upon irradiation with light can also be used. The photoacid generator acts as an acid that initiates cationic polymerization and includes ionic sulfonium salts and iodonium salts, etc., consisting of a cation and anion. The photoacid generator may be used alone or in combination of two or more.

[0076] The amount of polymerization initiator added is not particularly limited and may vary depending on the material used, but is preferably 0.5 parts by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 5 parts by mass or less, relative to the entire sealing member (100 parts by mass). By having the amount added within the above preferred range, curing can proceed properly, the amount of uncured material remaining can be reduced, and excessive outgassing can be prevented.

[0077] The desiccant (also called a moisture absorber) is a material that has the function of physically or chemically adsorbing and absorbing moisture, and by incorporating it into the sealing member, moisture resistance can be further enhanced and the effects of outgassing can be reduced. The desiccant is not particularly limited and can be appropriately selected according to the purpose, but particulate form is preferred, and examples include inorganic water-absorbing materials such as calcium oxide, barium oxide, magnesium oxide, magnesium sulfate, sodium sulfate, calcium chloride, silica gel, molecular sieves, and zeolites, with zeolites, which have a high moisture absorption capacity, being preferred. The desiccant may be used alone or in combination of two or more types.

[0078] The curing accelerator (also called a curing catalyst) is a material that speeds up the curing rate and is mainly used with thermosetting epoxy resins. The curing accelerator is not particularly limited and can be appropriately selected depending on the purpose. Examples include tertiary amines or tertiary amine salts such as DBU (1,8-diazabicyclo(5,4,0)-undecene-7) and DBN (1,5-diazabicyclo(4,3,0)-nonene-5); imidazoles such as 1-cyanoethyl-2-ethyl-4-methylimidazole and 2-ethyl-4-methylimidazole; and phosphines or phosphonium salts such as triphenylphosphine and tetraphenylphosphonium·tetraphenylborate. The curing accelerator may be used alone or in combination of two or more.

[0079] The coupling agent is not particularly limited as long as it is a material that has the effect of increasing molecular bonding strength, and can be appropriately selected depending on the purpose, for example, silane coupling agents. Specifically, the coupling agent can be 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, N-(2-(vinylbenzylamino)ethyl)3-aminopropyltrimethoxysilane hydrochloride, and 3-methacryloxypropyltrimethoxysilane. The coupling agent may be used alone or in combination of two or more.

[0080] In this disclosure, for example, a sheet-like adhesive can be used. The sheet-like adhesive is, for example, a sheet on which a resin layer has been formed in advance, and the sheet can be made of glass, a film with high gas barrier properties, or the like. Alternatively, the sheet may be formed using only a sealing resin. The sheet-like adhesive can also be attached to a sealing film. It is also possible to create a structure on the sealing film with a hollow portion before bonding it to the device.

[0081] When sealing using the aforementioned sealing film, it is positioned opposite the support so as to sandwich the photoelectric conversion device. The shape, structure, size, and type of the support for the sealing film are not particularly limited and can be appropriately selected according to the purpose. The sealing film forms a barrier layer on the surface of the support that prevents the passage of moisture and oxygen, and this layer may be formed on one side of the support or on both sides.

[0082] The barrier layer may be composed of a material whose main components are, for example, a metal oxide, a metal, or a mixture formed from a polymer and a metal alkoxide. Examples of the metal oxide include aluminum oxide, silicon oxide, and aluminum. Examples of the polymer include polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose. Examples of the metal alkoxide include tetraethoxysilane, triisopropoxyaluminum, 3-glycidoxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-isocyanatetopropyltriethoxysilane.

[0083] The barrier layer may be transparent or opaque, for example. Furthermore, the barrier layer may be a single layer formed from a combination of the above materials, or a multi-layered structure. The barrier layer can be formed using known methods, including vacuum deposition methods such as sputtering, dipping, roll coating, screen printing, spraying, and gravure printing.

[0084] [wiring] In order to efficiently extract the current generated by light, it is preferable to connect lead wires (wirings) to the electrodes and back electrode of the photoelectric conversion element (e.g., solar cell) disclosed herein. The lead wires are connected to the first electrode and the second electrode using a conductive material such as solder, silver paste, or graphite. The conductive material may be used alone, or in a mixture of two or more types or in a laminated structure. Furthermore, the area to which the lead wires are attached may be covered with an acrylic resin or epoxy resin for physical protection.

[0085] The aforementioned lead wires are a general term for wires used to electrically connect power sources, electronic components, etc., in an electrical circuit, and examples include vinyl-coated wires and enameled wires.

[0086] [application] The applications and methods of use of the photoelectric conversion element disclosed herein are not particularly limited, and it can be widely used in the same applications as general photoelectric conversion elements (e.g., general solar cells). The photoelectric conversion element disclosed herein (e.g., solar cell) can be applied to a power supply device by combining it with, for example, a circuit board that controls the generated current. Examples of devices that utilize a power supply device include electronic desktop calculators and solar-powered radio-controlled watches. It is also possible to apply the photoelectric conversion element disclosed herein as a power supply device to mobile phones, electronic paper, thermometers and hygrometers, etc. Furthermore, it can be used as an auxiliary power source to extend the continuous use time of rechargeable or battery-powered electrical appliances, or for nighttime use when combined with a secondary battery. It can also be used as a self-contained power source that does not require battery replacement or power wiring. [Examples]

[0087] The following describes embodiments of this disclosure. However, this disclosure is not limited to the following embodiments.

[0088] [Example 1] A 150 nm thick indium oxide (ITO) film with 10% tin doping was formed on a 125 μm thick PET film using sputtering. An 80 nm layer of indium oxide was then formed on this ITO film using sputtering. 1 mL of a DMF solution (0.1 mmol / L) containing the compound of formula (4) was placed on the indium oxide, and a monolayer (hole transporter in the hole transport layer) was formed on the ITO (first electrode) using a spin coater (3,000 rpm, 30 seconds) and a hot plate (110°C, 10 minutes). Next, a solution of an alumina dispersion (a dispersion with an average particle size of alumina of 50 nm, an alumina content of 20 wt%, and 2-propanol as the dispersion medium) diluted 50 times with 2-propanol was added to the hole transporter at a rate of 0.1 mL. A hole transport layer, in which the hole transport material and insulating compound were mixed, was formed using a spin coater (3,000 rpm, 30 seconds) and a hot plate (100°C, 15 minutes). Next, a solution of cesium iodide (0.738 g), formamidine iodide (7.512 g), methylamine bromide (0.905 g), lead iodide (23.888 g), and lead bromide (1.022 g) dissolved in DMF (40.0 mL) and dimethyl sulfoxide (DMSO, 12.0 mL) was deposited on the substrate using spin coating. Spin coating was performed at 3000 rpm, and chlorobenzene (0.3 mL) was added dropwise 30 seconds after the start. Then, the mixture was heated at 150°C for 10 minutes to obtain a perovskite layer (photoelectric conversion layer). Next, ethylenediamine hydroiodide (0.5 nm) (interface layer), C60 (20 nm) (electron transport layer), vasocuproin (BCP, 8 nm) (electron injection layer), and Ag (100 nm) (second electrode) were deposited by vacuum deposition to fabricate a photoelectric conversion element. After fabrication, the solar cell characteristics of the photoelectric conversion element were evaluated. The measurement results are shown in Table 1.

[0089] [ka]

[0090] The photovoltaic conversion characteristics of the photovoltaic device fabricated in Example 1 were measured by a method compliant with the output measurement method for silicon crystalline solar cells of JIS C8913:1998. A solar simulator (SMO-250III type manufactured by Spectral Instruments Co., Ltd.) combined with an air mass filter equivalent to AM1.5G was adjusted to a light intensity of 100 mW / cm 2 using a secondary standard Si solar cell as the measurement light source. While irradiating the test sample of the perovskite solar cell (the photovoltaic device fabricated in Example 1) with light, the I-V curve characteristics were measured using a source meter (Model 2400 universal source meter manufactured by Keithley Instruments Inc.), and the short-circuit current (Isc), open-circuit voltage (Voc), fill factor (FF), short-circuit current density (Jsc), and photovoltaic conversion efficiency (PCE) obtained from the measurement of the I-V curve characteristics were determined. In the subsequent examples and comparative examples, the solar cell characteristics were evaluated in the same manner.

[0091] Equation 1: Short-circuit current density (Jsc; mA / cm 2 ) = Isc (mA) / effective light-receiving area S (cm 2 ) Equation 2: Photovoltaic conversion efficiency (PCE; %) = Voc (V) × Jsc (mA / cm 2 ) × FF × 100 / 100 (mW / cm 2 )

[0092] The doping concentration of the transparent conductive laminate in the obtained photovoltaic device was 10% for ITO and 0% for indium oxide. Also, the measurement results of a single layer film of ITO formed on glass using a spectroscopic ellipsometer (SE-2100 manufactured by Nippon Semilab Co., Ltd., measurement wavelength: 245 to 2100 nm, spot diameter 500 μm, measurement incident angle 70°, integration time 2000 ms) are shown in FIG. 4. The value of the refractive index n at 900 nm was 1.22. A single layer film of indium oxide was fabricated in the same manner as ITO and measured with a spectroscopic ellipsometer. The measurement results are shown in FIG. 5. From FIG. 5, the value of the refractive index at 900 nm was 1.86.

[0093] [Example 2] A photoelectric conversion element was fabricated in the same manner as in Example 1, except that the indium oxide film thickness was changed from 80 nm to 120 nm, and the solar cell characteristics were evaluated. The results are shown in Table 1.

[0094] [Example 3] A photoelectric conversion element was fabricated in the same manner as in Example 1, except that the indium oxide film thickness was changed from 80 nm to 40 nm, and the solar cell characteristics were evaluated. The results are shown in Table 1.

[0095] [Example 4] A photoelectric conversion element was fabricated in the same manner as in Example 1, except that the indium oxide film thickness of 80 nm was changed to 50 nm for IWO, and the solar cell characteristics were evaluated. The results are shown in Table 1. In addition, the spectroscopic ellipsometer measurement of IWO was performed in the same manner as for ITO in Example 1. As a result, the refractive index of IWO at 900 nm was 1.94.

[0096] [Example 5] A photoelectric conversion element was fabricated in the same manner as in Example 1, except that the IWO film thickness in Example 4 was changed from 50 nm to 25 nm, and the solar cell characteristics were evaluated. The results are shown in Table 1.

[0097] [Example 6] A photoelectric conversion element was fabricated in the same manner as in Example 1, except that the IWO film thickness in Example 4 was changed from 50 nm to 80 nm, and the solar cell characteristics were evaluated. The results are shown in Table 1.

[0098] [Comparative Example 1] A photoelectric conversion element was fabricated in the same manner as in Example 1, except that an ITO-only film was used instead of the 80 nm indium oxide film used in Example 1, and the solar cell characteristics were evaluated. The results are shown in Table 1.

[0099] [Comparative Example 2] A photoelectric conversion element was fabricated in the same manner as in Example 1, except that the 150 nm ITO film in Comparative Example 1 was changed to a 120 nm IWO film, and the solar cell characteristics were evaluated. The results are shown in Table 1.

[0100] [Table 1]

[0101] [Example 7] On a 125 μm thick PET film, a first transparent film made of magnesium oxide (MgO) was formed using sputtering as an optical adjustment film to a thickness (T1) of 20 nm. On this first transparent film, a second transparent film of indium oxide was formed with a thickness of 250 nm using the same sputtering method. On the indium oxide film (on the surface of the indium oxide film) of the transparent conductive film composed of the first and second transparent films, 1 mL of a DMF solution (0.1 mmol / L) containing the compound of formula (4) was placed, and a monolayer (hole transporter in the hole transport layer) was formed on the first transparent film (transparent conductive layer as the first electrode) using a spin coater (3,000 rpm, 30 seconds) and a hot plate (110°C, 10 minutes). Next, a solution of an alumina dispersion (a dispersion with an average particle size of alumina of 50 nm, an alumina content of 20 wt%, and 2-propanol as the dispersion medium) diluted 50 times with 2-propanol was added to the hole transporter at a rate of 0.1 mL. A hole transport layer, in which the hole transport material and insulating compound were mixed, was formed using a spin coater (3,000 rpm, 30 seconds) and a hot plate (100°C, 15 minutes). Next, a solution of cesium iodide (0.738 g), formamidine iodide (7.512 g), methylamine bromide (0.905 g), lead iodide (23.888 g), and lead bromide (1.022 g) dissolved in DMF (40.0 mL) and dimethyl sulfoxide (DMSO, 12.0 mL) was deposited on the substrate using spin coating. Spin coating was performed at 3000 rpm, and chlorobenzene (0.3 mL) was added dropwise 30 seconds after the start. Then, the mixture was heated at 150°C for 10 minutes to obtain a perovskite layer (photoelectric conversion layer). Next, ethylenediamine hydroiodide (0.5 nm) was deposited (interface layer), C60 (20 nm) (electron transport layer), vasocuproin (BCP, 8 nm) (electron injection layer), and indium-doped zinc oxide (IZO) (100 nm) was deposited by vacuum deposition (second electrode) to fabricate a photoelectric conversion element. After fabrication, the solar cell characteristics of the photoelectric conversion element were evaluated.

[0102] [Example 8] A photoelectric conversion device was fabricated in the same manner as in Example 7, except that a first transparent film made of zinc oxide (ZnO) as an optical adjustment film was formed to have a film thickness (T1) of 50 nm by sputtering instead of the first transparent film made of magnesium oxide (MgO) in Example 7, and the photovoltaic characteristics were evaluated. The measurement results of Examples 7 and 8 are shown in Table 2.

[0103]

Table 2

[0104] The refractive indices of the first and second transparent films shown in Table 2 are defined as the average refractive index for light with wavelengths from 300 to 1200 nm. The average refractive index N1 of magnesium oxide (MgO) as the first transparent film is 1.73, and the average refractive index N1 of zinc oxide (ZnO) is 1.96. The average refractive index N2 of indium oxide (In2O3) as the second transparent film is 1.996 (about 2.0). Thus, since the average refractive index (N{1}) of the first transparent film and the average refractive index (N{2}) of the second transparent film satisfy the relationship N{1}<N{2}, reflection due to light interference generated at the interface between each film is suppressed, a transparent conductive film laminate with high transparency and excellent light transmission characteristics is formed. As a result, the amount of light reaching the photoelectric conversion layer (perovskite layer) that has passed through the first and second transparent films increases, and it becomes possible to fabricate a photoelectric conversion device with a high photoelectric conversion efficiency with a PCE (Power Conversion Efficiency) exceeding 20%.

[0105] When the perovskite layer of Example 7 or 8 is used for the photoelectric conversion layer of the photoelectric conversion device, the average refractive index Np of the perovskite layer is 2.4, and the average refractive index N{2} of indium oxide (In2O3) as the second transparent film (transparent conductive film) is between 1.9 and 2.3. In order to satisfy the relationship N{1}<N{2}, it is preferable to adjust the average refractive index N{1} of the optical adjustment film as the first transparent film to be in the range of 1.7 to 2.1, preferably in the range of 1.8 to 2.0. This makes it possible to enhance the light transmission characteristics of the transparent conductive laminate.

[0106] Unlike Examples 1 to 6, the second transparent film (transparent conductive film) in Example 7 or 8 functions as a current transfer film with a single film of only the second transparent film (transparent conductive film). Therefore, the film thickness T2 of the second transparent film (transparent conductive film) is set to 250 nm. On the other hand, the film thickness T1 of the first transparent film (MgO) in Example 7 is 20 nm, and the film thickness T1 of the first transparent film (ZnO) in Example 8 is 50 nm. The transparent conductive laminate of Example 7 or 8 is preferably formed in the range where the film thickness T1 is 10 to 100 nm and the film thickness T2 is 100 to 500 nm, and the relationship T1 < T2 is satisfied for each film thickness. Further, it is more preferable to satisfy the following relational expression. 70% ≦ T2 / (T1 + T2) ≦ 95%

[0107] The second transparent film (transparent conductive film) in Examples 7 and 8 is formed as indium oxide (In2O3) with a doping concentration (D2) of 0% in order to increase the average transmittance. In general, tin (Sn) or the like is added as a doping agent to the second transparent film (transparent conductive film) in order to lower the electrical resistance value. However, when the density of free electrons (carrier concentration) increases due to this doping agent, the influence that free electrons absorb visible light appears, and the average transmittance tends to decrease. The second transparent film (transparent conductive film) in this example does not add a doping agent, but it is considered that the electrical resistance value has become low due to crystal defects such as oxygen vacancies generated during sputtering film formation, or reactions with compounds present at the interfaces with the first transparent film, the perovskite layer, or the hole transport layer. Further, since the second transparent film (transparent conductive film) is not affected by the doping agent, the average transmittance is relatively high.

[0108] FIG. 7 is a graph showing the relationship between the average transmittance of the transparent conductive laminate used in the photoelectric conversion elements of Examples 7 and 8 and the average refractive index of the optical adjustment film. The average transmittance shown here is the average value of the transmittances in the wavelength range of 800 to 1100 nm. The average transmittance of a conventional transparent conductive laminate (PET-In2O3) in which the second transparent film (second transparent conductive film) is formed directly on a PET film (average refractive index 1.63) without using the first transparent film (optical adjustment film) is 0.820. When silica (SiO2) is used for the optical adjustment film, the average refractive index is 1.46, N1 > N2, and the average transmittance decreases to 0.80. In contrast, the average transmittance of Example 7 (optical adjustment film: MgO) is 0.825, and the average transmittance of Example 8 (optical adjustment film: ZnO) increases to 0.835. By optimizing the average refractive index of the optical adjustment film to satisfy the relationship N1 < N2, the light transmission characteristics are improved. In particular, it is shown that the average transmittance of infrared rays increases.

[0109] As long as the average refractive index of the optical adjustment film, which is the first transparent film, satisfies the relationship N1 < N2, it may be an oxide, nitride, etc. other than magnesium oxide (MgO) and zinc oxide (ZnO). For example, ZnMgO, SnO2, MoO3, YMnO3 can be mentioned, but it is not limited thereto. The optical adjustment film functions as an insulating film, but may also have a gas barrier function.

[0110] The present disclosure has been described above using embodiments and examples. However, the present disclosure is not limited to the embodiments and examples described above, and can be arbitrarily and appropriately combined, changed, or selected within the scope not departing from the gist of the present disclosure as needed.

Industrial Applicability

[0112] 1. Transparent conductive laminate 2a, 2b First and second transparent films (transparent conductive films) 10, 20 Photoelectric conversion elements 11, 21 Support 12, 22 First electrode 13, 23 Electron transport layer 14, 24 Photoelectric conversion layer 15, 25 Hole transport layer 16, 26 Second electrode

Claims

1. A transparent conductive laminate comprising a transparent conductive film consisting of two or more transparent films formed on a light-transmitting support, characterized in that the dope concentration (D1) of the first transparent film closer to the support and the dope concentration (D2) of the second transparent film further away from the support are given by the following formula. D1>D2. .. .. (1)

2. The transparent conductive laminate according to claim 1, characterized in that the first and second transparent films are mainly composed of an indium (In) metal oxide, and the doping component is tin (Sn) or tungsten (W).

3. A laminate comprising a transparent conductive film composed of two or more transparent films formed on a light-transmitting support, characterized in that the refractive index (N1) of the first transparent film on the side closer to the support and the refractive index (N2) of the second transparent film on the side further away from the support are given by the following formula. N1<N2. .. .. (2)

4. The transparent conductive laminate according to claim 1 or 3, characterized in that the film thickness of the first transparent film (T1) and the film thickness of the second transparent film (T2) are given by the following formulas. T1>T2. .. .. (3)

5. The transparent conductive laminate according to claim 3, characterized in that the first transparent film is an optically modified film mainly composed of a metal oxide, and the second transparent film is a transparent conductive film mainly composed of an indium (In) metal oxide.

6. A photoelectric conversion element characterized by using the transparent conductive film of the transparent conductive laminate according to claim 1 or 3 as an electrode for a photoelectric conversion element.

7. A photoelectric conversion element comprising, in the order of a transparent conductive laminate, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a second electrode, wherein the first electrode is a transparent conductive film of the laminate, and the hole transport layer is formed in the second transparent film of this transparent conductive film.

8. The photoelectric conversion element according to claim 7, characterized in that the hole transport layer contains a compound represented by the following general formula (4). 【Chemistry 1】 In the aforementioned chemical formula (4), Ar has a structure that includes an aromatic ring, and constitutes the aromatic ring. The atom may or may not contain a heteroatom, and Ar is a substitution other than -L-Z. The group may or may not have a group, and there may be one or more -L-Z groups. If there are multiple L and Z groups, each L and each Z may be the same or different from each other. Each L is either an atomic group bonding Ar and Z, or a covalent bond, and each Z is a group that can form a chemical bond or hydrogen bond with a metal oxide.

9. The photoelectric conversion element according to claim 8, characterized in that the hole transport layer contains a compound represented by the general formula (4) and a p-type metal oxide.

10. The photoelectric conversion element according to claim 9, characterized in that the p-type metal oxide is selected from nickel oxide, copper oxide, aluminum copper oxide, and aluminum nickel oxide.

11. The photoelectric conversion element according to claim 7, characterized in that the photoelectric conversion layer is a perovskite layer containing a perovskite structure.

12. The photoelectric conversion element according to claim 11, further comprising insulating nanoparticles between the hole transport layer and the perovskite layer.

13. The photoelectric conversion element according to claim 12, wherein the median particle size of the insulating nanoparticles is in the range of 1 to 100 nm.

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