Solar battery

Abstract

To provide a solar battery that exhibits excellent photoelectric conversion characteristics.SOLUTION: In a solar battery, a first electrode, a hole transport layer, a photoelectric conversion layer, and a second electrode are included in this order. The hole transport layer includes a hole transport material that is a polymer with a number average molecular weight of 1,000-1,000,000, having a coupling group represented by the general formula (I): -CH=CH-S-. Preferably, the first electrode is a transparent electrode including a metal oxide, and the hole transport material includes a copolymer of a compound represented by the general formula (II) and a compound represented by the general formula (III).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a solar cell.

Background Art

[0002] In recent years, as clean energy, photovoltaic power generation has attracted attention, and the development of solar cells has been progressing. As one of them, as a next-generation solar cell that can be manufactured at low cost, a solar cell using a perovskite material as a light absorption layer has rapidly attracted attention. For example, Non-Patent Document 1 reports a solution-type solar cell using a perovskite material as a light absorption layer. Non-Patent Document 2 also reports that a solid-state perovskite solar cell exhibits high efficiency.

[0003] As a basic structure of a perovskite solar cell, there are a normal structure in which an electron transport layer, a light absorption layer (perovskite layer), a hole transport layer (also referred to as a hole transport layer), and a back electrode are laminated in this order on an electrode, and a reverse structure in which a hole transport layer, a light absorption layer, an electron transport layer, and a back electrode are laminated in this order on an electrode. Sometimes, a porous electron transport layer is provided between the electron transport layer and the perovskite layer. Among these, generally, an organic semiconductor hole transport material is used for the hole transport layer (for example, Non-Patent Documents 3 to 9).

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non - Patent Document 5

Non - Patent Document 6

Non - Patent Document 7

Non - Patent Document 8

Non - Patent Document 9

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the conventional perovskite solar cells do not have sufficient photoelectric conversion efficiency. In order to improve the photoelectric conversion efficiency of solar cells, it is particularly important to improve the characteristics of the hole transport layer. As hole transport materials used in the hole transport layer, for example, traxene compounds (Non-Patent Document 3), diketopyrrolopyrrole compounds (Non-Patent Document 4), thiophene compounds (Non-Patent Documents 5 and 6), dithienopyrrole (Non-Patent Document 7), etc. have been reported so far. However, almost no compounds have been reported that can exhibit a photoelectric conversion efficiency sufficient to be useful as perovskite solar cells. Therefore, Spiro-OMeTAD ([2,2’,7,7’-tetrakis(N,N-di-p-methoxyphenylamino)-9,9’-spirobifluorene]), which was developed as a hole transport material for dye-sensitized solar cells, has been proposed, but it is known to have low heat resistance (Non-Patent Document 8). Also, a polymer material having a triphenylamine skeleton called PTAA (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]) is known to have low light resistance. Furthermore, when these materials are used as hole transport materials for the p buffer layer, it is necessary to add LiTFSI salt (lithium bis(trifluoromethanesulfonyl)imide) as an additive to improve the conductivity, which is considered to be one of the causes of device degradation (Non-Patent Document 9). From such a current situation, there is a particular need for a material in which the hole transport layer exhibits excellent photoelectric conversion characteristics.

[0006] Therefore, an object of the present invention is to provide a solar cell exhibiting excellent photoelectric conversion characteristics.

Means for Solving the Problems

[0007] Basically, the present invention is based on the finding of an embodiment that the above problems can be solved by including a hole transport material in which the hole transport layer has a linking group represented by -CH=CH-S- and is a polymer having a number average molecular weight of 1,000 or more and 1,000,000 or less.

[0008] A first aspect of the present invention relates to a solar cell. This solar cell includes a first electrode, a hole transport layer, a photoelectric conversion layer, and a second electrode in this order.

[0009] The first electrode is preferably a transparent electrode containing a metal oxide. An example of the transparent electrode is an ITO film. The ITO film may be formed, for example, on a glass substrate. The transparent electrode may be appropriately selected from those known in solar cells. The film thickness of the transparent electrode may also be appropriate according to the application and composition.

[0010] The hole transport layer contains a hole transport material which is a polymer having a number average molecular weight of 1,000 or more and 1,000,000 or less and having a linking group represented by the following general formula (I). The number average molecular weight may be measured according to JIS K 7252-1 (ISO 16014-1). The number average molecular weight of the hole transport material may be 1,000 or more and 500,000 or less, or may be 5,000 or more and 500,000 or less. -CH=CH-S-...(I) The hole transport material preferably includes a copolymer of a compound represented by the following general formula (II) and a compound represented by the following general formula (III). The hole transport layer may contain, as the hole transport material, something other than the copolymer of formula (II) and formula (III). Also, the hole transport material may be a copolymer further containing elements other than formula (II) and formula (III). Either or both of the compound represented by formula (II) and the compound represented by formula (III) preferably contain an aromatic hydrocarbon ring or a heterocyclic ring.

[0011] Hereinafter, the compound represented by formula (II) will be described.

Chemical formula

[0012] The substituent in the aliphatic hydrocarbon, aromatic hydrocarbon, or heterocycle which may have a substituent may be a known substituent depending on the use. Examples of the substituent group are as follows in Substituent Group A below. Substituent Group A: Halogen; Hydroxy group; Carboxy group; Cyano group; Hydrogen atoms may be substituted by 1 to 3 of halogen, hydroxy group, carboxy group, carbamoyl group, sulfo group, phosphonic acid group, boronic acid (-B(OH) 2 ), alkoxysilyl group, or silyl halide group in C 1 -C 6 Alkyl group; C which may have 1 to 3 hydrogen atoms substituted by a halogen, a hydroxy group, a carboxy group, a carbamoyl group, a sulfo group, a phosphonic acid group, a boronic acid, an alkoxysilyl group, or a halogenated silyl group 2 -C 6 an alkenyl group; C which may have 1 to 3 hydrogen atoms substituted by a halogen, a hydroxy group, a carboxy group, a carbamoyl group, a sulfo group, a phosphonic acid group, a boronic acid, an alkoxysilyl group, or a halogenated silyl group 2 -C 6 an alkynyl group; C which may have 1 to 3 hydrogen atoms substituted by a halogen, a hydroxy group, a carboxy group, a carbamoyl group, a sulfo group, a phosphonic acid group, a boronic acid, an alkoxysilyl group, or a halogenated silyl group 1 -C 6 an alkoxy group; C which may have 1 to 3 hydrogen atoms substituted by a halogen, a hydroxy group, a carboxy group, a carbamoyl group, a sulfo group, a phosphonic acid group, a boronic acid, an alkoxysilyl group, or a halogenated silyl group 1 -C 6 an alkylthio group; C which may have 1 to 3 hydrogen atoms substituted by a halogen, a hydroxy group, a carboxy group, a carbamoyl group, a sulfo group, a phosphonic acid group, a boronic acid, an alkoxysilyl group, or a halogenated silyl group 3 -C 7 an alicyclic hydrocarbon group; C which may have 1 to 3 hydrogen atoms substituted by a halogen, a hydroxy group, a carboxy group, a carbamoyl group, a sulfo group, a phosphonic acid group, a boronic acid, an alkoxysilyl group, or a halogenated silyl group 7 -C 16 an aralkyl group; C 1 -C 4 an alkoxy-carbonyl group, C 1 -C 4 an alkyl group, C 1 -C 4 an alkylsulfonyl group, or C 6 -C 10A carbamoyl group which may be mono- or di-substituted by a substituent selected from an arylsulfonyl group; A C in which 1 to 3 hydrogen atoms may be substituted by a halogen, a hydroxy group, a carboxy group, a carbamoyl group, a sulfo group, a phosphonic acid group, a boronic acid, an alkoxysilyl group, or a halogenated silyl group 6 -C 10 aryl group; and It shows a group consisting of a 5- to 7-membered aromatic heterocyclic group in which 1 to 3 hydrogen atoms may be substituted by a halogen, a hydroxy group, a carboxy group, a carbamoyl group, a sulfo group, a phosphonic acid group, a boronic acid, an alkoxysilyl group, or a halogenated silyl group.

[0013] Examples of the compound represented by formula (II) may be appropriately selected from those represented by A-1 to A43 described below.

[0014] Examples of the compound represented by formula (II) are the compounds represented by the following formula (II’).

Chemical formula

[0015] In formula II’, R 11 , R 12 , and R 13 may be the same or different and each represents a substituent on the benzene ring. n 11 , n 12 , and n 13 may be the same or different and each represents an integer of 0 to 5. When n 11 , n 12 , or n 13 is 2 or more, R 11 , R 12 , and R 13 may be the same or different. However, in formula II’, at least one substituent is an ethynyl group. In formula II’, R 11 , R 12 , and R 13It is preferably an ethynyl group. Further, the ethynyl group is preferably present at the para position. However, even in that case, R 11 and R 12 and R 13 may have substituents other than the ethynyl group. For example, R 11 may represent an ethynyl group (-C≡CH) and other substituents. The other substituents may be appropriately selected from the above-described substituent group A. Adjacent benzene rings may be directly or indirectly connected (except for the parts bonded to N and S).

[0016] Examples of the compound represented by formula (II) are the compounds represented by the following formula (II'').

Chemical formula

[0017] In formula II'', X 11 to X 18 may be the same or different and represent a carbon atom or a nitrogen atom. All of them may represent carbon atoms. Also, any one or two of them may be nitrogen atoms. In formula II'', R 21 may be a hydrogen atom or any substituent selected from the substituent group A. In formula II'', R 22 and R 23 may be the same or different and represent substituents of the benzene ring. n 22 and n 23 may be the same or different and represent an integer from 0 to 4. n 22 and n 23 when 2 or more, R 22 and R 23 may be the same or different. However, in formula II'', at least one substituent is an ethynyl group. In formula II'', n 22 and n 23 are preferably those which are ethynyl groups. However, even in that case, R 22 and R 23It may have a substituent other than an ethynyl group. For example, R 22 may represent an ethynyl group (-C≡CH) and another substituent. The other substituent may be appropriately selected from the above-described substituent group A.

[0018]

Chemical formula

[0019] The compound represented by formula (III) may be any compound that can provide a thiol group and can form a copolymer with the compound represented by formula (II). When obtaining the polymer, the molar ratio of the compound represented by formula (II) to the compound represented by formula (III) may be adjusted so that the ethynyl group of the compound represented by (II) and the thiol group of the compound represented by formula (III) are about 1:1 (within 50% before and after, or within 30% before and after). In the polymer, the compound represented by formula (II) and the compound represented by formula (III) may each contain a plurality of types. The compound represented by formula (III) is preferably one compound containing two or more thiol groups.

[0020] Examples of the compound represented by formula (III) may be appropriately selected from those represented by A-1 to A43 described below.

[0021] An example of the compound represented by formula (III) is the compound represented by the following formula (III’).

Chemical formula

[0022] In formula III’, X 31 represents a sulfur atom, an oxygen atom, or a methylene group, and a sulfur atom is preferred. In formula III’, R 31 , and R 32 may be the same or different from each other and represent substituents of the benzene ring. n31 and n 32 may be the same or different and each represents an integer of 1 to 5. n 31 and n 32 , when there are two or more, R 31 and R 32 may be the same or different. However, in formula III’, at least one substituent is a thiol group (-SH). In formula III’, n 31 and n 32 being a thiol group is preferred. However, even in that case, R 31 and R 32 may have substituents other than the thiol group. For example, R 31 may represent a thiol group and other substituents. The other substituents may be appropriately selected from the above-mentioned substituent group A. In addition, adjacent benzene rings may be directly or indirectly connected (except for the parts bonded to N and S).

[0023] Examples of the compound represented by formula (III) are compounds represented by the following formula (III’’).

Chemical formula

[0024] In formula III’’, R 33 represents a substituent of the benzene ring. n 33 represents an integer of 1 to 6, with 2 to 4 being preferred. n 33 , when there are two or more, R 33 may be the same or different. However, in formula III’’, at least one substituent is a thiol group (-SH). The other substituents may be appropriately selected from the above-mentioned substituent group A. In formula III’’, R 33 being a thiol group is preferred. However, even in that case, R 33It may have substituents other than the thiol group. When the compound represented by Formula III’’ has two thiol groups (-SH), the two thiol groups may be present at any of the meta, ortho, and para positions. Among these, those with two thiol groups at the para position are preferred. When the compound represented by Formula III’’ has three thiol groups (-SH), those with thiol groups at the 1, 3, and 5 positions are preferred. When the compound represented by Formula III’’ has four thiol groups (-SH), those with thiol groups at the 1, 2, 4, and 5 positions are preferred. Other than the thiol group, it may be unsubstituted, or a hydrogen atom may be substituted by any group appropriately selected from the substituent group A.

[0025] The hole transport material is preferably covalently bonded to the transparent electrode. In this case, it is preferable that the hole transport material has a substituent of the hole transport material which is any of a phosphonic acid group, a carboxy group, a sulfo group, a boronic acid group, a trihalogenated silyl group, and a trialkoxysilyl group, and is covalently bonded to the transparent electrode by the substituent of the hole transport material.

[0026] The photoelectric conversion layer preferably contains a compound containing a perovskite structure.

[0027] The second electrode may appropriately employ a known electrode in a solar cell.

Advantages of the Invention

[0028] According to the present invention, a solar cell exhibiting excellent photoelectric conversion characteristics can be provided. This solar cell is preferably a perovskite solar cell.

Brief Description of the Drawings

[0029]

Figure 1

Modes for Carrying Out the Invention

[0030] [Solar Cell] Hereinafter, the configuration of the solar cell of the present invention and each component will be described more specifically with examples. However, the solar cell of the present invention is not limited to the following examples. In the following, mainly, the case where the solar cell of the present invention is a solar cell will be described.

[0031] FIG. 1 shows an example of the configuration of the solar cell of the present invention. Note that FIG. 1 is schematically drawn with appropriate omissions, exaggerations, etc. for convenience of explanation. As shown in the figure, the solar cell of the present invention is a perovskite solar cell and shows an inverted structure.

[0032] [Support 11] The support 11 is not particularly limited. For example, a substrate that can be used for a solar cell such as a general solar cell may be appropriately used. Examples of the substrate include glass, plastic plate, plastic film, inorganic crystal, etc. Further, a substrate having at least one kind of film such as a metal film, a semiconductor film, a conductive film, and an insulating film formed on a part or all of the surface of these substrates can also be preferably used as the support 11. The size, thickness, etc. of the support 11 are not particularly limited, and may be the same as or similar to those of a solar cell such as a general solar cell.

[0033] [First Electrode 12] The first electrode 12 is a layer that supports the hole transport layer 13 and has a function of extracting holes from the photoelectric conversion layer 14. Further, the first electrode 12 is, for example, a layer that functions as a cathode (positive electrode).

[0034] The first electrode 12 may be formed directly on the support 11, for example. The first electrode 12 may be a transparent electrode formed from a conductor, for example. The transparent electrode is not particularly limited, but for example, a tin-doped indium oxide (ITO) film, an impurity-doped indium oxide (In 2 O 3) A film, an impurity-doped zinc oxide (ZnO) film, a fluorine-doped tin dioxide (FTO) film, a laminated film formed by laminating two or more of these, gold, silver, copper, aluminum, tungsten, titanium, chromium, nickel, and cobalt, etc. may be mentioned. These may be used alone or as a mixture of two or more, and may be in a single layer or laminated. Also, these films may function as, for example, a diffusion prevention layer. The thickness of the first electrode 12 is not particularly limited, but for example, it is preferable to adjust so that the sheet resistance becomes 5 to 15 Ω / □ (per unit area). The method for forming the first electrode 12 is not particularly limited, but for example, it can be obtained by a known film formation method according to the material to be formed. Also, the shape of the first electrode 12 is not particularly limited, and for example, it may be in a film shape or formed in a lattice shape such as a mesh shape. The method for forming the first electrode 12 on the support 11 is not particularly limited, and for example, a known method may be used, and for example, vacuum film formation such as vacuum evaporation or sputtering is preferable. Also, a patterned first electrode 12 may be used. The patterning method is not particularly limited, and examples include a method of immersing in a laser or an etching solution, a method of patterning using a mask during vacuum film formation, etc., and any method may be used in the present invention. Also, the first electrode 12 may be used in combination with a metal wiring or the like for the purpose of reducing the electrical resistance value. The material of the metal wiring (metal lead wire) is not particularly limited, and examples include aluminum, copper, silver, gold, platinum, nickel, etc. The metal lead wire can be formed on the first substrate by, for example, evaporation, sputtering, crimping, etc., and an ITO or FTO layer can be provided thereon, or it can be used in combination by providing it on ITO or FTO.

[0035] [Hole transport layer 13] The hole transport layer 13 is a polymer having a molecular weight of 1,000 or more having a linking group represented by the above chemical formula (I) as described above. Further, as the hole transport material having a substituent represented by the general formula (I), a polymer obtained by reacting a compound represented by the general formula (II) and a compound represented by the general formula (III) is used. In general formulas (II) and (III), A and B represent aliphatic hydrocarbons such as ethane, hexane, and ethylene, aromatic hydrocarbons such as phenyl, naphthyl, biphenyl, and triphenylamine, and heterocycles such as thiophene, pyrrole, and benzothiophene, and n represents an integer of 2 or more. Specific examples of A in general formula (II) and B in general formula (III) are listed below as A-1 to A-43. Although the compounds in the figures do not show substituents, they may have substituents as described above. Examples of the substituents are any of the substituents selected from substituent group A.

[0036]

Chemical formula

[0037]

Chemical formula

[0038]

Chemical formula

[0039]

Chemical formula

[0040]

Chemical formula

[0041] In A-1 to A-51, X contains at least one ethyne (ethynyl group) in the case of the general formula (II), and may further contain an acidic group that forms a chemical bond with the metal oxide electrode, or may be any of the above-described substituent groups A. In the case of the general formula (III), X contains at least one thiol, and may further contain an acidic group that forms a chemical bond with the metal oxide electrode, or may be any of the above-described substituent groups A. Examples of the acidic group include carboxylic acid, sulfonic acid, phosphonic acid, boronic acid, alkoxysilyl group, and halogenated silyl group. Although not described in A-1 to A-51, as described above, it may have a substituent. Specific examples thereof include, in addition to the substituent group A, an alkyl group such as a methyl group or an n-hexyl group, an alkoxy group such as a methoxy group or an isopropoxy group, an aryl group such as a phenyl group or a naphthyl group, and a halogen such as chlorine or bromine. Further, the carbon atoms constituting the ring in A-1 to A-51 may be substituted with various elements, and examples of such elements are N, S, or O. Further, at least one of the general formula (II) or the general formula (III) is preferably an aromatic hydrocarbon or a heterocycle.

[0042] The hole transport layer in the present invention is formed by polymerizing a compound represented by the general formula (II) and a compound represented by the general formula (III) through a thiol-yne reaction (alkyne hydrothiolation reaction). The thiol-yne reaction is the name of a chemical reaction between a thiol and an alkyne. Usually, the reaction proceeds with a radical initiator, UV irradiation, heating, etc., and an alkenyl sulfide is produced. This alkenyl sulfide is a mixture of the E-form and the Z-form, and in the present invention, it may be the E-form, the Z-form, or a mixture. Also, not all of the alkyne which is a substituent in the general formula (II) and the thiol which is a substituent in the general formula (III) need to react, and the unreacted substituents may remain as they are. Therefore, the substituents before the reaction do not have to be in a 1:1 ratio. By performing polymerization by heat (temperature increase), compared with the case of performing polymerization by UV, it is possible to uniformize the polymerization by thermal vibration and form a dense polymerization. Furthermore, by performing polymerization by heat, compared with the case of performing polymerization by UV, an effect of promoting the removal of the solvent used during coating can also be expected.

[0043] As a method for forming the hole transport layer in the present invention, the compound represented by the general formula (II) and the compound represented by the general formula (III) may be polymerized in an organic solvent, and the solution may be directly coated to form the hole transport layer, or after being isolated once, it may be dissolved or dispersed in an organic solvent again and then coated. Also, each compound may be coated, the solvent may be dried to form a film, and then polymerization may be performed.

[0044] The hole transport layer of the present invention may contain an inorganic hole transport material or an organic hole transport material in addition to the hole transport material polymerized by the thiol-yne reaction. Examples of the inorganic hole transport material include compound semiconductors containing monovalent copper such as CuI, CuInSe 2 , CuS, etc.; GaP, NiO, CiO, FeO, Bi 2 O 3 , MoO 3 , Cr 2Examples of the compound containing a metal other than copper such as O include. Among them, from the viewpoint of more efficiently receiving only holes and obtaining higher hole mobility, a semiconductor containing monovalent copper is preferable, and NiO, CuI or CuSCN is more preferable. 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; polyaniline derivatives and the like.

[0045] [Photoelectric conversion layer 14] The photoelectric conversion layer 14 is not particularly limited and may be the same as the photoelectric conversion layer used in a solar cell such as a general solar cell. The photoelectric conversion layer 14 contains a perovskite compound. The perovskite compound may be, for example, a compound represented by the following chemical formula (IV). XαYβZγ...(IV)

[0046] In the formula (IV), the ratio of α:β:γ is 3:1:1, and β and γ represent integers greater than 1. X represents a halogen ion, Y represents an organic compound having an amino group, and Z represents a metal ion. The perovskite layer is preferably disposed 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, it can be 3:1.05:0.95. Also, X is not particularly limited and can be appropriately selected according to the purpose. Examples of X include halogen ions such as chlorine, bromine, and iodine. These can be used alone or in combination of two or more. As Y, alkylamine compound ions (organic compounds having an amino group) such as methylamine, ethylamine, n-butylamine, and formamidine, and not limited to organic ones, alkali metal ions such as cesium, potassium, and rubidium can be mentioned. The alkylamine compound ions and alkali metal ions can be used alone or in combination of two or more, respectively. Also, an organic (alkylamine compound ion) and an inorganic (alkali metal ion) can be used in combination. For example, cesium ion and formamidine can be used in combination. Z is not particularly limited and can be appropriately selected according to the purpose. Examples of Z include metals such as lead, indium, antimony, tin, copper, and bismuth. These can be used alone or in combination of two or more. Among these, especially lead, the combination of lead and tin is particularly preferred. Also, the perovskite layer preferably exhibits a layered perovskite structure in which a layer composed of a metal halide and a layer in which organic cation molecules are arranged are alternately laminated. The perovskite layer may contain an alkali metal. When the perovskite layer contains at least an alkali metal, it is advantageous in that the output increases. Examples of the alkali metal include cesium, rubidium, and potassium. Among these, cesium is preferred.

[0047] As described above, the photoelectric conversion layer 14 may be a perovskite layer formed from a perovskite compound. There is no particular limitation on the method for forming such a perovskite layer, and it can be appropriately selected according to the purpose. For example, a method of applying a solution in which a metal halide and an alkylammonium halide are dissolved or dispersed and then drying it can be mentioned.

[0048] In addition, as a method for forming a perovskite layer, for example, a two-step precipitation method in which a solution in which a metal halide is dissolved or dispersed is applied and dried, and then immersed in a solution in which an alkylammonium halide is dissolved to form a perovskite compound can be mentioned. Other examples include a method of adding a poor solvent (a solvent with low solubility) for the perovskite compound while applying a solution in which a metal halide and an alkylammonium halide are dissolved or dispersed to precipitate crystals. Furthermore, a method of vapor-depositing a metal halide in a gas filled with methylamine or the like can also be mentioned. Furthermore, a method of adding a poor solvent for the perovskite compound while applying a solution in which a metal halide and an alkylammonium halide are dissolved or dispersed to precipitate crystals is particularly preferred. There is no particular limitation on the method for applying these solutions, and it can be appropriately selected according to the purpose. Examples include dipping method, spin coating method, spraying method, dip method, roller method, air knife method, etc. Also, as a method for applying a solution, a method of precipitating in a supercritical fluid using carbon dioxide or the like may be used. As a method of adding the above-mentioned poor solvent to precipitate crystals, examples of the poor solvent used include 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, halogen-based solvents such as dichloromethane and chloroform, and fluorine-based solvents such as chlorofluorocarbon, hydrochlorofluorocarbon, and hydrofluorocarbon.

[0049] The thickness of the optoelectronic transport layer 14 (for example, a light absorption layer, for example, a perovskite layer) is not particularly limited, but from the viewpoint of further suppressing performance deterioration due to defects and peeling, 50 to 1200 nm is preferable, and 200 to 1000 nm is more preferable.

[0050] [Electron transport layer 15] The material used for the electron transport layer 15 is not particularly limited and can be appropriately selected according to the purpose, but a semiconductor material is preferable. The semiconductor material is not particularly limited, and known materials can be used. For example, elemental semiconductors, compound semiconductors, organic n-type semiconductors, etc. can be mentioned.

[0051] The elemental semiconductor is not particularly limited, and examples thereof include silicon, germanium, etc.

[0052] The compound semiconductor is not particularly limited, and examples thereof 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-selenide, copper-indium-sulfide, etc.

[0053] The organic n-type semiconductor is not particularly limited. For example, it can include perylene tetracarboxylic dianhydride, perylene tetracarboxydiimide compound, naphthalenediimide-thiophene copolymer, benzobisimidazole benzophenanthroline polymer, C60, C70, fullerene compounds such as PCBM ([6,6]-phenyl-C61-butyric acid methyl ester), carbonyl bridge-bithiazole compound, Alq3 (tris(8-quinolinolato)aluminum), triphenylene bipyridyl compound, silole compound, oxadiazole compound, and the like.

[0054] Among the aforementioned materials used for the electron transport layer 15, an organic n-type semiconductor is particularly preferred.

[0055] The material used for forming the electron transport layer 15 may be used alone or in combination of two or more. Also, the crystal form of the semiconductor material is not particularly limited and can be appropriately selected according to the purpose, and it may be a single crystal, polycrystal, or amorphous.

[0056] The film thickness of the electron transport layer 15 is not particularly limited and can be appropriately selected according to the purpose, but is preferably 5 nm to 1000 nm, and more preferably 10 nm to 700 nm.

[0057] The method for forming the electron transport layer 15 is not particularly limited and can be appropriately selected according to the purpose. For example, methods for forming a thin film in a vacuum (vacuum film forming method), wet film forming methods, etc. can be mentioned. Examples of the vacuum film forming method include sputtering method, pulsed laser deposition method (PLD method), ion beam sputtering method, ion assist method, ion plating method, vacuum evaporation method, atomic layer deposition method (ALD method), chemical vapor deposition method (CVD method), etc. Examples of the wet film forming method include a method of forming by applying a solvent in which an electron transport material is dissolved, and in the case of an oxide semiconductor, the sol-gel method. The sol-gel method is a method of producing a gel from a solution through chemical reactions such as hydrolysis, polymerization, and condensation, and then promoting densification by heat treatment. When the sol-gel method is used, the method for applying the sol solution is not particularly limited and can be appropriately selected according to the purpose. For example, dip method, spray method, wire bar method, spin coating method, roller coating method, blade coating method, gravure coating method, and as wet printing methods, letterpress, offset, gravure, intaglio, rubber plate, screen printing, etc. can be mentioned. Also, the temperature during the heat treatment after applying the sol solution is preferably 80°C or higher, more preferably 100°C or higher.

[0058] After forming the electron transport layer 15, an electron injection layer (hole blocking layer) may be formed between it and the second electrode 16. Examples of the material used for the electron injection layer include BCP (bathocuproine), and it may be doped with cesium. The electron injection layer is preferably 1 nm to 100 nm, more preferably 3 nm to 20 nm.

[0059] [Second Electrode 16] The second electrode 16 (which may be, for example, a back electrode) is a layer having a function of extracting holes from the photoelectric conversion layer 14 through the electron transport layer. Also, the second electrode 16 is, for example, a layer that acts as a cathode (positive electrode).

[0060] The second electrode 16 may be formed directly on the hole transport layer 15. Further, the material of the second electrode 16 is not particularly limited, and for example, the same material as that of the first electrode 12 can be used. As for the second electrode 16, there are no particular restrictions on its shape, structure, and size, and it can be appropriately selected according to the purpose. Examples of the material of the second electrode 16 include metals, carbon compounds, conductive metal oxides, and conductive polymers.

[0061] Examples of the metal include platinum, gold, silver, copper, aluminum, etc. Examples of the carbon compound include graphite, fullerene, carbon nanotube, graphene, etc. Examples of the conductive metal oxide include ITO, FTO, ATO, etc. Examples of the conductive polymer include polythiophene, polyaniline, etc.

[0062] The material used for forming the second electrode 16 may be used alone, or two or more kinds may be used in combination (mixed) or laminated. The second electrode 16 can be formed by appropriately using methods such as coating, laminating, vacuum evaporation, CVD, bonding, etc. on the electron transport layer 15 according to the type of the material used and the type of the hole transport layer 13.

[0063] In the solar cell of the present invention, it is preferable that at least one of the first electrode 12 and the second electrode 16 is substantially transparent. When using the solar cell of the present invention, it is preferable to make the electrode transparent and allow incident light to enter from the electrode side. In this case, it is preferable to use a material that reflects light for the back electrode (the electrode on the side opposite to the transparent electrode, for example, the second electrode), and metals, glass, plastic, or metal thin films with a deposited conductive oxide are preferably used. Also, providing an antireflection layer on the electrode on the incident light side is an effective means.

[0064] Furthermore, the configuration of the solar cell of the present invention is not limited to the configuration of FIG. 1. For example, the support 11 may be disposed on the side opposite to that of FIG. 1 (the upper side of the second electrode 16 in FIG. 1), and the second electrode 16, the hole transport layer 15, the photoelectric conversion layer 14, the electron transport layer 13, and the first electrode 12 may be laminated in this order on the support 11. Also, for example, as described above, other components may or may not be present between the layers of the support 11, the first electrode 12, the electron transport layer 13, the photoelectric conversion layer 14, the hole transport layer 15, and the second electrode 16. Also, 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 solar cell of the present invention is not limited thereto. For example, in the solar cell of the present invention, conversely, the first electrode may be a back electrode and the second electrode may be a transparent electrode.

[0065] [Sealing] The solar cell of the present invention (for example, a solar cell) is preferably sealed in order to protect the device (the solar cell of the present invention) from water and oxygen. The structure of the seal is not particularly limited, and for example, it may be the same as that of a general solar cell (for example, a solar cell). Specifically, for example, a sealing material may be applied only to the outer peripheral portion of the solar cell of the present invention and covered with glass or a film, or a sealing material may be applied to the entire surface of the solar cell of the present invention and covered with glass or a film, or only a sealing material may be applied to the entire surface of the solar cell of the present invention.

[0066] The material of the sealing member is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferable to use an epoxy resin or an acrylic resin and cure it, but it may not be cured or only a part of it may be cured.

[0067] The epoxy resin is not particularly limited, and examples thereof include a water-dispersion type, a solvent-free type, a solid type, a heat-curing type, a curing agent mixed type, an ultraviolet-curing type, etc. Among these, the heat-curing type and the ultraviolet-curing type are preferable, and the ultraviolet-curing type is more preferable. Note that even in the case of the ultraviolet-curing type, heating is possible, and it is preferable to perform heating even after ultraviolet curing. Specific examples of the epoxy resin include bisphenol A type, bisphenol F type, novolac type, cycloaliphatic type, long-chain aliphatic type, glycidylamine type, glycidyl ether type, glycidyl ester type, etc. These may be used alone or in combination of two or more. Further, it is preferable to mix a curing agent and various additives with the epoxy resin as necessary. Epoxy resin compositions already commercially available can be used in the present invention. Among them, there are also epoxy resin compositions developed and commercially available for use in solar cells and organic EL elements, and they can be particularly effectively used in the present invention. Examples of commercially available epoxy resin compositions include TB3118, TB3114, TB3124, TB3125F (manufactured by Three Bond Co., Ltd.), WorldRock5910, WorldRock5920, WorldRock8723 (manufactured by Kyoritsu Chemical Industry Co., Ltd.), WB90US(P), WB90US-HV (manufactured by Moresco), etc.

[0068] The acrylic resin is not particularly limited, and for example, those developed and commercially available for use in solar cells and organic EL elements can be effectively used. Examples of commercially available acrylic resin compositions include TB3035B, TB3035C (manufactured by Three Bond Co., Ltd.), etc.

[0069] The hardener is not particularly limited and can be appropriately selected according to the purpose. Examples include amine-based, acid anhydride-based, polyamide-based, and other hardeners. Examples of amine-based hardeners include aliphatic polyamines such as diethylenetriamine and triethylenetetramine, and aromatic polyamines such as metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone. Examples of acid anhydride-based hardeners include phthalic anhydride, tetra- and hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, pyromellitic anhydride, het anhydride, and dodecenyl succinic anhydride. Examples of other hardeners include imidazoles and polymercaptans. These can be used alone or in combination of two or more.

[0070] The additive is not particularly limited and can be appropriately selected according to the purpose. Examples include fillers, gap agents, polymerization initiators, desiccants (humidity absorbers), curing accelerators, coupling agents, plasticizers, colorants, flame retardant aids, antioxidants, and organic solvents. Among these, fillers, gap agents, curing accelerators, polymerization initiators, and desiccants (humidity absorbers) are preferred, and fillers and polymerization initiators are more preferred. By containing a filler as an additive, the ingress of moisture and oxygen can be suppressed, and furthermore, effects such as reduction of volume shrinkage during curing, reduction of outgassing amount during curing or heating, improvement of mechanical strength, and control of thermal conductivity and fluidity can be obtained. Therefore, including a filler as an additive is very effective for maintaining stable output in various environments.

[0071] In addition, regarding the output characteristics and durability of a solar cell, not only the influence of invading moisture and oxygen but also the influence of outgassing generated during the curing or heating of the encapsulating member cannot be ignored. In particular, the influence of outgassing generated during heating has a great impact on the output characteristics during storage in a high-temperature environment. By including a filler, a gap filler, and a desiccant in the encapsulating member, these can not only suppress the intrusion of moisture and oxygen themselves, but also reduce the amount of the encapsulating member used, thereby obtaining the effect of reducing outgassing. Including a filler, a gap filler, and a desiccant in the encapsulating member is effective not only during curing but also when storing the solar cell in a high-temperature environment.

[0072] There are no particular restrictions on the filler, and it can be appropriately selected according to the purpose. For example, crystalline or amorphous silica, silicate minerals such as talc, inorganic fillers such as alumina, aluminum nitride, silicon nitride, calcium silicate, and calcium carbonate can be mentioned. Among these, hydrotalcite is particularly preferable. Also, these may be used alone or in combination of two or more.

[0073] 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 preferable range, the effect of suppressing the intrusion of moisture and oxygen can be sufficiently obtained, the viscosity becomes appropriate, the adhesion to the substrate and the defoaming property are improved, and it is also effective for controlling the width of the encapsulating portion and workability.

[0074] 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 with respect to the entire encapsulating member (100 parts by mass). When the content of the filler is within the above preferable range, the effect of suppressing the intrusion of moisture and oxygen can be sufficiently obtained, the viscosity is also appropriate, and the adhesion and workability are also good.

[0075] The gap agent is also referred to as a gap control agent or a spacer agent. By including a gap material as an additive, it becomes possible to control the gap of the sealing portion. For example, when a sealing member is provided on the first substrate or the first electrode and the second substrate is placed thereon for sealing, since the sealing member is mixed with the gap agent, the gap of the sealing portion is aligned with the size of the gap agent, so that the gap of the sealing portion can be easily controlled.

[0076] The gap agent is not particularly limited. For example, those that are granular, have a uniform particle size, and have high solvent resistance and heat resistance are preferable, and can be appropriately selected according to the purpose. As the gap agent, those having high affinity with the epoxy resin and a spherical particle shape are preferable. Specifically, glass beads, silica fine particles, organic resin fine particles, etc. are preferable. These may be used alone or in combination of two or more. The particle size of the gap agent can be selected according to the gap of the sealing portion to be set, but is preferably 1 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less.

[0077] The polymerization initiator is not particularly limited. For example, polymerization initiators that initiate polymerization using heat or light can be mentioned, and can be appropriately selected according to the purpose. For example, thermal polymerization initiators, photoinitiators, etc. can be mentioned. A thermal polymerization initiator is a compound that generates active species such as radicals or cations by heating, and examples include azo compounds such as 2,2'-azobisbutyronitrile (AIBN) and peroxides such as benzoyl peroxide (BPO). As the thermal cationic polymerization initiator, benzenesulfonic acid esters, alkylsulfonium salts, etc. are used. In the case of an epoxy resin, a photo cationic polymerization initiator is preferably used as the photoinitiator. When a photo cationic polymerization initiator is mixed with the epoxy resin and light irradiation is performed, the photo cationic polymerization initiator decomposes to generate an acid, and the acid causes the polymerization of the epoxy resin, and the curing reaction proceeds. The photo cationic polymerization initiator has effects such as less volume shrinkage during curing, no oxygen inhibition, and high storage stability.

[0078] Examples of the photo cationic polymerization initiator include aromatic diazonium salts, aromatic iodonium salts, aromatic sulfonium salts, metacellon compounds, silanol-aluminum complexes, etc. Further, as the polymerization initiator, a photoacid generator having a function of generating an acid by irradiating light can also be used. The photoacid generator acts as an acid that initiates cationic polymerization, and examples thereof include onium salts such as ionic sulfonium salt-based and iodonium salt-based compounds composed of a cationic part and an anionic part. These may be used alone or in combination of two or more.

[0079] The addition amount of the polymerization initiator is not particularly limited and may vary depending on the material used. However, it is preferably 0.5 parts by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 5 parts by mass or less, based on the entire sealing member (100 parts by mass). When the addition amount is within the above preferable range, curing proceeds appropriately, the remaining uncured material can be reduced, and the generation of outgas can be prevented.

[0080] The desiccant (also referred to as a moisture absorbent) is a material having a function of physically or chemically adsorbing and absorbing moisture. By incorporating it into the sealing member, the moisture resistance can be further enhanced and the influence of outgas can be reduced. There is no particular limitation on the desiccant, and it can be appropriately selected according to the purpose. However, those in particulate form are preferred. Examples thereof 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. Among these, zeolite with a large moisture absorption amount is preferred. These may be used alone or in combination of two or more.

[0081] The above-mentioned curing accelerator (also referred to as a curing catalyst) is a material that accelerates the curing rate and is mainly used in thermosetting epoxy resins. There are no particular restrictions on the above-mentioned curing accelerator, and it can be appropriately selected according to the purpose. For example, 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), imidazole-based compounds such as 1-cyanoethyl-2-ethyl-4-methylimidazole and 2-ethyl-4-methylimidazole, phosphines or phosphonium salts such as triphenylphosphine and tetraphenylphosphonium·tetraphenylborate, etc. can be mentioned. These can be used alone or in combination of two or more.

[0082] The above-mentioned coupling agent is not particularly limited as long as it is a material having the effect of enhancing the molecular binding force, and can be appropriately selected according to the purpose. For example, silane coupling agents can be mentioned. Specifically, 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, 3-methacryloxypropyltrimethoxysilane and other silane coupling agents can be mentioned. These can be used alone or in combination of two or more.

[0083] In the present invention, for example, a sheet-like adhesive can be used. The sheet-like adhesive is, for example, one in which a resin layer is previously formed on a sheet, and glass, a film having high gas barrier properties, or the like can be used for the sheet. Also, a sheet may be formed only of a sealing resin. It is also possible to attach the sheet-like adhesive onto a sealing film. It is also possible to form a structure having a hollow portion on the sealing film and then bond it to the device.

[0084] When sealing using the sealing film, it is disposed to face a support so as to sandwich the photoelectric conversion device. Regarding the base material of the sealing film, there are no particular restrictions on its shape, structure, size, and type, and it can be appropriately selected according to the purpose. The sealing film has a barrier layer formed on the surface of the base material to prevent the passage of moisture and oxygen, and it may be formed on only one surface or both surfaces of the base material.

[0085] The barrier layer may be composed of a material mainly composed of, for example, a metal oxide, a metal, a mixture formed from a polymer and a metal alkoxide, or the like. Examples of the metal oxide include aluminum oxide, silicon oxide, aluminum, and the like. Examples of the polymer include polyvinyl alcohol, polyvinyl pyrrolidone, methyl cellulose, and the like. Examples of the metal alkoxide include tetraethoxysilane, triisopropoxyaluminum, 3-glycidoxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and the like.

[0086] The barrier layer may be, for example, transparent or opaque. Also, the barrier layer may be a single layer formed by a combination of the above materials or a plurality of laminated structures. As a method for forming the barrier layer, a known method can be used, and vacuum film formation methods such as sputtering, and coating methods such as dipping, roll coating, screen printing, spraying, and gravure printing can be used.

[0087] [Wiring] In order to efficiently extract the current generated by light, it is preferable to connect lead wires (wiring) to the front electrode and the back electrode of the solar cell (for example, a solar cell) of the present invention. The lead wires are connected to the first electrode and the second electrode using a conductive material such as solder, silver paste, or graphite, for example. The conductive material may be used alone or in a mixture or laminated structure of two or more kinds. Also, the portion where the lead wire is attached may be covered with an acrylic resin or an epoxy resin from the viewpoint of physical protection.

[0088] A lead wire is a general term for electric wires for electrically connecting power sources, electronic components, etc. in an electric circuit, and examples thereof include vinyl wires and enameled wires.

[0089] [Application] The use and usage method of the solar cell of the present invention are not particularly limited, and for example, it can be widely used for the same uses as general solar cells (for example, general solar cells). The solar cell (for example, a solar cell) of the present invention can be applied to a power supply device by combining it with a circuit board that controls the generated current, for example. Examples of devices using the power supply device include electronic desktop calculators and solar radio watches. In addition, it is also possible to apply the solar cell of the present invention as a power supply device to mobile phones, electronic paper, thermohygrometers, etc. Further, it can be applied as an auxiliary power source for extending the continuous use time of rechargeable or dry battery-powered electrical appliances, or for night use by combining it with a secondary battery. It can also be used as a self-sufficient power source that does not require battery replacement or power wiring.

Example

[0090] Hereinafter, examples of the present invention will be described. However, the present invention is not limited to the following examples.

[0091] [Example 1] A solar cell, which is a solar cell of the present invention, was fabricated (manufactured) as follows.

[0092] The compound represented by the following (B-1) and the compound represented by the following (B-2) were dissolved in toluene (0.5 mM) at a ratio of 2:3, and 100 μL was placed on the ITO of an ITO glass substrate (a glass substrate serving as a support with a first electrode formed thereon). An organic film was formed on the ITO using a spin coater (3,000 rpm, 30 seconds). This film was heated at 120 °C for 10 minutes to form a hole transport layer. Next, a solution prepared by dissolving cesium iodide (0.738 g), formamidinium iodide (7.512 g), methylammonium bromide (0.905 g), lead iodide (23.888 g), and lead bromide (1.022 g) in DMF (40.0 mL) and dimethyl sulfoxide (DMSO, 12.0 mL) was formed into a film on the above substrate using spin coating. Spin coating was performed at 3,000 rpm, and chlorobenzene (0.3 mL) was dropped 30 seconds after the start. Then, it was heated at 150 °C for 10 minutes to obtain a perovskite layer (photoelectric conversion layer). Subsequently, ethylenediamine dihydroiodide was 0.5 nm (interface layer), C60 was 20 nm (electron transport layer), bathocuproine (BCP, 8 nm) (electron injection layer), and Ag (100 nm) (second electrode) were formed into films by vacuum evaporation to fabricate a solar cell.

[0093] [Chemical formula]

[0094] [Evaluation of solar cell characteristics] The photoelectric conversion characteristics of the upper solar cell alone, the lower solar cell alone, and the tandem solar cell fabricated in Example 1 were measured by a method conforming to the output measurement method of silicon crystalline solar cells in JIS C8913:1998. The results are shown in Table 1. A solar simulator (SMO-250III type manufactured by Spectral Instruments Co., Ltd.) combined with an air mass filter equivalent to AM1.5G was used, and a secondary reference Si solar cell was used to measure 100 mW / cm 2Adjust the light quantity to be used as a measurement light source, and while irradiating light on a test sample (sealed device fabricated in Example 1) of a perovskite solar cell, measure the I-V curve characteristics using a source meter (model 2400 universal source meter manufactured by Keithley Instruments Inc.), and determine the short-circuit current (Isc), open-circuit voltage (Voc), fill factor (FF), short-circuit current density (Jsc), and photoelectric conversion efficiency (PCE) obtained from the measurement of the I-V curve characteristics.

[0095] Equation 1: Short-circuit current density (Jsc; mA / cm 2 ) = Isc (mA) / effective light-receiving area S (cm 2 ) Equation 2: Photoelectric conversion efficiency (PCE; %) = Voc (V) × Jsc (mA / cm 2 ) × FF × 100 / 100 (mW / cm 2 )

[0096] [Example 2] A solar cell of Example 2 was fabricated and evaluated in the same manner as in Example 1, except that B-2 in Example 1 was changed to the following B-3. The results of the solar cell characteristics are shown in Table 1 below.

[0097]

Chemical formula

[0098] [Example 3] A solar cell of Example 2 was fabricated and evaluated in the same manner as in Example 1, except that B-2 in Example 1 was changed to the following B-4. The results of the solar cell characteristics are shown in Table 1 below.

[0099]

Chemical formula

[0100] [Example 4] The compound represented by the following (B-5) was dissolved in N,N-dimethylformamide (0.1 mM), 100 μL was placed on the ITO of an ITO glass substrate, left standing for 1 minute, and then an organic film was formed on the ITO using a spin coater (3,000 rpm, 30 seconds). Next, the compound represented by the following (B-2) was dissolved in toluene (0.5 mM), 100 μL was placed on the previously formed organic film, and after using a spin coater (3,000 rpm, 30 seconds), it was heated at 120 °C for 10 minutes to form a hole transport layer. Next, a solution prepared by dissolving cesium iodide (0.738 g), formamidinium iodide (7.512 g), methylamine bromide (0.905 g), lead iodide (23.888 g), and lead bromide (1.022 g) in DMF (40.0 mL) and dimethyl sulfoxide (DMSO, 12.0 mL) was formed into a film on the above substrate using spin coating. Spin coating was performed at 3,000 rpm, and chlorobenzene (0.3 mL) was dropped 30 seconds after the start. Thereafter, it was heated at 150 °C for 10 minutes to obtain a perovskite layer (photoelectric conversion layer). Next, ethylenediamine dihydroiodide was 0.5 nm (interface layer), C60 was 20 nm (electron transport layer), bathocuproine (BCP, 8 nm) (electron injection layer), and Ag (100 nm) (second electrode) were formed into films by vacuum evaporation to fabricate a solar cell.

[0101] [Chemical formula]

[0102] [Comparative Example 1] A solar cell was fabricated and evaluated in the same manner as in Example 1, except that the (B-1) in Example 1 was changed to triphenylamine. The results of the solar cell characteristics are shown in Table 1 below.

[0103] [Comparative Example 2] A solar cell was fabricated and evaluated in the same manner as in Example 1, except that the (B-2) in Example 1 was changed to diphenyl sulfide. The results of the solar cell characteristics are shown in Table 1 below.

[0104] [Comparative Example 3] The solar cell of Example 4 was fabricated and evaluated in the same manner as in Example 4, except that the above (B-5) in Example 4 was changed to the compound shown below (ref-1: reference - 1). The results of the solar cell characteristics are shown in Table 1 below.

[0105]

Chemical formula

[0106]

Table 1

[0107] As described above, it was confirmed by this example that good solar cell characteristics can be obtained by using the configuration of the solar cell of the present invention.

[0108] The present invention has been described above using embodiments and examples. However, the present invention 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 invention.

Industrial Applicability

[0109] As described above, according to the present invention, a solar cell exhibiting excellent photoelectric conversion characteristics can be provided. The solar cell of the present invention is useful, for example, as a solar cell. The applications and usage methods of the solar cell of the present invention are not particularly limited, and can be applied to a wide range of fields in the same applications and usage methods as general solar cells (for example, general solar cells).

Explanation of Reference Numerals

[0110] 11 Support 12 First Electrode 13 Hole Transport Layer 14 Photoelectric Conversion Layer 15 Electron Transport Layer 16 Second Electrode

Claims

1. A solar cell comprising a first electrode, a hole transport layer, a photoelectric conversion layer, and a second electrode in this order, wherein the hole transport layer contains a hole transport material which is a polymer having a number average molecular weight of 1,000 or more and 1,000,000 or less and having a linking group represented by the following general formula (I). -CH=CH-S-... (I)

2. The solar cell according to Claim 1, wherein the first electrode is a transparent electrode containing a metal oxide.

3. The solar cell according to Claim 1, wherein the hole transport material contains a copolymer of a compound represented by the following general formula (II) and a compound represented by the following general formula (III). 【Chemical 1】 (In general formula (II), A represents an aliphatic hydrocarbon, an aromatic hydrocarbon, or a heterocycle which may have a substituent, and n represents an integer of 2 or more.) 【Chemical Formula 2】 (In general formula (III), B represents an aliphatic hydrocarbon, an aromatic hydrocarbon, or a heterocycle which may have a substituent, and m represents an integer of 2 or more.)

4. The solar cell according to Claim 2, wherein the hole transport material is covalently bonded to the transparent electrode.

5. The solar cell according to Claim 2, wherein the hole transport material has a substituent of the hole transport material which is any one of a phosphonic acid group, a carboxy group, a sulfo group, a boronic acid group, a trihalogenated silyl group, and a trialkoxysilyl group, and is covalently bonded to the transparent electrode by the substituent of the hole transport material.

6. The solar cell according to any one of Claims 1 to 5, wherein the photoelectric conversion layer contains a compound containing a perovskite structure.

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