Compound, hole transport material, and photoelectric conversion element using the same

Abstract

To provide a compound useful as a hole transport material for a photoelectric converter that allows an electric current to be efficiently taken out, and a photoelectric converter and a solar battery that employ the compound in a hole transport layer thereby inhibiting decline in photoelectric conversion characteristics and exhibiting high durability.SOLUTION: The compound is represented by the general formula (1) in the figure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a compound, a hole transport material, and a photoelectric conversion element using the same. [Background technology]

[0002] In recent years, solar power generation has attracted attention as a clean energy source, and the development of solar cells has been actively pursued. Among these, the development of solar cells using perovskite materials in the photoelectric conversion layer (hereinafter referred to as perovskite solar cells) has attracted attention as a next-generation solar cell that can be manufactured at low cost using a solution process (e.g., Patent Document 1, Non-Patent Documents 1 and 2).

[0003] Perovskite solar cells often use hole transport materials in their devices. The purposes of these materials include (1) enhancing the ability to selectively transport holes and thereby improving photoelectric conversion efficiency, and (2) protecting the perovskite material, which is susceptible to moisture and oxygen, by bonding with the perovskite photoelectric conversion layer (e.g., Non-Patent Document 3). Spiro-OMeTAD, a spirobifluorene-based organic compound, is often used as a standard hole transport material, but there have been few reports of hole transport materials that contribute more significantly to photoelectric conversion properties than this material. Furthermore, photoelectric conversion elements and solar cells using Spiro-OMeTAD as a hole transport material are known to have a problem in that their photoelectric conversion properties deteriorate over time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2017 / 104792 [Non-patent literature]

[0005] [Non-Patent Document 1] Journal of the American Chemical Society, 2009, Vol. 131, pp. 6050-6051 [Non-patent document 2] Science, 2012, Vol. 388, P. 643-647 [Non-patent document 3] Chem. Sci.,2019,10,P.6748-6769 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a compound useful as a hole transport material for a photoelectric conversion element that can extract current efficiently, and to provide a photoelectric conversion element and a solar cell that have high durability and that suppress deterioration of photoelectric conversion characteristics by using the compound in a hole transport layer. [Means for solving the problem]

[0007] In order to solve the above problems, the inventors conducted extensive research into improving photoelectric conversion properties and discovered that by designing and developing a compound having a specific structure and using the compound as a hole transport layer in a photoelectric conversion element, a photoelectric conversion element and a perovskite solar cell exhibiting high photoelectric conversion efficiency can be obtained.

[0008] 1. A compound represented by the following general formula (1):

[0009] [ka]

[0010] [In the formula, R 1 ~R 4 are each independently hydrogen atoms, a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent; a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent; a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent; a substituted aromatic hydrocarbon group having 6 to 36 carbon atoms; or a heterocyclic group having 5 to 36 ring atoms which may have a substituent, R 1 and R 2 , R 3 and R 4 Adjacent groups may be bonded to each other to form a ring. 1 and X 2 represents a divalent group, and X 1 and R 1 or R 2 may be bonded to form a ring, and X 2 and R 3 or R 4 may be bonded to form a ring.

[0011] 2. In the general formula (1), X 1 and X 2 A compound represented by the following general formula (2):

[0012] [ka]

[0013] [In the formula, R 5 ~R 9 are each independently hydrogen atoms, a linear or branched alkyl group having 1 to 10 carbon atoms which may have a substituent; a linear or branched alkenyl group having 2 to 10 carbon atoms which may have a substituent; a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent; an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent; or an optionally substituted heterocyclic group having 5 to 18 ring atoms, R 5 and R 6 and R 7 and R 8 may be bonded to each other to form a ring. Y represents an oxygen atom, a sulfur atom, or a selenium atom; Z represents CR 10 or a nitrogen atom, R 10 is a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms which may have a substituent; a linear or branched alkenyl group having 2 to 10 carbon atoms which may have a substituent; a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent; an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent; or an optionally substituted heterocyclic group having 5 to 18 ring atoms, R 9 and R 10 may be bonded to each other to form a ring. m and n represent integers of 0 to 2, provided that either m or n is 1 or 2.]

[0014] 3. In the general formula (1), R 1 ~R 4 is a compound which is a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 36 carbon atoms which has a substituent.

[0015] 4. A hole transport material represented by the compound described above.

[0016] 5. A photoelectric conversion element using the hole transport material described above. [Effects of the Invention]

[0017] By using the compound according to the present invention and a hole transport layer using the compound, it is possible to obtain a photoelectric conversion element and a perovskite solar cell having good photoelectric conversion efficiency. [Brief explanation of the drawings]

[0018] [Figure 1] 1A and 1B are schematic cross-sectional views illustrating the configurations of photoelectric conversion elements according to examples of the present invention and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the preferred embodiments thereof. The compound of the present invention is used as a hole transport material in a photoelectric conversion element and a perovskite-type photoelectric conversion element.

[0020] <Photoelectric conversion element> The photoelectric conversion element of the present invention typically has a conductive support 1, an electron transport layer 2, a photoelectric conversion layer 3, a hole transport layer 4, and a counter electrode 5, as shown in the schematic cross-sectional view of FIG.

[0021] The compounds of the present invention represented by the general formula (1) will be specifically explained below, but the present invention is not limited thereto.

[0022] A compound represented by general formula (1), R 1 ~R 4 are each independently hydrogen atoms, a linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent; a linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent; a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent; a substituted aromatic hydrocarbon group having 6 to 36 carbon atoms; Or it represents a heterocyclic group having 5 to 36 ring atoms which may have a substituent.

[0023] In general formula (1), R 1 ~R 4Specific examples of the "straight-chain or branched alkyl group having 1 to 20 carbon atoms" in the "straight-chain or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by the formula (1) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, an isooctyl group, a nonyl group, and a decyl group.

[0024] In general formula (1), R 1 ~R 4 Specific examples of the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms" in the "straight-chain or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent" represented by the formula (1) include ethenyl group (vinyl group), 1-propenyl group, 2-propenyl group (allyl group), 1-methylethenyl group, 1-butenyl group, 2-butenyl group, 1-pentenyl group, 1-hexenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-ethylethenyl group, and straight-chain or branched alkenyl groups having 2 to 20 carbon atoms in which a plurality of these alkenyl groups are bonded.

[0025] In general formula (1), R 1 ~R 4 Specific examples of the "cycloalkyl group having 3 to 10 carbon atoms" in the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by the formula (1) include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecyl group, a cyclododecyl group, a 4-methylcyclohexyl group, and a 4-ethylcyclohexyl group.

[0026] In general formula (1), R 1 ~R 4Specific examples of the "aromatic hydrocarbon group having 6 to 36 carbon atoms" in the "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" represented by the formula (1) include a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a biphenyl group, an anthracenyl group (anthryl group), a phenanthryl group, a fluorenyl group, an indenyl group, a pyrenyl group, a perylenyl group, a fluoranthenyl group, a triphenylenyl group, etc. In the present invention, the aromatic hydrocarbon group includes a "condensed polycyclic aromatic group".

[0027] In general formula (1), R 1 ~R 4 Specific examples of the "heterocyclic group having 5 to 36 ring atoms" in the "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by the formula (I) include a pyridyl group, a pyrimidinyl group, a triazinyl group, a thienyl group, a furyl group (furanyl group), a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a triazolyl group, a quinolyl group, an isoquinolyl group, a naphthyldinyl group, an acridinyl group, a phenanthrolinyl group, a benzofuranyl group, a benzothienyl group, an oxazolyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a thiazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, and a carbonyl group.

[0028] In general formula (1), R 1 ~R 4 Examples of the "substituent" in the "optionally substituted linear or branched alkyl group of 1 to 18 carbon atoms," "optionally substituted linear or branched alkenyl group of 2 to 20 carbon atoms," "optionally substituted cycloalkyl group of 3 to 10 carbon atoms," "optionally substituted aromatic hydrocarbon group of 6 to 36 carbon atoms," or "optionally substituted heterocyclic group of 5 to 36 ring atoms" represented by the above formula (I) specifically include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a cyano group; a hydroxyl group; a nitro group; a nitroso group; a carboxyl group; a phosphate group; a thioxo group (>C=S); a trimethylsilyl group; Carboxylic acid ester groups such as methyl ester groups and ethyl ester groups; linear or branched alkyl groups having 1 to 18 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, n-hexyl, 2-ethylhexyl, heptyl, octyl, isooctyl, nonyl, and decyl; linear or branched alkenyl groups having 2 to 18 carbon atoms, such as ethenyl (vinyl), 1-propenyl, 2-propenyl (allyl), 1-butenyl, 2-butenyl, 1-pentenyl, 1-hexenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl, and 1-ethylethenyl; Alkoxy groups having 1 to 18 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, a t-butoxy group, a pentyloxy group, or a hexyloxy group; Aromatic hydrocarbon groups having 6 to 30 carbon atoms, such as phenyl, naphthyl, anthryl, phenanthryl, and pyrenyl groups; heterocyclic groups having 5 to 30 ring atoms, such as a pyridyl group, a pyrimidinyl group, a triazinyl group, a thienyl group, a furyl group (a furanyl group), a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a triazolyl group, a quinolyl group, an isoquinolyl group, a naphthyldinyl group, an acridinyl group, a phenanthrolinyl group, a benzofuranyl group, a benzothienyl group, an oxazolyl group, an indolyl group, a carbazolyl group, a benzoxazolyl group, a thiazolyl group, a benzothiazolyl group, a quinoxalinyl group, a benzimidazolyl group, a pyrazolyl group, a dibenzofuranyl group, a dibenzothienyl group, or a carbonylyl group; an amino group having 0 to 18 carbon atoms, which may be an unsubstituted amino group (-NH2), a monosubstituted amino group such as an ethylamino group, an acetylamino group, or a phenylamino group, or a disubstituted amino group such as a diethylamino group, a diphenylamino group, or an acetylphenylamino group; Thio groups having 0 to 18 carbon atoms, such as unsubstituted thio groups (thiol groups: —SH), methylthio groups, ethylthio groups, propylthio groups, phenylthio groups, and biphenylthio groups; These "substituents" may be contained in only one or in multiple numbers, and when multiple "substituents" are contained, they may be the same or different. Furthermore, these "substituents" may further have the substituents exemplified above.

[0029] In general formula (1), R 1 ~R 4 is preferably a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 36 carbon atoms which has a substituent.

[0030] In general formula (1), R 1 and R 2 , R 3 and R 4 Adjacent groups may be bonded to each other via a single bond, an oxygen atom, a sulfur atom, a selenium atom, or a nitrogen atom to form a ring. 1 and R 2 , R 3 and R 4 When forming a ring, it is preferably a single bond, an oxygen atom, or a sulfur atom.

[0031] In general formula (1), X 1 and X 2 represents a divalent group. X 1 and R 1 or R 2 , and X 2 and R 3 or R 4 may be bonded to each other via a single bond, an oxygen atom, a sulfur atom, a selenium atom or a nitrogen atom to form a ring, and when a ring is formed, it is preferably a single bond.

[0032] In general formula (1), X 1 and X 2 is preferably a divalent group represented by the general formula (2).

[0033] In general formula (2), R 5 ~R 9 are each independently hydrogen atoms, a linear or branched alkyl group having 1 to 10 carbon atoms which may have a substituent; a linear or branched alkenyl group having 2 to 10 carbon atoms which may have a substituent; a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent; an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent; Alternatively, it represents a heterocyclic group having 5 to 18 ring atoms which may have a substituent.

[0034] In general formula (2), R 5 ~R 9 In the "straight-chain or branched alkyl group having 1 to 10 carbon atoms which may have a substituent," the "straight-chain or branched alkyl group having 1 to 10 carbon atoms" represented by the formula (1) includes, for example, 1 ~R 4 Among the "straight-chain or branched alkyl groups having 1 to 20 carbon atoms which may have a substituent" represented by the above formula, the same as the "straight-chain or branched alkyl groups having 1 to 10 carbon atoms" can be mentioned.

[0035] In general formula (2), R 5 ~R 9 The "straight-chain or branched alkenyl group having 2 to 10 carbon atoms" in the "straight-chain or branched alkenyl group having 2 to 10 carbon atoms which may have a substituent" represented by the formula (1) includes, for example, 1 ~R 4 Among the "straight-chain or branched alkenyl groups having 2 to 20 carbon atoms which may have a substituent" represented by the following formula, the same as the "straight-chain or branched alkenyl groups having 2 to 10 carbon atoms" can be mentioned.

[0036] In general formula (2), R 5 ~R 9 In the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by the general formula (1), the "cycloalkyl group having 3 to 10 carbon atoms" is represented by the general formula (1),1 ~R 4 Examples of the cycloalkyl group include the same as the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by the following formula:

[0037] In general formula (2), R 5 ~R 9 In the "aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent" represented by the formula (1), the "aromatic hydrocarbon group having 6 to 18 carbon atoms" is represented by the formula (1), 1 ~R 4 Among the "aromatic hydrocarbon groups having 6 to 36 carbon atoms which may have a substituent" represented by the following formula, the same as the "aromatic hydrocarbon groups having 6 to 18 carbon atoms" can be mentioned.

[0038] In general formula (2), R 5 ~R 9 In the "heterocyclic group having 5 to 18 ring atoms which may have a substituent" represented by the formula (1), the "heterocyclic group having 5 to 18 ring atoms" is represented by the formula (1), 1 ~R 4 Among the "heterocyclic group having 5 to 36 ring atoms which may have a substituent" represented by the following formula, the same as the "heterocyclic group having 5 to 18 ring atoms" can be mentioned.

[0039] In general formula (2), R 5 ~R 9 Examples of the "substituent" in the "straight-chain or branched alkyl group having 1 to 10 carbon atoms which may have a substituent", "straight-chain or branched alkenyl group having 2 to 10 carbon atoms which may have a substituent", "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent", "aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent" or "heterocyclic group having 5 to 18 ring atoms which may have a substituent" represented by the formula (1) include R 1 ~R 4Examples of the "substituent" in the "straight-chain or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by the following formula (1) include the same ones as those in the range of the number of carbon atoms and the number of ring atoms.

[0040] In general formula (2), R 5 and R 6 and R 7 and R 8 may be bonded to each other via a single bond, an oxygen atom, a sulfur atom, a selenium atom, or a nitrogen atom to form a ring.

[0041] In the general formula (2), Y represents an oxygen atom, a sulfur atom, or a selenium atom, and Z represents CR 10 or a nitrogen atom.

[0042] R 10 is a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms which may have a substituent; a linear or branched alkenyl group having 2 to 10 carbon atoms which may have a substituent; a cycloalkyl group having 3 to 10 carbon atoms which may have a substituent; an aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent; Alternatively, it represents a heterocyclic group having 5 to 18 ring atoms which may have a substituent.

[0043] In general formula (2), R 10 In the "straight-chain or branched alkyl group having 1 to 10 carbon atoms which may have a substituent" represented by the formula (2), the "straight-chain or branched alkyl group having 1 to 10 carbon atoms" is, for example, 5 ~R 9 Among the "straight-chain or branched alkyl groups having 1 to 20 carbon atoms which may have a substituent" represented by the above formula, the same as the "straight-chain or branched alkyl groups having 1 to 10 carbon atoms" can be mentioned.

[0044] In general formula (2), R10 The "straight-chain or branched alkenyl group having 2 to 10 carbon atoms" in the "straight-chain or branched alkenyl group having 2 to 10 carbon atoms which may have a substituent" represented by the general formula (2) includes, for example, 5 ~R 9 Examples of the alkyl group include the same as the "straight or branched alkenyl group having 2 to 10 carbon atoms which may have a substituent" represented by the following formula:

[0045] In general formula (2), R 10 In the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by the general formula (2), the "cycloalkyl group having 3 to 10 carbon atoms" is represented by the general formula (2), 5 ~R 9 Examples of the cycloalkyl group include the same as the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by the following formula:

[0046] In general formula (2), R 10 In the "aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent" represented by the general formula (2), the "aromatic hydrocarbon group having 6 to 18 carbon atoms" is represented by the general formula (2), 5 ~R 9 Examples of the aromatic hydrocarbon group include the same as the "optionally substituted aromatic hydrocarbon group having 6 to 18 carbon atoms" represented by the following formula:

[0047] In general formula (2), R 10 In the "heterocyclic group having 5 to 18 ring atoms which may have a substituent" represented by the general formula (2), the "heterocyclic group having 5 to 18 ring atoms" represented by the general formula (2) is R 5 ~R 9 Examples of the heterocyclic group include the same as the "heterocyclic group having 5 to 18 ring atoms which may have a substituent" represented by the following formula:

[0048] In general formula (2), R 10Examples of the "substituent" in the "straight-chain or branched alkyl group having 1 to 10 carbon atoms which may have a substituent", "straight-chain or branched alkenyl group having 2 to 10 carbon atoms which may have a substituent", "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent", "aromatic hydrocarbon group having 6 to 18 carbon atoms which may have a substituent" or "heterocyclic group having 5 to 18 ring atoms which may have a substituent" represented by the formula (1) include R 1 ~R 4 Examples of the "substituent" in the "straight-chain or branched alkyl group having 1 to 18 carbon atoms which may have a substituent" represented by the following formula (1) include the same ones as those in the range of the number of carbon atoms and the number of ring atoms.

[0049] In general formula (2), R 9 and R 10 may be bonded to each other via a single bond, an oxygen atom, a sulfur atom, a selenium atom, or a nitrogen atom to form a ring.

[0050] In general formula (2), m and n represent integers of 0 to 2; when m is 0, n is 1 or 2; when n is 0, m is 1 or 2; and when either m or n is 1 or more, both being 0 are excluded. m is preferably 1. In addition, the thiazolothiazole ring, which is the central skeleton of general formula (1), may be bonded to either the phenyl group or the 5-membered heterocyclic group represented by general formula (2).

[0051] Specific examples of the compound represented by the general formula (1) of the present invention are shown below, but the present invention is not limited to these. Furthermore, the following exemplary compounds are shown with some hydrogen atoms, carbon atoms, etc. omitted, and are examples of possible isomers, but all other isomers are included. Furthermore, each may be a mixture of two or more isomers.

[0052] [ka]

[0053]

change

[0054]

change

[0055]

change

[0056]

change

[0057]

change

[0058]

change

[0059]

change

[0060]

change

[0061]

change

[0062]

change

[0063]

change

[0064]

change

[0065]

change

[0066]

change

[0067]

change

[0068]

change

[0069]

change

[0070]

change

[0071]

change

[0072]

change

[0073]

change

[0074] The compound of the present invention represented by the general formula (1) can be synthesized by known methods.

[0075] For example, compound (A-2) of the present invention can be synthesized by Suzuki-Miyaura cross-coupling reaction between a compound represented by the following formula (3) and a boronic acid compound represented by the following general formulas (4) and (5) or a boronic ester compound represented by the following general formulas (6) and (7).

[0076] [ka]

[0077] [ka]

[0078] [ka]

[0079] The compound of the present invention represented by the general formula (1) can be purified by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization using a solvent, etc. Alternatively, it is effective to use a compound with increased purity by combining these methods. Furthermore, these compounds can be identified by nuclear magnetic resonance analysis (NMR).

[0080] The compound of the present invention represented by the general formula (1) can be used as a hole transport material contained in a hole transport layer for organic electronic devices such as photoelectric conversion elements and organic EL elements.

[0081] Preferred embodiments of the photoelectric conversion element of the present invention will be described below.

[0082] As shown in FIG. 1, the photoelectric conversion element of the present invention preferably comprises a conductive support 1, an electron transport layer 2, a photoelectric conversion layer 3, a hole transport layer 4, and a counter electrode 5, but is not limited thereto. Furthermore, the photoelectric conversion element of the present invention is preferably used as a solar cell, and is more preferably a perovskite-type photoelectric conversion element, but is not limited thereto. In the present invention, the perovskite-type photoelectric conversion element preferably comprises a conductive support (electrode) 1, an electron transport layer 2, a photoelectric conversion layer (perovskite layer) 3, a hole transport layer 4, and a counter electrode 5, in this order. Alternatively, the photoelectric conversion element may be configured in the order of a conductive support, a hole transport layer, a photoelectric conversion layer (perovskite layer), an electron transport layer, and a counter electrode.

[0083] <Conductive Support> In the photoelectric conversion element of the present invention, the conductive support 1 shown in FIG. 1 must be translucent enough to transmit light that contributes to photoelectric conversion. Furthermore, since the conductive support is a member that functions to extract current from the photoelectric conversion layer, it is preferably a conductive substrate. Specific examples of conductive materials include conductive transparent oxide semiconductors such as tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), tungsten-doped indium oxide (IWO), zinc-aluminum oxide (AZO), fluorine-doped tin oxide (FTO), indium oxide (In2O3), and indium-tin composite oxide. However, tin-doped indium oxide (ITO) and fluorine-doped tin oxide (FTO) are preferred.

[0084] <Electron transport layer> In the photoelectric conversion element of the present invention, the electron transport layer 2 shown in Fig. 1 is a layer located between the conductive support 1 and the photoelectric conversion layer (perovskite layer) 3, and is preferably, but not particularly limited to, formed on the conductive support 1. The electron transport layer is used to improve the efficiency of electron transfer from the photoelectric conversion layer to the electrode and to block the transfer of holes.

[0085] In the present invention, specific examples of the semiconductor that forms the electron transport layer include metal oxides such as tin oxide (SnO, SnO2, SnO3, etc.), titanium oxide (TiO2, etc.), tungsten oxide (WO2, WO3, W2O3, etc.), zinc oxide (ZnO), niobium oxide (Nb2O5, etc.), tantalum oxide (Ta2O5, etc.), yttrium oxide (YO3, etc.), and strontium titanate (SrTiO3, etc.); metal sulfides such as titanium sulfide, zinc sulfide, zirconium sulfide, copper sulfide, tin sulfide, indium sulfide, tungsten sulfide, cadmium sulfide, and silver sulfide; metal selenides such as titanium selenide, zirconium selenide, indium selenide, and tungsten selenide; and elemental semiconductors such as silicon and germanium. It is preferable to use one or more of these semiconductors. In the present invention, it is preferable to use one or more semiconductors selected from tin oxide, titanium oxide, and zinc oxide.

[0086] In the present invention, the paste containing the semiconductor fine particles may be a commercially available product, or a paste (electron transport layer coating liquid) prepared by dispersing commercially available semiconductor fine powder in a solvent may be used. Specific examples of solvents used in preparing the paste include, but are not limited to, water; alcoholic solvents such as methanol, ethanol, and isopropyl alcohol; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and hydrocarbon solvents such as n-hexane, cyclohexane, benzene, and toluene. These solvents may be used alone or in combination.

[0087] In the present invention, the semiconductor fine powder may be dispersed in a solvent after grinding the powder in a mortar or the like, or a dispersing machine such as a ball mill, a paint conditioner, a vertical bead mill, a horizontal bead mill, or an attritor may be used. When preparing a paste, it is preferable to add a surfactant or the like to prevent aggregation of the semiconductor fine particles, and it is also preferable to add a thickener such as polyethylene glycol to increase the viscosity.

[0088] In the present invention, the electron transport layer can be obtained using a known film-forming method depending on the material to be formed. The electron transport layer can be formed by any coating method using a coating liquid. Examples of the method include, but are not limited to, a wet coating method such as spin coating, inkjet printing, doctor blade printing, drop casting, squeegee printing, screen printing, reverse roll coating, gravure coating, kiss coating, roll brushing, spray coating, air knife coating, wire barber coating, pipe doctor printing, impregnation coating, or curtain coating, followed by baking to remove solvents and additives to form a film; sputtering, vapor deposition, electrodeposition, electrodeposition, and microwave irradiation. In the present invention, it is preferable to form a film by spin coating using the electron transport layer coating liquid prepared by the above method, but this is not limiting. The spin coating conditions can be appropriately set. The atmosphere in which the film is formed is not particularly limited, and the film may be formed in air.

[0089] When a dense electron transport layer is used, the thickness of the electron transport layer is preferably 5 nm to 100 nm, more preferably 10 nm to 50 nm, from the viewpoint of further improving photoelectric conversion efficiency. In the present invention, when a porous (mesoporous) metal oxide is used in addition to the dense layer, the thickness is preferably 20 to 200 nm, more preferably 50 to 150 nm.

[0090] <Photoelectric conversion layer> In the photoelectric conversion element of the present invention, a photoelectric conversion layer (perovskite layer) 3 is preferably formed on the electron transport layer 2 shown in FIG.

[0091] In the present invention, when used as a perovskite photoelectric conversion element, the perovskite material of the photoelectric conversion layer represents a series of materials having a structure represented by the general formula ABX3, where A, B, and X represent an organic cation or a monovalent metal cation, a metal cation, and a halide anion, respectively. For example, A=K+ , Rb + , Cs + , CH3NH3 + (hereinafter, MA: methylammonium), NH=CHNH2 + (hereinafter FA: formamidinium), CH3CH2NH3 + (hereinafter, EA: ethylammonium; B = Pb, Sn; X = I) - , Br - Examples of suitable perovskite materials include, but are not limited to, perovskite materials having any of the following compositions: MAPbI3, FAPbI3, EAPbI3, CsPbI3, MASnI3, FASnI3, EASnI3, MAPbBr3, FAPbBr3, EAPbBr3, MASnBr3, FASnBr3, and EASnBr3; and mixed-cation, mixed-anion perovskite materials having any of the following compositions: FAMA)Pb(IBr)3, K(FAMA)Pb(IBr)3, Rb(FAMA)Pb(IBr)3, and Cs(FAMA)Pb(IBr)3. It is preferable to use one or more of these perovskite materials. Furthermore, the perovskite material may contain a light-absorbing agent other than the perovskite material.

[0092] Any coating method can be used to coat the photoelectric conversion layer (perovskite layer) of the photoelectric conversion element of the present invention with a coating liquid, and examples thereof include the same methods as those used to form the electron transport layer.

[0093] The perovskite precursor may be a commercially available material, and in the present invention, it is preferable to use a precursor consisting of lead halide, methylammonium halide, formamidine halide, or cesium halide in any composition, but the present invention is not limited to this.

[0094] From the viewpoint of precursor solubility, examples of the solvent for the perovskite precursor solution of the present invention include, but are not limited to, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone, etc. Furthermore, these solvents may be used alone or in combination of two or more, and it is preferable to use a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide.

[0095] In the present invention, the atmosphere during deposition of the photoelectric conversion layer (perovskite layer) is preferably a dry atmosphere, more preferably a dry inert gas atmosphere such as a glove box, because preventing moisture contamination allows for the reproducible production of highly efficient perovskite solar cells. It is also preferable to use a solvent with a low moisture content after dehydration using a molecular sieve or the like.

[0096] In the present invention, the temperature at which the photoelectric conversion layer (perovskite layer) is heated using a hot plate or the like is preferably 50 to 200° C., more preferably 70 to 150° C., from the viewpoint of producing a perovskite material from the precursor. The heating time is preferably about 10 to 90 minutes, more preferably about 10 to 60 minutes.

[0097] The film thickness of the photoelectric conversion layer (perovskite layer) of the present invention is preferably 50 to 1000 nm, more preferably 300 to 700 nm, from the viewpoint of further suppressing performance degradation due to defects and peeling, and in order to ensure that the photoelectric conversion layer has sufficient light absorption rate and does not cause the device resistance to become too high.

[0098] <Hole transport layer> In the photoelectric conversion element of the present invention, the hole transport layer 4 shown in FIG. 1 is a layer having a function of transporting holes, and is a layer located between the photoelectric conversion layer (perovskite layer) 3 and the counter electrode 5. The hole transport layer is used to improve the efficiency of hole transfer from the photoelectric conversion layer to the electrode and to block the transfer of electrons. For example, a conductor, a semiconductor, an organic hole transport material, etc. can be used for the hole transport layer, and an additive may be included for the purpose of further improving the hole transport properties.

[0099] The hole transport layer of the present invention is a layer containing, as a hole transport material, a compound represented by the general formula (1). The hole transport layer of the present invention may contain one or more compounds represented by the general formula (1), and may also contain other hole transport materials not belonging to the present invention.

[0100] Specific examples of other hole transport materials that do not belong to the hole transport material of the present invention include, for example, compound semiconductors containing monovalent copper, such as CuI, CuInSe2, and CuS; and compounds containing metals other than copper, such as GaP, NiO, CoO, FeO, Bi2O3, MoO2, and Cr2O3. These metal oxides may be mixed in the hole transport layer or may be laminated on the hole transport material. Examples of organic hole transport materials 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.

[0101] As a method for coating the hole transport layer of the photoelectric conversion element of the present invention with a coating liquid, any coating method can be used, and the same methods as those for forming the electron transport layer can be used.

[0102] In the present invention, the solvent used in the coating solution for the hole transport layer during film formation is, for example, an aromatic organic solvent such as benzene, toluene, xylene, mesitylene, tetralin (1,2,3,4-tetrahydronaphthalene), monochlorobenzene (chlorobenzene), o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, or nitrobenzene; an alkyl halide organic solvent such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, or dichloromethane; a nitrile solvent such as benzonitrile or acetonitrile; tetrahydrofuran, dioxane, or the like; Examples of suitable solvents include, but are not limited to, ether solvents such as ethanol, diisopropyl ether, c-pentyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate and propylene glycol monomethyl ether acetate; and alcohol solvents such as methanol, isopropanol, n-butanol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, cyclohexanol, and 2-n-butoxyethanol. These solvents may be used alone or in combination. The solvent can be selected based on the structure of the substance. Depending on the solubility of the substance, heating may be performed appropriately to dissolve it. Aromatic organic solvents and halogenated alkyl organic solvents are particularly preferred.

[0103] In the present invention, the thickness of the hole transport layer is preferably from 5 to 500 nm, more preferably from 10 to 250 nm, from the viewpoint of further improving photoelectric conversion efficiency.

[0104] In the present invention, the hole transport layer is preferably formed in a dry atmosphere, since this prevents moisture from being mixed in, allowing for the production of highly efficient perovskite solar cells with good reproducibility. It is also preferable to use a dehydrated solvent with a moisture content of 10 ppm or less.

[0105] <Additives> In the present invention, the hole transport layer may contain a dopant (or an oxidizing agent) or a basic compound (or a basic additive) as an additive. Incorporating an additive into the hole transport layer and increasing the carrier concentration of the hole transport material in the hole transport layer (doping) leads to an improvement in the conversion efficiency of the photoelectric conversion element. In the present invention, when the hole transport layer contains a dopant and a basic additive as additives, the amount of the additive is preferably 3.5 equivalents or less per equivalent of the hole transport material.

[0106] In the present invention, when a dopant is contained, specific examples of the dopant include lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), silver bis(trifluoromethanesulfonyl)imide, tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tri[bis(trifluoromethane)sulfonimide] (FK209), NOSbF6, SbCl5, SbF5, etc. In the present invention, it is preferable to use lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), but the dopant is not limited thereto.

[0107] In the present invention, when a dopant is used, the amount of the dopant is preferably 2.0 equivalents or less, more preferably 0.5 equivalents or less, per equivalent of the hole transport material contained in the hole transport layer.

[0108] In the present invention, a basic compound (basic additive) may be contained as an additive in the hole transport layer. Specific examples of the basic compound contained in the present invention include 4-tert-butylpyridine (tBP), 2-picoline, and 2,6-lutidine. A basic compound is often used in combination with a dopant. In the present invention, it is also desirable to use a basic compound in combination with a dopant, and it is preferable to use tert-butylpyridine.

[0109] In the present invention, when a basic compound is used, it is preferably used in an amount of 5 equivalents or less, more preferably 3 equivalents or less, relative to 1 equivalent of the hole transport material of the present invention.

[0110] Opposite In the present invention, the counter electrode 5 shown in Fig. 1 is disposed opposite the conductive support 1 and formed on the hole transport layer 4, thereby enabling exchange of charges with the hole transport layer. In the photoelectric conversion element of the present invention, it is preferable to provide a metal electrode as a counter electrode on the hole transport layer 4, but it is also possible to add an electron blocking layer made of an organic material or an inorganic compound semiconductor between the hole transport layer 4 and the counter electrode 5.

[0111] In the present invention, specific examples of materials used for the counter electrode include metals such as platinum, titanium, stainless steel, aluminum, gold, silver, nickel, magnesium, chromium, cobalt, and copper, or alloys thereof. Among these, it is preferable to use gold, silver, or a silver alloy, as it exhibits high electrical conductivity even in a thin film. Examples of silver alloys include silver-gold alloys, silver-copper alloys, silver-palladium alloys, silver-copper-palladium alloys, and silver-platinum alloys, which are less susceptible to sulfidation or chlorination and improve the stability of the thin film.

[0112] In the present invention, the counter electrode is preferably made of a material that can be formed by a method such as vapor deposition.

[0113] When a metal electrode is used as the counter electrode, the thickness thereof is preferably 10 nm or more, more preferably 50 nm or more, in order to obtain good conductivity.

[0114] In the photoelectric conversion element of the present invention, the conductive support serves as the cathode, and the counter electrode serves as the anode. It is preferable to irradiate light such as sunlight from the conductive support side. When irradiated with sunlight, the photoelectric conversion layer (perovskite layer) absorbs the light and enters an excited state, generating electrons and holes. These electrons move through the electron transport layer, and the holes move through the hole transport layer to the electrode, causing a current to flow, and the element functions as a photoelectric conversion element.

[0115] When evaluating the performance (characteristics) of the photoelectric conversion element of the present invention, the short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency are measured. The short-circuit current density is the current flowing between the output terminals when the output terminals are short-circuited. 2 The open-circuit voltage is the voltage between the output terminals when they are open. The fill factor is the maximum output (product of current and voltage) divided by the product of the short-circuit current density and the open-circuit voltage, and is mainly affected by the internal resistance. The photoelectric conversion efficiency is the ratio of maximum output (W) to 1cm 2 The value is calculated by dividing the light intensity (W) per unit area by 100 and expressing it as a percentage.

[0116] The photoelectric conversion element of the present invention can be applied to perovskite solar cells, various optical sensors, etc. The perovskite solar cell of the present invention is obtained by arranging a required number of photoelectric conversion elements, each of which contains a hole transport material containing the compound represented by general formula (1) as a hole transport layer, into modules and providing predetermined electrical wiring.

[0117] Although the preferred embodiment has been described above, the present invention is not limited to this, and may be modified as appropriate within the scope of the present invention. [Example]

[0118] The present invention will be specifically described below by way of examples with reference to the drawings, but the present invention is not limited to the following examples. 1 The analysis was performed using a 1H-NMR (1H-NMR (JNM-ECZ400S / L1 nuclear magnetic resonance spectrometer manufactured by JEOL Ltd.)).

[0119] [Synthesis Example 1] Synthesis of Compound (A-2) A reaction vessel was charged with the compound of formula (8) (0.30 g), [4-[bis(4-methoxyphenyl)amino]phenyl]boronic acid (0.52 g, manufactured by TCI), tetrakis(triphenylphosphine)palladium(0) (0.03 g, manufactured by Kanto Chemical), potassium carbonate (0.24 g, manufactured by Kanto Chemical), toluene (10 mL), ethanol (1.2 mL), and water (1.2 mL), and the mixture was degassed under reduced pressure. The mixture was stirred under reflux for 5 hours under an argon atmosphere. After the reaction was completed, toluene (10 mL) and water (20 mL) were added. The mixture was separated, and the organic layer was washed twice with water (30 mL). The organic layer was concentrated, and the crude product was purified using a silica gel column (toluene) to obtain the compound represented by formula (A-2) (0.49 g, 83% yield) as a red powder.

[0120] <NMR measurement results> 1 H-NMR (400MHz, CDCl3): δ(ppm)=3.81(12H), 6.86(8H), 6.92(4H), 7.10(8H), 7.17(2H), 7.45(4H), 7.49(2H).

[0121] [ka]

[0122] [Synthesis Example 2] Synthesis of Compound (A-1) A reaction vessel was charged with the compound of formula (8) (0.40 g), the compound of formula (9) (1.09 g), tetrakis(triphenylphosphine)palladium(0) (0.03 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.28 g, manufactured by Kanto Chemical Co., Inc.), toluene (10 mL), ethanol (1.6 mL), and water (1.6 mL), and the mixture was degassed under reduced pressure. The mixture was stirred under reflux for 25 hours under an argon atmosphere. After the reaction was completed, the reaction solution was poured into water (150 mL). The mixture was filtered, and the collected solid was washed with water (20 mL) and methanol (20 mL). The crude product was purified using a silica gel column (toluene:hexane = 9:1 (volume ratio)) to obtain the compound represented by formula (A-1) as a red powder (yield: 0.64 g, 63%).

[0123] <NMR measurement results> 1 H-NMR (400MHz, CDCl3): δ(ppm)=0.92(12H), 1.34(16H), 1.47(8H), 1.78(8H) , 3.95(12H), 6.84(8H), 6.91(4H), 7.07(8H), 7.17(2H), 7.43(4H), 7.49(2H).

[0124] [ka]

[0125] [Synthesis Example 3] Synthesis of Compound (A-5) A reaction vessel was charged with the compound of formula (8) (0.30 g), the compound of formula (10) (1.23 g), tetrakis(triphenylphosphine)palladium(0) (0.03 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.24 g, manufactured by Kanto Chemical Co., Inc.), toluene (10 mL), ethanol (1.2 mL), and water (1.2 mL), and the mixture was degassed under reduced pressure. The mixture was stirred under reflux for 41 hours under an argon atmosphere. After the reaction was completed, the reaction solution was poured into water (150 mL). The mixture was filtered, and the collected solid was washed with water (30 mL) and methanol (30 mL). The crude product was purified using a silica gel column (chloroform) to obtain the compound represented by formula (A-5) as a red powder (yield: 0.05 g, 5%).

[0126] <NMR measurement results> 1 H-NMR (400MHz, CDCl3): δ(ppm)=3.81(24H), 6.78(16H), 7.00(16H), 7.15(4H), 7.35(4H), 7.41(2H), 7.60-7.69(10H), 7.87(4H).

[0127] [ka]

[0128] [Synthesis Example 4] Synthesis of Compound (A-37) A reaction vessel was charged with the compound of formula (11) below (2.0 g), rubeanic acid (0.22 g, manufactured by TCI), and DMF (12 mL), and the mixture was stirred at 130°C for 25 hours under an argon atmosphere. After the reaction was completed, the reaction solution was poured into a beaker containing 300 mL of water. The mixture was filtered, and the collected solid was washed with water (30 mL) and methanol (30 mL) and then dried. The crude product was purified using a silica gel column (toluene) to obtain the compound represented by formula (A-37) below as a reddish-brown powder (yield: 0.07 g, 9%).

[0129] <NMR measurement results> 1 H-NMR (400MHz, CDCl3): δ(ppm)=1.56(2H), 1.68(2H), 1.77(2H), 1.92(4H), 2.08(2H), 3.87(2H), 4.87(2H), 6.84(2H), 7.19(8H), 7.62(2H), 7.74(2H).

[0130] [ka]

[0131] [Example 1] Fabrication of photoelectric conversion element and evaluation of current-voltage characteristics A flat ITO-coated glass (conductive support 1, manufactured by Geomatec Co., Ltd.) was ultrasonically cleaned with isopropyl alcohol and then treated with UV ozone. A tin(IV) oxide dispersion (electron transport layer coating solution) consisting of a 15% HO colloidal dispersion (manufactured by Alfa Aesar) and purified water in a volume ratio of 1:9 was spin-coated onto the substrate, and then heated on a hot plate at 150°C for 30 minutes to form an electron transport layer 2 with a thickness of approximately 20 nm.

[0132] In a glove box under a nitrogen stream, formamidine hydroiodide (1 M, manufactured by Tokyo Chemical Industry Co., Ltd.), lead(II) iodide (1.1 M, manufactured by Tokyo Chemical Industry Co., Ltd.), methylamine hydrobromide (0.2 M, manufactured by Tokyo Chemical Industry Co., Ltd.), and lead(II) bromide (0.2 M, manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in a mixed solvent of dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1. A dimethyl sulfoxide solution of cesium iodide (1.5 M, manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the solution so that the amount of cesium charged was 5% by composition ratio, to prepare a perovskite precursor solution. In a glove box under a nitrogen atmosphere, the prepared perovskite precursor solution was dropped onto a tin oxide thin film, spin-coated, and 0.3 mL of chlorobenzene was added dropwise during spin-coating to coat the perovskite precursor. The film was then heated on a hot plate at 100°C for 1 hour to form a Cs(MAFA)Pb(IBr)3 layer (photoelectric conversion layer 3) with a thickness of approximately 500 nm.

[0133] In a glove box under a nitrogen gas flow, a chlorobenzene solution of dopant containing 150 mM 4-tert-butylpyridine and 25 mM lithium bis(trifluoromethanesulfonyl)imide was prepared. Compound (A-1), which is the hole transport material obtained in Synthesis Example 1, was dissolved in the chlorobenzene solution at room temperature to a concentration of 50 mM to prepare a coating solution for the hole transport layer. In a glove box under a nitrogen atmosphere, the hole transport layer coating solution was spin-coated onto the Cs(MAFA)Pb(IBr) 3 layer (photoelectric conversion layer) to form a hole transport layer 4 with a thickness of about 200 nm.

[0134] Gold was deposited on the hole transport layer 4 by vacuum deposition at a vacuum level of 1×10 -4 A gold electrode (counter electrode 5) was formed by depositing a film of about 80 nm at about Pa, and a photoelectric conversion element was fabricated.

[0135] The intensity was 100 mW / cm generated by a simulated solar irradiation device (OTENTO-SUN III model manufactured by Bunkoukeiki Co., Ltd.). 2The photoelectric conversion element was irradiated from the conductive support side with light of 1000 kJ / cm2 and the current-voltage characteristics were measured using a source meter (KEITHLEY, Model 2400 General-Purpose Source Meter) to obtain the initial photoelectric conversion efficiency. The photoelectric conversion element was stored in a desiccator containing silica gel for 30 days after the initial photoelectric conversion efficiency measurement, and the current-voltage characteristics were measured again to obtain the photoelectric conversion efficiency after 30 days.

[0136] Using the obtained initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 30 days, which is photoelectric conversion over time, the retention rate (%) was calculated according to the following formula (a-1).

[0137]

number

[0138] [Example 2] A photoelectric conversion element was prepared in the same manner as in Example 1, except that compound (A-5) was dissolved in a chlorobenzene solution of the dopant at 10 mM at 120° C., and the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 30 days were measured in the same manner as in Example 1. The retention rate (%) of the photoelectric conversion efficiency after 30 days from the measurement of the initial photoelectric conversion efficiency is shown in Table 1.

[0139] [Example 3] A photoelectric conversion element was prepared in the same manner as in Example 1, except that compound (A-37) was dissolved at 80° C. at 50 mM in a chlorobenzene solution of the dopant, and the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 30 days were measured in the same manner as in Example 1. The retention rate (%) of the photoelectric conversion efficiency after 30 days from the measurement of the initial photoelectric conversion efficiency is shown in Table 1.

[0140] [Comparative Example 1] A photoelectric conversion element was fabricated in the same manner as in Example 1, except that Spiro-OMeTAD (manufactured by Sigma-Aldrich), a standard hole transport material represented by the following formula (B-1), was used by dissolving it in a chlorobenzene solution of the dopant at room temperature, and the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 30 days were obtained in the same manner as in Example 1. The retention rate (%) of the photoelectric conversion efficiency after 30 days from the measurement of the initial photoelectric conversion efficiency is shown in Table 1.

[0141] [ka]

[0142] [Table 1]

[0143] The results in Table 1 demonstrate that the photoelectric conversion element prepared using the compound of the present invention exhibits a superior retention rate of photoelectric conversion efficiency and has high durability compared to the photoelectric conversion element prepared using the standard compound of the comparative example. [Industrial Applicability]

[0144] Use of the hole transport material for photoelectric conversion elements according to the present invention makes it possible to extract current efficiently, and the material is useful for highly durable photoelectric conversion elements and perovskite solar cells. As solar cells that can efficiently convert solar energy into electrical energy, the material can provide clean energy, and can also be applied to organic electroluminescence (EL) elements, image sensors, and the like. [Explanation of symbols]

[0145] 1. Conductive support 2 Electron transport layer 3 Photoelectric conversion layer 4. Hole transport layer 5. Opposite

Claims

1. A hole transport material represented by the following general formula (1): 【Chemistry 1】 [In the formula, R １ and R ２ , R ３ and R ４ Adjacent groups may be bonded to each other to form a ring. Also, X １ and X ２ is represented by the following general formula (2). X １ and R １ or R ２ may be bonded to form a ring, and X ２ and R ３ or R ４ may be bonded to form a ring. 【Chemistry 2】 [In the formula, R ５ ~R ９ represents a hydrogen atom. Y represents a sulfur atom, and Z represents CR １０ represents R １０ represents a hydrogen atom. m is 1 and n is an integer of 0 or 1. however, (i) When m is 1 and n is 1, R 1 to R 4 represent phenyl groups having a substituent. Furthermore, the "substituent" in the phenyl group having substituents R 1 to R 4 is selected from an alkoxy group having 1 to 6 carbon atoms or a diphenylamino group, and when the "substituent" in the phenyl group having substituents R 1 to R 4 is a diphenylamino group, it further has the above-mentioned alkoxy group having 1 to 6 carbon atoms as a substituent. (ii) When m is 1 and n is 0, R 1 and R 3 are cyclopentyl groups; R 2 and R 4 represent phenyl groups having a substituent. The "substituent" in the phenyl group having a substituent of R 2 and R 4 is a linear or branched alkyl group having 1 to 6 carbon atoms.]

2. The hole transport material according to claim 1, wherein the compound represented by the general formula (1) is selected from the following structures (A-1), (A-2), (A-5) or (A-37). 【Transformation 3】

3. A photoelectric conversion element using the hole transport material according to claim 1 or 2.

4. A perovskite solar cell comprising the photoelectric conversion element according to claim 3.

Images