Compound, hole transport material for photoelectric conversion element, hole transport layer, photoelectric conversion element using the same, and solar cell

Abstract

A compound represented by general formula (1), where X1 and X2 are each independently represented by general formula (2).

Description

Technical Field

[0001] The present invention relates to a compound, a hole transport material for a photoelectric conversion element, a hole transport layer, a photoelectric conversion element using the same, and a solar cell.

Background Art

[0002] In recent years, as clean energy, solar power generation has attracted attention, and the development of solar cells has been actively carried out. Among them, as a next-generation solar cell that can be manufactured at low cost and by a solution process, the development of a solar cell using a perovskite material as a photoelectric conversion layer (hereinafter referred to as a perovskite solar cell) has attracted attention (for example, Patent Document 1, Non-Patent Documents 1 to 2).

[0003] In perovskite solar cells, a hole transport material is often used in the device. The purposes of use include (1) enhancing the function of selectively transporting holes to improve the photoelectric conversion efficiency, and (2) protecting the perovskite material, which is easily affected by moisture and oxygen when joined to the perovskite photoelectric conversion layer (for example, Non-Patent Document 3). Spiro-OMeTAD, a spirobifluorene-based organic compound, is often used as a standard hole transport material, but there are few reports of hole transport materials that contribute more highly to the photoelectric conversion characteristics than this material.

[0004] When using a hole transport material in a perovskite solar cell device, in the conventional method of fabricating the device using an organic compound as the hole transport material, a dopant, which is an additive, is added to the hole transport material. This dopant is used to reduce the electrical resistance of the hole transport material (for example, Non-Patent Documents 3 to 4).

[0005] However, the use of a dopant as an additive is a concern because it may reduce the durability of the photoelectric conversion device using an organic compound and shorten the overall life of the device (for example, Non-Patent Document 3). Therefore, the development of a photoelectric conversion device having a hole transport layer that does not contain a dopant or has a reduced dopant content is desired. Further, if the dopant can be eliminated or its content reduced, it becomes possible to reduce the additive cost and the manufacturing process cost.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] The problem to be solved by the present invention is to provide a novel hole transport material for a photoelectric conversion device that can be used to construct a highly durable photoelectric conversion device and solar cell when used in a photoelectric conversion device and a solar cell, and a photoelectric conversion device and a solar cell using the same.

Means for Solving the Problems

[0009] To solve the above problems, as a result of intensive studies, the inventors have found that a compound having a specific structure can be used as a hole transport material for a photoelectric conversion element to obtain a highly durable photoelectric conversion element and a solar cell. That is, the gist of the present invention is as follows.

[0010] 1. A compound represented by the following general formula (1), wherein X 1 and X 2 are each independently represented by the following general formula (2).

[0011] [Chemical formula]

[0012] [In the formula, R 1 and R 2 are each independently a nitrile group, a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms, a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent, a thio group having 1 to 18 carbon atoms which may have a substituent, an amino group having 1 to 20 carbon atoms which may have a substituent, or a linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent, R 3 to R 22 are each independently a hydrogen atom, a halogen atom, a carboxyl group, a trimethylsilyl group, a linear or branched alkyl group having 1 to 18 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 linear or branched alkynyl 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 linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, A cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, An acyl group having 1 to 20 carbon atoms which may have a substituent, A thio group having 1 to 18 carbon atoms which may have a substituent, An amino group having 1 to 20 carbon atoms which may have a substituent, An aromatic hydrocarbon group having 6 to 36 carbon atoms having a substituent, or a heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent, R 1 and R 2 may be bonded to each other to form a ring, R 3 ~R 7 、R 8 ~R 12 、R 13 ~R 17 and R 18 ~R 22 may be bonded to adjacent groups to form a ring, R 7 and R 8 and R 17 and R 18 may be bonded to each other to form a ring. However, when R 1 and R 2 are nitrile groups and R 5 is a methoxy group, R 10 、R 15 、R 20 shall be the above groups other than at least one methoxy group.]

[0013]

Chemical formula

[0014] [In the formula, R 23 ~R28 each independently represents a hydrogen atom, 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 linear or branched alkynyl 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 linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, a thio group having 1 to 18 carbon atoms which may have a substituent, an amino group having 1 to 20 carbon atoms which may have a substituent, an aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent, or a heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent, R 23 and R 24 、R 25 and R 26 and R 27 and R 28 may be bonded to each other to form a ring. Y 1 represents an oxygen atom, a sulfur atom or a selenium atom, and m and n each represent an integer of 0 to 2. However, either m or n is 1 or 2.]

[0015] 2. In the general formula (1), R 1 and R 2 each independently represents a nitrile group, a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent, or a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent The compound according to 1 above.

[0016] 3. The compound according to 1 or 2 above, wherein m in the general formula (2) is 1.

[0017] 4. A hole transport material for a photoelectric conversion element containing the compound according to any one of 1 to 3 above.

[0018] 5. A hole transport layer comprising a composition containing the hole transport material for a photoelectric conversion element according to 4 above and a dopant which is an additive in an amount of 0 to 0.5 equivalents with respect to 1 equivalent of the hole transport material for a photoelectric conversion element.

[0019] 6. A photoelectric conversion element containing the hole transport material for a photoelectric conversion element according to 5 above.

[0020] 7. A solar cell containing the photoelectric conversion element according to 6 above.

Advantages of the Invention

[0021] According to the compound of the present invention and the hole transport material for a photoelectric conversion element containing the same, it has become possible to produce a highly durable photoelectric conversion element and a solar cell.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The hole transport material for a photoelectric conversion element of the present invention is used for a photoelectric conversion element and a solar cell.

[0024] 〈Photoelectric Conversion Element〉 In a typical example, the photoelectric conversion element of the present invention has a conductive support 1, a hole blocking layer 2, an electron transport layer 3, a photoelectric conversion layer 4, a hole transport layer 5, and a counter electrode 6, as shown in the first schematic cross-sectional view of FIG. 1. Further, in another typical example, the photoelectric conversion element of the present invention has a conductive support 7, an electron transport layer 8, a photoelectric conversion layer 9, a hole transport layer 10, and a counter electrode 11, as shown in the second schematic cross-sectional view of FIG. 2.

[0025] Hereinafter, the compound represented by the general formula (1), which is a hole transport material for the photoelectric conversion element of the present invention, will be specifically described, but the present invention is not limited thereto.

[0026] A compound represented by the general formula (1), R 1 and R 2 are each independently a nitrile group, a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms, a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent, a thio group having 1 to 18 carbon atoms which may have a substituent, an amino group having 1 to 20 carbon atoms which may have a substituent, or a linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent, and is preferably electron-withdrawing.

[0027] In the present invention, examples of the "halogen atom" include fluorine, chlorine, bromine, and iodine.

[0028] In the general formula (1), R 1 , R 2Examples of the "linear or branched perfluoroalkyl group having 1 to 4 carbon atoms" represented by [0] include, specifically, a methyl group, an ethyl group, an n-propyl group, an n-butyl group, etc., in which the hydrogen atoms in a linear or branched alkyl group having 1 to 4 carbon atoms are completely substituted (perfluorinated) with fluorine atoms.

[0029] In general formula (1), R 1 , R 2 Examples of the "linear or branched acyl group having 1 to 20 carbon atoms which may have a substituent" represented by [8] include, specifically, an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group, a benzoylacetyl group, a benzoyl group, etc. When an alkyl chain is included, those in which the hydrogen atoms are completely substituted (perfluorinated) with fluorine atoms are included. Also, those bonded to an amino group (-CO-N<) may be used.

[0030] In general formula (1), R 1 , R 2 Examples of the "linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent" represented by

[16] include, specifically, a methoxycarbonyl group, an ethoxycarbonyl group, etc. When an alkyl chain is included, those in which the hydrogen atoms are completely substituted (perfluorinated) with fluorine atoms are included.

[0031] In general formula (1), R 1 , R 2 Examples of the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by

[24] include, specifically, a methylthio group, an ethylthio group, a propylthio group, a phenylthio group, a biphenylthio group, etc.

[0032] In general formula (1), R 1 , R 2In the "amino group having 1 to 20 carbon atoms which may have a substituent" represented by, as the "amino group having 1 to 20 carbon atoms", specifically, as a monosubstituted amino group, an ethylamino group, an acetylamino group, a phenylamino group, etc., and as a disubstituted amino group, a diethylamino group, a diphenylamino group, an acetylphenylamino group, etc. can be mentioned.

[0033] In general formula (1), R 1 , R 2 In the "linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent" represented by, as the "linear or branched alkylsulfonyl group having 1 to 18 carbon atoms", specifically, -SO2A 1 (A 1 represents a linear or branched alkyl group having 1 to 18 carbon atoms which may have the above-mentioned substituent) is a group represented by, and examples of A 1 include the methyl group, ethyl group, n-propyl group, n-butyl group, etc. mentioned as examples of the linear or branched alkyl group having 1 to 20 carbon atoms which may have the above-mentioned substituent.

[0034] In general formula (1), R 1 , R 2 In the "acyl group having 1 to 20 carbon atoms which may have a substituent", "linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent", "thio group having 1 to 18 carbon atoms which may have a substituent", "amino group having 1 to 20 carbon atoms which may have a substituent" or "linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent", as the "substituent", specifically, halogen atoms such as fluorine atom, chlorine atom, bromine atom, iodine atom; cyano group; hydroxyl group; nitro group; nitroso group; carboxyl group; phosphoric acid group; thioxo group (>C=S); carboxylic acid ester groups such as methyl ester group, ethyl ester group; A linear or branched alkyl group having 1 to 18 carbon atoms, such as 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, or a decyl group; A linear or branched alkenyl group having 2 to 20 carbon atoms, such as an ethenyl group (vinyl group), a 1-propenyl group, a 2-propenyl group (allyl group), a 1-butenyl group, a 2-butenyl group, a 1-pentenyl group, a 1-hexenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2-propenyl group, or a 1-ethylethenyl group; A linear or branched alkoxy group 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; An aromatic hydrocarbon group having 6 to 30 carbon atoms, such as a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, or a pyrenyl group; A heterocyclic group having 5 to 30 ring-forming atoms, such as 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, or a carbonyl group; An amino group having 0 to 18 carbon atoms, which is 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; A thio group having 0 to 18 carbon atoms, which is an unsubstituted thio group (thiol group: —SH), a methylthio group, an ethylthio group, a propylthio group, a phenylthio group, or a biphenylthio group; Examples thereof include the like. These "substituents" may contain only one, or may contain a plurality, and when a plurality are contained, they may be the same or different from each other. Further, these "substituents" may further have the substituents exemplified above.

[0035] In general formula (1), R 1 and R 2 may be bonded to each other to form a ring, or may be bonded to each other by a single bond, a bond through an oxygen atom, a sulfur atom, a selenium atom or a bond through a nitrogen atom to form a ring, and in that case, it is preferable to form a ring through a single bond. Further, it is more preferable that it is an acidic heterocyclic ring such as a barbituric acid type, a thiobarbituric acid type, a rhodanine type, a thiohydantoin type, an indanedione type or the like.

[0036] In general formula (1), R 3 ~R 22 are each independently a hydrogen atom, a halogen atom, a carboxyl group, a trimethylsilyl group, a linear or branched alkyl group having 1 to 18 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 linear or branched alkynyl 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 linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, an acyl group having 1 to 20 carbon atoms which may have a substituent, a thio group having 1 to 18 carbon atoms which may have a substituent, an amino group having 1 to 20 carbon atoms which may have a substituent, an aromatic hydrocarbon group having 6 to 36 carbon atoms having a substituent, represents a heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent.

[0037] In the present invention, examples of the "halogen atom" include fluorine, chlorine, bromine and iodine.

[0038] In general formula (1), R 3 ~R 22 In the "linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent" represented by, specific examples of the "linear or branched alkyl group having 1 to 20 carbon atoms" include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, isopentyl group, n-hexyl group, 2-ethylhexyl group, heptyl group, octyl group, isooctyl group, nonyl group, decyl group and the like.

[0039] In general formula (1), R 3 ~R 22 In the "linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent" represented by, specific examples of the "linear or branched alkenyl group having 2 to 20 carbon atoms" 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-ethylethene group, or a linear or branched alkenyl group having 2 to 20 carbon atoms in which a plurality of these alkenyl groups are bonded and the like.

[0040] In general formula (1), R 3 ~R 22In the "linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent" represented by, specific examples of the "linear or branched alkynyl group having 2 to 20 carbon atoms" include an ethynyl group, 1-propynyl group, 2-propynyl group, 1-butynyl group, 2-butynyl group, 1-methyl-2-propynyl group, 1-pentynyl group, 2-pentynyl group, 1-methyl-n-butynyl group, 2-methyl-n-butynyl group, 3-methyl-n-butynyl group, 1-hexynyl group, and the like.

[0041] In general formula (1), R 3 ~R 22 In the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by, specific examples of the "cycloalkyl group having 3 to 10 carbon atoms" include a cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclodecyl group, cyclododecyl group, 4-methylcyclohexyl group, 4-ethylcyclohexyl group, and the like.

[0042] In general formula (1), R 3 ~R 22 In the "linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by, specific examples of the "linear or branched alkoxy group having 1 to 20 carbon atoms" include a methoxy group, ethoxy group, propoxy group, n-butoxy group, n-pentyloxy group, n-hexyloxy group, heptyloxy group, octyloxy group, nonyloxy group, decyloxy group, isopropoxy group, isobutoxy group, s-butoxy group, t-butoxy group, isooctyloxy group, t-octyloxy group, phenoxy group, tolyloxy group, biphenylyloxy group, terphenylyloxy group, naphthyloxy group, anthryloxy group, phenanthryloxy group, fluorenyloxy group, indenyl oxy group, and the like.

[0043] In general formula (1), R 3 ~R 22In the "linear or branched cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by, specific examples of the "linear or branched cycloalkoxy group having 3 to 10 carbon atoms" include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, a cyclohexyloxy group, a 4-methylcyclohexyloxy group, and the like.

[0044] In General Formula (1), R 3 ~R 22 In the "acyl group having 1 to 20 carbon atoms which may have a substituent" represented by, as the "acyl group having 1 to 20 carbon atoms", in General Formula (1), R 1 , R 2 The same ones as the "acyl group having 1 to 20 carbon atoms which may have a substituent" represented by can be listed.

[0045] In General Formula (1), R 3 ~R 22 In the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by, as the "thio group having 1 to 18 carbon atoms", in General Formula (1), R 1 , R 2 The same ones as the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by can be listed.

[0046] In General Formula (1), R 3 ~R 22 In the "amino group having 1 to 20 carbon atoms which may have a substituent" represented by, as the "amino group having 1 to 20 carbon atoms", in General Formula (1), R 1 , R 2 The same ones as the "amino group having 1 to 20 carbon atoms which may have a substituent" represented by can be listed.

[0047] In General Formula (1), R 3 ~R 22In the "aryl group having 6 to 36 carbon atoms which may have a substituent" represented by [0], specific examples of the "aryl group having 6 to 36 carbon atoms" 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, and the like. In the present invention, the aryl group includes a "condensed polycyclic aryl group".

[0048] In general formula (1), R 3 ~R 22 Specific examples of the "heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent" represented by [8] include a pyridyl group, a pyrimidyl 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, a carbonyl group, and the like.

[0049] In general formula (1), R 3 ~R 22The "linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent", "linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent", "linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent", "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent", "alkoxy group having 1 to 20 carbon atoms which may have a substituent", "linear or branched cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent", "acyl group having 1 to 20 carbon atoms which may have a substituent", "thio group having 1 to 18 carbon atoms which may have a substituent", "amino group having 1 to 20 carbon atoms which may have a substituent", "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" or "heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent" represented by the following formula, the "substituent" in these groups is, in general formula (1), R 1 and R 2 in the "substituent" in the "linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent" represented by the following formula and the like can be the same as those mentioned below.

[0050] In general formula (1), R 3 to R 7 , R 8 to R 12 , R 13 to R 17 and R 18 to R 22 may be bonded to each other between adjacent groups to form a ring. R 7 and R 8 and R 17 and R 18 may be bonded to each other by a single bond, a bond through an oxygen atom, a sulfur atom, a selenium atom or a bond through a nitrogen atom to form a ring. Further, R 7 and R 8 and R 17 and R 18 when forming a ring, it is preferable that they are bonded to each other by a single bond, a bond through an oxygen atom or a sulfur atom to form a ring.

[0051] In general formula (1), R 1 and R 2 are nitrile groups, and when R 5 is a methoxy group, R 10 , R 15 , R 20 shall be the above groups other than at least one methoxy group.

[0052] In general formula (1), it is preferable that R 1 and R 2 are each independently a nitrile group, a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent, or a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent. Also, R 1 and R 2 may be nitrile groups. Further, R 1 may be a nitrile group, and R 2 may be a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent. Also, R 1 and R 2 may be linear or branched alkoxycarbonyl groups having 1 to 18 carbon atoms which may have a substituent. Also, R 1 and R 2 may be linear or branched acyl groups having 1 to 18 carbon atoms which may have a substituent, and may be bonded to each other to form a ring.

[0053] In general formula (1), it is preferable that R 3 ~R 22 are a hydrogen atom, a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, or an amino group having 1 to 20 carbon atoms which may have a substituent. Also, R 5 , R 10 , R 15 and R 20 may be linear or branched alkoxy groups having 1 to 20 carbon atoms which may have a substituent, for example, a methoxy group. Also, R 5 and R 15is a linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, R 10 and R 20 may be an amino group having 1 to 20 carbon atoms which may have a substituent, and the amino group may have a linear or branched alkoxy group having 1 to 20 carbon atoms. Also, R 5 、R 10 、R 15 and R 20 may be an amino group having 1 to 20 carbon atoms which may have a substituent, and the amino group may have a linear or branched alkoxy group having 1 to 20 carbon atoms. Also, R 7 and R 8 and R 17 and R 18 may be bonded to each other through a single bond, an oxygen atom, or a sulfur atom to form a ring.

[0054] In general formula (1), X 1 and X 2 are preferably represented by general formula (2).

[0055] In general formula (2), R 23 ~R 28 are each independently a hydrogen atom, 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 linear or branched alkynyl 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 linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, a thio group having 1 to 18 carbon atoms which may have a substituent, an amino group having 1 to 20 carbon atoms which may have a substituent, an optionally substituted aromatic hydrocarbon group having 6 to 36 carbon atoms, or an optionally substituted heterocyclic group having 5 to 36 ring-forming atoms.

[0056] In General Formula (2), R 23 ~R 28 In the “linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent” represented by, examples of the “linear or branched alkyl group having 1 to 20 carbon atoms” are the same as those of the “linear or branched alkyl group having 1 to 20 carbon atoms which may have a substituent” represented by R 3 ~R 22 in General Formula (1).

[0057] In General Formula (2), R 23 ~R 28 In the “linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent” represented by, examples of the “linear or branched alkenyl group having 2 to 20 carbon atoms” are the same as those of the “linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent” represented by R 3 ~R 22 in General Formula (1).

[0058] In General Formula (2), R 23 ~R 28 In the “linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent” represented by, examples of the “linear or branched alkynyl group having 2 to 20 carbon atoms” are the same as those of the “linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent” represented by R 3 ~R 22 in General Formula (1).

[0059] In General Formula (2), R 23 ~R 28In the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by , the "cycloalkyl group having 3 to 10 carbon atoms" in the general formula (1), R 3 ~R 22 The same as the "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent" represented by can be mentioned.

[0060] In the general formula (2), for the "linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by R 23 ~R 28 The "linear or branched alkoxy group having 1 to 20 carbon atoms" in it, in the general formula (1), R 3 ~R 22 The same as the "linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent" represented by can be mentioned.

[0061] In the general formula (2), for the "cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by R 23 ~R 28 The "cycloalkoxy group having 3 to 10 carbon atoms" in it, in the general formula (1), R 3 ~R 22 The same as the "cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent" represented by can be mentioned.

[0062] In the general formula (2), for the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by R 23 ~R 28 The "thio group having 1 to 18 carbon atoms" in it, in the general formula (1), R 1 、R 2 The same as the "thio group having 1 to 18 carbon atoms which may have a substituent" represented by can be mentioned.

[0063] In the general formula (2), R 23 ~R 28In the “amino group having 1 to 20 carbon atoms which may have a substituent” represented by, as the “amino group having 1 to 20 carbon atoms” in the general formula (1), R 1 and R 2 the same ones as the “amino group having 1 to 20 carbon atoms which may have a substituent” represented by can be mentioned.

[0064] In the general formula (2), as the “aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent” represented by R 23 to R 28 the same ones as the “aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent” represented by R 3 to R 22 in the general formula (1) can be mentioned.

[0065] In the general formula (2), as the “heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent” represented by R 23 to R 28 the same ones as the “heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent” represented by R 3 to R 22 in the general formula (1) can be mentioned.

[0066] In the general formula (2), R 23 to R 28The "linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent", "linear or branched alkenyl group having 2 to 20 carbon atoms which may have a substituent", "linear or branched alkynyl group having 2 to 20 carbon atoms which may have a substituent", "cycloalkyl group having 3 to 10 carbon atoms which may have a substituent", "alkoxy group having 1 to 20 carbon atoms which may have a substituent", "linear or branched cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent", "acyl group having 1 to 20 carbon atoms which may have a substituent", "thio group having 1 to 18 carbon atoms which may have a substituent", "amino group having 1 to 20 carbon atoms which may have a substituent", "aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent" or "heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent" represented by, the "substituent" in the general formula (1), R 1 , R 2 The same ones as the "substituent" in the "acyl group having 1 to 18 carbon atoms which may have a substituent" etc. represented by can be cited.

[0067] In the general formula (2), R 23 and R 24 , R 25 and R 26 and R 27 and R 28 may be bonded to each other to form a ring by a single bond, a bond through an oxygen atom, a sulfur atom, a selenium atom, or a bond through a nitrogen atom.

[0068] In the general formula (2), Y 1 represents an oxygen atom, a sulfur atom or a selenium atom.

[0069] In general formula (2), m and n each represent an integer from 0 to 2. When m is 0, n is 1 to 2. When n is 0, m is 1 to 2. It is assumed that either m or n is 1 or more, and the case where both are 0 is not included. It is preferable that m is 1. Also, the cyclopentadithiophene moiety, which is the central skeleton of general formula (1), may be bonded from either the phenyl group or the 5-membered heterocyclic group represented by general formula (2).

[0070] In general formula (2), it is preferable that m is 1 and n is 0 or 1. In general formula (2), when m is 1 and n is 1, it is preferable that the 5-membered heterocyclic group is bonded to the cyclopentadithiophene moiety, which is the central skeleton of general formula (1).

[0071] Specific examples of the compound represented by general formula (1) of the present invention are shown below, but the present invention is not limited thereto. Also, the following exemplified compounds are described with some hydrogen atoms, carbon atoms, etc. omitted, and show one example of the possible isomers, and all other isomers are included. Also, mixtures of two or more isomers may be used respectively.

[0072]

Chemical formula

[0073]

Chemical formula

[0074]

Chemical formula

[0075]

Chemical formula

[0076]

Chemical formula

[0077]

Chem.

[0078]

Chem.

[0079]

Chem.

[0080]

Chem.

[0081]

Chem.

[0082]

Chem.

[0083]

Chem.

[0084]

Chem.

[0085]

Chem.

[0086]

Chem.

[0087] The hole transport material for a photoelectric conversion element of the present invention represented by the general formula (1) can be synthesized by a known method.

[0088] For example, like the compound (A-1), X 1 and X 2 compounds represented by m = 1 and n = 0 in the general formula (2) are synthesized by performing a Suzuki-Miyaura cross-coupling reaction between a dibromo compound represented by the following formula (3) and a boronic acid compound represented by the general formulas (4) and (5) or a boronic acid ester compound represented by the general formulas (6) and (7), and further by a Knoevenagel condensation reaction with a compound represented by the general formula (8).

[0089]

Chemical formula

[0090] As a purification method of the compound represented by the general formula (1) of the present invention, column purification by column chromatography, adsorption purification using silica gel, activated carbon, activated clay, etc., recrystallization or crystallization using a solvent, etc. can be performed. Alternatively, it is effective to use a compound with increased purity by using these methods in combination. Also, the identification of these compounds can be performed by nuclear magnetic resonance analysis (NMR).

[0091] Hereinafter, preferred embodiments of the photoelectric conversion element of the present invention will be described.

[0092] As shown in FIG. 1, the photoelectric conversion element of the present invention preferably has a configuration including a conductive support 1, a hole blocking layer 2, an electron transport layer 3, a photoelectric conversion layer 4, a hole transport layer 5, and a counter electrode 6, but is not limited thereto. Further, the photoelectric conversion element of the present invention is preferably a perovskite type photoelectric conversion element. In the present invention, the perovskite type photoelectric conversion element preferably includes, in FIG. 1, a conductive support 1, a hole blocking layer 2, an electron transport layer 3, a photoelectric conversion layer (perovskite layer) 4, a hole transport layer 5, and a counter electrode 6, and in FIG. 2, a conductive support 7, an electron transport layer 8, a photoelectric conversion layer (perovskite layer) 9, a hole transport layer 10, and a counter electrode 11 in this order, but the electron transport layer may be absent. Further, it 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.

[0093] 〈Conductive support〉 In the present invention, the conductive support needs to have translucency that can transmit light contributing to photoelectric conversion. Further, since the conductive support is a member having a function of extracting current from the photoelectric conversion layer, it is preferably a conductive substrate. Specific examples of the conductive material include conductive transparent oxide semiconductors such as indium tin oxide (ITO) doped with tin, fluorine-doped tin oxide (FTO), and indium-tin composite oxide, but it is preferable to use a glass substrate coated with indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) thin film.

[0094] 〈Hole blocking layer〉 In the photoelectric conversion element of the present invention, it is preferable that a hole blocking layer 2 is formed on the conductive support 1 shown in FIG. 1. Specific examples of the semiconductor of the hole blocking layer include titanium oxide (such as TiO2), tungsten oxide (such as WO2, WO3, W2O3), zinc oxide (ZnO), niobium oxide (such as Nb2O5), tantalum oxide (such as Ta2O5), yttrium oxide (such as Y2O3), strontium titanate (such as SrTiO3), fullerene derivatives, carbon nanotubes, etc. One or more of these can be used. In the present invention, titanium oxide is preferable.

[0095] The thickness of the hole blocking layer is not particularly limited, and from the viewpoint of further preventing the photoelectric conversion layer from being in contact with the conductive support and short-circuiting, it is preferably about 5 to 100 nm, and more preferably about 30 to 90 nm.

[0096] The hole blocking layer can be obtained by using a known film-forming method according to the material to be formed. Examples of the method for producing the hole blocking layer include the spin coating method of a dispersion containing semiconductor fine particles, the spray pyrolysis method of spraying a precursor solution of a semiconductor onto a conductive support placed on a heated hot plate, and the ALD method of vaporizing a precursor and reacting and depositing it, etc., but it is not limited to these. In the present invention, a commercially available product may be used as the dispersion containing semiconductor fine particles.

[0097] When using a commercially available dispersion containing semiconductor fine particles, a dry atmosphere is preferable from the viewpoint of being able to manufacture a highly efficient perovskite solar cell with good reproducibility by preventing aggregation of the semiconductor fine particles due to moisture in the atmosphere.

[0098] 〈Electron transport layer〉 In the photoelectric conversion element of the present invention, an electron transport layer 3 is preferably formed on the hole blocking layer 2 shown in FIG. 1, and in FIG. 2, an electron transport layer 8 is preferably formed on the conductive support 7. The embodiment is not particularly limited. When the configuration of FIG. 1 is adopted, it is preferably a thin film having a porous structure. By having a porous structure, the active surface area of the photoelectric conversion layer can be significantly increased, the photoelectric conversion efficiency can be improved, and an electron transport layer excellent in electron collection can be obtained. The electron transport layer is used to improve the movement efficiency of electrons from the photoelectric conversion layer to the electrode and to block the movement of holes.

[0099] Specific examples of the semiconductor forming 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 (Y2O3, etc.), strontium titanate (SrTiO3, etc.); metal sulfides such as titanium sulfide, zinc sulfide, zirconium sulfide, copper sulfide, tin sulfide, indium sulfide, tungsten sulfide, cadmium sulfide, silver sulfide; metal selenides such as titanium selenide, zirconium selenide, indium selenide, tungsten selenide; elemental semiconductors such as silicon and germanium. These semiconductors are preferably used alone or in combination of two or more. In the present invention, it is preferable to use one or more selected from titanium oxide, zinc oxide, and tin oxide as the semiconductor.

[0100] The electron transport layer can be obtained by using a known film formation method according to the material to be formed. Examples of the film formation method of the electron transport layer include wet coating methods such as spin coating, doctor blade method, squeegee method, and screen printing method of a paste containing semiconductor fine particles on a conductive substrate, and then removing the solvent and additives by firing to form a film, and sputtering method, evaporation method, electrodeposition method, electrolysis method, microwave irradiation method, etc., but are not limited thereto. The atmosphere for film formation is not particularly limited and may be in the air.

[0101] The film thickness of the electron transport layer is not particularly limited, and from the viewpoint of better collecting electrons from the photoelectric conversion layer, it is preferably about 10 to 500 nm, more preferably about 50 to 400 nm. The semiconductor particle size is preferably 5 to 500 nm, more preferably 10 to 100 nm.

[0102] In the present invention, a commercially available product may be used as the paste containing semiconductor fine particles, or a paste prepared by dispersing commercially available semiconductor fine powder in a solvent may also be used. Specific examples of the solvent used when preparing the paste include water; alcohol 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, but are not limited thereto. These solvents can be used as a single solvent or a mixed solvent of two or more.

[0103] In the present invention, as a method for dispersing semiconductor fine powder in a solvent, it may be carried out after grinding the powder in a mortar or the like, or a disperser such as a ball mill, a paint conditioner, a vertical bead mill, a horizontal bead mill, or an attritor may be used. When preparing the paste, it is preferable to add a surfactant or the like to prevent aggregation of the semiconductor fine particles, and it is preferable to add a thickener such as polyethylene glycol to thicken it.

[0104] 〈Photoelectric conversion layer〉 In the photoelectric conversion element of the present invention, it is preferable that a photoelectric conversion layer 4 is formed on the electron transport layer 3 shown in FIG. 1, and in FIG. 2, a photoelectric conversion layer 9 is formed on the electron transport layer 8, but it is not limited thereto.

[0105] In the present invention, when used as a perovskite-type photoelectric conversion element, the perovskite material as the photoelectric conversion layer represents a series of materials having a structure represented by the general formula ABX3. Here, A, B, and X represent an organic cation or a monovalent metal cation, a metal cation, and a halide anion, respectively. As an example, A = K+ , Rb + , Cs + , CH3NH3 + (Hereinafter, MA: Methylammonium), NH=CHNH2 + (Hereinafter, FA: Formamidinium), CH3CH2NH3 + (Hereinafter, EA: Ethylammonium); B = Pb, Sn; X = I - , Br - can be mentioned. Specifically, perovskite materials represented by any composition such as CH3NH3PbI3 (MAPBI3), C2H5NH3PbI3, CH3NH3PbBr3, C2H5NH3PbBr3, CH3NH3PbBr3, C2H5NH3PbCl3, CH3NH3PbCl3, C2H5NH3PbCl3, CsSnI3, CH3NH3SnI3, C2H5NH3SnI3, CsSnBr3, CH3NH3SnBr3, C2H5NH3SnBr3, CsSnCl3, CH3NH3SnCl3, C2H5NH3SnCl3, and perovskite materials of mixed cations and mixed anions represented by any composition of (FAMA)Pb(IBr)3, K(FAMA)Pb(IBr)3, Rb(FAMA)Pb(IBr)3, Cs(FAMA)Pb(IBr)3 can be used, but are not limited thereto. It is preferable to use one or more of these perovskite materials. Further, it may contain a light absorber other than the perovskite material.

[0106] Depending on the material, the photoelectric conversion layer can be obtained by a known film formation method such as the anti-solvent method or the two-step method. In the present invention, it is preferable to produce by the anti-solvent method, but is not limited thereto.

[0107] In the present invention, when forming the photoelectric conversion layer by the anti-solvent method, a perovskite precursor solution of the perovskite material is prepared, and a specific solvent is added while spin-coating it on the electron transport layer. After the spin-coating is completed, the photoelectric conversion layer is obtained by heating.

[0108] The perovskite precursor may use commercially available materials. In the device configuration of FIG. 1 in the present invention, it is preferable to use a PbI2 / MAI(1:1)-DMF complex (Tokyo Chemical Industry). In the device configuration of FIG. 2, it is preferable to use a precursor composed of a lead halide, a methylammonium halide, a formamidinium halide, and a cesium halide in an arbitrary composition, but it is not limited thereto. Note that MAI is an abbreviation for methylammonium iodide, and DMF is an abbreviation for N,N-dimethylformamide.

[0109] In the present invention, solvents for the perovskite precursor solution include, but are not limited to, dimethyl sulfoxide, dimethylformamide, γ-butyrolactone, etc. from the viewpoint of the solubility of the precursor. These solvents may be used alone or in combination of two or more, and it is preferable to use DMF or dimethyl sulfoxide.

[0110] The specific solvent added during spin coating of the perovskite precursor solution is preferably a poor solvent, such as aromatic organic solvents like toluene, benzene, chlorobenzene, orthodichlorobenzene, nitrobenzene; ether solvents like diethyl ether, tetrahydrofuran (THF); alcohol solvents like methanol, ethanol, isopropanol, butanol, octanol; long-chain hydrocarbon solvents like hexane; pyridine; acetonitrile, etc., but it is not limited thereto. These solvents may be used alone or in combination of two or more. Among them, aromatic organic solvents are preferred, and chlorobenzene and toluene are more preferred. The addition amount only needs to be sufficiently diffused over the entire device substrate composed of a conductive support, a hole blocking layer, and an electron transport layer that rotates by spin coating, and is not particularly limited.

[0111] In the present invention, the temperature when heating the photoelectric conversion layer (perovskite layer) by a hot plate or the like is preferably 50 to 150°C, more preferably 70 to 120°C, from the viewpoint of generating the perovskite material from the precursor. Also, the heating time is preferably about 10 to 90 minutes, more preferably about 30 to 60 minutes.

[0112] From the viewpoint of being able to reproducibly manufacture a highly efficient perovskite solar cell by preventing the incorporation of moisture, the atmosphere during the film formation of the perovskite material is preferably a dry atmosphere, and more preferably a dry inert gas atmosphere such as a glove box. Further, it is preferable to perform dehydration with a molecular sieve or the like and use a solvent having a low water content.

[0113] From the viewpoint of further suppressing performance deterioration due to defects and peeling, the thickness of the photoelectric conversion layer (perovskite layer) of the present invention is preferably 50 to 1000 nm, and more preferably 200 to 700 nm.

[0114] 〈Hole transport layer〉 The hole transport layer is a layer having a function of transporting holes. For the hole transport layer, for example, a conductor, a semiconductor, an organic hole transport material, etc. can be used. The material can function as a hole transport material that receives holes from the photoelectric conversion layer (perovskite layer) and transports the holes. In the present embodiment, high efficiency can be achieved even without containing a dopant as an additive, but a dopant may be contained for the purpose of further improving the hole transport characteristics. Since there is concern that the dopant may reduce the durability of the photoelectric conversion element and shorten the life of the entire element, it is desirable to reduce the amount used.

[0115] The hole transport layer of the present invention is a layer containing the compound represented by the general formula (1) as a hole transport material for a photoelectric conversion element. By using the compound represented by the general formula (1) in the hole transport layer, a highly durable photoelectric conversion element and a solar cell can be constructed. Further, the compound represented by the general formula (1) can achieve good photoelectric conversion efficiency when used in the hole transport layer. In addition, the compound represented by the general formula (1) can achieve sufficient photoelectric conversion efficiency without reducing or using a dopant when used in the hole transport layer, and can efficiently extract current. By reducing or not using a dopant, a photoelectric conversion element and a solar cell can be constructed by a simple process and at low cost. In the hole transport layer of the present invention, one or more compounds represented by the general formula (1) may be used in combination, or may be used in combination with other hole transport materials not belonging to the present invention. Specific examples of other hole transport materials include, for example, compound semiconductors containing monovalent copper such as CuI, CuInSe2, and CuS; compounds containing metals other than copper such as GaP, NiO, CoO, FeO, Bi2O3, MoO2, and Cr2O3. 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; polyaniline derivatives and the like. The hole transport layer may contain a dopant (oxidizing agent) as an additive as needed.

[0116] The hole transport layer 5 shown in FIG. 1 of the present invention is preferably formed by coating and drying on the above-described photoelectric conversion layer 4 (perovskite layer). The hole transport layer 10 shown in FIG. 2 is preferably formed by coating and drying on the above-described photoelectric conversion layer 9 (perovskite layer). Specifically, as the film-forming method, there are methods such as spin coating, screen printing, roll coating, dip coating, spraying, knife coating, bar coating, die coating, curtain coating, etc. In the present invention, the spin coating method is preferred. Note that the conditions for spin coating can be set as appropriate.

[0117] In the present invention, the solvents used during film formation include aromatic organic solvents such as benzene, toluene, xylene, mesitylene, tetralin (1,2,3,4-tetrahydronaphthalene), monochlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, nitrobenzene, etc.; halogenated alkyl organic solvents such as dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, dichloromethane, etc.; nitrile solvents such as benzonitrile, acetonitrile, etc.; ether solvents such as tetrahydrofuran, dioxane, diisopropyl ether, c-pentyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, etc.; ester solvents such as ethyl acetate, propylene glycol monomethyl ether acetate, etc.; alcohol solvents such as methanol, isopropanol, n-butanol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, cyclohexanol, 2-n-butoxyethanol, etc., but are not limited thereto. Further, the above solvents may be used alone or in combination of two or more, and the solvent to be used can be selected according to the structure. In particular, it is preferable to use aromatic organic solvents and halogenated alkyl organic solvents.

[0118] In the present invention, when drying after applying the hole transport layer as described above, there are no particular restrictions on the conditions, but it is desirable to carry out the drying to the extent that the solvent can be removed. It is preferable to heat at about 50 to 120 °C using a hot plate or the like, and the heating time is preferably about 10 to 60 minutes.

[0119] In the present invention, from the viewpoint of further improving the photoelectric conversion efficiency, the film thickness of the hole transport layer is preferably about 10 to 500 nm.

[0120] The atmosphere during film formation of the hole transport layer is preferably a dry atmosphere from the viewpoint of being able to manufacture a highly efficient perovskite solar cell with good reproducibility by preventing the mixing of moisture, and a dry atmosphere such as a glove box is more preferable. Further, dehydration is preferably performed using a molecular sieve or the like, and a solvent with a low water content is preferably used.

[0121] 〈Additive〉 In the present invention, a composition containing a hole transport material for a photoelectric conversion element and an additive such as a dopant (or an oxidizing agent) or a basic compound (or a basic additive) may be used for the hole transport layer. Incorporating an additive into the hole transport layer to improve the carrier concentration of the hole transport material for the photoelectric conversion element in the hole transport layer (doping) leads to an improvement in the conversion efficiency of the photoelectric conversion element. In the present invention, when using a composition containing a dopant and a basic additive as additives for the hole transport layer, it is preferably a composition containing 0 to 3.5 equivalents of the additive with respect to 1 equivalent of the hole transport material for the photoelectric conversion element.

[0122] In the present invention, when a dopant is contained for the purpose of further improving the hole transport property, specific examples of the dopant include tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tris[bis(trifluoromethane)sulfonimide] (FK209), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), silver bis(trifluoromethanesulfonyl)imide, NOSbF6, SbCl5, SbF5, and the like. In the present invention, it is preferable to use lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0123] In the present invention, when using a composition containing a dopant, it is preferably a composition containing 0 to 2.0 equivalents of the dopant with respect to 1 equivalent of the hole transport material for the photoelectric conversion element, and more preferably a composition containing 0 to 0.5 equivalents of the dopant.

[0124] Further, a basic compound (basic additive) may be contained as an additive for the hole transport layer. In the present invention, when a basic compound is contained, specific examples include 4-tert-butylpyridine (TBP), 2-picoline, 2,6-lutidine, and the like. The basic compound is often used in combination when using a dopant. Also in the present invention, when using a dopant, it is desirable to use it in combination.

[0125] In the present invention, when using a composition containing a basic compound, it is preferably a composition containing 0 to 5 equivalents of the basic compound with respect to 1 equivalent of the hole transport material for the photoelectric conversion element, and more preferably a composition containing 0 to 3 equivalents of the basic compound.

[0126] <Counter electrode> In the present invention, the counter electrode 6 shown in FIG. 1 is disposed opposite to the conductive support 1 and formed on the hole transport layer 5. In the device configuration of FIG. 2, it is similarly formed on the hole transport layer 10, enabling charge transfer with the hole transport layer. In the photoelectric conversion device of the present invention, it is preferable to provide a metal electrode as the counter electrode in the form of a hole transport layer, but an electron blocking layer can also be added between the hole transport layer and the counter electrode.

[0127] Specific examples of materials used as the counter electrode include metals such as platinum, titanium, stainless steel, aluminum, gold, silver, nickel, or alloys thereof.

[0128] In the present invention, materials that can be formed by methods such as vapor deposition are preferred for the counter electrode. Also, the film thickness of the counter electrode is not particularly limited, and it is preferably about 50 to 150 nm, for example.

[0129] In the photoelectric conversion device 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 side of the conductive support. When irradiated with light such as sunlight, the photoelectric conversion layer (perovskite layer) absorbs the light and enters an excited state, generating electrons and holes. The current flows as these electrons move through the electron transport layer and the holes move through the hole transport layer to the electrodes, enabling the device to function as a photoelectric conversion device.

[0130] When evaluating the performance (characteristics) of the photoelectric conversion device of the present invention, measurements of short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency are performed. The short-circuit current density represents the current flowing per 1 cm between both terminals when the output terminals are short-circuited, and the open-circuit voltage represents the voltage between both terminals when the output terminals are open. Also, the fill factor is the value obtained by dividing the maximum output (the product of current and voltage) by the product of the short-circuit current density and the open-circuit voltage, and is mainly influenced by the internal resistance. The photoelectric conversion efficiency is obtained as a value expressed as a percentage by multiplying 100 by the value obtained by dividing the maximum output (W) by the light intensity (W) per 1 cm. 2 The open-circuit voltage represents the voltage between both terminals when the output terminals are open. Also, the fill factor is the value obtained by dividing the maximum output (the product of current and voltage) by the product of the short-circuit current density and the open-circuit voltage, and is mainly influenced by the internal resistance. The photoelectric conversion efficiency is obtained as a value expressed as a percentage by multiplying 100 by the value obtained by dividing the maximum output (W) by the light intensity (W) per 1 cm. 2 It is obtained as a value expressed as a percentage by multiplying 100 by the value obtained by dividing the maximum output (W) by the light intensity (W) per 1 cm.

[0131] In the present invention, when evaluating the durability of a photoelectric conversion element, the evaluation is performed based on the retention rate (%) of the photoelectric conversion efficiency over time in a dry atmosphere. The dry atmosphere is a state in which a desiccant such as silica gel is placed in a sealed container such as a desiccator and the humidity is 5%RH or less.

[0132] The photoelectric conversion element of the present invention can be applied to solar cells, various optical sensors, and the like. The solar cell of the present invention is preferably a perovskite solar cell. The perovskite solar cell is formed by using the compound represented by the general formula (1) as a hole transport material for a photoelectric conversion element to form a photoelectric conversion element including a hole transport layer for a photoelectric conversion element as a cell, arranging a required number of the cells in an array to modularize, and providing predetermined electrical wiring.

[0133] As described above, the preferred embodiments have been described, but the present invention is not limited thereto, and may be appropriately modified without departing from the scope of the present invention.

Examples

[0134] Hereinafter, the present invention will be specifically described with reference to the drawings by way of examples. However, the present invention is not limited to the following examples. In addition, the identification of the compound obtained in the synthesis example was performed by 1 1H-NMR (1H-NMR, nuclear magnetic resonance apparatus manufactured by JEOL Ltd., JNM-ECZ400S / L1 type).

[0135] [Synthesis Example 1] Synthesis of Compound (A-1) 3,3'-Dibromo-5,5'-bis(trimethylsilyl)-2,2'-bithiophene (10.0 g, manufactured by TCI) was added to the reaction vessel, and the vessel was purged with argon. Dehydrated tetrahydrofuran (106 mL) was added, and the mixture was cooled to -78 °C in a dry ice-acetone bath. A hexane solution of n-butyllithium (1.55 mol / L, 29.0 mL, manufactured by Kanto Chemical Co., Inc.) was added dropwise. Then, the temperature was raised to -30 °C over 4 hours, and dimethylcarbamoyl chloride (1.2 mL, manufactured by TCI) was added. After stirring at -30 °C for 20 minutes, the temperature was gradually raised to 0 °C over 3 hours. Then, the temperature was raised to room temperature. Water (150 mL) was added, and after liquid separation, the organic layer was washed with water (150 mL) and saturated brine (100 mL). The aqueous layer was extracted three times with chloroform (40 mL). The organic layer was dried over anhydrous magnesium sulfate, and the solvent was distilled off to obtain a red solid as the crude product. This crude product was purified by a silica gel column (hexane / ethyl acetate = 97 / 3 (volume ratio)) to obtain the compound represented by the following formula (9) as a red solid (yield: 5.76 g, yield 80%).

[0136] The compound of formula (9) (3.5 g) obtained above and tetrahydrofuran (hereinafter referred to as THF, 21 mL) were charged into the reaction vessel and cooled to 5 °C or lower in an ice bath. N-Bromosuccinimide (4.9 g, manufactured by TCI) and N,N-dimethylformamide (hereinafter referred to as DMF, 7 mL) were added thereto in several portions. Then, the mixture was returned to room temperature and stirred for 2 hours. After completion of the reaction, the reaction solution was poured into a beaker containing water (400 mL). After stirring for 30 minutes, this solution was filtered. The obtained solid was dried under reduced pressure at 70 °C to obtain the compound represented by the following formula (10) as a purple solid (yield: 3.53 g, yield: 97%).

[0137]

Chemical formula

[0138] 4-Bromoanisole (10.60 g, manufactured by TCI), diphenylamine (8.72 g, manufactured by TCI), palladium acetate (0.015 g), sodium tert-butoxide (11.90 g, manufactured by Kanto Chemical), tri-tert-butylphosphine (0.017 g, manufactured by Kanto Chemical), and toluene (110 mL) were charged into a reaction vessel, and degassing was carried out under reduced pressure. The mixture was heated under reflux for 3 hours in an argon atmosphere. After completion of the reaction, it was cooled and filtered by suction. The residue was washed with toluene (50 mL), and the filtrate was concentrated. The obtained crude product was purified by an amino silica gel column (toluene / hexane = 1 / 1 (volume ratio)), and then recrystallized (toluene / methanol) to obtain the compound of the following formula (11) as a white solid (yield: 11.02 g, yield: 78%).

[0139] The compound of formula (11) (10.50 g) obtained above and THF (71 mL) were charged into a reaction vessel and cooled to 5°C or lower. N-Bromosuccinimide (14.30 g, manufactured by TCI) was added thereto, and the mixture was stirred at 5°C or lower for 2 hours. After completion of the reaction, the reaction solution was poured into a beaker containing 300 mL of water. Toluene (100 mL) was added thereto. This was separated, and the aqueous layer was extracted twice with toluene (40 mL). The organic layer was dried over sodium sulfate and concentrated. The crude product was purified by a silica gel column (toluene / hexane = 1:1 (volume ratio)) to obtain the compound of the following formula (12) as a yellow oil (yield: 16.50 g, yield: 100%).

[0140] [Chemical formula]

[0141] Into the reaction vessel were charged the compound of formula (12) (16.40 g) obtained above, 4,4'-dimethoxydiphenylamine (2.90 g, manufactured by TCI), tris(dibenzylideneacetone)dipalladium(0) (0.68 g, manufactured by Kanto Chemical), sodium t-butoxide (3.67 g, manufactured by Kanto Chemical), 1,1'-bis(diphenylphosphino)ferrocene (0.56 g, manufactured by Kanto Chemical), and toluene (25 mL), and degassing was carried out under reduced pressure. Under an argon atmosphere, the mixture was heated to reflux for 4 hours. After completion of the reaction, it was cooled to 40 °C or lower and filtered by suction. The residue was washed with toluene (50 mL), and the filtrate was concentrated. The crude product was purified by a silica gel column (toluene / hexane = 1 / 1 (volume ratio)) to obtain the compound of the following formula (13) as a yellow solid (yield: 2.76 g, yield: 38%).

[0142] Into the reaction vessel were charged the compound of formula (13) (10.0 g) obtained above and anhydrous THF (130 mL), and degassing was carried out under reduced pressure. Under an argon atmosphere, it was cooled to -70 °C or lower in an acetone-dry ice bath. Thereto, an n-butyllithium hexane solution (1.55 M, 17.0 mL, manufactured by Kanto Chemical) was added dropwise little by little. After completion of the dropwise addition, it was stirred at -70 °C or lower for 1 hour, and triisopropyl borate (6.0 mL, manufactured by TCI) was added dropwise. After completion of the dropwise addition, the temperature was gradually raised to room temperature, and it was stirred at room temperature for 1 hour. Water (55 mL) was poured into the reaction solution to terminate the reaction. The reaction solution was separated, and the aqueous layer was extracted twice with toluene (40 mL). The organic layer was dried over sodium sulfate and concentrated. The crude product was purified by a silica gel column (toluene → THF) to obtain the compound represented by the following formula (14) as a yellow powder (yield: 5.75 g, yield: 62%).

[0143] [Chemical formula]

[0144] Into a reaction vessel, 1.00 g of the compound of the above formula (10), 4.59 g of the compound of the above formula (14), 19.0 g of potassium carbonate (manufactured by Kanto Chemical Co., Inc.), 0.15 mg of tetrakis(triphenylphosphine)palladium(0) (manufactured by Kanto Chemical Co., Inc.), and 150 mL of toluene were charged and degassed. Then, it was heated under reflux for 68 hours under an argon atmosphere. After completion of the reaction, it was cooled to 50 °C or lower and filtered through celite. The residue was washed with 100 mL of toluene, and the filtrate was concentrated. The crude product was subjected to silica gel column chromatography (toluene → toluene / acetone = 100 / 1 (volume ratio)). Again, it was purified by silica gel column chromatography (toluene / acetone = 100 / 1 (volume ratio)), and the compound represented by the following formula (15) was obtained as a blackish green powder (yield: 1.34 g, yield: 40%).

[0145]

Chemical formula

[0146] Into a reaction vessel, 0.57 g of the compound of the above formula (15), 0.13 g of malononitrile (manufactured by TCI), and 15 mL of THF were charged and stirred under an argon atmosphere. Thereto, a solution of acetic acid - pyridine (volume ratio 1:1) (3.6 mL) was added. It was stirred under heating under reflux for 6 hours. After completion of the reaction, 30 mL of water and 20 mL of toluene were added. This was separated, and the aqueous layer was extracted twice with 30 mL of toluene. The organic layer was dried over magnesium sulfate and concentrated. The crude product was purified by column chromatography (toluene), and the compound represented by the following formula (A-1) was obtained as a blackish green powder (yield: 0.493 g, yield: 83%).

[0147] 1 1H-NMR (400 MHz, DMSO-d6): δ (ppm) = 3.72 (12H), 3.73 (6H), 6.7 - 6.8 (8H), 6.89 (8H), 6.92 (8H), 7.00 (8H), 7.05 (4H), 7.23 (2H), 7.33 (4H).

[0148]

Chemical formula

[0149] [Synthesis Example 2] Synthesis of Compound (A-11) 3,6-Dibromocarbazole (5.0 g, manufactured by TCI), 1-chloro-4-fluorobenzene (7.83 g, manufactured by TCI), cesium carbonate (19.5 g, manufactured by Kanto Chemical Co., Inc.), and DMF (15 mL) were charged into a reaction vessel. The mixture was stirred at 130 °C for 38 hours under an argon atmosphere. After completion of the reaction, the reaction solution was poured into a beaker containing saturated brine (250 mL). This was filtered, and the filtrate was washed with water (50 mL) and methanol (10 mL). The crude product was purified by silica gel column (toluene) to obtain the compound represented by the following formula (16) as a white powder (yield: 6.04 g, yield: 92%).

[0150] [Chemical formula]

[0151] The compound of the above formula (16) (5.0 g), 4,4'-dimethoxydiphenylamine (5.27 g, manufactured by TCI), palladium acetate (0.11 g, manufactured by Kanto Chemical Co., Inc.), sodium-t-butoxide (5.19 g, manufactured by Kanto Chemical Co., Inc.), tri-t-butylphosphine (33% xylene solution) (0.67 g, manufactured by Kanto Chemical Co., Inc.), and toluene (30 mL) were charged into a reaction vessel, and degassing was performed under reduced pressure under an argon atmosphere. The mixture was heated under reflux for 4 hours. After completion of the reaction, the reaction solution was filtered through Celite. The residue was washed with toluene (30 mL), and the filtrate was concentrated. The crude product was purified by silica gel column (toluene → toluene / acetone = 100 / 1 (volume ratio)) to obtain the compound represented by the following formula (17) as a yellow powder (yield: 3.10 g, yield: 39%).

[0152] Into the reaction vessel were charged the compound of formula (17) (3.10 g) obtained above, bis(pinacolato)diboron (2.13 g, manufactured by TCI), potassium acetate (2.06 g, manufactured by Kanto Chemical Co., Inc.), 1,1'-bis(diphenylphosphino)ferrocene dichloropalladium (0.343 g, manufactured by Kanto Chemical Co., Inc.), and 1,4-dioxane (27 mL). The mixture was degassed under reduced pressure in an argon atmosphere. It was heated under reflux for 37 hours. After completion of the reaction, it was cooled to 40 °C or lower and filtered through celite. The filtrate was concentrated, and the crude product was purified by silica gel column (toluene / acetone = 200 / 1 (volume ratio)). It was purified again by silica gel column (toluene) to obtain the compound of the following formula (18) as a yellow powder (yield: 2.56 g, yield: 74%).

[0153]

Chemical formula

[0154] Into the reaction vessel were charged the compound of formula (10) (0.43 g), the compound of formula (18) (2.56 g), tetrakis(triphenylphosphine)palladium(0) (0.058 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.44 g, manufactured by Kanto Chemical Co., Inc.), toluene (7 mL), ethanol (2 mL), and water (2 mL). The mixture was degassed under reduced pressure. It was heated under reflux for 7 hours in an argon atmosphere. After completion of the reaction, toluene (20 mL) and water (10 mL) were added. This was separated by liquid separation, the aqueous layer was extracted twice with toluene (20 mL), and the organic layer was concentrated. The crude product was purified by silica gel column (toluene / acetone = 100 / 1 (volume ratio)) to obtain the compound represented by the following formula (19) as a black-blue powder (yield: 1.65 g, yield: 84%).

[0155]

Chemical formula

[0156] The compound of the above formula (19) (0.56 g), malononitrile (0.09 g, manufactured by TCI), and THF (15 mL) were charged into a reaction vessel and stirred under an argon atmosphere. A solution of acetic acid - pyridine (1:1) (2.6 mL) was added thereto. The mixture was stirred for 16 hours under heating under reflux. After completion of the reaction, water (30 mL) was added. This was filtered and washed with water (30 mL) and methanol (20 mL). The crude product was recrystallized (chloroform / acetone) to obtain the compound represented by the following formula (A - 11) as a green powder (yield: 0.52 g, yield rate: 91%).

[0157] 1 H-NMR(400MHz, THF-d8): δ(ppm)=3.68(24H) 6.72(16H), 6.91(16H), 7.08(4H), 7.3(4H), 7.66(8H), 7.76(2H), 7.90(4H).

[0158]

Chemical formula

[0159] [Synthesis Example 3] Synthesis of Compound (A - 12) The compound of the above formula (10) (0.43 g), the compound of the following formula (20) (2.04 g), tetrakis(triphenylphosphine)palladium(0) (0.058 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.44 g, manufactured by Kanto Chemical Co., Inc.), toluene (7 mL), ethanol (2 mL), and water (2 mL) were charged into a reaction vessel and degassed under reduced pressure. The mixture was heated under reflux for 7 hours under an argon atmosphere. After completion of the reaction, toluene (20 mL) and water (10 mL) were added. This was separated by liquid separation, the aqueous layer was extracted twice with toluene (20 mL), and the organic layer was concentrated. The crude product was purified by silica gel column (toluene) and silica gel column (toluene:hexane = 2 / 1 (volume ratio)) to obtain the compound of the following formula (21) as a black-purple powder (yield: 1.42 g, yield rate: 86%).

[0160]

Chemical formula

[0161] The compound of the above formula (21) (0.60 g), malononitrile (0.12 g, manufactured by TCI), and THF (19 mL) were charged into a reaction vessel and stirred under an argon atmosphere. A solution of acetic acid - pyridine (1:1) (3.2 mL) was added thereto. The mixture was stirred under heating under reflux for 54 hours. After completion of the reaction, the reaction solution was poured into water (200 mL). This was filtered and washed with water (30 mL) and methanol (20 mL). After washing the crude product with toluene, recrystallization (chloroform / acetone) was carried out to obtain the compound represented by the following formula (A - 12) as a green powder (yield: 0.30 g, yield rate: 48%).

[0162] 1 1H - NMR (400 MHz, THF - d8): δ (ppm) = 6.84 (8H), 7.00 (16H), 7.13 (16H), 7.19 (4H), 7.39 (4H), 7.55 (2H), 7.68 (4H), 7.86 (4H), 7.93 (4H).

[0163]

Chemical formula

[0164] [Synthesis Example 4] Synthesis of Compound (A - 26) The compound of the above formula (10) (0.43 g), the compound of the following formula (22) (2.52 g), tetrakis(triphenylphosphine)palladium(0) (0.058 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.44 g, manufactured by Kanto Chemical Co., Inc.), toluene (7 mL), ethanol (2 mL), and water (2 mL) were charged into a reaction vessel and degassed under reduced pressure. Under an argon atmosphere, the mixture was heated under reflux for 7 hours. After completion of the reaction, toluene (20 mL) and water (10 mL) were added. This was separated into layers, the aqueous layer was extracted twice with toluene (20 mL), and the organic layer was concentrated. The crude product was purified by a silica gel column (toluene / ethyl acetate = 50 / 1 (volume ratio)) to obtain the compound represented by the following formula (23) as a black powder (yield: 1.52 g, yield rate: 75%).

[0165]

Chemical formula

[0166] The compound of the above formula (23) (0.56 g), malononitrile (0.09 g, manufactured by TCI), and THF (15 mL) were charged into a reaction vessel and stirred under an argon atmosphere. A solution of acetic acid - pyridine (1:1) (2.6 mL) was added thereto. The mixture was stirred under heating under reflux for 16 hours. After completion of the reaction, water (30 mL) was added. This was filtered and washed with water (30 mL) and methanol (20 mL). The crude product was recrystallized (chloroform / acetone) to obtain the compound represented by the following formula (A-26) as a green powder (yield: 0.51 g, yield: 88%).

[0167] 1 H-NMR (400 MHz, THF-d8): δ (ppm) = 3.67 (24H) 6.65 (16H), 6.84 (16H), 6.96 (4H), 7.11 (4H), 7.57 (8H), 7.59 (2H), 7.80 (4H).

[0168]

Chemical formula

[0169] [Synthesis Example 5] Synthesis of Compound (A-41) The compound of the above formula (10) (0.43 g), the compound of the following formula (24) (2.48 g), tetrakis(triphenylphosphine)palladium(0) (0.058 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.44 g, manufactured by Kanto Chemical Co., Inc.), toluene (7 mL), ethanol (2 mL), and water (2 mL) were charged into a reaction vessel, and degassing was carried out under reduced pressure. The mixture was heated under reflux for 7 hours under an argon atmosphere. After completion of the reaction, toluene (20 mL) and water (10 mL) were added. This was separated into layers, the aqueous layer was extracted twice with toluene (20 mL), and the organic layer was concentrated. The crude product was purified by a silica gel column (toluene / ethyl acetate = 50 / 1 (volume ratio)) to obtain the compound of the following formula (25) as a black powder (yield: 1.52 g, yield: 77%).

[0170]

Chemical formula

[0171] The compound of the above formula (25) (0.55 g), malononitrile (0.09 g, manufactured by TCI), and THF (15 mL) were charged into a reaction vessel and stirred under an argon atmosphere. A solution of acetic acid - pyridine (1:1) (2.6 mL) was added thereto. The mixture was stirred under heating under reflux for 16 hours. After completion of the reaction, water (30 mL) was added. This was filtered and washed with water (30 mL) and methanol (20 mL). The crude product was recrystallized (chloroform / acetone) to obtain the compound represented by the following formula (A - 41) as a green powder (yield: 0.51 g, yield: 90%).

[0172] 1 1H - NMR (400 MHz, THF - d8): δ (ppm) = 3.68 (24H), 6.68 (16H), 6.88 (16H), 7.00 (4H), 7.15 (4H), 7.62 (8H), 7.64 (2H), 7.85 (4H).

[0173] [Chemical Formula]

[0174] [Synthesis Example 6] Synthesis of Compound (A - 56) The compound of the above formula (10) (0.88 g), [4 - [bis(4 - methoxyphenyl)amino]phenyl]boronic acid (2.10 g, manufactured by TCI), tetrakis(triphenylphosphine)palladium(0) (0.12 g, manufactured by Kanto Chemical Co., Inc.), potassium carbonate (0.90 g, manufactured by Kanto Chemical Co., Inc.), toluene (13 mL), ethanol (4.5 mL), and water (4.5 mL) were charged into a reaction vessel and degassed under reduced pressure. The mixture was heated under reflux for 6 hours under an argon atmosphere. After completion of the reaction, toluene (10 mL) and water (10 mL) were added. This was separated into layers, and the aqueous layer was extracted twice with toluene (20 mL). The organic layer was concentrated, and the crude product was purified by a silica gel column (toluene / acetone = 100 / 1 (volume ratio)). It was purified again by a silica gel column (toluene) to obtain the compound of the following formula (26) as a black - green powder (yield: 1.86 g, yield: 93%).

[0175]

Chem.

[0176] The compound of the above formula (26) (0.6 g), diethyl malonate (0.37 g, manufactured by TCI), and THF (14 mL) were charged into a reaction vessel and stirred under an argon atmosphere. It was cooled to 5°C or lower in an ice bath, and carbon tetrachloride (0.9 mL, manufactured by Junsei Chemical Co., Ltd.), titanium tetrachloride (0.5 mL, manufactured by Wako Pure Chemical Industries, Ltd.), and THF (8 mL) were charged. It was cooled again to 5°C or lower, and pyridine (1 mL) and THF (1 mL) were charged. Then, the temperature was raised to room temperature and stirred at room temperature for 17 hours. After completion of the reaction, the reaction solution was poured into a beaker containing 50 mL of water, and toluene (30 mL) was added thereto. This was separated, and the organic layer was washed twice with a 10% aqueous sodium carbonate solution (50 mL). The organic layer was dried over magnesium sulfate and concentrated. The crude product was purified by a silica gel column (toluene) to obtain the compound represented by the following formula (A-56) as a blackish green powder (yield: 0.56 g, yield: 79%).

[0177] 1 H-NMR (400 MHz, CDCl3): δ (ppm) = 1.38 (6H), 3.81 (12H), 4.40 (4H), 6.84 (8H), 6.90 (4H), 7.07 (8H), 7.31 (4H), 7.36 (2H).

[0178]

Chem.

[0179] [Synthesis Example 7] Synthesis of Compound (A-58) Into a reaction vessel were charged 1.33 g of the compound of the following formula (27), 2.10 g of [4-[bis(4-methoxyphenyl)amino]phenyl]boronic acid (manufactured by TCI), 0.12 g of tetrakis(triphenylphosphine)palladium(0) (manufactured by Kanto Chemical Co., Inc.), 0.90 g of potassium carbonate (manufactured by Kanto Chemical Co., Inc.), 13 mL of toluene, 4.5 mL of ethanol, and 4.5 mL of water, and degassing was carried out under reduced pressure. Under an argon atmosphere, the mixture was heated to reflux for 6 hours. After completion of the reaction, 10 mL of toluene and 10 mL of water were added. This was separated by liquid separation, and the aqueous layer was extracted twice with 20 mL of toluene. The organic layer was concentrated, and the crude product was purified by a silica gel column (toluene) to obtain the compound represented by the following formula (A-58) as a blackish green powder (yield: 2.11 g, yield: 86%).

[0180] 1 1H-NMR (400 MHz, CDCl3): δ (ppm) = 1.32 (6H), 3.81 (12H), 4.59 (4H), 6.84 (8H), 6.90 (4H), 7.08 (8H), 7.33 (4H), 7.69 (2H).

[0181] [Chemical formula]

[0182] [Synthesis Example 8] Synthesis of Compound (A-63) The compound of the above formula (26) (0.6 g), methyl cyanoacetate (0.23 g, manufactured by TCI), and THF (14 mL) were charged into a reaction vessel and stirred under an argon atmosphere. The mixture was cooled to 5 °C or lower in an ice bath, and carbon tetrachloride (0.9 mL, manufactured by Junsei Chemical Co., Ltd.), titanium tetrachloride (0.5 mL, manufactured by Wako Pure Chemical Industries, Ltd.), and THF (8 mL) were added. It was cooled again to 5 °C or lower, and pyridine (1 mL) and THF (1 mL) were added. Then, the temperature was raised to room temperature, and the mixture was stirred at room temperature for 18 hours and at 60 °C for 14 hours. After completion of the reaction, the reaction solution was poured into a beaker containing water (50 mL), and toluene (30 mL) was added thereto. This was separated by liquid separation, and the organic layer was washed twice with a 10% aqueous sodium carbonate solution (50 mL). The organic layer was dried over magnesium sulfate and then concentrated. The crude product was purified by a silica gel column (toluene) to obtain the compound represented by the following formula (A-63) as a blackish green powder (yield: 0.51 g, yield: 77%).

[0183] 1 1H-NMR (400 MHz, CDCl3): δ (ppm) = 3.81 (12H), 3.95 (3H), 6.84 (8H), 6.90 (4H), 7.07 (8H), 7.34 (4H), 7.68 (1H), 7.82 (1H).

[0184] [Chemical formula]

[0185] [Synthesis Example 9] Synthesis of Compound (A-66) Into the reaction vessel were charged the compound of the above formula (10) (0.88 g), 4-(diphenylamino)phenylboronic acid (1.73 g, manufactured by Sigma-Aldrich), tetrakis(triphenylphosphine)palladium(0) (0.12 g, manufactured by Kanto Chemical), potassium carbonate (0.90 g, manufactured by Kanto Chemical), toluene (13 mL), ethanol (4.5 mL), and water (4.5 mL), and degassing was carried out under reduced pressure. Under an argon atmosphere, it was heated to reflux for 13 hours. After completion of the reaction, the reaction solution was poured into a beaker containing ethanol (50 mL). This was filtered and washed twice with water (50 mL) and then with ethanol (20 mL). The crude product was purified by a silica gel column (toluene → chloroform). Thereafter, the crystals were dispersed and washed with toluene, and the compound represented by the following formula (28) was obtained as a black-blue powder (yield: 1.14 g, yield: 67%).

[0186]

Chemical formula

[0187] Into the reaction vessel were charged the compound of the above formula (28) (0.60 g), malononitrile (0.23 g, manufactured by TCI), and THF (50 mL), and it was stirred under an argon atmosphere. Thereto was added a solution of acetic acid - pyridine (1:1) (5.6 mL). It was stirred under heating to reflux for 32 hours. After completion of the reaction, the reaction solution was poured into a beaker containing water (300 mL). This was filtered and washed with water (20 mL) and then with methanol (20 mL). The crude product was dispersed and washed with acetone and recrystallized (from chloroform), and the compound represented by the following formula (A-66) was obtained as a black powder (yield: 0.44 g, yield: 69%).

[0188] 1 1H-NMR (400 MHz, THF-d8): δ (ppm) = 7.01 (8H), 7.06 (8H), 7.23 (8H), 7.45 (4H), 7.49 (2H).

[0189]

Chemical formula

[0190] [Synthesis Example 10] Synthesis of Compound (A-98) Into a reaction vessel were charged the compound of the above formula (10) (0.88 g), the compound of the following formula (29) (2.55 g), potassium carbonate (0.90 g, manufactured by Kanto Chemical Co., Inc.), tetrakistriphenylphosphine palladium (0.12 g, manufactured by Kanto Chemical Co., Inc.), toluene (13 mL), ethanol (4.5 mL), and water (4.5 mL), and the mixture was heated under reflux for 6 hours. After completion of the reaction, the reaction solution was poured into a beaker containing water (150 mL), and further toluene (20 mL) was added, followed by liquid separation. The organic layer was dried over magnesium sulfate and then concentrated. The crude product was purified by silica gel column (toluene) to obtain the compound represented by the following formula (30) as a blackish blue powder (yield: 1.81 g, yield rate: 84%).

[0191] [Chemical formula]

[0192] Into a reaction vessel were charged the compound of the above (30) (0.60 g), malononitrile (0.22 g, manufactured by TCI), and THF (29 mL), and the mixture was stirred under an argon atmosphere. Thereto was added a mixture of acetic acid and pyridine (volume ratio = 1:1) (5.0 mL), and the mixture was heated under reflux for 21 hours. After completion of the reaction, the reaction solution was poured into a beaker containing water (150 mL). This was filtered, and the solid was washed with (20 mL) and methanol (20 mL). The crude product was purified by silica gel column (toluene) and then recrystallized (chloroform:acetone) to obtain the compound represented by the following formula (A-98) as a black solid (yield: 0.54 g, yield rate: 84%).

[0193] 1 1H-NMR (400 MHz, CDCl3): δ (ppm) = 2.48 (2H), 7.02 - 7.06 (12H), 7.18 - 7.21 (8H), 7.38 (4H), 7.45 (2H).

[0194] [Chemical formula]

[0195] [Synthesis Example 11] Synthesis of Compound (A-114) Into a reaction vessel were charged the compound of the following formula (31) (0.32 g), [4-[bis(4-methoxyphenyl)amino]phenyl]boronic acid (0.49 g, manufactured by TCI), tetrakis(triphenylphosphine)palladium(0) (0.03 g, manufactured by Kanto Chemical), potassium carbonate (0.22 g, manufactured by Kanto Chemical), toluene (4 mL), ethanol (1.3 mL), and water (1.3 mL), and degassing was carried out under reduced pressure. The mixture was stirred under heating under reflux for 6 hours in an argon atmosphere. After completion of the reaction, the reaction solution was poured into water (100 mL). After adding 20 mL of toluene thereto, liquid separation was carried out. The organic layer was dried over magnesium sulfate and then concentrated. The crude product was purified by a silica gel column (toluene) to obtain the compound represented by the following formula (32) as a blackish green powder (yield: 0.40 g, yield: 69%).

[0196] [Chemical formula]

[0197] Into a reaction vessel were charged the compound of the above formula (32) (0.35 g), diethyl malonate (0.27 mL, manufactured by TCI), and THF (11 mL), and the mixture was stirred in an argon atmosphere. Pyridine (0.48 mL, manufactured by Nacalai Tesque) was added thereto, and then titanium tetrachloride (0.24 mL, manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the mixture was stirred at room temperature for 9 hours. After completion of the reaction, the reaction solution was poured into a beaker containing water (150 mL). This was filtered, washed with water (30 mL) and methanol (20 mL), and dried. The crude product was purified by a silica gel column (toluene / ethyl acetate = 50 / 1 (volume ratio)) to obtain the compound represented by the following formula (A-114) as a blackish green powder (yield: 0.32 g, yield: 82%).

[0198] 1 1H-NMR (400 MHz, THF-d8): δ (ppm) = 1.35 (6H), 3.73 (12H), 4.39 (4H), 6.81 - 6.88 (12H), 7.02 (8H), 7.12 (2H), 7.15 (2H), 7.39 - 7.42 (6H).

[0199]

Chem.

[0200] [Synthesis Example 12] Synthesis of Compound (A-115) Into a reaction vessel were charged 0.32 g of the compound of the above formula (31), 1.15 g of the compound of the following formula (33), 0.03 g of tetrakis(triphenylphosphine)palladium(0) (manufactured by Kanto Chemical Co., Inc.), 0.22 g of potassium carbonate (manufactured by Kanto Chemical Co., Inc.), 4 mL of toluene, 1.3 mL of ethanol, and 1.3 mL of water, and degassing was carried out under reduced pressure. Stirring was performed under heating under reflux for 6 hours in an argon atmosphere. After completion of the reaction, the reaction solution was poured into 100 mL of water. After adding 20 mL of toluene thereto, liquid separation was carried out. The organic layer was dried over magnesium sulfate and then concentrated. The crude product was purified by a silica gel column (toluene / ethyl acetate = 40 / 1 (volume ratio)) to obtain the compound represented by the following formula (34) as a blackish green powder (yield: 0.64 g, yield: 61%).

[0201]

Chem.

[0202] Into a reaction vessel were charged 0.32 g of the compound of the above formula (34), 0.05 g of malononitrile (manufactured by TCI), and 8 mL of THF, and stirring was performed in an argon atmosphere. Thereto was added a mixture of acetic acid and pyridine (volume ratio = 1:1) (1.4 mL), and heating under reflux was carried out for 20 hours. After completion of the reaction, the reaction solution was poured into a beaker containing 150 mL of water. This was filtered, washed with 20 mL of water and 20 mL of methanol, and then dried. The crude product was purified by a silica gel column (toluene / ethyl acetate = 40 / 1 (volume ratio)) to obtain the compound represented by the following formula (A-115) as a blackish green powder (yield: 0.26 g, yield: 81%).

[0203] 11H-NMR (400 MHz, THF-d8): δ (ppm) = 3.67 (24H), 6.69 - 6.71 (16H), 6.88 - 6.90 (16H), 7.07 (4H), 7.28 - 7.31 (6H), 7.47 (4H), 7.61 (4H), 7.64 (4H), 7.89 (4H).

[0204] [Chemical formula]

[0205] [Example 1] Fabrication of a photoelectric conversion element and evaluation of its photoelectric conversion characteristics A glass substrate (conductive support 1, manufactured by Solaronix) coated with a fluorine-doped tin oxide (FTO) thin film that has been etched was ultrasonically cleaned with acetone and then subjected to UV ozone treatment. On this substrate, a titanium oxide (TiO₂) solution for the hole blocking layer (Ti-Nanoxide BL / SC, manufactured by Solaronix) was spin-coated. After coating, it was fired at 500 °C for 1 hour using an electric furnace to obtain a TiO₂ thin film (hole blocking layer 2) with a film thickness of 50 - 70 nm. Subsequently, a titanium oxide (TiO₂) dispersion for the electron transport layer prepared by mixing titanium oxide (TiO₂) paste (PST-18NR, manufactured by Nippon Shokubai Catalysts & Chemicals Co., Ltd.) and ethanol at a weight ratio of 1:4 was spin-coated on this substrate. After coating, it was fired at 450 °C for 30 minutes using an electric furnace to obtain a mesoporous titanium oxide (TiO₂) thin film (electron transport layer 3) with a film thickness of 330 nm.

[0206] Next, PbI₂ / MAI (1:1)-DMF complex (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in dimethyl sulfoxide to prepare a 1.5 M solution. At room temperature, the prepared dimethyl sulfoxide solution was spin-coated on the mesoporous titanium oxide (TiO₂) thin film, and 0.3 mL of chlorobenzene was dropped during spin coating to form a film, which was then heated and dried at 110 °C for 1 hour using a hot plate to form a CH₃NH₃PbI₃ layer (photoelectric conversion layer 4) with a thickness of approximately 500 nm.

[0207] Next, a chlorobenzene solution was prepared in which 4-tert-butylpyridine, which is a basic compound of the additive, was 75 mM and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 0.5 equivalent), which is a dopant of the additive, was 12.5 mM, and this was used as the doping solution. Using the prepared doping solution and compound (A-1), which is a hole transport material for a photoelectric conversion element obtained in Synthesis Example 1, a 50 mM chlorobenzene solution was prepared and used as the hole transport layer solution. At room temperature, the hole transport layer solution was spin-coated on the CH3NH3PbI3 layer (photoelectric conversion layer 4) and dried by heating at 70 °C for 30 minutes using a hot plate to form a hole transport layer 5 with a thickness of approximately 300 nm.

[0208] On the hole transport layer 5, gold was vacuum-deposited at a degree of vacuum of about 1 × 10 -4 Pa to form a gold electrode (counter electrode 6) by film formation of 80 to 100 nm, and a photoelectric conversion element was fabricated.

[0209] Light generated by a simulated sunlight irradiation device (OTENTO-SUN III type manufactured by Spectral Instruments Co., Ltd.) was irradiated from the transparent electrode side of the photoelectric conversion element, and the current-voltage characteristics were measured using a source meter (Model 2400 General-Purpose SourceMeter manufactured by KEITHLEY), with the light intensity adjusted to 100 mW / cm 2 The initial photoelectric conversion efficiency was obtained from the measured current-voltage characteristic values. Also, the photoelectric conversion element was stored for 168 hours after the measurement of the initial photoelectric conversion efficiency in a desiccator equipped with silica gel, and the photoelectric conversion efficiency after storage (photoelectric conversion efficiency over time) was evaluated. Further, as an evaluation of durability, the retention rate (%) of the photoelectric conversion efficiency after storage for 168 hours from the measurement of the initial photoelectric conversion efficiency was calculated from the following formula (a-1). The calculated retention rate (%) is shown in Table 2.

[0210]

Equation

[0211] [Example 2] Using the compound (A-11), which is a hole transport material for a photoelectric conversion element obtained in Synthesis Example 2, a 50 mM solution in chlorobenzene was prepared and used as the hole transport layer solution. A photoelectric conversion element was fabricated in the same manner as in Example 1, except that the compound (A-11) was used and bis(trifluoromethanesulfonyl)imide lithium (LiTFSI), which is a dopant for the additive, and 4-tert-butylpyridine, which is a basic compound of the additive, were not used (0 mM). The initial photoelectric conversion efficiency was obtained by measuring the current-voltage characteristics. In addition, the photoelectric conversion efficiency (photoelectric conversion efficiency over time) after storing the photoelectric conversion element of Example 2 in a desiccator equipped with silica gel for 168 hours from the measurement of the initial photoelectric conversion efficiency was obtained. Table 1 shows the ratio of the photoelectric conversion efficiency after 168-hour storage of Example 2 to the photoelectric conversion efficiency after 168-hour storage of Comparative Example 1 described later (storage under the same conditions as those of Example 2) (hereinafter, the ratio to Comparative Example 1). Table 2 shows the retention rate (%) of the photoelectric conversion efficiency after 168-hour storage from the measurement of the initial conversion efficiency as an evaluation of the durability of the photoelectric conversion element of Example 2. Here, the ratio to Comparative Example 1 shown in Table 1 indicates the value obtained by dividing the photoelectric conversion efficiency (photoelectric conversion efficiency over time) after 168-hour storage of the example by the photoelectric conversion efficiency (photoelectric conversion efficiency over time) after 168-hour storage of Comparative Example 1.

[0212] [Example 3] A photoelectric conversion element was fabricated in the same manner as in Example 1, except that the compound (A-11) was used. The initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 168-hour storage were obtained by measuring the current-voltage characteristics. Table 1 shows the ratio of the photoelectric conversion efficiency after 168-hour storage from the measurement of the initial photoelectric conversion efficiency to that of Comparative Example 1. Table 2 shows the retention rate (%) of the photoelectric conversion efficiency after 168-hour storage from the measurement of the initial conversion efficiency as an evaluation of the durability.

[0213] [Example 4] A photoelectric conversion device was fabricated in the same manner as in Example 2 except that compound (A-56) was used, and the current-voltage characteristics were measured to obtain the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after storage for 168 hours. Further, the ratio of the photoelectric conversion efficiency after storage for 168 hours to that of Comparative Example 1 based on the measurement of the initial photoelectric conversion efficiency is shown in Table 1, and the retention rate (%) of the photoelectric conversion efficiency after storage for 168 hours from the measurement of the initial conversion efficiency is shown in Table 2 as an evaluation of durability.

[0214] [Example 5] A photoelectric conversion device was fabricated in the same manner as in Example 1 except that compound (A-56) was used, and the current-voltage characteristics were measured to obtain the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after storage for 168 hours. Further, the ratio of the photoelectric conversion efficiency after storage for 168 hours to that of Comparative Example 1 based on the measurement of the initial photoelectric conversion efficiency is shown in Table 1, and the retention rate (%) of the photoelectric conversion efficiency after storage for 168 hours from the measurement of the initial conversion efficiency is shown in Table 2 as an evaluation of durability.

[0215] [Example 6] A photoelectric conversion device was fabricated in the same manner as in Example 2 except that compound (A-63) was used, and the current-voltage characteristics were measured to obtain the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after storage for 168 hours. Further, the ratio of the photoelectric conversion efficiency after storage for 168 hours to that of Comparative Example 1 based on the measurement of the initial conversion efficiency is shown in Table 1, and the retention rate (%) of the photoelectric conversion efficiency after storage for 168 hours from the measurement of the initial conversion efficiency is shown in Table 2 as an evaluation of durability.

[0216] [Example 7] A photoelectric conversion device was fabricated in the same manner as in Example 1 except that compound (A-63) was used, and the current-voltage characteristics were measured to obtain the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after storage for 168 hours. Further, the ratio of the photoelectric conversion efficiency after storage for 168 hours to that of Comparative Example 1 based on the measurement of the initial conversion efficiency is shown in Table 1.

[0217] [Comparative Example 1] A photoelectric conversion device 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, and the current-voltage characteristics were measured to obtain the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after storage for 168 hours. The initial photoelectric conversion efficiency was 6.03%. As an evaluation of durability, Table 2 shows the retention rate (%) of the photoelectric conversion efficiency after storage for 168 hours from the measurement of the initial photoelectric conversion efficiency.

[0218]

Chemical formula

[0219]

Table 1

[0220]

Table 2

[0221] From the results in Table 1, it was found that Compound (A-11) and Compound (A-56) showed higher and sufficient photoelectric conversion efficiency than the compounds of the comparative examples that are commonly used. Also, it was found that Compound (A-63) showed a high photoelectric conversion efficiency equivalent to that of the compounds of the comparative examples that are commonly used. Furthermore, it was found that Compound (A-11), Compound (A-56), and Compound (A-63) can be used in the hole transport layer of the photoelectric conversion device even without reducing or using the dopant, which is an additive. From this, it is possible to reduce the manufacturing cost by reducing the doping amount in the photoelectric conversion device containing Compound (A-11), Compound (A-56), or Compound (A-63), and it is possible to fabricate it by a simpler process and at a lower cost that does not require a doping operation.

[0222] Also, from the results in Table 2, the photoelectric conversion elements using a hole transport layer containing Compound (A-1), Compound (A-11), Compound (A-56), or Compound (A-63) showed a high level of photoelectric conversion efficiency even after 168 hours, and it was found that the retention rate was superior to that of the compounds in the comparative examples.

[0223] [Example 8] Fabrication of a Photoelectric Conversion Element and Evaluation of Current-Voltage Characteristics A glass substrate with a FLAT ITO film (conductive support 7, manufactured by Diomatic) was ultrasonically cleaned with isopropyl alcohol and then subjected to UV ozone treatment. On this substrate, a tin oxide dispersion (coating solution for the electron transport layer) with a volume ratio of Tin(IV) oxide, 15% in H2O colloidal dispersion (manufactured by Alfa Aesar) and purified water of 1:9 was applied by spin coating. Thereafter, the electron transport layer 8 with a film thickness of about 20 nm was formed by heating on a hot plate at 150 °C for 30 minutes.

[0224] In a glove box under a nitrogen stream, formamidinium hydroiodide (1M, manufactured by Tokyo Chemical Industry), lead(II) iodide (1.1M, manufactured by Tokyo Chemical Industry), methylammonium hydrobromide (0.2M, manufactured by Tokyo Chemical Industry), and lead(II) bromide (0.2M, manufactured by Tokyo Chemical Industry) were dissolved in a mixed solvent with a volume ratio of dimethylformamide and dimethyl sulfoxide of 4:1. Thereto, a dimethyl sulfoxide solution of cesium iodide (1.5M, manufactured by Tokyo Chemical Industry) was added so that the charged amount of cesium was 5% in the composition ratio, and a perovskite precursor solution was prepared. In a glove box under a nitrogen atmosphere, the prepared perovskite precursor solution was dropped onto the tin oxide thin film and spin-coated, and 0.3 mL of chlorobenzene was dropped during the spin coating to apply the perovskite precursor. Thereafter, the Cs(MAFA)Pb(IBr)3 layer (photoelectric conversion layer 9) with a film thickness of about 500 nm was formed by heating on a hot plate at 100 °C for 1 hour.

[0225] In a glove box under a nitrogen stream, a chlorobenzene solution of a dopant was prepared with 4-tert-butylpyridine at 150 mM and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 0.5 equivalent) at 25 mM. The hole-transporting material (Compound (A-63)) obtained in Synthesis Example 11 was dissolved in the chlorobenzene solution at 50 mM at room temperature to obtain a coating solution for the hole-transporting layer. In a glove box under a nitrogen atmosphere, the coating solution for the hole-transporting layer was spin-coated on the Cs(MAFA)Pb(IBr)3 layer (photoelectric conversion layer 9) to form a hole-transporting layer 10 with a film thickness of about 200 nm.

[0226] Gold was vacuum-deposited on the hole-transporting layer 10 by the vacuum evaporation method at a degree of vacuum of about 1 × 10 -4 Pa to form a gold electrode (counter electrode 11) with a film thickness of about 80 nm, thereby fabricating a photoelectric conversion device.

[0227] Light with an intensity of 100 mW / cm 2 generated by a simulated sunlight irradiation device (OTENTO-SUN III type manufactured by Spectral Instruments Co., Ltd.) was irradiated from the conductive support side of the photoelectric conversion device, and the initial photoelectric conversion efficiency was obtained by measuring the current-voltage characteristics using a source meter (Model 2400 General-Purpose SourceMeter manufactured by KEITHLEY). The photoelectric conversion device was stored in a desiccator equipped with silica gel for 30 days after the initial photoelectric conversion efficiency measurement, and the photoelectric conversion efficiency after 30 days (720 hours later) was obtained by measuring the current-voltage characteristics again. Table 3 shows the ratio of the photoelectric conversion efficiency after 720 hours of storage, which is the photoelectric conversion over time from the initial photoelectric conversion efficiency measurement of the photoelectric conversion device of Example 8, to the photoelectric conversion efficiency of the photoelectric conversion device of Comparative Example 2 described below after being stored in the same manner as the photoelectric conversion device of Example 8 (hereinafter, the ratio to Comparative Example 2). Table 4 shows the retention rate (%) of the photoelectric conversion efficiency after 720 hours of storage from the initial photoelectric conversion efficiency measurement as an evaluation of durability.

[0228] [Example 9] Using the compound (A-63), which is a hole transport material for a photoelectric conversion element obtained in Synthesis Example 11, a 50 mM chlorobenzene solution was prepared and used as the hole transport layer solution. A photoelectric conversion element was fabricated in the same manner as in Example 8, except that bis(trifluoromethanesulfonyl)imide lithium (LiTFSI), which is a dopant of the additive, and 4-tert-butylpyridine, which is a basic compound of the additive, were not used (0 mM), and the initial photoelectric conversion efficiency was obtained by measuring the current-voltage characteristics. Further, the photoelectric conversion element was stored in a desiccator equipped with silica gel for 30 days from the measurement of the initial photoelectric conversion efficiency, and the photoelectric conversion efficiency after 30 days (after 720 hours) was obtained by measuring the current-voltage characteristics again. Table 3 shows the ratio of the photoelectric conversion efficiency after 720 hours of storage, which is the photoelectric conversion over time from the measurement of the initial photoelectric conversion efficiency, to Comparative Example 2, and Table 4 shows the retention rate (%) of the photoelectric conversion efficiency after 720 hours of storage from the measurement of the initial photoelectric conversion efficiency as an evaluation of durability.

[0229] [Example 10] A photoelectric conversion element was fabricated in the same manner as in Example 8, except that the compound (A-114) was used, and the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 30 days (after 720 hours) were obtained by measuring the current-voltage characteristics. Table 3 shows the ratio of the photoelectric conversion efficiency after 720 hours of storage from the measurement of the initial photoelectric conversion efficiency to Comparative Example 2, and Table 4 shows the retention rate (%) of the photoelectric conversion efficiency after 720 hours of storage from the measurement of the initial conversion efficiency as an evaluation of durability.

[0230] [Example 11] A photoelectric conversion element was fabricated in the same manner as in Example 9, except that the compound (A-114) was used, and the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 30 days (after 720 hours) were obtained by measuring the current-voltage characteristics. Table 3 shows the ratio of the photoelectric conversion efficiency after 720 hours of storage from the measurement of the initial conversion efficiency to Comparative Example 1, and Table 4 shows the retention rate (%) of the photoelectric conversion efficiency after 720 hours of storage from the measurement of the initial conversion efficiency as an evaluation of durability.

[0231] [Example 12] A photoelectric conversion device was fabricated in the same manner as in Example 8 except that compound (A-115) was used, and the current-voltage characteristics were measured to obtain the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 30 days (720 hours). Also, the ratio of the photoelectric conversion efficiency after storage for 720 hours from the measurement of the initial photoelectric conversion efficiency to Comparative Example 2 is shown in Table 3, and as an evaluation of durability, the retention rate (%) of the photoelectric conversion efficiency after storage for 720 hours from the measurement of the initial conversion efficiency is shown in Table 4.

[0232] [Example 13] A photoelectric conversion device was fabricated in the same manner as in Example 9 except that compound (A-115) was used, and the current-voltage characteristics were measured to obtain the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 30 days (720 hours). Also, the ratio of the photoelectric conversion efficiency after storage for 720 hours from the measurement of the initial conversion efficiency to Comparative Example 1 is shown in Table 3, and as an evaluation of durability, the retention rate (%) of the photoelectric conversion efficiency after storage for 720 hours from the measurement of the initial conversion efficiency is shown in Table 4.

[0233] [Comparative Example 2] A photoelectric conversion device was fabricated in the same manner as in Example 8 except that Spiro-OMeTAD (manufactured by Sigma-Aldrich), a standard hole transport material represented by the formula (B-1) shown in Comparative Example 1, was used, and the current-voltage characteristics were measured to obtain the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after 30 days (720 hours). The initial photoelectric conversion efficiency was 13.2%. The retention rate (%) of the photoelectric conversion efficiency after storage for 720 hours from the measurement of the initial conversion efficiency is shown in Table 4.

[0234]

Table 3

[0235]

Table 4

[0236] From the results in Table 3, it was found that Compound (A-63), Compound (A-114), and Compound (A-115) showed sufficient photoelectric conversion efficiency, which was higher than that of the standard comparative compounds used. Furthermore, it was found that Compound (A-63), Compound (A-114), and Compound (A-115) can be used for the hole transport layer of a photoelectric conversion device even without reducing or using a dopant as an additive. From this, it can be seen that a photoelectric conversion device containing Compound (A-63), Compound (A-114), or Compound (A-115) can reduce the manufacturing cost by reducing the doping amount, and can be manufactured by a simpler process and at a lower cost without requiring a doping operation.

[0237] Also, from the results in Table 4, the photoelectric conversion device using a hole transport layer containing Compound (A-63), Compound (A-114), or Compound (A-115) showed a high level of photoelectric conversion efficiency even after 720 hours, and its retention rate was found to be superior to that of the compounds in the comparative examples.

[0238] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Japanese Patent Application No. 2020-129304) filed on July 30, 2020, the entire contents of which are incorporated herein by reference. Also, all references cited herein are incorporated in their entirety.

Industrial Applicability

[0239] By using the hole transport layer for a photoelectric conversion device according to the present invention, it is useful for a highly efficient and highly durable photoelectric conversion device and a perovskite solar cell capable of efficiently extracting current, and can provide clean energy as a solar cell capable of efficiently converting solar energy into electrical energy.

Explanation of Signs

[0240] 1 Conductive support 2 Hole-blocking layer 3 Electron-transporting layer 4 Photoelectric conversion layer 5 Hole-transporting layer 6 Counter electrode 7 Conductive support 8 Electron-transporting layer 9 Photoelectric conversion layer 10 Hole-transporting layer 11 Counter electrode

Claims

1. A compound represented by the following general formula (1), wherein X in general formula (1) １ and X ２ are each independently represented by the following general formula (2). 【Chemical Formula 1】 [In the formula, R １ and R ２ are each independently a nitrile group, a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms, a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent, a thio group having 1 to 18 carbon atoms which may have a substituent, an amino group having 1 to 20 carbon atoms which may have a substituent, or a linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent, R ３ to R ２２ are each independently a hydrogen atom, a halogen atom, a carboxyl group, a trimethylsilyl group, a linear or branched alkyl group having 1 to 18 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 linear or branched alkynyl 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 linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, an acyl group having 1 to 20 carbon atoms which may have a substituent, A thio group having 1 to 18 carbon atoms which may have a substituent, An amino group having 1 to 20 carbon atoms which may have a substituent, An aromatic hydrocarbon group having 6 to 36 carbon atoms having a substituent, Or a heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent, (1) When R1 and R2 are nitrile groups, (i) R5 and R15 are linear or branched alkoxy groups having 1 to 20 carbon atoms which may have a substituent, and R10 and R20 are amino groups having 1 to 20 carbon atoms which may have a substituent, or (ii) R5, R10, R15 and R20 are amino groups having 1 to 20 carbon atoms which may have a substituent, or (iii) R5, R10, R15 and R20 are thio groups having 1 to 18 carbon atoms which may have a substituent, (2) When R1 and R2 are each independently a linear or branched perfluoroalkyl group having 1 to 4 carbon atoms, a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent, a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent, a thio group having 1 to 18 carbon atoms which may have a substituent, an amino group having 1 to 20 carbon atoms which may have a substituent, or a linear or branched alkylsulfonyl group having 1 to 18 carbon atoms which may have a substituent, R5, R10, R15 and R20 are each independently A carboxyl group, a trimethylsilyl group, A linear or branched alkyl group having 1 to 18 carbon atoms which may have a substituent, A cycloalkyl group having 3 to 10 carbon atoms which may have a substituent, A linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, an acyl group having 1 to 20 carbon atoms which may have a substituent, a thio group having 1 to 18 carbon atoms which may have a substituent, an amino group having 1 to 20 carbon atoms which may have a substituent, an aromatic hydrocarbon group having 6 to 36 carbon atoms having a substituent, or a heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent, R １ and R ２ may be bonded to each other to form a ring, R ３ ~R ７ , R ８ ~R １２ , R １３ ~R １７ and R １８ ~R ２２ may be bonded to each other between adjacent groups to form a ring, R ７ and R ８ and R １７ and R １８ may be bonded to each other to form a ring. ] [Chemical Formula 2] [In the formula, R ２３ ~R ２８ are each independently a hydrogen atom, 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 linear or branched alkynyl 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 linear or branched alkoxy group having 1 to 20 carbon atoms which may have a substituent, a cycloalkoxy group having 3 to 10 carbon atoms which may have a substituent, a thio group having 1 to 18 carbon atoms which may have a substituent, an amino group having 1 to 20 carbon atoms which may have a substituent, An aromatic hydrocarbon group having 6 to 36 carbon atoms which may have a substituent, or a heterocyclic group having 5 to 36 ring-forming atoms which may have a substituent, R ２３ and R ２４ , R ２５ and R ２６ and R ２７ and R ２８ may be bonded to each other to form a ring. Y １ represents an oxygen atom, a sulfur atom or a selenium atom, and m and n each represent an integer of 0 to 2. However, either m or n is 1 or 2. ]

2. In the general formula (1), R １ and R ２ are each independently a nitrile group, a linear or branched acyl group having 1 to 18 carbon atoms which may have a substituent, or a linear or branched alkoxycarbonyl group having 1 to 18 carbon atoms which may have a substituent is the compound according to claim 1.

3. The compound according to claim 1 or claim 2, wherein m in the general formula (2) is 1.

4. A hole transport material for a photoelectric conversion element containing the compound according to any one of claims 1 to 3.

5. A hole transport layer comprising the hole transport material for a photoelectric conversion element according to claim 4 and a dopant which is an additive in an amount of 0 to 0.5 equivalents with respect to 1 equivalent of the hole transport material for a photoelectric conversion element.

6. A photoelectric conversion element comprising the hole transport layer according to claim 5.

7. A solar cell comprising the photoelectric conversion element according to claim 6.

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