Composition and photoelectric conversion element

Abstract

Disclosed is a composition for forming a hole transport layer, the composition containing a charge transport polymer having a unit which is represented by a specific structural formula, tetraaryl borate ions, a first solvent that is an aromatic compound containing an oxygen atom, and a second solvent that does not contain an oxygen atom.　The present invention can provide: a composition which contains a polymer having an aromatic amine structural unit and an electron-accepting compound that improves conductivity, contains a mixed solvent that sufficiently dissolves the polymer and the electron-accepting compound, and can be suitably applied to the formation of a hole transport layer; and a photoelectric conversion element which has a hole transport layer that is formed using the composition.

Description

Composition and photoelectric conversion element

[0001] The present invention relates to a composition and a photoelectric conversion element.

[0002] In photoelectric conversion elements in which an active layer, a buffer layer, and the like are disposed between a pair of electrodes, the development of organic-inorganic hybrid semiconductor compounds as materials for the active layer is progressing, and among these, compounds having a perovskite structure (perovskite semiconductor compounds) have attracted attention. Organic semiconductor compounds and the like are used as hole transport layers in photoelectric conversion elements. In particular, polymers having aromatic amine structural units have been used as materials for hole transport layers in recent years because they are expected to contribute to power generation efficiency due to their high charge mobility and because they are soluble in solvents, allowing for layer formation by coating (Patent Documents 1 to 3).

[0003] International Publication No. 2017 / 018529 JP 2022-145231 A JP 2022-150357 A

[0004] However, hole transport layers of conventional photoelectric conversion elements have been formed using compositions containing halogen-containing solvents such as chlorobenzene. Although halogen-containing solvents have a high dissolving power for various materials, they have a significant impact on the human body and the environment, making it necessary to replace them with other solvents. Therefore, the present invention aims to provide a composition suitable for forming a hole transport layer, which contains a polymer having an aromatic amine structural unit and an electron-accepting compound that improves electrical conductivity, and a mixed solvent that sufficiently dissolves them, and a photoelectric conversion element having a hole transport layer formed using the composition.

[0005] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by using a first solvent that is an aromatic compound containing an oxygen atom and a second solvent that does not contain an oxygen atom in a composition for forming a hole transport layer, and have thus completed the present invention. The present invention has the following aspects.

[0006] [1] A composition comprising a charge-transporting polymer having a unit represented by the following formula (1), a tetraarylborate ion represented by the following formula (2), a first solvent which is an aromatic compound containing an oxygen atom, and a second solvent which does not contain an oxygen atom.

[0007]

[0008] In formula (1), R １ ~R ５ each independently represents a hydrogen atom or a monovalent aliphatic hydrocarbon group, R １ and R ５ At least one of Ar is a monovalent aliphatic hydrocarbon group, １ represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent.

[0009]

[0010] In formula (2), Ar １１ , Ar １２ , Ar １３ , and Ar １４ each independently represents a monovalent aromatic hydrocarbon group which may have a substituent, or a monovalent aromatic heterocyclic group which may have a substituent, and Ar １１ , Ar １２ , Ar １３ , and Ar １４ At least one of the groups has a fluorine atom or a fluorine-substituted alkyl group as a substituent.

[0011] [2] The composition according to [1] above, wherein the first solvent, which is an aromatic compound containing an oxygen atom, is an aromatic ether compound or an aromatic ester compound. [3] The composition according to [1] above, wherein the second solvent not containing an oxygen atom is an aromatic compound. [4] The composition according to any one of [1] to [3] above, wherein the second solvent not containing an oxygen atom is an alkylated aromatic compound. [5] The composition according to any one of [1] to [4] above, wherein the volume ratio of the first solvent to the second solvent is 5:95 to 90:10. [6] The composition according to [5] above, wherein the volume ratio of the first solvent to the second solvent is 5:95 to 19:81. [7] The composition according to R in formula (1) １and R ５ [8] The composition according to any one of the above [1] to [6], wherein R in the formula (1) is a monovalent aliphatic hydrocarbon group. １ and R ５ is a methyl group. [9] The composition according to any one of [1] to [8] above, which is for forming a hole transport layer.

[10] A photoelectric conversion device having a pair of electrodes having an upper electrode and a lower electrode, an active layer located between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound, and a hole transport layer located between the active layer and the upper electrode or the lower electrode, wherein the hole transport layer is a layer formed using the composition according to any one of [1] to [8] above.

[0012]

[11] A composition comprising a charge transporting polymer having a unit represented by the following formula (1), a tetraarylborate ion represented by the following formula (2), a first solvent having a polar term (δP) of the Hansen solubility parameter of 3.0 or more, and a second solvent having a polar term (δP) of the Hansen solubility parameter of less than 3.0.

[0013]

[0014] In formula (1), R １ ~R ５ each independently represents a hydrogen atom or a monovalent aliphatic hydrocarbon group, R １ and R ５ At least one of Ar is a monovalent aliphatic hydrocarbon group, １ represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent.

[0015]

[0016] In formula (2), Ar １１ , Ar １２ , Ar １３ , and Ar １４ each independently represents a monovalent aromatic hydrocarbon group which may have a substituent, or a monovalent aromatic heterocyclic group which may have a substituent, and Ar １１ , Ar １２ , Ar １３ , and Ar１４ At least one of the groups has a fluorine atom or a fluorine-substituted alkyl group as a substituent.

[12] The composition according to the above-mentioned

[11] , which is for forming a hole transport layer.

[0017] According to the present invention, it is possible to provide a composition that includes a polymer having an aromatic amine structural unit and an electron-accepting compound that improves electrical conductivity, and a mixed solvent that sufficiently dissolves them, and that can be suitably used for forming a hole transport layer, and a photoelectric conversion element that has a hole transport layer formed using the composition.

[0018] It is a schematic diagram showing an example of a photoelectric conversion element, a schematic diagram showing an example of a solar cell including a photoelectric conversion element, and a schematic diagram showing an example of a solar cell module including a photoelectric conversion element.

[0019] Hereinafter, several embodiments will be described with reference to the drawings. However, the following description is of typical examples, and the present invention is not limited to the following description. The dimensional ratios in the drawings are for the convenience of explanation and may differ from the actual ones.

[0020] [Composition] The composition of the present invention is a composition for forming a hole transport layer of a photoelectric conversion element and an electroluminescent element, and comprises a charge transport polymer having a unit represented by the following formula (1), a tetraarylborate ion represented by the following formula (2), a first solvent which is an aromatic compound containing an oxygen atom, and a second solvent which does not contain an oxygen atom.

[0021]

[0022] In formula (1), R １ ~R ５ each independently represents a hydrogen atom or a monovalent aliphatic hydrocarbon group, R １ and R ５ At least one of Ar is a monovalent aliphatic hydrocarbon group, １ represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent.

[0023]

[0024] In formula (2), Ar１１ , Ar １２ , Ar １３ , and Ar １４ each independently represents a monovalent aromatic hydrocarbon group which may have a substituent, or a monovalent aromatic heterocyclic group which may have a substituent, and Ar １１ , Ar １２ , Ar １３ , and Ar １４ At least one of the groups has a fluorine atom or a fluorine-substituted alkyl group as a substituent.

[0025] The charge transport polymer having the aromatic amine structural unit represented by formula (1) is a polymer having a side chain at the ortho position (R １ and R ５ ) has a monovalent aliphatic hydrocarbon group in at least one of the groups. Therefore, there is steric hindrance between the polymer and the aromatic hydrocarbon group or aromatic heterocyclic group forming the main chain. Therefore, the charge-transporting polymer of the present invention has excellent solubility in aromatic solvents with low polarity. Generally, polymers having aromatic ring structural units are substituted with long-chain alkyl groups to dissolve them in solvents used during coating. However, this is not necessary for polymers having units represented by formula (1) because the solubility is improved by steric hindrance.

[0026] By including the tetraarylborate ion represented by formula (2) in the composition, the conductivity of the formed hole transport layer is improved. This is because the tetraarylborate ion functions as an electron-accepting compound. Furthermore, the tetraarylborate ion represented by formula (2) has excellent thermal and chemical stability because it has a substituent, which is an electron-withdrawing group, a fluorine atom or a fluorine-substituted alkyl group. Generally, ionic compounds have low solubility in organic solvents, but the tetraarylborate ion represented by formula (2) has excellent solubility in organic solvents with a certain degree of polarity because four aromatic hydrocarbon groups or aromatic heterocyclic groups are substituted for the boron atom.

[0027] The composition of the present invention contains a first solvent, which is an aromatic compound containing oxygen atoms, and a second solvent containing no oxygen atoms, in order to dissolve a charge-transporting polymer having a unit represented by formula (1) and a tetraarylborate ion represented by formula (2). The aromatic compound containing oxygen atoms (first solvent) has a relatively high polarity and is able to dissolve tetraarylborate ions favorably. The second solvent containing no oxygen atoms is able to dissolve a polymer having an aromatic ring structural unit favorably.

[0028] <Charge Transporting Polymer> The composition of the present invention contains a charge transporting polymer having a unit represented by the following formula (1).

[0029]

[0030] In formula (1), R １ ~R ５ each independently represents a hydrogen atom or a monovalent aliphatic hydrocarbon group, R １ and R ５ At least one of Ar is a monovalent aliphatic hydrocarbon group, １ represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent. １ and R ５ It is preferable that both R are monovalent aliphatic hydrocarbon groups, since this results in greater steric hindrance and improves the solubility. １ ~R ５ Examples of the monovalent aliphatic hydrocarbon group that can be selected from are an alkyl group, an alkynyl group, and an alkenyl group. From the viewpoint of chemical stability, an alkyl group having 1 to 24 carbon atoms is preferred. From the viewpoint of adhesion to the active layer containing the perovskite semiconductor compound, a smaller number of carbon atoms is preferred, and an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a s-butyl group, or a t-butyl group is more preferred, with a methyl group being the most preferred. That is, R １ and R ５ It is particularly preferred that both of are methyl groups.

[0031] Ar １Examples of the aromatic hydrocarbon group as options include groups derived from the aromatic hydrocarbon group P1 below. Examples of the aromatic heterocyclic group include groups derived from the aromatic heterocyclic group P2 below. Examples of the substituent that the aromatic hydrocarbon group or aromatic heterocyclic group may have include one or more types selected from the substituent group Z1 below.

[0032] Aromatic hydrocarbon group P1: a 6-membered monocyclic ring or 2- to 5-condensed rings such as a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, an acenaphthene ring, a fluoranthene ring, and a fluorene ring.

[0033] Aromatic heterocyclic ring group P2: a 5- or 6-membered monocyclic ring or 2- to 4-condensed ring, such as a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, a carbazole ring, a pyrroloimidazole ring, a pyrrolopyrazole ring, a pyrrolopyrrole ring, a thienopyrrole ring, a thienothiophene ring, a furopyrrole ring, a furofuran ring, a thienofuran ring, a benzisoxazole ring, a benzisothiazole ring, a benzimidazole ring, a pyridine ring, a pyrazine ring, a pyridazine ring, a pyrimidine ring, a triazine ring, a quinoline ring, an isoquinoline ring, a cinnoline ring, a quinoxaline ring, a phenanthridine ring, a benzimidazole ring, a perimidine ring, a quinazoline ring, a quinazolinone ring, or an azulene ring.

[0034] Examples of the substituent that the aromatic hydrocarbon group and aromatic heterocyclic group may have include one or more types selected from the following substituent group Z1. Substituent group Z1: alkyl groups preferably having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methyl group or an ethyl group; aryloxy groups preferably having 4 to 36 carbon atoms, more preferably 5 to 24 carbon atoms, such as a phenoxy group, a naphthoxy group or a pyridyloxy group; alkoxycarbonyl groups preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a methoxycarbonyl group or an ethoxycarbonyl group; dialkylamino groups preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a dimethylamino group or a diethylamino group; acyl groups preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as an acetyl group or a benzoyl group; halogen atoms such as a fluorine atom or a chlorine atom; haloalkyl groups preferably having 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, such as a trifluoromethyl group; alkylthio groups preferably having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methylthio group or an ethylthio group; Arylthio groups preferably having 4 to 36 carbon atoms, more preferably 5 to 24 carbon atoms, such as a phenylthio group, a naphthylthio group, or a pyridylthio group; siloxy groups preferably having 2 to 36 carbon atoms, more preferably 3 to 24 carbon atoms, such as a trimethylsiloxy group or a triphenylsiloxy group; a cyano group; aromatic hydrocarbon groups preferably having 6 to 36 carbon atoms, more preferably 6 to 24 carbon atoms, such as a phenyl group or a naphthyl group; and aromatic heterocyclic groups preferably having 3 to 36 carbon atoms, more preferably 4 to 24 carbon atoms, such as a thienyl group or a pyridyl group. Each of the above substituents may further have a substituent, examples of which include the groups exemplified in the above-mentioned substituent group Z1. The formula weight of the substituent group Z1, including the further substituted groups, is preferably 500 or less, more preferably 250 or less.

[0035] Ar １As described above, represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent, and a plurality of aromatic hydrocarbon groups and / or aromatic heterocyclic groups may be linked together. In terms of deepening the ionization potential, it is preferable that two to five groups are linked together. In terms of solubility, it is preferable that two or three groups are linked together, and in terms of deeper ionization potential, it is preferable that four or five groups are linked together.

[0036] <Tetraarylborate ion> The composition of the present invention contains a tetraarylborate ion represented by the following formula (2).

[0037]

[0038] In formula (2), Ar １１ , Ar １２ , Ar １３ , and Ar １４ each independently represents a monovalent aromatic hydrocarbon group which may have a substituent, or a monovalent aromatic heterocyclic group which may have a substituent, and Ar １１ , Ar １２ , Ar １３ , and Ar １４ At least one of the groups has a fluorine atom or a fluorine-substituted alkyl group as a substituent. Examples of the aromatic hydrocarbon group include groups derived from the aromatic hydrocarbon group P1. Examples of the aromatic heterocyclic group include groups derived from the aromatic heterocyclic group P2. Examples of the substituent that the aromatic hydrocarbon group or aromatic heterocyclic group may have include one or more types selected from the substituent group Z1.

[0039] The amount of tetraarylborate ions is preferably large because it facilitates improved conductivity. Specifically, the amount of tetraarylborate ions as an electron-accepting compound is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, even more preferably 0.05 parts by mass or more, and particularly preferably 0.1 parts by mass or more, relative to 100 parts by mass of the charge-transporting polymer of the present invention. On the other hand, the amount of tetraarylborate ions is preferably small from the viewpoint of suppressing the generation of leakage current in the photoelectric light-emitting device. Specifically, the amount is preferably 50 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 15 parts by mass or less, relative to 100 parts by mass of the charge-transporting polymer of the present invention. The amount of tetraarylborate ions in the composition is particularly preferably 0.1 to 15 parts by mass, relative to 100 parts by mass of the charge-transporting polymer of the present invention.

[0040] <First Solvent as an Aromatic Compound Containing an Oxygen Atom> The composition of the present invention contains a first solvent as an aromatic compound containing an oxygen atom. As the first solvent as an aromatic compound containing an oxygen atom, an aromatic ether compound or an aromatic ester compound is preferred because they readily dissolve tetraarylborate ions and cation radicals of charge-transporting polymers having tetraarylborate ions as counter anions. It is preferable that the first solvent has a relatively high polarity. The polarity is expressed by the polar term (δP) of the Hansen Solubility Parameter. The δP of the first solvent is preferably 3.0 or more, more preferably 3.5 or more, and even more preferably 4.0 or more. Furthermore, it is preferably 12.5 or less, more preferably 10.0 or less, and even more preferably 9.0 or less.

[0041] The aromatic ether compound used as the first solvent is preferably an alkoxybenzene which may have an alkyl group and is represented by the following formula (3), in that it has high solubility and moderate volatility.

[0042]

[0043] In the above formula, i represents an integer of 0 to 5. ５１ , R ５２represents an alkyl group which may have a substituent. i is an integer of 0 to 3, and more preferably 0 or 1, in terms of a low boiling point and high volatility.

[0044] R ５１ , R ５２ R is preferably an alkyl group having 1 to 12 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a s-butyl group, a t-butyl group, a pentyl group, an isopentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group. ５１ , R ５２ may have a phenyl group as a substituent, and in this case, the alkyl group having the substituent is preferably a benzyl group or a 2-phenylethyl group.

[0045] The aromatic ether compound used as the first solvent is preferably phenoxybenzene which may have an alkyl group and is represented by the following formula (4), because it has a high boiling point and is suitable for large-area coating.

[0046]

[0047] In the above formula, j and k represent integers of 0 to 5. ５３ , R ５４ represents an alkyl group which may have a substituent. j and k are preferably integers of 0 to 2, more preferably 0 or 1, in that the boiling point is not too high and the volatility is appropriate.

[0048] R ５３ , R ５４ As the R ５１ , R ５２ The specific examples and preferred ranges are the same as those of the alkyl group described above.

[0049] The aromatic ester used as the first solvent is preferably a benzoic acid ester which may have an alkyl group and is represented by the following formula (5).

[0050]

[0051] In the above formula, q represents an integer of 0 to 5. ５５ , R５６ represents an alkyl group which may have a substituent. q is preferably an integer of 0 to 2, more preferably 0 or 1, in that the boiling point is low and the volatility is high.

[0052] R ５５ , R ５６ As the R ５１ , R ５２ The specific examples and preferred ranges are the same as those of the alkyl group described above.

[0053] The aromatic ether compound and / or aromatic ester compound used as the first solvent may be used alone or in any combination and ratio of two or more thereof. That is, only one aromatic ether compound may be used, only one aromatic ester compound may be used, or one or more aromatic ether compounds and one or more aromatic ester compounds may be used in any combination and ratio.

[0054] <Second Solvent Not Containing Oxygen Atoms> The composition of the present invention contains a second solvent not containing oxygen atoms. As the second solvent not containing oxygen atoms, aromatic compounds are preferred because they easily dissolve the cation radicals of the charge transport polymer and the charge transport polymer having a tetraarylborate ion as a counter anion. Among these, alkylated aromatic compounds such as alkylated benzene, alkylated naphthalene, or alkylated biphenyl are preferred. The second solvent preferably has low polarity. The polarity is expressed by the polar term (δP) of the Hansen solubility parameter. The second solvent preferably has a δP of less than 3.0, more preferably 2.0 or less, and even more preferably 1.0 or less.

[0055] As the second solvent, an alkylated benzene represented by the following formula (6) is preferred because it has high solubility and moderate volatility.

[0056]

[0057] In the above formula, r represents an integer of 1 to 5. ６１represents an alkyl group which may have a substituent. r is preferably an integer of 1 to 3, more preferably 1 or 2, in terms of a low boiling point and high volatility.

[0058] R ６１ As the R ５１ , R ５２ The specific examples and preferred ranges are the same as those of the alkyl group described above.

[0059] As the second solvent, alkylated naphthalene represented by the following formula (7) is preferred because it has high solubility and moderate volatility.

[0060]

[0061] In the above formula, s represents an integer of 1 to 5. ６２ represents an alkyl group which may have a substituent. s is preferably an integer of 1 to 3, more preferably 1 or 2, in terms of a low boiling point and high volatility.

[0062] R ６２ As the R ５１ , R ５２ The alkyl group is the same as that described in 1., and specific examples and preferred ranges are also the same. As the second solvent, an alkylated naphthalene represented by the following formula (8) is preferred because it has a high boiling point and is suitable for large-area coating.

[0063]

[0064] In the above formula, s and t represent integers of 1 to 5. ６２ represents an alkyl group which may have a substituent. s and t are each preferably an integer of 1 to 3, more preferably 1 or 2, in that the boiling point is not too high and the volatility is appropriate.

[0065] R ６２ As the R ５１ , R ５２ The specific examples and preferred ranges are the same as those of the alkyl group described above.

[0066] The alkylated benzenes and / or alkylated naphthalenes and / or alkylated biphenyls used as the second solvent may be used alone or in any combination and ratio of two or more thereof. That is, only one alkylated benzene may be used, only one alkylated naphthalene may be used, or only one alkylated biphenyl may be used, or one or more alkylated benzenes and one or more alkylated naphthalenes (or alkylated biphenyls) may be used in any combination and ratio.

[0067] <Mixing Ratio of First Solvent and Second Solvent> The composition of the present invention contains a first solvent and a second solvent. The ratio between these solvents is not particularly limited as long as the effects of the present invention are achieved. However, the ratio (volume ratio) of the first solvent to the second solvent is preferably in the range of 5:95 to 90:10. When the volume ratio of the first solvent to the second solvent is in this range, the charge transport polymer and the tetraarylborate ion can be sufficiently dissolved, and the cation radical charge transport polymer of the charge transport polymer having the tetraarylborate ion as a counter anion can be sufficiently dissolved. From the above viewpoints, the ratio (volume ratio) of the first solvent to the second solvent is preferably in the range of 5:95 to 19:81. Furthermore, when an aromatic ether compound is used as the first solvent, the volume ratio is more preferably in the range of 10:90 to 80:20, and even more preferably in the range of 10:90 to 60:40. Furthermore, when an aromatic ester compound is used as the first solvent, the volume ratio of the first solvent to the second solvent is more preferably in the range of 10:90 to 60:40, and even more preferably in the range of 10:90 to 40:60.

[0068] [Photoelectric Conversion Element] One embodiment of the present invention relates to a photoelectric conversion element. The photoelectric conversion element includes a pair of electrodes having an upper electrode and a lower electrode, an active layer positioned between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound, and a hole transport layer positioned between the active layer and the upper electrode or the lower electrode. The hole transport layer is formed using the composition described above. In the photoelectric conversion element 100 shown in FIG. 1 , a lower electrode 101, an active layer 103, and an upper electrode 105 are arranged in this order. A buffer layer 102 may be arranged between the lower electrode 101 and the active layer 103. The buffer layer 102 may be, for example, a hole transport layer. A buffer layer 104 may be arranged between the upper electrode 105 and the active layer 103. The buffer layer 104 may be, for example, an electron transport layer. The buffer layer 102 and the buffer layer 104 may be, for example, an electron transport layer, respectively. The photoelectric conversion element 100 may include a substrate 106 and may include other layers not shown, such as an insulator layer and a work function tuning layer.

[0069] (Active Layer) In FIG. 1 , the active layer 103 is a layer where photoelectric conversion takes place. When the photoelectric conversion element 100 receives light, the light is absorbed by the active layer 103, generating carriers, which are then extracted from the lower electrode 101 and the upper electrode 105. The active layer contains an organic-inorganic hybrid semiconductor compound. An organic-inorganic hybrid semiconductor compound is a compound in which an organic component and an inorganic component are combined at the molecular level or nano-level, and which exhibits semiconductor properties. The organic-inorganic hybrid semiconductor compound is preferably a compound having a perovskite structure (hereinafter may be referred to as a "perovskite semiconductor compound").

[0070] The perovskite semiconductor compound refers to a semiconductor compound having a perovskite structure. ３ ; Perovskite) etc. ABX ３ This is a crystal structure represented by the composition ABX. ３In the perovskite structure with the composition, six X atoms surround the B site ion. － are regularly surrounded by the hexahedron to form a BX6 octahedron. The perovskite semiconductor compound is not particularly limited, but can be selected from, for example, those listed in Galasso et al., Structure and Properties of Inorganic Solids, Chapter 7 - Perovskitetye and related structures. Also, for example, the perovskite semiconductor compound can be a compound having the general formula AMX ３ AMX expressed as ３ of the type or of general formula A ２ MX ４ A represented by ２ MX ４ Here, M represents a divalent cation, A represents a monovalent cation, and X represents a monovalent anion.

[0071] There are no particular limitations on the monovalent cation A, but those described in the above-mentioned book by Galasso can be used. More specific examples include cations containing elements from Groups 1 and 13 to 16 of the periodic table. Among these, cesium ions, rubidium ions, potassium ions, optionally substituted ammonium ions, and optionally substituted phosphonium ions are preferred. Examples of optionally substituted ammonium ions include primary ammonium ions and secondary ammonium ions. There are also no particular limitations on the substituents. Specific examples of optionally substituted ammonium ions include alkylammonium ions and arylammonium ions. In particular, to avoid steric hindrance, monoalkylammonium ions that form a three-dimensional crystal structure are preferred, and from the perspective of improving stability, alkylammonium ions substituted with one or more fluorine groups are preferred. Furthermore, two or more types of cations may be used in combination as cation A.

[0072] Examples of the monovalent cation A include a methylammonium ion, a methylammonium monofluoride ion, a methylammonium difluoride ion, a methylammonium trifluoride ion, an ethylammonium ion, an isopropylammonium ion, an n-propylammonium ion, an isobutylammonium ion, an n-butylammonium ion, a t-butylammonium ion, a dimethylammonium ion, a diethylammonium ion, a phenylammonium ion, a benzylammonium ion, a phenethylammonium ion, a guanidium ion, a formamidinium ion, an acetamidinium ion, and an imidazolium ion.

[0073] The divalent cation M is not particularly limited, but is preferably a divalent metal cation or semimetal cation. For example, a cation of a group 14 element of the periodic table can be mentioned. More specifically, a lead cation (Pb ２＋ ), tin cations (Sn ２＋ ), germanium cation (Ge ２＋ ) In addition, two or more types of cations may be used in combination as the cation M. From the viewpoint of obtaining a stable photoelectric conversion element, it is particularly preferable to use a lead cation or two or more types of cations including a lead cation.

[0074] Examples of monovalent anions X include halides, acetate ions, nitrate ions, sulfate ions, dihydrogen borate ions, acetylacetonate ions, hydrogen carbonate ions, citrate ions, hydrogen sulfide ions, hydrogen tellurium ions, thiocyanate ions, and 2,4-pentanedionate ions. Examples of X include halides, or combinations of halides with other anions. X may be one type, or two or more types in any combination and ratio. The band gap of the active layer can be adjusted by the type and combination of X. Since the band gap of the active layer tends to be appropriately narrow, X is preferably a halide ion such as a chloride ion, bromide ion, or iodide ion, and more preferably a bromide ion or iodide ion.

[0075] The perovskite semiconductor compound is preferably a halide-based organic / inorganic perovskite semiconductor compound. ３ NH ３ PbI ３ , C.H. ３ NH ３ PbBr ３ , C.H. ３ NH ３ PbCl ３ , C.H. ３ NH ３ SnI ３ , C.H. ３ NH ３ SnBr ３ , C.H. ３ NH ３ SnCl ３ , C.H. ３ NH ３ PbI （３－ｘ） Cl ｘ , C.H. ３ NH ３ PbI （３－ｘ） Br ｘ , C.H. ３ NH ３ PbBr （３－ｘ） Cl ｘ , C.H. ３ NH ３ Pb （１－ｙ） Sn ｙ I ３ , C.H. ３ NH ３ Pb （１－ｙ） SnyBr ３ , C.H. ３ NH ３ Pb （１－ｙ） Sn ｙ Cl ３ , C.H. ３ NH ３ Pb （１－ｙ） Sn ｙ I （３－ｘ） Cl ｘ , C.H. ３ NH ３ Pb （１－ｙ） Sn ｙ I （３－ｘ） Br ｘ , and C.H. ３ NH ３ Pb （１－ｙ） Sn ｙ Br（３－ｘ） Cl ｘ , and CH in the above compounds ３ NH ３ Instead of CFH ２ NH ３ , C.F. ２ HNH ３ , C.F. ３ NH ３ , N.H. ２ CH=NH ２ , Cs, or a mixture thereof. x is an arbitrary value of 0 or more and 3 or less, and y is an arbitrary value of 0 or more and 1 or less.

[0076] The active layer may contain two or more organic-inorganic hybrid semiconductor compounds. For example, the active layer may contain two or more organic-inorganic hybrid semiconductor compounds in which at least one of A, B, and X is different. The active layer may have a laminate structure formed of multiple layers containing different materials or components. The amount of the organic-inorganic hybrid semiconductor compound contained in the active layer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, so as to obtain good semiconductor characteristics. There is no particular upper limit to the amount of the organic-inorganic hybrid semiconductor compound contained in the active layer. In addition, the active layer may contain additives other than the organic-inorganic hybrid semiconductor compound contained in the active layer. Examples of additives include inorganic compounds such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates, and ammonium salts, or organic compounds.

[0077] There is no particular limit to the thickness of the active layer. In order to be able to absorb more light, the active layer is preferably thick. For example, it is preferably 10 nm or more, more preferably 50 nm or more, even more preferably 100 nm or more, particularly preferably 150 nm or more, and most preferably 200 nm or more. On the other hand, it is preferable that the active layer is thin in order to reduce the series resistance and increase the charge extraction efficiency. Specifically, the active layer thickness is preferably 1500 nm or less, more preferably 1200 nm or less, and even more preferably 800 nm or less. The active layer thickness is particularly preferably 200 nm or more and 800 nm or less.

[0078] The method for forming the active layer is not particularly limited, and any method can be used. Examples include coating methods and vapor deposition methods (or co-evaporation methods). Coating methods are preferred because they allow for easy formation of the active layer. For example, a method can be used in which a coating liquid containing an organic-inorganic hybrid semiconductor compound or a precursor thereof is applied, and then heated and dried as necessary to form the active layer. Furthermore, after applying the coating liquid, the organic-inorganic hybrid semiconductor compound can also be precipitated by further applying a solvent in which the organic-inorganic hybrid semiconductor compound has low solubility.

[0079] The organic-inorganic hybrid semiconductor compound precursor refers to a compound that becomes an organic-inorganic hybrid semiconductor compound after being applied as a coating liquid. For example, an organic-inorganic hybrid semiconductor compound precursor that becomes an organic-inorganic hybrid semiconductor compound by heating can be used. For example, a compound represented by the general formula AX and a compound represented by the general formula MX ２ and a solvent, and the mixture is heated and stirred to prepare a coating solution. The coating solution is applied and then dried by heating, thereby obtaining a compound represented by the general formula AMX ３ The solvent is not particularly limited as long as it dissolves the organic-inorganic hybrid semiconductor compound and optional additives, and examples thereof include organic solvents such as N,N-dimethylformamide. ２ and a solvent, and the mixture is heated and stirred to obtain a coating liquid, and then a coating liquid obtained by mixing a compound represented by the general formula AX and a solvent is applied to the coating liquid, thereby obtaining a coating liquid of the general formula AMX ３ Alternatively, an active layer containing a perovskite semiconductor compound represented by the following formula may be prepared.

[0080] The coating liquid can be applied by any method, including, for example, spin coating, inkjet coating, doctor blade coating, drop casting, reverse roll coating, gravure coating, kiss coating, roll brush coating, spray coating, air knife coating, wire bar coating, pipe doctor coating, impregnation / coating, and curtain coating.

[0081] The active layer of the photoelectric conversion element may contain an organic-inorganic hybrid semiconductor compound other than a perovskite semiconductor compound, such as an organic alkoxide-coordinated metal oxide or an organic molecule-coordinated transition metal complex.

[0082] 1, the buffer layer is a layer located between the active layer 103 and at least one of the pair of electrodes 101, 105. The buffer layer is used, for example, to improve the efficiency of carrier movement from the active layer 103 to the lower electrode 101 or the upper electrode 105. The photoelectric conversion element has a hole transport layer as a buffer layer. It is preferable that the photoelectric conversion element further has an electron transport layer.

[0083] (Hole Transport Layer) The hole transport layer is formed using the composition of the present invention described above. The composition contains a charge transport polymer having a unit represented by formula (1) and a tetraarylborate ion represented by formula (2) as solutes. The composition contains a mixed solvent including a first solvent, which is an aromatic compound containing an oxygen atom that easily dissolves tetraarylborate ions and cation radicals of a charge transport polymer having a tetraarylborate ion as a counter anion, and a second solvent that does not contain an oxygen atom that easily dissolves the charge transport polymer and cation radicals of a charge transport polymer having a tetraarylborate ion as a counter anion. Thus, the solute in the composition is easily dissolved uniformly. The hole transport layer formed using the composition, which is a uniformly dissolved solution, has uniform film quality, thereby suppressing leakage current and stabilizing the performance of the resulting photoelectric conversion element.

[0084] The content of the charge transporting polymer in the hole transport layer is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more in the hole transport layer (total mass: 100% by mass) from the viewpoints of adhesion to the active layer containing the organic-inorganic hybrid semiconductor compound and high hole transporting properties. Here, the upper limit is 100% by mass, but when carrier mobility is increased by adding an electron transporting compound to the hole transport layer, the total amount with the electron accepting compound becomes the upper limit, which is 100% by mass.

[0085] The hole transport layer may contain a semiconductor compound other than the charge transport polymer having a unit represented by formula (1) as long as the effects of the present invention are achieved. As the other semiconductor compound, for example, a conventionally known semiconductor compound may be used.

[0086] As other organic semiconductor compounds, various low molecular weight compounds and polymer compounds are known. Examples of low molecular weight organic semiconductor compounds include polycyclic aromatic compounds. Examples include acene compounds such as tetracene and pentacene, oligothiophene compounds, phthalocyanine compounds, perylene compounds, rubrene compounds, arylamine compounds such as triarylamine compounds, and carbazole compounds.

[0087] Examples of the polymeric organic semiconductor compound include conjugated polymers such as polythiophene-based polymers, polyacetylene-based polymers, polyaniline-based polymers, polyphenylene-based polymers, polyphenylene vinylene-based polymers, polyfluorene-based polymers, and polypyrrole-based polymers, and arylamine polymers other than the above-mentioned charge transporting polymers.

[0088] When forming a hole transport layer, it is preferable to use an electron-accepting compound in addition to a semiconductor compound such as a charge-transporting polymer. The use of an electron-accepting compound can improve the conductivity. As the electron-accepting compound, a compound having oxidizing power and the ability to accept one electron from the charge-transporting polymer of the present invention is preferred. More specifically, a compound having an electron affinity of 4.0 eV or more is preferred, and a compound having an electron affinity of 5.0 eV or more is more preferred.

[0089] Examples of such electron-accepting compounds include one or more compounds selected from the group consisting of triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples include organically substituted onium salts such as 4-isopropyl-4'-methyldiphenyliodonium tetrakispentafluorophenylborate and triphenylsulfonium tetrafluoroborate (WO 2005 / 089024, WO 2017 / 164268); high-valent inorganic compounds such as iron(III) chloride (JP 11-251067 A) and ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene; aromatic boron compounds such as tris(pentafluorophenyl)borane (JP 2003-31365 A); fullerene derivatives; and iodine.

[0090] As the electron-accepting compound, a compound containing a tetraarylborate ion represented by the following formula (2) is preferred, because it is thermally and chemically stable and has high solubility in organic solvents.

[0091] The amount of the electron-accepting compound is preferably large because the conductivity of the hole-transport layer is likely to be improved. Therefore, specifically, the amount of the electron-accepting compound is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, even more preferably 0.05 parts by mass or more, and particularly preferably 0.1 parts by mass or more, per 100 parts by mass of the semiconductor compound. The amount of the electron-accepting compound is preferably small from the viewpoint of suppressing the generation of leakage current in the photoelectric light-emitting element. Therefore, specifically, the amount is preferably 50 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the semiconductor compound. When an electron-accepting compound is used to form the hole-transport layer, the amount of the electron-accepting compound is particularly preferably 0.1 to 15 parts by mass, per 100 parts by mass of the semiconductor compound.

[0092] The electron-accepting compound preferably undergoes a charge transfer reaction with at least one organic semiconductor compound before or after the formation of the hole-transporting layer. As the electron-accepting compound, a hypervalent iodine compound is preferred because it has excellent solubility and is likely to generate an electron-accepting active site that functions as an oxidizing agent upon heating or the like. Hypervalent iodine compounds are known to exhibit electron-accepting properties (i.e., function as an oxidizing agent). A hypervalent iodine compound is a compound containing hypervalent iodine, and is defined as a compound containing iodine with an oxidation number of three or more. For example, the electron-accepting compound is preferably an iodine(III) compound or an iodine(V) compound.

[0093] Examples of iodine(V) compounds containing pentavalent iodine include periodinane compounds such as Dess-Martin periodinane, and examples of iodine(III) compounds containing trivalent iodine include compounds having an oxidized iodobenzene structure such as (diacetoxyiodo)benzene, and diaryliodonium salts.

[0094] The electron-accepting compound is preferably an organic compound containing trivalent iodine, and more preferably a diaryliodonium salt, because it exhibits good electron-accepting properties and is less likely to undergo a reverse reaction if the molecule is destroyed during the oxidation process. ＋ -Ar]X － Here, each of the two Ar's represents an aromatic group. The aromatic group is not particularly limited, and examples thereof include aromatic hydrocarbon groups such as those exemplified in the aromatic hydrocarbon group P1 and aromatic heterocyclic groups such as those exemplified in the aromatic heterocyclic group P2. X － represents any anion. － Examples of the X ions include halide ions, trifluoroacetate ions, tetrafluoroborate ions, and tetrakis(pentafluorophenyl)borate ions. X ions are preferred because they have high solubility and can smoothly proceed with the reaction to produce the coating solution. －is preferably an anion having a fluorine atom. In terms of thermal and chemical stability and high solubility in organic solvents, a tetraarylborate ion represented by formula (2) is particularly preferred.

[0095] The ionization potential of the hole transport layer is preferably within a specific range, as this provides good matching with the holes generated in the active layer and makes it easy to suppress energy loss. For example, -5.8 eV or more is preferred, -5.75 eV or more is more preferred, and -5.70 eV or more is even more preferred. On the other hand, the ionization potential of the hole transport layer is preferably -5.2 eV or less, more preferably -5.4 eV or less, even more preferably -5.45 eV or less, and particularly preferably -5.50 eV or less. The ionization potential of the hole transport layer is particularly preferably -5.70 eV or more and -5.50 eV or less. As described above, the ionization potential of the hole transport layer can be adjusted by using a charge transport polymer. A more detailed method for adjusting the ionization potential to the desired range is, for example, controlling the electronic state of the compound in the charge transport polymer of the present invention by appropriately arranging the type of aromatic group forming the main chain and the type and position of the substituent. Alternatively, the electronic state of the compound contained in the hole transport layer may be adjusted by using an electron-accepting compound, which will be described later, in the hole transport layer in combination. The adjustment of the electronic state may be performed by oxidizing or reducing the whole or part of the compound.

[0096] The thickness of the hole transport layer is preferably thick in order to prevent current leakage due to the formation of a conductive path between the upper and lower electrodes and the active layer when the active layer located between the upper and lower electrodes has high charge transport ability. Therefore, specifically, the thickness is preferably 20 nm or more, more preferably 40 nm or more, and even more preferably 60 nm or more. In order to prevent resistance in charge transport by the hole transport layer and to reduce costs by saving the amount of compound contained in the hole transport layer, a thin thickness is preferable. Specifically, the thickness is preferably 1000 nm or less, more preferably 750 nm or less, and even more preferably 500 nm or less.

[0097] (Electrode) In FIG. 1, the electrode has the function of collecting holes and electrons generated by light absorption in the active layer 103. The photoelectric conversion element 100 according to one embodiment of the present invention has a pair of electrodes, one of which is called an upper electrode and the other is called a lower electrode. When the photoelectric conversion element 100 has a substrate or is provided on a substrate, the electrode closer to the substrate can usually be called the lower electrode, and the electrode farther from the substrate can be called the upper electrode. Furthermore, a transparent electrode can also be called the lower electrode, and an electrode that is less transparent than the lower electrode can also be called the upper electrode. The photoelectric conversion element 100 shown in FIG. 1 has a lower electrode 101 and an upper electrode 105.

[0098] The pair of electrodes can be an anode suitable for collecting holes and a cathode suitable for collecting electrons. In this case, the photoelectric conversion element 100 may have a forward configuration in which the lower electrode 101 is the anode and the upper electrode 105 is the cathode, or an inverted configuration in which the lower electrode 101 is the cathode and the upper electrode 105 is the anode. It is sufficient that either one of the pair of electrodes is light-transmitting, or both may be light-transmitting. Light-transmitting means that the transmittance of normal sunlight (wavelength 350 to 700 nm) is 40% or more. The sunlight transmittance of the electrode is preferably high, since more light passes through the transparent electrode to reach the active layer, and is particularly preferably 70% or more.

[0099] The sunlight transmittance can be measured using a spectrophotometer (e.g., Hitachi High-Tech U-4100). There are no particular limitations on the components and manufacturing methods of the lower electrode 101 and upper electrode 105, or the anode and cathode, and known techniques can be used. For example, components and manufacturing methods described in known documents such as WO 2013 / 171517, WO 2013 / 180230, or JP 2012-191194A can be used.

[0100] (Electron Transport Layer) The photoelectric conversion element may have an electron transport layer. The material for the electron transport layer may be any material capable of improving the efficiency of electron extraction from the active layer to the cathode. Examples of such materials include inorganic compounds, organic compounds, and perovskite semiconductor compounds described in known publications such as WO 2013 / 171517, WO 2013 / 180230, and JP 2012-191194 A. Examples of inorganic compounds include salts of alkali metals such as lithium, sodium, potassium, and cesium, and metal oxides such as zinc oxide, titanium oxide, aluminum oxide, and indium oxide. Examples of the organic compound include bathocuproine (BCP), bathophenanthrene (Bphen), (8-hydroxyquinolinato)aluminum (Alq3), boron compounds, oxadiazole compounds, benzimidazole compounds, naphthalenetetracarboxylic anhydride (NTCDA), perylenetetracarboxylic anhydride (PTCDA), fullerene compounds, and phosphine compounds having a double bond with an element of Group 16 of the periodic table, such as phosphine oxide compounds and phosphine sulfide compounds.

[0101] When the photoelectric conversion element includes an electron transport layer, the thickness thereof is preferably thick, since when the active layer located between the upper and lower electrodes has high charge transport capability, current leakage due to the formation of a conductive path between the upper and lower electrodes and the active layer is unlikely to occur, the influence of the unevenness of the lower electrode can be covered, and the wettability of the active layer is easily controlled. Therefore, specifically, a thickness of 1 nm or more is preferable, 5 nm or more is more preferable, and 10 nm or more is even more preferable. On the other hand, a thin thickness is preferable in terms of unlikely occurrence of resistance in charge transport by the electron transport layer and cost reduction by saving the amount of compound contained in the electron transport layer. Specifically, a thickness of 200 nm or less is preferable, 150 nm or less is more preferable, and 100 nm or less is even more preferable.

[0102] (Substrate) The photoelectric conversion element may have a substrate. In FIG. 1, the photoelectric conversion element 100 has a substrate 106 that serves as a support, but the photoelectric conversion element according to the present invention may not have the substrate 106. When a substrate is used, the material of the substrate 106 is not particularly limited as long as it does not significantly impair the effects of the present invention. For example, materials described in publicly known documents such as WO 2013 / 171517, WO 2013 / 180230, or JP 2012-191194 A can be used.

[0103] (Method for manufacturing photoelectric conversion element) The method for manufacturing the photoelectric conversion element of the present invention is not particularly limited as long as it is a method that can incorporate the charge transport polymer of the present invention into the hole transport layer, and a method for manufacturing a photoelectric conversion element using a known perovskite semiconductor compound can be applied. For example, a hole transport layer can be formed by preparing a coating liquid containing a charge transport polymer, an electron accepting compound, and a solvent, and using a wet film formation method such as a spin coating method or an ink jet method. An electron transport layer can also be formed by a similar coating method. These buffer layers can also be formed by a dry film formation method such as a vacuum deposition method. However, it is preferable to form the hole transport layer by a coating method. It is more preferable to coat a coating liquid containing the above-mentioned charge transport polymer of the present invention, an electron accepting compound, and a solvent.

[0104] In Fig. 1, the photoelectric conversion element 100 can be manufactured by stacking the layers that make up the photoelectric conversion element 100. For example, known methods such as a sheet-to-sheet method or a roll-to-roll method can be applied. The roll-to-roll method is a method in which a flexible substrate wound in a roll is unwound and processed while being transported intermittently or continuously until it is wound up by a take-up roll. The roll-to-roll method makes it possible to process long substrates on the order of kilometers in length in a batch, and therefore the roll-to-roll method is more suitable for mass production than the sheet-to-sheet method.

[0105] The size of the roll that can be used in the roll-to-roll system is not particularly limited as long as it can be handled by a roll-to-roll manufacturing apparatus, but the outer diameter is preferably 5 m or less, more preferably 3 m or less, and even more preferably 1 m or less. On the other hand, it is preferably 10 cm or more, more preferably 20 cm or more, and even more preferably 30 cm or more. The outer diameter of the roll core is preferably 4 m or less, more preferably 3 m or less, and even more preferably 0.5 m or less. On the other hand, it is preferably 1 cm or more, more preferably 3 cm or more, even more preferably 5 cm or more, particularly preferably 10 cm or more, and most preferably 20 cm or more. When the outer diameter of the roll is within the above range, the roll is easy to handle, and the layers formed in each step are less likely to be damaged by bending stress. The roll width is preferably 5 cm or more, more preferably 10 cm or more, and even more preferably 20 cm or more. On the other hand, it is preferably 5 m or less, more preferably 3 m or less, and even more preferably 2 m or less. A large width makes the roll easy to handle and increases the degree of freedom in the size of the photoelectric conversion element.

[0106] When manufacturing the photoelectric conversion element 100, the photoelectric conversion element 100 may be heated after the upper electrode 105 is laminated (this heating step may be referred to as an annealing treatment step). The annealing treatment step is preferably performed at a high temperature, since this increases the adhesion between the layers of the photoelectric conversion element 100, for example, between the buffer layer 102 and the lower electrode 101, and between the buffer layer 102 and the active layer 103, and can improve the thermal stability, durability, etc. of the photoelectric conversion element.

[0107] The heating temperature is preferably 50°C or higher, and more preferably 80°C or higher. Heating is preferably performed at low temperatures to prevent thermal decomposition of the organic compounds contained in the photoelectric conversion element 100. For example, 300°C or lower is preferred, 280°C or lower is more preferred, and 250°C or lower is even more preferred. In the annealing process, stepwise heating using different temperatures within the above temperature range may be performed. The heating time within the above preferred temperature range is preferably 1 minute or longer, more preferably 3 minutes or longer, to improve adhesion while suppressing thermal decomposition. Furthermore, 180 minutes or shorter is preferred, and 60 minutes or shorter is more preferred. The annealing process is preferably terminated when the open-circuit voltage, short-circuit current, and fill factor, which are the photoelectric conversion characteristics of the solar cell, reach certain values. Furthermore, the annealing process is preferably performed under atmospheric pressure in an inert gas atmosphere to prevent thermal oxidation of the constituent materials. The heating method may involve placing the photoelectric conversion element on a heat source such as a hot plate, or placing the photoelectric conversion element in a heated atmosphere such as an oven. The heating may be carried out batchwise or continuously.

[0108] (Photoelectric Conversion Characteristics) The photoelectric conversion characteristics of the photoelectric conversion element 100 can be determined as follows. The photoelectric conversion element 100 is irradiated with light of an appropriate spectrum at a certain irradiation intensity, and the current-voltage characteristics are measured. From the obtained current-voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be determined. Here, the short-circuit current density (Jsc) is the current density when the voltage value is 0 (V), and the open-circuit voltage (Voc) is the current density when the current value is 0 (mA / cm ２ ) The fill factor (FF) is a factor that represents internal resistance. If the maximum output is Pmax, the fill factor (FF) is expressed by the following formula: FF = Pmax / (Voc × Jsc) If the incident energy is Pin, the photoelectric conversion efficiency (PCE) is given by the following formula: PCE = (Pmax / Pin) × 100 = (Voc × Jsc × FF / Pin) × 100 The incident energy Pin is, for example, 100 mW / cm for sunlight with an intensity of AM 1.5G.２ When white LED light with a color temperature of 5000K is irradiated and the illuminance on the light receiving surface is 200 lux, the ２ The color temperature of 5000K is defined by the JIS Z8725:2015 standard.

[0109] [Example of Use] The thin-film solar cell 14 shown in Figure 2 comprises, in this order, a weather-resistant protective film 1, an ultraviolet-cutting film 2, a gas barrier film 3, a getter material film 4, a sealing material 5, a solar cell element 6 having a photoelectric conversion element (not shown), a sealing material 7, a getter material film 8, a gas barrier film 9, and a back sheet 10. The thin-film solar cell 14 is configured so that light is irradiated from the side on which the protective film 1 is formed (the lower side in Figure 2), causing the solar cell element 6 to generate electricity. The thin-film solar cell 14 does not need to have all of these components, and necessary components can be selected as desired.

[0110] The thin-film solar cell 14 may be used alone, or a plurality of thin-film solar cells 14 may be connected together, or may be used as a component of a solar cell module in combination with other components. For example, as shown in Fig. 3, a solar cell module 13 having thin-film solar cells 14 on a substrate 12 may be fabricated, and this solar cell module 13 may be installed at the location of use.

[0111] The selection of each of the above-mentioned components and their manufacturing methods can be achieved by applying well-known techniques, such as those described in publicly known documents such as WO 2013 / 171517, WO 2013 / 180230, or JP 2012-191194 A.

[0112] There are no limitations on the applications of the photoelectric conversion element and the solar cell and solar cell module provided with the same, and examples of applications include solar cells for building materials, solar cells for automobiles, solar cells for interior decoration, solar cells for railways, solar cells for ships, solar cells for airplanes, solar cells for spacecraft, solar cells for home appliances, solar cells for mobile phones, and solar cells for toys.

[0113] The present invention will be described in detail below using examples, but the present invention is not limited to these examples. [Example 1] (First Solvent: Anisole, Second Solvent: Mesitylene) 40 mg of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) as a charge transport polymer was weighed into a vial, and 0.9 mL of mesitylene was added in a glove box. The mixture was stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. Separately, anisole was added to 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (TPFB) to prepare an 80 mg / mL dopant solution. Next, 0.1 mL of the dopant solution was added to the undoped hole transport solution, and the mixture was heated and stirred at 130°C for 1 hour. The mixture was then filtered through a PTFE filter (pore size 0.45 μm) to prepare a hole transport layer composition containing anisole as a first solvent and mesitylene as a second solvent. The volume ratio of the first solvent, anisole, to the second solvent, mesitylene, was 10:90. The evaluation results are shown in Table 1. The polar terms (δP) of the Hansen solubility parameters of anisole and mesitylene were 4.4 and 0.6, respectively.

[0114] [Examples 2 to 9] Compositions for hole transport layers were prepared in the same manner as in Example 1, except that the amount of mesitylene was changed so that the volume ratio of the first solvent, anisole, to the second solvent, mesitylene, was the ratio shown in Table 1. Since the amount of mesitylene was less than 0.9 mL, methyl benzoate was added in an amount that, combined with the mesitylene, made up 0.9 mL, and the mixture was further stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. The evaluation results are shown in Table 1.

[0115] Example 10 (First Solvent: Methyl Benzoate, Second Solvent: Mesitylene) 40 mg of PTAA was weighed into a vial as a charge transport polymer, and 0.9 mL of mesitylene was added in a glove box. The mixture was stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. Separately, methyl benzoate was added to TPFB to prepare an 80 mg / mL dopant solution. Next, 0.1 mL of the dopant solution was added to the undoped hole transport solution, and the mixture was heated and stirred at 130°C for 1 hour. After that, the mixture was filtered through a PTFE filter (pore size 0.45 μm) to prepare a hole transport layer composition having a first solvent, methyl benzoate, and a second solvent, mesitylene. The volume ratio of the first solvent, methyl benzoate, to the second solvent, mesitylene, was 10:90. The evaluation results are shown in Table 1. The polarity term (δP) of the Hansen solubility parameter of methyl benzoate is 8.2.

[0116] Examples 11 to 15 Compositions for hole transport layers were prepared in the same manner as in Example 10, except that the amount of mesitylene was changed so that the volume ratio of the first solvent methyl benzoate to the second solvent mesitylene was the ratio shown in Table 1. Since the amount of mesitylene was less than 0.9 mL, methyl benzoate was added in an amount that, combined with the mesitylene, made up 0.9 mL, and the mixture was further stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. The evaluation results are shown in Table 1.

[0117] Example 16 (First Solvent: Ethyl Benzoate, Second Solvent: Mesitylene) 40 mg of PTAA was weighed into a vial as a charge transport polymer, and 0.9 mL of mesitylene was added in a glove box. The mixture was stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. Separately, ethyl benzoate was added to TPFB to prepare an 80 mg / mL dopant solution. Next, 0.1 mL of the dopant solution was added to the undoped hole transport solution, and the mixture was heated and stirred at 130°C for 1 hour. After that, the mixture was filtered through a PTFE filter (pore size 0.45 μm) to prepare a hole transport layer composition having a first solvent, ethyl benzoate, and a second solvent, mesitylene. The volume ratio of the first solvent, ethyl benzoate, to the second solvent, mesitylene, was 10:90. The evaluation results are shown in Table 1. The polarity term (δP) of the Hansen solubility parameter of ethyl benzoate is 6.2.

[0118] Examples 17 to 21 Compositions for hole transport layers were prepared in the same manner as in Example 16, except that the amount of mesitylene was changed so that the volume ratio of the first solvent ethyl benzoate to the second solvent mesitylene was the ratio shown in Table 1. Since the amount of mesitylene was less than 0.9 mL, ethyl benzoate was added in an amount that, combined with the mesitylene, made up 0.9 mL, and the mixture was further stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. The evaluation results are shown in Table 1.

[0119] [Comparative Example 1] (Mesitylene alone as second solvent) 40 mg of PTAA was weighed into a vial as a charge transport polymer, and 0.9 mL of mesitylene was added in a glove box. The mixture was stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. Separately, mesitylene was added to TPFB to prepare an 80 mg / mL dopant solution. Next, 0.1 mL of the dopant solution was added to the undoped hole transport solution, and the mixture was heated and stirred at 130°C for 1 hour, and then filtered with a PTFE filter (pore size 0.45 μm) to prepare a hole transport layer composition containing mesitylene alone as the solvent.

[0120] [Comparative Example 2] (First Solvent: Anisole Alone) 40 mg of PTAA was weighed into a vial as a charge transport polymer, and 0.9 mL of anisole was added in a glove box. The mixture was stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. Separately, anisole was added to TPFB to prepare an 80 mg / mL dopant solution. Next, 0.1 mL of the dopant solution was added to the undoped hole transport solution, and the mixture was heated and stirred at 130°C for 1 hour. The mixture was then filtered through a PTFE filter (pore size 0.45 μm) to prepare a hole transport layer composition containing anisole as the first solvent alone.

[0121] [Comparative Example 3] (First Solvent: Methyl Benzoate Alone) 40 mg of PTAA was weighed into a vial as a charge transport polymer, and 0.9 mL of methyl benzoate was added in a glove box. The mixture was stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. Separately, methyl benzoate was added to TPFB to prepare an 80 mg / mL dopant solution. Next, 0.1 mL of the dopant solution was added to the undoped hole transport solution, and the mixture was heated and stirred at 130°C for 1 hour. The mixture was then filtered through a PTFE filter (pore size 0.45 μm) to prepare a hole transport layer composition containing methyl benzoate as the first solvent alone.

[0122] [Comparative Example 4] (First Solvent: Ethyl Benzoate Alone) 40 mg of PTAA was weighed into a vial as a charge transport polymer, and 0.9 mL of ethyl benzoate alone was added in a glove box. The mixture was stirred at room temperature to prepare a 44 mg / mL undoped hole transport solution. Separately, ethyl benzoate was added to TPFB to prepare an 80 mg / mL dopant solution. Next, 0.1 mL of the dopant solution was added to the undoped hole transport solution, and the mixture was heated and stirred at 130°C for 1 hour. The mixture was then filtered through a PTFE filter (pore size 0.45 μm) to prepare a hole transport layer composition containing ethyl benzoate alone as the first solvent.

[0123] (Evaluation) The appearance of the prepared inks and the surface of the spin-coated film were inspected to evaluate the presence or absence of precipitation of solids. Next, each ink was divided into two portions, and stored in a glove box (room temperature) and a refrigerator (5°C), respectively, and then the presence or absence of precipitation was confirmed. (Evaluation criteria: initial, 1 month) ○: No precipitation occurred △: Slight precipitation occurred ×: Precipitation occurred (Evaluation criteria: overall evaluation) ◎: No precipitation occurred for 1 month at either room temperature or in the refrigerator ○: No precipitation occurred for 1 month at room temperature, but precipitation occurred in the refrigerator △: Slight precipitation ×: Precipitation occurred

[0124]

[0125] (Evaluation Results) As is clear from the results of Comparative Example 1, when the first solvent, an aromatic compound containing oxygen atoms, was not included, precipitation was sometimes observed immediately after heating and stirring. As in Comparative Examples 2, 3, and 4, when the first solvent, an aromatic compound containing oxygen atoms, was used alone, precipitation was observed from the beginning or occurred after one month of storage at room temperature. Furthermore, it was found that in a composition containing a charge-transporting polymer having a specific structural unit and a tetraarylborate ion, there is a preferred volume ratio of the first solvent, an aromatic compound containing oxygen atoms, to the second solvent not containing oxygen atoms. That is, it was found that by adjusting the volume ratio of the first solvent to the second solvent, a composition having high solubility of the charge-transporting polymer and the tetraarylborate ion can be obtained.

[0126] According to the present invention, there are provided a charge transport polymer that can be suitably applied to the formation of a hole transport layer, even when a photoelectric conversion element having an active layer containing a perovskite semiconductor compound has an inverted structure, a composition containing the charge transport polymer, and a photoelectric conversion element having a crosslinked product of the charge transport polymer. In other words, a polymer having an aromatic amine structural unit, which is expected to contribute to power generation efficiency due to its high charge mobility, exhibits high solubility in solvents, allowing layer formation by coating and enabling photoelectric conversion elements to be produced with high productivity. Therefore, it can be seen that the present invention is a technology of great industrial value.

[0127] REFERENCE SIGNS LIST 1 Weather-resistant protective film 2 UV-cut film 3, 9 Gas barrier film 4, 8 Getter material film 5, 7 Sealant 6 Solar cell element 10 Back sheet 12 Substrate 13 Solar cell module 14 Thin-film solar cell 100 Photoelectric conversion element 101 Lower electrode 102 Buffer layer 103 Active layer 104 Buffer layer 105 Upper electrode 106 Substrate

Claims

1. A composition comprising a charge-transporting polymer having a unit represented by the following formula (1), a tetraarylborate ion represented by the following formula (2), a first solvent which is an aromatic compound containing an oxygen atom, and a second solvent which does not contain an oxygen atom. In formula (1), R １ ~R ５ each independently represents a hydrogen atom or a monovalent aliphatic hydrocarbon group, R １ and R ５ At least one of Ar is a monovalent aliphatic hydrocarbon group, １ represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent. In formula (2), Ar １１ , Ar １２ , Ar １３ , and Ar １４ each independently represents a monovalent aromatic hydrocarbon group which may have a substituent, or a monovalent aromatic heterocyclic group which may have a substituent, and Ar １１ , Ar １２ , Ar １３ , and Ar １４ At least one of the groups has a fluorine atom or a fluorine-substituted alkyl group as a substituent.

2. The composition according to claim 1, wherein the first solvent, which is an aromatic compound containing an oxygen atom, is an aromatic ether compound or an aromatic ester compound.

3. The composition of claim 1, wherein the second solvent containing no oxygen atoms is an aromatic compound.

4. The composition of claim 3, wherein the oxygen-free second solvent is an alkylated aromatic compound.

5. The composition of claim 1, wherein the volume ratio of the first solvent to the second solvent is 5:95 to 90:

10.

6. The composition according to claim 5, wherein the volume ratio of the first solvent to the second solvent is from 5:95 to 19:

81.

7. R in the formula (1) １ and R ５ The composition of claim 1 , wherein is a monovalent aliphatic hydrocarbon group.

8. R in the formula (1) １ and R ５ The composition of claim 7 , wherein is a methyl group.

9. The composition according to any one of claims 1 to 8, which is used to form a hole transport layer.

10. A photoelectric conversion element having a pair of electrodes having an upper electrode and a lower electrode, an active layer located between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound, and a hole transport layer located between the active layer and the upper electrode or the lower electrode, wherein the hole transport layer is a layer formed using the composition according to any one of claims 1 to 8.

11. A composition comprising a charge-transporting polymer having a unit represented by the following formula (1), a tetraarylborate ion represented by the following formula (2), a first solvent having a polar term (δP) of the Hansen solubility parameter of 3.0 or more, and a second solvent having a polar term (δP) of the Hansen solubility parameter of less than 3.

0. In formula (1), R １ ~R ５ each independently represents a hydrogen atom or a monovalent aliphatic hydrocarbon group, R １ and R ５ At least one of Ar is a monovalent aliphatic hydrocarbon group, １ represents a divalent aromatic hydrocarbon group which may have a substituent, or a divalent aromatic heterocyclic group which may have a substituent. In formula (2), Ar １１ , Ar １２ , Ar １３ , and Ar １４ each independently represents a monovalent aromatic hydrocarbon group which may have a substituent, or a monovalent aromatic heterocyclic group which may have a substituent, and Ar １１ , Ar １２ , Ar １３ , and Ar １４ At least one of the groups has a fluorine atom or a fluorine-substituted alkyl group as a substituent.

12. The composition according to claim 11, which is used to form a hole transport layer.

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