Compound and hole transport material

Abstract

A compound according to the present invention is represented by formula (1) or formula (2). In formula (1) and formula (2), R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, and R20 each independently represent a hydrogen atom, a C1 to C8 alkyl group, a C1 to C8 alkoxy group, a C2 to C8 dialkylamino group, a fluorine atom, or a cyano group, and at least one of R1 ≠ R11, R2 ≠ R12, R3 ≠ R13, R4 ≠ R14, R5 ≠ R15, R6 ≠ R16, R7 ≠ R17, R8 ≠ R18, R9 ≠ R19, and R10 ≠ R20 is satisfied.

Description

Compound and hole transport material

[0001] The present invention relates to a compound and a hole transport material.

[0002] In recent years, solar cells have attracted attention as a clean energy source. Among organic solar cells, solar cells having a photoelectric conversion layer containing a perovskite compound (hereinafter also referred to as "perovskite solar cells") exhibit particularly high photoelectric conversion efficiency. For this reason, research on perovskite solar cells has been actively conducted in recent years. Under these circumstances, the development of new hole transport materials is being promoted in order to further improve photoelectric conversion efficiency.

[0003] For example, Patent Document 1 describes a compound as a hole transport material in which the same specific substituents are bonded to the 2-, 2'-, 7-, and 7'-positions of 9,9'-spirobifluorene.

[0004] Patent No. 7261945

[0005] Hole transport materials are required to have high hole mobility. Furthermore, in order to fabricate lightweight and flexible solar cells, it is desirable to form each layer by coating the material to achieve thin film formation. However, the inventors of the present application have found that spirobifluorene-based organic compounds, which have a symmetric structure centered on a spiro atom, tend to be difficult to dissolve in organic solvents, making it difficult to form thin films with high hole mobility.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a novel compound and hole transport material that have excellent solubility in organic solvents and high hole mobility.

[0007] The compound of the present invention is represented by formula (1) or formula (2).

[0008] In the formula (1) and the formula (2), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a dialkylamino group having 2 to 8 carbon atoms, a fluorine atom, or a cyano group, and R 1 ≠R 11 , R 2 ≠R 12 , R 3 ≠R 13 , R 4 ≠R 14 , R 5 ≠R 15 , R 6 ≠R 16 , R ７ ≠R 17 , R 8 ≠R 18 , R 9 ≠R 19 , and R 10 ≠R 20 At least one of the following conditions is satisfied.

[0009] The hole transport material of the present invention contains a compound represented by the formula (1) or (2).

[0010] The compound of the present invention has excellent solubility in organic solvents and high hole mobility, and therefore can be suitably used as a hole transport material.

[0011] FIG. 1 shows the structure of compound (H-1) synthesized in Example 1 of the present invention. 1 2 is a H-NMR chart of the compound shown in FIG. 1This is a partially enlarged view of a H-NMR chart. FIG. 3 is a mass spectrum of compound (H-1) synthesized in Example 1 of the present invention. FIG. 4 is a partially enlarged view of the mass spectrum shown in FIG. 3. FIG. 5 is a diagram showing a hole mobility measurement apparatus using the MIS-CELIV method. FIG. 6 is a graph showing the time course of a linearly increasing reverse voltage in hole mobility measurement using the MIS-CELIV method. FIG. 7 is a graph showing the time course of a transient current generated by application of a reverse voltage in hole mobility measurement using the MIS-CELIV method. FIG. 8 is a graph showing the transmission current waveform observed when the reverse voltage application rate A was 150 kV / s and the forward voltage VFB was changed from 0 V to -10 V. FIG. 9 is a graph showing the electric field dependence of hole mobility predicted from the transient current observed under the conditions of a reverse voltage application rate A of 100 to 350 kV / s and a forward voltage VFB of -10 V.

[0012] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. The present invention can be modified in various ways within the scope of the object of the present invention, and embodiments obtained by appropriately combining the technical means described in different embodiments are also included in the technical scope of the present invention.

[0013] Hereinafter, the compound name may be followed by "system" to collectively refer to the compound and its derivatives. When the compound name is followed by "system" to represent the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, general formulas and chemical formulas will be collectively referred to as "formulas." Furthermore, "each independently" in the description of a formula means that it may represent the same group or different groups. Furthermore, each component described below may be used alone or in combination of two or more types.

[0014] [First embodiment: Compound] The first embodiment of the present invention relates to a compound represented by the following formula (1) (hereinafter may be referred to as compound (1)) or a compound represented by the following formula (2) (hereinafter may be referred to as compound (2)). Compounds (1) and (2) are 9,9'-spirobifluorene derivatives (spirobifluorene-based organic compounds).

[0015] In formula (1) and formula (2), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a dialkylamino group having 2 to 8 carbon atoms, a fluorine atom, or a cyano group.

[0016] In Formula (1) and Formula (2), substituents represented by the same symbol represent the same group. For example, two R 1 represent the same group. 1 represent the same group. 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 The same is true for .

[0017] Additionally, alkyl chains of substituents used herein are straight or branched and unsubstituted unless otherwise specified.

[0018] The alkyl group having 1 to 8 carbon atoms is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group.

[0019] The alkoxy group having 1 to 8 carbon atoms is preferably an alkoxy group having 1 to 3 carbon atoms, and more preferably a methoxy group.

[0020] Examples of the dialkylamino group having from 2 to 8 carbon atoms include a dimethylamino group, a diethylamino group, an ethylmethylamino group, and a dipropylamino group. Of these dialkylamino groups, a dimethylamino group is more preferred.

[0021] Compound (1) and compound (2) are compounds represented by the formula (1) and formula (2), respectively, where R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 satisfies at least one of the following conditions (a) to (j): (a) R 1 ≠R 11 , (b) R 2 ≠R 12 , (c) R 3 ≠R 13 , (d) R 4 ≠R 14 , (e) R 5 ≠R 15 , (f) R 6 ≠R 16 , (g) R 7 ≠R 17 , (h) R 8 ≠R 18 , (i) R 9 ≠R 19 , (j) R 10 ≠R 20

[0022] That is, compound (1) has a structure in which amino groups different from the amino groups bonded to the 2'- and 7'-positions of 9,9'-spirobifluorene are bonded to the 2'- and 7'-positions, respectively. Therefore, compound (1) has an asymmetric structure in the vertical direction in formula (1) with the spiro atom (spiro carbon at the 9,9'-positions) at the center.

[0023] On the other hand, compound (2) has a structure in which amino groups different from the amino groups bonded to the 7- and 7-positions are bonded to the 2- and 2'-positions of 9,9'-spirobifluorene. Therefore, compound (2) has an asymmetric structure in the left-right direction in formula (2) with the spiro atom (spiro carbon at the 9,9'-positions) at the center.

[0024] Compounds (1) and (2) have excellent solubility in organic solvents and high hole mobility. According to the studies of the present inventors, 9,9'-spirobifluorene derivatives having a symmetric structure centered on a spiro atom tend to be less soluble in organic solvents. As described above, compounds (1) and (2) have an asymmetric structure in the vertical or horizontal direction centered on the spiro atom. Therefore, in compounds (1) and (2), the aryl group of the amino group bonded to the 9,9'-spirobifluorene in formula (1) or formula (2) twists and stands up relative to the plane of the 9,9'-spirobifluorene. As a result, the molecules of compound (1) or compound (2) do not adhere too closely to each other, making it difficult for the molecules of compound (1) or compound (2) to aggregate. As a result, the solubility of compounds (1) and (2) in organic solvents is improved. Therefore, the compounds (1) and (2) have superior solubility in organic solvents and high hole mobility compared to 9,9'-spirobifluorene derivatives having a symmetric structure centered on a spiro atom.

[0025] Therefore, Compound (1) and Compound (2) can be used to form a thin film using a solution of Compound (1) or Compound (2) dissolved in an organic solvent, and can form a thin film having high hole mobility. Therefore, Compound (1) and Compound (2) can be suitably used as a hole transport material, for example, for forming a hole transport layer.

[0026] Furthermore, the hole transport material is required to have an appropriate ionization potential so that injected holes can be efficiently transferred to the photoelectric conversion layer. The ionization potentials (hereinafter sometimes referred to as "I.P.") of compounds (1) and (2) are close to, and slightly shallower than, the I.P. of perovskite. The I.P. of perovskite is, for example, 5.3 to 5.7 eV. Therefore, when compounds (1) and (2) are used as hole transport materials in perovskite solar cells, they can efficiently extract charges generated in the photoelectric conversion layer to the outside. This can improve the energy conversion efficiency of the solar cell. Therefore, compounds (1) and (2) are particularly suitable as hole transport materials for perovskite solar cells.

[0027] In order to obtain a compound having improved solubility in an organic solvent, high hole mobility, and an I.P. slightly shallower than that of perovskite, compound (1) and compound (2) are prepared by adding a compound represented by the formula (1) and formula (2) below, where R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 In this case, it is preferable that at least one of R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 However, it is preferred that the fluorine atom or cyano group is not contained.

[0028] In other words, compound (1) and compound (2) are compounds represented by the formula (1) and formula (2), respectively, where R 1 , R 2 , R 3 , R4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 At least one of R is a fluorine atom or a cyano group, 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a dialkylamino group having 2 to 8 carbon atoms.

[0029] In addition, in order to obtain a compound having improved solubility in an organic solvent, high hole mobility, and an I.P. slightly shallower than that of perovskite, compound (1) and compound (2) are prepared by adding a compound represented by the formula (1) and formula (2) below, where R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 It is more preferable that at least one of R is a fluorine atom. 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 More preferably, at least one of R is a methoxy group. 13 and R 18 It is more preferable that R is a methoxy group. 3 and R 8More preferred are compounds in which at least one of R 3 and R 8 Among such compounds (1) and (2), compounds in which at least one of R 3 and R 8 and each is a fluorine atom.

[0030] Suitable examples of compound (1) for obtaining a compound having improved solubility in organic solvents, high hole mobility, and an I.P. slightly shallower than that of perovskite include compounds represented by formulas (H-1), (H-2), (H-3), (H-4), (H-5), and (H-6) (hereinafter, these may be referred to as compounds (H-1), (H-2), (H-3), (H-4), (H-5), and (H-6), respectively).

[0031] Furthermore, a suitable example of compound (2) for improving solubility in organic solvents, obtaining a compound with high hole mobility and an I.P. slightly shallower than that of perovskite is formula (H-7) (hereinafter, may be referred to as compound (H-7)).

[0032] Compounds (H-1) to (H-4) and (H-7) are compounds represented by the formula (1) and the formula (2), where R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 At least one of R is a fluorine atom or a cyano group, 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a dialkylamino group having 2 to 8 carbon atoms. These compounds (H-1) to (H-4) and (H-7) have an I.P. close to the I.P. of perovskite and are more suitable as hole transport materials for perovskite solar cells.

[0033] Compounds (H-1) to (H-3) and (H-7) are compounds represented by the formula (1) and the formula (2), where R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 At least one of R is a fluorine atom, 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 In addition, these compounds (H-1) to (H-3) and (H-7) are compounds in which at least one of R 13 and R 18 is a methoxy group. These compounds (H-1) to (H-3) and (H-7) have I.P. values ​​closer to that of perovskite and are therefore more suitable as hole transport materials for perovskite solar cells.

[0034] In addition, in formula (1), R 3 and R 8 In the compound (1), at least one of the groups represented by the formula (I) is a fluorine atom or a cyano group, and has an I.P. closer to that of perovskite, and is particularly suitable as a hole transport material for perovskite solar cells. An example of such a compound is compound (H-1).

[0035] In addition, in formula (2), R 3 and R8 In the compound (2), at least one of the groups represented by the formula (I) is a fluorine atom or a cyano group, and has an I.P. closer to that of perovskite, and is particularly suitable as a hole transport material for perovskite solar cells. An example of such a compound is compound (H-7).

[0036] [Method for Producing Compound (1)] Next, a method for producing compound (1) will be described. Compound (1) is produced, for example, by the reaction represented by the following reaction formula (R-1) (hereinafter, sometimes referred to as reaction (R-1)) and the reaction represented by reaction formula (R-2) (hereinafter, sometimes referred to as reaction (R-2)), or by a method equivalent thereto. The method for producing compound (1) includes, for example, reaction (R-1) and reaction (R-2).

[0037] In reaction (R-1), R 1 ~R 10 are R in formula (1), respectively. 1 ~R 10 is synonymous with.

[0038] In reaction (R-1), 1 molar equivalent of a compound represented by formula (S-1) (2,2',7,7'-tetrabromo-9,9'-spirobi[9H-fluorene]) (hereinafter, may be referred to as compound (S-1)) is reacted with 2 molar equivalents of a secondary amine compound represented by formula (A) (hereinafter, may be referred to as secondary amine (A)) to obtain 1 molar equivalent of a compound represented by formula (I) (dibromo form), which is an intermediate.

[0039] The reaction (R-1) is preferably carried out in an inert gas atmosphere, such as nitrogen gas or argon gas.

[0040] Reaction (R-1) can be carried out in a solvent, such as a benzene derivative such as xylene or toluene, a hydrophilic solvent such as tetrahydrofuran, 1,4-dioxane or dimethylformamide, or a hydrophobic solvent such as 2-methyltetrahydrofuran or cyclohexyl methyl ether.

[0041] Reaction (R-1) may be carried out in the presence of a palladium catalyst, such as [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](3-chloropyridyl)palladium(II) dichloride (PEPPSI®-IPr catalyst), palladium(II) chloride, palladium(II) acetate, palladium(II) trifluoroacetate, tris(dibenzylideneacetone)dipalladium(0), di-μ-chlorobis[(η-allyl)palladium(II)], or bis(acetylacetonato)palladium(II).

[0042] The reaction (R-1) may be carried out in the presence of a base, such as lithium bis(trimethylsilyl)amide, sodium tert-butoxide, potassium tert-butoxide, sodium methylate, tripotassium phosphate, or cesium fluoride.

[0043] The palladium catalyst may be used in combination with an organic phosphorus ligand. Examples of the organic phosphorus ligand include triarylphosphines such as triphenylphosphine and tri-o-tolylphosphine; trialkylphosphines such as tri-tert-butylphosphine and tricyclohexylphosphine; trialkylphosphonium borate salts such as tri-tert-butylphosphonium tetraphenylborate and tri-tert-butylphosphonium tetrafluoroborate; bidentate phosphines such as 2,2'-bis(diphenylphosphino)diphenyl ether, 9,9-dimethyl-4,5-bis(diphenylphosphino)-9H-xanthene, and 1,1'-bis(diphenylphosphino)ferrocene; and [4-(N,N-dimethylamino)phenyl]di-tert-butylphosphine. The palladium catalyst may be a palladium catalyst coordinated with an organic phosphorus ligand.

[0044] The reaction temperature of the reaction (R-1) is preferably 40° C. or higher and 80° C. or lower. The reaction time of the reaction (R-1) is preferably 1 hour or higher and 10 hours or lower.

[0045] In reaction (R-2), R 11~R 20 are R in formula (1), respectively. 11 ~R 20 is synonymous with.

[0046] In reaction (R-2), 1 molar equivalent of compound (I) obtained in reaction (R-1) is reacted with 2 molar equivalents of a secondary amine compound represented by formula (B) (hereinafter, sometimes referred to as secondary amine (B)) to obtain 1 molar equivalent of the target compound (1). Reaction (R-2) is the same as reaction (R-1), except that secondary amine (A) is replaced with secondary amine (B). Therefore, although explanations are omitted, the inert gas, solvent, palladium-based catalyst, base, and organophosphorus-based ligand are also the same as those in reaction (R-1).

[0047] The reaction temperature of the reaction (R-2) is preferably the reflux temperature, and the reaction time of the reaction (R-2) is preferably 1 hour or more and 10 hours or less.

[0048] [Method for Producing Compound (2)] Next, a method for producing compound (2) will be described. Compound (2) is produced, for example, according to the reaction formula (r-1) below (hereinafter, may be referred to as reaction (r-1)), the reaction formula (r-2) below (hereinafter, may be referred to as reaction (r-2)), and the reaction formula (r-3) below (hereinafter, may be referred to as reaction (r-3)), or by a method equivalent thereto. The method for producing compound (2) includes, for example, reaction (r-1), reaction (r-2), and reaction (r-3).

[0049] In reaction (r-1), R 11 ~R 20 are R in formula (2), respectively. 11 ~R 20 is synonymous with.

[0050] In reaction (r-1), 1 molar equivalent of a compound (2,2'-dibromo-9,9'-spirobi[9H-fluorene]) represented by formula (S-2) (hereinafter, sometimes referred to as compound (S-2)) is reacted with 2 molar equivalents of a secondary amine (B) represented by formula (B) to obtain 1 molar equivalent of a compound represented by formula (IA) (hereinafter, sometimes referred to as intermediate (IA)). Reaction (r-1) is the same as reaction (R-1), except that compound (S-1) is changed to compound (S-2) and secondary amine (A) is changed to secondary amine (B). Therefore, although explanations are omitted, the inert gas, solvent, palladium-based catalyst, base, and organophosphorus-based ligand are also the same as those in reaction (R-1).

[0051] The reaction temperature of the reaction (r-1) is preferably the reflux temperature, and the reaction time of the reaction (r-1) is preferably 1 hour or more and 10 hours or less.

[0052] In reaction (r-2), R 11 ~R 20 are R in formula (2), respectively. 11 ~R 20 is synonymous with.

[0053] Reaction (r-2) is a bromination reaction in which 1 molar equivalent of intermediate (IA) obtained in reaction (r-1) is reacted with 2 molar equivalents of bromine to obtain 1 molar equivalent of an intermediate compound represented by formula (IB) (dibromo compound) (hereinafter, may be referred to as intermediate (IB)).

[0054] The reaction (r-2) is preferably carried out in an inert gas atmosphere, such as nitrogen gas or argon gas.

[0055] Reaction (r-2) can be carried out in a solvent, such as chloroform.

[0056] In order to promote the reaction (r-2), the reaction (r-2) may be carried out in the presence of a catalyst. For example, a Lewis acid catalyst is preferably used. Examples of the Lewis acid catalyst include zinc chloride, zinc bromide, zinc iodide, iron(III) chloride, and iron(III) bromide. Among these, anhydrous iron(III) bromide is preferred.

[0057] Reaction (r-2) can be carried out at room temperature. The reaction temperature of reaction (r-2) is preferably 15° C. or higher and 40° C. or lower. The reaction time of reaction (r-1) is preferably 1 hour or higher and 15 hours or lower.

[0058] In reaction (r-3), 1 molar equivalent of intermediate (IB) obtained in reaction (r-2) is reacted with 2 molar equivalents of secondary amine (A) to obtain 1 molar equivalent of the target compound (2). Reaction (r-3) is the same as reaction (R-1), except that compound (S-1) is replaced with intermediate (IB). Therefore, although explanations are omitted, the inert gas, solvent, palladium catalyst, base, and organophosphorus ligand are also the same as those in reaction (R-1).

[0059] The reaction temperature of the reaction (r-3) is preferably the reflux temperature, and the reaction time of the reaction (r-3) is preferably 1 hour or more and 10 hours or less.

[0060] The target compound (1) or compound (2) can be isolated by purifying the resulting reaction product. Examples of purification methods include purification by column chromatography, adsorption purification using silica gel, activated clay, etc., recrystallization or crystallization using a solvent, etc. Nuclear magnetic resonance analysis (NMR) or the like can be used to identify the resulting compound.

[0061] [Second embodiment: hole transport material] The second embodiment of the present invention relates to a hole transport material. Compound (1) or compound (2) according to the first embodiment of the present invention can be used as a hole transport material. The hole transport material according to this embodiment contains compound (1) or compound (2).

[0062] As described in the first embodiment, compound (1) and compound (2) have excellent solubility in organic solvents and high hole mobility. Therefore, a hole transport material containing compound (1) or compound (2) has excellent solubility in organic solvents, can be used to form a thin film by dissolving compound (1) or compound (2) in an organic solvent, and can form a thin film with high hole mobility.

[0063] Furthermore, as described in the first embodiment, the I.P. of compound (1) and compound (2) is close to the I.P. of perovskite (e.g., 5.3 to 5.7 eV) and is slightly shallower than the I.P. of perovskite. Therefore, when a hole transport material containing compound (1) or compound (2) is used in a perovskite solar cell, it can efficiently extract charges generated in the photoelectric conversion layer to the outside. This can improve the energy conversion efficiency of the solar cell. Therefore, the hole transport material according to this embodiment can be particularly suitably used as a hole transport material for perovskite solar cells.

[0064] The hole transport material according to this embodiment may be a compound (1) represented by formula (1) or a compound (2) represented by formula (2), which may be used alone or in combination of two or more thereof. The hole transport material according to this embodiment may further contain a hole transport material other than compound (1) or compound (2).

[0065] The hole transport material according to this embodiment may further contain additives as needed. As the additives, conventionally known additives such as an interface treatment agent can be used.

[0066] EXAMPLES The present invention will be described in more detail below using examples, although the present invention is not limited to the following examples.

[0067] Compounds (H-1) to (H-7) described in the first embodiment were synthesized by the following methods as Examples 1 to 7. Furthermore, as Comparative Examples 1 to 3, a comparative compound represented by formula (h-1) (hereinafter sometimes referred to as compound (h-1)), a comparative compound represented by formula (h-2) (hereinafter sometimes referred to as compound (h-2)), and a comparative compound represented by formula (h-3) (hereinafter sometimes referred to as compound (h-3)) were synthesized by the following methods.

[0068] <Synthesis of Compound (H-1)> In order to synthesize Compound (H-1), first, a compound represented by Formula (I-1) (hereinafter, sometimes referred to as intermediate (I-1)) was synthesized as intermediate (I), as shown in the following reaction scheme.

[0069] (Synthesis of Intermediate (I-1))

[0070] In the above reaction, a 500 mL two-neck flask equipped with a thermometer and a stirrer was used as a reaction vessel. Into this reaction vessel, 0.0110 mol (2.522 g) of a secondary amine compound (A) represented by formula (A-1) (Mw: 229.3) (hereinafter, sometimes referred to as secondary amine (A-1)) and 0.0080 mol (5.056 g) of compound (S-1) (2,2',7,7'-tetrabromo-9,9'-spirobi[9H-fluorene]) (Mw: 631.4) were added. 0.00020 mol (0.1358 g) of [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](3-chloropyridyl)palladium(II) dichloride (PEPPSI®-IPr catalyst) and 0.0120 mol (2.008 g) of lithium bis(trimethylsilyl)amide as a base were charged into a reaction vessel, and the atmosphere inside the reaction vessel was replaced with nitrogen while stirring at room temperature. Thereafter, 170 g of 2-methyltetrahydrofuran as an organic solvent was charged into the reaction vessel, and the temperature of the reaction solution inside the reaction vessel was raised to 60°C while stirring with a magnetic stirrer, and the reaction solution was allowed to react for 5 hours. Then, disappearance of the secondary amine (A-1) was confirmed by TLC (thin layer chromatography).

[0071] Next, 7.4 g of activated clay "SA-1" (manufactured by Japan Activated Clay Co., Ltd.) was added to the reaction solution in the reaction vessel, and after further stirring at 60°C for 20 minutes, the reaction solution in the reaction vessel was subjected to a clay adsorption treatment by filtering. The obtained filtrate was then concentrated using an evaporator and crystallized with methanol, and the precipitated solid was collected by filtration.

[0072] Next, the compound (S-1) contained in a large amount in the obtained solid was removed by column chromatography (developing solvent: toluene:isohexane=8:2). Thereafter, the solid was vacuum-dried in a vacuum oven at 100°C for 5 hours to obtain a pale yellow dibromo intermediate (I-1) (Mw: 928.7). The yield of intermediate (I-1) was 2.20 g, and the yield was 29.6%.

[0073] (Synthesis of Compound (H-1)) Next, compound (H-1) was synthesized as shown in the following reaction scheme.

[0074] In the above reaction, a 500 mL two-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was used as a reaction vessel. 0.0052 mol (1.061 g) of secondary amine (A-2) (Mw: 205.2) as secondary amine (B), 0.0022 mol (2.000 g) of intermediate (I-1), 0.000065 mol (0.0592 g) of tris(dibenzylideneacetone)dipalladium(0) as a palladium catalyst, 0.00026 mol (0.0686 g) of [4-(N,N-dimethylamino)phenyl]di-tert-butylphosphine as an organophosphorus ligand, and 0.0056 mol (0.5381 g) of sodium tert-butoxide as a base were charged into the reaction vessel, and the atmosphere inside the reaction vessel was replaced with nitrogen while stirring at room temperature. Thereafter, 75 g of xylene was added to the reaction vessel as an organic solvent, and the reaction solution in the reaction vessel was heated to the reflux temperature while being stirred with a magnetic stirrer, and the reaction was carried out for 5 hours. Then, disappearance of intermediate (I-1) was confirmed by TLC.

[0075] Next, 3.0 g of the above-mentioned activated clay "SA-1" was added to the reaction solution in the reaction vessel, and after further stirring at 80°C for 20 minutes, the reaction solution in the reaction vessel was filtered and a clay adsorption treatment was carried out to recover the filtrate. Next, 3.0 g of activated clay "SA-1" was again added to the recovered filtrate, and after further stirring at 80°C for 20 minutes, the reaction solution in the reaction vessel was filtered and a clay adsorption treatment was carried out twice to recover the filtrate. Next, the obtained filtrate was concentrated using an evaporator to obtain a brown oil.

[0076] The resulting oil was purified by column chromatography (developing solvent: toluene:isohexane=7:3) and then concentrated using an evaporator. The concentrated oil was dissolved in a small amount of tetrahydrofuran (THF), and the resulting solution was added dropwise using a dropper to a beaker containing 200 g of isohexane and stirred. The precipitated solid was collected by filtration.

[0077] The filtered solid was then dried in a vacuum oven at 100°C for 12 hours to obtain a pale yellow compound (H-1) (Mw: 1177.3) as a product. The yield of compound (H-1) was 0.80 g, and the yield was 32.0%.

[0078] The resulting product: 1 H-NMR analysis (proton nuclear magnetic resonance analysis, solvent: acetone-d6, magnetic field strength: 600 MHz) and mass spectrometry were performed. 1 From the chemical shift values ​​of the H-NMR spectrum and the mass spectrum, it was confirmed that the obtained product was the target compound (H-1). 1 The H-NMR chart is shown in FIG. 3 and FIG. 4 show the mass spectrum of the obtained compound (H-1). 1 Fig. 4 is a partial enlargement of the H-NMR chart. Fig. 4 is a partial enlargement of the mass spectrum shown in Fig. 3. It was confirmed that the target compounds were obtained in the same manner for compounds (H-2) to (H-7) and (h-1) to (h-3) and their respective intermediates.

[0079] <Synthesis of Compound (H-2)> First, as shown in the following reaction scheme, a compound represented by formula (I-2) (hereinafter, sometimes referred to as intermediate (I-2)) was synthesized as intermediate (I) in the same manner as in the synthesis of intermediate (I-1), except that a secondary amine compound represented by formula (A-3) (hereinafter, sometimes referred to as secondary amine (A-3)) was used instead of secondary amine (A-1). That is, intermediate (I-2) was synthesized in the same manner as in the synthesis of intermediate (I-1), except that 0.0110 mol of secondary amine (A-3) was used instead of 0.0110 mol of secondary amine (A-1).

[0080] Next, as shown in the following reaction scheme, compound (H-2) was obtained in the same manner as in the synthesis of compound (H-1), except that intermediate (I-2) was used instead of intermediate (I-1) and secondary amine (A-1) was used instead of secondary amine (A-2). That is, compound (H-2) was synthesized in the same manner as in the synthesis of compound (H-1), except that 0.0022 mol of intermediate (I-2) was used instead of 0.0022 mol of intermediate (I-1) and 0.0052 mol of secondary amine (A-1) was used instead of 0.0052 mol of secondary amine (A-2).

[0081] <Synthesis of Compound (H-3)> First, as shown in the following reaction scheme, a compound represented by formula (I-3) (hereinafter, sometimes referred to as intermediate (I-3)) was synthesized as intermediate (I) in the same manner as in the synthesis of intermediate (I-2), except that a secondary amine compound represented by formula (A-4) (hereinafter, sometimes referred to as secondary amine (A-4)) was used instead of secondary amine (A-3).

[0082] Next, as shown in the following reaction scheme, compound (H-3) was obtained in the same manner as in the synthesis of compound (H-1), except that intermediate (I-3) was used instead of intermediate (I-2) and secondary amine (A-1) was used instead of secondary amine (A-2).

[0083] <Synthesis of Compound (H-4)> First, as shown in the following reaction scheme, a compound represented by formula (I-4) (hereinafter, sometimes referred to as intermediate (I-4)) was synthesized as intermediate (I) in the same manner as in the synthesis of intermediate (I-2), except that a secondary amine compound represented by formula (A-5) (hereinafter, sometimes referred to as secondary amine (A-5)) was used instead of secondary amine (A-3).

[0084] Next, as shown in the following reaction scheme, compound (H-4) was obtained in the same manner as in the synthesis of compound (H-1), except that intermediate (I-4) was used instead of intermediate (I-2) and secondary amine (A-1) was used instead of secondary amine (A-2).

[0085] <Synthesis of Compound (H-5)> First, as shown in the following reaction scheme, a compound represented by formula (I-5) (hereinafter, sometimes referred to as intermediate (I-5)) was synthesized as intermediate (I) in the same manner as in the synthesis of intermediate (I-2), except that a secondary amine compound represented by formula (A-6) (hereinafter, sometimes referred to as secondary amine (A-6)) was used instead of secondary amine (A-3).

[0086] Next, as shown in the following reaction scheme, compound (H-5) was obtained in the same manner as in the synthesis of compound (H-1), except that intermediate (I-5) was used instead of intermediate (I-2) and secondary amine (A-1) was used instead of secondary amine (A-2).

[0087] <Synthesis of Compound (H-6)> First, as shown in the following reaction scheme, a compound represented by formula (I-6) (hereinafter, sometimes referred to as intermediate (I-6)) was synthesized as intermediate (I) in the same manner as in the synthesis of intermediate (I-2), except that a secondary amine compound represented by formula (A-7) (hereinafter, sometimes referred to as secondary amine (A-7)) was used instead of secondary amine (A-3).

[0088] Next, as shown in the following reaction scheme, compound (H-6) was obtained in the same manner as in the synthesis of compound (H-1), except that intermediate (I-6) was used instead of intermediate (I-2) and secondary amine (A-1) was used instead of secondary amine (A-2).

[0089] <Synthesis of Compound (H-7)> In order to synthesize Compound (H-7), first, a compound represented by Formula (I-7A) (hereinafter, sometimes referred to as intermediate (I-7A)) was synthesized as intermediate (IA), as shown in the following reaction scheme.

[0090] (Synthesis of Intermediate (I-7A))

[0091] In the above reaction, a 500 mL two-neck flask equipped with a thermometer, a stirrer, and a reflux condenser was used as a reaction vessel. Into this reaction vessel were charged 0.0354 mol (7.27 g) of secondary amine (A-2) as the secondary amine (B), 0.0148 mol (7.00 g) of compound (S-2) (2,2′-dibromo-9,9′-spirobi[9H-fluorene]) (Mw: 472.2), 0.00044 mol (0.060 g) of tris(dibenzylideneacetone)dipalladium(0) as a palladium catalyst, 0.00177 mol (0.47 g) of [4-(N,N-dimethylamino)phenyl]di-tert-butylphosphine as an organic phosphorus ligand, and 0.0384 mol (3.688 g) of sodium tert-butoxide as a base, and the atmosphere in the reaction vessel was replaced with nitrogen while stirring at room temperature. Thereafter, 300 g of xylene was added as an organic solvent to the reaction vessel, and the reaction solution in the reaction vessel was heated to the reflux temperature while being stirred with a magnetic stirrer, and the reaction was carried out for 4 hours. Then, disappearance of compound (S-2) was confirmed by TLC.

[0092] After the reaction, the liquid temperature of the reaction solution in the reaction vessel was cooled to 80 ° C. Subsequently, 11.4 g of the above-mentioned activated clay "SA-1" was added to the reaction solution in the reaction vessel, and after further stirring for 30 minutes, the reaction solution in the reaction vessel was filtered and a clay adsorption treatment was carried out to recover the filtrate. Next, 11.4 g of activated clay "SA-1" was added again to the recovered filtrate, and after further stirring at 80 ° C. for 20 minutes, the reaction solution in the reaction vessel was filtered and a clay adsorption treatment to recover the filtrate was carried out twice. Next, the obtained filtrate was concentrated using an evaporator to obtain a brown oil.

[0093] The resulting oil was purified by column chromatography (developing solvent: toluene) and then concentrated using an evaporator. The concentrated oil was dissolved in a small amount of THF, and the resulting solution was added dropwise using a dropper to a beaker containing 200 g of isohexane and stirred. The precipitated solid was collected by filtration.

[0094] The solid collected by filtration was then vacuum-dried in a vacuum oven at 100°C for 3 hours to obtain a pale yellow intermediate (I-7A) (N2,N2,N7,N7-tetrakis(4-fluorophenyl)-9,9'-spirobi[fluorene]-2,7-diamine). The yield of intermediate (I-7A) was 6.2 g, and the yield was 58.0%.

[0095] Next, as shown in the following reaction scheme, a compound represented by formula (I-7B) (hereinafter, sometimes referred to as intermediate (I-7B)) was synthesized as intermediate (IB).

[0096] (Synthesis of Intermediate (I-7B))

[0097] In the above reaction, a 500 mL two-neck flask equipped with a dropping funnel, a thermometer, and a stirrer was used as the reaction vessel. 0.0078 mol (5.638 g) of the synthesized intermediate (I-7A) and 0.0156 mol (4.610 g) of anhydrous iron(III) bromide as a catalyst were charged into this reaction vessel, and the atmosphere inside the reaction vessel was replaced with nitrogen while stirring at room temperature. Then, 121 g of chloroform as an organic solvent was charged into the reaction vessel, and 0.0312 mol (4.982 g) of bromine was added dropwise using a dropping funnel over 10 minutes. After the addition of bromine, the mixture was stirred at room temperature for 12 hours to react intermediate (I-7A) with bromine.

[0098] After the reaction, 100 g of an aqueous solution of sodium hydrogen sulfite (3.247 g of sodium hydrogen sulfite, remainder: water) was added to the reaction solution in the reaction vessel, and the mixture was stirred for 10 minutes to decompose the remaining bromine.

[0099] Next, the aqueous layer of the reaction solution in the reaction vessel was discarded using a separatory funnel, and the remaining organic layer was washed with 200 g of water, and the aqueous layer was discarded again, thereby washing the organic layer with water. After this water washing was performed three times, 20 g of anhydrous sodium sulfate was added to the obtained organic layer to dehydrate it.

[0100] Next, 6.8 g of the activated clay "SA-1" described above was added to the organic layer, and the mixture was stirred at 60°C for 20 minutes. Next, after the organic layer returned to room temperature, it was filtered, and the filtrate was concentrated using an evaporator and crystallized with methanol. The precipitated solid was then filtered off, yielding a pale yellow solid. The filtered solid was then vacuum-dried in a vacuum oven at 100°C for 3 hours, yielding intermediate (I-7B). The yield of intermediate (I-7B) was 4.86 g, a yield of 70.8%.

[0101] (Synthesis of Compound (H-7)) Next, as shown in the following reaction scheme, a pale yellow compound (H-7) was obtained in the same manner as in the synthesis of compound (H-1), except that intermediate (I-7B) was used instead of intermediate (I-1) and secondary amine (A-1) was used instead of secondary amine (A-2). The yield of compound (H-1) was 0.58 g, which was a 31.2% yield.

[0102] <Synthesis of Compound (h-1)> Compound (h-1) was synthesized according to the following reaction scheme.

[0103] In the above reaction, a 500 mL two-neck flask equipped with a reflux condenser, a thermometer, and a stirrer was used as a reaction vessel. Into this reaction vessel were charged 0.0354 mol (8.75 g) of the secondary amine (A-4), 0.0074 mol (4.67 g) of the compound (S-1) (2,2′,7,7′-tetrabromo-9,9′-spirobi[9H-fluorene]), 0.00044 mol (0.060 g) of tris(dibenzylideneacetone)dipalladium(0) as a palladium catalyst, 0.00177 mol (0.47 g) of [4-(N,N-dimethylamino)phenyl]di-tert-butylphosphine as an organic phosphorus ligand, and 0.0384 mol (3.688 g) of sodium tert-butoxide as a base, and the atmosphere inside the reaction vessel was replaced with nitrogen while stirring at room temperature. Thereafter, 150 g of xylene was added as an organic solvent to the reaction vessel, and the reaction solution in the reaction vessel was heated to the reflux temperature while being stirred with a magnetic stirrer, and the reaction was carried out for 4 hours. Then, disappearance of compound (S-1) was confirmed by TLC.

[0104] After the reaction, the temperature of the reaction solution in the reaction vessel was cooled to 80°C. Next, 6.1 g of the activated clay "SA-1" described above was added to the reaction solution in the reaction vessel, and after stirring at 80°C for 20 minutes, the reaction solution in the reaction vessel was filtered and the filtrate was collected, and a clay adsorption treatment was carried out twice. The obtained filtrate was then concentrated using an evaporator to obtain a brown oil.

[0105] The resulting oil was purified by column chromatography (developing solvent: toluene) and then concentrated using an evaporator. The concentrated oil was dissolved in a small amount of THF, and the resulting solution was added dropwise using a dropper to a beaker containing 100 g of isohexane and stirred. The precipitated solid was collected by filtration.

[0106] The filtered solid was then dried in a vacuum oven at 100°C for 3 hours to obtain a pale yellow compound (h-1) as a product. The yield of compound (h-1) was 6.10 g, and the yield was 63.6%.

[0107] <Synthesis of Compound (h-2)> As shown in the following reaction scheme, compound (h-2) was synthesized in the same manner as in the synthesis of compound (h-1), except that a secondary amine compound represented by formula (A-8) (hereinafter, may be referred to as secondary amine (A-8)) was used instead of secondary amine (A-4).

[0108] <Synthesis of Compound (h-3)> As shown in the following reaction scheme, compound (h-3) was synthesized in the same manner as in the synthesis of compound (h-1), except that secondary amine (A-2) was used instead of secondary amine (A-4).

[0109] <Evaluation> The obtained compounds (H-1) to (H-7) and compounds (h-1) to (h-3) were evaluated for I.P., hole mobility, and solubility in organic solvents by the following methods. The evaluation results are shown in Table 1 below. Unless otherwise specified, the evaluation was carried out at a temperature of 23°C and a humidity of 50% RH.

[0110] [I.P.] Powders of each of compounds (H-1) to (H-7) and compounds (h-1) to (h-3) were used as samples, and the ionization potential of the samples was measured by irradiating the samples directly with light in an air atmosphere using an air photoelectron spectrometer ("AC-3" (trade name) manufactured by Riken Keiki Co., Ltd.) and measuring the threshold energy for emitting photoelectrons.

[0111] An atmospheric photoelectron spectrometer can measure photoelectrons from a sample surface without placing the sample in a vacuum. Ultraviolet light emitted from a deuterium lamp is monochromatized by a spectrometer and irradiated onto the sample. The wavelength of the ultraviolet light and the energy of one photon are increased in steps within the wavelength range of 412 to 180 nm and the range of 3.0 to 7.0 eV, respectively. When the energy of the irradiated light exceeds the IP of the sample, photoelectrons are emitted from the sample surface into the atmosphere and captured by an open counter.

[0112] [Hole Mobility] The hole mobility was evaluated by the MIS-CELIV method. The method for evaluating the hole mobility using the MIS-CELIV method will be described below.

[0113] The MIS-CELIV method is a technique in which externally injected charges are accumulated at the interface of an insulating layer, and the electron or hole mobility is determined from the transient current waveform resulting from the extraction of the accumulated charges.

[0114] 5 is a diagram showing a hole mobility measurement device 20 using the MIS-CELIV method. A highly n-doped silicon wafer with a thermal silicon oxide (SiO2) layer 21b laminated on the surface of a Si layer 21a was used as the measurement substrate 21. A hole transport layer 5 was formed on the surface of this measurement substrate 21 by spin coating. Next, a hole injection layer 22 made of molybdenum trioxide (MoO3) and an Al electrode 23 were sequentially vapor-deposited on the surface of the hole transport layer 5. A circuit including a waveform generator 25, an oscilloscope 27, and a resistor 29 was then connected to the Si layer 21a and the Al electrode 23.

[0115] The thickness of each layer was 30 nm for the SiO layer 21b, approximately 100 nm for the hole transport layer 5, 5 nm for the hole injection layer 22 (MoO), and 100 nm for the Al electrode 23. The film thicknesses were measured using a stylus film thickness step meter (Dektak XT, manufactured by Bruker).

[0116] 6 and 7 are graphs showing the time course of reverse voltage and transient current, respectively, in the measurement of hole mobility by the MIS-CELIV method. FB When a voltage is applied, holes h are transported from the Al electrode 23 to the hole transport layer 5 via the hole injection layer 22. + As shown in FIG. 5, holes h are injected into the interface between the SiO2 layer (insulating layer) 21b and the hole transport layer (semiconductor) 5. + is accumulated.

[0117] In this state, by applying a reverse voltage that increases linearly at a voltage rise rate A=dV / dt as shown in FIG. 6, the accumulated holes h + The transient phenomenon of the MIS-CELIV method is caused by the displacement current j0 due to the sum of the geometric capacitances of the insulating layer and the semiconductor, and the accumulated holes h + The saturation current j due to the sat That is, the accumulated holes h + Extraction of the saturation current j satThe current peak Δj is determined by: The hole mobility μ is determined by the following equation (i):

[0118] In formula (i), ε ｓ is the dielectric constant of the semiconductor, ε ｉ is the dielectric constant of the insulating layer, d ｓ is the semiconductor film thickness, d ｉ is the thickness of the insulating layer, and A is the reverse voltage application speed. Carrier transport time t tr is the characteristic time t until the value of j0 doubles. 2j0 It is related to.

[0119] When the capacitance Ci of the insulating layer is sufficiently larger than the capacitance Cs of the semiconductor (Ci / Cs≧1), t tr is defined by the following equation (ii) taking into account the applied voltage drop due to a finite insulating layer.

[0120] FIG. 8 shows the relationship between the forward voltage V and the reverse voltage V under the condition of a reverse voltage application rate A=150 kV / s (i.e., kV / sec) for a device in which NPB (naphthylphenylbiphenyldiamine, film thickness 290 nm) is laminated on the SiO2 layer 21b as the hole transport layer 3. FB 8 is a graph showing the transmission current waveform observed when V is changed from 0 V to −10 V. FB At θ = 0 V, the transmission current is a square wave consisting of only the displacement current j0, which is derived from the total capacitance of the SiO2 layer 21b and the hole transport layer 5. This flat response is due to the number of holes h0 accumulated in the hole transport layer 3. + indicates that does not exist.

[0121] V FB When a voltage of -2 to -10 V is applied, holes h+ are injected from the Al electrode 23 through the hole injection layer 22 into the hole transport layer 3, and are accumulated at the interface between the SiO2 layer 21 b and the hole transport layer 5, resulting in a current peak Δj due to hole extraction. FB Increasing Δj increases the sat = 172 [A / m 2 The transient current of the MIS-CELIV is ultimately limited by the displacement current of the insulating layer (SiO2 layer 21b).

[0122] That is, sufficient holes h are transported from the interface between the SiO2 layer 21b and the hole transport layer 5. + V before it is supplied FB In the low region, V FB Δj increases linearly with FB Even if V is increased, Δj saturates and remains unchanged. FB When the potential V is -10 V, sufficient holes h + It is clear that accumulation

[0123] FIG. 9 shows the reverse voltage application rate A=100 to 350 kV / s (i.e., kV / sec), forward voltage V FB 6 is a graph showing the electric field dependence of hole mobility predicted from the transient current observed under the condition of V = −10 V. The charge dependence of hole mobility shown in FIG. 6 can be analyzed using the following equation (iii) to calculate the hole mobility μ0 in an electric field of 0.

[0124] The hole mobilities of the compounds (H-1) to (H-7) and the compounds (h-1) to (h-3) were measured by the above-mentioned MIS-CELIV method using the measurement device 20 shown in FIG.

[0125] First, a highly n-doped silicon wafer substrate having a 30 nm thick thermally oxidized silicon (SiO) layer was ultrasonically cleaned for 20 minutes in a solution of ultrapure water mixed with 20% Cicaclean. Next, this silicon wafer substrate was ultrasonically cleaned for 10 minutes in ultrapure water, followed by ultrasonic cleaning for 10 minutes in acetone. Subsequently, this silicon wafer substrate was ultrasonically cleaned for 10 minutes in IPA (isopropyl alcohol), followed by UV ozone cleaning for 20 minutes.

[0126] Onto the thus cleaned substrate, 300 μL of a 3% chloroform solution of the hole transport material was dropped in the atmosphere, and a hole transport layer (thickness: about 200 nm) was laminated by spin coating using a spin coater at 5000 rpm for 60 seconds.

[0127] Next, a hole injection layer of molybdenum trioxide (MoO3) and an Al electrode were deposited on the hole transport layer at a deposition rate of MoO3 of 0.1 Å / s (i.e., Å / sec), a deposition rate of Al of 10 to 15 Å / s, and a vacuum of 1×10 －３ A measurement device was fabricated by vapor deposition at 200 Pa. The device structure was Si / SiO (30 nm) / hole transport layer (200 nm) / MoO (5 nm) / Al (100 nm).

[0128] The fabricated measurement device was set in the measurement device 20 shown in FIG. 5, and a forward voltage of VFB = -10 [V] was applied under the condition of a reverse voltage application rate A = 150 kV. The t ２ｊ０ The hole mobility was calculated from the above equations (i) and (ii). The transient phenomenon of MIS-CELIV was measured under medium vacuum (<10 Pa) using a waveform generator (Agilent (registered trademark) 33511B, manufactured by Agilent Technologies, Inc.) and an oscilloscope (Agilent (registered trademark) DSO-X2004A, manufactured by Agilent Technologies, Inc.).

[0129] [Solubility in Organic Solvents] Compounds (H-1) to (H-7) and compounds (h-1) to (h-3) were each dissolved in chlorobenzene at a concentration of 9.1% by mass. The evaluation criteria were as follows: A (Good): Completely dissolved at room temperature. B (Slightly poor): Completely dissolved by heating. C (Poor): Not completely dissolved even when heated.

[0130] In Table 1, "I.P." indicates ionization potential (unit: eV). In Table 1, "mobility" indicates hole mobility, and "solubility" indicates the evaluation results of solubility when compounds (H-1) to (H-7) and compounds (h-1) to (h-3) are each dissolved in chlorobenzene at a concentration of 9.1% by mass. In Table 1, "Mw" indicates the molecular weight of compounds (H-1) to (H-7) and compounds (h-1) to (h-3).

[0131] Table 1 is as follows:

[0132] Compounds (H-1) to (H-6) are compounds (1) represented by formula (1), and compound (H-7) is compound (2) represented by formula (2). Compounds (H-1) to (H-7) have excellent solubility in organic solvents and a high hole mobility of 0.20 eV or more. Furthermore, the I.P. of compounds (H-1) to (H-7) is close to the I.P. of perovskite (e.g., 5.3 to 5.7 eV) and is slightly shallower than the I.P. of perovskite. Therefore, compounds (H-1) to (H-7) can be suitably used as hole transport materials for perovskite solar cells. In particular, compounds (H-1) to (H-3) and (H-7) are particularly suitable as hole transport materials for perovskite solar cells because their I.P. is closer to the I.P. of perovskite.

[0133] On the other hand, compounds (h-1) to (h-3) were not compounds represented by formula (1) or formula (2). Compounds (h-1) to (h-3) had a symmetric structure centered on a spiro atom, and had lower solubility in organic solvents and lower hole mobility compared to compounds (H-1) to (H-6). In particular, compound (h-3) had a structure in which the same substituents were bonded to the 2-, 2'-, 7-, and 7'-positions of 9,9'-spirobifluorene, and was not completely soluble in chlorobenzene even when heated at the above-mentioned concentration, and also had an I.P. that exceeded the I.P. of perovskite.

[0134] The compound according to the present invention can be used, for example, as a hole transport material. Furthermore, the compound and hole transport material according to the present invention can be suitably used, for example, as a hole transport material for solar cells, particularly as a hole transport material for perovskite solar cells. Furthermore, the solar cell according to the present invention can be used, for example, as a large-scale power supply, a power supply for outdoor equipment, a power supply for indoor electronic equipment, and a portable power supply.

[0135] 20 Measuring device 21 Measurement substrate 21a Si layer 21b SiO2 layer 22 Hole injection layer 23 Al electrode 25 Waveform generator 27 Oscilloscope 29 Resistor

Claims

1. A compound represented by formula (1) or formula (2). (In the formula (1) and the formula (2), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a dialkylamino group having 2 to 8 carbon atoms, a fluorine atom, or a cyano group, and R 1 ≠R 11 , R 2 ≠R 12 , R 3 ≠R 13 , R 4 ≠R 14 , R 5 ≠R 15 , R 6 ≠R 16 , R 7 ≠R 17 , R 8 ≠R 18 , R 9 ≠R 19 , and R 10 ≠R 20 At least one of the following is satisfied.) 2. In the formula (1) and the formula (2), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 At least one of R represents a fluorine atom or a cyano group; 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 and each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a dialkylamino group having 2 to 8 carbon atoms.

3. In the formula (1) and the formula (2), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 At least one of R represents a fluorine atom; 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , and R 20 3. The compound of claim 2, wherein at least one of represents a methoxy group.

4. In the formula (1) and the formula (2), R 13 and R 18 The compound of claim 3 , wherein represents a methoxy group.

5. The compound according to claim 2, wherein in formula (1) and formula (2), at least one of R3 and R8 represents a fluorine atom or a cyano group.

6. The compound according to claim 1, wherein the formula (1) is represented by formula (H-2), (H-3), (H-4), (H-5), or (H-6).

7. The compound according to claim 1, wherein the formula (1) is represented by formula (H-1) and the formula (2) is represented by formula (H-7).

8. A hole transport material comprising the compound according to any one of claims 1 to 7.

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