Power generation device and its manufacturing method

Abstract

To improve power generation efficiency under low illuminance of a power generation device including an active layer containing an organic-inorganic hybrid semiconductor compound.SOLUTION: A power generation device includes: a pair of electrodes consisting of 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 at least one of the pair of electrodes. The hole transport layer contains a carbazole compound represented by a specific chemical formula and a polytriarylamine compound represented by a specific chemical formula.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a power generating device and a method for manufacturing the same. [Background technology]

[0002] A known power generation device (photoelectric conversion element) has an active layer, a buffer layer, etc., arranged between a pair of electrodes. Organic-inorganic hybrid semiconductor compounds have been developed as materials for this active layer, and compounds with a perovskite structure (perovskite semiconductor compounds) have attracted particular attention. On the other hand, as a material for the hole transport layer, which is one of the buffer layers, for example, phthalocyanine-based organic semiconductor compounds have been proposed (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-066096 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional power generation devices equipped with a hole transport layer often suffer from reduced power generation efficiency in low-light environments, such as indoors where fluorescent lamps or LEDs are used as light sources, which is particularly important for energy harvesting applications.

[0005] An object of the present invention is to improve the power generation efficiency under low illumination conditions in a power generation device having an active layer containing an organic-inorganic hybrid semiconductor compound. [Means for solving the problem]

[0006] The present inventors have discovered that a power generation device having excellent power generation efficiency can be obtained even in low-illumination environments such as indoors by combining a hole transport layer containing a specific carbazole compound and a specific polytriarylamine compound with an active layer containing an organic-inorganic hybrid semiconductor compound, and have completed the present invention. That is, the present invention has the following aspects.

[0007] [1] A power generating device having a pair of electrodes composed of 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 at least one of the pair of electrodes, wherein the hole transport layer contains a carbazole compound represented by the following formula (I) and a polytriarylamine compound, the polytriarylamine compound contains a repeating unit represented by the following formula (IV), and 80 mol % or more of all repeating units of the polytriarylamine compound are repeating units represented by the following formula (IV). [2] The power generating device according to [1], wherein the carbazole compound includes a carbazole compound represented by the following formula (II) or (III): [3] The power generating device according to [1] or [2], wherein the ionization potential of the active layer is −6.0 eV or more and −5.7 eV or less, the band gap of the active layer is 1.6 eV or more and 2.3 eV or less, and the ionization potential of the hole transport layer is −5.9 eV or more and −5.2 eV or less. [4] The power generating device according to any one of [1] to [3], wherein the organic-inorganic hybrid semiconductor compound is a compound having a perovskite structure. [5] The power generating device according to any one of [1] to [4], wherein the thickness of the active layer is 200 nm or more and 800 nm or less. [6] The power generating device according to any one of [1] to [5], which has a photoelectric conversion efficiency of 25% or more when irradiated with white LED light having a color temperature of 5000K and the illuminance on the light receiving surface is 200 lux. [7] A method for producing a power generating device according to any one of [1] to [6], comprising a step of forming the hole transport layer by a coating method, in which a liquid containing the carbazole compound, the polytriarylamine compound, and a dopant is applied in the coating method. [8] The method for producing a power generating device according to [7], wherein the dopant is a diaryliodonium salt containing trivalent iodine.

[0008] [ka] (Ar in the formula 1 ~Ar 4 are each independently a monovalent aromatic group which may have a substituent, and may have a fused ring structure. 1 and ring 1, Ar 3 and ring 2 may each independently form a fused ring structure. 1 and Ar 2 , Ar 3 and Ar 4 may each independently form a fused ring structure. At least one of these fused ring structures forms a carbazole structure. The diarylamino group (N(Ar 3 )(Ar 4 )) is located in either the meta or para position relative to the bond between ring 1 and ring 2.

[0009] [ka] (In formula (IV), X is CR 1a R 2a , SiR 1a R 2a , N.R. 3a , S, and R 1a , R 2a and R 3a each independently represents a hydrogen atom, an optionally substituted aromatic group, or an optionally substituted alkyl group; R 1a and R2a may be bonded to each other to form a ring, and Ar 1a and Ar 2a each independently represents a direct bond or an aromatic group which may have a non-bridging substituent, Ar 3a represents an aromatic group which may have a non-crosslinkable substituent.

[0010] [ka] (Ar in the formula 5 and Ar 6 R are each an aromatic group which may have an independent monovalent substituent, and the aromatic group may have a fused ring structure. The monovalent substituent is an arbitrary substituent which substitutes any hydrogen atom of the aromatic group, and may be an alkyl group, an aromatic group, an alkoxy group, or a thioalkyl group. 1 ~R 3 are each independently a hydrogen atom, a halogen atom, or an alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, or aromatic group which may have a substituent.

[0011] [ka] (In the formula, Ar 7 and Ar 8 R are each an aromatic group which may have an independent monovalent substituent, and the aromatic group may have a fused ring structure. The monovalent substituent is an arbitrary substituent which substitutes any hydrogen atom of the aromatic group, and may be an alkyl group, an aromatic group, an alkoxy group, or a thioalkyl group. 4 ~R 9 are each independently a hydrogen atom, a halogen atom, or an alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, or aromatic group which may have a substituent. [Effects of the Invention]

[0012] According to the present invention, it is possible to improve the power generation efficiency of a power generation device using an organic-inorganic hybrid semiconductor compound, particularly in a low-illumination environment such as indoors. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of an embodiment of a power generation device of the present invention. [Figure 2] 1 is a cross-sectional view schematically illustrating an example of an embodiment of a solar cell equipped with a power generation device of the present invention. [Figure 3] 1 is a cross-sectional view schematically illustrating an example of a solar cell module including a power generation device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following describes in detail an embodiment of the present invention. The following description of the components is an example of an embodiment of the present invention, and the present invention is not limited to the contents thereof as long as the gist of the present invention is not impaired.

[0015] A power generating device according to one embodiment of the present invention is a power generating device having a pair of electrodes composed of 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 at least one of the pair of electrodes. Here, the hole transport layer contains a specific carbazole compound and a specific polytriarylamine compound, which will be described later.

[0016] In the power generating device of this embodiment, it is preferable that the ionization potential of the active layer is −6.0 eV or more and −5.7 eV or less, the band gap of the active layer is 1.6 eV or more and 2.3 eV or less, and the ionization potential of the hole transport layer is −5.9 eV or more and −5.2 eV or less.

[0017] The ionization potential is the minimum energy (eV) of light required for the irradiation energy to eject a photoelectron. The ionization potential in this specification is a value obtained by measuring the number of photoelectrons generated when light is applied to the surface of the active layer or hole transport layer to be evaluated using an open counter that requires oxygen.

[0018] In the open counter, photoelectrons are captured by oxygen molecules in the atmosphere, and ionized oxygen molecules are measured. In other words, the emitted photoelectrons can be observed as ionized oxygen molecules. As the energy of the irradiated light is increased, the threshold at which photoelectrons begin to be emitted becomes a value equivalent to the ionization potential (eV).

[0019] The number of photoelectrons generated when light of a certain energy is irradiated onto the surface of an object to be evaluated basically depends only on the characteristics of the area near the surface where the light is irradiated, and is not affected by the film thickness of the object to be evaluated, the presence or absence of a layer formed below the film to be evaluated, or the type of layer formed below the film to be evaluated. Therefore, the thickness of the active layer or hole transport layer to be measured does not need to be strictly uniform, and the active layer may be formed to a thickness of, for example, 400 nm to 600 nm and the hole transport layer may be formed to a thickness of, for example, 5 nm to 100 nm and used for measurement.

[0020] The presence or absence of a layer formed under the film to be evaluated and the type of layer formed under the film to be evaluated do not substantially affect the measurement results, but measuring the film to be evaluated only on conductive glass with a thin film of ITO (indium tin oxide) is effective in reducing noise as much as possible and increasing the reliability of the results. The conductive glass provided with thin film ITO used in this case can be a commercially available product. The resistance value (surface resistivity) of the thin film ITO is not particularly limited and can be, for example, 2 Ω / sq. to 1000 Ω / sq.

[0021] The band gap is the energy level (and the difference in energy) between the top of the highest occupied energy band (the valence band) and the bottom of the lowest empty band (the conduction band) in the band structure. In this specification, the band gap of the active layer is considered to be the same value as the band gap of the semiconductor compound that constitutes the active layer, and is a value calculated from the absorption edge wavelength and absorbance of that semiconductor compound. The power generation device of the present invention has particularly excellent power generation efficiency in low-illumination environments. In this specification, a low illuminance environment generally means an environment of 10 to 5000 lux, with an environment of 100 to 300 lux being preferable, and an environment of 200 lux being more preferable.

[0022] <Power generation device> A power generation device according to the present invention will be described with reference to FIG. 1, which is a schematic cross-sectional view thereof. FIG. 1 is a schematic cross-sectional view of a power generation device 100, which is an example of an embodiment of a power generation device according to the present invention. In the power generation device 100, 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. Alternatively, 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. Conversely, the buffer layer 102 and the buffer layer 104 may be, for example, an electron transport layer and a hole transport layer, respectively. The power generation device 100 may include a substrate 106 and may include other layers (not shown), such as an insulator layer and a work function tuning layer.

[0023] 1, the active layer 103 is a layer where photoelectric conversion takes place. When the power generating device 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.

[0024] [Active layer]

[0025] In this embodiment, the active layer contains an organic-inorganic hybrid semiconductor compound, which is a compound in which an organic component and an inorganic component are combined at the molecular or nano level and which exhibits semiconductor properties.

[0026] In this embodiment, the organic-inorganic hybrid semiconductor compound is preferably a compound having a perovskite structure (hereinafter, sometimes referred to as a perovskite semiconductor compound). A perovskite semiconductor compound refers to a semiconductor compound having a perovskite structure. The perovskite structure generally refers to a crystal structure expressed by the ABX3 composition formula, such as perovskite (CaTiO3; perovskite). In this perovskite structure expressed by the ABX3 composition formula, six X ions regularly surround a B-site ion, forming a BX6 octahedron. The perovskite semiconductor compound is not particularly limited, and can be selected from, for example, those listed in Galasso et al., "Structure and Properties of Inorganic Solids," Chapter 7 - Perovskite type and related structures. Examples of perovskite semiconductor compounds include AMX3-type compounds represented by the general formula AMX3, and A2MX4-type compounds represented by the general formula A2MX4. Here, M represents a divalent cation, A represents a monovalent cation, and X represents a monovalent anion.

[0027] 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.

[0028] Specific 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.

[0029] There is no particular limitation on the divalent cation M, but it is preferably a divalent metal cation or semimetal cation. Specific examples include cations of elements in Group 14 of the periodic table, and more specific examples include lead cations (Pb 2+ ), tin cation (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 power generating device, it is particularly preferable to use a lead cation or two or more types of cations including a lead cation.

[0030] Examples of the monovalent anion X include a halide ion, acetate ion, nitrate ion, sulfate ion, borate ion, acetylacetonate ion, carbonate ion, citrate ion, sulfur ion, tellurium ion, thiocyanate ion, titanate ion, zirconate ion, 2,4-pentanedionate ion, and silicofluoride ion. In one embodiment of the present invention, X may be a halide ion or a combination of a halide ion and another anion. One type of X may be used, or two or more types may be used 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, a bromide ion, or an iodide ion, and more preferably a bromide ion or an iodide ion.

[0031] Preferred examples of the perovskite semiconductor compound include organic-inorganic perovskite semiconductor compounds, and particularly preferred are halide-based organic-inorganic perovskite semiconductor compounds. Specific examples of perovskite semiconductor compounds include CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3SnI3, CH3NH3SnBr3, CH3NH3SnCl3, and CH3NH3PbI (3-x) Cl x , CH3NH3PbI (3-x) Br x , CH3NH3PbBr (3-x) Cl x , CH3NH3Pb (1-y) Sn y I3, CH3NH3Pb (1-y) Sn y Br3, CH3NH3Pb (1-y) Sn yCl3, CH3NH3Pb (1-y) Sn y I( 3-x) Cl x , CH3NH3Pb (1-y) Sn y I (3-x) Br x , and CH3NH3Pb (1-y) Sn y Br (3-x) Cl x , and in the above compounds, CFH2NH3, CF2HNH3, CF3NH3, NH2CH=NH instead of CH3NH3 3、 Compounds using Cs or Rb are also included. Here, 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. Among these, CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbI (3-x) Cl x , CH3NH3PbI (3-x) Br x , CH3NH3PbBr (3-x) Cl x , and NH2CH=NH instead of CH3NH3 in the above compounds 3、 Compounds using Cs or Rb, etc.

[0032] 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 also 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. The active layer may also have a laminate structure formed of multiple layers containing different materials or having different components.

[0033] 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, based on the total mass of the active layer, so as to obtain good semiconductor properties. There is no particular upper limit. The active layer may also contain additives other than the organic-inorganic hybrid semiconductor compound. Examples of additives include inorganic compounds such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates, or ammonium salts, or organic compounds.

[0034] The ionization potential of the active layer is preferably high, in order to fully absorb light in the long wavelength region of a visible light source that provides white light and to easily increase power generation efficiency. Specifically, the ionization potential is preferably −6.0 eV or higher, more preferably −5.95 eV or higher, and even more preferably −5.9 eV or higher. On the other hand, the ionization potential of the active layer is preferably low in order to reduce the loss of voltage obtained from a light source in the visible light region and to increase the power generation efficiency, and specifically, it is preferably −5.7 eV or less, more preferably −5.75 eV or less, even more preferably −5.8 eV or less, and particularly preferably −5.9 eV or less.

[0035] The band gap of the active layer is preferably large in order to sufficiently provide the energy required for separating excitons generated in the semiconductor by low-intensity light such as indoor light into positive and negative charges, and to facilitate high power generation efficiency. Specifically, the band gap is preferably 1.6 eV or more, more preferably 1.65 eV or more, even more preferably 1.7 eV or more, and most preferably 1.75 eV or more. On the other hand, the band gap of the active layer is preferably small so that it provides appropriate energy (without excess energy) for excitons generated by indoor light, etc., and thus facilitates high power generation efficiency. Specifically, the band gap is preferably 2.3 eV or less, more preferably 2.25 eV or less, even more preferably 2.2 eV or less, and most preferably 2.15 eV or less.

[0036] Furthermore, since this particularly facilitates improving power generation efficiency with low-illuminance light sources such as fluorescent lamps and LED lamps, which are visible light sources widely used indoors, it is particularly preferred that the ionization potential and band gap of the active layer both be within the above-mentioned preferred ranges. Specifically, it is particularly preferred that the ionization potential of the active layer be in the range of -6.0 eV to -5.7 eV and that the band gap be in the range of 1.6 eV to 2.3 eV.

[0037] The ionization potential of the active layer can be adjusted to the desired range by, for example, adjusting the type of organic-inorganic hybrid semiconductor compound. Specifically, when the above-mentioned perovskite semiconductor compound is used, the ionization potential can be adjusted by adjusting the type of cation. More specifically, the composition of the organic or inorganic ammonium salt, which is the precursor used to form the perovskite semiconductor compound described below, can be appropriately adjusted by mixing the composition of the organic or inorganic ammonium salt in a composition ratio containing a modifying component and processing it. The band gap of the active layer can be adjusted to the desired range by, for example, adjusting the type of organic-inorganic hybrid semiconductor compound. Specifically, when using the perovskite semiconductor compound described above, the band gap can be adjusted by adjusting the type and ratio of the anions. More specifically, examples include selecting the ratio of halogen species in a metal halide compound used as a precursor for forming the perovskite semiconductor compound described below, or mixing the composition of an organic or inorganic ammonium salt used as a precursor with a corresponding halogen composition in a composition ratio containing a modified component, and processing the mixture.

[0038] There is no particular limit to the thickness of the active layer. A thick active layer 103 is preferable in terms of being able to absorb more light. Specifically, a thickness of 10 nm or more is preferable, 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, a thin active layer is preferable in terms of reducing the series resistance and increasing the charge extraction efficiency. Specifically, the thickness of the active layer is preferably 1500 nm or less, more preferably 1200 nm or less, and even more preferably 800 nm or less. That is, a thickness of 200 nm or more and 800 nm or less is particularly preferable for the active layer 103.

[0039] The method for forming the active layer is not particularly limited, and the active layer can be formed by any method. Specific examples include a coating method and a vapor deposition method (or a co-evaporation method). The coating method is preferred because it allows the active layer to be formed easily. 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.

[0040] 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. A specific example is an organic-inorganic hybrid semiconductor compound precursor that becomes an organic-inorganic hybrid semiconductor compound by heating. For example, a compound represented by the general formula AX, a compound represented by the general formula MX2, and a solvent are mixed and heated and stirred to prepare a coating liquid, and this coating liquid is then applied and dried by heating to prepare an active layer containing a perovskite semiconductor compound represented by the general formula AMX3. The solvent is not particularly limited as long as it dissolves the organic-inorganic hybrid semiconductor compound and optional additives, and examples include organic solvents such as N,N-dimethylformamide.

[0041] Alternatively, an active layer containing a perovskite semiconductor compound represented by the general formula AMX3 may be produced by mixing a compound represented by the general formula MX2 with a solvent, heating and stirring the mixture, applying a coating liquid obtained by mixing a compound represented by the general formula AX with a solvent, and then applying a coating liquid obtained by mixing the compound represented by the general formula AX with a solvent.

[0042] 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 barber coating, pipe doctor coating, impregnation coating, and curtain coating.

[0043] [Buffer layer] 1, the buffer layer is a layer located between the active layer 103 and at least one of the pair of electrodes 101 and 105. The buffer layer can be 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, and is preferably a hole transport layer or an electron transport layer, more preferably a hole transport layer.

[0044] [Hole transport layer] The hole transport layer contains a carbazole compound represented by formula (I) described below (hereinafter may be referred to as the "carbazole compound of the present invention," "carbazole compound represented by formula (I)," "compound represented by formula (I)," or simply "carbazole compound") and a specific polytriarylamine compound described below (hereinafter may be referred to as the "polytriarylamine compound of the present invention" or simply "polytriarylamine compound"). In the power generation device of the present invention, the hole transport layer contains the carbazole compound of the present invention and the polytriarylamine compound of the present invention, so that the ionization potential of the hole transport layer can be set within a suitable range described later, and high power generation efficiency can be achieved under low illuminance. The carbazole compound according to the present invention is preferred because it is electronically robust compared to other aromatic tertiary amines and can maintain a suitable hole transport layer, since the unshared electron pair on the basic nitrogen atom is stabilized by the aromaticity of the carbazole group. For the same reason, it is also highly preferred in that it can easily achieve a deep ionization potential (Ip). Furthermore, the polytriarylamine compound according to the present invention has an extended conjugated moiety, which allows electron delocalization and high stability. Therefore, the power-generating device according to the present invention, which includes a hole-transporting layer containing the polytriarylamine compound according to the present invention, can achieve an ionization potential within the preferred range described below, thereby achieving high power generation efficiency under low illumination. The polytriarylamine compound according to the present invention is a polytriarylamine having a structure in which at least four aromatic rings are arranged linearly via the amino nitrogen atom N of the arylamine, and two aromatic rings not directly bonded to the N atom are connected via an X moiety. This makes the polytriarylamine compound more electronically robust than other polytriarylamines and preferable because it can maintain a suitable hole-transporting layer. For the same reason, it is also highly preferable because it can easily achieve a deep ionization potential (Ip).

[0045] The carbazole compound and the polytriarylamine compound according to the present invention are organic semiconductor compounds. Generally, a semiconductor compound refers to a compound that can be used as a semiconductor material that exhibits semiconductor properties. In this specification, "semiconductor properties" are defined by the magnitude of carrier mobility in a solid state. As is well known, carrier mobility is an index that indicates how fast (or how many) charges (electrons or holes) can be moved. Specifically, in this specification, a "semiconductor" is a compound having a carrier mobility of preferably 1.0×10 at room temperature (25° C.). -6 cm 2 / V·s or more, preferably 1.0×10 -5 cm 2 / V·s or more, more preferably 5.0×10 -5 cm 2 / V·s or more, and particularly preferably 1.0×10-4 cm 2 / V·s or more. The carrier mobility can be measured, for example, by measuring the I-V characteristics of a field-effect transistor or by the time-of-flight method. <Carbazole compounds> The carbazole compound according to the present invention is represented by formula (I).

[0046] [ka] (Ar in the formula 1 ~Ar 4 are each independently a monovalent aromatic group which may have a substituent, and may have a fused ring structure. 1 and ring 1, Ar 3 and ring 2 may each independently form a fused ring structure. 1 and Ar 2 , Ar 3 and Ar 4 may each independently form a fused ring structure. At least one of these fused ring structures forms a carbazole structure. The diarylamino group (N(Ar 3 )(Ar 4 )) is located in either the meta or para position relative to the bond between ring 1 and ring 2. The molecular weight of the compound represented by formula (I) is preferably high in terms of robustness and heat resistance, and is preferably low in terms of solubility in solvents. Therefore, the molecular weight of the compound represented by formula (I) is preferably 200 or more, more preferably 400 or more. On the other hand, it is preferably 3000 or less, more preferably 2000 or less. Ar 1 ~Ar 4 The formula weight of Ar is preferably high in terms of durability and heat resistance, and is preferably low in terms of solubility in solvents. 1 ~Ar 4The formula weight of the hydroxyl group, including any substituents, is preferably 72 or more, more preferably 144 or more. On the other hand, it is preferably 1000 or less, more preferably 600 or less. From the viewpoints of hole transport ability and robustness, the number of carbazole structures contained in the compound represented by formula (I) is preferably 1 or more, and more preferably 2 or more. From the viewpoints of hole transport ability, robustness, and ease of synthesis, the compound having two carbazole structures preferably has the carbazole structures positioned point-symmetrically.

[0047] The carbazole compound represented by formula (I) contained in the hole transport layer preferably includes a carbazole compound represented by formula (II) or formula (III). A hole transport layer containing a suitable carbazole compound is likely to exhibit a suitable ionization potential, as described below. That is, when the hole transport layer contains the carbazole compounds represented by formula (II) and / or formula (III), the total amount thereof is preferably the preferred content, as described below. The carbazole compound represented by formula (II) (hereinafter, sometimes simply referred to as "compound represented by formula (II)") will be described.

[0048] [ka] (Ar in the formula 5 and Ar 6 R are each an aromatic group which may have an independent monovalent substituent, and the aromatic group may have a fused ring structure. The monovalent substituent is an arbitrary substituent which substitutes any hydrogen atom of the aromatic group, and may be an alkyl group, an aromatic group, an alkoxy group, or a thioalkyl group. 1 ~R 3 are each independently a hydrogen atom, a halogen atom, or an alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, or aromatic group which may have a substituent.

[0049] Ar 5 and Ar 6The aromatic group constituting the formula (I) may have either a monocyclic structure or a polycyclic structure, or may have a fused ring structure, or may have a structure in which these are linked by any divalent linking group or single bond (direct bond). Here, the aromatic group may be an aromatic hydrocarbon group or an aromatic heterocyclic group.

[0050] Examples of the aromatic hydrocarbon group include polycyclic aromatic hydrocarbon groups in which a benzene ring is bonded via a carbon-carbon single bond, such as a phenyl group, a biphenyl group, or a terphenyl group; and groups derived from a 6-membered single ring or 2 to 5 condensed rings, such as 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, or a fluorene ring.

[0051] Examples of aromatic heterocyclic groups include groups derived from a 5- or 6-membered single 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.

[0052] Ar 5 and Ar 6 The number of carbon atoms of each of the groups is preferably 30 or less, and more preferably 20 or less, from the viewpoints of high film-forming properties of the hole transport layer and facilitating setting of the ionization potential in a suitable range described later. Specific preferred Ar 5 , Ar 6are each independently, for example, a biphenyl group, a terphenyl group, a quaterphenyl group, etc., and Ar 5 and Ar 6 and are most preferably terphenyl groups. The terphenyl group may be any of ortho, meta, and para isomers, but the para isomer is preferred because the film-forming properties and ionization potential tend to fall within the preferred ranges described below. It is preferred that the hydrogen atoms of the terphenyl group are not substituted with a substituent.

[0053] Examples of the substituent that the aromatic group may have include an alkyl group (preferably a chain having 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms), an aromatic group (i.e., a monovalent aromatic hydrocarbon group or aromatic heterocyclic group), an alkoxy group (preferably having 1 to 12 carbon atoms), a thioalkyl group, a halogen atom, a hydroxyl group, a cyano group, an amino group (preferably a dialkylamino group having 2 to 12 carbon atoms, an alkylarylamino group having 7 to 20 carbon atoms, or a diarylamino group having 12 to 30 carbon atoms), a carboxyl group, an ester group, an alkylcarbonyl group, an acetyl group, a sulfonyl group, a silyl group, a boryl group, a nitrile group, an alkenyl group, an alkynyl group, a thio group, a seleno group, etc. Of these, an alkyl group, an aromatic group, an alkoxy group, or a thioalkyl group is preferred. The substituent may be one or more types selected from the following substituent group Z.

[0054] (Substituent group Z) an alkyl group preferably having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methyl group or an ethyl group; an alkenyl group preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a vinyl group; an alkynyl group preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as an ethynyl group; an alkoxy group preferably having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methoxy group or an ethoxy group; an aryloxy group 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; an alkoxycarbonyl group preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a methoxycarbonyl group or an ethoxycarbonyl group; a dialkylamino group preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a dimethylamino group or a diethylamino group; diarylamino groups preferably having 10 to 36 carbon atoms, more preferably 12 to 24 carbon atoms, such as a diphenylamino group, a ditolylamino group, or an N-carbazolyl group; an arylalkylamino group preferably having 6 to 36 carbon atoms, more preferably 7 to 24 carbon atoms, such as a phenylmethylamino group;

[0055] an acyl group preferably having 2 to 24 carbon atoms, and preferably having 2 to 12 carbon atoms, such as an acetyl group or a benzoyl group; Halogen atoms such as fluorine atoms and chlorine atoms; a haloalkyl group preferably having 1 to 2 carbon atoms, more preferably 1 to 6 carbon atoms, such as a trifluoromethyl group; an alkylthio group preferably having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methylthio group or an ethylthio group; an arylthio group 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; a silyl group preferably having 2 to 36 carbon atoms, more preferably 3 to 24 carbon atoms, such as a trimethylsilyl group or a triphenylsilyl 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; cyano group; an aromatic hydrocarbon group preferably having 6 to 36 carbon atoms, more preferably 6 to 24 carbon atoms, such as a phenyl group or a naphthyl group; an aromatic heterocyclic group 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 these substituents may further have a substituent, examples of which include the groups exemplified in the above-mentioned group Z of substituents.

[0056] From the viewpoint of the solubility in a solvent and film-forming properties of the compound represented by formula (II), the formula weight of each substituent is preferably 500 or less, and more preferably 250 or less, including the case where the substituent is further substituted with another substituent.

[0057] In formula (II), Ar 5 and Ar 6 can be regarded as a substituent of the hydrogen atom of triphenylamine. 5 and Ar 6 are substituents substituting different phenyl groups, and their positions may be independently ortho, meta, or para relative to the central nitrogen atom, but are preferably para in consideration of the conformational stability of the compound and ease of synthesis. 5 and Ar 6 The remaining phenyl groups to which the phenyl group is not bonded are bonded to the nitrogen atoms of the carbazole via phenylene groups, as shown in formula (II).

[0058] R in formula (II) 1 ~R 3 are each independently a hydrogen atom, a halogen atom, or an optionally substituted alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, or aromatic group (i.e., a monovalent aromatic hydrocarbon group or aromatic heterocyclic group). Examples of the substituents that these groups may have are the same as those in the above-mentioned substituent group Z. R 1 ~R 3 are each independently preferably one or more selected from a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, and an alkoxy group having 1 to 3 carbon atoms, and more preferably a hydrogen atom.

[0059] The carbazole compound represented by formula (III) (hereinafter, sometimes simply referred to as "compound represented by formula (III)") will be described. [ka] (In the formula, Ar 7and Ar 8 R are each an aromatic group which may have an independent monovalent substituent, and the aromatic group may have a fused ring structure. The monovalent substituent is an arbitrary substituent which substitutes any hydrogen atom of the aromatic group, and may be an alkyl group, an aromatic group, an alkoxy group, or a thioalkyl group. 4 ~R 9 are each independently a hydrogen atom, a halogen atom, or an alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, or aromatic group which may have a substituent.

[0060] Ar 7 and Ar 8 The aromatic group constituting the 5 and Ar 6 is the same as:

[0061] Ar 7 and Ar 8 The number of carbon atoms in 5 and Ar 6 However, it is more preferable that it is 10 or less. Specific preferred Ar 7 and Ar 8 are each independently exemplified by a phenyl group, a biphenyl group, a terphenyl group, and a tetraphenyl group, and Ar 7 and Ar 8 It is most preferable that both of are phenyl groups. It is preferable that the hydrogen atoms of the phenyl groups are not substituted with a substituent.

[0062] In formula (III), Ar 7 and Ar 8 are substituents substituting different phenyl groups, and may be independently located at any of the ortho-, meta-, or para-positions relative to the nitrogen atom of the carbazole structure. However, in consideration of the conformational stability of the compound, ease of synthesis, and the like, the meta- or para-positions are preferred, and the meta-position is more preferred.

[0063] R in formula (III) 4 ~R 9are each independently a hydrogen atom, a halogen atom, or an alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, or aromatic group (i.e., a monovalent aromatic hydrocarbon group or aromatic heterocyclic group) which may have a substituent. Examples of the substituents which these groups may have are the same as those in the above-mentioned substituent group Z. R 4 ~R 9 are each independently preferably one or more selected from a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, and an alkoxy group having 1 to 3 carbon atoms, and more preferably a hydrogen atom. The carbazole compound represented by formula (I) can be synthesized by a known method as described in the Examples below. The compound contained in the hole transport layer is the carbazole compound represented by formula (I). 1 H-NMR, 13 This can be confirmed by analytical methods such as C-NMR, X-ray crystal structure analysis using single crystals, and LC-MS.

[0064] <Polytriarylamine compounds> The polytriarylamine compound according to the present invention is a polymeric compound containing repeating units represented by the following formula (IV), in which 80 mol % or more of all repeating units are repeating units represented by the following formula (I). The proportion of repeating units represented by the following formula (IV) contained in the polytriarylamine compound according to the present invention is preferably high, since this tends to increase the charge transport property of the polytriarylamine compound. Specifically, the polytriarylamine compound preferably contains repeating units represented by the following formula (IV) in an amount of 90 mol % or more, more preferably 95 mol % or more, of all repeating units. In particular, it is preferred that all repeating units are repeating units represented by formula (I), since this simplifies the synthesis route.

[0065] [ka]

[0066] In formula (IV), X is CR1a R 2a , SiR 1a R 2a , N.R. 3a , S, and R 1a , R 2a and R 3a each independently represents a hydrogen atom, an optionally substituted aromatic group, or an optionally substituted alkyl group; R 1a and R 2a may be bonded to each other to form a ring, and Ar 1a and Ar 2a each independently represents a direct bond or an aromatic group which may have a non-bridging substituent, Ar 3a represents an aromatic group which may have a non-crosslinkable substituent.

[0067] The polytriarylamine compound according to the present invention is a useful compound as an organic semiconductor compound. The polytriarylamine compound according to the present invention is stably oxidized by a dopant and can exhibit better semiconductor properties. In addition, the polytriarylamine compound has high electrochemical stability and high hole transport ability, and is suitable for wet film formation.

[0068] Ar in formula (IV) 1a and Ar 2a each independently represents a direct bond or an aromatic group which may have a non-crosslinking substituent. In addition, Ar in formula (IV) 3a represents an aromatic group which may have a non-crosslinkable substituent.

[0069] In this specification, the aromatic group may be an aromatic hydrocarbon group or an aromatic heterocyclic group. In addition, it may have either a monocyclic structure or a polycyclic structure, or a fused ring structure, or may have a structure in which these are linked by any divalent linking group or single bond (direct bond).

[0070] Ar 1a ~Ar 3aThe aromatic group that can be selected from the group 1 includes an aromatic hydrocarbon group, an aromatic heterocyclic group, and a non-benzene-based aromatic compound. Among these, an aromatic hydrocarbon group or an aromatic heterocyclic group is preferred. Examples of the aromatic hydrocarbon group include groups derived from the following [Aromatic hydrocarbon group P1]. Examples of the aromatic heterocyclic group include groups derived from the following [aromatic heterocyclic group P2].

[0071] [Aromatic hydrocarbon group P1] Six-membered monocyclic rings 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.

[0072] [Aromatic heterocyclic group P2] Five- or six-membered monocyclic rings or two- to four-fused rings, 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.

[0073] Ar 1a ~Ar 3a In terms of solubility in organic solvents and heat resistance, Ar is preferably an aromatic group which may have a substituent, and more preferably a group derived from a ring selected from the group consisting of a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a triphenylene ring, a pyrene ring, a thiophene ring, a pyridine ring, and a fluorene ring. 1a and Ar 2aAs the ring, a divalent group in which one or more rings selected from the above group are linked by a direct bond or a -CH=CH- group is also preferred, and a biphenylene group and a terphenylene group are more preferred.

[0074] Ar 1a ~Ar 3a The substituent that Ar may have is a non-crosslinkable substituent. The non-crosslinkable substituent means a group that does not contain a crosslinkable group. 1a ~Ar 3a may have a substituent, but does not have a substituent containing a crosslinkable group.

[0075] Here, the crosslinkable group refers to a group that reacts with the same or different group of another molecule located nearby when exposed to heat and / or active energy rays, thereby forming a new chemical bond. The non-crosslinkable substituent is not particularly limited, and examples thereof include one or more types selected from the following [Substituent group Z1].

[0076] [Substituent group Z1] an alkyl group preferably having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methyl group or an ethyl group; an aryloxy group 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; an alkoxycarbonyl group preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a methoxycarbonyl group or an ethoxycarbonyl group; a dialkylamino group preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms, such as a dimethylamino group or a diethylamino group;

[0077] an acyl group preferably having 2 to 24 carbon atoms, and preferably having 2 to 12 carbon atoms, such as an acetyl group or a benzoyl group; Halogen atoms such as fluorine atoms and chlorine atoms; a haloalkyl group preferably having 1 to 2 carbon atoms, more preferably 1 to 6 carbon atoms, such as a trifluoromethyl group; an alkylthio group preferably having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, such as a methylthio group or an ethylthio group; an arylthio group 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; cyano group; an aromatic hydrocarbon group preferably having 6 to 36 carbon atoms, more preferably 6 to 24 carbon atoms, such as a phenyl group or a naphthyl group; an aromatic heterocyclic group 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 substituent group Z1.

[0078] The formula weight of the substituent group Z1 including further substituted groups is preferably 500 or less, more preferably 250 or less. Ar has improved solubility in organic solvents. 1a ~Ar 3a The group of substituents Z1 that may be contained in each of the groups are preferably an alkyl group having 1 to 12 carbon atoms and an alkoxy group having 1 to 12 carbon atoms.

[0079] X in formula (IV) is CR a R 2a , SiR 1a R 2a , N.R. 3a , O, S. X in formula (IV) is a CR copolymer having good durability and low manufacturing costs. 1a R 2a and NR 3a is preferred, and CR 1a R 2a is more preferred. The polytriarylamine compound according to the present invention may contain repeating units in which X is different from each other.

[0080] R in X of formula (I)1a , R 2a and R 3a R each independently represents a hydrogen atom, an aromatic group which may have a substituent, or an alkyl group which may have a substituent. a1 and R 2a may be bonded to each other to form a ring.

[0081] R 1a , R 2a , and R 3a Examples of the aromatic hydrocarbon group that can be selected from the group P1 include groups derived from the above-mentioned [Aromatic hydrocarbon group P1]. Also, R 1a , R 2a , and R 3a Examples of the aromatic heterocyclic group that can be selected from include groups derived from the above-mentioned [Aromatic Heterocyclic Group P2]. R 1a , R 2a , and R 3a The alkyl group selected from the above is preferably an alkyl group having 4 to 20 carbon atoms, more preferably an alkyl group having 6 to 12 carbon atoms.

[0082] R 1a , R 2a , and R 3a The substituent that may be possessed by may be either a non-crosslinkable substituent or a crosslinkable substituent. Examples of the non-crosslinkable substituent include the above-mentioned [Substituent group Z1], and preferred embodiments are also the same. The crosslinkable substituent is not particularly limited, and examples thereof include one or more types selected from the following [Substituent group Z2]. [Substituent group Z2]

[0083] [ka]

[0084] In the formula, R 21 ~R 25 Each independently represents a hydrogen atom or an alkyl group. 41represents an aromatic group which may have a substituent. The benzocyclobutene ring may have a substituent. The substituents may join together to form a ring.

[0085] As the crosslinkable group, cationically polymerizable groups such as an epoxy group, a cyclic ether group such as an oxetane group, and a vinyl ether group are preferred because they are highly reactive and easily crosslinkable with organic solvents. Among them, an oxetane group is particularly preferred because it is easy to control the rate of cationic polymerization, and a vinyl ether group is preferred because it is less likely to cause deterioration of the element due to the generation of hydroxyl groups during cationic polymerization.

[0086] In the polytriarylamine compound according to the present invention, the triarylamine structure (a structure in which three aromatic hydrocarbon groups or aromatic heterocyclic groups are bonded to the same nitrogen atom) in the main chain of formula (IV) is connected to two benzene rings, thereby enhancing its contribution to hole transport properties. Furthermore, since the triarylamine structure does not contain a crosslinkable functional group, the repeating unit of formula (IV) contains almost no components that are not involved in hole transport properties, and therefore the polytriarylamine compound according to the present invention can be strongly involved in hole transport properties. Furthermore, since the triarylamine structure does not contain a crosslinkable functional group, there is no need to use a monomer for introducing a crosslinkable group when synthesizing the polytriarylamine compound according to the present invention, and therefore the production cost is low.

[0087] The molecular weight of the polytriarylamine compound according to the present invention is preferably high because it tends to increase the durability (retention rate of photoelectric conversion efficiency) of a power generation device using the polytriarylamine compound in a hole transport layer. Specifically, the number-average molecular weight of the polytriarylamine compound according to the present invention is preferably 8,500 or more, more preferably 9,000 or more, even more preferably 10,000 or more, particularly preferably 15,000 or more, and most preferably 20,000 or more. Furthermore, the weight-average molecular weight of the polytriarylamine compound according to the present invention is preferably 15,000 or more, more preferably 20,000 or more, even more preferably 30,000 or more, particularly preferably 35,000 or more, and most preferably 40,000 or more. On the other hand, the molecular weight of the polytriarylamine compound according to the present invention is preferably low from the viewpoint of cost and solubility in solvents, and the weight-average molecular weight of the polytriarylamine compound according to the present invention is preferably 500,000 or less, more preferably 300,000 or less, and even more preferably 200,000 or less.

[0088] When the polytriarylamine compound simultaneously satisfies the above-mentioned preferred ranges for the number average molecular weight and the weight average molecular weight, the retention rate of the photoelectric conversion efficiency of a power generation device using the polytriarylamine compound in a hole transport layer may be further improved. The number average molecular weight and weight average molecular weight of the polytriarylamine compound are the number average and weight average molecular weights measured by GPC in terms of polystyrene.

[0089] The synthesis method of the polytriarylamine compound is not particularly limited, but it can be polymerized using two types of monomers, an arylamine compound and a dibromo compound. For example, it can be synthesized by the method described in JP-A-2009-263665, and can be synthesized by oxidative polymerization or a coupling reaction using a transition metal catalyst. The number average molecular weight and weight average molecular weight of the polytriarylamine compound can be adjusted by the reaction temperature, reaction time, catalyst, etc. The structure and content of the polytriarylamine compound in the hole transport layer may be, for example, 1 It can be analyzed by methods such as H-NMR, high-performance liquid chromatography (HPLC), and liquid chromatography mass spectrometry (LC-MS).

[0090] The total content of the carbazole compound and the polytriarylamine compound according to the present invention contained in the hole transport layer is preferably high, since this facilitates the ionization potential of the hole transport layer to be within the preferred range described below. Specifically, the content in the hole transport layer (total mass: 100% by mass) is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. Here, the upper limit is 100% by mass, but when carrier mobility is increased by adding a dopant to the hole transport layer, the total amount including the dopant is 100% by mass. The power generation device of the present invention can achieve particularly high power generation efficiency at low illuminance by containing both the carbazole compound of the present invention and the polytriarylamine compound of the present invention in the hole transport layer. The reason for this is presumably that the carbazole compound of the present invention is electronically robust compared to other aromatic tertiary amines because the unshared electron pair on the basic nitrogen atom is stabilized by the aromaticity of the carbazole group, making it possible to maintain a moderate hole transport ability, and for the same reason, it is likely to have a deep ionization potential (Ip). The polytriarylamine compound of the present invention has a broad range of conjugated moieties, which allows electron delocalization and excellent stability, resulting in a well-balanced functional expression. The relative amounts of the carbazole compound according to the present invention and the polytriarylamine compound according to the present invention contained in the hole transport layer are preferably higher in the polytriarylamine compound in terms of electron delocalization in the polymer compound and excellent stability, and more preferably higher in the polytriarylamine compound relative to the carbazole compound. On the other hand, a higher amount of the carbazole compound is preferred in terms of deepening the ionization potential (Ip). Furthermore, the carbazole compound according to the present invention is also preferred in that it has no molecular weight distribution, is easily purified, and is easily produced inexpensively compared to polymer compounds such as polytriarylamine. Therefore, specifically, the polytriarylamine compound according to the present invention is preferably 50% by mass or more of the total amount of both compounds. Furthermore, the polytriarylamine compound according to the present invention is preferably 80% by mass or less of the total amount of both compounds.

[0091] (Other semiconductor compounds) The hole transport layer may contain semiconductor compounds other than the carbazole compound and polytriarylamine compound of the present invention, as long as the effects of the present invention are not impaired. Examples of other semiconductor compounds include conventionally known semiconductor compounds. Various low-molecular-weight compounds and polymeric compounds are known as other organic semiconductor compounds. Examples of low-molecular-weight organic semiconductor compounds include polycyclic aromatic compounds, such as acene compounds (e.g., tetracene or pentacene), oligothiophene compounds, phthalocyanine compounds, perylene compounds, rubrene compounds, and arylamine compounds other than the triarylamine compounds of the present invention. Examples of polymeric organic semiconductor compounds include conjugated polymers such as polythiophene-based polymers, polyacetylene-based polymers, polyaniline-based polymers, polyphenylene-based polymers, polyphenylenevinylene-based polymers, polyfluorene-based polymers, and polypyrrole-based polymers, as well as arylamine polymers other than the triarylamine compounds of the present invention.

[0092] When forming the hole transport layer, it is preferable to use a dopant, which can adjust the properties such as the conductivity and hole transport ability. The amount of the dopant is preferably large because it is likely to improve the conductivity and hole transport ability of the hole transport layer. Specifically, the amount of the dopant is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, still 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 total amount of the carbazole compound according to the present invention and the polytriarylamine compound according to the present invention. On the other hand, the amount of the dopant is preferably small because it suppresses the generation of leakage current in the power generation device and tends to improve power generation efficiency, particularly under low-illumination environments. Specifically, the amount of the dopant is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less, relative to 100 parts by mass of the total amount of the carbazole compound according to the present invention and the polytriarylamine compound according to the present invention. That is, when a dopant is used to form the hole transport layer, the amount of the dopant is particularly preferably 0.1 to 12 parts by mass per 100 parts by mass of the total amount of the carbazole compound according to the present invention and the polytriarylamine compound according to the present invention.

[0093] <Dopant> By using a dopant in forming the hole transport layer, the conductivity and hole transport ability of the hole transport layer can be further optimized relative to the active layer. Examples of substances that can be used as dopants include hypervalent iodine compounds, boron compounds such as tetrakis(pentafluorophenyl)borate, molybdenum compounds such as tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2-dithiolene]molybdenum, and organic compounds having a tetracyanoquinodimethane skeleton such as 2,3,4,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane. The dopant preferably undergoes a charge transfer reaction with at least one of the organic semiconductor compounds before or after the formation of the hole transport layer. As the dopant, a hypervalent iodine compound is preferred because it has excellent solubility and easily generates an electron-accepting active site that functions as an oxidizing agent upon heating or the like.

[0094] It is known that hypervalent iodine compounds act as dopants for organic semiconductor compounds and exhibit electron-accepting properties (i.e., oxidizing properties). Electron-accepting dopants can improve the electrical conductivity or hole-transporting ability of organic semiconductor compounds by removing electrons from the organic semiconductor compounds.

[0095] Hypervalent iodine compounds are defined as compounds containing hypervalent iodine, with an oxidation state of iodine of three or more. For example, iodine(III) compounds or iodine(V) compounds are preferred as dopants. Examples of iodine(V) compounds containing pentavalent iodine include periodinane compounds such as Dess-Martin periodinane. Examples of iodine(III) compounds containing trivalent iodine include compounds with an oxidized iodobenzene structure, such as (diacetoxyiodo)benzene, and diaryliodonium salts. Organic compounds containing trivalent iodine are preferred as dopants because they exhibit good electron-accepting properties and are less likely to undergo reverse reactions if the molecules are destroyed during the oxidation process. Diaryliodonium salts are particularly preferred.

[0096] Diaryliodonium salts are compounds containing [Ar-I + -Ar]X - Here, each of the two Ar represents an aromatic group. The aromatic group is not particularly limited, and examples thereof include the aromatic groups exemplified in the substituent group Z. X - represents any anion. -Examples of the cations include halide ions, trifluoroacetate ions, tetrafluoroborate ions, and tetrakis(pentafluorophenyl)borate ions. X is preferred because it has high solubility and the reaction for producing the coating solution can proceed smoothly. - is preferably an anion having a fluorine atom.

[0097] Preferred examples of the dopant include those represented by the following formula (Q): In formula (Q), X - represents any anion, specific examples of which are as described above. [R 11 -I + -R 12 ]X - (Q)

[0098] In formula (Q), R 11 and R 12 are each independently a monovalent organic group. Examples of monovalent organic groups include aliphatic groups and aromatic groups.

[0099] Examples of the aliphatic group include an aliphatic hydrocarbon group having 1 to 20 carbon atoms and an aliphatic heterocyclic group having 4 to 20 carbon atoms. Specific examples include alkyl groups including cycloalkyl groups, alkenyl groups, and alkynyl groups, and specific examples include a methyl group, an ethyl group, a butyl group, a cyclohexyl group, and a tetrahydrofuryl group.

[0100] Examples of aromatic groups include aromatic hydrocarbon groups having 6 to 20 carbon atoms and aromatic heterocyclic groups having 2 to 20 carbon atoms. Specific examples include a phenyl group, a naphthyl group, a biphenyl group, a thienyl group, and a pyridyl group.

[0101] The aliphatic group and aromatic group may have a substituent, such as a halogen atom, a hydroxyl group, a cyano group, an amino group, a carboxyl group, an ester group, an alkylcarbonyl group, an acetyl group, a sulfonyl group, a silyl group, a boryl group, a nitrile group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a thio group, a seleno group, an aromatic hydrocarbon group, or an aromatic heterocyclic group.

[0102] R 11 and R 12 is preferably an aromatic hydrocarbon group having 6 to 20 carbon atoms, more preferably a phenyl group. Here, it is preferable that the aromatic hydrocarbon group has no substituent or has an alkyl group having 1 to 6 carbon atoms. R 11 and R 12 is particularly preferably a phenyl group having an alkyl group at the para position. The ionization potential of the hole transport layer is preferably in a specific range, since it matches well with the holes generated in the active layer and is easy to suppress energy loss. Specifically, it is preferably -5.9 eV or more, more preferably -5.8 eV or more, even more preferably -5.75 eV or more, and particularly preferably -5.70 eV or more. On the other hand, the ionization potential of the hole transport layer is preferably -5.2 eV or less, more preferably -5.3 eV or less, particularly preferably -5.4 eV or less, especially preferably -5.45 eV or less, and most preferably -5.5 eV or less. That is, the ionization potential of the hole transport layer is particularly preferably -5.8 eV or more and -5.2 eV or less.

[0103] As described above, the ionization potential of the hole transport layer can be adjusted by using the carbazole compound and the polytriarylamine compound according to the present invention. A more detailed method for adjusting the ionization potential to the desired range is, for example, controlling the electronic state of the compound by appropriately arranging the type and position of the substituent of the aromatic compound in the carbazole compound or triarylamine compound represented by formula (I). Furthermore, the electronic state of the compound contained in the hole transport layer can be adjusted by using a dopant, etc., as described below, in combination with the hole transport layer, i.e., by oxidizing or reducing the whole or part of the compound.

[0104] The thickness of the hole transport layer of the power generation device according to the present invention 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 conduction path between the upper and lower electrodes and the active layer is unlikely to occur. Specifically, the thickness is preferably 20 nm or more, more preferably 40 nm or more, and even more preferably 60 nm or more. On the other hand, a thin thickness is preferable, since it is unlikely to cause resistance in charge transport by the hole transport layer and reduces costs by reducing the amount of compound contained in the hole transport layer. Specifically, the thickness is preferably 1000 nm or less, more preferably 750 nm or less, and even more preferably 500 nm or less.

[0105] [electrode] In FIG. 1, the electrode has the function of collecting holes and electrons generated by light absorption in the active layer 103. A power generation device 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 a lower electrode. When the power generation device 100 has a substrate or is provided on a substrate, the electrode closer to the substrate can generally be called the lower electrode, and the electrode farther from the substrate can generally be called the upper electrode. A transparent electrode can also be called the lower electrode, and an electrode less transparent than the lower electrode can also be called the upper electrode. The power generation device 100 shown in FIG. 1 has a lower electrode 101 and an upper electrode 105.

[0106] The pair of electrodes can be an anode suitable for collecting holes and a cathode suitable for collecting electrons. In this case, the power generating device 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.

[0107] Either one of the pair of electrodes may be 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, and particularly preferably 70% or more, since more light passes through the transparent electrode to reach the active layer. The sunlight transmittance can be measured using a spectrophotometer (e.g., U-4100 manufactured by Hitachi High-Technologies Corporation).

[0108] There are no particular limitations on the components and manufacturing methods of the lower electrode 101 and the upper electrode 105, or the anode and the 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 2012-191194 A can be used.

[0109] [Electron transport layer] The power generating device according to the present invention may have an electron transport layer. The material of the electron transport layer may be any material capable of improving the efficiency of electron extraction from the active layer to the cathode. Specific examples include inorganic compounds, organic compounds, and perovskite semiconductor compounds described in known publications such as International Publication No. 2013 / 171517, International Publication No. 2013 / 180230, and Japanese Patent Application Laid-Open No. 2012-191194. 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 (Alq), 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 or phosphine sulfide compounds.

[0110] When the power generating device according to the present invention includes an electron transport layer, the thickness of the layer is preferably thick, because when the active layer located between the upper and lower electrodes has high charge transport capacity, 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 compensated for, and the wettability of the active layer is easily controlled. Specifically, the thickness is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. On the other hand, a thin thickness is preferable in terms of the resistance to charge transport by the electron transport layer being unlikely to occur and the cost reduction due to the reduction in the amount of compound contained in the electron transport layer. Specifically, the thickness is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 10 nm or less.

[0111] [Base material] The power generation device according to the present invention may have a substrate. In FIG. 1, the power generation device 100 has a substrate 106 serving as a support, but the power generation device according to the present invention does not have to 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 known documents such as WO 2013 / 171517, WO 2013 / 180230, or JP 2012-191194 A can be used.

[0112] <Manufacturing method for power generation devices> The method for manufacturing the power-generating device of the present invention is not particularly limited as long as it can incorporate the above-described carbazole compound and polytriarylamine compound into the hole transport layer, and known methods for manufacturing power-generating devices using perovskite semiconductor compounds can be applied. For example, a hole transport layer can be formed by preparing a coating solution containing the above-described carbazole compound, polytriarylamine compound, dopant, and solvent, and using a wet film-forming method such as spin coating or inkjet printing. An electron transport layer can also be formed by a similar coating method. Furthermore, these buffer layers can also be formed by a dry film-forming method such as vacuum deposition. However, the hole transport layer is preferably formed by a coating method, and more preferably by applying a liquid containing the above-described carbazole compound, polytriarylamine compound, and dopant. That is, the method for manufacturing the power-generating device of the present invention includes a step of forming the hole transport layer by a coating method, and more preferably by applying a liquid containing the above-described carbazole compound, polytriarylamine compound, and dopant during this coating method.

[0113] 1, the power generating device 100 can be manufactured by stacking the layers that make up the power generating device 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 rolled flexible substrate 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 one go, making it more suitable for mass production than the sheet-to-sheet method.

[0114] The size of the roll that can be used in the roll-to-roll method is not particularly limited as long as it can be handled by the roll-to-roll manufacturing equipment, 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.

[0115] These diameters make the roll easy to handle and the layers formed in each step less susceptible to damage from 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 power generation device.

[0116] When manufacturing the power generating device 100, the power generating device 100 may be heated after the upper electrode 105 is laminated (this heating step may be referred to as an annealing treatment step).

[0117] The annealing step is preferably performed at a high temperature, since this increases the adhesion between the layers of the power-generating device 100, for example, between the buffer layer 102 and the lower electrode 101, or between the buffer layer 102 and the active layer 103, thereby improving the thermal stability and durability of the power-generating device. Specifically, a temperature of 50°C or higher is preferred, and 80°C or higher is more preferred. On the other hand, the annealing step is preferably performed at a low temperature, since the organic compounds contained in the power-generating device 100 are less susceptible to thermal decomposition. Specifically, a temperature of 300°C or lower is preferred, more preferably 280°C or lower, and even more preferably 250°C or lower. In the annealing step, stepwise heating using different temperatures within the above temperature range may be performed.

[0118] The heating time within the above preferred temperature range is preferably 1 minute or more, more preferably 3 minutes or more, in order to improve adhesion while suppressing thermal decomposition, and is preferably 180 minutes or less, more preferably 60 minutes or less. The annealing process is preferably terminated when the open circuit voltage, short circuit current, and fill factor, which are parameters of solar cell performance, reach certain values. The annealing process is preferably carried out under normal pressure and in an inert gas atmosphere to prevent thermal oxidation of the constituent materials. The heating method may involve placing the power generation device on a heat source such as a hot plate, or placing the power generation device in a heated atmosphere such as an oven. Heating may be carried out batchwise or continuously.

[0119] [Photoelectric conversion characteristics] The photoelectric conversion characteristics of the power generation device 100 can be determined as follows: The power generation device 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 the photoelectric conversion efficiency (PCE), short-circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be determined. As an example, by irradiating the power generation device 100 with white LED light having a color temperature of 5000K at an appropriate irradiation intensity (illuminance), the current-voltage characteristics at each illuminance can be measured.

[0120] One embodiment of the power generation device according to the present invention has excellent power generation efficiency at low illuminance (10 to 5000 lux), and can achieve a photoelectric conversion efficiency of 20% or more when using a white light source such as white LED light with a color temperature of 5000 K. Furthermore, when irradiated with white LED light with a color temperature of 5000 K and the illuminance of the light-receiving surface is 200 lux, the photoelectric conversion efficiency can be achieved to 25% or more.

[0121] 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 ) is the voltage value when the fill factor (FF) is a factor that represents the internal resistance. The fill factor (FF) is expressed by the following equation, where Pmax is the maximum output. FF=Pmax / (Voc×Jsc) Furthermore, the photoelectric conversion efficiency (PCE) is given by the following equation, where Pin is the incident energy. PCE=(Pmax / Pin)×100=(Voc×Jsc×FF / Pin)×100 The photoelectric conversion efficiency (PCE) is the output (maximum output) at the optimum operating point of the current-voltage curve of the power generating device measured with a specified amount of irradiated light, divided by the total amount of energy contained in the irradiated light (%). For example, the total energy amount of sunlight with an intensity of AM1.5G is 100mW / cm 2 If white LED light with a color temperature of 5000K is irradiated and the illuminance on the light receiving surface is 200 lux, the 2 In this specification, the color temperature of 5000K is defined by the JIS Z8725:2015 standard.

[0122] [Solar Cell] The power generation device according to the present invention has excellent photoelectric conversion efficiency even under low illumination, making it suitable as an indoor solar cell. Figure 2 shows an example of a solar cell equipped with the power generation device of the present invention. It is a thin-film solar cell 14 equipped with the power generation device 100 described above, and includes, in this order: a weather-resistant protective film 1, an ultraviolet-blocking film 2, a gas barrier film 3, a getter material film 4, an encapsulant 5, a solar cell element 6 having the power generation device 100 (not shown), an encapsulant 7, a getter material film 8, a gas barrier film 9, and a backsheet 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 include all of these components; required components can be selected as desired.

[0123] 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.

[0124] 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.

[0125] There are no limitations on the uses of the power generation device of the present invention and the solar cell or solar cell module equipped with the same, and examples of uses 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. The power generation device of the present invention and a solar cell or solar cell module including the same exhibit excellent photoelectric conversion efficiency in low-illumination environments, and are therefore particularly suitable for energy harvesting applications. [Example]

[0126] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples.

[0127] <Measurement method etc.> [Molecular weight] The number average molecular weight Mn and the weight average molecular weight Mw were measured by GPC under the following conditions and calculated in terms of polystyrene. (Measurement conditions) Pump: LC-10AT (Shimadzu Corporation), Oven: CTO-10A (Shimadzu Corporation), Analysis: Lab-Solution (Shimadzu Corporation), Column: Two Agilent Technologies GPC columns (PLgel MIXED-B 10 μm, inner diameter 7.5 mm, length 30 cm) connected in series. Mobile phase: tetrahydrofuran, Flow rate: 1.0mL / min, Oven temperature: 40℃, Sample concentration: 0.01 to 5% by mass Injection volume: 5μL, Detector: differential refractive index detector (Shimadzu Corporation, RID-10A) and UV-vis detector (Shimadzu Corporation, RID-10A), Molecular weight standards: polystyrene.

[0128] [Ionization potential measurement] An active layer or hole transport layer containing the semiconductor compound to be evaluated was formed on a glass substrate with a thin film of ITO. This was then irradiated with light, and the number of photoelectrons generated was measured using an open counter, which requires oxygen. This open counter measures ionized oxygen molecules by trapping photoelectrons in oxygen molecules in the atmosphere. As the energy of the irradiated light is increased, a threshold is observed at which photoelectrons begin to be emitted. This threshold, i.e., the minimum energy (eV) required for the irradiated energy to eject photoelectrons, corresponds to the ionization potential (eV). This type of ionization potential measurement using the photoelectron coefficient method was performed using a series of instruments, such as the "AC-3" from Riken Keiki Co., Ltd. The thickness of the active layer or hole transport layer used for measurement does not substantially affect the measured values. For example, an active layer formed to a thickness of 400 nm to 600 nm or a hole transport layer formed to a thickness of 5 nm to 100 nm may be measured. Furthermore, the active layer or hole transport layer used for measurement need only be exposed to the atmosphere and does not need to be formed in contact with the surface of the thin-film ITO. For example, an active layer laminated on the surface of a hole transport layer formed on a thin-film ITO may be measured. In measuring this active layer, the type and performance of the hole transport layer do not substantially affect the measured values. In other words, the ionization potential of the active layer and hole transport layer is not affected by the lamination environment (the presence or absence and type of an underlying layer). The conductive glass with thin film ITO used above can be a commercially available product, and the resistance value (surface resistivity) of the thin film ITO is not particularly limited and can be, for example, 2 Ω / sq. to 1000 Ω / sq. Specifically, in the following measurements, the ionization potential of the active layer was measured by sequentially coating 150 μL of active layer coating solution 1 and 120 μL of active layer coating solution 2 (described below) on a glass substrate on which a thin film of ITO (indium tin oxide, surface resistivity: 7-10 Ω / sq.) had been formed, in the same manner as in the method for forming an active layer in the method for fabricating a power generation device described below, to form a 650 nm-thick active layer of perovskite semiconductor compound directly on the glass substrate on which the thin film of ITO had been formed. The ionization potential was determined based on the number of photoelectrons generated by irradiating the surface of the formed active layer with light. The measurement apparatus used was an AC-3 manufactured by Riken Keiki Co., Ltd. The ionization potential of the hole transport layer was determined by applying 120 μL of the hole transport layer coating solution (described below) to a glass substrate on which thin-film ITO (surface resistivity: 7-10 Ω / sq.) had been formed, in the same manner as in the hole transport layer formation method in the power generation device fabrication method described below, to form a 100 nm-thick hole transport layer directly on the glass substrate on which thin-film ITO had been formed. The ionization potential was determined based on the number of photoelectrons generated by irradiating the surface of the hole transport layer with light. The equipment used was an "AC-3" manufactured by Riken Keiki Co., Ltd. and a "PCR-101" photon yield measurement system manufactured by Optel Corporation.

[0129] [Band gap calculation] Regarding the band gap of the active layer, 150 μL of active layer coating liquid 1 and 120 μL of active layer coating liquid 2, which will be described later, were sequentially applied onto a transparent glass substrate in the same manner as in the method for forming an active layer in the method for producing a power generation device, which will be described later, to form an active layer of a perovskite semiconductor compound with a thickness of 650 nm directly on the glass substrate.

[0130] The transmission spectrum of the formed active layer was measured, and the horizontal axis wavelength was converted to eV, and the vertical axis transmittance was converted to √(ahν) (where α is the absorption coefficient, h is Planck's constant, and ν is the frequency). The rise of this absorption was fitted as a straight line, and the eV value where it intersected with the baseline was calculated as the band gap. This transmission spectrum was measured using a spectrophotometer (Hitachi High-Tech U-4100). The fitting and band gap calculation were performed according to the method described in the literature (Yamashita Daisuke, Ishizaki Atsushi: Analytical Chemistry 66, 333 (2017)).

[0131] [Measurement of photoelectric conversion efficiency of power generation devices] White LED light with a color temperature of 5000K was irradiated onto the power generation device. The irradiance was adjusted using an illuminance meter so that the illuminance on the light-receiving surface of the power generation device was 200 lux. Under this environment, a source meter was used to measure the current-voltage curve (IV curve) and determine its maximum output value. This value was divided by the total energy content of the irradiated light to obtain the photoelectric conversion efficiency (%) of the power generation device. The color temperature was measured in accordance with JIS Z8725:2015. Specifically, in the following measurements, a 1 mm square metal mask was attached to the power generation device obtained in each example, and the current-voltage characteristics between the ITO transparent conductive film and the upper electrode were measured. A source meter (Keithley, Model 2400) was used for the measurements. The illumination light source used was the indoor light evaluation LED light source BLD-100 manufactured by Bunkoukeiki Co., Ltd., and white LED light with a color temperature of 5000 K was irradiated onto the power generation device. At this time, the illumination intensity was adjusted using an illuminance meter so that the illuminance on the light receiving surface of the power generation device was 200 lux. From these measurement results, the short-circuit current density Jsc (mA / cm 2 The open circuit voltage Voc (V), fill factor FF, and photoelectric conversion efficiency PCE (%) were calculated. These values ​​were calculated based on the measurement results immediately after the power generation device was fabricated and are shown in Table 1.

[0132] [Example 1] (Preparation of Coating Solution for Electron Transport Layer) Ultrapure water was added to a 15 mass % aqueous dispersion of tin (IV) oxide (manufactured by Alfa Aesar) to prepare a 7.5 mass % aqueous dispersion of tin oxide.

[0133] (Preparation of coating solution for active layer) Lead (II) iodide was weighed into a vial and placed in a glove box. N,N-dimethylformamide was added as a solvent to adjust the lead (II) iodide concentration to 1.3 mol / L, and the mixture was then heated and stirred at 100°C for 1 hour to prepare coating solution 1 for the active layer.

[0134] Next, formamidine hydrobromide (FABr), methylamine hydrobromide (MABr), and methylamine hydrochloride (MACl) were weighed out in a mass ratio of 7.25:1:1.5 and placed in another vial. Isopropyl alcohol was added as a solvent to this vial to prepare coating solution 2 for the active layer, with a total concentration of 0.49 mol / L of FABr, MABr, and MACl.

[0135] (Synthesis of carbazole compound A) A carbazole compound A represented by the following formula (A) was synthesized by the method described in a prior literature (Yang, J. Wet. al., Phys. Chem. Chem. Phys. 2015, 17, 24468).

[0136] [ka]

[0137] (Synthesis of Polytriarylamine Compounds) Using the following compound 1 (349.4 mg, 1 mmol) and the following compound 5 (783.7 mg, 0.98 mmol), and using the reaction conditions described in a patent document (JP 2019-175970 A) as reference, 570 mg of the following polymer compound 4 was obtained. The weight-average molecular weight of the obtained polymer compound 4 was 37,500, and the PDI (weight-average molecular weight / number-average molecular weight) was 1.4.

[0138] [ka]

[0139] (Preparation of Coating Solution for Hole Transport Layer) 20 mg of carbazole compound A and 40 mg of polytriarylamine compound (polymer compound 4) were added to 1.65 cm of an o-dichlorobenzene solution containing 4.8 mg of 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (TPFB; manufactured by TCI), an electron-accepting dopant. 3 Next, this solution was heated and stirred at 150° C. for 1 hour to prepare a coating solution for the hole transport layer.

[0140] (Fabrication of power generation devices) A glass substrate (manufactured by Geomatec Co., Ltd.) having a patterned indium tin oxide (ITO) transparent conductive film was subjected to ultrasonic cleaning using ultrapure water, drying by nitrogen blowing, and UV-ozone treatment.

[0141] The above-mentioned coating liquid for the electron transport layer was spin-coated onto the glass substrate at room temperature at a speed of 2000 rpm to a thickness of 35 nm, and then heated on a hot plate at 150°C for 10 minutes to form an electron transport layer.

[0142] The glass substrate with this electron transport layer formed was placed in a glove box, and active layer coating solution 1 (150 μL) heated to 100°C was dropped onto the electron transport layer, spin-coated at 2000 rpm, and annealed on a hot plate at 100°C for 10 minutes to form a lead iodide layer. After the glass substrate with the lead iodide layer formed was returned to room temperature, active layer coating solution 2 (120 μL) was spin-coated onto the lead iodide layer at 2000 rpm, heated on a hot plate at 150°C for 20 minutes, and then cooled to room temperature (25°C) to form an active layer (650 nm thick) of an organic-inorganic perovskite semiconductor compound. The ionization potential and band gap of this active layer were measured by the above-mentioned methods.

[0143] The hole transport layer coating solution (120 μL) was spin-coated onto this active layer at a speed of 1000 rpm, and then heated on a hot plate at 90°C for 5 minutes, and then cooled to room temperature (25°C) to form a hole transport layer (thickness 100 nm). The ionization potential of this hole transport layer was measured by the method described above.

[0144] On this hole transport layer, MoO3 having a thickness of 10 nm, IZO having a thickness of 200 nm, and aluminum having a thickness of 50 nm were deposited in this order by a resistance heating vacuum deposition method to form an upper electrode. In this manner, a power generating device was fabricated. Table 1 shows the ionization potential and band gap of the active layer, the ionization potential of the hole transport material, and the photoelectric conversion efficiency of this power generation device when irradiated with white LED light at a color temperature of 5000 K and the illuminance on the light-receiving surface was 200 lux.

[0145] [Example 2] A power generating device was fabricated and measured in the same manner as in Example 1, except that the amounts of the carbazole compound and the polyethanolamine compound used were changed to 30 mg of the carbazole compound and 30 mg of the polyethanolamine compound. The results are shown in Table 1.

[0146] [Example 3] A power generating device was fabricated and measured in the same manner as in Example 1, except that the amounts of the carbazole compound and the polyethanolamine compound used were changed to 12 mg of the carbazole compound and 48 mg of the polyethanolamine compound. The results are shown in Table 1.

[0147] [Comparative Example 1] PTAA (poly(triaryl amine)) was synthesized. A power generating device was fabricated in the same manner as in Example 1, except that the mixture of a carbazole compound and a polytriarylamine compound in Example 1 was replaced with this PTAA, and various measurements were carried out. The results are shown in Table 1.

[0148] [Table 1]

[0149] The results in Table 1 confirm that the power generation devices of Examples 1 to 3, which have a hole transport layer containing a carbazole compound and a polytriarylamine compound according to the present invention, have superior conversion efficiencies when using a low-illuminance white LED as a light source to the power generation device of Comparative Example 1, which has a hole transport layer containing a polytriarylamine compound. The ionization potential of the active layer in each power generation device of each Example was −6.0 eV or more and −5.7 eV or less, the band gap of the active layer was 1.6 eV or more and 2.3 eV or less, and the ionization potential of the hole transport material was −5.8 eV or more and −5.2 eV or less. Therefore, it is believed that the combined use of the carbazole compound according to the present invention and the polytriarylamine according to the present invention brought the energy states of the active layer and the hole transport layer into suitable ranges, thereby achieving excellent conversion efficiency under low-illuminance conditions. [Explanation of symbols]

[0150] 1 Weatherproof protective film 2. UV-blocking film 3,9 Gas barrier film 4,8 Getter material film 5,7 Encapsulant 6. Solar cell elements (power generation devices) 10 Back Seat 12 Base material 13 Solar cell modules 14 Thin-film solar cells 100 Power generation devices 101 Lower electrode 102 Buffer layer 103 Active layer 104 Buffer Layer 105 Upper electrode 106 Base material

Claims

1. A power generating device comprising a pair of electrodes composed of 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 at least one of the pair of electrodes, the hole transport layer contains a carbazole compound represented by the following formula (I) and a polytriarylamine compound, The polytriarylamine compound contains a repeating unit represented by the following formula (IV), and 80 mol % or more of all repeating units of the polytriarylamine compound are repeating units represented by the following formula (IV), The power generating device includes a carbazole compound represented by the following formula (II) or (III): 【Chemistry 1】 (Ar in the formula １ ~Ar ４ are each independently a monovalent aromatic group which may have a substituent, and may have a condensed ring structure. １ and ring 1, Ar ３ and ring 2 may each independently form a fused ring structure. １ and Ar ２ , Ar ３ and Ar ４ may each independently form a fused ring structure. At least one of these fused ring structures forms a carbazole structure. The diarylamino group (N(Ar) ３ ) (Ar ４ )) is located in either the meta or para position relative to the bond between ring 1 and ring 2. 【Chemistry 2】 (In formula (IV), X is CR １ａ R ２ａ , SiR １ａ R ２ａ , N.R. ３ａ , S, and R １ａ , R ２ａ and R ３ａ each independently represents a hydrogen atom, an optionally substituted aromatic group, or an optionally substituted alkyl group; R １ａ and R ２ａ may be bonded to each other to form a ring, and Ar １ａ and Ar ２ａ each independently represents a direct bond or an aromatic group which may have a non-bridging substituent, Ar ３ａ represents an aromatic group which may have a non-crosslinkable substituent. 【Transformation 3】 (Ar in the formula ５ and Ar ６ R are each an aromatic group which may have an independent monovalent substituent, and the aromatic group may have a fused ring structure. The monovalent substituent is an arbitrary substituent which substitutes an arbitrary hydrogen atom of the aromatic group, and may be an alkyl group, an aromatic group, an alkoxy group, or a thioalkyl group. １ ~R ３ are each independently a hydrogen atom, a halogen atom, or an alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, or aromatic group which may have a substituent. 【Chemistry 4】 (In the formula, Ar ７ and Ar ８ R are each an aromatic group which may have an independent monovalent substituent, and the aromatic group may have a fused ring structure. The monovalent substituent is an arbitrary substituent which substitutes an arbitrary hydrogen atom of the aromatic group, and may be an alkyl group, an aromatic group, an alkoxy group, or a thioalkyl group. ４ ~R ９ are each independently a hydrogen atom, a halogen atom, or an alkyl group, alkenyl group, alkynyl group, alkoxy group, aryloxy group, or aromatic group which may have a substituent.

2. 2. The power generating device according to claim 1, wherein the active layer has an ionization potential of −6.0 eV or more and −5.7 eV or less, the active layer has a band gap of 1.6 eV or more and 2.3 eV or less, and the hole transport layer has an ionization potential of −5.9 eV or more and −5.2 eV or less.

3. The power generating device according to claim 1 or 2, wherein the organic-inorganic hybrid semiconductor compound is a compound having a perovskite structure.

4. 4. The power generating device according to claim 1, wherein the active layer has a thickness of 200 nm or more and 800 nm or less.

5. 5. The power generating device according to claim 1, wherein the photoelectric conversion efficiency is 25% or more when irradiated with white LED light having a color temperature of 5000K and the illuminance on the light receiving surface is 200 lux.

6. 6. A method for manufacturing a power generating device according to claim 1, comprising: forming the hole transport layer by a coating method, wherein the coating method involves coating a liquid containing the carbazole compound, the polytriarylamine compound, and a dopant.

7. The method for producing a power generating device according to claim 6 , wherein the dopant is a diaryliodonium salt containing trivalent iodine.

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