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.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 generating device having excellent power generation efficiency even in low-illumination environments such as indoors can be obtained by combining a hole transport layer containing a specific carbazole compound with an active layer containing an organic-inorganic hybrid semiconductor compound, and have completed the present invention.

[0007] [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, wherein the hole transport layer contains a carbazole compound represented by the following formula (I): (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. [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 −5.3 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 manufacturing a power generating device according to any one of claims 1 to 6, comprising a step of forming the hole transport layer by a coating method, wherein the coating method involves coating a liquid containing the carbazole compound and a dopant. [8] The method for producing a power generating device according to [7], wherein the dopant is a diaryliodonium salt containing trivalent iodine.

[0008] [ka]

[0009] [ka]

[0010] [ka] [Effects of the Invention]

[0011] 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]

[0012] [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

[0013] 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 described below.

[0014] 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 −5.3 eV or less. 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.

[0015] 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.

[0016] <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.

[0017] 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.

[0018] [Active layer]

[0019] 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.

[0020] In this embodiment, the organic-inorganic hybrid semiconductor compound is preferably a compound having a perovskite structure (hereinafter, may be referred to as a perovskite semiconductor compound). A perovskite semiconductor compound refers to a semiconductor compound having a perovskite structure. There are no particular limitations on the perovskite semiconductor compound, and it 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.

[0021] 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.

[0022] 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.

[0023] 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+ ) can be mentioned. 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.

[0024] Examples of monovalent anions X include halides, acetate ions, nitrate ions, sulfate ions, borate ions, acetylacetonate ions, carbonate ions, citrate ions, sulfur ions, tellurium ions, thiocyanate ions, titanate ions, zirconate ions, 2,4-pentanedionate ions, and silicofluorides. 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 is likely to be appropriately narrow, X is preferably a halide ion such as chloride ion, bromide ion, or iodide ion, and more preferably bromide ion or iodide ion.

[0025] Preferred examples of perovskite semiconductor compounds include organic-inorganic perovskite semiconductor compounds, and particularly 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 y Cl3, 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 yBr (3-x) Cl x , and in the above compounds, instead of CH3NH3, CFH2NH3, CF2HNH3, CF3NH3, NH2CH=NH 3、 Compounds using Cs or Rb are included. Here, x is an arbitrary value between 0 and 3, and y is an arbitrary value between 0 and 1. Preferred are CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbCl3, CH3NH3PbI (3-x) Cl x , CH3NH3PbI (3-x) Br x , CH3NH3PbBr (3-x) Cl x , CH3NH3Pb (1-y) Sn y Br3, CH3NH3Pb (1-y) Sn y Cl3, CH3NH3Pb (1-y) Sn y I (3-x) Cl x , CH3NH3Pb (1-y) Sn y I (3-x) Br x , CH3NH3Pb (1-y) Sn y Br (3-x) Cl x and NH2CH=NH instead of CH3NH3 in the above compounds. 3、 Compounds using Cs or Rb are preferred, and 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.

[0026] 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 have a laminated structure formed of multiple layers containing different materials or having different components.

[0027] 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.

[0028] 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, and even more preferably −5.9 eV or less.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] A precursor of an organic-inorganic hybrid semiconductor compound 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 upon 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. 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 thereof include organic solvents such as N,N-dimethylformamide.

[0035] 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.

[0036] [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.

[0037] [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 according to the present invention," "the carbazole compound represented by formula (I)," or "the compound represented by formula (I)"). In the power generation device of the present invention, the hole transport layer contains the carbazole compound of the present invention, which allows the ionization potential of the hole transport layer to be within the preferred range described below, thereby enabling high power generation efficiency under low illumination. Furthermore, in the carbazole compound of the present invention, the unshared electron pair on the basic nitrogen atom is stabilized by the aromaticity of the carbazole group, making it electronically robust compared to other aromatic tertiary amines and allowing for the maintenance of an appropriate hole transport layer. For the same reason, it is also highly preferred in that it is easy to achieve a deep ionization potential (Ip). The compound represented by formula (I) is also preferred in that it has no molecular weight distribution, is easily purified, and is inexpensively produced, compared to polymeric compounds such as polytriarylamine.

[0038] <Carbazole compounds> The carbazole compound represented by formula (I) is an organic semiconductor compound. Generally, a semiconductor compound refers to a compound that can be used as a semiconductor material exhibiting 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 indicating 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.

[0039] [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 4 The 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.

[0040] The content of the carbazole compound represented by formula (I) in the hole transport layer is preferably high, since this makes it easier to set the ionization potential of the hole transport layer within the preferred range described below. Specifically, the content of the carbazole compound in the hole transport layer (total mass: 100 mass%) is preferably 40 mass% or more, more preferably 50 mass% or more, and even more preferably 60 mass% or more. Here, the upper limit is 100 mass%, but when carrier mobility is increased by adding a dopant to the hole transport layer, the total amount including the dopant is 100 mass%.

[0041] 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 described above. The carbazole compound represented by formula (II) (hereinafter, sometimes simply referred to as "compound represented by formula (II)") will be described.

[0042] [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.

[0043] Ar 5 and Ar 6 The 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.

[0044] 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.

[0045] 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.

[0046] 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 and Ar 6 are each independently, for example, a biphenyl group, a terphenyl group, a quaterphenyl group, etc., and Ar 5 and Ar 6and 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.

[0047] 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.

[0048] (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;

[0049] 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.

[0050] 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.

[0051] 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).

[0052] 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.

[0053] The carbazole compound represented by formula (III) (hereinafter, sometimes simply referred to as "compound represented by formula (III)") will be described.

[0054] [ka] (In the formula, Ar7 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.

[0055] Ar 7 and Ar 8 The aromatic group constituting the 5 and Ar 6 is the same as:

[0056] 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.

[0057] 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.

[0058] R in formula (III) 4 ~R9 are 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.

[0059] (Other semiconductor compounds) The hole transport layer may contain a semiconductor compound other than the carbazole compound represented by formula (I), 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 (e.g., triarylamine compounds). Examples of polymeric organic semiconductor compounds include conjugated polymers (e.g., polythiophene polymers, polyacetylene polymers, polyaniline polymers, polyphenylene polymers, polyphenylene vinylene polymers, polyfluorene polymers, and polypyrrole polymers), and arylamine polymers (e.g., triarylamine polymers).

[0060] When forming the hole transport layer, it is preferable to use a dopant in addition to the carbazole compound described above. By using a dopant, the properties such as the conductivity and hole transport ability of the layer can be adjusted. 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 part by mass or more, more preferably 0.01 part by mass or more, still more preferably 0.05 part by mass or more, and particularly preferably 0.1 part by mass or more, relative to 100 parts by mass of the carbazole compound. On the other hand, the amount of the dopant is preferably small because it suppresses leakage current in the power generating device and tends to improve power generation efficiency, particularly under low-illumination conditions, and therefore, specifically, the amount 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, per 100 parts by mass of the carbazole compound. 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 relative to 100 parts by mass of the carbazole compound.

[0061] <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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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)

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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 12is particularly preferably a phenyl group having an alkyl group at the para position. The ionization potential of the hole transport layer is preferably within a specific range, since it provides good matching with the holes generated in the active layer and makes it easy to suppress energy loss. Specifically, it is preferably -5.9 eV or higher, more preferably -5.75 eV or higher, and even more preferably -5.70 eV or higher. On the other hand, the ionization potential of the hole transport layer is preferably -5.3 eV or lower, more preferably -5.45 eV or lower, and even more preferably -5.5 eV or lower. That is, the ionization potential of the hole transport layer is particularly preferably -5.9 eV or higher and -5.3 eV or lower.

[0071] As described above, the ionization potential of the hole transport layer can be adjusted by using the carbazole 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 represented by formula (I). Alternatively, the electronic state of the compound contained in the hole transport layer can be adjusted by, for example, oxidizing or reducing the whole or part of the compound by using a dopant, etc., described later, in combination with the hole transport layer.

[0072] 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.

[0073] [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.

[0074] 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.

[0075] 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).

[0076] 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.

[0077] [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 and organic compounds described in known publications such as WO 2013 / 171517, WO 2013 / 180230, and JP 2012-191194 A, as well as the organic-inorganic perovskite semiconductor compound according to the present invention. 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.

[0078] 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.

[0079] [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.

[0080] <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 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, a dopant, and a 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 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 and dopant in this coating method.

[0081] 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.

[0082] When manufacturing the power-generating device 100, after the upper electrode 105 is laminated, the power-generating device 100 may be heated, for example, within a temperature range of 50°C to 80°C and 280°C to 300°C (this heating step may be referred to as an annealing step). The annealing step is preferably performed at a high temperature, since it is more likely to improve the adhesion between the layers of the power-generating device 100, such as between the buffer layer 102 and the lower electrode 101, or between the buffer layer 102 and the active layer 103. Specifically, it is preferably performed at 50°C or higher. By improving the adhesion between the layers, the thermal stability and durability of the power-generating device can be improved. 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 likely to be thermally decomposed. Specifically, it is preferably performed at 300°C or lower. In the annealing step, stepwise heating using different temperatures within the above temperature range may be performed.

[0083] The heating time in the above-mentioned suitable temperature range is preferably 1 to 3 minutes or more and 60 to 180 minutes or less, in order to easily improve adhesion while suppressing thermal decomposition. 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.

[0084] [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, the power generation device 100 is irradiated with white LED light with a color temperature of 5000 K at an appropriate irradiation intensity (illuminance), and the current-voltage characteristics at each illuminance can be measured.

[0085] 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. 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 is. In this specification, the color temperature of 5000K is defined by the JIS Z8725:2015 standard.

[0086] [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.

[0087] 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.

[0088] 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.

[0089] 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]

[0090] 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.

[0091] [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. Light was then irradiated onto the layer, and the number of photoelectrons generated was measured using an open-circuit counter, which requires oxygen. This open-circuit 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 photoelectron coefficient method for ionization potential measurements was performed using Riken Keiki's AC-2, AC-3, and other series. 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.

[0092] [Band gap calculation] The band gap of the active layer can be considered to be the same as the band gap of the semiconductor compound that constitutes the active layer, and was calculated from the absorption edge wavelength and absorbance of the semiconductor compound. A thin film of the semiconductor compound (approximately 20-500 nm thick) was formed on an appropriate substrate, such as a transparent glass substrate, using standard methods. The transmission spectrum was measured, and the horizontal axis was converted to wavelength (eV) and the vertical axis was converted to transmittance (√(αhν)) (where α is the absorption coefficient, h is Planck's constant, and ν is the frequency). The absorption peak was fitted as a straight line, and the band gap (eV) at the point where it intersected the baseline was calculated. This transmission spectrum was measured using a spectrophotometer, such as the 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)).

[0093] [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.

[0094] [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.

[0095] (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.

[0096] 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.

[0097] (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).

[0098] [ka]

[0099] (Preparation of Coating Solution for Hole Transport Layer) An o-dichlorobenzene solution containing 40 mM of carbazole compound A and 5.0 mM of 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (TPFB; manufactured by TCI) as an electron-accepting dopant was prepared. Next, this solution was heated and stirred at 150°C for 1 hour to prepare a coating solution for a hole transport layer.

[0100] (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.

[0101] The above-mentioned electron transport layer coating solution was then spin-coated onto the glass substrate at room temperature at a speed of 2000 rpm to a thickness of approximately 35 nm, and then heated on a hot plate at 150°C for 10 minutes to form an electron transport layer.

[0102] 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.

[0103] The hole transport layer coating solution (120 μL) was spin-coated onto this active layer at a speed of 2000 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.

[0104] On this hole transport layer, MoO3 having a thickness of 10 nm, IZO having a thickness of 30 nm, and silver having a thickness of 100 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.

[0105] [Example 2] A power generating device was fabricated and measured in the same manner as in Example 1, except that a carbazole compound B represented by the following formula (B) was used instead of the carbazole compound A. The results are shown in Table 1.

[0106] [ka]

[0107] Here, the carbazole compound B was synthesized by the method described in a prior art document (JP-A-2010-206191).

[0108] [Comparative Example 1] A power generating device was fabricated and measured in the same manner as in Example 1, except that poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA, manufactured by Sigma-Aldrich) was used as the hole transport layer coating solution instead of carbazole compound A. The results are shown in Table 1.

[0109] [Table 1]

[0110] As shown in Table 1, the power generating devices of Examples 1 and 2, which had hole transport layers containing carbazole compound A or B, were superior to Comparative Example 1 in conversion efficiency when using a low-illuminance white LED as a light source. Here, the ionization potential of the active layer in the power generation devices 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 layer was −5.9 eV or more and −5.3 eV or less. Therefore, it is considered that by using the carbazole compound according to the present invention, the energy states of the active layer and the hole transport layer fall into suitable ranges, and excellent conversion efficiency was achieved under low illuminance. On the other hand, in the power generating device of Comparative Example 1, the hole transport layer did not contain the carbazole compound according to the present invention, and therefore the conversion efficiency was poor. It should be noted that Example 1 is a reference example. [Explanation of symbols]

[0111] 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 power generating device, wherein the hole transport layer contains a carbazole compound represented by the following formula (II): 【Chemistry 1】 (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.

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 −5.3 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. 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 and a dopant.

6. The method for producing a power generating device according to claim 5 , wherein the dopant is a diaryliodonium salt containing trivalent iodine.

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