JP2023063837A - Power generation device and method for manufacturing the same - Google Patents

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 and a method for manufacturing the same are provided, the power generation device including: 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 triarylamine compound represented by a specific chemical formula.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a power generation device and a manufacturing method thereof.

2. Description of the Related Art A power generation device (photoelectric conversion element) in which an active layer, a buffer layer, and the like are arranged between a pair of electrodes is known. Organic-inorganic hybrid semiconductor compounds have been developed as materials for the active layer, and among them, compounds having a perovskite structure (perovskite semiconductor compounds) have attracted attention.
On the other hand, as a material for the hole transport layer, for example, a phthalocyanine-based organic semiconductor compound has been proposed (Patent Document 1).

JP 2017-066096 A

However, in the conventional hole-transporting layer, the power generation efficiency sometimes deteriorates in a low-illumination environment such as a room where fluorescent lamps, LEDs, and the like are used as light sources, which are important in energy harvesting applications.
An object of the present invention is to improve power generation efficiency under low illumination in a power generation device having an active layer containing an organic-inorganic hybrid semiconductor compound.

The present inventors have found that a power generation device having excellent power generation efficiency even in low-light environments such as indoors can be obtained by employing a hole transport layer containing a specific triarylamine compound. , completed the present invention. That is, the present invention has the following aspects.

（式（Ｉ）中、Ｑ１は下記式（Ｑ１－１）で表される基であり、Ｑ２は下記式（Ｑ２－１）で表される基であり、Ｑ３は下記式（Ｑ３－１）で表される基であり、ｎ^１、ｎ^２、ｎ^３、ｎ^４は、各々くり返し数である。）

（式（Ｑ１－１）、（Ｑ２－１）、（Ｑ３－１）において、Ｒ^１～Ｒ^１８は、各々独立に、水素原子、ハロゲン原子または置換基を有していてもよい有機基を表す。Ｒ^５はＲ^１と結合する単結合であってもよく、Ｒ^１０及びＲ^１１は互いに結合して環を形成していてもよく、Ｒ^１６及びＲ^１７は互いに結合して環を形成していてもよい。）
［２］前記式（Ｉ）におけるＱ１が下記式（Ｑ１－２）で表される基であり、Ｑ２が下記式（Ｑ２－２）で表される基であり、Ｑ３が下記式（Ｑ３－２）で表される基である、［１］に記載の発電デバイス。

（式（Ｑ１－２）、（Ｑ２－２）、（Ｑ３－２）において、Ｒ^３１～Ｒ^３６は、各々独立に、水素原子、ハロゲン原子または置換基を有していてもよい有機基を表す。Ｒ^２～Ｒ^４、Ｒ^６～Ｒ^８、Ｒ^９、Ｒ^１２、Ｒ^１３、Ｒ^１４、Ｒ^１５、Ｒ^１８は、各々前記式（Ｑ１－１）、（Ｑ２－１）、（Ｑ３－１）におけるものと同じである。）
［３］前記活性層のイオン化ポテンシャルが－６．０ｅＶ以上－５．７ｅＶ以下であり、かつ、前記活性層のバンドギャップが１．６ｅＶ以上２．３ｅＶ以下であるとともに、前記正孔輸送層のイオン化ポテンシャルが－５．８ｅＶ以上－５．２ｅＶ以下である、［１］又は［２］に記載の発電デバイス。
［４］前記有機無機ハイブリッド型半導体化合物が、ペロブスカイト構造を有する化合物である、［１］～［３］の何れか一項に記載の発電デバイス。
［５］前記活性層の厚みが２００ｎｍ以上８００ｎｍ以下である、［１］～［４］の何れか一項に記載の発電デバイス。
［６］色温度５０００Ｋの白色ＬＥＤ光を照射し、受光面の照度が２００ルクスであるときの光電変換効率が２５％以上である、［１］～［５］の何れか一項に記載の発電デバイス。
［７］［１］～［６］の何れか一項に記載の発電デバイスの製造方法であって、前記正孔輸送層を塗布法により形成する工程を有し、前記塗布法において、前記式（Ｉ）に記載のトリアリールアミン化合物およびドーパントを含有する液を塗布する、発電デバイスの製造方法。
［８］前記ドーパントが、３価のヨウ素を含むジアリールヨードニウム塩である、［７］に記載の発電デバイスの製造方法。 [1] 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 at least the active layer and the pair of electrodes a hole transport layer positioned between one and
A power-generating device, wherein the hole-transporting layer contains a triarylamine compound represented by the following formula (I).

(In formula (I), Q1 is a group represented by the following formula (Q1-1), Q2 is a group represented by the following formula (Q2-1), and Q3 is a group represented by the following formula (Q3-1). and each of n ¹ , n ² , n ³ and n ⁴ is a repeating number.)

(In formulas (Q1-1), (Q2-1), and (Q3-1), R ¹ to R ¹⁸ each independently represent a hydrogen atom, a halogen atom, or an optionally substituted organic group. R ⁵ may be a single bond bonded to R ¹ , R ¹⁰ and R ¹¹ may be bonded together to form a ring, R ¹⁶ and R ¹⁷ may be bonded together to form a ring may be.)
[2] Q1 in the formula (I) is a group represented by the following formula (Q1-2), Q2 is a group represented by the following formula (Q2-2), and Q3 is a group represented by the following formula (Q3- The power generation device according to [1], which is a group represented by 2).

(In formulas (Q1-2), (Q2-2), and (Q3-2), R ³¹ to R ³⁶ each independently represent a hydrogen atom, a halogen atom, or an optionally substituted organic group. R ² to R ⁴ , R ⁶ to R ⁸ , R ⁹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁸ are represented by the above formulas (Q1-1), (Q2-1) and (Q3 - Same as in 1).)
[3] The ionization potential of the active layer is −6.0 eV or more and −5.7 eV or less, the bandgap of the active layer is 1.6 eV or more and 2.3 eV or less, and the hole transport layer has The power generation device according to [1] or [2], which has an ionization potential of −5.8 eV or more and −5.2 eV or less.
[4] The power generation 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 generation device according to any one of [1] to [4], wherein the active layer has a thickness of 200 nm or more and 800 nm or less.
[6] The photoelectric conversion efficiency according to any one of [1] to [5], wherein a white LED light with a color temperature of 5000 K is irradiated and the photoelectric conversion efficiency is 25% or more when the illuminance of the light receiving surface is 200 lux. power generation device.
[7] The method for manufacturing the power generation device according to any one of [1] to [6], comprising a step of forming the hole transport layer by a coating method, wherein the coating method includes: A method for producing a power generation device, comprising applying a liquid containing the triarylamine compound according to (I) and a dopant.
[8] The method for producing a power generation device according to [7], wherein the dopant is a diaryliodonium salt containing trivalent iodine.

INDUSTRIAL APPLICABILITY According to the present invention, in a power generation device using an organic-inorganic hybrid semiconductor compound, the power generation efficiency can be improved particularly under a low illumination environment such as indoors.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which represents typically an example of embodiment of the electric power generation device of this invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view schematically showing an example of an embodiment of a solar cell provided with the power generation device of the present invention; BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view schematically showing an example of a solar cell module provided with the power generation device of the present invention;

A power generation device according to one embodiment of the present invention comprises 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, A power generation device comprising an active layer and a hole transport layer positioned between at least one of the pair of electrodes.
Here, the hole transport layer contains a specific triarylamine compound to be described later.

In the power generation device of the present embodiment, the ionization potential of the active layer is −6.0 eV or more and −5.7 eV or less, and the bandgap 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 preferably −5.8 eV or more and −5.2 eV or less.
The power generation device of the present invention is particularly excellent in power generation efficiency in a low illumination environment.
In this specification, the low illuminance environment generally means an environment of 10 to 5000 lux. The environment in which the power generation device of the present invention is applied is more preferably an environment of 100 to 300 lux, more preferably an environment of 200 lux.

Embodiments of the present invention are described in detail below. The description of the constituent elements described below is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to these contents as long as it does not exceed the gist of the present invention.

<Triarylamine compound>
The triarylamine compound used in the present invention is a compound represented by the following formula (I) (hereinafter referred to as "compound (1)").

In formula (I), Q1 is a group represented by the following formula (Q1-1), Q2 is a group represented by the following formula (Q2-1), and Q3 is a group represented by the following formula (Q3-1). and n ¹ , n ² , n ³ and n ⁴ are repeating numbers.

In formulas (Q1-1), (Q2-1) and (Q3-1), R ¹ to R ¹⁸ each independently represent a hydrogen atom, a halogen atom or an optionally substituted organic group. . R ⁵ may be a single bond bonded to R ¹ , R ¹⁰ and R ¹¹ may be bonded together to form a ring, and R ¹⁶ and R ¹⁷ may be bonded together to form a ring. may

Compound (1) is a compound useful as an organic semiconductor compound. In addition, it has high electrochemical stability and high hole transport ability, and is suitable for wet film formation.
Compound (1) is electronically robust compared to other aromatic tertiary amines because the lone pair of electrons on the basic nitrogen atom is stabilized by the aromaticity of the triarylamino group. , and it is considered that a more appropriate hole transport layer can be maintained.

Furthermore, while compound (1) is a low-molecular-weight compound in which aromatic rings are linked on a straight chain, by appropriately selecting R ¹ to R ¹⁸ in the formula, Solubility in organic solvents and the like can be sufficiently ensured, and it is also suitable for coating film properties. Compound (1) can improve interlayer adhesion after film formation by being excellent in coating film properties.

Compound (1) can be stably oxidized by a dopant and exhibit better semiconductor properties. In the power generation device of the present invention, since the hole transport layer contains the compound (1), the ionization potential of the hole transport layer can be set to a suitable range described later, and high power generation efficiency can be achieved under low illuminance. can do.

A semiconductor compound generally refers to a compound that can be used as a semiconductor material that exhibits semiconductor properties. As used herein, "semiconductor properties" are defined by the magnitude of carrier mobility in the solid state. Carrier mobility, as is well known, is a measure of how fast (or how much) a charge (electron or hole) can be moved.

Specifically, the “semiconductor” in this specification preferably has a carrier mobility of 1.0×10 ⁻⁶ cm ² /V·s or more at room temperature (25° C.), more preferably 1.0×10 ⁻ It is 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. Note that the carrier mobility can be measured, for example, by measuring IV characteristics of a field effect transistor or by a time-of-flight method.

Halogen atoms as options for R ¹ to R ¹⁸ in formulas (Q1-1), (Q2-1) and (Q3-1) include fluorine and chlorine atoms.
The organic groups that are options for R ¹ -R ¹⁸ may be aliphatic or aromatic groups. Among them, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group or an aromatic group is preferred.

The aromatic groups that are optional for R ¹ -R ¹⁸ may be aromatic hydrocarbon groups or aromatic heterocyclic groups. In addition, it may be either a monocyclic structure or a polycyclic structure, may have a condensed ring structure, or have a structure in which these are connected by any divalent linking group or single bond (direct bond) may be

Examples of the aryl group possessed by the aromatic hydrocarbon group as an option for R ¹ to R ¹⁸ and the aryloxy group as an option for R ¹ to R ¹⁸ include groups derived from the following [aromatic hydrocarbon group P1] can be mentioned. Further, examples of the aromatic heterocyclic group that can be selected for R ¹ to R ¹⁸ include groups derived from the following [aromatic heterocyclic group P2].

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

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

From the viewpoint of solubility in organic solvents and heat resistance, R ¹ to R ¹⁸ are preferably aromatic groups which may have substituents, such as benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, triphenylene ring, pyrene ring. A ring-derived group selected from the group consisting of a ring, a thiophene ring, a pyridine ring, and a fluorene ring is more preferred.

A group in which one or two or more rings selected from the above group are directly bonded or linked by a -CH=CH- group is also preferred, and a group derived from biphenylene and terphenylene is more preferred.
R ⁵ -R 1 group when R ⁵ is a single bond bonded to ^{R 1 ,} R ¹⁰ -R ¹¹ group when R ¹⁰ and R ¹¹ are bonded together to form a ring, and R ¹⁶ and R ¹⁷ are preferably a biphenylene group or a terphenylene group when the R ¹⁶ -R ¹⁷ groups are bonded to each other to form a ring.

The substituents that R ¹ to R ¹⁸ may have are preferably non-crosslinkable substituents. A non-crosslinkable substituent means a group that does not contain a crosslinkable group. That is, R ¹ to R ¹⁸ may have substituents, but preferably do not have substituents containing crosslinkable groups.

The term "crosslinkable group" as used herein refers to a group that reacts with the same or different groups of other nearby molecules to form new chemical bonds by heat and/or irradiation with active energy rays.
The non-crosslinkable substituents are not particularly limited, but include, for example, one or more selected from the following [substituent group Z1].

[Substituent group Z1]
preferably an alkyl group 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, 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;
Dialkylamino groups preferably having 2 to 24 carbon atoms, more preferably 2 to 12 carbon atoms such as dimethylamino group and diethylamino group;

Acyl groups preferably having 2 to 24 carbon atoms, preferably 2 to 12 carbon atoms such as acetyl group and benzoyl group;
halogen atoms such as fluorine atoms and chlorine atoms;
preferably a haloalkyl group having 1 to 2 carbon atoms, more preferably 1 to 6 carbon atoms, such as a trifluoromethyl group;
preferably an alkylthio group having 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms such as a methylthio group and 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, a pyridylthio group;
siloxy groups preferably having 2 to 36 carbon atoms, more preferably 3 to 24 carbon atoms such as trimethylsiloxy group and triphenylsiloxy group;
cyano group;
Aromatic hydrocarbon groups preferably having 6 to 36 carbon atoms, more preferably 6 to 24 carbon atoms such as phenyl group and naphthyl group;
An aromatic heterocyclic group preferably having 3 to 36 carbon atoms, more preferably 4 to 24 carbon atoms such as thienyl group and pyridyl group;
Each of the above substituents may further have a substituent, examples of which include the groups exemplified in the substituent group Z1.

The formula weight of the substituent group Z1 is preferably 500 or less, more preferably 250 or less, including the further substituted groups.
From the viewpoint of improving the solubility in organic solvents, the substituent group Z1 which R ¹ to R ¹⁸ may have is each independently an alkyl group having 1 to 12 carbon atoms and an alkoxy group having 1 to 12 carbon atoms. is preferred.

The crosslinkable substituents that R ¹ to R ¹⁸ may have are not particularly limited, but include, for example, one or more selected from the following [substituent group Z2].
[Substituent group Z2]

In the formula, R ²¹ to R ²⁵ each independently represent a hydrogen atom or an alkyl group. Ar41 represents an aromatic group optionally having a substituent. Incidentally, the benzocyclobutene ring may have a substituent. Moreover, the substituents may form a ring.

As the crosslinkable group, a cyclic ether group such as an epoxy group or an oxetane group, or a cationically polymerizable group such as a vinyl ether group is preferable in terms of high reactivity and easy crosslinkage with an organic solvent. Among them, an oxetane group is particularly preferable because the rate of cationic polymerization can be easily controlled, and a vinyl ether group is preferable because deterioration of the device due to generation of hydroxyl groups during cationic polymerization hardly occurs.

In compound (1), Q1 in formula (I) is a group represented by the following formula (Q1-2), Q2 is a group represented by the following formula (Q2-2), and Q3 is a group represented by the following formula ( A group represented by Q3-2) is preferable.

In formulas (Q1-2), (Q2-2) and (Q3-2), R ³¹ to R ³⁶ each independently represent a hydrogen atom, a halogen atom or an optionally substituted organic group. . R ² to R ⁴ , R ⁶ to R ⁸ , R ⁹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁸ are represented by the above formulas (Q1-1), (Q2-1) and (Q3-1), respectively. ) is the same as in
R ³¹ to R ³⁶ are preferably alkyl groups, more preferably alkyl groups having 1 to 24 carbon atoms, still more preferably alkyl groups having 1 to 12 carbon atoms, and particularly preferably methyl and ethyl groups.

n ¹ and n ² in formula (I) are preferably 1-8, more preferably 2-6. n ³ and n ⁴ are preferably 1-8, more preferably 2-6.
When n ¹ to n ⁴ are in the above preferable range, the solubility in a solvent is maintained while securing the hole transport ability and the ionization potential (HOMO) at a certain depth due to the delocalization of the electron distribution. It becomes easier, and compatibility with film-forming property becomes possible.
In addition, n ¹ in formula (I) is the same as n ² , and n ³ is n ⁴ because symmetry can be maintained in order to prevent localization of charges in the molecule and to ensure charge transfer ability. preferably the same.

The molecular weight of compound (1) is preferably high from the standpoint of robustness and heat resistance, and is preferably low from the standpoint of solubility in a solvent. Therefore, the molecular weight of compound (1) 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.

Each formula weight of ^{R 1} to R ¹⁸ (R ⁵ -R 1 group when R ⁵ is a single bond bonding to ^{R 1 ,} R ¹⁰ - when R 10 and R ¹¹ are bonded to each other to form a ring) R ¹¹ group, and when R ¹⁶ and R ¹⁷ are bonded to each other to form a ring, each formula weight of R ¹⁶ -R ¹⁷ groups) is preferably high from the viewpoint of robustness and heat resistance. In terms of solubility in a solvent, it is preferably low. Therefore, the formula weight of each of R ¹ to R ¹⁸ is preferably 72 or more, more preferably 144 or more, including any substituents. On the other hand, it is preferably 1000 or less, more preferably 600 or less.

In compound (1), a 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 (I) is attached to two benzene rings. Continuity enhances the contribution to hole transport properties.
In addition, when the triarylamine structure does not have a crosslinkable functional group, compared to a compound having a crosslinkable functional group, it is easier to reduce the number of structures that are not involved in hole-transporting properties, so that it can be strongly involved in hole-transporting properties.
Furthermore, when no crosslinkable functional group exists in the triarylamine structure, it is not necessary to use a raw material for introducing a crosslinkable group during synthesis. Therefore, the manufacturing cost is also low.

The method for synthesizing compound (1) is not particularly limited, but it can be synthesized, for example, by the method described in JP-A-2009-263665.
The structure and content of compound (1) in the hole-transporting layer are analyzed by methods such as ¹ H-NMR, high-efficiency liquid chromatography (HPLC), and liquid chromatography-mass spectrometry (LC-MS). be able to.

<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 the 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 can be, for example, a hole transport layer. A buffer layer 104 may be arranged between the upper electrode 105 and the active layer 103 . The buffer layer 104 can be, for example, an electron transport layer. Conversely, buffer layer 102 and buffer layer 104 may be an electron transport layer and a hole transport layer, respectively. The power generation device 100 may have a substrate 106 and may have other layers not shown such as an insulator layer and a work function tuning layer.

[Active layer]
In the embodiment of FIG. 1, the active layer 103 is the layer in which photoelectric conversion takes place. When the power generation device 100 receives light, the light is absorbed by the active layer 103 to generate carriers, and the generated carriers are extracted from the lower electrode 101 and the upper electrode 105 .
In this embodiment, the active layer contains an organic-inorganic hybrid semiconductor compound. An organic-inorganic hybrid semiconductor compound is a compound in which an organic component and an inorganic component are combined at the molecular level or nano level, and is a compound exhibiting semiconductor properties.

In the present 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 is a semiconductor compound having a perovskite structure. The perovskite structure is a crystal structure represented by a composition of ABX ₃ such as perovskite (CaTiO ₃ ; perovskite). In the perovskite structure having this ABX ₃ composition, six X ions regularly surround the B site ion to form a BX ₆ -octahedron.

Although there are no particular restrictions on the perovskite semiconductor compound, for example, Galasso et al. Structures and Properties of Inorganic Solids, Chapter 7 - Perovskite types and related structures. Further, for example, perovskite semiconductor compounds include AMX _3- type compounds represented by the general formula AMX ₃ and A ₂ MX _4- type compounds represented by the general formula A ₂ MX ₄ . Here, M is a divalent cation, A is a monovalent cation, and X is a monovalent anion.

Although there is no particular limitation on the monovalent cation A, those described in the above-mentioned Galasso can be used. More specific examples include cations containing elements of 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 no particular restrictions on the substituents, either. Specific examples of optionally substituted ammonium ions include alkylammonium ions and arylammonium ions. In particular, in order to avoid steric hindrance, a monoalkylammonium ion having a three-dimensional crystal structure is preferable, and from the viewpoint of improving stability, it is preferable to use an alkylammonium ion substituted with one or more fluorine groups. Moreover, as the cation A, two or more kinds of cations may be used in combination.

Specific examples of the monovalent cation A include methylammonium ion, methylammonium monofluoride ion, methylammonium difluoride ion, methylammonium trifluoride ion, ethylammonium ion, isopropylammonium ion, n-propylammonium ion, and isobutylammonium ion. , n-butylammonium ion, t-butylammonium ion, dimethylammonium ion, diethylammonium ion, phenylammonium ion, benzylammonium ion, phenethylammonium ion, guanidinium ion, formamidinium ion, acetamidinium ion or imidazolium ions and the like.

Although the divalent cation M is not particularly limited, it is preferably a divalent metal cation or metalloid cation. Specific examples include cations of Group 14 elements of the periodic table, and more specific examples include lead cations (Pb ²⁺ ), tin cations (Sn ²⁺ ), and germanium cations (Ge ²⁺ ). Moreover, as the cation M, two or more kinds of cations may be used in combination. From the viewpoint of obtaining a stable power generation device, it is particularly preferable to use lead cations or two or more kinds of cations containing lead cations.

Examples of monovalent anions X include halide ions, acetate ions, nitrate ions, sulfate ions, borate ions, acetylacetonate ions, carbonate ions, citrate ions, sulfur ions, tellurium ions, thiocyanate ions, titanates. ions, zirconate ions, 2,4-pentanedionate ions, silicofluoride ions, and the like.

In one embodiment of the present invention, X includes halide ions or combinations of halide ions and other anions. One type of X may be used, or two or more types may be used in any combination and ratio. Here, the bandgap of the active layer described above can be adjusted by the type and combination of X. X is preferably a halide ion such as chloride ion, bromide ion and iodide ion, more preferably bromide ion and iodide ion, since the bandgap of the active layer tends to be moderately narrowed.

The perovskite semiconductor compound is preferably a halide-based organic-inorganic perovskite semiconductor compound. Specific _{examples of perovskite semiconductor compounds include CH3NH3PbI3 , CH3NH3PbBr3 , CH3NH3PbCl3 , CH3NH3SnI3 , CH3NH3SnBr3 , CH3NH3SnCl3 .} , CH ₃ NH ₃ PbI _(3-x) Cl _x , CH ₃ NH ₃ PbI _(3-x) Br _x , CH ₃ NH ₃ PbBr _(3-x) Cl _x , CH ₃ NH ₃ Pb _(1-y) Sn _y I ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y Br ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y Cl ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y I _{(3 -x)} Cl _x , CH ₃ NH ₃ Pb _(1-y) Sn _y I _(3-x) Br _x , and CH ₃ NH ₃ Pb _(1-y) Sn _y Br _(3-x) Cl _x , and , the above compounds in which CH ₃ NH ₃ is replaced with CFH ₂ NH ₃ , CF ₂ HNH ₃ , or CF ₃ NH ₃ , and the like. Note that x is 0 or more and 3 or less, and y is any value of 0 or more and 1 or less.

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 be a laminate structure formed of multiple layers containing different materials or having different components.

The amount of the organic-inorganic hybrid semiconductor compound contained in the active layer is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass so as to obtain good semiconductor properties. The above should be considered. There is no particular upper limit to the amount of the organic-inorganic hybrid semiconductor compound contained in the active layer. Further, the active layer may contain additives other than the organic-inorganic hybrid semiconductor compound contained in the active layer. Examples of additives include inorganic or organic compounds, such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates or ammonium salts.

The ionization potential of the active layer is preferably high in terms of sufficiently filling the absorbable region in the long wavelength region with respect to the light source in the visible light region that emits white light and easily increasing the power generation efficiency. Therefore, specifically, -6.0 eV or more is preferable, -5.95 eV or more is more preferable, and -5.9 eV or more is even more preferable.
On the other hand, it is preferable that the ionization potential of the active layer is low from the viewpoint of reducing the loss of the voltage obtained with respect to the light source in the visible light region and easily increasing the power generation efficiency. Therefore, specifically, -5.7 eV or less is preferable, and -5.8 eV or less is more preferable.

The bandgap of the active layer should be large in that the energy required for separating the excitons generated in the semiconductor by low-intensity light such as indoor light into positive and negative charges is sufficiently satisfied, and the power generation efficiency tends to be high. is preferred. Therefore, specifically, it is preferably 1.6 or more, more preferably 1.65 eV or more, still more preferably 1.7 eV or more, and particularly preferably 1.75 eV or more.
On the other hand, the bandgap of the active layer is preferably small in that it provides an appropriate amount of energy for excitons generated by indoor light or the like (does not result in excess energy) and tends to increase power generation efficiency. Therefore, specifically, it is preferably 2.3 eV or less, more preferably 2.25 eV or less, still more preferably 2.2 eV or less, and most preferably 2.15 eV or less.

In addition, since it is particularly easy to improve the power generation efficiency for low-illuminance light sources such as fluorescent lamps and LED lamps, which are visible light sources widely used indoors and indoors, both the ionization potential and bandgap of the active layer are the above-mentioned preferable. A range is particularly preferred. More specifically, it is particularly preferable that the active layer has an ionization potential of -6.0 eV or more and -5.7 eV or less and a bandgap of 1.6 eV or more and 2.3 eV or less.

As a method of adjusting the ionization potential of the active layer to the desired range, for example, it can be adjusted by the kind of the organic-inorganic hybrid semiconductor compound. Specifically, for example, when the above perovskite semiconductor compound is used, it can be adjusted depending on the type of its cation. More specifically, the composition of an organic or inorganic ammonium salt, which is a precursor used for forming a perovskite semiconductor compound described below, is mixed at a composition ratio containing a modified component, and the mixture is appropriately adjusted by, for example, processing. be done.

As a method for adjusting the bandgap of the active layer to the desired range, for example, it can be adjusted according to the type of the organic-inorganic hybrid semiconductor compound. Specifically, for example, when the perovskite semiconductor compound described above is used, it can be adjusted by the type and ratio of its anions. More specifically, the selection of the halogen type ratio of the metal halide compound used as a precursor for forming the perovskite semiconductor compound described later, or the composition of the organic or inorganic ammonium salt used as the precursor, the corresponding halogen composition, For example, they may be mixed in a composition ratio containing the modified component and processed.

There is no particular limitation on the thickness of the active layer. The thickness of the active layer is preferably thick because it can absorb more light. Specifically, it is preferably 10 nm or more, more preferably 50 nm or more, still 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 layer is preferable in that the series resistance is reduced and the charge extraction efficiency is likely to be increased. 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, the thickness of the active layer is particularly preferably 200 nm or more and 800 nm or less.

The method of forming the active layer is not particularly limited, and it 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 preferable because the active layer can be easily formed. For example, there is a method of forming an active layer by applying a coating liquid containing an organic-inorganic hybrid semiconductor compound or a precursor thereof and, if necessary, drying by heating. Further, after applying the coating liquid, the organic-inorganic hybrid semiconductor compound can be precipitated by further applying a solvent in which the organic-inorganic hybrid semiconductor compound has low solubility.

A precursor of an organic-inorganic hybrid semiconductor compound means a compound that becomes an organic-inorganic hybrid semiconductor compound after being applied as a coating liquid. As a specific example, an organic-inorganic hybrid semiconductor compound precursor that becomes an organic-inorganic hybrid semiconductor compound by heating can be used.

For example, a compound represented by the general formula AX, a compound represented by the general formula _MX2 , and a solvent are mixed and heated and stirred to prepare a coating liquid, and the coating liquid is applied and heated. By drying, an active layer containing a perovskite semiconductor compound represented by the general formula AMX ₃ can be produced. 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.

Further, a coating liquid obtained by mixing a compound represented by the general formula _MX2 and a solvent and heating and stirring is applied, and then the compound represented by the general formula AX and the solvent are mixed. An active layer containing a perovskite semiconductor compound represented by the general formula AMX ₃ may be produced by applying a coating liquid.

Any method can be used to apply the coating liquid, and examples include spin coating, ink jet method, doctor blade method, drop casting method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, A spray coating method, an air knife coating method, a wire barber coating method, a pipe doctor method, an impregnation/coating method, a curtain coating method, or the like can be used.

The active layer in the power generation device of the present invention may contain an organic-inorganic hybrid semiconductor compound other than the perovskite semiconductor compound. Examples of organic-inorganic hybrid semiconductor compounds other than perovskite semiconductor compounds include organic alkoxide coordination metal oxides and organic molecular coordination transition metal complexes.

As described above, in the power generation device of the present embodiment, the ionization potential of the active layer is −6.0 eV or more and −5.7 eV or less, and the bandgap of the active layer is 1.6 eV or more and 2.3 eV or less. In addition, the ionization potential of the hole transport layer is preferably -5.8 eV or more and -5.2 eV or less.

The ionization potential is the lowest energy (eV) of light required for the irradiation energy to eject a photoelectron.
The ionization potential as used herein 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. .

The open counter measures ionized oxygen molecules by capturing photoelectrons in oxygen molecules in the atmosphere. That is, emitted photoelectrons can be observed as ionized oxygen molecules.
As the energy of the irradiated light is increased, the threshold at which photoelectron emission starts becomes a value corresponding to the ionization potential (eV).

The number of photoelectrons generated when light of a certain energy is applied to the surface to be evaluated basically depends only on the characteristics of the vicinity of the outermost surface irradiated with light, and the film thickness of the evaluation target, It is not affected by 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.
Therefore, it is not necessary to strictly match the thickness of the active layer or the hole transport layer used for measurement, and the active layer may be formed with a thickness of, for example, 400 nm to 600 nm and used for measurement. The hole transport layer may be formed to a thickness of, for example, 5 nm to 100 nm and used for measurement.

Although the presence or absence of a layer formed under the film under evaluation and the type of layer formed under the film under evaluation do not substantially affect the measurement results, a conductive layer with thin ITO (indium tin oxide) It is effective to reduce noise and increase the reliability of the results by forming a film of only the object to be evaluated on the flexible glass and measuring it.
A commercial product can be used for the electrically conductive glass provided with the thin film ITO used in this case. The resistance value (surface resistivity) of the thin film ITO is not particularly limited, and can be, for example, 2Ω/sq. to 1000Ω/sq.

The bandgap is the energy level (and the difference in energy between them) between the top of the highest energy band occupied by electrons in the band structure (the valence band) and the bottom of the lowest empty band (the conduction band) is.
The bandgap of the active layer in this specification is a value calculated from the absorption edge wavelength and absorbance of the semiconductor compound, which is assumed to be the same as the bandgap of the semiconductor compound forming the active layer.

[Buffer layer]
In FIG. 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 transfer 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. is more preferable.

[Hole transport layer]
The hole transport layer contains compound (1) described above.
Compound (1) can delocalize electrons by having an extended conjugation site component, and has high stability. Therefore, in the power generation device of the present invention, since the hole transport layer contains the compound (1), the ionization potential can be set to a suitable range described later, and high power generation efficiency can be achieved under low illuminance. can be done.
Compound (1) is preferable in that it has no molecular weight distribution, is easy to be highly purified, and is easy to produce at low cost, as compared with polymer compounds such as polytriarylamine.

The content of the compound (1) contained in the hole transport layer is preferably large from the viewpoint that the ionization potential of the hole transport layer can be easily adjusted to the suitable range described below. Therefore, specifically, it is preferably contained in the hole transport layer (total mass: 100% by mass) in an amount of 40% by mass or more, more preferably 50% by mass or more, and more preferably 60% by mass or more. more preferably. Here, the upper limit is 100% by mass, but when the carrier mobility is increased by using a dopant when forming the hole transport layer, the total amount of the component derived from the dopant is 100% by mass.

The hole transport layer may contain a semiconductor compound other than the compound (1) as long as the effects of the present invention are exhibited. As other semiconductor compounds, for example, conventionally known semiconductor compounds may be used. Various low-molecular compounds and high-molecular compounds are known as other organic semiconductor compounds. Low-molecular-weight organic semiconductor compounds include polycyclic aromatic compounds, and specific examples include acene compounds such as tetracene or pentacene, oligothiophene compounds, phthalocyanine compounds, perylene compounds, rubrene compounds, compounds ( Arylamine compounds other than 1), carbazole compounds, and the like are included. Further, as the high-molecular organic semiconductor compound, polythiophene-based polymer, polyacetylene-based polymer, polyaniline-based polymer, polyphenylene-based polymer, polyphenylene vinylene-based polymer, polyfluorene-based polymer, or conjugated polymer such as polypyrrole-based polymer, or triaryl Arylamine polymers such as amine polymers are included.

When forming the hole transport layer, it is preferable to use a dopant in addition to the semiconductor compound such as the compound (1) described above. By using a dopant, properties such as conductivity and hole transport ability can be controlled.
A large amount of the dopant is preferable because the conductivity and the hole-transporting ability of the hole-transporting layer are likely to be improved. Therefore, specifically, the amount of the dopant is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, further preferably 0.05 parts by mass or more, with respect to 100 parts by mass of the semiconductor compound. .1 part by mass or more is particularly preferred.

On the other hand, it is preferable that the amount of the dopant is small because it suppresses the generation of leakage current in the power generation device and facilitates the improvement of the power generation efficiency particularly in a low illumination environment. Therefore, specifically, it 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 semiconductor compound.
That is, when a dopant is used to form the hole transport layer, the amount of the dopant is particularly preferably 0.001 to 12 parts by mass with respect to 100 parts by mass of the semiconductor compound.

The use of dopants in forming the hole transport layer allows the conductivity and hole transport capability of the hole transport layer to be more optimized relative to the active layer.
Substances that can be used as dopants include, for example, hypervalent iodine compounds, boron compounds such as tetrakis(pentafluorophenyl)borate, tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2 molybdenum compounds such as -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 forming the hole transport layer. As the dopant, a hypervalent iodine compound is preferred because it is highly soluble and easily produces an electron-accepting active site that functions as an oxidant by heating or the like.

Hypervalent iodine compounds are known to act as dopants for organic semiconductor compounds and exhibit electron-accepting properties (that is, act as oxidants). Also, the electron-accepting dopant can improve the conductivity or hole-transporting ability of the organic semiconductor compound by removing electrons from the organic semiconductor compound.

A hypervalent iodine compound is a compound containing hypervalent iodine and is defined as a compound containing iodine with a valence of 3 or higher in the oxidation number. For example, the dopant is preferably an iodine (III) compound or an iodine (V) compound. 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 having a structure in which iodobenzene is oxidized, such as (diacetoxyiodo)benzene, and diaryliodonium salts. The dopant is preferably an organic compound containing trivalent iodine, more preferably a diaryliodonium salt, in that it exhibits good electron-accepting properties and is less likely to cause a reverse reaction if the molecule is destroyed during the oxidation process. .

A diaryliodonium salt is a salt having the [Ar-I ⁺ -Ar]X ^- structure. Here, two Ars each represent an aromatic group. The aromatic group is not particularly limited, and examples thereof include aromatic hydrocarbon groups such as those exemplified in the aromatic hydrocarbon group P1 and aromatic heterocyclic groups such as those exemplified in the aromatic heterocyclic group P2. X ⁻ represents any anion. X ^- includes, for example, halide ion, trifluoroacetate ion, tetrafluoroborate ion, tetrakis(pentafluorophenyl)borate ion, and the like. X ^{1 −} is preferably an anion having a fluorine atom in terms of high solubility and smooth progress of the coating liquid production reaction.

Preferred examples of dopants include those represented by the following formula (II). In formula (II), X ^- represents an arbitrary anion, and specific examples are as described above.
[R ⁵¹ -I ⁺ -R ⁵² ]X ^- (II)

In formula (II), R ⁵¹ and R ⁵² are each independently a monovalent organic group. Examples of monovalent organic groups include aliphatic groups and aromatic groups. Examples of aliphatic groups include aliphatic hydrocarbon groups having 1 to 20 carbon atoms or aliphatic heterocyclic groups having 4 to 20 carbon atoms.
Specifically, for example, the aliphatic group includes an alkyl group containing a cycloalkyl group, an alkenyl group, or an alkynyl group, and specific examples include a methyl group, an ethyl group, a butyl group, a cyclohexyl group, or a tetrahydro A furyl group and the like can be mentioned.

The aromatic group includes, for example, an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms. Specific examples include a phenyl group, a naphthyl group, a biphenyl group, a thienyl group, a pyridyl group, and the like.

In addition, said aliphatic group and aromatic group may have a substituent. Examples of substituents include halogen atoms, hydroxyl groups, cyano groups, amino groups, carboxyl groups, ester groups, alkylcarbonyl groups, acetyl groups, sulfonyl groups, silyl groups, boryl groups, nitrile groups, alkyl groups, alkenyl groups, and alkynyl groups. groups, alkoxy groups, thio groups, seleno groups, aromatic hydrocarbon groups, aromatic heterocyclic groups, and the like.

R ⁵¹ and R ⁵² are preferably aromatic hydrocarbon groups having 6 to 20 carbon atoms, more preferably phenyl groups. Here, the aromatic hydrocarbon group preferably has no substituent or has an alkyl group having 1 to 6 carbon atoms. R ¹¹ and R ¹² are particularly preferably phenyl groups having an alkyl group at the para-position.

The dopant dissolves in various solvents and is easily mixed with the semiconductor compound, and the semiconductor compound is easily oxidized by treatments such as heating, light irradiation, and mixing with a co-oxidizing agent, and is easy to form a uniform film. It preferably has any partial structure represented by IVa) to (IVf).

The ionization potential of the hole-transporting layer is preferably within a specific range in terms of good matching with holes generated in the active layer and easy suppression of energy loss. Specifically, it is preferably −5.8 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 −5.2 eV or less, more preferably −5.4 eV or less, still more preferably −5.45 eV or less, and particularly preferably −5.5 eV or less. That is, it is particularly preferable that the ionization potential of the hole transport layer is −5.8 eV or more and −5.2 eV or less.

The ionization potential of the hole transport layer can be adjusted by using compound (1) as described above. As a more detailed method for adjusting the ionization potential to the desired range, for example, in compound (1), the electronic state of the compound is controlled by appropriately arranging the types and positions of the substituents of the aromatic compound. to do. In addition, the electronic state of the compound contained in the hole-transport layer is adjusted, that is, the whole or part of the compound is oxidized or reduced by using a dopant or the like described later in the hole-transport layer. be done.

The thickness of the hole transport layer of the power generation device according to the present invention is such that when the active layer located between the upper and lower electrodes has a high charge transport ability, the current is generated by forming a conductive path through the upper and lower electrodes and the active layer. It is preferable that the thickness is thick in terms of preventing the leakage of . Therefore, specifically, it is preferably 20 nm or more, more preferably 40 nm or more, and even more preferably 60 nm or more. On the other hand, it is preferable that the hole transport layer is thin in terms of resistance in charge transport by the hole transport layer and cost reduction by saving the amount of the compound contained in the hole transport layer. Specifically, it is preferably 1000 nm or less, more preferably 750 nm or less, still more preferably 600 nm or less, particularly preferably 500 nm or less, and most preferably 400 nm or less.

[electrode]
In FIG. 1, the electrodes have the function of collecting holes and electrons generated by light absorption in the active layer 103 . A power generation device 100 according to an embodiment of the present invention has a pair of electrodes, one of which is called an upper electrode and the other is called a lower electrode. When the power generation device 100 has or is provided on a substrate, the electrode closer to the substrate can generally be referred to as the lower electrode, and the electrode farther from the substrate can be referred to as the upper electrode. Also, the transparent electrode can be called a lower electrode, and the electrode having a lower transparency than the lower electrode can be called an upper electrode. A power generation device 100 shown in FIG. 1 has a lower electrode 101 and an upper electrode 105 .

As the pair of electrodes, an anode suitable for collecting holes and a cathode suitable for collecting electrons can be used. In this case, the power generation device 100 may have a forward configuration with the bottom electrode 101 being the anode and the top electrode 105 being the cathode, or the bottom electrode 101 being the cathode and the top electrode 105 being the anode. It may have an inverted configuration.

Either one of the pair of electrodes may be translucent, or both may be translucent. Having translucency 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, particularly preferably 70% or more, because more light passes through the transparent electrode and reaches the active layer. The sunlight transmittance can be measured with a spectrophotometer (eg, U-4100 manufactured by Hitachi High-Tech).

There are no particular limitations on the lower electrode 101 and upper electrode 105, or the constituent members of the anode and cathode, and the manufacturing method thereof, and known techniques can be used. For example, members described in known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, or Japanese Patent Application Laid-Open No. 2012-191194 and manufacturing methods thereof can be used.

[Electron transport layer]
The power generation device according to the present invention may have an electron transport layer. Any material that can improve the efficiency of electron extraction from the active layer to the cathode can be used as the material of the electron transport layer. Specific examples include inorganic compounds, organic compounds, or perovskite semiconductor compounds described in known documents such as WO 2013/171517, WO 2013/180230, and JP-A-2012-191194. For example, inorganic compounds include salts of alkali metals such as lithium, sodium, potassium, or cesium, and metal oxides such as zinc oxide, titanium oxide, aluminum oxide, or indium oxide. Examples of organic compounds include bathocuproine (BCP), bathophenanthrene (Bphen), (8-hydroxyquinolinato)aluminum (Alq ₃ ), boron compounds, oxadiazole compounds, benzimidazole compounds, and naphthalenetetracarboxylic anhydride (NTCDA). , perylenetetracarboxylic anhydride (PTCDA), fullerene compounds, or phosphine compounds having a Group 16 element of the periodic table and a double bond, such as phosphine oxide compounds or phosphine sulfide compounds.

When the power generation device according to the present invention is provided with an electron transport layer, the thickness thereof is such that when the active layer located between the upper and lower electrodes has a high charge transport ability, the conduction path through the upper and lower electrodes and the active layer. A thick layer is preferable because current leakage due to formation is unlikely to occur, the influence of unevenness of the lower electrode can be covered, and the wettability of the active layer can be easily controlled. Therefore, specifically, it is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. On the other hand, it is preferable that the electron transport layer is thin in terms of resistance in charge transport by the electron transport layer and cost reduction by saving the amount of the compound contained in the electron transport layer. Specifically, it is preferably 200 nm or less, more preferably 150 nm or less, and even more preferably 10 nm or less.

[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 base material 106 that serves as a support, but the power generation device according to the present invention may not have the base material 106 . The material of the substrate 106 in the case of having a substrate is not particularly limited as long as it does not significantly impair the effects of the present invention. Materials described in publicly known documents such as JP-A-2003-300160 can be used.

[Method for producing power generation device]
The method for producing the power generation device of the present invention is not particularly limited as long as it is a method that allows the compound (1) to be contained in the hole transport layer, and a known method for producing a power generation device using a perovskite semiconductor compound. can be applied. For example, the hole transport layer can be formed by preparing a coating liquid containing the compound (1), a dopant, and a solvent and using a wet film formation method such as a spin coating method or an inkjet method. An electron transport layer can also be formed by a similar coating method. These buffer layers can also be formed by a dry film-forming method such as a vacuum deposition method.

However, the hole transport layer is preferably formed by a coating method, and more preferably by coating a liquid containing the compound (1) and a dopant. That is, the method for producing the power generation device of the present invention has a step of forming a hole transport layer by a coating method, and in this coating method, a liquid containing the above-described compound (1) and a dopant can be applied. more preferred.

In FIG. 1 , the power generation device 100 can be manufactured by laminating each layer constituting the power generation device 100 . For example, a known method such as a sheet-to-sheet (sheet-fed) method or a roll-to-roll method can be applied.
In addition, the roll-to-roll method is a method in which a flexible base material wound in a roll is unwound and processed while being intermittently or continuously transported until it is wound up by a winding roll. . According to the roll-to-roll method, long substrates on the order of km can be collectively processed, so the roll-to-roll method is more suitable for mass production than the sheet-to-sheet method.

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 production equipment of the roll-to-roll method, but the outer diameter is preferably 5 m or less, more preferably 3 m or less, and still more preferably 1 m or less. is. On the other hand, it is preferably 10 cm or longer, more preferably 20 cm or longer, and even more preferably 30 cm or longer. The outer diameter of the roll core is preferably 4 m or less, more preferably 3 m or less, still more preferably 0.5 m or less. On the other hand, it is preferably 1 cm or more, more preferably 3 cm or more, still more preferably 5 cm or more, particularly preferably 10 cm or more, and most preferably 20 cm or more.

With these diameters, the rolls are easy to handle, and the layers formed in each step are less likely to be destroyed by bending stress. The roll width is preferably 5 cm or more, more preferably 10 cm or more, still 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. The large width makes the roll easy to handle and increases the degree of freedom in the size of the power generation device.

When manufacturing the power generation device 100, the power generation device 100 may be heated after the upper electrode 105 is laminated (this heating process may be referred to as an annealing treatment process).

The annealing process increases the adhesion between each layer of the power generation device 100, for example, the adhesion between the buffer layer 102 and the lower electrode 101, the buffer layer 102 and the active layer 103, etc., and improves the thermal stability and durability of the power generation device. It is preferable to carry out at a high temperature from the viewpoint that the properties and the like can be improved. Specifically, the temperature is preferably 50°C or higher, more preferably 80°C or higher. On the other hand, it is preferable to carry out at a low temperature in that the organic compound contained in the power generation device 100 is difficult to thermally decompose. Specifically, the temperature is preferably 300° C. or lower, more preferably 280° C. or lower, and even more preferably 250° C. or lower. In the annealing treatment step, stepwise heating using different temperatures within the above temperature range may be performed.

The heating time in the above preferred temperature range is preferably 1 minute or longer, more preferably 3 minutes or longer, in order to improve adhesion while suppressing thermal decomposition. Also, it 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 the photoelectric conversion characteristics of the solar cell, reach constant values. In order to prevent thermal oxidation of the constituent materials, the annealing process is preferably carried out under normal pressure and in an inert gas atmosphere. As a heating method, the power generation device may be placed on a heat source such as a hot plate, or the power generation device may be placed in a heating atmosphere such as an oven. Moreover, heating may be performed in a batch system or in a continuous system.

[Photoelectric conversion characteristics]
The photoelectric conversion characteristics of the power generation device 100 can be obtained as follows. The power generation device 100 is irradiated with light of an appropriate spectrum at a certain irradiation intensity, and current-voltage characteristics are measured. From the resulting current-voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be obtained.

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 voltage value when the current value is 0 (mA/cm ² ). . A fill factor (FF) is a factor representing internal resistance.
The fill factor (FF) is expressed by the following equation, where Pmax is the maximum output.
FF=Pmax/(Voc×Jsc)
Moreover, the photoelectric conversion efficiency (PCE) is given by the following equation, where Pin is the incident energy.
PCE = (Pmax/Pin) x 100
= (Voc x Jsc x FF/Pin) x 100

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

The above incident energy Pin is, for example, 100 mW/ ^cm2 for sunlight with an intensity of AM1.5G, and is 100 μW/cm2 when white LED light with a color temperature of 5000 K is irradiated and the illuminance of the light receiving surface is 200 lux. ² .
In addition, the color temperature of 5000K in this specification is defined by the standard of JIS Z8725:2015.

<Solar cell>
INDUSTRIAL APPLICABILITY The power generation device according to the present invention has excellent photoelectric conversion efficiency under low illuminance, and is suitable as an indoor solar cell. FIG. 2 shows an example of a solar cell equipped with the power generation device of the present invention, which is a thin-film solar cell 14 equipped with the power generation device 100 described above, comprising a weather resistant protective film 1, an ultraviolet cut film 2, and a gas barrier film 3. , a getter material film 4, a sealing material 5, a solar cell element 6 having a power generation device 100 (not shown), a sealing material 7, a getter material film 8, a gas barrier film 9, and a back sheet 10 , in this order. Light is irradiated from the side of the thin-film solar cell 14 on which the protective film 1 is formed (lower side in FIG. 2), and the solar cell element 6 generates power. It should be noted that the thin-film solar cell 14 does not need to have all of these constituent members, and necessary constituent members can be arbitrarily selected.

The thin-film solar cell 14 may be used alone, or a plurality of thin-film solar cells 14 may be connected and used, or may be used as a component of a solar cell module combined with other components. . For example, as shown in FIG. 3, a solar cell module 13 having thin-film solar cells 14 on a base material 12 is produced, and this solar cell module 13 can be installed and used at a place of use.

The selection of each component described above and the manufacturing method thereof may apply well-known techniques. The described technique is included.

Applications of the power generation device of the present invention and the solar cell or solar cell module provided with the same are not limited, and examples include solar cells for building materials, solar cells for automobiles, solar cells for interiors, solar cells for railways, solar cells for ships, Applications include solar cells for airplanes, solar cells for spacecraft, solar cells for household appliances, solar cells for mobile phones, solar cells for toys, and the like.
The power generation device of the present invention and the solar cell or solar cell module equipped with the same exhibit excellent photoelectric conversion efficiency in a low-illumination environment, and are particularly suitable for energy harvesting applications.

EXAMPLES Hereinafter, examples of embodiments of the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples.

<Measurement method, etc.>
[Measurement of ionization potential]
Regarding the ionization potential of the active layer, a thin film ITO (indium tin oxide, surface resistivity: 7 to 10 Ω / sq.) was formed on a glass substrate, and the active layer was formed in the same manner as in the method for producing a power generation device described later. Then, 150 μL of the active layer coating solution 1 and 120 μL of the active layer coating solution 2 described later were sequentially applied to form an active layer of a perovskite semiconductor compound having a thickness of 650 nm directly on the glass substrate on which the thin ITO film was formed. formed.
It was determined based on the photon yield generated by irradiating the surface of the formed active layer with light. As a device, a photon yield measurement device (“PCR-101” manufactured by Optel) was used.

Regarding the ionization potential of the hole-transporting layer, on a glass substrate on which a thin film of ITO (surface resistivity: 7 to 10 Ω/sq.) is formed, the same as the method of forming a hole-transporting layer in the method of manufacturing a power generation device described later. Then, 120 μL of a hole transport layer coating solution described later was applied to form a hole transport layer having a thickness of 100 nm directly on the glass substrate on which the thin ITO film was formed.
It was determined based on the photon yield generated by irradiating the surface of the formed hole transport layer with light. As a device, a photon yield measurement device (“PCR-101” manufactured by Optel) was used.

Specifically, a glass substrate having a thin film of ITO formed thereon and a single layer of an active layer or a hole transport layer formed thereon is placed in the device and measured by a light quantum yield measurement device. The photon yield was measured to derive the following formula (1). Subsequently, the ionization potential IP of the hole transport layer was calculated as the value of X when Y=0 in Equation (2).
3√Y=A×X+B Formula (1)
IP=(3√Y-B)/A=-B/A Formula (2)

[Calculation of bandgap]
Regarding the bandgap of the active layer, 150 μL of the active layer coating liquid 1 and 120 μL of the active layer coating liquid 2 were coated on the transparent glass substrate in the same manner as in the method of forming the active layer in the method of manufacturing the power generating device, which will be described later. were sequentially applied to directly form an active layer of a perovskite semiconductor compound having a thickness of 650 nm on the glass substrate.

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 means the absorption coefficient, h means the Planck constant, ν means frequency). The rise of this absorption was fitted as a straight line, and the eV value crossing the baseline was calculated as the bandgap. This transmission spectrum was measured using a spectrophotometer (Hitachi High Tech U-4100).
The above fitting and calculation of the bandgap were performed according to the method described in the literature (Daisuke Yamashita, Atsushi Ishizaki: Analytical Chemistry 66, 333 (2017)).

[Evaluation of power generation device]
A metal mask of 1 mm square was attached to the power generation device obtained in each example, and current-voltage characteristics between the ITO transparent conductive film and the upper electrode were measured. A source meter (manufactured by Keithley, model 2400) was used for the measurement.

As an irradiation light source, an indoor light evaluation LED light source BLD-100 manufactured by Spectroscopy Instruments Co., Ltd. was used, and white LED light with a color temperature of 5000K was irradiated to the power generation device. At this time, the irradiation intensity was adjusted using an illuminometer so that the light-receiving surface of the power generation device had an illuminance of 200 lux.
From these measurement results, the short-circuit current density Jsc (mA/cm ² ), open-circuit voltage Voc (V), fill factor FF, and photoelectric conversion efficiency PCE (%) were calculated.

<Synthesis example>
The method for synthesizing Compound 1 used in Examples is shown below.
First, 2-amino-9,9-dihexylfluorene (1.75 g, 5.0 mmol) and 4-bromobiphenyl (1.17 g, 5.0 mmol) were used. ), 2.2 g of the following intermediate 1 was obtained.

Intermediate 1 is ¹ H-NMR analysis (400 MHz, solvent: heavy dichloromethane), δ7.61-7.17 (m, 16H), δ2.35-1.93 (m, 4H), δ1.17- 1.05 (m, 12H), δ1.18-0.79 (t, 6H), δ0.7-0.63 (m, 4H).
Intermediate 2 was also obtained by the method described in Patent Document (Patent No. 6442977).

Using intermediate 1 (1.0 g, 1.99 mmol) and the following intermediate 2 (755 mg, 0.95 mmol) obtained by the method described in the patent document (Patent No. 6442977), JP 2019-175970 1.4 g of the following compound 1, which is compound (1), was obtained with reference to the method described in .

Compound 1 is ¹ H-NMR analysis (400 MHz, solvent: heavy dichloromethane), δ7.84-7.26 (m, 54H), δ2.13-2.09 (m, 4H), δ1.98-1 .86 (m, 8H), .delta.1.18-1.09 (m, 36H), .delta.0.83-0.63 (m, 30H).

<Example 1>
[Preparation of Coating Liquid for Electron Transport Layer]
An aqueous dispersion of 7.5% by mass of tin oxide was prepared by adding ultrapure water to a 15% by mass aqueous dispersion of tin (IV) oxide (manufactured by Alfa Aesar).

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

Next, formamidine hydrobromide (FABr), methylamine hydrobromide (MABr), and methylamine hydrochloride (MACl) were mixed 7.25:1:1.5 in another vial. and introduced into the glove box. By adding isopropyl alcohol as a solvent to this solution, an active layer coating solution 2 having a total concentration of FABr, MABr and MACl of 0.49 mol/L was prepared.

[Preparation of Coating Liquid for Hole Transport Layer]
Compound 1 was added to 40 mM in o-dichlorobenzene solution containing 5.0 mM of 4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (TPFB; manufactured by TCI) as an electron-accepting dopant. was added to Next, the resulting mixed solution was heated and stirred at 150° C. for 1 hour to prepare a hole transport layer coating solution.

[Production of power generation device]
A glass substrate (manufactured by Geomatec) having a patterned ITO transparent conductive film was subjected to ultrasonic cleaning using ultrapure water, drying by nitrogen blow, and UV-ozone treatment.

On top of this, the electron-transporting layer coating solution described above was spin-coated onto the glass substrate at a speed of 2000 rpm at room temperature (25° C.) to a thickness of 35 nm, and then heated on a hot plate at 150° C. for 10 minutes. By doing so, an electron transport layer was formed.

The glass substrate on which the electron transport layer was formed was introduced into a glove box, and the active layer coating liquid 1 (150 μL) heated to 100° C. was dropped onto the electron transport layer, spin-coated at a speed of 2000 rpm, and hot plate was applied. A lead iodide layer was formed by thermal annealing at 100° C. for 10 minutes. Furthermore, after the glass substrate on which the lead iodide layer was formed was returned to room temperature, the active layer coating liquid 2 (120 μL) was spin-coated onto the lead iodide layer at a speed of 2000 rpm, and then coated on a hot plate at 150° C. for 20 minutes. An active layer (thickness 650 nm) of perovskite semiconductor compound was formed by heating for minutes and then cooling to room temperature.

On this active layer, a hole transport layer coating solution (120 μL) was spin-coated at a speed of 1000 rpm, further heated on a hot plate at 90° C. for 5 minutes, and then cooled to room temperature (25° C.) to remove holes. A transport layer (100 nm thick) was formed.

MoO ₃ with a thickness of 10 nm, IZO (indium zinc oxide) with a thickness of 30 nm, and aluminum with a thickness of 50 nm were deposited in this order on the hole transport layer by a resistance heating vacuum deposition method to form an upper electrode. .
A power generation device was produced as described above.
Measurement of the ionization potential and bandgap of the active layer, the ionization potential of the hole-transporting material, and the photoelectric conversion characteristics of this power generation device when the illuminance of the light-receiving surface is 200 lux when a white LED light with a color temperature of 5000K is irradiated. Table 1 shows the results. Note that the photoelectric conversion characteristics are values calculated based on the measurement results immediately after the power generation device was produced.

<Comparative Example 1>
Example 1 except that poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA, manufactured by Sigma-Aldrich) was used instead of compound 1 used in Example 1. A power generation device was produced in the same manner. Each measurement result is shown in Table 1.

From the results in Table 1, the power generation device of Example 1 having a hole transport layer containing Compound 1 is superior to the power generation device of Comparative Example 1 in terms of conversion efficiency using a low-illuminance white LED as a light source. was substantiated.

Next, durability against continuous light irradiation was evaluated. Specifically, the power generation device was sealed by adhering the sliding glass with the inner side recessed to the upper surface of the power generation device using a sealing material (UV curable resin). This sealed power generation device was used as a power generation device for durability testing.

The sealed power generation device was used as an open circuit, irradiated with light with an illuminance of 5800 Lx (1.74 mW/cm ² ), allowed to stand in the atmosphere for 1000 hours, and current-voltage characteristics were measured every 100 to 300 hours. .
The photoelectric conversion efficiency was obtained from the resulting current-voltage curve. The photoelectric conversion efficiency was measured at an illuminance of 200 Lx at the start of light irradiation, 200 hours after irradiation, 500 hours after irradiation, and 1000 hours after irradiation. Table 2 shows the results.

From the results in Table 2, the power generation device of Example 1 having a hole transport layer containing Compound 1 has higher conversion efficiency than the power generation device of Comparative Example 1 with a low-illuminance white LED as a light source. proved to be excellent.
The reason why the photoelectric conversion efficiency at 0 hours in Table 2 is slightly different from the conversion efficiency in Table 1 is that the sealed power generation device evaluated in Table 1 was measured again as a power generation device for durability testing. because he did.

In the power generation device of Example 1, the ionization potential of the active layer is −6.0 eV or more and −5.7 eV or less, the bandgap of the active layer is 1.6 eV or more and 2.3 eV or less, and the hole transport material is Since the ionization potential was −5.8 eV or more and −5.2 eV or less, it is considered that the combination of these achieved excellent conversion efficiency under low illumination and also achieved excellent durability.

1 Weather resistant protective film 2 Ultraviolet cut film 3, 9 Gas barrier film 4, 8 Getter material film 5, 7 Sealing material 6 Solar cell element (power generation device)
10 Backsheet 12 Base Material 13 Solar Cell Module 14 Thin Film Solar Cell 100 Power Generation Device 101 Lower Electrode 102 Buffer Layer 103 Active Layer 104 Buffer Layer 105 Upper Electrode 106 Base Material

Claims (8)

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 at least one of the active layer and the pair of electrodes. a hole-transporting layer positioned therebetween;
A power-generating device, wherein the hole-transporting layer contains a triarylamine compound represented by the following formula (I).

(In formula (I), Q1 is a group represented by the following formula (Q1-1), Q2 is a group represented by the following formula (Q2-1), and Q3 is a group represented by the following formula (Q3-1). and each of n ¹ , n ² , n ³ and n ⁴ is a repeating number.)

(In formulas (Q1-1), (Q2-1), and (Q3-1), R ¹ to R ¹⁸ each independently represent a hydrogen atom, a halogen atom, or an optionally substituted organic group. R ⁵ may be a single bond bonded to R ¹ , R ¹⁰ and R ¹¹ may be bonded together to form a ring, R ¹⁶ and R ¹⁷ may be bonded together to form a ring may be.) Q1 in the formula (I) is a group represented by the following formula (Q1-2), Q2 is a group represented by the following formula (Q2-2), and Q3 is a group represented by the following formula (Q3-2). 2. The power generation device of claim 1, which is a group represented by:

(In formulas (Q1-2), (Q2-2), and (Q3-2), R ³¹ to R ³⁶ each independently represent a hydrogen atom, a halogen atom, or an optionally substituted organic group. R ² to R ⁴ , R ⁶ to R ⁸ , R ⁹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁸ are represented by the above formulas (Q1-1), (Q2-1) and (Q3 - Same as in 1).) The ionization potential of the active layer is −6.0 eV or more and −5.7 eV or less, the bandgap 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 The power generation device according to claim 1 or 2, which is -5.8 eV or more and -5.2 eV or less. The power generation device according to any one of claims 1 to 3, wherein the organic-inorganic hybrid semiconductor compound is a compound having a perovskite structure. The power generation device according to any one of claims 1 to 4, wherein the active layer has a thickness of 200 nm or more and 800 nm or less. The power generation device according to any one of claims 1 to 5, wherein the photoelectric conversion efficiency is 25% or more when irradiated with white LED light having a color temperature of 5000K and the illuminance of the light receiving surface is 200 lux. 7. The method for manufacturing the power generation 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 comprises the and a dopant. The method for manufacturing a power generation device according to claim 7, wherein the dopant is a diaryliodonium salt containing trivalent iodine.

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