JP2022151016A - Photoelectric conversion element and power generation device - Google Patents

Abstract

To provide a photoelectric conversion element using an organic-inorganic hybrid semiconductor compound as an active layer, which achieves an improvement in durability while maintaining high performance.SOLUTION: There is provided a photoelectric conversion element including a pair of electrodes comprising an upper electrode and a lower electrode, and an active layer located between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound. In the photoelectric conversion element, an organic semiconductor compound having a hole transporting ability is located between the active layer and at least one of the pair of electrodes, the organic semiconductor compound having a hole transporting ability is a polymer compound, and the polymer compound includes a condensed polycyclic aromatic skeleton.SELECTED DRAWING: Figure 4-1

Description

TECHNICAL FIELD The present invention relates to photoelectric conversion elements and power generation devices.

2. Description of the Related Art As a photoelectric conversion element, one in which an active layer, a buffer layer, and the like are arranged between a pair of electrodes is known. For the purpose of improving the photoelectric conversion efficiency, the use of an organic-inorganic hybrid semiconductor compound as an active layer has been studied, and in particular, a compound having a perovskite structure has attracted attention.

Organic semiconductor compounds and the like are used as hole transport materials for such photoelectric conversion devices. For example, Patent Document 1 discloses that poly(3-hexylthiophene-2 ,5-diyl) (hereinafter also referred to as P3HT) is disclosed.

JP 2019-149564 A

However, there is still room for further improvement in terms of the high performance and high durability required for photoelectric conversion elements.
An object of the present invention is to improve durability while maintaining high performance in a photoelectric conversion device using an organic-inorganic hybrid semiconductor compound as an active layer.

The present inventors have investigated how to solve the above problems, and have solved the above problems by placing a compound containing a specific condensed polycyclic aromatic skeleton having hole-transporting ability between the electrode and the active layer. can be solved, and completed the present invention.

（式（Ｉ）中、環Ａ及び環Ｂはそれぞれ独立して、５員環芳香族複素環を表し、環Ｃは置換基を有していてもよい環を表す。Ｘ^１及びＸ^２はそれぞれ独立して、活性基を表す。Ｒ^１及びＲ^２はそれぞれ独立して、水素原子、ハロゲン原子、及びヘテロ原子を有していてもよい炭化水素基から選択される。）
［３］前記式（Ｉ）で表される化合物が、式（ＩＩ）及び式（ＩＩＩ）で表される縮合多環芳香族骨格から選択される化合物を含む、［２］に記載の光電変換素子。

（式（ＩＩ）及び式（ＩＩＩ）中、Ｘ^１、Ｘ^２、Ｒ^１、Ｒ^２及び環Ｃは前記式（Ｉ）中の定義の通りである。Ｘ^１１及びＸ^２１はそれぞれ独立して、周期表第１６族元素から選ばれる原子である。）
［４］前記式（ＩＩ）又は式（ＩＩＩ）で表される化合物が、式（ＩＶ）、式（Ｖ）、式（ＶＩ）又は式（ＶＩＩ）で表される縮合多環芳香族骨格を含む化合物である、［３］に記載の光電変換素子。

（式（ＩＶ）、式（Ｖ）、式（ＶＩ）及び式（ＶＩＩ）中、Ｘ^１、Ｘ^２、Ｒ^１及びＲ^２は前記式（Ｉ）中の定義の通りである。式（ＩＶ）中、Ｚ^１はＺ^１１（Ｒ^３）（Ｒ^４）、Ｚ^１２（Ｒ^５）又はＺ^１３を示し、Ｚ^１１は周期表第１４族元素から選ばれた原子を示し、Ｒ^３及びＲ^４は前記式（１）のＲ^１及びＲ^２と同義であり、Ｚ^１２は周期表第１５族元素から選ばれた原子を示し、Ｒ^５はＲ^３及びＲ^４と同義であり、Ｚ^１３は周期表第１６族元素から選ばれた原子を示す。
式（Ｖ）において、Ｒ^６及びＲ^７は水素原子、ハロゲン原子、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルキニル基、置換基を有していてもよい芳香族基、置換基を有していてもよいアルコキシ基及び置換基を有していてもよいアリールオキシ基から選択される。
式（ＶＩ）において、Ｒ^８～Ｒ^１１はＲ^３及びＲ^４と同義であり、Ｒ^１２及びＲ^１３は前記式（１）のＲ^１及びＲ^２と同義であり、Ｚ^２及びＺ^３はそれぞれ独立して、周期表第１４族元素から選ばれた原子を示す。
式（ＶＩＩ）において、Ｒ^１４及びＲ^１５はＲ^３及びＲ^４と同義であり、Ｚ^４は、周期表第１６族元素から選ばれた原子を示す。
［５］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］～［４］のいずれかに記載の光電変換素子。
［６］前記ペロブスカイト構造を有する化合物が、ＣｓＰｂ_{（１－ｙ）}Ｍ_ｙＸ_３（但し、Ｍは金属元素、Ｘはハロゲン元素、ｙは０≦ｙ≦１を満たす実数である）で表される、［５］に記載の光電変換素子。
［７］［１］～［６］のいずれかに記載の光電変換素子を備えた、５，０００ルクス以下の低照度向け光環境発電デバイス。 That is, the present invention includes the following.
[1] A photoelectric conversion element having a pair of electrodes composed of an upper electrode and a lower electrode, and an active layer located between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound,
an organic semiconductor compound having a hole-transporting ability is positioned between the active layer and at least one of the pair of electrodes, and the organic semiconductor compound having a hole-transporting ability is a polymer compound; A photoelectric conversion device, wherein the compound comprises a condensed polycyclic aromatic skeleton.
[2] The photoelectric conversion device according to [1], wherein the polymer compound contains a condensed polycyclic aromatic skeleton represented by the following formula (I).

(In formula (I), ring A and ring B each independently represent a 5-membered aromatic heterocyclic ring, and ring C represents a ring optionally having a substituent. X ¹ and X ² are Each independently represents an active group, and each of R ¹ and R ² is independently selected from a hydrogen atom, a halogen atom, and a hydrocarbon group which may have a heteroatom.)
[3] The photoelectric conversion according to [2], wherein the compound represented by formula (I) includes a compound selected from the condensed polycyclic aromatic skeleton represented by formula (II) and formula (III). element.

(In formula (II) and formula (III), X ¹ , X ² , R ¹ , R ² and ring C are as defined in formula (I) above. X ¹¹ and X ²¹ are each independently , an atom selected from the elements of Group 16 of the periodic table.)
[4] The compound represented by formula (II) or formula (III) has a condensed polycyclic aromatic skeleton represented by formula (IV), formula (V), formula (VI) or formula (VII) The photoelectric conversion device according to [3], which is a compound containing

(In Formula (IV), Formula (V), Formula (VI) and Formula (VII), X ¹ , X ² , R ¹ and R ² are as defined in Formula (I) above. Formula (IV ), Z ¹ represents Z ¹¹ (R ³ ) (R ⁴ ), Z ¹² (R ⁵ ) or Z ¹³ , Z ¹¹ represents an atom selected from Group 14 elements of the periodic table, R ³ and R ⁴ has the same definition as R ¹ and R ² in the formula (1), Z ¹² represents an atom selected from elements of Group 15 of the periodic table, R ⁵ has the same definition as R ³ and R ⁴ , and Z ¹³ represents an atom selected from the elements of group 16 of the periodic table.
In formula (V), R ⁶ and R ⁷ are a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted an optionally substituted alkynyl group, an optionally substituted aromatic group, an optionally substituted alkoxy group, and an optionally substituted aryloxy group.
In formula (VI), R ⁸ to R ¹¹ have the same meanings as R ³ and R ⁴ , R ¹² and R ¹³ have the same meanings as R ¹ and R ² in formula (1) above, and Z ² and Z ³ are Each independently indicates an atom selected from Group 14 elements of the periodic table.
In Formula (VII), R ¹⁴ and R ¹⁵ have the same definitions as R ³ and R ⁴ , and Z ⁴ represents an atom selected from Group 16 elements of the periodic table.
[5] The photoelectric conversion device according to any one of [1] to [4], wherein the organic-inorganic hybrid semiconductor compound is a compound having a perovskite structure.
[6] The compound having a perovskite structure is represented by CsPb _(1-y) M _y X ₃ (where M is a metal element, X is a halogen element, and y is a real number satisfying 0≦y≦1). The photoelectric conversion device according to [5].
[7] A photoenergy harvesting device for low illuminance of 5,000 lux or less, comprising the photoelectric conversion element according to any one of [1] to [6].

INDUSTRIAL APPLICABILITY According to the present invention, a photoelectric conversion device using an organic-inorganic hybrid semiconductor compound can be improved in durability while maintaining high performance.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which represents typically the photoelectric conversion element as one Embodiment. 1 is a cross-sectional view schematically showing a solar cell as one embodiment; FIG. 1 is a cross-sectional view schematically showing a solar cell module as one embodiment; FIG. 4 is a graph comparing performances of photoelectric conversion elements of Examples and Comparative Examples. Specifically, (a) Jsc and (b) Voc are shown, respectively. 4 is a graph comparing performances of photoelectric conversion elements of Examples and Comparative Examples. Specifically, (c) FF, (d) PCE, and (e) hysteresis index are shown, respectively.

A photoelectric conversion device according to one embodiment of the present invention includes a pair of electrodes composed of an upper electrode and a lower electrode, and an active layer located between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound. A photoelectric conversion element having
an organic semiconductor compound having a hole-transporting ability is positioned between the active layer and at least one of the pair of electrodes, and the organic semiconductor compound having a hole-transporting ability is a polymer compound; A photoelectric conversion device in which the compound contains a condensed polycyclic aromatic skeleton.

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.

[1. Photoelectric conversion element according to one embodiment]
FIG. 1 is a cross-sectional view schematically showing one embodiment of a photoelectric conversion element according to the present invention. The photoelectric conversion element shown in FIG. 1 is a photoelectric conversion element used in a general thin-film solar cell, but the photoelectric conversion element according to the present invention is not limited to that shown in FIG.
In the photoelectric conversion element 100 shown in FIG. 1, a lower electrode 101, an active layer 103, and an upper electrode 105 are arranged in this order. In the photoelectric conversion element 100, the buffer layer 102 existing between the lower electrode 101 and the active layer 103 can be a hole transport layer containing an organic semiconductor compound. In this case, a dopant can be further contained together with the organic semiconductor compound. However, the photoelectric conversion element 100 may have a buffer layer 104 between the upper electrode 105 and the active layer 103, and in this case, the buffer layer 104 may be the above-mentioned hole transport layer. Also, as shown in FIG. 1, the photoelectric conversion element 100 may have a substrate 106 and may have other layers such as an insulator layer and a work function tuning layer.

[2. electrode]
The electrode has a function of collecting holes and electrons generated by light absorption in the active layer 103 . A photoelectric conversion element 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 photoelectric conversion element 100 has a substrate or is provided on a substrate, an electrode closer to the substrate can be called a lower electrode, and an electrode farther from the substrate can be called an 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 photoelectric conversion element 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 photoelectric conversion element 100 may have a forward configuration in which the lower electrode 101 is the anode and the upper electrode 105 is the cathode, or a reverse configuration in which the lower electrode 101 is the cathode and the upper electrode 105 is the anode. It may have a mold configuration.

Either one of the pair of electrodes may be translucent, or both may be translucent. Having translucency refers to transmitting 40% or more of sunlight. In addition, it is preferable that the transparent electrode has a sunlight transmittance of 70% or more so that more light can pass through the transparent electrode and reach the active layer 103 . The light 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 their manufacturing methods, and well-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.

[3. active layer]
In the embodiment of FIG. 1, the active layer 103 is the layer in which photoelectric conversion takes place. When the photoelectric conversion element 100 receives light, the light is absorbed by the active layer 103 to generate carriers, which are extracted from the lower electrode 101 and the upper electrode 105 .
The active layer 103 is positioned between the pair of electrodes and contains an organic-inorganic hybrid semiconductor material. An organic-inorganic hybrid semiconductor material is a material in which an organic component and an inorganic component are combined at the molecular level or the nano level, and indicates a material exhibiting semiconductor properties.

In the present embodiment, the organic-inorganic hybrid semiconductor material is preferably a compound having a perovskite structure (hereinafter sometimes referred to as a perovskite semiconductor compound). 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. For example, perovskite semiconductor compounds include those of the AMX ₃ type, represented by the general formula AMX ₃ , or those of the A ₂ MX ₄ type, represented by the general formula A ₂ MX ₄ . Here, M denotes a divalent cation, A denotes a monovalent cation, and X denotes 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. A combination of two or more cations can also be used as the cation A.

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⁺ ). A combination of two or more cations can also be used as the cation M. From the viewpoint of obtaining a stable photoelectric conversion 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 order to adjust the bandgap, X may be one type of anion or a combination of two or more types of anions. In one embodiment, X includes halide ions or combinations of halide ions and other anions. Examples of halide ions X include chloride ions, bromide ions, iodide ions, and the like. From the viewpoint of not widening the bandgap of the semiconductor too much, it is preferable to mainly use iodide ions or bromide ions, but iodide ions and bromide ions may be combined in an appropriate ratio.

_{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 , CF ₃ NH ₃ or Cs, 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. In the present embodiment, the compound is preferably CsPb _(1-y) M _y X ₃ (where M is a metal element, X is a halogen element, and y is a real number that satisfies 0≦y≦1). , M can be a metal element such as Sn or Ge. Compounds that are _CsPbX3 are particularly preferred, and compounds composed of these inorganic elements ensure the lattice stability of perovskite structure ABX3 crystals, and in particular retain _three -dimensional stability depending on the cation/anion shape and size. This is preferable from the viewpoint of satisfying a parameter called a possible tolerance factor.

The active layer 103 may contain two or more perovskite semiconductor compounds. For example, the active layer 103 may contain two or more perovskite semiconductor compounds in which at least one of A, B and X is different. The active layer 103 may also have a laminated structure formed of multiple layers containing different materials or having different components.

The amount of the perovskite semiconductor compound contained in the active layer 103 is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more so as to obtain good semiconductor characteristics. be. There is no particular upper limit. Also, the active layer 103 may contain an additive in addition to the perovskite semiconductor compound. Examples of additives include inorganic or organic compounds, such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates or ammonium salts.

There is no particular limitation on the thickness of the active layer 103 . In order to absorb more light, the thickness of the active layer 103 is 10 nm or more in one embodiment, 50 nm or more in another embodiment, 100 nm or more in another embodiment, and 120 nm or more in another embodiment. is. On the other hand, the thickness of the active layer 103 is 1500 nm or less in one embodiment, 1200 nm or less in another embodiment, and 800 nm or less in still another embodiment in order to reduce the series resistance or improve the charge extraction efficiency. is.

A method for forming the active layer 103 is not particularly limited, and any method can be used. Specific examples include a coating method and a vapor deposition method (or a co-evaporation method). A coating method can be used because the active layer 103 can be easily formed. For example, there is a method of forming the active layer 103 by applying a coating liquid containing a perovskite semiconductor compound or a precursor thereof and drying it by heating as necessary. In addition, after applying such a coating liquid, a perovskite semiconductor compound can be precipitated by further applying a solvent in which the perovskite semiconductor compound has a low solubility.

A perovskite semiconductor compound precursor refers to a material that can be converted into a perovskite semiconductor compound after application of a coating liquid. As a specific example, a perovskite semiconductor compound precursor that can be converted into a perovskite semiconductor compound by heating can be used. For example, a coating liquid can be prepared by mixing a compound represented by the general formula AX, a compound represented by the general _formula MX2, and a solvent, followed by heating and stirring. The active layer 103 containing the perovskite semiconductor compound represented by the general formula AMX ₃ can be produced by applying this coating liquid and heat-drying it. The solvent is not particularly limited as long as it dissolves the perovskite semiconductor compound and the additive, and examples thereof include organic solvents such as N,N-dimethylformamide.

Any method can be used as a method for applying 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.

Although the range of the ionization potential of the active layer is not particularly limited, it is preferably −5.5 eV or more and −4.0 eV or less, more preferably −5.2 eV or more and −4.6 eV or less, and particularly preferably −5. It is 0 eV or more and -4.4 eV or less.
The bandgap of the active layer is preferably 2.6 eV or more and 1.2 eV or less, more preferably 2.4 eV or more and 1.4 eV or less, and particularly preferably 2.2 eV or more and 1.6 eV or less.
By setting the ionization potential and bandgap of the active layer within the above ranges, it is possible to improve the power generation efficiency of fluorescent lamps and LED lamps, which are visible light sources widely used indoors and indoors, which is preferable.
In particular, when the bandgap of the active layer is within the above range, the energy generated by receiving the indoor light source is sufficient to separate the excitons generated in the semiconductor into positive and negative charges, and is not excessive, Power generation efficiency can be improved.

The ionization potential can be calculated by irradiating a sample with light and measuring the minimum energy (eV) required for the irradiation energy to eject photoelectrons. Any measuring instrument can be used, and for example, AC-2, AC-3 manufactured by Riken Keiki Co., Ltd. can be used.
Also, the bandgap can be calculated from the absorption edge wavelength and the absorbance of the semiconductor compound. Specifically, a semiconductor compound thin film is formed on a suitable sample such as a transparent glass substrate, its transmission spectrum is measured, the horizontal axis wavelength is converted to eV, and the vertical axis transmittance is converted to √(ahν), By fitting this rising edge of absorption as a straight line, the eV value at which it crosses the baseline can be calculated as the bandgap. The transmission spectrum can be measured, for example, using a spectrophotometer such as Hitachi High-Tech U-4100.

Methods for adjusting the ionization potential of the active layer within the desired range include, for example, appropriately changing the cationic component in the perovskite semiconductor compound.
As a method for adjusting the bandgap of the active layer to the desired range, for example, the composition ratio of the halogen element in the perovskite semiconductor compound is appropriately changed.

[4. buffer layer]
The buffer layer is a layer located between the active layer 103 and at least one of the pair of electrodes 101 and 105 . A buffer layer can be used, for example, to improve carrier transfer efficiency from the active layer 103 to the lower electrode 101 or the upper electrode 105 .

In this embodiment, a specific organic semiconductor compound having hole-transporting ability is located between the active layer and at least one of the pair of electrodes. Therefore, a specific organic semiconductor compound having a hole-transporting ability shown below may be contained in the buffer layer shown below, or may be contained between the active layer and the pair of electrodes separately from the buffer layer. good.
As a mode in which a specific organic semiconductor compound having a hole-transporting ability is included between the active layer and the pair of electrodes separately from the buffer layer,
(i) a method in which it is present between the active layer and the hole transport layer, for example, a method in which the interface of the active layer on the side of the hole transport layer is modified with a specific organic semiconductor compound having hole transport ability;
(ii) a method of placing the layer between the active layer and the electron-transporting layer, for example, a method of modifying the interface of the active layer on the electron-transporting layer side with a specific organic semiconductor compound having hole-transporting ability.
Modification methods include a method of providing a layer containing a specific organic semiconductor compound having the hole-transporting ability.

An organic semiconductor compound having hole-transporting ability is a polymer compound containing a condensed polycyclic aromatic skeleton. The polymer compound containing a condensed polycyclic aromatic skeleton is not particularly limited as long as it has a hole-transporting ability, but it is an organic semiconductor compound containing a condensed polycyclic aromatic skeleton represented by the following formula (I). is preferred.

In the above formula (I), ring A and ring B each independently represent a 5-membered aromatic heterocyclic ring, ring C
represents a ring optionally having a substituent. X ¹ and X ² each independently represent an active group. R ¹ and R ² are each independently selected from hydrogen atoms, halogen atoms, and hydrocarbon groups which may have heteroatoms.
The active group is not particularly limited as long as it is a group showing a monovalent oxidation number, and includes a hydrogen atom, a halogen, a hydrocarbon group, an aryl group, and various organometallic groups MR (where M is a metal compound, R is is a monovalent organic group), and the like. Although the hydrocarbon group is not particularly limited, it is preferably a hydrocarbon group having 1 to 16 carbon atoms.

In addition, the compound represented by formula (I) preferably contains a compound selected from the condensed polycyclic aromatic skeletons represented by formula (II) and formula (III).

In formulas (II) and (III) above, X ¹ , X ² , R ¹ , R ² and ring C are as defined in formula (I) above. X ¹¹ and X ²¹ are each independently atoms selected from Group 16 elements of the periodic table.

Furthermore, the compound represented by formula (II) or formula (III) contains a condensed polycyclic aromatic skeleton represented by formula (IV), formula (V), formula (VI), or formula (VII) Compounds are more preferred.

In Formula (IV), Formula (V), Formula (VI) and Formula (VII), X ¹ , X ² , R ¹ and R ² are as defined in Formula (I) above. In formula (IV), Z ¹ represents Z ¹¹ (R ³ ) (R ⁴ ), Z ¹² (R ⁵ ) or Z ¹³ , Z ¹¹ represents an atom selected from elements of Group 14 of the periodic table, and R ³ and R ⁴ have the same meanings as R ¹ and R ² in the formula (1), Z ¹² represents an atom selected from Group 15 elements of the periodic table, and R ⁵ has the same meanings as R ³ and R ⁴ . , Z ¹³ denote atoms selected from Group 16 elements of the periodic table.
In formula (V), R ⁶ and R ⁷ are a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted an optionally substituted alkynyl group, an optionally substituted aromatic group, an optionally substituted alkoxy group, and an optionally substituted aryloxy group.
In formula (VI), R ⁸ to R ¹¹ have the same meanings as R ³ and R ⁴ , R ¹² and R ¹³ have the same meanings as R ¹ and R ² in formula (1) above, and Z ² and Z ³ are Each independently indicates an atom selected from Group 14 elements of the periodic table.
In Formula (VII), R ¹⁴ and R ¹⁵ have the same definitions as R ³ and R ⁴ , and Z ⁴ represents an atom selected from Group 16 elements of the periodic table.

Specific examples of the compound represented by formula (I) include the following compounds.

(organic semiconductor compound)
The buffer layer includes an organic semiconductor compound. A semiconducting compound refers to a compound that exhibits semiconducting properties and can be used as a semiconducting material. In this specification, the term "semiconductor" is defined by the magnitude of carrier mobility in a solid state. Carrier mobility, as is well known, is a measure of how fast (or how much) charges (electrons or holes) can be moved. Specifically, the “semiconductor” in this specification preferably has a carrier mobility at room temperature of 1.0×10 ⁻⁶ cm ² /V·s or more, 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. 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.
In the present specification, an organic semiconductor compound having hole-transporting ability refers to an organic semiconductor compound having a hole carrier mobility within the above range.

In the present invention, the buffer layer may be formed using an organic semiconductor compound other than the above-described organic semiconductor compound containing a condensed polycyclic aromatic skeleton. The type is not particularly limited, and conventionally known ones can be used, for example. Low-molecular-weight compounds and high-molecular-weight 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, oligothiophenes, phthalocyanines, perylenes, rubrenes, or thoria. and arylamine compounds such as arylamine compounds. 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.

The organic semiconductor compound is preferably an arylamine compound, more preferably a triarylamine compound. An arylamine compound is an arylamine structure (
A bond between an aryl group and a nitrogen atom), including arylamine-based polymers. An arylamine-based polymer is a polymer in which a repeating unit includes an arylamine structure, and is also called a polyarylamine-based compound. A triarylamine-based compound is a compound having a triarylamine structure (three aryl groups bonded to the same nitrogen atom), and includes triarylamine-based polymers. A triarylamine polymer is a polymer in which a repeating unit contains a triarylamine structure, and is also called a polytriarylamine-based compound. Such an arylamine-based compound or triarylamine-based compound is preferable in that it can be stably oxidized by a dopant and can exhibit good semiconductor properties, and among them, triarylamine-based compounds are more preferable.

Here, the aryl group (or aromatic group) refers to an aromatic hydrocarbon group or an aromatic heterocyclic group, which is a monocyclic group, a condensed ring group, and a monocyclic or condensed ring group. things, including The aromatic group is not particularly limited, but preferably has 30 or less carbon atoms, more preferably 12 or less carbon atoms. Specific examples of aromatic hydrocarbon groups include a phenyl group, a naphthyl group, a biphenyl group, and the like. Specific examples of the aromatic heterocyclic group include thienyl group, furyl group, pyrrolyl group, pyridyl group, imidazolyl group and the like.

The aromatic group may have further substituents. The substituents that the aromatic group may have are not particularly limited, but are halogen atoms, hydroxyl groups, cyano groups, amino groups, carboxyl groups, ester groups, alkylcarbonyl groups, acetyl groups, sulfonyl groups, silyl groups, Boryl group, nitrile group, alkyl group, alkenyl group, alkynyl group, alkoxy group, thio group, seleno group, aromatic hydrocarbon group, aromatic heterocyclic group and the like. A preferred substituent of the aryl group is an amino group or an alkyl group having 1 to 6 carbon atoms. Here, the amino group is 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.

(dopant)
The buffer layer may have dopants as additives in order to optimize the conductivity and hole transport capacity of the hole transport layer with respect to the active layer.
Substances that can be used as dopants include boron compounds such as tetrakis(pentafluorophenyl)borate, and molybdenum compounds such as tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2-dithiolene]molybdenum. , 2,3,4,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane and other organic compounds having a tetracyanoquinodimethane skeleton.

The content of the dopant can be, for example, in the range of 0.001 to 10% by mass with respect to the total amount of the organic semiconductor material and the dopant.
A dopant content of 0.001% by mass or more tends to improve the conductivity and hole transport capability of the buffer layer relative to the active layer. More preferably, it is 0.01% by mass or more, still more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass or more.
Also, by setting the dopant content to 10% by mass or less, the occurrence of leak current in the photoelectric conversion element is suppressed, and there is a tendency that the power generation efficiency can be further improved particularly in a low illuminance region. More preferably, it is 8% by mass or less, and still more preferably 6% by mass or less.

The ionization potential of the hole transport layer is preferably in the range of −0.6 eV or more and +0.6 eV or less, more preferably −0.4 eV or more and +0.4 eV or less, with respect to the ionization potential of the active layer. It is preferably in the range of -0.2 eV or more and +0.2 eV or less. When the ionization potential of the hole-transporting layer is within the above range, it is possible to smoothly transfer holes from the active layer without reducing the hole-transporting ability, and it is possible to suppress energy loss and voltage loss. .
Methods for adjusting the ionization potential of the hole transport layer to the desired range include, for example, introducing an electron-withdrawing functional group into the coating conversion type material constituting the hole transport layer, or To delocalize electrons and improve stability by expanding the conjugated site component of , and to select the central metal of the coating conversion type material.

As described above, the photoelectric conversion device 100 can have the buffer layer 102 between the lower electrode 101 and the active layer 103, or have the buffer layer 104 between the upper electrode 105 and the active layer 103. can be done. Also, the photoelectric conversion element 100 can have both the buffer layer 102 and the buffer layer 104 . Here, the buffer layer 102 provided between the lower electrode 101 and the active layer 103 and the buffer layer 104 provided between the upper electrode 105 and the active layer 103 may be made of different materials. That is, one buffer layer may be a hole transport layer containing an organic semiconductor compound, while the other buffer layer may be an electron transport layer or the like composed of a different substance. As described above, the hole transport layer containing the organic semiconductor compound may be positioned between the lower electrode 101 and the active layer 103, or may be positioned between the active layer 103 and the upper electrode 105. may be However, when a hole transport layer containing an organic semiconductor compound is formed by a coating method, the active layer 103 may be immersed in the coating solvent, which may affect the active layer 103. The layer is preferably located between the bottom electrode 101 and the active layer 103 .

A buffer layer provided between the anode and the active layer is sometimes called a hole transport layer, and a buffer layer provided between the cathode and the active layer is sometimes called an electron transport layer. In the present invention, a buffer layer containing an organic semiconductor compound is used as a hole transport layer, since the amount of transported charge tends to be easily controlled in the nip stacked photoelectric conversion device.

In the present invention, a buffer layer containing the above organic semiconductor compound or its dopant can be suitably used as a hole transport layer, but the material of the buffer layer is not particularly limited. For example, for the hole transport layer, any material that can improve the efficiency of extracting holes from the active layer to the anode can be used. Specifically, the inorganic compounds, organic compounds, or organic-inorganic perovskite compounds according to the present invention are described in known documents such as WO 2013/171517, WO 2013/180230, or JP-A-2012-191194. is mentioned. For example, inorganic compounds include metal oxides such as copper oxide, nickel oxide, manganese oxide, iron oxide, molybdenum oxide, vanadium oxide, and tungsten oxide. Examples of organic compounds include conductive polymers obtained by doping polythiophene, polypyrrole, polyacetylene, triphenylenediamine or polyaniline with dopants, polythiophene derivatives having sulfonyl groups as substituents, conductive organic compounds such as arylamines, Nafion, or Lithium-doped spiro-OMeTAD is mentioned.

Similarly, for the electron transport layer, any material that can improve the efficiency of electron extraction from the active layer to the cathode can be used. Specifically, the inorganic compounds, organic compounds, or organic-inorganic perovskite compounds according to the present invention are described in known documents such as WO 2013/171517, WO 2013/180230, or JP-A-2012-191194. is mentioned. 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 (Alq3), boron compounds, oxadiazole compounds, benzimidazole compounds, naphthalenetetracarboxylic anhydride (NTCDA), Examples include perylenetetracarboxylic anhydride (PTCDA), fullerene compounds, and phosphine compounds having a Group 16 element of the periodic table and a double bond, such as phosphine oxide compounds or phosphine sulfide compounds.

The thickness of the buffer layer, including the hole transport layer in the present invention, is not particularly limited, but is 0.5 nm or more in one embodiment, 1 nm or more in another embodiment, and 5 nm or more in another embodiment. while 1 μm or less in one embodiment, 500 nm or less in another embodiment, 200 nm or less in yet another embodiment, and 150 nm or less in still another embodiment. When the film thickness of the buffer layer is within the above range, the carrier transfer efficiency can be easily improved, and the photoelectric conversion efficiency can be improved.

In addition, the formation method of the buffer layer, including the hole transport layer in the present invention, is not limited, and the formation method can be selected according to the characteristics of the material. For example, the buffer layer can be formed by preparing a coating liquid containing the above-described organic semiconductor compound and solvent and using a wet film formation method such as a spin coating method or an inkjet method.
The solvent used in the coating liquid preferably dissolves the precursor compound in an amount of 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more.

Specific examples of the above solvents include aromatic solvents such as toluene, xylene, methylene, and cyclohexylbenzene; halogen-containing solvents such as 1,2-dichloroethane, chlorobenzene, and o-dichlorobenzene; ethylene glycol dimethyl ether, ethylene glycol diethyl ether, Aliphatic ethers such as propylene glycol-1-monomethyl ether acetate (PGMEA), 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene , 2,3-dimethylanisole, ether solvents such as aromatic ethers such as 2,4-dimethylanisole; ethyl acetate, n-butyl acetate, ethyl lactate, aliphatic esters such as n-butyl lactate; phenyl acetate, propion Organic solvents such as ester solvents such as aromatic esters such as phenyl acid, methyl benzoate, ethyl benzoate, isopropyl benzoate, propyl benzoate, and n-butyl benzoate. Aromatic solvents such as toluene, xylene, methylylene, and cyclohexylbenzene, ester solvents such as ethyl benzoate, anisole, trifluoromethoxyanisole, pentafluoromethoxybenzene, and 3-(trifluoromethyl), due to their low surface tension Ether solvents such as anisole and ethyl (pentafluorobenzoate) are preferred. These may use only 1 type, and may use 2 or more types by arbitrary combinations and ratios.

[5. Base material]
The photoelectric conversion element 100 usually has a base material 106 that serves as a support. However, the photoelectric conversion element according to the present invention does not have to have the substrate 106 . The material of the base material 106 is not particularly limited as long as it does not significantly impair the effects of the present invention. can be used.

[6. Method for producing a photoelectric conversion element]
By forming each layer constituting the photoelectric conversion element 100 according to the method described above, the photoelectric conversion element 100 can be produced. There is no particular limitation on the method of forming each layer constituting the photoelectric conversion element 100, and the layers can be formed by a sheet-to-sheet (Manyo) method or a roll-to-roll method.

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 transported intermittently or continuously until it is wound up by a winding roll. be. 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. On the other hand, when each layer is formed by a roll-to-roll method, the film may be damaged or partially peeled off due to the contact between the film-forming surface and the roll due to its structure.

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 a roll-to-roll manufacturing apparatus, but the upper limit of the outer diameter is preferably 5 m or less, more preferably 3 m or less, more preferably 3 m or less. 1 m or less. On the other hand, the lower limit is preferably 10 cm or more, more preferably 20 cm or more, and still more preferably 30 cm or more. The upper limit of the outer diameter of the roll core is preferably 4 m or less, more preferably 3 m or less, and even more preferably 0.5 m or less. On the other hand, the lower limit is preferably 1 cm or more, more preferably 3 cm or more, more preferably 5 cm or more, still more preferably 10 cm or more, and particularly preferably 20 cm or more. It is preferable that these diameters are equal to or less than the above upper limit because the handleability of the roll is high. . The lower limit of the width of the roll is preferably 5 cm or more, more preferably 10 cm or more, and still more preferably 20 cm or more. On the other hand, the upper limit is preferably 5 m or less, more preferably 3 m or less, and more preferably 2 m or less. It is preferable that the width is equal to or less than the upper limit because the roll is easy to handle.

Further, after laminating the upper electrode 105, the photoelectric conversion element 100 can be heated in a temperature range of 50° C. or higher or 80° C. or higher, or 300° C. or lower, 280° C. or lower, or 250° C. or lower (this step may be referred to as an annealing treatment step). Performing the annealing process at a temperature of 50° C. or higher improves the adhesion between the layers of the photoelectric conversion element 100, for example, the adhesion between the buffer layer 102 and the lower electrode 101, the buffer layer 102 and the active layer 103, and the like. effect is obtained. By improving the adhesion between each layer, the thermal stability, durability, etc. of the photoelectric conversion element can be improved. Setting the temperature of the annealing treatment process to 300° C. or lower reduces the possibility of thermal decomposition of the organic compound contained in the photoelectric conversion element 100 . In the annealing treatment step, stepwise heating using different temperatures within the above temperature range may be performed.

The heating time is 1 minute or more in one embodiment, 3 minutes or more in another embodiment, 180 minutes or less in one embodiment, and 180 minutes or less in another embodiment, in order to improve adhesion while suppressing thermal decomposition. 60 minutes or less. The annealing process can be terminated when the open-circuit voltage, short-circuit current and fill factor, which are parameters of solar cell performance, reach constant values. Also, the annealing process can be performed under normal pressure in an inert gas atmosphere in order to prevent thermal oxidation of the constituent materials. As a heating method, the photoelectric conversion element may be placed on a heat source such as a hot plate, or the photoelectric conversion element 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.

[7. Photoelectric conversion characteristics]
The photoelectric conversion characteristics of the photoelectric conversion element 100 can be obtained as follows. The photoelectric conversion element 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. As an example, by irradiating the photoelectric conversion element 100 with white LED light having a color temperature of 5000 K at an appropriate irradiation intensity (illuminance), the current-voltage characteristics at each illuminance can be measured.

The photoelectric conversion device of the present invention is excellent in power generation efficiency in a low illuminance region (10 to 5000 lux), and can achieve a photoelectric conversion efficiency of 20% or more particularly when a light source such as white LED light is used. Also, the photoelectric conversion efficiency at 200 lux can be 25% or higher. There is no particular limit to the upper limit of this efficiency, and the higher the efficiency, the better.
The photoelectric conversion efficiency (PCE) is the output (maximum output) at the optimum operating point of the current-voltage curve of the photoelectric conversion element measured by a predetermined irradiation light, and the total amount of energy that the irradiation light has (for example, It is a value (%) divided by 100 mW/cm ² for sunlight with an intensity of AM 1.5G.

[8. power generation device]
In one embodiment, the photoelectric conversion element 100 according to the present invention is suitably used as a power generation device, especially as a solar cell for low-illuminance environments such as indoors. FIG. 2 is a cross-sectional view schematically showing the configuration of a solar cell according to one embodiment of the present invention, and FIG. 2 shows a solar cell which is a solar cell according to one embodiment of the present invention. As shown in FIG. 2, the thin-film solar cell 14 according to the present embodiment includes a weather-resistant protective film 1, an ultraviolet cut film 2, a gas barrier film 3, a getter material film 4, a sealing material 5, and a solar cell. An element 6, a sealing material 7, a getter material film 8, a gas barrier film 9, and a back sheet 10 are provided in this order. The thin-film solar cell 14 according to this embodiment has the photoelectric conversion element according to the present invention as the solar cell element 6 . Then, light is irradiated from the side where 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.
In this specification, a low illumination environment means 10 to 5000 lux, typically around 200 lux.

There are no particular restrictions on these constituent members constituting the photoelectric conversion element and the method of manufacturing the same, and well-known techniques can be used. For example, techniques described in known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, and Japanese Patent Application Laid-Open No. 2012-191194 can be used.

Applications of the solar cell according to the present embodiment, particularly the thin-film solar cell 14 described above, are not limited and can be used for any application. For example, the solar cell according to one embodiment includes solar cells for building materials, solar cells for automobiles, solar cells for interiors, solar cells for railroads, solar cells for ships, solar cells for airplanes, solar cells for spacecraft, solar cells for home appliances, and so on. It can be used as a battery, a solar cell for mobile phones or a solar cell for toys. As described above, it has excellent change efficiency in a low-illuminance environment, so it is particularly suitable for energy harvesting applications.

The solar cell according to this embodiment, particularly the thin-film solar cell 14 described above, may be used as it is, or may be used as a component of a solar cell module. For example, as shown in FIG. 3, a solar cell module 13 having the solar cell according to the present embodiment, particularly the above-described solar cell 14, on a substrate 12 is produced, and the solar cell module 13 is installed at a place of use. can be used.

EXAMPLES The present invention will be described in more detail below with reference to examples, but it goes without saying that the scope of the present invention is not limited by the description of the examples below.
(Synthesis of Polymer 1)
Tin chloride SnCl ₂ (99.9%) was purchased from Fuji Film Wako, and lead iodide PbI ₂ (II) (99.99%) and cesium bromide CsBr (99.0%) were purchased from Tokyo Kasei Kogyo. Poly(3-hexylthiophene-2,5-diyl) regioregular
(P3HT) was purchased from Sigma-Aldrich. Ethanol (99.5%), DMSO (99.9%), and DMF (99.8%) were purchased from Fuji Film Wako, respectively, and tin (II) oxide 15% aqueous colloidal dispersion was purchased from Alfa Aeser. Pd EnCat(R)TPP30, trimethyl(phenyl)tin were purchased from Merck. Silica gel 60 was purchased from Kanto Kagaku. SCAVENGER diamine silica was purchased from Fuji Silysia Chemical.

1,3-dibromo-5-octylthieno[3,4-c]pyrrole-4,6-dione (monomer 1) is described in Non-Patent Document [Org. Lett. 2004, 6, 3381-3384].
4,4-bis(2-ethylhexyl)-2,6-bis(trimethylstannyl)-dithieno[3,2-b:2′,3′-d]silole (monomer 2) and 4,4-di- n-Octyl-2,6-bis(trimethylstannyl)-dithieno[3,2-b:2',3'-d]silole (monomer 3) was synthesized according to WO2013/0658364.

Monomer 1 (98.9 mmol), Monomer 2 (47.0 mg), Monomer 3 (47.0 mg), Pd(PPh ₃ ) ₄ (12 mg, 3 mol% relative to Monomer 1), Pd EnCat (R) (25 mg, 3 mol% with respect to monomer 1) was placed in a 50 mL flask under a nitrogen stream, toluene (5.3 mL) and DMF (1.3 mL) were added, and the mixture was stirred at 90°C for 1 hour, and further stirred at 100°C for 2 hours. . The resulting solution was diluted 4-fold with toluene and stirred for an additional 0.5 hours.
After adding 43 μL of trimethyl(phenyl)tin to this solution and stirring at 100° C. for 6 hours, 2.0 mL of phenyl bromide was further added and stirring was performed at 100° C. for 11 hours to carry out terminal treatment. The reaction mixture was allowed to cool to room temperature and methanol was added. The generated precipitate was filtered and vacuum dried at room temperature. The resulting solid was dissolved in chloroform and stirred with SCAVENGER diamine silica at room temperature for 1 hour. The mixture was passed through a silica gel chromatograph (silica gel 60, developing solvent chloroform) to obtain a chloroform solution of the product. Ethyl acetate was added to the solution, and the resulting solid was filtered and vacuum dried at 50° C. to obtain the product polymer 1 (poly[DTS(EH)TPD-r-DTS(nC8)TPD]). Polymer 1 had an average molecular weight Mw of 3.2×10 ⁵ and a PDI of 5.2. Yield was 83%.

(scheme)

(Example: Production of photoelectric conversion element)
The ITO-coated glass substrate was ultrasonically cleaned with IPA/water (1:1 volume ratio) for 10 minutes and acetone for 5 minutes, respectively, dried and then UV-ozone surface treated for 10 minutes. A solution obtained by diluting a SnO ₂ colloid solution with pure water to 1/10 was spin-coated on this substrate at 5,000 rpm for 30 seconds, and baked at 150° C. for 40 minutes. A 0.1 M tin chloride solution was prepared by mixing 189 mg of tin chloride with a mixed solution of 10 mL of ethanol and 36 μL of water for 1 hour. This tin chloride solution was aged in the atmosphere in a transparent vial for 3 days or longer, then spin-coated on the tin oxide film at 6,000 rpm for 30 seconds, further baked at 100° C. for 10 minutes, and then baked at 180° C. for 1 hour to form a SnOx film ( electron transport layer) was prepared.
A 1.25 M CsPbI ₂ Br solution prepared by stirring CsBr and PbI ₂ in a mixed solvent of DMSO/DMF (volume ratio 4:6) at room temperature for 1 hour was applied on the obtained SnOx film at 1,000 rpm for 10 minutes. seconds, then spin-coated at 3,000 rpm for 30 seconds. After storing this coating film at room temperature for 10 minutes, it was heated on a hot plate at 180° C. for 10 minutes to form a perovskite layer (active layer).
A hole transport layer was formed by dissolving Polymer 1 in chlorobenzene at a concentration of 7 mg/mL and spin-coating the solution at 3,000 rpm for 30 seconds. All these operations were performed in a clean room environment in which the humidity was controlled to 20% or less. Finally, a photoelectric conversion element was obtained by forming a gold electrode by vapor deposition under a high vacuum condition of 1×10 ⁻³ Pa or less.

(Comparative example)
A photoelectric conversion device was fabricated in the same manner as in Example except that P3HT was dissolved in chlorobenzene at a concentration of 10 mg/mL and spin-coated at 3,000 rpm for 30 seconds to form a hole transport layer.

(Evaluation of photoelectric conversion element)
A PEC-L01 solar simulator (Peccell Technologies) was used to irradiate simulated sunlight of AM 1.5 G (100 mW/cm ² ) to perform IV measurement. A white LED light source of 200 lx (60 μW/cm ² ) to 1000 lx (300 μW/cm ² ) was used as an indoor light source.
Table 1 shows the parameters obtained by IV measurement at AM 1.5 G for the photoelectric conversion element produced in Example and the photoelectric conversion element produced in Comparative Example, and FIG. 4-1 shows the statistical data. and Figure 4-2.

Table 2 shows the parameters obtained when the illuminance of the photoelectric conversion element manufactured in Example and the photoelectric conversion element manufactured in Comparative Example was varied from 200 lx to 1000 lx.

From these results, it can be seen that the photoelectric conversion elements (Examples) according to the present invention are excellent in both open-circuit voltage and hysteresis and exhibit high performance in both simulated sunlight and LED low-illuminance light.

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 10 back sheet 12 base material 13 solar cell module 14 thin film solar cell 100 photoelectric conversion element 101 lower part Electrode 102 Buffer layer 103 Active layer 104 Buffer layer 105 Upper electrode 106 Base material

Claims (7)

A photoelectric conversion element having a pair of electrodes composed of an upper electrode and a lower electrode, and an active layer positioned between the pair of electrodes and containing an organic-inorganic hybrid semiconductor compound,
an organic semiconductor compound having a hole-transporting ability is positioned between the active layer and at least one of the pair of electrodes, and the organic semiconductor compound having a hole-transporting ability is a polymer compound; A photoelectric conversion device, wherein the compound comprises a condensed polycyclic aromatic skeleton. 2. The photoelectric conversion device according to claim 1, wherein the polymer compound contains a condensed polycyclic aromatic skeleton represented by the following formula (I).

(In formula (I), ring A and ring B each independently represent a 5-membered aromatic heterocyclic ring, and ring C represents a ring optionally having a substituent. X ¹ and X ² are Each independently represents an active group, and each of R ¹ and R ² is independently selected from a hydrogen atom, a halogen atom, and a hydrocarbon group which may have a heteroatom.) 3. The photoelectric conversion device according to claim 2, wherein the compound represented by formula (I) includes a compound selected from the condensed polycyclic aromatic skeletons represented by formula (II) and formula (III).

(In formula (II) and formula (III), X ¹ , X ² , R ¹ , R ² and ring C are as defined in formula (I) above. X ¹¹ and X ²¹ are each independently , an atom selected from the elements of Group 16 of the periodic table.) The compound represented by formula (II) or formula (III) is a compound containing a condensed polycyclic aromatic skeleton represented by formula (IV), formula (V), formula (VI), or formula (VII) 4. The photoelectric conversion device according to claim 3.

(In Formula (IV), Formula (V), Formula (VI) and Formula (VII), X ¹ , X ² , R ¹ and R ² are as defined in Formula (I) above. Formula (IV ), Z ¹ represents Z ¹¹ (R ³ ) (R ⁴ ), Z ¹² (R ⁵ ) or Z ¹³ , Z ¹¹ represents an atom selected from Group 14 elements of the periodic table, R ³ and R ⁴ has the same definition as R ¹ and R ² in the formula (1), Z ¹² represents an atom selected from elements of Group 15 of the periodic table, R ⁵ has the same definition as R ³ and R ⁴ , and Z ¹³ represents an atom selected from the elements of group 16 of the periodic table.
In formula (V), R ⁶ and R ⁷ are a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted an optionally substituted alkynyl group, an optionally substituted aromatic group, an optionally substituted alkoxy group, and an optionally substituted aryloxy group.
In formula (VI), R ⁸ to R ¹¹ have the same meanings as R ³ and R ⁴ , R ¹² and R ¹³ have the same meanings as R ¹ and R ² in formula (1) above, and Z ² and Z ³ are Each independently indicates an atom selected from Group 14 elements of the periodic table.
In Formula (VII), R ¹⁴ and R ¹⁵ have the same definitions as R ³ and R ⁴ , and Z ⁴ represents an atom selected from Group 16 elements of the periodic table. 5. The photoelectric conversion device according to claim 1, wherein the organic-inorganic hybrid semiconductor compound is a compound having a perovskite structure. The compound having a perovskite structure is represented by CsPb _(1-y) M _y X ₃ (where M is a metal element, X is a halogen element, and y is a real number satisfying 0≦y≦1). Item 6. The photoelectric conversion device according to item 5. A light energy harvesting device for low illuminance of 5,000 lux or less, comprising the photoelectric conversion element according to any one of claims 1 to 6.

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