JP2023128265A - Photoelectric conversion element and method for manufacturing the same - Google Patents

Abstract

To provide a photoelectric conversion element which has a high open-circuit voltage and whose photoelectric conversion efficiency hardly decreases even by long-term light irradiation.SOLUTION: The photoelectric conversion element includes a lower electrode, an intermediate layer, an active layer, and an upper electrode in this order. The active layer contains an organic-inorganic hybrid perovskite semiconductor compound. The intermediate layer contains a compound represented by the following formula (I). (Q is a carboxylic acid ion or a sulfonic acid ion; M1 and M2 are each a specific chain aliphatic hydrocarbon group; M3 is one of an ether bond and -NH-, or a structure in which these bonds are bonded via an alkylene group; R1 and R2 are each a specific chain saturated aliphatic hydrocarbon group; and R3 is a specific aliphatic hydrocarbon group.)SELECTED DRAWING: Figure 1

Description

The present invention relates to a photoelectric conversion element having an intermediate layer containing a specific compound and a method for manufacturing the same.

As a photoelectric conversion element, one in which an active layer, a buffer layer, etc. are arranged between a pair of electrodes is known. In order to improve the photoelectric conversion efficiency of this photoelectric conversion element, the use of organic-inorganic hybrid semiconductor compounds as the active layer is being considered, and compounds with a perovskite structure are attracting particular attention (for example, Patent Document 1) .

JP2017-066096A

Photoelectric conversion devices using organic-inorganic hybrid perovskite semiconductor compounds are expected to be put to practical use from the viewpoint of energy harvesting, etc., as a clean power generation method using familiar light energy. On the other hand, when exposed to light for a long time, the photoelectric conversion efficiency may decrease, and the deterioration behavior is not uniform. One possible cause of this decrease in photoelectric conversion efficiency is that defects in the active layer or defects occurring at the interface between the active layer and the buffer layer induce sudden leakage or instability. Further, such defects on the bonding surface may cause a problem of lowering the open circuit voltage of the photoelectric conversion element.

An object of the present invention is to provide a photoelectric conversion element that has a high open-circuit voltage and whose photoelectric conversion efficiency does not easily decrease even under long-term light irradiation.

The present inventors conducted extensive studies to solve the above-mentioned problems. As a result, the inventors found that the above-mentioned problems can be solved by providing an intermediate layer containing a specific compound between the active layer and the lower electrode, and have completed the present invention.

That is, the gist of the present invention is as follows.

[1] A photoelectric conversion element having a lower electrode, an intermediate layer, an active layer, and an upper electrode in this order, wherein the active layer contains an organic-inorganic hybrid perovskite semiconductor compound, and the intermediate layer is represented by formula (I). A photoelectric conversion element containing a compound.

(In formula (I), Q is a carboxylic acid ion or a sulfonic acid ion, and M ¹ and M ² are each independently a chain aliphatic hydrocarbon having 1 to 10 carbon atoms, which may have a substituent. group, M ³ is an ether bond, any one of -CO- and -NH-, or a structure in which these bonds are bonded via an alkylene group, and R ¹ and R ² are each independently is a hydrogen atom or a chain saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms, and R ³ is a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms.)

[2] The photoelectric conversion element according to [1], further comprising an electron transport layer between the intermediate layer and the lower electrode.

[3] The photoelectric conversion element according to [2], wherein the electron transport layer contains a metal oxide.

[4] The photoelectric conversion element according to [3], wherein the metal oxide is tin oxide.

[5] The photoelectric conversion element according to any one of [1] to [4], wherein the intermediate layer has a thickness of 0.5 nm or more and 100 nm or less.

[6] A method for producing a photoelectric conversion element having, in this order, a lower electrode, an intermediate layer, an active layer containing an organic-inorganic hybrid perovskite semiconductor compound, and an upper electrode, which contains a compound represented by the following formula (I). A method for manufacturing a photoelectric conversion element, comprising the step of applying a solution.

(In formula (I), Q is a carboxylic acid ion or a sulfonic acid ion, and M ¹ and M ² are each independently a chain aliphatic hydrocarbon having 1 to 10 carbon atoms, which may have a substituent. group, M ³ is an ether bond, any one of -CO- and -NH-, or a structure in which these bonds are bonded via an alkylene group, and R ¹ and R ² are each independently is a hydrogen atom or a chain saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms, and R ³ is a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms.)

According to the present invention, it is possible to provide a photoelectric conversion element that has a high open-circuit voltage and whose photoelectric conversion efficiency does not easily decrease even under long-term light irradiation.

1 is a schematic cross-sectional view of a photoelectric conversion element as an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view of a photoelectric conversion element module as an embodiment of the present invention.

Embodiments of the present invention will be described in detail below, but these descriptions are only examples (representative examples) of the embodiments of the present invention, and the present invention is not limited to these contents unless the gist thereof is exceeded.

[Photoelectric conversion element]
A photoelectric conversion element according to an embodiment of the present invention (hereinafter sometimes referred to as "photoelectric conversion element according to the present invention", "photoelectric conversion element of the present invention", or simply "photoelectric conversion element") has a lower electrode. , a photoelectric conversion element having an intermediate layer, an active layer, and an upper electrode in this order, the active layer containing an organic-inorganic hybrid perovskite semiconductor compound, and the intermediate layer containing a compound represented by the following formula (I) (hereinafter, It is a photoelectric conversion element containing a "specific compound according to the present invention" or simply "specific compound".

(In formula (I), Q is a carboxylic acid ion or a sulfonic acid ion, and M ¹ and M ² are each independently a chain aliphatic hydrocarbon having 1 to 10 carbon atoms, which may have a substituent. group, M ³ is an ether bond, any one of -CO- and -NH-, or a structure in which these bonds are bonded via an alkylene group, and R ¹ and R ² are each independently is a hydrogen atom or a chain saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms, and R ³ is a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms.)

According to the present invention, by providing an intermediate layer containing the above-mentioned specific compound between the active layer and the lower electrode, in the photoelectric conversion element, the open circuit voltage is increased, the photoelectric conversion efficiency is improved, and a good A filmy active layer can be formed, and the light resistance of the photoelectric conversion element can be improved. That is, it is possible to provide a photoelectric conversion element that has a high open-circuit voltage and whose photoelectric conversion efficiency does not easily decrease even under long-term light irradiation.

Hereinafter, the structure of the photoelectric conversion element of the present invention will be explained using FIG. 1. FIG. 1 is a sectional view showing one embodiment of a photoelectric conversion element of the present invention. The photoelectric conversion element shown in FIG. 1 is a photoelectric conversion element used in a general solar cell, but the photoelectric conversion element according to the present invention is not limited to the element having the structure shown in FIG. 1.

In the photoelectric conversion element 100 shown in FIG. 1, a lower electrode 101, an active layer 104, an intermediate layer 103, and an upper electrode 106 are arranged in this order. The photoelectric conversion element 100 may further include a buffer layer 102 existing between the lower electrode 101 and the intermediate layer 103 and a buffer layer 105 existing between the upper electrode 106 and the active layer 104. Further, it may include the base material 107, and may include other layers such as an insulator layer and a work function tuning layer.

[electrode]
The photoelectric conversion element 100 shown in FIG. 1 has a lower electrode 101 and an upper electrode 106. The electrode has a function of collecting holes and electrons generated by light absorption in the active layer 104. The photoelectric conversion element 100 according to this embodiment 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 base material or is provided on a base material, an electrode closer to the base material may be called a lower electrode, and an electrode farther from the base material may be called an upper electrode. Further, a transparent electrode may be called a lower electrode, and an electrode having lower transparency than the lower electrode may be called an upper electrode.

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 an anode and the upper electrode 106 is a cathode, or a reverse configuration in which the lower electrode 101 is a cathode and the upper electrode 106 is an anode. It may be a type configuration.

Either one of the pair of electrodes may be translucent, or both may be translucent. Translucency usually means that the transmittance of visible light (wavelength 350 to 700 nm) is 40% or more. The visible light transmittance of the electrode is preferably high because more light passes through the transparent electrode and reaches the active layer, and particularly preferably 70% or more. The transmittance of visible light can be measured with a spectrophotometer (for example, U-4100 manufactured by Hitachi High-Technology).
There are no particular restrictions on the constituent members of the lower electrode 101 and the upper electrode 106, or the anode and cathode, and the manufacturing method thereof, and they can be manufactured using known techniques. For example, it can be produced by the method described in International Publication No. 2013/171517, International Publication No. 2013/180230, or Japanese Patent Application Publication No. 2012-191194.

[Active layer]
The active layer 104 included in the photoelectric conversion element 100 is located between a pair of electrodes. The active layer 104 is a layer that contains an organic-inorganic hybrid perovskite semiconductor compound and performs photoelectric conversion. When the photoelectric conversion element 100 receives light, the light is absorbed by the active layer 104 and carriers are generated, and the generated carriers are taken out from the lower electrode 101 and the upper electrode 106.

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 refers to a compound that exhibits semiconductor properties.
A perovskite semiconductor compound refers to a semiconductor compound having a perovskite structure.

The organic-inorganic hybrid perovskite semiconductor compound is not particularly limited, but for example, the compound described by Galasso et al. Compounds listed in Structure and Properties of Inorganic Solids, Chapter 7 - Perovskite type and related structures can be used. For example, examples of the organic-inorganic hybrid perovskite semiconductor compound include an AMX ₃ type compound represented by the general formula AMX ₃ or an A ₂ MX ₄ type compound represented by the general formula A ₂ MX ₄ . Here, M represents a divalent cation, A represents a monovalent cation, and X represents a monovalent anion.

Although there is no particular restriction on the monovalent cation A, the cations described in the above-mentioned book by Galasso can be used. More specific examples include cations containing elements of Group 1 and Groups 13 to 16 of the periodic table. Among these, cesium ion, rubidium ion, potassium ion, ammonium ion which may have a substituent, or phosphonium ion which may have a substituent are preferable. Examples of ammonium ions that may have substituents include primary ammonium ions and secondary ammonium ions. There are no particular restrictions on the substituents. Specific examples of ammonium ions that may have substituents include alkylammonium ions and arylammonium ions. In particular, a monoalkylammonium ion having a three-dimensional crystal structure is preferred because steric hindrance is unlikely to occur, and an alkyl ammonium ion substituted with a fluorine atom is preferably used because of its high stability. Moreover, as the cation A, two or more types of cations may be used in combination.

Specific examples of monovalent cation A include methylammonium ion, monofluoromethylammonium ion, difluoridemethylammonium ion, trifluoridemethylammonium 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, phenethyl ammonium ion, guanidium ion, formamidinium ion, acetamidinium ion or imidazolium Examples include ions.

The divalent cation M is not particularly limited either, but a divalent metal cation or a metalloid cation is preferred. Specific examples include cations of Group 14 elements of the periodic table. More specifically, lead cations (Pb ²⁺ ), tin cations (Sn ²⁺ ), and germanium cations (Ge ²⁺ ) can be mentioned. Moreover, as the cation M, two or more types of cations may be used in combination. In addition, from the viewpoint of high stability of the photoelectric conversion element, it is particularly preferable to use a lead cation or two or more types of cations containing a lead cation.

Examples of the monovalent anion ion, zirconate ion, 2,4-pentanedionate ion, silicofluoride ion, etc. X may be one type of anion or a combination of two or more types of anions.
X is preferably a halide ion or a combination of a halide ion and another anion. By selecting the type and combination of X, the bandgap of the active layer can be adjusted to a preferable range described below. Since the band gap of the active layer tends to be appropriately narrowed, X is preferably a halide ion such as a chloride ion, a bromide ion, or an iodide ion, and more preferably a bromide ion or an iodide ion.

The organic-inorganic hybrid perovskite semiconductor compound is preferably a halide-based organic-inorganic hybrid perovskite semiconductor compound because its light absorption characteristics and charge mobility are suitable for photoelectric conversion.

Specific examples of halide organic-inorganic hybrid perovskite semiconductor compounds include CH ₃ NH ₃ PbI ₃ , CH ₃ NH ₃ PbBr ₃ , CH ₃ NH ₃ PbCl ₃ , CH ₃ NH ₃ SnI ₃ , CH ₃ NH ₃ SnBr ₃ , CH ₃ NH ₃ SnCl ₃ , 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 compounds in which CFH _{2 NH 3 ,} CF ₂ HNH ₃ , or CF ₃ NH ₃ is used instead of CH ₃ NH 3 in the above-mentioned compounds. Note that x represents an arbitrary value of 0 or more and 3 or less, and y represents an arbitrary value of 0 or more and 1 or less.

The active layer 104 may contain two or more types of semiconductor compounds, or may contain two or more types of organic-inorganic hybrid perovskite semiconductor compounds. For example, the active layer 104 may contain two or more organic-inorganic hybrid perovskite semiconductor compounds in which at least one of A, M, and X is different. Furthermore, the active layer 104 may have a laminated structure formed of a plurality of layers containing different materials or components.

The active layer 104 may contain components other than the organic-inorganic hybrid perovskite semiconductor compound (hereinafter sometimes referred to as "other components"). Examples of other components include additives of inorganic compounds or organic compounds, such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates, or ammonium salts. Further, it may contain a semiconductor compound other than the organic-inorganic hybrid perovskite semiconductor compound.
The amount of the organic-inorganic hybrid perovskite semiconductor compound contained in the active layer 104 is preferably 50% by mass or more, more preferably 70% by mass or more, and 80% by mass or more, since it has excellent semiconductor properties. It is even more preferable that there be. There is no particular upper limit to the amount of the organic-inorganic hybrid perovskite semiconductor compound contained in the active layer 104.

The grain size of the organic-inorganic hybrid berovskite semiconductor compound contained in the active layer is preferably large in order to reduce the number of grain boundaries and thereby make defects less likely to occur. Therefore, the particle size of the organic-inorganic hybrid perovskite semiconductor compound in the active layer is preferably 0.7 μm or more, more preferably 0.8 μm or more, and even more preferably 0.9 μm or more. The particle size of the organic-inorganic hybrid perovskite semiconductor compound can be increased by forming an active layer on an intermediate layer containing a specific compound by a coating method. On the other hand, from the viewpoint of forming an active layer with a uniform particle size, it is preferable that the particle size of the organic-inorganic hybrid berovskite semiconductor compound is small. Therefore, the particle size of the organic-inorganic hybrid perovskite semiconductor compound in the active layer is preferably 3.0 μm or less, particularly 2.0 μm or less. The particle size of the organic-inorganic hybrid perovskite semiconductor compound can be measured by scanning electron microscopy. Specifically, the surface of the active layer was measured using a scanning electron microscope "S-4800" manufactured by Hitachi High-Technology Co., Ltd., and the obtained scanning electron microscopy image of particles of an organic-inorganic hybrid perovskite semiconductor compound was It is sufficient to set a boundary and calculate the arithmetic mean of the circle-equivalent surface area diameters of ten arbitrary particles. Specifically, the particle size of the organic-inorganic hybrid perovskite semiconductor compound can be measured and calculated by the method detailed in the Examples section.

The range of the ionization potential of the active layer 104 is not particularly limited. However, it is preferably -5.5 eV or more, and -5.2 eV or more, in terms of the fact that the power generation efficiency tends to be high compared to fluorescent lamps and LED lamps, which are visible light sources widely used indoors. It is more preferable that it is -5.0 eV or more, and on the other hand, it is preferably -4.0 eV or less, more preferably -4.6 eV or less, and -4.4 eV or less. It is more preferable that
Here, the ionization potential of the active layer can be calculated by irradiating a sample with light and measuring the minimum energy (eV) required for the irradiation energy to repel photoelectrons. Any measuring device can be used, and for example, AC-2, AC-3, etc. manufactured by Riken Keiki Co., Ltd. can be used.
Further, the bandgap range of the active layer is not particularly limited. However, the power generation efficiency tends to be higher for fluorescent lamps and LED lamps, which are visible light sources widely used indoors, etc. In particular, energy from indoor light sources separates excitons generated in semiconductors into positive and negative charges. It is preferably 2.6 eV or more, more preferably 2.4 eV or more, and still more preferably 2.2 eV or more, since it is sufficient and not excessive, and the power generation efficiency tends to be high. On the other hand, it is preferably 1.2 eV or less, more preferably 1.4 eV or less, and even more preferably 1.6 eV or less.

Here, the bandgap can be calculated from the absorption edge wavelength and absorbance of the semiconductor compound. Specifically, a semiconductor compound is deposited on a suitable sample such as a transparent glass substrate, its transmission spectrum is measured, the horizontal axis wavelength is converted to eV, the vertical axis transmittance is converted to √(ahν), and this By fitting the absorption rise as a straight line, the eV value that intersects with the baseline can be calculated as the band gap. The transmission spectrum can be measured using, for example, a spectrophotometer such as U-4100 manufactured by Hitachi High-Tech.

The ionization potential of the active layer can be adjusted by, for example, the type and amount of the cation component in the organic-inorganic hybrid perovskite semiconductor compound.
Further, the band gap of the active layer can be adjusted by, for example, the type and amount of the halogen element in the organic-inorganic hybrid perovskite semiconductor compound.

There is no particular restriction on the thickness of the active layer 104. The active layer 104 is preferably thick in terms of absorbing more light. Specifically, it is preferably 10 nm or more, more preferably 50 nm or more, even more preferably 100 nm or more, and particularly preferably 120 nm or more. On the other hand, the active layer 104 is preferably thin because the series resistance of the photoelectric conversion element is reduced and the charge extraction efficiency is likely to be increased. Specifically, it is preferably 1500 nm or less, more preferably 1200 nm or less, and even more preferably 800 nm or less.

The method for forming the active layer 104 is not particularly limited, and can be formed by any method. Specifically, a coating method and a vapor deposition method (or co-evaporation method) can be mentioned. The coating method is preferable in that the active layer 104 can be easily formed. Specifically, for example, a coating liquid containing an organic-inorganic hybrid perovskite semiconductor compound or its precursor and a solvent is applied to a layer below the active layer (in the present invention, usually the above-mentioned intermediate layer), Examples include a method of forming the active layer 104 by heating and drying as necessary.
Further, after applying such a coating liquid, the organic-inorganic hybrid perovskite semiconductor compound can be precipitated by applying a poor solvent for the organic-inorganic hybrid perovskite semiconductor compound.

The precursor of an organic-inorganic hybrid perovskite semiconductor compound refers to a material that can be converted into an organic-inorganic hybrid perovskite semiconductor compound by heating or the like. Specifically, for example, a precursor of an organic-inorganic hybrid perovskite semiconductor compound is prepared by mixing a compound represented by the general formula AX, a compound represented by the general formula _MX2 , and a solvent and heating and stirring the mixture. A coating liquid containing the following can be prepared. Then, by applying this coating liquid, dropping a poor solvent as needed, and heating and drying it, an active layer 104 containing an organic-inorganic hybrid perovskite semiconductor compound represented by the general formula _AMX3 can be manufactured. can. Alternatively, a coating liquid containing a compound represented by the general formula AX and a solvent and a coating liquid containing a compound represented by the general formula _MX2 and a solvent are prepared, and these two types of coating liquids are sequentially applied. By stacking layers containing a precursor of the organic-inorganic hybrid perovskite semiconductor compound AMX ₃ and heating and drying them, the organic-inorganic hybrid perovskite semiconductor compound AMX ₃ can be precipitated to form the active layer 104. can.

The solvent for the active layer forming coating solution is not particularly limited as long as it can dissolve the organic-inorganic hybrid perovskite semiconductor precursor and other components, if used. Specifically, for example, organic solvents such as dimethylformamide (DMF), dimethyl sulfoxide, and N-methylpyrrolidone are preferable for the coating solution of a precursor containing a lead compound in terms of solubility and high boiling point. Formamide (DMF) is more preferred. Further, when forming an active layer by sequentially applying coating liquids, isopropyl alcohol, ethanol, etc. can be used as the coating liquid of a precursor such as a halide. These solvents may be used alone or in combination of two or more.

Any method can be used to apply the coating liquid. Specifically, for example, spin coating method, inkjet method, doctor blade method, drop casting method, reverse roll coating method, gravure coating method, kiss coating method, roll brushing method, spray coating method, air knife coating method, wire barber coating method. , pipe doctor method, impregnation/coating method, curtain coating method, etc.

[Middle layer]
The intermediate layer 103 contains a specific compound represented by the following formula (I).

(In formula (I), Q is a carboxylic acid ion or a sulfonic acid ion, and M ¹ and M ² are each independently a chain aliphatic hydrocarbon having 1 to 10 carbon atoms, which may have a substituent. group, M ³ is an ether bond, any one of -CO- and -NH-, or a structure in which these bonds are bonded via an alkylene group, and R ¹ and R ² are each independently is a hydrogen atom or a chain saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms, and R ³ is a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms.)

The reason why the photoelectric conversion efficiency, light resistance, and open circuit voltage of the photoelectric conversion element of the present invention are improved by having an intermediate layer containing a specific compound is estimated as follows.
When forming the active layer, the specific compound coordinates with the precursor of the organic-inorganic hybrid perovskite semiconductor compound, thereby suppressing the nucleation rate of the crystal of the organic-inorganic hybrid perovskite semiconductor compound. As a result, it becomes difficult to form many microcrystals, and the crystal growth rate slows down, promoting the formation of crystals with large grain sizes. Formation of crystals with large grain sizes reduces grain boundaries, making it possible to suppress the generation of defects between grains. Furthermore, it is estimated that the flatness and smoothness of the active layer surface can be improved, and it is possible to reduce irregularities on the active layer surface and electrode layer that may cause sudden leakage.

The carboxylate ion or sulfonate ion (Q) of the specific compound is believed to repair cation defect sites in the active layer. Further, it is believed that the quaternary ammonium ion -N ⁺ R ¹ R ² - (cation moiety) of the specific compound suppresses the generation of defects in the active layer and repairs anion defect sites in the active layer. As a result, it is thought that the open circuit voltage increases, the photoelectric conversion efficiency improves, and the light resistance also improves. From this viewpoint, in the photoelectric conversion element of the present invention, it is preferable that the active layer is provided in contact with the intermediate layer.

It is presumed that the vinyl group of a specific compound has the effect of increasing the efficiency of electron transport through a π-bonded electron cloud. Further, the carbonyl group of the specific compound is thought to coordinate with the precursor of the active layer, thereby retarding crystal growth and promoting the formation of crystals with large particle sizes. Furthermore, the presence of the specific linking group M ³ adjacent to this carbonyl group tends to improve the photoelectric conversion efficiency.

When the photoelectric conversion element of the present invention has an electron transport layer, a dipole is formed at the interface by the anion part coordinated to the electron transport layer and the cation part coordinated to the active layer. Here, it is considered that by providing the intermediate layer according to the present invention between the active layer and the electron transport layer, the work function of the electron transport layer is reduced, band alignment is improved, and electron transport efficiency is improved. Therefore, it is preferable that the photoelectric conversion element of the present invention further includes an electron transport layer between the intermediate layer and the lower electrode.

M ¹ and M ² of the specific compound are each independently a chain aliphatic hydrocarbon group having 1 to 10 carbon atoms which may have a substituent. The number of carbon atoms in the aliphatic hydrocarbon group is preferably large in that the distance between the anion and cation is increased and the ionicity is strengthened, but on the other hand, it is preferable that the number of carbon atoms in the aliphatic hydrocarbon group is small in terms of ease of synthesis. Therefore, the number of carbon atoms in the aliphatic hydrocarbon group is preferably 2 or more, and on the other hand, it is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less. .

The substituents that the aliphatic hydrocarbon group may have are not limited as long as they do not significantly impair the effects of the present invention. Examples of substituents that the aliphatic hydrocarbon group may have include a vinyl group, an aryl group, a hydroxy group, an aldehyde group, a carbonyl group, an amino group, a nitro group, a sulfonic acid group, a thienyl group, a pyridinyl group, and an isothiocyanate group. group, amide group, nitrile group, carboxy group, cyano group, thiol group, imino group, etc. Among these, substituents are electron-donating in that they have the potential to repair defects by coordinating with cationic defects such as non-coordinating lead ion defects and iodine vacancies and lead clusters existing in the active layer. It is preferable that On the other hand, in view of the possibility of repairing anionic defects such as Pb-I antisites and uncoordinated iodine ions, the substituent is preferably electron-withdrawing.

^M3 of the specific compound is an ether bond, any one of -CO- and -NH-, or a structure in which these bonds are bonded via an alkylene group. Among these, -NH- and -CO- are preferred from the viewpoint of contributing to defect repair in the active layer, and -NH- is more preferred.

R ¹ and R ² of the specific compound are each independently a hydrogen atom or a saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms. R ¹ and R ² are preferably not bulky from the viewpoint of series resistance of the photoelectric conversion element and ease of coordination to defect sites of the perovskite semiconductor compound. Therefore, R ¹ and R ² are preferably a hydrogen atom or a methyl group.

R ³ of the specific compound is a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms. It is preferable that the aliphatic hydrocarbon group has a large number of carbon atoms in order to improve hydrophobicity and protect the active layer. It is preferable that it is small and not bulky in that it is unlikely to become a hindrance factor. Therefore, R ³ is preferably a chain aliphatic hydrocarbon group, more preferably a chain saturated aliphatic hydrocarbon group, and the number of carbon atoms thereof is preferably 4 or less, and 3 or less. More preferably, the number is 2 or less or hydrogen atoms are even more preferable.

The molecular weight of the specific compound is preferably high in terms of ease of coating the active layer and improving the light resistance of the photoelectric conversion element. It is preferable that it is low since it can become a high resistance component in the element. From these viewpoints, the molecular weight of the specific compound is preferably 100 or more, on the other hand, preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less.

The intermediate layer 103 may contain components other than the specific compound to the extent that the effects of the present invention are not significantly impaired. Specific examples of components other than the specific compound include KF, KCl, KBr, KI, CsF, CsCl, CsBr, CsI, and zwitterions that do not correspond to the specific compound.

The amount of the specific compound contained in the intermediate layer is preferably large in terms of photoelectric conversion efficiency and light resistance of the photoelectric conversion element of the present invention. From this point of view, the amount of the specific compound contained in the intermediate layer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and 95% by mass or more. % or more, and most preferably 100% by mass.

The thickness of the intermediate layer 103 is preferably thin in that it is unlikely to become a barrier to electron transport from the active layer 104 to the cathode, and on the other hand, it is preferably thick in that it is easy to form a uniform intermediate layer 103. From these viewpoints, the thickness of the intermediate layer 103 is preferably 0.5 nm or more, more preferably 1 nm or more, and on the other hand, preferably 100 nm or less, more preferably 50 nm or less. The thickness is preferably 10 nm or less, and more preferably 10 nm or less.

The intermediate layer 103 is preferably formed by a coating method. That is, the method for manufacturing a photoelectric conversion element of the present invention preferably includes a step of applying a solution containing the specific compound according to the present invention.
Specifically, it is preferable to prepare a solution containing a specific compound and apply the solution to form the intermediate layer. The solvent used for the solution of the specific compound is not limited as long as there is no problem with the solubility or coatability of the components contained in the intermediate layer, such as the specific compound. Examples of the solvent include alcohols such as methanol, ethanol, and isopropyl alcohol, and water. Only one type of these may be used, or two or more types may be used in combination.

The concentration of the specific compound in the intermediate layer forming solution is preferably high from the viewpoint of repairing defects in the active layer and buffer layer, and on the other hand, it is preferably low from the viewpoint of facilitating the formation of a uniform film. Therefore, it is preferably 0.01 mg/mL or more, and on the other hand, it is preferably 20 mg/mL or less, more preferably 10 mg/mL or less, and even more preferably 5 mg/mL or less. .

The intermediate layer forming solution is preferably applied by spin coating, since it facilitates the formation of a uniform thin film layer, and the rotational speed is preferably 2000 to 4000 rpm.
Further, since it is easy to dry uniformly in a short time, it is preferable to heat-dry the coating after application. The heating temperature at that time is preferably 150°C or lower, more preferably 100°C or lower, for example 70 to 100°C.

[Buffer layer]
The photoelectric conversion element of the present invention may have a buffer layer. A buffer layer is a layer provided between an active layer and an electrode. When the buffer layer is provided on the side where the intermediate layer is provided between the active layer and the electrode, the buffer layer is preferably provided between the electrode and the intermediate layer.

In FIG. 1, buffer layers 102 and 105 are provided between active layer 104 and at least one of the pair of electrodes 101 and 106. The buffer layer can be used, for example, to improve carrier transfer efficiency from the active layer 104 to the lower electrode 101 or the upper electrode 106, and is preferably a hole transport layer or an electron transport layer. When the photoelectric conversion device of the present invention has a buffer layer, as described above, it is more preferable to have an electron transport layer.

The thicknesses of the buffer layers 102 and 105 are not particularly limited and can be set as appropriate depending on the application. The thickness of the buffer layer is preferably thick in that it covers the base layer without defects and easily satisfies the function as a semiconductor, and specifically, it is preferably 0.5 nm or more, and more preferably 1 nm or more. The thickness is preferably 5 nm or more, and more preferably 5 nm or more. On the other hand, from the viewpoint of carrier transport efficiency of holes and electrons by the buffer layer, it is preferably thin, and specifically, it is preferably 1 μm or less, more preferably 500 nm or less, and 300 nm or less. It is even more preferable that the thickness be 200 nm or less.

There are no restrictions on the method of forming the buffer layer, and an appropriate method can be selected from known forming methods depending on the characteristics of the material. For example, the buffer layer can be formed by preparing a coating liquid containing an organic semiconductor compound, a dopant, and a solvent, which will be described later, and using a wet film forming method such as a spin coating method or an inkjet method. Further, the buffer layer can also be formed by a dry film forming method such as a vacuum evaporation method.

<Electron transport layer>
The photoelectric conversion element of the present invention preferably has an electron transport layer as a buffer layer in contact with the intermediate layer, from the viewpoint of efficient electron extraction and coordination of the specific compound to defects in the electron transport layer.
The form of the electron transport layer is not particularly limited, and any material that can improve the efficiency of extracting electrons from the active layer to the cathode can be used. Specifically, inorganic compounds, organic compounds, or perovskite semiconductor compounds described in known documents such as WO 2013/171517, WO 2013/180230, or JP 2012-191194 are exemplified. For example, examples of the inorganic compound 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. Organic compounds include bathocuproine (BCP), bathophenanthrene (BPHeN), (8-hydroxyquinolinato)aluminum (Alq ₃ ), boron compounds, oxadiazole compounds, benzimidazole compounds, naphthalenetetracarboxylic anhydride (NTCDA) , perylenetetracarboxylic anhydride (PTCDA), fullerene compounds, or phosphine compounds having a double bond with a Group 16 element of the periodic table, such as a phosphine oxide compound or a phosphine sulfide compound. From the viewpoint of stable film formation and durability, the electron transport layer preferably contains an inorganic compound, more preferably contains a metal oxide, and even more preferably contains tin oxide.

<Hole transport layer>
The buffer layer as a hole transport layer is not particularly limited as long as it has a hole transport ability, but it preferably contains an organic semiconductor compound that has a hole transport ability, and other materials may be used as long as the effects of the present invention can be obtained. May contain substances. In the case of the NiP stacked photoelectric conversion element, the amount of transported charge can be easily controlled by the hole transport layer. Hereinafter, in this item, the buffer layer will also be referred to as a hole transport layer.

(organic semiconductor compound)
A semiconductor compound refers to a compound that can be used as a semiconductor material that exhibits semiconductor properties. Note that in this specification, a "semiconductor" is defined by the magnitude of carrier mobility in a solid state. As is well known, carrier mobility is an indicator of how fast (or how much) charges (electrons or holes) 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 ⁻⁵ cm ² /V・S or more, more preferably 5.0×10 ⁻⁵ cm ² /V・S or more, particularly preferably 1.0×10 ⁻⁴ cm ² /V・S or more It is. Note that carrier mobility can be measured, for example, by measuring the IV characteristics of a field effect transistor, or by a time-of-flight method.

Although an organic semiconductor compound is used as the semiconductor compound in this specification, the type thereof is not particularly limited, and for example, conventionally known compounds can be used. Low molecular weight compounds and high molecular weight compounds are known as organic semiconductor compounds. Examples of low-molecular 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, and tria Examples include arylamine compounds such as lylamine compounds, carbazole compounds, and the like. In addition, as a polymeric organic semiconductor compound, a conjugated polymer such as a polythiophene-based polymer, a polyacetylene-based polymer, a polyaniline-based polymer, a polyphenylene-based polymer, a polyphenylene vinylene-based polymer, a polyfluorene-based polymer, or a polypyrrole-based polymer, or a triaryl Included are arylamine polymers such as amine polymers.

The organic semiconductor compound is preferably an arylamine compound, more preferably a triarylamine compound. The arylamine compound refers to a compound having an arylamine structure (a bond between an aryl group and a nitrogen atom), and includes an arylamine polymer. The arylamine polymer is a polymer whose repeating unit contains an arylamine structure, and is also referred to as a polyarylamine compound. Moreover, a triarylamine-based compound is a compound having a triarylamine structure (bonds of three aryl groups to the same nitrogen atom), and includes a triarylamine-based polymer. A triarylamine polymer is a polymer whose repeating units include a triarylamine structure, and is also referred to as a polytriarylamine compound. Such arylamine compounds or triarylamine compounds are preferred because they can be stably oxidized by dopants and exhibit good semiconductor properties, and triarylamine compounds are particularly preferred.

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

The aryl group may further have a substituent. Substituents that the aromatic group may have include, but are not particularly limited to, halogen atoms, hydroxyl groups, cyano groups, amino groups, carboxyl groups, ester groups, alkylcarbonyl groups, acetyl groups, sulfonyl groups, silyl groups, Examples include 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. Preferred substituents on the aryl group include an amino group and 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.

The hole transport layer may contain multiple semiconductor compounds. As the semiconductor compound, for example, a conventionally known semiconductor compound may be used, and the above-mentioned low molecular compounds and high molecular compounds may be used. Examples of low-molecular 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, and triaryls. Examples include arylamine compounds such as amine compounds, carbazole compounds, and the like. In addition, as the polymeric organic semiconductor compound, conjugated polymers such as polythiophene-based polymers, polyacetylene-based polymers, polyaniline-based polymers, polyphenylene-based polymers, polyphenylene vinylene-based polymers, polyfluorene-based polymers, or polypyrrole-based polymers, or the aforementioned Examples include arylamine polymers other than high-molecular organic semiconductor compounds.

(dopant)
The buffer layer as a hole transport layer contains a dopant for the above-mentioned organic semiconductor compound, but its form is not particularly limited. The dopant is a substance for optimizing the conductivity and hole transport ability of the hole transport layer relative 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. It is preferable that the dopant causes a charge transfer reaction with at least one organic semiconductor compound before or after the formation of the hole transport layer. As the dopant, a hypervalent iodine compound is preferable because it has excellent solubility and produces an electron-accepting active site that functions as an oxidizing agent when heated or the like.

It is known that this hypervalent iodine compound acts as a dopant for an organic semiconductor compound and exhibits electron-accepting properties (that is, acts as an oxidizing agent). Further, the electron-accepting dopant can improve the conductivity or hole transport ability of the organic semiconductor compound by depriving the semiconductor compound of electrons. Thus, hypervalent iodine compounds can improve the charge transport properties of organic semiconductor compounds.

A hypervalent iodine compound is a compound containing hypervalent iodine, and is defined as a compound containing iodine with an oxidation number of +3 or more. For example, the dopant can be an iodine (III) compound or an iodine (V) compound. The iodine (V) compound containing pentavalent iodine can be, for example, a periodinane compound such as Dess-Martin periodinane. Examples of the iodine (III) compound 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, since it exhibits good electron acceptability and is unlikely to cause a reverse reaction if the molecule is destroyed during the oxidation process, and among them, diaryliodonium salts are more preferably used. .

A diaryliodonium salt is a salt having an [Ar-I ⁺ -Ar]Y ^- structure. Here, each of the two Ar represents an aryl group. The aryl group (aromatic group) is not particularly limited, and may be, for example, those already mentioned for organic semiconductor compounds. Y ⁻ represents any anion. Y ^- may be, for example, a halide ion, trifluoroacetate ion, tetrafluoroborate ion, or tetrakis(pentafluorophenyl)borate ion. ^Y.sup.- is preferably an anion containing a fluorine atom, since it has high solubility and the coating solution production reaction can proceed smoothly.

Preferred examples of dopants include those represented by the following formula (II). In formula (II), Y ^- represents any anion, and specific examples are as described above.

[R ¹¹ -I ⁺ -R ¹² ]Y ^-... (II)
In formula (II), R ¹¹ and R ¹² are each independently a monovalent organic group. Examples of monovalent organic groups include aliphatic groups or 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. For example, examples of aliphatic hydrocarbon groups include alkyl groups including cycloalkyl groups, alkenyl groups, and alkynyl groups, and specific examples include methyl groups, ethyl groups, butyl groups, and cyclohexyl groups. Furthermore, examples of the aliphatic heterocyclic group include a tetrahydrofuryl group.
Examples of the aromatic group include an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms. For example, examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, a biphenyl group, and the like. Further, examples of the aromatic heterocyclic group include a thienyl group and a pyridyl group.

In addition, the above-mentioned aliphatic group and aromatic group may have a substituent. There are no particular restrictions on the substituents that may be present, but include halogenyl groups, hydroxyl groups, cyano groups, amino groups, carboxyl groups, ester groups, alkylcarbonyl groups, acetyl groups, sulfonyl groups, silyl groups, and boryl groups. , a nitrile group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a thio group, a seleno group, an aromatic hydrocarbon group, an aromatic heterocyclic group, and the like.

R ¹¹ and R ¹² are preferably each independently an aromatic hydrocarbon group having 6 to 20 carbon atoms, more preferably a phenyl group. Here, the aromatic hydrocarbon group preferably has no substituent or an alkyl group having 1 to 6 carbon atoms. In particular, R ¹¹ and R ¹² are preferably phenyl groups having an alkyl group at the para position.

The content of the dopant in the hole transport layer is not particularly limited, but the content of the dopant chemically assists charge transport in the hole transport layer and provides hole mobility above a certain level, while the content of the dopant is an organic material responsible for charge transport. From the viewpoint of ensuring the charge transport path (path) in the semiconductor compound, the content is usually 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 0.2% by mass or more. It is more preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less, and 15% by mass or less. The content is more preferably 12% by mass or less, even more preferably 10% by mass or less.

In addition, in the hole transport layer, the content ratio of the dopant to the organic semiconductor compound (dopant/organic semiconductor compound) is not particularly limited; From the viewpoint of ensuring the charge transport path (path) in the organic semiconductor compound responsible for charge transport while imparting mobility, the content is usually 0.01% by mass or more, preferably 0.1% by mass or more, It is more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and usually 30% by mass or less, and 20% by mass or more. It is preferably at most 15% by mass, more preferably at most 12% by mass, and particularly preferably at most 10% by mass.

In addition, when a photoelectric conversion element has a plurality of buffer layers, any one layer corresponding to the hole transport layer among them only needs to satisfy the above-mentioned content range.

(Other substances)
The buffer layer as a hole transport layer may contain substances other than the above-mentioned organic semiconductor compound and dopant, for example, a photoelectric conversion (active layer) material, an adhesive functional material, a filler, or a strength auxiliary material. It's okay to be there.

[Base material]
The photoelectric conversion element 100 usually has a base material 107 that serves as a support. However, the photoelectric conversion element of the present invention does not have the base material 107 as an essential component, and may not have the base material. The material of the base material 107 is not particularly limited as long as it does not significantly impair the effects of the present invention, and for example, it may be selected from known documents such as WO 2013/171517, WO 2013/180230, or JP 2012-191194. The materials described in can be used.

[Other layers]
The photoelectric conversion element of the present invention may have layers or parts other than the above-mentioned layers.

[Method for manufacturing photoelectric conversion element]
The photoelectric conversion element of the present invention can be manufactured by sequentially forming each layer and member that constitute the photoelectric conversion element 100. There is no particular restriction on the method of forming each layer constituting the photoelectric conversion element 100, and the layers can be formed by a sheet-to-sheet method or a roll-to-roll method. However, as described above, the method for manufacturing a photoelectric conversion element of the present invention preferably includes a step of applying a solution containing the specific compound according to the present invention.

The roll-to-roll method is a method in which a flexible base material wound into a roll is unrolled and processed while being conveyed intermittently or continuously until it is wound up by a take-up roll. According to the roll-to-roll method, it is possible to process long substrates on the order of kilometers at once, so it is more suitable for mass production than the sheet-to-sheet method. On the other hand, the sheet-to-sheet method is preferable in that scratches and peeling due to contact with the rolls are less likely to occur.

The size of the roll used in the roll-to-roll method is not particularly limited as long as it can be handled by the roll-to-roll manufacturing apparatus. However, it is preferable to have a small size so that the roll can be easily handled, and on the other hand, a large size is preferable because each layer is less likely to be damaged by bending stress. Therefore, specifically, the outer diameter of the roll is preferably 5 m or less, more preferably 3 m or less, and even more preferably 1 m or less. On the other hand, the outer diameter of the roll is preferably 10 cm or more, more preferably 20 cm or more, and even more preferably 30 cm or more. The outer diameter of the roll core is preferably 4 m or less, more preferably 3 m or less, and even more preferably 0.5 m or less. On the other hand, the outer diameter of the roll core is preferably 1 cm or more, more preferably 3 cm or more, even more preferably 5 cm or more, particularly preferably 10 cm or more, and 20 cm or more. Most preferably.

It is preferable that the roll width is short in terms of ease of handling the roll, and on the other hand, it is preferable that the roll width is long in terms of increasing the degree of freedom in the size of the photoelectric conversion element. From these viewpoints, the roll width is preferably 5 cm or more, more preferably 10 cm or more, and even more preferably 20 cm or more. On the other hand, the roll width is preferably 5 m or less, more preferably 3 m or less, and even more preferably 2 m or less.

The method for manufacturing a photoelectric conversion element of the present invention includes at least the following steps of forming an electrode, forming an intermediate layer, forming an active layer, and forming an upper electrode. Further, as described above, the intermediate layer is preferably formed by a coating method. That is, the method for manufacturing a photoelectric conversion element of the present invention preferably includes a step of forming an intermediate layer by applying a solution containing the specific compound represented by formula (I).
Further, as described above, it is preferable that the active layer is also formed by a coating method, and it is more preferable that the intermediate layer and the active layer are formed by a coating method. That is, the method for manufacturing a photoelectric conversion element of the present invention preferably includes a step of forming an active layer by a coating method, and a step of forming an intermediate layer by a coating method and a step of forming an active layer by a coating method are performed in this order. It is preferable to have.

The adhesion between each layer of the photoelectric conversion element, such as the buffer layer 102 and the lower electrode 101, the buffer layer 102 and the active layer 104, is improved, and the thermal stability and light resistance of the photoelectric conversion element are likely to be improved. It is preferable to include a heating process (hereinafter sometimes referred to as "annealing process") after electrode lamination. As for the heating temperature, it is preferable to conduct the heating at a high temperature since the adhesion between each layer tends to be high, and on the other hand, it is preferable to conduct the heating at a low temperature because the organic compound contained in each layer of the photoelectric conversion element is difficult to thermally decompose. is preferred. From these viewpoints, the heating temperature is preferably 50°C or higher, more preferably 80°C or higher. On the other hand, it is preferable to carry out at 300°C or lower, more preferably to carry out at 280°C or lower, and even more preferably to carry out at 250°C or lower. Heating may be performed by increasing the temperature in stages.

The heating time is preferably 1 minute or more, more preferably 3 minutes or more, from the viewpoint of easily improving interlayer adhesion without thermally decomposing the organic compound, and on the other hand, 180 minutes or less. The duration is preferably 60 minutes or less, and more preferably 60 minutes or less.

The heating step is usually terminated when the open circuit voltage, short circuit current, and fill factor of the photoelectric conversion element reach constant values. The heating step is preferably performed under normal pressure in an inert gas atmosphere in order to prevent thermal oxidation of the constituent materials of the photoelectric conversion element. 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. Further, the heating may be performed in a batch manner or in a continuous manner.

[Photoelectric conversion characteristics]
The photoelectric conversion characteristics of the photoelectric conversion element can be determined as follows. The photoelectric conversion element is irradiated with light of an appropriate spectrum, and the current-voltage characteristics are measured. From the obtained 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 of the photoelectric conversion element, and shunt resistance are determined. You can ask for it. For example, the current-voltage characteristics can be measured by irradiating the photoelectric conversion element with white LED light having a color temperature of 5000K.

The open-circuit voltage of the photoelectric conversion element of the present invention is preferably high in that the photoelectric conversion efficiency tends to be high. Specifically, it is preferably 0.9V or more, and more preferably 1.0V or more. As described above, the open circuit voltage can be increased by providing an intermediate layer containing a specific compound.

The photoelectric conversion element of the present invention has excellent power generation efficiency in a low illuminance region (10 to 5000 lux). In particular, when a light source such as a white LED light is used, the photoelectric conversion efficiency can be 20% or more. Moreover, the photoelectric conversion efficiency at 200 lux can be made 25% or more. There is no particular limit to the upper limit of photoelectric conversion efficiency, and the higher it is, the better.

Note that this photoelectric conversion efficiency (PCE) is the total energy amount (for example, In the case of sunlight with an intensity of AM1.5G, the value (%) divided by 100 mW/cm ² is the photoelectric conversion efficiency (PCE).

Moreover, the photoelectric conversion element of the present invention has excellent light resistance due to the provision of the intermediate layer containing the specific compound, and a decrease in photoelectric conversion efficiency after light irradiation is suppressed.

[Photoelectric conversion module]
The photoelectric conversion element of the present invention can improve light resistance by sealing.

FIG. 2 shows a cross-sectional configuration of a photoelectric conversion module according to an embodiment of the present invention. In FIG. 2, the photoelectric conversion module 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 photoelectric conversion 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 photoelectric conversion module 14 according to this embodiment includes the above-described photoelectric conversion element of the present invention as the photoelectric conversion element 6. By irradiating light from the side where the protective film 1 is formed (lower side in FIG. 2), the photoelectric conversion element 6 can generate electricity. Note that the photoelectric conversion module 14 does not need to include all of these constituent members, and can arbitrarily select necessary constituent members.

There are no particular restrictions on each component constituting the photoelectric conversion module and its manufacturing method, and known techniques can be used. For example, techniques described in International Publication No. 2013/171517, International Publication No. 2013/180230, and Japanese Patent Application Publication No. 2012-191194 can be used.

[Application]
There are no restrictions on the use of the photoelectric conversion element and photoelectric conversion module of the present invention, and they can be used for any purpose. For example, it can be used for building materials, automobiles, interiors, railways, ships, aerospace, home appliances, telephones, toys, etc. The photoelectric conversion element of the present invention is suitable for use in power generation using sunlight and indoor light. Furthermore, the photoelectric conversion element of the present invention exhibits excellent conversion efficiency in a low-illuminance environment and is suitable for energy harvesting applications. As used herein, low light environment usually means between 10 and 5000 lux, typically around 200 lux. Energy harvesting is a technology that harvests small amounts of energy from the surrounding environment and converts it into electricity.

EXAMPLES Hereinafter, an example of an embodiment of the present invention will be described in detail using Examples, but the present invention is not limited to the following Examples.

[Measurement of photoelectric conversion efficiency]
The photoelectric conversion efficiency was measured by irradiating the photoelectric conversion element with white LED light having a color temperature of 5000 K using the following method. At this time, the irradiation intensity was adjusted using a luminometer so that the light receiving surface of the photoelectric conversion element had an illuminance of 200 lux. Under this environment, a current-voltage curve (IV curve) was measured using a source meter, and its maximum output value was determined. This value was divided by the total energy amount of the above-mentioned irradiation light to obtain the photoelectric conversion efficiency (%) of the photoelectric conversion element. Here, the above-mentioned color temperature was measured in accordance with JIS Z8725:2015.
Specifically, in the following measurements, a 1 mm square metal mask was attached to the photoelectric conversion element obtained in each example, and the 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 the irradiation light source, an LED light source BLD-100 for indoor light evaluation manufactured by Bunko Keiki Co., Ltd. was used, and the photoelectric conversion element was irradiated with white LED light having a color temperature of 5000K. At this time, the irradiation intensity was adjusted using a luminometer so that the light receiving surface of the photoelectric conversion element had an illuminance of 200 lux. From this measurement result, short circuit current density Jsc (mA/cm ² ), open circuit voltage Voc (V), fill factor FF, and photoelectric conversion efficiency PCE (%) were calculated. The evaluation was based on the average value of three photoelectric conversion elements in each example and comparative example.

[Evaluation of light resistance]
The light resistance of the photoelectric conversion element to continuous light irradiation was evaluated by the following method. The evaluation was based on the average value of three photoelectric conversion elements in each example and comparative example.
First, a getter material (HD-S050914W-40SS, manufactured by Dynic) was attached to a ground glass with a concave inner surface. A photoelectric conversion module was produced by sealing the photoelectric conversion element by adhering the above-mentioned ground glass to the upper surface of the photoelectric conversion element using a sealing material (UV curable resin). A light resistance test was conducted on this photoelectric conversion module as follows.
The photoelectric conversion module was set as an open circuit, irradiated with light with an illuminance of 5800Lx (1.74mW/cm ² ), left standing in the atmosphere at room temperature (25°C) for 1000 hours, and the current-voltage characteristics were measured every 100 to 300 hours. was measured.
The photoelectric conversion efficiency at an illuminance of 200 Lx was determined from the obtained current-voltage curve. The photoelectric conversion efficiency was measured at the start of light irradiation, 500 hours after irradiation, 1000 hours after irradiation, and 3000 hours after irradiation.

[Particle size of perovskite compound]
The particle size of the perovskite compound was measured by observing the surface of the active layer with a scanning electron microscope. Specifically, we set the grain boundaries in a scanning electron microscope image obtained using a scanning electron microscope "S-4800" manufactured by Hitachi High-Technology Co., Ltd., and calculated the circle-equivalent surface area diameter of any 10 particles. The arithmetic mean was calculated.

[Example 1]
<Preparation of coating liquid for electron transport layer>
A 7.5% by mass aqueous tin oxide dispersion was prepared by adding ultrapure water to a 15% by mass aqueous dispersion of tin (IV) oxide (manufactured by Alfa Aesar).

<Preparation of coating liquid for active layer>
Lead (II) iodide was weighed into a vial and introduced into the glove box. Coating solution 1 for active layer was prepared by adding N,N-dimethylformamide as a solvent so that the concentration of lead (II) iodide was 1.3 mol/L, and then heating and stirring at 100 ° C. for 1 hour. did.
Cesium fluoride was weighed into another vial and introduced into the glove box. Coating liquid 2 for active layer was prepared by adding isopropyl alcohol as a solvent and stirring so that the concentration of cesium fluoride was 7 mg/mL.
In another vial, formamidine hydrobromide (FABr), methylamine hydrobromide (MABr) and methylamine hydrochloride (MACl) were mixed in a mass ratio of 7.25:1:1.5. I weighed it out and put it in the glove box. By adding isopropyl alcohol as a solvent to this, active layer coating liquid 3 having a total concentration of FABr, MABr, and MACl of 0.49 mol/L was prepared.
2-Phenylethylammonium iodide was weighed into another vial and introduced into the glove box. Coating liquid 4 for active layer was prepared by adding isopropyl alcohol as a solvent so that the concentration of 2-phenylethylammonium iodide was 1 mg/mL.

<Preparation of coating liquid for intermediate layer>
A compound represented by the following formula (II) (manufactured by TCI, 3-[(3-Acrylamidopropyl)dimethylammonio]propanoate) was weighed into a vial, and the concentration was 1 mg/mL (intermediate layer coating liquid 1). An intermediate layer coating liquid was prepared to have a concentration of 3 mg/mL (intermediate layer coating liquid 2). Methanol was used as the solvent.

<Preparation of coating solution for hole transport layer>
A 60 mg/mL o-dichlorobenzene solution of the compound represented by the following formula (2) (hole transporting compound) was prepared. Separately, a 56 mg/mL solution of the compound represented by the following formula (3) (electron-accepting dopant) in o-dichlorobenzene was prepared. A solution of the compound represented by formula (3) is added to a solution of the compound represented by formula (2), and the compound represented by formula (3) is added in an amount of 5 mol per 100 mol of the compound represented by formula (2). It was added so that The resulting mixed solution was heated and stirred at 150° C. for 1 hour to prepare a coating solution for a hole transport layer.

<Manufacture of photoelectric conversion element>
A glass substrate (manufactured by Geomatec) provided with a patterned ITO transparent conductive film (lower electrode) was subjected to ultrasonic cleaning using ultrapure water, drying with nitrogen blowing, and UV-ozone treatment.
On top of this, the above-mentioned electron transport layer coating liquid was spin-coated at room temperature (25°C) at a rotation speed of 2000 rpm to a thickness of 35 nm, and then heated on a hot plate at 150°C for 10 minutes. , an electron transport layer (thickness: 50 nm) was formed.
The glass substrate on which this electron transport layer was formed was introduced into a glove box, and after spin-coating the above-mentioned intermediate layer solution 1 at a rotation speed of 4000 rpm, the glass substrate was heated at 100° C. for 10 minutes on a hot plate. , an intermediate layer (estimated thickness of 10 nm or less) was formed.
Coating solution 1 for active layer (150 μL) heated to 100°C was dropped onto this intermediate layer, spin-coated at a rotation speed of 2000 rpm, and then heated on a hot plate at 100°C for 10 minutes to remove iodine. A lead oxide layer was formed.
On the lead iodide layer, active layer coating solution 2 (120 μL) was spin-coated at a rotation speed of 2000 rpm, and active layer coating solution 3 (120 μL) was further spin-coated at a rotation speed of 2000 rpm, and then on a hot plate. After heating at 150 °C for 20 minutes and cooling to room temperature (25 °C), active layer coating solution 4 (150 μL) was spin coated at a rotation speed of 2000 rpm, and heated at 100 °C for 10 minutes on a hot plate. An active layer (thickness: 650 nm) of an organic-inorganic hybrid perovskite semiconductor compound was formed.
After spin-coating the hole transport layer coating solution (150 μL) on this active layer at a rotation speed of 1000 rpm, heating it on a hot plate at 120 ° C. for 5 minutes and cooling it to room temperature (25 ° C.). A hole transport layer (thickness: 100 nm) was formed.
On this hole transport layer, MoO ₃ with a thickness of 10 nm was deposited by a resistance heating vacuum evaporation method, then IZO (indium zinc oxide) was formed with a thickness of 30 nm by a vacuum sputtering method, and further by a resistance heating vacuum evaporation method. Silver was deposited to a thickness of 100 nm to form an upper electrode.
A photoelectric conversion element was manufactured as described above.

The three photoelectric conversion elements manufactured in this manner were irradiated with white LED light having a color temperature of 5000 K, and the photoelectric conversion characteristics of each element were measured when the illuminance of the light receiving surface was 200 lux. The average values of the results are shown in Table 1. Note that the photoelectric conversion characteristics are values calculated based on measurement results immediately after manufacturing the photoelectric conversion element.
Further, for the three photoelectric conversion elements whose photoelectric conversion characteristics were measured, a photoelectric conversion module was manufactured as described above, and its light resistance was evaluated. The results are shown in Table 2.

[Example 2]
In Example 1, a photoelectric conversion element and a photoelectric conversion module were manufactured in the same manner as in Example 1, except that coating liquid 2 for intermediate layer was used instead of coating liquid 1 for intermediate layer, and the photoelectric conversion characteristics and Light resistance was measured. The measurement results are shown in Tables 1 and 2.

[Comparative example 1]
In Example 1, a photoelectric conversion element and a photoelectric conversion module were manufactured in the same manner as in Example 1 except that no intermediate layer was formed, and their photoelectric conversion characteristics and light resistance were measured. The measurement results are shown in Tables 1 and 2.

From the results in Table 1, the photoelectric conversion element of the present invention has a higher open-circuit voltage and improved photoelectric conversion efficiency by providing an intermediate layer containing the specific compound of the present invention between the active layer and the lower electrode. This was confirmed.

The results in Table 2 confirm that the light resistance of the photoelectric conversion element of the present invention is improved by providing an intermediate layer containing the specific compound according to the present invention between the active layer and the lower electrode.
Here, in the photoelectric conversion element of the present invention, by providing an intermediate layer containing the specific compound according to the present invention between the active layer and the lower electrode, defects at the interface between the electron transport layer and the active layer are suppressed, and It is thought that, by suppressing defects in the active layer, the open circuit voltage was increased, the photoelectric conversion efficiency was improved, and the light resistance was also improved.

[Example 3]
In Example 1, a compound represented by the following formula (I-2) (manufactured by Sigma-Aldrich, [2-(Methacryloyloxy)ethyl]dimethyl-(3- A photoelectric conversion element was manufactured in the same manner as in Example 1, except that the intermediate layer was formed using (sulfopropyl) ammonium hydroxide) and the step of applying active layer coating liquid 3 was not performed in forming the active layer. Its photoelectric conversion characteristics were measured. The results are shown in Table 3.

[Example 4]
In Example 2, the intermediate layer was formed using the compound represented by the above formula (I-2) instead of the compound represented by the formula (I-1), and the active layer coating was performed in forming the active layer. A photoelectric conversion element was manufactured in the same manner as in Example 2, except that the step of applying Liquid 3 was not performed, and its photoelectric conversion characteristics were measured. The results are shown in Table 3.

[Comparative example 2]
In Example 3, a compound represented by the following formula (X-1) (manufactured by TCI, 3-(1-pyridinio)-1-propanesulfonate) was used instead of the compound represented by formula (I-2). A photoelectric conversion element was manufactured in the same manner as in Example 3 except that the photoelectric conversion element was used, and its photoelectric conversion characteristics were measured. The results are shown in Table 3.

[Comparative example 3]
In Example 4, a photoelectric conversion element was produced in the same manner as in Example 4, except that the compound represented by the above formula (X-1) was used instead of the compound represented by formula (I-2). was manufactured and its photoelectric conversion characteristics were measured. The results are shown in Table 3.

[Comparative example 4]
In Example 3, a photoelectric conversion element was manufactured in the same manner as in Example 3 except that no intermediate layer was formed, and its photoelectric conversion characteristics were measured. The results are shown in Table 3.

From the results in Table 3, the photoelectric conversion device of the present invention has a high open circuit voltage and a photoelectric conversion device by providing an intermediate layer containing the specific compound of the present invention between the active layer and the lower electrode. It was confirmed that efficiency improved.

[Reference example 1]
In Example 1, the active layer was formed in the same manner as in Example 1, except that the step of applying active layer coating liquid 2 and active layer coating liquid 4 was not performed. The average particle size of the perovskite compound in this active layer was determined. The results are shown in Table 4.

[Reference example 2]
In Example 3, the active layer was formed in the same manner as in Example 3, except that the step of applying active layer coating liquid 4 was not performed. The average particle size of the perovskite compound in this active layer was determined. The results are shown in Table 4.

[Reference example 3]
In Comparative Example 4, the active layer was formed in the same manner as in Comparative Example 4, except that the step of applying active layer coating liquid 4 was not performed. The average particle size of the perovskite compound in this active layer was determined. The results are shown in Table 4.

The results in Table 4 confirm that the particle size of the perovskite compound in the active layer is expanded by providing an intermediate layer containing the specific compound according to the present invention between the active layer and the lower electrode. Furthermore, considering the results in Tables 1 to 3, it can be seen that the photoelectric conversion element and photoelectric conversion module of the present invention in which an intermediate layer containing the specific compound according to the present invention is provided between the active layer and the lower electrode, As the particle size of the perovskite compound increases, the number of grain boundaries of the perovskite compound decreases, making it easier to suppress charge recombination in the active layer. It was estimated that the open circuit voltage was higher, the photoelectric conversion efficiency was improved, and the light resistance was improved compared to the conversion element or photoelectric conversion module.

1 Weatherproof protective film 2 Ultraviolet cut film 3, 9 Gas barrier film 4, 8 Getter material film 5, 7 Sealing material 6 Photoelectric conversion element 10 Back sheet 14 Photoelectric conversion module 100 Photoelectric conversion element 101 Lower electrode 102 Buffer layer 103 Intermediate layer 104 Active layer 105 Buffer layer 106 Upper electrode 107 Base material

Claims (6)

A photoelectric conversion element having a lower electrode, an intermediate layer, an active layer, and an upper electrode in this order, the active layer containing an organic-inorganic hybrid perovskite semiconductor compound, and the intermediate layer containing a compound represented by formula (I). A photoelectric conversion element containing.

(In formula (I), Q is a carboxylic acid ion or a sulfonic acid ion, and M ¹ and M ² are each independently a chain aliphatic hydrocarbon having 1 to 10 carbon atoms, which may have a substituent. group, M ³ is an ether bond, any one of -CO- and -NH-, or a structure in which these bonds are bonded via an alkylene group, and R ¹ and R ² are each independently is a hydrogen atom or a chain saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms, and R ³ is a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms.) The photoelectric conversion element according to claim 1, further comprising an electron transport layer between the intermediate layer and the lower electrode. The photoelectric conversion element according to claim 2, wherein the electron transport layer contains a metal oxide. The photoelectric conversion element according to claim 3, wherein the metal oxide is tin oxide. The photoelectric conversion element according to any one of claims 1 to 4, wherein the intermediate layer has a thickness of 0.5 nm or more and 100 nm or less. A method for producing a photoelectric conversion element having a lower electrode, an intermediate layer, an active layer containing an organic-inorganic hybrid perovskite semiconductor compound, and an upper electrode in this order, the method comprising: preparing a solution containing a compound represented by the following formula (I); A method for manufacturing a photoelectric conversion element, comprising a step of coating.

(In formula (I), Q is a carboxylic acid ion or a sulfonic acid ion, and M ¹ and M ² are each independently a chain aliphatic hydrocarbon having 1 to 10 carbon atoms, which may have a substituent. M ³ is either an ether bond or a -NH- bond, or a structure in which these bonds are bonded via an alkylene group, and R ¹ and R ² are each independently a hydrogen atom or It is a chain saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms, and R ³ is a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms.)

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