WO2017170869A1

WO2017170869A1 - Perovskite film production method, perovskite film, solar battery and perovskite film forming solvent

Info

Publication number: WO2017170869A1
Application number: PCT/JP2017/013266
Authority: WO
Inventors: 藤原　隆; しのぶ寺川; 安達　千波矢; 正幸八尋
Original assignee: 国立大学法人九州大学; 公益財団法人九州先端科学技術研究所
Priority date: 2016-03-30
Filing date: 2017-03-30
Publication date: 2017-10-05

Abstract

By bringing a mixed solvent that comprises a second solvent and a third solvent into contact with a Perovskite precursor film that contains a first solvent, a Perovskite film is produced by the first solvent moving from the Perovskite precursor film to the mixed solvent, wherein the first solvent has a higher solubility in the main component of the Perovskite precursor film than that of the second solvent and the third solvent, and the second solvent and the third solvent have different solubilities in the first solvent. This invention makes it possible to form, with good reproducibility, a Perovskite film having excellent film properties.

Description

Method for producing perovskite film, perovskite film, solar cell, and solvent for forming perovskite film

The present invention relates to a method for producing a perovskite film, a perovskite film, a solar cell, and a solvent for forming a perovskite film.

Organic / inorganic perovskites have attracted attention as photoelectric conversion materials for solar cells and semiconductor materials for various electronic devices. Organic inorganic perovskites are ionic compounds composed of organic cations, divalent metal ions such as Sn ²⁺ and Pb ^2+, and halogen ions. Each ion forms the same crystal structure (perovskite structure) as perovskite. The three-dimensional perovskite regularly arranged in the three-dimensional direction, the inorganic layer in which the inorganic skeleton corresponding to the octahedral part of the perovskite structure is two-dimensionally arranged, and the organic layer made of oriented organic cations are alternately arranged. Two-dimensional perovskites that form a layered structure laminated on each other are known. Among these, the three-dimensional perovskite has been confirmed to be useful as a photoelectric conversion material for solar cells, and further studies are being promoted for practical use.
Here, when the organic / inorganic perovskite is used, for example, as a photoelectric conversion material for a solar cell, the organic / inorganic perovskite is formed into a film on the support to form a photoelectric conversion layer. Therefore, the film quality of the formed perovskite film is the battery performance. Will be greatly affected. Therefore, in order to improve the characteristics and practicality of the perovskite solar cell, it is essential to develop a method for forming a perovskite film that can form a high-quality perovskite film.

As a method for forming a perovskite film, Non-Patent Document 1 describes a method (Low-Temperature Vapor-Assisted Solution Process: LT-VASP method) in which a gas phase process is combined with a wet process. Here, the LT-VASP method is a VASP method in which a SnI ₂ film (solid) formed by spin coating is reacted with methylammonium iodide vapor to form a CH ₃ NH ₃ SnI ₃ (perovskite) film. The reaction is performed by providing a step between the substrate on which the SnI ₂ film is formed and the Petri dish containing methylammonium iodide. The same document, by providing such step, during the reaction, SnI ₂ film low temperature is maintained for SnI ₂ crystallization is suppressed than methyl ammonium, that the surface is smooth perovskite film is formed Are listed.

Non-Patent Document 1: J. Phys. Chem. Lett. 2016, 7, 776-782

As described above, Non-Patent Document 1 describes that a perovskite film having a smooth surface was formed by using the LT-VASP method. However, the solar cell using the perovskite film by the LT-VASP method has a large variation in characteristics, and the conversion efficiency fluctuates in the range of 0.5 to 1.8% in the measurement results published in this document. . For this reason, the LT-VASP method is not stable enough to be introduced into an actual production line and cannot be said to be a practical method.
Therefore, the present inventors began studying a method for forming a perovskite film having a mechanism different from that of the LT-VASP method. When the perovskite precursor film formed by a wet process is brought into contact with a solvent, depending on the type of the solvent, The solvent in the perovskite precursor film is diffused into the solvent and converted into a solid perovskite film having good film quality (hereinafter, a method for forming such a perovskite film is referred to as a “solvent replacement method”). . The LT-VASP method described in Non-Patent Document 1 described above is a method of forming a perovskite film by a reaction between a solid SnI ₂ film and methylammonium iodide vapor. This is greatly different from the solvent substitution method which the present inventors have made, in that perovskite is formed after the removal of.
Under such circumstances, the present inventors have further studied a method for forming a perovskite film by a solvent replacement method, can form a perovskite film having good film quality with good reproducibility, and have excellent performance. Intensive study was carried out for the purpose of stably obtaining the obtained solar cell.

As a result of diligent investigation, the present inventors used a mixed solvent in which at least two kinds of solvents were mixed as the solvent for contacting the perovskite precursor film in the above solvent replacement method, and each solvent used for this mixed solvent. It was found that a perovskite film having a good film quality can be formed with good reproducibility by defining the relationship of solubility in the solvent contained in the perovskite precursor film. The present invention has been proposed based on these findings, and specifically has the following configuration.

[1] By bringing the mixed solvent of the second solvent and the third solvent into contact with the perovskite precursor film containing the first solvent, the first solvent moves from the perovskite precursor film into the mixed solvent. A method for producing a perovskite film, wherein the first solvent is more soluble in the main component of the perovskite precursor film than the second solvent and the third solvent, and the second solvent and the third solvent are A method for producing a perovskite film having different solubility in a first solvent.
[2] The method for producing a perovskite film according to [1], wherein the perovskite precursor film is formed on a substrate.
[3] The method for producing a perovskite film according to [1] or [2], wherein the perovskite precursor film is immersed in the mixed solvent.
[4] The mixing ratio of the second solvent and the third solvent in the mixed solvent is set so that the first solvent in the perovskite precursor film is brought into contact with the perovskite precursor film at 25 ° C. The perovskite according to any one of [1] to [3], wherein a diffusion constant for diffusing into the mixed solvent is a ratio that is in a range of 1 × 10 ⁻¹³ m ² / s to 1 × 10 ² m ² / s A method for producing a membrane.
[5] The mixing is performed at a temperature at which a diffusion constant at which the first solvent in the perovskite precursor film diffuses into the mixed solvent is in the range of 1 × 10 ⁻¹³ m ² / s to 1 × 10 ² m ² / s. The method for producing a perovskite film according to any one of [1] to [4], wherein a solvent is brought into contact with the perovskite precursor film.
[6] A diffusion constant k _{2 in} which the first solvent diffuses into the second solvent when the second solvent is brought into contact with the perovskite precursor film at 25 ° C., and the perovskite precursor film at 25 ° C. The absolute value (| k ₂ −k ₃ |) of the difference from the diffusion constant k _{3 in} which the first solvent diffuses into the third solvent when the third solvent is brought into contact is 1 × 10 ⁻¹³ m ² / s. The method for producing a perovskite film according to any one of [1] to [5], which is in a range of ˜1 × 10 ² m ² / s.
[7] The method for producing a perovskite film according to any one of [1] to [6], wherein the first solvent is dimethyl sulfoxide, N-methyl-2-pyrrolidone, dimethylformamide, or γ-butyrolactone.
[8] Any of [1] to [7], wherein the second solvent and the third solvent are toluene, chlorobenzene, hexane, or cyclohexane (however, the second solvent and the third solvent are different solvents). 2. A method for producing a perovskite film according to item 1.
[9] The method for producing a perovskite film according to any one of [1] to [7], wherein the second solvent is toluene or chlorobenzene, and the third solvent is hexane or cyclohexane.
[10] The method for producing a perovskite film according to any one of [1] to [9], wherein the perovskite precursor film includes a perovskite type compound represented by the following general formula (4).
A ³ BX ₃ (4)
[In the general formula (4), A ³ represents an organic cation, B represents a divalent metal ion, and X represents a halogen ion. The three Xs may be the same as or different from each other. ]
[11] The method for producing a perovskite film according to any one of [1] to [10] 1 to 10, wherein the perovskite precursor film contains at least one of Pb and Sn.
[12] The perovskite film according to any one of [1] to [11], wherein the perovskite precursor film includes at least one of methylammonium iodide, formamidium iodide, and cesium iodide. Production method.
[13] The method for producing a perovskite film according to any one of [1] to [12], wherein the perovskite precursor film contains at least one of I and F.
[14] The method for producing a perovskite film according to any one of [1] to [13] 1 to 13, wherein the mixed solvent is contacted with the perovskite precursor film for 0.1 second to 180 minutes.
[15] The method for producing a perovskite film according to any one of [1] to [14], wherein when the mixed solvent is in contact with the perovskite precursor film, the temperature of the mixed solvent is changed with time. .
[16] The contact film according to any one of [1] to [15], wherein after the mixed solvent is brought into contact with the perovskite precursor film, the obtained perovskite film is annealed at 0 to 200 ° C. A method for producing a perovskite film.
[17] The method according to any one of [1] to [15], wherein after the mixed solvent is brought into contact with the perovskite precursor film, a fourth solvent is brought into contact with the perovskite precursor film in contact with the mixed solvent. The manufacturing method of the perovskite film | membrane of description.
[18] The method for producing a perovskite film according to [17], wherein the fourth solvent has lower solubility in the main component of the perovskite precursor film than the first solvent.
[19] The method for producing a perovskite film according to [17] or [18], wherein the fourth solvent is the same solvent as one of the second solvent and the third solvent.
[20] The method for producing a perovskite film according to [17], wherein the second solvent is toluene or chlorobenzene, the third solvent is hexane or cyclohexane, and the fourth solvent is toluene or chlorobenzene.
[21] The method for producing a perovskite film according to any one of [17] to [20], wherein the temperature of the fourth solvent is higher than the temperature of the mixed solvent.
[22] The contact according to any one of [17] to [21], wherein after the fourth solvent is brought into contact with the perovskite precursor film, the obtained perovskite film is annealed at 0 to 200 ° C. Manufacturing method of perovskite film.

[23] A perovskite film produced by the production method according to any one of [1] to [22].
[24] The perovskite film according to [23], containing the first solvent at a concentration of more than 0 and less than 10,000 ppm.
[25] The perovskite film according to [23] or [24], containing the second solvent at a concentration of more than 0 and less than 5,000 ppm.
[26] The perovskite film according to any one of [23] to [25], which contains the third solvent at a concentration of more than 0 and less than 5,000 ppm.

[27] A solar cell having the perovskite film according to any one of [23] to [26].

[28] A solvent to be contacted with a perovskite precursor film containing a first solvent, and the perovskite film is moved by moving the first solvent from the perovskite precursor film into the contacted solvent by performing the contact. A perovskite film forming solvent, wherein the perovskite film forming solvent is a mixture of two or more solvents including at least a second solvent and a third solvent, wherein the first solvent is A solvent for forming a perovskite film, wherein the solubility of the perovskite precursor film in the main component is greater than that of the second solvent and the third solvent, and the second solvent and the third solvent have different solubility in the first solvent.

According to the method for producing a perovskite film of the present invention, a perovskite film having good film quality can be produced with good reproducibility. Moreover, the solar cell of this invention has the perovskite film | membrane manufactured by the manufacturing method of the perovskite film | membrane of this invention, The dispersion | variation in the characteristic between batteries is small, and the outstanding performance can be obtained stably.

It is a schematic sectional drawing which shows the layer structural example of the solar cell of this invention. In Example 3, it shows the surface state of the perovskite film when the rotational speed during spin coating of the precursor solution is 8000 rpm, (a) is a scanning electron micrograph, (b) is an interatomic It is a force micrograph. In Example 3, it shows the surface state of the perovskite film when the rotational speed during spin coating of the precursor solution is 6000 rpm, (a) is a scanning electron micrograph, (b) is an interatomic It is a force micrograph. In Examples 9 and 10 and Comparative Examples 5 to 8, it is a graph showing the time change of the transmitted light intensity of the perovskite precursor film while being immersed in the immersion tank. FIGS. 9 and 10 are scanning electron micrographs and atomic force micrographs (inset) of the perovskite films produced in Comparative Examples 5 to 8, and (a) is a photograph of the perovskite films produced in Example 9. (B) is a photograph of the perovskite film produced in Comparative Example 5, (c) is a photograph of the perovskite film produced in Comparative Example 6, (d) is a photograph of the perovskite film produced in Example 10, and (e) is a comparison. (F) is a photograph of the perovskite film produced in Comparative Example 8; 2 is an optical density spectrum of a perovskite film produced in Examples 9 and 10 and Comparative Examples 5 to 8. It is an X-ray diffraction spectrum of the perovskite film produced in Examples 9 and 10 and Comparative Examples 5 to 8, wherein (a) is an X-ray diffraction spectrum for each perovskite film separately, (b) The vertical axis scale of the X-ray diffraction spectrum of (a) is converted into a logarithmic scale, and these logarithmic spectra are superimposed and displayed. 2 is a photograph of perovskite films produced in Examples 9 to 18. 2 is a scanning electron micrograph of the perovskite film produced in Examples 19 and 20. FIG. 3 is a scanning electron micrograph of the perovskite film produced in Examples 21-23. 2 is a scanning electron micrograph of the perovskite film produced in Examples 24-27. 6 is a graph showing current density-voltage characteristics (photocurrent characteristics) measured without covering with batteries 1 to 4 having a perovskite film manufactured in Examples 1 to 4. 6 is a graph showing current density-voltage characteristics (photocurrent characteristics) measured with batteries covered with a photomask for batteries 1 to 4 having a perovskite film manufactured in Examples 1 to 4. 5 is a graph showing the wavelength dependence of photoelectric conversion characteristics measured with batteries covered with a photomask for batteries 1 to 4 having a perovskite film manufactured in Examples 1 to 4. 3 is a graph showing current density-voltage characteristics of a battery having a perovskite film formed using toluene at 25 ° C. FIG. 6 is a graph showing current density-voltage characteristics of a battery having a perovskite film formed using toluene at 15 ° C. FIG. For the

batteries

5 and 6 having the perovskite film manufactured in Examples 9 and 10 and the comparative batteries 1 to 4 having the perovskite film manufactured in Comparative Examples 5 to 8, the current density-voltage measured without being covered with a photomask. It is a graph which shows a characteristic (photocurrent characteristic). Current density measured with the photomask covered for the

batteries

5 and 6 having the perovskite film manufactured in Examples 9 and 10 and the comparative batteries 1 to 4 having the perovskite film manufactured in Comparative Examples 5 to 8− It is a graph which shows a voltage characteristic (photocurrent characteristic). For the

batteries

5 and 6 having the perovskite film produced in Examples 9 and 10 and the comparative batteries 1 to 4 having the perovskite film produced in Comparative Examples 5 to 8, the current density-voltage measured without irradiating light It is a graph which shows a characteristic (dark current characteristic). 6 is a graph showing the wavelength dependence of photoelectric conversion characteristics of

batteries

5 and 6 having a perovskite film manufactured in Examples 9 and 10 and comparative batteries 1 to 4 having a perovskite film manufactured in Comparative Examples 5 to 8. FIG.

Battery

5,6 having a perovskite membrane prepared in Examples 9, 10, and a graph showing a short-circuit current J _SC of comparative battery 1-4 having a perovskite membrane prepared in Comparative Example 5-8. 6 is a graph showing open circuit voltages V _OC of

batteries

5 and 6 having a perovskite film manufactured in Examples 9 and 10 and comparative batteries 1 to 4 having a perovskite film manufactured in Comparative Examples 5 to 8. FIG. 6 is a graph showing fill factor (FF) of

batteries

5 and 6 having a perovskite film manufactured in Examples 9 and 10 and comparative batteries 1 to 4 having a perovskite film manufactured in Comparative Examples 5 to 8. FIG. 6 is a graph showing energy conversion efficiencies η of

batteries

5 and 6 having a perovskite film manufactured in Examples 9 and 10 and comparative batteries 1 to 4 having a perovskite film manufactured in Comparative Examples 5 to 8. FIG. It is a histogram of the short-circuit current J _SC of the battery 5 having a perovskite membrane prepared in Example 9. 10 is a histogram of an open circuit voltage V _OC of a battery 5 having a perovskite film manufactured in Example 9. 10 is a histogram of fill factor (FF) of a battery 5 having a perovskite film manufactured in Example 9. 10 is a histogram of energy conversion efficiency η of a battery 5 having a perovskite film manufactured in Example 9. It is a graph which shows the time-dependent change of a solar cell characteristic when the battery 5 which has the perovskite film | membrane manufactured in Example 9 is driven continuously. 30 is a graph in which the range of 0 to 5 hours of the graph of FIG. 29 is enlarged and displayed. 14 is a graph showing current density-voltage characteristics (photocurrent characteristics, dark current characteristics) of a battery 7 manufactured in Example 19. 22 is a graph showing current density-voltage characteristics (photocurrent characteristics, dark current characteristics) of the battery 8 manufactured in Example 20. 14 is a graph showing hysteresis of current density-voltage characteristics (photocurrent characteristics and dark current characteristics) of the battery 7 manufactured in Example 19. 14 is a graph showing the wavelength dependence of photoelectric conversion characteristics of the battery 7 manufactured in Example 19. It is a graph which shows the lifetime characteristic test result of the battery 7 manufactured in Example 19, and the battery 8 manufactured in Example 20. FIG. 42 is a graph showing current density-voltage characteristics (photocurrent characteristics, dark current characteristics) of the battery 12 manufactured in Example 27. 42 is a graph showing hysteresis of current density-voltage characteristics (photocurrent characteristics, dark current characteristics) of the battery 12 manufactured in Example 27. FIG.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit, and “room temperature” means 25 ° C. means. In addition, the isotope species of the hydrogen atom present in the molecule of the compound used in the present invention is not particularly limited. For example, all the hydrogen atoms in the molecule may be ¹ H, or a part or all of the hydrogen atoms are ² H. [Deuterium D] may also be used.

<< Method for Producing Perovskite Film >>
In the method for producing a perovskite film of the present invention, the first solvent is brought into the mixed solvent from the perovskite precursor film by bringing the mixed solvent of the second solvent and the third solvent into contact with the perovskite precursor film containing the first solvent. A method for producing a perovskite film by moving, wherein the first solvent has a higher solubility in the main component of the perovskite precursor film than the second solvent and the third solvent, and the second solvent and the third solvent are the first solvent. It is specified so that the solubility in is different.
The “perovskite precursor film” in the present invention is a film containing a perovskite type compound and a first solvent. Here, the perovskite compound is capable of forming a perovskite crystal structure. The ions constituting the perovskite type compound may form a salt in the perovskite precursor film or may exist as free ions.
In the present invention, the term “perovskite film” means that the first solvent in the perovskite precursor film moves into the mixed solvent of the second solvent and the third solvent, so that each ion of the perovskite compound forms a perovskite crystal. Thus, the film has a perovskite crystal structure and is regularly arranged. The perovskite crystal structure may be a three-dimensional perovskite structure, a two-dimensional perovskite structure, or a composite structure in which both perovskite structures are combined.
The “main component of the perovskite precursor film” in the present invention refers to a perovskite type compound contained in the perovskite precursor film, and “the solubility of the perovskite precursor in the main component” in the first solvent is: The saturation concentration at 25 ° C. of a solution obtained by dissolving the perovskite compound in a first solvent.
In this specification, “diffusion” is a concept that includes all the movements of a substance that are observed in the process of mixing a substance with another substance. For this reason, “diffusion” includes not only molecular diffusion but also diffusion by convection and turbulent diffusion. Further, the “diffusion constant” in the present specification can be determined, for example, by optical evaluation of a transient refractive index change at the time of solvent mixing.

Here, generally, when converting a liquid film formed by a wet process into a solid film, the solvent in the liquid film is diffused (volatilized) into the atmosphere and removed. However, in such a method, the diffusion constant of the solvent is almost determined by the temperature of the liquid film and the atmosphere, and since there are no other factors that significantly change the diffusion constant, the diffusion constant of the solvent can be controlled widely and precisely. difficult. On the other hand, when the present inventors examined the film quality of the perovskite film formed by the wet process, the diffusion constant of the solvent diffusing from the liquid film (perovskite precursor film) has a great influence on the film quality of the perovskite film. Turned out to be. From this point of view, it is difficult to control the diffusion constant widely and precisely in the method of diffusing the solvent in the liquid film into the atmosphere, so the perovskite film should be formed with good film quality and good reproducibility. I can't.
On the other hand, in the method for producing a perovskite film of the present invention, the first solvent in the perovskite precursor film is brought into contact with the perovskite precursor film by bringing the mixed solvent of the second solvent and the third solvent into contact with the perovskite precursor film. In which a perovskite film having a higher solubility in the main component of the perovskite precursor film than the second solvent and the third solvent is used as the first solvent. As the solvent and the third solvent, those having different solubility in the first solvent are used. When the first solvent contained in the perovskite precursor film has higher solubility in the main component of the perovskite precursor film than the second solvent and the third solvent, the perovskite precursor film and the mixed solvent are mixed from the precursor film. The diffusion of the first solvent into the solvent proceeds more preferentially than the diffusion of the second solvent and the third solvent into the precursor film. As a result, the content of the first solvent in the perovskite precursor film is reduced, and a solid perovskite film is formed. At this time, the diffusion constant of the first solvent into the mixed solvent is effectively determined by the type and solubility of the first to third solvents, the mixing ratio of the second solvent and the third solvent, in addition to the temperature of each solvent. Therefore, by controlling these, the diffusion constant can be adjusted widely and precisely. Therefore, according to the method for producing a perovskite precursor film of the present invention, the first solvent can be reliably diffused from the perovskite precursor film with an appropriate diffusion constant, and a perovskite film having good film quality can be obtained with good reproducibility. Can be manufactured.
Hereinafter, materials and conditions used in the method for producing a perovskite film of the present invention will be described in detail.

<Perovskite precursor film>
As described above, the perovskite precursor film in the present invention includes a perovskite type compound and a first solvent, and forms a film. The perovskite compound can form a perovskite crystal structure.
The present invention can be effectively applied to, for example, a perovskite type compound composed of an ionic compound composed of an organic cation, a divalent metal ion, and a halogen ion. Examples of such perovskite compounds include compounds represented by the following general formulas (1) to (4). Among these, the compounds represented by the general formulas (1) to (3) are compounds capable of forming a two-dimensional perovskite structure, and the compounds represented by the general formula (4) are compounds capable of forming a three-dimensional perovskite structure. It is.

[Compound represented by general formula (1)]
A ₂ BX ₄ (1)
In the general formula (1), A represents an organic cation, B represents a divalent metal ion, and X represents a halogen ion. Two A's and four X's may be the same or different.
Compound represented by the general formula (1) includes an inorganic layer inorganic framework BX ₄ is formed by arranging two-dimensionally corresponding to octahedral portion of the perovskite type structure, organic cations A ₂ is oriented formed by arranging two-dimensional A layered structure in which organic layers are alternately stacked can be formed. Here, the inorganic skeleton BX ₄ has a structure in which a divalent metal ion B is arranged at the center of an octahedron having the halogen ion X as a vertex, and the adjacent octahedrons share the vertex. The organic cation A is oriented with the cationic group facing the inorganic layer side. Then, a perovskite structure is formed with the upper and lower four cationic groups of each octahedron as the apexes of cubic crystals and the apexes of each octahedron as the face centers of cubic crystals.

The organic cation represented by A is preferably ammonium represented by the following general formula (5).
R ₄ N ⁺ (5)
In the general formula (5), R represents a hydrogen atom or a substituent, and at least one of the four Rs is a substituent having 2 or more carbon atoms. Of the four Rs, the number of substituents having 2 or more carbon atoms is preferably 1 or 2, and more preferably 1. Further, it is preferable that one of four Rs constituting ammonium is a substituent having 2 or more carbon atoms, and the rest are hydrogen atoms. When two or more of R are substituents, the plurality of substituents may be the same as or different from each other. Examples of the substituent having 2 or more carbon atoms and other substituents include, but are not limited to, an alkyl group, an aryl group, a heteroaryl group, and the like. These substituents further include an alkyl group, an aryl group, It may be substituted with a heteroaryl group, halogen or the like. The number of carbon atoms of the substituent having 2 or more carbon atoms is preferably 2 to 30, more preferably 2 to 10, and further preferably 2 to 5 for an alkyl group. In the aryl group, it is preferably 6 to 20, more preferably 6 to 18, and further preferably 8 to 10. The heteroaryl group is preferably 5 to 19, more preferably 5 to 17, and still more preferably 7 to 9. Examples of the hetero atom that the heteroaryl group has include a nitrogen atom, an oxygen atom, and a sulfur atom. The thickness of the organic layer is controlled according to the long axis length of the substituent represented by R (for example, the chain length of the alkyl group), thereby controlling the characteristics of the functional layer composed of this compound. Can do.

The organic cation represented by A preferably has at least one of an alkylene group and an aromatic ring, preferably has both an alkylene group and an aromatic ring, and has a structure in which the alkylene group and the aromatic ring are linked. Is more preferable, and ammonium represented by the following general formula (5a) is more preferable.
Ar (CH ₂ ) _n1 NH ₃ ⁺ (5a)
In general formula (5a), Ar represents an aromatic ring. n1 is an integer of 1 to 20.
The aromatic ring of the organic cation may be an aromatic hydrocarbon or an aromatic heterocycle, but is preferably an aromatic hydrocarbon. Examples of the hetero atom of the aromatic heterocycle include a nitrogen atom, an oxygen atom, and a sulfur atom. The aromatic hydrocarbon is preferably a condensed polycyclic hydrocarbon having a structure in which a benzene ring and a plurality of benzene rings are condensed, such as a benzene ring, a naphthalene ring, a phenanthrene ring, an anthracene ring, a chrysene ring, a tetracene ring, A perylene ring is preferable, a benzene ring or a naphthalene ring is preferable, and a benzene ring is more preferable. The aromatic heterocycle is preferably a pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, pyrrole ring, thiophene ring, furan ring, carbazole ring or triazine ring, and a pyridine ring, pyrazine ring, pyrimidine ring or pyridazine ring. And more preferably a pyridine ring. The aromatic ring possessed by the organic cation may have a substituent such as an alkyl group, an aryl group, a halogen atom (preferably a fluorine atom), and is present in the aromatic ring or a substituent bonded to the aromatic ring. The hydrogen atom may be a deuterium atom.
In the general formula (5a), n1 is an integer of 1 to 20, and preferably an integer of 2 to 10.
As the organic cation represented by A, formamidinium, cesium, and the like can be used in addition to ammonium.

Examples of the divalent metal ion represented by B include Cu ²⁺ , Ni ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Pd ²⁺ , Ge ²⁺ , Sn ²⁺ , Pb ²⁺ and Eu ^2+. ²⁺ and Pb ²⁺ are preferable, and Sn ²⁺ is more preferable.
Examples of the halogen ion represented by X include fluorine, chlorine, bromine and iodine ions. All three halogen ions represented by X may be the same, or a combination of two or three types of halogen ions. Preference is given to the case where all three X are the same halogen ion, and it is more preferable that all three X are iodine ions.
Preferable specific examples of the perovskite type compound represented by the general formula (1) include [CH ₃ (CH ₂ ) n ₂ NH ₃ )] ₂ SnI ₄ (n2 = 2 to 17), (C ₄ H ₉ C ₂ H ₄ NH ₃ ) ₂ SnI ₄ , (CH ₃ (CH ₂ ) _{n 3} (CH ₃ ) CHNH ₃ ) ₂ SnI ₄ [n3 = 5-8], (C ₆ H ₅ C ₂ H ₄ NH ₃ ) ₂ SnI ₄ , ( Tin-based perovskites such as C ₁₀ H ₇ CH ₂ NH ₃ ) ₂ SnI ₄ and (C ₆ H ₅ C ₂ H ₄ NH ₃ ) ₂ SnBr ₄ , [CH ₃ (CH ₂ ) n ₂ NH ₃ )] ₂ PbI ₄ ( _{_{_{_{n2 = 2 ~ 17), (}}}} C 4 H 9 C 2 H 4 NH 3) 2 PbI 4, (CH 3 (CH 2) n3 (CH 3) CHNH 3) 2 PbI 4 [n3 = 5 ~ 8], ( C ₆ H ₅ C ₂ H ₄ NH ₃ ) ₂ Lead-based perovskites such as PbI ₄ , (C ₁₀ H ₇ CH ₂ NH ₃ ) ₂ PbI ₄ and (C ₆ H ₅ C ₂ H ₄ NH ₃ ) ₂ PbBr ₄ may be mentioned. However, the perovskite compound that can be used in the present invention is not limited to these compounds.

[Compound represented by formula (2)]
A ² ₂ A ¹ _n−1 B _n X _{3n + 1} (2)
A ^{2 in the} general formula (2) represents an organic cation having a carbon number larger than that of A ¹ . B and X in the general formula (2) have the same meanings as B and X in the general formula (1), respectively. A ^{2 in the} general formula (2) has the same meaning as A in the general formula (1). Regarding preferred ranges and specific examples of A ² , B, and X in the general formula (2), preferred ranges and specific examples of A, B, and X in the general formula (1) can be referred to, respectively. Here, two A ^{2 s} and a plurality of Xs may be the same as or different from each other. When a plurality of A ¹ and B are present, A ¹ and B may be the same as or different from each other.

The organic cation represented by A ¹ is an organic cation having a carbon number smaller than that of A ² and is preferably ammonium represented by the following general formula (6).
General formula (6)
R ¹¹ ₄ N ⁺
In the general formula (6), R ¹¹ represents a hydrogen atom or a substituent, and at least one of the four R ¹¹ is a substituent. The number of substituents in the four R ¹¹ is preferably 1 or 2, and more preferably 1. That is, it is preferable that one of the four R ¹¹ constituting ammonium is a substituent and the remaining is a hydrogen atom. When two or more of R ¹¹ are substituents, the plurality of substituents may be the same as or different from each other. Although it does not specifically limit as a substituent, An alkyl group and an aryl group (A phenyl group, a naphthyl group, etc.) can be mentioned, These substituents may be further substituted by the alkyl group, the aryl group, etc. The number of carbon atoms of the substituent is preferably 1-30, more preferably 1-20, and still more preferably 1-10 for an alkyl group. The aryl group is preferably 6 to 30, more preferably 6 to 20, and still more preferably 6 to 10.
As the organic cation represented by A ¹ and A ² , formamidinium, cesium, and the like can be used in addition to ammonium.

The compound represented by the general formula (2) forms a layered structure in which an inorganic layer composed of an inorganic skeleton B _n X _{3n + 1} forming an octahedron and an organic layer composed of an organic cation A ² are alternately stacked. . n corresponds to the number of octahedrons laminated in each inorganic layer and is an integer of 1 to 100. When n is 2 or more, the organic cation A ¹ is arranged at a position corresponding to the apex of the cubic crystal between each octahedron.

As a preferable specific example of the organic-inorganic perovskite type compound represented by the general formula (2), a compound represented by the following general formula (2a) can be exemplified.
(C ₄ H ₉ NH ₃ ) ₂ (CH ₃ NH ₃ ) _n-1 Sn _n I _{3n + 1} (2a)
In the general formula (2a), n is an integer of 1 to 100, preferably an integer of 1 to 5. Specifically, (C ₄ H ₉ NH ₃ ) ₂ SnI ₄ , (C ₄ H ₉ NH ₃ ) ₂ (CH ₃ NH ₃ ) Sn ₂ I ₇ , (C ₄ H ₉ NH ₃ ) ₂ (CH ₃ NH _₃₎ ₂ Sn ₃ I _10, a _{_{_{_{(C 4 H 9 NH 3)}}}} 2 (CH 3 NH 3) 3 Sn 4 I 13, (C 4 H 9 NH 3) 2 (CH 3 NH 3) 4 Sn 5 I 16 Can be mentioned. As preferred specific examples of the organic-inorganic perovskite type compound represented by the general formula (2), (CH ₃ (CH ₂ ) _n NH ₃ ) ₂ PbI ₄ (n = 2 to 17), (C ₄ H ₉ C ₂ H ₄ NH ₃ ) ₂ PbI ₄ , (CH ₃ (CH ₂ ) _n (CH ₃ ) CHNH ₃ ) ₂ PbI ₄ [n = 5-8], (C ₆ H ₅ C ₂ H ₄ NH ₃ ) ₂ PbI ₄ can also include like _{_{_{_{(C 10 H 7 CH 2 NH}}}} 3) 2 PbI 4 and _{_{_{_{(C 6 H 5 C 2 H}}}} 4 NH 3) 2 PbBr 4. However, the perovskite compound that can be used in the present invention is not limited to these compounds.

[Compound represented by formula (3)]
A ² ₂ A ¹ _m B _m X _{3m + 2} (3)
A ^{2 in the} general formula (3) represents an organic cation having a carbon number larger than that of A ¹ . B and X in the general formula (3) have the same meanings as B and X in the general formula (1), respectively. Regarding preferred ranges and specific examples of B and X in the general formula (3), preferred ranges and specific examples of B and X in the general formula (1) can be referred to respectively. A ¹ in the general formula (3) has the same meaning as A ¹ in formula (2). For the preferred range and specific examples of A ^{1 in} the general formula (3), reference can be made to the preferred range and specific examples of A ^{1 in} the general formula (2).
Here, two A ^{2 s} and a plurality of Xs may be the same as or different from each other. When a plurality of A ¹ and B are present, A ¹ and B may be the same as or different from each other.

The compound represented by the general formula (3) forms a layered structure in which an inorganic layer composed of an inorganic skeleton B _m X _{3m + 2} and an organic layer composed of an organic cation A ² are alternately stacked. m corresponds to the number of layers in each inorganic layer and is an integer of 1 to 100.

The organic cation represented by A ² is an organic cation having a carbon number larger than that of A ¹ , and is preferably ammonium represented by the general formula (6), and is represented by the following general formula (7). More preferably, it is ammonium.
General formula (7)
(R ¹² ₂ C = NR ¹³ ₂ ) ⁺
In the general formula (7), R ¹² and R ¹³ each independently represent a hydrogen atom or a substituent, and each R ¹² may be the same or different, and each R ¹³ is the same. May be different. Examples of the substituent include, but are not limited to, an alkyl group, an aryl group, an amino group, a halogen atom, and the like. The alkyl group, aryl group, and amino group mentioned here further include an alkyl group, an aryl group, and an amino group. And may be substituted with a halogen atom or the like. The number of carbon atoms of the substituent is preferably 1-30, more preferably 1-20, and still more preferably 1-10 for an alkyl group. The aryl group is preferably 6 to 30, more preferably 6 to 20, and still more preferably 6 to 10. The thickness of the organic layer is controlled according to the long axis length of the substituent represented by R ¹² (for example, the chain length of the alkyl group), thereby controlling the characteristics of the functional layer constituted by this mixture. be able to. As a combination of R ¹² and R ¹³ , for example, an amino group or a halogen atom can be selected as R ¹² , and a hydrogen atom or an alkyl group can be selected and combined as R ¹³ . Alternatively, an amino group or a halogen atom can be selected as R ¹² and a hydrogen atom can be selected and combined as R ¹³ .
As the organic cation represented by A ² , formamidinium, cesium, and the like can be used in addition to ammonium.

Preferable specific examples of the organic / inorganic perovskite type compound represented by the general formula (3) include a compound represented by the following general formula (3a).
[NH ₂ C (I) = NH ₂ ] ₂ (CH ₃ NH ₃ ) _m Sn _m I _{3m + 2} (3a)
In the general formula (3a), m is an integer of 2 to 100, preferably an integer of 2 to 5. Specifically, [NH ₂ C (I) ═NH ₂ ] ₂ (CH ₃ NH ₃ ) ₂ Sn ₂ I ₈ , [NH ₂ C (I) ═NH ₂ ] ₂ (CH ₃ NH ₃ ) ₃ Sn ₃ I ₁₁ , [NH ₂ C (I) ═NH ₂ ] ₂ (CH ₃ NH ₃ ) ₄ Sn ₄ I ₁₄ may be mentioned. However, the perovskite compound that can be used in the present invention is not limited to these compounds.

The total number of inorganic layers and organic layers formed by the compounds represented by the general formulas (1) to (3) is preferably 1 to 100, more preferably 1 to 50, and 5 to 20 More preferably.

[Compound represented by the general formula (4)]
A ³ BX ₃ (4)
In the general formula (4), A ³ represents an organic cation. B and X in the general formula (4) have the same meanings as B and X in the general formula (1), respectively. Regarding preferred ranges and specific examples of B and X in the general formula (4), preferred ranges and specific examples of B and X in the general formula (1) can be referred to respectively. Further, B of the compound represented by the general formula (4) is preferably a fluorine ion, and is preferably a combination of iodine ion and fluorine ion. For the preferred range and specific examples of A ^{3 in} the general formula (4), the preferred range and specific examples of A ^{1 in} the general formula (2) can be referred to. The three Xs may be the same or different from each other.

The compound represented by the general formula (4) has a cubic unit cell, the organic cation A is arranged at each vertex of the cubic crystal, the metal ion B is arranged at the body center, and each surface of the cubic crystal. A cubic perovskite structure in which halogen ions X are arranged in the center is formed. Here, an octahedron is formed by the inorganic skeleton of metal ions B and halogen ions X.

Preferred specific examples of the perovskite type compound represented by the general formula (4) include CH ₃ NH ₃ PbI ₃ , CH ₃ NH ₃ PbCl ₃ , CH ₃ NH ₃ PbBr ₃ , CH ₃ NH ₃ SnI ₃ , and CH ₃ NH _3. Examples include SnI _q F _3-q (where q is an integer of 0 to 2), CH ₃ NH ₃ SnCl ₃ , CH ₃ NH ₃ SnBr ₃ , (NH ₂ ) ₂ CHSnI ₃ , and CH ₃ NH ₃ PbI ₃ , CH ₃ NH ₃ SnI _q F _3-q , (NH ₂ ) ₂ CHSnI ₃ are preferred. However, the perovskite compound that can be used in the present invention is not limited to these compounds.

Among the perovskite compounds listed above, preferred are those containing at least one of Sn ²⁺ and Pb ²⁺ as divalent metal ions, and those containing at least one of methylammonium, formamidinium and cesium as organic cations. , Which contains at least one of I ⁻ and F ⁻ as a halogen ion. Among the compounds represented by the general formulas (1) to (4), the compound represented by the general formula (4) is preferable, and CH ₃ NH ₃ SnI ₃ is most preferable.

[Other compounds]
The present invention can also be applied to organic-inorganic perovskite compounds represented by general formulas other than those described above and inorganic perovskite-type compounds.
For example, the present invention can be applied to a perovskite compound represented by the following general formula. In the following general formula, A, B, and C each represent an organic cation or an inorganic cation, X represents a halogen anion, and x represents 0 or 1.
General formula AX ₃
Exemplary Compound BiI ₃
General formula ABX ₄
Exemplary Compound AgBiI ₄
General formula A ₂ BX ₄
Exemplary Compound (CH ₃ CH ₂ CH ₂ CH ₂ NH ₃ ) ₂ CuBr ₄
(F—C ₈ H ₈ NH ₃ ) ₂ CuBr ₄
General formula A ₃ BX ₆
Exemplified compound Ag ₃ BiI ₆
[NH ₂ (CH ₂ CH ₃ ) ₂ ] ₃ Bi (Cl _1-x Br _x ) ₆
General formula AB ₂ X ₇
Exemplary compounds AgBi ₂ I ₇ ,
General formula A ₂ BCX ₆
Exemplary Compound Cs ₂ AgBiBr ₆
Cs ₂ AgBiCl ₆
General formula A ₃ B ₂ X ₉
Exemplary Compound (CH ₃ NH ₃ ) ₃ Bi ₂ I ₉
Cs ₃ Bi ₂ I ₉
[(NH ₂ ) ₂ CH] ₃ Bi ₂ I ₉
(NH ₄ ) ₃ Bi ₂ I ₉
Cs ₃ Bi ₂ Br ₉
(CH ₃ NH ₃ ) ₃ Sb ₂ I ₉
General formula A ₂ BCX ₆
Exemplary Compound Cs ₂ InAgCl ₆
(CH ₃ NH ₃ ) ₂ KBiCl ₆
General formula ABC ₂
Exemplary Compound AgBiS ₂

Moreover, a perovskite type compound may be used individually by 1 type, and may be used in combination of 2 or more type. Preferable combinations include combinations of two or more of CH ₃ NH ₃ SnI ₃ and CH ₃ NH ₃ SnI _q F _3-q (where q is an integer of 0 to 2).

The amount per unit area of the perovskite type compound in the perovskite precursor film is preferably 1.0 × 10 ⁻⁶ mol / m ² to 1.0 × 10 ⁻² mol / m ² , and 2.5 × 10 ⁻⁵ mol / m ^2. It is more preferably from 2.5 × 10 ⁻³ mol / m ² , and further preferably from 1.0 × 10 ⁻⁴ mol / m ² to 3.0 × 10 ⁻⁴ mol / m ² .

[First solvent]
The first solvent is a solvent having higher solubility in the main component (perovskite type compound) of the perovskite precursor film than the second solvent and the third solvent described later, and is a solvent having compatibility with the second solvent and the third solvent. Preferably there is.
The solubility of the first solvent in the perovskite type compound is preferably 1 mol / l-solvent or more, more preferably 10 mol / l-solvent or more, and further preferably 100 mol / l-solvent or more. The solubility of the first solvent in the perovskite type compound is preferably such that the difference between the solubility of the second solvent and the third solvent in the perovskite type compound is greater than or equal to 2 mol / l-solvent. / l-solvent or more is more preferable, and 10 mol / l-solvent or more is more preferable. Further, the solubility of the first solvent in the perovskite compound is preferably such that the difference between the solubility of the second solvent and the third solvent in the perovskite compound is 2 mol / l-solvent or more. / l-solvent or more is more preferable, and 100 mol / l-solvent or more is more preferable.

Although the solvent that can be used as the first solvent varies depending on the types of the second solvent and the third solvent, dimethyl sulfoxide (DMSO) has high solubility in the perovskite compound and is compatible with a wide range of organic solvents. And polar aprotic solvents such as N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and γ-butyrolactone (GBL), and dimethyl sulfoxide and N-methyl-2-pyrrolidone are used. Is preferred. These solvents may be used alone or in combination of two or more.
In this specification, the polar aprotic solvent means a solvent having a dielectric constant of 10 or more and not having a proton donating property. The dielectric constant can be measured, for example, by a parallel plate method using an impedance analyzer.

The perovskite precursor film may be composed only of the perovskite type compound and the first solvent, or may contain other components. As other components, there may be mentioned oxidizing agents, reducing agents, solvents other than the first to third solvents, and the like.

The perovskite precursor film as described above is preferably formed on a substrate. The substrate can be appropriately selected according to the use of the obtained perovskite film. As the material of the substrate, for example, silicon (Si), silicon oxide (SiO ₂ ), glass, metal, inorganic materials such as gallium arsenide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), Examples thereof include resins such as aromatic polyester (liquid crystal polymer) and polyimide (PI). The substrate may have a single layer configuration or a multilayer configuration. When it is a multilayer structure, each layer may be comprised with the same material, and may be comprised with a different material. In addition, a substrate in which an organic layer or an inorganic layer serving as a functional film of an element is formed on a substrate made of any of these materials may be used.

[Method of forming perovskite precursor film]
The perovskite precursor film can be formed by a wet process. Hereinafter, a method for forming a perovskite precursor film by a wet process will be described.
First, a solution containing a perovskite type compound and a first solvent is prepared. For example, a perovskite type compound (R ₄ NBX ₃ ) represented by the general formula (4) and having A ³ of (R ₄ N) ⁺ is an ammonium halide R ₄ NX as shown in the following reaction formula (8). And a metal halide BX ₂ can be synthesized in a first solvent.
R ₄ NX + BX ₂ → R ₄ NBX ₃ (8)
In the reaction formula (8), R is synonymous with R in the general formula (5), and B and X are synonymous with B and X in the general formula (1). The solution is prepared to contain either the perovskite type compound R ₄ NBX ₃ or its precursor, which is the product of this reaction. Usually, a solution containing a product obtained by reacting R ₄ NX and BX ₂ which are reaction raw materials in a first solvent can be used.

The content of the perovskite compound in the solution is preferably 5 to 88% by mass, more preferably 23 to 75% by mass, and still more preferably 31 to 52% by mass with respect to the total amount of the solution.

Next, the prepared solution is applied to the support surface and dried to obtain a perovskite precursor film.
The application method of the solution is not particularly limited, and conventionally known application methods such as a gravure application method, a bar application method, a printing method, a spray method, a spin coating method, a dip method, and a die coating method can be used. The spin coating method is preferably used because a thin coating film can be uniformly formed.

<A mixed solvent of the second solvent and the third solvent>
The second solvent and the third solvent are solvents having lower solubility in the main component of the perovskite precursor film than in the first solvent and different in solubility in the first solvent.
When the mixed solvent of the second solvent and the third solvent is brought into contact with the perovskite precursor film, it functions as a receiving medium in which the first solvent in the perovskite precursor film moves into the mixed solvent and is received. As a result, the content of the first solvent in the perovskite precursor film is reduced, and each ion constituting the perovskite compound is arranged to form a perovskite crystal. As a result, a perovskite film having a perovskite crystal structure is obtained. That is, in the present invention, this mixed solvent is used as a solvent for forming the perovskite film.
The solubility of the second solvent and the third solvent in the perovskite type compound (the main component of the perovskite precursor film) is preferably 0.1 mol / l-solvent or less, and preferably 0.01 mol / l-solvent or less. More preferred is 0.001 mol / l-solvent or less.
Further, the combination of the second solvent and the third solvent includes a diffusion constant k _{2 at} which the first solvent diffuses into the second solvent when the second solvent is brought into contact with the perovskite precursor film at 25 ° C., and at 25 ° C. When the third solvent is brought into contact with the perovskite precursor film, the absolute value (| k ₂ −k ₃ |) of the difference of the diffusion constant k ₃ in which the first solvent diffuses into the third solvent is 1 × 10 ⁻¹³ m ² / A combination that falls within the range of s to 1 × 10 ² m ² / s is preferable, and a combination that falls within the range of 1 × 10 ⁻¹² m ² / s to 1 × 10 ⁰ m ² / s is more preferable, and 1 × 10 ^−11. More preferably, the combination is in the range of m ² / s to 1 × 10 ⁻² m ² / s.

Solvents that can be used as the second solvent and the third solvent vary depending on the type of the first solvent, but include nonpolar solvents such as toluene, chlorobenzene, hexane, benzene, xylene, and heptane because of their low solubility in perovskite compounds. A combination of toluene and hexane is preferred. By using these nonpolar solvents in combination with dimethyl sulfoxide or N-methyl-2-pyrrolidone exemplified as the first solvent, the first solvent contained in the perovskite precursor film is appropriately diffused into the mixed solvent. A perovskite film having good film quality can be obtained with good reproducibility. The mixed solvent is preferably a solvent in which the second solvent is selected from toluene and chlorobenzene, and the third solvent is a solvent selected from hexane and cyclohexane.
In the present specification, a nonpolar solvent means a solvent having a dielectric constant of 10 or less. The dielectric constant can be measured, for example, by a parallel plate method using an impedance analyzer.

The mixing ratio of the second solvent and the third solvent is a factor that influences the diffusion constant of the first solvent moving from the perovskite precursor film into the mixed solvent. The type of solvent used for the first to third solvents and the desired solvent It can be appropriately selected according to the diffusion constant. Specifically, the mixing ratio of the second solvent and the third solvent is such that when the mixed solvent is brought into contact with the perovskite precursor film at 25 ° C., the first solvent in the perovskite precursor film diffuses into the mixed solvent. The diffusion constant is preferably in the range of 1 × 10 ⁻¹³ m ² / s to 1 × 10 ² m ² / s, and in the range of 1 × 10 ⁻¹² m ² / s to 1 × 10 ⁻¹³ m ⁰ / s. More preferably, the ratio is in the range of 1 × 10 ⁻¹¹ m ² / s to 1 × 10 ⁻² m ² / s. For example, when the first solvent is a polar aprotic solvent such as dimethyl sulfoxide or N-methyl-2-pyrrolidone, and the second solvent and the third solvent are both nonpolar solvents such as toluene or hexane The mixing ratio of the second solvent and the third solvent in the volume (second solvent: third solvent) is preferably 1: 0.1 to 1:10, preferably 1: 0.5 to 1: 2. More preferably. In particular, perovskite precursor film is I ^- and F ^- include both, and, when adjusting the mixed solvent to 5 ~ 20 ° C. is brought into contact with the perovskite precursor film, second solvent: third solvent Is preferably 1: 0.6 to 1: 1.5, more preferably 1: 0.7 to 1: 1.3, whereby a perovskite film having an extremely good film quality can be formed.
In addition, the mixing ratio of the second solvent and the third solvent may be gradually changed as time passes in the contact step between the perovskite precursor film and the mixed solvent described later. As a result, the diffusion constant of the first solvent moving from the perovskite precursor film into the mixed solvent can be controlled more precisely.

The mixed solvent may be composed of two types of solvents, a second solvent and a third solvent, or may be composed of three or more types of solvents by adding other solvents such as a fourth solvent and a fifth solvent. Also good. However, the other solvent to be added is a solvent having a lower solubility in the main component of the perovskite precursor film than the first solvent, and a solvent having a different solubility in the first solvent from the other solvent constituting the mixed solvent. preferable. By adding another solvent to the mixed solvent, the diffusion constant of the first solvent moving from the perovskite precursor film to the mixed solvent side can be controlled more precisely.

<Contact process of mixed solvent to perovskite precursor film>
In the method for producing a perovskite precursor film of the present invention, a perovskite film is produced by bringing a mixed solvent of a second solvent and a third solvent into contact with the perovskite precursor film. When the mixed solvent of the second solvent and the third solvent is brought into contact with the perovskite precursor film, the first solvent in the perovskite precursor film moves into the mixed solvent, and the content of the first solvent in the perovskite precursor film Decrease. As a result, each ion constituting the perovskite type compound is arranged so as to form a perovskite type crystal, and a perovskite film having a perovskite type crystal structure is obtained. At this time, in the manufactured perovskite film, the first to third solvents may be completely removed, or at least one of the first to third solvents may remain in the film. For the preferable range of the content of each solvent when at least one of the first to third solvents remains in the perovskite film, the corresponding description of << perovskite film >> can be referred to.

The method for bringing the perovskite precursor film into contact with the mixed solvent is not particularly limited, and any method may be used, but it is preferable that the entire outer surface of the perovskite precursor film be brought into contact with the mixed solvent. An immersion method in which the precursor film is immersed in a mixed solvent can be suitably used. When the immersion method is used, the volume of the mixed solvent is preferably 10 ¹ to 10 ¹⁰ times, more preferably 10 ⁴ to 10 ⁸ times, more preferably 10 ⁶ to 10 times the volume of the perovskite precursor film. More preferably, it is ⁷ times.

The time for bringing the mixed solvent into contact with the perovskite precursor film is preferably 0.1 second to 180 minutes. The mixed solvent is preferably stirred while the perovskite precursor film is in contact. By adjusting the length of time for which the mixed solvent is brought into contact with the perovskite precursor film, the grain size and the number of grains of the obtained perovskite film can be controlled. For example, it is possible to control so that the grain size of the perovskite film is large and the number of grains is reduced by shortening the immersion time in the mixed solvent. In addition, by increasing the immersion time in the mixed solvent, it is possible to control the perovskite film so that the grain size is small and the number of grains is large.
The temperature of the mixed solvent brought into contact with the perovskite precursor film is preferably set with the diffusion constant of the first solvent diffusing from the perovskite precursor film into the mixed solvent as an index. Specifically, the contact of the mixed solvent with the perovskite precursor film has a diffusion constant of 1 × 10 ⁻¹³ m ² / s to 1 × 10 ² m ² / s at which the first solvent in the perovskite precursor film diffuses into the mixed solvent. Is preferably performed at a temperature within a range of 1 × 10 ⁻¹² m ² / s to 1 × 10 ⁰ m ² / s, and a diffusion constant of 1 × 10 ⁻¹¹ m ² is preferable. It is more preferable to carry out at a temperature in the range of / s to 1 × 10 ⁻² m ² / s.
Further, the temperature of the mixed solvent brought into contact with the perovskite precursor film is preferably −50 to 50 ° C., more preferably 0 to 25 ° C., further preferably 5 to 20 ° C., and particularly preferably 10 to 15 ° C. In particular, by setting the temperature of the mixed solvent to 5 to 20 ° C., preferably 10 to 15 ° C., it is possible to obtain a perovskite film having a smooth surface and high density and highly oriented perovskite crystals. For example, when the first solvent is a polar aprotic solvent such as dimethyl sulfoxide or N-methyl-2-pyrrolidone, and the second solvent and the third solvent are both nonpolar solvents such as toluene or hexane In particular, it is preferable to bring the mixed solvent into contact with the perovskite precursor film at −50 to 50 ° C., and in particular, when the mixed solvent is brought into contact with the perovskite precursor film in the above preferable temperature range, the perovskite having good film quality is obtained. A film can be formed effectively.
The temperature of the mixed solvent brought into contact with the perovskite precursor film may be kept constant while the mixed solvent is in contact with the perovskite precursor film, or may be controlled so as to change over time. The temperature change pattern is a pattern in which the temperature rises over time, a pattern in which the temperature falls over time, a pattern that falls after the temperature rises, a pattern that rises after the temperature falls, and a temperature rise and fall Examples include alternately repeating patterns.

Further, as described in the section of <mixed solvent of second solvent and third solvent>, when the mixed solvent is in contact with the perovskite precursor film, the mixing of the second solvent and the third solvent in the mixed solvent is performed. The ratio may be gradually changed over time. The change pattern of the mixing ratio is a pattern in which the mixing ratio of the second solvent gradually increases with time, a pattern in which the mixing ratio of the second solvent gradually decreases with time, and the mixing ratio of the second solvent is constant. A pattern that decreases after increasing to a value, a pattern that increases after the mixing ratio of the second solvent decreases to a certain value, a pattern that alternately repeats the process of increasing and decreasing the mixing ratio of the second solvent, etc. It is done.
As described above, the perovskite film obtained by bringing the mixed solvent into contact with the perovskite precursor film may be annealed thereafter. The temperature of the annealing treatment is preferably 0 to 200 ° C, more preferably 25 to 150 ° C, and further preferably 70 to 100 ° C. Moreover, the grain size and the number of grains of the obtained perovskite film can be controlled by adjusting the annealing conditions. For example, it is possible to control the perovskite film to have a large grain size and a small number of grains by increasing the temperature at the start of the annealing process or setting the annealing process temperature higher. In addition, it is possible to control the perovskite film to have a small grain size and a large number of grains by lowering the temperature at the start of annealing or setting the annealing temperature lower.

<Other processes>
In the method for producing a perovskite film of the present invention, other processes may be performed in addition to the above <contact process of the mixed solvent with the perovskite precursor film>. As another step, a step of bringing the fourth solvent into contact with the perovskite precursor film brought into contact with the mixed solvent can be exemplified. Thereby, the formation process of the perovskite film can be divided into a process that proceeds in the contact process of the mixed solvent and a process that proceeds in the contact process of the fourth solvent, and the conditions in each process are independently controlled, Each forming process can proceed under optimum conditions. As a result, it is possible to form a perovskite film having better film quality. Specifically, the perovskite film grows through a nucleation process and a nucleus growth process. Therefore, for example, it is preferable to proceed mainly with the nucleation process in the contact step of the mixed solvent and to proceed mainly with each growth process in the contact step of the fourth solvent. It is preferable to select the type and temperature of the solvent and the type and temperature of the fourth solvent.
The fourth solvent used in the step of bringing the fourth solvent into contact may be any one that works to improve the film quality of the perovskite film by further contacting the perovskite precursor film in contact with the mixed solvent. Although not particularly limited, it is preferable that the solubility of the perovskite precursor film in the main component is smaller than that of the first solvent. For specific examples of the solvent that can be used as the fourth solvent, reference can be made to specific examples of the solvent that can be used for the second solvent and the third solvent. In addition, diethyl ether, anisole and the like can be preferably used as the fourth solvent. The fourth solvent may be the same as one of the second solvent and the third solvent, or may be different from any of the solvents, but is preferably the same as either one. Preferable combinations of the second to fourth solvents include a combination in which the second solvent is toluene or chlorobenzene, the third solvent is hexane or cyclohexane, and the fourth solvent is toluene or chlorobenzene.
The fourth solvent may be brought into contact with the perovskite precursor film alone, or may be mixed with another solvent and brought into contact with the perovskite precursor film. The solvent mixed with the fourth solvent is not particularly limited, but the mixed solvent of the fourth solvent and the other solvent preferably has a composition different from the mixed solvent of the second solvent and the third solvent.
Moreover, when performing the contact process of a 4th solvent, it is preferable to set the temperature of a 4th solvent higher than the temperature of the mixed solvent in the contact process of a mixed solvent. As a result, the nucleus growth process proceeds rapidly in the fourth solvent contact step, and a perovskite film with better film quality can be formed.
Furthermore, in the method for producing a perovskite film of the present invention, one or more solvent contact steps can be performed after the fourth solvent contact step by changing the type of solvent and the composition of the mixed solvent. As a result, the process of forming the perovskite film can be further subdivided and performed under optimum conditions, and a perovskite film with even better film quality can be formed.
As a method for bringing the perovskite precursor film into contact with the fourth solvent, for example, an immersion method in which the perovskite precursor film is immersed in the fourth solvent can be used. In the following description, performing the contact process of the mixed solvent by the immersion method and then performing the contact process of the fourth solvent by the immersion method is referred to as “two-stage immersion method”. In addition to this, performing one or more solvent contact steps by the dipping method is collectively referred to as “multi-stage dipping method”. Moreover, performing only the contact process of said mixed solvent by an immersion method is called "single immersion method."

<< Perovskite film >>
Next, the perovskite film of the present invention will be described.
The perovskite film of the present invention is manufactured by the method for manufacturing a perovskite film of the present invention. For the explanation of the method for producing the perovskite film of the present invention, the preferred range of materials and conditions to be used, and specific examples, the << Method for producing perovskite film >> column can be referred to. Since the perovskite film of the present invention is manufactured by such a method for manufacturing a perovskite film, the perovskite film has good film quality, and the difference in film quality between the perovskite films is kept small. Therefore, excellent element characteristics can be stably obtained by using this perovskite film as a functional film of a solar cell or an electronic device.
In the perovskite film of the present invention, the first to third solvents used in the production process may be completely removed, but may contain at least one of the first to third solvents. When the perovskite film contains the first solvent, the content of the first solvent is preferably more than 0 and less than 10,000 ppm in terms of the concentration relative to the total mass of the perovskite film. When the perovskite film contains the second solvent, the content of the second solvent is preferably more than 0 and less than 5,000 ppm in terms of the concentration relative to the total mass of the perovskite film. When the perovskite film contains a third solvent, the content of the third solvent is preferably more than 0 and less than 5,000 ppm in terms of the concentration relative to the total mass of the perovskite film.
The thickness of the perovskite film varies depending on the use of the perovskite film, but when it has a two-dimensional perovskite crystal structure, it is preferably 10 nm to 500 nm, more preferably 20 nm to 200 nm, and more preferably 50 nm to More preferably, it is 100 nm. Further, when it has a three-dimensional perovskite crystal structure, it is preferably 10 nm to 1000 nm, more preferably 50 nm to 500 nm, and further preferably 200 nm to 400 nm.

<< Solar cell >>
Next, the solar cell of the present invention will be described.
The solar cell of the present invention is characterized by having the perovskite film of the present invention. For the structure of the perovskite film of the present invention, the column of << perovskite film >> can be referred to. By having such a perovskite film, the solar cell of the present invention can stably obtain excellent battery characteristics. In the solar cell of the present invention, the photoelectric conversion layer is preferably composed of the perovskite film of the present invention, and the photoelectric conversion layer is the perovskite film of the present invention and includes a compound represented by the general formula (4). More preferably, it is made of a material.

The solar cell of the present invention preferably has a structure in which a power generation layer is formed at least between a transparent electrode and a counter electrode, and between the transparent electrode and the counter electrode. The power generation layer includes at least a photoelectric conversion layer, may be composed of only a photoelectric conversion layer, or may have one or more functional layers in addition to the photoelectric conversion layer. Examples of such other functional layers include a hole capturing layer, an electron blocking layer, an electron transporting layer, and a hole blocking layer. A specific structure example of the photoelectric conversion element is shown in FIG. In FIG. 1, 1 is a transparent substrate, 2 is a transparent electrode, 3 is a hole capture layer, 4 is a photoelectric conversion layer, 5 is an electron transport layer, and 6 is a counter electrode. In the configuration of FIG. 1, the transparent electrode 2 functions as a positive electrode for collecting holes, and the counter electrode 6 functions as a negative electrode for collecting electrons. Further, the photoelectric conversion element may be one in which the hole capturing layer 3 and the electron transporting layer 5 are arranged at positions opposite to the positional relationship shown in FIG. That is, the transparent substrate 1, the transparent electrode 2, the electron transport layer 5, the photoelectric conversion layer 4, the hole capturing layer 3, and the counter electrode 6 may be laminated in this order. In this case, the transparent electrode 2 functions as a negative electrode for collecting electrons, and the counter electrode 6 functions as a positive electrode for collecting holes.
Below, each member and each layer of a photoelectric conversion element are demonstrated.

(Transparent substrate)
The photoelectric conversion element of the present invention is preferably supported on a transparent substrate. The transparent substrate is not particularly limited as long as it is conventionally used for a photoelectric conversion element. For example, a substrate made of glass, transparent plastic, quartz, or the like can be used. Examples of the transparent plastic include polyesters such as polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), polycarbonate, polyolefin, polyimide, Teflon (registered trademark), and the like.

(Transparent electrode)
As the transparent electrode in the photoelectric conversion element, a material using a conductive inorganic compound, a conductive metal oxide, a conductive polymer and a mixture thereof as an electrode material is preferably used. Specific examples of such electrode materials include conductive inorganic compounds such as CuI, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide (SnO ₂ ), indium zinc oxide (IZO), Conductive metal oxides such as gallium-doped zinc oxide, aluminum-doped zinc oxide (AZO), zinc oxide (ZnO), and niobium-doped titanium oxide, and conductive properties such as polyacetylene, polypyrrole, polythiophene, and polyphenylene vinylene Examples include polymers. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. The transparent electrode may be formed by forming a thin film by a method such as vapor deposition or sputtering of these electrode materials, and forming a pattern of a desired shape by a photolithography method. A pattern may be formed through a mask. Or when using the material which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. The surface resistance of the transparent conductive film is preferably 15Ω / □ or less, more preferably 5Ω / □ or less. Further, although depending on the material, the film thickness is usually selected from the range of 0.01 to 10.0 μm, preferably 0.3 to 1.0 μm.

(Counter electrode)
As the counter electrode, in addition to the electrode material exemplified for the transparent electrode, an electrode material made of a metal, an alloy, a carbon material, or a mixture thereof is used.
Specific examples of metals and alloys used as the electrode material include metals and alloys such as aluminum, gold, silver, platinum, copper, tungsten, molybdenum, and titanium. The counter electrode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The surface resistance of the counter electrode is preferably 15Ω / □ or less, more preferably 5Ω / □ or less. The thickness of the counter electrode is usually selected from the range of 0.01 to 2.0 μm.

(Photoelectric conversion layer)
The photoelectric conversion layer is composed of the perovskite film of the present invention. When the photoelectric conversion layer is irradiated with light from the transparent substrate side, the perovskite type compound of the perovskite film is photoexcited to generate spatially separated holes and electrons (carriers). Of these carriers, holes are diffused to the positive hole capturing layer side and taken out to the positive electrode, and electrons are diffused to the electron transporting layer side and taken out to the negative electrode, resulting in a potential difference (electromotive force) between the electrodes.
The thickness of the photoelectric conversion layer is preferably 10 to 1000 nm, more preferably 100 to 500 nm, and further preferably 200 to 400 nm. Thereby, it is possible to avoid the photoelectric conversion element from becoming too thick and to obtain sufficient power generation characteristics.

(Hole capture layer)
The hole capturing layer is made of a hole capturing material (hole transporting material) having a function of capturing holes injected from the photoelectric conversion layer and transporting them to the positive electrode side, and can be provided as a single layer or a plurality of layers. In addition to the function of capturing and transporting holes, the hole capturing material may have hole injection and electron barrier properties.
As a hole capturing material, spiro-OMeTAD (2,2 ′, 7,7′-tetrakis- (N, N-di-p-methoxyphenylamine) 9,9′-spirobifluorene)), poly (3 , 4-ethylenedioxythiophene): poly (4-styrenesulfonate) (PEDOT: PSS), P3HT (poly (3-hexylthiophene)), PCPDTBT (poly [2,1,3-benzothiadiazole-4,7- Diyl [4,4-bis (2-ethylhexyl) -4H-cyclopenta [2,1-b: 3,4-b ′] dithiophene-2,6-diyl]]), PVK (poly (N-vinylcarbazole)) ), HTM-TFSI (1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide), Li-TFSI (lithium bis (trifluoro) (Romethanesulfonyl) imide), tBP (tert-butylpyridine) and the like. Among them, spiro-OMeTAD, P3HT, PCPDTBT, and PVK are preferably used, and spiro-OMeTAD is more preferably used. Also, as hole-capturing materials, from thiophenyl, phenenyl, dithiazolyl, benzothiazolyl, diketopyrrolopyrrolyl, ethoxydithiophenyl, amino, triphenylamino, carbozolyl, ethylenedioxythiophenyl, dioxythiophenyl and fluorenyl Organic compounds, polymers or copolymers having one or more selected groups can also be used, and inorganic hole transport materials such as CuI, CuBr, CuSCN, Cu ₂ O, CuO, CIS, etc. can also be used. it can.
The thickness of the hole capturing layer is not particularly limited, but is preferably about 0.01 to 0.5 μm.

(Electron transport layer)
The electron transport layer is made of a material having a function of transporting electrons injected from the photoelectric conversion layer to the negative electrode side, and can be provided as a single layer or a plurality of layers. The electron transport material may have a function of blocking holes in addition to a function of transporting electrons.
As an electron transport material, fullerene, perylene, fullerene or a derivative of perylene, poly {[N, N′-bis (2-octyldodecyl) -naphthalene-1,4,5,8-bis (dicarboximide) -2 , 6-Diyl] -alt-5,50- (2,20-bithiophene)} (P (NDI2OD-T2)) and the like, and various electrolytes can also be used.
Further, as an electron transport material, metal oxides such as TiO ₂ , WO ₃ , ZnO, Nb ₂ O ₅ , Ta ₂ O ₅ , and SrTiO ₃ , and donor-added metal oxides obtained by adding a donor to these metal oxides are used. May be. When TiO ₂ is employed, the crystal form is preferably anatase type. The metal oxide used for the electron transport material preferably has a porous structure, and more preferably has a porous structure with a pore size in the nano order. Thereby, the surface area of the electron transport layer itself increases, and when the photoelectric conversion layer is formed thereon, the surface area of the photoelectric conversion layer at the interface with the electron transport layer also increases. As a result, the efficiency of electron injection from the photoelectric conversion layer to the electron transport layer is increased, and the photoelectric conversion efficiency can be improved. Examples of the porous structure include a structure in which a granular body, a linear body (a linear body: a needle shape, a tube shape, a column shape, etc.) are aggregated to form a porous shape as a whole. The porous structure does not need to extend over the entire electron transport layer. For example, the negative electrode side portion may have a smooth structure and the photoelectric conversion layer side portion may have a porous structure. When the electron transport layer has a porous structure in expectation of an increase in the surface area of the photoelectric conversion layer, it is preferable to dispose the electron transport layer closer to the transparent electrode than the photoelectric conversion layer. As a result, after forming the electron transport layer having a porous structure, it becomes a production procedure for forming a photoelectric conversion layer thereon, so a photoelectric conversion layer reflecting the surface shape of the electron transport layer, that is, a photoelectric conversion layer having a large surface area. Can be easily obtained.
The thickness of the electron transport layer is not particularly limited, but is preferably about 0.01 to 0.5 μm.

(Hole blocking layer)
The hole blocking layer is provided between the electron transport layer and the negative electrode as necessary. The hole blocking layer has a function of an electron transport layer in a broad sense. The hole blocking layer has a role of blocking holes from reaching the negative electrode while transporting electrons to the negative electrode, and can thereby generate a large electromotive force between the transparent electrode and the counter electrode. As the material for the hole blocking layer, a material having a HOMO level deeper than the HOMO level of the material constituting the electron transport layer can be selected from the materials for the electron transport layer described above.

(Electronic block layer)
The electron blocking layer is provided between the hole capturing layer and the positive electrode as necessary. The electron blocking layer has a function of transporting holes in a broad sense. The electron blocking layer has a role of blocking electrons from reaching the positive electrode while transporting holes to the positive electrode, thereby generating a large electromotive force between the transparent electrode and the counter electrode. As a material for the electron block layer, a material having a LUMO level shallower than the LUMO level of the material constituting the hole transport layer can be selected and used from the material for the hole trapping layer.

When producing the above photoelectric conversion elements, the method for forming each functional layer constituting the power generation layer is not particularly limited, and may be produced by either a dry process or a wet process.

When this photoelectric conversion element is irradiated with light such as sunlight from the transparent substrate side, the perovskite type compound contained in the photoelectric conversion layer is excited to generate carriers. Of the carriers, holes are transported to the positive electrode side and taken out to the positive electrode, and electrons are transported to the negative electrode side and taken out to the negative electrode. An electromotive force is generated between the positive electrode and the negative electrode. A current flowing from the positive electrode to the negative electrode can be obtained by connecting a conductor between the positive electrode and the negative electrode where the electromotive force is generated.

The photoelectric conversion element of the present invention may be used as a single element or a tandem type in which a plurality of elements are stacked. By using a tandem type, high conversion efficiency can be realized. In addition, by stacking elements having different characteristics, the characteristics of the stacked elements as a whole can be precisely controlled, and optimal characteristics suitable for the application can be realized.

Hereinafter, the features of the present invention will be described more specifically with reference to synthesis examples and examples. The following materials, processing details, processing procedures, and the like can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. The perovskite film was evaluated using an X-ray diffractometer [λ = 1.54Å (CuKα)] (Rigaku Corp .: Ultimate IV) and a spectrofluorimeter (JASCO Corp .: FP-6500). Was evaluated using a solar simulator (spectrometer: OTENTO-SAN III), a measurement system (manufactured by System Engineers: OSA-11), and a source meter (manufactured by Keithley: 2400 series).

[Production and evaluation of perovskite films]
Example 1
A precursor solution was prepared by dissolving tin iodide (SnI ₂ ) and methylammonium iodide (CH ₃ NH ₃ I) in dimethyl sulfoxide (DMSO) at a concentration of 1M.
On the other hand, PEDOT: PSS (manufactured by Heraeus, Clevious 4083) is formed to a thickness of 30 to 50 nm on a glass substrate on which a positive electrode made of indium tin oxide (ITO) having a thickness of 100 nm is formed by spin coating. And a PEDOT: PSS layer to be a hole trapping layer was formed by annealing at 200 ° C. The substrate on which this PEDOT: PSS layer was formed was carried into a glove box substituted with nitrogen. Then, the prepared precursor solution was dropped on the PEDOT: PSS layer through a filter having a pore diameter of 0.45 μm, and the substrate was rotated at 500 rpm for 10 seconds, and then rotated at 8000 rpm for 30 seconds, and spin coated to form perovskite. A precursor film was formed.
Next, a mixed solvent (immersion tank) in which ultra-dehydrated toluene (second solvent) and ultra-dehydrated hexane (third solvent) are mixed at a volume ratio of 1: 1 is set to 10 to 15 ° C. on a cool plate. The temperature was adjusted. While stirring the mixed solvent, the substrate on which the perovskite precursor film was formed was immersed in the mixed solvent for 2 minutes. Thereafter, the substrate was taken out and annealed at 100 ° C. for 5 minutes to produce a perovskite film.
Separately from this, a perovskite film was produced in the same manner as described above except that when the precursor solution was spin-coated, the substrate was rotated at 500 rpm for 10 seconds and then rotated at 6000 rpm for 30 seconds.

(Examples 2 to 4)
When preparing the precursor solution, instead of dissolving tin iodide in dimethyl sulfoxide at a concentration of 1M, except that tin iodide and tin fluoride (SnF ₂ ) are dissolved in a total amount of 1M, A perovskite film was produced in the same manner as in Example 1. The specific composition of the precursor solution is shown in Table 1.

(Examples 5 and 6)
Except that the super-dehydrated toluene: super-dehydrated hexane (volume ratio) was set to 1: 1.3 or 1: 1.5 in the solvent (immersion tank) in which the perovskite precursor film was immersed, the same as in Example 1. A perovskite film was produced.

(Examples 7 and 8)
Except that the super-dehydrated toluene: super-dehydrated hexane (volume ratio) was 1: 1.3 or 1: 1.5 in the solvent (immersion tank) for immersing the perovskite precursor film, it was the same as in Example 3. A perovskite film was produced.

(Comparative Example 1)
A perovskite film was used in the same manner as in Example 1 except that a super-dehydrated toluene and ultra-dehydrated hexane were used instead of a mixed solvent of ultra-dehydrated toluene and ultra-dehydrated hexane as a solvent (immersion tank) for immersing the perovskite precursor film. Manufactured.

(Comparative Example 2)
A perovskite membrane was prepared in the same manner as in Example 1 except that a super-dehydrated hexane and a super-dehydrated hexane were used instead of a mixed solvent of ultra-dehydrated toluene and ultra-dehydrated hexane as a solvent (immersion tank) for immersing the perovskite precursor film. Manufactured.

(Comparative Example 3)
As a solvent for the precursor solution, N-methyl-2-pyrrolidone (NMP) is used instead of dimethyl sulfoxide, and as a solvent (immersion tank) for immersing the substrate on which the perovskite precursor film is formed, ultra-dehydrated toluene A perovskite membrane was produced in the same manner as in Example 1 except that ultra-dehydrated toluene was used alone instead of using a mixed solvent of ultra-dehydrated hexane.

(Comparative Example 4)
As in Example 5, except that a super-dehydrated toluene and ultra-dehydrated hexane mixed solvent was used as a solvent (immersion tank) for immersing the substrate on which the perovskite precursor film was formed, instead of using a mixed solvent of ultra-dehydrated toluene and ultra-dehydrated hexane. A perovskite film was manufactured.
Table 1 shows the composition of the precursor solution and immersion bath used in each example and each comparative example.

The perovskite precursor films and the perovskite films formed in Examples 1, 3, 5 to 8 and each comparative example were visually observed. Here, the perovskite precursor film and the perovskite film were distinguished using dark color change as an index. Further, the surface of the perovskite film formed in Example 3 was observed with a scanning electron microscope and an atomic force microscope, and an arithmetic average roughness Ra and a ten-point average roughness Rz were obtained. In Example 3, the scanning electron micrograph (magnification 20000 times) of the perovskite film produced at a spin coating speed of 8000 rpm in the precursor solution is shown in FIG. 100,000) is shown in FIG. In Example 3, a scanning electron micrograph (magnification 20000 times) of the perovskite film produced at a spin-coating speed of the precursor solution of 6000 rpm is shown in FIG. 100,000) is shown in FIG.
Comparing Example 1 with Comparative Examples 1 and 2 and Comparative Examples 3 and 4, in Comparative Examples 1 and 3 where toluene was used alone in the immersion tank, the perovskite precursor film was instantaneously immersed after the substrate was immersed in the immersion tank. Converted to a perovskite film. Further, in Comparative Examples 2 and 4 in which hexane was used alone in the immersion bath, it took 30 seconds or more for the perovskite precursor film to be converted into the perovskite film. On the other hand, in Example 1 using a mixed solvent of toluene: hexane = 1: 1 in the immersion tank, the perovskite precursor film was converted into the perovskite film in an appropriate time of about 5 to 10 seconds after the substrate was immersed. The perovskite film formed by the conversion had better film quality than the perovskite film formed in each comparative example.
Next, when the compositions of the precursor solutions are the same and Examples 1, 5, and 6 or Examples 3, 7, and 8 in which the composition of the immersion bath is changed are compared, the perovskite films having good film quality are obtained. Of the examples 1, 5 and 6 that were formed but only SnI ₂ was used as the tin halide, the perovskite film having better film quality was obtained in Example 6 in which toluene: hexane was 1: 1.5. I was able to get it. On the other hand, in Examples 3, 7 and 8 using SnI ₂ and SnF ₂ as tin halides, it is possible to obtain a perovskite film with better film quality in Example 3 where toluene: hexane is 1: 1. did it. This tendency was the same when the number of revolutions when spin-coating the precursor solution was 8000 rpm or 6000 rpm.
Further, from the observation with an atomic force microscope, the arithmetic average roughnesses Ra and Rz of the perovskite film formed in Example 3 are Ra when the spin coating rotational speed of the precursor solution is 8000 rpm, Ra is 5.52 nm, Rz Was 76.93 nm, and when the spin coating rotational speed of the precursor solution was 6000 rpm, Ra was 3.02 nm and Rz was 48.33 nm, and a smooth surface could be obtained.

[Effects of mixed solvent temperature and mixing ratio]
Example 9
When preparing the precursor solution, instead of dissolving tin iodide in dimethyl sulfoxide at a concentration of 1M, tin iodide and tin fluoride are combined in a total amount of 1M, and tin iodide and tin fluoride are mixed. Examples were dissolved except that the ratio (SnI ₂ : SnF ₂ ) was 80 mol%: 20 mol%, and the temperature of the mixed solvent (immersion tank) in which the perovskite precursor film was immersed was adjusted to 13 ° C. A perovskite film was produced in the same manner as in Example 1.

(Comparative Example 5)
A perovskite membrane was prepared in the same manner as in Example 9 except that ultra-dehydrated toluene was used alone instead of a mixed solvent of ultra-dehydrated toluene and ultra-dehydrated hexane as a solvent (immersion tank) for immersing the perovskite precursor film. Manufactured.

(Comparative Example 6)
A perovskite membrane was prepared in the same manner as in Example 9 except that a super-dehydrated hexane was used alone instead of a mixed solvent of ultra-dehydrated toluene and ultra-dehydrated hexane as a solvent (immersion tank) for immersing the perovskite precursor film. Manufactured.

(Example 10)
A perovskite film was produced in the same manner as in Example 9 except that the temperature of the mixed solvent (immersion tank) in which the perovskite precursor film was immersed was adjusted to 25 ° C.

(Comparative Example 7)
A perovskite membrane was prepared in the same manner as in Example 10 except that a super-dehydrated toluene and ultra-dehydrated hexane were used instead of a mixed solvent of ultra-dehydrated toluene and ultra-dehydrated hexane as a solvent (immersion tank) for immersing the perovskite precursor film Manufactured.

(Comparative Example 8)
A perovskite membrane was prepared in the same manner as in Example 10 except that a super-dehydrated hexane and a super-dehydrated hexane were used instead of a mixed solvent of ultra-dehydrated toluene and ultra-dehydrated hexane as a solvent (immersion tank) for immersing the perovskite precursor film. Manufactured.
Table 2 shows the composition of the precursor solution and immersion bath used in Examples 9 and 10 and Comparative Examples 5 to 8, and the temperature of the immersion bath when the perovskite film is immersed.

In Examples 9 and 10 and Comparative Examples 5 to 8, visible light (532 nm) was incident on the perovskite precursor film while being immersed in the immersion bath from the glass substrate side, and the temporal change in the transmitted light intensity was measured. The results are shown in FIG. In addition, scanning electron micrographs (magnification 5000 times) and atomic force micrographs (inset, magnification 100000 times) of the perovskite films produced in the examples and comparative examples are shown in FIG. Table 3 shows the root mean square roughness Rq by thickness and atomic force microscope observation. The optical density spectrum of the perovskite film produced in each example and each comparative example is shown in FIG. 6, and the X-ray diffraction spectrum is shown in FIG. FIG. 7 (a) shows X-ray diffraction spectra arranged separately for each perovskite film, and FIG. 7 (b) shows the X-ray diffraction spectrum of FIG. 7 (a) converted into a logarithmic scale. The logarithmic spectrum is superimposed and displayed.

As shown in Table 3, each of the perovskite membranes of Examples 9 and 10 using a mixed solvent of toluene and hexane in the immersion tank was manufactured in the same manner except that toluene alone was used in the immersion tank. Alternatively, the surface roughness Rq was smaller than that of the perovskite film of Comparative Example 6 or 8 manufactured in the same manner except that hexane alone was used in the perovskite film of No. 7 and the immersion tank, and the film quality was good.
However, when Example 9 and Example 10 are compared, the perovskite membrane of Example 9 in which the temperature of the immersion bath is adjusted to 13 ° C. is more than the perovskite membrane of Example 10 in which the temperature of the immersion bath is adjusted to 25 ° C. Also, the surface roughness Rq was small and the coverage on the substrate was high (see scanning electron micrograph in FIG. 5).
Further, from FIG. 6, the perovskite film of Example 9 in which the temperature of the immersion bath was adjusted to 13 ° C. was optical in the shorter wavelength region than the perovskite film of Example 10 in which the temperature of the immersion bath was adjusted to 25 ° C. A tendency of high concentration was observed. The low optical density in the short wavelength region in the perovskite film of Example 10 is considered to be due to the scattering loss of short wavelength light due to fluctuations in the film density. In comparison, the perovskite film of Example 9 has a high optical density in the short wavelength region and a thin film thickness, suggesting that it is formed with a higher density.
Further, from FIG. 7, a diffraction peak derived from the perovskite type crystal structure was confirmed from any X-ray diffraction spectrum. A mixed solvent of toluene and hexane was used for the immersion tank, and the temperature of the immersion tank was 13 The diffraction peaks derived from the (001) plane, the (002) plane, and the (003) plane observed in the perovskite film of Example 9 adjusted to ° C. are far more than the diffraction peaks observed in other perovskite films. The strength was high. From this, it was shown that the perovskite-type crystal of Example 9 is highly oriented.
FIG. 4 shows the change in the transmitted light intensity of the perovskite precursor film during immersion in the immersion bath, where the transmitted light intensity is the degree of conversion from the perovskite precursor film to the perovskite film. It becomes an indicator. Specifically, when the transmitted light intensity indicated by the vertical axis is 1, the perovskite precursor film is in a state before conversion, and when the transmitted light intensity becomes substantially constant at 0, the perovskite precursor film is completely This means that it has been converted to a perovskite film. Referring to FIG. 4, it can be seen that results having the same tendency as the results obtained from the comparison between Example 1 and Comparative Examples 1 to 4 are obtained. That is, in Comparative Examples 5 and 7 using toluene alone in the immersion tank, the perovskite precursor film was converted to a perovskite film at a relatively fast rate, and in Comparative Examples 6 and 8 using hexane alone in the immersion tank, It took 30 seconds or more for the perovskite precursor film to be converted into a perovskite film. In contrast, in Example 9 in which a mixed solvent of toluene and hexane was used in the immersion tank, the perovskite precursor film was converted to a perovskite film in an appropriate time of 10 to 15 seconds. On the other hand, in Example 10, although the conversion rate is slightly lower than that in Comparative Example 7 using toluene alone, the conversion from the perovskite precursor film to the perovskite film proceeds faster than in Example 9.
From the above, in order to optimize the formation rate of the perovskite film by controlling the diffusion rate of the first solvent from the perovskite precursor film to the immersion tank, and to obtain a perovskite film with better film quality, the temperature of the immersion tank It was found that control is important, and the temperature of the immersion bath is preferably adjusted to 5 to 20 ° C, more preferably adjusted to 10 to 15 ° C.

(Examples 11 to 14)
A perovskite film was produced in the same manner as in Example 9 except that the mixing ratio of the mixed solvent (immersion tank) in which the perovskite precursor film was immersed was changed as shown in Table 4.

(Examples 15 to 18)
A perovskite film was produced in the same manner as in Example 10 except that the mixing ratio of the mixed solvent (immersion tank) in which the perovskite precursor film was immersed was changed as shown in Table 4.
The precursor solution used in Examples 11 to 18, the composition of the immersion bath, and the temperature of the immersion bath when dipping the perovskite membrane are shown in Table 4, and the perovskite membrane produced in Examples 9 to 18 was photographed with a digital camera. A photograph is shown in FIG.

The photograph of the perovskite film in FIG. 8 shows that the darker the color, the less light scattering, the denser the film, and the better the film quality. Referring to FIG. 8, the photographs of the perovskite films of Examples 9 to 18 using a mixed solvent of toluene and hexane in the immersion tank all show a dark dark color, and a perovskite film with good film quality is formed. I was able to confirm that. In particular, the perovskite membranes of Examples 9 and 11 to 14 manufactured at a dipping bath temperature of 13 ° C. were photographed more than the perovskite membranes of Examples 10 and 15 to 18 manufactured at a dipping bath temperature of 25 ° C. The darker the color was, and the closer the mixing ratio of toluene and hexane was to 1: 1, the darker the color of the photograph and the better the film quality. Therefore, when the perovskite film is produced by adjusting the temperature of the immersion bath to 5 to 20 ° C., the second solvent: third solvent (volume ratio) is 1: 0.6 to 1: 1.5, It was found that a perovskite film with better film quality can be obtained by setting the ratio to 1: 0.7 to 1: 1.3.

[Effect of annealing conditions]
(Example 19)
It is dissolved in dimethyl sulfoxide so that tin iodide becomes 1M, and the mixing molar ratio of tin iodide and tin fluoride (SnI ₂ : SnF ₂ ) is 100: 15. A precursor solution was prepared by dissolving ((NH ₂ ) ₂ CHI) at a concentration of 1M.
Next, a glass substrate on which a positive electrode made of ITO having a thickness of 100 nm and a PEDOT: PSS layer having a thickness of 30 nm were formed was prepared. Then, the prepared precursor solution was dropped onto the PEDOT: PSS layer through a filter having a pore diameter of 0.45 μm, and the substrate was rotated at 6000 rpm for 30 seconds to spin coat, thereby forming a perovskite precursor film.
Next, the temperature of a mixed solvent (immersion tank) in which ultra-dehydrated toluene (second solvent) and ultra-dehydrated hexane (third solvent) are mixed at a volume ratio of 1: 5 is adjusted to 7 ° C., and the mixed solvent is stirred. Then, the substrate on which the perovskite precursor film was formed was immersed in the mixed solvent for 3 minutes. Thereafter, the substrate was taken out from the dipping bath and annealed at 70 ° C. for 20 minutes to obtain a perovskite film with a thickness of 200 nm.

(Example 20)
After removing the substrate from the immersion bath and allowing to stand at room temperature for 10 minutes, the temperature was gradually raised from room temperature to 70 ° C., and then annealed at 70 ° C. for 20 minutes to obtain a perovskite film with a thickness of 200 nm. A perovskite film was produced in the same manner as in Example 19 except that.

Table 5 shows the precursor solution used in Example 19 and Example 20, the composition of the immersion bath, the temperature of the immersion bath when dipping the perovskite film, and the annealing treatment conditions. Scanning of the perovskite film manufactured in each example FIG. 9 shows a scanning electron micrograph (magnification 10,000 times).

Referring to FIG. 9, the perovskite film of Example 19 annealed at 70 ° C. for 20 minutes has a large grain size, while the perovskite film of Example 20 annealed while raising the temperature from room temperature to 70 ° C. has a grain size. It was confirmed to be small. From this, it is possible to increase the grain size of the perovskite film and reduce the number of grains by increasing the temperature at the start of annealing or setting the annealing temperature higher. all right. It was also found that the grain size of the perovskite film can be reduced and the number of grains can be increased by lowering the temperature at the start of annealing or setting the annealing temperature lower. .

[Effect of immersion time]
(Examples 21 to 23)
It is dissolved in dimethyl sulfoxide so that tin iodide becomes 1M, and the mixing molar ratio of tin iodide and tin fluoride (SnI ₂ : SnF ₂ ) is 100: 15. A precursor solution was prepared by dissolving ((NH ₂ ) ₂ CHI) at a concentration of 1M.
Next, a glass substrate on which a positive electrode made of ITO having a thickness of 100 nm and a PEDOT: PSS layer having a thickness of 30 nm were formed was prepared. Then, the prepared precursor solution was dropped onto the PEDOT: PSS layer through a filter having a pore diameter of 0.45 μm, and the substrate was rotated at 6000 rpm for 30 seconds to spin coat, thereby forming a perovskite precursor film.
Next, the temperature of a mixed solvent (immersion tank) in which ultra-dehydrated toluene (second solvent) and ultra-dehydrated hexane (third solvent) are mixed at a volume ratio of 1: 5 is adjusted to 7 ° C., and the mixed solvent is stirred. However, the substrate on which the perovskite precursor film was formed was immersed in the mixed solvent for the time shown in Table 6. Thereafter, the substrate was taken out of the immersion bath and annealed at 70 ° C. for 2 to 4 minutes to obtain a perovskite film with a thickness of 200 nm.
Table 6 shows the precursor solution used in each example, the composition of the dipping bath, the temperature of the dipping bath and the dipping time when dipping the perovskite membrane, and a scanning electron micrograph of the perovskite membrane manufactured in each example ( The magnification is 10,000 times).

Referring to FIG. 10, it was confirmed that the grain size of the perovskite film became smaller as the immersion time in the precursor solution was increased to 2 minutes, 3 minutes, and 4 minutes. From this, it was found that the grain size of the perovskite film can be increased and the number of grains can be reduced by shortening the immersion time in the precursor solution. It was also found that the grain size of the perovskite film can be reduced and the number of grains can be increased by increasing the immersion time in the precursor solution.

[Evaluation of perovskite films produced using a two-step dipping method]
(Example 24)
A perovskite film was produced in the same manner as in Example 19 except that the super-dehydrated toluene: super-dehydrated hexane (volume ratio) was set to 1: 2.5 in the immersion tank in which the perovskite precursor film was immersed.

(Example 25)
In this example, a perovskite film was manufactured using a two-step dipping method.
First, a perovskite precursor film was formed under the same conditions as in Example 24, and a substrate on which this perovskite precursor film was formed was mixed with a super-dehydrated toluene: super-dehydrated hexane = 1: 2.5 mixed solvent (first immersion). Immersion was carried out by dipping in a tank. Next, the substrate was taken out from the first immersion tank, immersed in ultra-dehydrated toluene (second immersion tank) adjusted to 25 ° C., and immersed for 2 minutes while stirring the ultra-dehydrated toluene. Thereafter, the substrate was taken out from the second immersion bath and annealed at 70 ° C. for 20 minutes to produce a perovskite film.

(Example 26)
A perovskite film was produced in the same manner as in Example 24 except that the super-dehydrated toluene: super-dehydrated hexane (volume ratio) was set to 1: 1.7 in the immersion tank in which the perovskite precursor film was immersed.

(Example 27)
In this example, a perovskite film was manufactured using a two-step dipping method.
A perovskite film was produced in the same manner as in Example 25 except that the super-dehydrated toluene: super-dehydrated hexane (volume ratio) was set to 1: 1.7 in the immersion tank in which the perovskite precursor film was immersed.
Table 7 shows the precursor solution used in each example, the composition of the first and second immersion tanks, the temperature of the immersion tank when dipping the perovskite film, and the type of immersion method. FIG. 11 shows a scanning electron micrograph (magnification 10,000 times) of the perovskite film.

From FIG. 11, it can be seen that the perovskite films of Examples 25 and 27 in which the immersion treatment was performed in two stages were formed more densely than the perovskite films in Examples 24 and 26 formed by a single immersion process. Recognize. From this, it was found that a perovskite film with better quality (high coverage) can be obtained by performing the immersion treatment in multiple stages using a plurality of immersion tanks.

[Manufacture and evaluation of solar cells]
In Example 3, a perovskite film manufactured by setting the spin coat rotational speed of the precursor solution to 6000 rpm was prepared. On the perovskite film, two organic layers and an electrode were formed at a vacuum degree of 1 × 10 ⁻⁴ Pa by a vacuum deposition method. First, on the perovskite layer, by depositing a C ₆₀ to a thickness of 30 nm, was formed thereon an organic layer of the two layers by depositing a thickness of 10nm and BCP. Furthermore, Ag was vapor-deposited with a thickness of 100 nm thereon to form an electrode. The obtained laminate (substrate / ITO positive electrode / PEDOT: PSS layer / perovskite film / C60 layer / BCP layer / Ag negative electrode) was accommodated in a glass sealing tube and sealed with a UV curable resin to obtain a solar cell. . Separately, a total of 23 solar cells with 6 elements were manufactured under the same conditions.
Each manufactured battery was irradiated with AM1.5 pseudo-sunlight at 100 mW / cm ² irradiance, and short-circuit current Jsc, open-circuit voltage Voc, FF (fill factor), and energy conversion efficiency η were measured. As a result, the short-circuit current Jsc is 16.64 ± 0.92 mA / cm ² , the open circuit voltage Voc is 0.44 ± 0.01 V, the FF is 0.40 ± 0.04, and the energy conversion efficiency η is 2.96 ± 0. It was .34%, and a very stable characteristic could be obtained.

For the perovskite films produced in Examples 1 to 4, C ₆₀ , BCP, and Ag were sequentially deposited under the same conditions as described above, and the resulting laminate (substrate / ITO positive electrode / PEDOT: PSS layer / perovskite). Membrane / C60 layer / BCP layer / Ag negative electrode) was housed in a glass sealing tube and sealed with a UV curable resin to obtain solar cells (batteries 1, 2-a, 2-b, 3-5). Of the perovskite films manufactured in Examples 1 to 4, the one used for manufacturing the solar cell is a perovskite film in which the number of revolutions of the substrate is set to 8000 rpm when the precursor solution is spin-coated.
Each produced solar cell was irradiated with AM1.5 pseudo-sunlight at 100 mW / cm ² irradiance, and the solar cell characteristics were evaluated. Moreover, also when the light incident surface of each solar cell is covered with a photomask (t0.2 mm stainless steel mask (black chrome treatment), opening 1.8 × 1.8 mm ² ), the solar cell characteristics are obtained under the same light irradiation conditions. evaluated.
The results of measuring the current density-voltage characteristics without covering each battery with a photomask are shown in FIG. 12, and the example numbers and solar cell characteristics of the perovskite films used are shown in Table 8. FIG. 13 shows the results of measuring the current density-voltage characteristics with the battery covered with a photomask, FIG. 14 shows the results of measuring the wavelength-dependent IPCE of the photoelectric conversion characteristics, and Table 8 shows the solar cell characteristics. . In each figure and Table 8, the battery 2-a and the battery 2-b are solar cells using the perovskite films having the highest conversion efficiency and the lowest perovskite films produced in Example 2, respectively.

12 to 14 and Table 8, it was found that all the batteries produced in each example had excellent solar cell characteristics.

[Influence on solar cell characteristics by temperature control]
Using a N-methyl-2-pyrrolidone (NMP) solution (concentration 1M) of lead methylammonium iodide (MAPbI ₃ ) as a precursor solution, a perovskite precursor film was formed in the same manner as in Example 1. Next, toluene whose temperature was adjusted to 25 ° C. on a cool plate was stirred, and the substrate on which the perovskite precursor film was formed was immersed in it for 2 minutes. Thereafter, the substrate was taken out and annealed at 100 ° C. for 5 minutes to produce a perovskite film.
Separately, a perovskite film was produced in the same manner as described above except that toluene whose temperature was adjusted to 15 ° C. on a cool plate was used.
Using these perovskite films, a laminate (substrate / ITO positive electrode / PEDOT: PSS layer / perovskite film / C60 layer / BCP layer / Ag negative electrode) was produced in the same manner as described in [Production and evaluation of solar cells] above. ), Housed in a glass sealing tube, and sealed with a UV curable resin to obtain a solar cell. Four solar cells each having a perovskite film formed using toluene at each temperature were manufactured.
The results of measuring the current density-voltage characteristics of a solar cell having a perovskite film formed using toluene at 25 ° C. are shown in FIG. 15, and the current of the solar cell having a perovskite film formed using toluene at 15 ° C. is shown in FIG. The results of measuring the density-voltage characteristics are shown in FIG. As is clear from the comparison between FIG. 15 and FIG. 16, it was confirmed that by controlling the temperature of the solvent brought into contact with the perovskite precursor film, a solar cell with high power generation efficiency can be stably produced with high reproducibility. . This result is because the formation rate of the perovskite film can be optimized by controlling the diffusion rate by controlling the temperature of the solvent in contact with the perovskite precursor film.

The perovskite films produced in Examples 9 and 10 and Comparative Examples 5 to 8 were also laminated (substrate / ITO positive electrode / PEDOT: PSS) by the same method as described in [Production and evaluation of solar cells] above. Layer / perovskite film / C60 layer / BCP layer / Ag negative electrode) and housed in a glass sealing tube, and sealed with a UV curable resin to form solar cells (

batteries

5 and 6, comparative batteries 1 to 4) did. Table 9 shows an example number of the perovskite film used in each solar cell. Separately, under the same conditions as the

batteries

5 and 6 and the comparative batteries 1 to 4, the battery 5 has 6 elements of 4 cells, and the battery 6 and the comparative batteries 1 to 4 have 4 cells. One or two of each was produced.
Each manufactured solar cell was irradiated with simulated sunlight under the same conditions as described in [Manufacturing and Evaluation of Solar Cell] above, and the solar cell characteristics were evaluated.
FIG. 17 shows the results of measuring the current density-voltage characteristics (photocurrent characteristics) without covering each solar cell with a photomask, and the current density-voltage characteristics (photocurrent characteristics) with each solar cell covered with a photomask. ) Is shown in FIG. 18, and the result of measuring the current density-voltage characteristic (dark current characteristic) without irradiating the pseudo-sunlight is shown in FIG. FIG. 20 shows the wavelength dependence of photoelectric conversion characteristics (IPCE) of each solar cell, and FIG. 21 to FIG. 24 and Table 9 show the short circuit current JSC _{, the} open circuit voltage V _OC , the fill factor FF, and the energy conversion efficiency η. . In addition, histograms showing variations in the solar cell characteristics of the battery 5 are shown in FIGS. 25 to 28, and changes with time in the solar cell characteristics when the battery 5 is continuously driven are shown in FIGS. FIG. 30 is a graph in which the range of 0 to 5 hours of the graph of FIG. 29 is enlarged and displayed.

17 to 30 and Table 9, it was found that

batteries

5 and 6 produced using the perovskite films of Examples 9 and 10 have sufficient solar cell characteristics. In particular, in the battery 5 using the perovskite film of Example 9 (perovskite film manufactured at a dipping bath temperature of 13 ° C.), very excellent solar cell characteristics can be obtained, as well as variations in characteristics and during continuous driving. The characteristic deterioration was suppressed to a small level and stable characteristics could be obtained. It is epoch-making that the degradation of the solar cell characteristics is suppressed in this way in the Sn-based solar cell, and the manufacturing method of the present invention makes it possible to realize an Sn-based solar cell that can be driven for a long time. Could also be confirmed.

[Evaluation of solar cells manufactured with different annealing conditions]
On the perovskite film produced in Example 19, C ₆₀ , BCP, and Ag were sequentially deposited under the same conditions as described in [Production and evaluation of solar cells] above, and the resulting laminate (substrate / ITO positive electrode / PEDOT: PSS layer / perovskite film / C60 layer / BCP layer / Ag negative electrode) were housed in a glass sealing tube and sealed with a UV curable resin to obtain a solar cell (battery 7). Separately, three solar cells (all referred to as “battery 7”) were manufactured under the same conditions as battery 7.
Each manufactured battery was irradiated with simulated sunlight under the same conditions as described in [Manufacturing and Evaluation of Solar Cell] above, and the solar cell characteristics were evaluated. FIG. 31 shows current density-voltage characteristics (photocurrent characteristics) measured by irradiating pseudo-sunlight for four batteries 7 and current density-voltage characteristics (dark current characteristics) measured without irradiating pseudo-sunlight. Show. FIG. 33 shows the result of measuring the hysteresis of the current density-voltage characteristic of the battery having the maximum current density among the four batteries 7, and the result of measuring the wavelength dependence of the photoelectric conversion characteristic (IPCE). FIG. 34 shows the short circuit current Jsc, the open circuit voltage Voc, the FF (fill factor), the energy conversion efficiency η, the series resistance Rs, and the parallel resistance Rsh. Moreover, a closed circuit including a resistance of 1 kΩ is created, and AM1.5 pseudo-sunlight is continuously irradiated at 100 mW / cm ² irradiance, and short circuit current Jsc, open circuit voltage Voc, FF (fill factor), energy conversion FIG. 35 shows the life characteristic test result obtained by measuring the change in efficiency η.
Similarly, a solar cell (referred to as “battery 8”) manufactured using the perovskite film manufactured in Example 20 was also manufactured. FIG. 32 shows current density-voltage characteristics (photocurrent characteristics) measured by irradiating pseudo-sunlight for four batteries 8 and current density-voltage characteristics (dark current characteristics) measured without irradiating pseudo-sunlight. Show. FIG. 34 shows the result of measuring the wavelength dependence of photoelectric conversion characteristics (IPCE), FIG. 35 shows the result of life characteristic test, short circuit current Jsc, open circuit voltage Voc, FF (fill factor), energy conversion efficiency η, series Table 10 shows the resistance Rs and the parallel resistance Rsh.

31 to 35 and Table 10, it was found that the battery in which the perovskite film contains formamidinium also has excellent solar cell characteristics, is not deteriorated by light, and has particularly high energy conversion efficiency. In addition, the battery 7 using the perovskite film obtained by annealing at 70 ° C. for 20 minutes has the battery 8 using the perovskite film obtained by annealing while raising the temperature from room temperature to 70 ° C. over 20 minutes. It was confirmed that the performance (Jsc) is much better than that.

[Evaluation of solar cell with perovskite film formed using two-step dipping method]
On the perovskite films produced in Examples 24 to 27, C ₆₀ , BCP, and Ag were sequentially deposited under the same conditions as described in [Production and evaluation of solar cells] above, and the resulting laminate was obtained. (Substrate / ITO positive electrode / PEDOT: PSS layer / perovskite film / C60 layer / BCP layer / Ag negative electrode) is housed in a glass sealing tube and sealed with a UV curable resin to form solar cells (batteries 9 to 12). did. Separately, three solar cells (all referred to as “batteries 9 to 12”) were manufactured under the same conditions as those of the batteries 9 to 12. Table 11 shows the example number of the perovskite film used in each battery and the type of immersion bath method used in each example.

Each manufactured battery was irradiated with simulated sunlight under the same conditions as described in [Manufacturing and Evaluation of Solar Cell] above, and the solar cell characteristics were evaluated. For the short circuit current Jsc, open circuit voltage Voc, FF (fill factor), and energy conversion efficiency η, the measured value of the battery 9 is subtracted from the measured value of the battery 10 and the measured value of the battery 12 is subtracted from the measured value of the battery 12. Values are shown in Table 12. In Table 12, “ΔJsc”, “ΔVoc”, “ΔFF”, and “Δη” represent differences between the respective batteries in the short-circuit current Jsc, the open-circuit voltage Voc, FF (fill factor), and the energy conversion efficiency η, respectively. “-” Indicates that the characteristic value in the column is not measured. Also, current density-voltage characteristics (photocurrent characteristics) measured by irradiating pseudo-sunlight for four batteries 12 and current density-voltage characteristics (dark current characteristics) measured without irradiating pseudo-sunlight are shown. 36 shows the result of measuring the hysteresis of the current density-voltage characteristic of the battery having the maximum current density among the four batteries 12, and shows the result of measuring the short-circuit current Jsc, the open-circuit voltage Voc, FF (fill factor). ), Energy conversion efficiency η, series resistance Rs, parallel resistance Rsh are shown in Table 13.

As shown in Table 12, the

batteries

10 and 12 in which the perovskite film was formed by using the two-stage immersion method had battery characteristics much better than the

batteries

9 and 11 in which the perovskite film was formed by using the single immersion method. Was. From this, it was found that the solar cell characteristics can be further improved by forming a perovskite film by performing multi-stage immersion treatment.

According to the method for producing a perovskite film of the present invention, a perovskite film having good film quality can be produced with good reproducibility, so that a solar cell or an electronic device having excellent element characteristics can be stably supplied. For this reason, this invention has high industrial applicability.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent electrode 3 Hole capture layer 4 Photoelectric conversion layer 5 Electron transport layer 6 Counter electrode

Claims

By contacting the perovskite precursor film containing the first solvent with the mixed solvent of the second solvent and the third solvent, the first solvent moves from the perovskite precursor film into the mixed solvent, thereby changing the perovskite film. A method of manufacturing comprising:
The first solvent is more soluble in the main component of the perovskite precursor film than the second solvent and the third solvent,
The method for producing a perovskite film, wherein the second solvent and the third solvent have different solubility in the first solvent.
The method for producing a perovskite film according to claim 1, wherein the perovskite precursor film is formed on a substrate.
The method for producing a perovskite film according to claim 1 or 2, wherein the perovskite precursor film is immersed in the mixed solvent.
The mixing ratio of the second solvent and the third solvent in the mixed solvent is such that the first solvent in the perovskite precursor film is mixed when the mixed solvent is brought into contact with the perovskite precursor film at 25 ° C. The method for producing a perovskite film according to any one of claims 1 to 3, wherein a diffusion constant for diffusing into the solvent is a ratio in a range of 1 x 10 -13 m 2 / s to 1 x 10 2 m 2 / s.
A diffusion constant by which the first solvent in the perovskite precursor film diffuses into the mixed solvent is:
The perovskite film according to any one of claims 1 to 4, wherein the mixed solvent is brought into contact with the perovskite precursor film at a temperature in a range of 1x10 -13 m 2 / s to 1x10 2 m 2 / s. Manufacturing method.
A diffusion constant k 2 in which the first solvent diffuses into the second solvent when the second solvent is brought into contact with the perovskite precursor film at 25 ° C., and the third percolation to the perovskite precursor film at 25 ° C. The absolute value (| k 2 −k 3 |) of the difference from the diffusion constant k 3 in which the first solvent diffuses into the third solvent when contacting with the solvent is 1 × 10 −13 m 2 / s to 1 × 10 −. The method for producing a perovskite film according to any one of claims 1 to 5, which is in a range of 13 m 2 / s.
The method for producing a perovskite film according to any one of claims 1 to 6, wherein the first solvent is dimethyl sulfoxide, N-methyl-2-pyrrolidone, dimethylformamide, or γ-butyrolactone.
8. The method according to claim 1, wherein the second solvent and the third solvent are toluene, chlorobenzene, hexane, or cyclohexane (provided that the second solvent and the third solvent are different solvents). A method for producing a perovskite film.
The method for producing a perovskite film according to any one of claims 1 to 7, wherein the second solvent is toluene or chlorobenzene, and the third solvent is hexane or cyclohexane.
The method for producing a perovskite film according to any one of claims 1 to 9, wherein the perovskite precursor film contains a perovskite type compound represented by the following general formula (4).
A 3 BX 3 (4)
[In the general formula (4), A 3 represents an organic cation, B represents a divalent metal ion, and X represents a halogen ion. The three Xs may be the same as or different from each other. ]
The method for producing a perovskite film according to any one of claims 1 to 10, wherein the perovskite precursor film contains at least one of Pb and Sn.
The method for producing a perovskite film according to any one of claims 1 to 11, wherein the perovskite precursor film contains at least one of methylammonium iodide, formamidine iodide, and cesium iodide.
The method for producing a perovskite film according to any one of claims 1 to 12, wherein the perovskite precursor film contains at least one of I and F.
The method for producing a perovskite film according to any one of claims 1 to 13, wherein the mixed solvent is contacted with the perovskite precursor film for 0.1 second to 180 minutes.
The method for producing a perovskite film according to any one of claims 1 to 14, wherein when the mixed solvent is in contact with the perovskite precursor film, the temperature of the mixed solvent is changed with time.
The method for producing a perovskite film according to any one of claims 1 to 15, wherein after the mixed solvent is brought into contact with the perovskite precursor film, the obtained perovskite film is annealed at 0 to 200 ° C. .
The perovskite film according to any one of claims 1 to 15, wherein after the mixed solvent is brought into contact with the perovskite precursor film, a fourth solvent is brought into contact with the perovskite precursor film in contact with the mixed solvent. Production method.
The method for producing a perovskite film according to claim 17, wherein the fourth solvent is less soluble in the main component of the perovskite precursor film than the first solvent.
The method for producing a perovskite film according to claim 17 or 18, wherein the fourth solvent is the same solvent as one of the second solvent and the third solvent.
The method for producing a perovskite film according to claim 17, wherein the second solvent is toluene or chlorobenzene, the third solvent is hexane or cyclohexane, and the fourth solvent is toluene or chlorobenzene.
The method for producing a perovskite film according to any one of claims 17 to 20, wherein a temperature of the fourth solvent is higher than a temperature of the mixed solvent.
The production of a perovskite film according to any one of claims 17 to 21, wherein the perovskite precursor film is contacted with the fourth solvent, and then the obtained perovskite film is annealed at 0 to 200 ° C. Method.
A perovskite film produced by the production method according to any one of claims 1 to 22.
24. The perovskite film according to claim 23, wherein the first solvent is contained at a concentration of more than 0 and less than 10,000 ppm.
The perovskite film according to claim 23 or 24, comprising the second solvent at a concentration of more than 0 and less than 5,000 ppm.
The perovskite film according to any one of claims 23 to 25, which contains the third solvent at a concentration of more than 0 and less than 5,000 ppm.
A solar cell comprising the perovskite film according to any one of claims 23 to 26.
A solvent to be contacted with a perovskite precursor film containing a first solvent, wherein the first solvent moves from the perovskite precursor film into the contacted solvent by the contact, thereby producing a perovskite film. A perovskite film forming solvent, which can be
The perovskite film forming solvent is a mixture of two or more solvents including at least a second solvent and a third solvent,
The first solvent is more soluble in the main component of the perovskite precursor film than the second solvent and the third solvent,
The perovskite film-forming solvent, wherein the second solvent and the third solvent have different solubility in the first solvent.