JPWO2016121700A1 - Tin (II) halide perovskite thin film and method for producing the same, and electronic device and photoelectric conversion apparatus using the same - Google Patents

Abstract

In the X-ray diffraction chart, the tin halide (II) -based perovskite compound of the present invention has a diffraction angle 2θ of 10 ° to 50 ° with respect to the diffraction peak of the plane index (002) corresponding to the tin (II) halide-based perovskite compound. The intensity ratio of the diffraction peak with the highest intensity corresponding to the tin (IV) compound existing in the range of 0 ° or less is 10% or less.

Description

  The present invention relates to a tin (II) halide perovskite thin film, a method for producing the same, and an electronic device and a photoelectric conversion apparatus using the same.

  In recent years, solar cells that can directly convert light energy from the sun into electricity have attracted attention as one of renewable energy technologies.

  There are various types of solar cells, such as silicon-based, compound-based, and organic-based, depending on the semiconductor used as the raw material. The energy conversion efficiency is approaching that of current mainstream silicon solar cells.

As the perovskite compound, for example, various compositions such as a transition metal oxide represented by the chemical formula ABO ₃ are known. However, most of the conventional studies have been related to lead-based perovskite compounds. For example, Patent Document 1 proposes a solar cell in which photoelectric conversion efficiency is improved by combining an inorganic hole transport layer with a light absorption layer made of a lead iodide-based layered perovskite compound. In Non-Patent Document 1, research on power generation performance of a solar cell including a perovskite layer made of CH ₃ NH ₃ Sn _x Pb _(1-x) I ₃ is reported.

JP 2014-175473 A

J. Phys. Chem. Lett. 2014, 5, 1004-1011

  However, although solar cells using lead-based perovskite compounds have been able to obtain higher energy conversion efficiency than in the early days of research, from the standpoint of practicality, conversion efficiency is still not improved. There was a problem that it was necessary.

  On the other hand, research on compounds that can replace lead-based perovskite compounds is also underway in consideration of environmental considerations, and tin-based perovskite compounds are listed as candidates, but tin-based perovskite compounds were used. In the solar cell, there is a problem that it is difficult to obtain the energy conversion efficiency as obtained with the lead-based perovskite compound.

  One of the factors that hinder the improvement of energy conversion efficiency of solar cells using tin-based perovskite compounds is a by-product other than the target tin (II) -based perovskite compounds in the process of thinning the perovskite compounds, That is, it is known that the purity of the thin film is lowered by the formation of the tin (IV) compound.

  More specifically, perovskite compounds are generally known to have variations in thin film performance due to the effects of moisture and oxygen contained in the atmosphere, so film formation methods using organic solvents are usually employed. Has been. Above all, from the viewpoint of ensuring stable performance with a certain accuracy, the perovskite thin film is generally produced in a nitrogen atmosphere using a high boiling point organic solvent such as DMF or DMSO. On the other hand, however, when DMF or DMSO is used, the purity of the thin film is lowered due to the formation of a tin (IV) compound in the process of thinning the tin-based perovskite compound and the remaining part of DMF or DMSO. As a result, there has been a concern that the photoelectric conversion efficiency of the solar cell and the element lifetime are likely to be reduced as a result.

  In addition, since DMF and DMSO have high solubility in perovskite compounds, the remaining of these organic solvents in the thin film may cause re-dissolution of the perovskite layer and layers adjacent to the perovskite and dissolution of substrates such as plastic films. It has also been a concern that it may cause a decrease in device life.

For example, in a solar cell including a CH ₃ NH ₃ SnI ₃ perovskite layer formed using DMF described in Non-Patent Document 1, solar power generation performance is not obtained, and as a factor thereof, this CH ₃ NH ₃ SnI _{In the 3} perovskite layer, it has been shown that the presence of Sn ⁴⁺ produced by the oxidation of Sn ²⁺ increases the carrier concentration, leading to a decrease in semiconductor characteristics and an increase in conductor characteristics. It has also been shown to decrease to 90% in 1 minute. Similarly, CsSnI ₃ has also been reported to have a large conductor temperature characteristic (see Journal of Solid State Chemistry 114, 159-163 (1995)).

  The present invention has been made in view of the circumstances as described above, and provides a high-purity tin (II) halide perovskite thin film, a method for producing the same, and an electronic device and a photoelectric conversion apparatus using the same. It is an object.

  Another object of the present invention is to provide a method for producing a high-purity metal halide (II) perovskite thin film using an aqueous solvent without using an organic solvent.

  As a result of diligent studies to achieve the above object, the present inventors have come up with a solution that cannot be conceived from the properties of perovskite compounds known hitherto. That is, the present inventors apply a conventional perovskite compound raw material (precursor) dissolved or suspended in an aqueous solvent or a hydrolyzate solution of the perovskite compound to dry the conventional organic material. It has been found that a tin (II) halide perovskite thin film having a high purity can be obtained as compared with a case where it is produced by a film forming method using a solvent or a vapor deposition method. It has also been found that by using the perovskite layer thus obtained as a light absorption layer, the photoelectric conversion efficiency and the element life of the photoelectric conversion device can be significantly improved. Further, the perovskite compound is not limited to a tin (II) halide perovskite compound, and conventional metal halide (II) perovskite compounds including lead halides can be increased by an aqueous solvent without using an organic solvent. It has been found that a thin film of purity can be produced.

  Based on these new findings, the present inventors have made further studies and completed the present invention.

That is, this invention includes the following aspects.
(1) A tin (II) halide perovskite thin film having a diffraction angle 2θ of 10 ° with respect to the diffraction peak of the plane index (002) corresponding to the tin (II) halide perovskite compound in the X-ray diffraction chart. A tin (II) halide perovskite thin film characterized in that the intensity ratio of the diffraction peak having the highest intensity corresponding to the tin (IV) compound existing in the range of 50 ° or less is 10% or less.
(2) The tin (II) halide perovskite thin film according to (1), wherein the contents of DMF and DMSO are each less than 0.5% by weight.
(3) The tin (II) halide perovskite compound is composed of CsSnX ₃ (where X represents halogen), and the tin (IV) compound is composed of Cs ₂ SnX ₆ (where X represents halogen). The halogenation according to (1) or (2), wherein the diffraction peak having the highest intensity corresponding to the tin (IV) compound is a diffraction peak having a plane index (222) or a plane index (400) Tin (II) perovskite thin film.
(4) The tin (II) halide perovskite compound is composed of RNH _{(2 + m)} SnX ₃ (wherein R represents a hydrocarbon group, X represents a halogen, and m is 0 or 1). (IV) The compound consists of (RNH _{(2 + m)} ) ₂ SnX ₆ (wherein R represents a hydrocarbon group, X represents a halogen, and m is 0 or 1), and corresponds to the tin (IV) compound. The tin halide (II) according to (1) or (2), wherein the diffraction peak having the highest intensity is a diffraction peak having a plane index (003), a plane index (101) or a plane index (012). ) System perovskite thin film.
(5) It is formed on the substrate surface using an aqueous solution of a first precursor containing tin (II) halide and an aqueous solution of a second precursor containing halide. ) Tin (II) halide perovskite thin film according to any one of the above.
(6) It is formed on a substrate surface using an aqueous solution prepared by adding an aqueous solvent to a mixture of a first precursor containing tin (II) halide and a second precursor containing halide. The tin (II) halide perovskite thin film according to any one of (1) to (4).
(7) The tin (II) halide perovskite thin film according to (6), wherein the mixture is a powder.
(8) A tin (II) halide perovskite compound obtained from an aqueous solution of a first precursor containing tin (II) halide and a second precursor containing halide is vaporized and formed on the substrate surface. The tin (II) halide perovskite thin film according to any one of claims 1 to 4, wherein the thin film is a perovskite thin film.
(9) An electronic device using the tin (II) halide perovskite thin film according to any one of (1) to (8).
(10) A photoelectric conversion apparatus using the tin (II) halide perovskite thin film according to any one of (1) to (8) or the electronic device according to (9).
(11) including a step of preparing an aqueous solution of a metal halide (II) -based perovskite compound, and a step of applying the aqueous solution of the metal halide (II) -based perovskite compound to a substrate surface to remove the solvent. A method for producing a metal halide (II) -based perovskite thin film.
(12) A step of preparing an aqueous solution of a metal halide (II) -based perovskite compound, and removing a solvent of the aqueous solution of the metal halide (II) -based perovskite compound to obtain a metal halide (II) -based perovskite compound. And a method for producing a metal halide (II) perovskite thin film comprising vaporizing the metal halide (II) perovskite compound to form a film on the substrate surface.
(13) The metal halide (II) -based perovskite thin film according to (11) or (12), wherein the metal halide (II) is tin (II) halide or lead (II) halide Manufacturing method.
(14) A metal halide (II) -based perovskite thin film obtained by the method for producing a metal halide (II) -based perovskite thin film according to any one of (11) to (13) .

  According to the present invention, a high-purity tin (II) halide perovskite thin film, a production method thereof, an electronic device and a photoelectric conversion apparatus using the same are provided. The present invention also provides a method for producing a high-purity metal halide (II) perovskite thin film with an aqueous solvent without using an organic solvent.

  The above-described object and other objects, features, and advantages will become more apparent from the preferred embodiments described below and the accompanying drawings.

Is an X-ray diffraction chart showing the results of simulation of X-ray diffraction pattern of CsSnBr _3. Simulation results of X-ray diffraction pattern of the cs ₂ SnBr ₆ is an X-ray diffraction chart showing the. CH is a ₃ NH ₃ SnBr ₃ X-ray diffraction chart showing the results of simulation of X-ray diffraction pattern of. _(CH 3 _{NH 3)} is an X-ray diffraction chart showing the results of simulation of X-ray diffraction pattern of 2 SnBr _6. It is an X-ray diffraction chart which shows the result analyzed about the thin film obtained in Example 1 and comparative example 1 using the X-ray diffractometer. (A): Example 1, (b): Comparative Example 1. It is an X-ray-diffraction chart which shows the result analyzed about the thin film obtained in Example 2 and Comparative Example 2 using the X-ray-diffraction apparatus. (A): Example 2, (b): Comparative Example 2. It is an X-ray diffraction chart which shows the result analyzed about the thin film obtained in Example 3 using the X-ray diffractometer. It is a graph which shows the current-voltage characteristic (IV characteristic) of the solar cell element obtained in Example 5.

  Hereinafter, embodiments of the present invention will be described in detail. The description of the constituent elements described below is an example (representative example) of the embodiment of the present invention, and the specific form is not limited to these embodiments, and the design is within the scope not departing from the gist of the present invention. Any change or the like is included in the present invention.

<Tin (II) halide perovskite thin film>
The tin (II) halide perovskite thin film of the present invention has a diffraction angle 2θ of 10 ° or more and 50 ° with respect to the diffraction peak of the plane index (002) corresponding to the tin (II) halide perovskite compound in the X-ray diffraction chart. The intensity ratio of the diffraction peak with the highest intensity corresponding to the tin (IV) compound existing in the range of 0 ° or less is 10% or less.

That is, in the tin (II) halide perovskite thin film of the present embodiment, a tin (IV) compound (for example, Cs ₂ SnBr ₆ or (CH ₃ NH ₃ ) ₂ SnBr ₆ ) generated by modifying Sn ²⁺ to Sn ^4+. Etc.) is suppressed, the semiconductor characteristics of the perovskite thin film and the energy conversion efficiency as a solar cell material are hardly reduced. Further, the tin (II) halide perovskite thin film of this embodiment is a lead-free perovskite thin film having such a high purity that the presence of organic solvents such as DMF and DMSO can be ignored.

  The film thickness of the tin (II) halide perovskite thin film of the present invention can be appropriately set according to the use of the thin film as long as the object and effect of the present invention are not impaired. It is 100 micrometers, More preferably, it is 50 nm-10 micrometers.

(Chemical structure)
The tin (II) halide perovskite thin film according to the first embodiment of the present invention is composed of the general formula (1): CsSnX ₃ .

  In the general formula (1), X represents halogen, and examples thereof include Cl, Br, and I.

Formula (1): Specific examples of the halogenated tin (II) perovskite thin film represented by CsSnX _3, for _{example, CsSnCl 3, CsSnBr 3, CsSnI} 3, and CsSnIBr _2, and the like.

In the first embodiment, tin (IV) compounds have the general formula _(2): composed of Cs 2 SnX _6.

  In the general formula (2), X represents a halogen, and is a halogen that can form a structure of a tin (IV) compound according to the type of X in the general formula (1). For example, Cl, Br, I are Can be mentioned.

Specific examples of the tin (IV) compound represented by the general formula (2): Cs ₂ SnX ₆ include, for example, Cs ₂ SnCl ₆ , Cs ₂ SnBr ₆ , Cs ₂ SnI ₆ , and Cs ₂ SnI ₂ Br _4. Is mentioned.

The tin (II) halide perovskite thin film according to the second embodiment of the present invention is made of the general formula (3): RNH _{(2 + m)} SnX ₃ .

  In the general formula (3), X represents halogen, and examples thereof include Cl, Br, and I.

  In the general formula (3), R represents a hydrocarbon group. The hydrocarbon group is not particularly limited as long as the tin (II) halide perovskite thin film can have a structure in which organic ammonium molecular layers and tin (II) halide layers are alternately stacked.

In the general formula (3), m is 0 or 1. According to the type of R, m takes such a value that a tin (II) halide perovskite thin film can form a structure in which organic ammonium molecular layers and tin (II) halide layers are alternately stacked. For example, m is 1 when R is a methyl group or an ethyl group. For example, when R is CH ₃ CH, m is 0.

Specific examples of the tin (II) halide perovskite thin film represented by the general formula (3): RNH _{(2 + m)} SnX ₃ include, for example, CH ₃ NH ₃ SnCl ₃ , CH ₃ NH ₃ SnBr ₃ , and CH ₃ NH. _{3 SnI 3, CH 3 NH 3} SnIBr 2, CH 3 CH 2 NH 3 SnCl 3, CH 3 CH 2 NH 3 SnBr 3, CH 3 CH 2 NH 3 SnI 3, CH 3 CH 2 NH 3 SnIBr 2, (CH 3 CH = NH ₂ ) SnCl ₃ , (CH ₃ CH═NH ₂ ) SnBr ₃ , (CH ₃ CH═NH ₂ ) SnI _{3 and the} like.

In the first and second embodiments, tin (IV) compounds have the general formula _{(4) :( RNH (2 +} m)) consist of 2 SnX _6.

  In the general formula (4), X represents a halogen, and is a halogen that can form a structure of a tin (IV) compound according to the type of X in the general formula (3). For example, Cl, Br, and I are Can be mentioned.

  In the above general formula (4), R represents a hydrocarbon group. The hydrocarbon group is a functional group that can form the structure of the tin (IV) compound according to the type of R in the general formula (3).

In the general formula (4), m is 0 or 1. m takes such a value that the structure of the tin (IV) compound can be formed according to the type of R. For example, m is 1 when R is a methyl group or an ethyl group. For example, when R is CH ₃ CH, m is 0.

Specific examples of the tin (IV) compound represented by the general formula (4): (RNH _{(2 + m)} ) ₂ SnX ₆ include, for example, (CH ₃ NH ₃ ) ₂ SnCl ₆ , (CH ₃ NH ₃ ) ₂ SnBr. ₆ , (CH ₃ NH ₃ ) ₂ SnI ₆ , (CH ₃ NH ₃ ) ₂ SnI ₂ Br ₄ , (CH ₃ CH ₂ NH ₃ ) ₂ SnCl ₆ , (CH ₃ CH═NH ₂ ) ₂ SnCl ₆ , (CH ₃ CH═NH ₂ ) ₂ SnBr ₆ , (CH ₃ CH═NH ₂ ) ₂ SnI _{6 and the} like.

  In addition, the chemical structure of the tin (II) halide perovskite thin film of the present invention is not limited to the above-described embodiment, and in the range that does not inhibit the purpose and effect of the present invention, depending on the use of the perovskite thin film, Various design changes are possible. In addition, the chemical structure of the tin (IV) compound may be one or two or more structures according to the chemical structure of the tin (II) halide perovskite thin film of the present invention.

(X-ray diffraction)
In the present embodiment, the composition of the tin (II) halide perovskite thin film can be analyzed and evaluated by a commonly used analytical technique. For example, the composition of the tin (II) halide perovskite thin film of this embodiment can be analyzed and evaluated using an X-ray diffraction chart generally obtained by a known X-ray diffraction method.

  As an X-ray diffraction phenomenon, when X-rays having a wavelength similar to the distance between atoms are incident on a material in which atoms are regularly arranged (the arrangement plane is called a lattice plane), the X-rays scattered by each atom are reflected. It is known that they interfere with each other in certain directions and produce intense X-rays. As understood from the Bragg formula (2d sin θ = nλ), an incident X-ray having a known wavelength λ is incident on the material, and a diffraction angle 2θ (angle formed by the incident X-ray direction and the diffraction X-ray direction) and its X An X-ray diffraction pattern can be obtained by measuring the line intensity. In the X-ray diffraction method, the crystalline substance constituting the sample can be specified by comparing the X-ray diffraction pattern obtained for the measurement sample with an X-ray diffraction pattern by a known database or simulation.

In the present embodiment, the measurement conditions and the like for the X-ray diffraction method are not particularly limited, but in the present specification, as an example, using the X-ray diffraction apparatus (Rigaku Rad B-system) manufactured by Rigaku Corporation, the following Measurement shall be performed according to the measurement conditions.
(Measurement condition)
X-ray source: Cu Kα
X-ray wavelength: 1.5405 mm, 1.5443 mm
Reading width: 0.02 °
Scanning speed: 5 deg / min
Measurement range: 2θ = 10 to 70 °
Measurement temperature: room temperature.

  The composition of the tin (II) halide perovskite thin film of this embodiment can be analyzed and evaluated as follows using an X-ray diffraction chart, for example.

  First, the diffraction peak corresponding to the tin (II) halide perovskite compound is obtained by, for example, analyzing the X-ray diffraction pattern (measurement pattern) in the X-ray diffraction chart of the measurement sample, the tin halide according to a simulation or a generally known database, etc. (II) Compared with the X-ray diffraction pattern (reference pattern) of the perovskite compound, whether a combination (peak set) of a plurality of peaks including the diffraction peak with the highest intensity in the reference pattern exists in the measurement pattern By confirming whether or not, the diffraction peak corresponding to the target tin (II) halide perovskite compound can be identified. In addition, by specifying the diffraction peak of the plane index (002) among the identified peaks, the diffraction peak of the plane index (002) corresponding to the tin (II) halide perovskite compound can be determined. In identifying a diffraction peak, an error or the like that occurs in a range that is normally recognized in the field is considered, and it is understood that the error or the like is caused by a measurement apparatus to be used, measurement conditions, or the like.

Here, the case of CsSnBr ₃ will be specifically described as the tin (II) halide perovskite thin film according to the first embodiment of the present invention.

FIG. 1A is an X-ray diffraction chart showing a result of simulating an X-ray diffraction pattern of CsSnBr ₃ . As shown in FIG. 1A, CsSnBr ₃ has a cubic perovskite structure (Pm3m), and is calculated as lattice constant a = b = c = 5.808A. At the diffraction angles 2θ = 15.24 °, 21.62 °, 26.56 °, and 30.76 °, four characteristic peaks are observed, and the plane indices (001), (011), (111), respectively. ) And (002). Therefore, in CsSnBr ₃ , for example, a combination of two or more peaks selected from the above four peaks can be used as a peak set for identifying a diffraction peak. Moreover, since the peak intensity of the plane index (002) is 80 or more among these peaks, it is considered that identification in the measurement pattern is relatively easy. Therefore, in CsSnBr ₃ , the peak at the diffraction angle 2θ = 30.76 ° is used as the diffraction peak of the plane index (002) in the reference pattern, and more specifically, for example, near the diffraction angle 2θ = 30.76 °. The peak existing in the range of diffraction angle 2θ = 30.76 ° ± 0.5 ° can be determined as the diffraction peak of the plane index (002) in the measurement pattern. For more details on the X-ray diffraction pattern of CsSnBr ₃ , see K. Yamada, H Kawaguchi, T. Matsui, T. Okuda and S. Ichiba, Bull. Chem. Soc. Jpn, 63, 2521-2525 (1990). ), And JD Donaldson, J. Silver, S. Hadjiminolis, SD Ross, J. Chem. Soc. Dalton Transactions, Inorganic Chemistry (1972-1999), 1500-1506 (1975).

In addition, as the tin (II) halide perovskite thin film according to the second embodiment of the present invention, for example, a case of CH ₃ NH ₃ SnBr ₃ will be specifically described.

FIG. 2A is an X-ray diffraction chart showing a result of simulating an X-ray diffraction pattern of CH ₃ NH ₃ SnBr ₃ . As shown in FIG. 2A, CH ₃ NH ₃ SnBr ₃ has a cubic perovskite structure (Pm3m), and the lattice constant a = b = c = 5.901A is calculated. At the diffraction angles 2θ = 15.00 °, 21.28 °, 26.14 °, and 30.27 °, four characteristic peaks are observed, and the plane indices (001), (011), (111), respectively. ) And (002). Therefore, in CH ₃ NH ₃ SnBr ₃ , for example, a combination of two or more peaks selected from the above four peaks can be used as a peak set for identifying a diffraction peak. Moreover, since the peak intensity of the plane index (002) is 80 or more among these peaks, it is considered that identification in the measurement pattern is relatively easy. Therefore, in CH ₃ NH ₃ SnBr ₃ , a peak existing in the vicinity of the diffraction angle 2θ = 30.27 °, more specifically, for example, in the range of the diffraction angle 2θ = 30.27 ° ± 0.5 °, It can be determined as the diffraction peak of the plane index (002). For more details on the X-ray diffraction pattern of CH ₃ NH ₃ SnBr ₃ , see K. Yamada, H Kawaguchi, T. Matsui, T. Okuda and S. Ichiba, Bull. Chem. Soc. Jpn, 63, 2521. -2525 (1990), and K. Yamada, K. Nakada, Y. Takeuchi, K. Nawa, and Y. Yamane, Bull. Chem. Soc. Jpn. Vol. 84, No. 9, 926-932 (2011) Please refer to.

  Next, the diffraction peak corresponding to the tin (IV) compound is, for example, the X-ray diffraction pattern (measurement pattern) in the X-ray diffraction chart of the measurement sample. Compared with the X-ray diffraction pattern (reference pattern), by confirming whether a combination (peak set) of a plurality of peaks including the diffraction peak with the highest intensity in the reference pattern exists in the measurement pattern, A diffraction peak corresponding to the tin (IV) compound to be detected can be identified. Further, by specifying the diffraction peak with the highest intensity among the identified peaks, the diffraction peak with the highest intensity corresponding to the tin (IV) compound can be determined. In specifying the diffraction peak, the composition of the tin (II) halide perovskite thin film of the present invention is more accurately determined according to the chemical structure of the tin (IV) compound, the reference pattern of the X-ray diffraction chart, and the like. From the viewpoint of analysis / evaluation, it is preferable to include a diffraction peak having a diffraction angle 2θ in the range of 10 ° to 50 ° in the peak set. In identifying a diffraction peak, an error or the like that occurs in a range that is normally recognized in the field is taken into consideration, and it is understood that this error or the like is caused by a measurement device to be used, measurement conditions, or the like.

  Since the tin (II) halide perovskite thin film of the present embodiment is a high-purity thin film having a high content of the target tin (II) halide perovskite compound, it is preferable to use tin in the X-ray diffraction chart. (IV) A diffraction peak corresponding to the compound is not identified. Thereby, it can be evaluated that the tin (II) halide perovskite thin film according to the present embodiment is a thin film substantially not containing a tin (IV) compound.

  In the present specification, regarding a tin (II) halide-based perovskite thin film, “substantially free of a tin (IV) compound” does not mean that the thin film does not contain any tin (IV) compound. It is meant that the thin film has the function and effect of the present invention even when the thin film contains a tin (IV) compound. That is, the tin (II) halide perovskite thin film according to this embodiment suppresses the deterioration of semiconductor characteristics by suppressing the formation of tin (IV) compounds other than the target tin (II) halide perovskite compound. For example, a thin film containing a tin (IV) compound only to an extent that does not hinder the improvement of photoelectric conversion efficiency and device lifetime in a photoelectric conversion element using the thin film.

  In another embodiment of the tin (II) halide perovskite thin film of the present invention, in the X-ray diffraction pattern in the X-ray diffraction chart of the measurement sample, the diffraction peak corresponding to the tin (II) halide perovskite compound and tin ( IV) When both diffraction peaks corresponding to the compound are identified, that is, when the measurement sample is evaluated as a thin film containing a tin (II) halide perovskite compound and a tin (IV) compound. Is a content ratio of a tin (II) halide perovskite compound in the measurement sample, that is, as an index for evaluating the purity of a tin (II) halide perovskite thin film, for example, halogenation in the X-ray diffraction chart For the diffraction peak of the plane index (002) corresponding to the tin (II) perovskite compound The intensity ratio of the diffraction peak having the highest intensity corresponding to the tin (IV) compound existing in the diffraction angle 2θ of 10 ° or more and 50 ° or less can be used.

  In the tin (II) halide perovskite compound of this embodiment, the diffraction angle 2θ is 10 ° with respect to the diffraction peak of the plane index (002) corresponding to the tin (II) halide perovskite compound determined as described above. The intensity ratio of the highest intensity diffraction peak corresponding to the tin (IV) compound existing in the range of 50 ° or less is 10% or less, preferably 1% or less, more preferably 0.1% or less. is there.

That said intensity ratio is low, in the tin halide (II) perovskite thin film of the present embodiment, tin caused ^{by Sn 2+} is denatured ^{Sn 4+} (IV) compounds (for _example, Cs 2 SnBr ₆ (CH ₃ NH _{3) 2} SnBr _6, etc.) content is low, and it means that high purity tin halide (II) perovskite thin films. Such a high-purity tin (II) halide perovskite thin film is expected to be less likely to cause deterioration in semiconductor characteristics and energy conversion efficiency as a solar cell material.

  In this specification, “intensity” of a diffraction peak related to an X-ray diffraction chart refers to the X-ray intensity at a specific diffraction angle 2θ, that is, the height of a diffraction peak. In addition, when the diffraction peak corresponding to the tin (IV) compound to be detected is not identified in the X-ray diffraction chart of the measurement sample, the tin (IV) compound is “not detected (ND)”, and the intensity ratio is Interpreted as substantially less than 1%. On the other hand, when the diffraction peak corresponding to the target tin (II) halide perovskite compound is not identified in the X-ray diffraction chart of the measurement sample, the tin halide (II) perovskite compound is not detected (ND). The thin film of the measurement sample is evaluated as substantially free of the tin (II) halide perovskite compound.

  Note that, in the tin (II) halide perovskite thin film of this embodiment, in the X-ray diffraction chart, the evaluation of the purity of the thin film is assisted in place of the diffraction peak intensity ratio or by the diffraction peak intensity ratio. As a thing, a diffraction peak area (peak height x peak half value width) can also be considered as needed.

  In addition, in the X-ray diffraction chart of the tin (II) halide perovskite thin film of the present invention, the tin halide (II) used for calculating the intensity ratio with the highest intensity diffraction peak corresponding to the tin (IV) compound. ) The selection of the diffraction peak corresponding to the perovskite compound is not limited to the plane index (002) diffraction peak, but the chemical structure, crystal structure, and X-ray diffraction chart standard of the tin (II) halide perovskite compound. Depending on the pattern and the like, it is permissible to appropriately change the tin (II) halide perovskite thin film of the present invention for the purpose of obtaining the purity of the thin film more accurately.

  In the tin (II) halide perovskite thin film according to the first embodiment of the present invention, the highest intensity diffraction peak corresponding to the above tin (IV) compound has a plane index (222) or a plane index (400). It is preferable that it is a diffraction peak.

Here, as the tin (IV) compound according to the first embodiment of the present invention, for example, a case of Cs ₂ SnBr ₆ will be specifically described.

FIG. 1B is an X-ray diffraction chart showing a result of simulating an X-ray diffraction pattern of Cs ₂ SnBr ₆ . As shown in FIG. 1B, Cs ₂ SnBr ₆ has a cubic sodium chloride structure (Fm3m) and is calculated to have a lattice constant a = b = c = 10.834A. At diffraction angles 2θ = 14.15 °, 23.20 °, 27.28 °, 28.52 ° and 33.05 °, five characteristic peaks are observed, respectively, and the surface index (111), (220 ), (311), (222) and (400). Therefore, in Cs ₂ SnBr ₆ , for example, a combination of two or more peaks selected from the above five peaks can be used as a peak set for identifying a diffraction peak. Moreover, since the peak intensity of the plane index (222) and the plane index (400) is 70 or more among these peaks, it is considered that identification in the measurement pattern is relatively easy. Therefore, in Cs ₂ SnBr ₆ , the diffraction angles 2θ = 28.52 ° and 33.05 ° are used as the diffraction peaks of the plane index (222) and the plane index (400) in the reference pattern, respectively. = 28.52 ° and near 33.05 °, more specifically, for example, peaks existing in the ranges of diffraction angles 2θ = 28.52 ° ± 0.5 ° and 33.05 ° ± 0.5 ° Can be determined as the diffraction peaks of the plane index (222) and the plane index (400), respectively, in the measurement pattern. The X-ray diffraction pattern of Cs ₂ SnBr ₆ can also be obtained from ICSD # 158957.

  In the tin (II) halide perovskite thin film according to the second embodiment of the present invention, the highest intensity diffraction peak corresponding to the above tin (IV) compound has a plane index (003) and a plane index (101). ) Or a plane index (012) diffraction peak.

Here, as the tin (IV) compound according to the second embodiment of the present invention, for example, the case of (CH ₃ NH ₃ ) ₂ SnBr ₆ will be specifically described.

FIG. 2B is an X-ray diffraction chart showing a result of simulating an X-ray diffraction pattern of (CH ₃ NH ₃ ) ₂ SnBr ₆ . As shown in FIG. 2B, (CH ₃ NH ₃ ) ₂ SnBr ₆ belongs to the trigonal space group R3, and the lattice constants are calculated as a = b = 7.580A and c = 22.204A. Three characteristic peaks are seen at diffraction angles 2θ = 11.98 °, 14.06 °, and 15.67 °, identified as plane indices (003), (101), and (012), respectively. . Therefore, in (CH ₃ NH ₃ ) ₂ SnBr ₆ , a combination of two or more peaks selected from the above three peaks can be used as a peak set for identifying a diffraction peak. In addition, since these peaks all have a peak intensity of 70 or more, it is considered that identification in the measurement pattern is relatively easy. Therefore, in (CH ₃ NH ₃ ) ₂ SnBr ₆ , the peaks at diffraction angles 2θ = 11.98 °, 14.06 °, and 15.67 ° are respectively represented by the plane index (003) and the plane index in the reference pattern. As a diffraction peak of (101) or plane index (012), near diffraction angles 2θ = 11.98 °, 14.06 °, and 15.67 °, more specifically, for example, diffraction angle 2θ = 1.11. Peaks existing in the ranges of 98 ° ± 0.5 °, 14.06 ° ± 0.5 °, and 15.67 ° ± 0.5 ° are respectively represented by a plane index (003) and a plane index ( 101) or a plane index (012) diffraction peak.

(Content of organic solvent)
As will be described later, the tin (II) halide perovskite thin film of this embodiment can produce the desired perovskite thin film without using an organic solvent in the production method. Therefore, in the method for producing a tin (II) halide perovskite thin film, the organic solvent that is not used as a solvent for the precursor solution (solution of the raw material compound) described later is used in the tin (II) halide perovskite thin film of this embodiment. Does not contain the organic solvent (content 0% by weight), or even if it is included in a very small amount (trace) (content less than 0.1% by weight), It is understood that it is a content rate that does not interfere with performance. In addition, the total value of the content rate of the said organic solvent in a precursor can also be used as an estimated value of the content rate of the said organic solvent in the tin (II) halide perovskite thin film of this embodiment.

  Specifically, in the tin (II) halide perovskite thin film of the present embodiment, the contents of DMF and DMSO, which are organic solvents having strong solubility in perovskite compounds and plastic substrate materials, are respectively Significantly lower than the perovskite film. More specifically, the tin (II) halide perovskite thin film of this embodiment has a DMF and DMSO content of less than 0.5% by weight, preferably less than 0.05% by weight, respectively. More preferably, it is less than 0.005% by weight. Even more preferably, in the tin (II) halide perovskite thin film of this embodiment, the contents of DMF and DMSO measured by a measuring apparatus exemplified below are each below the detection limit of the apparatus.

  Therefore, for example, in the element containing the tin (II) halide perovskite thin film of this embodiment formed on the surface of a plastic substrate, remelting of the perovskite layer and the layer adjacent to the perovskite by DMF and DMSO and the dissolution of the substrate are suppressed. In addition, the device life can be improved.

  In the present embodiment, the method for measuring the content of the organic solvent, the measurement conditions, and the like are not particularly limited, but in the present specification, measurement is performed using gas chromatography mass spectrometry (GC / MS) as an example. Shall.

For example, the content of DMF can be measured under the following measurement conditions. By dividing the mass of the obtained DMF by the mass of the measurement sample, the DMF content in the sample can be obtained.
(Measurement condition)
Measuring device: Agilent 5975 inert GC / MS system (manufactured by Agilent Technologies)
Heat desorption device TDS 3 (Gestel Co., Ltd.)
Column: HP-5ms (30m × φ250μm × 0.25μm)
Column temperature: maintained at 35 ° C. for 5 minutes, then increased to 200 ° C. at 10 ° C./min and maintained for 5 minutes Carrier gas: He (1 mL / min)
Ionization method: EI (70 eV)

  For example, when a perovskite layer including a tin (II) halide perovskite thin film of this embodiment is formed as a constituent element of the photoelectric conversion element, the content of the organic solvent in the perovskite layer is measured, Using the measured value, the content of the organic solvent in the tin (II) halide perovskite thin film of this embodiment can be determined.

<Method for producing tin (II) halide perovskite thin film>
Next, a method for producing a tin (II) halide perovskite thin film of the present invention will be described. The tin (II) halide perovskite thin film of the present invention can be produced using an aqueous solution of a tin (II) halide perovskite compound described in detail below. That is, the tin (II) halide perovskite thin film of the present invention can form a high-purity thin film with an aqueous solvent without using an organic solvent.

  In a first embodiment of the method for preparing an aqueous solution of a tin (II) halide-based perovskite compound, an aqueous solution of a first precursor containing a tin (II) halide and an aqueous solution of a second precursor containing a halide And an aqueous solution of the first precursor and an aqueous solution of the second precursor are mixed.

  In the present specification, the “precursor” refers to a raw material compound that provides a target tin (II) halide perovskite compound, and is used as a generic term for two or more raw material compounds. Further, when individual raw material compounds among the precursors are distinguished, they are described as “first precursor”, “second precursor” and the like, respectively.

  In this embodiment, the precursor includes a first precursor that includes a tin (II) halide and a second precursor that includes a halide. The structure and number of the precursors can be appropriately designed according to the target tin (II) halide perovskite compound.

  In the present embodiment, the mixing ratio of the first precursor and the second precursor is not particularly limited. The mixing ratio of the first precursor and the second precursor is, for example, 1: 5 to 5: 1, preferably 1: 2 to 2: 1, and more preferably equimolar.

  In the present specification, an “aqueous solution of a precursor” refers to a solution in which a precursor is dissolved or suspended in water or a solvent containing water as a main component (hereinafter, also collectively referred to as “aqueous solvent”). .

  In this embodiment, the concentration of the aqueous solution of the precursor is not particularly limited, and is, for example, 0.1 to 0.5M.

  The mixing time of the aqueous solution of the precursor is not particularly limited as long as the target tin (II) halide perovskite compound is produced. The mixing time is, for example, 1 to 60 minutes.

  The temperature of the aqueous solution of the precursor during mixing is not particularly limited as long as the target tin (II) halide perovskite compound is produced. The temperature of the aqueous solution of the precursor during mixing is, for example, 25 to 90 ° C.

  In this embodiment, the preparation of the aqueous solution of the precursor and the mixing of the aqueous solution of the precursor can be performed in the atmosphere. In addition, from the viewpoint of reducing the influence of moisture and oxygen contained in the atmosphere and more effectively suppressing the formation of tin (IV) compounds, the preparation and precursor of an aqueous solution of the precursor are prepared and maintained in a nitrogen atmosphere or under reduced pressure. Mixing of aqueous solutions of the substance may be performed.

Hereinafter, as an example of a method for preparing an aqueous solution of a tin (II) halide perovskite compound according to the present embodiment, an aqueous solution of a tin (II) halide perovskite compound represented by the general formula (1): CsSnX ₃ The preparation method of will be described. In a method for preparing an aqueous solution of a CsSnX ₃ perovskite compound, the precursor includes a first precursor that includes a tin (II) halide and a second precursor that includes a halide, for example, the first precursor is SnX ₂ And the second precursor is CsX.

Hereinafter, a method for preparing an aqueous solution of the CsSnBr ₃ perovskite compound will be specifically described.

In the method for preparing an aqueous solution of a CsSnBr ₃ perovskite compound, the first precursor containing tin (II) halide is SnBr ₂ and the second precursor containing halide is CsBr. Hereinafter, SnBr ₂ and CsBr are collectively referred to as a precursor.

First, an aqueous solution of SnBr _{2 and} an aqueous solution of CsBr are prepared. The concentration of the aqueous solution of the precursor is not particularly limited, but can be, for example, about 0.1M.

As the aqueous solvent, for example, water (H ₂ O) can be used. The precursors SnBr ₂ and CsBr are both water-soluble, but the aqueous solution of SnBr ₂ becomes cloudy. This is because Sn (OH) ₂ is generated by the reaction of Sn ²⁺ generated by dissolving SnBr ₂ in H ₂ O and H ₂ O (ie, hydrolysis reaction of SnBr ₂ ). Conceivable.

In the method for preparing an aqueous solution of a tin (II) halide perovskite compound of the present embodiment, Sn ²⁺ is stabilized by the formation of the above tin (II) hydroxide, and the purity is higher than that of the conventional method. It is estimated that a tin (II) halide perovskite compound is obtained.

Accordingly, the aqueous solvent is not limited to H ₂ O, and the above tin (II) hydroxide (Sn (OH) ₂ ) is obtained by reaction with the first precursor tin (II) halide (SnBr ₂ ). ), A solvent having an active hydroxyl group that gives a structure similar to the structure (eg, Sn (OC _n H _{2n + 1} ) ₂ structure) may be used. Specific examples include alcohols such as ethanol, isopropyl alcohol, methoxypropylene, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate. In addition, in order to further improve the dissolution stability and dispersion stability of the target tin (II) halide perovskite compounds, esters such as ethyl acetate and propylene glycol monomethyl ether acetate, and ketones such as methyl ethyl ketone, isobutyl methyl ketone and acetone 0-80 weights of solvents such as ethers such as diethyl ether, dipropylene ether, aromatic solvents such as toluene, xylene and chlorobenzene, heterocyclic aromatic solvents such as tetrahydrofuran, acids such as acetic acid and formic acid, etc. %, Preferably 0 to 50% by weight.

  The aqueous solvent can be appropriately selected in consideration of the solubility of the precursor in the aqueous solvent. Moreover, the aqueous solvent may be used individually by 1 type, and the mixed solvent which combined 2 or more types may be used. Further, from the viewpoint of reducing the influence of oxygen contained in the solvent, the aqueous solvent may be subjected to deoxygenation treatment. In addition, the aqueous solvent may contain any additive or the like as long as the object and effects of the present invention are not impaired.

Next, an aqueous solution (white turbid solution) of SnBr _{2 and} an aqueous solution of CsBr are mixed. As a result, an aqueous solution of the CsSnBr ₃ perovskite compound is obtained. In addition, this mixed solution becomes cloudy, and when it is left for a while, precipitation separation occurs. This is considered to be due to the generation of CsHSnO ₂ .

In this embodiment, when preparing an aqueous solution of a tin (II) halide perovskite compound represented by the general formula (3): RNH _{(2 + m)} SnX ₃ , for example, a tin (II) halide is included. Similar to the above method except that SnX ₂ is used as the first precursor and RNH _{(2 + m)} X is used as the second precursor containing halide, the aqueous tin (II) halide perovskite compound of interest A solution can be obtained.

  In a second embodiment of the method for preparing an aqueous solution of a tin (II) halide perovskite compound of the present invention, the first precursor and the second precursor are mixed, an aqueous solvent is added to the mixture, and An aqueous solution of the mixture is prepared.

  In the present embodiment, the mixing ratio of the first precursor and the second precursor is not particularly limited. The mixing ratio of the first precursor and the second precursor is, for example, 1: 5 to 5: 1, preferably 1: 2 to 2: 1, and more preferably equimolar.

  Although the density | concentration of the aqueous solution of the mixture of a precursor is not specifically limited, For example, it is 0.1-0.5M.

  The mixing time of the precursor is not particularly limited as long as the target tin (II) halide perovskite compound is produced. The mixing time is, for example, 1 to 60 minutes.

  The temperature of the aqueous solution of the precursor mixture is not particularly limited as long as the target tin (II) halide perovskite compound is produced. The temperature of the aqueous solution of the mixture is, for example, 25 to 90 ° C.

  In this embodiment, the mixing of the precursors and the preparation of the aqueous solution of the mixture of precursors can be performed in the atmosphere. In addition, from the viewpoint of reducing the influence of moisture and oxygen contained in the atmosphere and more effectively suppressing the formation of tin (IV) compounds, the preparation and precursor of an aqueous solution of the precursor are prepared and maintained in a nitrogen atmosphere or under reduced pressure. Mixing of aqueous solutions of the substance may be performed.

  In the second embodiment of the method for preparing an aqueous solution of a tin (II) halide perovskite compound of the present invention, the precursor mixture is preferably a powder. When the mixture of precursors is a powder, the production rate of the target tin (II) halide perovskite compound can be improved, and the production efficiency of the tin (II) halide perovskite compound can be improved.

  The method for powdering the precursor is not particularly limited. For example, the precursor can be mixed into a powder by mixing the precursor in a mortar and grinding with a pestle.

  The tin (II) halide perovskite thin film of the present invention is a high-purity thin film without using an organic solvent by using an aqueous solution of the tin (II) halide perovskite compound obtained as described above. A film can be formed.

  Specifically, an aqueous solution of a tin (II) halide perovskite compound prepared as described above is generally applied to a substrate surface using a known coating method to remove the solvent, thereby The tin (II) halide perovskite thin film of the invention can be formed into a film (film).

  The tin (II) halide perovskite thin film of the present invention can be formed in the atmosphere. In addition, from the viewpoint of reducing the influence of moisture and oxygen contained in the atmosphere, more effectively suppressing the formation of tin (IV) compounds, and increasing the purity of the thin film, halogenation is performed in a nitrogen atmosphere or under reduced pressure. A tin (II) perovskite thin film may be formed. In addition, when an aqueous solvent that has been subjected to deoxygenation treatment is used, the influence of oxygen contained in the solvent is reduced, the production of tin (IV) compounds is more effectively suppressed, and the purity is increased. It is expected that a high thin film will be obtained.

  When the aqueous solution of tin (II) halide perovskite compound is in a suspended state, the aqueous solution suspension may be applied to the substrate surface, and the aqueous solution is allowed to stand for a while. The resulting supernatant or precipitate may be applied to the substrate surface.

  In addition, the aqueous solution of the first precursor and the aqueous solution of the second precursor separately prepared in the method for preparing the aqueous solution of the tin (II) halide perovskite compound according to the first embodiment, respectively, The tin (II) halide perovskite compound may be formed by separately applying to the surface and mixing the aqueous solution of the precursor on the substrate surface, and then forming a thin film by removing the solvent. .

  Since the tin (II) halide perovskite thin film of the present invention thus obtained does not use a high-boiling organic solvent such as DMF or DMSO, the production of tin (IV) compound is suppressed in the process of thinning, The resulting thin film is so pure that the presence of the organic solvent can be ignored. Therefore, the use of the tin (II) halide perovskite thin film of the present invention is expected to improve, for example, the photoelectric conversion efficiency and element lifetime of solar cells. The high boiling point organic solvent is an organic solvent having a boiling point of 120 ° C. or higher.

  In addition to forming a film (film), the tin (II) halide perovskite prepared as described above is used from the viewpoint of obtaining crystals of the target tin (II) halide perovskite compound. Form a crystal nucleus of a tin (II) halide perovskite compound by leaving the container containing the aqueous solution of the compound as it is, and removing the solvent from the surface of the aqueous solution using a heating means if necessary. Thus, a tin (II) halide perovskite crystal can be produced.

Further, the tin halide (II) -based perovskite thin film of the present invention is a tin halide (II) obtained by removing a solvent from an aqueous solution of a tin (II) halide-based perovskite compound prepared as described above. The perovskite compound) can be formed into a film (film) by vaporizing it or the like using a generally known method to form a film on the substrate surface. In this specification, “vaporization and the like” specifically includes, for example, evaporation, sublimation, ablation (a phenomenon in which the surface of a substance is decomposed by evaporation or erosion) in the air or under reduced pressure. . In the present invention, a high-purity tin (II) halide perovskite compound can be obtained by using an aqueous solution of a tin (II) halide perovskite compound prepared as described above. High purity tin (II) halide perovskite thin film is formed on the substrate surface even by vaporization, which has been considered difficult in the past due to concerns about the denaturation of Sn ²⁺ to Sn ⁴⁺ due to exposure to the surface. A film can be formed.

  The method for removing the solvent of the aqueous solution of the tin halide (II) -based perovskite compound is not particularly limited. For example, the container containing the aqueous solution of the tin (II) halide-based perovskite compound is left as it is. Accordingly, the tin (II) halide perovskite compound can be obtained by removing the solvent from the surface of the aqueous solution using a heating means.

  For example, the tin (II) halide perovskite compound thus obtained is vaporized using a generally available apparatus to form a film on the substrate surface, whereby the tin (II) halide system of the present invention is used. A perovskite thin film can be formed.

  A method for preparing an aqueous solution of a tin (II) halide perovskite compound and a method for producing a tin (II) halide perovskite thin film according to this embodiment are not limited to tin-based perovskite compounds, The present invention can also be applied to metal halide (II) perovskite thin films made of a divalent metal halide containing a lead halide perovskite compound or the like.

  Examples of the divalent metal include, but are not limited to, Sn, Pb, Ca, Sr, Cd, Cu, Ni, Mn, Fe, Co, Pd, Ge, and Yb.

  For example, in the method for producing a metal halide (II) perovskite thin film by a coating method, a step of preparing an aqueous solution of a metal halide (II) perovskite compound, and an aqueous solution of the metal halide (II) perovskite compound Applying a solution to the substrate surface to remove the solvent.

  Further, in the method for producing a metal halide (II) -based perovskite thin film by a vapor deposition method, a step of preparing an aqueous solution of a metal halide (II) -based perovskite compound, an aqueous solution of the metal halide (II) -based perovskite compound Removing the solvent to obtain a metal halide (II) -based perovskite compound, and vaporizing the metal halide (II) -based perovskite compound to form a film on the substrate surface.

  Thus, by using an aqueous solution of a metal halide (II) perovskite compound, a high-purity metal halide (II) perovskite thin film can be formed without using an organic solvent.

<Electronic device>
An electronic device using the tin (II) halide perovskite thin film of the present invention has, for example, two or more electrodes using the tin (II) halide perovskite thin film of the present invention as a semiconductor material. It is a device that controls the current flowing between and the voltage generated by electricity, light, magnetism, chemical substances, or the like, or a device that generates light, electric field, magnetism, etc. by the applied voltage or current.

  For example, there are an element that controls current and voltage by applying voltage and current, an element that controls voltage and current by applying a magnetic field, and an element that controls voltage and current by applying a chemical substance. Examples of this control include rectification, switching, amplification, and oscillation. The corresponding devices currently implemented in silicon and the like include resistors, rectifiers (diodes), switching elements (transistors, thyristors), amplifier elements (transistors), memory elements, chemical sensors, etc., or combinations of these elements. Examples include integrated devices. In addition, a solar cell that generates an electromotive force by light, or an optical element such as a photodiode or a phototransistor that generates a photocurrent can be used.

<Photoelectric conversion device>
The photoelectric conversion apparatus using the tin (II) halide perovskite thin film of the present invention or the electronic device using the tin halide (II) perovskite thin film of the present invention includes, for example, the tin (II) halide of the present invention. A photoelectric conversion device including a light absorption layer including a perovskite-based thin film and a hole transport layer. With such a photoelectric conversion device, a photoelectric conversion device having a high photoelectric conversion efficiency can be realized more simply than a conventional photoelectric conversion device.

  Below, the specific structure of the photoelectric conversion apparatus using the tin (II) halide perovskite thin film of this invention is illustrated.

(1) Light-absorbing layer The light-absorbing layer is not particularly limited as long as it includes the tin (II) halide perovskite thin film of the present invention, and may be a single layer or a multilayer. In the case of a multilayer, each of the layers may be a layer containing the tin (II) halide perovskite thin film of the present invention, and at least one layer is a layer containing the tin (II) halide perovskite thin film of the present invention. There may be. In addition, the tin halide type | system | group perovskite thin film of this invention may be used individually by 1 type, and may be used in combination of 2 or more type.

  The thickness of the light absorption layer is preferably 0.5 to 10,000 nm, more preferably 0.5 to 10 nm, from the viewpoint that when the film is excessively thick, performance deterioration due to defects and peeling is likely to occur. When the light absorption layer is a multilayer, the total thickness of the light absorption layer is preferably within the above range.

  As a method for forming the light absorption layer, generally known methods can be employed. For example, the light absorption layer is formed by applying an aqueous solution of a target tin (II) halide-based perovskite compound on an electron transport layer or an intermediate layer, which will be described later, and by spin coating or die coating. Can be obtained. By adopting such a non-vacuum process, a photoelectric conversion device can be more easily manufactured.

  An aqueous solution of a tin (II) halide perovskite compound used for forming a tin (II) halide perovskite thin film of the present invention can be prepared as described above, and the description thereof is omitted here.

  The conditions of the spin coating method and the die coating method can be appropriately set according to the desired film thickness.

  After film formation by the spin coating method or die coating method, it is preferable to remove excess solvent by drying or heating in accordance with generally known methods.

(2) Hole transport layer The hole transport layer is not particularly limited as long as it is a layer containing an organic hole transport material or an inorganic hole transport material (hereinafter collectively referred to as “hole transport material”), and is a single layer. May be multi-layered. In the case of a multilayer, each layer may be a layer containing a hole transport material, or at least one layer may be a layer containing a hole transport material.

  Examples of the organic hole transport material include 2,2 ′, 7,7′-tetrakis (N, N-diphenylamino) -9,9′-spirobifluorene (Spiro-TAD), 2,2 ′, 7, Fluorene derivatives such as 7′-tetrakis (N, N-di-p-methoxyphenylamino) -9,9′-spirobifluorene (Spiro-MeOTAD), poly (3-hexylthiophene) (P3HT), polyethylenedioxy Examples thereof include polythiophene derivatives such as thiophene (PEDOT), carbazole derivatives such as polyvinylcarbazole, triphenylamine derivatives, diphenylamine derivatives, polysilane derivatives, and polyaniline derivatives.

Examples of the inorganic hole transport material include iodides such as CuSCN and copper iodide (CuI), cobalt complexes such as MoO ₃ , NiO, selenium, and layered cobalt oxide.

Among these hole transport materials, Spiro-TAD, Spiro-MeOTAD, P3HT, CuSCN, CuI, MoO ₃ and NiO are preferable. A hole transport material may be used individually by 1 type, and may be used in combination of 2 or more type.

  The thickness of the hole transport layer is not particularly limited, but is preferably about 0.002 to 10 μm. When the hole transport layer is a multilayer, the total thickness of the hole transport layer is preferably within the above range.

  As a method for forming the hole transport layer, generally known methods can be adopted. However, it is preferable to form the hole transport layer by a non-vacuum process such as a plating method or a spray method as in the case of the light absorption layer.

  The arrangement relationship between the light absorption layer and the hole transport layer is such that the light absorption layer is located on the intermediate layer side, the electron transport layer side, the translucent conductive layer side, or the translucent substrate side, which will be described later. The relationship is located on the second electrode side. Specifically, for example, the light absorption layer is formed on the intermediate layer, the electron transport layer, the translucent conductive layer, or the translucent substrate, preferably on the intermediate layer or the electron transport layer, more preferably on the intermediate layer. A hole transport layer is formed on the light absorption layer.

(3) Intermediate layer The intermediate layer is particularly a layer containing a dielectric material, a material having absorption characteristics in the visible region or near infrared region, and / or a material that suppresses the backflow of electrons to the electron transport layer described later. It is not limited. Examples of the intermediate layer include aluminum oxide, magnesium oxide, barium titanium oxide, selenium, tellurium, antimony sulfide, lead sulfide, Pb-Sn-Se (1-n), CdS, and Pb-Cdn-Se (1-n ), A layer containing at least one metal selected from the group consisting of the following (hereinafter also referred to as “interlayer inorganic material”) or a compound or alloy thereof. The intermediate layer may be a single layer or multiple layers. In the case of a multilayer, each of the layers may be a layer containing an intermediate layer inorganic material, or at least one layer may be a layer containing an intermediate layer inorganic material. The intermediate layer preferably includes a layer containing at least one metal selected from the group consisting of magnesium oxide, aluminum oxide, barium titanium oxide, selenium, and tellurium, or a compound thereof, more preferably aluminum oxide or Examples include a layer containing selenium.

  The thickness of the intermediate layer can be made thinner than that of conventional solar cells, preferably about 0.002 to 5.0 μm, and more preferably about 0.01 to 1.0 μm. When the intermediate layer is a multilayer, the total thickness of the intermediate layer is preferably within the above range. By setting the thickness of the intermediate layer within the above range, pinholes are not generated in the intermediate layer, a certain strength can be maintained, and light can be absorbed more efficiently.

  As a method for forming the intermediate layer, generally known methods can be adopted, but as a method for forming a layer containing aluminum oxide, magnesium oxide, barium titanium oxide as the intermediate layer, for example, a sputtering method, a dipping method, Examples thereof include spraying, vapor deposition, ion plating, and plasma CVD. Examples of a method for forming a layer containing selenium or tellurium as the intermediate layer include non-vacuum processes such as a plating method (preferably an electrolytic plating method), a spray coating method, and a spin coating method.

  The arrangement relationship between the light absorption layer and the intermediate layer is such that the intermediate layer is located on the electron transport layer side, the translucent conductive layer side, or the translucent substrate side, and the light absorption layer is on the hole transport layer side or the second electrode. It is a relationship located on the side. Specifically, for example, the intermediate layer is formed on the electron transport layer, the translucent conductive layer, or the translucent substrate, preferably the electron transport layer, and the light absorption layer is formed on the intermediate layer.

(4) Electron transport layer In the photoelectric conversion device of the present invention, the light absorption layer is preferably formed on the electron transport layer. Moreover, when forming an intermediate | middle layer, it is preferable that an intermediate | middle layer is formed on an electron carrying layer.

  The electron transport layer may have a smooth structure or a porous structure. The porous structure is not particularly limited, but has a porous property as a whole by gathering granular materials, linear bodies (linear bodies: needles, tubes, columns, etc.), etc. It is preferable. The pore size is preferably nanoscale. When the electron transport layer has a porous structure, since it is nanoscale, the active surface area of the light absorption layer can be remarkably increased, the photoelectric conversion efficiency can be improved, and an electron transport layer excellent in electron collection can be obtained. In the case of adopting a porous structure, it is not necessary to have a porous structure over the entire thickness of the electron transport layer, for example, a smooth structure, a light absorbing layer or an intermediate layer on the side close to the light-transmitting conductive layer described later The side close to can also have a porous structure.

The electron transport layer is preferably a layer containing an organic electron transport material or an inorganic electron transport material, for example. Examples of the organic electron transport material include [6,6] -phenyl-C61-methylbutyrate (PC61BM), [6,6] -phenyl-C71-methylbutyrate (PC71BM), and the like. Examples of the inorganic electron transport material include a porous electron transport material. Examples of the porous electron transport material include TiO ₂ , WO ₃ , ZnO, Nb ₂ O ₅ , Ta ₂ O ₅ , and SrTiO ₃ . 1 type (s) or 2 or more types can be employ | adopted. In addition, when using a semiconductor, the donor may be doped. Thereby, an electron carrying layer turns into a window layer for introducing into a light absorption layer, and the electric power obtained from the light absorption layer can be taken out efficiently. When TiO ₂ is employed as the porous electron transport material, the crystal form is preferably an anatase type.

  The thickness of the electron transport layer is preferably about 10 to 2000 nm, and more preferably about 20 to 1500 nm. By setting the thickness of the electron transport layer within the above range, the leakage current can be more reliably suppressed and electrons from the light absorption layer can be collected.

  As a method for forming the electron transport layer, generally known methods can be adopted. However, by forming the electron transport layer by, for example, a non-vacuum process such as a spray method, the photoelectric conversion device of the present invention can be more easily performed. Can be manufactured. In addition, there is an advantage that the area can be easily increased and the quality is stabilized.

(5) Translucent conductive layer In the photoelectric conversion device of the present invention, the light absorption layer is preferably formed on the translucent conductive layer. Moreover, when forming an intermediate | middle layer or an electron carrying layer, it is preferable that an intermediate | middle layer or an electron carrying layer is formed on a translucent conductive layer.

  The translucent conductive layer is preferably a layer containing a transparent conductive oxide, for example. As the transparent conductive oxide, for example, one or more of fluorine-doped tin oxide, indium tin oxide, gallium-doped zinc oxide, aluminum-doped zinc oxide, niobium-doped titanium oxide, etc. should be adopted. Can do. Thereby, a translucent conductive layer becomes a window layer for introducing into a light absorption layer, and the electric power obtained from the light absorption layer can be taken out efficiently.

  The thickness of the translucent conductive layer is preferably about 0.01 to 10.0 μm, and more preferably about 0.3 to 1.0 μm. By setting the thickness of the translucent conductive layer within the above range, the sheet resistance can be reduced, and as a result, the series resistance of the photoelectric conversion device can be reduced, so that the fill factor characteristic can be maintained.

(6) Translucent board | substrate In the photoelectric conversion apparatus of this invention, it is preferable that a translucent conductive layer is formed on a translucent board | substrate.

  Although it does not restrict | limit especially as a translucent board | substrate, For example, it is preferable to comprise from glass, a plastics, etc. Thereby, it can become a window layer for introducing light into the light absorption layer.

  The thickness of a translucent board | substrate is not specifically limited, It is preferable to set it as about 0.1-5.0 mm.

  For example, a substrate with a transparent conductive film such as a glass with an ITO film or a glass with an FTO film can be used as the light-transmitting substrate and the light-transmitting conductive layer.

(7) Second electrode layer In the photoelectric conversion device of the present invention, a second electrode layer is preferably provided on the hole transport layer.

  The material constituting the second electrode layer is not particularly limited, but for example, carbon, gold, tungsten, molybdenum, titanium, silver, platinum, aluminum and the like are preferable. In addition, alloys of metals such as gold, tungsten, molybdenum, and titanium are preferably used.

  The thickness of the second electrode layer is not particularly limited, but is preferably about 0.01 to 2.0 μm.

  By using the photoelectric conversion device of the present invention as the power generation means and supplying the generated power of the power generation means to the load, it can be applied to various applications. Specifically, the photoelectric conversion device of the present invention, the inverter device that converts the direct current output from the photoelectric conversion device of the present invention into an alternating current, an electric motor, a photoelectric conversion device having a load such as a lighting device, etc. can do. As its use, for example, it can be used as a solar cell or the like installed on the roof, wall surface, etc. of a building.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these Examples.

<Example 1>
SnBr ₂ 41.7 mg was added _{H 2} O 1.5mL SnBr 2 aqueous 0.1M a (cloudy solution) was prepared in, 0.1M of the addition of _H 2 O 1.5 mL in CsBr 31.9 mg A CsBr aqueous solution was prepared.

An aqueous solution (white turbid solution) of the CsSnBr ₃ perovskite compound was obtained by mixing an aqueous solution of these two kinds of precursors at room temperature (25 ° C.) in the atmosphere.

  A suspension of this mixed solution is applied to the surface of a 42 mm square glass substrate, and the glass substrate is placed on a hot plate heated to 70 ° C. and dried under reduced pressure for 10 minutes to remove the solvent. Got.

<Comparative Example 1>
An attempt was made to obtain a thin film using dimethylformamide (DMF) instead of H ₂ O used in Example 1 as a solvent for the precursor solution.
However, since CsBr has low solubility in DMF, a thin film could not be formed.

Therefore, a CsSnBr ₃ perovskite thin film was formed by DMF as follows.

First, as in Example 1, a CsSnBr ₃ perovskite thin film was formed on the glass substrate surface.
When 0.1 mL of DMF was dropped onto the thin film, DMF penetrated into the thin film, and the blackish brown color of the thin film faded to become a yellow liquid. This is thought to be due to the CsSnBr ₃ perovskite compound being decomposed into SnBr ₂ and CsBr to form a precursor DMF solution.

  Next, the glass substrate on which the DMF solution of this precursor was placed was placed on a hot plate heated to 100 ° C. and dried under reduced pressure for 10 minutes to remove the solvent, thereby obtaining a brown thin film.

  The results of analyzing the thin films obtained in Example 1 and Comparative Example 1 using an X-ray diffractometer (RIGAKU Rad B-system, manufactured by Rigaku Corporation) are shown in FIG. 3A is the thin film obtained in Example 1, and FIG. 3B is the thin film obtained in Comparative Example 1.

First, when comparing the X-ray diffraction chart of Example 1 (FIG. 3A) with the X-ray diffraction chart of CsSnBr ₃ (tin (II) compound) (FIG. 1A), the peak set corresponding to CsSnBr ₃ (2θ) = 15.24 °, 21.62 °, 26.56 °, 30.76 °) to 15.26 °, 21.40 °, 26.49 °, and 30.70 °, respectively, with a slight shift. Since it exists, it was confirmed in Example 1 that a CsSnBr ₃ perovskite compound was obtained.

On the other hand, in the X-ray diffraction chart of Example 1, peak sets (2θ = 14.15 °, 23.30 °, 27.27 °) in the X-ray diffraction chart (FIG. 1B) of Cs ₂ SnBr ₆ (tin (IV) compound). 28 °, 28.52 °, 33.05 °) were not confirmed, and Cs ₂ SnBr ₆ could not be identified.

From this result, it was found that the thin film of Example 1 was a high-purity CsSnBr ₃ perovskite thin film substantially free of Cs ₂ SnBr ₆ .

In the thin film of Example _1, Cs 2 SnBr ₆ (tin (IV) compound) for the diffraction peaks of corresponding surface exponent (222) or a plane index (400) is not detected, CsSnBr ₃ (tin (II) The intensity ratio of the plane index (002) corresponding to the compound) to the peak (2θ = 30.70 °) could not be determined (peak intensity ratio <1%).

Next, the X-ray diffraction chart of Comparative Example 1 (FIG. 3B) corresponds to Cs ₂ SnBr ₆ when compared with the X-ray diffraction chart of Cs ₂ SnBr ₆ (tin (IV) compound) (FIG. 1B). Peak sets (2θ = 14.15 °, 23.30 °, 27.28 °, 28.52 °, 33.05 °) with slight shifts, respectively, 14.04 °, 23.16 °, Since it exists in 28.42 degrees, 29.30 degrees, and 33.16 degrees, it was confirmed in Comparative Example 1 that Cs ₂ SnBr ₆ was obtained.

On the other hand, in the X-ray diffraction chart of Comparative Example 1, the peak set (2θ = 15.24 °, 21.62 °, 26.56 ° in the X-ray diffraction chart (FIG. 1A) of CsSnBr ₃ (tin (II) compound). 30.76 °) was not confirmed, and CsSnBr ₃ could not be identified.

From this result, it was found that the thin film of Comparative Example 1 was a thin film made of Cs ₂ SnBr ₆ (tin (IV) compound) substantially free of CsSnBr ₃ .

In the thin film of Comparative Example 1, since the peak of CsSnBr ₃ (tin (II) compound) corresponding surface exponent (002) is not _detected, plane index corresponding to the Cs 2 SnBr ₆ (tin (IV) compound) The intensity ratio of (222) to the diffraction peak (2θ = 29.30 °) could not be determined.

<Example 2>
By addition of _H 2 O 1.5 mL to prepare an SnBr ₂ aqueous 0.1M in SnBr ₂ 41.7 _mg, 0.1M of the addition of _H 2 O 1.5 mL in CH ₃ NH ₃ Br 16.8mg A CH ₃ NH ₃ Br aqueous solution was prepared.

An aqueous solution of a CH ₃ NH ₃ SnBr ₃ perovskite compound was obtained by mixing an aqueous solution of these two types of precursors in the air at room temperature (25 ° C.).

  This mixed solution was applied to the surface of a 42 mm square glass substrate, and the glass substrate was placed on a hot plate heated to 70 ° C. and dried under reduced pressure for 10 minutes to remove the solvent, thereby obtaining a black brown thin film.

<Comparative example 2>
A pale yellow thin film was obtained in the same manner as in Example 2 except that dimethylformamide (DMF) was used instead of H ₂ O.

  The results of analyzing the thin films obtained in Example 2 and Comparative Example 2 using an X-ray diffractometer (RIGAKU Rad B-system, manufactured by Rigaku Corporation) are shown in FIG. 4A is the thin film obtained in Example 2, and FIG. 4B is the thin film obtained in Comparative Example 2.

First, when comparing the X-ray diffraction chart of Example 2 (FIG. 4A) with the X-ray diffraction chart of CH ₃ NH ₃ SnBr ₃ (tin (II) compound) (FIG. 2A), CH ₃ NH ₃ SnBr ₃ corresponding to ₃ (2θ = 15.00 °, 21.28 °, 26.14 °, 30.27 °), with slight shifts, 14.23 °, 21.15 °, and 26. respectively. 15 °, since there to 30.20 °, it was confirmed _{that CH 3 NH} 3 SnBr 3 perovskite compound in example 2 were obtained.

On the other hand, in the X-ray diffraction chart of Example 2, the peak set (2θ = 11.98 °, 14.4) in the X-ray diffraction chart (FIG. 2B) of (CH ₃ NH ₃ ) ₂ SnBr ₆ (tin (IV) compound). (06 °, 15.67 °) was not confirmed, and (CH ₃ NH ₃ ) ₂ SnBr ₆ could not be identified.

From this result, it was found that the thin film of Example 2 was a high-purity CH ₃ NH ₃ SnBr ₃ perovskite thin film substantially free of (CH ₃ NH ₃ ) ₂ SnBr ₆ .

In the thin film of Example 2, a diffraction peak of plane index (003), plane index (101), or plane index (012) corresponding to (CH ₃ NH ₃ ) ₂ SnBr ₆ (tin (IV) compound) was detected. Therefore, the intensity ratio with respect to the peak (2θ = 30.20 °) of the plane index (002) corresponding to CH ₃ NH ₃ SnBr ₃ (tin (II) compound) could not be obtained (peak intensity ratio). <1%).

Next, regarding the X-ray diffraction chart of Comparative Example 2 (FIG. 4B), when compared with the X-ray diffraction chart (FIG. 2B) of (CH ₃ NH ₃ ) ₂ SnBr ₆ (tin (IV) compound), ( The peak sets (2θ = 11.98 °, 14.06 °, 15.67 °) corresponding to CH ₃ NH ₃ ) ₂ SnBr ₆ are shifted slightly, while 11.35 °, 13.15 °, Since it existed at 15.10 °, it was confirmed that (CH ₃ NH ₃ ) ₂ SnBr ₆ was obtained in Comparative Example 2.

On the other hand, in the X-ray diffraction chart of Comparative Example 2, the peak set (2θ = 15.00 °, 21.28 °) in the X-ray diffraction chart (FIG. 2A) of CH ₃ NH ₃ SnBr ₃ (tin (II) compound), 26.14 °, 30.27 °) was not confirmed, and CH ₃ NH ₃ SnBr ₃ could not be identified.

From this result, it was found that the thin film of Comparative Example 2 was a thin film made of (CH ₃ NH ₃ ) ₂ SnBr ₆ (tin (IV) compound) substantially free of CH ₃ NH ₃ SnBr ₃ .

In addition, in the thin film of Comparative Example 2, since the diffraction peak of the plane index (002) corresponding to the CH ₃ NH ₃ SnBr ₃ perovskite compound (tin (II) compound) was not detected, (CH ₃ NH ₃ ) ₂ SnBr ₆ The intensity ratio of the plane index (101) corresponding to (tin (IV) compound) to the diffraction peak (2θ = 13.15 °) could not be determined.

<Example 3>
In the same manner as in Example 2, an aqueous solution of CH ₃ NH ₃ SnBr ₃ perovskite compound was obtained by mixing an aqueous SnBr ₂ solution and an aqueous CH ₃ NH ₃ Br solution at room temperature (25 ° C.). The solvent of this aqueous solution was evaporated to dryness to obtain a powdery body of CH ₃ NH ₃ SnBr ₃ perovskite compound.

  This powdery body was set in a sublimation cell of an evaporation machine (EHB-400, manufactured by Eiko Co., Ltd.), and heated to 300 ° C. under reduced pressure to obtain a bright red thin film on the surface of the glass substrate.

  About the obtained thin film, the result of having analyzed using the X-ray-diffraction apparatus (The Rigaku company make, RIGAKU Rad B-system) is shown in FIG.

Compared with the X-ray diffraction chart (FIG. 2A) of CH ₃ NH ₃ SnBr ₃ (tin (II) compound) for the X-ray diffraction chart of Example 3 (FIG. 5), the peak corresponding to CH ₃ NH ₃ SnBr ₃ While the set (2θ = 15.00 °, 21.28 °, 30.27 °, 34.00) is slightly shifted, 15.20 °, 21.40 °, 30.60 °, and 34.20, respectively. Therefore, in Example 3, it was confirmed that a CH ₃ NH ₃ SnBr ₃ perovskite compound was obtained.

On the other hand, in the X-ray diffraction chart of Example 3, the peak set (2θ = 11.98 °, 14.3) in the X-ray diffraction chart (FIG. 2B) of (CH ₃ NH ₃ ) ₂ SnBr ₆ (tin (IV) compound). (06 °, 15.67 °) was not confirmed, and (CH ₃ NH ₃ ) ₂ SnBr ₆ could not be identified.

From this result, it was found that the thin film of Example 3 was a high-purity CH ₃ NH ₃ SnBr ₃ perovskite thin film substantially free of (CH ₃ NH ₃ ) ₂ SnBr ₆ .

In the thin film of Example 3, a diffraction peak of plane index (003), plane index (101) or plane index (012) corresponding to (CH ₃ NH ₃ ) ₂ SnBr ₆ (tin (IV) compound) was detected. Therefore, the intensity ratio with respect to the peak (2θ = 30.60 °) of the plane index (002) corresponding to CH ₃ NH ₃ SnBr ₃ (tin (II) compound) could not be obtained (peak intensity ratio). <1%).

  Regarding the thin films of Examples 1 to 3 and Comparative Examples 1 and 2 obtained as described above, the structure of the target tin (II) halide perovskite compound, the solvent of the precursor solution, the film formation method, and the X-ray The profiles of the diffraction chart are summarized in Tables 1 and 2 below.

<Example 4 and Comparative Example 3>
SnBr ₂ 0.142 g and CsBr 0.108 g were placed in a sample bottle at room temperature (25 ° C.) atmosphere, 1.5 mL of H ₂ O was added, and nominally 0.25 g of CsSnBr ₃ perovskite compound (hereinafter “ A 0.1 M black suspension solution in which "PVS") was dispersed was obtained.

  This solution was applied to the surface of a 2.7 mm square glass substrate and dried under reduced pressure at 75 ° C. for 10 minutes to remove the solvent, thereby obtaining a black-brown PVS thin film (1) (Example 4).

  Next, when 0.2 mL of dimethylformamide (DMF) is dropped on the PVS thin film (1), DMF penetrates into the PVS thin film (1), and the black brown color of the thin film fades to become a yellow liquid. Of DMF was obtained.

  The glass substrate on which the DMF solution of this precursor was placed was placed on a hot plate heated to 100 ° C. and dried under reduced pressure for 10 minutes to remove the solvent, thereby obtaining a PVS thin film (2) (Comparative Example 3). .

  This PVS thin film (2) was partially blackish brown in appearance. From this result, it was confirmed that when an organic solvent such as DMF was used as the solvent of the precursor solution, the purity of the thin film was lowered. This is considered to be mainly due to the formation of tin (IV) compound during the thinning process and the remaining DMF.

  The obtained PVS thin film (2) was peeled from the glass substrate to obtain 0.172 g of PVS (2).

  About this PVS (2), the content of DMF was measured by gas chromatography mass spectrometry (GC / MS) according to the following procedure. In addition, since DMSO is not used as a solvent in this test example, DMSO is not included in the sample.

(Measurement condition)
Measuring device: Agilent 5975 inert GC / MS system (manufactured by Agilent Technologies)
Heat desorption device TDS 3 (Gestel Co., Ltd.)
Column: HP-5ms (30m × φ250μm × 0.25μm)
Column temperature: maintained at 35 ° C. for 5 minutes, then increased to 200 ° C. at 10 ° C./min and maintained for 5 minutes Carrier gas: He (1 mL / min)
Ionization method: EI (70 eV)

  As a sample pretreatment, the process of heating the sample at 180 ° C. for 10 minutes (in a He stream, 150 mL) and collecting the generated component (DMF contained in the sample) in a collection tube was repeated twice. The components collected in this manner were introduced into a measuring apparatus, and DMF was quantified. As a result of dividing the mass of the obtained DMF by the mass of the sample, the DMF content in the PVS (2) was 0.5% by weight (3.0 mol /%).

  In Example 4, since DMF and DMSO were not used as solvents, DMF and DMSO were not included in the thin film. For confirmation, the PVS thin film (1) obtained in Example 4 was used as a glass substrate. The content of DMF was measured in the same manner as described above using PVS (1) obtained by peeling off the PMF. As a result, DMF was below the detection limit.

<Example 5>
Using the tin (II) halide perovskite thin film of the present invention, a solar cell element having a <glass / F-doped SnO ₂ / TiO ₂ / porous TiO ₂ / CsSnBr ₃ / spiro-OMeTAD / Au> structure as a cell structure Was made.

First, a TiO ₂ film was formed on an F-doped SnO ₂ glass substrate on a hot plate in the air by a spray pyrolysis method (SPD method) to obtain a 100 nm film.
Next, about 1 μm of porous TiO ₂ was formed on this film by spin printing to obtain a three-dimensional titania electrode.
Then, an aqueous solution of a CsSnBr ₃ perovskite compound obtained in the same manner as in Example 1 was supplied onto this electrode to obtain a CsSnBr ₃ thin film having a thickness of 1 μm by a coating method, which was dried and then heated.
Further, a spiro-OMeTAD solution was applied onto the CsSnBr ₃ thin film by a spin coating method so that the dry film thickness was 300 nm, and dried at 90 ° C. for 1 hour.
And Au back electrode was formed into a film by the vapor deposition method, and the target solar cell element (element size 1.5 * 1.5mm) was obtained.
As a spiro-OMeTAD solution, chlorobenzene 2 mL, lithium bis (trifluoromethanesulfonyl) imide (Li-TFSI) 5.16 mg, Spiro-OMeTAD (lumtech) 166.6 mg, 4-tert-butylpyridine (tBP ) A solution in which 16 μL was dissolved was used.

  FIG. 6 is a graph showing current-voltage characteristics (IV characteristics) of the obtained solar cell element. The photoelectric conversion efficiency (PCE) of the solar cell element produced in this example was 0.13%. From this result, it was confirmed that a photoelectric conversion element using a high-purity tin (II) halide perovskite thin film formed with an aqueous solvent as a light absorption layer was produced without using an organic solvent. It is considered that the photoelectric conversion efficiency is further improved by controlling the thickness of the perovskite layer.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2015-017667 for which it applied on January 30, 2015, and takes in those the indications of all here.

Claims (14)

  A tin (II) halide perovskite thin film having a diffraction angle 2θ of 10 ° or more and 50 ° with respect to a diffraction peak of a plane index (002) corresponding to a tin (II) halide perovskite compound in an X-ray diffraction chart. A tin (II) halide perovskite thin film characterized in that the intensity ratio of the diffraction peak having the highest intensity corresponding to a tin (IV) compound existing in the following range is 10% or less.   The tin (II) halide perovskite thin film according to claim 1, wherein the content of the organic solvent having a boiling point of 120 ° C or higher is less than 0.5% by weight. The tin (II) halide perovskite compound is composed of CsSnX ₃ (where X represents halogen), and the tin (IV) compound is composed of Cs ₂ SnX ₆ (where X represents halogen). The tin (II) halide system according to claim 1 or 2, wherein the diffraction peak having the highest intensity corresponding to the compound (IV) is a diffraction peak having an area index (222) or an area index (400). Perovskite thin film. The tin (II) halide perovskite compound is composed of RNH _{(2 + m)} SnX ₃ (wherein R represents a hydrocarbon group, X represents a halogen, m is 0 or 1), and the tin (IV) The compound consists of (RNH _{(2 + m)} ) ₂ SnX ₆ (wherein R represents a hydrocarbon group, X represents a halogen, and m is 0 or 1), and has the highest strength corresponding to the tin (IV) compound. 3. The tin (II) halide perovskite thin film according to claim 1, wherein the high diffraction peak is a diffraction peak of plane index (003), plane index (101) or plane index (012).   5. The substrate according to claim 1, wherein the substrate is formed using an aqueous solution of a first precursor containing tin (II) halide and an aqueous solution of a second precursor containing halide. A tin (II) halide perovskite thin film according to claim 1.   A substrate formed using an aqueous solution prepared by adding an aqueous solvent to a mixture of a first precursor containing tin (II) halide and a second precursor containing halide. Item 5. The tin (II) halide perovskite thin film according to any one of Items 1 to 4.   7. The tin (II) halide perovskite thin film according to claim 6, wherein the mixture is a powder.   A tin (II) halide-based perovskite compound obtained from an aqueous solution of a tin (II) halide-containing first precursor and a halide-containing second precursor is formed on the substrate surface by vaporization The tin (II) halide perovskite thin film according to any one of claims 1 to 4.   An electronic device using the tin (II) halide perovskite thin film according to any one of claims 1 to 8.   A photoelectric conversion apparatus using the tin (II) halide perovskite thin film according to any one of claims 1 to 8 or the electronic device according to claim 9. A step of preparing an aqueous solution of a metal halide (II) -based perovskite compound, and a step of applying the aqueous solution of the metal halide (II) -based perovskite compound to a substrate surface to remove the solvent. A method for producing a metal halide (II) perovskite thin film. Preparing an aqueous solution of a metal halide (II) -based perovskite compound,
Removing the solvent of the aqueous solution of the metal halide (II) -based perovskite compound to obtain a metal halide (II) -based perovskite compound; and vaporizing the metal halide (II) -based perovskite compound to form a substrate surface A method for producing a metal halide (II) -based perovskite thin film comprising a step of forming a film.   The method for producing a metal halide (II) perovskite thin film according to claim 11 or 12, wherein the metal halide (II) is tin (II) halide or lead (II) halide.   A metal (II) halide perovskite thin film obtained by the method for producing a metal halide (II) perovskite thin film according to any one of claims 11 to 13.

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