JP7153307B2 - Perovskite compound, and thermoelectric conversion material and thermoelectric conversion element containing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to perovskite compounds, and thermoelectric conversion materials and thermoelectric conversion elements containing the same.

Perovskite compounds are known for their extremely high photoelectric conversion efficiency. A perovskite solar cell containing this perovskite compound is attracting attention as a next-generation printable solar cell, and various related technologies have been reported (Non-Patent Document 1). Among them, environmentally safe Pb-free perovskite solar cells that do not contain Pb have attracted attention.

On the other hand, in addition to the photoelectric conversion materials as described above, attention has also been paid to thermoelectric conversion materials that utilize a phenomenon in which the temperature difference of an object is directly converted into voltage (the Seebeck effect). By using this thermoelectric conversion material, for example, it is possible to obtain electrical energy by utilizing waste heat from factories and garbage incinerators, and it is expected as a clean energy technology.

Perovskite compounds have also been studied as thermoelectric conversion materials for a long time, and research is being conducted toward their practical use (see, for example, Patent Documents 1 and 2).

JP-A-64-5911 JP 2010-27631 A

M. Saliba, T. Matsui,; J.Y. Seo, K. Domanski, J.P. Correa-Baena, M.K. Nazeeruddin, S.M. Zakeeruddin, W.Tress, A. Abate, A. Hagfeldt and M Gratzel. : improved stability, reproducibility and high efficiency. Energy Environ. Sci., 2016, 9, pp. 1989-1997

In addition to a high Seebeck coefficient, thermoelectric conversion materials are desired to have high electrical conductivity and low thermal conductivity. However, since carriers carry electric charges and phonons, the higher the electrical conductivity, the higher the thermal conductivity. Generally, it is difficult to achieve both.

An object of the present invention is to provide a perovskite compound suitable for thermoelectric conversion materials. Another object of the present invention is to provide a thermoelectric conversion material and a thermoelectric conversion element containing this perovskite compound.

The present inventors have studied the use of Pb _- free Sn-based halogenated perovskite compounds used in perovskite solar cells as thermoelectric conversion materials. In the perovskite compound comprising Sn and Y as the metal B, compared to the case where the metal B is Sn alone, the conductivity is improved and the thermal conductivity is decreased, and it is useful as a thermoelectric conversion material It was discovered that it is, and came to complete this invention.

That is, the present invention is as follows.
[1] A compound consisting of ABX ₃ (A is a cation, B is a metal, X is a halogen, and each of A, B and X may be composed of a plurality of elements),
A perovskite compound, wherein B contains Sn and a metal of Group 3 of the periodic table.
[2] The perovskite compound according to [1] above, wherein B contains Sn and Y.
[3] The perovskite compound according to [2] above, wherein B consists of Sn and Y.
[4] The element composition ratio of Sn and Group 3 metals in B is 90 to 99.99% for Sn and 0.01 to 10% for Group 3 metals. The perovskite compound according to any one of [1] to [3] above.
[5] The perovskite compound according to any one of [1] to [4] above, wherein A is an organic amine or an alkali metal.

[6] A thermoelectric conversion material containing the perovskite compound according to any one of [1] to [5] above.
[7] A thermoelectric conversion element comprising a thermoelectric conversion layer containing the perovskite compound according to any one of [1] to [5] above.

The perovskite compound of the present invention has high electrical conductivity and low thermal conductivity, and is therefore useful as a thermoelectric conversion material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the results of XRD measurement of the perovskite compound of the present invention, (a) is a diagram showing an X-ray diffraction pattern, (b) is a diagram showing a shift of the second peak position, ( c) is a diagram showing the relationship between the Y substitution rate and the crystallite size, and (d) is a diagram showing the relationship between the Y substitution rate and crystal strain. 1 is a schematic diagram of a device for evaluating electronic physical properties of a perovskite compound prepared in Example 1. FIG. FIG. 2 is a diagram showing electrical conductivity of perovskite compounds of the present invention; (a) is a diagram showing the carrier density of the perovskite compound of the present invention, and (b) is a diagram showing the carrier mobility of the perovskite compound of the present invention. 1 is a schematic diagram of a device for evaluating thermoelectric properties of a perovskite compound prepared in Example 1. FIG. FIG. 2 is a diagram showing the thermal conductivity of perovskite compounds of the present invention; 1 is a diagram showing the relationship between electrical conductivity and thermal conductivity of perovskite compounds of the present invention. FIG.

[Perovskite compound]
The perovskite compound of the present invention is a compound comprising ABX ₃ (A: cation, B: metal, X: halogen), wherein B contains Sn and a metal of Group 3 of the periodic table. In addition, A, B and X may each be composed of one element or may be composed of a plurality of elements. A perovskite compound has a _cubic structure, represented by ABX3, with a metal B at the body center, a cation A at each vertex, and a halogen X at the face center.

The perovskite compound of the present invention satisfies the requirements as a thermoelectric conversion material, which have hitherto been difficult to achieve at the same time, such as high electrical conductivity and low thermal conductivity. Also, the perovskite compound of the present invention does not contain Pb, which poses a high environmental risk. Conventionally used PbTe-based thermoelectric conversion materials are scarce in resources, highly toxic, poor in heat resistance and oxidation resistance, and cause environmental pollution due to vaporization and oxidative decomposition at high temperatures. However, the present invention does not have such a problem.

Therefore, the perovskite compound of the present invention is suitable as a thermoelectric conversion material. Specifically, the perovskite compound of the present invention can be applied, for example, to a thermoelectric conversion layer in a thermoelectric conversion element.

The metal B in the perovskite compound of the present invention contains Sn and a Group 3 metal of the periodic table as described above. Specific examples of metals of Group 3 of the periodic table include Sc (scandium), Y (yttrium), lanthanides, actinides, and the like, with Y being particularly preferred. That is, metal B preferably contains Sn and Y, and particularly preferably consists of these two.

The element composition ratio of Sn and the metal of Group 3 of the periodic table in metal B can be appropriately adjusted within the range in which the effect of the present invention is exhibited, and Sn is preferably 90% or more, and 95% or more. It is more preferably 98% or more. The Group 3 metal of the periodic table is preferably 0.01% or more, more preferably 0.1% or more, and even more preferably 0.3% or more. Specifically, it is preferable that Sn is 90 to 99.99% and the metal of Group 3 of the periodic table is 0.01 to 10%, Sn is 95 to 99.9%, and the period It is more preferable that the Group 3 metal of the periodic table is 0.1 to 5%, Sn is 98 to 99.7%, and the periodic table Group 3 metal is 0.3 to 2%. More preferred.

Examples of the cation A include alkali metals and organic amines, with alkali metals being preferred. Cesium is preferred as the alkali metal. Examples of organic amines include primary, secondary, tertiary, and quaternary organic ammonium compounds, which may have N-containing heterocycles or carbocycles. Specifically, methylammonium (MA), formamidinium (FA: NH ₂ CH=NH ²⁺ ), ethylenediammonium (EA), pyrazinium, 2-phenylethylammonium (PEA), benzylamine, 4- Examples include 4-Fluoroaniline, 4-Fluorobenzylamine, 4-Fluorophenethylamine, Phenethylammonium, etc. Two or more of them may be combined. Among these, methylammonium (MA) and formamidinium (FA) are preferable, and a combination thereof is particularly preferable, from the viewpoint of a three-dimensional structure with a wide absorption wavelength width.

Examples of halogen X include F, Cl, Br, and I, and two or more thereof may be combined. Among these, I is preferable from the viewpoint of the magnitude of carrier mobility.

The perovskite compound (ABX ₃ ) of the present invention can be produced, for example, by dissolving AX and BX ₂ in an organic solvent and forming a film. When preparing an AB ¹ B ² X ₃ perovskite compound, for example, an AB 1 X 3 precursor solution in which AX and B ¹ X ₂ are dissolved in an organic solvent, and an AB ¹ X ₃ precursor solution in which AX and B ² X ₂ are dissolved in an organic solvent It can be produced by mixing the AB ² X ₃ precursor solution prepared in a predetermined ratio to form a film.

The organic solvent is not particularly limited as long as it can dissolve the precursor substance. 2-imidazolidinone, acetylacetone, tert-butylpyridine, dimethylethyleneurea (DMI), dimethylpropyleneurea (DMU), tetramethylurea (TMU) and the like can be mentioned, and two or more of them may be combined. Among these, N,N-dimethylformamide (DMF) and dimethylsulfoxide (DMSO) are preferred in terms of solubility.

The film formation method of the precursor solution is not particularly limited, and may be a vapor deposition method such as a vacuum deposition method or a coating method. method is preferred. Examples of coating methods include conventionally known coating methods such as dip coating, die coating, bar coating, spin coating, offset, spray coating, and printing. Among these methods, the spin coating method is preferable from the viewpoint of thin film uniformity and dense polycrystalline structure.

The perovskite compound of the present invention can be suitably used as a thermoelectric conversion material that converts thermal energy into electrical energy. Specifically, the perovskite compound of the present invention can be applied to a thermoelectric conversion layer in a thermoelectric conversion element. A thermoelectric conversion element using the perovskite compound of the present invention can be used, for example, for power generation using heat (exhaust heat) emitted from automobiles, factories, and garbage incinerators.

Examples of the present invention are shown below, but the scope of the present invention is not limited to these.

[Example 1]
<Preparation of perovskite compound>
By changing the composition ratio of Sn and Y, the perovskite compound Cs of the present invention (Sn)_1-x(Y)_x I₃(x = 0,0.01,0.05,0.1,0.2 (Y 0%, 1%, 5%, 10%, 20%)) were prepared. Specifically, it is as shown below.

Deposition of perovskite films was performed in a nitrogen purged glovebox.
A CsSnI ₃ precursor solution was prepared by dissolving SnI ₂ (596 mg), and CsI (416 mg) in DMF (1773 μL) and DMSO (227 μL). Meanwhile, _CsYI3 precursor solution was prepared by dissolving _YI3 (5.2 mg) and CsI (4.2 mg) in DMF (500 μL). Finally, a CsSn(Y)I ₃ precursor solution was prepared by mixing CsSnI ₃ precursor solution and CsYI ₃ precursor solution.

The precursor solution was filtered through a 0.2 μm filter and spin-coated onto the substrate (PEDOT:PSS) at 5000 rpm for 50 seconds. In the spin-coating process, toluene as an anti-solvent was dropped onto the substrate before the perovskite solution was completely dried in order to flatten the surface of the perovskite.
After spin-coating, the perovskite film was annealed on a hot plate at 70°C for 10 minutes.

(XRD measurement)
XRD measurement of the prepared perovskite compound was performed. The results are shown in FIG.
As shown in FIG. 1(b), the peak position of the perovskite compound in which Y is substituted by 1% is shifted to the right. Moreover, as shown in FIG. 1(c), the crystallite size of the perovskite compound in which Y is substituted by 1% has grown. In addition, as shown in FIG. 1(d), the perovskite compound in which Y is substituted by 1% has a small crystal strain.

Moreover, XPS measurement of the prepared perovskite compound revealed that the perovskite structure was stabilized by doping with Y.

[Example 2]
The perovskite compound (Cs (Sn)_1-x(Y)_x I₃), a device was fabricated and its physical properties were evaluated. In the same manner as in Example 1, the composition ratio of Sn and Y was changed, and the effects thereof were investigated.

<Evaluation of electronic properties>
(Measurement of electrical conductivity)
A device for evaluating electronic physical properties as shown in FIG. 2 was prepared, and the perovskite compound (Cs (Sn)_1-x(Y)_x I₃) was calculated for electrical conductivity (S/cm). The results are shown in FIG.

As shown in FIG. 3, the perovskite compound of the present invention doped with 1% Y has improved electrical conductivity compared to the undoped one.

(Measurement of carrier density and carrier mobility)
A device for evaluating electronic physical properties as shown in FIG. 2 was prepared, and the perovskite compound of the present invention (Cs (Sn)_1-x(Y)_x I₃) were measured for carrier density and carrier mobility. The results are shown in FIG.

As shown in FIG. 4(a), the perovskite compound of the present invention doped with 1% Y has improved carrier density compared to the undoped one. Further, as shown in FIG. 4(b), the reduction in carrier mobility of the perovskite compound of the present invention doped with 1% Y was relatively small.

<Thermoelectric property evaluation>
(Measurement of thermal conductivity)
A device for evaluating thermoelectric properties as shown in FIG. 5 was prepared, and the perovskite compound of the present invention (Cs (Sn)_1-x(Y)_x I₃) was calculated for thermal conductivity (W/(m K)). The results are shown in FIG.

As shown in FIG. 6, the perovskite compounds of the present invention doped with Y at 1%, 5% and 10% had lower thermal conductivity than those without doping.

<Evaluation of electronic physical properties and thermoelectric physical properties>
(Relationship between electrical conductivity and thermal conductivity)
FIG. 7 shows the relationship between the electrical conductivity and thermal conductivity measured above.
As shown in FIG. 7, the perovskite compound of the present invention doped with Y by 1% had improved electrical conductivity and decreased thermal conductivity as compared to the undoped one. That is, it has been found that both high electrical conductivity and low thermal conductivity are achieved, and that the material is useful as a thermoelectric conversion material.

INDUSTRIAL APPLICABILITY The perovskite compound of the present invention has high electrical conductivity and low thermal conductivity, and is industrially useful because it can be used as a thermoelectric conversion material.

Claims (6)

A thermoelectric conversion material containing a perovskite compound consisting of ABX ₃ (A is a cation, B is a metal, X is a halogen, and each of A, B and X may be composed of a plurality of elements),
B comprises Sn and a Group 3 metal of the periodic table ;
The element composition ratio of Sn and Group 3 metals in B is 90 to 99.99% Sn and 0.01 to 10% metals in Group 3 of the periodic table . Thermoelectric conversion material. 2. The thermoelectric conversion material according to claim 1, wherein B contains Sn and Y. 3. The thermoelectric conversion material according to claim 2, wherein B consists of Sn and Y. 4. The thermoelectric conversion material according to any one of claims 1 to 3 , wherein A is an organic amine or an alkali metal. A thermoelectric conversion element comprising a thermoelectric conversion layer containing the thermoelectric conversion material according to any one of claims 1 to 4 . A compound consisting of ABX ₃ (A is a cation, B is a metal, X is a halogen, and each of A, B and X may be composed of a plurality of elements),
B comprises Sn and a Group 3 metal of the periodic table;
A perovskite compound characterized in that the element composition ratio of Sn and a Group 3 metal of the periodic table in B is 90 to 95% Sn and 5 to 10% of a Group 3 metal of the periodic table.

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