JP2018056473A - Perovskite solar battery arranged by use of pyridine derivative - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a perovskite solar battery having high stability, which enables the suppression of the aging of a perovskite solar battery.SOLUTION: A perovskite solar battery 10 comprises: a translucent conductive support 4; a hole-blocking layer 3; an electron transport layer 5; a perovskite layer 6; a hole transport layer 7; and a backside electrode 8. In the perovskite solar battery, the hole transport layer 7 includes a pyridine derivative. The pyridine derivative is represented by the general formula (I) below. (Rand Rare selected from a hydrogen atom and an aliphatic hydrocarbon group, provided that at least one of Rand Ris a substituted or unsubstituted aliphatic hydrocarbon group.)SELECTED DRAWING: Figure 1

Description

  The present invention relates to a perovskite solar cell, and more particularly to a perovskite solar cell using a pyridine derivative.

  In recent years, perovskite solar cells have been studied as next-generation solar cells, and are expected to be inexpensive and highly efficient solar cells. The photoelectric conversion efficiency is reported to be about 20%, but there is a problem that the conversion efficiency does not last for a long time (see Non-Patent Documents 1 and 2).

  In order to prevent the deterioration of the solar cell due to air or moisture, a method of sealing the perovskite solar cell is used. On the other hand, in order to improve the long-term stability of a solar cell, it is necessary to suppress the degradation reaction inside the solar cell caused by the material, and this problem has not been sufficiently solved (see Non-Patent Document 3).

Science, 348, 1234 (2015) Science, 353, 58 (2016) J. et al. Mater. Chem. A, 2,13587 (2014)

  Provided is a perovskite solar cell that suppresses deterioration of the perovskite solar cell with time and has high stability.

As a result of various studies, the present inventors have found that the above object can be achieved by adding a pyridine derivative having a hydrocarbon group at the ortho position to the hole transport layer of the perovskite solar cell. That is, the configuration and characteristics of the present invention are as follows.
In a perovskite solar cell including a translucent conductive support, a hole blocking layer, an electron transport layer, a perovskite layer, a hole transport layer, and a back electrode, the hole transport layer is made of an organic material, and the organic layer is A perovskite solar cell comprising a pyridine derivative represented by the following general formula (I), wherein at least one of ortho positions is substituted with a substituted or unsubstituted aliphatic hydrocarbon.

Here, R ¹ and R ² are selected from a hydrogen atom or an aliphatic hydrocarbon group, and at least one of R ¹ and R ² is a substituted or unsubstituted aliphatic hydrocarbon group. R ¹ and R ² may be the same or different.

  In the solar cell of the present invention, the conversion efficiency does not decrease even after 1000 hours have elapsed since it was fabricated. The present invention makes it possible to provide a perovskite solar cell having long-term conversion efficiency.

It is a cross-sectional schematic diagram which shows an example of a structure of the perovskite solar cell of this invention.

  The perovskite solar cell of the present invention includes at least a translucent conductive support, a hole blocking layer, an electron transport layer, a perovskite layer, a hole transport layer, and a back electrode, and the hole transport layer is made of an organic material. FIG. 1 shows an example of the configuration of the perovskite solar cell of the present invention. In the solar cell 10 of the present invention, the hole blocking layer 3 and the perovskite infiltrated (diffused and mixed) on the translucent conductive support 4 composed of the transparent support substrate 1 and the translucent conductive layer 2 formed thereon. An electron transport layer 5, a perovskite layer 6, a hole transport layer 7, and a back electrode 8 are sequentially stacked.

  The material which comprises the translucent electroconductive support body 4 is not specifically limited, A well-known material can be used. Examples of the material of the translucent conductive layer 2 include indium tin composite oxide (ITO), tin oxide doped with fluorine (FTO), and zinc oxide. These are formed on a transparent support substrate 1 such as glass by a conventional method such as sputtering or spraying. The film thickness of these translucent conductive layers 2 is preferably 0.02 to 5 μm from the viewpoint of sheet resistance and light transmittance. The film resistance of the translucent conductive layer 2 is preferably as low as possible, and is preferably 40Ω / □ or less. In particular, the translucent conductive support 4 obtained by laminating the translucent conductive layer 2 in which tin oxide is doped with fluorine on soda-lime float glass is suitable.

  In order to reduce the resistance of the translucent conductive layer 2, a metal lead wire may be added. The material of the metal lead wire is preferably platinum, gold, silver, copper, aluminum, nickel, titanium or the like. The metal lead wire is preferably formed on the transparent support substrate 1 by sputtering or vapor deposition, and a light-transmitting conductive layer such as tin oxide or ITO is preferably formed thereon. Moreover, after forming the translucent conductive layer 2 such as tin oxide or ITO, the metal lead wire may be formed by sputtering, vapor deposition or the like. However, since the amount of incident light is reduced by providing the metal lead wire, the thickness of the metal lead wire is preferably 0.1 mm to several mm.

  The material which comprises the hole blocking layer 3 is not specifically limited, For example, a titanium oxide, a tin oxide, a zinc oxide etc. are mentioned, Preferably it is a titanium oxide.

  In the present invention, the hole blocking layer 3 can be produced by a thermal decomposition method. For example, a solution containing a titanium compound such as titanium diisopropoxide bis (acetylacetonate) is sprayed on FTO glass, heated at 400 to 600 ° C. for 10 to 60 minutes, and then cooled to room temperature.

The material which comprises the electron carrying layer 5 is not specifically limited, For example, titanium oxide, tin oxide, zinc oxide, aluminum oxide, niobium oxide, yttrium oxide etc. which are metal oxides are mentioned, Preferably it is titanium oxide. Two or more of these metal oxides can also be used.
Note that an electron transport layer made of a semiconductor may be formed on the electron transport layer 5.

The material constituting the perovskite layer 6 is not particularly _{limited, CH 3 NH 3 PbI 3,} CH (NH 2) 2 PbI 3, CsPbI 3, CH 3 NH 3 SnI 3, CH 3 NH 3 Sn x Pb (1-x ₎ I ₃ , (CH ₃ NH ₃ ) _x (CH (NH ₂ ) ₂ ) _(1-x) PbI _{3 and the} like, preferably CH ₃ NH ₃ PbI ₃ , CH (NH ₂ ) ₂ PbI ₃ . Moreover, a part of the iodide ions constituting the perovskite may be substituted with chloride ions or bromide ions.

  In the present invention, a highly stable perovskite solar cell 10 is obtained by adding a pyridine derivative having a hydrocarbon group at the ortho position to the hole transport layer 7 of the perovskite solar cell 10. The hole transport material constituting the hole transport layer 7 is not particularly limited, and examples thereof include p-type conductive polymers such as polyaniline, polythiophene, and polypyrrole; and p-type low-molecular organic semiconductors such as thiophene, thiadiazole, and spirobifluorene. . Preferably, 2,2 ', 7,7'-tetrakis (N, N-di-p-methoxyphenylamino) -9,9-spirobifluorene (spiro-OMeTAD) is used. The thickness of the hole transport layer 7 is preferably 20 to 100 nm, and more preferably 40 to 60 nm. When the thickness of the hole transport layer 7 is less than 20 nm, the coverage is decreased, and when the thickness is more than 100 nm, the resistance increases, which is not preferable.

  The hole transport layer may be added with a lithium salt, a cobalt complex, or the like. Preferably, lithium bis (trifluoromethanesulfonyl) imide, tris (1- (pyridin-2-yl) -1H-pyrazole) cobalt (III) tris (bis (trifluoromethanesulfonyl) imide) is used. It is preferable that the addition concentration with respect to spiro-OMeTAD of lithium salt and a cobalt complex is 20-60 mol% and 1-20 mol%, respectively.

The hole transport layer is preferably added with a pyridine derivative represented by the following general formula (I) in which at least one of the ortho positions is substituted with a substituted or unsubstituted aliphatic hydrocarbon.

Here, R ¹ and R ² are selected from a hydrogen atom or an aliphatic hydrocarbon group, and at least one of R ¹ and R ² is a substituted or unsubstituted aliphatic hydrocarbon group. R ¹ and R ² may be the same or different.

Alternatively, the pyridine derivative is represented by the general formula (I), R ¹ and R ² are selected from a hydrogen atom or an aliphatic hydrocarbon group, and at least one carbon number of R ¹ and R ² is 3 or more and 20 or less. It is.
When at least one carbon number of R ¹ and R ² is 3 or more and 20 or less, the photoelectric conversion efficiency can be maintained at a particularly high level for a long period of time.
Examples of such pyridine derivatives include compounds represented by the following formulas (A1) to (A5).





The concentration of the pyridine derivative added is preferably 50 to 300 mol%, more preferably 150 to 250 mol%, based on spiro-OMeTAD. By setting the addition concentration of the pyridine derivative to 50 mol% or more, it becomes possible to maintain the photoelectric conversion efficiency at a high level for a long time.

  The hole transport layer 7 can be produced by a spin coating method. For example, spiro-OMeTAD is dissolved in an organic solvent such as chlorobenzene, and to the spiro-OMeTAD, a lithium salt is added at a concentration of 35 mol%, a cobalt complex is added at 10 mol%, and a pyridine derivative is added at a concentration of 200 mol%, followed by stirring. This solution is spin-coated on a perovskite thin film at 2000 to 4000 rpm for 20 to 40 seconds, and then dried at room temperature.

  The material of the back electrode 8 is not particularly limited, and a known material can be used. Examples of the material include metals such as gold, silver, copper, and aluminum, tin oxide, indium tin oxide (ITO), aluminum zinc oxide (AZO), indium zinc oxide (IZO), and gallium zinc oxide (GZO). And other conductive transparent materials.

  About the other layer of a solar cell, it can produce by the well-known method as shown, for example in a following example.

Example 1
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
1. Preparation of Titanium Oxide Thin Film (1) FTO glass having a size of 2.0 cm × 2.4 cm was washed to prepare a translucent conductive support 4, and then the translucent conductive support 4 was heated to 500 ° C. Placed on hot plate.
(2) Titanium diisopropoxide bis (acetylacetonate) was dissolved in ethanol at a concentration of 0.02 mol / L.
(3) The solution obtained in the above (2) was applied to the FTO glass heated in the above (1) by a spray method. After spraying, heating was continued at 500 ° C. for 10 minutes to form a 30 nm thick hole blocking layer 3.
(4) Commercially available titanium oxide nanoparticles (manufactured by Diesol, 18NRT) were dispersed in ethanol at a weight ratio of 2: 7 to prepare a titanium oxide suspension.
(5) The suspension obtained in (4) above was applied to FTO glass provided with the hole blocking layer 3 by spin coating. In the spin coating method, rotation was performed at 1000 rpm for 18 seconds and then at 5000 rpm for 18 seconds. Thereafter, the film was dried at 70 ° C. for 10 minutes and baked at 500 ° C. for 45 minutes to form a 300 nm thick titanium oxide thin film. In the titanium oxide thin film, the perovskite is diffused and mixed with the subsequent production of the perovskite layer 6 to become the electron transport layer 5.
(6) The FTO glass provided with a titanium oxide thin film was moved to a glove box filled with nitrogen gas, and then subjected to spin coating of a perovskite layer.

2. Preparation of Perovskite Layer 6 (1) Methyl ammonium iodide CH ₃ NH ₃ I and lead iodide PbI ₂ having a molar ratio of 1: 1 were dissolved in dimethyl sulfoxide. The concentration of PbI ₂ · CH ₃ NH ₃ I was 1.25 mol / L.
(2) The above solution heated to 70 ° C. was applied by spin coating to FTO glass provided with a titanium oxide thin film similarly heated to 70 ° C.
(3) In the spin coating method, the substrate was rotated at 1000 rpm for 12 seconds and then at 5000 rpm for 30 seconds. While rotating at 5000 rpm, a small amount of toluene was added dropwise. After obtaining a uniform perovskite precursor thin film, it was immediately heated on a hot plate heated to 100 ° C. for 10 minutes to form a perovskite layer 6.

3. Preparation of Spiro-OMeTAD Layer (Hole Transport Layer 7) (1) A 170 mg / mL acetonitrile solution of lithium bis (trifluoromethanesulfonyl) imide was prepared.
(2) A 300 mg / mL acetonitrile solution of tris (1- (pyridin-2-yl) -1H-pyrazole) cobalt (III) tris (bis (trifluoromethanesulfonyl) imide) was prepared.
(3) 75 μL of the lithium solution obtained in (1) above, 150 mg of spiro-OMeTAD, and 58 μL of the cobalt solution obtained in (2) above were dissolved in 2 mL of chlorobenzene.
(4) 2-Amylpyridine represented by the above formula (A1) was dissolved in the solution obtained in the above (3). The concentration of 2-amylpyridine was 196 mol% with respect to spiro-OMeTAD.
(5) The solution obtained in the above (4) was spin-coated on a perovskite thin film at 3000 rpm for 30 seconds. Thereafter, the hole transport layer 7 having a thickness of 50 nm was formed by drying at room temperature.

4). Gold thin film deposition (preparation of back electrode 8)
The perovskite layer and the spiro-OMeTAD layer in the part that becomes the positive electrode of the battery were removed. A gold thin film having a thickness of 100 nm was vapor-deposited under a high vacuum (3 × 10 ⁻⁴ Pa or less) with a vacuum vapor deposition device to form the back electrode 8.

When the obtained solar cell was irradiated with AM1.5 artificial sunlight (intensity 1000 W / m ² ) in a solar simulator (WXS-155S-10, manufactured by Wacom Denso Co., Ltd.), the conversion efficiency was 14.82%. Obtained. Here, the light irradiation area was 1.02 cm ² .

(Example 2)
A solar cell was produced in the same manner as in Example 1 except that 2-octylpyridine represented by the above formula (A2) was used as the pyridine derivative in producing the hole transport layer.

When the obtained solar cell was irradiated with artificial sunlight of AM1.5 (intensity 1000 W / m ² ) in a solar simulator, a conversion efficiency of 14.74% was obtained.

(Example 3)
A solar cell was produced in the same manner as in Example 1 except that 2-dodecylpyridine represented by the above formula (A3) was used as the pyridine derivative in producing the hole transport layer.

When the obtained solar cell was irradiated with artificial sunlight of AM 1.5 (intensity 1000 W / m ² ) in a solar simulator, a conversion efficiency of 14.52% was obtained.

Example 4
A solar cell was produced in the same manner as in Example 1 except that 2-isopropylpyridine represented by the above formula (A4) was used as the pyridine derivative in producing the hole transport layer.

When the obtained solar cell was irradiated with artificial sunlight of AM 1.5 (intensity 1000 W / m ² ) in a solar simulator, a conversion efficiency of 14.61% was obtained.

(Example 5)
A solar cell was produced in the same manner as in Example 1, except that 2,6-diisobutylpyridine represented by the above formula (A5) was used as the pyridine derivative in producing the hole transport layer.

When the obtained solar cell was irradiated with artificial sunlight of AM1.5 (intensity 1000 W / m ² ) in a solar simulator, a conversion efficiency of 14.35% was obtained.

(Comparative Example 1)
A solar cell was produced in the same manner as in Example 1 except that 4-tert-butylpyridine represented by the following formula (A6) was used as the pyridine derivative in producing the hole transport layer.

When the obtained solar cell was irradiated with artificial sunlight of AM 1.5 (intensity 1000 W / m ² ) in a solar simulator, a conversion efficiency of 13.14% was obtained.

(Comparative Example 2)
A solar cell was produced in the same manner as in Example 1 except that pyridine was used as the pyridine derivative in producing the hole transport layer.

When the obtained solar cell was irradiated with artificial sunlight of AM1.5 (intensity 1000 W / m ² ) in a solar simulator, a conversion efficiency of 12.58% was obtained.

The solar cells obtained in Example 1 and Comparative Example 1 were stored in a desiccator that was a dark place filled with air having a humidity of less than 5% for 1000 hours, and AM1.5 simulated sunlight (intensity 1000 W / intensity) was stored in a solar simulator. m ² ). The solar cells of Examples 1 to 5 showed 100% of the initial conversion efficiency, and the solar cell of Comparative Example 1 showed 70% of the initial conversion efficiency.
Moreover, as Table 1 showed, it was confirmed that the solar cell of Examples 1-5 has a higher photoelectric conversion efficiency and high stability than the solar cell of Comparative Examples 1-2.

  As described above, the present invention can provide a perovskite solar cell having a long-term photoelectric conversion efficiency by adding a pyridine derivative having a hydrocarbon group at the ortho position to the hole transport layer of the perovskite solar cell. To do. The present invention is expected to be used for practical application of perovskite solar cells.

DESCRIPTION OF SYMBOLS 1 Transparent support substrate 2 Translucent conductive layer 3 Hole blocking layer 4 Translucent conductive support 5 Electron transport layer (Electron transport layer which perovskite infiltrated)
6 Perovskite layer 7 Hole transport layer 8 Back electrode 10 Solar cell

Claims (4)

In a perovskite solar cell including a transparent conductive support, a hole blocking layer, an electron transport layer, a perovskite layer, a hole transport layer, and a back electrode,
A perovskite solar cell, wherein the hole transport layer contains a pyridine derivative,
A perovskite solar cell, wherein the pyridine derivative is a pyridine derivative represented by the following general formula (I), wherein at least one of ortho positions is substituted with a substituted or unsubstituted aliphatic hydrocarbon.

(R ¹ and R ² are selected from a hydrogen atom or an aliphatic hydrocarbon group, and at least one of R ¹ and R ² is a substituted or unsubstituted aliphatic hydrocarbon group.) ^{2. At} least one of R ¹ and R ² of the pyridine derivative represented by the general formula (I) is a substituted or unsubstituted aliphatic hydrocarbon group having 3 to 20 carbon atoms. The perovskite solar cell described in 1.   The perovskite solar cell according to claim 1 or 2, wherein the hole transport layer uses spiro-OMeTAD as a hole transport material. The perovskite solar cell according to any one of claims 1 to 3, wherein the electron transport layer is composed of titanium oxide nanoparticles.