JP3598829B2 - Method for manufacturing oxide semiconductor electrode - Google Patents

Description

【００４５】
図４〜図６，および表１より知られるごとく，上記本発明の製造方法により製造した酸化物半導体電極（実施例Ｅ１，Ｅ２）は，従来の方法により作製した酸化物半導体電極（比較例Ｃ１）に比べて，エネルギー変換効率や曲線因子を増大させることができ太陽電池の性能が大きく向上することが分かる。
【００４６】
【発明の効果】
上述のごとく，本発明によれば，酸化物半導体層の比表面積を低下させることなく，電子の移動制限を緩和することができ，エネルギー変換効率に優れた，酸化物半導体電極の製造方法を提供することができる。
【図面の簡単な説明】
【図１】実施形態例における，酸化物半導体層の製造過程を示す説明図。
【図２】実施形態例における，酸化物半導体電極の製造過程を示す説明図。
【図３】実施形態例における，色素増感型太陽電池の構成を示す説明図。
【図４】実施形態例における，実施例Ｅ１の電圧と電流との関係を示す説明図。
【図５】実施形態例における，実施例Ｅ２の電圧と電流との関係を示す説明図。
【図６】実施形態例における，比較例Ｃ１の電圧と電流との関係を示す説明図。
【図７】従来例における，酸化物半導体電極の構成を示す説明図。
【符号の説明】
１．．．色素増感型太陽電池，
２．．．酸化物半導体電極，
２１．．．酸化物半導体層，
２３．．．色素，
３．．．対向電極，
４．．．電解液，
５．．．透明電極，[0001]
【Technical field】
The present invention relates to a method for manufacturing an oxide semiconductor electrode, more specifically, a method for manufacturing an oxide semiconductor electrode used for a dye-sensitized solar cell or the like.
[0002]
[Prior art]
BACKGROUND ART Conventionally, as shown in FIG. 3 described later, a dye-sensitized solar cell 1 is known. The dye-sensitized solar cell 1 has an oxide semiconductor electrode 2 having a transparent electrode 5 disposed on a light receiving surface 20 and a counter electrode 3 facing the oxide semiconductor electrode 2, and is provided between the electrodes by a spacer 81. The gap is filled with the electrolyte 4.
[0003]
In the conventional dye-sensitized solar cell 1, electrons are generated in the oxide semiconductor electrode 2 by the light 99 that passes through the transparent electrode 5 and irradiates the oxide semiconductor electrode 2. Then, electrons in the oxide semiconductor electrode 2 are collected by the transparent electrode 5 and extracted from the transparent electrode 5.
As shown in FIG. 7, a conventional oxide semiconductor electrode 2 includes a porous electrode base 921 formed by partially sintering fine particles (particle size: nm order) of an oxide semiconductor such as TiO _{2 and the} like. It consists of a dye 923 such as a ruthenium complex disposed on the surface.
[0004]
[Problem to be solved]
However, the conventional oxide semiconductor electrode 2 has the following problem.
That is, as described above, the electrode substrate 921 in the conventional oxide semiconductor electrode 2 is made porous by partially sintering the oxide semiconductor fine particles. Therefore, a large number of discontinuous portions exist in the contact portion or the non-contact portion of these fine particles. In the discontinuous portion, the movement of electrons is restricted, and the photocurrent decreases.
[0005]
On the other hand, when another large-sized oxide semiconductor is used in place of the fine particles, the specific surface area decreases, and the amount of the dye arranged on the surface decreases.
Therefore, it has been difficult to produce a solar cell with high energy conversion efficiency using a conventional oxide semiconductor electrode.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is capable of relaxing the electron transfer restriction without lowering the specific surface area of the oxide semiconductor, and having excellent energy conversion efficiency. An object of the present invention is to provide a method for manufacturing an oxide semiconductor electrode.
[0007]
[Means for solving the problem]
According to the first aspect of the present invention, an oxide semiconductor layer is formed by contacting a supercritical fluid in which a precursor of an oxide semiconductor is dissolved on a substrate having a high specific surface area to precipitate an oxide semiconductor. Next, there is provided a method for manufacturing an oxide semiconductor electrode, characterized by obtaining an oxide semiconductor electrode comprising an oxide semiconductor layer by removing the base material.
[0008]
According to a third aspect of the present invention, an oxide semiconductor layer is formed by contacting a supercritical fluid in which an oxide semiconductor precursor is dissolved on a substrate having a high specific surface area to precipitate an oxide semiconductor. Removing the base material and then disposing a dye on the surface of the oxide semiconductor layer to obtain an oxide semiconductor electrode composed of the oxide semiconductor layer and the dye. In a method for manufacturing a semiconductor electrode.
[0009]
The most remarkable point in the invention is that an oxide semiconductor layer is formed by depositing or coating an oxide semiconductor on the substrate having the high specific surface area, and then removing the substrate.
[0010]
As the substrate having a high specific surface area, a material that can be removed by oxidation or dissolution in a liquid phase or a gas phase is used. For example, various porous materials such as activated carbon, polymer permeable membrane, porous oxide, and porous metal can be used. Among them, activated carbon is particularly preferable because it is easily removed thereafter.
[0011]
The specific surface area of the substrate is preferably 5 m ² / g or more. When the specific surface area of the base material is less than 5 m ² / g, the specific surface area of the obtained oxide semiconductor layer is too small, and a sufficient amount of the dye is disposed, for example, in the case of a solar cell (Claim 2). May not be possible.
[0012]
The formation of the oxide semiconductor layer on the base material is performed by precipitation as described above. Specifically, utilizing a method using a supercritical fluid.
[0013]
A method using a supercritical fluid (hereinafter, referred to as a supercritical coating method) can form a uniform oxide semiconductor layer in a short time . This supercritical coating method is performed by, for example, bringing a supercritical fluid in which a precursor is dissolved into contact with the surface of the base material, and then depositing the precursor to form the oxide semiconductor layer.
[0014]
Note that as the oxide semiconductor, for example, titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), indium oxide (In ₂ O ₃ ), and oxide Zirconium (ZrO ₂ ), lanthanum oxide (La ₂ O ₃ ), tantalum oxide (Ta ₂ O ₅ ), strontium titanate (SrTiO ₃ ), barium titanate (BaTiO ₃ ), or the like can be used.
[0015]
The supercritical fluid generally refers to a liquid placed at a temperature and pressure above the critical point of a substance. However, the supercritical fluid in the present invention is a fluid having a temperature of at least the critical point, and the pressure does not need to be in the above-defined range. The fluid in this state has the same dissolving power as a liquid, and has the property of diffusivity and viscosity close to that of a gas. Therefore, a large amount of precursor can be easily and quickly transported into the micropores. The above dissolving ability can be adjusted by temperature, pressure, entrainer (additive) and the like.
[0016]
Examples of the supercritical fluid include hydrocarbons such as methane, ethane, propane, butane, ethylene and propylene, methanol, ethanol, propanol, iso-propanol, butanol, iso-butanol, sec-butanol, tert-butanol and the like. Ketones such as alcohol, acetone and methyl ethyl ketone, carbon dioxide, water, ammonia, chlorine, chloroform, freons and the like can be used.
[0017]
In order to adjust the solubility of the precursor in a supercritical fluid, alcohols such as methanol, ethanol and propanol, ketones such as acetone and ethyl methyl ketone, and aromatic hydrocarbons such as benzene, toluene and xylene are used. It can be used as an entrainer.
[0018]
The precursor is a substance that can become the oxide semiconductor after the reaction, such as metal or metalloid alkoxide, metal or metalloid acetylacetate, metal or metalloid organic acid salt, metal Alternatively, one or a mixture of two or more of metalloid nitrate, metal or metalloid oxychloride, metal or metalloid chloride, or the like can be used.
[0019]
Specifically, for example, as precursors of TiO ₂ , titanium n-butoxide (Titanium n-butoxide: Ti [O (CH ₂ ) ₃ CH ₃ ] ₄ ) and titanium isopropoxide (Titanium isopropoxide: Ti [OCH (CH ₃ ) ₂ ] ₄ ), titanium ethoxide (Titanium ethoxide: Ti (OC ₂ H ₅ ) ₄ ) or the like can be used.
[0020]
In the case of an oxide semiconductor electrode for a solar cell (claim 2), a dye is disposed on the surface of the modification layer as described above.
As the dye, for example, metal complexes or organic dyes such as ruthenium complexes, particularly ruthenium bipyridine complexes, phthalocyanine, cyanine, merocyanine, porphyrin, chlorophyll, pyrene, methylene blue, thionin, xanthene, coumarin, and rhodamine, and derivatives thereof are used. Can be.
[0021]
The arrangement of the dye on the modified layer can be performed as follows.
For example, the dye can be adsorbed by immersing the oxide semiconductor in a solution in which a dye such as a ruthenium complex is dissolved in an alcohol such as ethanol or an organic solvent such as acetonitrile. At this time, the solution can be heated to adjust the dye adsorption performance.
[0022]
When actually producing an oxide semiconductor electrode for a solar cell, a large number of the above oxide semiconductor layers are produced, a film is formed on the transparent electrode, and a dye is disposed thereon. Is preferred. This makes it possible to streamline the manufacturing process.
[0023]
Next, the operation and effect of the above invention will be described.
In the above invention, the oxide semiconductor layer is formed on the substrate having the high specific surface area by deposition or coating. Therefore, the obtained oxide semiconductor layer has a shape with a high specific surface area obtained by transferring the surface shape of the base material as it is. Therefore, particularly in the case of a solar cell (claim 2), a sufficient amount of dye can be disposed on the surface of the oxide semiconductor layer.
[0024]
Further, as described above, the oxide semiconductor layer is formed by depositing or coating an oxide semiconductor on a base material. The oxide semiconductor layer can greatly increase the size of the oxide semiconductor particles while maintaining a high specific surface area as compared with conventional oxide semiconductor particles. Therefore, the oxide semiconductor layer is formed in a state in which there is almost no discontinuous portion related to the movement of electrons, such as a crystal grain boundary, as compared with a conventional case where particles are partially sintered. Therefore, the movement of electrons can be performed more smoothly than before.
In addition, the oxide semiconductor electrode can obtain higher energy conversion efficiency than the conventional one by securing the amount of the dye and relaxing the restriction of the electron transfer.
[0025]
The oxide semiconductor electrode (Claim 1) is used as an ordinary battery, an electrochromic device, an electrode for photolysis of water, and the like, in addition to the oxide semiconductor electrode for a solar cell (Claim 2). can do.
[0026]
As described above, according to the present invention, it is possible to provide a method for manufacturing an oxide semiconductor electrode which can ease the restriction of electron transfer without lowering the specific surface area of the oxide semiconductor layer and has excellent energy conversion efficiency. can do.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment Example A method of manufacturing an oxide semiconductor electrode for a solar cell according to an embodiment of the present invention will be described with reference to FIGS.
In this example, the oxide semiconductor electrodes for a solar cell were respectively formed by two types of manufacturing methods according to the present invention (Example E1 and Example E2) and a conventional manufacturing method for comparison (Comparative Example C1). Manufactured. Then, a dye-sensitized solar cell was constructed using the obtained oxide semiconductor electrode, and its characteristics were compared.
Hereinafter, each of Examples E1 and E2 and Comparative Example C1 will be described in detail.
[0028]
(Example E1)
In the present embodiment, as shown in FIG. 1, an oxide semiconductor layer 21 is formed by depositing or coating an oxide semiconductor on a base material 7 having a high specific surface area, and then removing the base material 7 and then removing the oxide semiconductor layer 21. By arranging the dye 23 on the surface of the product semiconductor layer 21, the oxide semiconductor electrode 2 for a solar cell comprising the oxide semiconductor layer 21 and the dye 23 was obtained.
[0029]
In manufacturing the oxide semiconductor layer 21, first, as shown in FIG. 1A, a large number of activated carbon powders (M30, manufactured by Osaka Gas Co., Ltd.) as the base material 7 were prepared. This activated carbon powder is a porous material having a specific surface area of 3100 m ² / g.
Next, in the presence of the activated carbon powder 7, an isopropanol solution in which 3.5 mol / l of titanium isopropoxide {Ti (iso-PrO) ₄ } as a precursor was dissolved was supercritical carbon dioxide (150 ° C., 374 atm). Was dissolved. Then, this state was maintained for 3 hours.
[0030]
As a result, as shown in FIG. 1 (b), the supercritical carbon dioxide 210 containing the precursor was in very uniform contact with the surface of the porous activated carbon powder 7 (including the walls inside the pores).
Thereafter, the supercritical carbon dioxide was decompressed and removed. Next, after drying at room temperature for 10 hours, a heat treatment was performed for 10 hours in an air stream at a temperature of 570 ° C. Thereby, as shown in FIG. 1C, the oxide semiconductor layer 21 made of TiO _{2 having} a high specific surface area was formed, and the activated carbon powder as the base material 7 was burned. Note that burn-out traces of the base material 7 remained as hollow portions 201 inside the oxide semiconductor layer 21.
[0031]
Next, in the present example, the oxide semiconductor layer 21 made of TiO ₂ was coated with ion-exchanged water: acetylacetone: surfactant (polyethylene glycol mono-4-octylphenyl ether) = 100: 2: 1 (volume ratio). The mixture was mixed with a solvent at 37.5% by weight to prepare a TiO ₂ -containing solution.
[0032]
Next, a fluorine-doped SnO ₂ -coated glass (made by Asahi Glass) as a transparent electrode 5 was prepared, and the TiO ₂ -containing solution was applied to an area of 10 mm × 10 mm on the surface thereof. Next, after drying at room temperature for 10 hours, heat treatment was performed for 30 minutes in an air stream at a temperature of 450 ° C. Thereby, as shown in FIG. 2A, the oxide semiconductor layer 21 having a high specific surface area was disposed on the transparent electrode 5.
[0033]
Next, as shown in FIGS. 1D and 2B, a dye 23 was disposed on the oxide semiconductor layer 21 as follows.
First, a ruthenium complex (cis-Di (thiocyanato) -N, N'-bis (2,2'-bipyridyl-4,4'dicarboxylic acid) -ruthenium (II)) was added to anhydrous ethanol dehydrated with magnesium ethoxide. A solution dissolved at a concentration of 2.85 × 10 ⁻⁴ mol / l was prepared. Next, the transparent electrode provided with the above-described oxide semiconductor layer 21 was immersed in this solution for 24 hours. As a result, as shown in FIGS. 1D and 2B, the ruthenium complex as the dye 23 is adsorbed on the surface and the inner surface of the oxide semiconductor layer 21, and the oxide semiconductor electrode 2 for a solar cell is formed. Obtained.
[0034]
In this example, after the activated carbon powder 7 inside the oxide semiconductor layer 21 was burned off and removed, the oxide semiconductor layer 21 was disposed on the transparent electrode 5. Of course, it may be performed after disposition on the electrode 5.
[0035]
(Example E2)
Example E2 is an example in which the precursor in the supercritical coating method for forming the oxide semiconductor layer 21 in Example E1 was changed.
That is, an activated carbon powder 7 similar to the above was prepared, and in the presence thereof, an n-butanol solution {2.9 mol / l} in which titanium n-butoxide {Ti (n-BuO) ₄ } was dissolved as a precursor was dissolved. It was dissolved in supercritical carbon dioxide (150 ° C., 371 atm). This state was maintained for 3 hours.
[0036]
As a result, similarly to the above, the supercritical carbon dioxide containing the precursor adhered to the surface of the porous activated carbon powder 7 very uniformly.
Thereafter, the supercritical carbon dioxide was removed under reduced pressure and dried at room temperature for 10 hours. Next, heat treatment was performed for 10 hours in an air stream at a temperature of 570 ° C. As a result, the activated carbon powder as the substrate 7 was burned off, and a large number of oxide semiconductor layers 21 made of TiO ₂ and having a high specific surface area were formed.
Otherwise, the oxide semiconductor electrode 2 was manufactured in the same manner as in Example E1.
[0037]
(Comparative Example C1)
Comparative Example C2 is an example in which a large number of TiO ₂ fine particles were used instead of the oxide semiconductor layer 21 in Example E1.
That is, first, TiO ₂ particles (P25 manufactured by Nippon Aerosil Co., Ltd.) are prepared, and they are ion-exchanged water: acetylacetone: surfactant (polyethylene glycol mono-4-octylphenyl ether)｝ = 100: 2: 1 (volume ratio). Was mixed with 37.5% by weight of the solvent to prepare a TiO ₂ -containing solution.
[0038]
Next, a fluorine-doped SnO ₂ -coated glass (made by Asahi Glass) as a transparent electrode 5 was prepared, and the TiO ₂ -containing solution was applied to an area of 10 mm × 10 mm on the surface thereof. Next, after drying at room temperature for 10 hours, heat treatment was performed for 30 minutes in an air stream at a temperature of 450 ° C. Thus, an electrode substrate 921 (FIG. 7) made of TiO ₂ was formed on the transparent electrode 5.
[0039]
Next, in disposing the dye 923 on the electrode substrate 921, a solution was prepared by dissolving a ruthenium complex at a concentration of 2.85 × 10 ⁻⁴ mol / l in anhydrous ethanol dehydrated with magnesium ethoxide. The transparent electrode 5 provided with the above-described electrode substrate 21 was immersed in this solution for 24 hours to adsorb the ruthenium complex (dye) 3. Otherwise, in the same manner as in Example E1, an oxide semiconductor electrode 2 was produced.
[0040]
Next, a dye-sensitized solar cell 1 was formed using the oxide semiconductor electrodes manufactured by the above-described manufacturing methods (Examples E1, E2, and Comparative Example C1).
As shown in FIG. 3, with the transparent electrode 5 facing outward, the oxide semiconductor electrode 2 is opposed to a counter electrode 3 (10 mm × 20 mm) made of fluorine-doped SnO ₂ coated glass prepared by depositing platinum at 50 °. In addition, a gap is formed between them with a spacer 81 interposed therebetween. Then, the electrolyte solution 4 was impregnated into the gap to obtain a dye-sensitized solar cell 1.
The electrolyte 4 is a solution obtained by dissolving 3.13 g of tetra-n-propylammonium iodide (0.13 g) and iodine 0.18 g in a mixed solution of 21.14 g of ethylene carbonate and 4.0 ml of acetonitrile. is there.
[0041]
Next, in this example, the characteristics of the dye-sensitized solar cell 1 constituted by each of the above oxide semiconductor electrodes were compared. Specifically, each of the dye-sensitized solar cells 1 was irradiated with 730 W / m ² pseudo sunlight using a solar simulator (WXS-85 manufactured by Wacom Denso), and the voltage was swept by a potentiostat. The relationship between the voltage and current at that time was measured.
[0042]
The measurement results are shown in FIGS. In these figures, the voltage (V) is plotted on the horizontal axis and the current (mA) is plotted on the vertical axis. 4 shows the results of Example E1, FIG. 5 shows the results of Example E2, and FIG. 6 shows the results of Comparative Example C1, respectively.
[0043]
In addition, the energy conversion efficiency and the fill factor were determined from the above measurement results. The energy conversion efficiency is represented by (maximum output × 100) / (incident light energy). The fill factor is represented by the maximum output / (short circuit current × open voltage). The short-circuit current is shown as S1 and the open-circuit voltage is shown as S2 in FIGS.
In addition, the above-mentioned fill factor is an index indicating the performance of solar electricity similarly to the energy conversion efficiency, and it is desirable that this value be larger.
Table 1 shows the energy conversion efficiency and fill factor of each dye-sensitized solar cell.
[0044]
[Table 1]

[0045]
As can be seen from FIGS. 4 to 6 and Table 1, the oxide semiconductor electrodes (Examples E1 and E2) manufactured by the manufacturing method of the present invention are the same as the oxide semiconductor electrodes manufactured by the conventional method (Comparative Example C1). It can be seen that the energy conversion efficiency and the fill factor can be increased as compared with (), and the performance of the solar cell is greatly improved.
[0046]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a method for manufacturing an oxide semiconductor electrode, which can ease the electron transfer restriction without lowering the specific surface area of the oxide semiconductor layer and has excellent energy conversion efficiency. can do.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a manufacturing process of an oxide semiconductor layer in an embodiment.
FIG. 2 is an explanatory view showing a manufacturing process of the oxide semiconductor electrode in the embodiment.
FIG. 3 is an explanatory diagram showing a configuration of a dye-sensitized solar cell in an embodiment.
FIG. 4 is an explanatory diagram showing the relationship between the voltage and the current of Example E1 in the embodiment.
FIG. 5 is an explanatory diagram showing the relationship between the voltage and the current of Example E2 in the embodiment.
FIG. 6 is an explanatory diagram showing a relationship between a voltage and a current of a comparative example C1 in the embodiment.
FIG. 7 is an explanatory diagram showing a configuration of an oxide semiconductor electrode in a conventional example.
[Explanation of symbols]
1. . . Dye-sensitized solar cells,
2. . . Oxide semiconductor electrode,
21. . . Oxide semiconductor layer,
23. . . Pigment,
3. . . Counter electrode,
4. . . Electrolyte,
5. . . Transparent electrode,

Claims (4)

A supercritical fluid in which a precursor of an oxide semiconductor is dissolved is brought into contact with a substrate having a high specific surface area to precipitate an oxide semiconductor and form an oxide semiconductor layer.
Next, an oxide semiconductor electrode comprising an oxide semiconductor layer is obtained by removing the base material.   2. The method according to claim 1, wherein the base is made of activated carbon. A supercritical fluid in which a precursor of an oxide semiconductor is dissolved is brought into contact with a substrate having a high specific surface area to precipitate an oxide semiconductor and form an oxide semiconductor layer.
Then, after removing the substrate,
A method for producing an oxide semiconductor electrode for a solar cell, comprising obtaining an oxide semiconductor electrode comprising an oxide semiconductor layer and a dye by disposing a dye on the surface of the oxide semiconductor layer.   4. The method according to claim 3, wherein the base is made of activated carbon.

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