JP2000021461A - Method for manufacturing oxide semiconductor electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a modification layer up to the inside such as a pore of an electrode base body, and to improve energy convering efficiency by contacting a supercritical fluid by dissolving a precursor of the decorative layer with the surface of the electrode base body composed of a porous oxide semiconductor, and next, forming the modification layer on the electrode base body surface by depositing the precursor as oxide. SOLUTION: When manufacturing an electrode base boady 21, first a TiO2 containing solution is manufactured by mixing TiO particles in a solvent of ion exchange water: acetylacetone: a surface active agent. Next, the TiO2 containing solution is applied to the surface of fluorine-doped SnO2 coat glass as a transparent electrode to form the electrode base body 21 by heat treating. Next, an isopropanol solution by dissolving titanium isopropoxide as a precursor is dissolved in supercritical carbon dioxide, and after uniformly sticking it to the surface of the electrode base body 21, the supercritical carbon dioxide is removed under reduced pressure to uniformly form a modification layer 22. Next, processing is performed for arranging pigment 23 on the modification layer 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an oxide semiconductor electrode, more specifically, a method for manufacturing an oxide semiconductor electrode used in a dye-sensitized solar cell or the like.

[0002]

2. Description of the Related Art A dye-sensitized solar cell 1 has been conventionally known as shown in FIG. The dye-sensitized solar cell 1 has a transparent electrode 5, an oxide semiconductor electrode 2 disposed such that a light receiving surface 20 is in contact with the transparent electrode 5, and a counter electrode 3 facing the same. The gap between the electrodes is filled with the electrolyte 4 by a spacer 81.

In this conventional dye-sensitized solar cell 1, electrons are generated in the oxide semiconductor electrode 2 by light 99 passing through the transparent electrode 5 and irradiating the oxide semiconductor electrode 2. And the electrons in the oxide semiconductor electrode 2 are
Collected on the transparent electrode 5 and taken out from the transparent electrode 5.

[0004] The oxide semiconductor electrode 2 is formed as shown in FIG.
As shown in FIG. 1, a porous electrode substrate 21 formed by partially sintering oxide semiconductor fine particles such as TiO ₂ , a modified layer 22 formed on the surface thereof, and a ruthenium complex or the like disposed thereon. It is composed of Dye 23. Modification layer 22
Is provided for the purpose of improving the energy conversion efficiency of the solar cell, and is made of an oxide such as TiO ₂ . The formation of the modification layer 22 is performed by applying an aqueous solution such as titanium tetrachloride on the electrode substrate 21 and then performing a heat treatment.

[0005]

However, the conventional oxide semiconductor electrode 2 has the following problems. That is,
The modification layer 22 in the conventional oxide semiconductor electrode 2 is
It is difficult to form uniformly on the electrode substrate 21. That is, when the aqueous solution of titanium tetrachloride or the like is applied on the electrode substrate 21, the diffusion of the aqueous solution and the influence of the viscosity cause
The aqueous solution blocks pores and the like of the electrode substrate 21 and does not penetrate deep inside. Therefore, the modified layer 22 obtained after the heat treatment is not formed inside the pores or the like of the electrode substrate 21 either.
It will be in an uneven state. Therefore, the effect of improving the energy conversion efficiency by the modified layer 22 was not sufficient.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and provides an oxide semiconductor electrode having excellent energy conversion efficiency, in which a modification layer can be formed inside pores and the like of an electrode substrate. It is something to offer.

[0007]

According to the first aspect of the present invention, a supercritical fluid in which a precursor of a modification layer is dissolved is brought into contact with the surface of an electrode substrate made of a porous oxide semiconductor. A method for producing an oxide semiconductor electrode, comprising forming a modified layer on at least a part of the surface of the electrode substrate by depositing the modified layer as an oxide.

According to a second aspect of the present invention, a supercritical fluid in which a precursor of a modification layer is dissolved is brought into contact with the surface of an electrode substrate made of a porous oxide semiconductor, and then the precursor is oxidized. Forming a modified layer on at least a part of the surface of the electrode substrate, and then disposing a dye on the modified layer to obtain an oxide semiconductor electrode comprising the electrode substrate, the modified layer, and the dye A method for manufacturing an oxide semiconductor electrode for a solar cell, comprising the steps of:

The most remarkable point in the above invention is that
The modification layer is formed using a supercritical fluid in which the precursor is dissolved.

[0010] The supercritical fluid generally refers to a liquid placed at a temperature and pressure higher than the critical point of a substance. However, the supercritical fluid in the present invention is a fluid having a temperature at least at a critical point or higher, and the pressure does not need to be in the range defined above. 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 carried into the micropores. The above dissolving capacity depends on temperature, pressure,
It can be adjusted by an entrainer (additive) or the like.

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 and tert-. Alcohols such as butanol, ketones such as acetone and methyl ethyl ketone, carbon dioxide, water, ammonia, chlorine, chloroform, freons and the like can be used.

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 carbons such as benzene, toluene and xylene are used. Hydrogen or the like can be used as the entrainer.

The precursor may be a metal or metalloid alkoxide, a metal or metalloid acetylacetate, a metal or metalloid organic acid salt, a metal or metalloid nitrate, a metal or metalloid nitrate, or a metal or metalloid nitrate. /
And a mixture of two or more kinds of metalloid oxychloride, metal or / and metalloid chloride, and the like.

Specifically, for example, as a precursor of TiO ₂ , titanium n-butoxide (Titanium n-butoxide: T
i [O (CH ₂ ) ₃ CH ₃ ] ₄ ), titanium isopropoxide
(Titanium isopropoxide: Ti [OCH (C
H ₃ ) ₂ ] ₄ ), titanium ethoxide
e: Ti (OC ₂ H ₅ ) ₄ ) or the like can be used.

The electrode substrate may be, for example, an oxidized
Porous by partially sintering fine particles of semiconductor
Can be applied. Specific materials and
For example, titanium oxide (TiO_Two), Tin oxide (Sn
O_Two), Zinc oxide (ZnO), niobium oxide (Nb
_TwoO_Five), Indium oxide (In)_TwoO_Three) 、 Zirconium oxide
(ZrO_Two), Lanthanum oxide (La_TwoO_Three) 、 Tan oxide
Tal (Ta_TwoO _Five), Strontium titanate (SrTi
O_Three), Barium titanate (BaTiO) _Three)
Can be.

The above-mentioned modified layer is provided as a second oxide semiconductor on the surface of an electrode substrate made of an oxide semiconductor electrode (first oxide semiconductor) in order to improve the function of the oxide semiconductor electrode. . The modified layer includes, 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 zirconium oxide (ZrO ₂ ). 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. Different combinations can be taken.

Since the modified layer has a large specific surface area, when a dye is arranged as described later, the amount of the dye attached can be improved. In addition, since there are fewer impurities than the electrode substrate, electrons easily move from the dye in the electrode substrate or in the electrode. In addition, since the contact area between the particles of the electrode substrate is increased, the electrons can easily move.

In the case of the above-mentioned 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, rhodamine, and derivatives thereof are used. Can be.

The deposition of the precursor as an oxide is carried out, for example, by bringing a supercritical fluid into contact with the electrode substrate, removing the supercritical fluid, drying, and, if necessary, performing a heat treatment or the like. be able to.

The arrangement of the dye on the modified layer can be performed, for example, 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.

Next, the operation and effect of the above invention will be described. In the present invention, a supercritical fluid in which the precursor is dissolved is brought into contact with the electrode substrate. At this time, since the supercritical fluid has extremely excellent diffusivity and viscosity as described above, the supercritical fluid sufficiently penetrates into the fine pores in the porous electrode substrate. Further, since the supercritical fluid has an excellent dissolving ability as described above, the supercritical fluid penetrates into the micropores in a state where a large amount of the precursor is dissolved.

Therefore, when the precursor in the supercritical fluid is deposited as an oxide, the oxide is uniformly deposited including the inside of the micropores. Therefore, the modification layer can be formed on the surface of the electrode substrate in a very uniform state.

Further, in the case of an oxide semiconductor electrode for a solar cell (claim 2), an extremely excellent oxide for a solar cell can be obtained by further disposing a dye on such a uniform modification layer. A semiconductor electrode can be obtained. That is,
The presence of the uniform modification layer can increase the amount of the dye adsorbed and reduce the electric resistance of the entire electrode. Therefore, an effect of increasing the voltage due to an increase in the current value, a decrease in the leak current, and the like can be obtained, and the high rate characteristics and the energy conversion efficiency can be significantly improved as compared with the conventional case. In addition, by applying a highly conductive oxide or an oxide capable of increasing the open-circuit voltage to the modification layer, the characteristics of the solar cell can be improved.

The above-mentioned oxide semiconductor electrode (Claim 1)
Can be 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).

As described above, according to the present invention, it is possible to form a modification layer inside pores or the like of an electrode substrate on at least a part of the surface of the electrode substrate, and to obtain an oxide having excellent energy conversion efficiency. A method for manufacturing a semiconductor electrode can be provided.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment A method for 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, two types of manufacturing methods (Examples E1 and E2) according to the present invention and two conventional types of manufacturing methods (Comparative Examples C1 and C2) for comparison were used, respectively. An oxide semiconductor electrode was 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 Examples C1 and C2 will be described in detail.

Example E1 In this example, as shown in FIG. 2, a supercritical fluid in which a precursor was dissolved was brought into contact with the surface of an electrode substrate 21 made of a porous oxide semiconductor.
The precursor is deposited as an oxide to form a modification layer 22 on the surface of the electrode substrate, and then a dye 23 is disposed on the modification layer 22 to form the electrode substrate 21 and the modification layer 2.
An oxide semiconductor electrode 2 for a solar cell was manufactured, which was composed of 2 and a dye 23.

In preparing the electrode substrate 21, first, TiO ₂ particles (P25, manufactured by Nippon Aerosil Co., Ltd.) are prepared and ion-exchanged water: acetylacetone: surfactant (polyethylene glycol mono-4-octyl phenyl ether) = 100: 2: 1 (volume ratio) was mixed with 37.5% by weight to prepare a TiO ₂ -containing solution.

Next, a fluorine-doped SnO ₂ coated glass (made by Asahi Glass) as the transparent electrode 5 was prepared, and the above TiO ₂ -containing solution was applied to an area of 10 mm × 10 mm on the surface thereof. Then, after drying at room temperature for 10 hours,
Heat treatment was performed for 30 minutes in an air stream at 50 ° C.
Thereby, on the fluorine-doped SnO ₂ coated glass,
An electrode substrate 21 (Ti) made of a porous oxide semiconductor
O ₂ ) was formed.

Next, in the presence of the electrode substrate 21, titanium isopropoxide @ Ti (iso-
PrO) ₄ } was dissolved in 3.5 mol / l isopropanol solution in supercritical carbon dioxide (150 ° C., 374 at
m). This state was maintained for 3 hours.

As a result, the supercritical carbon dioxide containing the precursor adhered to the surface of the porous electrode substrate 21 very uniformly. Then, the supercritical carbon dioxide was decompressed and removed. 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, the modification layer 22 made of TiO ₂ is formed on the electrode substrate 21.
Was formed uniformly.

Next, a dye 23 was arranged on the modified layer 22 made of TiO ₂ as follows. First, anhydrous ruthenium complex (cis-Di (thiocyanato) -N, N'-bis (2,2'-bipyridyl-4,
4'dicarboxylic acid) -ruthenium (II)) 2.85 × 1
A solution dissolved at a concentration of 0 ^-4 mol / l was prepared. Next, the electrode substrate 21 on which the aforementioned modified layer 22 was formed was immersed in this solution for 24 hours to adsorb the ruthenium complex as the dye 22. As a result, an oxide semiconductor electrode 2 for a solar cell was obtained.

(Embodiment E2) Embodiment E2 is an example in which the precursor in the supercritical coating method at the time of forming the modifying layer 22 in Embodiment E1 is changed. That is, an electrode substrate 21 similar to the above was produced, and in the presence of the same, titanium n
Dissolved n- of butoxide {Ti (n-BuO) ₄ }
A butanol solution {2.9 mol / l} was dissolved in supercritical carbon dioxide (150 ° C., 371 atm). This state was maintained for 3 hours.

Thereafter, the supercritical carbon dioxide was removed under reduced pressure and dried at room temperature for 10 hours. Next, at a temperature of 450
The modified layer 22 was formed on the electrode substrate 21 by performing a heat treatment for 30 minutes in an air stream at a temperature of ° C. Others are Example E
In the same manner as in Example 1, an oxide semiconductor electrode 2 was produced.

(Comparative Example C1) This Comparative Example C1 is a comparative example of Example E.
1 is an example in which the modification layer 22 is formed not by a supercritical coating method but by a conventional surface treatment method using an aqueous solution of titanium tetrachloride. That is, the electrode substrate 21 was produced in the same manner as described above. Next, in forming the modification layer 22, a concentration of 0.2 mol / l
Of titanium tetrachloride aqueous solution was added dropwise and left standing at room temperature for 10 hours in a closed vessel to partially hydrolyze. Thereafter, unreacted titanium tetrachloride was washed off with deionized water. Further, a heat treatment was performed for 30 minutes in an air stream at a temperature of 450 ° C. to form a modified layer 22 made of TiO 2. Otherwise, an oxide semiconductor electrode was manufactured in the same manner as in Example E1.

(Comparative Example C2) This Comparative Example C2 is a comparative example of Example E
This is an example in which the formation of the modification layer 22 in No. 1 is omitted. That is, directly on the electrode substrate 21 manufactured in the same manner as above,
Dye 23 was arranged in the same manner as above. Otherwise, an oxide semiconductor electrode was manufactured in the same manner as in Example E1.

Next, each of the above manufacturing methods (Examples E1 and E
2, a dye-sensitized solar cell 1 was formed using the oxide semiconductor electrodes prepared in Comparative Examples C1 and C2). FIG.
As shown in the figure, the transparent electrode 5 is set outside and the opposing electrode 3 (10 mm) made of fluorine-doped SnO ₂ coated glass on which the separately prepared oxide semiconductor electrode 2 and platinum prepared by evaporation at 50 ° are deposited.
× 20 mm). Also, between these
A gap is formed with the spacer 81 interposed. Then, the electrolyte solution 4 was impregnated into the gap to obtain a dye-sensitized solar cell 1. The electrolyte 4 was prepared by adding tetra-n-propylammonium iodide (Tetra-n-prn) to a mixed solution of 21.14 g of ethylene carbonate and 4.0 ml of acetonitrile.
opylammonium Iodide) 3.13 g and iodine 0.18 g
Is dissolved.

Next, in this example, the characteristics of the dye-sensitized solar cell 1 constituted by each of the above oxide semiconductor electrodes were compared. More specifically, a solar simulator (WXS-8 manufactured by Wacom Denso) is provided for each dye-sensitized solar cell 1.
Using 5), irradiate 730 W / m ² pseudo sunlight,
The relationship between the voltage and the current when the voltage was swept with a potentiostat was measured.

The measurement results are shown in FIGS. In these figures, the horizontal axis represents voltage (V) and the vertical axis represents current (mA). FIG. 3 shows the embodiment E1, and FIG.
2, FIG. 5 shows the results of Comparative Example C1, and FIG. 6 shows the results of Comparative Example C2.

From the above measurement results, the energy conversion efficiency and the fill factor were determined. Energy conversion efficiency is
It is represented by (maximum output × 100) / (incident light energy). The fill factor is represented by the maximum output / (short circuit current × open circuit voltage). Note that the short-circuit current is denoted by S1,
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.

[0041]

[Table 1]

As can be seen from FIGS. 3 to 6 and Table 1, Comparative Example C2 having no modified layer resulted in the lowest energy conversion efficiency. Also, from the comparison between Examples E1 and E2 and Comparative Example C1, not only the formation of the modified layer but also the formation of the modified layer by the above-mentioned supercritical coating method increases the energy conversion efficiency and the fill factor. It can be seen that it is very effective in improving the performance of the solar cell.

[0043]

As described above, according to the present invention, it is possible to provide a method for manufacturing an oxide semiconductor electrode having a high energy conversion efficiency, in which a modified layer can be formed inside pores and the like of an electrode substrate. be able to.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a dye-sensitized solar cell in an embodiment.

FIG. 2 is an explanatory diagram illustrating a structure of an oxide semiconductor electrode in the embodiment.

FIG. 3 is an explanatory diagram showing a relationship between a voltage and a current of Example E1 in the embodiment.

FIG. 4 is an explanatory diagram showing a relationship between a voltage and a current of Example E2 in the embodiment.

FIG. 5 is an explanatory diagram showing a relationship between a voltage and a current of a comparative example C1 in the embodiment.

FIG. 6 is an explanatory diagram showing a relationship between a voltage and a current of a comparative example C2 in the embodiment.

[Explanation of symbols]

 1. . . 1. dye-sensitized solar cell, . . 21. oxide semiconductor electrode; . . Electrode base, 22. . . Modification layer, 23. . . Pigment, 3. . . 3. counter electrode; . . Electrolyte, 5. . . Transparent electrode,

Continuing from the front page (72) Inventor Shinji Inagaki 41, Chuchu-Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside of Toyota Central R & D Laboratories Co., Ltd. Address 1 Toyota Central R & D Co., Ltd. F-term (reference) 4M104 BB36 CC01 DD51 DD79 FF06 GG05 HH20 5F051 AA14 5H032 AA06 AS16 BB05 BB10 EE16

Claims (2)

[Claims] 1. A supercritical fluid in which a precursor of a modification layer is dissolved is brought into contact with the surface of an electrode substrate made of a porous oxide semiconductor, and then the precursor is deposited as an oxide to form a surface of the electrode substrate. Forming a modified layer on at least a part of the oxide semiconductor electrode. 2. A surface of an electrode substrate made of a porous oxide semiconductor is brought into contact with a supercritical fluid in which a precursor of a modification layer is dissolved, and then the precursor is deposited as an oxide to form a surface of the electrode substrate. Forming a modified layer on at least a portion of the oxide layer, and then disposing a dye on the modified layer to obtain an oxide semiconductor electrode comprising an electrode substrate, the modified layer, and the dye. Of manufacturing a semiconductor electrode.