JP2002289269A - Manufacturing method of photoelectrode for dye sensitized solar cell and manufacturing method of dye sensitized solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a photoelectrode for a dye sensitized solar cell, showing an excellent photoelectric transducing efficiency, and a manufacturing method of a dye sensitized solar cell. SOLUTION: The manufacturing method of the photoelectrode 10 for a dye sensitized solar cell, comprising a semiconductor electrode 2 with a light receiving surface F2 and a transparent electrode 1 arranged to adjoin the light receiving surface of the semiconductor electrode, is characterized in that it comprises a surface treatment process wherein electromagnetic waves within a wavelength range of 180-450 nm are emitted to the back surface F22 on the opposite side of the light receiving surface of the semiconductor electrode, and a pigment adsorption process wherein sensitizing pigment P2 is adsorbed to the back surface obtained through the surface treatment process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a photoelectrode for a dye-sensitized solar cell and a method for producing a dye-sensitized solar cell.

[0002]

2. Description of the Related Art In recent years, various developments of solar cells have been promoted with increasing interest in global warming and energy problems. Among such solar cells, dye-sensitized solar cells are expected to be put to practical use because the materials used are inexpensive and can be manufactured by a relatively simple process. Various studies have been made to improve the energy conversion efficiency (power generation efficiency) η (%) of the dye-sensitized solar cell for practical use. The energy conversion efficiency η of the dye-sensitized solar cell is represented by the following equation (1). η = 100 × (V _oc × I _sc × F.F.) / I ₀ (1) where I ₀ is the incident light intensity I ₀ [mWc
m ^-2 ], V _oc is the open circuit voltage [V], _Isc is the short circuit current density [mA]
cm ⁻² ] and FF indicate a fill factor.

[0003] The above-mentioned studies include, for example, Japanese Patent Application Laid-Open
Japanese Patent Application No. 0-285980 discloses that a surface of a semiconductor electrode in contact with an electrolyte is subjected to an oxidation treatment, and thereafter, a photoelectrode manufactured by adsorbing a sensitizing dye on the surface is provided. Dye-sensitized solar cells intended to improve η have been proposed. As the method of the oxidation treatment, there are a method using an aqueous solution containing hydrogen peroxide or hypochlorite as an oxidizing agent or a mixed gas containing ozone as an oxidizing agent, and a method using an active oxygen as an oxidizing agent or an oxidizing agent. There has been proposed a method of irradiating ultraviolet rays in an atmosphere containing oxygen serving as a seed source (in air or the like).

[0004]

SUMMARY OF THE INVENTION However, the present inventors have made the following even a dye-sensitized solar cell provided with a photoelectrode treated as described in JP-A-2000-285980. It has been found that there is a problem as described above, and sufficient energy conversion efficiency cannot be obtained, and it is still insufficient.

That is, when the sensitizing dye is adsorbed after the semiconductor electrode is immersed in an aqueous solution of hydrogen peroxide or hypochlorite to perform an oxidation treatment, the surface itself of the semiconductor electrode is oxidized and the surface is oxidized. However, there is a problem that it is not possible to sufficiently remove impurities such as an organic compound that inhibits a photoelectric conversion reaction existing on the surface. . If the impurities remaining on the surface of the semiconductor electrode cannot be sufficiently removed, the energy conversion efficiency will be significantly reduced. In the case where hypochlorite is used, the metal cation component (for example, an alkali metal component such as sodium) constituting the hypochlorite remains after the treatment, and it may be sufficiently removed. Due to the difficulty, the energy conversion efficiency has been reduced.

Further, when ultraviolet rays are irradiated in an atmosphere containing oxygen, the surface itself of the semiconductor electrode can be oxidized to change the fine structure of the surface. There has been a problem that impurities such as an organic compound or an inorganic compound (a nitric acid compound or the like) that inhibit the reaction cannot be sufficiently removed. Also,
In this case, when the ultraviolet rays are excessively irradiated, a reduction product (oxygen anion) of oxygen may be generated and may remain on the surface of the semiconductor electrode. If the oxygen reduction product remains on the surface of the semiconductor electrode as described above, when the sensitizing dye is adsorbed after the oxidation treatment, the oxygen reduction product reacts with the sensitizing dye. There was a problem that it would. As a result, the initial characteristics and durability (life) of the obtained photoelectrode and the solar cell provided with the photoelectrode are significantly reduced.

The present invention has been made in view of the above-mentioned problems of the prior art, and is directed to a method of manufacturing a photoelectrode for a dye-sensitized solar cell capable of obtaining excellent photoelectric conversion efficiency, and a dye-sensitized solar cell. An object of the present invention is to provide a method for manufacturing a battery.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the oxidation reaction of the surface of the semiconductor electrode was performed while irradiating the surface with electromagnetic waves of a specific wavelength region. The present inventors have found that conducting the treatment in water or in an electrolyte solution is effective in improving the photoelectric conversion efficiency of the obtained photoelectrode, and have reached the present invention.

That is, the present invention is a method of manufacturing a photoelectrode for a dye-sensitized solar cell having a semiconductor electrode having a light receiving surface and a transparent electrode disposed adjacent to the light receiving surface of the semiconductor electrode. In water or in an electrolyte solution, 180 to 450
for a dye-sensitized solar cell, comprising: a surface treatment step of irradiating electromagnetic waves in a wavelength region of nm, and a dye adsorption step of adsorbing a sensitizing dye on the back surface of the semiconductor electrode obtained by the surface treatment step. Provided is a method for manufacturing a photoelectrode.

The energy corresponding to the band gap of the semiconductor material forming the semiconductor electrode in the liquid is applied to the back surface of the semiconductor electrode which comes into contact with the electrolyte when the dye-sensitized solar cell is formed. When an electromagnetic wave having a higher energy (photon energy) in the above wavelength range is irradiated, electrons and holes (holes) induced by light are generated on the back surface. Since the photogenerating holes have high oxidizing power, it is possible to oxidize impurities such as organic compounds and inorganic compounds and water contained in the semiconductor material on the back surface of the semiconductor electrode. On the other hand, photogenerated electrons have a high reducing power, so they directly reduce water molecules in the liquid or reduce hydrogen ions generated by ionization of water molecules to generate hydrogen gas, or reduce oxygen to reduce oxygen ions. Or generate Further, in the present invention, since the surface treatment reaction proceeds in the liquid phase, the amount of generated oxygen anion is small, and the reaction between the oxygen anion and the sensitizing dye as described above can be reduced. And, by the above photocatalytic action, impurities that inhibit the photoelectric conversion reaction contained in the semiconductor material forming the semiconductor electrode can be sufficiently oxidized and removed, so that the dye-sensitized solar cell having excellent photoelectric conversion efficiency can be obtained. Photoelectrodes can be obtained.

[0011] In the present specification, the "back surface of the semiconductor electrode" is in contact with the electrolyte of the semiconductor electrode when a dye-sensitized solar cell is constructed using the photoelectrode having the semiconductor electrode as described above. Shows the side of the side that will be.

Further, the present invention is a method for manufacturing a photoelectrode for a dye-sensitized solar cell, comprising a semiconductor electrode having a light receiving surface, and a transparent electrode disposed adjacent to the light receiving surface of the semiconductor electrode. Thus, to constitute an electrochemical cell having a semiconductor electrode as a working electrode, in water or in an electrolyte solution, while applying a bias voltage to the semiconductor electrode, on the back surface opposite to the light-receiving surface of the semiconductor electrode, 180 to 450 nm A photoelectrode for a dye-sensitized solar cell, comprising: a surface treatment step of irradiating electromagnetic waves in a wavelength region; and a dye adsorption step of adsorbing a sensitizing dye on the back surface of the semiconductor electrode obtained by the surface treatment step. And a method for producing the same.

In this manufacturing method, similarly to the above-described manufacturing method, by irradiating electromagnetic waves in the above-mentioned wavelength range in a liquid, the photoelectric conversion reaction contained in the semiconductor material constituting the semiconductor electrode is inhibited. Therefore, a photoelectrode for a dye-sensitized solar cell having excellent photoelectric conversion efficiency can be obtained. Furthermore, in the case of this manufacturing method, when irradiating electromagnetic waves in the above wavelength range, an electrochemical cell having a semiconductor electrode as a working electrode is configured and a bias voltage is applied to the semiconductor electrode. Impurities that inhibit the photoelectric conversion reaction contained in the semiconductor material can be efficiently and more reliably oxidized and removed.

The "electrochemical cell" in this case is
There is no particular limitation as long as the semiconductor electrode constituting the photoelectrode is used as a working electrode. For example, a so-called two-electrode electrochemical system including a working electrode (semiconductor electrode) and a counter electrode also serving as a reference electrode is used. The cell may be a so-called three-electrode electrochemical cell including a working electrode, a reference electrode, and a counter electrode. In any electrochemical cell, by adjusting the bias voltage applied to the semiconductor electrode, the back surface of the semiconductor electrode is used as a reaction field where the oxidation reaction proceeds selectively, and the counter electrode is used as a reaction field where the reduction reaction proceeds selectively. It can be. Therefore, the impurities can be efficiently and more reliably oxidized and removed as compared with the case where only the electromagnetic wave in which the oxidation reaction and the reduction reaction proceed simultaneously on the back surface of the semiconductor electrode is applied. However, from the viewpoint of more precisely controlling the potential of the working electrode with respect to the reference electrode and allowing the desired oxidation reaction to proceed more selectively and reliably, it is preferable to use a three-electrode electrochemical cell.

"Applying a bias voltage to the semiconductor electrode" means that in the electrochemical cell, the potential of the working electrode is set to a potential at which the oxidation reaction of the impurity can proceed with respect to the potential of the reference electrode. Indicates adjustment. Here, the bias voltage indicates a value obtained by subtracting the potential of the reference electrode from the potential of the working electrode. The reference electrode at this time is not particularly limited, either, and an electrode that can be appropriately used can be selected according to an electrolyte solution or the like used in the electrochemical cell. For example, a standard hydrogen electrode (hereinafter, referred to as SHE),
Known electrodes such as a silver-silver chloride electrode (hereinafter, referred to as “Ag-AgCl”) and a calomel electrode can be used.

Further, the range of the potential of the working electrode (semiconductor electrode) capable of promoting the oxidation reaction of the impurities is determined by the semiconductor material constituting the semiconductor electrode to be used, the impurities contained in the semiconductor material, and the reference electrode to be used. Is determined as appropriate. For example, by changing the potential of the semiconductor electrode with respect to the reference electrode while irradiating an electromagnetic wave, the potential range in which the impurity can be oxidized may be determined experimentally (see FIG. 6 described later). It may be theoretically obtained from the overvoltage of the oxidation reaction of the impurity on the semiconductor electrode to be used and thermodynamic data such as the oxidation-reduction potential of the impurity. For example, the semiconductor material forming the semiconductor electrode is titanium oxide, and the reference electrode is an Ag-AgCl electrode ([C
l ^-]: saturated, for example in the case of a saturated KCl solution) is
The potential of the working electrode is -0.5 to 1.5 V vs. Ag-Ag
Cl is preferable, and -0.3 to +1.5 Vvs. Ag-A
gCl is more preferred.

In the present invention, in any of the above two manufacturing methods, the wavelength of the electromagnetic wave applied to the back surface of the semiconductor electrode in the surface treatment step is preferably 180 nm or more. When the wavelength exceeds 450 nm, the photocatalytic function does not appear and the effect does not appear. And, from the same viewpoint as above, when the semiconductor material forming the semiconductor electrode is titanium oxide,
The wavelength of the electromagnetic wave applied to the back surface of the semiconductor electrode is 180 to
It is more preferably 450 nm,
More preferably, it is nm.

In the present invention, in any of the above two manufacturing methods, it is preferable to further irradiate an ultrasonic wave in the surface treatment step. Thereby, diffusion of a liquid (water or an electrolyte solution) of an oxidation product generated from an impurity that inhibits a photoelectric conversion reaction contained in the semiconductor material on the back surface of the semiconductor electrode can be performed more smoothly. As a result, the impurities can be oxidized and removed more efficiently and more reliably.

Further, the present invention has a photoelectrode having a semiconductor electrode having a light receiving surface, a transparent electrode arranged adjacent to the light receiving surface of the semiconductor electrode, and a counter electrode. A method for producing a dye-sensitized solar cell in which a counter electrode and a counter electrode are disposed opposite each other via an electrolyte, wherein the photoelectrode is produced by the method for producing a dye-sensitized solar cell photoelectrode of the present invention described above. A method for producing a dye-sensitized solar cell is provided.

As described above, by using the photoelectrode manufactured by the above-described method for manufacturing a photoelectrode for a dye-sensitized solar cell, a dye-sensitized solar cell having excellent energy conversion efficiency can be manufactured. .

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a photoelectrode for a dye-sensitized solar cell and a method for manufacturing a dye-sensitized solar cell according to the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding parts will be denoted by the same reference characters, without redundant description.

First, the basic structure of the photoelectrode for a dye-sensitized solar cell and the dye-sensitized solar cell manufactured according to the present invention will be described. FIG. 1 is a schematic cross-sectional view showing an example of a photoelectrode manufactured by the method for manufacturing a photoelectrode for a dye-sensitized solar cell according to the present invention. FIG. 2 shows a region 1 shown in FIG.
It is a typical expanded sectional view of the part of 00. FIG. 3 is a schematic cross-sectional view showing an example of a dye-sensitized solar cell manufactured by the method for manufacturing a dye-sensitized solar cell of the present invention.

Photoelectrode 1 for dye-sensitized solar cell shown in FIG.
0 is mainly a semiconductor electrode 2 having a light receiving surface F2;
And the transparent electrode 1 disposed adjacent to the light receiving surface F2 of the semiconductor electrode 2. The dye-sensitized solar cell 20 illustrated in FIG. 3 mainly includes the photoelectrode 10 illustrated in FIG. 1, the counter electrode CE, and the spacer S.
0 and the electrolyte E filled in the gap formed between the counter electrode CE. The semiconductor electrode 2 of the photoelectrode 1 is in contact with the electrolyte E on the back surface F22 side.

In this dye-sensitized solar cell 20, electrons are generated in the semiconductor electrode 2 by the light that passes through the transparent electrode 1 and irradiates the semiconductor electrode 2. Then, the electrons generated in the semiconductor electrode 2 are collected by the transparent electrode 1 and taken out.

The structure of the transparent electrode 1 is not particularly limited, and a transparent electrode mounted on a usual dye-sensitized solar cell can be used. For example, the transparent electrode 1 shown in FIGS.
Has a configuration in which a transparent conductive film 3 for transmitting light is coated on the side of the semiconductor electrode 2 of a transparent substrate 4 such as a glass substrate. As the transparent conductive film 3, a transparent electrode used for a liquid crystal panel or the like may be used. For example, fluorine-doped SnO ₂ coated glass, ITO coated glass,
ZnO: Al coated glass and the like can be mentioned. Further, a metal electrode having a structure in which light can be transmitted, such as a mesh or a stripe, may be provided on the substrate 4 such as a glass substrate.

As the transparent substrate 4, a transparent substrate used for a liquid crystal panel or the like may be used. Specific examples of the transparent substrate material include a transparent glass substrate, a substrate in which light reflection is prevented by appropriately roughening the surface of the glass substrate, and a substrate that transmits light such as a frosted glass-like translucent glass substrate.
The material may not be glass as long as it transmits light, and may be a transparent plastic plate, a transparent plastic film, an inorganic transparent crystal, or the like.

As shown in FIG. 2, the semiconductor electrode 2 mainly includes the porous semiconductor particles P1 and the porous semiconductor particles P1.
And the sensitizing dye P2 adsorbed on the surface of the polymer. The semiconductor that is a constituent material of the semiconductor electrode 2 is not particularly limited, and an oxide semiconductor, a sulfide semiconductor, or the like can be used. Examples of the oxide semiconductor include TiO ₂ , ZnO, SnO ₂ , Nb ₂ O ₅ , In ₂ O ₃ ,
WO ₃ , ZrO ₂ , La ₂ O ₃ , Ta ₂ O ₅ , SrTiO ₃ ,
BaTiO ₃ or the like can be used. As the sulfide semiconductor, for example, CdS or the like can be used. In addition to the above semiconductors, Si, GaAs, and the like can be used.

The sensitizing dye P2 contained in the semiconductor electrode 2 is not particularly limited, and may be any dye having absorption in a visible light region and / or an infrared light region.
As the sensitizing dye P2, a metal complex, an organic dye, or the like can be used. As the metal complex, copper phthalocyanine, metal phthalocyanine such as titanyl phthalocyanine,
Chlorophyll or its derivatives, hemin, ruthenium,
Osmium, iron and zinc complexes (eg, cis-dicyanate-bis (2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium (II)) and the like.
As the organic dye, metal-free phthalocyanine, cyanine dye, metalocyanine dye, xanthene dye, triphenylmethane dye and the like can be used.

Further, the thickness of the semiconductor electrode 2 is 5 to 30 μm.
m, more preferably 5 to 15 μm, even more preferably 8 to 13 μm.
When the thickness of the semiconductor electrode is less than 5 μm, the amount of dye adsorbed decreases, and the tendency for light to be unable to be absorbed effectively increases. On the other hand, when the thickness of the semiconductor electrode exceeds 30 μm, the electric resistance increases, the loss amount of carriers injected into the semiconductor increases, and the ion diffusion resistance increases. I ₃ by electron injection from ^{- -} after I for dye out of the counter electrode is inhibited, the output characteristics of the battery becomes large tends to decrease.

The counter electrode CE is not particularly limited, and may be the same as the counter electrode usually used for a silicon solar cell, a liquid crystal panel, or the like. For example, it may have the same configuration as the above-mentioned transparent electrode 1. A metal thin film electrode such as Pt is formed on the same transparent conductive film 3 as the transparent electrode 1, and the metal thin film electrode is placed on the electrolyte E side. It may be arranged to face. Also, a small amount of platinum may be adhered to the transparent conductive film 3 of the transparent electrode 1, or a metal thin film such as platinum or a conductive film such as carbon may be used.

Further, the composition of the electrolyte E is also photo-excited and
Redox to reduce dye after electron injection into chromium
There is no particular limitation as long as it contains the original species.^-/ I_Three ^-etc
Iodine-based redox solution containing a redox species of
Used. Specifically, I ^-/ I_Three ^-The system electrolyte is iodine
Ammonium iodide and lithium iodide and iodine
Mixtures and the like can be used. Other, Br
^-/ Br_Three ^-System, quinone / hydroquinone system, etc.
Electrolytes such as acetonitrile, propylene carbonate, and ethylene
Electrochemically inert solvents such as carbonates (and
And a mixed solvent thereof can also be used.

The constituent material of the spacer S is not particularly limited, and for example, silica beads or the like can be used.

Next, the method for manufacturing the dye-sensitized solar cell photoelectrode of the present invention and the dye-sensitized solar cell photoelectrode 10 of the present invention will be described with reference to the dye-sensitized solar cell photoelectrode 10 and the dye-sensitized solar cell 20 shown in FIG. A method for manufacturing a solar cell will be described.

As described above, the method for producing a photoelectrode for a dye-sensitized solar cell according to the present invention comprises the following steps: 1) in water or in an electrolyte solution, on the back surface opposite to the light-receiving surface of the semiconductor electrode;
A surface treatment step of irradiating electromagnetic waves in a wavelength region of 180 to 450 nm (hereinafter, referred to as “surface treatment step 1”), or
2) constituting an electrochemical cell having a semiconductor electrode as a working electrode,
A surface treatment step of applying an electromagnetic wave in a wavelength region of 180 to 450 nm to the back surface opposite to the light receiving surface of the semiconductor electrode while applying a bias voltage to the semiconductor electrode in water or in an electrolyte solution (hereinafter referred to as “surface treatment”). Process 2 ”)
And a dye adsorbing step of adsorbing the sensitizing dye on the back surface F22 of the semiconductor electrode obtained through any one of these surface treatment steps.

The method for producing a photoelectrode for a dye-sensitized solar cell of the present invention may include the above-mentioned surface treatment step 1 or surface treatment step 2 and a dye adsorption step, and the other production steps are not particularly limited. Not done. Further, the method for producing a dye-sensitized solar cell of the present invention is a method for producing a dye-sensitized solar cell using the photoelectrode produced by the method for producing a photoelectrode for a dye-sensitized solar cell described above. Other manufacturing steps are not particularly limited.

Hereinafter, the surface treatment step 1 or the surface treatment step 2
Electrode 1 not adsorbing sensitizing dye for use in
An example of a manufacturing method of No. 0 will be described.

First, when the transparent electrode 1 is manufactured, the above-mentioned fluorine-doped SnO _{2 is formed} on a substrate 4 such as a glass substrate.
And the like can be formed by a known method such as spray coating the transparent conductive film 3.

Next, on the transparent conductive film 3 of the transparent electrode 1, Ti
The semiconductor electrode 2 can be formed by evaporating a semiconductor such as O ₂ into a film. As a method of depositing a semiconductor on the transparent conductive film 3 in a film form, a known method can be used. For example, electron beam evaporation, resistance heating evaporation,
A physical vapor deposition method such as sputter vapor deposition or cluster ion beam vapor deposition may be used, and a metal or the like is evaporated in a reactive gas such as oxygen and a reaction vapor deposition method is used to deposit a reaction product on the transparent conductive film 3. Is also good. Further, a chemical vapor deposition method such as CVD can be used by controlling the flow of a reaction gas.

Next, after a semiconductor vapor deposition film to be the semiconductor electrode 2 is formed on the transparent conductive film 3, a heat treatment is applied to the semiconductor vapor deposition film under a predetermined temperature condition as needed to cause a phase transition. Is also good. Thus, for example, when the semiconductor vapor-deposited film is formed in an amorphous phase, it can be crystallized to be an anatase phase. As a result, the efficiency of injecting electrons from the dye into the semiconductor is improved by the formation of a clear band structure by crystallization, the growth of the crystal grains of the semiconductor and the accompanying improvement in the connectivity between the crystal grains, or the semiconductor vapor deposition. The movement of electrons in the film is facilitated, and the energy conversion efficiency can be further improved. Furthermore,
When the above heat treatment is performed in a non-oxidizing atmosphere, a semiconductor vapor-deposited film having a large amount of oxygen vacancies can be obtained, and the electrical conductivity of the semiconductor vapor-deposited film can be increased, so that the energy conversion efficiency can be further improved.

Another method for forming the semiconductor electrode 2 on the transparent conductive film 3 of the transparent electrode 1 is as follows. That is, first, a dispersion liquid in which porous semiconductor particles P1 such as titanium oxide (having an average particle diameter of about 1 to 1000 nm, preferably 1 to 100 nm) is prepared. The solvent of the dispersion is not particularly limited as long as the porous semiconductor particles P1 can be dispersed, such as water, an organic solvent, or a mixed solvent of both. Further, a surfactant and a viscosity modifier may be added to the dispersion as needed. Next, the dispersion is applied on the transparent conductive film 3 of the transparent electrode 1 and then dried. As a coating method at this time, a bar coater method, a printing method, or the like can be used. Then, after drying, the semiconductor electrode 2 (porous semiconductor film) is formed by heating and baking in air, an inert gas or nitrogen. The firing temperature at this time is preferably 300 to 800 ° C. Firing temperature 300
If the temperature is lower than 0 ° C., the adhesion between the porous semiconductor particles P1 and the adhesion to the substrate are weakened, and the strength is not sufficient. If the firing temperature exceeds 800 ° C., the adhesion between the semiconductor particles P1 proceeds,
The surface area of the semiconductor electrode 2 (porous semiconductor film) is reduced.

Next, the surface treatment step 1 in the present invention will be described. FIG. 4 is a process chart showing an example of the above-described surface treatment process 1. As shown in FIG.
In the above, the electrolyte solution E10 is placed in a container 30 that can transmit electromagnetic waves in a wavelength region of 180 to 450 nm, and the photoelectrode 10 containing no sensitizing dye P2 is further immersed therein. Then, while irradiating the ultrasonic wave US into the electrolyte solution E10, the back surface F of the semiconductor electrode 2 constituting the photoelectrode 10 is formed.
An electromagnetic wave in a wavelength region of 180 to 450 nm is irradiated toward 22. Thereby, on the back surface F22 of the semiconductor electrode 2, the impurities I2 (R) such as organic substances that inhibit the photoelectric conversion reaction contained in the semiconductor electrode 2 are oxidized to become oxidation products I2 (Ox) such as carbon dioxide, and Electrode 2
It is removed from the inside into the electrolyte solution E10. At this time, on the back surface F22, an oxidation reaction of water in the electrolyte solution E10 also occurs, and oxygen may be generated.

The light source of the electromagnetic wave includes, for example, a metahalide lamp, sunlight, a high-pressure mercury lamp, a xenon lamp, and the like. Further, the irradiation intensity of the electromagnetic wave applied per unit area of the back surface F22 is 1 mW / cm.
It is preferably ^{2 to} 50 W / cm ² . Irradiation intensity is 1
If it is less than mW / cm ² , the oxidation reaction may not proceed sufficiently. On the other hand, the irradiation intensity is also 50 W / cm ²
If it exceeds, the electrolyte may be heated and evaporated. The processing temperature when performing this surface treatment step 1 is 5
To 100 ° C, more preferably 40 to 80 ° C. If the processing temperature exceeds 100 ° C., an excessive oxidation reaction occurs. If the processing temperature is lower than 5 ° C., the oxidation reaction may not proceed sufficiently.

Examples of the oscillation source of the ultrasonic wave US include an ultrasonic homogenizer and an ultrasonic cleaner. In addition, from the viewpoint of the semiconductor electrode irradiation area, ultrasonic US
Is preferably 10 to 500 W, and 2
It is preferably 0 to 200 W. Further, from the viewpoint of cavity generation, the frequency of the ultrasonic wave US is 20 to 150.
Preferably, it is kHz. As described above, in the surface treatment step 1, the ultrasonic wave US10 may not be applied, and only the electromagnetic wave may be applied.

The electrolyte solution E10 is not particularly limited as long as impurities that inhibit the photoelectric conversion reaction are sufficiently removed. For example, acetonitrile and propylene carbonate can be used. Further, a liquid obtained by mixing ion-exchanged water with acetonitrile, propylene carbonate, or the like may be used. Further, as described above, in the surface treatment step 1, water such as ion-exchanged water may be used instead of the electrolyte solution E10.

Next, an example of the surface treatment step 2 in the present invention will be described. FIG. 5 is a process chart showing an example of the surface treatment process 2. As shown in FIG.
In, the electrolyte solution E20 is placed in a container 32 that can transmit electromagnetic waves in a wavelength range of 180 to 450 nm. Then, the reference electrode RE connected to the potentiostat 40, the counter electrode CE10, and the photoelectrode 10 containing no sensitizing dye P2 are immersed in the electrolyte solution E20,
An electrochemical cell 50 having the photoelectrode 10 (semiconductor electrode 2) as a working electrode is configured.

Then, while activating the potentiostat 40 to apply a bias voltage to the semiconductor electrode 2 and irradiating the ultrasonic wave US into the electrolyte solution E10, the photoelectrode 10
180 to the back surface F22 of the semiconductor electrode 2 constituting
An electromagnetic wave in a wavelength region of 450 nm is irradiated. In the potentiostat 40, a potential control circuit in which the reference electrode RE and the photoelectrode 10 (semiconductor electrode 2) are connected, and a photoelectrode 10
There is provided a current measurement circuit in which the (semiconductor electrode 2) and the counter electrode CE10 are connected. Thereby, the semiconductor electrode 2
Most of the current corresponding to the oxidation reaction mainly occurring on the back surface of the substrate flows through the counter electrode CE10, and the potential control circuit precisely controls the potential of the photoelectrode 10 (semiconductor electrode 2) with respect to the reference electrode RE according to a predetermined bias voltage value. Is done.

As a result, on the back surface F22 of the semiconductor electrode 2, the impurities I2 (R) such as organic substances that inhibit the photoelectric conversion reaction contained in the semiconductor electrode 2 are oxidized to become oxidation products I2 (Ox) such as carbon dioxide. Is removed from the semiconductor electrode 2 into the electrolyte solution E10. At this time, an oxidation reaction of water in the electrolyte solution E10 also occurs on the back surface F22, and oxygen may be generated. On the other hand, on the counter electrode CE, a reduction reaction corresponding to the oxidation reaction on the back surface F22 proceeds, for example, water or hydrogen ions in the electrolyte solution E10 are reduced to generate hydrogen and the like.

In this surface treatment step 2, irradiation conditions (light source, irradiation intensity) of the electromagnetic wave irradiating the back surface F22 of the semiconductor electrode 2, treatment temperature, irradiation conditions of the ultrasonic wave US (oscillation source,
The conditions such as the oscillation output and the frequency) are the same as those in the surface treatment step 1 described above.
Is the same as In this surface treatment step 2,
Similarly to the surface treatment step 1, the ultrasonic wave US10 may not be applied, and only the electromagnetic wave may be applied.

Here, the working electrode (semiconductor electrode 2)
And a case where a so-called three-electrode electrochemical cell 50 composed of a reference electrode RE and a counter electrode CE10 is used. In the surface treatment step 2, a counter electrode serving as both a working electrode (semiconductor electrode) and a reference electrode is used. And a so-called two-electrode electrochemical cell composed of

The same electrolyte solution E10 as that used in the surface treatment step 1 can be used. Further, in this surface treatment step 2, as in the case of the surface treatment step 1, water such as ion-exchanged water may be used instead of the electrolyte solution E10.

Next, the dye adsorption step in the present invention will be described. In the dye adsorption step, the dye is sensitized by incorporating the sensitizing dye P2 into the semiconductor electrode 2 (semiconductor vapor deposition film) obtained through the surface treatment step 1 or the surface treatment step 2 by a known method such as an immersion method. This is a step of completing the photoelectrode 10 for a sensitive solar cell. The sensitizing dye P2 may be attached (such as chemical adsorption, physical adsorption, or deposition) to the back surface F22 of the oxidized semiconductor electrode 2 in the above-described surface treatment step 1 or surface treatment step 2. As the attachment method, for example, a method of immersing the back surface F22 of the semiconductor electrode 2 in a solution containing a dye can be used. At this time, the adsorption and deposition of the sensitizing dye can be promoted by heating and refluxing the solution. At this time, in addition to the dye, a metal such as silver or a metal oxide such as alumina may be contained in the semiconductor electrode 2 (semiconductor vapor deposition film) as necessary.

The photoelectrode for a dye-sensitized solar cell has its photoelectric conversion depending on the amount of the sensitizing dye P2 adsorbed on the semiconductor electrode 2 (porous semiconductor film) constituting the photoelectrode, the bonding state thereof, the fine structure of the surface, and the like. Although the efficiency is affected, the back surface F22 of the semiconductor electrode 2 is subjected to the surface treatment step 1 or the surface treatment step 2 so that the back surface F22 of the semiconductor electrode 2 has a fine surface structure advantageous for the photoelectric conversion reaction, the amount of the sensitizing dye P2, and the bonding thereof State.

After the photoelectrode 10 is manufactured in this manner, a counter electrode CE is manufactured by a known method, and the counter electrode CE is assembled with the photoelectrode 10 and the spacer S as shown in FIG.
The inside is filled with the electrolyte E, and the dye-sensitized solar cell 20 is completed.

[0054]

EXAMPLES Hereinafter, the method for producing a photoelectrode for a dye-sensitized solar cell and the method for producing a dye-sensitized solar cell according to the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the embodiment.

(Example 1) FIG.
To produce a dye-sensitized solar cell photoelectrode having the same configuration as the dye-sensitized solar cell photoelectrode 10 shown in
Using a dye-sensitized solar cell photoelectrode, a 100 mm-thick structure having the same configuration as the dye-sensitized solar cell 20 shown in FIG.
A dye-sensitized solar cell having a scale of 100 mm was manufactured.

First, TiO ₂ particles (average particle size: 25 to 2)
(00 nm) in a nitric acid solution and stirred to prepare a titania slurry. Next, a cellulosic binder was added as a thickener to the titania slurry and kneaded to prepare a paste. On the other hand, a transparent electrode in which a fluorine-doped SnO ₂ conductive film (thickness: 500 nm) was formed on a glass substrate was prepared. Then, the paste described above was screen-printed on the SnO ₂ conductive film, and then dried. Then, it baked under the conditions of 450 degreeC in air. By repeating this screen printing and baking, a semiconductor electrode made of TiO ₂ (area of the light receiving surface; 90 mm × 90 mm, layer thickness: 20 μm) is formed on the SnO ₂ conductive film, and does not contain a sensitizing dye. A photoelectrode was prepared.

Next, the back surface of the semiconductor electrode was oxidized according to the above-described surface treatment step 1. That is, FIG.
First, the photoelectrode was immersed in ion-exchanged water. Next, the temperature of the ion-exchanged water is maintained at 50 ° C., and ultrasonic waves (output: 150 W, frequency: 100 KHz)
While irradiating an electromagnetic wave (light source: 500 W high-pressure mercury lamp, irradiation intensity: 100 mW
/ Cm ² ).

Next, a dye was adsorbed on the back surface of the oxidized semiconductor electrode as follows. First, a solution of ruthenium complex [cis-Di (thiocyanato) -N, N'-bis (2,
2'-bipyridyl-4,4'dicarboxylic acid) -ruthenium (I
I)] was dissolved at a concentration of 3 × 10 ⁻⁴ mol / L to prepare a ruthenium complex solution. Next, the semiconductor electrode is immersed in this solution,
Left for 0 hours. As a result, the ruthenium complex serving as a dye was adsorbed on the semiconductor electrode at about 1.5 × 10 ⁻⁷ mol / cm ² . Next, in order to improve the open-circuit voltage Voc, the semiconductor electrode after the adsorption of the ruthenium complex was immersed in an acetonitrile solution for 15 minutes, and then dried in a nitrogen gas stream maintained at 25 ° C. to complete the photoelectrode 10.

Next, as a counter electrode, a platinum electrode (thickness of Pt thin film: 500
nm), and an iodine-based redox solution containing iodine and lithium iodide was prepared as the electrolyte E. Further, a spacer S (trade name: “Surlyn”) manufactured by Dupont and having a shape corresponding to the size of the semiconductor electrode is prepared, and as shown in FIG. The dye-sensitized solar cell was completed by filling the inside with the above-mentioned electrolyte.

Example 2 A photoelectrode for a dye-sensitized solar cell similar to that of Example 1 except that the oxidation treatment of the back surface of the semiconductor electrode was performed in the following manner in accordance with the above-mentioned surface treatment step 2 A dye-sensitized solar cell was manufactured in the same manner as in Example 1.

That is, as shown in FIG. 3, first, a reference electrode, a counter electrode, and a photoelectrode containing no sensitizing dye connected to a potentiostat were immersed in an aqueous solution of sodium sulfate. An electrochemical cell having a photoelectrode (semiconductor electrode) as a working electrode was configured. The reference electrode is A
g-AgCl electrodes ([Cl ^-]: saturated, saturated KCl aqueous solution) was used, a counter electrode was a platinum wire. Then, the potentiostat is operated, and the potential of the semiconductor electrode with respect to the reference electrode becomes 0.2 V vs. the potential of the semiconductor electrode. An electromagnetic wave was applied to the back surface of the semiconductor electrode under the same conditions as in Example 1 while applying a bias voltage to the semiconductor electrode so that Ag-AgCl was obtained.

Here, the potential of the above-mentioned semiconductor electrode is a value previously obtained from the following experimental data, and it is necessary to sufficiently oxidize and remove impurities contained in the semiconductor material (TiO ₂ ) constituting the semiconductor electrode. Is a possible value. Hereinafter, experimental data for determining the potential range of the semiconductor electrode capable of oxidizing impurities will be described.

FIG. 6 shows the results of measurement while applying a bias voltage while changing the bias voltage to the photoelectrode manufactured by the same method as the manufacturing method of the second embodiment. 5 is a graph showing an example of a current-potential characteristic curve of a photoelectrode. In this case, an electrochemical cell connected to a potentiostat having the same configuration as described above was used, and the irradiation conditions of the electromagnetic wave were the same as above. As shown in FIG. 6, when the potential of the semiconductor electrode with respect to the reference electrode is increased from the negative side to the positive side,
When the potential of the semiconductor electrode is about -0.5 Vvs. Ag-AgCl
It can be observed that the photocurrent sharply increases from the potential region beyond. From this, the potential of the semiconductor electrode becomes about-
0.5Vvs. It can be seen that impurities in the semiconductor electrode are oxidized and removed in the potential region exceeding Ag-AgCl. When the potential of the semiconductor electrode is 0.2 Vvs. A
In the case of g-AgCl, the photocurrent was maximized, and it was found that the oxidation reaction of impurities in the semiconductor electrode proceeded most efficiently near this potential.

(Example 3) A photoelectrode for a dye-sensitized solar cell and a dye-sensitized solar cell similar to those in Example 1 except that the oxidation treatment of the back surface of the semiconductor electrode was performed as follows. It was manufactured by the same manufacturing method as in Example 1.

The oxidation treatment of the back surface of the semiconductor electrode was performed under the same conditions as in Example 1 except that no ultrasonic wave was applied. That is, the same photoelectrode as in Example 1 was first immersed in ion-exchanged water. Next, the temperature of the ion-exchanged water was maintained at 50 ° C., and an electromagnetic wave (light source; high-pressure mercury lamp of 500 W, irradiation intensity;
0 mW / cm ² ).

(Example 4) A photoelectrode for a dye-sensitized solar cell and a dye-sensitized solar cell similar to those in Example 1, except that the back surface of the semiconductor electrode was oxidized as follows. It was manufactured by the same manufacturing method as in Example 1.

The oxidation treatment of the back surface of the semiconductor electrode was performed under the same conditions as in Example 1 except that ultrasonic waves were not applied and an electrolyte solution was used instead of ion-exchanged water. That is, first, an aqueous sodium sulfate solution (solute concentration; 0.1 mol / L) was prepared as an electrolyte solution, and the same photoelectrode as in Example 1 was immersed in this electrolyte solution. Next, the temperature in the electrolyte solution was maintained at 50 ° C., and an electromagnetic wave (light source; high-pressure mercury lamp of 500 W, irradiation intensity; 100 mW / cm ² ) was irradiated toward the back surface of the semiconductor electrode.

(Example 5) A photoelectrode for a dye-sensitized solar cell and a dye-sensitized solar cell similar to those in Example 1, except that the back surface of the semiconductor electrode was oxidized as follows. It was manufactured by the same manufacturing method as in Example 2.

The oxidation treatment of the back surface of the semiconductor electrode was performed under the same conditions as in Example 2 except that the ultrasonic wave was further irradiated under the same conditions as in Example 1. That is,
First, an aqueous sodium sulfate solution was prepared as an electrolyte solution. Then, the reference electrode connected to the potentiostat, the counter electrode, and the photoelectrode containing no sensitizing dye were immersed in an aqueous sodium sulfate solution, and the same as in Example 2 in which the photoelectrode was used as a working electrode. An electrochemical cell was constructed. Then, the potentiostat is operated, and the potential of the semiconductor electrode with respect to the reference electrode becomes 0.2 V vs. the potential of the semiconductor electrode. Ag-AgC
Under the same conditions as in Example 1, an electromagnetic wave and an ultrasonic wave were applied to the back surface of the semiconductor electrode while applying a bias voltage to the semiconductor electrode so as to obtain l.

Comparative Example 1 A photoelectrode for a dye-sensitized solar cell and a dye-sensitized solar cell as in Example 1 were prepared in the same manner as in Example 1 except that the oxidation treatment of the back surface of the semiconductor electrode was not performed.
It was manufactured by the same manufacturing method as described above.

(Comparative Example 2) A dye-sensitized solar cell similar to that of Example 1 was manufactured by the same method as that of Example 1 except that an electromagnetic wave having a wavelength of 650 nm was irradiated in the oxidation treatment of the back surface of the semiconductor electrode. A photoelectrode for use and a dye-sensitized solar cell were produced.

Note that, in addition to the above-mentioned Comparative Example 2, the same manufacturing method as that of Example 1 was employed except that the back surface of the semiconductor electrode was irradiated with an electromagnetic wave having a wavelength exceeding 450 nm in the oxidation treatment. Similar photoelectrodes for dye-sensitized solar cells and dye-sensitized solar cells were prepared and subjected to a battery characteristic test described later. The characteristics were almost the same as those of Comparative Example 2 described above.

[Battery Characteristics Test] A battery characteristics test was performed.
The energy conversion efficiencies η of the dye-sensitized solar cells of Examples 1 to 5 and Comparative Examples 1 and 2 were measured. The battery characteristic test was performed by irradiating 1000 W / m ² pseudo sunlight from a xenon lamp through an AM filter using a solar simulator. The current-voltage characteristics were measured using an IV tester, and the open-circuit voltage (Voc / V),
Short circuit current (Isc / mA · cm ⁻² ), Fill factor (FF)
And energy conversion efficiency (η /%). Table 1 shows the results.

[0074]

[Table 1]

As is evident from the results shown in Table 1, the energy conversion efficiencies of the dye-sensitized solar cells of Examples 1 to 5 are shown in Comparative Examples 1 and 2 corresponding to the respective dye-sensitized solar cells. The value was higher than the energy conversion efficiency η of the solar cell.

[0076]

As described above, according to the present invention,
Since impurities that inhibit the photoelectric conversion reaction contained in the semiconductor material forming the semiconductor electrode can be sufficiently oxidized and removed, a photoelectrode for a dye-sensitized solar cell having excellent photoelectric conversion efficiency can be obtained. In addition, by using a photoelectrode for a dye-sensitized solar cell having excellent photoelectric conversion efficiency, a dye-sensitized solar cell having excellent energy conversion efficiency can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a photoelectrode manufactured by a method for manufacturing a photoelectrode for a dye-sensitized solar cell according to the present invention.

FIG. 2 is a schematic enlarged sectional view of a portion of a region 100 shown in FIG.

FIG. 3 is a schematic cross-sectional view showing one example of a dye-sensitized solar cell manufactured by the method for manufacturing a dye-sensitized solar cell of the present invention.

FIG. 4 is a process chart showing an example of a surface treatment step of the method for producing a photoelectrode for a dye-sensitized solar cell of the present invention.

FIG. 5 is a process chart showing another example of the surface treatment step shown in FIG. 4;

6 is a graph showing current-potential characteristic curves of a photoelectrode in a case where an electromagnetic wave is irradiated and a case where an electromagnetic wave is not irradiated, which is measured while applying a bias voltage to a photoelectrode in the surface treatment step shown in FIG. It is a graph which shows an example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transparent electrode, 2 ... Semiconductor electrode, 3 ... Transparent conductive film, 4 ...
Substrate, 10: photoelectrode for dye-sensitized solar cell, 20: dye-sensitized solar cell, 30, 32: container, 40: potentiostat, 50: electrochemical cell, 100: dye-sensitized solar cell Partial area of the photoelectrode 10, C1... Current-potential characteristic curve of the photoelectrode when irradiating ultraviolet rays, C2... Current-potential characteristic curve of the photoelectrode in the dark, CE... Counter electrode of the dye-sensitized solar cell 20, CE10. A counter electrode of the electrochemical cell 50,
E: electrolyte of the dye-sensitized solar cell 20, E10: electrolyte solution, E20: electrolyte solution of the electrochemical cell 50, F1,
F2, F3, light receiving surface, F22, back surface of semiconductor electrode 2,
I2 (R): impurity, I2 (Ox): impurity I2 (R)
L10: electromagnetic wave, P1: porous semiconductor particles, P2: sensitizing dye, RE: reference electrode, S: spacer, US10: ultrasonic wave.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuo Higuchi 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. (72) Inventor Hirozumi Higashi Hirozumi, Aichi-gun, Aichi-gun 41, Chuchu-Yokomichi, Toyota Chuo Research Institute, Inc. (72) Inventor Tomomi Motohiro 41, Nagakute-machi, Aichi-gun, Aichi Prefecture, Nagatochi-Yokomichi 41 Toyota Central Research Institute, Inc. (72) Inventor Shungo Fukumoto 2-1, 1-1 Asahi-machi, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Tomoyuki Toyama 2-1-1 Asahi-machi, Kariya-shi, Aichi Aisin Seiki Co., Ltd. 2-1-1 Asahimachi Aisin Seiki Co., Ltd. F-term (reference) 5F051 AA14 CB30 FA02 FA03 FA04 GA03 5H032 AA06 AS16 BB05 BB07 BB1 0 CC11 CC16 CC17 EE16 EE17 HH07 HH08

Claims (4)

[Claims] 1. A method for manufacturing a photoelectrode for a dye-sensitized solar cell, comprising: a semiconductor electrode having a light receiving surface; and a transparent electrode disposed adjacent to the semiconductor electrode on the light receiving surface. Or, in an electrolyte solution, a surface treatment step of irradiating an electromagnetic wave in a wavelength region of 180 to 450 nm on a back surface of the semiconductor electrode opposite to the light receiving surface, and the back surface of the semiconductor electrode obtained by the surface treatment process A method for adsorbing a sensitizing dye to a photoelectrode for a dye-sensitized solar cell. 2. A method of manufacturing a photoelectrode for a dye-sensitized solar cell, comprising: a semiconductor electrode having a light receiving surface; and a transparent electrode disposed adjacent to the semiconductor electrode on the light receiving surface. An electrochemical cell having a semiconductor electrode as a working electrode,
In water or in an electrolyte solution, while applying a bias voltage to the semiconductor electrode, a back surface opposite to the light receiving surface of the semiconductor electrode, a surface treatment step of irradiating an electromagnetic wave in a wavelength region of 180 to 450 nm, A method of adsorbing a sensitizing dye to the back surface of the semiconductor electrode obtained by a surface treatment step, a method of manufacturing a photoelectrode for a dye-sensitized solar cell, the method comprising: 3. The method for manufacturing a photoelectrode for a dye-sensitized solar cell according to claim 1, wherein an ultrasonic wave is further applied in the surface treatment step. 4. A semiconductor device comprising: a semiconductor electrode having a light-receiving surface; a photoelectrode having a transparent electrode disposed adjacent to the semiconductor electrode on the light-receiving surface; and a counter electrode, wherein the semiconductor electrode and the counter electrode are provided. And a method for producing a dye-sensitized solar cell, wherein the photoelectrode is disposed opposite to each other via an electrolyte, wherein the photoelectrode is a method for producing a photoelectrode for a dye-sensitized solar cell according to claim 1. A method for producing a dye-sensitized solar cell, characterized by comprising: