JP4777592B2 - Counter electrode and dye-sensitized solar cell having the same - Google Patents

Description

【０１０３】
表１に示した結果から明らかなように、多孔質膜を形成させた実施例１の対向電極を有する色素増感型太陽電池は、優れたエネルギー変換効率を有するものであることが確認された。
【０１０４】
【発明の効果】
以上説明したように、本発明の対極及び色素増感型太陽電池によれば、電解質中に存在する酸化還元対の酸化体を還元体に還元する還元反応を速やかに進行させることのできる、優れた電極特性を有する対極、及び、その対極を備えており優れたエネルギー変換効率を得ることができる色素増感型太陽電池を提供することができる。
【図面の簡単な説明】
【図１】本発明の対極の第１実施形態を示す模式断面図である。
【図２】図１に示した対極ＣＥ１を備えた色素増感型太陽電池の基本構成の一例を示す模式断面図である。
【図３】本発明の対極の第２実施形態の基本構成を示す模式断面図である。
【図４】図３に示した対極ＣＥ２を、図３におけるｙ軸方向に沿う方向からみた場合の本構成を示す模式断面図である。
【符号の説明】
１…透明電極、２…半導体電極、３…透明導電膜、４…透明基板、５…多孔質膜、５２・・・柱状組織、６・・・基板、８・・・中心軸、９・・・法線方向、１０…光電極、２０…色素増感型太陽電池、ＣＥ１、ＣＥ２…対極、Ｅ…電解質層、Ｆ１，Ｆ２，Ｆ３…受光面、Ｆ２２…半導体電極２の裏面、Ｆ５ａ・・・多孔質膜が形成している面、Ｓ…スペーサ、θ・・・基板の法線方向に対する傾き。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a counter electrode and a dye-sensitized solar cell including the counter electrode.
[0002]
[Prior art]
In recent years, various developments of solar cells have been promoted with increasing interest in global warming and energy problems. Among the solar cells, since the dye-sensitized solar cell was proposed by Gretzell et al., Its practical use is expected from the advantages such as the low cost of materials used and the fact that it can be manufactured by a relatively simple process. .
[0003]
In such a dye-sensitized solar cell, a redox pair (for example, I_Three ^-/ I^-A reduction reaction (for example, I_Three ^-I^-Therefore, there is a demand for a counter electrode having electrode characteristics capable of promptly proceeding a reduction reaction). As such a counter electrode, for example, a platinum catalyst electrode in which a platinum catalyst precursor ink is printed on a conductive substrate and then changed to a catalyst (platinum film) by heating is known (for example, JP, 2001-250595, A). In addition, as a board | substrate which has the said electroconductivity, it is ITO, SnO on board | substrates, such as glass.₂A transparent electrode on which a thin film such as ZnO is formed and a substrate made of metal such as stainless steel are known.
[0004]
[Patent Document 1]
JP 2001-250595 A
[0005]
[Problems to be solved by the invention]
However, as in the conventional counter electrode described above, the present inventors applied a platinum catalyst precursor ink on a conductive substrate and then heat-treated to form a platinum agglomerate to form a reduction catalyst film ( Even when a platinum film is provided, a redox pair (for example, I_Three ^-/ I^-A reduction reaction (for example, I_Three ^-I^-It has been found that the reduction reaction) is not sufficiently advanced and excellent electrode characteristics cannot be obtained. The present inventors have also found that a dye-sensitized solar cell having such a counter electrode has a problem that sufficient energy conversion efficiency has not yet been obtained.
[0006]
In the case of a conventional counter electrode, for example, a transparent conductive film made of transparent conductive glass is SnO.₂In the case of a film, chloroplatinic acid and a transparent conductive film SnO₂There is a problem that the film reacts to increase the resistance of the transparent conductive glass substrate to deteriorate the electrode characteristics.
[0007]
Further, the conventional counter electrode has a problem that the aggregation of platinum (Pt) particles easily occurs depending on the conditions of the heat treatment, and the reduction ability is reduced, thereby deteriorating the electrode characteristics.
[0008]
Furthermore, in the conventional counter electrode, if the heating conditions and atmosphere management at the time of manufacturing the counter electrode are not precisely adjusted, dispersion of the platinum particles in the porous film occurs, and the battery performance in each lot is reduced. There was a problem of causing a variation.
[0009]
The present invention has been made in view of the above-described problems of the prior art, and is an excellent electrode capable of promptly proceeding with a reduction reaction for reducing an oxidant of a redox pair present in an electrolyte to a reductant. It is an object of the present invention to provide a counter electrode having characteristics and a dye-sensitized solar cell including the counter electrode and capable of obtaining excellent energy conversion efficiency.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have a catalytic activity for promoting a reduction reaction of an oxidant contained in an electrolyte layer on one surface of a flat plate substrate as a counter electrode. It has been found that the reduction reaction rate at the counter electrode can be increased by forming a porous film made of a conductive material. In addition, the present inventors have formed a porous film made of a conductive metal oxide material, and further have a catalytic activity for promoting a reduction reaction of an oxidant contained in the electrolyte layer in the porous film. It has been found that the reduction reaction rate at the counter electrode can be increased by dispersing the catalyst particles made of the material having the present invention, and the present invention has been achieved.
[0011]
That is, the present invention relates to a dye-sensitized solar cell having at least a light-transmitting semiconductor electrode containing a dye having a photosensitizing action and an electrolyte layer made of an electrolytic solution containing at least a chemical species serving as a redox pair. A counter electrode disposed opposite to the semiconductor electrode via the electrolyte layer,
A flat substrate;
A porous film made of a conductive material formed on one surface of the substrate;
At least,
The conductive material provides a counter electrode characterized by having a catalytic activity for promoting a reduction reaction from an oxidant constituting the redox pair to a reductant constituting the redox pair.
[0012]
According to the present invention, by forming a porous film made of a conductive material having catalytic activity that promotes the reduction reaction of the oxidant contained in the electrolyte layer, the reduction reaction rate at the counter electrode is increased, A counter electrode having excellent electrode characteristics can be obtained. As a result, by using this counter electrode, a dye-sensitized solar cell capable of obtaining excellent energy conversion efficiency can be obtained.
[0013]
Although the reason why the reduction reaction rate at the counter electrode can be increased by forming the porous film having the above-described structure has not been clearly clarified, the conventional structure described above is obtained by using the porous film. The present inventors infer that this is because the reaction area that functions as a reduction catalyst is increased and the reduction reaction rate is increased as compared with a conductive film that is not a porous film (for example, a platinum film).
[0014]
In addition, the present inventors, in the counter electrode of the present invention, described above, chloroplatinic acid and SnO which is a transparent conductive film₂It was also confirmed that there is no problem that the resistance of the transparent conductive glass substrate increases due to the reaction with the film.
[0015]
The present inventors have also confirmed that the above-described counter electrode of the present invention does not cause the above-described problem of deteriorating electrode characteristics because the porous membrane itself functions as a catalyst.
[0016]
Furthermore, the inventors of the present invention have a good dispersion state of the platinum particles in the counter electrode of the present invention, so that the problems caused by variations in the dispersion state of the platinum particles in the porous film described above do not occur. I also confirmed that.
[0017]
Here, in the present invention, the “dye having a photosensitizing action” refers to a metal complex dye and an organic dye. The “light-transmissive semiconductor electrode” refers to a semiconductor electrode that transmits light having a wavelength of 200 nm to 10 μm. Furthermore, the “electrolytic solution” refers to an electrolyte solution or a solution obtained by adding a gelling agent to the electrolyte solution and gelling.
[0018]
The present invention also provides a dye-sensitized solar cell having at least a light-transmitting semiconductor electrode containing a dye having a photosensitizing action and an electrolyte layer made of an electrolytic solution containing at least a chemical species that serves as a redox pair. A counter electrode disposed opposite to the semiconductor electrode via the electrolyte layer,
A flat substrate;
A porous film made of a conductive metal oxide material formed on one surface of the substrate;
At least,
On the surface and / or inside of the porous membrane, catalyst particles made of a material having catalytic activity for promoting a reduction reaction from an oxidant constituting the redox pair to a reductant constituting the redox pair are dispersed. Being
Provide a counter electrode characterized by
[0019]
As described above, a porous film made of a conductive metal oxide material is formed, and further, a material having catalytic activity that promotes a reduction reaction of an oxidant contained in the electrolyte layer in the porous film. By dispersing the catalyst particles, the reduction reaction rate at the counter electrode can be increased, and a counter electrode having excellent electrode characteristics can be obtained. As a result, by using this counter electrode, a dye-sensitized solar cell capable of obtaining excellent energy conversion efficiency can be obtained.
[0020]
Although the reason for obtaining the above effect has not been clearly clarified, it is not a conventional porous film when the catalyst particles are dispersed in the conductive film by using the porous film having the above structure. The present inventors speculate that it is because it is possible to disperse a larger amount of catalyst particles than a conductive film (for example, a platinum film).
[0021]
In the case of the counter electrode having this configuration, the porous film made of a metal oxide material has light reflectivity. Therefore, also from this viewpoint, the energy conversion efficiency of the dye-sensitized solar cell can be increased by using the counter electrode having this configuration.
[0022]
In addition, the present inventors have also described the above-described chloroplatinic acid and SnO which is a transparent conductive film in the counter electrode having this configuration.₂It was also confirmed that there is no problem that the resistance of the transparent conductive glass substrate increases due to the reaction with the film.
[0023]
In addition, the present inventors have confirmed that, in the counter electrode having this configuration, the catalyst particles are dispersed on the surface and / or the inside of the porous membrane, so that the above-described problem of deteriorating the electrode characteristics does not occur. .
[0024]
Furthermore, the present inventors have found that the counter electrode having this configuration has a good dispersion state of the platinum particles, so that the problem caused by the dispersion in the dispersion state of the platinum particles in the porous film described above does not occur. Also confirmed.
[0025]
Furthermore, the present invention is a photoelectrode having a light-transmitting semiconductor electrode having a light-receiving surface and containing a dye having a photosensitizing action, and a transparent electrode disposed adjacently on the light-receiving surface;
A counter electrode disposed opposite to the semiconductor electrode;
An electrolyte layer that is disposed between the semiconductor electrode and the counter electrode, and is made of an electrolytic solution containing at least a chemical species that is a redox pair;
A dye-sensitized solar cell having at least
Provided is a dye-sensitized solar cell, wherein the counter electrode is the above-described counter electrode of the present invention.
[0026]
Thus, by using the counter electrode of the present invention described above, the reduction reaction rate at the counter electrode is increased, and a dye-sensitized solar cell having excellent energy conversion efficiency can be easily constructed.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the counter electrode and the dye-sensitized solar cell of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.
[0028]
[First Embodiment]
FIG. 1 is a schematic cross-sectional view showing a first embodiment of a counter electrode of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of the basic configuration of the dye-sensitized solar cell including the counter electrode CE1 shown in FIG. In addition, the dye-sensitized solar cell 20 shown in FIG. 2 shows a preferred embodiment of the dye-sensitized solar cell of the present invention.
[0029]
The counter electrode CE1 shown in FIGS. 1 and 2 is a redox pair (for example, I_Three ^-/ I^-A reduction reaction (for example, I_Three ^-I^-The structure described below is intended for promptly proceeding the reduction reaction).
[0030]
That is, the counter electrode CE1 has at least a flat substrate 6 and a porous film 5 formed on one surface of the substrate. The porous membrane 5 includes (1) a porous membrane made of a conductive material having catalytic activity for promoting a reduction reaction of an oxidant contained in the electrolyte layer, and (2) a metal oxide having conductivity. A porous film in which a porous film made of a material is formed, and further, catalyst particles made of a material having catalytic activity for promoting a reduction reaction of an oxidant contained in the electrolyte layer is dispersed in the porous film Are formed as a porous film.
[0031]
The porous membrane 5 has the above-described configuration (1) or (2), so that the electrode reaction in the counter electrode CE1, that is, the redox couple (for example, I_Three ^-/ I^-A reduction reaction (for example, I_Three ^-I^-(Reduction reaction to reduce to) can proceed rapidly.
[0032]
First, the porous membrane 5 having the configuration (1) will be described. The conductive material having the catalytic activity that constitutes the porous membrane 5 is preferably a metal material or a conductive carbon material. The metal material is not particularly limited, but is preferably at least one metal selected from the group consisting of transition metals. Precious metal elements (Pt, Pd, Rh, Ru, Ir, Os, Au, Ag) Is more preferable, and platinum is more preferable. Thus, when the conductive material is a metal, the light entering from the photoelectrode 10 side is reflected on the surface of the porous membrane 5 on the electrolyte layer E side, and the light utilization of the photoelectrode 10 is further improved. Can do. Further, the conductive carbon material is not particularly limited, and examples thereof include activated carbon, graphite, activated char, coke, hard carbon, carbon fiber, and soft carbon.
[0033]
Further, catalyst particles made of a material having catalytic activity for promoting the reduction reaction of the oxidant constituting the redox couple are further dispersed on the surface and / or inside of the porous membrane 5 having the structure (1). Preferably it is. In this case, the catalyst particles are preferably metal particles and / or particles made of a conductive carbon material. Such metal particles are composed of the same metal material as the porous film 5. Further, such metal particles are more preferably made of platinum. Further, the particles made of the conductive carbon material are composed of the same material as the conductive carbon material in the porous film 5.
[0034]
The particles made of the metal particles and the conductive carbon material are preferably nano-sized particles, and more preferably particles having an average particle diameter of 1 to 50 nm.
[0035]
By dispersing such metal particles having catalytic activity and / or particles made of a conductive carbon material, the reduction reaction rate at the counter electrode can be more reliably increased.
[0036]
Next, the porous membrane 5 having the configuration (2) will be described. The porous film 5 having the configuration (2) is made of a metal oxide material. Examples of such a metal oxide material include TiO 2.₂ZnO, SnO₂, Nb₂O_Five, In₂O_Three, WO_Three, SrTiO_Three, BaTiO_Three, In₂O_ThreeAnd SnO₂And ITO (indium tin oxide) or the like can be used. In these metal oxide materials, tin oxide (SnO₂), Tin oxide (SnO)₂) And indium oxide (In₂O_Three) Or indium tin oxide (ITO).
[0037]
The catalyst particles contained in the porous film 5 having the configuration (2) are preferably metal particles and / or particles made of a conductive carbon material. Such metal particles and particles made of a conductive carbon material are the same as the metal particles and particles made of a conductive carbon material contained in the porous film 5 having the configuration (1) described above. It is possible to use.
[0038]
By dispersing such metal particles having catalytic activity and / or particles made of a conductive carbon material, the reduction reaction rate at the counter electrode can be more reliably increased.
[0039]
The substrate 6 serves as a support for the porous membrane 5. The structure of the board | substrate 6 is not specifically limited, For example, you may use the thing similar to the transparent substrate 4 in the transparent electrode 1 mentioned later.
[0040]
Here, in the counter electrode CE <b> 1 shown in FIGS. 1 and 2, it is preferable that a conductive film (not shown) is further disposed between the substrate 6 and the porous film 5. By further disposing such a conductive film, it is possible to obtain more sufficient conductivity in the counter electrode CE1. The configuration of such a transparent conductive film is not particularly limited. For example, the transparent conductive film 3 described later may be used, and a conductive film made of a metal and a metal oxide conductive material may be used. It may be used.
[0041]
Next, the dye-sensitized solar cell 20 shown in FIG. 2 will be described. The dye-sensitized solar cell 20 mainly includes an electrolyte layer filled in a gap formed between the photoelectrode 10 and the counter electrode CE1 by the spacer S and the photoelectrode 10, the counter electrode CE1 of the present invention described above. E. A photoelectrode 10 shown in FIG. 2 mainly has a light-transmitting semiconductor electrode 2 having a light-receiving surface F2 and containing a dye having a photosensitizing action, and is adjacent to the light-receiving surface F2 of the semiconductor electrode 2. And the transparent electrode 1 arranged in a row. The semiconductor electrode 2 is in contact with an electrolyte layer E made of an electrolytic solution containing at least a chemical species that becomes a redox pair on the back surface F22 opposite to the light receiving surface F2.
[0042]
The dye-sensitized solar cell 20 has a photosensitizing dye (hereinafter referred to as “sensitizing dye”) that is adsorbed in the semiconductor electrode 2 by the light that passes through the transparent electrode 1 and is applied to the semiconductor electrode 2. ) Is excited, and electrons are injected from the sensitizing dye into the semiconductor electrode 2. The electrons injected in the semiconductor electrode 2 are collected in the transparent electrode 1 and taken out to the outside.
[0043]
The structure of the transparent electrode 1 is not specifically limited, The transparent electrode mounted in a normal dye-sensitized solar cell can be used. For example, the transparent electrode 1 shown in FIG. 2 has a configuration in which a so-called transparent conductive film 3 is coated on the semiconductor electrode 2 side 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.
[0044]
For example, fluorine-doped SnO₂Coated glass, ITO coated glass, ZnO: Al coated glass, antimony-doped tin oxide (SnO₂-Sb), etc. In addition, a transparent electrode obtained by doping cations or anions with different valences into tin oxide or indium oxide, or a metal electrode having a structure capable of transmitting light, such as a mesh shape or a stripe shape, provided on a substrate such as a glass substrate Good.
[0045]
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 transparent glass substrates, materials that prevent the reflection of light by appropriately roughening the surface of the glass substrate, and materials that transmit light, such as a ground glass-like translucent glass substrate. Note that 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 described above, when a transparent plastic plate and a transparent plastic film are used as the substrate, the substrate may be bent flexibly.
[0046]
The light-transmitting semiconductor electrode 2 containing a dye having a photosensitizing action shown in FIG. 2 is composed of an oxide semiconductor layer containing oxide semiconductor particles as a constituent material. The oxide semiconductor particles contained in the semiconductor electrode 2 are not particularly limited, and a known oxide semiconductor or the like can be used. As an oxide semiconductor, for example, TiO₂, ZnO, SnO₂, Nb₂O_Five, In₂O_Three, WO_Three, SrTiO_Three, BaTiO_ThreeEtc. can be used. Among these oxide semiconductors, anatase TiO₂Is preferred.
[0047]
The sensitizing dye contained in the semiconductor electrode 2 is not particularly limited as long as it is a dye having absorption in the visible light region and / or the infrared light region. More preferably, any material that emits electrons when excited by light having a wavelength of at least 200 nm to 10 μm may be used. As such a sensitizing dye, a metal complex, an organic dye, or the like can be used. Metal complexes include metal phthalocyanines such as copper phthalocyanine and titanyl phthalocyanine, chlorophyll or derivatives thereof, hemin, ruthenium, osmium, iron and zinc complexes (eg cis-dicyanate-N, N′-bis (2,2′-bipyridyl) -4,4'-dicarboxylate) ruthenium (II)) and the like. As the organic dye, metal-free phthalocyanine, cyanine dye, merocyanine dye, xanthene dye, triphenylmethane dye, and the like can be used.
[0048]
Further, the electrolyte layer E is not particularly limited as long as it is an electrolyte containing a chemical species that becomes a redox pair for reducing the dye after photoexcitation and electron injection into the semiconductor. Or a gel-like one obtained by adding a known gelling agent (polymer or low-molecular gelling agent) thereto.
[0049]
The solvent of the liquid electrolyte solution used for the electrolyte layer E is not particularly limited as long as it is a compound that can dissolve the solute component, but is electrochemically inactive, has a high relative dielectric constant, and has a low viscosity. Those dissolved in a solvent (and mixed solvents thereof) are preferable. For example, nitrile compounds such as methoxypropionitrile and acetonitrile, lactone compounds such as γ-butyrolactone and valerolactone, carbonates such as ethylene carbonate and propylene carbonate Compounds, propylene carbonate, etc. are mentioned.
[0050]
Examples of the solute of the liquid electrolyte solution used for the electrolyte layer E include an oxidation-reduction pair, a compound having an action of promoting the transfer of electrons, and the like, each of which may be contained singly or in combination. Good.
[0051]
In addition, as such a redox pair, I_Three ^-/ I^-System electrolyte, Br_Three ^-/ Br^--Based electrolytes, redox electrolytes such as hydroquinone / quinone-based electrolytes, etc., but the oxidant constituting the redox pair is I_Three ^-And the reductant constituting the redox pair is I^-I_Three ^-/ I^-When an electrolyte made of such an iodine-based redox solution is used in the electrolytic solution, the porous membrane 5 is made of platinum or a conductive carbon material, and the catalyst particles are platinum or conductive. It is preferably made of a carbon material.
[0052]
More specifically, examples of the substance constituting the redox pair include halogens such as iodine, bromine and chlorine, halides such as dimethylpropylimidazolium iodide, tetrapropylammonium iodide and lithium iodide. . Examples of additives for efficiently transferring electrons include heterocyclic compounds such as 4-t-butylpyridine.
[0053]
The constituent material of the spacer S is not particularly limited, and for example, silica beads or the like can be used.
[0054]
Further, as a sealing material used for integrating the photoelectrode 10, the counter electrode CE, and the spacer S for the purpose of sealing the electrolyte layer E, it can be sealed so that the components of the electrolyte layer E do not leak to the outside as much as possible. Any material can be used as long as it is not particularly limited. For example, an epoxy resin, a silicone resin, an ethylene / methacrylic acid copolymer, a thermoplastic resin made of surface-treated polyethylene, or the like can be used.
[0055]
Next, an example of a method for manufacturing the dye-sensitized solar cell 20 shown in FIG. 2 will be described.
[0056]
When the transparent electrode 1 is manufactured, the fluorine-doped SnO described above on the substrate 4 such as a glass substrate.₂It can form using well-known thin film manufacturing techniques, such as spray-coating the transparent conductive films 3, such as. For example, in addition to this, it can be formed using a known thin film manufacturing technique such as a vacuum deposition method, a sputtering method, a CVD method, and a sol-gel method.
[0057]
Examples of a method for forming the semiconductor electrode 2 on the transparent conductive film 3 of the transparent electrode 1 include the following methods. That is, first, a dispersion liquid in which oxide semiconductor particles having a predetermined size (for example, a particle diameter of about 10 to 30 nm) is dispersed is prepared. The solvent of this dispersion liquid is not particularly limited as long as it can disperse oxide semiconductor particles such as water, an organic solvent, or a mixed solvent of both. Moreover, you may add surfactant and a viscosity modifier to a dispersion liquid as needed.
[0058]
Next, the dispersion is applied onto 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 firing in air, inert gas or nitrogen.
[0059]
Next, a sensitizing dye is contained in the semiconductor electrode 2 by a known technique such as an adhesion method. The sensitizing dye is contained by adhering to the semiconductor electrode 2 (chemical adsorption, physical adsorption or deposition). As this adhesion method, for example, a method of immersing the semiconductor electrode 2 in a solution containing a dye can be used. At this time, adsorption and deposition of the sensitizing dye can be promoted by heating and refluxing the solution. At this time, a metal such as silver or a metal oxide such as alumina may be contained in the semiconductor electrode 2 in addition to the pigment, if necessary.
[0060]
The surface oxidation treatment for removing impurities that inhibit the energy conversion reaction contained in the semiconductor electrode 2 may be appropriately performed by a known method every time each layer is formed or when all the layers are formed. .
[0061]
Other methods for forming the semiconductor electrode 2 on the transparent conductive film 3 of the transparent electrode 1 include the following methods. That is, on the transparent conductive film 3 of the transparent electrode 1 TiO₂A method of vapor-depositing a semiconductor such as a film may be used. As a method for depositing a semiconductor on the transparent conductive film 3, a known thin film manufacturing technique can be used. For example, a physical vapor deposition method such as electron beam vapor deposition, resistance heating vapor deposition, sputter vapor deposition, or cluster ion beam vapor deposition may be used. Metal or the like is evaporated in a reactive gas such as oxygen, and the reaction product is converted into the transparent conductive film 3. A reactive vapor deposition method may be used. Furthermore, chemical vapor deposition such as CVD can be used by controlling the flow of the reaction gas.
[0062]
Next, an example of a method for manufacturing the counter electrode CE1 will be described. When the counter electrode CE1 is manufactured, for example, a method described in Japanese Patent Application Laid-Open No. 2000-231943 can be used. More specifically, a vacuum deposition method, a sputtering method, an ion method is used on a flat substrate 6. Conductive materials or conductive metal oxides by using known thin film manufacturing techniques such as physical vapor deposition such as plating and laser ablation, and chemical vapor deposition such as plasma CVD and thermal CVD A porous film 5 made of a material can be formed.
[0063]
When such a thin film is manufactured by vapor deposition, the porous material having the above-described structure is adjusted by adjusting the conditions such as the partial pressure of vapor deposition particles made of the constituent material, the partial pressure of the carrier gas, and the temperature of the substrate 6. The film 5 can be formed.
[0064]
When a transparent conductive film made of a transparent conductive material is further disposed between the substrate 6 and the porous film 5, the above-described transparent conductive material is sprayed on the substrate 6 such as a glass substrate. The porous film 5 can be formed using a known thin film manufacturing technique such as coating, and then using the above-described method. Moreover, also when forming a transparent conductive film, it is possible to use well-known thin film manufacturing techniques, such as a vacuum evaporation method, sputtering method, CVD method, and sol-gel method.
[0065]
Furthermore, as a method of dispersing metal particles having catalytic activity and / or particles made of a conductive carbon material on the surface and / or inside of the porous membrane 5, the above-described materials and precursor raw materials are water, organic It is dissolved in a solvent or a mixture thereof, and the solution is dropped on the porous membrane to adhere, and after drying, it is baked at 300 to 700 ° C. for 10 minutes to 1 hour to form particles and porous. It can be dispersed in the membrane. Formation and dispersion of such catalyst particles can be performed in the atmosphere, and the time and temperature in the heat treatment can be adjusted as appropriate.
[0066]
After the photoelectrode 10 and the counter electrode CE1 are manufactured in this manner, the photoelectrode 10 and the counter electrode CE are assembled so as to face each other via the spacer S as shown in FIG. At this time, the space defined between the photoelectrode 10 and the counter electrode CE is filled with the electrolytic solution by the spacer S, and the dye-sensitized solar cell 20 is completed.
[0067]
[Second Embodiment]
Next, a second embodiment of the counter electrode of the present invention will be described.
[0068]
FIG. 3 is a schematic cross-sectional view showing the basic configuration of the second embodiment of the counter electrode of the present invention. 4 is a schematic cross-sectional view showing this configuration when the counter electrode CE2 shown in FIG. 3 is viewed from the direction along the y-axis direction in FIG. 3 and 4 show an xyz orthogonal coordinate system having a z axis parallel to the normal direction 9 of the substrate surface of the porous film 5a for convenience of the following description. That is, FIG. 3 shows a schematic cross-sectional view of the counter electrode CE2 when cut along a plane consisting of the z-axis and the y-axis, and FIG. 4 shows the counter electrode CE2 when cut along a plane consisting of the z-axis and the x-axis. A schematic cross-sectional view is shown.
[0069]
The counter electrode CE2 shown in FIGS. 3 and 4 has the same configuration as the above-described counter electrode CE1 except for the configuration of the porous film 5a described later. The configuration of the dye-sensitized solar cell (not shown) provided with the counter electrode CE2 is the same as that of the dye-sensitized solar cell 20 shown in FIG. 2 except that the counter electrode CE2 is provided instead of the counter electrode CE1. It is. Therefore, in the following description, the counter electrode CE2 will be described. In addition, the same code | symbol is attached | subjected about the element same as the element demonstrated regarding the counter electrode CE1 shown in the above-mentioned FIG.1 and FIG.2, and the overlapping description is abbreviate | omitted.
[0070]
The porous film 5a includes (1) a porous film made of a conductive material having catalytic activity for promoting a reduction reaction of an oxidant contained in the electrolyte layer, and (2) a metal oxide material having conductivity. A porous film in which catalyst particles made of a material having catalytic activity for promoting a reduction reaction of an oxidant contained in the electrolyte layer are dispersed in the porous film, and Is formed as a porous film. The counter electrode CE2 has the same configuration as the counter electrode CE1 except that the shape of the porous film 5a is different from the porous film 5 of the counter electrode CE1 of the first embodiment described above as described below.
[0071]
That is, as shown in FIGS. 3 and 4, the porous film 5a is composed of a flat substrate 6 and a porous film 5a made of a conductive material formed on one surface F5a of the substrate. The membrane 5a is composed of a plurality of columnar structures 52 integrated so as to keep electrical contact with each other, and the plurality of columnar structures 52 are formed on the surface F5a of the substrate. Further, as shown in FIG. 3, the plurality of columnar structures 52 are formed on the substrate surface F5a so that each central axis 8 is parallel or oblique to the normal direction 9 of the substrate surface F5a. It is preferable that the inclination angles θ of the plurality of columnar structures 52 with respect to the normal direction 9 of the surface F5a of the substrate are each 80 ° or less. Furthermore, it is more preferable that each of the plurality of columnar structures 52 is formed on the substrate surface F5a so that the central axes 8 thereof are substantially parallel to each other. Here, the state “the central axis 8 is parallel or oblique to the normal direction 9 of the surface F5a of the substrate” means that the direction of the central axis 8 and the normal direction 9 are parallel (that is, the inclination angle θ is 0 state) and an oblique state (that is, a state where the inclination angle θ is inclined in the range of 0 ° <θ ≦ 80 ° and is not parallel to the normal direction 9). In the following description, the porous film 5a having the above structure is referred to as an “obliquely deposited film” for convenience, but the “obliquely deposited film” is not necessarily limited to the deposited film having such a structure. Instead, the film obtained by the oblique vapor deposition method to be described later is called “an oblique vapor deposition film”.
[0072]
As shown in FIG. 3, when the porous film 5a forms a columnar structure 52, a porous film having a large reaction surface area can be easily formed in the manufacturing process because a porous film having high porosity is easily formed. The structure can be constructed more reliably and easily. Therefore, the electrode reaction at the counter electrode CE2, that is, the reduction reaction for reducing the oxidant of the redox pair existing in the electrolyte to the reductant can be more rapidly advanced.
[0073]
The inclination angles θ of the plurality of columnar structures 52 with respect to the normal direction 9 of the substrate surface F5a are preferably 0 to 80 °, respectively. When such an inclination angle exceeds the upper limit, the mechanical strength of the porous film is lowered, the adhesion to the substrate is lowered, and the film tends to peel off.
[0074]
When the porous film 5a is made of a metal material or a metal oxide material, the structure of the surface (hereinafter referred to as “upper surface”) of the obliquely deposited film that is in contact with the electrolyte layer E has a diffraction function having the following functions. A structure having lattice stripes (patterns) is preferable. That is, the function is that light in a specific wavelength region in which the excitation level of the sensitizing dye at the time of photosensitization can be higher than the Fermi level of the semiconductor electrode 2 (more negative potential). It is a function that can selectively reflect only. The light in the specific wavelength region is not particularly limited as long as it is light having a wavelength that excites the sensitizing dye as described above, and may be light in the visible light region and / or the infrared light region, It is preferable that the light has a wavelength of at least 200 nm to 10 μm.
[0075]
As a surface structure having such a function, a so-called “blazed grating”, which is a grating having an angled grating groove so as to reflect only the light that can excite the sensitizing dye as shown in FIG. What is formed so that it may become a structure of "is preferable.
[0076]
The conductivity of the porous layer 5a (obliquely deposited film) can be adjusted by adjusting the deposition conditions.
[0077]
Next, an example of a manufacturing method of the counter electrode CE2 shown in FIGS. 3 and 4 will be described. When manufacturing the counter electrode CE2 having the porous film (obliquely deposited film) 5a shown in FIG. 3, Japanese Patent Publication No. 7-3486, Japanese Patent Publication No. 7-7130, Japanese Patent No. 2751140, Japanese Patent Laid-Open No. 4-218662. The methods described in JP-A-10-147858, JP-A-10-81955, JP-A-2000-231943, and the like can be used. More specifically, the porous film 5a is formed by an oblique vapor deposition method in which vapor deposition particles of the constituent material of the porous film are incident from a direction having a predetermined inclination with respect to the normal direction 9 of the surface of the flat substrate 6. It is possible to form.
[0078]
In the above-described oblique vapor deposition method, the incident angle θ1 (not shown) when the vapor deposition particles of the constituent material of the porous film are incident on the surface of the substrate 6 instead of being parallel to the normal direction 9 of the surface of the substrate 6 is Preferably, the angle is 30 to 80 ° with respect to the normal direction 9 of the surface. The incident angle θ1 is defined with reference to the normal direction 9 of the surface of the substrate 6 in the same manner as the inclination angle θ described above. However, the incident angle θ1 of the vapor deposition particles of the constituent material of the porous film and the inclination angle θ of the central axis 8 of the columnar structure 52 to be formed are not bound to each other, and they do not necessarily coincide with each other. Good.
[0079]
Thereby, the plurality of columnar structures 52 in the porous film 5a formed on the substrate 6 are formed on the surface F5a of the substrate 6. The counter electrode CE2 having this columnar structure has a larger surface area than the porous film 5 formed by depositing vapor deposition particles from the normal direction 9 of the surface F5a of the substrate 6, and can further increase the reduction reaction rate at the counter electrode. It becomes possible.
[0080]
When the incident angle θ1 of the vapor deposition particles is less than the lower limit value, the self-shielding effect in vapor deposition is not significant, so that a clear columnar structure 52 tends not to be formed. On the other hand, when the incident angle θ1 of the vapor deposition particles exceeds the upper limit, the porous film 5a has a very sparse structure, and there is a possibility that the mechanical strength is lowered and cannot be used. Further, since the projected area of the substrate viewed from the vapor deposition source is small, there is a tendency that the film forming speed is slow.
[0081]
As a method of causing the vapor deposition particles to enter from a direction having a predetermined inclination with respect to the normal direction 9 of the surface F5a of the substrate 6 in the oblique vapor deposition method, the substrate 6 is inclined at a predetermined angle with respect to the incident direction of the vapor deposition particles. May be tilted. Further, the substrate 6 is relatively moved at a high speed with respect to the vapor deposition particle supply source to create a relative movement of the vapor deposition particles with respect to the substrate 6, and the vapor deposition particles are inclined with respect to the normal direction 9 of the surface F <b> 5 a of the substrate 6. The oblique vapor deposition film may be formed by incidence, or two vapor deposition particle supply sources may be provided, and vapor deposition particles may be simultaneously vaporized with the incident directions of the vapor deposition particles with respect to the surface F5a of the substrate 6 being two directions.
[0082]
As a vapor deposition method for performing such oblique vapor deposition, various known vapor deposition methods can be used. For example, physical vapor deposition methods such as electron beam vapor deposition, resistance heating vapor deposition, sputter vapor deposition, and cluster ion beam vapor deposition may be used, and chemical vapor deposition methods such as plasma CVD method and thermal CVD method may be used.
[0083]
Further, during vapor deposition, the specific surface area may be increased by gradually moving the substrate or the supply source of the vapor deposition particles in a plane direction perpendicular to the incident direction of the vapor deposition particles to deposit the vapor deposition particles in a spiral shape.
[0084]
When a transparent conductive film made of a transparent conductive material is further disposed between the substrate 6 and the porous film 5a, the transparent conductive material described above is placed on the substrate 6 such as a glass substrate. The porous film 5 can be formed by using a known thin film manufacturing technique such as spray coating, and then using the method described above.
[0085]
Furthermore, as a method of dispersing metal particles having catalytic activity and / or particles made of a conductive carbon material on the surface and / or inside of the porous membrane 5, the same method as the method in the first embodiment described above is used. Is possible.
[0086]
【Example】
Hereinafter, the counter electrode and the dye-sensitized solar cell of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
[0087]
Example 1
A counter electrode having the same configuration as that of the counter electrode CE2 shown in FIG. 3 is prepared by the following procedure, and further, the counter electrode has the same configuration as that of the dye-sensitized solar cell 20 shown in FIG. 1 except that this counter electrode is used. Dye-sensitized solar cell (light-receiving surface area: 4 cm²) Was produced.
[0088]
TiO 2 was added to a liquid composed of acetylacetone, ion-exchanged water, and a surfactant (trade name; “tritonX” manufactured by Aldrich).₂Slurry (TiO2) for forming a semiconductor electrode in which particles (Degussa, trade name: “P25”) are dispersed₂Particle content: 11% by mass, TiO₂The average particle size of the particles: about 10 nm or less, referred to as slurry 1) was prepared.
[0089]
Next, a paste for forming a semiconductor electrode (hereinafter referred to as paste 1) was prepared by adding and mixing polyethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., number average molecular weight: 2000) as a thickener in slurry 1. . TiO in paste 1₂The mass ratio of particles to polyethylene glycol is TiO₂Particle: Polyethylene glycol was adjusted to be 10: 3.
[0090]
On the other hand, SnO doped with fluorine on the glass substrate 4 (transparent conductive glass)₂Transparent electrode 1 having a conductive film 3 (film thickness: 600 nm) (manufactured by Nippon Sheet Glass Co., Ltd., surface resistance: about 10 Ω / cm)², Thickness; 1 mm). And this SnO₂On the conductive film 3, the above-mentioned paste 1 was applied to a thickness of 100 μm using a doctor blade, and then dried at a temperature of 25 ° C. for 30 minutes.
[0091]
Thereafter, the transparent electrode 1 to which the paste 1 was applied was transferred into an electric furnace and baked in the atmosphere at 450 ° C. for 30 minutes. Next, the transparent electrode 1 was taken out from the electric furnace and cooled. In this way, SnO₂Semiconductor electrode 2 (light-receiving surface area; 4 cm) on conductive film 3², Thickness of layer made of semiconductor film; 8 μm, TiO₂Coating amount: 15 g / cm²) Was formed, and the photoelectrode 10 in a state containing no dye (metal complex dye and organic dye) was produced.
[0092]
Then, the pigment | dye was made to adsorb | suck to the back surface of the semiconductor electrode 2 of the photoelectrode 10 as follows. First, a ruthenium complex [cis-Di (thiocyanato) -N, N'-bis (2,2'-bipyridyl-4,4'dicarboxylic acid) -ruthenium (II)]] was used as a sensitizing dye, and this was converted to ethanol. Dissolved solution (sensitizing dye concentration; 3 × 10^-Fourmol / L) was prepared. Next, the semiconductor electrode 2 was immersed in this solution and allowed to stand for 12 hours under a temperature condition of 25 ° C. in a dark place. Next, the semiconductor electrode 2 was taken out from this solution, washed with ethanol, and naturally dried in a dark place. As a result, a sensitizing dye is about 1.2 × 10 6 inside the semiconductor electrode 2.^-7mol / cm²The adsorbed photoelectrode 10 was completed.
[0093]
Next, a counter electrode having the same shape and size as the photoelectrode 10 was produced. First, a transparent conductive glass substrate (F-doped tin oxide coated glass substrate) was placed in an oblique direction with respect to the normal line of the platinum target in a vacuum chamber of a sputtering device (device name: special-type sputtering device) (glass substrate surface). And the normal of the target was 20 degrees). Using high frequency sputtering, platinum (Pt) was obliquely deposited in an argon gas atmosphere (film forming conditions: Ar gas pressure 3 × 10^-3torr (3.99 × 10^-1Pa), input power: 30 to 100 W). A platinum (Pt) oblique vapor deposition film having a film thickness (100 nm) and inclined at an angle of 30 ° with respect to the normal direction of the substrate surface was obtained.
[0094]
Furthermore, an isopropanol solution containing chloroplatinic acid (concentration 0.005 mol / L) is dropped onto the obtained platinum oblique vapor deposition film on the platinum oblique vapor deposition film, dried, and then subjected to heat treatment at 400 ° C. for 1 hour in the atmosphere. As a result, a counter electrode for oblique deposition of platinum was obtained. The form of the obtained film was confirmed to be an oblique columnar structure as shown in FIG. 3 and a structure in which platinum nanoparticles (average particle diameter of 5 nm or less) were dispersed.
[0095]
In addition, an iodine redox solution (tetrabutylammonium iodide concentration; 0.65 mol / L, iodine concentration; 0.1 mol / L, solvent; methoxypropionitrile) was prepared as the electrolytic solution E.
[0096]
Furthermore, a spacer S (trade name: “High Milan”) manufactured by Mitsui DuPont Polychemical Co., Ltd. having a shape matched to the size of the semiconductor electrode 2 was prepared. Then, as shown in FIG. 1, the photoelectrode 10, the counter electrode CE, and the spacer S are opposed to each other, and the electrolyte solution E is filled therein by utilizing a capillary phenomenon, thereby completing a dye-sensitized solar cell. I let you.
[0097]
(Comparative Example 1)
Next, a counter electrode CE having the same shape and size as the photoelectrode 10 was produced. First, an isopropanol solution containing chloroplatinic acid (concentration 0.005 mol / L) is dropped on a transparent conductive glass, dried in the air, and then baked at 450 ° C. for 30 minutes, whereby a platinum sintered counter electrode CE is obtained. Got.
[0098]
As a counter electrode, a dye-sensitized solar cell was produced in the same procedure and conditions as in Example 1 except that the platinum sintered counter electrode was used instead of the platinum oblique deposition counter electrode.
[0099]
[Battery characteristics evaluation test]
The battery characteristic evaluation test was performed according to the following procedure, and the short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and start-up of the dye-sensitized solar cells of Example 1 and Comparative Example 1 were started. The initial energy conversion efficiency (η (%)) was measured. The energy conversion efficiency (η (%)) of the dye-sensitized solar cell is represented by the following formula (A). Here, in the following formula (A), P₀Is the incident light intensity [mWcm^-2], Voc is the open circuit voltage [V], Jsc is the short-circuit current density [mA · cm^-2], FF shows a Filling Factor.
η = 100 × (Voc × Jsc × F.F.) / P₀... (A)
[0100]
The battery characteristic evaluation test uses a solar simulator (trade name; “WXS-85-H type”, manufactured by Wacom), and the irradiation conditions of pseudo-sunlight from a xenon lamp light source through an AM filter (AM1.5), 100 mW / cm²(So-called “1Sun” irradiation condition) was performed under measurement conditions.
[0101]
About each dye-sensitized solar cell, the current-voltage characteristic was measured at room temperature using an IV tester, and the open circuit voltage (Voc / V) and short circuit current density (Jsc / mA · cm).^-2), A fill factor (F.F.) was obtained, and energy conversion efficiency η [%] was obtained from these. The obtained results are shown in Table 1.
[0102]
[Table 1]

[0103]
As is clear from the results shown in Table 1, it was confirmed that the dye-sensitized solar cell having the counter electrode of Example 1 in which the porous film was formed has excellent energy conversion efficiency. .
[0104]
【The invention's effect】
As described above, according to the counter electrode and the dye-sensitized solar cell of the present invention, the reduction reaction for reducing the oxidant of the oxidation-reduction pair present in the electrolyte to the reductant can proceed rapidly, and is excellent. It is possible to provide a counter electrode having electrode characteristics, and a dye-sensitized solar cell including the counter electrode and capable of obtaining excellent energy conversion efficiency.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a first embodiment of a counter electrode of the present invention.
2 is a schematic cross-sectional view showing an example of a basic configuration of a dye-sensitized solar cell including the counter electrode CE1 shown in FIG.
FIG. 3 is a schematic cross-sectional view showing a basic configuration of a second embodiment of a counter electrode of the present invention.
4 is a schematic cross-sectional view showing this configuration when the counter electrode CE2 shown in FIG. 3 is viewed from a direction along the y-axis direction in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Transparent electrode, 2 ... Semiconductor electrode, 3 ... Transparent electrically conductive film, 4 ... Transparent substrate, 5 ... Porous film | membrane, 52 ... Columnar structure | tissue, 6 ... Substrate, 8 ... Center axis, 9 ... Normal direction, 10 ... photoelectrode, 20 ... dye-sensitized solar cell, CE1, CE2 ... counter electrode, E ... electrolyte layer, F1, F2, F3 ... light-receiving surface, F22 ... back surface of semiconductor electrode 2, F5a ... The surface on which the porous film is formed, S: spacer, θ: inclination with respect to the normal direction of the substrate.

Claims (8)

It is provided in a dye-sensitized solar cell having at least a light-transmitting semiconductor electrode containing a dye having a photosensitizing action, and an electrolyte layer made of an electrolytic solution containing at least a chemical species serving as a redox pair, A counter electrode disposed opposite to the semiconductor electrode via the electrolyte layer,
A flat substrate;
A porous film made of platinum formed on one surface of the substrate;
At least,
The porous film is composed of a plurality of columnar structures integrated so as to keep electrical contact with each other, and each of the plurality of columnar structures has a central axis in a normal direction of the surface of the substrate. It is formed on the surface of the substrate so as to be parallel or oblique to the substrate,
A catalyst particle made of a material having a catalytic activity for promoting a reduction reaction of an oxidant constituting the redox couple is further dispersed on the surface and / or inside of the porous membrane, and the catalyst particle is platinum. Rukoto Oh in the particle,
The counter electrode characterized by.   The counter electrode according to claim 1, wherein a conductive film is further disposed between the substrate and the porous film. The oxidant constituting a redox pair is I ₃ ^- is and, reductant constituting the redox pair is I ^- counter electrode according to claim 1 or 2, characterized in that a. Counter according to any one of claims 1 to 3, the inclination angle of the plurality of columnar structure with respect to the normal direction of the surface of the substrate to be smaller than or equal to 80 °, respectively, and wherein. Wherein the plurality of like each central axis of the columnar structure is substantially parallel to each other, a counter electrode according to any one of claims 1-4, characterized in that, formed on the surface of the substrate. The porous film is formed by an oblique vapor deposition method in which vapor deposition particles of a constituent material of the porous film are incident from a direction having a predetermined inclination with respect to a normal direction of the surface of the substrate. The counter electrode according to any one of claims 1 to 5 . The incident angle when the vapor deposition particles of the constituent material of the porous film are incident on the surface of the substrate is 30 to 80 ° with respect to the normal direction of the surface of the substrate. 6. The counter electrode according to 6 . A light-transmitting semiconductor electrode including a dye having a light-receiving surface and having a photosensitizing action, and a photoelectrode having a transparent electrode disposed adjacently on the light-receiving surface;
A counter electrode disposed opposite to the semiconductor electrode;
An electrolyte layer that is disposed between the semiconductor electrode and the counter electrode, and is made of an electrolytic solution containing at least a chemical species that becomes a redox pair;
A dye-sensitized solar cell having at least
The counter electrode is the counter electrode according to any one of claims 1 to 7 ,
A dye-sensitized solar cell characterized by

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