JP4422236B2 - Photoelectric conversion element and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoelectric conversion element comprising a metal oxide semiconductor electrode, a dye adsorbed on the surface thereof, an electrolyte having a redox couple, and a counter electrode, and in particular, a photoelectric conversion element capable of obtaining high photoelectric conversion efficiency. The present invention relates to a conversion element.
[0002]
[Prior art]
There are several types of solar cells, but most of them are diode type using silicon semiconductor junctions. These solar cells are currently expensive to manufacture, which is a factor that hinders their spread. Dye-sensitized wet solar cells have been studied for a long time because of the possibility of cost reduction, but recently Graetzel et al. Announced that they have performance comparable to silicon solar cells (J. Am. Chem. Soc. 115 (1993) 6382 and Japanese Patent No. 2664194), the expectation for practical use is increasing. The basic structure of the dye-sensitized wet solar cell includes a metal oxide semiconductor electrode, a dye adsorbed on the surface thereof, an electrolyte having a redox pair, and a counter electrode. Graetzel et al. Significantly improved photoelectric conversion efficiency by making a metal oxide semiconductor electrode such as titanium oxide (TiO ₂ ) porous to increase the surface area and adsorbing a ruthenium complex as a dye on a single molecule basis.
[0003]
Since then, several proposals have been made to further improve the characteristics. For example, Japanese Patent Laid-Open No. 9-237641 discloses that the open circuit voltage is increased by using niobium oxide (Nb ₂ O ₅ ) as the metal oxide semiconductor. Japanese Patent Laid-Open No. 8-81222 discloses that lattice defects and impurities are removed by etching the surface of the TiO ₂ electrode film, thereby improving the conversion efficiency.
[0004]
However, in order to improve the photoelectric conversion efficiency of the dye-sensitized wet solar cell, it is most important how to absorb a lot of irradiated light. That is, in the conventional dye-sensitized wet solar cell, since the amount of light energy to be absorbed is small, the converted electric energy is also small.
[0005]
In the above-mentioned document, Graetzel et al. Say that the counter electrode is made of a sputtered platinum film to give light reflectivity, and the reflected light of the irradiated light can be reused to increase the photoelectric conversion efficiency.
[0006]
However, the light-reflective platinum sputtering film at this time also serves as a counter electrode, and thus is close to the metal oxide semiconductor electrode. Therefore, the reflected light is once transmitted through the dye-adsorbed titanium oxide layer, and most of the light is in a wavelength range that is not the absorption range of the dye, so the effect of improving the photoelectric conversion efficiency by reflected light is extremely high. Limited.
[0007]
[Problems to be solved by the invention]
The present invention provides a photoelectric conversion element capable of improving the photoelectric conversion efficiency under the same intensity of light irradiation by solving the problems of the prior art and increasing the absorption efficiency of the irradiated light energy. The task is to do.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, according to the present invention, a photoelectric conversion element comprising a metal oxide semiconductor electrode, a dye adsorbed on the surface thereof, an electrolytic solution having a redox pair, and a counter electrode is viewed from the direction in which light enters. And a metal oxide semiconductor electrode, a counter electrode, and a light reflecting layer are provided in this order , and the area of the metal oxide semiconductor electrode is smaller than the area of the light reflecting layer. An element is provided. According to the invention, in the above configuration, the photoelectric conversion further includes a light scattering layer, and the metal oxide semiconductor electrode, the counter electrode, the light scattering layer, and the light reflection layer are provided in this order. An element is provided. Further, according to the present invention, in the above configuration, further comprising a supporting substrate of the counter electrode, the light reflecting layer is provided on a surface of the formed on a supporting substrate, and a counter electrode side opposite The photoelectric conversion element characterized by this is provided.
Furthermore, according to the present invention, in the method for producing a photoelectric conversion element having the above-described structure, comprising a metal oxide semiconductor electrode, a dye adsorbed on the surface thereof, an electrolytic solution having a redox pair, and a counter electrode, A support substrate having an adsorbed metal oxide semiconductor electrode and a support substrate having a counter electrode are bonded together so that the metal oxide semiconductor electrode and the counter electrode face each other, and the counter electrode of the support substrate having the counter electrode And a support substrate having a light reflecting layer on the surface opposite to the substrate . A method for producing a photoelectric conversion element is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the structure of the photoelectric conversion element in this invention is demonstrated using figures. The embodiments of the present invention are not limited to these.
[0010]
First, FIG. 1 shows a typical configuration example of a conventional dye-sensitized wet solar cell.
1 is a transparent substrate such as glass, 2 is a transparent conductive film made of ITO, SnO ₂ : F, ZnO: Al, 3 is a porous metal oxide semiconductor layer, 4 is a ruthenium bipyridyl complex, zinc porphyrin, copper phthalocyanine, chlorophyll Dye such as Rose Bengal and Eosin, 5 is an electrolytic solution having a redox pair such as I ⁻ / I ₃ ⁻ and Br ⁻ / Br ₃ ⁻ , and 6 is a counter electrode made of Pt or the like. Light is incident from above.
[0011]
Next, an example of an embodiment of the present invention will be described below with reference to FIG.
1 is a transparent substrate such as glass, 2 is a transparent conductive film made of ITO, SnO ₂ : F, ZnO: Al, 3 is a porous metal oxide semiconductor layer, 4 is a ruthenium bipyridyl complex, zinc porphyrin, copper phthalocyanine, chlorophyll , Rose bengal, eosin, and the like, 5 is an electrolytic solution having a redox pair such as I ⁻ / I ₃ ⁻ , Br ⁻ / Br ₃ ⁻ , 6 is a counter electrode made of Pt, and 7 is a light reflecting layer. . Light is incident from above.
[0012]
The light reflecting layer 7 in the present invention does not have a function as a counter electrode. Therefore, the interval between the metal oxide semiconductor layer 3 and the light reflecting layer 7 can be set arbitrarily. Therefore, in this cell configuration, in addition to the conventional light from above, the light reflected by the light reflecting layer 7 (visible light from the outside that does not pass through the metal oxide semiconductor layer 3) is increased. Since it is absorbed in the dye-sensitive dye 4, the generated current is increased as compared with the prior art, and the photoelectric conversion efficiency is improved.
Furthermore, by making the area of the metal oxide semiconductor layer 3 smaller than the area of the light reflecting layer 7, more external light is reflected by the light reflecting layer, so that the photoelectric conversion efficiency is improved. In this case, the area of the metal oxide semiconductor layer 3 is 20 to 95%, preferably 50 to 90% of the area of the light reflecting layer 7.
[0013]
An example of another embodiment of the present invention will be described below with reference to FIG.
1 is a transparent substrate such as glass, 2 is a transparent conductive film made of ITO, SnO ₂ : F, ZnO: Al, 3 is a porous metal oxide semiconductor layer, 4 is a ruthenium bipyridyl complex, zinc porphyrin, copper phthalocyanine, chlorophyll Dye such as rose bengal and eosin, 5 is an electrolytic solution having a redox couple such as I ⁻ / I ₃ ⁻ , Br ⁻ / Br ₃ ⁻ , 6 is a counter electrode made of Pt, 7 is a light reflecting layer, 8 Is a light scattering layer. Light is incident from above.
[0014]
Compared with the conventional cell, this cell configuration sensitizes light reflected from the light reflecting layer 7 (visible light from the outside not transmitted through the metal oxide semiconductor layer 3) in addition to conventional light from above. Since the light absorbed by the dye 4 and the reflected light is scattered by the light scattering layer 8, the amount of light absorbed by the sensitizing dye 4 is larger than that of the embodiment of FIG. The photoelectric conversion efficiency is also improved.
[0015]
An example of another embodiment of the present invention will be described below with reference to FIG.
1 is a transparent substrate such as glass, 2 is a transparent conductive film made of ITO, SnO ₂ : F, ZnO: Al, 3 is a porous metal oxide semiconductor layer, 4 is a ruthenium bipyridyl complex, zinc porphyrin, copper phthalocyanine, chlorophyll , Rose bengal, eosin, and the like, 5 is an electrolytic solution having a redox pair such as I ⁻ / I ₃ ⁻ , Br ⁻ / Br ₃ ⁻ , 6 is a counter electrode made of Pt, and 7 is a light reflecting layer. . Light is incident from above.
[0016]
In this embodiment, the support substrate and the counter electrode are shared. For this reason, in addition to the effect by embodiment shown in FIG. 2, there exists an advantage that a structure is simplified.
[0017]
The light reflecting layer is effective in the order of the metal oxide semiconductor layer, the counter electrode, and the light reflecting layer, or in the order of the counter electrode, the metal oxide semiconductor layer, and the light reflecting layer. The order of the counter electrode and the light reflecting layer is more preferable. This is because light directly irradiated rather than reflected light contributes more to photoelectric conversion, and therefore it is preferable to eliminate loss due to light absorption by the counter electrode and the electrolyte as much as possible.
[0018]
Next, an example of a method for manufacturing the solar cell will be described with respect to the configuration of FIG.
First, two sheets of, for example, an SnO ₂ : F film 2 formed on one side by a sputtering method, a CVD method, a sol-gel method or the like are prepared on a glass substrate 1. Since the SnO ₂ : F film functions as a current collector, the sheet resistance is 50 Ω / □ or less, preferably 10 Ω / □ or less.
For the substrate, ceramics, glass, heat-resistant plastic, etc. that can withstand the heating and firing temperature can be applied.
In particular, when producing a semiconductor electrode, a metal or a transparent electrode such as ITO or SnO ₂ can be applied.
After the porous metal oxide semiconductor thin film 3 is formed on the substrate on which the transparent conductive film is formed, a sensitizing dye such as a ruthenium bipyridyl complex is adsorbed. The thickness of the titanium oxide thin film is preferably about 1 to 20 μm. This increases the amount of light absorbed by increasing the film thickness. On the other hand, if the film thickness of the metal oxide semiconductor layer is increased more than necessary, the internal resistance of the cell increases. Because there is.
[0019]
In order to apply the coating solution for forming the metal oxide semiconductor layer on the substrate, a known method such as dipping, spin coating, spray coating, or the like can be used.
A surfactant can be added to the coating solution in order to improve the film-forming property on the substrate. In addition, the viscosity of the coating solution can be controlled by adding glycols such as ethylene glycol or water-soluble polymers.
[0020]
In order to adsorb the dye to the metal oxide semiconductor layer, the metal oxide semiconductor electrode may be immersed in a solution in which the dye is dissolved in a solvent such as water, alcohol, or toluene. As the dye, dyes such as ruthenium bipyridyl complex, zinc porphyrin, copper phthalocyanine, chlorophyll, rose bengal, and eosin that can absorb and excite light in the visible light region and inject electrons into the metal oxide can be used. . In addition, it is preferable to have a functional group such as a carboxyl group, a hydroxyl group, or a sulfone group in the dye molecule because the dye is chemically fixed on the surface of the metal oxide. A typical example is a ruthenium complex represented by [ruthenium (4,4′-dicarboxy-2,2′-bipyridine) ₂ (isothiocyanato) ₂ ].
[0021]
For example, a Pt (fine particle) layer 6 is formed on another substrate on which the SnO ₂ : F film is formed by sputtering, vapor deposition, electrochemical method, or the like. The film thickness is preferably about 1 to 50 nm which is light transmissive.
As the light reflecting layer 7, a metal plate made of an arbitrary material whose surface is processed so as to totally reflect light can be used.
[0022]
In the present invention, the light scattering layer 8 is used to reach the entire metal oxide semiconductor layer 3 when light incident on the light reflection layer 7 without being transmitted through the metal oxide semiconductor layer 3 is reflected. It is provided and can be formed on the light reflecting layer 7, and this layer can be formed of a metal oxide or polymer fine particles, or a glass surface finely roughened. The thickness of the light scattering layer 8 is preferably about 1 to 100 μm.
[0023]
After the three substrates formed as described above are overlapped via a spacer, for example, an electrolyte solution 5 having a redox couple is injected into I− / I ₃ ⁻ and sealed with a sealant. As the electrolyte solution, a solution obtained by adding iodine and tetrapropylammonium iodide to a mixed solvent of ethylene carbonate and acetonitrile can be suitably used.
The cell formed in this manner is made of, for example, lead glass containing CeO ₂ or the like (a commercially available sharp cut filter such as L-40 or L-42 may be used) as a member that absorbs ultraviolet light. You may stick together.
[0024]
【Example】
The invention is illustrated by the following examples. However, the present invention is not limited to these examples.
[0025]
[Example 1] (Element structure of FIG. 2)
An SnO ₂ : F film 2 was formed on one side of each of the two glass substrates 1 by a sol-gel method so that the sheet resistance was 10Ω / □. Among these, for one substrate, a light-transmitting Pt film was formed on the SnO ₂ : F film 2 by electrolysis of hexachloroplatinic acid.
Moreover, 10 ml of water and 0.2 ml of acetylacetone were added to 3 g of anatase type titanium oxide powder (manufactured by Ishihara Techno Co., Ltd.) and mixed so as to break up the aggregation of the titanium oxide powder in a mortar to prepare a coating solution. This coating solution was applied onto the glass substrate 1 (area 0.5 cm ² ), naturally dried for 30 minutes, and then heated and fired at 450 ° C. for 30 minutes to obtain a titanium oxide semiconductor electrode having a thickness of about 10 μm.
This porous titanium oxide semiconductor electrode is immersed in an ethanol solution of a ruthenium complex represented by [ruthenium (4,4′-dicarboxy-2,2′-bipyridine) ₂ (isothiocyanato) ₂ ] and refluxed for 10 minutes. The ruthenium complex was adsorbed on the surface of the TiO ₂ electrode.
These two substrates are overlapped with a bead or rod-like insulating spacer while maintaining a gap of about 10 μm, and a redox electrolyte solution in which iodine and tetrapropylammonium iodide are added to a mixed solvent of ethylene carbonate and acetonitrile is prepared. After the injection, it was sealed with an epoxy adhesive.
Further, a Pt film (area: 1 cm ² ) deposited to a thickness of 100 nm on a glass substrate was stacked through a 2 cm spacer and sealed with an epoxy adhesive to produce a photoelectric conversion element. The photoelectric conversion efficiency of this photoelectric conversion element under pseudo-sunlight irradiation (AM1.5, 100 mW / cm ² ) was 7.5%.
[0026]
[Example 2] (Element structure of FIG. 3)
An SnO ₂ : F film 2 was formed on one side of two glass substrates by a sol-gel method so that the sheet resistance was 10Ω / □. Among these, for one substrate, a light-transmitting Pt film was formed on the SnO ₂ : F film 2 by electrolysis of hexachloroplatinic acid.
Moreover, 10 ml of water and 0.2 ml of acetylacetone were added to 3 g of anatase type titanium oxide powder (manufactured by Ishihara Techno Co., Ltd.) and mixed so as to break up the aggregation of the titanium oxide powder in a mortar to prepare a coating solution. This coating solution was applied to another glass substrate (area 0.5 cm ² ), naturally dried for 30 minutes, and then heated and fired at 450 ° C. for 30 minutes to obtain a titanium oxide semiconductor electrode having a thickness of about 10 μm.
This porous titanium oxide semiconductor electrode is immersed in an ethanol solution of a ruthenium complex represented by [ruthenium (4,4′-dicarboxy-2,2′-bipyridine) ₂ (isothiocyanato) ₂ ] and refluxed for 10 minutes. The ruthenium complex was adsorbed on the surface of the TiO ₂ electrode.
A redox electrolyte solution in which these two substrates are overlapped with a bead or rod-shaped insulating spacer while maintaining a gap of about 10 μm, and iodine and tetrapropylammonium iodide are added to a mixed solvent of ethylene carbonate and acetonitrile. Was injected and then sealed with an epoxy adhesive.
Further, a Pt film (area 1 cm ² ) is deposited to a thickness of 100 nm on a glass substrate by a vacuum evaporation method, and the opposite surface is superposed with a fine rough surface processed through a 2 cm spacer, and an epoxy adhesive. Then, a photoelectric conversion element was manufactured.
The photoelectric conversion efficiency of this photoelectric conversion element under pseudo-sunlight irradiation (AM1.5, 100 mW / cm ² ) was 7.7%.
[0027]
[Example 3] (Element structure of FIG. 4)
An SnO ₂ : F film 2 was formed on one side of each of the two glass substrates so as to have a sheet resistance of 10Ω / □ by a sol-gel method. Among these, for one substrate, a light-transmitting Pt film is formed on the SnO ₂ : F film 2 by electrolysis of hexachloroplatinic acid, and a Pt film (area 1 cm ² ) is formed on the opposite surface by vacuum evaporation. Deposited to a thickness of 100 nm.
Moreover, 10 ml of water and 0.2 ml of acetylacetone were added to 3 g of anatase type titanium oxide powder (manufactured by Ishihara Techno Co., Ltd.) and mixed so as to break up the aggregation of the titanium oxide powder in a mortar to prepare a coating solution. This coating solution was applied onto the glass substrate 1 (area 0.5 cm ² ), naturally dried for 30 minutes, and then heated and fired at 450 ° C. for 30 minutes to obtain a titanium oxide semiconductor electrode having a thickness of about 10 μm.
This porous titanium oxide semiconductor electrode is immersed in an ethanol solution of a ruthenium complex represented by [ruthenium (4,4′-dicarboxy-2,2′-bipyridine) ₂ (isothiocyanato) ₂ ] and refluxed for 10 minutes. The ruthenium complex was adsorbed on the surface of the TiO ₂ electrode.
These two substrates were overlapped with a bead or rod-shaped insulating spacer while maintaining a gap of about 10 μm, and an oxidation-reduction electrolyte solution in which iodine and tetrapropylammonium iodide were added to a mixed solvent of ethylene carbonate and acetonitrile. After the injection, it was sealed with an epoxy adhesive to produce a photoelectric conversion element.
The photoelectric conversion efficiency of this photoelectric conversion element under pseudo-sunlight irradiation (AM 1.5, 100 mW / cm ² ) was 7.3%.
[0028]
[Comparative Example 1] (Element structure of FIG. 1)
An SnO ₂ : F film 2 was formed on one side of each of the two glass substrates 1 by a sol-gel method so that the sheet resistance was 10Ω / □. Among these, for one substrate, a light-transmitting Pt film was formed on the SnO ₂ : F film 2 by electrolysis of hexachloroplatinic acid.
Moreover, 10 ml of water and 0.2 ml of acetylacetone were added to 3 g of anatase type titanium oxide powder (manufactured by Ishihara Techno Co., Ltd.) and mixed so as to break up the aggregation of the titanium oxide powder in a mortar to prepare a coating solution. This coating solution was applied on the other glass substrate (area 0.5 cm ² ), naturally dried for 30 minutes, and then heated and fired at 450 ° C. for 30 minutes to obtain a titanium oxide semiconductor electrode having a thickness of about 10 μm. .
This porous titanium oxide semiconductor electrode is immersed in an ethanol solution of a ruthenium complex represented by [ruthenium (4,4′-dicarboxy-2,2′-bipyridine) ₂ (isothiocyanato) ₂ ] and refluxed for 10 minutes. The ruthenium complex was adsorbed on the surface of the TiO ₂ electrode.
These two substrates were overlapped with a bead or rod-shaped insulating spacer while maintaining a gap of about 10 μm, and an oxidation-reduction electrolyte solution in which iodine and tetrapropylammonium iodide were added to a mixed solvent of ethylene carbonate and acetonitrile. After the injection, it was sealed with an epoxy adhesive to produce a photoelectric conversion element.
The photoelectric conversion efficiency of this photoelectric conversion element under simulated sunlight irradiation (AM1.5, 100 mW / cm ² ) was 6.9%.
[0029]
【The invention's effect】
According to the present invention, by providing the light reflection layer, the amount of light absorption is increased, and the photoelectric conversion efficiency is improved.
In addition, when the area of the metal oxide semiconductor layer is smaller than the area of the light reflection layer, light from the outside is reflected, so that the amount of light absorption is increased and the photoelectric conversion efficiency is improved.
Further, by providing the scattering layer, the light absorption efficiency is improved, and the photoelectric conversion efficiency is further improved.
Further, by adopting a structure in which the counter electrode is disposed between the light reflecting layer and the metal oxide semiconductor layer, the reflected light intensity can be further increased, and the photoelectric conversion efficiency is further improved.
Furthermore, by providing a light reflecting layer on the same substrate as the counter electrode, manufacturing and material costs can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an example of a conventional photoelectric conversion element.
FIG. 2 is a cross-sectional view schematically showing an example of a photoelectric conversion element according to the present invention.
FIG. 3 is a cross-sectional view schematically showing another example of the photoelectric conversion element according to the present invention.
FIG. 4 is a cross-sectional view schematically showing another example of the photoelectric conversion element according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent conductive film 3 Metal oxide semiconductor layer 4 Sensitizing dye 5 Electrolyte solution which has a redox pair Counter electrode 7 Light reflection layer 8 Light scattering layer

Claims (4)

In a photoelectric conversion element comprising a metal oxide semiconductor electrode, a dye adsorbed on the surface thereof, an electrolytic solution having a redox pair, and a counter electrode, the metal oxide semiconductor electrode and the counter electrode as viewed from the direction in which light enters , Provide a light reflection layer in the order of the light reflection layer,
And the area of the said metal oxide semiconductor electrode is smaller than the area of the said light reflection layer, The photoelectric conversion element characterized by the above-mentioned.   The photoelectric conversion element according to claim 1, further comprising a light scattering layer, which is provided in the order of a metal oxide semiconductor electrode, a counter electrode, a light scattering layer, and a light reflection layer.   The support substrate for the counter electrode is further provided, and the light reflecting layer is provided on the support substrate and provided on a surface opposite to the counter electrode side. Photoelectric conversion element. In the manufacturing method of the photoelectric conversion element in any one of Claims 1-3 which consists of a metal oxide semiconductor electrode, the pigment | dye adsorbed on the surface, the electrolyte solution which has a redox couple, and a counter electrode. A support substrate having an adsorbed metal oxide semiconductor electrode and a support substrate having a counter electrode are bonded together so that the metal oxide semiconductor electrode and the counter electrode face each other, and further the counter electrode of the support substrate having the counter electrode And a support substrate having a light reflecting layer having an area larger than the area of the metal oxide semiconductor electrode on the surface opposite to the surface of the metal oxide semiconductor electrode .

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