JP4824197B2 - Photoelectrode and dye-sensitized solar cell provided with the same - Google Patents

Description

【０１２６】
表１に示した結果から明らかなように、実施例１〜実施例７の色素増感型太陽電池のエネルギー変換効率ηは、それぞれに対応する比較例１〜比較例７の色素増感型太陽電池のエネルギー変換効率ηよりも高い値を示すことが確認された。
【０１２７】
【発明の効果】
以上説明したように、本発明によれば、優れた光電変換効率を有する光電極を構成することができる。また、この光電極を用いることにより、優れたエネルギー変換効率を有する色素増感型太陽電池を構成することができる。
【図面の簡単な説明】
【図１】本発明の光電極の好適な一実施形態を示す模式断面図である。
【図２】図１に示した領域１００の部分の模式拡大断面図である。
【図３】図１に示した光電極を備えた色素増感型太陽電池を示す模式断面図である。
【図４】図１に示した光電極の半導体電極の内部構造の他の形態を示す模式断面図である。
【図５】図１に示した光電極の半導体電極の内部構造の更に他の形態を示す模式断面図である。
【図６】図１に示した光電極の半導体電極の内部構造の更に他の形態を示す模式断面図である。
【図７】図１に示した光電極の半導体電極の内部構造の更に他の形態を示す模式断面図である。
【図８】図１に示した光電極の半導体電極の内部構造の更に他の形態を示す模式断面図である。
【図９】図１に示した光電極の他の実施形態を示す模式断面図である。
【図１０】図１に示した光電極の半導体電極の内部構造の更に他の形態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…基板、１０，１１，１２，１３，１４…光電極，２０…色素増感型太陽電池、２１…最内部の層、２２…最外部の層、６３…内部層、１００…光電極１０の部分領域、ＣＥ…対極、Ｅ…電解質、Ｆ１，Ｆ２，Ｆ３，…受光面、Ｆ２２…半導体電極２の裏面、Ｌ１０…入射光、Ｐ１…酸化物半導体粒子、Ｐ２…増感色素、Ｐ３…酸化物半導体粒子、Ｐ４…酸化物半導体粒子、Ｒ２１，Ｒ２２…細孔（空隙）部分、Ｓ…スペーサー。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoelectrode and a dye-sensitized solar cell including the photoelectrode.
[0002]
[Prior 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 they are inexpensive and can be manufactured by a relatively simple process.
[0003]
In conventional dye-sensitized solar cells, since the absorption coefficient of the sensitizing dye contained in the semiconductor electrode is small, even if light in the infrared to near-infrared wavelength region is incident on the semiconductor electrode, the semiconductor It penetrated without being sufficiently absorbed in the electrode, and did not contribute to the progress of the photoelectric conversion reaction.
[0004]
For this reason, various studies for improving the photoelectric conversion efficiency in the photoelectrode and improving the energy conversion efficiency of the battery have been conducted for practical application of the dye-sensitized solar cell. The energy conversion efficiency η (%) of the dye-sensitized solar cell is represented by the following formula (1). In the following formula (1), P₀Is the incident light intensity [mWcm^-2], V_ocIs the open circuit voltage [V], I_scIs the short-circuit current density [mAcm^-2], FF shows a fill factor.
η = 100 × (V_oc× I_sc× F.F.) / P₀... (1)
[0005]
As for the above examination, for example, in Japanese Patent Laid-Open No. 10-255863, a semiconductor electrode (light absorbing particle layer) having a small semiconductor particle having an average particle diameter of, for example, 80 nm or less as a constituent material is in contact with the electrolyte solution. On the surface, a layer (light reflecting particle layer) made of large semiconductor particles having an average particle diameter of 200 to 500 nm, for example, is provided to constitute a photoelectrode, and incident light incident on the semiconductor electrode is scattered. Thus, a dye-sensitized solar cell intended to improve the absorption efficiency has been proposed.
[0006]
Japanese Patent Laid-Open No. 2000-106222 discloses a semiconductor electrode in which semiconductor particles having a large particle size (average particle size: 10 to 300 nm) and semiconductor particles having a small particle size (average particle size: 10 nm or less) are mixed. Thus, a dye-sensitized solar cell intended to improve the absorption efficiency by scattering incident light incident on the semiconductor electrode has been proposed.
[0007]
[Problems to be solved by the invention]
However, the present inventors have disclosed a dye-sensitized solar cell provided with the photoelectrode described in JP-A-10-255863 and a dye-sensitized solar cell provided with the photoelectrode described in JP-A-2000-106222. In any of the batteries, sufficient incident light absorption efficiency is not obtained in the semiconductor electrode constituting the photoelectrode, and sufficient energy conversion efficiency as a battery cannot be obtained, which is still insufficient. I found.
[0008]
That is, in the dye-sensitized solar cells described in the above two publications, as a result of light scattering by the large semiconductor crystal particles, the optical path length passing through the semiconductor electrode is longer than when there is no large semiconductor particle. Although the utilization rate of the light increases, there is a problem that a part of the light passes through the semiconductor electrode because it uses the scattering phenomenon.
[0009]
In particular, as in the dye-sensitized solar cell described in the above two publications, the ratio of incident light that is transmitted without being absorbed by the semiconductor electrode when large semiconductor particles having a spherical shape are mixed in the semiconductor electrode. As a result, the light confinement effect in the semiconductor electrode is reduced, and the incident light absorption efficiency is reduced. In addition, when the number of large semiconductor crystal particles increases, the total surface area of the semiconductor surface to which the dye is adsorbed decreases, resulting in a decrease in light absorption rate.
[0010]
Further, in any of the dye-sensitized solar cells described in the above two publications, the size of the pores formed in the semiconductor electrode is small, and when the sensitizing dye is adsorbed in the semiconductor electrode, It was difficult to sufficiently adsorb to a sufficient time, and it took time. Furthermore, since the size of the pores formed in the semiconductor electrode is small, it is difficult to efficiently supply the reactant during power generation of the battery, and the resistance component (overvoltage component) based on the diffusion rate limiting of the reactant ) Increases and the photoelectric conversion efficiency decreases.
[0011]
Moreover, the conventional dye-sensitized solar cell cannot sufficiently prevent the occurrence of leakage current during power generation in the semiconductor electrode constituting the photoelectrode. The generation of a large leakage current is caused by the open circuit voltage V of the battery in equation (1)._ocTherefore, if the generation of leakage current cannot be sufficiently suppressed, a battery having high energy conversion efficiency cannot be configured.
[0012]
This invention is made | formed in view of the subject which the said prior art has, and aims at providing the dye-sensitized solar cell which has the photoelectrode which has the outstanding photoelectric conversion efficiency, and the outstanding energy conversion efficiency. .
[0013]
[Means for Solving the Problems]
As a result of intensive research to achieve the above object, the present inventors have configured the semiconductor electrode constituting the photoelectrode to be composed of at least a plurality of layers, and set the dye adsorption density in each layer to the position closest to the transparent electrode. Decreasing from the disposed layer to the layer disposed farthest from the transparent electrode, and / or the specific surface area of the oxide semiconductor in each layer from the layer disposed closest to the transparent electrode to the transparent electrode It has been found that an electrode structure capable of efficiently proceeding the photoelectric conversion reaction can be constructed by reducing the layer to the layer farthest from the position, and the present invention has been achieved.
[0014]
That is, the present invention is a photoelectrode having a semiconductor electrode having a light receiving surface and a transparent electrode disposed adjacently on the light receiving surface, and the semiconductor electrode is composed of a plurality of layers containing a dye. Each of the plurality of layers is composed of a porous film composed of oxide semiconductor particles, and the innermost layer in which the dye adsorption density per unit volume of the porous film in each layer is located closest to the transparent electrode To the outermost layer disposed at the farthest position with respect to the transparent electrode.
[0015]
In the photoelectrode of the present invention, the dye adsorption density in the semiconductor electrode is gradually decreased along the thickness direction of the semiconductor from the light receiving surface of the semiconductor electrode to the surface that contacts the electrolyte of the semiconductor electrode (hereinafter referred to as the back surface). Therefore, the photoelectric conversion reaction can be preferentially performed in a region close to the transparent electrode even in the semiconductor electrode. Therefore, the loss amount of electrons generated by the photoelectric conversion reaction and moving in the oxide semiconductor toward the transparent electrode in the semiconductor electrode can be efficiently reduced. That is, the conduction resistance component of electrons can be reduced, and at the surface of the oxide semiconductor particles,_Three ^-(Essentially I₂) And I^-The frequency of occurrence of a reaction that generates (leakage current) can be reduced. Thereby, the outstanding photoelectric conversion efficiency can be obtained.
[0016]
Here, in the present invention, “the dye adsorption density in each layer decreases from the innermost layer arranged at the position closest to the transparent electrode to the outermost layer arranged at the position farthest from the transparent electrode. Is the state where the dye adsorption density of the innermost layer located at one end is finally smaller than the dye adsorption density of the outermost layer located at the other end, and when multiple layers are viewed as a whole 3 shows a state in which the dye adsorption density of each layer is generally decreased from the innermost layer to the outermost layer.
[0017]
For example, the dye adsorption density may be monotonically decreasing from the innermost layer to the outermost layer. Further, for example, among the layers arranged between the innermost layer and the outermost layer, the dye adsorption density of some adjacent layers may have the same value. Further, among the layers arranged between the innermost layer and the outermost layer, when comparing the dye adsorption density of some adjacent layers, the dye of the layer located on the outermost layer side The adsorption density may be larger than the dye adsorption density of the layer located on the innermost layer side. However, from the viewpoint of allowing the photoelectric conversion reaction in the semiconductor electrode to proceed more efficiently, the dye adsorption density monotonically decreases from the innermost layer to the outermost layer, or the innermost layer and the outermost layer. Among the layers disposed between the two layers, a state in which the dye adsorption density of some adjacent layers has the same value is preferable.
[0018]
In the photoelectrode of the present invention, the dye adsorption density in the innermost layer is 1 × 10.^-13~ 1x10^-11mol / cm^ThreeAnd the difference between the dye adsorption density in the innermost layer and the dye adsorption density in the outermost layer is 1 × 10^-14~ 9.9 × 10^-12mol / cm^ThreeIs preferable. Thereby, the photoelectric conversion efficiency in a semiconductor electrode can be improved more precisely.
[0019]
Here, the dye adsorption density in the innermost layer is 1 × 10^-13mol / cm^ThreeIf it is less than the range, the amount of the sensitizing dye in the electrode may be reduced. On the other hand, the dye adsorption density in the innermost layer is 1 × 10^-11mol / cm^ThreeIf it exceeds 1, the incident light is absorbed, but there is a possibility that the amount of the sensitizing dye that is effectively electron-injected decreases. Further, the difference between the dye adsorption density in the innermost layer and the dye adsorption density in the outermost layer is 1 × 10.^-14mol / cm^ThreeIf it is less than the range, the amount of the sensitizing dye that injects electrons in the region of the semiconductor electrode close to the transparent electrode decreases, so that the battery characteristics may be deteriorated. On the other hand, this difference is 9.9 × 10^-12mol / cm^ThreeIf it exceeds, the total amount of sensitizing dye in the electrode may be reduced.
[0020]
From the same viewpoint as described above, the dye adsorption density in the innermost layer is 2 × 10.^-13~ 5x10^-12mol / cm^ThreeMore preferably, 4 × 10^-13~ 2x10^-12mol / cm^ThreeMore preferably. The difference between the dye adsorption density in the innermost layer and the dye adsorption density in the outermost layer is 5 × 10.^-14~ 4.9 × 10^-12mol / cm^ThreeMore preferably, 1 × 10^-13~ 1.9 × 10^{- 12}mol / cm^ThreeMore preferably.
[0021]
Furthermore, in the photoelectrode of the present invention, it is preferable that the average value of the specific surface area of the oxide semiconductor in each layer decreases from the innermost layer to the outermost layer. Adjusting the average value of the specific surface area of the oxide semiconductor in each layer so as to satisfy the above conditions is one method for reducing the dye adsorption density in each layer from the innermost layer to the outermost layer. In this case, the photoelectric conversion reaction is preferentially performed in a region near the transparent electrode in the semiconductor electrode, and the generation of leakage current can be more reliably reduced in the region far from the transparent electrode in the semiconductor electrode.
[0022]
Here, in the present invention, the state that “the average value of the specific surface area of the oxide semiconductor in each layer decreases from the innermost layer to the outermost layer” is the same as in the case of the dye adsorption density in each layer described above. In addition, the average value of the specific surface area of the oxide semiconductor of the outermost layer located at one end is finally smaller than the average value of the specific surface area of the oxide semiconductor of the innermost layer located at the other end, When a plurality of layers are viewed as a whole, the average value of the specific surface areas of the oxide semiconductors of the respective layers is schematically reduced from the innermost layer to the outermost layer.
[0023]
Also in this case, for example, the average value of the specific surface area of the oxide semiconductor may monotonously decrease from the innermost layer to the outermost layer. For example, among the layers arranged between the innermost layer and the outermost layer, the average value of the specific surface areas of the oxide semiconductors of some adjacent layers is the same value. Also good. Furthermore, when the average value of the specific surface areas of the oxide semiconductors of some adjacent layers among the layers arranged between the innermost layer and the outermost layer is compared, the outermost layer side The average value of the specific surface area of the oxide semiconductor of the layer located in the layer may be larger than the average value of the specific surface area of the oxide semiconductor of the layer located on the innermost layer side. However, from the viewpoint of more efficiently proceeding the photoelectric conversion reaction in the semiconductor electrode, the average value of the specific surface area of the oxide semiconductor monotonously decreases from the innermost layer to the outermost layer, or the innermost Of the layers arranged between the outermost layer and the outermost layer, it is preferable that the average value of the specific surface areas of the oxide semiconductors of some adjacent layers be the same.
[0024]
In this case, the average value of the specific surface area of the oxide semiconductor in the innermost layer is 20 to 500 m.²The difference between the average value of the specific surface area of the oxide semiconductor in the innermost layer and the average value of the specific surface area of the oxide semiconductor in the outermost layer is 3 to 480 m.²/ G is preferable. Thereby, the photoelectric conversion efficiency in a semiconductor electrode can be improved more precisely.
[0025]
Here, the average value of the specific surface area of the oxide semiconductor in the innermost layer is 20 m.²If it is less than / g, the amount of sensitizing dye in the electrode may be reduced. On the other hand, the average value of the specific surface area of the oxide semiconductor in the innermost layer is 500 m.²If it exceeds / g, incident light is absorbed, but the amount of sensitizing dye that is effectively injected with electrons may decrease. The difference between the average value of the specific surface area of the oxide semiconductor in the innermost layer and the average value of the specific surface area of the oxide semiconductor in the outermost layer is 3 m.²If it is less than / g, the amount of sensitizing dye that injects electrons in the region of the semiconductor electrode close to the transparent electrode decreases, so that the battery characteristics may deteriorate. On the other hand, this difference is 480m²If it exceeds / g, the total amount of sensitizing dye in the electrode may be reduced.
[0026]
From the same viewpoint as described above, the average value of the specific surface area of the oxide semiconductor in the outermost layer is 10 to 250 m.²/ G is more preferably 20 to 100 m²More preferably, it is / g. The difference between the average value of the specific surface area of the oxide semiconductor in the outermost layer and the average value of the specific surface area of the oxide semiconductor in the innermost layer is 5 to 240 m.²/ G is more preferably 10 to 90 m²More preferably, it is / g.
[0027]
In the photoelectrode of the present invention, as a method of adjusting the dye adsorption density of each layer constituting the semiconductor electrode so as to satisfy the above-mentioned conditions, the average value of the specific surface area of the oxide semiconductor in each layer is set to the above-mentioned conditions. In addition to adjusting so as to fill, the method of adjusting the porosity of each layer to increase the porosity from the innermost layer closest to the transparent electrode to the outermost layer farthest, and the pore size for each layer There is a method of adjusting the maximum value of the distribution or the average value of the pore size distribution so as to satisfy the condition of the dye adsorption density.
[0028]
The present invention also includes a photoelectrode having a semiconductor electrode having a light receiving surface, a transparent electrode disposed adjacent to the light receiving surface of the semiconductor electrode, and a counter electrode. Provided is a dye-sensitized solar cell disposed opposite to an electrolyte, wherein the photoelectrode is the above-described photoelectrode of the present invention. Thus, the dye-sensitized solar cell which has the outstanding energy conversion efficiency can be comprised by using the photoelectrode of this invention mentioned above.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the photoelectrode 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.
[0030]
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of the photoelectrode of the present invention. FIG. 2 is a schematic enlarged sectional view of a portion of the region 100 shown in FIG. 3 is a schematic cross-sectional view showing a dye-sensitized solar cell including the photoelectrode shown in FIG.
[0031]
A photoelectrode 10 shown in FIG. 1 mainly includes a semiconductor electrode 2 having a light receiving surface F2 and a transparent electrode 1 disposed adjacent to the light receiving surface F2 of the semiconductor electrode 2. Further, the dye-sensitized solar cell 20 shown in FIG. 3 mainly fills a gap formed between the photoelectrode 10 and the counter electrode CE by the photoelectrode 10, the counter electrode CE, and the spacer S shown in FIG. The electrolyte E is made. And the semiconductor electrode 2 is contacting the electrolyte E in the back surface F22 on the opposite side to the light-receiving surface F2.
[0032]
The dye-sensitized solar cell 20 generates electrons in the semiconductor electrode 2 by the light L10 that is transmitted through the transparent electrode 1 and irradiated onto the semiconductor electrode 2. The electrons generated in the semiconductor electrode 2 are collected by the transparent electrode 1 and taken out to the outside.
[0033]
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 in FIGS. 1 and 3 has a configuration in which a so-called transparent conductive film 3 for transmitting light 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. For example, fluorine-doped SnO₂Examples include coated glass, ITO coated glass, ZnO: Al coated glass, and the like. Further, a metal electrode having a structure capable of transmitting light, such as a mesh shape or a stripe shape, may be provided on the substrate 4 such as a glass substrate.
[0034]
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.
[0035]
As shown in FIGS. 1 and 2, the semiconductor electrode 2 is composed of three layers composed of a porous film composed of oxide semiconductor particles. That is, the semiconductor electrode 2 includes an innermost layer 21 disposed at a position closest to the transparent electrode 1, an outermost layer 22 disposed at a position farthest from the transparent electrode 1, and an innermost layer 21. And an inner layer 23 disposed between the outermost layer 22 and the outermost layer 22.
[0036]
When the dye adsorption density in each of the three layers is compared, the dye adsorption density for each layer decreases from the innermost layer 21 to the outermost layer 22. In this photoelectrode 10, by providing the semiconductor electrode 2 having the above structure, the photoelectric conversion efficiency in the semiconductor electrode 2 is improved.
[0037]
Here, when the structure of each of the three layers is formed in accordance with the condition of the dye adsorption density described above, the dye adsorption density in the innermost layer 21 is preferably 1 × 10.^-13~ 1x10^-11mol / cm^ThreeThe difference between the dye adsorption density in the innermost layer 21 and the dye adsorption density in the outermost layer 22 is preferably 1 × 10^-14~ 9.9 × 10^-12mol / cm^ThreeIt is adjusted to become.
[0038]
One method for adjusting the dye adsorption density for each layer so as to satisfy the above conditions is a method for adjusting the average value of the specific surface area of the oxide semiconductor in each layer as described above.
[0039]
Here, when the dye adsorption density of each of the three layers is formed in accordance with the condition of the average value of the specific surface area of the oxide semiconductor of each layer, the average value of the specific surface area of the oxide semiconductor in the innermost layer 21 is preferable. 20 ~ 500m²The difference between the average value of the specific surface area of the oxide semiconductor in the innermost layer 21 and the average value of the specific surface area of the oxide semiconductor in the outermost layer 22 is preferably 3 to / g. 480m²/ G.
[0040]
And as a method of adjusting the average value of the specific surface area of the oxide semiconductor in each layer, there is a method of adjusting the average particle size of the oxide semiconductor particles constituting each layer. Here, when adjusting the average particle diameter of the oxide semiconductor particles constituting each layer, the average particle diameter of the oxide semiconductor particles for each layer is adjusted by increasing from the innermost layer 21 to the outermost layer 22. Like that.
[0041]
In this case, the average particle size of the oxide semiconductor particles P3 in the outermost layer 22 is preferably 50 to 500 nm, and more preferably 70 to 400 nm. The difference between the average particle diameter of the oxide semiconductor particles P3 in the outermost layer 22 and the average particle diameter of the oxide semiconductor particles P1 in the outermost layer 21 is preferably 20 to 300 nm, and preferably 25 to 250 nm. More preferably.
[0042]
If the average particle size of the oxide semiconductor particles in the outermost layer is less than 50 nm, the incident light is absorbed, but the amount of sensitizing dye that is effectively electron-injected may be reduced. On the other hand, when the average particle diameter of the oxide semiconductor particles in the outermost layer exceeds 500 nm, the amount of sensitizing dye in the electrode may be reduced. Further, when the difference between the average particle diameter of the oxide semiconductor particles in the outermost layer and the average particle diameter of the oxide semiconductor particles in the innermost layer is less than 10 nm, electron injection is performed in the region of the semiconductor electrode close to the transparent electrode Since the amount of the sensitizing dye to be reduced decreases, the battery characteristics may be deteriorated. On the other hand, if this difference exceeds 400 nm, the total amount of sensitizing dye in the electrode may be reduced.
[0043]
FIG. 2 shows an example in which the dye adsorption density of each layer is adjusted to satisfy the above conditions by controlling the particle size of the oxide semiconductor particles (P1 and P3) constituting each layer of the semiconductor electrode 2. Is shown.
[0044]
Hereinafter, this case will be described. The innermost layer 21 of the semiconductor electrode 2 shown in FIG. 2 is mainly composed of oxide semiconductor particles P1 having a small average particle diameter and sensitizing dye P2 adsorbed on the surface of the oxide semiconductor particles P1. . The inner layer 23 and the outermost layer 22 are mainly composed of the oxide semiconductor particles P1, the oxide semiconductor particles P3 having an average particle size larger than that of the oxide semiconductor particles P1, and the oxide semiconductor particles P1 and the oxide layers. And a sensitizing dye P2 adsorbed on the surface of the physical semiconductor particle P3.
[0045]
Here, the average particle diameter of the oxide semiconductor particles P1 is preferably adjusted to be 5 to 100 nm. The average particle diameter of the oxide semiconductor particles P3 is preferably adjusted to be larger than 100 nm. And the compounding ratio of the oxide semiconductor particle P3 with respect to the total amount of the oxide semiconductor particle P1 and the oxide semiconductor particle P3 in the outermost layer 22 is the oxide semiconductor particle P1 and the oxide semiconductor particle P3 in the inner layer 23. It is adjusted to be larger than the blending ratio of the oxide semiconductor particles P3 with respect to the total amount.
[0046]
As a result, the average particle diameter of the oxide semiconductor particles for each layer increases from the innermost layer 21 to the outermost layer 22. As a result, the dye adsorption density for each layer decreases from the innermost layer 21 to the outermost layer 22. In the case of this photoelectrode 10, the innermost layer 21 does not substantially contain the oxide semiconductor particles P3.
[0047]
The oxide semiconductor particles P1 and the oxide semiconductor particles P3 are not particularly limited, and known oxide semiconductors and the like can be used. As an oxide semiconductor, for example, TiO₂, ZnO, SnO₂, Nb₂O_Five, In₂O_Three, WO_Three, ZrO₂, La₂O_Three, Ta₂O_Five, SrTiO_Three, BaTiO_ThreeEtc. can be used.
[0048]
Moreover, the sensitizing dye P2 contained in the first semiconductor layer 5 and the second semiconductor layer 6 of the semiconductor electrode 2 is not particularly limited, and the dye has absorption in the visible light region and / or the infrared light region. If it is. As this sensitizing dye P2, 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-bis (2,2′-bipyridyl-4,4′- Dicarboxylate) ruthenium (II)) and the like. As the organic dye, metal-free phthalocyanine, cyanine dye, methocyanine dye, xanthene dye, triphenylmethane dye, and the like can be used.
[0049]
Moreover, it is preferable that the thickness of the semiconductor electrode 2 is 3-50 micrometers, It is more preferable that it is 5-30 micrometers, It is still more preferable that it is 6-18 micrometers. When the thickness of the semiconductor electrode is less than 3 μm, the amount of dye adsorbed decreases, and the tendency that light cannot be effectively absorbed increases. On the other hand, when the thickness of the semiconductor electrode exceeds 50 μm, the electrical resistance increases and the loss amount of carriers injected into the semiconductor increases, and the ion diffusion resistance increases, and photoexcitation causes electron injection into the semiconductor. I for later dyes^-I by electron injection from_Three ^-Of the battery to the counter electrode is hindered, and the tendency of the output characteristics of the battery to decrease increases.
[0050]
Further, the counter electrode CE is not particularly limited, and for example, the same counter electrode as that normally used for a silicon solar cell, a liquid crystal panel, or the like may be used. For example, it may have the same structure as the transparent electrode 1 described above, a metal thin film electrode such as Pt is formed on the transparent conductive film 3 similar to the transparent electrode 1, and the metal thin film electrode is placed on the electrolyte E side. It may be arranged to face. Alternatively, a small amount of platinum may be attached to the transparent conductive film 3 of the transparent electrode 1, or a metal thin film such as platinum, a conductive film such as carbon, or the like may be used.
[0051]
Furthermore, the composition of the electrolyte E is not particularly limited as long as it contains a redox species for reducing the dye after photoexcitation and electron injection into the semiconductor.^-/ I_Three ^-An iodine redox solution containing a redox species such as the above is preferably used. Specifically, I^-/ I_Three ^-As the system electrolyte, an ammonium salt of iodine or a mixture of lithium iodide and iodine can be used. Other, Br^-/ Br_Three ^-A quinone / hydroquinone redox electrolyte dissolved in an electrochemically inert solvent (and mixed solvent thereof) such as acetonitrile, propylene carbonate, and ethylene carbonate can also be used.
[0052]
The constituent material of the spacer S is not particularly limited, and for example, silica beads or the like can be used.
[0053]
Next, an example of a manufacturing method of the photoelectrode 10 shown in FIG. 1 and the dye-sensitized solar cell 20 shown in FIG. 3 will be described.
[0054]
First, when the transparent electrode 1 is manufactured, the fluorine-doped SnO described above on the substrate 4 such as a glass substrate.₂The transparent conductive film 3 can be formed using a known method such as spray coating.
[0055]
Next, as a method of forming each layer of the semiconductor electrode 2 on the transparent conductive film 3 of the transparent electrode 1, for example, there are the following methods. That is, first, a dispersion for forming the innermost layer 21 in which semiconductor particles P1 such as titanium oxide are dispersed is prepared. The solvent of the dispersion is not particularly limited as long as it can disperse the oxide semiconductor particles P1, 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. 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.
[0056]
Then, after drying, the innermost layer 21 (porous semiconductor film) of the semiconductor electrode 2 is formed by heating and baking in air, inert gas or nitrogen. The firing temperature at this time is preferably 300 to 800 ° C. at normal pressure. If the firing temperature is lower than 300 ° C., the adhesion between the oxide semiconductor particles P1 and the adhesion to the substrate may be weakened, and sufficient strength may not be obtained. If the firing temperature exceeds 800 ° C., the sticking between the oxide semiconductor particles P1 proceeds, and the surface area of the semiconductor electrode 2 (porous semiconductor film) may be reduced.
[0057]
Moreover, the firing temperature can be lowered by pressing the semiconductor powder on the transparent conductive film 3 of the transparent electrode 1 or the firing step can be omitted.
[0058]
Next, when the inner layer 23 is formed on the innermost layer 21, for example, a predetermined amount of the oxide semiconductor particles P3 is further added to the dispersion for forming the innermost layer 21. The inner layer 23 can be formed in the same manner as the method for forming the innermost layer 21 described above except that a dispersion having the above composition is prepared. Further, when the outermost layer 22 is formed on the inner layer 23, for example, a predetermined amount of the oxide semiconductor particles P3 is further added to the dispersion for forming the innermost layer 21. The outermost layer 22 can be formed on the inner layer 23 in the same manner as the method for forming the innermost layer 21 described above, except that a dispersion having a composition is prepared.
[0059]
Next, the sensitizing dye P2 is contained in the semiconductor electrode 2 by a known method such as an adhesion method. The sensitizing dye P2 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. The dye adsorption density of each layer of the electrode can also be adjusted by repeating the process of forming each layer and adsorbing the sensitizing dye by changing the concentration of the dye solution and the solvent.
[0060]
The surface oxidation treatment for removing impurities that inhibit the photoelectric 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 in a film shape, a known method 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]
After producing the photoelectrode 10 in this manner, a counter electrode CE is produced by a known method, and this, the photoelectrode 10 and the spacer S are assembled as shown in FIG. The dye-sensitized solar cell 20 is completed.
[0063]
The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.
[0064]
For example, in the above embodiment, as a method of decreasing the dye adsorption density for each layer from the innermost layer 21 to the outermost layer 22, the average particle diameter of the oxide semiconductor particles for each layer is changed from the innermost layer 21. In the present invention, the method of adjusting by increasing the outermost layer 22 has been described. However, in the present invention, the dye adsorption density for each layer is decreased from the innermost layer 21 to the outermost layer 22. The method is not particularly limited.
[0065]
For example, each of the plurality of layers of the semiconductor electrode may be adjusted by containing one kind of oxide semiconductor particles having different average particle sizes, and each of the plurality of layers of the semiconductor electrode has a different average particle size. Adjustment may be made by including at least two kinds of oxide semiconductor particles, and adjustment may be made by containing at least two kinds of oxide semiconductor particles having different average particle diameters in at least one of the plurality of layers of the semiconductor electrode. May be.
[0066]
Specifically, for example, as shown in FIG. 4, the innermost layer 21 of the semiconductor electrode 2 also contains oxide semiconductor particles P3, and the oxide semiconductor particles P1 and the oxide semiconductor particles P3 in each layer The composition ratio of the oxide semiconductor particles P3 with respect to the total amount may increase from the innermost layer 21 to the outermost layer 22.
[0067]
For example, as shown in FIG. 5, the semiconductor material constituting the outermost layer 22 of the semiconductor electrode 2 is only one kind of oxide semiconductor particle P3, and the semiconductor material constituting the innermost layer 21 is 1 There are only two types of oxide semiconductor particles P1, and the semiconductor material constituting the inner layer 23 may be two types of oxide semiconductor particles P1 and P3.
[0068]
Furthermore, for example, as shown in FIG. 6, the semiconductor material constituting the innermost layer 21 of the semiconductor electrode 2 is only one kind of oxide semiconductor particle P1, and the semiconductor material constituting the inner layer 23 is one kind. There may be a configuration in which only the oxide semiconductor particles P3 and the semiconductor material constituting the outermost layer 22 is only one kind of oxide semiconductor particles P4 having an average particle size larger than that of the oxide semiconductor particles P3.
[0069]
Further, for example, as shown in FIG. 7, the semiconductor material constituting each of the innermost layer 21, the inner layer 23, and the outermost layer 22 of the semiconductor electrode 2 is one kind of oxide semiconductor particles P1, and each layer is A configuration may be adopted in which the adsorption amount of the sensitizing dye adsorbed on each of the oxide semiconductor particles P <b> 1 is adjusted so as to decrease from the innermost layer 21 to the outermost layer 22.
[0070]
Further, for example, as shown in FIG. 8, the semiconductor materials constituting the innermost layer 21 and the inner layer 23 of the semiconductor electrode 2 are two types of oxide semiconductor particles P1 and P3, and the innermost layer 21 and the inner layer In the layer 23, the compounding ratio of the oxide semiconductor particles P3 with respect to the total amount of the oxide semiconductor particles P1 and P3 increases from the innermost layer 21 to the inner layer 23, and the semiconductor material constituting the outermost layer 22 However, there may be a configuration in which only one kind of oxide semiconductor particle P4 having an average particle size larger than that of the oxide semiconductor particle P3 is used.
[0071]
For example, in the above-described embodiment, the photoelectrode including the semiconductor electrode having a three-layer structure and the dye-sensitized solar cell including the semiconductor electrode have been described. However, the photoelectrode and the dye-sensitized solar cell of the present invention are It is not limited to this. For example, the photoelectrode of the present invention may have a configuration including the semiconductor electrode 2 composed of four or more layers, like the photoelectrode 14 shown in FIG. For example, the semiconductor electrode 2 of the photoelectrode 14 shown in FIG. 7 includes an innermost layer 21 and an outermost layer 22, an inner layer 23 disposed between the innermost layer 21 and the outermost layer 22, and 24. In this case, the dye adsorption density in each of the four layers of the semiconductor electrode 2 is adjusted so as to decrease from the innermost layer 21 to the outermost layer 22. Moreover, you may have a structure provided with the semiconductor electrode (not shown) which has a two-layer structure.
[0072]
In the above embodiment, the method of adjusting the particle size of the oxide semiconductor particles constituting each layer has been described as the method for adjusting the dye adsorption density for each layer of the semiconductor electrode. The method for adjusting the dye adsorption density for each layer of the semiconductor electrode is not particularly limited.
[0073]
Other methods for adjusting the dye adsorption density for each layer of the semiconductor electrode include a method for adjusting the maximum value of the pore size distribution or the average value of the pore size distribution for each layer, and a method for adjusting the porosity of each layer. is there.
[0074]
First, a method for adjusting the maximum value of the pore size distribution or the average value of the pore size distribution for each layer will be described.
[0075]
When adjusting the maximum value of the pore size distribution for each layer or the average value of the pore size distribution, comparing the maximum value of the pore size distribution or the average value of the pore size distribution in each of the maximum value of the pore size distribution for each layer, The maximum value of the pore size distribution for each layer or the average value of the pore size distribution is adjusted so as to increase from the innermost layer 21 to the outermost layer 22.
[0076]
The maximum value of the pore size distribution in the outermost layer 22 is preferably adjusted to be 10 to 1000 nm, and the maximum value of the pore size distribution in the outermost layer 22 and the pore size distribution in the innermost layer 21 are adjusted. The difference from the maximum value is preferably adjusted to be 3 to 990 nm. Alternatively, the average value of the pore size distribution in the outermost layer 22 is preferably adjusted to be 10 to 500 nm, and the average value of the pore size distribution in the outermost layer and the pore size distribution in the innermost layer 21 are adjusted. The difference from the average value is preferably adjusted to 3 to 490 nm.
[0077]
When the maximum value of the pore size distribution in the outermost layer 22 is less than 10 nm, the specific surface area per unit volume in the outermost layer 22 is increased and incident light is absorbed, but the sensitizing dye is effectively injected with electrons. The amount may be reduced. On the other hand, if the maximum value of the pore size distribution in the outermost layer 21 exceeds 1000 nm, the specific surface area per unit volume in the outermost layer 21 may decrease, and the amount of sensitizing dye in the electrode may decrease. Further, if the difference between the maximum value of the pore size distribution in the outermost layer 22 and the maximum value of the pore size distribution in the innermost layer 22 is less than 3 nm, an increase in electron injection in the region of the semiconductor electrode close to the transparent electrode. Since the amount of dye-sensitive material decreases, the battery characteristics may deteriorate. On the other hand, if this difference exceeds 990 nm, the total amount of sensitizing dye in the electrode may be reduced.
[0078]
From the same viewpoint as described above, the maximum value of the pore diameter distribution in the outermost layer 22 is more preferably 10 to 500 nm, and still more preferably 12 to 300 nm. Further, the difference between the maximum value of the pore size distribution in the outermost layer 22 and the maximum value of the pore size distribution in the innermost layer 21 is more preferably 3 to 500 nm, and still more preferably 5 to 300 nm.
[0079]
On the other hand, from the same viewpoint as in the case of the maximum value of the pore diameter distribution in each layer described above, the average value of the pore diameter distribution in the outermost layer 22 is 10 to 500 nm, and the pore diameter distribution in the outermost layer 22. And the average value of the pore size distribution in the innermost layer 21 is preferably 3 to 490 nm. Thereby, the photoelectric conversion efficiency in a semiconductor electrode can be improved more precisely. Also in this case, the average value of the pore diameter distribution in the outermost layer 22 is more preferably 12 to 300 nm, and further preferably 12 to 200 nm. Further, the difference between the average value of the pore size distribution in the outermost layer 22 and the average value of the pore size distribution in the innermost layer 21 is more preferably 3 to 300 nm, and further preferably 5 to 200 nm.
[0080]
In addition, the pore diameter distribution curve for obtaining the maximum value of the pore diameter distribution or the average value of the pore diameter distribution of each layer of the semiconductor electrode can be obtained by the method described below. That is, a porous material similar to the porous film constituting each layer is cooled to a liquid nitrogen temperature (−196 ° C.), nitrogen gas is introduced, and the adsorption amount is obtained by a constant volume method or a gravimetric method, and then introduced. The nitrogen gas pressure is gradually increased, and the amount of nitrogen gas adsorbed against each equilibrium pressure is plotted to obtain an adsorption isotherm. The pore diameter distribution curve can be obtained by a calculation method such as Cranston-Inklay method, Dollimore-Heal method, BJH method using this adsorption isotherm. Further, the pore distribution curve can be obtained by injecting high-pressure mercury into the pores of the sample by using a mercury intrusion method.
[0081]
Next, a method for adjusting the porosity of each layer will be described. In this method, when each layer of a semiconductor electrode is manufactured, a predetermined amount of a substance other than slurry or paste oxide semiconductor particles containing oxide semiconductor particles for forming each layer is mixed and finally removed. This is a method of forming pores (voids) that satisfy the condition of the dye adsorption density in each layer described above, and the porosity of each layer is increased from the innermost layer closest to the transparent electrode to the outermost layer farthest. It is a way to go.
[0082]
More specifically, as a method for forming such pores, for example, as a method for producing a semiconductor electrode, a slurry or paste containing oxide semiconductor particles for forming an oxide semiconductor film of each layer is used as a transparent electrode. Substances that can be removed by advancing an oxidation reaction or the like by heat treatment in a slurry or paste when using a method of applying or printing to the substrate, then drying and further heat-treating (for example, organic matter such as polyethylene glycol) There is a method of removing the above by heat treatment. In this case, the pore size distribution for each layer of the semiconductor electrode can be controlled by adjusting the amount of the substance that can be removed by the heat treatment.
[0083]
In addition, when using the above-described method for forming a semiconductor electrode as a method for forming other pores, a predetermined amount of material that cannot be removed by heat treatment is added to the above slurry or paste instead of the material that can be removed by heat treatment. There is also a method of removing from the semiconductor electrode after the heat treatment. Specifically, for example, there is a method in which salts such as potassium chloride and sodium chloride are added to the above slurry or paste and the salts are eluted with water after the heat treatment. Furthermore, as another method for forming pores, there is a method in which a predetermined amount of fine particles that can be eluted by acid or alkali are added and the fine particles are removed after heat treatment when the above-described method for producing a semiconductor electrode is used. .
[0084]
In addition, as another method of forming pores, a method of removing a part of an oxide semiconductor constituting each layer of the semiconductor electrode by dissolving or the like after the semiconductor electrode is manufactured or each time each layer of the semiconductor electrode is manufactured There is also. As a removing method in this case, for example, there is a method of dissolving a part of the oxide semiconductor with a solution containing an oxidizing agent. Further, instead of using a solution containing an oxidant, a method of electrochemically dissolving a part of an oxide semiconductor constituting each layer of the semiconductor electrode in the solution, or an oxide semiconductor constituting each layer of the semiconductor electrode There is a method of photoelectrochemically dissolving a part in a solution irradiated with light.
[0085]
By using such a method of forming pores, for example, as shown in FIG. 10, a photoelectrode having an innermost layer 21 and an outermost layer 22 can be configured. That is, the innermost layer 21 and the outermost layer 22 of the semiconductor electrode 2 shown in FIG. 10 are each composed of only one kind of oxide semiconductor particle P1 to which the sensitizing dye P2 is adsorbed. The size of the void portion R21 formed between the oxide semiconductor particles P1 in the layer 21 is smaller than the size of the void portion R22 formed between the oxide semiconductor particles P1 in the outermost layer 22. Is formed. Here, also in this case, the semiconductor electrode 2 may have a configuration of three or more layers.
[0086]
【Example】
Hereinafter, the photoelectrode 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 photoelectrode having the same configuration as that of the photoelectrode 10 shown in FIG. 1 is prepared by the following procedure, and further, the same configuration as that of the dye-sensitized solar cell 20 shown in FIG. 3 using this photoelectrode. 5 × 20 mm scale dye-sensitized solar cells having
[0088]
In the autoclave, a chemical species containing Ti (titanium alkoxide), ion-exchanged water, a pH adjuster (nitric acid, ammonia, etc.) is added, and under a predetermined reaction condition, a hydrolysis reaction of the chemical species containing Ti proceeds. The resulting TiO₂By proceeding crystallization of the particles, TiO with an average particle size of 27 nm₂A colloid solution (hereinafter referred to as colloid solution 1) containing particles (anatase, hereinafter referred to as P27) was prepared. Next, TiO having an average particle diameter of 128 nm was obtained by the same procedure as that of the colloid solution 1 except that the reaction conditions in the autoclave were changed.₂Colloidal solution (hereinafter referred to as colloidal solution 2) containing particles (anatase, hereinafter referred to as P128), TiO having an average particle size of 112 nm₂Colloidal solution (hereinafter referred to as colloid solution 3) containing particles (anatase, hereinafter referred to as P112), TiO having an average particle diameter of 198 nm₂A colloidal solution (hereinafter referred to as colloid solution 4) containing particles (anatase, hereinafter referred to as P198) was prepared. TiO contained in these colloidal solutions 1 to 4₂The average particle diameter of the particles was determined by analyzing dynamic light scattering of laser light using a light scattering photometer (manufactured by Otsuka Electronics Co., Ltd.).
[0089]
Next, TiO 2 is obtained by subjecting each of the colloid solutions 1 to 4 to solvent dilution and solvent removal.₂The following paste was prepared by adjusting the concentration of the particles and adding a cellulose-based viscosity modifier.
[0090]
That is, the paste containing only P27 using the colloid solution 1 (P27 content; 12 mass%, hereinafter referred to as paste 1), the colloid solution 1 and the colloid solution 4 are used, and the mass ratio of P27 and P198 is set. P27: P198 = 7: 3 paste (hereinafter referred to as paste 2), colloid solution 1 and colloid solution 4 were used, and the mass ratio of P27 and P198 was set to P27: P198 = 1: 1 (hereinafter referred to as “paste”). The paste 3), the colloid solution 1 and the colloid solution 3 are used, and the mass ratio of P27 and P112 is set to P27: P112 = 3: 7 (hereinafter referred to as paste 4), the colloid solution 1 and the colloid solution 3 A paste in which the mass ratio of P27 and P112 is P27: P112 = 1: 1 (hereinafter referred to as paste 5), colloid Paste containing only P128 using liquid 2 (content of P128; 12% by mass, hereinafter referred to as paste 6), paste containing only P198 using colloidal solution 4 (content of P198; 12% by mass, Hereinafter, paste 7) was prepared.
[0091]
On the other hand, SnO doped with fluorine on the glass substrate 4 (transparent conductive glass)₂A transparent electrode 1 (thickness: 1.1 mm) on which a conductive film 3 (film thickness: 700 nm) was formed was prepared.
[0092]
Then, paste 1 was used for forming the innermost layer 21, paste 2 was used for forming the inner layer 23, and paste 3 was used for forming the outermost layer 22. That is, this SnO₂The above-described paste 1 was screen-printed on the conductive film 3 and then dried. Then, it baked for 30 minutes on condition of 450 degreeC in air | atmosphere. Furthermore, by repeating this screen printing and baking using paste 2 and paste 3, SnO₂A semiconductor electrode having the same structure as the semiconductor electrode 2 shown in FIG. 1 was formed on the conductive film, and a photoelectrode containing no sensitizing dye was produced.
[0093]
Then, the pigment | dye was made to adsorb | suck to the back surface of a semiconductor electrode as follows. First, a ruthenium complex [cis-Di (thiocyanato) -N, N'-bis (2,2'-bipyridyl-4,4'dicarboxylic acid) -ruthenium (II)]] is used as a sensitizing dye, and an ethanol solution thereof is used. (Sensitizing dye concentration; 3 × 10^-Fourmol / L) was prepared. Next, the semiconductor electrode was immersed in this solution and allowed to stand under a temperature condition of 80 ° C. for 20 hours. Thereby, the sensitizing dye was adsorbed inside the semiconductor electrode 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 of 4-tert-butylpyridine for 15 minutes and then dried in a nitrogen stream maintained at 25 ° C. 12 was completed.
[0094]
In addition, about this semiconductor electrode, the area of a light-receiving surface; 10 cm²The thickness of the semiconductor electrode: 12 μm, the layer thickness of the innermost layer 21; 4 μm, the layer thickness of the inner layer 23; 4 μm, the layer thickness of the outermost layer 22; 4 μm, and the dye in the innermost layer 21 Adsorption density: 1.50 × 10^-12mol / cm^ThreeAverage value of specific surface area of oxide semiconductor in innermost layer 21; 83 m²/ G, the dye adsorption density in the inner layer 23; 1.13 × 10^-12mol / cm^ThreeThe average value of the specific surface area of the oxide semiconductor in the inner layer 23; 62 m²/ G, dye adsorption density in the outermost layer 22; 1.06 × 10^-12mol / cm^ThreeAverage value of specific surface area of oxide semiconductor in outermost layer 22; 52 m²/ G.
[0095]
Here, the dye adsorption density in each layer was measured using the following two methods. The first dye adsorption density was measured by the following procedure. That is, after the sensitizing dye is adsorbed to the oxide semiconductor film constituting each layer whose thickness and surface area are known, the sensitizing dye is adsorbed to the oxide semiconductor film by being immersed in a predetermined amount of solution capable of eluting the sensitizing dye. The dye was eluted. The absorption spectrum of the solution of this sensitizing dye is measured, the dye concentration is determined from the absorbance and the molar absorption coefficient of the sensitizing dye determined in advance, and divided by the volume of the oxide semiconductor film to absorb the dye on the oxide semiconductor film. Density was calculated. In addition, in this invention, since the semiconductor electrode was comprised by laminating | stacking several layers, it was shaved off for every layer and the pigment | dye adsorption density for every layer was computed.
[0096]
The second dye adsorption density was measured by the following procedure. That is, the concentration of the constituent element of the oxide semiconductor film and the constituent element of the sensitizing dye while ion sputtering the oxide semiconductor film from the surface of the transparent electrode in the normal direction of the surface using a secondary ion mass spectrometer By calculating the ratio, the distribution of the dye adsorption density for each layer was examined. The dye adsorption density of each layer was measured by obtaining the element ratio of Ti and Ru as the concentration ratio of the constituent elements of the oxide semiconductor film and the constituent elements of the sensitizing dye, and further determining the sputtering rate.
[0097]
Then, the dye adsorption density was determined by appropriately combining the above two measurement methods.
[0098]
Moreover, the average value of the specific surface area of the oxide semiconductor in each layer was measured as follows. That is, a porous oxide semiconductor film constituting each layer of the semiconductor electrode after application (screen printing) under the same conditions and further heat treatment was scraped off to form a powder, and a gas adsorption measuring device (Quantachrome) The isotherm adsorption line for this sample was obtained by the nitrogen adsorption method using “AUTOSORB”), and calculated by the BJH method. Even when layers with different structures are laminated, each layer is surface ground with a diamond grindstone, etc., and the powder for each layer is collected and measured and analyzed in the same manner to obtain a pore diameter distribution curve, and an average value of specific surface areas is obtained. It was.
[0099]
(Example 2)
Except that the semiconductor electrode was manufactured as follows, the same configuration as that of the photoelectrode 10 shown in FIG. 1 and the dye-sensitized solar cell 20 shown in FIG. A photoelectrode and a dye-sensitized solar cell were prepared.
[0100]
That is, except that the paste 2 prepared in Example 1 was used for forming the innermost layer 21, the paste 3 was used for forming the inner layer 23, and the paste 7 was used for forming the outermost layer 22. A semiconductor electrode having the same configuration as that of the semiconductor electrode 2 shown in FIG. 1 was formed on the transparent electrode 1 by the same procedure as in Example 1.
[0101]
In addition, about this semiconductor electrode, the area of a light-receiving surface; 1.0 cm²The thickness of the semiconductor electrode: 12 μm, the layer thickness of the innermost layer 21; 4 μm, the layer thickness of the inner layer 23; 4 μm, the layer thickness of the outermost layer 22; 4 μm, and the dye in the innermost layer 21 Adsorption density: 1.13 × 10^-12mol / cm^ThreeAverage value of specific surface area of oxide semiconductor in innermost layer 21; 62 m²/ G, the dye adsorption density in the inner layer 23; 1.06 × 10^-12mol / cm^ThreeThe average value of the specific surface area of the oxide semiconductor in the inner layer 23; 62 m²/ G, dye adsorption density in the outermost layer 22; 0.36 × 10^-12mol / cm^ThreeAverage value of specific surface area of oxide semiconductor in outermost layer 22; 20 m²/ G.
[0102]
(Example 3)
Except that the semiconductor electrode was manufactured as follows, the same configuration as that of the photoelectrode 10 shown in FIG. 1 and the dye-sensitized solar cell 20 shown in FIG. A photoelectrode and a dye-sensitized solar cell were prepared.
[0103]
That is, except that the paste 4 prepared in Example 1 was used for forming the innermost layer 21, the paste 5 was used for forming the inner layer 23, and the paste 6 was used for forming the outermost layer 22. A semiconductor electrode having the same configuration as that of the semiconductor electrode 2 shown in FIG. 1 was formed on the transparent electrode 1 by the same procedure as in Example 1.
[0104]
In addition, about this semiconductor electrode, the area of a light-receiving surface; 1.0 cm²The thickness of the semiconductor electrode: 12 μm, the layer thickness of the innermost layer 21; 4 μm, the layer thickness of the inner layer 23; 4 μm, the layer thickness of the outermost layer 22; 4 μm, and the dye in the innermost layer 21 Adsorption density: 1.20 × 10^-12mol / cm^ThreeAverage value of specific surface area of oxide semiconductor in innermost layer 21; 66 m²/ G, the dye adsorption density in the inner layer 23; 0.98 × 10^-12mol / cm^ThreeAverage value of specific surface area of oxide semiconductor in inner layer 23; 54 m²/ G, dye adsorption density in the outermost layer 22; 0.42 × 10^-12mol / cm^ThreeAverage value of specific surface area of oxide semiconductor in outermost layer 22; 23 m²/ G.
[0105]
(Example 4)
A slurry (hereinafter referred to as “slurry 1”) in which 8% by mass of polyethylene glycol (average molecular weight; 20000) was added to the colloidal solution 1 prepared in Example 1 was prepared. Similarly, a slurry in which 25% by mass of polyethylene glycol was added to colloid solution 1 (hereinafter referred to as slurry 2) and a slurry in which 40% by mass of polyethylene glycol was added (hereinafter referred to as slurry 3) were prepared.
[0106]
The slurry 1 was applied onto the transparent electrode 1 by a bar coating method, dried, and then fired at 450 ° C. to form the innermost layer 21. Next, the slurry 2 is used to form the inner layer 23, and the slurry 3 is used to form the outermost layer 22 and the inner layer 23 and the outermost layer 22 are formed in the same procedure as the innermost layer 21. And formed.
[0107]
Then, a semiconductor electrode having the same configuration as the semiconductor electrode 2 shown in FIG. 1 was formed on the transparent electrode 1 by the same procedure as in Example 1. In addition, about this semiconductor electrode, the area of a light-receiving surface; 1.0 cm²The thickness of the semiconductor electrode: 12 μm, the layer thickness of the innermost layer 21; 4 μm, the layer thickness of the inner layer 23; 4 μm, the layer thickness of the outermost layer 22; 4 μm, and the dye adsorption of the innermost layer 21 Density: 1.15 × 10^-12mol / cm^Three, Dye adsorption density of inner layer 23; 1.02 × 10^-12mol / cm^Three, Dye adsorption density of outermost layer 22; 0.95 × 10^-12mol / cm^ThreeThe porosity of the innermost layer 21 was 51%, the porosity of the inner layer 23 was 54%, and the porosity of the outermost layer 22 was 60%.
[0108]
(Example 5)
A slurry in which 8% by mass of polyethylene glycol (average molecular weight; 20000) was added to the solution in which P27: P198 = 5: 5 using the colloid solution 1 and the colloid solution 4 prepared in Example 1 (hereinafter referred to as slurry 4) ) Was prepared. Similarly, a slurry in which 25% by mass of polyethylene glycol was added to the colloidal solution (hereinafter referred to as slurry 5) and a slurry in which 40% by mass of polyethylene glycol was added (hereinafter referred to as slurry 6) were prepared.
[0109]
Then, the slurry 4 was applied onto the transparent electrode 1 by a bar coating method, dried, and then fired at 450 ° C. to form the innermost layer 21. Next, the slurry 5 is used to form the inner layer 23, and the slurry 6 is used to form the outermost layer 22, and the inner layer 23 and the outermost layer 22 are formed in the same procedure as the formation of the innermost layer 21. And formed.
[0110]
Then, a semiconductor electrode having the same configuration as the semiconductor electrode 2 shown in FIG. 1 was formed on the transparent electrode 1 by the same procedure as in Example 1. In addition, about this semiconductor electrode, the area of a light-receiving surface; 1.0 cm²The thickness of the semiconductor electrode: 12 μm, the layer thickness of the innermost layer 21; 4 μm, the layer thickness of the inner layer 23; 4 μm, the layer thickness of the outermost layer 22; 4 μm, and the dye adsorption of the innermost layer 21 Density; 1.08 × 10^-12mol / cm^Three, Dye adsorption density of inner layer 23; 0.88 × 10^-12mol / cm^Three, Dye adsorption density of outermost layer; 0.72 × 10^-12mol / cm^ThreeThe porosity of the innermost layer 21 was 56%, the porosity of the inner layer 23 was 58%, and the porosity of the outermost layer 22 was 63%.
(Example 6)
The slurry 1 prepared in Example 4 was applied onto the transparent electrode 1 by a bar coating method, dried, and then fired at 450 ° C. to form the innermost layer 21. Next, the outermost layer 22 was formed by the same procedure as the formation of the innermost layer 21 using the slurry 3 for forming the outermost layer 22.
[0111]
Then, a semiconductor electrode having the same configuration as the semiconductor electrode 2 shown in FIG. 10 was formed on the transparent electrode 1 by the same procedure as in Example 1. In addition, about this semiconductor electrode, the area of a light-receiving surface; 1.0 cm²The thickness of the semiconductor electrode: 8 μm, the layer thickness of the innermost layer 21; 4 μm, the layer thickness of the outermost layer 22; 4 μm, the dye adsorption density of the innermost layer 21; 1.15 × 10^-12mol / cm^Three, Dye adsorption density of outermost layer 22; 0.95 × 10^-12mol / cm^ThreeThe porosity of the innermost layer 21 was 51%, and the porosity of the outermost layer 22 was 60%.
[0112]
(Example 7)
The slurry 4 prepared in Example 5 was applied onto the transparent electrode 1 by a bar coating method, dried, and then fired at 450 ° C. to form the innermost layer 21. Next, the outermost layer 22 was formed by the same procedure as the formation of the innermost layer 21 using the slurry 6 for forming the outermost layer 22.
[0113]
A semiconductor electrode having the same configuration as the semiconductor electrode 2 shown in FIG. 8 was formed on the transparent electrode 1 by the same procedure as in Example 1. In addition, about this semiconductor electrode, the area of a light-receiving surface; 1.0 cm²The thickness of the semiconductor electrode: 8 μm, the layer thickness of the innermost layer 21; 4 μm, the layer thickness of the outermost layer 22; 4 μm, the dye adsorption density of the innermost layer 21; 1.08 × 10^-12mol / cm^Three, Dye adsorption density of outermost layer; 0.72 × 10^-12mol / cm^ThreeThe porosity of the innermost layer 21 was 56%, and the porosity of the outermost layer 22 was 63%.
[0114]
(Comparative Example 1)
A semiconductor electrode composed of only one layer using only the paste 1 prepared in Example 1 (light receiving surface area; 1.0 cm)², Layer thickness: 12 μm, dye adsorption density in the layer: 1.50 × 10^-12mol / cm^ThreeThe average value of the specific surface area of the oxide semiconductor in the layer; 82 m²/ G), a photoelectrode and a dye-sensitized solar cell were prepared by the same procedure as in Example 1. In this case, printing, drying, and firing of the paste 1 on the transparent electrode 1 were performed by repeating three times.
[0115]
(Comparative Example 2)
A semiconductor electrode consisting of only one layer using only the paste 2 used in Example 1 (light receiving surface area; 1.0 cm)², Layer thickness: 12 μm, dye adsorption density in the layer; 1.13 × 10^-12mol / cm^ThreeThe average value of the specific surface area of the oxide semiconductor in the layer; 62 m²/ G), a photoelectrode and a dye-sensitized solar cell were prepared by the same procedure as in Example 1. In this case, printing, drying, and baking of the paste 2 on the transparent electrode 1 were performed by repeating three times.
[0116]
(Comparative Example 3)
A photoelectrode and a dye-sensitized solar cell were produced by the same procedure as in Example 1 except that the semiconductor electrode was produced as follows.
[0117]
That is, except that the paste 7 prepared in Example 1 was used for forming the innermost layer 21, the paste 3 was used for forming the inner layer 23, and the paste 2 was used for forming the outermost layer 22. A semiconductor electrode having the same configuration as that of the semiconductor electrode 2 shown in FIG. 1 was formed on the transparent electrode 1 by the same procedure as in Example 1.
[0118]
In addition, about this semiconductor electrode, the area of a light-receiving surface; 1.0 cm²The thickness of the semiconductor electrode: 12 μm, the layer thickness of the innermost layer 21; 4 μm, the layer thickness of the inner layer 23; 4 μm, the layer thickness of the outermost layer 22; 4 μm, and the dye in the innermost layer 21 Adsorption density: 0.36 × 10^-12mol / cm^ThreeAverage value of specific surface area of oxide semiconductor in innermost layer 21; 20 m²/ G, the dye adsorption density in the inner layer 23; 1.06 × 10^-12mol / cm^ThreeThe average value of the specific surface area of the oxide semiconductor in the inner layer 23; 52 m²/ G, dye adsorption density in outermost layer 22; 1.13 × 10^-12mol / cm^ThreeAverage value of specific surface area of oxide semiconductor in outermost layer 22; 62 m²/ G.
[0119]
(Comparative Example 4)
Using only the slurry 1 used in Example 4, a semiconductor electrode consisting of only one layer (the area of the light receiving surface; 1.0 cm) by the same procedure as in Example 4²A photoelectrode and a dye-sensitized solar cell were prepared by the same procedure as in Example 1 except that the thickness of the semiconductor electrode; 12 μm) was prepared. In this case, the application, drying, and firing of the slurry 1 on the transparent electrode 1 were repeated three times. Moreover, about this semiconductor electrode, the pigment | dye adsorption density of the layer which consists of an oxide semiconductor film of a semiconductor electrode; 1.15 * 10^-12mol / cm^ThreePorosity: 51%.
[0120]
(Comparative Example 5)
Using only the slurry 4 used in Example 5, a semiconductor electrode consisting of only one layer by the same procedure as in Example 4 (light receiving surface area; 1.0 cm)²A photoelectrode and a dye-sensitized solar cell were prepared by the same procedure as in Example 1 except that the thickness of the semiconductor electrode; 12 μm) was prepared. In this case, the application, drying, and firing of the slurry 1 on the transparent electrode 1 were repeated three times. Moreover, about this semiconductor electrode, the pigment | dye adsorption density of the layer which consists of an oxide semiconductor film of a semiconductor electrode; 1.08 * 10^-12mol / cm^ThreeThe porosity was 56%.
[0121]
(Comparative Example 6)
Using only the slurry 1 used in Example 4, a semiconductor electrode consisting of only one layer (the area of the light receiving surface; 1.0 cm) by the same procedure as in Example 4²A photoelectrode and a dye-sensitized solar cell were produced by the same procedure as in Example 1 except that the thickness of the semiconductor electrode; 8 μm) was produced. In this case, the application, drying, and firing of the slurry 1 onto the transparent electrode 1 were performed twice. Moreover, about this semiconductor electrode, the pigment | dye adsorption density of the layer which consists of an oxide semiconductor film of a semiconductor electrode; 1.15 * 10^-12mol / cm^ThreePorosity: 51%.
[0122]
(Comparative Example 7)
Using only the slurry 4 used in Example 5, a semiconductor electrode consisting of only one layer by the same procedure as in Example 4 (light receiving surface area; 1.0 cm)²A photoelectrode and a dye-sensitized solar cell were produced by the same procedure as in Example 1 except that the thickness of the semiconductor electrode; 8 μm) was produced. In this case, the application, drying and firing of the slurry 4 onto the transparent electrode 1 were repeated twice. Moreover, about this semiconductor electrode, the pigment | dye adsorption density of the layer which consists of an oxide semiconductor film of a semiconductor electrode; 1.08 * 10^-12mol / cm^ThreeThe porosity was 56%.
[0123]
[Battery characteristics test]
A battery characteristic test was performed, and the energy conversion efficiency η of the dye-sensitized solar cells of Examples 1 to 7 and Comparative Examples 1 to 7 was measured. The battery characteristic test was performed using a solar simulator (trade name; “WXS-85-H type” manufactured by Wacom) and 100 mW / cm from a xenon lamp through an AM filter (AM-1.5).²It was performed by irradiating the simulated sunlight. Current-voltage characteristics are measured using an IV tester, and leakage current (I / mA · cm^-2), Open circuit voltage (Voc / V), short circuit current (Isc / mA · cm)^-2), Fill factor (F.F.) and energy conversion efficiency (η /%).
[0124]
Table 1 shows the results of battery characteristic tests obtained for the dye-sensitized solar cells of Examples 1 to 7 and Comparative Examples 1 to 7.
[0125]
[Table 1]

[0126]
As is clear from the results shown in Table 1, the energy conversion efficiencies η of the dye-sensitized solar cells of Examples 1 to 7 are the dye-sensitized solars of Comparative Examples 1 to 7 corresponding to each. It was confirmed that the value was higher than the energy conversion efficiency η of the battery.
[0127]
【The invention's effect】
As described above, according to the present invention, a photoelectrode having excellent photoelectric conversion efficiency can be configured. Moreover, the dye-sensitized solar cell which has the outstanding energy conversion efficiency can be comprised by using this photoelectrode.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of a photoelectrode of the present invention.
FIG. 2 is a schematic enlarged cross-sectional view of a portion of a region 100 shown in FIG.
3 is a schematic sectional view showing a dye-sensitized solar cell including the photoelectrode shown in FIG. 1. FIG.
4 is a schematic cross-sectional view showing another embodiment of the internal structure of the semiconductor electrode of the photoelectrode shown in FIG. 1. FIG.
FIG. 5 is a schematic cross-sectional view showing still another form of the internal structure of the semiconductor electrode of the photoelectrode shown in FIG.
6 is a schematic cross-sectional view showing still another embodiment of the internal structure of the semiconductor electrode of the photoelectrode shown in FIG. 1. FIG.
7 is a schematic cross-sectional view showing still another embodiment of the internal structure of the semiconductor electrode of the photoelectrode shown in FIG. 1. FIG.
FIG. 8 is a schematic cross-sectional view showing still another embodiment of the internal structure of the semiconductor electrode of the photoelectrode shown in FIG.
FIG. 9 is a schematic cross-sectional view showing another embodiment of the photoelectrode shown in FIG.
10 is a schematic cross-sectional view showing still another embodiment of the internal structure of the semiconductor electrode of the photoelectrode shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Transparent electrode, 2 ... Semiconductor electrode, 3 ... Transparent electrically conductive film, 4 ... Board | substrate 10, 11, 12, 13, 14 ... Photoelectrode, 20 ... Dye-sensitized solar cell, 21 ... Innermost layer, 22 ... outermost layer, 63 ... inner layer, 100 ... partial region of photoelectrode 10, CE ... counter electrode, E ... electrolyte, F1, F2, F3 ... light receiving surface, F22 ... back surface of semiconductor electrode 2, L10 ... incident light P1 ... oxide semiconductor particles, P2 ... sensitizing dye, P3 ... oxide semiconductor particles, P4 ... oxide semiconductor particles, R21, R22 ... pore (void) portion, S ... spacer.

Claims (5)

A photoelectrode having a semiconductor electrode having a light receiving surface and a transparent electrode disposed adjacent to the light receiving surface,
The semiconductor electrode is composed of oxide semiconductor particles having substantially the same particle size on which a sensitizing dye is adsorbed,
The semiconductor electrode is composed of a plurality of layers containing a dye,
Each of said plurality of layers is a porous membrane composed of the oxide semiconductor particles,
The outermost layer in which the dye adsorption density per unit volume of the porous film in each layer is located farthest from the innermost layer arranged at the position closest to the transparent electrode. A photoelectrode characterized by decreasing over the period. The dye adsorption density in the innermost layer is 1 × 10 ⁻¹³ to 1 × 10 ⁻¹¹ mol / cm ³ , and the dye adsorption density in the innermost layer and the dye adsorption in the outermost layer 2. The photoelectrode according to claim 1, wherein a difference from the density is 1 × 10 ^{−14 to} 9.9 × 10 ⁻¹² mol / cm ³ .   3. The photoelectrode according to claim 1, wherein an average value of a specific surface area of the oxide semiconductor in each of the layers decreases from the innermost layer to the outermost layer. The average value of the specific surface area of the oxide semiconductor in the innermost layer is 20 to 500 m ² / g, and the average value of the specific surface area of the oxide semiconductor in the innermost layer and the outermost layer 4. The photoelectrode according to claim 3, wherein a difference from an average value of a specific surface area of the oxide semiconductor is 3 to 480 m ² / g. A photoelectrode having a semiconductor electrode having a light-receiving surface and a transparent electrode disposed adjacent to the light-receiving surface of the semiconductor electrode, and a counter electrode, the semiconductor electrode and the counter electrode being interposed via an electrolyte A dye-sensitized solar cell disposed opposite to each other,
The said photoelectrode is a photoelectrode in any one of Claims 1-4, The dye-sensitized solar cell characterized by the above-mentioned.

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