JP2002352868A - Photoelectrode and dye-sensitized solar cell having the same - Google Patents

Abstract

[PROBLEMS] To provide a photoelectrode having excellent incident light absorption efficiency and a dye-sensitized solar cell having excellent energy conversion efficiency. SOLUTION: The photoelectrode 10 has a semiconductor electrode 2 having a light receiving surface F2 and a transparent electrode 1 arranged adjacent to the light receiving surface F2. The semiconductor electrode 2 is composed of a plurality of layers of three or more layers, each of the plurality of layers contains oxide semiconductor particles as a semiconductor material, and
The average particle diameter of the oxide semiconductor particles contained in each layer is determined by the distance between the innermost layer 21 located closest to the transparent electrode and the outermost layer 22 located farthest from the transparent electrode.
It is characterized by increasing toward.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectrode and a dye-sensitized solar cell having the same.

[0002]

2. Description of the Related Art In recent years, various developments of solar cells have been promoted with increasing interest in global warming and energy problems. Among such solar cells, dye-sensitized solar cells are expected to be put to practical use because the materials used are inexpensive and can be manufactured by a relatively simple process.

In a conventional dye-sensitized solar cell, light in the infrared to near-infrared wavelength region enters the semiconductor electrode due to the small absorption coefficient of the sensitizing dye contained in the semiconductor electrode. Was also not sufficiently absorbed in the semiconductor electrode and penetrated, and did not contribute to the progress of the photoelectric conversion reaction.

[0004] Therefore, for practical use of a dye-sensitized solar cell, various studies have been made to improve the energy conversion efficiency of the battery by improving the absorption efficiency of incident light in the semiconductor electrode provided in the photoelectrode. Has been done. The energy conversion efficiency η of the dye-sensitized solar cell
(%) Is represented by the following equation (1). Further, in the following formulas (1), P ₀ is the incident light intensity [mWcm ^-2], V _oc is the open-circuit voltage [V], I _sc is the short circuit current density [mAcm ^-2], F.F. The fill factor ( Fill Factor). η = 100 × (V _oc × I _sc × F.F.) / P ₀ (1)

[0005] The above-mentioned studies are described in, for example, Japanese Patent Application Laid-Open
No. 2,558,633 discloses that the average particle size is, for example, 80 nm.
On the surface of the semiconductor electrode (light absorbing particle layer) having the following small semiconductor particles as a constituent material, which is in contact with the electrolyte solution,
An optical electrode is formed by providing a layer (light reflecting particle layer) using large semiconductor particles having an average particle diameter of, for example, 200 to 500 nm as a constituent material, and scattering light incident on the semiconductor electrode to absorb the light. Dye-sensitized solar cells intended to improve efficiency have been proposed.

Japanese Patent Application Laid-Open No. 2000-106222 discloses that a semiconductor particle having a large particle diameter (average particle diameter: 10 to 300 nm) and a semiconductor particle having a small particle diameter (average particle diameter: 10 nm or less) are provided in a semiconductor electrode. A dye-sensitized solar cell has been proposed which is intended to improve the absorption efficiency by mixing incident light into the semiconductor electrode and scattering the incident light.

[0007]

SUMMARY OF THE INVENTION However, the present inventors have disclosed a dye-sensitized solar cell having a photoelectrode disclosed in Japanese Patent Application Laid-Open No.
In any of the dye-sensitized solar cells provided with the photoelectrode described in Japanese Patent No. 6222, sufficient incident light absorption efficiency is not obtained in the semiconductor electrode constituting the photoelectrode, and the photovoltaic cell has a sufficient efficiency. It was found that energy conversion efficiency could not be obtained and it was still insufficient.

That is, in each of the dye-sensitized solar cells described in the above two publications, as a result of light scattering by large semiconductor crystal particles, an optical path passing through the inside of the semiconductor electrode as compared with a case where no large semiconductor particles are present. Although the length becomes longer and the light utilization rate increases, there is a problem in that the scattering phenomenon is used to the last, and a part of the light will necessarily pass through the semiconductor electrode. In particular, as in the dye-sensitized solar cells described in the above two publications, when large spherical semiconductor particles are mixed in the semiconductor electrode, the proportion of incident light that is transmitted without being absorbed in the semiconductor electrode Becomes larger,
As a result, the effect of confining light 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 on which the dye is adsorbed decreases, the light absorption rate decreases, and the energy conversion efficiency decreases.

The present invention has been made in view of the above-mentioned problems of the prior art, and provides a photoelectrode having excellent incident light absorption efficiency and a dye-sensitized solar cell having excellent energy conversion efficiency. With the goal.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the semiconductor electrode constituting the photoelectrode has a structure composed of at least three or more layers. Increases the oxide semiconductor particles contained in the layer from the layer located closest to the transparent electrode to the layer located farthest from the transparent electrode, thereby confining the incident light in the semiconductor electrode. The inventors have found that the effect can be greatly improved, and arrived at the present invention.

That is, the present invention relates to a photoelectrode having a semiconductor electrode having a light receiving surface and a transparent electrode disposed adjacent to the light receiving surface, wherein the semiconductor electrode comprises three or more layers. And each layer of the plurality of layers contains oxide semiconductor particles as a semiconductor material, and
The average particle size of the oxide semiconductor particles included in each layer increases from the innermost layer disposed closest to the transparent electrode to the outermost layer disposed farthest from the transparent electrode. And a photoelectrode characterized by the following.

[0012] With the above structure of the semiconductor electrode, the amount of scattered light on the oxide semiconductor particles in each layer can be reduced.
It can be gradually increased along the thickness direction of the semiconductor from the light-receiving surface of the semiconductor electrode to the surface (hereinafter referred to as the back surface) that comes into contact with the electrolyte of the semiconductor electrode. Therefore, the photoelectrode of the present invention is the same as disclosed in
No. 863, JP-A-2000-106222
The light scattering efficiency in the semiconductor electrode can be more reliably improved as compared with any of the photoelectrodes described in the publication. Therefore, the photoelectrode of the present invention can obtain excellent incident light absorption efficiency.

Here, in the present invention, the condition that “the average particle diameter of the oxide semiconductor particles contained in each layer increases from the innermost layer to the outermost layer” means that the outermost layer located at one end is the outermost layer. The average particle size of the oxide semiconductor particles of the layer is finally larger than the average particle size of the oxide semiconductor particles of the innermost layer located at the other end, and when the plurality of layers are viewed as a whole, each layer 2 shows a state in which the average particle size of the oxide semiconductor particles of FIG. 1 is approximately increasing from the innermost layer to the outermost layer.

[0014] For example, the average particle size of the oxide semiconductor particles may be monotonously increased from the innermost layer to the outermost layer. Further, for example, even in a state in which the average particle diameter of the oxide semiconductor particles in some adjacent layers among the layers arranged between the innermost layer and the outermost layer has the same value. Good. Further, among the layers arranged between the innermost layer and the outermost layer, when comparing the average particle size of the oxide semiconductor particles of some adjacent layers, the layer on the innermost layer side The average particle size of the layer located may be larger than the average particle size of the layer located on the side of the outermost layer. However, from the viewpoint of sufficiently securing the incident light absorption efficiency of the semiconductor electrode, a state in which the average particle size of the oxide semiconductor particles monotonically increases from the innermost layer to the outermost layer, or Among the layers arranged between the layer and the outermost layer, a state in which the average particle diameter of the oxide semiconductor particles in some adjacent layers is preferably the same value is preferable.

In the photoelectrode of the present invention, the average particle diameter of the oxide semiconductor particles in the outermost layer is 50 to 50.
0 nm, and the difference between the average particle size of the oxide semiconductor particles in the outermost layer and the average particle size of the oxide semiconductor particles in the innermost layer is preferably 10 to 400 nm. Thereby, the light scattering efficiency in the semiconductor electrode can be more precisely improved.

Here, if the average particle size of the oxide semiconductor particles in the outermost layer is less than 50 nm, the amount and ratio of large-diameter particles that scatter light that can be absorbed by the sensitizing dye are reduced, and light scattering efficiency is reduced. May be insufficient. On the other hand, the average particle diameter of the oxide semiconductor particles in the outermost layer is 500 n.
If it exceeds m, the amount of the sensitizing dye in the electrode may decrease, and the incident light absorption efficiency may decrease. Further, when the difference between the average particle size of the oxide semiconductor particles in the outermost layer and the average particle size of the oxide semiconductor particles in the innermost layer is less than 10 nm, the light confinement effect may be insufficient. . On the other hand, if the difference exceeds 400 nm, the average particle size of the oxide semiconductor particles in the outermost layer may increase, and the amount of the sensitizing dye in the electrode may decrease.

From the same viewpoint as above, the average particle size of the oxide semiconductor particles in the outermost layer is 70 to 400.
nm, more preferably 80 to 300 nm. Further, the difference between the average particle size of the oxide semiconductor particles in the outermost layer and the average particle size of the oxide semiconductor particles in the innermost layer is more preferably 20 to 300 nm, and more preferably 25 to 250 nm. More preferred.

Further, in the photoelectrode of the present invention, the oxide semiconductor particles contained in each layer of the semiconductor electrode have an average particle diameter of 5 to 10%.
Consisting of small-diameter particles having a diameter of 0 nm and large-diameter particles having an average particle diameter exceeding 100 nm, the mixing ratio of the large-diameter particles with respect to the total amount of the small-diameter particles and the large-diameter particles increases from the innermost layer to the outermost layer. You may be doing.

As described above, the oxide semiconductor particles to be contained in each layer of the semiconductor electrode can be obtained by mixing and using the above-mentioned small-diameter particles and large-diameter particles, and further by setting the compounding conditions as described above. As described above, the average particle size of the oxide semiconductor particles included in each layer can be increased from the innermost layer to the outermost layer.

Here, in this case, if the average diameter of the small particles is less than 5 nm, the pore diameter in the semiconductor electrode layer becomes small, so that the adsorption time of the sensitizing dye is increased, There is a possibility that diffusion into the inside becomes difficult. On the other hand, when the average diameter of the small-diameter particles exceeds 100 nm, the amount of the sensitizing dye in the electrode may decrease. If the average diameter of the large-diameter particles is 100 nm or less, the light scattering effect is small and the light confinement effect may be insufficient. And
From the same viewpoint as above, the average diameter of the small-diameter particles is 10 to 8
The thickness is more preferably 0 nm, and further preferably 15 to 70 nm. The average diameter of the large-diameter particles is 1
It is more preferably larger than 00 nm and equal to or smaller than 600 nm, and further preferably 120 to 450 nm.

In this case, from the viewpoint of satisfying the same condition as the above-described condition regarding the average particle size of the oxide semiconductor particles included in each layer, the combination of the small-diameter particles and the large-diameter particles in the outermost layer is considered. The mixing ratio of the large-diameter particles to the amount is 5-1.
00 mass%, preferably 20 to 100 mass%
Is more preferable.

Further, in the photoelectrode of the present invention, the oxide semiconductor particles contained in each of the plurality of layers except for the innermost layer of the semiconductor electrode are composed of a small particle having an average particle diameter of 5 to 100 nm and an average particle diameter of 5 to 100 nm. Is composed of large-diameter particles exceeding 100 nm, and the oxide semiconductor particles contained in the innermost layer are small-diameter particles,
The compounding ratio of the large-diameter particles with respect to the total amount of the small-diameter particles and the large-diameter particles increases from the layer located closest to the innermost layer to the outermost layer among the plurality of layers. You may.

As described above, as the oxide semiconductor particles contained in each layer of the semiconductor electrode, the above-mentioned small diameter particles are used as the oxide semiconductor particles contained in the innermost layer, and a plurality of layers excluding the innermost layer are used. The oxide semiconductor particles contained in each layer of the oxide semiconductor particles contained in each layer may be used by mixing the above-mentioned small-diameter particles and large-diameter particles. Can be increased from the innermost layer to the outermost layer as described above.

Also in this case, the average diameter of the small-diameter particles is 10
-80 nm, more preferably 15-70 nm
Is more preferable. Further, the average diameter of the large-diameter particles is more preferably larger than 100 nm and 600 nm or less, and further preferably 120 to 450 nm. Furthermore, the compounding ratio of the large-diameter particles with respect to the total amount of the small-diameter particles and the large-diameter particles in the outermost layer is preferably 5 to 100% by mass, and more preferably 20 to 100% by mass.

Further, the photoelectrode of the present invention may be one in which at least one of a plurality of layers of the semiconductor electrode contains at least two kinds of oxide semiconductor particles having different average particle diameters. Also in this case, the average particle size of the oxide semiconductor particles included in each layer can be increased from the innermost layer to the outermost layer as described above. For example,
Of the plurality of layers of the semiconductor electrode, only one layer composed of at least two types of oxide semiconductor particles having different average particle diameters may be used, and each of the other layers may be a layer composed of one type of oxide semiconductor particles. In this case, the average particle diameter is 5 to 10 as at least two kinds of oxide semiconductor particles having different average particle diameters.
Small-diameter particles having a diameter of 0 nm and large-diameter particles having an average particle diameter of more than 100 nm may be used.

According to the present invention, there is provided 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. There is provided a dye-sensitized solar cell in which a counter electrode and a counter electrode are opposed to each other via an electrolyte, wherein the photoelectrode is the above-described photoelectrode of the present invention. As described above, by using the above-described photoelectrode of the present invention, a dye-sensitized solar cell having excellent energy conversion efficiency can be configured.

[0027]

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

[First Embodiment] FIG. 1 is a schematic sectional view showing a first embodiment of the photoelectrode of the present invention. FIG.
FIG. 2 is a schematic enlarged sectional view of a region 100 shown in FIG. 1. FIG. 3 is a schematic sectional view showing a dye-sensitized solar cell including the photoelectrode shown in FIG.

The photoelectrode 10 shown in FIG. 1 is mainly composed of a semiconductor electrode 2 having a light receiving surface F2 and a transparent electrode 1 arranged adjacent to the light receiving surface F2 of the semiconductor electrode 2. . Further, the dye-sensitized solar cell 2 shown in FIG.
0 is mainly the photoelectrode 10 shown in FIG.
And an electrolyte E filled in a gap formed between the photoelectrode 10 and the counter electrode CE by the spacer S. The semiconductor electrode 2 is in contact with the electrolyte E on the back surface F22 opposite to the light receiving surface F2.

In the dye-sensitized solar cell 20, electrons are generated in the semiconductor electrode 2 by the light L10 transmitted through the transparent electrode 1 and applied to the semiconductor electrode 2. And
Electrons generated in the semiconductor electrode 2 are collected by the transparent electrode 1 and taken out.

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

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

As shown in FIGS. 1 and 2, the semiconductor electrode 2
Is composed of three layers using oxide semiconductor particles as a constituent material. That is, the semiconductor electrode 2 is the transparent electrode 1
, And an outermost layer 22 disposed farthest from the transparent electrode 1.
And an inner layer 23 disposed between the innermost layer 21 and the outermost layer 22. When the average particle size of the oxide semiconductor particles included in each of the three layers is compared, the average particle size of the oxide semiconductor particles of each layer increases from the innermost layer 21 to the outermost layer 22. I have. Furthermore, the average particle size of the oxide semiconductor particles in the outermost layer is preferably adjusted to be 70 to 400 nm, and the average particle size of the oxide semiconductor particles in the outermost layer and the average particle size of the oxide semiconductor particles in the outermost layer are adjusted. The difference from the average particle diameter of the semiconductor particles is preferably adjusted to 20 to 300 nm. Since the photoelectrode 10 includes the semiconductor electrode 2 having the above structure, the efficiency of absorbing incident light in the semiconductor electrode 2 is improved.

That is, as shown in FIG.
Part of the light L10 incident from the light receiving surface F1 and passing through the innermost layer 21 is efficiently reflected and scattered on the oxide semiconductor particles P3 having a larger average particle diameter contained in the inner layer 23. It becomes light L12 and is efficiently returned to the innermost layer 21 again. Further, a part of the light (not shown) transmitted through the inner layer 23 is also efficiently reflected on the oxide semiconductor particles P3 contained in the outermost layer 22, and scattered light (not shown) And is efficiently returned to the innermost layer 21 again.
Due to the high light confinement effect in each layer of the semiconductor electrode 2, excellent incident light absorption efficiency can be obtained in the semiconductor electrode 2.

As shown in FIG. 2, the innermost layer 21 of the semiconductor electrode 2 is mainly composed of oxide semiconductor particles (small diameter particles).
P1 and a sensitizing dye P2 adsorbed on the surface of the oxide semiconductor particles P1. The inner layer 23 and the outermost layer 22 mainly include the oxide semiconductor particles P1.
And oxide semiconductor particles (large-diameter particles) P3 having a larger particle size than the oxide semiconductor particles P1, and a sensitizing dye P2 adsorbed on the surfaces of the oxide semiconductor particles P1 and the oxide semiconductor particles P3. It is configured.

Here, the oxide semiconductor particles (small diameter particles) P
The average particle size of 1 is preferably adjusted to be 5 to 100 nm. In addition, oxide semiconductor particles (large-diameter particles)
The average particle size of P3 is preferably adjusted to be greater than 100 nm. The mixing ratio of the oxide semiconductor particles P3 with respect to the total amount of the oxide semiconductor particles P1 and the oxide semiconductor particles P3 in the outermost layer 22 is determined by the ratio of the oxide semiconductor particles P1 and the oxide semiconductor particles P3 in the inner layer 23. Is adjusted so as to be larger than the mixing ratio of the oxide semiconductor particles P3 with respect to the total amount of as a result,
The average particle size of the oxide semiconductor particles in each layer is the innermost layer 2
It will increase from 1 to the outermost layer 22. In the case of the photoelectrode 10, the innermost layer 21 has
Oxide semiconductor particles P3 are not substantially contained.

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 the oxide semiconductor, for example, TiO ₂ , ZnO, SnO ₂ , Nb ₂ O ₅ ,
In ₂ O ₃ , WO ₃ , ZrO ₂ , La ₂ O ₃ , Ta ₂ O ₅ , Sr
TiO ₃ , BaTiO ₃ or the like can be used.

Further, 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 sensitizing dye P2 is absorbed in a visible light region and / or an infrared light region. Any pigment may be used. This sensitizing dye P
As 2, a metal complex, an organic dye, or the like can be used. Examples of the metal complex include metal phthalocyanines such as copper phthalocyanine and titanyl phthalocyanine, chlorophyll or derivatives thereof, hemin, ruthenium, osmium, iron and zinc complexes (for example, cis-dicyanate-bis (2,
2′-bipyridyl-4, 4′-dicarboxylate) ruthenium (II)) and the like. As the organic dye, metal-free phthalocyanine, cyanine dye, metalocyanine dye, xanthene dye, triphenylmethane dye and the like can be used.

The thickness of the semiconductor electrode 2 is 3 to 50 μm.
m, more preferably 5 to 30 μm, even more preferably 6 to 18 μm.
When the thickness of the semiconductor electrode is less than 3 μm, the amount of dye adsorbed is reduced, and the tendency for light to be unable to be effectively absorbed increases. On the other hand, when the thickness of the semiconductor electrode exceeds 50 μm, the electric resistance increases, the loss amount of carriers injected into the semiconductor increases, and the ion diffusion resistance increases. I ₃ by electron injection from ^{- -} after I for dye out of the counter electrode is inhibited, the output characteristics of the battery becomes large tends to decrease.

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

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

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

Next, an example of a method for manufacturing the photoelectrode 10 shown in FIG. 1 and the dye-sensitized solar cell 20 shown in FIG. 3 will be described.

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

Next, 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 is the following method. That is, first, a dispersion liquid for forming the innermost layer 21 in which the semiconductor particles P1 such as titanium oxide are dispersed is prepared. The solvent of this dispersion is water, an organic solvent,
Alternatively, there is no particular limitation as long as the oxide semiconductor particles P1 can be dispersed, such as a mixed solvent of both. Further, a surfactant and a viscosity modifier may be added to the dispersion as needed.
Next, the dispersion is applied on the transparent conductive film 3 of the transparent electrode 1,
Then it is dried. As a coating method at this time, a bar coater method, a printing method, or the like can be used. 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 300 to 800
C is preferred. If the sintering temperature is lower than 300 ° C., fixation between the oxide semiconductor particles P1 and adhesion to the substrate may be weakened, resulting in insufficient strength. Firing temperature 800
If the temperature exceeds ° C, fixation between the oxide semiconductor particles P1 proceeds, and the surface area of the semiconductor electrode 2 (porous semiconductor film) may be reduced.

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 added to the dispersion for forming the innermost layer 21. Other than preparing a dispersion having the composition further added,
The inner layer 23 can be formed in the same manner as the method of forming the innermost layer 21 described above. Furthermore, 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 outermost layer 21 described above. Except for preparing the dispersion having the composition, the outermost layer 22 can be formed on the inner layer 23 in the same manner as in the method of forming the innermost layer 21 described above.

Next, the sensitizing dye P2 is contained in the semiconductor electrode 2 by a known method such as an immersion method. The sensitizing dye P2 is contained by being attached to the semiconductor electrode 2 (chemical adsorption, physical adsorption, deposition, or the like). As the attachment method, for example, a method of immersing the semiconductor electrode 2 in a solution containing a dye can be used. At this time, the adsorption and deposition of the sensitizing dye can be promoted by heating and refluxing the solution. At this time, in addition to the dye, a metal such as silver or a metal oxide such as alumina may be contained in the semiconductor electrode 2 as necessary.

A surface oxidation treatment for removing impurities that inhibit the photoelectric conversion reaction contained in the semiconductor electrode 2 is appropriately performed by a known method every time each layer is formed or when all the layers are formed. You may.

Another method for forming the semiconductor electrode 2 on the transparent conductive film 3 of the transparent electrode 1 is as follows. That is, TiO _{2 is formed} on the transparent conductive film 3 of the transparent electrode 1.
Alternatively, a method of depositing a semiconductor in a film form may be used. As a method of depositing a semiconductor on the transparent conductive film 3 in a film form, a known method can be used. For example, physical vapor deposition methods such as electron beam vapor deposition, resistance heating vapor deposition, sputter vapor deposition, and cluster ion beam vapor deposition may be used. A reactive vapor deposition method of depositing on top may be used. Further, a chemical vapor deposition method such as CVD can be used by controlling the flow of a reaction gas.

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

[Second Embodiment] A second embodiment of the photoelectrode of the present invention will be described below with reference to FIG. The same elements as those described in regard to the above-described first embodiment are denoted by the same reference numerals, and redundant description will be omitted. FIG. 4 is a schematic sectional view showing the internal structure of the semiconductor electrode according to the second embodiment of the photoelectrode of the present invention.

The photoelectrode 11 (not shown) of the present embodiment is
As shown in FIG. 4, the innermost layer 21 of the semiconductor electrode 2 also contains the oxide semiconductor particles (large-diameter particles) P3, and the oxide semiconductor particles P1 (small-diameter particles) and the oxide semiconductor particles in each layer. The mixing ratio of the oxide semiconductor particles (large-diameter particles) P3 to the total amount of the (large-diameter particles) P3 is the innermost layer 2
It has the same configuration as the photoelectrode 10 shown in FIG. 1 except that it increases from 1 to the outermost layer 22.
Thus, the average particle diameter of the oxide semiconductor particles in each layer increases from the innermost layer 21 to the outermost layer 22. Since the photoelectrode 11 includes the semiconductor electrode 2 having the above structure, the absorption efficiency of incident light in the semiconductor electrode 2 is improved.

The dye-sensitized solar cell (not shown) having the photoelectrode 11 is the same as that of FIG.
Has the same configuration as the dye-sensitized solar cell 10 shown in FIG. The method for manufacturing the photoelectrode 11 and the dye-sensitized solar cell including the photoelectrode 11 is not particularly limited. For example, the photoelectrode 11 and the dye-sensitized solar cell 20 may be manufactured in the same manner as described above. can do.

[Third Embodiment] A third embodiment of the photoelectrode of the present invention will be described below with reference to FIG. The same elements as those described in regard to the above-described first embodiment are denoted by the same reference numerals, and redundant description will be omitted. FIG. 5 is a schematic sectional view showing the internal structure of the semiconductor electrode of the third embodiment of the photoelectrode of the present invention.

The photoelectrode 12 (not shown) of this embodiment is
As shown in FIG. 5, the outermost layer 22 of the semiconductor electrode 2 has the same configuration as the photoelectrode 10 shown in FIG. 1 except that the semiconductor material constituting the outermost layer 22 is only one kind of oxide semiconductor particles P3. ing. That is, the semiconductor electrode 2 shown in FIG. 5 has two types of oxide semiconductor particles (the oxide semiconductor particles P1 (small-diameter particles) and the oxide semiconductor particles (large-diameter particles) P3) in which only the inner layer 22 has a different average particle size. And the other layers are formed of one kind of oxide semiconductor particles. Also in this case, the average particle size of the oxide semiconductor particles in each layer increases from the innermost layer 21 to the outermost layer 22. Since the photoelectrode 12 includes the semiconductor electrode 2 having the above-described structure, the efficiency of absorbing incident light in the semiconductor electrode 2 is improved.

The dye-sensitized solar cell (not shown) having the photoelectrode 12 is the same as that of FIG.
Has the same configuration as the dye-sensitized solar cell 10 shown in FIG. The method of manufacturing the photoelectrode 12 and the dye-sensitized solar cell including the photoelectrode 12 is not particularly limited. For example, the photoelectrode 12 and the dye-sensitized solar cell 20 may be manufactured by the same method as that described above. can do.

[Fourth Embodiment] Hereinafter, a third embodiment of the photoelectrode of the present invention will be described with reference to FIG. The same elements as those described in regard to the above-described first embodiment are denoted by the same reference numerals, and redundant description will be omitted. FIG. 6 is a schematic sectional view showing the internal structure of the semiconductor electrode of the third embodiment of the photoelectrode of the present invention.

The photoelectrode 13 (not shown) of the present embodiment is
As shown in FIG. 6, the semiconductor material constituting the inner layer 23 of the semiconductor electrode 2 is only one kind of oxide semiconductor particles P3, and the semiconductor material constituting the outermost layer 22 is one kind of oxide semiconductor particles. Except for only P4, it has the same configuration as the photoelectrode 10 shown in FIG. Note that, in this case, the average particle size of the oxide semiconductor particles P4 included in the outermost layer 22 is adjusted to be larger than the average particle size of the oxide semiconductor particles P3. Also in this case, the average particle size of the oxide semiconductor particles in each layer increases from the innermost layer 21 to the outermost layer 22. Since the photoelectrode 13 includes the semiconductor electrode 2 having the above structure, the efficiency of absorbing incident light in the semiconductor electrode 2 is improved.

The dye-sensitized solar cell (not shown) having the photoelectrode 13 is the same as that of FIG.
Has the same configuration as the dye-sensitized solar cell 10 shown in FIG. The method for manufacturing the photoelectrode 13 and the dye-sensitized solar cell including the photoelectrode 13 is not particularly limited. For example, the photoelectrode 13 and the dye-sensitized solar cell 20 may be manufactured by the same method as that described above. can do.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

For example, in the above embodiment, the photoelectrode provided with the semiconductor electrode having a three-layer structure and the dye-sensitized solar cell provided with the same have been described. The solar cell 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, such as 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, when the average particle diameters of the oxide semiconductor particles included in the four layers of the semiconductor electrode 2 are compared, the average particle diameter of the oxide semiconductor particles in each layer is from the innermost layer 21 to the outermost layer. Is adjusted so as to increase toward the layer 22.

[0062]

EXAMPLES 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.

(Embodiment 1) FIG.
A photoelectrode having the same configuration as the photoelectrode 12 shown in FIG. 3 was produced, and a 5 × 20 mm scale having the same configuration as the dye-sensitized solar cell 20 shown in FIG. 3 except that this photoelectrode was used. Was manufactured.

First, TiO ₂ particles (anatase, manufactured by Nippon Aerosil Co., Ltd., trade name: “P25”, average particle size: 25 n
m, hereinafter referred to as P25), acetylacetone, ion-exchanged water, surfactant (trade name, manufactured by Tokyo Chemical Industry Co., Ltd .; “Tri
ton-X "), and kneaded to prepare a slurry for forming the innermost layer 21 (P25 content; 15% by mass, hereinafter referred to as slurry 1).

Next, P25 and commercially available large-diameter TiO ₂ particles (anatase, average particle size: 180 nm, hereinafter P180)
) And the mass ratio between P25 and P180 is P
Slurry for forming the inner layer 23 (P25 content: 7.5% by mass, P180
7.5 mass%, hereinafter referred to as slurry 2).

Next, a slurry for forming the internal layer 23 (P180 content; 15% by mass; hereinafter, referred to as slurry 3) was prepared by the same preparation procedure as that for the slurry 1 except that only P180 was used. did.

On the other hand, glass substrate 4 (transparent conductive glass)
Fluorine-doped SnO ₂ conductive film 3 (film thickness: 70
0 nm) was formed on the transparent electrode 1 (thickness: 1.1 mm). Then, the above-mentioned slurry 1 was applied on this SnO ₂ conductive film 3 using a bar coder, and then dried. Then, it baked for 30 minutes under the conditions of 450 degreeC in air | atmosphere.

[0068] Further, by repeating the firing the coating using a slurry 2 and slurry 3, the area of the semiconductor electrode (light receiving surface of the same structure as the semiconductor electrode 2 shown in FIG. 5 on the SnO ₂ conductive film; 1 0.0 cm ² , layer thickness; 15 μm, layer thickness of the innermost layer 21; 5 μm, layer thickness of the inner layer 23;
m, the layer thickness of the outermost layer 22; 5 μm) to form a photoelectrode containing no sensitizing dye.

Thereafter, the dye was adsorbed on the back surface of the semiconductor electrode as follows. First, a ruthenium complex [cis-Di (thiocyanato) -N, N'-bis (2,2'-bipyridy) is used as a sensitizing dye.
l-4,4'dicarboxylic acid) -ruthenium (II)] and ethanol solution (sensitizing dye concentration; 3 × 10 ^-4 mo
1 / L). Next, the semiconductor electrode was immersed in this solution, and allowed to stand at 80 ° C. for 20 hours. As a result, the sensitizing dye is applied to the inside of the semiconductor electrode 2 by about 1.0 ×
10 ^-7 mol / cm ^{2 was} adsorbed. Next, the open circuit voltage Vo
To improve c, the semiconductor electrode after adsorption of the ruthenium complex was immersed in a solution of 4-tert-butylpyridine in acetonitrile for 15 minutes, and then dried in a nitrogen stream maintained at 25 ° C. to complete the photoelectrode 12. .

Next, as a counter electrode having the same shape and size as the above-mentioned photoelectrode, a transparent conductive glass electrode on which Pt is deposited by electron beam evaporation (thickness of Pt thin film: 3n)
m) was prepared. Further, as the electrolyte E, an iodine-based redox solution containing iodine, lithium iodide, and imidazolium salt was prepared. Further, a spacer S (trade name: "Himilan") manufactured by Mitsui Dupont Polychemical Co., Ltd. having a shape corresponding to the size of the semiconductor electrode is prepared. As shown in FIG. 3, the photoelectrode 12, the counter electrode CE and the spacer S are prepared. And the above-mentioned electrolyte was filled therein to complete a dye-sensitized solar cell.

(Example 2) The photoelectrode 10 shown in FIG. 2 and the dye-sensitized type shown in FIG. 3 were manufactured in the same procedure as in Example 1 except that the semiconductor electrode was manufactured as follows. A photoelectrode and a dye-sensitized solar cell having the same configuration as the solar cell 20 were produced.

First, using P25 and P180, P2
The mass ratio of P5 to P180 is P25: P180 = 7: 3
A slurry for forming the internal layer 23 (P25 content; 10.5% by mass, P180 content; 4.5% by mass, Slurry 4) was prepared.

Then, the innermost layer 21 is formed using the slurry 1 described above, and the inner layer 23 is formed using the slurry 4.
And the outermost layer 22 is formed using the slurry 2 described above.
Was formed. Otherwise in the same manner as in Example 1, the area of the semiconductor electrode (light receiving surface of the same structure as the semiconductor electrode 2 shown in FIG. 1 on SnO ₂ conductive film; 1 cm ^2, thickness; 15 [mu] m, the innermost layer 21 Layer thickness: 5 μm, layer thickness of inner layer 23: 5 μm
m, the layer thickness of the outermost layer 22; 5 μm) to form a photoelectrode containing no sensitizing dye.

Example 3 The photoelectrode 10 shown in FIG. 1 and the dye-sensitized type shown in FIG. 3 were manufactured in the same procedure as in Example 1 except that the semiconductor electrode was manufactured as follows. A photoelectrode and a dye-sensitized solar cell having the same configuration as the solar cell 20 were produced.

In an autoclave, a chemical species containing Ti (titanium alkoxide), ion-exchanged water, and a pH adjuster (such as nitric acid and ammonia) are put, and under predetermined reaction conditions, the hydrolysis reaction of the chemical species containing Ti is performed. The colloid solution containing TiO ₂ particles (anatase, hereinafter, referred to as P27) having an average particle diameter of 27 nm (hereinafter, referred to as P27) by allowing the TiO ₂ particles to proceed, and then crystallization of the obtained TiO ₂ particles.
Colloidal solution 1) was prepared. Next, except that the reaction conditions in the autoclave were changed, a T
iO ₂ particles (anatase, hereinafter, referred to as P56) colloidal solution containing (hereinafter, referred to as a colloidal solution 2), an average particle diameter of 112 nm TiO ₂ particles (anatase, or less, P
112) and a colloid solution (hereinafter, referred to as colloid solution 4) containing TiO ₂ particles having an average particle diameter of 198 nm (anatase, hereinafter, referred to as P198). The average particle size of the TiO ₂ particles contained in these colloid solutions 1 to 4 was determined by analyzing dynamic light scattering of laser light using a light scattering photometer (manufactured by Otsuka Electronics Co., Ltd.).

Next, the concentration of the TiO ₂ particles is adjusted by diluting the solvent or removing the solvent with respect to each of the colloid solutions 1 to 4, and further, by adding a cellulose-based viscosity modifier, the paste shown below is prepared. Was prepared.

That is, by using the colloid solution 1
7 only (P27 content; 12% by mass,
Hereinafter, the paste 1), the colloid solution 1 and the colloid solution 4 are used to change the mass ratio between P27 and P198 to P2.
7: P198 = 7: 3 paste (hereinafter referred to as paste 2), colloid solution 1 and colloid solution 4 were used to determine the mass ratio of P27 and P198 to P27: P198 =
A paste having a ratio of 1: 1 (hereinafter referred to as paste 2) was prepared.

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, a semiconductor electrode having the same configuration as the semiconductor electrode 2 and the semiconductor electrode 2 shown in FIG. 1 cm ² , layer thickness; 12 μm, layer thickness of the innermost layer 21; 4 μm, layer thickness of the inner layer 23; 4 μm, layer thickness of the outermost layer 22; 4 μm).

Example 4 A photoelectrode 10 shown in FIG. 1 and a dye-sensitized type shown in FIG. 3 were manufactured in the same procedure as in Example 1 except that the semiconductor electrode was manufactured as follows. A photoelectrode and a dye-sensitized solar cell having the same configuration as the solar cell 20 were produced.

That is, the paste 2 used in Example 3 was used for forming the innermost layer 21. Example 3
Was used to form the internal layer 23. Further, a paste containing only P198 (P198 content; 12% by mass; hereinafter, referred to as paste 4) was prepared using the colloid solution 4 and used for forming the outermost layer 22.

A semiconductor electrode having the same structure as the semiconductor electrode 2 shown in FIG. 1 (the area of the light receiving surface; 1.0 cm ² , layer thickness: 12 μm,
Thickness of innermost layer 21; 4 μm, thickness of inner layer 23;
μm, the thickness of the outermost layer 22; 4 μm).

Example 5 A photoelectrode 10 shown in FIG. 1 and a dye-sensitized type shown in FIG. 3 were manufactured in the same procedure as in Example 1 except that the semiconductor electrode was manufactured as follows. A photoelectrode and a dye-sensitized solar cell having the same configuration as the solar cell 20 were produced.

That is, using the colloid solution 1 and the colloid solution 3 prepared in Example 3, P27 and P1
A paste (P27 content: 8.4% by mass; P112 content: 3.6% by mass; hereinafter, referred to as paste 5) having a mass ratio of P27: P112 = 7: 3 with respect to 12 was prepared. Was used to form the innermost layer 21.

Further, using the colloid solutions 1 and 3 prepared in Example 3, P27 and P112 were used.
(P27 content; 6% by mass; P112 content; 6% by mass; hereinafter, referred to as paste 6) was prepared with a mass ratio of P27: P112 = 1: 1. Used for formation. Further, the outermost layer 22 was formed using the paste 4 prepared in Example 4.

Then, a semiconductor electrode having the same configuration as the semiconductor electrode 2 shown in FIG. 1 (area of the light receiving surface; 1.0 cm ² , layer thickness: 12 μm,
Thickness of innermost layer 21; 4 μm, thickness of inner layer 23;
μm, the thickness of the outermost layer 22; 4 μm).

Example 6 The P prepared in Example 3
The innermost layer 21 was formed using the paste 1 consisting of only 27. In addition, a paste containing only P56 (P56 content; 12% by mass, hereinafter referred to as paste 7) was prepared using the colloid solution 2 prepared in Example 3, and used for forming the inner layer 23. . Example 4
Was used to form the outermost layer 22 using the paste 4 consisting of only P198 prepared in the above.

A semiconductor electrode having the same configuration as the semiconductor electrode 2 shown in FIG. 1 (the area of the light receiving surface) was formed on the transparent electrode 1 by the same procedure as in Example 1 except that the pastes were screen-printed. 1.0 cm ² , film thickness 12 μm,
Thickness of innermost layer 21; 4 μm, thickness of inner layer 23;
μm, the thickness of the outermost layer 22; 4 μm).

Comparative Example 1 Slurry 1 used in Example 1
A photoelectrode and a dye-sensitized type were prepared in the same manner as in Example 1 except that a semiconductor electrode (area of the light receiving surface; 1.0 cm ² , layer thickness; 15 μm) consisting of only one layer was prepared using only A solar cell was manufactured. In this case, the application of the slurry 1 onto the transparent electrode 1, drying and firing were repeated three times.

Comparative Example 2 Slurry 1 used in Example 1
A slurry containing a high concentration of P25 at a high concentration (P25 content; 40% by mass; hereinafter, referred to as slurry 5) was prepared in the same manner except that the amount of the solvent at the time of preparation was reduced. Then, a photoelectrode was formed in the same procedure as in Example 1 except that a semiconductor electrode (light receiving surface area: 1.0 cm ² , layer thickness: 15 μm) consisting of only one layer was prepared using only the slurry 5. And a dye-sensitized solar cell was produced. In this case, the application, drying and firing of the slurry 1 on the transparent electrode 1 were performed only once.

Comparative Example 3 Slurry 4 used in Example 1
A photoelectrode and a dye-sensitized type were prepared in the same manner as in Example 1 except that a semiconductor electrode (area of the light receiving surface; 1.0 cm ² , layer thickness; 15 μm) consisting of only one layer was prepared using only A solar cell was manufactured. In this case, the application of the slurry 4 onto the transparent electrode 1, drying and firing were repeated three times.

Comparative Example 4 Paste 1 Used in Example 3
The photoelectrode and the dye-sensitized type were manufactured in the same procedure as in Example 1 except that a semiconductor electrode (area of the light-receiving surface; 1.0 cm ² , layer thickness; 12 μm) consisting of only one layer was prepared using only A solar cell was manufactured. In this case, the application, drying and firing of the paste 1 on the transparent electrode 1 were repeated three times.

(Comparative Example 5) Paste 4 used in Example 4
The photoelectrode and the dye-sensitized type were manufactured in the same procedure as in Example 1 except that a semiconductor electrode (area of the light-receiving surface; 1.0 cm ² , layer thickness; 12 μm) consisting of only one layer was prepared using only A solar cell was manufactured. In this case, the application, drying and baking of the paste 4 on the transparent electrode 1 were repeated three times.

Comparative Example 6 Paste 2 used in Example 1
The photoelectrode and the dye-sensitized type were manufactured in the same procedure as in Example 1 except that a semiconductor electrode (area of the light-receiving surface; 1.0 cm ² , layer thickness; 12 μm) consisting of only one layer was prepared using only A solar cell was manufactured. In this case, the application of the paste 2 on the transparent electrode 1, drying and baking were repeated three times.

(Comparative Example 7) Using the colloid solution 1 and the colloid solution 2 prepared in Example 3, P27 and P27 were used.
A paste having a mass ratio of P27: P56 = 7: 3 with respect to 56 (P27 content; 8.4% by mass, P112 content; 3.6% by mass, hereinafter referred to as paste 8) was prepared. A paste was prepared using the colloid solution 1 and the colloid solution 2 prepared in Example 3 so that the mass ratio between P27 and P56 was P27: P56 = 1: 1 (P27 content; 6% by mass, P56 content) 6% by mass, hereinafter referred to as paste 9). Further, a paste containing only P56 (P56 content; 100% by mass; hereinafter, referred to as paste 10) was prepared using the colloid solution 2 prepared in Example 3.

Then, the innermost layer 2 is formed using the paste 8.
1 is formed, the inner layer 23 is formed using the paste 2,
The outermost layer 22 is formed by using the paste 10, and a semiconductor electrode including three layers (area of the light receiving surface; 1.0 cm ² ,
A photoelectrode and a dye-sensitized solar cell were manufactured in the same procedure as in Example 1 except that a layer thickness of 12 μm) was manufactured.

(Comparative Example 8) P prepared in Example 3
The innermost layer 21 was formed by repeating application, drying and baking on the transparent electrode 1 by screen printing twice using the paste 1 consisting of only 27. Example 4
The outermost layer 22 was formed on the innermost layer 21 by application, drying, and baking on the innermost layer 21 using the paste 4 consisting of only P198 prepared in the above.

Then, a semiconductor electrode having the same structure as the semiconductor electrode 2 shown in FIG. 1 (area of the light receiving surface: 1.0 cm ² , thickness 12 μm,
(The thickness of the innermost layer 21; 8 μm; the thickness of the outermost layer 22; 4 μm).

[Battery Characteristics Test] A battery characteristics test was performed.
The energy conversion efficiencies η of the dye-sensitized solar cells of Examples 1 to 7 and Comparative Example 1 were measured. The battery characteristics test was performed using a solar simulator (trade name, manufactured by Wacom; "WXS-8").
5-H type ") and an AM filter (AM-1.5)
The irradiation was performed by irradiating 100 mW / cm ² of simulated sunlight from a xenon lamp passed through. The current-voltage characteristics were measured using an IV tester, and the open-circuit voltage (Voc /
V), short-circuit current (Isc / mA · cm ⁻² ), fill factor (FF) and energy conversion efficiency (η /%) were determined.
Table 1 shows the configurations of the photoelectrodes included in each of the dye-sensitized solar cells of Examples 1 to 7 and Comparative Examples 1 to 8 and the results of the battery characteristics test.

[0099]

[Table 1]

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 6 were corresponding to those of Comparative Examples 1 to 8, respectively. It was confirmed that the value exhibited a value higher than the energy conversion efficiency η of the sensitive solar cell.

[0101]

As described above, according to the present invention,
Since a high light confinement effect can be obtained in the semiconductor electrode forming the photoelectrode, a photoelectrode having an excellent utilization factor of incident light can be formed. Further, by using this photoelectrode, a dye-sensitized solar cell having excellent energy conversion efficiency can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of a photoelectrode of the present invention.

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

FIG. 3 is a schematic sectional view showing a dye-sensitized solar cell including the photoelectrode shown in FIG.

FIG. 4 is a schematic sectional view showing the internal structure of a semiconductor electrode according to a second embodiment of the photoelectrode of the present invention.

FIG. 5 is a schematic sectional view showing an internal structure of a semiconductor electrode according to a third embodiment of the photoelectrode of the present invention.

FIG. 6 is a schematic sectional view showing the internal structure of a semiconductor electrode according to a fourth embodiment of the photoelectrode of the present invention.

FIG. 7 is a schematic sectional view showing another embodiment of the photoelectrode shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transparent electrode, 2 ... Semiconductor electrode, 3 ... Transparent conductive film, 4 ...
Substrates, 10, 11, 12, 13, 14 ... Photoelectrodes, 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, L
12: scattered light, P1: oxide semiconductor particles, P2: sensitizing dye, P3: oxide semiconductor particles, P4: oxide semiconductor particles, S: spacer.

Continuing from the front page (72) Inventor Azusa Tsukigase 41, Chukumi-Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central R & D Laboratories Co., Ltd. No. 1 Inside Toyota Central Research Laboratories Co., Ltd. 1-41, Toyoda Central Research Laboratories Co., Ltd. 2-1-1 Asahi-cho, Kariya-shi, Aisin Seiki Co., Ltd. (72) Inventor Toshiyuki Sano 2-1-1, Asahi-cho, Kariya-shi, Aichi F-term (reference) 5F051 AA14 CB29 DA20 FA03 5H032 AA06 AS16 CC14 CC16 EE02 EE07 EE16 HH00 HH01 HH05

Claims (6)

[Claims] 1. A photoelectrode comprising: a semiconductor electrode having a light receiving surface; and a transparent electrode disposed adjacently on the light receiving surface, wherein the semiconductor electrode is composed of a plurality of three or more layers. Each layer of the plurality of layers contains oxide semiconductor particles as a semiconductor material, and the average particle diameter of the oxide semiconductor particles contained in each layer is at a position closest to the transparent electrode. The photoelectrode is increased from an innermost layer disposed to an outermost layer disposed farthest from the transparent electrode. 2. An average particle size of the oxide semiconductor particles in the outermost layer is 50 to 500 nm, and an average particle size of the oxide semiconductor particles in the outermost layer and the innermost layer 2. The photoelectrode according to claim 1, wherein the difference from the average particle size of the oxide semiconductor particles in (a) is 10 to 400 nm. 3. The oxide semiconductor particles having an average particle size of 5
A large particle having an average particle diameter of more than 100 nm, and a mixing ratio of the large particle with respect to the total amount of the small particle and the large particle is from the innermost layer to the innermost layer. The photoelectrode according to claim 1, wherein the photoelectrode increases toward an outer layer. 4. The oxide semiconductor particles contained in each of the plurality of layers excluding the innermost layer have an average particle size of 5 to 5.
The oxide semiconductor particles contained in the innermost layer are the small-diameter particles, and the large-diameter particles having an average particle size exceeding 100 nm are the small-diameter particles and the large-diameter particles, The compounding ratio of the large-diameter particles with respect to the total amount increases from a layer disposed closest to the innermost layer to the outermost layer among the plurality of layers, 3. The photoelectrode according to 1 or 2. 5. The method according to claim 1, wherein at least one of the plurality of layers includes:
The photoelectrode according to claim 1, wherein the photoelectrode contains at least two kinds of the oxide semiconductor particles having different average particle diameters. 6. A photoelectrode having a semiconductor electrode having a light receiving surface, a transparent electrode disposed adjacent to the semiconductor electrode on the light receiving surface, and a counter electrode, wherein the semiconductor electrode and the counter electrode are provided. Are dye-sensitized solar cells opposed to each other via an electrolyte, wherein the photoelectrode is the photoelectrode according to any one of claims 1 to 5. .