JP2003187883A - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element where photoelectric conversion efficiency is substantially improved by restraining losses caused by an internal resistance of a collector, and by enhancing the capture ratio of incident light at a semiconductor layer, carrying a dye, which is a photoelectric conversion layer. <P>SOLUTION: The photoelectric conversion element comprises an optically transparent substrate to which the semiconductor layer carrying a sensitizing dye is adhered, an electrode facing the semiconductor layer on the substrate, an electrolyte layer disposed between the semiconductor layer on the substrate and the electrode. The collector composed of a conductive porous membrane is provided on the side of the smeiconductor layer contacting with the electrolyte layer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photoelectric conversion device having excellent photoelectric conversion efficiency.

[0002]

2. Description of the Related Art Photovoltaic conversion elements such as solar cells are highly expected as a clean energy source and have already been used.
N-junction type silicon solar cells have been put to practical use. However, the silicon-based solar cell requires a raw material of a high-purity material, and its manufacturing process also requires a high temperature process of about 1000 ° C. and a vacuum process, so that reduction in manufacturing cost is a major issue. Therefore, in recent years, high purity materials and high energy processes have been relatively unnecessary,
Wet solar cells, which perform charge separation by the potential gradient generated at the solid-liquid interface, have been attracting attention.

In particular, a so-called dye-sensitized solar system which improves photoelectric conversion efficiency by adsorbing a light-absorbing dye on the surface of a semiconductor electrode and absorbing visible light having a wavelength longer than the band gap of the semiconductor electrode by the dye. Research on batteries is being actively conducted.

However, a major problem of the conventional dye-sensitized solar cell is that only the sensitizing dye supported in a single layer on the semiconductor surface can inject electrons into the semiconductor. That is, single-crystal or poly-crystal semiconductors that have been often used for semiconductor electrodes so far have a smooth surface and no internal pores, and the effective area for supporting the sensitizing dye is equal to the electrode area. There is a problem that the amount of dye carried is small.

Therefore, when such an electrode is used, the monolayer sensitizing dye carried on the electrode can absorb only 1% or less of the incident light even at the maximum absorption wavelength, and the light utilization efficiency is extremely poor. Become. Attempts have been made to make the sensitizing dye multi-layered in order to enhance the light-collecting power, but in general, sufficient effects have not been obtained.

Under such circumstances, Gretzel et al., As a means for solving such a problem, Japanese Patent No. 26:
As described in Japanese Patent No. 64194, a method has been proposed in which a titanium oxide electrode is made porous so that a sensitizing dye is supported and the internal area is remarkably increased. Here, this titanium oxide porous film was produced by the sol-gel method. The porosity of this film is about 50%, forming a nanoporous structure with a very high internal surface area. For example, when the film thickness is 8 μm, the roughness factor (ratio of the actual area inside the porous area to the substrate area) reaches about 720. When this surface is geometrically calculated, the amount of the sensitizing dye carried on the surface reaches 1.2 × 10 ⁻⁷ mol / cm ² , and in fact, about 98% of the incident light is absorbed at the maximum absorption wavelength. .

This new dye-sensitized solar cell, also called a Graetzel cell, has a dramatic increase in the amount of the sensitizing dye supported by the above-mentioned titanium oxide being made porous, and it efficiently absorbs sunlight and becomes a semiconductor. A major feature is the development of a sensitizing dye that has a significantly high electron injection speed.

Gretzell et al. Developed a bis (bipyridyl) Ru (II) complex as a sensitizing dye for dye-sensitized solar cells. Its Ru complexes of the general formula cis -X ₂ Bis (2,2'-bipyridyl-4,4'-dicarboxylate) having the structure of Ru (II). X is Cl-, CN-, SC
N-. A systematic study was conducted on their fluorescence, visible light absorption, electrochemical and photoredox behavior. Of these, cis- (diisocyanate) -bis (2,2'-bipyridyl-4,4'-dicarboxylate) Ru (II) has remarkably excellent performance as a solar absorber and a dye sensitizer. Was shown to have.

The visible light absorption of this dye sensitizer is due to the charge transfer transition from the metal to the ligand. Further, the carboxyl group of the ligand is directly coordinated with the Ti ion on the surface to form a close electronic contact between the dye sensitizer and titanium oxide. Due to this electronic contact, electrons are injected from the dye sensitizer into the conduction band of titanium oxide at an extremely fast rate of 1 picosecond or less, and in the opposite direction, the conduction band of titanium oxide due to the oxidized dye sensitizer is applied. Recapturing of electrons injected into is believed to occur on the order of microseconds. This speed difference creates the directionality of photoexcited electrons, which is the reason why charge separation is performed with extremely high efficiency. And this is p
This is a difference from a pn-junction solar cell in which charge separation is performed by a potential gradient on the n-junction surface, which is an essential feature of the Gretzel cell.

Next, the structure of the Gretzel cell will be described. FIG. 3 is a schematic cross-sectional view of a conventional Gretzel cell. The Gretzel cell is composed of a glass substrate 30 coated with a transparent electrode 31 made of fluorine-doped tin oxide and a glass substrate 3 coated with a platinum electrode 34.
5 is a sandwich type cell in which an electrolyte solution 33 containing a redox couple is enclosed between the cell and the cell 5. On the glass substrate 30,
A semiconductor layer 32 composed of ultrafine titanium oxide particles is laminated on the transparent electrode 31, and a sensitizing dye is adsorbed on the semiconductor layer 32 to form a semiconductor electrode. The electrolyte solution 33 is injected by sandwiching the sealing material 36 between the two glass substrates 30 and 35 and injecting the electrolyte solution 33 into a very small gap between the glass substrates 30 and 35 by utilizing a capillary phenomenon. The electrolyte solution 33 uses a mixed solvent of ethylene carbonate and acetonitrile and is a solute of tetra-n-propylammonium iodide and iodine. I ⁻ / I ₃ ⁻
Of redox couples. The platinum electrode 34 coated as the counter electrode has a catalytic action for cathodic reduction of I ₃ ⁻ of this redox couple to I ⁻ .

The conventional dye-sensitized solar cell having the above structure performs photoelectric conversion by the following mechanism. First, the light 37 incident on the dye-sensitized solar cell passes through the glass substrate 30 and the transparent electrode 31 having translucency, is absorbed by the sensitizing dye adsorbed on the semiconductor layer 32, and absorbs sunlight. Then excited electrons are generated. The excited electrons generated are the semiconductor layer 32.
To the transparent electrode 31 (current collector) after passing through the sintered semiconductor particles. The sensitizing dye that has lost the excited electrons receives electrons from the reduced electrolyte of the redox couple contained in the electrolyte solution 33 and returns to the original state. The redox couple contained in the electrolyte solution 33 that has lost the electrons and is in the oxidized state receives electrons from the platinum electrode 34 (counter electrode) and returns to the reduced state.

[0012]

In a dye-sensitized solar cell, the internal resistance generated at the interface between the current collector (transparent electrode) made of a transparent conductive film and the semiconductor layer, and the interface between semiconductor particles causes a photoelectric conversion of the solar cell. It becomes a factor of lowering the conversion efficiency. Therefore, in general, a solution in which semiconductor particles are dispersed is applied to a glass substrate with a transparent electrode made of a transparent conductive film and then sintered at a high temperature to avoid isolation of the semiconductor particles and ensure an electron transfer path. Has been done.

However, according to this method, the resistance of the current collector made of the transparent conductive film increases due to the heat applied during firing, which causes a decrease in the photoelectric conversion efficiency of the solar cell. Here, although the loss due to the resistance can be reduced by increasing the thickness of the current collector made of the transparent conductive film, the problem that the light transmittance of the transparent conductive film is newly reduced occurs, and the photoelectric conversion efficiency of the solar cell is increased. Is difficult to improve.

From the viewpoint of reducing the resistance loss of the current collector, the constituent material of the current collector has a lower resistivity than that of the conventional transparent conductive film, and has a resistivity due to heat during firing. Metal material that does not rise, eg A
u, Pt, Ag, Cu, Al, Ni, Zn, Ti or C
r and the like and alloys thereof are preferable. However, in the configuration of FIG. 3, when the current collector is replaced with the above-mentioned metal or its alloy from the transparent conductive film so far, the light transmittance of the current collector becomes low, so that the photoelectric conversion layer (semiconductor layer) becomes There is a problem that the amount of light reaching the unit is significantly reduced. for that reason,
It is difficult to use the constituent material as a current collector for fixing the semiconductor particles.

Further, in the conventional photoelectric conversion element, light that cannot be completely absorbed by the semiconductor layer supporting the sensitizing dye, which is the photoelectric conversion layer, passes through the photoelectric conversion layer, so that it is difficult to effectively use the incident light. There was also a problem. If a film having a high light reflectance is provided on the counter electrode, the light can be returned to the photoelectric conversion layer and absorbed. However, in this case, since the electrolyte layer exists between the photoelectric conversion layer and the counter electrode, there is a problem in that light is absorbed by the components in the electrolyte layer when passing through the electrolyte layer, resulting in light loss.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, and suppresses the loss caused by the internal resistance of the current collector (transparent electrode), and also the sensitizing dye which is the photoelectric conversion layer. An object of the present invention is to provide a photoelectric conversion element in which the photoelectric conversion efficiency is dramatically improved by increasing the ratio of incident light trapped in the semiconductor layer carrying the.

[0017]

To achieve the above object, the photoelectric conversion element of the present invention comprises a light-transmissive substrate on which a semiconductor layer carrying a sensitizing dye is adhered, and the semiconductor layer of the substrate. A photoelectric conversion element comprising an electrode facing each other, and an electrolyte layer disposed between the semiconductor layer of the substrate and the electrode, wherein a conductive porous film is provided on a side of the semiconductor layer in contact with the electrolyte layer. It is characterized in that a current collector made of is provided. Accordingly, a current collector having a low resistivity can be provided in the semiconductor layer regardless of the light transmittance of the current collector.

In the photoelectric conversion element of the present invention, as the current collector, a conductive porous film having a hole through which ions in the electrolyte solution can pass is used, and the through hole formed in the conductive porous film is used. Then, the ions in the electrolyte solution move between the semiconductor layer supporting the sensitizing dye and the counter electrode, and the charge can be transferred.

Further, incident light that has not been completely absorbed by the semiconductor layer supporting the sensitizing dye, which is the photoelectric conversion layer, is reflected by the conductive porous film and returned to the photoelectric conversion layer again. Compared with the case of utilizing the reflection of No. 1, the light absorption by the components in the electrolyte layer is reduced, and the incident light can be efficiently converted into electricity.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the photoelectric conversion element of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the photoelectric conversion element of the present invention. As shown in the figure, in the photoelectric conversion element 1 of the present invention, a semiconductor layer 3 carrying a sensitizing dye is formed on one surface of a transparent substrate 2 which is transparent to light. Further, a current collector 4 made of a conductive porous film is laminated on the side of the semiconductor layer 3 carrying the sensitizing dye opposite to the transparent substrate 2. The photoelectric conversion element of the present invention is significantly different from the conventional photoelectric conversion element shown in FIG. 3 in that the stacking order of the semiconductor layer 3 and the current collector 4 on the transparent substrate 2 is opposite.

The other substrate 8 may be made of a light transmissive material or a material having no light transmissive property. The first conductive film 6 and the second conductive film 6 are formed on one surface of the substrate 8.
A counter electrode 9 made of the conductive film 7 is formed. An electrolyte layer 5 made of an electrolyte solution is arranged between the first conductive film 6 and the current collector 4. In addition, 10 is a sealing material and 11 is incident light. The electrolyte solution is also held in the pores inside the semiconductor layer 3 having a porous structure supporting the sensitizing dye. Therefore, the ions in the electrolyte solution can freely move between the semiconductor layer 3 and the counter electrode 9 via the through hole of the current collector 4.

In FIG. 1, the transparent electrode is not provided on the transparent substrate 2, but the transparent electrode may be provided on the transparent substrate 2 as in the conventional photoelectric conversion element.

A photoelectric conversion element having a photoelectric conversion layer on the light-receiving surface side of a current collector is disclosed in Japanese Patent Laid-Open No. 10-112337.
It is described in Japanese Patent Publication No. However, JP-A-10-112
In the structure of the photoelectric conversion element described in Japanese Patent No. 337, the incident light reaches the photoelectric conversion layer after passing through the electrolytic solution layer that absorbs visible light, so that light transmission loss due to the electrolytic solution occurs. On the other hand, in the structure of the photoelectric conversion element of the present invention, the incident light reaches the photoelectric conversion layer directly, so that the light transmission loss due to the electrolytic solution does not occur. Further, in the structure of the present invention, by using a material having a high light reflectance as a current collector such as a porous metal film, the light passing through the photoelectric conversion layer is reflected by the current collector and reused. It can be performed. Also in this case, the presence of the current collector in contact with the photoelectric conversion layer makes it possible to minimize the influence of the light transmission loss due to the electrolytic solution on the reused light.

The conductive porous film forming the current collector is
It can be formed by applying conductive fine particles and then baking or by using a film forming method such as vapor deposition, sputtering, or ion plating. As the constituent material of the conductive porous film, a metal is preferable from the viewpoint of conductivity and light reflectance, and Au, Pt, Ag, Cu, Al, Ni, Zn, Ti.
Alternatively, a metal such as Cr or an alloy of those metals is preferably used.

When the conductive fine particles are fired to form a porous film made of a sintered body, specifically, a paste in which the conductive fine particles are dispersed is applied onto the semiconductor layer carrying the sensitizing dye. Then, a method of firing after drying may be used. The particle size of the conductive fine particles is preferably in the range of 5 nm to 1 μm. Within this range, conductive fine particles do not easily agglomerate to form a uniform film, and a film having uniform resistance is formed to stabilize the characteristics of the solar cell and make the film thickness uniform. Therefore, there is no short circuit with the counter electrode. The conductive fine particles may be composed of particles having a uniform particle size or may be a mixture of particles having different particle sizes.

When a thin film forming method such as vapor deposition, sputtering or ion plating is used, since the semiconductor layer is porous and its surface has irregularities, it is formed on the semiconductor layer by the shadowing effect. The thin film also becomes a porous film.

The thickness of the conductive porous film is not particularly limited, but is preferably 10 nm or more in order to have good conductivity, and is 1 μm or less at the maximum in order not to impair the ionic conductivity of the electrolyte. Is desirable. Figure 2
FIG. 3 is an enlarged conceptual view of a state in which a conductive porous film is formed on a semiconductor layer. In FIG. 2, 20 is a semiconductor layer, 21 is a conductive porous film, 22 is titanium oxide particles, and 23 is a through hole of the conductive porous film. As can be seen from FIG. 2, the larger the thickness of the conductive porous film 21, the higher the conductivity. However, if the film thickness is too large, the through holes 23 are closed and the conduction of ions is hindered, so that the internal resistance increases. Therefore, the photoelectric conversion efficiency is reduced.

Further, it is also effective to provide a film made of an oxide semiconductor on the surface of the conductive porous film. By providing a film of an oxide semiconductor, it is possible to prevent the conductive porous film from being deteriorated and to suppress the same reduction reaction that occurs at the counter electrode from occurring on the surface of the conductive porous film. . Examples of the method for forming a film of an oxide semiconductor on the surface of a conductive porous film for such purposes include methods such as electrolytic plating, electroless plating and liquid phase deposition, and in the case of a titanium oxide semiconductor film. Examples include treatment in a TiCl ₄ aqueous solution. Examples of the oxide semiconductor for coating the surface of the conductive porous film include titanium oxide, tungsten pentoxide, strontium tungstic acid, strontium titanate, niobium pentoxide, cadmium sulfide, zinc oxide, tin oxide, indium trioxide. One or more known semiconductors such as the above can be used.

The material of the transparent substrate 2 is not particularly limited as long as it has a light-transmitting property, but glass or a transparent film is usually used. Since the transparent film is flexible,
Suitable for applications that require flexibility. The higher the light transmittance of the transparent substrate 2, the better. The preferred light transmittance is 50
% Or more, and more preferably 80% or more.

As the substrate 8, in addition to the same glass and transparent film as the transparent substrate 2, a metal or the like can be used. The substrate 8 may be opaque, but is preferably transparent in that light can be incident from the substrates on both sides.

Semiconductor layer 3 in the photoelectric conversion device of the present invention
The semiconductor layer itself may be the same as the semiconductor layer used in the conventional photoelectric conversion element. By supporting a sensitizing dye on the semiconductor layer 3, a photoelectric conversion element having high photoelectric conversion efficiency can be obtained.

As a material for forming the semiconductor layer 3, C is used.
d, Zn, In, Pb, Mo, W, Sb, Bi, Cu,
Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, S
R, Ga, Si, Cr oxides, SrTiO ₃ , CaT
perovskite such as iO ₃ , or CdS, ZnS,
_{In 2 S 3, PbS, Mo} 2 S, WS 2, Sb 2 S 3, Bi 2
S ₃ , ZnCdS ₂ , Cu ₂ S sulfide, CdSe, In ₂
Se ₃ , WSe ₂ , HgS, PbSe, CdTe metal chalcogenide, GaAs, Si, Se, Cd
₂ P ₃ , Zn ₂ P ₃ , InP, AgBr, PbI ₂ , Hg
I ₂ , BiI ₃ , or a complex containing at least one selected from the above semiconductors, for example, CdS / TiO ₂ , C
dS / AgI, Ag ₂ S / AgI, CdS / ZnO, C
dS / HgS, CdS / PbS, ZnO / ZnS, Zn
O / ZnSe, CdS / HgS, CdS _x / CdS
e _1-x , CdS _x / Te _1-x , CdSe _x / Te _1-x , Zn
S / CdSe, ZnSe / CdSe, CdS / ZnS,
TiO ₂ / Cd ₃ P ₂ , CdS / CdSeCd _y Zn
_1-y S and CdS / HgS / CdS are mentioned. Among them, TiO ₂ is preferable in the Graetzel cell in terms of avoiding photodissolution in the electrolytic solution and high photoelectric conversion characteristics.

The particle size of the semiconductor particles used for forming the semiconductor layer 3 is generally preferably in the range of 5 to 1000 nm. Within this range, the pore diameter of the semiconductor layer 3 becomes appropriate, the redox substance in the electrolyte solution moves smoothly, and the decrease in photocurrent does not occur.
Further, since the surface area of the semiconductor layer 3 can be increased, it is possible to obtain a sufficient amount of the sensitizing dye supported, and as a result, a large photocurrent can be obtained. A particularly preferable range of the particle size of the semiconductor particles is 10 to 100 nm.

The thickness of the semiconductor layer 3 is 0.1 to 100 μm.
It is preferably within the range. Within this range,
A sufficient photoelectric conversion effect can be obtained, and the transparency to visible light and near infrared light does not deteriorate. A more preferable range of the film thickness of the semiconductor layer 3 is 1 to 50 μm, and a particularly preferable range is 5 to 30 μm.

As the sensitizing dye used for supporting on the semiconductor layer 3, any dye commonly used in conventional dye-sensitized photoelectric conversion elements can be used. Such dyes are known to those skilled in the art. Such dyes are, for example, R
uL ₂ (H ₂ O) ₂ type ruthenium-cis-diaqua-bipyridyl complex or ruthenium-tris (Ru
L ₃ ), ruthenium-bis (RuL ₂ ), osnium-tris (OsL ₃ ), osnium-bis (OsL ₂ ) -type transition metal complex, or zinc-tetra (4-carboxyphenyl) porphyrin, iron-hexacyanide complex,
Examples include phthalocyanine. As an organic dye,
9-phenylxanthene dye, coumarin dye, acridine dye, triphenylmethane dye, tetraphenylmethane dye, quinone dye, azo dye, indigo dye, cyanine dye, merocyanine dye, xanthene dye And so on. Among these, the ruthenium-bis (RuL ₂ ) derivative is particularly preferable because it has a broad absorption spectrum in the visible light region.

As a method of supporting the sensitizing dye on the semiconductor layer 3, for example, a method of immersing the transparent substrate 2 having the semiconductor layer 3 in a solution in which the sensitizing dye is dissolved can be mentioned. As a solvent for this solution, any solvent capable of dissolving a sensitizing dye such as water, alcohol, toluene and dimethylformamide can be used. Further, as a dipping method, heating and reflux or application of ultrasonic waves can be performed when the transparent substrate 2 having the semiconductor layer 3 is dipped in the sensitizing dye solution for a certain period of time. After the dye is loaded on the semiconductor layer 3, it may be washed with alcohol or heated under reflux in order to remove the sensitizing dye remaining on the semiconductor layer 3 without being loaded.

The amount of the sensitizing dye supported on the semiconductor particles is preferably in the range of 1 × 10 ^-8 to 1 × 10 ^-6 mol / cm ² . Within this range, the effect of improving the photoelectric conversion efficiency can be obtained economically and sufficiently.

The electrolyte used in the electrolyte layer 5 of the photoelectric conversion element 1 of the present invention is not particularly limited as long as the solvent contains a pair of redox-based constituents consisting of an oxidant and a reductant. It is preferable that the oxidant and the reductant are redox-based constituent substances having the same charge. The redox-type constituents in this specification mean a pair of substances that reversibly exist in the form of an oxidant and a reductant in a redox reaction. Such a redox system constituent itself is known to those skilled in the art. Examples of the redox component that can be used in the present invention include chlorine compound-chlorine, iodine compound-iodine, bromine compound-bromine, thallium ion (III) -thallium ion (I), mercury ion (II) -mercury ion ( I), ruthenium ion (III) -ruthenium ion (II), copper ion (I
I) -copper ion (I), iron ion (III) -iron ion (II), vanadium ion (III) -vanadium ion (II), manganate ion-permanganate ion, ferricyanide-ferrocyanide, Examples thereof include quinone-hydroquinone and fumaric acid-succinic acid. Of course, other redox-based constituents can also be used. Among them, iodine compound-iodine is preferable, and as the iodine compound, lithium iodide,
Metal iodides such as potassium iodide, tetraalkylammonium iodides, iodides such as pyridinium iodides 4
Particularly preferred are secondary ammonium salt compounds and diimidazolium iodide compounds such as dimethylpropylimidazolium iodide.

The solvent used to dissolve the electrolyte is preferably a compound which dissolves the redox constituents and has excellent ionic conductivity. As the solvent, either an aqueous solvent or an organic solvent can be used, but an organic solvent is preferable because it further stabilizes the redox constituents. For example, carbonate compounds such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, methyl acetate, methyl propionate, ester compounds such as γ-butyrolactone, diethyl ether, 1,2-dimethoxyethane,
Ether compounds such as 1,3-dioxosilane, tetrahydrofuran, 2-methyl-tetrahydrofuran, heterocyclic compounds such as 3-methyl-2-oxazodirinone, 2-methylpyrrolidone, nitrile compounds such as acetonitrile, methoxyacetonitrile, propionitrile, sulfolane Aprotic polar compounds such as didimethylsulfoxide and dimethylformamide. Each of these may be used alone, or 2
It is also possible to mix and use more than one type. Among them, carbonate compounds such as ethylene carbonate and propylene carbonate, 3-methyl-2-oxazozinone,
Heterocyclic compounds such as 2-methylpyrrolidone and nitrile compounds such as acetonitrile, methoxyacetonitrile and propionitrile are particularly preferable.

The electrolyte used in the present invention is not limited to the above-mentioned electrolyte solution, that is, the electrolyte solution, and the gel electrolyte formed by holding the above-mentioned electrolyte solution on a polymer support or the like or gelled at room temperature. A salt type electrolyte or the like can also be used.

The counter electrode 9 functions as the positive electrode of the photoelectric conversion element 1. Therefore, the material of the first conductive film 6 of the counter electrode 9 is preferably a material having a catalytic action of giving electrons to the reductant of the electrolyte. Such materials are, for example, platinum,
Metals such as gold, silver, copper, aluminum, rhodium, and indium, or graphite, indium-tin composite oxide (ITO), conductive metal oxides such as fluorine-doped tin oxide, and the like. Of these, platinum and graphite are particularly preferable. Further, it is preferable that the substrate 8 on the side where the counter electrode 9 is provided is provided with the transparent second conductive film 7 on the surface where the counter electrode 9 is attached. Examples of the material of the second conductive film 7 include ITO which is a metal oxide generally used as a transparent electrode, tin oxide doped with fluorine, and the like. Further, when the constituent material of the current collector 4 and the constituent material of the counter electrode 9 are the same material, the same reduction reaction as that performed in the counter electrode 9 is performed on the surface of the current collector 4, so that the current collector 4 It is desirable to use different materials from the constituent materials of 4 and the counter electrode 9.

As the sealing material, epoxy resin, silicone resin, modified polyolefin hot melt resin or the like can be used.

[0043]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

Example 1 Water containing 0.01 g / dm ³ of the surfactant “Nonipol 100” manufactured by Sanyo Kasei Co., Ltd.,
Mixture with acetylacetone (volume mixing ratio = 20/1)
Inside, titanium dioxide particles "P25" manufactured by Nippon Aerosil Co., Ltd.
(Average particle size 20 nm) was dispersed to a concentration of about 2% by mass to prepare a slurry liquid. Next, this slurry liquid was used as a conductive glass "F-SnO" having a thickness of 1 mm manufactured by Asahi Glass Co., Ltd.
₂ "(a glass substrate with a transparent electrode having a surface coated with fluorine-doped SnO ₂ to give conductivity, surface resistance: 10 Ω / □), and dried to obtain 500 dried products. A porous titanium oxide film with a thickness of 7 μm was formed on the conductive glass by baking in air for 30 minutes at 0 ° C. Next, a gold paste (average particle size: 0.5) manufactured by Daiken Kagaku Kogyo Co., Ltd.
μm) is applied over the porous titanium oxide film and dried, and the obtained dried product is baked in air at 500 ° C. for 30 minutes to collect the current collector of the present invention on the porous titanium oxide film. A porous gold film having a maximum thickness of 3 μm was formed as a body (conductive porous film). Subsequently, this substrate was treated with an ethanol solution containing 3 × 10 ⁻⁴ mol / dm ^{3 of} a sensitizing dye represented by [Ru (4,4′-dicarboxyl-2,2′-bipyridine) ₂ (NCS) ₂ ]. And the dye adsorption treatment was performed while refluxing at 80 ° C.

The semiconductor electrode thus obtained and its counter electrode were brought into contact with an electrolyte solution and hermetically sealed to form a photoelectric conversion element. In this case, as the counter electrode, 20 n of platinum was added to the conductive glass "F-SnO ₂ " manufactured by Asahi Glass Co., Ltd.
The thing vapor-deposited by the thickness of m was used. The distance between both electrodes was 0.1 mm. As an electrolyte solution, 0.5 mol
/ Dm ³ tetrapropylammonium iodide and 0.04 mol / dm ³ iodine-containing mixed solution of ethylene carbonate and acetonitrile (volume mixing ratio = 8
0/20) was used.

A hot melt resin "Bynel" manufactured by DuPont was used as the sealing material.

The photoelectric conversion element thus obtained is
450W / m with a Senon lamp ²Irradiate light of illuminance
Then, when the output of the solar cell was measured, photoelectric conversion
The efficiency was 7.0%.

(Example 2) A glass obtained by forming a porous gold film on a porous titanium oxide film in the same manner as in Example 1 and then laminating the porous titanium oxide film and the porous gold film. The substrate was dipped in a 0.05 mol / dm ³ TiCl ₄ aqueous solution for 2 hours to form a TiO ₂ film on the porous gold film, dried, and baked in air at 500 ° C. for 30 minutes. Less than,
When a photoelectric conversion element was constructed in the same manner as in Example 1 from the sensitizing dye supporting treatment and the output as a solar cell was measured, the photoelectric conversion efficiency was 7.2%.

Example 3 A porous titanium oxide film was formed in the same manner as in Example 1, and then a porous gold film having a maximum thickness of 20 nm was formed on the porous titanium oxide film by sputtering. did. Sputtering uses "Ion coater IB-3" manufactured by Eiko Engineering Co., Ltd.
Ultimate vacuum of 20 Pa, deposition rate of about 1.0 in air atmosphere
I went at Å / sec. Hereinafter, when a photoelectric conversion element was configured in the same manner as in Example 2 and the output as a solar cell was measured, the photoelectric conversion efficiency was 7.9%.

(Example 4) A porous gold film was formed on a porous titanium oxide film in the same manner as in Example 3, and this was then immersed in a 0.1 mol / dm ³ TiCl ₄ aqueous solution for about 15 minutes. It was immersed for a time, taken out, washed with water, dried, and baked at 500 ° C. for 30 minutes. Hereinafter, a photoelectric conversion element was formed in the same manner as in Example 1 from the sensitizing dye supporting treatment, and the output as a solar cell was measured. The photoelectric conversion efficiency was 8.5%.
Met.

Comparative Example 1 A photoelectric conversion device was constructed in the same manner as in Example 1 except that the porous gold film was not formed on the porous titanium oxide film. When the output as a solar cell was measured using this conventional photoelectric conversion element in the same manner as in Example 1, the photoelectric conversion efficiency was 4.8%.

From the results of Examples 1 to 4 and Comparative Example 1 described above, the semiconductor layer having the sensitizing dye carried on the glass substrate and the conductive porous film having the through holes through which the ions in the electrolyte can pass. The photoelectric conversion elements of Examples 1 to 4 of the present invention in which a current collector is laminated have significantly improved photoelectric conversion efficiency as compared with the photoelectric conversion element of Comparative Example 1 in which only a conventional transparent conductive film is used as a current collector. did. In particular, the photoelectric conversion efficiencies of the photoelectric conversion elements of Examples 3 and 4 in which the thickness of the conductive porous film was set to a range of 1 μm or less at the maximum were higher than those of the photoelectric conversion elements of Examples 1 and 2 out of the range. A high value was obtained, and a photoelectric conversion element having more excellent characteristics was obtained.

Further, from the results of Examples 2, 3 and 4, if the titanium oxide semiconductor film is formed on the conductive porous film by immersing the substrate in the TiCl ₄ aqueous solution, photoelectric conversion with excellent characteristics can be achieved. It can be seen that a device is obtained.

[0054]

As described above, the light-transmissive substrate on which the semiconductor layer supporting the sensitizing dye is deposited, the electrode facing the semiconductor layer of the substrate, and the semiconductor layer of the substrate. A photoelectric conversion element comprising an electrolyte layer disposed between the electrode, and a photoelectric conversion element provided with a current collector made of a conductive porous film on a side of the semiconductor layer in contact with the electrolyte layer. As a result, the photoelectric conversion efficiency of the photoelectric conversion element can be dramatically improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a photoelectric conversion element of the present invention.

FIG. 2 is an enlarged conceptual view of a state in which a conductive porous film is formed on a semiconductor layer.

FIG. 3 is a schematic cross-sectional view of a conventional Gretzel cell.

[Explanation of symbols]

1 Photoelectric conversion element 2 transparent substrate 3 semiconductor layers 4 Current collector (conductive porous film) 5 Electrolyte layer 6 First conductive film 7 Second conductive film 8 substrates 9 counter electrodes 10 Sealant 11 incident light 20 semiconductor layers 21 Conductive porous membrane 22 Titanium oxide particles 23 Through hole 30 glass substrate 31 transparent electrode 32 semiconductor layer 33 Electrolyte solution 34 Platinum pole 35 glass substrate 36 Sealant 37 incident light

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Osamu Ishida             Hitachi Ma, 1-88, Torora, Ibaraki City, Osaka Prefecture             Within Kucsel Co., Ltd. (72) Inventor Katsunori Kojima             Hitachi Ma, 1-88, Torora, Ibaraki City, Osaka Prefecture             Within Kucsel Co., Ltd. (72) Inventor Tetsuya Taki             Hitachi Ma, 1-88, Torora, Ibaraki City, Osaka Prefecture             Within Kucsel Co., Ltd. F-term (reference) 5F051 AA14 FA14 GA03 GA05                 5H032 AA06 AS16 CC11 EE01 EE02                       EE16 HH04

Claims (7)

[Claims] 1. A light-transmissive substrate, to which a semiconductor layer carrying a sensitizing dye is applied, an electrode facing the semiconductor layer of the substrate, and between the semiconductor layer of the substrate and the electrode. A photoelectric conversion element comprising an arranged electrolyte layer,
A photoelectric conversion element, wherein a collector made of a conductive porous film is provided on a side of the semiconductor layer which is in contact with the electrolyte layer. 2. The photoelectric conversion element according to claim 1, wherein the conductive porous film is made of a fired body of conductive fine particles. 3. The particle diameter of the conductive fine particles is 5 nm to
The photoelectric conversion element according to claim 2, which has a thickness of 1 μm. 4. The conductive porous film is Au, Pt, A
The photoelectric conversion element according to any one of claims 1 to 3, which is formed from at least one element selected from the group consisting of g, Cu, Al, Ni, Zn, Ti, and Cr. 5. The maximum thickness of the conductive porous film is 1 μm.
The photoelectric conversion element according to claim 1, wherein the photoelectric conversion element has a length of m or less. 6. The photoelectric conversion element according to claim 1, wherein the current collector made of the conductive porous film is covered with an oxide semiconductor. 7. The oxide semiconductor is at least selected from the group consisting of titanium oxide, tungsten pentoxide, strontium tungstate, strontium titanate, niobium pentoxide, cadmium sulfide, zinc oxide, tin oxide and indium trioxide. The photoelectric conversion element according to claim 6, which is one kind.