JP2003178817A - Photoelectric transducer and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric transducer which reduces inner resistance of a cell and which shows high photocurrent-voltage property having a high shape factor. <P>SOLUTION: This is the photoelectric transducer which has a transparent electrode 5 coated by a semiconductor layer 7 carrying a sensitizing dye, a counter electrode 15 opposing to the semiconductor layer 7 of the transparent electrode 5, and an electrolyte layer 13 arranged between the semiconductor layer 7 between the transparent electrode 5 and the counter electrode 15 and which arranges a current collector 9 to be contacted with the transparent electrode 5 in the vicinity of the semiconductor layer 7. This is made to be the photoelectric transducer wherein the distance between the current collector 9 and the semiconductor layer 7 is within 1 cm and wherein surface resistance of the current collector 9 is smaller than that of the transparent electrode 5. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photoelectric conversion element exhibiting a photocurrent-voltage characteristic having a high form factor.

[0002]

2. Description of the Related Art Solar cells are greatly expected as a clean energy source, and pn junction type solar cells and the like have already been put to practical use. On the other hand, a photochemical cell that takes out electric energy by utilizing a chemical reaction in a photoexcited state has been developed by many researchers, but in terms of practical use, it is far beyond the pn junction type solar cell, which has a proven track record. The current situation is that there are none.

Among conventional photochemical cells, a sensitized wet solar cell utilizing a redox reaction composed of a sensitizer and an electron acceptor is known. For example, there is a system in which a thionine dye and iron (II) ion are combined. Since the discovery of the Honda-Fujishima effect, photochemical cells that utilize the photocharge separation of metals and their oxides are also known.

Here, the operation principle of the photochemical cell will be described. When a semiconductor comes into contact with a metal, a Schottky junction can be formed due to the work function relationship between the metal and the semiconductor, but similar joining can be made even when the semiconductor is in contact with a solution. For example,
Fe ²⁺ / Fe ³⁺ , Fe (CN) ₆ ^4- / Fe (C
N) ₆ ³⁻ , I ⁻ / I ₂ , Br ⁻ / Br ₂ , hydroquinone /
When an n-type semiconductor is immersed in this solution when a redox system such as quinone is contained, electrons near the surface of the semiconductor move to the oxidant in the solution and reach an equilibrium state. As a result, the vicinity of the surface of the semiconductor is positively charged and a potential gradient is generated. Along with this, a potential gradient also occurs in the conduction band and valence band of the semiconductor.

In this state, when the surface of the semiconductor electrode immersed in the redox solution is irradiated with light, light having an energy larger than the band gap of the semiconductor is absorbed, and electrons are converted into the conduction band and the valence band near the surface. Generates holes. The electrons excited in the conduction band are transferred to the inside of the semiconductor due to the potential gradient existing near the surface of the semiconductor, while the holes generated in the valence band rob the electrons from the reductant in the redox solution.

When a circuit is formed between the metal electrode and the semiconductor electrode by immersing the metal electrode in the redox solution, the reductant deprived of the electron by the hole diffuses in the solution, receives the electron from the metal electrode, and is reduced again. To be done. By repeating this cycle, the semiconductor electrode functions as a negative electrode and the metal electrode functions as a positive electrode, and power can be supplied to the outside. Therefore, the photoelectromotive force is the difference between the redox level of the redox solution and the Fermi level in the semiconductor. The above is the principle of the photochemical cell.

In such a photochemical cell, in order to increase the photoelectromotive force, a redox solution having a low redox level, that is, a strong oxidizing power is used, and the redox level and the Fermi level in the semiconductor are used. Is to use a semiconductor having a large band gap.

However, if the oxidizing power of the redox solution is too large, an oxide film is formed on the surface of the semiconductor itself,
The photocurrent stops within a short time. Regarding the band gap, the band gap is generally 3.0 eV.
Below, further, there is a problem that a semiconductor of 2.0 eV or less is easily dissolved in a solution due to a current flowing during photoelectric conversion. For example, n-Si forms an inactive oxide film on the surface when irradiated with light in water, and n-GaAs and n-CdS are oxidatively dissolved.

In order to solve these problems, attempts have been made to cover the semiconductor with a protective film, and a p-type conductive polymer such as polypyrrole, polyaniline, or polythiophene having a hole transporting property is used as the semiconductor protective film. A device to be used for is proposed. However, there is a problem with durability,
It could only be used stably for a few days at best.

In order to solve the problem of photodissolution, it is possible to use a semiconductor having a bandgap of 3 eV or more. However, in order to efficiently absorb sunlight having an intensity peak near 2.5 eV, the bandgap is required. Is too big. Therefore, only the ultraviolet part of sunlight is absorbed, the visible light region occupying most of the sunlight is not absorbed at all, and the photoelectric conversion efficiency is extremely low.

Therefore, in order to achieve both effective use of the visible light region and photostability of a semiconductor having a large bandgap, a sensitizing dye that absorbs visible light on the long wavelength side smaller than the bandgap of the semiconductor is supported on the semiconductor. Dye-sensitized solar cells are known. What is different from the conventional wet type solar cell using a semiconductor is that the dye is irradiated with light to excite electrons,
The point is that the photocharge separation process in which excited electrons move from the dye to the semiconductor is used as the photoelectric conversion process.

This dye-sensitized solar cell is often regarded as being associated with photosynthesis. Initially, chlorophyll was considered as a pigment as in photosynthesis, but unlike natural chlorophyll, which is constantly exchanged for new chlorophyll, the pigment used in solar cells has a problem in terms of stability.
The photoelectric conversion efficiency of the solar cell was less than 0.5%. Therefore, it is very difficult to construct a solar cell by directly simulating the natural photosynthesis process.

As described above, the dye-sensitized solar cell attempts to absorb long-wavelength visible light by taking a hint from photosynthesis, but in reality, the conduction mechanism of electrons becomes complicated, so that the light energy is rather lost. Increased loss became a problem.
In a solid solar cell, absorption efficiency can be improved by increasing the thickness of the layer that absorbs light. However, in the dye-sensitized solar cell, electrons can be injected into the semiconductor electrode only in the monomolecular layer of the dye on the surface, and the absorption efficiency cannot be improved by increasing the thickness of the light absorption layer. Therefore, in order to eliminate unnecessary light absorption, it is desirable that the dye on the surface of the semiconductor is a monomolecular layer and the area of the monomolecular layer is large.

Further, in order to efficiently inject the excited electrons in the dye into the semiconductor, it is preferable that the dye is chemically bonded to the semiconductor surface. For example, regarding a semiconductor using titanium oxide, it is important that the dye has a carboxyl group in order to chemically bond with the semiconductor surface.

It is the group of Fujihira et al. That has made significant improvements in this respect. In 1977, they reported to the magazine Nature that the photocurrent was 10 times or more that of the conventional adsorption method because the carboxyl group of rhodamine B was ester-bonded with the hydroxyl group on the surface of SnO ₂ .
The reason for this is that the ester bond is closer to the surface of the semiconductor in the dye than in the conventional amide bond because the π orbital in which the electron absorbing the light energy exists is present in the dye.

However, even if the electrons can be effectively injected into the semiconductor, there is a possibility that the electrons in the conduction band will be recombined with the ground level of the dye, and that they will be recombined with the redox substance. Due to such a problem, the photoelectric conversion efficiency remained low despite the above improvement in electron injection.

As described above, a major problem of the conventional dye-sensitized solar cell is that only a sensitizing dye carried 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 sensitizing dye of the monolayer 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, have proposed 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, 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. The Gretzell cell is a conductive glass substrate 2 coated with a transparent conductive film of tin oxide doped with fluorine.
It is a sandwich type cell in which an electrolyte solution containing a redox couple is enclosed between sheets. One of the glass substrates has a porous film composed of ultrafine titanium oxide particles laminated on a transparent conductive film, and further has a sensitizing dye adsorbed thereon to form a working electrode. On the other hand, the transparent conductive film is coated with a small amount of platinum to form a counter electrode. A spacer is sandwiched between two glass substrates, and an electrolyte solution is injected into a very small gap between them using a capillary phenomenon. The electrolyte solution uses a mixed solvent of ethylene carbonate and acetonitrile and is a solute of tetra-n-propylammonium iodide and iodine, and contains a redox couple of I ⁻ / I ₃ ⁻ . The platinum coated on the counter electrode has a catalytic action for cathodic reduction of I ₃ ⁻ of this redox couple to I ⁻ .

The operating principle of the Gretzel cell is basically the same as that of a conventional wet solar cell using a semiconductor. However, the reason why the photocharge separation response is uniform and efficient in any part of the porous electrode such as the Gretzell cell is mainly because the electrolyte layer is a liquid. That is,
This is because the solution can be uniformly diffused into the pores and an ideal electrochemical interface can be formed simply by immersing the dye-supporting porous electrode in the solution.

[0025]

As is well known, the form factor of the photocurrent-voltage characteristic of the solar cell is related to the internal resistance of the cell, not limited to the Gretzell cell. Gretzell
Most cells use a transparent substrate coated with a transparent electrode as an electrode substrate, but since an oxide semiconductor (SnO ₂ etc.) is usually used as a transparent electrode, the internal resistance of the cell increases and the shape factor increases. There was a problem that became low.

On the other hand, in order to prevent the reduction of the shape factor due to the internal resistance of the electrode, Japanese Unexamined Patent Publication No. 10-112337 proposes a cell structure in which a metal plate is used instead of the transparent electrode. However, since this cell structure has to irradiate light from the counter electrode side, it is difficult to use incident light efficiently. In addition, instead of the well-known sandwich type cell structure, a known example proposing a special structure intended to reduce internal resistance (Japanese Patent Laid-Open No. 11-2
No. 66028), or a method of simply applying a conductive paste to a transparent electrode is also known, but a sufficient effect has not been obtained.

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems. By providing a current collector in the vicinity of the semiconductor layer on the transparent electrode, the internal resistance of the cell is reduced and a high shape is achieved. It is an object of the present invention to provide a photoelectric conversion element exhibiting a photocurrent-voltage characteristic of a factor.

[0028]

In order to achieve the above object, the photoelectric conversion device of the present invention comprises a first electrode to which a semiconductor layer carrying a sensitizing dye is applied, and the first electrode described above. A photoelectric conversion element comprising: a second electrode facing a semiconductor layer; and an electrolyte layer arranged between the semiconductor layer of the first electrode and the second electrode, the photoelectric conversion element comprising: It is characterized in that a current collector that is in contact with the first electrode is disposed in the vicinity.

Further, in the photoelectric conversion element of the present invention, it is preferable that the distance between the current collector and the semiconductor layer is within 1 cm.

Further, in the photoelectric conversion element of the present invention, it is preferable that the surface resistance of the current collector is smaller than the surface resistance of the first electrode.

Further, in the photoelectric conversion element of the present invention, the material forming the current collector is preferably metal or carbon.

Further, in the photoelectric conversion element of the present invention, the surface resistance of the current collector is preferably 10Ω / □ or less.

Further, in the method for manufacturing a photoelectric conversion element of the present invention, the first electrode on which the semiconductor layer carrying the sensitizing dye is coated, and the second electrode facing the semiconductor layer of the first electrode. A current collector having an electrode and an electrolyte layer disposed between the semiconductor layer of the first electrode and the second electrode, and a current collector in contact with the first electrode in the vicinity of the semiconductor layer. A method for manufacturing a photoelectric conversion element to be formed, the method comprising:
The current collector is formed by placing the electrode on the electrode by any one of vapor deposition, sputtering or coating.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic cross-sectional view showing an example of the photoelectric conversion element of the present invention. As illustrated, the photoelectric conversion element 1 of the present invention has a transparent electrode 5 (first electrode) formed on one surface of the transparent substrate 3. This transparent electrode 5
A semiconductor layer 7 carrying a sensitizing dye is formed on one surface of the one. In addition, a current collector 9 that is in contact with the transparent electrode 5 is arranged near the semiconductor layer 7. Further, the counter electrode 15 is provided so as to face the semiconductor layer 7 carrying the sensitizing dye.
(Second electrode) is present. The counter electrode 15 is another substrate 17
Is formed on one surface. Semiconductor layer 7 and counter electrode 1
An electrolyte layer 13 is present between the electrodes 5 and 5. Also, the sealing material 1
1 is arranged so as to hold the electrolyte layer 13 between the semiconductor layer 7 and the counter electrode 15.

In the present invention, the current collector 9 needs to be arranged near the semiconductor layer 7. In particular, the distance between the current collector 9 and the semiconductor layer 7 is preferably within 1 cm.
If the distance between the current collector 9 and the semiconductor layer 7 is within 1 cm,
The effect that the internal resistance of the photoelectric conversion element 1 of the present invention can be further reduced can be obtained, and the photoelectric conversion element exhibiting a photocurrent-voltage characteristic with a higher form factor can be provided. The distance between the current collector 9 and the semiconductor layer 7 in the present invention means the incident light 1
9 means the shortest distance between the end of the semiconductor layer 7 and the end of the current collector 9 when the photoelectric conversion element 1 is viewed from the direction of 9 and the current collector 9 is viewed from the normal direction of the semiconductor layer 7. .

In this case, as shown in FIG. 3, the current collector 9 is arranged so as to surround only a part of the semiconductor layer 7, and at least a part of the end part of the current collector 9 is 1 cm from the end part of the semiconductor layer 7.
The effect of the present invention can be obtained if they are arranged within the distance. Further, it is most effective to arrange the current collector 9 so as to surround the semiconductor layer 7 and arrange the current collector 9 around the semiconductor layer 7 as shown in FIG.

In the present invention, the surface resistance of the current collector 9 is preferably smaller than that of the transparent electrode 5. As a result, it is possible to provide a photoelectric conversion element exhibiting a photocurrent-voltage characteristic having a higher form factor. The surface resistance of the current collector 9 is preferably 10Ω / □ or less, and more preferably 1Ω / □ or less. When the surface resistance is within this range, the current collecting effect of the current collector 9 is more sufficient, and a photoelectric conversion element exhibiting a photocurrent-voltage characteristic with a higher form factor can be obtained.

As a constituent material of the current collector 9 disposed on the transparent electrode 5, indium-tin composite oxide (ITO) generally used as a material of the transparent electrode, antimony or fluorine is doped. Further, it is preferable to use a material such as metal or carbon that has higher electrical conductivity than a metal oxide such as tin oxide.

In the present invention, the effect of the present invention can be obtained if at least a part of the end portion of the current collector 9 is arranged in the vicinity of the semiconductor layer 7. Therefore, as shown in an example of FIG. The stopper 11 may be disposed on the current collector 9. In this case, if the adhesion between the transparent electrode 5 and the current collector 9 is not strong,
The current collector 9 may peel off from the transparent electrode 5 due to the adhesive strength of the sealing material 11, and the reliability of the photoelectric conversion element of the present invention may be impaired. In order to prevent such a decrease in reliability, no photoelectric conversion element in which the current collector 9 is arranged near the semiconductor layer 7 has been proposed so far. Therefore, in most cases, the sealing material 11 is arranged around the semiconductor layer 7, and the current collector is arranged outside the sealing material 11. However, the present inventors have found that it is difficult to obtain a photoelectric conversion element having a high form factor with the conventional positional relationship between the semiconductor layer and the current collector, and the present invention has solved the conventional problems.

Therefore, in the present invention, the current collector 9 needs to be formed on the transparent electrode 5 by a method capable of obtaining a strong adhesion with the transparent electrode 5. For example, it is necessary to use a method of forming a metal on the transparent electrode 5 by using a vacuum process such as vapor deposition or sputtering, and a method of applying an epoxy resin containing a metal powder on the transparent electrode 5.

In the present invention, the material of the transparent substrate 3 is not particularly limited as long as it is a translucent material, but glass or a transparent film is usually used. The higher the light transmittance of the transparent substrate 3, the better. The light transmittance is preferably 50% or more, more preferably 80% or more.

As the substrate 17, besides the same glass and transparent film as the transparent substrate 3, a metal or the like can be used.
The substrate 17 may be opaque, but is preferably transparent in that light can be incident from the substrates on both sides.

The material of the transparent electrode 5 formed on one surface of the transparent substrate 3 is an indium-tin composite oxide (IT) which is a metal oxide generally used as a transparent electrode.
O) and tin oxide doped with fluorine.

The lower the surface resistance of the transparent electrode 5, the better. The preferred surface resistance range is 50Ω / □ or less,
It is more preferably 30Ω / □ or less. The lower limit of the surface resistance is not particularly limited, but is usually 0.1Ω / □.

The transparent electrode 5 preferably has a higher light transmittance. The light transmittance is preferably 50% or more, more preferably 80% or more. The film thickness of the transparent electrode 5 is 0.1
It is preferably in the range of 10 μm. Within this range, an electrode film having a uniform film thickness can be formed, and the light transmittance does not decrease, and sufficient light can be incident on the semiconductor layer 7. In this case, it is preferable that the light is incident from the transparent electrode 5 on the side on which the semiconductor layer 7 carrying the sensitizing dye is deposited.

The counter electrode 15 functions as the positive electrode of the photoelectric conversion element 1, and can be formed in the same manner as the transparent electrode 5 on the side on which the semiconductor layer 7 carrying the sensitizing dye is deposited. As the counter electrode 15 of the photoelectric conversion element 1 in the present invention, a material having a catalytic action of giving electrons to the reduced body of the electrolyte is preferable in order to efficiently act as the positive electrode of the photoelectric conversion element 1. Such materials are, for example, metals such as platinum, gold, silver, copper, aluminum, rhodium and indium, graphite, or conductive metal oxides such as ITO and fluorine-doped tin oxide. Of these, platinum and graphite are particularly preferable. The substrate 17 on the side where the counter electrode 15 is disposed may have a transparent conductive film (not shown) on the surface where the counter electrode 15 is attached. This transparent conductive film can be formed from the same material as the transparent electrode 5, for example. In this case, the counter electrode 15 is also preferably transparent.

For the semiconductor layer 7, a slurry liquid containing semiconductor particles is formed by a known and conventional method, for example, a coating method using a doctor blade or a bar coater, a spray method, a dip coating method, a screen printing method, a spin coating method, or the like. The semiconductor layer 7 can be formed by applying on the surface of the transparent electrode 5 on the transparent substrate 3 and then heat-treating at a temperature in the range of 400 to 600 ° C. Semiconductor layer 7
Regarding the film thickness of, the desired film thickness can be obtained by repeating the coating and the heat treatment. Further, when a film sheet such as polyethylene terephthalate (PET) is used as the transparent substrate 3, when the semiconductor layer 7 is heat-treated at a temperature within the above range, the film sheet is deformed or ITO is used.
There is a problem that the transparent electrode 5 is peeled off from the film sheet. In this case, heat treatment is performed at a temperature of 200 ° C. or lower, or pressure is applied to the semiconductor layer 7, so that
Can be formed. The pressure applied to the semiconductor layer 7 is
For example, when using a high pressure jack, 1
It may be a press weight within the range of up to 15t. In the case of press load smaller than 1 t, the semiconductor layer 7 becomes brittle,
It may be easily peeled off from the film sheet. Also,
In the case of a large press load exceeding 15 t, the pressure is too large and the transparent electrode 5 such as ITO may be broken. When the semiconductor layer 7 is formed by applying pressure, the thickness of the semiconductor layer 7 can be adjusted to an arbitrary thickness by repeating the application and pressurization.

The semiconductor layer 7 has a film thickness of 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 7 is 1 to 50 μm, a particularly preferable range is 5 to 30 μm, and a most preferable range is 10 to 20 μm.

As a semiconductor material forming the semiconductor layer 7
Is Cd, Zn, In, Pb, Mo, W, Sb, Bi,
Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Z
R, Sr, Ga, Si, Cr oxides, SrTiO 3₃,
CaTiO₃Perovskite, or CdS, Z
nS, In₂S₃, PbS, Mo₂S, WS₂, Sb₂S₃,
Bi ₂S₃, ZnCdS₂, Cu₂S sulfide, CdSe,
In₂Se₃, WSe₂, HgS, PbSe, CdTe
Metal chalcogenide, other GaAs, Si, Se, C
d₂P₃, Zn₂P₃, InP, AgBr, PbI₂, Hg
I₂, BiI₃Or at least selected from the above semiconductors
Composites containing one or more, eg CdS / TiO₂, C
dS / AgI, Ag₂S / 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,
TiO₂/ Cd₃P₂, CdS / CdSeCd_yZn
_1-yS, CdS / HgS / CdS, etc. are mentioned. Inside
Also TiO₂However, in the Gretzell cell,
It is preferable in terms of avoiding photodissolution and high photoelectric conversion characteristics.

The particle size of the semiconductor particles is generally 5 to 100.
It is preferably within the range of 0 nm. Within this range, the pore diameter of the semiconductor layer 7 becomes appropriate, the redox substances in the electrolyte solution move smoothly, the decrease in photocurrent does not occur, and the surface area of the semiconductor layer 7 is reduced. Since the amount can be increased, a sufficient amount of the sensitizing dye can be 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.

By controlling the film thickness of the semiconductor layer 7 or the particle size of the semiconductor particles, the roughness factor of the semiconductor layer 7 (the ratio of the actual area inside the semiconductor layer to the substrate area) can be determined. The roughness factor is preferably 20 or more, and more preferably 150 or more. When the roughness factor is less than 20, the amount of the sensitizing dye carried is insufficient and the photoelectric conversion characteristics are not improved. The upper limit of the roughness factor is generally 5000.
It is a degree. The roughness factor increases as the thickness of the semiconductor layer 7 increases, and the surface area of the semiconductor layer 7 increases.
An increase in the amount of sensitizing dye carried can be expected. However, when the film thickness becomes too thick, the influence of the light transmittance of the semiconductor layer 7 and the resistance loss begins to appear. Further, by adding a surfactant, polyethylene glycol, a cellulosic material, etc. to the semiconductor layer 7 and burning them during the heat treatment of the semiconductor layer 7, the semiconductor layer 7 is made porous or the particle size of the semiconductor particles is changed. If you increase the porosity of the film by doing
It is possible to increase the roughness factor without increasing the film thickness. However, if the porosity is too high, the contact area between semiconductor particles decreases, and the effect of resistance loss must be taken into consideration. From such a thing,
The porosity of the semiconductor layer 7 is preferably 50% or more, and its upper limit value is generally about 80%. The porosity of the film can be calculated from the measurement result of the adsorption-desorption isotherm curve of nitrogen gas or krypton gas under the temperature of liquid nitrogen.

As the sensitizing dye, 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 include, for example, RuL ₂ (H ₂ O) ₂ type ruthenium-
Cis - diaqua - bipyridyl complexes or ruthenium - tris (RuL _3), ruthenium - bis (RuL _2), osmium - tris (OsL _3), osmium - bis (Os
L ₂₎ type transition metal complexes, or zinc - tetra (4-carboxyphenyl) porphyrin, iron - Hekisashianido complex, phthalocyanine, and the like. Organic dyes include 9-phenylxanthene dyes, coumarin dyes, acridine dyes, triphenylmethane dyes, tetraphenylmethane dyes, quinone dyes, azo dyes, indigo dyes, cyanine dyes, merocyanine dyes. Examples thereof include dyes and xanthene dyes. 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 7, for example, a method of immersing the transparent substrate 3 on which the semiconductor layer 7 is adhered 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 refluxing or application of ultrasonic waves can be performed when the transparent substrate 3 having the semiconductor layer 7 adhered to the sensitizing dye solution is dipped for a certain period of time. After the dye is loaded on the semiconductor layer 7, it may be washed with alcohol or heated under reflux in order to remove the sensitizing dye remaining on the semiconductor layer 7 without being loaded. Further, when alcohol is used as the solvent for coating the surface of the semiconductor particles on which the sensitizing dye is not supported, it is preferable to dissolve t-butylpyridine in the alcohol. When t-butylpyridine is present in alcohol, t-butylpyridine is present at the semiconductor particle / electrolyte interface.
By using butylpyridine, the surface of the semiconductor particles and the electrolyte can be separated, the leakage current can be suppressed, and the characteristics of the photoelectric conversion element can be significantly improved.

The amount of the sensitizing dye supported on the semiconductor particles may be in the range of 1 × 10 ^-8 to 1 × 10 ^-6 mol / cm ² , and particularly 0.1 × 10 ^{-7 to} 9.0. × 10 ^-7 mol
/ Cm ² is preferred. Within this range, the effect of improving the photoelectric conversion efficiency can be obtained economically and sufficiently.

The electrolyte used in the electrolyte layer 13 in 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 (II) -copper ion (I), iron ion (III) -iron ion (II),
Examples thereof include vanadium ion (III) -vanadium ion (II), manganate ion-permanganate ion, ferricyanide-ferrocyanide, quinone-hydroquinone, and fumaric acid-succinic acid. Of course, other redox-based constituents can also be used. Among them, iodine compounds-
Iodine is preferable, and examples of the iodine compound include metal iodides such as lithium iodide and potassium iodide, quaternary ammonium iodide compounds such as tetraalkylammonium iodide and pyridinium iodide, and iodine such as dimethylpropylimidazolium iodide. Particularly preferred are diimidazolium chloride compounds.

The solvent used for dissolving 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 preferred because it makes the redox constituents more stable. For example, carbonate compounds such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate and propylene carbonate, ester compounds such as methyl acetate, methyl propionate and γ-butyrolactone, diethyl ether, 1,2-dimethoxyethane, 1 , 3-
Ether compounds such as dioxosilane, tetrahydrofuran, 2-methyl-tetrahydrofuran, 3-methyl-2
-Heterocyclic compounds such as oxazodilinone and 2-methylpyrrolidone, nitrile compounds such as acetonitrile, methoxyacetonitrile and propionitrile, and aprotic polar compounds such as sulfolane, didimethylsulfoxide and dimethylformamide. These can be used alone or in combination of two or more. Of these, carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone and 2-methylpyrrolidone, and nitrile compounds such as acetonitrile, methoxyacetonitrile and propionitrile are particularly preferable.

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

[0058]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only those 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 38% by mass to prepare a slurry liquid. Next, this slurry liquid was used as a conductive glass "F-Sn" manufactured by Asahi Glass Co., Ltd. and having a thickness of 1 mm.
O ₂ "(fluorine-doped SnO ₂ was coated on the surface to give conductivity to a glass substrate with a transparent electrode, surface resistance: 10 Ω / □), and the obtained dried product was dried. A titanium oxide film having a thickness of 10 μm was formed on the conductive glass by heating in air for 30 minutes at 0 ° C. The size of the obtained titanium oxide film was 8 mm in length and 8 mm in width. A conductive glass provided with a titanium film was treated with a sensitizing dye represented by [Ru (4,4′-dicarboxyl-2,2′-bipyridine) ₂ (NCS) ₂ ] at 3 × 10 ^−4.
Immersion in ethanol solution containing mol / dm ³ at 80 ℃
The dye adsorption treatment was carried out while refluxing.

Next, a silver paste "Silvest P-255" manufactured by Tokuriki Kagaku Kenkyusho Co., Ltd. was applied to the conductive glass as a current collector of the present invention. The surface resistance of this current collector is 0.
It was 07Ω / □. As shown in FIG. 3, the shape of the current collector was a U shape surrounding the titanium oxide film. The three sides of the current collector surrounding the titanium oxide film were separated from the titanium oxide film by the distances shown in Table 1.

The semiconductor electrode thus obtained and its counter electrode were brought into contact with an electrolyte solution to form a photoelectric conversion element. In this case, the counter electrode used was deposited to a thickness of 20nm platinum to Asahi Glass Co., Ltd. of the conductive glass "F-SnO _2". Distance between both electrodes is 0.1mm
And As an electrolyte solution, 0.5 mol / dm ³ of tetrapropylammonium iodide and 0.04 mo
A mixed solution of ethylene carbonate containing 1 / dm ³ of iodine and acetonitrile (volume mixing ratio = 80/20) was used.

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

The photoelectric conversion element thus obtained was subjected to simulated sunlight (100 mW / c by a solar simulator).
m ² , AM 1.5) and the photocurrent-voltage characteristics were measured. The results are shown in Table 1.

[0064]

[Table 1]

Comparative Example 1 A photoelectric conversion element was manufactured in the same manner as in Example 1 except that the current collector was not arranged, and the photocurrent-voltage characteristics were measured in the same manner as in Example 1. As a result, open-circuit voltage 712 mV, short-circuit current density 7.62 m
A / cm ² and a shape factor of 0.43.

As is clear from the measurement results of Example 1 (Table 1) and Comparative Example 1, in Example 1 in which the current collector is arranged, the form factor is higher than that of Comparative Example 1.
Further, it can be seen that in Example 1, the shape factor is particularly high when the distance between the current collector and the titanium oxide film is within 1 cm.

(Example 2) A titanium oxide paste for screen printing was prepared in accordance with EP0855526A1. Next, a titanium oxide paste was applied to the same conductive glass as that used in Example 1 by screen printing, and heat treatment and dye loading were performed in the same manner as in Example 1. Further, as the current collector of the present invention, a silver paste "conductive resin material 3380" manufactured by ThreeBond Co., Ltd. was applied to the conductive glass by screen printing so as to have various surface resistances. The shape of the current collector was U-shaped as in Example 1. The distance between the titanium oxide film and the three sides of the current collector surrounding the titanium oxide film was 0.4 cm. Hereinafter, the photoelectric conversion element of the present invention was prepared in the same manner as in Example 1.

The photocurrent-voltage characteristics of the photoelectric conversion element thus obtained were measured in the same manner as in Example 1. The results are shown in Table 2.

[0069]

[Table 2]

As is clear from Table 2, the surface resistance of the current collector is the surface resistance of the conductive glass (10 Ω / □).
It can be seen that the effect of improving the form factor is particularly obtained when the value is smaller.

Example 3 A pre-patterned mask was attached to the same conductive glass as that used in Example 1 and gold was evaporated. Next, a titanium oxide film was screen-printed on the conductive glass by the same method as in Example 2 so that the distance between the patterned gold and the titanium oxide film was 3 cm. Hereinafter, the photoelectric conversion element of the present invention was prepared in the same manner as in Example 1. The surface resistance of the vapor-deposited gold was 0.01 Ω / □. When the shape factor of the photocurrent-voltage characteristic of the photoelectric conversion element thus produced was measured in the same manner as in Example 1, it was 0.67. This shows that using gold as the current collector is extremely effective in improving the form factor.

[0072]

As described above, the first electrode to which the semiconductor layer supporting the sensitizing dye is deposited, the second electrode facing the semiconductor layer of the first electrode, and the second electrode. It is a photoelectric conversion element provided with the electrolyte layer arrange | positioned between the said semiconductor layer of one electrode, and the said 2nd electrode, Comprising: The electrical power collector which contacts the said 1st electrode in the vicinity of the said semiconductor layer. By disposing the photoelectric conversion element in which is arranged, it is possible to provide a photoelectric conversion element exhibiting a photocurrent-voltage characteristic having a high form factor.

[Brief description of drawings]

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

FIG. 2 is a plan view of a transparent electrode to which a semiconductor layer of a photoelectric conversion element of the present invention is applied, as viewed from the counter electrode side.

FIG. 3 is a plan view of a transparent electrode to which a semiconductor layer of a photoelectric conversion element of the present invention is applied, as viewed from the counter electrode side.

[Explanation of symbols] 1 Photoelectric conversion element of the present invention 3 transparent substrate 5 Transparent electrode 7 Semiconductor layer 9 Current collector 11 Sealant 13 Electrolyte layer 15 counter electrode 17 board 19 incident light

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Osamu Ishida             Hitachi Ma, 1-88, Torora, Ibaraki City, Osaka Prefecture             Within Kucsel Co., Ltd. (72) Inventor Takashi Sekiguchi             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 CB13 CB14 CB15 FA03                       FA06 FA10 FA14 FA16 FA24                 5H032 AA06 AS16 BB05 CC11 EE01                       HH04 HH08

Claims (6)

[Claims] 1. A first electrode to which a semiconductor layer carrying a sensitizing dye is deposited, a second electrode facing the semiconductor layer of the first electrode, and the semiconductor of the first electrode. A photoelectric conversion element comprising a layer and an electrolyte layer arranged between the second electrode and the first layer in the vicinity of the semiconductor layer.
A photoelectric conversion element having a current collector arranged in contact with the electrode of. 2. The distance between the current collector and the semiconductor layer is
The photoelectric conversion element according to claim 1, which is within 1 cm. 3. The photoelectric conversion element according to claim 1, wherein the surface resistance of the current collector is smaller than the surface resistance of the first electrode. 4. The photoelectric conversion element according to claim 1, wherein the material forming the current collector is metal or carbon. 5. The photoelectric conversion element according to claim 1, wherein the surface resistance of the current collector is 10 Ω / □ or less. 6. A first electrode, to which a semiconductor layer carrying a sensitizing dye is deposited, a second electrode facing the semiconductor layer of the first electrode, and the semiconductor of the first electrode. A method for manufacturing a photoelectric conversion element, comprising a layer and an electrolyte layer disposed between the second electrode, and forming a current collector in contact with the first electrode in the vicinity of the semiconductor layer. A method for manufacturing a photoelectric conversion element, wherein the current collector is formed by placing a conductive material on the first electrode by any one of vapor deposition, sputtering, and coating. Method.