JPH11339866A - Photoelectric conversion element and pigment sensitizing solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a leakage of an electrode and prevent a short circuit between a working film and a counter electrode by providing a working electrode having a semiconductor film covered with a pigment, the counter electrode arranged to face it, and a solid film made of a polymer porous film pinched between them, and holding the electrolyte in the voids of the solid film. SOLUTION: A working electrode 10 is provided with a light transmitting conductive layer 2 provided on the surface of a glass 1 and a semiconductor layer 3 covered with a pigment on it to form a photo-electrode. A counter electrode 11 is provided with a light transmitting conductive layer 7 carrying platinum 6 on the surface of a glass 8. An electrolyte 4 is filled in the voids of the semiconductor layer 3 and a solid layer 5 made of a polymer porous film. The polymer porous film made of polyethylene can be used for the solid layer 5. A semiconductor adsorbing the pigment is not limited in particular as far as it is generally used as a photoelectric converting material, and titanium oxide or zinc oxide can be used, for example.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion element, and more particularly to a photoelectric conversion element used for a solar cell or the like.

[0002]

2. Description of the Related Art A photoelectric conversion material is such that, when irradiated with light, electrons bound to atoms in the material can move freely by light energy, whereby free electrons and holes for free electrons ( A material that can continuously extract electric energy, that is, a material that can convert light energy into electric energy in order to generate holes and efficiently separate these free electrons and holes. . Such a photoelectric conversion material is used for, for example, a solar cell.

[0003] Solar cells using organic compounds include pn junction type solar cells, Schottky junction type solar cells, and dye-sensitized type solar cells. Among them, dye-sensitized solar cells have been widely noted because of their high conversion efficiency. Dye-sensitized solar cells are mainly composed of, for example, a semiconductor electrode and a counter electrode on which a dye is adsorbed, and an electrolyte layer sandwiched between these electrodes. Then, the generated electrons move to the counter electrode through the electric circuit, and the electrons that have moved to the counter electrode move as ions in the electrolyte and return to the semiconductor electrode, and this can be repeated to extract electric energy. Things.

As an electrolyte used in the dye-sensitized solar cell, an electrolyte is mainly used. However, there is a problem that the electrolyte cannot be held sufficiently, and the electrolyte leaks or volatilizes from a gap between the working electrode and the counter electrode. In addition, there is a problem that the working electrode and the counter electrode come into contact with each other to cause a short circuit.

[0005] In view of the above, there has been reported a method using a solid electrolyte instead of an electrolytic solution. For example, JP-A-7-28
No. 8142 describes a solar cell using an ion conductor containing a redox system in a solid. JP-A-8-236165 and JP-A-9-27352 describe solar cells using a solid polymer electrolyte. WO 93/20569 also describes a solar cell using a solid electrolyte.

Further, Solar Energy Materials and Sol
ar Cells, vol. 44 (1996), pp99-117, a rutile-type titanium oxide layer and a counter electrode made of graphite were deposited on an anatase-type titanium oxide electrode layer. A solar cell having a structure in which a layer is filled with an electrolyte is described.

[0007]

Problems to be Solved by the Invention
Although the problem of liquid leakage can be solved by using a solid electrolyte as disclosed in Japanese Unexamined Patent Publication No. Hei 9-288352, Japanese Unexamined Patent Publication No. Hei 9-236165, Japanese Unexamined Patent Publication No. There is a problem that conversion efficiency is low due to low conductivity of the ionic conductor. Further, WO93 / 20569 has a problem that the conversion efficiency is low because electrons are not efficiently transferred because the contact area between the working electrode and the electrolyte layer is small.

Further, Solar Energy Material and Sola
r Cells, vol. 44 (1996) pp99-117, a short circuit can be prevented because there is a rutile type titanium oxide layer between the electrode and the counter electrode, but when a semiconductor such as titanium oxide is used, the electrolytic solution is The problem of leakage or volatilization has not been solved, and the rutile-type titanium oxide layer adsorbs the dye, so that the dye adsorption efficiency is poor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a high conductivity and a large contact area between a working electrode and an electrolyte layer. And further, a photoelectric conversion element having excellent photoelectric conversion efficiency by preventing a short circuit between the working electrode and the counter electrode,
An object is to provide a solar cell using the photoelectric conversion element.

[0010]

According to the present invention, there is provided a photoelectric conversion element comprising: a working electrode having a semiconductor film coated with a dye; a counter electrode provided to face the working electrode; and a counter electrode provided between the working electrode and the counter electrode. A solid layer made of a polymer porous membrane sandwiched between the solid layers, wherein an electrolyte is held in a void of the solid layer. Further, the solid layer is a polymer porous membrane having conductivity. Further, the average pore diameter of the solid layer is in the range of 0.01 to 5 μm. The average porosity of the solid layer is in the range of 30 to 60%. Further, the present invention provides a dye-sensitized solar cell using the photoelectric conversion element.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a dye-sensitized solar cell according to the present invention will be described with reference to FIG. The dye-sensitized solar cell according to the present invention includes a working electrode 10, a counter electrode 11 facing the working electrode 10, and a solid layer 5 made of a polymer porous film sandwiched between the working electrode 10 and the counter electrode 11. , Electrolyte 4. The working electrode 10 is configured by providing a light-transmitting conductive layer 2 provided on the surface of glass 1 and a semiconductor layer 3 coated with a dye thereon, thereby forming a photoelectrode. The counter electrode 11 is configured by providing a light transmitting conductive layer 7 carrying platinum 6 on the surface of glass 8. The electrolyte 4 is filled in the gaps between the semiconductor layer 3 covered with the dye and the solid layer 5 composed of the polymer porous film.

In the present invention, the working electrode 10 and the counter electrode 11
As the solid layer 5 made of a polymer porous film sandwiched between the layers, a polymer porous film made of a polyolefin resin such as polyethylene or polypropylene, a polyamide resin, a polyimide resin, a cellulose resin, or the like can be used. It may be a layer or a laminate of the same or different materials.

Especially for use as a photoelectric conversion element,
It is necessary that the solid layer composed of the polymer porous membrane has a property strong against light. Moreover, it is preferable that it is strong against heat. If it is weak to light or heat, there is a problem that the long-term stability is deteriorated. Further, it is necessary that the solid layer composed of the polymer porous membrane is insoluble in the used electrolyte and does not change its shape or properties in the electrolyte. When dissolved or reacted in the electrolytic solution, there arise problems that the electrolytic solution cannot be held or the shape of the battery changes.

Further, the solid layer 5 composed of a polymer porous membrane may have conductivity. Examples of the conductive polymer include polyacetylene, poly (D-phenylene), polypyrrole, polythiophene, and polyaniline, but are not limited thereto. These conductive polymers may have a dopant added thereto.

The average porosity of the solid layer 5 of the present invention is 30 to 6
0%, preferably 30-55%, more preferably 35%
~ 45%. When the average porosity is less than 30%, the carrying amount of the electrolyte decreases, so that the electric resistance of the solid layer 5 increases and the performance as a battery decreases. On the other hand, when the average porosity is 6
If it exceeds 5%, the mechanical strength and the ability to hold the electrolytic solution decrease.

The solid layer 5 of the present invention has an average pore size of 0.1.
It is from 0.01 to 5 μm, preferably from 0.05 to 3 μm, more preferably from 0.1 to 1 μm. Average pore size is 0.01μ
If it is less than m, the ion permeability decreases, the electric resistance increases, and the function as a battery is not sufficient. On the other hand, when the average pore size is 5
If it exceeds μm, the ability to hold the electrolytic solution is reduced.

The thickness of the solid layer 5 is preferably 10 to 50 μm, more preferably 15 to 25 μm. Solid layer 5
If the thickness is less than 10 μm, the mechanical strength is not sufficient,
Another problem is that short circuits are likely to occur. On the other hand, if the thickness of the solid layer 5 exceeds 50 μm, the volume ratio of the closed solid layer per battery increases, which is not preferable because the battery capacity decreases. In addition, since the distance between the electrodes is large, there is a problem that the diffusion of the electric charge is deteriorated.

The semiconductor to which the dye used in the present embodiment is adsorbed is not particularly limited as long as it is generally used for a photoelectric conversion material.
One or more known semiconductors such as titanium oxide, zinc oxide, tungsten oxide, barium titanate, strontium titanate, and cadmium sulfide can be used. Among them, titanium oxide is preferred from the viewpoint of stability and safety. The titanium oxide used in the present invention includes various titanium oxides such as anatase-type titanium oxide, rutile-type titanium oxide, amorphous titanium oxide, meta-titanium oxide and ortho-titanium oxide, or titanium hydroxide, titanium-containing titanium oxide and the like. Either may be used.

As a method of coating the semiconductor layer with a dye, for example, there is a method of immersing a semiconductor film formed on a substrate in a solution in which the dye is dissolved. The dye that can be used here is preferably a dye that functions as a photosensitizer, and particularly has an absorption in a visible light region and / or an infrared light region and has a carboxyl group, a hydroxyalkyl group, a hydroxyl group, a sulfone in a molecule. Organic dyes having one or more bonding groups such as a group, a carboxyalkyl group, a mercapto group, a phosphino group or a phosphonyl group are preferred. This is because visible light and / or infrared light of sunlight can be absorbed and excited to generate electrons, and the bonding group can firmly adsorb the semiconductor. Specifically, metal-free phthalocyanine dyes; NK1194, NK
Cyanine dyes such as 3422 (manufactured by Japan Photochromic Research Laboratories); merocyanine dyes such as NK2426 and NK2501 (manufactured by Japan Photochromic Research Institute); xanthene dyes such as rose bengal and rhodamine B; malachite green and crystal violet Triphenylmethane dyes; metal phthalocyanines such as copper phthalocyanine or titanyl phthalocyanine, chlorophyll, hemin,
Or a complex containing at least one of ruthenium, osmium, iron, and zinc (Japanese Unexamined Patent Publication No. Hei.
No. 15097) and metal complex salts. Among them, metal complexes are preferred because of their excellent spectral sensitizing effect and durability.

The conductive film used as the electrode is not particularly limited. For example, a transparent conductive film such as ITO and SnO ₂ is preferable. The manufacturing method and the film thickness of these electrodes can be appropriately selected.

The electrolyte 4 is not particularly limited, and preferably contains a redox system (charge transfer relay). Preferred redox systems include iodine (I ₂ ) / iodine (I ₃ ⁻ ) solutions, bromine (Br ₂ ) / bromine (Br ₃ ⁻ ) solutions, hydroxy solutions, or transition metal complex solutions that carry unbound electrons. be able to. Charge transfer relays present in the electrolyte transport charge from one electrode to the other. Charge transfer relays act as pure mediators and do not undergo chemical changes during battery operation. The electrolyte in the photoelectric conversion element of the present invention is preferably dissolved in an organic solvent in which the dye coated on the semiconductor is insoluble. This offers the advantage of having long-term stability.

Preferred solvents for the electrolyte include, but are not limited to, water, alcohols and mixtures thereof, non-volatile organic solvents such as propylene carbonate, ethylene carbonate and methylpyrrolidone, and non-volatile organic solvents such as acetonitrile, Mixtures with viscosity reducing agents such as ethyl acetate or tetrahydrofuran and the like can be mentioned.
Other solvents can include dimethyl sulfoxide or dichloroethane. If miscible,
Any mixture of the above solvents can be used.

In a solar cell having such a configuration, when the dye adsorbed on the semiconductor for a photoelectric conversion material is irradiated with sunlight, the dye absorbs light in the visible region to excite it. The electrons generated by the excitation move to the counter electrode 11 through the semiconductor and the external circuit. The electrons transferred to the counter electrode 11 reduce the oxidation-reduction system in the electrolyte. On the other hand, the dye that has transferred electrons to the semiconductor is in an oxidized state. In this manner, electrons flow and a solar cell using the photoelectric conversion element of the present invention can be formed.

Hereinafter, embodiments of the photoelectric conversion element and the solar cell of the present invention will be described, but the present invention is not limited thereto. (Example 1) 4.0 g of commercially available titanium oxide particles (manufactured by Teica Co., Ltd., trade name: AMT-600, anatase type crystal, average coarse diameter: 20 nm, specific surface area: 50 m ^{2 /} g) and 20 ml of diethylene glycol monomethyl ether were mixed with glass beads. It was used and dispersed with a paint shaker for 6 hours to obtain a titanium oxide suspension.

Next, this titanium oxide suspension is applied to a glass plate having a thickness of about 10 μm using a doctor blade, and is preliminarily dried at 100 ° C. for 30 minutes.
After baking for 0 minutes, a titanium oxide film having a thickness of about 8 μm was obtained.

Further, formula (1):

[0027]

Embedded image

The dye represented by the formula was dissolved in ethanol.
The concentration of this dye was 2 × 10 ^-4 mol / l.

Subsequently, the glass substrate provided with the titanium oxide film obtained above was immersed in the dye solution for 30 minutes.
A semiconductor for a photoelectric conversion material (sample A) was obtained. Next, Sample A was used as one electrode, and a transparent conductive glass plate supporting platinum was used as a counter electrode. A thickness of 1 between these two electrodes
A 5 μm polyethylene porous membrane is sandwiched, and an electrolytic solution is put therein.
After encapsulating this side surface with resin, a lead wire was attached, and a photoelectric conversion element (sample B) of the present invention was prepared. The electrolytic solution was prepared by mixing tetrapropylammonium iodide and iodine in a mixed solvent of acetonitrile / ethylene carbonate having a volume ratio of 1: 4 at a concentration of 0.46 mol / l and 0.06 mol / l, respectively. 1 was used.

When the obtained photoelectric conversion element of sample B was irradiated with light having an intensity of 100 W / m ^{2 by} a solar simulator, η (conversion efficiency) was 1.7%, which was useful as a solar cell. all right. After leaving this sample B for one month at room temperature, in the air and in the dark, it was irradiated with light having an intensity of 100 W / m ^{2 by} a solar simulator. As a result, η (conversion efficiency) was 1.6%.

Comparative Example 1 Sample A was used as one electrode, and a transparent conductive glass plate carrying platinum was used as a counter electrode.
The same electrolytic solution as in Example 1 was put between these two electrodes, the side surface was sealed with resin, and a lead wire was attached to obtain a sample D. When this sample D was irradiated with light having an intensity of 100 W / m ^{2 by} a solar simulator, η was 1.8%. This sample D was stored at room temperature for one month in air.
After standing in the dark, use a solar simulator at 100 W / m
Irradiation of light having an intensity of ² resulted in η (conversion efficiency) of 0.3.
3%.

As is clear from Example 1 and Comparative Example 1, when a solid layer composed of a polymer porous membrane sandwiched between a working electrode and a counter electrode is provided, a photoelectric conversion element exhibiting long-term stable photoelectric conversion efficiency is provided. Can be obtained.

Example 2 A photoelectric conversion device (sample E) of the present invention was prepared in the same manner as in Example 1 except that the porous polyethylene film was replaced with a porous polyacetylene film to which iodine having conductivity was added. did. 100 W / m of the obtained photoelectric conversion element of sample E was measured with a solar simulator.
Irradiation with light of intensity ² resulted in η (conversion efficiency) of 2.
1%, which proved to be useful as a solar cell. After leaving this sample E for one month at room temperature, in the air, and in the dark, it was irradiated with light having an intensity of 100 W / m ^{2 by} a solar simulator. As a result, η (conversion efficiency) was 1.8%.

As is clear from Examples 2 and 1, when a solid layer made of a conductive polymer porous membrane sandwiched between the working electrode and the counter electrode is provided, the photoelectric conversion efficiency is improved, It was found that a photoelectric conversion element exhibiting photoelectric conversion efficiency that was stable for a period could be obtained.

The photoelectric conversion element obtained as described above is not limited to the solar cell described in the present embodiment,
It can be suitably used for photoelectric conversion devices such as optical switching devices and sensors.

[0036]

According to the present invention, leakage and volatilization of the electrolytic solution by the polymer porous membrane are reduced, the electrolytic solution can be sufficiently retained, and short-circuit can be prevented. It is possible to obtain a photoelectric conversion element exhibiting photoelectric conversion efficiency that is stable for a period. In addition, since the polymer porous membrane is sandwiched between the electrodes after dye adsorption, it does not hinder dye adsorption.

Further, when a conductive polymer porous membrane is used, electrons move not only through the electrolytic solution but also through the polymer porous membrane, so that the conversion efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a layer configuration of a photoelectric conversion element of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass 2 Light-transmitting conductive layer 3 Dye-coated semiconductor layer 4 Electrolyte 5 Solid layer made of polymer porous film 6 Platinum 7 Light-transmitting conductive layer 8 Glass 10 Working electrode 11 Counter electrode

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Yoneda 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Koichi Ui 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside the corporation

Claims (5)

[Claims] 1. A solid body comprising a working electrode having a semiconductor film coated with a dye, a counter electrode provided opposite to the working electrode, and a polymer porous film sandwiched between the working electrode and the counter electrode. And an electrolyte solution is held in the voids of the solid layer. 2. The photoelectric conversion device according to claim 1, wherein the solid layer is a polymer porous film having conductivity. 3. The solid layer has an average pore size of 0.01 to 5 μm.
The photoelectric conversion device according to claim 1, wherein the range is m. 4. The solid layer has an average porosity of 30 to 60%.
The photoelectric conversion device according to claim 1, wherein: 5. A dye-sensitized solar cell using the photoelectric conversion element according to claim 1.