JP2002237335A - Photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element, which has excellent photoelectric conversion efficiency and reliability over a long period of time, by solving a problem of moisture in electrolysis liquid and a problem of a distance between a semiconductor layer and an opposite electrode. SOLUTION: In the photoelectric conversion element which has the electrode, which a semiconductor layer is attached on one side surface of it, an opposite electrode which stands face to face against the above semiconductor layer of this electrode, and an electrolyte layer arranged between the above semiconductor layer of this electrode and the opposite electrode, particles which have a hydro-extracting action and insulation nature are compounded into the electrolysis liquid which constitutes the above electrolyte layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a photoelectric conversion element. More specifically, the present invention relates to a photoelectric conversion element having an improved structure in which electrolyte leakage hardly occurs.

[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, photochemical cells that extract electric energy using a chemical reaction in a photo-excited state have been developed by many researchers, but in terms of practical application, they far exceed pn junction type solar cells, which have already been proven. Did not.

[0003] Among conventional photochemical batteries, a type utilizing an oxidation-reduction reaction comprising a sensitizer and an electron acceptor is known. For example, there is a system in which a thionin dye and iron (II) ion are combined. Since the discovery of the Honda-Fujishima effect,
Photochemical cells utilizing photocharge separation of metals and their oxides are also known.

When a semiconductor comes into contact with a metal, a Schottky junction can be formed depending on the work function of the metal and the semiconductor. The same junction can be made when the semiconductor is in contact with the solution. For example, Fe ²⁺ / Fe ³⁺ , Fe (CN) _{6
^{4- / Fe (CN) 6 3-}} , I - / I 2, Br - / Br 2, when it contains a redox system such as hydroquinone / quinone, a semiconductor near the surface when immersed the n-type semiconductor in a solution Electrons move to the oxidizing agent in the solution to reach an equilibrium state. As a result, the vicinity of the surface of the semiconductor is positively charged and a potential gradient is generated.
Accordingly, a gradient also occurs in the conduction band and the valence band of the semiconductor.

When light is applied to the surface of a semiconductor electrode immersed in an oxidation-reduction solution, light having energy equal to or greater than the band gap of the semiconductor is absorbed, and electrons are transferred to the conduction band near the surface.
Generates holes in the valence band. The electrons excited in the conduction band are transmitted to the inside of the semiconductor by the above-described potential gradient existing near the surface of the semiconductor, while the holes generated in the valence band rob electrons from the reductant in the redox solution.

When a circuit is formed between a metal electrode and a semiconductor by immersing the metal electrode in an oxidation-reduction solution, the reduced form whose electrons have been deprived of holes diffuses through the solution, receives electrons from the metal electrode, and is reduced again. You. By repeating this cycle, the semiconductor electrode functions as a negative electrode and the metal electrode functions as a positive electrode, so that electric power can be supplied to the outside. Therefore, the photovoltaic power is the difference between the redox level of the redox solution and the Fermi level in the semiconductor.

In order to increase the photovoltaic power, it is necessary to use a redox solution having a low oxidation-reduction level, that is, a strong oxidation power, and a large difference between the oxidation-reduction level and the Fermi level in a semiconductor. That is, a semiconductor which can be produced, that is, has a large band gap is used.

[0008] 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. The band gap is generally 3.0 eV.
The semiconductor having a voltage of 2.0 eV or less has a problem that it is easily dissolved in a solution by a current flowing at the time of photoelectric conversion. For example, n-Si forms an inactive oxide film on the surface by light irradiation in water, and n-GaAs and n-CdS dissolve oxidatively.

In order to solve these problems, attempts have been made to coat a semiconductor with a protective film. A p-type conductive polymer such as polypyrrole, polyaniline, or polythiophene having a hole transporting property is coated with a semiconductor protective film. Ingenuity has been proposed. However, there is a problem with durability,
At best, it was stable for only a few days.

In order to solve the problem of photodissolution, use of a semiconductor having a band gap of 3 eV or more is considered.
The intensity peak is too large to efficiently absorb sunlight having a peak near 2.5 eV. Therefore, only ultraviolet rays of sunlight can be absorbed, and the visible region which occupies most of the sunlight is not absorbed at all, and the photoelectric conversion efficiency is extremely low.

In order to achieve both effective use of the visible light region and photostability of a semiconductor having a large band gap, a dye having a semiconductor loaded with a sensitizing dye that absorbs visible light of a longer wavelength smaller than the band gap of the semiconductor. Sensitized solar cells are known. The difference from a conventional wet solar cell using a semiconductor is a photocharge separation process in which electrons are excited by irradiating light to a dye, and the excited electrons move from the dye to the semiconductor.

Dye-sensitized solar cells are often considered in connection with photosynthesis. At first, chlorophyll was considered as a pigment, as in photosynthesis.However, unlike natural chlorophyll, which is constantly replaced with new chlorophyll, pigments used in solar cells have problems in terms of stability. Also had a photoelectric conversion efficiency of less than 0.5%. It is very difficult to simulate the process of photosynthesis in nature as it is to construct a solar cell.

As described above, the dye-sensitized solar cell is intended to absorb long-wavelength visible light with a hint from photosynthesis. However, in practice, the conduction mechanism of electrons has become complicated, and thus the dye-sensitized solar cell has rather a loss. Growth was a problem. In a solid-state solar cell, the absorption efficiency can be increased by increasing the thickness of the light-absorbing layer. However, for dye-sensitized solar cells, electrons can be injected into the semiconductor electrode only from the monolayer on the surface. Therefore, in order to eliminate useless absorption of light, it is desirable that the dye on the semiconductor surface be a monomolecular layer.

Furthermore, in order for electrons in the excited dye to be efficiently injected into the semiconductor, the dye is preferably chemically bonded to the semiconductor surface. For example, with respect to titanium oxide, it is important that the dye has a carboxyl group in order to chemically bond to the semiconductor surface.

An important improvement in this regard is that of Fu.
It is a group of jihira and others. They reported in 1977 to Nature magazine that the photocurrent was more than 10 times that of the conventional adsorption method due to the ester bond of the carboxyl group of Rhodamine B with the hydroxyl group on the surface of SnO ₂ . This is because the ester bond of the ester bond is closer to the surface of the semiconductor in the dye than the conventional amide bond, in which the electron which absorbed light energy exists.

However, even if electrons can be effectively injected into the semiconductor, the electrons in the conduction band may recombine with the ground level of the dye or may recombine with the redox substance. Due to such a problem, the photoelectric conversion efficiency remained low despite the above-described 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. In other words, single-crystal and polycrystalline semiconductors, which have been often used for semiconductor electrodes, have a smooth surface and no pores inside, and the effective area where the sensitizing dye is carried is equal to the electrode area. Is small.

Therefore, when such an electrode is used, the sensitizing dye of the monolayer supported on the electrode can absorb only 1% or less of the incident light even at the maximum absorption wavelength, and the light use efficiency is extremely poor. Become. Attempts have been made to increase the number of sensitizing dyes in order to increase the light-collecting power, but generally no sufficient effect has been obtained.

Grettzel et al., As a means for solving such a problem, made the titanium oxide electrode porous, carried a sensitizing dye, and significantly increased the internal area (for example,
Patent No. 2664196). This titanium oxide porous film was prepared by a sol-gel method, and the porosity of the film was about 50%, and a nanoporous structure having a very high internal surface area was formed. For example, with a film thickness of 8 μm, the roughness factor (the ratio of the actual area inside the porous body to the substrate area) reaches about 720. When this surface is geometrically calculated, the concentration of the sensitizing dye is 1.2 × 10 ⁻⁷ mol / c.
m ² , indeed about 98% of the incident light will be absorbed at the wavelength of maximum absorption.

The new dye-sensitized solar cell, also called a Gretzell cell, has a dramatic increase in the amount of sensitizing dye carried due to the above-mentioned porous titanium oxide, and has an ability to efficiently absorb sunlight and to adhere to a semiconductor. A major feature is that a sensitizing dye having an extremely high electron injection speed has been developed.

Have developed a bis (bipyridyl) Ru (II) complex for dye-sensitized solar cells. The Ru complex has the structure of the general formula cis-X2bis (2,2'-bipyridyl-4,4'-dicarboxylate) Ru (II). X is Cl-, CN-, SCN-. A systematic study was performed on the fluorescence, visible light absorption, electrochemical and photo-redox behavior of these. Of these,
It has been shown that cis- (diisocyanate) -bis (2,2′-bipyridyl-4,4′-dicarboxylate) Ru (II) has remarkably excellent performance as a solar absorber and a dye sensitizer. Was done.

The visible light absorption of the dye sensitizer is a charge transfer transition from a metal to a ligand. Also, the carboxyl group of the ligand coordinates directly to the Ti ion on the surface, forming a close electronic contact between the dye sensitizer and titanium oxide. Due to this electronic contact, electron injection from the dye sensitizer into the conduction band of titanium oxide occurs at a very high speed of 1 picosecond or less, and the conduction band of titanium oxide by the oxidized dye sensitizer in the opposite direction. It is said that the re-capture of the injected electrons occurs on the order of microseconds. This difference in speed produces the directionality of photoexcited electrons, which is the reason why charge separation is performed with extremely high efficiency. This is a difference from a pn junction solar cell that separates electric charges by a potential gradient of a pn junction surface, and is an essential feature of the Gretzell cell.

The structure of the Grettzel cell is a sandwich type cell in which an electrolyte solution containing a redox couple is sealed between two conductive glass substrates coated with a transparent conductive film of fluorine-doped tin oxide. One of the glass substrates is one in which a porous film composed of colloidal titanium oxide ultrafine particles is laminated on a transparent conductive film, and a sensitizing dye is further adsorbed to form a working electrode. The other is a transparent conductive film coated with a small amount of platinum to serve as a counter electrode. A spacer is sandwiched between two glass substrates, and an electrolyte solution is injected into a very small gap between the two glass substrates by using a capillary phenomenon. The electrolyte solution uses a mixed solvent of ethylene carbonate and acetonitrile, obtained by the iodide tetra -n- propyl ammonium and iodine as solutes, I ^- /
Including the I ^3- of oxidation-reduction pair. Platinum coated on the counter electrode is an I ^3- this redox couple I ^- there is a catalytic effect of cathodic reduction to.

The principle of operation of the Grettzel 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 performed uniformly and efficiently in any part of the porous electrode such as the Gretzell cell is mainly because the electrolyte layer is a liquid. That is, only by immersing the dye-carrying porous electrode in the solution, the solution is uniformly diffused into the porous material and an ideal electrochemical interface can be formed.

However, in the conventional Grettzel cell, there is a problem that when a small amount of water is present in the electrolytic solution, the sensitizing dye and the electrolyte are decomposed and the photoelectric conversion characteristics are deteriorated. For this reason, after the water in the electrolytic solution is completely removed, the water is injected into the electrolyte layer of the photoelectric conversion element. In addition, depending on the use state of the photoelectric conversion element, the semiconductor layer sometimes comes into contact with the counter electrode, or the distance between the semiconductor layer and the counter electrode becomes non-uniform, so that the photoelectric conversion characteristics may be deteriorated.

[0026]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the problem of moisture in an electrolytic solution and the problem of the distance between a semiconductor layer and a counter electrode, and to achieve excellent photoelectric conversion efficiency and long-term reliability. To provide a photoelectric conversion element.

[0027]

The object of the present invention is to provide at least an electrode having a semiconductor layer deposited on one surface, a counter electrode facing the semiconductor layer of the electrode, and a semiconductor layer of the electrode. In a photoelectric conversion element having an electrolyte layer disposed between the electrode and a counter electrode, the problem is solved by blending particles having a dehydrating action and an insulating property into an electrolyte solution constituting the electrolyte layer.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of the photoelectric conversion device of the present invention will be specifically described with reference to the drawings. Figure 1
1 is a schematic sectional view of an example of the photoelectric conversion element of the present invention. As shown, the photoelectric conversion element 1 of the present invention has an electrode 3 formed on one surface of a substrate 2. A dye-sensitized semiconductor layer 6 is formed on one surface of the electrode 3. Further, the counter electrode 4 is opposed to the dye-sensitized semiconductor layer 6.
Exists. The counter electrode 4 is formed on one surface of another substrate 7. An electrolyte layer 5 exists between the dye-sensitized semiconductor layer 6 and the counter electrode 4, and the electrolyte layer 5 is composed of particles 8 having a dehydrating action and an insulating property and an electrolyte 9.

The feature of the photoelectric conversion device of the present invention is that, as shown in FIG.
That is, particles 8 having a dehydrating action and an insulating property are blended. The presence of the particles 8 removes the water in the electrolyte solution 9 constituting the electrolyte layer 5, and can remove the adverse effects caused by the presence of the water. Further, since the particles have an insulating action, the presence of the particles prevents the contact between the semiconductor electrode and the counter electrode, and exerts an effect of keeping the distance between the electrodes constant. By the above operation, the presence of particles having a dehydrating effect and insulating properties in the electrolyte solution 9 can provide a photoelectric conversion element having high photoelectric conversion characteristics.

The particles 8 having a dehydrating action and an insulating property that can be used in the photoelectric conversion element 1 of the present invention are, for example, boron compounds B ₂ O ₃ , H ₃ BO ₃ , (CH ₃ O) ₃ B, (C ₂
H ₅ O) ₃ B, (CH ₃ O) ₃ BB ₂ O ₃ and the like, activated alumina, zeolite, silica gel, magnesium oxide, calcium oxide, phthalic anhydride, succinic anhydride, and the like. One type of these particles may be used, or two or more types may be used in combination.

The use of a dehydrating agent and spacers made of insulating particles such as glass beads and plastic beads in place of the particles 8 having a dehydrating action and insulating properties does not solve the problem. Because the electrolyte layer 5
The inside is a region where the redox substance moves, and the presence of the dehydrating agent and the spacer has an effect of preventing the movement of the redox substance. Therefore, although it is important to solve the problem of moisture and the problem of the distance between electrodes, the addition of a dehydrating agent and a spacer that hinders the movement of the redox substance has an adverse effect. Therefore, also in the present invention, it is not preferable to use particles having only a dehydrating action and particles having only an insulating property in combination.

In the photoelectric conversion device 1 of the present invention, if the distance between the dye-sensitized semiconductor layer 6 and the counter electrode 4 exceeds 1 mm, the moving distance of the redox body becomes too long, and the photoelectric conversion characteristics deteriorate. Tend. Therefore, the dye-sensitized semiconductor layer 6
Preferably, the distance between the electrode and the counter electrode 4 is 1 mm or less. Therefore, the particle size of the particles 8 having the dehydrating action and the insulating property must be 1 mm or less. In addition, the smaller the particle size of the particles 8 having the dehydrating action and the insulating property, the shorter the distance between the dye-sensitized semiconductor layer 6 and the counter electrode 4, so that the characteristics themselves will not adversely affect the characteristics. Absent.
However, when the diameter of the particles is 0.1 μm or less, it is difficult to arrange the particles in a single layer, and it is difficult to control the distance between the dye-sensitized semiconductor layer 6 and the counter electrode 4 by the particles. Becomes Therefore, the dye-sensitized semiconductor layer 6
From the viewpoint of controlling the distance between the electrode 8 and the counter electrode 4, it is preferable that the particle size of the particles 8 be 0.1 μm or more. Generally, when the photoelectric conversion element 1 is designed, the distance between the dye-sensitized semiconductor layer 6 and the counter electrode 4 is determined in advance. Therefore, the photoelectric conversion element 1 is arranged in the electrolyte layer 9 based on the design distance value. The particle size of the particles 8 having a dehydrating action and an insulating property is also determined by itself.

In the photoelectric conversion device 1 of the present invention, the substrate 2
Glass and plastic can be used as and. Because plastic is flexible, it is suitable for applications requiring flexibility. Since the substrate 2 functions as a light incident side substrate, it is preferably transparent. On the other hand, the substrate 7 may be transparent or opaque, but is preferably transparent because light can be incident from both substrates.

The electrode 3 formed on one surface of the substrate 2
It has a conductive agent layer on metal itself or glass or plastic. Preferred conductive agents include metals (eg, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), carbon, and conductive metal oxides (indium-tin composite oxide, fluorine-doped tin oxide, etc.). No.

The lower the surface resistance of the electrode 3, the better. A preferred range of the surface resistance is 50 Ω / □ or less, more preferably 30 Ω / □ or less. The lower limit is not particularly limited, but is usually 0.1 Ω / □.

The higher the light transmittance of the electrode 3, the better. The preferred light transmittance is 50% or more, and more preferably 80%. The electrode 3 preferably has a conductive agent layer on glass or plastic. The thickness of the electrode 3 is preferably 0.1 to 10 μm. The electrode 3 has a thickness of 0.
When the thickness is less than 1 μm, it is difficult to form an electrode film having a uniform thickness. On the other hand, when the film thickness is more than 10 μm, the light transmittance decreases, and sufficient light does not enter the dye-sensitized semiconductor layer 7. When the transparent electrode 3 is used, it is preferable that light is incident from the electrode 3 on the side on which the dye-sensitized semiconductor layer 6 is applied.

The counter electrode 4 functions as a positive electrode of the photoelectric conversion element 1 and has the same meaning as the electrode 3 on the side on which the dye-sensitized semiconductor layer 6 is attached. As the counter electrode 4 of the photoelectric conversion element 1 in the present invention, a material having a catalytic action of giving electrons to a reductant of the electrolyte is preferable in order to efficiently act as a positive electrode of the photoelectric conversion element 1. Examples of such a material include metals (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), graphite, and conductive metal oxides (indium-tin composite oxide, fluorine-doped tin oxide, etc.). ). Of these, platinum and graphite are particularly preferred. The substrate 7 on which the counter electrode 4 is provided may have a transparent conductive film (not shown) on the surface on which the counter electrode 4 is attached. This transparent conductive film can be formed, for example, from the same material as the electrode 3 described above. In this case, it is preferable that the counter electrode 4 is also transparent.

The thickness of the dye-sensitized semiconductor layer 6 is 0.1 μm to
It is preferable that it is within the range of 100 μm. When the thickness of the dye-sensitized semiconductor layer 7 is less than 0.1 μm, a sufficient photoelectric conversion effect may not be obtained. On the other hand, when the film thickness is 1
If the thickness is more than 00 μm, disadvantages such as remarkable deterioration of the transmittance with respect to visible light and near-infrared light occur, which is not preferable. A more preferable range of the film thickness of the semiconductor layer 6 is 1
μm to 50 μm, and a particularly preferred range is 5 μm to 3 μm.
0 μm, and the most preferable range is 10 μm to 20 μm.
It is.

The semiconductor particles used in the dye-sensitized semiconductor layer 6 include Cd, Zn, In, Pb, Mo, W,
Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe,
Oxides of V, Sn, Zr, Sr, Ga, Si, Cr, S
Perovskite such as rTiO ₃ , CaTiO ₃ , or CdS, ZnS, In ₂ S ₃ , PbS, Mo
₂ S, WS ₂ , Sb ₂ S ₃ , Bi ₂ S ₃ , ZnCd
S ₂ , Cu ₂ S sulfide, CdSe, In ₂ Se ₃ , W
Se ₂ , HgS, PbSe, CdTe metal chalcogenide, GaAs, Si, Se, Cd ₂ P ₃ , Zn
₂ P ₃ , InP, AgBr, PbI ₂ , HgI ₂ , Bi
I ₃ is preferred. Alternatively, a composite containing at least one or more selected from the above semiconductors, for example, CdS / TiO
₂ , CdS / AgI, Ag ₂ S / AgI, CdS / Zn
O, CdS / HgS, CdS / PbS, ZnO / Zn
S, ZnO / ZnSe, CdS / HgS, CdS _x / C
_{dSe 1-x, CdS x /} Te 1-x, CdSe x / T
e _1-x , ZnS / CdSe, ZnSe / CdSe, C
_{dS / ZnS, TiO 2 / Cd} 3 P 2, CdS / CdS
eCd _y Zn _1-y S, the CdS / HgS / CdS preferred.

As the sensitizing dye carried on the semiconductor particles, 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, RuL ₂ (H ₂ O) ₂
Type ruthenium-cis-diaqua-bipyridyl complex or ruthenium-tris (RuL 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, 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 Dyes, xanthene-based dyes, and the like. Among them, a ruthenium-bis (RuL ₂ ) derivative is preferable.

As a method for supporting the sensitizing dye on the semiconductor particles, any method known to those skilled in the art can be used. For example, as described in Japanese Patent Application No. 2000-092803, a method in which pores are formed inside semiconductor particles and the sensitizing dye is carried on the porous semiconductor particles can be used. According to this method, the sensitizing dye can be supported not only on the outer surface of the semiconductor particles but also in the pores, and the amount of the sensitizing dye supported can be increased. As a result, the photoelectric conversion efficiency can be increased.

The electrolyte used in the electrolyte layer 5 in the photoelectric conversion element 1 of the present invention is not particularly limited as long as the solvent contains a pair of oxidation-reduction constituents composed of an oxidant and a reductant. An oxidation-reduction constituent material in which the oxidized form and the reduced form have the same charge is preferable. In the present specification, the oxidation-reduction-based constituents are:
It refers to a pair of substances that are reversibly present in the oxidized and reduced forms. Such redox components are known to those skilled in the art. Redox-based constituents that can be used in the present invention include, for example, chlorine compounds-chlorine, iodine compounds-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), vanadium ion (III)-vanadium ion (II), manganate ion-permanganate ion, ferricyanide-ferrocyanide, quinone-hydroquinone , Fumaric acid-succinic acid, and the like. Needless to say, other redox components can also be used. Among them, an iodine compound-iodine is preferable. Examples of the iodine compound include metal iodides such as lithium iodide and potassium iodide, quaternary ammonium salt compounds such as tetraalkylammonium iodide and pyridinium iodide, and dimethylpropyl iodide. Diimidazolium iodide compounds such as imidazolium are particularly preferred.

The solvent used for dissolving the electrolyte is preferably a compound that dissolves the redox constituents and has excellent ion conductivity. As the solvent, any of an aqueous solvent and an organic solvent can be used, but an organic solvent is preferable in order to further stabilize the oxidation-reduction constituent material. For example, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, carbonate compounds such as propylene carbonate, methyl acetate, methyl propionate, ester compounds such as gamma-butyrolactone,
Diethyl ether, 1,2-dimethoxyethane, 1,3
Ether compounds such as dioxosilane, tetrahydrofuran and 2-methyl-tetrahydrafuran, 3-methyl-
Heterocyclic compounds such as 2-oxazodilinone and 2-methylpyrrolidone, acetonitrile, methoxyacetonitrile,
Nitrile compounds such as propionitrile, sulfolane,
Aprotic polar compounds such as didimethylsulfoxide and dimethylformamide; Each of these can be used alone, or two or more of them can be used in combination. Among them, carbonates such as ethylene carbonate and propylene carbonate
Compounds, heterocyclic compounds such as 3-methyl-2-oxazodylinone and 2-methylpyrrolidone, and nitrile compounds such as acetonitrile, methoxyacetonitrile and propionitrile are particularly preferred. Therefore, the solution obtained by dissolving the electrolyte in the solvent is the electrolyte solution 9.

[0044]

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

Example 1 Titanium oxide particles (P25, manufactured by Nippon Aerosil Co., Ltd., particle size: 20 nm) in a mixture of water containing a surfactant and acetylacetone (volume mixing ratio = 20/1) having a concentration of about 38 wt%.
To prepare a slurry liquid. Next, this slurry liquid was applied to a conductive glass substrate having a thickness of 1 mm (manufactured by Asahi Glass, F-
(SnO ₂ , 10Ω / sq) and dried, and the obtained dried product was baked in air at 500 ° C. for 30 minutes to form a porous titanium oxide film having a thickness of 10 μm on the substrate. Next, together with the substrate provided with the porous titanium oxide film, [Ru
(4,4'-dicarboxyl-2,2'-bipyridine) _2- (NCS) ₂ ]
Was immersed in a sensitizing dye solution represented by the formula (1), and dye adsorption treatment was performed while refluxing at 80 ° C. The particle size was measured using a scanning electron microscope (S4000, manufactured by Hitachi), and 100 particles were selected from an arbitrary range of the electron micrograph, and the average value of the particle sizes was defined as the particle size.

An electrolyte was sandwiched between the semiconductor electrode obtained as described above and its counter electrode to form a photoelectric conversion element. In this case, as a counter electrode, conductive glass in which platinum was deposited to a thickness of 20 nm was used. A particle size of 50 between both electrodes
It was prepared by sandwiching 0 μm boron oxide (B ₂ O ₃ ) particles and an electrolytic solution. As an electrolyte, tetrapropylammonium iodide (0.46M) and iodine (0.
6M) and a mixture of ethylene carbonate and acetonitrile (volume mixing ratio = 80/20) was used.

Comparative Example 1 Titanium oxide particles (manufactured by Nippon Aerosil Co., Ltd., P25, average particle diameter: 20 nm) were mixed in a liquid mixture of water containing a surfactant and acetylacetone (volume mixing ratio = 20/1) at a concentration of about 38 wt.
% To prepare a slurry liquid. Next, this slurry liquid was applied to a conductive glass substrate having a thickness of 1 mm (manufactured by Asahi Glass Co., Ltd., F
-SnO ₂ , 10Ω / sq) and dried. The obtained dried product was fired at 500 ° C. for 30 minutes in air to form a 10 μm thick porous titanium oxide film on the substrate.
Next, together with the substrate provided with the porous titanium oxide film,
[Ru (4,4'-dicarboxyl-2,2'-bipyridine) _2- (NCS)
₂ ], and the dye was adsorbed while refluxing at 80 ° C.

An electrolyte was sandwiched between the semiconductor electrode obtained as described above and its counter electrode to form a photoelectric conversion element. In this case, as a counter electrode, conductive glass in which platinum was deposited to a thickness of 20 nm was used. The distance between both electrodes is 0.1
mm. This is 0.1 m on the outer periphery of the photoelectric conversion element.
It was adjusted by inserting a film having a thickness of m. As the electrolyte, tetrapropylammonium iodide (0.4
6M) and a mixture of ethylene carbonate and acetonitrile containing iodine (0.6 M) (volume mixing ratio = 80/2).
0) was used.

Comparative Example 2 Titanium oxide particles (manufactured by Nippon Aerosil Co., Ltd., P25, average particle diameter: 20 nm) were mixed in a liquid mixture of water containing a surfactant and acetylacetone (volume mixing ratio = 20/1) at a concentration of about 38 wt.
% To prepare a slurry liquid. Next, this slurry liquid was applied to a conductive glass substrate having a thickness of 1 mm (manufactured by Asahi Glass Co., Ltd., F
-SnO ₂ , 10Ω / sq) and dried. The obtained dried product was fired at 500 ° C. for 30 minutes in air to form a 10 μm thick porous titanium oxide film on the substrate.
Next, together with the substrate provided with the porous titanium oxide film,
[Ru (4,4'-dicarboxyl-2,2'-bipyridine) _2- (NCS)
₂ ], and the dye was adsorbed while refluxing at 80 ° C.

An electrolyte was sandwiched between the semiconductor electrode obtained as described above and its counter electrode to form a photoelectric conversion element. In this case, as a counter electrode, conductive glass in which platinum was deposited to a thickness of 20 nm was used. It was prepared by sandwiching boron oxide (B ₂ O ₃ ) particles having a particle diameter of 3 mm and an electrolytic solution between the two electrodes. As the electrolytic solution, a mixed solution of ethylene carbonate containing tetrapropylammonium iodide (0.46 M) and iodine (0.6 M) and acetonitrile (volume mixing ratio = 80/20) was used.

Comparative Example 3 Titanium oxide particles (manufactured by Nippon Aerosil Co., Ltd., P25, average particle diameter: 20 nm) were mixed in a mixed solution of water containing surfactant and acetylacetone (volume mixing ratio = 20/1) at a concentration of about 38 wt.
% To prepare a slurry liquid. Next, this slurry liquid was applied to a conductive glass substrate having a thickness of 1 mm (manufactured by Asahi Glass Co., Ltd., F
-SnO ₂ , 10Ω / sq) and dried. The obtained dried product was fired at 500 ° C. for 30 minutes in air to form a 10 μm thick porous titanium oxide film on the substrate.
Next, together with the substrate provided with the porous titanium oxide film,
[Ru (4,4'-dicarboxyl-2,2'-bipyridine) _2- (NCS)
₂ ], and the dye was adsorbed while refluxing at 80 ° C.

An electrolyte was sandwiched between the semiconductor electrode obtained as described above and its counter electrode to form a photoelectric conversion element. In this case, as a counter electrode, conductive glass in which platinum was deposited to a thickness of 20 nm was used. It was prepared by sandwiching glass beads having an average particle diameter of 500 μm and an electrolytic solution between the two electrodes. As the electrolytic solution, a mixed solution of ethylene carbonate containing tetrapropylammonium iodide (0.46 M) and iodine (0.6 M) and acetonitrile (volume mixing ratio = 80/20) was used.

Comparative Example 4 Titanium oxide particles (manufactured by Nippon Aerosil Co., Ltd., P25, average particle diameter: 20 nm) were mixed in a liquid mixture of water containing surfactant and acetylacetone (volume mixing ratio = 20/1) at a concentration of about 38 wt.
% To prepare a slurry liquid. Next, this slurry liquid was applied to a conductive glass substrate having a thickness of 1 mm (manufactured by Asahi Glass Co., Ltd., F
-SnO ₂ , 10Ω / sq) and dried. The obtained dried product was fired at 500 ° C. for 30 minutes in air to form a 10 μm thick porous titanium oxide film on the substrate.
Next, together with the substrate provided with the porous titanium oxide film,
[Ru (4,4'-dicarboxyl-2,2'-bipyridine) _2- (NCS)
₂ ], and the dye was adsorbed while refluxing at 80 ° C.

An electrolyte was sandwiched between the semiconductor electrode obtained as described above and its counter electrode to form a photoelectric conversion element. In this case, as a counter electrode, conductive glass in which platinum was deposited to a thickness of 20 nm was used. It was prepared by sandwiching between glass and glass oxide particles having an average particle diameter of 500 μm and boron oxide (B ₂ O ₃ ) particles having an average particle diameter of 20 μm, and an electrolytic solution. As an electrolyte, tetrapropylammonium iodide (0.46M) and iodine (0.
6M) and a mixture of ethylene carbonate and acetonitrile (volume mixing ratio = 80/20) was used.

Assembled in Example 1 and Comparative Examples 1-4
Evaluate the photoelectric conversion efficiency and long-term reliability of the photoelectric conversion element
Was. Regarding the photoelectric conversion efficiency, 45 mW
/ Cm ²Xenon lamp light, and the photocurrent-voltage characteristics
The properties were measured and determined. Long-term reliability is with JISC8917
Before and after the heat resistance (high temperature storage) test B-1 described in Annex 9
The conversion efficiency retention rate is calculated from the conversion efficiency of
It was judged. In addition, heat resistance described in Appendix 9 of JISC8917
The method of the property (high temperature storage) test B-1 is shown below. Also,
Table 1 summarizes the measurement results.

Heat Resistance (High Temperature Storage) Test Method The heat resistance (high temperature storage) test includes the heat resistance (high temperature storage) test B- described in Annex 9 of the environmental test method and durability test method for the C8917 crystalline solar cell module. Performed according to 1. The test method is described below. (1) Prior to the test, measure the conversion efficiency of the sample. (2) After heating from room temperature to 85 ° C. in a thermostat, the temperature is maintained at 85 ± 2 ° C. for 1000 ± 12 h. The output terminals in the test chamber are kept open. (3) After the test, the surface is cleaned with a clean cloth and the like, and then left at room temperature for 24 hours or more to evaluate the conversion efficiency of the sample. (4) From the conversion efficiency values before and after the test, a conversion efficiency retention rate defined by the following equation was determined. (Conversion efficiency retention rate) = ｛(Conversion efficiency before heat resistance test)-
(Conversion efficiency after heat resistance test)｝ × 100 / (Conversion efficiency before heat resistance test)

[0057]

TABLE 1 specimen photoelectric conversion efficiency (%) Conversion Efficiency Retention (%) Example 1 5.4 99 Comparative Example 1 5.2 2 Comparative Example 2 3.0 98 Comparative Example 3 5.3 1 Comparative Example 4 2.8 85

As is evident from the results shown in Table 1, Example 1 of the present invention shows almost the same photoelectric conversion efficiency as Comparative Example 1, and shows a high conversion efficiency retention rate. Further, in Example 1 of the present invention using boron oxide particles having an average particle diameter of 500 μm, the photoelectric conversion efficiency showed a higher value than Comparative Example 2 using boron oxide particles having an average particle diameter of 3 mm. Regarding the above, by reducing the average particle diameter of boron oxide, the distance between the semiconductor layer and the counter electrode was shortened, and the electron transfer reaction mediated by the oxidation-reduction pair was quickly performed. Infer that this is the cause.

In Example 1 in which boron oxide particles were provided between an electrode provided with a porous titanium oxide film and an electrode provided with platinum, the photoelectric conversion efficiency was higher than that in Comparative Example 3 in which glass beads were provided. Were almost the same, but the conversion efficiency retention was high. It is presumed that the photoelectric conversion efficiencies of the above-described photoelectric conversion efficiencies were approximately the same because both had an average particle diameter of 500 μm. Concerning the conversion efficiency retention, it is inferred that the boron oxide particles have a dehydration action that glass beads do not contribute to improving the conversion efficiency retention.

In Comparative Example 4 in which boron oxide particles having an average particle size of 20 μm having a dehydrating effect were added to Comparative Example 3, the conversion efficiency retention was improved as compared with Comparative Example 3, but at the same time, the photoelectric conversion efficiency was improved. Tended to decrease.

[0061]

As described above, according to the present invention,
By arranging particles having a dehydrating action and an insulating property in the electrolyte layer, a photoelectric conversion element having excellent photoelectric conversion efficiency and long-term reliability can be obtained.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoelectric conversion element of this invention 2, 7 Substrate 3 Electrode 4 Counter electrode 5 Electrolyte layer 6 Dye-sensitized semiconductor layer 8 Particles having dehydration action and insulating property 9 Electrolyte

Claims (3)

[Claims] 1. An electrode having a semiconductor layer deposited on at least one surface thereof, a counter electrode facing the semiconductor layer of the electrode, and a electrode disposed between the semiconductor layer and the counter electrode of the electrode. A photoelectric conversion element having an electrolyte layer, wherein particles having a dehydrating action and an insulating property are blended in an electrolyte solution constituting the electrolyte layer. 2. The particles having a dehydrating action and an insulating property include B ₂ O ₃ , H ₃ BO ₃ , (CH ₃ O) ₃ B, and (C _{2
H 5 O) 3 B, (} CH 3 O) 3 B-B 2 O 3, activated alumina, zeolite, silica gel, wherein magnesium oxide, calcium oxide, to be selected from the group consisting of phthalic anhydride and succinic anhydride The photoelectric conversion element according to claim 1. 3. The photoelectric conversion element according to claim 1, wherein the particles having the dehydrating action and the insulating property have a particle size in a range of 0.1 μm to 1 mm.