JP2001229984A - Photoelectric conversion element and photoelectric cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element with an superior energy conversion efficiency, and a photoelectric cell using the same. SOLUTION: In a photoelectric conversion element, having at least the first electrode, the second electrode, a semiconductor layer being sensitized by the pigment, and an electric charge migration layer the first electrode is light reflective, the second electrode is light transmissive, and an amount of photoabsorption of the electric charge migration layer is 1/4 or lower than that of the semiconductor layer being sensitized by the pigment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photoelectric conversion element using a semiconductor sensitized with a dye. Furthermore, the present invention relates to a photovoltaic cell using the photoelectric conversion element.

[0002]

2. Description of the Related Art At present, photovoltaic power generation is the main technology for practical use in which monocrystalline silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, and compound solar cells such as cadmium telluride and indium copper selenide are improved. The power generation efficiency of about 10% is obtained as the solar energy conversion efficiency. However, in order to popularize these materials in the future, it is necessary to overcome the problems that the energy cost for material production is high, the environmental load for commercialization is large, and the energy payback time is long for users. For this reason, many photovoltaic cells that use an organic material that can easily be made large in area as a photosensitive material in place of silicon have been proposed so far, aiming at low cost,
There is a problem that the energy conversion efficiency is as low as 1% or less and the durability is poor. Under these circumstances, Nature (No. 35)
3, 737-740, 1991) and U.S. Pat.No. 4,492,721 disclose a photoelectric conversion element and a photovoltaic cell using semiconductor fine particles sensitized by a dye, as well as materials and manufacturing techniques required for the production thereof. Was. The proposed battery is a wet solar cell using a titanium dioxide porous thin film spectrally sensitized by a ruthenium complex as a working electrode. The first advantage of this method is that an inexpensive oxide semiconductor such as titanium dioxide can be used without having to purify it to high purity, and therefore it can be provided as an inexpensive photoelectric conversion element. Dye absorption is broad, and sunlight can be converted into electricity over a wide visible light wavelength range. Third, energy conversion efficiency is high. However, in order to increase the energy conversion efficiency to 10% or more, it is necessary to further increase the efficiency (light absorption efficiency, charge transport efficiency, etc.) of the photoelectric conversion element. Further, in consideration of application to a solar cell, there is a great demand for its durability. Conventionally, various proposals have been made to enhance the stability of the charge transporting material, but the stability of the charge transporting material and the photoelectric conversion efficiency have not been compatible with each other, and there has been a problem that the conversion efficiency at low temperatures cannot be sufficiently obtained. Was.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoelectric conversion element excellent in energy conversion efficiency and a photovoltaic cell using the same. It is still another object of the present invention to provide a photoelectric conversion element having excellent durability and reduced temperature dependence of energy conversion efficiency, and a photovoltaic cell (particularly, a solar cell) using the same.

[0004]

The object of the present invention has been attained by the following items which specify the present invention and preferred embodiments thereof.

(1) In a photoelectric conversion element having at least a first electrode, a second electrode, a semiconductor layer sensitized by a dye, and a charge transfer layer, the first electrode is light-reflective,
The second electrode is light-transmitting, and the light absorption of the charge transfer layer is one of the light absorption of the semiconductor layer sensitized by the dye.
/ 4 or less. (2) The photoelectric conversion device according to (1), wherein, in the photoelectric conversion element, a stacking order is a first electrode, a semiconductor layer sensitized by a dye, a charge transfer layer, and a second electrode. element. (3) at least one of the dyes used for sensitizing the semiconductor is 80
The photoelectric conversion element according to (1) or (2), which has absorption in a longer wavelength than 0 nm. (4) The photoelectric conversion element according to any one of (1) to (3), wherein the semiconductor layer is a porous layer made of semiconductor fine particles. (5) a gel electrolyte as a charge transport material in the charge transfer layer;
The photoelectric conversion element according to any one of (1) to (4), wherein a molten salt electrolyte or a solid electrolyte is used. (6) The photoelectric conversion element according to any one of (1) to (5), wherein the charge transfer layer is made of a non-conductive porous body and a charge transport material. (7) The photoelectric conversion according to any one of (1) to (6), wherein the second electrode is used as a counter electrode, and the surface thereof is treated with chloroplatinic acid or platinum fine particles are attached. element. (8) A photovoltaic cell using the photoelectric conversion element according to any one of (1) to (7). (9) A photovoltaic module comprising the photocell of (8).

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a photoelectric conversion element
It has at least a first electrode, a second electrode, a semiconductor layer sensitized by a dye, and a charge transfer layer, wherein the first electrode is light-reflective and the second electrode is light-transmissive. Here, the light transmittance (transparency) means that the wavelength is at least 40.
A light transmittance of 0 nm to 900 nm refers to a material having a transmittance of 50% or more, and light reflectivity means that the reflectance of light having a wavelength of 400 nm to 900 nm is at least.
Say more than 30%. Usually, there is a semiconductor layer (that is, a photosensitive layer) sensitized by a dye and a charge transfer layer between the first electrode and the second electrode. The first electrode may be in contact with either the photosensitive layer or the charge transfer layer, but is laminated in the order of the first electrode (light reflective), the photosensitive layer, the charge transfer layer, and the second electrode (light transparent). Preferably. That is, in a photoelectric conversion element in which a photosensitive layer is provided on a conductive support and the charge transfer layer and the counter electrode are laminated, the conductive support is a reflective first electrode, and the counter electrode is a light-emitting layer. An embodiment that is a permeable second electrode is preferred. In this case, light is emitted from the transparent counter electrode side.

In the present invention, it is necessary that the light absorption of the charge transfer layer is not more than 1/4 of the light absorption of the semiconductor layer sensitized by the dye. The light absorption amount referred to in the present invention refers to a value obtained by integrating the absorption intensity at each wavelength with respect to light of all wavelengths that can be absorbed and photoelectrically converted by a semiconductor layer (photosensitive layer) sensitized by a dye. In the case of the light absorption amount of the semiconductor layer sensitized by the dye, the absorption intensity of the dye, the amount of the dye, the adsorption state, absorption by the semiconductor, scattering,
The light absorption varies depending on the thickness of the layer. Also, the light absorption of the charge transfer layer varies depending on the absorption of the charge transport material, absorption and reflection by coexisting substances, the thickness of the layer, and the like. The above requirement is that light absorption by the charge transfer layer
In order to reduce the amount of light to be photoelectrically converted, it is based on the fact that the smaller the absorption, the higher the photoelectric conversion efficiency, and if the absorption ratio becomes 1/4 or less, the effect is more than expected. Because we found that it became smaller.

[1] Photoelectric Conversion Element The photoelectric conversion element of the present invention preferably comprises a conductive layer 10, a photosensitive layer 20, a charge transfer layer 30, and a counter electrode conductive layer 40, as shown in FIG.
The photosensitive layer 20 is composed of the semiconductor fine particles 21 sensitized by the dye 22 and the charge transport material 23 that has penetrated into the gaps between the semiconductor fine particles 21. Charge transport material 23
Is composed of the same components as the material used for the charge transfer layer 30. Further, a substrate 50 may be provided on the conductive layer 10 side and / or the counter electrode conductive layer 40 side in order to impart strength to the photoelectric conversion element.
Hereinafter, in the present invention, a layer composed of the conductive layer 10 and the optional substrate 50 is referred to as a “conductive support”, and a layer composed of the counter electrode conductive layer 40 and the optional substrate 50 is referred to as a “counter electrode”. A photovoltaic cell that connects the photoelectric conversion element to an external circuit to perform work (called an electrochemical photovoltaic cell when the charge transfer layer is an ion-conductive electrolyte, and includes a solar cell)
It is. Note that any one of the conductive layer 10 and the counter electrode conductive layer 40 in FIG. 1 and the substrate 50 may be the transparent conductive layer 10a or the transparent counter electrode conductive layer 40a, and the transparent substrate 50a, respectively. Preferably, the counter electrode conductive layer 40 is reflective (ie, the first electrode) and light transmissive (ie, the second electrode) (40a).

In the photoelectric conversion device of the present invention shown in FIG. 1, light incident on the photosensitive layer 20 containing the semiconductor fine particles 21 sensitized by the dye 22 excites the dye 22 and the like, and the excited dye
High-energy electrons in 22 and the like are transferred to the conduction band of the semiconductor fine particles 21 and further reach the conductive layer 10 by diffusion. At this time, molecules such as the dye 22 are oxidized. In the photovoltaic cell, the electrons in the conductive layer 10 return to an oxidant such as the dye 22 through the counter electrode conductive layer 40 and the charge transfer layer 30 while working in an external circuit, and the dye 22 is regenerated. The photosensitive layer 20 functions as a negative electrode. The boundary between the respective layers (for example, the boundary between the conductive layer 10 and the photosensitive layer 20, the boundary between the photosensitive layer 20 and the charge transfer layer 30, the charge transfer layer
At the boundary between the layer 30 and the counter electrode conductive layer 40, etc.), the constituent components of each layer may be mutually diffused and mixed. Hereinafter, each layer will be described in detail.

(A) Conductive Support The conductive support serves as an electrode when the supported dye-sensitized semiconductor layer acts as a photoanode. The conductive support comprises (1) a single layer of a conductive layer or (2) two layers of a conductive layer and a substrate. A substrate is not necessarily required if a conductive layer that maintains sufficient strength and sealing properties is used.

In the case of (1), a conductive layer having sufficient strength, such as metal, and having conductivity is used as the conductive layer.
The preferable thickness in this case is 1 μm or more and 10 cm or less.

In the case of (2), a substrate having a conductive layer containing a conductive agent on the photosensitive layer side can be used. Preferred conductive agents are metals (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), carbon, or conductive metal oxides (indium-tin composite oxide, tin oxide doped with fluorine, etc.). Is mentioned. Preferred conductive agents are electrochemically stable noble metals (platinum, gold) or conductive metal oxides (tin oxide, indium-tin composite oxide, etc.). The thickness of the conductive layer is not particularly limited,
It is preferably from 3 nm to 10 μm. In the case of a metal material, the thickness is preferably 5 μm or less, more preferably 5 nm or more and 3 μm or less.

The lower the surface resistance of the conductive support, the better. The preferred range of the surface resistance is 100 Ω / □ or less, more preferably 40 Ω / □ or less. The lower limit of the surface resistance is not particularly limited, but is usually about 0.1Ω / □.

The conductive support is preferably a light-reflective one. Specifically, a light-reflective metal plate (platinum, aluminum, etc.), a transparent support (glass, plastic) described later.
Examples thereof include a metal thin film (platinum, gold, and the like) provided thereon, and a transparent conductive layer (metal oxide) provided on a light-reflective support. Light reflectivity refers to light (400 to 900 nm).
(Visible light range) means 30% or more, and particularly preferably 50% or more.

(B) Counter electrode The counter electrode functions as the positive electrode of the photoelectric conversion element. The counter electrode may have a single-layer structure of a counter electrode conductive layer made of a conductive material, or may be composed of a counter electrode conductive layer and a support substrate, similarly to the above-described conductive support. Examples of the conductive material used for the counter electrode conductive layer include metals (eg, platinum, gold, silver, copper, aluminum, magnesium, rhodium, indium, and the like), carbon, and conductive metal oxides (indium-tin composite oxide, tin oxide). Fluorine-doped, etc.)
Is mentioned. An example of a preferable support substrate for the counter electrode is glass or plastic, to which the above-described conductive agent is applied or vapor-deposited. The thickness of the counter electrode conductive layer is not particularly limited, but is preferably 3 nm to 10 μm. When the counter electrode conductive layer is made of metal, its thickness is preferably 5 μm or less, more preferably in the range of 5 nm to 3 μm. The lower the surface resistance of the counter electrode layer, the better. The preferable range of the surface resistance is 80 Ω / □ or less, more preferably 20 Ω / □.
It is as follows.

In the present invention, the counter electrode is preferably transparent (light transmitting). Transparency means light (400-900n)
(visible light range of m) means 50% or more, and particularly preferably 70% or more. As the transparent counter electrode, glass or plastic coated with a conductive metal oxide is preferable. Of these, conductive glass in which a conductive layer made of tin dioxide doped with fluorine is deposited on a transparent substrate made of low-cost soda-lime float glass is particularly preferable. Further, it is more preferable to improve the oxidation-reduction reactivity with the charge transport material by, for example, bonding platinum fine particles to the surface of the conductive layer by treating with chloroplatinic acid. In addition, for a low-cost and flexible photoelectric conversion element or photovoltaic cell, a transparent polymer film provided with the above conductive layer is preferably used. For the transparent polymer film, tetraacetyl cellulose (TA
C), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndioctatic polysterene (SPS), polyphenylene sulfide (P
PS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyestersulfone (PES), polyetherimide (PE)
I), cyclic polyolefin, brominated phenoxy and the like. When a transparent conductive support is used, it is preferable that light is incident from the support side. In this case, the coating amount of the conductive metal oxide is preferably 0.01 to 100 g per 1 m ² of a glass or plastic support.

When a transparent conductive layer is used for the conductive support or the counter electrode, it is preferable to use a metal lead for the purpose of reducing the resistance. The material of the metal lead is preferably a metal such as aluminum, copper, silver, gold, platinum, and nickel, and particularly preferably aluminum and silver. The metal leads are preferably provided in a pattern such as a parallel line or a grid on a transparent substrate by vapor deposition or sputtering, and a transparent conductive layer made of tin oxide doped with fluorine or an ITO film is preferably provided thereon. It is also preferable to provide a metal lead on the transparent conductive layer after providing the transparent conductive layer on a transparent substrate. The decrease in the amount of incident light due to the installation of the metal leads is preferably 1 to 10%, more preferably 1 to 5%.

In order for light to reach the photosensitive layer, at least one of the conductive support carrying the semiconductor layer and the counter electrode must be substantially transparent. In the photoelectric conversion element and the photovoltaic cell of the present invention, it is preferable that the counter electrode is transparent, light enters from the counter electrode side, and the conductive support supporting the semiconductor layer has a property of reflecting light. Although it is not clear why the laminated structure in which light is incident from the counter electrode in the embodiment of the present invention is preferable, it is presumed as follows. That is, the charge transfer speed in the charge transfer layer is relatively slower than the electron transfer speed in the semiconductor of the semiconductor fine particle film. The charge transfer layer in the gap between the semiconductor fine particles has a long diffusion distance because the diffusion is not linear, and the diffusion charge transfer speed has a large influence. Since the semiconductor fine particle layer is sensitized by the dye, it naturally has light absorption. Therefore, the dye closer to the incident light side absorbs more light. Therefore,
Compared to the case where the light is incident from the charge transfer layer side, when the light is incident from the semiconductor fine particle side, in order to reduce the excited dye, more charges need to diffuse between the semiconductor particles, and the current is limited to that. Therefore, it is considered that the photoelectric conversion efficiency is low. In addition, gel electrolytes, molten salt electrolytes, solid electrolytes, etc. may have a lower charge transfer rate,
In such a case, it is considered that the incidence from the charge transfer layer side is more effective because the influence of the charge diffusion between the semiconductor fine particles is particularly small.

(C) Photosensitive Layer In the photosensitive layer, the semiconductor acts as a so-called photoreceptor, absorbs light to separate charges, and generates electrons and holes. In a dye-sensitized semiconductor, light absorption and the resulting generation of electrons and holes mainly occur in the dye, and the semiconductor is responsible for receiving and transmitting the electrons. The semiconductor layer serving as the photosensitive layer may have a single-layer structure or a multilayer structure. At least one of the semiconductor layers is sensitized by a dye.

(1) Semiconductor The semiconductor used in the present invention is preferably an n-type semiconductor which gives an anode current by conducting electrons as carriers under photoexcitation. Specific semiconductors include simple semiconductors such as silicon and germanium, III-V compound semiconductors, metal chalcogenides (eg, oxides, sulfides, selenides, etc.), or compounds having a perovskite structure (eg, strontium titanate) , Calcium titanate, sodium titanate, barium titanate, potassium niobate, etc.).

Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxide, cadmium, zinc, lead and silver. , Antimony or bismuth sulfide, cadmium or lead selenide, cadmium telluride and the like. Other compound semiconductors include phosphides such as zinc, gallium, indium and cadmium, selenides of gallium-arsenic or copper-indium, and sulfides of copper-indium.

Preferred specific examples of the semiconductor used in the present invention
Is Si, TiO_Two, SnO_Two, Fe_TwoO_Three, WO_Three, ZnO, Nb_TwoO_Five, CdS, Z
nS, PbS, Bi_TwoS_Three, CdSe, CdTe, GaP, InP, GaAs, CuIn
S_Two, CuInSe_TwoEtc., more preferably TiO_Two, ZnO, Sn
O_Two, Fe_TwoO_Three, WO_Three, Nb_TwoO_Five, CdS, PbS, CdSe, InP, GaAs,
CuInS_TwoOr CuInSe_TwoAnd particularly preferably TiO_TwoAlso
Is Nb _TwoO_FiveAnd most preferably TiO_TwoIt is.

The semiconductor used in the present invention may be single crystal or polycrystal. From the viewpoint of conversion efficiency, a single crystal is preferable,
From the viewpoints of production cost, securing of raw materials, energy payback time, and the like, polycrystal is preferable, and a porous film made of semiconductor fine particles is particularly preferable.

The particle size of the semiconductor fine particles is generally on the order of nm to μm, but the average particle size of the primary particles obtained from the diameter when the projected area is converted into a circle is preferably from 5 to 200 nm, and from 8 to 200 nm. 100 nm is more preferred. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is preferably 0.01 to 100 μm.

Two or more types of fine particles having different particle size distributions may be mixed. In this case, the average size of the small particles is 5 nm.
It is preferred that: For the purpose of improving the light capture rate by scattering incident light, semiconductor particles having a large particle size, for example, about 300 nm may be mixed.

As for the method of producing semiconductor fine particles, there is a method of sol-gel method by Akio Sakuhana, Agne Shofusha (1998), and a thin film coating technique by sol-gel method by the Technical Information Association (1995). ), Tadao Sugimoto, "Synthesis of Monodisperse Particles and Size Morphology Control by New Synthetic Gel-Sol Method", Materia, Vol. 35, No. 9, 1012-1018.
The gel-sol method described on page (1996) is preferred. Also De
Also preferred is a method developed by Gussa to produce oxides by high temperature hydrolysis of chlorides in oxyhydrogen salts.

When the semiconductor fine particles are titanium oxide, any of the above-mentioned sol-gel method, gel-sol method, and high-temperature hydrolysis method in chloride oxyhydrogen salt are preferred. Applied Technology "Gihodo Publishing (1997)
The sulfuric acid method and the chlorine method described in (1) can also be used. Further, the sol-gel method is described in Barb et al., Journal of American Ceramic Society, Vol.
12, No. 3, pp. 3157-3171 (1997), and Burnside et al., Chemistry of Materials, No. 10
Vol. 9, No. 9, pages 2419 to 2425 are also preferable.

Titanium oxide mainly has two types of crystal forms, anatase type and rutile type. Depending on the production method and heat history, any type can be used, and often it is obtained as a mixture of both types. The titanium oxide of the present invention preferably has a high anatase content, more preferably 80% or more. Anatase has a shorter long-wavelength wavelength of light absorption than rutile, and has less damage to the photoelectric conversion element due to ultraviolet rays. The anatase content can be determined by the X-ray diffraction method, and can be determined from the ratio of the diffraction peak intensities derived from anatase and rutile.

(2) Semiconductor fine particle layer In order to coat semiconductor fine particles on a conductive support, in addition to the method of coating a dispersion or colloid solution of semiconductor fine particles on a conductive support, the above-mentioned sol-gel A method can also be used. In consideration of mass production of photoelectric conversion elements, physical properties of semiconductor fine particle liquid, flexibility of a conductive support, and the like, a wet film forming method is relatively advantageous. As a wet film forming method, a coating method and a printing method are typical.

As a method for preparing a dispersion of semiconductor fine particles, in addition to the above-mentioned sol-gel method, a method of grinding with a mortar, a method of dispersing while pulverizing using a mill, or a method of preparing a solvent when synthesizing a semiconductor. A method of precipitating fine particles in the solution and using it as it is, may be mentioned.

Examples of the dispersion medium include water and various organic solvents (eg, methanol, ethanol, isopropyl alcohol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.). At the time of dispersion, if necessary, a polymer such as polyethylene glycol, a surfactant, an acid, a chelating agent, or the like may be used as a dispersion aid. By changing the molecular weight of polyethylene glycol, it is possible to form a film that does not easily peel off or to adjust the viscosity of the dispersion liquid. Therefore, it is preferable to add polyethylene glycol.

The application method includes a roller method and a dipping method as an application system, an air knife method and a blade method as a metering system, and a method in which the application and the metering can be the same part.
-4589, the wire bar method, US Patent 268
The slide hopper method, extrusion method, curtain method, and the like described in Nos. 1294, 2761419, and 2761791 are preferable. As a general-purpose machine, a spin method or a spray method is also preferable. As the wet printing method, intaglio printing, rubber printing, screen printing, and the like are preferable, including three major printing methods of letterpress, offset and gravure. From these, a preferable film forming method is selected according to the liquid viscosity and the wet thickness.

The viscosity of the dispersion of semiconductor fine particles greatly depends on the type and dispersibility of the semiconductor fine particles, the type of solvent used, and additives such as a surfactant and a binder. For a high viscosity liquid (for example, 0.01 to 500 Poise), an extrusion method, a casting method, a screen printing method, or the like is preferable. For a low-viscosity liquid (for example, 0.1 Poise or less), a slide hopper method, a wire bar method, or a spin method is preferable, and a uniform film can be formed. If a certain amount of coating is used, application by the extrusion method is possible even in the case of a low-viscosity liquid. As described above, a wet film forming method may be appropriately selected according to the viscosity of the coating solution, the coating amount, the support, the coating speed, and the like.

The layer of semiconductor fine particles is not limited to a single layer, but a multi-layer coating of a dispersion of semiconductor fine particles having different particle diameters, or a coating layer containing semiconductor fine particles of different types (or different binders and additives) may be formed in multiple layers. It can also be applied. Multilayer coating is effective even when the film thickness is insufficient by one coating. The extrusion method or the slide hopper method is suitable for multilayer coating. In the case of multi-layer coating, multi-layer coating may be performed at the same time, or several to dozens of times may be sequentially applied. Furthermore, a screen printing method can also be preferably used in the case of successive coating.

In general, as the thickness of the semiconductor fine particle layer (same as the thickness of the photosensitive layer) becomes larger, the amount of dye carried per unit projected area increases, so that the light capture rate increases, but the diffusion distance of generated electrons increases. Therefore, the loss due to charge recombination also increases. Therefore, the preferred thickness of the semiconductor fine particle layer is
It is 0.1-100 μm. When used for a solar cell, the thickness of the semiconductor fine particle layer is preferably 0.5 to 30 μm, more preferably 1 to 25 μm. Support 1 m ² per coating amount of the semiconductor fine particles 0.
It is preferably from 5 to 400 g, more preferably from 1 to 100 g.

After applying the semiconductor fine particles on the conductive support, the semiconductor fine particles are brought into electronic contact with each other,
Heat treatment is preferably performed to improve the strength of the coating film and the adhesion to the support. A preferred heating temperature range is from 40 ° C to 700 ° C, more preferably from 100 ° C to 600 ° C. The heating time is about 10 minutes to 10 hours. When a support having a low melting point or softening point such as a polymer film is used, high-temperature treatment is not preferable because it causes deterioration of the support. It is preferable that the temperature be as low as possible from the viewpoint of cost. The lowering of the temperature can be attained by the above-mentioned combined use of small semiconductor particles of 5 nm or less, heat treatment in the presence of a mineral acid, and the like.

For the purpose of increasing the surface area of the semiconductor fine particles after the heat treatment, increasing the purity in the vicinity of the semiconductor fine particles, and increasing the efficiency of electron injection from the dye into the semiconductor fine particles, for example, chemical plating using an aqueous titanium tetrachloride solution or titanium plating Electrochemical plating using an aqueous solution of titanium chloride may be performed.

The semiconductor fine particles preferably have a large surface area so that many dyes can be adsorbed. Therefore, the surface area in a state where the layer of semiconductor fine particles is coated on the support is preferably 10 times or more the projected area,
Further, it is preferably 100 times or more. The upper limit is not particularly limited, but is usually about 1000 times.

(3) Dye The dye used in the photosensitive layer is preferably a metal complex dye, a phthalocyanine dye or a methine dye. Two or more dyes can be mixed in order to widen the wavelength range of photoelectric conversion as much as possible and to increase the conversion efficiency. The dyes to be mixed and their proportions can be selected so as to match the wavelength range and intensity distribution of the desired light source. In the present invention, in order to enhance the photoelectric conversion efficiency, it is preferable that at least one of the sensitizing dyes used has absorption at 800 nm or more.

The dye preferably has an appropriate interlocking group for the surface of the semiconductor fine particles. Preferred linking groups include a COOH group, an OH group,
SO ₃ H group, a cyano group, -P (O) (OH) 2 group, -OP (O) (OH) 2 group, or oxime, dioxime, hydroxyquinoline, a π conductivity, such as salicylate and α- ketoenolate Chelating groups. Above all, COOH group, -P
(O) (OH) ₂ group, -OP (O) (OH) ₂ group is particularly preferred. These groups may form a salt with an alkali metal or the like, or may form an inner salt. In the case of a polymethine dye, if the methine chain contains an acidic group as in the case of forming a squarylium ring or a croconium ring, this portion may be used as a bonding group.

Hereinafter, preferred dyes used in the photosensitive layer will be specifically described.

(A) Metal complex dye When the dye is a metal complex dye, the metal atom is ruthenium.
Ru is preferred. Ruthenium complex dyes include:
For example, U.S. Pat.Nos. 4,492,721, 4,684,537, 5,084,365
No. 5,350,644, No. 5463057, No. 5,525,440, JP-A-7
-249790, Japanese Translation of PCT International Publication No. 10-504512, and WO98 / 50393.

The ruthenium complex dye used in the present invention is preferably represented by the following general formula (I): (A ₁ ) _p Ru (Ba) (Bb) (Bc) (I) In the general formula (I), A ₁ is C
1, represents a ligand selected from the group consisting of SCN, H ₂ O, Br, I, CN, NCO and SeCN, and p is an integer of 0 to 3. B-
a, Bb and Bc are each independently the following formulas B-1 to B-8:

[0044]

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(Where Ra represents a hydrogen atom or a substituent; examples of the substituent include a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkyl group having 7 to 12 carbon atoms) A substituted aralkyl group, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, a carboxylic acid group, a phosphoric acid group (these acid groups may form a salt); The alkyl part of the aralkyl group may be linear or branched, and the aryl group and the aryl part of the aralkyl group may be monocyclic or polycyclic (condensed ring, ring assembly). Represents an organic ligand. Ba, Bb and Bc may be the same or different.

Preferred specific examples of the metal complex dye are shown below, but the present invention is not limited thereto.

[0047]

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[0048]

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[0049]

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(B) Methine Dye A methine dye preferably used in the present invention is disclosed in
-35836, JP-A-11-158395, JP-A-11-163378, JP-A-11-214730,
Dyes described in the specifications of JP-A-11-214731, European Patents 892411 and 911841. For the synthesis of these dyes, see FM Hamer, Heterocyclic Compounds-Cyanine Dyes and Relative Compounds.
ated Compounds), John Wiley & Sons-New York, London,
Published in 1964, DMSturmer
Author, Heterocyclic Compounds-Special topics in heterogeneous
cyclic chemistry) ", Chapter 18, Section 14, 482
515 pages, John Willie and Sons (Jo
hn Wiley & Sons)-New York, London, 197
7th year, "Rodd's Chemistry of Carbon Compounds"
2nd.Ed.vol.IV, part B, 1977, Chapter 15, Chapter 36
9-422, Elsevier Science Public Company, Inc.
ompanyInc.), New York, UK Patent 1,077,611
No. Ukrainskii Khimicheskii Zhurnal, Vol. 40, No. 3
No. 253-258, Dyes and Pigments, No. 21
Volumes 227-234 and in the references cited therein.

(4) Adsorption of Dye on Semiconductor Fine Particles The dye is adsorbed on the semiconductor fine particles by dipping a conductive support having a well-dried semiconductor fine particle layer in a dye solution or by dissolving the dye solution in a semiconductor solution. A method of applying to the fine particle layer can be used. In the former case, a dipping method, a dipping method, a roller method, an air knife method, or the like can be used. In the case of the immersion method, the dye may be adsorbed at room temperature,
It may be carried out by heating and refluxing as described in JP-A-7-249790. In addition, as the latter coating method, a wire bar method, a slide hopper method, an extrusion method,
There are a curtain method, a spin method, a spray method and the like, and a printing method includes letterpress, offset, gravure, screen printing and the like. The solvent can be appropriately selected according to the solubility of the dye. For example, alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane, halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform,
Chlorobenzene, etc.), ethers (diethyl ether,
Tetrahydrofuran), dimethylsulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters ( Ethyl acetate, butyl acetate, etc.), carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc.), hydrocarbons (hexane, petroleum ether, benzene, toluene, etc.) And a mixed solvent thereof.

As for the viscosity of the solution of the dye, a high-viscosity liquid (for example, 0.01 to 500
For se), various printing methods other than the extrusion method are suitable, and for low-viscosity liquids (for example, 0.1 Poise or less), the slide hopper method, the wire bar method, or the spin method are suitable. It is possible.

Thus, the viscosity of the coating solution of the dye, the coating amount,
The method for adsorbing the dye may be appropriately selected according to the conductive support, the coating speed, and the like. The time required for dye adsorption after coating should be as short as possible in consideration of mass production.

Since the presence of unadsorbed dye causes disturbance of device performance, it is preferable to remove the dye by washing immediately after adsorption. Using a wet cleaning tank, polar solvents such as acetonitrile,
It is preferable to perform washing with an organic solvent such as an alcohol solvent. Further, in order to increase the adsorption amount of the dye, it is preferable to perform a heat treatment before the adsorption. After the heat treatment, do not return to room temperature to avoid water adsorbing on the surface of the semiconductor fine particles.
Preferably, the dye is adsorbed quickly between 40 and 80 ° C.

The total amount of the dye used is preferably 0.01 to 100 mmol per unit surface area (1 m ² ) of the conductive support. The amount of dye adsorbed on the semiconductor fine particles is 1 g of the semiconductor fine particles.
It is preferably 0.01 to 1 mmol per unit. By using such a dye adsorption amount, a sufficient sensitizing effect in a semiconductor can be obtained. On the other hand, if the amount of the dye is too small, the sensitizing effect becomes insufficient, and if the amount of the dye is too large, the dye not adhering to the semiconductor floats and causes a reduction in the sensitizing effect.

For the purpose of reducing the interaction between dyes such as association, a colorless compound may be co-adsorbed on the semiconductor fine particles. Examples of the hydrophobic compound to be co-adsorbed include a steroid compound having a carboxyl group (for example, chenodeoxycholic acid). Further, an ultraviolet absorber can be used in combination.

For the purpose of accelerating the removal of excess dye, the surface of the semiconductor fine particles may be treated with an amine after adsorbing the dye. Preferred amines are pyridine,
4-t-butylpyridine, polyvinylpyridine and the like. When these are liquids, they may be used as they are, or may be used after being dissolved in an organic solvent.

(D) Charge transfer layer The charge transfer layer is a layer containing a charge transport material having a function of replenishing electrons to the oxidized dye. Examples of typical charge transporting materials that can be used in the present invention include, as an ion transporting material, a solution in which redox pair ions are dissolved (electrolyte solution), and a redox pair solution impregnated in a gel of a polymer matrix. A so-called gel electrolyte, a molten salt electrolyte containing a redox counter ion, and a solid electrolyte can be used. In addition to a charge transporting material involving ions, an electron transporting material or a hole (hole) transporting material may be used as a material relating to electric conduction in which carrier movement in a solid is involved. These can be used in combination.

(1) Molten Salt Electrolyte A molten salt electrolyte is preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability. When using a molten salt electrolyte for the photoelectric conversion element of the present invention, for example, WO95 / 18456, JP-A-8-259543
Known electrochemical salts such as pyridinium salts, imidazolium salts, triazolium salts, and the like, described in No. No., Electrochemistry, Vol. 65, No. 11, p. 923 (1997) and the like can be used.

The molten salt which can be preferably used includes those represented by any of the following formulas (Ya), (Yb) and (Yc).

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In the general formula (Ya), Q _y1 is 5 together with a nitrogen atom.
Or an atomic group capable of forming a 6-membered aromatic cation. Q _y1 is preferably composed of one or more atoms selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom and a sulfur atom.

The 5-membered ring formed by Q _y1 is preferably an oxazole ring, a thiazole ring, an imidazole ring, a pyrazole ring, an isoxazole ring, a thiadiazole ring, an oxadiazole ring or a triazole ring. It is more preferably a ring or an imidazole ring, particularly preferably an oxazole ring or an imidazole ring. The 6-membered ring formed by Q _y1 is preferably a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring or a triazine ring, and more preferably a pyridine ring.

In the general formula (Yb), A _y1 represents a nitrogen atom or a phosphorus atom.

R in the general formulas (Ya), (Yb) and (Yc)
_{y1 to Ry6} each independently represent a substituted or unsubstituted alkyl group (preferably having 1 to 24 carbon atoms, which may be linear, branched, or cyclic; for example, methyl Group, ethyl group, propyl group, isopropyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, t-
Octyl, decyl, dodecyl, tetradecyl,
2-hexyldecyl group, octadecyl group, cyclohexyl group, cyclopentyl group, etc.) or a substituted or unsubstituted alkenyl group (preferably having 2 to 24 carbon atoms, which may be linear or branched, For example, a vinyl group or an allyl group), more preferably an alkyl group having 2 to 18 carbon atoms or an alkenyl group having 2 to 18 carbon atoms, and particularly preferably an alkyl group having 2 to 6 carbon atoms. .

Further, two or more of R _{y1 to} R _{y4 in} the general formula (Yb) may be linked to each other to form a non-aromatic ring containing A _y1, and R in the general formula (Yc) Two or more of _{y1 to Ry6} may be connected to each other to form a ring structure.

Q in the general formulas (Ya), (Yb) and (Yc)
_y1 and R _y1 to R _y6 may have a substituent, examples of preferred substituents, a halogen atom (F, Cl, Br, I
), A cyano group, an alkoxy group (such as a methoxy group and an ethoxy group), an aryloxy group (such as a phenoxy group), an alkylthio group (such as a methylthio group and an ethylthio group), an alkoxycarbonyl group (such as an ethoxycarbonyl group), and a carbonate group ( Ethoxycarbonyloxy group, etc.), acyl group (acetyl group, propionyl group, benzoyl group, etc.), sulfonyl group (methanesulfonyl group, benzenesulfonyl group, etc.), acyloxy group (acetoxy group, benzoyloxy group, etc.), sulfonyloxy group ( Methanesulfonyloxy group, toluenesulfonyloxy group, etc.), phosphonyl group (diethylphosphonyl group, etc.), amide group (acetylamino group, benzoylamino group, etc.), carbamoyl group (N, N-
Dimethylcarbamoyl group), alkyl group (methyl group,
Ethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, 2-carboxyethyl group, benzyl group, etc., aryl group (phenyl group, toluyl group, etc.), heterocyclic group (pyridyl group, imidazolyl group, furanyl group) etc),
Alkenyl groups (vinyl group, 1-propenyl group, etc.) and the like.

According to the general formula (Y-a), (Y-b) or (Y-c)
The compound represented by_y1Or R_y1~ R _y6Multimer through
May be formed.

These molten salts may be used alone or
The iodine anion may be used in combination with a molten salt obtained by replacing the iodine anion with another anion. As the anion to replace the iodine anion,
Halide ions (Cl ^-, Br ^{-, _{etc.), NSC -, BF 4 -}} , P
_{^{F 6 -, ClO 4 -,}} (CF 3 SO 2) 2 N -, (CF 3 CF 2 SO 2) 2 N -, CF 3 SO 3 -,
Preferred examples include CF ₃ COO ⁻ , Ph ₄ B ⁻ , (CF ₃ SO ₂ ) ₃ C ^{−, and} more preferably (CF ₃ SO ₂ ) ₂ N ⁻ or BF ₄ ⁻ . Also, other iodine salts such as LiI can be added.

Specific examples of the molten salt preferably used in the present invention are shown below, but are not limited thereto.

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It is preferable not to use a solvent for the molten salt electrolyte. Although a solvent described below may be added, the content of the molten salt is preferably 50% by mass or more based on the entire electrolyte composition. Further, it is preferable that 50% by mass or more of the salt is an iodine salt, and it is more preferable that the amount is 70% or more.

It is preferable to add iodine to the electrolyte composition. In this case, the content of iodine is preferably 0.1 to 20% by mass, and more preferably 0.5 to 5% by mass with respect to the whole electrolyte composition. Is more preferred.

(2) Electrolyte When an electrolyte is used for the charge transfer layer, the electrolyte is an electrolyte,
It is preferable to be composed of a solvent and an additive. Book
The electrolyte of the invention is I_TwoAnd iodide combinations (iodide
Include LiI, NaI, KI, CsI, CaI_Two Such
Metal iodide or tetraalkyl ammonium
Iodide, pyridinium iodide, imidazolium
Iodine salts of quaternary ammonium compounds such as iodide
Etc.), Br _TwoAnd bromide (the bromide is L
iBr, NaBr, KBr, CsBr, CaBr_Two Such
Metal bromide or tetraalkylammonium
Quaternary ammonium such as romide and pyridinium bromide
Bromide salts), ferrocyanate salts
Ferricyanate and ferrocene-ferricinium ions
Which metal complex, sodium polysulfide, alkyl thiol
-Sulfur compounds such as alkyl disulfide, viologen
Dyes, hydroquinone-quinone and the like can be used.
You. Among them I_TwoAnd LiI and pyridinium iodide,
Quaternary ammonium compounds such as imidazolium iodide
In the present invention, an electrolyte containing a combination of various iodine salts is preferred.
No. The above-mentioned electrolytes may be used as a mixture.

The preferred electrolyte concentration is 0.1M or more and 15M or less, more preferably 0.2M or more and 10M or less. When iodine is added to the electrolyte, a preferable concentration of iodine is 0.01 M or more and 0.5 M or less.

The solvent used for the electrolyte in the present invention is a compound capable of exhibiting excellent ionic conductivity by lowering the viscosity and improving the ionic mobility or increasing the dielectric constant and improving the effective carrier concentration. Desirably. Examples of such a solvent include carbonate compounds such as ethylene carbonate and propylene carbonate, 3-methyl-
Heterocyclic compounds such as 2-oxazolidinone, dioxane, ether compounds such as diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, chain ethers such as polypropylene glycol dialkyl ether, methanol, ethanol,
Alcohols such as ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, and polypropylene glycol monoalkyl ether; polyhydric alcohols such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, and glycerin; acetonitrile; Nitrile compounds such as glutaronitrile, methoxyacetonitrile, propionitrile, and benzonitrile; aprotic polar substances such as dimethyl sulfoxide and sulfolane; and water can be used.

Further, according to the present invention, J. Am. Ceram. Soc.,
80 (12) 3157-3171 (1997), ter-butylpyridine, and basic compounds such as 2-picoline and 2,6-lutidine can also be added. The preferred concentration range when adding a basic compound is 0.05M or more and 2M or less.

(3) Gel Electrolyte In the present invention, the electrolyte may be gelled (solidified) by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization containing a polyfunctional monomer, or crosslinking reaction of a polymer. it can. To gel by adding a polymer, use
lymer Electrolyte Reviews-1 and 2¨ (JRMacCallum
And CA Vincent, ELSEVIER APPLIED SCIENCE), but polyacrylonitrile and polyvinylidene fluoride can be particularly preferably used. For gelation by adding an oil gelling agent, use J. Chem Soc. Japan, Ind. Chem.Sec., 4
6,779 (1943), J. Am. Chem. Soc., 111,5542 (1989), J.
Chem. Soc., Chem. Com mun., 1993, 390, Angew. Che
m. Int. Ed. Engl., 35, 1949 (1996), Chem. Lett., 199
6, 885, J. Chm. Soc., Chem. Commun., 1997, 545, but preferred compounds are those having an amide structure in the molecular structure.

When the gel electrolyte is formed by polymerization of polyfunctional monomers, a solution is prepared from the polyfunctional monomers, polymerization initiator, electrolyte, and solvent, and the solution is prepared by a method such as a casting method, a coating method, a dipping method, or an impregnation method. A method in which a sol-like electrolyte layer is formed on an electrode supporting a dye and then gelled by radical polymerization is preferable. The polyfunctional monomer is preferably a compound having two or more ethylenically unsaturated groups. The preferred mass composition range of the polyfunctional monomer in the total amount of the monomers is 0.5% by mass to 70% by mass.
It is preferably at most 1.0 mass%, more preferably at least 1.0 mass% and at most 50 mass%.

The above-mentioned monomers are generally described in Takatsu Otsu and Masayoshi Kinoshita: Experimental Method for Polymer Synthesis (Chemical Doujin) and Takatsu Otsu: Lecture Polymerization Reaction Theory 1 Radical Polymerization (I) (Chemical Doujin) It can be polymerized by radical polymerization, which is a simple polymer synthesis method. The monomer for a gel electrolyte that can be used in the present invention can be radically polymerized by heating, light, electron beam, or electrochemically, but it is particularly preferable to radically polymerize by heating. The polymerization initiator preferably used when the crosslinked polymer is formed by heating,
For example, 2,2'-azobis (isobutyronitrile),
Azo initiators such as 2,2'-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate), peroxide initiators such as benzoyl peroxide, etc. It is. The preferable addition amount of the polymerization initiator is 0.01% by mass or more based on the total amount of the monomers.
0 mass% or less, more preferably 0.1 mass% or more and 10 mass% or less. The mass composition range of the monomers in the gel electrolyte is preferably from 0.5% by mass to 70% by mass, and more preferably from 1.0% by mass to 50% by mass.

When the electrolyte is gelled by the crosslinking reaction of the polymer, it is desirable to use a polymer having a crosslinkable reactive group and a crosslinking agent together. In this case, a preferable crosslinkable reactive group is a nitrogen-containing heterocyclic ring (for example, a pyridine ring, an imidazole ring, a thiazole ring, an oxazole ring, a triazole ring, a morpholine ring, a piperidine ring, a piperazine ring, etc.), and a preferable crosslinking agent. Is a bifunctional or higher functional reagent capable of electrophilic reaction with a nitrogen atom (for example, alkyl halide, aralkyl halide, sulfonic acid ester, acid anhydride, acid chloride, isocyanate, etc.).

(4) Hole Transport Material In the present invention, an organic or inorganic hole transport material or a combination thereof can be used in place of the electrolyte.

(A) Organic hole transporting material As the organic hole transporting material applicable to the present invention, N, N'-
Diphenyl-N, N'-bis (4-methoxyphenyl)-(1,
1'-biphenyl) -4,4'-diamine (J. Hagen et al., Synth
etic Metal 89 (1997) 215-220), 2,2 ', 7,7'-tetrakis (N, N-di-p-methoxyphenylamine) 9,9'-spirobifluorene (Nature, Vol. 395, 8 Oct. 1998, p583-585 and WO97 / 10617), 1,1-bis {4- (di-p-tolylamino)
An aromatic diamine compound in which a tertiary aromatic amine unit of phenyl @ cyclohexane is linked (JP-A-59-194393), and 4,4-bis [(N-1-naphthyl) -N-phenylamino] biphenyl Aromatic amine containing two or more tertiary amines represented by two or more fused aromatic rings substituted with a nitrogen atom (JP-A-5-234681), and a derivative of triphenylbenzene having a starburst structure Aromatic triamine (U.S. Pat. No. 4,923,774, JP-A-4-3086)
No. 88), and aromatic diamines such as N, N′-diphenyl-N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (US Pat. , 764, 625), α,
α, α ′, α′-Tetramethyl-α, α′-bis (4-di-p-tolylaminophenyl) -p-xylene (JP-A-3-269084), p-phenylenediamine derivative, whole molecule As a sterically asymmetric triphenylamine derivative (Japanese Unexamined Patent Publication No.
JP-A-129271), a compound in which a pyrenyl group is substituted with a plurality of aromatic diamino groups (JP-A-4-175395), and an aromatic diamine in which a tertiary aromatic amine unit is linked by an ethylene group (JP-A-4-264189) JP-A-5-25473, an aromatic diamine having a styryl structure (JP-A-4-290851), a benzylphenyl compound (JP-A-4-364153), and a tertiary amine linked by a fluorene group (JP-A-5-25473).
JP-A-5-320455), triamine compounds (JP-A-5-239455), and pisdipyridylaminobiphenyl (JP-A-5-320).
634), N, N, N-triphenylamine derivatives (JP-A-6-1972), aromatic diamines having a phenoxazine structure (JP-A-7-138562), and diaminophenylphenanthridine derivatives (JP-A-7-138562). The aromatic amines shown in, for example, Kaihei 7-252474) can be preferably used. Α-octylthiophene and α, ω-dihexyl-α
-Octylthiophene (Adv. Mater. 1997, 9, N0.7, p55
7), hexadodecyldodecithiophene (Angew.Chem. In
t. Ed. Engl. 1995, 34, No. 3, p303-307), 2,8-dihexylanthra [2,3-b: 6,7-b '] dithiophene (JACS, Vol12
0, N0.4, 1998, p664-672) and the like,
Polypyrrole (K. Murakoshi et al.,; Chem. Lett. 199
7, p471), ¨ Handbook of Organic Conductive Molec
ules and Polymers Vol.1,2,3,4¨ (by NALWA, published by WILEY) Polyacetylene and its derivatives, poly (p-phenylene) and its derivatives, poly (p-
Conductive polymers such as phenylenevinylene) and derivatives thereof, polythienylenevinylene and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof, and polytoluidine and derivatives thereof can be preferably used. Natur for hole transport material
e, Vol. 395, 8 Oct. 1998, p583-585. To control dopant levels, compounds containing cation radicals such as tris (4-bromophenyl) aminium hexachloroantimonate were used. A salt such as Li [(CF ₃ SO ₂ ) ₂ N] may be added for controlling the potential of the oxide semiconductor surface (compensating for the space charge layer).

(B) Inorganic hole transport material As the inorganic hole transport material, a p-type inorganic compound semiconductor is used.
Can be. Bandgap of p-type inorganic compound semiconductor
The tip is preferably large so as not to hinder dye absorption.
The band gap of the p-type inorganic compound semiconductor is 2 eV or more.
And more preferably 2.5 eV or more.
Good. In addition, ionization potential of p-type inorganic compound semiconductor
Shall uses a dye adsorption electrode to reduce dye holes.
Needs to be smaller than the ionization potential of
Charge transfer by the dye used in the photoelectric conversion device of the present invention
Potential of p-type inorganic compound semiconductor used for layer
The preferred range of the signal varies, but is generally 4.5 eV or less.
It is preferably 5.5 eV or less, and more preferably 4.7 eV or more.
It is preferably 3 eV or less. Preferably used in the present invention
The p-type inorganic compound semiconductor is a compound semiconductor containing monovalent copper.
It is a conductor and as a compound semiconductor containing monovalent copper, CuI,
 CuSCN, CuInSe_Two, Cu (In, Ga) Se_Two, CuGaSe_Two, Cu _TwoO, CuS,
 CuGaS_Two, CuInS_Two, CuAlSe_TwoAnd the like. In this
Also, CuI and CuSCN are preferable, and CuI is most preferable. copper
-Type inorganic compounds that can be used other than compounds containing
As semiconductors, GaP, NiO, CoO, FeO, Bi_TwoO_Three, MoO_Two, C
r_TwoO_ThreeAnd the like.

(5) Formation of charge transfer layer

There are two methods for forming the charge transfer layer. One is a method in which a counter electrode is first stuck on a semiconductor fine particle-containing layer carrying a sensitizing dye, and a liquid charge transfer layer is sandwiched in the gap. Another one
One is to apply the charge transfer layer directly on the semiconductor fine particle-containing layer, and the counter electrode is applied thereafter.

As the method of sandwiching the charge transfer layer in the former case, a normal pressure process utilizing a capillary phenomenon by immersion or the like and a vacuum process of replacing the gas phase with a liquid phase at a pressure lower than normal pressure can be used.

In the latter case, the wet charge transfer layer is provided with a counter electrode in an undried state, and measures are taken to prevent liquid leakage at the edge. In the case of a gel electrolyte, there is also a method of applying it by a wet method and solidifying it by a method such as polymerization. In this case, a counter electrode can be provided after drying and fixing. As a method for applying a wet organic hole transport material or a gel electrolyte in addition to the electrolytic solution, the immersion method, the roller method, the dipping method, the air knife method, the extrusion method, and the slide method are the same as the method for applying the semiconductor fine particle-containing layer and the dye. A hopper method, a wire bar method, a spin method, a spray method, a casting method, various printing methods and the like can be considered.

In the case of a solid electrolyte or a solid hole (hole) transporting material, the charge transfer layer can be formed by a dry film forming process such as a vacuum evaporation method or a CVD method, and then a counter electrode can be provided. The organic hole transporting material can be introduced into the inside of the electrode by a method such as a vacuum evaporation method, a casting method, a coating method, a spin coating method, a dipping method, an electrolytic polymerization method, and a photoelectrolytic polymerization method.
In the case of an inorganic solid compound, it can be introduced into the electrode by a method such as a casting method, a coating method, a spin coating method, a dipping method, and an electrolytic plating method.

In consideration of mass production, in the case of an electrolyte which cannot be solidified or a wet hole transport material, it is possible to cope by sealing the edge portion immediately after coating, but it is possible to solidify. In the case of a hole transport material, it is more preferable to solidify the film by, for example, photopolymerization or thermal radical polymerization after forming the hole transport layer by wet application. As described above, the film application method may be appropriately selected depending on the physical properties of the liquid and the process conditions.

The charge transfer layer has a certain thickness so as not to cause a short circuit between the photosensitive layer (semiconductor layer) and the counter electrode. However, if the charge transfer layer is too thick, it is not preferable in terms of photoelectric conversion efficiency. The thickness of the charge transfer layer is preferably from 0.05 μm to 100 μm, and more preferably from 0.1 μm to 50 μm. In the present invention, an embodiment in which the charge transfer layer is a non-conductive porous layer containing a charge transport material is also preferably used. The non-conductive porous layer referred to here is a layer of a porous body made of a non-conductive substance or a semiconductor substance that does not exhibit a charge transport function, and impregnates voids with the charge transport material. The porosity is preferably 30% by volume or more.
Note that the charge transport material is also present in the porous photosensitive layer formed by the semiconductor fine particles.

The water content in the charge transfer layer was 10,
2,000 ppm or less, more preferably 2,0 ppm
It is at most 00 ppm, particularly preferably at most 100 ppm.

(E) Other layers In particular, when a hole transporting material is used for the charge transfer layer, a dense semiconductor is previously placed between the conductive support and the photosensitive layer in order to prevent a short circuit between the counter electrode and the conductive support. It is preferable to apply the thin film layer as an undercoat layer. Preferred as the undercoat layer are TiO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, and Nb ₂ O ₅ , more preferably TiO ₂ . The undercoat layer is, for example, Electroc
himi. Acta 40, 643-652 (1995) can be applied by a spray pyrolysis method. The preferred thickness of the undercoat layer is 5 to 1000 nm or less, more preferably 10 to 500 nm.

A functional layer such as a protective layer or an antireflection layer may be provided on one or both of the conductive support serving as an electrode and the counter electrode. When such a functional layer is formed in multiple layers, a simultaneous multilayer coating method or a sequential coating method can be used, but from the viewpoint of productivity, the simultaneous multilayer coating method is preferable.
In the simultaneous multi-layer coating method, a slide hopper method or an extrusion method is suitable in consideration of productivity and uniformity of a coating film. In forming these functional layers, an evaporation method, a sticking method, or the like can be used depending on the material.

(F) Specific Example of Internal Structure of Photoelectric Conversion Element As described above, the internal structure of the photoelectric conversion element can take various forms according to the purpose. 2 to 6 exemplify an internal structure of a photoelectric conversion element which can be preferably applied to the present invention.

FIG. 2 shows a structure in which the photosensitive layer 20 and the charge transfer layer 30 are interposed between the reflective conductive layer 10 and the transparent counter electrode conductive layer 40a, and light is incident from the counter electrode side. It has become. FIG. 3 shows that a metal lead 11 is partially provided on a transparent substrate 50a, a transparent conductive layer 10a is further provided, an undercoat layer 60 and a photosensitive layer 2 are provided.
0, a charge transfer layer 30 and a light-reflective counter electrode conductive layer 40 are provided in this order, and a support substrate 50 is further disposed, so that light is incident from the transparent conductive layer side. FIG.
Has a reflective conductive layer 10 on a supporting substrate 50, provides a photosensitive layer 20 via an undercoat layer 60, and further has a charge transfer layer 30
And a transparent counter electrode conductive layer 40a, and a transparent substrate 50a partially provided with a metal lead 11 is disposed with the metal lead 11 side inward, so that light is incident from the counter electrode side. FIG. 5 shows a transparent conductive layer 10a and a photosensitive layer 2 on a transparent substrate 50a.
0, a charge transfer layer 30 and a reflective counter electrode conductive layer 40 are provided,
A support substrate 50 is disposed thereon, and has a structure in which light enters from the transparent conductive layer side. FIG. 6 has the conductive layer 10 on the support substrate 50, and provides the photosensitive layer 20 via the undercoat layer 60,
Further provided a charge transfer layer 30 and a transparent counter electrode conductive layer 40a,
The transparent substrate 50a is disposed thereon, and has a structure in which light enters from the counter electrode side. Among them, FIGS.
And configurations of 6 are preferred.

[2] Photovoltaic cell The photovoltaic cell of the present invention allows the photoelectric conversion element to work in an external circuit, and includes a solar cell. It is preferable that the side surface of the photovoltaic cell is sealed with a polymer, an adhesive, or the like in order to prevent deterioration of components and volatilization of the contents. The external circuit itself connected to the conductive support and the counter electrode via a lead may be a known one. When the photoelectric conversion element of the present invention is applied to a so-called solar cell, the structure inside the cell is basically the same as the structure of the above-described photoelectric conversion element. Hereinafter, a module structure when the photoelectric conversion element of the present invention is applied to a solar cell will be described.

The dye-sensitized solar cell of the present invention can have a module structure basically similar to a conventional solar cell module. The solar cell module generally has a structure in which cells are formed on a support substrate made of metal, ceramic, or the like, and the cells are covered with a filling resin, protective glass, or the like, and light is taken in from the opposite side of the support substrate. Specifically, a module structure called a superstrate type, a substrate type, or a potting type, a substrate-integrated module structure used in an amorphous silicon solar cell, and the like are known. The module structure of the dye-sensitized solar cell of the present invention can be appropriately selected depending on the purpose of use, the place of use, and the environment.

In a typical superstrate type or substrate type module, cells are arranged at fixed intervals between supporting substrates which are transparent on one or both sides and have been subjected to an antireflection treatment, and adjacent cells are made of metal leads or flexible. It is connected by wiring or the like, and a current collecting electrode is arranged on the outer edge, so that generated power is taken out to the outside. Between the substrate and the cell, various kinds of plastic materials such as ethylene vinyl acetate (EVA) may be used in the form of a film or a filling resin, depending on the purpose, in order to protect the cell and improve current collection efficiency. Also,
When used in places where it is not necessary to cover the surface with a hard material, such as places where there is little external impact, the surface protective layer is made of a transparent plastic film, or a protective function is provided by curing the above-mentioned filling resin. It is possible to eliminate the support substrate on one side. The periphery of the support substrate is fixed in a sandwich shape with a metal frame in order to secure the inside sealing and the rigidity of the module, and the space between the support substrate and the frame is hermetically sealed with a sealing material. Also,
If a flexible material is used for the cell itself, the supporting substrate, the filling material, and the sealing material, a solar cell can be formed on a curved surface.

The super-straight type solar cell module has a structure in which, for example, a front substrate sent from a substrate supply device is conveyed by a belt conveyor or the like, and a cell is formed thereon with a sealing material-cell connection lead wire and a back surface sealing. After laminating sequentially with materials and the like, a back substrate or a back cover can be placed, and a frame can be set on the outer edge to produce.

On the other hand, in the case of the substrate type, while the support substrate sent out from the substrate supply device is transported by a belt conveyor or the like, the cells are sequentially laminated thereon with the inter-cell connection lead wire, the sealing material, and the like. It can be manufactured by placing a front cover and setting a frame on the periphery.

In the case of a module structure, a conductive layer is provided on a substrate,
Selective plating, selective etching, CVD, P, etc. so that the photosensitive layer, charge transfer layer, counter electrode, etc. are arranged three-dimensionally and at regular intervals.
Semiconductor process technology such as VD, laser scribing after pattern coating or wide coating, plasma CVM
(Solar Energy Materials and Solar Cells, 48, p373
-381 etc.), and a desired module structure can be obtained by patterning by a mechanical method such as grinding.

The other members and steps will be described below in detail. As a sealing material, weather resistance imparting, electrical insulation imparting,
Various materials such as liquid EVA (ethylene vinyl acetate), film EVA, and a mixture of vinylidene fluoride copolymer and acrylic resin can be used according to the purpose of improving the light collection efficiency and cell protection (impact resistance). It is. It is preferable to use a sealing material having high weather resistance and moisture resistance between the outer edge of the module and the frame surrounding the periphery. In addition, the strength and light transmittance can be increased by mixing a transparent filler into the sealing material.

When fixing the sealing material on the cell, a method suitable for the physical properties of the material is used. In the case of film-like materials, various methods such as roll pressing, bar coating, spray coating, screen printing, etc. are possible. is there.

When a flexible material such as PET or PEN is used as the support substrate, a roll-shaped support is drawn out to form a cell thereon, and then the sealing layer is continuously laminated by the above method. Can be highly productive.

In order to increase the power generation efficiency, the surface of the substrate (generally tempered glass) on the light intake side of the module is subjected to an anti-reflection treatment. As the anti-reflection treatment method,
There are a method of laminating an antireflection film and a method of coating an antireflection layer.

By treating the surface of the cell by a method such as grooving or texturing, it is possible to increase the utilization efficiency of incident light.

In order to increase the power generation efficiency, it is most important that light is taken into the module without loss. However, it is also important that light transmitted through the photoelectric conversion layer is reflected and returned efficiently to the photoelectric conversion layer side. is there. As a method of increasing the light reflectance, a method in which a support substrate surface is mirror-polished and then Ag or Al is deposited or plated, and Al-Mg or Al-Ti
For example, a method of forming a texture structure in the lowermost layer by annealing treatment.

In order to increase the power generation efficiency, it is important to reduce the inter-cell connection resistance from the viewpoint of suppressing the internal voltage drop. As a method of connecting the cells, wire bonding and connection using a conductive flexible sheet are generally used.However, a method of fixing the cells using a conductive adhesive tape or a conductive adhesive and simultaneously electrically connecting the cells, There is also a method of pattern-coating a conductive hot melt at a desired position.

In the case of a solar cell using a flexible support such as a polymer film, the cells are sequentially formed by the above-described method while the roll-shaped support is being sent out, cut into a desired size, and the peripheral portion is made flexible and moisture-proof. The battery body can be manufactured by sealing with a material having a property.
Also, Solar Energy Materials and Solar Cells, 48,
A module structure called “SCAF” described in p383-391 can also be used. Further, a solar cell using a flexible support can be used by being adhered and fixed to a curved glass or the like.

As described in detail above, solar cells having various shapes and functions can be manufactured according to the purpose of use and environment of use.

[0118]

The present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the examples unless it exceeds the gist of the invention.

[Example 1] 1. Preparation of Transparent Conductive Support and Transparent Counter Electrode A 1.9 mm thick non-alkali glass substrate was uniformly coated with fluorine-doped tin dioxide over the entire surface by a CVD method, and had a thickness of 600 nm and a sheet resistance of about 10 Ω / □. ,
A transparent conductive support having a light transmittance (500 nm) of 85% and having a conductive tin dioxide film coated on one side, and a transparent counter electrode were formed. Further, when used as a counter electrode, a terminal treated with chloroplatinic acid was prepared by masking the terminal portion of this electrode and spin-coating a conductive surface with a chloroplatinic acid solution. (Opposite to photocells 105 and 205)

[0120] 2. Preparation of coating solution containing titanium dioxide particles J. J. Barbe et al. Am. Ceramic S
oc. According to the production method described in the article of Vol. 80, p. 3157, titanium tetraisopropoxide is used as a titanium raw material, and the temperature of the polymerization reaction in the autoclave is 230 ° C.
And a titanium dioxide dispersion having a titanium dioxide concentration of 11% by mass was synthesized. The average size of the obtained titanium dioxide particles was about 10 nm. 30% by mass of polyethylene glycol (molecular weight: 2
000, manufactured by Wako Pure Chemical Industries, Ltd.) and mixed to obtain a coating solution.

3. Preparation of Titanium Dioxide Electrode Adsorbing Dye In the photovoltaic cells 101, 103, 201 and 103, the coating solution prepared in 2 was coated on the transparent conductive support prepared in 1 above by a doctor blade method to a thickness of 60 μm, After drying at 25 ° C. for 30 minutes, it was baked in air in an electric furnace at 450 ° C. for 30 minutes. The coating amount of titanium dioxide was 9 g / m ² and the film thickness was 6 μm. In the photovoltaic cells 102, 104, 202, and 204, the coating liquid similarly prepared in 2 was applied to a thickness of 60 μm by a doctor blade method on a reflective conductive substrate obtained by depositing platinum on the transparent conductive support of 1 above. After drying at 25 ° C. for 30 minutes, it was baked in an electric furnace at 550 ° C. for 30 minutes in the air. The amount of titanium dioxide applied was
9 g / m ² , and a film thickness of 6 μm
m. Take out the electrode in dry air 12
While cooled to 0 ° C., it was immersed in an organic solution of the dye material R-1 (dye 3 × 10 ⁻⁴ mol / liter, solvent: 2-propanol) at 40 ° C. for 12 hours. The dyed glass was washed with ethanol and dried naturally in the dark.
The amount of the dye adsorbed was about 1.5 × 10 ⁻³ mol per 1 m ^{2 of the} titanium dioxide coated area.

4. Photovoltaic cell fabrication In photovoltaic cells 101, 103 and 201, 203, a color sensitized TiO having a transparent conductive support fabricated as described above was used.
_Two electrodes (2 cm x 1.5 cm) are sandwiched between the counter electrode (platinum-deposited glass) of the same size and a frame-type spacer made of polyethylene (thickness: 20 µm) at the terminal end in the long side direction. A certain width of 2 mm was alternately put outside and superposed. The entire cell was sealed with an epoxy resin adhesive except for the surface of the TiO ₂ transparent electrode as a light receiving part. Next, a small hole for liquid injection is made on the side surface of the spacer, and the photovoltaic cells 101 and 103 use the electrolytic solution (methoxyacetonitrile: compound 1: LiI: I
₂ : t-butylpyridine = 30: 6: 1: 0.5: 5
(Mass ratio)). Also, photovoltaic cells 201 and 2
03, the room temperature molten salt electrolyte (Y7-2: Y8-1: I
₂ = 15: 35: 1 (mass ratio). In this manner, the light receiving area is about 2 cm ² , conductive glass (a transparent conductive agent layer is provided on the glass), dye-sensitized TiO ₂ layer (photosensitive layer), charge transfer layer, platinum layer Then, a photovoltaic cell in which the counter electrode was a light-reflective electrode, in which a support glass was laminated in order, was assembled.

Photocells 102, 104, 105, 202, 204 and 205
Then, the color-sensitized TiO ₂ electrode (2 cm × 1.5 cm) having the light-reflective conductive support prepared in the above 3 was replaced with the transparent counter electrode produced in the above 1 having the same size, and a polyethylene frame. With the mold spacer (8 μm in thickness) interposed therebetween, terminal ends for terminals of 2 mm in width were alternately put outside in the direction of the long side and superposed. The entire cell was sealed with an epoxy resin adhesive except for the surface of the transparent counter electrode serving as a light receiving portion.
Next, a small hole for liquid injection is made on the side surface of the spacer, and the photovoltaic cells 102, 104 and
At 105, the electrolyte was impregnated, and at photocells 202, 204, and 205, the molten salt electrolyte was impregnated. In this way, the light receiving area is about 2 cm ² , and the reflective conductive glass (a platinum deposited conductive agent layer is provided on the glass), the dye-sensitized TiO 2
Assemble a photovoltaic cell in which _two layers, a charge transfer layer, and a transparent counter electrode (a transparent conductive agent layer is provided on glass) are sequentially laminated, and the conductive support of the photosensitive layer is a light-reflective electrode. Was.

The liquid thickness of the electrolytic transfer layer (electrolyte) and (molten salt electrolyte) with respect to the light absorption of the color-sensitized 6 μm thick TiO ₂ layer prepared on the transparent conductive support as described above. Table 1 shows the relative values of the light absorption amounts of 2 μm and 14 μm when the light absorption amount of the dye-sensitized TiO ₂ layer was set to 1.

[0125]

[Table 1]

5. Measurement of photoelectric conversion efficiency A 500 W xenon lamp (USHIO Inc.) and a correction filter for sunlight simulation (AM manufactured by Oriel)
1.5G), and the incident light intensity on the battery is 100 mW
Simulated sunlight adjusted to / cm ² was irradiated. An ohmic contact was made with a conductive wire to a terminal provided at the end of the conductive glass and platinum-deposited glass of the fabricated photovoltaic cell, and the electrical response of both electrodes was input to a current / voltage measuring device (Source measure unit 238 made by Keithley). Irradiation light from a light source was incident on the transparent electrode side of the battery, and the current-voltage characteristics were measured with the photocell controlled at 50 ° C. The short-circuit current (Jsc) and the conversion efficiency (η) of the photovoltaic cell thus determined, and the Js of the photovoltaic cell using the electrolytic solution and the molten salt electrolyte, respectively.
Table 2 collectively shows the ratios of c and η to the comparative examples.

[0127]

[Table 2]

Compared with the above comparative photocells 101 and 102,
It can be seen that Jsc is high in both 103 and 104 of the present invention, and the conversion efficiency is accordingly high. It can be seen that 105 in which the transparent counter electrode was treated with the chloroplatinic acid solution had a greater improvement effect than 104 which was not treated. Further, even in the case of a molten salt electrolyte having a high stability of the charge transfer layer and excellent durability (photovoltaic cells 201 to 205), compared to comparative photovoltaic cells 201 and 202, 20
It can be seen that both 3 and 204 have a high Jsc, and accordingly a high conversion efficiency. It can be seen that 205 obtained by treating the transparent counter electrode with a chloroplatinic acid solution has a greater improvement effect than 204 not treated. Furthermore, from the ratio of Jsc and η to the comparative example,
It can be seen that the improvement effect in the photovoltaic cell using the configuration of the present invention is greater in the case of the molten salt electrolyte. In addition to the above examples, similar results were obtained in a photovoltaic cell using a gel electrolyte instead of the molten salt electrolyte. In addition, one photocell
When the temperature was controlled at 0 ° C., the same measurement was carried out, and it was found that the increase rate of Jsc was remarkable, particularly when a molten salt electrolyte was used, and the temperature dependence of the conversion efficiency was small.

[0129]

According to the present invention, a dye-sensitized photoelectric conversion element and a photovoltaic cell having excellent energy conversion efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 2 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 3 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 4 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 5 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 6 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

[Explanation of symbols]

 10: conductive layer 10a: transparent conductive layer 11: metal lead 20: photosensitive layer 21: semiconductor fine particles 22: dye 23: charge transport material 30: charge transfer layer 40: Counter conductive layer 40a: Transparent counter conductive layer 50: Substrate 50a: Transparent substrate 60: Undercoat layer

Claims (9)

[Claims] 1. A photoelectric conversion device having at least a first electrode, a second electrode, a semiconductor layer sensitized by a dye and a charge transfer layer, wherein the first electrode is light-reflective and the second electrode is light-transmissive. And the amount of light absorbed by the charge transfer layer is 1 / th of the amount of light absorbed by the semiconductor layer sensitized by the dye.
A photoelectric conversion element having a density of 4 or less. 2. The photoelectric conversion device according to claim 1, wherein a stacking order is:
The photoelectric conversion device according to claim 1, wherein the first electrode, the semiconductor layer sensitized by the dye, the charge transfer layer, and the second electrode are arranged in this order. 3. The photoelectric conversion device according to claim 1, wherein at least one of the dyes used for sensitizing the semiconductor has absorption at a wavelength longer than 800 nm. 4. The photoelectric conversion device according to claim 1, wherein said semiconductor layer is a porous layer made of semiconductor fine particles. 5. The photoelectric conversion device according to claim 1, wherein a gel electrolyte, a molten salt electrolyte or a solid electrolyte is used as the charge transport material in the charge transfer layer. 6. The charge transfer layer according to claim 1, wherein the charge transfer layer comprises a nonconductive porous material and a charge transport material.
6. The photoelectric conversion element according to any one of 5. 7. Use of the second electrode as a counter electrode, and
The photoelectric conversion element according to any one of claims 1 to 6, wherein the surface thereof is treated with chloroplatinic acid or platinum fine particles are attached. 8. A photovoltaic cell using the photoelectric conversion element according to claim 1. 9. A photovoltaic module comprising the photovoltaic cell according to claim 8.