JP2002075471A - Photoelectric conversion element and photocell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element with a photoelectric conversion efficiency heightened by preventing an inverse current not related to light irradiation, especially, a photoelectric conversion element with flexible substrate, and to provide a photocell using above photoelectric conversion element. SOLUTION: A photocell, using the photoelectric conversion element comprising a conductive layer, a sensitized layer including semiconductor intensified by pigment, an electric charge transfer layer, an opposite pole, and a layer interposed between the sensitized layer and the conductive layer composed of a semiconductor of which, the electric potential of the lower end of conduction band is lower than that of the semiconductor constituting the sensitized layer; and the photoelectric element with a polymer film substrate; is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photoelectric conversion element using semiconductor fine particles sensitized with a dye and a photovoltaic cell using the same.

[0002]

2. Description of the Related Art Solar power generation includes single crystal silicon solar cells,
BACKGROUND ART Polycrystalline silicon solar cells, amorphous silicon solar cells, and compound solar cells such as cadmium telluride and indium copper selenide have been put to practical use or are subject to main research and development. However, it is necessary to overcome problems such as production cost, securing of raw materials, and long energy payback time in order to spread the technology. On the other hand, there have been proposed many solar cells using an organic material intended to have a large area and a low price, but have a problem that conversion efficiency is low and durability is poor. Under these circumstances, Nature (No. 353)
Vol., Pp. 737-740, 1991) and U.S. Pat. No. 4,492,721 disclose a photoelectric conversion element and a solar cell using semiconductor fine particles sensitized with a dye, and materials and manufacturing techniques for producing the same. Was done. The proposed battery is a wet solar battery 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 photoelectric conversion element can be provided because an inexpensive oxide semiconductor such as titanium dioxide can be used without purification with high purity. The second advantage is that since the absorption of the dye used is broad, light in almost the entire wavelength region of visible light can be converted into electricity. However, there is a problem that a sufficient take-out voltage cannot be obtained. This is because a reverse current flows from the electrode to the charge transporting material irrespective of light irradiation, and there is no means for sufficiently preventing the reverse current.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photoelectric conversion element having an improved photoelectric conversion efficiency by preventing a reverse current flowing regardless of the presence or absence of light irradiation. Another object of the present invention is to provide such a photoelectric conversion element using a flexible substrate. It is a further object of the present invention to provide a flexible photovoltaic cell with improved photoelectric conversion efficiency.

[0004]

According to the present invention, the above-mentioned object of the present invention is achieved by providing a photoelectric conversion element and a photovoltaic cell having the following structures. 1. A conductive layer, a photosensitive layer containing a semiconductor sensitized by a dye,
In a photoelectric conversion element having a charge transport layer and a counter electrode, a layer formed of a semiconductor whose conduction band lower end potential is lower than that of a semiconductor forming the photosensitive layer is provided between the photosensitive layer and the conductive layer. Photoelectric conversion element. 2. 2. The photoelectric conversion device according to the above item 1, wherein the semiconductor constituting the photosensitive layer is titanium oxide, and the semiconductor having a lower conduction band potential is zirconium oxide, strontium titanate, niobium oxide or zinc oxide. . 3. The semiconductor constituting the photosensitive layer is at least one selected from zinc oxide, tin oxide and tungsten oxide, and the semiconductor having a lower conduction band lower potential is zirconium oxide, strontium titanate, niobium oxide, zinc oxide Or 1 is titanium oxide
3. The photoelectric conversion element according to item 1. 4. 4. The photoelectric conversion device according to any one of the above items 1 to 3, wherein the charge transport layer contains a molten salt electrolyte or a hole transport material. 5. The conductive layer or the counter electrode has a substrate, and the substrate is a polymer film, a metal foil, a metal plate, a polymer film having a metal layer on the surface, or a glass plate having a metal layer on the surface. The photoelectric conversion element according to any one of the above items 1 to 4, wherein 6. A photovoltaic cell using the photoelectric conversion element described in any one of 1 to 5 above.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION [1] Photoelectric conversion element The photoelectric conversion element of the present invention preferably has a conductive layer 10, an undercoat layer 60, a photosensitive layer 20,
The charge transport layer 30 and the counter electrode conductive layer 40 are laminated in this order, and 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 permeated the voids between the semiconductor fine particles 21 (that is, A charge transport material is made to penetrate into the voids of the semiconductor fine particle layer sensitized by the dye). The charge transport material 23 is composed of the same components as the materials used for the charge transport layer 30. In addition, in order to impart strength to the photoelectric conversion element, a substrate is used as a base for the conductive layer 10 and / or the counter electrode conductive layer 40.
50 may be provided. 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”. Note that the conductive layer 10, the counter electrode conductive layer 40 in FIG. 1,
The substrate 50 includes a transparent conductive layer 10a and a transparent counter electrode conductive layer 40, respectively.
a, The transparent substrate 50a may be used. A photovoltaic cell is made for the purpose of generating electrical work by connecting this photoelectric conversion element to an external load (power generation), and an optical sensor is made for the purpose of sensing optical information. Of the photovoltaic cells, a case where the charge transport material 23 is mainly composed of an ion transport material is particularly called a photoelectrochemical cell, and a case where the main purpose is power generation by sunlight is called a solar cell.

In the photoelectric conversion device of the present invention shown in FIG. 1, when the semiconductor fine particles are n-type, 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. Then, the high-energy electrons in the excited dye 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 transport layer 30 while working in an external circuit, and the dye 22 is regenerated. The photosensitive layer 20 functions as a negative electrode (photo anode), and the counter electrode 40 functions as a positive electrode. At the boundary of each layer (for example, the boundary between the conductive layer 10 and the photosensitive layer 20, the boundary between the photosensitive layer 20 and the charge transport layer 30, the boundary between the charge transport layer 30 and the counter electrode conductive layer 40, etc.), They may be mutually diffused and mixed. Hereinafter, each layer will be described in detail.

(A) Undercoat layer In the present invention, the undercoat layer, that is, the layer located between the photosensitive layer (semiconductor fine particle layer) and the electrode (conductive layer), has a lower potential than the conduction band lower potential of the dye-sensitized semiconductor. By using a semiconductor having a lower potential at the bottom of the conduction band, electron transfer from the electrode to the charge transporting material does not occur unless a higher potential is applied, so that the reverse current during light irradiation is small and apparent forward electron transfer. , And high photoelectric conversion efficiency can be obtained. The potential at the bottom of the conduction band of the semiconductor according to the present invention is that of the semiconductor fine particles actually used for the photoelectric conversion element, and this potential may be different from the value of a large crystal. The semiconductor fine particles used for the photosensitive layer and the semiconductor used for the undercoat layer may have different conduction band lower potentials even if they have the same composition. In general, the semiconductor of the undercoat layer tends to have a higher potential at the lower end of the conduction band than the semiconductor fine particles of the photosensitive layer, although it differs depending on the method of making. In particular, when the undercoat layer is formed by spray pyrolysis or sintering to increase the crystallinity, the tendency is remarkable. The spray pyrolysis can be produced, for example, with an apparatus such as an SPD thin film forming apparatus manufactured by Make Co., Ltd. When the semiconductor constituting the color-sensitized semiconductor fine particle layer is titanium oxide, the semiconductor used for the undercoat layer is preferably zirconium oxide, strontium titanate, niobium oxide or zinc oxide, and more preferably strontium titanate. , Niobium oxide. When the semiconductor constituting the color-sensitized semiconductor fine particle layer is zinc oxide, tin oxide and / or tungsten oxide, the semiconductor used for the undercoat layer is preferably zirconium oxide, strontium titanate, niobium oxide, zinc oxide or titanium oxide. And more preferably strontium titanate, niobium oxide and zinc oxide.

The undercoat layer is made of, for example, Electrochim. Acta 4
In addition to the spray pyrolysis method described in U.S. Pat.
The preferred thickness of the undercoat layer is 5 to 1000 nm or less, 10 to 5
00 nm is more preferred.

The effect of the semiconductor of the undercoat layer differs depending on the type of the charge transporting material. That is, compared with the case where the charge transport material is a conventional wet electrolyte (so-called electrolyte solution), the effect of the molten salt type electrolyte is larger than that of the conventional case. Is remarkable. This is considered to be because the more the reverse electron transfer from the electrode to the charge transporting material, the greater the effect. This effect is remarkable when the support has flexibility. For example, when the support used for the conductive layer and / or the counter electrode is a conductive polymer film having a thickness of 200 μm or less. In the case of a metal having a thickness of 60 μm or less, the effect is remarkable. This seems to correspond to the fact that, when microscopic destruction occurs in the photosensitive semiconductor fine particle layer based on the deformation of the support, the chance of contact between the electrode and the charge transporting material increases. Furthermore, the effect of the undercoat layer of the present invention was more remarkable when the conductive material of the electrode was a metal than an oxide semiconductor (including a doped material).

(B) Conductive Support The conductive support comprises (1) a single layer of a conductive layer, or (2) two layers of a conductive layer and a substrate. In the case of (1), a material having sufficient strength and sealing property is used as the conductive layer. For example, a metal material (platinum, gold, silver, copper, zinc,
Titanium, aluminum, and the like, or alloys containing them) can be used. 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 include metals (for example, platinum, gold, silver, copper, zinc, titanium, aluminum, indium and the like or alloys containing these), carbon, and conductive metal oxides (indium-tin composite oxide, tin oxide). And the like doped with fluorine or antimony). The thickness of the conductive layer is preferably about 0.02 to 10 μm.

The lower the surface resistance of the conductive support, the better. The preferred range of the surface resistance is 50 Ω / □ or less, more preferably 20 Ω / □ or less.

When light is irradiated from the conductive support side, the conductive support is preferably substantially transparent.
The term “substantially transparent” means that the region is in the visible to near infrared region (400 to 120).
0 nm) means that the transmittance is 10% or more in part or all of the light, preferably 50% or more.
% Or more is more preferable. In particular, it is preferable that the transmittance in a wavelength region where the photosensitive layer has sensitivity is high.

[0013] The transparent conductive support is preferably formed by coating or vapor-depositing a transparent conductive layer made of a conductive metal oxide on the surface of a transparent substrate such as glass or plastic. Preferred as the transparent conductive layer is tin dioxide or indium-tin oxide (ITO) doped with fluorine or antimony. As the transparent substrate, a glass substrate such as soda glass which is advantageous in terms of cost and strength and alkali-free glass which is not affected by alkali elution, and a transparent polymer film can be used.
Transparent polymer film materials include triacetyl cellulose (TAC) and polyethylene terephthalate (PE).
T), polyethylene naphthalate (PEN), syndiotactic polysterene (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyester sulfone (PES), polyimide ( PI), polyetherimide (PEI), cyclic polyolefin, brominated phenoxy and the like. To ensure sufficient transparency, the amount of conductive metal oxide applied should be 1 m ² of glass or plastic support.
It is preferably 0.01 to 100 g per unit.

It is preferable to use a metal lead for the purpose of lowering the resistance of the transparent conductive support. The material of the metal lead is preferably a metal such as platinum, gold, nickel, titanium, aluminum, copper, or silver. The metal lead is preferably provided on a transparent substrate by vapor deposition, sputtering, or the like, and a transparent conductive layer made of conductive tin oxide or an ITO film is preferably provided thereon. The decrease in the amount of incident light due to the installation of metal leads is preferably 10
%, More preferably 1 to 5%.

(C) Photosensitive Layer In the photosensitive layer, the semiconductor acts as a photoreceptor, absorbs light to separate charges, and generates electrons and holes. In a dye-sensitized semiconductor, light absorption and thus generation of electrons and holes mainly occur in the dye, and semiconductor fine particles have a role of receiving and transmitting the electrons (or holes). 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.

(1) Semiconductor The semiconductor is a simple semiconductor such as silicon or germanium, a III-V compound semiconductor, a metal chalcogenide (eg, oxide, sulfide, selenide, or a composite thereof), or Compounds having a perovskite structure (for example, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate, etc.) can be used.

Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium,
Hafnium, strontium, indium, cerium,
Examples include oxides of yttrium, lanthanum, vanadium, niobium, or tantalum, sulfides of cadmium, zinc, lead, silver, antimony or bismuth, selenides of cadmium or lead, tellurides of cadmium, and the like. Other compound semiconductors include zinc, gallium, indium,
Examples include phosphides such as cadmium, selenides of gallium-arsenic or copper-indium, and sulfides of copper-indium. Furthermore, MxOySz or M ₁ xM ₂ yOz
(M, M ₁ and M ₂ are metal elements, O is oxygen, x,
Compounds such as y and z are the number of combinations having a neutral valence) can also be preferably used.

Preferred examples of the semiconductor used for the photosensitive layer include Si, TiO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, Z
nS, PbS, Bi ₂ S ₃ , CdSe, CdTe, SrTiO ₃ , GaP, InP, GaA
s, CuInS ₂ , CuInSe _{2 and the} like, more preferably TiO ₂ , Zn
_{O, SnO 2, Fe 2 O} 3, WO 3, Nb 2 O 5, CdS, PbS, CdSe, SrTi
O ₃ , InP, GaAs, CuInS ₂ or CuInSe ₂ , particularly preferably TiO ₂ or Nb ₂ O ₅ , most preferably TiO ₂ . TiO ₂ is preferably TiO ₂ containing 70% or more of anatase type crystal, particularly preferably 100% TiO _{2 of} anatase type crystal.
It is. It is also effective to dope a metal for the purpose of improving electron conductivity in these semiconductors. The metal to be doped is preferably a divalent or trivalent metal. It is also effective to dope the semiconductor with a monovalent metal for the purpose of preventing a reverse current from flowing from the semiconductor to the charge transport layer.

The semiconductor used for the photosensitive layer is preferably polycrystalline from the viewpoints of production cost, securing of raw materials, energy payback time and the like, and a porous film composed of semiconductor fine particles is particularly preferred. In addition, a part of the amorphous portion may be included.

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 30 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 preferably 25 nm or less, more preferably 10 nm or less.
For the purpose of improving the light capture rate by scattering incident light, it is also preferable to mix semiconductor particles having a large particle diameter, for example, about 100 nm or more and about 300 nm.

Two or more different types of semiconductor fine particles may be mixed. When two or more kinds of semiconductor fine particles are mixed and used, one kind is TiO ₂ , ZnO, Nb ₂ O ₅ or SrTiO ₃
It is preferred that Another type is SnO ₂ , Fe
It is preferably ₂ O ₃ or WO ₃ . More preferred combinations include ZnO and SnO ₂ , ZnO and WO ₃ or ZnO, SnO ₂
Mention may be made of a combination, such as WO _3. When two or more kinds of semiconductor fine particles are used as a mixture, the respective particle diameters may be different. In particular, a combination in which the particle size of the semiconductor fine particles described in the first type is large and the semiconductor fine particles described in the second and subsequent types is small is preferable. Preferably, the combination is such that the particles having a large particle diameter are 100 nm or more and the particles having a small particle diameter are 15 nm or less.

As a method for producing semiconductor fine particles, Sakuhana Shizuo's "Sol-Gel Method Science" Agne Shofusha (1998) and Technical Information Association "Sol-Gel Method for Thin Film Coating" (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, both the above-mentioned sol-gel method and the high-temperature hydrolysis method in chloride oxyhydrogen salt are preferred, but furthermore, Manabu Kiyono's “Physical properties and applied technology of titanium oxide” published by Gihodo. (1997). The sulfuric acid method and the chlorine method described in (1997) can also be used. Further, as a sol-gel method, Barbe et al., Journal of American Ceramic Society, Vol. 80, No. 12, 3157-3171
Page (1997), Burnside et al., Chemistry of Materials, Vol. 10, No. 9, 2419-2425.
The method described on page is also preferred.

(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 is used. 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. Typical wet film forming methods include a coating method, a printing method, an electrolytic deposition method, and an electrodeposition method. In addition, a method of oxidizing a metal, a method of depositing a metal solution in a liquid phase by ligand exchange (LPD method), a method of vapor deposition by sputtering, a CVD method, or a metal that thermally decomposes on a heated substrate An SPD method in which an oxide precursor is sprayed to form a metal oxide can also be used.

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, citronellol, terpineol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.). At the time of dispersion, a polymer such as polyethylene glycol, hydroxyethyl cellulose, carboxymethyl cellulose, a surfactant, an acid, a chelating agent, or the like may be used as a dispersing aid, if necessary. By changing the molecular weight of polyethylene glycol, it is possible to adjust the viscosity of the dispersion, to form a semiconductor layer that is difficult to peel off, and to control the porosity of the semiconductor layer. Therefore, it is preferable to add polyethylene glycol.

The application method includes a roller method and a dip method as an application system, an air knife method and a blade method as a metering system.
-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 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.

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 photovoltaic cell, the thickness of the semiconductor fine particle layer is preferably 1 to 30 μm, more preferably 2 to 25 μm. Support 1 m ² per coating amount of the semiconductor fine particles 0.5
-100 g is preferable, and 3-50 g is more preferable.

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 40 ° C to 700 ° C, more preferably 100 ° C to 600 ° C.
is there. 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. Also, from a cost perspective, the lowest possible temperature (for example, 50
C. to 350 C.). Low temperature can be achieved by heat treatment in the presence of small semiconductor particles of 5 nm or less, mineral acid, metal oxide precursor, etc. In addition, irradiation of ultraviolet rays, infrared rays, microwaves, etc., electric field, and application of ultrasonic waves Can also be performed. At the same time, in order to remove unnecessary organic substances and the like, it is preferable to use a combination of heating, decompression, oxygen plasma treatment, pure water washing, solvent washing, gas washing and the like in addition to the above-mentioned irradiation and application.

After the heat treatment, for example, a chemical plating treatment using an aqueous solution of titanium tetrachloride may be used to increase the surface area of the semiconductor fine particles, increase the purity near the semiconductor fine particles, and increase the efficiency of electron injection from the dye into the semiconductor fine particles. Electrochemical plating using an aqueous solution of titanium trichloride may be performed. In order to prevent a reverse current from flowing from the semiconductor fine particles to the charge transport layer, it is also effective to adsorb an organic substance having low electron conductivity other than the dye on the particle surface. As the organic substance to be adsorbed, a substance having a hydrophobic group is preferable.

The semiconductor fine particle layer preferably has a large surface area so that many dyes can be adsorbed. The surface area in a state where the layer of the semiconductor fine particles is applied on the support is preferably 10 times or more, and more preferably 100 times or more with respect to the projected area. The upper limit is not particularly limited, but is usually about 1000 times.

(3) Dye The sensitizing dye used in the photosensitive layer may be any compound that has absorption in the visible or near infrared region and can sensitize a semiconductor. Dyes, porphyrin dyes or phthalocyanine dyes are preferred. Further, two or more dyes can be used in combination or mixed in order to widen the wavelength range of photoelectric conversion as much as possible and to increase the conversion efficiency. In this case, the pigments to be used or mixed and the ratio thereof can be selected so as to match the wavelength range and the intensity distribution of the target light source.

[0034] Such a dye is formed by a suitable interlocking group having an adsorption ability to the surface of the semiconductor fine particles.
It is preferable to have Preferred linking groups include
COOH group, OH group, SO ₃ H group, -P (O) (OH) ₂ group or -OP (O) (OH)
Acidic groups such as ₂ groups or oxime, dioxime,
Chelating groups having π conductivity such as hydroxyquinoline, salicylate or α-keto enolate. Above all, COOH group, -P (O) (OH) ₂ group or -OP (O) (OH)
_Two groups are particularly preferred. These groups may form a salt with an alkali metal or the like, or may form an intramolecular 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 sensitizing dyes for use in the photosensitive layer will be specifically described. (A) Organic metal complex dye When the dye is a metal complex dye, a metal phthalocyanine dye, a metal porphyrin dye or a ruthenium complex dye is preferable, and a ruthenium complex dye is particularly preferable. Ruthenium complex dyes include, for example, U.S. Pat.
684537, 5084365, 5350644, 5463057,
No. 5525440, JP-A-7-249790, JP-T10-504512,
Complex dyes described in International Publication WO98 / 50393, JP-A-2000-26487 and the like can be mentioned.

The ruthenium complex dye used in the present invention is preferably represented by the following general formula (I): (A1) pRu (Ba) (Bb) (Bc)... In the general formula (I), A1
Represents a monodentate or bidentate ligand, Cl, SCN, H ₂ O, B
Ligands selected from the group consisting of r, I, CN, NCO, SeCN, β-diketones, oxalic acid and dithiocarbamic acid derivatives are preferred. p is an integer of 0 to 3. Ba, Bb
And Bc are each independently the following formulas B-1 to B-10:

[0037]

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(In the above formula, 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 aralkyl group having 7 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, or the above-mentioned acidic group (these May form a salt)
And the alkyl moiety of the alkyl group and the aralkyl group may be linear or branched, and the aryl moiety of the aryl group and the aralkyl group may be monocyclic or polycyclic (condensed ring, ring assembly). . ) Represents an organic ligand selected from the compounds represented by Ba, Bb and Bc
May be the same or different, and only one or two of them may be present.

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

[0040]

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[0041]

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[0042]

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(B) Methine Dye Preferred methine dyes for use in the present invention are polymethine dyes such as cyanine dyes, merocyanine dyes, and squarylium dyes. Examples of the polymethine dye preferably used in the present invention are described in JP-A-11-35836, JP-A-11-67285, JP-A-11-86916, JP-A-11-97725, and JP-A-11-158395.
JP-A-11-163378, JP-A-11-214
No. 730, JP-A-11-214731, JP-A-11-
238905, JP-A-2000-26487, European Patents 892411, 911841 and 9910
No. 92, each of which is described in the specification. Specific examples of preferred methine dyes are shown below.

[0044]

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(4) Adsorption of Dye on Semiconductor Fine Particles The dye is adsorbed on the semiconductor fine particles by immersing 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 or may be heated and refluxed as described in JP-A-7-249790. Examples of the latter coating method include a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, and a spray method. Preferred solvents for dissolving the dye include, 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, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methyl Pyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.),
Examples include carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc.), hydrocarbons (hexane, petroleum ether, benzene, toluene, etc.) and mixed solvents thereof. .

The total amount of the dye adsorbed is preferably 0.01 to 100 mmol per unit surface area (1 m ² ) of the porous semiconductor electrode substrate. The amount of the dye adsorbed on the semiconductor fine particles is preferably in the range of 0.01 to 1 mmol per 1 g of the semiconductor fine particles. With such an amount of dye adsorbed, a sufficient sensitizing effect in the 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. In order to increase the amount of the dye adsorbed, it is preferable to perform a heat treatment before the adsorption. After the heat treatment, the temperature of the semiconductor electrode substrate is maintained at 60 to 150
It is preferable to carry out the dye adsorption operation quickly at a temperature of between ° C. For the purpose of reducing the interaction such as aggregation between the dyes, a colorless compound may be added to the dyes and co-adsorbed to the semiconductor fine particles. Compounds that are effective for this purpose have surface-active properties,
It is a compound having a structure, and examples thereof include a steroid compound having a carboxyl group (for example, chenodeoxycholic acid) and sulfonates such as those described below.

[0047]

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The unadsorbed dye is preferably removed by washing immediately after the adsorption. It is preferable to perform cleaning with a polar solvent such as acetonitrile and an organic solvent such as an alcohol solvent using a wet cleaning tank. After adsorbing the dye, the surface of the semiconductor fine particles may be treated with an amine or a quaternary salt. Preferred amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like, and preferred quaternary salts include tetrobutylammonium iodide and tetrahexylammonium iodide. When these are liquids, they may be used as they are or may be used by dissolving them in an organic solvent.

(D) Charge Transport Layer The charge transport layer is a layer containing a charge transport material having a function of replenishing an oxidized dye with electrons. Examples of typical charge transport materials that can be used in the present invention include:
(I) As an ion transport material, a solution (electrolytic solution) in which a redox couple ion is dissolved, a so-called gel electrolyte in which a redox couple solution is impregnated in a gel of a polymer matrix, a molten salt electrolyte containing a redox counter ion, Furthermore, a solid electrolyte is mentioned. In addition to the charge transporting material involving ions, an electron transporting material or a hole transporting material may be used as (ii) a charge transporting material involving carrier movement in a solid. These charge transport materials are:
Can be used together.

(1) Molten Salt Electrolyte Molten salt electrolyte is particularly preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability. A molten salt electrolyte is a liquid at room temperature or an electrolyte having a low melting point, such as WO
95/18456, JP-A-8-259543, Electrochemistry, Volume 65, 11
No., p.923 (1997), etc., and known electrolytes such as pyridinium salts, imidazolium salts, and triazolium salts. A molten salt that becomes liquid at a temperature of 100 ° C. or lower, particularly around room temperature, is preferred.

Examples of the molten salt that can be preferably used include those represented by the following general formulas (Ya), (Yb) and (Yc).

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In the general formula (Ya), Qy ₁ represents an atomic group capable of forming a 5- or 6-membered aromatic cation together with a nitrogen atom. Qy ₁ 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. 5 formed by Qy ₁
The membered ring is preferably an oxazole ring, a thiazole ring, an imidazole ring, a pyrazole ring, an isoxazole ring, a thiadiazole ring, an oxadiazole ring, a triazole ring, an indole ring or a pyrrole ring, and is preferably an oxazole ring, a thiazole ring or an imidazole ring. Is more preferable, and an oxazole ring or an imidazole ring is particularly preferable. The 6-membered ring formed by Qy ₁ 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), Ay ₁ represents a nitrogen atom or a phosphorus atom.

R in the general formulas (Ya), (Yb) and (Yc)
y _{1 to} Ry ₆ 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, a methyl group, an ethyl group, Propyl, isopropyl, pentyl, hexyl, octyl, 2-ethylhexyl, t-octyl, decyl, dodecyl, tetradecyl, 2-hexyldecyl, octadecyl, cyclohexyl, cyclopentyl, etc.) Or a substituted or unsubstituted alkenyl group (preferably having 2 to 24 carbon atoms, linear, branched or, for example, a vinyl group, an allyl group, etc.), and more preferably an alkyl group having 2 to 18 carbon atoms or carbon number. An alkenyl group having 2 to 18 carbon atoms, particularly preferably an alkyl group having 2 to 6 carbon atoms.

Further, two or more of Ry ₁ to Ry _{4 in} the general formula (Yb) may be linked to each other to form a non-aromatic ring containing Ay _1, and Ry in the general formula (Yc) 2 out of _{1 to} Ry ₆
Two or more may be connected to each other to form a ring structure.

Q in the general formulas (Ya), (Yb) and (Yc)
y ₁ and Ry _{1 to} Ry ₆ may have a substituent. Examples of preferred substituents include a halogen atom (F, Cl, Br, I
), Cyano group, alkoxy group (methoxy group, ethoxy group, methoxyethoxy group, methoxyethoxyethoxy group, etc.), aryloxy group (phenoxy group, etc.), alkylthio group (methylthio group, ethylthio group, etc.), alkoxycarbonyl group (ethoxy Carbonyl group), 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, benzoyl group) Oxy group), 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),
Examples include an alkenyl group (vinyl group, 1-propenyl group, etc.), a silyl group, a silyloxy group, and the like.

The compound represented by formula (Ya), (Yb) or (Yc) may form a multimer via Qy ₁ or Ry _{1 to} Ry ₆ .

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.), SCN -, BF 4 -}} , P
_{^{F 6 -, ClO 4 -,}} (CF 3 SO 2) 2 N -, (CF 3 CF 2 SO 2) 2 N -, CH 3 SO 3 -,
Preferred examples include CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , Ph ₄ B ⁻ , (CF ₃ SO ₂ ) ₃ C ^{− and the} like, and SCN ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , (CF ₃ SO ₂ ) ₂ N
^- or BF ₄ ^- and more preferable. Further, other iodine salts such as LiI and alkali metal salts such as CF ₃ COOLi, CF ₃ COONa, LiSCN and NaSCN can also be added. The addition amount of the alkali metal salt is preferably about 0.02 to 2% by mass, and more preferably 0.1 to 1% by mass.

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

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[0062]

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[0065]

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The above molten salt electrolyte is preferably in a molten state at room temperature, and it is more preferable not to use a solvent. Although the solvent described below may be added, the content of the molten salt is preferably at least 50% by mass, particularly preferably at least 90% by mass, based on the entire electrolyte composition. Further, it is preferable that 50% by mass or more of the salt is an iodine salt.

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 relative to the whole electrolyte composition, and 0.5 to 20% by mass.
More preferably, it is 5% by mass.

(2) Electrolyte When an electrolyte is used for the charge transport 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_TwoSuch
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_TwoSuch
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
The electrolyte which combines the iodine salt of the above is preferable. Mentioned above
The electrolytes may be used as a mixture.

The preferred electrolyte concentration is 0.1 to 10M,
More preferably, it is 0.2-4M. In addition, when adding iodine to the electrolyte solution, a preferable concentration of added iodine is 0.01%.
~ 0.5M.

The solvent used for the electrolyte may be a compound having a low viscosity to improve ionic mobility, or a compound having a high dielectric constant and an effective carrier concentration to exhibit excellent ionic conductivity. desirable. Examples of such a solvent include carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether compounds such as dioxane and diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, and polyethylene. Chain ethers such as glycol dialkyl ether and polypropylene glycol dialkyl ether, alcohols such as methanol, ethanol, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether and polypropylene glycol monoalkyl ether, ethylene glycol, Propylene glycol, polyethylene glycol,
Polyhydric alcohols such as polypropylene glycol and glycerin, acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, nitrile compounds such as benzonitrile, dimethyl sulfoxide, non-proton polar substances such as sulfolane, water and the like, Can also be used as a mixture.

Further, according to the present invention, J. Am. Ceram. Soc.,
80 tert- as described in (12) 3157-3171 (1997)
It is preferable to add a basic compound such as butylpyridine, 2-picoline or 2,6-lutidine to the above-mentioned molten salt electrolyte or electrolytic solution. A preferred concentration range when a basic compound is added is 0.05 to 2M.

(3) Gel Electrolyte In the present invention, the above-mentioned molten salt electrolyte or the electrolytic solution is gelled by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization containing a polyfunctional monomer, and crosslinking reaction of the polymer. (Solidification). When gelling by adding a polymer, use the “Polymer Electrolyte Re
The compounds described in views-1 and 2 ”(co-edited by JR MacCallum and CA Vincent, ELSEVIER APPLIED SCIENCE) can be used, but especially polyacrylonitrile,
Polyvinylidene fluoride can be preferably used. J. C when gelling by adding an oil gelling agent
hemSoc. Japan, Ind. Chem.Sec., 46,779 (1943), J.A.
m. Chem. Soc., 111,5542 (1989), J. Chem. Soc., Che
m. Com mun., 1993, 390, Angew. Chem. Int. Ed. Eng
l., 35, 1949 (1996), Chem. Lett., 1996, 885, J. Chm.
Although compounds described in Soc., Chem. Commun., 1997, 545 can be used, preferred compounds are compounds having an amide structure in the molecular structure. An example in which the electrolytic solution is gelled is described in JP-A-11-185683, and an example in which the molten salt electrolyte is gelled is described in JP-A-2000-58140, and is applicable to the present invention.

When the electrolyte is gelled by a 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, preferred crosslinkable reactive groups are an amino group, a nitrogen-containing heterocycle (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, and the like), Preferred crosslinking agents are bifunctional or higher-functional reagents capable of electrophilic reaction with a nitrogen atom (for example, alkyl halides, aralkyl halides, sulfonic acid esters, acid anhydrides, acid chlorides, isocyanates, α, β-unsaturated) Sulfonyl group,
α, β-unsaturated carbonyl group, α, β-unsaturated nitrile group, etc.)
The crosslinking technique described in 00-86724 can also be applied.

(4) Hole transporting material In the present invention, a solid hole transporting material such as an organic or inorganic material or a combination of both can be used instead of an ion-conductive electrolyte such as a molten salt. (A) Organic hole transport material As the organic hole transport material applicable to the present invention, J. Hage
n et al., Synthetic Metal 89 (1997) 215-220, Nature, V
ol.395, 8 Oct. 1998, p583-585 and WO97 / 10617, JP-A-59-194393, JP-A-5-234681, U.S. Pat.No.4,923,774, JP-A-4-308688. Gazette, U.S. Pat.No. 4,764,625, JP-A-3-269084, JP-A-4-1
No. 29271, JP-A-4-175395, JP-A-4-26418
No. 9, JP-A-4-290851, JP-A-4-364153, JP-A-5-25473, JP-A-5-239455, JP-A-5-320634, JP-A-6-1972 JP, JP-A-7-138562, JP-A-7-252474, JP-A-11-144773
And the triphenylene derivatives described in JP-A-11-149821, JP-A-11-148067, JP-A-11-176489 and the like can be preferably used. Also, Ad
v. Mater. 1997, 9, N0.7, p557, Angew. Chem. Int. Ed.
Engl. 1995, 34, No. 3, p303-307, JACS, Vol120, N0.4, 19
98, p664-672, etc .; polypyrrole described in K. Murakoshi et al., Chem. Lett. 1997, p471; “Handbook of Organic Conductive”.
Molecules and Polymers Vol.1,2,3,4 ”(NALWA, W
Polyacetylene and its derivatives, poly (p-phenylene) and its derivatives, poly
Conductive polymers such as (p-phenylenevinylene) and its derivatives, polythienylenevinylene and its derivatives, polythiophene and its derivatives, polyaniline and its derivatives, and polytoluidine and its derivatives can be preferably used.

For hole transporting materials, Nature, Vol.
95, 8 Oct. 1998, p583-585, to add a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate to control the dopant level, A salt such as Li [(CF ₃ SO ₂ ) ₂ N] may be added in order to control the potential of the oxide semiconductor surface (compensate for the space charge layer).

(B) Inorganic hole transport material As the inorganic hole transport material, a p-type inorganic compound semiconductor can be used. The p-type inorganic compound semiconductor for this purpose preferably has a band gap of 2 eV or more,
Further, it is preferably 2.5 eV or more. Further, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than the ionization potential of the dye adsorption electrode from the condition that the holes of the dye can be reduced. Although the preferred range of the ionization potential of the p-type inorganic compound semiconductor varies depending on the dye used, it is generally preferably 4.5 eV or more and 5.5 eV or less, and more preferably 4.7 eV to 5.3 eV. Preferred p-type inorganic compound semiconductors are compound semiconductors containing monovalent copper, and examples of compound semiconductors containing monovalent copper include CuI, CuSCN, CuInSe ₂ , Cu (In, Ga) Se ₂ , C
uGaSe ₂ , Cu ₂ O, CuS, CuGaS ₂ , CuInS ₂ , CuAlSe _{2 and the} like. Among these, CuI and CuSCN are preferred, and CuI
Is most preferred. As the addition of the p-type inorganic compound semiconductor may be used GaP, NiO, CoO, FeO, the _{Bi 2 O 3, MoO 2,} Cr 2 O 3 or the like.

(5) Formation of Charge Transport Layer There are two methods for forming the charge transport layer. One is a method in which a counter electrode is first stuck on the photosensitive layer, and a liquid charge transport layer is sandwiched between the gaps. The other is a method in which a charge transport layer is provided directly on the photosensitive layer, and a counter electrode is subsequently provided.

In the former case, as a method of sandwiching the charge transport layer, a normal pressure process utilizing a capillary phenomenon due to immersion or the like,
Alternatively, a vacuum process in which the gas phase in the gap is replaced with a liquid phase at a pressure lower than normal pressure can be used.

In the latter case, the wet charge transport layer is provided with a counter electrode in an undried state to take measures to prevent liquid leakage at the edge. Further, in the case of a gel electrolyte, there is 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 immobilization. As a method for applying a wet organic hole transport material or a gel electrolyte in addition to the electrolytic solution, a method similar to the method for applying the semiconductor fine particle layer or the dye described above can be used.

In the case of a solid electrolyte or a solid hole transporting material, a charge transporting layer may be formed by a dry film forming process such as a vacuum evaporation method or a CVD method, and then a counter electrode may be provided. The organic hole transporting material can be introduced into 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 inorganic solid compounds, casting, coating,
It can be introduced into the inside of the electrode by a method such as spin coating, immersion, electrolytic deposition, electroless plating and the like.

(E) Counter Electrode 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-mentioned conductive support. As a conductive material used for the counter electrode conductive layer, metal (for example, platinum, gold, silver, copper, aluminum, magnesium, indium, or the like), carbon, or conductive metal oxide (indium-tin composite oxide, fluorine-doped tin oxide, Etc.). Among them, platinum, gold, silver, copper, aluminum and magnesium can be preferably used as the counter electrode layer. 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. The lower the surface resistance of the counter electrode layer, the better. The preferred range of the surface resistance is 50 Ω / □ or less, and more preferably 20 Ω / □ or less.

Since light may be irradiated from one or both of the conductive support and the counter electrode, at least one of the conductive support and the counter electrode must be substantially transparent in order for the light to reach the photosensitive layer. I just want it. From the viewpoint of improving power generation efficiency,
It is preferable that the conductive support is made transparent and light is incident from the conductive support side. In this case, the counter electrode preferably has a property of reflecting light. As such a counter electrode, glass or plastic on which a metal or a conductive oxide is deposited, or a metal thin film can be used.

For the counter electrode, a conductive material may be applied directly on the charge transport layer, plated or vapor-deposited (PVD, CVD), or the conductive layer side of the substrate having the conductive layer may be attached. As in the case of the conductive support, particularly when the counter electrode is transparent, it is preferable to use a metal lead for the purpose of reducing the resistance of the counter electrode. In addition, a preferable material and a setting method of the metal lead,
The decrease in the amount of incident light due to the installation of the metal leads is the same as in the case of the conductive support.

(F) Other Layers The conductive support serving as an electrode and the outer surface of one or both of the counter electrodes, between the conductive layer and the substrate or in the middle of the substrate,
A functional layer such as a protective layer and an antireflection layer may be provided. For forming these functional layers, a coating method, a vapor deposition method, a sticking method or the like can be used depending on the material.

(G) 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. When roughly divided into two, a structure in which light can enter from both sides and a structure in which light can be entered only from one side are possible. 2 to 9 exemplify an internal structure of a photoelectric conversion element which can be preferably applied to the present invention.

FIG. 2 shows the transparent conductive layer 10 a and the transparent counter electrode conductive layer 4.
The photosensitive layer 20 and the charge transport layer 30 are interposed between the photosensitive layer 20 and the light transport layer 0a, and have a structure in which light enters from both sides.
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, a photosensitive layer 20, a charge transport layer 30, and a counter electrode conductive layer 40 are provided in this order, and further supported. The substrate 50 is arranged, and has a structure in which light is incident from the conductive layer side. FIG. 4 shows that the conductive layer 10 is provided on the support substrate 50, the photosensitive layer 20 is provided via the undercoat layer 60, the charge transport layer 30 and the transparent counter electrode conductive layer 40a are provided, and the metal lead 11 is partially provided. The provided transparent substrate 50a is arranged with the metal lead 11 side inside, and has a structure in which light enters from the counter electrode side. FIG. 5 shows a case where a metal lead 11 is partially provided on a transparent substrate 50a, and transparent conductive layers 10a and 40a are further provided.
The undercoat layer 60, the photosensitive layer 20, and the charge transport layer 30 are interposed between the pair of transparent conductive layers, and have a structure in which light enters from both sides.

FIG. 6 shows a transparent conductive layer 10a on a transparent substrate 50a.
Undercoat layer 60, photosensitive layer 20, charge transport layer 30, and counter conductive layer
40 is provided, and a support substrate 50 is disposed thereon, and has a structure in which light is incident from the conductive layer side. FIG. 7 shows a supporting substrate.
A conductive layer 10 is provided on the substrate 50, a photosensitive layer 20 is provided via an undercoat layer 60, a charge transport layer 30 and a transparent counter electrode conductive layer 40a are provided, and a transparent substrate 50a is disposed thereon. In this structure, light enters from the side. FIG. 8 shows a transparent substrate 50.
a on the transparent conductive layer 10a, the photosensitive layer through the undercoat layer 60
20 and further a charge transport layer 30 and a transparent counter electrode conductive layer 40
a, on which a transparent substrate 50a is arranged,
Light is incident from both sides. FIG. 9 shows that a conductive layer 10 is provided on a supporting substrate 50 and a photosensitive layer is provided via an undercoat layer 60.
20, a solid charge transport layer 30 is further provided, and a counter electrode conductive layer 40 or a metal lead 11 is partially provided on the solid charge transport layer 30, so that light is incident from the counter electrode side.

[2] Photocell The photocell of the present invention has the above-mentioned photoelectric conversion element work with an external load. Among photovoltaic cells, a case where the charge transport material is mainly composed of an ion transport material is particularly called a photoelectrochemical cell, and a case where the main purpose is power generation by sunlight is called 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 device of the present invention is applied to a solar cell, the structure inside the cell is basically the same as the structure of the above-described photoelectric conversion device. Further, the dye-sensitized solar cell of the present invention can have a module structure basically similar to that of a conventional solar cell module. The solar cell module
Generally, cells are formed on a supporting substrate such as metal or ceramic, and the cells are covered with a filling resin or protective glass to take in light from the opposite side of the supporting substrate. It is also possible to adopt a structure in which a cell is formed thereon using a transparent material such as that described above, and light is taken in from the transparent support substrate side. Specifically, a superstrate type, a substrate type, a module structure called a potting type, a substrate-integrated module structure used in amorphous silicon solar cells and the like are known, and the dye-sensitized solar cell of the present invention is also used. These module structures can be appropriately selected depending on the use location and environment. Specifically, it is preferable to adopt the structure and embodiment described in Japanese Patent Application No. 11-8457.

[0090]

The present invention will be specifically described below with reference to examples. Examples 1-2 and Comparative Examples 1-3 (1) Preparation of Semiconductor Dispersion (1-1) Titanium Dioxide Dispersion (Dispersion A) 142.1 g of titanium tetraisopropoxide and 149.2 g of triethanolamine Was mixed at room temperature in a dry box and allowed to stand for 2 hours. Remove the mixed solution from the dry box, add distilled water and add a total volume of 1000 ml.
To obtain a mother liquor. 100 ml of mother liquor,
2.85 ml of acetic acid was added to distilled water to make 100 ml and mixed. After heating in a sealed container at 100 ° C. for 24 hours to form a white gel, the temperature was increased to 140 ° C. and heating was continued for 72 hours. After cooling to room temperature, the supernatant was removed and a pale reddish brown precipitate was obtained. The weight of the precipitate containing water was 33 g. 1.0 g of polyethylene glycol having a molecular weight of 500,000 was added to the obtained precipitate, and the mixture was kneaded with a kneader for 20 minutes to obtain a titanium dioxide dispersion having a mass concentration of 12%. The average particle size of the titanium dioxide particles contained in Dispersion A was about 16 nm. (1-2) Zinc oxide dispersion 80 ml of distilled water was added to 16 g of zinc oxide powder manufactured by Wako Pure Chemical Industries, Ltd., and polyethylene glycol 2.0 having a molecular weight of 20,000 was further added.
g was added and kneaded with a kneader for 20 minutes to obtain a titanium dioxide dispersion having a mass concentration of 16%.

(2) Preparation of TiO ₂ electrode adsorbing dye (2-1) Electrode A Conductive glass coated with fluorine-doped tin oxide (manufactured by Nippon Sheet Glass; area resistance 10Ω / □, 25 mm × 100 m)
m) An imide film is pasted on a part (3 mm from the end) on the conductive surface side of the above m) and masked, and the above titanium dioxide dispersion is prepared using a stainless steel rod designed so that the distance from the conductive glass to the rod is 200 μm. A was applied. After the application, the adhesive tape was peeled off and air-dried at room temperature for 30 minutes. Next, this glass was placed in an electric furnace (muffle furnace FP-32 manufactured by Yamato Scientific).
And fired in air at 450 ° C. for 30 minutes.
The glass was taken out, cooled in a dry environment with a dew point of -40 ° C until the electrode surface reached 120 ° C, and then a (dehydrated) ethanol / t-butanol / acetonitrile solution of dye A (1: 1: 2, dye concentration: 3) (× 10 ⁻⁴ mol / l) at 40 ° C. for 3 hours for adsorption. The dye-adsorbed electrode was washed with (dehydrated) acetonitrile and dried naturally to obtain an electrode A. The coating amount of the thus obtained photosensitive layer (the titanium dioxide layer on which the dye was adsorbed) was about 7.0 g / m ² . Dye A

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(2-2) Electrode B Conductive glass coated with fluorine-doped tin oxide (manufactured by Nippon Sheet Glass; area resistance 10Ω / □, 25 mm × 100 m)
m) (3 mm from the end) on the conductive surface side was masked with a stainless steel plate, placed on a hot plate heated to 400 ° C., and 5.68 g of Ti (Oi—C ₃ H ₇ ) _{4 was} added to acetylacetone.
A spray solution dissolved in 4.11 ml and 80 ml of dehydrated ethanol was sprayed to prepare an undercoat layer. The thickness of the undercoat layer is about
It was 50 nm. After slowly cooling to room temperature, an imide film was stuck on the same portion as the stainless masked portion and masked, and the distance from the conductive glass to the rod was 200 μm.
The above titanium dioxide dispersion A was applied using a stainless steel rod devised so that After the application, the adhesive tape was peeled off and air-dried at room temperature for 30 minutes. Next, this glass was put into an electric furnace (muffle furnace FP-32 manufactured by Yamato Scientific),
It baked at 450 degreeC in air for 30 minutes. The dye was adsorbed in the same manner as the electrode A, and the electrode B was produced.

(2-3) Electrode C Nb (OC ₂ H ₅ ) ₅ 6.36
4.1 g of acetylacetone and 80 ml of dehydrated ethanol
An electrode C was prepared in the same manner as above except that the spray solution was dissolved. The number of sprays was adjusted so that the thickness of the undercoat layer was about 50 nm. (2-4) Electrode D An electrode D was prepared in the same manner as the electrode A, except that the zinc oxide dispersion B was used instead of the titanium dioxide dispersion A.
The amount of zinc oxide applied was about 6.5 g / m ² . (2-5) Electrode E An electrode D was produced in the same manner as the electrode B except that the zinc oxide dispersion B was used instead of the titanium dioxide dispersion A. The amount of zinc oxide applied was about 6.5 g / m ² .

(3) Formation of charge transport layer The dye-sensitized electrodes A to E were cut into a size of 26 mm × 18 mm, and the undercoat layer and the semiconductor layer were removed except for a central portion of 14 mm × 14 mm. Each of these electrodes and the same size platinum-deposited glass (counter electrode, platinum layer thickness = 1 μm, glass thickness = 1.1 μm, with two holes for injecting a charge transport agent) were arranged as shown in FIG. Ionomer (Himilan 17) manufactured by DuPont-Mitsui Polychemicals Co., Ltd.
02) Stretched frame type spacer (10μm thick)
Was heated and pressed at 125 ± 5 ° C. for 30 seconds.
A molten salt electrolyte solution (compound D-1: compound D-2: iodine: lithium trifluoroacetate: sodium trifluoroacetate = 35: 15: 1: 1: 1 (mass ratio)) heated to 70 ° C. was similarly used. The solution was injected from a hole provided at the opposite electrode of the device heated to 70 ° C. After injection, keep at 70 ° C for 1 hour,
The mixture was aged at room temperature under reduced pressure for 16 hours.

After a lapse of time, the hole was sealed by thermocompression using the same member and glass as the spacer. further,
The entire surface was sealed with an epoxy resin adhesive except for the surface of the TiO ₂ transparent electrode substrate as the light receiving portion.

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(4) Measurement of Photoelectric Conversion Efficiency Simulated sunlight was generated by passing light of a 500 W xenon lamp (made by Ushio) through a spectral filter (AM1.5D made by Oriel). The intensity of this light was 100 mW / cm ² . Simulated sunlight was irradiated, and electricity generated between the conductive glass and the counter electrode layer of the photovoltaic cell was measured with a current / voltage measuring device (Keithley SMU2400 type). The open circuit voltage (Voc) is shown in Table 1. Further, Table 1 shows a charged voltage (VD1) when a reverse current flows at 1 mA / cm ² , similarly measured in a state where the photoelectric conversion element is shielded from light. The numbers in parentheses in Table 1 were calculated from the ionization potential obtained from the UPS measurement and the band gap obtained from the spectral absorption.
However, the value of the photosensitive layer semiconductor on the undercoat semiconductor layer is the same as the value obtained when there is no undercoat semiconductor.

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The following are clear from the results shown in Table 1. In the case of Comparative Example 1 in which the undercoat layer was not provided and in the case of Comparative Example 2 in which the titanium oxide semiconductor fine particle layer had the same conduction band lower potential as 4.5 eV and that of the titanium oxide semiconductor in the undercoat layer also at 4.5 eV, the open-circuit voltage and the reverse current Both loading voltages are small. On the other hand, the conduction band bottom potential of the titanium oxide semiconductor fine particle layer is 4.5 eV, and that of the undercoat layer niobium oxide semiconductor is 4.2 eV.
In the case of the first embodiment, the open circuit voltage (Voc) and the reverse current are 1 mA / c.
The reverse current is greatly suppressed for both the load voltage (VD1) when flowing m ² . When the semiconductor of the photosensitive layer is zinc oxide, Example 2 is similarly advantageous over Comparative Example 3.

Examples 3-4 and Comparative Examples 4-6 Instead of the glass electrodes of Examples 1-2 and Comparative Examples 1-3, respectively, a transparent conductive PET film (Toyo Metallizing Co., Ltd.) was used.
Made, Methrista T-R60, 60Ω □, about 100μm
(Thickness) was used, and the same electrode and the same film as described above were subjected to the same tests as those of Examples and Comparative Examples. The same tendency was obtained. The electrodes B, C, and E showed less performance degradation when the completed element was bent than the electrodes A and D.

[0102]

According to the photoelectric conversion element of the present invention, a reverse current unrelated to light irradiation is prevented, and the photoelectric conversion efficiency is high. Further, when a flexible substrate is used, it has robustness against deformation. A photovoltaic cell to which the photoelectric conversion element of the present invention using a flexible substrate is applied has a high photoelectric conversion efficiency and is excellent in robustness against deformation, and thus is suitably used for a solar cell or a paper-shaped photocell that is installed on a curved surface portion.

[Brief description of the drawings]

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

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

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

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

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

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

FIG. 7 is a schematic partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 8 is a schematic partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 9 is a schematic partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 10 is a schematic plan view of a photoelectric conversion element manufactured in an example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 dye-adsorbed titanium dioxide electrode 2 counter electrode (platinum vapor-deposited glass) 3 light receiving portion where semiconductor layer is present 10 conductive layer 10 a transparent conductive layer 11 metal lead 20 photosensitive layer 21 semiconductor fine particle 22 dye 23 charge transport material 30 charge transport layer 40 counter electrode conductive Layer 40a Transparent counter electrode conductive layer 50 Substrate 50a Transparent substrate 60 Undercoat layer

Claims (6)

[Claims] 1. A photoelectric conversion device having a conductive layer, a photosensitive layer containing a semiconductor sensitized by a dye, a charge transport layer, and a counter electrode, wherein a semiconductor constituting the photosensitive layer is provided between the photosensitive layer and the conductive layer. A photoelectric conversion element comprising a layer made of a semiconductor whose conduction band lower end potential is lower. 2. The semiconductor according to claim 1, wherein the semiconductor constituting the photosensitive layer is titanium oxide, and the semiconductor having a lower conduction band potential is zirconium oxide, strontium titanate, niobium oxide or zinc oxide. 3. The photoelectric conversion element according to item 1. 3. The semiconductor constituting the photosensitive layer is zinc oxide,
The semiconductor, which is at least one selected from tin oxide and tungsten oxide and has a lower conduction band lower potential, is zirconium oxide, strontium titanate, niobium oxide, zinc oxide or titanium oxide. Item 7. The photoelectric conversion element according to Item 1. 4. The photoelectric conversion device according to claim 1, wherein the charge transport layer contains a molten salt electrolyte or a hole transport material. 5. The conductive layer or the counter electrode has a substrate, which is a polymer film, a metal foil, a metal plate, a polymer film having a metal layer on the surface, or a glass plate having a metal layer on the surface. The photoelectric conversion element according to any one of claims 1 to 4, wherein 6. A photovoltaic cell using the photoelectric conversion element according to claim 1.