JP5114536B2 - Method for producing photoelectric conversion element, photoelectric conversion element and photoelectrochemical cell - Google Patents

Description

  The present invention relates to a photoelectric conversion element, and more particularly to a photoelectric conversion element using semiconductor fine particles sensitized with a dye.

  Photoelectric conversion elements are used in various optical sensors, copying machines, and photovoltaic power generation devices. Various systems such as those using metals, semiconductors, organic pigments and dyes, or combinations thereof have been put to practical use as photoelectric conversion elements.

  Patent Documents 1 to 9 disclose a photoelectric conversion element (hereinafter abbreviated as a dye-sensitized photoelectric conversion element) using semiconductor fine particles sensitized with a dye, or a material and a manufacturing technique for producing the photoelectric conversion element. Yes. The advantage of this method is that an inexpensive oxide semiconductor such as titanium dioxide can be used without being purified with high purity, and therefore a relatively inexpensive photoelectric conversion element can be provided. However, such a photoelectric conversion element does not necessarily have a sufficiently high conversion efficiency, and further improvement in conversion efficiency has been desired.

US Pat. No. 4,927,721 US Pat. No. 4,684,537 US Pat. No. 5,084,365 US Pat. No. 5,350,644 US Pat. No. 5,463,057 US Pat. No. 5,525,440 International Publication No. 98/50393 JP 7-249790 A Japanese National Patent Publication No. 10-504521

  An object of the present invention is to provide a dye-sensitized photoelectric conversion element having improved conversion efficiency.

As a result of research, it has been found that the object of the present invention is met by the following means.
1.
A method for producing a photoelectric conversion element having at least a layer of a semiconductor fine particle film adsorbed with a dye and a conductive support,
The layer of the semiconductor fine particle film is composed of a plurality of layers having different light scattering properties. The plurality of layers include a low scattering layer having the lowest light scattering property as the first layer on the light incident side, and the light scattering property having the low light scattering property. Having a higher scattering layer than the scattering layer,
Creating a dispersion A containing semiconductor fine particles having an average particle diameter of 5 to 50 nm;
A step of mixing the dispersion A containing semiconductor fine particles having an average particle diameter of 5 to 50 nm with the semiconductor fine particles having an average particle diameter of 100 to 500 nm to prepare the dispersion B;
Forming the low scattering layer with the dispersion A, and forming the high scattering layer with the dispersion B;
The manufacturing method of the photoelectric conversion element characterized by including.
2.
A method for producing a photoelectric conversion element having at least a layer of a semiconductor fine particle film adsorbed with a dye and a conductive support,
Comprises at least three layers layers different light scattering properties of the semiconductor fine particle film, the light scattering of the low have low scattering layer on the light incident side, the deepest in the light-scattering highly have high scattering layer, the light in the middle and coordinated scattering layer in scattering is an intermediate of the two layers,
Creating a dispersion A containing semiconductor fine particles having an average particle diameter of 5 to 50 nm;
A step of mixing the dispersion A containing semiconductor fine particles having an average particle diameter of 5 to 50 nm with the semiconductor fine particles having an average particle diameter of 100 to 500 nm to prepare the dispersion B;
Forming the low scattering layer with the dispersion A, and
Forming the medium scattering layer with the dispersion B;
The manufacturing method of the photoelectric conversion element characterized by including.
3.
The low scattering layer is composed of only semiconductor fine particles having low light scattering property, and the medium scattering layer is composed of a mixture of semiconductor fine particles having high light scattering property and semiconductor fine particles having low light scattering property. A method for producing a photoelectric conversion element.
4).
The low scattering layer is composed of semiconductor particles having an average particle size of 5 to 50 nm and low light scattering properties, and the medium scattering layer contains a mixture of semiconductor particles having an average particle size of 100 to 500 nm and semiconductor particles having an average particle size of 5 to 50 nm. 4. The method for producing a photoelectric conversion element as described in 3 above, wherein:
5.
Fine semiconductor particles of titanium oxide, zinc oxide, magnesium oxide, niobium oxide, tin oxide, tungsten oxide, silicon oxide, in any one of the above 1 to 4, characterized in that an oxide semiconductor selected from aluminum oxide The manufacturing method of the photoelectric conversion element of description.
6).
All the semiconductor fine particles are titanium oxides, The manufacturing method of the photoelectric conversion element as described in any one of said 1-5 characterized by the above-mentioned.
7).
The method for producing a photoelectric conversion element according to any one of the above 1 to 6, wherein a ruthenium complex dye having a group selected from the group containing a bonding group is used as the dye.
8).
A photoelectric conversion element obtained by the method for manufacturing a photoelectric conversion element according to any one of 1 to 7 above.
9.
9. A photoelectrochemical cell using the photoelectric conversion element as described in 8 above.
10.
The photoelectrochemical cell according to 9 above, comprising a conductive support, a photosensitive layer, a charge transport layer, and a counter electrode conductive layer in this order,
The photosensitive layer contains a charge transport material that has penetrated into the gaps between the semiconductor fine particles, and is composed of a plurality of layers having different light scattering properties. The plurality of layers have the low scattering layer and the high scattering layer. ,
A photoelectrochemical cell characterized by having no total reflection layer on the light incident side.
In addition, although this invention has the structure of said 1-10, it described below also for reference below.
(1) A photoelectric conversion element having at least a layer of a semiconductor fine particle film on which a dye is adsorbed and a conductive support, wherein the layer of the semiconductor fine particle film is composed of a plurality of layers having different light scattering properties, A photoelectric conversion element characterized in that a layer having the lowest light scattering property is disposed on the photoelectric conversion element.
(2) The photoelectric conversion device according to (1), wherein the photoelectric conversion device according to (1) does not have a total reflection layer on the light incident side (front side from the photosensitive layer).
(3) The layer of the semiconductor fine particle film is composed of at least three layers having different light scattering properties, a layer having a low light scattering property on the light incident side, a layer having a high light scattering property at the innermost side, and the light scattering property in the middle. A layer which is an intermediate between two layers (a layer having a light scattering property intermediate between the low light scattering property layer and the high light scattering property layer and having a medium light scattering property) is arranged (1 ) The photoelectric conversion element described.
(4) The layer having low light scattering property is composed only of semiconductor particles having low light scattering property, and the layer having medium light scattering property is composed of a mixture of semiconductor particles having high light scattering property and semiconductor particles having low light scattering property, The layer having a high light scattering property contains at least semiconductor fine particles having a high light scattering property, and the photoelectric conversion element according to (3).
(5) The layer having a low light scattering property is composed of semiconductor fine particles having an average particle size of 5 to 50 nm, and the layer having a high light scattering property contains at least semiconductor fine particles having an average particle size of 100 to 500 nm and has a moderate light scattering property. The layer contains a mixture of semiconductor fine particles having an average particle diameter of 100 to 500 nm and semiconductor fine particles having an average particle diameter of 5 to 50 nm. The photoelectric conversion element according to (4),
(6) The semiconductor fine particles are oxide semiconductors selected from titanium oxide, zinc oxide, magnesium oxide, niobium oxide, tin oxide, tungsten oxide, silicon oxide, and aluminum oxide (1) to (5) The photoelectric conversion element in any one of.
(7) The photoelectric conversion element as described in any one of (1) to (6), wherein the semiconductor fine particles are all titanium oxide.
(8) The photoelectric conversion element as described in any one of (1) to (7), wherein a ruthenium complex dye having a group selected from the group containing a bonding group is used as the dye.
(9) A photoelectrochemical cell using the photoelectric conversion device according to any one of (1) to (8).
(10) In a photoelectrochemical cell having a conductive support, a photosensitive layer, a charge transport layer, and a counter electrode conductive layer in this order, the photosensitive layer contains a charge transport material that has penetrated into the voids between the semiconductor fine particles, and has different light scattering properties. A photoelectrochemical cell comprising a plurality of layers, wherein a layer having the lowest light scattering property is disposed on a light incident side, and no total reflection layer is provided on a light incident side.
(11) A plurality of layers having different light scattering properties are a layer having a low light scattering property on the light incident side, a layer having a high light scattering property at the innermost side, and a layer having a light scattering property intermediate between the two layers. (10) The photoelectrochemical cell according to (10).
(12) The layer having low light scattering property is composed of only semiconductor particles having low light scattering property, and the layer having medium light scattering property is composed of a mixture of semiconductor particles having high light scattering property and semiconductor particles having low light scattering property, (1) The photoelectrochemical cell according to (11), wherein the layer having a high light scattering property contains at least semiconductor fine particles having a high light scattering property.
(13) The layer having a low light scattering property is composed of semiconductor fine particles having an average particle size of 5 to 50 nm, and the layer having a high light scattering property contains at least semiconductor fine particles having an average particle size of 100 to 500 nm and has a moderate light scattering property. The photoelectrochemical cell according to (12), wherein the layer contains a mixture of semiconductor fine particles having an average particle diameter of 100 to 500 nm and semiconductor fine particles having an average particle diameter of 5 to 50 nm.

  From the results of the examples, it is apparent that a dye-sensitized photoelectric conversion element having improved conversion efficiency as compared with the prior art was obtained by the present invention.

It is a fragmentary sectional view which shows the structure of the preferable photoelectric conversion element of this invention, and is sectional drawing which shows the structure of the photoelectrochemical cell created in the Example. It is a fragmentary sectional view which shows the structure of the preferable photoelectric conversion element of this invention. It is a fragmentary sectional view which shows the structure of the preferable photoelectric conversion element of this invention. It is a fragmentary sectional view which shows the structure of the preferable photoelectric conversion element of this invention. It is a fragmentary sectional view which shows the structure of the preferable photoelectric conversion element of this invention. It is a fragmentary sectional view which shows the structure of the preferable photoelectric conversion element of this invention. It is a fragmentary sectional view which shows the structure of the preferable photoelectric conversion element of this invention. It is a fragmentary sectional view which shows the structure of the preferable photoelectric conversion element of this invention. It is a fragmentary sectional view which shows the structure of the preferable photoelectric conversion element of this invention. 3 is a partial cross-sectional view illustrating a structure of a photoelectric conversion element used in Example 1. FIG.

[1] Photoelectric Conversion Element The photoelectric conversion element of the present invention is preferably formed by laminating a conductive layer 10, an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30, and a counter electrode conductive layer 40 in this order, as shown in FIG. The photosensitive layer 20 is composed of semiconductor fine particles 21 sensitized by the dye 22 and a charge transport material 23 that has penetrated into the gaps between the semiconductor fine particles 21. The charge transport material 23 is composed of the same components as the material used for the charge transport layer 30. Further, a substrate 50 may be provided as a base for the conductive layer 10 and / or the counter electrode conductive layer 40 in order to impart strength to the photoelectric conversion element. In the present invention, the layer composed of the conductive layer 10 and the optionally provided substrate 50 is referred to as “conductive support”, and the layer composed of the counter electrode conductive layer 40 and the optionally provided substrate 50 is referred to as “counter electrode”.
In the present invention, the photosensitive layer 20 is composed of a plurality of layers having different light scattering properties. Note that the conductive layer 10, the counter electrode conductive layer 40, and the substrate 50 in FIG. 1 may be the transparent conductive layer 10a, the transparent counter electrode conductive layer 40a, and the transparent substrate 50a, respectively. A photocell is made for the purpose of generating electrical work by connecting this photoelectric conversion element to an external load (power generation), and a photosensor is made for the purpose of sensing optical information. Among the photovoltaic cells, the case where the charge transport material 23 is mainly made of an ion transport material is particularly called a photoelectrochemical cell, and the case where the main purpose is power generation by sunlight is called a solar cell.

(A) 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. If a conductive layer that can maintain sufficient strength and sealing properties is used, a substrate is not always necessary.

  In the case of (1), a conductive layer having sufficient strength as metal and having conductivity is 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 are metals (eg, 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. 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 range of the surface resistance is preferably 100Ω / □ or less, more preferably 40Ω / □ or less. The lower limit of the surface resistance is not particularly limited, but is usually about 0.1Ω / □.

In the present invention, substantially transparent means that the light transmittance is 10% or more, preferably 50% or more, particularly preferably 70% or more.
In the present invention, since the light scattered by the high light scattering rate layer is almost absorbed by the low light scattering rate layer, it is not necessary to provide a total reflection layer.
In the present invention, providing a high refractive material thin film as disclosed in JP-A-10-255863 is contrary to the original purpose of providing an inexpensive photoelectric conversion element because the manufacturing process becomes complicated and the cost increases. Is not preferable.

The transparent conductive support is preferably formed by applying 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. In particular, 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 preferable. In order to obtain a flexible photoelectric conversion element or solar cell at low cost, it is preferable to use a transparent polymer film provided with a conductive layer. Transparent polymer film materials include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polyester (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate. (PAr), polysulfone (PSF), polyester sulfone (PES), polyetherimide (PEI), cyclic polyolefin, brominated phenoxy and the like. In order to ensure sufficient transparency, the coating amount of the conductive metal oxide is preferably 0.01 to 100 g per 1 m ² of the glass or plastic support.

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

(B) Photosensitive layer In the photosensitive layer, the semiconductor acts as a so-called photoconductor, absorbs light, separates charges, and generates electrons and holes. In the dye-sensitized semiconductor fine particles, light absorption and generation of electrons and holes thereby occur mainly in the dye, and the semiconductor fine particles play a role of receiving and transmitting the electrons. The semiconductor used in the present invention is preferably an n-type semiconductor which gives an anode current when conductor electrons become carriers under photoexcitation.

  According to the study by the present inventors, the light scattering property is low on the light incident side, and the light scattering property becomes higher as the light advances, than in the case where the photosensitive layer has a uniform single layer structure in the film thickness direction. In the case of a multi-layer structure, it was found that the light capture rate was higher, and consequently the conversion efficiency was higher. The simplest example of such a layer configuration is a two-layer configuration of a low scattering layer and a high scattering layer from the light incident side. In addition to this, there may be a configuration of three or more layers including a low scattering layer, a medium scattering layer, and a high scattering layer, and a more complicated configuration. In the present invention, it is essential that the lowest scattering layer is the first layer on which light is incident. Of these, the above-described three or more layers are preferable, and the three-layer configuration is more preferable.

  The light scattering property of the photosensitive layer can be adjusted by the type, particle diameter, porosity, or void size of the semiconductor fine particles used. Among these, it is preferable to adjust by the particle diameter of the semiconductor fine particles.

(1) Semiconductor fine particles Semiconductor fine particles include simple semiconductors such as silicon and germanium, III-V compound semiconductors, metal chalcogenides (for example, oxides, sulfides, selenides, etc.), 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, yttrium, lanthanum, vanadium, niobium, or tantalum oxides, cadmium, zinc, lead, silver, antimony or Examples thereof include bismuth sulfide, cadmium or lead selenide, and cadmium telluride. Examples of other compound semiconductors include phosphides such as zinc, gallium, indium, and cadmium, gallium-arsenic or copper-indium selenides, and copper-indium sulfides.

Preferred specific examples of the semiconductor used in the present invention are Si, TiO ₂ , SnO ₂ , Al ₂ O ₃ , MgO, Fe ₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, ZnS, PbS, Bi ₂ S. ₃ , CdSe, CdTe, GaP, InP, GaAs, CuInS ₂ , CuInSe ₂ etc., more preferably TiO ₂ , ZnO, SnO ₂ , WO ₃ , Nb ₂ O ₅ , TiO ₂ , Al ₂ O ₃ , MgO Yes, particularly preferably TiO ₂ . Further, two or more kinds of semiconductor fine particles may be mixed and used.

  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 5 to 500 nm. Among these, the semiconductor fine particles having an average particle diameter in the range of 5 to 50 nm have a low scattering property, and thus are mainly used for the low scattering layer. Semiconductor fine particles having an average particle diameter in the range of 100 to 500 nm have a high scattering property and are therefore mainly used for a high scattering layer.

In the present invention, the low scattering layer on which light is first incident is a layer containing semiconductor particles having an average particle size of 5 to 50 nm, preferably 5 to 30 nm and having low scattering properties, and particles having a high scattering property and a particle size of 100 nm or more. The content of is 10% by weight or less, preferably 5% by weight or less.
The photoelectric conversion element of the present invention has at least one high scattering layer in addition to the low scattering layer. The high scattering layer is a layer containing highly scattering semiconductor fine particles having an average particle diameter of 100 to 500 nm, preferably 200 to 400 nm. The high scattering layer may be a single semiconductor fine particle, that is, one having a particle size distribution peak of only 100 to 500 nm, or a mixture of two or more different types of fine particles, that is, a particle size distribution. Those having a plurality of peaks may be used. In the latter case, at least one of the particle size distribution peaks is in the range of 100 to 500 nm.

  When the photosensitive layer has a two-layer structure of a low scattering layer and a high scattering layer, it is preferable to mix two or more kinds of fine particles as constituents of the high scattering layer rather than using a single semiconductor fine particle. Specifically, the high scattering layer is particularly preferable when semiconductor fine particles having an average particle diameter of 5 to 50 nm and semiconductor fine particles having an average particle diameter of 100 to 500 nm are mixed. At this time, the content of the larger semiconductor fine particles is preferably 10 to 90% by weight, more preferably 10 to 50% by weight.

  In the case of a three-layer configuration of a low scattering layer, a medium scattering layer, and a high scattering layer, it is preferable that two or more kinds of fine particles are mixed in the medium scattering layer rather than a single semiconductor fine particle. Specifically, the medium scattering layer is particularly preferable when semiconductor fine particles having an average particle diameter of 5 to 50 nm and semiconductor fine particles having an average particle diameter of 100 to 500 nm are mixed. At this time, the content of the larger semiconductor fine particles is preferably 5 to 70% by weight, more preferably 10 to 50% by weight. Further, in the case of four or more layers, a composition in which the light scattering rate increases from the low light scattering layer side toward the high light scattering layer is desirable. The high scattering layer may be a single semiconductor fine particle having an average particle diameter of 100 to 500 nm or a mixture of two or more kinds of semiconductor fine particles. When the mixing ratio of semiconductor fine particles having an average particle diameter of 5 to 50 nm and semiconductor fine particles having an average particle diameter of 100 to 500 nm is defined, the content of the larger semiconductor fine particles is preferably 30 to 100% by weight, and 50 to 100% by weight. More preferred. Moreover, the content rate of the larger semiconductor particle is larger than that of the middle scattering layer.

  Semiconductor fine particles are prepared by Sakuo Sakuo's "Sol-gel Method Science" Agne Jofusha (1998), Technical Information Association "Sol-gel Method Thin Film Coating Technology" (1995), etc. The sol-gel method described, Tadao Sugimoto's "Synthesis of monodisperse particles by the new synthesis gel-sol method and size morphology control", Materia, Vol. 35, No. 9, pp. 1012-1018 (1996) The gel-sol method described in 1 is preferred. Also preferred is a method developed by Degussa to produce an oxide by high-temperature hydrolysis of chloride in an oxyhydrogen salt.

  When the semiconductor fine particles are titanium oxide, the above sol-gel method, gel-sol method, and high-temperature hydrolysis method in oxyhydrogen salt of chloride are all preferred, but Kiyoshi Manabu's “Titanium oxide properties and applied technology” The sulfuric acid method and the chlorine method described in Gihodo Publishing (1997) can also be used. Further, as the sol-gel method, the method described in Journal of American Ceramic Society of Barb et al., Vol. 80, No. 12, pp. 3157-3171 (1997), and the chemistry of Burnside et al. The method described in Materials, Vol. 10, No. 9, pages 2419-2425 is also preferable.

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

  In addition to the sol-gel method described above, a method for producing a dispersion of semiconductor fine particles includes a method of grinding with a mortar, a method of dispersing while grinding using a mill, or a fine particle in a solvent when synthesizing a semiconductor. The method of depositing and using as it is is mentioned.

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

  As application methods, roller method, dip method, etc. as application system, air knife method, blade method, etc. as metering system, and application and metering can be made the same part, disclosed in Japanese Patent Publication No. 58-4589 The wire bar method, the slide hopper method, the extrusion method, the curtain method, etc. described in US Pat. Nos. 2,681,294, 2761419, 2761791 and the like are preferable. Moreover, a spin method and a spray method are also preferable as a general purpose machine. As the wet printing method, intaglio, rubber plate, screen printing and the like are preferred, including the three major printing methods of letterpress, offset and gravure. From these, a preferred 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 surfactants and binders. 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 low-viscosity liquids (for example, 0.1 Poise or less), the slide hopper method, wire bar method, or spin method is preferable, and a uniform film can be formed. If there is a certain amount of coating, coating by the extrusion method is possible even in the case of a low viscosity liquid. Thus, a wet film forming method may be selected as appropriate according to the viscosity of the coating solution, the coating amount, the support, the coating speed, and the like.

  In the present invention, the semiconductor fine particle layer has a multilayer structure. For this purpose, a dispersion of semiconductor fine particles having different particle diameters can be applied in multiple layers, or a coating layer containing different types of semiconductor fine particles (or different binders and additives) can be applied in multiple layers. For the multilayer coating, an extrusion method or a slide hopper method is suitable. In the case of applying multiple layers, the multiple layers may be applied at the same time, or may be successively applied several times to several dozen times. Further, screen printing can be preferably used as long as it is sequentially overcoated.

In general, as the thickness of the semiconductor fine particle layer (same as the thickness of the photosensitive layer) increases, the amount of supported dye increases per unit projected area, and thus the light capture rate increases. Loss due to coupling also increases. Therefore, the preferable thickness of the semiconductor fine particle layer is 0.1 to 100 μm. When used in a solar cell, the thickness of the semiconductor fine particle layer is preferably 1 to 30 μm, and more preferably 2 to 25 μm. The total coating amount of the semiconductor fine particles is preferably 0.5 to 100 g, more preferably 5 to 50 g per 1 m ² of the support.

  In the present invention, the ratio of the light scattering layer closest to the incident light to the entire semiconductor fine particle layer is preferably 10 to 80%, more preferably 20 to 60% of the total film thickness. A typical film thickness of the low scattering layer is 1 to 20 μm. A typical film thickness when a medium scattering layer is present is 1 to 10 μm. A typical film thickness of the high scattering layer is 1 to 10 μm.

  After the semiconductor fine particles are applied on the conductive support, the semiconductor fine particles are preferably brought into contact with each other electronically, and heat treatment is preferably performed in order to improve the coating strength and the adhesion to the support. A preferable heating temperature range is 40 ° C. or more and 700 ° C. or less, and more preferably 100 ° C. or more and 600 ° C. or less. The heating time is about 10 minutes to 10 hours. When using a support having a low melting point or softening point such as a polymer film, high temperature treatment is not preferable because it causes deterioration of the support. Moreover, it is preferable that it is as low as possible also from a viewpoint of cost. The temperature can be lowered by using a combination of small semiconductor fine particles of 5 nm or less as described above, heat treatment in the presence of a mineral acid, or the like. In order to obtain a photosensitive layer having a multilayer structure, coating and heat treatment may be sequentially repeated.

  In order to increase the surface area of semiconductor fine particles after heat treatment, increase the purity near the semiconductor fine particles, and increase the efficiency of electron injection from the dye to the semiconductor fine particles, for example, chemical plating treatment using titanium tetrachloride aqueous solution or titanium trichloride aqueous solution You may perform the electrochemical plating process using.

  The semiconductor fine particles preferably have a large surface area so that many dyes can be adsorbed. For this reason, the surface area of the semiconductor fine particle layer coated on the support is preferably 10 times or more, more preferably 100 times or more 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 can be arbitrarily used as long as it is a compound that has absorption in the visible region and near infrared region and can sensitize semiconductors, but organometallic complex dyes, methine dyes, porphyrins. A dye or a phthalocyanine dye is preferable. Moreover, in order to make the wavelength range of photoelectric conversion as wide as possible and increase the conversion efficiency, two or more kinds of dyes can be used together or mixed. In this case, it is possible to select the dye to be used or mixed and the ratio thereof so as to match the wavelength range and intensity distribution of the target light source.

Such a dye preferably has an appropriate interlocking group capable of adsorbing to the surface of the semiconductor fine particles. It is particularly preferred because it is equally adsorbed. Preferred linking groups include COOH groups, OH groups, SO ₃ H groups, acidic groups such as —P (O) (OH) ₂ groups or —OP (O) (OH) ₂ groups, or oximes, dioximes, hydroxy groups Examples include chelating groups having π conductivity such as quinoline, salicylate or α-ketoenolate. Of these, a COOH group (carboxyl group), —P (O) (OH) ₂ group (phosphonyl group) or —OP (O) (OH) ₂ group (phosphoryl group) is particularly preferred. These groups may form a salt with an alkali metal or the like, or may form an internal salt. In the case of a polymethine dye, if the methine chain contains an acidic group as in the case where the methine chain forms a squarylium ring or a croconium ring, this part may be used as a linking group.

Hereinafter, preferred sensitizing dyes used in the photosensitive layer will be specifically described.
(A) Organometallic 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. Examples of the ruthenium complex dye include, for example, U.S. Pat. Nos. 4,972,721, 4,684,537, 5,844,365, 5,350,644, 5,630,57, 5,525,440, JP-A-7-249790, JP-T-10-504512, and International Patent Publications. (IPC) No. 98/50393, JP-A 2000-26487, and the like.

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

(However, Ra represents _a hydrogen atom or a substituent, and examples of the substituent include a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, and a substituted or unsubstituted group having 7 to 12 carbon atoms. Examples include aralkyl groups, substituted or unsubstituted aryl groups having 6 to 12 carbon atoms, or the above-mentioned acidic groups (these acidic groups may form a salt) and chelating groups, alkyl groups and aralkyls. The alkyl part of the group may be linear or branched, and the aryl part of the aryl group and the aralkyl group may be monocyclic or polycyclic (fused ring, ring assembly).) Represents a ligand. Ba, Bb and Bc may be the same or different, and may be any one or two.

  Although the preferable specific example of an organometallic complex pigment | dye is shown below, this invention is not limited to these.

(B) Methine dyes Preferred methine dyes for use in the present invention are polymethine dyes such as cyanine dyes, merocyanine dyes, and squarylium dyes. Examples of polymethine dyes preferably used in the present invention include JP-A-11-35836, JP-A-11-67285, JP-A-11-86916, JP-A-11-97725, JP-A-11-158395, and JP-A-11. -163378, JP-A-11-214730, JP-A-11-214731, JP-A-11-238905, JP-A-2000-26487, European Patents 892411, 911841, and 991092 It is a pigment. Specific examples of preferred methine dyes are shown below.

(4) Adsorption of dye to semiconductor fine particles In order to adsorb the dye to semiconductor fine particles, a conductive support having a well-dried semiconductor fine particle layer is immersed in the dye solution, or the dye solution is applied to the semiconductor fine particle layer. A coating method can be used. In the former case, an immersion method, a dip method, a roller method, an air knife method or the like can be used. In the case of the immersion method, the adsorption of the dye may be performed at room temperature or may be performed by heating and refluxing as described in JP-A-7-249790. Examples of the latter application method include a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, and a spray method. In addition, a dye can be applied in an image form by an inkjet method or the like, and the image itself can be used as a photoelectric conversion element. 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 compounds, etc. Hydrocarbon (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.), carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone) , Cyclohexanone, etc.), Examples include hydrocarbons (hexane, petroleum ether, benzene, toluene, etc.) and mixed solvents thereof.

The total amount of dye adsorbed is preferably 0.01 to 100 mmol per unit 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. By using such an amount of dye adsorbed, a sensitizing effect in a semiconductor can be sufficiently 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 attached to the semiconductor floats, which causes a reduction in the sensitizing effect. In order to increase the adsorption amount of the dye, it is preferable to perform a heat treatment before the adsorption. In order to avoid water adsorbing on the surface of the semiconductor fine particles after the heat treatment, it is preferable to quickly perform the dye adsorption operation at a temperature of the semiconductor electrode substrate of 60 to 150 ° C. without returning to normal temperature. Further, 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 on the semiconductor fine particles. Compounds effective for this purpose are compounds having surface active properties and structures, and examples thereof include steroid compounds having a carboxyl group (for example, chenodeoxycholic acid) and sulfonates such as the following examples.

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

(C) Charge Transport Layer The charge transport layer is a layer containing a charge transport material having a function of replenishing electrons to the dye oxidant. Examples of typical charge transport materials that can be used in the present invention include: (i) a solution (electrolyte) in which redox pair ions are dissolved as an ion transport material; Examples include so-called gel electrolytes impregnated in the above, molten salt electrolytes containing redox counterions, and solid electrolytes, and compositions containing these electrolytes (electrolyte compositions) can be used for the charge transport layer.
In addition to charge transport materials that involve ions, (ii) electron transport materials and hole transport materials can also be used as charge transport materials that involve carrier movement in solids. These charge transport materials can be used in combination.

(1) Molten salt electrolyte The molten salt electrolyte is particularly preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability.
The molten salt electrolyte is an electrolyte that is liquid at room temperature or has a low melting point. For example, WO95 / 18456, JP-A-8-259543, Electrochemistry, Vol. 65, No. 11, 923 (1997) And the like, known electrolytes such as pyridinium salts, imidazolium salts, and triazolium salts described in the above. A molten salt that becomes liquid at 100 ° C. or lower, particularly near room temperature, is preferred.

  Examples of the molten salt that can be preferably used include those represented by any of the following general formulas (Y-a), (Y-b), and (Y-c).

In the general formula (Ya), Q _y1 represents an atomic group capable of forming a 5- or 6-membered aromatic cation with a nitrogen atom. Q _y1 is preferably composed of one or more atoms selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom and sulfur atom. The 5-membered ring formed by Q _y1 is preferably an oxazole ring, thiazole ring, imidazole ring, pyrazole ring, isoxazole ring, thiadiazole ring, oxadiazole ring, triazole ring, indole ring or pyrrole ring, A 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 Q _y1 is preferably a pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring or triazine ring, more preferably a pyridine ring.

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

R _{y1 to} R _y6 in the general formulas (Ya), (Yb) and (Yc) are each independently a substituted or unsubstituted alkyl group (preferably having 1 to 24 carbon atoms, linear or branched). Or may be cyclic. For example, methyl, ethyl, propyl, isopropyl, pentyl, hexyl, octyl, 2-ethylhexyl, t-octyl, decyl, dodecyl Group, tetradecyl group, 2-hexyldecyl group, octadecyl group, cyclohexyl group, cyclopentyl group, etc.) or a substituted or unsubstituted alkenyl group (preferably having 2 to 24 carbon atoms, linear or branched) And may be, 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, particularly preferably 2 to 6 carbon atoms. The alkyl It is.

Two or more of R _{y1 to} R _{y4 in} the general formula (Yb) may be connected to each other to form a non-aromatic ring containing A _y1, and R _{y1 to} R in the general formula (Yc) Two or more of _y6 may be connected to each other to form a ring structure.

Q _y1 and R _{y1 to} R _y6 in the general formulas (Ya), (Yb), and (Yc) may have a substituent. Examples of preferred substituents include halogen atoms (F, Cl, Br , I etc.), 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 (Ethoxycarbonyl group etc.), Carbonate ester 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.), phospho Nyl group (diethylphosphonyl group, etc.), BR> A amide group (acetylamino group, benzoylamino group, etc.), carbamoyl group (N, N-dimethylcarbamoyl group, etc.), 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 group (Vinyl group, 1-propenyl group, etc.), silyl group, silyloxy group and the like.

The compound represented by the general formula (Ya), (Yb) or (Yc) may form a multimer via Q _y1 or R _{y1 to} R _y6 .

These molten salts may be used singly or as a mixture of two or more, and may be used in combination with a molten salt in which the iodine anion is replaced with another anion. The anionic replaced with iodine anion, halide ions (Cl ^-, Br ^{-, _{etc.), SCN -, BF 4 -}} , PF 6 -, ClO 4 -, (CF 3 SO 2) 2 N -, (CF 3 CF 2 SO ₂ ) ₂ N ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , Ph ₄ B ⁻ , (CF ₃ SO ₂ ) ₃ C ^{− and the} like are preferable examples, and SCN ⁻ , CF ₃ SO ₃ ⁻ , CF ₃ COO ⁻ , (CF ₃ SO ₂ ) ₂ N ^— or BF ₄ ^— is 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 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 listed below, but are not limited thereto.

  The molten salt electrolyte is preferably in a molten state at room temperature, and preferably does not use a solvent. Although the solvent described later may be added, the content of the molten salt is preferably 50% by mass or more, and particularly preferably 90% by mass or more with respect to the entire electrolyte composition. Moreover, it is preferable that 50 mass% or more is an iodine salt among salts.

  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 0.5 to 5% by mass with respect to the entire electrolyte composition. More preferred.

(2) Electrolytic Solution When an electrolytic solution is used for the charge transport layer, the electrolytic solution is preferably composed of an electrolyte, a solvent, and an additive. The electrolyte of the present invention is a combination of I ₂ and iodide (as iodides, metal iodides such as LiI, NaI, KI, CsI, and CaI ₂ , tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide, etc. 4) Iodine salt of a quaternary ammonium compound), a combination of Br ₂ and bromide (as bromide, bromide of a metal bromide such as LiBr, NaBr, KBr, CsBr, CaBr ₂ , or a quaternary ammonium compound such as tetraalkylammonium bromide, pyridinium bromide) ), Metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ions, sulfur compounds such as sodium polysulfide and alkylthiol-alkyldisulfides, viologen dyes, hydroquino - it can be used as the quinone. Among these, electrolytes in which iodine salts of quaternary ammonium compounds such as I ₂ and LiI, pyridinium iodide, and imidazolium iodide are combined are preferable. The electrolytes described above may be used in combination.

  A preferable electrolyte concentration is 0.1 M or more and 10 M or less, and more preferably 0.2 M or more and 4 M or less. In addition, when iodine is added to the electrolytic solution, the preferable concentration of iodine is 0.01M or more and 0.5M or less.

  The solvent used for the electrolyte is desirably a compound that has low viscosity and improved ion mobility, or has a high dielectric constant and improved effective carrier concentration, and can exhibit excellent ion conductivity. 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, polypropylene glycol monoalkyl ether, ethylene glycol, Propylene glycol, polyethylene glycol, polyp Examples include polyhydric alcohols such as pyrene glycol and glycerol, nitrile compounds such as acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile, aprotic polar substances such as dimethyl sulfoxide and sulfolane, and water. Can also be used in combination.

  In the present invention, bases such as tert-butylpyridine, 2-picoline, 2,6-lutidine and the like described in J. Am. Ceram. Soc., 80 (12) 3157-3171 (1997) are also used. It is preferable to add a functional compound to the aforementioned molten salt electrolyte or electrolytic solution. A preferable 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 is gelled (solidified) by the techniques such as polymer addition, oil gelling agent addition, polymerization including polyfunctional monomers, polymer crosslinking reaction, and the like. ) Can also be used. In the case of gelation by addition of a polymer, compounds described in “Polymer Electrolyte Reviews-1 and 2” (JRMacCallum and CA Vincent, edited by ELSEVIER APPLIED SCIENCE) can be used, but in particular, polyacrylonitrile, polyfluoride Vinylidene can be preferably used. In the case of gelation by adding an oil gelling agent, Journal of Industrial Science (J. Chem Soc. Japan, Ind. Chem. Sec.), 46,779 (1943), J. Am. Chem. Soc., 111,5542 (1989), J. Chem. Soc., Chem. Com mun., 1993, 390, Angew. Chem. Int. Ed. Engl., 35, 1949 (1996), Chem. Lett., 1996, 885, J. Chm. Soc. ,
Although compounds described in Chem. Commun., 1997, 545 can be used, preferred compounds are compounds having an amide structure in the molecular structure. An example of gelling the electrolyte is described in JP-A-11-185863, and an example of gelling the molten salt electrolyte is described in JP-A-2000-58140, which can also be applied to the present invention.

  When the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a crosslinkable reactive group and a crosslinking agent in combination. In this case, preferred crosslinkable reactive groups are amino groups and nitrogen-containing heterocycles (for example, pyridine ring, imidazole ring, thiazole ring, oxazole ring, triazole ring, morpholine ring, piperidine ring, piperazine ring, etc.) Preferred crosslinking agents include bifunctional or higher functional reagents capable of electrophilic reaction with nitrogen atoms (for example, alkyl halides, halogenated aralkyls, sulfonic acid esters, acid anhydrides, acid chlorides, isocyanate compounds, α , Β-unsaturated sulfonyl group-containing compound, α, β-unsaturated carbonyl group-containing compound, α, β-unsaturated nitrile group-containing compound, etc.) and described in JP-A Nos. 2000-17076 and 2000-86724. Existing crosslinking techniques can also be applied.

(4) Hole transport material In the present invention, instead of an ion conductive electrolyte such as a molten salt, a solid hole transport material that is organic or inorganic or a combination of both can be used.
(A) Organic hole transport material Organic hole transport materials applicable to the present invention include J. Hagen et al., Synthetic Metal 89 (1997) 215-220, Nature, Vol. 395, 8 Oct. 1998, p583-585 and WO97 / 10617, JP-A-59-194393, JP-A-5-234681, JP-A-4,923,774, JP-A-4-308688, US-A-4,764, No. 625, JP-A-3-269084, JP-A-4-129271, JP-A-4-175395, JP-A-4-264189, 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-A-7-138562, JP-A-7-252474, JP-A-11 Aromatic amines shown in JP-A-144773 and the like, and triphenylene derivatives described in JP-A-11-149821, JP-A-11-148067, JP-A-11-176489 and the like can be preferably used. Also, Adv. Mater. 1997, 9, N0.7, p557, Angew. Chem. Int. Ed. Engl. 1995, 34, No. 3, p303-307, JACS, Vol120, N0.4, 1998, p664- Oligothiophene compounds described in 672 etc., K. Murakoshi
et al.,; Chem. Lett. 1997, p471, polyacetylene described in “Handbook of Organic Conductive Molecules and Polymers Vol.1,2,3,4” (by NALWA, published by WILEY) and its Conductivity of derivatives, poly (p-phenylene) and its derivatives, poly (p-phenylene vinylene) and its derivatives, polythienylene vinylene and its derivatives, polythiophene and its derivatives, polyaniline and its derivatives, polytoluidine and its derivatives A polymer can be preferably used.

Hole transport materials contain tris (4-bromophenyl) aminium hexachloroantimonate to control dopant levels as described in Nature, Vol. 395, 8 Oct. 1998, p583-585. Add a cation radical-containing compound, or add a salt such as Li [(CF ₃ SO ₂ ) ₂ N] to control the potential of the oxide semiconductor surface (space charge layer compensation). It doesn't matter.

(B) Inorganic hole transport material A p-type inorganic compound semiconductor can be used as the inorganic hole transport material. The p-type inorganic compound semiconductor for this purpose preferably has a band gap of 2 eV or more, and more preferably 2.5 eV or more. Also, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than the ionization potential of the dye-adsorbing electrode from the condition that the holes of the dye can be reduced. Although the preferable 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 or more and 5.3 eV or less. Preferred p-type inorganic compound semiconductors are compound semiconductors containing monovalent copper. Examples of compound semiconductors containing monovalent copper include CuI, CuSCN, CuInSe ₂ , Cu (In, Ga) Se ₂ , CuGaSe ₂ , Cu ₂ O, CuS, CuGaS ₂ , CuInS ₂ , CuAlSe _{2 and the} like. Among these, CuI and CuSCN are preferable, and CuI is most preferable. As other p-type inorganic compound semiconductors, GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , Cr ₂ O _{3 and the} like can be used.

(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 bonded onto 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 for sandwiching the charge transport layer, a normal pressure process using a capillary phenomenon due to immersion or 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, in the wet charge transport layer, a counter electrode is provided without being dried, and measures for preventing liquid leakage at the edge portion are taken. In the case of a gel electrolyte, there is a method in which it is applied in a wet manner and solidified by a method such as polymerization. In this case, the counter electrode can be applied after drying and fixing. As a method for applying the wet organic hole transporting material and the gel electrolyte in addition to the electrolytic solution, the same methods as those for the semiconductor fine particle layer and the dye can be used.

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

(D) 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, like the conductive support described above. As a conductive material used for the counter electrode conductive layer, metal (for example, platinum, gold, silver, copper, aluminum, magnesium, indium, etc.), carbon, or conductive metal oxide (indium-tin composite oxide, fluorine-doped tin oxide, Etc.). Among these, 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, and the above-described conductive agent is applied or vapor-deposited on the glass or plastic. 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 range of the surface resistance is preferably 50Ω / □ or less, more preferably 20Ω / □ or less.

  Since light may be irradiated from one or both of the conductive support and the counter electrode, in order for light to reach the photosensitive layer, at least one of the conductive support and the counter electrode may be substantially transparent. . From the viewpoint of improving the power generation efficiency, it is preferable to make the conductive support transparent so that 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 deposited with a metal or conductive oxide, or a metal thin film can be used.

  The counter electrode may be formed by directly applying, plating, or vapor-depositing (PVD, CVD) a conductive material on the charge transport layer, or attaching the conductive layer side of the substrate having the conductive layer. Further, as in the case of the conductive support, it is preferable to use a metal lead for the purpose of reducing the resistance of the counter electrode, particularly when the counter electrode is transparent. In addition, the material and installation method of a preferable metal lead, the fall of the incident light amount by metal lead installation, etc. are the same as the case of a conductive support body.

(E) Other layers In order to prevent a short circuit between the counter electrode and the conductive support, it is preferable to coat a dense semiconductor thin film layer as an undercoat layer between the conductive support and the photosensitive layer in advance. This is particularly effective when an electron transport material or a hole transport material is used for the transport layer. Preferred as the undercoat layer is TiO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, or Nb ₂ O ₅ , and more preferably TiO ₂ . The undercoat layer can be applied by, for example, a sputtering method in addition to the spray pyrolysis method described in Electrochim. Acta 40, 643-652 (1995). The preferred thickness of the undercoat layer is 5 to 1000 nm or less, and more preferably 10 to 500 nm.

  Moreover, you may provide functional layers, such as a protective layer and an antireflection layer, in the outer surface of one or both of the electroconductive support body which acts as an electrode, and a counter electrode, between an electroconductive layer and a board | substrate, or in the middle of a board | substrate. For forming these functional layers, a coating method, a vapor deposition method, a bonding method, or the like can be used depending on the material.

(F) Specific examples 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. If roughly divided into two, a structure that allows light to enter from both sides and a structure that allows only one side are possible. 2 to 9 illustrate the internal structure of a photoelectric conversion element that can be preferably applied to the present invention.

  In FIG. 2, a photosensitive layer 20 and a charge transport layer 30 are interposed between a transparent conductive layer 10a and a transparent counter electrode conductive layer 40a, and light is incident from both sides. In FIG. 3, a part of the metal lead 11 is provided on the transparent substrate 50a, the transparent conductive layer 10a is further provided, the undercoat layer 60, the photosensitive layer 20, the charge transport layer 30 and the counter electrode conductive layer 40 are provided in this order and further supported. A substrate 50 is disposed, and light is incident from the conductive layer side. In FIG. 4, a conductive layer 10 is further provided on a support 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 metal lead 11 is partly provided. The transparent substrate 50a provided with the metal lead 11 side is arranged inside, and light is incident from the counter electrode side. FIG. 5 shows that an undercoat layer 60, a photosensitive layer 20, and a charge transport layer 30 are interposed between a pair of metal leads 11 provided on a transparent substrate 50a and a transparent conductive layer 10a (or 40a). In this structure, light enters from both sides. In FIG. 6, a transparent conductive layer 10a, an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30 and a counter electrode conductive layer 40 are provided on a transparent substrate 50a, and a support substrate 50 is disposed thereon. It is a structure where light enters. In FIG. 7, 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 further provided, and the transparent substrate 50a is disposed thereon. In this structure, light is incident from the counter electrode side. In FIG. 8, the transparent conductive layer 10a is provided on the transparent substrate 50a, 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 transparent substrate 50a is provided thereon. It is arranged and has a structure in which light enters from both sides. In FIG. 9, a conductive layer 10 is provided on a support substrate 50, a photosensitive layer 20 is provided via an undercoat layer 60, a solid charge transport layer 30 is further provided, and a part of the counter electrode conductive layer 40 or the metal lead 11 is provided thereon. It has a structure in which light is incident from the counter electrode side.

[2] Photocell The photovoltaic cell of the present invention is one in which the photoelectric conversion element is caused to work with an external load.
Of the photovoltaic cells, the case where the charge transport material is mainly composed of an ion transport material is particularly called a photoelectrochemical cell, and the case where the main purpose is power generation by sunlight is called a solar cell. In order to prevent deterioration of components and volatilization of the contents of the photovoltaic cell, it is preferable to seal the side surface with a polymer or an adhesive. 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 solar cell, the structure inside the cell is basically the same as the structure of the photoelectric conversion element described above. Moreover, the dye-sensitized solar cell of the present invention can basically have the same module structure as a conventional solar cell module. The solar cell module generally has a structure in which cells are formed on a support substrate such as metal or ceramic, and the cell is covered with a filling resin or protective glass, and light is taken in from the opposite side of the support substrate. It is also possible to use a transparent material such as tempered glass for the support substrate, configure a cell thereon, and take in light from the transparent support substrate side. Specifically, a module structure called a super straight type, a substrate type, a potting type, a substrate integrated module structure used in an amorphous silicon solar cell, 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 place of use and the environment. Specifically, the structure and aspect described in JP-A-2000-268892 are preferable.

Hereinafter, the present invention will be specifically described by way of examples.
Example 1
1. Preparation of coating solution containing titanium dioxide particles (1) Preparation of coating solution for low scattering layer Except that the autoclave temperature was set to 240 ° C, the method described in Barbe et al., Journal of American Ceramic Society, vol. A titanium dioxide dispersion having a titanium dioxide concentration of 10% by weight was obtained by the above method. The resulting titanium dioxide particles (particle A) had an average particle size of about 16 nm. To this dispersion, 20% by weight of polyethylene glycol (molecular weight 20000, manufactured by Wako Pure Chemical Industries) with respect to titanium dioxide and 10% by weight of ethanol with respect to the whole liquid were added. Nitric acid was added thereto to adjust the pH to 1.3 to obtain a coating solution A. This coating solution had a solid content of 10.7% and a TiO ₂ content of 8.9%.
(2) Preparation of coating solution for high scattering layer Kanto Chemical's anatase TiO ₂ (particle B: particle size 100 nm to 300 nm) was mixed with the coating solution (A) at the ratio shown in Table 1 for 3 hours at 45 ° C. The mixture was stirred to obtain coating liquids B-1 to B-4.

2. Preparation of Titanium Dioxide Electrode Adsorbed Dye The coating liquid A obtained above is applied to the conductive surface side of transparent conductive glass (made by Nippon Sheet Glass, surface resistance is about 10Ω / cm ² ) coated with fluorine-doped tin oxide. After applying using a blade and drying at 25 ° C. for 30 minutes, it was baked at 450 ° C. for 30 minutes in an electric furnace (muffle furnace FP-32 manufactured by Yamato Scientific). As a result, a low scattering layer was applied. The coating amount of titanium dioxide for the low scattering layer is as shown in Table 2. The coating liquids B-1 to B-4 were applied to the thicknesses shown in Table 2 in the same manner, dried at 25 ° C. for 30 minutes, and then baked at 450 ° C. for 30 minutes in an electric furnace. As a result, a highly scattering layer was applied. After calcination, it was immersed for 16 hours in an adsorbing solution containing 0.3 mmol / l of the following dye (A). The adsorption temperature is 25 ° C., and the solvent of the adsorbent is a 1: 1: 2 (volume ratio) mixture of ethanol, t-butanol, and acetonitrile. The dyed titanium dioxide electrode was washed sequentially with ethanol and acetonitrile.

  In order to obtain the optical absorptance of the dye adsorption electrodes E-1, E-4, and E-8 used in the photoelectric conversion elements C-1, C-4, and C-8 in Example 1, an optical density measuring device (X-RITE310) was obtained. Type), the visible light transmission density and the visible light reflection density were measured, and the visible light absorption rate was obtained. The results are summarized in Table 2.

From Table 2, when comparing the case of each single layer, the incident light is transmitted through the single layer of the low light scattering rate layer and the light scattering is strong in the single layer of the high light scattering rate layer, so that a lot of incident light is reflected. I understand that. Comparing the low light scattering rate layer single layer electrode and the high light scattering rate layer single layer electrode of the present invention and the comparative example, the electrode composition of the present invention has the best visible light absorptivity compared to the two types of single layers. It was confirmed that light can be used more efficiently.
3. Preparation of photoelectric conversion element The color-sensitized TiO ₂ electrode substrate (2 cm × 2 cm) prepared as described above was superposed on a platinum-deposited glass having the same size (see FIG. 1). Next, using a capillary phenomenon in the gap between the two glasses, an electrolytic solution (1,3-dimethylimidazolium iodide 0.65 mol / liter, iodine 0.05 mol / liter, t-butylpyridine 0.1 mol / liter) l of acetonitrile solution) was soaked and introduced into the TiO ₂ electrode to obtain photoelectric conversion elements C-1 to C-9 shown in Table 3.

According to this example, as shown in FIG. 10, the conductive glass 1 (the conductive agent layer 3 is formed on the glass 2), the TiO ₂ electrode 4 on which the dye is adsorbed, the electrolytic solution 5, and the platinum layer 6 And the photoelectric conversion element by which the glass 7 was laminated | stacked in order was created.

4). Measurement of photoelectric conversion efficiency Simulated sunlight was generated by passing light from a 500 W xenon lamp (USHIO) through a spectral filter (AM1.5 manufactured by Oriel). The intensity of this light was 100 mW / cm ² on the vertical plane. A silver paste was applied to the end of the conductive glass of the photoelectrochemical cell to form a negative electrode, and this negative electrode and platinum-deposited glass (positive electrode) were connected to a current-voltage measuring device (Keutley SMU238 type). While simulating sunlight was irradiated vertically, current-voltage characteristics were measured to obtain conversion efficiency. Table 3 shows the conversion efficiency of the photoelectric conversion elements prepared in the examples.

From the comparison between C-2 to C-5 (the present invention) and C-1, C-6 to C-9 (the comparative example), the cell of the present invention having the low scattering layer and the high scattering layer is only one of them. It can be seen that the conversion efficiency is higher than that of the cell. In the present invention, since light scattered by the high scattering layer is almost absorbed by the low scattering layer, it is not necessary to provide a total reflection layer.
Moreover, the description of the text that the ratio of the particles B (large particles having high scattering properties) in the two-layered high scattering layer is more preferably 10 to 50% was supported.

Example 2
1. Preparation of coating solution containing titanium dioxide particles (1) Preparation of coating solution for low scattering layer Coating solution A of Example 1 was used.
(2) Preparation of coating solution for medium scattering layer Coating solution B-2 in Example 1 was used.
(3) Preparation of coating solution for high scattering layer 6.7 g of anatase TiO ₂ (particle B: particle size 100 nm to 300 nm) manufactured by Kanto Chemical, ₂ g of polyethylene glycol (molecular weight 20000, manufactured by Wako Pure Chemical Industries), 2.6 g of ethanol, 53 ml of distilled water was mixed and stirred at 45 ° C. for 3 hours. Finally, 1.3 ml of concentrated nitric acid was added and stirred well to obtain coating solution C.

2. Preparation of Titanium Dioxide Electrode Adsorbed Dye A low scattering layer on the conductive surface side of transparent conductive glass coated with tin oxide doped with fluorine (made by Nippon Sheet Glass, surface resistance is about 10Ω / cm ² ) as in Example 1. Was applied. The amount of titanium dioxide applied in the low scattering layer is as shown in Table 4. The coating liquid B-2 was applied thereon to the thickness shown in Table 4, dried at 25 ° C. for 30 minutes, and then baked at 450 ° C. for 30 minutes in an electric furnace. This provided a medium scattering layer. Further, the coating liquid C was applied thereon to the thickness shown in Table 4, dried at 25 ° C. for 30 minutes, and then baked at 450 ° C. for 30 minutes in an electric furnace. As a result, a highly scattering layer was applied. Thereafter, a photoelectric conversion element was prepared in the same manner as in Example 1, and the conversion efficiency was measured. The results are shown in Table 4.

  As is clear from Example 2, it can be seen that the photoelectric conversion element having a three-layer structure according to the present invention has extremely high conversion efficiency and is excellent. From Table 4, [from comparison of C-11, C-12, C-13, and C-14] the photoelectric conversion element of the three-layer structure of the present invention absorbs light more than the photoelectric conversion element of the two-layer structure of the present invention. High rate and good conversion efficiency.

1 ... conductive glass 2 ... conductive agent layer 3 ... TiO ₂ electrode 4 ... dye layer 5 ... electrolyte 6 ... platinum layer 7 ... Glass
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 transport layer
40 ... Counterelectrode conductive layer
40a ・ ・ ・ Transparent counter electrode conductive layer
50 ... Board
50a ・ ・ ・ Transparent substrate
60 ... Undercoat layer

Claims (10)

A method for producing a photoelectric conversion element having at least a layer of a semiconductor fine particle film adsorbed with a dye and a conductive support,
The layer of the semiconductor fine particle film is composed of a plurality of layers having different light scattering properties. The plurality of layers include a low scattering layer having the lowest light scattering property as the first layer on the light incident side, and the light scattering property having the low light scattering property. Having a higher scattering layer than the scattering layer,
Creating a dispersion A containing semiconductor fine particles having an average particle diameter of 5 to 50 nm;
A step of mixing the dispersion A containing semiconductor fine particles having an average particle diameter of 5 to 50 nm with the semiconductor fine particles having an average particle diameter of 100 to 500 nm to prepare the dispersion B;
Forming the low scattering layer with the dispersion A, and forming the high scattering layer with the dispersion B;
The manufacturing method of the photoelectric conversion element characterized by including. A method for producing a photoelectric conversion element having at least a layer of a semiconductor fine particle film adsorbed with a dye and a conductive support,
Comprises at least three layers layers different light scattering properties of the semiconductor fine particle film, the light scattering of the low have low scattering layer on the light incident side, the deepest in the light-scattering highly have high scattering layer, the light in the middle and coordinated scattering layer in scattering is an intermediate of the two layers,
Creating a dispersion A containing semiconductor fine particles having an average particle diameter of 5 to 50 nm;
A step of mixing the dispersion A containing semiconductor fine particles having an average particle diameter of 5 to 50 nm with the semiconductor fine particles having an average particle diameter of 100 to 500 nm to prepare the dispersion B;
Forming the low scattering layer with the dispersion A, and
Forming the medium scattering layer with the dispersion B;
The manufacturing method of the photoelectric conversion element characterized by including.   3. The low scattering layer is composed of only semiconductor particles having low light scattering property, and the medium scattering layer is composed of a mixture of semiconductor particles having high light scattering property and semiconductor particles having low light scattering property. Manufacturing method of the photoelectric conversion element.   The low scattering layer is composed of semiconductor particles having an average particle size of 5 to 50 nm and low light scattering properties, and the medium scattering layer contains a mixture of semiconductor particles having an average particle size of 100 to 500 nm and semiconductor particles having an average particle size of 5 to 50 nm. The manufacturing method of the photoelectric conversion element of Claim 3 characterized by the above-mentioned. Fine semiconductor particles of titanium oxide, zinc oxide, magnesium oxide, niobium oxide, tin oxide, tungsten oxide, silicon oxide, any one of claims 1 to 4, characterized in that an oxide semiconductor selected from aluminum oxide The manufacturing method of the photoelectric conversion element of description. All the semiconductor fine particles are titanium oxides, The manufacturing method of the photoelectric conversion element as described in any one of Claims 1-5 characterized by the above-mentioned. The method for producing a photoelectric conversion element according to any one of claims 1 to 6, wherein a ruthenium complex dye having a group selected from the group containing a bonding group is used as the dye. It is obtained by the manufacturing method of the photoelectric conversion element as described in any one of Claims 1-7, The photoelectric conversion element characterized by the above-mentioned.   A photoelectric cell comprising the photoelectric conversion device according to claim 8. The photoelectrochemical cell according to claim 9, comprising a conductive support, a photosensitive layer, a charge transport layer, and a counter electrode conductive layer in this order.
The photosensitive layer contains a charge transport material that has penetrated into the gaps between the semiconductor fine particles, and is composed of a plurality of layers having different light scattering properties. The plurality of layers have the low scattering layer and the high scattering layer. ,
A photoelectrochemical cell characterized by having no total reflection layer on the light incident side.

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