JP2006156214A - Dye-sensitized solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell which has low cost and high conversion efficiency using a simple manufacturing method. <P>SOLUTION: By making fluorides of metal elements of groups IIa, IIb, IVa in the periodic table acted on a substrate having a roughened aluminum surface, this is the dye-sensitized solar cell wherein the substrate is used as an electrode in which a metal oxide semiconductor layer is formed on the aluminum surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a dye-sensitized solar cell that can be easily and inexpensively manufactured and has high conversion efficiency.

Global warming caused by CO ₂ concentration increases caused by the use of large amounts of fossil fuels, further increase in energy demand associated with population growth have been recognized as problems associated to the fate of mankind. For this reason, in recent years, the use of sunlight that is infinite and does not generate harmful substances has been energetically studied. What is currently put into practical use as sunlight, which is a clean energy source, includes residential single crystal silicon, polycrystalline silicon, amorphous silicon, and inorganic solar cells such as cadmium telluride and indium copper selenide.

  However, these inorganic solar cells also have drawbacks. For example, a silicon system is required to have a very high purity. Naturally, the purification process is complicated, the number of processes is large, and the manufacturing cost is high. In addition, there is a demand for weight reduction and the like, and in particular, it is disadvantageous in that payback to the user is long, and there is a problem in the spread.

  On the other hand, many solar cells using organic materials have been proposed. As an organic solar cell, a Schottky photoelectric conversion element that joins a p-type organic semiconductor and a metal having a low work function, a p-type organic semiconductor and an n-type inorganic semiconductor, or a p-type organic semiconductor and an electron-accepting organic compound are joined. There are heterojunction photoelectric conversion elements and the like, and organic semiconductors used are synthetic dyes and pigments such as chlorophyll and perylene, conductive polymer materials such as polyacetylene, or composite materials thereof. A battery material is formed by thinning these by a vacuum deposition method, a casting method, a dipping method, or the like. However, although these organic materials have advantages such as low cost and easy area enlargement, there are many problems that the conversion efficiency is as low as 1% or less and the durability is poor.

  Under such circumstances, a solar cell exhibiting good characteristics has been reported by Dr. Gretzell of Switzerland (see Non-Patent Document 1). This document also discloses materials and manufacturing techniques necessary for battery fabrication. The proposed battery is called a dye-sensitized solar cell or a Gretzel solar cell, and is a wet solar cell using a titanium oxide porous thin film spectrally sensitized with a ruthenium complex as a working electrode. The advantage of this method is that inexpensive metal oxide semiconductors such as titanium oxide do not need to be purified to a high purity, and therefore inexpensive and more usable light extends over a wide visible light region, and there are many visible light components. It can convert sunlight into electricity effectively.

  FIG. 7a shows a typical configuration of a conventional general dye-sensitized solar cell (Gretzel type solar cell). FIG. 7b shows the charge gradient of the metal oxide semiconductor layer constituting the electrode. The electrode 20 of the dye-sensitized solar cell includes a transparent substrate 21, a transparent conductive layer 22, and a dye-sensitized metal oxide semiconductor layer 23. As the transparent substrate 21, a film or a glass substrate is generally used, and as the transparent conductive layer 22, a metal such as platinum or gold, carbon, indium-tin composite oxide (ITO) or fluorine is doped. A metal oxide such as tin oxide (FTO) is generally used, and as the metal oxide semiconductor layer 23, a titanium oxide layer or a zinc oxide layer is generally used. A sensitizing dye is adsorbed to the metal oxide semiconductor layer by an immersion method or the like. As the electrolyte layer 24, a gel electrolyte or a solid electrolyte in which a redox couple is dispersed in an organic solvent and contained in a polymer is used. The counter electrode 25 is formed by providing a substrate 26 with a metal such as platinum or gold, carbon, or a conductive metal oxide such as ITO or FTO.

  In the Gretzel solar cell, electrons generated in the metal oxide semiconductor layer 23 by electron transfer from the sensitizing dye excited by the light irradiation P are provided on the substrate 26 through the transparent conductive layer 22 and the lead wire 27. The counter electrode 25 thus formed reduces the oxidant of the redox couple in the electrolyte layer 24 to produce a reductant. A series of electron flow e as shown in FIG. 7a is continuously generated by reducing the sensitized dye oxidant generated in the metal oxide semiconductor layer 23 by the electron transfer to the oxide semiconductor particles. As a result, a circuit is formed and a photocurrent flows. Since the amount of light absorbed in the oxide semiconductor layer 23 decreases due to the filter effect of the dye as the depth X from the irradiation surface increases, a charge gradient as shown in FIG. Occurs. This charge gradient becomes a driving force, and a reverse current f is generated in the oxide semiconductor layer 23, resulting in a problem that the photoelectric conversion efficiency is lowered. Here, Y represents the charge density in the metal oxide semiconductor layer.

  Further, as a method of providing a metal oxide semiconductor layer on the transparent substrate 21 provided with the transparent conductive layer 22, a sol-gel method, a CVD method, a sputtering method, a pyrosol method, and the like are known. In order to obtain sufficient photoelectric conversion efficiency, baking at 400 ° C. or higher is necessary. Therefore, a glass substrate coated with the above-mentioned ITO or FTO having high heat resistance must be used as a transparent substrate. There was also a problem that it was very expensive.

On the other hand, in the republished patent WO98 / 11020 (Patent Document 1), the titanium fluoride solution is TiF ₆ ² + 2H ₂ O → TiO ₂ + 6F ⁻ + 4H ^+.
It is described that a titanium oxide thin film having photocatalytic activity can be formed on a substrate at a low temperature by using a fluorine scavenger that promotes the above reaction, and can be applied to solar cells and the like. As the fluorine scavenger, boron compounds such as boric acid, metaboric acid and boron oxide as uniform scavenger, aluminum chloride, sodium hydroxide, ammonia water, etc., as the heterogeneous scavenger, aluminum, titanium, iron, nickel, Examples include metals such as magnesium, copper, zinc, and germanium, ceramics such as glass, boron compounds such as silicon, orthoboric acid, metaboric acid, and boron oxide, and compounds such as calcium oxide, aluminum oxide, silicon oxide, and magnesium oxide. .

  However, the above document does not disclose that a titanium oxide film is formed on a substrate having a roughened aluminum surface and used as an electrode. Further, even if a titanium oxide film is formed on a glass substrate by the method of the above literature and used as an electrode of a Gretzel battery as shown in FIG. 7, or an electrode of a battery having a structure as shown in FIG. When used as, the high photoelectric conversion efficiency aimed by the present invention cannot be obtained. Furthermore, in the glass substrate and the stainless steel substrate used in the implementation of the above documents, even if the surface is roughened, sufficiently high photoelectric conversion characteristics aimed by the present invention cannot be obtained. Furthermore, in the method of the above literature, the reaction rate for forming the titanium oxide film is still slow, and further improvement has been desired.

  In WO 2004/057064 (Patent Document 2), Ia, IIa, IIb, IVb, Vb are prepared by using, as a template, a micropore of anodized aluminum that forms a porous film as aluminum oxide that is a fluorine scavenger. Forming oxide nanostructures (nanohole arrays or nanorods) of group Ia, IIa, IIb, IVb and Vb metal elements by the action of fluoride solutions of group metal elements, and using them for dye-sensitized solar cells Has been proposed. According to the above document, after nanostructures are formed by a substitution reaction of anodized aluminum micropores and fluoride, the remaining alumina is treated with phosphoric acid aqueous solution and dissolved to separate the nanostructures (separation) Step), a nanostructure is baked on a transparent glass substrate to form an electrode (baking step), and is used as a Gretzel battery as schematically shown in FIG. However, between the separation step and the firing step, for example, when separating the nanostructure from the template, or when moving the nanostructure to the transparent glass electrode, etc. As a result of defects such as cracks in the oxide semiconductor layer formed on the electrode due to the load, sufficiently high photoelectric conversion characteristics aimed by the present invention could not be obtained.

Patent Document 2 described above forms metal oxide nanoholes and nanorods by substitution reaction of alumina and metal oxide using regular pores (micropores) of anodized alumina. On the other hand, as shown in FIG. 5 to be described later, the present invention forms a film by depositing metal oxide fine particles on a roughened aluminum surface. The manufacturing method is different. Furthermore, when the nanorod produced in Patent Document 2 is used as an electrode of a battery having a structure as shown in FIG. 1 using an anodized aluminum substrate as an electrode without performing the separation step, the high photoelectric conversion characteristics aimed by the present invention are achieved. I could not get.
Republished patent WO 98/11020, pages 1 to 5 WO2004 / 057064, page 1 to page 38 Nature, 353, 737 (1991)

  An object of the present invention is to provide a dye-sensitized solar cell which is inexpensive and has high conversion efficiency using a very simple production method.

The above object of the present invention has been achieved by the following invention.
1) A substrate on which a metal oxide semiconductor layer is formed on an aluminum surface by applying a fluoride of a metal element of groups IIa, IIb, and IVa of the periodic table to a substrate having a roughened aluminum surface. A dye-sensitized solar cell, characterized by being used as:
2) The dye-sensitized solar cell according to 1), wherein a center line surface roughness of the aluminum surface is 0.1 μm or more.
3) A dye-sensitized solar cell in which a metal mesh electrode provided on a transparent substrate is disposed as a counter electrode of the electrode.

  According to the present invention, a dye-sensitized solar cell having low conversion efficiency and high conversion efficiency was obtained using an extremely simple production method.

  A schematic cross-sectional view of a preferred embodiment of the dye-sensitized solar cell of the present invention is shown in FIG. 1, and FIG. 2a schematically shows the flow of electrons by light irradiation. FIG. 2b shows the charge gradient of the metal oxide semiconductor layer constituting the electrode. The dye-sensitized solar cell of the present invention includes an electrode 10, an electrolyte layer 13, a metal mesh electrode (counter electrode) 14, a transparent substrate 15, and lead wires 16. In the electrode 10 of the present invention, a metal oxide semiconductor layer 12 is formed by a method of the present invention on a substrate 11 having a roughened aluminum surface, and the metal oxide semiconductor layer is dyed with a sensitizing dye as described later. It has been sensitized. A substrate 10 having an aluminum surface is short-circuited through a metal mesh electrode 14 as a counter electrode and a lead wire 16. The metal mesh electrode is made of a net-like metal mesh as shown in FIGS. 3A and 3B, for example, and is held on a transparent substrate 15 that also serves as a protective layer. The irradiation light P passes through the transparent substrate 15, passes through the gap between the metal mesh electrodes 14, passes through the electrolyte layer 13, and is absorbed by the metal oxide semiconductor layer 12 to generate photoelectrons. Photoelectrons flow from the metal oxide semiconductor through the aluminum layer 11, through the lead wire 16 to the metal mesh electrode 14 of the counter electrode, and reduce the oxidant in the electrolyte layer 13 to form a reductant. The reductant reduces the oxidized dye that has lost electrons due to the irradiation light. As a result of a series of electron movements by the light irradiation described above, a photovoltaic force is generated and a photocurrent flows.

  In the dye-sensitized solar cell of the present invention, light is irradiated through the transparent substrate 15, the gap between the metal mesh electrode 14 and the electrolyte layer 13 as shown in FIG. The direction of the gradient (see FIG. 2b) is the same as the forward flow e of the circuit comprising the solar cell, and the reverse charge gradient in the metal oxide semiconductor layer as generated in the Gretzel type solar cell. For this reason (see FIG. 7b), the photoelectric conversion efficiency does not decrease. Further, as shown in FIG. 5 to be described later, since the metal oxide fine particles are directly formed on the conductive metal aluminum, the electric resistance between the metal oxide semiconductor layer 12 and the substrate 11 is small, and the electrons are efficiently generated. Flows.

In the metal oxide semiconductor layer of the present invention, aluminum captures fluorine ions of fluoride of a metal element by the following reaction formula (1-1) or (1-2), thereby oxidizing the metal surface on the aluminum surface according to the reaction formula (2). A reaction in which a physical semiconductor layer is formed is used. In the case where a fluoride of a IIa and IIb metal is allowed to act, the metal oxide according to the following reaction formula (1-1), and in the case where a fluoride of a IVa group metal is allowed to act, according to the following reaction formula (1-2): A semiconductor layer is formed.
MF ₂ + H ₂ O → MO + 2H ⁺ + 2F ⁻ (1-1)
MF ₆ ²⁻ + 2H ₂ O → MO ₂ + 4HF + 2F ⁻ (1-2)
Al ₂ O ₃ + 12F ⁻ + 12H ⁺ → 2H ₃ AlF ₆ + 3H ₂ O (2)

Here, M represents a metal element of group IIa, IIb, or IVa of the periodic table, and specifically, magnesium, calcium, strontium, barium, titanium, zirconium, hafnium, or zinc. Examples of fluorides of these metal elements include magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), strontium fluoride (SrF ₂ ), barium fluoride (BaF ₂ ), potassium titanium fluoride (K _2). TiF ₆ ), sodium titanium fluoride (Na ₂ TiF ₆ ), ammonium titanium fluoride ((NH ₄ ) ₂ TiF ₆ ), potassium zirconium fluoride (K ₂ ZrF ₆ ), hafnium fluoride (HfF ₄ ), fluoride And zinc tetrahydrate (ZnF ₂ .4H ₂ O). Preferred metal elements are titanium and zinc, and particularly preferred is titanium.

  Further, a fluorine scavenger as described in republished patent WO98 / 11020 can be used in combination. Fluorine scavengers include homogeneous scavengers and heterogeneous scavengers. Boron compounds such as boric acid, metaboric acid and boron oxide, aluminum chloride, sodium hydroxide, aqueous ammonia and the like as uniform scavengers, and aluminum, titanium, iron, nickel, magnesium, copper, zinc, Examples thereof include metals such as germanium, ceramics such as glass, boron compounds such as silicon, orthoboric acid, metaboric acid, and boron oxide, calcium oxide, aluminum oxide, silicon oxide, and magnesium oxide.

The preferred use amount of the fluorides of the metal elements of Group IIa, IIb, and IVa of the present invention varies depending on the type of fluoride, the time and temperature at which the fluoride acts, the surface area of the aluminum substrate, the degree of roughening, etc. However, it is in the range of 1 × 10 ⁻⁵ mol / L to 2 × 10 ⁻¹ mol / L, more preferably in the range of 5 × 10 ^{−4 to} 5 × 10 ⁻² mol / L.

  As the thickness of the metal oxide semiconductor layer of the present invention increases, the amount of supported dye per unit projected area also increases, so the light capture rate increases, but the diffusion distance of the generated electrons also increases, so that charge re-generation is increased. There are also many bonds. Therefore, the thickness of the metal oxide semiconductor layer is preferably 0.5 to 30 μm, and more preferably 1 to 15 μm.

  The degree of roughening of the roughened aluminum surface of the present invention is preferably 0.1 μm or more in terms of centerline average roughness Ra. Here, the center line average roughness Ra (hereinafter, simply referred to as Ra) is measured by the following method. That is, two-dimensional roughness measurement is performed with a stylus type roughness meter (for example, Surfcom 1400D, manufactured by Tokyo Seimitsu Co., Ltd.), the average roughness defined in ISO 4287 is measured six times, and the average value is the center line. Average roughness. The conditions for the two-dimensional roughness measurement are a cut-off value of 0.8 mm, a side constant length of 4 mm, and a stylus tip diameter of 2 μm.

  When metal oxide fine particles (microcrystals) are formed on the aluminum surface by the action of a metal element fluoride, the metal surface fine particles are precipitated by roughening the aluminum surface in advance. A metal oxide semiconductor layer overlapped with is formed. On the other hand, in the case of a smooth aluminum surface that is not roughened, coarse metal oxide particles are formed, so that good photoelectric conversion efficiency cannot be obtained.

  In the present invention, in order to obtain higher photoelectric conversion efficiency, the Ra of the roughened aluminum surface is preferably 0.2 μm or more. Further, by increasing Ra, even if a relatively high concentration metal fluoride solution is applied, the coarsening of the metal oxide particles is suppressed, so that the metal oxide fine particles can be formed at a high production rate. it can. The upper limit of Ra on the aluminum surface is about 5 μm, preferably 3 μm or less, and more preferably 2 μm or less.

In the present invention, the aluminum surface is preferably roughened so that fine pits having an opening diameter of 0.01 μm to 0.30 μm are formed in addition to Ra of 0.1 μm or more. The fine pits are preferably 50 or more per 100 μm ² , more preferably 100 or more, and the upper limit is preferably up to 15,000. The average opening diameter of the fine pits is preferably 0.03 μm to 0.2 μm, and the depth of the fine pits is more preferably 1/3 or more of the opening diameter. The center depth of the fine pit is preferably about 1/2 to 3 times the opening diameter of the pit. The shape, opening diameter, and depth of these fine pits can be easily confirmed by an enlarged photograph at a magnification of about 50,000 times using a scanning electron microscope or a tunnel microscope.

FIG. 4 schematically shows the shape of a roughened aluminum surface that is preferably used in the present invention. 4a is a cross-sectional view and FIG. 4b is a plan view. The shape of the aluminum surface is a structure in which the large wave structure 1 and the fine pits 2 are superimposed. The average wavelength of the large wave structure is preferably 3 to 100 μm, more preferably 5 to 80 μm. This average wavelength can be measured by the same method as Ra described above, and the average peak interval Sm defined by ISO 4287 is measured six times, and the average value is taken as the average wavelength.
The opening diameter of the fine pits is as described above.

  The substrate having a roughened aluminum surface according to the present invention may be aluminum itself (aluminum plate) or a composite material in which an aluminum layer is provided on a substrate of another material. good. As other substrates, various materials such as metals, metal oxides, ceramics, plastics, polymer films, and fibers can be used. In the present invention, an aluminum plate is preferably used as the substrate. The thickness of the substrate having a roughened aluminum surface is preferably in the range of 20 μm to 500 μm, more preferably in the range of 50 μm to 300 μm.

  The aluminum content of the present invention is 99.0% or less of pure aluminum with an aluminum content of 99.0% or more, and aluminum containing additives and impurities such as copper, manganese, silicon, magnesium, and zinc. This means various aluminum alloys such as JIS standard 2000-7000 series.

  In the present invention, the roughening of the aluminum surface can be performed using various methods as described later, but in the case of a composite material in which an aluminum layer is provided on the substrate made of the other material, The surface of the aluminum surface itself is reflected by reflecting the shape of the rough surface of the substrate of the original material on the aluminum surface by roughening the substrate itself made of another material in advance and then providing an aluminum layer by a method such as coating, bonding, or vapor deposition. Instead of directly roughening, it is possible to use a method of indirectly roughening. Further, the indirect surface roughening method and the direct surface roughening of the aluminum surface can be used in combination.

  As a roughening method (so-called graining) of the aluminum surface of the present invention, mechanical graining treatment such as ball graining, wire graining, brush graining, acid treatment or alkali treatment, chloride or fluoride, etc. Chemical surface roughening treatment by chemically dissolving aluminum, electrolytic surface roughening by etching aluminum by passing an alternating electric field using acid as electrolyte, and surface roughening using these methods together Method can be used. For example, JP-A 48-28123, 53-123204, 54-146234, 55-25381, 55-132294, 56-55291, 56-150593, 56-28893, 58-167196, U.S. Pat.Nos. 2,344,510, 3,861,917, 4,301,229, U.S. Pat.No. 2,344,510, U.S. Pat. 229, U.S. Pat. No. 3,861,917, and Canadian Patent No. 955449 are roughened as described in West German Patent No. 1,813,443 and Japanese Patent Laid-Open No. 7-56344. You can refer to the method.

  By using the roughening method as described above, roughening with Ra of 0.1 μm or more can be realized. In the present invention, it is further preferable to form the fine pits as described above on the aluminum surface, and such fine pits can be formed by chemical surface roughening treatment or electrolytic surface roughening treatment. In particular, fine pits can be stably formed by electrolytic surface roughening.

Preferred methods for electrolytic graining treatment, for example, include a method of electrolytic graining in a hydrochloric acid or an electrolytic solution of nitric acid, the quantity of electricity is in the range of 100~400C / dm ² is preferred. Specifically, in an electrolytic solution containing 0.1 to 50% by mass, preferably 0.5 to 10% by mass of hydrochloric acid or nitric acid, the temperature is 20 to 100 ° C., preferably 30 to 70 ° C., and the time is 1 second to 30%. min, preferably 2 seconds to 1 minute, it is preferable to perform the electrolysis at a current density of 100~400C / dm ^2.

  In the present invention, a preferred roughening method for roughening the aluminum surface is a combination of mechanical roughening and electrolytic roughening. As a result, a composite structure in which a large wave structure and fine pits are superimposed can be stably formed at a low cost.

  After the roughening treatment as described above, the aluminum surface is washed with an acid or an alkali in order to remove dirt remaining on the surface, and then washed with water and dried. Moreover, an anodizing process can also be given after water washing. For the anodizing treatment, an aqueous solution of sulfuric acid, phosphoric acid, oxalic acid or the like is mainly used as an electrolytic bath. After anodizing, it is washed with water and dried.

  By treating a substrate having a roughened aluminum surface as described above with a metal fluoride, a metal oxide semiconductor layer in which metal oxide fine particles (microcrystals) are seamlessly overlapped on the aluminum surface is formed. Is done. FIG. 5 is a diagram schematically illustrating a generation state of the metal oxide semiconductor layer. 5a is a cross-sectional view and FIG. 5b is a plan view. Metal oxide fine particles (microcrystals) 3 are densely formed on the aluminum surface to form a metal oxide semiconductor layer 4.

  FIG. 6 is a scanning electron micrograph of titanium oxide fine particles (microcrystals) formed on the aluminum surface by the method of the present invention. The magnification is 30,000 times. As can be seen from the photograph, titanium oxide microcrystals of anatase structure having a size of about 0.01 to 0.3 μm are densely overlapped with no gap to form a layer.

  Specific examples of the dye in the dye-sensitized solar cell of the present invention include JP 7-500630 A, JP 10-233238 A, JP 2000-26487 A, JP 2000-323191 A, JP-A-2001-59062 and the like, JP-A-11-86916, JP-A-11-214730, JP-A-2000-106224, JP-A-2001-76773, and Japanese Patent Application 2001-2001. In the cyanine dyes described in JP-A No. 186599, JP-A-11-214731, JP-A-11-238905, JP-A-2001-52766, JP-A-2001-76775, JP-A-2001-192395, etc. Described merocyanine dyes, JP-A-10-92477, JP-A-11-273754, JP-A-10-273754 9-arylxanthene compounds described in JP-A No. 11-273755 and Japanese Patent Application No. 2001-214126, triarylmethane compounds described in JP-A No. 10-93118, Japanese Patent Application No. 2001-214126, and JP-A No. 10-93118. Coumarin compounds, acridine compounds, JP-A 47-37543, JP-A 53-95033, JP-A 53-132347, JP-A 53-133445, JP JP 54-12742, JP 54-20736, JP 54-20737, JP 54-21728, JP 54-2234, JP 55-69148 JP, 55-69654, JP 55-79449, JP 55-117151, JP 5 -46237, JP-A 56-1116039, JP-A 56-111040, JP-A 56-119134, JP-A 56-143437, JP-A 57-63537, JP-A-57-63538, JP-A-57-63541, JP-A-57-63542, JP-A-57-63549, JP-A-57-66438, JP-A-57- No. 74746, JP-A 57-78542, JP-A 57-78543, JP-A 57-90056, JP-A 57-90057, JP-A 57-90632, JP-A-57-116345, JP-A-57-202349, JP-A-58-4151, JP-A-58-90644, JP-A-58-144358, JP JP 58-177955 A, JP 59-31962 A, JP 59-33253 A, JP 59-71059 A, JP 59-72448 A, and JP 59-78356 A. Publication, JP 59-136351, JP 59-201060, JP 60-15642, JP 60-14351, JP 60-179746, JP JP 61-11754, JP 61-90164, JP 61-90165, JP 61-90166, JP 61-112154, JP 61-269165 JP, 61-281245, JP 61-51063, JP 62-267363, JP 63-68844, JP 63-89866. Japanese Patent Laid-Open No. 63-139355, Japanese Patent Laid-Open No. 63-142033, Japanese Patent Laid-Open No. 63-183450, Japanese Patent Laid-Open No. 63-282743, Japanese Patent Laid-Open No. 64-21455, and Japanese Patent Laid-Open No. 64-21455. JP-A-64-78259, JP-A-1-200277, JP-A-1-202757, JP-A-1-319754, JP-A-2-72372, JP-A-2-254467, and JP-A-3- No. 95561, JP-A-3-27863, JP-A-4-96068, JP-A-4-96069, JP-A-4-147265, JP-A-5-142841, and JP-A-5-303226. Gazette, JP-A-6-324504, JP-A-7-168379, Japanese Patent Application No. 2001-161942, Japanese Patent Application No. 2001-175875 And the phthalocyanine compounds and porphyrin compounds described in JP-A-9-199744, JP-A-10-233238, JP-A-11-204821, JP-A-11-265738, etc. These are used in the dye-sensitized solar cell of the present invention as at least one or a mixture of two or more.

  As the electrolyte layer 13 of the present invention, an electrolytic solution in which a redox couple is dissolved in an organic solvent, a gel electrolyte in which a liquid in which the redox couple is dissolved in an organic solvent is impregnated in a polymer matrix, a molten salt containing the redox couple, a solid An electrolyte, an organic hole transport material, or the like can be used.

  The electrolytic solution used for the electrolyte layer of the present invention is preferably composed of an electrolyte, a solvent, and an additive. Preferred electrolytes are metal iodide-iodine combinations such as lithium iodide, sodium iodide, potassium iodide, cesium iodide, and calcium iodide, and quaternary compounds such as tetraalkylammonium iodide, pyridinium iodide, and imidazolium iodide. Iodine salt of ammonium compound-iodine combination, metal bromide-bromine combination such as lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide, quaternary ammonium such as tetraalkylammonium bromide, pyridinium bromide Bromine-bromine combinations of compounds, metal complexes such as ferrocyanate-ferricyanate, ferrocene-ferricinium ions, sulfur compounds such as sodium polysulfide, alkylthiol-alkyldisulfides, viologen Dye, hydroquinone - quinones, and the like. The above-mentioned electrolytes may be a single combination or a mixture. In addition, a salt in a molten state at room temperature can be used as the electrolyte. When this molten salt is used, it is not necessary to use a solvent.

  The electrolyte concentration in the electrolytic solution is preferably 0.05 to 20M, and more preferably 0.1 to 15M. Solvents used for the electrolyte include carbonate solvents such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether solvents such as dioxane, diethyl ether and ethylene glycol dialkyl ether, methanol, ethanol Alcohol solvents such as polypropylene glycol monoalkyl ether, nitrile solvents such as acetonitrile and benzonitrile, aprotic polar solvents such as dimethyl sulfoxide and sulfolane are preferred.

  Also, basic compounds such as t-butylpyridine, 2-picoline, 2,6-lutidine and the like can be added.

  In the present invention, the electrolyte can be gelled by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization including polyfunctional monomers, or a crosslinking reaction of the polymer. Preferable polymers in the case of gelation by polymer addition include polyacrylonitrile, polyvinylidene fluoride and the like. Preferred gelling agents for gelation by adding an oil gelling agent include dibenzylden-D-sorbitol, cholesterol derivatives, amino acid derivatives, alkylamide derivatives of trans- (1R, 2R) -1,2-cyclohexanediamine, alkylureas Derivatives, N-octyl-D-gluconamide benzoate, double-headed amino acid derivatives, quaternary ammonium derivatives and the like can be mentioned.

  Preferred monomers for polymerization with a polyfunctional monomer include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, and the like. be able to. Furthermore, esters and amides derived from acrylic acid such as acrylamide and methyl acrylate and α-alkyl acrylic acid, esters derived from maleic acid and fumaric acid such as dimethyl maleate and diethyl fumarate, butadiene, cyclohexane and the like. Dienes such as pentadiene, aromatic vinyl compounds such as styrene, p-chlorostyrene and sodium styrene sulfonate, vinyl esters, acrylonitrile, methacrylonitrile, vinyl compounds having a nitrogen-containing heterocyclic ring, vinyl having a quaternary ammonium salt A monofunctional monomer such as a compound, N-vinylformamide, vinylsulfonic acid, vinylidene fluoride, vinyl alkyl ethers, N-phenylmaleimide may be contained. The polyfunctional monomer in the total amount of the monomer is preferably 0.5 to 70% by weight, more preferably 1.0 to 50% by weight.

  The above-mentioned monomers can be polymerized by radical polymerization. The monomer for gel electrolyte that can be used in the present invention can be radically polymerized by heating, light, electron beam or electrochemical. The polymerization initiator used when the crosslinked polymer is formed by heating is 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2. Azo initiators such as 2,2′-azobis (2-methylpropionate) and peroxide initiators such as benzoyl peroxide are preferable. The addition amount of these polymerization initiators is preferably 0.01 to 20 parts by mass and more preferably 0.1 to 10 parts by mass with respect to the total amount of monomers.

  When the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a reactive group necessary for the crosslinking reaction and a crosslinking agent in combination. Preferable examples of the crosslinkable reactive group include nitrogen-containing heterocycles such as pyridine, imidazole, thiazole, oxazole, triazole, morpholine, piperidine, piperazine, etc. Preferred crosslinking agents include alkyl halides, halogens Bifunctional or higher functional reagents capable of electrophilic reaction with nitrogen atoms such as aralkyl fluoride, sulfonic acid ester, acid anhydride, acid chloride, and isocyanate can be exemplified.

  When an inorganic solid compound is used instead of the electrolyte, copper iodide, copper thiocyanide, or the like can be introduced into the electrode by a casting method, a coating method, a spin coating method, a dipping method, electrolytic plating, or the like.

  In the present invention, an organic charge transport material can be used instead of the electrolyte. Charge transport materials include hole transport materials and electron transport materials. Examples of the former include, for example, oxadiazoles disclosed in Japanese Patent Publication No. 34-5466, triphenylmethanes disclosed in Japanese Patent Publication No. 45-555, and Japanese Patent Publication No. 52-4188. Pyrazolines shown in the above, hydrazones shown in JP-B-55-42380, oxadiazoles shown in JP-A-56-123544, etc., JP-A-54-58445 And tetrasylbenzidines disclosed in JP-A No. 58-65440, and stilbenes disclosed in JP-A No. 60-98437. Among them, examples of the charge transport material used in the present invention are shown in JP-A-60-24553, JP-A-2-96767, JP-A-2-183260, and JP-A-2-226160. Particularly preferred are the hydrazones described, and the stilbenes shown in JP-A-2-51162 and JP-A-3-75660. Moreover, these can be used individually or in mixture of 2 or more types.

  On the other hand, examples of the electron transport material include chloranil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 1,3,7-trinitrodibenzothiophene, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, etc. . These electron transport materials can be used alone or as a mixture of two or more.

  Further, as a sensitizer that further increases the sensitizing effect, a certain kind of electron-withdrawing compound can be added. Examples of the electron-withdrawing compound include 2,3-dichloro-1,4-naphthoquinone, 1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone, 2-chloroanthraquinone, phenanthrenequinone and other quinones, 4-nitro Aldehydes such as benzaldehyde, ketones such as 9-benzoylanthracene, indandione, 3,5-dinitrobenzophenone, or 3,3 ', 5,5'-tetranitrobenzophenone, phthalic anhydride, 4-chloronaphthalic anhydride Acid anhydrides such as terephthalalmalononitrile, 9-anthrylmethylidenemalononitrile, 4-nitrobenzalmalononitrile, or cyano compounds such as 4- (p-nitrobenzoyloxy) benzalmalononitrile, 3-benzalphthalide , 3- (α-cyano- - Nitorobenzaru) phthalide, or 3- (alpha-cyano -p- Nitorobenzaru) -4,5,6,7 can be mentioned phthalides such as tetrachloro phthalide like.

  When forming an electrolyte layer using these charge transport materials, it is preferable to use a resin together, polystyrene resin, polyvinyl acetal resin, polysulfone resin, polycarbonate resin, polyester resin, polyphenylene oxide resin, polyarylate resin, acrylic resin, A methacrylic resin, a phenoxy resin, etc. are mentioned. Among these, polystyrene resin, polyvinyl acetal resin, polycarbonate resin, polyester resin, and polyarylate resin are excellent. These resins can be used alone or in admixture of two or more as a copolymer.

  Some of these resins are weak in mechanical strength such as pulling, bending, and compression. To improve this property, a plasticizing substance can be added. Specific examples include phthalic acid esters (for example, DOP and DBP), phosphoric acid esters (for example, TCP and TOP), sebacic acid esters, adipic acid esters, nitrile rubber, chlorinated hydrocarbons, and the like. If these substances are added more than necessary, the properties are adversely affected, so the ratio is preferably 20% or less with respect to the binder resin. In addition, an antioxidant, an anti-curl agent, etc. can be added as needed. 0.001-20 mass parts is preferable with respect to 1 mass part of charge transport materials, and, as for the amount of resin used, 0.01-5 mass parts or less are more preferable.

  There are two main methods for forming the electrolyte layer 13. One is a method in which a transparent substrate 15 provided with a metal mesh electrode 14 is pasted on the electrode 10 of the present invention on which a metal oxide semiconductor layer is formed, and a liquid electrolyte layer 13 is sandwiched between the transparent substrates 15. . The other is a method of applying the electrolyte layer 13 directly on the electrode 10 of the present invention. In this case, the transparent substrate 15 provided with the metal mesh electrode 14 is newly applied thereafter.

  In the former case, examples of the method for sandwiching the electrolyte layer include a normal pressure process using capillary action due to immersion and a vacuum process in which the gas phase is replaced with a liquid phase at a pressure lower than normal pressure. In the latter case, in the wet electrolyte layer, it is necessary to provide a counter electrode without being dried to prevent liquid leakage at the edge portion. 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 that case, you may provide a counter electrode after drying and fixing. In addition to the electrolyte solution, the organic charge transport material solution and the gel electrolyte can be applied in the same manner as the semiconductor fine particle-containing layer and the dye, as in the immersion method, roller method, dipping method, air knife method, and extrusion method. , Slide hopper method, wire bar method, spin method, spray method, casting method, various printing methods, and the like.

The metal mesh electrode 14 provided on the transparent substrate 15 is a mesh-like electrode represented by a grid-like metal mesh as shown in FIG. The shape of the mesh electrode is preferably as large as possible for the purpose of passing the irradiation light through the gap, but the electrode area should be as large as possible for the purpose of improving the efficiency of electron transfer at the counter electrode. Is preferred. Therefore, it is preferable that the counter electrode is as thick as possible, and the mesh opening is as wide as possible. Mesh thickness range 1μm~30μm metal mesh electrode, preferably in the range of 3 to 15 [mu] m, between the size of the opening of the mesh of 0.001 mm ² to 5 mm ^2, preferably 0.0025 mm ² ~ 1 mm between ^2, the ratio of the openings of the electrode upper limit is 75% or more preferably 80% or more is 95%.

  The metal mesh electrode 14 can be provided on the transparent substrate 15 by various methods such as adhesion, coating, and vapor deposition. As a preferable material for the mesh electrode, platinum, rhodium, ruthenium, ruthenium oxide, carbon or a material obtained by plating platinum on a conductive material can be used, and the most preferable electrode material is a platinum electrode.

  Hereinafter, the present invention will be described by way of examples.

Example 1
An aluminum coil of JIS-A1050 having a width of 300 mm and a thickness of 0.24 mm was immersed in a 4% sodium hydroxide aqueous solution at 60 ° C. for 10 seconds, washed with water, and then 40 A · dm ² in a 1.8% hydrochloric acid electrolyte at 28 ° C. The aluminum coil of the present invention is obtained by electrolytically roughening by flowing a 60 Hz single layer AC current for 30 seconds, washing with water, dipping in a solution containing 10% phosphoric acid at 50 ° C. for 20 seconds, washing with water and drying. It was. Ra of this aluminum surface was 0.68 μm.

(Fluoride treatment of aluminum substrate)
The aluminum coil was cut into 50 mm × 50 mm, immersed in the following fluoride solution at 25 ° C. for 30 minutes, washed with water, and sintered at 200 ° C. for 1 hour to form about 1 g / m ² of titanium oxide on the surface. An aluminum substrate was obtained.
(Fluoride solution)
Titanium fluoride potassium 0.025 mol Phosphoric acid 2 g
Sodium metaphosphate 10g
Add sodium hydroxide to adjust to pH 4.0 Add pure water to make a total volume of 1,000 ml.

(Adsorption of sensitizing dye)
A sensitizing dye represented by cis-di (thiocyanato) -N, N-bis (2,2′-bipyridyl-4-carboxylate-4′-tetobutylammonium carboxylate) ruthenium (II) was dissolved in ethanol. The concentration of this dye was 3 × 10 ⁻⁴ mol / L. Next, put an aluminum substrate in this ethanol solution. The aluminum substrate was immersed for 12 hours at room temperature, and the aluminum substrate was dye-sensitized to obtain the electrode 10 of FIG.

(Creation of dye-sensitized solar cell)
A platinum mesh electrode 14 is attached to a polyester film substrate 15 having a thickness of 200 μm, an electrolyte is placed between the electrode 10 and the side surface is encapsulated with resin, and then a lead wire 16 is attached to the dye-sensitized solar cell of the present invention. A battery was obtained. Platinum mesh electrode has a rectangular opening, such as shown in Figure 3a, the area of the opening portion is the ratio of the opening at 0.01 mm ² was used having a thickness of 12μm at 90%. In addition, as for electrolyte, in the solvent of acetonitrile, lithium iodide, 1,2-dimethyl-3-propyl imidazolium iodide, iodine, and t-butyl pyridine, respectively, the concentration is 0.1 mol / L, 0.3 What was melt | dissolved so that it might become mol / L, 0.05 mol / L, and 0.5 mol / L was used.

(Comparative Example 1)
Instead of the roughened aluminum plate of Example 1, the aluminum coil of JIS-A1050 was immersed in a 4% sodium hydroxide aqueous solution at 60 ° C for 10 seconds without being roughened, washed with water, A dye-sensitized solar cell was produced in the same manner as in Example 1 except that an anodized film of 5 g / m ² was formed in an aqueous solution of% phosphoric acid by an indirect power feeding method, washed with water, and dried.

(Comparative Example 2)
Oxygen and argon were both supplied at a rate of 5 ml / min on a 2 mm-thick glass substrate (50 mm × 50 mm) coated with FTO using a counter target type vacuum vapor deposition apparatus as a target of 100 mm × 200 mm metal titanium. Thereafter, the pressure in the apparatus was set to 5 mTorr, and sputtering was performed at 10 KW for 60 minutes to form a 1 g / m ² titanium oxide layer. Using this substrate instead of the aluminum substrate, dye sensitization was performed in the same manner as in Example 1 to obtain the electrode 20 of FIG. Platinum is vapor-deposited to a thickness of 12 μm on a polyester film substrate (50 mm × 50 mm) 26 having a thickness of 200 μm to form a counter electrode 25, an electrolyte is inserted between the electrodes 20, and this side surface is sealed with resin, and then lead A wire 27 was attached to obtain a dye-sensitized solar cell of Comparative Example 2. The same electrolyte as in Example 1 was used.

When the solar cell of the present invention was irradiated with light of 100 W / m ^{2 with} a solar simulator from the metal mesh electrode side, Voc (voltage in an open circuit state) was 0.68 V, and Joc (when the circuit was short-circuited) The density of the flowing current was 1.15 mA / cm ² , the FF (fill factor) was 0.67, and η (conversion efficiency) was 3.40%. This proved useful as a solar cell. The aluminum plate before treatment with the fluoride used in Comparative Example 1 has regular micropores on a smooth surface (Ra is less than 0.1 μm), and when a solar cell is formed using this aluminum plate Voc was 0.67 V, Joc was 0.22 mA / cm ² , FF was 0.07, η was 0.45%, and the performance of the solar cell was inferior. When the solar cell of Comparative Example 2 is irradiated with light from the glass substrate side on which titanium oxide is formed, Voc is 0.62 V, Joc is 0.85 mA / cm ² , and FF is 0.51. η was 2.45%, which was inferior in performance as a solar cell compared to the present invention.

The schematic sectional drawing of the preferable form of the dye-sensitized solar cell of this invention. The schematic sectional drawing which shows typically the flow of the electron at the time of the light irradiation of the dye-sensitized solar cell of this invention. The top view which shows the example of the structure of the metal mesh electrode of this invention. The schematic diagram of the shape of the roughened aluminum surface. The schematic diagram of the production | generation state of the metal oxide semiconductor layer formed in the aluminum surface. The scanning electron micrograph of the titanium oxide semiconductor layer formed in the roughened aluminum surface of this invention. 1 is a schematic cross-sectional view showing a typical configuration of a dye-sensitized solar cell (Gretzel type solar cell) and the flow of electrons.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Large wave structure 2 Fine pit 3 Fine particle of metal oxide semiconductor 4 Metal oxide semiconductor layer 10 Electrode 11 in which metal oxide semiconductor layer is formed on aluminum surface Substrate having roughened aluminum surface 12 Metal oxide semiconductor layer 13 Electrolyte layer 14 Metal mesh electrode 15 Transparent substrate 16 Lead wire P Irradiation light

Claims (3)

  A substrate having a metal oxide semiconductor layer formed on the aluminum surface by using a fluoride of a metal element of groups IIa, IIb, and IVa of the periodic table on a substrate having a roughened aluminum surface is used as an electrode. A dye-sensitized solar cell characterized by the above.   The dye-sensitized solar cell according to claim 1, wherein the surface roughness of the center line of the aluminum surface is 0.1 µm or more.   A dye-sensitized solar cell in which a metal mesh electrode provided on a transparent substrate is disposed as a counter electrode of the electrode according to claim 1.

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