JP4456933B2 - Method for producing dye-sensitized solar cell electrode - Google Patents

Description

  The present invention relates to a method for producing a dye-sensitized solar cell electrode, and more particularly, to a method for producing a dye-sensitized solar cell electrode capable of improving the photovoltaic power generation performance of a solar cell.

  The dye-sensitized solar cell has been proposed since a photoelectric conversion element using dye-sensitized semiconductor fine particles was proposed ["Nature", Vol. 353, pages 737-740, (1991)], silicon-based solar cells. It is attracting attention as a new solar battery that replaces batteries. In particular, dye-sensitized solar cells using a plastic film as a support can be made flexible and lightweight, and many studies have been made.

  Among plastic films, a polyester film is a material useful as a support for a dye-sensitized solar cell because it is inexpensive but highly transparent and has heat resistance. However, there has been a problem that practical photovoltaic power generation performance cannot be obtained unless the physical properties of the polyester film are appropriately designed and the semiconductor layer is sintered at a temperature matched thereto.

  The semiconductor layer of a dye-sensitized solar cell generally sinters fine particles to form a porous structure for the purpose of adsorbing more dye.

  However, when a plastic film is used as a support, the temperature for this sintering cannot be sufficiently increased, and as a result, the charge carrier transport efficiency is reduced. There is a problem that the photovoltaic power generation performance is remarkably inferior.

JP-A-11-288745 JP 2001-160426 A JP 2002-50413 A

  The present invention solves such problems of the prior art, and provides an electrode capable of producing a plastic substrate dye-sensitized solar cell having excellent adhesion between a transparent conductive layer and a porous semiconductor layer and having high photovoltaic power generation performance. For the purpose.

  That is, the present invention forms a transparent conductive layer on one side of a polyester film in which the absolute value of the difference between the heat shrinkage rates in the longitudinal direction and the width direction of the film when treated at 200 ° C. for 10 minutes is 0.8% or less, Further, a porous semiconductor layer is formed by baking at least one oxide selected from the group consisting of titanium oxide, zinc oxide and tin oxide at 170 to 250 ° C., for a dye-sensitized solar cell It is a manufacturing method of an electrode.

  According to the present invention, the polyester film having an absolute value of the difference in thermal shrinkage between the longitudinal direction and the width direction of the film when treated at 200 ° C. for 10 minutes is 0.8% or less, and transparent formed on one side thereof Provided is a dye-sensitized solar cell electrode comprising a conductive layer and a porous semiconductor layer made of at least one oxide selected from titanium oxide, zinc oxide and tin oxide formed thereon. .

  ADVANTAGE OF THE INVENTION According to this invention, the electrode which is excellent in the adhesiveness of a transparent conductive layer and a porous semiconductor layer, and can produce a plastic base material dye-sensitized solar cell with high photovoltaic performance can be obtained.

Hereinafter, the present invention will be described in detail.
[Polyester film]
In the present invention, the polyester constituting the polyester film is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof.

  Specific examples of such polyesters include polyethylene terephthalate, polyethylene isophthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-naphthalate, and the like. It may be a blend of these copolymers or a small proportion of other resins. Among these polyesters, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable because of a good balance between mechanical properties and optical properties. In particular, polyethylene-2,6-naphthalate is most preferable because it is superior to polyethylene terephthalate in terms of mechanical strength, small heat shrinkage, and a small amount of oligomer generated during heating.

  The polyester may be a homopolymer or a copolymer obtained by copolymerizing the third component, but a homopolymer is preferred. When the polyester is polyethylene terephthalate, isophthalic acid copolymerized polyethylene terephthalate is optimal as the copolymer. The isophthalic acid copolymerized polyethylene terephthalate preferably contains 5 mol% or less of isophthalic acid. The polyester may be copolymerized with a copolymer component or copolymer alcohol component other than isophthalic acid in a range that does not impair the properties thereof, for example, in a proportion of 3 mol% or less with respect to the total acid component or the total alcohol component. . Examples of the copolymer acid component include aromatic dicarboxylic acids such as phthalic acid and 2,6-naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and 1,10-decanedicarboxylic acid. Examples of the alcohol component include aliphatic diols such as 1,4-butanediol, 1,6-hexanediol and neopentyl glycol, and alicyclic diols such as 1,4-cyclohexanedimethanol. it can. These can be used alone or in combination of two or more.

  When the polyester is polyethylene-2,6-naphthalenedicarboxylate, naphthalenedicarboxylic acid is used as the main dicarboxylic acid component, and ethylene glycol is used as the main glycol component. Examples of naphthalenedicarboxylic acid include 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and 1,5-naphthalenedicarboxylic acid. Among these, 2,6-naphthalenedicarboxylic acid is preferable. Here, “main” means at least 90 mol%, preferably at least 95 mol% of all repeating units in the constituent components of the polymer that is a component of the film of the present invention.

  In the case of a copolymer, a compound having two ester-forming functional groups in the molecule can be used as a copolymer component constituting the copolymer. Examples of such a compound include oxalic acid, adipic acid, phthalic acid, and sebacic acid. , Dodecanedicarboxylic acid, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, phenylindanedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, tetralindicarboxylic acid, decalindicarboxylic acid, diphenylether Dicarboxylic acid such as dicarboxylic acid, oxycarboxylic acid such as p-oxybenzoic acid, p-oxyethoxybenzoic acid, or propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, cyclohexanedi Divalent compounds such as methylene glycol, neopentyl glycol, ethylene oxide adduct of bisphenol sulfone, ethylene oxide adduct of bisphenol A, 9,9′-bis [4- (2-hydroxyethoxy) phenyl] fluorene, diethylene glycol, polyethylene glycol Alcohol can be preferably used.

  These compounds may be used alone or in combination of two or more. Of these, the acid component is preferably isophthalic acid, terephthalic acid, 4,4′-diphenyldicarboxylic acid, 2,7-naphthalenedicarboxylic acid, p-oxybenzoic acid, and the glycol component is trimethylene. Glycol, cyclohexanedimethylene glycol, neopentyl glycol, ethylene oxide adduct of bisphenol sulfone, 9,9′-bis [4- (2-hydroxyethoxy) phenyl] fluorene.

  The polyethylene-2,6-naphthalenedicarboxylate may be one in which a terminal hydroxyl group and / or a carboxyl group is partially or entirely blocked with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. Further, it may be one obtained by copolymerizing a very small amount of an ester-forming compound such as trimellitic acid, glycerin, pentaerythritol and the like within a range in which a substantially linear polymer is obtained.

  The polyester in the present invention is a conventionally known method, for example, a method of directly obtaining a low polymerization degree polyester by reaction of dicarboxylic acid and glycol, or a lower alkyl ester of dicarboxylic acid and glycol are conventionally known transesterification catalysts, such as sodium It can be obtained by performing a polymerization reaction in the presence of a polymerization catalyst after reacting with one or more of compounds containing potassium, magnesium, calcium, zinc, strontium, titanium, zirconium, manganese, and cobalt. it can. As a polymerization catalyst, antimony compounds such as antimony trioxide and antimony pentoxide, germanium compounds represented by germanium dioxide, tetraethyl titanate, tetrapropyl titanate, tetraphenyl titanate or a partial hydrolyzate thereof, titanyl ammonium oxalate , Titanium compounds such as potassium titanyl oxalate and titanium trisacetylacetonate can be used.

  When polymerization is performed via a transesterification reaction, a phosphorus compound such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, or normal phosphoric acid is usually added for the purpose of deactivating the transesterification catalyst before the polymerization reaction. However, the content of polyethylene-2,6-naphthalenedicarboxylate as the phosphorus element is preferably 20 to 100 ppm from the viewpoint of thermal stability of the polyester.

  The polyester may be converted into chips after melt polymerization, and further subjected to solid phase polymerization under heating under reduced pressure or in an inert gas stream such as nitrogen.

  In the present invention, the polyester is preferably a polyester having 90% by mole or more, preferably 95% or more, more preferably 97% or more of ethylene terephthalate units or ethylene-2,6-naphthalenedicarboxylate units.

  The intrinsic viscosity of the polyester is preferably 0.40 dl / g or more, and more preferably 0.40 to 0.90 dl / g. If the intrinsic viscosity is less than 0.40 dl / g, process cutting may occur frequently. On the other hand, if it is higher than 0.9 dl / g, melt viscosity is high and melt extrusion becomes difficult, and the polymerization time is long and uneconomical.

  It is preferable that the polyester film in the present invention contains substantially no particles. If the particles are contained, high transparency may be impaired, or the surface may become rough and it may be difficult to process the transparent conductive layer.

  In the polyester film of the present invention, the absolute value of the difference in thermal shrinkage between the longitudinal direction and the width direction of the film when treated at 200 ° C. for 10 minutes is 0.8% or less, preferably 0.5% or less, more preferably 0.3% or less. When the absolute value of the difference in thermal shrinkage exceeds 0.8%, when the semiconductor layer is baked, the adhesion between the transparent conductive layer of the laminated film and the porous semiconductor deteriorates, and when a dye-sensitized solar cell is produced As a result, sufficient photovoltaic performance cannot be obtained.

  In addition, when the polyester film is treated at 200 ° C. for 10 minutes, the heat shrinkage rate in the longitudinal direction of the film is preferably small in order to improve the adhesion between the transparent conductive layer and the porous semiconductor, and preferably 0 to 0.00. 5%, more preferably 0 to 0.3%.

  In order to perform photovoltaic power generation more efficiently, the polyester film in the present invention preferably has a haze value of 1.5% or less. A more preferred haze value is 1.0% or less, particularly preferably 0.5% or less.

  The three-dimensional centerline average roughness of the polyester film in the present invention is preferably 0.0001 to 0.02 μm on both sides, more preferably 0.0001 to 0.015 μm, and more preferably 0.0001 to 0.010 μm. is there. In particular, it is preferable that the three-dimensional center line average roughness of at least one surface is 0.0001 to 0.005 μm because the transparent conductive layer can be easily processed. The most preferable surface roughness of at least one surface is 0.0005 to 0.004 μm.

  It is preferable that the thickness of the polyester film in this invention is 10-500 micrometers, More preferably, it is 20-400 micrometers, More preferably, it is 50-300 micrometers.

  Next, the preferable manufacturing method of the polyester film in this invention is demonstrated. The glass transition temperature is abbreviated as Tg. In the polyester film of the present invention, the polyester is melt-extruded into a film form, cooled and solidified with a casting drum to form an unstretched film, and this unstretched film is once or twice or more in the longitudinal direction at Tg to (Tg + 60) ° C. The film is stretched so that the magnification is 3 to 6 times, and then stretched so that the magnification is 3 to 5 times in the width direction at Tg to (Tg + 60) ° C., and further 1 to 1 at Tm 180 ° C. to 255 ° C. if necessary. It can be obtained by performing a heat treatment for 60 seconds. In order to reduce the difference in thermal shrinkage between the longitudinal direction and the width direction of the polyester film and the thermal shrinkage in the longitudinal direction, a method of shrinking in the longitudinal direction in a heat treatment step as disclosed in JP-A-57-57628 Alternatively, as shown in JP-A-1-275031, a method of relaxing heat treatment in a suspended state may be used.

[Transparent conductive layer]
In the present invention, the transparent conductive layer formed on the polyester film is usually a conductive metal oxide (for example, fluorine-doped tin oxide, indium-tin composite oxide (ITO), indium-zinc composite oxide (IZO)). Etc.), metal thin films (eg, platinum, gold, silver, copper, aluminum, etc.), carbon materials can be used. This conductive layer may be a laminate of two or more or a composite. Of these, ITO and IZO are particularly preferred because of their high light transmittance and low resistance. The range of the surface resistance is preferably 100Ω / □ or less, and more preferably 40Ω / □ or less.

  The surface tension of the transparent conductive layer in the present invention is preferably 40 mN / m or more, more preferably 65 mN / m or more. When the surface tension is less than 40 mN / m, the adhesion between the transparent conductive layer and the porous semiconductor may be inferior. Particularly, when the surface tension is 65 mN / m or more, an aqueous coating liquid in which the main component of the solvent is water. The formation of the porous semiconductor layer by coating is easy and preferable.

  In order to achieve the above surface tension, (1) a method of activating the surface of a transparent conductive thin film with an acidic or alkaline solution, (2) a method of activating by irradiating the surface of the thin film with ultraviolet rays or an electron beam, Or (3) It is good to form a transparent conductive layer by the method of giving and activating by corona treatment and plasma treatment. Among them, the method of activating the surface by plasma treatment is particularly preferable because high surface tension can be obtained.

[Easily adhesive layer]
Moreover, in order to improve the adhesiveness of a polyester film and a transparent conductive layer, it is preferable to provide an easily bonding layer on the polyester film before providing a transparent conductive layer.

  The thickness of the easy adhesion layer is preferably 10 to 200 nm, more preferably 20 to 150 nm. If the thickness of the easy-adhesion layer is less than 10 nm, the effect of improving the adhesion is poor, and if it exceeds 200 nm, cohesive failure of the easy-adhesion layer tends to occur and the adhesion may be lowered.

  As a method of providing the easy-adhesion layer, a method of applying by coating in the production process of the polyester film is preferable, and it is preferable to apply to the polyester film before the orientation crystallization is completed. Here, examples of the polyester film before the crystal orientation is completed include, for example, an unstretched film, a uniaxially oriented film in which the unstretched film is oriented in either the longitudinal direction or the transverse direction, and two in the longitudinal direction and the transverse direction. It is possible to use a film stretched and oriented at a low magnification in the direction (a biaxially stretched film before it is finally re-stretched in the machine direction or the transverse direction to complete orientation crystallization). In particular, it is preferable to apply the aqueous coating liquid of the above composition to an unstretched film or a uniaxially stretched film oriented in one direction, and perform longitudinal stretching and / or lateral stretching and heat setting as it is.

  As the constituent material of the easy-adhesion layer, it exhibits excellent adhesion to both the polyester film and the transparent conductive layer. Specifically, polyester resin, acrylic resin, urethane acrylic resin, silicon acrylic resin, melamine resin, polysiloxane Resins can be exemplified. These resins can be used alone or as a mixture of two or more.

[Hard coat]
Furthermore, in order to improve the adhesion between the polyester film and the transparent conductive layer, particularly the durability of the adhesion, it is preferable to provide a hard coat layer on the easy adhesion layer before providing the transparent conductive layer. As a method of providing a hard coat layer, a method of coating on a polyester film provided with an easy adhesion layer is preferable. The hard coat layer may be composed of any material that exhibits excellent adhesion to both the easy-contact layer and the transparent conductive layer, such as an acrylic resin, a urethane resin, a silicon resin, a UV curable resin, and an epoxy resin. Examples thereof include a resin component such as a resin and a mixture of these with inorganic particles such as alumina, silica and mica. The thickness of the hard coat layer is preferably from 0.01 to 20 μm, particularly preferably from 1 to 10 μm.

[Antireflection layer]
For the purpose of increasing the light transmittance and improving the photovoltaic power generation efficiency, an antireflection layer may be provided on the surface opposite to the transparent conductive layer. As a method for providing the antireflection layer, a method in which a material having a refractive index different from that of the polyester film is formed in a single layer or two or more layers is preferably employed. In the case of a single layer structure, it is better to use a material having a refractive index smaller than that of the base film, and in the case of a multilayer structure of two or more layers, the layer adjacent to the laminated film has a larger refractive than the polyester film. It is preferable to select a material having a refractive index smaller than that of a material having a refractive index and a layer laminated thereon.

As a material constituting such an antireflection treatment layer, any material can be used as long as it satisfies the above-described refractive index relationship regardless of whether it is an organic material or an inorganic material. Preferred examples include CaF ₂ , MgF ₂ , Examples of the dielectric include NaAlF ₄ , SiO ₂ , ThF ₄ , ZrO ₂ , Nd ₂ O ₃ , SnO ₂ , TiO ₂ , CeO ₂ , ZnS, and In ₂ O ₃ .

  The method for laminating the antireflection treatment layer may be a dry coating method such as a vacuum deposition method, a sputtering method, a CVD method, or an ion plating method, or a wet coating method such as a gravure method, a reverse method, or a die method. Furthermore, prior to the lamination of the antireflection treatment layer, a known pretreatment such as a corona discharge treatment, a plasma treatment, a sputter etching treatment, an electron beam irradiation treatment, an ultraviolet ray irradiation treatment, a primer treatment, and an easy adhesion treatment may be performed.

[Porous semiconductor layer]
In the present invention, a porous semiconductor layer is formed on the transparent conductive layer of the laminated film described above. The porous semiconductor layer is formed by baking at least one oxide selected from the group consisting of titanium oxide, zinc oxide and tin oxide at 170 to 250 ° C. on the transparent conductive layer. This oxide constitutes a porous semiconductor layer as an n-type semiconductor. A semiconductor material in which a plurality of these semiconductors are combined may be used.

  In the present invention, for the semiconductor fine particle layer coated on the support film, in order to enhance the electronic contact between the semiconductor fine particles and to improve the adhesion to the support, 170 to 250 ° C., The heat treatment is preferably performed at 180 to 230 ° C., more preferably 190 to 220 ° C., and the porous semiconductor layer is baked on the film. When the heat treatment temperature is less than 170 ° C., the electronic contact of the semiconductor fine particles cannot be sufficiently enhanced, and when a dye-sensitized solar cell is produced, the photovoltaic power generation efficiency is lowered. On the other hand, when the heat treatment is performed at a temperature exceeding 250 ° C., the polyester film support is significantly deformed by heating, and the adhesion between the transparent conductive layer and the porous semiconductor layer is reduced.

  This porous semiconductor layer has a structure in which ultrafine semiconductor particles are sintered or fused. The particle size of the ultrafine particles is preferably 5 to 100 nm, particularly preferably 5 to 50 nm as the average particle size of the primary particles. Two or more kinds of fine particles having different particle size distributions may be mixed. For the purpose of scattering incident light and improving the light capture rate, semiconductor particles having a large particle size, for example, primary particles having an average particle size of about 300 nm are used. You may mix.

  Ultrafine particles constituting the porous semiconductor layer may be, for example, a known sol-gel method or gas phase pyrolysis method (published by Technical Education Publishing Co., 2001, supervised by Shozo Yanagida, “Basics and Applications of Dye-sensitized Solar Cells” or 1995. (See “Thin-film coating technology by sol-gel method” published by Japan Technical Information Association).

  The porous semiconductor layer is formed by, for example, a coating method, that is, by applying a dispersion containing the porous semiconductor on the transparent conductive layer of the laminated film and heating and drying to fix the porous layer on the support. Is desirable.

  At this time, in order to adjust the dispersion of semiconductor fine particles, in addition to the sol-gel method described above, a method of precipitating fine particles as a coprecipitation product of a chemical reaction in a solvent, ultrasonic irradiation or mechanical pulverization to form ultrafine particles. A method of pulverizing and dispersing can be used. As a dispersion medium, water or various organic solvents are used. When dispersing, for example, a polymer such as polyethylene glycol, hydroxyethyl cellulose, carboxymethyl cellulose, a surfactant, an acid or a chelating agent is used as a dispersion aid. Add a small amount, apply onto a support, and form a film.

  This coating should be performed using any method conventionally used for coating processing, such as the roller method, dipping method, air knife method, blade method, wire bar method, slide hopper method, extrusion method, and curtain method. Can do. Further, a spin method or a spray method using a general-purpose machine can be used. Application may be made using wet printing such as intaglio, rubber plate, screen printing, as well as 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.

  In addition, a method of supporting a thin film of particles by electrodeposition can be used. That is, the semiconductor fine particles are added to an appropriate low-conductivity solvent such as pure water, polar organic solvents such as alcohol, acetonitrile and THF, nonpolar organic solvents such as hexane and chloroform, or a mixed solvent thereof, so that there is no aggregation. The conductive resin sheet electrode to be electrodeposited and the counter electrode are made to face each other in parallel at a constant interval, the dispersion liquid is injected into the gap, and a DC voltage is applied between the electrodes. In this way, by selecting the concentration of the dispersion and the electrode interval, an electrodeposition film having a constant and uniform thickness is formed on the substrate electrode.

Dispersion of semiconductor fine particles, semiconductor fine particles support 1 m ² per may preferably 0.5~5~20g / ^{m 2,} more preferably applied in an amount of 5 to 10 g / ^{m 2.}

  In the present invention, with respect to the coated layer of semiconductor fine particles, 170 to 250 ° C., preferably 180 to 230 ° C., in order to enhance the electronic contact between the semiconductor fine particles and improve the adhesion to the support. More preferably, heat treatment is performed at 190 to 220 ° C., and the porous semiconductor layer is baked on the film. When the heat treatment temperature is less than 170 ° C., the electronic contact of the semiconductor fine particles cannot be sufficiently enhanced, and when a dye-sensitized solar cell is produced, the photovoltaic power generation efficiency is lowered. On the other hand, when the heat treatment is performed at a temperature exceeding 250 ° C., the polyester film support is significantly deformed by heating, and the adhesion between the transparent conductive layer and the porous semiconductor layer is reduced.

  Further, the semiconductor fine particles may be irradiated with ultraviolet light or the like that the fine particles absorb strongly, or the fine particle layer may be heated by irradiating the microwaves to enhance the physical bonding between the fine particles. .

  The porous semiconductor layer is preferably formed to have a thickness of 1 to 30 μm, more preferably 2 to 10 μm, and particularly preferably 2 to 6 μm. Within this range, high transparency can be obtained.

An undercoat layer may be provided on the transparent conductive layer in advance for the purpose of preventing the transparent conductive layer carrying the porous semiconductor from being electrically short-circuited with the counter electrode. As the undercoat layer, TiO ₂ , SnO ₂ , ZnO, Nb ₂ O ₅ , particularly TiO ₂ is preferable. This undercoat layer can be provided by, for example, a sputtering method in addition to the spray pyrolysis method described in Electrochim, Acta 40, 643 to 652 (1995). The preferred thickness of the undercoat layer is 5 to 1000 nm or less, particularly 10 to 500 nm.

[Preparation of dye-sensitized solar cell]
In order to produce a dye-sensitized solar cell using the electrode obtained by the present invention, for example, the following method can be used.
(1) A dye is adsorbed on the porous semiconductor layer of the electrode of the present invention. It has the property of absorbing light in the visible and infrared regions, such as organometallic complex dyes represented by ruthenium bipyridine complexes (ruthenium complexes), cyanine dyes, coumarin dyes, xanthene dyes, porphyrin dyes, etc. A dye solution is prepared by dissolving a dye in a solvent such as alcohol or toluene, and the porous semiconductor layer is immersed, or sprayed or applied to the porous semiconductor layer. (Electrode A)
(2) As the counter electrode, a thin platinum layer formed by sputtering on the transparent conductive layer side of the laminated film of the present invention is used. (Electrode B)
(3) The electrode A and the electrode B are overlapped by inserting a thermocompression-bondable polyethylene film frame spacer (thickness 20 μm), the spacer portion is heated to 120 ° C., and both electrodes are pressure-bonded. Further, the edge portion is sealed with an epoxy resin adhesive.
(4) An electrolyte aqueous solution containing lithium iodide and iodine (molar ratio 3: 2) and 3% by weight of nylon beads having an average particle diameter of 20 μm as a spacer through a small hole for injecting an electrolyte provided in the corner of the sheet in advance. inject. Thoroughly deaerate the inside and finally seal the small holes with an epoxy resin adhesive.

Next, the present invention will be described in more detail with reference to examples.
In addition, each characteristic value in an example was measured with the following method.
(1) Intrinsic viscosity Intrinsic viscosity ([η] dl / g) was measured with an o-chlorophenol solution at 35 ° C.

(2) Film thickness Using a micrometer (K-402B type manufactured by Anritsu Co., Ltd.), measurement is performed at 10 cm intervals in the continuous film forming direction and the width direction of the film, and a total of 300 film thicknesses are measured. did. The average value of the film thicknesses of the obtained 300 locations was calculated and used as the film thickness.

(3) Heat shrinkage rate The film was held in an oven set at 200 ° C. for 10 minutes in an unstrained state, and the dimensional change before and after each heat treatment in the film longitudinal direction (MD) and width direction (TD) Was calculated by the following equation as the heat shrinkage rate, and the heat shrinkage rate in the longitudinal direction (MD) and the width direction (TD) was obtained.
Thermal shrinkage% = ((L0−L) / L0) × 100
However, L0: Distance between gauge points before heat treatment, L: Distance between floating points after heat treatment

(4) Thickness of coating layer A small piece of film is embedded in an epoxy resin (Epomount manufactured by Refinetech Co., Ltd.), sliced to 50 nm thickness with the embedded resin using Microtome2050 manufactured by Reichert-Jung, and transmitted. The film was observed with a scanning electron microscope (LEM-2000) at an acceleration voltage of 100 KV and a magnification of 100,000, and the thickness of the coating layer was measured.

(5) Surface resistance value Any five points were measured using a 4-probe type surface resistivity measuring device [Made by Mitsubishi Chemical Corporation, Loresta GP], and the average value was used as a representative value.

(6) Surface tension Contact angles: θw and θy of water having a known surface tension and water-containing methylene to the transparent conductive thin film were measured using a contact angle meter (“CA-X type” manufactured by Kyowa Interface Science Co., Ltd.) It measured on 25 degreeC and 50% RH conditions. Using these measured values, the surface tension γs of the transparent conductive thin film was calculated as follows.
The surface tension γs of the transparent conductive thin film is the sum of the dispersive component γsd and the polar component γsp. That is,
γs = γsd + γsp (Formula 1)
From the Young equation,
γs = γsw + γw · cos θw (Formula 2)
γs = γsy + γy · cos θy (Formula 3)
Here, γsw is the tension acting between the transparent conductive thin film and water, γsw is the tension acting between the transparent conductive thin film and methylene iodide, γw is the surface tension of water, and γy is the surface tension of methylene iodide. It is.
From the Fowkes equation,
γ _sw = γ _s + γ _w −2 × (γ _sd · γ _wd ) ^1/2 −2 × (γ _sp · γ _wp ) ^1/2 (Formula 4)
γ _sy = γ _s + γ _y −2 × (γ _sd · γ _yd ) ^1/2 −2 × (γ _sp · γ _yp ) ^1/2 (Formula 5)
It is. Where γ _wd is the dispersive component of the surface tension of water, γ _wp is the polar component of the surface tension of water, γ _yd is the dispersive component of the surface tension of methylene iodide, and γ _yp is the surface tension of methylene iodide. It is a polar component.
By solving the simultaneous equations of Equations 1 to 5, the surface tension γ _s = γ _sd + γ _sp of the transparent conductive thin film can be calculated. At this time, the surface tension of water (γ _w ): 72.8 mN / m, the surface tension of methylene iodide (γ _y ): 50.5 mN / m, the dispersive component of the surface tension of water (γ _wd ): 21. 8 mN / m, polar component of surface tension of water (γ _wp ): 51.0 mN / m, dispersive component of surface tension of methylene iodide (γ _y d): 49.5 mN / m, surface tension of methylene iodide Polar component (γ _yp ): 1.3 mN / m was used.

(7) Adhesiveness of porous semiconductor layer Gauze was reciprocated 5 times with a load of 50 g / cm ^{2 on} the surface of the porous semiconductor layer, and the degree of peeling was evaluated with the aim. The case where peeling was not observed was indicated by ◯, the case where peeling was partially observed was indicated by Δ, and the case where peeling was completely observed was indicated by ×.

(8) photovoltaic efficiency: 25mm to form a ^2-sized dye-sensitized solar cell, the I-V measurements in the ^second irradiation under AM1.5 simulated solar light 100 mW / cm, open circuit voltage, short circuit current density, fill factor, We calculated photovoltaic power generation efficiency. In addition, the spectrophotometer CEP-2000 type | mold spectral sensitivity measuring apparatus was used for the measurement.

[Example 1]
<Creation of film polymer>
Using 100 parts of dimethyl naphthalene-2,6-dicarboxylate and 60 parts of ethylene glycol as a transesterification catalyst, 0.03 part of manganese acetate tetrahydrate, and gradually increasing the temperature from 150 ° C. to 238 ° C. for 120 minutes A transesterification reaction was performed. On the way, when the reaction temperature reached 170 ° C., 0.024 part of antimony trioxide was added, and after the transesterification reaction, trimethyl phosphate (135 ° C. in ethylene glycol, 0.11 to 0.16 MPa for 5 hours) was added. The solution heat-treated under pressure: 0.023 parts in terms of trimethyl phosphate was added. Thereafter, the reaction product is transferred to a polymerization reactor, heated to 290 ° C., subjected to a polycondensation reaction under a high vacuum of 27 Pa or less, and contains substantially no particles having an intrinsic viscosity of 0.62 dl / g. Polyethylene-2,6-naphthalenedicarboxylate was obtained.

<Creation of polyester film>
The polyethylene-2,6-naphthalenedicarboxylate pellets were dried at 170 ° C. for 6 hours, then fed to an extruder hopper, melted at a melting temperature of 305 ° C., and filtered through a stainless steel fine wire filter having an average opening of 17 μm. The film was extruded through a 3 mm slit die on a rotary cooling drum having a surface temperature of 60 ° C. and rapidly cooled to obtain an unstretched film. The unstretched film thus obtained was preheated at 120 ° C., and further heated by an IR heater at 850 ° C. from above 15 mm between low-speed and high-speed rolls and stretched 3.2 times in the longitudinal direction. The following coating agent A was applied to one side of the film after the longitudinal stretching with a roll coater so that the coating thickness after drying was 0.08 μm, thereby forming an easy-contact layer.

  Subsequently, it was supplied to the tenter and laterally at 140 ° C. 3. Stretched 3 times. The obtained biaxially oriented film was heat-set at a temperature of 244 ° C. for 5 seconds to obtain a polyester film having an intrinsic viscosity of 0.58 dl / g and a thickness of 125 μm. The thermal shrinkage in the longitudinal direction of the polyester film when treated at 200 ° C. for 10 minutes is 0.58%, the thermal shrinkage in the width direction is 0.12%, and the difference between the thermal shrinkage in the longitudinal direction and the width direction is 0. .46%.

<Coating agent A>
92 parts of dimethyl terephthalate, 12 parts of dimethyl isophthalate, 17 parts of 5-sodium sulfoisophthalic acid, 54 parts of ethylene glycol and 62 parts of diethylene glycol were charged into the transesterification reactor, and 0.05 part of tetrabutoxy titanium was added thereto. The temperature was controlled at 230 ° C. in a nitrogen atmosphere, and the resulting methanol was distilled off to conduct a transesterification reaction. Subsequently, the temperature of this reaction system was gradually raised to 255 ° C., and the inside of the system was subjected to a polycondensation reaction under a reduced pressure of 1 mmHg to obtain a copolyester.

  25 parts of this polyester was dissolved in 75 parts of tetrahydrofuran, and 75 parts of water was dropped into the resulting solution under high-speed stirring at 10,000 rpm to obtain a milky white dispersion, and then this dispersion was subjected to a reduced pressure of 20 mmHg. Distillation was performed, and tetrahydrofuran was distilled off to obtain an aqueous dispersion of polyester having a solid content of 25% by weight.

  Next, 3 parts of sodium lauryl sulfonate as a surfactant and 181 parts of ion-exchanged water are charged into a four-necked flask and the temperature is raised to 60 ° C. in a nitrogen stream, and then 0.5% ammonium persulfate is used as a polymerization initiator. 0.2 part of sodium hydrogen nitrite was added, and a mixture of 70 parts of methyl methacrylate, 25 parts of ethyl acrylate and 5 parts of N-methylol acrylamide as the monomers was added over 3 hours, and the liquid temperature was 60- It was added dropwise while adjusting to 70 ° C. After completion of dropping, the reaction was continued with stirring while maintaining the same temperature range for 2 hours, and then cooled to obtain an acrylic aqueous dispersion having a solid content of 35% by weight.

  On the other hand, silica filler (average particle size: 100 nm) (trade name Snowtex ZL manufactured by Nissan Chemical Co., Ltd.) is 0.3% by weight, polyoxyethylene (n = 9) lauryl ether (manufactured by Kao Corporation) as a wetting agent. An aqueous solution to which 0.4% by weight of Emergen 109P) was added was prepared.

  Coating agent A was prepared by mixing 10 parts by weight of the above polyester aqueous dispersion, 3 parts by weight of the acrylic water dispersion and 87 parts by weight of the aqueous solution.

<Transparent conductive layer formation>
A transparent conductive layer made of ITO having a film thickness of 280 nm was formed on one surface on which the easy-contact layer of the polyester film was formed by the method described in Example 6 of JP-A-63-908. The surface resistance value of the transparent conductive layer was 18Ω / □. Next, using a normal pressure plasma surface treatment apparatus (AP-T03-L manufactured by Sekisui Chemical Co., Ltd.), the surface of the transparent conductive layer was subjected to plasma treatment at 1 m / min under a nitrogen stream (60 L / min). At this time, the surface resistance value was 18Ω / □, and the surface tension was 71.5 mN / m.

<Antireflection layer>
A Y ₂ O ₃ layer having a thickness of 75 nm and a refractive index of 1.89 is formed on the surface of the laminated film opposite to the surface on which the transparent conductive layer is formed, and a TiO ₂ layer having a refractive index of 2.3 and a thickness of 120 nm is formed thereon. Further, a SiO ₂ film having a thickness of 90 nm and a refractive index of 1.46 was formed thereon by a high frequency sputtering method to form an antireflection treatment layer. In forming each electrostatic thin film, the degree of vacuum was 1 × 10 ⁻³ Torr, and Ar: 55 sccm and O ₂ : 5 sccm were flowed as gases. The substrate was kept at room temperature without heating or cooling during the film forming process.

<Porous semiconductor layer formation>
On the transparent conductive layer of the laminated film, a commercially available paste for forming a low-temperature-forming porous titanium dioxide layer (SP-200 manufactured by Showa Denko) is applied with a bar coater and heat-treated at 200 ° C. for 30 minutes in the atmosphere. And a porous titanium dioxide layer was formed to a thickness of 5 μm, and an electrode of a dye-sensitized solar cell was prepared. When the adhesion was evaluated, no peeling was observed and the evaluation was good.

<Creation of dye-sensitized solar cell>
This electrode was immersed in a 300 μM ethanol solution of ruthenium complex (Ru535bisTBA, manufactured by Solaronix) for 24 hours to adsorb the ruthenium complex on the surface of the photoactive electrode. A counter electrode was prepared by depositing a Pt film on the transparent conductive layer of the laminated film by sputtering. The electrode and the counter electrode are overlapped via a thermocompression-bondable polyethylene film frame spacer (thickness 20 μm), the spacer portion is heated to 120 ° C., and both electrodes are pressure-bonded. Further, the edge portion is sealed with an epoxy resin adhesive. Electrolyte solution (0.5 M lithium iodide, 0.05 M iodine, 0.5 M 4-tert-butylpyridine, 0.5 M 1,2-dimethyl-3-propylimidazolium iodide, average particle size 20 μm (3-methoxypropionitrile solution containing 3% by weight of nylon beads) and then sealed with an epoxy adhesive.

As a result of performing IV measurement (effective area 25 mm ² ) of the completed dye-sensitized solar cell, the open-circuit voltage, the short-circuit current density, and the fill factor were 0.71 V, 7.1 mA / cm ² , and 0.68, respectively. As a result, the photovoltaic power generation efficiency was 3.4%.

[Examples 2 and 3 and Comparative Example 1]
A laminated film, an electrode, and a dye-sensitized solar cell were obtained in the same manner as in Example 1 except that the longitudinal stretch ratio, lateral stretch ratio, and heat setting temperature were changed as shown in Table 1 when the polyester film was prepared. Table 1 shows the thermal shrinkage ratio and the difference after treatment at 200 ° C. for 10 minutes in the longitudinal and lateral directions of the polyester film, the adhesion of the porous semiconductor layer, and the photovoltaic power generation efficiency of the dye-sensitized solar cell. Met.

[Example 4]
A polyester film was prepared in the same manner as in Example 1 except that the coating agent for forming the easy-adhesion layer was changed to the coating agent B. After the polyester film was suspended, the relaxation rate was 0.9% and the temperature was 205 ° C. Heat relaxed. The thermal shrinkage in the longitudinal direction of the polyester film when treated at 200 ° C. for 10 minutes is 0.13%, the thermal shrinkage in the width direction is 0.03%, and the difference between the thermal shrinkage in the longitudinal direction and the width direction is 0. 10%.

<Hard coat>
Using the obtained polyester film, a UV curable hard coat agent (Desolite R7501 manufactured by JSR) was applied to the easy-contact layer side so as to have a thickness of about 5 μm, and UV cured to form a hard coat layer.

<Transparent conductive layer formation>
A transparent conductive layer made of ITO having a thickness of 400 nm was formed on one surface on which the hard coat layer was formed by a direct current magnetron sputtering method using an ITO target (tin concentration was 10% by weight in terms of tin dioxide). The transparent conductive layer is formed by the sputtering method after the inside of the chamber is evacuated to 5 × 10 ⁻⁴ Pa before plasma discharge, and then a mixed gas of argon and oxygen (oxygen concentration is 0.5 vol%) is introduced into the chamber. Then, the pressure was set to 0.3 Pa, and 1000 W was applied to the ITO target. The surface resistance value of the transparent conductive layer was 19Ω / □.

  Next, using a normal pressure plasma surface treatment apparatus (AP-T03-L manufactured by Sekisui Chemical Co., Ltd.), the surface of the transparent conductive layer was subjected to plasma treatment at 1 m / min under a nitrogen stream (60 L / min). At this time, the surface resistance value was 20Ω / □, and the surface tension was 71.8 mN / m.

  Example 1 except that an antireflection layer was formed on the surface of the laminated film opposite to the surface on which the transparent conductive layer was formed, as in Example 1, and then the heat treatment temperature after applying the titanium dioxide paste was 220 ° C. A porous semiconductor layer was formed in the same manner as described above to prepare an electrode of a dye-sensitized solar cell. When the adhesion evaluation was performed, no peeling was observed, and the evaluation was good.

Using this electrode, a dye-sensitized solar cell was prepared in the same manner as in Example 1. As a result of the IV measurement (effective area 25 mm ² ), the open circuit voltage, the short circuit current density, and the fill factor are 0.70 V, 8.5 mA / cm ² , and 0.72, respectively. Was 4.3%.

<Coating agent B>
A reactor was charged with 66 parts of dimethyl 2,6-naphthalenedicarboxylate, 47 parts of dimethyl isophthalate, 8 parts of dimethyl 5-sodium sulfoisophthalate, 54 parts of ethylene glycol, and 62 parts of diethylene glycol, and 0.05 parts of tetrabutoxy titanium. Was added and heated under a nitrogen atmosphere while controlling the temperature at 230 ° C., and the produced methanol was distilled off to conduct a transesterification reaction. Subsequently, the temperature of the reaction system was gradually raised to 255 ° C., and the pressure inside the system was reduced to 1 mmHg to carry out a polycondensation reaction to obtain a polyester. 25 parts of this polyester was dissolved in 75 parts of tetrahydrofuran, and 75 parts of water was dropped into the resulting solution under high-speed stirring at 10,000 rpm to obtain a milky white dispersion. Then, this dispersion was subjected to a reduced pressure of 20 mmHg. Distillation was performed, and tetrahydrofuran was distilled off to obtain an aqueous dispersion of polyester having a solid content of 25% by weight.

  Next, 3 parts of sodium lauryl sulfonate as a surfactant and 181 parts of ion-exchanged water are charged into a four-necked flask and the temperature is raised to 60 ° C. in a nitrogen stream, and then 0.5% ammonium persulfate is used as a polymerization initiator. Part, 0.2 part of sodium hydrogen nitrite is added, and further monomers 30.1 parts of methyl methacrylate, 21.9 parts of 2-isopropenyl-2-oxazoline, polyethylene oxide (n = 10) methacrylic acid A mixture of 39.4 parts and 8.6 parts of acrylamide was added dropwise over 3 hours while adjusting the liquid temperature to 60 to 70 ° C. After completion of dropping, the reaction was continued with stirring while maintaining the same temperature range for 2 hours, and then cooled to obtain an acrylic aqueous dispersion having a solid content of 35% by weight.

  On the other hand, 0.2% by weight of silica filler (average particle size: 100 nm) (trade name Snowtex ZL manufactured by Nissan Chemical Co., Ltd.), polyoxyethylene (n = 7) lauryl ether (Sanyo Chemical Co., Ltd.) as a wetting agent An aqueous solution containing 0.3% by weight of the trade name NAROACTY N-70) was prepared.

  A coating agent B was prepared by mixing 8 parts by weight of the polyester aqueous dispersion, 7 parts by weight of the acrylic water dispersion and 85 parts by weight of the aqueous solution.

[Examples 5 and 6 and Comparative Examples 2 and 3]
In Example 4, electrodes were prepared by changing the heat treatment temperature of the porous semiconductor layer as shown in Table 2. Table 2 shows the adhesion of the porous semiconductor layer and the photovoltaic efficiency of the dye-sensitized solar cell prepared using this electrode.

  The present invention can be suitably used as a method for producing a dye-sensitized solar cell electrode.

Claims (2)

  A transparent conductive layer is formed on one side of a polyester film in which the absolute value of the difference in thermal shrinkage between the longitudinal direction and the width direction of the film when treated at 200 ° C. for 10 minutes is 0.8% or less. A method for producing a dye-sensitized solar cell electrode, comprising forming a porous semiconductor layer by baking at least one oxide selected from the group consisting of zinc and tin oxide at 170 to 250 ° C.   The electrode for dye-sensitized solar cells manufactured with the manufacturing method of Claim 1.