KR20120112113A - Composition for transparent conductive film of solar cell and transparent conductive film - Google Patents

Abstract

PURPOSE: A transparent conductive membrane composition is provided to easily obtain a transparent conductive film capable of improving powder generation efficiency of a thin film solar cell. CONSTITUTION: A transparent conductive membrane composition comprises conductive oxide particles and a binder cured by heating. The binder comprises organotrialkoxysilane indicated in chemical formula 1: R^1Si(OR^2)3 and/or a hydrolysate thereof. In chemical formula 1, R^1 is a C1-12 monovalent hydrocarbon group, R^2 is a C1-4 linear or branched alkyl group. A comprised amount of the organotrialkoxysilane and/or a hydrolysate thereof is 50-95 parts by weight based on 100.0 parts by weight of the binder.

Description

Transparent conductive film composition and transparent conductive film for solar cells TECHNICAL FIELD OF COMPARATIVE CONFICT FILM OF SOLAR CELL AND TRANSPARENT CONDUCTIVE FILM

This invention relates to the composition for transparent conductive films, and a transparent conductive film. More specifically, it is related with the composition for transparent conductive films for thin film solar cells, a transparent conductive film, the solar cell containing this transparent conductive film, and the manufacturing method of the transparent conductive film for thin film solar cells.

At present, the environmental protection of the clean energy research and development, commercialization is in progress, the solar cell is attracting attention because the solar energy as an energy source is endless and pollution-free. Conventionally, bulk solar cells of single crystal silicon or polycrystalline silicon have been used for solar cells. However, since bulk solar cells have high manufacturing costs and low productivity, development of solar cells in which the amount of silicon is reduced is urgently needed. .

So, for example, the thickness is 0.3? Development of thin-film solar cells using semiconductors such as amorphous silicon having a thickness of 2 µm has been energetically performed. Since this thin film solar cell is a structure which forms the semiconductor layer of the quantity required for photoelectric conversion on a glass substrate or a heat resistant plastic substrate, it has advantages, such as being thin, light weight, low cost, and easy to enlarge a large area.

The thin film solar cell has a super straight structure and a sub straight structure, and since the super straight structure injects sunlight from the light-transmissive substrate side, it is usually formed in the order of the substrate-transparent electrode-photoelectric conversion layer-backside electrode. Take the structure

In this thin film solar cell, electrodes and reflecting films have conventionally been formed by a vacuum film forming method such as sputtering, but in general, a large cost is required for the introduction, maintenance and operation of a large vacuum film forming apparatus. In order to improve this point, the technique of forming a transparent conductive film and a conductive reflecting film by the wet coating method which is a cheaper manufacturing method using the composition for transparent conductive films and the composition for a conductive reflecting film is disclosed (patent document 1).

Japanese Unexamined Patent Publication No. 2009-88489

This invention makes it a subject to improve the transparent conductive film manufactured by said wet coating method. The present inventors improved the composition for a transparent conductive film, and the reflection light at the transparent conductive film-photoelectric conversion layer interface increases by increasing the difference of the refractive index of the transparent conductive film used by a wet coating method, and the refractive index of a photoelectric conversion layer, It was found that the power generation efficiency of a thin film solar cell can be improved by the returned light to this increased photoelectric conversion layer. The same technique can be applied to sub-straight solar cells and bulk silicon solar cells.

This invention relates to the composition for transparent conductive films for thin film solar cells which solved the said subject by the structure shown below, and a transparent conductive film.

The 1st aspect of this invention contains electroconductive oxide particle and the binder hardened | cured by heating, and a binder is a general formula (1): R <^1> Si (OR <^2> ) ₃ (In formula, R <^1>). Silver has 1? Is a 12-valent monovalent hydrocarbon group, R ² Carbon number: 1? Organotrialkoxysilane and / or its hydrolyzate represented by the formula (4) which is a linear or branched alkyl group of 4), The composition for transparent conductive films for thin film solar cells characterized by the above-mentioned.

The 2nd aspect of this invention is a composition for transparent conductive films which concerns on the said 1st aspect, The organotrialkoxysilane represented by the said General formula (1): R <^1> Si (OR <^2> ) ₃ , and / or its hydrolyzate , Binder: 50? It is a composition for transparent conductive films for thin film solar cells containing 95 mass parts.

A third aspect of the present invention is the composition for transparent conductive films according to the first or second aspect, wherein the binder is an organotrialkoxysilane represented by the general formula (1): R ¹ Si (OR ² ) ₃ . And a binder component formed of a water, an organic solvent, and a mixture of both or one of an acid and an alkali as a catalyst, and a composition for a transparent conductive film for a thin film solar cell.

The 4th aspect of this invention is a composition for transparent conductive films which concerns on the aspect in any one of said 1st-3rd, Any one or both of the polymeric binder or nonpolymeric binder in which the said binder is further hardened by heating. It is a composition for transparent conductive films for thin film solar cells comprising a.

5th aspect of this invention is a composition for transparent conductive films for thin film solar cells which concerns on any one of said 1st-4th aspect, The said binder contains silsesquioxane, The composition for transparent conductive films characterized by the above-mentioned. to be.

A 6th aspect of this invention is a composition for transparent conductive films for thin film solar cells which further contains a coupling agent as a composition for thin film solar cells which concerns on any one of said 1st-5th.

A 7th aspect of this invention is a composition for transparent conductive films for thin film solar cells which concerns on the said 6th aspect, Comprising: It is a composition for transparent conductive films for thin film solar cells whose said coupling agent is a silane coupling agent.

The composition for transparent conductive films for thin film solar cells of this invention which concerns on any one of the above may further contain a low resistance agent and a water-soluble cellulose derivative. Moreover, composition for transparent conductive films: About 65 mass parts, 65? A 99 mass parts dispersion medium may also be included.

An eighth aspect of the present invention includes conductive oxide particles and a cured binder, wherein the cured binder is represented by General Formula (1): R ¹ Si (OR ² ) ₃ (wherein R ¹ Silver has 1? Is a 12-valent monovalent hydrocarbon group, R ² Carbon number: 1? It is a transparent conductive film for thin film solar cells containing the hydrolyzate of organotrialkoxysilane represented by the linear or branched alkyl group of 4).

A ninth aspect of the present invention is a transparent conductive film for a thin film solar cell according to the eighth aspect, wherein the cured binder contains silsesquioxane.

A tenth aspect of the present invention is the transparent conductive film for the thin film solar cell according to the eighth or ninth aspect, wherein the cured binder further includes a cured polymer binder or a nonpolymer binder. It is a transparent conductive film.

The transparent conductive film for the thin film solar cell of the said invention can be manufactured using said composition for transparent conductive films.

An eleventh aspect of the present invention is a thin film solar cell including a transparent conductive film according to any one of the eighth to tenth aspects as a solar cell.

Said thin film solar cell may be equipped with a base material, a transparent electrode layer, a light conversion layer, and the transparent conductive film of this invention.

The manufacturing method of the transparent conductive film for thin film solar cells of this invention is a manufacturing method of the transparent conductive film of a thin film solar cell provided with a base material, a transparent electrode layer, a photoelectric conversion layer, and a transparent conductive film in this order, on a transparent electrode layer of a base material. After the composition for transparent conductive films of this invention was apply | coated by the wet coating method on the formed photoelectric conversion layer, and a transparent conductive coating film was formed, the base material which has a transparent conductive coating film is 130 degreeC. It baked at 400 degreeC, and thickness: 0.03? It is a manufacturing method of the transparent conductive film for thin film solar cells characterized by forming a 0.5 micrometer transparent conductive film.

That is, the 12th aspect of this invention is a manufacturing method of the transparent conductive film for thin film solar cells, As a manufacturing method of the transparent conductive film of a thin film solar cell provided with a base material, a transparent electrode layer, a photoelectric conversion layer, and a transparent conductive film in this order. , On the photoelectric conversion layer formed on the transparent electrode layer of the base material, conductive oxide particles and a binder cured by heating, wherein the binder is a general formula (1): R ¹ Si (OR ² ) ₃ (wherein ^One Silver has 1? Is a 12-valent monovalent hydrocarbon group, R ² Carbon number: 1? After applying the composition for transparent conductive films containing organotrialkoxysilane represented by the linear or branched alkyl group of 4, and / or its hydrolyzate by a wet coating method, and forming a transparent conductive coating film, a transparent conductive coating film Is the substrate having a 130? It baked at 400 degreeC, and thickness: 0.03? It is a manufacturing method of the transparent conductive film characterized by forming a transparent conductive film of 0.5 micrometer.

A thirteenth aspect of the present invention is a method for producing a transparent conductive film for a thin film solar cell according to the twelfth aspect, wherein the composition for transparent conductive film is represented by the general formula (1): R ¹ Si (OR ² ) ₃ . Organotrialkoxysilane and / or its hydrolyzate is 50? To 100 parts by mass of a binder; It is 95 mass parts, The manufacturing method of the transparent conductive film characterized by the above-mentioned.

A fourteenth aspect of the present invention is the method for producing a transparent conductive film according to the thirteenth aspect, wherein the binder of the composition for transparent conductive film is an organo represented by the general formula (1): R ¹ Si (OR ² ) ₃ . It is a manufacturing method of the transparent conductive film characterized by including the binder component formed from the non-alkoxysilane, water, an organic solvent, and a mixture of both or one of the acid and alkali as a catalyst.

Said binder component is 0 to said mixture. 30 at a temperature of 60 ℃? It can form by reacting for 360 minutes.

A fifteenth aspect of the present invention is a method for producing a transparent conductive film for a thin film solar cell according to the twelfth to fourteenth aspects, wherein the composition for transparent conductive film is further cured by heating with a polymeric binder or a nonpolymeric binder. It is a manufacturing method of the transparent conductive film containing any one or both of them.

A sixteenth aspect of the present invention is a method for producing a transparent conductive film for a thin film solar cell according to the twelfth to fifteenth aspects, wherein the binder contains silsesquioxane.

A seventeenth aspect of the present invention is a method for producing a transparent conductive film for a thin film solar cell according to any one of the twelfth to sixteenth aspects, wherein the composition for transparent conductive film further comprises a coupling agent. It is a manufacturing method.

An eighteenth aspect of the present invention is a method for producing a transparent conductive film for a thin film solar cell according to the seventeenth aspect, wherein the coupling agent is a silane coupling agent.

A nineteenth aspect of the present invention is a method for producing a transparent conductive film for a thin film solar cell according to any one of the twelfth to eighteenth aspects, which is a wet coating method, a spray coating method, a dispenser coating method, a spin coating method, It is a manufacturing method of the transparent conductive film using the knife coating method, the slit coating method, the inkjet coating method, the die coating method, the screen printing method, the offset printing method, or the gravure printing method.

The composition for transparent conductive films of this invention can be apply | coated and baked on a photoelectric conversion layer by a wet coating method. It is thought that a micropore structure is formed in the transparent conductive film after hardening, and the refractive index of a transparent conductive film falls by this micropore structure. Therefore, the difference between the refractive index of a transparent conductive film and the refractive index of a photoelectric conversion layer becomes large, the reflected light in a transparent conductive film-photoelectric conversion layer interface increases, and the return light to this increased photoelectric conversion layer produces the power generation efficiency of a thin film solar cell. It is possible to improve. Therefore, using the composition for transparent conductive films of this invention, the transparent conductive film which can improve the power generation efficiency of a thin film solar cell can be obtained simply.

According to the transparent conductive film for the thin film solar cell of the present invention, the reflected light at the transparent conductive film-photoelectric conversion layer interface increases, and the returned light to the increased photoelectric conversion layer facilitates the thin film solar cell having improved power generation efficiency. You can get it.

According to the method for producing a transparent conductive film for the thin film solar cell of the present invention, a transparent conductive film can be formed without using a large amount of vacuum equipment, and a thin film solar cell with high power generation efficiency can be produced easily and at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the cross section of the thin film solar cell of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated concretely based on embodiment. In addition, unless otherwise indicated,% is the mass% except the case where numerical value is inherent.

[Composition for Transparent Conductive Film for Super Straight Thin Film Solar Cell]

Transparent conductive film compositions for the thin film solar cell of the present invention (referred to as a transparent conductive film composition is) is, the conductive oxide particles and comprises a binder that is cured by heat, and the binder is the general formula ^(1): R 1 Si (OR ² ) ₃ (wherein R ¹ Silver has 1? Is a 12-valent monovalent hydrocarbon group, R ² Carbon number: 1? Organotrialkoxysilane and / or its hydrolyzate represented by (4) is a linear or branched alkyl group.

Electroconductive oxide particle gives electroconductivity to the hardened | cured material of the composition for transparent conductive films, ie, a transparent conductive film. The conductive oxide particles are selected from the group consisting of tin oxide powder of ITO (Indium Tin Oxide), ATO (Antimony Tin Oxide), and Al, Co, Fe, In, Sn, and Ti. Preferred are zinc oxide powders containing at least one metal, such as ITO, ATO, AZO (Aluminum Zinc Oxide: Aluminum Doped Zinc Oxide), IZO (Indium Zinc Oxide: Indium Doped Zinc Oxide), TZO ( Tin Zinc Oxide: tin dope zinc oxide) is more preferable. Moreover, in order to maintain stability in a dispersion medium, the average particle diameter of electroconductive oxide fine particles is 10? It is preferable to exist in the range of 100 nm, Among these, 20? It is more preferable in it being in the range of 60 nm. Here, an average particle diameter is measured by the BET method by specific surface area measurement. For example, specific surface area measurement can be performed using QUANTACHROME AUTOSORB-1 by Quantachrome Instruments.

The binder is a general formula (1): R ¹ Si (OR ² ) ₃ (In formula, R ¹ Silver has 1? Is a 12-valent monovalent hydrocarbon group, R ² Carbon number: 1? Organotrialkoxysilane and / or its hydrolyzate which are represented by the linear or branched alkyl group of 4). This organotrialkoxysilane and / or its hydrolyzate is considered to form a micropore structure in a transparent conductive film, and this micropore structure can reduce the refractive index of a transparent conductive film.

Examples of R ¹ include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group and dodecyl group; Cycloalkyl groups such as cyclohexyl group; Aralkyl groups such as 2-phenylpropyl group; Functional group containing at least 1 sort (s) chosen from the group which consists of an aryl group, such as a phenyl group and a tolyl group, is preferable, A methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, or a phenyl group controls hydrolysis reaction, It is more preferable from the viewpoint of micropore structure formation. R ¹ Since silver provides a stress relaxation property to a transparent conductive film, the fall of conversion efficiency in a heat cycle test can be suppressed and a stable thin film solar cell can be provided in a long term.

A methyl group, an ethyl group, a propyl group, a butyl group etc. are mentioned as R <^2> , A methyl group, an ethyl group, or a methyl ethyl group is more preferable from a viewpoint of hydrolysis reaction control.

Examples of the organotrialkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltris (methoxyethoxy) silane, ethyltrimethoxysilane, phenyltrimethoxysilane and phenyl Triethoxysilane etc. are mentioned, Methyl trimethoxysilane, methyl triethoxysilane, phenyl trimethoxysilane, and phenyl triethoxysilane are preferable from a viewpoint of hydrolysis reaction control.

The binder is a binder formed by using the organotrialkoxysilane represented by the general formula (1): R ¹ Si (OR ² ) ₃ , water and an organic solvent, and a mixture of both or one of an acid and an alkali as a catalyst. You may also contain a component. In said mixture, hydrolysis and polycondensation reaction of organotrialkoxysilane generate | occur | produce, and the binder containing this component will contain the said organotrialkoxysilane and / or its hydrolyzate.

Examples of the acid used as the catalyst include hydrochloric acid, nitric acid, phosphoric acid, formic acid, acetic acid, propionic acid, oxalic acid and citric acid, and nitric acid, formic acid and acetic acid are preferable from the viewpoint of hydrolysis reaction control. The thing used for hydrolysis is ion-exchange water and pure water. For 1 mole of organotrialkoxysilane, the catalyst is 1 × 10 ⁻³ ? 1 * 10 <^-1> mol is preferable and water is 2? 10 moles are preferred. As for the acid and alkali to be used as a catalyst, it is preferable to slowly add as low a concentration as possible to gently control the hydrolysis and polycondensation reactions.

Examples of the alkali used for promoting the polycondensation of the hydrolyzate include sodium hydroxide, potassium hydroxide, ammonia, monomethylamine, monoethylamine, and the like, and ammonia and monoethylamine are used to control polycondensation reaction and low residue. It is preferable from a viewpoint of an impurity. The amount of alkali added is 1 × 10 ⁻³ ? With respect to 100 parts by mass of the mixture of water and water and an organic solvent. About 5 parts by weight is preferable. For example, when ammonia is used, it is 0.001 to 100 parts by mass of water and a mixture of water and an organic solvent. About 1 weight part is preferable.

As an organic solvent used for reaction, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, acetone, diethyl ether, tetrahydrofuran, diacetone alcohol And methanol, ethanol, isopropanol, acetone and diacetone alcohol are preferable. One type of organic solvent may mix 2 or more types. An organic solvent is used as a diluent for adjusting reaction rate. The amount of the organic solvent added is such that in the reaction system in which an organic solvent is added to silicon alkoxide, water and a catalyst, the concentration of silica in the silicon alkoxide is 3? It is preferable to adjust so that it may be about 30 mass%.

As hydrolysis conditions, in order to make the hydrolysis reaction and polycondensation reaction rate as gentle as possible, and to obtain the hydrolyzate which melt | dissolved without producing particle | grains, temperature is preferably 0 ?. 60 ° C., more preferably 0? 50 ℃, the time is preferably 30? 360 minutes, more preferably 60? 240 minutes.

The hydrolyzate of organotrialkoxysilane is preferred from the viewpoint of easily forming a micropore structure if it contains silsesquioxane. The organotrialkoxysilane becomes silsesquioxane when a hydrolysis reaction advances. Here, silsesquioxanes, and the silicon-containing polymer consisting of the siloxane bond represented by the general formula R ¹ SiO _3/2 (wherein, R ¹ Silver has 1? 12 is a monovalent hydrocarbon group), and is represented by the following general formula (1):

Is a generic term for polysiloxanes having as the basic structural unit.

In addition to the organotrialkoxysilane and / or its hydrolyzate, when the binder contains a composition containing any one or both of a polymer binder or a nonpolymer binder cured by heating, the adhesion and processability of the transparent conductive film It is preferable because it improves. Examples of the polymeric binder include acrylic resins, polycarbonates, polyesters, alkyd resins, polyurethanes, acrylic urethanes, polystyrenes, polyacetals, polyamides, polyvinyl alcohols, polyvinyl acetates, celluloses, and siloxane polymers. . In addition, in the polymeric binder, hydrolysates of aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum or tin, metal soap, metal complexes, metal alkoxides or metal alkoxides It is preferable that dissolution is included. Examples of the nonpolymeric binders include metal soaps, metal complexes, metal alkoxides, halosilanes, 2-alkoxyethanol, β-diketones, alkyl acetates, and the like. The metal contained in the metal soap, the metal complex, or the metal alkoxide is preferably aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum, tin, indium, or antimony. More preferable are alkoxides of silicon and aluminum (for example, tetraethoxysilane, tetramethoxysilane, aluminum ethoxide and aluminum isopropoxide). By curing these polymeric binders and nonpolymeric binders by heating, it is possible to form a transparent conductive film having a low haze rate and a volume resistivity at low temperature. In addition, a metal alkoxide may be a hydrolyzate or this dehydration product.

It is preferable that a binder adds a coupling agent according to the other component to be used. The coupling agent forms a silsesquioxane and a micropore structure, improves the bondability between the conductive oxide particles and the binder, or the transparent conductive film formed of the transparent conductive film composition, and the photoelectric conversion laminated on the substrate. It is added in order to improve the adhesiveness of a layer or a conductive reflective film. As a coupling agent, a silane coupling agent, an aluminum coupling agent, a titanium coupling agent, etc. are mentioned.

Silane coupling agent, vinyl silane _{(CH 2 = CH [Si (} OCH 2 CH 3) 3]), vinyltrimethoxysilane _{(CH 2 = CH [Si (} OCH 3) 3]), vinyltris (2-methoxyethoxy) silane (CH ₂ = CH [Si (OCH ₂ CH ₂ OCH ₃ ) ₃ ]), formula (2):

Indicated by 3-glycidoxypropyltrimethoxysilane, formula (3):

Indicated by 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane (HSCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ ), 3-mercaptopropyltriethoxysilane (HSCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ ), 3-aminopropyltriethoxysilane (H ₂ NCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ ), 3-aminopropyltrimethoxysilane (H ₂ NCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ ), 3-isocyanatepropyltriethoxysilane (O = C = NCH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ ), 3-isocyanatepropyltrimethoxysilane (O = C = NCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ ), Formula (4):

3-methacryloxypropyltrimethoxysilane represented by the formula (5):

Indicated by 3-methacryloxypropyltriethoxysilane, formula (6):

3-acryloxypropyltrimethoxysilane represented by the formula (7):

N-phenyl-3-aminopropyl trimethoxysilane represented by these is mentioned. Among them, vinyltriethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl Triethoxysilane is preferable at the point of hydrolysis reaction control and micropore structure formation.

The composition for transparent conductive films contains electroconductive oxide particles 98 to 100 parts by mass of solid content (conductive oxide particles, binder, etc.) in the composition for transparent conductive films. It is preferable to include 65 mass parts, and 95? It is more preferable if it contains 70 mass parts. It is because adhesiveness falls when it exceeds an upper limit, and electroconductivity falls below a lower limit. More preferably, the amount of conductive oxide particles is 90? To 100 parts by mass of solid content. You may include 70 mass parts.

Content of a binder is 5-5 with respect to solid content (electroconductive oxide particle, a binder, etc.): 100 mass parts in the composition for transparent conductive films. 50 mass parts is preferable, and 10? It is more preferable if it is 30 mass parts.

General formula (1): Content of the organotrialkoxysilane represented by R <^1> Si (OR <^2> ) ₃ , and / or its hydrolyzate is 50 mass parts with respect to a binder: 100 mass parts. 95 mass parts is preferable. When exceeding an upper limit, the adhesiveness and workability of a transparent conductive film may fall, and below the lower limit, sufficient thickening effect is hard to be acquired.

A binder is a binder component formed of a material comprising an organotrialkoxysilane represented by the general formula (1): R ¹ Si (OR ² ) ₃ , water and an organic solvent, and a mixture of both or one of an acid and an alkali as a catalyst. : For 100 parts by mass 55? When it contains 100 mass parts, content of the organotrialkoxysilane and / or its hydrolyzate in a binder can be adjusted in said range. More preferable content of this component is 55? 90 parts by mass, more preferably 65? 85 parts by mass.

Content of a coupling agent in the case of containing a coupling agent is 0.2 to 100 mass parts with respect to solid content (electroconductive oxide particle, a binder, a coupling agent, etc.) which occupies for the composition for transparent conductive films. 10 mass parts is preferable, and 0.3? 7 mass parts is more preferable.

It is preferable that the composition for transparent conductive films contains a dispersion medium in order to make film formation favorable. As a dispersion medium, Water; Alcohols such as methanol, ethanol, isopropyl alcohol and butanol; Ketones such as acetone, methyl ethyl ketone, cyclohexanone and isophorone; Hydrocarbons such as toluene, xylene, hexane and cyclohexane; Amides such as N, N-dimethylformamide and N, N-dimethylacetamide; Sulfoxides such as dimethyl sulfoxide and glycols such as ethylene glycol; And glycol ethers such as ethyl cellosolve. Content of a dispersion medium is 65 to 65 mass parts for compositions for transparent conductive films, in order to acquire favorable film-forming property. It is preferable if it is 99 mass parts.

Moreover, it is preferable to add a low resistance agent, a water-soluble cellulose derivative, etc. according to the component to be used. As the low resistance agent, one or two or more selected from the group consisting of cobalt, iron, indium, nickel, lead, tin, titanium, and zinc acid salts and organic acid salts are preferable. For example, a mixture of nickel acetate and ferric chloride, zinc naphthenate, a mixture of tin octylate and antimony chloride, a mixture of indium nitrate and lead acetate, a mixture of titanium acetyl acetate and cobalt octylate, and the like. The content of these low resistance agents is 0.2? With respect to 100 parts by mass of the conductive oxide powder. 15 parts by mass is preferred. The water-soluble cellulose derivative is a non-ionic surfactant, but compared with other surfactants, the ability to disperse the conductive oxide powder is very high, and the transparency of the transparent conductive film formed by addition of the water-soluble cellulose derivative is improved. do. Examples of the water-soluble cellulose derivatives include hydroxypropyl cellulose and hydroxypropyl methyl cellulose. The addition amount of the water-soluble cellulose derivative is 0.2? To 100 parts by mass of the conductive oxide powder. 5 mass parts is preferable.

The composition for transparent conductive films can be manufactured by mixing a desired component with a paint shaker, a ball mill, a sand mill, a centrifugal mill, three rolls, etc. by a conventional method, and disperse | distributing electroconductive oxide particle, a silsesquioxane particle, etc. Of course, it can also manufacture by a conventional stirring operation.

[Transparent Conductive Film for Super Straight Thin Film Solar Cell]

The transparent conductive film (hereinafter referred to as a transparent conductive film) for the thin film solar cell of the present invention contains conductive oxide particles and a cured binder, and the cured binder is represented by General Formula (1): R ¹ Si (OR ^2). ) ₃ (wherein R ¹ And R ² It is characterized by including the hydrolyzate of organotrialkoxysilane represented by the above).

About the hydrolyzate of transparent conductive film electroconductive oxide particle and organo trialkoxysilane, it is as above-mentioned, and the hardened binder hardens the above-mentioned binder. That is, what hardened | cured the composition for transparent conductive films for thin film solar cells mentioned above turns into a transparent conductive film.

The manufacturing method of the transparent conductive film of this invention is a manufacturing method of the transparent conductive film of the thin film solar cell which has a base material, a transparent electrode layer, a photoelectric conversion layer, and a transparent conductive film in this order, Comprising: On the photoelectric conversion layer formed on the transparent electrode layer of a base material After applying the composition for transparent conductive films by the wet coating method to form a transparent conductive coating film, the base material which has a transparent conductive coating film is 130-degree. It baked at 400 degreeC, and thickness: 0.03? A 0.5 µm transparent conductive film is formed.

First, the composition for transparent conductive films is apply | coated by the wet coating method on the photoelectric conversion layer of the thin film solar cell provided with a base material, a transparent electrode layer, a photoelectric conversion layer, and a transparent conductive film in this order. Application | coating here has the thickness after baking 0.03? 0.5 μm, preferably 0.05? The thickness is 0.2 μm. Subsequently, the coating film was heated at a temperature of 20? 120 ° C., preferably 25 ° C. 1 at 60 ℃? 30 minutes, preferably 2? Dry for 10 minutes. In this way, a transparent conductive coating film is formed.

As the base material, any one of a light-transmissive substrate made of glass, ceramics, or a polymer material, or two or more types of light-transmissive laminates selected from the group consisting of glass, ceramics, a polymer material, and silicon can be used. As a polymer substrate, the board | substrate formed with organic polymers, such as a polyimide and PET (polyethylene terephthalate), is mentioned.

The wet coating method is preferably any of spray coating, dispenser coating, spin coating, knife coating, slit coating, inkjet coating, screen printing, offset printing or die coating. It is not limited to this, Any method can be used.

The spray coating method is a method in which the composition for transparent conductive film is applied to the substrate in the form of fog by compressed air or the dispersion itself is pressurized in the form of fog, and the dispenser coating method is, for example, It is a method of apply | coating to a base material by discharging a dispersion from the fine nozzle of the tip of a syringe by putting the composition for transparent conductive films into a syringe, and pressing the piston of this syringe. The spin coating method is a method of dropping the composition for transparent conductive film onto a rotating substrate, and expanding the dropped conductive composition for transparent conductive film to the peripheral edge of the substrate by the centrifugal force. It is a method of providing the base material with space | interval of this so that a movement to a horizontal direction is possible, supplying the composition for transparent conductive films on the base material of an upstream rather than this knife, and moving a base material horizontally to a downstream side. The slit coating method is a method of flowing a composition for transparent conductive film out of a narrow slit and applying it on a substrate. The inkjet coating method fills a composition for a transparent conductive film in an ink cartridge of a commercially available inkjet printer, and performs inkjet printing on the substrate. It is a way. The screen printing method is a method of transferring the composition for transparent conductive films to a base material through the plate image formed on it using the yarn as a pattern indicating material. The offset printing method is a printing method using the water repellency of the composition for transparent conductive films in which the composition for transparent conductive films attached to the plate is directly transferred from the plate to the rubber sheet and transferred from the rubber sheet to the base material without directly adhering to the substrate. . The die coating method is a method of distributing the composition for transparent conductive films supplied in a die to a manifold, extruding it from a slit into a thin film, and coating the surface of the substrate to travel. The die coating method includes a slot coat method, a slide coat method, and a curtain coat method.

Finally, the substrate having the transparent conductive coating film is placed in the atmosphere or in an inert gas atmosphere such as nitrogen or argon. 400 ° C., preferably 150? 5 at a temperature of 350 ℃? 60 minutes, preferably 15? Hold for 40 minutes and bake. Here, the thickness of the transparent conductive film after baking is 0.03? The reason why the composition for transparent conductive film is applied so as to be within a range of 0.5 μm is that a thickening effect is not sufficiently obtained when the thickness after baking is less than 0.03 μm or more than 0.5 μm.

The firing temperature of the substrate having the coating film is 130? The reason for setting it as 400 degreeC is because the problem which surface resistance value becomes too high in the transparent conductive film in a composite film below 130 degreeC arises. Moreover, when it exceeds 400 degreeC, production advantages, such as a low temperature process, cannot be utilized, ie, manufacturing cost will increase and productivity will fall. In particular, amorphous silicon, microcrystalline silicon, or a hybrid silicon solar cell using them is relatively weak in heat, and the conversion efficiency is lowered by the firing step.

The firing time of the substrate having the coating film is 5? The range for 60 minutes is because when the firing time is less than the lower limit, a problem that the surface resistance value becomes too high in the transparent conductive film in the composite film occurs. It is because when a baking time exceeds an upper limit, manufacturing cost will increase more than necessary, productivity will fall, and the conversion efficiency of a solar cell will fall.

By the above, the transparent conductive film of this invention can be formed. Thus, since the manufacturing method of this invention can remove a vacuum process, such as a vacuum vapor deposition method and a sputtering method, as much as possible by using a wet coating method, a transparent conductive film can be manufactured more inexpensively. Moreover, since the transparent conductive film of this invention contains the hydrolyzate of organotrialkoxysilane, it is thought that the micropore which has a silsesquioxane structure as a representative structure is formed, and the refractive index of a transparent conductive film falls. When the refractive index difference between the photoelectric conversion layer and the transparent conductive film becomes larger than before, the reflected light from the transparent conductive film to the photoelectric conversion layer increases, and the photoelectric conversion efficiency is improved by the light confinement effect. In addition, the hydrolyzate (such as silsesquioxane) of the organotrialkoxysilane has a hydrocarbon group, and therefore, stress relaxation property is imparted to the transparent conductive film. For example, -40? The fall of the conversion efficiency after the accelerated durability test using the heat cycle test which repeats the cold-heat cycle at 90 degreeC is small compared with the prior art, and it becomes a long-term stable thin film solar cell.

[Thin Film Solar Cell]

The thin film solar cell of this invention contains the transparent conductive film for said thin film solar cells. An example of the cross section of the thin film solar cell of this invention is shown in FIG. 1 is a case of a super straight thin film solar cell. The super straight thin film battery is provided in the order of the base material 10, the transparent electrode layer 3, the photoelectric conversion layer 2, the transparent conductive film 1, and the conductive reflecting film 4, and from the board | substrate 10 side. Sunlight enters. Many of the incident solar rays are reflected by the conductive reflection film 4, return to the photoelectric conversion layer 2, and improve conversion efficiency. Here, the reflection of sunlight also occurs at the interface between the transparent conductive film 1 and the photoelectric conversion layer 2, and since the transparent conductive film 1 using the composition for transparent conductive films of the present invention has a low refractive index, the transparent conductive film ( 1) By increasing the reflected light at the interface between the photoelectric conversion layer 2, the power generation efficiency of the thin film solar cell can be improved.

In the process of manufacturing the super straight thin film battery as described above, the transparent electrode layer 3 is formed on the substrate 10 and the photoelectric conversion layer 2 is formed on the transparent electrode layer 3. The transparent conductive film 1 is formed. In that case, the transparent conductive film 1 can be manufactured by the manufacturing method of the transparent conductive film of this invention.

Although the thin film solar cell of this invention is not limited by the kind of a base material, a transparent electrode, a photoelectric conversion layer, etc., For example, a base material is any of the transparent substrates which consist of glass, ceramics, or a polymeric material, or glass, Two or more types of light-transmissive laminates selected from the group consisting of ceramics, polymer materials, and silicon can be used. For example, it may be a laminate of glass and SiO ₂ as a base material. The transparent electrode layer is SnO ₂ Film and the like. The photoelectric conversion layer can be formed, for example, as a laminate of p-type a-Si: H (amorphous silicon hydride), i-type a-Si (amorphous silicon), and n-type μc-Si (microcrystalline silicon carbide). .

<Examples>

Although an Example demonstrates this invention in detail below, this invention is not limited to these.

Table 1? The total amount is 60 g so that the composition shown in 3 (the numerical value represents the mass part) is put into a 100 cm 3 glass bottle, and dispersed in a paint shaker for 6 hours using 100 g of zirconia beads having a diameter of 0.3 mm. , Example 1? 20, the transparent conductive film composition of the comparative example 1 was produced. In addition, Table 1? In the column of the ratio of 3, electroconductive oxide particle was abbreviate | omitted to "degrees", and a coupling agent was abbreviate | omitted to "cuff." Wherein a binder 1 containing (R ¹ Si (OR ² ) ₃ )? 5 and SiO ₂ binder 1? 7 was produced as follows.

[Binder 1 Including (R ¹ Si (OR ² ) ₃ )]

Using a 500 cm 3 glass four-necked flask, 140 g of methyltrimethoxysilane and 140 g of methyl alcohol were added, and a solution of 1.7 g of 60% nitric acid dissolved in 120 g of pure water was stirred while stirring. It was added to, and it was made to react at 50 degreeC after that for 3 hours, and the hydrolysis reaction liquid was obtained. Furthermore, the alkali solution which added 0.1 g of ammonia water to 30 g of pure water and 70 g of ethanol mixed liquid was prepared by putting into a hydrolysis reaction liquid over 120 minutes using the tube pump.

[Binder 2 Including (R ¹ Si (OR ² ) ₃ )]

Using a 500 cm 3 glass four-necked flask, 140 g of methyltriethoxysilane and 140 g of methyl alcohol were added and a solution of 1.5 g of formic acid dissolved in 120 g of pure water was added at a time while stirring. Then, it was made to react at 50 degreeC for 3 hours, and the hydrolysis reaction liquid was obtained. Furthermore, the alkali solution which added 0.05 g of ammonia water to the liquid mixture of 30 g pure water and 70 g ethanol was manufactured by putting into a hydrolysis reaction liquid using the tube pump over about 90 minutes.

[Binder 3 Including (R ¹ Si (OR ² ) ₃ )]

0.5 g of methyltrimethoxysilane, 2.3 g of phenyltrimethoxysilane, and 80 g of ethanol were added using a 200 cm 3 glass four-necked flask, and 0.03 g of formic acid was added while stirring. The solution dissolved in pure water was added at once, and the hydrolysis liquid A was obtained by making it react at 20 degreeC after that for 1 hour. Using a 500 cm 3 glass four-necked flask, a solution in which 0.25 potassium potassium hydroxide was dissolved in 100 g of pure water was added and kept at 20 ° C. while stirring, and the hydrolysis solution A was added thereto using a tube pump for 2 hours. It dripped over, and after dripping, it stirred for further 2 hours and manufactured.

[Binder 4 Including (R ¹ Si (OR ² ) ₃ )]

Using a 500 cm 3 glass four-necked flask, 120 g of methyltriethoxysilane, 25 g of phenyltriethoxysilane, and 140 g of ethanol were added, and 0.05 g of nitric acid was stirred with 30 g of The solution dissolved in pure water was dripped over 90 minutes using the tube pump, and after dripping It produced by making it react at 30 degreeC for 4 hours.

[Binder 5 Including (R ¹ Si (OR ² ) ₃ )]

Using a 500 cm 3 glass four-necked flask, 140 g of methyltrimethoxysilane, 10 g of 3-aminopropyltrimethoxysilane, and 140 g of methyl alcohol were added, and 1.7 g of 60 was stirred. The solution which melt | dissolved nitric acid in 120 g of pure waters was added at once, it was made to react at 50 degreeC after that for 3 hours, and the hydrolysis reaction liquid was obtained. Furthermore, the alkali solution which added 0.1 g of ammonia water to 30 g of pure water and 70 g of ethanol mixed liquid was prepared by putting into a hydrolysis reaction liquid over 120 minutes using the tube pump.

[SiO ₂ Binder 1]

Using a 500 cm 3 glass four-necked flask, 140 g of tetraethoxysilane and 140 g of ethyl alcohol were added and a solution of 1.7 g of 60% nitric acid dissolved in 120 g of pure water was stirred at a time. It produced by making it add and react for 3 hours at 50 degreeC after that.

[SiO ₂ binder 2]

Using a 500 cm 3 glass four-necked flask, 85 g of tetraethoxysilane and 100 g of ethyl alcohol were added, and a solution of 0.09 g of 60% nitric acid dissolved in 110 g of pure water at room temperature was stirred while stirring. 10, using a tube pump? It took 15 minutes. Subsequently, a mixed solution of 45 g of aluminum tri-sec-butoxide and 60 g of ethyl alcohol, which had been mixed in advance into the obtained mixed solution, was charged with 10? It took 15 minutes. It stirred for about 30 minutes at room temperature, and manufactured by making it react at 50 degreeC for 3 hours.

[SiO ₂ binder 3]

Using a 500 cm 3 glass four-necked flask, 115 g of tetraethoxysilane and 175 g of ethyl alcohol were added and a solution of 1.4 g of 35% hydrochloric acid dissolved in 110 g of pure water was stirred at a time. It produced by making it add and react for 3 hours at 45 degreeC after that.

[SiO ₂ binder 4]

Using a 500 cm 3 glass four-necked flask, 130 g of tetraethoxysilane and 145 g of ethyl alcohol were added and a solution of 1.25 g of 30% ammonia water dissolved in 124 g of pure water was stirred at a time while stirring. It produced by making it add and react for 3 hours at 45 degreeC after that.

[SiO ₂ binder 5]

Using a 500 cm 3 glass four-necked flask, 145 g of tetraethoxysilane and 140 g of ethyl alcohol were added and, while stirring, a solution of 0.015 g of 60% nitric acid dissolved in 115 g of pure water at a time was stirred. It produced by making it add and react for 3 hours at 50 degreeC after that.

[SiO ₂ binder 6]

Using a 500 cm 3 glass four-necked flask, 140 g of tetraethoxysilane, 5 g of 3-glycidoxypropyltriethoxysilane, and 140 g of ethyl alcohol were added and stirred, and 1.7 g of The solution which melt | dissolved 60% nitric acid in 120 g of pure water was added at once, and it manufactured by making it react at 50 degreeC after that for 3 hours.

[SiO ₂ binder 7]

Using a 500 cm 3 glass four-necked flask, 145 g of tetraethoxysilane, 2 g of vinyltriethoxysilane, and 140 g of ethyl alcohol were added and 115 g of 0.015 g of 60% nitric acid was stirred. The solution dissolved in the pure water of was added at once, and it reacted at 50 degreeC after that for 3 hours.

[Coupling Agent]

Vinyltriethoxysilane was used for the silane coupling agent. Titanium coupling agents include general formula (8):

A titanium coupling agent having a dialkylpyrophosphite group represented by was used.

[Mixed solvent]

The mixed liquid 1 (mass ratio 4: 2: 1) of isopropanol, ethanol, and N, N-dimethylformamide was used for the mixed solvent 1, and the mixed liquid (mass ratio 98: 2) of ethanol and butanol was used for the mixed solvent 2.

[Non-polymer type binder]

In the nonpolymer binder 1, a mixed liquid of 2-n-butoxyethanol and 3-isopropyl-2,4-pentanedione is used, and in the nonpolymer binder 2, 2,2-dimethyl-3,5-hexanedione and A mixture of 2-isobutoxyethanol, 2-hexyloxyethanol, and n-propyl acetate (mass ratio 4: 1: 1) was used for the nonpolymeric binder 3 as a mixed liquid of isopropyl acetate (mass ratio 1: 1).

[Example 1? 20]

In Example 1, ITO powder having an average particle diameter of 25 nm is mixed as conductive oxide particles in ethanol to be a dispersion medium, and a binder 1 containing (R ¹ Si (OR ² ) ₃ ) as a binder in the blending ratio shown in Table 1 It mixed at the ratio of 25 mass% with respect to solid content in the composition for transparent conductive films.

In the embodiment 2, IPA is the dispersion medium, the binder comprising a ^{(R 1 Si (OR 2)} 3) mixing the ITO powder having an average particle size of 25 ㎚ and, as a binder, a conductive oxide particle 1, SiO ₂ binder 1 The thing mixed by the ratio of 90 to 10 was mixed in the ratio of 30 mass% with respect to solid content in the composition for transparent conductive films.

In Example 3, ATO powder having an average particle diameter of 40 nm is mixed as conductive oxide particles in ethanol to be a dispersion medium, and binder 2 and SiO ₂ binder 2 containing (R ¹ Si (OR ² ) ₃ ) as a binder. What mixed at the ratio of 85 to 15 was mixed at the ratio of 10 mass% with respect to solid content in the composition for transparent conductive films.

In Example 4, TZO powder having an average particle diameter of 30 nm is mixed as conductive oxide particles in IPA serving as a dispersion medium, and binder 2 and SiO ₂ binder 1 containing (R ¹ Si (OR ² ) ₃ ) as a binder. What mixed in the ratio of 70 to 30 was mixed in the ratio of 30 mass% with respect to solid content in the composition for transparent conductive films.

In Example 5, ITO powder with an average particle diameter of 30 nm was mixed as ethanol used as a dispersion medium, and the binder 3 containing (R ¹ Si (OR ² ) ₃ ) as a binder, and the SiO ₂ binder 5 were used. What mixed at the ratio of 85 to 15 was mixed at the ratio of 15 mass% with respect to solid content in the composition for transparent conductive films.

In Example 6, ITO powder having an average particle diameter of 35 nm is mixed as conductive oxide particles in mixed solvent 1 serving as a dispersion medium, and binder 3 and (silane coupling agent) containing (R ¹ Si (OR ² ) ₃ ) as a binder. , they were mixed in a proportion of 20% by mass relative to the solid content in the transparent conductive film composition of a mixture of SiO ₂ binder, 7 to 80 ratio of 20 containing.

Carried out in ethanol example 7, which is a dispersion medium, a binder comprising a ^{(R 1 Si (OR 2)} 3) mixing the ITO powder having an average particle size of 40 ㎚ and, as a binder, a conductive oxide particle 1, SiO ₂ binder 4 What mixed in the ratio of 70 to 30 was mixed in the ratio of 20 mass% with respect to solid content in the composition for transparent conductive films.

Example 8, in ethanol as a dispersion medium, a mixture of ITO powder having an average particle size of 25 ㎚, and a binder as a conductive oxide particle ^{(R 1 Si (OR 2)} 3) binding agents 4, and a non-polymer type binder 1 containing , A titanium coupling agent having a dialkylpyrophosphite group represented by the formula (8), mixed at a ratio of 30% by mass to a solid content in the transparent conductive film composition It mixed at the ratio of 0.5 mass% with respect to the composition mass which combined the electroconductive oxide particle used as solid matter after coating film formation, and a binder component.

In Example 9, a binder containing (R ¹ Si (OR ² ) ₃ ) containing an silane coupling agent as a binder, in which ATO powder having an average particle diameter of 50 nm is mixed as conductive oxide particles in mixed solvent 2 serving as a dispersion medium. and a mixture of 5, SiO ₂ 2 to 70 binder ratio of 30, for the solid content in the transparent conductive film composition, was mixed in a proportion of 30% by mass.

In Example 10, a binder containing (R ¹ Si (OR ² ) ₃ ) containing an silane coupling agent as a binder, in which ATO powder having an average particle diameter of 30 nm is mixed as conductive oxide particles in mixed solvent 1 serving as a dispersion medium. to 5 and, SiO ₂ binding agent 1 were mixed in a ratio of 60 to 40, for the solid content in the transparent conductive film composition, it was mixed in a proportion of 15% by mass.

Embodiment 11, in a mixed solvent 2, which is a dispersion medium, mixing the ITO powder having an average particle size of 40 ㎚ as the conductive oxide particles and a binder, ^{(R 1 Si (OR 2)} 3) binder 1, a non-polymer type, including What mixed binder 3 in the ratio of 80 to 20 was mixed in the ratio of 30 mass% with respect to solid content in the composition for transparent conductive films.

Example 12 In, in a mixed solvent 2, which is a dispersing medium, mixing the ITO powder having an average particle size of 35 ㎚ as the conductive oxide particles and a binder, ^{(R 1 Si (OR 2)} 3) binder 2 with a silane coupling agent containing , they were mixed in a proportion of 25% by mass relative to the solid content in the transparent conductive film composition of a mixture of SiO ₂ binder, 6 to 65 to 35 percentage of the containing.

In Example 13, ITO powder having an average particle diameter of 30 nm was mixed as conductive oxide particles in ethanol serving as a dispersion medium, and binder 2 and SiO ₂ binder 3 containing (R ¹ Si (OR ² ) ₃ ) as a binder. What mixed in the ratio of 90 to 10 was mixed in the ratio of 25 mass% with respect to solid content in the composition for transparent conductive films, and solid content after coating film formation of a silane coupling agent (Shin-Etsu Silicone Co., Ltd. product KBE-1003) It mixed at the ratio of 0.7 mass% with respect to the composition mass which combined the electroconductive oxide particle and binder component which become.

In Example 14, IZO powder having an average particle diameter of 25 nm was mixed as conductive oxide particles in IPA serving as a dispersion medium, and binder 1 containing (R ¹ Si (OR ² ) ₃ ) as a binder, SiO ₂ binder 2, and And the nonpolymer binder 2 were mixed in a ratio of 65 to 30 to 5 at a ratio of 25% by mass with respect to the solid content in the composition for transparent conductive films.

In Example 15, and butanol which is a dispersion medium, a binder comprising a ^{(R 1 Si (OR 2)} 3) mixing the ITO powder having an average particle size of 25 ㎚ and, as a binder, a conductive oxide particles 3 and, SiO ₂ binder 4 The thing mixed by the ratio of 60 to 40 was mixed in the ratio of 10 mass% with respect to solid content in the composition for transparent conductive films.

In Example 16, IZO powder having an average particle diameter of 25 nm was mixed as conductive oxide particles in IPA serving as a dispersion medium, binder 4 containing (R ¹ Si (OR ² ) ₃ ) as a binder, and SiO ₂ binder 7 and And the nonpolymer binder 1 were mixed in a ratio of 70 to 20 to 10 at a ratio of 25% by mass with respect to the solid content in the composition for transparent conductive films.

In Example 17, a binder comprising (R ¹ Si (OR ² ) ₃ ) containing an silane coupling agent as a binder in IZO powder having an average particle diameter of 25 nm as conductive oxide particles in mixed solvent 1 serving as a dispersion medium. to 5 and, SiO ₂ binder 3 are mixed in a ratio of 90 to 10, about the transparent conductive film of the solid content of the composition were mixed in a ratio of 30 mass%.

In Example 18, TZO powder having an average particle diameter of 30 nm was mixed as conductive oxide particles in mixed solvent 1 serving as a dispersion medium, and binder 3 comprising (R ¹ Si (OR ² ) ₃ ) as a binder and a SiO ₂ binder What mixed 5 and the nonpolymer binder 3 in the ratio of 85 to 12: 3 was mixed in the ratio of 15 mass% with respect to solid content in the composition for transparent conductive films.

In Example 19, ITO powder having an average particle diameter of 50 nm was mixed as conductive oxide particles in mixed solvent 1 serving as a dispersion medium, and binder 1 and SiO ₂ binder containing (R ¹ Si (OR ² ) ₃ ) as a binder. What mixed 2 in the ratio of 75 to 25 was mixed in the ratio of 15 mass% with respect to solid content in the composition for transparent conductive films.

In Example 20, Binder 5 containing (R ¹ Si (OR ² ) ₃ ) containing ATO powder having an average particle diameter of 40 nm as conductive oxide particles and containing a silane coupling agent as a binder in IPA serving as a dispersion medium. A mixture of a SiO ₂ binder 1 and a SiO ₂ binder 7 containing a silane coupling agent in a ratio of 55:30 to 15 was mixed at a ratio of 30% by mass with respect to the solid content in the composition for transparent conductive films.

Comparative Example 1

In Comparative Example 1, ITO powder having an average particle diameter of 25 nm was mixed as conductive oxide particles in IPA serving as a dispersion medium, and SiO ₂ binder 1 was mixed at a ratio of 30% by mass with respect to the solid content in the composition for transparent conductive films as a binder.

[Evaluation of Composition for Transparent Conductive Film]

Regarding the refractive index evaluation, Example 1? 20, the transparent electrode film was formed by the wet coating method (spin coating method, die coating method, spray coating method, offset printing method) with respect to the glass substrate for which the optical constant is already known about the composition for transparent conductive films shown in Comparative Example 1 After, 160? 20 at 220 ℃? By firing for 60 minutes, thickness 0.05? A 0.2 micrometer transparent conductive film was formed. About the film | membrane, it measured using the spectroscopic ellipsometry apparatus (M-2000 by J. A. Woollam Japan Co., Ltd.), analyzed the data about the transparent electrode film part, and calculated | required the optical constant. From the analyzed optical constant, the value of 633 nm was made into the refractive index. Table 1? 3 shows these results.

As shown in Fig. 1, first, SiO ₂ having a thickness of 50 nm is formed on one main surface. A glass substrate is formed, layer (not shown) as the substrate 10, and the SiO ₂ A surface electrode layer (SnO ₂ ) of 800 nm thick having an uneven texture on the surface and doped with F (fluorine) Film) 3 was formed as a transparent electrode layer 3. The transparent electrode layer 3 was patterned using a laser processing method to form an array, and wirings were formed to electrically interconnect them. Next, the photoelectric conversion layer 2 was formed on the transparent electrode layer 3 using the plasma CVD method. In this embodiment, the photoelectric conversion layer 2 includes p-type a-Si: H (amorphous silicon hydride), i-type a-Si (amorphous silicon), and n-type μc- in this order from the substrate 10 side. It obtained by laminating | stacking the film | membrane which consists of Si (microcrystalline silicon carbide). The photoelectric conversion layer 2 was patterned using a laser processing method. This was used for evaluation of the composition for transparent conductive films shown in the Example as a solar cell which film-forming has already advanced.

Example 1? 20, the thickness for baking about the composition for transparent conductive films shown in the comparative example 1 with respect to the photovoltaic cell which film-forming already advanced is 0.07? After coating by the wet coating method (spin coating method, die coating method, spray coating method, offset printing method, screen printing method) so that it becomes 0.15 micrometer, the temperature is 25? It dried at the low temperature of 60 degreeC for 5 minutes, and formed the transparent conductive film 1. Table 1? 3 shows a coating method.

Subsequently, the thickness after baking of the composition for electrically conductive reflection films prepared on the transparent conductive film 1 by the following method is 0.05? After coating by a wet coating method so as to be 2.0 ㎛, a temperature of 25? It dried at low temperature of 60 degreeC for 5 minutes, and formed the electroconductive reflection film. Then, 160? 20 at 220 ℃? By baking for 60 minutes, the composite film was formed on the solar cell. Table 1? 3, the film thickness after baking of the transparent conductive film 1 is shown. Here, the film thickness was measured by cross section observation by a Hitachi High-Technologies scanning electron microscope (SEM, device name: S-4300, SU-8000). In addition, the preparation method of the composition for electroconductive reflection films was carried out as follows.

First, silver nitrate was dissolved in deionized water to prepare an aqueous metal ion solution. Sodium citrate was dissolved in deionized water to prepare a 26% by weight aqueous sodium citrate solution. Particulate ferrous sulfate was added directly to this aqueous sodium citrate solution and dissolved in a nitrogen gas stream maintained at 35 ° C to prepare a reducing agent aqueous solution containing citrate ions and ferrous ions in a molar ratio of 3: 2. Subsequently, in the state which maintained the said nitrogen gas stream at 35 degreeC, the stirrer of the magnetic stirrer was put into a reducing agent aqueous solution, the stirrer was rotated at the rotation speed of 100 rpm, and the said reducing agent aqueous solution was stirred, and the said metal salt was carried out in this reducing agent aqueous solution. The aqueous solution was added dropwise to synthesize. Here, the addition amount of the metal salt aqueous solution with respect to the reducing agent aqueous solution adjusted the density | concentration of each solution so that it may become 1/10 or less of the quantity of the reducing agent aqueous solution, and even if it dropped the aqueous metal salt aqueous solution of room temperature, the reaction temperature was maintained at 40 degreeC. Moreover, the mixing ratio of the said reducing agent aqueous solution and the metal salt aqueous solution was adjusted so that the ferrous ion equivalent added as a reducing agent may be three times the metal ion equivalent. After the dropping of the aqueous metal salt solution to the reducing agent aqueous solution was completed, stirring of the mixed solution was further continued for 15 minutes to generate metal particles in the mixed liquid, thereby obtaining a metal particle dispersion liquid in which the metal particles were dispersed. The pH of the metal particle dispersion was 5.5, and the stoichiometric amount of the metal particles in the dispersion was 5 g / liter. The obtained dispersion liquid was left to stand at room temperature to precipitate the metal particles in the dispersion liquid, and the aggregates of the precipitated metal particles were separated by decantation. Deionized water was added to the separated metal agglomerate to obtain a dispersion, and after desalting by ultrafiltration, the content of metal (silver) was made 50 mass% by substitution washing with methanol again. Thereafter, the centrifugal separator was used to adjust the centrifugal force of the centrifugal separator to separate relatively large silver particles having a particle size exceeding 100 nm, thereby obtaining a primary particle size of 10? Silver nanoparticles in the range of 50 nm were adjusted so as to contain 71% by number average. In other words, the number average primary particle size 10? It adjusted so that the ratio of the silver nanoparticle which occupies in 50 nm of range might be 71%. As for the obtained silver nanoparticles, the protective agent of the organic main chain whose carbon skeleton is C3 was chemically modified.

Next, 10 mass parts of obtained metal nanoparticles were disperse | distributed by adding and mixing to 90 mass parts of mixed solutions containing water, ethanol, and methanol. Furthermore, the composition for electrically conductive reflection films was obtained by adding 4 mass% of polyvinylpyrrolidone, 1 mass% of silver citrate, and 95 mass% of metal nanoparticles to this dispersion liquid as an additive. The thickness after baking the obtained composition for conductive reflection films on the transparent conductive film 1 is 0.05? After coating by the wet coating method to be 2.0 ㎛, 160? 20 at 220 ℃? By baking on 60-minute heat processing conditions, the electroconductive back surface reflective film 4 was formed on the transparent conductive film 1.

Subsequently, in evaluating power generation efficiency as a solar cell, as a reinforcement film on a conductive reflection film, the composition for reinforcement film was apply | coated by the die coating apparatus on the solar cell which film-forming already advanced to the conductive reflection film, and for reinforcement film After removing a solvent from the coating film for reinforcement films by vacuum drying so that the thickness after baking a composition may be 350 nm, a solar cell is hold | maintained at 180 degreeC for 20 minutes in a hot air drying furnace, and the coating film for reinforcement films is thermosetted. To obtain a reinforcing film for a conductive reflection film. In addition, the preparation method of the composition for reinforcement film was as follows.

First, a mixed liquid of ethanol and butanol (mass ratio 98: 2) with 8 mass% of ITO particles having an average particle diameter of 25 nm as conductive oxide fine particles, a titanium coupling agent having a dialkylpyrophosphite group as a coupling agent, and a dispersion medium. 2) was mixed at 90 mass% and stirred at a rotational speed of 800 rpm at room temperature for 1 hour. Next, 60 g of this mixture was placed in a 100 cc glass bottle, and dispersed in a paint shaker for 6 hours using 100 g of 0.3 mm diameter zirconia beads to prepare a dispersion of ITO particles. Here, the titanium coupling agent which has a dialkyl pyrophosphite group is represented by said Formula (8). Next, after mixing 4 mass% of the dispersion liquid of ITO particle with 86 mass% of ethanol which is a dispersion medium, the SiO ₂ binder 1 was further mixed by 10 mass%, and the base liquid of the composition for reinforcement film was obtained, and this base liquid 95 mass% and 5 mass% of fumed silica dispersion liquids were mixed as an additive, it disperse | distributed and mixed for 10 minutes at room temperature with an ultrasonic vibrator, and the mixture was mixed uniformly as a whole, and the coating liquid which is a composition for reinforcement films was prepared.

The solar cell formed up to the reinforcement film for a conductive reflection film patterns the photoelectric conversion layer 2 and the transparent conductive film 1 formed on it, the conductive reflection film 4, and the reinforcement film for a conductive reflection film using a laser processing method. Was carried out.

As an evaluation method of a solar cell, the value of (Jsc) which is an output characteristic and a short circuit current at the time of confirming IV characteristic curve by performing lead wire wiring to the board | substrate after the process which patterned using the laser processing method is an Example. Using the photoelectric conversion layer obtained by the same manufacturing method as described above, the relative output evaluation when the transparent conductive film, the conductive reflecting film, and the reinforcing film were all set to 100 as the super straight solar cell formed by the sputtering method was performed. Table 1? 3 shows these results.

Here, all of the super straight solar cells formed by the sputtering method are SiO ₂ having a thickness of 50 nm on one main surface as shown in FIG. 1. A glass substrate is formed, layer (not shown) as the substrate 10, and the SiO ₂ A surface electrode layer (SnO ₂ ) of 800 nm thick having an uneven texture on the surface and doped with F (fluorine) Film) (3). The transparent electrode layer 3 was patterned using a laser processing method to form an array, and wirings were formed to electrically interconnect them. Next, the photoelectric conversion layer 2 was formed on the transparent electrode layer 3 using the plasma CVD method. In this embodiment, the photoelectric conversion layer 2 includes p-type a-Si: H (amorphous silicon hydride), i-type a-Si (amorphous silicon), and n-type μc- in this order from the substrate 10 side. It obtained by laminating | stacking the film | membrane which consists of Si (microcrystalline silicon carbide). After patterning the photoelectric conversion layer 2 using a laser processing method, a 80 nm thick transparent conductive film (ZnO layer) 1 is formed on the photoelectric conversion layer 2 using a magnetron in-line sputtering apparatus. And a conductive reflective film (silver electrode layer) 4 having a thickness of 200 nm are sequentially formed.

Table 1? As is clear from 3, Example 1? The refractive index is low at all 20, and the relative power generation efficiency is 108? High at 122, and relative short-circuit current density at 102? As high as 106. In particular, organotrialkoxysilane and / or its hydrolyzate are 55? Example 2 containing 90 mass parts; At 20, the relative power generation efficiency is 113? Very high at 122% and relative short-circuit current density of 103? 106%, higher than Example 1. Moreover, in Example 16, 17, and 20 containing a silane coupling agent, relative generation efficiency is 121-? It was remarkably high as 122%. In contrast, as a binder, General Formula (1): R ¹ Si (OR ² ) ₃ (wherein R ¹ and R ² In Comparative Example 1 which does not contain an organotrialkoxysilane and / or its hydrolyzate represented by a specific hydrocarbon group), the refractive index was high, and both the relative power generation efficiency and the relative short circuit current density were approximately 100%. Further, in that as a binder comprising 100 parts by mass of the binder 1 containing ^{(R 1 Si (OR 2)} 3) Example 1, natatjiman the most refractive index, due to laser processing carried out after the formation of up to the reinforcing layer for a conductive reflective film Since the workability at the time of patterning was bad, it is thought that relative power generation efficiency and relative short-circuit current density fell.

As described above, the transparent conductive film composition of the present invention is applied on the photoelectric conversion layer by a wet coating method, and can be fired, as a binder, the general formula (1) of R ¹ Si (OR ²⁾ ₃ (formula, R ¹ , R ² Is a specific hydrocarbon group), and the transparent conductive film with low refractive index was obtained by using the compound containing the organotrialkoxysilane and / or its hydrolyzate. Therefore, it turned out that the transparent conductive film which can improve the power generation efficiency of a thin film solar cell can be obtained simply.

Claims (19)

Conductive oxide particles and a binder cured by heating, the binder is a general formula (1): R ¹ Si (OR ² ) ₃ (wherein R ¹ Silver has 1? It is a 12-valent monovalent hydrocarbon group, and R <^2> has carbon: 1? Organotrialkoxysilane and / or its hydrolyzate represented by (4). The composition for transparent conductive films for thin film solar cells characterized by the above-mentioned. The method of claim 1,
The organotrialkoxysilane and / or its hydrolyzate represented by said general formula (1): R <^1> Si (OR <^2> ) ₃ are 50: 50 mass parts with respect to a binder: 100 mass parts. The composition for transparent conductive films for thin film solar cells containing 95 mass parts. The method of claim 2,
The binder is a binder formed of, as a material, an organotrialkoxysilane represented by the general formula (1): R ¹ Si (OR ² ) ₃ , water, an organic solvent, and a mixture of both or one of an acid and an alkali as a catalyst. A composition for transparent conductive films for thin film solar cells, comprising the component. The method of claim 2,
The binder further comprises any one or both of a polymer binder or a nonpolymer binder cured by heating, wherein the composition for a transparent conductive film for a thin film solar cell. The method according to any one of claims 1 to 4,
Said binder contains silsesquioxane, The composition for transparent conductive films for thin film solar cells characterized by the above-mentioned. The method according to any one of claims 1 to 4,
A composition for transparent conductive films for thin film solar cells, further comprising a coupling agent. The method according to claim 6,
The composition for transparent conductive films for thin film solar cells whose said coupling agent is a silane coupling agent. Conductive oxide particles and a cured binder, wherein the cured binder is represented by the general formula (1): R ¹ Si (OR ² ) ₃ (wherein R ¹ Silver has 1? Is a 12-valent monovalent hydrocarbon group, R ² Carbon number: 1? And a hydrolyzate of an organotrialkoxysilane represented by (4), which is a linear or branched alkyl group of 4). The method of claim 8,
The cured binder includes silsesquioxane, wherein the transparent conductive film for a thin film solar cell. 10. The method according to claim 8 or 9,
The cured binder further comprises a cured polymer or non-polymer binder, the transparent conductive film for a thin film solar cell. The thin film solar cell containing the transparent conductive film for the thin film solar cell of Claim 8 or 9. As a manufacturing method of the transparent conductive film of a thin film solar cell provided with a base material, a transparent electrode layer, a photoelectric conversion layer, and a transparent conductive film in this order,
On the photoelectric conversion layer formed on the transparent electrode layer of a base material, electroconductive oxide particle | grains and the binder which harden | cure by heating are included, and a binder is General formula (1): R <^1> Si (OR <^2> ) ₃ (In formula, R <^1>). Silver has 1? Is a 12-valent monovalent hydrocarbon group, R ² Carbon number: 1? After applying the composition for transparent conductive films containing organotrialkoxysilane represented by the linear or branched alkyl group of 4, and / or its hydrolyzate by a wet coating method, and forming a transparent conductive coating film, a transparent conductive coating film Base material having 130? It baked at 400 degreeC, and thickness: 0.03? A method for producing a transparent conductive film for a thin film solar cell, characterized by forming a 0.5 µm transparent conductive film. 13. The method of claim 12,
The transparent conductive film composition of the general formula ^{(1): R 1 Si (} OR 2) represented by Li ₃ Organic note alkoxysilane and / or a hydrolyzate thereof, the binder: about 100 parts by mass, 50? The manufacturing method of the transparent conductive film for thin film solar cells containing 95 mass parts. The method of claim 13,
The binder is a binder formed of, as a material, an organotrialkoxysilane represented by the general formula (1): R ¹ Si (OR ² ) ₃ , water, an organic solvent, and a mixture of both or one of an acid and an alkali as a catalyst. A component is a manufacturing method of the transparent conductive film for thin film solar cells characterized by the above-mentioned. 15. The method of claim 14,
The binder further comprises any one or both of a polymer binder or a nonpolymer binder which is cured by heating. A method for producing a transparent conductive film for a thin film solar cell, characterized by the above-mentioned. The method according to any one of claims 13 to 15,
Said binder of said composition for transparent conductive films contains silsesquioxane, The manufacturing method of the transparent conductive film for thin film solar cells characterized by the above-mentioned. 16. The method according to any one of claims 13 to 15,
The manufacturing method of the transparent conductive film for thin film solar cells in which the said composition for transparent conductive films contains a coupling agent further. The method of claim 17,
The said coupling agent is a silane coupling agent, The manufacturing method of the transparent conductive film for thin film solar cells. 16. The method according to any one of claims 13 to 15,
The thin film solar cell, wherein the wet coating method is a spray coating method, a dispenser coating method, a spin coating method, a knife coating method, a slit coating method, an inkjet coating method, a die coating method, a screen printing method, an offset printing method, or a gravure printing method. Method for producing a transparent conductive film for.

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