JP2012216814A - Transparent conductive film composition for thin-film solar cell and transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent conductive film which improves the power generation efficiency of a thin-film solar cell by increasing a difference in refractive index between itself and a photoelectric conversion layer, because this results in increase in reflected light on transparent conductive film-photoelectric conversion layer interface, and increased return light to the photoelectric conversion layer helps to improve power generation efficiency, as well as provide a transparent conductive film composition, or the one used in a thin-film solar cell wet coating process, from which this transparent conductive film can be fabricated.SOLUTION: A transparent conductive film composition for thin-film solar cells includes conductive oxide particulates, silica particles having on their surfaces conductive oxide nanoparticles in average diameter of 1 to 50 nm, and a binder. This composition contains 2 to 45 pts.mass of silica particles having conductive oxide nanoparticles on their surfaces to total 100 pts.mass of conductive oxide particulates and silica particles having conductive oxide nanoparticles on their surfaces.

Description

  The present invention relates to a transparent conductive film composition and a transparent conductive film. In more detail, it is related with the composition for transparent conductive films for thin film solar cells, and a transparent conductive film.

  Currently, clean energy is being researched, developed and put into practical use from the standpoint of environmental protection, and solar cells are attracting attention because of the inexhaustible and non-polluting nature of sunlight as an energy source. Conventionally, single-crystal silicon or polycrystalline silicon bulk solar cells have been used for solar cells. However, since the bulk solar cells are high in production cost and low in productivity, the solar cells save as much silicon as possible. The development of is urgent.

  Therefore, development of a thin film solar cell using a semiconductor such as amorphous silicon having a thickness of, for example, 0.3 to 2 μm has been vigorously performed. This thin-film solar cell has a structure in which a semiconductor layer in an amount necessary for photoelectric conversion is formed on a glass substrate or a heat-resistant plastic substrate, so that it is thin, lightweight, low cost, and easy to increase in area. There is.

  Thin-film solar cells have a superstrate structure and a substrate structure, and the superstrate type structure allows sunlight to enter from the translucent substrate side. Therefore, the order is usually substrate-transparent electrode-photoelectric conversion layer-backside electrode. The structure formed by is taken. On the other hand, the substrate structure usually has a structure formed in the order of substrate-back electrode-photoelectric conversion layer-transparent electrode.

  In this thin-film solar cell, the electrodes and the reflective film are conventionally 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-scale vacuum film-forming apparatus. . In order to improve this point, there is a technique for forming a transparent conductive film and a conductive reflective film by a wet coating method, which is a cheaper manufacturing method, using a composition for transparent conductive film and a composition for conductive reflective film. (Patent Document 1).

JP 2009-88489 A

  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 transparent conductive film, decreased the refractive index of the transparent conductive film used in the wet coating method, and determined the difference between the refractive index of the transparent conductive film and the refractive index of the photoelectric conversion layer. It has been found that by increasing the size, the reflected light at the transparent conductive film-photoelectric conversion layer interface increases, and the increased return light to the photoelectric conversion layer can improve the power generation efficiency of the thin-film solar cell. This method can be applied to any of a super straight type solar cell, a substrate type solar cell and a bulk silicon solar cell, and is particularly suitable for a super straight type.

This invention relates to the composition for transparent conductive films for thin film solar cells which solved the said subject with the structure shown below, and a transparent conductive film.
(1) Conductive oxide fine particles, silica particles having an average particle diameter of 1 to 50 nm and having conductive oxide nanoparticles on the surface, and a binder, the conductive oxide fine particles and the conductive oxide 2. A transparent conductive film for thin-film solar cells, comprising 2 to 45 parts by mass of silica particles having conductive oxide nanoparticles on the surface with respect to a total of 100 parts by mass of silica particles having nanoparticles on the surface Composition.
(2) conductive oxide fine particles, silica particles having an average particle diameter of 1 to 50 nm, having conductive oxide nanoparticles on the surface, and a cured binder, the conductive oxide fine particles and the conductive Transparent for thin film solar cells, comprising 2-45 parts by mass of silica particles having conductive oxide nanoparticles on the surface with respect to 100 parts by mass in total with silica particles having oxide nanoparticles on the surface Conductive film.
(3) A thin film solar cell comprising the transparent conductive film for a thin film solar cell according to (2).
(4) It 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 converting layer, and a transparent conductive film in this order, Comprising: Transparent of said (1) description on a photoelectric converting layer After apply | coating the composition for electrically conductive films by the wet-coating method and forming a transparent conductive coating film, the base material which has a transparent conductive coating film is baked at 130-400 degreeC, thickness: 0.03-0 A method for producing a transparent conductive film, which forms a 5 μm transparent conductive film.

  The composition for transparent conductive film of the present invention (1) can be applied and baked on the photoelectric conversion layer by a wet coating method, and is obtained depending on the content of silica particles having conductive oxide nanoparticles on the surface. The refractive index of the transparent conductive film can be lowered. That is, the difference between the refractive index of the transparent conductive film and the refractive index of the photoelectric conversion layer increases, the reflected light at the transparent conductive film-photoelectric conversion layer interface increases, and the increased return light to the photoelectric conversion layer, A transparent conductive film capable of improving the power generation efficiency of the thin film solar cell can be easily obtained.

  According to the present invention (2), reflected light at the transparent conductive film-photoelectric conversion layer interface increases, and a thin film solar cell with improved power generation efficiency can be obtained easily by the increased return light to the photoelectric conversion layer. Can do. According to the present invention (3), a thin film solar cell with improved power generation efficiency can be provided.

  According to the present invention (4), a transparent conductive film can be formed without using expensive vacuum equipment, and a thin-film solar cell with high power generation efficiency can be manufactured easily and at low cost.

It is a schematic diagram of the cross section of the thin film solar cell using the transparent conductive film of this invention.

  Hereinafter, the present invention will be specifically described based on embodiments. Unless otherwise indicated, “%” means “% by mass” unless otherwise specified.

[Composition for transparent conductive film for thin film solar cell]
The composition for transparent conductive film for thin film solar cells of the present invention (hereinafter referred to as “transparent conductive film composition”) is composed of conductive oxide fine particles and conductive oxide nano particles having an average particle size of 1 to 50 nm. The conductive oxide nanoparticles are included with respect to a total of 100 parts by mass of the silica particles including particles on the surface and the binder including the conductive oxide fine particles and the conductive oxide nanoparticles on the surface. It contains 2 to 45 parts by mass of silica particles on the surface.

  Silica particles having conductive oxide nanoparticles on the surface with an average particle diameter of 1 to 50 nm (hereinafter referred to as conductive oxide shell silica core particles) have good wettability with the photoelectric conversion layer, and the thickness of the film Unevenness can be reduced, and the refractive index of the transparent conductive film after curing is reduced. In FIG. 1, the schematic diagram of the cross section of the thin film solar cell using the transparent conductive film of this invention is shown. FIG. 1 shows an example of a super straight type. In FIG. 1, the thin-film solar cell includes a base material 10, a transparent electrode layer 3, a photoelectric conversion layer 2, a transparent conductive film 1, and a conductive reflective film 4, and sunlight enters from the substrate 10 side. Most of the incident sunlight is reflected by the conductive reflective film 4 and returns to the photoelectric conversion layer 2 to improve the conversion efficiency. Here, sunlight is also reflected at the interface between the transparent conductive film 1 and the photoelectric conversion layer 2, and the transparent conductive film 1 using the composition for transparent conductive film of the present invention has a low refractive index. The reflected light at the interface between the film 1 and the photoelectric conversion layer 2 can be increased, and the power generation efficiency of the thin film solar cell can be improved.

The conductive oxide of the conductive oxide nanoparticles is preferably at least one selected from the group consisting of ITO, ATO, In ₂ O ₃ , and SnO ₂ from the viewpoint of transparency and conductivity. ITO is more preferable. The reason why the average particle diameter of the conductive oxide shell silica core particles is set to 1 to 50 nm is that the conductive oxide shell silica core particles are less likely to cause secondary agglomeration due to lack of particle stability when smaller than 1 nm. This is because it is difficult, and if it is larger than 50 nm, the formability of the transparent conductive film deteriorates and is not suitable. Here, the average particle diameter of the conductive oxide shell silica core particles is measured with a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd./LA-950), and the particle diameter reference is calculated as the number. Of 50% average particle diameter (D ₅₀ ). The number-based average particle diameter measured by the laser diffraction / scattering particle size distribution measuring device is the value obtained when the particle diameters of 50 arbitrary particles were measured in an image observed with a transmission electron microscope TEM (JEOL JEM-2010F). It almost coincides with the average particle size.

  As an example, the conductive oxide shell silica core particle is obtained by dispersing the silica core particle in a solution containing the conductive oxide nanoparticle precursor and coating the surface of the silica core particle with the conductive oxide nanoparticle precursor. It can be manufactured by firing.

  The conductive oxide fine particles are made of ITO (Indium Tin Oxide), ATO (Antimony Tin Oxide) tin oxide powder, Al, Co, Fe, In, Sn, and Ti. Zinc oxide powder containing at least one metal selected from the group is preferred, among which ITO, ATO, AZO (Aluminum Zinc Oxide), IZO (Indium Zinc Oxide), TZO (Tin Zinc Oxide) is more preferable. The average particle diameter of the conductive oxide fine particles is preferably in the range of 10 to 100 nm in order to maintain stability in the dispersion medium, and more preferably in the range of 20 to 60 nm. . Here, the average particle diameter of the conductive oxide fine particles is measured using a BET method based on a specific surface measurement by QUANTACHROME AUTOSORB-1.

  The binder is preferably a composition containing one or both of a polymer type binder and a non-polymer type binder that are cured by heating. Examples of the polymer binder include acrylic resin, polycarbonate, polyester, alkyd resin, polyurethane, acrylic urethane, polystyrene, polyacetal, polyamide, polyvinyl alcohol, polyvinyl acetate, cellulose, and siloxane polymer. Polymeric binders include aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum or tin metal soaps, metal complexes, or metal alkoxide hydrolysates. It is preferable. Examples of the non-polymer type binder include metal soap, metal complex, metal alkoxide, halosilanes, 2-alkoxyethanol, β-diketone, and alkyl acetate. The metal contained in the metal soap, metal complex, or metal alkoxide is preferably aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum, tin, indium, or antimony. More preferred are alkoxides of silicon and aluminum (for example, tetraethoxysilane, tetramethoxysilane, aluminum ethoxide, and aluminum isopropoxide). These polymer-type binders and non-polymer-type binders are cured by heating, thereby enabling formation of a transparent conductive film having a low haze ratio and volume resistivity at low temperatures. The metal alkoxide may be a hydrolyzate or a dehydrated product.

When the metal alkoxide is to be cured, together with moisture for initiating the hydrolysis reaction, as a catalyst, an acid such as hydrochloric acid, nitric acid, phosphoric acid (H ₃ PO ₄ ), hydrofluoric acid, ammonia water, aqueous sodium hydroxide solution, etc. It is preferable to contain an alkali. From the viewpoint that the catalyst is easily volatilized and hardly remains after heating and curing, no halogen remains, P or the like which is weak in water resistance does not remain, and an alkali metal salt such as Na does not remain. Is more preferable. In the case of nitric acid, since N remains and acts as a donor even if it diffuses into the underlying photoelectric conversion layer (n-type), the conversion efficiency of the photoelectric conversion layer is not low, but rather the conversion efficiency is high. Can be.

  The composition for transparent conductive film contains 98 to 55 parts by mass of conductive oxide fine particles, preferably 95 to 95 parts by mass with respect to 100 parts by mass in total of the conductive oxide fine particles and the conductive oxide shell silica core particles. Including 65 parts by mass. This is because if the upper limit is exceeded, the effect of increased reflection is difficult to obtain, and if it is less than the lower limit, the conductivity is lowered.

  The composition for transparent conductive film contains 2 to 45 parts by mass of conductive oxide shell silica core particles, preferably 5 to 100 parts by mass in total of the conductive oxide fine particles and the conductive oxide shell silica core particles. Including ~ 35 parts by mass. This is because the refractive index of the transparent conductive film after curing cannot be sufficiently lowered below the lower limit, and the conductivity decreases below the upper limit.

  The content ratio of these binders is 5 to 50 parts by mass with respect to 100 parts by mass of the solid content in the composition for transparent conductive film (conductive oxide fine particles, conductive oxide shell silica core particles, and binder). Preferably, it is 10-30 parts by mass. Moreover, when using a metal alkoxide as a binder and nitric acid as a catalyst, when the nitric acid is 0.03 to 3 parts by mass with respect to 100 parts by mass of the metal alkoxide, the curing rate of the binder and the remaining amount of nitric acid From the viewpoint of In addition, when there is little quantity of the nitric acid which is a catalyst, the polymerization rate of the hydrolyzate of the metal alkoxide which is a binder will become slow. In addition, in the case of a hydrolysis solution having a network structure with a high degree of polymerization at the time of curing by firing, it is considered that the stress applied when shrinking is in a form that assists the contact between the conductive particles. : It is preferable in water being 10-120 mass parts with respect to 100 mass parts. If the amount of water required for hydrolysis is insufficient, a strong transparent conductive film may not be obtained.

  It is preferable to add a coupling agent to the composition for transparent conductive films according to the other components used. It consists of conductive oxide fine particles, conductive oxide shell silica core particles and binder, and a transparent conductive film formed from this transparent conductive film composition, a photoelectric conversion layer or This is for improving the adhesion with the conductive reflective film. Examples of the coupling agent include a silane coupling agent, an aluminum coupling agent, and a titanium coupling agent. The content of the coupling agent is the solid content (conductive oxide fine particles, conductive oxide shell silica core particles, binder, silane coupling agent, etc.) in the transparent conductive film composition: 100 parts by mass 0.2-5 mass parts is preferable, and 0.5-2 mass parts is more preferable.

  The composition for transparent conductive film preferably contains a dispersion medium in order to improve film formation. 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; N, N-dimethyl Examples include amides such as formamide and N, N-dimethylacetamide; sulfoxides such as dimethyl sulfoxide; glycols such as ethylene glycol; glycol ethers such as ethyl cellosolve and the like. In order to obtain good film formability, the content of the dispersion medium is preferably 65 to 99 parts by mass with respect to 100 parts by mass of the transparent conductive film composition.

  Moreover, it is preferable to add a low resistance agent, a water-soluble cellulose derivative, etc. according to the component to be used. The low resistance agent is preferably one or more selected from the group consisting of cobalt, iron, indium, nickel, lead, tin, titanium and zinc mineral salts and organic acid salts. 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 can be mentioned. The content of these low resistance agents is preferably 0.2 to 15 parts by mass with respect to 100 parts by mass of the conductive oxide powder. Although the water-soluble cellulose derivative is a non-ionizing surfactant, it has a very high ability to disperse the conductive oxide powder even when added in a small amount compared to other surfactants, and by adding the water-soluble cellulose derivative, The transparency of the formed transparent conductive film is also improved. Examples of the water-soluble cellulose derivative include hydroxypropyl cellulose and hydroxypropyl methylcellulose. The addition amount of the water-soluble cellulose derivative is preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the conductive oxide powder.

  The composition for transparent conductive film is prepared by mixing desired components with a paint shaker, a ball mill, a sand mill, a centrimill, a triple roll, etc., by a conventional method, and adding conductive oxide fine particles, conductive oxide shell silica core particles, and the like. Can be dispersed and manufactured. Of course, it can also be produced by a normal stirring operation.

[Transparent conductive film for thin film solar cells]
The transparent conductive film for a thin film solar cell of the present invention includes conductive oxide fine particles, conductive oxide shell silica core particles, and a cured binder, and the conductive oxide fine particles and the conductive oxide shell silica core. The conductive oxide shell silica core particles are contained in an amount of 2 to 45 parts by mass with respect to 100 parts by mass in total of the particles.

  The conductive oxide fine particles and the conductive oxide shell silica core particles are as described above, and the cured binder is obtained by curing the above-described binder, that is, the above-described composition for transparent conductive film for thin-film solar cells. It is a cured product.

  The manufacturing method of the transparent conductive film 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 converting layer, and a transparent conductive film in this order, Comprising: On a photoelectric converting layer The transparent conductive film composition is applied by a wet coating method to form a transparent conductive film, and then the substrate having the transparent conductive film is baked at 130 to 400 ° C. to obtain a thickness of 0 A transparent conductive film having a thickness of 0.03 to 0.5 μm is formed.

  First, the said composition for transparent conductive films is apply | coated by the wet coating method on the photoelectric converting layer of a thin film solar cell provided with a base material, a transparent electrode layer, a photoelectric converting layer, and a transparent conductive film in this order. The application here is performed so that the thickness after firing is 0.03 to 0.5 μm, preferably 0.05 to 0.2 μm. Subsequently, this coating film is preferably dried at a temperature of 20 to 120 ° C., more preferably 25 to 60 ° C., preferably 1 to 30 minutes, more preferably 2 to 10 minutes. In this way, a transparent conductive coating film is formed.

  As the base material, a light-transmitting substrate made of glass, ceramics, or a polymer material, or two or more kinds of light-transmitting laminates selected from the group consisting of glass, ceramics, a polymer material, and silicon are used. can do. Examples of the polymer substrate include a substrate formed of an organic polymer such as polyimide or PET (polyethylene terephthalate).

  Further, the wet coating method may be any one of 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 screen printing method, an offset printing method, or a die coating method. Although it is preferable, the present invention is not limited to this, and any method can be used.

  The spray coating method is a method of applying the transparent conductive film composition to the substrate in a mist form by compressed air, or applying the dispersion itself to the substrate in a mist form, and the dispenser coating method is For example, the transparent conductive film composition is placed in a syringe, and a dispersion is discharged from a fine nozzle at the tip of the syringe by pushing a piston of the syringe, and applied to a substrate. The spin coating method is a method in which a transparent conductive film composition is dropped onto a rotating substrate, and the dropped transparent conductive film composition is spread on the periphery of the substrate by its centrifugal force. Provides a base material with a predetermined gap from the tip of the knife so that it can move in the horizontal direction, and supplies the composition for transparent conductive film on the base material upstream of the knife, so that the base material is placed downstream. It is a method of moving horizontally. The slit coating method is a method in which a transparent conductive film composition is allowed to flow out of a narrow slit and applied onto a substrate, and the inkjet coating method is performed by filling a commercially available ink jet printer ink cartridge with the transparent conductive film composition. , A method of inkjet printing on a substrate. The screen printing method is a method in which a transparent conductive film composition is transferred to a substrate through a plate image formed thereon using wrinkles as a pattern indicating material. In the offset printing method, the composition for transparent conductive film attached to the plate is not directly attached to the substrate, but is transferred from the plate to a rubber sheet once, and then transferred from the rubber sheet to the substrate again. This is a printing method that utilizes the water repellency of water. The die coating method is a method in which the composition for a transparent conductive film supplied into a die is distributed by a manifold and extruded onto a thin film from a slit, and the surface of a traveling substrate is applied. The die coating method includes a slot coat method, a slide coat method, and a curtain coat method.

  Finally, the substrate having a transparent conductive coating is placed in the air or in an inert gas atmosphere such as nitrogen or argon at a temperature of 130 to 400 ° C., preferably 150 to 350 ° C., preferably 5 to 60 minutes, More preferably, it is fired by holding for 15 to 40 minutes. Here, the reason for applying the transparent conductive film composition so that the thickness of the transparent conductive film after firing is in the range of 0.03 to 0.5 μm is that the thickness after firing is less than 0.03 μm, or This is because when the thickness exceeds 0.5 μm, the enhanced reflection effect cannot be obtained sufficiently.

  The reason why the firing temperature of the base material having the coating film is in the range of 130 to 400 ° C. is that when the temperature is lower than 130 ° C., the transparent conductive film in the composite film has a problem that the surface resistance value becomes too high. On the other hand, if it exceeds 400 ° C., the production merit of a low temperature process cannot be utilized, that is, the manufacturing cost increases and the productivity decreases. In particular, amorphous silicon, microcrystalline silicon, or a hybrid silicon solar cell using these is relatively weak against heat, and the conversion efficiency is lowered by the firing process.

  The reason why the firing time of the substrate having the coating film is preferably 5 to 60 minutes is that when the firing time is less than the lower limit value, the surface resistance value becomes too high in the transparent conductive film in the composite film. This is because if the firing time exceeds the upper limit value, the manufacturing cost is increased more than necessary, the productivity is lowered, and the conversion efficiency of the solar battery cell is lowered.

  As described above, the transparent conductive film of the present invention can be formed. As described above, the manufacturing method of the present invention can eliminate a vacuum process such as a vacuum deposition method and a sputtering method as much as possible by using a wet coating method, and thus can manufacture a transparent conductive film at a lower cost.

  Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto.

First, silica particles having ITO nanoparticles on the surface (hereinafter referred to as ITO shell silica core particles) were prepared. Paint shaker using a zirconia bead having a diameter of 0.3 mm: 100 g in a glass bottle of 200 cm ³ with a total of 60 g so as to have the composition shown in Tables 1 to 5 (the numerical value indicates parts by mass). The compositions for transparent conductive films of Examples 1 to 24 and Comparative Examples 1 to 4 were produced by dispersing for 6 hours. In Tables 1 to 5, the conductive oxide fine particles are omitted, the ITO shell silica core particles are CS, and the coupling agent is a cup. Table 6 shows the average particle diameter of the ITO shell silica core particles used. Here, the ITO shell silica core particles 1 to 5 and the SiO ₂ binders 1 to 7 used as the binder were prepared as follows.

[ITO shell silica core particle 1]
As silica core particles, fumed silica powder (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL R812S) was prepared. Tri-t-butoxy indium: 90 g and tetra-t-butoxy tin: 10 g were added to 2-butanol: 50 g and mixed, and then acetylacetone: 75 g was added to the solution to obtain an alkoxide mixed solution 1 Was prepared.

  Next, a solution in which 33% hydrochloric acid: 60 g and 2-butanol: 240 g were mixed was prepared, added to the alkoxide mixed solution 1, and reacted at room temperature for 5 hours to obtain an ITO precursor solution. Into the obtained ITO precursor solution: 100 g, fumed silica powder: 10 g was added and stirred at 100 ° C. for 24 hours to coat the surface of the fumed silica powder with the ITO precursor. The obtained ITO precursor shell silica core particles were collected by filtration, washed, and then fired in a reducing atmosphere at 320 ° C. for 3 hours to produce ITO shell silica core particles 1.

[ITO shell silica core particle 2]
Fumed silica powder (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL RX200) was prepared as silica core particles. Tri-t-butoxy indium: 90 g and tetra-t-butoxy tin: 10 g were added to 2-butanol: 50 g, mixed, acetylacetone: 75 g was added to the solution, and alkoxide mixed solution 2 Was prepared.

  Next, a solution in which 33% hydrochloric acid: 60 g and 2-butanol: 240 g were mixed was prepared, added to the alkoxide mixed solution 2, and reacted at room temperature for 5 hours to obtain an ITO precursor solution. Into the obtained ITO precursor solution: 100 g, fumed silica powder: 10 g was added and stirred at 100 ° C. for 24 hours to coat the surface of the fumed silica powder with the ITO precursor. The obtained ITO precursor shell silica core particles were collected by filtration, washed, and then fired in a reducing atmosphere at 320 ° C. for 3 hours to produce ITO shell silica core particles 2.

[ITO shell silica core particle 3]
Fumed silica powder (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL RX200) was prepared as silica core particles. A 10 mass% indium trichloride solution: 180 g and a 5 mass% tin tetrachloride solution: 20 g were mixed to prepare a mixed solution 1.

  Pure water: 5 g of fumed silica powder is added to 100 g, and while stirring at 50 ° C., mixed solution 1 and 28% ammonia water: 200 g are added dropwise at the same time, and the ITO precursor is put on the surface of the fumed silica powder. Coated. The obtained ITO precursor shell silica core particles were collected by filtration, washed, and then fired at 320 ° C. for 3 hours in a reducing atmosphere to produce ITO shell silica core particles 3.

[ITO shell silica core particles 4]
Fumed silica powder (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL R812) was prepared as silica core particles. 5 mass% indium trichloride aqueous solution: 100g and 5 mass% tin tetrachloride aqueous solution: 20g were mixed, and the liquid mixture 2 was prepared.

  Pure water: 5 g of fumed silica powder is added to 100 g, and while stirring at 50 ° C., mixed liquid 2 and 28% ammonia water: 30 g are added dropwise at the same time, and the ITO precursor is put on the surface of the fumed silica powder. Coated. The obtained ITO precursor shell silica core particles were collected by filtration, washed, and then fired at 320 ° C. for 3 hours in a reducing atmosphere. Then, after dispersing in ethanol and centrifuging to settle a powder having a large particle size, ITO shell silica core particles 4 were produced using particles having a small particle size remaining in the supernatant.

[ITO shell silica core particles 5]
As silica core particles, fumed silica powder (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL OX50) was prepared. 12 mass% indium trichloride aqueous solution: 150g and 10 mass% tin tetrachloride aqueous solution: 15g were mixed, and the liquid mixture 3 was prepared.

  Pure water: 5 g of fumed silica powder is added to 100 g, and while stirring at 50 ° C., mixed solution 3 and 28% ammonia water: 15 g are added dropwise at the same time, and the ITO precursor is put on the surface of the fumed silica powder. Coated. The obtained ITO precursor shell silica core particles were collected by filtration, washed, and then fired in a reducing atmosphere at 320 ° C. for 3 hours to produce ITO shell silica core particles 5.

[SiO ₂ binder 1]
Using a four-neck flask made of 500 cm ³ glass, add 140 g of tetraethoxysilane and 140 g of ethyl alcohol, and stir a solution of 1.7 g of 60% nitric acid in 120 g of pure water at a time. In addition, it was then produced by reacting at 50 ° C. for 3 hours.

[SiO ₂ binder 2]
Using a 500 cm ³ glass four-necked flask, add 85 g of tetraethoxysilane and 100 g of ethyl alcohol and stir a solution of 0.09 g of 60% nitric acid in 110 g of pure water at room temperature while stirring. The tube pump was used for 10 to 15 minutes. Thereafter, a mixed solution of 45 g of aluminum tri-sec-butoxide and 60 g of ethyl alcohol mixed in advance was added to the obtained mixed solution over a period of 10 to 15 minutes using a tube pump. . The mixture was stirred at room temperature for about 30 minutes and then reacted at 50 ° C. for 3 hours.

[SiO ₂ binder 3]
Using a four-necked flask made of 500 cm ³ glass, add 115 g of tetraethoxysilane and 175 g of ethyl alcohol and stir a solution of 1.4 g of 35% hydrochloric acid in 110 g of pure water at a time. In addition, it was produced by reacting at 45 ° C. for 3 hours.

[SiO ₂ binder 4]
Using a four-necked flask made of 500 cm ³ glass, add 130 g of tetraethoxysilane and 145 g of ethyl alcohol and stir a solution of 1.25 g of 30% aqueous ammonia in 124 g of pure water while stirring. And then reacted at 45 ° C. for 3 hours.

[SiO ₂ binder 5]
Using a 500 cm ³ glass four-necked flask, 90 g of tetraethoxysilane and 100 g of ethyl alcohol were added, and 0.9 g of 60% nitric acid was dissolved in 110 g of pure water at room temperature while stirring. The solution was added over a period of 10 to 15 minutes. Thereafter, a mixed solution of 40 g of aluminum tri-sec-butoxide and 60 g of ethyl alcohol previously mixed with the obtained mixed solution was 10 It was added over a period of ~ 15 minutes. The mixture was stirred at room temperature for about 30 minutes and then reacted at 50 ° C. for 3 hours.

[SiO ₂ binder 6]
Using a four-necked flask made of 500 cm ³ glass, add 125 g of tetraethoxysilane and 160 g of ethyl alcohol, and stir a solution of 0.6 g of 60% nitric acid in 115 g of pure water at a time. In addition, it was then produced by reacting at 50 ° C. for 3 hours.

[SiO ₂ binder 7]
Using a four-necked flask made of 500 cm ³ glass, add 145 g of tetraethoxysilane and 140 g of ethyl alcohol and stir a solution of 0.045 g of 60% nitric acid in 115 g of pure water at a time. In addition, it was then produced by reacting at 50 ° C. for 3 hours.

[Coupling agent]
Vinyltriethoxysilane was used as the silane coupling agent. For the titanium coupling agent, the formula (1):

The titanium coupling agent which has the dialkyl pyrophosphite group represented by these was used.
[Mixed solvent]
The mixed solvent 1 is a mixture of isopropanol, ethanol and N, N-dimethylformamide (mass ratio 4: 2: 1), and the mixed solvent 2 is a mixture of ethanol and butanol (mass ratio 98: 2). Using.

[Non-polymer type binder]
The non-polymer type binder 1 is a mixture of 2-n-butoxyethanol and 3-isopropyl-2,4-pentanedione, and the non-polymer type binder 2 is 2,2-dimethyl-3,5-hexanedione. And non-polymer binder 3 is a mixture of 2-isobutoxyethanol, 2-hexyloxyethanol and n-propyl acetate (mass ratio 4: 1: 1). Was used.

[Examples 1 to 24]
In Example 1, first, as shown in Table 1 below, in an IPA serving as a dispersion medium, an ITO powder having an average particle size of 25 nm and an ITO shell silica core particle 1 having an average particle size of 15 nm are used as a conductive oxide powder. The SiO ₂ binder 1 as a binder at a ratio of 90:10 was mixed at a ratio of 30% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder. .

  In Example 2, an ATO powder having an average particle size of 40 nm and an ITO shell silica core particle 2 having an average particle size of 20 nm as conductive oxide powder in ethanol as a dispersion medium in a ratio of 95: 5 and a binder The non-polymer type binder 1 was mixed at a ratio of 10% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 3, in IPA serving as a dispersion medium, TZO powder having an average particle diameter of 30 nm and ITO shell silica core particle 2 having an average particle diameter of 20 nm as a conductive oxide powder were mixed at a ratio of 85:15 and a binder. The SiO ₂ binder 2 was mixed at a ratio of 30% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 4, an ITO powder having an average particle diameter of 30 nm and an ITO shell silica core particle 1 having an average particle diameter of 15 nm as conductive oxide powder in ethanol serving as a dispersion medium in a ratio of 85:15, and a binder The SiO ₂ binder 7 was mixed at a ratio of 25% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 5, an ITO powder having an average particle size of 35 nm and an ITO shell silica core particle 1 having an average particle size of 15 nm as a conductive oxide powder in a mixed solvent 1 serving as a dispersion medium in a ratio of 85 to 15, In addition, the SiO ₂ binder 6 was mixed as a binder at a ratio of 20% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 6, an ITO powder having an average particle size of 40 nm and an ITO shell silica core particle 3 having an average particle size of 35 nm were mixed as a conductive oxide powder in ethanol serving as a dispersion medium in a ratio of 82:18 and a binder. The SiO ₂ binder 2 was mixed at a ratio of 20% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

  In Example 7, in ethanol serving as a dispersion medium, ITO powder having an average particle diameter of 25 nm and ITO shell silica core particles 1 having an average particle diameter of 15 nm are used as a conductive oxide powder in a ratio of 82 to 18, and as a binder. Titanium having a dialkylpyrophosphite group represented by the chemical formula (1) is 30% by mass with respect to a total of 100% by mass of the conductive oxide fine particles, the ITO shell silica core particles, and the binder. The coupling agent is in a ratio of 0.5% by mass with respect to a total of 100% by mass of the conductive oxide fine particles, the ITO shell silica core particles, the binder, and the coupling agent that are solids after the coating is formed. Mixed.

  In Example 8, in the mixed solvent 2 serving as a dispersion medium, an ATO powder having an average particle diameter of 50 nm and an ITO shell silica core particle 2 having an average particle diameter of 20 nm as a conductive oxide powder are in a ratio of 80 to 20. Further, the non-polymer type binder 2 as a binder was mixed at a ratio of 30% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 9, in the mixed solvent 1 serving as a dispersion medium, an ATO powder having an average particle diameter of 30 nm and an ITO shell silica core particle 1 having an average particle diameter of 15 nm as a conductive oxide powder are in a ratio of 80:20. Further, the SiO ₂ binder 3 as a binder was mixed at a ratio of 15% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 10, an ITO powder having an average particle size of 40 nm and an ITO shell silica core particle 1 having an average particle size of 15 nm as a conductive oxide powder in a mixed solvent 2 serving as a dispersion medium in a ratio of 80 to 20, also a SiO ₂ binding agent 4 as a binder, per 100 wt% of the conductive oxide microparticles and ITO shell silica core particles and a binder were mixed at a ratio of 30 mass%.

In Example 11, an ITO powder having an average particle diameter of 35 nm and an ITO shell silica core particle 3 having an average particle diameter of 35 nm as a conductive oxide powder in a mixed solvent 2 serving as a dispersion medium in a ratio of 80 to 20, also a SiO ₂ binding agent 5 as a binder, per 100 wt% of the conductive oxide microparticles and ITO shell silica core particles and a binder were mixed at a ratio of 25 mass%.

In Example 12, ITO powder having an average particle diameter of 30 nm and ITO shell silica core particles 1 having an average particle diameter of 15 nm as conductive oxide powder in ethanol serving as a dispersion medium in a ratio of 78 to 22, and binder The SiO ₂ binder 6 is 25% by mass with respect to a total of 100% by mass of the conductive oxide fine particles, the ITO shell silica core particles and the binder, and a silane coupling agent (KBE-1003 manufactured by Shin-Etsu Silicone Co., Ltd.). ) Was mixed at a ratio of 0.7% by mass with respect to a total of 100% by mass of the conductive oxide fine particles, the ITO shell silica core particles, the binder, and the coupling agent, which would be solids after the coating was formed. .

In Example 13, in IPA as a dispersion medium, an IZO powder having an average particle diameter of 25 nm and an ITO shell silica core particle 2 having an average particle diameter of 20 nm as a conductive oxide powder in a ratio of 75 to 25 and a binder The SiO ₂ binder 1 was mixed at a ratio of 25% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

  In Example 14, an ITO powder having an average particle diameter of 25 nm and an ITO shell silica core particle 3 having an average particle diameter of 35 nm were mixed as a conductive oxide powder in butanol serving as a dispersion medium in a ratio of 75 to 25 and a binder. The non-polymer type binder 3 was mixed at a ratio of 10% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 15, in IPA as a dispersion medium, an IZO powder having an average particle diameter of 25 nm and an ITO shell silica core particle 1 having an average particle diameter of 15 nm as a conductive oxide powder in a ratio of 75 to 25 and a binder The SiO ₂ binder 7 was mixed at a ratio of 25% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 16, in the mixed solvent 1 serving as a dispersion medium, an IZO powder having an average particle size of 25 nm and an ITO shell silica core particle 2 having an average particle size of 20 nm as a conductive oxide powder in a ratio of 70:30. Further, the SiO ₂ binder 5 was mixed as a binder at a ratio of 30% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

  In Example 17, in a mixed solvent 1 serving as a dispersion medium, TZO powder having an average particle diameter of 30 nm and ITO shell silica core particle 1 having an average particle diameter of 15 nm as a conductive oxide powder are in a ratio of 70:30. Further, the non-polymer type binder 2 as a binder was mixed at a ratio of 15% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 18, in a mixed solvent 1 serving as a dispersion medium, an ITO powder having an average particle size of 40 nm and an ITO shell silica core particle 1 having an average particle size of 15 nm as a conductive oxide powder in a ratio of 65 to 35, also a SiO ₂ binding agent 2 as a binder, per 100 wt% of the conductive oxide microparticles and ITO shell silica core particles and a binder were mixed at a ratio of 15 mass%.

In Example 19, in IPA as a dispersion medium, an ATO powder having an average particle diameter of 40 nm and an ITO shell silica core particle 2 having an average particle diameter of 20 nm as a conductive oxide powder were mixed at a ratio of 65 to 35, and a binder. The SiO ₂ binder 7 was mixed at a ratio of 30% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 20, an ITO powder having an average particle diameter of 25 nm and an ITO shell silica core particle 2 having an average particle diameter of 20 nm as conductive oxide powder in ethanol as a dispersion medium in a ratio of 60 to 40, and a binder The SiO ₂ binder 1 was mixed at a ratio of 30% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 21, ITO powder having an average particle size of 30 nm and ITO shell silica core particles 2 having an average particle size of 20 nm as conductive oxide powder in IPA serving as a dispersion medium in a ratio of 98 to 2, and binder The SiO ₂ binder 7 was mixed at a ratio of 20% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 22, ITO powder having an average particle diameter of 25 nm and ITO shell silica core particles 3 having an average particle diameter of 35 nm as a conductive oxide powder in butanol serving as a dispersion medium in a ratio of 65:45, and a binder The SiO ₂ binder 6 was mixed at a ratio of 15% by mass with respect to a total of 100% by mass of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 23, an ITO powder having an average particle diameter of 30 nm and an ITO shell silica core particle 4 having an average particle diameter of 1 nm as conductive oxide powder in ethanol serving as a dispersion medium in a ratio of 90:10 and a binder The SiO ₂ binder 5 was mixed at a ratio of 20% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Example 24, an ATO powder having an average particle diameter of 30 nm and an ITO shell silica core particle 5 having an average particle diameter of 50 nm were mixed as a conductive oxide powder in IPA serving as a dispersion medium at a ratio of 80:20 and a binder. The SiO ₂ binder 4 was mixed at a ratio of 30% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

[Comparative Examples 1-4]
In Comparative Example 1, in IPA serving as a dispersion medium, ITO powder having an average particle diameter of 25 nm as a conductive oxide powder, SiO ₂ binder 1 as a binder, and a total of 100 masses of the conductive oxide fine particles and the binder. % Was mixed at a ratio of 30% by mass.

In Comparative Example 2, an ITO powder having an average particle diameter of 25 nm and an ITO shell silica core particle 1 having an average particle diameter of 15 nm as a conductive oxide powder in IPA serving as a dispersion medium in a ratio of 99: 1 and a binder The SiO ₂ binder 1 was mixed at a ratio of 25% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Comparative Example 3, ITO powder having an average particle diameter of 25 nm and ITO shell silica core particles 1 having an average particle diameter of 15 nm as conductive oxide powder in IPA serving as a dispersion medium in a ratio of 53 to 47 and binder The SiO ₂ binder 1 was mixed at a ratio of 30% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

In Comparative Example 4, an ITO powder having an average particle diameter of 25 nm and an ITO shell silica core particle 1 having an average particle diameter of 15 nm were mixed as a conductive oxide powder in IPA serving as a dispersion medium in a ratio of 50:50 and a binder. The SiO ₂ binder 1 was mixed at a ratio of 25% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ITO shell silica core particles, and the binder.

[Examples 25-27]
Next, silica particles having ATO nanoparticles on the surface (hereinafter referred to as ATO shell silica core particles), In ₂ O ₃ (hereinafter referred to as IO shell silica core particles), and SnO ₂ (hereinafter referred to as TO shell silica core particles). ) Was produced. A total of 60 g in a glass bottle of 100 cm ³ so that the composition shown in Table 7 (the numerical value indicates parts by mass) is put in a glass bottle of 100 cm ³ , and the diameter is 0.3 mm. The composition for transparent conductive films of Examples 25-27 was produced by carrying out time dispersion. In Table 7, conductive oxide fine particles are omitted, ATO shell silica core particles are ATO, IO shell silica core particles are IO, TO shell silica core particles are TO, and a coupling agent is a cup. Here, the ATO shell silica core particles, the IO shell silica core particles, and the TO shell silica core particles were produced as follows.

[ATO shell silica core particles]
Fumed silica powder (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL RX200) was prepared as silica core particles. A 15% by mass antimony trichloride solution: 150 g and a 5% by mass tin tetrachloride solution: 20 g were mixed to prepare a mixed solution 4.

  Pure water: 5 g of fumed silica powder is put into 100 g, and while stirring at 50 ° C., mixed solution 4 and 28% ammonia water: 15 g are added dropwise at the same time, and the ATO precursor is put on the surface of the fumed silica powder. Coated. The obtained ATO precursor shell silica core particles were collected by filtration, washed, and then fired at 350 ° C. for 4 hours in a reducing atmosphere to produce ATO shell silica core particles.

[IO shell silica core particles]
As silica core particles, fumed silica powder (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL R812S) was prepared. 30% by mass indium trichloride aqueous solution: 200 g was prepared.

  Pure water: 5 g of fumed silica powder is put into 100 g, and while stirring at 50 ° C., an indium trichloride aqueous solution and 28% ammonia water: 30 g are added dropwise at the same time to the surface of the fumed silica powder. Coated. The obtained ATO precursor shell silica core particles were collected by filtration, washed, and then fired at 320 ° C. for 3 hours in a reducing atmosphere to produce ATO shell silica core particles.

[TO shell silica core particles]
Fumed silica powder (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL RX200) was prepared as silica core particles. 20% by mass tin tetrachloride aqueous solution: 200 g was prepared.

  Pure water: 5 g of fumed silica powder is put into 100 g, and while stirring at 50 ° C., a tin tetrachloride aqueous solution and 28% ammonia water: 30 g are added dropwise at the same time to form a TO precursor on the surface of the fumed silica powder. Coated. The obtained TO precursor shell silica core particles were collected by filtration, washed, and then fired in a reducing atmosphere at 320 ° C. for 3 hours to produce TO shell silica core particles.

In Example 25, an ITO powder having an average particle diameter of 30 nm and an ATO shell silica core particle having an average particle diameter of 20 nm as conductive oxide powder in ethanol as a dispersion medium in a ratio of 75 to 25 and as a binder The SiO ₂ binder 3 was mixed at a ratio of 15% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the ATO shell silica core particles, and the binder.

In Example 26, in IPA serving as a dispersion medium, ITO powder having an average particle size of 35 nm and IO shell silica core particles having an average particle size of 25 nm as a conductive oxide powder were used in a ratio of 70:30 and as a binder. The SiO ₂ binder 5 was mixed at a ratio of 25% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the IO shell silica core particles, and the binder.

In Example 27, an ITO powder having an average particle size of 30 nm and a TO shell silica core particle having an average particle size of 25 nm as a conductive oxide powder in a mixed solvent 1 serving as a dispersion medium in a ratio of 80 to 20, As a binder, the SiO ₂ binder 7 was mixed at a ratio of 20% by mass with respect to 100% by mass in total of the conductive oxide fine particles, the TO shell silica core particles, and the binder.

[Evaluation of composition for transparent conductive film]
About refractive index evaluation, about the composition for transparent conductive films shown in Examples 1-27 and Comparative Examples 1-4, with respect to the glass substrate whose optical constant is known, the wet coating method (spin coating method, die coating method, After forming the transparent electrode film by spray coating method or offset printing method), the transparent conductive film having a thickness of 0.07 to 0.15 μm was formed by baking at 130 to 400 ° C. for 5 to 60 minutes. The film was measured using a spectroscopic ellipsometry apparatus (JA Woollam Japan Co., Ltd. M-2000), data was analyzed for the transparent electrode film portion, and the optical constant was determined. From the analyzed optical constant, a value of 633 nm was taken as the refractive index. Tables 1 to 5 and 7 show the evaluation results of the refractive index.

As shown in FIG. 1, first, a glass substrate having an SiO ₂ layer (not shown) having a thickness of 50 nm formed on one main surface is prepared as a substrate 10, and an uneven texture is formed on the surface of this SiO ₂ layer. Then, a surface electrode layer (SnO ₂ film) 3 having a thickness of 800 nm and doped with F (fluorine) was formed as the transparent electrode layer 3. The transparent electrode layer 3 was patterned using a laser processing method to form an array, and wirings for electrically connecting them were formed. Next, the photoelectric conversion layer 2 was formed on the transparent electrode layer 3 using a plasma CVD method. In this embodiment, the photoelectric conversion layer 2 includes p-type a-Si: H (amorphous silicon carbide), i-type a-Si (amorphous silicon), and n-type μc-Si in this order from the substrate 10 side. A film made of (microcrystalline silicon carbide) was obtained by stacking. The photoelectric conversion layer 2 was patterned using a laser processing method. This was utilized for the evaluation of the composition for transparent conductive films shown in Examples as a solar battery cell in which film formation had already progressed.

  About the composition for transparent conductive films shown in Examples 1-27 and Comparative Examples 1-4, the thickness after baking will be 0.07-0.15 micrometer with respect to the photovoltaic cell in which film-forming has already progressed. Thus, after apply | coating with the wet coating method (spin coating method, die coating method, spray coating method, offset printing method), it dried for 5 minutes at the low temperature of 25-60 degreeC, and formed the transparent conductive coating film. Tables 1 to 5 and 7 show coating methods.

  Then, after applying the conductive reflective film composition prepared by the following method on the transparent conductive coating film by a wet coating method so that the thickness after firing becomes 0.05 to 2.0 μm, the temperature The conductive reflective coating film was formed by drying at a low temperature of 25 to 60 ° C. for 5 minutes. Subsequently, the transparent conductive film 1 and the electroconductive reflective film 4 were formed by baking at 130-400 degreeC for 5 to 60 minutes. Tables 1 to 5 and 7 show the baking conditions for the transparent conductive film and the conductive reflective film, and the film thickness after baking of the transparent conductive film 1. Here, the film thickness was measured by cross-sectional observation using a scanning electron microscope (SEM, apparatus names: S-4300, SU-8000) manufactured by Hitachi High-Technologies. In addition, the preparation method of the composition for electroconductive reflective films was as follows.

  First, silver nitrate was dissolved in deionized water to prepare a metal ion aqueous solution. In addition, sodium citrate was dissolved in deionized water to prepare a sodium citrate aqueous solution having a concentration of 26% by weight. Reduction in which granular ferrous sulfate is directly added and dissolved in this aqueous sodium citrate solution in a nitrogen gas stream maintained at 35 ° C. to contain a citrate ion and a ferrous ion in a molar ratio of 3: 2. An aqueous agent solution was prepared. Next, with the nitrogen gas stream maintained at 35 ° C., a magnetic stirrer stirrer is placed in the reducing agent aqueous solution, the stirrer is rotated at a rotation speed of 100 rpm, and the reducing agent aqueous solution is stirred, The metal salt aqueous solution was dropped into the reducing agent aqueous solution and synthesized. Here, the amount of the metal salt aqueous solution added to the reducing agent aqueous solution is adjusted so that the concentration of each solution is adjusted to 1/10 or less of the amount of the reducing agent aqueous solution. The reaction temperature was maintained at 40 ° C. The mixing ratio of the reducing agent aqueous solution and the metal salt aqueous solution was adjusted so that the equivalent of ferrous ions added as a reducing agent was three times the equivalent of metal ions. After the addition of the aqueous metal salt solution to the reducing agent aqueous solution was completed, stirring of the mixed solution was continued for an additional 15 minutes to generate metal particles inside the mixed solution to obtain a metal particle dispersion in which the metal particles were dispersed. The pH of the metal particle dispersion was 5.5, and the stoichiometric amount of metal particles in the dispersion was 5 g / liter. The obtained dispersion was allowed to stand at room temperature, thereby precipitating metal particles in the dispersion and separating aggregates of the precipitated metal particles by decantation. Deionized water was added to the separated metal agglomerated to form a dispersion, subjected to desalting treatment by ultrafiltration, and further subjected to substitution washing with methanol, whereby the metal (silver) content was set to 50% by mass. Thereafter, using a centrifuge, the centrifugal force of the centrifuge is adjusted to separate relatively large silver particles having a particle size of more than 100 nm, whereby silver nanoparticles having a primary particle diameter of 10 to 50 nm are separated. Was adjusted to contain 71% by number average. That is, the ratio of the silver nanoparticles occupying the range of the primary particle diameter of 10 to 50 nm with respect to 100% of all silver nanoparticles on the number average was adjusted to 71%. The obtained silver nanoparticles were chemically modified with an organic main chain protective agent having a carbon skeleton of 3 carbon atoms.

  Next, 10 parts by mass of the obtained metal nanoparticles were dispersed by adding to 90 parts by mass of a mixed solution containing water, ethanol and methanol. Further, 4% by mass of polyvinylpyrrolidone, 1% by mass of silver citrate, and 95% by mass of the metal nanoparticles are added to the dispersion as additives, so that the composition for conductive reflective film is added. Got. As mentioned above, after apply | coating the obtained composition for electroconductive reflective films with a wet coating method so that the thickness after baking on a transparent conductive coating film may be 0.05-2.0 micrometers, it is 130- The conductive back surface reflection film 4 was formed on the transparent conductive film 1 by baking at 400 ° C. for 5 to 60 minutes.

  Next, when evaluating power generation efficiency as a solar battery cell, a reinforcing film composition as a reinforcing film on the conductive reflective film is formed on the solar battery cell which has already been formed to the conductive reflective film by a die coating apparatus. After the solvent is removed from the coating film for reinforcing film by vacuum drying so that the thickness after firing the composition for reinforcing film is 350 nm, the solar battery cell is heated at 180 ° C. in a hot air drying furnace. For 20 minutes, the coating film for reinforcing film was thermally cured to obtain a reinforcing film for conductive reflective film. In addition, the preparation method of the composition for reinforcing films was as follows.

First, 8% by mass of ITO particles having an average particle diameter of 25 nm as conductive oxide fine particles, 2% by mass of titanium coupling agent having a dialkylpyrophosphite group as a coupling agent, and a mixture of ethanol and butanol as a dispersion medium The liquid (mass ratio 98: 2) was mixed with 90% by mass and stirred at room temperature at a rotation speed of 800 rpm for 1 hour. Next, 60 g of this mixture was placed in a 200 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 to prepare a dispersion of ITO particles. Here, the titanium coupling agent having a dialkyl pyrophosphite group is represented by the above chemical formula (1). Next, 4% by mass of the dispersion liquid of ITO particles was mixed with 86% by mass of ethanol as a dispersion medium, and then the SiO ₂ binder 1 was further mixed at 10% by mass to obtain a base liquid of the composition for reinforcing film. It was. Next, 95% by mass of this base solution and 5% by mass of fumed silica dispersion as an additive are mixed, and dispersed and mixed at room temperature for 10 minutes by an ultrasonic vibrator, and the mixture is thoroughly blended to form a reinforcing membrane. A coating liquid, which is a composition for use, was prepared.

  The solar battery cell formed up to the reinforcing film for the conductive reflective film is obtained by converting the photoelectric conversion layer 2, the transparent conductive film 1 formed thereon, the conductive reflective film 4, and the conductive reflective film reinforcing film into a laser. Patterning was performed using a processing method.

  As an evaluation method of the solar battery cell, there are output characteristics and short-circuit current density when lead wire wiring is performed on a processed substrate subjected to patterning using a laser processing method and an IV characteristic curve is confirmed. The solar cell in which the transparent conductive film, the conductive reflective film, and the reinforcing film were all formed by the sputtering method using a photoelectric conversion layer obtained by the same manufacturing method as in the example was used as the value of (Jsc). Relative output evaluation was performed. Tables 1-5 and 7 show these results.

Here, as shown in FIG. 1, a thin-film solar cell formed entirely by sputtering is a glass substrate in which a SiO ₂ layer (not shown) having a thickness of 50 nm is first formed on one main surface. The surface electrode layer (SnO ₂ film) 3 having an uneven texture on the surface and doped with F (fluorine) was formed on the SiO ₂ layer. The transparent electrode layer 3 was patterned using a laser processing method to form an array, and wirings for electrically connecting them were formed. Next, the photoelectric conversion layer 2 was formed on the transparent electrode layer 3 using a plasma CVD method. In this embodiment, the photoelectric conversion layer 2 includes p-type a-Si: H (amorphous unit cost silicon), i-type a-Si (amorphous silicon), and n-type μc-Si in this order from the substrate 10 side. A film made of (microcrystalline silicon carbide) was obtained by stacking. After patterning the photoelectric conversion layer 2 using a laser processing method, a transparent conductive film (ZnO layer) 1 having a thickness of 80 nm and a thickness of 200 nm are formed on the photoelectric conversion layer 2 using a magnetron inline sputtering apparatus. A conductive reflective film (silver electrode layer) 4 is formed sequentially.

  As is apparent from Tables 1 to 4 and 7, in all of Examples 1 to 27, the refractive index is as low as 1.55 to 1.76, the relative power generation efficiency is 115 to 120%, and the relative short-circuit current density is 103 to 103. It was as high as 107%. On the other hand, as can be seen from Table 5, the refractive index is high in Comparative Example 1 that does not include conductive oxide shell silica core particles and Comparative Example 2 in which the content of conductive oxide shell silica core particles is low. The relative power generation efficiency and the relative short-circuit current density were both about 100%. In Comparative Examples 3 and 4 having a large content of conductive oxide shell silica core particles, the relative power generation efficiency was low despite the low refractive index. This is considered to be because the conductivity of the transparent conductive film was lowered.

  As described above, the composition for transparent conductive film of the present invention can be applied and baked on the photoelectric conversion layer by a wet coating method, and the transparent film obtained by the content of the conductive oxide shell silica core particles. The refractive index of the conductive film could be adjusted. 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.

DESCRIPTION OF SYMBOLS 10 Base material 1 Transparent conductive film 2 Photoelectric conversion layer 3 Transparent electrode layer 4 Conductive reflective film

Then, 33% hydrochloric acid: 60 g and, 2-butanol: a 240g a solution, prepare mixed and added to the alkoxide mixed solution 1 to obtain an ITO precursor solution by reacting at room temperature for 5 hours. Into the obtained ITO precursor solution: 100 g, fumed silica powder: 10 g was added and stirred at 100 ° C. for 24 hours to coat the surface of the fumed silica powder with the ITO precursor. The obtained ITO precursor shell silica core particles were collected by filtration, washed, and then fired in a reducing atmosphere at 320 ° C. for 3 hours to produce ITO shell silica core particles 1.

Then, 33% hydrochloric acid: 60 g and, 2-butanol: a 240g a solution, prepare mixed and added to the alkoxide mixed solution 2 to obtain an ITO precursor solution by reacting at room temperature for 5 hours. Into the obtained ITO precursor solution: 100 g, fumed silica powder: 10 g was added and stirred at 100 ° C. for 24 hours to coat the surface of the fumed silica powder with the ITO precursor. The obtained ITO precursor shell silica core particles were collected by filtration, washed, and then fired in a reducing atmosphere at 320 ° C. for 3 hours to produce ITO shell silica core particles 2.

First, silver nitrate was dissolved in deionized water to prepare a metal ion aqueous solution. In addition, sodium citrate was dissolved in deionized water to prepare a sodium citrate aqueous solution having a concentration of 26% by weight. Reduction in which granular ferrous sulfate is directly added and dissolved in this aqueous sodium citrate solution in a nitrogen gas stream maintained at 35 ° C. to contain a citrate ion and a ferrous ion in a molar ratio of 3: 2. An aqueous agent solution was prepared. Next, with the nitrogen gas stream maintained at 35 ° C., a magnetic stirrer stirrer is placed in the reducing agent aqueous solution, the stirrer is rotated at a rotation speed of 100 rpm, and the reducing agent aqueous solution is stirred, The metal salt aqueous solution was dropped into the reducing agent aqueous solution and synthesized. Here, the addition amount of the metal salt solution to the reducing agent aqueous solution, as will become 1/10 or less of the amount of the reducing agent aqueous solution, by manufactured by adjusting the concentration of each solution was added dropwise a metal salt aqueous solution at room temperature However, the reaction temperature was kept at 40 ° C. The mixing ratio of the reducing agent solution and the metallic salt aqueous solution is equivalent of ferrous ions added as the reducing agent, it was made so adjusted as to be 3 times the equivalent of a metal ion. After the addition of the aqueous metal salt solution to the reducing agent aqueous solution was completed, stirring of the mixed solution was continued for an additional 15 minutes to generate metal particles inside the mixed solution to obtain a metal particle dispersion in which the metal particles were dispersed. The pH of the metal particle dispersion was 5.5, and the stoichiometric amount of metal particles in the dispersion was 5 g / liter. The obtained dispersion was allowed to stand at room temperature, thereby precipitating metal particles in the dispersion and separating aggregates of the precipitated metal particles by decantation. Deionized water was added to the separated metal agglomerated to form a dispersion, subjected to desalting treatment by ultrafiltration, and further subjected to substitution washing with methanol, whereby the metal (silver) content was set to 50% by mass. Thereafter, using a centrifugal separator, and, prepare centrifugal force of the centrifuge, by separating the relatively large silver particles having a particle size of more than 100 nm, the silver nano-in range of the primary particle diameter 10~50nm particles by the number average was made adjusted to contain 71%. That is, the proportion of silver nanoparticles occupying a range of primary particle size 10~50nm for 100% of all the silver nanoparticles by the number average was made adjustment so that the 71%. The obtained silver nanoparticles were chemically modified with an organic main chain protective agent having a carbon skeleton of 3 carbon atoms.

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

Claims (4)

  Conductive oxide fine particles, silica particles having an average particle diameter of 1 to 50 nm, having conductive oxide nanoparticles on the surface, and a binder, comprising conductive oxide fine particles and conductive oxide nanoparticles The composition for a transparent conductive film for a thin film solar cell, comprising 2 to 45 parts by mass of silica particles having conductive oxide nanoparticles on the surface with respect to a total of 100 parts by mass of silica particles on the surface .   The conductive oxide fine particles and the conductive oxide nano particles comprising conductive oxide fine particles, silica particles having conductive oxide nanoparticles having an average particle diameter of 1 to 50 nm on the surface, and a cured binder. A transparent conductive film for a thin-film solar cell, comprising 2 to 45 parts by mass of silica particles having conductive oxide nanoparticles on the surface with respect to 100 parts by mass in total with silica particles having particles on the surface.   The thin film solar cell containing the transparent conductive film for thin film solar cells of Claim 2.   It 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 converting layer, and a transparent conductive film in this order, Comprising: The composition for transparent conductive films of Claim 1 on a photoelectric converting layer. After the object is applied by a wet coating method to form a transparent conductive coating film, the substrate having the transparent conductive coating film is baked at 130 to 400 ° C., and the thickness is 0.03 to 0.5 μm. A manufacturing method of a transparent conductive film which forms a conductive film.