JP2012151388A - Composition for transparent conductive film of solar cell and transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composition for a transparent conductive film used in the wet coating method for thin film solar cell, and to provide a transparent conductive film created by that composition, the transparent conductive film enhances power generation efficiency of a thin film solar cell by increasing the difference of refractive index between the transparent conductive film and a photoelectric conversion layer thereby increasing reflection light on the interface of the transparent conductive film-photoelectric conversion layer and returning increased light to the photoelectric conversion layer, and the composition for transparent conductive film can form this transparent conductive film.SOLUTION: The composition for the transparent conductive film of a thin film solar cell contains conductive oxide particles, anisotropic magnesium fluoride particles having an average grain size of 1-50 nm, and a binder. For total 100 pts.mass of the conductive oxide particles and anisotropic magnesium fluoride particles, 2-35 pts.mass of anisotropic magnesium fluoride particles are contained.

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 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 solar energy. 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 the advantage that it is thin, lightweight, low-cost, and easy to increase in area because it has a structure in which a semiconductor layer of an amount necessary for photoelectric conversion is formed on a glass substrate or a heat-resistant plastic substrate. is there.

  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-type structure usually has a structure formed in the order of substrate-back surface electrode-photoelectric conversion layer-transparent electrode.

  In these thin-film solar cells, the electrodes and the reflective film have been conventionally formed by a vacuum film formation method such as sputtering, but in general, a large cost is required for the introduction, maintenance, and operation of a large-scale vacuum film formation apparatus. is there. 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 inventors have improved the composition for transparent conductive film, and increased the difference between the refractive index of the transparent conductive film used in the wet coating method and the refractive index of the photoelectric conversion layer, thereby producing a transparent conductive film-photoelectric conversion. It has been found that the reflected light at the layer interface increases, and the power generation efficiency of the thin film solar cell can be improved by the increased return light to the photoelectric conversion layer. This technique can be applied to any of a super straight type thin film solar cell, a substrate type thin film solar cell, and a bulk silicon solar cell, and is particularly suitable for a super straight type thin film solar cell.

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) The conductive oxide particles, the average particle diameter: 1 to 50 nm of anisotropic magnesium fluoride particles, and a binder, the total of 100 masses of the conductive oxide particles and anisotropic magnesium fluoride particles The composition for transparent conductive films for thin film solar cells, comprising 2 to 35 parts by mass of anisotropic magnesium fluoride particles with respect to parts.
(2) The composition for a transparent conductive film for a thin-film solar cell according to the above (1), wherein the binder is a polymer-type binder and / or a non-polymer-type binder that is cured by heating.
(3) The above (2) description, wherein the non-polymer type binder is at least one selected from the group consisting of metal soap, metal complex, metal alkoxide, halosilane, 2-alkoxyethanol, β-diketone, and alkyl acetate. A transparent conductive film composition for thin film solar cells.
(4) Total of conductive oxide particles and anisotropic magnesium fluoride particles, including conductive oxide particles, average particle diameter: 1 to 50 nm anisotropic magnesium fluoride particles, and a cured binder A transparent conductive film for a thin film solar cell, comprising 2 to 35 parts by mass of anisotropic magnesium fluoride particles with respect to 100 parts by mass.
(5) The transparent conductive film for a thin-film solar cell according to (4), wherein the binder is a polymer-type binder and / or a non-polymer-type binder.
(6) The above (5) description, wherein the non-polymer type binder is at least one selected from the group consisting of metal soaps, metal complexes, metal alkoxides, halosilanes, 2-alkoxyethanol, β-diketone, and alkyl acetate. Transparent conductive film for thin film solar cells.
(7) A thin film solar cell comprising the transparent conductive film for a thin film solar cell according to any one of (4) to (6).
(8) 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, Comprising: Any one of Claims 1-3 on a photoelectric converting layer. After applying the composition for transparent conductive film of description by a wet coating method to form a transparent conductive coating film, the base material which has a transparent conductive coating film is baked at 130-400 degreeC, thickness: 0. A method for producing a transparent conductive film, comprising forming a transparent conductive film having a thickness of 03 to 0.5 μm.
(9) 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. The method for producing a transparent conductive film according to (8) above.

  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 depending on the content of anisotropic magnesium fluoride particles, The refractive index 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 (4), the 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 (7), 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 “conductive film composition”) includes conductive oxide particles, anisotropic magnesium fluoride particles having an average particle size of 1 to 50 nm, And 2 to 35 parts by mass of anisotropic magnesium fluoride particles with respect to 100 parts by mass in total of the conductive oxide particles and anisotropic magnesium fluoride particles.

  The conductive oxide particles are made of ITO (Indium Tin Oxide), tin oxide powder of ATO (Antimony Tin Oxide) or Al, Co, Fe, In, Sn, and Ti. Zinc oxide powder containing at least one kind of metal selected from the group is preferable, and among them, ITO, ATO, AZO (Aluminum Zinc Oxide), IZO (Indium Zinc Oxide), TZO (Tin Zinc Oxide: tin-doped 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 is measured by a BET method by specific surface measurement by QUANTACHROME AUTOSORB-1 or a dynamic light scattering method by LB-550 manufactured by Horiba. Unless otherwise specified, measurement is performed using the BET method based on specific surface measurement by QUANTACHROME AUTOSORB-1.

Anisotropic magnesium fluoride particles have an average particle size of 1 to 50 nm. If the particle size is smaller than 1 nm, the stability of the particles is insufficient, so that secondary agglomeration is likely to occur, and it is difficult to prepare a sample. This is because it is not suitable because it interferes with the contact of the device. Here, the average particle size of anisotropic magnesium fluoride particles is measured with a laser diffraction / scattering particle size distribution measuring device (manufactured by Horiba, Ltd./LA-950), and the particle size 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 analyzer is the particle diameter of any 50 particles in an image observed with a scanning electron microscope (S-4300 and SU-8000 manufactured by Hitachi High-Technologies). Is approximately the same as the average particle diameter when actually measured. Whether the shape is anisotropic or spherical is an image observed with the above-mentioned scanning electron microscope, and the identified aspect ratio (major axis / minor axis) is 1.5 or more. Identify. Moreover, the average particle diameter of anisotropic magnesium fluoride particles means the average value of the diameter (major axis) of anisotropic magnesium fluoride particles. The aspect ratio (major axis / minor axis) of the anisotropic magnesium fluoride particles is preferably in the range of 1.5 to 5. The minor axis is preferably in the range of 0.5 to 30 nm, and particularly preferably in the range of 0.5 to 20 nm. Anisotropic magnesium fluoride particles have a higher light scattering effect due to particle anisotropy than spherical magnesium fluoride particles, and reflected light at the transparent conductive film-photoelectric conversion layer interface increases. Magnesium fluoride can produce particles on the order of nano to micron, and since the surface of the particles is hydrophilic, it can be dispersed in a solvent such as alcohol.

  Here, the refractive index of magnesium fluoride is generally 1.37, which is lower than that of calcium fluoride (refractive index: 1.43), and lowers the refractive index of the transparent conductive film after curing. Other fluorides include sodium fluoride (refractive index: 1.34), which is not suitable for use in the present invention because of its high solubility in water.

  Further, the anisotropic magnesium fluoride particles have good wettability with the photoelectric conversion layer, and can reduce film thickness unevenness. 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 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. Non-polymer type binders include metal soaps, metal complexes, metal alkoxides, 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 65 parts by mass of conductive oxide particles, preferably 95 to 70 parts by mass with respect to 100 parts by mass in total of the conductive oxide particles and anisotropic magnesium fluoride particles. Including parts. This is because if the upper limit is exceeded, the adhesiveness is lowered, and if it is less than the lower limit, the conductivity is lowered.

  2 to 35 parts by mass, preferably 5 to 30 parts by mass of anisotropic magnesium fluoride particles are contained with respect to 100 parts by mass in total of the conductive oxide particles and anisotropic magnesium fluoride particles. 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 of these binders is 5 to 50 parts by mass with respect to 100 parts by mass of solid content (conductive oxide particles, anisotropic magnesium fluoride particles, and binder) in the composition for transparent conductive film. And preferably 10 to 30 parts by mass. Moreover, when using a metal alkoxide as a binder and nitric acid as a catalyst, the curing rate of the binder and the remaining amount of nitric acid when the nitric acid is 0.03 to 3 parts by mass with respect to 100 parts by mass of the metal alkoxide. From the viewpoint of If the amount of nitric acid as the catalyst is small, the polymerization rate of the hydrolyzate of the metal alkoxide as the binder is slowed down, and if the amount of water required for hydrolysis is insufficient, a strong transparent conductive film can be obtained. There is a risk of being lost. 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.

  It is preferable to add a coupling agent to the composition for transparent conductive films according to the other components used. It is composed of conductive fine particles, anisotropic magnesium fluoride particles and binder, and a transparent conductive film formed from the composition for transparent conductive film, a photoelectric conversion layer or a conductive reflection laminated on the substrate. This is for improving the adhesion to the 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 a solid content (conductive oxide particles, anisotropic magnesium fluoride 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.

  In the transparent conductive film composition, the desired components are mixed by a conventional method using a paint shaker, ball mill, sand mill, centrimill, triple roll, etc., and conductive oxide particles, anisotropic magnesium fluoride particles, etc. are dispersed. And can be 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 comprises conductive oxide particles, anisotropic magnesium fluoride particles having an average particle size of 1 to 50 nm, and a cured binder, 2 to 35 parts by mass of anisotropic magnesium fluoride particles are included with respect to 100 parts by mass of anisotropic magnesium fluoride particles in total.

  The conductive oxide particles and the anisotropic magnesium fluoride are as described above, and the cured binder is obtained by curing the above-mentioned binder, that is, the above-described composition for transparent conductive film for thin-film solar cells. It has been cured.

  Here, the anisotropic magnesium fluoride particles are obtained, for example, by dropping an aqueous ammonium fluoride solution into an aqueous magnesium chloride solution or an aqueous magnesium acetate solution to obtain a reaction solution containing a precursor of anisotropic magnesium fluoride particles. Then, anisotropic magnesium fluoride particles can be generated by dropping a magnesium chloride aqueous solution or a magnesium acetate aqueous solution and an ammonium fluoride aqueous solution dropwise into the reaction solution. The produced anisotropic magnesium fluoride particles can be separated from the aqueous solution by washing filtration such as centrifugation. The washing filtration is preferably repeated a plurality of times in order to remove unreacted substances and by-product ionic species.

  The method for producing a transparent conductive film of the present invention is a method for producing a transparent conductive film of a thin-film solar cell comprising a base material, a transparent electrode layer, a photoelectric conversion layer, and a transparent conductive film, After applying the transparent conductive film composition 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. to obtain a thickness of 0.03 to 0.03. A 0.5 μm transparent conductive film 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. 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, the coating film is dried at a temperature of 20 to 120 ° C., preferably 25 to 60 ° C., for 1 to 30 minutes, preferably 2 to 10 minutes. In this way, a transparent conductive coating film is formed.

  The base material is 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. Can be used. 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 the transparent conductive coating is placed in the atmosphere 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, preferably Hold for 15-40 minutes and fire. 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 if the thickness exceeds 0.5 μm, the effect of increasing reflection 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, when the temperature exceeds 400 ° C., the merit in production such as 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 base material having the coating film is in the range of 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. If the firing time exceeds the upper limit, the manufacturing cost will increase more than necessary, resulting in a decrease in productivity, and a problem that the conversion efficiency of the solar battery cell will be reduced.

  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.

Zirconia beads (microhaika, manufactured by Showa Shell Sekiyu KK) with a total diameter of 60 g and placed in a 100 cm ³ glass bottle so as to have the composition shown in Tables 1 to 3 (numerical values indicate parts by mass) : The transparent conductive film composition of Examples 1-19 and Comparative Examples 1-4 was produced by disperse | distributing for 6 hours with a paint shaker using 100g. Note that in the column in a ratio of Table 1, and the electrically conductive oxide particles, the anisotropy magnesium fluoride particles and MgF _2, were omitted coupling agent and cup. Table 4 shows the average particle size of the anisotropic magnesium fluoride (MgF ₂ ) particles used. Here, anisotropic magnesium fluoride particles 1 to 3 and SiO ₂ binders 1 to 7 used as binders were produced as follows.

[Anisotropic magnesium fluoride particles 1]
It warmed to 45 ° C., while magnesium chloride aqueous solution 250 cm ³ the stirring, the aqueous solution of ammonium fluoride in 250 cm ^3, using a tube pump is added dropwise over 1 hour to obtain a reaction solution A. 200 cm ³ of magnesium chloride aqueous solution and 200 cm ³ of ammonium fluoride aqueous solution are dropped into the reaction solution A over 2 hours using a tube pump, and the produced colloidal particles are repeatedly washed and filtered by centrifugation 8 times. Thus, 10 g of anisotropic magnesium fluoride particles having an average particle diameter of 15 nm were obtained.

[Anisotropic magnesium fluoride particles 2]
Into a 300 cm ³ magnesium acetate aqueous solution heated to 45 ° C. and stirred, 200 cm ³ ammonium fluoride aqueous solution was dropped over 1 hour using a tube pump to obtain a reaction solution B. 200 cm ³ of magnesium acetate aqueous solution and 200 cm ³ of ammonium fluoride aqueous solution are dropped into the reaction solution B using a tube pump over 2 hours, and the produced colloidal particles are washed and filtered by centrifugation 8 times. Repeatedly, 10 g of anisotropic magnesium fluoride particles having an average particle diameter of 20 nm were obtained.

[Anisotropic magnesium fluoride particles 3]
Into a 250 cm ³ aqueous potassium fluoride solution heated to 55 ° C. and stirred, a 300 cm ³ aqueous magnesium chloride solution was added dropwise over 1 hour using a tube pump to obtain a reaction solution C. A 300 cm ³ aqueous magnesium chloride solution and a 250 cm ³ aqueous potassium fluoride solution are dropped into the reaction solution C over 3 hours using a tube pump, and the resulting colloidal particles are washed and filtered by centrifugation 5 times. Repeatedly, 15 g of anisotropic magnesium fluoride particles having an average particle diameter of 30 nm were obtained.

[SiO ₂ binder 1]
Using a four-necked flask made of 50 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 while stirring. 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 50 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-neck flask made of 500 cm ³ glass, add 145 g of tetraethoxysilane and 140 g of ethyl alcohol, and stir a solution of 0.015 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 19]
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 anisotropic magnesium fluoride having an average particle size of 15 nm as a conductive oxide powder. Particle 1 is mixed at a ratio of 98 to 2, and SiO ₂ binder 1 as a binder is mixed at a ratio of 30% by mass with respect to solid particles obtained by combining conductive oxide particles and anisotropic magnesium fluoride particles. did.

  In Example 2, in ethanol as a dispersion medium, an ATO powder having an average particle size of 40 nm and anisotropic magnesium fluoride particles 2 having an average particle size of 20 nm as a conductive oxide powder in a ratio of 95: 5, Further, the non-polymer type binder 1 as a binder was mixed at a ratio of 10% by mass with respect to solid particles obtained by combining conductive oxide particles and anisotropic magnesium fluoride particles.

In Example 3, in IPA serving as a dispersion medium, TZO powder having an average particle size of 30 nm and anisotropic magnesium fluoride particles 2 having an average particle size of 20 nm as a conductive oxide powder were in a ratio of 92 to 8, Further, the SiO ₂ binder ₂ as a binder was mixed at a ratio of 30% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Example 4, in ethanol as a dispersion medium, ITO powder with an average particle size of 30 nm and anisotropic magnesium fluoride particles 1 with an average particle size of 15 nm as a conductive oxide powder in a ratio of 92 to 8, Further, the SiO ₂ binder 7 as a binder was mixed at a ratio of 25 mass% with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Example 5, in a mixed solvent 1 serving as a dispersion medium, an ITO powder having an average particle diameter of 35 nm and an anisotropic magnesium fluoride particle 1 having an average particle diameter of 15 nm as a conductive oxide powder are in a ratio of 90 to 10. In addition, the SiO ₂ binder 6 as a binder was mixed at a ratio of 20% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Example 6, in ethanol as a dispersion medium, ITO powder having an average particle diameter of 40 nm and anisotropic magnesium fluoride particles 3 having an average particle diameter of 30 nm as a conductive oxide powder were in a ratio of 90 to 10, Further, the SiO ₂ binder ₂ as a binder was mixed at a ratio of 20% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

  In Example 7, in ethanol serving as a dispersion medium, ITO powder having an average particle diameter of 25 nm and anisotropic magnesium fluoride particles 1 having an average particle diameter of 15 nm as a conductive oxide powder in a ratio of 85 to 15, Non-polymer type binder 1 as a binder is 30% by mass with respect to solid particles obtained by combining conductive oxide particles and anisotropic magnesium fluoride particles, and further has a dialkylpyrophosphite group represented by chemical formula (1). Titanium coupling agent is mixed at a ratio of 0.5% by mass with respect to the amount of the composition material including the conductive oxide particles, anisotropic magnesium fluoride particles, and the binder component, which are solids after the coating is formed. did.

  In Example 8, in a mixed solvent 2 serving as a dispersion medium, an ATO powder having an average particle diameter of 50 nm and an anisotropic magnesium fluoride particle 2 having an average particle diameter of 20 nm as a conductive oxide powder are in a ratio of 85 to 15. In addition, the non-polymer type binder 2 as a binder was mixed at a ratio of 30% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Example 9, in a mixed solvent 1 serving as a dispersion medium, an ATO powder having an average particle size of 30 nm and an anisotropic magnesium fluoride particle 1 having an average particle size of 15 nm as a conductive oxide powder are in a ratio of 85 to 15. In addition, the SiO ₂ binder 3 as a binder was mixed at a ratio of 15 mass% with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Example 10, in the mixed solvent 2 serving as a dispersion medium, ITO powder having an average particle diameter of 40 nm and anisotropic magnesium fluoride particles 1 having an average particle diameter of 15 nm as a conductive oxide powder are in a ratio of 82 to 18. In addition, the SiO ₂ binder 4 as a binder was mixed at a ratio of 30% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Example 11, in a mixed solvent 2 serving as a dispersion medium, ITO powder having an average particle size of 35 nm and anisotropic magnesium fluoride particles 3 having an average particle size of 30 nm as a conductive oxide powder were in a ratio of 82 to 18. In addition, the SiO ₂ binder 5 as a binder was mixed at a ratio of 25 mass% with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Example 12, in ethanol serving as a dispersion medium, ITO powder having an average particle size of 30 nm and anisotropic magnesium fluoride particles 1 having an average particle size of 15 nm as a conductive oxide powder were in a ratio of 80 to 20, Further, the SiO ₂ binder 6 as a binder is 25% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles, and a silane coupling agent (KBE- manufactured by Shin-Etsu Silicone Co., Ltd.). 1003) was mixed at a ratio of 0.7% by mass with respect to the amount of the composition material including the conductive oxide particles, the anisotropic magnesium fluoride particles, and the binder component, which are solids after the coating was formed.

In Example 13, in IPA as a dispersion medium, IZO powder having an average particle diameter of 25 nm and anisotropic magnesium fluoride particles 2 having an average particle diameter of 20 nm as a conductive oxide powder in a ratio of 80 to 20, Further, the SiO ₂ binder 1 as a binder was mixed at a ratio of 25% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

  In Example 14, in butanol as a dispersion medium, ITO powder having an average particle diameter of 25 nm and anisotropic magnesium fluoride particles 3 having an average particle diameter of 30 nm as a conductive oxide powder in a ratio of 80 to 20, Further, the non-polymer type binder 3 as a binder was mixed at a ratio of 10% by mass with respect to solid particles obtained by combining conductive oxide particles and anisotropic magnesium fluoride particles.

In Example 15, in IPA serving as a dispersion medium, IZO powder having an average particle diameter of 25 nm and anisotropic magnesium fluoride particles 1 having an average particle diameter of 15 nm as a conductive oxide powder in a ratio of 80 to 20, Further, the SiO ₂ binder 3 as a binder was mixed at a ratio of 25 mass% with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Example 16, a 78:22 ratio of IZO powder having an average particle diameter of 25 nm and anisotropic magnesium fluoride particles 2 having an average particle diameter of 20 nm as a conductive oxide powder in the mixed solvent 1 serving as a dispersion medium. In addition, the SiO ₂ binder 5 as a binder was mixed at a ratio of 30% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

  In Example 17, in a mixed solvent 1 serving as a dispersion medium, TZO powder having an average particle size of 30 nm and anisotropic magnesium fluoride particles 1 having an average particle size of 15 nm as a conductive oxide powder were in a ratio of 77 to 23. In addition, the non-polymer type binder 2 as a binder was mixed at a ratio of 15% by mass with respect to solid particles obtained by combining conductive oxide particles and anisotropic magnesium fluoride particles.

In Example 18, in a mixed solvent 1 serving as a dispersion medium, ITO powder having an average particle diameter of 50 nm and anisotropic magnesium fluoride particles 1 having an average particle diameter of 15 nm as a conductive oxide powder are in a ratio of 70:30. In addition, the SiO ₂ binder ₂ as a binder was mixed at a ratio of 15% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Example 19, in IPA serving as a dispersion medium, ATO powder having an average particle size of 40 nm and anisotropic magnesium fluoride particles 2 having an average particle size of 20 nm as a conductive oxide powder in a ratio of 65 to 35, Further, the SiO ₂ binder 7 as a binder was mixed at a ratio of 30% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

[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, and SiO ₂ binder 1 as a binder were 30% by mass with respect to the conductive oxide particles. Mixed in ratio.

In Comparative Example 2, in IPA serving as a dispersion medium, ITO powder having an average particle diameter of 25 nm and anisotropic magnesium fluoride particles 1 having an average particle diameter of 15 nm as a conductive oxide powder are in a ratio of 99: 1. Further, the SiO ₂ binder 1 as a binder was mixed at a ratio of 25% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

In Comparative Example 3, in IPA serving as a dispersion medium, ITO powder having an average particle diameter of 25 nm and anisotropic magnesium fluoride particles 1 having an average particle diameter of 15 nm as conductive oxide powders were in a ratio of 63 to 37. Further, the SiO ₂ binder 1 as a binder was mixed at a ratio of 30% by mass with respect to solid particles obtained by combining conductive oxide particles and anisotropic magnesium fluoride particles.

In Comparative Example 4, in ethanol serving as a dispersion medium, ITO powder having an average particle diameter of 25 nm and anisotropic magnesium fluoride particles 1 having an average particle diameter of 15 nm as conductive oxide powders are in a ratio of 50:50. Further, the SiO ₂ binder 1 as a binder was mixed at a ratio of 25% by mass with respect to the solid particles obtained by combining the conductive oxide particles and the anisotropic magnesium fluoride particles.

[Evaluation of composition for transparent conductive film]
About refractive index evaluation, about the composition for transparent conductive films shown in Examples 1-19 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 0.05 to 0.2 μm was formed by baking at 160 to 220 ° C. for 20 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 3 show these results.

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 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. 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 1-19 and Comparative Examples 1-4, the thickness after baking will be 0.01-0.5 micrometer with respect to the photovoltaic cell in which film-forming has already progressed. Thus, after applying by a wet coating method (spin coating method, die coating method, spray coating method, offset printing method), the transparent conductive film 1 was formed by drying at a low temperature of 25 to 60 ° C. for 5 minutes. . Tables 1 to 3 show coating methods.

  Next, the conductive reflective film composition prepared by the following method is applied on the transparent conductive film 1 by a wet coating method so that the thickness after firing is 0.05 to 2.0 μm, and then the temperature is increased. The conductive reflective film was formed by drying at a low temperature of 25 to 60 ° C. for 5 minutes. Subsequently, the composite film was formed on the photovoltaic cell by baking at 160-220 degreeC for 20-60 minutes. Tables 1 to 3 show the film thickness after firing 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 aqueous ferric sulfate is directly added and dissolved in this sodium citrate aqueous solution in a nitrogen gas stream maintained at 35 ° C. to contain citrate ions and ferrous ions 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. After apply | coating the obtained composition for electroconductive reflective films on the transparent conductive film 1 with a wet coating method so that the thickness after baking may be 0.05-2.0 micrometers, it is 20-160 degreeC at 160-220 degreeC. The conductive back surface reflection film 4 was formed on the transparent conductive film 1 by firing under heat treatment conditions for 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 100 cc glass bottle and dispersed with a paint shaker for 6 hours using 100 g of zirconia beads having a diameter of 0.3 mm (manufactured by Showa Shell Sekiyu KK: Microhaika) to prepare a dispersion of ITO particles. . Here, the titanium coupling agent having a dialkylpyrophosphite group is represented by the chemical formula (1) given in the above embodiment. The SiO ₂ binder was prepared in the same manner as the SiO ₂ binder 1 described above. 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. After that, 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 to 3 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.

  Regarding adhesion evaluation, solar cells in which film formation has already progressed for the compositions for transparent conductive films shown in Examples 1 to 19 and Comparative Examples 1 to 4 by a method according to the tape test (JIS K-5600). After the transparent electrode film and the conductive reflective film are formed on the cell, the composite film is formed on the solar cell by baking at 160 to 220 ° C. for 20 to 60 minutes, and then the film is applied to the film. When the tape was brought into close contact and peeled off, the film was evaluated according to three levels: excellent, acceptable, and impossible depending on the degree of film peeling or turning up. The case where the film formation does not stick to the tape side and only the adhesive tape is peeled off is excellent, and the case where the peeling of the adhesive tape and the state in which the photoelectric conversion layer 2 serving as the base material is exposed is allowed. The case where the entire surface of the photoelectric conversion layer 2 as a base material was exposed by peeling was regarded as impossible. Tables 1 to 3 show these results.

  As is clear from Tables 1 to 3, in all of Examples 1 to 19, the refractive index is low, the adhesion is good, the relative power generation efficiency is remarkably high as 108 to 118%, and the relative short-circuit current density is also 104 to 107. % Was high. In contrast, Comparative Example 1 that does not include anisotropic magnesium fluoride particles and Comparative Example 2 that includes only 1 part by mass of anisotropic magnesium fluoride particles have a high refractive index, relative power generation efficiency, and relative short-circuit current. Both densities were approximately 100%. In Comparative Example 3 containing 37 parts by mass of magnesium fluoride particles and Comparative Example 4 containing 50 parts by mass, both the relative power generation efficiency and the relative short-circuit current density were low.

  As described above, the transparent conductive film composition of the present invention can be applied and baked on the photoelectric conversion layer by a wet coating method, and the transparent conductive film obtained can be obtained depending on the content of anisotropic magnesium fluoride particles. The refractive index of the 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.

  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 refractive index of the obtained transparent conductive film is determined depending on the content of anisotropic magnesium fluoride particles. I was able to adjust. 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

Claims (9)

  The conductive oxide particles, the anisotropic magnesium fluoride particles having an average particle diameter of 1 to 50 nm, and the binder, and a total of 100 parts by mass of the conductive oxide particles and the anisotropic magnesium fluoride particles And the composition for transparent conductive films for thin film solar cells characterized by including 2-35 mass parts of anisotropic magnesium fluoride particles.   The composition for transparent conductive films for thin film solar cells according to claim 1, wherein the binder is a polymer-type binder and / or a non-polymer-type binder that is cured by heating.   The thin film solar cell according to claim 2, wherein the non-polymer type binder is at least one selected from the group consisting of metal soap, metal complex, metal alkoxide, halosilanes, 2-alkoxyethanol, β-diketone, and alkyl acetate. For transparent conductive film.   A total of 100 parts by mass of conductive oxide particles and anisotropic magnesium fluoride particles, including conductive oxide particles, anisotropic magnesium fluoride particles having an average particle diameter of 1 to 50 nm, and a cured binder On the other hand, the transparent conductive film for thin film solar cells characterized by containing 2-35 mass parts of anisotropic magnesium fluoride particles.   The transparent conductive film for thin film solar cells according to claim 4, wherein the binder is a polymer-type binder and / or a non-polymer-type binder.   The thin film solar cell according to claim 5, wherein the non-polymer type binder is at least one selected from the group consisting of metal soap, metal complex, metal alkoxide, halosilanes, 2-alkoxyethanol, β-diketone, and alkyl acetate. Transparent conductive film.   The thin film solar cell containing the transparent conductive film for thin film solar cells of any one of Claims 4-6.   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, Comprising: Transparent of any one of Claims 1-3 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 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. The manufacturing method of the transparent conductive film of 8.