JP5359667B2 - Composite film for super straight type solar cell and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite film for super straight type solar cells comprising a transparent conductive film formed by a wet coating method and a conductive reflection film without reducing a back reflectance, and also to provide a method of manufacturing the composite film for super straight type solar cells. <P>SOLUTION: In the composite film, on a photoelectric conversion layer 13, the transparent conductive film 14 is formed of: a first layer 14a including a binder component ; and a second layer 14b where a binder component in which 1-30% of the volume of the first layer 14a is exposed from the first layer 14a is not included, and the conductive reflection film 15 having a thickness of 0.05-2.0 &mu;m is formed by applying a composition for conductive reflection films including metal nano particles onto the transparent conductive film 14 by the wet coating method for baking. In this case, an average diameter of a pore, which appears on a contact surface on the side of the photoelectric conversion layer 13 of the conductive reflection film 15, is not more than 100 nm, an average depth where the pore is positioned, is not more than 100 nm, and the number density of the pore is not more than 30/&mu;m<SP>2</SP>. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a composite film suitably used for a super straight type solar cell and a method for producing the same. More specifically, the present invention relates to a composite film suitable for a super straight type solar cell composed of a transparent conductive film and a conductive reflective film, and a manufacturing method thereof.

  Currently, clean energy research and development is underway from the standpoint of environmental protection. In particular, solar cells are attracting attention because of the infinite amount of sunlight, which is a resource, and no pollution. Conventionally, for solar power generation using a solar cell, a bulk solar cell in which a bulk crystal of single crystal silicon or polycrystalline silicon is manufactured and sliced to be used as a thick plate semiconductor has been used. However, the above silicon crystal used for bulk solar cells requires a lot of energy and time for crystal growth, and it is difficult to increase mass production efficiency because of the complicated manufacturing process required in the subsequent manufacturing process. It was difficult to provide solar cells.

  On the other hand, a thin film semiconductor solar cell using a semiconductor such as amorphous silicon having a thickness of several micrometers or less (hereinafter referred to as a thin film solar cell) is a photoelectric conversion layer on an inexpensive substrate such as glass or stainless steel. It is only necessary to form as many semiconductor layers as necessary. Therefore, this thin film solar cell is considered to become the mainstream of future solar cells because it is thin and light, low in manufacturing cost, and easy to increase in area.

  Thin film solar cells are classified into a super straight type and a substrate type depending on the structure. In a super straight type solar cell in which light is incident from the translucent substrate side, the order is usually substrate-transparent electrode-photoelectric conversion layer-back electrode. The structure formed by is taken. For super straight solar cells with a photoelectric conversion layer formed of a silicon-based material, for example, it is considered to increase the power generation efficiency by taking a structure formed in the order of transparent electrode, amorphous silicon, polycrystalline silicon, and back electrode. (See, for example, Non-Patent Document 1). In the structure shown in this non-patent document 1, amorphous silicon or polycrystalline silicon constitutes a photoelectric conversion layer.

  In particular, when the photoelectric conversion layer is composed of a silicon-based material, the absorption coefficient of the photoelectric conversion layer is relatively small. Therefore, when the photoelectric conversion layer has a film thickness of the order of several micrometers, part of the incident light is the photoelectric conversion layer. The transmitted light does not contribute to power generation. Therefore, the back electrode is used as a reflection film, or a reflection film is formed on the back electrode, and the light that has not been absorbed and transmitted through the photoelectric conversion layer is reflected by the reflection film, and then returned to the photoelectric conversion layer again to generate power. It is generally done to improve.

  In the development so far in the thin film solar cell, the electrode and the reflective film have been formed by a vacuum film forming method such as a sputtering method. However, since a large cost is generally required for maintaining and operating a large-scale vacuum film forming apparatus, it is expected to develop a cheaper manufacturing method by replacing this with a wet film forming method.

  As an example of a conductive reflective film formed by a wet film forming method, it is disclosed that a reflective film formed on the back side of a photoelectric conversion element is formed using an electroless plating method (for example, Patent Document 1). reference.).

  In addition, as a simpler method, a method in which a metal having a high reflectance such as silver is used as a nanoparticle and this is applied has been studied (for example, see Patent Document 2). Moreover, the method of apply | coating a metal nanoparticle is mentioned as a method of forming the metal coating film which exhibits a high metal-tone metallic luster on the base-material surface (for example, refer patent document 3). Furthermore, in the super straight type solar cell, the transparent electrode located on the substrate side among the transparent electrodes of the super straight type solar cell taking a structure such as substrate-transparent electrode-photoelectric conversion layer-transparent electrode-back surface reflecting electrode, There is a method in which a coating liquid in which conductive oxide fine particles are dispersed in a dispersion medium is applied and then dried and cured by a heating method (for example, see Patent Document 4).

JP 05-95127 A (Claim 1, paragraph [0015]) JP 09-246577 A (paragraph [0035]) JP 2000-239853 A (Claim 3, paragraph [0009]) JP-A-10-12059 (paragraph [0028], paragraph [0029])

Shozo Yanagida et al., “The Forefront of Thin-Film Solar Cell Development: Toward High Efficiency, Mass Production, and Popularization”, NTS Corporation, March 2005, p. 113 FIG. 1 (a)

  However, the electroless plating method described in Patent Document 1 includes a process of forming a plating protective film on the surface side, treating the side to be plated with a hydrofluoric acid solution, and then immersing it in an electroless plating solution. In addition to the complicated process, the generation of waste liquid is also expected. Moreover, in the method of applying the metal nanoparticles described in Patent Documents 2 and 3, the reflectance (hereinafter referred to as back surface reflectance) when evaluated from the substrate side of the reflective film applied to the substrate surface is opposite. It tends to be lower than the reflectance on the exposed surface side that hits the side surface (hereinafter referred to as surface reflectance). It is presumed that the porosity is reduced between the reflective film and the base material, and light is repeatedly reflected inside the holes, so that the reflectance is lowered. In addition, when the reflected light passing through the holes is incident on the base material at an incident angle larger than the critical angle, the reflected light is totally reflected at the interface between the holes and the base material, and the total reflected light increases. By doing so, it is estimated that the reflectance decreases. Moreover, in the said patent document 4, the wet film-forming method is used only about the transparent conductive film located in the base material side in a super straight type solar cell, About the transparent conductive film located in the back surface reflective electrode side from the former It is formed by sputtering, which is a vacuum process that has been used.

  The objective of this invention is providing the composite film of the superstrate type solar cell comprised by the transparent conductive film formed using a wet coating method, and an electroconductive reflective film, without reducing a back surface reflectance. .

  Another object of the present invention is to eliminate a vacuum process such as a vacuum deposition method and a sputtering method as much as possible, and to produce a composite film for a super straight type solar cell at a lower cost by using a wet coating method. It is to provide.

A first aspect of the present invention is a composite film in which a transparent conductive film is formed on a photoelectric conversion layer of a super straight solar cell and a conductive reflective film is formed on the transparent conductive film. The conductive oxide fine particle dispersion is applied onto the layer using a wet coating method to form a conductive oxide fine particle coating, and then the binder dispersion is wet applied onto the oxide fine particle coating. A first layer containing a binder component on the photoelectric conversion layer and a second layer that does not contain a binder component in which 1 to 30% of the volume of the first layer is exposed from the first layer by impregnating and firing using a construction method The conductive reflective film is formed to have a thickness of 0.05 to 2.0 μm by applying and baking a composition for conductive reflective film containing metal nanoparticles on a transparent conductive film using a wet coating method. Formed on the photoelectric conversion layer side of the conductive reflective film. The average diameter of pores appearing on the surface is 100nm or less, 100nm or less average depth pores is located, the composite film for a superstrate solar cell number density of pores are characterized in that 30 or / [mu] m ² or less It is.

  A second aspect of the present invention is an invention based on the first aspect, wherein the binder dispersion liquid is for a super straight type solar cell including one or both of a polymer type binder and a non-polymer type binder that are cured by heating. It is a composite membrane.

  A third aspect of the present invention is an invention based on the second aspect, wherein the polymer binder is an acrylic resin, polycarbonate, polyester, alkyd resin, polyurethane, acrylic urethane, polystyrene, polyacetal, polyamide, polyvinyl alcohol, polyacetic acid. It is a composite film for a super straight type solar cell that is one or more selected from the group consisting of vinyl, cellulose and siloxane polymer.

  A fourth aspect of the present invention is an invention based on the second aspect, wherein the polymer binder is made of aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum or tin. It is a composite film for a super straight type solar cell that contains one or more hydrolysates of metal soap, metal complex or metal alkoxide.

  A fifth aspect of the present invention is the invention based on the second aspect, wherein the nonpolymer binder is selected from the group consisting of alkoxysilanes, halosilanes, 2-alkoxyethanol, β-diketone and alkyl acetate. It is a composite film for a super straight type solar cell that is a seed or two or more kinds.

  A sixth aspect of the present invention is the invention based on the first aspect, wherein the dispersion of conductive oxide fine particles is selected from the group consisting of a silane coupling agent, an aluminum coupling agent and a titanium coupling agent. It is a composite film for super straight type solar cells containing one or more kinds.

  A seventh aspect of the present invention is the invention based on the first aspect, wherein the conductive reflective film is selected from the group consisting of polyvinylpyrrolidone, polyvinylpyrrolidone copolymer and water-soluble cellulose. It is a composite film for a super straight type solar cell containing the above substances.

  An eighth aspect of the present invention is an invention based on the first aspect, wherein the conductive reflective film is for a super straight type solar cell in which the proportion of silver in the metal element contained in the film is 75% by mass or more. It is a composite membrane.

  A ninth aspect of the present invention is a composite film for a super straight type solar cell according to the first aspect, wherein the thickness of the conductive reflective film is in the range of 0.05 to 2.0 μm. is there.

  A tenth aspect of the present invention is an invention based on the first aspect, wherein the number of particles having a particle size in the range of 10 to 50 nm is 70 in terms of number average, with respect to the metal nanoparticles in which the conductive reflective film is contained in the film. % Or more of the composite film for a super straight solar cell.

  An eleventh aspect of the present invention is an invention based on the first aspect, wherein the conductive reflective film includes 75% by mass or more of silver nanoparticles as metal nanoparticles, and the metal nanoparticles have a carbon skeleton of 1 carbon. Formed with a composition for conductive reflective film that is chemically modified with a protective agent for organic molecular main chain of ~ 3, and the metal nanoparticles contain 70% or more of metal nanoparticles having a primary particle diameter in the range of 10 to 100 nm in average number It is the composite film for super straight type solar cells.

  A twelfth aspect of the present invention is the invention based on the first aspect, wherein the conductive reflective film is made of gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, iron, chromium and manganese. Super straight type formed of a composition for conductive reflective film containing metal nanoparticles composed of one or two or more mixed compositions or alloy compositions selected from the group of 0.02% by mass or more and less than 25% by mass It is a composite film for solar cells.

  A thirteenth aspect of the present invention is an invention based on the first aspect, wherein the conductive reflective film includes 1% by mass or more of water and 2% by mass or more of alcohols as a dispersion medium. It is the composite film for super straight type solar cells formed of the composition.

  A fourteenth aspect of the present invention is the invention based on the first aspect, wherein the conductive reflective film is selected from the group consisting of organic polymers, metal oxides, metal hydroxides, organometallic compounds, and silicone oils. Furthermore, it is a composite film for a super straight type solar cell formed of a composition for conductive reflective film containing one or more additives.

  The fifteenth aspect of the present invention is the invention based on the fourteenth aspect, wherein the organic polymer is one or more selected from the group consisting of polyvinylpyrrolidone, polyvinylpyrrolidone copolymer and water-soluble cellulose. This is a composite film for a super straight solar cell.

  A sixteenth aspect of the present invention is the invention based on the fourteenth aspect, wherein the metal oxide is aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum, tin, A composite film for a super straight solar cell, which is an oxide or composite oxide containing at least one selected from the group consisting of indium and antimony.

  A seventeenth aspect of the present invention is the invention based on the fourteenth aspect, wherein the metal hydroxide is aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum, tin , A composite film for a solar cell for a super straight solar cell, which is a hydroxide containing at least one selected from the group consisting of indium and antimony.

  An eighteenth aspect of the present invention is the invention based on the fourteenth aspect, wherein the organometallic compound is composed of silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum and tin. It is a composite film for a super straight type solar cell, which is at least one metal soap, metal complex or metal alkoxide selected from the above.

  A nineteenth aspect of the present invention is a wet coating method in which a dispersion of conductive oxide fine particles and a binder dispersion are applied on a photoelectric conversion layer of a superstrate solar cell laminated on a substrate via a transparent conductive film. A transparent conductive coating film is formed by applying the composition for conductive reflective film on the transparent conductive coating film by a wet coating method to form a conductive reflective coating film. A transparent conductive film having a thickness of 0.01 to 0.5 μm and a conductive reflective film having a thickness of 0.05 to 2.0 μm are obtained by baking a substrate having a reflective coating film at 130 to 400 ° C. A transparent conductive coating film is formed by coating the oxide fine particle dispersion liquid to form a coating film of oxide fine particles, and then coating the oxide fine particle coating film with a binder dispersion liquid. Is formed by impregnation by a wet coating method, the transparent conductive film is the above A supermarket characterized in that a first layer including a binder component and a second layer not including a binder component exposed from the first layer are formed on the photoelectric conversion layer by a first layer including a binder component. It is a manufacturing method of the composite film for straight type solar cells.

  A twentieth aspect of the present invention is an invention based on the nineteenth aspect, wherein the wet coating method is a spray coating method, a dispenser coating method, a spin coating method, a knife coating method, a slit coating method, an ink jet coating method, or screen printing. It is a manufacturing method of the composite film for super straight type solar cells which is any one of the method, the offset printing method and the die coating method.

According to a twenty-first aspect of the present invention, there is provided a base material, a transparent conductive film formed on the base material, a photoelectric conversion layer formed on the transparent conductive film, and first to first layers formed on the photoelectric conversion layer. A superstrate solar cell having the composite film according to the eighteenth aspect or the composite film manufactured by the method according to the nineteenth or twentieth aspect.

As described above, according to the present invention, in the composite film in which the transparent conductive film is formed on the photoelectric conversion layer of the super straight type solar cell and the conductive reflective film is formed on the transparent conductive film, the transparent conductive film After forming a coating film of conductive oxide fine particles on the photoelectric conversion layer by a wet coating method, a photoelectric conversion is performed by impregnating and baking a binder dispersion liquid on the coating film of oxide fine particles using the wet coating method. Since the first layer containing the binder component on the layer and 1 to 30% of the volume of the first layer are formed by the second layer not containing the binder component exposed from the first layer, the conductive reflective film increases A reflection effect is produced, and a sufficient reflectance is obtained. Further, the average diameter of pores appearing on the contact surface on the photoelectric conversion layer side of the conductive reflective film is 100 nm or less, the average depth at which the pores are located is 100 nm or less, and the number density of the pores is 30 / μm ² or less. When a translucent substrate having a transmittance of 98% or more is used, a high diffuse reflectance of 80% or more of the theoretical reflectance can be achieved in the wavelength range of 500 to 1200 nm.

  Furthermore, a composite film can be manufactured at low cost by eliminating a vacuum process such as a vacuum deposition method and a sputtering method as much as possible and using a wet coating method.

It is the figure which represented typically the cross section of the composite film for super straight type solar cells of this invention. It is the figure which represented typically the cross section before baking of the composite film for super straight type solar cells of this invention. It is a figure which represents typically the top view of the thin film solar cell formed in Examples 1-37 and Comparative Examples 1,2. It is the figure which represented typically the cross section of the thin film solar cell formed in Examples 1-37 and Comparative Examples 1,2.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
In a super straight type thin film solar cell, a transparent conductive film and a photoelectric conversion layer are generally laminated in this order on a base material, a transparent conductive film is further formed on the photoelectric conversion layer, and the conductive film is formed on the transparent conductive film. It has a structure in which a reflective film is formed.
The present invention relates to a composite film for a super straight solar cell comprising a transparent conductive film formed on a photoelectric conversion layer of a super straight solar cell and a conductive reflective film formed on the transparent conductive film. .

  FIG. 1 is a diagram schematically showing a cross section of the composite membrane of the present invention. As shown in FIG. 1, the characteristic structure of the composite film of the present invention is that the transparent conductive film 14 is electrically conductive by applying a dispersion of conductive oxide fine particles on the photoelectric conversion layer 13 using a wet coating method. After forming the coating film of the conductive oxide fine particles, the first layer containing the binder component on the photoelectric conversion layer 13 by impregnating and baking the binder dispersion liquid on the coating film of the oxide fine particles using a wet coating method. 14a and 1-30% of the volume of the first layer 14a is formed by the second layer 14b that does not contain the binder component exposed from the first layer 14a.

  When the transparent conductive film is formed by a vacuum film forming method such as a sputtering method, the refractive index of the film of the transparent conductive film is determined by the material of the target material. Therefore, the transparent conductive film is formed by a vacuum film forming method such as a sputtering method. With a conductive film, it is difficult to obtain a desired refractive index. On the other hand, in the case of a transparent conductive film formed using a wet coating method, it is generally formed by applying a composition in which conductive oxide fine particles and other components are mixed, and therefore formed using a wet coating method. A desired low refractive index can be obtained by adjusting the composition of the film. The refractive index of the transparent conductive film is 1.5-2. Since the transparent conductive film having a low refractive index gives a reflection enhancing effect on the optical design to the conductive reflective film to be bonded, the conductive reflective film bonded to the transparent conductive film formed using the wet coating method is Thus, a higher reflectance can be obtained than a conductive reflective film bonded to a transparent conductive film having a high refractive index formed by a vacuum film forming method such as a conventional sputtering method.

  For example, a single transparent film formed by applying a composition prepared by containing conductive oxide fine particles and a binder component together and then firing the transparent conductive film formed by using a wet coating method. A conductive film is mentioned. On the other hand, the transparent conductive film in the composite film of the present invention first forms a coating film of conductive oxide fine particles not containing a binder component on the photoelectric conversion layer, and the conductive oxide film on the coating film of the oxide fine particles. By applying and impregnating a binder dispersion containing no fine particles, a part of the coating film of oxide fine particles is baked in a state of being exposed from the applied binder dispersion. That is, as shown in FIG. 1, the transparent conductive film 14 in the composite film of the present invention is composed of a first layer 14a whose lower layer is a conductive oxide fine particle layer containing a binder component. Further, the upper layer is constituted by a second layer 14b which is a conductive oxide fine particle layer which is formed by being exposed from the binder dispersion and does not contain a binder component.

  In the composite film of the present invention, since the transparent conductive film is configured as described above, a single film formed by applying and baking a composition containing conductive oxide fine particles and a binder component together. Compared with a composite film having a transparent conductive film, a fill factor, which is one of factors that determine conversion efficiency, increases when a solar battery cell is configured. The reason why the second layer 14b is set to 1 to 30% of the volume of the first layer 14a is to obtain sufficient adhesion and a high fill factor. If it is less than the lower limit, the fill factor decreases, and if it exceeds the upper limit, the adhesiveness decreases.

  The transparent conductive film 14 has a thickness of 0.01 to 0.5 μm, and the conductive reflective film 15 has a thickness of 0.05 to 2.0 μm. When the thickness of the transparent conductive film is less than the lower limit, the shortening current of the solar battery cell is reduced, and when the thickness exceeds the upper limit, the fill factor is remarkably reduced. Among these, the thickness of the transparent conductive film is preferably 0.05 to 0.1 μm. If the thickness of the conductive reflective film is less than the lower limit value, the shortening current of the solar battery cell is reduced, and if the thickness exceeds the upper limit value, the amount of material used is increased more than necessary and the material is wasted.

  The conductive reflective film 15 is formed by applying a composition for conductive reflective film containing metal nanoparticles on the upper transparent conductive film 14 using a wet coating method. Therefore, the formed conductive reflective film is characterized in that good film formability and high diffuse reflectance are obtained. When forming a film on a substrate such as glass, good film formability and high diffuse reflectance can be obtained even when the film is formed by a vacuum deposition method such as sputtering, but it is formed using a wet coating method. When a film is formed on the formed transparent conductive film by a vacuum deposition method such as sputtering, the residual solvent in the transparent conductive film adversely affects the formed conductive reflective film. It is difficult to form a reflective film.

  As described above, in the composite film of the present invention, the optical reflection enhancement effect provided by the transparent conductive film having a low refractive index formed by using the wet coating method and the good film forming property of the conductive reflective film. In addition, a high reflectance can be obtained due to the high diffuse reflectance.

Further, the average diameter of pores appearing on the contact surface on the photoelectric conversion layer 13 side of the conductive reflective film 15 is 100 nm or less, the average depth at which the pores are located is 100 nm or less, and the number density of the pores is 30 / μm ² or less. It is characterized by being. When a translucent substrate having a transmittance of 98% or more is used, a conductive reflective film that can achieve a high diffuse reflectance of 80% or more of the theoretical reflectance in the wavelength range of 500 to 1200 nm is obtained. This wavelength range of 500 to 1200 nm almost covers the convertible wavelengths when polycrystalline silicon is used as the photoelectric conversion layer. When the average diameter of the pores is set to 100 nm or less, the reflection spectrum generally shows items with high reflectance on the long wavelength side and low values on the short wavelength side, but when the average diameter of the pores exceeds 100 nm, the reflectance starts to decrease. This is because the inflection point is shifted to the longer wavelength side, so that a good reflectance cannot be obtained. The average pore depth is set to 100 nm or less because when the average pore depth exceeds 100 nm, the gradient (inclination) of the reflection spectrum increases and a good reflectance cannot be obtained. The reason why the number density of the pores is set to 30 / μm ² or less is that when the number density of the pores exceeds 30 / μm ² , the reflectance on the long wavelength side is lowered and a good reflectance cannot be obtained. is there.

In addition, since the conductive reflective film constituting the composite film contains one or more substances selected from the group consisting of polyvinylpyrrolidone, polyvinylpyrrolidone copolymer and water-soluble cellulose, the conductive reflective film The average diameter of pores appearing on the contact surface on the transparent conductive film side of the film can be easily reduced to 100 nm or less, the average depth to 100 nm or less, and the number density to 30 / μm ² or less. Moreover, in the electroconductive reflective film which comprises this composite film, since the ratio of silver in the metal element contained in a film | membrane is 75 mass% or more, a high reflectance is obtained. If it is less than 75% by mass, the reflectance of the conductive reflective film formed using this composition tends to decrease. Moreover, since the thickness of the electroconductive reflective film which comprises a composite film is 0.05-2.0 micrometers, the surface resistance value of an electrode required for a solar cell is obtained. Furthermore, with respect to the metal nanoparticles in which the conductive reflective film constituting the composite film is contained in the film, the particles having a particle size in the range of 10 to 50 nm are 70% or more in number average. Rate is obtained.

  For the formation of the transparent conductive film, ITO (Indium Tin Oxide), tin oxide powder of ATO (Antimony Tin Oxide), and a group consisting of Al, Co, Fe, In, Sn and Ti Conductive oxide fine particles such as zinc oxide powder containing one or more metals selected from the above are preferably used, among which ITO, ATO, AZO (Aluminum Zinc Oxide), IZO Particularly preferred are (Indium Zinc Oxide) and TZO (Tin Zinc Oxide). The average particle diameter of the conductive oxide fine particles is preferably in the range of 2 to 100 nm in order to obtain sufficient conductivity and good film formability, and of these, in the range of 5 to 50 nm. Is particularly preferred.

  The coating film of conductive oxide fine particles is formed by preparing a dispersion in which the conductive oxide fine particles are dispersed in a dispersion medium, and applying the dispersion using a wet coating method. This dispersion medium includes 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, Examples thereof include amides such as N-dimethylformamide and N, N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, glycols such as ethylene glycol, and glycol ethers such as ethyl cellosolve. The content ratio of the dispersion medium in the dispersion is preferably in the range of 50 to 99.99% by mass in order to obtain good film formability. The content ratio of the conductive oxide fine particles in the dispersion is preferably in the range of 0.01 to 50% by mass. The content of the conductive oxide fine particles within the above range is not preferable because it is difficult to form a uniform film below the lower limit, and a transparent conductive film having a thickness of 500 nm or less is formed when the upper limit is exceeded. This is because it becomes difficult.

  It is preferable to add a coupling agent to the dispersion of the conductive oxide fine particles depending on the other components used. This is for improving the bonding property between the conductive fine particles and the binder and the adhesion between the transparent conductive film and the photoelectric conversion layer or the conductive reflective film. Examples of the coupling agent include a silane coupling agent, an aluminum coupling agent, and a titanium coupling agent.

  Examples of the silane coupling agent include vinyltriethoxyxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane. Examples of the aluminum coupling agent include an aluminum coupling agent containing an acetoalkoxy group represented by the following formula (1). Moreover, as a titanium coupling agent, the titanium coupling agent which has the dialkyl pyrophosphite group shown by following formula (2)-(4), and the dialkyl phosphite group shown by following formula (5) are used. The titanium coupling agent which has is mentioned.

バインダ分散液は、バインダ成分として、加熱により硬化するポリマー型バインダ又はノンポリマー型バインダのいずれか一方又は双方を含む。ポリマー型バインダとしては、アクリル樹脂、ポリカーボネート、ポリエステル、アルキッド樹脂、ポリウレタン、アクリルウレタン、ポリスチレン、ポリアセタール、ポリアミド、ポリビニルアルコール、ポリ酢酸ビニル、セルロース及びシロキサンポリマなどが挙げられる。またポリマー型バインダには、アルミニウム、シリコン、チタン、クロム、マンガン、鉄、コバルト、ニッケル、銀、銅、亜鉛、モリブデン又は錫の金属石鹸、金属錯体或いは金属アルコキシドの加水分解体が含まれることが好ましい。ノンポリマー型バインダとしては、金属石鹸、金属錯体、金属アルコキシド、ハロシラン類、２−アルコキシエタノール、β−ジケトン及びアルキルアセテートなどが挙げられる。また金属石鹸、金属錯体又は金属アルコキシドに含まれる金属は、アルミニウム、シリコン、チタン、クロム、マンガン、鉄、コバルト、ニッケル、銀、銅、亜鉛、モリブデン、錫、インジウム又はアンチモンである。これらポリマー型バインダ、ノンポリマー型バインダが、加熱により硬化することで、低温での低いヘイズ率及び体積抵抗率の透明導電膜の形成を可能とする。バインダ分散液中のこれらバインダの含有割合は、０．０１〜５０質量％の範囲内が好ましく、０．５〜２０質量％の範囲内が特に好ましい。

The binder dispersion contains one or both of a polymer type binder and a non-polymer type binder that are cured by heating as a binder component. 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. The polymer binder may include aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum or tin metal soap, metal complex or metal alkoxide hydrolyzate. preferable. Non-polymer type binders include metal soaps, metal complexes, metal alkoxides, halosilanes, 2-alkoxyethanol, β-diketones, and alkyl acetates. The metal contained in the metal soap, metal complex or metal alkoxide is aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum, tin, indium or antimony. These polymer-type binder and non-polymer-type binder are cured by heating, thereby enabling formation of a transparent conductive film having a low haze ratio and volume resistivity at low temperatures. The content of these binders in the binder dispersion is preferably in the range of 0.01 to 50% by mass, and particularly preferably in the range of 0.5 to 20% by mass.

  For the adjustment of the binder dispersion, it is preferable to use a dispersion medium of the same type as the dispersion medium used to prepare the dispersion used for forming the conductive oxide fine particle layer. In order to form a uniform film, the content of the dispersion medium is preferably in the range of 50 to 99.99% by mass.

  Moreover, it is preferable to add a low resistance agent, a water-soluble cellulose derivative, etc. according to the component 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 ratio of these low resistance agents is preferably 0.1 to 10% by mass. Moreover, the transparency in the transparent conductive film formed improves by addition of a water-soluble cellulose derivative. Examples of the water-soluble cellulose derivative include hydroxypropyl cellulose and hydroxypropyl methylcellulose. The addition amount of the water-soluble cellulose derivative is preferably in the range of 0.1 to 10% by mass.

  The conductive reflective film composition used when forming the conductive reflective film in the composite film of the present invention is a composition in which metal nanoparticles are dispersed in a dispersion medium. The metal nanoparticles contain 75% by mass or more, preferably 80% by mass or more of silver nanoparticles. The reason for limiting the content of silver nanoparticles to the range of 75% by mass or more with respect to 100% by mass of all metal nanoparticles is that the reflection of the conductive reflective film formed using this composition is less than 75% by mass. This is because the rate drops. Silver nanoparticles are chemically modified with a protective agent having an organic molecular main chain having a carbon skeleton of 1 to 3 carbon atoms.

  The number of carbons in the carbon skeleton of the organic molecular main chain of the protective agent that chemically modifies the metal nanoparticles was limited to the range of 1 to 3 because the protective agent was released by the heat during firing when the carbon number was 4 or more. Alternatively, it is difficult to be decomposed (separated / burned), and a large amount of organic residue remains in the film, which deteriorates or deteriorates and decreases the conductivity and reflectivity of the conductive reflective film.

  The silver nanoparticles contain 70% or more, preferably 75% or more, of silver nanoparticles having a primary particle size in the range of 10 to 50 nm in terms of number average. The content of the metal nanoparticles in the range of the primary particle size of 10 to 50 nm is limited to a range of 70% or more with respect to 100% of all metal nanoparticles on the number average. Since the specific surface area increases and the proportion of organic matter increases, even organic molecules that are easily desorbed or decomposed (separated and burned) by the heat during firing, the organic molecules occupy a large proportion. A large amount of organic residue remains, and the residue is altered or deteriorated to reduce the conductivity and reflectivity of the conductive reflective film, or the particle size distribution of the metal nanoparticles is widened and the density of the conductive reflective film is likely to decrease. This is because the conductivity and reflectivity of the conductive reflective film are lowered. Furthermore, the primary particle size of the metal nanoparticles is within the range of 10 to 50 nm because the metal nanoparticles with the primary particle size within the range of 10 to 50 nm correlate with stability over time (aging stability) by statistical methods. Because it is.

  On the other hand, the metal nanoparticles other than silver nanoparticles are one or a mixture of two or more selected from the group consisting of gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, iron, chromium and manganese. It is a metal nanoparticle which consists of a composition or an alloy composition, and metal nanoparticles other than this silver nanoparticle are 0.02 mass% or more and less than 25 mass% with respect to 100 mass% of all metal nanoparticles, Preferably it is 0.03. It is contained in an amount of 20% by mass to 20% by mass. The reason why the content of metal nanoparticles other than silver nanoparticles is limited to the range of 0.02% by mass or more and less than 25% by mass with respect to 100% by mass of all metal nanoparticles is particularly less than 0.02% by mass. Although there is no major problem, within the range of 0.02 to 25% by mass, the conductivity of the conductive reflective film after a weather resistance test (a test held in a constant temperature and humidity chamber at a temperature of 100 ° C. and a humidity of 50% for 1000 hours) And 25% by mass or more, the conductivity and reflectivity of the conductive reflective film immediately after baking are lowered, and the conductive reflection after the weather resistance test is characteristic. This is because the film has lower conductivity and reflectance than the conductive reflection film before the weather resistance test.

  Moreover, the composition for electroconductive reflective films contains the 1 type (s) or 2 or more types of additive chosen from the group which consists of an organic polymer, a metal oxide, a metal hydroxide, an organometallic compound, and a silicone oil. The metal oxide, metal hydroxide, organometallic compound or silicone oil contained in the composition as an additive increases the chemical bond with the transparent conductive film or the anchor effect, or is transparent with the metal nanoparticles in the firing process. By improving the wettability with the conductive film, the adhesion with the transparent conductive film can be improved without impairing the conductivity.

  When a conductive reflective film is formed using a composition that does not contain the above metal oxide or the like, the surface roughness of the formed conductive reflective film increases, but the uneven shape on the surface of the conductive reflective film has a photoelectric conversion efficiency. It is said that there is a condition for optimizing the thickness, and it is impossible to form a conductive reflective film surface having excellent photoelectric conversion efficiency simply by having a large surface roughness. As in the composition of the present invention, it is possible to form a surface having an optimized surface roughness by adjusting the type, concentration, and the like of the metal oxide.

The content of the additive is 0.1 to 20%, preferably 0.2 to 10% of the mass of the silver nanoparticles constituting the metal nanoparticles. If the content of the additive is less than 0.1%, pores having a large average diameter may appear or the pore density may be increased. If the content of the additive exceeds 20%, the conductivity of the formed conductive reflective film will be adversely affected, resulting in a problem that the volume resistivity exceeds 2 × 10 ⁻⁵ Ω · cm.

  As the organic polymer used as the additive, one or more selected from the group consisting of polyvinylpyrrolidone (hereinafter referred to as PVP), a PVP copolymer and water-soluble cellulose is used. Specifically, examples of the PVP copolymer include a PVP-methacrylate copolymer, a PVP-styrene copolymer, and a PVP-vinyl acetate copolymer. Examples of the water-soluble cellulose include cellulose ethers such as hydroxypropylmethylcellulose, methylcellulose, and hydroxyethylmethylcellulose.

  The metal oxide used as an additive is at least one selected from the group consisting of aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum, tin, indium and antimony An oxide or a composite oxide containing Specifically, the composite oxide is ITO, ATO, IZO or the like.

  The metal hydroxide used as an additive is at least one selected from the group consisting of aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum, tin, indium and antimony. Examples include hydroxides containing seeds.

  The organometallic compound used as the additive is at least one selected from the group consisting of silicon, titanium, aluminum, antimony, indium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum and tin. Metal soap, metal complex or metal alkoxide. Examples of the metal soap include chromium acetate, manganese formate, iron citrate, cobalt formate, nickel acetate, silver citrate, copper acetate, copper citrate, tin acetate, zinc acetate, zinc oxalate, and molybdenum acetate. Examples of the metal complex include an acetylacetone zinc complex, an acetylacetone chromium complex, and an acetylacetone nickel complex. Examples of the metal alkoxide include titanium isopropoxide, methyl silicate, isoanatopropyltrimethoxysilane, aminopropyltrimethoxysilane and the like.

  As the silicone oil used as the additive, both straight silicone oil and modified silicone oil can be used. The modified silicone oil further has an organic group introduced into part of the side chain of the polysiloxane (side chain type), an organic group introduced into both ends of the polysiloxane (both end type), and both ends of the polysiloxane. Those having an organic group introduced into one of them (one end type) and those having an organic group introduced into a part of both side chains and both ends of the polysiloxane (both side chain end type) can be used. The modified silicone oil includes a reactive silicone oil and a non-reactive silicone oil. Both types can be used as the additive of the present invention. Reactive silicone oil means amino modification, epoxy modification, carboxy modification, carbinol modification, mercapto modification, and heterogeneous functional group modification (epoxy group, amino group, polyether group). Indicates polyether modification, methylstyryl group modification, alkyl modification, higher fatty acid ester modification, fluorine modification, and hydrophilic special modification.

  The dispersion medium constituting the conductive reflective film composition is preferably composed of an alcohol or an alcohol-containing aqueous solution. Examples of the alcohols used as the dispersion medium include one or more selected from the group consisting of methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, glycerol, isobornyl hexanol and erythritol. The alcohol-containing aqueous solution contains 1% by mass or more, preferably 2% by mass or more of water, and 2% by mass or more, preferably 3% by mass or more of alcohols with respect to 100% by mass of all the dispersion media. Is preferred. For example, when the dispersion medium is composed of only water and alcohols, it contains 98% by mass of alcohol when it contains 2% by mass of water, and 98% by mass of water when it contains 2% by mass of alcohol. The reason why the water content is in the range of 1% by mass or more with respect to 100% by mass of all the dispersion media is obtained by applying the composition for conductive reflective film by a wet coating method when the content is less than 1% by mass. It is difficult to sinter the film at a low temperature, and the conductivity and reflectance of the film after firing are reduced, so that the content of alcohols is in the range of 2% by mass or more with respect to 100% by mass of all dispersion media. If the amount is less than 2% by mass, it is difficult to sinter a film obtained by applying the composition by a wet coating method at a low temperature as described above, and the conductivity and reflectance of the electrode after firing are reduced. Because it will do.

  Furthermore, it is preferable that the protective medium chemically modified on the surface of the dispersion medium, that is, the metal nanoparticle contains one or both of a hydroxyl group (—OH) and a carbonyl group (—C═O). When a hydroxyl group (—OH) is contained in a protective agent that chemically modifies metal nanoparticles such as silver nanoparticles, the composition has excellent dispersion stability and has an effective action for low-temperature sintering of a coating film. When a carbonyl group (—C═O) is contained in a protective agent that chemically modifies metal nanoparticles such as silver nanoparticles, the composition has excellent dispersion stability as described above, and can be used for low-temperature sintering of a coating film. There is an effective action.

The method for producing the composition for conductive reflective film to be used is as follows.
(a) When the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent for chemically modifying the silver nanoparticles is set to 3 First, silver nitrate is dissolved in water such as deionized water to prepare an aqueous metal salt solution. On the other hand, the aqueous solution of sodium citrate having a concentration of 10 to 40% obtained by dissolving sodium citrate in deionized water or the like is mixed with granular or powdered sulfuric acid in a stream of inert gas such as nitrogen gas. Iron is directly added and dissolved to prepare an aqueous reducing agent solution containing citrate ions and ferrous ions in a molar ratio of 3: 2. Next, the aqueous metal salt solution is added dropwise to and mixed with the reducing agent aqueous solution while stirring the reducing agent aqueous solution in the inert gas stream. Here, by adjusting the concentration of each solution so that the addition amount of the metal salt aqueous solution is 1/10 or less of the amount of the reducing agent aqueous solution, the reaction temperature is 30 to 30 even when the metal salt aqueous solution at room temperature is dropped. It is preferable to keep the temperature at 60 ° C. The mixing ratio of the two aqueous solutions is such that the equivalent of ferrous ions added as a reducing agent is three times the equivalent of metal ions, that is, (number of moles of metal ions in the aqueous metal salt solution) × ( It is prepared so as to satisfy the formula of metal ion valence) = 3 × (ferrous ion in reducing agent aqueous solution). After the dropping of the aqueous metal salt solution is completed, the mixture is further stirred for 10 to 300 minutes to prepare a dispersion composed of metal colloid. This dispersion is allowed to stand at room temperature, and the aggregates of the precipitated metal nanoparticles are separated by decantation, centrifugation, etc., and then water such as deionized water is added to the separation to form a dispersion, followed by ultrafiltration. The metal (silver) content is adjusted to 2.5 to 50% by mass by performing desalting treatment by the above, followed by substitution washing with alcohols. Thereafter, by adjusting the centrifugal force of the centrifuge using a centrifuge to separate coarse particles, the silver nanoparticles having a primary particle size in the range of 10 to 50 nm are 70% or more in average number of silver nanoparticles. It adjusts so that the ratio for which the silver nanoparticle in the range of the primary particle size of 10-50 nm with respect to 100% of all the silver nanoparticles may account for 70% or more may be prepared. Thereby, a dispersion in which the carbon skeleton of the carbon skeleton of the organic molecular main chain of the protective agent for chemically modifying the silver nanoparticles is 3 is obtained.

  Subsequently, the obtained dispersion is adjusted so that the final metal content (silver content) with respect to 100% by mass of the dispersion is in the range of 2.5 to 95% by mass. When the dispersion medium is an alcohol-containing aqueous solution, it is preferable to adjust the solvent water and the alcohol to 1% or more and 2% or more, respectively. When the composition further contains an additive, the dispersion is one or two selected from the group consisting of organic polymers, metal oxides, metal hydroxides, organometallic compounds, and silicone oils. The above additives are added at a desired ratio. Content of an additive is adjusted so that it may become in the range of 0.1-20 mass% with respect to 100 mass% of compositions obtained. As a result, a composition in which silver nanoparticles chemically modified with a protective agent for an organic molecular main chain having 3 carbon skeletons is dispersed in a dispersion medium is obtained.

(b) When the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent that chemically modifies the silver nanoparticles is 2, except that the sodium citrate used when preparing the reducing agent aqueous solution is replaced with sodium malate A dispersion is prepared in the same manner as in the above (a). As a result, a dispersion having 2 carbon atoms in the carbon skeleton of the organic molecular main chain that chemically modifies the silver nanoparticles can be obtained.

(c) When the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent for chemically modifying the silver nanoparticles is 1, except that sodium citrate used when preparing the reducing agent aqueous solution is replaced with sodium glycolate A dispersion is prepared in the same manner as in the above (a). Thereby, a dispersion in which the carbon skeleton of the carbon skeleton of the organic molecular main chain for chemically modifying the silver nanoparticles is 1 is obtained.

(d) When the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent for chemically modifying metal nanoparticles other than silver nanoparticles is 3, the metal constituting the metal nanoparticles other than silver nanoparticles is gold, Examples include platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, iron, chromium and manganese. The silver nitrate used to prepare the aqueous metal salt solution is chloroauric acid, chloroplatinic acid, palladium nitrate, ruthenium trichloride, nickel chloride, cuprous nitrate, tin dichloride, indium nitrate, zinc chloride, iron sulfate, sulfuric acid A dispersion is prepared in the same manner as in the above (a) except that it is replaced with chromium or manganese sulfate. Thereby, the dispersion whose carbon number of the carbon skeleton of the organic molecular principal chain of the protective agent which chemically modifies metal nanoparticles other than silver nanoparticles is 3 is obtained.

  In addition, when the carbon number of the carbon skeleton of the organic molecular main chain of the protective agent that chemically modifies the metal nanoparticles other than the silver nanoparticles is 1 or 2, the silver nitrate used when preparing the metal salt aqueous solution is the above kind. A dispersion is prepared in the same manner as in the above (b) and (c) except that the metal salt is replaced. Thereby, the dispersion whose carbon number of carbon skeleton of the organic molecular principal chain of the protective agent which chemically modifies metal nanoparticles other than silver nanoparticles is 1 or 2 is obtained.

  When the metal nanoparticles include metal nanoparticles other than silver nanoparticles together with silver nanoparticles, for example, a dispersion containing silver nanoparticles produced by the method of (a) is used as the first dispersion, When the dispersion containing metal nanoparticles other than the silver nanoparticles produced by the method (d) is used as the second dispersion, 75% by mass or more of the first dispersion and less than 25% by mass of the second dispersion are obtained. Mixing is performed so that the total content of the first and second dispersions is 100% by mass. The first dispersion is not limited to the dispersion containing the silver nanoparticles produced by the method (a), but the dispersion containing the silver nanoparticles produced by the method (b) or the above (c). You may use the dispersion containing the silver nanoparticle manufactured by the method.

Next, the manufacturing method of the composite film of this invention is demonstrated.
In the production method of the present invention, as shown in FIG. 2, first, conductive oxide fine particles are placed on the photoelectric conversion layer 13 of the superstrate solar cell laminated on the base material 11 via the transparent conductive film 12. The dispersion prepared by dispersing in a dispersion medium is applied by a wet coating method to form a conductive oxide fine particle coating 24a. The application here is such that the thickness after firing is 0.01 to 0.5 μm, preferably 0.05 to 0.1 μm. The coating film 24a 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.

  Next, the binder dispersion liquid 24b is impregnated on the conductive oxide fine particle coating film 24a by a wet coating method. At this time, in the transparent conductive film formed after firing, the binder dispersion 24b is coated with conductive oxide fine particles so that the second layer containing no binder component is exposed by 1 to 30% of the volume of the first layer. The film 24a is completely impregnated to a predetermined depth. Moreover, application | coating here is 0.05-0.5 with respect to the total mass of the microparticles | fine-particles contained in the coating film of the apply | coated conductive oxide microparticles | fine-particles in the binder component in the binder dispersion liquid to apply. It is preferable to apply so as to be a mass ratio (the mass of the binder component in the binder dispersion to be applied / the mass of the conductive oxide fine particles). If it is less than the lower limit, sufficient adhesion is difficult to obtain, and if it exceeds the upper limit, the surface resistance tends to increase. The transparent conductive coating film 24 comprising the conductive oxide fine particle coating film 24a impregnated with the binder dispersion 24b has a temperature of 20 to 120 ° C., preferably 25 to 60 ° C. for 1 to 30 minutes, preferably 2 to 10 minutes. dry.

  Next, the conductive reflective film composition is applied onto the transparent conductive coating film 24 by a wet coating method. The coating here is performed so that the thickness after firing is 0.05 to 2.0 μm, preferably 0.1 to 1.5 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, the conductive reflective coating film 25 is formed.

  The wet coating method is particularly preferably 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. However, the present invention is not limited to this, and any method can be used.

  The spray coating method is a method in which the dispersion is atomized by compressed air and applied to the substrate, or the dispersion itself is pressurized and atomized to apply to the substrate. The dispenser coating method is, for example, a method in which the dispersion is injected into a syringe. The dispersion is discharged from the fine nozzle at the tip of the syringe and applied to the substrate by pushing the piston of the syringe. The spin coating method is a method in which a dispersion is dropped onto a rotating substrate, and the dropped dispersion is spread to the periphery of the substrate by its centrifugal force. The knife coating method leaves a predetermined gap from the tip of the knife. In this method, the substrate is provided so as to be movable in the horizontal direction, the dispersion is supplied onto the substrate upstream of the knife, and the substrate is moved horizontally toward the downstream side. The slit coating method is a method in which a dispersion is discharged from a narrow slit and applied onto a substrate, and the inkjet coating method is a method in which a dispersion is filled in an ink cartridge of a commercially available inkjet printer and ink jet printing is performed on the substrate. is there. The screen printing method is a method in which wrinkles are used as a pattern indicating material and a dispersion is transferred to a substrate through a plate image formed thereon. The offset printing method is a printing method utilizing the water repellency of ink, in which the dispersion attached to the plate is not directly attached to the substrate, but is transferred from the plate to a rubber sheet and then transferred from the rubber sheet to the substrate again. . The die coating method is a method in which a dispersion supplied in a die is distributed by a manifold and extruded onto a thin film from a slit to coat the surface of a traveling substrate. The die coating method includes a slot coat method, a slide coat method, and a curtain coat method.

  Finally, the substrate 11 having a coating film is heated to 130 to 400 ° C., preferably 150 to 350 ° C. in the air or an inert gas atmosphere such as nitrogen or argon, for 5 to 60 minutes, preferably 15 to 40. Hold for a minute and fire. Here, the reason for applying the dispersion of conductive oxide fine particles so that the thickness of the transparent conductive film after firing is 0.01 to 0.5 μm is that the shortening current of the solar battery cell is less than 0.01 μm. This is because the fill factor is remarkably reduced when the thickness is reduced and exceeds 0.5 μm. The reason for applying the conductive reflective film composition so that the thickness of the conductive reflective coating film after firing is 0.05 to 2.0 μm is that the surface resistance value is too high below 0.05 μm. In addition, sufficient conductivity as an electrode of a solar cell cannot be obtained, and if it exceeds 2.0 μm, there is no problem in characteristics, but the amount of material used is more than necessary and the material is wasted. is there.

  The reason why the firing temperature is in the range of 130 to 400 ° C. is that when the temperature is less than 130 ° C., the surface resistance value of the transparent conductive film in the composite film becomes too high. In addition, since the metal nanoparticles are not sufficiently sintered in the conductive reflective film and are not easily detached or decomposed (separated / burned) by the heat during firing of the protective agent, This is because a large amount of organic residue remains, and the residue is altered or deteriorated, so that the conductivity and reflectivity of the conductive reflective film are lowered. On the other hand, when the temperature exceeds 400 ° C., the merit in the production of the low temperature process cannot be utilized, that is, the manufacturing cost increases and the productivity decreases. In particular, amorphous silicon, microcrystalline silicon, or hybrid silicon solar cells using these are relatively weak against heat, and the conversion efficiency is reduced 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, the surface resistance value of the transparent conductive film in the composite film becomes too high. In addition, since the metal nanoparticles are not sufficiently sintered in the conductive reflective film and are not easily detached or decomposed (separated / burned) by the heat during firing of the protective agent, This is because a large amount of organic residue remains, and the residue is altered or deteriorated, so that the conductivity and reflectivity of the conductive reflective film are lowered. If the firing time exceeds the upper limit, the characteristics are not affected, but the manufacturing cost is increased more than necessary and the productivity is lowered. Furthermore, it is because the malfunction which the conversion efficiency of a photovoltaic cell falls arises.

  As described above, the composite film of the present invention can be formed. Thus, since the manufacturing method of the present invention uses a wet coating method, vacuum processes such as vacuum deposition and sputtering can be eliminated as much as possible, and a composite film can be manufactured at a lower cost.

Next, examples of the present invention will be described in detail together with comparative examples.
<Examples 1-32>
Conductive oxide fine particle dispersions and binder dispersions were prepared with the components and proportions of classifications 1 to 8 shown in Table 1 below. The classification numbers in Table 1 of the dispersions used in each example are shown in Tables 2 and 3.
In Category 1, as shown in Table 1 below, as conductive oxide fine particles, IZO powder having an average particle size of 0.025 μm is 20% by mass, isopropanol is 80% by mass as a dispersion medium, and the total amount is 60 g. A dispersion liquid of conductive oxide fine particles was prepared by placing in a 100 cc glass bottle and dispersing with a paint shaker for 6 hours using 100 g of zirconia beads having a diameter of 0.3 mm (Microhaika, Showa Shell Sekiyu KK). In addition, 10% by mass of a non-polymer binder 2-n-butoxyethanol and 3-isopropyl-2,4-pentanedione as a binder, 88.2% by mass of isopropanol as a dispersion medium, and indium nitrate as a low resistance agent A mixture of lead acetate and a mixture of lead acetate (mass ratio 1: 1) was mixed at a ratio of 1.8% by mass, and stirred at room temperature for 1 hour at a rotation speed of 200 rpm to prepare a binder dispersion.

  In category 2, as shown in the following Table 1, 7.5% by mass of ITO powder having an average particle size of 0.025 μm as conductive oxide fine particles and a titanium coupling agent represented by the above formula (4) as a coupling agent 0.2% by mass, a mixed liquid of isopropanol, ethanol and N, N-dimethylformamide (mass ratio 4: 2: 1) as a dispersion medium was used as a first mixed liquid, and this was a ratio of 92.3% by mass. A dispersion of conductive oxide fine particles was prepared in the same manner as in Category 1. In addition, a binder dispersion was prepared in the same manner as in Category 1 with 10% by mass of 2,4-pentanedione as a non-polymer type binder as a binder and 90% by mass of the first mixed liquid as a dispersion medium. .

  In classification 3, as shown in Table 1 below, 10% by mass of ATO powder having an average particle size of 0.025 μm as the conductive oxide fine particles, and 0% of the titanium coupling agent represented by the above formula (4) as the coupling agent. A dispersion of conductive oxide fine particles was prepared in the same manner as in Category 1 at a ratio of 0.02% by mass and 89.98% by mass of the first mixed liquid as a dispersion medium. Further, a binder dispersion was prepared in the same manner as in Category 1 with 10% by mass of 2-n-propoxyethanol as a non-polymer type binder as a binder and 90% by mass of the first mixed liquid as a dispersion medium. .

  In category 4, as shown in Table 1 below, 10% by mass of AZO powder having an average particle size of 0.025 μm as the conductive oxide fine particles, and 1 of the titanium coupling agent represented by the above formula (3) as the coupling agent. A dispersion of conductive oxide fine particles was prepared in the same manner as in Category 1 at a mass percentage of 89% by mass of the first mixed liquid as a dispersion medium. Further, a mixture of 2,2-dimethyl-3,5-hexanedione and isopropyl acetate (mass ratio 1: 1) as a binder is 10% by mass, and the first mixture as a dispersion medium is 90% by mass, A binder dispersion was prepared in the same manner as in Category 1.

  In Category 5, as shown in Table 1 below, 5% by mass of TZO powder having an average particle size of 0.025 μm as the conductive oxide fine particles and 0% of the titanium coupling agent represented by the above formula (5) as the coupling agent are used. A dispersion of conductive oxide fine particles was prepared in the same manner as in Category 1 at a ratio of 0.5% by mass and 94.5% by mass of the first mixed liquid as a dispersion medium. Further, 10% by mass of a mixed liquid (mass ratio 4: 1: 1) of 2-isobutoxyethanol, 2-hexyloxyethanol and n-propyl acetate as a binder, and 90% by mass of the first mixed liquid as a dispersion medium. A binder dispersion was prepared in the same manner as in category 1 in proportion.

  In Category 6, first, ATO powder having an average particle size of 0.010 μm was suspended in water to adjust the pH to 7, and treated with a bead mill for 30 minutes. The treatment liquid was mixed with the first mixed liquid as a dispersion medium and adjusted to a solid concentration of 18.5% to obtain a dispersion of conductive oxide fine particles. In addition, 5% by mass of gelatin as a binder, 1% by mass of hydroxypropyl cellulose as a water-soluble cellulose derivative, and 94% by mass of water as a dispersion medium are mixed at a temperature of 30 ° C. for 1 hour and stirred at a rotation speed of 200 rpm. By doing so, a binder dispersion was prepared.

In category 7, as shown in Table 1 below, 6% by mass of ATO powder having an average particle size of 0.025 μm as conductive oxide fine particles and a mixed liquid of ethanol and butanol (mass ratio 98: 2) as a dispersion medium are used. As a second mixed liquid, 9.0% by mass of the titanium coupling agent represented by the above formula (3) as a coupling agent, and 85% by mass of the conductive oxide fine particles in the same manner as in Category 1 A dispersion was prepared. Further, a binder dispersion was prepared by mixing 10% by mass of the SiO ₂ binder as the binder and 90% by mass of the second mixed liquid as the dispersion medium. The SiO ₂ binder used as the binder was a 500 ml glass four-necked flask, 140 g of tetraethoxysilane and 240 g of ethyl alcohol were added, and 11.0 g of 12N-HC was dissolved in 25 g of pure while stirring. And then reacted at 80 ° C. for 6 hours.

In classification 8, as shown in Table 1 below, 8% by mass of ITO powder having an average particle size of 0.025 μm as the conductive oxide fine particles, and 2 of the titanium coupling agent represented by the above formula (2) as the coupling agent. A dispersion of conductive oxide fine particles was prepared in the same manner as in Category 1 at a ratio of 0.0% by mass and 90% by mass of the second mixed liquid as a dispersion medium. Also, a binder dispersion was prepared by mixing 10% by mass of the SiO ₂ binder as the binder and 90% by mass of the second mixed liquid as the dispersion medium.

Next, a conductive reflective film composition was prepared by the following procedure.
First, silver nitrate was dissolved in deionized water to prepare an aqueous metal salt solution. In addition, sodium citrate was dissolved in deionized water to prepare an aqueous sodium citrate solution having a concentration of 26% by mass. 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 added dropwise to the reducing agent aqueous solution and mixed. 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 to the metal salt aqueous solution is such that the molar ratio of citrate ions and ferrous ions in the reducing agent aqueous solution to the total valence of metal ions in the metal salt aqueous solution is 3 times the mole. It was made to become. After the addition of the aqueous metal salt solution to the reducing agent aqueous solution was completed, stirring of the mixed solution was further continued for 15 minutes to generate metal particles 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 to precipitate the metal particles in the dispersion, and the aggregates of the precipitated metal particles were separated by decantation. Deionized water was added to the separated metal agglomerated to form a dispersion, subjected to desalting by ultrafiltration, and further washed with substitution with methanol, so that the metal (silver) content was 50% by mass. Thereafter, the centrifugal force of the centrifuge is adjusted using a centrifuge to separate relatively large silver particles having a particle size exceeding 100 nm, thereby obtaining silver nanoparticles having a primary particle size of 10 to 50 nm. It adjusted so that it might contain 71% by a number average. That is, the ratio of the silver nanoparticles in the range of the primary particle diameter of 10 to 50 nm to the silver nanoparticles of 100% on the number average was adjusted to 71%. The obtained silver nanoparticles were chemically modified with a protective agent for an organic molecular main chain having a carbon skeleton of 3 carbon atoms.

  Next, 10 parts by mass of the obtained metal nanoparticles are dispersed by adding and mixing in 90 parts by mass of a mixed solution containing water, ethanol and methanol. Further, the additives shown in the following Tables 2 to 4 are added to this dispersion. Was added so that it might become a ratio shown in Table 2-Table 4, and the composition for electroconductive reflective films was obtained, respectively. In addition, the metal nanoparticle which comprises the composition for electroconductive reflective films contains 75 mass% or more of silver nanoparticles.

  In addition, when containing metal nanoparticles other than silver nanoparticles together with silver nanoparticles as metal nanoparticles, the dispersion of silver nanoparticles obtained by the above method is used as the first dispersion, and instead of silver nitrate, Metal nanoparticles other than silver nanoparticles are produced in the same manner as in the method for producing silver nanoparticles, except that a metal salt of a type that forms metal nanoparticles other than silver nanoparticles shown in the following Tables 2 to 4 is used. The dispersion of the metal nanoparticles is used as the second dispersion, and before adding the additive, the first dispersion and the second dispersion are made to have the ratios shown in Tables 2 to 4 below. By mixing the dispersion, a composition for a conductive reflective film was obtained.

  Finally, a composite film was formed using the conductive oxide fine particle dispersion, binder dispersion and conductive reflective film composition prepared above. Specifically, first, on the base materials shown in the following Tables 2 to 4, the conductivity prepared above by various film forming methods so that the thickness after firing becomes 0.01 to 0.5 μm. After the oxide fine particle dispersion was applied, it was dried at a temperature of 25 ° C. for 5 minutes to form a conductive oxide fine particle coating. Next, the conductive oxide fine particle coating film is impregnated with the binder dispersion prepared as described above by various film forming methods to a predetermined depth of the conductive oxide fine particle coating film, and the temperature is 25 ° C. A transparent conductive coating film was formed by drying for a minute. In the binder dispersion, the mass of the binder component in the binder dispersion is based on the mass ratio shown in the following Tables 2 to 4 with respect to the total mass of the fine particles contained in the coating film of the coated conductive oxide fine particles (coating The weight of the binder component in the binder dispersion liquid / the mass of the conductive oxide fine particles) was applied. Next, on the transparent conductive coating film, the composition for a conductive reflective film prepared above was applied by various film forming methods so that the thickness after firing was 0.05 to 2.0 μm, and then the temperature was changed. The conductive reflective coating film was formed by drying at 25 ° C. for 5 minutes. Subsequently, the composite film was formed on the base material by baking under the heat treatment conditions shown in the following Tables 2 to 4.

Moreover, the composite film of this invention was formed on the photoelectric converting layer of a super straight type solar cell, and the thin film solar cell was formed. Specifically, first, as shown in FIG. 3, a microcrystalline silicon having a thickness of 1.7 μm as a photoelectric conversion layer 33 is formed on a glass substrate 31 having a textured SnO ₂ film 32 by plasma CVD. Layers were deposited. Next, a composite film composed of the transparent conductive film 34 and the conductive reflective film 35 was formed on the photoelectric conversion layer 33 under the same conditions as when the composite film was formed on the substrate. Next, a mask pattern is placed on the surface of the conductive reflective film 35, and the ITO film 36 is formed with a thickness of 200 nm by magnetron sputtering. Then, the ITO film 36 is not formed by using laser patterning. The portion was removed to obtain a thin film solar cell as shown in the top view of FIG. In FIG. 4, each region indicated by reference numeral 51 functions as each cell of the thin film solar cell 50.
In Tables 2 to 4, “PVP” represents polyvinylpyrrolidone having Mw of 360,000, and “PET” represents polyethylene terephthalate.

<Comparative Example 1>
The binder dispersion liquid is at a mass ratio of 150% (the mass of the binder liquid to be applied / the mass of the conductive oxide fine particles) with respect to the total mass of the oxide fine particles contained in the coating film of the applied conductive oxide fine particles. A composite film was formed on the substrate in the same manner as in Example 1 except that it was applied.

<Comparative example 2>
The binder dispersion is 200% by mass (mass of binder liquid to be applied / mass of conductive oxide fine particles) with respect to the total mass of oxide fine particles contained in the coating film of the applied conductive oxide fine particles. A composite film was formed on the substrate in the same manner as in Example 1 except that it was applied.

＜比較試験１＞
実施例１〜３７及び比較例１〜２で得られた複合膜における透明導電膜の膜厚を評価した。評価結果を次の表５及び表６にそれぞれ示す。先ず、焼成後の透明導電膜の厚さをＳＥＭ（日立製作所社製の電子顕微鏡：Ｓ８００）を用いて膜断面から直接計測した。また、これらの透明導電膜について、第２層の露出割合を測定した。具体的には、収束イオンビーム（ＦＩＢ）法で加工して試料断面を露出させ、この試料の断面を走査型電子顕微鏡（ＳＥＭ）で観察することにより行った。

<Comparison test 1>
The film thickness of the transparent conductive film in the composite film obtained in Examples 1-37 and Comparative Examples 1-2 was evaluated. The evaluation results are shown in the following Table 5 and Table 6, respectively. First, the thickness of the transparent conductive film after firing was directly measured from the cross section of the film using an SEM (Hitachi, Ltd., electron microscope: S800). Moreover, the exposure rate of the 2nd layer was measured about these transparent conductive films. Specifically, the cross section of the sample was exposed by processing by a focused ion beam (FIB) method, and the cross section of the sample was observed with a scanning electron microscope (SEM).

<Comparison test 2>
About the base material which formed the conductive reflective film obtained in Examples 1-37 and Comparative Examples 1-2, the distribution of the pores in the contact surface on the base material side, the back surface reflectance, and the thickness of the conductive reflective film were evaluated. did. The evaluation results are shown in the following Table 5 and Table 6, respectively.

  As a method for measuring the pores, different measurement methods were used depending on whether or not the conductive reflective film can be peeled off from the transparent conductive film.

  In an example in which the conductive reflective film can be peeled off from the transparent conductive film, first, an adhesive is applied to a jig having a smooth surface to the conductive reflective film adhered on the transparent conductive film, and this is electrically conductive. After pressing onto the reflective reflective film and holding it until the adhesive is sufficiently dry and has a high adhesive force, the jig is applied to the transparent conductive film using a tensile tester (manufactured by Shimadzu Corporation: EZ-TEST). On the other hand, the conductive reflective film was peeled off from the transparent conductive film by pulling up vertically.

  Next, the surface of the conductive reflective film that was peeled off from the transparent conductive film and exposed on the jig was the contact surface on the base material side, and an uneven image of this surface was observed using an atomic force microscope (AFM). did. The observed concavo-convex image was analyzed, and the average diameter, average depth and number density of vacancies appearing on the film surface were evaluated. The average diameter was determined by measuring the longest diameter and the shortest diameter of each opening and calculating the average value.

  As another method of peeling the conductive reflective film from the transparent conductive film, a method of peeling the conductive reflective film from the transparent conductive film by sticking a double-sided tape on the conductive reflective film and pulling up one end thereof. Was also used.

  In an example in which the conductive reflective film cannot be peeled off from the transparent conductive film, first, the conductive reflective film adhered on the transparent conductive film was processed by the focused ion beam (FIB) method to expose the sample cross section. . By observing the cross section of this sample with a scanning electron microscope (SEM), the shape of the interface between the conductive reflective film and the transparent conductive film was observed. About this interface image, the diameter, average depth, and number density of the opening were evaluated. Here, the diameter of the evaluated opening was determined by regarding the length of the opening in the cross-sectional view as the diameter.

  The back surface reflectance of the conductive reflective film was evaluated by measuring the diffuse reflectance of the conductive reflective film at wavelengths of 500 nm and 1100 nm using a combination of an ultraviolet-visible spectrophotometer and an integrating sphere.

  The film thickness of the conductive reflective film was measured by cross-sectional observation with a scanning electron microscope (SEM).

<Comparison test 3>
The adhesion of the composite films obtained in Examples 1-37 and Comparative Examples 1-2 to the substrate was evaluated. The evaluation results are shown in Table 5 and Table 6 below. Qualitatively evaluated by the adhesive tape peeling test on the base material on which the composite film is formed. “Good” indicates that only the adhesive tape is peeled from the base material. “Neutral” indicates that the adhesive tape is peeled off. And the state where the substrate surface is exposed are mixed, and “defect” indicates a case where the entire surface of the substrate surface is exposed by peeling off the adhesive tape.

<Comparison test 4>
About the thin film solar cell obtained in Examples 1-37 and Comparative Examples 1-2, the cell defect rate was evaluated for every cell 51 shown in FIG. The results are shown in the following Tables 5 and 6. Specifically, as shown in FIG. 3, a probe 37 is provided so as to connect the surface of the SnO ₂ film 32 from which the photoelectric conversion layer 33 and the like have been removed by the laser patterning method and the ITO film 36, and an IV tracer 38 is provided therebetween. installed. In this state, the power when AM1.5 light was irradiated from the glass substrate 31 side at an irradiation intensity of 100 mW / cm ² was evaluated. The case where the fill factor was 0.5 or less was regarded as defective, and the number of defective cells with respect to the total number of cells 50 evaluated in each example and comparative example was evaluated as the cell defect rate.

表５及び表６から明らかなように、比較例１，２のうち、比較例２では、実施例１〜３７に比べて密着性が悪い結果となった。比較例１，２では５００ｎｍの反射率及び１１００ｎｍの反射率ともに実施例１〜３７と同様の高い反射率が得られたものの、セル不良率が高い結果となった。一方、実施例１〜３７では、セル不良率が５％以下と高い評価が得られた。

As is clear from Tables 5 and 6, in Comparative Examples 1 and 2, Comparative Example 2 resulted in poor adhesion as compared with Examples 1 to 37. In Comparative Examples 1 and 2, the same high reflectance as in Examples 1 to 37 was obtained for both the reflectance of 500 nm and the reflectance of 1100 nm, but the cell defect rate was high. On the other hand, in Examples 1 to 37, the cell defect rate was as high as 5% or less.

INDUSTRIAL APPLICABILITY The present invention is extremely suitable as a technique for manufacturing an electrode provided on the opposite side of a light receiving surface suitable for a super straight type solar cell characterized by using a transparent substrate such as glass as a light receiving surface. It is.
In addition, by using the present invention, it is possible to replace the transparent conductive film and the conductive reflective film, which have been conventionally formed by the vacuum film formation method, with a coating and baking process, and a significant reduction in manufacturing cost is expected. it can.

13 Photoelectric Conversion Layer 14 Transparent Conductive Film 14a Conductive Oxide Fine Particle Layer 14b Binder Layer 15 Conductive Reflective Film

Claims (21)

In a composite film in which a transparent conductive film is formed on a photoelectric conversion layer of a super straight type solar cell, and a conductive reflective film is formed on the transparent conductive film,
The transparent conductive film is formed by applying a dispersion of conductive oxide fine particles on the photoelectric conversion layer by a wet coating method to form a coating film of conductive oxide fine particles, and then applying the oxide fine particles. By impregnating and baking a binder dispersion on the film using a wet coating method, 1-30% of the volume of the first layer containing the binder component on the photoelectric conversion layer and the first layer is the first layer. And a second layer that does not contain a binder component exposed from
The conductive reflective film is formed to a thickness of 0.05 to 2.0 μm by applying and baking a composition for conductive reflective film containing metal nanoparticles on the transparent conductive film using a wet coating method. ,
The average diameter of pores appearing on the contact surface on the photoelectric conversion layer side of the conductive reflective film is 100 nm or less, the average depth at which the pores are located is 100 nm or less, and the number density of the pores is 30 / μm ² or less. A composite film for a super straight type solar cell.   The composite film for a super straight type solar cell according to claim 1, wherein the binder dispersion contains one or both of a polymer type binder and a non-polymer type binder that are cured by heating.   The polymer type binder is one or more selected from the group consisting of acrylic resin, polycarbonate, polyester, alkyd resin, polyurethane, acrylic urethane, polystyrene, polyacetal, polyamide, polyvinyl alcohol, polyvinyl acetate, cellulose, and siloxane polymer. The composite film for a super straight type solar cell according to claim 2.   Polymer type binder contains one or more of aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum or tin metal soap, metal complex or metal alkoxide hydrolyzate The composite film for a super straight type solar cell according to claim 2.   The composite for a super straight solar cell according to claim 2, wherein the non-polymeric binder is one or more selected from the group consisting of alkoxysilanes, halosilanes, 2-alkoxyethanol, β-diketone and alkyl acetate. film.   The superstrate solar of Claim 1 in which the dispersion liquid of electroconductive oxide fine particles contains the 1 type (s) or 2 or more types of coupling agent selected from the group which consists of a silane coupling agent, an aluminum coupling agent, and a titanium coupling agent. Composite membrane for batteries.   The composite film for a superstrate solar cell according to claim 1, wherein the conductive reflective film contains one or more substances selected from the group consisting of polyvinylpyrrolidone, a polyvinylpyrrolidone copolymer, and water-soluble cellulose.   The composite film for a super straight solar cell according to claim 1, wherein the ratio of silver in the metal element contained in the conductive reflective film is 75% by mass or more.   The composite film for a super straight solar cell according to claim 1, wherein the thickness of the conductive reflective film is in the range of 0.05 to 2.0 µm.   2. The super straight solar cell according to claim 1, wherein the number of particles having a particle diameter in the range of 10 to 50 nm is 70% or more in terms of number average with respect to the metal nanoparticles in which the conductive reflective film is contained in the film. Composite membrane. The conductive reflective film contains 75% by mass or more of silver nanoparticles as metal nanoparticles,
The metal nanoparticles are chemically modified with an organic molecular main chain protective agent having a carbon skeleton of 1 to 3 carbon atoms,
2. The super straight type solar cell according to claim 1, wherein the metal nanoparticles are formed of a composition for a conductive reflective film containing 70% or more of metal nanoparticles having a primary particle size in the range of 10 to 100 nm in average number. Composite membrane.   Metal whose conductive reflective film is composed of one or more mixed compositions or alloy compositions selected from the group consisting of gold, platinum, palladium, ruthenium, nickel, copper, tin, indium, zinc, iron, chromium and manganese The composite film for a super straight type solar cell according to claim 1, wherein the composite film is formed of a composition for conductive reflective film containing nanoparticles of 0.02% by mass or more and less than 25% by mass.   The composite film for a super straight solar cell according to claim 1, wherein the conductive reflective film is formed of a composition for conductive reflective film containing 1% by mass or more of water and 2% by mass or more of alcohols as a dispersion medium. .   By the composition for conductive reflective films, wherein the conductive reflective film contains one or more additives selected from the group consisting of organic polymers, metal oxides, metal hydroxides, organometallic compounds, and silicone oils The composite film for a super straight solar cell according to claim 1 formed.   The composite film for a superstrate solar cell according to claim 14, wherein the organic polymer is one or more selected from the group consisting of polyvinylpyrrolidone, polyvinylpyrrolidone copolymer and water-soluble cellulose.   An oxide or composite oxide in which the metal oxide contains at least one selected from the group consisting of aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum, tin, indium and antimony The composite film for a super straight type solar cell according to claim 14, which is a product.   The metal hydroxide is a hydroxide containing at least one selected from the group consisting of aluminum, silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum, tin, indium and antimony. The composite film according to claim 14 for a certain super straight type solar cell.   The organometallic compound is at least one metal soap, metal complex or metal alkoxide selected from the group consisting of silicon, titanium, chromium, manganese, iron, cobalt, nickel, silver, copper, zinc, molybdenum and tin. 14. A composite film for a super straight solar cell according to 14. The conductive conductive fine particle dispersion and the binder dispersion are applied onto the photoelectric conversion layer of the super straight type solar cell laminated on the base material via the transparent conductive film by a wet coating method to form a transparent conductive coating film. Forming,
After forming the conductive reflective coating film by applying the composition for conductive reflective film on the transparent conductive coating film by a wet coating method,
By baking the substrate having the transparent conductive film and the conductive reflective film at 130 to 400 ° C., the transparent conductive film having a thickness of 0.01 to 0.5 μm and 0.05 to 2.0 μm A method of forming a composite film comprising a conductive reflective film having a thickness,
The transparent conductive coating is formed by coating the oxide fine particle dispersion to form a coating of oxide fine particles, and then impregnating the oxide fine particle coating with a binder dispersion by a wet coating method,
The transparent conductive film is formed of a first layer including a binder component on the photoelectric conversion layer and a second layer not including the binder component in which 1 to 30% of the volume of the first layer is exposed from the first layer. A method for producing a composite film for a super straight type solar cell.   20. The composite according to claim 19, wherein the wet coating method is one of a spray coating method, a dispenser coating method, a spin coating method, a knife coating method, a slit coating method, an ink jet coating method, a screen printing method, an offset printing method or a die coating method. A method for producing a membrane.   The base material, the transparent conductive film formed on the base material, the photoelectric conversion layer formed on the transparent conductive film, and any one of claims 1 to 18 formed on the photoelectric conversion layer. A superstrate solar cell comprising the composite film according to claim 19 or the composite film produced by the method according to claim 19 or 20.

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