JP2009212507A - Light scattering film for solar battery, optical member for solar battery and solar battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light scattering film for a solar battery which is free from a defect arising in a semiconductor layer formed thereupon and has high heat resistance and a high optical confinement effect, and to provide an optical member for a solar battery and a solar battery having high conversion efficiency. <P>SOLUTION: The light scattering film 2 for the solar battery has a flat surface 2b formed by dispersing scattered particles having a refractive index smaller than that of inorganic binder matrix in the inorganic binder matrix, the light scattering film 2 for the solar battery is characterized in that the transmissivity of the light scattering film 2 is ≤70% and the haze rate thereof is 20 to 90%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light scattering film for a solar cell, an optical member for a solar cell, and a solar cell.

In recent years, solar cells have been actively researched as an alternative energy to petroleum energy and with the increasing need for clean energy.
Examples of solar cells include single crystal silicon solar cells, polycrystalline silicon solar cells, thin film silicon solar cells, compound semiconductor solar cells, and dye-sensitized solar cells. Further, the thin film silicon solar cell includes an amorphous silicon solar cell and a microcrystalline silicon solar cell. Furthermore, there are a tandem solar cell in which an amorphous silicon solar cell and a microcrystalline silicon solar cell are stacked, and a triple solar cell in which three solar cells are stacked.

  In the various types of solar cells described above, improving the conversion efficiency (photoelectric conversion efficiency) is a common problem. In order to solve this problem, Patent Documents 1 and 2 disclose a configuration in which a light scatterer is embedded in a transparent electrode on the light incident surface side. However, by embedding the light scatterer in the transparent electrode, the conductivity of the transparent electrode is remarkably deteriorated, and a photoelectric conversion element (solar cell) with high conversion efficiency cannot be realized.

  Among these, thin-film silicon solar cells have abundant constituent materials on the earth, are easy to increase in area, can be thinly formed, and consume constituent materials. It has excellent features such as low volume and high technical maturity.

  However, the thin film silicon solar cell has a problem that the generated current value cannot be increased. In general, in a solar cell, the value of a current generated with the amount of light absorption can be increased. Therefore, it is necessary to increase the thickness of the i layer that contributes to light absorption in the photoelectric conversion layer. However, when an amorphous silicon solar cell is used as a thin-film silicon solar cell, increasing the film thickness of the i layer increases the photodegradation rate, and the conversion efficiency decreases rather than considering long-term use. When a microcrystalline silicon solar cell is used as a thin-film silicon solar cell, increasing the thickness of the i layer requires a longer production time and lowers productivity. Furthermore, in both the case of amorphous silicon solar cells and microcrystalline silicon solar cells, if the i layer is thickened, the built-in electric field is less likely to be applied, so that the output voltage and the curve factor are deteriorated and conversion efficiency cannot be improved. It was.

  Therefore, a method for increasing the amount of light absorbed in the i layer without increasing the thickness of the i layer has been studied. In Patent Document 3, a structure called a “texture structure” having an uneven surface structure is provided on the light-receiving surface side of the i layer by a transparent conductive film, and incident light is scattered by the “texture structure”. A method of increasing the amount of light absorbed by the i layer by increasing the path length of light passing through the layer is disclosed. However, as described in Non-Patent Document 1, this uneven surface structure of “texture structure” induces many defects in the semiconductor film and deteriorates the output voltage and the fill factor when the semiconductor film is formed thereon. In some cases, the conversion efficiency deteriorated.

Patent Document 4 discloses an example in which a thin film in which insulating fine particles are dispersed in a binder is provided on the light receiving surface side of the i layer. Since this thin film forms an uneven shape on the binder surface due to the shape of the insulating fine particles, it scatters incident light on the surface like the “texture structure” and increases the amount of light absorbed by the i layer. Can be made. However, when a semiconductor film is formed on this thin film, a defect is caused in a part of the semiconductor film due to the uneven shape of the surface, and the defect causes a reflection loss to deteriorate the conversion efficiency.
Therefore, a light scattering film having a high light confinement effect without causing defects in the semiconductor layer formed thereon is desired. At the same time, an optical member having the light scattering film and a solar cell having the light scattering film or the optical member and having high conversion efficiency are required.

JP 2006-171026 A JP 2006-128478 A Japanese Patent No. 2862174 Japanese Patent No. 3706835

Y. Nasuno et al., Japanese Journal Applied Physics (Jpn. J. Appl. Phys. Lett.), 40, L303 (2001).

  The present invention has been made in view of the above circumstances, does not cause defects in a semiconductor layer, has high heat resistance, and has a high light confinement effect, a solar cell light scattering film, a solar cell optical member, and a conversion The object is to obtain a highly efficient solar cell.

In order to achieve the above object, the present invention employs the following configuration. That is,
The light scattering film for solar cells of the present invention is a light scattering film having a flat surface in which inorganic scattering particles having a refractive index different from that of the inorganic binder matrix are dispersed in an inorganic binder matrix, and the light scattering film The film has a transmittance of 70% or more and a haze ratio of 20 to 90%.

  In the light scattering film for a solar cell of the present invention, the flat surface preferably has a surface roughness of 1 nm or more and 100 nm or less.

  In the light scattering film for a solar cell of the present invention, it is preferable that a difference in refractive index between the inorganic binder matrix and the inorganic scattering particles is 0.05 to 0.6.

The light scattering film for a solar cell of the present invention comprises an organic silicon compound in which the inorganic binder matrix is represented by the chemical formula (1), a hydrolyzed polymer of the organosilicon compound, a metal alkoxide represented by the chemical formula (2), and the metal alkoxide. It is preferable that it consists of 1 or more types of materials chosen from the chelate derivative | guide_body or the polymer of the said metal alkoxide chelate derivative | guide_body.
(R ₁ ) _x Si (OR ₂ ) _4-x (1)
Where R ₁ is an alkyl group having 1 to 6 carbon atoms or an organic group having a reactive functional group at the terminal, R ₂ is an alkyl group having 1 to 3 carbon atoms, and x is an integer satisfying 0 ≦ x ≦ 3. is there.
M (OR ₃ ) n (2)
However, M is a metal of any one of Al, Ti, Zr and Zn, R ₃ is an alkyl group having 1 to 4 carbon atoms, and n is a valence of the metal M.

  In the light scattering film for a solar cell of the present invention, the inorganic binder matrix is preferably baked at a temperature of 400 ° C. or higher.

  An optical member for a solar cell according to the present invention comprises the light scattering film for a solar cell described above and a transparent substrate disposed on the surface opposite to the flat surface of the light scattering film for the solar cell. And

  The solar cell of the present invention comprises a photoelectric conversion layer, and the light scattering film for solar cell described above is provided on the light capturing side of the photoelectric conversion layer.

  In the solar cell of the present invention, the photoelectric conversion layer has at least one of single crystal silicon, polycrystalline silicon, thin film silicon, chalcopyrite compound, cadmium tellurium, a dye, or an organic semiconductor material.

  According to the above configuration, a light scattering film for solar cells, an optical member for solar cells, and a solar cell with high conversion efficiency are provided that do not cause defects in the semiconductor layer, have high heat resistance, and have a high light confinement effect. can do.

It is a figure which shows the solar cell which is embodiment of this invention. It is a figure which shows the solar cell which is embodiment of this invention. It is a figure which shows the solar cell which is embodiment of this invention. It is a figure which shows the solar cell which is embodiment of this invention. It is a figure which shows the solar cell which is embodiment of this invention. It is a figure which shows the solar cell which is embodiment of this invention. It is a figure which shows the solar cell which is embodiment of this invention. It is a graph which shows the open circuit voltage of the solar cell of Examples 1-4 and Comparative Examples 1 and 2, a fill factor, a short circuit current, and conversion efficiency.

Hereinafter, modes for carrying out the present invention will be described.
(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing an example of a solar cell according to an embodiment of the present invention.
A solar cell light scattering film 2, an upper electrode layer 3, a photoelectric conversion layer 4, and a lower electrode layer 5 are laminated in this order on the substrate 1 to constitute a solar cell 100.
The substrate 1 has a light capturing surface 1a, and one surface 2a of the solar cell light scattering film 2 is bonded to the opposite surface 1b. The other surface side of the solar cell light scattering film 2 is flat and has a flat surface 2b. In this way, the solar cell optical member 10 composed of the substrate 1 and the solar cell light scattering film 2 is formed.
The photoelectric conversion layer 4 is formed by stacking a p-type thin film silicon layer 41, an i-type thin film silicon layer 42, and an n-type thin film silicon layer 43 in this order. The lower electrode layer 5 is formed by laminating a lower transparent conductive electrode 51 and a metal electrode 52 in this order.
A structure in which the substrate 1, the upper electrode layer 3, the photoelectric conversion layer 4, and the lower electrode layer 5 are laminated in this order is referred to as “super straight type”.

  In the “super straight type” structure, light is incident on the substrate 1 from the light capturing surface 1 a and passes through the inside of the substrate 1, as indicated by an arrow A in FIG. It is configured to be incident on the solar cell light scattering film 2 bonded to the surface 1b opposite to 1a. Further, the light passes through the solar cell light scattering film 2 and the upper electrode layer 3 and enters the photoelectric conversion layer 4. Photoelectric power is generated in the photoelectric conversion layer 4 so that light is converted into electric power.

  The substrate 1 is preferably made of a transparent material. This is because if it is transparent, light is not lost in the substrate 1 and the conversion efficiency in the photoelectric conversion layer 4 can be improved. Examples of the transparent material include glass, quartz, and transparent polyimide.

The substrate 1 is preferably made of a heat resistant material. In the step of forming the thin film silicon layer of the upper electrode layer 3 and the photoelectric conversion layer 4, a heat film formation at a temperature of 200 ° C. or higher or a post-heat treatment is required.
In addition, when the solar cell is used outdoors, the substrate surface may be heated by sunlight, so that it is desirable to be heat resistant.

The solar cell light scattering film 2 is configured by dispersing inorganic scattering particles in an inorganic binder matrix.
The inorganic binder matrix and the inorganic scattering particles are preferably made of a transparent material. It is because the conversion efficiency in the photoelectric conversion layer 4 can be improved by transmitting light from the solar cell light scattering film 2 to the photoelectric conversion layer 4 without loss.

The refractive index difference between the inorganic binder matrix and the inorganic scattering particles is preferably 0.05 to 0.60, more preferably 0.10 to 0.4, and still more preferably 0.15 to 0.3.
When the refractive index difference between the inorganic binder matrix and the inorganic scattering particles is less than 0.05, it is not preferable because light cannot be effectively scattered, and the refractive index difference between the inorganic binder matrix and the inorganic scattering particles is 0. In the case of exceeding .60, the light cannot be sufficiently incident on the photoelectric conversion layer 4 for solar cells, which is not preferable.
The refractive index difference between the inorganic binder matrix and the inorganic scattering particles indicates the refractive index difference in the ultraviolet region, visible light region, and infrared region, but the inorganic binder matrix and the inorganic scattering in the wavelength region where the transmittance is at least 70% or more. The difference in refractive index from the particles may be 0.05 to 0.60.

Moreover, it is preferable that the light-scattering film | membrane 2 for solar cells is a film | membrane which has the flat surface 2b, It is preferable that the surface roughness of the flat surface 2b is 1-100 nm, and 1-50 nm is more preferable. Here, the surface roughness refers to a so-called arithmetic average roughness Ra.
If the surface roughness Ra is 100 nm or less, the upper electrode layer 3, the photoelectric conversion layer 4, and the lower electrode layer 5 to be formed thereon can be formed flat, so that there is a defect in the thin film silicon layer of the photoelectric conversion layer. Is not induced.
When the surface roughness Ra of the flat surface 2b exceeds 100 nm, the flatness of the upper electrode layer 3, the photoelectric conversion layer 4 and the lower electrode layer 5 laminated on the flat surface 2b cannot be increased, This is not preferable because defects in the thin film silicon layers 41 to 43 constituting the photoelectric conversion layer 4 may increase.
If the surface roughness Ra of the flat surface 2b is less than 1 nm, it is difficult to form a light scattering film for a solar cell, which is not preferable because production efficiency is lowered.
The surface roughness Ra can be measured, for example, with a contact-type film thickness meter (trade name “Dektak 16000” manufactured by ULVAC, Inc.).

The transmittance of the solar cell light scattering film 2 is preferably 70% or more, more preferably 88% or more, and still more preferably 90% or more.
When the transmittance of the solar cell light scattering film 2 is less than 70%, light cannot be sufficiently incident on the photoelectric conversion layer 4, and the conversion efficiency in the photoelectric conversion layer 4 cannot be improved. It is not preferable.
The transmittance of the light scattering film for solar cell 2 indicates the transmittance for light in the ultraviolet region, visible light region, and infrared region, but the transmittance must be 70% or more in all regions from ultraviolet to infrared. However, the transmittance may be 70% in a specific part of the region, for example, only in the visible light region.
The transmittance of the solar cell light scattering film 2 is measured, for example, by measuring the transmittance with a spectrometer (trade name “U4000” manufactured by Hitachi, Ltd.) using air as a reference and collecting the transmitted light with an integrating sphere. it can.

Moreover, it is preferable that the light-scattering film | membrane 2 for solar cells is a film | membrane with a haze rate of 20 to 90%, and 50 to 79% is more preferable.
If the haze ratio of the solar cell light scattering film 2 is less than 20%, the light scattering property is lowered and light cannot be effectively confined. If it exceeds 90%, the transmittance may decrease, which is not preferable.
The haze ratio of the light scattering film 2 for solar cells indicates the haze ratio for light in the ultraviolet region, visible light region, and infrared region, and the haze rate is 20 to 90% in the wavelength region where the transmittance is at least 70% or more. If it becomes.
In addition, the haze rate of the light-scattering film 2 for solar cells can be measured with a haze meter (trade name “HM-150” manufactured by Murakami Color Research Co., Ltd.), for example.

When the transmittance of the light scattering film 2 for solar cells is 70% or more and the haze ratio is 20 to 90%, an excellent light confinement effect is exhibited. The light confinement effect refers to an effect in which light incident inside the solar cell 100 is not radiated from the inside of the solar cell 100 to the outside.
As shown in FIG. 1, the solar cell 100 has a light capturing surface 1 a on one surface side, and the other surface side is constituted by a metal electrode 52. Therefore, in the case where the solar cell light scattering film 2 is not provided in the solar cell 100, the light that has not been converted into electrical energy by the photoelectric conversion layer 4 out of the light incident from the light capturing surface 1 a is one surface of the metal electrode 52. In some cases, the light is reflected by 52a and emitted to the outside. However, by providing the solar cell light scattering film 2 having a light confinement effect on the light capturing surface 1 a side of the photoelectric conversion layer 4, light incident from the light capturing surface 1 a side and reflected by the one surface 52 a of the metal electrode 52. To the outside can be prevented.

The inorganic binder matrix constituting the solar cell light scattering film 2 is composed of an organosilicon compound represented by the chemical formula (1), a hydrolyzed polymer of the organosilicon compound, a metal alkoxide represented by the chemical formula (2), and the metal alkoxide. It consists of 1 or more types of materials chosen from the chelate derivative or the polymer of the chelate derivative of the said metal alkoxide.
(R ₁ ) _x Si (OR ₂ ) _4-x (1)
Where R ₁ is an alkyl group having 1 to 6 carbon atoms or an organic group having a reactive functional group at the terminal, R ₂ is an alkyl group having 1 to 3 carbon atoms, and x is an integer satisfying 0 ≦ x ≦ 3. is there.
M (OR ₃ ) n (2)
However, M is a metal of any one of Al, Ti, Zr and Zn, R ₃ is an alkyl group having 1 to 4 carbon atoms, and n is a valence of the metal M.
The valence n is 3 when the metal M is Al, 4 when the metal M is Ti, 4 when the metal M is Zr, and 4 when the metal M is Zn. 4.

A film made of an inorganic binder matrix is formed using an inorganic binder such as a sol-gel binder or a glass binder, or is formed by baking after film formation using an organic-inorganic composite binder. In particular, it is preferable to use an organic-inorganic composite binder.
In order to give heat resistance, it is necessary to reduce the residual organic matter, and it is desirable to perform a baking process at 400 ° C. or higher.

Examples of the sol-gel binder include a binder obtained by hydrolytic polymerization by adding a catalyst such as water and hydrochloric acid to the metal alkoxide represented by the chemical formula (2). Examples of the glass binder include sodium silicate and lithium silicate. And so on.
As the organic-inorganic composite binder, an organic-inorganic composite binder made of an organosilicon compound represented by the chemical formula (1) such as a silane coupling agent, or a metal alkoxide represented by the chemical formula (2) or a chelate derivative of a metal alkoxide is used. Examples thereof include organic-inorganic composite binders by a sol-gel method.

When the organosilicon compound represented by the chemical formula (1) is used, an inorganic binder matrix having a silica-based inorganic binder and a refractive index in the range of 1.4 to 1.5 is obtained.
In addition, when the metal alkoxide represented by the chemical formula (2) using any metal of Al, Ti, Zr, and Zn, the chelate derivative of the metal alkoxide, or the like is used, the refractive index is 1.6 to 2.0. A range of inorganic binder matrix is obtained.
The material of the inorganic binder matrix can be appropriately selected according to the refractive index of the inorganic scattering particles to be used.

Among the organosilicon compounds represented by the chemical formula (1), examples of the organosilicon compound with x = 0 include tetramethoxysilane, tetraethoxysilane, tetra-iso-propoxysilane, and tetra-n-propoxysilane. .
Examples of the organic silicon compound in which x = 1 and R ₁ is an alkyl group include methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, and hexyltrimethoxysilane.
Moreover, as an organosilicon compound which is a compound of x = 1 and R ₁ has an organic group having a reactive functional group at the end, an epoxy group, an isocyanate group, an ethylene oxide group, an amino group as the reactive functional group Acryl group and the like, and 3-glycidoxypropyltrimethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, and the like. .

The organosilicon compound represented by the chemical formula (1) can also be used as a hydrolyzed polymer obtained by adding water (including a catalyst such as hydrochloric acid) in advance and hydrolyzing a part thereof to perform dehydration polymerization.
In addition, as the hydrolysis polymer, a polymer having a large molecular weight or the like from an oligomer of about 2 to 10-mer can be used, and the molecular weight of the hydrolysis polymer is not particularly limited, but is not relatively large. Since it is stable as a liquid and has a low viscosity, it is easy to use and preferable.
Furthermore, a plurality of organosilicon compounds represented by the chemical formula (1) can be used in combination. For example, by combining an organosilicon compound with x = 0 and an organosilicon compound with x = 1, even when a thick film of several μm is formed, the film can be formed without causing cracks.

Examples of the metal alkoxide represented by the chemical formula (2) include aluminum triisopropoxide, titanium tetrabutoxide, zirconium tetrabutoxide and the like.
The metal alkoxide chelate derivatives include aluminum tris (acetylacetonate), aluminum monoacetylacetonate bis (ethyl acetoacetate), aluminum diisopropoxy monomethyl acetoacetate, titanium diisopropoxy bis (acetylacetonate), Examples thereof include titanium tetraacetylacetonate, titanium diisopropoxybis (ethylacetoacetate), zirconium tetraacetylacetonate, zirconium tributoxymonoacetylacetonate, zirconium dibutoxybis (acetylacetonate), and the like.

It is also possible to use a combination of a plurality of metal alkoxides represented by the chemical formula (2) and chelate derivatives of the metal alkoxides.
In addition, as the metal alkoxide represented by the chemical formula (2) and the chelate derivative of the metal alkoxide, it is also possible to use a polymer subjected to hydrolysis reaction and dehydration polycondensation in advance.
Furthermore, the compounds of the chemical formula (1) and the chemical formula (2) can be mixed and used as an inorganic binder matrix, and the material can be appropriately selected according to the application and the particle refractive index.

Further, the refractive index of the inorganic binder matrix can be adjusted by dispersing fine oxide particles such as TiO ₂ or SnO ₂ as an auxiliary material in the inorganic binder matrix. If the oxide fine particles are added too much, the transmittance of the light scattering film for solar cell 2 is lowered. Therefore, the amount of the oxide fine particles is preferably 10% by mass or less. As the oxide fine particles, it is preferable to use fine particles having an average particle size on the order of several nm.

Next, an inorganic oxide is preferable as the material of the inorganic scattering particles constituting the light scattering film 2 for solar cells. For example, a fine particle filler such as silica having a refractive index of about 1.40 to 1.50 or a hollow filler such as airgel (porous silica or the like) can be used.
Further, as the inorganic scattering particles having a high refractive index of 1.6 or more, a material made of an inorganic oxide such as aluminum oxide, tin oxide, titanium oxide, zirconium oxide, zinc oxide or the like is appropriately selected according to the refractive index of the inorganic binder matrix. You can choose.
In addition, the inorganic scattering particles may be composed of two or more kinds of different kinds of particles. For example, aluminum oxide particles and tin oxide particles may be mixed in the inorganic binder matrix.

In order to improve the dispersibility in the inorganic binder matrix, an appropriate treatment may be performed on the surface of the inorganic scattering particles.
For example, the inorganic scattering particles for the inorganic binder matrix can be obtained by coating the surface with a silane coupling agent or a surfactant, or by chemically treating the surface with an alcohol, amine, or organic acid. The dispersibility of can be improved.

The combination of the inorganic binder matrix and the inorganic scattering particles can be selected based on the difference in refractive index between the inorganic binder matrix and the inorganic scattering particles, and can be selected regardless of which refractive index is higher.
For example, when a silica-based inorganic binder using an organosilicon compound represented by the chemical formula (1) is used, the refractive index of the inorganic binder matrix is approximately in the range of 1.4 to 1.5. By combining with aluminum oxide particles around 6 or tin oxide particles having a refractive index of about 1.9, the difference in refractive index thereof is preferably 0.2 to 0.5. Note that both aluminum oxide particles and tin oxide particles may be added to the inorganic binder matrix.
In the case of using an organic-inorganic composite binder in which a silica-based inorganic binder composed of an organosilicon compound represented by chemical formula (1) and a metal alkoxide chelate derivative represented by chemical formula (2) are used, it is formed by firing. Since the refractive index of the inorganic binder matrix is in the range of 1.6 to 1.8, by using silica particles having a refractive index of about 1.4 to 1.5 as the inorganic scattering particles, the refractive index difference between them is 0. .2 to 0.3, which is preferable.
In addition, the said combination is an illustration to the last, and is not limited to this combination.

The average particle diameter of the inorganic scattering particles is preferably 1.0 to 10.0 μm, more preferably 1.0 to 3.0 μm, and still more preferably 1.2 to 1.45 μm.
When the average particle size of the inorganic scattering particles is less than 1.0 μm, it is not preferable because sufficient scattering cannot be obtained, and when the average particle size of the inorganic scattering particles exceeds 10.0 μm, the particle size is large. It is not preferable because it sinks in the liquid.
The average particle size of the inorganic scattering particles is measured with a particle size distribution analyzer SD-2000 (manufactured by Sysmex Corporation). When the inorganic scattering particles are spherical, the average value of the diameters of the inorganic scattering particles is Yes, when the inorganic scattering particles are spheroids, the average value of the minor axis.

  As the inorganic scattering particles, it is more preferable to use a mixture of two types of inorganic scattering particles having different average particle diameters. This is because, by using a mixture of two types of inorganic scattering particles having different average particle diameters, light on the long wavelength side can be more scattered, and the amount of power generation can be increased in the photoelectric conversion layer 4. For example, it is preferable to use a mixture of inorganic scattering particles having an average particle diameter of 1.0 to 1.9 μm and scattering particles having an average particle diameter of 1.5 to 1.9 μm.

  The film thickness of the solar cell light scattering film 2 is preferably larger than the average particle diameter of the inorganic scattering particles. When the film thickness of the light scattering film 2 is smaller than the average particle diameter of the inorganic scattering particles, an uneven shape due to the inorganic scattering particles is formed on the surface of the light scattering film 2, and the surface roughness of the flat surface 2b is 100 mm. This is because it becomes difficult to make the following.

The content of inorganic scattering particles dispersed in the inorganic binder matrix is preferably 40% by mass or less.
When the content of the inorganic scattering particles dispersed in the inorganic binder matrix exceeds 40% by mass, the inorganic scattering particles cannot be uniformly dispersed, and characteristics such as the transmittance and haze ratio of the light scattering film 2 for solar cells. This is not preferable because there is a possibility that the film may vary in the plane.

  The light scattering film 2 for a solar cell is prepared by first preparing a solution in which inorganic scattering particles are dispersed in an uncured inorganic binder matrix, and applying this solution to a spin coating method, a roll coating method, a spray method, a bar coating method, or a die coating. A film is formed on the surface of the substrate using a wet process such as a method, a flow coating method, or a dipping method. The solution can contain additives such as an organic solvent, a dispersion aid, a leveling agent, and a coupling agent.

  Moreover, it is desirable that the light scattering film 2 for solar cells is made of a heat resistant material. In the process of forming the photoelectric conversion layer 4, high temperature film formation of 200 ° C. or higher is performed, and in the process of forming the upper electrode 3, a temperature close to 400 to 500 ° C. is applied when a thermal CVD method is employed. Therefore, heat resistance is desirable.

In addition, the solar cell light scattering film 2 preferably has a thermal expansion coefficient close to that of Si, and is preferably lower than 60 ppm / ° C.
Furthermore, it is desirable that the solar cell light scattering film 2 is provided with ultraviolet resistance by adding an ultraviolet absorber or including an ultraviolet absorbing functional layer. This is because when the solar cell is used outdoors, the substrate surface is exposed to ultraviolet rays by sunlight. An ultraviolet absorbing functional layer may be provided outside the solar cell light scattering film 2. For example, an ultraviolet absorption functional layer may be provided between the solar cell light scattering film 2 and the substrate.

As a material of the upper electrode layer 3, a transparent conductive oxide is preferable.
For example, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium oxide (CdO), indium cadmium oxide (CdIn ₂ O ₄ ), cadmium tin oxide (Cd ₂ SnO ₄ ), Examples include zinc tin oxide (Zn ₂ SnO ₄ ) and indium zinc oxide (In—Zn—O).
Further, impurities may be added (dope) to the transparent conductive oxide. For example, indium oxide is doped with tin (Sn), molybdenum (Mo), titanium (Ti), tin oxide is doped with antimony (Sb) and fluorine (F), zinc oxide is doped with indium, aluminum, gallium ( Ga) can be doped.
In particular, tin oxide doped with fluorine and zinc oxide doped with gallium or aluminum are preferred. Since the upper electrode layer 3 is exposed to hydrogen plasma in the next step of forming the photoelectric conversion layer 4, a material resistant to a reducing atmosphere such as F-doped SnO ₂ or Ga-doped or Al-doped ZnO is preferable. is there.

  Examples of the method for forming the upper electrode layer 3 include a sputtering method, a vapor deposition method, a CVD (Chemical Vapor Deposition) method, a sol-gel method, and the like, but are not limited thereto.

The photoelectric conversion layer 4 is formed by stacking a p-type thin film silicon layer 41, an i-type thin film silicon layer 42, and an n-type thin film silicon layer 43.
The material constituting the photoelectric conversion layer 4 may be either crystalline or amorphous silicon. Alternatively, a material containing 30% or more of silicon such as crystalline and amorphous silicon carbide or silicon germanium may be used.

  For the formation of the photoelectric conversion layer 4, a production method such as a plasma CVD method, a photo CVD method, or a hot-wire CVD method is used. In particular, it is preferable to use a plasma CVD method. This is because the plasma CVD method can form a film with good film quality with high productivity.

In the process of forming the photoelectric conversion layer 4, the p-type thin film silicon layer 41 is first formed by doping p-type dopants such as boron, gallium, and aluminum.
Examples of the raw material used for the p-type doping include a boron source such as diborane, B (CH ₃ ) ₃ , and BF ₃ , a gallium source such as trimethyl gallium and triethyl gallium, and an aluminum source such as trimethylaluminum. Examples thereof include triethylaluminum, but are not limited to these materials.

  In addition, by doping carbon when forming the p-type thin film silicon layer 41, the band gap of the p-type thin film silicon layer can be increased, and more light can be guided into the i layer. It can be set as the structure which can produce | generate a carrier. In this case, methane can be cited as the carbon source of the raw material.

The i-type thin film silicon layer 42 is formed without doping with the dopant after the p-type thin film silicon layer 41 is formed.
The n-type thin film silicon layer 43 is formed by forming an i-type thin film silicon layer 42 and then doping phosphorus or the like as an n-type dopant.

The lower electrode layer 5 is formed by sequentially laminating a lower transparent conductive electrode 51 and a metal electrode 52.
Examples of the method for forming the lower electrode layer 5 include, but are not limited to, a sputtering method, a vapor deposition method, a CVD (Chemical Vapor Deposition) method, and a sol-gel method.

The material of the lower transparent conductive electrode 51 may be any material that is conductive and made of a transparent oxide.
For example, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium oxide (CdO), indium cadmium oxide (CdIn ₂ O ₄ ), cadmium tin oxide (Cd ₂ SnO ₄ ), Examples include zinc tin oxide (Zn ₂ SnO ₄ ) and indium zinc oxide (In—Zn—O).
Further, an impurity may be added (doped) to the above oxide. For example, indium oxide is doped with tin (Sn), molybdenum (Mo), titanium (Ti), tin oxide is doped with antimony (Sb) and fluorine (F), zinc oxide is doped with indium, aluminum, gallium ( Ga) can be doped.

  The material of the metal electrode 52 is preferably a metal such as Al, Au, Ag, Cu, Pt, or Cr, and particularly preferably Al. This is because Al has specular reflectivity and can confine light in the device and can efficiently extract carriers generated in the photoelectric conversion layer 4. Moreover, the alloy containing the said metal may be sufficient.

(Embodiment 2)
FIG. 2 is a schematic cross-sectional view showing another example of a solar cell that is an embodiment of the present invention.
The solar cell light scattering film 2, the upper electrode layer 3, the photoelectric conversion layer 4, the lower photoelectric conversion layer 6, and the lower electrode layer 5 are sequentially stacked on the substrate 1 to form a solar cell 101.
The substrate 1 has a light capturing surface 1a, and one surface 2a of the solar cell light scattering film 2 is bonded to the opposite surface 1b. The other surface side of the solar cell light scattering film 2 is flat and has a flat surface 2b. In this way, the optical member 10 composed of the substrate 1 and the solar cell light scattering film 2 is formed.
The photoelectric conversion layer 4 is formed by stacking a p-type thin film silicon layer 41, an i-type thin film silicon layer 42, and an n-type thin film silicon layer 43 in this order.
The lower photoelectric conversion layer 6 is formed by stacking a p-type thin film silicon layer 61, an i-type thin film silicon layer 62, and an n-type thin film silicon layer 63 in this order. The lower electrode layer 5 is formed by laminating a lower transparent conductive electrode 51 and a metal electrode 52 in this order.
A structure in which the substrate 1, the upper electrode layer 3, the photoelectric conversion layer 4, the lower photoelectric conversion layer 6, and the lower electrode layer 5 are laminated in this order is referred to as “tandem type”.
In addition, about the member same as Embodiment 1, the same code | symbol is attached | subjected and shown.

  In the “tandem type” structure, light is incident on the substrate 1 from the light capturing surface 1 a and passes through the inside of the substrate 1, as indicated by an arrow A in FIG. It is configured to be incident on the solar cell light scattering film 2 bonded to the surface 1b opposite to 1a. Further, the light passes through the solar cell light scattering film 2 and the upper electrode layer 3 and enters the photoelectric conversion layer 4 and the lower photoelectric conversion layer 6. Photoelectric power is generated in the photoelectric conversion layer 4 and the lower photoelectric conversion layer 6 so that light is converted into electric power.

As shown in FIG. 2, the “tandem type” has a structure in which two photoelectric conversion layers of the photoelectric conversion layer 4 and the lower photoelectric conversion layer 6 are connected in series. Since it has two photoelectric conversion layers, the magnitude | size of a photovoltaic power can be raised rather than the solar cell which has only one photoelectric conversion layer.
Note that, in the “tandem type”, when the solar cell element having a large band gap is installed on the light incident side, light can be used more effectively. Therefore, the photoelectric conversion layer 4 is an amorphous silicon solar cell, an amorphous silicon carbide solar cell, or The microcrystalline silicon carbide solar cell and the lower photoelectric conversion layer 6 are preferably a microcrystalline silicon solar cell or a silicon germanium solar cell. Furthermore, a “triple type” solar cell in which three more photoelectric conversion layers 4 are provided in series by providing the photoelectric conversion layer 4 is also preferably used. In this case, it is preferable to use an i layer having a high band gap in order from the photoelectric conversion layer side close to the substrate.

(Embodiment 3)
FIG. 3 is a schematic cross-sectional view showing still another example of the solar cell according to the embodiment of the present invention.
The lower electrode layer 5, the photoelectric conversion layer 4, the upper electrode layer 3, and the solar cell light scattering film 2 are sequentially laminated on the substrate 11 to constitute the solar cell 103.
A lower electrode layer 5 is provided on the substrate 11. The lower electrode layer 5 is formed by laminating a metal electrode 52 and a lower transparent conductive electrode 51 in this order. On the lower transparent conductive electrode 51, the photoelectric conversion layer 4 is provided.
The photoelectric conversion layer 4 is formed by laminating an n-type thin film silicon layer 43, an i-type thin film silicon layer 42, and a p-type thin film silicon layer 41 in this order. An upper electrode layer 3 is provided on the photoelectric conversion layer 4.
Furthermore, one surface of the upper electrode layer 3 is bonded to the flat surface 2 b of the solar cell light scattering film 2. Therefore, the upper electrode layer 3, the photoelectric conversion layer 4, and the lower electrode layer 5 are configured to ensure flatness. On the other surface side of the flat surface 2 b of the solar cell light scattering film 2, a light capturing surface 2 a is provided so that light can be captured inside the solar cell 103.
In addition, a structure in which the upper electrode layer 3, the photoelectric conversion layer 4, the lower electrode layer 5, and the substrate 11 are stacked in this order is referred to as a “substrate type”.
In addition, about the member same as Embodiment 1, it attaches and shows the same code | symbol.

  In the “substrate type” structure, as shown by the arrow A in FIG. 3, the light is incident on the solar cell light scattering film 2 from the light capturing surface 2 a, and the solar cell light scattering film. After passing through the inside, the light is incident on the upper electrode layer 3 joined to the flat surface 2b opposite to the light capturing surface 2a. Further, the light passes through the upper electrode layer 3 and enters the photoelectric conversion layer 4. Photoelectric power is generated in the photoelectric conversion layer 4 so that light is converted into electric power.

  The substrate 11 may be an opaque material. In the “substrate type” structure, light is incident from the surface opposite to the substrate 11, that is, the light capturing surface 2 a of the light scattering film 2 for solar cell, and is photoelectrically converted in the photoelectric conversion layer 4 to generate photovoltaic power. It is. For example, transparent materials such as glass, quartz, and transparent polyimide can be used, but opaque polyimide, stainless steel thin plate, and the like can also be used.

(Embodiment 4)
FIG. 4 is a schematic cross-sectional view showing still another example of the solar cell according to the embodiment of the present invention. In addition, about the member same as Embodiment 1, it attaches and shows the same code | symbol.
As shown in FIG. 4, the solar cell 104 is configured by sequentially laminating a lower electrode layer 9, a photoelectric conversion layer 8, and a solar cell light scattering film (light confinement layer) 2 on a substrate 11. In the photoelectric conversion layer 8, the light absorption layer 81, the high resistance buffer layer 7, and the upper electrode layer 3 are laminated in this order from the lower electrode layer 9 side.
The surface (one main surface) of the upper electrode layer 3 opposite to the high resistance buffer layer 7 is joined to the flat surface 2b of the light scattering film 2 for solar cells. The surface opposite to the flat surface 2 b of the solar cell light scattering film 2 is a light capturing surface 2 a, which is configured to be able to capture light into the solar cell 104.

The material of the high resistance buffer layer 7 is preferably cadmium sulfide (CdS), zinc oxide (ZnO), zinc sulfide (ZnS), zinc hydroxide (Zn (OH) ₂ ), indium sulfide (InS), or the like. A combination of these materials may also be used.
The photoelectric conversion layer 8 is formed of a chalcopyrite compound composed of a part or all of copper (Cu), indium (In), gallium (Ga), selenium (Se), and the like.
The lower electrode layer 9 is preferably, for example, molybdenum (Mo), but is not limited thereto.

(Embodiment 5)
FIG. 5 is a schematic cross-sectional view showing still another example of the solar cell according to the embodiment of the present invention. In addition, about the member same as Embodiment 1, it attaches and shows the same code | symbol.
As shown in FIG. 5, in the solar cell 105, the optical member 10, the upper electrode layer 3, the photoelectric conversion layer 12, and the lower electrode layer 13 are sequentially stacked. The optical member 10 is formed by laminating a substrate 1 and a solar cell light scattering film 2. An upper electrode layer 3 is bonded to the surface 2b of the solar cell light scattering film 2 opposite to the substrate 1.

The photoelectric conversion layer 12 is configured by laminating a cadmium sulfide (CdS) layer 12a and a cadmium tellurium (CdTe) layer 12b in this order from the upper electrode layer 3 side.
For example, the lower electrode layer 13 is preferably carbon (C), but is not limited thereto.
Light incident on the solar cell 105 from the light capturing surface 1a of the substrate 1 is incident on the solar cell light scattering film 2 from the light capturing surface 2a, and enters the upper electrode layer 3 from the surface 2b opposite to the light capturing surface 2a. Incident. Thereafter, the light enters the photoelectric conversion layer 12.

(Embodiment 6)
FIG. 6 is a schematic cross-sectional view showing still another example of the solar cell according to the embodiment of the present invention. In addition, about the member same as Embodiment 1, it attaches and shows the same code | symbol.
As shown in FIG. 6, in the solar cell 106, the optical member 10, the upper electrode layer 3, the photoelectric conversion layer 14, and the lower electrode layer 5 ′ are sequentially laminated. The optical member 10 is formed by laminating a substrate 1 and a solar cell light scattering film 2. The substrate 1 is bonded to the light capturing surface 2a of the solar cell light scattering film 2, and the upper electrode layer 3 is bonded to the surface 2b of the solar cell light scattering film 2 opposite to the substrate 1. Further, the lower electrode layer 5 ′ is formed by sequentially laminating the metal electrode 52 and the lower transparent conductive electrode 51 from the photoelectric conversion layer 14 side.

The photoelectric conversion layer 14 is configured by laminating an electrode layer 14a, a dye layer 14b, and an electrolyte layer 14c in this order from the upper electrode layer 3 side.
The dye layer 14b only needs to be supported on the electrode layer 14a, and the photoelectric conversion layer 14 is limited to a configuration in which the electrode layer 14a, the dye layer 14b, and the electrolyte layer 14c are separated as shown in FIG. It is not a thing. For example, the photoelectric conversion layer 14 may have a two-layer configuration of an electrode layer 14a and an electrolyte layer 14c in which a dye layer 14b is attached on the molecular surface, and the electrolyte layer 14c is mixed with the electrode layer 14a and the dye layer 14b, respectively. A two-layer structure may be used.

The substrate 11 can be a transparent resin film such as polyethylene terephthalate (PET).
The electrode layer 14a is preferably made of a porous semiconductor, and examples of the porous semiconductor include titanium oxide (TiO ₂ ).
The dye layer 14b is a layer containing a dye and is preferably made of a light absorbing material, and examples of the light absorbing material include a ruthenium (Ru) complex dye.
The electrolyte layer 14c is preferably made of an electrolyte, and examples of the electrolyte include an iodine solution. Further, the state of the electrolyte layer 14c may be any of solid, liquid, and gas, and may be in an intermediate state between them.

(Embodiment 7)
FIG. 7 is a schematic cross-sectional view showing still another example of the solar cell according to the embodiment of the present invention. In addition, about the member same as Embodiment 1, it attaches and shows the same code | symbol.
As shown in FIG. 7, in the solar cell 107, the optical member 10, the upper electrode layer 3, the photoelectric conversion layer 15, and the lower electrode layer 16 are sequentially laminated. The optical member 10 is formed by laminating a substrate 1 and a solar cell light scattering film 2. The substrate 1 is bonded to the light capturing surface 2 a of the solar cell light scattering film 2, and the upper electrode layer 3 is bonded to the surface 2 b of the solar cell light scattering film 2 opposite to the substrate 1. For example, aluminum (Al) is preferably used as the lower electrode layer 16, but is not limited thereto.

The photoelectric conversion layer 15 is configured by laminating an organic semiconductor p layer 15a, an organic semiconductor i layer 15b, and an organic semiconductor n layer 15c in this order from the upper electrode layer 3 side.
Note that the photoelectric conversion layer 15 is a two-layer configuration of an organic semiconductor p layer 15a and an organic semiconductor n layer 15c, or two layers selected from the group of an organic semiconductor p layer 15a, an organic semiconductor i layer 15b, and an organic semiconductor n layer 15c. Alternatively, a single layer configuration in which three layers of components are mixed may be used.

The photoelectric conversion layer 15 is preferably made of an organic semiconductor material that exhibits semiconductor properties. Examples of the organic semiconductor material include copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), poly-3-hexylthiophene (P3HT), and fullerene derivatives.
Hereinafter, the effects of the present invention will be described.

  In the light scattering film for solar cell 2 that is an embodiment of the present invention, inorganic scattering particles having a refractive index different from that of the inorganic binder matrix are dispersed in the inorganic binder matrix, so that light is effectively scattered in the solar cell. Can be made.

  The solar cell light scattering film 2 according to an embodiment of the present invention has a flat surface 2b, and the surface roughness of the flat surface 2b is 1 nm or more and 100 nm or less. In other words, many defects are induced in the semiconductor film, the output voltage and the fill factor are deteriorated, and the conversion efficiency is not deteriorated.

  Since the light-scattering film for solar cells 2 according to the embodiment of the present invention has a transmittance of 70% or more and a haze ratio of 20 to 90%, the light confinement effect can be improved. The conversion efficiency of 101 and 103 can be improved.

  Since the light scattering film 2 for solar cells according to the embodiment of the present invention has a refractive index difference between the inorganic binder matrix and the inorganic scattering particles of 0.05 to 0.60, the light confinement effect can be improved. The conversion efficiency of the solar cells 100, 101, 103 can be improved.

  The light scattering film for solar cell 2 according to an embodiment of the present invention includes an organic silicon compound having an inorganic binder matrix represented by the chemical formula (1), a hydrolyzed polymer of the organosilicon compound, and a metal alkoxide represented by the chemical formula (2). The flat surface 2b can be easily formed by film formation on the flat surface 2b because the metal alkoxide chelate derivative or the metal alkoxide chelate derivative polymer is used. Defects can be prevented from occurring in the semiconductor layer to be formed. Moreover, the refractive index difference between the inorganic binder matrix and the inorganic scattering particles can be 0.05 to 0.60, and the light confinement effect can be improved.

  The solar cell light scattering film 2 according to the embodiment of the present invention has a structure in which the inorganic binder matrix is baked at a temperature of 400 ° C. or higher, so that the residual organic matter can be reduced and heat resistance can be imparted.

  The solar cell optical member 10 according to the embodiment of the present invention is a transparent solar cell light scattering film 2 described above and a transparent surface 2a opposite to the flat surface 2b of the solar cell light scattering film 2. Since it is composed of the substrate 1, it does not cause defects in the semiconductor layer formed on the light scattering film 2 for solar cells, and also has an effect of improving the light confinement effect. Efficiency can be improved.

  The solar cells 100, 101, and 103 that are embodiments of the present invention are solar cells including the photoelectric conversion layer 4, and the light scattering film for solar cell described above at least on the light capturing side of the photoelectric conversion layer 4. 2 is provided, the solar cell can be provided with a semiconductor film having no defect, and the light confinement effect can be enhanced, so that a solar cell with high conversion efficiency can be obtained.

  In the solar cells 100, 101, and 103 according to the embodiments of the present invention, the photoelectric conversion layer 4 is composed of at least one of single crystal silicon, polycrystalline silicon, and thin film silicon. High solar cell.

  In the solar cell 104 according to the embodiment of the present invention, since the photoelectric conversion layer 8 is composed of a chalcopyrite compound, the light confinement effect is enhanced and a solar cell with high conversion efficiency can be obtained.

  The solar cell 105 according to the embodiment of the present invention has a configuration in which the photoelectric conversion layer 12 is made of cadmium tellurium. Therefore, the light confinement effect is enhanced, and a solar cell with high conversion efficiency can be obtained.

  The solar cell 106 according to the embodiment of the present invention has a configuration in which the photoelectric conversion layer 14 includes a dye, so that the light confinement effect is enhanced and the solar cell can have high conversion efficiency.

In the solar cell 107 according to the embodiment of the present invention, since the photoelectric conversion layer 15 is composed of an organic semiconductor material, the light confinement effect is enhanced, and the solar cell can have high conversion efficiency.
Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited only to these examples.

Example 1
First, 41.0 parts by mass of tetraethoxysilane and 11.6 parts by mass of 3-glycidoxypropyltrimethoxysilane (80/20 by mole ratio) were mixed, and then 14.4 parts by mass of isopropyl alcohol and 0.1N 33.2 parts by mass of hydrochloric acid was added and subjected to a hydrolysis reaction for 1 hour to obtain a silica-based organic / inorganic composite binder having a solid content of 20 wt%.
6 parts by mass of alumina oxide particles (refractive index: 1.62) having an average particle diameter of 1 μm were mixed with 100 parts by mass of this silica-based organic / inorganic composite binder to prepare a coating solution for forming a light scattering film for solar cells.

Next, this coating solution is applied onto a Corning 1737 glass substrate using a bar coater, dried at 120 ° C. for 5 minutes with a dryer, and further baked at 500 ° C. for 30 minutes, whereby a thickness of 2 is applied onto the Corning 1737 glass substrate. A solar cell light scattering film having a thickness of 0.0 μm was formed, and a solar cell optical member including a glass substrate and a solar cell light scattering film was produced.
The surface of the light scattering film for solar cells was extremely flat, and the surface roughness Ra was 15 nm. Moreover, the haze rate of the light-scattering film for solar cells was 63%, and the transmittance was 80%.
The same operation was carried out with the coating solution to which no alumina oxide particles were added, and a film made of only the silica-based organic-inorganic composite binder was prepared, and the refractive index was measured to be 1.40. And the refractive index difference was 0.22.

Next, a ZnO: Ga (Ga: 5 wt%) ceramic target was sputtered using a DC magnetron sputtering apparatus, and a gallium-doped zinc oxide transparent conductive film was formed on a light scattering film for solar cells at a film formation temperature of 250 ° C. to a thickness of 200 nm. Filmed to form the upper electrode layer.
Next, using a plasma CVD apparatus, a p-type amorphous silicon carbide layer having a thickness of 20 nm, an i-type amorphous silicon layer having a thickness of 300 nm, and an n-type amorphous silicon layer having a thickness of 25 nm are formed on the gallium-doped zinc oxide transparent conductive film. Were formed in this order to form a photoelectric conversion layer. The respective film formation temperatures were 200 ° C. for the p-type amorphous silicon carbide layer, 280 ° C. for the i-type amorphous silicon layer, and 280 ° C. for the n-type amorphous silicon layer.
Subsequently, using a DC magnetron sputtering apparatus, a ZnO: Ga (Ga: 5 wt%) ceramic target was sputtered to form a gallium-doped zinc oxide transparent conductive film having a thickness of 15 nm to form a lower transparent electrode.
Finally, a metal electrode made of aluminum with a film thickness of 100 nm is formed on the lower transparent electrode by a vacuum deposition apparatus, and a lower electrode made of the lower transparent electrode and the metal electrode is formed. A solar cell sample (Example 1 sample) was produced.

(Example 2)
First, 6 parts by mass of tin oxide particles (refractive index: 1.86) having an average particle diameter of 1 μm are mixed with 100 parts by mass of the silica-based organic / inorganic composite binder used in Example 1 to form a light scattering film for a solar cell. The coating solution was adjusted.

Next, a solar cell light scattering film having a thickness of 2.0 μm was formed in the same manner as in Example 1, and a solar cell optical member including a glass substrate and a solar cell light scattering film was produced.
The surface of the light scattering film for solar cells was extremely flat, and the surface roughness Ra was 20 nm. Further, this solar cell light scattering film had a haze ratio of 82.0% and a transmittance of 78%. From the result of Example 1, since the refractive index of a silica type organic inorganic composite binder is 1.40, the refractive index difference of a silica type organic inorganic composite binder and a tin oxide particle was 0.46.

  Further, in the same manner as in Example 1, an upper electrode layer, a photoelectric conversion layer, a lower electrode composed of a lower transparent electrode and a metal electrode are sequentially laminated, and a “super straight type” solar cell sample (Example 2 sample) is obtained. Produced.

(Example 3)
First, 50 parts by mass of titanium-diisopropoxybis (acetylacetonate) as a titanium chelate is mixed with 50 parts by mass of the silica-based organic / inorganic composite binder used in Examples 1 and 2, and silicon oxide having an average particle size of 1.5 μm. 6 parts by mass of particles (refractive index 1.44) were mixed to prepare a coating solution for forming a solar cell light scattering film.

Next, a solar cell light scattering film having a thickness of 2.5 μm was formed in the same manner as in Example 1, and a solar cell optical member including a glass substrate and a solar cell light scattering film was produced.
The surface of the light scattering film for solar cells was extremely flat, and the surface roughness Ra was 37 nm. Moreover, the haze rate of this light-scattering film for solar cells was 50.5%, and the transmittance was 85%.
The same operation was performed with the coating solution to which no silicon oxide particles were added, and a coating film of only the silica-based organic-inorganic composite binder in Example 3 was prepared. The refractive index was measured to be 1.65. And the refractive index difference between the silicon oxide particles was 0.21.

  Further, in the same manner as in Example 1, an upper electrode layer, a photoelectric conversion layer, a lower electrode composed of a lower transparent electrode and a metal electrode are sequentially laminated, and a “super straight type” solar cell sample (Example 3 sample) is obtained. Produced.

Example 4
A metal electrode 100 nm film made of aluminum is formed on a Corning 1737 glass substrate by vacuum deposition, and then a ZnO: Ga (Ga: 5 wt%) ceramic target is sputtered using a DC magnetron sputtering apparatus to form a Ga-doped ZnO film of 15 nm. did. Subsequently, an n-type amorphous silicon layer with a thickness of 25 nm, an i-type amorphous silicon layer with a thickness of 300 nm, and a p-type amorphous silicon carbide layer with a thickness of 20 nm are formed in this order using a plasma CVD apparatus to form a photoelectric conversion layer. did. The respective film formation temperatures were 280 ° C. for the n-type amorphous silicon layer, 280 ° C. for the i-type amorphous silicon layer, and 200 ° C. for the p-type amorphous silicon carbide layer. Next, using a DC magnetron sputtering apparatus, an ITO (Sn doped In ₂ O ₃ , Sn: 10 wt%) ceramic target was sputtered to form an upper electrode made of ITO having a thickness of 80 nm.

Next, the same coating liquid as prepared in Example 1 was applied onto the upper electrode using a bar coater, dried at 120 ° C. for 5 minutes in a dryer to form a coating film, and further 280 ° C. Was baked for 30 minutes to form a light scattering film for solar cells (thickness: 2.0 μm) to produce a “substrate type” solar cell sample (Example 4 sample). In addition, simultaneously with forming the solar cell light scattering film on the upper electrode of the solar cell sample, the solar cell light scattering film was formed on the haze rate measuring glass substrate to prepare a haze rate measuring sample.
The surface of the light scattering film for solar cells was extremely flat, and the surface roughness Ra was 15 nm. Moreover, the haze rate of the light-scattering film for solar cells was 55.0%, and the transmittance was 80%. In addition, the measurement of the haze rate was performed using the said haze rate measurement sample.
The same operation was carried out with the coating solution to which no alumina oxide particles were added, and a film made of only the silica-based organic-inorganic composite binder was prepared, and the refractive index was measured to be 1.40. And the refractive index difference was 0.22.

(Comparative Example 1)
First, using a DC magnetron sputtering apparatus, a ZnO: Ga (Ga: 5 wt%) ceramic target was sputtered, and an Asahi-Type-U substrate having a haze ratio of 10% (Asahi Glass Co., Ltd., haze ratio of 10%, transmission) On top of this, a gallium-doped zinc oxide transparent conductive film was deposited to a thickness of 200 nm at a deposition temperature of 250 ° C. to form an upper electrode layer.
Next, using a plasma CVD apparatus, a p-type amorphous silicon carbide layer having a thickness of 20 nm, an i-type amorphous silicon layer having a thickness of 300 nm, and an n-type amorphous silicon layer having a thickness of 25 nm are formed on the gallium-doped zinc oxide transparent conductive film. Were formed in this order to form a photoelectric conversion layer.
Subsequently, using a DC magnetron sputtering apparatus, a ZnO: Ga (Ga: 5 wt%) ceramic target was sputtered to form a gallium-doped zinc oxide transparent conductive film having a thickness of 15 nm to form a lower transparent electrode.
Finally, a metal electrode made of aluminum with a film thickness of 100 nm is formed on the lower transparent electrode by a vacuum deposition apparatus, and a lower electrode made of the lower transparent electrode and the metal electrode is formed. A solar cell sample (Comparative Example 1 sample) was prepared.

(Comparative Example 2)
5 parts by mass of melamine / formaldehyde condensation particles (made by Nippon Shokubai Co., Ltd., trade name “Eposter S12”), 20 parts by mass of alkali-soluble acrylic resin, polyfunctional acrylic monomer (manufactured by Toagosei Co., Ltd., product) 10 parts by mass of the name “Aronix M-400”), 0.5 parts by mass of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals, trade name “Irgacure 907”), and an organic solvent (propylene glycol monomethyl ether acetate) Was sufficiently mixed with 120 parts by mass to prepare a coating solution for forming a solar cell light scattering film. Melamine / formaldehyde condensation particles (refractive index: 1.51) having an average particle diameter of 1 to 2 μm were used.
Next, a predetermined amount of the above coating solution was dropped onto a Corning 1737 glass substrate, and this glass substrate was rotated at a rotation speed of 800 rpm for 5 seconds to form a coating film. The coating film was dried and then fired at 230 ° C. for 60 minutes to form a 2.5 μm-thick solar cell light scattering film on a Corning 1737 glass substrate. The glass substrate and the solar cell light scattering film An optical member for a solar cell comprising:
The surface of the produced solar cell light-scattering film was extremely flat, and the surface roughness Ra was 23 nm. Moreover, the haze rate of the light-scattering film for solar cells was 58.2%, and the transmittance was 90%. Furthermore, the refractive index of the binder matrix of the light-scattering film for solar cells was 1.63.

Next, a ZnO: Ga (Ga: 5 wt%) ceramic target was sputtered using a DC magnetron sputtering apparatus, and a gallium-doped zinc oxide transparent conductive film was formed on a light scattering film for solar cells at a film formation temperature of 250 ° C. to a thickness of 200 nm. Filmed to form the upper electrode layer.
Next, using a plasma CVD apparatus, a p-type amorphous silicon carbide layer having a thickness of 20 nm, an i-type amorphous silicon layer having a thickness of 300 nm, and an n-type amorphous silicon layer having a thickness of 25 nm are formed on the gallium-doped zinc oxide transparent conductive film. Were formed in this order to form a photoelectric conversion layer. The respective film formation temperatures were 200 ° C. for the p-type amorphous silicon carbide layer, 280 ° C. for the i-type amorphous silicon carbide layer, and 280 ° C. for the n-type amorphous silicon carbide layer.
Subsequently, using a DC magnetron sputtering apparatus, a ZnO: Ga (Ga: 5 wt%) ceramic target was sputtered to form a gallium-doped zinc oxide transparent conductive film having a thickness of 15 nm to form a lower transparent electrode.
Finally, a metal electrode made of aluminum having a film thickness of 100 nm is formed on the lower transparent electrode at room temperature by a vacuum deposition apparatus, and a lower electrode made of the lower transparent electrode and the metal electrode is formed. A solar cell sample (Comparative Example 2 sample) was prepared.

The characteristic measurement experiment of the solar cell sample produced in Examples 1-4 and Comparative Examples 1 and 2 was conducted.
In a 25 ° C. atmosphere, a solar simulator creates pseudo-sunlight of AM 1.5, 100 mW / cm ² and irradiates each solar cell sample with four voltages: open-circuit voltage, fill factor, short-circuit current, and conversion efficiency. Characteristics were measured.
The characteristics of the light scattering films for solar cells of Examples 1 to 4 and Comparative Examples 1 and 2 are collectively shown in Table 1, and the characteristics of the solar cells of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 2 and FIG. 4 shows. Here, the transmittance is expressed as an average value of transmittance measured values (measured with air as a reference) using an integrating sphere at wavelengths of 400 nm to 800 nm.
As can be seen from Table 2 and FIG. 4, the open-circuit voltage, the fill factor, the short-circuit current, and the conversion efficiency of the solar cell samples of Examples 1 to 4 are higher than those of the solar cell samples of Comparative Examples 1 and 2, and are excellent. It can be seen that power generation characteristics are exhibited.

DESCRIPTION OF SYMBOLS 1 ... Substrate (transparent substrate), 1a ... Light capturing surface, 1b ... Opposite surface, 2 ... Light scattering film for solar cell, 2a ... Light capturing surface, 2b ... Flat surface, 3 ... Upper electrode layer, 4 ... Photoelectric Conversion layer, 5 ... lower electrode layer, 5 '... lower electrode layer, 6 ... lower photoelectric conversion layer, 7 ... high resistance buffer layer, 8 ... photoelectric conversion layer, 9 ... lower electrode layer, 10 ... optical member for solar cell, DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 12 ... Photoelectric converting layer, 12a ... CdS layer, 12b ... CdTe layer, 13 ... Lower electrode layer, 14 ... Photoelectric converting layer, 14a ... Electrode layer, 14b ... Dye layer (dye), 14c ... Electrolyte layer, DESCRIPTION OF SYMBOLS 15 ... Photoelectric converting layer, 15a ... Organic semiconductor p layer, 15b ... Organic semiconductor i layer, 15c ... Organic semiconductor n layer, 41 ... p-type thin film silicon layer, 42 ... i-type thin film silicon layer, 43 ... n-type thin film silicon layer 51 ... lower transparent conductive electrode, 52 ... metal electrode, 61 ... p-type Film silicon layer, 62 ... i-type thin film silicon layer, 63 ... n-type thin film silicon layer, 81 ... light absorption layer, 100,101,103,104,105,106,107 ... solar cell.

Claims (8)

  In the inorganic binder matrix, inorganic scattering particles having a refractive index different from that of the inorganic binder matrix are dispersed, and a light scattering film having a flat surface, the transmittance of the light scattering film is 70% or more, A light scattering film for a solar cell, wherein the haze ratio is 20 to 90%.   2. The solar cell light scattering film according to claim 1, wherein the flat surface has a surface roughness of 1 nm to 100 nm.   The light scattering film for solar cell according to claim 1, wherein a difference in refractive index between the inorganic binder matrix and the inorganic scattering particles is 0.05 to 0.6. . The inorganic binder matrix is an organosilicon compound represented by the chemical formula (1), a hydrolyzed polymer of the organosilicon compound, a metal alkoxide represented by the chemical formula (2), a chelate derivative of the metal alkoxide, or a chelate derivative of the metal alkoxide. It consists of 1 or more types of materials chosen from a polymer, The light-scattering film for solar cells of any one of Claims 1-3 characterized by the above-mentioned.
(R ₁ ) _x Si (OR ₂ ) _4-x (1)
Where R ₁ is an alkyl group having 1 to 6 carbon atoms or an organic group having a reactive functional group at the terminal, R ₂ is an alkyl group having 1 to 3 carbon atoms, and x is an integer satisfying 0 ≦ x ≦ 3. is there.
M (OR ₃ ) n (2)
However, M is a metal of any one of Al, Ti, Zr and Zn, R ₃ is an alkyl group having 1 to 4 carbon atoms, and n is a valence of the metal M.   The light scattering film for a solar cell according to claim 4, wherein the inorganic binder matrix is fired at a temperature of 400 ° C. or higher.   It consists of the light-scattering film for solar cells of any one of Claims 1-5, and the transparent base | substrate arrange | positioned at the surface on the opposite side to the said flat surface of the said light-scattering film for solar cells, An optical member for a solar cell.   A solar cell comprising a photoelectric conversion layer, wherein the light-scattering film for a solar cell according to any one of claims 1 to 5 is provided on a light capturing side of the photoelectric conversion layer.   The solar cell according to claim 7, wherein the photoelectric conversion layer includes at least one of single crystal silicon, polycrystalline silicon, thin film silicon, chalcopyrite compound, cadmium tellurium, a dye, or an organic semiconductor material. .

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