JP2011077089A - Backside sealing material for solar cell, and solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backside sealing material for a solar cell and a solar cell module, capable of improving the efficiency of conversion while suppressing degradation of adhesion between the solar cell and a backside protective sheet. <P>SOLUTION: A backside sealing material 1A for the solar cell includes a light diffusion resin layer 2 containing a transparent resin 2a and a light diffusion particle 2b diffused in the transparent resin 2a, and a transparent resin layer 3 which contains a transparent resin 3a and is stacked on each side of the light diffusion resin layer 2. The solar cell module uses the backside sealing material 1A for the solar cell. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solar cell module, and in particular, can effectively use incident light incident between solar cells to increase conversion efficiency, and can suppress a decrease in adhesion with a glass plate or a back surface protection sheet. The present invention relates to a back surface side sealing material for solar cells excellent in and a solar cell module using the same.

In recent years, interest in global warming has increased, and various efforts have been made to suppress carbon dioxide emissions. Increasing fossil fuel consumption leads to an increase in atmospheric carbon dioxide, and the greenhouse effect raises the Earth's temperature, significantly affecting the global environment. As a solution for this problem, expectations for solar power generation are particularly high in terms of cleanliness and non-pollution.
A solar cell constitutes the heart of a solar power generation system that directly converts solar energy into electricity, and is a solar cell made of a single crystal, polycrystal, or amorphous silicon semiconductor (a single solar cell element) ). In solar cells, solar cells are not used as they are, and generally several to several tens of solar cells are wired in series and in parallel. Moreover, in order to protect a photovoltaic cell over a long period (about 20 years), various packaging is performed and unitized. The unit incorporated in this packaging is called a solar cell module, and generally covers the surface exposed to sunlight with a glass surface, fills the gap with a sealing material made of thermoplastic, and protects the back surface with a back surface protection sheet. To do.

However, in the solar cell module, sunlight incident on the gap between the plurality of installed solar cells and the solar cells does not contribute to power generation. Therefore, various efforts have been made to effectively use sunlight incident on the gap for the purpose of improving the conversion efficiency. For example, the following solar cell modules (1) and (2) are shown.
(1) A solar battery module in which a concave and convex shape is imparted to a sealing material in a gap portion between a solar battery cell and a solar battery cell, and a light reflecting surface is formed by plating or vapor deposition on a back surface portion of the concave and convex shape (Patent Document 1) ).
(2) A solar cell module in which light-reflective particles are contained in the entire back surface side sealing material that seals the back surface side of the solar battery cell (Patent Document 2).
In the solar cell modules (1) and (2), the light that has passed through the gap between the solar cell and the solar cell is reflected by the light reflecting surface or the light reflecting particles, and the reflected light is reflected again by the glass surface. The light is used for photoelectric conversion by reaching the solar battery cell.

JP 2002-43600 A JP 2005-101381 A

However, in the solar cell module (1), since it is necessary to perform plating or vapor deposition for forming a light reflecting surface on the concave and convex back surface of the sealing material, the manufacturing process increases and the manufacturing becomes complicated. In addition, it is difficult to match the position where the light reflecting surface is formed to the position corresponding to the gap between the solar battery cell and the solar battery cell.
Moreover, in the solar cell module (2), when the back surface side sealing material contains a sufficient amount of light-reflective particles to improve the conversion efficiency, the back surface side sealing material, the solar battery cell, and the back surface There is a problem that the adhesion between the side sealing material and the back surface protective sheet is lowered, and the weather resistance of the solar cell module is lowered.

  The present invention provides a back side sealing for solar cells that can effectively improve the conversion efficiency by effectively using sunlight incident on the gap between the solar cells while suppressing a decrease in adhesion between the solar cells and the back surface protective sheet. An object is to provide a solar cell module using the stopper and the solar cell back surface side sealing material.

The present invention employs the following configuration in order to solve the above problems.
[1] A light diffusing resin layer containing a transparent resin and light diffusing particles dispersed in the transparent resin, and a transparent resin layer containing a transparent resin, which are respectively laminated on both sides of the light diffusing resin layer. The solar cell back surface side sealing material which seals the back surface side of the photovoltaic cell characterized by having.
[2] The back side for solar cell according to [1], wherein the light diffusing particles are light diffusing particles having an average particle size of 0.02 to 6 μm and a refractive index of 1.7 to 2.8. Sealing material.
[3] The [1] or [1], wherein the content of the light diffusing particles in the light diffusing resin layer is 0.1 to 30 parts by mass with respect to 100 parts by mass of the transparent resin in the light diffusing resin layer. 2] The back surface side sealing material for solar cells as described in 2].
[4] The solar cell backside sealing material according to any one of [1] to [3], wherein the light diffusion resin layer and the transparent resin layer are formed by a multilayer extrusion method.
[5] A solar battery cell, a sealing material layer for embedding and sealing the solar battery cell, a glass plate positioned on the light receiving surface side of the solar battery cell in the sealing material layer, A back surface protection sheet positioned on the back surface side of the solar battery cell in the sealing material layer, and the sealing material layer seals the front surface side of the solar battery cell, The solar cell module currently formed with the back surface side sealing material for solar cells in any one of [1]-[4].

The solar cell back surface sealing material of the present invention increases the conversion efficiency by effectively using sunlight incident on the gap between the solar cells while suppressing a decrease in adhesion between the solar cells and the back surface protective sheet. Can do.
The solar cell module of this invention is excellent in the adhesiveness of the back surface side sealing material for solar cells, a photovoltaic cell, and a back surface protection sheet, and is excellent also in conversion efficiency.

It is sectional drawing which showed an example of embodiment of the back surface side sealing material for solar cells of this invention. It is sectional drawing which showed other embodiment examples of the back surface side sealing material for solar cells of this invention. It is sectional drawing which showed an example of embodiment of the solar cell module of this invention. It is sectional drawing which showed 1 process of the manufacturing method of the solar cell module of this invention. It is sectional drawing which showed 1 process of the manufacturing method of the solar cell module of this invention. It is sectional drawing which showed the path | route of the light which passes between the photovoltaic cells of the solar cell module of this invention.

[Back side sealing material for solar cells]
The back side sealing material for solar cells of the present invention (hereinafter simply referred to as “back side sealing material”) is a sealing material that seals the back side of solar cells in a solar cell module. It is used together with a surface-side sealing material that seals the light-receiving surface side (surface side) in the cell to form a sealing material layer that embeds and seals the solar cells.

  The back side sealing material of the present invention contains a transparent resin and a light diffusing resin layer containing light diffusing particles dispersed in the transparent resin, and a transparent resin laminated on both sides of the light diffusing resin layer. A transparent resin layer. That is, the back surface side sealing material of the present invention comprises a laminate of three or more layers having one or more light diffusing resin layers and two or more transparent resin layers located on both sides of the light diffusing resin layer. Have.

Hereinafter, an example of an embodiment of the back side sealing material of the present invention will be shown and described in detail.
As shown in FIG. 1, the back side sealing material of the present invention has a back side sealing having a laminated body in which a transparent resin layer 3, a light diffusion resin layer 2, and a transparent resin layer 3 are laminated in this order. As shown in FIG. 2, the stop material 1 </ b> A or a laminate having a five-layer structure in which the transparent resin layer 3, the light diffusion resin layer 2, the transparent resin layer 3, the light diffusion resin layer 2, and the transparent resin layer 3 are laminated in this order. The back surface side sealing material 1B which has a body is preferable.

The light diffusing resin layer 2 contains a transparent resin 2a and light diffusing particles 2b dispersed in the transparent resin 2a. The transparent resin in the present invention means a resin having a light transmittance of 80% or more of standard light D65 line at a thickness of 1 mm.
In the solar battery module, the light diffusion resin layer 2 plays a role of reflecting sunlight that has passed through the gap between the solar battery cell and the solar battery cell.

As the transparent resin 2a, a known transparent resin that is usually used as a sealing material for sealing solar cells can be used.
Examples of the transparent resin 2a include polyolefins such as polyethylene and polypropylene; ionomers; ethylene-vinyl acetate copolymer (hereinafter referred to as “EVA”); polyvinyl fluoride; polyvinyl chloride, or copolymers thereof. Can be mentioned. Among these, EVA is preferable from the viewpoint of excellent transparency and low cost, and EVA having a vinyl acetate unit content of 10 to 40% by mass is more preferable.

As the light diffusing particles 2b, particles having little light absorption and excellent light reflectivity can be used, and inorganic fine particles are preferable. Examples of the inorganic fine particles include inorganic oxide particles such as silica, titanium oxide, alumina, silica alumina, zirconia, magnesium oxide, zinc oxide, barium oxide, and strontium oxide, calcium carbonate, barium carbonate, barium chloride, barium sulfate, and nitric acid. Examples thereof include inorganic fine particles such as barium, barium hydroxide, aluminum hydroxide, strontium carbonate, strontium chloride, strontium sulfate, strontium nitrate, strontium hydroxide, and glass particles. Of these, white light diffusing particles are preferable from the viewpoint of excellent light reflectivity, and titanium oxide, magnesium oxide, and alumina are more preferable.
These light diffusion particles 2b may be used alone or in combination of two or more.

  The average particle diameter of the light diffusing particles 2b is preferably 0.02 to 6 μm, and more preferably 0.02 to 2 μm. If the average particle diameter of the light diffusing particles 2b is within the above range, the sunlight reflection performance is improved. Therefore, the amount of sunlight that reaches the light receiving surface of the solar cell out of the sunlight that has entered the solar cell module. Increases and the conversion efficiency is improved. In addition, since light absorption in the visible light wavelength region becomes small, it is easy to suppress light loss. Furthermore, it is easy to suppress a color such as yellow on the back surface side sealing material by the light diffusing particles 2b.

  The refractive index of the light diffusing particle 2b is preferably 1.7 to 2.8, and more preferably 2.2 to 2.8. If the refractive index of the light diffusing particles 2b is 1.7 or more, the refractive index is higher than that of the transparent resin 2a, so that the difference in refractive index with the transparent resin 2a is increased and the light scattering property is improved. Reflective performance is easy to obtain. Therefore, conversion efficiency is improved. If the refractive index of the light diffusing particle 2b is 2.8 or less, the production cost can be suppressed because it is inexpensive and easily available.

As the light diffusing particles 2b, particles having excellent light reflectivity corresponding to the effective wavelength of the solar battery cell can be used. In particular, light diffusing particles 2b having excellent light reflectivity with respect to light having a wavelength of 400 to 1000 nm in sunlight are preferable.
The light diffusion particle 2b is particularly preferably a light diffusion particle having an average particle size of 0.02 to 6 μm and a refractive index of 1.7 to 2.8.

  0.1-30 mass parts is preferable with respect to 100 mass parts of transparent resin 2a, and, as for content of the light-diffusion particle | grains 2b in the light-diffusion resin layer 2, 1-25 mass parts is more preferable. When the content of the light diffusing particles 2b is 0.1 parts by mass or more with respect to 100 parts by mass of the transparent resin 2a, excellent light reflectivity is easily obtained, and the conversion efficiency of the solar cell module is improved. If the content of the light diffusing particles 2b is 30 parts by mass or less with respect to 100 parts by mass of the transparent resin 2a, it is easy to sufficiently knead the transparent resin and the light diffusing particles in the production of the back surface side sealing material. The dispersion state tends to be good. Therefore, it is easy to obtain a back side sealing material that is uniformly formed into a sheet.

The transparent resin layer 3 is a layer containing a transparent resin 3a. Examples of the transparent resin 3a include the same resins as those mentioned for the transparent resin 2a. As the transparent resin 3a, EVA is preferable, and EVA having a vinyl acetate unit content of 10 to 40% by mass is more preferable.
The transparent resin 2a of the light diffusing resin layer 2 and the transparent resin 3a of the transparent resin layer 3 may be the same type of resin or different types of resins. It is preferable that the resin is.

In the back surface side sealing material of this invention, it is preferable to bridge | crosslink the transparent resin in a sealing material with a heat | fever or light from the point which the heat resistance of a solar cell module and physical strength improve.
When performing thermal crosslinking, it is preferable to mix an organic peroxide in each layer. The organic peroxide is preferably one that decomposes at a temperature of 70 ° C. or higher to generate radicals.
For example, as an organic peroxide having a half-life of 10 hours and a decomposition temperature of 50 ° C. or higher, 2,5-dimethylhexane-2,5-dihydroxyperoxide, 2,5-dimethyl-2,5-di (t- Butylperoxy) hexyne-3, di-t-butyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, α, Examples include α′-bis (t-butylperoxyisopropyl) benzene, n-butyl-4,4-bis- (t-butylperoxy) valerate, t-butylperoxybenzoate, and benzoyl peroxide.

  When performing photocuring, it is preferable to mix a photosensitizer in each layer. For example, hydrogen abstraction type (bimolecular reaction type) such as benzophenone, orthobenzoylmethyl benzoate, 4-benzoyl-4′-methyldiphenyl sulfide, isopropylthioxanthone; internal cleavage type such as benzoin ether and benzyldimethyl ketal; 2-hydroxy Α-hydroxyalkylphenone type such as 2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, alkylphenylglyoxylate, diethoxyacetophenone; 2-methyl-1- [4 (methylthio) Α-aminoalkylphenone type such as phenyl] -2-morpholinopropane-1,2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, and the like. Further, acyl phosphine oxide or the like may be used.

The light diffusion resin layer 2 and the transparent resin layer 3 may be blended with an epoxy group-containing compound for the purpose of improving adhesion and promoting a curing reaction.
Examples of the epoxy group-containing compound include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, acrylic glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, Compounds such as phenol glycidyl ether, pt-butylphenyl glycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, glycidyl methacrylate, butyl glycidyl ether, and mass average molecular weight containing an epoxy group from several hundreds Examples include thousands of oligomers and polymers having a mass average molecular weight of thousands to hundreds of thousands.

In addition, the light diffusion resin layer 2 and the transparent resin layer 3 are provided with an acryloxy group-containing compound, a methacryloxy group for the purpose of improving the crosslinking, adhesion, mechanical strength, heat resistance, moist heat resistance, weather resistance, and the like of the sealing material. A containing compound or an allyl group-containing compound may be blended.
As the acryloxy group-containing compound and the methacryloxy group-containing compound, (meth) acrylic acid derivatives such as alkyl esters and amides of (meth) acrylic acid are preferable.
Examples of the alkyl group include methyl group, ethyl group, dodecyl group, stearyl group, lauryl group, cyclohexyl group, tetrahydrofurfuryl group, aminoethyl group, 2-hydroxyethyl group, 3-hydroxypropyl group, and 3-chloro-2. -A hydroxypropyl group etc. are mentioned. Examples of the alkyl ester of (meth) acrylic acid include esters of (meth) acrylic acid and polyfunctional alcohols (ethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane, pentaerythritol, etc.). Can be mentioned.
Examples of amides of (meth) acrylic acid include acrylamide.
Examples of the allyl group-containing compound include triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl isophthalate, and diallyl maleate.

  In addition, the light diffusion resin layer 2 and the transparent resin layer 3 may be blended with an inorganic compound that imparts flame retardancy, an ultraviolet absorber that imparts weather resistance, and an antioxidant that prevents oxidative degradation.

  0.2-1.0 mm is preferable and, as for the total thickness of the back surface side sealing material (back surface side sealing material 1A, 1B) of this invention, 0.3-0.6 mm is more preferable. When the total thickness of the back surface side sealing material is 0.2 mm or more, the adhesion between the sealing material layer in the solar cell module, the solar battery cell and the back surface protection sheet is improved, and the conversion efficiency is also improved. If the total thickness of the back surface side sealing material is 1.0 mm or less, it is easy to sufficiently ensure the transmittance of the transparent resin layer to 80% or more.

The ratio _d B / _{d A} of back-surface-side sealing member (back-surface-side sealing member 1A, 1B) and the thickness _{d A} of the light-diffusing resin layer 2 in, the transparent resin layer 3 thickness _{d B} of the present invention is limited It is preferable that it is 1/19 to 1/1, and it is more preferable that it is 1/10 to 1/1.
If the ratio d _{B /} d _A is 1/19 or more, it is possible to suppress the thickness of the transparent resin layer 3 is too thin, it becomes easy to mold the back side encapsulant. If the ratio d _B / d _A is 1/1 or less, it is easy to suppress the thickness of the light diffusing resin layer 2 from becoming too thin. Therefore, the content of the light diffusing particles 2b can be suppressed, and the back surface sealing material is molded. Becomes easier.

  As a manufacturing method of the back surface side sealing material of this invention, the method of shape | molding the light-diffusion resin layer 2 and the transparent resin layer 3 by a multilayer extrusion method using a some extruder is preferable. That is, a transparent resin, a light diffusing particle, and a light diffusing resin composition containing various additives as needed, and a transparent resin and a transparent resin composition containing various additives as needed, respectively, A method in which each layer is formed by an extrusion method to obtain a back side sealing material is preferable. By using the multi-layer extrusion method, it is possible to produce a back side sealing material that is superior in quality at a lower cost without increasing the number of steps in spite of being a complex laminate of three or more layers.

If the back surface side sealing material of this invention is used, in a solar cell module, while suppressing the fall of the adhesiveness of a back surface side sealing material and a photovoltaic cell, and a back surface side sealing material and a back surface protection sheet, conversion efficiency Can be increased.
In addition, the back surface side sealing material of this invention is not limited to the said back surface side sealing agent 1A, 1B. For example, the back surface side sealing material which has a laminated body of 7 layers or more may be sufficient.

[Solar cell module]
The solar cell module of this invention is a solar cell module manufactured using the back surface side sealing material of this invention mentioned above. Hereinafter, as an example of an embodiment of the solar cell module of the present invention, a solar cell module 10 using the back side sealing material 1A will be described.
As shown in FIG. 3, the solar cell module 10 includes a plurality of solar cells 12 (four in this embodiment) and a sealing material layer that seals the solar cells 12 so as to be embedded therein. 11, a glass plate 13 positioned on the light receiving surface 12 a side of the solar battery cell 12 in the sealing material layer 11, and a back surface protection sheet 14 positioned on the back surface 12 b side of the solar battery cell 12 in the sealing material layer 11. Have.

  The sealing material layer 11 is formed by the front surface side sealing material 1C and the back surface side sealing material 1A. In the back surface side sealing material 1A in the sealing material layer 11, the transparent resin layer 3 is in contact with the solar battery cell 12 and the back surface protection sheet 14, and the light diffusion resin layer 2 is formed between the solar battery cell 12 and the back surface protection sheet 14. Located between.

  The surface side sealing material 1C is a sealing material that seals the light receiving surface 12a side of the solar battery cell 12, and a known sealing material that does not include light diffusion particles can be used. Examples of the transparent resin in the front-side sealing material 1C include the same resins as those mentioned for the transparent resin 2a described above, and the preferred embodiments are also the same. Moreover, the various additives mentioned above may be added to the surface side sealing material 1C as needed.

Moreover, the silane coupling agent may be mix | blended with the surface side sealing material 1C in order to improve adhesiveness with the glass plate 13. FIG.
Examples of the silane coupling agent include vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-glycine. Sidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N -Β (aminoethyl) -γ-aminopropyltrimethoxysilane and the like.

  The thickness of the surface side sealing material 1C is preferably 0.2 to 1.0 mm, and more preferably 0.3 to 0.6 mm.

The solar battery cell 12 is a cell having a function of converting sunlight incident on the light-receiving surface by photoelectric effect into electricity. The solar battery cell 12 is made of, for example, a single crystal silicon substrate or a polycrystalline silicon substrate, has a PN junction formed therein, electrodes are provided on the light receiving surface 12a and the back surface 12b, and antireflection is provided on the light receiving surface 12a. Examples thereof include a cell provided with a film.
The thickness of the solar battery cell 4 is usually about 0.3 mm, and the size is often about 150 mm square of polycrystalline silicon solar battery cells.

Examples of the glass plate 13 include white plate glass, tempered glass, double tempered glass, and heat ray reflective glass, and white plate tempered glass is preferable.
The thickness of the glass plate 13 is preferably 3 to 5 mm.

As the back surface protection sheet 14, for example, a fluorine-based resin sheet having a laminated structure in which an aluminum foil is sandwiched so that moisture does not permeate from the back surface side of the solar cell module, alumina, or silica is deposited. Examples thereof include a polyethylene terephthalate (PET) sheet.
As for the thickness of the back surface protection sheet 14, 15-400 micrometers is preferable.

  As a manufacturing method of the solar cell module 10, a well-known manufacturing method can be used except using the back surface side sealing material of this invention, for example, as shown in FIG. 4, the back surface protection sheet 14, sealing material sheet 1A, solar battery cell 12, sealing material sheet 1C, and glass plate 13 are laminated in this order to form a laminated body 10A, and the photoelectric conversion cell 12 is embedded in the sealing material sheets 1A and 1C by vacuum lamination. A method of forming the sealing material layer 11 by cross-linking and curing the transparent resin of the sealing material and integrating them together is mentioned.

Specifically, the method which has the following process (1)-(4) is mentioned.
(1) As shown to Fig.5 (a), the several photovoltaic cell 12 connected by the glass plate 13, the surface side sealing material 1C, and the electrode on the heated top plate 100 (about 120-160 degreeC). The back side sealing material 1A and the back side protective sheet 14 are laminated in this order to form a laminate.
(2) The chamber 101 and the chamber 102 are evacuated.
(3) The chamber 102 is opened to the atmosphere, and the heat-resistant rubber sheet 103 is adhered to the laminate.
(4) Due to the heat and pressure resulting from the adhesion in step (3), as shown in FIG. 5 (b), EVA, which is a sealing material, is melted, solar cells 12 are embedded in the sealing material, glass The sealing material is crosslinked and solidified while adhering to the plate 13 and the back surface protection sheet 14 to form the sealing material layer 11.

  The cross-linking reaction in the step (4) is classified into a case where a cross-linking reaction is performed in an oven provided in another line after lamination and a case where a cross-linking reaction is performed inside a laminator. The former is a type called standard cure, and the latter is a type called fast cure, and a desired method can be used.

The solar cell module 10 demonstrated above can obtain the outstanding conversion efficiency by using the back surface side sealing material of this invention.
In the solar cell module of the present invention, as shown in FIG. 6, sunlight F incident between the solar cells 12 and the solar cells 12 is diffused by the light diffusion resin layer 2 in the back surface side sealing material 1A. The sunlight F reflected by the particles 2 b and further reflected by the glass plate 13 is reflected again by the glass plate 13, and a part thereof reaches the light receiving surface 12 a of the solar battery cell 12. Thus, since the sunlight F which passed between the photovoltaic cell 12 and the photovoltaic cell 12 can be utilized for electric power generation, conversion efficiency improves.

Moreover, in the solar cell module of this invention, suppression of the adhesive fall of a back surface side sealing material and a photovoltaic cell and a back surface side sealing material and a back surface protection sheet and the outstanding conversion efficiency can be made compatible. The reason for obtaining this effect is considered as follows.
In the conventional solar cell module described in Patent Document 2, it is considered that the adhesiveness between the solar battery cell and the back surface protective sheet was lowered because the light-reflective particles were entirely blended with the back surface side sealing material. .
On the other hand, the back side sealing material of the present invention has a light diffusing resin layer containing light diffusing particles and a transparent resin layer not containing light diffusing particles located on both sides of the light diffusing resin layer. In the solar cell module, a transparent resin layer not containing light diffusing particles is in contact with the solar cell and the back surface protective sheet. Therefore, the fall of the adhesiveness of a back surface side sealing material and a photovoltaic cell and a back surface side sealing material and a back surface protection sheet is suppressed. In addition, since the back side sealing material has such a configuration, the light diffusion particles can be blended in a high concentration in the light diffusion resin layer without reducing the adhesion with the solar battery cell or the back surface protection sheet. Conversion efficiency becomes higher.

  In addition, the solar cell module of this invention is not limited to the thing using 1 A of back surface side sealing materials mentioned above. For example, the back surface side sealing material 1B may be used.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following description. In the present embodiment, “part” means “part by mass”.
[Example 1]
For the production of the light diffusing resin layer and the transparent resin layer of the back side sealing material, the following light diffusing resin composition and transparent resin composition are used, and multilayer extrusion is performed by an extruder having a screw diameter of 65 mm and an extruder having a screw diameter of 40 mm. Then, a sheet-like back side sealing material composed of three layers in which a transparent resin layer, a light diffusion resin layer, and a transparent resin layer were sequentially laminated was produced. At this time, the thickness of the light diffusion resin layer is adjusted to 0.40 mm, the thickness of each of the two transparent resin layers is adjusted to 0.05 mm, and the total thickness of the back side sealing material is adjusted to 0.50 mm. did.
Light diffusing resin composition:
Transparent resin EVA (vinyl acetate unit: 30% by mass) 100 parts Light diffusing particles Titanium oxide (average particle size 0.2 μm, refractive index 2.72) 15 parts Crosslinking agent 2,5-dimethyl-2,5-di (t -Butylperoxy) hexane
0.7 parts Crosslinking aid Triallyl isocyanurate 0.7 parts UV absorber Benzophenone UV absorber 0.3 part Antioxidant Phosphorous antioxidant 0.1 part Light stabilizer Hindered amine light stabilizer 0.3 Part The transparent resin composition had the same composition as the light diffusing resin composition except that it did not contain light diffusing particles.

[Examples 2 and 3]
A back surface side sealing material was produced in the same manner as in Example 1 except that the blending amount of titanium oxide as light diffusing particles was changed as shown in Table 1.

[Example 4]
The back-side sealing material was prepared in the same manner as in Example 1 except that the light diffusing particles added to the light diffusing resin composition were changed to 5 parts of magnesium oxide having a refractive index of 1.72 and an average particle diameter of 0.2 μm. Produced.

[Example 5]
A back side sealing material was prepared in the same manner as in Example 1 except that the light diffusing particles added to the light diffusing resin composition were changed to 5 parts of alumina having a refractive index of 1.77 and an average particle size of 0.2 μm. did.

[Example 6]
Example except that the amount of titanium oxide was changed to 20 parts, the thickness of the light diffusion resin layer was changed to 0.20 mm, and the thickness of the transparent resin layers on both sides of the light diffusion resin layer was changed to 0.15 mm, respectively. In the same manner as in Example 1, a back side sealing material was produced.

[Comparative Example 1]
Using the transparent resin composition of Example 1, a back side sealing material composed of a single transparent resin layer having a thickness of 0.50 mm was produced.

[Examples 2 and 3]
Using the light diffusing resin composition in which the blending amount of titanium oxide in the light diffusing resin composition of Example 1 was changed as shown in Table 1, a back side sealing material composed of a single light diffusing resin layer was produced.

[Evaluation methods]
The glass plate 13, the front surface side sealing material 1 </ b> C, the solar battery cell 12, the back surface side sealing material 1 </ b> A, and the back surface protection sheet 14 shown below are laminated to form a laminate 10 </ b> A as shown in FIG. 4. The laminated body 10A is heated and pressure-bonded at 140 ° C. with a vacuum laminator to embed the solar battery cells 12 in the front surface side sealing material 1C and the back surface side sealing material 1A. The sealing material layer 11 was formed by crosslinking and curing, and the solar cell module illustrated in FIG. 3 was produced.
Glass plate 13: White plate tempered glass (thickness 3 mm).
Surface side sealing material 1C: Sealing material produced using the transparent resin composition of Example 1 (thickness 0.5 mm).
Back side sealing material 1A: Back side sealing material created in each example.
Back surface protection sheet: A 38 μm-thick polyvinyl fluoride resin sheet (PVF) having a 300 nm-thick aluminum deposited layer on a 38 μm-thick polyvinyl fluoride resin sheet (PVF) via an acrylic resin adhesive Laminated sheet.

About the obtained solar cell module, as shown below, adhesiveness and conversion efficiency were evaluated.
(Evaluation of adhesion between sealing material layer and back surface protection sheet)
The obtained solar cell module was stored in an 85 ° C.-85% RH environment for 1000 hours, and then the adhesion between the sealing material layer and the back surface protective sheet was evaluated. The adhesiveness is cut at the interface between the back surface protection sheet 14 and the sealing material layer 11 as a trigger for peeling with a cutter knife, and the back surface protection sheet 14 is fixed to the chuck of the adhesive strength measuring machine, and the back surface side is at an angle of 90 °. The adhesive strength between the sealing material / back surface protective sheet was measured and evaluated according to the following criteria. As an adhesive strength measuring machine, Tenshiron universal testing machine RTC-1250 manufactured by Orientec Co., Ltd. was used. The measurement conditions were 15 mm wide adhesive strength measurement, and the peeling rate was 300 mm / min.
○: Adhesive strength was 30 N / 15 mm or more.
X: The adhesive strength was less than 30 N / 15 mm.

(Conversion efficiency evaluation)
The conversion efficiency of the solar cell module was measured by a method based on JIS C8913.
The evaluation results of Examples and Comparative Examples are shown in Table 1. About the conversion efficiency, the relative value when the conversion efficiency obtained in Comparative Example 1 was set to “1” was described.

As shown in Table 1, in Examples 1 to 6 using the back side sealing material of the present invention consisting of a three-layer structure in which a transparent resin layer, a light diffusion resin layer, and a transparent resin layer are laminated, in a solar cell module Adhesion between the sealing material layer and the back surface protective sheet was excellent. Moreover, the conversion efficiency was excellent compared with the comparative example 1 using the back surface side sealing material which consists of a single layer transparent resin layer.
On the other hand, in the comparative example 2 using the back surface side sealing material which consists of a single layer of light-diffusion resin layer, although the conversion efficiency of the solar cell module improved, the adhesiveness of a sealing material layer and a back surface protection sheet is inferior. It was.
Moreover, in the comparative example 3 whose compounding quantity of a titanium oxide is 0.1 part, although the adhesiveness of a sealing material layer and a back surface protection sheet is excellent, the improvement of conversion efficiency was not seen.

  DESCRIPTION OF SYMBOLS 1A, 1B Back surface side sealing material for solar cells 2 Light diffusion resin layer 2a Transparent resin 2b Light diffusion particle 3 Transparent resin layer 3a Transparent resin 10 Solar cell module 11 Sealing material layer 12 Solar cell 13 Glass plate 14 Back surface protection sheet

Claims (5)

  A transparent resin and a light diffusing resin layer containing light diffusing particles dispersed in the transparent resin, and a transparent resin layer containing a transparent resin, which is laminated on each side of the light diffusing resin layer. A solar cell back surface side sealing material for sealing a back surface side of a solar battery cell, which is characterized.   The back side sealing material for solar cells according to claim 1, wherein the light diffusing particles are light diffusing particles having an average particle diameter of 0.02 to 6 µm and a refractive index of 1.7 to 2.8.   The sun according to claim 1 or 2, wherein the content of the light diffusing particles in the light diffusing resin layer is 0.1 to 30 parts by mass with respect to 100 parts by mass of the transparent resin in the light diffusing resin layer. Battery back side sealing material.   The back surface side sealing material for solar cells in any one of Claims 1-3 in which the said light-diffusion resin layer and the said transparent resin layer are shape | molded by the multilayer extrusion method. A solar battery cell, a sealing material layer for embedding and sealing the solar battery cell, a glass plate positioned on the light receiving surface side of the solar battery cell in the sealing material layer, and the sealing material A back surface protection sheet located on the back surface side of the solar cell in the layer,
The solar in which the said sealing material layer is formed with the surface side sealing material which seals the surface side of the said photovoltaic cell, and the back surface side sealing material for solar cells in any one of Claims 1-4. Battery module.

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