JP2012209406A - Solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar battery module capable of reliably reusing light which is originally a loss.SOLUTION: There is provided a solar battery module comprising: a translucent front plate; a backside sheet arranged on a back side of the front plate; a solar battery cell arranged between the backside sheet and the front plate; and a sealing member which seals the solar battery cell between the front panel and the backside sheet. The backside sheet 14 includes: a weather-resistant layer 147 facing the front panel via the sealing member; a light reflective metal layer 143 formed on the weather-resistant layer 147 via an adhesive layer 144; and a translucent insulating layer 141 formed on the light reflective metal layer 143 via a convexo-concave structure layer 142. The light reflective metal layer 143 is formed integrally with the convexo-concave structure layer 142 so as to form a convexo-concave shape. A second reflective layer 145, configured to reflect light which has passed through the light reflective metal layer 143, is formed between the weather-resistant layer 147 and the adhesive layer 144.

Description

  The present invention relates to a solar cell module.

In recent years, the widespread use of solar panels has increased greatly, from relatively small ones mounted on small electronic devices such as calculators to large areas used for solar panels installed in houses for home use and large-scale power generation facilities The use is promoted in various fields such as a solar cell power generation system and a power source for an artificial satellite (see, for example, Patent Document 1).
Solar cells convert incident light energy into electrical energy, and are classified into crystalline silicon type, amorphous silicon type, organic compound type, etc., depending on the type of material used. Of these, most of the solar cells that are currently on the market are crystalline silicon solar cells. These crystalline silicon solar cells (hereinafter abbreviated as “silicon solar cells”) are further divided into single crystal and polycrystalline types. are categorized.

Single crystal silicon solar cells have the advantage that the substrate quality is good, and thus it is easy to increase the efficiency, but the substrate is expensive to manufacture. On the other hand, polycrystalline silicon solar cells have the disadvantage that they are difficult to achieve high efficiency because of the poor substrate quality, but have the advantage that they can be manufactured at low cost, and are now mainstream.
With regard to increasing the efficiency of polycrystalline silicon solar cells, for example, a texture structure is formed on the surface of a silicon substrate used for solar cells, thereby reducing reflection of sunlight on the surface of the silicon substrate and improving conversion efficiency. It is illustrated.

  On the other hand, regarding single crystal silicon solar cells, the reflection of sunlight is reduced by forming fine pyramids or inverted pyramids by anisotropic etching such as an alkaline solution. This anisotropic etching utilizes the fact that the etching rate of single crystal silicon differs between the Si (100) crystal orientation plane and the Si (111) crystal orientation plane. (For example, refer to Patent Document 2).

However, when such anisotropic etching is applied to polycrystalline silicon, the etching with alkaline aqueous solution depends on the crystal plane orientation, so the pyramid structure in polycrystalline silicon cannot be formed uniformly, and the entire silicon substrate There is a problem that the reflectance cannot be effectively reduced.
In order to solve such problems, as a method of forming a texture on a polycrystalline silicon substrate, a method of forming fine protrusions on the surface of the polycrystalline silicon substrate by a reactive ion etching method has been proposed. (For example, refer to Patent Document 3). According to this technique, the fine protrusions are uniformly formed without being influenced by the surface orientation of the irregular crystal in the polycrystalline silicon, so that the reflectance is more effective particularly in the solar cell using the polycrystalline silicon. Can be reduced.

  It is also known that the conversion efficiency can be further improved by combining a surface antireflection film. That is, since crystalline silicon has a large refractive index of 6.00 to 3.50 in the wavelength range of 400 nm to 1100 nm, it has a reflection loss of about 54% in the short wavelength region and about 34% in the long wavelength region. In order to reduce this reflection loss, a surface antireflection film can be formed from transparent materials having different refractive indexes, thereby improving the conversion efficiency.

Further, studies have been made to increase the light receiving area by miniaturizing the electrodes formed on the silicon substrate and improve the conversion efficiency by taking in a large amount of sunlight (for example, see Patent Document 4).
Due to the progress of high efficiency technology as described above, conversion efficiency of about 18% has recently been achieved at the research level even in polycrystalline silicon solar cells, and the theoretical limit of conversion efficiency in polycrystalline silicon solar cells ( 20-30%).

Of the sunlight that entered from the front of the solar cell module in order to increase the light utilization efficiency, there was an attempt to reuse the sunlight that was incident on the back sheet without entering the solar cell that performs energy conversion in the solar cell module. It is done.
In a general crystalline silicon-based solar cell module, gaps are formed between a plurality of solar cells in the solar cell module in order to reduce leakage current. Therefore, there is sunlight that does not enter the solar battery cell but is incident on the back sheet, and if the sunlight can be reused, the light utilization efficiency can be improved.

  Therefore, by arranging a back sheet provided with a reflector and reflecting sunlight incident on the back sheet from the gap between the solar cells, the light utilization efficiency is improved by re-entering the solar cells. Yes. As the reflecting material, it is possible to use a reflecting material that scatters and reflects light, such as a resin material mixed with a white pigment or a metal material with a matte surface treatment. Moreover, it is possible to further improve the light utilization efficiency by making the surface of the reflecting material have an uneven structure. (For example, refer to Patent Document 5).

JP 2001-295437 A JP 62-35582 A Japanese Patent Publication No. 60-27195 JP 2000-332279 A Japanese Patent Laid-Open No. 10-284747

As described above, the conventional solar cell module has many requests to improve the conversion efficiency by increasing the light utilization efficiency, but there is also a light that becomes a loss, so the conversion efficiency should be sufficiently improved. It cannot be said that it is made. In addition, the above-described conventional method of reusing light that has been lost, for example, by reflecting light incident on a region between adjacent solar cells with a back surface material, leads to sufficient reuse of lost light. However, it is strongly desired to further improve the power generation efficiency by more reliably reusing the lost light.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solar cell module capable of more reliably reusing light that would otherwise be lost.

  In order to solve the above-mentioned problem, a solar cell module according to the invention of claim 1 includes a translucent front plate, a back sheet disposed on the back side of the front plate, the back sheet and the front plate. A solar battery module, and a solar cell module comprising a sealing material for sealing the solar battery cell between the front plate and the back sheet, wherein the back sheet is A weather-resistant layer facing the front plate via the sealing material, a light-reflective metal layer formed on the weather-resistant layer via an adhesive layer, and a concavo-convex structure on the light-reflective metal layer A light-transmitting insulating layer formed through the layer, wherein the light-reflective metal layer is formed integrally with the concavo-convex structure layer in a concavo-convex shape, and reflects light transmitted through the light-reflective metal layer A second reflective layer is formed between the weather resistant layer and the adhesive layer. .

A solar cell module according to a second aspect of the present invention is the solar cell module according to the first aspect, wherein the second reflective layer is made of a metal foil.
A solar cell module according to a third aspect of the present invention is the solar cell module according to the first or second aspect, wherein the second reflective layer is formed with a thickness of 10 μm or more and 50 μm or less.

The solar cell module according to claim 4 is the solar cell module according to any one of claims 1 to 3, wherein the uneven structure layer and the light reflective metal layer have a prism-shaped uneven structure. The apex angle of the concavo-convex structure is 120 ° ± 5 °.
The solar cell module according to claim 5 is the solar cell module according to any one of claims 1 to 4, wherein the uneven structure layer and the light-reflecting metal layer have a prism-shaped uneven structure. The pitch between the tops of the concavo-convex structure is 10 μm or more and 30 μm or less.

According to the solar cell module of the first and second aspects of the present invention, even if light incident on the back sheet from the front plate of the solar cell module passes through the light-reflecting metal layer, it is formed between the weather resistant layer and the adhesive layer. Since the light is reflected by the second reflective layer, the light that is originally lost can be more reliably reused.
According to the solar cell module of the invention of claim 3, the second reflective layer has a thickness of less than 10 μm or more than 50 μm, and bonding defects such as a decrease in reflectivity due to pinholes and wrinkles It is possible to prevent a decrease in the process yield due to.

According to the solar cell module of the fourth aspect of the invention, it is possible to prevent multiple reflections by the prism as in the case where the apex angle of the concavo-convex structure is smaller than 115 °, and the apex angle of the concavo-convex structure is greater than 125 °. As in the case, it is possible to prevent the light totally reflected by the light reflective metal layer from being totally reflected at the interface between the translucent front plate and the air.
According to the solar cell module of the fifth aspect of the present invention, when light is reflected by the concavo-convex structure, such as when the pitch between the tops of the concavo-convex structure is smaller than 10 μm, light diffraction occurs, or between the tops of the concavo-convex structures. It is possible to prevent bubbles from entering the inside of the sheet as in the case where the pitch is larger than 30 μm.

It is a longitudinal cross-sectional view which shows schematic structure of the solar cell module which concerns on one Embodiment of this invention. It is a figure which shows the longitudinal cross-section of the back surface sheet of the solar cell module shown in FIG. It is a longitudinal cross-sectional view which shows the structure of the photovoltaic cell of the solar cell module shown in FIG. It is a perspective view which shows an example of the uneven structure layer of the back surface sheet shown in FIG. It is a figure for demonstrating the effect | action of the uneven structure layer formed in the back surface sheet shown in FIG. It is a figure which shows typically the angle which the light which injected into the back surface sheet shown in FIG. 2 reflects in a light reflective metal layer. It is a figure which shows the effective utilization range of the light reflected by the light reflective metal layer shown in FIG. It is a figure for demonstrating the effect | action of the 2nd reflective layer formed in the back surface sheet shown in FIG. It is a longitudinal cross-sectional view of the back surface sheet which shows 2nd Embodiment of the solar cell module which concerns on this invention. It is a longitudinal cross-sectional view of the back surface sheet for demonstrating the 3rd-5th embodiment of the solar cell module which concerns on this invention. It is a longitudinal cross-sectional view which shows schematic structure of the solar cell back surface sheet | seat used as a comparative example.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a schematic configuration of a solar cell module according to an embodiment of the present invention. A solar cell module 1 shown in FIG. 1 generates power by receiving light from a light source L, and includes a front plate 11, a sealing material 13, solar cells 12, and a back sheet (solar cell). The back sheet 14 is laminated from the top to the bottom in the figure.

In addition, as the light source L, the artificial illumination of the sun or a room lamp is normally employ | adopted. Moreover, the solar cell module 1 shown in FIG. 1 shows a structure in which the front plate 11, the sealing material 13, the solar cells 12, and the back sheet 14 are thermally laminated with a vacuum laminator, and these are integrally molded. .
The front plate 11 is disposed on the forefront of the solar cell module 1. The front plate 11 protects the solar battery cell 12 from impact, dirt, moisture intrusion, and the like, and is made of a transparent material having a high light transmittance.

  As shown in FIG. 1, light H <b> 0 that is perpendicularly incident on the incident surface 110 of the front plate 11 out of the light emitted from the light source L is incident on the front plate 11 and then transmitted through the front plate 11 to seal the sealing material. 13 is incident. The normal line NG of the incident surface 110 is, for example, a direction parallel to the normal line N of the plane P when the front plate 11 is placed on the plane P parallel to the horizontal plane. The light H0 incident perpendicularly to the incident surface 110 indicates the light H0 incident on the front plate 11 in parallel with the normal line NG, that is, the light H0 incident on the solar cell module 1.

The front plate 11 is made of glass such as tempered glass or sapphire glass, or a resin sheet such as PC (polycarbonate) or PEN (polyethylene naphthalate). The thickness of the front plate 11 is about 3 to 5 mm for tempered glass, and about 5 mm for a resin sheet.
The light transmitted through the front plate 11 enters the sealing material 13. The sealing material 13 has a sheet shape with a thickness of about 0.4 to 1 mm, and a plurality of solar cells 12 are fixed therein. The light H0 incident on the front plate 11 passes through the sealing material 13 and becomes light H1 incident on the solar battery cell 12, and a part of the light H1 passes through the sealing material 13 and enters the back sheet 14. It becomes light H1.

  In order to transmit the light H0 incident on the front plate 11, the sealing material 13 is made of a material having a high light transmittance. Moreover, as a material of the sealing material 13, the material which has durability, such as a weather resistance, high temperature resistance, high humidity resistance, and a weather resistance, and an electrical insulation is suitable. As a material that satisfies this condition, for example, a thermoplastic synthetic resin material mainly composed of EVA (ethylene vinyl acetate copolymer), PVB (polyvinyl butyral), or the like having a vinyl acetate content of 20 to 30% by mass is given. It is done.

  The solar battery cell 12 has a function of converting light incident on the light receiving surface J into electricity by photoelectric effect. Examples of the solar battery cell 12 include a single crystal silicon type, a polycrystalline silicon type, an amorphous silicon type, and a CIGS (Cu • In • Ga • Se compound) thin film type. Here, the single crystal or polycrystalline silicon is used. Type solar cells are used. A plurality of solar cells 12 are connected by electrodes (not shown) to form a module.

  In the present embodiment, the light H <b> 1 that has entered the solar battery cell 12 from the sealing material 13 is converted into electricity by the solar battery cell 12. In addition, when the light H0 incident perpendicularly to the incident surface 110 of the front plate 11 is compared with the light incident obliquely, the light incident obliquely has a high ratio of being reflected by the incident surface 110 and is incident on the solar battery cell 12. The amount of light that contributes to power generation is small. Therefore, power generation can be performed most efficiently when the incident light H0 is incident on the incident surface 110 perpendicularly.

  In FIG. 2, the structure of the back surface sheet 14 of the solar cell module 1 is shown. The back sheet 14 of the solar cell module 1 has a function of reflecting light transmitted through the solar cell 12 itself or light H1 transmitted through the sealing material 13 without being incident on the solar cell 12, as shown in FIG. As described above, in order from the front surface side, at least the translucent insulating layer 141, the concavo-convex structure layer 142, the light reflective metal layer 143, the adhesive layer 144, the second reflective layer 145, the adhesive layer 146, and the weather resistant layer 147. Are stacked in order. The translucent insulating layer 141 is disposed on the front side of the back sheet 14 and is formed of a material having electrical insulation.

Here, one of the important performances required for the back sheet 14 is electrical insulation. This electrical insulation is an indispensable performance for preventing a short circuit or leakage during long-term use since the solar cell module 1 includes electrodes inside. Moreover, in the solar cell module 1, the electrical insulation of the surface by the side of the photovoltaic cell 12 is calculated | required especially.
FIG. 3 shows the structure of the solar battery cell 12. As shown to Fig.3 (a), the photovoltaic cell 12 has the some electrode 22c. The plurality of electrodes 22c are for taking out the electric power generated in the solar battery cell 12, and the solar battery cell 12 is usually near the center of the filling layer formed by the sealing material 13 and is light-reflective. Since it is away from the metal layer 143, current leakage due to short-circuiting of the electrode 22c does not occur.

  However, since the solar battery cell 12 is sealed with the softened sealing material 13, for example, as shown in FIG. 3B, suppose that the light-reflective metal layer 143 is disposed toward the front side. The electrode 22c of the solar battery cell 12 and the light reflective metal layer 143 may come into contact with each other. In this case, the electrode 22c is short-circuited through the light reflective metal layer 143, and the current leaks.

In order to prevent this short-circuit, as shown in FIG. 3C, the above-described short-circuit can be prevented by disposing the light-transmitting insulating layer 141 on the front surface side of the light-reflecting metal layer 143. When the thickness of the light-transmitting insulating layer 141 is insufficient, as shown in FIG. 3C, the insulating layer 141 breaks down and discharge occurs between the electrode 22c and the light reflective uneven structure layer 142. Current leakage due to d occurs.
One of the numerical standards indicating the electrical insulation is a dielectric breakdown voltage. This breakdown voltage is an index that the insulation state is broken when a voltage higher than the breakdown voltage is applied, and it can be said that a higher breakdown voltage is more electrically stable.

  For example, according to “Solar Power Generation System Components” published by the Industrial Research Council, the approximate breakdown voltage (kV) of various plastic films for electrical insulation (25 μm) is PET (polyethylene terephthalate) 6.5, PEN (Polyethylene naphthalate) 7.5, PVC (stretched hard vinyl chloride) 4.0, PC (polycarbonate) 5.0, OPP (stretched polypropylene) 6.0, PE (polyethylene) 4.0, TAC (triacetate) 0, PI (polyimide) 7.0. All of these satisfy the dielectric breakdown voltage as an insulating material (reference JISC2318 / biaxially oriented polyethylene terephthalate film for electricity). The dielectric breakdown voltage of a DuPont tedlar, which is a typical PVF (poly, fluoride, vinyl) product, is about 3.0 kV.

As one of the insulation performances of the solar cell module, in the JISC8918 / crystalline solar cell module, there is an abnormality such as dielectric breakdown even when a DC voltage of 2 times the maximum system voltage (usually 600 to 1000 V) +1000 V is applied for 1 minute. It stipulates that it will not happen.
From the above, it is desirable that the average value of the dielectric breakdown voltage is 3 kV or more, and the various materials described above satisfy this standard (reference JISC2151 / electric plastic film test method 17.2.2 flat plate electrode method). . When the dielectric breakdown voltage is smaller than 3 kV, the possibility of short circuit or leakage due to long-term use increases.

The translucent insulating layer 141 in the present embodiment is composed of a resin film made of any of the various materials described above. The material used for the light-transmitting insulating layer 141 is preferably a transparent or translucent material, and preferably has fewer elements that cause light scattering.
The light incident on the back sheet 14 is reflected by the light reflective metal layer 143 after passing through the light transmissive insulating layer 141, passes through the light transmissive insulating layer 141 again, and becomes reflected light from the back sheet 14. Therefore, if the transparency is high and there are few scattering elements, the efficiency when the light incident on the back sheet 14 becomes reflected light becomes high.

Further, the material used for the light-transmitting insulating layer 141 is not limited to the above, and any material that satisfies the reference value of the dielectric breakdown voltage can be used as appropriate. For example, it is possible to employ a synthetic resin film mainly composed of EVA, PVB or the like. The use of these resins is preferable because the adhesion with the sealing material 13 is improved.
The light-transmitting insulating layer 141 may be a single layer or a multilayer. In the case of a single layer, any of the above materials can be selected according to the required characteristics.

As a constitution method in the case of a multilayer, for example, a method of bonding a fluororesin film such as PVF to a PET film, a method of forming a fluororesin coating film such as PVF on a PET film, and EVA or PVB as a main component on a PET film And a method of attaching a synthetic resin film to be bonded.
A fluororesin such as PVF, or a synthetic resin mainly composed of EVA, PVB, or the like is preferable because it satisfies the electrical insulation standard and improves adhesion with the sealing material 13. However, to obtain sufficient strength with a single layer, it is necessary to increase the thickness, which causes a high cost. Therefore, it is preferable to have a multilayer structure in combination with a base material that ensures strength. In particular, with respect to the fluororesin, a method of forming a coating film can be adopted, and this method is preferable because the process can be simplified as compared with the method of laminating the fluororesin film.

  Moreover, it is good also as a multilayer structure which laminated | stacked one of the above-mentioned materials (for example, PET film). In order to increase the insulation, it is known that the multilayer structure covers the insulation defects and the reliability is higher than the single-sheet structure. Therefore, the insulating property can be further improved in the multilayer structure in which two layers are bonded together rather than the single PET film layer. Note that the layer structure of the light-transmitting insulating layer 141 is not limited to the above, and can be changed as appropriate according to required characteristics.

  The uneven structure layer 142 is made of an ultraviolet curable resin or a thermosetting resin. The resin that can be used for the concavo-convex structure layer 142 is not particularly limited as long as it is an ultraviolet curable resin or a thermosetting resin. For example, poly (meth) acrylic resin, polyurethane resin, fluorine resin Resin, silicone resin, polyimide resin, epoxy resin, polyethylene resin, polypropylene resin, methacrylic resin, polymethylpentene resin, cyclic polyolefin resin, acrylonitrile- (poly) styrene copolymer (AS resin) , Polystyrene resins such as acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resins, polycarbonate resins, polyester resins, polyamide resins, polyamideimide resins, polyarylphthalate resins, polysulfone resins Resin, polyphenyle Sulfide resins, polyether sulfone resins, triethylene naphthalate resins, polyether imide resins, acetal resins, and cellulose resins.

Moreover, what mixed these 1 type (s) or 2 or more types can also be used as a material of the uneven | corrugated structure layer 142, In addition to the above-mentioned resin, for example, a scattering reflector, a hardening | curing agent, a plasticizer, a dispersing agent, various Various additives such as a leveling agent, an ultraviolet absorber, an antioxidant, a viscosity modifier, a lubricant, and a light stabilizer may be appropriately blended.
The concavo-convex structure layer 142 has, for example, a concavo-convex structure 421 as shown in FIG. 4, and the concavo-convex structure 421 has a prism shape. The uneven structure layer 142 may be a single layer or a multilayer. As a method for forming such a concavo-convex structure layer 142, in the case of a single layer, there are a pressing method using a mold, a casting method, an extrusion molding method, an injection molding method, and the like. In these methods, it is possible to form the concavo-convex structure 421 simultaneously with the sheet formation.

  Further, as another method of forming the concavo-convex structure layer 142, in the case of a multilayer, an ultraviolet curable resin is applied or injected onto the concavo-convex formation surface of a flat stamper or a roll stamper, and a base material 422 is disposed thereon, For example, the mold may be released from the stamper after the curing process. These methods have the advantage of good moldability because the viscosity of the resin used can be lowered.

  As a metal mold | die used here, it can obtain by the electroforming process of the mother die obtained by the cutting process of the metal plate with a cutting tool, cutting tool cutting, and drawing or etching by an electron beam. The mold formed by such processing has an inverted structure of the concavo-convex structure 421 on the surface. For example, by cutting a metal plate with a tool having a desired shape, a mold having a reverse structure of a desired concavo-convex structure 421 is obtained. The mold may be plate-shaped or roll-shaped, but is preferably a roll-shaped mold. If it is a roll-shaped metal mold | die, continuous embossing is possible and it is suitable as a preparation method of a back surface sheet which requires a large area.

  The substrate used in the above production method is not particularly limited, and PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PVC (stretched hard vinyl chloride), PC (polycarbonate), OPP (stretched polypropylene), A film made of a resin material such as PE (polyethylene), TAC (triacetate), and PI (polyimide) can be used. In the case where the concavo-convex structure layer 142 is a multilayer, the light-transmitting insulating layer 141 can be employed as the base material 422 that supports the concavo-convex structure 421.

  The light-reflective metal layer 143 is formed such that a metal such as aluminum or silver has a layer shape following the concavo-convex structure 421 of the concavo-convex structure layer 142. The means for forming the light-reflective metal layer 143 is not particularly limited as long as the metal layer can be uniformly formed. (A) Physical vapor such as a vacuum deposition method, a sputtering method, an ion plating method, an ion cluster beam method, or the like. Chemical vapor deposition methods (chemical vapor deposition method; CVD method) such as phase growth method (physical vapor deposition method; PVD method), (b) plasma chemical vapor deposition method, thermal chemical vapor deposition method, and photochemical vapor deposition method ) Is adopted. Among these, a vacuum deposition method that can form a high-quality metal layer with high productivity is preferable. Any one of an electron beam heating method, a resistance heating method, and an induction heating method may be used as appropriate as a heating means of a vacuum evaporation apparatus using a vacuum evaporation method.

  The metal used for the light-reflective metal layer 143 is not particularly limited as long as it has a metallic luster and any of the above forming methods is possible. For example, aluminum (Al), silver (Ag), Examples thereof include metals such as gold (Au), copper (Cu), nickel (Ni), chromium (Cr), tin (Sn), zirconium (Zr), and alloys thereof, and may be formed of a single layer. Metals may be stacked and used. Among them, aluminum which is highly reflective and can form a dense metal layer relatively easily and is inexpensive is preferable.

  If the thickness of the light reflective metal layer 143 is less than 10 nm, the light incident on the light reflective metal layer 143 cannot be sufficiently reflected, whereas the thickness of the light reflective metal layer 143 is 20 nm or more. If it exists, the light which injects into the light reflective metal layer 143 can be reflected more reliably. Further, when the thickness of the light reflective metal layer 143 exceeds 200 nm, cracks that can be visually confirmed are likely to occur in the light reflective metal layer 143, whereas the thickness of the light reflective metal layer 143 is 100 nm or less. Cracks that cannot be visually confirmed are less likely to occur. Therefore, the thickness of the light reflective metal layer 143 is preferably 10 nm to 200 nm, and more preferably 20 nm to 100 nm.

The light reflective metal layer 143 is formed in a shape following the uneven structure 421 of the uneven structure layer 142, and the light reflective metal layer 143 has an uneven structure. That is, the light reflecting metal layer 143 has a function of reflecting light incident on the light reflecting metal layer 143 in a predetermined direction. In order to have such a reflection function, it is desirable that the reflection surface of the light reflective metal layer 143 is a specular reflection surface.
The second reflective layer 145 is not particularly limited as long as it is a metal foil having a metallic luster and a high reflectance. Examples of the material include aluminum (Al), silver (Ag), gold (Au), and copper. Examples thereof include metals such as (Cu) and nickel (Ni), alloys thereof, and stainless steel. Among them, an aluminum foil that has a high reflectance and is inexpensive is suitable.

  In particular, aluminum foil is known to be a material excellent in water vapor barrier properties. Therefore, the function of preventing the oxidation of the electrodes and the like in the solar cell module and the hydrolysis of the resin material can be further provided, and the oxidation of the electrodes and the like in the solar cell module in a high-temperature and high-humidity environment, the resin of the uneven structure layer It is possible to prevent material deterioration, corrosion of the light-reflective metal layer, etc., and reflect the light incident on the solar cell back sheet from the front side in a specific direction, re-enter the solar cell, and light It is possible to maintain the effect of improving the use efficiency of the product over a long period of time.

  If the thickness of the metal foil is smaller than 10 μm, many pinholes are generated in the metal foil, which makes it impossible to obtain a sufficient reflectivity, and defects such as wrinkles are liable to occur during bonding. While the process yield decreases, if the thickness of the metal foil is 20 μm or more, a sufficient reflectance can be obtained, and defects such as wrinkles are less likely to occur during bonding. In addition, when the thickness of the metal foil exceeds 50 μm, the flexibility of the metal foil is lowered, and thus defects such as bending are likely to occur. On the other hand, if the thickness of the metal foil is 40 μm or less, the bending or the like Defects are less likely to occur. Therefore, the thickness of the second reflective layer 145 is preferably 10 μm or more and 50 μm or less, and more preferably 20 μm or more and 40 μm or less.

  The second reflective layer 145 is bonded to the light reflective metal layer 143 through the adhesive layer 144. The adhesive layer 144 that bonds the light reflective metal layer 143 and the second reflective layer 145 has an adhesive strength that does not deteriorate even when used outdoors for a long period of time, does not cause delamination, and has a small degree of yellowing. Etc. are required. As a material satisfying these requirements, a laminating adhesive in which one or more of polyurethane, polyacrylic, polyester, epoxy, polyvinyl acetate, and cellulose resins are mixed may be mentioned.

Further, a deterioration inhibitor may be added in order to prevent deterioration of the adhesive due to long-term outdoor exposure, and examples of the deterioration inhibitor include additives such as carbodiimine and epoxy. In addition to deterioration inhibitors, various additives such as curing agents, plasticizers, dispersants, various leveling agents, ultraviolet absorbers, antioxidants, viscosity modifiers, lubricants, light stabilizers, and the like are appropriately blended. May be.
In addition, the method of laminating the second reflective layer 145 and the light reflective metal layer 143 includes a dry lamination method, a non-solvent dry lamination method, a hot melt lamination method, a sandwich / extrusion lamination method using an extrusion lamination method, and the like. These known methods can be used as appropriate.

  The weather resistant layer 147 is required to have long-term weather resistance such as high temperature resistance, high humidity resistance, hydrolysis resistance, and flame resistance. In order to satisfy these requirements, generally, a type of PET with improved hydrolysis resistance, such as a fluororesin film such as PVF (polyvinyl fluoride), a fluororesin coating film, or a low oligomer PET (polyethylene terephthalate) film A film or the like is used. In addition, a PEN film having excellent weather resistance may be used. The material of the weathering layer 147 is not limited to the above, and any material that satisfies the long-term weather resistance standard value can be used as appropriate.

The weather resistant layer 147 may be a single layer or a multilayer. In the case of a single layer, any of the above materials can be selected according to the required characteristics. PVF is suitable because it is particularly excellent in long-term weather resistance. In addition, a hydrolysis-resistant PET film such as a low-oligomer PET film is suitable because it is inexpensive and excellent in long-term weather resistance.
Examples of the case where the weather resistant layer 147 has a multilayer structure include a PET film bonded with a fluororesin film such as PVF (poly, fluoride, vinyl) via an adhesive layer, or a fluororesin such as PVF on the PET film. Examples include those having a coating film formed thereon.

  Fluororesin such as PVF is very excellent in long-term weather resistance, and even if it exhibits a sufficient performance even with a single layer, it is necessary to increase the thickness to obtain sufficient strength with a single layer, which is expensive. It becomes a factor. Therefore, it is preferable to have a multilayer structure in combination with a base material that ensures strength. The layer structure of the weather resistant layer 147 is not limited to the above, and can be changed as appropriate according to the required characteristics.

  The weather resistant layer 147 is bonded via the second reflective layer 145 and the adhesive layer 146. For the adhesive layer 146, it is possible to use the same adhesive, deterioration preventing agent, and various additives as the adhesive layer 144. Moreover, the method of bonding the weather resistant layer 147 and the second reflective layer 145 as the water vapor barrier layer appropriately uses various methods similar to the method of bonding the second reflective layer 145 and the light reflective metal layer 143. Can do.

  It is desirable that the uneven structure 421 has a prism shape. The pitch of the convex portions of the uneven structure 421 is desirably 30 μm or less. If the pitch is larger than 30 μm, the height of the structure increases as the pitch increases. Therefore, the second reflective layer 145 as a water vapor barrier layer is pasted via the light reflective metal layer 143 and the adhesive layer 144. At the time of matching, problems such as easy entry of bubbles are likely to occur, which is not preferable. In addition, it is necessary to increase the thickness of the adhesive layer 144, which makes it difficult to form the adhesive layer 144, and causes an increase in cost. In this respect, if the pitch is 30 μm or less, there is a low possibility that problems such as bubbles occur at the time of bonding, and this is preferable from the viewpoint of moldability and cost.

  In addition, the pitch of the convex portions of the concavo-convex structure 421 is desirably 10 μm or more. When the pitch is 10 μm or less, light can be diffracted when light is reflected by the uneven structure layer 143. Since the diffracted light is dispersed and spread, it is difficult to control and is not preferable for reflecting in a specific direction. Furthermore, it is not preferable because the time for cutting the mold is long, the tact is reduced, and the production efficiency is deteriorated. In this respect, if the pitch is 10 μm or more, the light can be accurately reflected in a specific direction, which is further preferable from the viewpoint of power generation efficiency.

  As another method for forming a metal layer having a concavo-convex structure such as the light-reflective metal layer 143, for example, a method of coating a resin film with a concavo-convex structure with a resin containing metal particles or flakes, etc. However, this method is not preferable because the effect of improving the light utilization efficiency is small because the specular reflectivity is poor.

Next, the effect | action of the uneven structure layer 144 formed in the back surface sheet 14 is demonstrated.
As shown in FIG. 5, out of the light H <b> 0 incident from the incident surface 110 of the solar cell module 1, the light H <b> 1 transmitted through the solar cell module 1 and incident on the back sheet 14 is formed on the concavo-convex structure layer 144. The light reflecting metal layer 143 is reflected. The reflected light H <b> 2 is reflected again at the interface between the front plate 11 and the atmosphere, becomes light H <b> 3 incident on the light receiving surface J of the solar battery cell 12, and is photoelectrically converted. Therefore, if the light H3 incident on the light receiving surface J of the solar battery cell 12 increases, the amount of photoelectric conversion increases, and the improvement of the light utilization efficiency can be expected.
In this regard, in the present embodiment, the light reflective metal layer 143 having a concavo-convex structure can reflect light incident from the front side in a specific direction. When the reflected light is incident again, the light H3 incident on the light receiving surface J of the solar battery cell 12 increases. Therefore, it is possible to improve the light utilization efficiency and increase the amount of power generation.

FIG. 5C shows the relationship between the apex angle θ and the reflection angle α (incident angle α) of the prism that constitutes the light-reflective metal layer 143 having an uneven structure. Here, α is a reflection angle (or incident angle) of light with respect to the normal of the prism surface. As shown in FIG. 5C, when light is incident perpendicular to the incident surface 110, the following relational expression (1) is established between the apex angle θ and the reflection angle α.
α = (180−θ) / 2 (1)
The light H2 reflected by the light reflective metal layer 143 having the concavo-convex structure is reflected at the interface between the front plate 11 and the atmosphere. At this time, the incident angle of the incident light H2 is 2α. Here, when 2α is greater than or equal to the critical angle γ, the light is totally reflected at the interface between the front plate and the atmosphere, so that the incident light H2 has very little loss and becomes reflected light H3 (see FIG. 5A).

On the other hand, when 2α is smaller than the critical angle γ, transmitted light H4 is generated in addition to the reflected light H3 (see FIG. 5B). When the transmitted light H4 is generated, the amount of the reflected light H3 decreases and the amount of the light H3 incident on the light receiving surface J of the solar battery cell 12 decreases. Therefore, the incident angle 2α of the incident light H2 is greater than or equal to the critical angle γ. It is desirable to become.
The critical angle γ is determined by the refractive index n1 of the front plate 11 and the refractive index n2 of the atmosphere, and the following relational expression (2) is established.
sinγ = n1 / n2 (2)
However, n1> n2
For example, when glass such as tempered glass is used for the front plate 11, the refractive index n1 is about 1.5 and the atmospheric refractive index n2 is about 1.0, so the critical angle γ is about 42 °. .

From the above, in order to effectively use the reflected light H2 from the light-reflecting metal layer 143 having the concavo-convex structure, 2α needs to be equal to or greater than the critical angle γ, and the critical angle γ is 42 as described above. When the angle is °, it is required that the reflection angle α at the light-reflective metal layer 143 having the concavo-convex structure is 21 ° or more, that is, the apex angle θ of the prism is 138 ° or less.
FIG. 6 is a diagram schematically illustrating an angle at which light incident on the back sheet 14 is reflected by the light reflective metal layer 143. As shown in FIG. 6A, when the apex angle θ of the prism is smaller than 120 °, multiple reflection occurs because the reflection angle is large, and the incident angle 2α at the interface between the front plate 11 and the atmosphere is Since there is a high possibility of being 42 ° or less, the reflected light H2 cannot be used effectively.

  As shown in FIG. 6B, when the apex angle θ of the prism is 120 ° or more and 138 ° or less, the incident angle 2α at the interface between the front plate 11 and the atmosphere is 42 ° or more, and the reflected light It is possible to use H2 effectively. As shown in FIG. 6C, when the apex angle θ of the prism is larger than 138 °, the incident angle 2α at the interface between the front plate 11 and the atmosphere is 42 ° or less as described above. Therefore, the reflected light H2 cannot be used effectively.

FIG. 7 is a diagram showing an effective use range of the reflected light H2 reflected by the light reflective metal layer 143 of the back sheet 14. As shown in FIG. As shown in FIG. 7, when the light incident on the back sheet 14 is reflected by the region M of the light reflective metal layer 143, the reflected light H2 is incident on the solar battery cell 12 before entering the interface between the front plate 11 and the atmosphere. Therefore, the reflected light H2 cannot be used effectively. On the other hand, in the region N, since the reflected light H2 is totally reflected at the interface between the front plate 11 and the atmosphere, the reflected light H2 can be used effectively.
The light reflected in the region farther from the solar cell 12 than the region O is totally reflected at the interface between the front plate 11 and the atmosphere, but does not enter the solar cell 12 and again enters the light reflective metal layer 143. Therefore, the reflected light H2 cannot be used effectively.

Here, the distance from the edge of the solar battery cell 12 to the edge perpendicular to the prism-shaped groove direction of the region M is Lm, and the edge orthogonal to the prism-shaped groove direction of the region O from the edge of the solar battery cell 12 When the distance to the side is Lo and the difference between the distance Lm and the distance Lo is Ln, the Lm, Ln, and Lo are determined by the apex angle θ of the prism and are expressed by the following equations (3) to (5).
Lm = La · cos φ / tan (θ−90 °) (3)
Ln = Lo−Lm (4)
Lo = Lb · cos φ / tan (θ−90 °) (5)
Where La: distance between the light-reflective metal layer forming the concavo-convex structure and the front surface of the solar cell, Lb: distance between the light-reflective metal layer forming the concavo-convex structure and the front surface of the front plate, φ : Angle formed between the edge of the solar battery cell when viewed from the front side and the groove direction of the prism shape of the concavo-convex structure layer, and θ: The apex angle of the prism shape of the concavo-convex structure layer.

  Table 1 shows that the distance La between the light reflective metal layer 143 and the front surface side of the solar battery cell 12 is 0.75 mm, the light reflective metal layer 143 having a concavo-convex structure, and the front surface side surface of the front plate 11. The distances Lb, Ln, and Lo when the distance Lb is 4.25 mm and the apex angle θ of the prism shape is 120 °, 125 °, 130 °, 135 °, and 138 ° are shown. At this time, the angle φ formed between the edge of the solar battery cell 12 when observed from the front side and the prismatic groove direction of the concavo-convex structure layer 144 is 0 °.

From Table 1, it can be seen that the distance Ln is the longest when the apex angle θ of the prism shape is 120 °, and the region N where the reflected light can be effectively used is the widest. Therefore, when the apex angle θ is 120 °, it is preferable because the light utilization efficiency can be enhanced most. At this time, since the incident angle of the incident light in the actual use environment is not limited to 0 °, the apex angle θ is set to 120 ° ± 5 ° in order to make the reflected light effective even when the incident angles are different. Is more desirable.
Note that the angle φ formed by the edge of the solar battery cell 12 when viewed from the front side and the prismatic groove direction of the concavo-convex structure layer 144 can be freely set in the range of 0 ° to 90 °. . For example, when the angle φ is set to 45 °, the range in which the reflected light can be used effectively becomes wide.

  It is also possible to provide a plurality of regions having different angles φ formed by the edges of the solar battery cell 12 when viewed from the front side and the prism-shaped groove direction of the concavo-convex structure layer 144. For example, it is possible to increase the range in which the reflected light can be effectively used by arranging the regions having the angle φ of 0 ° and the regions having the 90 ° alternately.

Next, the operation of the second reflective layer 145 formed on the back sheet 14 will be described with reference to FIG.
As shown in FIG. 8B, when the second reflective layer 145 is not formed on the back sheet 14, the light incident on the back sheet 14 is transmitted without being reflected by the light reflective metal layer 143. Ingredients are lost. On the other hand, as shown in FIG. 8A, when the second reflective layer 145 is formed, the component that is transmitted without being reflected by the light reflective metal layer 143 is reflected by the second reflective layer 145, It can be used effectively.

  The light reflective metal layer 143 is formed in a thin film shape having a thickness of 10 nm to 200 nm so as to follow the concavo-convex structure 421 of the concavo-convex structure layer 142. If the thickness of the light-reflective metal layer 143 is within this range, light can be sufficiently reflected, but it is difficult to eliminate defects such as pinholes, and transmitted light is slightly generated. Since the second reflective layer 145 uses a metal foil having a thickness of 10 μm or more and 50 μm or less, there are almost no defects such as pinholes, and almost all the light transmitted through the light reflective metal layer 143 is reflected and effectively used. can do.

Note that a method of directly forming the uneven structure 421 on the metal foil used as the second reflective layer 145 and removing the light reflective metal layer 143 is also conceivable. It is difficult to obtain a concavo-convex structure and it is not preferable because it is difficult to improve the light utilization efficiency.
As mentioned above, although one Embodiment of this invention was described in detail, unless it deviates from the technical idea of this invention, it is not limited to these, A some design change etc. are possible.

  For example, the back sheet of the solar cell module shown in FIG. 1 may have the layer configuration shown in FIG. 9 or FIG. That is, the back sheet 20 shown in FIG. 9 uses a PET film as the translucent insulating layer 141. An uneven structure layer 142 and a light-reflective metal layer 143 are laminated on the back side of the translucent insulating layer 141, and an aluminum foil is disposed as a second reflective layer 145 via an adhesive layer 144. Yes. Further, a weather resistant layer 147 made of a hydrolysis resistant PET film is disposed through an adhesive layer 146. In this case, the concavo-convex structure layer 142 has a multilayer structure, and the light-transmitting insulating layer 141 also serves as the base material 422 that supports the concavo-convex structure 421.

  In FIG. 10, the back sheet indicated by reference numeral 30 uses an EVA film as the light-transmitting insulating layer 141. An uneven structure layer 142 and a light-reflective metal layer 143 are laminated on the back side of the translucent insulating layer 141, and an aluminum foil is disposed as a second reflective layer 145 via an adhesive layer 144. Yes. Further, a weather resistant layer 147 made of a hydrolysis resistant PET film is disposed through an adhesive layer 146. In this case, the concavo-convex structure layer 142 has a multilayer structure, and a PET film is used as the base material 422 that supports the concavo-convex structure 421. In addition, the base material 422 constituting the light-transmitting insulating layer 141 and the uneven structure layer 142 is bonded through an adhesive layer 148.

  In FIG. 10, the code | symbol 40 has shown the back surface sheet using a different film for the weathering layer 147. In FIG. In this back sheet 40, an EVA film is used as the translucent insulating layer 141. An uneven structure layer 142 and a light-reflective metal layer 143 are laminated on the back side of the translucent insulating layer 141, and an aluminum foil is disposed as a second reflective layer 145 via an adhesive layer 144. Yes. Further, a weather resistant layer 147 made of a PVF film is disposed through an adhesive layer 146. In this case, the concavo-convex structure layer 142 has a multilayer structure, and a PET film is used as the base material 422 that supports the concavo-convex structure 421. In addition, the base material 422 constituting the light-transmitting insulating layer 141 and the uneven structure layer 142 is bonded through an adhesive layer 148.

  In FIG. 10, the code | symbol 50 has shown the back surface sheet | seat which uses a different film for the translucent insulating layer 141 and the weather resistant layer 147. In FIG. In the back sheet 50, a PVF film is used as the translucent insulating layer 141. An uneven structure layer 142 and a light-reflective metal layer 143 are laminated on the back side of the translucent insulating layer 141, and an aluminum foil is disposed as a second reflective layer 145 via an adhesive layer 144. Yes. Further, a weather resistant layer 147 made of a PVF film is disposed through an adhesive layer 146. In this case, the concavo-convex structure layer 142 has a multilayer structure, and a PET film is used as the base material 422 that supports the concavo-convex structure 421. In addition, the base material 422 constituting the light-transmitting insulating layer 141 and the uneven structure layer 142 is bonded through an adhesive layer 148.

Such back sheets 20, 30, 40, and 50 also include the light-reflective metal layer 143 as in the case of the back sheet 14 shown in FIG. 2, and thus can efficiently reflect light toward the front side. . Therefore, it is possible to increase the power generation amount by improving the light use efficiency of the solar cell module 1.
Further, the backsheets 14, 20, 30, 40, 50 are not limited to use in the solar cell module 1, but are desired to improve light utilization efficiency such as light utilization efficiency of light emitting elements such as LED lighting and EL elements. Can be diverted to optical elements and display members.

Next, comparative examples and examples will be described.
(Comparative Example 1)
As Comparative Example 1, the back sheet 60 shown in FIG. 11, that is, the back sheet 60 in which the translucent insulating layer 141, the concavo-convex structure layer 142, the light reflective metal layer 143, the adhesive layer 144, and the weather resistant layer 147 were laminated in this order was produced. . The back sheet 60 has a configuration in which the second reflective layer 145 and the adhesive layer 146 are omitted from the back sheet 20 shown in FIG.

  Evaluation is performed by laminating a back sheet 20, an EVA film, a solar battery cell, an EVA film, and a tempered glass in this order, and heat laminating with a vacuum laminator. This was carried out by measuring the corrosion resistance of the light reflective metal layer 143. At this time, the angle formed by the edge of the solar battery cell when observed from the front side and the prism-shaped groove direction of the concavo-convex structure layer was set to 45 °.

Example 1
As Example 1, the back sheet 20 shown in FIG. 9, that is, the translucent insulating layer 141, the concavo-convex structure layer 142, the light reflective metal layer 143, the adhesive layer 144, the second reflective layer 145, the adhesive layer 146, and the weathering layer. The back sheet 20 laminated in the order of 147 was produced.
Evaluation is based on the conversion efficiency measurement and the high-temperature and high-humidity test of Sample 2 for evaluation prepared by laminating the back sheet 20, EVA film, solar battery cell, EVA film, and tempered glass in this order, and performing thermal lamination with a vacuum laminator. The measurement was performed by measuring the corrosion resistance of the light reflective metal layer 143. At this time, the angle between the edge of the solar battery cell when observed from the front side and the prism-shaped groove direction of the concavo-convex structure layer was set to 45 °, and an aluminum foil having a thickness of 7 μm was used for the second reflective layer 145.

(Example 2)
As Example 1, the back sheet 20 shown in FIG. 9, that is, the translucent insulating layer 141, the concavo-convex structure layer 142, the light reflective metal layer 143, the adhesive layer 144, the second reflective layer 145, the adhesive layer 146, and the weathering layer. The back sheet 20 laminated in the order of 147 was produced.
Evaluation is based on the conversion efficiency measurement and the high-temperature and high-humidity test of the sample 3 for evaluation produced by laminating the back sheet 20, EVA film, solar battery cell, EVA film, and tempered glass in this order, and performing thermal lamination with a vacuum laminator. The measurement was performed by measuring the corrosion resistance of the light reflective metal layer 143. At this time, the angle formed by the edge of the solar battery cell when observed from the front side and the prism-shaped groove direction of the concavo-convex structure layer was set to 45 °, and an aluminum foil having a thickness of 20 μm was used for the second reflective layer 145.

(Example 3)
As Example 1, the back sheet 20 shown in FIG. 9, that is, the translucent insulating layer 141, the concavo-convex structure layer 142, the light reflective metal layer 143, the adhesive layer 144, the second reflective layer 145, the adhesive layer 146, and the weathering layer. The back sheet 20 laminated in the order of 147 was produced.
Evaluation is based on the conversion efficiency measurement and the high-temperature and high-humidity test of the sample 4 for evaluation produced by laminating the back sheet 20, the EVA film, the solar battery cell, the EVA film, and the tempered glass in this order and performing thermal lamination with a vacuum laminator. The measurement was performed by measuring the corrosion resistance of the light reflective metal layer 143. At this time, the angle formed by the edge of the solar battery cell when observed from the front side and the prism-shaped groove direction of the concavo-convex structure layer was set to 45 °, and a copper foil having a thickness of 20 μm was used for the second reflective layer 145.

(Measurement of conversion efficiency)
The conversion efficiencies of Comparative Example 1 and Evaluation Samples 1 to 4 of Examples 1 to 3 were measured. The measurement was performed using a solar simulator (Newport 34903A) and an IV curve tracer (ADMT 6244).
Table 2 shows the conversion efficiencies of the evaluation samples 1 to 4.

  It is confirmed that higher conversion efficiencies are obtained in the evaluation samples 2 to 4 in Examples 1 to 3 in which the second reflective layer 145 is provided than in the evaluation sample 1 in Comparative Example 1 in which the second reflective layer 145 is not provided. did. Among Examples 1 to 3, the conversion efficiency is higher in Examples 2 and 3 in which the thickness of the second reflective layer 145 is sufficient than in Example 1 in which the thickness of the second reflective layer 145 is insufficient. It was confirmed that it was obtained. Furthermore, when Example 2 in which the metal foil used for the second reflective layer 145 is an aluminum foil is compared with Example 3 using a copper foil, the aluminum foil is more copper foil if the thickness of the metal foil is the same. It was confirmed that higher conversion efficiency was obtained. From this result, it was confirmed that the use efficiency of light can be improved by providing the second reflective layer 145.

(Implementation of high temperature and high humidity test)
In the samples 1 to 4 for evaluation of Comparative Example 1 and Examples 1 to 3, a high-temperature and high-humidity test (1000 hours under an environment of 85 ° C. and 85% temperature) was performed in order to evaluate long-term weather resistance (reference JISC 8990). / Ground-mounted crystalline silicon solar cell (PV) module-10.13 high temperature and high humidity test for design qualification and type approval requirements).
(Evaluation of corrosion resistance of light reflective metal layer)
In evaluation samples 1 to 4, the conversion efficiency was measured again after the high-temperature and high-humidity test.

In the evaluation sample 1 of Comparative Example 1 in which the second reflective layer 145 was not provided, the reduction in conversion efficiency after the test was large, whereas the evaluation sample 2 in Examples 1 to 3 in which the second reflective layer 145 was provided. In -4, it was confirmed that the decrease in conversion efficiency after the test was small. Among Examples 1 to 3, the conversion efficiency is higher in Examples 2 and 3 in which the thickness of the second reflective layer 145 is sufficient than in Example 1 in which the thickness of the second reflective layer 145 is insufficient. It was confirmed that it was maintained. Furthermore, when Example 2 in which the metal foil used for the second reflective layer 145 is an aluminum foil is compared with Example 3 using a copper foil, the aluminum foil is more copper foil if the thickness of the metal foil is the same. It was confirmed that higher conversion efficiency was maintained.
From this result, it is possible to prevent a decrease in conversion efficiency due to the high temperature and high humidity test by providing the second reflective layer 145. That is, it was confirmed that corrosion of the light reflective metal layer 143 can be prevented.

  DESCRIPTION OF SYMBOLS 1 ... Solar cell module, 11 ... Translucent front board, 12 ... Solar cell, 13 ... Sealing material, 14, 20, 30, 40, 50 ... Back sheet, 22c ... Electrode, 110 ... Incident surface, 141 ... Translucent insulating layer, 142 ... uneven structure layer, 143 ... light reflective metal layer, 144 ... adhesive layer, 145 ... second reflective layer, 146 ... adhesive layer, 147 ... weather resistant layer, 421 ... uneven structure, 422 ... base Wood.

Claims (5)

A front plate having translucency, a back sheet disposed on the back side of the front plate, a solar cell disposed between the back sheet and the front plate, and the solar cell as the front plate And a solar cell module comprising a sealing material for sealing between the back sheet and the back sheet,
The back sheet includes a weather resistant layer facing the front plate via the sealing material, a light reflective metal layer formed on the weather resistant layer via an adhesive layer, and the light reflective metal layer. A light-transmitting insulating layer formed on the concavo-convex structure layer, the light-reflective metal layer formed integrally with the concavo-convex structure layer in a concavo-convex shape, and transmitted through the light-reflective metal layer A solar cell module, wherein a second reflective layer that reflects light is formed between the weather-resistant layer and the adhesive layer.   The solar cell module according to claim 1, wherein the second reflective layer is made of a metal foil.   The solar cell module according to claim 1, wherein the second reflective layer is formed with a thickness of 10 μm or more and 50 μm or less.   The concavo-convex structure layer and the light-reflecting metal layer have a prism-shaped concavo-convex structure, and an apex angle of the concavo-convex structure is 120 ° ± 5 °. The solar cell module according to.   5. The concavo-convex structure layer and the light-reflective metal layer have a prism-shaped concavo-convex structure, and the pitch between the tops of the concavo-convex structure is 10 μm or more and 30 μm or less. The solar cell module according to item.

Images