JP2013115216A - Solar cell backside sheet and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reuse such light, that becomes loss essentially, more reliably in a solar cell backside sheet or a solar cell module.SOLUTION: The solar cell module includes a sealing material internally sealing a solar cell, a translucent front plate laminated on the sealing material and entering light thereinto, and a backside sheet 14 laminated on the reverse side of the translucent front plate so as to sandwich the sealing material. The backside sheet 14 consists of a laminate having, sequentially from the sealing material side, at least a translucent insulating layer 141, an uneven structure layer 142 having an uneven structure 142b of fine uneven shape, a light reflective metal layer 143 formed along the uneven structure, and a weather-resistant layer 147, in this order. The mean transmittance of the translucent insulating layer 141 at a wavelength of 400-1200 nm is 90-100%.

Description

  The present invention relates to a solar cell back sheet and 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 of solar cell power generation systems and power supplies for artificial satellites has been promoted in various fields (see, for example, Patent Document 1).

This solar cell converts incident light energy into electric energy, and the main one of the solar cells is classified into crystalline silicon type, amorphous silicon type, organic compound type, etc., depending on the type of material used. Among these, most of those currently on the market are crystalline silicon solar cells, which are further classified into single crystal type and polycrystalline type.
The single-crystal silicon solar cell has the advantage that it is easy to increase the efficiency because the quality of the substrate is good, but has the disadvantage that the manufacturing cost of the substrate is high. On the other hand, although the polycrystalline silicon solar cell has the disadvantage that it is difficult to increase the efficiency because the quality of the substrate is inferior, it has the advantage that it can be manufactured at a low cost, and is currently the mainstream.

Various studies have been conducted on the improvement of the efficiency of such polycrystalline silicon solar cells.
As an example, a texture structure is formed on the surface of a silicon substrate used in a solar cell, thereby reducing the reflection of sunlight on the surface of the silicon substrate and improving the conversion efficiency.

  In single crystal silicon, 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, a method of forming fine protrusions on the surface of the polycrystalline silicon substrate by the reactive ion etching method has been proposed as a method of forming a texture on the polycrystalline silicon substrate. (For example, see 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 region of 400 nm to 1100 nm, there is 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 the high efficiency technology as described above, conversion efficiency of about 18% has been achieved at the research level recently even in polycrystalline silicon solar cells, and the theoretical limit of conversion efficiency in polycrystalline silicon solar cells (20 ~ 30%).

Therefore, among the sunlight incident from the front of the solar cell module in order to increase the light utilization efficiency, the sunlight incident on the back sheet without being incident on the solar cell that performs energy conversion in the solar cell module is reused. Attempts have been made.
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 is incident on the back sheet without entering the solar battery cell, 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-mentioned 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.

  In view of the above circumstances, an object of the present invention is to provide a solar cell back sheet and a solar cell module that can more reliably reuse light that would originally be lost.

In order to solve the above problems, the present invention proposes the following means.
That is, the solar cell module according to the present invention includes a sealing material in which solar cells are sealed, a translucent front plate that is laminated on the sealing material and allows light to enter the sealing material, A solar cell module having a solar cell back sheet laminated on the opposite side to the translucent front plate across a sealing material, wherein the solar cell back sheet is at least in order from the sealing material side, The translucent insulating layer, a concavo-convex structure layer having a fine concavo-convex structure, a light-reflective metal layer formed along the concavo-convex structure, and a laminate having a weather resistance layer in this order, and the translucency The average transmittance of the insulating layer at 400 nm to 1200 nm is 90% or more and 100% or less.

  According to the solar cell module having such a feature, since the average transmittance of 400 to 1200 nm of the light-transmitting insulating layer is 90% or more, the loss of light passing through the light-transmitting insulating layer is small and more reliably. Light can be reused.

  The solar cell module according to the present invention is characterized in that a refractive index of the concavo-convex structure layer is larger than a refractive index of the sealing material and smaller than a refractive index of the translucent insulating layer.

  According to the solar cell module having such a feature, the effect of reusing light can be further enhanced.

  In the solar cell module according to the present invention, the sum of the thickness of the uneven structure layer and the thickness of the translucent insulating layer is 10 minutes of the sum of the thickness of the sealing material and the thickness of the translucent front plate. 1 or less.

  According to the solar cell module having such a feature, the effect of reusing light can be further enhanced.

  The solar cell module according to the present invention is characterized in that a barrier layer that suppresses corrosion of the light reflective metal layer is further provided on the adhesive layer side of the light reflective metal layer.

  According to the solar cell module having such a feature, the effect of reusing light can be maintained for a long time.

  The solar cell module according to the present invention is characterized in that the barrier layer is a metal foil.

  According to the solar cell module having such a feature, the effect of reusing light can be maintained for a long time.

  The solar cell module according to the present invention is characterized in that the barrier layer has a thickness of 7 μm or more and 50 μm or less.

When the thickness of the barrier layer is smaller than 7 μm, the pinholes are increased, so that a sufficient water vapor barrier property cannot be obtained. Further, defects such as wrinkles are likely to occur at the time of bonding, and the process yield tends to decrease.
When the thickness of the barrier layer exceeds 50 μm, the flexibility is lowered, so that defects such as breakage are likely to occur, and the process yield tends to be lowered. If it is 50 micrometers or less, since sufficient flexibility is maintained, defects, such as a bend, do not arise easily.

  The solar cell module according to the present invention is characterized in that a thickness of the light reflective metal layer is 30 nm or more and 100 nm or less.

  If the thickness of the light reflective metal layer is smaller than 30 nm, the light incident on the light reflective metal layer cannot be sufficiently reflected. If the thickness is 40 nm or more, the light incident on the light-reflecting metal layer can be more reliably reflected. On the other hand, when the thickness of the light reflective metal layer exceeds 100 nm, cracks that can be visually confirmed are likely to occur in the light reflective metal layer. In addition, if it is 90 nm or less, since it becomes difficult to generate | occur | produce the crack which cannot be confirmed visually, it is more preferable.

  The solar cell module according to the present invention is characterized in that the concavo-convex shape of the concavo-convex structure layer is a triangular prism having an apex angle of 120 ° ± 5 °.

  The solar cell module according to the present invention is characterized in that the pitch of the tops of the triangular prism-shaped irregularities is 10 μm or more and 30 μm or less.

If the top pitch is larger than 30 μm, the height of the structure increases as the pitch increases, so that problems such as easy entry of air bubbles are likely to occur when pasting together through a weather-resistant layer and an adhesive layer. It is not preferable. In addition, it is necessary to increase the thickness of the adhesive layer, which makes it difficult to form and causes a high cost.
When the pitch is smaller than 10 μm, light can be diffracted when the light is reflected by the uneven structure layer. In this case, the diffracted light becomes light that is spread by spectroscopy, and thus is difficult to control, and is not preferable for reflection in a specific direction. Furthermore, it is not preferable because the time for cutting the mold becomes long, the production tact is extended, and the production efficiency is deteriorated.

  According to the solar cell module having such a feature, the light reflecting metal layer along the concavo-convex shape of the triangular prism-shaped concavo-convex structure layer directs light incident on the solar cell back sheet from the sealing material side in a specific direction. It is possible to improve the light utilization efficiency by making the light reflected and re-enter the solar battery cell, and the average reflectance of the light-transmitting insulating layer at 400 to 1200 nm is 90% or more, thereby ensuring more certainty. Light utilization efficiency can be improved.

  The solar cell backsheet according to the present invention is a solar cell backsheet that covers one surface of a sealing material in which solar cells are sealed, and has a translucent insulating layer and a fine concavo-convex structure. It consists of a laminated body having a concavo-convex structure layer, a light-reflective metal layer formed along the concavo-convex structure, and a weather resistant layer in this order, and the average transmittance at 400 nm to 1200 nm of the translucent insulating layer is 90% or more It is characterized by being 100% or less.

  According to the solar cell back sheet having such characteristics, it is a solar cell back sheet that can be suitably used in the solar cell module according to the present invention.

  According to the solar cell back sheet and the solar cell module according to the present invention, the light reflecting metal layer having the concavo-convex structure along the concavo-convex shape of the concavo-convex structure layer reflects light incident on the solar cell back sheet from the sealing material side. Thus, it is possible to re-enter the solar cell and improve the light use efficiency, and the light-transmitting insulating layer has an average reflectance of 400 to 1200 nm of 90% or more, so that the light can be more reliably obtained. It is possible to improve the use efficiency of the.

It is a longitudinal cross-sectional view which shows schematic structure of the solar cell module of embodiment of this invention. It is a longitudinal cross-sectional view which shows schematic structure of the solar cell back surface sheet of embodiment of this invention. It is a longitudinal cross-sectional view which shows schematic structure containing the electrode of the solar cell module of embodiment of this invention. It is a perspective view which shows an example of the uneven structure of the solar cell back surface sheet of embodiment of this invention. It is a longitudinal cross-sectional view of the solar cell module of the comparative example which does not have a translucent insulating layer. It is a schematic explanatory drawing explaining an effect | action of the solar cell back surface sheet in the solar cell module of embodiment of this invention. It is a typical optical path diagram explaining the effect | action by the difference in the vertex angle of an uneven structure. It is the top view of the solar cell module of embodiment of this invention, and its AA sectional drawing. It is a typical optical path diagram explaining the effect | action by the difference in the refractive index of a sealing material and an uneven structure layer. It is a longitudinal cross-sectional view which shows schematic structure of the solar cell back surface sheet of the 1st structural example of embodiment of this invention. It is a longitudinal cross-sectional view which shows schematic structure of the solar cell back surface sheet of the 2nd, 3rd, 4th structural example of embodiment of this invention. 6 is a longitudinal sectional view showing a schematic configuration of a solar cell back sheet of Comparative Example 2. FIG.

Hereinafter, embodiments of a solar cell back sheet and a solar cell module of the present invention will be described in detail with reference to the accompanying 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. FIG. 2 is a longitudinal sectional view showing a schematic configuration of the solar cell backsheet according to the embodiment of the present invention. FIG. 3 is a longitudinal sectional view showing a schematic configuration including electrodes of the solar cell module according to the embodiment of the present invention. FIG. 4 is a perspective view showing an example of the concavo-convex structure of the solar cell backsheet according to the embodiment of the present invention.

As shown in FIG. 1, the solar cell module 1 of the present embodiment includes a front plate 11 (translucent front plate), a sealing material 13, solar cells 12 sealed with the sealing material 13, It is a device that includes a back sheet 14 (solar cell back sheet) and generates power by receiving light from a light source L arranged on the outside of the solar cell module 1 corresponding to the front plate 11.
As the light source L, for example, the sun, artificial lighting of an indoor lamp, or the like can be employed.
The front plate 11, the sealing material 13 sealing the solar battery cells 12, and the back sheet 14 are laminated in this order. The solar cell module 1 of this embodiment is integrated by thermally laminating the laminated body by these with a vacuum laminator.

The front plate 11 is a plate-like member or a sheet-like member that is disposed on the forefront of the solar cell module 1 and protects the solar cells 12 from impact, dirt, moisture intrusion, and the like. Further, the front plate 11 is made of a transparent material having a high transmittance so that the light from the light source L enters inside.
Examples of suitable materials for the front plate 11 include glass such as tempered glass and sapphire glass, or resin sheets such as PC (polycarbonate) and PEN (polyethylene naphthalate).
The thickness of the front plate 11 is preferably about 3 to 5 mm for tempered glass and about 5 mm for a resin sheet, for example.

The sealing material 13 is a sheet-like member that separates the front plate 11 and the back sheet 14 from each other by a predetermined distance, seals the solar battery cell 12 inside, and fixes the position of the solar battery cell 12.
The thickness of the sealing material 13 (the separation distance between the front plate 11 and the back sheet 14) is preferably about 0.4 mm to 1 mm.
As a material of the sealing material 13, the transmittance with respect to the wavelength light emitted from the light source L is high, it has electrical insulation, and is excellent in durability such as weather resistance, high temperature resistance, high humidity resistance, and weather resistance. Material is preferred. As a suitable material satisfying such conditions, for example, a thermoplastic synthesis mainly composed of EVA (ethylene vinyl acetate copolymer) or PVB (polyvinyl butyral) having a vinyl acetate content of 20 to 30%. A resin material can be mentioned.

The solar battery cell 12 is a member having a function of converting light incident on the light receiving surface J into electricity by photoelectric effect. As the type of the solar battery cell 12, a crystalline silicon cell such as a single crystal silicon type or a polycrystalline silicon type can be adopted.
In this embodiment, the solar cell 12 employs a single crystal or polycrystalline silicon type as an example.
A plurality of the solar cells 12 are arranged with the light receiving surface J facing the front plate 11 and spaced in the direction along the front plate 11. Each solar cell 12 is connected by an electrode 22c (see FIG. 3, not shown in FIG. 1) described later to form a module.

The back sheet 14 is a multi-layered sheet-like member having a function of reflecting light transmitted through the solar battery cell 12 itself or light transmitted through the sealing material 13 without being incident on the solar battery cell 12.
In the present embodiment, as shown in FIG. 2, the layer structure of the back sheet 14 is a translucent insulating layer 141, an uneven structure layer 142, a light reflective metal layer 143, an adhesive layer 144, and a barrier layer 145. And an adhesive layer 146 and a weather resistant layer 147, which are laminated in this order.

The translucent insulating layer 141 is a layered portion constituting one surface of the back sheet 14. In the solar cell module 1, the translucent insulating layer 141 is arranged in parallel with the front plate 11, and the front plate 11 It is laminated in close contact with the opposite side.
The light-transmitting insulating layer 141 is made of a material having electrical insulation and an average transmittance of 90% to 100% in a wavelength range of 400 nm to 1200 nm.
By having an average transmittance in such a range, it is possible to reduce a light amount loss during transmission through the light-transmitting insulating layer 141.
In addition, the light-transmitting insulating layer 141 is preferably a film with few impurities that serve as light scattering elements, for example, scattering particles.

  One important performance 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 therein. Further, the back sheet 14 is particularly required to have electrical insulation on the surface on the solar cell 12 side. In the present embodiment, this electrical insulation is ensured by the translucent insulating layer 141.

One of numerical standards indicating electrical insulation is a 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.
As one of the insulation performances of the solar cell module, it is determined that there is no abnormality such as dielectric breakdown even when a DC voltage of 2 times the maximum system voltage +1000 V is applied for 1 minute (“JISC8918 / crystalline solar cell Module "). The maximum system voltage is usually 600-1000V. For example, considering the case where the maximum system voltage is 1000 V, it is required that there is no abnormality such as dielectric breakdown even when a DC voltage of twice the maximum system voltage +1000 V, that is, 3000 V (3 kV) is applied for 1 minute.
For this reason, it is preferable that the average value of the dielectric breakdown voltage of the material used for the translucent insulating layer 141 is 3 kV or more.
For example, according to “Solar Power Generation System Components” (Electrical and Electronic Materials Study Group, Industrial Research Committee, 2008), the approximate value of the dielectric breakdown voltage of various plastic films for electrical insulation (25 μm) is PET (polyethylene Terephthalate) is 6.5 kV, PEN is 7.5 kV, PVC (stretched hard vinyl chloride) is 4.0 kV, PC is 5.0 kV, OPP (stretched polypropylene) is 6.0 kV, PE (polyethylene) is 4.0 kV, TAC (Triacetate) is 3.0 kV and PI (polyimide) is 7.0 kV. Therefore, all of these materials satisfy the preferable dielectric breakdown voltage of the light-transmitting insulating layer 141 as an insulating material (for PET, see “JISC2318 / Biaxially oriented polyethylene terephthalate film for electrical use”. For the method of measuring the dielectric breakdown voltage, refer to “JIS C2151 / Electric Plastic Film Test Method 17.2.2 Plate Electrode Method”).
Moreover, it is known that the dielectric breakdown voltage of Tedlar (registered trademark) of DuPont, which is a representative product of PVF (polyvinyl fluoride), is about 3.0 kV, and PVF also satisfies a preferable dielectric breakdown voltage. Material.
Accordingly, any of the materials listed above is a preferable material for the light-transmitting insulating layer 141.

  However, the material that can be used for the translucent insulating layer 141 is not limited to the above, and any appropriate material can be adopted as long as it can achieve the reference value of the insulating performance of the solar cell module 1. is there. For example, it is also possible to employ a synthetic resin film mainly composed of EVA (ethylene / vinyl acetate copolymer), PVB (polyvinyl butyral), or the like. The use of these resins is preferable because the adhesion with the sealing material 13 is improved.

Further, 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 configuration method in the case of a multilayer, an appropriate configuration can be adopted according to required characteristics. For example, a method of bonding a fluororesin film such as PVF on a PET film, a fluororesin coating film such as PVF on a PET film And a method of bonding a synthetic resin film mainly composed of EVA, PVB or the like to a PET film.
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, in order 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 compared to the method of laminating the fluororesin film.

  The light-transmitting insulating layer 141 may have a multilayer structure in which two layers of any of the above-described materials, for example, a PET film are bonded together. In order to increase the insulation, it is known that the multilayer structure covers the insulation defects and has higher reliability than the single-sheet structure. Therefore, the insulating property can be further improved in the multilayer structure in which two layers are bonded to each other than the single layer of PET film.

The thickness of the light-transmitting insulating layer 141 is preferably 25 μm or more and 300 μm or less. Within this range, 50 μm or more, or 250 μm or less, or 50 μm or more and 250 μm or less is a more preferable range.
Although depending on the dielectric breakdown voltage of the material, if the thickness of the light-transmitting insulating layer 141 is less than 25 μm, sufficient insulation may not be obtained. If the thickness is 50 μm or more, it is possible to ensure insulation more reliably.
When the thickness of the translucent insulating layer exceeds 300 μm, it may be difficult to make the average transmittance 90% or more. If it is 250 micrometers or less, since it is easier to make average transmittance 90% or more, it is more preferable.

As shown in FIG. 3, the translucent insulating layer 141 is disposed in a positional relationship so as to cover the sealing material 13 and the electrode 22 c electrically connected to the solar battery cell 12 from the side opposite to the front plate 11. ing.
The electrode 22c shown in FIG. 3 forms a module by connecting a plurality of solar cells 12 in series. The electrode portion on the front plate 11 side of the solar cells 12 and the others adjacent to the solar cells 12 The front plate 11 of the solar battery cell 12 and the electrode portion on the opposite side are electrically connected.
For this reason, a part of electrode 22c exists in the position closer to the translucent insulating layer 141 than the photovoltaic cell 12. FIG.

  Therefore, when the thickness of the light-transmitting insulating layer 141 is too thin, dielectric breakdown occurs even if the dielectric breakdown voltage of the material is high, and a current is generated between the electrode 22c and a light-reflecting metal layer 143, which will be described later. However, it is possible to prevent the leakage by setting the thickness of the light-transmitting insulating layer 141 within the above-described preferable range.

The material of the concavo-convex structure layer 142 is not particularly limited as long as it has translucency and can form the shape of the concavo-convex structure 142b described later. For example, an ultraviolet curable resin, a thermosetting resin, a thermoplastic resin, or the like can be used.
However, the material of the concavo-convex structure layer 142 is preferably a material whose refractive index is larger than the refractive index of the sealing material 13 and smaller than the refractive index of the light-transmitting insulating layer 141. The reason why it is preferable to set the refractive index within such a range will be described later together with the explanation of the optical path in the back sheet 14.
The kind of ultraviolet curable resin or thermosetting resin used for the concavo-convex structure layer 142 is not particularly limited. For example, poly (meth) acrylic resin, polyurethane resin, fluorine resin, silicone resin, polyimide resin , Epoxy resin, polyethylene resin, polypropylene resin, methacrylic resin, polymethylpentene resin, cyclic polyolefin resin, acrylonitrile- (poly) styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin) and other polystyrene resins, polyvinyl chloride resins, polycarbonate resins, polyester resins, polyamide resins, polyamideimide resins, polyarylphthalate resins, polysulfone resins, polyphenylene sulfide resins, polyethers Rusuruhon resins, triethylene naphthalate resins, polyether imide resins, acetal resins, cellulose resins and the like, may be used by mixing these resins singly or in combination.

  In addition to the above resins, various additions such as scattering reflectors, curing agents, plasticizers, dispersants, various leveling agents, ultraviolet absorbers, antioxidants, viscosity modifiers, lubricants, light stabilizers, etc. An agent may be appropriately blended.

Examples of the thermoplastic resin include resin materials such as PET, PEN, PVC, PC, OPP, PE, PI, and PMMA (polymethyl methacrylate resin).
As another resin material, TAC is also suitable.

The shape of the concavo-convex structure layer 142 is such that the surface 142 a in contact with the light-transmitting insulating layer 141 is a plane along the light-transmitting insulating layer 141, and the uneven structure 142 b ( An uneven shape is formed.
The uneven structure layer 142 may be a single layer or a multilayer.

In the present embodiment, the concavo-convex structure 142b has a triangular prism-like unit configuration in which a cross section of an isosceles triangle having an apex angle θ extends in one direction, as schematically shown in FIG. The ridgeline Q has a concavo-convex shape that is adjacent to each other in a direction orthogonal to the extending direction so as to align with the plane. That is, the concavo-convex structure 142b is a repetition of a unit configuration adjacent to a mountain shape in which two strip-shaped flat surfaces form a constant apex angle θ. The pitch at which the tops are arranged is a constant value P.
With this configuration, in this embodiment, the opening angle of the valley portion of the concavo-convex structure 142b in the direction orthogonal to the extending direction of the unit configuration of the concavo-convex structure 142b is equal to the apex angle θ. The valley bottom line V of the valley is parallel to the ridge line Q.
The apex angle θ of the concavo-convex structure 142b is preferably 120 ° ± 5 °.
In the present embodiment, the plane in which the ridge line Q and the valley line V of the concavo-convex structure 142b are aligned is a plane parallel to the surface of the translucent insulating layer 141 in a state assembled to the back sheet 14.

Moreover, it is preferable that the pitch P of the top part of the uneven structure 142b is 10 micrometers or more and 30 micrometers or less.
If the pitch P is smaller than 10 μm, light may be diffracted when the light is reflected by the light reflective metal layer 143 along the concavo-convex structure 142b. This diffracted light is spectrally spread and becomes difficult to control, and is not preferable for reflection in a specific direction. Furthermore, it takes a long time to cut the mold for manufacturing the concavo-convex structure 142b, which extends the manufacturing tact and decreases the production efficiency.
On the other hand, if the pitch P is 10 μm or more, since diffraction does not occur, light can be accurately reflected in a specific direction, which is preferable from the viewpoint of power generation efficiency.
If the pitch P is larger than 30 μm, the height difference of the concavo-convex structure 142b becomes large. Therefore, when the barrier layer 145 is bonded to the light reflective metal layer 143 through the adhesive layer 144 by the bonding method described later, bubbles enter. This is not preferable because problems such as easy occurrence are likely to occur. In addition, it becomes difficult to form the adhesive layer 144. In addition, since it is necessary to increase the thickness of the adhesive layer 144, the cost increases.
On the other hand, if the pitch P is 30 μm or less, there is a low possibility that problems such as bubbles will occur at the time of bonding, and this is preferable from the viewpoint of moldability and cost.

  Examples of the method for forming the single-layered uneven structure layer 142 include a pressing method using a mold, a casting method, an extrusion molding method, and an injection molding method. In these methods, the concavo-convex structure 142b can be formed simultaneously with the formation of the concavo-convex structure layer 142 into a sheet shape.

Further, as a method for forming the multilayer concavo-convex structure layer 142, a flat stamper having a concavo-convex formation surface corresponding to the inverted structure of the concavo-convex structure 142b or a roll stamper mold is used, and the concavo-convex formation surface is UV-cured. There is a method in which a mold resin is applied or injected, a base material is disposed thereon, and the mold is released from the stamper after the curing treatment.
In addition, such a method has an advantage that the moldability is good because the viscosity of the resin used for forming the concavo-convex structure 142b can be lowered.

According to such a method, the light-transmissive insulating layer 141 is constituted by a sheet-like member, and the uneven structure layer 142 laminated on the light-transmissive insulating layer 141 is formed by using the sheet-like member as a base material. be able to.
In addition, when a sheet-like member including one layer or two or more layers different from the light-transmitting insulating layer 141 is used as the base material, the multilayer uneven structure layer 142 can be formed.
The material of the base material used here is not particularly limited, and for example, a film made of a resin material such as PET, PEN, PVC, PC, OPP, PE, TAC, PI, PMMA can be used.

The mold used to form the concavo-convex structure layer 142 can be obtained by cutting a metal plate with a cutting tool, electroforming of a mother die obtained by cutting with a cutting tool, drawing with an electron beam, or etching. The mold formed by such processing has an inverted structure of the concavo-convex structure 142b on the surface.
The inverted structure of the concavo-convex structure 142b can be formed, for example, by cutting a metal plate with a cutting tool having a cross-sectional shape orthogonal to the extending direction of the concavo-convex structure 142b to be formed.
The mold may be plate-shaped or roll-shaped, but it is preferable to use a roll-shaped mold. If it is a roll-shaped metal mold | die, a continuous embossing is possible and it is especially suitable when a large area is required.

The light-reflecting metal layer 143 is formed on the concavo-convex structure 142b so as to follow the concavo-convex structure 142b, and reflects light incident through the concavo-convex structure layer 142 to the concavo-convex structure layer 142 side. Is a metal-containing layer.
The metal used for the light reflective metal layer 143 is not particularly limited as long as it has a metallic luster and can form a reflective surface. For example, a simple substance or an alloy such as aluminum (Al), silver (Ag), gold (Au), copper (Cu), nickel (Ni), chromium (Cr), tin (Sn), zirconium (Zr), and the like can be given. .
The light reflective metal layer 143 may be formed as a single layer, or a plurality of metals and alloys may be laminated. Among these, aluminum is particularly preferable because it has high reflectivity, can form a dense metal layer relatively easily, and is inexpensive.

The thickness of the light reflective metal layer 143 is preferably 30 nm or more and 100 nm or less. Within this range, 40 nm or more, or 90 nm or less, or 40 nm or more and 90 nm or less is a more preferable range.
If the thickness of the light reflective metal layer 143 is smaller than 30 nm, the light incident on the light reflective metal layer 143 cannot be sufficiently reflected. If the thickness is 40 nm or more, the light incident on the light-reflective metal layer 143 can be more reliably reflected.
When the thickness of the light reflective metal layer 143 exceeds 100 nm, cracks that can be visually confirmed are likely to occur in the light reflective metal layer 143. The thickness of 90 nm or less is more preferable because cracks that cannot be visually confirmed are less likely to occur.

Since the light reflective metal layer 143 having such a configuration has a triangular reflection surface in a cross section following the concavo-convex structure 142b, when light transmitted through the concavo-convex structure layer 142 is incident, the light is incident on the incident direction. It has a function of reflecting in a specific direction according to. In order to efficiently reflect the reflected light in a specific direction, it is desirable that the reflection surface by the light reflective metal layer 143 is a specular reflection surface.
In order to form the light-reflective metal layer 143 on the specular reflection surface, the triangular prism-shaped flat surface of the concavo-convex structure 142b is formed into a smooth flat surface having surface accuracy corresponding to the mirror surface, and the light-reflective metal layer 143 is formed. What is necessary is just to form the metal or alloy to comprise in the dense layer film closely_contact | adhered to the uneven structure 142b.

The means for forming the light reflective metal layer 143 is not particularly limited as long as the metal layer can be uniformly formed. For example, (a) physical vapor deposition method (PVD method) such as vacuum deposition method, sputtering method, ion plating method, ion cluster beam method, (b) plasma chemical vapor deposition method, thermochemistry A chemical vapor deposition method (Chemical Vapor Deposition method; CVD method) such as a vapor deposition method or a photochemical vapor deposition method can be employed.
Among these, a vacuum deposition method that can form a high-quality metal layer with high productivity is particularly 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.
According to these forming means, fine particles of metal or alloy can be densely laminated, so that it is easy to form a specular reflection surface.

The adhesive layer 144 is a layered portion for attaching a barrier layer 145 described later to the light reflective metal layer 143.
Since the solar cell module 1 is often used outdoors for a long period of time, the adhesive layer 144 has an adhesive strength that does not deteriorate due to long-term outdoor use and does not cause delamination, and the degree of yellowing is small. Required.
In order to satisfy these requirements, as the adhesive layer 144, a laminating adhesive in which one or more of polyurethane, polyacrylic, polyester, epoxy, polyvinyl acetate, and cellulose resins are mixed is used. can do.

In addition, a deterioration preventing agent may be added to the adhesive layer 144 in order to prevent deterioration of the adhesive due to long-term outdoor exposure. Examples of the deterioration preventing agent include additives such as carbodiimine and epoxy.
Furthermore, for example, various additives such as a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, a lubricant, and a light stabilizer may be appropriately blended. Good.

The barrier layer 145 is provided to suppress the entry of substances that cause deterioration of the inside of the solar cell module 1, for example, water vapor and oxygen from the outside, and prevent corrosion and deterioration of each part inside the solar cell module 1. In this embodiment, the protective layer is made of a metal foil.
In this embodiment, the barrier layer 145 is bonded to the light reflective metal layer 143 through the adhesive layer 144.
As the bonding method, for example, known methods such as a dry lamination method, a non-solvent dry lamination method, a hot melt lamination method, and a sandwich / extrusion lamination method using an extrusion lamination method can be appropriately used.

The type of the metal foil is not particularly limited as long as it is a material that can block a substance that causes corrosion of the light reflective metal layer 143 such as water vapor.
Examples of the material that can be used for the barrier layer 145 include simple metals or alloys such as Al, Ag, Au, Cu, and Ni, or stainless steel.
These metal foils are known to be materials having excellent water vapor barrier properties. Therefore, it is possible to suppress or prevent oxidation of the electrodes 22c and the like inside the solar cell module 1 in a high temperature and high humidity environment, deterioration of the resin material of the uneven structure layer 142, corrosion of the light reflective metal layer 143, and the like.
In particular, since the corrosion of the light-reflective metal layer 143 and the deterioration of the concavo-convex structure layer 142 can be suppressed or prevented, the reflection function by the action of the concavo-convex structure layer 142 and the light-reflective metal layer 143, which will be described later, and the light use efficiency The improvement effect can be sustained over a long period of time.
Among the above metal foils, aluminum is particularly suitable because it has a high water vapor barrier property and is inexpensive.

The thickness of the barrier layer 145 is preferably 7 μm or more and 50 μm. Within this range, 20 μm or more, or 40 μm or less, or 20 μm or more and 40 μm or less is a more preferable range.
If the thickness of the barrier layer 145 is less than 7 μm, pinholes may increase and sufficient water vapor barrier properties may not be obtained. Further, when the metal foil is bonded to the adhesive layer 144, defects such as wrinkles are likely to occur, and the process yield may be reduced. If the thickness is 20 μm or more, the pinhole is almost zero, so that a sufficient water vapor barrier property can be obtained, and defects such as wrinkles at the time of bonding hardly occur.
When the thickness of the barrier layer 145 exceeds 50 μm, the flexibility is lowered, so that defects such as breakage are likely to occur, and the process yield is lowered. If it is 40 micrometers or less, since sufficient flexibility is maintained, defects, such as a bend, will not arise more easily.

The adhesive layer 146 is a layered portion for bonding a weather resistant layer 147 described later to the barrier layer 145.
For the adhesive layer 146, the same adhesive, deterioration preventing agent, and various additives as those of the adhesive layer 144 can be used.

The weather resistant layer 147 is a layered portion constituting the surface of the back sheet 14 opposite to the translucent insulating layer 141. In the present embodiment, when the solar cell module 1 is assembled, the outermost surface on the opposite side of the front plate 11 of the solar cell module 1 is configured.
The weather resistant layer 147 is composed of a sheet-like member that satisfies the long-term weather resistance such as high temperature resistance, high humidity resistance, hydrolysis resistance, and flame resistance required in the usage environment of the solar cell module 1. And is attached to the barrier layer 145.
As a bonding method, various methods similar to the method of bonding the barrier layer 145 and the light reflective metal layer 143 can be appropriately used.

As a material of the weather resistant layer 147, any material that satisfies the long-term weather resistance target value can be adopted as appropriate.
Examples of sheet-like members that satisfy long-term weather resistance requirements include a fluororesin film such as PVF, a fluororesin coating film, or a PET film of a type with improved hydrolysis resistance such as a low oligomer PET film. it can. A PEN film having excellent weather resistance is also suitable.

Further, 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 film obtained by bonding a fluororesin film such as PVF to the PET film via an adhesive layer, a film obtained by forming a fluororesin coating film such as PVF on the PET film, and the like. Can be mentioned.
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.

Next, the effect | action of the back surface sheet 14 and the solar cell module 1 of this embodiment is demonstrated.
FIGS. 5A and 5B are longitudinal sectional views of comparative solar cell modules having no light-transmitting insulating layer. 6A, 6B, 6C, and 6D are schematic explanatory views for explaining the operation of the solar cell back sheet in the solar cell module according to the embodiment of the present invention. FIGS. 7A, 7B, and 7C are schematic optical path diagrams for explaining the effect of the difference in apex angle of the concavo-convex structure. It is a longitudinal cross-sectional view explaining the effect | action of the solar cell back surface sheet in the solar cell module of embodiment of this invention. Fig.8 (a) is a typical top view of the solar cell module of embodiment of invention. FIG.8 (b) is AA sectional drawing in Fig.8 (a). FIGS. 9A, 9B, and 9C are schematic optical path diagrams for explaining the effect of the difference in refractive index between the sealing material and the concavo-convex structure layer.

First, the operation of the light-transmitting insulating layer 141 will be described with reference to comparative examples shown in FIGS.
As shown in FIG. 3, in the solar cell module 1, the sealing material 13 is covered with the translucent insulating layer 141 excellent in electrical insulation. For this reason, since the electrical distance between the conductive light-reflecting metal layer 143 and the solar battery cells 12 and the electrodes 22c is increased, discharge leakage is prevented.
Further, by appropriately setting the dielectric breakdown voltage of the light-transmitting insulating layer 141, dielectric breakdown can be prevented.

On the other hand, the solar cell modules 1A and 1B of the comparative example shown in FIGS. 5A and 5B are both translucent insulating layer 141 and concavo-convex structure layer 142 from solar cell module 1 of the present embodiment. The light reflective metal layer 143 is in contact with the sealing material 13.
In such a configuration, in order to prevent a discharge leak between the electrode 22c and the light reflective metal layer 143, the sealing material 13 allows sufficient electrical contact between the electrode 22c and the light reflective metal layer 143. It is necessary to keep a distance.
For this reason, as shown in the solar cell module 1A, it is necessary to provide a wide space between the electrode 22c and the light-reflective metal layer 143. Therefore, the thickness of the solar cell module 1A is increased, and the size of the solar cell module 1A is increased. End up.
Further, since the solar battery cell 12 also needs to be separated from the light reflective metal layer 143 in the same manner as the electrode 22c, a light transmission region by the sealing material 13 is provided between the back surface of the solar battery cell 12 and the light reflective metal layer 143. Is formed. For this reason, since the reflected light of the light-reflective metal layer 143 is likely to go around the back surface of the solar battery cell 12, the light use efficiency is deteriorated as compared with the solar battery module 1.

On the other hand, when the distance between the light-reflective metal layer 143 and the electrode 22c is short as in the solar cell module 1B, a discharge leak tends to occur between them, and the durability of the solar cell module 1 is reduced.
Moreover, since the sealing material 13 is softened when the temperature rises, the electrode 22c or the solar battery cell 12 and the light-reflecting metal layer 143 may come into contact when receiving an external force such as vibration. In this case, the electrode 22c is short-circuited through the light reflective metal layer 143.

Next, the optical path of incident light in the solar cell module 1 will be described, and the operation of the back sheet 14 will be described.
As shown in FIG. 1, among the light emitted from the light source L, the light H <b> 0 perpendicularly incident on the incident surface 110 that is the outermost surface of the front plate 11 is incident on the front plate 11 and then transmitted through the front plate 11. And enters the sealing material 13. Note that the normal line NG of the incident surface 110 is, for example, a direction parallel to the normal line NS of the plane S when the front plate 11 is placed on the plane S parallel to the horizontal plane.
The light incident obliquely on the incident surface 110 is reflected at the incident surface 110 more than the vertically incident light H0, and the amount of light incident on the solar battery cell 12 is reduced, so that light that can be used for power generation is obtained. Less. Therefore, power generation can be performed most efficiently when the light H0 is incident on the incident surface 110 perpendicularly.

Light H <b> 1 emitted from the front plate 11 enters the sealing material 13. The light H <b> 1 vertically enters the light receiving surface J of the solar battery cell 12 arranged in parallel with the incident surface 110 of the front plate 11 on the solar battery cell 12. This light H1 is converted into electricity by the solar battery cell 12 and used for power generation.
On the other hand, the light H <b> 1 incident on the gap between the solar cells 12 is incident on the back sheet 14.
As shown in FIG. 6C, the back sheet 14 is formed by laminating a translucent insulating layer 141, a concavo-convex structure layer 142, and a light reflective metal layer 143 from the sealing material 13 side. After passing through the light-transmitting insulating layer 141 and the concavo-convex structure layer 142, the light is incident obliquely on the light-reflective metal layer 143, and a specific oblique direction corresponding to the inclination direction of the light-reflective metal layer 143 with respect to the incident direction Is reflected as reflected light H2. For this reason, the reflected light H2 travels in an oblique direction toward the front plate 11 in the sealing material 13.
At least a part of the reflected light H2 is reflected on the back surface by the incident surface 110 of the front plate 11, and travels in the sealing material 13 toward the back sheet 14 as reflected light H3. For example, the reflected light H3 reflected at the portion of the front plate 11 facing the solar battery cell 12 or in the vicinity thereof enters the light receiving surface J of the solar battery cell 12 as shown in FIG. Used for power generation.
As a result, the light H1 incident on the gap between the adjacent solar cells 12 contributes to power generation by the solar cells 12 without causing a light loss, and therefore, compared with the case where the back sheet 14 is not provided. Utilization efficiency is improved.

The light use efficiency of power generation by the solar cell module 1 can be improved as the light loss in the back sheet 14 is smaller.
In the present embodiment, the average transmittance at 400 nm to 1200 nm of the light-transmitting insulating layer 141 is 90% or more and 100% or less, so that the light amount loss and reflection when the light H1 enters the light-transmitting insulating layer 141 are reflected. The light amount loss when the light H2 is emitted from the translucent insulating layer 141 is less than 10%, respectively, and the light amount loss can be suppressed.
Further, if the light-reflecting metal layer 143 is formed on the specular reflection surface, scattering at the time of reflection is suppressed, and the reflected light H2 can be more easily directed in a specific reflection direction, thereby further improving the light utilization efficiency. Can do.

When the back sheet 14 has the above-described preferable configuration, the light utilization efficiency of power generation can be further improved.
First, the action of the apex angle θ of the concavo-convex structure 142b will be described.
In this embodiment, the refractive indexes of the materials of the front plate 11, the sealing material 13, the translucent insulating layer 141, and the concavo-convex structure layer 142 are not necessarily the same. In the description, it is assumed that the refractive indexes are the same. A person skilled in the art can easily understand the detailed optical path when the refractive index is different from the following description.
In particular, when describing the action based on the difference in the refractive index, it will be described without permission.

As shown in FIG. 6D, when the light H1 reaches the concavo-convex structure 142b, it enters the back surface of the concavo-convex structure 142b at an incident angle α. Since the light reflective metal layer 143 is in close contact with the surface side of the concavo-convex structure 142b, it is reflected at the emission angle α of the light H1. That is, the reflected light H2 is reflected in a direction that forms an angle 2α with respect to the incident direction of the light H1.
When the respective units are expressed in degrees between the apex angle θ and the emission angle α, the following equation (1) is established.

α = (180−θ) / 2 (1)

Here, considering the relationship between the reflected light H2 and the reflection surface by the adjacent uneven structure 142b, the adjacent reflection surface is inclined by θ / 2 with respect to the incident direction.
In order to prevent the reflected light H2 from entering the adjacent reflecting surface and changing the reflection direction, it is necessary to satisfy the following equation (2).

2α ≦ θ / 2 (2)

  By solving the above equations (1) and (2), it can be seen that the condition for preventing the reflected light H2 from being reflected on the adjacent reflecting surface is θ ≧ 120 (°).

When the reflected light H2 reaches the front plate 11 as shown in FIG. 6C, it is an interface between the front plate 11 and the atmosphere of the external environment where the solar cell module 1 is installed, for example, the atmosphere. The back surface is reflected by the incident surface 110 to form reflected light H3. At this time, the incident angle of the reflected light H2 with respect to the incident surface 110 is 2α.
Here, as shown in FIG. 6A, when 2α is equal to or larger than the critical angle γ on the back surface of the incident surface 110, the reflected light H2 is totally reflected by the incident surface 110, so that the reflected light H2 has very little loss and is reflected light. H3.
On the other hand, as shown in FIG. 6B, when 2α is smaller than the critical angle γ, transmitted light H4 that passes through the incident surface 110 to the outside is generated in addition to the reflected light H3. When the transmitted light H4 is generated, the amount of the reflected light H3 is reduced, and the amount of the reflected light H3 incident on the light receiving surface J of the solar battery cell 12 is reduced. Therefore, the incident angle 2α of the reflected light H2 is greater than or equal to the critical angle γ. It is desirable that
The critical angle γ is determined by the refractive index n1 of the front plate 11 and the refractive index n2 of the atmosphere in the external environment (where n1> n2), and is expressed by the following equation (3).

sinγ = n1 / n2 (3)

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 refractive index n2 is about 1.0 when the atmosphere of the external environment is air. Is about 42 °.
From the above, in order to effectively use the reflected light H2 from the light-reflective metal layer 143, 2α needs to be equal to or greater than the critical angle γ, and when the critical angle γ is 42 ° as described above, The reflection angle α at the light-reflecting metal layer 143 that forms the structure is preferably 21 ° or more, that is, the apex angle θ of the concavo-convex structure 142b is preferably 138 ° or less.

As shown in FIG. 7A, when the apex angle θ is smaller than 120 °, the reflection angle of the reflected light H2 is increased and reflected in a direction with a shallower angle than the inclination of the adjacent reflecting surface. Therefore, the reflected light H2 is reflected by the adjacent reflecting surface, and multiple reflection occurs. As a result, the reflected light H2 travels as the re-reflected light H2 ′ along the same optical path as when the reflection angle of the reflected light H2 is reduced.
As a result, since the incident angle 2α at the incident surface 110 is likely to be 42 ° or less, the re-reflected light H2 ′ is transmitted through the incident surface 110 to the outside as the transmitted light H4, resulting in a light amount loss. . Depending on the magnitude of the apex angle θ, the re-reflected light H2 ′ is reflected to some extent at the incident surface 110 and returns to the sealing material 13, but the re-reflected light H2 ′ is a multiple-reflected light and is therefore more than the reflected light H2. The amount of light will surely decrease.
Therefore, in any case, the reflected light H2 cannot be used effectively.

On the other hand, as shown in FIG. 7B, when the apex angle θ is 120 ° or more and 138 ° or less, the incident angle 2α at the incident surface 110 is 42 ° or more, and the reflected light H2 is effective. It is possible to use it.
Further, as shown in FIG. 7C, when the apex angle θ is larger than 138 °, the incident angle 2α at the incident surface 110 is 42 ° or less as described above, so that light is effectively used. I can't do it.

Next, the relationship between the positional relationship between the reflected light H2 and the solar battery cell 12 and the light utilization efficiency will be described.
For example, as shown in FIG. 8A, a region M having a width Lm and a region N having a width Ln from the side close to the solar cell 12 are considered as rectangular regions adjacent to the end side 12a of the solar cell 12. .
In the region M, as shown in FIG. 8B, the reflected light M2, m2 from the back sheet 14 hits the solar battery cell 12 before entering the incident surface 110, resulting in a loss of light amount, and the reflected light M2, This is an area where m2 cannot be used effectively.
In the region N, as shown in FIG. 8B, all of the reflected light N2 and n2 from the back sheet 14 reaches the incident surface 110, and is reflected to the sealing material 13 side as reflected light N3 and n3. In this case, the reflected light N2 and n2 can be effectively used in order to reach the light receiving surface J of the solar battery cell 12.
In the region O where the distance from the end of the solar battery cell 12 exceeds (Lm + Ln), the reflected light reflected by the incident surface 110 is incident again on the back sheet 14 before reaching the solar battery cell 12 and is reflected again. It is an area to be done. After re-reflection, it may or may not reach the light receiving surface J, but even if it reaches, the light is attenuated because it is reflected by the back sheet 14 a plurality of times. Therefore, it is an area where the reflected light cannot be used effectively.

  The distances Lm, Ln, and Lo are determined by the apex angle θ and the like, and are obtained from the following expressions (4), (5), and (6).

Lm = La · cos φ / tan (θ−90) (4)
Ln = Lo−Lm (5)
Lo = Lb · cos φ / tan (θ−90) (6)

Here, La is the distance between the light receiving surface J and the reflecting surface formed by the light reflecting metal layer 143, Lb is the distance between the incident surface 110 and the reflecting surface formed by the light reflecting metal layer 143, φ (°) is an angle formed between the edge 12a of the solar battery cell 12 and the ridgeline Q (see FIG. 8A) of the top of the concavo-convex structure layer 142 when viewed from the direction of the light H0.
In addition, the distance with respect to the reflective surface formed with the light reflective metal layer 143 shall be measured from the virtual plane which passes along the center of the unevenness | corrugation of the uneven structure 142b.

A specific example of the sizes of the areas M and N will be described. As conditions for the solar cell module 1 of the specific example, La = 0.75 (mm), Lb = 4.25 (mm), and φ = 0 (°).
Table 1 below shows calculation results of the distances Lm, Ln, and Lo when the apex angle θ is 120 °, 125 °, 130 °, 135 °, and 138 ° under this condition.
Here, it is assumed that the refractive indexes of the concavo-convex structure layer 142, the translucent insulating layer 141, the sealing material 13, and the front plate 11 are all the same. For this reason, each thickness is not related to the following description of the optical path.

According to Table 1, while the apex angle θ changes from 120 ° to 138 °, the distance Lm decreases from 1.30 mm to 0.68 mm, and the distance Ln decreases from 12.10 mm to 6.30 mm. I understand that It can be seen that the distance Ln is the longest when the apex angle θ is 120 °. That is, it can be seen that the area N where the reflected light can be used effectively is the widest. It can also be seen that the distance Ln is the shortest when the apex angle θ is 138 °.
For this reason, when the apex angle θ is 120 °, the light utilization efficiency can be enhanced most, which is preferable.

However, the incident light in the actual use environment is not limited to an incident angle of 0 ° with respect to the front plate 11 depending on, for example, the installation state of the solar cell module 1. Even when the apex angle θ is smaller than 120 °, the efficiency is slightly inferior, but the reflection at the incident surface 110 is not lost. Therefore, the apex angle θ may be smaller than 120 ° as long as it is close to 120 °.
Therefore, if the incident angle varies in the vicinity of 0 °, the apex angle θ is preferably set as appropriate within a range of 120 ° ± 5 °.
In addition, when it is known in advance that the incident angle is a specific angle other than 0 °, the optimal vertex angle θ may be set by performing the same calculation as described above at the specific angle in that case. Is possible.

Next, the preferable refractive index action of the concavo-convex structure layer 142, the translucent insulating layer 141, and the sealing material 13 will be described based on the optical paths when the refractive indexes are different. In this description, the refractive indexes of the concavo-convex structure layer 142, the translucent insulating layer 141, and the sealing material 13 are n ₁₄₂ , n ₁₄₁ , and n ₁₃ , respectively. For simplicity, it is assumed that the refractive index of the front plate 11 is equal to the refractive index n ₁₃ of the sealing material 13.
In addition, as shown in FIGS. 9A, 9B, and 9C, the refraction angle (the light traveling through the translucent insulating layer 141 when entering the translucent insulating layer 141 from the concavo-convex structure layer 142). The angle is represented by β1, and the refraction angle (the angle of light traveling through the sealing material 13) when entering the sealing material 13 from the translucent insulating layer 141 is represented by β2. The refraction angles β1 and β1 are defined as angles from the normal line of each interface, but in the solar cell module 1, both of these coincide with the incident direction of the light H1.

In the solar cell module 1, the refractive index n ₁₄₂ of the concavo-convex structure layer 142 is preferably smaller than the refractive index n ₁₄₁ of the translucent insulating layer 141 and larger than the refractive index n ₁₃ of the sealing material 13.
When the refractive index n ₁₄₂ is larger than the refractive index n ₁₄₁ , a critical angle exists, and thus the light reflected by the light reflective metal layer 143 and the light-transmitting structure layer 142 at a larger angle than the critical angle. When it enters the interface with the insulating layer 141, it returns to the inside of the concavo-convex structure layer 142 by total reflection, and the reflected light cannot be used effectively.
The critical angle is the smallest incident angle at which total reflection occurs when light is incident on a small material from a material having a large refractive index. Conversely, when the refractive index n ₁₄₂ is smaller than the refractive index n ₁₄₁ , Is preferable because there is no critical angle, that is, total reflection cannot occur, and the light reflected by the light reflective metal layer 143 can be used effectively.

When the refractive index n ₁₄₂ is smaller than the refractive index n ₁₃ , the refraction angle β2 when entering the sealing material 13 from the translucent insulating layer 141 is larger than the angle 2α of light traveling through the concavo-convex structure layer 142. Therefore, the effect of effectively using the light reflected by the light reflective metal layer 143 is reduced, that is, the region N in which the reflected light can be effectively used is narrowed.
When the refractive index n ₁₄₂ is larger than the refractive index n ₁₃ , the refraction angle β2 is larger than the angle 2α, so that the effect of effectively using the light reflected by the light reflective metal layer 143 is increased. Since the area | region N which can utilize reflected light effectively becomes wide, it is preferable.

  The above operation will be described based on a specific example. The conditions of the specific example were set to La = 0.75 (mm), Lb = 4.25 (mm), and φ = 0 (°) similarly to the calculation in Table 1. The apex angle and refractive index conditions were θ = 120 (°) and 2α = 60 (°).

FIG. 9A shows a schematic optical path diagram in the case of n ₁₄₂ = n ₁₃ = 1.48 and n ₁₄₁ = 1.6.
In this case, the light H0 incident on the light reflective metal layer 143 is reflected by the light reflective metal layer 143 as light h1 in the direction of 2α = 60 (°). It enters the layer 141 at an incident angle of 60 °. Since the refractive index of the light-transmitting insulating layer 141 is n ₁₄₁ = 1.6, the light h1 is refracted at the interface and travels through the light-transmitting insulating layer 141 as light h2. At this time, since the refraction angle β1 is 53.2 °, the light h2 enters the sealing material 13 at an angle of 53.2 °. Since the refractive index of the sealing material 13 is n ₁₃ = 1.48, the light h2 is refracted at the interface and travels through the sealing material 13 as light h3. At this time, the refraction angle β2 is 60 ° and enters the front plate 11 at an angle of 60 °. Since the refractive index of the front plate 11 is 1.48, the light h3 travels straight and enters the back side of the incident surface 110 at an angle of 60 °. Thereby, the light h3 is totally reflected at the point r1, and the reflected light H3 is formed.

FIG. 9B shows a schematic optical path diagram in the case of n ₁₄₂ = 1.45, n ₁₃ = 1.48, and n ₁₄₁ = 1.6. That is, an example in which the refractive index of the uneven structure layer 142 is smaller than the refractive index of the sealing material 13 is shown.
In this case, the light h1 reflected by the light-reflective metal layer 143 is incident on the light-transmitting insulating layer 141 at an incident angle of 60 ° as in the case of FIG. 9A.
The light h1 is refracted at the interface and travels through the light-transmitting insulating layer 141 as light h2. At this time, in this example, since refraction from the concavo-convex structure layer 142 of n ₁₄₂ = 1.45 to the light-transmitting insulating layer 141 of n ₁₄₁ = 1.6, the refraction angle β1 is 51.7 °. . For this reason, the light h2 enters the sealing material 13 at an angle of 51.7 °. Since the refractive index of the sealing material 13 is n ₁₃ = 1.48, the light h2 is refracted at the interface and travels through the sealing material 13 as light h3. At this time, the refraction angle β2 is 58 ° and is incident on the front plate 11 at an angle of 58 °. Since the refractive index of the front plate 11 is 1.48, the light h3 travels straight and enters the back side of the incident surface 110 at an angle of 58 °. Thereby, the light h3 is totally reflected at the point r2, and the reflected light H3 is formed.
However, since the angle of the light incident on the incident surface 110 is smaller than when the refractive index of the concavo-convex structure layer 142 is 1.48, the position of the reflected point r2 as compared with the case of FIG. Is close to the incident position of the light H1. Further, coupled with the decrease in the reflection angle of the reflected light H3, the distance that the reflected light H3 reaches becomes shorter.

FIG. 9C shows a schematic optical path diagram in the case of n ₁₄₂ = 1.51, n ₁₃ = 1.48, and n ₁₄₁ = 1.6. That is, an example in which the refractive index of the uneven structure layer 142 is larger than the refractive index of the sealing material 13 is shown.
In this case, the light h1 reflected by the light-reflective metal layer 143 is incident on the light-transmitting insulating layer 141 at an incident angle of 60 ° as in the case of FIG. 9A.
The light h1 is refracted at the interface and travels through the light-transmitting insulating layer 141 as light h2. At this time, in this example, refraction from the concavo-convex structure layer 142 with n ₁₄₂ = 1.51 to the light-transmitting insulating layer 141 with n ₁₄₁ = 1.6 is performed, so the refraction angle β1 is 54.8 °. For this reason, the light h2 is incident on the sealing material 13 at an angle of 54.8 °. Since the refractive index of the sealing material 13 is n ₁₃ = 1.48, the light h2 is refracted at the interface and travels through the sealing material 13 as light h3. At this time, the refraction angle β2 is 62.1 °, and the light enters the front plate 11 at an angle of 62.1 °. Since the refractive index of the front plate 11 is 1.48, the light h3 travels straight and enters the back side of the incident surface 110 at an angle of 62.1 °. Thereby, the light h3 is totally reflected at the point r3, and the reflected light H3 is formed.
However, since the angle of the light incident on the incident surface 110 is larger than when the refractive index of the concavo-convex structure layer 142 is 1.48, the position of the reflected point r3 as compared with the case of FIG. Becomes far from the incident position of the light H1. Furthermore, coupled with an increase in the reflection angle of the reflected light H3, the distance that the reflected light H3 reaches becomes longer.

Table 2 below shows distances Lm, Ln, and Lo when the refractive index of the uneven structure layer 142 is changed. Here, conditions other than the value of the refractive index n ₁₄₂ are the same as in the above specific example. The thickness of the concavo-convex structure layer 142 is 0.05 mm, the thickness of the translucent insulating layer 141 is 0.2 mm, the thickness of the sealing material 13 is 1 mm, and the thickness of the front plate 11 is 3 mm.
The refractive index n ₁₄₂ is set to 1.45, 1.48, 1.51, 1.54, 1.57, and 1.6 including the example described above.

According to Table 2 above, while n ₁₄₂ changes from 1.45 to 1.6, the distance Lm increases from 1.2 mm to 2.0 mm, and the distance Ln increases from 11.2 mm to 18.6 mm. It can be seen that it has increased.
From this, it can be seen that the greater the refractive index of the concavo-convex structure layer 142, the longer the distance Ln, that is, the wider the region N in which the reflected light can be used effectively.

In addition, said Formula (4), (5), (6) assumes that the refractive index of concavo-convex structure layer 142, translucent insulating layer 141, sealing material 13, and front plate 11 is all the same. . Therefore, in the calculation of Table 2 having different refractive indexes, the distances Lm, Ln, and Lo are calculated by performing the following correction in consideration of the difference in refractive index.
For example, if the refractive index _{n 142} of the concavo-convex structure layer 142 is 1.51, the angle of light incident on the incident surface 110 is 62.1 °. This corresponds to the apex angle θ being 117.9 ° when the refractive indexes of all the layers are the same. Therefore, the distances Lm, Ln, and Lo when the apex angle θ was 117.9 ° were calculated. When all the refractive indexes are the same, if the apex angle θ is 117.9 °, multiple reflections are actually made. However, here, only correction is assumed for calculation. An apex angle of 62.1 ° corresponding to a different refractive index is not a condition for multiple reflection because the optical path differs depending on the refractive index.
However, strictly speaking, since the refractive indexes of the concavo-convex structure layer 142 and the translucent insulating layer 141 are different, there is a slight error from the actual distances Lm, Ln, and Lo. However, if the sum of the thicknesses of the concavo-convex structure layer 142 and the translucent insulating layer 141 is 1/10 or less of the sum of the thicknesses of the sealing material 13 and the front plate 11, the error is negligibly small. . Therefore, it is preferable that the sum of the thicknesses of the concavo-convex structure layer 142 and the translucent insulating layer 141 is 1/10 or less of the sum of the thicknesses of the sealing material 13 and the front plate 11 because the calculation becomes easy. .

In addition, the refractive index used for the calculation of the above specific example is demonstrated.
As the refractive index of the sealing material 13, 1.48 which is the refractive index of EVA which is most commonly used is adopted. The refractive index of EVA is generally said to be about 1.48.
As the refractive index of the translucent insulating layer 141, 1.6, which is the refractive index of the most commonly used PET film, was adopted. The refractive index of the PET film is said to be about 1.57 to 1.63, although it varies depending on the stretching direction.
As the refractive index of the front plate 11, 1.48, which is the same as the refractive index of the sealing material 13, was adopted for the sake of simplicity of explanation. The most commonly used front plate 11 is tempered glass, and the refractive index is said to be about 1.5. However, in the effect of the present invention, the refractive index of the front plate is 1. Since there is no significant difference between the case of 48 and the case of 1.5, the same effect can be obtained even when tempered glass is used in actual use.
Such a refractive index of each layer is an example, and is not limited to the above, and can be appropriately changed according to required characteristics.

  As described above, according to the back sheet 14 and the solar cell module 1 of the present embodiment, the light-reflecting metal layer 143 having the concavo-convex structure 142b along the concavo-convex shape of the concavo-convex structure layer 142 causes the sealing material 13 side. It is possible to reflect the light incident on the back sheet 14 of the solar battery and re-enter the solar battery cell 12 to improve the light utilization efficiency. The average reflection of the light-transmitting insulating layer 141 at 400 to 1200 nm is possible. When the rate is 90% or more, the light use efficiency can be improved more reliably.

[First configuration example]
Next, the back surface sheet of the first configuration example of the present embodiment will be described.
FIG. 10: is a longitudinal cross-sectional view which shows schematic structure of the solar cell back surface sheet of the 1st structural example of embodiment of this invention.

As shown in FIG. 10, the back sheet 20 of this configuration example is similar to the back sheet 14 of the above-described embodiment, the light-transmitting insulating layer 141, the concavo-convex structure layer 142, the light-reflective metal layer 143, the adhesive layer 144, A barrier layer 145, an adhesive layer 146, and a weather resistant layer 147 are provided in this order, and can be used in the solar cell module 1 of the above embodiment as shown in FIG.
However, this configuration example is an example in which the uneven structure layer 142 is formed of a single layer.

In the back sheet 20, a PET film is used as the translucent insulating layer 141.
The concavo-convex structure layer 142 is formed by molding an ultraviolet curable resin whose main component is an acrylate compound. For this reason, in this structural example, the translucent insulating layer 141 also serves as a base material that supports the uneven structure layer 142 when the uneven structure layer 142 is formed.
The barrier layer 145 uses an aluminum foil.
The weathering layer 147 uses a PET film having hydrolysis resistance.

[Second configuration example]
Next, the back surface sheet of the second configuration example of the present embodiment will be described.
FIG. 11: is a longitudinal cross-sectional view which shows schematic structure of the solar cell back surface sheet of the 2nd, 3rd, 4th structural example of embodiment of this invention.

As shown in FIG. 11, the back sheet 30 of this configuration example is similar to the back sheet 14 of the above embodiment, the light-transmitting insulating layer 141, the uneven structure layer 142, the light reflective metal layer 143, the adhesive layer 144, A barrier layer 145, an adhesive layer 146, and a weather resistant layer 147 are provided in this order, and can be used in the solar cell module 1 of the above embodiment as shown in FIG.
However, this configuration example is an example in which the uneven structure layer 142 is composed of multiple layers.
In the back sheet 30, an EVA film is used as the translucent insulating layer 141.
The concavo-convex structure layer 142 of this configuration example includes two layers of a base material 422 having the surface 142a of the concavo-convex structure layer 142 and a concavo-convex structure portion 421 having the concavo-convex structure 142b. Here, the base material 421 is a base material that supports the uneven structure portion 421 when the uneven structure portion 421 is formed.
The base material 422 is made of a PET film, and the concavo-convex structure portion 421 is made of an ultraviolet curable resin containing an acrylate compound as a main component.
In addition, the uneven structure layer 142 of this configuration example is bonded to the light-transmitting insulating layer 141 through an adhesive layer 148 made of an adhesive mainly composed of a urethane compound on the surface 142a side, a barrier layer 145, and weather resistance The layer 147 is made of the same material as in the first configuration example.

[Third configuration example]
Next, the back surface sheet of the third configuration example of the present embodiment will be described.
As shown in FIG. 11, the back sheet 40 of this configuration example has a layer configuration similar to that of the second configuration example, and the material of the weathering layer 147 is replaced with a PVF film.

[Fourth configuration example]
Next, the back surface sheet of the fourth configuration example of this embodiment will be described.
As shown in FIG. 11, the back sheet 50 of this configuration example is obtained by replacing the material of the light-transmitting insulating layer 141 and the weathering layer 147 with a PVF film in the second configuration example.

  Since the back sheet 20, 30, 40, 50 of the first to fourth configuration examples includes the light reflective metal layer 143 similarly to the back sheet 14 of the embodiment, the light is efficiently emitted toward the front side. Can be reflected. Therefore, it is possible to increase the power generation amount by improving the light use efficiency of the solar cell module 1.

  In the above description, the example in which the barrier layer 145 and the weathering layer 147 are arranged via the adhesive layer 146 has been described. However, the barrier layer 145 and the weathering layer 147 are joined via the adhesive layer 146. However, the adhesive layer 146 may be deleted and the weather resistant layer 147 may be directly laminated on the barrier layer 145.

In the above description, the example is described in which the angle φ formed by the edge 12a of the solar battery cell 12 when viewed from the direction of the light H0 and the ridge line Q at the top of the uneven structure layer 142 is 0 °. The angle φ is not limited to 0 °, and can be freely set to an appropriate angle from 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.

  In the above description, the example in which the angle φ is constant in the entire region has been described, but it is also possible to provide a plurality of regions having different angles φ. 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.

  In the above description, the back sheets 14, 20, 30, 40, and 50 are not limited to use in the solar cell module 1, but light such as improvement in light use efficiency of light emitting elements such as LED lighting and EL elements. It can be diverted to an optical element or display member for which utilization efficiency is desired to be improved.

  As mentioned above, although embodiment in 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, it is possible to change the combination of all the constituent elements described above, or to delete some constituent elements.

  Next, examples of the solar cell back sheet and solar cell module of the embodiment of the present invention will be described together with comparative examples.

[Example 1]
As Example 1, the back sheet 20 shown in FIG. 10, that is, the translucent insulating layer 141, the concavo-convex structure layer 142, the light reflective metal layer 143, the adhesive layer 144, the barrier layer 145, the adhesive layer 146, and the weather resistant layer 147. The back sheet 20 laminated in this order was produced.
For the light-transmitting insulating layer 141 of this example, a PET film (Toyobo Cosmo Shine (registered trademark) A4300) (thickness: 250 μm) with an average transmittance of 400 to 1200 nm of 91% was used. Further, an ultraviolet curable resin having a refractive index of 1.55 was used for the uneven structure layer 142.
The angle φ was set to φ = 45 (°).

[Example 2]
As Example 2, the back sheet 20 shown in FIG.
For the light-transmitting insulating layer 141 of this example, a PET film (Toyobo Cosmo Shine (registered trademark) A4300) (thickness: 250 μm) with an average transmittance of 400 to 1200 nm of 91% was used. The uneven structure layer 142 was made of an ultraviolet curable resin having a refractive index of 1.46. As the sealing material 13, an EVA film having a refractive index of 1.48 was used.
The angle φ was set to φ = 45 (°).

[Example 3]
As Example 3, the back sheet 20 shown in FIG.
For the light-transmitting insulating layer 141 of this example, a PET film (Toyobo Cosmo Shine (registered trademark) A4300) (thickness: 250 μm) with an average transmittance of 400 to 1200 nm of 91% was used. Further, an ultraviolet curable resin having a refractive index of 1.67 was used for the uneven structure layer 142. As the sealing material 13, an EVA film having a refractive index of 1.48 was used.
The angle φ was set to φ = 45 (°).

[Comparative Example 1]
The back sheet (not shown) of Comparative Example 1 is made of a white PET film (Toray Lumirror (registered trademark) E20) (thickness: 250 μm) used for a conventional solar cell back sheet.

[Comparative Example 2]
As Comparative Example 2, the back sheet 20 shown in FIG. 10, that is, the translucent insulating layer 141, the concavo-convex structure layer 142, the light reflective metal layer 143, the adhesive layer 144, the barrier layer 145, the adhesive layer 146, and the weather resistant layer 147. The back sheet 20 laminated in this order was produced.
A PET film (Toray Lumirror (registered trademark) S10) (thickness: 250 μm) having an average transmittance of 400% to 1200 nm of 82% was used for the light-transmitting insulating layer 141 of this comparative example. Further, an ultraviolet curable resin having a refractive index of 1.55 was used for the uneven structure layer 142.
The angle φ was set to φ = 45 (°).

[Comparative Example 3]
FIG. 12 is a longitudinal sectional view showing a schematic configuration of the solar cell backsheet of Comparative Example 3.
As Comparative Example 2, a back sheet 60 was produced as shown in FIG.
The back sheet 60 is obtained by deleting the barrier layer 145 and the adhesive layer 146 from the back sheet 20 of the first configuration example. That is, the light-transmitting insulating layer 141, the concavo-convex structure layer 142, the light-reflecting metal layer 143, the adhesive layer 144, and the weathering layer 147 are laminated in this order.
For the translucent insulating layer 141 of this comparative example, a PET film (Toray Lumirror (registered trademark) S10) (thickness: 250 μm) having an average transmittance of 400 to 1200 nm of 82% was used. Further, an ultraviolet curable resin having a refractive index of 1.55 was used for the uneven structure layer 142. As the sealing material 13, an EVA film having a refractive index of 1.48 was used.
The angle φ was set to φ = 45 (°).

[Evaluation]
In order to perform the evaluation, the EVA film, the solar battery cell 12, the EVA film, and the tempered glass are laminated in this order on each of the back sheets of Examples 1 to 3 and Comparative Examples 1 to 3, and heat lamination is performed using a vacuum laminator. The sample for evaluation of a solar cell module was produced. Hereinafter, solar cell modules using Examples 1 to 3 are referred to as Evaluation Samples 1 to 3, and solar cell modules using Comparative Examples 1 to 3 are referred to as Evaluation Samples 4 to 6.
Here, the EVA film comprises the sealing material 13 of a photovoltaic cell, and the thing with a refractive index of 1.48 was used. Further, tempered glass constitutes the front plate 11 and has a refractive index of 1.50.
For the evaluation, the initial conversion efficiency (hereinafter referred to as the conversion efficiency before the high-temperature and high-pressure test) of each evaluation sample is measured, and then a high-temperature and high-humidity test is performed to evaluate the long-term weather resistance. This was carried out by measuring the conversion efficiency after the wet test.
All of the conversion efficiency measurements were performed using a solar simulator (Newport 34903A) and an IV curve tracer (ADMTFT 6244).
The high temperature and high humidity test is performed at 85 ° C. and 85 ° C. in accordance with 10.13 high temperature and high humidity test of JIS C 8990 / ground-installed crystalline silicon solar cell (PV) module-design qualification and type certification requirements. % Environment for 1000 hours.

  These evaluation results are shown in Table 3 below.

In evaluation sample 1 of Example 1 having an average transmittance of 91%, evaluation sample 2 of Example 2, and evaluation sample 3 of Example 3, evaluation of Comparative Example 1 using a general white PET film It was confirmed that the efficiency improvement effect was obtained in all cases when the sample 4 was used as a reference. Among them, in the evaluation sample 1 of Example 1 in which the refractive index of the concavo-convex structure layer 142 is larger than the refractive index of the sealing material 13 and smaller than the refractive index of the translucent insulating layer 141, the high temperature and high humidity of Comparative Example 1 An efficiency improvement effect of 4% was obtained before the high-temperature and high-humidity test with respect to the conversion efficiency before the test. On the other hand, in the evaluation sample 2 of Example 2 in which the refractive index of the concavo-convex structure layer 142 is smaller than the refractive index of the sealing material 13, an efficiency improvement effect of 2% was obtained. Moreover, in the sample 3 for evaluation of Example 3 in which the refractive index of the concavo-convex structure layer 142 is larger than the refractive index of the translucent insulating layer 141, an efficiency improvement effect of 2.5% was obtained.
From this result, it was confirmed that if the average transmittance at 400 to 1200 nm is 90% or more, the light utilization efficiency can be improved. Furthermore, when the refractive index of the concavo-convex structure layer is larger than the refractive index of the sealing material and smaller than the refractive index of the translucent insulating layer, it was confirmed that the effect of improving the light utilization efficiency can be further enhanced. .

In the samples 4 and 6 for evaluation of Comparative Examples 1 and 3 in which the barrier layer 145 was not provided, the conversion efficiency after the test was greatly reduced, whereas the samples 1 for evaluation in Examples 1 to 3 in which the barrier layer was provided 3 and Comparative Sample 2 for evaluation sample 5 confirmed that the decrease in conversion efficiency after the test was small.
From this result, by providing the barrier layer 145, it is possible to prevent a decrease in conversion efficiency due to the high-temperature and high-humidity test, that is, it is possible to prevent corrosion of the light-reflecting metal layer 143, and light reuse. It was confirmed that the efficiency improvement effect by can be sustained over a long period of time.

1 Solar cell module 11 Front plate (translucent front plate)
12 solar cell 12a end side 13 sealing material 14, 20, 30, 40, 50 back sheet (solar cell back sheet)
22c Electrode 110 Incident surface 141 Translucent insulating layer 142 Uneven structure layer 142a Surface 142b Uneven structure 143 Light reflective metal layers 144, 146 Adhesive layer 145 Barrier layer 147 Weather resistant layer 421 Uneven structure portion 422 Base material H0, H1 Light H2, H3, M2, m2, N2, n2, N3, n3 Reflected light H2 ′ Re-reflected light H4 Transmitted light J Light-receiving surface n ₁₃ , n ₁₄₂ , n ₁₄₁ Refractive index P Pitch θ Vertical angle

Claims (10)

A sealing material that encapsulates the solar cells therein, a translucent front plate that is laminated on the sealing material and allows light to enter the sealing material, and the translucent front plate sandwiching the sealing material A solar cell module having a solar cell back sheet laminated on the opposite side to the face plate,
The solar cell back sheet is:
In order from the sealing material side, at least a translucent insulating layer, a concavo-convex structure layer having a fine concavo-convex structure, a light-reflective metal layer formed along the concavo-convex structure, and a weathering layer in this order. Comprising a laminate having
The solar cell module, wherein an average transmittance of the light-transmitting insulating layer at 400 nm to 1200 nm is 90% or more and 100% or less. 2. The solar cell module according to claim 1, wherein a refractive index of the concavo-convex structure layer is larger than a refractive index of the sealing material and smaller than a refractive index of the translucent insulating layer. The sum of the thickness of the concavo-convex structure layer and the thickness of the translucent insulating layer is 1/10 or less of the sum of the thickness of the sealing material and the thickness of the translucent front plate. The solar cell module according to claim 1 or 2. The barrier layer which suppresses corrosion of the said light reflective metal layer is further provided in the said adhesion layer side of the said light reflective metal layer, The any one of Claim 1 to 3 characterized by the above-mentioned. Solar cell module. The solar cell module according to any one of claims 1 to 4, wherein the barrier layer is a metal foil. 6. The solar cell module according to claim 1, wherein the barrier layer has a thickness of 7 μm or more and 50 μm or less. 7. The solar cell module according to claim 1, wherein the thickness of the light reflective metal layer is 30 nm or more and 100 nm or less. 8. The solar cell module according to claim 1, wherein the uneven shape of the uneven structure layer is a triangular prism shape having an apex angle of 120 ° ± 5 °. 9. The solar cell module according to claim 1, wherein a pitch of the tops of the triangular prism-shaped concavo-convex shapes is 10 μm or more and 30 μm or less. It is a solar battery back sheet that covers one surface of a sealing material that seals solar cells inside,
A transparent insulating layer, a concavo-convex structure layer having a fine concavo-convex structure, a light reflective metal layer formed along the concavo-convex structure, and a laminate having a weather resistance layer in this order,
The solar cell back sheet, wherein the translucent insulating layer has an average transmittance of from 90% to 100% at 400 nm to 1200 nm.

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