JP2012204460A - Solar battery backside sheet and solar battery module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve light reuse efficiency.SOLUTION: In a solar battery module 1, a front panel 2 is arranged on a front side of a sealing layer 4, in which a solar battery cell 3 is sealed, and a backside sheet 5 is arranged on a back side of the sealing layer 4. The backside sheet 5 is formed by sequentially stacking a translucent insulating layer 7, a convexo-concave structure layer 8, a light reflective metal layer 9, an adhesive layer 10, and a weather-resistant layer 11. A convexo-concave structure 15, which is formed of minute convex portions and concave portions, is formed on a surface of the convexo-concave structure layer 8 on the side of the light reflective metal layer 9. The light reflective metal layer 9 is formed by transcribing a convexo-concave shape of the convexo-concave structure 15 into the light reflective metal layer 9. The convexo-concave structure 15 has a configuration in which a number of linear convex portions or concave portions having a random length (long axis), width (short axis), and difference in height of approximately several microns are aligned in parallel. The light reflective metal layer 9 has a one-directional dispersion structure which is restricted such that incident light will be strongly dispersed in a short-axis direction and will not be dispersed in a long-axis direction when the incident light is reflected.

Description

  The present invention provides a solar cell back sheet that is disposed on the back surface of a solar cell module and that can effectively reuse light incident on the back sheet without entering the solar cell, and the solar cell back sheet. The present invention relates to a solar cell module using

  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).

Solar cells convert light energy into electrical energy, and the main types of solar cells are classified into crystalline silicon type, amorphous silicon type, organic compound type, etc., depending on the type of materials 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.
A single-crystal silicon solar cell has the advantage that it is easy to achieve high efficiency because the quality of the substrate is good, but it has the disadvantage that the manufacturing cost of the substrate is high. On the other hand, polycrystalline silicon solar cells have the disadvantage of being difficult to achieve high efficiency due to poor substrate quality, but have the advantage of being able to be manufactured at low cost, becoming the mainstream of current solar cells. Yes.

Various studies have been made on the improvement of the efficiency of polycrystalline silicon solar cells. As an example, a texture structure is formed on the surface of a silicon substrate used for a solar cell, thereby reducing the reflection of sunlight on the surface of the silicon substrate and improving the photoelectric conversion efficiency.
On the other hand, in a solar cell of single crystal silicon, the reflection of sunlight is reduced by forming a fine pyramid or inverted pyramid texture structure 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 (see, for example, Patent Document 2).

  However, when such anisotropic etching is applied to a polycrystalline silicon solar cell, the etching with an alkaline aqueous solution depends on the crystal plane orientation, so the pyramid structure in the polycrystalline silicon cannot be formed uniformly. There has been a problem that the reflectance of the entire silicon substrate 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, a reflection loss of about 54% occurs 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.
Furthermore, it has been studied to increase the light receiving area by miniaturizing an electrode formed on a silicon substrate and improve conversion efficiency by taking in a large amount of sunlight (see, for example, 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%).
Then, in order to raise light utilization efficiency further, the trial which reuses the sunlight which injects into a back surface sheet, without entering in a photovoltaic cell among the sunlight which injected from the front surface of a solar cell module is performed.

That is, in a general crystalline silicon solar cell module, gaps are formed between a plurality of solar cells in the solar cell module in order to reduce leakage current. Therefore, the light utilization efficiency can be improved if a part of sunlight incident on the back surface sheet can be reused without entering the solar battery cell.
Therefore, by placing a back sheet with a reflector on the back side of the solar cells in the solar cell module and reflecting sunlight incident on the back sheet from the gap between the solar cells, the solar cells are reincident on the solar cells. As a result, the light utilization efficiency is improved. As the reflecting material, for example, a reflecting material that scatters and reflects light, such as a resin material mixed with a white pigment or a metallic material with a matte surface treatment, can be used. Moreover, it is possible to further improve light utilization efficiency by making the surface of a reflective material into an uneven structure (for example, refer 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

However, in the conventional solar cell module, the conversion efficiency is improved by increasing the light use efficiency by the above-described means, but there is also a loss of light, so that the conversion efficiency can be sufficiently improved. It cannot be said that it is made.
For example, in the conventional method in which light incident on a region between adjacent solar cells is reflected by the back surface material and reused, in the solar cell module 50 shown in FIG. The back sheet 52 is provided with a reflecting member 53 in which prisms having a height of, for example, about 5 mm are arranged in parallel on the back side of the translucent insulating layer.
Of the incident light incident from the front plate of the solar cell module 50, incident light that passes through the solar cell 51 or passes through the gap between the solar cells 51 is reflected by the reflecting member 53. Most of the light is reflected on the back and side surfaces of the solar battery cell 51, and little light is re-reflected by the front plate and re-enters the solar battery cell 5. For this reason, it cannot be said that the loss light is sufficiently reused, and it is strongly desired to further improve the power generation efficiency by more reliably reusing the loss light.

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

The solar cell back sheet according to the present invention is a solar cell back sheet disposed on the back side of a solar cell module in which a translucent front plate is laminated on the front side of a sealing layer in which solar cells are sealed. The light having a concavo-convex structure layer in which a concavo-convex structure is formed on a surface opposite to the translucent insulating layer, and a fine concavo-convex shape following the concavo-convex structure, in order from the front side A reflective metal layer, an adhesive layer, and a weather resistant layer are laminated, and the light reflective metal layer has a unidirectional scattering structure that reflects incident light by a fine uneven shape and scatters light in one direction. It is characterized by that.
The solar battery back sheet according to the present invention follows the concavo-convex structure when, for example, light that has passed through the solar battery cell or light that has passed through the solar battery cell enters, penetrates the translucent insulating layer and enters the concavo-convex structure layer. Incident light is reflected by a light-reflective metal layer having a fine uneven shape, and the light-reflective metal layer scatters and reflects light in one direction by a unidirectional scattering structure. The light emitted from the light-transmitting insulating layer of the sheet and scattered in one direction increases the amount of reflected light that is reflected at an angle close to the incident light. The ratio at which the reflected light can be reused increases because it re-enters the solar cell.

In addition, the unidirectional scattering structure has a plurality of linear irregularities with a major axis, minor axis, and height difference of several microns each, arranged in parallel in the major axis direction, and reflects the reflected light in the minor axis direction. It is characterized in that it is scattered.
Since the linear concavo-convex portions are randomly formed and arranged in parallel to the major axis direction, the reflected light can be regulated as scattered light in one direction in the minor axis direction and reused more reliably.

Moreover, the major axis direction of the concavo-convex part may be arranged at an angle in a range of 35 ° to 55 ° with respect to the end side of the solar battery cell.
According to the solar cell backsheet having such a feature, scattered light is emitted in both directions substantially perpendicular to the major axis direction, which is the minor axis direction of the concavo-convex portion, and the reflected light contributing to reuse is increased, resulting in more reliable light. Can be reused.

Moreover, the major axis direction of the concavo-convex portion may be arranged substantially parallel to the end side of the solar battery cell.
According to the solar cell backsheet having such a feature, scattered light is emitted in both directions substantially perpendicular to the major axis direction, which is the minor axis direction of the concavo-convex portion, and the reflected light contributing to reuse is increased, resulting in more reliable light. Can be reused.

Moreover, the barrier layer for preventing corrosion of a light reflective metal layer may be provided in the uneven | corrugated structure layer side or / and the contact bonding layer side with respect to the light reflective metal layer.
According to such a back sheet of a solar cell, even in a high-temperature and high-humidity environment, the barrier layer prevents the light-reflecting metal layer from being corroded. The effect of improving the light utilization efficiency can be maintained for a long time by diffusely reflecting the light and re-entering the solar battery cell.

The barrier layer may be disposed in close contact with the light reflective metal layer.
Thereby, the effect which a barrier layer prevents deterioration of a light reflective metal layer can be heightened.

The barrier layer may be made of a valve metal or an alloy containing the valve metal.
The valve metal refers to a metal that forms an oxide film on the surface and becomes passive, and such a valve metal or an alloy containing the valve metal has an excellent corrosion resistance, so it is adopted as a barrier layer. Corrosion of the light reflective metal layer can be prevented over a long period of time.
The barrier layer may be made of an inorganic oxide.
Inorganic oxides are known for their excellent water vapor barrier properties and gas barrier properties. By adopting such inorganic oxides as barrier layers, deterioration of the light-reflective metal layer can be prevented over a long period of time. be able to.

The solar cell module according to the present invention is characterized in that any of the above-described solar cell backsheets is disposed on the backside thereof.
According to such a solar cell module, the uneven structure formed in the light-reflective metal layer is a unidirectional scattering structure in which the scattering direction is limited, so that light can be reused more reliably. .

According to the solar cell back sheet and solar cell module according to the present invention, the light reflecting metal layer having a fine concavo-convex shape following the concavo-convex structure of the concavo-convex structure layer reflects incident light to the back sheet, and Since the light-reflective metal layer scatters and reflects light in one direction due to the one-way scattering structure, the reflected light is emitted from the light-transmitting insulating layer of the back sheet and scattered in one direction. The amount of reflected light that is reflected at an angle close to that of the light increases, and these lights are re-incident on the solar cells of the solar cell module, for example, by being reflected by the translucent front plate. To do.
In particular, the light-reflecting metal layer can be controlled to scatter light in one direction by the unidirectional scattering structure, so that the light can be reused more reliably.

It is a longitudinal cross-sectional view which shows schematic structure of the solar cell module by 1st embodiment of this invention. It is an enlarged longitudinal cross-sectional view which shows schematic structure of the back surface sheet of the solar cell module shown in FIG. (A), (b), (c) is a longitudinal cross-sectional view explaining schematic structure of the solar cell module containing an electrode. It is a principal part top view which shows the uneven structure of the uneven structure layer of the back surface sheet in this embodiment. It is sectional drawing which shows the uneven structure of an uneven structure layer. It is a figure which shows the relationship between the light reflective metal layer in which the uneven structure shown in FIG. 4, FIG. 5 was formed, and reflected light. (A) is principal part explanatory drawing which shows the structure by which the uneven | corrugated | grooved part of the light-reflective metal layer was arranged at an angle of 45 degrees with respect to the edge of a photovoltaic cell, (b) is the uneven | corrugated | grooved part of a light-reflective metal layer It is principal part explanatory drawing which shows the structure arranged in parallel with one edge side of the photovoltaic cell. It is a longitudinal cross-sectional view which shows schematic structure by the 1st modification of the back surface sheet in 1st embodiment. It is a longitudinal cross-sectional view which shows schematic structure by the 2nd modification of the back surface sheet in 1st embodiment. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet by 2nd embodiment of this invention. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet by the 1st modification of the back surface sheet by 2nd embodiment. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet by the 2nd modification of the back surface sheet by 2nd embodiment. It is a longitudinal cross-sectional view which shows schematic structure of the back surface sheet by the 3rd modification of the back surface sheet by 2nd embodiment. It is a figure similar to FIG. 6 at the time of using a prism as the conventional back material.

Hereinafter, a solar cell module according to an embodiment 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 a first embodiment of the present invention. A solar cell module 1 shown in FIG. 1 includes a front plate 2 on which light from a light source L such as sunlight is incident, a sealing layer 4 that seals solar cells 3, and a back sheet 5 that are roughly stacked. Configured. In addition, as the light source L, artificial lighting such as an indoor lamp is usually employed in addition to the sun.
Moreover, the solar cell module 1 is integrally molded by heat laminating the front plate 2, the sealing layer 4, the solar cell 3 and the back sheet 5 with a vacuum laminator in a laminated state.

The front plate 2 is disposed on the forefront of the solar cell module 1 and protects the solar cells 3 from impact, dirt, moisture intrusion, etc., and is made of a transparent plate having a high transmittance. There is no.
As shown in FIG. 1, among the light emitted from the light source L, the light H0 that is perpendicularly incident on the incident surface 2 a of the front plate 2 is incident on the front plate 2, is transmitted, and is incident on the sealing layer 4. The The normal line NG of the incident surface 2a is, for example, a direction parallel to the normal line N of the plane P when the front plate 2 is placed on the plane P parallel to the horizontal plane. The light H0 incident perpendicularly to the incident surface 2a indicates light incident on the front plate 2 parallel to the normal line NG.

  The front plate 2 is made of glass such as tempered glass or sapphire glass, or a resin sheet such as PC (polycarbonate) or PEN (polyethylene naphthalate). Further, the thickness of the front plate 2 is about 3 to 5 mm for tempered glass and about 5 mm for a resin sheet.

The sealing layer 4 is made of, for example, a sheet-shaped sealing material having a thickness of about 0.4 to 1 mm, and a plurality of solar cells 3 are dispersed and fixed therein. The light H0 incident on the front plate 2 is transmitted through the sealing layer 4 to become light H1 incident on the solar cells 3, and part of the light H1 passes through the sealing layer 4 between the solar cells 3 and is on the back sheet. 5 becomes incident light.
The sealing layer 4 is made of a material having a high light transmittance in order to transmit the light H1, and is preferably a material having durability such as weather resistance, high temperature resistance, high humidity resistance, weather resistance, and electrical insulation. As a sealing material satisfying this condition, for example, a thermoplastic synthetic resin material whose main component is EVA (ethylene vinyl acetate copolymer) or PVB (polyvinyl butyral) having a vinyl acetate content of 20 to 30%. Is used.

The solar cell 3 has a function of converting light incident on the light receiving surface 3a into electricity by a photoelectric effect, and is a single crystal silicon type, a polycrystalline silicon type, an amorphous silicon type, CIGS (Cu · In · Ga · Se compound) ) There are many types such as a thin film type. Here, a single crystal or polycrystalline silicon type solar cell is used.
A plurality of solar cells 3 are connected by electrodes (not shown) to form a module.

  In the present embodiment, the light H <b> 1 incident on the solar battery cell 3 from the sealing layer 4 is converted into electricity by the solar battery cell 3. In addition, the light incident obliquely with respect to the incident surface 2a of the front plate 2 has a higher ratio of being reflected on the incident surface 2a and less light incident on the solar cells 3 than the vertically incident light H0. . That is, there is little light available for power generation. Therefore, power generation can be performed most efficiently when the incident light H0 is perpendicularly incident on the incident surface 2a.

  Next, the back surface sheet 5 in this embodiment is demonstrated with reference to FIG. The back sheet 5 has a function of reflecting light transmitted through the solar cells 3 itself and light H1 transmitted through the sealing layer 4 without being incident on the solar cells 3, and at least translucent in order from the front side. The insulating layer 7, the concavo-convex structure layer 8, the light reflective metal layer 9, the adhesive layer 10, and the weather resistant layer 11 are laminated in order.

The translucent insulating layer 7 is disposed on the front side of the back sheet 5 and is made of a material having electrical insulation.
Here, one of the important performances required for the back sheet 5 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. Moreover, in the solar cell module 1, it is calculated | required that especially the surface by the side of the photovoltaic cell 3 is electrically insulating.

The necessity of the translucent insulating layer 7 will be described with reference to the configuration of the solar cell module 1A shown in FIG. The solar cell module 1 </ b> A shown in FIG. 3 is configured, for example, by laminating a front plate 2, a sealing layer 4, and a light reflective metal layer 9. And in the sealing layer 4, the several photovoltaic cell 3 is arranged on both sides of the electrode 13, and the photovoltaic cell 3 is connected by the electrode 13, and the produced | generated electric power can be taken out.
In solar cell module 1 </ b> A having the above-described schematic configuration shown in FIG. 3A, solar cell 3 is usually near the center of sealing layer 4 in the thickness direction and away from light-reflecting metal layer 9. , Current leakage due to short circuit of the electrode 13 does not occur.

However, since the sealing layer 4 that seals the solar cells 3 is made of a softened sealing material, the light-reflective metal layer 9 is relatively close to the front plate 2 side as shown in FIG. If it arrange | positions to, the photovoltaic cell 3 and the light-reflective metal layer 9 may contact. At this time, the electrode 13 is short-circuited through the light-reflective metal layer 9, and a problem that current leaks occurs.
On the other hand, as shown in FIG. 3C, in the solar cell module 1A, the light-transmitting insulating layer 7 is disposed between the light-reflecting metal layer 9 and the sealing layer 4, thereby causing the short circuit described above. Can be prevented.
If the thickness of the light-transmitting insulating layer 7 is insufficient, the light-transmitting insulating layer 7 breaks down between the electrode 13 and the light-reflecting metal layer 9 as shown in FIG. Discharge d may occur and current leakage may occur.

Here, there is a dielectric breakdown voltage as one of the numerical standards indicating electrical insulation. This breakdown voltage is an index that the insulation state is broken when a voltage higher than the breakdown voltage is applied, and it can be said that a higher breakdown voltage is more electrically stable.
For example, according to Reference 1 (“Photovoltaic power generation system constituent material” (Industry Research Committee)), the approximate breakdown voltage (kV) of various plastic films for electrical insulation (25 μm) is PET (polyethylene terephthalate). 6.5, PEN (polyethylene naphthalate) 7.5, PVC (stretched hard vinyl chloride) 4.0, PC (polycarbonate) 5.0, OPP (stretched polypropylene) 6.0, PE (polyethylene) 4.0, TAC (Triacetate) 3.0 and PI (polyimide) 7.0. All of these satisfy the dielectric breakdown voltage as an insulating material (reference JISC2318 / biaxially oriented polyethylene terephthalate film for electricity).
Moreover, the dielectric breakdown voltage of Tedlar (registered trademark) manufactured by DuPont, which is a representative product of PVF (poly, fluoride, vinyl), is about 3.0 kV.

As one of the insulation performances of the solar cell module 1, it is defined that there is no abnormality such as dielectric breakdown even if a DC voltage of twice the maximum system voltage + 1000V is applied for 1 minute (reference JISC8918 / Crystalline Solar Battery module). The maximum system voltage is usually 600-1000V.
For the above reasons, it is desirable that the average value of the breakdown voltage is 3 kV or more, and the above-mentioned various materials satisfy this standard (reference JISC2151 / electric plastic film test method 17.2.2 flat plate electrode method) ). When the dielectric breakdown voltage is smaller than 3 kV, the possibility of short circuit or leakage due to long-term use increases.

Therefore, the translucent insulating layer 7 in the present embodiment is configured by a resin film made of any of the various insulating materials described above. The material used for the translucent insulating layer 7 is preferably a transparent or translucent material, and preferably has fewer elements that cause light scattering.
The light incident on the back sheet 5 is transmitted through the translucent insulating layer 7 and then reflected by the light reflective metal layer 9, and is transmitted through the translucent insulating layer 7 again to become reflected light from the back sheet 5. Therefore, if the transparency of the translucent insulating layer 7 is high and there are few scattering elements, the efficiency with which the light incident on the back sheet 5 becomes reflected light increases.

  Moreover, the material used for the translucent insulating layer 7 is not limited to the above-described material, and any material that satisfies the reference value of the dielectric breakdown voltage can be used as appropriate. For example, it is possible to employ a synthetic resin film mainly composed of EVA, PVB or the like. The use of these resins is preferable because the adhesion with the sealing layer 4 is improved.

The translucent insulating layer 7 may be a single layer or a multilayer. In the case of a single layer, any of the above materials can be selected according to the required characteristics.
As a constitution method when the translucent insulating layer 7 is a multilayer, for example, a method of bonding a fluororesin film such as PVF on a PET film, a method of forming a fluororesin coating film such as PVF on a PET film, EVA on a PET film And a method of bonding a synthetic resin film mainly composed of PVB or the like.
A fluororesin such as PVF, and a synthetic resin mainly composed of EVA, PVB, or the like are preferable because they satisfy electrical insulation standards and improve adhesion with the sealing layer 4. However, to obtain sufficient strength with a single layer, it is necessary to increase the thickness, which causes a high cost. Therefore, the translucent insulating layer 7 preferably has 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 also be adopted, and this configuration is preferable because the process can be simplified compared to the method of laminating the fluororesin film.

The translucent insulating layer 7 may have a multilayer structure in which two layers of any of the above materials, for example, PET films are bonded together. In order to increase the insulation, it is known that the multilayer structure covers the insulation defects and the reliability is higher than the single-sheet structure. Therefore, the insulating property of the translucent insulating layer 7 can be further improved by the multilayer structure in which two layers are bonded together than the single PET film layer.
In addition, the layer structure of the translucent insulating layer 7 is not limited to the above-described one, and can be appropriately changed according to required characteristics.

Next, the uneven structure layer 8 will be described.
The uneven structure layer 8 is made of an ultraviolet curable resin or a thermosetting resin.
The type of resin used as the concavo-convex structure layer 8 is not particularly limited as long as it is an ultraviolet curable resin or a thermosetting resin. For example, poly (meth) acrylic resin, polyurethane resin, fluorine resin, silicone Resin, polyimide resin, epoxy resin, polyethylene resin, polypropylene resin, methacrylic resin, polymethylpentene resin, cyclic polyolefin resin, acrylonitrile- (poly) styrene copolymer (AS resin), acrylonitrile- Polystyrene resin such as butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, polycarbonate resin, polyester resin, polyamide resin, polyamideimide resin, polyaryl phthalate resin, polysulfone resin, polyphenylene Sulfide Resins, polyethersulfone resins, reethylene naphthalate resins, polyetherimide resins, acetal resins, cellulose resins and the like can be used, and these resins can be used alone or in combination. .
Further, as the uneven structure layer 8, in addition to the above-mentioned resin, for example, a scattering reflector, a curing agent, a plasticizer, a dispersant, various leveling agents, an ultraviolet absorber, an antioxidant, a viscosity modifier, a lubricant, a light stabilizer Various additives such as an agent may be appropriately blended.
Further, the uneven structure layer 8 may be formed of a single layer or a multilayer of any of the materials described above.

In the concavo-convex structure layer 8, a concavo-convex structure 15 having a fine concavo-convex shape is formed on a surface in close contact with the light reflective metal layer 9. The light-reflective metal layer 9 is transferred with a concavo-convex shape following the concavo-convex shape of the concavo-convex structure 15.
The concavo-convex structure 15 forms a unidirectional scattering structure in which a restriction is imposed on the scattering direction of the reflected light when the light H1 is reflected by the light reflective metal layer 9. Unidirectional scattering means that scattering is limited in a scattering direction and scattering in a specific direction, unlike normal isotropic scattering.
As shown in FIG. 4, the concavo-convex structure 15 has a large number of linear or rod-like convex portions and / or concave portions each having a length (major axis), width (minor axis) and height difference of about several microns. It is configured by an elongated fine concavo-convex structure whose length, width, height or depth (height difference) and the like are set at random. Moreover, the concavo-convex structure 15 has a configuration in which fine concave portions and convex portions are randomly arranged substantially parallel to the long axis direction. In such a concavo-convex structure 15, the irradiation light H <b> 1 is scattered in the minor axis direction of the fine elongated slits or protrusions and is not scattered in the major axis direction, so that the scattering direction can be controlled.

Further, as shown in FIGS. 5A to 5C, the concave and convex portions formed by the concavo-convex structure 15 of the concavo-convex structure layer 8 have, for example, an elevation difference of about h = 1 to 3 μm, and the major axis direction thereof. As the cross-sectional shape orthogonal to the shape, an appropriate shape such as a substantially polygonal shape such as a chamfered rectangle or triangle, a semicircular shape, or a semielliptical shape can be adopted. Alternatively, the cross-sectional shape in the minor axis direction shown in FIGS. 5A to 5C may be a shape in which a quadrangular shape, an elliptical shape, a semicircular shape, a convex arc shape, etc. are mixed, while referring to FIGS. 4 and 5. Thus, the cross-sectional shape in the major axis direction is mainly a chamfered square shape.
The concavo-convex structure layer 8 having the concavo-convex structure 15 shown in FIG. 5 is shown upside down with respect to the other drawings.
In the light-reflective metal layer 9 to which such a concavo-convex structure 15 is transferred, as shown in FIG. 6, incident light is scattered in the short axis direction of elongated fine concave portions and convex portions, and thus is scattered by the cross-sectional shape thereof. The direction can be controlled.
This is because the cross-sectional shape in the minor axis direction is less likely to scatter light because the difference between the height direction and the width direction is small, and the sectional shape in the major axis direction is longer in the width direction than in the height direction. This is because scattering of light hardly occurs.

Further, the light-reflective metal layer 9 having a surface shape onto which the concavo-convex structure 15 is transferred has a solar cell 3 of, for example, a quadrangle, and its major axis direction is 45 ° ± 10 ° with respect to any one of its end sides. It is preferable that they are arranged in a range, that is, in a range of 35 ° to 55 °, preferably 45 ° (see FIG. 7A).
By arranging in this way, the incident light H0 incident on the front plate 2 at a substantially right angle is incident on the back sheet 5 and is reflected by the light-reflective metal layer 9 that follows the concave-convex structure 15 as shown in FIG. When the light is reflected and reflected toward the solar battery cell 3, the light is scattered in the short axis direction of the linear or rod-like concave portion or convex portion and is not so scattered in the long axis direction.

Therefore, the reflection direction is regulated so that a lot of the reflected light H2 is reflected at a reflection angle close to the incident light H1, and is totally reflected by the front plate 2 without colliding with the solar battery cell 3, and the light receiving surface of the solar battery cell 3 Re-enters 3a. And the light of reflected light H2 is compared with the back sheet 52 which used the prism shown in FIG. The angle with respect to the reflective metal layer 9 becomes close to vertical.
Therefore, as shown in FIG. 6, the incident light H1 incident on the back sheet 5 is reflected by the light-reflecting metal layer 9 following the concavo-convex shape of the concavo-convex structure 15, thereby increasing the area contributing to reuse and generating power. Efficiency can be increased.

  Moreover, it is also preferable that the light-reflective metal layer 9 having the concavo-convex shape of the concavo-convex structure 15 is disposed so that the major axis direction of the concave portion and the convex portion is substantially parallel to each end side of the solar battery cell 3. (Refer FIG.7 (b)). By arranging in this way, the area contributing to reuse can be further increased, and the power generation efficiency can be further increased.

In addition, the structure (refer FIG.7 (b)) arrange | positioned so that the major axis direction of the uneven structure 15 in the light reflective metal layer 9 may become substantially parallel with respect to each edge of the photovoltaic cell 3, Compared with the configuration in which the major axis direction of the concavo-convex structure 15 is arranged in the range of 35 ° to 55 ° with respect to the edge of the solar battery cell 3 (see FIG. 7A), the power generation efficiency can be further improved. It is.
However, the arrangement of the light-reflective metal layer 9 in which the major axis direction of the concavo-convex structure 15 is set in the range of 35 ° to 55 ° with respect to the end side of the solar battery cell 3 is the end side of the solar battery cell 3. Compared to an arrangement that is substantially parallel to the solar cell 3, the alignment with respect to the solar battery cell 3 is easy, and it is preferable when workability is important.

As a method for forming the concavo-convex structure layer 8 made of a resin material, in the case of a single layer, a pressing method using a mold, a casting method, an extrusion molding method, an injection molding method, or the like can be given. In these methods, it is possible to form the concavo-convex structure 15 on one surface simultaneously with sheet formation.
Further, as another method for forming the concavo-convex structure layer 8 (concavo-convex structure 15) made of a resin material, in the case of a multilayer, a thermosetting resin, an ultraviolet curable resin or an electron beam is formed on the concavo-convex forming surface of a flat stamper or a roll stamper. Examples of the method include applying or injecting a curable resin or the like to form the concavo-convex structure 15, placing a base material on the other surface facing the curable resin, and curing it, and releasing from the stamper after the curing process. These methods have the advantage that the moldability is good because the viscosity of the resin used can be lowered.
When the concavo-convex structure layer 8 is a multilayer, the translucent insulating layer 7 can be used as a base material for supporting the other surface of the concavo-convex structure layer 8 having the concavo-convex structure 15 formed on one surface. (See FIGS. 10 and 11).

A mold used for processing the concavo-convex structure 15 of the concavo-convex structure layer 8 is 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, or the like. be able to. The mold formed by such processing has an inverted structure of the concavo-convex structure 15 on the surface.
For example, by cutting a metal plate with a tool having a desired shape, a mold in which an inverted structure of the desired uneven structure 15 is formed can be obtained. The mold may be plate-shaped or roll-shaped, but is preferably a roll-shaped mold. If it is a roll-shaped metal mold | die, continuous embossing is possible and it is suitable as a preparation method of a back surface sheet which requires a large area.

  The base material of the mold used in the above manufacturing method is not particularly limited, and PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PVC (stretched hard vinyl chloride), PC (polycarbonate), OPP (stretched) A film made of a resin material such as polypropylene), PE (polyethylene), TAC (triacetate), or PI (polyimide) can be used.

Next, the light reflective metal layer 9 will be described.
The light reflective metal layer 9 is made of, for example, a metal such as aluminum or silver, and is formed in a layer shape having a shape following the uneven shape of the uneven structure 15 of the uneven structure layer 8. The means for forming the light reflective metal layer 9 is not particularly limited as long as the metal layer can be formed with a uniform thickness. For example, (a) vacuum deposition, sputtering, ion plating, ion cluster beam, etc. Physical vapor deposition method (Physical Vapor Deposition method; PVD method), (b) Chemical vapor deposition method (Chemical Vapor Deposition method, such as plasma chemical vapor deposition method, thermal chemical vapor deposition method, photochemical vapor deposition method; CVD method) is employed.
Among these methods, a vacuum deposition method that can form a high-quality metal layer with high productivity is preferable. Any one of an electron beam heating method, a resistance heating method, and an induction heating method may be used as appropriate as a heating means of a vacuum evaporation apparatus using a vacuum evaporation method.

  The metal used for the light-reflective metal layer 9 is not particularly limited as long as it has a metallic luster and any one of the above forming methods is possible. Examples of the light reflective metal layer 9 include aluminum (Al), silver (Ag), gold (Au), copper (Cu), nickel (Ni), chromium (Cr), tin (Sn), zirconium (Zr), and the like. These single metals or alloys may be mentioned, and may be formed as a single layer or may be formed by laminating a plurality of metals. Among them, aluminum that is highly reflective and can form a dense metal layer relatively easily and is inexpensive is preferable.

  The lower limit of the thickness of the light reflective metal layer 9 is preferably 10 nm, and particularly preferably 20 nm. On the other hand, the upper limit of the thickness of the light reflective metal layer 9 is preferably 200 nm, and particularly preferably 100 nm. If the thickness of the light reflective metal layer 9 is smaller than the lower limit of 10 nm, the light incident on the light reflective metal layer 9 cannot be sufficiently reflected. If the thickness is 20 nm or more, the light incident on the light-reflective metal layer 9 can be more reliably reflected. On the other hand, if the thickness of the light-reflective metal layer 9 exceeds the upper limit of 200 nm, cracks that can be visually confirmed are likely to occur in the light-reflective metal layer 9, and cracks that cannot be visually confirmed if the thickness is 100 nm or less. Hard to occur.

The light reflective metal layer 9 is formed in a shape obtained by transferring the uneven structure 15 of the uneven structure layer 8, and the light reflective metal layer 9 has an uneven structure. When the size, shape, and arrangement of the fine concave portions and convex portions of the concavo-convex structure formed on the light reflective metal layer 9 are made regular, the reflected light becomes a diffracted light and has a defect of being split. Therefore, it is possible to prevent the reflected light from becoming diffracted light by randomly setting the length, width, depth or height of the linear concave and convex portions and the arrangement thereof.
The light reflective metal layer 9 has a function of scattering and reflecting light incident on the light reflective metal layer 9 in a predetermined direction, that is, the minor axis direction of the concavo-convex structure 15.
In addition, as another method for forming a metal layer having a concavo-convex structure such as the light-reflecting metal layer 9, for example, a method of directly forming the concavo-convex structure 15 on a metal foil can be cited. Since the thickness of the reflective metal layer 9 is increased, the resistance is low, and it is easy to energize the aluminum frame for fixing the module, the wiring connected to the terminal BOX, etc., which is not preferable.

  Next, the weather resistant layer 11 connected to the light reflective metal layer 9 through the adhesive layer 10 is required to have long-term weather resistance such as high temperature resistance, high humidity resistance, hydrolysis resistance, and flame resistance. In order to satisfy these requirements, generally, a type of PET with improved hydrolysis resistance, such as a fluororesin film such as PVF (polyvinyl fluoride), a fluororesin coating film, or a low oligomer PET (polyethylene terephthalate) film A film or the like is used. In addition, you may use the PEN film etc. which are excellent in a weather resistance. The material of the weather resistant layer 11 is not limited to the above, and any material that satisfies the long-term weather resistance standard value can be used as appropriate.

  The weather resistant layer 11 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 this weather resistant layer 11 having a multilayer structure include a PET film laminated with a fluororesin film such as PVF (poly, fluoride, vinyl) via an adhesive layer, and a PET film such as PVF. The thing etc. which formed the fluororesin coating film are 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 a factor of high cost Become. 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 11 is not limited to the above, and can be changed as appropriate according to the required characteristics.

The adhesive layer 10 is required to have an adhesive strength that does not deteriorate due to long-term outdoor use and does not cause delamination, and that the degree of yellowing is small. In order to satisfy these requirements, a laminating adhesive in which one or more of polyurethane, polyacrylic, polyester, epoxy, polyvinyl acetate, and cellulose resins are mixed can be used.
In order to prevent deterioration of the adhesive due to long-term outdoor exposure, a deterioration inhibitor may be added to the adhesive layer 10. Examples of the deterioration preventing agent include additives such as carbodiimine and epoxy.
Further, the adhesive layer 10 contains 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 as appropriate. May be.

  The weather-resistant layer 11 may be bonded to the light-reflective metal layer 9 by the adhesive layer 10, for example, sandwich extrusion using a dry lamination method, a non-solvent dry lamination method, a hot melt lamination method, or an extrusion lamination method. A known method such as a lamination method can be appropriately used.

Since the solar cell module 1 and the back sheet 5 thereof according to the present embodiment have the above-described configuration, the concavo-convex structure 15 of the concavo-convex structure layer 8 and the light-reflecting metal layer 9 following this shape are linear and fine. It has a unidirectional scattering structure that scatters light in the minor axis direction of the concave and convex portions, and the light-reflective metal layer 9 has a linear shape with a height difference of about 1 to 3 μm and a length of about several microns and a random length. Since the concave portions and the convex portions are arranged in parallel and at random, the concave and convex portions and the convex portions are strongly scattered in the short axis direction, and the scattering direction can be controlled by the cross-sectional shape.
Therefore, the reflection angle of the reflected light H2 with respect to the light-reflective metal layer 9 increases with a large angle close to a right angle. Therefore, the reflected light H2 is re-reflected by the front plate 2 without colliding with the back surface or side surface of the solar battery cell 3, and the solar battery. Since a larger amount of light can be incident on the light receiving surface 3a of the cell 3, more reflected light H2 can be reused as compared with a reflecting member using a conventional prism.

In addition, this invention is not limited to the above-mentioned embodiment, A suitable change etc. are possible unless the summary of this invention is changed. Hereinafter, modified examples and other embodiments of the present invention will be described with reference to the drawings.
FIG. 8 is a longitudinal sectional view showing a schematic configuration of the back sheet 18 according to the first modification of the back sheet 5 according to the first embodiment.
The back sheet 18 has a function of reflecting light transmitted through the solar cells 3 itself and light H1 transmitted through the sealing layer 4 without being incident on the solar cells 3, and at least translucent in order from the front side. The insulating layer 7, the concavo-convex structure layer 8, the light-reflecting metal layer 9, the barrier layer 19, the adhesive layer 10, and the weathering layer 11 are sequentially laminated, and the barrier layer 19 is provided. Except for this, the configuration is the same as that of the back sheet 5. With respect to the material and the manufacturing method used, the same material can be used except that the barrier layer 19 is formed, and the same manufacturing method can be adopted.

  The barrier layer 19 is formed of a valve metal or an alloy containing the valve metal so as to follow a concavo-convex structure of the light reflective metal layer 9. As a means for forming the barrier layer 19 employing a valve metal or an alloy containing a valve metal, a uniform metal layer is formed without causing deterioration such as shrinkage or yellowing in the light reflective metal layer 9 and the concavo-convex structure layer 8. Although it will not specifically limit if possible, various means are possible, (a) Physical vapor deposition methods (Physical Vapor Deposition method; PVD, such as a vacuum evaporation method, sputtering method, an ion plating method, an ion cluster beam method) (B) Chemical vapor deposition method (chemical vapor deposition method; CVD method) such as plasma chemical vapor deposition method, thermal chemical vapor deposition method, photochemical vapor deposition method or the like is employed. Among these, a vacuum deposition method that can form a high-quality metal layer with high productivity is preferable. Any one of an electron beam heating method, a resistance heating method, and an induction heating method may be used as appropriate as a heating means of a vacuum evaporation apparatus using a vacuum evaporation method.

  The valve metal used for the barrier layer 19 refers to a metal that forms an oxide film on the surface and becomes passive, for example, aluminum (Al), chromium (Cr), titanium (Ti), zirconium (Zr), tantalum (Ta). Niobium (Nb), hafnium (Hf), zinc (Zn), tungsten (W), bismuth (Bi), antimony (Sb), and the like, and these metals can be used alone or in an alloy. Further, it may be formed as a single layer, or a plurality of metals may be stacked. Among these, chromium is preferable because it exhibits excellent corrosion resistance and can form a dense metal layer relatively easily.

The barrier layer 19 may be formed of an inorganic oxide such as silicon oxide or aluminum oxide so as to follow a concavo-convex structure of the light reflective metal layer 9. The means for forming the barrier layer 19 employing an inorganic oxide is particularly limited as long as the inorganic oxide layer can be formed without causing deterioration such as shrinkage and yellowing in the light reflective metal layer 9 and the uneven structure layer 8. Although various means are possible, they are generally formed by vacuum deposition. Sputtering, ion plating, plasma vapor deposition (CVD), or the like can be used as means other than this vacuum vapor deposition. However, considering productivity, the vacuum deposition method is the best at present. Any one of an electron beam heating method, a resistance heating method, and an induction heating method may be appropriately used as a heating means of the vacuum evaporation apparatus by this vacuum evaporation method.
Further, in order to improve the adhesion between the barrier layer 19 and the light-reflecting metal layer 9 and the denseness of the barrier layer 19, a plasma assist method or an ion beam assist method can be used. Further, in order to increase the transparency of the barrier layer 19, reactive vapor deposition in which oxygen gas or the like is blown may be performed during vapor deposition.

  The inorganic oxide used for the barrier layer 19 is not particularly limited as long as it has transparency and has a gas barrier property of oxygen and water vapor, and any one of the above forming methods is possible. For example, inorganic oxides such as silicon oxide, aluminum oxide, tin oxide, magnesium oxide, or a mixture thereof can be given. Among these, silicon oxide that can form a dense inorganic oxide layer relatively easily and has excellent long-term stability is preferable.

  The optimum thickness of the barrier layer 19 varies depending on the type and configuration of the inorganic compound used. In general, the thickness is preferably in the range of 5 to 300 nm, and the value is appropriately selected depending on the degree of required barrier properties. Is done. However, if the film thickness is less than 5 nm, a uniform film may not be obtained or the film thickness may not be sufficient, and the function as a gas barrier material may not be sufficiently achieved. If the film thickness exceeds 300 nm, the inorganic oxide thin film layer cannot be kept flexible, and there is a risk that the inorganic oxide thin film layer will crack due to external factors such as bending and pulling after the film formation. . More preferably, it exists in the range of 10-150 nm. If the thickness of the barrier layer 19 is less than 10 nm, sufficient barrier properties may not be obtained depending on the type and configuration of the inorganic oxide. On the other hand, when the film thickness exceeds 150 nm, cracks and pinholes are likely to occur, and the barrier property may be lowered.

  The barrier layer 19 is formed on the weather resistant layer 11 side with respect to the light reflective metal layer 9. The barrier layer 19 includes water vapor that may enter from the weather resistant layer 11 side in a high temperature and high humidity environment, carboxylic acid that may be generated by hydrolysis of the resin material used for the adhesive layer 10, and the like. The component that corrodes the light-reflecting metal layer 9 generated on the weathering layer 11 side is blocked, and the light-reflecting metal layer 9 is prevented from corroding.

FIG. 9 is a longitudinal sectional view showing a schematic configuration of the back sheet 21 according to the second modification. In the back sheet 21, unlike the above-described first modification, the barrier layer 19 is disposed on the concave-convex structure layer 8 side of the light reflective metal layer 9.
The barrier layer 19 arranged in this manner is an outgas containing an acetic acid component generated when EVA is used for the sealing layer 4 in a high temperature and high humidity environment, or a resin material used for the concavo-convex structure layer 8. The component which corrodes the light-reflective metal layer 9 generated on the concave-convex structure 15 side, such as carboxylic acid which may be generated by hydrolysis of the light, is blocked, and corrosion of the light-reflective metal layer 9 is prevented.

  Moreover, in the back surface sheet 21, you may provide the barrier layer 19 on both surfaces of the light-reflective metal layer 9, ie, both the uneven | corrugated structure layer 8 side and the weather-resistant layer 11 side (not shown). At this time, it is preferable because components that corrode the light-reflective metal layer 9 that may occur on the uneven structure layer 8 side and the weathering layer 11 side can be blocked from both sides.

FIG. 10 shows a back sheet 23 according to the second embodiment of the present invention.
This back sheet 23 uses a PET film as the translucent insulating layer 7. A concavo-convex structure layer 8 and a light-reflective metal layer 9 are laminated on the back side of the translucent insulating layer 7, and a weather-resistant layer 11 made of a hydrolysis-resistant PET film via an adhesive layer 10. Is arranged. In the second embodiment, the concavo-convex structure layer 8 has a multilayer structure, and the translucent insulating layer 7 also serves as the base material 8 </ b> A that supports the concavo-convex structure layer 8.

FIG. 11 is a modification of the back sheet 23 according to the second embodiment.
In the back sheet 25 according to the first modification shown in FIG. 11, a PET film is used as the translucent insulating layer 7. An uneven structure layer 8, a light-reflective metal layer 9, and a barrier layer 19 are sequentially laminated on the back side of the translucent insulating layer 7, and further, from a hydrolysis-resistant PET film via an adhesive layer 10. The weathering layer 11 is arranged. In addition, the concavo-convex structure layer 8 has a multilayer structure, and the translucent insulating layer 7 also serves as the base material 8 A that supports the concavo-convex structure layer 8.

Moreover, FIG. 12 shows the 2nd modification of the back surface sheet 23 by 2nd embodiment.
In the back sheet 27 according to the second modification shown in FIG. 12, an EVA film is used as the translucent insulating layer 7. On the back side of the translucent insulating layer 7, a multi-layered concavo-convex structure layer 8 having a concavo-convex structure 15, a light-reflective metal layer 9, and a barrier layer 19 are laminated. Further, a weathering layer 11 made of a hydrolysis-resistant PET film is disposed through the adhesive layer 10. At this time, the translucent insulating layer 7 and the base material 28 of the concavo-convex structure layer 8 are bonded together via the adhesive layer 29.

Moreover, FIG. 13 shows the 3rd modification of the back surface sheet 23 by 2nd embodiment.
In the back sheet 31 according to the third modification shown in FIG. 13, a PET film is used as the translucent insulating layer 7. An uneven structure layer 8, a light reflective metal layer 9, and a barrier layer 19 are laminated on the back surface side of the translucent insulating layer 7, and further comprises a PET film 32 and a PVF film 33 with an adhesive layer 10 interposed therebetween. A weathering layer 11 is disposed. At this time, the PET film 32 and the PVF 33 constituting the weather resistant layer 11 are bonded together via the adhesive layer 34. The translucent insulating layer 7 and the concavo-convex structure layer 8 are bonded together with an adhesive layer 35 interposed therebetween.

Similarly to the back sheet 5 according to the first embodiment, the light-reflective metal layer in which the concavo-convex structure 15 is formed in the back sheets 18, 21, 23, 25, 27, and 31 according to the respective modified examples and the second embodiment. 9 is included, light can be efficiently reflected toward the front side. Therefore, it is possible to increase the power generation amount by improving the light use efficiency of the solar cell module 1.
Moreover, each back sheet 5, 18, 21, 23, 25, 27, 31 is not restricted to the use to the solar cell module 1, but light emission efficiency improvement of light emitting elements, such as LED lighting and an EL element, is carried out. It can be diverted to an optical element or display member for which utilization efficiency is desired to be improved.

Next, with respect to the back sheet 5 of the solar cell module 1 according to the embodiment of the present invention, comparative examples and examples were produced and evaluated. This evaluation test will be described.
(Comparative example)
As a comparative example of the back sheet 5, the basic configuration of the back sheet 5 shown in FIG. 2 was used. Then, instead of the light-reflecting metal layer 9 having a unidirectional scattering structure following the shapes of the concavo-convex structure layer 8 and the concavo-convex structure 15, a white PET film (Toray Lumirror E20) showing isotropic scattering is used. The other components of the back sheet, ie, the translucent insulating layer 7, the adhesive layer 10, and the weather resistant layer 11 made of hydrolysis resistant PET film, were the same as those in the following examples.
And on the back sheet provided with the white PET film by a comparative example, the EVA film as a lower layer of the sealing layer 4, the photovoltaic cell 3, and the EVA film as an upper layer of the sealing layer 4 similarly to the following Example The solar cell module of the comparative example was produced by laminating in order of tempered glass as the front plate 2 and performing thermal lamination with a vacuum laminator. This was designated as Sample 1 for evaluation.

(Example)
As an example of the back sheet 5, the back sheet 5 shown in FIG. 2 was used. That is, a translucent insulating layer 7 made of a PET film, a concavo-convex structure layer 8 having a concavo-convex structure 15, a light-reflective metal layer 9 having a unidirectional scattering structure having the shape of the concavo-convex structure 15, an adhesive layer 10, The back sheet 5 laminated | stacked in order of the weather resistant layer 11 which consists of a hydrolysable PET film was produced.
In order to evaluate the back sheet 5, the back sheet 5, the EVA film as the lower layer of the sealing layer 4, the solar cell 3, the EVA film as the upper layer of the sealing layer 4, and the tempered glass as the front plate 2 are sequentially laminated. And the solar cell module 1 was produced by performing thermal lamination with a vacuum laminator. This was designated as Sample 2 for evaluation.

(Measurement of conversion efficiency)
The photoelectric conversion efficiency of the evaluation sample 1 of the comparative example and the evaluation sample 2 of the example obtained as described above was measured. A solar simulator (34903A made by Newport) was used as the light source L, and an IV curve tracer (6244 made by ADMT) was used as the solar cell evaluation device.
When the photoelectric conversion efficiency of the samples 1 and 2 for evaluation was measured, it was as shown in Table 1.

一方向性散乱構造を有する光反射性金属層９を設けた実施例では、等方散乱性を示す白色ＰＥＴフィルムを用いた比較例よりも、高い光電変換効率が得られることを確認できた。

In the Example which provided the light reflective metal layer 9 which has a unidirectional scattering structure, it has confirmed that a high photoelectric conversion efficiency was obtained rather than the comparative example using the white PET film which shows isotropic scattering.

1 Solar cell module 2 Front plate (translucent front plate)
3 Solar cell 4 Sealing layer 5, 18, 21, 23, 25, 27, 31 Back sheet (solar cell back sheet)
20 Back sheet (Solar cell back sheet)
7 Translucent insulating layer 8 Uneven structure layer 8a Uneven structure 9 Light reflective metal layer 10 Adhesive layer 11 Weather resistant layer 19 Barrier layer

Claims (9)

A solar battery back surface sheet disposed on the back side of a solar cell module in which a translucent front plate is laminated on the front side of a sealing layer in which solar cells are sealed,
In order from the front side, at least a light-transmitting insulating layer, a concave-convex structure layer having a concave-convex structure formed on a surface opposite to the light-transmitting insulating layer, and a light-reflective metal having a fine concave-convex shape following the concave-convex structure Layer, adhesive layer, and weathering layer,
The solar cell backsheet, wherein the light reflective metal layer has a unidirectional scattering structure in which incident light is reflected by a fine uneven shape to scatter light in one direction.   In the unidirectional scattering structure, a plurality of linear concavo-convex portions each having a major axis, a minor axis, and a height difference of about several microns are randomly arranged parallel to the major axis direction, and reflected light is arranged in the minor axis direction. The solar cell back surface sheet according to claim 1, which is scattered.   The long axis direction of the said uneven | corrugated | grooved part is a solar cell back surface sheet described in Claim 2 arranged at the angle of the range of 35 degrees-55 degrees with respect to the edge side of a photovoltaic cell.   The long axis direction of the said uneven | corrugated | grooved part is a solar cell back surface sheet described in Claim 2 arranged substantially parallel to the edge side of a photovoltaic cell.   The barrier layer for preventing the corrosion of the said light reflective metal layer is provided in the said uneven structure layer side or / and the said adhesion layer side with respect to the said light reflective metal layer. The solar cell back surface sheet | seat described in 1 item | term.   The solar cell backsheet according to claim 5, wherein the barrier layer is disposed in close contact with the light-reflective metal layer.   The solar cell backsheet according to claim 5 or 6, wherein the barrier layer is made of a valve metal or an alloy containing the valve metal.   The solar cell back sheet according to claim 5, wherein the barrier layer is made of an inorganic oxide.   A solar cell module comprising the solar cell back sheet according to any one of claims 1 to 8 disposed on a back side thereof.

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