JP2014017315A - Rear surface protective sheet for solar battery - Google Patents

Abstract

The present invention provides a black solar cell back surface protective sheet in which absorption of light in the near infrared region and infrared region of sunlight is suppressed.
A solar battery back surface protective sheet disposed on the back side of a solar battery cell,
(1) The back surface protection sheet for solar cells is composed of a laminate of one layer or two layers, at least one of which is composed of Fe, Cu, Ni, Cr, Bi, Mn, Sr, Y, and Al. Containing a composite metal oxide comprising two or more metals selected from the group,
(2) The back surface protection sheet for solar cells is black with an average reflectance in the wavelength region of 400 to 750 nm of 10% or less, and the average reflectance in the wavelength region of 750 to 2000 nm is 50% or more.
The back surface protection sheet for solar cells characterized by the above-mentioned.
[Selection figure] None

Description

  The present invention relates to a solar cell back surface protective sheet disposed on the back surface side of a solar battery cell.

  A solar battery back surface protection sheet is generally laminated on the back surface side of the solar battery cell, and these are collectively referred to as a solar battery module.

  When the solar cell module is arranged on the roof or roof of a building, it may be required that the solar cell back surface protection sheet be black in consideration of appearance and design. Therefore, conventionally, as a black solar cell back surface protection sheet, for example, a mode using a black resin film kneaded with a black pigment such as carbon black, and a black coating as a base resin film (for example, polyethylene terephthalate film) There have been proposed an embodiment using an applied material, an embodiment in which a black pigment such as carbon black is added to an adhesive layer for bonding resin films (Patent Documents 1 and 2, etc.).

  However, the conventional solar cell back surface protection sheet using carbon black as a black pigment is inferior in electrical insulation, absorbs light in the near infrared region and infrared region of sunlight, and the back surface protection sheet for solar cells and It has been pointed out as a problem that the temperature of the solar battery cell easily rises and the power generation efficiency decreases. In particular, when the solar battery cell is based on crystalline silicon, the power generation efficiency is said to decrease at a rate of about 0.4% / ° C. due to the temperature rise.

  Therefore, development of the back surface protection sheet for black solar cells in which absorption of light in the near infrared region and infrared region of sunlight is suppressed is desired.

JP 2009-249421 JP 2011-091303 JP

  An object of this invention is to provide the back surface protection sheet for black solar cells by which absorption of the light of the near-infrared region and infrared region of sunlight is suppressed.

  As a result of intensive studies to achieve the above object, the inventor of the present invention includes a specific composite metal oxide in the layer constituting the solar cell back surface protective sheet, so that the light of the solar cell back surface protective sheet can be obtained. The present inventors have found that the above object can be achieved when the reflectance of the light source is controlled within a specific range, and the present invention has been completed.

That is, this invention relates to the following back surface protection sheet for solar cells.
1. A solar cell back surface protective sheet disposed on the back side of a solar cell,
(1) The back surface protection sheet for solar cells is composed of a laminate of one layer or two layers, at least one of which is composed of Fe, Cu, Ni, Cr, Bi, Mn, Sr, Y, and Al. Containing a composite metal oxide comprising two or more metals selected from the group,
(2) The back surface protection sheet for solar cells is black with an average reflectance in the wavelength region of 400 to 750 nm of 10% or less, and the average reflectance in the wavelength region of 750 to 2000 nm is 50% or more.
The back surface protection sheet for solar cells characterized by the above-mentioned.
2. Of the layers constituting the solar cell back surface protective sheet, the layer closest to the back surface of the solar cell contains polyethylene having a density of 0.90 to 0.93 g / cm ³ as a resin component. Back protection sheet for solar cells.
3. The solar cell back surface protective sheet according to item 1 or 2, wherein a layer closest to the back surface of the solar cell among the layers constituting the solar cell back surface protective sheet contains the composite metal oxide.
4. A solar cell module comprising the solar cell and the back surface protective sheet for solar cell according to any one of Items 1 to 3 disposed on the back side thereof.

  Hereinafter, the back surface protection sheet for solar cells of this invention and the solar cell module which has arrange | positioned it to the back surface side of a photovoltaic cell are demonstrated in detail.

Back surface protection sheet for solar cells The back surface protection sheet for solar cells of the present invention is disposed on the back surface side of the solar cells,
(1) The back surface protection sheet for solar cells is composed of a laminate of one layer or two layers, at least one of which is composed of Fe, Cu, Ni, Cr, Bi, Mn, Sr, Y, and Al. Containing a composite metal oxide comprising two or more metals selected from the group,
(2) The back surface protection sheet for solar cells is black with an average reflectance in the wavelength region of 400 to 750 nm of 10% or less, and the average reflectance in the wavelength region of 750 to 2000 nm is 50% or more.
It is characterized by that.

  The back surface protection sheet for solar cells of the present invention having the above characteristics is selected from the group consisting of Fe, Cu, Ni, Cr, Bi, Mn, Sr, Y and Al in the layer constituting the back surface protection sheet for solar cells. By containing the composite metal oxide containing two or more kinds of metals, the average light reflectance of the back surface protection sheet for solar cells is controlled within a predetermined range. Specifically, when the average reflectance in the wavelength region of 400 to 750 nm is 10% or less, the solar cell back surface protective sheet is black when viewed from the solar cell arrangement side. In addition, since the average reflectance in the wavelength range of 750 to 2000 nm (near infrared region and infrared region) is 50% or more, light absorption in the near infrared region and infrared region is suppressed, and power generation efficiency due to temperature rise The decline of the is suppressed. Moreover, since reflected light can be re-incident on a photovoltaic cell, the utilization factor of sunlight can be raised. Specifically, the effect of improving the power generation efficiency by the effective use of light is obtained particularly when the average reflectance in the wavelength region of 750 to 1200 nm is 50% or more. In particular, when the average reflectance in the wavelength region of 1200 to 2000 nm is 50% or more, the effect of suppressing the temperature rise of the solar cell module can be obtained.

  The layer structure of the back surface protective sheet for solar cell of the present invention is composed of one or two or more layers, and the composite metal oxide is contained in any one of the layers, thereby providing a predetermined average reflectance requirement. For example, the two-layer configuration illustrated in FIG. 1 (the adhesive layer is not counted as a layer) can be exemplified as a preferred embodiment.

  In the solar cell back surface protective sheet 10 shown in FIG. 1, the first resin layer 11 and the second resin layer 12 that are closest to the back surface of the solar battery cell are bonded by an adhesive layer 13. With this layer configuration, it is preferable that the first metal layer 11 contains the composite metal oxide in order to more easily satisfy a predetermined average reflectance requirement. And when the back surface protection sheet for solar cells is visually recognized from the solar cell side, it is black, and the light in the near infrared region and infrared region of sunlight is efficiently reflected to further reduce the power generation efficiency due to the temperature rise. It can be surely suppressed.

Hereinafter, the layer configuration of FIG. 1 will be described as a representative example.
≪First resin layer≫
The resin component constituting the first resin layer is not particularly limited. For example, polyethylene (PE) (high-density polyethylene, low-density polyethylene, linear low-density polyethylene (LLDPE)), polypropylene (PP), polyolefin-based polyolefin such as polybutene, etc. Resin, (meth) acrylic resin, polyvinyl chloride resin, polystyrene resin, polyvinylidene chloride resin, saponified ethylene-vinyl acetate copolymer, polyvinyl alcohol, polycarbonate resin, fluorine resin (polyvinylidene fluoride, Polyvinyl fluoride, ethylene tetrafluoroethylene), polyvinyl acetate resin, acetal resin, polyester resin (polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate), polyamide resin, polyphenylene ether resin, etc. The film or sheet of can be used. These films or sheets contain one or more resin components and may be stretched in a uniaxial or biaxial direction.

  Generally, a sealing material is disposed in the lowermost layer of the solar battery cell, and an ethylene-vinyl acetate copolymer (EVA) is widely used as the material of the sealing material. Since the adhesiveness between the sealing material and the back surface protection sheet for solar cells affects the long-term reliability of the solar cell module, the resin component constituting the first resin layer has an adhesive property in consideration of the material of the sealing material. It is preferable to select from a point.

For example, when the sealing material is EVA, polyethylene (PE) (high density polyethylene, low density polyethylene, linear low density polyethylene (LLDPE)) is preferable as the resin component, and among these, LLDPE is more preferable. In the present invention, when LLDPE having a density of 0.90 to 0.93 g / cm ³ is used as the resin component of the first resin layer and the first resin layer contains a composite metal oxide, the density of the first resin layer is 1.00. It is preferable to set to about ˜2.00 g / cm ³ .

  In the present invention, as described above, it is preferable that the first resin layer contains a composite metal oxide. The composite metal oxide used in the present invention is a composite metal oxide (solid solution) containing two or more metals selected from the group consisting of Fe, Cu, Ni, Cr, Bi, Mn, Sr, Y and Al. . The composite metal oxide can be obtained by firing a mixture of these two or more metals at 800 to 1400 ° C. to form a composite. The obtained composite metal oxide is black, and the first resin layer is black by containing the composite metal oxide in the first resin layer, and the black is also seen when the solar battery back surface protection sheet is viewed from the solar battery cell side. It becomes. The average particle diameter of the composite metal oxide is not limited, but is appropriately selected in consideration of the thickness of the resin layer containing the composite metal oxide and the content of the composite metal oxide.

  Commercially available products can also be used as the black composite metal oxide. For example, (Product name “Black 6350”, Fe—Cr composite oxide), (Product name “Black 6301”, Mn—Bi composite) Oxide), (Product name "Black 6302", Mn-Sr complex oxide), (Product name "Black 6303", Mn-Y complex oxide), (Product name "Black 3702", Cu-Cr series) (Composite oxide), (Product name "Black 3250", Cu-Cr-Mn composite oxide), (Product name "Black 3500", Cu-Fe-Cr composite oxide), (Product name "Black 8057" , Co-Ni-Fe-Mn complex oxide), (Product name "Black 3078", Fe-Mn-Al complex oxide), (Product name "Black 3331", Cu-Fe-Mn complex oxide) ) And (product name “Black 3300”, Cu—Fe—Mn-based composite oxide) (all manufactured by Asahi Sangyo Co., Ltd.).

  In addition, the composite metal oxide is within a range that does not affect the predetermined average reflectance, Co, Zn, Al, Si, Cr, Ti, Ni, P, Ba, Sr, Ti, Cr, Sb, Fe, Zn Etc. may further be included. In that case, it may be fired in a state containing these metals and combined.

  When the first resin layer contains a composite metal oxide, it is preferable to contain about 5 to 40 parts by weight of the composite metal oxide with respect to 100 parts by weight of the resin component constituting the first resin layer. It is more preferable to contain ~ 20 parts by weight. If the content of the composite metal oxide is less than 5 parts by weight, the degree of black may be insufficient, and a desired average reflectance is difficult to obtain. On the other hand, when the content of the composite metal oxide exceeds 40 parts by weight, it is difficult to obtain an effect corresponding to the content, and the cost is increased.

  In the present invention, an average reflectance of 10% or less in a wavelength region of 400 to 750 nm means black, but this average reflectance is measured by a spectrophotometer (product name “V-570”). , Manufactured by JASCO Corporation), the average value of the values measured at intervals of 2 nm for the reflectance in the wavelength region of 400 to 750 nm. And if an average reflectance is 10% or less, the request | requirement of black designability can be satisfy | filled. The same applies to the method of measuring the average reflectance in other wavelength regions.

  As described above, since black is contained by containing a specific composite metal oxide, it absorbs light in the near infrared region and infrared region of sunlight as compared with the case of using a single color black pigment (such as carbon black). Can be suppressed. And since the average reflectance in the wavelength region of 750 to 2000 nm of the back surface protective sheet for solar cells is 50% or more, the light in the near infrared region and the infrared region is efficiently reflected, and the power generation efficiency decreases due to the temperature rise. Is suppressed. Specifically, the effect of improving the power generation efficiency by the effective use of light is obtained particularly when the average reflectance in the wavelength region of 750 to 1200 nm is 50% or more. In particular, when the average reflectance in the wavelength region of 1200 to 2000 nm is 50% or more, the effect of suppressing the temperature rise of the solar cell module can be obtained. Moreover, since the composite metal oxide used by this invention is excellent in weather resistance, the solar cell back surface protection sheet excellent in weather resistance can be produced.

  This is because most of the light is absorbed in all wavelengths in the visible, near-infrared, and infrared regions when a monochromatic black pigment is used for the first resin layer. When the metal oxide is used to make it black, the visible wavelength is absorbed, but the near-infrared and infrared wavelengths are hardly absorbed and reflected. Therefore, light in the near-infrared and infrared wavelengths can be re-entered into the solar cell by reflecting it with the first resin layer. Efficiency can be further increased.

  As a method for forming the first resin layer, for example, T-die extrusion molding, inflation molding, or the like can be used. It can also be formed by multilayer extrusion simultaneously with the second resin layer described later. As a method of adding the composite metal oxide to the first resin layer, a masterbatch containing the composite metal oxide is prepared in advance, and a predetermined amount of the masterbatch is mixed with the matrix resin of the first resin layer for various molding methods. It is preferable to provide. Here, the resin component contained in the masterbatch is preferably the same component as the matrix resin of the first resin layer, and the content of the composite metal oxide in the masterbatch is 100% by weight of the resin component in the masterbatch. The amount of the composite metal oxide is preferably 20 to 70 parts by weight with respect to the part, and preferably 40 to 60 parts by weight in consideration of the dispersion state at the time of forming the first resin layer.

The thickness of the first resin layer is not limited and can be appropriately set according to the properties of the final product, but is preferably 30 to 200 μm, more preferably 50 to 100 μm. When the first resin layer contains a composite metal oxide, if the thickness is less than 30 μm, it may be difficult to obtain sufficient reflectivity in the near-infrared region and the infrared region. On the other hand, when the thickness exceeds 100 μm, the effect is saturated and the cost becomes high.
≪Second resin layer≫
The second resin layer is preferably excellent in weather resistance and electrical insulation. Examples of the resin component constituting the second resin layer include polyethylene (PE) (high-density polyethylene, low-density polyethylene, linear low-density polyethylene (LLDPE)), polypropylene (PP), polyolefin resins such as polybutene, ( (Meth) acrylic resin, polyvinyl chloride resin, polystyrene resin, polyvinylidene chloride resin, saponified ethylene-vinyl acetate copolymer, polyvinyl alcohol, polycarbonate resin, fluorine resin (polyvinylidene fluoride, polyvinyl fluoride) , Ethylene tetrafluoroethylene), polyvinyl acetate resin, acetal resin, polyester resin (polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate), polyamide resin, polyphenylene ether resin, etc. Can use a sheet. These films or sheets may contain one or more resin components and may be stretched in a uniaxial or biaxial direction.

  When the second resin layer is composed of a single layer film, the thickness is preferably 50 to 300 μm, and more preferably 75 to 250 μm.

  When the second resin layer is composed of a laminated film, a laminate of a film having excellent weather resistance and a film having excellent electrical insulation is preferable. In this case, the film having excellent electrical insulation is disposed on the first resin layer side. As a film excellent in weather resistance, a fluorine-based film (at least one of polyvinylidene fluoride, polyvinyl fluoride, and ethylene tetrafluoroethylene) having a thickness of 10 to 150 μm is particularly preferable. Moreover, as a film excellent in electrical insulation, a PET film having a thickness of 50 to 250 μm is particularly preferable.

  A white pigment such as titanium oxide or barium sulfate may be added to the second resin layer for the purpose of absorbing or reflecting light in the ultraviolet region. At this time, if the first resin layer contains a composite metal oxide and is black, even if a white pigment is added to the second resin layer, the black design when viewed from the solar cell side Does not affect. When the first resin layer does not contain the composite metal oxide, the second resin layer contains the composite metal oxide, but at this time, the first resin layer contains the composite metal oxide so as not to affect the black color of the second resin layer. It is preferable not to add a white pigment to one resin layer.

Also, other than the color pigment, known additives such as ultraviolet absorbers, moisture absorbers (drying agents), oxygen absorbers, and antioxidants are added to the second resin layer as long as the effects of the present invention are not affected. Instead, it may be added to the first resin layer.
≪Adhesive layer≫
An adhesive layer may be provided between the first resin layer and the second resin layer as necessary. For example, when the first resin layer and the second resin layer are laminated by an extrusion coating method, a dry lamination method, a thermal lamination method, or the like, it is preferable to provide an adhesive layer between the layers.

  Examples of the adhesive layer include a two-component curable urethane adhesive, a polyether urethane adhesive, a polyester adhesive, a polyester polyol adhesive, and a polyester polyurethane polyol adhesive. Among these, the dry lamination method using the urethane type adhesive agent containing at least 1 sort (s) of aromatic isocyanate and aliphatic isocyanate can be employ | adopted suitably.

  As thickness of an adhesive bond layer, 3-15 micrometers is preferable and 5-10 micrometers is more preferable.

Solar cell module The back surface protective sheet for solar cell of the present invention is a solar cell module by being arranged on the back surface side of the solar cell. The configuration of the solar battery cell is not limited, but a configuration in which a tempered glass for a solar battery, EVA, a crystalline Si cell, and EVA (encapsulant) are stacked in this order from the front surface is common.

  The solar cell back surface protective sheet according to the present invention includes two types selected from the group consisting of Fe, Cu, Ni, Cr, Bi, Mn, Sr, Y, and Al in the layer constituting the solar cell back surface protective sheet. By containing the composite metal oxide containing the above metal, the average reflectance of light of the back protective sheet for solar cells is controlled within a predetermined range. Specifically, when the average reflectance in the wavelength region of 400 to 750 nm is 10% or less, the solar cell back surface protective sheet is black when viewed from the solar cell arrangement side. In addition, since the average reflectance in the wavelength range of 750 to 2000 nm (near infrared region and infrared region) is 50% or more, light absorption in the near infrared region and infrared region is suppressed, and power generation efficiency due to temperature rise The decline of the is suppressed. Moreover, since reflected light can be re-incident on a photovoltaic cell, the utilization factor of sunlight can be raised. Specifically, the effect of improving the power generation efficiency by the effective use of light is obtained particularly when the average reflectance in the wavelength region of 750 to 1200 nm is 50% or more. In particular, when the average reflectance in the wavelength region of 1200 to 2000 nm is 50% or more, the effect of suppressing the temperature rise of the solar cell module can be obtained.

It is the figure which illustrated the layer structure of the back surface protection sheet for solar cells of this invention. FIG. 3 is a schematic diagram of a temperature rise comparison device (made of wooden box) for examining a temperature rise comparison of solar cell modules in Test Example 1.

  The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

Example 1
For 100 parts by mass of LLDPE (product name “Evolue”, manufactured by Mitsui Chemicals, Inc.) with a density of 0.91 g / cm ³ , composite metal oxide (product name “Black 6302”, Mn-Sr composite oxide, Asahi Industries 65 parts by weight) was added and sufficiently kneaded to prepare an LLDPE masterbatch.

LLDPE masterbatch is added so that the content of the composite metal oxide is 20 parts by weight with respect to 100 parts by weight of LLDPE (product name “Evolue”, manufactured by Mitsui Chemicals, Inc.) with a density of 0.92 g / cm ³ Film formation by a T-die extruder was performed to obtain a black LLDPE film (density 1.03 g / cm ³ ) having a thickness of 50 μm as the first resin layer.

  Prepare a PET film (made by Teijin) with a thickness of 255μm as the second resin layer, and adhere it to the first resin layer by the dry laminating method using the dry laminating adhesive, Produced.

The adhesive for dry laminating is a polyurethane adhesive in which 100 parts by mass (product name “Takelac A315”, manufactured by Mitsui Chemicals) and 10 parts by mass (product name “Takenate A50”, manufactured by Mitsui Chemicals) are mixed. The solid content was adjusted to 5 g / m ² and used.

Example 2
Example 1 except that the content of the composite metal oxide was 40 parts by weight with respect to 100 parts by weight of LLDPE (product name “Evolue” manufactured by Mitsui Chemicals, Inc.) with a density of 0.924 g / cm ³ A black back surface protection sheet for solar cell was prepared.

Example 3
As the first resin layer, an LLDPE film (density 0.924 g / cm ³ ) with a thickness of 50 μm was prepared.

  20 parts by weight of the composite metal oxide used in Example 1 is added to 100 parts by weight of PET (product name “Byron”, manufactured by Toyobo Co., Ltd.), sufficiently dispersed by a twin-screw kneader, and T-die extrusion Film formation was performed by a machine, and a black PET film having a thickness of 250 μm was obtained as the second resin layer.

  The second resin layer was adhered to the first resin layer by a dry laminating method using a dry laminating adhesive, thereby producing a black solar cell back surface protective sheet.

  The dry laminating adhesive is the same as that used in Example 1.

Comparative Example 1
As the first resin layer, a transparent PE film (manufactured by Tosero) with a thickness of 50 μm was prepared.

  As the second resin layer, a transparent PET film with a thickness of 250 μm (manufactured by Teijin) and black ethylenetetrafluoroethylene (ETFE) (manufactured by Asahi Kasei) with a thickness of 25 μm were adhered by a dry laminating method using an adhesive for dry laminating. A laminated film was prepared. The black pigment contained in black ETFE is only carbon black.

  The second resin layer was adhered to the first resin layer by a dry laminating method using a dry laminating adhesive, thereby producing a black solar cell back surface protective sheet.

  The dry laminating adhesive is the same as that used in Example 1.

Comparative Example 2
20 parts by weight of carbon black was added to 100 parts by mass of LLDPE (product name “Evolue”, manufactured by Mitsui Chemicals, Inc.) having a density of 0.910 g / cm ³ and sufficiently kneaded to prepare an LLDPE master batch.

Add LLDPE masterbatch so that the content of carbon black is 5 parts by weight with respect to 100 parts by weight of LLDPE (product name “Evolue” manufactured by Mitsui Chemicals, Inc.) with a density of 0.924 g / cm ³ Film formation by an extruder was performed to obtain a black LLDPE film (density 0.93 g / cm ³ ) having a thickness of 50 μm as the first resin layer.

  Prepare a PET film (manufactured by Teijin) with a thickness of 250 μm as the second resin layer, and adhere it to the first resin layer by the dry laminating method using an adhesive for dry laminating. Produced.

  The dry laminating adhesive is the same as that used in Example 1.

Test example 1
The average reflectance in each wavelength range of 400 to 750 nm (visible range) and 750 to 2000 nm (near infrared range and infrared range) of the black solar cell back surface protective sheet prepared in Examples and Comparative Examples, and a solar cell module A comparison of temperature rise was made.
<Average reflectance>
The average reflectance in each wavelength range was measured with a spectrophotometer (product name “V-570”, manufactured by JASCO Corporation).

The measurement results are shown in Table 1 below.
<Temperature rise comparison>
Solar cell tempered glass, EVA, crystalline Si cell and EVA (sealing material) were laminated in this order, and a solar cell was produced with a vacuum laminator (manufactured by NPC, LM-140X200S). The sealing material EVA is the back surface of the solar battery cell.

  Next, each solar cell back surface protection sheet obtained in Examples and Comparative Examples was attached to the back surface of the solar cell, and a solar cell module was produced using a vacuum laminator.

  The temperature rise comparison of each solar cell module was performed. Specifically, a black solar cell back surface protection sheet as an example and a black solar cell back surface protection sheet as a comparative example are disposed at each position of the temperature rise comparison device (made of wooden box) shown in FIG. did. Specifically, “Comparative Example 1 and Example 1”, “Comparative Example 1 and Example 2”, “Comparative Example 2 and Example 2” and “Comparative Example 2 and Example 3” are compared with the temperature. An increase comparison was made.

  The back surface protection sheets for black solar cells of Examples and Comparative Examples were arranged so as to be equidistant from the heat source (incandescent bulb), respectively. Install two thermocouples at the specified positions on the tempered glass side for solar cells and the back protective sheet side for black solar cells, turn on the heat source (incandescent bulb), compare the temperature rise values in time series, and The difference was compared. The temperature difference is calculated by (Example side) − (Comparative example side), and if the value is − (negative), it indicates that the temperature increase in the Example is suppressed more than that in the Comparative example.

  Table 1 shows the measurement results.

  As is clear from the results in Table 1, the average reflectance in the wavelength region of 750 to 2000 nm (near infrared region and infrared region) is remarkably large although the solar cell modules of Examples 1 to 3 are black, Compared with Comparative Examples 1 and 2, the temperature rise is remarkably suppressed.

10. Back protection sheet for solar cells
11. First resin layer
12. Second resin layer
13. Adhesive layer

Claims (4)

A solar cell back surface protection sheet disposed on the back surface side of the solar battery cell,
(1) The back surface protection sheet for solar cells is composed of a laminate of one layer or two layers, at least one of which is composed of Fe, Cu, Ni, Cr, Bi, Mn, Sr, Y, and Al. Containing a composite metal oxide comprising two or more metals selected from the group,
(2) The back surface protection sheet for solar cells is black with an average reflectance in the wavelength region of 400 to 750 nm of 10% or less, and the average reflectance in the wavelength region of 750 to 2000 nm is 50% or more.
The back surface protection sheet for solar cells characterized by the above-mentioned. 2. The solar cell according to claim 1, wherein a layer closest to the back surface of the solar battery cell among the layers constituting the back protective sheet for solar cell contains polyethylene having a density of 0.90 to 0.93 g / cm ³ as a resin component. Back surface protection sheet.   3. The solar cell back surface protective sheet according to claim 1, wherein a layer closest to the back surface of the solar battery cell among the layers constituting the solar cell back surface protective sheet contains the composite metal oxide.   4. A solar cell module comprising the solar cell and the back surface protective sheet for solar cell according to claim 1, which is disposed on the back surface side of the solar cell.

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