JP2020161630A - Solar cell module and mobile body - Google Patents

Abstract

To provide a solar cell module in which a solar cell is less likely to be damaged or a tab wiring is not easily broken even if there is a temperature change.SOLUTION: A solar cell module includes in order from a light receiving surface side: a surface protection substrate 20; a first sealing material layer 22; a photoelectric conversion unit 10, a second sealing material layer 24, and a back surface protective substrate 26. The second sealing material layer 24 includes: a filler-containing layer 24A containing a granular filler 28 having a primary dispersion diameter of 10 to 600 nm; and a filler-free layer 24B containing no filler.SELECTED DRAWING: Figure 3

Description

The present invention relates to a solar cell module and a moving body.

The solar cell module has, as a basic configuration, a first substrate (surface protection substrate), a first resin layer (encapsulating material layer), a photoelectric conversion unit, and a second resin layer (encapsulating material layer). ) And the second substrate (back surface protection substrate) are provided in this order. That is, the photoelectric conversion unit is protected by covering the front and back surfaces of the photoelectric conversion unit with the first substrate, the first resin layer, the second resin layer, and the second substrate. In such a configuration, in the photoelectric conversion unit, a plurality of solar cells are arranged in a matrix, and adjacent solar cells are electrically connected to each other by tab wiring. Then, in this way, the photoelectric conversion unit electrically connects a plurality of solar cells to each other by a plurality of tab wirings so as to increase the output voltage, for example.

Conventionally, a glass substrate has been generally used as the surface protection substrate of the solar cell module, but in recent years, a resin substrate has been used instead of the glass substrate for weight reduction (Patent Documents). 1). Then, since the optimum material for the front and back protective substrates is selected according to each role, the materials for the front and back protective substrates have become different.

Japanese Unexamined Patent Publication No. 2013-145807

Generally, the coefficient of linear expansion of resin is larger than the coefficient of linear expansion of glass, and the influence of thermal expansion and contraction due to temperature change is large. Then, when the surface protection substrate made of resin is thermally expanded and contracted, stress is applied to the resin layer that adheres to the surface protection substrate. Therefore, the thermal stress of the surface protection substrate and the resin layer tends to increase in proportion to the degree of temperature change that occurs in the solar cell module.

When a large thermal stress is applied to the resin layer due to the temperature change generated in the solar cell module, the solar cell in contact with the resin layer may be damaged, or the tab wiring electrically connecting the solar cells may be cut. There is a risk of

The present invention has been made in view of the problems of the prior art. An object of the present invention is to provide a solar cell module in which the solar cell is less likely to be damaged or the tab wiring is not easily broken even when a temperature change occurs.

In order to solve the above problems, the solar cell module according to the aspect of the present invention includes a surface protection substrate, a first encapsulant layer, a photoelectric conversion unit, and a second encapsulant layer in order from the light receiving surface side. , A back surface protective substrate, and at least one of the first encapsulant layer and the second encapsulant layer is a granular filler having a primary dispersion diameter of 10 to 600 nm or an average fiber diameter of 0.3 to 0. It contains a filler-containing layer containing 6 μm fibrous filler and a filler-free layer containing neither the granular filler nor the fibrous filler.

According to the present disclosure, it is possible to provide a solar cell module in which the solar cell is less likely to be damaged or the tab wiring is not easily broken even when a temperature change occurs.

FIG. 1 is a top view showing a solar cell module according to the present embodiment. FIG. 2 is a partial cross-sectional view of the solar cell module shown in FIG. FIG. 3 is a partial cross-sectional view showing the solar cell module shown in FIG. 2 in a further enlarged manner. FIG. 4 is a partial cross-sectional view of a solar cell module having a form different from that of the solar cell module shown in FIG. FIG. 5 is a partial cross-sectional view of a solar cell module having a form different from that of the solar cell module shown in FIG. FIG. 6 is a partial cross-sectional view showing an enlarged main part of the solar cell module shown in FIG. FIG. 7 is a graph showing changes in the coefficient of linear expansion with respect to the filler content in the filler-containing layers of Reference Examples 1 to 3. FIG. 8 is a graph showing the change in elastic modulus with respect to the filler content in the filler-containing layers of Reference Examples 1 to 3. FIG. 9 is a graph showing changes in elastic modulus with respect to measurement temperature in Examples 1 and 2 and Comparative Example 1.

Hereinafter, the solar cell module according to the present embodiment will be described in detail. The dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

<Solar cell module>
Hereinafter, the solar cell module according to the present embodiment will be described with reference to the drawings. FIG. 1 is a top view showing the solar cell module 100 according to the present embodiment. As shown in FIG. 1, a Cartesian coordinate system including an x-axis, a y-axis, and a z-axis is defined. The x-axis and y-axis are orthogonal to each other in the plane of the solar cell module 100. The z-axis is perpendicular to the x-axis and the y-axis and extends in the thickness direction of the solar cell module 100. Further, the positive directions of the x-axis, the y-axis, and the z-axis are defined in the direction of the arrow in FIG. 1, and the negative direction is defined in the direction opposite to the arrow. Of the two main surfaces forming the solar cell module 100 and parallel to the xy plane, the main plane arranged on the positive side of the z-axis is the "light receiving surface". The main plane arranged on the negative side of the z-axis is the "back surface". The "light receiving surface" means a surface on which light is mainly incident, and the "back surface" may mean a surface opposite to the light receiving surface. Further, the positive direction side of the z-axis is sometimes called the "light receiving surface side", and the negative direction side of the z-axis is sometimes called the "back surface side".

The solar cell module 100 includes a plurality of solar cell cells 10, a plurality of tab wirings 12, and a plurality of connection wirings 14. Each of the plurality of solar cell 10s absorbs incident light and generates a photovoltaic force. The solar cell 10 is formed of, for example, a semiconductor material such as crystalline silicon, gallium arsenide (GaAs) or indium phosphide (InP). The structure of the solar cell 10 is not particularly limited, but here, as an example, it is assumed that crystalline silicon and amorphous silicon are laminated. Although omitted in FIG. 1, on the light receiving surface and the back surface of each solar cell 10, a plurality of finger electrodes extending in the x-axis direction parallel to each other and extending in the y-axis direction so as to be orthogonal to the plurality of finger electrodes. A plurality of, for example, two bus bar electrodes are provided. The busbar electrode connects each of the plurality of finger electrodes.

The plurality of solar cell 10s are arranged in a matrix on the xy plane. Here, four solar cells 10 are arranged in the x-axis direction, and five solar cells 10 are arranged in the y-axis direction. The number of solar cells 10 arranged in the x-axis direction and the number of solar cells 10 arranged in the y-axis direction are not limited to these. The five solar cells 10 arranged side by side in the y-axis direction are connected in series by the tab wiring 12 to form one solar cell string 16. Further, as described above, since the four solar cells 10 are arranged in the x-axis direction, the four solar cell strings 16 extending in the y-axis direction are arranged in parallel in the x-axis direction.
The solar cell string 16 indicates a combination of a plurality of solar cell cells 10 and a plurality of tab wirings 12.

In order to form the solar cell string 16, the tab wiring 12 electrically connects the bus bar electrode on the light receiving surface side of one of the adjacent solar cell 10s and the bus bar electrode on the other back surface side. That is, the adjacent solar cells 10 are electrically connected to each other by the tab wiring 12. The tab wiring 12 is an elongated metal foil, and for example, a copper foil coated with solder, silver, or the like is used. Resin is used to connect the tab wiring 12 and the bus bar electrode. This resin may be either conductive or non-conductive. In the latter case, the tab wiring 12 and the bus bar electrode are brought into direct contact with each other to be electrically connected. Further, the tab wiring 12 and the bus bar electrode may be connected by solder instead of resin.

Further, on the positive and negative directions of the y-axis of the solar cell string 16, a plurality of connection wirings 14 extend in the x-axis direction, and the connection wiring 14 electrically connects two adjacent solar cell strings 16. Connecting. In the above configuration, each of the solar cell 10 and the solar cell string 16 may be a "photoelectric conversion unit", and the combination of the plurality of solar cell strings 16 and the connection wiring 14 is a "photoelectric conversion unit". May be good. A frame (not shown) may be attached to the edge of the solar cell module 100. The frame protects the edge portion of the solar cell module 100 and is used when the solar cell module 100 is installed on a roof or the like.

The solar cell module of the present embodiment includes a front surface protection substrate, a first encapsulant layer, a photoelectric conversion unit, a second encapsulant layer, and a back surface protection substrate in this order from the light receiving surface side. Then, at least one of the first encapsulant layer and the second encapsulant layer has a filler-containing layer containing a predetermined filler and a filler-free layer not containing the filler. The first encapsulant layer or the second encapsulant layer having the filler-containing layer and the filler-free layer has a low coefficient of thermal expansion and a high elastic modulus (tensile elastic modulus) due to the presence of the filler-containing layer. On the other hand, the filler-free layer has a low elastic modulus. As described above, the filler-containing layer and the filler-free layer having different physical properties are combined, and the encapsulant layer having both layers is less likely to undergo thermal expansion due to a temperature change and has high flexibility. As a result, the movement (displacement) of the solar cell can be suppressed, and the tab wiring and the solar cell can be prevented from being damaged or the tab wiring can be prevented from being broken.

FIG. 2 is a cross-sectional view showing a part of the solar cell module 100 along the line AA of FIG. The solar cell module 100 includes a solar cell 10, a tab wiring 12, a connection wiring 14, a solar cell string 16, a surface protection substrate 20, a first encapsulant layer 22, a second encapsulant layer 24, and a back surface protective layer 26. I have. The upper side of FIG. 2 corresponds to the light receiving surface (front surface) side, and the lower side corresponds to the back surface side. Therefore, in the solar cell module 100, in order from the light receiving surface side, the surface protection substrate 20, the first sealing material layer 22, the photoelectric conversion unit (solar cell 10, tab wiring 12, connection wiring 14), and the second The sealing material layer 24 and the back surface protective layer 26 are laminated. Note that FIG. 2 does not show the filler-containing layer and the filler-free layer described later.
Each layer will be described below in sequence.

[Surface protection board]
The surface protection substrate 20 is located on the sunlight receiving surface side of the solar cell module 100 and is a substrate made of a transparent resin. Examples of the transparent resin constituting the surface protection substrate 20 include polyethylene (PE), polypropylene (PP), cyclic polyolefin, polycarbonate (PC), polymethylmethacrylate (PMMA), polytetrafluoroethylene (PTFE), and polystyrene (PS). ), Polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), at least one selected from the group can be used. Among these, it is preferable to use polycarbonate (PC) as the surface protection substrate 20. This is because polycarbonate (PC) is excellent in impact resistance and translucency, and is therefore suitable for protecting the surface of the solar cell module 100. Further, the surface protection substrate 20 may include a hard coat layer made of silicon-based or acrylic urethane-based on its surface. Further, the surface protection substrate 20 or the hard coat layer may contain an ultraviolet absorber, a gloss adjuster, and an antireflection component.

The thickness of the surface protection substrate 20 is preferably 2 to 6 mm, more preferably 3 to 5 mm. In the present embodiment, the thickness of the back surface protective layer 26 is 10% or less of the thickness of the front surface protection substrate 20, but conversely, the thickness of the front surface protection substrate 20 is the thickness of the back surface protection layer 26. It is more than 10 times that. That is, the mechanical strength that is lowered because the back surface protective layer 26 is thin is guaranteed by the thick surface protective substrate 20. By setting the thickness of the surface protection substrate 20 in such a range, the solar cell module 100 can be appropriately protected and light can efficiently reach the photoelectric conversion unit (solar cell 10).

The tensile elastic modulus of the surface protective substrate 20 is preferably 1.0 to 10.0 GPa, and more preferably 2.3 to 2.5 GPa. By setting the tensile elastic modulus of the surface protection substrate 20 in such a range, the surface of the solar cell module 100 can be appropriately protected. The tensile elastic modulus can be measured by, for example, JIS K7161-1 (Plastic-How to obtain tensile properties-Part 1: General rules) as follows.
Et = (σ2-σ1) / (ε2-ε1) (1)
In the above formula (1), Et represents the tensile elastic modulus (Pa), σ1 represents the stress at strain ε1 = 0.0005 (Pa), and σ2 represents the stress at strain ε2 = 0.0025 (Pa).

The total light transmittance of the surface protection substrate 20 is preferably 80% or more, and preferably 90 to 100%. By setting the total light transmittance of the surface protection substrate 20 in this range, light can be efficiently reached to the photoelectric conversion unit (solar cell 10). The total light transmittance can be measured by, for example, JIS K7361-1 (Plastic-Transparent Material Total Light Transmittance Test Method-Part 1: Single Beam Method).

The coefficient of thermal expansion of the surface protection substrate 20 is not particularly limited and may be 40 to 110 (× 10 ^-6 K ^-1 ). The coefficient of thermal expansion can be measured according to JIS K 7197: 2012.

[1st encapsulant layer, 2nd encapsulant layer]
The first encapsulant layer 22 and the second encapsulant layer 24 seal the photoelectric conversion portion. The first encapsulant layer 22 is arranged on the lower side of the front surface protection substrate 20, and the second encapsulant layer 24 is arranged on the upper side of the back surface protection layer 26.

The first encapsulant layer 22 is preferably located on the upper side (light receiving side) of the photoelectric conversion unit and has translucency because it transmits light and guides it to the photoelectric conversion unit. Specifically, the total light transmittance of the first encapsulant layer 22 is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. Further, the total light transmittance of the first encapsulant layer 22 may be 100% or less, or 95% or less. By setting the total light transmittance of the first encapsulant layer 22 in such a range, light can be efficiently reached to the solar cell 10. Further, the total light transmittances of the first encapsulant layer 22 and the second encapsulant layer 24 may be the same or different from each other. In the present specification, the total light transmittance can be measured by a method such as JIS K7361-1 (test method for total light transmittance of plastic-transparent material-Part 1: single beam method).

The sealing material used for the first sealing material layer 22 and the second sealing material layer 24 includes, for example, at least one resin selected from the group consisting of a thermoplastic resin, a thermosetting resin, and a gel. Is preferable. These resins may be modified resins or unmodified resins. The thermoplastic resin is, for example, at least one resin selected from the group consisting of ethylene-vinyl acetate copolymer (EVA), olefin resin, polyvinyl butyral (PVB), polyethylene terephthalate (PET) and polyimide (PI). Is preferably contained. The thermosetting resin preferably contains, for example, at least one resin selected from the group consisting of epoxy, urethane and polyimide. The gel preferably contains, for example, at least one gel selected from the group consisting of silicone gels, acrylic gels and urethane gels. The sealing materials used for the first sealing material layer 22 and the second sealing material layer 24 may be the same or different from each other.

Among the above resins, from the viewpoint of protecting the solar cell 10, the material constituting the first encapsulant layer 22 and the second encapsulant layer 24 is more preferably a thermoplastic resin. It is more preferable that it is at least one of an ethylene-vinyl acetate copolymer (EVA) and an olefin resin.

The olefin-based resin includes, for example, at least one of polyolefin and olefin-based thermoplastic elastomer (TPO). Olefin-based thermoplastic elastomers (TPOs) consist of blends of polyolefins and ordinary rubber. The rubber phase in the olefin-based thermoplastic elastomer (TPO) may have no or few cross-linking points.

Examples of the polyolefin include homopolymers of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene, and homopolymers thereof. Examples thereof include copolymers.

Examples of the rubber used for the olefin-based thermoplastic elastomer (TPO) include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), and acrylonitrile-butadiene copolymer. Examples thereof include rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), ethylene-propylene rubber (EPM) and ethylene-propylene-diene rubber (EPDM).

In the present embodiment, at least one of the first encapsulant layer 22 and the second encapsulant layer 24 has a filler-containing layer and a filler-free layer. The filler-containing layer contains a granular filler having a primary dispersion diameter of 10 to 600 nm or a fibrous filler having an average fiber diameter of 0.3 to 0.6 μm. In other words, the filler-containing layer is a layer in which the granular filler or the fibrous filler is added to the layer made of the sealing material. The filler-free layer is a layer in which neither a granular filler nor a fibrous filler is added to the layer made of the sealing material.
Hereinafter, the granular filler and the fibrous filler may be collectively referred to as "filler".

FIG. 3 is an enlarged view of a main part of FIG. 2, and in the form shown in FIG. 3, the second encapsulant layer 24 has a filler-containing layer 24A and a filler-free layer 24B. More specifically, it has a filler-containing layer 24A in contact with the lower side (back surface side) of the solar cell 10, and has a filler-free layer 24B below the filler-containing layer 24A. The filler-containing layer 24A contains a large number of granular fillers 28, whereas the filler-free layer 24B does not contain the granular filler 28. As described above, such a second encapsulant layer 24 is less likely to undergo thermal expansion due to a temperature change and has high flexibility. As a result, the movement (displacement) of the solar cell 10 can be suppressed, and damage to the tab wiring 12 and the solar cell 10 and breakage of the tab wiring 12 can be prevented.
Hereinafter, each of the granular filler and the fibrous filler will be described.

(Granular filler)
The granular filler is a granular filler having a primary dispersion diameter of 10 to 600 nm. Specific examples of the granular filler include silica, alumina, barium sulfate, talc, clay, mica powder, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum borate, barium titanate, etc. Examples thereof include strontium titanate, calcium titanate, potassium titanate, bismuth titanate, titanium oxide, barium zirconate, calcium zirconate and the like. Among these, fumed silica and alumina are preferable from the viewpoint of low coefficient of thermal expansion. These granular fillers may be used alone or in admixture of two or more. Silica sol is preferable from the viewpoint of cost, and examples of commercially available organosilica sol include, for example, trade name MA-ST-S (methanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name MT-ST (methanol-dispersed silica sol, Nissan Chemical Industry Co., Ltd.), Product name MA-ST-UP (methanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), Product name MA-ST-M (methanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), Product name MA-ST-L (methanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name IPA-ST-S (isopropanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name IPA-ST (isopropanol-dispersed silica sol, manufactured by Nissan Chemical Co., Ltd.) (Manufactured by Kogyo Co., Ltd.), trade name IPA-ST-UP (isopropanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name IPA-ST-L (isopropanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name IPA- ST-ZL (isopropanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name NPC-ST-30 (n-propyl cellosolve dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name PGM-ST (1-methoxy-2) -Propanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd., trade name DMAC-ST (dimethylacetamide dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name XBA-ST (xylene-n-butanol mixed solvent-dispersed silica sol, Nissan Chemical) (Manufactured by Kogyo Co., Ltd.), trade name EAC-ST (ethyl acetate-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name PMA-ST (propylene glycol monomethyl ether acetate-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name MeOH -ST (Methyl ethyl ketone dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name MEK-ST-UP (methyl ethyl ketone dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name MEK-ST-L (methyl ethyl ketone dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.) (Manufactured by Co., Ltd.) and trade name MIBK-ST (methyl isobutyl ketone dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.) and the like can be mentioned. Further, from the viewpoint of easy dispersibility, particles whose surface is treated with acrylic resin or the like are preferable.
Further, the primary dispersion diameter of the granular filler is 10 to 600 nm, but if it is less than 10 nm, the dispersion stability becomes insufficient, and if it exceeds 600 nm, the solar cell may be damaged by the pressure at the time of laminating. The primary dispersion diameter is preferably 10 to 100 nm, more preferably 10 to 80 nm. The primary dispersion diameter can be obtained by a laser diffraction / scattering method.

(Fibrous filler)
The fibrous filler is a fibrous filler having an average fiber diameter of 0.3 to 0.6 μm. Further, the fibrous filler has an aspect ratio of 10 or more. Specific examples include potassium titanate fiber, carbon fiber (carbon fiber), glass wool, glass fine powder, carbon black, carbon nanotube, graphene, kaolin, nanoclay and the like, and potassium titanate fiber is preferable. The aspect ratio of the fibrous filler is the ratio of the length in the long axis direction to the maximum value of the length in the direction perpendicular to the long axis (length in the long axis direction / direction perpendicular to the long axis). The length of).
The average fiber diameter of the fibrous filler is 0.3 to 0.6 μm, but if it is less than 0.3 μm, it becomes difficult to exhibit the low thermal expansion effect, and if it exceeds 0.6 μm, the pressure at the time of laminating causes the solar cell. May be damaged. The average fiber diameter is preferably 0.3 to 0.5 μm, more preferably 0.3 to 0.4 μm. For the average fiber diameter, the numerical value published by the manufacturer in the catalog etc. may be adopted in the case of a marketed product, or if it is unknown, it should be obtained by observing with a scanning electron microscope (magnification: 10000 times). Can be done.

On the other hand, the aspect ratio of the fibrous filler is preferably 15 to 100, more preferably 30 to 100, from the viewpoint of increasing the coefficient of thermal expansion of the filler-containing layer. The larger the aspect ratio of the fibrous filler, the more effective it can be even if the content is small.

The granular filler or fibrous filler is preferably an inorganic filler from the viewpoint of lowering the thermal expansion coefficient of the filler-containing layer and increasing the elastic modulus.

In the present embodiment, the content of the granular filler or the fibrous filler in the filler-containing layer is preferably 9 to 50% by volume. When the content of the granular filler or the fibrous filler is 9 to 50% by volume, the coefficient of thermal expansion of the filler-containing layer can be sufficiently lowered and the elastic modulus can be sufficiently increased. The content is preferably 10 to 40%, more preferably 15 to 35%.

In FIG. 3 above, the second encapsulant layer 24 is a layer having a filler-containing layer 24A and a filler-free layer 24B. In the present embodiment, the first encapsulant layer 22 may be a layer having a filler-containing layer 22B and a filler-free layer 22A, and such a form is shown in FIG. In FIG. 4, the first encapsulant layer 22 has a filler-containing layer 22B in contact with the upper side (light receiving surface side) of the solar cell 10, and has a filler-free layer 22A above the filler-containing layer 22B.
Further, in the present embodiment, both the first encapsulant layer 22 and the second encapsulant layer 24 may be layers having a filler-containing layer and a filler-free layer. Such a form is shown in FIG. In FIG. 5, the first encapsulant layer 22 has a filler-containing layer 22B in contact with the upper side (light receiving surface side) of the solar cell 10, and has a filler-free layer 22A above the filler-containing layer 22B. Similarly, the second encapsulant layer 24 has a filler-containing layer 24A in contact with the lower side (back surface side) of the solar cell 10 and a filler-free layer 24B below the filler-containing layer 24A.

In the forms shown in FIGS. 4 and 5, the fillers contained in the filler-containing layers 22B and 24A are the same as those in FIG. However, since the first encapsulant layer 22 is located on the light receiving side of the photoelectric conversion unit, there is a concern that the light transmitted by the filler may be scattered and adversely affect the photoelectric conversion unit. In such a case, it can be appropriately adjusted by using a filler having a small size or reducing the content of the filler.

In each of FIGS. 3 to 5, the filler-containing layer 22B or the filler-containing layer 24A is located closer to the photoelectric conversion unit (solar cell 10 side) than the filler-free layer 22A or 24B. As described above, by locating the filler-containing layer having a low coefficient of thermal expansion and a high elastic modulus on the photoelectric conversion unit side, it becomes easy to suppress the movement (displacement) of the solar cell due to the temperature change. From such a viewpoint, it is more preferable that the filler-containing layer is in contact with the photoelectric conversion unit rather than simply located on the photoelectric conversion unit side.

In order to suppress the movement (displacement) of the solar cell due to the temperature change, the tensile elastic modulus of the filler-containing layer is preferably 5 to 1000 times, preferably 10 to 100 times, the tensile elastic modulus of the filler-free layer. Is more preferable. In order to improve the tensile elastic modulus of the filler-containing layer, the filler content may be increased.

On the other hand, when the first encapsulant layer 22 or the second encapsulant layer 24 is a layer having a filler-containing layer and a filler-free layer, the tensile elastic modulus of the layer may be 0.01 to 1 GPa. It is preferably 0.05 to 0.5 GPa, more preferably 0.05 to 0.5 GPa. When the first encapsulant layer 22 or the second encapsulant layer 24 is a layer having neither a filler-containing layer nor a filler-free layer, the tensile elastic modulus of the layer is 0.005 to 0.015 GPa. It is preferably 0.05 to 0.012 GPa, and more preferably 0.05 to 0.012 GPa. By setting the tensile elastic modulus in such a range, the solar cell 10 can be protected from an external impact or the like. The tensile elastic modulus of the first encapsulant layer 22 and the second encapsulant layer 24 may be the same or different from each other. In addition, in this specification, a tensile elastic modulus can be measured in the same manner as the above-mentioned surface protection substrate.

Further, since the fibrous filler has a higher effect of lowering the coefficient of thermal expansion than the granular filler, it is preferable to use the fibrous filler to reduce the coefficient of thermal expansion. However, if the filler-containing layer of the first encapsulant layer contains a fibrous filler, it may affect the transmission of light. Therefore, the fibrous filler is preferably used for the filler-containing layer of the second encapsulant layer. That is, when the filler-containing layer is provided in both the first encapsulant layer 22 and the second encapsulant layer 24 (FIG. 5), a granular filler is used for the filler-containing layer 22B of the first encapsulant layer 22. It is preferable to use a fibrous filler for the filler-containing layer 24A of the second encapsulant layer 24.

Further, in the present embodiment, the granular filler and the fibrous filler may be used in combination in the filler-containing layer as long as the effect is not impaired.
Further, in the present embodiment, a filler having another shape such as a plate-shaped filler may be used in combination as long as the effect is not impaired.

In the present embodiment, it is preferable that a mixed layer in which the components constituting the respective layers are mixed is formed between the filler-containing layer and the filler-free layer. In the presence of the mixed layer, the filler-containing layer and the filler-free layer are firmly bonded to each other, and peeling of both layers can be prevented. FIG. 6 is a view showing a state in which the main part of FIG. 3 is further enlarged, and as shown in FIG. 6, a mixed layer 24C is formed between the filler-containing layer 24A and the filler-free layer 24B. Since the mixed layer 24C is formed by, for example, hot-pressing the filler-containing layer 24A and the filler-free layer 24B, each component of both layers is mixed, and the filler is formed from the filler-containing layer 24A to the filler-free layer 24B. It will gradually decrease toward.
Although the second encapsulant layer 24 has been described with reference to FIG. 6, it is preferable that the first encapsulant layer 22 also has a mixed layer formed therein.

The thickness of the first encapsulant layer 22 and the second encapsulant layer 24 is not particularly limited, but is preferably 0.1 mm to 10 mm, and more preferably 0.2 mm to 1.0 mm. With such a range, the solar cell 10 can be appropriately protected and light can efficiently reach the solar cell 10. The thicknesses of the first encapsulant layer 22 and the second encapsulant layer 24 may be the same or different from each other.
The thickness of the filler-containing layer contained in the first encapsulant layer 22 and the second encapsulant layer 24 is 10 from the viewpoint of lowering the coefficient of thermal expansion of the filler-containing layer and increasing the elastic modulus. It is preferably ~ 300 μm, more preferably 50-100 μm.

Further, in both the first encapsulant layer 22 and the second encapsulant layer 24, the same encapsulant may be used for the filler-containing layer and the filler-free layer, or different encapsulants may be used. May be good. However, from the viewpoint of the bonding strength between the filler-containing layer and the filler-free layer, it is preferable to use the same sealing material.

On the other hand, in a solar cell module, in order to prevent thermal expansion due to a temperature change, for example, it is conceivable to arrange a highly flexible intermediate layer (for example, a layer made of a gel-like polymer) between any of the layers. Be done. However, in the present embodiment, since the presence of the first encapsulant layer and / or the second encapsulant layer suppresses thermal expansion, it is not always necessary to provide such an intermediate layer. Further, since the first encapsulant layer and / or the second encapsulant layer contains a filler, a gas barrier effect may be exhibited, and gas barrier measures may be unnecessary or reduced.

In the present embodiment, the method for forming the first encapsulant layer 22 and the second encapsulant layer 24 having the filler-containing layer and the filler-free layer as described above is not particularly limited, and various film forming methods can be used. Can be applied. For example, a film corresponding to the filler-containing layer and a film corresponding to the filler-free layer can be prepared in advance, and both films can be laminated and heat-pressed. The heat pressing of both films may be performed after laminating all the layers constituting the solar cell module. Further, the film corresponding to the filler-containing layer can be produced by a casting method. For example, first, a filler is added to a solution obtained by dispersing or dissolving the sealing material in a solvent to obtain a mixed solution. Next, it can be obtained by pouring the mixed solution into a mold and heat-curing it while adding a cross-linking agent as needed.

[Back side protective layer]
The back surface protective layer 26 protects the back surface side of the solar cell module 100 as a back sheet. Materials constituting the back surface protective layer 26 include glass, fiber reinforced plastic (FRP), polyimide (PI), cyclic polyolefin, polycarbonate (PC), polymethylmethacrylate (PMMA), polyetheretherketone (PEEK), and polystyrene (). At least one selected from the group consisting of PS), polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) can be used. Examples of the fiber reinforced plastic (FRP) include glass fiber reinforced plastic (GFRP), carbon fiber reinforced plastic (CFRP), and aramid fiber reinforced plastic (AFRP). Examples of glass fiber reinforced plastic (GFRP) include glass epoxy. The material forming the back surface protective layer 26 preferably contains at least one selected from the group consisting of fiber reinforced plastic (FRP), polymethylmethacrylate (PMMA) and polyetheretherketone (PEEK). The back surface protective layer 26 is preferably made of a fiber reinforced resin such as a fiber reinforced plastic in order to secure sufficient strength thereof. Further, the fiber reinforced plastic may be a UD (UniDirection) material in which fibers are arranged in one direction, or may be a woven material woven by intersecting fibers. When the UD material is used for the back surface protective layer 26, it is difficult to expand and contract in the fiber direction, so that damage to the solar cell 10 and cutting of the tab wiring 12 can be suppressed depending on the direction in which the UD material is arranged. The back surface protective layer 26 is preferably made of carbon fiber reinforced plastic because it is less likely to bend and is lightweight. Further, in order to increase the efficiency of power generation on the back surface, the main layer may contain titanium oxide or the like to improve the reflectance. In addition, the surface may be plated.

The thickness of the back surface protective layer 26 is not particularly limited, but is preferably 0.01 mm or more and 10 mm or less, more preferably 0.05 mm or more and 5.0 mm or less, and 0.07 mm or more and 1.0 mm or less. It is more preferable to have. In particular, in the case of fiber reinforced plastic, it is preferable that the diameter of one fiber is the lower limit of the thickness. By setting the thickness of the back surface protective layer 26 in such a range, the deflection of the back surface protective layer 26 can be suppressed and the weight of the solar cell module 100 can be further reduced.

When the back surface protective layer 26 is thin (for example, 0.2 mm or less), in addition to weight reduction and thinning, the influence of heat shrinkage when a temperature difference occurs in the back surface protective layer 26 becomes small. The rigidity of the back surface protective layer 26 is reduced. Therefore, the warp of the entire solar cell module 100 can be reduced.

Further, when the back surface protective layer 26 is thin, the gas release property inside the solar cell module 100 can be improved. For example, when EVA is used as the sealing material for the first sealing material layer 22 and the second sealing material layer 24, acetic acid may be generated due to the decomposition of EVA, but if the back surface protective layer 26 is thin, acetic acid is external. It becomes easy to diverge.

Further, when the back surface protective layer 26 is made of UD fiber reinforced plastic and the thickness of the back surface protective layer 26 is reduced, the desired portion is reinforced by partially superimposing the UD material as necessary. , The characteristics can be changed in the back surface protective layer 26. When the UD materials are superposed, the fibers of the UD material may be superposed in the same direction, or the fibers of the UD material may be superposed in different directions such as vertical, depending on the desired characteristics.

Further, when the thickness of the back surface protective layer 26 becomes thin, the back surface protective layer 26 can be bonded while following the shapes of the first encapsulant layer 22 and the second encapsulant layer 24, and the first encapsulant layer 26 can be attached. It is possible to prevent air bubbles from being mixed between the layer 22 and the second sealing material layer 24 and the back surface protective layer 26. Further, for example, even if the front surface protection substrate 20 has a curved surface, the back surface protection layer 26 is adapted to the shape of the front surface protection substrate 20 via the first encapsulant layer 22 and the second encapsulant layer 24. Can be pasted together. Therefore, the solar cell module 100 having a curved surface shape can be easily manufactured while suppressing the mixing of air bubbles. Further, since the back surface protective layer 26 has high followability, it is difficult for a local load to be applied to the solar cell 10 or the like when, for example, each layer is laminated to manufacture a curved solar cell module 100, so that the solar cell Damage to the cell 10 can be suppressed. Further, when the thickness of the back surface protective layer 26 becomes thin, the first encapsulant layer 22 and the second encapsulant layer 24 can be quickly heated and crosslinked, so that the manufacturing time of the solar cell module 100 can be shortened. In addition to this, it is possible to prevent the surface protection substrate 20 from being thermally deformed.

The coefficient of thermal expansion of the back surface protective layer 26 is preferably 0 to 30 (× 10 ^-6 K ^-1 ), and more preferably 2 to 25 (× 10 ^-6 K ^-1 ). When the coefficient of thermal expansion of the back surface protective layer 26 is within this range, the thermal shock resistance can be improved.

The solar cell module 100 of the present embodiment may be mounted on the roof of a building or a moving body. At this time, the solar cell module 100 may have a curved surface shape so as to match the shape of the roof. Further, the surface protection substrate 20 may have a curved shape that protrudes toward the light receiving surface side. The solar cell module 100 and the surface protection substrate 20 may have, for example, a bow shape protruding toward the light receiving surface side.

Further, the solar cell module 100 according to the present embodiment may be mounted on a moving body. Examples of the moving body include vehicles such as automobiles, trains, ships, and the like. When the solar cell module 100 of the present embodiment is mounted on an automobile, it is preferably installed on the upper surface portion of the automobile body such as a bonnet or a roof. In each of the moving bodies, the current generated by the solar cell module 100 of the present embodiment is supplied to an electric device such as a fan and a motor, and is used for driving and controlling the electric device.

Hereinafter, the present embodiment will be described in more detail with reference to Examples, but the present embodiment is not limited thereto.

[Reference example 1]
(Preparation of filler-containing layer)
Prepare 100 g of ethylene-vinyl acetate resin (EVA, manufactured by Mitsui DuPont Polychemical Co., Ltd., Evaflex 450) so as to be 10% by mass with respect to xylene, and prepare an ultrasonic disperser (UPS200, manufactured by Heelscher). The dispersion / dissolution treatment was carried out using. The obtained liquid was divided into five, and granular filler 1 (manufactured by Nissan Chemical Industries, Ltd., MEK-AC2140Z) was added to 20% by volume, 26% by volume, 36% by volume, 60% by volume, and 77% by volume of each. The mixture was mixed to obtain a mixed solution having five different concentrations. Next, each of the obtained mixed solutions was dispersed using the above-mentioned ultrasonic disperser to obtain a uniform mixed solution. Dialkyl peroxide (Parkmill D, manufactured by NOF CORPORATION) was added to this mixed solution as a radical initiator (crosslinking agent) so as to have an EVA solid content of 1% by mass. The composition of the granular filler 1 is SiO ₂ , and the primary dispersion diameter is 12 nm.

The obtained solution was poured into an A4 size stainless steel vat and the solvent was volatilized to obtain a sheet material having a thickness of about 1 mm. The obtained sheet material was pressed with a solar cell desktop module laminator (manufactured by Nisshinbo Mechatronics Co., Ltd.) to obtain a sample of a crosslinked encapsulant layer. Specifically, the solar cell desktop module laminator is a diaphragm type vacuum laminator, which is evacuated for 10 minutes in a hot plate temperature environment of 145 ° C. to generate a differential pressure of −70 kPa, and the sheet material is formed by a diaphragm sheet. Was pressurized for 5 minutes.
Viscoelasticity measurement (DMS) and linear thermal expansion measurement (DMS) were carried out on the samples obtained as described above to obtain elastic modulus (tensile elastic modulus) and linear expansion coefficient.

[Reference example 2]
A sample was prepared in the same manner as in Reference Example 1 except that the granular filler 1 was replaced with the granular filler 2 (MEK-AC5140Z manufactured by Nissan Chemical Industries, Ltd.). Further, the obtained sample was subjected to viscoelasticity measurement (DMS) and linear thermal expansion measurement (DMS) in the same manner as in Reference Example 1. The composition of the granular filler 2 is SiO ₂ , and the primary dispersion diameter is 80 nm.

[Reference example 3]
A sample was prepared in the same manner as in Reference Example 1 except that the granular filler 1 was replaced with the fibrous filler 1 (manufactured by Otsuka Chemical Co., Ltd., Tismo D). Further, the obtained sample was subjected to viscoelasticity measurement (DMS) and linear thermal expansion measurement (DMS) in the same manner as in Reference Example 1. The fibrous filler 1 was potassium titanate (K ₂ Ti ₈ O ₁₇ ), the average fiber diameter was 300 nm, and the average fiber length was 10 μm (aspect ratio: 33.3).

A graph depicting the change in the coefficient of linear expansion with respect to the content of the filler is shown in FIG. As shown in FIG. 7, all the reference examples show that the coefficient of linear expansion is lowered by containing the filler.

Further, FIG. 8 shows a graph depicting the change in elastic modulus with respect to the content of the filler. As shown in FIG. 8, all the reference examples show that the elastic modulus is increased by containing the filler.

From the above Reference Examples 1 to 3, it can be seen that the coefficient of linear expansion is lowered and the elastic modulus is improved by containing the filler in the sealing material. By laminating the filler-containing layer having such physical properties and the filler-free layer having a low elastic modulus, as shown in the following examples, it is difficult to thermally expand due to a temperature change and the flexibility is increased. It becomes a high encapsulant layer.

[Example 1]
First, two 0.6 mm laminates are produced by laminating a filler-containing layer having a granular filler content of 26% by volume in Reference Example 1 and a film made of EVA of 0.6 mm as a filler-free layer. The first encapsulant layer and the second encapsulant layer were used, respectively.
Next, a photoelectric conversion unit was prepared, and the photoelectric conversion unit was sealed with the first encapsulant layer and the second encapsulant layer. At this time, the orientation of the first encapsulant layer and the second encapsulant layer was such that the respective filler-containing layers were in contact with the photoelectric conversion portion. Further, a surface protection substrate having a thickness of 3 mm was laminated on the first encapsulant layer, and a back surface protection base layer having a thickness of 0.1 mm was laminated on the second encapsulant layer. Next, a solar cell module was produced by compressing and heating at 145 ° C. while reducing the pressure. As the surface protection substrate, polycarbonate (coefficient of linear expansion 5.6 × ^10-5 K ^-1 ) was used. A solar cell was used as the photoelectric conversion unit. Carbon fiber reinforced plastic (CFRP) was used for the back surface protective layer.

[Example 2]
A solar cell module was produced in the same manner as in Example 1 except that the filler-containing layer was replaced with the filler-containing layer having a granular filler content of 36% by volume in Reference Example 1.

[Example 3]
A solar cell module was produced in the same manner as in Example 1 except that the filler-containing layer was replaced with the filler-containing layer containing the fibrous filler of Reference Example 3.

[Comparative Example 1]
A solar cell module was produced in the same manner as in Example 1 except that the first encapsulant layer and the second encapsulant layer were replaced with a film made of EVA having a thickness of 0.6 mm. That is, the granular filler 1 was not used in either the first encapsulant layer or the second encapsulant layer.

FIG. 9 shows the relationship between the elastic modulus of the solar cell module with respect to the measured temperature in Examples 1 and 2 and Comparative Example 1. From FIG. 9, it can be seen that the elastic modulus increases as the content of the granular filler 1 increases regardless of the measurement temperature.

On the other hand, the solar cell modules of Examples 1 to 3 and Comparative Example 1 were tested for thermal shock resistance as shown below.
(Heat impact resistance)
The thermal shock resistance is based on the temperature cycle test of JIS C8990: 2009 (IEC61215: 2005) (ground-based crystalline silicon solar cell (PV) module-requirements for design eligibility confirmation and type certification) as follows. The test was carried out under various test conditions. That is, the solar cell modules of each Example and Comparative Example were installed in the test tank, and the temperature of the solar cell module was periodically changed between −40 ° C. ± 2 ° C. and + 85 ° C. ± 2 ° C. After performing such a temperature cycle test for 25 cycles, 50 cycles, and 200 cycles, the connecting members connecting the solar cells to each other were visually confirmed. Then, the one in which the connecting member was not cut in 200 cycles was evaluated as ⊚, and the one in which the connecting member was not cut in 50 cycles and the connecting member was cut in 200 cycles was evaluated as ◯. Further, the one in which the connecting member was not cut in 25 cycles and the connecting member was cut in 50 cycles was evaluated as Δ, and the one in which the connecting member was cut in 25 cycles was evaluated as ×. The temperature change rate between the lower limit and the upper limit is about 1.4 ° C./hour, the holding time of the lower limit temperature is 60 minutes, the holding time of the upper limit temperature is 1 hour and 20 minutes, and the time of one cycle is 5 hours and 20 minutes. It was a minute. In addition, the temperature cycle test was performed at least three times. The evaluation results are shown in Table 1.

From Table 1, it can be seen that in each of the examples, the connecting member was not cut in 200 cycles, and the heat impact resistance was excellent. On the other hand, in Comparative Example 1 in which the filler-containing layer was not provided, the connecting member was cut in only 25 cycles, and the heat impact resistance was poor.

10 Solar cell (photoelectric conversion unit)
12 Tab wiring 14 Connection wiring 16 Solar cell string (photoelectric conversion unit)
20 Surface protection substrate 22 First encapsulant layer 22A Filler-free layer 22B Filler-containing layer 24 Second encapsulant layer 24A Filler-containing layer 24B Filler-free layer 24C Mixed layer 26 Back surface protective layer 28 Granular filler 100 Solar cell module

Claims (9)

A front surface protection substrate, a first encapsulant layer, a photoelectric conversion unit, a second encapsulant layer, and a back surface protection substrate are provided in this order from the light receiving surface side.
At least one of the first encapsulant layer and the second encapsulant layer contains a granular filler having a primary dispersion diameter of 10 to 600 nm or a fibrous filler having an average fiber diameter of 0.3 to 0.6 μm. A solar cell module having a filler-containing layer and a filler-free layer containing neither the granular filler nor the fibrous filler. The solar cell module according to claim 1, wherein the filler-containing layer is located closer to the photoelectric conversion unit than the filler-free layer. The solar cell module according to claim 1 or 2, wherein a mixed layer in which components constituting the respective layers are mixed is formed between the filler-containing layer and the filler-free layer. The solar cell module according to any one of claims 1 to 3, wherein the tensile elastic modulus of the filler-containing layer is 5 to 1000 times the tensile elastic modulus of the filler-free layer. The solar cell module according to any one of claims 1 to 3, wherein the thickness of the filler-containing layer is 10 to 300 μm. The solar cell module according to any one of claims 1 to 5, wherein the granular filler or the fibrous filler is an inorganic filler. The solar cell module according to any one of claims 1 to 6, wherein the fibrous filler has an aspect ratio of 15 to 100. The solar cell module according to any one of claims 1 to 7, wherein the content of the granular filler or the fibrous filler in the filler-containing layer is 9 to 50% by volume. A moving body comprising the solar cell module according to any one of claims 1 to 8.

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