Patent Application
20200035847
One or more embodiments of the invention relate to a solar cell module.
Solar cells that include crystalline semiconductor substrates such as a single-crystalline silicon substrate and a polycrystalline silicon substrate have a small area for one substrate, and thus in practical use, a plurality of solar cells are electrically connected through wiring members and modularized for increasing output. No light enters the regions provided with wiring members at the light-receiving surfaces of the solar cells, thus causing shadowing loss. A method is known in which, by using a light-diffusion wiring member with uneven structure on the light-receiving side, irradiation light is reflected at the inclined surface of the unevenness in various directions to make the light on solar cells, thereby improving the light utilizing efficiency.
In connection of the light-receiving surface (uneven formed surface) of the light-diffusion wiring member on a back electrode of the solar cell, because of the small area of contact between the uneven formed surface and the electrode, insufficient connection may cause an electrical loss due to an increase in resistance, or decreased reliability. Patent Document 1 and Patent Document 2 propose wiring members configured such that the region connected to the light-receiving surface of a solar cell is provided with surface unevenness, whereas the region connected to the back surface of the solar cell is not provided with surface unevenness. In such a wiring member, both a surface connected to a light-receiving electrode of the solar cell and a surface connected to a back electrode of the solar cell are formed in a flat surface, thus the wiring member and the solar cell are stably connected with a solder or the like.
One or more embodiments of the present invention provide a solar cell module capable of achieving a balance between light utilizing efficiency and long-term reliability.
The solar cell module includes a solar cell string, a light-transmitting light-receiving-surface protection member disposed on the light-receiving side, a back-surface protection member disposed on the back side, and an encapsulant that encapsulates the solar cell string between the light-receiving-surface protection member and the back-surface protection member. For the solar cell string, a first solar cell and a second solar cell arranged apart from each other are connected by a strip-shaped wiring member.
The wiring member has a first principal surface connected to an electrode arranged on a back surface of the first solar cell, and a second principal surface connected to an electrode arranged on a light-receiving surface of the second solar cell. The wiring member has, along an extending direction, an uneven region where the first principal surface is provided with unevenness, and a flat region where the first principal surface is not provided with unevenness or is provided with unevenness that is smaller in height than the uneven region. The uneven region is arranged so as to extend from the light-receiving surface of the second solar cell to the back surface of the first solar cell.
In the solar cell module according to one or more embodiments of the present invention, the first principal surface of the wiring member is provided with unevenness, and the solar cell module is thus excellent in light utilizing efficiency. The part of the wiring member disposed on the back surface of the solar cell has both the flat region and the uneven region, and the flat region can improve the reliability of the electrical connection between the solar cell and the wiring member. The encapsulant filling the gap between the unevenness of the wiring member disposed on the back surface of the solar cell and the solar cell contributes to adhesiveness and cushioning action, thereby making it possible to improve the reliability of the solar cell module.
A light-receiving-surface protection member 91 with light transmissivity is disposed on the light-receiving side (the upper side in
In one or more embodiments, as the cell, a type of solar cells that are configured to be interconnected with a wiring member can be used, such as a crystalline silicon solar cell or a solar cell including a semiconductor substrate other than silicon such as GaAs. In one or more embodiments, irregularities on the order of about 1 to 10 μm in height may be formed on the light-receiving surface of the photoelectric conversion section 50 of the cell. Optical confinement efficiency can be enhanced and reflectance can be reduced by forming irregularities on the light-receiving surface,
In one or more embodiments, the light-receiving electrode 60 disposed on the light-receiving surface of the photoelectric conversion section 50 has a specific pattern shape, and light can be captured from a section where no electrode is disposed. The pattern shape of the light-receiving electrode 60 is not particularly limited. As shown in
In one or more embodiments, the wiring member 81 has a first principal surface disposed to face the light receiving side and a second principal surface disposed to face the back side. In the solar cell string 100, the first principal surface of the wiring member 81 is connected to the back electrode 70 of the first cell 101, and the second principal surface of the wiring member 81 is connected to the light-receiving electrode 60 of the second cell 102.
In one or more embodiments, adhesive materials 96, 97 for bonding the electrodes 60, 70 formed on the cell and the wiring member 81 are disposed therebetween. As the adhesive material, a solder, a conductive adhesive, a conductive film, or the like is used. In the solar cell string 100, the wiring members are flat at both of the surface connected to the light-receiving electrode 60 and the surface connected to the back electrode 70, and there is thus a tendency that adhesion strength and adhesion reliability are improved in a case where a solder is used as the adhesive materials 96 and 97.
The length of the wiring member 81 along the x direction is approximately twice the length of one side of the cell along the x direction in one or more embodiments. In the module, as shown in
In one or more embodiments, the entire region 81b disposed on the light-receiving surface of the second cell 102 of the wiring member 81 is encompassed in the uneven region 820. The uneven region 820 further extends over the bent part 825, and also a region 822 on the +x side from the bent part 825. Along the x direction, most part of the region 81a disposed on the back surface of the first cell 101 is the flat region 810, but the end of the region 81a on the side (−x side) closer to the bent part 825 overlaps with the uneven region 822. In one or more embodiments, in the solar cell string 100, the uneven region 820 of the wiring member 81 is arranged so as to extend from the light-receiving surface of the second cell 102 to the back surface of the first cell 101.
In one or more embodiments, the region 81b and bent part 825 disposed on the light-receiving surface of the cell are entirely included in the uneven region 820, and thus, as shown in
In one or more embodiments, the first principal surface of the wiring member is provided with unevenness, thereby scattering and reflecting light irradiation from the light-receiving side to the wiring member at the unevenness of the surface. The light scattered and reflected by the uneven region 820 of the wiring member is reflected again by the light-receiving-surface protection member 91, and capable of entering the cell from the region where the wiring member is not disposed, thereby allowing the light utilizing efficiency of the module to be improved. In the solar cell string 100, the first principal surface of the wiring member is provided with unevenness over the entire region of the gap between the adjacent cells, thus allowing light irradiation to the wiring member disposed in the gap between the cells to also enter the cells by scattering and reflecting the light, and allowing the light utilizing efficiency of the module to be further improved.
The material of the wiring member may have low resistance in one or more embodiments. Materials containing copper as main constituent may be used because of its low cost. In order to increase the amount of light reflected by the uneven structure at the surface of the wiring member, the surface of the first principal surface of the uneven region 820 may be coated with a highly light reflective material such as gold, silver, copper, or aluminum. In some embodiments, a metal layer containing silver as a main constituent may be formed.
The uneven structure in the uneven region 820 of the wiring member is not particularly limited as long as the uneven structure is capable of scattering and reflecting light, and may have a regular shape or an irregular shape. Examples of the uneven shape include pyramidal shapes such as square pyramidal shape and inverted square pyramidal shape, and columnar shapes such as triangular prismatic shapes and semicircular columnar shapes. In one or more embodiments, because light irradiation to the wiring member can be scattered and reflected at a large angle, a columnar shape that extends in parallel to the first principal surface may be selected, and in a cross section perpendicular to the extending direction, the cross sectional shape of the columnar may be a triangle. In one or more embodiments, the uneven region 820 may have a triangular prism-shaped projected part or the uneven region 820 may have a plurality of triangular prism-shaped projected parts arranged in parallel. In a case where the cross-sectional shape of the projected part is triangle, the elevation angle of the slope of the projected part may be 20 to 70°. Although the height of the projected part is not particularly limited, the height may be 5 to 100 μm or 10 to 80 μm.
The width of the wiring member can be appropriately selected depending on the electrode configuration of the cell (for example, the width and number of bus bar electrodes), and may be about 0.5 to 3 mm in one or more embodiments. Typically, the width of the wiring member is set to about the same as the width of the bus bar electrode. In a case where a small-width bus bar (thin-wire bus bar) is disposed on the cell surface, the width of the wiring member may be made larger than the width of the bus bar electrode. As described later, for the wiring member, the width W1 of the flat region 810 and the width W2 of the uneven region 820 may be different from each other.
Although the wiring member 81 with the projected part extending parallel to the extending direction (x direction) is shown in
As shown in
As viewed along the x direction, most part of the region 81a of the wiring member 81, which is arranged on the back side of the first cell, is flat region 810 in one or more embodiments. Thus, the contact area between the back-surface bus bar electrode 72 of the cell and the wiring member 81 is increased, thereby making it possible to improve the adhesion strength and adhesion reliability between the electrode and the wiring member. In addition, as with the connection to the light-receiving-surface bus bar electrode 62, it is possible to use a solder as the adhesive material 97 for the connection between the back-surface bus bar electrode 72 and the wiring member 81. As just described, the first principal surface is provided with unevenness in the region 81b where the wiring member 81 is disposed on the light-receiving surface of the cell, whereas the first principal surface is formed to be a flat part in the region 81a where the wiring member 81 is disposed on the back surface. Accordingly, the improved light utilizing efficiency by scattering and reflection and the improved adhesion strength and adhesion reliability with the cell can be made compatible.
In one or more embodiments, the uneven region 820 of the wiring member 81 also extends over the region 822 on the +x side from the bent part 825, and the region 822 overlaps with the region 81a disposed on the back surface of the first cell 101. Thus, at the end of the first cell 101, as shown in
In one or more embodiments, no bus bar electrode is disposed in the vicinity of the end edge of the cell, and thus, the back surface bus bar electrode is not disposed in the part where the uneven region 822 of the wiring member 81 and the back surface of the cell face each other. The wiring member 81 and the back-surface bus bar electrode 72 may be connected or may not be connected in the part where the uneven region 822 of the wiring member 81 and the back-surface bus bar electrode 72 of the cell face each other. The proportion of the uneven region 822 is low with respect to the entire region 81a of the wiring member 81 disposed on the back side of the first cell. Since the flat region 810 of wiring member 81 is connected to the back surface bus bar electrode with the adhesive material 97 such as a solder interposed therebetween, the electrical connection between the back-surface bus bar electrode 72 and wiring member 81 can be sufficiently secured, even if the region 822 is not connected to the back surface bus bar electrode.
In one or more embodiments, in the module 200, the solar cell string 100 is encapsulated between the light-receiving-surface protection member 91 and the back-surface protection member 92, and thus, as shown in
It is enough the length L of the uneven region 820 (822) along the x direction in the region 81a disposed on the back side of the first cell of the wiring member 81 is larger than 0. In a case where L is larger than 0, the first principal surface of the wiring member has unevenness over the entire region of the gap between the first cell 101 and the second cell 102, thus allowing the light utilizing efficiency of the module to be further improved. L may be 2 mm or more, 3 mm or more, or 4 mm or more, from the viewpoint of enhancing the cushioning action and adhesion with the encapsulant, with the uneven region of the wiring member disposed on the back surface of the first cell. On the other hand, L may be 20 mm or less, 10 mm or less, or 8 mm or less, from the viewpoint of sufficiently securing the electrical connection between the back electrode of the cell and the wiring member.
For the wiring member 81, along the y direction, the width W2 of the uneven region 820 may be larger than the width W1 of the flat region 810. As described above, the bent part 825 is formed in the uneven region 820 of the wiring member 81 in one or more embodiments. When the module undergoes a temperature change, the cell and the wiring member undergo a volume change. Since the cell and the wiring member are fixed with the adhesive materials 96 and 97 interposed therebetween, the distortion generated due to a difference in dimensional change between the cell and the wiring member tends to be concentrated on the wiring member located in the gap between the adjacent cells. In particular, the bent part of the wiring member is more likely to be cracked or fractured as compared with the other parts. When the width W2 of the uneven region 820 is relatively large, strength of the bent part 825 is enhanced, so that the long-term reliability of the module against temperature changes and the like tend to be improved.
The method for manufacturing the wiring member with the flat region 810 and the uneven region 820 along the extending direction is not particularly limited. For example, as shown in
The method for forming the uneven region and the flat region on the surface of the wiring member is not particularly limited. For example, a processed region where unevenness is formed by roller processing, press processing, etc., and a non-processed region where unevenness is not formed may be alternately arranged along the extending direction. Alternatively, after forming unevenness along the entire extending direction, the uneven shape may be crushed by press processing or the like to form a flat region.
A wiring member in which the width W2 of the uneven region 820 is larger than the width W1 of the flat region 810 can be easily obtained by forming unevenness by press processing in the uneven region and the flat region is remain unprocessed. In the press processing, unevenness is formed on the first principal surface by pressing from the first principal surface side, and the width W1 of the processed region becomes larger than the width W2 of the non-processed region.
When the unevenness is formed by pressing a roller while traveling the flat wiring member along the extending direction, unevenness is less likely to be formed at the start of pressing the roller. Thus, when an attempt is made to alternately form the uneven region and the flat region along the extending direction, the uneven shape of the uneven region may be ununiform or the unevenness height may be insufficient in the vicinity of the boundary between the uneven region and the flat region. In contrast, in the press processing, intermittent processing is carried out along the extending direction, thus allowing unevenness to be formed reliably even in the vicinity of the boundary. Furthermore, the pressing can easily form not only unevenness extending in parallel to the extending direction of the wiring member, but also unevenness extending at a predetermined angle with respect to the extending direction of the wiring member, and unevenness extending in a direction perpendicular to the extending direction of the wiring member.
When unevenness is formed by the press-processing, the width W2 of the uneven region 820 becomes larger than the width W1 of the flat region 810, and accordingly, the average thickness d2 of the wiring member in the uneven region 820 is smaller than the thickness d1 of the wiring member of the flat region 810. As shown in
In preparation of the module, first, a solar cell string 100 in which a plurality of cells are connected to each other via the wiring member is prepared. As mentioned above, the electrode of the cell and the wiring member 80 may be connected with a solder interposed therebetween. In this regard, the flat region of the first principal surface of the wiring member is connected to the back electrode 70 of the cell, and the second principal surface of the wiring member is connected to the light-receiving electrode 60 of the cell.
The solar cell string is sandwiched between the light-receiving-surface protection member 91 and the back-surface protection member 92 with the encapsulant 95 interposed, thereby forming a solar cell module. In one or more embodiments, a laminate in which the light-receiving surface encapsulant, the solar cell string, the back surface encapsulant and the back-surface protection member are placed in this order on the light-receiving-surface protection member is heated at predetermined conditions to cure the encapsulant. As described above, in a case where the uneven region 822 of the wiring member disposed on the back surface of the cell is not connected to the back electrode of the cell, the recessed part of the unevenness is filled with the encapsulant 95 getting around, thus contributing to the improved durability of the module by cushioning action and adhesion improvement action.
In one or more embodiments, the light-receiving-surface protection member 91 is light-transmissive, and glass, light-transmissive plastic or the like can be used. As the back-surface protection member 92, a resin film of polyethylene terephthalate (PET) or the like, or a laminated film having a structure in which an aluminum foil is sandwiched between resin films can be used. As the encapsulant 95, a transparent resin such as high-density polyethylene (HDPE), high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), ethylene/α-olefin copolymer, ethylene/vinyl acetate copolymer (EVA), ethylene/vinyl acetate/triallyl isocyanurate (EVAT), polyvinyl butyrate (PVB), silicon, urethane, acryl or epoxy may be used.
Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-067240 | Mar 2017 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2018/013465 | Mar 2018 | US |
| Child | 16587454 | US |
