Solar cell module

Abstract

To provide a solar cell module capable of suppressing solder fracture due to a thermal contraction difference between a solar cell and a connection member.SOLUTION: The solar battery module includes a first cell 10A having a plurality of negative electrode side connection pads 111 provided along one side on the rear surface side, a second cell 10B having a plurality of positive electrode side connection pads 112 provided along one side on the rear surface side, and an interconnector 20 for electrically connecting the first cell 10A and the second cell 10B. The interconnector 20 includes a main body portion 21 whose longitudinal direction is a direction parallel to the connection sides of the first cell 10A and the second cell 10B, and a plurality of connection tabs 22 protruding from the main body portion 21 to both sides in the lateral direction. The connection tabs 22 include a plurality of tabs soldered to the first cell side 10A and a plurality of tabs soldered to the second cell side 10B. The main body portion 21 has a curved portion 211 curved along the longitudinal direction between the connection tabs 22 adjacent to each other along the longitudinal direction.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to solar cell modules. [Background technology]

[0002] Solar cell modules made up of multiple solar cell cells connected together are commonly used. Patent Document 1 discloses a solar cell module in which back electrode type solar cell cells are connected via a connecting member. The connecting member in Patent Document 1 is configured to solder three points (three-point connection) to one side of one solar cell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5547248 Summary of the Invention [Problem to be solved by the invention]

[0004] Back-side electrode solar cells have improved bonding strength compared to conventional double-sided electrode solar cells because they can secure sufficient wiring area without having to worry about light loss due to wiring. Meanwhile, in recent years, solar cells are not only required for installation on residential roofs, but also for installation on mobile objects such as automobiles. Solar cells for automobiles require higher temperature resistance than conventional solar cells for residential use, and further improvements in bonding strength are required to prevent solder fracture due to differences in thermal contraction between the solar cell and the connecting member.

[0005] The present disclosure has been made in view of the above-mentioned problems, and aims to provide a solar cell module that can improve the bonding strength between the solar cell and the connection member. [Means for solving the problem]

[0006] In order to solve the above problems, a solar cell module according to a first aspect of the present disclosure includes a first cell which is a back electrode type solar cell and has a plurality of negative electrode side connection pads provided along one side of the back surface thereof, and a second cell which is a back electrode type solar cell and has a plurality of positive electrode side connection pads provided along one side of the back surface thereof, and in a state where the side of the first cell on which the negative electrode side connection pads are provided faces the side of the second cell on which the positive electrode side connection pads are provided, the plurality of negative electrode side connection pads of the first cell and the plurality of positive electrode side connection pads of the second cell are arranged. and a connection member that electrically connects the connection pad to the first cell, the connection member having a main body portion whose longitudinal direction is parallel to the connection sides of the first cell and the second cell, and a plurality of connection tabs that protrude from the main body portion on both sides in the short direction, the connection tabs each having a plurality of tabs that are solder-connected to the negative electrode side connection pad of the first cell and a plurality of tabs that are solder-connected to the positive electrode side connection pad of the second cell, and the main body portion having a curved portion that is curved along the longitudinal direction between the connection tabs that are adjacent along the longitudinal direction.

[0007] The solar cell module may also be configured such that a sheet is disposed between the first cell and the second cell and the connecting member, and a low-elasticity resin is disposed between the sheet and the curved portion of the connecting member.

[0008] In the solar cell module, the low-elasticity resin preferably has an elastic modulus of 0.5 to 10 MPa (temperature range of -40 to 85°C), and may further have adhesive properties. For example, the low-elasticity resin may be a silicone-based resin.

[0009] Furthermore, a second aspect of the present disclosure is a method for manufacturing a solar cell module, which is a method for manufacturing a solar cell module that manufactures the solar cell module described above, and includes a first step of placing a sheet to cover the gap between the first cell and the second cell at a cell connection portion where the first cell and the second cell are connected by the connection member, a second step of supplying low-elasticity resin to a predetermined location on the sheet, a third step of placing the connection member on the sheet and the low-elasticity resin, and a fourth step of solder-connecting the connection tabs of the connection member to the connection pads of the first cell and the second cell, and is characterized in that in the fourth step, the curved portion is formed by the low-elasticity resin present between the sheet and the connection member. [Effects of the Invention]

[0010] The solar cell module of the present disclosure has the advantage that the connecting member absorbs thermal contraction by deforming the curved portion, thereby significantly reducing the stress acting on the solder and preventing breakage due to solder fatigue. [Brief explanation of the drawings]

[0011] [Figure 1A] FIG. 1 is a plan view of a back electrode type solar cell. [Figure 1B] FIG. 2 is a rear view of a back electrode type solar cell. [Figure 2] FIG. 2 is a rear view showing a cell connection portion in the solar cell module of the first embodiment. [Figure 3] 3 is a cross-sectional view taken along the longitudinal direction of a main body portion of a cell connection portion of the first embodiment. FIG. [Figure 4] FIG. 10 is a schematic cross-sectional view showing a part of a cell connection portion when an interconnector without a curved portion is used as a comparative example. [Figure 5] FIG. 10 is a schematic cross-sectional view showing a part of a cell connection portion when an interconnector having a curved portion is used. [Figure 6] FIG. 10 is a rear view showing a cell connection portion in the solar cell module of the second embodiment. [Figure 7] FIG. 10 is a cross-sectional view taken along the longitudinal direction of a main body portion of a cell connection portion of a second embodiment. [Figure 8] 10A and 10B are schematic cross-sectional views showing intermediate steps in the solder connection process of the interconnector at the cell connection portion. [Figure 9] 10A and 10B are schematic cross-sectional views showing intermediate steps in the solder connection process of the interconnector at the cell connection portion. [Figure 10] 10A to 10C are schematic cross-sectional views showing an example of a step of soldering an interconnector. [Figure 11] 10A and 10B are diagrams illustrating a first action when the interconnector is thermally shrunk. [Figure 12] 10A and 10B are diagrams illustrating a second action when the interconnector is thermally shrunk. DETAILED DESCRIPTION OF THE INVENTION

[0012] [First embodiment] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Figures 1A and 1B are a plan view and a back view of a solar cell 10 used in a solar cell module (hereinafter referred to as the module) according to an embodiment of the present disclosure. Figure 2 is a back view showing the connection portions (cell connection portions) between solar cells 10 in the module.

[0013] The solar cell 10 is a back electrode type solar cell, and as shown in FIG. 1B, has a plurality of connection pads 11 on the back surface (the surface opposite the light-receiving surface). The connection pads 11 include a negative electrode connection pad 111 provided along one side (the bottom side in the figure) of the solar cell 10, and a positive electrode connection pad 112 provided along one side (the top side in the figure) opposite the negative electrode connection pad 111. As a result, as shown in FIG. 1A, the solar cell 10 does not have a connection pad 11 on the light-receiving surface, which is the front side, which improves the design. Note that the connection pads 11 are not limited to being provided in three locations along one side of the solar cell 10 as in the example of FIG. 1B, and may be provided in multiple locations.

[0014] At the cell connection portion of this module, two solar cells 10 (two adjacent solar cells 10) included in this module are connected using an interconnector (connecting member) 20. In FIG. 2, the solar cell 10 on the upper side in the figure is the first cell 10A, and the solar cell 10 on the lower side in the figure is the second cell 10B. At the cell connection portion between the first cell 10A and the second cell 10B, the side of the first cell 10A on which the negative electrode side connection pad 111 is formed serves as the connection side, and the side of the second cell 10B on which the positive electrode side connection pad 112 is formed serves as the connection side. As shown in FIG. 2, at the cell connection portion, the connection sides of the first cell 10A and the second cell 10B are arranged facing each other, and the interconnector 20 electrically connects the negative electrode side connection pad 111 of the first cell 10A and the positive electrode side connection pad 112 of the second cell 10B. Note that the connection pads 11 are not shown in FIG. 2 to simplify the drawing.

[0015] The module may have a solar cell string in which three or more solar cells 10 are connected in series at two or more cell connection points. The module may also have a solar cell array in which multiple solar cell strings are connected in parallel.

[0016] The interconnector 20 is a thin plate-like member made of a highly conductive metal (e.g., copper). The interconnector 20 has an elongated shape having a longitudinal direction and a lateral direction (a direction perpendicular to the longitudinal direction) in a plan view, and has a main body 21 extending along the longitudinal direction, and a plurality of connection tabs 22 protruding from the main body 21 on both sides in the lateral direction. The connection tabs 22 are provided in correspondence with the connection pads 11 of the solar cell 10, and in FIG. 2, three connection tabs 22 are provided on one side (upper side) and the other side (lower side) of the main body 21 in the lateral direction.

[0017] The number of connection points of the interconnector 20 to one solar cell 10 is not limited to three, and may be two, or four or more. The number of connection points of the first cell 10A to the interconnector 20 and the number of connection points of the second cell 10B to the interconnector 20 do not have to be the same.

[0018] The interconnector 20 is arranged so that the longitudinal direction of the main body 21 is parallel to the connection sides of the solar cell 10, and the connection tabs 22 are soldered to the connection pads 11. That is, in Fig. 2, the connection tab 22 provided on the upper side of the main body 21 is soldered to the negative electrode side connection pad 111 of the first cell 10A, and the connection tab 22 provided on the lower side is soldered to the positive electrode side connection pad 112 of the second cell 10B. As a result, at the cell connection portion, two adjacent solar cell cells 10 are connected in series via the interconnector 20.

[0019] FIG. 3 is a cross-sectional view along the longitudinal direction of the main body 21 at the cell connection portion (a view of the III-III cross-section in FIG. 2 as seen from below in FIG. 2). As shown in FIG. 3, the main body 21 has a curved portion 211 that curves along the longitudinal direction between adjacent connection tabs 22 along the longitudinal direction. Note that member 30 in FIG. 3 is solder that connects the connection pad 11 and the connection tab 22. The term "curved" here is not limited to a bow-like curved shape (curved shape) as shown in FIG. 3, but also includes a pseudo-curved shape having multiple bends (V-bends) and a wave-shaped curved shape having multiple convex or concave portions.

[0020] The curved portion 211 is provided in this module to prevent solder fracture between the connection pad 11 of the solar cell 10 and the connection tab 22 of the interconnector 20. This will be explained below.

[0021] Fig. 4 is a schematic cross-sectional view (the cross-sectional portion corresponds to Fig. 3) showing a part of a cell connection portion when an interconnector 20' without a curved portion 211 is used as a comparative example. In Fig. 4, connection tab 22c is the connection tab 22 at the center in the longitudinal direction, and connection tab 22e is the connection tab 22 at an end in the longitudinal direction.

[0022] The interconnector 20', which is a metal member, has a relatively large coefficient of thermal expansion, while the solar cell 10, which is primarily made of silicon, has a relatively small coefficient of thermal expansion. In other words, the interconnector 20' experiences greater thermal expansion and contraction with temperature changes than the solar cell 10. For example, if the distance between the connection tabs 22e and 22c in the longitudinal direction of the interconnector 20' is 50 mm and the temperature changes from 85°C to -40°C, the solar cell 10 shrinks by 15 μm in the longitudinal direction between these connection tabs, while the interconnector 20' shrinks by 113 μm in the longitudinal direction. In other words, the difference in shrinkage between the interconnector 20' and the solar cell 10 is 98 μm. This difference in shrinkage generates stress in the solder 30 connecting the connection pad 11 and the connection tab 22, making it more likely to break due to solder fatigue. Such solder fracture is more likely to occur in the connection tab 22e near the end, which is subjected to stress from one side, than in the connection tab 22c near the longitudinal center, which is subjected to equal stress from both the left and right sides. Furthermore, in this module, the connection process (soldering process) of the interconnector 20 is performed at a high temperature, for example, of 183°C or higher, so under normal usage conditions of this module, the interconnector 20' will shrink more than the solar cell 10 in both high temperature and low temperature environments.

[0023] 5 is a schematic cross-sectional view (the cross-sectional portion corresponds to FIG. 3) showing a part of a cell connection portion when an interconnector 20 having a curved portion 211 is used. Even in this case, the interconnector 20 experiences greater thermal expansion and contraction in response to temperature changes than the solar cell 10 (under normal usage environments, the interconnector 20 experiences greater contraction than the solar cell 10). However, the interconnector 20 absorbs this thermal contraction through deformation of the curved portion 211, thereby significantly reducing the stress acting on the solder 30 and preventing breakage due to solder fatigue.

[0024] The curved portion 211 preferably has an effective amount of curvature. The amount of curvature here refers to the amount of deformation that the curved portion 211 can undergo until it is fully expanded into a flat plate shape, and corresponds to the amount by which the difference in shrinkage between the interconnector 20 and the solar cell 10 can be absorbed. In the bowed curved shape of this embodiment, the distance in the thickness direction between the part of the curved portion 211 that contacts the connection tab 22 and the apex of the curved portion is indicated by the curve height h (shown in FIG. 3 ). The curve height h is preferably approximately 0.1 mm to 1.0 mm, and more preferably approximately 0.5 mm to 1.0 mm. An effective amount of curvature is achieved when the curve height h is approximately 0.1 mm or greater, and a sufficiently effective amount of curvature is achieved when the curve height h is approximately 0.5 mm or greater. A sufficiently effective amount of curvature is a amount of curvature that can absorb the difference in shrinkage between the interconnector 20 and the solar cell 10 (reducing the stress acting on the solder 30) when the difference in shrinkage between the interconnector 20 and the solar cell 10 is at its maximum within the operating temperature range of this module (usually when the temperature is lowest). Furthermore, by making the curvature height about 1.0 mm or less, the step between the solar cell 10 and the interconnector 20 can be kept to a certain level, making manufacturing easier.

[0025] In this embodiment, the module can be manufactured by forming a curved portion 211 in the interconnector 20 before solder connection by bending or the like, and then soldering the interconnector 20 with the curved portion 211 formed to the solar cell 10.

[0026] Furthermore, the interconnector 20 with the curved portion 211 formed therein has a shorter longitudinal length than before the curved portion 211 was formed. In other words, if the connection pads 11 of the solar cell 10 and the connection tabs 22 of the interconnector 20 are designed without taking the curved portion 211 into consideration, forming the curved portion 211 in the interconnector 20 will cause a longitudinal misalignment between the connection pads 11 and the connection tabs 22. However, this misalignment occurs on the order of 10 to 100 μm, which is a small error range, and therefore there is no particular need to adjust this misalignment. Of course, the position of the connection pads 11 (or the connection tabs 22) may be adjusted taking this misalignment into consideration.

[0027] Second Embodiment Fig. 6 is a back view showing the connection portion (cell connection portion) between solar cells 10 in this module. Fig. 7 is a cross-sectional view along the longitudinal direction of main body portion 21 at the cell connection portion (a view of the VII-VII cross-section in Fig. 6 as seen from below in Fig. 6).

[0028] As shown in Figures 6 and 7, in this embodiment, a sheet 40 is inserted between the interconnector 20 and the solar cell 10 at the cell connection portion. When viewing this module from the back side, the sheet 40 is arranged so as to cover the gap between two adjacent solar cell 10 at the cell connection portion. In addition, a low-elasticity resin 50 is arranged between the sheet 40 and the interconnector 20. The low-elasticity resin 50 may have adhesive properties and bond the sheet and the interconnector 20 together.

[0029] As described above, the back electrode type solar cell enhances its design by not providing connection pads 11 on the light-receiving surface. However, in the configuration of the first embodiment, when the module is viewed from the light-receiving surface side, the interconnectors 20 are visible through the gaps between the solar cells 10, which somewhat reduces the design. In contrast, in the present embodiment, the interconnectors 20 are concealed from view from the light-receiving surface side by the sheet 40, which further improves the design of the module. From the viewpoint of design, it is preferable that the sheet 40 be a color similar to the color of the light-receiving surface of the solar cells 10, and black is preferable.

[0030] In this embodiment, the sheet 40 and the low-elasticity resin 50 can be used to form the curved portion 211 in the interconnector 20. A specific method for this will be described below. Figures 8 and 9 are schematic cross-sectional views (the cross-sectional locations correspond to Figure 7) showing intermediate steps in the solder connection process of the interconnector 20 at the cell connection portion. Note that in this solder connection process, the back surface of the solar cell 10 faces upward.

[0031] First, as shown in Fig. 8, a sheet 40 is placed so as to cover the gap between two adjacent solar cells 10 at the cell connection portion (first step). At this time, the sheet 40 may or may not be adhered to the solar cells 10. Furthermore, a low-elasticity resin 50 is supplied to a predetermined location on the sheet 40 (second step), and solder 30 (solder paste or the like) is supplied onto the connection pads 11.

[0032] Here, the predetermined location where the low-elasticity resin 50 is supplied is a position (preferably an intermediate position) between two adjacent connection tabs 22 in the longitudinal direction of the interconnector 20. If the low-elasticity resin 50 has adhesive properties, the sheet 40 is partially bonded to a part (preferably the central part) of the curved portion 211 of the interconnector 20 by the low-elasticity resin 50.

[0033] 9, the interconnector 20 is placed on the sheet 40 and the low-elasticity resin 50 (third step). In this embodiment, the curved portion 211 is not formed in the interconnector 20 before solder connection, and the interconnector 20 at this point is flat.

[0034] Finally, the connection tabs 22 of the interconnector 20 are soldered to the connection pads 11 (for example, by applying pressure and heat from above) (fourth step), thereby completing the module shown in FIG. 7. At this time, the low-elasticity resin 50 is present between the sheet 40 and the interconnector 20, and the low-elasticity resin 50 inhibits displacement of the interconnector 20, forming curved portions 211 in the interconnector 20. The connection tabs 22 are preferably soldered from the center toward the ends in the longitudinal direction. If the low-elasticity resin 50 has an elastic modulus of 0.5 MPa or more, deformation of the low-elasticity resin 50 can be kept small, allowing the curved portions 211 to be formed.

[0035] The thickness of the low-elasticity resin 50 may be sufficient to form an effective amount of curvature (curvature height h in FIG. 7) in the curved portion 211, and in this embodiment, it is preferably about 0.1 mm to 1.0 mm, and more preferably about 0.5 mm to 1.0 mm.

[0036] In this manner, in this embodiment, the curved portion 211 can be formed in the interconnector 20 during the process of soldering the interconnector 20 to the connection pad 11 of the solar cell 10. Therefore, it is not necessary to previously form the curved portion 211 in the interconnector 20 before soldering, and the manufacturing process of this module can be simplified.

[0037] In the example of FIG. 7 , bending deformation occurs only in the interconnector 20, but in reality, bending deformation may also occur in the sheet 40 due to the action of the low-elasticity resin 50. In this case, if the bending deformation in the sheet 40 is large and the bending deformation in the interconnector 20 is small, the amount of bending of the curved portion 211 may be insufficient. For this reason, in this embodiment, it is preferable that the bending rigidity of the sheet 40 is equal to or larger than the bending rigidity of the interconnector 20. In this way, if the sheet 40 has a certain degree of bending rigidity, an effective amount of bending can be obtained in the curved portion 211. Incidentally, as long as an effective amount of bending can be obtained in the curved portion 211, bending deformation of the sheet 40 is also acceptable in the process of soldering the interconnector 20.

[0038] 10 is a schematic cross-sectional view (viewed from the right of FIG. 6 at the XX cross section in FIG. 6) showing an example of the step of soldering interconnector 20. Alternatively, as shown in FIG. 10, in the step of soldering interconnector 20, auxiliary base 60 may be placed below sheet 40 so as to suppress bending deformation of sheet 40 by auxiliary base 60. If bending deformation of sheet 40 is suppressed by auxiliary base 60, it becomes easy to impart an effective amount of bending to bending portion 211 regardless of the bending rigidity of sheet 40.

[0039] In this embodiment as well, the interconnector 20 can absorb the thermal contraction by the deformation of the curved portion 211, thereby significantly alleviating the stress acting on the solder 30 and suppressing breakage due to solder fatigue. In this embodiment, when the curved portion 211 is deformed, the following first or second action is caused to occur so that the low-elasticity resin 50 and the sheet 40 do not hinder the deformation. Of course, the first and second actions may occur simultaneously.

[0040] (First action) FIG. 11 is a schematic cross-sectional view (the cross-sectional location corresponds to FIG. 7) illustrating the first effect. When thermal contraction occurs in the interconnector 20, the curved portion 211 deforms so as to reduce its amount of curvature (curve height). The curved portion 211, whose curve height has been reduced, applies a downward pressing force in the figure to the low-elasticity resin 50, and the low-elasticity resin 50 applies a downward pressing force in the figure to the sheet 40. At this time, the sheet 40 is bent downward by the pressing force. That is, in the first effect, deformation occurs in the sheet 40 together with the curved portion 211, so that the low-elasticity resin 50 and the sheet 40 do not hinder the deformation of the curved portion 211. Note that, in order for the first effect to occur, the sheet 40 needs to have a certain degree of flexibility. If the sheet 40 is made of resin, sufficient flexibility can be ensured to cause the first effect.

[0041] (Second effect) FIG. 12 is a schematic cross-sectional view illustrating the second effect (the cross-sectional portion corresponds to FIG. 7). In the second effect, when the bending portion 211 is deformed (the amount of bending is reduced) due to thermal contraction, the low-elasticity resin 50 is subjected to a pressing force from the bending portion 211 and deforms so as to reduce its thickness. That is, in the second effect, the low-elasticity resin 50 deforms together with the bending portion 211, so that the low-elasticity resin 50 and the sheet 40 do not hinder the deformation of the bending portion 211. Note that, in order to produce the second effect, the low-elasticity resin 50 must have a certain degree of flexibility. In this case, the low-elasticity resin 50 preferably has an elastic modulus of 10 MPa or less, and is preferably made of a resin with a low glass transition temperature, such as a silicone-based resin.

[0042] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be determined based on the claims. [Explanation of symbols]

[0043] 10 solar cells 10A 1st cell 10B Second cell 11 Connection Pad 111 Negative connection pad 112 Positive connection pad 20 Interconnector (connecting member) 21 Main body 211 Curved section 22 Connections tab 30 Solder 40 sheets 50 Low elasticity resin

Claims

1. a first cell which is a back electrode type solar cell and has a plurality of negative electrode side connection pads provided along one side of the back surface; a second cell which is a back electrode type solar cell and has a plurality of positive electrode side connection pads provided along one side of the back surface; a connection member that electrically connects the plurality of negative electrode side connection pads of the first cell and the plurality of positive electrode side connection pads of the second cell in a state in which the side on which the negative electrode side connection pads of the first cell are provided and the side on which the positive electrode side connection pads of the second cell are provided are disposed opposite each other, the connection member has a main body portion whose longitudinal direction is parallel to the connection sides of the first cell and the second cell, and a plurality of connection tabs protruding from the main body portion on both sides in the lateral direction, the connection tabs include a plurality of tabs solder-connected to the negative electrode side connection pads of the first cells and a plurality of tabs solder-connected to the positive electrode side connection pads of the second cells; The solar cell module according to claim 1, wherein the main body portion has a curved portion that is curved along the longitudinal direction between the connection tabs that are adjacent along the longitudinal direction.

2. The solar cell module according to claim 1, a sheet is disposed between the first cell and the second cell and the connecting member; A solar cell module, characterized in that a low-elasticity resin is disposed between the sheet and the curved portion of the connecting member.

3. The solar cell module according to claim 2, The solar cell module is characterized in that the low-elasticity resin has an elastic modulus of 0.5 to 10 MPa.

4. The solar cell module according to claim 2, The solar cell module is characterized in that the low-elasticity resin has adhesive properties.

5. The solar cell module according to claim 2, The solar cell module is characterized in that the low-elasticity resin is a silicone-based resin.

6. A method for manufacturing the solar cell module according to claim 2, comprising the steps of: a first step of placing a sheet at a cell connection portion where the first cell and the second cell are connected by the connection member so as to cover a gap between the first cell and the second cell; a second step of supplying a low-elasticity resin to a predetermined location on the sheet; a third step of placing the connection member on the sheet and the low-elasticity resin; a fourth step of soldering the connection tabs of the connection member to the connection pads of the first cell and the second cell; In the fourth step, the curved portion is formed by the low-elasticity resin present between the sheet and the connection member.

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