Connection method of solar cell strings

Abstract

A solar battery string connection method comprising: a first current collector electrode forming process (P1) for forming a plurality of first current collector electrodes (3) on one surface (2A) of a solar battery cell (1); a second current collector electrode forming process (P2) for forming, on the other surface (2B) of the solar battery cell (1), second current collector electrodes (4) through application of a pasty second current collector electrode material including a metal component and a synthetic resin component; a division guideline forming process (P3) for forming, in the solar battery cell (1), a plurality of division guidelines (R) respectively at positions which are between each two adjacent first current collector electrodes (3) of the plurality of first current collector electrodes and which are between each two adjacent second current collector electrodes of the plurality of second current collector electrodes; a dividing process (P4) for dividing the solar battery cell (1) by cutting the cell along the plurality of division guidelines (R) into a plurality of small-piece cells (11-15) respectively having the first current collector electrodes (3) and the second current collector electrodes (4); an overlaying process (P5) for overlaying the plurality of small-piece cells (11-15) such that the first current collector electrodes (3) of the divided plurality of small-piece cells (11-15) are respectively brought into contact with the second current collector electrodes (4) of other small-piece cells (11-15); and a curing process (P6) for curing the pasty second current collector electrodes (4).

Description

Cross - reference to related applications

[0001] This application claims the priority of Japanese Patent Application No. 2021 - 060048, and is incorporated by reference into the description of this application specification.

Technical Field

[0002] The present invention relates to a method for connecting solar cell strings that electrically connect a plurality of solar cells.

Background Art

[0003] The planar shape of a solar cell is generally substantially rectangular. When connecting solar cells to each other, a collector electrode extending in the long - side direction is applied to a position close to one end in the short - side direction on the light - receiving surface of the solar cell and then cured. A back - side electrode extending in the long - side direction is applied to a position close to the other end in the short - side direction on the back surface opposite to the light - receiving surface of the solar cell and then cured. Thereafter, the two solar cells are overlapped so that a conductive member is interposed between the back - side electrode of one solar cell and the collector electrode of the other solar cell. By applying pressure and heat to the overlapped solar cells, the back - side electrode of one solar cell and the collector electrode of the other solar cell come into contact with the conductive member and are electrically connected, and the connection of the solar cells to each other is completed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, since the back - side electrode and the collector electrode are connected using a conductive member, it is a method with excellent productivity compared to the case of connecting using tab wires. However, a method with even more excellent productivity is desired.

[0006] Therefore, in view of such circumstances, an object of the present invention is to provide a method for connecting solar cell strings with excellent productivity and a solar cell string obtained by the connection method.

Means for Solving the Problems

[0007] The method for connecting solar cell strings according to the present invention includes: a first current collecting electrode forming step of forming a plurality of first current collecting electrodes on one surface of a solar cell; a second current collecting electrode forming step of applying a paste-like second current collecting electrode material containing a metal component and a synthetic resin component to each location facing each of the plurality of first current collecting electrodes on the other surface of the solar cell to form a plurality of second current collecting electrodes; a dividing guide line forming step of forming each of a plurality of dividing guide lines configured to make the solar cell easily divisible into a plurality of small cells between each two adjacent first current collecting electrodes among the plurality of first current collecting electrodes formed on one surface and between each two adjacent second current collecting electrodes among the plurality of second current collecting electrodes formed on the other surface; a dividing step of cutting the solar cell along the plurality of dividing guide lines to divide it into a plurality of small cells each having the first current collecting electrode and the second current collecting electrode; a stacking step of stacking the plurality of small cells such that the first current collecting electrode of each small cell and the second current collecting electrode of another small cell are in contact with each other; and a curing step of curing the paste-like second current collecting electrode material after stacking the plurality of small cells. It is characterized by comprising these steps.

[0008] Also, the method for connecting solar cell strings is such that the solar cell is configured in a substantially rectangular shape, the division guide lines are linear grooves formed substantially parallel to a pair of opposite sides of the solar cell, each of the first and second current collectors includes a bus bar electrode, the first current collector forming step includes a step of forming the bus bar electrode of the first current collector at a position close to one of the pair of sides on one surface of each of the plurality of small cells to be divided, the second current collector forming step includes a step of forming the bus bar electrode of the second current collector at a position close to the other of the pair of sides on the other surface of each of the plurality of small cells, and the overlapping step may be a step of overlapping the bus bar electrode of the first current collector and the bus bar electrode of the second current collector.

[0009] Also, in the method for connecting solar cell strings, the synthetic resin component of the second current collector material can be mainly composed of an acrylic resin or a silicone resin.

[0010] Also, the method for connecting solar cell strings may further include a step of attaching a transparent synthetic resin so as to straddle the plurality of small cells that are overlapped, before curing the second current collector material.

Brief Description of the Drawings

[0011]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5

Figure 6

Embodiment for Carrying Out the Invention

[0012] Hereinafter, a method for connecting a solar cell string according to an embodiment of the present invention will be described with reference to the drawings.

[0013] The solar cell 1 of this embodiment includes a substantially rectangular semiconductor substrate 2, a front-side current collector 3 which is a first current collector formed in plurality on the front surface 2A which is one surface of the semiconductor substrate 2, and a back-side current collector 4 which is a second current collector formed in plurality on the back surface 2B which is the other surface (see FIG. 2B). As will be described later, this solar cell 1 is divided into a plurality (five in FIG. 3B) of small cells 11 to 15, and the plurality of small cells 11 to 15 are singly connected to form a solar cell string 5 (see FIG. 4A). The solar cell 1 is plate-shaped, for example, substantially rectangular plate-shaped.

[0014] The semiconductor substrate 2 is formed by slicing a silicon single crystal ingot thinly in the transverse direction. In this embodiment, the shape of the semiconductor substrate 2 is shown as being substantially rectangular (square shape or rectangular shape), but other shapes than these may be used. In FIGS. 1A to 3B, the left-right direction of the paper surface is taken as left and right, and the up-down direction of the paper surface is taken as up and down, and will be described below.

[0015] The front-side collector electrode 3 is formed in each of the sections obtained by dividing the surface 2A of the semiconductor substrate 2 into five equal parts in the left-right direction. As shown in FIG. 1B, each front-side collector electrode 3 includes a plurality (ten in the figure) of front-side finger electrodes 31 and a front-side busbar electrode 32 that is wider than the front-side finger electrodes 31 for collecting the current collected by the plurality of front-side finger electrodes 31. Note that the widths of the front-side finger electrodes 31 and the front-side busbar electrode 32 are dimensions in the direction orthogonal to the extending direction of the electrodes. The plurality of front-side finger electrodes 31 are linear electrodes parallel to two opposite sides 2a and 2b among the four sides of the semiconductor substrate 2, and are formed at intervals in the directions of the remaining two sides 2c and 2d. Further, the front-side busbar electrode 32 extends in a direction substantially orthogonal to the front-side finger electrodes 31 so as to connect the same ends (right ends, the side of one side 2d) in the longitudinal direction of the plurality of front-side finger electrodes 31.

[0016] The back-side collector electrode 4 is formed in each of the sections obtained by dividing the back surface 2B of the semiconductor substrate 2 into five equal parts in the left-right direction. As shown in FIG. 2B, each back-side collector electrode 4 includes a plurality (ten in the figure) of back-side finger electrodes 41 and a back-side busbar electrode 42 that is wider than the back-side finger electrodes 41 for collecting the current collected by the plurality of back-side finger electrodes 41. Note that the widths of the back-side finger electrodes 41 and the back-side busbar electrode 42 are dimensions in the direction orthogonal to the extending direction of the electrodes. The plurality of back-side finger electrodes 41 are linear and parallel to two opposite sides 2a and 2b among the four sides of the semiconductor substrate 2, and are formed at intervals in the directions of the remaining two sides 2c and 2d. Further, the back-side busbar electrode 42 extends in a direction substantially orthogonal to the back-side finger electrodes 41 so as to connect the same ends (left ends, the ends on the side opposite to the front-side busbar electrode 32, the side of the other side 2c) in the longitudinal direction of the plurality of back-side finger electrodes 41.

[0017] As shown in Fig. 5, the method for connecting solar cell strings includes a first collector electrode forming step P1 of forming a plurality of front-side collector electrodes 3 on the front surface 2A of a solar cell 1, a second collector electrode forming step P2 of applying a paste-like second collector electrode material containing a metal component and a synthetic resin component to each location on the back surface 2B of the solar cell 1 facing the first collector electrode (without curing it after application) to form a plurality of back-side collector electrodes 4, and a dividing guide line forming step P3 of forming each of a plurality of dividing guide lines R (see Fig. 3A) on the solar cell 1. The method for connecting solar cell strings also includes a dividing step P4 of cutting the solar cell 1 along the plurality of dividing guide lines R to divide it into a plurality of small cells 11 to 15 (see Fig. 3B) each having a first collector electrode and a second collector electrode, a stacking step P5 of stacking a plurality of small cells 12 and 11 (see Fig. 4A) such that the front-side bus bar electrode 32 of the front-side collector electrode 3 of one of the divided small cells 12 abuts against the back-side bus bar electrode 42 of the back-side collector electrode 4 of the other small cell 11, and a curing step P6 of curing the paste-like back-side collector electrode 4 after stacking the plurality of small cells 12 and 11. In the dividing guide line forming step P3, each of the plurality of dividing guide lines R configured to facilitate dividing the solar cell 1 into a plurality of small cells 11 to 15 is formed between every two adjacent first collector electrodes 3 among the plurality of first collector electrodes 3 formed on the front surface 2A and between every two adjacent second collector electrodes 4 among the plurality of second collector electrodes 4 formed on the back surface 2B. Therefore, it is not necessary to dispose a conductive member different from each of the collector electrodes 3 or 4 between the front-side collector electrode 3 and the back-side collector electrode 4, resulting in excellent productivity. Also, by dividing a solar cell having a plurality of front-side collector electrodes 3 and a plurality of back-side collector electrodes 4 into a plurality of small cells, the productivity is excellent compared to a configuration in which a front-side collector electrode 3 and a back-side collector electrode 4 are formed on each of the plurality of small cells after dividing the solar cell into the plurality of small cells.

[0018] The first electrode formation step P1 includes a step of forming a front-side bus bar electrode 32 of the front-side collector electrode 3 at a position close to one of the pair of sides 2c and 2d of the solar cell 1 on the surface of each of the plurality of small pieces of cells 11 to 15 to be divided. Further, the second electrode formation step P2 includes a step of forming a back-side bus bar electrode 42 of the back-side collector electrode 4 at a position close to the other side 2c of the pair of sides 2c and 2d on the back surface of each of the plurality of small pieces of cells 11 to 15. Also, the superposition step P5 is a step of superposing the front-side bus bar electrode 32 of the front-side collector electrode 3 and the bus bar electrode 42 of the back-side collector electrode 4.

[0019] The procedure of the connection method of the solar cell string will be described. First, a semiconductor substrate 2 shown in FIG. 1A is prepared, and as shown in FIG. 1B, a front-side finger electrode 31 and a front-side bus bar electrode 32 are formed in each of the sections obtained by dividing the surface of the semiconductor substrate 2 into five equal parts in the left-right direction. The front-side finger electrode 31 and the front-side bus bar electrode 32 are formed by applying a conductive metal paste in a desired shape by screen printing or the like and then firing and curing it in a firing furnace. Note that the material constituting the metal paste may be different materials for the front-side finger electrode 31 and the front-side bus bar electrode 32, or the same material.

[0020] Next, as shown in FIG. 2A, the semiconductor substrate 2 is turned upside down so that the back surface 2B of the semiconductor substrate 2 faces upward. Then, as shown in FIG. 2B, on the back surface 2B of the semiconductor substrate 2 as well, a back-side finger electrode 41 and a back-side bus bar electrode 42 are formed in each of the sections obtained by dividing the surface into five equal parts in the left-right direction. At this time, the front-side bus bar electrode 32 is formed at a position close to one side 2d (the right side 2d) of the semiconductor substrate 2, whereas the back-side bus bar electrode 42 is formed at a position close to the other side 2c (the left side 2c) of the semiconductor substrate 2, which is different. That is, the front-side bus bar electrode 32 and the back-side bus bar electrode 42 are formed at one end (the right end 2d) and the other end (the left end 2c) in the left-right direction within the section, and are formed at different positions in the up-down direction.

[0021] The back-side finger electrode 41 and the back-side bus bar electrode 42 are left as they are with a conductive metal paste applied in a desired shape by screen printing or the like. After application, the metal paste is not cured (no curing treatment is performed). The material (the second current collector material) constituting the metal paste has a metal component mainly composed of a metal such as silver and a synthetic resin component containing a synthetic resin. In this embodiment, the synthetic resin component is mainly composed of a thermosetting resin such as a thermosetting acrylic resin or a silicone resin. Note that this synthetic resin component may be mainly composed of an acrylic-based, epoxy-based, or urethane-based ultraviolet curable resin, or may be mainly composed of a thermoplastic resin. When a thermoplastic resin is used as the synthetic resin component, heating is performed up to the temperature at which the thermoplastic resin softens, and temperature control is performed so that the thermoplastic resin does not solidify until the front-side bus bar electrode 32 and the back-side bus bar electrode 42 are connected. When a thermosetting resin such as a thermosetting acrylic resin or a silicone resin is used as the synthetic resin component, since the second current collector material has a large elasticity even after curing, an external force can be absorbed well.

[0022] When the formation of the back-side current collector 4 is completed, as shown in FIG. 3A, a division guide line R that divides into five sections is formed in the semiconductor substrate 2 by irradiating the semiconductor substrate 2 with a laser beam. By repeatedly irradiating the laser beam, the semiconductor substrate 2 can be cut and divided into five small pieces of cells 11 to 15 (see FIG. 3B). The division guide line is a linear groove substantially parallel to the left and right sides 2c and 2d of the semiconductor substrate 2. In this embodiment, the semiconductor substrate 2 is cut by a laser beam. However, a division guide line R may be formed in the semiconductor substrate 2 by a laser beam, and cutting may be performed along the division guide line R using a diamond cutter or the like.

[0023] With the five small cells 11 to 15 in a state where their back surfaces face upward, as shown in FIGS. 4A and 4B, the downward-facing front-side bus bar electrode 32 (see FIG. 4B) located at the right end of the front surface 2A of the upper small cell 11 is overlapped with the upward-facing back-side bus bar electrode 42 located at the left end of the back surface 2B of the lower small cell 12, and the upper small cell 11 is stacked on the lower small cell 12. At this time, since the back-side bus bar electrode 42 is in a state where it is not cured (a state having elasticity), the back-side bus bar electrode 42 easily adheres to the cured front-side bus bar electrode 32. After the superposition of all five small cells is completed, by firing in a firing furnace, the back-side finger electrodes 41 and the back-side bus bar electrode 42 are cured and all the small cells 11 to 15 are electrically connected in series (this connection is called a singling connection). After the connection, the small cells 11 to 15 connected between the front-side protective material and the back-side protective material are arranged and sealed with a sealing resin, whereby the solar cell string 5 is completed. Thus, in the solar cell string 5 configured by connecting a plurality of small cells 11 to 15, the output per unit area can be increased. In this embodiment, since the non-cured back-side bus bar electrode 42 is connected with the upward orientation, it is possible to suppress the deformation of the back-side bus bar electrode 42 so as to droop downward when the connection is made with the downward orientation.

[0024] Further, the present invention further includes a step (not shown) of pasting a transparent synthetic resin across the plurality of small pieces of cells 11 to 15 that are overlapped before curing the second current collector material. Specifically, as shown in FIG. 6, after the overlapping of all the five small pieces of cells 11 to 15 is completed and before curing the back-side current collector 4, a transparent synthetic resin (thermosetting resin) 16 is pasted in a tape shape (or may be in a thread shape) on the back surface 2B of the small pieces of cells 11 to 15 so as to span all the small pieces of cells 11 to 15 by using a dispenser 17 or the like. After pasting, by baking in a firing furnace, the synthetic resin (thermosetting resin) 16 is thermally cured, and the connection between the small pieces of cells can be reinforced, which is preferable. In FIG. 6, the synthetic resin is pasted at four locations, but it may be pasted at only one location, or at any number of locations such as two locations, three locations, or five or more locations.

[0025] Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

[0026] In the above embodiment, both the back-side finger electrode 41 and the back-side bus bar electrode 42 of the back-side current collector 4 are not cured after coating, but a process of curing the back-side finger electrode 41 may be performed, and only the back-side bus bar electrode 42 may not be cured.

[0027] According to the present invention, by adopting a configuration in which the first current collector and the second current collector are directly connected, it is possible to provide a method for connecting a solar cell string with excellent productivity and a solar cell string obtained by the connection method.

[0028] The method for connecting a solar cell string according to the present invention includes: a first current collecting electrode forming step of forming a plurality of first current collecting electrodes on one surface of a solar cell; a second current collecting electrode forming step of applying a paste-like second current collecting electrode material containing a metal component and a synthetic resin component to each location facing each of the plurality of first current collecting electrodes on the other surface of the solar cell to form a plurality of second current collecting electrodes; a dividing guide line forming step of forming each of a plurality of dividing guide lines configured to facilitate dividing the solar cell into a plurality of small cells between each two adjacent first current collecting electrodes among the plurality of first current collecting electrodes formed on one surface and between each two adjacent second current collecting electrodes among the plurality of second current collecting electrodes formed on the other surface; a dividing step of cutting the solar cell along the plurality of dividing guide lines to divide it into a plurality of small cells each having the first current collecting electrode and the second current collecting electrode; a stacking step of stacking the plurality of small cells such that the first current collecting electrode of each small cell and the second current collecting electrode of another small cell are in contact with each other; and a curing step of curing the paste-like second current collecting electrode material after stacking the plurality of small cells.

[0029] According to such a configuration, after stacking both small cells so that the first current collecting electrode of one small cell and the second current collecting electrode of the other small cell are stacked, by simply curing the second current collecting electrode, the first current collecting electrode and the second current collecting electrode are electrically connected. Therefore, since it is not necessary to dispose a conductive member different from each current collecting electrode between the first current collecting electrode and the second current collecting electrode, the productivity is excellent. Further, by dividing the solar cell having a plurality of first current collecting electrodes and a plurality of second current collecting electrodes into a plurality of small cells, after dividing the solar cell into a plurality of small cells, the productivity is excellent as compared with a configuration in which the first current collecting electrode and the second current collecting electrode are formed in each of the plurality of small cells.

[0030] Also, the method for connecting a solar cell string is such that the solar cell is configured in a substantially rectangular shape, the division guide line is a linear groove formed substantially parallel to a pair of opposite sides of the solar cell, each of the first current collector electrode and the second current collector electrode includes a bus bar electrode, the first current collector electrode forming step includes a step of forming the bus bar electrode of the first current collector electrode at a position close to one of the pair of sides on one surface of each of the plurality of small cells to be divided, the second current collector electrode forming step includes a step of forming the bus bar electrode of the second current collector electrode at a position close to the other of the pair of sides on the other surface of each of the plurality of small cells, and the overlapping step may be a step of overlapping the bus bar electrode of the first current collector electrode and the bus bar electrode of the second current collector electrode.

[0031] As described above, by performing so-called singling connection, which connects the bus bar electrode of the second current collector electrode on the other surface formed at a position close to the other side and the bus bar electrode of the first current collector electrode on one surface formed at a position close to one side, the output per unit area of a solar cell string configured by connecting a plurality of small cells can be increased.

[0032] Also, the method for connecting a solar cell string is such that the synthetic resin component of the second current collector material can be mainly composed of an acrylic resin or a silicone resin.

[0033] As described above, by mainly using an acrylic resin or a silicone resin, since the second current collector material has high elasticity even after curing, it can absorb external forces well.

[0034] Also, the method for connecting a solar cell string may further include a step of attaching a transparent synthetic resin so as to straddle the plurality of overlapped small cells before curing the second current collector material.

[0035] As described above, by attaching a transparent synthetic resin so as to straddle the plurality of overlapped small cells, the connection between the small cells can be strengthened.

Description of Symbols

[0036] 1…Solar cell, 2…Semiconductor substrate, 2A…Front surface (one side), 2B…Back surface, 2a, 2b, 2c, 2d…Sides, 3…Front surface side collector electrode (first collector electrode), 4…Back surface side collector electrode (second collector electrode), 5…Solar cell string, 11~15…Chip cells, 16…Synthetic resin (thermosetting resin), 17…Dispenser, 31…Front surface side finger electrode, 32…Front surface side bus bar electrode, 41…Back surface side finger electrode, 42…Back surface side bus bar electrode, P1…First collector electrode formation process, P2…Second collector electrode formation process, P3…Division guide line formation process, P4…Division process, P5…Overlay process, P6…Hardening process, R…Division guide line (scribe line)

Claims

【Claim 1】 a first current collector forming step of forming a plurality of first current collectors on one surface of a solar cell; a second current collector forming step of applying a paste-like second current collector material containing a metal component and a synthetic resin component to each location facing each of the plurality of first current collectors on the other surface of the solar cell to form a plurality of second current collectors; a dividing guide line forming step of forming each of a plurality of dividing guide lines configured to facilitate dividing the solar cell into a plurality of small cells between each two adjacent first current collectors among the plurality of first current collectors formed on one surface and between each two adjacent second current collectors among the plurality of second current collectors formed on the other surface; a dividing step of cutting the solar cell along the plurality of dividing guide lines to divide it into a plurality of small cells each having the first current collector and the second current collector; a stacking step of stacking the plurality of small cells such that the first current collector of each small cell of the plurality of divided small cells is brought into contact with the second current collector of another small cell; a curing step of curing the paste-like second current collector material after the plurality of small cells are stacked; and before curing the second current collector material, further comprising a step of sticking a transparent thermosetting resin across the plurality of stacked small cells, a method for connecting a solar cell string, characterized in that.

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