WO2016065936A1

WO2016065936A1 - Method for manufacturing solar cell module

Info

Publication number: WO2016065936A1
Application number: PCT/CN2015/084055
Authority: WO
Inventors: Zhiqiang Zhao; Liguo Wang; Ye Tian; Shuping KANG; Zhanfeng Jiang; Long He
Original assignee: Byd Company Limited
Priority date: 2014-10-31
Filing date: 2015-07-15
Publication date: 2016-05-06

Abstract

A manufacturing method of a solar cell module is disclosed. The method includes: welding in high frequency a conductive wire constituted by a metal wire with a cell; superposing an upper cover plate, a front adhesive layer, the cell, a back adhesive layer and a back plate in sequence, and laminating them to obtain the solar cell module.

Description

METHOD FOR MANUFACTURING SOLAR CELL MODULE

FIELD

The present disclosure relates to a field of solar cells, and more particularly, to a solar cell module and a manufacturing method thereof.

BACKGROUND

A solar cell module is one of the most important components of a solar power generation device. Sunlight irradiates onto a cell from its front surface and is converted to electricity within the cell. Primary grid lines and secondary grid lines are disposed on the front surface. The primary grid lines and the secondary grid lines cover part of the front surface of the cell, which blocks out part of the sunlight, and the part of sunlight irradiating onto the primary grid lines and the secondary grid lines cannot be converted into electric energy. Thus, the primary grid lines and the secondary grid lines need to be designed as fine as possible in order for the solar cell module to receive more sunlight. However, the primary grid lines and the secondary grid lines serve to conduct current, and in terms of resistivity, the finer the primary grid lines and the secondary grid lines are, the smaller the conductive cross section area thereof is, which causes greater loss of electricity due to increased resistivity. Therefore, the primary grid lines and the secondary grid lines shall be designed to get a balance between light blocking and electric conduction, and to take the cost into consideration.

The traditional solar cell module mainly adopts the structure of three primary grid lines. For the cell with three primary grid lines, the welding of the primary grid lines usually adopts the contact welding process, like iron welding. Currently, the solar cell module tends to have a structure of multiple primary grid lines, so as to increase the distance between the secondary grid lines and the primary grid lines, and the resulting series resistance of the cell, so as to improve the power generation performance. However, as for the structure of multiple primary grid lines, the difficulty of welding the primary grid lines is increased due to many welding points and hard positioning.

SUMMARY

The present disclosure is based on discoveries and understanding of the applicant to the following facts and problems.

In prior art, the primary grid lines and the secondary grid lines of the solar cells are made of expensive silver paste, which results in complicated manufacturing process of the primary grid lines and the secondary grid lines and high cost. When the cells are connected to form a module, the primary grid lines on the front surface of a cell are welded with back electrodes of another adjacent cell by a solder strip. Consequently, the welding of the primary grid lines is complicated, and the manufacturing cost of the cells is high.

In prior art, two primary grid lines are usually disposed on the front surface of the cell, and formed by applying silver paste to the front surface of the cell. The primary grid lines have a great width (for example, up to over 2mm) , which consumes a large amount of silver, and makes the cost high.

In prior art, a solar cell with three primary grid lines is provided, but this kind of solar cell still consumes a large amount of silver, and has a high cost. Moreover, three primary grid lines increase the shading area, which lowers the photoelectric conversion efficiency.

In addition, the number of the primary grid lines is limited by the solder strip. The larger the number of the primary grid lines is, the finer a single primary grid line is, and hence the solder strip needs to be narrower. Therefore, it is more difficult to weld the primary grid lines with the solder strip and to produce the narrower solder strip, and thus the cost of the welding rises up.

Consequently, from the perspective of lowering the cost and reducing the shading area, the prior art replaces the silver primary grid lines printed on the cell with metal wires, for example, copper wires. The copper wires are welded with the secondary grid lines to output the current. Since the silver primary grid lines are no longer used, the cost can be reduced considerably. The copper wire has a smaller diameter to reduce the shading area, so the number of the copper wires can be raised up to 10. This kind of cell may be called a cell without primary grid lines, in which the metal wire replaces the silver primary grid lines and solder strips in the traditional solar cells.

In prior art, there is a technical solution that the electrical connection of the metal wire and the cells is formed by laminating a transparent film pasted with metal wires and the cells, i.e. multiple parallel metal wires being fixed on the transparent film by adhesion, then being stuck on the cell, and finally being laminated to contact with the secondary grid lines on the cell. In other words, the metal wires are in contact with the secondary grid lines by the laminating process, so as to output the current. However, in this technical solution, the transparent film weakens the absorption rate of light, and a plurality of parallel metal wires may be in bad connection with the cells, which may affect the electrical performance. Thus, the number of the metal wires needs to be increased. If the number of the metal wires is increased, the absorption rate of light from the front surface is affected, and the performance of the product is degraded. Consequently, the product in this technical solution is not promoted and commercialized. Moreover, as said above, the number of the parallel metal wires is limited by the distance between adjacent metal wires. Since the metal wires are pasted and fixed on the transparent film by a bonding layer, the bonding layer may melt or be softened in the laminating process, and thus the metal wires will drift to some extent.

In prior art, copper wires are disposed in the adhesive layer of the solar cell module to serve as the primary grid lines, and the primary grid lines and the cell are connected by laminating the module. However, since the melting point of the adhesive layers is lower than the temperature of laminating the module. In the laminating process, the metal wire disposed in the adhesive layers will drift, which lowers the photoelectric conversion efficiency of the solar cell module.

In prior, multiple parallel metal wires form electric connection with the cells by infrared radiation, but the process is difficult to realize, and the welding cost is high.

Thus, in the field of solar cells, the structure of the solar cell is not complicated, but each component is crucial. The production of the primary grid lines takes various aspects into consideration, such as shading area, electric conductivity, equipment, process, cost, etc., and hence becomes a difficult and hot issue in the solar cell technology. In the market, a solar cell with two primary grid lines is replaced with a solar cell with three primary grid lines in 2007 through huge efforts of those skilled in the art. A few factories came up with a solar cell with four primary grid lines around 2014. The concept of multiple primary grid lines is put forward in the recent years, but still there is no fairly mature product.

The present disclosure seeks to solve at least one of the problems existing in the related art to at least some extent.

The present disclosure provides a method for manufacture a solar cell without primary grid lines. The solar cell without primary grid lines obtained needs neither primary grid line nor sold strip disposed on the cells, and thus lowers the cost. The solar cell without primary grid lines can be commercialized for mass production, easy to manufacture with simple equipment, especially in low cost, and moreover have high photoelectric conversion efficiency.

According to embodiments of the present disclosure, the method includes: welding in high frequency a conductive wire constituted by a metal wire with a cell； superposing an upper cover plate, a front adhesive layer, the cell, a back adhesive layer and a back plate in sequence, and laminating them to obtain the solar cell module.

According to embodiments of the present disclosure, the method welds in high frequency the conductive wires with the cell, and laminates the cover plate, the front adhesive layer, the cell, the back adhesive layer and the back plate to obtain the solar cell module. The method may implement the welding of the conductive wires and the cells, avoid insufficient welding, and prevent the conductive wires from drifting in the laminating process. The method is easy to implement in low cost, and the solar cell module obtained has high photoelectric conversion efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a plan view of a solar cell array according to an embodiment of the present disclosure；

Fig. 2 is a longitudinal sectional view of a solar cell array according to an embodiment of the present disclosure；

Fig. 3 is a transverse sectional view of a solar cell array according to embodiments of the present disclosure；

Fig. 4 is a schematic diagram of a metal wire for forming a conductive wire according to embodiments of the present disclosure；

Fig. 5 is a plan view of a solar cell array according to another embodiment of the present disclosure；

Fig. 6 is a plan view of a solar cell array according to another embodiment of the present disclosure；

Fig. 7 is a schematic diagram of a metal wire extending reciprocally according to embodiments of the present disclosure；

Fig. 8 is a schematic diagram of two cells of a solar cell array according to embodiments of the present disclosure；

Fig. 9 is a sectional view of a solar cell array formed by connecting, by a metal wire, the two cells according to Fig. 8；

Fig. 10 is a schematic diagram of a solar cell module according to embodiments of the present disclosure；

Fig. 11 is a sectional view of part of the solar cell module according to Fig. 10；

Fig. 12 is a schematic diagram of a solar cell array according to another embodiment of the present disclosure；

Fig. 13 is a schematic diagram of a process of manufacturing a solar cell module according to an embodiment of the present disclosure；

Fig. 14 is another schematic diagram of a process of manufacturing a solar cell module according to an embodiment of the present disclosure；

Fig. 15 is a schematic diagram of a process of manufacturing a solar cell module according to another embodiment of the present disclosure；

Fig. 16 is another schematic diagram of a process of manufacturing a solar cell module according to another embodiment of the present disclosure.

Reference numerals:

100 cell module

10 upper cover plate

20 front adhesive layer

30 cell array

31 cell

31A first cell

31B second cell

311 cell substrate

312 secondary grid line

312A front secondary grid line

312B back secondary grid line

3121 edge secondary grid line

3122 middle secondary grid line

313 back electric field

314 back electrode

32 conductive wire

32A front conductive wire

32B back conductive wire

321 metal wire

322 connection material layer

33 short grid line

40 back adhesive layer

50 back plate

70 pressing plate

71 pressing block

80 coil

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described in detail and examples of the embodiments will be illustrated in the drawings, where same or similar reference numerals are used to indicate same or similar members or members with same or similar functions. The embodiments described herein with reference to the drawings are explanatory, which are used to illustrate the present disclosure, but shall not be construed to limit the present disclosure.

Part of technical terms in the present disclosure will be elaborated herein for clarity and convenience of description.

According to embodiments of the present disclosure, a cell 31 includes a cell substrate 311, secondary grid lines 312 disposed on a front surface (the surface on which light is incident) of the cell substrate 311, a back electric field 313 disposed on a back surface of the cell substrate 311, and back electrodes 314 disposed on the back electric field 313. Thus, the secondary grid lines 312 can be called the secondary grid lines 312 of the cell 31, the back electric field 313 called the back electric field 313 of the cell 31, and the back electrodes 314 called the back electrodes 314 of the cell 31.

A cell substrate 311 can be an intermediate product obtained by subjecting, for example, a silicon chip to processes of felting, diffusing, edge etching and silicon nitride layer depositing. However, it shall be understood that the cell substrate 311 in the present disclosure is not limited to be formed by the silicon chip, but includes any other suitable solar cell substrate 311.

In other words, the cell 31 comprises a silicon chip, some processing layers on a surface of the silicon chip, secondary grid lines on a shiny surface (namely a front surface) , and a back electric field 313 and back electrodes 314 on a shady surface (namely a back surface) , or includes other equivalent solar cells of other types without any front electrode.

A cell unit includes a cell 31 and conductive wires 32 constituted by a metal wire S.

A a solar cell array 30 includes a plurality of cells 31 and conductive wires 32 which connect adjacent cells 31 and are constituted by the metal wire S. In other words, the solar cell array 30 is formed of a plurality of cells 31 connected by the conductive wires 32.

In the solar cell array 30, the metal wire S constitutes the conductive wires 32 of the cell unit, and extends between surfaces of the adjacent cells 31, which shall be understood in a broad sense that the metal wire S may extend between front surfaces of the adjacent cells 31, or may extend between a front surface of a first cell 31 and a back surface of a second cell 31 adjacent to the first cell 31. When the metal wire S extends between the front surface of the first cell 31 and the back surface of the second cell 31 adjacent to the first cell 31, the conductive wires 32 may include front conductive wires 32A extending on the front surface of the cell 31 and electrically connected with the secondary grid lines 312 of the cell 31, and back conductive wires 32B extending on the back surface of the cell 31 and electrically connected with the back electrodes 314 of the cell 31. Part of the metal wire S between the adjacent cells 31 can be called connection conductive wires.

In the present disclosure, the cell substrate 311, the cell 31, the cell unit, the cell array 30 and the solar cell module are only for the convenience of description, and shall not be construed to limit the present disclosure.

All the ranges disclosed in the present disclosure include endpoints, and can be individual or combined. It shall be understood that the endpoints and any value of the ranges are not limited to an accurate range or value, but also include values proximate the ranges or values.

In the present disclosure, the orientation terms such as “upper” and “lower” usually refer to the orientation “upper” or “lower” as shown in the drawings under discussion, unless specified otherwise； “front surface” refers to a surface of the solar cell module facing the light in practical application (for example, when the module is in operation) , i.e. a shiny surface on which light is incident, while “back surface” refers to a surface of the solar cell module back to the light in practical application.

In the following, a method for manufacturing a solar cell module according to the embodiments of the present disclosure will be described with respect to the drawings.

Specifically, the method according to the embodiments of the present disclosure includes: welding in high frequency a conductive wire 32 constituted by a metal wire with a cell 31； superposing an upper cover plate 10, a front adhesive layer 20, the cell 31, a back adhesive layer 40 and a back plate 50 in sequence, and laminating them to obtain the solar cell module.

In other words, in the process of laminating the solar cell module, the conductive wires 32 constituted by the metal wire are welded with the cell 31 in high frequency； then the upper cover plate 10, the front adhesive layer 20, the cell 31, the back adhesive layer 40 and the back plate 50 are superposed in sequence and laminated, so as to obtain the solar cell module 100.

In the following, the high-frequency welding method will be described with respect to the drawings.

Specifically, as shown in Fig. 13 and Fig. 14, an execution mode of high-frequency welding includes: arranging the conductive wires 32 on the cell 31 based on the requirements； placing the conductive wires 32 and the cell 31 between upper and lower pressing plates 70, in which a pressing block 71 is disposed on the upper pressing plate 70； surrounding the peripheries of the cell 31 by coils 80； generating high-frequency current in the coils 80 by a high-frequency power supply, so as to generate induced current in the cell 31 close to the coils 80 and the conductive wires 32, to heat the cell 31 and the conductive wires 32 by the induced current, and to weld the cell 31 and the conductive wires 32.

As shown in Fig. 15 and Fig. 16, an execution mode of high-frequency welding includes: placing the conductive wires 32 and the cell 31 between upper and lower pressing plates 70, in which a pressing block 71 is disposed on the upper pressing plate 70； disposing the coils 80 at one side of the cell 31； generating high-frequency current in the coils 80 by a high-frequency power supply, so as to generate induced current in the cell 31 close to the coils 80 and the conductive wires 32, to heat the cell 31 and the conductive wires 32 by the induced current, and to weld the cell 31 and the conductive wires 32.

In the first execution mode of high-frequency welding, the process of manufacturing the solar cell module 100 may include: superposing the upper cover plate 10, the front adhesive layer 20, the cell 31, the back adhesive layer 40 and the back plate 50 sequentially from up to down； arranging the conductive wires 32 on the cell 31 based on the requirements； placing the conductive wires 32 and the cell 31 between upper and lower pressing plates 70, in which a pressing block 71 is disposed on the upper pressing plate 70； surrounding the peripheries of the cell 31 by coils 80； generating high-frequency current in the coils 80 by a high-frequency power supply, so as to generate induced current in the cell 31 close to the coils 80 and the conductive wires 32, to heat the cell 31 and the conductive wires 32 by the induced current, and to weld the cell 31 and the conductive wires 32. Meanwhile, the induced current heats the cell 31, the adhesive layers (including the front adhesive layer 20 and the back adhesive layer 40) , the cover plates (including the upper cover plate 10 and the back plate 50) , and they are laminated by the pressing block 71, so as to obtain the solar cell module 100.

In the second execution mode of high-frequency welding, the process of manufacturing the solar cell module 100 may include: superposing the upper cover plate 10, the front adhesive layer 20, the cell 31, the back adhesive layer 40 and the back plate 50 sequentially from up to down； placing the conductive wires 32 and the cell 31 between upper and lower pressing plates 70, in which a pressing block 71 is disposed on the upper pressing plate 70； disposing the coils 80 at one side of the cell 31； generating high-frequency current in the coils 80 by a high-frequency power supply, so as to generate induced current in the cell 31 close to the coils 80 and the conductive wires 32, to heat the cell 31 and the conductive wires 32 by the induced current, and to weld the cell 31 and the conductive wires 32. Meanwhile, the induced current heats the cell 31, the adhesive layers (including the front adhesive layer 20 and the back adhesive layer 40) , the cover plates (including the upper cover plate 10 and the back plate 50) , and they are laminated by the pressing block 71, so as to obtain the solar cell module 100.

Consequently, the method for manufacturing the solar cell module according to the embodiments of the present disclosure adopts the high-frequency welding to weld the conductive wires and the cell, and assembles the cover plate, the front adhesive layer, the cell, the back adhesive layer and the back plates by laminating to obtain the solar cell module. The method can achieve the welding of the conductive wires and the cells, avoid insufficient welding, and prevent the conductive wires from drifting in the laminating process. The method is easy to implement in low cost, and the solar cell module obtained has high photoelectric conversion efficiency.

According to an embodiment of the present disclosure, the conductive wire and the cell are welded before or when they are laminated. Thus, the process of assembling the conductive wires 32 and the cell 31 is more flexible, and they are easier to manufacture.

In the present disclosure, there are at least two cells 31, and the conductive wire 32extends reciprocally between a surface of a first cell 31 and a surface of a second cell 31 adjacent to the first cell 31.

That’s to say, in some specific embodiments of the present disclosure, there are multiple cells 31 to constitute the cell array 30, adjacent cells 31 connected by the conductive wires 32 that extend reciprocally between a surface of a first cell 31 and a surface of a second cell 31 adjacent to the first cell 31. The conductive wires 32 and the cells 31 are connected by high-frequency welding.

Specifically, the solar cell array 30 according to the embodiments of the present disclosure includes a plurality of cells 31. The adjacent cells 31 are connected with a plurality of conductive wires 32 which are constituted by a metal wire S. The metal wire S is electrically connected with the cells 31 by high-frequency welding and extends reciprocally between the surfaces of the adjacent cells 31.

The cell unit is formed by the cell 31 and the conductive wires 32 constituted by the metal wire S which extends on the surface of the cell 31. In other words, the solar cell array 30 according to the embodiments of the present disclosure are formed with a plurality of cell units； the conductive wires 32 of the plurality of cells are formed by the metal wire S which extends reciprocally between the surfaces of the cells 31.

It shall be understood that the term “extending reciprocally” in the application can be called “winding” which refers to that the metal wire S extends between the surfaces of the cells 31 along a reciprocal route.

In the present disclosure, it shall be understood in a broad sense that “the metal wire S extends reciprocally between surfaces of the cells 31. For example, the metal wire S may extend reciprocally between a front surface of a first cell 31 and a back surface of a second cell 31 adjacent to the first cell 31； the metal wire S may extend from a surface of the first cell 31 through surfaces of a predetermined number of middle cells 31 to a surface of the last cell 31, and then extends back from the surface of the last cell 31 through the surfaces of a predetermined number of middle cells 31 to the surface of the first cell 31, extending reciprocally like this.

In addition, when the cells 31 are connected in parallel by the metal wire S, the metal wire S can extend on front surfaces of the cells 31, such that the metal wire S constitutes front conductive wires 32A. Alternatively, a first metal wire S extends reciprocally between the front surfaces of the cells 31, and a second metal wire S extends reciprocally between the back surfaces of the cells 31, such that the first metal wire S constitutes front conductive wires 32A, and the second metal wire S constitutes back conductive wires 32B.

When the cells 31 are connected in series by the metal wire S, the metal wire S can extend reciprocally between a front surface of a first cell 31 and a back surface of a second cell 31 adjacent to the first cell 31, such that part of the metal wire S which extends on the front surface of the first cell 31 constitutes front conductive wires 32A, and part thereof which extends on the back surface of the second cell 31 constitutes back conductive wires 32B. In the present disclosure, unless specified otherwise, the conductive wires 32 can be understood as the front conductive wires 32A, the back conductive wires 32B, or the combination thereof.

The term “extending reciprocally” can be understood as that the metal wire S extends reciprocally once to form to two conductive wires 32 which are formed by winding a metal wire S. For example, two adjacent conductive wires form a U-shape structure or a V-shape structure, yet the present disclosure is not limited to the above.

In the solar cell array 30 according to the embodiments of the present disclosure, the conductive wires 32 of the plurality of cells 31 are constituted by the metal wire S which extends reciprocally； and the adjacent cells 31 are connected by the conductive wires 32. Hence, the conductive wires 32 of the cells are not necessarily made of expensive silver paste, and can be manufactured in a simple manner without using a solder strip to connect the cells. It is easy and convenient to connect the metal wire S with the secondary grid lines and the back electrodes, so that the cost of the cells is reduced considerably.

Moreover, since the conductive wires 32 are constituted by the metal wire S which extends reciprocally, the width of the conductive wires 32 (i.e. the width of projection of the metal wire on the cell) may be decreased, thereby decreasing the shading area of the conductive wires 32. Further, the number of the conductive wires 32 can be adjusted easily, and thus the resistance of the conductive wires 32 is reduced, compared with the primary grid lines made of the silver paste, and the photoelectric conversion efficiency is improved. Since the metal wire S extends reciprocally to form the conductive wires, when the cell array 30 is used to manufacture the solar cell module 100, the metal wire S will not tend to shift, i.e. the metal wire is not easy to “drift” , which will not affect but further improve the photoelectric conversion efficiency.

Therefore, the solar cell array 30 according to the embodiments of the present disclosure has low cost and high photoelectric conversion efficiency.

Moreover, it shall be noted that in the present disclosure, the conductive wires 32 can be constituted by the metal wire S which is coated with the conductive adhesive and extends reciprocally between the surfaces of the adjacent cells, or can be arranged by multiple metal wires in parallel to and spaced apart from each other. It is understandable for those skilled in the art that in the technical solution a plurality of individual metal wires are spaced apart from each other to form the primary grid lines of the traditional structure, which will not be described in detail.

In the following, the solar cell array 30 according to specific embodiments of the present disclosure will be described with reference to the drawings.

The solar cell array 30 according to a specific embodiment of the present disclosure is illustrated with reference to Fig. 1 to Fig. 3.

In the embodiment shown in Fig. 1 to Fig. 3, two cells 31 in the solar cell array 30 are shown. In other words, it shows two cells 31 connected with each other via the conductive wires 32 constituted by the metal wire S.

It can be understood that the cell 31 comprises a cell substrate 311, secondary grid lines 312 (i.e. front secondary grid lines 312A) disposed on a front surface of the cell substrate 311, a back electric field 313 disposed on a back surface of the cell substrate 311, and back electrodes 314 disposed on the back electric field 313. In the present disclosure, it shall be understood that the back electrodes 314 may be back electrodes of a traditional cell, for example, printed by the silver paste, or may be back secondary grid lines 312B similar to the secondary grid lines on the front surface of the cell substrate, or may be multiple discrete welding portions, unless specified otherwise. The secondary grid lines refer to the secondary grid lines 312 on the front surface of the cell substrate 311, unless specified otherwise.

As shown in Fig. 1 to Fig. 3, the solar cell array in the embodiment includes two

cells

31A, 31B (called a first cell 31A and a second cell 31B respectively for convenience of description) . The metal wire S extends reciprocally between the front surface of the first cell 31A (a shiny surface, i.e. an upper surface in Fig. 2) and the back surface of the second cell 31B, such that the metal wire S constitutes front conductive wires of the first cell 31A and back conductive wires of the second cell 31B. The metal wire S is electrically connected with the secondary grid lines of the first cell 31A by high-frequency welding, and electrically connected with the back electrodes of the second cell 31B by high-frequency welding.

In some embodiments, the metal wire extends reciprocally between the first cell 31A and the second cell 31B for 10 to 60 times to form 20 to 120 conductive wires. Preferably, as shown in Fig. 1, the metal wire extends reciprocally for 12 times to form 24 conductive wires 32, and there is only one metal wire. In other words, a single metal wire extends reciprocally for 12 times to form 24 conductive wires, and the distance of the adjacent conductive wires can range from 2.5mm to 15mm. In this embodiment, the number of the conductive wires is increased, compared with the traditional cell, such that the distance between the secondary grid lines and the conductive wires which the current runs through is decreased, so as to reduce the resistance and improve the photoelectric conversion efficiency. In the embodiment shown in Fig. 1, the adjacent conductive wires form a U-shape structure, for convenience of winding the metal wire. Alternatively, the present disclosure is not limited to the above. For example, the adjacent conductive wires can form a V-shape structure.

It shall be noted that in the present disclosure, the metal wire S refers to a metal wire for extending reciprocally on the cells 31 to form the conductive wires 32； and the conductive wires 32 may include a metal wire body 321 and a connection material layer 322 coating the metal wire body 321, i.e. the metal wire S can consist of the metal wire body 321 and the connection material layer 322 coating the metal wire body 321. In the embodiment of the present disclosure, unless specified otherwise, the metal wire refers to the metal wire S for extending reciprocally on the cells 31 to form the conductive wires 32.

In some embodiments, preferably, the metal wire body 321 is a copper wire, i.e. the metal wire S can be a copper wire, too. In other words, the metal wire does not include the coating layer, but the present disclosure does not limited thereto. For example, the metal wire body 321 can be an aluminum wire. In the present disclosure, preferably, the metal wire body 321 has a circular cross section, such that more sunlight can reach the cell substrate to further improve the photoelectric conversion efficiency.

In some specific embodiments of the present disclosure, the connection material layer coating the metal wire body 321 is the welding layer, which is an alloy layer. The alloy layer contains Sn and at least one of Bi, In, Ag, Sb, Pb and Zn. Preferably, the alloy contains Sn, Bi, and at least one of In, Ag, Sb, Pb and Zn.

In the alloy, based on the total weight of the alloy, the amount of Bi is 15 to 60 weight percent, Sn 30 to 75 weight percent, Cu 0 to 20 weight percent, In 0 to 40 weight percent, Ag 0 to 3 weight percent, Sb 0 to 20 weight percent, Pb 0 to 10 weight percent, and Zn 0 to 20 weight percent.

Further, the alloy is at least one selected from 50％Sn-48％Bi-1.5％Ag-0.5％Cu, 58％Bi-42％Sn and 65％Sn-20％Bi-10％Pb-5％Zn.

Alternatively, the alloy layer has a thickness of 1 to 100μm, and the conductive wire has a cross section of 0.01 to 0.5mm².

In some specific embodiments of the present disclosure, the method further includes applying a welding layer to a position where the conductive wire 32 is welded with the cell 31, before the conductive wires constituted by the metal wire and the cell are welded by high-frequency welding.

The welding layer can be disposed on the cell 31, or the metal wire body 321. Preferably, the welding layer is disposed on the metal wire body 321. In other words, in the present disclosure, the metal wire body 321 is coated with the welding layer, i.e. the connection material layer 322 is the welding layer. Preferably, the ratio of a thickness of the welding layer and a diameter of the metal wire body 321 is (0.02-0.5) : 1.

The welding layer may be a metal with a lower melting point or an alloy. The tin alloy can be a conventional tin alloy, for example, containing Sn, and at least one of Bi, Pb, Ag and Cu, more specifically, i.e. SnBi, SnPb, SnBiCu, SnPbAg, etc, so as to avoid insufficient soldering between the conductive wires 32 and the secondary grid lines 312 and/or the back electrodes 314 of the cell, and to render the solar cell module higher photoelectric conversion efficiency.

In some embodiments, preferably, before the metal wire and the cell are high-frequency welded, the metal wire extends under strain, i.e. straightening the metal wire. After the metal wire is connected with the secondary grid lines and the back electrodes of the cell, the strain of the metal wire can be released, so as to further avoid the drifting of the conductive wires when the solar cell module is manufactured, and to guarantee the photoelectric conversion efficiency.

In some specific embodiments of the present disclosure, the secondary grid line has a width of 40 to 80μm and a thickness of 5 to 20μm； there are 50 to 120 secondary grid lines, a distance between adjacent secondary grid lines ranging from 0.5 to 3mm. thus, the structure of the secondary grid lines 312 is more reasonable, so as to obtain a larger sunlight area and higher photoelectric conversion efficiency.

Fig. 5 is a schematic diagram of a solar cell array according to another embodiment of the present disclosure. As shown in Fig. 5, the metal wire extends reciprocally between the front surface of the first cell 31A and the front surface of the second cell 31B, such that the metal wire constitutes front conductive wires 32A of the first cell 31A and back conductive wires 2B of the second cell 31B. In such a way, the first cell 31A and the second cell 31B are connected in parallel. Of course, it can be understood that preferably the back electrodes of the first cell 31A and the back electrodes of the second cell 31B can be connected via back conductive wires constituted by another metal wire which extends reciprocally. Alternatively, the back electrodes of the first cell 31A and the back electrodes of the second cell 31B can be connected in a traditional manner.

Fig. 12 shows a schematic diagram of a solar cell array according to another embodiment of the present disclosure. As shown in Fig. 12, short grid lines 33 and secondary grid lines 312 are disposed at the front surface of the cell 31； the secondary grid lines 312 include middle secondary grid lines intersected with the conductive wires and edge secondary grid lines non-intersected with the conductive wires； the short lines 33 are connected with the edge secondary grid lines, and connected with the conductive wires or at least one middle secondary grid line. Preferably, the short grid lines 33 are perpendicular to the secondary grid lines 312.

Consequently, the short grid lines 33 are disposed at the edges of the shiny surface of the cell 31, so as to avoid partial current loss because the conductive wires 32 cannot reach the secondary grid lines 312 at the edges of the cell 31 in the winding process, and to further improve the photoelectric conversion efficiency of the solar cell module 100.

The solar cell array 30 according to another embodiment of the present disclosure is illustrated with reference to Fig. 6.

The solar cell array 30 according to the embodiment of the present disclosure comprises n×m cells 31. In other words, a plurality of cells 31 are arranged in an n×m matrix form, n representing a column, and m representing a row. More specifically, in the embodiment, 36 cells 31 are arranges into six columns and six rows, i.e. n＝m＝6. It can be understood that the present disclosure is not limited thereto. For example, the column number and the row number can be different. For convenience of description, in Fig. 6, in a direction from left to right, the cells 31 in one row are called a first cell 31, a second cell 31, a third cell 31, a fourth cell 31, a fifth cell 31, and a sixth cell 31 sequentially； in a direction from up to down, the columns of the cells 31 are called a first column of cells 31, a second column of cells 31, a third column of cells 31, a fourth column of cells 31, a fifth column of cells 31, and a sixth column of cells 31 sequentially.

In a row of the cells 31, the metal wire extends reciprocally between a surface of a first cell 31 and a surface of a second cell 31 adjacent to the first cell 31； in two adjacent rows of cells 31, the metal wire extends reciprocally between a surface of a cell 31 in a a^th row and a surface of a cell 31 in a (a+1) ^th row, and m-1≥a≥1.

As shown in Fig. 6, in a specific example, in a row of the cells 31, the metal wire extends reciprocally between a front surface of a first cell 31 and a back surface of a second cell 31 adjacent to the first cell 31, so as to connect the cells 31 in one row in series. In two adjacent rows of cells 31, the metal wire extends reciprocally between a front surface of a cell 31 at an end of the a^th row and a back surface of a cell 31 at an end of the (a+1) ^th row, to connect the two adjacent rows of cells 31 in series.

More preferably, in the two adjacent rows of cells 31, the metal wire extends reciprocally between the surface of the cell 31 at an end of the a^th row and the surface of the cell 31 at an end of the (a+1) ^th row, the end of the a^th row and the end of the (a+1) ^th row located at the same side of the matrix form, as shown in Fig. 6, located at the right side thereof.

More specifically, in the embodiment as shown in Fig. 6, in the first row, a first metal wire extends reciprocally between a front surface of a first cell 31 and a back surface of a second cell 31； a second metal wire extends reciprocally between a front surface of the second cell 31 and a back surface of a third cell 31； a third metal wire extends reciprocally between a front surface of the third cell 31 and a back surface of a fourth cell 31； a fourth metal wire extends reciprocally between a front surface of the fourth cell 31 and a back surface of a fifth cell 31； a fifth metal wire extends reciprocally between a front surface of the fifth cell 31 and a back surface of a sixth cell 31.In such a way, the adjacent cell bodies 31 in the first row are connected in series by corresponding metal wires.

A sixth metal wire extends reciprocally between a front surface of the sixth cell 31 in the first row and a back surface of a sixth cell 31 in the second row, such that the first row and the second row are connected in series. A seventh metal wire extends reciprocally between a front surface of the sixth cell 31 in the second row and a back surface of a fifth cell 31 in the second row； a eighth metal wire extends reciprocally between a front surface of the fifth cell 31 in the second row and a back surface of a fourth cell 31 in the second row, until a eleventh metal wire extends reciprocally between a front surface of a second cell 31 in the second row and a back surface of a first cell 31 in the second row, and then a twelfth metal wire extends reciprocally between a front surface of the first cell 31 in the second row and a back surface of a first cell 31 in the third row, such that the second row and the third row are connected in series. Sequentially, the third row and the fourth row are connected in series, the fourth row and the fifth row connected in series, the fifth row and the sixth row connected in series, such that the cell array 30 is manufactured. In this embodiment, a bus bar is disposed at the left side of the first cell 31 in the first row and the left side of the first cell 31 in the sixth row respectively； a first bus bar is connected with the conductive wires extending from the left side of the first cell 31 in the first row, and a second bus bar is connected with the conductive wires extending from the left side of the first cell 31 in the sixth row.

As said above, the cell bodies in the embodiments of the present disclosure are connected in series by the conductive wires–the first row, the second row, the third row, the fourth row, the fifth row and the sixth row are connected in series by the conductive wires. As shown in the figures, alternatively, the second and third row, and the fourth and fifth rows can be connected in parallel with a diode respectively to avoid light spot effect. The diode can be connected in a manner commonly known to those skilled in the art, for example, by a bus bar.

However, the present disclosure is not limited to the above. For example, the first and second rows can be connected in series, the third and fourth rows connected in series, the fifth and sixth rows connected in series, and meanwhile the second and third rows are connected in parallel, the fourth and fifth connected in parallel. In such a case, a bus bar can be disposed at the left or right side of corresponding rows respectively.

Alternatively, the cells 31 in the same row can be connected in parallel. For example, a metal wire extends reciprocally from a front surface of a first cell 31 in a first row through the front surfaces of the second to the sixth cells 31.

In some specific embodiments of the present disclosure, the binding force between the metal wire and the cells 31 ranges from 0.1N to 0.8N. That’s to say, the binding force between the conductive wires 32 and the cells 31 ranges from 0.1N to 0.8N. Preferably, the binding force between the metal wire and the cells ranges from 0.2N to 0.6N. so as to secure the welding between the cells and the metal wire, to avoid sealing-off of the cells in the operation and the transferring process and performance degradation due to poor connection, and to lower the cost.

In some specific embodiments of the present disclosure, for a typical cell with a dimension of 156mm×156mm, the solar cell module has a series resistance of 380 to 440mΩ per 60 cells. The present disclosure is not limited to 60 cells, and there may be 30 cells, 72 cells, etc. When there are 72 cells, the series resistance of the solar cell module is 456 to 528mΩ, and the electrical performance of the cells is better.

In some specific embodiments of the present disclosure, for a typical cell with a dimension of 156mm×156mm, the solar cell module has an open-circuit voltage of 37.5-38.5V per 60 cells. The present disclosure is not limited to 60 cells, and there may be 30 cells, 72 cells, etc. The short-circuit current is 8.9 to 9.4A, and has nothing to do with the number of the cells.

In some specific embodiments of the present disclosure, the solar cell module has a fill factor of 0.79 to 0.82, which is independent from the dimension and number of the cells, and can affect the electrical performance of the cells.

In some specific embodiments of the present disclosure, for a typical cell with a dimension of 156mm×156mm, the solar cell module has a working voltage of 31.5-32V per 60 cells. The present disclosure is not limited to 60 cells, and there may be 30 cells, 72 cells, etc. The working current is 8.4 to 8.6A, and has nothing to do with the number of the cells.

In some specific embodiments of the present disclosure, for a typical cell with a dimension of 156mm×156mm, the solar cell module has a conversion efficiency of 16.5-17.4％, and a power of 265-280W per 60 cells.

A method for manufacturing the solar cell module 100 according to the embodiments of the present disclosure will be illustrated with respect to Fig. 7 to Fig. 9.

Specifically, the method includes the following steps: forming a plurality of conductive wires 32 by a metal wire which extends reciprocally between a surface of a first cell 31 and a surface of a second cell 31 adjacent to the first cell 31, welding the plurality of the conductive wires 32 with the secondary grid lines 312 on the front surface of the cell 31, such that adjacent cells 31 are connected by the conductive wires 32 to obtain the cell array； superposing an upper cover plate 10, a front adhesive layer 20, the cell array 30, a back adhesive layer 40 and a back plate 50 in sequence, in which the front surface of the cell 31 faces the front adhesive layer 20, and the back surface thereof faces the back adhesive layer 40, and laminating them to obtain the solar cell module 100.

The method includes the steps of preparing a solar array 30, superposing the upper cover plate 10, the front adhesive layer 20, the cell array 30, the back adhesive layer 40 and the back plate 50 in sequence, and laminating them to obtain the solar cell module 100. It can be understood that the method further includes other steps, for example, sealing the gap between the upper cover plate 10 and the back plate 50 by a sealant, and fixing the above components together by a U-shape frame, which are known to those skilled in the art, and thus will be not described in detail herein.

The method includes a step of forming a plurality of conductive wires by a metal wire which extends reciprocally surfaces of cells 31 and is electrically connected with the surfaces of cells 31, such that the adjacent cells 31 are connected by the plurality of conductive wires to constitute a cell array 30.

Specifically, as shown in Fig. 7, the metal wire extends reciprocally for 12 times under strain. As shown in Fig. 8, a first cell 31 and a second cell 31 are prepared. As shown in Fig. 9, a front surface of the first cell 31 is connected with a metal wire, and a back surface of the second cell 31 is connected with the metal wire, such that the cell array 30 is formed. Fig. 9 shows two cells 31. When the cell array 30 has a plurality of cells 31, the metal wire which extends reciprocally connects the front surface of the first cell 31 and the back surface of the second cell 31 adjacent to the first cell 31, i.e. connecting a secondary grid line of the first cell 31 with a back electrode of the second cell 31 by the metal wire. The metal wire extends reciprocally under strain from two clips at two ends thereof.

In the embodiment shown in Fig. 9, the adjacent cells are connected in series. As said above, the adjacent cells can be connected in parallel by the metal wire based on practical requirements.

The cell array 30 obtained is superposed with the upper cover plate 10, the front adhesive layer 20, the back adhesive layer 40 and the back plate 50 in sequence, in which a front surface of the cell 31 faces the front adhesive layer 20, a back surface thereof facing the back adhesive layer 40, and laminating them to obtain the solar cell module 100. It can be understood that the metal wire can be welded with the cell 31 when or before they are laminated.

In the following, the solar cell module 100 of the present disclosure will be described with respect to specific examples.

Example 1

Example 1 is used to illustrate the solar cell module 100 according to the present disclosure and the manufacturing method thereof.

(1) Manufacturing a metal wire S

An alloy layer of Sn40％-Bi55％-Pb5％ (melting point: 125℃) is attached to a surface of a copper wire, in which the copper wire has a cross section of 0.04mm², and the alloy layer has a thickness of 16μm. Hence, the metal wire S is obtained.

(2) Manufacturing a solar cell module 100

A POE adhesive layer in 1630×980×0.5mm is provided (melting point: 65℃) , and a glass plate in 1633×985×3mm and a polycrystalline silicon cell 31 in 156×156×0.21mm are provided correspondingly. The cell 31 has 91 secondary grid lines (silver, 60μm in width, 9μm in thickness) on its front surface, each of which substantially runs through the cell 31 in a longitudinal direction, and the distance between the adjacent secondary grid lines is 1.7mm. The cell 31 has five back electrodes (tin, 1.5mm in width, 10μm in thickness) on its back surface. Each back electrode substantially runs through the cell 31 in a longitudinal direction, and the distance between the adjacent back electrodes is 31mm.

60 cells 31 are arranged in a matrix form (six rows and ten columns) . In two adjacent cells 31 in a row, a metal wire extends reciprocally between a front surface of a first cell 31 and a back surface of a second cell 31 under strain. The metal wire extends reciprocally under strain from two clips at two ends thereof, so as to form 15 parallel conductive wires. The distance between parallel adjacent conductive wires is 9.9mm. Then, an upper glass plate, an upper POE adhesive layer, multiple cells arranged in a matrix form and welded with the metal wire, a lower POE adhesive layer and a lower glass plate are superposed sequentially from up to down, in which the shiny surface of the cell 31 faces the front adhesive layer 20, the shady surface of the cell 31 facing the back adhesive layer 40, and the conductive wires 32 are connected with the cell 31 by high-frequency welding, and finally they are laminated in a laminator. In such way, a solar cell module A1 is obtained.

Example 2

Example 2 is used to illustrate the solar cell module 100 according to the present disclosure and the manufacturing method thereof.

(1) Manufacturing a metal wire S

(2) Manufacturing a solar cell module 100

60 cells 31 are arranged in a matrix form (six rows and ten columns) . In two adjacent cells 31 in a row, a metal wire extends reciprocally between a front surface of a first cell 31 and a back surface of a second cell 31 under strain. The metal wire extends reciprocally under strain from two clips at two ends thereof, so as to form 15 parallel conductive wires. The secondary grid lines of the first cell 31 are welded with the conductive wires and the back electrodes of the second cell 31 are welded with the conductive wires. The distance between parallel adjacent conductive wires is 9.9mm. 10 cells are connected in series into a row, and six rows of the cells of such kind are connected in series into a cell array via the bus bar. Then, an upper glass plate, an upper POE adhesive layer, multiple cells arranged in a matrix form and welded with the metal wire, a lower POE adhesive layer and a lower glass plate are superposed sequentially from up to down, in which the shiny surface of the cell 31 faces the front adhesive layer 20, such that the front adhesive layer 20 contacts with the conductive wires 32 directly； and the shady surface of the cell 31 faces the back adhesive layer 40, and finally they are laminated in a laminator, in which the front adhesive layer 20 fills between adjacent conductive wires 32. In such way, a solar cell module A1 is obtained.

Comparison example 1

The differences between Comparison example 1 and Example 2 lie in that the conductive wires and the cell are connected by far infrared welding. In such a way, a solar cell module D1 is obtained.

Example 3

The solar cell module is manufactured according to the method in Example 2, but the difference compared with Example 2 lies in that a short grid line 33 (silver, 0.1mm in width) is disposed on the secondary grid line of the shiny surface of the cell 31, and is perpendicular to the secondary grid line for connecting part of the secondary grid line at the edge of the shiny surface of the cell with the conductive wire, as shown in Fig. 12, so as to obtain a solar cell module A3.

Example 4

The solar cell module is manufactured according to the method in Example 2, but the difference compared with Example 2 lies in that the cells of six columns and ten rows are connected in such a manner that in two adjacent rows of cells, the conductive wires extends from a shiny surface of a cell 31 at an end of the a^th row (a≥1) to form electrical connection with a back surface of a cell 31 at an adjacent end of the (a+1) ^th row, so as to connect the two adjacent rows of cells. The conductive wires for connecting the two adjacent rows of cells 31 are arranged in perpendicular to the conductive wires for connecting the adjacent cells 31 in the two rows. In such a way, the solar cell module A4 is obtained.

Testing example 1

(1) Whether the metal wire in the solar cell module drifts is observed with the naked eyes；

(2) According to the method disclosed in IEC904-1, the solar cell modules manufactured in the above examples and the comparison example are tested with a single flash simulator under standard test conditions (STC) : 1000W/m² of light intensity, AM1.5 spectrum, and 25℃. The photoelectric conversion efficiency of each cell is recorded. The testing result is shown in Table 1.

Table 1

The fill factor refers to a ratio of the power at the maximum power point of the solar cell module and the maximum power theoretically at zero resistance, and represents the proximity of the actual power with respect to the theoretic maximum power, in which the greater the value is, the higher the photoelectric conversion efficiency is. Generally, the series resistance is small, so the fill factor is great. The photoelectric conversion efficiency refers to a ratio of converting the optical energy into electric energy by the module under a standard lighting condition (1000W/m² of light intensity) . The series resistance is equivalent to the internal resistance of the solar module, in which the greater the value is, the poorer the performance of the module is. The fill factor represents a ratio of the actual maximum power and the theoretical maximum power of the module, in which the greater the value is, the better the performance of the module is. The open-circuit voltage refers to the voltage of the module in an open circuit under a standard lighting condition. The short-circuit current refers to the current of the module in a short circuit under a standard lighting condition. The working voltage is the output voltage of the module working with the largest power under a standard lighting condition. The working current is the output current of the module working with the largest power under a standard lighting condition. The power is the maximum power which the module can reach under a standard lighting condition.

It can be indicated from Table 1 that for the solar cell module according to the embodiments of the present disclosure, the metal wire will not drift, and higher photoelectric conversion efficiency can be obtained.

In the specification, it is to be understood that terms such as “central, ” “longitudinal, ” “lateral, ” “length, ” “width, ” “thickness, ” “upper, ” “lower, ” “front, ” “rear, ” “left, ” “right, ” “vertical, ” “horizontal, ” “top, ” “bottom, ” “inner, ” “outer, ” “clockwise, ” and “counterclockwise” should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the present disclosure be constructed or operated in a particular orientation.

In addition, terms such as “first” and “second” are used herein for purposes of description and are not intended to indicate or imply relative importance or significance or to imply the number of indicated technical features. Thus, the feature defined with “first” and “second” may comprise one or more of this feature. In the description of the present disclosure, “aplurality of” means two or more than two, unless specified otherwise.

In the present disclosure, unless specified or limited otherwise, a structure in which a first feature is “on” or “below” a second feature may include an embodiment in which the first feature is in direct contact with the second feature, and may also include an embodiment in which the first feature and the second feature are not in direct contact with each other, but are contacted via an additional feature formed therebetween. Furthermore, a first feature “on, ” “above, ” or “on top of” a second feature may include an embodiment in which the first feature is right or obliquely “on, ” “above, ” or “on top of” the second feature, or just means that the first feature is at a height higher than that of the second feature； while a first feature “below, ” “under, ” or “on bottom of” a second feature may include an embodiment in which the first feature is right or obliquely “below, ” “under, ” or “on bottom of” the second feature, or just means that the first feature is at a height lower than that of the second feature.

Reference throughout this specification to “an embodiment, ” “some embodiments, ” or “some examples” means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Thus, these terms throughout this specification do not necessarily refer to the same embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes, modifications, alternatives and variations can be made in the embodiments without departing from the scope of the present disclosure.

Claims

A method for manufacturing a solar cell module, comprising:

welding in high frequency a conductive wire constituted by a metal wire with a cell；

superposing an upper cover plate, a front adhesive layer, the cell, a back adhesive layer and a back plate in sequence, and laminating them to obtain the solar cell module.
The method according to claim 1, wherein the conductive wire and the cell are welded before or when they are laminated.
The method according to claim 1 or 2, wherein there are at least two cells, and the conductive wire extends reciprocally between a surface of a first cell and a surface of a second cell adjacent to the first cell.
The method according to claim 3, wherein the conductive wire extends reciprocally for 10 to 60 times.
The method according to claim 3, wherein the conductive wire extends reciprocally between a front surface of the first cell and a back surface of the second cell.
The method according to any one of claims 3 to 4, wherein two adjacent conductive wires form a U-shape structure or a V-shape structure.
The method according to any one of claims 1 to 6, wherein the cells are arranged in an n×m matrix form, n representing a column, and m representing a row；

in a row of cells, the metal wire extends reciprocally between a surface of a first cell and a surface of a second cell adjacent to the first cell； in two adjacent rows of cells, the metal wire extends reciprocally between a surface of a cell in a a^th row and a surface of a cell in a (a+1) ^th row, and m-1≥a≥1.
The method according to claim 7, wherein in two adjacent rows of cells, the metal wire extends reciprocally between a surface of a cell at an end of the a^th row and a surface of a cell at an end of the (a+1) ^th row, the end of the a^th row and the end of the (a+1) ^th row located at the same side of the matrix form.
The method according to claim 8, wherein in a row of cells, the metal wire extends reciprocally between a front surface of a first cell and a back surface of a second cell adjacent to the first cell；

in two adjacent rows of cells, the metal wire extends reciprocally between a front surface of a cell at an end of the a^th row and a back surface of a cell at an end of the (a+1) ^th row, to connect the two adjacent rows of cells in series.
The method according to any one of claims 7 to 9, wherein there is a metal wire extending reciprocally between adjacent cells in a row； and there is a metal wire extending reciprocally between cells in adjacent rows.
The method according to any one of claims 1 to 10, wherein the metal wire is a copper wire.
The method according to any one of claims 1 to 11, wherein a secondary grid line on a front surface of the cell has a width of 40 to 80μm and a thickness of 5 to 20μm； there are 50 to 120 secondary grid lines, a distance between adjacent secondary grid lines ranging from 0.5 to 3mm.
The method according to any one of claims 1 to 12, wherein the metal wire is coated with an alloy layer.
The method according to claim 13, wherein the alloy layer contains Sn, and at least one of Bi, In, Ag, Sb, Pb and Zn.
The method according to claim 13, wherein the alloy layer contains Sn, Bi, and at least one of In, Ag, Sb, Pb and Zn.
The method according to any one of claims 13 to 15, wherein the alloy layer has a thickness of 1 to 100μm, and the conductive wire has a cross section of 0.01 to 0.5mm².
The method according to claim 1 or 2, further comprising: applying a welding layer to a position where the conductive wire is welded with the cell, before they are welded.
The method according to claim 17, wherein a ratio of a thickness of the welding layer and a diameter of the conductive wire is (0.02-0.5) : 1.
The method according to any one of claims 1 to 18, wherein a distance between two adjacent conductive wires ranges from 2.5mm to 15mm.
The method according to claim 1, wherein the conductive wire is formed by a plurality of metal wires arranged parallel to and spaced from each other, or by a metal wire extending reciprocally.
The method according to any one of claims 1 to 20, wherein there are 10 to 60 conductive wires.