WO2016065940A1

WO2016065940A1 - Solar cell unit, solar cell array, solar cell module and manufacturing method thereof

Info

Publication number: WO2016065940A1
Application number: PCT/CN2015/084061
Authority: WO
Inventors: Zhiqiang Zhao; 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 solar cell unit, a solar cell array (30), a solar cell module (100) and a manufacturing method thereof are disclosed. The solar cell unit includes a cell (31) comprising a cell substrate (311), secondary grid lines (312) spaced apart from each other in a front surface of the cell substrate (311), a back electric field (313) disposed in a back surface of the cell substrate (311), and back welding portions spaced apart from each other in the back electric field (313), the back welding portions formed by applying silver paste or a tin alloy to the back field; front conductive wires (32A) constituted by a metal wire and electrically connected with the front secondary grid lines (312); and back conductive wires (312B) constituted by a metal wire and electrically connected with the back electric field (313) via the back welding portions.

Description

SOLAR CELL UNIT, SOLAR CELL ARRAY, SOLAR CELL MODULE AND MANUFACTURING METHOD THEREOF

FIELD

The present disclosure relates to a field of solar cells, and more particularly, to a solar cell unit, a solar cell array, 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 to a cell from its front surface and is converted to electricity within the cell. The cell includes a cell substrate and conductive wires and secondary grid lines disposed on the front surface of the cell. The conductive wires and secondary grid lines cover part of the front surface of the cell, which block part of the sunlight, and then the part of sunlight irradiating to the conductive wires and the secondary grid lines cannot be converted into electric energy. Thus, the conductive wires 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 conductive wires and the secondary grid lines serve to conduct current, and in terms of resistivity, the finer the conductive wires and the secondary grid lines are, the smaller the cross section area thereof is, which causes greater loss of electricity due to increased resistivity. Therefore, the conductive wires 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.

SUMMARY

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

In prior art, the front surface of the solar cell is usually provided with the primary grid lines and the secondary grid lines to output the current generated by the photoelectric effect or chemistry effect. In order to improve the efficiency of the solar cells, solar cell manufacturers conducted extensive researches on how to increase the number of the primary grid lines. In prior art, the number of primary grid lines has been successfully increased from two to three, or even five.

However, in the prior art, the primary grid lines are formed by printing the paste containing expensive silver, so the manufacturing cost is very high, and the increase of the silver primary grid lines absolutely causes an increase in cost. Moreover, the current silver primary grid line has a great width (for example, up to over 2mm) , such that the increase of the silver primary grid lines will enlarge the shading area, and make the photoelectric conversion efficiency low.

Consequently, in order to lower the cost and reduce the shading area, in prior art, the silver primary grid lines printed on the cells are replaced with metal wires, such as copper wires which serve as the primary grid lines to output the current. Since the silver primary grid lines are no longer used, the cost can be reduced considerably； the diameter of the copper wire is relatively small, so the shading area can be decreased. Thus, the number of the primary grid lines can be further increased up to 10, and the cell of this kind may be called a cell without primary grid lines, in which the metal wire replaces the silver primary grid lines and welding strips in the traditional solar cell.

After extensive researches, the inventor of the present disclosure finds if a cell is manufacture in this way that multiple parallel metal wires are drawn simultaneously, cut off, and then welded to the cell simultaneously, due to limitations of sophistication of equipment and process, for example, the influence of stress, the solar cell is bent to some extent when disposed at a free state, so the metal wire needs to remain strained to flatten the cell (a test proves that the minimum strain is at least 2N for a copper wire with a diameter of 0.2mm) . In order to keep the strain, each metal wire needs to be provided with clips or similar equipment at the two ends thereof, and the equipment occupies certain space, but the space in the cell is limited. Thus, in the prior art, at most ten metal wires can be drawn, fixed and welded to a single cell, and it will be difficult to increase the number of the metal wires. The larger the number of the metal wires is, the more free ends there are, such that the equipment needs to control more metal wires at the same time, which is demanding as for the wiredrawing equipment. Moreover, the space of the solar cells is limited. For example, the dimension of a single cell is 156mm×156mm. In such limited space, the multiple metal wires need to be controlled accurately at the same time, which is demanding as for the equipment, especially as for the accuracy. Currently, it is still hard to control and weld multiple metal wires simultaneously in actual production, so the number of the conductive wires is limited, usually at most ten around, which is difficult to realize.

In order to solve the above problem, relevant patents (US20100275976 and US20100043863) provide a technical solution that multiple metal wires are fixed on a transparent film. That’s to say, multiple parallel metal wires are fixed on the transparent film by adhesion； then, the transparent film bound with the multiple parallel metal wires is attached to the cell； finally the metal wires contact with the secondary grid lines on the cell by lamination. By this method, the multiple metal wires are fixed via the transparent film, which solves the problem of controlling the multiple metal wires simultaneously, and further increases the number of the metal wires. However, the technical solution almost abandons the welding process. That’s to say, the metal wires are not connected with the secondary grid lines by the welding process； instead, the metal wires contact with the secondary grid lines by the laminating process, so as to output the current.

The above technical solution can further increase the number of the metal wires, but the transparent film may affect the light absorption, which causes kind of shading, and thus lowers the photoelectric conversion efficiency.

Furthermore, the above technical solution cannot connect the metal wires with the secondary grid lines by the welding process, because the melting temperature of the transparent film must be higher than the welding temperature (usually around 140℃) , otherwise the transparent film will melt in the process of welding, which may lose the function of fixing the metal wires, and then the metal wires drift, resulting in poor welding effects.

Moreover, it is known to those skilled in the art that the solar cells in use are sealed to prevent moisture and air from penetrating the cells, which may cause corrosion and short circuit. The encapsulating material at present is EVA whose melting point is 70℃ to 80℃, much lower than the welding temperature. If the welding process is employed, as said above, the melting temperature of the transparent film must be higher than the welding temperature, which is higher than the melting point of the encapsulating material. Thus, in the encapsulating process, the encapsulating material (EVA) will melt at the encapsulating temperature, but the transparent film will not, such that the melting encapsulating material cannot penetrate the solid transparent film to completely seal the cells. Hence, the sealing effect is poor, and the actual product tends to fail. In terms of encapsulating, the melting temperature of the transparent film needs to be lower than the welding temperature, which is an evident paradox.

Therefore, the technical solution of fixing the metal wires via the transparent film cannot adopt the welding process to weld the metal wires with the secondary grid lines, or the metal wires are merely in contact with the secondary grid lines on the cells, i.e. the metal wires are only placed on the secondary grid lines. Thus, the connection strength of the metal wires and the secondary grid lines is so low that the metal wires tend to separate from the secondary grid lines in the laminating process or in use, which causes bad contact, low efficiency of the cells, or even failure thereof. Consequently, the product in this technical solution is not promoted and commercialized. There is no fairly mature solar cell without primary grid lines.

In the current solar cell without primary grid lines, since the conductive wires are metal wires of very small diameter, the welding of the conductive wires and the secondary grid lines is relatively difficult, which may cause insufficient welding and bad contact, thereby lowering the efficiency of the cells considerably and even resulting in failure thereof.

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

The solar cell with multiple primary grid lines provided in the present disclosure can be commercialized for mass production, and easy to manufacture with simple equipment, especially in low cost.

Thus, the present disclosure provides a solar cell unit that is easy to manufacture in low cost, and improves the photoelectric conversion efficiency.

The present disclosure further provides a solar cell array that is easy to manufacture in low cost, and improves the photoelectric conversion efficiency.

The present disclosure further provides a solar cell module with the above solar cell array, and the solar cell module is easy to manufacture in low cost, and improves the photoelectric conversion efficiency.

The present disclosure further provides a method for manufacturing the solar cell module.

According to a first aspect of embodiments of the present disclosure, a solar cell unit includes a cell including a cell substrate, secondary grid lines spaced apart from each other in a front surface of the cell substrate, a back electric field disposed in a back surface of the cell substrate, and back welding portions spaced apart from each other in the back electric field, the back welding portions formed by applying silver paste or a tin alloy to the back field； front conductive wires constituted by a metal wire and electrically connected with the front secondary grid lines； and back conductive wires constituted by a metal wire and electrically connected with the back electric field via the back welding portions.

As for the solar cell unit according to embodiments of the present disclosure, the back electric field is disposed on the back surface of the cell substrate and back welding portions are disposed on the back electric field, such that the back conductive wires are welded with the back welding portions formed by silver paste or a tin alloy, which can improve connection performance of the back conductive wires and the back electric field considerably. Moreover, the solar cell unit in the present disclosure has simple production process –only screen printing design in need, and low cost.

According to a second aspect of embodiments of the present disclosure, a solar cell array includes a plurality of cell units which are the solar cell units according to the above embodiment, adjacent cells being connected by a metal wire which extends reciprocally between a surface of a first cell and a surface of a second cell adjacent to the first cell, to form the front conductive wires and/or the back conductive wires.

According to a third aspect of embodiments of the present disclosure, a solar cell module includes an upper cover plate, a front adhesive layer, a cell array, a back adhesive layer and a lower cover plate superposed in sequence, the cell array being a solar cell array according to the above embodiments.

According to a fourth aspect of embodiments of the present disclosure, a method for manufacturing a solar cell module includes: providing a cell which includes a cell substrate, secondary grid lines spaced apart from each other in a front surface of the cell substrate, a back electric field disposed in a back surface of the cell substrate, and back welding portions spaced apart from each other in the back electric field, the back welding portions formed by applying silver paste or a tin alloy to the back field； connecting front conductive wires constituted by a metal wire with the front secondary grid lines, and connecting back conductive wires constituted by a metal wire with the back secondary grid lines, to obtain a solar cell unit； superposing an upper cover plate, a front adhesive layer, the solar cell unit, a back adhesive layer and a lower cover plate in sequence, in which a front surface of the solar cell unit faces the front adhesive layer, a back surface thereof facing the back adhesive layer, and laminating them to obtain the solar cell module.

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 back welding portion of a solar cell unit according to an 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

313 back electric field

314 back electrode

32 conductive wire

32A front conductive wire

32B back conductive wire

321 metal wire body

322 welding layer

33 short grid line

40 back adhesive layer

50 lower cover plate

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 one embodiment of the present disclosure, a cell unit” includes a cell 31 and conductive wires 32, so the conductive wires 32 can be called the conductive wires 32 of the cell unit.

A cell 31 includes a cell substrate 311, a secondary grid line 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 a back welding portion 314 disposed on the back electric field 313. Thus, the secondary grid line 312 can be called the secondary grid line 312 of the cell 31, the back electric field 313 called the back electric field 313 of the cell 31, and the back welding portion 314 called the back welding portion 314 of the cell 31.

The 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.

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

The cell unit, the cell 31 and the cell substrate 311 are used to illustrate the present disclosure, but shall not be construed to limit the present disclosure.

A solar cell array 30 is arranged by a plurality of cells, i.e. by a plurality of cells 31 connected by a conductive wire 32.

In the solar cell array 30, a metal wire S constitutes the conductive wire 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 surfaces of the adjacent cells 31, or may be connected with a secondary grid line 312 of the cell 31, or may be connected with a secondary grid line 312 of a first cell 31 and a back welding portion 314 of a second cell 31 adjacent to the first cell 31, or a part of the metal wire S is connected with the secondary grid line 312 and the other part of the metal wire S is connected with a back welding portion 314 of the cell 31.

That’s to say, the metal wire S can extend between front surfaces of adjacent cells 31, or 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 wire 32 may include a front conductive wire 32A extending on the front surface of the cell 31 and electrically connected with the secondary grid lien 312 of the cell 31, and a back conductive wire 32B extending on the back surface of the cell 31 and electrically connected with the back welding portion 314 of the cell 31. Part of the metal wire S between the adjacent cells 31 can be called a connection conductive wire.

All the ranges disclosed in the present disclosure include terminals, and can be individual or combined. It shall be understood that the terminals 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, the solar cell unit will be described according to the embodiments of the present disclosure.

As shown in Fig. 1 to Fig. 12, the solar cell unit according to the embodiments of the present disclosure includes a cell 31, front conductive wires 32A and back conductive wires 32B.

Specifically, the cell 31 includes a cell substrate 311, secondary grid lines 312 spaced apart from each other in a front surface of the cell substrate 311, a back electric field 313 disposed in a back surface of the cell substrate 311, and back welding portions 314 spaced apart from each other in the back electric field 313, the back welding portions 314 formed by applying silver paste or a tin alloy to the back field 313； front conductive wires 32A constituted by a metal wire S and electrically connected with the front secondary grid lines 312A； and back conductive wires 32B constituted by a metal wire S and electrically connected with the back electric field 313 via the back welding portions 314.

In other words, the solar cell unit according to the present disclosure is mainly formed with the cell 31 and conductive wires 32； the cell 31 is mainly constituted by the cell substrate 311 and secondary grid lines 312. In the present disclosure, the front secondary grid lines 312A disposed on the front surface of the cell substrate 311 will be described in detail.

A plurality of front secondary grid lines 312A spaced from each other are disposed on the front surface of the cell substrate 311； front conductive wires 32A are disposed on the front surface of the cell substrate 311 and located on the front secondary grid lines 312A. The front conductive wires 32A are constituted by a metal wire S and electrically connected with the front secondary grid lines 312A.

The back electric field 313 is disposed on the back surface of the cell substrate 311； the back welding portions 314 are formed by applying silver paste or a tin alloy to the back field 313； the back conductive wires 32B are disposed on the back surface of the cell substrate 311 and located on the back welding portions 314, and are constituted by a metal wire S and electrically connected with the back welding portions 314.

It shall be noted that the solar cell unit mainly employs a structure of three conductive wires –three conductive wires printed by silver paste and sintered on the front and back surfaces respectively. The width of the conductive wire usually ranges from 1.4mm to 2mm.

In the solar cell unit without primary grid lines, the primary grid lines are usually replaced by multiple metal wires, and the secondary grid lines on the front surface are remained to connect the metal wires with the cells. The silver conductive wires on the back surface are replaced by the metal wires. However, the metal wires and the aluminum sintering layer on the back surface, i.e. the back electric fields, have poor welding performance. In the present disclosure, if the back conductive wires 32B constituted by the metal wire S are directly welded with the back electric field 313, the welding performance tends to be poor, which affects the welding effect.

Thus, in the solar cell unit according to the embodiments of the present disclosure, back electric fields 313 are disposed in the back surface of the cell substrate 311, and back welding portions 314 are disposed on the back electric fields 313. The front conductive wires 32A are welded with the back welding portions 314 formed by the silver paste or the tin alloy, which can improve the connection performance of the front conductive wires 32A and the back electric fields 313 considerably. Moreover, the solar cell unit in the present disclosure has simple production process –only screen printing design in need, and low cost.

According to an embodiment of the present disclosure, the tin alloy contains at least one of Cu, Ag, Pb, Bi, Zn, In, Fe and Ni, and Sn. In other words, the tin alloy is formed with Sn and at least one of Cu, Ag, Pb, Bi, Zn, In, Fe and Ni, such that the welding performance of the back welding portions 314 and the back conductive wires 32B will be better.

Alternatively, the back welding portions 314 are arranged into multiple rows spaced apart from each other； each row extends in a direction orthogonal to the back conductive wires 32B, and the back welding portions 314 in each row are spaced apart from each other. Thus, the back welding portions 314 of this structure can further reduce the amount of materials to reduce the cost.

Specifically, as shown in Fig. 1, the front secondary grid lines 312A on the cell substrate 311 extend in a direction from up to down, while the conductive wires 32A (including front conductive wires 32A and back conductive wires 32B) extend in a direction from left to right. Correspondingly, as shown in Fig. 3 and Fig. 13, the back welding portions 314 are arranged into multiple rows spaced apart from each other in the direction from left to right, and the back welding portions 314 in each row are orthogonal to the back conductive wires 32B respectively.

That’s to say, in the embodiment of the present disclosure, the structure of the back welding portions 314 is similar to that of the front secondary grid lines 312A. The back welding portions 314 can be understood as the back secondary grid lines 312B on the cell substrate 311. The back welding portions 314 only provide paste at the positions which need welding, rather than fill the whole cell substrate 311 with the past, which reduces the amount of raw materials considerably to lower the cost.

In some specific embodiments of the present disclosure, the back welding portions 314 have a width in a direction parallel to the back conductive wires 32B than the front conductive wires 312A. Preferably, a distance between adjacent rows of the back welding portions 314 is greater than that between adjacent front secondary grid lines 312A.

Specifically, the back welding portions 314 do not need to consider the shading problem, so they can be arranged into a broader structure with respect to the front secondary grid lines 312A, thereby occupying a larger area. Since the back electric fields 313 have a much better conductive performance, the distance between the back welding portions 314 can be much greater than that of the front secondary grid lines 312A.

Preferably, there are 5 to 30 rows of back welding portions 314. Further, the back welding portions 314 have a width of 0.05 to 3mm in the direction parallel to the back conductive wires 32B. More preferably, the width of the back welding portions 314 is 0.2 to 1.5mm.

That’s to say, the back welding portions 314 are arranged into 5 to 30 rows in the direction of left to right, and each back welding portion 314 has a preferable width of 0.2 to 1.5mm in the direction of left to right. Thus, on the basis of cost control, the welding performance of the back welding portions 314 and the back conductive wires 32B can be guaranteed effectively.

According to an embodiment of the present disclosure, part of the back welding portions 314 is inserted into the back electric field 313. Preferably, the back welding portions 314 are higher than the back electric fields 313 by 0.003-0.03mm. Further, the back welding portions 314 are higher than the back electric fields 313 by 0.005-0.01mm.

In other words, the back electric field 313 are disposed on the back surface of the cells substrate 311, and at least one part of the upper portion of the back welding portions 314 is inserted into the back electric field 313, and the back welding portions 314 are higher than the back electric fields 313 by 0.005-0.01mm in the direction from up to down. Therefore, the welding performance of the back welding portions 314 and the back conductive wires 32B can be further guaranteed effectively.

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

According to the embodiments of the present disclosure, the solar cell array 30 includes a plurality of solar cells which are the solar cells according to the above embodiment, cells 31 of adjacent cells being connected by the metal wire S. The metal wire S extends reciprocally between a surface of a first cell 31 and a surface of a second cell 31 adjacent to the first cell 31, to form front conductive wires 32A and/or back conductive wires 32B.

That’s to say, two adjacent cells 31 are connected by the conductive wires 32. The conductive wires 32 include the front conductive wires 32A located on the upper surface of the cell 31 and the back conductive wires 32B located on the lower surface of the cell 31. The conductive wires 32A and the back conductive wires 32B are both constituted by metal wires S.

Since the solar cell unit according to the above embodiment of the present disclosure has the above technical effect, the solar cell array 30 according to the embodiment of the present disclosure has the corresponding technical effect, i.e. improving the welding performance of the back conductive wires 32B and the back electric fields 313 effectively.

Specifically, in the present disclosure, the metal wire S extends reciprocally between a front surface of the first cell 31 and a back surface of the second cell 31, the front conductive wires 32A being formed by the metal wire S extending on the front surface of the first cell 31, and the back conductive wires 32B being formed by the metal wire S extending on the back surface of the second cell 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 body 321 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 a surface of a first cell 31 and a surface of a second cell 31 adjacent to the first cell 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, such that the metal wire S constitutes front conductive wires 32A of the cells. Alternatively, a first metal wire S extends reciprocally on a front surface of a cell 31, and a second metal wire S extends reciprocally on a back surface of the cell 31, such that the first metal wire S constitutes a front conductive wire 32A, and the second metal wire S constitutes a back conductive wire 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 a front conductive wire 32A, and part thereof which extends on the back surface of the second cell 31 constitutes a back conductive wire 32B. In the present disclosure, unless specified otherwise, the conductive wire 32 can be understood as the front conductive wire 32A, the back conductive wire 32B, or the combination thereof.

The term “extending reciprocally” can be understood as that the metal wire body 321 extends reciprocally once to form to two conductive wires 32 which form a U-shape or V-shape structure by the metal wire body 321 extending reciprocally, yet the present disclosure is not limited to the above.

In the solar cell array 30 according to the embodiments of the present disclosure, a plurality of conductive wires 32 of the cell units are constituted by the metal wire body 321 which extends reciprocally； and the adjacent cells 31 are connected by the conductive wires 32. Hence, the conductive wires 32 of the cell units in the present disclosure are used to output the current, and are not necessarily printed by 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 body 321 with the secondary grid line and the back electrode, so that the cost of the cells is reduced considerably.

Moreover, since the conductive wires 32 are constituted by the metal wire body 321 which extends reciprocally, the width of the conductive wires 32 (i.e. the width of projection of the metal wire on the cell) is much smaller than that of the current primary grid lines printed by silver paste, thereby decreasing the shading area. 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 conductive wires made of the silver paste, and the efficiency of photoelectric conversion is improved. Since the metal wire body 321 extends reciprocally to form the conductive wires, when the cell array 30 is used to manufacture the solar cell module 100, the metal wire body 321 is easier to control accurately and 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.

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 cell units in the solar cell array 30 are shown. In other words, it shows two cells bodies 31 connected with each other via the conductive wire 32 constituted by the metal wire S.

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

Specifically, in an embodiment of the present disclosure, the metal wire extends reciprocally between a front surface of a first cell 31 and a back surface of a second cell 31.

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 a front conductive wire of the first cell 31A and a back conductive wire of the second cell 31B. The metal wire S is electrically connected with the secondary grid line of the first cell 31A (for example, being welded or bounded by a conductive adhesive) , and electrically connected with the back welding portion of the second cell 31B.

In an embodiment of the present disclosure, back welding portions 314 are disposed on the back surface of the cell substrate 311, and the metal wire is welded with the back welding portions 314.

That’s to say, in the embodiment, front secondary grid lines 312A are disposed on the front surface of the cell substrate 311, and back welding portions 314 are disposed on the back surface thereof. When the conductive wires 32 are located on the front surface of the cell substrate 311, the conductive wires 32 are welded with the front secondary grid lines 312A； when the conductive wires 32 are located on the back surface of the cell substrate 311, the conductive wires 32 are welded with the back welding portions 314 on the back surface of the cell substrate 311.

In some embodiments, there is a metal wire S. The metal wire S extends reciprocally between the first cell 31A and the second cell 31B for 1o to 60 times. Preferably, as shown in Fig. 1, the metal wire extends reciprocally for 12 times to form 24 conductive wires, 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 line and the conductive wire 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 forms 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 forms a V-shape structure.

In some embodiments, preferably, the metal wire is a copper wire, yet the present disclosure is not limited thereto. For example, the metal wire body 321 may be an aluminum wire. 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.

More preferably, as shown in Fig. 4, the metal wire body 321 is coated with a connection material layer 322, such as a conductive adhesive layer or a welding layer. The metal wire is welded with the secondary grid line and/or the back welding portion by the welding layer, such that it is convenient to electrically connect the metal wire with the secondary grid line and/or the back welding portion, and to avoid drifting of the metal wire in the connection process so as to guarantee the photoelectric conversion efficiency. Of course, the electrical connection of the metal wire with the cell can be conducted when or before the solar cell module is laminated, and preference is given to the latter.

In some embodiments, preferably, before the metal wire contact the cell, the metal wire extends under strain, i.e. straightening the metal wire. After the metal wire is connected with the secondary grid line and the back welding portion of the cell, the strain of the metal wire can be released, so as to further avoid the drifting of the conductive wire when the solar cell module is manufacture, and to guarantee the 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 of the first cell 31A and the second cell 31B. In such a way, the first cell 31A and the second cell are connected in parallel. Of course, it can be understood that preferably the back electrode of the first cell 31A and the back electrode of the second cell 31B can be connected via a back conductive wire constituted by another metal wire which extends reciprocally. Alternatively, the back electrode of the first cell 31A and the back electrode of the second cell 31B can be connected in a traditional manner.

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, 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 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 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 the 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 cells 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 manufacture. 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 a conductive wire extending from the left side of the first cell 31 in the first row, and a second bus bar is connected with a conductive wire extending from the left side of the first cell 31 in the sixth row.

As said above, the cells 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 Figs. 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 cells 31 in the second row to the sixth row.

In some specific embodiments of the present disclosure, a 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.

Preferably, there is a metal wire extending reciprocally between adjacent cells 31 in a row； and there is a metal wire extending reciprocally between cells 31 in adjacent rows. Thus, adjacent cells 31 can be connected by a single metal wire that extends reciprocally for several times, which is easier to manufacture in lower cost.

In an embodiment of the present disclosure, the metal wire is coated with a welding layer. The ratio of the thickness of the welding layer and the diameter of the metal wire is (0.02-0.5) : 1.

That’s to say, in the cell array 30, the ratio of the thickness of the welding layer and the diameter of the conductive wire 32 (including the front conductive wire 32A and back conductive wire 32B) is (0.02-0.5) : 1.

In the present disclosure, the conductive wires 32 (including the front conductive wires 32A and back conductive wires 32B) consist of a metal wire and a welding layer coating the metal wire. The welding layer may coat the metal wire completely or partially. When the welding layer coats the metal wire partially, the alloy layer is, preferably, formed at a position where the welding layer is welded with the secondary grid lines 312 of the cell 31. When the welding layer coats the metal wire completely, the welding layer can coat the periphery of the metal wire in a circular manner. The thickness of the welding layer can fall into a relatively wide range. Preferably, the welding layer has a thickness of 1 to 100μm, more preferably, 1 to 30μm.

The alloy with a low melting point for forming the welding layer may be a conventional alloy with a low melting point which can be 100 to 220℃. Preferably, the alloy with the low melting point contains Sn, and at least one of Bi, In, Ag, Sb, Pb and Zn, more preferably, containing Sn, Bi, and at least one of In, Ag, Sb, Pb and Zn.

Specifically, the alloy may be at least one of Sn-Bi alloy, In-Sn alloy, Sn-Pb alloy, Sn-Bi-Pb alloy, Sn-Bi-Ag alloy, In-Sn-Cu alloy, Sn-Bi-Cu alloy and Sn-Bi-Zn alloy. Most preferably, the alloy is Bi-Sn-Pb alloy, for example, containing 40 weight percent of Sn, 55 weight percent of Bi, and 5 weight percent of Pb (i.e. Sn40％-Bi55％-Pb5％) . The thickness of the welding layer can be 0.001 to 0.06mm. The conductive wire 32 may have a cross section of 0.01 to 0.5mm². The metal wire can be conventional in the art, for example, a copper wire.

The solar cell module 100 according to embodiments of the present disclosure is illustrated with reference to Fig. 10 and Fig. 11.

As shown in Fig. 10 and Fig. 11, the solar cell module 100 according to embodiments of the present disclosure includes an upper cover plate 10, a front adhesive layer 20, the cell array 30, a back adhesive layer 40 and a lower cover plate 50 superposed sequentially along a direction from up to down.

The front adhesive layer 20 and the back adhesive layer 40 are adhesive layers commonly used in the art. Preferably, the front adhesive layer 20 and the back adhesive layer 40 are polyethylene-octene elastomer (POE) and/or ethylene-vinyl acetate copolymer (EVA) . In the present disclosure, polyethylene-octene elastomer (POE) and/or ethylene-vinyl acetate copolymer (EVA) are conventional products in the art, or can be obtained in a method known to those skilled in the art.

In the embodiments of the present disclosure, the upper cover plate 10 and the lower cover plate 50 can be selected and determined by conventional technical means in the art. Preferably, the upper cover plate 10 and the lower cover plate 50 can be transparent plates respectively, for example, glass plates.

In the process of manufacturing the solar cell module 100, the conductive wire can be first welded with the secondary grid lines and the back welding portion of the cell 31, and then superposed and laminated.

Other components of the solar cell module 100 according to the present disclosure are known in the art, which will be not described in detail herein.

Specifically, the solar module 100 includes an upper cover plate 10, a front adhesive layer 20, the cell array 30, a back adhesive layer 40 and a lower cover plate 50. The cell array 30 includes a plurality of cells 31, and adjacent cells 31 are connected by the plurality of conductive wires 32. The conductive wires 32 are constituted by the metal wire S which extends reciprocally between surfaces of adjacent cells. The conductive wires 32 are welded with the secondary grid lines. The front adhesive layer 20 contacts with the conductive wires 32 directly and fills between the adjacent conductive wires 32.

That’s to say, the solar cell module 100 according to the present disclosure includes an upper cover plate 10, a front adhesive layer 20, the cell array 30, a back adhesive layer 40 and a lower cover plate 50 superposed sequentially along a direction from up to down. The cell array 30 includes a plurality of cells 31 and conductive wires 32 for connecting the plurality of cells 31. The conductive wires are constituted by the metal wire S which extends reciprocally between surfaces of two adjacent cells 31.

The conductive wires 32 are electrically connected with the cells 31, in which the front adhesive layer 20 on the cells 31 contacts with the conductive wires 32 directly and fills between the adjacent conductive wires 32, such that the front adhesive layer 20 can fix the conductive wires 32, and separate the conductive wires 32 from air and moisture from the outside world, so as to prevent the conductive wires 32 from oxidation and to guarantee the photoelectric conversion efficiency.

Thus, in the solar cell module 100 according to embodiments of the present disclosure, the conductive wires 32 constituted by the metal wire S which extends reciprocally replace traditional primary grid lines and solder strips, so as to reduce the cost. The metal wire S extends reciprocally to decrease the number of free ends of the metal wire S and to save the space for arranging the metal wire S, i.e. without being limited by the space. The number of the conductive wires 32 constituted by the metal wire which extends reciprocally may be increased considerably, which is easy to manufacture, and thus is suitable for mass production. The front adhesive layer 20 contacts with the conductive wires 32 directly and fills between the adjacent conductive wires 32, which can effectively isolate the conductive wires from air and moisture to prevent the conductive wires 32 from oxidation to guarantee the photoelectric conversion efficiency.

In some specific embodiments of the present disclosure, the metal wire S extends reciprocally between a front surface of a first cell and a back surface of a second cell adjacent to the first cell； the front adhesive layer 20 contacts with the conductive wires on the front surface of the first cell 31 directly and fills between the adjacent conductive wires 32 on the front surface of the first cell 31； the back adhesive layer 40 contacts with the conductive wires 32 on the back surface of the second cell 31 directly and fills between the adjacent conductive wires 32 on the back surface of the second cell 31.

In other words, in the present disclosure, the two adjacent cells 31 are connected by the metal wire S. In the two adjacent cells 31, the front surface of the first cell 31 is connected with the metal wire S, and the back surface of the second cell 31 is connected with the metal wire S.

The front adhesive layer 20 on the first cell 31 whose front surface is connected with the metal wire S is in direct contact with the metal wire S on the front surface of the first cell 31 and fills between the adjacent conductive wires 32. The back adhesive layer 40 on the second cell 31 whose back surface is connected with the metal wire S is in direct contact with the metal wire S on the back surface of the second cell 31 and fills between the adjacent conductive wires 32 (as shown in Fig. 2) .

Consequently, in the solar cell module 100 according to the present disclosure, not only the front adhesive layer 20 can separate the conductive wires 32 on the front surfaces of part of the cells 31 from the outside world, but also the back adhesive layer 40 can separate the conductive wires 32 on the back surfaces of part of the cells 31 from the outside world, so as to further guarantee the photoelectric conversion efficiency of the solar cell module 100.

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 according to the embodiments of the present disclosure includes the following steps:

providing a cell 31 which includes a cell substrate 311, secondary grid lines 312 spaced apart from each other in a front surface of the cell substrate 311, a back electric field 313 disposed in a back surface of the cell substrate 311, and back welding portions 314 spaced apart from each other in the back electric field 313, the back welding portions 314 formed by applying silver paste or a tin alloy to the back field 313； connecting front conductive wires 32A constituted by a metal wire with the front secondary grid lines 312A, and connecting back conductive wires 32B constituted by a metal wire with the back field 313 via the back welding portions 314, to obtain a solar cell unit； superposing the upper cover plate 10, the front adhesive layer 20, the cell array 30, the back adhesive layer 40 and the lower cover 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 lower cover 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 lower cover 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.

The back electric filed 313 is disposed on the back surface of the cell substrate 311, and back welding portions 314 are formed on the back electric field 313 by applying the silver paste or the tin alloy (for example applying the silver paste or the tin alloy by screen printing) . The back conductive wires 32B are disposed on the back surface of the cell substrate 311 and are located on the back welding portions 314. The back conductive wires 32B are constituted by the metal wire S and are electrically connected with the back welding portions 314.

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 welding portion of the second cell 31 by the metal wire. The metal wire extends reciprocally under strain from two clips at two ends thereof. The metal wire can be winded only with the help of two clips, which saves the clips considerably and then reduces the assembling space.

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 lower cover 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 connected with the cell 31 when or before they are laminated.

The front adhesive layer 20 is disposed in direct contact with the conductive wires 32. In the process of laminating, the front adhesive layer 20 melts and fills the gaps between adjacent conductive wires 32. The back adhesive layer 40 is disposed in direct contact with the conductive wires 32. In the process of laminating, the back adhesive layer 40 melts and fills the gaps between adjacent conductive wires 32.

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

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

(2) Manufacturing a solar cell module 100

A POE adhesive layer in 1630×980×0.5mm are 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) , 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 welding portions on its back surface, and the back welding portions are formed by applying the silver paste to the back electric field. Each back welding portion substantially runs through the cell 31 in a longitudinal direction, and the distance between the adjacent back welding portions is 31mm.

60 cells 31 are arranged in a matrix form (six rows and ten columns) . In two adjacent cells 31, the metal wire extends reciprocally between a front surface of a first cell 31 and a back surface of a second cell 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 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 at a welding temperature of 160℃. 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 difference of Comparison example 1 and Example 1 lies in that no welding portion is disposed on the back surface of the cell, i.e. the back conductive wires being welded with the back electric filed directly. Thus, a solar cell module D1 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

A copper wire is attached to an alloy layer of Sn40％-Bi55％-Pb5％ (melting point: 125℃) , in which the copper wire has a cross section of 0.03mm², and the alloy layer has a thickness of 10μm, so as to obtain the metal wire S.

(2) Manufacturing a solar cell module

A EVA adhesive layer in 1630×980×0.5mm are provided (melting point: 60℃) , and a glass plate in 1650×1000×3mm 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) , 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 non-continuous back welding portions on its back surface, and the back welding portions are formed by applying the silver paste to the back electric field. Each back welding portion substantially runs through the cell 31 in a longitudinal direction, and the distance between the adjacent back welding portions is 31mm.

60 cells 31 are arranged in a matrix form (six rows and ten columns) . In two adjacent cells 31, the metal wire extends reciprocally between a front surface of a first cell 31 and a back surface of a second cell under strain, so as to form 20 parallel conductive wires. The secondary grid line of the first cell 31 is welded with the primary grid, and the back welding portion of the second cell 31 is welded with the primary grid, and the distance between parallel conductive wires is 7mm. 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 thereof facing the back adhesive layer 40, and they are laminated in a laminator so as to obtain a solar cell module A2.

Example 3

The solar cell module is manufactured according to the method in Example 1, but the difference compared with Example 1 lies in that the back surface of the cell is provided with 20 welding portions, so as to obtain a solar cell module A3.

Performance test

(1) Welding-binding force test between the edge secondary grid lines and the metal wire

The welding-binding force in the solar cell modules A1-A5 and D1 will be tested in the following method respectively:

1. Placing the cell horizontally at a testing position of a tensile tester, and pressing blocks on the cell, in which the pressing blocks are disposed at two sides of the metal wire, such that the cell will not be pulled up during the test；

2. Clamping the metal wire at a pull ring of a tension meter that forms an angle of 45° with the cell；

3. Actuating the tension meter, such that the tension meter moves uniformly along a vertical direction, pulls up the metal wire from the surface of the cell and records the pull data tested, in which the data is averaged to obtain the pull data of the metal wire.

(2) Photoelectric conversion efficiency test

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

It can be indicated from Fig. 1 that the solar cell module according to the embodiments of the present disclosure has greater welding-binding force between the metal wire and the back welding portions, i.e. higher welding strength between the metal wire and the back surface of the cell, and obtains relatively high photoelectric conversion efficiency.

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, “a plurality 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 solar cell unit, comprising:

a cell including a cell substrate, secondary grid lines spaced apart from each other in a front surface of the cell substrate, a back electric field disposed in a back surface of the cell substrate, and back welding portions spaced apart from each other in the back electric field, the back welding portions being formed by applying a silver paste or a tin alloy to the back field；

a front conductive wire constituted by a metal wire and electrically connected with the front secondary grid lines； and

a back conductive wire constituted by a metal wire and electrically connected with the back electric field via the back welding portions.
The solar cell unit according to claim 1, wherein the tin alloy contains at least one of Cu, Ag, Pb, Bi, Zn, In, Fe and Ni, and Sn.
The solar cell unit according to claim 1 or 2, wherein the back welding portions are arranged into multiple rows spaced apart from each other； each row extends in a direction orthogonal to the back conductive wires, and the back welding portions in each row are spaced apart from each other.
The solar cell unit according to claim 3, wherein the back welding portions have a width in a direction parallel to the back conductive wires greater than a width of the front conductive wires.
The solar cell unit according to claim 3, wherein a distance between two adjacent rows of welding portions is greater than that between adjacent secondary grid lines.
The solar cell unit according to claim 3, wherein there are 5 to 30 rows.
The solar cell unit according to any one of claims 1 to 6, wherein the back welding portions have a width of 0.05 to 3mm in the direction parallel to the back conductive wires.
The solar cell unit according to claim 7, wherein the back welding portion has a width of 0.2 to 1.5mm.
The solar cell unit according to any one of claims 1 to 8, wherein part of the back welding portions is inserted into the back electric field.
The solar cell unit according to any one of claims 1 to 9, wherein the back welding portions are higher than the back electric field by 0.003-0.03mm.
The solar cell unit according to claim 10, wherein the back welding portions are higher than the back electric field by 0.005-0.01mm.
A solar cell array, comprising a plurality of cell units which are the solar cell units according to any one of claims 1 to 11, adjacent cells being connected by a metal wire which extends reciprocally between a surface of a first cell and a surface of a second cell adjacent to the first cell to form a front conductive wire and/or a back conductive wire.
The solar cell array according to claim 12, wherein the metal wire extends reciprocally between a front surface of the first cell and a back surface of the second cell, the front conductive wire is formed by the metal wire extending on the front surface of the first cell, and the back conductive wire is formed by the metal wire extending on the back surface of the second cell.
The solar cell array according to claim 13, wherein the metal wire extends reciprocally between the front surface of the first cell and the back surface of the second cell for 10 to 60 times.
The solar cell array according to claim 13, wherein a distance between two adjacent front conductive wires ranges from 2.5mm to 15mm.
The solar cell array according to claim 13, wherein the two adjacent front conductive wires form a U-shape structure or a V-shape structure.
The solar cell array according to claim 12, wherein the cells are arranged in an n×m matrix form, n representing a column number, and m representing a row number；

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 solar cell array according to claim 17, 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 solar cell array according to claim 18, 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 the cell at the end of the a^th row and a back surface of the cell at the end of the (a+1) ^th row, to connect the two adjacent rows of cells in series.
The solar cell array according to any one of claims 17 to 19, wherein there is one metal wire extending reciprocally between adjacent cells in a row； and there is one metal wire extending reciprocally between cells in adjacent rows.
The solar cell array according to any one of claims 17 to 20, wherein the metal wire is coated with a welding layer, and a ratio of a thickness of the welding layer to a diameter of the metal wire is (0.02-0.5) : 1.
The solar cell array according to claim 21, wherein the welding layer contains Sn, and at least one of Bi, In, Ag, Sb, Pb and Zn.
The solar cell array according to claim 21, wherein the welding layer contains Sn, Bi, and at least one of In, Ag, Sb, Pb and Zn.
The solar cell array according to claim 17, wherein the metal wire includes a copper wire.
A solar cell module, comprising an upper cover plate, a front adhesive layer, a cell array, a back adhesive layer and a lower cover plate superposed in sequence, the cell array being a solar cell array according to any one of claims 12 to 24.
A method for manufacturing a solar cell module, comprising:

providing a cell which includes a cell substrate, secondary grid lines spaced apart from each other in a front surface of the cell substrate, a back electric field disposed in a back surface of the cell substrate, and back welding portions spaced apart from each other in the back electric field, the back welding portions formed by applying silver paste or a tin alloy to the back field；

connecting front conductive wires constituted by a metal wire with the front secondary grid lines, and connecting back conductive wires constituted by a metal wire with the back secondary grid lines, to obtain a solar cell unit；

superposing an upper cover plate, a front adhesive layer, the solar cell unit, a back adhesive layer and a lower cover plate in sequence, in which a front surface of the solar cell unit faces the front adhesive layer, a back surface thereof facing the back adhesive layer, and laminating them to obtain the solar cell module.
The method according to claim 26, wherein there are multiple cells； and adjacent cells are connected by the conductive wires to form the cell array according to any one of claims 12 to 24.
The method according to claim 26, wherein the metal wire extends reciprocally on any one of a front surface and a back surface of the cell.