Back contact solar cell module and photovoltaic system

Abstract

The invention is suitable for the field of photovoltaic technology, and provides a back contact solar cell module and a photovoltaic system, the back contact solar cell module comprises a composite welding strip and a plurality of back contact solar cells, the composite welding strip is arranged on the backlight surfaces of the plurality of back contact solar cells, and the composite welding strip comprises a first conductive layer; the second conducting layer is arranged on the outer surface of the first conducting layer, the first conducting layer comprises an aluminum element, and the second conducting layer comprises a copper element or a nickel element; the mass ratio of the second conductive layer to the first conductive layer of the composite welding strip is the component ratio C of the composite welding strip, and the component ratio C of the composite welding strip is greater than or equal to 0.1. According to the invention, the yield strength of the composite welding strip is controlled within the preset range, so that the problem that the composite welding strip is easy to warp to cause the warping of a battery piece can be avoided; compared with a traditional copper solder strip, the cost is greatly reduced, and the production cost of a battery assembly is effectively reduced.

Description

Technical Field

[0001] The present application belongs to the field of photovoltaic technology, and in particular to a back-contact solar cell module and a photovoltaic system. Background Art

[0002] Solar energy is an inexhaustible clean energy. With the development of the solar energy industry, the installed capacity of photovoltaics has been rising. With the continuous innovation of technology, the cost of electricity per kilowatt-hour has continued to decline, and the demand for grid parity has also increased. How to reduce costs and increase efficiency has become the top priority of the industry. On the photovoltaic module side, conventional photovoltaic welding ribbons are made of oxygen-free copper, and the production cost of photovoltaic welding ribbons is relatively high. With the continuous updating and iteration of current component battery technology, Topcon, heterojunction, and IBC have emerged, and the demand for welding ribbons is also constantly changing. On the premise of meeting the conductivity, it is an urgent problem to prepare low-cost welding ribbons to replace conventional oxygen-free copper welding ribbons, keep the cost of welding ribbons at a low level, and make them inexpensive and of good quality.

[0003] Although the current conventional composite welding tape has reduced the production cost, when a certain welding temperature is used for welding, the composite welding tape is very likely to warp due to the different thermal expansion coefficients of different metals, causing the contact part between the battery cell and the composite welding tape to be forced to deform, which in turn causes the battery cell to warp, resulting in battery cell cracking, and thus increasing the defective rate of battery components.

[0004] How to control the warping of the composite welding ribbon in the back-contact solar cell module becomes the key. This has positive significance for breaking the market's inherent perception of high efficiency and high cost of IBC batteries, allowing IBC batteries to gain a larger application market. Summary of the invention

[0005] In a first aspect, the present application provides a back-contact solar cell module, aiming to solve the problem of how to control the warping of a composite welding ribbon in a back-contact solar cell module.

[0006] The present application is implemented as follows: a back-contact solar cell assembly comprises a composite welding strip and a plurality of back-contact solar cells, wherein the composite welding strip is arranged on the back-light surface of the plurality of back-contact solar cells, the composite welding strip comprises a first conductive layer; a second conductive layer, wherein the second conductive layer is arranged on the outer surface of the first conductive layer, wherein the first conductive layer comprises an aluminum element, and the second conductive layer comprises a copper element or a nickel element; the mass ratio of the second conductive layer and the first conductive layer of the composite welding strip is a composite welding strip component ratio C, wherein the composite welding strip component ratio C is greater than or equal to 0.1, the composite welding strip has a first connecting portion, wherein the first connecting portion is arranged between two adjacent back-contact solar cells, wherein an angle a of the first connecting portion relative to the back-light surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 60°, and the angle a and the yield strength σs of the composite welding strip satisfy the following relationship: (90 / 1.63) × cos a≤σs≤cos a × 90, wherein a is greater than or equal to 0° and less than or equal to 60°.

[0007] The present application arranges the composite welding strip on the back-light surface of multiple back-contact solar cells. Compared with the double-sided cell structure, the arrangement of the composite welding strip on the single side of the back-contact solar cell significantly reduces the bending degree of the composite welding strip, making it possible for the composite welding strip to connect multiple back-contact solar cells without warping within the set yield strength range. By controlling the yield strength of the composite welding tape within a predetermined range, the problem of the composite welding tape being prone to warping and causing warping of the battery cell can be avoided. The morphology, composition and size of the composite welding tape can be designed in a diversified manner to meet the process requirements of various types of solar cell modules. Compared with traditional copper welding tapes, the cost is greatly reduced, thereby effectively reducing the production cost of the battery module. In addition, the present application also sets the angle a of the first connecting portion of the composite welding tape relative to the backlight surface of the back-contact solar cell and the yield strength of the composite welding tape to satisfy the relationship: (90 / 1.63) × cos a≤σs≤cos a × 90, wherein a is greater than or equal to 0° and less than or equal to 60°, further ensuring that when the composite welding tape is used for series welding between battery cells, the composite welding tape and the battery cell have a good fit, the welding is stable and does not deform, especially in the overlapping area of ​​the battery cell, the composite welding tape can achieve a smooth transition connection, and can avoid the occurrence of cold welding and desoldering of the composite welding tape in the overlapping area of ​​the battery cell.

[0008] Optionally, a plurality of the back-contact solar cells are arranged at intervals, and an angle a formed by the first connecting portion relative to a backlight surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 20°.

[0009] Optionally, an angle a formed by the first connecting portion relative to the backlight surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 10°.

[0010] Optionally, an angle a formed between the first connection portion and the backlight surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 5°.

[0011] Optionally, a plurality of the back-contact solar cells are partially overlapped and arranged, and an angle a formed by the first connecting portion relative to a backlight surface of the back-contact solar cell is greater than or equal to 10° and less than or equal to 60°.

[0012] Optionally, an angle a formed between the first connection portion and the backlight surface of the back-contact solar cell is greater than or equal to 10° and less than or equal to 45°.

[0013] Optionally, the composite welding strip component ratio C is greater than or equal to 0.2.

[0014] Optionally, the component ratio C of the composite welding strip is in the range of 0.25 to 2.4.

[0015] Optionally, the composite welding strip further includes a composite structural layer, the first conductive layer and the second conductive layer are composited to form the composite structural layer, and the composite structural layer is arranged between the first conductive layer and the second conductive layer.

[0016] Optionally, the thickness of the composite structure layer is 0-30 microns.

[0017] Optionally, components of the composite structural layer include at least one of Al4 Cu9, AlCu, Al2Cu, Al2Cu3, Al3Cu4 and Cu.

[0018] Optionally, the composite welding strip further includes a conductive connecting layer, and the conductive connecting layer is arranged on the surface of the second conductive layer.

[0019] Optionally, the thickness of the conductive connection layer is 1 to 20 microns.

[0020] Optionally, the conductive connection layer comprises at least one of Sn, Bi and Pb.

[0021] Optionally, based on the first preset temperature, components of the conductive connection layer include Sn, Bi, and Pb; wherein the content of Bi is 10% to 40%, the content of Sn is 20% to 50%, and the content of Pb is 30% to 60%.

[0022] Optionally, based on the second preset temperature, components of the conductive connection layer include Sn and Pb; wherein the content of Sn is 50% to 70%, and the content of Pb is 30% to 50%.

[0023] Optionally, the resistance of the composite welding strip is greater than or equal to 60 milliohms and less than or equal to 150 milliohms.

[0024] Optionally, a connecting layer is further included, and the connecting layer is arranged between the first conductive layer and the second conductive layer.

[0025] Optionally, the tie layer comprises zinc.

[0026] Optionally, the composite welding strip is a flat welding strip.

[0027] Optionally, when the thickness of the composite welding strip is 0.1 mm, the width of the composite welding strip is less than 2.5 mm; or, when the width of the composite welding strip is 2.5 mm, the thickness of the composite welding strip is greater than 0.1 mm.

[0028] Optionally, when the width of the composite welding strip is 0.4~0.8mm and the thickness of the composite welding strip is 0.2~0.3mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 58~68MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

[0029] Optionally, when the width of the composite welding strip is 0.8~1.4mm and the thickness of the composite welding strip is 0.12~0.2mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 65~75MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 70~80MPa.

[0030] Optionally, when the width of the composite welding strip is 1.4~1.8mm and the thickness of the composite welding strip is 0.1~0.15mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 65~75MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 70~80MPa.

[0031] Optionally, when the width of the composite welding strip is 1.8~2.2mm and the thickness of the composite welding strip is 0.12~0.2mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

[0032] Optionally, when the width of the composite welding strip is 1.8~2.2mm and the thickness of the composite welding strip is 0.05~0.12mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

[0033] Optionally, when the width of the composite welding strip is 2.2~2.8mm and the thickness of the composite welding strip is 0.12~0.2mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

[0034] Optionally, the composite welding strip is a round wire welding strip, and the diameter length of the composite welding strip is greater than or equal to 0.07 mm and less than or equal to 0.4 mm.

[0035] Optionally, when the diameter length of the composite welding strip is 0.07~0.2mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 65~75MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 70~80MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 72~82MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 75~85MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 80~90MPa.

[0036] Optionally, when the diameter length of the composite welding strip is 0.2~0.3mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 58~68MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

[0037] Optionally, when the diameter length of the composite welding strip is 0.3~0.4mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 58~68MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

[0038] Optionally, the composite welding strip is a triangular welding strip, and the diameter length of the circumscribed circle of the composite welding strip is greater than or equal to 0.07 mm and less than or equal to 0.4 mm.

[0039] Optionally, a ratio of a thickness of the first conductive layer to a thickness of the second conductive layer is greater than or equal to 5 and less than or equal to 9.

[0040] Optionally, the thickness of the second conductive layer is 0.01-0.05 mm.

[0041] Optionally, the composite welding strip includes a plurality of free portions and a plurality of second connecting portions connected between the plurality of free portions, the second connecting portions are connected to the back-contact solar cells, and the free portions are separated from the back-contact solar cells.

[0042] Optionally, a maximum spacing distance between the free portion and the back contact solar cell is 0.1-0.4 mm.

[0043] In a second aspect, a photovoltaic system is provided, comprising the above-mentioned back-contact solar cell module. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the structure of the first composite welding strip provided in the present application; Figure 2 It is a schematic diagram of the structure of the second composite welding strip provided in the present application; Figure 3 It is a schematic diagram of the structure of the third composite welding strip provided in the present application; Figure 4 It is a schematic diagram of the structure of the fourth composite welding strip provided in the present application; Figure 5 It is a schematic diagram of the structure of the fifth composite welding strip provided in the present application; Figure 6 It is a schematic diagram of the structure of the sixth composite welding strip provided in the present application; Figure 7It is a schematic diagram of the structure of the seventh composite welding strip provided in the present application; Figure 8 It is a schematic diagram of the structure of the eighth composite welding strip provided in the present application; Fig. 9 It is a schematic structural diagram of the first back-contact solar cell module provided in the present application; Fig.10 It is a schematic diagram of the structure of the second back-contact solar cell module provided in the present application.

[0045] Description of reference numerals: 100. Composite welding strip; 101. First conductive layer; 102. Second conductive layer; 103. First connecting portion; 104. Composite structural layer; 105. Conductive connecting layer; 106. Free portion; 107. Second connecting portion; 108. Connecting layer; 200. Back contact solar cell. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0047] In the description of the present application, it should be understood that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0049] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0050] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0051] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the various specific processes and material examples provided by the present application, but those of ordinary skill in the art can appreciate the application of other processes and / or the use of other materials.

[0052] like Figure 1 As shown, in some embodiments, a back-contact solar cell assembly includes a composite welding ribbon 100 and a plurality of back-contact solar cells 200, and the composite welding ribbon 100 is arranged on the backlight surface of the plurality of back-contact solar cells 200. Compared with the double-sided cell structure, the composite welding ribbon 100 is arranged on the single side of the back-contact solar cell 200, which significantly reduces the bending degree of the composite welding ribbon 100, so that it is possible for the composite welding ribbon 100 to connect the plurality of back-contact solar cells 200 within a set yield strength range. It should be pointed out that, in this embodiment, each back-contact solar cell 200 is electrically and physically connected to the composite welding ribbon 100 mainly by welding, but it can be understood that they can also be connected to each other by other methods, which are set according to the needs of use and are not specifically limited here.

[0053] The composite welding strip 100 includes a first conductive layer 101 and a second conductive layer 102. The second conductive layer 102 is arranged on the outer surface of the first conductive layer 101. The first conductive layer 101 includes aluminum elements, and the second conductive layer 102 includes copper elements or nickel elements. In the embodiment of the present application, the metallurgical bonding of the double-layer conductive material is achieved between the first conductive layer 101 and the second conductive layer 102 by electroplating, casting, forging or cold rolling, and the present application is not limited to this. In some embodiments, the material of the second conductive layer 102 includes one or more of nickel, tin, bismuth, silver, copper, aluminum, titanium, lead, indium, and gallium, that is, the material of the second conductive layer 102 can be a single material, or a combination or alloy of multiple materials, as long as it can achieve conductivity and facilitate welding, and is not limited to the materials listed in this embodiment. In the embodiment of the present application, the material of the second conductive layer 102 is preferably copper, which has good ductility and good conductivity. The material of the first conductive layer 101 can be aluminum, aluminum alloy, zinc, nickel or other metal materials. Taking into account the functional requirements of conductivity, the first conductive layer 101 is preferably made of aluminum, which has a soft texture, high stability, high corrosion resistance, low cost, and is convenient for subsequent deep processing and compounding.

[0054] The composite welding strip 100 has a corresponding yield strength based on the preset size and the corresponding composite welding strip component ratio C, wherein the composite welding strip component ratio C is the mass ratio of the second conductive layer 102 and the first conductive layer 101, and the composite welding strip component ratio C is greater than or equal to 0.1. In the embodiment of the present application, the corresponding yield strength is set for the composite welding strip 100 with different preset sizes and different composite welding strip component ratios C. By setting the yield strength of different types of composite welding strips 100 differently, the problem of warping of the composite welding strip 100 after hot pressing annealing can be better controlled. In addition, the R&D personnel have devoted a lot of effort to research and test, and finally obtained the conclusion that the yield strength is the key reason affecting the warping of the composite welding strip 100. Based on this cognition, the R&D personnel optimized the applicable range of the yield strength of different types of composite welding strips 100, and finally successfully solved the problem of warping of the battery cell. While reducing the cost, the applicability and ease of use of the composite welding strip 100 are guaranteed, which is convenient for promotion and application.

[0055] It can be understood that the present application sets the mass ratio of the second conductive layer 102 and the first conductive layer 101 to be greater than or equal to 0.1, and further, the mass ratio of the second conductive layer 102 and the first conductive layer 101 is set to be greater than or equal to 0.2. Preferably, the mass ratio of the second conductive layer 102 and the first conductive layer 101 is 0.25~2.4. In such an embodiment, the mass ratio of the second conductive layer 102 and the first conductive layer 101 can be 0.25, 0.26, 0.28, 0.3, 0.4, 0.6, 0.8, 1.2, 1.6, 1.8, 2.2, 2.4, or any value between 0.25-2.4, and is not specifically limited here. The mass ratio of the second conductive layer 102 and the first conductive layer 101 is within this range. On the one hand, the production cost of the composite welding strip 100 can be effectively reduced. On the other hand, in the composite welding strip 100, the bonding strength between the first conductive layer 101 and the second conductive layer 102 is an important consideration. For example, during the cold rolling composite process, when the copper-aluminum thickness ratio decreases (i.e., the thickness of aluminum increases relatively), the aluminum strip undergoes more severe plastic deformation, thereby forming more cracks at the interface. These cracks are conducive to the entry of more metal compounds and promote interface bonding, making the bond between the copper strip and the aluminum strip more secure. When the aluminum layer is too thick, due to the difference in yield stress between copper and aluminum, the time required to reach a common plastic strain becomes longer, which may cause the density of the bonding interface to deteriorate, thereby affecting the bonding strength. Within this range, the bonding strength between the first conductive layer 101 and the second conductive layer 102 is high, and the formed composite welding strip 100 can resist external stress and prevent peeling or falling off between the two layers due to force.

[0056] Secondly, the change in the mass ratio of the second conductive layer 102 to the first conductive layer 101 will also affect the mechanical properties of the composite welding strip 100. For example, when the aluminum content is high, the composite strip may exhibit better toughness and ductility; and when the copper content is high, the conductivity, strength and hardness of the composite strip may be improved. When the mass ratio of the second conductive layer 102 to the first conductive layer 101 is within this range, the composite welding strip 100 formed has good ductility and high structural strength, and can achieve stable connection between battery cells.

[0057] In some embodiments, Fig. 9 and Fig.10As shown, the composite welding strip 100 has a first connection portion 103, and the angle a of the first connection portion 103 relative to the backlight surface of the back contact solar cell is greater than or equal to 0° and less than or equal to 60°. The angle a and the yield strength σs of the composite welding strip 100 satisfy the following relationship: (90 / 1.63) × cos a≤σs≤cos a × 90, wherein a is greater than or equal to 0° and less than or equal to 60°. When the composite welding strip 100 is used for serial welding between cells, the cells are arranged in different forms. The first connection portion 103 is provided to achieve high-quality connection between cells. In some embodiments, multiple back contact solar cells are arranged at intervals. At this time, the composite welding strip 100 can maintain a straight shape to connect multiple back contact solar cells. The angle a of the first connection portion relative to the backlight surface of the back contact solar cell is greater than or equal to 0° and less than or equal to 20°. Preferably, the angle a of the first connection portion relative to the backlight surface of the back contact solar cell is greater than or equal to 0° and less than or equal to 10°. Furthermore, the angle a of the first connection portion relative to the backlight surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 5°. In some embodiments, a plurality of back-contact solar cells are partially overlapped, and the angle a of the first connection portion 103 relative to the back-contact solar cell is greater than or equal to 10° and less than or equal to 60°. Preferably, the angle a of the first connection portion relative to the backlight surface of the back-contact solar cell is greater than or equal to 10° and less than or equal to 45°. Since the battery cell itself has a certain thickness, the local overlapping area of ​​the back-contact solar cell has a step structure, and the composite welding strip 100 is partially bent when passing through the overlapping area. The bent portion is also the first connection portion 103. The angle of the first connection portion 103 relative to the backlight surface of the back-contact solar cell is determined according to the local bending degree of the composite welding strip 100 and the thickness of the battery cell. The present application specially designs the composite welding strip 100 to further ensure that when the composite welding strip 100 is used for series welding between battery cells, the composite welding strip 100 and the battery cell have a good fit, and the welding is stable and does not deform, especially in the overlapping area between the battery cells. The composite welding strip 100 can achieve a smooth transition connection, which can avoid the occurrence of cold welding and desoldering of the composite welding strip 100 in the overlapping area of ​​the battery cells.

[0058] It is particularly noted that the angle a of the first connection portion 103 relative to the back-contact solar cell 200 is the angle formed by the straight line between the two points where the first connection portion 103 contacts two adjacent back-contact solar cells 200 and the surface of the back-contact solar cell 200, such as Fig.10 shown.

[0059] The yield strength of the composite welding strip 100 can be measured by a tensile test. Specifically, a sample (in this case, the composite welding strip 100) is placed in a tensile testing machine, and a tensile force is gradually applied while measuring and recording a stress-strain curve. This curve reflects the relationship between the deformation and the stress of the sample during the tensile process. Through this curve, the yield strength of the composite welding strip 100, that is, the stress value of the sample at the beginning of plastic deformation, can be determined.

[0060] The present application sets the corresponding yield strength for the composite welding strip 100 based on different sizes and corresponding component ratios, thereby controlling the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of the composite welding strip 100 being easily warped and causing warping of the battery cell. The morphology, components and sizes of the composite welding strip 100 can be designed in a diversified manner to meet the process requirements of various types of solar cell modules. Compared with traditional copper welding strips, the cost is greatly reduced, thereby effectively reducing the production cost of the battery module.

[0061] In some embodiments, the composite welding strip 100 includes a composite structural layer 104, the first conductive layer 101 and the second conductive layer 102 are composited to form the composite structural layer 104, and the composite structural layer 104 is arranged between the first conductive layer 101 and the second conductive layer 102. The composite of the first conductive layer 101 and the second conductive layer 102 refers to metallurgically combining the first conductive layer 101 and the second conductive layer 102 by forging, casting, etc. The composite structural layer 104 is an intermetallic compound formed during the metallurgical bonding of the first conductive layer 101 and the second conductive layer 102. The composite structural layer 104 can achieve a close combination of the first conductive layer 101 and the second conductive layer 102, and can produce a consistent change when subjected to external stress, without delamination or peeling. Further, the thickness of the composite structural layer 104 is 0 to 30 microns. Preferably, the thickness of the composite structural layer 104 is 15 to 30 microns. In such an embodiment, the thickness of the composite structure layer 104 can be 15 microns, 20 microns, 25 microns, 30 microns or any value between 15 and 30 microns, and is not specifically limited here. The thickness of the composite structure layer 104 is within this range, which can ensure that the first conductive layer 101 and the second conductive layer 102 have a high bonding strength and peeling strength, and prevent the two layers from peeling or falling off due to force.

[0062] Furthermore, the components of the composite structure layer 104 include at least one of Al4 Cu9, AlCu, Al2Cu, Al2Cu3, Al3Cu4 and Cu, and the formation of intermetallic compounds is the key to achieving effective connection. These compounds can form strong chemical bonds at the connection interface, thereby improving the connection strength. By controlling the process parameters (such as temperature, time, pressure, etc.) of the combination of the first conductive layer 101 and the second conductive layer 102, the type and amount of the intermetallic compounds can be adjusted to optimize the connection performance. In addition, the above-mentioned intermetallic compounds can further enhance the corrosion resistance of the composite welding strip 100.

[0063] In some embodiments, the composite welding strip 100 further includes a conductive connection layer 105, which is disposed on the surface of the second conductive layer 102. Specifically, the conductive connection layer 105 and the second conductive layer 102 can be metallurgically bonded by hot dipping. During the hot pressing connection between the composite welding strip 100 and the battery cell, the conductive connection layer 105 melts and then cools to realize the welding of the composite welding strip 100 and the battery cell. Further, the thickness of the conductive connection layer 105 is 1 to 20 microns. Preferably, the thickness of the conductive connection layer 105 is 10 to 15 microns. In such an embodiment, the thickness of the conductive connection layer 105 can be 10 microns, 12 microns, 13 microns, 15 microns or any value between 10 and 15 microns, which is not specifically limited here.

[0064] Further, the components of the conductive connection layer 105 include at least one of Sn, Bi, and Pb, and a low-temperature composite welding strip 100 or a high-temperature composite welding strip 100 can be formed by setting the components of the conductive connection layer 105. Specifically, based on the first preset temperature, the first preset temperature is the welding temperature of the composite welding strip 100 and the battery cell, and the range of the first preset temperature is 200°C to 300°C. The low-temperature composite welding strip 100 can achieve the connection of metal materials at a lower temperature, avoiding the damage of electronic components or specific materials caused by high temperature. Specifically, the components of the conductive connection layer 105 include Sn, Bi, and Pb; wherein the content of Bi is 10% to 40%, the content of Sn is 20% to 50%, and the content of Pb is 30% to 60%. By controlling the content ratio of Sn, Bi, and Pb, the melting point of the conductive connection layer 105 and the thermal expansion coefficient of the conductive connection layer 105 can be controlled.

[0065] Based on the second preset temperature, the second preset temperature is the welding temperature of the composite welding strip 100 and the battery cell. Specifically, the second preset temperature ranges from 500°C to 600°C. The high-temperature composite welding strip 100 can ensure the strength and stability of welding. Specifically, the components of the conductive connection layer 105 include Sn and Pb; wherein the content of Sn is 50% to 70%, and the content of Pb is 30% to 50%. By controlling the content ratio of Sn and Pb, the melting point of the conductive connection layer 105 and the thermal expansion coefficient of the conductive connection layer 105 can be controlled.

[0066] like Figure 1-Figure 6 As shown, it should be noted that the conductive connection layer 105 can be arranged on a single side of the composite welding strip 100 facing the back contact battery cell, and the conductive connection layer 105 can also be arranged on both sides of the composite welding strip 100 facing the back contact battery cell and away from the back contact battery cell. The arrangement of the conductive connection layer 105 and the composite welding strip 100 is set according to the production process requirements, and this application does not impose any restrictions.

[0067] In some embodiments, the resistance of the composite welding strip 100 is greater than or equal to 60 milliohms and less than or equal to 150 milliohms. When the resistance value of the composite welding strip 100 is within the above range, the series resistance of the component can be significantly reduced, thereby improving the transmission efficiency of the current. This means that the solar cell can more efficiently convert light energy into electrical energy and reduce energy loss during the transmission process.

[0068] In some embodiments, the composite welding strip 100 further includes a connecting layer 108, and the connecting layer 108 is disposed between the first conductive layer 101 and the second conductive layer 102. For example, in the electroplating process, since copper plating on aluminum is difficult, the present application sets a connecting layer 108 between the first conductive layer 101 and the second conductive layer 102 to achieve a good combination of the first conductive layer 101 and the second conductive layer 102. Preferably, the connecting layer 108 includes zinc. Of course, in other embodiments, the connecting layer 108 may also include other materials, which is not limited in the present application.

[0069] In the embodiment of the present application, the composite welding strip 100 may have different morphological structures. Based on different morphological structures, the composite welding strip 100 has different size characteristics. For example, the composite welding strip 100 is a flat welding strip, and the preset size includes the width and thickness of the composite welding strip 100. In particular, when the thickness of the composite welding strip 100 is 0.1 mm, the width of the composite welding strip 100 is less than 2.5 mm; or, when the width of the composite welding strip 100 is 2.5 mm, the thickness of the composite welding strip 100 is greater than 0.1 mm. In this way, the structural stability and sufficient structural strength of the flat composite welding strip 100 can be ensured, thereby achieving a stable connection between the composite welding strip 100 and the battery cell.

[0070] like Figure 1-Figure 6 As shown, an example based on the composite welding strip 100 being a flat welding strip is as follows: In some embodiments, when the width of the composite welding strip 100 is 0.4~0.8mm and the thickness of the composite welding strip 100 is 0.2~0.3mm: the composite welding strip component ratio C is 0.2~0.3, and the yield strength is 50~60MPa; or, the composite welding strip component ratio C is 0.3~0.8, and the yield strength is 55~65MPa; or, the composite welding strip component ratio C is 0.8~1.2, and the yield strength is 58~68MPa; or, the composite welding strip component ratio C is 1.2~2, and the yield strength is 60~70MPa; or, the composite welding strip component ratio C is 2~3, and the yield strength is 65~75MPa. The setting of the component ratio can be selected according to the production process and the type of battery cell. In this way, based on the same size and morphology, the composite welding strip 100 sets the corresponding yield strength according to the above-mentioned different component ratios, adaptively adjusts the mechanical properties of the composite welding strip 100, and controls the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of warping of the battery cell due to deformation of the composite welding strip 100.

[0071] In some embodiments, when the width of the composite welding strip 100 is 0.8~1.4 mm and the thickness of the composite welding strip 100 is 0.12~0.2 mm: the composite welding strip component ratio C is 0.2~0.3, and the yield strength is 55~65 MPa; or, the composite welding strip component ratio C is 0.3~0.8, and the yield strength is 60~70 MPa; or, the composite welding strip component ratio C is 0.8~1.2, and the yield strength is 62~72 MPa; or, the composite welding strip component ratio C is 1.2~2, and the yield strength is 65~75 MPa; or, the composite welding strip component ratio C is 2~3, and the yield strength is 70~80 MPa. The setting of the component ratio can be selected according to the production process and the type of battery cell. In this way, based on the same size and morphology, the composite welding strip 100 sets the corresponding yield strength according to the above-mentioned different component ratios, adaptively adjusts the mechanical properties of the composite welding strip 100, and controls the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of warping of the battery cell due to deformation of the composite welding strip 100.

[0072] In some embodiments, when the width of the composite welding strip 100 is 1.4~1.8 mm and the thickness of the composite welding strip 100 is 0.1~0.15 mm: the composite welding strip component ratio C is 0.2~0.3, and the yield strength is 55~65 MPa; or, the composite welding strip component ratio C is 0.3~0.8, and the yield strength is 60~70 MPa; or, the composite welding strip component ratio C is 0.8~1.2, and the yield strength is 62~72 MPa; or, the composite welding strip component ratio C is 1.2~2, and the yield strength is 65~75 MPa; or, the composite welding strip component ratio C is 2~3, and the yield strength is 70~80 MPa. The setting of the component ratio can be selected according to the production process and the type of battery cell. In this way, based on the same size and morphology, the composite welding strip 100 sets the corresponding yield strength according to the above-mentioned different component ratios, adaptively adjusts the mechanical properties of the composite welding strip 100, and controls the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of warping of the battery cell due to deformation of the composite welding strip 100.

[0073] In some embodiments, when the width of the composite welding strip 100 is 1.8~2.2 mm and the thickness of the composite welding strip 100 is 0.12~0.2 mm: the composite welding strip component ratio C is 0.2~0.3, and the yield strength is 50~60 MPa; or, the composite welding strip component ratio C is 0.3~0.8, and the yield strength is 55~65 MPa; or, the composite welding strip component ratio C is 0.8~1.2, and the yield strength is 60~70 MPa; or, the composite welding strip component ratio C is 1.2~2, and the yield strength is 62~72 MPa; or, the composite welding strip component ratio C is 2~3, and the yield strength is 65~75 MPa. The setting of the component ratio can be selected according to the production process and the type of battery cell. In this way, based on the same size and morphology, the composite welding strip 100 sets the corresponding yield strength according to the above-mentioned different component ratios, adaptively adjusts the mechanical properties of the composite welding strip 100, and controls the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of warping of the battery cell due to deformation of the composite welding strip 100.

[0074] In some embodiments, when the width of the composite welding strip 100 is 1.8~2.2 mm and the thickness of the composite welding strip 100 is 0.05~0.12 mm: the composite welding strip component ratio C is 0.2~0.3, and the yield strength is 50~60 MPa; or, the composite welding strip component ratio C is 0.3~0.8, and the yield strength is 55~65 MPa; or, the composite welding strip component ratio C is 0.8~1.2, and the yield strength is 60~70 MPa; or, the composite welding strip component ratio C is 1.2~2, and the yield strength is 62~72 MPa; or, the composite welding strip component ratio C is 2~3, and the yield strength is 65~75 MPa. The setting of the component ratio can be selected according to the production process and the type of battery cell. In this way, based on the same size and morphology, the composite welding strip 100 sets the corresponding yield strength according to the above-mentioned different component ratios, adaptively adjusts the mechanical properties of the composite welding strip 100, and controls the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of warping of the battery cell due to deformation of the composite welding strip 100.

[0075] In some embodiments, when the width of the composite welding strip 100 is 2.2~2.8mm and the thickness of the composite welding strip 100 is 0.12~0.2mm: the composite welding strip component ratio C is 0.2~0.3, and the yield strength is 50~60MPa; or, the composite welding strip component ratio C is 0.3~0.8, and the yield strength is 55~65MPa; or, the composite welding strip component ratio C is 0.8~1.2, and the yield strength is 60~70MPa; or, the composite welding strip component ratio C is 1.2~2, and the yield strength is 62~72MPa; or, the composite welding strip component ratio C is 2~3, and the yield strength is 65~75MPa. The setting of the component ratio can be selected according to the production process and the type of battery cell. In this way, based on the same size and morphology, the composite welding strip 100 sets the corresponding yield strength according to the above-mentioned different component ratios, adaptively adjusts the mechanical properties of the composite welding strip 100, and controls the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of warping of the battery cell due to deformation of the composite welding strip 100.

[0076] like Figure 7 As shown, in some embodiments, the composite welding tape 100 is a round wire welding tape, and the diameter length of the composite welding tape 100 is greater than or equal to 0.07 mm and less than or equal to 0.4 mm. Within this diameter range, the composite welding tape 100 can provide sufficient welding area to ensure the strength and stability of welding.

[0077] Based on the composite welding strip 100 being a round wire welding strip, an example is as follows; In some embodiments, when the diameter length of the composite welding strip 100 is 0.07-0.2 mm: the composite welding strip component ratio C is 0.2-0.3, and the yield strength is 65-75 MPa; or, the composite welding strip component ratio C is 0.3-0.8, and the yield strength is 70-80 MPa; or, the composite welding strip component ratio C is 0.8-1.2, and the yield strength is 72-82 MPa; or, the composite welding strip component ratio C is 1.2-2, and the yield strength is 75-85 MPa; or, the composite welding strip component ratio C is 2-3, and the yield strength is 80-90 MPa. The setting of the component ratio can be selected according to the production process and the type of battery cell. In this way, based on the same size and morphology, the composite welding strip 100 sets the corresponding yield strength according to the above different component ratios, adaptively adjusts the mechanical properties of the composite welding strip 100, and controls the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of easy warping of the battery cell due to deformation of the composite welding strip 100.

[0078] In some embodiments, when the diameter length of the composite welding strip 100 is 0.2-0.3 mm: the composite welding strip component ratio C is 0.2-0.3, and the yield strength is 50-60 MPa; or, the composite welding strip component ratio C is 0.3-0.8, and the yield strength is 55-65 MPa; or, the composite welding strip component ratio C is 0.8-1.2, and the yield strength is 58-68 MPa; or, the composite welding strip component ratio C is 1.2-2, and the yield strength is 60-70 MPa; or, the composite welding strip component ratio C is 2-3, and the yield strength is 65-75 MPa. The setting of the component ratio can be selected according to the production process and the type of battery cell. In this way, based on the same size and morphology, the composite welding strip 100 sets the corresponding yield strength according to the above different component ratios, adaptively adjusts the mechanical properties of the composite welding strip 100, and controls the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of easy warping of the battery cell due to deformation of the composite welding strip 100.

[0079] In some embodiments, when the diameter length of the composite welding strip 100 is 0.3-0.4 mm: the composite welding strip component ratio C is 0.2-0.3, and the yield strength is 50-60 MPa; or, the composite welding strip component ratio C is 0.3-0.8, and the yield strength is 55-65 MPa; or, the composite welding strip component ratio C is 0.8-1.2, and the yield strength is 58-68 MPa; or, the composite welding strip component ratio C is 1.2-2, and the yield strength is 60-70 MPa; or, the composite welding strip component ratio C is 2-3, and the yield strength is 65-75 MPa. The setting of the component ratio can be selected according to the production process and the type of battery cell. In this way, based on the same size and morphology, the composite welding strip 100 sets the corresponding yield strength according to the above different component ratios, adaptively adjusts the mechanical properties of the composite welding strip 100, and controls the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of easy warping of the battery cell due to deformation of the composite welding strip 100.

[0080] like Figure 8 As shown, in some embodiments, the composite welding strip 100 is a triangular welding strip, and the diameter length of the circumscribed circle of the composite welding strip 100 is greater than or equal to 0.07 mm and less than or equal to 0.4 mm. Within this size range, the composite welding strip 100 can provide a sufficient welding area to ensure the strength and stability of the welding.

[0081] In some embodiments, the ratio of the thickness of the first conductive layer 101 to the thickness of the second conductive layer 102 is greater than or equal to 5 and less than or equal to 9. For example, the ratio of the thickness of the first conductive layer 101 to the thickness of the second conductive layer 102 can be 5, 6, 7, 8, 9, etc., or any value between 5 and 9, and is not specifically limited here. Within this ratio range, when affected by external forces or environmental factors (such as temperature and humidity changes), the thicker first conductive layer 101 can better resist deformation, thereby maintaining the integrity and performance of the first conductive layer 101. Although the second conductive layer 102 is thinner, the composite welding strip 100 formed by combining with the thicker first conductive layer 101 can avoid warping and can form a more continuous and stable conductive path, thereby improving the conductive efficiency. Preferably, the thickness of the second conductive layer 102 is 0.01~0.05mm. Exemplarily, for example, 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, etc., or any value between 0.01 mm and 0.05 mm, which is not specifically limited here.

[0082] The thickness of the first conductive layer 101 and the second conductive layer 102 mentioned in the present application refers to the average thickness of the first conductive layer 101 and the second conductive layer 102 film layers.

[0083] like Figure 3As shown, in some embodiments, the first conductive layer 101 has a first surface and a second surface arranged opposite to each other in the thickness direction, and the first surface and the second surface are respectively provided with a second conductive layer 102. Among them, the second conductive layer 102 covering the first surface has a first thickness, and the second conductive layer 102 covering the second surface has a second thickness, wherein the first surface is arranged toward the battery cell, and the second surface is arranged away from the battery cell. Optionally, the second thickness is greater than the first thickness. Through such a structural design, the connection state between the composite welding strip 100 and the battery cell can be made more stable, and the deformation caused by the change of the external environment temperature can be reduced.

[0084] This application is attached Figure 1-Figure 8 The structures of the composite welding strip 100 in the embodiment are only several typical embodiments designed in the present application, and the structures of the composite welding strip 100 in the present application are not limited to these several embodiments.

[0085] like Fig. 9 As shown, the composite welding strip 100 includes a plurality of free portions 106 and a plurality of second connection portions 107 connected between the plurality of free portions 106, the second connection portions 107 are connected to the solar cell, and the free portions 106 are separated from the solar cell. Further, in one embodiment of the present application, the free portion 106 is a deformation buffer structure, and the composite welding strip 100 is connected to the back contact solar cell 200 through each of its second connection portions 107, and the specific manufacturing process is to spot weld each of the second connection portions 107 of a composite welding strip 100 with each of the welding points on a main grid in the back contact solar cell 200, and each of the free portions 106 is separated from the back contact solar cell 200 to form a deformation buffer structure, wherein the deformation buffer structure is various bending shapes such as arc, S-shaped, rectangular, or folded line. It should be noted that each of the second connection portions 107 is in the same horizontal plane, so that each of the second connection portions 107 can contact the solder joint of the back contact solar cell 200, and each of the free portions 106 is bent and deformed to be in a different horizontal plane from the second connection portion 107 and extend out of the second connection portion 107. Further, the maximum spacing distance between the free portion 106 and the solar cell is 0.1-0.4 mm. In this way, when the composite welding strip 100 is bent to form the free portion 106, the composite welding strip 100 can have sufficient buffer margin compared to the existing straight state to cope with the contraction or expansion of the composite welding strip 100.

[0086] Therefore, after the welding of each second connection portion 107 of the composite welding strip 100 and the welding point of the back contact solar cell 200 is completed, the free portion 106 can provide a certain buffer between two adjacent welding points, so that when the composite welding strip 100 shrinks more due to the difference in thermal expansion coefficient with the back contact solar cell 200 after returning to room temperature, the buffer can be used to compensate for the deformation of the composite welding strip 100 shrinkage, reduce the stress caused by thermal expansion and contraction, and reduce the warping problem of the back contact solar cell 200 caused by welding, so that the back contact solar cell 200 after welding can be straighter than the existing one. At the same time, the shrinking composite welding strip 100 can also lower the protruding height of the free portion 106, and can also make the composite welding strip 100 that performs deformation compensation after welding become straighter, so as to achieve low warping of the entire back contact solar cell 200 assembly.

[0087] In some embodiments, a plurality of back contact solar cells 200 are partially overlapped to form an overlapped area, and the first connection portion 103 of the composite welding tape 100 is arranged in the overlapped area. It is ensured that when the composite welding tape 100 is used for series welding between cells, the composite welding tape 100 and the cell have good adhesion, and the welding is stable and does not deform, especially in the overlapped area of ​​the cell, the composite welding tape 100 can achieve a smooth transition connection, and can avoid the composite welding tape 100 from being cold-welded or desoldering in the overlapped area of ​​the cell.

[0088] A photovoltaic system, the photovoltaic system includes the above-mentioned battery assembly. In this embodiment, the photovoltaic system can be used in photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be used in equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be used in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array may be an array combination of multiple battery assemblies. For example, multiple battery assemblies can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter to convert it into the alternating current required by the mains power grid and then connected to the mains network to realize solar power supply.

[0089] In the description of this specification, the description with reference to the terms "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0090] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A back contact solar cell module, characterized in that: The invention comprises a composite welding strip and a plurality of back-contact solar cells, wherein the composite welding strip is arranged on the back-light surface of the plurality of back-contact solar cells, the composite welding strip comprises a first conductive layer; a second conductive layer, wherein the second conductive layer is arranged on the outer surface of the first conductive layer, wherein the first conductive layer comprises an aluminum element, and the second conductive layer comprises a copper element or a nickel element; the mass ratio of the second conductive layer and the first conductive layer of the composite welding strip is a composite welding strip component ratio C, wherein the composite welding strip component ratio C is greater than or equal to 0.1, the composite welding strip has a first connecting portion, wherein the first connecting portion is arranged between two adjacent back-contact solar cells, wherein an angle a of the first connecting portion relative to the back-light surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 60°, and wherein the angle a and the yield strength σs of the composite welding strip satisfy the following relationship: (90 / 1.63) ×cos a≤σs≤cos a × 90, Wherein, a is greater than or equal to 0° and less than or equal to 60°.

2. The back contact solar cell module according to claim 1, characterized in that: The plurality of back-contact solar cells are arranged at intervals, and an angle a formed by the first connecting portion relative to a backlight surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 20°.

3. The back contact solar cell module according to claim 2, characterized in that: An angle a formed between the first connection portion and the backlight surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 10°.

4. The back contact solar cell module according to claim 3, characterized in that: An angle a formed between the first connection portion and the backlight surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 5°.

5. The back contact solar cell module according to claim 1, characterized in that: The plurality of back-contact solar cells are partially overlapped and arranged, and an angle a formed by the first connecting portion relative to a backlight surface of the back-contact solar cell is greater than or equal to 10° and less than or equal to 60°.

6. The back contact solar cell module according to claim 5, characterized in that: An included angle a of the first connection portion relative to the backlight surface of the back contact solar cell is greater than or equal to 10° and less than or equal to 45°.

7. The back contact solar cell module according to claim 1, characterized in that: The component ratio C of the composite welding strip is greater than or equal to 0.

2.

8. The back contact solar cell module according to claim 1, characterized in that: The component ratio C of the composite welding strip is in the range of 0.25 to 2.

4.

9. The back contact solar cell module according to claim 1, characterized in that: The composite welding strip further includes a composite structural layer, the first conductive layer and the second conductive layer are composited to form the composite structural layer, and the composite structural layer is arranged between the first conductive layer and the second conductive layer.

10. The back contact solar cell module according to claim 9, characterized in that: The thickness of the composite structure layer is 0-30 microns.

11. The back contact solar cell module according to claim 9, characterized in that: The components of the composite structure layer include at least one of Al4 Cu9, AlCu, Al2Cu, Al2Cu3, Al3Cu4 and Cu.

12. The back contact solar cell module according to claim 1, characterized in that: The composite welding strip further includes a conductive connection layer, and the conductive connection layer is arranged on the surface of the second conductive layer.

13. The back contact solar cell module according to claim 12, characterized in that: The thickness of the conductive connection layer is 1 to 20 microns.

14. The back contact solar cell module according to claim 12, characterized in that: The conductive connection layer comprises at least one of Sn, Bi and Pb.

15. The back contact solar cell module according to claim 14, characterized in that: Based on the first preset temperature, the components of the conductive connection layer include Sn, Bi, and Pb; wherein the content of Bi is 10% to 40%, the content of Sn is 20% to 50%, and the content of Pb is 30% to 60%.

16. The back contact solar cell module according to claim 14, characterized in that: Based on the second preset temperature, the components of the conductive connection layer include Sn and Pb; wherein the content of Sn is 50% to 70%, and the content of Pb is 30% to 50%.

17. The back contact solar cell module according to claim 1, characterized in that: The resistance of the composite welding strip is greater than or equal to 60 milliohms and less than or equal to 150 milliohms.

18. The back contact solar cell module according to claim 1, characterized in that: The invention also includes a connecting layer, wherein the connecting layer is arranged between the first conductive layer and the second conductive layer.

19. The back contact solar cell module according to claim 18, characterized in that: The tie layer includes zinc.

20. The back contact solar cell module according to claim 1, characterized in that: The composite welding strip is a flat welding strip.

21. The back contact solar cell module according to claim 20, characterized in that: When the thickness of the composite welding strip is 0.1 mm, the width of the composite welding strip is less than 2.5 mm; or, when the width of the composite welding strip is 2.5 mm, the thickness of the composite welding strip is greater than 0.1 mm.

22. The back contact solar cell module according to claim 20, characterized in that: When the width of the composite welding strip is 0.4~0.8mm and the thickness of the composite welding strip is 0.2~0.3mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 58~68MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

23. The back contact solar cell module according to claim 20, characterized in that: When the width of the composite welding strip is 0.8~1.4mm and the thickness of the composite welding strip is 0.12~0.2mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 65~75MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 70~80MPa.

24. The back contact solar cell module according to claim 20, characterized in that: When the width of the composite welding strip is 1.4~1.8mm and the thickness of the composite welding strip is 0.1~0.15mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 65~75MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 70~80MPa.

25. The back contact solar cell module according to claim 20, characterized in that: When the width of the composite welding strip is 1.8~2.2mm and the thickness of the composite welding strip is 0.12~0.2mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

26. The back contact solar cell module according to claim 20, characterized in that: When the width of the composite welding strip is 1.8~2.2mm and the thickness of the composite welding strip is 0.05~0.12mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

27. The back contact solar cell module according to claim 20, characterized in that: When the width of the composite welding strip is 2.2~2.8mm and the thickness of the composite welding strip is 0.12~0.2mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 62~72MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

28. The back contact solar cell module according to claim 1, characterized in that: The composite welding strip is a round wire welding strip, and the diameter length of the composite welding strip is greater than or equal to 0.07 mm and less than or equal to 0.4 mm.

29. The back contact solar cell module according to claim 28, characterized in that: When the diameter of the composite welding strip is 0.07~0.2mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 65~75MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 70~80MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 72~82MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 75~85MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 80~90MPa.

30. The back contact solar cell module according to claim 28, characterized in that When the diameter of the composite welding strip is 0.2~0.3mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 58~68MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

31. The back contact solar cell module according to claim 28, characterized in that When the diameter of the composite welding strip is 0.3~0.4mm: the component ratio C of the composite welding strip is 0.2~0.3, and the yield strength is 50~60MPa; or, the component ratio C of the composite welding strip is 0.3~0.8, and the yield strength is 55~65MPa; or, the component ratio C of the composite welding strip is 0.8~1.2, and the yield strength is 58~68MPa; or, the component ratio C of the composite welding strip is 1.2~2, and the yield strength is 60~70MPa; or, the component ratio C of the composite welding strip is 2~3, and the yield strength is 65~75MPa.

32. The back contact solar cell module according to claim 1, characterized in that: The composite welding strip is a triangular welding strip, and the diameter length of the circumscribed circle of the composite welding strip is greater than or equal to 0.07 mm and less than or equal to 0.4 mm.

33. The back contact solar cell module according to claim 1, characterized in that: A ratio of a thickness of the first conductive layer to a thickness of the second conductive layer is greater than or equal to 5 and less than or equal to 9.

34. The back contact solar cell module according to claim 1, characterized in that: The thickness of the second conductive layer is 0.01-0.05 mm.

35. The back contact solar cell module according to claim 1, characterized in that: The composite welding strip includes a plurality of free portions and a plurality of second connection portions connected between the plurality of free portions, the second connection portions are connected to the back contact solar cell, and the free portions are separated from the back contact solar cell.

36. The back contact solar cell module according to claim 35, characterized in that The maximum spacing distance between the free portion and the back contact solar cell is 0.1-0.4 mm.

37. A photovoltaic system, characterized in that: The photovoltaic system comprises a back-contact solar cell assembly as described in any one of claims 1 to 36.

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