Back-contact solar cell module and photovoltaic system

Abstract

The present disclosure is applicable to the technical field of photovoltaics. Provided are a back-contact solar cell module and a photovoltaic system. The back-contact solar cell module comprises a composite solder ribbon and a plurality of back-contact solar cells, wherein the composite solder ribbon is arranged on backlight surfaces of the plurality of back-contact solar cells. The composite solder ribbon comprises: a first conductive layer; and a second conductive layer, which is arranged on an outer surface of the first conductive layer, wherein the first conductive layer comprises aluminum, the second conductive layer comprises copper or nickel, and the mass ratio of the second conductive layer of the composite solder ribbon to the first conductive layer thereof is a composite solder ribbon component ratio C, which is greater than or equal to 0.1. In the present disclosure, the yield strength of a composite solder ribbon is controlled within a predetermined range, thereby avoiding the problem of cell warping caused by the warping tendency of the composite solder ribbon; and compared with a conventional copper solder ribbon, the composite solder ribbon greatly reduces the cost, thereby effectively lowering the production cost of a cell module.

Description

Back contact solar cell modules and photovoltaic systems

[0001] Cross-references

[0002] This disclosure incorporates, in its entirety, Chinese Patent Application No. 202411823605.0, filed on December 12, 2024, entitled “A Back Contact Solar Cell Module and Photovoltaic System,” which is incorporated herein by reference. Technical Field

[0003] This disclosure pertains to the field of photovoltaic technology, and particularly relates to a back-contact solar cell module and photovoltaic system. Background Technology

[0004] Solar energy is an inexhaustible and clean energy source, and with the development of the solar energy industry, photovoltaic (PV) installations have been steadily increasing. As technology continues to innovate and the cost per kilowatt-hour continues to decline, the demand for grid parity is also rising. Therefore, cost reduction and efficiency improvement have become top priorities for the industry. In the PV module sector, conventional PV solder ribbons are made of oxygen-free copper, resulting in relatively high manufacturing costs. With the continuous upgrading of module and cell technologies, such as Topcon, heterojunction, and IBC, the demand for solder ribbons is constantly evolving. Under the premise of meeting conductivity requirements, developing low-cost solder ribbons to replace conventional oxygen-free copper solder ribbons, and controlling solder ribbon costs to achieve high quality at a low price, is an urgent problem to be solved.

[0005] While conventional composite welding ribbons reduce manufacturing costs, when welding at a certain temperature, the different thermal expansion coefficients of the different metals can easily cause warping of the composite welding ribbon. This results in forced deformation of the contact area between the battery cell and the composite welding ribbon, leading to cell warping, cell cracking, and ultimately increasing the defect rate of the battery module.

[0006] Controlling the warping of composite solder ribbons in back-contact solar cell modules is crucial. This is significant in breaking the market's perception of IBC cells as having high efficiency but high cost, and enabling IBC cells to gain a larger application market. Summary of the Invention

[0007] In one aspect, this disclosure provides a back-contact solar cell module designed to address how to control warping of composite solder strips in a back-contact solar cell module.

[0008] This disclosure is implemented as follows: a back-contact solar cell module includes a composite solder ribbon and multiple back-contact solar cells. The composite solder ribbon is disposed on the back surface of the multiple back-contact solar cells. The composite solder ribbon includes a first conductive layer and a second conductive layer disposed on the outer surface of the first conductive layer. The first conductive layer includes aluminum, and the second conductive layer includes copper or nickel. The mass ratio of the second conductive layer to the first conductive layer of the composite solder ribbon is the composite solder ribbon component ratio C, which is greater than or equal to 0.1. The composite solder ribbon has a first connecting portion disposed between two adjacent back-contact solar cells. The angle α between the first connecting portion and the back surface of the back-contact solar cells is greater than or equal to 0° and less than or equal to 60°. The angle α and the yield strength σs of the composite solder ribbon satisfy the following relationship: (90 / 1.63)×cos α≤σs≤cos α×90, where α is greater than or equal to 0° and less than or equal to 60°.

[0009] This disclosure places a composite solder strip on the back surface of multiple back-contact solar cells. Compared to a bifacial cell structure, placing the composite solder strip on one side of the back-contact solar cell significantly reduces the bending degree of the composite solder strip, making it possible to connect multiple back-contact solar cells without warping within a set yield strength range. By controlling the yield strength of the composite solder ribbon within a predetermined range, the problem of cell warping caused by the composite solder ribbon can be avoided. The morphology, composition, and size of the composite solder ribbon can be designed in a variety of ways to meet the process requirements of various types of solar cell modules. Compared with traditional copper solder ribbon, it greatly reduces costs, thereby effectively reducing the production cost of cell modules. In addition, this disclosure also satisfies the following relationship between the angle α of the first connection part of the composite solder ribbon relative to the back surface of the back contact solar cell and the yield strength of the composite solder ribbon: (90 / 1.63)×cos α≤σs≤cos α×90, where α is greater than or equal to 0° and less than or equal to 60°. This further ensures that when using the composite solder ribbon for inter-cell string welding, the composite solder ribbon and the cell have good adhesion and the welding is stable and does not deform. In particular, in the overlapping area of ​​the cells, the composite solder ribbon can achieve a smooth transition connection, which can avoid the phenomenon of poor welding or desoldering of the composite solder ribbon in the overlapping area of ​​the cells.

[0010] In some embodiments, a plurality of back-contact solar cells are spaced apart, and the angle α between the first connection portion and the back surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 20°.

[0011] In some embodiments, the angle α between the first connection portion and the back surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 10°.

[0012] In some embodiments, the angle α between the first connection portion and the back surface of the back-contact solar cell is greater than or equal to 0° and less than or equal to 5°.

[0013] In some embodiments, multiple back-contact solar cells are partially overlapped, and the angle α between the first connecting portion and the back surface of the back-contact solar cell is greater than or equal to 10° and less than or equal to 60°.

[0014] In some embodiments, the angle α between the first connection portion and the back surface of the back-contact solar cell is greater than or equal to 10° and less than or equal to 45°.

[0015] In some embodiments, the proportion C of the composite solder strip component is greater than or equal to 0.2.

[0016] In some embodiments, the proportion C of the composite solder strip component ranges from 0.25 to 2.4.

[0017] In some embodiments, the composite solder strip further includes a composite structure layer, wherein the first conductive layer and the second conductive layer are composited to form the composite structure layer, and the composite structure layer is disposed between the first conductive layer and the second conductive layer.

[0018] In some embodiments, the thickness of the composite structure layer is 0 to 30 micrometers.

[0019] In some embodiments, the components of the composite structural layer include at least one of Al4Cu9, AlCu, Al2Cu, Al2Cu3, Al3Cu4, and Cu.

[0020] In some embodiments, the composite solder strip further includes a conductive connection layer disposed on the surface of the second conductive layer.

[0021] In some embodiments, the thickness of the conductive interconnect layer is 1 to 20 micrometers.

[0022] In some embodiments, the conductive interconnect layer comprises at least one of Sn, Bi, and Pb.

[0023] In some embodiments, based on a first preset temperature, the conductive connection layer comprises 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%.

[0024] In some embodiments, based on a second preset temperature, the conductive connection layer comprises Sn and Pb; wherein the content of Sn is 50% to 70% and the content of Pb is 30% to 50%.

[0025] In some embodiments, the resistance of the composite solder strip is greater than or equal to 60 milliohms and less than or equal to 150 milliohms.

[0026] In some embodiments, a connection layer is further included, which is disposed between the first conductive layer and the second conductive layer.

[0027] In some embodiments, the connecting layer comprises zinc.

[0028] In some embodiments, the composite solder strip is a flat solder strip.

[0029] In some embodiments, when the thickness of the composite solder strip is 0.1 mm, the width of the composite solder strip is less than 2.5 mm; or, when the width of the composite solder strip is 2.5 mm, the thickness of the composite solder strip is greater than 0.1 mm.

[0030] In some embodiments, when the width of the composite welding strip is 0.4–0.8 mm and the thickness of the composite welding strip 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.

[0031] In some embodiments, when the width of the composite welding strip is 0.8–1.4 mm and the thickness of the composite welding strip 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.

[0032] In some embodiments, when the width of the composite welding strip is 1.4–1.8 mm and the thickness of the composite welding strip 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.

[0033] In some embodiments, when the width of the composite welding strip is 1.8–2.2 mm and the thickness of the composite welding strip 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.

[0034] In some embodiments, when the width of the composite welding strip is 1.8–2.2 mm and the thickness of the composite welding strip 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.

[0035] In some embodiments, when the width of the composite welding strip is 2.2–2.8 mm and the thickness of the composite welding strip 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.

[0036] In some embodiments, the composite welding strip is a round wire welding strip, and the diameter of the composite welding strip is greater than or equal to 0.07 mm and less than or equal to 0.4 mm.

[0037] In some embodiments, when the diameter of the composite welding strip 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.

[0038] In some embodiments, when the diameter of the composite welding strip 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.

[0039] In some embodiments, when the diameter of the composite welding strip 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.

[0040] In some embodiments, the composite welding strip is a triangular welding strip, and the diameter of the outer circle of the composite welding strip is greater than or equal to 0.07 mm and less than or equal to 0.4 mm.

[0041] In some embodiments, the ratio of the thickness of the first conductive layer to the thickness of the second conductive layer is greater than or equal to 5 and less than or equal to 9.

[0042] In some embodiments, the thickness of the second conductive layer is 0.01 to 0.05 mm.

[0043] In some embodiments, the composite solder strip includes a plurality of free portions and a plurality of second connecting portions connected between the plurality of free portions, wherein the second connecting portions are connected to the back contact solar cell and the free portions are disconnected from the back contact solar cell.

[0044] In some embodiments, the maximum distance between the free portion and the back-contact solar cell is 0.1 to 0.4 mm.

[0045] Secondly, a photovoltaic system comprising the aforementioned back-contact solar cell module. Attached Figure Description

[0046] Figure 1 is a structural schematic diagram of the first type of composite welding strip provided in this application;

[0047] Figure 2 is a structural schematic diagram of the second type of composite welding strip provided in this application;

[0048] Figure 3 is a structural schematic diagram of the third type of composite welding strip provided in the current application;

[0049] Figure 4 is a structural schematic diagram of the fourth type of composite welding strip provided in the current application;

[0050] Figure 5 is a structural schematic diagram of the fifth type of composite welding strip provided in this application;

[0051] Figure 6 is a structural schematic diagram of the sixth type of composite welding strip provided in this application;

[0052] Figure 7 is a structural schematic diagram of the seventh type of composite welding strip provided in this application;

[0053] Figure 8 is a structural schematic diagram of the eighth type of composite welding strip provided in this application;

[0054] Figure 9 is a structural schematic diagram of the first type of back-contact solar cell module provided in this application;

[0055] Figure 10 is a schematic diagram of the structure of the second type of back-contact solar cell module provided in this application.

[0056] Explanation of reference numerals in the attached drawings: 100, composite solder strip; 101, first conductive layer; 102, second conductive layer; 103, first connecting part; 104, composite structure layer; 105, conductive connecting layer; 106, free part; 107, second connecting part; 108, connecting layer; 200, back contact solar cell. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided 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 denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this disclosure and are not intended to limit this disclosure.

[0058] In the description of this disclosure, it should be understood that the terms “length”, “width”, “upper”, “lower”, “left”, “right”, “horizontal”, “top”, “bottom”, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0059] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0060] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0061] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0062] The following disclosure provides numerous different embodiments or examples for implementing various structures of this disclosure. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this disclosure. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this disclosure, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0063] As shown in Figures 1 to 10, in some embodiments, a back-contact solar cell module includes a composite solder ribbon 100 and multiple back-contact solar cells 200. The composite solder ribbon 100 is disposed on the back surface of the multiple back-contact solar cells 200. Compared with the bifacial cell structure, the composite solder ribbon 100 is disposed on one side of the back-contact solar cell 200, which significantly reduces the bending degree of the composite solder ribbon 100. This makes it possible for the composite solder ribbon 100 to connect multiple back-contact solar cells 200 within a set yield strength range. It should be noted that in this embodiment, the back-contact solar cells 200 and the composite solder ribbon 100 are mainly electrically and physically connected by welding. However, it is understood that they can also be connected to each other in other ways, which are set according to the needs of use and are not specifically limited here.

[0064] The composite welding strip 100 includes a first conductive layer 101 and a second conductive layer 102. The second conductive layer 102 is disposed on the outer surface of the first conductive layer 101. The first conductive layer 101 includes aluminum, and the second conductive layer 102 includes copper or nickel. In this embodiment, the first conductive layer 101 and the second conductive layer 102 are metallurgically bonded together by electroplating, casting, forging, or cold rolling, and this disclosure is not limited thereto. 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 conduct electricity and facilitate welding, and is not limited to the materials listed in this embodiment. In this embodiment, copper is preferably selected as the material of the second conductive layer 102 because it has good ductility and good conductivity. The first conductive layer 101 can be made of metals such as aluminum, aluminum alloy, zinc, and nickel. While taking into account the functional requirements of conductivity, aluminum is the preferred material for the first conductive layer 101 because it is soft, highly stable, highly corrosion resistant, inexpensive, and easy to process and composite later.

[0065] The composite solder ribbon 100 has a corresponding yield strength based on a preset size and a corresponding composite solder ribbon component ratio C. The composite solder ribbon component ratio C is the mass ratio of the second conductive layer 102 to the first conductive layer 101, and C is greater than or equal to 0.1. In this embodiment, corresponding yield strengths are set for composite solder ribbons 100 with different preset sizes and different composite solder ribbon component ratios C. By setting differences in the yield strength of different types of composite solder ribbons 100, the problem of warping that easily occurs after hot-pressing annealing of the composite solder ribbon 100 can be better controlled. Furthermore, the researchers have devoted considerable effort to research and testing, ultimately concluding that yield strength is the key factor affecting the warping of the composite solder ribbon 100. Based on this understanding, the researchers optimized the applicable range of the yield strength of different types of composite solder ribbons 100, ultimately successfully solving the problem of cell warping. While reducing costs, the applicability and ease of use of the composite solder ribbon 100 are ensured, facilitating its widespread application.

[0066] Understandably, this disclosure sets the mass ratio of the second conductive layer 102 to the first conductive layer 101 to be greater than or equal to 0.1, and further sets the mass ratio of the second conductive layer 102 to the first conductive layer 101 to be greater than or equal to 0.2. In some embodiments, the mass ratio of the second conductive layer 102 to the first conductive layer 101 is 0.25 to 2.4. In such embodiments, the mass ratio of the second conductive layer 102 to 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 and 2.4, and is not specifically limited herein. Having the mass ratio of the second conductive layer 102 to the first conductive layer 101 within this range can effectively reduce the manufacturing cost of the composite solder ribbon 100, and the bonding strength between the first conductive layer 101 and the second conductive layer 102 in the composite solder ribbon 100 is an important consideration. For example, during the cold rolling composite process, when the copper-aluminum thickness ratio decreases (i.e., the aluminum thickness relatively increases), the aluminum strip undergoes more severe plastic deformation, resulting in more cracks at the interface. These cracks facilitate the entry of more metal compounds and promote interfacial bonding, making the bond between the copper and aluminum strips stronger. When the aluminum layer is too thick, the time required to reach common plastic strain increases due to the difference in yield stress between copper and aluminum, which may lead to a decrease in the density of the bonding interface, thus 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 resulting composite weld strip 100 can resist external stress, preventing the two layers from peeling or detaching due to force.

[0067] Secondly, changes in the mass ratio of the second conductive layer 102 to the first conductive layer 101 also affect the mechanical properties of the composite ribbon 100. For example, when the aluminum content is high, the composite ribbon may exhibit better toughness and ductility; while when the copper content is high, the conductivity, strength, and hardness of the composite ribbon may be improved. When the mass ratio of the second conductive layer 102 to the first conductive layer 101 is within this range, the resulting composite ribbon 100 has good ductility and high structural strength, enabling stable connections between battery cells.

[0068] In some embodiments, as shown in Figures 9 and 10, the composite solder ribbon 100 has a first connecting portion 103. The angle α between the first connecting portion 103 and the back surface of the back contact solar cell is greater than or equal to 0° and less than or equal to 60°. The angle α and the yield strength σs of the composite solder ribbon 100 satisfy the following relationship: (90 / 1.63)×cos α≤σs≤cos α×90, where α is greater than or equal to 0° and less than or equal to 60°. When using the composite solder ribbon 100 for string welding between solar cells, the solar cells are arranged in different ways. The first connecting portion 103 is provided to achieve a high-quality connection between the solar cells. In some embodiments, multiple back contact solar cells are spaced apart. In this case, the composite solder ribbon 100 can connect multiple back contact solar cells while maintaining a straight shape. The angle α between the first connecting portion and the back surface of the back contact solar cell is greater than or equal to 0° and less than or equal to 20°. In some embodiments, the angle α between the first connecting portion and the back surface of the back contact solar cell is greater than or equal to 0° and less than or equal to 10°. Further, the angle α between the first connecting portion and the back surface of the back contact solar cell is greater than or equal to 0° and less than or equal to 5°. In some embodiments, multiple back contact solar cells are partially overlapped, and the angle α between the first connecting portion 103 and the back contact solar cell is greater than or equal to 10° and less than or equal to 60°. In some embodiments, the angle α between the first connecting portion and the back surface of the back contact solar cell is greater than or equal to 10° and less than or equal to 45°. Because the solar cell itself has a certain thickness, the partially overlapping area of ​​the back contact solar cells has a stepped structure. The composite welding ribbon 100 is partially bent through the overlapping area; the bent portion is the first connecting portion 103. The angle between the first connecting portion 103 and the back surface of the back contact solar cell is determined based on the degree of local bending of the composite welding ribbon 100 and the thickness of the solar cell. This disclosure, through a special design of the composite welding ribbon 100, further ensures that when using the composite welding ribbon 100 for string welding between battery cells, the composite welding ribbon 100 and the battery cells have good adhesion and the welding is stable and does not deform. In particular, in the overlapping area between battery cells, the composite welding ribbon 100 can achieve a smooth transition connection, which can avoid the phenomenon of incomplete welding or desoldering of the composite welding ribbon 100 in the overlapping area of ​​battery cells.

[0069] It should be noted that the angle α between the first connecting part 103 and the back contact solar cell 200 is the angle formed by the straight line between the first connecting part 103 and the two points of contact between the two adjacent back contact solar cells 200 and the surface of the back contact solar cell 200, as shown in Figure 10.

[0070] The yield strength of the composite welding strip 100 can be measured by a tensile test. Specifically, the specimen (in this case, the composite welding strip 100) is placed in a tensile testing machine, and tension is gradually applied while the stress-strain curve is measured and recorded. This curve reflects the relationship between the deformation of the specimen and the stress it is subjected to during the tensile process. The yield strength of the composite welding strip 100, i.e., the stress value of the specimen at the beginning of plastic deformation, can be determined from this curve.

[0071] This disclosure sets corresponding yield strengths for the composite solder ribbon 100 based on different sizes and corresponding component ratios, thereby controlling the yield strength of the composite solder ribbon 100 within a predetermined range. This avoids the problem of warping of the solar cells caused by the composite solder ribbon 100. The morphology, composition, and size of the composite solder ribbon 100 can be designed in a variety of ways to meet the process requirements of various types of solar cell modules. Compared with traditional copper solder ribbons, this greatly reduces costs and effectively reduces the production cost of solar cell modules.

[0072] In some embodiments, the composite welding strip 100 includes a composite structural layer 104, formed by a first conductive layer 101 and a second conductive layer 102, with the composite structural layer 104 disposed between the first conductive layer 101 and the second conductive layer 102. The first conductive layer 101 and the second conductive layer 102 are composited by metallurgically bonding them together through methods such as forging or casting. The composite structural layer 104 is an intermetallic compound formed during the metallurgical bonding process of the first conductive layer 101 and the second conductive layer 102. The composite structural layer 104 enables a tight bond between the first conductive layer 101 and the second conductive layer 102, and can undergo uniform changes under external stress without delamination or peeling. Further, the thickness of the composite structural layer 104 is 0–30 micrometers. In some embodiments, the thickness of the composite structural layer 104 is 15–30 micrometers. In such an embodiment, the thickness of the composite structure layer 104 can be any value between 15 micrometers, 20 micrometers, 25 micrometers, 30 micrometers, or 15 to 30 micrometers, and is not specifically limited herein. Within this range, the thickness of the composite structure layer 104 ensures high bonding strength and peel strength between the first conductive layer 101 and the second conductive layer 102, preventing peeling or detachment of the two layers due to stress.

[0073] Furthermore, the composite structural layer 104 comprises at least one of Al4Cu9, AlCu, Al2Cu, Al2Cu3, Al3Cu4, and Cu. The formation of intermetallic compounds is key to achieving effective bonding. These compounds can form strong chemical bonds at the bonding interface, thereby improving the bonding strength. By controlling the process parameters (such as temperature, time, and pressure) for bonding the first conductive layer 101 and the second conductive layer 102, the type and quantity of intermetallic compounds can be controlled, thereby optimizing the bonding performance. In addition, the aforementioned intermetallic compounds can further enhance the corrosion resistance of the composite welding ribbon 100.

[0074] In some embodiments, the composite welding ribbon 100 further includes a conductive connection layer 105 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-dip plating. During the hot-pressing connection process between the composite welding ribbon 100 and the battery cell, the conductive connection layer 105 melts and then cools to achieve welding between the composite welding ribbon 100 and the battery cell. Further, the thickness of the conductive connection layer 105 is 1 to 20 micrometers. In some embodiments, the thickness of the conductive connection layer 105 is 10 to 15 micrometers. In such embodiments, the thickness of the conductive connection layer 105 can be any value between 10 micrometers, 12 micrometers, 13 micrometers, 15 micrometers, or 10 to 15 micrometers, and is not specifically limited here.

[0075] Furthermore, the conductive connection layer 105 comprises at least one of Sn, Bi, and Pb. By adjusting the composition of the conductive connection layer 105, a low-temperature composite solder ribbon 100 or a high-temperature composite solder ribbon 100 can be formed. Specifically, based on a first preset temperature, which is the welding temperature between the composite solder ribbon 100 and the battery cell, and ranging from 200°C to 300°C, the low-temperature composite solder ribbon 100 can achieve the connection of metal materials at a lower temperature, avoiding damage to electronic components or specific materials caused by high temperatures. Specifically, the conductive connection layer 105 comprises 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 and thermal expansion coefficient of the conductive connection layer 105 can be controlled.

[0076] Based on a second preset temperature, which is the welding temperature of the composite welding ribbon 100 and the battery cell, specifically, the second preset temperature ranges from 500℃ to 600℃. The high-temperature composite welding ribbon 100 can ensure the strength and stability of the welding. Specifically, the conductive connection layer 105 comprises Sn and Pb; wherein the Sn content is 50% to 70%, and the Pb content is 30% to 50%. By controlling the ratio of Sn and Pb content, the melting point of the conductive connection layer 105 and the coefficient of thermal expansion of the conductive connection layer 105 can be controlled.

[0077] As shown in Figures 1-6, it should be noted that the conductive connection layer 105 can be disposed on one side of the composite welding strip 100 facing the back contact cell, or the conductive connection layer 105 can be disposed on both sides of the composite welding strip 100 facing the back contact cell and away from the back contact 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 disclosure does not impose any restrictions.

[0078] In some embodiments, the resistance of the composite solder ribbon 100 is greater than or equal to 60 milliohms and less than or equal to 150 milliohms. When the resistance value of the composite solder ribbon 100 is within the above range, the series resistance of the component can be significantly reduced, thereby improving the current transmission efficiency. This means that the solar cell can more effectively convert light energy into electrical energy and reduce energy loss during transmission.

[0079] In some embodiments, the composite welding strip 100 further includes a connecting layer 108 disposed between the first conductive layer 101 and the second conductive layer 102. For example, in the electroplating process, since it is difficult to plate copper on aluminum, this disclosure provides a connecting layer 108 between the first conductive layer 101 and the second conductive layer 102 to achieve a good bond between the first conductive layer 101 and the second conductive layer 102. In some embodiments, the connecting layer 108 includes zinc. Of course, in other embodiments, the connecting layer 108 may also include other materials, and this disclosure does not limit this.

[0080] In this embodiment, the composite solder ribbon 100 can have different morphological structures. Based on different morphological structures, the composite solder ribbon 100 has different dimensional characteristics. For example, the composite solder ribbon 100 is a flat solder ribbon, and the preset dimensions include the width and thickness of the composite solder ribbon 100. Specifically, when the thickness of the composite solder ribbon 100 is 0.1 mm, the width of the composite solder ribbon 100 is less than 2.5 mm; or, when the width of the composite solder ribbon 100 is 2.5 mm, the thickness of the composite solder ribbon 100 is greater than 0.1 mm. This ensures the structural stability and sufficient structural strength of the flat composite solder ribbon 100, thereby achieving a stable connection between the composite solder ribbon 100 and the battery cell.

[0081] As shown in Figures 1-6, an example of a flat solder strip based on composite solder strip 100 is as follows:

[0082] In some embodiments, when the width of the composite welding strip 100 is 0.4–0.8 mm and the thickness 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 component ratio can be selected according to the production process and the type of battery cell. Thus, based on the same size and morphology, the composite welding strip 100 can be set with corresponding yield strength according to the different component ratios mentioned above. The mechanical properties of the composite welding strip 100 can be adjusted adaptively, and the yield strength of the composite welding strip 100 can be controlled within a predetermined range. This can avoid the problem of battery cell warping caused by deformation of the composite welding strip 100.

[0083] 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 component ratio can be selected according to the production process and the type of battery cell. Thus, based on the same size and morphology, the composite welding strip 100 can be set with corresponding yield strength according to the different component ratios mentioned above. The mechanical properties of the composite welding strip 100 can be adjusted adaptively, and the yield strength of the composite welding strip 100 can be controlled within a predetermined range. This can avoid the problem of battery cell warping caused by deformation of the composite welding strip 100.

[0084] 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 component ratio can be selected according to the production process and the type of battery cell. Thus, based on the same size and morphology, the composite welding strip 100 can be set with corresponding yield strength according to the different component ratios mentioned above. The mechanical properties of the composite welding strip 100 can be adjusted adaptively, and the yield strength of the composite welding strip 100 can be controlled within a predetermined range. This can avoid the problem of battery cell warping caused by deformation of the composite welding strip 100.

[0085] 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 component ratio can be selected according to the production process and the type of battery cell. Thus, based on the same size and morphology, the composite welding strip 100 can be set with corresponding yield strength according to the different component ratios mentioned above. The mechanical properties of the composite welding strip 100 can be adjusted adaptively, and the yield strength of the composite welding strip 100 can be controlled within a predetermined range. This can avoid the problem of battery cell warping caused by deformation of the composite welding strip 100.

[0086] 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 component ratio can be selected according to the production process and the type of battery cell. Thus, based on the same size and morphology, the composite welding strip 100 can be set with corresponding yield strength according to the different component ratios mentioned above. The mechanical properties of the composite welding strip 100 can be adjusted adaptively, and the yield strength of the composite welding strip 100 can be controlled within a predetermined range. This can avoid the problem of battery cell warping caused by deformation of the composite welding strip 100.

[0087] In some embodiments, when the width of the composite welding strip 100 is 2.2–2.8 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 component ratio can be selected according to the production process and the type of battery cell. Thus, based on the same size and morphology, the composite welding strip 100 can be set with corresponding yield strength according to the different component ratios mentioned above. The mechanical properties of the composite welding strip 100 can be adjusted adaptively, and the yield strength of the composite welding strip 100 can be controlled within a predetermined range. This can avoid the problem of battery cell warping caused by deformation of the composite welding strip 100.

[0088] As shown in Figure 7, in some embodiments, the composite welding strip 100 is a round wire welding strip with a diameter greater than or equal to 0.07 mm and less than or equal to 0.4 mm. Within this diameter range, the composite welding strip 100 can provide sufficient welding area to ensure the strength and stability of the weld.

[0089] The following is an example of a composite welding strip 100 made of round wire welding strip;

[0090] In some embodiments, when the diameter 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 component ratio can be selected according to the production process and the type of solar cell. Thus, based on the same dimensional morphology, the composite welding strip 100 can be set with corresponding yield strengths according to the different component ratios mentioned above, adaptively adjusting the mechanical properties of the composite welding strip 100 and controlling its yield strength within a predetermined range. This avoids the problem of solar cell warping caused by deformation of the composite welding strip 100.

[0091] In some embodiments, when the diameter 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 component ratio can be selected according to the production process and the type of solar cell. Thus, based on the same dimensional morphology, the composite welding strip 100 can be set with corresponding yield strengths according to the different component ratios mentioned above, adaptively adjusting the mechanical properties of the composite welding strip 100 and controlling its yield strength within a predetermined range. This avoids the problem of solar cell warping caused by deformation of the composite welding strip 100.

[0092] In some embodiments, when the diameter 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 component ratio can be selected according to the production process and the type of battery cell. Thus, based on the same size and morphology, the composite welding strip 100 can be set with corresponding yield strengths according to the different component ratios mentioned above, adaptively adjusting the mechanical properties of the composite welding strip 100 and controlling its yield strength within a predetermined range. This avoids the problem of battery cell warping caused by deformation of the composite welding strip 100.

[0093] As shown in Figure 8, in some embodiments, the composite welding strip 100 is a triangular welding strip, and the diameter 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 sufficient welding area to ensure the strength and stability of the weld.

[0094] 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. Exemplarily, 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, or 9, or any value between 5 and 9, without specific limitation. Within this ratio range, when subjected to external forces or environmental factors (such as changes in temperature and humidity), 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 solder strip 100 formed by combining with the thicker first conductive layer 101 can avoid warping, forming a more continuous and stable conductive path, thereby improving conductivity. In some embodiments, the thickness of the second conductive layer 102 is 0.01–0.05 mm. For example, such as 0.01mm, 0.02mm, 0.03mm, 0.04mm and 0.05mm, or any value between 0.01mm and 0.05mm, without any specific limitation herein.

[0095] The thickness of the first conductive layer 101 and the second conductive layer 102 mentioned in this disclosure is the average thickness of the first conductive layer 101 and the second conductive layer 102 film.

[0096] As shown in Figure 3, in some embodiments, the first conductive layer 101 has a first surface and a second surface disposed opposite to each other in the thickness direction, and a second conductive layer 102 is disposed on the first surface and the second surface, respectively. 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. The first surface faces the solar cell, and the second surface is disposed away from the solar cell. In some embodiments, the second thickness is greater than the first thickness. This structural design makes the connection between the composite solder ribbon and the solar cell more stable and reduces deformation caused by changes in ambient temperature.

[0097] The composite solder strip structures shown in Figures 1-8 of this disclosure are merely a few typical embodiments of the design in this disclosure, and the composite solder strip structures in this disclosure are not limited to these embodiments.

[0098] As shown in Figure 9, the composite welding ribbon 100 includes multiple free portions 106 and multiple second connecting portions 107 connected between the multiple free portions 106. The second connecting portions 107 are connected to the solar cell, and the free portions 106 are detached from the solar cell. Further, in some embodiments of this disclosure, the free portions 106 are deformation buffer structures. The composite welding ribbon 100 and the back contact solar cell 200 are connected through their respective second connecting portions 107. Specifically, during manufacturing, each second connecting portion 107 of a composite welding ribbon 100 is spot-welded to each solder point on a main grid of the back contact solar cell 200, while each free portion 106 is detached from the back contact solar cell 200 to form a deformation buffer structure. The deformation buffer structure can be various bent shapes such as arc, S-shape, rectangle, or zigzag. It should be noted that all the second connecting portions 107 are on the same horizontal plane, so that each second connecting portion 107 can contact the solder joint of the back contact solar cell 200, while each free portion 106 is bent and deformed to extend out of the second connecting portion 107 at a different horizontal plane. Furthermore, the maximum distance between the free portion 106 and the solar cell is 0.1–0.4 mm. In this way, when the composite solder ribbon 100 is bent to form the free portion 106, the composite solder ribbon 100 has sufficient buffer margin compared to its existing straight state to cope with the contraction or expansion of the composite solder ribbon 100.

[0099] Therefore, after the second connecting portions 107 of the composite solder ribbon 100 are welded to the solder joints of the back contact solar cell 200, its free portion 106 can provide a certain buffer between adjacent solder joints. This buffer compensates for the shrinkage deformation of the composite solder ribbon 100 when it shrinks more due to the difference in thermal expansion coefficients with the back contact solar cell 200 after returning to room temperature. This reduces the stress caused by thermal expansion and contraction, thereby reducing the warping problem of the back contact solar cell 200 caused by welding. As a result, the back contact solar cell 200 after welding can be straighter than the existing type. At the same time, the shrinking composite solder ribbon 100 can also lower the protrusion height of the free portion 106, and make the composite solder ribbon 100, which undergoes deformation compensation after welding, also become straighter, thereby achieving low warping of the entire back contact solar cell 200 module.

[0100] In some embodiments, multiple back-contact solar cells 200 are partially overlapped to form an overlap region, and the first connecting portion 103 of the composite solder ribbon 100 is disposed in the overlap region. This ensures good adhesion between the composite solder ribbon 100 and the solar cells during string welding between the cells, resulting in stable and deformation-free welding. In particular, the composite solder ribbon 100 can achieve a smooth transition connection in the overlap region of the solar cells, preventing incomplete welding or detachment of the composite solder ribbon 100 in the overlap region.

[0101] A photovoltaic (PV) system includes the aforementioned battery modules. In this embodiment, the PV system can be applied in PV power plants, such as ground-mounted, rooftop, and floating power plants, and also in devices or apparatuses that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it is understood that the application scenarios of the PV system are not limited to these; that is, the PV system can be applied in all fields that require solar energy for power generation. Taking a PV power generation network as an example, the PV system may include a PV array, a combiner box, and an inverter. The PV array may be an array combination of multiple battery modules; for example, multiple battery modules can form multiple PV arrays. The PV array is connected to the combiner box, which can collect the current generated by the PV array. The collected current flows through the inverter and is converted into AC power required by the mains grid before being connected to the mains grid to achieve solar power supply.

[0102] In the description of this specification, references to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least some embodiments or examples of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0103] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A back-contact solar cell module, comprising a composite solder ribbon and a plurality of back-contact solar cells, wherein the composite solder ribbon is disposed on the back surface of the plurality of back-contact solar cells, the composite solder ribbon comprising a first conductive layer; a second conductive layer disposed on the outer surface of the first conductive layer, the first conductive layer comprising aluminum, and the second conductive layer comprising copper or nickel; the mass ratio of the second conductive layer to the first conductive layer of the composite solder ribbon is a composite solder ribbon component ratio C, the composite solder ribbon component ratio C being greater than or equal to 0.1, the composite solder ribbon having a first connecting portion disposed between two adjacent back-contact solar cells, the included angle α of the first connecting portion relative to the back surface of the back-contact solar cells being greater than or equal to 0° and less than or equal to 60°, the included angle α and the yield strength σs of the composite solder ribbon satisfying the following relationship: (90 / 1.63)×cos α≤σs≤cos α×90, in, a is greater than or equal to 0° and less than or equal to 60°.

2. The back-contact solar cell module as described in claim 1, wherein, The plurality of back-contact solar cells are spaced apart, and the angle α between the first connecting portion and the back 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 as described in claim 2, wherein, The angle α between the first connecting portion and the back 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 as described in claim 3, wherein, The angle α between the first connecting portion and the back 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 as described in claim 1, wherein, Multiple back-contact solar cells are partially overlapped, and the angle α between the first connecting portion and the back 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 as described in claim 5, wherein, The angle α between the first connecting portion and the back 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 as described in claim 1, wherein, The proportion C of the composite welding strip components is greater than or equal to 0.

2.

8. The back-contact solar cell module as described in claim 1, wherein, 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 as claimed in claim 1, wherein, The composite welding strip further includes a composite structure layer, wherein the first conductive layer and the second conductive layer are combined to form the composite structure layer, and the composite structure layer is disposed between the first conductive layer and the second conductive layer.

10. The back-contact solar cell module as claimed in claim 9, wherein, The thickness of the composite structure layer is 0–30 micrometers.

11. The back-contact solar cell module as claimed in claim 9, wherein, The components of the composite structure layer include at least one of Al4Cu9, AlCu, Al2Cu, Al2Cu3, Al3Cu4, and Cu.

12. The back-contact solar cell module as claimed in claim 1, wherein, The composite welding strip further includes a conductive connection layer, which is disposed on the surface of the second conductive layer.

13. The back-contact solar cell module as claimed in claim 12, wherein, The thickness of the conductive connection layer is 1 to 20 micrometers.

14. The back-contact solar cell module as claimed in claim 12, wherein, The conductive interconnect layer comprises at least one of Sn, Bi, and Pb.

15. The back-contact solar cell module as claimed in claim 14, wherein, Based on a first preset temperature, the conductive connection layer comprises 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 as claimed in claim 14, wherein, Based on a second preset temperature, the conductive connection layer comprises 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 as claimed in claim 1, wherein, The resistance of the composite solder strip is greater than or equal to 60 milliohms and less than or equal to 150 milliohms.

18. The back-contact solar cell module as claimed in claim 1, wherein, It also includes a connecting layer disposed between the first conductive layer and the second conductive layer.

19. The back-contact solar cell module as claimed in claim 18, wherein, The connecting layer comprises zinc.

20. The back-contact solar cell module as claimed in claim 1, wherein, The composite welding strip is a flat welding strip.

21. The back-contact solar cell module as claimed in claim 20, wherein, When the thickness of the composite solder strip is 0.1 mm, the width of the composite solder strip is less than 2.5 mm; or, when the width of the composite solder strip is 2.5 mm, the thickness of the composite solder strip is greater than 0.1 mm.

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

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

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

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

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

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

28. The back-contact solar cell module as claimed in claim 1, wherein, The composite welding strip is a round wire welding strip, and the diameter 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 as claimed in claim 28, wherein, When the diameter of the composite welding strip is 0.07–0.2 mm: the component ratio C of the composite welding strip is 0.2–0.3, and the yield strength is 65–75 MPa; or, the component ratio C of the composite welding strip is 0.3–0.8, and the yield strength is 70–80 MPa; or, the component ratio C of the composite welding strip is 0.8–1.2, and the yield strength is 72–82 MPa; or, the component ratio C of the composite welding strip is 1.2–2, and the yield strength is 75–85 MPa; or, the component ratio C of the composite welding strip is 2–3, and the yield strength is 80–90 MPa.

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

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

32. The back-contact solar cell module as claimed in claim 1, wherein, The composite welding strip is a triangular welding strip, and the diameter of the outer 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 as claimed in claim 1, wherein, The ratio of the thickness of the first conductive layer to the 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 as claimed in claim 1, wherein, The thickness of the second conductive layer is 0.01 to 0.05 mm.

35. The back-contact solar cell module as claimed in claim 1, wherein, The composite solder strip includes multiple free portions and multiple second connecting portions connected between the multiple free portions. The second connecting portions are connected to the back contact solar cell, and the free portions are disconnected from the back contact solar cell.

36. The back-contact solar cell module as described in claim 35, wherein, The maximum distance between the free part and the back-contact solar cell is 0.1 to 0.4 mm.

37. A photovoltaic system comprising a back-contact solar cell module as described in any one of claims 1 to 36.

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