Composite solder strip, back contact solar cell module and photovoltaic system

Abstract

The utility model is suitable for the field of photovoltaic technology, and provides a composite welding strip, a back contact solar cell module and a photovoltaic system. The second conducting layer is arranged on the outer surface of the first conducting layer, the first conducting layer comprises aluminum, and the second conducting layer comprises copper; the connecting layer is arranged between the first conductive layer and the second conductive layer, and the yield strength of the composite welding strip is greater than or equal to 45MPa and less than or equal to 75MPa. According to the invention, the yield strength of the composite welding strip is controlled within a 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, and the battery piece yield strength is improved. 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] This application belongs to the field of photovoltaic technology, and in particular relates to a composite welding strip, a back contact solar cell module, and a photovoltaic system. Background Technology

[0002] 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.

[0003] 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.

[0004] 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. Utility Model Content

[0005] In a first aspect, this application provides a composite solder strip designed to address the problem of how to control warping of the composite solder strip.

[0006] This application is implemented as follows: a composite solder strip is used to be disposed on the back surface of a back-contact solar cell, comprising a first conductive layer comprising aluminum; a second conductive layer disposed on the outer surface of the first conductive layer comprising copper; and a connecting layer disposed between the first conductive layer and the second conductive layer. The yield strength of the composite solder strip is greater than or equal to 45 MPa and less than or equal to 75 MPa.

[0007] This application places composite solder ribbons on the back surface of multiple back-contact solar cells. Compared to bifacial cell structures, placing the composite solder ribbons on only one side of the back-contact solar cells significantly reduces the bending degree of the composite solder ribbons, 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 ribbons within a predetermined range, the problem of cell warping caused by the composite solder ribbons can be avoided. The morphology and size of the composite solder ribbons can be designed in various ways to meet the process requirements of various types of solar cell modules. Compared to traditional copper solder ribbons, this greatly reduces costs, thereby effectively reducing the production cost of cell modules. In addition, the connection layer between the first conductive layer and the second conductive layer ensures high bonding strength and peel strength between the first and second conductive layers, preventing the two layers from peeling or falling off due to stress.

[0008] Optionally, the yield strength of the composite welding strip is greater than or equal to 55 MPa and less than or equal to 75 MPa.

[0009] Optionally, the thickness of the connecting layer is greater than 0 and less than or equal to 30 micrometers.

[0010] Optionally, the composite welding strip has a first connecting portion for connecting two adjacent back-contact solar cells. 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 60°.

[0011] Optionally, when 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°, the yield strength of the composite solder strip is greater than or equal to 50 MPa and less than or equal to 75 MPa.

[0012] Optionally, when 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 60°, the yield strength of the composite solder strip is greater than or equal to 45MPa and less than or equal to 65MPa.

[0013] Optionally, the composite welding strip further includes a conductive connection layer disposed on the surface of the second conductive layer.

[0014] Optionally, the thickness of the conductive connection layer is 1 to 20 micrometers.

[0015] Optionally, the connecting layer includes a composite structure, wherein the first conductive layer and the second conductive layer are composited to form the composite structure.

[0016] Optionally, the connecting layer comprises zinc.

[0017] Optionally, 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.

[0018] Optionally, the thickness of the second conductive layer is 0.01 to 0.05 mm.

[0019] Optionally, the resistance of the composite solder strip is greater than or equal to 60 milliohms and less than or equal to 150 milliohms.

[0020] Optionally, the composite solder 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 being used to connect to the back contact solar cell, and the free portions being used to detach from the back contact solar cell.

[0021] Optionally, the composite welding strip is a flat welding strip.

[0022] Optionally, 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.

[0023] Optionally, when the width of the composite welding strip is 0.4 to 0.8 mm and the thickness of the composite welding strip is 0.2 to 0.3 mm, the yield strength of the composite welding strip is 45 to 75 MPa.

[0024] Optionally, when the width of the composite welding strip is 0.8 to 1.4 mm and the thickness of the composite welding strip is 0.12 to 0.2 mm, the yield strength of the composite welding strip is 60 to 75 MPa.

[0025] Optionally, when the width of the composite welding strip is 1.4 to 1.8 mm and the thickness of the composite welding strip is 0.1 to 0.15 mm, the yield strength of the composite welding strip is 55 to 75 MPa.

[0026] Optionally, when the width of the composite welding strip is 1.8 to 2.2 mm and the thickness of the composite welding strip is 0.12 to 0.2 mm, the yield strength of the composite welding strip is 45 to 75 MPa.

[0027] Optionally, when the width of the composite welding strip is 1.8 to 2.2 mm and the thickness of the composite welding strip is 0.05 to 0.12 mm, the yield strength of the composite welding strip is 45 to 75 MPa.

[0028] Optionally, when the width of the composite welding strip is 2.2 to 2.8 mm and the thickness of the composite welding strip is 0.12 to 0.2 mm, the yield strength of the composite welding strip is 45 to 75 MPa.

[0029] Optionally, 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.

[0030] Optionally, when the diameter of the composite welding strip is 0.07–0.2 mm, the yield strength of the composite welding strip is 65–75 MPa; or, when the diameter of the composite welding strip is 0.2–0.3 mm, the yield strength of the composite welding strip is 45–75 MPa; or, when the diameter of the composite welding strip is 0.3–0.4 mm, the yield strength of the composite welding strip is 45–75 MPa.

[0031] Optionally, 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.

[0032] Secondly, a back-contact solar cell module includes the aforementioned composite solder strip and back-contact solar cells, wherein the composite solder strip is disposed on the back surface of a plurality of the back-contact solar cells.

[0033] Thirdly, a photovoltaic system comprising the aforementioned back-contact solar cell module. Attached Figure Description

[0034] Figure 1 This is a structural schematic diagram of the first type of composite welding strip provided in the current application;

[0035] Figure 2 This is a structural schematic diagram of the second type of composite welding strip provided in the current application;

[0036] Figure 3 This is a structural schematic diagram of the third type of composite welding strip provided in the current application;

[0037] Figure 4 This is a structural schematic diagram of the fourth type of composite welding strip provided in the current application;

[0038] Figure 5 This is a structural schematic diagram of the fifth type of composite welding strip provided in the current application;

[0039] Figure 6 This is a structural schematic diagram of the sixth type of composite welding strip provided in the current application;

[0040] Figure 7 This is a schematic diagram of the structure of the first type of back-contact solar cell module provided in this application;

[0041] Figure 8 This is a schematic diagram of the structure of the second type of back-contact solar cell module provided in the current application.

[0042] Explanation of reference numerals in the attached figures:

[0043] 100. Composite welding strip; 101. First conductive layer; 102. Second conductive layer; 103. First connecting part; 104. Connecting layer; 105. Conductive connecting layer; 106. Free part; 107. Second connecting part; 200. Back contact solar cell. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this application 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 application, and should not be construed as limiting this application. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0045] In the description of this application, 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 application and simplifying the description, and do not 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 application.

[0046] 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 application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" 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 application according to the specific circumstances.

[0048] In this application, 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 being 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 being 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.

[0049] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. 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 application. 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 application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0050] like Figure 1 As shown, 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 use needs and are not specifically limited here.

[0051] 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. 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 application is not limited in this regard. 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.

[0052] In this embodiment, the composite solder strip 100 further includes a connecting layer 104, which is disposed between the first conductive layer 101 and the second conductive layer 102.

[0053] In some embodiments, since copper plating on aluminum is difficult to perform in the electroplating process, this application provides a connecting layer 104 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. Preferably, the connecting layer 104 includes zinc. Of course, in other embodiments, the connecting layer 104 may also include other materials, and this application does not limit this.

[0054] In some embodiments, the connecting layer 104 includes a composite structure, in which a first conductive layer 101 and a second conductive layer 102 are compositely formed, and the composite structure is disposed between the first conductive layer 101 and the second conductive layer 102. The composite structure of the first conductive layer 101 and the second conductive layer 102 refers to the metallurgical bonding of the first conductive layer 101 and the second conductive layer 102 through methods such as forging or casting. The composite structure is an intermetallic compound formed during the metallurgical bonding process of the first conductive layer 101 and the second conductive layer 102. The composite structure enables a tight bond between the first conductive layer 101 and the second conductive layer 102, and can produce a uniform change when subjected to external stress, without delamination or peeling. Further, the thickness of the composite structure is 0–30 micrometers. Preferably, the thickness of the composite structure is 15–30 micrometers. In such embodiments, the thickness of the composite structure can be any value between 15 micrometers, 20 micrometers, 25 micrometers, 30 micrometers, or 15–30 micrometers, and is not specifically limited herein. The thickness of the composite structure is within this range, which can ensure that the first conductive layer 101 and the second conductive layer 102 have high bonding strength and peel strength, and prevent the two layers from peeling or falling off due to force.

[0055] Furthermore, the composite structure comprises at least one of Al4Cu9, AlCu, Al2Cu, Al2Cu3, Al3Cu4, and Cu, and 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, pressure, etc.) 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.

[0056] In some embodiments, the yield strength of the composite solder strip is greater than or equal to 45 MPa and less than or equal to 75 MPa. Preferably, the yield strength of the composite solder strip is greater than or equal to 55 MPa and less than or equal to 75 MPa. By controlling the yield strength of the composite solder strip within a predetermined range, the problem of cell warping caused by the composite solder strip can be avoided. The morphology and size of the composite solder strip 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 strips, this greatly reduces costs, thereby effectively reducing the production cost of cell modules.

[0057] In this embodiment, corresponding yield strengths are set for composite solder strips 100 of different preset sizes. By setting differences in yield strength for different types of composite solder strips 100, the problem of warping that easily occurs after hot-pressing annealing of composite solder strips 100 can be better controlled. Furthermore, the researchers devoted considerable effort to research and testing, ultimately concluding that yield strength is the key factor affecting the warping of composite solder strips 100. Based on this understanding, the researchers optimized the applicable range of yield strength for different types of composite solder strips 100, ultimately successfully solving the problem of cell warping. This approach ensures the applicability and ease of use of composite solder strips 100 while reducing costs, facilitating widespread application.

[0058] In some embodiments, such as Figure 7 and Figure 8 As shown, 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°. 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°. Preferably, 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°. Because the composite solder strip has a low degree of bending, its yield strength is greater than or equal to 50 MPa and less than or equal to 75 MPa. In other words, the composite solder strip can have a large yield strength to achieve the connection of two adjacent back-contact solar cells.

[0059] 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°. Preferably, 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°. Since 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 application employs a special design for the composite welding ribbon 100 to further ensure good adhesion between the composite welding ribbon 100 and the solar cells during string welding between cells. The welding is stable and does not deform, especially in the overlapping areas between solar cells, where the composite welding ribbon 100 can achieve a smooth transition connection, preventing incomplete welding or detachment of the composite welding ribbon 100 in these areas. Due to the high degree of bending of the composite welding ribbon, its yield strength must be greater than or equal to 45 MPa and less than or equal to 65 MPa. This means the composite welding ribbon needs a relatively low yield strength to achieve the connection between two adjacent back-contact solar cells.

[0060] It should be noted that the angle α between the first connecting portion 103 and the back contact solar cell 200 is the angle formed by the straight line between the first connecting portion 103 and the two adjacent points of contact between the two back contact solar cells 200 and the surface of the back contact solar cell 200, such as... Figure 8 As shown.

[0061] 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.

[0062] In some embodiments, the composite welding strip 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 strip 100 and the battery cell, the conductive connection layer 105 melts and then cools to achieve welding between the composite welding strip 100 and the battery cell. Further, the thickness of the conductive connection layer 105 is 1 to 20 micrometers. Preferably, 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 herein.

[0063] like Figures 1-4 As shown, 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 application does not impose any restrictions.

[0064] 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.

[0065] 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.

[0066] like Figures 1-4 As shown, an example of a flat solder strip based on composite solder strip 100 is as follows:

[0067] 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 yield strength of the composite welding strip is 45–75 MPa. Thus, based on the same dimensional morphology, by setting a corresponding yield strength for the composite welding strip 100, the mechanical properties of the composite welding strip 100 can be adaptively adjusted, and the yield strength of the composite welding strip 100 can be controlled within a predetermined range. This avoids the problem of cell warping caused by deformation of the composite welding strip 100.

[0068] For example, the yield strength of the composite weld strip being 45 to 75 MPa means that the yield strength of the composite weld strip is between 45 MPa and 75 MPa. Specifically, it can be 45 MPa, 50 MPa, 60 MPa, 65 MPa, 75 MPa, etc., or any value between 45 and 75 MPa, and there is no specific limitation here.

[0069] 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 yield strength of the composite welding strip is 60–75 MPa. Thus, based on the same dimensional morphology, by setting a corresponding yield strength for the composite welding strip 100, the mechanical properties of the composite welding strip 100 can be adaptively adjusted, and the yield strength of the composite welding strip 100 can be controlled within a predetermined range. This avoids the problem of cell warping caused by deformation of the composite welding strip 100.

[0070] For example, the yield strength of the composite weld strip being 60-75 MPa means that the yield strength of the composite weld strip is between 60 MPa and 75 MPa. Specifically, it can be 60 MPa, 65 MPa, 70 MPa, 75 MPa, etc., or any value between 60 and 75 MPa, and there is no specific limitation here.

[0071] In some embodiments, when the width of the composite welding strip 100 is 1.4 to 1.8 mm and the thickness of the composite welding strip 100 is 0.1 to 0.15 mm, the yield strength of the composite welding strip is 55 to 75 MPa. Thus, based on the same size and morphology, the composite welding strip 100 is set with a corresponding yield strength, and the mechanical properties of the composite welding strip 100 are adaptively adjusted to control the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of cell warping caused by deformation of the composite welding strip 100.

[0072] For example, the yield strength of the composite weld strip being 60-75 MPa means that the yield strength of the composite weld strip is between 60 MPa and 75 MPa. Specifically, it can be 60 MPa, 65 MPa, 70 MPa, 75 MPa, etc., or any value between 60 and 75 MPa, and there is no specific limitation here.

[0073] In some embodiments, when the width of the composite welding strip 100 is 1.8 to 2.2 mm and the thickness of the composite welding strip 100 is 0.12 to 0.2 mm, the yield strength of the composite welding strip is 45 to 75 MPa. Thus, based on the same size and morphology, the composite welding strip 100 is set with a corresponding yield strength, and the mechanical properties of the composite welding strip 100 are adaptively adjusted to control the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of cell warping caused by deformation of the composite welding strip 100.

[0074] In some embodiments, when the width of the composite welding strip 100 is 1.8 to 2.2 mm and the thickness of the composite welding strip 100 is 0.05 to 0.12 mm, the yield strength of the composite welding strip is 45 to 75 MPa. Thus, based on the same size and morphology, the composite welding strip 100 is set with a corresponding yield strength, and the mechanical properties of the composite welding strip 100 are adaptively adjusted to control the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of cell warping caused by deformation of the composite welding strip 100.

[0075] In some embodiments, when the width of the composite welding strip 100 is 2.2 to 2.8 mm and the thickness of the composite welding strip 100 is 0.12 to 0.2 mm, the yield strength of the composite welding strip is 45 to 75 MPa. Thus, based on the same size and morphology, the composite welding strip 100 is set with a corresponding yield strength, and the mechanical properties of the composite welding strip 100 are adaptively adjusted to control the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of cell warping caused by deformation of the composite welding strip 100.

[0076] like Figure 5 As shown, in some embodiments, the composite welding strip 100 is a round wire welding strip, and the diameter 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 diameter range, the composite welding strip 100 can provide sufficient welding area to ensure the strength and stability of the weld.

[0077] The following is an example of a composite welding strip 100 made of round wire welding strip;

[0078] In some embodiments, when the diameter of the composite welding strip 100 is 0.07 to 0.2 mm, the yield strength of the composite welding strip is 65 to 75 MPa. Thus, based on the same size and morphology, the composite welding strip 100 is set with a corresponding yield strength, and the mechanical properties of the composite welding strip 100 are adaptively adjusted to control the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of cell warping caused by deformation of the composite welding strip 100.

[0079] For example, the yield strength of the composite weld strip being 65-75 MPa means that the yield strength of the composite weld strip is between 65 MPa and 75 MPa. Specifically, it can be 65 MPa, 70 MPa, 75 MPa, etc., or any value between 65 and 75 MPa, and there is no specific limitation here.

[0080] In some embodiments, when the diameter of the composite welding strip 100 is 0.2 to 0.3 mm, the yield strength of the composite welding strip is 45 to 75 MPa. Thus, based on the same size and morphology, the composite welding strip 100 is set with a corresponding yield strength, and the mechanical properties of the composite welding strip 100 are adaptively adjusted to control the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of cell warping caused by deformation of the composite welding strip 100.

[0081] In some embodiments, when the diameter of the composite welding strip 100 is 0.3 to 0.4 mm, the yield strength of the composite welding strip is 45 to 75 MPa. Thus, based on the same size and morphology, the composite welding strip 100 is set with a corresponding yield strength, and the mechanical properties of the composite welding strip 100 are adaptively adjusted to control the yield strength of the composite welding strip 100 within a predetermined range, thereby avoiding the problem of cell warping caused by deformation of the composite welding strip 100.

[0082] like Figure 6 As shown, 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.

[0083] This application controls the yield strength of the composite solder strip 100 within a predetermined range by setting corresponding yield strengths based on different sizes. This avoids the problem of warping of the solar cell caused by the composite solder strip 100. The shape and size of the composite solder strip 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 strips, this greatly reduces costs and effectively reduces the production cost of solar cell modules.

[0084] 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, 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. Preferably, 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, 0.05mm, or any value between 0.01mm and 0.05mm, without any specific limitation.

[0085] The thickness of the first conductive layer 101 and the second conductive layer 102 mentioned in this application is the average thickness of the first conductive layer 101 and the second conductive layer 102 film.

[0086] like Figure 2 As shown, 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. Optionally, the second thickness is greater than the first thickness. This structural design makes the connection between the composite solder ribbon 100 and the solar cell more stable and reduces deformation caused by changes in ambient temperature.

[0087] This application is attached Figures 1-6 The structure of the composite solder strip 100 in this application is only one of the typical embodiments designed in this application, and the structure of the composite solder strip 100 in this application is not limited to these embodiments.

[0088] like Figure 7As shown, the composite solder 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 back contact solar cell, and the free portions 106 are detached from the back contact solar cell. Further, in one embodiment of this application, the free portions 106 are deformation buffer structures. The composite solder 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 solder 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.

[0089] 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.

[0090] 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.

[0091] 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 power plants, rooftop power plants, and floating power plants, and can also be applied to equipment or devices 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 to generate electricity. Taking a PV power generation system grid 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 power grid before being connected to the mains power grid to achieve solar power supply.

[0092] In the description of this specification, the use of terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., refers to specific features, structures, materials, or characteristics described in connection with the embodiments or examples, which are included in at least one embodiment or example of this application. 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.

[0093] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A composite solder strip, said composite solder strip being disposed on the back surface of a back-contact solar cell, characterized in that, The composite welding strip comprises a first conductive layer comprising aluminum; a second conductive layer disposed on the outer surface of the first conductive layer comprising copper; and a connecting layer disposed between the first conductive layer and the second conductive layer. The yield strength of the composite welding strip is greater than or equal to 45 MPa and less than or equal to 75 MPa.

2. The composite welding strip as described in claim 1, characterized in that, The yield strength of the composite welding strip is greater than or equal to 55 MPa and less than or equal to 75 MPa.

3. The composite welding strip as described in claim 1, characterized in that, The thickness of the connecting layer is greater than 0 and less than or equal to 30 micrometers.

4. The composite welding strip as described in claim 1, characterized in that, The composite welding strip has a first connecting portion for connecting two adjacent back-contact solar cells. 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 60°.

5. The composite welding strip as described in claim 4, characterized in that, When 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°, the yield strength of the composite solder strip is greater than or equal to 50MPa and less than or equal to 75MPa.

6. The composite welding strip as described in claim 4, characterized in that, When 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 60°, the yield strength of the composite solder strip is greater than or equal to 45MPa and less than or equal to 65MPa.

7. The composite welding strip as described in claim 1, characterized in that, The composite welding strip further includes a conductive connection layer, which is disposed on the surface of the second conductive layer.

8. The composite welding strip as described in claim 7, characterized in that, The thickness of the conductive connection layer is 1 to 20 micrometers.

9. The composite welding strip as described in claim 1, characterized in that, The connecting layer includes a composite structure, wherein the first conductive layer and the second conductive layer are combined to form the composite structure.

10. The composite welding strip as described in claim 1, characterized in that, The connecting layer comprises zinc.

11. The composite welding strip as described in claim 1, characterized in that, 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.

12. The composite welding strip as described in claim 1, characterized in that, The thickness of the second conductive layer is 0.01 to 0.05 mm.

13. The composite welding strip as described in claim 1, characterized in that, The resistance of the composite solder strip is greater than or equal to 60 milliohms and less than or equal to 150 milliohms.

14. The composite welding strip as described in claim 1, characterized in that, The composite solder strip includes multiple free portions and multiple second connecting portions connected between the multiple free portions. The second connecting portions are used to connect with the back contact solar cell, and the free portions are used to detach from the back contact solar cell.

15. The composite welding strip as described in claim 1, characterized in that, The composite welding strip is a flat welding strip.

16. The composite welding strip as described in claim 15, characterized in that, 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.

17. The composite welding strip as described in claim 15, characterized in that, When the width of the composite welding strip is 0.4 to 0.8 mm and the thickness of the composite welding strip is 0.2 to 0.3 mm, the yield strength of the composite welding strip is 45 to 75 MPa.

18. The composite welding strip as described in claim 15, characterized in that, 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 yield strength of the composite welding strip is 60–75 MPa.

19. The composite welding strip as described in claim 15, characterized in that, When the width of the composite welding strip is 1.4 to 1.8 mm and the thickness of the composite welding strip is 0.1 to 0.15 mm, the yield strength of the composite welding strip is 55 to 75 MPa.

20. The composite welding strip as described in claim 15, characterized in that, When the width of the composite welding strip is 1.8 to 2.2 mm and the thickness of the composite welding strip is 0.12 to 0.2 mm, the yield strength of the composite welding strip is 45 to 75 MPa.

21. The composite welding strip as described in claim 15, characterized in that, When the width of the composite welding strip is 1.8 to 2.2 mm and the thickness of the composite welding strip is 0.05 to 0.12 mm, the yield strength of the composite welding strip is 45 to 75 MPa.

22. The composite welding strip as described in claim 15, characterized in that, When the width of the composite welding strip is 2.2 to 2.8 mm and the thickness of the composite welding strip is 0.12 to 0.2 mm, the yield strength of the composite welding strip is 45 to 75 MPa.

23. The composite welding strip as described in claim 1, characterized in that, 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.

24. The composite welding strip as described in claim 23, characterized in that, When the diameter of the composite welding strip is 0.07–0.2 mm, the yield strength of the composite welding strip is 65–75 MPa; or, when the diameter of the composite welding strip is 0.2–0.3 mm, the yield strength of the composite welding strip is 45–75 MPa; or, when the diameter of the composite welding strip is 0.3–0.4 mm, the yield strength of the composite welding strip is 45–75 MPa.

25. The composite welding strip as described in claim 1, characterized in that, 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.

26. A back-contact solar cell module, characterized in that, The invention includes the composite solder strip and back contact solar cell as described in any one of claims 1-25, wherein the composite solder strip is disposed on the back surface of the plurality of back contact solar cells.

27. A photovoltaic system, characterized in that, The photovoltaic system includes the back-contact solar cell module as described in claim 26.

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