Back contact photovoltaic modules

Abstract

This disclosure relates to the field of photovoltaic technology, and provides a back-contact photovoltaic module that can improve the fixing accuracy and stability of the solder ribbon, thereby improving the welding quality and thus enhancing product reliability. The back-contact photovoltaic module includes: a cell string, the cell string comprising multiple back-contact solar cells and multiple solder ribbons; wherein, the back-contact solar cell includes a substrate, grid lines, and welding units; the substrate includes a front side and a back side disposed opposite to each other, the grid lines are disposed on the back side of the substrate, and the welding units are disposed on the side of the grid lines facing away from the substrate; the solder ribbons are bridging between two adjacent back-contact solar cells, and the two ends of the solder ribbons are disposed on the side of the welding units of the two adjacent back-contact solar cells facing away from the substrate; the solder ribbons are doped with a first magnetic material, and the welding units are doped with a second magnetic material, wherein either the first magnetic material or the second magnetic material is a permanent magnet material, and the other is a ferromagnetic material.

Description

Technical Field

[0001] This disclosure relates to the field of photovoltaic technology, and in particular to a back-contact photovoltaic module. Background Technology

[0002] Photovoltaic power generation converts solar energy into electrical energy through photovoltaic modules, thus providing a green, environmentally friendly, and renewable energy production method, which is now widely used in many fields. A photovoltaic module consists of a string of cells, which in turn contains multiple solar cells interconnected via solder strips.

[0003] Back-contact solar cells are a promising type of solar cell. However, high-temperature welding of the back-contact solar cell and the solder strip can lead to warping of the back-contact solar cell, resulting in cracking and microcracks. Therefore, a low-temperature welding process (i.e., lamination welding) is used to connect the solder strip and the back-contact solar cell. Currently, before the implementation of low-temperature welding, the fixing accuracy and stability of the solder strip cannot meet the requirements, resulting in low welding quality and poor product reliability. Summary of the Invention

[0004] This disclosure provides a back-contact photovoltaic module that can improve the fixing accuracy and stability of the solder strip, thereby improving the welding quality and enhancing product reliability.

[0005] According to some embodiments of the present disclosure, one aspect of the present disclosure provides a back-contact photovoltaic module, including: a battery string, the battery string including a plurality of back-contact solar cells and a plurality of solder strips;

[0006] The back-contact solar cell includes a substrate, grid lines, and a welding unit; the substrate includes a front side and a back side disposed opposite to each other, the grid lines are disposed on the back side of the substrate, and the welding unit is disposed on the side of the grid lines away from the substrate;

[0007] The solder strip is bridging two adjacent back-contact solar cells, and both ends of the solder strip are located on the side of the welding unit of the two adjacent back-contact solar cells away from the substrate.

[0008] The welding strip is doped with a first magnetic material, and the welding unit is doped with a second magnetic material. Either the first magnetic material or the second magnetic material is a permanent magnet material, and the other is a ferromagnetic material.

[0009] According to some embodiments of this disclosure, the first magnetic material in the solder strip is uniformly distributed.

[0010] According to some embodiments of this disclosure, the mass percentage of the first magnetic material in the solder strip is 5% to 10%.

[0011] According to some embodiments of this disclosure, the mass percentage of the first magnetic material doped in the two end regions of the solder strip is greater than the mass percentage of the first magnetic material doped in the middle region of the solder strip.

[0012] According to some embodiments of this disclosure, the mass percentage of the first magnetic material doped in the two end regions of the solder strip is 6% to 10%, and the mass percentage of the first magnetic material doped in the middle region of the solder strip is 2% to 6%.

[0013] According to some embodiments of this disclosure, the solder strip includes a conductive layer and a plating layer, the plating layer being disposed around the conductive layer; wherein the plating layer is doped with the first magnetic material.

[0014] According to some embodiments of this disclosure, the coating includes tin, lead, bismuth, and neodymium iron boron.

[0015] According to some embodiments of this disclosure, the welding unit includes a plurality of welding portions, which are spaced apart on the side of the grid line away from the substrate; the welding portions are doped with the second magnetic material, and the mass percentage of the second magnetic material in the welding portions is 5% to 10%.

[0016] According to some embodiments of this disclosure, the welded portion includes tin, lead, bismuth, and iron.

[0017] According to some embodiments of this disclosure, the permanent magnet material includes neodymium iron boron, and the ferromagnetic material includes iron, nickel, or cobalt.

[0018] This disclosure provides a back-contact photovoltaic module. By doping the solder ribbon with a first magnetic material and the welding unit with a second magnetic material, where either the first or second magnetic material is a permanent magnet and the other is a ferromagnetic material, the welding unit and solder ribbon are fixed based on the magnetic adsorption of the permanent magnet material onto the ferromagnetic material. Compared to low-temperature dispensing technology, this method eliminates the need for curing adhesives, allowing direct magnetic fixation of the solder ribbon and welding unit. Furthermore, the strong magnetic adsorption of the permanent magnet material onto the ferromagnetic material results in high fixation accuracy, strong stability, and high welding quality. Compared to low-temperature coating technology, this method eliminates the need for an additional thin film layer and reduces process steps, facilitating mass production and minimizing costs. The back-contact photovoltaic module provided by this disclosure improves the fixation accuracy and stability of the solder ribbon, thereby enhancing welding quality and ultimately improving product reliability. Attached Figure Description

[0019] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this disclosure or the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of a battery string structure provided in an embodiment of the present disclosure;

[0021] Figure 2 For along Figure 1 Cross-sectional view in the MM1 direction;

[0022] Figure 3 For along Figure 1 Cross-sectional view along the NN1 direction;

[0023] Figure 4 This is a schematic diagram of the structure of a back-contact photovoltaic module provided in an embodiment of this disclosure.

[0024] Figure label:

[0025] Back contact solar cell-1, substrate-11, front side-111, back side-112, grid line-12, welding unit-13, welding part-131, solder ribbon-2, conductive layer-21, plating layer-22, encapsulating film-3, cover plate-4. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of this disclosure will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0027] In the description of the embodiments disclosed herein, "at least one" means one or more, "at least one layer" means one or more layers, "multiple" means two or more, "multiple layers" means two or more layers, and "multiple pieces" means two or more pieces, unless otherwise explicitly specified.

[0028] In the description of the embodiments disclosed herein, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0029] In the description of the embodiments of this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this disclosure. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] In the description of the embodiments of this disclosure, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of 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. Therefore, they should not be construed as limitations on the embodiments of this disclosure. For example, if the device or element in the illustration is inverted, then the element described as "below," "under," "below," or "bottom" of other elements or features will be oriented "above" or "top" of said other elements or features. Therefore, the term "below" may cover both above and below orientations depending on the context in which the term is used, which will be obvious to those skilled in the art. Materials may be oriented in other ways (e.g., rotated 90 degrees, inverted, flipped), and the spatial relative descriptive terms used herein may be interpreted accordingly.

[0032] In the description of the embodiments of this disclosure, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0033] In the accompanying drawings corresponding to the embodiments of this disclosure, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. Furthermore, when describing a component as "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor on a portion of the edge of the entire surface.

[0034] In the description of the embodiments of this disclosure, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. The formation or placement of a second component above or on a first component, or on the surface of a first component, or on one side of a first component, may include embodiments where the first and second components are in direct contact, and may also include embodiments where an additional component may be placed between the first and second components, thereby preventing direct contact between the first and second components. For simplicity and clarity, various components may be drawn at different scales. In the drawings, some layers / components may be omitted for simplicity. Unless otherwise specified, the formation or placement of a second component on the surface of a first component refers to direct contact between the first and second components. The term "component" may refer to: layer, film, region, portion, structure, etc.

[0035] A back-contact solar cell is a type of crystalline silicon solar cell where both the emitter and base electrodes are located on the back of the cell. Back-contact cells have no metal grid electrodes obstructing the light on the front, increasing light absorption efficiency and significantly improving short-circuit current. Simultaneously, the use of amorphous or microcrystalline silicon, or doping methods, to passivate the cell surface enhances the open-circuit voltage. These factors effectively increase the conversion efficiency of back-contact cells, making them a promising technology with excellent future prospects.

[0036] Among related technologies, low-temperature dispensing and low-temperature coating technologies are used to improve the fixation accuracy and stability of the solder ribbon. Low-temperature dispensing technology mainly involves applying adhesive to the solder ribbon and using the curing action of the adhesive to fix the ribbon to the surface of the solar cell. However, the adhesive has a long curing time and unstable fixation strength, which can easily lead to solder ribbon misalignment and affect welding quality. Low-temperature coating technology involves covering the surfaces of the solar cell and solder ribbon with a thin film, and then using heat or pressure to bond the film to the solder ribbon, thereby achieving fixation. However, using low-temperature coating technology increases cost and process complexity, which is not conducive to mass production.

[0037] Based on this, the present disclosure provides a back-contact photovoltaic module, with reference to... Figures 1 to 3 As shown, the back-contact photovoltaic module includes: a cell string, which includes multiple back-contact solar cells 1 and multiple solder strips 2; wherein, the back-contact solar cell 1 includes a substrate 11, grid lines 12 and soldering units 13; Reference Figure 2 and Figure 3 As shown, the substrate 11 includes a front side 111 and a back side 112 disposed opposite to each other. The grid line 12 is disposed on the back side 112 of the substrate 11, and the welding unit 13 is disposed on the side of the grid line 12 away from the substrate 11. The solder strip 2 is connected between two adjacent back contact solar cells 1, and the two ends of the solder strip 2 are disposed on the side of the welding unit 13 of the two adjacent back contact solar cells 1 away from the substrate 11. The solder strip 2 is doped with a first magnetic material, and the welding unit 13 is doped with a second magnetic material. Either the first magnetic material or the second magnetic material is a permanent magnet material, and the other is a ferromagnetic material.

[0038] In this embodiment of the present disclosure, the welding unit is disposed on the side of the grid line away from the substrate, the welding strip is bridging between two adjacent back-contact solar cells, and the two ends of the welding strip are disposed on the side of the welding unit of the two adjacent back-contact solar cells away from the substrate; thus, the grid lines of the two adjacent back-contact solar cells are electrically connected through the welding strip.

[0039] It should be noted that the internal magnetic domains of permanent magnet materials arrange themselves in an orderly manner under the influence of an external magnetic field, forming a stable remanence, and can maintain a high degree of magnetism even after the external magnetic field is removed. Ferromagnetic materials refer to materials that exhibit strong magnetism under the influence of an external magnetic field and can retain their magnetism after magnetization, mainly including iron, cobalt, nickel and their alloys. Ferromagnetic materials have the characteristic of spontaneous magnetization, that is, the magnetic moments of adjacent atoms or ions within the ferromagnetic material will spontaneously align in the same direction, forming a magnetic domain structure. When the external magnetic field disappears, the material can still maintain a certain degree of magnetization. Permanent magnet materials have an attractive force to ferromagnetic materials (such as iron, nickel, cobalt, etc.), which is due to the magnetic interaction between the magnetic field around the magnet and the magnetic properties of the ferromagnetic material. However, the static magnetic attraction or repulsion force of permanent magnets to non-ferromagnetic materials (such as copper, aluminum, etc.) is extremely weak and can usually be ignored.

[0040] In this embodiment, the welding strip is doped with a first magnetic material, and the welding unit is doped with a second magnetic material. Either the first or second magnetic material is a permanent magnet, and the other is a ferromagnetic material. That is, the welding strip is doped with a permanent magnet, and the welding unit is doped with a ferromagnetic material. In this case, the welding strip has a strong magnetic attraction to the welding unit. Alternatively, the welding strip is doped with a ferromagnetic material, and the welding unit is doped with a permanent magnet. In this case, the welding unit has a strong magnetic attraction to itself. Based on the magnetic attraction of the permanent magnet to the ferromagnetic material, high fixing accuracy and high stability are achieved for the welding strip and the welding unit. Therefore, in the fabrication process of the back-contact photovoltaic module, the welding strip and the welding unit are fixed by magnetic attraction. In the subsequent low-temperature welding process, the positions of the welding strip and the welding unit will not shift, thus obtaining a back-contact photovoltaic module with high welding quality and high reliability.

[0041] In this embodiment of the disclosure, the substrate is used to receive incident light and generate photogenerated carriers. In some embodiments, the substrate can be a semiconductor substrate, such as silicon, germanium, silicon germanium, or silicon on insulator. The substrate can be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type dopant element, which can be any one of Group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type dopant element, which can be any one of Group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In). In some embodiments, the substrate material can be an elemental semiconductor material. Specifically, the elemental semiconductor material is composed of a single element, such as silicon or germanium. Among them, the elemental semiconductor material can be in a single crystal state, a polycrystalline state, an amorphous state, or a microcrystalline state (a state that simultaneously has a single crystal state and an amorphous state is called a microcrystalline state). For example, silicon can be at least one of single crystal silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. If the substrate material is silicon, then the substrate material can include at least one of single crystal silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon.

[0042] In this embodiment of the disclosure, the back-contact photovoltaic module includes multiple cell strings, which are electrically connected in series and / or parallel. Within each cell string, multiple back-contact solar cells are electrically connected in series.

[0043] refer to Figure 1 As shown, the back-contact solar cell 1 may include multiple grid lines 12 arranged along the OA direction, and each grid line extends along the OB direction; Reference Figure 2 and Figure 3 As shown, the substrate 11 of the back-contact solar cell includes a front side 111 and a back side 112 disposed opposite to each other along the thickness direction OC of the substrate.

[0044] In this embodiment, the back-contact solar cell can be an IBC (Interdigitated Back Contact) cell, an HPBC (Hybrid Passivated Back Contact) cell, a TBC cell combining TOPCon (Tunnel Oxide Passivated Contact) and IBC technologies, or an HBC cell combining HIT / HJT (Heterojunction Technology) and IBC technologies. Of course, it can also be other types of back-contact solar cells. The size of the back-contact solar cell is not limited; for example, it can be a complete cell, half a cell, or a quarter cell.

[0045] The back-contact photovoltaic module provided in this disclosure can be applied to distributed photovoltaic scenarios such as building integrated photovoltaic (BIPV) using corrugated steel roofs, photovoltaic tiles, or photovoltaic curtain walls, and can also be applied to other scenarios requiring photoelectric conversion. This back-contact photovoltaic module is characterized by its high quality and high performance.

[0046] In the back-contact photovoltaic module provided in this disclosure, the welding unit and welding strip are fixed by doping the solder ribbon with a first magnetic material and the welding unit with a second magnetic material. Either the first magnetic material or the second magnetic material is a permanent magnet, and the other is a ferromagnetic material. The fixing of the welding unit and the solder ribbon is achieved based on the magnetic adsorption effect of the permanent magnet on the ferromagnetic material. Compared to low-temperature dispensing technology, no adhesive curing is required, and the solder ribbon and welding unit can be directly magnetically fixed. Furthermore, the permanent magnet has a strong magnetic adsorption force on the ferromagnetic material, resulting in high fixing accuracy and stability of the solder ribbon and welding unit, and high welding quality. Compared to low-temperature coating technology, no additional thin film layer is required, and no additional process steps are needed, which is beneficial for mass production and can minimize costs. The back-contact photovoltaic module provided in this disclosure can improve the fixing accuracy and stability of the solder ribbon, thereby improving welding quality and ultimately enhancing product reliability.

[0047] It is understandable that the distribution of the first magnetic material in the solder strip determines the magnetic distribution of the solder strip. In some embodiments, the first magnetic material in the solder strip is uniformly distributed, resulting in a uniform magnetic distribution, which is beneficial for manufacturing. Methods for doping the first magnetic material into the solder strip include, but are not limited to: incorporating first magnetic particles into the raw material of the solder strip, and then uniformly distributing the first magnetic particles throughout the solder strip through processes such as rolling and stretching.

[0048] If the proportion of the first magnetic material in the solder ribbon is too high, it will result in excessively strong magnetism, thus affecting the quality and stability of the signal transmitted by the solder ribbon. If the proportion of the first magnetic material in the solder ribbon is too low, it will result in insufficient magnetism, thus affecting the fixation stability of the solder ribbon and the welding unit. Therefore, the proportion of the first magnetic material in the solder ribbon needs to be selected within an appropriate range. In some embodiments, the mass percentage of the first magnetic material in the solder ribbon is 5% to 10%, thereby ensuring that the solder ribbon has sufficient magnetism to achieve stable fixation with the welding unit without affecting the signal transmission quality and stability as much as possible. Specifically, the mass percentage of the first magnetic material in the solder ribbon is 5%, 6%, 7%, 8%, 9%, or 10%.

[0049] Since the solder ribbon bridges between two adjacent back-contact solar cells, in order to further enhance the magnetic adsorption between the two ends of the solder ribbon and the welding unit, and thus further improve the fixation stability and reliability of the solder ribbon and the welding unit, in some other embodiments, reference is made to... Figure 3 As shown, the mass percentage of the first magnetic material doped in the two end regions D1 of the solder ribbon 2 is greater than the mass percentage of the first magnetic material doped in the middle region D of the solder ribbon 2. That is, the distribution of the first magnetic material in the solder ribbon is a non-uniform distribution with high concentrations at both ends and low concentrations in the middle; this structure is suitable for situations where there is a gap between two adjacent back-contact solar cells.

[0050] If the proportion of the first magnetic material doped in the two ends of the solder ribbon differs too much from that in the middle region, the magnetism in the two ends will be too strong, affecting the quality and stability of the signal transmitted by the solder ribbon. Conversely, if the proportion of the first magnetic material doped in the two ends of the solder ribbon differs too little from that in the middle region, the effect on improving the fixation stability and reliability of the solder ribbon and the welding unit will be limited. Therefore, the proportions of the first magnetic material doped in the two ends of the solder ribbon and the middle region need to be selected within an appropriate range. In some embodiments, the mass percentage of the first magnetic material doped in the two ends of the solder ribbon is 6% to 10%, and the mass percentage of the first magnetic material doped in the middle region of the solder ribbon is 2% to 6%. This ensures that the two ends of the solder ribbon have sufficient magnetism to achieve stable fixation with the welding unit without significantly affecting the signal transmission quality and stability. Specifically, the mass percentage of the first magnetic material doped in the two ends of the solder strip is 6%, 7%, 8%, 9% or 10%, and the mass percentage of the first magnetic material doped in the middle region of the solder strip is 2%, 3%, 4%, 5% or 6%. In this case, the difference between the mass percentage of the first magnetic material doped in the two ends of the solder strip and the mass percentage of the first magnetic material doped in the middle region of the solder strip is 0% to 8%.

[0051] In some embodiments, reference Figure 2 and Figure 3 As shown, the solder ribbon 2 includes a conductive layer 21 and a plating layer 22, with the plating layer 22 surrounding the conductive layer 21; wherein the plating layer 22 is doped with a first magnetic material. The overall cross-sectional shape of the solder ribbon can be circular, rectangular, or triangular, etc. In this solder ribbon, the conductive layer is used for signal transmission, and the plating layer is used for contact and fixation with the soldering unit. The material of the conductive layer includes, but is not limited to, copper or silver; the material of the plating layer includes, but is not limited to, tin doped with the first magnetic material, or a tin alloy doped with the first magnetic material.

[0052] In some embodiments, neodymium iron boron (NdFeB) material can be incorporated into tin-lead-bismuth material to obtain a coating comprising tin, lead, bismuth, and NdFeB; wherein, NdFeB is a permanent magnet material, i.e., the coating is doped with a permanent magnet material. The specific mass percentages of tin, lead, and bismuth in the tin-lead-bismuth material are not limited; for example, Sn43Pb43Bi14 can be used, i.e., Sn and Pb each account for 43%, and Bi accounts for 14%. The mass percentage of NdFeB material incorporated into the tin-lead-bismuth material can be 5% to 10%, and the NdFeB material is uniformly distributed throughout the solder strip through processes such as rolling and stretching. In actual processes, the physical morphology of NdFeB material is granular, while the physical morphology of tin-lead-bismuth material is powdery. Physical doping can be achieved by directly mixing NdFeB particles and tin-lead-bismuth powder.

[0053] It should be noted that if the solder strip coating is doped with neodymium iron boron (NdFeB), then the corresponding welding unit is doped with ferromagnetic material. The distribution of NdFeB doped in the solder strip coating, or the distribution of ferromagnetic material doped in the solder strip coating, is the same as the distribution of the first magnetic material in the solder strip mentioned above, and will not be repeated here.

[0054] In some embodiments, reference Figure 1 and Figure 3 As shown, the welding unit 13 includes a plurality of welding portions 131, which are spaced apart on the side of the grid line 12 away from the substrate 11; the welding portions 131 are doped with a second magnetic material, and the mass percentage of the second magnetic material in the welding portions 131 is 5% to 10%.

[0055] In this embodiment, multiple welding portions can be evenly spaced on the side of the gate line facing away from the substrate. It should be noted that, to further enhance the welding quality of the gate line and the solder strips, solder pads can be provided in the area of ​​the gate line to be welded (i.e., the area intersecting with the solder strips). The solder pads and the gate line can be an integral structure, and the welding portions can be located on the side of the solder pad facing away from the substrate. The shape of the solder pads includes, but is not limited to, polygons such as quadrilaterals, pentagons, and hexagons, as well as circles. Solder pads can be provided in all intersection areas of the gate line and multiple solder strips. Depending on the actual electrical connection, welding portions can be provided on some solder pads, and not on the remaining solder pads. Alternatively, in the intersection areas of the gate line and multiple solder strips, solder pads can be provided in the intersection areas corresponding to the electrical connection, and no solder pads can be provided in the remaining intersection areas.

[0056] In this embodiment, the solder strip is electrically connected to the gate line through multiple welding sections, which reduces welding material and lowers costs, while also minimizing the impact of welding on the gate line. The second magnetic material in the welding section has a mass percentage of 5% to 10%, ensuring sufficient magnetism for high-precision and high-stability fixing with the solder strip, while also reducing the impact on the gate line. The mass percentage of the second magnetic material in the welding section is 5%, 6%, 7%, 8%, 9%, or 10%.

[0057] In some embodiments, iron can be incorporated into a tin-lead-bismuth material to obtain a weld portion comprising tin, lead, bismuth, and iron. The iron is a ferromagnetic material, meaning the weld portion is doped with a ferromagnetic material. In this case, the solder strip is doped with a permanent magnet material.

[0058] In tin-lead-bismuth materials, the specific mass percentage of tin, lead, and bismuth is not limited. For example, Sn43Pb43Bi14 can be used, meaning Sn and Pb each account for 43%, and Bi accounts for 14%. The mass percentage of iron doped into the tin-lead-bismuth material can be 5% to 10%, and the iron is evenly distributed throughout the solder strip through processes such as rolling and stretching. In actual processes, the iron material is in powder form, and the tin-lead-bismuth material is also in powder form. Physical doping can be achieved by directly mixing the iron powder and the tin-lead-bismuth powder.

[0059] In some embodiments, the permanent magnet material includes neodymium iron boron (NdFeB), and the ferromagnetic material includes iron, nickel, or cobalt. Specifically, the solder ribbon is doped with NdFeB, and the solder ribbon unit is doped with iron, nickel, or cobalt; or, the solder ribbon is doped with iron, nickel, or cobalt, and the solder ribbon unit is doped with NdFeB. NdFeB uses the rare earth element neodymium (Nd) to provide magnetic properties, iron (Fe) as the main metallic component, and boron (B) to promote the formation of a tetragonal crystal structure; the three combine to form an intermetallic compound. NdFeB has characteristics such as high remanence, high coercivity, and high energy product, making it a third-generation rare earth permanent magnet material with excellent overall performance. In the embodiments of this disclosure, the permanent magnet material is NdFeB, and the ferromagnetic material is iron, nickel, or cobalt, thereby ensuring high fixation accuracy and high stability of the solder ribbon and soldering unit.

[0060] It should be noted that the number of cell strings included in the back-contact photovoltaic module provided in this disclosure, and the number of back-contact solar cells included in each cell string, can be selected according to actual requirements. Figure 1 The illustration uses a battery string with four back-contact solar cells as an example, but in actual applications, the number of back-contact solar cells in the battery string is far more than this. Figure 1 The arrangement and connection relationship of multiple back-contact solar cells shown are completed by stringing them together, then they are arranged in a layout, and then the interconnection between the solder strip and the cell is achieved by a low-temperature welding process.

[0061] In some embodiments, reference Figure 4 As shown, the back-contact photovoltaic module also includes an encapsulating film 3 and a cover plate 4. The encapsulating film 3 is used to cover the surface of the battery string, and the cover plate 4 is used to cover the surface of the encapsulating film 3 away from the battery string.

[0062] In some embodiments, the encapsulating film includes a first encapsulating layer and a second encapsulating layer. The first encapsulating layer covers one of the front or back sides of the back contact battery, and the second encapsulating layer covers the other of the front or back sides of the back contact battery. Specifically, at least one of the first or second encapsulating layer may be an organic encapsulating film such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyethylene octene elastomer (POE) film, or polyethylene terephthalate (PET) film. Alternatively, at least one of the first or second encapsulating layer may also be an EP film, EPE film, or PVP film. Among them, EP film refers to a co-extruded film composed of stacked EVA film and POE film; EPE film refers to a co-extruded film formed by sequentially stacking EVA film, POE film, and EVA film; and PVP film refers to a co-extruded film formed by stacking POE film, EVA film, and POE film. Co-extruded films can be prepared by sequentially extruding one or more raw materials onto another pre-made film during the film processing, or by bonding different types of pre-made films together.

[0063] In some cases, the first encapsulation layer and the second encapsulation layer still have a boundary line before lamination. After lamination, the back contact photovoltaic module will no longer have the concept of a first encapsulation layer and a second encapsulation layer. That is, the first encapsulation layer and the second encapsulation layer have formed an integral encapsulation film.

[0064] In some embodiments, the cover plate can be a glass cover plate, a plastic cover plate, or other cover plate with light-transmitting function. Specifically, the surface of the cover plate facing the encapsulating film can be an uneven surface or a textured surface containing multiple raised structures, thereby increasing the utilization rate of incident light. The cover plate includes a first cover plate and a second cover plate, the first cover plate being opposite to the first encapsulation layer, and the second cover plate being opposite to the second encapsulation layer.

[0065] Those skilled in the art will understand that the above embodiments are specific examples of implementing this disclosure, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of this disclosure. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this disclosure.

Claims

1. A back-contact photovoltaic module, characterized in that, include: A battery string, comprising multiple back-contact solar cells and multiple solder strips; The back-contact solar cell includes a substrate, grid lines, and a welding unit; the substrate includes a front side and a back side disposed opposite to each other, the grid lines are disposed on the back side of the substrate, and the welding unit is disposed on the side of the grid lines away from the substrate; The solder strip is bridging two adjacent back-contact solar cells, and both ends of the solder strip are located on the side of the welding unit of the two adjacent back-contact solar cells away from the substrate. The welding unit includes multiple welding sections, which are spaced apart on the side of the grid line away from the substrate. The welding strip is doped with a first magnetic material, and the welding part is doped with a second magnetic material. The first magnetic material is neodymium iron boron, and the second magnetic material is iron, nickel, or cobalt.

2. The back-contact photovoltaic module according to claim 1, characterized in that, The first magnetic material in the welding strip is uniformly distributed.

3. The back-contact photovoltaic module according to claim 2, characterized in that, The mass percentage of the first magnetic material in the solder strip is 5% to 10%.

4. The back-contact photovoltaic module according to claim 1, characterized in that, The mass percentage of the first magnetic material doped in the two end regions of the solder strip is greater than the mass percentage of the first magnetic material doped in the middle region of the solder strip.

5. The back-contact photovoltaic module according to claim 4, characterized in that, The mass percentage of the first magnetic material doped in the two ends of the solder strip is 6% to 10%, and the mass percentage of the first magnetic material doped in the middle region of the solder strip is 2% to 6%.

6. The back-contact photovoltaic module according to claim 1, characterized in that, The solder strip includes a conductive layer and a plating layer, the plating layer being disposed around the conductive layer; wherein the plating layer is doped with the first magnetic material.

7. The back-contact photovoltaic module according to claim 6, characterized in that, The coating comprises tin, lead, bismuth, and neodymium iron boron.

8. The back-contact photovoltaic module according to claim 1, characterized in that, The mass percentage of the second magnetic material in the welded part is 5% to 10%.

9. The back-contact photovoltaic module according to claim 8, characterized in that, The welded portion includes tin, lead, bismuth, and iron.

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