Back contact photovoltaic module and photovoltaic system

Abstract

The application discloses a back contact photovoltaic module and a photovoltaic system, and relates to the technical field of solar cells.The back contact photovoltaic module comprises a plurality of cell strings arranged along a first direction and electrically connected, each cell string comprises a plurality of cell pieces arranged along a second direction and electrically connected, and the first direction and the second direction are arranged in a cross manner;in the same cell string, two adjacent cell pieces are arranged in a local overlapping manner, and a piece-to-piece overlapping area is formed;along the second direction, the ratio of the width of the piece-to-piece overlapping area to the length of a single cell piece is 0.25%-3.5%.The back contact photovoltaic module can reduce the risk of hidden cracks, light leakage and edge chipping of the cell pieces in the packaging process, and maximally improve the power of the module.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a back contact photovoltaic module and a photovoltaic system. BACKGROUND

[0002] In the technical field of photovoltaic modules, back contact photovoltaic modules have shown significant advantages in improving photoelectric conversion efficiency due to their unique electrode structure design, and have become one of the key development directions in the industry. A back contact photovoltaic module is usually composed of an array of back contact cell pieces, which includes a plurality of back contact cell strings.

[0003] In the preparation process of a conventional back contact cell string, two adjacent back contact cell pieces are usually arranged in a spaced manner, i.e., there is a fixed piece spacing. Although this design is convenient for operation in early production processes, as the photovoltaic industry continues to improve the power generation per unit area of the module, the disadvantages of this design have become increasingly apparent: the existence of the piece spacing directly occupies the effective light receiving area of the module, resulting in a limited coverage area of the cell pieces per unit area, which in turn restricts the improvement of the power generation of the module.

[0004] To solve the above problems, the industry has gradually formed a technical improvement trend of "stacked piece arrangement" - by partially stacking adjacent back contact cell pieces in a photovoltaic module, the piece spacing in the conventional spaced arrangement is eliminated. This technical solution can increase the effective light receiving area of the module, and under the same module size, it can increase the coverage ratio of the cell pieces, thereby directly improving the power generation per unit area of the photovoltaic module.

[0005] However, the present inventors have found in actual production that although the use of the stacked piece arrangement can solve the inherent defects of the conventional spaced arrangement, new technical problems arise in the subsequent lamination process of the module: due to the stacking thickness of the cell pieces in the stacked area, the pressure distribution inside the module during lamination is uneven, the local pressure in the stacked area is higher than that in the non-stacked area, which causes the stacked back contact cell pieces to be prone to hidden cracks during the lamination process, and the unreasonable overlapping method also causes quality problems such as light leakage and edge damage (i.e., "edge damage") between the cell pieces. Therefore, how to further optimize the overlapping method of the back contact cell pieces to reduce the hidden cracks, light leakage and edge damage caused during the lamination process has become a key technical problem that needs to be solved in the industry. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a back contact photovoltaic module that can reduce the hidden cracks, light leakage and edge damage caused by the lamination process in the stacked area, and maximize the improvement of the power of the module.

[0007] Another technical problem to be solved by the present invention is to provide a photovoltaic system that can reduce microcracks and edge defects caused by the encapsulation process in the stacking area, and maximize the power of the module.

[0008] To solve the above-mentioned technical problems, the present invention provides a back-contact photovoltaic module, including a plurality of battery strings arranged and electrically connected along a first direction, each of the battery strings including a plurality of battery cells arranged and electrically connected along a second direction, wherein the first direction and the second direction are intersected.

[0009] In the same battery string, two adjacent battery cells are partially overlapped, and the overlapping area is called the inter-cell overlap area.

[0010] Along the second direction, the width of the inter-cell overlap region is d1, and the length of a single cell is D1, wherein the ratio of d1 to D1 is 0.25% to 3.5%.

[0011] As an improvement to the above technical solution, along the second direction, the battery cell includes mutually parallel chamfered edges and straight edges; along the third direction, the battery cell has a light-receiving surface and a backlight surface; the first direction, the second direction, and the third direction are intersecting each other; the straight edge is the cutting edge formed after the entire battery cell is cut.

[0012] In one embodiment, viewed from the backlight side of the battery cell, in two adjacent battery cells within the same battery string, the straight edge of one battery cell overlaps the chamfered edge of the adjacent battery cell.

[0013] In one embodiment, viewed from the backlight side of the battery cell, in two adjacent battery cells within the same battery string, the chamfered edge of one battery cell overlaps the straight edge of the adjacent battery cell.

[0014] As an improvement to the above technical solution, two adjacent battery strings are partially overlapped, and the overlapping area is the inter-string overlap area;

[0015] Along the first direction, the width of the inter-string overlapping region is d2, the width of a single solar cell is D2, and the ratio of d2 to D2 is 0.2% to 1.1%.

[0016] As an improvement to the above technical solution, along the second direction, the ratio of the width d1 of the inter-cell overlap region to the length D1 of the cell is 0.4% to 2.0%.

[0017] As an improvement to the above technical solution, along the second direction, the ratio of the width d1 of the inter-cell overlap region to the length D1 of the cell is 0.6%~1.0%.

[0018] As an improvement to the above technical solution, along the first direction, the ratio of the width d2 of the inter-string overlapping region to the width D2 of the battery cell is 0.3% to 0.7%.

[0019] As an improvement to the above technical solution, the width d1 of the inter-piece overlapping region is 0.3mm~2.0mm.

[0020] As an improvement to the above technical solution, the width d2 of the inter-string overlapping region is 0.5mm~2.0mm.

[0021] As an improvement to the above technical solution, along the second direction, the chamfered edges of the battery cells in two adjacent battery strings face opposite directions.

[0022] As an improvement to the above technical solution, along the first direction, adjacent battery cells include a first battery cell and a second battery cell; along the second direction, adjacent battery cells include a first battery cell and a third battery cell.

[0023] The inter-string overlap region includes a first inter-string overlap region, which is formed by the overlap of a first battery cell, a second battery cell, and a third battery cell.

[0024] As an improvement to the above technical solution, the inter-string overlapping area includes a second inter-string overlapping area, which is formed by the overlap of the straight edge of the second battery cell and the straight edge of the third battery cell.

[0025] The second inter-string overlap region includes a third inter-string overlap region, which is the area remaining after subtracting the first inter-string overlap region from the overlap region of the third and second battery cells.

[0026] As an improvement to the above technical solution, the area of ​​the first inter-string overlapping area is S1, the area of ​​the second inter-string overlapping area is S2, and the area of ​​the third inter-string overlapping area is S3, where S2 = 2*S1 + S3.

[0027] As an improvement to the above technical solution, the ratio of S1 to S3 is 1:6 to 1:3.

[0028] As an improvement to the above technical solution, the first inter-string overlapping area is triangular in shape, and the third inter-string overlapping area is hexagonal in shape.

[0029] In one embodiment, the battery string includes at least one first battery string and at least one second battery string, wherein the first battery string and the second battery string are arranged alternately along a first direction;

[0030] Viewed from the backlight side of the battery cells, in the first battery string, the chamfered edge of one of two adjacent battery cells overlaps the straight edge of the other adjacent battery cell; in the second battery string, the straight edge of one of two adjacent battery cells overlaps the chamfered edge of the other adjacent battery cell.

[0031] In the second direction, the chamfered edges of the cells in the first battery string and the chamfered edges of the cells in the second battery string face opposite directions.

[0032] As an improvement to the above technical solution, the second battery string is partially stacked on the backlight surface of the first battery string.

[0033] As an improvement to the above technical solution, in the first direction, the two sides of the chamfered edge of the battery cell are respectively provided with chamfers connected to the chamfered edge;

[0034] The width of the chamfer in the second direction is d3, and the width of the chamfer in the first direction is d4, wherein d3 is 0.8~1.5mm and d4 is 0.8~1.5mm.

[0035] Accordingly, the present invention also provides a photovoltaic system including the aforementioned back-contact photovoltaic module.

[0036] Implementing the present invention has the following beneficial effects: The back-contact photovoltaic module of the present invention, by adopting a partially overlapping structural design for multiple cells arranged along the second direction in the cell string, effectively eliminates the inter-cell spacing between adjacent cells in the traditional back-contact photovoltaic module, increases the effective light-receiving area of ​​the module, and improves the power generation per unit area of ​​the photovoltaic module.

[0037] Meanwhile, the ratio of the width d1 of the inter-cell overlap area in the second direction to the length D1 of a single cell in the second direction is limited to 0.25%~3.5%. A suitable overlap width ensures a good stacking structure between adjacent cells, reducing issues such as microcracks, light leakage, and edge damage during encapsulation, and maximizing module power. It also ensures the module's CTM value remains within a high range, reducing module costs. If the ratio of d1 to D1 is too small, a good stacking structure cannot be formed between cells, leading to microcracks in the stacked area during lamination. Insufficient overlap width also causes cell displacement due to film flow during lamination, easily resulting in light leakage and edge damage, leading to decreased module power and poor appearance. If the ratio of d1 to D1 is too large, the cells in the overlapped area cannot receive direct sunlight, reducing the module's CTM and increasing module costs.

[0038] Furthermore, by further optimizing the overlapping method, the straight edge of the light-receiving surface of one of two adjacent cells in the cell string is stacked on the chamfered edge of the back-lighting surface of the adjacent cell. That is, from the perspective of the light-receiving surface of the photovoltaic module, the straight edge of the cell with cutting damage is covered by the chamfered edge of the other cell without cutting damage. This can avoid the impact of the low-conversion-efficiency straight edge of the cell on the overall efficiency of the photovoltaic module, and further improve the module power. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the structure of a back-contact photovoltaic module on the back surface according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the back-contact photovoltaic module on the back surface according to another embodiment of the present invention;

[0041] Figure 3 yes Figure 2 A partially enlarged view of the back-contact photovoltaic module of the embodiment shown;

[0042] Figure 4 yes Figure 2 A partially enlarged view of the back-contact photovoltaic module of the embodiment shown;

[0043] Figure 5 This is a schematic diagram of the back contact photovoltaic module on the back surface according to another embodiment of the present invention;

[0044] Figure 6 yes Figure 5 A partially enlarged view of the back-contact photovoltaic module of the embodiment shown;

[0045] In the diagram: Battery string 1, first battery string 11, second battery string 12, battery cell 13, cell overlap area 14, string overlap area 15, backlight surface 16, chamfered edge 131, straight edge 132, chamfer 133, first string overlap area 151, second string overlap area 152, third string overlap area 153. Detailed Implementation

[0046] 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.

[0047] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "first direction", "second direction", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They 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. Therefore, they should not be construed as limitations on this application.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] It should be pointed out that, Figures 1 to 6 In the diagram, the light gray dashed area represents the part of the solar cell that is shaded when viewed from the back of the photovoltaic module; the black solid area represents the part of the solar cell that is not shaded when viewed from the back of the photovoltaic module.

[0053] See Figure 1 As shown, this embodiment provides a back-contact photovoltaic module, including a plurality of battery strings 1 arranged and electrically connected along a first direction, each battery string 1 including a plurality of battery cells 13 arranged and electrically connected along a second direction, the first direction and the second direction being intersected; specifically, the first direction and the second direction are perpendicular to each other;

[0054] In the same battery string 1, two adjacent battery cells 13 are partially overlapped, and the overlapping area is called the inter-cell overlap area 14.

[0055] Along the second direction, the width of the inter-cell overlap region 14 is d1, and the length of a single cell 13 is D1, wherein the ratio of d1 to D1 is 0.25% to 3.5%.

[0056] The back-contact photovoltaic module of the present invention, by adopting a partially overlapping structural design for multiple cells 13 arranged along the second direction in the same cell string 1, effectively eliminates the inter-cell spacing between adjacent cells 13 in traditional back-contact photovoltaic modules, increases the effective light-receiving area of ​​the module, and thus improves the power generation per unit area of ​​the photovoltaic module.

[0057] To further explain, in the process of using a stacked structure to achieve the technical goal of increasing the effective light-receiving area and thus improving the power generation of the module, the ratio of the width d1 of the inter-cell overlap area 14 in the second direction to the length D1 of the single cell 13 in the second direction is designed to be within a reasonable range. If the ratio of d1 to D1 is not designed reasonably, it is very easy to cause quality problems such as microcracks, light leakage and edge damage (i.e., "edge chipping") in the encapsulation process (especially the lamination process). Specifically, if the ratio of d1 to D1 is too small, the overlapping contact area of ​​adjacent cells 13 will be too small, making it difficult to form a stable stacked connection structure. This will not only easily cause microcracks in the cells, but also result in insufficient overlap width. During the lamination process, the flow of the encapsulant film will cause the cells to shift, which can easily lead to edge damage and light leakage at the stack, resulting in a decrease in module power and poor appearance. If the ratio of d1 to D1 is too large, the cells in the overlapping area cannot receive sunlight from the front, which will result in a smaller CTM (the ratio of the output power of the photovoltaic module to the theoretical total power of all cells inside under ideal conditions) of the module, increasing the module cost.

[0058] This invention optimizes the overlapping method, limiting the ratio of d1 to D1 to 0.25%~3.5%. Within this ratio range, on the one hand, it ensures that a sufficiently strong and stable stacked structure is formed between adjacent cells 13, reducing the risk of microcracks, light leakage, and edge chipping during the cell encapsulation process, maximizing module power, and reducing appearance defects; on the other hand, a d1 to D1 ratio within the range of 0.25%~3.5% ensures that the CTM value (the ratio of module power to the sum of cell power) of the battery module is within a high range, reducing the production cost of photovoltaic modules.

[0059] Along the second direction, the battery cell 13 includes a chamfered edge 131 and a straight edge 132 that are parallel to each other. Along the third direction, the battery cell 13 has a light-receiving surface and a backlighting surface 16. The first direction, the second direction and the third direction are intersecting each other. The straight edge is the cutting edge formed after the whole battery cell is cut.

[0060] It should be noted that the battery cell 13 in this embodiment can be a half-cell obtained by dicing a whole battery cell. All four corners of the whole battery cell are chamfered 133. The battery cell 13 formed after dicing has a chamfered edge 131 at one end and a straight edge 132 at the other end. The chamfered edge 131 is the original side edge of the whole battery cell, that is, the non-cut edge; the straight edge 132 is the cut edge formed by dicing the whole battery cell, and the angles on both sides are right angles, that is, the straight edge 132 is the cut edge.

[0061] In one embodiment of this invention, viewed from the backlighting surface of the solar cell 13, in two adjacent solar cells 13 within the same solar cell string 1, the straight edge 132 of one solar cell 13 is stacked on the chamfered edge 131 of the adjacent solar cell 13. This is so that, viewed from the light-receiving surface of the solar cell 13, the straight edge 132 of the solar cell is blocked by the chamfered edge 131 of the other solar cell 13. By further optimizing the overlapping method, the power of the module can be further improved. Specifically, the straight edge 132 of the solar cell 13 is formed by laser cutting. During the laser thermal cracking process, the silicon wafer at this cutting edge is damaged, forming suspended Si-H bonds, causing surface recombination and reducing the efficiency of the solar cell in that area. This embodiment optimizes the overlapping method of the solar cells 13 so that, in the same solar cell string, the overlapping method of adjacent solar cells 13 is such that the straight edge 132 of one solar cell 13 is stacked on the backlighting surface 16 of the chamfered edge 131 of the adjacent solar cell 13. This optimized design places the chamfered edge 131 (i.e., the structurally complete and more efficient uncut edge) of the solar cell 13 closer to the upper layer of the front glass of the module, enabling it to receive sunlight more fully for photoelectric conversion; while the less efficient straight edge 132 is placed on the backlight side, that is, the straight edge 132 is covered by the chamfered edge 131 and does not participate in receiving sunlight for power generation. Therefore, this optimized design can further increase the module power.

[0062] Furthermore, by limiting the ratio of d1 to D1 to within the range of 0.25% to 3.5%, the affected area of ​​laser thermal cracking in the straight edge 132 can be effectively blocked, maximizing the module power. If the ratio of d1 to D1 is small, that is, the width of the inter-cell overlap area is too small, an effective overlap structure cannot be formed, resulting in poor light transmission due to microcracks, and the affected area of ​​laser thermal cracking cannot be effectively blocked, leading to a decrease in module power. If the width of the inter-cell overlap area is too large, significantly exceeding the affected area of ​​laser thermal cracking, further increasing the stack width will not increase the module power and will reduce the module's CTM (Cellular Time Tolerance).

[0063] It is worth noting that, in this embodiment, the overlapping method between adjacent cells in a portion of the cell string can be configured such that, viewed from the back surface of the cell 13, in two adjacent cells 13 within the same cell string 1, the straight edge 132 of one cell 13 overlaps the chamfered edge 131 of the adjacent cell 13. Alternatively, the overlapping method can be adopted for all cells in all cell strings of the back-contact photovoltaic module.

[0064] See Figure 1As shown, in all the battery strings 1 in this embodiment, the partial overlap between two adjacent battery cells 13 within the battery string is achieved in the following manner: Viewed from the backlight side of the battery cell 13, in the same battery string 1, the straight edge 132 of one battery cell 13 is stacked on top of the chamfered edge 131 of the adjacent battery cell 13. This ensures that, viewed from the light-receiving side of the photovoltaic module, except for the battery cells located at the end of the photovoltaic module in the second direction, the straight edges 132 of the remaining battery cells are all blocked by the chamfered edges 131 of the adjacent battery cells 13. This overlap method can further improve the module power.

[0065] It should be noted that, in this application, two adjacent cells within the same cell string 1 can also be overlapped in the following manner: Viewed from the back surface of the cell, in two adjacent cells within the same cell string, the chamfered edge of one cell is stacked on top of the straight edge of the adjacent cell, so that when viewed from the light-receiving surface of the cell, the straight edge of the cell is on top (i.e., the straight edge is closer to the front glass of the module), and the chamfered edge is on the bottom. The power output of the photovoltaic module in this embodiment is slightly lower than that of the above embodiment, but still within a good range, and the module CTM and leakage defect rate in this embodiment are similar to those in the above embodiment.

[0066] In some embodiments, the ratio of the width d1 of the inter-cell overlap region 14 in the second direction to the length D1 of the single cell 13 in the second direction can be 0.25%, 0.35%, 0.4%, 0.6%, 0.8%, 0.83%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.2%, or 3.5%, but is not limited thereto.

[0067] Optionally, in some embodiments, the ratio of the width d1 of the inter-cell overlap region 14 to the length D1 of the single cell 13 along the second direction is 0.4% to 2.0%. In other embodiments, the ratio of the width d1 of the inter-cell overlap region 14 to the length D1 of the single cell 13 is 0.6% to 1.0%.

[0068] Specifically, multiple battery strings 1 can be electrically connected in series or in parallel, and multiple battery cells 13 in the same battery string can also be electrically connected in series or in parallel.

[0069] In one embodiment, multiple battery strings 1 can be electrically connected in parallel, and multiple battery cells 13 in the same battery string 1 can be electrically connected in series. In another embodiment, multiple battery strings 1 can be electrically connected in series, and multiple battery cells 13 in the same battery string can also be electrically connected in series.

[0070] It is worth noting that in this application, a preset distance gap can be provided between two adjacent battery strings 1. Furthermore, two adjacent battery strings 1 can also be partially overlapped. In this embodiment, a preset distance gap is provided between two adjacent battery strings 1, and the gap between adjacent battery strings 1 can be set using conventional methods in the art.

[0071] In one embodiment of this example, along the second direction, the chamfered edges of the battery cells in two adjacent battery strings face the same direction.

[0072] In another embodiment of this invention, along the second direction, the chamfered edges of the battery cells in two adjacent battery strings face opposite directions.

[0073] See Figure 2 As shown, another embodiment of a back-contact photovoltaic module is disclosed, wherein two adjacent cell strings 1 are partially overlapped, and the overlapping area is the inter-string overlap area 15; by partially overlapping the adjacent cell strings 1, the spacing between the cell strings can be eliminated, the light-receiving area of ​​the back-contact photovoltaic module can be further increased, and the module power can be further improved.

[0074] Along the first direction, the width of the inter-string overlap region 15 is d2, and the width of a single cell 13 is D2, with the ratio of d2 to D2 being 0.2% to 1.1%. Within this range, a stable stacking structure can be formed, which can reduce defects such as light leakage, edge chipping, and microcracks between cell strings during the module encapsulation process, maximize the module power, and ensure the long-term operational reliability of the module. Furthermore, the ratio of d2 to D2 within the range of 0.2% to 1.1% can avoid excessively wide inter-string overlap, which would result in wasted cells 13 and reduced module CTM.

[0075] Specifically, the ratio of d2 to D2 is exemplarily 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or 1.1%, but is not limited thereto.

[0076] More preferably, along the first direction, the ratio of the width d2 of the inter-string overlapping region 15 to the width D2 of the single cell 13 is 0.3% to 0.7%.

[0077] Specifically, in this application, the chamfered edges of the battery cells in two adjacent battery strings can be oriented in the same or different directions, both of which can achieve better electrical performance.

[0078] See Figures 2 to 4 As shown, in this embodiment, the chamfered edges of the battery cells in two adjacent battery strings face opposite directions.

[0079] In one embodiment, along a first direction, adjacent battery cells include a first battery cell and a second battery cell; along a second direction, adjacent battery cells include a first battery cell and a third battery cell.

[0080] The inter-string overlap region includes a first inter-string overlap region 151, which is formed by the overlap of a first battery cell, a second battery cell, and a third battery cell.

[0081] In one embodiment, the inter-string overlapping region includes a second inter-string overlapping region 152, which is formed by the overlap of the straight edge of the second battery cell and the straight edge of the third battery cell.

[0082] The second inter-string overlap region 152 includes a third inter-string overlap region 153, which is the area remaining after subtracting the first inter-string overlap region 151 from the overlap region of the third battery cell and the second battery cell.

[0083] In one embodiment, the area of ​​the first inter-string overlapping area 151 is S1, the area of ​​the second inter-string overlapping area 152 is S2, and the area of ​​the third inter-string overlapping area 153 is S3, where S2 = 2 * S1 + S3.

[0084] It is worth noting that in back-contact photovoltaic modules, when adjacent cell strings overlap and adjacent cells 13 within the same cell string overlap, a composite overlapping region (i.e., the first inter-string overlapping region 151) is formed, where the inter-cell overlapping region 14 and the inter-string overlapping region 15 overlap. This composite overlapping region easily forms a structure with multiple layers of cells 13 stacked together. Due to the influence of the multiple layers of cells 13 stacked together, the stress on the cells 13 within the composite overlapping region is significantly higher than in other areas of the module. During the lamination process, microcracks are easily generated in the composite overlapping region, and in severe cases, it may even cause the straight edge 132 of the cells 13 to chip, seriously affecting the structural stability and photoelectric conversion performance of the back-contact photovoltaic module.

[0085] The first inter-string overlapping region 151 of the battery cells formed by the overlapping method of the adopted embodiment has three layers, which avoids the formation of a four-layer battery cell structure in the composite overlapping region, reduces the thickness of the composite overlapping region, reduces the stress borne by the battery cell 13 in this region, and can further reduce microcrack defects and alleviate the problem of chipped corners at the cutting edge.

[0086] In one implementation, the ratio of S1 to S3 is 1:6 to 1:3. Within this range, the ratio of S1 to S3 is beneficial to further reduce hidden crack defects and alleviate the problem of chipped corners at the cutting edges.

[0087] In one embodiment, the first inter-string overlapping area 151 is triangular in shape, and the third inter-string overlapping area 153 is hexagonal in shape.

[0088] See Figure 5 and Figure 6 As shown, another embodiment of a back-contact photovoltaic module is disclosed. In this embodiment, the battery string includes at least one first battery string 11 and at least one second battery string 12, and the first battery string 11 and the second battery string 12 are arranged alternately along a first direction.

[0089] Viewed from the backlight side of the battery cells, in the first battery string, the chamfered edge of one of two adjacent battery cells overlaps the straight edge of the other adjacent battery cell; in the second battery string, the straight edge of one of two adjacent battery cells overlaps the chamfered edge of the other adjacent battery cell.

[0090] Viewed from the back of the battery cell, in the first battery string 11, the chamfered edge 131 of one of two adjacent battery cells 13 is stacked on the straight edge 132 of the other adjacent battery cell 13, that is, the straight edge 132 of the battery cell 13 in the first battery string 11 is closer to the front glass of the module; in the second battery string 12, the straight edge 132 of one of two adjacent battery cells 13 is stacked on the chamfered edge 131 of the other adjacent battery cell 13, that is, the chamfered edge 131 of the battery cell 13 in the second battery string 12 is closer to the front glass of the module;

[0091] Also see Figure 5 In one embodiment of the shown example, in the second direction, the chamfered edges 131 of the battery cells 13 in the first battery string 11 and the chamfered edges 131 of the battery cells 13 in the second battery string 12 are oriented in opposite directions, and the second battery string 12 is partially stacked on the backlight surface 16 of the first battery string 11.

[0092] It should be noted that in back-contact photovoltaic modules, when adjacent cell strings overlap and adjacent cells 13 within the same cell string overlap, a composite overlapping region is formed where the inter-cell overlapping region 14 and the inter-string overlapping region 15 overlap. This composite overlapping region easily forms a structure with multiple layers of cells 13 stacked together. Due to the influence of the multiple layers of cells 13 stacked together, the stress on the cells 13 within the composite overlapping region is significantly higher than in other areas of the module. During the lamination process, microcracks are easily generated in the composite overlapping region, and in severe cases, it may even cause the straight edge 132 of the cells 13 to chip, seriously affecting the structural stability and photoelectric conversion performance of the back-contact photovoltaic module.

[0093] To address this issue, this embodiment further optimizes the overlapping method between the solar cells 13. In the first solar cell string 11, the chamfered edge 131 of one of two adjacent solar cells 13 is stacked on the backlight surface 16 of the straight edge 132 of the other adjacent solar cell 13. That is, the straight edge 132 of the solar cell 13 in the first solar cell string 11 is closer to the front glass panel of the back-contact photovoltaic module. Similarly, in the second solar cell string 12, the straight edge 132 of one of two adjacent solar cells 13 is stacked on the backlight surface 16 of the chamfered edge 131 of the other adjacent solar cell 13. That is, the chamfered edge 131 of the solar cell 13 in the second solar cell string 12 is closer to the front glass panel of the back-contact photovoltaic module. Simultaneously, the second solar cell string 12 is partially stacked on the backlight surface 16 of the first solar cell string 11. Through this structural design, in the composite overlapping area where solar cells 13 overlap simultaneously with each other, a maximum of three layers of solar cells 13 can be formed. Compared to the structure where four layers of solar cells 13 are stacked in the composite overlapping region, the structural design of this embodiment can reduce the stress on the solar cells 13 in this region, further reducing the risk of microcracks in the solar cells 13, avoiding the occurrence of corner chipping at the cut edges, and ultimately ensuring that the back-contact photovoltaic module can stably perform its photoelectric conversion performance, further improving the module power. Figure 6 In the back-contact photovoltaic module shown, the chamfered edges 131 of the cell 13 in the first cell string 11 and the chamfered edges 131 of the cell 13 in the second cell string 12 are located in the same layer, so that the composite overlapping area forms only a three-layer cell 13 structure.

[0094] In some optional embodiments of the above examples, the width d1 of the inter-piece overlapping region 14 along the second direction is 0.3mm to 2.0mm.

[0095] In some optional embodiments of the above examples, the width d2 of the inter-string overlapping region 15 along the first direction is 0.5mm to 2.0mm.

[0096] In one embodiment of the above-described embodiment, in the first direction, both sides of the chamfered edge 131 of the battery cell 13 are provided with chamfers 133 connected to the chamfered edge;

[0097] The width of chamfer 133 in the second direction is d3, and the width of chamfer in the first direction is d4, where d3 is 0.8~1.5mm and d4 is 0.8~1.5mm.

[0098] Preferably, the solar cell 13 is a back-contact solar cell 13. The positive and negative electrodes of the back-contact solar cell 13 are both located on the back side of the back-contact solar cell 13, which can further increase the actual light-receiving area of ​​the back-contact photovoltaic module.

[0099] In some optional embodiments of the above examples, the length D1 of a single solar cell is 80mm to 110mm, and the width D2 of a single solar cell is 150mm to 250mm. Specifically, in some embodiments, the solar cell 13 can be a half-cell obtained by dicing a whole solar cell. A whole solar cell refers to a complete photovoltaic cell substrate that has not undergone dicing, such as a monocrystalline silicon / polycrystalline silicon solar cell with dimensions of 166mm×166mm, 182mm×182mm, or 210mm×210mm. Therefore, the dimensions of the solar cell 13 in this application can be 83mm×166mm, 91mm×182mm, or 105mm×210mm, that is, the length D1 of a single solar cell can be 83mm, 91mm, or 105mm, and the width D2 of a single solar cell can be 166mm, 182mm, or 210mm.

[0100] Accordingly, this embodiment also provides a photovoltaic system including the aforementioned back-contact photovoltaic module.

[0101] Specifically, the photovoltaic system of this embodiment may include at least one back-contact photovoltaic module as described in the above embodiments. In the photovoltaic system, the back-contact photovoltaic modules can be electrically connected in parallel or in series, depending on actual needs.

[0102] In the embodiments of this application, the photovoltaic system can be applied to photovoltaic 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, solar buildings, etc. Of course, it is understood that the application scenarios of the photovoltaic system are not limited to these; that is to say, the photovoltaic system can be applied in all fields that require the use of solar energy to generate electricity.

[0103] Taking a photovoltaic power generation system network as an example, a photovoltaic system may include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array may be an array combination of multiple photovoltaic modules. For example, multiple photovoltaic modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the combiner box, which can combine the current generated by the photovoltaic array. The combined 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 realize solar power supply.

[0104] The technical solution of the present invention will be further illustrated below through specific embodiments and comparative examples.

[0105] Examples 1-3

[0106] Examples 1-3 provide a back-contact photovoltaic module, including multiple cell strings arranged and electrically connected along a first direction, each cell string including multiple cells arranged and electrically connected along a second direction; in the same cell string, adjacent cells partially overlap, and the overlapping area is the inter-cell overlap area; along the second direction, the cells include mutually parallel chamfered edges and straight edges, and along the third direction, the cells have a light-receiving surface and a back-lighting surface, and the first direction, the second direction and the third direction are arranged perpendicular to each other;

[0107] In all the cell strings of the back-contact photovoltaic module in this embodiment, the straight edge of the light-receiving surface of one of two adjacent cells is stacked on the chamfered edge of the back-lighting surface of the other adjacent cell; along the second direction, the width of the inter-cell overlap area is d1, and the length of a single cell is D1. The ratio of d1 to D1 in Embodiments 1 to 3 is shown in Table 1 below.

[0108] Comparative Example 1

[0109] This comparative example provides a back-contact photovoltaic module. The structure of the back-contact photovoltaic module of Comparative Example 1 is basically the same as that of Example 1, except that the ratio of d1 to D1 in Comparative Example 1 is 0.10%.

[0110] Comparative Example 2

[0111] This comparative example provides a back-contact photovoltaic module. The structure of the back-contact photovoltaic module of Comparative Example 2 is basically the same as that of Example 1, except that the ratio of d1 to D1 in Comparative Example 1 is 5.19%.

[0112] Specifically, back-contact photovoltaic modules of the same size were fabricated using the same encapsulation process for Examples 1-3 and Comparative Examples 1-2. The module CTM, module power, light transmittance failure rate, and microcrack failure rate of the back-contact photovoltaic modules of Examples 1-3 and Comparative Examples 1-2 were tested. The light transmittance failure rate refers to the ratio of the number of photovoltaic modules with light transmittance problems in the overlapping area to the total number of photovoltaic module samples tested; the microcrack failure rate refers to the ratio of the number of photovoltaic modules with microcrack problems in the overlapping area to the total number of photovoltaic module samples tested. The test results are shown in Table 1 below:

[0113] Table 1 Test Results

[0114]

[0115] As can be seen from Table 1, by optimizing the overlapping method and controlling the ratio of the width of the overlapping area between cells to the length of a single cell, the present invention can reduce the risk of microcracks and light leakage that occur in the module after the encapsulation process, while improving the module power and ensuring that the module CTM is greater than 90%, thus reducing the module cost.

[0116] Examples 4-8

[0117] Examples 4-8 each provide a back-contact photovoltaic module. The back-contact photovoltaic modules of Examples 4-8 are basically the same as those of Example 2, except that in Examples 4-8, two adjacent cell strings are partially overlapped, and the overlapping area is called the inter-string overlap area. Furthermore, along the second direction, the chamfered edges of the cells in the two adjacent cell strings face opposite directions. Along the first direction, the width of the inter-string overlap area is d2, and the width of a single cell is D2. The ratio of d2 to D2 is 0.2% to 1.1%. The ratios of d2 and D2 in Examples 4 to 8 are shown in Table 2 below.

[0118] Specifically, back-contact photovoltaic modules of the same size were fabricated using the same encapsulation process from Examples 4 to 8. The module CTM, module power, light transmittance failure rate, and microcrack failure rate of the back-contact photovoltaic modules from Examples 4 to 8 were tested. The test results are shown in Table 2 below:

[0119] Table 2 Test results of Examples 4-8

[0120]

[0121] As shown in Table 2, based on Example 2, by partially overlapping adjacent cell strings, the spacing between strings can be eliminated, further increasing the effective light-receiving area per unit module area, thereby further improving module power. However, due to the partial overlap between cell strings, the overlapping of multiple layers of cells in the string-cell overlap area leads to a significant increase in light leakage and microcrack rates. This invention, by controlling the ratio of d2 to D2 within the range of 0.2% to 1.1%, can reduce light leakage and microcracks in the inter-string overlap area during module lamination, maximizing module power and ensuring long-term operational reliability. Furthermore, a d2 to D2 ratio within the range of 0.2% to 1.1% avoids excessively wide inter-string overlap, which would increase cell waste and reduce module CTM.

[0122] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A back-contact photovoltaic module, characterized in that, It includes multiple battery strings arranged and electrically connected along a first direction, each battery string including multiple battery cells arranged and electrically connected along a second direction, the first direction and the second direction being intersected; In the same battery string, two adjacent battery cells are partially overlapped, and the overlapping area is called the inter-cell overlap area. Along the second direction, the width of the inter-cell overlap region is d1, and the length of a single cell is D1, wherein the ratio of d1 to D1 is 0.25% to 3.5%. The battery strings are partially overlapped between two adjacent strings, and the overlapping area is the inter-string overlap area. Along the first direction, adjacent solar cells include a first solar cell and a second solar cell; along the second direction, adjacent solar cells include a first solar cell and a third solar cell. The inter-string overlap region includes a first inter-string overlap region, which is formed by the overlap of a first battery cell, a second battery cell, and a third battery cell.

2. The back-contact photovoltaic module according to claim 1, characterized in that, Along the second direction, the solar cell includes chamfered edges and straight edges that are parallel to each other; along the third direction, the solar cell has a light-receiving surface and a backlighting surface; the first direction, the second direction and the third direction are arranged to intersect each other. The straight edge is the cut edge formed after the entire battery cell is cut.

3. The back-contact photovoltaic module according to claim 2, characterized in that, Viewed from the back of the battery cell, in two adjacent battery cells within the same battery string, the straight edge of one battery cell overlaps the chamfered edge of the adjacent battery cell.

4. The back-contact photovoltaic module according to claim 3, characterized in that, Viewed from the back of the battery cell, in two adjacent battery cells within the same battery string, the chamfered edge of one battery cell overlaps the straight edge of the adjacent battery cell.

5. The back-contact photovoltaic module according to claim 3 or 4, characterized in that, Along the second direction, the chamfered edges of the cells in two adjacent battery strings face opposite directions.

6. The back-contact photovoltaic module according to any one of claims 1-4, characterized in that, Along the first direction, the width of the inter-string overlapping region is d2, the width of a single solar cell is D2, and the ratio of d2 to D2 is 0.2% to 1.1%.

7. The back-contact photovoltaic module according to claim 1, characterized in that, The inter-string overlap region includes a second inter-string overlap region, which is formed by the overlap of the straight edge of the second battery cell and the straight edge of the third battery cell. The second inter-string overlap region includes a third inter-string overlap region, which is the area remaining after subtracting the first inter-string overlap region from the overlap region of the third and second battery cells.

8. The back-contact photovoltaic module according to claim 7, characterized in that, The area of ​​the first inter-string overlapping region is S1, the area of ​​the second inter-string overlapping region is S2, and the area of ​​the third inter-string overlapping region is S3, where S2 = 2*S1 + S3.

9. The back-contact photovoltaic module according to claim 8, characterized in that, The ratio of S1 to S3 is 1:6 to 1:

3.

10. The back-contact photovoltaic module according to claim 7, characterized in that, The first overlapping area between strings is triangular in shape, and the third overlapping area between strings is hexagonal in shape.

11. The back-contact photovoltaic module according to claim 1, characterized in that, The battery string includes at least one first battery string and at least one second battery string, with the first battery string and the second battery string arranged alternately along a first direction; Viewed from the backlight side of the battery cells, in the first battery string, the chamfered edge of one of two adjacent battery cells overlaps the straight edge of the other adjacent battery cell; in the second battery string, the straight edge of one of two adjacent battery cells overlaps the chamfered edge of the other adjacent battery cell. In the second direction, the chamfered edges of the cells in the first battery string and the chamfered edges of the cells in the second battery string face opposite directions.

12. The back-contact photovoltaic module according to claim 11, characterized in that, The second battery string is partially stacked on the backlight surface of the first battery string.

13. The back-contact photovoltaic module according to claim 1, characterized in that, Along the second direction, the ratio of the width d1 of the inter-cell overlap region to the length D1 of a single cell is 0.4% to 2.0%.

14. The back-contact photovoltaic module according to claim 6, characterized in that, Along the first direction, the ratio of the width d2 of the inter-string overlapping region to the width D2 of a single solar cell is 0.3% to 0.7%.

15. The back-contact photovoltaic module according to claim 1, characterized in that, Along the second direction, the width d1 of the inter-piece overlapping region is 0.3mm to 2.0mm.

16. The back-contact photovoltaic module according to claim 6, characterized in that, Along the first direction, the width d2 of the inter-string overlapping region is 0.5mm to 2.0mm.

17. The back-contact photovoltaic module according to claim 2, characterized in that, In the first direction, the two sides of the chamfered edge of the battery cell are respectively provided with chamfers connected to the chamfered edge; The width of the chamfer in the second direction is d3, and the width of the chamfer in the first direction is d4, wherein d3 is 0.8~1.5mm and d4 is 0.8~1.5mm.

18. The back-contact photovoltaic module according to claim 1, characterized in that, The length of a single solar cell in the second direction is 80mm to 110mm, and the width of a single solar cell in the first direction is 150mm to 250mm.

19. A photovoltaic system, characterized in that, Includes the back-contact photovoltaic module as described in any one of claims 1-18.

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