A back contact cell assembly and photovoltaic system

Abstract

This invention discloses a back-contact solar cell module and photovoltaic system, relating to the field of photovoltaic cell technology. The back-contact solar cell module includes multiple cell strings arranged and electrically connected along a first direction, each cell string including multiple solar cells arranged and electrically connected along a second direction. Adjacent cell strings partially overlap, with the area of ​​a single solar cell covered by adjacent cell strings forming a first coverage area. Within the same cell string, adjacent solar cells partially overlap, with the area of ​​a single solar cell covered by adjacent solar cells within the same cell string forming a second coverage area. The sum of the areas of the first and second coverage areas is S1, and the total area of ​​a single solar cell is S2, with the ratio of S1 to S2 being 0.23% to 2.89%. The back-contact solar cell module provided by this invention can reduce the risk of microcracks, light leakage, and cell cracking during the cell encapsulation process, and maximize module power output.

Description

Technical Field

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

[0002] With the continuous expansion of photovoltaic (PV) applications, both large-scale ground-mounted PV power plants and distributed PV systems are placing higher demands on the power output of battery modules. The aim is to achieve higher power generation within limited installation space through more efficient module design, which has become one of the core driving forces for the continuous iteration of PV technology. To meet these needs, the industry is constantly exploring technical paths to improve module power. Among these, increasing the effective light-receiving area of ​​the battery module through stacking, thereby improving module power, has become an important development trend in the battery module field. This process, by partially overlapping adjacent cells within the same cell string, reduces the blank areas between cells in traditional gap-layout configurations, increasing the effective light-receiving area per unit area of ​​the battery module, and thus directly improving the module's power generation.

[0003] However, in the actual production and application of commercially available stacked solar modules, industry professionals have found that although the existing stacking method can indeed increase the light-receiving area of ​​the solar cells to a certain extent and have a positive effect on the improvement of module power, the actual power improvement effect of the module is still difficult to achieve the expected results. Therefore, how to further improve the power of solar modules has become a key technical pain point that the industry urgently needs to overcome. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a back contact battery assembly that can reduce the risk of microcracks, light leakage and cell cracking generated during the battery cell encapsulation process, and maximize the power of the assembly.

[0005] Another technical problem to be solved by the present invention is to provide a photovoltaic system that can reduce the risk of microcracks, light leakage and cell cracking generated during the encapsulation process of solar cells, and maximize the power of the photovoltaic system.

[0006] To solve the above-mentioned technical problems, the present invention provides a back contact battery assembly, 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.

[0007] The battery strings are partially overlapped between two adjacent battery strings, and the area of ​​a single battery cell covered by the adjacent battery strings is the first coverage area;

[0008] In the same battery string, two adjacent battery cells are partially overlapped, and the area of ​​a single battery cell covered by the adjacent battery cells in the same battery string is the second coverage area;

[0009] The sum of the areas of the first coverage area and the second coverage area is S1, and the total area of ​​a single battery cell is S2. The ratio of S1 to S2 is 0.23% to 2.89%.

[0010] As an improvement to the above technical solution, along the second direction, the two ends of the battery cell are respectively provided with a non-cut end and a cut end;

[0011] In the same battery string, the uncut end of one of two adjacent battery cells overlaps with the cut end of the other adjacent battery cell.

[0012] As an improvement to the above technical solution, in the third direction, the battery string has a light-receiving surface and a backlight surface, and the first direction, the second direction and the third direction are arranged to intersect each other;

[0013] Viewed from the backlight side of the battery string, in two adjacent battery cells within the same battery string, the cut end of one battery cell is stacked on top of the uncut end of the adjacent battery cell.

[0014] As an improvement to the above technical solution, the sum of the areas of the first coverage area and the second coverage area is S1, the total area of ​​a single battery cell is S2, and the ratio of S1 to S2 is 0.23%~1.56%.

[0015] As an improvement to the above technical solution, the ratio of S1 to S2 is 0.95%~1.56%.

[0016] As an improvement to the above technical solution, the area of ​​the first coverage area is S. 11 The area of ​​the second covered region is S 12 S 12 >S 11 .

[0017] As an improvement to the above technical solution, the area S of the first coverage area 11 and the area S of the second coverage area 12 The following relationship exists between them:

[0018] S 12 =1.2S 11 ~4.5S 11 .

[0019] As an improvement to the above technical solution, the area S of the first coverage area 11 50 mm2 ~150 mm 2 The area S of the second covered region 12 140 mm 2 ~550mm 2 .

[0020] As an improvement to the above technical solution, a transparent buffer strip is provided at the overlapping point of two adjacent battery strings, and in a third direction, the transparent buffer strip is located between the two adjacent battery strings.

[0021] As an improvement to the above technical solution, in the third direction, one side of the transparent buffer strip is in contact with the backlight side of the battery string, and the other side of the transparent buffer strip is in contact with the light-receiving side of another adjacent battery string.

[0022] In the first direction, the two sides of the transparent buffer strip extend to the outside of the first covered area.

[0023] As an improvement to the above technical solution, the width of the transparent buffer strip in the first direction is d1, and the width of the first covering area in the first direction is d2, wherein the ratio of d1 to d2 is 1.2 to 4.

[0024] As an improvement to the above technical solution, the ratio of d1 to d2 is 1.5 to 3.

[0025] As an improvement to the above technical solution, the ratio of the thickness of the battery cell to the thickness of the transparent buffer strip is 0.7 to 1.3.

[0026] As an improvement to the above technical solution, in the second direction, the end of the transparent buffer strip is flush with the end of the battery string;

[0027] Alternatively, the end of the transparent buffer strip extends in a second direction to the outside of the end of the battery string.

[0028] As an improvement to the above technical solution, the transparent buffer strip is made of one of the following materials: silicone, TPU, TPE, EVA, or POE.

[0029] As an improvement to the above technical solution, chamfers are provided on both sides of the uncut end of the battery cell along the first direction.

[0030] As an improvement to the above technical solution, the battery string includes at least one first battery string and at least one second battery string, the first battery string and the second battery string are arranged alternately along a first direction, and the second battery string is stacked on the backlight surface of the first battery string;

[0031] Viewed from the backlight side of the battery string, in the first battery string, the uncut end of one of two adjacent battery cells is stacked on top of the cut end of the other adjacent battery cell;

[0032] In the second battery string, the cut end of one of two adjacent battery cells is stacked on the backlight surface of the uncut end of the other adjacent battery cell.

[0033] As an improvement to the above technical solution, in the second direction, the uncut ends of the battery cells in the first battery string and the uncut ends of the battery cells in the second battery string are oriented in opposite directions.

[0034] Accordingly, the present invention also provides a photovoltaic system including the aforementioned back contact battery assembly.

[0035] Implementing the present invention has the following beneficial effects: by partially overlapping two adjacent battery cells in the same battery string, the effective light-receiving area of ​​the battery module per unit area can be increased, thereby improving the module power; and by partially overlapping adjacent battery strings, the effective light-receiving area of ​​the battery module per unit area can be further increased, thereby further improving the module power.

[0036] Meanwhile, by limiting the ratio of the sum of the areas of the first and second coverage areas (S1) to the total area of ​​a single solar cell (S2) to 0.23%~2.89%, a stable stacked structure can be ensured, reducing defects such as light leakage, edge chipping, and microcracks in the solar module during the encapsulation process. Furthermore, with the ratio of S1 to S2 within this range, cell waste can be reduced, improving the module's core thickness measurement (CTM) and thus lowering production costs.

[0037] Furthermore, by further optimizing the stacking method of the solar cells, when viewed from the backlight side of the solar cell string, the cut end of one solar cell is stacked on top of the uncut end of the adjacent solar cell in the same solar cell string. This ensures that when viewed from the light-receiving side of the solar cell string, the cut end of the solar cell is blocked by the uncut end of the other solar cell, thereby further improving the power of the module. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of a back contact battery assembly according to an embodiment of the present invention, wherein... Figure 1 Figure (A) shows the overall structure of the back contact battery assembly, and Figure (B) is an enlarged view of one of the battery cells in Figure (A).

[0039] Figure 2 This is a schematic diagram of the structure of a back contact battery assembly according to another embodiment of the present invention;

[0040] Figure 3 yes Figure 2 A partial schematic diagram of the embodiment shown in the thickness direction;

[0041] Figure 4 This is a schematic diagram of the structure of a back contact battery assembly according to another embodiment of the present invention;

[0042] Among them: battery string 1, transparent buffer strip 2, first battery string 11, second battery string 12, battery sheet 13, first covering area 14, second covering area 15, backlight surface 16, light-receiving surface 17, non-cut end 131, cut end 132, chamfer 133. Detailed Implementation

[0043] 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.

[0044] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "first direction", "second direction", "third 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.

[0045] 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.

[0046] 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.

[0047] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or reference 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.

[0048] See Figure 1 As shown, this embodiment discloses a back-contact battery assembly, 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.

[0049] The two adjacent battery strings 1 are partially overlapped, and the area of ​​a single battery cell 13 covered by the adjacent battery string 1 is the first coverage area 14;

[0050] In the same battery string 1, two adjacent battery cells 13 are partially overlapped, and the area of ​​a single battery cell 13 covered by the adjacent battery cells 13 in the same battery string 1 is the second coverage area 15.

[0051] The sum of the areas of the first coverage area 14 and the second coverage area 15 is S1, and the total area of ​​a single solar cell 13 is S2. The ratio of S1 to S2 is 0.23% to 2.89%. It can be understood that the first coverage area 14 and the second coverage area 15 can be the areas covered by the solar cell as seen from the back of the module (i.e., the backlight side), or the areas covered by the solar cell as seen from the front of the module (i.e., the light-receiving side). In this embodiment, the first coverage area 14 and the second coverage area 15 are the areas covered by the solar cell as seen from the back of the module.

[0052] It should be noted that, in combination Figure 1 As shown, in this embodiment, the first direction is the horizontal direction and the second direction is the vertical direction.

[0053] The back-contact battery assembly of this embodiment increases the effective light-receiving area of ​​the battery assembly per unit area by partially overlapping two adjacent battery cells 13 in the same battery string 1, thereby improving the assembly power; and by partially overlapping adjacent battery strings 1, the effective light-receiving area of ​​the battery assembly per unit area can be further increased, thereby further improving the assembly power.

[0054] Furthermore, the inventors discovered in practical applications that a reasonable stacking area plays a crucial role in reducing microcracks and light leakage defects in battery modules, as well as improving the power output of stacked battery modules. This embodiment, by limiting the ratio of the sum of the areas of the first covering region 14 and the second covering region 15 (S1) to the total area of ​​a single battery cell 13 (S2) to 0.23%~2.89%, ensures a stable stacking structure, reduces defects such as light leakage, edge chipping, and microcracks during the battery module encapsulation process, and facilitates further improvement in module power output. Moreover, within this range, the ratio of S1 to S2 reduces waste of battery cells 13, improves the module's core thickness measurement (CTM), and thus reduces production costs.

[0055] Specifically, if the stacking area (i.e., the sum of the areas of the first covering area 14 and the second covering area 15 (S1)) is designed to be too small, a stable stacking structure cannot be formed between adjacent cells 13 and adjacent cell strings 1. During subsequent module lamination, problems such as misalignment of the stacking areas and exposure of the edges of the cells 13 are very likely to occur, leading to light leakage in the module. Furthermore, an unstable stacking structure is prone to collisions between adjacent cells 13 and adjacent cell strings 1 during lamination, resulting in risks such as edge defects and microcracks. This not only leads to poor appearance of the module but also reduces the photoelectric conversion efficiency of the module, resulting in a decrease in module power and making it difficult to achieve the theoretical expectation. In addition, it will also affect the service life of the module. Conversely, if the stacking area is designed to be too large, although it can ensure the stability of the stacking structure, it will cause excessive overlap of the cells 13 and material waste, reducing the module's CTM and thus increasing production costs, making it difficult to achieve the optimal balance between power and cost.

[0056] In some implementations, the ratio of S1 to S2 may, for example, be 0.23% to 1.0%, 0.23% to 1.5%, 0.5% to 1.2%, 0.6% to 1.5%, 1.5% to 2.0%, or 2.0% to 2.89%, but is not limited thereto. Specifically, the ratio of S1 to S2 may, for example, be 0.23%, 0.5%, 0.6%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, or 2.89%, but is not limited thereto.

[0057] In some embodiments, the sum of the areas of the first coverage area 14 and the second coverage area 15 is S1, and the total area of ​​a single cell 13 is S2. The ratio of S1 to S2 is 0.23% to 1.56%. A ratio of S1 to S2 within this range ensures that the component's CTM value is greater than 92%, which helps to reduce production costs.

[0058] More preferably, the ratio of S1 to S2 is 0.95% to 1.56%. Within this range, the ratio of S1 to S2 can further reduce the proportion of defects such as light leakage and microcracks in the battery module, further improve the module power, and further reduce the CTM value, thereby further reducing production costs.

[0059] In some implementations, the area of ​​the first coverage area 14 is S. 11 The area of ​​the second coverage area 15 is S. 12 S 12 >S 11 By limiting S 12 >S 11 This is more conducive to forming a stable stacked structure, avoiding defects such as light leakage, edge chipping and microcracks in the battery module during the encapsulation process, and further improving the module power.

[0060] In some implementations, the area S of the first coverage area 14 11 The area S of the second coverage area 15 12 The following relationship exists between them:

[0061] S 12 =1.2S 11 ~4.5S 11 .

[0062] Specifically, S 11 and S 12 When the above formula is satisfied, it is beneficial to form a more stable stacked structure, further reducing defects such as light leakage, hidden cracks and edge chipping.

[0063] In some embodiments, the battery cell 13 of this embodiment can be a half-cell obtained by dicing a whole battery cell. All four corners of the whole battery cell are chamfered, and one end of the diced battery cell is a non-cut end 131, and the other end is a cut end 132. The edge of the non-cut end 131 is the original side edge of the whole battery cell 13, that is, the non-cut edge; the edge of the cut end 132 is the straight edge formed by dicing the whole battery cell 13, that is, the edge of the cut end 132 is the cut edge.

[0064] In some implementations, see Figure 1As shown, along the second direction, the two ends of the battery cell 13 are respectively provided with a non-cut end 131 and a cut end 132; in the same battery string, the non-cut end 131 of one of two adjacent battery cells 13 overlaps with the cut end 132 of the adjacent battery cell. Since the non-cut end 131 of the battery cell has chamfers on both sides, this overlapping method helps to reduce the corner breakage of the cut end.

[0065] In some embodiments, in the third direction, the battery string has a light-receiving surface 17 and a backlight surface 16, and the first direction, the second direction and the third direction are arranged to intersect each other;

[0066] Viewed from the backlighting surface 16 of the battery string, in two adjacent battery cells 13 within the same battery string, the cut end 132 of one battery cell 13 is stacked on top of the uncut end 131 of the adjacent battery cell 13, so that when viewed from the light-receiving surface 17 of the battery string, the cut end 132 of the battery cell 13 is blocked by the uncut end 131 of the other battery cell 13.

[0067] Specifically, in the slicing process of the solar cell 13, the cutting process (such as laser cutting) exerts physical stress on the crystal structure of the sliced ​​area, which can easily damage its internal crystal structure, thus easily forming microcracks that are difficult to observe with the naked eye at the cut end 132 of the solar cell 13. The presence of these microcracks leads to a decrease in the photoelectric conversion efficiency of the cut end 132 of the solar cell 13, and this efficiency level is lower than that of other areas of the solar cell 13 without cutting damage. To address the above problems, this embodiment optimizes the stacking method of the solar cells 13, so that in the same solar cell string 1, the cut end 132 of the solar cell 13 is stacked on the backlight surface 16 of the non-cut end 131 of another adjacent solar cell 13. This optimized design places the structurally complete and more efficient uncut end 131 of the solar cell 13 closer to the upper layer of the front glass panel of the module, enabling it to receive sunlight more fully for photoelectric conversion. Meanwhile, the less efficient cut end 132 is placed on the back side by the uncut end 131, reducing its proportion in the effective light-receiving area of ​​the module. This reduces the drag on the overall power of the module from the inefficient area of ​​the cut end 132, which is beneficial to further improve the power of the back contact solar cell module.

[0068] In some embodiments, the sum of the areas of the first coverage area and the second coverage area (S1) is 190 mm. 2 ~700mm 2 .

[0069] In some implementations, the area S of the first coverage area 14 11 50mm 2 ~150mm 2The area S of the second coverage area 15 12 140~550mm 2 .

[0070] Specifically, in some optional embodiments, the battery cell 13 can be a half-cell obtained by dicing a whole battery cell. The dimensions of the whole battery cell 13 are, for example, 182mm×182mm, 210mm×210mm, or 166mm×166mm, but are not limited to these. In battery assembly manufacturing, half-cell cells are typically cut from a whole battery cell along its centerline; therefore, the dimensions of the corresponding half-cell cells are, for example, 91mm×182mm, 105mm×210mm, or 83mm×166mm, and are again not limited to these. That is, in this embodiment, the area of ​​a single battery cell is equal to the area of ​​the half-cell cell minus the area of ​​the chamfer. Since the area of ​​the chamfer is small and negligible, the area of ​​a single battery cell is, for example, 13778mm². 2 16562mm 2 22050mm 2 The above are just a few optional embodiments; the size and area of ​​the battery cell of the present invention are not limited thereto.

[0071] The present invention also discloses another embodiment of the back contact battery assembly, see [link to relevant documentation]. Figure 2 and Figure 3 As shown, in this embodiment, two adjacent battery strings 1 are provided with a transparent buffer strip 2 at the overlap, and in the third direction, the transparent buffer strip 2 is located between the two adjacent battery strings 1; specifically, the first direction, the second direction and the third direction are perpendicular to each other, and in this embodiment, the third direction is the direction of the back contact battery assembly in terms of thickness.

[0072] It is worth noting that the overlapping areas between battery strings 1 are prone to microcracks and corner breakage during lamination, especially in areas where strings and cells overlap simultaneously (i.e., composite overlapping areas where inter-cell and inter-string overlapping areas overlap). Due to the double overlap, a multi-layered structure of battery cells 13 is easily formed. Due to the influence of the multi-layered battery cells 13, the stress on the battery cells 13 in the composite overlapping area is significantly higher than in other areas of the module. During lamination, microcracks are easily generated in the composite overlapping area, and in severe cases, corner breakage of the battery cells 13 may occur, seriously affecting the structural stability and photoelectric conversion performance of the back-contact battery module, leading to a decrease in module power. Therefore, in this embodiment, a transparent buffer strip 2 is provided at the overlap of two adjacent battery strings 1. Since the transparent buffer strip 2 is located between the two battery strings 1, it can also extend along the second direction to the entire composite overlapping area, preventing direct hard contact between silicon and silicon in the stacked area during lamination, alleviating the defects of microcracks and corner breakage in the stacked area, and further improving the output power of the battery module.

[0073] Further explanation: From a third-party perspective, the battery string 1 has a light-receiving surface 17 and a backlighting surface 16. One side of the transparent buffer strip 2 contacts the backlighting surface 16 of the battery string 1, and the other side of the transparent buffer strip 2 contacts the light-receiving surface 17 of the adjacent battery string 1. Specifically, the transparent buffer strip 2 and the battery string 1 can be bonded together with an adhesive to achieve contact, forming a strong adhesive structure between them. Alternatively, no adhesive can be used between them. Since adhesive films are provided on both the front and back sides of the battery string 1 during packaging, lamination can ensure close contact between the transparent buffer strip 2 and the battery string 1, forming a stable structure.

[0074] In the first direction, the transparent buffer strip 2 extends to the outside of the first covered area 14 on both sides. This structural design can provide better buffering between the battery strings 1, prevent the brittle battery pieces 13 from making direct hard contact, and reduce the risk of microcracks and corner breakage at the overlapping points between the battery strings 1.

[0075] It should be noted that the transparent buffer strip 2 in this embodiment is transparent and supported by a transparent material, which enables efficient light transmission and minimizes the obstruction of the light-receiving surface 17 of the solar cell 13. In practical applications, the transparent buffer strip 2 ensures that the light-receiving area of ​​the solar cell 13 is fully exposed, reducing the problem of local light loss caused by the presence of the buffer strip. This ensures that the solar cell 13 can effectively receive external light, providing strong support for the stable performance of subsequent photoelectric conversion efficiency and avoiding the problem of module power loss caused by the non-transparent buffer strip 2 obstructing the light-receiving surface 17.

[0076] In some embodiments, the width of the transparent buffer strip 2 in the first direction is d1, and the width of the first covering area 14 in the first direction is d2, wherein the ratio of d1 to d2 is 1.2 to 4. By controlling the ratio of d1 to d2 to be 1.2 to 4, a better buffering effect can be achieved, reducing microcrack defects.

[0077] Specifically, the ratio of d1 to d2 is exemplarily 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, or 4.0, but is not limited thereto.

[0078] More preferably, the width of the transparent buffer strip 2 in the first direction is d1, and the width of the first covering area 14 in the first direction is d2, wherein the ratio of d1 to d2 is 1.5 to 3.

[0079] In some embodiments, the ratio of the thickness of the battery cell 13 to the thickness of the transparent buffer strip 2 is 0.7 to 1.3, exemplarily 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, or 1.3, but not limited to these. A thickness ratio within this range provides a better buffering effect and reduces the risk of microcracks and corner breakage. If the thickness ratio is too small, the transparent buffer strip 2 becomes too thick, which not only fails to further reduce microcracks but also increases the risk of light leakage due to its transparency. Furthermore, an excessively thick transparent buffer strip 2 can easily compress the adhesive film of the battery assembly, leading to a decrease in battery assembly stability. If the thickness ratio is too large, the transparent buffer strip 2 becomes too thin, and the buffering effect will decrease.

[0080] In some embodiments, the thickness of the battery cell 13 is 0.1mm to 0.3mm, and the thickness of the transparent buffer strip 2 can be selected according to the ratio of the thickness of the battery cell 13 to the thickness of the transparent buffer strip 2 being 0.7 to 1.3.

[0081] To further explain, in the second direction, the end of the transparent buffer strip 2 is flush with the end of the battery string 1; or, the end of the transparent buffer strip 2 extends along the second direction to the outside of the end of the battery string 1, so that the entire overlapping area between the battery strings 1 is provided with a transparent buffer strip 2, further improving the buffering effect.

[0082] Preferably, the transparent buffer strip 2 is made of one of silicone, TPU, TPE, EVA, or POE. These materials have high light transmittance and can minimize the obstruction of the light-receiving surface of the solar cells. More preferably, the transparent buffer strip 2 is made of EVA or POE. These materials can act as a buffer in the early stages of the lamination process, preventing direct hard contact between the solar cells and mitigating defects such as microcracks and corner chipping in the stacked area. In the later stages of lamination, they will slowly melt and fuse with the molten adhesive film in the module, forming a stable overall structure between the layers of the module.

[0083] Accordingly, the present invention also discloses another embodiment of the back contact battery assembly, see [link to relevant documentation]. Figure 4 As shown, the battery string 1 includes at least one first battery string 11 and at least one second battery string 12. The first battery string 11 and the second battery string 12 are arranged alternately along a first direction, and the second battery string 12 is stacked on the backlight surface 16 of the first battery string 11.

[0084] Viewed from the backlight side of the battery string, in the first battery string 11, the uncut end 131 of one of the two adjacent battery cells 13 is stacked on the cut end 132 of the other adjacent battery cell 13; in the second battery string 12, the cut end 132 of one of the two adjacent battery cells 13 is stacked on the backlight side 16 of the uncut end 131 of the other adjacent battery cell 13.

[0085] To further explain, in this embodiment, in the second direction, the uncut ends 131 of the battery cells 13 in the first battery string 11 and the uncut ends 131 of the battery cells 13 in the second battery string 12 are oriented in opposite directions.

[0086] It should be noted that this embodiment further optimizes the overlapping method between the battery cells 13. In the first battery string 11, the uncut end 131 of the battery cell 13 is stacked on the backlight surface 16 of the cut end 132 of the adjacent battery cell 13, that is, the cut end 132 of the battery cell 13 in the first battery string 11 is closer to the front glass plate of the back contact battery assembly; while in the second battery string 12, the cut end 132 of the battery cell 13 is stacked on the backlight surface 16 of the uncut end 131 of the adjacent battery cell 13, that is, the uncut end 131 of the battery cell 13 in the second battery string 12 is closer to the front glass plate of the back contact battery assembly. At the same time, the second battery string 12 is partially stacked on the backlight surface 16 of the first battery string 11, and the orientations of the uncut end 131 of the battery cell 13 in the first battery string 11 and the uncut end 131 of the battery cell 13 in the second battery string 12 are opposite. Through the above structural design, in the composite overlapping area where battery strings and cells overlap simultaneously, a maximum of three layers of cells can be formed. Compared to the existing technology where four layers of cells are easily formed in the composite overlapping area, the structural design of this embodiment can further reduce the stress on the cells in this area, thereby reducing the risk of microcracks in the cells, avoiding the occurrence of corner breakage at the 132-degree angle, and ultimately ensuring that the back-contact battery module can stably perform its photoelectric conversion performance and improve the long-term stability of the module. Figure 4 In the back contact battery assembly shown, the uncut ends 131 of the battery cells 13 in the first battery string 11 and the uncut ends 131 of the chamfered edges 133 of the battery cells 13 in the second battery string 12 are located in the same layer, so that the composite overlapping area forms only a three-layer battery cell 13 structure.

[0087] Accordingly, this embodiment also provides a photovoltaic system including the back contact battery module described above.

[0088] Specifically, the photovoltaic system of this embodiment may include at least one back-contact battery module as described in the above embodiments. In the photovoltaic system, the back-contact battery modules can be electrically connected in parallel or in series, depending on actual needs.

[0089] 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.

[0090] 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 battery modules. For example, multiple battery 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.

[0091] The technical solution of the present invention will be further illustrated below through embodiments and comparative examples.

[0092] Examples 1 to 5 and Comparative Examples 1 to 2

[0093] Examples 1 to 5 and Comparative Examples 1 to 2 each provide a back contact battery assembly, including 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;

[0094] The cells are partially overlapped between two adjacent battery strings, and the area of ​​a single cell covered by the adjacent battery string is the first coverage area.

[0095] In the same battery string, two adjacent battery cells are partially overlapped, and the area of ​​a single battery cell covered by the adjacent battery cells in the same battery string is the second coverage area;

[0096] The sum of the areas of the first and second coverage areas is S1, and the total area of ​​a single battery cell is S2. The ratio of S1 to S2 is shown in Table 1. The area of ​​the first coverage area is S... 11 The area of ​​the second coverage area is S 12 And S 11 and S 12 The relationships between them are shown in Table 1.

[0097] Along the second direction, the two ends of the cell are the uncut end and the cut end, respectively. When viewed from the back of the cell string, in two adjacent cells within the same cell string, the cut end of one cell is stacked on top of the uncut end of the adjacent cell, so that when viewed from the light-receiving side of the cell string, the cut end of the cell is blocked by the uncut end of the adjacent cell.

[0098] Specifically, back-contact battery modules of the same size were fabricated using the same packaging process for Examples 1-5 and Comparative Examples 1-2. The module CTM, module power, light leakage defect rate, and microcrack defect rate of the back-contact battery modules of Examples 1-5 and Comparative Examples 1-2 were tested. The test results are shown in Table 1 below. The light leakage defect rate refers to the ratio of the number of battery modules with light leakage defects to the total number of battery modules in the tested sample, and the microcrack defect rate refers to the ratio of the number of battery modules with microcrack defects to the total number of battery modules in the tested sample.

[0099] Table 1

[0100]

[0101] As can be seen from the experimental data in Table 1, the present invention can reduce microcracks and light leakage defects in the module during the encapsulation process by optimizing the overlapping method, improve the module power and ensure that the module CTM is greater than 90%, thereby reducing the module production cost.

[0102] 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 battery assembly, 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; The battery strings are partially overlapped between two adjacent battery strings, and the area of ​​a single battery cell covered by the adjacent battery strings is the first coverage area; In the same battery string, two adjacent battery cells are partially overlapped, and the area of ​​a single battery cell covered by the adjacent battery cells in the same battery string is the second coverage area; The sum of the areas of the first coverage area and the second coverage area is S1, and the total area of ​​a single battery cell is S2. The ratio of S1 to S2 is 0.23% to 2.89%. Along the second direction, the two ends of the battery cell are respectively provided with a non-cut end and a cut end; The battery string includes at least one first battery string and at least one second battery string, the first battery string and the second battery string are arranged alternately along a first direction, and the second battery string is stacked on the backlight surface of the first battery string; From the third-party perspective, the battery string has a light-receiving surface and a backlight surface; from the backlight surface of the battery string, in the first battery string, the uncut end of one of two adjacent battery cells is stacked on the cut end of the other adjacent battery cell; in the second battery string, the cut end of one of two adjacent battery cells is stacked on the uncut end of the other adjacent battery cell. In the second direction, the uncut ends of the battery cells in the first battery string and the uncut ends of the battery cells in the second battery string are oriented in opposite directions.

2. The back contact battery assembly according to claim 1, characterized in that, The ratio of S1 to S2 is 0.23% to 1.56%.

3. The back contact battery assembly according to claim 1, characterized in that, The area of ​​the first covered region is S 11 The area of ​​the second covered region is S 12 S 12 >S 11 .

4. The back contact battery assembly according to claim 3, characterized in that, The area S of the first covered region 11 and the area S of the second coverage area 12 The following relationship exists between them: S 12 =1.2S 11 ~4.5S 11 。 5. The back contact battery assembly according to claim 4, characterized in that, The area S of the first covered region 11 50 mm 2 ~150 mm 2 ; The area S of the second coverage area 12 140 mm 2 ~550 mm 2 .

6. The back contact battery assembly according to claim 1, characterized in that, Two adjacent battery strings have a transparent buffer strip at their overlap, and in a third direction, the transparent buffer strip is located between the two adjacent battery strings.

7. The back contact battery assembly according to claim 6, characterized in that, In the third direction, one side of the transparent buffer strip is in contact with the backlight side of the battery string, and the other side of the transparent buffer strip is in contact with the light-receiving side of the adjacent battery string. In the first direction, the two sides of the transparent buffer strip extend to the outside of the first covered area.

8. The back contact battery assembly according to claim 7, characterized in that, The width of the transparent buffer strip in the first direction is d1, and the width of the first covering area in the first direction is d2, wherein the ratio of d1 to d2 is 1.2 to 4.

9. The back contact battery assembly according to claim 8, characterized in that, The ratio of d1 to d2 is 1.5 to 3.

10. The back contact battery assembly according to claim 6, characterized in that, The ratio of the thickness of the battery cell to the thickness of the transparent buffer strip is 0.7 to 1.

3.

11. The back contact battery assembly according to claim 7, characterized in that, In the second direction, the end of the transparent buffer strip is flush with the end of the battery string; Alternatively, the end of the transparent buffer strip extends in a second direction to the outside of the end of the battery string.

12. The back contact battery assembly according to claim 6, characterized in that, The transparent buffer strip is made of one of the following materials: silicone, TPU, TPE, EVA, or POE.

13. The back contact battery assembly according to claim 1, characterized in that, Along the first direction, the two sides of the uncut end of the battery cell are respectively provided with chamfers.

14. A photovoltaic system, characterized in that, Includes the back contact battery assembly as described in any one of claims 1-13.

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