Back contact solar cell, cell string, cell module and photovoltaic system

Abstract

The utility model discloses a back contact solar cell, a cell string, a cell assembly and a photovoltaic system, and relates to the field of silicon solar cells. Specifically, the back contact solar cell comprises a silicon substrate, a first doping layer, a second doping layer, a positive electrode grid line, a negative electrode grid line and a first PAD part. The second doping layer is in composite contact with the first doping layer at a preset position to form an electric leakage composite contact structure; each group of first PAD parts comprises a first PAD point and a second PAD point, the first PAD point is electrically connected with at least one positive grid line, and the second PAD point is electrically connected with at least one negative grid line; the positive grid line electrically connected with the first PAD point extends along a second direction, and the extension distance is l1; the distance between the first edge and the second edge is L, and l1 / L is greater than or equal to 0.9; the negative grid line electrically connected with the second PAD point extends along a second direction, and the extension distance is l2; l2 / L > = 0.9. According to the utility model, the hot spot effect can be accurately represented at the battery end.

Description

Technical Field

[0001] This utility model relates to the field of silicon solar cells, and in particular to a back-contact solar cell, a cell string, a cell module and a photovoltaic system. Background Technology

[0002] When one or more solar cells (or segments) in a photovoltaic module are partially or completely shaded, the shaded solar cells (segments) exhibit reverse voltage bias, becoming a load that consumes the power generated by the normal solar cells, thus generating a large amount of heat and causing the temperature of the solar cell to be higher than normal. This is the so-called hot spot effect. In existing technologies, to solve the hot spot problem, a diode is typically connected in anti-parallel across the two ends of the string unit to reduce the current of the shaded solar cell and weaken the hot spot effect. However, this parallel diode introduces power loss. To address this issue, a feasible approach is to directly form a leakage composite contact structure on the solar cell (see CN117976743B). This involves forming partial contacts between doped layers of different polarities during the solar cell fabrication process, effectively reducing the reverse voltage across the shaded solar cell, decreasing heat generation, and weakening the hot spot effect. Using this method, the control of the hot spot effect can be shifted forward to the solar cell end. Therefore, how to evaluate the hot spot effect at the solar cell end has become a technical problem that needs to be solved by those skilled in the art.

[0003] On the other hand, conventional hot spot effect testing typically involves shading one or more solar cells (or segments) in a solar module while the other solar cells (or segments) are exposed to sunlight. After a certain period of time, the temperature of the shaded solar cell segment is measured to characterize the hot spot effect. This is clearly unsuitable for testing the hot spot effect at the solar cell end. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a back-contact solar cell, a cell string, a cell module and a photovoltaic system, which can realize the quantitative evaluation of hot spot effect at the cell end.

[0005] To address the aforementioned problems, this utility model discloses a back-contact solar cell, comprising:

[0006] A silicon substrate comprising a light-receiving surface and a back-lighting surface disposed opposite to each other; having a first edge and a second edge in a second direction;

[0007] Multiple first doped layers and multiple second doped layers are disposed on the backlight surface. The multiple first doped layers and multiple second doped layers are alternately arranged along a first direction and extend along a second direction. The second doped layer makes composite contact with the first doped layer at a preset position to form a leakage composite contact structure. The first direction and the second direction intersect.

[0008] Multiple positive gate lines and multiple negative gate lines, wherein the positive gate lines are disposed on the first doped layer and the negative gate lines are disposed on the second doped layer; and

[0009] At least one set of first PAD sections, so that current can be passed through the first PAD sections and flow through the leakage composite contact structure;

[0010] Each group of first PADs includes a first PAD point and a second PAD point. The first PAD point is electrically connected to at least one of the positive grid lines, and the second PAD point is electrically connected to at least one of the negative grid lines.

[0011] The positive grid line electrically connected to the first PAD point extends along the second direction, with an extension distance of l1; the distance between the first edge and the second edge is L, and l1 / L≥0.9;

[0012] The negative grid line electrically connected to the second PAD point extends along the second direction, with an extension distance of l2; l2 / L≥0.9.

[0013] As an improvement to the above technical solution, the following is included: the relative distance between the first PAD point and the second PAD point in the second direction is l3, 0.9≤l1 / l3<1, 0.9≤l2 / l3<1.

[0014] As an improvement to the above technical solution, the first PAD point is located at the first edge, and the second PAD point is located at the second edge.

[0015] As an improvement to the above technical solution, it includes 1 to 12 groups of first PAD sections.

[0016] As an improvement to the above technical solution, the back-contact solar cell conforms to the following relationship:

[0017]

[0018] Among them, U rev U is the reverse breakdown voltage of the back-contact solar cell. rev0 The reverse voltage of the back-contact solar cell is denoted by x, which is the total number of positive and negative grid lines. x0 is a variable representing the first PAD section, x1 is the number of the first PAD points, x2 is the number of the second PAD points, A is a constant with a value ranging from 0.1 to 3.3, and B is a constant with a value ranging from 2 to 50.

[0019] As an improvement to the above technical solution, when multiple first PAD parts are provided, the multiple first PAD points are evenly distributed along the first direction; the multiple second PAD points are evenly distributed along the first direction.

[0020] As an improvement to the above technical solution, it also includes:

[0021] A first shunt gate line and a second shunt gate line, wherein the first shunt gate line is electrically connected to a plurality of positive gate lines and the second shunt gate line is electrically connected to a plurality of negative gate lines;

[0022] The first shunt gate line is electrically connected to the first PAD point, and the second shunt gate line is electrically connected to the second PAD point.

[0023] As an improvement to the above technical solution, the first shunt grid line is disposed at the first edge, and the positive grid line and the negative grid line are disposed on the side of the first shunt grid line facing the second edge;

[0024] The second shunt grid line is located at the second edge, and the positive grid line and the negative grid line are located on the side of the second shunt grid line facing the first edge.

[0025] As an improvement to the above technical solution, no grid line is provided between the first shunt grid line and the first edge;

[0026] No grid line is provided between the second shunt grid line and the second edge.

[0027] As an improvement to the above technical solution, the width of the first shunt gate line is greater than the width of the positive gate line, and the width of the second shunt gate line is greater than the width of the negative gate line.

[0028] As an improvement to the above technical solution, the distance between the first PAD point and the first edge is greater than the distance between the first shunt gate line and the first edge;

[0029] The distance between the second PAD point and the second edge is greater than the distance between the second shunt grid line and the second edge.

[0030] As an improvement to the above technical solution, the distance between the first PAD point and the first edge is 3mm to 5mm; the distance between the second PAD point and the second edge is 3mm to 5mm.

[0031] The distance between the first shunt grid line and the first edge is 0.2mm to 2mm, and the distance between the second shunt grid line and the second edge is 0.2mm to 2mm.

[0032] As an improvement to the above technical solution, the first PAD point is electrically connected to the first shunt grid line through the first connecting grid line;

[0033] The second PAD point is electrically connected to the second shunt grid line through the second connecting grid line.

[0034] As an improvement to the above technical solution, the first connecting gate line is located on the extension line of a positive gate line toward the first edge;

[0035] The second connecting gate line is located on the extension line of a negative gate line toward the second edge.

[0036] As an improvement to the above technical solution, the positive grid line includes a first positive sub-grid line, and the first PAD point is located at the end of the first positive sub-grid line and is electrically connected to the first positive grid line.

[0037] The negative grid line includes a first negative sub-grid line, and the second PAD point is located at the end of the first negative grid line and is electrically connected to the first negative grid line.

[0038] The first positive electrode grid line is arranged adjacent to the first negative electrode grid line.

[0039] As an improvement to the above technical solution, the first PAD point is electrically connected to at least three first positive electrode grid lines.

[0040] The second PAD point is electrically connected to at least three first negative electrode grid lines.

[0041] As an improvement to the above technical solution, at least one side of the first connecting gate line in the first direction is further provided with a second negative electrode gate line extending in the second direction. The second negative electrode gate line is electrically connected to at least one negative electrode gate line near the first PAD point and is insulated from the first PAD point; and / or

[0042] The second connecting grid line is further provided with a second positive sub-grid line extending along the second direction on at least one side in the first direction. The second positive sub-grid line is electrically connected to at least one positive grid line near the second PAD point and is insulated from the second PAD point.

[0043] As an improvement to the above technical solution, the second negative electrode grid line is located on the extension line of the first negative electrode grid line connected to the second PAD point towards the first edge; and / or

[0044] The second positive electrode grid line is located on the extension line of the first positive electrode grid line connected to the first PAD point to the second edge.

[0045] As an improvement to the above technical solution, the first PAD point and the second PAD point are square, circular, triangular or irregular in shape.

[0046] As an improvement to the above technical solution, the first PAD point and the second PAD point are square, with a width of 0.1mm to 1mm.

[0047] As an improvement to the above technical solution, it also includes:

[0048] At least one set of second PAD sections, which includes a plurality of third PAD points and a fourth PAD point; the third PAD point is electrically connected to at least one positive grid line and is insulated from the negative grid line; the fourth PAD point is electrically connected to at least one negative grid line and is insulated from the positive grid line.

[0049] The positive grid line electrically connected to the third PAD point extends along the second direction, with an extension distance of l4; and l4 / L≤0.1;

[0050] The negative grid line electrically connected to the fourth PAD point extends along the second direction, with an extension distance of l5, and l5 / L≤0.1.

[0051] As an improvement to the above technical solution, the silicon substrate has a third edge or a fourth edge disposed opposite to each other in a first direction;

[0052] The second PAD portion is provided at the third edge and the fourth edge.

[0053] As an improvement to the above technical solution, the geometric center of the third PAD point closest to the first edge and the geometric center of the first PAD point located at the first edge are located on the same straight line extending along the first direction and located on the backlight surface.

[0054] The geometric center of the fourth PAD point closest to the second edge and the geometric center of the second PAD point located at the second edge are located on the same straight line extending along the first direction and on the backlight surface.

[0055] Accordingly, this utility model also discloses a battery string, which includes the aforementioned back-contact solar cell.

[0056] Accordingly, this utility model also discloses a battery assembly, which includes the aforementioned back-contact solar cell or the aforementioned battery string.

[0057] Accordingly, this utility model also discloses a photovoltaic system, which includes the aforementioned battery components.

[0058] Implementing this utility model has the following beneficial effects:

[0059] The back-contact solar cell of this invention includes multiple first doped layers and multiple second doped layers disposed on the back side of a silicon substrate. The second doped layers form a leakage current composite contact structure by collaborating with the first doped layers at predetermined positions. Furthermore, at least one set of first PAD portions is provided on the back surface of the silicon substrate. Each set of first PAD portions includes a first PAD point and a second PAD point. The first PAD point is electrically connected to at least one positive grid line, and the second PAD point is electrically connected to at least one negative grid line. Based on the technical solution of this embodiment, a reverse current can be passed through the first PAD point and the second PAD point, flowing through the leakage current composite contact structure, thereby allowing the reverse breakdown voltage of the back-contact solar cell to be tested, providing a good foundation for characterizing hot spot effects at the cell end. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of the composition of a photovoltaic system in one embodiment of the present invention;

[0061] Figure 2 This is a schematic diagram of the structure of a back-contact solar cell assembly in one embodiment of the present invention;

[0062] Figure 3 This is a schematic diagram of the structure of a back-contact solar cell string in one embodiment of this utility model;

[0063] Figure 4 This is a schematic diagram of the structure of a back-contact solar cell string in another embodiment of the present invention;

[0064] Figure 5 This is a schematic diagram of the structure of a back-contact solar cell in one embodiment of the present invention;

[0065] Figure 6 This is a schematic diagram of the structure of the first doped layer and the second doped layer in one embodiment of the present invention;

[0066] Figure 7 This is a cross-sectional structural diagram of a back-contact solar cell in one embodiment of the present invention;

[0067] In the diagram, 100 represents the battery module, 110 the battery string, 120 the busbar, 111 the back contact solar cell, 112 the solder ribbon, 1 is the silicon substrate, 11 is the light-receiving surface, 12 is the back-lighting surface, 13 is the first edge, 14 is the second edge, 15 is the third edge, 16 is the fourth edge, 21 is the first doped layer, 22 is the second doped layer, 23 is the spacing region, 24 is the leakage current composite contact structure, 25 is the preset position, 31 is the positive grid line, and 311 is the... 312 is the first positive electrode grid line, 32 is the second positive electrode grid line, 321 is the first negative electrode grid line, 322 is the second negative electrode grid line, 40 is the insulating layer, 41 is the first hole, 42 is the second hole, 51 is the first PAD point, 52 is the second PAD point, 61 is the first shunt grid line, 62 is the second shunt grid line, 71 is the first connecting grid line, 72 is the second connecting grid line, 81 is the third PAD point, and 82 is the fourth PAD point. Detailed Implementation

[0068] 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.

[0069] In the description of this application, it should be understood that the terms "length", "width", "upper", "lower", "left", "right", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0070] 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.

[0071] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or mutual communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0072] 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.

[0073] 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.

[0074] refer to Figure 1 The photovoltaic system in one embodiment of this utility model includes the battery module 100 in one embodiment of this application. Multiple battery modules 100 can be connected in series or in parallel through a junction box to form a photovoltaic system. This photovoltaic system can be used in photovoltaic power plants, such as ground power plants, rooftop power plants, and floating power plants, and can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, and solar buildings, but is not limited thereto.

[0075] See Figure 2In one embodiment of the present invention, the battery assembly 100 includes at least one battery string 110 or at least one back-contact solar cell 111. Preferably, in one embodiment, the battery assembly 100 is composed of multiple battery strings 110, exemplarily 2, 4, 6, or 12 strings, but not limited thereto. Multiple battery strings 110 can be connected in series or parallel via busbars 120, solder strips 112, or other conductive media to form the battery assembly 100. Furthermore, for the mechanical connection of the multiple battery strings 110, and other usage requirements of the assembly (such as electrical connection of the multiple battery assemblies 100, weather resistance, etc.), it is necessary to introduce components such as insulating adhesive, junction boxes, frames, backplates, films, and glass, but not limited thereto.

[0076] refer to Figure 3 and Figure 4 In one embodiment of this utility model, the battery string 110 includes a plurality of back-contact solar cells 111 as described in one embodiment of this utility model, or segments formed by cutting back-contact solar cells 111. (See reference) Figure 3 Adjacent back-contact solar cells 111 (or their segments) can be stacked to form a cell string 110, and connected in series or parallel via solder ribbons 112 or conductive adhesive, but are not limited thereto. (See reference) Figure 4 Adjacent back-contact solar cells 111 (or their segments) can be connected in series or parallel using solder ribbons 112 and conductive adhesive, but are not limited to this. Correspondingly, since the back surface 12 of the back-contact solar cell 111 is provided with positive grid lines 31 and negative grid lines 32, insulating adhesive or insulating blocks are needed to prevent the solder ribbons 112 from short-circuiting them, but are not limited to this. To secure the solder ribbons 112, adhesives (e.g., UV adhesive), solder paste, etc., are also needed. To secure the back-contact solar cells of the cell string 110, adhesives, etc., are also introduced, but are not limited to this.

[0077] Specifically, refer to Figure 5 This utility model discloses a back-contact solar cell 111, which includes: a silicon substrate 1, a plurality of first doped layers 21, a plurality of second doped layers 22, a plurality of positive electrode grid lines 31, and a plurality of negative electrode grid lines 32. The silicon substrate 1 can be P-type monocrystalline silicon, N-type monocrystalline silicon, P-type polycrystalline silicon, or N-type polycrystalline silicon, but is not limited thereto; N-type monocrystalline silicon is preferred. The silicon substrate 1 includes a light-receiving surface 11 and a back-lighting surface 12 disposed opposite to each other.

[0078] The first doped layer 21 and the second doped layer 22 are disposed on the backlight surface 12. Specifically, the first doped layer 21 and the second doped layer 22 are alternately arranged along a first direction and extend along a second direction. A gap region 23 is provided between the first doped layer 21 and the second doped layer 22 to achieve insulation between the first doped layer 21 and the second doped layer 22. The first doped layer 21 may be one or more of a P-type doped polycrystalline silicon layer, a P-type doped amorphous silicon layer, or a P-type doped microcrystalline silicon layer, but is not limited thereto. Preferably, the first doped layer 21 is a P-type polycrystalline silicon layer; the P-type dopant element in the first doped layer 21 may be B, Al, or Ga, but is not limited thereto, with B being preferred. The second doped layer 22 may be an N-type doped polycrystalline silicon layer, an N-type doped amorphous silicon layer, or an N-type doped microcrystalline silicon layer, but is not limited thereto. Preferably, it is an N-type doped polycrystalline silicon layer. The N-type dopant element in the second doped layer 22 may be P, As, or Sb, but is not limited thereto. P is preferred.

[0079] The first direction and the second direction intersect. Specifically, the first direction can be vertical and the second direction can be horizontal, but it is not limited to these.

[0080] For details, see Figure 6 In this embodiment, at least one second doped layer 22 is in composite contact with the first doped layer 21 at a preset position 25 to form a leakage current composite contact structure 24. Based on this leakage current composite contact structure 24, the reverse voltage at both ends of the back contact solar cell 111 under peak current can be reduced, the heating power can be reduced, the probability of hot spot occurrence can be reduced, and the temperature of the hot spot area can be reduced when hot spot occurs.

[0081] Specifically, in one embodiment, at a predetermined position 25, the first doped layer 21 or the second doped layer 22 can be extended to a doped layer of the opposite polarity (such as the second doped layer 22 or the first doped layer 21), so that the two come into contact to form a leakage composite contact structure 24. In another embodiment, a conductive functional layer is formed at the predetermined position 25, so that the first doped layer 21 and the second doped layer 22 come into contact to form a leakage composite contact structure 24. In yet another embodiment, the leakage composite contact structure 24 can be formed by stacking the first doped layer 21 and the second doped layer 22. Specifically, the second doped layer 22 can be stacked on the first doped layer 21, or the first doped layer 21 can be stacked on the second doped layer 22. It should be noted that when a stacked structure is used, a dielectric layer can also be provided between the first doped layer 21 and the second doped layer 22. The dielectric layer can be a tunneling film layer, such as a silicon oxide tunneling passivation layer, but is not limited to this. Preferably, a second doped layer 22 is stacked on the first doped layer 21 at a preset position 25 to form a leakage current composite contact structure 24. Based on this structure, the leakage current composite contact structure 24 can be formed by etching the second doped layer 22, which is simple and reliable.

[0082] The positive gate line 31 can be a silver gate line, an aluminum gate line, a copper gate line, or a silver-clad copper gate line, but is not limited to these. The positive gate line 31 is disposed above and in contact with the first doped layer 21. Preferably, refer to Figure 7 In one embodiment, an insulating layer 40 is provided between the positive gate line 31 and the first doped layer 21. The positive gate line 31 contacts the first doped layer 21 through a first hole 41 provided on the insulating layer 40. The first hole 41 can be formed by laser process, etching process, or paste burn-through process, but is not limited thereto.

[0083] The negative electrode grid line 32 can be a silver grid line, an aluminum grid line, a copper grid line, or a silver-clad copper grid line, but is not limited to these. Preferably, see reference... Figure 7 In one embodiment, an insulating layer 40 is provided between the negative gate line 32 and the second doped layer 22. The negative gate line 32 contacts the second doped layer 22 through a second hole 42 provided on the insulating layer 40. The second hole 42 can be formed by laser process, etching process, or paste burn-through process, but is not limited thereto.

[0084] refer to Figure 5 In this embodiment, the back contact solar cell 111 includes at least one set of first PAD portions. Each set of first PAD portions includes a first PAD point 51 and a second PAD point 52. Reverse current is injected into the back contact solar cell 111 through the first PAD point 51 and the second PAD point 52, flowing through the leakage composite contact structure 24. This allows for the measurement of the reverse breakdown voltage of the back contact solar cell 111, providing a good foundation for characterizing the hot spot effect at the cell end. It should be noted that conventional hot spot testing is generally performed at the module end, where any one or more solar cells in the solar cell module are partially shaded, while other solar cells (or sections) are exposed to sunlight. After a certain period, the temperature of the shaded solar cells (or sections) is measured to characterize the hot spot effect. Existing technologies struggle to accurately quantify the hot spot effect at the cell end. In this embodiment, after introducing the leakage current composite contact structure 24, its reverse breakdown voltage is measured, which fully expresses the influence of the leakage current composite contact structure 24 on the reverse breakdown voltage. Furthermore, the hot spot effect is quantitatively characterized by the reverse breakdown voltage, providing a good foundation for the control of the hot spot effect of the module.

[0085] It is understood that the first PAD point 51 and the second PAD point 52 do not contact the first doped layer 21 and the second doped layer 22 below them to prevent leakage. That is, an insulating layer 40 is provided between the first PAD point 51 and the second PAD point 52 and the first doped layer 21 and the second doped layer 22. The insulating layer 40 may include one or more of the following: an aluminum oxide layer, an amorphous silicon layer, a silicon oxide layer, and a silicon nitride layer.

[0086] The positive grid line 31, electrically connected to the first PAD point 51, extends along the second direction with a distance of l1; the distance between the first edge 13 and the second edge 14 is L, where l1 / L ≥ 0.9; the negative grid line 32, electrically connected to the second PAD point 52, extends along the second direction with a distance of l2, where l2 / L ≥ 0.9. By controlling this extension distance, more reverse current can flow through the leakage current composite contact structure 24 at the preset position 25, thereby more accurately characterizing the influence of the leakage current composite contact structure 24 on the reverse breakdown voltage and evaluating the hot spot effect. Simultaneously, by controlling this ratio, the back contact solar cell 111 can collect more photogenerated carriers during use, thereby improving its conversion efficiency.

[0087] For example, l1 / L can be 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, or 0.99, but is not limited thereto. Preferably, it is 0.93 to 0.95. Similarly, l2 / L can be 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, or 0.99, but is not limited thereto. Preferably, it is 0.93 to 0.95.

[0088] Preferably, in one embodiment, the relative distance between the first PAD point 51 and the second PAD point 52 in the second direction is l3, where 0.9 ≤ l1 / l3 < 1 and 0.9 ≤ l2 / l3 < 1, to further improve the accuracy of the reverse breakdown voltage test and further improve the carrier collection efficiency, thereby improving the conversion efficiency of the back contact solar cell 111. Exemplarily, l1 / l3 is 0.93, 0.95, 0.96, 0.97, 0.98, or 0.99, but is not limited thereto. Preferably, it is 0.97 to 0.99. Exemplarily, l2 / l3 is 0.93, 0.95, 0.96, 0.97, 0.98, or 0.99, but is not limited thereto. Preferably, it is 0.97 to 0.99. It should be noted that in this embodiment, the relative distance between the first PAD point 51 and the second PAD point 52 in the second direction refers to the projected distance between their geometric centers in the second direction.

[0089] Specifically, the first PAD point 51 and the second PAD point 52 are square, circular, triangular, or irregular in shape, but are not limited to these. Preferably, in one embodiment, the first PAD point 51 and the second PAD point 52 are square, with a width of 0.1mm to 1mm. Based on this width, the first PAD point 51 and the second PAD point 52 can form good contact with the test probe of the test device. Here, the test probe refers to the probe used to inject current in the test equipment.

[0090] Specifically, in this embodiment, the first PAD section can be one or more groups. It is understood that a larger number of groups results in more accurate reverse breakdown voltage test results, but more first test points also mean occupying more backlight area 12, reducing the area available for arranging the positive grid line 31 and negative grid line 32, which is detrimental to conversion efficiency. Preferably, considering both conversion efficiency and test accuracy, the number of first PAD sections is set to 1 to 12 groups, exemplarily 1, 3, 5, 7, or 9 groups, but not limited to these. Preferably, it is 1 to 4 groups.

[0091] The following further explains the impact of the number of first PAD sections on the reverse breakdown voltage test results:

[0092] For an ideal diode, its current can be calculated using the following formula:

[0093]

[0094] Where, I DD I is the current flowing from the positive terminal to the negative terminal in an ideal diode. s ν is the reverse saturation current of the ideal diode; n is the emission coefficient, with a value of 1 to 2; k is the Boltzmann constant; T is the temperature; q is the space electron charge; and V is the voltage across the positive and negative terminals of the ideal diode.

[0095] After introducing the leakage current composite contact structure 24, the current of the diode with leakage current can be calculated by the following formula:

[0096]

[0097] Among them, I D I is the output current of a diode with leakage current. DD I is the current flowing from the positive terminal to the negative terminal in an ideal diode. S Let be the reverse saturation current of an ideal diode, n be the emission coefficient (1-2), k be the Boltzmann constant, T be the temperature, q be the space electron charge, V be the voltage across the diode's positive and negative terminals, and I be the voltage across the diode's negative terminals. S,R n is the reverse saturation current of a diode with leakage current. R Let n be the leakage emission coefficient. R ≥2.

[0098] Under non-ideal conditions, a diode can be reverse-biased, with a reverse breakdown current I. D,BR It can be represented as:

[0099]

[0100] Among them, I BR The breakdown inflection point current; V is the voltage across the positive and negative terminals of the diode, VBR n is the reverse breakdown voltage. BR The breakdown emission coefficient ranges from 0.95 to 1.02.

[0101] Therefore, without considering the series resistance (i.e., the grid line resistance and the contact resistance between the grid line and the doped layer), the current in the back contact solar cell 111 in this embodiment can be calculated by the following formula:

[0102]

[0103] In actual testing, due to the voltage division caused by the series resistance (gate line resistance, contact resistance between the gate line and the doped layer), when the applied voltage is V... W Let R be the line resistance of the gate line transmission of a pitch (PN cell). s Let x be the number of pitches through which the current flows, and assuming good contact between the gate line and the doped layer with minimal contact resistance, then the voltage division across the smallest unit diode is V = V0. w -xI D R s .

[0104] Therefore, taking into account the series resistance, the current of a single PN cell in the back contact battery in this embodiment can be calculated by the following formula:

[0105]

[0106] In the formula, V W For the applied voltage, R s The line resistance of the gate line transmission for a pitch (PN cell), where x is a variable characterizing the number of pitches between the positive gate line 31 and the first PAD point 51, is given by... Figure 6 For example, there are 6 first doped layers 21 and 6 second doped layers 22 between adjacent first PAD point 51 and second PAD point 52, totaling 6 PN units, then x = 6 ÷ 2 = 3.

[0107] It should be noted that in this embodiment, multiple first doped layers 21 and second doped layers 22 are provided on the back side of the back contact battery, which together with the silicon substrate 11 form multiple PN units, which can be approximated as being connected in parallel.

[0108] Therefore, when only one set of first PAD sections is provided on the back-contact solar cell 111 with z PN units (pitches), the measured current and voltage can be calculated by the following formula:

[0109]

[0110] Among them, I D2 The current measured when setting up a first set of PADs, V C2The voltage measured when setting up a first set of PADs.

[0111] If four sets of first PAD sections are set, the measured current and voltage can be calculated using the following formula:

[0112]

[0113] Among them, I D5 The current measured when setting up the first PAD section of the four groups, V C5 The voltage measured when setting up the first PAD section of the four groups.

[0114] From the above two equations, it can be unequivocally found that: I D5 >I D2 Therefore, for the same back-contact solar cell 111 under test, V C5 <V C2 That is, increasing the number of first PAD sections results in more accurate reverse breakdown voltage test results. Furthermore, increasing the number of test points can reduce test errors caused by broken grids such as the first shunt grid line 61 / second shunt grid line 62. However, as mentioned above, increasing the number of first test points is detrimental to improving conversion efficiency. Therefore, based on the above analysis, the inventors conducted extensive testing and proposed a specific correction method. Specifically, in one embodiment of this invention, the back contact solar cell 111 conforms to the following relationship:

[0115]

[0116] Among them, U rev U is the reverse breakdown voltage of the back contact solar cell 111. rev0 The reverse voltage of the back contact solar cell 111 is the test voltage. x is the total number of positive grid lines 31 and negative grid lines 32. x0 is a variable representing the first PAD section. x1 is the number of first PAD points 51. x2 is the number of second PAD points 52. A is a constant with a value range of 0.1 to 3.3. B is a constant with a value range of 2 to 50.

[0117] Based on the above relationship, the test results can be corrected to obtain an accurate reverse breakdown voltage when setting any group of first PAD sections. Specifically, research has found that when setting 1 to 4 groups of first PAD sections, the test error is ≤5%; when setting 4 to 6 groups, the test error is ≤3.5%; and when setting 8 to 10 groups, the test error is ≤1.5%.

[0118] In one embodiment, when multiple first PAD sections are provided, the multiple first PAD points 51 are evenly distributed along a first direction, which facilitates the uniform distribution of test current and avoids the phenomenon of excessively high reverse breakdown voltage during testing. Correspondingly, the multiple second PAD points 52 are also evenly distributed along the first direction.

[0119] In one embodiment, the first PAD point 51 is located at the first edge 13, and the second PAD point 52 is located at the second edge 14. It should be noted that both the positive gate line 31 and the negative gate line 32 have line resistance, resulting in voltage division on these gate lines after reverse current flows in. Furthermore, there is contact resistance between the positive gate line 31 and the first doped layer 21, and between the negative gate line 32 and the second doped layer 22, which also generates voltage division. Therefore, to more accurately characterize the reverse breakdown voltage of the back-contact solar cell 111, it is necessary to consider the voltage division due to gate line resistance and contact resistance. In this embodiment, the first PAD point 51 and the second PAD point 52 are located at the edge of the silicon substrate 1 in the second direction, while the positive gate line 31 and the negative gate line 32 extend along the second direction. Therefore, this embodiment allows the reverse current to flow through longer positive and negative gate lines 31 and 32 in the second direction, better characterizing the influence of gate line resistance voltage division and contact resistance voltage division on the reverse breakdown voltage.

[0120] It is understood that in this embodiment, the first PAD point 51 being located at the first edge 13 means that it is located close to the first edge 13. Specifically, the distance between the first PAD point 51 and the first edge 13 is 1mm to 10mm, such as 1.5mm, 3mm, 4.5mm, 6mm, 7.5mm, or 9mm, but is not limited to these. Specifically, the distance between the first PAD point 51 and the first edge 13 refers to the distance between the geometric center of the first PAD point 51 and the first edge 13.

[0121] It is understood that in this embodiment, the second PAD point 52 being located at the second edge 14 means that it is located close to the second edge 14. Specifically, the distance between the second PAD point 52 and the second edge 14 is 1mm to 10mm, with exemplary values ​​of 1.5mm, 3mm, 4.5mm, 6mm, 7.5mm, or 9mm, but not limited to these. Specifically, the distance between the second PAD point 52 and the second edge 14 refers to the distance between the geometric center of the second PAD point 52 and the second edge 14.

[0122] Specifically, in one embodiment, the back contact solar cell 111 further includes a first shunt grid line 61 and a second shunt grid line 62. The first shunt grid line 61 is electrically connected to a plurality of positive grid lines 31, and the second shunt grid line 62 is electrically connected to a plurality of negative grid lines 32. The first shunt grid line 61 is electrically connected to a first PAD point 51, and the second shunt grid line 62 is electrically connected to a second PAD point 52. Based on the above embodiment, the reverse current from the second PAD point 52 is shunted to a plurality of negative grid lines 32 via the second shunt grid line 62, and then flows through a plurality of positive grid lines 31 before being collected at the first PAD point 51 via the first shunt grid line 61. This achieves the effect of better characterizing the influence of grid line resistance voltage division and contact resistance voltage division on the accuracy of reverse breakdown voltage testing. In addition, it should be noted that when the number of first PAD points 51 is small, the number of PN cells passing through will also decrease accordingly. Although this test value can characterize the hot spot effect of the back contact solar cell 111 to some extent, it is not accurate enough. By introducing the first shunt grid line 61 and the second shunt grid line 62, the reverse current can flow through more PN cells, thereby effectively improving the accuracy of the test.

[0123] The first shunt grid line 61 and the second shunt grid line 62 can be straight or curved, and can be arranged parallel to the first direction or at an angle to the first direction, but are not limited thereto. Preferably, in one embodiment, the first shunt grid line 61 and the second shunt grid line 62 are straight and extend along the first direction, that is, they are parallel to the first direction. This reduces the length of the first shunt grid line 61 and the second shunt grid line 62 between the positive grid line 31 to be connected or the negative grid line 32 to be connected, and simplifies the grid line arrangement.

[0124] Preferably, in one embodiment, the width of the first shunt gate line 61 is greater than the width of the positive gate line 31, and the width of the second shunt gate line 62 is greater than the width of the negative gate line 32. This reduces the current loss caused by the first shunt gate line 61 and the second shunt gate line 62. Especially when the number of first PAD groups is small, this prevents excessive current loss caused by the first shunt gate line 61 and the second shunt gate line 62, ensuring that the test current is distributed to more positive gate lines 31 and negative gate lines 32 through the first shunt gate line 61 / second shunt gate line 62, thereby improving test accuracy. More preferably, the width of the first shunt gate line 61 is 1.5 to 3 times the width of the positive gate line 31, and the width of the second shunt gate line 62 is 1.5 to 3 times the width of the negative gate line 32.

[0125] In one embodiment, the first shunt gate line 61 is located at the first edge 13, and the second shunt gate line 62 is located at the second edge 14. This arrangement simplifies the gate structure and improves carrier collection efficiency and conversion efficiency. Since the first shunt gate line 61 / second shunt gate line 62 connects multiple positive gate lines 31 / negative gate lines 32 extending in the second direction, if the first shunt gate line 61 / second shunt gate line 62 were located in the center, multiple discontinuous insulation structures or other types of insulation structures would need to be set in the gate line regions with different polarities. This would complicate the gate structure, reduce the arrangement area of ​​the positive gate line 31 and the negative gate line 32, and decrease carrier collection.

[0126] It is understood that in this embodiment, the first shunt grid line 61 being located at the first edge 13 means that it is located close to the first edge 13. Specifically, the distance between the first shunt grid line 61 and the first edge 13 is 0.1mm to 3mm, exemplarily 0.5mm, 1mm, 1.5mm, 2mm, or 2.5mm, but not limited to these. Specifically, the distance between the first shunt grid line 61 and the first edge 13 refers to the distance between the centerline of the first shunt grid line 61 and the first edge 13.

[0127] It is understood that in this embodiment, the second shunt grid line 62 being located at the second edge 14 means that it is located close to the second edge 14. Specifically, the distance between the second shunt grid line 62 and the second edge 14 is 0.1mm to 3mm, exemplarily 0.5mm, 1mm, 1.5mm, 2mm, or 2.5mm, but not limited to these. Specifically, the distance between the second shunt grid line 62 and the second edge 14 refers to the distance between the centerline of the second shunt grid line 62 and the second edge 14.

[0128] Preferably, in one embodiment, the first shunt grid line 61 is disposed at the end of the positive grid line 31 near the first edge 13, that is, the positive grid line 31 and the negative grid line 32 are disposed on the side of the first shunt grid line 61 facing the second edge 14; and no other grid lines are disposed between the first shunt grid line 61 and the first edge 13. Based on the above configuration, the carrier collection area can be widened, and the conversion efficiency of the back contact solar cell 111 can be improved. In addition, the accuracy of the reverse breakdown voltage can also be improved.

[0129] Accordingly, in one embodiment, the second shunt grid line 62 is disposed at the end of the negative grid line 32 near the second edge 14, that is, the positive grid line 31 and the negative grid line 32 are disposed on the side of the second shunt grid line 62 facing the first edge 13, and no other grid lines are disposed between the second shunt grid line 62 and the second edge 14, so as to improve conversion efficiency and test accuracy.

[0130] It is foreseeable that, since the first shunt gate line 61 and the second shunt gate line 62 are located close to the edge of the back contact solar cell 111, there are fewer photogenerated carriers at the edge. Furthermore, since the first shunt gate line 61 and the second shunt gate line 62 extend along the first direction, opening them to contact the doped layer of the corresponding polarity would introduce more recombination losses. Therefore, the regions of the first shunt gate line 61 and the second shunt gate line 62 are not opened to contact the doped layer; they only serve as shunt / collector. Simultaneously, it is understandable that increasing the number of first PAD points 51 and second PAD points 52 can also reduce the impact of broken gates in the first shunt gate line 61 / second shunt gate line 62 on the test results.

[0131] Specifically, in one embodiment, when both the first PAD point 51 and the first shunt gate line 61 are located at the first edge 13, the distance between the first PAD point 51 and the first edge 13 is controlled to be greater than the distance between the first shunt gate line 61 and the first edge 13. Because the first PAD point 51 is relatively large and too close to the edge of the silicon substrate 1, it is prone to defects such as microcracks during printing. Furthermore, by controlling the first shunt gate line 61 to be closer to the first edge 13, a gap is formed between the first shunt gate line 61 and the first PAD point 51. A gate line can be placed within this gap, further improving the carrier collection efficiency and conversion efficiency. Specifically, based on this embodiment, the distance between the first PAD point 51 and the first edge 13 is controlled to be 3mm to 8mm, and the distance between the first shunt gate line 61 and the first edge 13 is controlled to be 0.2mm to 5mm.

[0132] Specifically, when a gap is formed between the first shunt gate line 61 and the first PAD point 51, the first shunt gate line 61 and the first PAD point 51 can be electrically connected through the first connecting gate line 71. Preferably, in one embodiment, the first connecting gate line 71 extends along the second direction and is located on the extension line of a positive gate line 31 to the first edge 13; that is, the first connecting gate line 71 is disposed above the first doped layer 21 corresponding to the positive gate line 31, and then the first connecting gate line 71 can be connected to the first doped layer 21 through the first hole 41, so that the first connecting gate line 71 can also collect carriers and improve the conversion efficiency.

[0133] Accordingly, in one embodiment, when both the second PAD point 52 and the second shunt gate line 62 are located at the second edge 14, the distance between the second PAD point 52 and the second edge 14 is controlled to be greater than the distance between the second shunt gate line 62 and the second edge 14. Since the second PAD point 52 is relatively large and too close to the edge of the silicon substrate 1, it is prone to defects such as microcracks during printing. Furthermore, by controlling the second shunt gate line 62 to be closer to the second edge 14, a gap is formed between the second shunt gate line 62 and the second PAD point 52. A gate line can be placed within this gap, further improving the carrier collection efficiency and conversion efficiency. Specifically, based on this embodiment, the distance between the second PAD point 52 and the second edge 14 is controlled to be 3mm to 8mm, and the distance between the second shunt gate line 62 and the second edge 14 is controlled to be 0.2mm to 5mm.

[0134] Specifically, when a gap is formed between the second shunt gate line 62 and the second PAD point 52, the second shunt gate line 62 and the second PAD point 52 can be electrically connected through the second connecting gate line 72. Preferably, in one embodiment, the second connecting gate line 72 extends along the second direction and is located on the extension line of a negative gate line 32 to the second edge 14; that is, the second connecting gate line 72 is disposed above the second doped layer 22 corresponding to the negative gate line 32, and then the second connecting gate line 72 can be connected to the second doped layer 22 through the second hole 42, so that the second connecting gate line 72 can also collect carriers and improve the conversion efficiency.

[0135] Specifically, in one embodiment, the positive grid line 31 includes a first positive sub-grid line 311, and the negative grid line 32 includes a first negative sub-grid line 321 disposed adjacent to the first positive grid line 31. A first PAD point 51 is located at the end of the first positive sub-grid line 311 near the first edge 13 and is electrically connected to the first positive grid line 311. A second PAD point 52 is located at the end of the first negative grid line 321 near the second edge and is electrically connected to the first negative grid line 321. Based on this embodiment, the first PAD point 51 and the second PAD point 52 in each group of first PAD portions are approximately located on the same straight line extending along the second direction, resulting in a more uniform stress distribution during printing and reducing the risk of chip cracking.

[0136] Specifically, in one embodiment, the first PAD point 51 is electrically connected to at least three first positive sub-gate lines 311; the second PAD point 52 is electrically connected to at least three first negative sub-gate lines 321. Although the first PAD point 51 / second PAD point 52 can distribute the reverse current through the first shunt gate line 61 / second shunt gate line 62, the first shunt gate line 61 / second shunt gate line 62 is relatively narrow, resulting in significant power consumption when the current density is too high. Therefore, connecting the first PAD point 51 / second PAD point 52 to at least three first positive sub-gate lines 311 / first negative sub-gate lines 321 optimizes the current distribution and improves test accuracy. More preferably, the first PAD point 51 is electrically connected to three first positive electrode grid lines 311; the second PAD point 52 is electrically connected to three first negative electrode grid lines 321. When the number of grid lines connected is too large, the size of the first PAD point 51 and the second PAD point 52 is too large, occupying a large area of ​​the grid lines for collecting charge carriers, which is not conducive to improving the conversion efficiency.

[0137] Preferably, in one embodiment, a second negative electrode gate line 322 extending in a second direction is further provided on at least one side of the first connecting gate line 71 in the first direction. The second negative electrode gate line 322 is electrically connected to at least one negative electrode gate line 32 near the first PAD point 51 and is insulated from the first PAD point 51. Through the second negative electrode gate line 322, charge carriers in the gap region between the first shunt gate line 61 and the first PAD point 51 can be collected, thereby improving the conversion efficiency. More preferably, in order to collect more charge carriers, the second negative electrode gate line 322 is disposed on the extension line of the first negative electrode gate line 321 connected to the second PAD point 52 towards the first edge 13; that is, the second negative electrode gate line 322 is disposed above the second doped layer 22 corresponding to the first negative electrode gate line 321, and then the second negative electrode gate line 322 can be connected to the second doped layer 22 through the second hole 42, so that the second negative electrode gate line 322 can also collect charge carriers, thereby improving the conversion efficiency.

[0138] Accordingly, in one embodiment, a second positive electrode gate line 312 extending along a second direction is further provided on at least one side of the second connecting gate line 72 in the first direction. The second positive electrode gate line 312 is electrically connected to at least one positive electrode gate line 31 near the second PAD point 52 and is insulated from the second PAD point 52. Through the second positive electrode gate line 312, charge carriers in the gap region between the second shunt gate line 62 and the second test PAD point can be collected, thereby improving the conversion efficiency. More preferably, in order to collect more charge carriers, the second positive electrode gate line 312 is disposed on the extension line of the first positive electrode gate line 311 connected to the first PAD point 51 towards the second edge 14; that is, the second positive electrode gate line 312 is disposed above the first doped layer 21 corresponding to the first positive electrode gate line 311, and then the second positive electrode gate line 312 can be connected to the first doped layer 21 through the first hole 41, so that the second positive electrode gate line 312 can also collect more charge carriers, thereby improving the conversion efficiency.

[0139] Specifically, in one embodiment, the back contact solar cell 111 further includes at least one set of second PAD portions, which are mainly used to connect the solder ribbon 112, so that the back contact solar cell 111 forms a cell string 110 and a cell assembly 100. Specifically, each set of second PAD portions includes a third PAD point 81 and a fourth PAD point 82, wherein the third PAD point 81 is electrically connected to at least one positive grid line 31 and is insulated from the negative grid line 32. The fourth PAD point 82 is electrically connected to at least one negative grid line 32 and is insulated from the positive grid line 31. That is, the third PAD point 81 is used to connect the positive solder ribbon 112, and the fourth PAD point 82 is used to connect the negative solder ribbon 112.

[0140] The positive grid line 31, electrically connected to the third PAD point 81, extends along the second direction with a distance of l4. Optionally, l4 / L ≤ 0.1. Based on this ratio, one aspect is to ensure an appropriate carrier transmission distance, reduce grid line transmission loss, and improve the power of the battery string 110 / battery assembly 100. Both aspects ensure a reasonable distribution of the third PAD point 81, improve welding pull force, and ensure the reliability of the battery assembly 100. For example, l4 / L is 0.01, 0.02, 0.04, 0.06, or 0.08, but is not limited to these. Preferably, l4 / L is 0.06 to 0.09.

[0141] The negative electrode grid line 32, electrically connected to the fourth PAD point 82, extends along the second direction with a distance of l5, and l5 / L ≤ 0.1. Based on this ratio, firstly, it ensures an appropriate carrier transport distance, reduces grid line transport losses, and increases the power of the battery string 110 / battery assembly 100. Secondly, it ensures a reasonable distribution of the fourth PAD point 82, increases welding pull force, and ensures the reliability of the battery assembly 100. Exemplarily, l5 / L is 0.01, 0.02, 0.04, 0.06, or 0.08, but is not limited to these. Preferably, l5 / L is 0.06 to 0.09.

[0142] Specifically, based on the above embodiments, the number of third PAD points 81 is 8 to 20, with 9, 11, 13, 15, 17 or 19 being exemplary, but not limited to these. More preferably, it is 12 to 20.

[0143] Accordingly, the number of fourth PAD points 82 is 8 to 20, with examples of 9, 11, 13, 15, 17 or 19, but not limited thereto. More preferably, it is 12 to 20.

[0144] Specifically, when a group of second PADs includes multiple third PAD points 81 and multiple fourth PAD points 82, the third PAD points 81 and fourth PAD points 82 are arranged alternately along the second direction. Based on this arrangement, the current transmission distance can be further optimized, losses reduced, and power increased. Furthermore, to simplify the electrode pattern and reduce printing stress, the multiple third PAD points 81 and fourth PAD points 82 in the same group are arranged in a row along the second direction.

[0145] Specifically, the second PAD portion can be disposed at the middle, edge, or other arbitrary position of the back contact solar cell 111. Preferably, in one embodiment, the silicon substrate 1 has a third edge 15 and a fourth edge 16 disposed opposite to each other in a first direction, and the second PAD portion is disposed at both the third edge 15 and the fourth edge 16. This arrangement can significantly improve the welding pull force and ensure the reliability of the cell string 110 / cell module 100.

[0146] It is understood that in this embodiment, the second PAD portion being located at the third edge 15 / fourth edge 16 means that both the third PAD point 81 and the fourth PAD point 82 are located close to the third edge 15 / fourth edge 16. More specifically, the distance between the third PAD point 81 / fourth PAD point 82 and the third edge 15 / fourth edge 16 is 1mm to 5mm, exemplarily 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, or 4.5mm, but not limited to these. It is understood that the distance between the third PAD point 81 / fourth PAD point 82 and the third edge 15 / fourth edge 16 refers to the distance between the geometric center of the third PAD point 81 / fourth PAD point 82 and the third edge 15 / fourth edge 16.

[0147] Preferably, in one embodiment, the geometric center of the third PAD point 81 closest to the first edge 13 and the geometric center of the first PAD point 51 located at the first edge 13 are located on the same straight line extending along the first direction and on the backlight surface 12; based on this embodiment, the first PAD point 51 can also be used for welding, which can further improve the welding pull force.

[0148] Accordingly, in one embodiment, the geometric center of the fourth PAD point 82 closest to the second edge 14 and the geometric center of the second PAD point 52 located at the second edge 14 are located on the same straight line extending along the first direction and on the backlight surface 12. Based on this embodiment, the second PAD point 52 can also be used for welding, which can further improve the welding pull force.

[0149] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the described embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0150] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A back-contact solar cell, characterized in that, include: A silicon substrate, comprising a light-receiving surface and a back-lighting surface disposed opposite to each other; It has a first edge and a second edge in the second direction; Multiple first doped layers and multiple second doped layers are disposed on the backlight surface. The multiple first doped layers and multiple second doped layers are alternately arranged along a first direction and extend along a second direction. The second doped layer makes composite contact with the first doped layer at a preset position to form a leakage composite contact structure. The first direction and the second direction intersect. Multiple positive gate lines and multiple negative gate lines, wherein the positive gate lines are disposed on the first doped layer and the negative gate lines are disposed on the second doped layer; and At least one set of first PAD sections, so that current can be passed through the first PAD sections and flow through the leakage composite contact structure; Each group of first PADs includes a first PAD point and a second PAD point. The first PAD point is electrically connected to at least one of the positive grid lines, and the second PAD point is electrically connected to at least one of the negative grid lines. The positive grid line electrically connected to the first PAD point extends along the second direction, with an extension distance of l1; the distance between the first edge and the second edge is L, and l1 / L≥0.9; The negative grid line electrically connected to the second PAD point extends along the second direction, with an extension distance of l2; l2 / L≥0.

9.

2. The back-contact solar cell as described in claim 1, characterized in that, include: The relative distance between the first PAD point and the second PAD point in the second direction is l3, 0.9≤l1 / l3<1, 0.9≤l2 / l3<1.

3. The back-contact solar cell as described in claim 1, characterized in that, The first PAD point is located at the first edge, and the second PAD point is located at the second edge.

4. The back-contact solar cell as described in claim 1, characterized in that, Includes the first PAD section of groups 1 to 12.

5. The back-contact solar cell according to any one of claims 1 to 4, characterized in that, The back-contact solar cell conforms to the following relationship: Among them, U rev U is the reverse breakdown voltage of the back-contact solar cell. rev0 The reverse voltage of the back-contact solar cell is denoted by x, which is the total number of positive and negative grid lines. x0 is a variable representing the first PAD section, x1 is the number of the first PAD points, x2 is the number of the second PAD points, A is a constant with a value ranging from 0.1 to 3.3, and B is a constant with a value ranging from 2 to 50.

6. The back-contact solar cell as described in claim 4, characterized in that, When multiple first PADs are provided, the multiple first PADs are evenly distributed along the first direction; the multiple second PADs are evenly distributed along the first direction.

7. The back-contact solar cell as described in claim 1, characterized in that, Also includes: A first shunt gate line and a second shunt gate line, wherein the first shunt gate line is electrically connected to a plurality of positive gate lines and the second shunt gate line is electrically connected to a plurality of negative gate lines; The first shunt gate line is electrically connected to the first PAD point, and the second shunt gate line is electrically connected to the second PAD point.

8. The back-contact solar cell as described in claim 7, characterized in that, The first shunt grid line is located at the first edge, and the positive grid line and the negative grid line are located on the side of the first shunt grid line facing the second edge; The second shunt grid line is located at the second edge, and the positive grid line and the negative grid line are located on the side of the second shunt grid line facing the first edge.

9. The back-contact solar cell as described in claim 8, characterized in that, No grid line is provided between the first shunt grid line and the first edge; No grid line is provided between the second shunt grid line and the second edge.

10. The back-contact solar cell as described in claim 7, characterized in that, The width of the first shunt gate line is greater than the width of the positive gate line, and the width of the second shunt gate line is greater than the width of the negative gate line.

11. The back-contact solar cell as described in claim 7, characterized in that, The distance between the first PAD point and the first edge is greater than the distance between the first shunt grid line and the first edge; The distance between the second PAD point and the second edge is greater than the distance between the second shunt grid line and the second edge.

12. The back-contact solar cell as described in claim 11, characterized in that, The distance between the first PAD point and the first edge is 3mm to 5mm; the distance between the second PAD point and the second edge is 3mm to 5mm; The distance between the first shunt grid line and the first edge is 0.2mm to 2mm, and the distance between the second shunt grid line and the second edge is 0.2mm to 2mm.

13. The back-contact solar cell as described in claim 7, characterized in that, The first PAD point is electrically connected to the first shunt grid line through the first connecting grid line; The second PAD point is electrically connected to the second shunt grid line through the second connecting grid line.

14. The back-contact solar cell as described in claim 13, characterized in that, The first connecting gate line is located on the extension line of a positive gate line toward the first edge; The second connecting gate line is located on the extension line of a negative gate line toward the second edge.

15. The back-contact solar cell as described in claim 13, characterized in that, The positive grid line includes a first positive sub-grid line, and the first PAD point is located at the end of the first positive grid line and is electrically connected to the first positive grid line. The negative grid line includes a first negative sub-grid line, and the second PAD point is located at the end of the first negative grid line and is electrically connected to the first negative grid line. The first positive electrode grid line is arranged adjacent to the first negative electrode grid line.

16. The back-contact solar cell as described in claim 15, characterized in that, The first PAD point is electrically connected to at least three first positive electrode grid lines. The second PAD point is electrically connected to at least three first negative electrode grid lines.

17. The back-contact solar cell as described in claim 15, characterized in that, The first connecting gate line is further provided with a second negative electrode gate line extending in a second direction on at least one side in the first direction. The second negative electrode gate line is electrically connected to at least one negative electrode gate line near the first PAD point and is insulated from the first PAD point; and / or The second connecting grid line is further provided with a second positive sub-grid line extending along the second direction on at least one side in the first direction. The second positive sub-grid line is electrically connected to at least one positive grid line near the second PAD point and is insulated from the second PAD point.

18. The back-contact solar cell as described in claim 17, characterized in that, The second negative electrode grid line is located on the extension line of the first negative electrode grid line connected to the second PAD point towards the first edge; and / or The second positive electrode grid line is located on the extension line of the first positive electrode grid line connected to the first PAD point to the second edge.

19. The back-contact solar cell as described in claim 1, characterized in that, The first PAD point and the second PAD point are square, circular, triangular or irregular in shape.

20. The back-contact solar cell as described in claim 1, characterized in that, The first PAD point and the second PAD point are square, with a width of 0.1mm to 1mm.

21. The back-contact solar cell as described in claim 1, characterized in that, Also includes: At least one set of second PAD sections, which includes a plurality of third PAD points and a fourth PAD point; the third PAD point is electrically connected to at least one positive grid line and is insulated from the negative grid line; the fourth PAD point is electrically connected to at least one negative grid line and is insulated from the positive grid line. The positive grid line electrically connected to the third PAD point extends along the second direction, with an extension distance of l4; and l4 / L≤0.1; The negative grid line electrically connected to the fourth PAD point extends along the second direction, with an extension distance of l5, and l5 / L≤0.

1.

22. The back-contact solar cell as described in claim 21, characterized in that, The silicon substrate has a third edge or a fourth edge that are disposed opposite to each other in a first direction; The second PAD portion is provided at the third edge and the fourth edge.

23. The back-contact solar cell as described in claim 22, characterized in that, The geometric center of the third PAD point closest to the first edge and the geometric center of the first PAD point located at the first edge are located on the same straight line extending along the first direction and on the backlight surface. The geometric center of the fourth PAD point closest to the second edge and the geometric center of the second PAD point located at the second edge are located on the same straight line extending along the first direction and on the backlight surface.

24. A battery string, characterized in that, Including the back-contact solar cell as described in any one of claims 1 to 23.

25. A battery assembly, characterized in that, It includes a back-contact solar cell as described in any one of claims 1 to 23 or a battery string as described in claim 24.

26. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 25.

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