Solar cell, module and system

Abstract

The present disclosure provides a solar cell, a module and a system. The solar cell comprises a silicon substrate, first doped layers, second doped layers, positive electrode grid lines, negative electrode grid lines and a first PAD portion. The second doped layers are in recombination contact with the first doped layers at predetermined positions, so as to form leakage recombination contact structures. A first PAD point and a second PAD point of the first PAD portion are electrically and respectively connected to at least one positive electrode grid line and at least one negative electrode grid line.

Description

Solar cell, module and system

[0001] Priority information

[0002] The present disclosure claims priority to and the benefit of the patent application No. 202411268533.8 filed with the China National Intellectual Property Office on September 10, 2024, and incorporates it herein by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates to the field of silicon solar cells, in particular to a solar cell, module and system. BACKGROUND

[0004] When one or more solar cell pieces (or sub-pieces) in a photovoltaic module are partially or completely shaded, the shaded solar cell pieces (sub-pieces) will exhibit a voltage reverse bias characteristic and become a load, consuming the power generated by the normal solar cells, thereby generating a large amount of heat, causing the temperature of the solar cell pieces to be too high, which is commonly referred to as the hot spot effect. In order to solve the hot spot problem in the prior art, a diode is generally connected in anti-parallel at both ends of a string unit, thereby reducing the current of the shaded solar cell and weakening the hot spot effect. However, the parallel diode will cause power loss. In order to solve this problem, one possible approach is to directly form a leakage recombination contact structure on the solar cell piece (see CN117976743B), that is, to form a partial contact between the differently doped layers during the fabrication of the solar cell piece, thereby effectively reducing the reverse voltage at both ends of the shaded solar cell piece and reducing heat generation, thereby weakening the hot spot effect. After using this method, the control of the hot spot effect can be moved to the solar cell piece end. Therefore, how to evaluate the hot spot effect at the solar cell piece end has become a technical problem to be solved by those skilled in the art.

[0005] On the other hand, in terms of conventional hot spot effect testing, any one or more solar cell pieces (or sub-pieces) in a solar cell module are generally shaded, and the other solar cell pieces (or sub-pieces) receive light, and after a certain period of time, the temperature of the shaded solar cell sub-pieces is tested to characterize the hot spot effect. This is obviously not suitable for testing the hot spot effect at the solar cell end. SUMMARY

[0006] The technical problem to be solved by the present disclosure is to provide a back contact solar cell, module and photovoltaic system, which can quantitatively evaluate the hot spot effect at the cell end.

[0007] In order to solve the above problems, the present disclosure discloses a back contact solar cell, comprising:

[0008] a silicon substrate comprising a light-receiving surface and a back surface arranged oppositely and having a first edge and a second edge arranged oppositely in a second direction;

[0009] a plurality of first doped layers and a plurality of second doped layers disposed on the back surface, the first doped layers and the second doped layers being alternately arranged along a first direction, and each of the first doped layers and at least part of the second doped layers extending along a second direction; the second doped layers being in composite contact with the first doped layers at preset positions to form a leakage composite contact structure; the first direction intersecting the second direction;

[0010] a plurality of positive gate lines and a plurality of negative gate lines, the positive gate lines being disposed on the first doped layers, and the negative gate lines being disposed on the second doped layers; and

[0011] at least one first PAD part, the first PAD part being used for passing current and the current flowing through the leakage composite contact structure;

[0012] wherein each of the first PAD parts comprises a first PAD point and a second PAD point, the first PAD point being electrically connected with at least one of the positive gate lines, and the second PAD point being electrically connected with at least one of the negative gate lines;

[0013] the positive gate line electrically connected with the first PAD point extending along the second direction and having an extension distance of l1, a distance between the first edge and the second edge being L, and l1 / L≥0.9;

[0014] the negative gate line electrically connected with the second PAD point extending along the second direction and having an extension distance of l2, and l2 / L≥0.9.

[0015] In some embodiments, a relative distance between the first PAD point and the second PAD point in the second direction is l3, and 0.9≤l1 / l3<1, 0.9≤l2 / l3<1.

[0016] In some embodiments, the first PAD point is disposed close to the first edge, and the second PAD point is disposed close to the second edge.

[0017] In some embodiments, the number of the first PAD parts is 1-12.

[0018] In some embodiments, the back contact solar cell satisfies the following relationship:

[0019] wherein U rev is a reverse breakdown voltage of the back contact solar cell, U rev0 is a test reverse voltage of the back contact solar cell, x is a total number of the positive gate lines and the negative gate lines, x0 is a variable representing the first PAD part, x1 is a number of the first PAD points, x2 is a number of the second PAD points, A is a constant, and a value range of A is 0.1-3.3, B is a constant, and a value range of B is 2-50.

[0020] In some embodiments, when a plurality of first PAD portions are provided, the plurality of first PAD points are uniformly distributed along the first direction with equal intervals, and the plurality of second PAD points are uniformly distributed along the first direction with equal intervals.

[0021] In some embodiments, the back contact solar cell further comprises: a first shunt grid line and a second shunt grid line; the first shunt grid line is electrically connected with the plurality of positive grid lines, and the second shunt grid line is electrically connected with the plurality of negative grid lines; the first shunt grid line is electrically connected with the first PAD point, and the second shunt grid line is electrically connected with the second PAD point.

[0022] In some embodiments, the first shunt grid line is arranged at the first edge, and the positive grid lines and the negative grid lines are arranged on a side of the first shunt grid line facing the second edge; the second shunt grid line is arranged close to the second edge, and the positive grid lines and the negative grid lines are arranged on a side of the second shunt grid line facing the first edge.

[0023] In some embodiments, no grid line is arranged between the first shunt grid line and the first edge, and no grid line is arranged between the second shunt grid line and the second edge.

[0024] In some embodiments, a width of the first shunt grid line in the second direction is greater than a width of the positive grid line in the first direction, and a width of the second shunt grid line in the second direction is greater than a width of the negative grid line in the first direction.

[0025] In some embodiments, a distance between the first PAD point and the first edge is greater than a distance between the first shunt grid line and the first edge; and a distance between the second PAD point and the second edge is greater than a distance between the second shunt grid line and the second edge.

[0026] In some embodiments, the distance between the first PAD point and the first edge is 3mm-5mm, and the distance between the second PAD point and the second edge is 3mm-5mm; the distance between the first shunt grid line and the first edge is 0.2mm-2mm, and the distance between the second shunt grid line and the second edge is 0.2mm-2mm.

[0027] In some embodiments, the first PAD point is electrically connected with the first shunt grid line through a first connecting grid line, and the second PAD point is electrically connected with the second shunt grid line through a second connecting grid line.

[0028] In some embodiments, the first connecting grid line is located on an extension line of a positive grid line towards the first edge, and the second connecting grid line is located on an extension line of a negative grid line towards the second edge.

[0029] In some embodiments, the positive grid lines include first positive sub-grid lines, the first PAD point is arranged at an end of the first positive sub-grid line and electrically connected with the first positive sub-grid line; the negative grid lines include first negative sub-grid lines, the second PAD point is arranged at an end of the first negative sub-grid line and electrically connected with the first negative sub-grid line; the first positive sub-grid lines are arranged adjacent to the first negative sub-grid lines.

[0030] In some embodiments, the first PAD point is electrically connected with at least 3 first positive sub-grid lines; the second PAD point is electrically connected with at least 3 first negative sub-grid lines.

[0031] In some embodiments, the back contact solar cell further satisfies at least one of the following:

[0032] The at least one side of the first connection grid line in the first direction is further provided with a second negative sub-grid line extending in the second direction, the second negative sub-grid line is electrically connected with at least one negative grid line close to the first PAD point and is insulated from the first PAD point;

[0033] The at least one side of the second connection grid line in the first direction is further provided with a second positive sub-grid line extending in the second direction, the second positive sub-grid line is electrically connected with at least one positive grid line close to the second PAD point and is insulated from the second PAD point.

[0034] In some embodiments, the back contact solar cell further satisfies at least one of the following:

[0035] The second negative sub-grid line is located on an extension line of the first negative sub-grid line connected with the second PAD point to the first edge;

[0036] The second positive sub-grid line is located on an extension line of the first positive sub-grid line connected with the first PAD point to the second edge.

[0037] In some embodiments, the first PAD point is square, circular, triangular or irregular, and the second PAD point is square, circular, triangular or irregular.

[0038] In some embodiments, the first PAD point is square, and the width of the first PAD point in the first direction or the second direction is 0.1mm-1mm; the second PAD point is square, and the width of the second PAD point in the first direction or the second direction is 0.1mm-1mm.

[0039] In some embodiments, the back contact solar cell further comprises:

[0040] The at least one second PAD part includes a plurality of third PAD points and fourth PAD points, the third PAD points are electrically connected with at least one positive grid line and are insulated from negative grid lines, the fourth PAD points are electrically connected with at least one negative grid line and are insulated from positive grid lines;

[0041] The positive electrode grid line electrically connected with the third PAD point extends along the second direction and has an extension distance of l4, and l4 / L≤0.1;

[0042] The negative electrode grid line electrically connected with the fourth PAD point extends along the second direction and has an extension distance of l5, and l5 / L≤0.1.

[0043] In some embodiments, the silicon substrate has a third edge or a fourth edge oppositely arranged in the first direction; the second PAD part is arranged near the third edge and near the fourth edge.

[0044] In some embodiments, the geometric center of the third PAD point closest to the first edge and the geometric center of the first PAD point arranged at the first edge are arranged on the same line extending along the first direction and located on the back surface of the backlight;

[0045] The geometric center of the fourth PAD point closest to the second edge and the geometric center of the second PAD point arranged at the second edge are arranged on the same line extending along the first direction and located on the back surface of the backlight.

[0046] Optionally, the application further discloses a battery string comprising the back contact solar cell.

[0047] Optionally, the application further discloses a battery assembly comprising the back contact solar cell or the battery string.

[0048] Optionally, the application further discloses a photovoltaic system comprising the battery assembly.

[0049] The application has the following beneficial effects:

[0050] The back contact solar cell comprises a plurality of first doped layers and a plurality of second doped layers arranged on the back surface of the silicon substrate, wherein the second doped layer is in complex contact with the first doped layer at a preset position to form a leakage complex contact structure; in addition, at least one first PAD part is arranged on the back surface of the silicon substrate, each first PAD part comprising a first PAD point and a second PAD point, the first PAD point being electrically connected with at least one positive electrode grid line, and the second PAD point being electrically connected with at least one negative electrode grid line. Based on the technical scheme of the embodiment, reverse current can be passed through the first PAD point and the second PAD point and flow through the leakage complex contact structure, and then the reverse breakdown voltage of the back contact solar cell is obtained by testing, which provides a good basis for characterizing the hot spot effect at the battery end. BRIEF DESCRIPTION OF DRAWINGS

[0051] Fig. 1 is a schematic diagram of a photovoltaic system in an embodiment of the present application;

[0052] Fig. 2 is a schematic diagram of a back contact solar cell assembly in an embodiment of the present application;

[0053] Fig. 3 is a schematic diagram of a structure of a back contact solar cell string in an embodiment of the present disclosure;

[0054] Fig. 4 is a schematic diagram of a structure of a back contact solar cell string in another embodiment of the present disclosure;

[0055] Fig. 5 is a schematic diagram of a structure of a back contact solar cell in an embodiment of the present disclosure;

[0056] Fig. 6 is a schematic diagram of a structure of a first doped layer and a second doped layer in an embodiment of the present disclosure;

[0057] Fig. 7 is a schematic diagram of a cross-sectional structure of a back contact solar cell in an embodiment of the present disclosure;

[0058] In the figures, 100, a cell assembly; 110, a cell string; 120, a busbar; 111, a back contact solar cell; 112, a solder strip; 1, a silicon substrate; 11, a light-receiving surface; 12, a back surface; 13, a first edge; 14, a second edge; 15, a third edge; 16, a fourth edge; 21, a first doped layer; 22, a second doped layer; 23, a spacing region; 24, a leakage recombination contact structure; 25, a preset position; 31, a positive grid line; 311, a first positive sub-grid line; 312, a second positive sub-grid line; 32, a negative grid line; 321, a first negative sub-grid line; 322, a second negative sub-grid line; 40, an insulating layer; 41, a first hole; 42, a second hole; 51, a first PAD point; 52, a second PAD point; 61, a first shunt grid line; 62, a second shunt grid line; 71, a first connection grid line; 72, a second connection grid line; 81, a third PAD point; 82, a fourth PAD point. DETAILED DESCRIPTION

[0059] In order to make the objects, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. The examples of the embodiments are shown in the accompanying drawings, wherein identical or similar reference numerals designate identical or similar elements or elements having identical or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be understood as limiting the present application. In addition, it should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0060] 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.

[0061] 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.

[0062] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0063] 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.

[0064] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For purposes of simplicity of the present disclosure, the description that follows uses specific examples and / or uses specific terminology in describing the components and arrangement of the specific examples. Of course, such specific examples are only examples and are not intended to limit the present application in any way. Furthermore, the present application can be used in any number of different examples with varying components and / or arrangements. Additionally, the present application provides examples of various specific processes and materials. One of ordinary skill in the art, however, can recognize that other processes and / or materials can be used without departing from the scope of the present application.

[0065] Referring to FIG. 1, a photovoltaic system in an embodiment of the present disclosure includes a cell assembly 100 in an embodiment of the present application. A plurality of cell assemblies 100 can be connected in series or in parallel through a junction box to form a photovoltaic system. The photovoltaic system can be used in a photovoltaic power station, such as a ground power station, a roof power station, a water surface power station, etc., and can also be applied to devices or apparatuses that use solar energy to generate electricity, such as a user solar power source, a solar street lamp, a solar car, a solar building, etc., but is not limited thereto.

[0066] Referring to FIGS. 2 to 4, the cell assembly 100 in an embodiment of the present disclosure includes at least one cell string 110 in an embodiment of the present disclosure or at least one back contact solar cell 111 in an embodiment of the present disclosure. Optionally, in an embodiment, the cell assembly 100 is composed of a plurality of the above-mentioned cell strings 110, and exemplary numbers of the cell strings 110 are 2, 4, 6, or 12, but are not limited thereto. The plurality of cell strings 110 can be connected in series or in parallel through busbars 120, solder strips 112, or other conductive media to form the cell assembly 100. In addition, in order to mechanically connect the plurality of cell strings 110 and meet other use requirements of the assembly (such as electrical connection of a plurality of cell assemblies 100, weather resistance, etc.), insulating glue, a junction box, a frame, a back plate, a film, glass, etc. are also required, but are not limited thereto.

[0067] Referring to FIGS. 3 and 4, the cell string 110 in an embodiment of the present disclosure includes a plurality of back contact solar cells 111 in an embodiment of the present disclosure or cut pieces formed by cutting the back contact solar cells 111. Referring to FIG. 3, adjacent back contact solar cells 111 (or cut pieces thereof) can be overlapped to form the cell string 110 and connected in series or in parallel through solder strips 112 or conductive glue, but are not limited thereto. Referring to FIG. 4, adjacent back contact solar cells 111 (or cut pieces thereof) can be connected in series or in parallel through solder strips 112 or conductive glue, but are not limited thereto.

[0068] Since the back surface 12 of the back contact solar cell 111 is provided with the positive grid lines and the negative grid lines, in order to prevent the solder strip 112 from short-circuiting the two, an insulating glue or an insulating block can also be introduced, but is not limited thereto. In order to meet the fixation of the solder strip 112, an adhesive (such as UV glue for example), solder paste, etc. can also be introduced. In order to achieve the fixation of the back contact solar cells of the cell string 110, an adhesive, etc. can also be introduced, but is not limited thereto.

[0069] Optionally, referring to FIGS. 5-7, an embodiment of the present disclosure discloses a back contact solar cell 111, which comprises a silicon substrate 1, a plurality of first doped layers 21, a plurality of second doped layers 22, a plurality of positive grid lines 31, and a plurality of negative 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, and can be N-type monocrystalline silicon, for example.

[0070] The silicon substrate 1 comprises an opposite light-receiving surface 11 and a back surface 12.

[0071] The first doped layers 21 and the second doped layers 22 are arranged on the back surface 12. The first doped layers 21 and the second doped layers 22 are alternately arranged along a first direction, and the first doped layers 21 and at least part of the second doped layers 22 extend along a second direction. The first direction intersects the second direction, and the first direction can be a vertical direction and the second direction can be a horizontal direction, but is not limited thereto.

[0072] The first doped layers 21 and the second doped layers 22 are provided with a spacing region 23 to achieve insulation between the first doped layers 21 and the second doped layers 22.

[0073] The first doped layers 21 can 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 are not limited thereto. The first doped layers 21 can be a P-type doped polycrystalline silicon layer. The P-type doped element in the first doped layers 21 can be B, Al, or Ga, but is not limited thereto, and can be B, for example.

[0074] The second doped layers 22 can be an N-type doped polycrystalline silicon layer, an N-type doped amorphous silicon layer, or an N-type doped microcrystalline silicon layer, but are not limited thereto. The second doped layers 22 can be an N-type doped polycrystalline silicon layer. The N-type doped element in the second doped layers 22 can be P, As, or Sb, but is not limited thereto, and can be P, for example.

[0075] Optionally, referring to FIG. 6, in this embodiment, at least one second doped layer 22 is in recombination contact with the first doped layer 21 at a preset position 25 to form a recombination contact structure 24. Based on the recombination contact structure 24, the reverse voltage across the back contact solar cell 111 at the peak current can be reduced, the heat generation power can be reduced, the probability of hot spot occurrence can be reduced, and the temperature of the hot spot area when the hot spot occurs can be reduced.

[0076] Optionally, in one embodiment, at the preset position 25, the first doped layer 21 can be extended to the doped layer (second doped layer 22) of another polarity, or the second doped layer 22 can be extended to the doped layer (first doped layer 21) of another polarity, so as to form a leakage recombination contact structure 24.

[0077] In another embodiment, a functional layer with a conductive effect is formed at the preset position 25, so that the first doped layer 21 and the second doped layer 22 are in contact to form a leakage recombination contact structure 24.

[0078] In yet another embodiment, the leakage recombination contact structure 24 can be formed by the stacked structure of the first doped layer 21 and the second doped layer 22. Optionally, 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 the stacked structure is used, a dielectric layer can also be arranged between the first doped layer 21 and the second doped layer 22. The dielectric layer can be a film layer with a tunneling effect, such as a silicon oxide tunneling passivation layer, but is not limited thereto. Optionally, at the preset position 25, the second doped layer 22 is stacked on the first doped layer 21 to form a leakage recombination contact structure 24. Based on this structure, the leakage recombination contact structure 24 can be formed by an etching process of the second doped layer 22, which is simple in process and strong in reliability.

[0079] The positive gate line 31 can be a silver gate line, an aluminum gate line, a copper gate line, or a silver-coated copper gate line, but is not limited thereto. The positive gate line 31 is arranged above the first doped layer 21 and in contact with the first doped layer 21. Optionally, referring to FIG. 7, in one embodiment, an insulating layer 40 is further arranged between the positive gate line 31 and the first doped layer 21. The positive gate line 31 is in contact with the first doped layer 21 through a first hole 41 arranged on the insulating layer 40. The first hole 41 can be formed by a laser process, an etching process, or a slurry burning process, but is not limited thereto.

[0080] The negative gate line 32 can be a silver gate line, an aluminum gate line, a copper gate line, or a silver-coated copper gate line, but is not limited thereto. Optionally, referring to FIG. 7, in one embodiment, an insulating layer 40 is further arranged between the negative gate line 32 and the second doped layer 22. The negative gate line 32 is in contact with the second doped layer 22 through a second hole 42 arranged on the insulating layer 40. The second hole 42 can be formed by a laser process, an etching process, or a slurry burning process, but is not limited thereto.

[0081] Referring to FIG. 5, in the present embodiment, the back contact solar cell 111 comprises at least one first PAD part, each first PAD part comprising a first PAD point 51 and a second PAD point 52. By injecting a reverse current through the first PAD point 51 and the second PAD point 52 and flowing through the leakage recombination contact structure 24, the reverse breakdown voltage of the back contact solar cell 111 can be tested, which provides a good basis for characterizing the hot spot effect at the cell end.

[0082] It should be noted that the conventional hot spot test is generally performed at the module end, i.e., any one or more solar cells in the solar cell module are shaded, and other solar cells (or pieces) receive light, and after a certain period of time, the temperature of the shaded solar cell (or piece) is tested to characterize the hot spot effect. The prior art is difficult to accurately quantify and characterize the hot spot effect at the cell end, and the present embodiment measures the reverse breakdown voltage after introducing the leakage recombination contact structure 24, which fully expresses the influence of the leakage recombination contact structure 24 on the reverse breakdown voltage, and further quantifies and characterizes the hot spot effect through the reverse breakdown voltage, which provides a good basis for controlling the hot spot effect of the module.

[0083] As a possible implementation, the first PAD point 51 and the second PAD point 52 are not in contact with the first doped layer 21 and the second doped layer 22 thereunder. Optionally, 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 can include one or more of an aluminum oxide layer, an amorphous silicon layer, a silicon oxide layer, and a silicon nitride layer. As another possible way, the first PAD point 51 and the second PAD point 52 can be in contact with the first doped layer 21 and the second doped layer 22 thereunder.

[0084] The positive grid line 31 electrically connected to the first PAD point 51 extends along the second direction, and the extension distance is l1; the distance between the first edge 13 and the second edge 14 is L, and l1 / L≥0.9; the negative grid line 32 electrically connected to the second PAD point 52 extends along the second direction, and the extension distance is l2; l2 / L≥0.9. By controlling the extension distance, the reverse current can flow more through the leakage recombination contact structure 24 at the preset position 25, and the influence of the leakage recombination contact structure 24 on the reverse breakdown voltage can be more accurately characterized, and the hot spot effect can be evaluated. At the same time, by controlling the ratio, the back contact solar cell 111 can collect more photo-generated carriers during use, and thus the conversion efficiency can be improved.

[0085] Exemplarily, the l1 / L is 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, but is not limited thereto, and is optionally 0.93-0.95. Exemplarily, the l2 / L is 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, but is not limited thereto, and is optionally 0.93-0.95.

[0086] Optionally, in an embodiment, the relative distance of the first PAD point 51 and the second PAD point 52 in the second direction is l3, 0.9≤l1 / l3<1, 0.9≤l2 / l3<1, so as to further improve the accuracy of the test reverse breakdown voltage and further improve the collection efficiency of the carriers and improve the conversion efficiency of the back contact solar cell 111. Exemplarily, the l1 / l3 is 0.93, 0.95, 0.96, 0.97, 0.98 or 0.99, but is not limited thereto, and is optionally 0.97-0.99. Exemplarily, the l2 / l3 is 0.93, 0.95, 0.96, 0.97, 0.98 or 0.99, but is not limited thereto, and is optionally 0.97-0.99. It should be noted that the relative distance of the first PAD point 51 and the second PAD point 52 in the second direction in the embodiment refers to the projection distance of the geometric centers of the two in the second direction.

[0087] Optionally, the first PAD point 51 and the second PAD point 52 are square, circular, triangular or irregular, but are not limited thereto. Optionally, in an embodiment, the first PAD point 51 and the second PAD point 52 are square, and the width of the first PAD point 51 and the second PAD point 52 can be 0.1mm-1mm. Based on the width, the first PAD point 51 and the second PAD point 52 can form good contact with the test probe of the test device. The test probe refers to the probe in the test equipment for injecting current. The width of the first PAD point 51 can be the width of the first PAD point 51 in the first direction or the second direction, and the width of the second PAD point 52 can be the width of the second PAD point 52 in the first direction or the second direction.

[0088] Optionally, the first PAD part in the embodiment can be one or more. It can be understood that when the number is large, the test result of the reverse breakdown voltage is more accurate, but a large number of first test points also means that more areas of the back light surface 12 are occupied, and the area for arranging the positive grid line 31 and the negative grid line 32 is less, which is not conducive to the conversion efficiency. Optionally, considering the conversion efficiency and test accuracy, the number of the first PAD point 51 is set to 1-12, exemplarily 1, 3, 5, 7 or 9, but is not limited thereto, and is optionally 1-4.

[0089] The following further illustrates the effect of the number of first PAD sections on the reverse breakdown voltage test results:

[0090] For an ideal diode, the current can be calculated by the following formula:

[0091] In the formula, I DD is the current flowing from the anode to the cathode in the ideal diode, I s is the reverse saturation current of the ideal diode; n is the emission coefficient, which is 1-2; k is the Boltzmann constant, T is the temperature, q is the spatial electronic charge, and V is the voltage between the anode and the cathode of the ideal diode.

[0092] After introducing the leakage current composite contact structure 24, the current of the diode with leakage current can be calculated by the following formula:

[0093] In the formula, I D is the output current of the diode with leakage current, I DD is the current flowing from the anode to the cathode in the ideal diode, I DR is the current flowing from the anode to the cathode in the ideal diode, I S is the reverse saturation current of the ideal diode, n is the emission coefficient, which is 1-2; k is the Boltzmann constant, T is the temperature, q is the spatial electronic charge, and V is the voltage between the anode and the cathode of the diode, I S,R is the reverse saturation current of the diode with leakage current, n R is the leakage emission coefficient, n R ≥ 2.

[0094] Under non-ideal conditions, the diode can be reversely broken down, and the reverse breakdown current I D,BR can be expressed as:

[0095] In the formula, I BR is the breakdown inflection current; V is the voltage between the anode and the cathode of the diode, V BR is the reverse breakdown voltage, n BR is the breakdown emission coefficient, which is 0.95-1.02.

[0096] Therefore, without considering the series resistance (i.e., the gate line resistance and the contact resistance between the gate line and the doped layer), the current in the back contact solar cell 111 of the embodiment can be calculated by the following formula:

[0097] In actual tests, due to the voltage division of the series resistance (the gate line resistance and the contact resistance between the gate line and the doped layer), when the applied voltage is V W , it is assumed that the line resistance of the gate line of one pitch (PN unit) is Rs , x is the number of pitches through which the current flows, and the grid line and the doped layer are in good contact, and the contact resistance is extremely small, then the voltage across the minimum unit diode is V = V w - xI D R s .

[0098] Therefore, the current of a single PN unit in the back contact cell in the embodiment can be calculated by the following formula after taking into account the series resistance:

[0099] In the formula, V W is the applied voltage, R s is the line resistance of the grid line of one pitch (PN unit), and x is a variable representing the number of pitches between the positive grid line 31 and the first PAD point 51. For example, in FIG. 6, there are 6 first doped layers 21 and 6 second doped layers 22 between adjacent first PAD points 51 or second PAD points 52, totaling 6 PN units, so x = 6 ÷ 2 = 3.

[0100] Here, it should be noted that in the embodiment, the back surface of the back contact solar cell is provided with a plurality of first doped layers 21 and second doped layers 22, which form a plurality of PN units with the silicon substrate 1, and the plurality of PN units can be approximately considered to be connected in parallel.

[0101] Therefore, when only one first PAD part is provided on the back contact solar cell 111 with z PN units (pitches), the measured current voltage can be calculated by the following formula:

[0102] In the formula, I D2 is the measured current when one first PAD part is provided, and V C2 is the measured voltage when one first PAD part is provided.

[0103] If four first PAD parts are provided, the measured current can be calculated by the following formula:

[0104] In the formula, I D5 is the measured current when four first PAD parts are provided, and V C5 is the measured voltage when four first PAD parts are provided.

[0105] From the above two formulas, it can be found without any doubt that I D5 > I D2 . Therefore, for the same back contact solar cell 111 to be tested, V C5 < V C2That is, when the first PAD part is increased, the test result of the reverse breakdown voltage is more accurate. In addition, increasing the number of test points can reduce the test error caused by the broken grid of the first shunt grid line 61 or the second shunt grid line 62. However, as described above, increasing the first test point is not conducive to the improvement of the conversion efficiency. Therefore, based on the above analysis, the present disclosure has carried out a large number of tests and proposed a specific correction method. Alternatively, in an embodiment of the present disclosure, the back contact solar cell 111 satisfies the following relationship:

[0106] wherein U rev is the reverse breakdown voltage of the back contact solar cell 111, U rev0 is the test reverse voltage of the back contact solar cell 111, x is the total number of positive grid lines 31 and negative grid lines 32, x0 is a variable representing the first PAD part, x1 is the number of first PAD points 51, x2 is the number of second PAD points 52, A is a constant, and the value range is 0.1-3.3, B is a constant, and the value range is 2-50.

[0107] Based on the above relationship, the test result can be corrected when setting any number of first PAD parts to obtain an accurate reverse breakdown voltage. Alternatively, when 1-4 first PAD parts are set, the test error is ≤5%, when 4-6 first PAD parts are set, the test error is ≤3.5%, and when 8-10 first PAD parts are set, the test error is ≤1.5%.

[0108] In an embodiment, when a plurality of first PAD parts are set, the plurality of first PAD points 51 are uniformly distributed along the first direction, which facilitates the uniform distribution of the test current and avoids the phenomenon of high reverse breakdown voltage in the test. Alternatively, the plurality of second PAD points 52 are also uniformly distributed along the first direction.

[0109] In one embodiment, the first PAD point 51 is disposed at the first edge 13, and the second PAD point 52 is disposed at the second edge 14. It should be noted that the positive grid lines 31 and the negative grid lines 32 both have line resistance, and after the reverse current flows in, there will be voltage division on these grid lines. In addition, there is a contact resistance between the positive grid lines 31 and the first doped layer 21, and between the negative grid lines 32 and the second doped layer 22, which will also cause voltage division. Therefore, in order to more accurately characterize the reverse breakdown voltage of the back contact solar cell 111, the grid line resistance voltage division and the contact resistance voltage division must be considered. In the present embodiment, the first PAD point 51 and the second PAD point 52 are disposed at the edge of the silicon substrate 1 in the second direction, and the positive grid lines 31 and the negative grid lines 32 both extend along the second direction. Therefore, the present embodiment can make the reverse current flow through longer positive grid lines 31 and negative grid lines 32 in the second direction, and can better characterize the influence of grid line resistance voltage division and contact resistance voltage division on the reverse breakdown voltage.

[0110] It can be understood that, in the present embodiment, the first PAD point 51 is disposed at the first edge 13, which means that it is disposed close to the first edge 13. Optionally, the distance between the first PAD point 51 and the first edge 13 is 1 mm to 10 mm, for example, 1.5 mm, 3 mm, 4.5 mm, 6 mm, 7.5 mm, or 9 mm, but is not limited thereto. Optionally, 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.

[0111] It can be understood that, in the present embodiment, the second PAD point 52 is disposed at the second edge 14, which means that it is disposed close to the second edge 14. Optionally, the distance between the second PAD point 52 and the second edge 14 is 1 mm to 10 mm, for example, 1.5 mm, 3 mm, 4.5 mm, 6 mm, 7.5 mm, or 9 mm, but is not limited thereto. Optionally, 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.

[0112] Optionally, in one embodiment, the back contact solar cell 111 further comprises a first shunt grid line 61 and a second shunt grid line 62, the first shunt grid line 61 is electrically connected with the plurality of positive grid lines 31, and the second shunt grid line 62 is electrically connected with the plurality of negative grid lines 32; the first shunt grid line 61 is electrically connected with the first PAD point 51, and the second shunt grid line 62 is electrically connected with the second PAD point 52. Based on the above-mentioned embodiment, the reverse current from the second PAD point 52 is shunted to the plurality of negative grid lines 32 through the second shunt grid line 62, and then flows through the plurality of positive grid lines 31 before being collected to the first PAD point 51 through the first shunt grid line 61, thereby achieving the effect of better characterizing the influence of grid line resistance voltage division and contact resistance voltage division on the reverse breakdown voltage test accuracy.

[0113] Further, it should be noted that when the number of first PAD points 51 is small, the number of PN units through which the reverse current flows will also decrease accordingly. Although this test value can to some extent represent the hot spot effect of the back contact solar cell 111, 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 units, thereby effectively improving the accuracy of the test.

[0114] The first shunt grid line 61 and the second shunt grid line 62 can be in a straight line or a curved line, and can be parallel to the first direction or have an included angle with the first direction, but are not limited thereto. Alternatively, in an embodiment, the first shunt grid line 61 and the second shunt grid line 62 are in a straight line and extend along the first direction, i.e., they are parallel to the first direction, which reduces the length of the first shunt grid line 61 or the second shunt grid line 62 between the positive grid lines 31 to be connected or the negative grid lines 32 to be connected, and simplifies the grid line arrangement.

[0115] Alternatively, in an embodiment, the width of the first shunt grid line 61 in the second direction is greater than the width of the positive grid line 31 in the first direction, and the width of the second shunt grid line 62 in the second direction is greater than the width of the negative grid line 32 in the first direction, so as to reduce the current loss of the first shunt grid line 61 and the second shunt grid line 62. Especially when the number of first PAD parts is small, the first shunt grid line 61 and the second shunt grid line 62 can prevent excessive current loss, ensure that the test current is dispersed to more positive grid lines 31 and negative grid lines 32 through the first shunt grid line 61 and the second shunt grid line 62, and improve the test accuracy. Alternatively, the width of the first shunt grid line 61 in the second direction is 1.5-3 times the width of the positive grid line 31 in the first direction, and the width of the second shunt grid line 62 in the second direction is 1.5-3 times the width of the negative grid line 32 in the first direction.

[0116] In an embodiment, the first shunt grid line 61 is arranged at the first edge 13, and the second shunt grid line 62 is arranged at the second edge 14. Based on this arrangement, the grid line structure can be simplified, the carrier collection efficiency can be improved, and the conversion efficiency can be improved. Since the first shunt grid line 61 is connected to a plurality of positive grid lines 31 extending in the second direction, and the second shunt grid line 62 is connected to a plurality of negative grid lines 32 extending in the second direction, if the first shunt grid line 61 or the second shunt grid line 62 is arranged at the center, a plurality of discontinuous insulation structures or other types of insulation structures need to be arranged in the regions of grid lines with different polarities, the grid line structure is complex, and the arrangement area of the positive grid lines 31 and the negative grid lines 32 is reduced, which reduces the collection of carriers.

[0117] It can be understood that the first shunt grid line 61 is arranged at the first edge 13 in the embodiment means that it is arranged close to the first edge 13. Optionally, the distance between the first shunt grid line 61 and the first edge 13 is 0.1mm-3mm, for example, 0.5mm, 1mm, 1.5mm, 2mm or 2.5mm, but not limited thereto. Wherein, the distance between the first shunt grid line 61 and the first edge 13 means the distance between the center line of the first shunt grid line 61 and the first edge 13.

[0118] It can be understood that the second shunt grid line 62 is arranged at the second edge 14 in the embodiment means that it is arranged close to the second edge 14. Optionally, the distance between the second shunt grid line 62 and the second edge 14 is 0.1mm-3mm, for example, 0.5mm, 1mm, 1.5mm, 2mm or 2.5mm, but not limited thereto. Wherein, the distance between the second shunt grid line 62 and the second edge 14 means the distance between the center line of the second shunt grid line 62 and the second edge 14.

[0119] Optionally, in an embodiment, the first shunt grid line 61 is arranged at the end of the positive grid line 31 close to the first edge 13, that is, the positive grid line 31 and the negative grid line 32 are arranged on the side of the first shunt grid line 61 facing the second edge 14, and no other grid line is arranged between the first shunt grid line 61 and the first edge 13. Based on the above arrangement, 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.

[0120] Optionally, in an embodiment, the second shunt grid line 62 is arranged at the end of the negative grid line 32 close to the second edge 14, that is, the positive grid line 31 and the negative grid line 32 are arranged on the side of the second shunt grid line 62 facing the first edge 13, and no other grid line is arranged between the second shunt grid line 62 and the second edge 14, so as to improve the conversion efficiency and the test accuracy.

[0121] It can be foreseen that since the first shunt grid line 61 and the second shunt grid line 62 are arranged close to the edge of the back contact solar cell 111, there are fewer photo-generated carriers at the edge, and the first shunt grid line 61 and the second shunt grid line 62 extend in the first direction. If the passivation layer on the doped layer is opened to make the first shunt grid line 61 and the second shunt grid line 62 contact the doped layer of the opposite polarity, more recombination loss will be introduced. Therefore, as an implementation manner, the first shunt grid line 61 and the second shunt grid line 62 are not in contact with the doped layer, and they only play the role of shunt or convergence. At the same time, it can be understood that by increasing the number of first PAD points 51 and second PAD points 52, the influence of the first shunt grid line 61 and the second shunt grid line 62 on the test results can also be reduced.

[0122] Optionally, in one embodiment, when the first PAD point 51 and the first shunt grid line 61 are both arranged at the first edge 13, the distance between the first PAD point 51 and the first edge 13 is greater than the distance between the first shunt grid line 61 and the first edge 13. Since the first PAD point 51 is relatively large, it is easy to cause defects such as hidden cracks during printing if it is too close to the edge of the silicon substrate 1. Moreover, by controlling the first shunt grid line 61 to be closer to the first edge 13, a spacing region is formed between the first shunt grid line 61 and the first PAD point 51, and a grid line can be arranged in the spacing region, thereby further improving the collection efficiency of carriers and improving the conversion efficiency. Optionally, based on this embodiment, the distance between the first PAD point 51 and the first edge 13 is 3mm-8mm, and the distance between the first shunt grid line 61 and the first edge 13 is 0.2mm-5mm.

[0123] Optionally, when a spacing region is formed between the first shunt grid line 61 and the first PAD point 51, the first shunt grid line 61 and the first PAD point 51 can be electrically connected by the first connecting grid line 71. Optionally, in one embodiment, the first connecting grid line 71 extends along the second direction, and the first connecting grid line 71 is located on the extension line of a positive grid line 31 towards the first edge 13, that is, the first connecting grid line 71 is arranged above the first doped layer 21 corresponding to the positive grid line 31, and then the first connecting grid line 71 and the first doped layer 21 can be connected through the first hole 41, so that the first connecting grid line 71 can also collect carriers and improve the conversion efficiency.

[0124] Optionally, in one embodiment, when the second PAD point 52 and the second shunt grid line 62 are both arranged at the second edge 14, the distance between the second PAD point 52 and the second edge 14 is greater than the distance between the second shunt grid line 62 and the second edge 14. Since the second PAD point 52 is relatively large, it is easy to cause defects such as hidden cracks during printing if it is too close to the edge of the silicon substrate 1. Moreover, by controlling the second shunt grid line 62 to be closer to the second edge 14, a spacing region is formed between the second shunt grid line 62 and the second PAD point 52, and a grid line can be arranged in the spacing region, thereby further improving the collection efficiency of carriers and improving the conversion efficiency. Optionally, based on this embodiment, the distance between the second PAD point 52 and the second edge 14 is controlled to be 3mm-8mm, and the distance between the second shunt grid line 62 and the second edge 14 is controlled to be 0.2mm-5mm.

[0125] Optionally, when a spacing region is formed between the second shunt grid line 62 and the second PAD point 52, the second shunt grid line 62 and the second PAD point 52 can be electrically connected through a second connecting grid line 72. Optionally, in an embodiment, the second connecting grid line 72 extends in the second direction, and the second connecting grid line 72 is located on an extension line of a negative grid line 32 towards the second edge 14, that is, the second connecting grid line 72 is arranged above the second doped layer 22 corresponding to the negative grid line 32, and the second connecting grid line 72 is connected with the second doped layer 22 through the second hole 42, so that the second connecting grid line 72 can also collect carriers, thereby improving the conversion efficiency.

[0126] Optionally, in an embodiment, the positive grid line 31 includes a first positive sub-grid line 311, the negative grid line 32 includes a first negative sub-grid line 321 arranged adjacent to the first positive sub-grid line 311, the first PAD point 51 is arranged at an end of the first positive sub-grid line 311 close to the first edge 13 and is electrically connected with the first positive sub-grid line 311. The second PAD point 52 is arranged at an end of the first negative sub-grid line 321 close to the second edge 14 and is electrically connected with the first negative sub-grid line 321. Based on this embodiment, the first PAD point 51 and the second PAD point 52 in each first PAD part are approximately arranged on the same line extending in the second direction, and the stress distribution is uniform during printing, which can reduce the risk of cracking.

[0127] Optionally, in an embodiment, the first PAD point 51 is electrically connected with at least three first positive sub-grid lines 311, and the second PAD point 52 is electrically connected with at least three first negative sub-grid lines 321. Although the first PAD point 51 and the second PAD point 52 can respectively distribute the reverse current through the first shunt grid line 61 and the second shunt grid line 62, the first shunt grid line 61 or the second shunt grid line 62 is relatively narrow, which can cause excessive current density and consume more power. Therefore, the first PAD point 51 is connected with at least three first positive sub-grid lines 311, and the second PAD point 52 is connected with at least three first negative sub-grid lines 321, so as to optimize the current distribution and improve the test accuracy. Optionally, the first PAD point 51 is electrically connected with three first positive sub-grid lines 311, and the second PAD point 52 is electrically connected with three first negative sub-grid lines 321, so as to avoid that when the number of connecting grid lines is too large, the size of the first PAD point 51 and the second PAD point 52 is too large, and a large area of the grid line for collecting carriers is occupied, thereby improving the conversion efficiency.

[0128] Optionally, in one embodiment, at least one side of the first connecting gate line 71 in the first direction is further provided with a second negative sub-gate line 322 extending in the second direction, the second negative sub-gate line 322 is electrically connected to at least one negative gate line 32 close to the first PAD point 51 and is insulated from the first PAD point 51. Through the second negative sub-gate line 322, the carriers in the interval between the first shunt gate line 61 and the first PAD point 51 can be collected, and the conversion efficiency is improved.

[0129] Optionally, in order to collect more carriers, the second negative sub-gate line 322 can be provided on the extension line of the first negative sub-gate line 321 connected to the second PAD point 52 towards the first edge 13; that is, the second negative sub-gate line 322 is arranged above the second doped layer 22 corresponding to the first negative sub-gate line 321, and then the second negative sub-gate line 322 is connected to the second doped layer 22 through the second hole 42, so that the second negative sub-gate line 322 can also collect carriers and improve the conversion efficiency.

[0130] Optionally, in one embodiment, at least one side of the second connecting gate line 72 in the first direction is further provided with a second positive sub-gate line 312 extending in the second direction, the second positive sub-gate line 312 is electrically connected to at least one positive gate line 31 close to the second PAD point 52 and is insulated from the second PAD point 52. Through the second positive sub-gate line 312, the carriers in the interval between the second shunt gate line 62 and the second test PAD point can be collected, and the conversion efficiency is improved.

[0131] Optionally, in order to collect more carriers, the second positive sub-gate line 312 can be provided on the extension line of the first positive sub-gate line 311 connected to the first PAD point 51 towards the second edge 14, that is, the second positive sub-gate line 312 is arranged above the first doped layer 21 corresponding to the first positive sub-gate line 311, and then the second positive sub-gate line 312 is connected to the first doped layer 21 through the first hole 41, so that the second positive sub-gate line 312 can also collect more carriers and improve the conversion efficiency.

[0132] Optionally, in one embodiment, the back contact solar cell 111 further comprises at least one second PAD part, which is mainly used for connecting the solder strip 112, so that the back contact solar cell 111 forms a cell string 110, a cell module 100.

[0133] Optionally, each second PAD part comprises a third PAD point 81 and a fourth PAD point 82, wherein the third PAD point 81 is electrically connected with at least one positive grid line 31 and insulated from the negative grid line 32. The fourth PAD point 82 is electrically connected with at least one negative grid line 32 and insulated from the positive grid line 31. That is, the third PAD point 81 is used to connect the positive solder strip 112, and the fourth PAD point 82 is used to connect the negative solder strip 112.

[0134] Optionally, the positive grid line 31 electrically connected with the third PAD point 81 extends in the second direction by a distance l4, and l4 / L≤0.1. Based on this ratio, on the one hand, the carrier transport distance is appropriate, thereby reducing the grid line transmission loss and improving the power of the battery string 110 and the battery assembly 100, and on the other hand, the third PAD point 81 is reasonably distributed, thereby improving the soldering tension and ensuring the reliability of the battery assembly 100. Illustratively, l4 / L is 0.01, 0.02, 0.04, 0.06, or 0.08, but is not limited thereto. Optionally, l4 / L is 0.06-0.09.

[0135] Optionally, the negative grid line 32 electrically connected with the fourth PAD point 82 extends in the second direction by a distance l5, and l5 / L≤0.1. Based on this ratio, on the one hand, the carrier transport distance is appropriate, thereby reducing the grid line transmission loss and improving the power of the battery string 110 and the battery assembly 100, and on the other hand, the fourth PAD point 82 is reasonably distributed, thereby improving the soldering tension and ensuring the reliability of the battery assembly 100. Illustratively, l5 / L is 0.01, 0.02, 0.04, 0.06, or 0.08, but is not limited thereto. Optionally, l5 / L is 0.06-0.09.

[0136] Optionally, based on the above embodiment, the number of third PAD points 81 is 8-20, illustratively 9, 11, 13, 15, 17, or 19, but is not limited thereto. Optionally, the number of third PAD points 81 is 12-20.

[0137] Optionally, the number of fourth PAD points 82 is 8-20, illustratively 9, 11, 13, 15, 17, or 19, but is not limited thereto. Optionally, the number of fourth PAD points 82 is 12-20.

[0138] Optionally, when a second PAD part includes a plurality of third PAD points 81 and a plurality of fourth PAD points 82, the third PAD points 81 and the fourth PAD points 82 are arranged alternately along the second direction. Based on the arrangement, the current transmission distance can be further optimized, the loss can be reduced, and the power can be improved. Optionally, in order to simplify the electrode pattern and reduce the printing stress, the plurality of third PAD points 81 and the plurality of fourth PAD points 82 in the same second PAD part are arranged in a row along the second direction.

[0139] Optionally, the second PAD part can be arranged at the middle, the edge, or any other position of the back contact solar cell 111.

[0140] In an embodiment, the silicon substrate 1 has a third edge 15 and a fourth edge 16 arranged oppositely along the first direction, and the second PAD part is arranged at the third edge 15 and the fourth edge 16. By this arrangement, the welding tension can be greatly improved, and the reliability of the cell string 110 / cell module 100 can be ensured.

[0141] It can be understood that, in the embodiment, the second PAD part arranged at the third edge 15 or the fourth edge 16 means that the third PAD points 81 and the fourth PAD points 82 are arranged close to the third edge 15 or the fourth edge 16. Optionally, the distance between the third PAD points 81 or the fourth PAD points 82 and the third edge 15, and the distance between the third PAD points 81 or the fourth PAD points 82 and the fourth edge 16 can be 1 mm to 5 mm, for example, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, or 4.5 mm, but are not limited thereto. It can be understood that the distance between the third PAD points 81 or the fourth PAD points 82 and the third edge 15 or the fourth edge 16 refers to the distance between the geometric center of the third PAD points 81 or the fourth PAD points 82 and the third edge 15 or the fourth edge 16.

[0142] Optionally, in an 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 arranged at the first edge 13 are arranged on the same line extending along the first direction and located on the back surface 12. Based on the embodiment, the first PAD point 51 can also be used for welding, and the welding tension can be further improved.

[0143] Optionally, in an 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 arranged at the second edge 14 are arranged on the same line extending along the first direction and located on the back surface 12. Based on the embodiment, the second PAD point 52 can also be used for welding, and the welding tension can be further improved.

[0144] In the description of the application, reference has been made to descriptive terms such as "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" meant to connote "one" or "some" but not "all" the features, structures, materials, or characteristics described in connection with the embodiments or examples. The use of terms such as "first", "second" and "third" does not imply a chronological or logical

[0145] While the embodiments of the application have been illustrated and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and alterations can be made therein without departing from the spirit and scope of the application, which is defined by the following claims and their equivalents.

Claims

1. A back contact solar cell, wherein, The application relates to a silicon substrate, which comprises a light-receiving surface and a back surface arranged oppositely and has a first edge and a second edge arranged oppositely in a second direction; a plurality of first doped layers and a plurality of second doped layers arranged on the back surface, the first doped layers and the second doped layers being arranged alternately in a first direction, and each of the first doped layers and at least part of the second doped layers extending in the second direction; the second doped layers being in composite contact with the first doped layers at preset positions to form a leakage composite contact structure; the first direction intersecting the second direction; a plurality of positive gate lines and a plurality of negative gate lines, the positive gate lines being arranged on the first doped layers, and the negative gate lines being arranged on the second doped layers; and at least one first PAD part for passing current, the current flowing through the leakage composite contact structure; wherein each of the first PAD parts comprises a first PAD point and a second PAD point, the first PAD point being electrically connected with at least one of the positive gate lines, and the second PAD point being electrically connected with at least one of the negative gate lines; the positive gate line electrically connected with the first PAD point extending in the second direction and having an extension distance of l1, the distance between the first edge and the second edge being L, and l1 / L being greater than or equal to 0.9; the negative gate line electrically connected with the second PAD point extending in the second direction and having an extension distance of l2, and l2 / L being greater than or equal to 0.9; the relative distance between the first PAD point and the second PAD point in the second direction being l3, and 0.9<=l1 / l3<1 and 0.9<=l2 / l3<1; the first PAD point being arranged close to the first edge, and the second PAD point being arranged close to the second edge; the first PAD part comprising 1-12 first PAD points; when a plurality of first PAD parts are arranged, the plurality of first PAD points are uniformly distributed in the first direction, and the plurality of second PAD points are uniformly distributed in the first direction; the first shunt gate line being electrically connected with a plurality of the positive gate lines, and the second shunt gate line being electrically connected with a plurality of the negative gate lines; the first shunt gate line being electrically connected with the first PAD point, and the second shunt gate line being electrically connected with the second PAD point; the first shunt gate line being arranged at the first edge, and the positive gate lines and the negative gate lines being arranged on one side of the first shunt gate line facing the second edge; the second shunt gate line being arranged close to the second edge, and the positive gate lines and the negative gate lines being arranged on one side of the second shunt gate line facing the first edge; no gate line being arranged between the first shunt gate line and the first edge, and no gate line being arranged between the second shunt gate line and the second edge; the width of the first shunt gate line in the second direction being greater than the width of the positive gate line in the first direction, and the width of the second shunt gate line in the second direction being greater than the width of the negative gate line in the first direction. ​ ​ ​ ​ ​ ​ ​ ​ 2. The back contact solar cell of claim 1, wherein, ​ 3. The back contact solar cell of claim 1, wherein, ​ 4. The back contact solar cell of claim 1, wherein, ​ 5. The back contact solar cell according to any one of claims 1 to 4, wherein The back contact solar cell satisfies the following relationship: wherein U rev is the reverse breakdown voltage of the back contact solar cell, U rev0 is the test reverse voltage of the back contact solar cell, x is the total number of positive and negative grid lines, x0 is a variable representing the first PAD section, x1 is the number of first PAD points, x2 is the number of second PAD points, A is a constant, the value range of A is 0.1-3.3, and B is a constant, the value range of B is 2-50.

6. The back contact solar cell of claim 4, wherein, ​ 7. The back contact solar cell of claim 1, wherein, ​ ​ ​ 8. The back contact solar cell of claim 7, wherein, ​ ​ 9. The back contact solar cell of claim 8, wherein, ​ 10. The back contact solar cell of claim 7, wherein, ​ 11. The back contact solar cell of claim 7, wherein, 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 of claim 11, wherein, The distance between the first PAD point and the first edge is 3mm-5mm, and the distance between the second PAD point and the second edge is 3mm-5mm. The distance between the first shunt grid line and the first edge is 0.2mm-2mm, and the distance between the second shunt grid line and the second edge is 0.2mm-2mm.

13. The back contact solar cell of claim 7, wherein, The first PAD point and the first shunt grid line are electrically connected through a first connecting grid line. The second PAD point and the second shunt grid line are electrically connected through a second connecting grid line.

14. The back contact solar cell of claim 13, wherein, The first connecting grid line is located on the extension line of a positive grid line to the first edge. The second connecting grid line is located on the extension line of a negative grid line to the second edge.

15. The back contact solar cell of claim 13, wherein, The positive grid line includes a first positive sub-grid line, and the first PAD point is arranged at the end of the first positive sub-grid line and is electrically connected with the first positive sub-grid line. The negative grid line includes a first negative sub-grid line, and the second PAD point is arranged at the end of the first negative sub-grid line and is electrically connected with the first negative sub-grid line. The first positive sub-grid line is arranged adjacent to the first negative sub-grid line.

16. The back contact solar cell of claim 15, wherein, The first PAD point is electrically connected with at least three first positive sub-grid lines. The second PAD point is electrically connected with at least three first negative sub-grid lines.

17. The back contact solar cell of claim 15, wherein, The back contact solar cell further satisfies at least one of the following: The at least one side of the first connecting grid line in the first direction is further provided with a second negative sub-grid line extending in the second direction, the second negative sub-grid line is electrically connected with at least one negative grid line close to the first PAD point and is insulated from the first PAD point. The at least one side of the second connecting grid line in the first direction is further provided with a second positive sub-grid line extending in the second direction, the second positive sub-grid line is electrically connected with at least one positive grid line close to the second PAD point and is insulated from the second PAD point.

18. The back contact solar cell of claim 17, wherein, The back contact solar cell further satisfies at least one of the following: The second negative sub-grid line is located on the extension line of the first negative sub-grid line connected with the second PAD point to the first edge. The second positive sub-grid line is located on the extension line of the first positive sub-grid line connected with the first PAD point to the second edge.

19. The back contact solar cell of claim 1, wherein, The first PAD point is square, circular, triangular or irregular, and the second PAD point is square, circular, triangular or irregular.

20. The back contact solar cell of claim 1, wherein, The first PAD point is square, and the width of the first PAD point in the first direction or the second direction is 0.1mm-1mm; the second PAD point is square, and the width of the second PAD point in the first direction or the second direction is 0.1mm-1mm.

21. The back contact solar cell of claim 1, wherein, Further comprising: at least one second PAD portion, the second PAD portion comprising a plurality of third PAD points and fourth PAD points, the third PAD points being electrically connected to at least one positive grid line and insulated from the negative grid line, the fourth PAD points being electrically connected to at least one negative grid line and insulated from the positive grid line; the positive grid line electrically connected to the third PAD points extends in the second direction by a distance l4, and l4 / L≤0.1; the negative grid line electrically connected to the fourth PAD points extends in the second direction by a distance l5, and l5 / L≤0.

1.

22. The back contact solar cell of claim 21, wherein, the silicon substrate has a third edge or a fourth edge oppositely arranged in the first direction; the second PAD portion is arranged near the third edge and near the fourth edge.

23. The back contact solar cell of claim 22, wherein, the geometric center of the third PAD point closest to the first edge and the geometric center of the first PAD point arranged at the first edge are arranged on the same line extending in the first direction and located on the back surface; the geometric center of the fourth PAD point closest to the second edge and the geometric center of the second PAD point arranged at the second edge are arranged on the same line extending in the first direction and located on the back surface.

24. A string of batteries, wherein, a back contact solar cell as claimed in any one of claims 1 to 23.

25. A battery assembly, wherein, a battery string as claimed in claim 24.

26. A photovoltaic system, wherein, a battery assembly as claimed in claim 25.

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