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

Abstract

The utility model discloses a back contact solar cell, a cell string, an assembly and a photovoltaic system, and relates to the field of silicon solar cells. 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, a first test point and a second test point. 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; the first test point comprises a first test PAD point and a second test PAD point, the first test PAD point is electrically connected with the positive grid line, and the second test PAD point is electrically connected with the negative grid line. The second test point comprises a third test PAD point and a fourth test PAD point, the third test PAD point is electrically connected with the positive grid line, and the fourth test PAD point is electrically connected with the negative grid line. By implementing the embodiment, the characterization of the hot spot resistance effect can be realized at the battery end.

Description

Technical Field

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

[0002] When one or more solar cells (or segments) in a photovoltaic module are partially or completely shaded, a voltage reverse bias occurs. The shaded solar cell (slice) then becomes a load, consuming the power normally generated by the solar cell, generating a large amount of heat and causing the temperature of the solar cell to rise. This is commonly known as the hot spot effect. To address the hot spot problem, conventional techniques typically connect a diode in anti-parallel at both ends of the string unit, thereby reducing the current flowing through the shaded solar cell and mitigating the hot spot effect. However, this parallel connection of diodes results in power loss. To address this issue, a feasible approach is to directly form a leaky composite contact structure on the solar cell (see CN117976743B). This involves creating partial contact between doped layers of different polarities during the solar cell manufacturing process, effectively reducing the reverse voltage across the shaded solar cell, reducing heat generation, and mitigating the hot spot effect. This approach allows control of the hot spot effect to be moved to the solar cell end. Therefore, evaluating the hot spot effect at the solar cell end has become a technical issue that those skilled in the art need to address.

[0003] Conventional hot spot testing, on the other hand, typically involves shielding one or more solar cells (or sub-cells) in a solar cell module, exposing the remaining solar cells (or sub-cells) to light. After a certain period of time, the temperature of the shielded solar cell is measured to characterize the hot spot effect. This is clearly not suitable for hot spot testing at the solar cell end. Utility Model Content

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

[0005] In order to solve the above problems, the utility model discloses a back-contact solar cell, which includes:

[0006] A silicon substrate comprising a light-receiving surface and a backlight surface disposed opposite to each other; the silicon substrate comprising a first preset area, a second preset area, and a third preset area, the third preset area being disposed between the first preset area and the second preset area; the third preset area being used for cutting the silicon substrate;

[0007] a plurality of first doped layers and a plurality of second doped layers, which are arranged on the backlight surface, the plurality of first doped layers and the plurality of second doped layers are alternately arranged in a first preset area and a second preset area along a first direction, and extend along a second direction, at least one of the second doped layers is in composite contact with at least one of the first doped layers at a preset position to form a leakage composite contact structure;

[0008] a plurality of positive gate lines and a plurality of negative gate lines, wherein the positive gate lines are provided on the first doped layer, and the negative gate lines are provided on the second doped layer;

[0009] at least one group of first test points within the first preset area, each group of first test points including a first test PAD point and a second test PAD point, the first test PAD point being electrically connected to at least one positive gate line within the first preset area, and the second test PAD point being electrically connected to at least one negative gate line within the first preset area; and

[0010] At least one group of second test points is arranged in the second preset area, and each group of second test points includes a third test PAD point and a fourth test PAD point, the third test PAD point is electrically connected to at least one positive gate line located in the second preset area, and the fourth test PAD point is electrically connected to at least one negative gate line located in the second preset area.

[0011] As an improvement to the above technical solution, the silicon substrate has a first edge and a second edge that are oppositely arranged in the second direction;

[0012] The first test PAD point and the fourth test PAD point are arranged close to the first edge;

[0013] The second test PAD point and the third test PAD point are located close to the second edge.

[0014] As an improvement of the above technical solution, the first test PAD point and the fourth test PAD point are located on the same straight line extending along the first direction and located on the backlight surface; and / or

[0015] The second test PAD point and the third test PAD point are located on the same straight line extending along the first direction and located on the backlight surface.

[0016] As an improvement of the above technical solution, it includes 1 to 6 groups of first test points and 1 to 6 groups of second test points.

[0017] As an improvement to the above technical solution, the following is also included:

[0018] A first shunt gate line and a second shunt gate line are provided in a first preset area; the first shunt gate line is electrically connected to a plurality of positive gate lines located in the first preset area, and the second shunt gate line is electrically connected to a plurality of negative gate lines located in the first preset area; the first shunt gate line is electrically connected to the first test PAD point, and the second shunt gate line is electrically connected to the second test PAD point; and / or

[0019] A third shunt gate line and a fourth shunt gate line are arranged in the second preset area; the third shunt gate line is electrically connected to several positive gate lines located in the second preset area, and the fourth shunt gate line is electrically connected to several negative gate lines located in the second preset area; the third shunt gate line is electrically connected to the third test PAD point, and the fourth shunt gate line is electrically connected to the fourth test PAD point.

[0020] As an improvement to the above technical solution, the silicon substrate has a first edge and a second edge that are oppositely arranged in the second direction;

[0021] The first shunt gate line is arranged close to the first edge, and the second shunt gate line is arranged close to the second edge; and / or

[0022] The third shunt gate line is disposed close to the second edge, and the fourth shunt gate line is disposed close to the first edge.

[0023] As an improvement of the above technical solution, the distance between the first test PAD point and the first edge is greater than the distance between the first shunt gate line and the first edge; and / or

[0024] The distance between the second test PAD point and the second edge is greater than the distance between the second shunt gate line and the second edge; and / or

[0025] The distance between the third test PAD point and the second edge is greater than the distance between the third shunt gate line and the second edge; and / or

[0026] The distance between the fourth test PAD point and the first edge is greater than the distance between the fourth shunt gate line and the first edge.

[0027] As an improvement of the above technical solution, the distance between the first test PAD point, the fourth test PAD point and the first edge is 3mm to 8mm; the distance between the second test PAD point, the third test PAD point and the second edge is 3mm to 8mm; and / or

[0028] The distances between the first and fourth shunt gate lines and the first edge are 0.2 mm to 5 mm, and the distances between the second and third shunt gate lines and the second edge are 0.2 mm to 5 mm.

[0029] As an improvement to the above technical solution, the first test PAD point is electrically connected to the first shunt gate line via a first connecting gate line; and / or

[0030] The second test PAD point is electrically connected to the second shunt gate line via a second connecting gate line; and / or

[0031] The third test PAD point is electrically connected to the third shunt gate line via a third connecting gate line; and / or

[0032] The fourth test PAD point is electrically connected to the fourth shunt gate line through a fourth connecting gate line.

[0033] As an improvement to the above technical solution, the first connecting grid line and a positive grid line located in the first preset area are arranged on the same straight line extending along the second direction and located on the backlight surface; and / or

[0034] The second connecting gate line and a cathode gate line located in the first predetermined area are arranged on the same straight line extending along the second direction and located on the backlight surface; and / or

[0035] The third connecting gate line and a positive gate line located in the second preset area are arranged on the same straight line extending along the second direction and located on the backlight surface; and / or

[0036] The fourth connecting gate line and a negative gate line located in the second preset area are arranged on the same straight line extending along the second direction and located on the backlight surface.

[0037] As an improvement to the above technical solution, the positive gate line includes a first positive sub-gate line provided in a first preset area and a second positive sub-gate line provided in a second preset area, the first test PAD point is provided at an end of the first positive sub-gate line and is electrically connected to the first positive sub-gate line; the third test PAD point is provided at an end of the second positive sub-gate line and is electrically connected to the second positive sub-gate line;

[0038] The negative gate line includes a first negative sub-gate line provided in a first preset area and a second negative sub-gate line provided in a second preset area, the second test PAD point is provided at an end of the first negative sub-gate line and is electrically connected to the first negative sub-gate line; the fourth test PAD point is provided at an end of the second negative sub-gate line and is electrically connected to the second negative sub-gate line;

[0039] The first positive sub-gate line is disposed adjacent to the first negative sub-gate line, and the second positive sub-gate line is disposed adjacent to the second negative sub-gate line.

[0040] As an improvement of the above technical solution, the first test PAD point is electrically connected to at least three first positive sub-grid lines; the second test PAD point is electrically connected to at least three first negative sub-grid lines; and / or

[0041] The third test PAD point is electrically connected to at least three second positive sub-gate lines; and the fourth test PAD point is electrically connected to at least three second negative sub-gate lines.

[0042] As an improvement to the above technical solution, a third negative sub-grid line is further provided on at least one side of the first connecting grid line, the third negative sub-grid line is electrically connected to one of the negative grid lines and is insulated from the first test PAD point; and / or

[0043] A third positive sub-grid line is further provided on at least one side of the second connecting grid line, the third positive sub-grid line is electrically connected to one of the positive grid lines and is insulated from the second test PAD point; and / or

[0044] A fourth negative sub-grid line is further provided on at least one side of the third connecting grid line, the fourth negative sub-grid line is connected to one of the negative grid lines and is insulated from the third test PAD point; and / or

[0045] A fourth positive sub-grid line is further provided on at least one side of the fourth connecting grid line. The fourth positive sub-grid line is connected to one of the positive grid lines and is insulated from the fourth test PAD point.

[0046] As an improvement of the above technical solution, the first test PAD point, the second test PAD point, the third test PAD point, and the fourth test PAD point are square, circular, triangular, or irregular in shape.

[0047] As an improvement of the above technical solution, the first test PAD point, the second test PAD point, the third test PAD point, and the fourth test PAD point are square, and their widths are 0.1 mm to 3 mm.

[0048] As an improvement to the above technical solution, the further comprising: at least two groups of welding points, which are arranged in the first preset area and the second preset area;

[0049] Each group of welding points includes a plurality of first welding PAD points and a plurality of second welding PAD points, and the plurality of first welding PAD points and the plurality of second welding PAD points are alternately arranged along the second direction.

[0050] As an improvement to the above technical solution, a first welding PAD point located in the first preset area and closest to the first edge and a first test PAD point located close to the first edge are arranged on the same straight line extending along the first direction and located on the backlight surface; and / or

[0051] A second welding PAD point located in the first preset area and closest to the second edge and a second test PAD point located close to the second edge are arranged on the same straight line extending along the first direction and located on the backlight surface;

[0052] The second welding PAD point located in the second preset area and closest to the first edge and the fourth test PAD point located close to the first edge are arranged on the same straight line extending along the first direction and located on the backlight surface; and / or

[0053] The first welding PAD point located in the second preset area and closest to the second edge and the third testing PAD point located close to the second edge are arranged on the same straight line extending along the first direction and located on the backlight surface.

[0054] Correspondingly, the present invention also discloses a battery string, which includes the above-mentioned back-contact solar cell sheet or the slices obtained by cutting the same.

[0055] Correspondingly, the present invention also discloses a battery assembly, characterized in that it includes the above-mentioned battery string, or the above-mentioned back-contact solar cell or slices thereof.

[0056] Correspondingly, the present invention also discloses a photovoltaic system, which includes the above-mentioned battery assembly.

[0057] The implementation of this utility model has the following beneficial effects:

[0058] In the back-contact solar cell of the present invention, at least one group of first test points is provided in a first preset area on the backlight surface of the silicon substrate, each group of first test points includes a first test PAD point and a second test PAD point, the first test PAD point is electrically connected to at least one positive grid line located in the first preset area, and the second test PAD point is electrically connected to at least one negative grid line located in the first preset area. At least one group of second test points is also provided in the second preset area, each group of second test points includes a third test PAD point and a fourth test PAD point, the third test PAD point is electrically connected to at least one positive grid line located in the second preset area 122, and the fourth test PAD point is electrically connected to at least one negative grid line located in the second preset area 122. Based on the technical solution of this embodiment, a reverse current can be passed into the back-contact solar cell through the first test point and the second test point, and the reverse breakdown voltage of the back-contact solar cell can be obtained by testing, which provides a good basis for characterizing the hot spot effect at the cell end. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a schematic diagram of the back structure of a back-contact solar cell in one embodiment of the present invention;

[0060] Figure 2 This is a schematic diagram of the arrangement structure of the first doping layer and the second doping layer in one embodiment of the present utility model;

[0061] Figure 3 1 is a schematic cross-sectional view of a back-contact solar cell according to an embodiment of the present invention;

[0062] Figure 4 It is a structural diagram of a battery string in one embodiment of the present utility model. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are merely used to explain the present application and are not intended to limit the present application.

[0064] In the description of this application, it should be understood that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on this application.

[0065] 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 the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the described features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0066] 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.

[0067] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0068] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art will appreciate the application of other processes and / or the use scenarios of other materials.

[0069] See also Figure 2 One embodiment of the present invention discloses a back-contact solar cell, comprising: a silicon substrate 1, a plurality of first doped layers 31, a plurality of second doped layers 32, a plurality of positive electrode grid lines 41, and a plurality of negative electrode grid lines 42. The silicon substrate 1 may be P-type monocrystalline silicon, N-type monocrystalline silicon, P-type polycrystalline silicon, or N-type polycrystalline silicon, but is not limited thereto. The silicon substrate 1 comprises a light-receiving surface 11 and a backlight surface 12 arranged opposite to each other. The backlight surface 12 is provided with a first preset area 121, a second preset area 122, and a third preset area 123. The first preset area 121 and the second preset area 122 are mainly used to form the first doped layer 31 and the second doped layer 32, and then to form an electrode structure later. The third preset area 123 is used to cut the silicon substrate 1 later to form cell slices. The first preset area 121 and the second preset area 122 are arranged alternately in sequence along the first direction, and the third preset area 123 is provided between the first preset area 121 and the second preset area 122.

[0070] It should be noted that there is no particular limit to the number of first preset areas 121, second preset areas 122, and third preset areas 123 provided in the embodiments of the present invention. For example, when a larger silicon substrate 1 is used, two to three cuts can be performed. In this case, two to three third preset areas 123 can be provided, and further, one to two first preset areas 121 and one to two second preset areas 122 can be provided, but the present invention is not limited thereto. When multiple first preset areas 121, second preset areas 122, and third preset areas 123 are provided, their arrangement relationship is still that the first preset areas 121 and the second preset areas 122 are alternately arranged along the first direction, and the third preset areas 123 are provided between the first preset areas 121 and the second preset areas 122. Preferably, in one embodiment, the backlight surface 12 is provided with one first preset area 121, one second preset area 122, and one third preset area 123, and the first preset area 121, the third preset area 123, and the second preset area 122 are arranged in sequence along the first direction.

[0071] The first doping layer 31 and the second doping layer 32 are disposed on the backlight surface 12. Specifically, the first doping layer 31 and the second doping layer 32 are alternately arranged along the first direction within the first preset region 121 and the second preset region 122, with a spacing region 33 provided between the first doping layer 31 and the second doping layer 32. The first doping layer 31 may be one or more of, but not limited to, a P-type doped polycrystalline silicon layer, a P-type doped amorphous silicon layer, or a P-type doped microcrystalline silicon layer. Preferably, the first doping layer 31 is a P-type polycrystalline silicon layer; the P-type doping element in the first doping layer 31 may be B, Al, or Ga, but not limited thereto, preferably B. The second doping layer 32 is an N-type doped polycrystalline silicon layer, an N-type doped amorphous silicon layer, or an N-type doped microcrystalline silicon layer, but not limited thereto. Preferably, it is an N-type doped polycrystalline silicon layer. The N-type doping element in the second doping layer 32 may be P, As, or Sb, but not limited thereto. Preferably, it is P.

[0072] For details, see Figure 2 In this embodiment, at least one second doping layer 32 is in composite contact with the first doping layer 31 at a preset position to form a leakage composite contact structure 34. Based on the leakage composite contact structure 34, the reverse voltage across the back-contact solar cell under peak current can be reduced, the heat generation power can be reduced, and the probability of hot spots occurring can be reduced.

[0073] Specifically, in one embodiment, at a preset position, the first doping layer 31 or the second doping layer 32 can be extended to the second doping layer 32 or the first doping layer 31, so that the two are in contact to form a leakage composite structure. In another embodiment, at a preset position, a functional layer with a conductive function is formed so that the first doping layer 31 and the second doping layer 32 are in contact to form a leakage composite contact structure 34. In yet another embodiment, the leakage composite contact structure 34 can be formed by a stacked structure of the first doping layer 31 and the second doping layer 32. Specifically, the second doping layer 32 can be stacked on the first doping layer 31, or the first doping layer 31 can be stacked on the second doping layer 32. Preferably, at a preset position, the second doping layer 32 is stacked on the first doping layer 31 to form the leakage composite contact structure 34. Based on this structure, the leakage composite contact structure 34 can be formed by etching the second doping layer 32, which is a simple process and has high reliability.

[0074] The positive electrode grid line 41 may be a silver grid line, an aluminum grid line, a copper grid line or a silver-clad copper grid line, but is not limited thereto. The positive electrode grid line 41 is disposed above the first doping layer 31 and contacts the first doping layer 31. Figure 3In one embodiment, an insulating layer 5 is provided between the positive gate line 41 and the first doped layer 31. The positive gate line 41 contacts the first doped layer 31 through a first hole 51 provided in the insulating layer 5. The first hole 51 may be formed by, but is not limited to, a laser process, an etching process, or a slurry burn-through process. The positive gate line 41 is provided only in the first and second predetermined regions 121 and 122; no positive gate line 41 is provided in the third predetermined region 123.

[0075] The negative electrode grid line 42 may be a silver grid line, an aluminum grid line, a copper grid line or a silver-clad copper grid line, but is not limited thereto. Figure 3 In one embodiment, an insulating layer 5 is further disposed between the negative gate line 42 and the second doped layer 32. The negative gate line 42 contacts the second doped layer 32 through a second hole 52 formed in the insulating layer 5. The second hole 52 can be formed by, but is not limited to, a laser process, an etching process, or a slurry burn-through process. The negative gate line 42 is disposed only in the first and second predetermined regions 121 and 122; no negative gate line 42 is disposed in the third predetermined region 123.

[0076] refer to Figure 1In this embodiment, at least one group of first test points is further provided within first preset region 121. Each group of first test points includes a first test PAD point 61 and a second test PAD point 62. First test PAD point 61 is electrically connected to at least one positive gate line 41 located within first preset region 121, and second test PAD point 62 is electrically connected to at least one negative gate line 42 located within first preset region 121. Correspondingly, at least one group of second test points is further provided within second preset region 122. Each group of second test points includes a third test PAD point 63 and a fourth test PAD point 64. Third test PAD point 63 is electrically connected to at least one positive gate line 41 located within second preset region 122, and fourth test PAD point 64 is electrically connected to at least one negative gate line 42 located within second preset region 122. Based on the technical solution of this embodiment, a reverse current can be introduced into the back-contact solar cell through the first test point and / or the second test point, and the reverse current is allowed to flow through the leakage composite contact structure 34, and then the reverse breakdown voltage of the back-contact solar cell is tested, which provides a good basis for characterizing the hot spot effect at the cell end. It should be noted that conventional hot spot tests are generally performed at the component end, that is, any one or more solar cell slices in the solar cell component are blocked, and the other solar cells (or slices) are exposed to light. After a period of time, the temperature of the blocked solar cells (or slices) is tested to characterize the hot spot effect. It is difficult for the existing technology to perform a more accurate quantitative characterization of the hot spot effect at the cell end. However, after introducing the leakage composite contact structure 34, this embodiment measures its reverse breakdown voltage, and then can quantitatively characterize the hot spot effect through the reverse breakdown voltage, providing a good basis for controlling the hot spot effect of the component.

[0077] It should be noted that, for improving the efficiency of high-efficiency solar cells, since their passivation characteristics are approaching theoretical limits, reducing the number of main grids and PAD points is a crucial method for further improving the photovoltaic conversion efficiency of solar cells. The welding technology of back-contact 0BB photovoltaic modules can effectively reduce the shading of the main grid and PAD points and the interruption of the cell's interdigital structure, thereby improving the collection of photogenerated carriers in back-contact solar cells. However, for 0BB cells, the difficulty in testing their reverse breakdown voltage is a major challenge in cell sorting. This stems from the difficulty in aligning the fine grids with the probes and PCBs used in conventional IV testing, making it impossible to test the reverse voltage characteristics and further characterize the cell's hot spot resistance. In this embodiment, by designing one or more PN units in the leakage composite structure 34 for testing, and then correcting the formula to obtain the reverse breakdown voltage under the actual operating conditions of the solar cell, the reduction in efficiency caused by the setting of the test PAD points can be minimized, and the hot spot resistance of the cell can be accurately characterized, greatly improving the testing and sorting efficiency of the solar cell and further enhancing the hot spot resistance of the photovoltaic module. It should be noted that the first test point and the second test point in this embodiment can not only be used to measure the reverse breakdown voltage, but can also be used to test other parameters of conventional back-contact solar cells, such as EL images, IV curves, open-circuit voltage, short-circuit current, conversion efficiency, etc. However, when performing these measurements, it is preferably necessary to fully connect the first test point and the second test point to the gate lines of the corresponding polarity to obtain the physical signal of the entire solar cell.

[0078] In addition, reference Figure 4 It should be noted that, since the back-contact solar cell in this embodiment needs to be cut into the first cell slice 210 and the second cell slice 220 in the later stage, it is necessary to set the first test point and the second test point in the first preset area 121 and the second preset area 122 respectively, so as to test the reverse breakdown voltage of the first cell slice 210 and the second cell slice 220 respectively, and then characterize the hot spot effect of the first cell slice 210 and the second cell slice 220.

[0079] Specifically, in this embodiment, the first test point and the second test point can be one group or multiple groups. It is understandable that when the number of groups is large, the test result of the reverse breakdown voltage is more accurate, but more first test points also means that more backlight surface 12 area is occupied, and the area for arranging positive gate lines 41 and negative gate lines 42 becomes less, which is not conducive to conversion efficiency. Preferably, considering the conversion efficiency and test accuracy, the number of first test points and second test points is set to 1 to 6 groups, exemplarily 1 group, 2 groups, 3 groups, 4 groups or 5 groups, but not limited thereto. Preferably, 1 to 4 groups.

[0080] The following further explains the influence of the number of the first test point and the second test point on the reverse breakdown voltage test results:

[0081] For an ideal diode, its current can be calculated as follows:

[0082]

[0083] Where, I DD is the current flowing from the positive electrode to the negative electrode in the ideal diode, I s is the reverse saturation current of the ideal diode; n is the emission coefficient, which is 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 electrodes of the ideal diode.

[0084] After the leakage composite contact structure 34 is introduced, the current of the diode with leakage current can be calculated by the following formula:

[0085]

[0086] Among them, I D is the output current of the diode with leakage current, I DD is the current flowing from the positive electrode to the negative electrode in the ideal diode, I S is the reverse saturation current of the ideal diode, n is the emission coefficient, and its value is 1 to 2; k is the Boltzmann constant, T is the temperature, q is the space electron charge, V is the voltage across the positive and negative electrodes 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.

[0087] Under non-ideal conditions, the diode can be reversely broken down, and the reverse breakdown current I D,BR It can be expressed as:

[0088]

[0089] Among them, I BR is the breakdown inflection point current; V is the voltage across the positive and negative electrodes of the diode, V BR is the reverse breakdown voltage, n BR is the breakdown emission coefficient, and its value range is 0.95~1.02.

[0090] Therefore, when the series resistance (i.e., the gate line resistance and the contact resistance between the gate line and the doped layer) is not taken into account, the current of the back-contact solar cell in this embodiment can be calculated by the following formula:

[0091]

[0092] In actual testing, due to the voltage division of series resistance (gate line resistance, contact resistance between gate line and doping layer), when the external voltage is VW When the gate line resistance of a pitch (PN unit) is R s , x is the number of pitches transmitted, and the gate line has good contact with the doped layer, and the contact resistance is extremely small, then the voltage across the minimum unit diode is V = V w -xI D R s .

[0093] Then, after taking into account the series resistance, the current of a single PN unit in the back-contact battery in this embodiment can be calculated by the following formula:

[0094]

[0095] Where V W is the external voltage, R s is the line resistance of the gate line transmission of a pitch (PN unit), x is the variable representing the number of pitches between the positive gate line 41 and the first test PAD point 61 / the third test PAD point 63, and Figure 2 For example, there are 6 first doping layers and 6 second doping layers between adjacent first test PAD points 61 / second test PAD points 62 , which is 6 PN units in total, so x=6÷2=3.

[0096] Here, it should be noted that, in this embodiment, a plurality of first doping layers 31 and second doping layers 32 are provided on the back of the back contact cell, which form a plurality of PN units with the silicon substrate 1. It can be approximately considered that the plurality of PN units are connected in parallel.

[0097] Therefore, when only one set of first test points is set on the first battery slice 210 having z pitches, the measured current and voltage can be calculated by the following formula:

[0098]

[0099] Among them, I D2 is the current measured when setting the first test point, V C2 This is the voltage measured when setting a set of first test points.

[0100] If four groups of first test points are set, the measured current and voltage can be calculated using the following formula:

[0101]

[0102] Among them, I D5 is the current measured when setting the first test point of the four groups, V C5 This is the voltage measured when setting the first test point of the four groups.

[0103] From the above two formulas, we can undoubtedly find that: I D5>I D2 Therefore, for the first battery slice 210 to be tested, V C5 <V C2 . That is, when the number of first test points 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 first shunt gate line 71 / the second shunt gate line 72 and other broken gates. However, as mentioned above, increasing the number of first test points is not conducive to improving the conversion efficiency. To this end, the utility model has conducted a large number of tests based on the above analysis and proposed a specific correction method, which will be described in detail below.

[0104] Among them, the first test PAD point 61 and the second test PAD point 62 can be set at any position in the first preset area 121. The third test PAD point 63 and the fourth test PAD point 64 can be set at any position in the second preset area 122, as long as the current injected therethrough can pass through at least one leakage composite contact structure 34. Preferably, in one embodiment, the silicon substrate 1 has a first edge 13 and a second edge 14 arranged opposite to each other in the second direction; the first test PAD point 61 and the fourth test PAD point 64 are arranged close to the first edge 13; the second test PAD point 62 and the third test PAD point 63 are arranged close to the second edge 14. It should be noted that both the positive gate line 41 and the negative gate line 42 have line resistance, and after the reverse current is passed, there will be a voltage divider on these gate lines; in addition, there is contact resistance between the positive gate line 41 and the first doped layer 31, and between the negative gate line 42 and the second doped layer 32, which will also generate a voltage divider. Therefore, in order to more accurately characterize the reverse breakdown voltage of the back-contact solar cell, it is necessary to consider the gate line line resistance voltage divider and the contact resistance voltage divider. In this embodiment, the first test PAD point 61, the second test PAD point 62, the third test PAD point 63, and the fourth test PAD point 64 are located near the edge of the silicon substrate 1 in the second direction, while the positive gate line 41 and the negative gate line 42 both extend along the second direction. Therefore, this embodiment allows the reverse current to flow through the longer positive gate line 41 and negative gate line 42 in the second direction, which can better characterize the effects of the gate line resistance voltage division and the contact resistance voltage division on the reverse breakdown voltage.

[0105] Preferably, in one embodiment, the first test PAD point 61 and the fourth test PAD point 64 are located on the same straight line extending along the first direction and located on the backlight surface 12. In this embodiment, the first test PAD point 61 is connected to the positive gate line 41 in the first preset area 121, and the fourth test PAD point 64 is connected to the negative gate line 42 in the second preset area 122, and the polarities of the two are different. Figure 4After the first test PAD point 61 and the fourth PAD point are set in the same straight line, when the back contact solar cell is cut into the first cell slice 210 and the second cell slice 220, when forming the cell string 200, the first test PAD point 61 and the fourth test PAD point 64 can be directly connected using the welding ribbon 230 to form a series connection of the first cell slice 210 and the second cell slice 220. That is, based on this embodiment, the first test PAD point 61 and the fourth test PAD point 64 can be used as welding PAD points at the same time to improve the welding tension. It should be noted that, see Figure 4 In the solar cell string 200, multiple solar cells or solar cell slices are included, which are generally connected in series or in parallel through the welding ribbon 230. The welding ribbon 230 is welded to the solar cells or solar cell slices. In order to increase the welding tension, it is usually necessary to set multiple welding PAD points. This embodiment introduces a first test PAD point 61 and a fourth test PAD point 62, which can also be used as welding PAD points. Therefore, the number of welding PAD points can be reduced and grid line paste can be saved.

[0106] Accordingly, in one embodiment, the second test PAD point 62 and the third test PAD point 63 are located on the same straight line extending along the first direction and located on the backlight surface 12. Based on this embodiment, the second test PAD point 62 and the third test PAD point 63 can also be used for welding to increase welding tension.

[0107] It should be noted that the distribution positions of the test PAD points in this embodiment are not limited to this. For example, in one embodiment, the first test PAD point 61 and the third test PAD point 63 with the same polarity can be arranged along the same straight line. In another embodiment, the first test PAD point 61 and the fourth test PAD point 64 can both be arranged close to the first edge 13, but in a staggered distribution in the second direction, but the present invention is not limited to this.

[0108] Specifically, in one embodiment, the back-contact solar cell also includes a first shunt gate line 71 and a second shunt gate line 72 arranged in a first preset area 121; the first shunt gate line 71 is electrically connected to a number of positive gate lines 41 located in the first preset area 121, and the second shunt gate line 72 is electrically connected to a number of negative gate lines 42 located in the first preset area 121; the first shunt gate line 71 is electrically connected to the first test PAD point 61, and the second shunt gate line 72 is electrically connected to the second test PAD point 62; based on the above embodiment, the reverse current from the first test PAD point 61 is shunted to multiple positive gate lines 41 via the first shunt gate line 71, and then flows through multiple negative gate lines 42 and then converges to the second test PAD point 62 via the second shunt gate line 72, thereby achieving the effect of better characterizing the influence of gate line resistance voltage division and contact resistance voltage division on the accuracy of reverse breakdown voltage test. In addition, it should be noted that: when the number of first test point groups set is small, the number of PN units passing through will also decrease accordingly. Although this test value can also characterize the hot spot effect of the back-contact solar cell to a certain extent, it is not accurate enough. By introducing the first shunt grid line 71 and the second shunt grid line 72, the reverse current can flow through more PN units, thereby effectively improving the accuracy of the test. Among them, the first shunt grid line 71 and the second shunt grid line 72 can be straight or curved, and can be set parallel to the first direction or set at an angle with the first direction, but are not limited to this. Preferably, in one embodiment, the first shunt grid line 71 and the second shunt grid line 72 are straight and extend along the first direction, that is, they are parallel to the first direction, which reduces the length of the first shunt grid line 71 and the second shunt grid line 72 between the positive grid line 41 to be connected or the negative grid line 42 to be connected, and reduces the influence of the first shunt grid line 71 and the second shunt grid line 72 on the test results. Accordingly, in one embodiment, the back-contact solar cell further includes a third shunt gate line 73 and a fourth shunt gate line 74 located within the second predetermined region 122; the third shunt gate line 73 is electrically connected to a plurality of positive gate lines 41 located within the second predetermined region 122, and the fourth shunt gate line 74 is electrically connected to a plurality of negative gate lines 42 located within the second predetermined region 122; the third shunt gate line 73 is electrically connected to a third test PAD point 63, and the fourth shunt gate line 74 is electrically connected to a fourth test PAD point 64. Based on the above embodiment, the accuracy of the test can be improved.

[0109] Specifically, the third shunt grid line 73 and the fourth shunt grid line 74 may be linear or curved, and may be arranged parallel to the first direction or at an angle thereto, but are not limited thereto. Preferably, in one embodiment, the third shunt grid line 73 and the fourth shunt grid line 74 are linear and extend along the first direction, i.e., they are parallel to the first direction. This reduces the length of the third shunt grid line 73 and the fourth shunt grid line 74 between the positive electrode grid line 41 to be connected or the negative electrode grid line 42 to be connected, thereby reducing the impact of the third shunt grid line 73 and the fourth shunt grid line 74 on the test results.

[0110] Preferably, in one embodiment, the first shunt gate line 71 is arranged near the first edge 13, and the second shunt gate line 72 is arranged near the second edge 14. Based on this arrangement, the gate line structure can be simplified, the carrier collection efficiency can be improved, and the conversion efficiency can be improved. Since the first shunt gate line 71 / the second shunt gate line 72 connects multiple positive gate lines 41 / negative gate lines 42 distributed in the first direction, if the first shunt gate line 71 / the second shunt gate line 72 is arranged in the center, multiple discontinuous insulation structures or other types of insulation structures need to be arranged in the gate line areas with different polarities. The gate line structure is complex and the arrangement area of ​​the positive gate line 41 and the negative gate line 42 is reduced, thereby reducing the collection of carriers. More preferably, the first shunt gate line 71 is arranged at the end of the positive gate line 41 near the first edge 13, and the second shunt gate line 72 is arranged at the end of the negative gate line 42 near the second edge 14.

[0111] In addition, it can be expected that since the first shunt grid line 71 / the second shunt grid line 72 are located at the two ends of the contact solar cell, the number of photogenerated non-equilibrium carriers generated at the edge is small. Usually, in order to reduce the recombination loss of metal contact, the first shunt grid line 71 / the second shunt grid line 72 can be designed as a non-burn-through / non-contact metal grid line. Since its function is to shunt / collect rather than collect carriers, its broken grid has little effect on efficiency. However, if it causes misjudgment of sorting due to its disconnection, it will cause a large amount of waste in production costs. At the same time, it can be understood that by increasing the number of settings of the first test PAD point 61 and the second test PAD point 62, the impact of the broken grid of the first shunt grid line 71 / the second shunt grid line 72 on the test results can also be reduced. Accordingly, the third shunt grid line 73 is set close to the second edge 14, and the fourth shunt grid line 74 is set close to the first edge 13. More preferably, the third shunt gate line 73 is disposed at the end of the positive gate line 41 close to the second edge 14 , and the fourth shunt gate line 74 is disposed at the end of the negative gate line 42 close to the first edge 13 .

[0112] It is foreseeable that, since the third shunt grid line 73 / fourth shunt grid line 74 is located at both ends of the back-contact solar cell, the number of photogenerated non-equilibrium carriers generated at the edge is small. Usually, in order to reduce the recombination loss of the metal contact, the third shunt grid line 73 / fourth shunt grid line 74 can be designed as a non-burn-through / non-contact metal grid line. Since its function is to shunt / collect rather than collect carriers, its broken gate has little effect on efficiency. However, if its disconnection causes misjudgment of sorting, it will cause a large waste of production costs. At the same time, it is understandable that by increasing the number of the third test PAD point 63 and the fourth test PAD point 64, the impact of the third shunt grid line 73 / fourth shunt grid line 74 broken gate on the test results can also be reduced.

[0113] Specifically, in one embodiment, when the first test PAD point 61 and the first shunt gate line 71 are both set close to the first edge 13, the distance between the first test PAD point 61 and the first edge 13 is controlled to be greater than the distance between the first shunt gate line 71 and the first edge 13. Since the first test PAD point 61 is relatively large and too close to the edge of the silicon substrate 1, defects such as hidden cracks are easily caused during printing. Moreover, by controlling the first shunt gate line 71 to be closer to the first edge 13, a spacing area is formed between the first shunt gate line 71 and the first test PAD point 61. A negative gate line 42 with a different polarity from the first test PAD point 61 can be set in the spacing area, further improving the carrier collection efficiency and improving the conversion efficiency.

[0114] Specifically, when a gap is formed between the first shunt gate line 71 and the first test PAD point 61, the first shunt gate line 71 can be electrically connected to the first test PAD point 61 via a first connecting gate line 81. Preferably, in one embodiment, the first connecting gate line 81 and a positive gate line 41 located in the first predetermined area 121 are arranged on the same straight line extending along the second direction and located on the backlight surface 12. That is, the first connecting gate line 81 is arranged above the first doped layer 31 corresponding to the positive gate line 41, and then the first connecting gate line 81 can be connected to the first doped layer 31 through the first hole 51, so that the first connecting gate line 81 can also collect carriers, thereby improving conversion efficiency.

[0115] Accordingly, in one embodiment, when the second test PAD point 62 and the second shunt gate line 72 are both located near the second edge 14, the distance between the second test PAD point 62 and the second edge 14 is controlled to be greater than the distance between the second shunt gate line 72 and the second edge 14. The second shunt gate line 72 and the second test PAD point 62 are electrically connected via a second connecting gate line 82. The second connecting gate line 82 and a negative gate line 42 located in the first predetermined area 121 are located on the same straight line extending along the second direction and located on the backlight surface 12 to improve carrier collection efficiency.

[0116] Accordingly, in one embodiment, when the third test PAD point 63 and the third shunt gate line 73 are both located near the second edge 14, the distance between the third test PAD point 63 and the second edge 14 is controlled to be greater than the distance between the third shunt gate line 73 and the second edge 14. The third connecting gate line 83 and a positive gate line 41 located in the second predetermined area 122 are located on the same straight line extending along the second direction and located on the backlight surface 12 to improve carrier collection efficiency.

[0117] Accordingly, in one embodiment, when the fourth test PAD point 64 and the fourth shunt gate line 74 are both located near the first edge 13, the distance between the fourth test PAD point 64 and the first edge 13 is greater than the distance between the fourth shunt gate line 74 and the first edge 13. The fourth connecting gate line 84 and a negative gate line 42 located in the second predetermined area 122 are located on the same straight line extending along the second direction and located on the backlight surface 12 to improve carrier collection efficiency.

[0118] For example, in one embodiment, the distance between the first test PAD point 61, the fourth test PAD point 64 and the first edge 13 is 3 mm to 8 mm; the distance between the second test PAD point 62, the third test PAD point 63 and the second edge 14 is 3 mm to 8 mm. The distance between the first shunt line 71, the fourth shunt line 74 and the first edge 13 is 0.2 mm to 5 mm, and the distance between the second shunt line 72, the third shunt line 73 and the second edge 14 is 0.2 mm to 5 mm.

[0119] Specifically, in one embodiment, the positive grid line 41 includes a first positive sub-grid line 411 provided in the first preset area 121, the negative grid line 42 includes a first negative sub-grid line 421 provided in the first preset area 121 and adjacent to the first positive grid line 41, and the first test PAD point 61 is provided at the end of the first positive sub-grid line 411 and is electrically connected to the first positive sub-grid line 411. The second test PAD point 62 is provided at the end of the first negative sub-grid line 421 and is electrically connected to the first negative sub-grid line 421. Based on this embodiment, the first test PAD point 61 and the second test PAD point 62 in each group of first test points are approximately arranged on the same straight line extending along the second direction, and the stress distribution during printing is more uniform, thereby reducing the risk of cracking.

[0120] Correspondingly, in another embodiment, positive grid line 41 further includes a second positive sub-grid line 412 disposed within second predetermined region 122, and negative grid line 42 further includes a second negative sub-grid line 422 disposed within second predetermined region 122 and adjacent to second positive sub-grid line 412. A third test PAD point 63 is disposed at an end of second positive sub-grid line 412 and electrically connected to second positive sub-grid line 412; and a fourth test PAD point 64 is disposed at an end of second negative sub-grid line 422 and electrically connected to second negative sub-grid line 422.

[0121] Specifically, in one embodiment, the first test PAD point 61 is electrically connected to at least three first positive sub-grid lines 411; the second test PAD point 62 is electrically connected to at least three first negative sub-grid lines 421. Although the first test PAD point 61 / the second test PAD point 62 can distribute the reverse current through the first shunt grid line 71 / the second shunt grid line 72, the first shunt grid line 71 / the second shunt grid line 72 are narrow, and when the current density is too large, more current is consumed. For this reason, the first test PAD point 61 / the second test PAD point 62 is connected to at least three first positive sub-grid lines 411 / the first negative sub-grid lines 421 to optimize the current distribution and improve the test accuracy. More preferably, the first test PAD point 61 is electrically connected to the three first positive sub-gate lines 411; the second test PAD point 62 is electrically connected to the three first negative sub-gate lines 421. When the number of connected gate lines is too large, the sizes of the first test PAD point 61 and the second test PAD point 62 are too large, occupying more area of ​​the gate lines for collecting carriers, which is not conducive to improving conversion efficiency.

[0122] Accordingly, in another embodiment, the third test PAD point 63 is electrically connected to at least three second positive sub-grid lines 412; and the fourth test PAD point 64 is electrically connected to at least three second negative sub-grid lines 422. Preferably, the third test PAD point 63 is electrically connected to three second positive sub-grid lines 412, and the fourth test PAD point 64 is electrically connected to three second negative sub-grid lines 422.

[0123] Preferably, in one embodiment, in order to further improve the collection efficiency of carriers, a third negative sub-grid line 423 is further provided on at least one side of the first connecting grid line 81, and the third negative sub-grid line 423 is electrically connected to a negative grid line 42 and is insulated from the first test PAD point 61. Through the third negative sub-grid line 423, the carriers in the gap between the first shunt grid line 71 and the first test PAD point 61 can be collected, thereby improving the conversion efficiency. A third positive sub-grid line 413 is further provided on at least one side of the second connecting grid line 82, and the third positive sub-grid line 413 is electrically connected to a positive grid line 41 and is insulated from the second test PAD point 62; through the third positive sub-grid line 413, the carriers in the gap between the second shunt grid line 72 and the second test PAD point 62 can be collected, thereby improving the conversion efficiency.

[0124] Correspondingly, in another embodiment, at least one side of the third connecting gate line 83 is further provided with a fourth negative sub-gate line 424, the fourth negative sub-gate line 424 is connected to a negative gate line 42, and is insulated from the third test PAD point 63; at least one side of the fourth connecting gate line 84 is further provided with a fourth positive sub-gate line 414, the fourth positive sub-gate line 414 is connected to a positive gate line 41, and is insulated from the fourth test PAD point 64.

[0125] Specifically, in this embodiment, the first test PAD point 61, the second test PAD point 62, the third test PAD point 63, and the fourth test PAD point 64 are square, circular, triangular, or irregular in shape, but are not limited thereto. Preferably, in one embodiment, the first test PAD point 61, the second test PAD point 62, the third test PAD point 63, and the fourth test PAD point 64 are square in shape, with a width of 0.1 mm to 3 mm to achieve good contact with the test electrode.

[0126] Specifically, in one embodiment, the device further includes: at least two groups of welding points, which are located in the first predetermined area 121 and the second predetermined area 122; each group of welding points includes a plurality of first welding PAD points 91 and a plurality of second welding PAD points 92, and the plurality of first welding PAD points 91 and the plurality of second welding PAD points 92 are arranged alternately along the second direction. Preferably, in one embodiment, two groups of welding points are provided in the first predetermined area 121, one group of welding points is located near the third edge 15 of the silicon substrate 1, and the other group is located near the third predetermined area 123. Similarly, two groups of welding points are provided in the second predetermined area 122, one group of welding points is located near the fourth edge 16 of the silicon substrate 1, and the other group is located near the third predetermined area 123.

[0127] Preferably, the first welding PAD point 91 located in the first preset area 121 and closest to the first edge 13 and the first test PAD point 61 located near the first edge 13 are arranged on the same straight line extending along the first direction and located on the backlight surface 12; the second welding PAD point 92 located in the first preset area 121 and closest to the second edge 14 and the second test PAD point 62 located near the second edge 14 are arranged on the same straight line extending along the first direction and located on the backlight surface 12; the second welding PAD point 92 located in the second preset area 122 and closest to the first edge 13 and the fourth test PAD point 64 located near the first edge 13 are arranged on the same straight line extending along the first direction and located on the backlight surface 12; and the first welding PAD point 91 located in the second preset area 122 and closest to the second edge 14 and the third test PAD point 63 located near the second edge 14 are arranged on the same straight line extending along the first direction and located on the backlight surface 12. Based on this embodiment, the welding tensile force can be further improved. The third edge 15 and the fourth edge 16 refer to two edges of the silicon substrate 1 that are opposite to each other in the second direction.

[0128] Accordingly, this embodiment further discloses a method for evaluating the hot spot effect of a back-contact solar cell, which is used to evaluate the hot spot effect of the above-mentioned back-contact solar cell, and includes:

[0129] S1: passing a reverse current through the first test point and / or the second test point to put the back-contact solar cell in a reverse bias state, measuring its test reverse voltage, and calculating the actual reverse breakdown voltage based on the test reverse voltage;

[0130] The actual reverse breakdown voltage is calculated according to the following formula:

[0131]

[0132] Among them, U rev is the actual reverse breakdown voltage, U is the test reverse voltage, x is the total number of positive gate lines and negative gate lines located in the first preset area or the total number of positive gate lines and negative gate lines located in the second preset area, l is the variable characterizing the test of the first test point or the variable of the second test point, n1 is the number of the first test PAD points or the number of the third test PAD points, n2 is the number of the second test PAD points or the number of the fourth test PAD points, A is a constant, and its value range is 0.1~3.3, and B is a constant, and its value range is 2~50.

[0133] Based on the above relationship, the test results can be corrected when setting any set of first and second test points to obtain an accurate reverse breakdown voltage. Specifically, research has found that when setting 1 to 6 sets of first and second test points, the test error is ≤5%, and when setting 4 to 6 sets, the test error is ≤3.5%.

[0134] S2: Evaluate the hot spot effect according to the actual reverse breakdown voltage;

[0135] Specifically, according to extensive research by the inventors, for a specific type of solar cell, different reverse breakdown voltages result in different hot spot temperatures under shading conditions. Therefore, the hot spot effect can be reasonably evaluated based on the reverse breakdown voltage.

[0136] Accordingly, this embodiment also discloses a cell string 200 comprising the aforementioned back-contact solar cells. Cell string 200 may be formed by shingling or welding multiple back-contact solar cells or their resulting slices, but is not limited thereto. Accordingly, to connect the multiple back-contact solar cells, cell string 200 components may also include, but are not limited to, soldering tape, insulating adhesive, adhesive, conductive adhesive, and the like.

[0137] Accordingly, this embodiment also discloses a battery assembly comprising the aforementioned back-contact solar cell or the aforementioned battery string 200. Preferably, in one embodiment, the battery assembly is composed of a plurality of the aforementioned battery strings 200, exemplified by, but not limited to, two, four, or six strings. Accordingly, to connect the battery strings, the battery assembly also requires, but is not limited to, components such as insulating adhesive, busbars, junction boxes, frames, backsheets, adhesive films, and glass.

[0138] Correspondingly, this embodiment also discloses a photovoltaic system, which includes the above-mentioned battery assembly. In this embodiment, the photovoltaic system can be applied to photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., 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, solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array can be an array combination of multiple battery assemblies. For example, multiple battery assemblies can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter to be converted into the alternating current required by the mains power grid and then connected to the mains power network to achieve solar power supply.

[0139] The above is a preferred embodiment of the utility model. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the utility model. These improvements and modifications are also considered to be within the scope of protection of the utility model.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate comprising a light-receiving surface and a backlight surface arranged opposite to each other; the silicon substrate comprising a first preset area, a second preset area, and a third preset area, wherein the third preset area is arranged between the first preset area and the second preset area; The third preset area is used for cutting the silicon substrate; a plurality of first doped layers and a plurality of second doped layers, which are arranged on the backlight surface, the plurality of first doped layers and the plurality of second doped layers are alternately arranged in a first preset area and a second preset area along a first direction, and extend along a second direction, at least one of the second doped layers is in composite contact with at least one of the first doped layers at a preset position to form a leakage composite contact structure; a plurality of positive gate lines and a plurality of negative gate lines, wherein the positive gate lines are provided on the first doped layer, and the negative gate lines are provided on the second doped layer; at least one group of first test points within the first preset area, each group of first test points including a first test PAD point and a second test PAD point, the first test PAD point being electrically connected to at least one positive gate line within the first preset area, and the second test PAD point being electrically connected to at least one negative gate line within the first preset area; and At least one group of second test points is arranged in the second preset area, and each group of second test points includes a third test PAD point and a fourth test PAD point, the third test PAD point is electrically connected to at least one positive gate line located in the second preset area, and the fourth test PAD point is electrically connected to at least one negative gate line located in the second preset area.

2. The back contact solar cell according to claim 1, wherein The silicon substrate has a first edge and a second edge opposite to each other in the second direction; The first test PAD point and the fourth test PAD point are arranged close to the first edge; The second test PAD point and the third test PAD point are located close to the second edge.

3. The back contact solar cell according to claim 2, wherein: The first test PAD point and the fourth test PAD point are located on the same straight line extending along the first direction and located on the backlight surface; and / or The second test PAD point and the third test PAD point are located on the same straight line extending along the first direction and located on the backlight surface.

4. The back contact solar cell according to claim 1, wherein It includes 1 to 6 groups of first test points and 1 to 6 groups of second test points.

5. The back contact solar cell according to claim 1, wherein Also includes: A first shunt gate line and a second shunt gate line are provided in a first preset area; the first shunt gate line is electrically connected to a plurality of positive gate lines located in the first preset area, and the second shunt gate line is electrically connected to a plurality of negative gate lines located in the first preset area; the first shunt gate line is electrically connected to the first test PAD point, and the second shunt gate line is electrically connected to the second test PAD point; and / or A third shunt gate line and a fourth shunt gate line are arranged in the second preset area; the third shunt gate line is electrically connected to several positive gate lines located in the second preset area, and the fourth shunt gate line is electrically connected to several negative gate lines located in the second preset area; the third shunt gate line is electrically connected to the third test PAD point, and the fourth shunt gate line is electrically connected to the fourth test PAD point.

6. The back contact solar cell according to claim 5, characterized in that The silicon substrate has a first edge and a second edge opposite to each other in the second direction; The first shunt gate line is arranged close to the first edge, and the second shunt gate line is arranged close to the second edge; and / or The third shunt gate line is disposed close to the second edge, and the fourth shunt gate line is disposed close to the first edge.

7. The back contact solar cell according to claim 6, wherein: The distance between the first test PAD point and the first edge is greater than the distance between the first shunt gate line and the first edge; and / or The distance between the second test PAD point and the second edge is greater than the distance between the second shunt gate line and the second edge; and / or The distance between the third test PAD point and the second edge is greater than the distance between the third shunt gate line and the second edge; and / or The distance between the fourth test PAD point and the first edge is greater than the distance between the fourth shunt gate line and the first edge.

8. The back contact solar cell according to claim 7, wherein: The distance between the first test PAD point, the fourth test PAD point and the first edge is 3mm to 8mm; the distance between the second test PAD point, the third test PAD point and the second edge is 3mm to 8mm; and / or The distances between the first and fourth shunt gate lines and the first edge are 0.2 mm to 5 mm, and the distances between the second and third shunt gate lines and the second edge are 0.2 mm to 5 mm.

9. The back contact solar cell according to claim 6, wherein: The first test PAD point is electrically connected to the first shunt gate line via a first connecting gate line; and / or The second test PAD point is electrically connected to the second shunt gate line via a second connecting gate line; and / or The third test PAD point is electrically connected to the third shunt gate line via a third connecting gate line; and / or The fourth test PAD point is electrically connected to the fourth shunt gate line through a fourth connecting gate line.

10. The back contact solar cell according to claim 9, characterized in that The first connecting gate line and a positive gate line located in the first predetermined area are arranged on the same straight line extending along the second direction and located on the backlight surface; and / or The second connecting gate line and a cathode gate line located in the first predetermined area are arranged on the same straight line extending along the second direction and located on the backlight surface; and / or The third connecting gate line and a positive gate line located in the second preset area are arranged on the same straight line extending along the second direction and located on the backlight surface; and / or The fourth connecting gate line and a negative gate line located in the second preset area are arranged on the same straight line extending along the second direction and located on the backlight surface.

11. The back contact solar cell according to claim 5, wherein: The positive gate line includes a first positive sub-gate line provided in a first preset area and a second positive sub-gate line provided in a second preset area, the first test PAD point is provided at an end of the first positive sub-gate line and is electrically connected to the first positive sub-gate line; the third test PAD point is provided at an end of the second positive sub-gate line and is electrically connected to the second positive sub-gate line; The negative gate line includes a first negative sub-gate line provided in a first preset area and a second negative sub-gate line provided in a second preset area, the second test PAD point is provided at an end of the first negative sub-gate line and is electrically connected to the first negative sub-gate line; the fourth test PAD point is provided at an end of the second negative sub-gate line and is electrically connected to the second negative sub-gate line; The first positive sub-gate line is disposed adjacent to the first negative sub-gate line, and the second positive sub-gate line is disposed adjacent to the second negative sub-gate line.

12. The back contact solar cell according to claim 11, wherein: The first test PAD point is electrically connected to at least three first positive sub-grid lines; the second test PAD point is electrically connected to at least three first negative sub-grid lines; and / or The third test PAD point is electrically connected to at least three second positive sub-gate lines; and the fourth test PAD point is electrically connected to at least three second negative sub-gate lines.

13. The back contact solar cell according to claim 10, wherein: A third negative sub-grid line is further provided on at least one side of the first connecting grid line, the third negative sub-grid line is electrically connected to one of the negative grid lines and is insulated from the first test PAD point; and / or A third positive sub-grid line is further provided on at least one side of the second connecting grid line, the third positive sub-grid line is electrically connected to one of the positive grid lines and is insulated from the second test PAD point; and / or A fourth negative sub-grid line is further provided on at least one side of the third connecting grid line, the fourth negative sub-grid line is connected to one of the negative grid lines and is insulated from the third test PAD point; and / or A fourth positive sub-grid line is further provided on at least one side of the fourth connecting grid line. The fourth positive sub-grid line is connected to one of the positive grid lines and is insulated from the fourth test PAD point.

14. The back contact solar cell according to claim 1, wherein The first test PAD point, the second test PAD point, the third test PAD point, and the fourth test PAD point are square, circular, or triangular.

15. The back contact solar cell according to claim 1, wherein The first test PAD point, the second test PAD point, the third test PAD point, and the fourth test PAD point are square, and their widths are 0.1 mm to 3 mm.

16. The back contact solar cell according to claim 2, wherein: Also includes: At least two groups of welding points, which are arranged in the first preset area and the second preset area; Each group of welding points includes a plurality of first welding PAD points and a plurality of second welding PAD points, and the plurality of first welding PAD points and the plurality of second welding PAD points are alternately arranged along the second direction.

17. The back contact solar cell according to claim 16, wherein: A first welding PAD point located in the first preset area and closest to the first edge and a first test PAD point located close to the first edge are located on the same straight line extending along the first direction and located on the backlight surface; and / or A second welding PAD point located in the first preset area and closest to the second edge and a second test PAD point located close to the second edge are arranged on the same straight line extending along the first direction and located on the backlight surface; The second welding PAD point located in the second preset area and closest to the first edge and the fourth test PAD point located close to the first edge are arranged on the same straight line extending along the first direction and located on the backlight surface; and / or The first welding PAD point located in the second preset area and closest to the second edge and the third testing PAD point located close to the second edge are arranged on the same straight line extending along the first direction and located on the backlight surface.

18. A battery string, characterized in that: The invention comprises the back contact solar cell sheet according to any one of claims 1 to 17 or the slices obtained by cutting the back contact solar cell sheet.

19. A battery assembly, characterized in that: comprising a battery string as claimed in claim 18, or The back-contact solar cell according to any one of claims 1 to 17 or the slices obtained by cutting the same.

20. A photovoltaic system, characterized in that: Comprising the battery assembly as claimed in claim 19.

Images