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

Abstract

The invention 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 present invention relates to the field of silicon solar cells, and 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 slices) in a photovoltaic module are partially or completely shielded, a voltage reverse bias will be generated. At this time, the shielded solar cell (slice) will become a load, consuming the power generated by the normal solar cell, thereby generating a large amount of heat, making the temperature of the solar cell higher, which is generally referred to as the hot spot effect. In the prior art, in order to solve the hot spot problem, a diode is generally connected in reverse parallel at both ends of the string unit to reduce the current of the shielded solar cell and weaken the hot spot effect. However, this parallel diode will produce power loss. In order to solve this problem, a feasible idea is to directly form a leakage composite contact structure on the solar cell (see CN117976743B), that is, in the process of making the solar cell, the doping layers of different polarities are partially contacted, thereby effectively reducing the reverse voltage at both ends of the shielded solar cell, reducing heat generation, and weakening the hot spot effect. After adopting this method, the control of the hot spot effect can be moved forward to the end of the solar cell. Therefore, how to evaluate the hot spot effect at the end of the solar cell has become a technical problem that needs to be solved by those skilled in the art.

[0003] On the other hand, conventional hot spot effect testing generally involves shielding any one or more solar cells (or sub-cells) in a solar cell module, while allowing other solar cells (or sub-cells) to receive light. After a certain period of time, the temperature of the shielded solar cell sub-cell 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 of the invention

[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 hot spot effect at the cell end.

[0005] In order to solve the above problems, the present invention discloses a back contact solar cell, which comprises:

[0006] A silicon substrate, comprising a light-receiving surface and a backlight surface arranged opposite to each other; the silicon substrate comprises a first preset area, a second preset area and a third preset area, 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;

[0007] A plurality of first doping layers and a plurality of second doping layers, which are arranged on the backlight surface, the plurality of first doping layers and the plurality of second doping layers are alternately arranged in a first preset area and a second preset area along a first direction, and extend along a second direction, and at least one of the second doping layers is in composite contact with at least one of the first doping 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 arranged on the first doped layer, and the negative gate lines are arranged on the second doped layer;

[0009] At least one group of first test points located in the first preset area, each group of the 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 electrode grid line located in the first preset area, and the second test PAD point is electrically connected to at least one negative electrode grid line located in 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 of the above technical solution, the silicon substrate has a first edge and a second edge that are arranged opposite to each other 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 disposed 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 a 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 of the above technical solution, it also includes:

[0018] A first shunt gate line and a second shunt gate line are arranged 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 a second preset area; the third shunt gate line is electrically connected to a plurality of positive gate lines located in the second preset area, and the fourth shunt gate line is electrically connected to a plurality of 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 of the above technical solution, the silicon substrate has a first edge and a second edge that are arranged opposite to each other 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 shunt gate line, the fourth shunt gate line and the first edge are 0.2 mm to 5 mm, and the distances between the second shunt gate line, the third shunt gate line and the second edge are 0.2 mm to 5 mm.

[0029] As an improvement of the above technical solution, the first test PAD point is electrically connected to the first shunt gate line through 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 of 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 negative gate 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

[0035] The third connecting grid line and a positive grid 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 of the above technical solution, the positive grid line includes a first positive sub-grid line arranged in a first preset area and a second positive sub-grid line arranged in a second preset area, the first test PAD point is arranged at the end of the first positive sub-grid line and is electrically connected to the first positive sub-grid line; the third test PAD point is arranged at the end of the second positive sub-grid line and is electrically connected to the second positive sub-grid line;

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

[0039] The first positive sub-grid line is disposed adjacent to the first negative sub-grid line, and the second positive sub-grid line is disposed adjacent to the second negative sub-grid 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-grid lines; and the fourth test PAD point is electrically connected to at least three second negative sub-grid lines.

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

[0045] A fourth positive sub-grid line is further disposed 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 of the above technical solution, it also includes: 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 of 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] A second welding PAD point located in the second preset area and closest to the first edge and a 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 it.

[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 the slices obtained by cutting thereof.

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

[0057] Correspondingly, the present invention also 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 back-contact solar cell, and comprises:

[0058] 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 through the test reverse voltage;

[0059] The hot spot effects were evaluated according to the actual reverse breakdown voltage.

[0060] Wherein, the actual reverse breakdown voltage is calculated according to the following formula:

[0061]

[0062] Among them, U revis 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, B is a constant, and its value range is 2~50.

[0063] The implementation of the present invention has the following beneficial effects:

[0064] In the back-contact solar cell of the present invention, at least one group of first test points is provided in the first preset area of ​​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 pole grid line located in the first preset area, and the second test PAD point is electrically connected to at least one negative pole 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 pole grid line located in the second preset area 122, and the fourth test PAD point is electrically connected to at least one negative pole 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 then 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 battery end. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 is a schematic diagram of the back structure of a back-contact solar cell in one embodiment of the present invention;

[0066] Figure 2 is a schematic diagram of the arrangement structure of the first doping layer and the second doping layer in one embodiment of the present invention;

[0067] Figure 3 is a schematic cross-sectional structure diagram of a back-contact solar cell in one embodiment of the present invention;

[0068] Figure 4 It is a schematic diagram of the structure of a battery string in one embodiment of the present invention. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals 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 should not be construed 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 are not intended to limit the present application.

[0070] In the description of the present 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, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0071] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0072] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0073] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0074] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, and does not indicate the relationship between the various embodiments and / or settings discussed in itself. In addition, the various specific processes and examples of materials provided by the present application, but those of ordinary skill in the art can be aware of the application of other processes and / or the use scenarios of other materials.

[0075] See also Figure 2 , an embodiment of the present invention discloses a back-contact solar cell, which includes: 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. Among them, 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. The silicon substrate 1 includes 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, and 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 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 arranged between the first preset area 121 and the second preset area 122.

[0076] It should be noted that there is no special restriction on the number of the first preset area 121, the second preset area 122, and the third preset area 123 in the embodiment of the present invention. For example, when a silicon substrate 1 of a larger specification is used, 2 to 3 cuts can be performed, and 2 to 3 third preset areas 123 can be set at this time, and then 1 to 2 first preset areas 121 and 1 to 2 second preset areas 122 can be set, but it is not limited to this. When multiple first preset areas 121, second preset areas 122, and third preset areas 123 are set, 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 set between the first preset areas 121 and the second preset areas 122. Preferably, in one embodiment, the backlight surface 12 is provided with a first preset area 121, a second preset area 122, and a 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.

[0077] The first doping layer 31 and the second doping layer 32 are arranged on the backlight surface 12. Specifically, the first doping layer 31 and the second doping layer 32 are arranged alternately in the first preset area 121 and the second preset area 122 along the first direction, and a spacing area 33 is provided between the first doping layer 31 and the second doping layer 32. The first doping layer 31 may be one or more of a P-type doped polysilicon layer, a P-type doped amorphous silicon layer or a P-type doped microcrystalline silicon layer, but not limited thereto. 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.

[0078] 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 can be reduced.

[0079] 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 effect 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 another embodiment, the leakage composite contact structure 34 can be formed by a structure in which the first doping layer 31 and the second doping layer 32 are stacked. 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 a leakage composite contact structure 34. Based on this structure, the leakage composite contact structure 34 can be formed by an etching process of the second doping layer 32, which is simple in process and highly reliable.

[0080] 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 further 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 on the insulating layer 5. The first hole 51 may be formed by a laser process, an etching process, or a slurry burn-through process, but is not limited thereto. The positive gate line 41 is only provided in the first preset area 121 and the second preset area 122, and the third preset area 123 is not provided with the positive gate line 41.

[0081] The negative electrode grid wire 42 may be a silver grid wire, an aluminum grid wire, a copper grid wire or a silver-clad copper grid wire, but is not limited thereto. Figure 3 In one embodiment, an insulating layer 5 is further provided between the negative electrode grid line 42 and the second doping layer 32, and the negative electrode grid line 42 contacts the second doping layer 32 through a second hole 52 provided on the insulating layer 5. The second hole 52 may be formed by a laser process, an etching process, or a slurry burn-through process, but is not limited thereto. The negative electrode grid line 42 is only provided in the first preset area 121 and the second preset area 122, and the third preset area 123 is not provided with the negative electrode grid line 42.

[0082] refer to Figure 1In this embodiment, at least one group of first test points is further provided in the first preset area 121, each group of first test points includes a first test PAD point 61 and a second test PAD point 62, the first test PAD point 61 is electrically connected to at least one positive grid line 41 located in the first preset area 121, and the second test PAD point 62 is electrically connected to at least one negative grid line 42 located in the first preset area 121. Correspondingly, at least one group of second test points is further provided in the second preset area 122, each group of second test points includes a third test PAD point 63 and a fourth test PAD point 64, the third test PAD point 63 is electrically connected to at least one positive grid line 41 located in the second preset area 122, and the fourth test PAD point 64 is electrically connected to at least one negative grid line 42 located in the second preset area 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 shielded, and other solar cells (or slices) are exposed to light. After a period of time, the temperature of the shielded solar cells (or slices) is tested to characterize the hot spot effect. It is difficult for the existing technology to accurately quantify the hot spot effect at the cell end. After the leakage composite contact structure 34 is introduced in this embodiment, its reverse breakdown voltage is measured, and then the hot spot effect can be quantitatively characterized by the reverse breakdown voltage, which provides a good basis for controlling the hot spot effect of the component.

[0083] It should be noted that, for the efficiency improvement of high-efficiency solar cells, since its passivation characteristics are close to the theoretical limit, reducing the main grid and PAD points is a crucial way to further improve the photoelectric conversion efficiency of solar cells. The welding technology of the back-contact 0BB photovoltaic module can effectively reduce the shielding of the main grid and PAD points and the characteristics of the interruption of the cell fork structure, which can improve the influence of the back-contact solar cell photogenerated carrier collection. However, for 0BB cells, the difficulty in testing their reverse breakdown voltage is the main difficulty in realizing cell sorting. It is due to the difficulty of aligning the fine grid with the probe and PCB board of the conventional IV test, and it is impossible to test the reverse voltage characteristics, and it is difficult to further characterize the anti-hot spot characteristics of the cell. In this embodiment, by designing one or more PN units of the leakage composite structure 34 for testing, and then correcting the formula to obtain the reverse breakdown voltage under the actual working state of the solar cell, the setting of the test PAD point can be minimized to reduce the reduction in efficiency, and the accurate characterization of the anti-hot spot characteristics of the cell can be completed, which greatly improves the test sorting efficiency of the solar cell and further improves the anti-hot spot characteristics of the photovoltaic module. It should be noted that the first test point and the second test point in the present embodiment can be used not only for measuring the reverse breakdown voltage, but also for testing 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 preferred 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.

[0084] In addition, reference Figure 4 It should be noted that, since the back-contact solar cell in this embodiment needs to be cut to form 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.

[0085] Specifically, in this embodiment, the first test point and the second test point can be 1 group or multiple groups. It can be understood 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 mean that more backlight surface 12 area is occupied, and the area for arranging positive grid lines 41 and negative grid lines 42 becomes smaller, which is not good for 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.

[0086] 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 result:

[0087] For an ideal diode, the current can be calculated as follows:

[0088]

[0089] In the formula, I DD is the current flowing from the positive electrode to the negative electrode in an 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.

[0090] After the leakage composite contact structure 34 is introduced, the current of the diode with leakage current can be calculated by the following formula:

[0091]

[0092] 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 an 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, 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.

[0093] Under non-ideal conditions, the diode can be reversely broken down, and the reverse breakdown current I D,BR It can be expressed as:

[0094]

[0095] 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.

[0096] Therefore, when the series resistance (i.e., the gate line resistance and the contact resistance between the gate line and the doping layer) is not taken into account, the current in the back-contact solar cell of this embodiment can be calculated by the following formula:

[0097]

[0098] 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 line resistance of a pitch (PN unit) gate line transmission is R s , x is the number of pitches through which the transmission current passes, 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 .

[0099] 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:

[0100]

[0101] Where V W is the applied voltage, R s is the line resistance of the gate line transmission of a pitch (PN unit), x is a 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 PAD points 62 , with a total of 6 PN units, then x=6÷2=3.

[0102] Here, it should be noted that in this embodiment, a plurality of first doping layers 31 and second doping layers 32 are arranged 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.

[0103] 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:

[0104]

[0105] 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.

[0106] If 4 groups of first test points are set, the measured current and voltage can be calculated by the following formula:

[0107]

[0108] Among them, I D5 is the current measured when setting the first test point of the four groups, V C5 It is the voltage measured when setting the first test point of four groups.

[0109] From the above two equations, we can undoubtedly find that: 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 the like. However, as mentioned above, increasing the first test point is not conducive to the improvement of conversion efficiency. To this end, the inventors have conducted a large number of tests based on the above analysis and proposed a specific correction method, which will be described later.

[0110] 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 through them 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 there are line resistances in the positive gate line 41 and the negative gate line 42. After the reverse current is passed, there will be voltage division on these gate lines; in addition, there are contact resistances 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 produce voltage division. 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 resistance voltage division and the contact resistance voltage division. 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 arranged close to the edge of the silicon substrate 1 in the second direction, and the positive gate line 41 and the negative gate line 42 are extended along the second direction. Therefore, in this embodiment, the reverse current can flow through the longer positive gate line 41 and the negative gate line 42 in the second direction, and the influence of the gate line line resistance voltage division and the contact resistance voltage division on the reverse breakdown voltage can be better characterized.

[0111] 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 grid line 41 in the first preset area 121, and the fourth test PAD point 64 is connected to the negative grid 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 test 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 the cell string 200 is formed, the first test PAD point 61 and the fourth test PAD point 64 can be directly connected by the welding strip 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, a plurality of solar cells or solar cell slices are included, which are generally connected in series or in parallel through a welding ribbon 230, and 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 a plurality of welding PAD points. The present embodiment introduces a first test PAD point 61 and a fourth test PAD point 62, which can also be used as welding PAD points, thereby reducing the number of welding PAD points and saving grid line paste.

[0112] 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.

[0113] It should be noted that the distribution positions of the test PAD points in this embodiment are not limited thereto. For example, in one embodiment, the first test PAD point 61 and the third test PAD point 63 with the same polarity may be arranged along the same straight line. In another embodiment, the first test PAD point 61 and the fourth test PAD point 64 may be arranged close to the first edge 13, but are staggered in the second direction, but are not limited thereto.

[0114] 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 plurality of positive gate lines 41 located in the first preset area 121, and the second shunt gate line 72 is electrically connected to a plurality of negative gate lines 42 located in the first preset area 121; the first shunt gate line 71 is electrically connected to a first test PAD point 61, and the second shunt gate line 72 is electrically connected to a second test PAD point 62; based on the above embodiment, the reverse current from the first test PAD point 61 is shunted to a plurality of positive gate lines 41 via the first shunt gate line 71, and then flows through a plurality of 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 the first test point groups set is small, the number of PN units passing through will also be reduced 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. Correspondingly, in one embodiment, the back-contact solar cell further includes a third shunt grid line 73 and a fourth shunt grid line 74 disposed in the second preset area 122; the third shunt grid line 73 is electrically connected to a plurality of positive grid lines 41 disposed in the second preset area 122, and the fourth shunt grid line 74 is electrically connected to a plurality of negative grid lines 42 disposed in the second preset area 122; the third shunt grid line 73 is electrically connected to a third test PAD point 63, and the fourth shunt grid line 74 is electrically connected to a fourth test PAD point 64. Based on the above embodiments, the accuracy of the test can be improved.

[0115] Specifically, the third shunt grid line 73 and the fourth shunt grid line 74 may be in a straight line or a curved line, and may be arranged parallel to the first direction or at an angle with the first direction, but are not limited thereto. Preferably, in one embodiment, the third shunt grid line 73 and the fourth shunt grid line 74 are in a straight line and extend along the first direction, that is, they are parallel to the first direction, which reduces the length of the third shunt grid line 73 and the fourth shunt grid line 74 between the positive grid line 41 to be connected or the negative grid line 42 to be connected, and reduces the influence of the third shunt grid line 73 and the fourth shunt grid line 74 on the test results.

[0116] Preferably, in one embodiment, the first shunt grid line 71 is arranged near the first edge 13, and the second shunt grid line 72 is arranged near 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 71 / the second shunt grid line 72 connects a plurality of positive grid lines 41 / negative grid lines 42 distributed in the first direction, if the first shunt grid line 71 / the second shunt grid line 72 is arranged in the center, a plurality of discontinuous insulating structures or other types of insulating structures need to be arranged in the grid line regions with different polarities, and the grid line structure is complicated, and the arrangement area of ​​the positive grid line 41 and the negative grid line 42 is reduced, thereby reducing the collection of carriers. More preferably, the first shunt grid line 71 is arranged at the end of the positive grid line 41 near the first edge 13, and the second shunt grid line 72 is arranged at the end of the negative grid line 42 near the second edge 14.

[0117] In addition, it can be expected that, since the first shunt grid line 71 / the second shunt grid line 72 is 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 composite 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 / converge rather than carrier collection, its broken grid has little effect on efficiency. However, if it causes misjudgment of sorting due to its disconnection, it will cause a large waste of 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 influence 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. Correspondingly, 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 pole gate line 41 close to the second edge 14 , and the fourth shunt gate line 74 is disposed at the end of the negative pole gate line 42 close to the first edge 13 .

[0118] It can be expected that, since the third shunt grid line 73 / the fourth shunt grid line 74 are 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 / the 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 grid has little effect on efficiency. However, if it causes misjudgment of sorting due to its disconnection, it will cause a large waste of production costs. At the same time, it can be understood that by increasing the number of settings of the third test PAD point 63 and the fourth test PAD point 64, the influence of the broken grid of the third shunt grid line 73 / the fourth shunt grid line 74 on the test results can also be reduced.

[0119] Specifically, in one embodiment, when the first test PAD point 61 and the first shunt gate line 71 are both arranged 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 is 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, and a negative gate line 42 with a different polarity from the first test PAD point 61 can be arranged in the spacing area, so as to further improve the collection efficiency of carriers and improve the conversion efficiency.

[0120] Specifically, when a spacing area 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 through the first connection gate line 81. Preferably, in one embodiment, the first connection gate line 81 and a positive gate line 41 located in the first preset 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 connection gate line 81 is arranged above the first doped layer 31 corresponding to the positive gate line 41, and then the first connection gate line 81 can be connected to the first doped layer 31 through the first hole 51, so that the first connection gate line 81 can also collect carriers to improve the conversion efficiency.

[0121] Accordingly, in one embodiment, when the second test PAD point 62 and the second shunt gate line 72 are both arranged close to 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 is electrically connected to the second test PAD point 62 through a second connecting gate line 82, and the second connecting gate line 82 and a negative gate line 42 located in the first preset area 121 are arranged on the same straight line extending along the second direction and located on the backlight surface 12 to improve the carrier collection efficiency.

[0122] Accordingly, in one embodiment, when the third test PAD point 63 and the third shunt gate line 73 are both arranged close to 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 preset area 122 are arranged on the same straight line extending along the second direction and located on the backlight surface 12 to improve the carrier collection efficiency.

[0123] Accordingly, in one embodiment, when the fourth test PAD point 64 and the fourth shunt gate line 74 are both arranged close to 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 preset area 122 are arranged on the same straight line extending along the second direction and located on the backlight surface 12 to improve the carrier collection efficiency.

[0124] Exemplarily, 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 grid line 71, the fourth shunt grid line 74 and the first edge 13 is 0.2 mm to 5 mm, and the distance between the second shunt grid line 72, the third shunt grid line 73 and the second edge 14 is 0.2 mm to 5 mm.

[0125] Specifically, in one embodiment, the positive grid line 41 includes a first positive sub-grid line 411 disposed in the first preset area 121, the negative grid line 42 includes a first negative sub-grid line 421 disposed in the first preset area 121 and adjacent to the first positive grid line 41, and the first test PAD point 61 is disposed 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 disposed 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 disposed on the same straight line extending along the second direction, and the stress distribution during printing is relatively uniform, thereby reducing the risk of cracking.

[0126] Correspondingly, in another embodiment, the positive grid line 41 further includes a second positive sub-grid line 412 disposed in the second preset area 122, and the negative grid line 42 further includes a second negative sub-grid line 422 disposed in the second preset area 122 and adjacent to the second positive sub-grid line 412. The third test PAD point 63 is disposed at the end of the second positive sub-grid line 412 and is electrically connected to the second positive sub-grid line 412; the fourth test PAD point 64 is disposed at the end of the second negative sub-grid line 422 and is electrically connected to the second negative sub-grid line 422.

[0127] 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 is 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 the conversion efficiency.

[0128] Correspondingly, 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.

[0129] Preferably, in one embodiment, in order to further improve the collection efficiency of carriers, a third negative sub-grid line 423 is 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 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 to improve the conversion efficiency. A third positive sub-grid line 413 is also 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 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 to improve the conversion efficiency.

[0130] 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, which is connected to a negative gate line 42 and 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, which is connected to a positive gate line 41 and insulated from the fourth test PAD point 64.

[0131] 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, 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, and their width is 0.1 mm to 3 mm to achieve good contact with the test electrode.

[0132] Specifically, in one embodiment, it further includes: at least two groups of welding points, which are arranged in the first preset area 121 and the second preset 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 alternately arranged along the second direction. Preferably, in one embodiment, two groups of welding points are arranged in the first preset area 121, one group of welding points is arranged near the third edge 15 of the silicon substrate 1, and the other group is arranged near the third preset area 123. Similarly, two groups of welding points are arranged in the second preset area 122, one group of welding points is arranged near the fourth edge 16 of the silicon substrate 1, and the other group is arranged near the third preset area 123.

[0133] 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; 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 tension 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.

[0134] Correspondingly, this embodiment also 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 back-contact solar cell, and includes:

[0135] 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 through the test reverse voltage;

[0136] The actual reverse breakdown voltage is calculated according to the following formula:

[0137]

[0138] 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, B is a constant, and its value range is 2~50.

[0139] Based on the above relationship, when setting any group of first test points and second test points, the test results can be corrected to obtain an accurate reverse breakdown voltage. Specifically, it is found that when setting 1 to 6 groups of first test points / second test points, the test error is ≤5%, and when setting 4 to 6 groups, the test error is ≤3.5%.

[0140] S2: Evaluate the hot spot effect according to the actual reverse breakdown voltage;

[0141] Specifically, according to a lot of research by the inventors, for a specific type of solar cell, when the reverse breakdown voltage is different, the temperature of the hot spot generated under the shielding condition is also different. Therefore, the hot spot effect can be reasonably evaluated based on the reverse breakdown voltage.

[0142] Accordingly, this embodiment also discloses a battery string 200, which includes the above-mentioned back-contact solar cell. The battery string 200 can be formed by stacking or welding multiple back-contact solar cells or their slices, but is not limited thereto. Accordingly, in order to complete the connection of multiple back-contact solar cells, the battery string 200 components also include welding strips, insulating glue, adhesive glue, conductive glue, etc., but are not limited thereto.

[0143] Accordingly, this embodiment also discloses a battery assembly, which includes the above-mentioned back-contact solar cell or the above-mentioned battery string 200. Preferably, in one embodiment, the battery assembly is composed of a plurality of the above-mentioned battery strings 200, exemplarily 2 strings, 4 strings or 6 strings, but not limited thereto. Accordingly, in order to form a connection between the battery strings, the battery assembly also needs to introduce insulating glue, bus bars, junction boxes, frames, back panels, adhesive films, glass and other components, but not limited thereto.

[0144] Correspondingly, the present embodiment also discloses a photovoltaic system, which includes the above-mentioned battery assembly. In the present 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 may 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 and is converted into the alternating current required by the mains power grid, and then connected to the mains network to realize solar power supply.

[0145] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A back contact solar cell, It is characterized in that include: A silicon substrate, comprising a light-receiving surface and a backlight surface arranged opposite to each other; the silicon substrate comprises a first preset area, a second preset area and a third preset area, and 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 doping layers and a plurality of second doping layers, which are arranged on the backlight surface, the plurality of first doping layers and the plurality of second doping layers are alternately arranged in a first preset area and a second preset area along a first direction, and extend along a second direction, and at least one of the second doping layers is in composite contact with at least one of the first doping 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 arranged on the first doped layer, and the negative gate lines are arranged on the second doped layer; At least one group of first test points located in the first preset area, each group of the 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 electrode grid line located in the first preset area, and the second test PAD point is electrically connected to at least one negative electrode grid line located in 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, It is characterized in that The silicon substrate has a first edge and a second edge oppositely arranged in a 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 disposed close to the second edge.

3. The back contact solar cell according to claim 2, It is characterized in that 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 a same straight line extending along the first direction and located on the backlight surface.

4. The back contact solar cell according to claim 1, It is characterized in that 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, It is characterized in that Also includes: A first shunt gate line and a second shunt gate line are arranged 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 a second preset area; the third shunt gate line is electrically connected to a plurality of positive gate lines located in the second preset area, and the fourth shunt gate line is electrically connected to a plurality of 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, It is characterized in that The silicon substrate has a first edge and a second edge oppositely arranged in a 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, It is characterized in that 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, It is characterized in that 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 shunt gate line, the fourth shunt gate line and the first edge are 0.2 mm to 5 mm, and the distances between the second shunt gate line, the third shunt gate line and the second edge are 0.2 mm to 5 mm.

9. The back contact solar cell according to claim 6, It is characterized in that 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, It is characterized in that The first connecting gate line and a positive gate 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 The second connecting gate line and a negative gate 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 The third connecting grid line and a positive grid 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, It is characterized in that The positive grid line includes a first positive sub-grid line arranged in a first preset area and a second positive sub-grid line arranged in a second preset area, the first test PAD point is arranged at the end of the first positive sub-grid line and is electrically connected to the first positive sub-grid line; the third test PAD point is arranged at the end of the second positive sub-grid line and is electrically connected to the second positive sub-grid line; The negative pole grid line includes a first negative pole sub-grid line arranged in a first preset area and a second negative pole sub-grid line arranged in a second preset area, the second test PAD point is arranged at an end of the first negative pole sub-grid line and is electrically connected to the first negative pole sub-grid line; the fourth test PAD point is arranged at an end of the second negative pole sub-grid line and is electrically connected to the second negative pole sub-grid line; The first positive sub-grid line is disposed adjacent to the first negative sub-grid line, and the second positive sub-grid line is disposed adjacent to the second negative sub-grid line.

12. The back contact solar cell according to claim 11, It is characterized in that 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-grid lines; and the fourth test PAD point is electrically connected to at least three second negative sub-grid lines.

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

15. The back contact solar cell according to claim 1, It is characterized in that 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 1, It is characterized in that 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, It is characterized in that 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 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; A second welding PAD point located in the second preset area and closest to the first edge and a 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, It is characterized in that The invention comprises a back-contact solar cell sheet as claimed in any one of claims 1 to 17 or slices obtained by cutting the same.

19. A battery assembly, It is characterized in that comprising a battery string as claimed in claim 18, or A back-contact solar cell as claimed in any one of claims 1 to 17 or a slice thereof.

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

21. A method for evaluating the hot spot effect of a back-contact solar cell, for evaluating the hot spot effect of the back-contact solar cell according to any one of claims 1 to 17, It is characterized in that include: 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 through the test reverse voltage; The hot spot effects were evaluated according to the actual reverse breakdown voltage. Wherein, the actual reverse breakdown voltage is calculated according to the following formula: Among them, U rev is the actual reverse breakdown voltage, U is the reverse voltage tested, x is the total number of positive and negative gate lines located in the first preset area or the total number of positive and negative gate lines located in the second preset area, l is the variable characterizing the first test point or the variable of the second test point, n ... total number of positive and negative gate lines located in the second preset area, l is the total number of positive and negative gate lines located in the second preset area, l is the total number of positive and negative gate lines located 1 is the number of the first test PAD points or the number of the third test PAD points, n 2 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.

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