Back contact solar cell, photovoltaic module and photovoltaic system

Abstract

The utility model provides a back contact solar cell. The back contact solar cell comprises a silicon substrate; the first polarity grid lines and the second polarity grid lines are arranged on the surface of the silicon substrate, the first polarity grid lines and the second polarity grid lines are arranged at intervals, the first polarity grid lines are located in a first polarity area, and the second polarity grid lines are located in a second polarity area; the width of the first polarity grid line close to the edge position of the back contact solar cell is greater than the width of the first polarity grid line close to the center position of the back contact solar cell; or the width of the second polarity grid line close to the edge position of the back contact solar cell is greater than the width of the second polarity grid line close to the center position of the back contact solar cell. The width of the edge grid lines with the same polarity is set to be larger than the width of the center grid line, so that the carrier collection capacity of the P region and the N region is balanced, and the adhesion capacity of metal and the electrode is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a back contact solar cell, a photovoltaic module and a photovoltaic system. BACKGROUND

[0002] The grid lines of a solar cell are responsible for leading the photo-generated current in the cell body to the outside of the cell. The optimization goal of the grid line design is to minimize the series resistance of the cell, thereby reducing power loss and improving the working efficiency of the cell.

[0003] The edge grid lines of some current solar cells have the same width as the middle grid lines of the same polarity, and the edge grid lines with the same width as the middle grid lines of the same polarity have the problems of relatively low current density in the edge region, relatively long current transmission path, relatively large total amount of metal paste (such as copper-tin paste), and weak mechanical strength and connection stability.

[0004] Therefore, the prior art has defects and needs to be improved. CONTENT OF THE INVENTION

[0005] The present application provides a back contact solar cell, a photovoltaic module and a photovoltaic system to solve the problems of some current solar cells that the edge grid lines of the same polarity have the same width as the middle grid lines of the same polarity, and the edge grid lines with the same width as the middle grid lines of the same polarity have the problems of relatively low current density in the edge region, relatively long current transmission path, relatively large total amount of metal paste, and weak mechanical strength and connection stability.

[0006] In a first aspect, the present application provides a back contact solar cell, comprising:

[0007] a silicon substrate;

[0008] a first polarity grid line and a second polarity grid line arranged on the surface of the silicon substrate, the first polarity grid line and the second polarity grid line are arranged at intervals, the first polarity grid line is located in a first polarity region, and the second polarity grid line is located in a second polarity region;

[0009] the width of the first polarity grid line at a position close to the edge of the back contact solar cell is greater than the width of the first polarity grid line at a position close to the center of the back contact solar cell; or

[0010] the width of the second polarity grid line at a position close to the edge of the back contact solar cell is greater than the width of the second polarity grid line at a position close to the center of the back contact solar cell.

[0011] The embodiment of the present application sets the width of the first polarity grid line close to the edge position of the back contact solar cell to be greater than the width of the first polarity grid line close to the center position of the back contact solar cell, sets the width of the second polarity grid line close to the edge position of the back contact solar cell to be greater than the width of the second polarity grid line close to the center position of the back contact solar cell, that is, sets the width of the edge grid line of the same polarity to be greater than the width of the center grid line, which is beneficial to balance the carrier collection capability of the first polarity region and the second polarity region, increase the adhesion capability of the metal and the electrode, reduce the resistance of the grid line at the edge, reduce the power loss in the current transmission process, and is beneficial to improve the fill factor and overall conversion efficiency of the cell; increasing the width of the grid line at the edge of the same polarity can more effectively collect the photo-generated carriers and current in the edge region, reduce the horizontal current transmission loss, and improve the conversion efficiency of the cell, while ensuring the performance of the cell, reducing the total amount of metal paste, which is beneficial to reduce the cost, and the wider grid line at the edge also has better mechanical strength and connection stability, which is beneficial to reduce the risk of damage to the cell in manufacturing and use.

[0012] Optionally, the first polarity grid line is a first polarity fine grid line, the second polarity grid line is a second polarity fine grid line, the plurality of first polarity fine grid lines and the plurality of second polarity fine grid lines are arranged alternately and spaced along the first direction, and extend along the second direction.

[0013] The embodiment of the present application sets the width of the first polarity grid line close to the edge position of the back contact solar cell to be greater than the width of the first polarity grid line close to the center position of the back contact solar cell, sets the width of the second polarity grid line close to the edge position of the back contact solar cell to be greater than the width of the second polarity grid line close to the center position of the back contact solar cell, that is, sets the width of the edge grid line of the same polarity to be greater than the width of the center grid line, which is beneficial to balance the carrier collection capability of the first polarity region and the second polarity region, increase the adhesion capability of the metal and the electrode, reduce the resistance of the grid line at the edge, reduce the power loss in the current transmission process, and is beneficial to improve the fill factor and overall conversion efficiency of the cell; increasing the width of the grid line at the edge of the same polarity can more effectively collect the photo-generated carriers and current in the edge region, reduce the horizontal current transmission loss, and improve the conversion efficiency of the cell, while ensuring the performance of the cell, reducing the total amount of metal paste, which is beneficial to reduce the cost, and the wider grid line at the edge also has better mechanical strength and connection stability, which is beneficial to reduce the risk of damage to the cell in manufacturing and use.

[0014] Optionally, the first polarity grid line is a first polarity main grid line, the second polarity grid line is a second polarity main grid line, the plurality of first polarity main grid lines and the plurality of second polarity main grid lines are arranged spaced along the second direction, and extend along the first direction.

[0015] The first polarity gate line is designed as a first polarity main gate line, the second polarity gate line is designed as a second polarity main gate line, a plurality of first polarity main gate lines and a plurality of second polarity main gate lines are arranged at intervals along the second direction and extend along the first direction, so that the photo-generated carriers and current in the edge region can be more effectively collected, the lateral current transmission loss is reduced, the conversion efficiency of the battery is improved, the total amount of metal paste is reduced while the battery performance is ensured, which is conducive to reducing the cost, and the wider fine gate line at the edge also has better mechanical strength and connection stability, which is conducive to reducing the risk of damage to the battery during manufacturing and use.

[0016] Optionally, the first polarity main gate line is further connected with a plurality of first polarity fine gate lines, and the second polarity main gate line is further connected with a plurality of second polarity fine gate lines.

[0017] The width of the first polarity fine gate line at the edge position of the back contact solar cell is greater than the width of the first polarity fine gate line at the central position of the back contact solar cell; or

[0018] The width of the second polarity fine gate line at the edge position of the back contact solar cell is greater than the width of the second polarity fine gate line at the central position of the back contact solar cell.

[0019] The width of the first polarity fine gate line at the edge position of the back contact solar cell is greater than the width of the first polarity fine gate line at the central position of the back contact solar cell; or the width of the second polarity fine gate line at the edge position of the back contact solar cell is greater than the width of the second polarity fine gate line at the central position of the back contact solar cell, which can improve the collection ability of the carriers of the first polarity fine gate line and the second polarity fine gate line at the edge position, is conducive to balancing the carrier collection ability of the first polarity region and the second polarity region, increasing the adhesion ability of the metal and the electrode, reducing the resistance of the gate line at the edge, reducing the power loss in the current transmission process, and is conducive to improving the fill factor and overall conversion efficiency of the battery.

[0020] Optionally, the average width of the first polarity gate line at the edge position of the back contact solar cell is greater than the average width of the first polarity gate line at the central position of the back contact solar cell; or

[0021] The average width of the second polarity gate line at the edge position of the back contact solar cell is greater than the average width of the second polarity gate line at the central position of the back contact solar cell.

[0022] The average width of the first polarity grid line at the edge position close to the back contact solar cell is greater than the average width of the first polarity grid line at the center position close to the back contact solar cell, or the average width of the second polarity grid line at the edge position close to the back contact solar cell is greater than the average width of the second polarity grid line at the center position close to the back contact solar cell, so that the average width of the first polarity grid line or the second polarity grid line at the edge position is greater than the average width of the first polarity grid line or the second polarity grid line at the center position, and the area ratio of the grid line at the edge position is greater than the area ratio of the grid line at the center position, thereby improving the carrier collection capability of the grid line at the edge position.

[0023] Optionally, at least one of the first polarity grid line and the second polarity grid line is a width-gradual grid line.

[0024] The embodiment of the present application reduces the total amount of metal paste while ensuring the performance of the cell by designing at least one of the first polarity grid line and the second polarity grid line as a width-gradual grid line, which is conducive to reducing costs, and the wider fine grid line at the edge also has better mechanical strength and connection stability, which is conducive to reducing the risk of damage to the cell during manufacturing and use.

[0025] Optionally, the first polarity grid line at the edge position close to the back contact solar cell is a width-gradual grid line, and the width of the width-gradual grid line gradually changes from thin to thick from the edge position of the back contact solar cell to the center position of the back contact solar cell or gradually changes from thick to thin from the edge position of the back contact solar cell to the center position of the back contact solar cell.

[0026] The embodiment of the present application is conducive to improving the carrier collection capability of the grid line at the edge position and saving paste by designing the grid line at the edge position as a width-gradual grid line.

[0027] Optionally, the first polarity grid line at the center position close to the back contact solar cell is a width-constant grid line.

[0028] The embodiment of the present application better balances the carrier collection capability of the edge region and the middle region of the cell by designing the first polarity grid line at the center position close to the back contact solar cell as a width-constant grid line, thereby improving the working efficiency of the cell.

[0029] Optionally, the second polarity grid line at the edge position of the back contact solar cell is a width-graduated grid line, the width of the width-graduated grid line gradually changes from thin to thick or gradually changes from thick to thin from the edge position of the back contact solar cell to the center position of the back contact solar cell.

[0030] The embodiment of the present application facilitates to improve the carrier collection capability of the grid line at the edge position and to save the paste by designing the grid line at the edge position as a width-graduated grid line.

[0031] Optionally, the second polarity grid line at the center position of the back contact solar cell is a width-constant grid line.

[0032] The embodiment of the present application better balances the carrier collection capability of the edge region and the middle region of the cell and improves the working efficiency of the cell by designing the second polarity grid line at the center position of the back contact solar cell as a width-constant grid line.

[0033] Optionally, the top view of the width-graduated grid line is one of a trapezoid and an irregular quadrilateral.

[0034] Optionally, when the top view of the width-graduated grid line is a trapezoid, the bottom angle of the trapezoid is set to 20 degrees to 90 degrees.

[0035] Optionally, when the top view of the width-graduated grid line is a trapezoid and the width-graduated grid line is a thin grid line, the length of the upper base of the trapezoid is greater than or equal to 10 microns and the length of the lower base of the trapezoid is less than or equal to 250 microns.

[0036] Optionally, when the top view of the width-graduated grid line is a trapezoid and the width-graduated grid line is a main grid line, the length of the upper base of the trapezoid is greater than or equal to 10 microns and the length of the lower base of the trapezoid is less than or equal to 1200 microns.

[0037] The embodiment of the present application facilitates to improve the carrier collection capability and reduce the resistance of the cell by reasonably setting the length of the bottom angle, the upper base and the lower base of the trapezoid.

[0038] Optionally, when the width-graduated grid line is a thin grid line, the width range is 10-250 microns.

[0039] Optionally, when the width-graduated grid line is a main grid line, the width range is 10-1200 microns.

[0040] The embodiments of the present application can reduce battery leakage, improve the collection capacity of carriers, and avoid frequent battery leakage and poor carrier collection capacity caused by unreasonable length design by reasonably setting the width range of the width gradually changing grid lines.

[0041] Optionally, a ratio of a height of the first polarity grid line at a position close to an edge of the back contact solar cell to a height of the first polarity grid line at a position close to a center of the back contact solar cell is greater than or equal to 0.8 times; and / or

[0042] A ratio of a height of the second polarity grid line at a position close to an edge of the back contact solar cell to a height of the second polarity grid line at a position close to a center of the back contact solar cell is greater than or equal to 0.8 times.

[0043] The embodiments of the present application set the height ratio to be greater than or equal to 0.8 times, so that the cross-sectional area of the first polarity grid line and the second polarity grid line at the edge position is larger. Since the higher the height of the grid line is, the larger the cross-sectional area of the grid line is, the smaller the resistance of the grid line is, the smaller the series resistance is, the higher the fill factor and the output power are. Therefore, by reasonably setting the height ratio of the first fine grid line and the second fine grid line, the resistance of the grid line can be reduced, and the collection capacity of carriers and the output power of the battery can be improved.

[0044] Optionally, a ratio of a length of the first polarity grid line at a position close to an edge of the back contact solar cell to a length of the first polarity grid line at a position close to a center of the back contact solar cell is 1.2-2.0; and / or

[0045] A ratio of a length of the second polarity grid line at a position close to an edge of the back contact solar cell to a length of the second polarity grid line at a position close to a center of the back contact solar cell is 1.2-2.0.

[0046] The embodiments of the present application can better balance the carrier collection capacity and the resistance of the grid line by setting the length ratio to be 1.2-2.0.

[0047] Optionally, a plurality of pad points are arranged on the first polarity main grid line and the second polarity main grid line, and the plurality of pad points are arranged at intervals along the length direction of the first polarity main grid line and the second polarity main grid line.

[0048] Optionally, the width of the first polarity main grid line and the second polarity main grid line gradually decreases from a position close to the pad point to a position away from the pad point.

[0049] The width of the first polarity main grid and the second polarity main grid gradually decreases from the position close to the pad point to the position away from the pad point, so that the stability of the connection between the first polarity main grid line and the second polarity main grid line and the pad point can be ensured, and the gradually decreasing width of the main grid is conducive to reducing the cost.

[0050] Optionally, the width of the first polarity main grid line and the second polarity main grid line is constant from the position close to the pad point to the position away from the pad point.

[0051] Optionally, the first polarity main grid line close to the edge position of the back contact solar cell is a first polarity edge main grid, and the width of the first polarity edge main grid ranges from 25 to 1200 microns; or

[0052] The second polarity main grid line close to the edge position of the back contact solar cell is a second polarity edge main grid, and the width of the second polarity edge main grid ranges from 25 to 1200 microns.

[0053] Optionally, the first polarity main grid line close to the middle position of the back contact solar cell is a first polarity middle main grid, and the width of the first polarity middle main grid ranges from 10 to 1200 microns; or

[0054] The second polarity main grid line close to the middle position of the back contact solar cell is a second polarity middle main grid, and the width of the second polarity middle main grid ranges from 10 to 1200 microns.

[0055] Optionally, the first polarity main grid line close to the edge position of the back contact solar cell is a first polarity edge main grid, and the width of the first polarity edge main grid is at least greater than the width of one pad point; or

[0056] The second polarity main grid line close to the edge position of the back contact solar cell is a second polarity edge main grid, and the width of the second polarity edge main grid is at least greater than the width of one pad point.

[0057] The width of the first polarity edge main grid or the second polarity edge main grid is set to be at least greater than the width of one pad point, which is conducive to reducing the resistance of the cell and improving the collection ability of the carriers.

[0058] Optionally, the first polarity main grid line close to the edge position of the back contact solar cell is a first polarity edge main grid, and a crossed short fine grid line is arranged at the position of the pad point close to the first polarity edge main grid; or

[0059] The second polarity main grid line close to the edge position of the back contact solar cell is a second polarity edge main grid, and a crossed short grid line is arranged close to the pad point of the second polarity edge main grid.

[0060] The embodiment of the present application facilitates current derivation by arranging a crossed short grid line close to the pad point of the first polarity edge main grid or the second polarity edge main grid.

[0061] Optionally, the first polarity grid line close to the edge position of the back contact solar cell is a first polarity edge grid line, the first polarity grid line close to the middle position of the back contact solar cell is a first polarity middle grid line, and the ratio of the width of the first polarity edge grid line to the width of the first polarity middle grid line is greater than 1.2; or

[0062] The second polarity grid line close to the edge position of the back contact solar cell is a second polarity edge grid line, the second polarity grid line close to the middle position of the back contact solar cell is a second polarity middle grid line, and the ratio of the width of the second polarity edge grid line to the width of the second polarity middle grid line is greater than 1.2.

[0063] Optionally, the ratio of the average width of the first polarity edge grid line to the average width of the first polarity middle grid line is greater than 1.2; or

[0064] The ratio of the average width of the second polarity edge grid line to the average width of the second polarity middle grid line is greater than 1.2.

[0065] The embodiment of the present application designs the width ratio or average width ratio of the first polarity edge grid line to the first polarity middle grid line and the second polarity edge grid line to the second polarity middle grid line to be greater than or equal to 1.2 times, so that the carrier collection capability of the first polarity edge grid line and the second polarity edge grid line is stronger than the carrier collection capability of the first polarity middle grid line and the second polarity middle grid line.

[0066] In a second aspect, the present application provides a photovoltaic module comprising the solar cell of any one of the above first aspect.

[0067] In a third aspect, the present application provides a photovoltaic system comprising the photovoltaic module of any one of the above second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0068] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and serve to explain the principles of the present application together with the description.

[0069] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those skilled in the field, other drawings can be obtained based on these drawings without any creative effort.

[0070] One or more embodiments are illustrated by way of example in the drawings that are not intended to be limiting of the embodiments so far as they may depart from the prior art. Identical reference numbers in the figures of the drawings represent the same element or component. The drawings in the specification and drawings are not necessarily to scale and the dimensions of certain features can have been exaggerated for the sake of clarity.

[0071] Fig. 1 A schematic diagram of a planar structure of a back contact solar cell is provided for the embodiments of the present application.

[0072] Fig. 2 A schematic diagram of a planar structure of a first polarity fine grid line is provided for the embodiments of the present application.

[0073] Fig. 3 A schematic diagram of a planar structure of a first polarity edge main grid is provided for the embodiments of the present application.

[0074] Legend of reference signs:

[0075] 1, silicon substrate; 2, first polarity fine grid line; 3, second polarity fine grid line; 4, first polarity main grid line; 5, second polarity main grid line; 6, pad point; 7, first polarity edge main grid; 8, second polarity edge main grid; 9, first polarity intermediate main grid; 10, second polarity intermediate main grid; 11, short fine grid line. DETAILED DESCRIPTION

[0076] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of protection of the present application.

[0077] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplicity, the elements and settings of particular examples in the following description will be described with reference to the drawings. Of course, these are merely examples and are intended to be illustrative only. Thus, the application is not limited to these examples and illustrations. Additionally, the reference numerals in the following description are in no way intended to limit their specific examples or uses. On the contrary, they are used merely for the reader's benefit in providing clarity of examples of the present application.

[0078] For the convenience of description, spatial relative terms can be used in the specification to describe the relative position relationship or movement condition of one element or feature relative to another element or feature as shown in the drawings, such as "inner", "outer", "inboard", "outboard", "under", "below", "on", "above", "front", "back", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the positions depicted in the drawings. For example, if the device in the drawings is turned over or the posture is changed or the movement state is changed, the directional indications will also change accordingly, for example: the element described as "under" or "below" other elements or features will be oriented as "above" or "above" other elements or features. Therefore, the example term "below" can include both the upper and lower positions. The device can be additionally oriented (rotated by 90 degrees or in other directions) and the spatial relative relationship descriptors used in the specification are interpreted accordingly.

[0079] To solve the technical problems in the prior art, the back contact solar cell provided by the application can balance the carrier collection capability of the first polarity region and the second polarity region, increase the adhesion capability of the metal and the electrode, reduce the resistance of the grid line at the edge, reduce the power loss in the current transmission process, and help improve the fill factor and overall conversion efficiency of the cell by setting the width of the edge grid line of the same polarity to be greater than the width of the center grid line, i.e. by setting the width of the edge grid line of the same polarity to be greater than the width of the center grid line. Increasing the width of the grid line at the edge of the same polarity can more effectively collect the photo-generated carriers and current in the edge region, reduce the lateral current transmission loss, and improve the conversion efficiency of the cell. While ensuring the performance of the cell, the total amount of metal paste is reduced, which helps reduce the cost. At the same time, the wider grid line at the edge also has better mechanical strength and connection stability, which helps reduce the risk of damage to the cell during manufacturing and use.

[0080] Figs. 1-3 The back contact solar cell provided by the embodiment of the application comprises:

[0081] The silicon substrate 1, the first polarity grid line and the second polarity grid line arranged on the surface of the silicon substrate 1, wherein the first polarity grid line and the second polarity grid line are arranged at intervals, the first polarity grid line is located in the first polarity region, and the second polarity grid line is located in the second polarity region;

[0082] The width of the first polarity grid line at a position close to the edge of the back contact solar cell is greater than the width of the first polarity grid line at a position close to the center of the back contact solar cell; or

[0083] The width of the second polarity grid line at a position close to the edge of the back contact solar cell is greater than the width of the second polarity grid line at a position close to the center of the back contact solar cell.

[0084] In the embodiment of the utility model, the first polarity grid line is the first polarity fine grid line 2, and the second polarity grid line is the second polarity fine grid line 3, and the first polarity fine grid line 2 and the second polarity fine grid line 3 are both provided in a plurality of numbers, which can be specifically one, two, three or more, the first polarity fine grid line 2 and the second polarity fine grid line 3 are alternately and spacedly arranged along the first direction, and both extend along the second direction. In the embodiment of the utility model, when the first polarity grid line is the first polarity fine grid line 2 and the second polarity grid line is the second polarity fine grid line 3, the first direction is the Y-axis direction in the figure, and the second direction is the X-axis direction in the figure. One of the first polarity region and the second polarity region is a P region, and the other is an N region, for example, the first polarity region is a P region, and the second polarity region is an N region, or the first polarity region is an N region, and the second polarity region is a P region.

[0085] By setting the width of the first polarity fine grid line 2 at the edge to be greater than the width of the first polarity fine grid line 2 at the center or the width of the second polarity fine grid line 3 at the edge to be greater than the width of the second polarity fine grid line 3 at the center, the carrier collection capability of the first polarity region and the second polarity region (for example, the P region or the N region) can be balanced, the adhesion of the metal and the electrode can be increased, the resistance of the first polarity fine grid line 2 or the second polarity fine grid line 3 at the edge can be reduced, the power loss in the current transmission process can be reduced, the photo-generated carriers in the edge region and the current in the edge region can be effectively collected, the lateral current transmission loss can be reduced, the conversion efficiency of the battery can be improved, the first polarity fine grid line 2 or the second polarity fine grid line 3 at the edge has better mechanical strength and connection stability, the amount of metal paste used is reduced, and the cost is reduced.

[0086] The silicon substrate 1 can be a single crystal silicon wafer, which is a single crystal formed by slowly cooling molten silicon raw material, has a compact and ordered crystal structure, and has high conductivity, conversion efficiency, stability and service life. The silicon substrate 1 can also be a polycrystalline silicon wafer, which is a form of elemental silicon. When molten elemental silicon solidifies under supercooling conditions, silicon atoms arrange in a diamond lattice form to form many crystal nuclei. If these crystal nuclei grow into grains with different crystal plane orientations, these grains combine to form polycrystalline silicon. The surface of the silicon substrate 1 can be a polished surface or a textured surface, which is not limited.

[0087] As another embodiment of the utility model, the first polarity grid line is the first polarity main grid line 4, the second polarity grid line is the second polarity main grid line 5, the first polarity main grid line 4 and the second polarity main grid line 5 are provided with several numbers, specifically can be 1, 2, 3 or more, the first polarity main grid line 4 and the second polarity main grid line 5 are sequentially alternately spaced along the second direction, and all extend along the first direction. In the embodiment of the utility model, when the first polarity grid line is the first polarity main grid line 4, and the second polarity grid line is the second polarity main grid line 5, the second direction is the X-axis direction in the figure, and the first direction is the Y-axis direction in the figure. By the width of the first polarity main grid line 4 located at the edge being greater than the width of the first polarity main grid line 4 located at the center or the width of the second polarity main grid line 5 located at the edge being greater than the width of the second polarity main grid line 5 located at the center, the carrier collection ability of P region and N region is balanced, the adhesion of metal and electrode is increased, the resistance of the first polarity main grid line 4 or the second polarity main grid line 5 at the edge is reduced, the power loss in the current transmission process is reduced, the photo-generated carriers of the edge region, the current of the edge region and the lateral current transmission loss are effectively collected, the conversion efficiency of the battery is improved, the first polarity main grid line 4 or the second polarity main grid line 5 at the edge has better mechanical strength and connection stability, and the use amount of metal paste is also reduced, and the cost is reduced.

[0088] As another embodiment of the utility model, in the case that the first polarity grid line is the first polarity main grid line 4 and the second polarity grid line is the second polarity main grid line 5, the first polarity main grid line 4 is further connected with several first polarity fine grid lines 2, the second polarity main grid line 5 is further connected with several second polarity fine grid lines 3, and the first polarity fine grid line 2 and the second polarity fine grid line 3 extend along the X-axis direction. And, the width of the first polarity fine grid line 2 at the edge position close to the back contact solar cell is greater than the width of the first polarity fine grid line 2 at the center position close to the back contact solar cell. That is, on the basis of the beneficial effects of the first polarity grid line being the first polarity main grid line 4 and the second polarity grid line being the second polarity main grid line 5, further has the beneficial effect that the width of the first polarity fine grid line 2 located at the edge is greater than the width of the first polarity fine grid line 2 located at the center, so that the performance of the back contact solar cell of the utility model is better;

[0089] As another embodiment of the utility model, the width of the second polarity fine grid line 3 at the edge position close to the back contact solar cell is greater than the width of the second polarity fine grid line 3 at the central position close to the back contact solar cell. That is, on the basis of the beneficial effect that the first polarity grid line is the first polarity main grid line 4 and the second polarity grid line is the second polarity main grid line 5, further has the beneficial effect that the width of the second polarity fine grid line 3 at the edge is greater than the width of the second polarity fine grid line 3 at the center, so that the back contact solar cell of the utility model has better performance. The carrier collection capability of the first polarity fine grid line 2 and the second polarity fine grid line 3 at the edge position can be improved, which is beneficial to balance the carrier collection capability of the first polarity region and the second polarity region, increase the adhesion of metal and electrode, reduce the resistance of the grid line at the edge, reduce the power loss in the current transmission process, and is beneficial to improve the fill factor and overall conversion efficiency of the cell.

[0090] In the embodiment of the utility model, the average width of the first polarity grid line at the edge position close to the back contact solar cell is greater than the average width of the first polarity grid line at the central position close to the back contact solar cell, that is, the overall width of the first polarity grid line at the edge is greater than the overall width of the first polarity grid line at the center, which is beneficial to balance the carrier collection capability of the P region and the N region, increase the adhesion of metal and electrode, reduce the resistance of the first polarity grid line at the edge, reduce the power loss in the current transmission process, effectively collect the photo-generated carriers of the edge region, the current of the edge region, reduce the lateral current transmission loss, improve the conversion efficiency of the cell, so that the first polarity grid line at the edge has better mechanical strength and connection stability, and also reduces the amount of metal paste used and the cost.

[0091] Or the average width of the second polarity grid line at the edge position close to the back contact solar cell is greater than the average width of the second polarity grid line at the central position close to the back contact solar cell, that is, the overall width of the second polarity grid line at the edge is greater than the overall width of the second polarity grid line at the center, which is beneficial to balance the carrier collection capability of the P region and the N region, increase the adhesion of metal and electrode, reduce the resistance of the second polarity grid line at the edge, reduce the power loss in the current transmission process, effectively collect the photo-generated carriers of the edge region, the current of the edge region, reduce the lateral current transmission loss, improve the conversion efficiency of the cell, so that the second polarity grid line at the edge has better mechanical strength and connection stability, and also reduces the amount of metal paste used and the cost.

[0092] As an embodiment of the utility model, at least one of the first polarity grid line and the second polarity grid line is a width-gradually-changing grid line. Specifically, when the first polarity grid line at the edge of the back contact solar cell is a width-gradually-changing grid line, the width of the width-gradually-changing grid line gradually changes from thin to thick, and gradually changes from the edge of the back contact solar cell to the center of the back contact solar cell, or the width of the width-gradually-changing grid line gradually changes from thick to thin, and gradually changes from the edge of the back contact solar cell to the center of the back contact solar cell, at this time, the first polarity grid line near the center of the back contact solar cell is a width-constant grid line; when the second polarity grid line at the edge of the back contact solar cell is a width-gradually-changing grid line, the width of the width-gradually-changing grid line gradually changes from thin to thick, and gradually changes from the edge of the back contact solar cell to the center of the back contact solar cell, or the width of the width-gradually-changing grid line gradually changes from thick to thin, and gradually changes from the edge of the back contact solar cell to the center of the back contact solar cell, at this time, the second polarity grid line near the center of the back contact solar cell is a width-constant grid line. The specific width change of the first polarity grid line and the second polarity grid line is not limited, as long as the average width of at least one of the first polarity grid line and the second polarity grid line at the edge is greater than that at the center. The embodiment of the application designs at least one of the first polarity grid line and the second polarity grid line as a width-gradually-changing grid line, which not only ensures the performance of the battery, but also reduces the total amount of metal paste, which is conducive to reducing the cost. At the same time, the wider fine grid line at the edge also has better mechanical strength and connection stability, which is conducive to reducing the risk of damage to the battery during manufacturing and use.

[0093] Preferably, the shape of the top view of the width-gradually-changing grid line is one of a trapezoid and an irregular quadrilateral, and the top view of the width-gradually-changing grid line is specifically a pattern formed on a plane composed of X and Y axes. When the top view of the width-gradually-changing grid line is a trapezoid, the angle of the bottom angle is set to 20-90°. When the top view of the width-gradually-changing grid line is a trapezoid and the width-gradually-changing grid line is a fine grid line, the length of the upper base is greater than or equal to 10 microns, and the length of the lower base is less than or equal to 250 microns; when the top view of the width-gradually-changing grid line is a trapezoid and the width-gradually-changing grid line is a main grid line, the length of the upper base is greater than or equal to 10 microns, and the length of the lower base is less than or equal to 1200 microns. The embodiment of the application reasonably sets the angle of the bottom angle, the length of the upper base and the lower base of the trapezoid, which is conducive to improving the collection ability of carriers and reducing the resistance of the battery.

[0094] In the embodiment of the utility model, when the width-gradually-changing grid line is a fine grid line, the width range of the width-gradually-changing grid line in the Y axis direction is 10-250 microns; when the width-gradually-changing grid line is a main grid line, the width range of the width-gradually-changing grid line in the X axis direction is 10-1200 microns, and the width range is large, which can meet the different width requirements of the main grid and the fine grid.

[0095] As an embodiment of the present application, the height ratio of the first polarity grid line at the edge position close to the back contact solar cell to the first polarity grid line at the center position close to the back contact solar cell is greater than or equal to 0.8 times; and / or the height ratio of the second polarity grid line at the edge position close to the back contact solar cell to the second polarity grid line at the center position close to the back contact solar cell is greater than or equal to 0.8 times.

[0096] The height ratio of the first polarity grid line at the edge position close to the back contact solar cell to the first polarity grid line at the center position close to the back contact solar cell is greater than or equal to 0.8 times; and / or the height ratio of the second polarity grid line at the edge position close to the back contact solar cell to the second polarity grid line at the center position close to the back contact solar cell is greater than or equal to 0.8 times.

[0097] As an embodiment of the present application, the length ratio of the first polarity grid line at the edge position close to the back contact solar cell to the first polarity grid line at the center position close to the back contact solar cell is 1.2-2.0; and / or the length ratio of the second polarity grid line at the edge position close to the back contact solar cell to the second polarity grid line at the center position close to the back contact solar cell is 1.2-2.0. By increasing the length of the first polarity grid line and / or the second polarity grid line at the edge position close to the back contact solar cell relative to the first polarity grid line and / or the second polarity grid line at the center position close to the back contact solar cell, the carrier collection capability of the first polarity grid line and / or the second polarity grid line is increased, which is beneficial to improving the working efficiency of the cell. The carrier collection capability and the resistance of the grid line can be better balanced.

[0098] The length ratio of the first polarity grid line at the edge position close to the back contact solar cell to the first polarity grid line at the center position close to the back contact solar cell, and the length ratio of the second polarity grid line at the edge position close to the back contact solar cell to the second polarity grid line at the center position close to the back contact solar cell can be any value among 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, and 2.0 times, which can be determined in combination with the size of the silicon substrate 1.

[0099] As an embodiment of the utility model, a plurality of pad points 6 are arranged on the first polarity main grid line 4 and the second polarity main grid line 5, and the plurality of pad points 6 are arranged at intervals along the length direction of the first polarity main grid line 4 and the second polarity main grid line 5; in the utility model, the first polarity main grid line 4 close to the edge position of the back contact solar cell is a first polarity edge main grid 7, the width range of which is 25-1200 microns, the second polarity main grid line 5 close to the edge position of the back contact solar cell is a second polarity edge main grid 8, the width range of which is 25-1200 microns, the first polarity main grid line 4 close to the middle position of the back contact solar cell is a first polarity middle main grid 9, the width range of which is 10-1200 microns, and the second polarity main grid line 5 close to the middle position of the back contact solar cell is a second polarity middle main grid 10, the width range of which is 10-1200 microns; in some embodiments, the width of the first polarity middle main grid 9 or the second polarity middle main grid 10 can be set to 600 microns, the width of the first polarity edge main grid 7 or the second polarity edge main grid 8 can be set to 750 microns-800 microns, for example, 750 microns, 780 microns, 800 microns, which can ensure that the performance of the cell sheet is optimal.

[0100] As an embodiment of the utility model, the width of the first polarity main grid line 4 and the second polarity main grid line 5 gradually decreases from the position close to the pad point 6 to the position away from the pad point 6; in this way, while the width of the first polarity main grid line 4 and the second polarity main grid line 5 gradually decreases, the current gradually decreases, which can ensure that the resistance of the first polarity main grid line 4 and the second polarity main grid line 5 causes relatively small power loss, and also makes the shielding rate of the first polarity main grid line 4 and the second polarity main grid line 5 lower and the amount of metal paste used less. Moreover, the stability of the connection between the first polarity main grid line 4 and the second polarity main grid line 5 and the pad point can be ensured, and the gradually decreasing width of the main grid is conducive to reducing the cost. In some embodiments, the width of the first polarity main grid line 4 and the second polarity main grid line 5 from the position close to the pad point 6 to the position away from the pad point 6 can also be set to be unchanged.

[0101] As an embodiment of the utility model, the width of the first polarity edge main grid 7, that is, the length in the X-axis direction, is at least greater than the width of one pad point 6; or the width of the second polarity edge main grid 8, that is, the length in the X-axis direction, is at least greater than the width of one pad point 6; specifically, it can be 1.0 times, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times or 2.0 times of the pad width. Preferably, the shape of the pad point 6 is a rectangle, a circle, an ellipse or a polygon with 5 sides or more; in the utility model, the pad point 6 is a rectangle, which has the advantages of being convenient to design and convenient to install.

[0102] As an embodiment of the utility model, the first polarity grid line close to the edge position of the back contact solar cell is a first polarity edge grid line, the first polarity grid line close to the middle position of the back contact solar cell is a first polarity middle grid line, and the ratio of the width of the first polarity edge grid line to the first polarity middle grid line is greater than 1.2; or the second polarity grid line close to the edge position of the back contact solar cell is a second polarity edge grid line, the second polarity grid line close to the middle position of the back contact solar cell is a second polarity middle grid line, and the ratio of the width of the second polarity edge grid line to the second polarity middle grid line is greater than 1.2.

[0103] Specifically, the ratio of the width of the first polarity edge grid line to the first polarity middle grid line or the ratio of the width of the second polarity edge grid line to the second polarity middle grid line can be 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times or more, and can be specifically determined in combination with the size of the silicon substrate 1 and the actual number of the first polarity edge grid line, the first polarity middle grid line, the second polarity edge grid line and the second polarity middle grid line. In some specific embodiments, when the ratio of the width of the first polarity edge grid line to the first polarity middle grid line or the ratio of the width of the second polarity edge grid line to the second polarity middle grid line is 1.4 times, the carrier collection capability of the P region and the N region is balanced, the adhesion capability of the metal and the electrode is increased, the resistance of the first polarity grid line or the second polarity grid line at the edge is reduced, the power loss in the current transmission process is reduced, the photo-generated carriers in the edge region, the current in the edge region and the lateral current transmission loss are effectively collected, the conversion efficiency of the cell is improved, the first polarity grid line or the second polarity grid line at the edge has better mechanical strength and connection stability, the amount of metal paste used is reduced, the cost is reduced, and the effect is best.

[0104] Further, a ratio of average widths of the first polarity edge gate line and the first polarity middle gate line is greater than 1.2, or a ratio of average widths of the second polarity edge gate line and the second polarity middle gate line is greater than 1.2. That is, the first polarity edge gate line or the second polarity edge gate line is not wider than 1.2 times of the first polarity middle gate line or the second polarity middle gate line at every position, wherein there can be a part of 1.05 times, 1.1 times, etc. lower than 1.2 times of the first polarity middle gate line or the second polarity middle gate line, as long as the ratio of average widths is greater than 1.2, that is, the width part not exceeding 1.2 times is allowed to exist in the design, the carrier collection capability of the P region and the N region is balanced, the adhesion capability of the metal and the electrode is increased, the resistance of the first polarity gate line or the second polarity gate line at the edge is reduced, the power loss in the current transmission process is reduced, the photo-generated carriers of the edge region, the current of the edge region, the lateral current transmission loss are effectively collected, the conversion efficiency of the battery is improved, the first polarity gate line or the second polarity gate line at the edge has better mechanical strength and connection stability, meanwhile, the use amount of the metal paste is reduced, the cost is reduced, and the fault tolerance is improved.

[0105] As an embodiment of the utility model, the short and thin gate line 11 is arranged at the position close to the pad point 6 of the first polarity edge main gate 7, or the short and thin gate line 11 is arranged at the position close to the pad point 6 of the second polarity edge main gate 8, for improving the backflow capability at the edge.

[0106] The utility model embodiment provides a kind of photovoltaic module, and photovoltaic module includes above-mentioned back contact solar cell, and photovoltaic module can also include metal frame, back plate, photovoltaic glass and adhesive film.Adhesive film can be filled between back contact solar cell front and back and photovoltaic glass, back contact solar cell etc., as filler, it can be transparent colloid of good light transmission and ageing resistance, for example, adhesive film can use EVA adhesive film or POE adhesive film, specific can be selected according to actual situation, not limited here.

[0107] Photovoltaic glass can be covered on the adhesive film of the front of back contact solar cell, and photovoltaic glass can be super white glass, which has high light transmittance, high transparency, and has superior physical, mechanical and optical properties, for example, the light transmittance of super white glass can reach more than 9%, which can protect the back contact solar cell as much as possible without affecting the efficiency of the back contact solar cell.Meanwhile, adhesive film can bond photovoltaic glass and back contact solar cell together, and the existence of adhesive film can seal and insulate the back contact solar cell and prevent water and moisture.

[0108] The back plate can be attached to the adhesive film on the back of the back contact solar cell. The back plate can protect and support the back contact solar cell, has reliable insulation, water resistance and aging resistance, and the back plate can have multiple choices, which can be tempered glass, organic glass, aluminum alloy TPT composite adhesive film, etc. The specific setting can be made according to the specific situation, which is not limited here. The whole composed of the back plate, the back contact solar cell, the adhesive film and the photovoltaic glass can be arranged on the metal frame. The metal frame serves as the main external support structure of the whole photovoltaic module, and can stably support and install the photovoltaic module. For example, the photovoltaic module can be installed at the required installation position through the metal frame.

[0109] The utility model embodiment provides a photovoltaic system, comprising the photovoltaic module described above.

[0110] In the embodiment, the photovoltaic system can be applied in a photovoltaic power station, such as a ground power station, a roof power station, a water surface power station, etc., and can also be applied in a device or apparatus that generates electricity by using solar energy, such as a user solar power source, a solar street lamp, a solar car, a solar building, 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 need to generate electricity by using solar energy. Taking a photovoltaic power generation system network as an example, the photovoltaic system can include a photovoltaic array, a current combiner box and an inverter. The photovoltaic array can be an array combination of a plurality of photovoltaic modules. For example, a plurality of photovoltaic modules can form a plurality of photovoltaic arrays. The photovoltaic array is connected to the current combiner box. The current combiner box can combine the current generated by the photovoltaic array. The combined current flows through the inverter to convert into alternating current required by the power grid, and then is connected to the power network to realize solar power supply.

[0111] In the above embodiments, the description of each embodiment focuses on different aspects. The parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0112] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0113] In addition, the terms "first", "second", etc. are used herein only to describe different instances, and do not imply or suggest relative importance or a number of the technical features indicated. Thus, the features defined with "first", "second", etc. can include one or more of the features explicitly or implicitly. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0114] In the present application, unless otherwise explicitly and specifically defined, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense, for example, it can be connected, or detachable, or integrated; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0115] In the present application, unless otherwise explicitly and specifically defined, the first feature "on" or "under" the second feature can include the first and second features directly contacting, or the first and second features not directly contacting but contacting through another feature between them. Moreover, the first feature "on", "above" and "on" the second feature includes the first feature directly above and obliquely above the second feature, or only indicates that the first feature is higher than the second feature in horizontal height. The first feature "below", "below" and "below" the second feature includes the first feature directly below and obliquely below the second feature, or only indicates that the first feature is lower than the second feature in horizontal height.

[0116] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present application.

[0117] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, these modifications and variations of the present application are intended to be included within the scope of the claims of the present application and their equivalents.

[0118] The above is merely specific embodiments of the present application, and the protection scope of the present application is not limited thereto, and any modification or replacement within the technical scope disclosed by the present application can be easily thought by those skilled in the art, and these modifications or replacements shall be encompassed in the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A back contact solar cell, characterized by, Comprising: a silicon substrate; a first polarity gate line and a second polarity gate line disposed on a surface of the silicon substrate, the first polarity gate line and the second polarity gate line are arranged alternately and spaced apart, the first polarity gate line is located in a first polarity region, and the second polarity gate line is located in a second polarity region; a width of the first polarity gate line at a position close to an edge of the back contact solar cell is greater than a width of the first polarity gate line at a position close to a center of the back contact solar cell; or a width of the second polarity gate line at a position close to an edge of the back contact solar cell is greater than a width of the second polarity gate line at a position close to a center of the back contact solar cell. The first polarity gate line is a first polarity fine gate line, and the second polarity gate line is a second polarity fine gate line, a plurality of the first polarity fine gate lines and a plurality of the second polarity fine gate lines are arranged alternately and spaced apart along a first direction and extend along a second direction.

2. The back contact solar cell of claim 1, wherein, The first polarity gate line is a first polarity main gate line, and the second polarity gate line is a second polarity main gate line, a plurality of the first polarity main gate lines and a plurality of the second polarity main gate lines are arranged spaced apart along a second direction and extend along a first direction.

3. The back contact solar cell of claim 1, wherein, The first polarity main gate line is further connected with a plurality of first polarity fine gate lines, and the second polarity main gate line is further connected with a plurality of second polarity fine gate lines.

4. The back contact solar cell of claim 3, wherein, A width of the first polarity fine gate line at a position close to an edge of the back contact solar cell is greater than a width of the first polarity fine gate line at a position close to a center of the back contact solar cell; or A width of the second polarity fine gate line at a position close to an edge of the back contact solar cell is greater than a width of the second polarity fine gate line at a position close to a center of the back contact solar cell. An average width of the first polarity gate line at a position close to an edge of the back contact solar cell is greater than an average width of the first polarity gate line at a position close to a center of the back contact solar cell; or An average width of the second polarity gate line at a position close to an edge of the back contact solar cell is greater than an average width of the second polarity gate line at a position close to a center of the back contact solar cell.

5. The back contact solar cell of claim 1, wherein, 6. The back contact solar cell according to claim 1, wherein At least one of the first polarity gate line and the second polarity gate line is a width-graduated gate line.

7. The back contact solar cell according to claim 6, wherein The first polarity gate line at a position close to an edge of the back contact solar cell is a width-graduated gate line, a width of the width-graduated gate line gradually changes from thin to thick or gradually changes from thick to thin from a position close to an edge of the back contact solar cell to a position close to a center of the back contact solar cell. The first polarity gate line at a position close to a center of the back contact solar cell is a width-constant gate line.

9. The back contact solar cell according to claim 6, wherein ​ 8. The back contact solar cell of claim 7, wherein, ​ ​ The second polarity grid line near the edge of the back contact solar cell is a width-graduated grid line, the width of the width-graduated grid line gradually changes from thin to thick or from thick to thin from the edge of the back contact solar cell to the center of the back contact solar cell.

10. The back contact solar cell of claim 9, wherein, The second polarity grid line near the center of the back contact solar cell is a width-constant grid line.

11. The back contact solar cell of claim 6, wherein, The shape of the top view of the width-graduated grid line is one of trapezoid, irregular quadrilateral.

12. The back contact solar cell of claim 11, wherein, When the shape of the top view of the width-graduated grid line is trapezoid, the bottom angle of the trapezoid is set to 20-90 degrees.

13. The back contact solar cell of claim 11, wherein, When the shape of the top view of the width-graduated grid line is trapezoid, and the width-graduated grid line is a thin grid line, the length of the upper base of the trapezoid is greater than or equal to 10 microns, and the length of the lower base of the trapezoid is less than or equal to 250 microns.

14. The back contact solar cell of claim 11, wherein, When the shape of the top view of the width-graduated grid line is trapezoid, and the width-graduated grid line is a main grid line, the length of the upper base of the trapezoid is greater than or equal to 10 microns, and the length of the lower base of the trapezoid is less than or equal to 1200 microns.

15. The back contact solar cell of claim 6, wherein, The width range of the thin grid line is 10-250 microns.

16. The back contact solar cell of claim 6, wherein, The width range of the main grid line is 10-1200 microns.

17. The back contact solar cell of claim 1 wherein, The ratio of the height of the first polarity grid line near the edge of the back contact solar cell to the height of the first polarity grid line near the center of the back contact solar cell is greater than or equal to 0.8 times; and / or The ratio of the height of the second polarity grid line near the edge of the back contact solar cell to the height of the second polarity grid line near the center of the back contact solar cell is greater than or equal to 0.8 times.

18. The back contact solar cell of claim 1 wherein, The ratio of the length of the first polarity grid line near the edge of the back contact solar cell to the length of the first polarity grid line near the center of the back contact solar cell is 1.2-2.0; and / or The ratio of the length of the second polarity grid line near the edge of the back contact solar cell to the length of the second polarity grid line near the center of the back contact solar cell is 1.2-2.

0.

19. The back contact solar cell of claim 3, wherein, The first polarity main grid line and the second polarity main grid line are provided with a plurality of pad points, and the plurality of pad points are arranged in intervals along the length direction of the first polarity main grid line and the second polarity main grid line.

20. The back contact solar cell of claim 19, wherein, The width of the first polarity main grid line and the second polarity main grid line gradually decreases from the position near the pad point to the position away from the pad point.

21. The back contact solar cell of claim 19, wherein, The width of the first polarity main grid line and the second polarity main grid line is constant from the position near the pad point to the position away from the pad point.

22. The back contact solar cell of claim 3, wherein, The first polarity main grid line near the edge of the back contact solar cell is a first polarity edge main grid, and the width range of the first polarity edge main grid is 25-1200 microns. Or The second polarity main grid lines near the edge position of the back contact solar cell are second polarity edge main grids, and the width of the second polarity edge main grids ranges from 25 to 1200 microns.

23. The back contact solar cell of claim 3, wherein, The first polarity main grid lines near the middle position of the back contact solar cell are first polarity middle main grids, and the width of the first polarity middle main grids ranges from 10 to 1200 microns; Or The second polarity main grid lines near the middle position of the back contact solar cell are second polarity middle main grids, and the width of the second polarity middle main grids ranges from 10 to 1200 microns.

24. The back contact solar cell of claim 19, wherein, The first polarity main grid lines near the edge position of the back contact solar cell are first polarity edge main grids, and the width of the first polarity edge main grids is at least greater than the width of one pad point; Or The second polarity main grid lines near the edge position of the back contact solar cell are second polarity edge main grids, and the width of the second polarity edge main grids is at least greater than the width of one pad point.

25. The back contact solar cell of claim 19, wherein, The first polarity main grid lines near the edge position of the back contact solar cell are first polarity edge main grids, and short and thin grid lines are arranged near the position of the pad point of the first polarity edge main grids; Or The second polarity main grid lines near the edge position of the back contact solar cell are second polarity edge main grids, and short and thin grid lines are arranged near the position of the pad point of the second polarity edge main grids.

26. The back contact solar cell of claim 1 wherein, The first polarity grid lines near the edge position of the back contact solar cell are first polarity edge grid lines, and the first polarity grid lines near the middle position of the back contact solar cell are first polarity middle grid lines, and the ratio of the width of the first polarity edge grid lines to the width of the first polarity middle grid lines is greater than 1.2; Or The second polarity grid lines near the edge position of the back contact solar cell are second polarity edge grid lines, and the second polarity grid lines near the middle position of the back contact solar cell are second polarity middle grid lines, and the ratio of the width of the second polarity edge grid lines to the width of the second polarity middle grid lines is greater than 1.

2.

27. The back contact solar cell of claim 26, wherein, The ratio of the average width of the first polarity edge grid lines to the average width of the first polarity middle grid lines is greater than 1.2; or The ratio of the average width of the second polarity edge grid lines to the average width of the second polarity middle grid lines is greater than 1.

2.

28. A photovoltaic module, characterized by The solar cell according to any one of claims 1 to 27.

29. A photovoltaic system characterized by, The photovoltaic module according to claim 28.

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