Back contact solar cell, cell module and photovoltaic system

Abstract

The invention is suitable for the technical field of solar cells, and provides a back contact solar cell, a cell assembly and a photovoltaic system, and the solar cell comprises a silicon substrate, the backlight surface of which is provided with a first region and a second region; the first passivation layer is arranged in the first region; the first doping layer is arranged on one surface, deviating from the silicon substrate, of the first passivation layer; the second passivation layer is arranged in the second region; the second doping layer is arranged on one surface, deviating from the silicon substrate, of the second passivation layer; at a preset position, an electric leakage contact layer is arranged in at least partial region between the first doping layer and the second doping layer, the electric leakage contact layer is connected with the first doping layer and the second doping layer, the thickness of the electric leakage contact layer is greater than that of the second passivation layer, and the ratio of the thickness of the electric leakage contact layer to the thickness of the second passivation layer is less than 4. According to the back contact solar cell, hot spot effect management and control can be achieved, normal power generation under a certain weak light condition is not affected, and hot spot effect management and control and power generation capacity of the back contact solar cell can be well balanced.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a back-contact solar cell, a cell assembly and a photovoltaic system. Background Art

[0002] Solar cells are devices that use the photovoltaic effect to directly convert light energy into electrical energy. Solar cells mainly include bifacial solar cells and back-contact solar cells. Among them, back-contact solar cells are a type of battery that places both the positive electrode and the negative electrode on the backlight side of the battery. The light-receiving side of the battery is not blocked by any metal electrode, which effectively increases the short-circuit current of the battery cell.

[0003] In the prior art, during the actual use of the back-contact solar cell, there may be obstructions such as leaves blocking the back-contact cell to form weak light conditions. When the cell is blocked by the obstruction and other weak light conditions, the temperature will rise to produce a hot spot effect. If the temperature generated by the hot spot exceeds a certain temperature value, it will cause problems such as delamination of the photovoltaic module, burning of the back panel, and bursting of the glass, thereby causing the entire solar cell to be scrapped, and in severe cases, it may cause a fire risk. In order to solve the above-mentioned hot spot effect problem, the P-type doped layer and the N-type doped layer at the preset position of the back-contact solar cell are usually directly connected to the leakage current by a thin passivation layer. When the back-contact solar cell is blocked by an obstruction, the P-type doped layer and the N-type doped layer are connected to the leakage current by the passivation layer to protect the back-contact solar cell. However, since the P-type doped layer and the N-type doped layer are connected to the leakage current by a thin passivation layer, the breakdown voltage threshold of the passivation layer is low, which affects the normal power generation of the back-contact solar cell under weak light conditions, and it is impossible to better balance the hot spot effect control of the back-contact solar cell and the power generation of the back-contact solar cell under weak light conditions. Summary of the invention

[0004] The present invention provides a back-contact solar cell, aiming to solve the problem that the back-contact solar cell in the prior art cannot well balance the hot spot effect control of the back-contact solar cell and the power generation of the back-contact solar cell under weak light conditions.

[0005] The present invention is implemented by providing a back contact solar cell, comprising:

[0006] A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first regions and second regions which are alternately arranged in sequence;

[0007] A first passivation layer, disposed in the first region;

[0008] A first doping layer, disposed on a side of the first passivation layer away from the silicon substrate;

[0009] A second passivation layer is disposed in the second region; and

[0010] A second doping layer, provided on a side of the second passivation layer away from the silicon substrate, wherein the second doping layer has a different doping type from the first doping layer;

[0011] At a preset position, a leakage contact layer is provided in at least a partial area between the first doped layer and the second doped layer, the leakage contact layer is arranged in contact with the first doped layer and the second doped layer, the thickness of the leakage contact layer is greater than the thickness of the second passivation layer, and the ratio of the thickness of the leakage contact layer to the thickness of the second passivation layer is less than 4.

[0012] Preferably, the first doping layer is a P-type doping layer, and the second doping layer is an N-type doping layer; or, the first doping layer is an N-type doping layer, and the second doping layer is a P-type doping layer.

[0013] Preferably, the ratio of the thickness of the leakage contact layer to the thickness of the second passivation layer is 1.5-3.

[0014] Preferably, the leakage contact layer has a thickness of 2 to 8 nanometers.

[0015] Preferably, the leakage contact layer has a thickness of 3 to 6 nanometers.

[0016] Preferably, the leakage contact layer has a thickness of 4 to 6 nanometers.

[0017] Preferably, the leakage contact layer is one of silicon oxide, silicon oxynitride, and aluminum oxide, or a combination of at least two of them.

[0018] Preferably, the thickness of the first passivation layer is greater than the thickness of the second passivation layer.

[0019] Preferably, the thickness of the leakage contact layer is greater than the thickness of the first passivation layer.

[0020] Preferably, the ratio of the thickness of the leakage contact layer to the thickness of the first passivation layer is greater than 3.

[0021] Preferably, both the leakage contact layer and the second passivation layer are provided with holes, and the average hole size of the leakage contact layer is smaller than the average hole size of the second passivation layer.

[0022] Preferably, both the leakage contact layer and the second passivation layer are provided with holes, and the hole density of the leakage contact layer is smaller than the hole density of the second passivation layer.

[0023] Preferably, one end of the leakage contact layer is connected to the second passivation layer, and the leakage contact layer extends from the second passivation layer to between the first doping layer and the second doping layer.

[0024] Preferably, the second region is a trench region, the first region is a non-trench region, and the leakage contact layer covers the sidewalls of the trench region close to the first region.

[0025] Preferably, the leakage contact layer and the second passivation layer are integrally formed.

[0026] Preferably, the leakage contact layer comprises a first portion and a second portion which are arranged in sequence along its extension direction, and the thickness of the second portion is greater than the thickness of the first portion.

[0027] Preferably, the leakage contact layer includes a plurality of first rarefied regions and a first non-rare region arranged around the first rarefied regions, and the thickness of the first rarefied regions is smaller than the thickness of the first non-rare region.

[0028] Preferably, the oxygen content of the first rarefied region is less than the oxygen content of the first non-rare region.

[0029] Preferably, the second passivation layer includes a plurality of second rarefied regions and a second non-rarely region arranged around the second rarefied regions, and the thickness of the second rarefied regions is smaller than the thickness of the second non-rarely region.

[0030] Preferably, the oxygen content of the second lean region is less than the oxygen content of the second non-lean region.

[0031] Preferably, within a unit area, the number of the first rarefied regions is less than the number of the second rarefied regions.

[0032] Preferably, at the preset position, an insulating layer is further provided in a region between the second doping layer and the first doping layer where the leakage contact layer is not provided, and the thickness of the insulating layer is greater than the thickness of the leakage contact layer.

[0033] Preferably, the insulating layer is disposed between an end of the second doped layer close to the first doped layer and the first doped layer, and one end of the leakage contact layer is connected to the insulating layer, and the other end is connected to the second passivation layer.

[0034] Preferably, the insulating layers are respectively arranged on both sides of the leakage contact layer; or, the leakage contact layers are respectively arranged on both sides of the insulating layer.

[0035] Preferably, a plurality of leakage contact layers and a plurality of the insulating layers are arranged between the first doping layer and the second doping layer, and the leakage contact layers and the insulating layers are alternately arranged between the first doping layer and the second doping layer.

[0036] Preferably, the insulating layer completely covers the region between the first doped layer and the second doped layer, the insulating layer is hollowed out to form at least one leakage contact region, and the leakage contact layer is arranged in the leakage contact region.

[0037] Preferably, the second region is a groove region, and the first region is a non-groove region; at the preset position, the first doped layer has a protruding portion extending above the groove region, and the second doped layer has a first wrapping portion extending below the protruding portion, and the leakage contact layer is at least partially disposed on the lower surface of the protruding portion and the upper surface of the first wrapping portion.

[0038] Preferably, the second doping layer further includes a second wrapping portion connected to the first wrapping portion and wrapping around a side surface of the protruding portion, and the leakage contact layer is at least partially disposed between the side surface of the protruding portion and the second wrapping portion.

[0039] Preferably, the second doping layer further includes a third wrapping portion connected to the second wrapping portion and wrapping around the upper surface of the protruding portion, and the leakage contact layer portion is arranged between the upper surface of the protruding portion and the third wrapping portion.

[0040] The present invention also provides a battery assembly, comprising the above-mentioned back-contact solar cell.

[0041] The present invention also provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0042] The present invention provides a back-contact solar cell, in which a leakage contact layer is arranged in at least a partial area between a first doped layer and a second doped layer at a preset position, the thickness of the leakage contact layer is greater than the thickness of the second passivation layer, and the ratio of the thickness of the leakage contact layer to the thickness of the second passivation layer is less than 4; by reasonably setting the thickness of the leakage contact layer, the breakdown voltage threshold of the leakage contact layer can be increased, and only after the breakdown voltage threshold is exceeded, the leakage contact layer conducts the first doped layer and the second doped layer to stop the power generation of the back-contact solar cell, thereby controlling the hot spot effect and avoiding the back-contact solar cell from overheating; and because the thickness of the leakage contact layer is reasonably set, the breakdown voltage threshold corresponding to the thickness of the leakage contact layer can avoid the leakage When the back-contact solar cell is blocked by an obstruction, the electrical contact layer is too easily broken down by voltage to turn on the first doped layer and the second doped layer and stop the back-contact solar cell from generating electricity. This allows the back-contact solar cell to generate electricity normally when the impact of the obstruction is small, thereby increasing the power generation under weak light conditions. When the back-contact solar cell is blocked by an obstruction with a large impact, the first doped layer and the second doped layer can be turned on to stop the back-contact solar cell from generating electricity to protect the back-contact solar cell. This can not only achieve good control of the hot spot effect of the back-contact solar cell, but also ensure the normal operation and power generation of the back-contact solar cell under certain weak light conditions, and can better balance the control of the hot spot effect and the power generation under weak light conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of the back side of a back-contact solar cell provided by an embodiment of the present invention;

[0044] Figure 2 The first back contact solar cell provided in the first embodiment of the present invention is Figure 1 Schematic diagram of the cross section in the AA direction;

[0045] Figure 3 The second back contact solar cell provided in the first embodiment of the present invention is Figure 1 Schematic diagram of the cross section in the AA direction;

[0046] Figure 4 The third back contact solar cell provided in the first embodiment of the present invention is Figure 1 Schematic diagram of the cross section in the AA direction;

[0047] Figure 5 The first back contact solar cell provided in the second embodiment of the present invention is Figure 1 Schematic diagram of the cross section in the AA direction;

[0048] Figure 6 The second back contact solar cell provided in the second embodiment of the present invention is Figure 1 Schematic diagram of the cross section in the AA direction;

[0049] Figure 7 The back contact solar cell provided in the third embodiment of the present invention is Figure 1 Schematic diagram of the cross section along the AA direction. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0051] The present invention provides a back-contact solar cell, in which a leakage contact layer is arranged in at least a partial area between a first doped layer and a second doped layer at a preset position, the thickness of the leakage contact layer is greater than the thickness of the second passivation layer, and the ratio of the thickness of the leakage contact layer to the thickness of the second passivation layer is less than 4; by reasonably setting the thickness of the leakage contact layer, the breakdown voltage threshold of the leakage contact layer can be increased, and only after the breakdown voltage threshold is exceeded, the leakage contact layer conducts the first doped layer and the second doped layer to stop the power generation of the back-contact solar cell, thereby controlling the hot spot effect and avoiding the back-contact solar cell from overheating; and because the thickness of the leakage contact layer is reasonably set, the breakdown voltage threshold corresponding to the thickness setting of the leakage contact layer can avoid When the back-contact solar cell is blocked by an obstruction, the leakage contact layer is too easily broken down by voltage to turn on the first doped layer and the second doped layer and stop the back-contact solar cell from generating electricity. This allows the back-contact solar cell to generate electricity normally when the impact of the obstruction is small, thereby increasing the power generation under weak light conditions. When the back-contact solar cell is severely blocked by an obstruction, the first doped layer and the second doped layer can be turned on to stop the back-contact solar cell from generating electricity to protect the back-contact solar cell. This can not only well realize the hot spot effect control of the back-contact solar cell, but also ensure the normal operation and power generation of the back-contact solar cell under certain weak light conditions, and can better balance the hot spot effect control and the power generation under weak light conditions.

[0052] Embodiment 1

[0053] Please refer to Figure 1-Figure 3 , an embodiment of the present invention provides a back contact solar cell, comprising:

[0054] A silicon substrate 1, wherein the backlight surface of the silicon substrate 1 has a plurality of first regions 11 and second regions 12 which are alternately arranged in sequence;

[0055] A first passivation layer 2, provided in the first region 11;

[0056] A first doped layer 3, provided on a side of the first passivation layer 2 facing away from the silicon substrate 1;

[0057] A second passivation layer 4 is provided in the second region 12; and

[0058] A second doping layer 5 is provided on a side of the second passivation layer 4 facing away from the silicon substrate 1, and the second doping layer 5 has a different doping type from the first doping layer 3;

[0059] At the preset position 100, a leakage contact layer 6 is provided in at least a partial area between the first doping layer 3 and the second doping layer 5, and the leakage contact layer 6 is arranged in contact with the first doping layer 3 and the second doping layer 5. The thickness d1 of the leakage contact layer 6 is greater than the thickness d2 of the second passivation layer 4, and the ratio of the thickness d1 of the leakage contact layer 6 to the thickness d2 of the second passivation layer 4 is less than 4.

[0060] The present invention provides a back-contact solar cell, in which a leakage contact layer 6 is arranged in at least a partial area between a first doping layer 3 and a second doping layer 5 at a preset position 100, the thickness of the leakage contact layer 6 is greater than the thickness d2 of the second passivation layer 4, and the ratio of the thickness d1 of the leakage contact layer 6 to the thickness d2 of the second passivation layer 4 is less than 4; when the back-contact solar cell is in normal working and power generation (without being blocked by an obstruction), the first doping layer 3 and the second doping layer 5 at the preset position 100 are insulated by the leakage contact layer 6, and the first doping layer 3 and the second doping layer 5 are not conductive to each other, and when the back-contact solar cell is blocked by an obstruction (such as leaves, branches, etc.), when the reverse voltage of the back-contact solar cell exceeds the breakdown voltage threshold of the leakage contact layer 6, the reverse voltage breaks down the leakage contact layer 6, and the leakage current passes through the leakage contact layer 6, so that the leakage contact layer 6 conducts the first doping layer 3 and the second doping layer 5, thereby protecting the back-contact solar cell and preventing the solar cell from generating a hot spot effect when blocked by an obstruction, thereby preventing the cell from being damaged by excessive temperature.

[0061] Since the thickness d1 of the leakage contact layer 6 of the present invention is greater than the thickness d2 of the second passivation layer 4, compared with the thickness of the second passivation layer 4, the thickness d1 of the leakage contact layer 6 is thickened, and the ratio of the thickness d1 of the leakage contact layer 6 to the thickness d2 of the second passivation layer 4 is less than 4, the leakage contact layer 6 is set within such a reasonable thickness range, and the thickness d1 of the leakage contact layer 6 is avoided from being too thick or too thin, and the thickness d1 of the leakage contact layer 6 is optimized. The breakdown voltage threshold of the leakage contact layer 6 can be improved. Only when the breakdown voltage threshold is exceeded, the leakage contact layer 6 will turn on the first doping layer 3 and the second doping layer 5 to stop the back contact solar cell from generating electricity, and the leakage contact layer 6 is avoided from being too easily broken down by voltage when the back contact solar cell is blocked by an obstruction. The first doped layer 3 and the second doped layer 5 are turned on to stop the power generation of the back contact solar cell, so that when the leakage current threshold is not exceeded, the leakage contact layer 6 still does not turn on the first doped layer 3 and the second doped layer 5, and the back contact solar cell can still generate electricity normally, thereby increasing the power generation of the back contact solar cell under weak light conditions; when the leakage current threshold is exceeded, the leakage contact layer 6 turns on the first doped layer 3 and the second doped layer 5, which can improve the power generation efficiency of the back contact solar cell under weak light conditions, and can not only realize the hot spot effect control of the back contact solar cell well, but also ensure the normal power generation of the back contact solar cell under certain weak light conditions, and can well balance the hot spot effect control effect of the back contact solar cell and the power generation under weak light conditions.

[0062] In an embodiment of the present invention, the silicon substrate 1 may be a P-type silicon substrate 1 or an N-type silicon substrate. The silicon substrate 1 includes a backlight surface and a light-receiving surface opposite to the backlight surface. The backlight surface of the silicon substrate 1 is provided with a plurality of first regions 11 and a plurality of second regions 12, and the first regions 11 and the second regions 12 are alternately arranged in sequence along the first direction X. At a non-preset position 100, that is, except for the preset position 100, the first region 11 and the second region 12 are spaced apart from each other; the first doped layer 3 and the second doped layer 5 at the preset position 100 are in contact through the leakage contact layer 6 to achieve hot spot effect control of the back-contact solar cell.

[0063] As an embodiment of the present invention, the back-contact solar cell further includes a first electrode 7 disposed in the first region 11 and a second electrode 8 disposed in the second region 12 . The first electrode 7 contacts the first doping layer 3 , and the second electrode 8 contacts the second doping layer 5 .

[0064] As an embodiment of the present invention, the back-contact solar cell also includes a back passivation layer 15 covering the first doping layer 3 and the second doping layer 5, the first electrode 7 passes through the back passivation layer 15 to contact the first doping layer 3, and the second electrode 8 passes through the back passivation layer 15 to contact the second doping layer 5.

[0065] In this embodiment, the back passivation layer 15 realizes the passivation and protection function of the back side of the back contact solar cell. The back passivation layer 15 can be one or a combination of silicon nitride, silicon oxynitride, silicon carbide, and aluminum oxide.

[0066] As an embodiment of the present invention, the first doping layer 3 is a P-type doping layer, and the second doping layer 5 is an N-type doping layer; or, the first doping layer 3 is an N-type doping layer, and the second doping layer 5 is a P-type doping layer.

[0067] In the embodiment of the present invention, the first doping layer 3 and the second doping layer 5 are one of doped polycrystalline silicon, doped microcrystalline silicon, doped nanocrystalline silicon, doped amorphous silicon, or a mixture of the above materials. For example, the first doping layer 3 is one of polycrystalline silicon, microcrystalline silicon, nanocrystalline silicon, amorphous silicon, or a mixture of the above materials with a P-type dopant; the second doping layer 5 is one of polycrystalline silicon, microcrystalline silicon, nanocrystalline silicon, amorphous silicon, or a mixture of the above materials with an N-type dopant. Among them, the P-type dopant is a IIIA group element dopant, and the N-type dopant is a VA group element dopant. For example, the P-type dopant can be a boron dopant, and the N-type dopant can be a phosphorus dopant.

[0068] In the embodiment of the present invention, the first doping layer 3 is electrically connected to the silicon substrate 1 through the first passivation layer 2, and the second doping layer 5 is electrically connected to the silicon substrate 1 through the second passivation layer 4. At the non-preset position 100, the first doping layer 3 and the second doping layer 5 remain insulated, and at the preset position 100, the first doping layer 3 and the second doping layer 5 form a leakage composite contact structure through the leakage contact layer 6. When the solar cell is blocked to a certain extent, when the leakage current of the solar cell reaches the maximum power point current, the leakage contact layer 6 conducts the first doping layer 3 and the second doping layer 5, so that the voltage across the blocked solar cell will be reduced, thereby reducing the heating power of the solar cell, thereby achieving the purpose of controlling the hot spot risk of the solar cell.

[0069] It should be noted that, in the embodiment of the present application, the number of the preset position 100 may be one or more than two. The specific position of the preset position 100 is not limited, and may be between any adjacent first area 11 and second area 12.

[0070] In some embodiments, the number of the preset positions 100 may be multiple, and they may be evenly distributed on the backlight surface of the back contact solar cell, for example, Figure 1 As shown, the number of the preset positions 100 may be 4, and the 4 preset positions 100 may be distributed at four corners on the backlight surface of the back contact solar cell, and the structures at the preset positions 100 may be completely the same or may not be completely the same.

[0071] As an embodiment of the present invention, the second region 12 is a trench region, and the first region 11 is a non-trench region; the leakage contact layer 6 covers the side wall of the trench region close to the first region 11, and the leakage contact layer 6 extends from one end of the second passivation layer 4 to between the first doped layer 3 and the second doped layer 5.

[0072] In this embodiment, one of the first region 11 and the second region 12 is located in the groove area, and the other is located in the non-groove area. The groove can achieve a good isolation effect between the first region 11 and the second region 12. Of course, the backlight surface may not need to be provided with a groove area, and an insulating gap or an insulating film layer may be directly provided between the first region 11 and the second region 12 to isolate the first region 11 and the second region 12. In this embodiment, the leakage contact layer 6 completely covers the side wall of the groove area close to the first region 11, the second doping layer 5 completely covers the leakage contact layer 6, one end of the leakage contact layer 6 contacts the second passivation layer 4, and the other end of the leakage contact layer 6 extends between the first doping layer 3 and the second doping layer 5, so as to facilitate the leakage contact layer 6 to contact the second passivation layer 4.

[0073] As a preferred embodiment of the present invention, the second region 12 is an N-doped region, the first region 11 is a P-doped region, the second region 12 is located in the trench region, and the first region 11 is located in the non-trench region, which facilitates the processing of the second region 12 and the first region 11.

[0074] In the embodiment of the present invention, the materials of the leakage contact layer 6 and the second passivation layer 4 may be the same or different.

[0075] As a preferred embodiment of the present invention, the leakage contact layer 6 and the second passivation layer 4 are made of the same material, and the leakage contact layer 6 and the second passivation layer 4 are integrally formed.

[0076] In this embodiment, when the leakage contact layer 6 and the second passivation layer 4 are processed and prepared, a film layer of the same thickness can be deposited simultaneously in the region where the leakage contact layer 6 is set on the backlight side of the silicon substrate 1 and the second region 12, and then a laser or wet etching process is used to remove the film layer of the second region 12 by a corresponding thickness to form the second passivation layer 4, and the film layer thickness corresponding to the region of the leakage contact layer 6 is retained, so that the thickness d1 of the leakage contact layer 6 is greater than the thickness d2 of the second passivation layer 4 and less than 4 times the thickness of the second passivation layer 4; or, when the leakage contact layer 6 and the second passivation layer 4 are processed and prepared, a film layer of the same thickness can be deposited simultaneously in the corresponding region of the leakage contact layer 6 on the backlight side of the silicon substrate 1 and the second region 12, and then a corresponding thickness is deposited on the film layer deposited in the corresponding region of the leakage contact layer 6 to form the leakage contact layer 6, and the second region 12 retains the original film layer thickness, and similarly the thickness d1 of the leakage contact layer 6 is greater than the thickness d2 of the second passivation layer 4 and less than 4 times the thickness of the second passivation layer 4.

[0077] In this embodiment, since the leakage contact layer 6 and the second passivation layer 4 are made of the same material, the leakage contact layer 6 and the second passivation layer 4 are integrally formed, which facilitates the preparation of the leakage contact layer 6 and improves the preparation efficiency of the leakage contact layer 6 and the second passivation layer 4. Of course, the leakage contact layer 6 and the second passivation layer 4 can also be deposited and prepared separately.

[0078] As an embodiment of the present invention, the leakage contact layer 6 is one of silicon oxide, silicon oxynitride, and aluminum oxide, or a combination of at least two of them.

[0079] In this embodiment, the specific material of the leakage contact layer 6 can be one of silicon oxide, silicon oxynitride, and aluminum oxide, or a combination of at least two of silicon oxide, silicon oxynitride, and aluminum oxide. The leakage contact layer 6 and the second passivation layer 4 are made of the same material, which facilitates the one-time deposition preparation of the leakage contact layer 6 and the second passivation layer 4. Preferably, the leakage contact layer 6 is a silicon oxide layer.

[0080] In the embodiment of the present invention, the first passivation layer 2 is arranged on the first region 11, and the first passivation layer 2 has passivation and tunneling functions; the first passivation layer 2 can be an oxide layer, such as a silicon oxide tunneling layer or other film layer having passivation and tunneling functions, and its specific type can be selected according to actual conditions, and is not specifically limited here. The second passivation layer 4 is arranged on the second region 12, and the second passivation layer 4 has passivation and tunneling functions; the first passivation layer 2 can be an oxide layer, such as a silicon oxide film layer or other film layer having a passivation function, and the specific materials of the first passivation layer 2 and the second passivation layer 4 can be selected according to actual conditions, and are not specifically limited here. Preferably, the first passivation layer 2, the second passivation layer 4, and the leakage contact layer 6 are all silicon oxide, which facilitates the preparation of the first passivation layer 2, the second passivation layer 4, and the leakage contact layer 6.

[0081] As an embodiment of the present invention, the ratio of the thickness d1 of the leakage contact layer 6 to the thickness d2 of the second passivation layer 4 is 1.5-3.

[0082] In this embodiment, the thickness d1 of the leakage contact layer 6 is 1.5 to 3 times the thickness d2 of the second passivation layer 4, which can well achieve a balance between the hot spot effect control of the back contact solar cell and the power generation efficiency under certain weak light conditions.

[0083] For example, the ratio of the thickness d1 of the leakage contact layer 6 to the thickness d2 of the second passivation layer 4 may be 1.5, or 1.8, or 1.9, or 2.0, or 2.2, or 2.5, or 2.7, or 2.8, or 2.9, or 30.

[0084] As an embodiment of the present invention, the thickness d1 of the leakage contact layer 6 is 2-8 nanometers.

[0085] In this embodiment, the thickness d1 of the leakage contact layer 6 is 2 to 8 nanometers, which can well realize the hot spot effect control of the back contact solar cell and ensure the good power generation efficiency of the back contact solar cell under weak light conditions. The thickness d1 of the leakage contact layer 6 can be flexibly set as needed. For example, the thickness d1 of the leakage contact layer 6 can be 2 nanometers, or 2.5 nanometers, or 3 nanometers, or 3.6 nanometers, or 3.9 nanometers, or 4 nanometers, or 4.1 nanometers, or 4.6 nanometers, or 5 nanometers, or 5.3 nanometers, or 5.8 nanometers, or 6 nanometers, or 6.1 nanometers, or 6.7 nanometers, or 7 nanometers, or 7.4 nanometers, or 7.6 nanometers, or 7.9 nanometers, or 8.0 nanometers.

[0086] As an embodiment of the present invention, the thickness d1 of the leakage contact layer 6 is 3-6 nanometers.

[0087] In this embodiment, the thickness d1 of the leakage contact layer 6 is 3-6 nanometers, which can further better balance the reliability of hot spot effect control of the back contact solar cell and the power generation efficiency under weak light conditions.

[0088] As an embodiment of the present invention, the thickness d1 of the leakage contact layer 6 is 4-6 nanometers.

[0089] In this embodiment, the thickness d1 of the leakage contact layer 6 is 4 to 6 nanometers, which can further better balance the reliability of hot spot effect control of the back contact solar cell and the power generation efficiency under weak light conditions, and facilitate the processing and preparation of the leakage contact layer 6.

[0090] As an embodiment of the present invention, the thickness d3 of the first passivation layer 2 is greater than the thickness d2 of the second passivation layer 4 .

[0091] In this embodiment, the thickness d3 of the first passivation layer 2 is greater than the thickness d2 of the second passivation layer 4, which can improve the passivation effect of the second passivation layer 4. In other embodiments, the thickness d3 of the first passivation layer 2 can also be less than or equal to the thickness d2 of the second passivation layer 4.

[0092] As an embodiment of the present invention, the thickness d1 of the leakage contact layer 6 is greater than the thickness d3 of the first passivation layer 2 .

[0093] In this embodiment, the thickness d1 of the leakage contact layer 6 is greater than the thickness d3 of the first passivation layer 2, and greater than the thickness d2 of the second passivation layer 4, which is beneficial to improving the breakdown voltage threshold of the leakage contact layer 6, so that when the leakage current is too small, the first doping layer 3 and the second doping layer 5 will not be turned on, which is beneficial to maintaining the power generation efficiency of the back contact solar cell under weak light conditions. Among them, the thickness d1 of the leakage contact layer 6 is greater than the thickness of at least one of the first passivation layer 2 and the second passivation layer 4, and the thickness d1 of the leakage contact layer 6 can also be greater than the thickness d2 of the first passivation layer 2 and the second passivation layer 4 at the same time.

[0094] As an embodiment of the present invention, the ratio of the thickness d1 of the leakage contact layer 6 to the thickness d3 of the first passivation layer 2 is greater than 3.

[0095] In this embodiment, the thickness d1 of the leakage contact layer 6 is greater than the thickness d2 of the second passivation layer 4, and the ratio of the thickness d1 of the leakage contact layer 6 to the thickness d3 of the first passivation layer 2 is greater than 3, which can better balance the reliability of hot spot effect control and maintain the power generation efficiency of the back contact solar cell under weak light conditions.

[0096] In the embodiment of the present invention, the leakage contact layer 6 can be a continuous structure or a discontinuous structure; it can be understood that when the leakage contact layer 6 is a continuous structure, the leakage contact layer 6 has no spacing area as a whole, so that the leakage contact layer 6 can completely cover the area between the first doped layer 3 and the second doped layer 5, which is beneficial to increase the contact area between the leakage contact layer 6 and the first doped layer 3 and the second doped layer 5, and improve the contact reliability between the leakage contact layer 6 and the first doped layer 3 and the second doped layer 5 in the case of leakage; when the leakage contact layer 6 is a discontinuous structure, the leakage contact layer 6 is at least provided with a partial spacing area, which can reduce the material consumption of the leakage contact layer 6.

[0097] As an embodiment of the present invention, both the leakage contact layer 6 and the second passivation layer 4 are provided with holes, and the average hole size of the leakage contact layer 6 is smaller than the average hole size of the second passivation layer 4 .

[0098] In this embodiment, the holes on the leakage contact layer 6 vertically penetrate the leakage contact layer 6 along the thickness d1 direction of the leakage contact layer 6, and the holes on the second passivation layer 4 vertically penetrate the second passivation layer 4 along the thickness d2 direction of the second passivation layer 4. The apertures of the holes in the leakage contact layer 6 may be equal or unequal; similarly, the apertures of the holes in the second passivation layer 4 may be equal or unequal. The average aperture of the holes in the leakage contact layer 6 can be understood as the average aperture of all holes in the leakage contact layer 6 or the average aperture of all holes per unit area; the average aperture of the holes in the second passivation layer 4 can be understood as the average aperture of all holes in the second passivation layer 4 or the average aperture of all holes per unit area. By making the average aperture size of the leakage contact layer 6 smaller than the average aperture size of the second passivation layer 4, the difficulty of current passing through the leakage contact layer 6 is also increased, which is conducive to improving the breakdown voltage threshold of the leakage contact layer 6 and avoiding being too sensitive to the control of the hot spot effect.

[0099] As an embodiment of the present invention, both the leakage contact layer 6 and the second passivation layer 4 are provided with holes, and the hole density of the leakage contact layer 6 is smaller than the hole density of the second passivation layer 4 .

[0100] In this embodiment, since the hole density of the leakage contact layer 6 is smaller than the hole density of the second passivation layer 4, that is, the number of holes per unit area of ​​the leakage contact layer 6 is smaller than the number of holes per unit area of ​​the second passivation layer 4, the difficulty of current passing through the leakage contact layer 6 can be increased, which is beneficial to increasing the breakdown voltage threshold of the leakage contact layer 6 and further preventing excessive sensitivity to the hot spot effect control.

[0101] As an embodiment of the present invention, one end of the leakage contact layer 6 is connected to the second passivation layer 4 , and the leakage contact layer 6 extends from the second passivation layer 4 to between the first doping layer 3 and the second doping layer 5 .

[0102] The thickness d1 of the leakage contact layer 6 may be uniform or non-uniform. Figure 2 and Figure 3 As shown, the thickness d1 of the leakage contact layer 6 is uniformly set, which is convenient for processing the leakage contact layer 6 and helps the leakage contact layer 6 to conduct the first doping layer 3 and the second doping layer 5 to achieve more uniform current distribution.

[0103] like Figure 4 As shown, as an embodiment of the present invention, the leakage contact layer 6 includes a first portion 61 and a second portion 61 arranged in sequence along its extension direction, and the thickness of the second portion 62 is greater than that of the first portion 61 .

[0104] It can be understood that the thickness d1 of the leakage contact layer 6 is unevenly set. Specifically, the leakage contact layer 6 includes adjacent and continuous first parts 61 and second parts 62 along its extension direction, and the thickness of the second part 62 is greater than the thickness of the first part 61, which is conducive to improving the reverse breakdown voltage threshold of the leakage contact layer 6, thereby ensuring that the leakage contact layer 6 can better balance the hot spot control effect and the power generation efficiency of the solar cell.

[0105] In the embodiment of the present invention, the second doping layer 5 may extend to above the first doping layer 3, or may not extend to above the first doping layer 3, which can be flexibly configured according to actual conditions. Figure 2 As shown, the second doping layer 5 may not extend above the first doping layer 3 to facilitate processing; Figure 3 and Figure 4 As shown, the second doping layer 5 may also extend above the first doping layer 3, which can increase the contact area between the second doping layer 5 and the first doping layer 3 when leakage current is turned on, making the leakage current distribution more uniform.

[0106] As an embodiment of the present invention, the leakage contact layer 6 includes a plurality of first rarefied regions and a first non-rare region disposed around the first rarefied regions, and the thickness of the first rarefied regions is smaller than the thickness of the first non-rare region.

[0107] In this embodiment, by setting a plurality of first thin areas and a plurality of first non-thin areas in the leakage contact layer 6, since the thickness of the first thin area of ​​the leakage contact layer 6 is less than the thickness of the first non-thin area, it is convenient for the first thin area to be broken down by voltage to conduct the first doped layer 3 and the second doped layer 5 when the solar cell is blocked, which is beneficial to improving the reliability of hot spot control.

[0108] As an embodiment of the present invention, the oxygen content of the first rarefied region of the leakage contact layer 6 is less than the oxygen content of the first non-rarely region. For example, when the leakage contact layer 6 is a silicon oxide layer, the oxygen content of the first rarefied region is lower than the oxygen content of the first non-rarely region. Since the thickness of the first rarefied region of the leakage contact layer 6 is less than the thickness of the first non-rarely region, it is beneficial to increase the current passing capacity of the first rarefied region when it is broken down by voltage.

[0109] As an embodiment of the present invention, the second passivation layer 4 includes a plurality of second rarefied regions and second non-rarely regions arranged around the second rarefied regions, and the thickness of the second rarefied regions is smaller than the thickness of the second non-rarely regions.

[0110] In this embodiment, since the thickness of the second rarefied region of the second passivation layer 4 is less than that of the second non-rare region, H can be quickly passed through the rarefied region, which can effectively improve the H passivation effect of the second passivation layer 4 and reduce the difficulty of heat treatment control.

[0111] As an embodiment of the present invention, the oxygen content of the second rarefied region is less than that of the second non-rarely-diluted region, which can also effectively improve the H passivation effect of the second passivation layer 4 .

[0112] As an embodiment of the present invention, the number of the first rarefied regions per unit area is less than the number of the second rarefied regions.

[0113] In the present embodiment, since the number of the first thin areas per unit area is smaller than the number of the second thin areas, the leakage contact layer 6 is less likely to be broken down by voltage than the second passivation layer 4, which is beneficial to improving the breakdown voltage threshold of the leakage contact layer 6 for controlling the hot spot effect, and can ensure the power generation efficiency of the battery under weak light conditions as much as possible.

[0114] Embodiment 2

[0115] Please refer to Figure 5 and Figure 6 On the basis of the first embodiment, in this embodiment, at the preset position 100, an insulating layer 9 is further provided in the area between the second doping layer 5 and the first doping layer 3 where the leakage contact layer 6 is not provided, and the thickness of the insulating layer 9 is greater than the thickness d1 of the leakage contact layer 6.

[0116] In the present embodiment, it can be understood that the region between the second doping layer 5 and the first doping layer 3 is provided with both a leakage contact layer 6 and an insulating layer 9, and the thickness of the insulating layer 9 is greater than the thickness d1 of the leakage contact layer 6, so that the second doping layer 5 and the first doping layer 3 are also insulated and isolated by the insulating layer 9, thereby improving the insulation effect between the second doping layer 5 and the first doping layer 3 of the back contact solar cell under normal working conditions, and avoiding the second doping layer 5 and the first doping layer 3 of the back contact solar cell from forming contact and conduction under normal power generation conditions.

[0117] In the embodiment of the present invention, the material of the insulating layer 9 may be the same as or different from the material of the leakage contact layer 6. Preferably, the material of the insulating layer 9 is the same as the material of the leakage contact layer 6, so that the insulating layer 9 and the leakage contact layer 6 can be deposited at one time. Preferably, the material of the insulating layer 9 and the material of the leakage contact layer 6 are both silicon oxide.

[0118] In the embodiment of the present invention, the specific arrangement structure of the insulating layer 9 and the leakage contact layer 6 in the area between the second doping layer 5 and the first doping layer 3 is not limited, as long as the leakage contact layer 6 is provided in part of the area between the second doping layer 5 and the first doping layer 3 and the insulating layer 9 is provided in part of the area.

[0119] Please refer to Figure 5 As an embodiment of the present invention, the insulating layer 9 is arranged between the end of the second doping layer 5 close to the first doping layer 3 and the first doping layer 3, and one end of the leakage contact layer 6 is connected to the insulating layer 9, and the other end is connected to the second passivation layer 4.

[0120] In this embodiment, the area between the second doped layer 5 and the first doped layer 3 is divided into two areas, wherein one area is provided with an insulating layer 9, and the other area is provided with a leakage contact layer 6, so as to facilitate the processing and preparation of the insulating layer 9 and the leakage contact layer 6. Specifically, the insulating layer 9 and the leakage contact layer 6 can be deposited at the same thickness at the same time, and then part of the thickness of the leakage contact layer 6 area is removed to form an insulating layer 9 having a thickness greater than that of the leakage contact layer 6.

[0121] As some other embodiments of the present invention, the insulating layer 9 may also be disposed on both sides of the leakage contact layer 6 ; or, the leakage contact layer 6 may be disposed on both sides of the insulating layer 9 .

[0122] In this embodiment, the area between the second doped layer 5 and the first doped layer 3 is divided into three areas, wherein a leakage contact layer 6 is arranged in the middle area and insulating layers 9 are arranged in the two side areas; or, an insulating layer 9 is arranged in the middle area and leakage contact layers 6 are arranged in the two side areas.

[0123] Please refer to Figure 6As an embodiment of the present invention, a plurality of leakage contact layers 6 and a plurality of insulating layers 9 are arranged between the first doping layer 3 and the second doping layer 5, and the leakage contact layers 6 and the insulating layers 9 are alternately arranged between the first doping layer 3 and the second doping layer 5 in sequence.

[0124] In this embodiment, the leakage contact layer 6 and the insulating layer 9 are alternately arranged between the first doping layer 3 and the second doping layer 5, which is beneficial for the first doping layer 3 and the second doping layer 5 to form insulation and leakage contact at multiple locations, and is beneficial for the insulation of the first doping layer 3 and the second doping layer under normal working conditions and the conduction of the first doping layer 3 and the second doping layer when the battery is blocked.

[0125] As another embodiment of the present invention, the insulating layer 9 completely covers the area between the first doped layer 3 and the second doped layer 5 , and the insulating layer 9 is hollowed out to form at least one leakage contact area, and the leakage contact layer 6 is arranged in the leakage contact area.

[0126] In this embodiment, the leakage contact region is specifically a through-hole structure. The leakage contact layer 6 is arranged in the leakage contact region for contacting the first doped layer 3 and the second doped layer 5 at the same time. The leakage contact region on the insulating layer 9 is used to arrange the leakage contact layer 6 to realize the first doped layer 3 and the second doped layer 5 being conductive or non-conductive, which is beneficial to improve the breakdown voltage threshold of the leakage contact layer 6.

[0127] Embodiment 3

[0128] Please refer to Figure 7 On the basis of the first or second embodiment, in this embodiment, the second region 12 is a trench region, and the first region 11 is a non-trench region; at the preset position 100, the first doped layer 3 has an extended portion 31 extending above the trench region, the second doped layer 5 has a first wrapping portion 51 extending below the extended portion, and the leakage contact layer 6 is at least partially disposed on the lower surface of the extended portion 31 and the upper surface of the first wrapping portion 51.

[0129] In the present embodiment, since the extending portion 31 of the first doped layer 3 extends above the groove area, at the preset position 100, the first wrapping portion of the second doped layer 5 can be conductive or non-conductive with the first doped layer 3 through the leakage contact layer 6. Since there is no silicon wafer part in the contact area between the first doped layer 3 and the second doped layer 5, the range of influence is relatively narrow, which can effectively reduce the composite influence of the interface area between the first doped layer 3 and the second doped layer 5, improve the electrical performance of the back contact solar cell, and improve the fill factor to improve the efficiency.

[0130] As an embodiment of the present invention, the second doping layer 5 also includes a second wrapping portion 52 connected to the first wrapping portion 51 and wrapping around the side surface of the protruding portion 31 , and the leakage contact layer 6 is partially arranged between the side surface of the protruding portion 31 and the second wrapping portion 52 .

[0131] In this embodiment, the second wrapping portion 52 of the second doping layer 5 wraps around the side surface of the protruding portion, and the leakage contact layer 6 is partially arranged between the side surface of the protruding portion and the second wrapping portion 52, which is beneficial to increasing the area of ​​the second doping layer 5 wrapping around the first doping layer 3, and is beneficial to further increasing the contact area between the leakage contact layer 6 and the second doping layer 5 and the first doping layer 3, so that the current distribution is more uniform when the leakage contact layer 6 is broken down by the breakdown voltage.

[0132] As an embodiment of the present invention, the second doping layer 5 also includes a third wrapping portion 53 connected to the second wrapping portion 52 and wrapping the upper surface of the protruding portion 31 , and the leakage contact layer 6 is partially arranged between the upper surface of the protruding portion 31 and the third wrapping portion 53 .

[0133] In this embodiment, the second wrapping portion 52 of the second doping layer 5 wraps around the upper surface of the protruding portion 31, and the leakage contact layer 6 is partially arranged between the upper surface of the protruding portion 31 and the third wrapping portion 53, which is beneficial to further increase the area of ​​the second doping layer 5 wrapping around the first doping layer 3, and is beneficial to further increase the contact area between the leakage contact layer 6 and the second doping layer 5 and the first doping layer 3, and further make the current distribution more uniform when the leakage contact layer 6 is broken down by the breakdown voltage.

[0134] As another embodiment of the present invention, the protruding portion 31 may be provided with a sharp end, and the second doping layer 5 surrounds the sharp end of the protruding portion.

[0135] In this embodiment, the end of the protruding portion 31 is a sharp end. Even if the second doping layer 5 surrounds the sharp end of the protruding portion 31, the second doping layer 5 and the sharp end of the protruding portion 31 are only in line-surface contact, which can reduce the contact area between the protruding portion 31 and the second doping layer 5 and reduce recombination. Figure 7 The end of the protruding portion 31 can also be arranged flush to facilitate processing.

[0136] In this embodiment, an insulating layer 9 may also be provided in the area between the second doping layer 5 and the first doping layer 3 where the leakage contact layer 6 is not provided, and the thickness of the insulating layer 9 is greater than the thickness d1 of the leakage contact layer 6, thereby improving the good insulation effect between the second doping layer 5 and the first doping layer 3 when the back contact solar cell is working normally.

[0137] Embodiment 4

[0138] The embodiment of the present invention further provides a battery assembly, which includes the back-contact solar cell of any one of the above-mentioned embodiments 1 to 3. It should be noted that the battery assembly has the same or similar beneficial effects as the above-mentioned back-contact solar cell, and the relevant parts between the two can be referenced to each other. In order to avoid repetition, they will not be described here.

[0139] Embodiment 5

[0140] The embodiment of the present invention further provides a photovoltaic system, which includes the battery assembly of the above-mentioned embodiment 4. It should be noted that the photovoltaic system has the same or similar beneficial effects as the back contact solar cell, and the relevant parts between the two can be referenced to each other. In order to avoid repetition, they will not be described here.

[0141] The present invention provides a back-contact solar cell, in which a leakage contact layer is arranged in at least a partial area between a first doped layer and a second doped layer at a preset position, the thickness of the leakage contact layer is greater than the thickness of the second passivation layer, and the ratio of the thickness of the leakage contact layer to the thickness of the second passivation layer is less than 4; by reasonably setting the thickness of the leakage contact layer, the breakdown voltage threshold of the leakage contact layer can be increased, and only after the breakdown voltage threshold is exceeded, the leakage contact layer conducts the first doped layer and the second doped layer to stop the back-contact solar cell from generating electricity, thereby controlling the hot spot effect and avoiding excessive temperature of the back-contact solar cell; and because the thickness of the leakage contact layer is reasonably set, the thickness of the leakage contact layer is set By setting a corresponding breakdown voltage threshold, the leakage contact layer can be prevented from being too easily broken down by voltage when the back contact solar cell is blocked by an obstruction, thereby turning on the first doped layer and the second doped layer and stopping the back contact solar cell from generating electricity, thereby increasing the power generation under weak light conditions. When the back contact solar cell is severely blocked by an obstruction, the first doped layer and the second doped layer can be turned on again to stop the back contact solar cell from generating electricity to protect the back contact solar cell. This can not only well realize the hot spot effect control of the back contact solar cell, but also ensure the normal operation and power generation of the back contact solar cell under certain weak light conditions, and can better balance the hot spot effect control and the power generation under weak light conditions.

[0142] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate, wherein a backlight surface of the silicon substrate has a plurality of first regions and second regions which are alternately arranged in sequence; A first passivation layer, disposed in the first region; A first doping layer, disposed on a side of the first passivation layer away from the silicon substrate; A second passivation layer, disposed in the second region; and A second doping layer, provided on a side of the second passivation layer away from the silicon substrate, wherein the second doping layer has a different doping type from the first doping layer; At a preset position, a leakage contact layer is provided in at least a partial area between the first doped layer and the second doped layer, the leakage contact layer is arranged in contact with the first doped layer and the second doped layer, the thickness of the leakage contact layer is greater than the thickness of the second passivation layer, and the ratio of the thickness of the leakage contact layer to the thickness of the second passivation layer is less than 4.

2. The back contact solar cell according to claim 1, characterized in that: The first doping layer is a P-type doping layer, and the second doping layer is an N-type doping layer; or, the first doping layer is an N-type doping layer, and the second doping layer is a P-type doping layer.

3. The back contact solar cell according to claim 1, characterized in that: The ratio of the thickness of the leakage contact layer to the thickness of the second passivation layer is 1.5-3.

4. The back contact solar cell according to claim 1, characterized in that: The thickness of the leakage contact layer is 2 to 8 nanometers.

5. The back contact solar cell according to claim 1, characterized in that: The thickness of the leakage contact layer is 3-6 nanometers.

6. The back contact solar cell according to claim 1, characterized in that: The thickness of the leakage contact layer is 4-6 nanometers.

7. The back contact solar cell according to claim 1, characterized in that: The leakage contact layer is one of silicon oxide, silicon oxynitride, and aluminum oxide, or a combination of at least two of them.

8. The back contact solar cell according to claim 1, characterized in that: The thickness of the first passivation layer is greater than the thickness of the second passivation layer.

9. The back contact solar cell according to claim 1, characterized in that: The thickness of the leakage contact layer is greater than the thickness of the first passivation layer.

10. The back contact solar cell according to claim 1, characterized in that: The ratio of the thickness of the leakage contact layer to the thickness of the first passivation layer is greater than 3.

11. The back contact solar cell according to claim 1, characterized in that: The leakage contact layer and the second passivation layer are both provided with holes, and the average hole size of the leakage contact layer is smaller than the average hole size of the second passivation layer.

12. The back contact solar cell according to claim 1, characterized in that: The leakage contact layer and the second passivation layer are both provided with holes, and the hole density of the leakage contact layer is smaller than the hole density of the second passivation layer.

13. The back contact solar cell according to claim 1, characterized in that: One end of the leakage contact layer is connected to the second passivation layer, and the leakage contact layer extends from the second passivation layer to between the first doping layer and the second doping layer.

14. The back contact solar cell according to claim 1, characterized in that: The second region is a trench region, the first region is a non-trench region, and the leakage contact layer covers the sidewall of the trench region close to the first region.

15. The back contact solar cell according to claim 1, characterized in that: The leakage contact layer and the second passivation layer are integrally formed.

16. The back contact solar cell according to claim 13, characterized in that: The leakage contact layer comprises a first portion and a second portion which are arranged in sequence along its extension direction, and the thickness of the second portion is greater than the thickness of the first portion.

17. The back contact solar cell according to claim 1, characterized in that: The leakage contact layer includes a plurality of first rarefied regions and a first non-rare region disposed around the first rarefied regions, and the thickness of the first rarefied regions is smaller than the thickness of the first non-rare region.

18. The back contact solar cell according to claim 17, characterized in that: The oxygen content of the first lean region is less than the oxygen content of the first non-lean region.

19. The back contact solar cell according to claim 17, characterized in that: The second passivation layer includes a plurality of second rarefied regions and a second non-rarely region disposed around the second rarefied regions, and the thickness of the second rarefied regions is smaller than the thickness of the second non-rarely region.

20. The back contact solar cell according to claim 19, characterized in that: The oxygen content of the second lean region is less than the oxygen content of the second non-lean region.

21. The back contact solar cell according to claim 19, characterized in that: The number of the first rarefied regions is smaller than the number of the second rarefied regions per unit area.

22. The back contact solar cell according to claim 1, characterized in that: At the preset position, an insulating layer is further disposed in a region between the second doping layer and the first doping layer where the leakage contact layer is not disposed, and the thickness of the insulating layer is greater than the thickness of the leakage contact layer.

23. The back contact solar cell according to claim 22, characterized in that The insulating layer is disposed between an end of the second doping layer close to the first doping layer and the first doping layer. One end of the leakage contact layer is connected to the insulating layer, and the other end is connected to the second passivation layer.

24. The back contact solar cell according to claim 22, characterized in that: The insulating layers are respectively arranged on both sides of the leakage contact layer; or, the leakage contact layers are respectively arranged on both sides of the insulating layer.

25. The back contact solar cell according to claim 22, characterized in that A plurality of leakage contact layers and a plurality of insulating layers are arranged between the first doping layer and the second doping layer, and the leakage contact layers and the insulating layers are alternately arranged between the first doping layer and the second doping layer in sequence.

26. The back contact solar cell according to claim 22, characterized in that The insulating layer covers the area between the first doping layer and the second doping layer, the insulating layer is hollowed out to form at least one leakage contact area, and the leakage contact layer is arranged in the leakage contact area.

27. The back contact solar cell according to claim 1, characterized in that The second region is a groove region, and the first region is a non-groove region; at the preset position, the first doped layer has a protruding portion extending above the groove region, and the second doped layer has a first wrapping portion extending below the protruding portion, and the leakage contact layer is at least partially disposed on the lower surface of the protruding portion and the upper surface of the first wrapping portion.

28. The back contact solar cell according to claim 27, characterized in that The second doping layer further includes a second wrapping portion connected to the first wrapping portion and wrapping around a side surface of the protruding portion, and the leakage contact layer is at least partially disposed between the side surface of the protruding portion and the second wrapping portion.

29. The back contact solar cell according to claim 28, characterized in that The second doping layer further includes a third wrapping portion connected to the second wrapping portion and wrapping around the upper surface of the protruding portion, and the leakage contact layer portion is disposed between the upper surface of the protruding portion and the third wrapping portion.

30. A battery assembly, characterized in that: A back-contact solar cell comprising the step of:

31. A photovoltaic system, characterized in that: Comprising a battery assembly as claimed in claim 30.

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