Back contact solar cell, cell module and photovoltaic system

Abstract

The utility model is suitable for the technical field of solar cells, and provides a back contact solar cell, a cell assembly and a photovoltaic system, the back contact solar cell comprises a silicon substrate, the back surface of the silicon substrate comprises a first area, a second area and an isolation area arranged between the first area and the second area, one of the first region and the second region is a P-type region, the other one is an N-type region, and the first region and the isolation region are polished surfaces; the isolation area and the first area are each provided with a plurality of first tower footings and a plurality of second tower footings, and at least part of the second tower footings are arranged on the first tower footings. According to the back contact solar cell provided by the utility model, the first region and the isolation region are arranged as the polished surfaces, so that the carrier transmission path of the back surface can be reduced, the surface recombination loss is reduced, the power generation efficiency of the back contact solar cell is improved, and the tower footing type of the isolation region is consistent with the tower footing type of the first region, so that the production cost of the cell can be reduced.

Description

Technical Field

[0001] This utility model relates to the field of solar cell technology, specifically to a back-contact solar cell, a battery module, and a photovoltaic system. Background Technology

[0002] Solar energy has received increasing attention and promotion from various countries in recent years, but the cost of photovoltaic power generation is a major factor restricting the wider application of photovoltaic products. Among them, back-contact solar cells, because their positive and negative electrodes are both designed on the back of the cell, completely avoid the shading of metal grid lines on the front surface compared to double-sided contact solar cells. This eliminates the optical losses caused by metal grid line shading and can significantly improve the cell conversion efficiency.

[0003] In existing technologies, the back side of a back-contact solar cell typically includes P-type and N-type regions arranged alternately, with an isolation region between them. This isolation region is usually designed with a pyramidal textured surface. This pyramidal textured surface increases the carrier transport path, leading to significant surface recombination losses and reduced cell power generation efficiency. Utility Model Content

[0004] This invention provides a back-contact solar cell, which aims to solve the problem of high back recombination loss and low power generation efficiency in existing back-contact solar cells.

[0005] This invention is implemented as follows: a back-contact solar cell is provided, including a silicon substrate. The back side of the silicon substrate includes a first region, a second region, and an isolation region disposed between the first region and the second region. One of the first region and the second region is a P-type region and the other is an N-type region. The first region and the isolation region are polished surfaces.

[0006] Both the isolation zone and the first area are provided with a number of first tower bases and a number of second tower bases, with at least some of the second tower bases placed on the first tower bases.

[0007] Preferably, the second region is a polished surface, and the second region is provided with a plurality of third tower bases.

[0008] Preferably, the longest diagonal length of the first tower base is 8 to 40 micrometers, and the longest diagonal length of the second tower base is 5 to 15 micrometers.

[0009] Preferably, the longest diagonal length of the first tower base is 25 to 35 micrometers, and the longest diagonal length of the second tower base is 7 to 9 micrometers.

[0010] Preferably, the ratio of the diagonal length of the first tower base to the diagonal length of the second tower base is 3 to 6.

[0011] Preferably, the longest diagonal length of the third tower base is 5 to 35 micrometers.

[0012] Preferably, the longest diagonal length of the third tower base is 20 to 30 micrometers.

[0013] Preferably, the surface of the second tower base of the isolation zone is provided with pits.

[0014] Preferably, the recess has an inverted pyramid structure.

[0015] Preferably, the isolation zone has a first height difference with the first area, the isolation zone has a second height difference with the second area, and the first height difference is less than the second height difference.

[0016] Preferably, the first height difference is 0 to 0.3 micrometers, and the second height difference is 1 to 4 micrometers.

[0017] This invention also provides a battery assembly, including the aforementioned back-contact solar cell.

[0018] This utility model also provides a photovoltaic system, including the above-mentioned battery components.

[0019] This invention provides a back-contact solar cell where both the isolation region and the first region are polished surfaces. This reduces the carrier transport path on the back side of the solar cell, decreases back-recombination losses, and improves the power generation efficiency of the back-contact solar cell. Furthermore, since both the isolation region and the first region are polished surfaces, the back reflection effect of incident light is increased, the transmission of incident light is reduced, and the short-circuit current of the cell is increased, thereby improving the cell conversion efficiency. On the other hand, both the isolation region and the first region are provided with a plurality of first bases and a plurality of second bases, with at least some of the second bases placed on the first bases. That is, the isolation region and the first region have the same base type, which can reduce the amount of silicon substrate thinning required, reduce the amount of chemicals used, and allow the use of thinner silicon substrates to manufacture the cell, thereby reducing the production cost of the cell. Attached Figure Description

[0020] Figure 1 A schematic diagram of the structure of a back-contact solar cell provided in an embodiment of this utility model;

[0021] Figure 2 A scanning electron microscope image of the first region, the isolation region, and the second region of a back-contact solar cell provided in an embodiment of this utility model;

[0022] Figure 3 This is a SEM image of the isolation region of a back-contact solar cell provided in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0024] This utility model embodiment provides a back-contact solar cell where both the isolation region and the first region are polished surfaces. This reduces the carrier transport path on the back side of the back-contact solar cell, reduces surface recombination losses, and improves the power generation efficiency of the back-contact solar cell. Furthermore, since both the isolation region and the first region are polished surfaces, the back reflection effect of incident light is increased, the transmission of incident light is reduced, and the short-circuit current of the cell is increased, thereby improving the cell conversion efficiency. On the other hand, both the isolation region and the first region are provided with a plurality of first bases and a plurality of second bases, with at least some of the second bases placed on the first bases. That is, the isolation region and the first region have the same base type, which can reduce the amount of silicon substrate thinning required, reduce the amount of chemicals used, and allow the use of thinner silicon substrates to manufacture the cell, thereby reducing the production cost of the cell.

[0025] Please refer to Figures 1-2 This utility model embodiment provides a back contact solar cell including a silicon substrate 1. The back side of the silicon substrate 1 includes a first region 11, a second region 12, and an isolation region 13 disposed between the first region 11 and the second region 12. One of the first region 11 and the second region 12 is a P-type region and the other is an N-type region. The first region 11 and the isolation region 13 are polished surfaces.

[0026] Both the isolation zone 13 and the first area 11 are provided with a number of first tower bases 102 and a number of second tower bases 103, with at least some of the second tower bases 103 placed on the first tower bases 102.

[0027] This utility model embodiment provides a back-contact solar cell. By setting both the isolation region 13 and the first region 11 as polished surfaces, the carrier transport path on the back side of the back-contact solar cell can be reduced, surface recombination loss can be reduced, and the power generation efficiency of the back-contact solar cell can be improved. Furthermore, since both the isolation region 13 and the first region 11 are polished surfaces, the back reflection effect of incident light can be increased, the transmission of incident light can be reduced, and the short-circuit current of the cell can be increased, thereby improving the cell conversion efficiency. On the other hand, both the isolation region 13 and the first region 11 are provided with a plurality of first bases 102 and a plurality of second bases 103, with at least some of the second bases 103 placed on the first bases 102. That is, the isolation region 13 and the first region 11 are of the same base type, which can reduce the amount of thinning required for the silicon substrate 1, reduce the amount of chemicals used, and allow the use of a thinner silicon substrate 1 to manufacture the cell, thereby reducing the production cost of the cell.

[0028] Furthermore, the combined presence of the first base 102 and the second base 103 in the first region 11 and the isolation region 13 increases the complexity of the surface morphology of the first region 11 and the isolation region 13. The diffuse back-reflected light, after multiple reflections through the structure of the first base 102 and the second base 103, can be more effectively absorbed by the silicon substrate 1. Due to the increased optical path length, the photon travel path in the silicon substrate 1 becomes longer, increasing the probability of absorption and thus improving the photoelectric response of the solar cell.

[0029] Furthermore, the combined arrangement of the first region 11 and the isolation region 13 due to the presence of the first tower base 102 and the second tower base 103 helps to disperse and release the stress generated when the silicon wafer grows a polycrystalline silicon film under high-temperature conditions. The superposition of the first tower base 102 and the second tower base 103 can provide multi-layered stress release paths, reduce stress concentration, and make the silicon wafer less prone to mechanical damage such as fragmentation, scratches, and edge chipping during automated production and transfer, thereby improving production efficiency and product quality.

[0030] The first base 102 and the second base 103 refer to microstructures disposed on the silicon substrate 1 of the solar cell. The first base 102 and the second base 103 typically appear in the form of a tower or a cone, with a planar top surface and a polygonal outer contour, specifically including at least one of rhombus, square, trapezoid, approximate rhombus, approximate square, and approximate trapezoid. The second base 103 may be disposed on at least a portion of the first base 102, or all of the first base 102 may be disposed on the second base 103. The number of second bases 103 disposed on the first base 102 is unlimited, and there may be one or more second bases 103 disposed on the first base 102. Some second bases 103 may be disposed on the first base 102, or they may be disposed side-by-side with the first base 102.

[0031] The first tower base 102 is formed on the first region 11 of the silicon substrate 1 by a certain process. After the first tower base 102 is formed, the second tower base 103 is formed on the first tower base 102 by a certain process. For example, the first tower base 102 can be formed on the first region 11 by alkaline polishing, and the second tower base 103 can be formed on the first tower base 102 by a second alkaline polishing.

[0032] As an embodiment of this utility model, the first region 11 is an N-type region and the second region 12 is a P-type region.

[0033] In this embodiment, the isolation region 13 has the same polished morphology as the N-type region of the back-contact solar cell. Specifically, the first base 102 and the second base 103 of the isolation region 13 are the same as the first base 102 and the second base 103 of the N-type region, which can reduce the amount of thinning required for the silicon substrate 1, reduce the amount of chemicals used, and allow the use of a thinner silicon substrate 1 to fabricate the cell, thereby reducing the production cost of the cell.

[0034] In another embodiment of this utility model, the first region 11 is a P-type region and the second region 12 is an N-type region.

[0035] In this embodiment, the isolation region 13 has the same polished morphology as the P-type region. The first base 102 and the second base 103 of the isolation region 13 are the same as those of the P-type region, which also reduces the amount of thinning required for the silicon substrate 1, lowers the amount of chemicals used, and allows for the use of a thinner silicon substrate 1 to fabricate the battery, thus reducing the battery production cost.

[0036] As an embodiment of the present invention, the second region 12 is a polished surface, and the second region 12 is provided with a plurality of third tower bases 101.

[0037] In this embodiment, by polishing the second region 12 to form several third bases 101, the carrier transport path on the back side of the back-contact solar cell can be further reduced, surface recombination loss can be reduced, passivation performance can be improved, thereby improving the power generation efficiency of the back-contact solar cell; moreover, polishing the second region 12 to form several third bases 101 can increase the back reflection effect of incident light, reduce the transmission of incident light, increase the short-circuit current of the cell, thereby improving the cell conversion efficiency.

[0038] The specific number of the third tower base 101 is not limited. The third tower base 101 also appears in the form of a tower or a cone, with a flat top surface and a polygonal outer contour, specifically including at least one of rhombus, square, trapezoid, approximate rhombus, approximate square, and approximate trapezoid. Optionally, some of the third tower bases 101 in the second region 12 can be formed by alkali polishing.

[0039] As an embodiment of the present invention, the longest diagonal length of the first tower base 102 is 8 to 40 micrometers, and the longest diagonal length of the second tower base 103 is 5 to 15 micrometers.

[0040] In this embodiment, since the top surfaces of the first tower base 102 and the second tower base 103 are mostly polygonal, the longest diagonal of the first tower base 102 is the longest diagonal in the first tower base 102, and the longest diagonal of the second tower base 103 is the longest diagonal in the second tower base 103. Furthermore, experiments have verified that the top surface shape of the tower base is not excessively long and narrow. Generally, the longer the longest diagonal, the larger the area of ​​the top surface of the tower base. Therefore, the longest diagonal of the first tower base 102 is also the longest diagonal of the first tower base 102 with the largest top surface area, and the longest diagonal of the second tower base 103 is also the longest diagonal in the second tower base 103 with the largest top surface area.

[0041] When measuring the longest diagonal length of the tower base, the surface calibration of the membrane layer can be directly measured using testing instruments such as optical microscopes, atomic force microscopes, scanning electron microscopes, and transmission electron microscopes.

[0042] In this embodiment, by setting the longest diagonal length of the first tower base 102 to 8-40 micrometers and the longest diagonal length of the second tower base 103 to 5-15 micrometers, surface recombination loss can be reduced and passivation performance can be improved. Furthermore, the back reflection effect of incident light can be significantly increased, the transmission of incident light can be reduced, and the short-circuit current of the battery can be increased, thereby improving the battery conversion efficiency.

[0043] For example, the longest diagonal length of the first tower base 102 can be any value among 8 micrometers, 9 micrometers, 10 micrometers, 12 micrometers, 14 micrometers, 15 micrometers, 17 micrometers, 19 micrometers, 20 micrometers, 21 micrometers, 24 micrometers, 25 micrometers, 28 micrometers, 30 micrometers, 32 micrometers, 34 micrometers, 35 micrometers, 38 micrometers, and 40 micrometers; the longest diagonal length of the second tower base 103 can be any value among 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, 11 micrometers, 12 micrometers, 13 micrometers, 14 micrometers, and 15 micrometers.

[0044] As an embodiment of the present invention, the longest diagonal length of the first tower base 102 is 25-35 micrometers, and the longest diagonal length of the second tower base 103 is 7-9 micrometers.

[0045] In this embodiment, the longest diagonal length of the first tower base 102 is further limited to 25-35 micrometers, and the longest diagonal length of the second tower base 103 is limited to 7-9 micrometers. This can further reduce recombination losses on the back side of the battery, improve passivation performance, and further increase the back reflection effect of incident light, reduce the transmission of incident light, increase the short-circuit current of the battery, thereby improving the battery conversion efficiency. At the same time, the optimized tower base structure can not only effectively release stress and reduce mechanical damage, but also improve the overall conversion efficiency of the battery.

[0046] As one embodiment of this utility model, the ratio of the longest diagonal length of the first tower base 102 to the longest diagonal length of the second tower base 103 is 3 to 6.

[0047] In this embodiment, by limiting the ratio of the diagonal length of the first tower base 102 to the diagonal length of the second tower base 103 to 3 to 6, the longest diagonal lengths of the first tower base 102 and the second tower base 103 are in this specific ratio. This ensures that the tower base structures in the two regions can work together in coordination and give full play to their respective advantages. This can better balance the recombination loss on the back of the battery and the back reflection effect of the incident light, thereby improving the overall conversion efficiency of the battery.

[0048] As one embodiment of this utility model, the longest diagonal length of the third tower base 101 is 5 to 35 micrometers.

[0049] In this embodiment, the longest diagonal length of the third tower base 101 is 5–35 micrometers. The design specifies the range of the longest diagonal length of the third tower base 101 to ensure that the tower base structures of the first region 11, the isolation region 13, and the second region 12 can work together in coordination while also leveraging their respective advantages. The third tower base 101 and the first tower base 102 can be the same or different.

[0050] For example, the longest diagonal length of the third tower base 101 can be any value among 5 micrometers, 6 micrometers, 7 micrometers, 9 micrometers, 10 micrometers, 12 micrometers, 14 micrometers, 15 micrometers, 17 micrometers, 19 micrometers, 20 micrometers, 21 micrometers, 24 micrometers, 25 micrometers, 28 micrometers, 30 micrometers, 32 micrometers, 34 micrometers, and 35 micrometers.

[0051] In this embodiment, by setting the longest diagonal length of the third tower base 101 of the second region 12 to 5-35 micrometers, the carrier transport path on the back side of the back contact solar cell can be further reduced, surface recombination loss can be reduced, passivation performance can be improved, thereby improving the power generation efficiency of the back contact solar cell; and the back reflection effect of incident light can be further increased, the transmission of incident light can be reduced, the short-circuit current of the cell can be increased, thereby improving the cell conversion efficiency.

[0052] As one embodiment of this utility model, the longest diagonal length of the third tower base 101 is 20-30 micrometers.

[0053] In this embodiment, the range of the longest diagonal length of the third tower base 101 is further optimized, further ensuring that the tower base structures of the first region 11, the isolation region 13, and the second region 12 can work together in coordination and give full play to their respective advantages.

[0054] Please refer to Figure 3As an embodiment of the present invention, the surface of the second tower base 103 of the isolation zone 13 is provided with a pit 104.

[0055] In this embodiment, the specific shape and number of the recesses 104 are not limited, and can be circular, triangular, trapezoidal, quadrilateral, polygonal, or other irregular recesses. By providing recesses 104 on the surface of the second base 103 of the isolation region 13, the presence of the recesses 104 of the second base 103 can increase the adhesion of the back film layer (such as alumina or silicon nitride film) of the isolation region 13 to the silicon substrate 1, avoiding the occurrence of bubble bursting during subsequent sintering processes, thereby improving the production yield of solar cells.

[0056] As one embodiment of this utility model, the recess 104 has an inverted pyramid structure.

[0057] In this embodiment, the pit 104 has an inverted pyramid structure, which can further improve the adhesion of the back film layer of the isolation region 13 to the silicon substrate 1, and further prevent the occurrence of bubble bursting during subsequent sintering processes, thereby improving the production yield of solar cells.

[0058] As an embodiment of the present invention, there is a first height difference between the isolation zone 13 and the first region 11, and a second height difference between the isolation zone 13 and the second region 12, wherein the first height difference is less than the second height difference.

[0059] In this embodiment, the first height difference is the difference between the average distance from the isolation region 13 to the front surface 10 of the silicon substrate 1 and the average distance from the first region 11 to the front surface 10 of the silicon substrate 1, and the second height difference is the difference between the average distance from the isolation region 13 to the front surface 10 of the silicon substrate 1 and the average distance from the second region 12 to the front surface 10 of the silicon substrate 1. Alternatively, the first height difference can also be the difference between the minimum distance from the isolation region 13 to the front surface 10 of the silicon substrate 1 and the minimum distance from the first region 11 to the front surface 10 of the silicon substrate 1, and the second height difference can be the difference between the minimum distance from the isolation region 13 to the front surface 10 of the silicon substrate 1 and the minimum distance from the second region 12 to the front surface 10 of the silicon substrate 1. Or, the first height difference can also be the difference between the maximum distance from the isolation region 13 to the front surface 10 of the silicon substrate 1 and the maximum distance from the first region 11 to the front surface 10 of the silicon substrate 1, and the second height difference can be the difference between the maximum distance from the isolation region 13 to the front surface 10 of the silicon substrate 1 and the maximum distance from the second region 12 to the front surface 10 of the silicon substrate 1.

[0060] The first height difference can be greater than or equal to 0, and the first height difference is greater than the second height difference. When the first height difference is equal to 0, the isolation zone 13 and the first region 11 are located on the same plane; when the first height difference is greater than 0, the isolation zone 13 and the first region 11 are located on different planes. Moreover, since the first height difference is less than the second height difference, the first region 11 and the second region 12 are located on different height planes, which helps to reduce the risk of leakage current between the first region 11 and the second region 12.

[0061] When the first region 11 is an N-type region and the second region 12 is a P-type region, the isolation region 13 and the N-type region have the same polishing morphology, the isolation region 13 and the P-type region have different polishing morphologies, and the first height difference between the isolation region 13 and the N-type region is less than the second height difference between the isolation region 13 and the P-type region.

[0062] When the first region 11 is a P-type region and the second region 12 is an N-type region, the isolation region 13 has the same polished morphology as the P-type region, but different polished morphologies as the N-type region. The first height difference between the isolation region 13 and the P-type region is smaller than the second height difference between the isolation region 13 and the N-type region, making it less likely for recombination centers and metal residues to form between the isolation region 13 and the P-type region, thereby improving the efficiency and reliability of the battery.

[0063] As one embodiment of this utility model, the first height difference is 0 to 0.3 micrometers; the second height difference is 1 to 4 micrometers.

[0064] In this embodiment, the first height difference is set to 0 to 0.3 micrometers and the second height difference is set to 1 to 4 micrometers, which can further reduce the risk of leakage between the first region 11 and the second region 12 and facilitate processing.

[0065] As an embodiment of this utility model, the first region 11 is an N-type region and the second region 12 is a P-type region. The first region 11 includes at least two types of first tower bases 102 of different sizes, and the second region 12 includes at least two types of third tower bases 102 of different sizes. The difference between the longest diagonal length of the first type of first tower base 102 and the longest diagonal length of the second type of first tower base 102 is less than the difference between the longest diagonal length of the first type of third tower base 102 and the longest diagonal length of the second type of third tower base 102. This makes the size distribution of the first tower base 102 in the first region 11 more uniform than that of the third tower base 101 in the second region 12. The uniformity of the second tower base 103 in the N-type region is significantly better than that of the third tower base 101 in the P-type region, which is beneficial to improving the performance of the N-type region.

[0066] In a preferred embodiment of the present invention, the isolation zone 13 and the first region 11 are located on the same plane, and there is a height difference between the isolation zone 13 and the second region 12.

[0067] In this embodiment, when the first region 11 is an N-type region and the second region 12 is a P-type region, the isolation region 13 and the N-type region are located on the same plane, and there is a height difference between the isolation region 13 and the P-type region. When the first region 11 is a P-type region and the second region 12 is an N-type region, the isolation region 13 and the P-type region are located on the same plane, and there is a height difference between the isolation region 13 and the N-type region. Because the isolation region 13 and the first region 11 are located on the same plane, the isolation region 13 will not form a concave structure near the first region 11, making it less likely to form a recombination center and metal residue, thereby improving the efficiency and reliability of the battery.

[0068] As one embodiment of this utility model, it also includes:

[0069] An N-type doped layer 2 is provided in the first region 11;

[0070] A P-type doped layer 3 is located in the second region 12.

[0071] In this embodiment, the thickness of the N-type doped layer 2 and the thickness of the P-type doped layer 3 can be the same or different.

[0072] In one embodiment of this utility model, the thickness of the N-type doped layer 2 is 100-300 nm, and the thickness of the P-type doped layer 3 is 100-300 nm.

[0073] In this embodiment, the thicknesses of the N-type doped layer 2 and the P-type doped layer 3 are 100–300 nm, which can be set according to actual conditions. For example, the thickness of the N-type doped layer 2 can be 200 nm, and the thickness of the P-type doped layer 3 can be 150 nm.

[0074] This utility model embodiment also provides a battery assembly, which includes the back-contact solar cell of the above embodiment. It should be noted that the battery assembly has the same or similar beneficial effects as the back-contact solar cell, and the related parts between the two can be referred to each other. To avoid repetition, they will not be described again here.

[0075] In this embodiment, multiple back-contact solar cells in the battery module can be connected in series to form a battery string, thereby achieving series current output. For example, the battery cells can be connected in series by setting solder strips (busbars, interconnecting strips), conductive backplates, etc.

[0076] It is understood that in such embodiments, the battery assembly may also include a metal frame, a backsheet, photovoltaic glass, and an encapsulating film. The encapsulating film may be filled between the front and back of the back-contact solar cell, the photovoltaic glass, adjacent cells, etc. As a filler, it may be a transparent colloid with good light transmittance and aging resistance. For example, the encapsulating film may be an EVA film or a POE film, and the specific choice can be made according to the actual situation, without limitation.

[0077] Photovoltaic glass can be applied to the encapsulating film on the front side of the back-contact solar cell. This photovoltaic glass can be ultra-clear glass, possessing high light transmittance, high transparency, and superior physical, mechanical, and optical properties. For example, ultra-clear glass can achieve a light transmittance of over 92%, protecting the solar cell while minimizing impact on its efficiency. Simultaneously, the encapsulating film bonds the photovoltaic glass and the back-contact solar cell together, providing sealing, insulation, and waterproofing.

[0078] The backsheet can be attached to the adhesive film on the back of the back-contact solar cell. The backsheet protects and supports the back-contact solar cell, providing reliable insulation, water resistance, and aging resistance. Multiple backsheet options are available, typically including tempered glass, acrylic glass, aluminum alloy TPT composite film, etc., and the specific choice depends on the specific circumstances and is not limited here. The backsheet, back-contact solar cell, adhesive film, and photovoltaic glass can be mounted on a metal frame. The metal frame serves as the main external support structure for the entire solar cell module, providing stable support and installation. For example, the solar cell module can be installed at the desired location using the metal frame.

[0079] This utility model embodiment also provides a photovoltaic system, which includes the battery module of the above embodiment. It should be noted that this photovoltaic system has the same or similar beneficial effects as the back-contact solar cell described above, and the related parts between the two can be referred to each other. To avoid repetition, they will not be described again here.

[0080] In this embodiment, the photovoltaic system can be applied in photovoltaic power plants, such as ground-mounted power plants, rooftop power plants, and floating power plants. It can also be applied to equipment or devices that utilize solar energy to generate electricity, such as user solar power supplies, solar streetlights, solar cars, and solar buildings. Of course, it is understood that the application scenarios of the photovoltaic system are not limited to these; that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking a photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array may be an array combination of multiple solar cell modules; for example, multiple solar cell modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the combiner box, which can collect the current generated by the photovoltaic array. The collected current flows through the inverter and is converted into AC power required by the mains power grid before being connected to the mains power grid to achieve solar power supply.

[0081] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A back-contact solar cell, characterized in that, The device includes a silicon substrate, the back side of which includes a first region, a second region, and an isolation region disposed between the first region and the second region. One of the first region and the second region is a P-type region and the other is an N-type region. The first region and the isolation region are polished surfaces. Both the isolation zone and the first area are provided with a number of first tower bases and a number of second tower bases, with at least some of the second tower bases placed on the first tower bases.

2. The back-contact solar cell according to claim 1, characterized in that, The second region is a polished surface, and the second region is provided with several third tower bases.

3. The back-contact solar cell according to claim 1, characterized in that, The longest diagonal length of the first tower base is 8 to 40 micrometers, and the longest diagonal length of the second tower base is 5 to 15 micrometers.

4. The back-contact solar cell according to claim 1, characterized in that, The longest diagonal length of the first tower base is 25 to 35 micrometers, and the longest diagonal length of the second tower base is 7 to 9 micrometers.

5. The back-contact solar cell according to claim 1, characterized in that, The ratio of the diagonal length of the first tower base to the diagonal length of the second tower base is 3 to 6.

6. The back-contact solar cell according to claim 2, characterized in that, The longest diagonal length of the third tower base is 5 to 35 micrometers.

7. The back-contact solar cell according to claim 2, characterized in that, The longest diagonal length of the third tower base is 20 to 30 micrometers.

8. The back-contact solar cell according to claim 1, characterized in that, The surface of the second tower base in the isolation zone is provided with pits.

9. The back-contact solar cell according to claim 8, characterized in that, The depression has an inverted pyramid structure.

10. The back-contact solar cell according to claim 1, characterized in that, The isolation zone has a first height difference from the first area, and the isolation zone has a second height difference from the second area, wherein the first height difference is less than the second height difference.

11. The back-contact solar cell according to claim 10, characterized in that, The first height difference is 0 to 0.3 micrometers, and the second height difference is 1 to 4 micrometers.

12. A battery assembly, characterized in that, Including the back-contact solar cell as described in any one of claims 1 to 11.

13. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 12.

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