Back contact solar cell, cell module and photovoltaic system

Abstract

The invention is applicable to 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, and the back surface of the silicon substrate comprises a P-type doped region, an N-type doped region and an isolation region; the P-type doped region is provided with a first suede, the first suede comprises a first pyramid-like structure, and / or the N-type doped region is provided with a second suede, the second suede comprises a second pyramid-like structure, and / or the isolation region is provided with a third suede, and the third suede comprises a third pyramid-like structure; the average base angle of the first pyramid-like structure is smaller than that of the second pyramid-like structure; and / or the average base angle of the first pyramid structure is smaller than the average base angle of the third pyramid structure; and / or the average base angle of the second pyramid structure is smaller than the average base angle of the third pyramid structure. According to the back contact solar cell, the sunlight utilization rate can be improved, the good passivation performance of the back face is achieved, and therefore the cell efficiency is improved.

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] Back contact (Interdigitated back contact, IBC) solar cells, also known as interdigitated back contact solar cells, have positive and negative electrode grid lines designed on the back of the cell, so that the front surface is completely free from the shading of metal grid lines, eliminating the optical loss caused by the shading of electrode grid lines. At the same time, the electrode grid lines can be designed to be wider than the existing ones, reducing the series resistance loss, thereby greatly improving the cell conversion efficiency. In addition, due to the design of no electrode grid lines on the front of the cell, the product appearance is more beautiful and suitable for a variety of application scenarios.

[0003] In the prior art, the back side of the silicon substrate of the back-contact solar cell is usually prepared into a polished surface by alkali polishing or acid polishing to increase the uniformity of the passivation contact structure and improve the overall passivation quality. However, this will reduce the reflection of sunlight entering the silicon substrate from the front side of the silicon substrate by the back side of the silicon substrate. Sunlight entering the silicon substrate from the front side of the silicon substrate is likely to be directly emitted and escaped from the back side of the silicon substrate, resulting in low solar light utilization of the cell and difficulty in improving cell efficiency. Summary of the invention

[0004] The present invention provides a back-contact solar cell, aiming to solve the problems of low sunlight utilization rate and difficulty in improving cell efficiency in the prior art back-contact solar cells.

[0005] The present invention is implemented in this way. A back-contact solar cell is provided, comprising a silicon substrate, wherein the silicon substrate comprises a front surface and a back surface which are arranged opposite to each other, wherein the back surface comprises a P-type doping region, an N-type doping region, and an isolation region arranged between the P-type doping region and the N-type doping region, wherein at least two of the P-type doping region, the N-type doping region, and the isolation region are provided with a velvet surface; the P-type doping region is provided with a first velvet surface, wherein the first velvet surface comprises a plurality of first-type pyramid structures, and / or the N-type doping region is provided with a second velvet surface, wherein the second velvet surface comprises a plurality of second-type pyramid structures, and / or the isolation region is provided with a third velvet surface, wherein the third velvet surface comprises a plurality of third-type pyramid structures;

[0006] The average base angle of the first type of pyramid structure is smaller than the average base angle of the second type of pyramid structure; and / or, the average base angle of the first type of pyramid structure is smaller than the average base angle of the third type of pyramid structure; and / or, the average base angle of the second type of pyramid structure is smaller than the average base angle of the third type of pyramid structure.

[0007] Preferably, the P-type doping region is provided with the first velvet surface, the N-type doping region is provided with the second velvet surface, and the isolation region is provided with a non-velvet surface.

[0008] Preferably, the P-type doping region is provided with the first velvet surface, the isolation region is provided with the third velvet surface, and the N-type doping region is provided with a non-velvet surface.

[0009] Preferably, the N-type doping region is provided with the second velvet surface, the isolation region is provided with the third velvet surface, and the P-type doping region is provided with a non-velvet surface.

[0010] Preferably, the P-type doping region is provided with the first texture surface, the N-type doping region is provided with the second texture surface, and the isolation region is provided with the third texture surface.

[0011] Preferably, the difference between the average base angle of the second type of pyramid structure and the average base angle of the first type of pyramid structure is greater than 5°; and / or the difference between the average base angle of the third type of pyramid structure and the average base angle of the second type of pyramid structure is greater than 5°; and / or the difference between the average base angle of the third type of pyramid structure and the average base angle of the first type of pyramid structure is greater than 10°.

[0012] Preferably, the average base angle of the first type of pyramid structure is 10-60°; the average base angle of the second type of pyramid structure is 20-70°; and the average base angle of the third type of pyramid structure is 30-85°.

[0013] Preferably, the average base angle of the first type of pyramid structure is 15-45°; the average base angle of the second type of pyramid structure is 20-55°; and the average base angle of the third type of pyramid structure is 40-75°.

[0014] Preferably, the top of the first type of pyramid structure is configured as a first arc surface; and / or the top of the second type of pyramid structure is configured as a second arc surface.

[0015] Preferably, the curvature of the first arc surface is smaller than the curvature of the second arc surface.

[0016] Preferably, a connection point between two adjacent first-type pyramid structures is configured as a third arc surface, and / or a connection point between two adjacent second-type pyramid structures is configured as a fourth arc surface.

[0017] Preferably, the curvature of the third arc surface is smaller than the curvature of the fourth arc surface.

[0018] Preferably, the top of the third type pyramid structure is sharply set, and the connection between two adjacent third type pyramid structures is sharply set.

[0019] Preferably, the height of the first type of pyramid structure is smaller than the height of the second type of pyramid structure.

[0020] Preferably, the height of the second type of pyramid structure is smaller than the height of the third type of pyramid structure.

[0021] Preferably, the roughness of the side surface of the first type of pyramid structure is smaller than the roughness of the side surface of the second type of pyramid structure.

[0022] Preferably, the roughness of the side surface of the second type pyramid structure is smaller than the roughness of the side surface of the third type pyramid structure.

[0023] Preferably, a fourth velvet surface is provided on the front side of the silicon substrate.

[0024] The present invention also provides a battery assembly, comprising the above-mentioned back-contact solar cell.

[0025] The present invention also provides a photovoltaic system, comprising the above-mentioned battery assembly.

[0026] A back-contact solar cell provided by the present invention is provided with a velvet surface on at least two of the P-type doping region, the N-type doping region and the isolation region on the back of the silicon substrate. On the one hand, the sunlight entering the silicon substrate from the front side of the silicon substrate is reflected by the velvet surface provided in the P-type doping region, the N-type doping region and the isolation region, so that the sunlight is reflected back and forth multiple times in the silicon substrate, which can reduce the sunlight directly emitted from the back side of the silicon substrate, increase the reflection path of the sunlight inside the silicon substrate, increase the absorption of the solar cell by the solar light, and greatly improve the utilization rate of the back-contact solar cell for the sunlight;

[0027] On the other hand, when at least two of the P-type doped region, the N-type doped region, and the isolation region are provided with a velvet surface, by controlling the average bottom angle of the first type of pyramid structure to be smaller than the average bottom angle of the second type of pyramid structure, and / or controlling the average bottom angle of the first type of pyramid structure to be smaller than the average bottom angle of the third type of pyramid structure, and / or controlling the average bottom angle of the second type of pyramid structure to be smaller than the average bottom angle of the third type of pyramid structure, the surface recombination loss on the back side of the silicon substrate can be reduced, and it is beneficial to the deposition of the film layer on the back side of the silicon substrate and to improve the passivation performance of the film layer on the back side, taking into account the optical performance of the back-contact solar cell and the passivation performance of the back side of the battery, achieving a match between good optical performance and good passivation performance of the battery, thereby improving battery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic structural diagram of a back-contact solar cell provided by an embodiment of the present invention;

[0029] Figure 2 A schematic structural diagram of a silicon substrate for a back-contact solar cell provided by an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of a partial structure of a first velvet surface of a back contact solar cell provided by an embodiment of the present invention;

[0031] Figure 4 A schematic diagram of a partial structure of a second velvet surface of a back contact solar cell provided by an embodiment of the present invention;

[0032] Figure 5 A partial structural schematic diagram of a third velvet surface of a back contact solar cell provided by an embodiment of the present invention;

[0033] Figure 6 A schematic structural diagram of a silicon substrate of a second back-contact solar cell provided by an embodiment of the present invention;

[0034] Figure 7 A schematic structural diagram of a silicon substrate of a third back-contact solar cell provided by an embodiment of the present invention;

[0035] Figure 8 A schematic structural diagram of a silicon substrate of a fourth back-contact solar cell provided by an embodiment of the present invention;

[0036] Fig. 9 A schematic diagram of a partial structure of a fourth velvet surface of a back contact solar cell provided by an embodiment of the present invention;

[0037] Fig.10 A schematic structural diagram of a silicon substrate of a fifth back-contact solar cell provided by an embodiment of the present invention;

[0038] Fig.11 A partial structural schematic diagram of another first velvet surface of a back contact solar cell provided by an embodiment of the present invention;

[0039] Fig.12 A partial structural schematic diagram of another second velvet surface of a back-contact solar cell provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] In the description of the present invention, it is necessary to understand that the orientations or positional relationships indicated by the terms "upper", "lower", "back", "front", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0042] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0043] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples, and the purpose is not to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use scenarios of other materials.

[0044] A back-contact solar cell provided by the present invention is provided with a velvet surface on at least two of the P-type doping region, the N-type doping region and the isolation region on the back of the silicon substrate. On the one hand, the sunlight entering the silicon substrate from the front side of the silicon substrate is reflected back and forth multiple times in the silicon substrate through the velvet surface provided in at least two of the P-type doping region, the N-type doping region and the isolation region, which can reduce the sunlight directly emitted from the back side of the silicon substrate, increase the reflection path of the sunlight inside the silicon substrate, increase the absorption of sunlight by the solar cell, and greatly improve the utilization rate of sunlight by the back-contact solar cell; on the other hand, at least two of the P-type doping region, the N-type doping region and the isolation region In the case of setting a velvet surface, by controlling the average bottom angle of the first type of pyramid structure to be smaller than the average bottom angle of the second type of pyramid structure, and / or controlling the average bottom angle of the first type of pyramid structure to be smaller than the average bottom angle of the third type of pyramid structure, and / or controlling the average bottom angle of the second type of pyramid structure to be smaller than the average bottom angle of the third type of pyramid structure, the surface recombination loss on the back side of the silicon substrate can be reduced, and it is beneficial to the deposition of the film layer on the back side of the silicon substrate and to improve the passivation performance of the film layer on the back side, taking into account the optical performance of the back-contact solar cell and the passivation performance of the back side of the battery, achieving a match between the good optical performance of the battery and the good passivation performance, thereby improving the battery efficiency.

[0045] Please refer to Figure 1-Figure 5 The present invention provides a back-contact solar cell, comprising a silicon substrate 1, wherein the silicon substrate 1 comprises a front side and a back side arranged opposite to each other, wherein the back side comprises a P-type doping region 2, an N-type doping region 3, and an isolation region 4 arranged between the P-type doping region 2 and the N-type doping region 3, wherein at least two of the P-type doping region 2, the N-type doping region 3, and the isolation region 4 are provided with a velvet surface; the P-type doping region 2 is provided with a first velvet surface 21, wherein the first velvet surface 21 comprises a plurality of first-type pyramid structures 211; and / or, the N-type doping region 3 is provided with a second velvet surface 31, wherein the second velvet surface 31 comprises a plurality of second-type pyramid structures 311; and / or, the isolation region 4 is provided with a third velvet surface 41, wherein the third velvet surface 41 comprises a plurality of third-type pyramid structures 411.

[0046] The average base angle of the first type of pyramid structure 211 is smaller than the average base angle of the second type of pyramid structure 311; and / or, the average base angle of the first type of pyramid structure 211 is smaller than the average base angle of the third type of pyramid structure 411; and / or, the average base angle of the second type of pyramid structure 311 is smaller than the average base angle of the third type of pyramid structure 411.

[0047] In the embodiment of the present invention, the silicon substrate 1 includes a front side and a back side that are arranged opposite to each other, the front side of the silicon substrate 1 is the side facing the sunlight when the back-contact solar cell is working, and the back side of the silicon substrate 1 is the side facing away from the sunlight when the back-contact solar cell is working. The P-type doping region 2 is a region where a P-type doping layer is arranged, the N-type doping region 3 is a region where an N-type doping layer is arranged, and the isolation region 4 is located between two adjacent P-type doping regions 2 and N-type doping regions 3 for physically isolating the P-type doping region 2 from the N-type doping region 3. The specific number of the P-type doping region 2 and the N-type doping region 3 is not limited. Optionally, there are multiple P-type doping regions 2 and N-type doping regions 3, and the P-type doping regions 2 and N-type doping regions 3 are arranged alternately and spaced in sequence, and an isolation region 4 is arranged between two adjacent P-type doping regions 2 and N-type doping regions 3.

[0048] In an embodiment of the present invention, at least two of the P-type doping region 2, the N-type doping region 3, and the isolation region 4 are provided with a velvet surface. Specifically, the P-type doping region 2, the N-type doping region 3, and the isolation region 4 are all provided with a velvet surface; or, the P-type doping region 2 and the N-type doping region 3 are provided with a velvet surface, and the isolation region 4 is not provided with a velvet surface; or, the N-type doping region 3 and the isolation region 4 are provided with a velvet surface, and the P-type doping region 2 is not provided with a velvet surface; or, the N-type doping region 3 and the isolation region 4 are provided with a velvet surface, and the P-type doping region 2 is not provided with a velvet surface.

[0049] In the embodiment of the present invention, the P-type doping region 2 is provided with a first velvet surface 21, which can be understood as that only a part of the P-type doping region 2 can be provided with the first velvet surface 21, or the entire P-type doping region 2 can be provided with the first velvet surface 21. When only a part of the P-type doping region 2 can be provided with the first velvet surface 21, each P-type doping region 2 can be provided with the first velvet surface 21, but at least one P-type doping region 2 has a part of the area provided with a non-velvet area, that is, at least one P-type doping region 2 has a part of the area provided as a polishing surface; or, only a part of the number of P-type doping regions 2 are provided with the first velvet surface 21, and another part of the number of P-type doping regions 2 are non-velvet areas, that is, another part of the number of P-type doping regions 2 are provided as polishing surfaces. In this way, the P-type doping region 2 is designed by combining the first velvet surface 21 and the polishing surface, and the first velvet surface 21 is used to improve the utilization rate of the P-type doping region 2 for sunlight, and the polishing surface is used to reduce the surface recombination loss of the P-type doping region 2, and it is beneficial to improve the passivation performance of the back film layer of the P-type doping region 2, which is beneficial to improve the battery efficiency.

[0050] In the embodiment of the present invention, the N-type doping region 3 is provided with a second velvet surface 31, which can be understood as that only a part of the N-type doping region 3 can be provided with the second velvet surface 31, or all of the N-type doping regions 3 can be provided with the second velvet surface 31. When only a part of the N-type doping region 3 can be provided with the second velvet surface 31, each N-type doping region 3 can be provided with the second velvet surface 31, but at least one N-type doping region 3 has a part of the area provided with a non-velvet surface area, that is, at least one N-type doping region 3 has a part of the area provided with a polishing surface; or, only a part of the number of N-type doping regions 3 are provided with the second velvet surface 31, and another part of the number of N-type doping regions 3 are non-velvet surfaces, that is, another part of the number of N-type doping regions 3 are provided with a polishing surface. In this way, the N-type doping region 3 is designed by combining the second velvet surface 31 with the polishing surface, and the second velvet surface 31 is used to improve the utilization rate of the N-type doping region 3 for sunlight, and the polishing surface is used to reduce the surface recombination loss of the N-type doping region 3, and it is beneficial to improve the passivation performance of the back film layer of the N-type doping region 3, which is beneficial to improve the battery efficiency.

[0051] The isolation area 4 is provided with the third suede surface 41 . It can be understood that only a part of the isolation area 4 can be provided with the third suede surface 41 , or the entire isolation area 4 can be provided with the third suede surface 41 .

[0052] The first type pyramid structures 211 of the first velvet surface 21 may also be arranged in a linear array or in an irregular arrangement. Similarly, the second type pyramid structures 311 of the second velvet surface 31 may also be arranged in a linear array or in an irregular arrangement. The third type pyramid structures 411 of the third velvet surface 41 may also be arranged in a linear array or in an irregular arrangement.

[0053] The first type of pyramid structure 211, the second type of pyramid structure 311, and the third type of pyramid structure 411 are all pyramid-like structures with a top or a pyramid-like structure with the top cut off; wherein the pyramid-like structure may be a pyramid-like structure with three side surfaces and one bottom surface, or the pyramid-like structure may be a pyramid-like structure with four side surfaces and one bottom surface; or, the pyramid-like structure may be a pyramid-like structure with five side surfaces and one bottom surface; or, the pyramid-like structure may be a pyramid-like structure with six side surfaces and one bottom surface; of course, the pyramid-like structure may also be a pyramid-like structure with a greater number of side surfaces and one bottom surface.

[0054] When the angles between the side surfaces of each pyramid-like structure and the bottom surface of the pyramid-like structure are equal, it is only necessary to measure the angle between any side surface of the pyramid-like structure and the bottom surface of the pyramid-like structure as the bottom angle of the pyramid-like structure. Of course, the angles between the side surfaces of each pyramid-like structure and the bottom surface of the pyramid-like structure may also be unequal. In this case, the average value of the angles between the side surfaces of the pyramid-like structure and the bottom surface of the pyramid-like structure is measured as the bottom angle of the pyramid-like structure.

[0055] Among them, Figure 3 As shown, the bottom angle B of the first type pyramid structure 211 is the angle between the side surface of the first type pyramid structure 211 and the bottom surface of the first type pyramid structure 211, and the bottom surface is a plane perpendicular to the thickness direction of the silicon substrate 1. Figure 4 As shown, the bottom angle C of the second type pyramid structure 311 is the angle between the side surface of the second type pyramid structure 311 and the bottom surface of the second type pyramid structure 311, and the bottom surface is a plane perpendicular to the thickness direction of the silicon substrate 1. Figure 5 As shown, the bottom angle D of the third type pyramid structure 411 is the angle between the side surface of the third type pyramid structure 411 and the bottom surface of the third type pyramid structure 411 , and the bottom surface is a plane perpendicular to the thickness direction of the silicon substrate 1 .

[0056] In the embodiment of the present invention, the average bottom angle of the first type pyramidal structure 211 is the average bottom angle of all the first type pyramidal structures 211 of the first velvet surface 21; the average bottom angle of the second type pyramidal structure 311 is the average bottom angle of a preset number of second type pyramidal structures 311 in the target area of ​​the second velvet surface 31; the average bottom angle of the third type pyramidal structure 411 is the average bottom angle of all the third type pyramidal structures 411 of the third velvet surface 41.

[0057] Alternatively, the average bottom angle of the first type pyramid structure 211 is the average bottom angle of a first preset number of first type pyramid structures 211 in the first suede 21, the average bottom angle of the second type pyramid structure 311 is the average bottom angle of a first preset number of second type pyramid structures 311 in the second suede 31, and the average bottom angle of the third type pyramid structure 411 is the average bottom angle of a first preset number of third type pyramid structures 411 in the third suede 41. Preferably, the first preset number is 2 to 10, and the average bottom angle of 2 to 10 first type pyramid structures 211 in the first suede 21 is measured as the average bottom angle of the first type pyramid structure 211, the average bottom angle of 2 to 10 second type pyramid structures 311 in the second suede 31 is measured as the average bottom angle of the second type pyramid structure 311, and the average bottom angle of 2 to 10 third type pyramid structures 411 in the third suede 41 is measured as the average bottom angle of the third type pyramid structure 411.

[0058] Alternatively, the average bottom angle of the first type pyramid structure 211 is the average bottom angle of the second preset number of first type pyramid structures 211 arranged along the first direction and having the highest height in the target area of ​​the first velvet surface 21; the average bottom angle of the second type pyramid structure 311 is the average bottom angle of the second preset number of second type pyramid structures 311 arranged along the first direction and having the highest height in the target area of ​​the second velvet surface 31; the average bottom angle of the third type pyramid structure 411 is the average bottom angle of the second preset number of third type pyramid structures 411 arranged along the first direction and having the highest height in the target area of ​​the third velvet surface 41. The target area may be a rectangular area of ​​20 μm×30 μm, and the second preset number may be 3 to 10.

[0059] For example, when comparing the average base angle of the first type pyramid structure 211, the average base angle of the second type pyramid structure 311, and the average base angle of the third type pyramid structure 411, a rectangular area of ​​20 μm×30 μm is taken as the set target area in the first velvet surface 21, the second velvet surface 31, and the third velvet surface 41, respectively, and the base angles of the three first type pyramid structures 211 arranged along the first direction and with the highest height are measured in the target area of ​​the first velvet surface 21, and the average base angle of the three first type pyramid structures 211 is calculated as the first type pyramid structure 211. The average bottom angle of the structure 211 is measured; the bottom angles of the three second-type pyramid structures 311 arranged along the first direction and with the highest height are measured in the target area of ​​the second suede surface 31, and the average bottom angle of the three second-type pyramid structures 311 is calculated as the average bottom angle of the second-type pyramid structures 311; the bottom angles of the three third-type pyramid structures 411 arranged along the first direction and with the highest height are measured in the target area of ​​the third suede surface 41, and the average bottom angle of the three third-type pyramid structures 411 is calculated as the average bottom angle of the third-type pyramid structures 411. Of course, other areas can also be set as the target area and the average bottom angles of other numbers of pyramid-like structures can be compared.

[0060] In the embodiment of the present invention, by setting a velvet surface on at least two of the P-type doping region 2, the N-type doping region 3 and the isolation region 4 on the back side of the silicon substrate 1 of the back contact solar cell, on the one hand, the sunlight entering the silicon substrate 1 from the front side of the silicon substrate 1 is reflected back and forth multiple times in the silicon substrate 1 through the velvet surfaces set in at least two of the P-type doping region 2, the N-type doping region 3 and the isolation region 4, which can reduce the sunlight directly emitted from the back side of the silicon substrate 1, increase the reflection path of the sunlight inside the silicon substrate 1, increase the absorption of sunlight by the solar cell, and greatly improve the utilization rate of sunlight by the back contact solar cell; on the other hand, when the velvet surface is set in the P-type doping region 2 and the N-type doping region 3, the average bottom angle of the first type of pyramid structure 211 is controlled to be smaller than the average bottom angle of the second type of pyramid structure 311, and when the velvet surface is set in the P-type doping region 2 and the isolation region 4, the first type of pyramid structure 211 is controlled to be smaller than the average bottom angle of the second type of pyramid structure 311. The average bottom angle of the pyramid structure 211 is smaller than the average bottom angle of the third pyramid structure 411. When the N-type doping region 3 and the isolation region 4 are provided with velvet, the average bottom angle of the second pyramid structure 311 is controlled to be smaller than the average bottom angle of the third pyramid structure 411. When the P-type doping region 2 and the N-type doping region 3 are provided with the second velvet 31, and the isolation region 4 is provided with velvet, the average bottom angle of the first pyramid structure 211 is smaller than the average bottom angle of the second pyramid structure 311, and the average bottom angle of the second pyramid structure 311 is smaller than the average bottom angle of the third pyramid structure 411, which can reduce the surface recombination loss on the back side of the silicon substrate 1, and is beneficial to the deposition of the film layer on the back side of the silicon substrate 1 and to improve the passivation performance of the film layer on the back side, thereby taking into account the good optical performance of the back-contact solar cell and the good passivation performance of the back side of the battery, achieving the matching of the good optical performance of the battery and the good passivation performance, and then improving the battery efficiency.

[0061] Please refer to Figure 2 As an embodiment of the present invention, the P-type doping region 2 is provided with a first velvet surface 21 , the N-type doping region 3 is provided with a second velvet surface 31 , and the isolation region 4 is provided with a third velvet surface 41 .

[0062] In this embodiment, the average base angle of the first type pyramid structure 211 is smaller than the average base angle of the second type pyramid structure 311 , and the average base angle of the second type pyramid structure 311 is smaller than the average base angle of the third type pyramid structure 411 .

[0063] In the embodiment of the present invention, a first velvet surface 21 is set in the P-type doping region 2 on the back side of the silicon substrate 1, a second velvet surface 31 is set in the N-type doping region 3, and a third velvet surface 41 is set in the isolation region 4. The first velvet surface 21, the second velvet surface 31, and the third velvet surface 41 are used to jointly reflect the sunlight entering the silicon substrate 1 from the front side of the silicon substrate 1. The sunlight entering the silicon substrate 1 from the front side of the silicon substrate 1 is reflected back and forth multiple times inside the silicon substrate 1 by the first velvet surface 21, the second velvet surface 31, and the third velvet surface 41, which can increase the reflection path of the sunlight inside the silicon substrate 1, reduce the sunlight directly emitted from the back side and escape, reduce the transmittance of the sunlight from the back side, increase the absorption of sunlight by the solar cell, and greatly improve the utilization rate of sunlight by the back-contact solar cell. At the same time, since the average bottom angle of the first type pyramid structure 211 is smaller than the average bottom angle of the second type pyramid structure 311, and the average bottom angle of the second type pyramid structure 311 is smaller than the average bottom angle of the third type pyramid structure 411, it is beneficial to reduce the surface recombination loss on the back side of the silicon substrate 1, and achieve a balance between the good optical performance of the back-contact battery and the good passivation performance of the back side of the battery; moreover, the reflection performance of the first velvet 21, the second velvet 31, and the third velvet 41 for the front transmitted light increases in sequence, and the surface passivation performance of the first velvet 21, the second velvet 31, and the third velvet 41 decreases in sequence, which is beneficial to achieve a good match between the optical performance and the passivation performance of the P-type doped region 2, the N-type doped region 3, and the isolation region 4, and further improves the battery efficiency.

[0064] Please refer to Figure 6 As another embodiment of the present invention, the P-type doping region 2 is provided with a first velvet surface 21 , the N-type doping region 3 is provided with a second velvet surface 31 , and the isolation region 4 is provided with a non-velvet surface 200 .

[0065] In this embodiment, only the P-type doping region 2 and the N-type doping region 3 are provided with a velvet surface, and the isolation region 4 is provided with a non-velvet surface 200, which can reduce the surface recombination loss of the isolation region 4 and balance the optical and passivation effects of the back side. The average bottom angle of the first type of pyramid structure 211 is less than the average bottom angle of the second type of pyramid structure 311. Among them, the non-velvet surface 200 provided in the isolation region 4 can be a polished surface.

[0066] In this embodiment, a first velvet surface 21 is provided on the P-type doping region 2 on the back side of the silicon substrate 1, and a second velvet surface 31 is provided on the N-type doping region 3. The first velvet surface 21 and the second velvet surface 31 are used to reflect the sunlight entering the silicon substrate 1 from the front side of the silicon substrate 1. The sunlight entering the silicon substrate 1 from the front side of the silicon substrate 1 is reflected back and forth multiple times inside the silicon substrate 1 by the first velvet surface 21 and the second velvet surface 31, which can increase the reflection path of the sunlight inside the silicon substrate 1, reduce the sunlight directly emitted from the back side and escape, reduce the transmittance of the sunlight from the back side, increase the absorption of the solar cell by the solar cell, and greatly improve the utilization rate of the sunlight by the back contact solar cell. At the same time, because the average bottom angle of the first type of pyramid structure 211 is smaller than the average bottom angle of the second type of pyramid structure 311, the surface of the P-type doping region 2 is flatter than the surface of the N-type doping region 3, which is conducive to reducing the surface recombination loss of the P-type doping region 2, improving the passivation effect of the P-type doping region 2, and achieving a balance between the passivation effect and optical performance of the P-type doping region 2 and the N-type doping region 3.

[0067] Please refer to Figure 7 As another embodiment of the present invention, the P-type doping region 2 is provided with a first velvet surface 21 , the isolation region 4 is provided with a third velvet surface 41 , and the N-type doping region 3 is provided with a non-velvet surface 200 .

[0068] In this embodiment, only the P-type doping region 2 and the isolation region 4 are provided with a velvet surface, and the N-type doping region 3 is provided with a non-velvet surface, which can reduce the surface recombination loss of the N-type doping region 3, improve the passivation effect of the N-type doping region 3, and balance the optical performance and passivation effect of the back side. At this time, the average bottom angle of the first type of pyramid structure 211 is less than the average bottom angle of the third type of pyramid structure 411. The non-velvet surface 200 provided in the isolation region 4 can be a polished surface.

[0069] In this embodiment, the first velvet surface 21 and the third velvet surface 41 are used to reflect the sunlight entering the silicon substrate 1 from the front side of the silicon substrate 1. The sunlight entering the silicon substrate 1 from the front side of the silicon substrate 1 is reflected back and forth multiple times inside the silicon substrate 1 through the first velvet surface 21 and the third velvet surface 41, which can increase the reflection path of the sunlight inside the silicon substrate 1, reduce the sunlight directly emitted from the back side and escape, reduce the transmittance of the sunlight from the back side, increase the absorption of the solar cell by the solar light, and greatly improve the utilization rate of the back contact solar cell for the sunlight. At the same time, because the average bottom angle of the first type of pyramid structure 211 is smaller than the average bottom angle of the third type of pyramid structure 411, the velvet surface of the P-type doping region 2 is flatter than the velvet surface of the isolation region 4, which is conducive to reducing the surface recombination loss of the P-type doping region 2, improving the passivation effect of the P-type doping region 2, and taking into account the passivation effect and optical performance of the P-type doping region 2.

[0070] Please refer to Figure 8As another embodiment of the present invention, the N-type doping region 3 is provided with a second velvet surface 31 , the isolation region 4 is provided with a third velvet surface 41 , and the P-type doping region 2 is provided with a non-velvet surface 200 .

[0071] In this embodiment, only the N-type doping region 3 and the isolation region 4 are provided with a velvet surface, and the P-type doping region 2 is provided with a non-velvet surface, which can reduce the surface recombination loss of the P-type doping region 2 and balance the optical performance and passivation effect of the back side. At this time, the average bottom angle of the second type of pyramid structure 311 is less than the average bottom angle of the third type of pyramid structure 411. The non-velvet surface 200 provided in the P-type doping region 2 can be a polished surface.

[0072] In this embodiment, the second velvet surface 31 and the third velvet surface 41 are used to reflect the sunlight entering the silicon substrate 1 from the front side of the silicon substrate 1. The sunlight entering the silicon substrate 1 from the front side of the silicon substrate 1 is reflected back and forth multiple times inside the silicon substrate 1 through the second velvet surface 31 and the third velvet surface 41, which can increase the reflection path of the sunlight inside the silicon substrate 1, reduce the sunlight directly emitted from the back side and escape, reduce the transmittance of the sunlight from the back side, increase the absorption of the solar cell by the solar light, and greatly improve the utilization rate of the back contact solar cell for the sunlight. At the same time, because the average bottom angle of the second type pyramid structure 311 is smaller than the average bottom angle of the third type pyramid structure 411, the velvet surface of the N-type doping region 3 is flatter than the velvet surface of the isolation region 4, which is conducive to reducing the surface recombination loss caused by the velvet surface of the N-type doping region 3, improving the passivation effect of the N-type doping region 3, and taking into account the passivation effect and optical performance of the N-type doping region 3. Moreover, the P-type doping region 2 is set to be non-velvet, which can maintain a good passivation effect of the P-type doping region 2, and can make the optical performance and passivation performance of the P-type doping region 2, the N-type doping region 3, and the isolation region 4 well matched, which is beneficial to further improve the battery efficiency.

[0073] Please refer again Figure 1 and Figure 2 As an embodiment of the present invention, a fourth velvet surface 10 is provided on the front side of the silicon substrate 1 .

[0074] In the embodiment of the present invention, at least a portion of the front surface of the silicon substrate 1 is provided with a fourth velvet surface 10 to reduce the light reflectivity of the front surface of the silicon substrate 1. The front surface of the silicon substrate 1 may be provided with the fourth velvet surface 10 only in a portion of the front surface, or the entire front surface of the silicon substrate 1 may be provided with the fourth velvet surface 10. Preferably, the entire front surface of the silicon substrate 1 is provided with the fourth velvet surface 10.

[0075] like Fig. 9As shown, in the embodiment of the present invention, the fourth velvet surface 10 includes a plurality of fourth-type pyramidal structures 101, and the base angle A of the fourth-type pyramidal structure 101 is the angle between the side surface of the fourth-type pyramidal structure 101 and the bottom surface of the fourth-type pyramidal structure 101. The arrangement of the plurality of fourth-type pyramidal structures 101 is not limited, and they can be arranged in a linear array or in an irregular arrangement, and adjacent fourth-type pyramidal structures 101 can also be stacked.

[0076] Preferably, the average bottom angle of the first type pyramid structure 211, the average bottom angle of the second type pyramid structure 311, and the average bottom angle of the third type pyramid structure 411 are all smaller than the average bottom angle of the fourth type pyramid structure 101, so that the sunlight entering the fourth velvet surface 10 on the front side of the silicon substrate 1 can be reflected as much as possible into the silicon substrate 1 through the first velvet surface 21 or the second velvet surface 31 or the third velvet surface 41, which can further improve the utilization rate of sunlight and further improve the battery efficiency. Preferably, the difference between the average bottom angle of the fourth type pyramid structure 101 and the average bottom angle of the first type pyramid structure 211, the average bottom angle of the second type pyramid structure 311, and the average bottom angle of the third type pyramid structure 411 is greater than 10°, which can further increase the sunlight reflection path, further improve the utilization rate of sunlight, and thus further improve the battery efficiency. Among them, the calculation method of the average base angle of the fourth type of pyramid structure 101 is the same as the calculation method of the average base angle of the first type of pyramid structure 211, the average base angle of the second type of pyramid structure 311, and the average base angle of the third type of pyramid structure 411, and will not be repeated here to save space.

[0077] As an embodiment of the present invention, the difference between the average base angle of the second type pyramid structure 311 and the average base angle of the first type pyramid structure 211 is greater than 5°.

[0078] In this embodiment, when the P-type doping region 2 and the N-type doping region 3 are provided with a velvet surface, the average bottom angle difference between the second type pyramid structure 311 and the first type pyramid structure 211 is controlled to be greater than 5°, under the premise of improving the utilization rate of sunlight by the P-type doping region 2 and the N-type doping region 3, so that the P-type doping region 2 and the N-type doping region 3 have a reasonable difference in optical performance and passivation performance, thereby well balancing the optical performance and passivation performance of the P-type doping region 2 and the N-type doping region 3, and realizing further optimization design of battery efficiency. For example, the average bottom angle difference between the second type pyramid structure 311 and the average bottom angle difference between the first type pyramid structure 211 can be 5 to 15°.

[0079] As an embodiment of the present invention, the difference between the average base angle of the second type pyramid structure 311 and the average base angle of the third type pyramid structure 411 is greater than 5°.

[0080] In this embodiment, when the N-type doping region 3 and the isolation region 4 are provided with a velvet surface, the difference between the average bottom angle of the third type pyramid structure 411 and the average bottom angle of the second type pyramid structure 311 is controlled to be greater than 5°, so that the N-type doping region 3 and the isolation region 4 have a reasonable difference in optical performance and passivation performance, thereby well balancing the optical performance and passivation performance of the N-type doping region 3 and the isolation region 4, and achieving further optimization of the battery efficiency. For example, the difference between the average bottom angle of the second type pyramid structure 311 and the average bottom angle of the third type pyramid structure 411 can be 5 to 15°.

[0081] As an embodiment of the present invention, the difference between the average base angle of the third type pyramid structure 411 and the average base angle of the first type pyramid structure 211 is greater than 10°.

[0082] In this embodiment, when the P-type doping region 2 and the isolation region 4 are provided with a velvet surface, the difference between the average bottom angle of the third type pyramid structure 411 and the average bottom angle of the first type pyramid structure 211 is controlled to be greater than 10°, so that the P-type doping region 2 and the isolation region 4 have a reasonable difference in optical performance and passivation performance, thereby well balancing the optical performance and passivation performance of the P-type doping region 2 and the isolation region 4, and achieving further optimization of the battery efficiency. For example, the difference between the average bottom angle of the third type pyramid structure 411 and the average bottom angle of the first type pyramid structure 211 can be 10 to 20°.

[0083] As an embodiment of the present invention, the difference between the average base angle of the second type of pyramid structure 311 and the average base angle of the first type of pyramid structure 211 is greater than 5°; the difference between the average base angle of the third type of pyramid structure 411 and the average base angle of the second type of pyramid structure 311 is greater than 5°; the difference between the average base angle of the third type of pyramid structure 411 and the average base angle of the first type of pyramid structure 211 is greater than 10°.

[0084] In the present embodiment, velvet is provided in the P-type doping region 2, the N-type doping region 3, and the isolation region 4, and the average bottom angle of the pyramid-like structure of the velvet in each region is controlled to have the above-mentioned size relationship, so that the P-type doping region 2, the N-type doping region 3, and the isolation region 4 have reasonable optical performance differences, thereby well balancing the optical performance and passivation performance of the P-type doping region 2, the N-type doping region 3, and the isolation region 4, and achieving further optimization design of battery efficiency.

[0085] As an embodiment of the present invention, the average base angle of the first type pyramid structure 211 is 10-60°; the average base angle of the second type pyramid structure 311 is 20-70°; and the average base angle of the third type pyramid structure 411 is 30-85°.

[0086] In this embodiment, the average bottom angle of the first type pyramid structure 211 is 10 to 60°; the average bottom angle of the second type pyramid structure 311 is 20 to 70°, and the average bottom angle of the third type pyramid structure 411 is 30 to 85°, which can achieve a balance between good optical performance and passivation effect of the P-type doping region 2, the N-type doping region 3, and the isolation region 4.

[0087] As an embodiment of the present invention, the average base angle of the first type pyramid structure 211 is 15-45°; the average base angle of the second type pyramid structure 311 is 20-55°; and the average base angle of the third type pyramid structure 411 is 40-75°.

[0088] In this embodiment, the average bottom angle of the first type pyramid structure 211 can be any value between 15 and 45 degrees, the average bottom angle of the second type pyramid structure 311 can be any value between 20 and 55 degrees, and the average bottom angle of the third type pyramid structure 411 can be any value between 40 and 75 degrees, as long as the average bottom angle of the first type pyramid structure 211 is smaller than the average bottom angle of the second type pyramid structure 311, and the average bottom angle of the second type pyramid structure 311 is smaller than the average bottom angle of the third type pyramid structure 411.

[0089] For example, the average base angle of the first type pyramid structure 211 can be any value among 15°, 16°, 17°, 18°, 20°, 22°, 24°, 25°, 28°, 30°, 32°, 35°, 38°, 40°, 42°, and 45°.

[0090] For example, the average base angle of the second type pyramid structure 311 can be any value among 20°, 21°, 22°, 23°, 25°, 27°, 29°, 30°, 35°, 38°, 40°, 42°, 45°, 48°, 49°, 50°, 52°, 54°, and 55°.

[0091] For example, the average base angle of the third type pyramid structure 411 can be any value among 40°, 42°, 45°, 48°, 50°, 52°, 55°, 57°, 58°, 60°, 61°, 63°, 65°, 70°, and 75°.

[0092] In this embodiment, the average bottom angle of the first type pyramid structure 211 is 15 to 45°; the average bottom angle of the second type pyramid structure 311 is 20 to 55°, and the average bottom angle of the third type pyramid structure 411 is 40 to 65°, which can further balance the good optical performance and passivation effect of the P-type doping region 2, the N-type doping region 3, and the isolation region 4.

[0093] As an embodiment of the present invention, the average bottom angle of the fourth type pyramid structure 101 is 50-85°. This allows more sunlight to enter the silicon substrate 1, reduces the reflection of sunlight on the front of the battery, increases the absorption of sunlight, and is beneficial to improving battery efficiency. At the same time, the differentiated design of the average bottom angle of the fourth type pyramid structure 101, the average bottom angle of the first type pyramid structure 211, the average bottom angle of the second type pyramid structure 311, and the average bottom angle of the third type pyramid structure 411 can improve the utilization rate of sunlight, and make the back of the battery have a lower back recombination loss, ensure a good back passivation effect, and achieve battery optimization design.

[0094] The average base angle of the fourth type pyramid structure 101 is any value between 50 and 85 degrees. For example, the average base angle of the fourth type pyramid structure 101 can be any value between 50 degrees, 52 degrees, 54 degrees, 55 degrees, 56 degrees, 58 degrees, 60 degrees, 61 degrees, 62 degrees, 63 degrees, 64 degrees, 65 degrees, 66 degrees, 67 degrees, 68 degrees, 69 degrees, 70 degrees, 72 degrees, 73 degrees, 75 degrees, and 85 degrees.

[0095] Please refer to Figure 10-12 As an embodiment of the present invention, the top of the first type pyramid structure 211 is set as a first arc surface 212, and / or the top of the second type pyramid structure 311 is set as a second arc surface 312.

[0096] In the present embodiment, when the P-type doping region 2 and the N-type doping region 3 are provided with a velvet surface, the top of the first type of pyramid structure 211 of the P-type doping region 2 is set as a first arc surface 212, and the top of the second type of pyramid structure 311 of the N-type doping region 3 is set as a second arc surface 312, that is, the top of the first type of pyramid structure 211 and the top of the second type of pyramid structure 311 are both smooth arc surfaces, which can reduce the surface recombination loss caused by the velveting of the P-type doping region 2 and the N-type doping region 3, facilitate the deposition of the back film layer of the P-type doping region 2 and the N-type doping region 3, and improve the passivation performance of the back film layer of the P-type doping region 2 and the N-type doping region 3.

[0097] As an embodiment of the present invention, the curvature of the first arc surface 212 is smaller than the curvature of the second arc surface 312 .

[0098] In the present embodiment, when the P-type doping region 2 and the N-type doping region 3 are provided with a velvet surface, the curvature of the first arc surface 212 is smaller than the curvature of the second arc surface 312, that is, the radius of the first arc surface 212 is larger than the radius of the second arc surface 312, and the top of the first type of pyramid structure 211 of the P-type doping region 2 is flatter than the top of the second type of pyramid structure 311 of the N-type doping region 3, which is more conducive to improving the passivation effect of the P-type doping region 2 and improving the battery efficiency.

[0099] As an embodiment of the present invention, the connection between two adjacent first-type pyramid structures 211 is configured as a third arc surface 213 , and / or the connection between two adjacent second-type pyramid structures 311 is configured as a fourth arc surface 313 .

[0100] In the present embodiment, when the P-type doping region 2 and the N-type doping region 3 are provided with a velvet surface, the connection between the adjacent first-type pyramid structures 211 of the P-type doping region 2 and the connection between the adjacent second-type pyramid structures 311 of the N-type doping region 3 are set to arc surfaces, which can further reduce the surface recombination loss caused by the velveting of the P-type doping region 2 and the N-type doping region 3, facilitate the deposition of the back film layer of the P-type doping region 2 and the N-type doping region 3, and improve the passivation performance of the back passivation layer of the P-type doping region 2 and the N-type doping region 3.

[0101] As an embodiment of the present invention, the curvature of the third arc surface 213 is smaller than the curvature of the fourth arc surface 313 .

[0102] In the present embodiment, when the P-type doping region 2 and the N-type doping region 3 are provided with a velvet surface, the curvature of the third arc surface 213 is smaller than the curvature of the fourth arc surface 313, that is, the radius of the third arc surface 213 is larger than the radius of the fourth arc surface 313, and the connection between the adjacent first-type pyramid structures 211 of the P-type doping region 2 is flatter than the connection between the adjacent second-type pyramid structures 311 of the N-type doping region 3, which is more conducive to further improving the passivation effect of the P-type doping region 2 and improving the battery efficiency.

[0103] As an embodiment of the present invention, the top of the third type pyramid structure 411 is sharp, and the connection between two adjacent third type pyramid structures 411 is sharp.

[0104] In the present embodiment, when the isolation region 4 is provided with a velvet surface, the top shape of the third-type pyramid structure 411 in the isolation region 4 is pointed, and the connection position of adjacent third-type pyramid structures 411 is also sharply set, so that the optical performance of the isolation region 4 is better than the optical performance of the P-type doping region 2 and the N-type doping region 3, ensuring the good optical performance of the isolation region 4, achieving the matching of the good optical performance of the isolation region 4 with the good passivation performance of the P-type doping region 2 and the N-type doping region 3, and realizing further improvement of the battery efficiency.

[0105] As an embodiment of the present invention, the height of the first type pyramid structure 211 is smaller than the height of the second type pyramid structure 311 .

[0106] The height of the first type pyramid structure 211 is the distance from the bottom surface of the first type pyramid structure 211 to its top, and the height of the second type pyramid structure 311 is the distance from the bottom surface of the second type pyramid structure 311 to its top. When the P-type doping region 2 and the N-type doping region 3 are provided with a velvet surface, since the height of the first type pyramid structure 211 is less than the height of the second type pyramid structure 311, the velvet surface of the P-type doping region 2 can be made flatter than the velvet surface of the N-type doping region 3, and the passivation performance of the P-type doping region 2 can be improved.

[0107] As an embodiment of the present invention, the height of the second type pyramid structure 311 is smaller than the height of the third type pyramid structure 411 .

[0108] In this embodiment, the height of the third type pyramid structure 411 is the distance from the bottom surface to the top of the third type pyramid structure 411. In the case where the N-type doping region 3 and the isolation region 4 are provided with a velvet surface, the height of the second type pyramid structure 311 is less than the height of the third type pyramid structure 411, which can improve the passivation performance of the N-type doping region 3, so that the passivation performance of the P-type doping region 2, the N-type doping region 3, and the isolation region 4 decreases in sequence, and the optical performance of the P-type doping region 2, the N-type doping region 3, and the isolation region 4 increases in sequence, so as to achieve a good matching design of the optical performance and passivation performance of the P-type doping region 2, the N-type doping region 3, and the isolation region 4, which is conducive to further improving the battery efficiency.

[0109] As an embodiment of the present invention, the roughness of the side surface of the first type pyramid structure 211 is smaller than the roughness of the side surface of the second type pyramid structure 311 .

[0110] In the present embodiment, when the P-type doping region 2 and the N-type doping region 3 are provided with a velvet surface, the roughness of the side surface of the first type of pyramid structure 211 is less than the roughness of the side surface of the second type of pyramid structure 311, that is, the undulation degree of the side surface of the first type of pyramid structure 211 is less than the undulation degree of the side surface of the second type of pyramid structure 311, which can enhance the light reflection effect of the N-type doping region 3, and is beneficial to enhance the optical performance of the N-type doping region 3, and can reduce the surface recombination loss of the P-type doping region 2, enhance the passivation effect of the P-type doping region 2, and is beneficial to balance the optical performance and passivation effect of the P-type doping region 2 and the N-type doping region 3.

[0111] As an embodiment of the present invention, the roughness of the side surface of the second type pyramid structure 311 is less than the roughness of the side surface of the third type pyramid structure 411 .

[0112] In the present embodiment, when the N-type doping region 3 and the isolation region 4 are provided with a velvet surface, the roughness of the side surface of the second-type pyramid structure 311 is less than the roughness of the side surface of the third-type pyramid structure 411, that is, the undulation degree of the side surface of the second-type pyramid structure 311 is less than the undulation degree of the side surface of the third-type pyramid structure 411, which can enhance the light reflection effect of the N-type doping region 3, and is beneficial to enhance the optical performance of the N-type doping region 3, and can reduce the surface recombination loss of the N-type doping region 3, enhance the passivation effect of the N-type doping region 3, and is beneficial to the balance between the optical performance and the passivation effect of the N-type doping region 3.

[0113] Please refer to Figure 1 As an embodiment of the present invention, the back contact solar cell further comprises:

[0114] A P-type doping layer 5 provided in the P-type doping region 2;

[0115] An N-type doping layer 6 is provided in the N-type doping region 3 .

[0116] In this embodiment, the P-type doped layer 5 is one or a combination of P-type polycrystalline silicon, P-type microcrystalline silicon, P-type nanocrystalline silicon, and P-type amorphous silicon, and the N-type doped layer 6 is one or a combination of N-type polycrystalline silicon, N-type microcrystalline silicon, N-type nanocrystalline silicon, and N-type amorphous silicon.

[0117] As an embodiment of the present invention, the back contact solar cell further includes:

[0118] A first passivation layer 7 disposed between the P-type doped layer 5 and the back surface of the silicon substrate 1;

[0119] A second passivation layer 8 is disposed between the N-type doped layer 6 and the back surface of the silicon substrate 1 .

[0120] The first passivation layer 7 and the second passivation layer 8 can be silicon oxide layers. The first passivation layer 7 and the second passivation layer 8 are used to passivate the back surface of the silicon substrate 1, further improving the passivation effect of the P-type doping region 2 and the N-type doping region 3.

[0121] As an embodiment of the present invention, it also includes:

[0122] A first electrode 15 is disposed on a side of the P-type doped layer 5 away from the silicon substrate 1, and the first electrode 15 is in contact with the P-type doped layer 5;

[0123] The second electrode 16 is disposed on a side of the N-type doping layer 4 facing away from the silicon substrate 1 , and the second electrode 16 is in contact with the N-type doping layer 4 .

[0124] As an embodiment of the present invention, the distribution density of the first type of pyramidal structure 211 in the area of ​​the P-type doping region 2 corresponding to the first electrode 15 is greater than the distribution density of the first type of pyramidal structure 211 in the area of ​​the P-type doping region 2 not corresponding to the first electrode 15, which is beneficial to improving the bonding tension between the first electrode 15 and the battery cell; similarly, the distribution density of the second type of pyramidal structure 311 in the area of ​​the N-type doping region 3 corresponding to the second electrode 16 is greater than the distribution density of the second type of pyramidal structure 311 in the area of ​​the N-type doping region 3 not corresponding to the second electrode 16, which is beneficial to improving the bonding tension between the second electrode 16 and the battery cell.

[0125] As an embodiment of the present invention, it also includes:

[0126] The back passivation layer 17 covers the P-type doping layer 5 , the N-type doping layer 6 and the isolation region 4 at the same time.

[0127] In this embodiment, the first electrode 15 passes through the back passivation layer 17 to contact the P-type doped layer 5; the second electrode 16 passes through the back passivation layer 17 to contact the N-type doped layer 4. The back passivation layer 17 can further improve the battery passivation effect and improve the battery efficiency. Among them, the back passivation layer 17 is at least one of an aluminum oxide film layer, a silicon oxide film layer, a silicon nitride film layer, a silicon carbide film layer, and a silicon oxynitride film layer, or a combination of multiple thereof. For example, in some embodiments, the back passivation layer 17 may include an aluminum oxide film layer and a silicon nitride film layer stacked in sequence, which is not specifically limited here.

[0128] The embodiment of the present invention further 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 relevant parts between the two can be referenced to each other. In order to avoid repetition, they will not be described here.

[0129] In this embodiment, multiple back-contact solar cells in the battery assembly can be connected in series in sequence to form a battery string, thereby realizing the series bus output of current. For example, the series connection of battery cells can be achieved by setting welding strips (bus bars, interconnecting strips), conductive back panels, etc.

[0130] It is understandable that in such an embodiment, the battery assembly may also include a metal frame, a back plate, photovoltaic glass and an adhesive film. The adhesive film may be filled between the front and back sides of the back contact solar cell and 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 adhesive film may be an EVA adhesive film or a POE adhesive film. The specific selection may be based on actual conditions and is not limited here.

[0131] Photovoltaic glass can cover the adhesive film on the front of the back contact solar cell. The photovoltaic glass can be ultra-white glass, which has high light transmittance, high transparency, and excellent physical, mechanical and optical properties. For example, the light transmittance of ultra-white glass can reach more than 92%, which can protect the back contact solar cell without affecting the efficiency of the back contact solar cell as much as possible. At the same time, the adhesive film can bond the photovoltaic glass and the back contact solar cell together. The presence of the adhesive film can seal and insulate the back contact solar cell and make it waterproof and moisture-proof.

[0132] The back sheet can be attached to the adhesive film on the back of the back contact solar cell. The back sheet can protect and support the back contact solar cell and has reliable insulation, water resistance and aging resistance. There are multiple options for the back sheet, which can usually be tempered glass, organic glass, aluminum alloy TPT composite adhesive film, etc. The specific configuration can be made according to the specific situation and is not limited here. The whole composed of the back sheet, back contact solar cell, adhesive film and photovoltaic glass can be set on a metal frame. The metal frame serves as the main external support structure of the entire back contact solar cell module and can stably support and install the back contact solar cell module. For example, the back contact solar cell module can be installed at the required location through the metal frame.

[0133] The embodiment of the present invention further provides a photovoltaic system, which includes the battery assembly of the above embodiment. It should be noted that the photovoltaic system has the same or similar beneficial effects as the above 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.

[0134] In this embodiment, the photovoltaic system can be applied to photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array may be an array combination of multiple back-contact solar cell modules. For example, multiple back-contact solar cell modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter and is converted into the alternating current required by the mains power grid, and then connected to the mains network to realize solar power supply.

[0135] In the description of this specification, the description with reference to the terms "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0136] 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: The invention comprises a silicon substrate, wherein the silicon substrate comprises a front side and a back side which are arranged opposite to each other, wherein the back side comprises a P-type doping region, an N-type doping region, and an isolation region arranged between the P-type doping region and the N-type doping region, and at least two of the P-type doping region, the N-type doping region, and the isolation region are provided with a velvet surface; the P-type doping region is provided with a first velvet surface, the first velvet surface comprises a plurality of first-type pyramid structures, and / or the N-type doping region is provided with a second velvet surface, the second velvet surface comprises a plurality of second-type pyramid structures, and / or the isolation region is provided with a third velvet surface, the third velvet surface comprises a plurality of third-type pyramid structures; The average base angle of the first type of pyramid structure is smaller than the average base angle of the second type of pyramid structure; and / or, the average base angle of the first type of pyramid structure is smaller than the average base angle of the third type of pyramid structure; and / or, the average base angle of the second type of pyramid structure is smaller than the average base angle of the third type of pyramid structure.

2. The back contact solar cell according to claim 1, characterized in that: The P-type doping region is provided with the first texture surface, the N-type doping region is provided with the second texture surface, and the isolation region is provided with a non-texture surface.

3. The back contact solar cell according to claim 1, characterized in that: The P-type doping region is provided with the first texture surface, the isolation region is provided with the third texture surface, and the N-type doping region is provided with a non-texture surface.

4. The back contact solar cell according to claim 1, characterized in that: The N-type doping region is provided with the second texture surface, the isolation region is provided with the third texture surface, and the P-type doping region is provided with a non-texture surface.

5. The back contact solar cell according to claim 1, characterized in that: The P-type doping region is provided with the first texture surface, the N-type doping region is provided with the second texture surface, and the isolation region is provided with the third texture surface.

6. The back contact solar cell according to claim 1, characterized in that: The difference between the average base angle of the second type of pyramid structure and the average base angle of the first type of pyramid structure is greater than 5°; and / or, the difference between the average base angle of the third type of pyramid structure and the average base angle of the second type of pyramid structure is greater than 5°; and / or, the difference between the average base angle of the third type of pyramid structure and the average base angle of the first type of pyramid structure is greater than 10°.

7. The back contact solar cell according to claim 1, characterized in that: The average base angle of the first type of pyramid structure is 10 to 60 degrees; the average base angle of the second type of pyramid structure is 20 to 70 degrees, and the average base angle of the third type of pyramid structure is 30 to 85 degrees.

8. The back contact solar cell according to claim 7, characterized in that: The average base angle of the first type of pyramid structure is 15 to 45 degrees; the average base angle of the second type of pyramid structure is 20 to 55 degrees, and the average base angle of the third type of pyramid structure is 40 to 75 degrees.

9. The back contact solar cell according to claim 1, characterized in that: The top of the first type of pyramid structure is configured as a first arc surface; and / or the top of the second type of pyramid structure is configured as a second arc surface.

10. The back contact solar cell according to claim 9, characterized in that: The curvature of the first arc surface is smaller than the curvature of the second arc surface.

11. The back contact solar cell according to claim 1, characterized in that: The connection point between two adjacent first-type pyramid structures is configured as a third arc surface, and / or the connection point between two adjacent second-type pyramid structures is configured as a fourth arc surface.

12. The back contact solar cell according to claim 11, characterized in that: The curvature of the third arc surface is smaller than the curvature of the fourth arc surface.

13. The back contact solar cell according to claim 1, characterized in that: The top of the third type pyramid structure is sharply arranged, and the connection between two adjacent third type pyramid structures is sharply arranged.

14. The back contact solar cell according to claim 1, characterized in that: The height of the first type of pyramid structure is smaller than the height of the second type of pyramid structure.

15. The back contact solar cell according to claim 1, characterized in that: The height of the second type of pyramid structure is smaller than the height of the third type of pyramid structure.

16. The back contact solar cell according to claim 1, characterized in that: The roughness of the side surface of the first type pyramid structure is smaller than the roughness of the side surface of the second type pyramid structure.

17. The back contact solar cell according to claim 1, characterized in that: The roughness of the side surface of the second type pyramid structure is smaller than the roughness of the side surface of the third type pyramid structure.

18. The back contact solar cell according to claim 1, characterized in that: The front surface of the silicon substrate is provided with a fourth velvet surface.

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

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

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