Solar cell and manufacturing method therefor, and photovoltaic module

Abstract

The present application relates to the technical field of photovoltaics, and provides a solar cell and a manufacturing method therefor, and a photovoltaic module. The solar cell comprises a silicon substrate, a front passivation and anti-reflection layer located on the light-facing side of the silicon substrate, and a back passivation and anti-reflection layer located on the shady side of the silicon substrate. The silicon substrate has a light-facing surface and a shady surface. The light-facing surface of the silicon substrate is provided with a first textured surface structure, and at least part of the region of the shady surface of the silicon substrate is provided with a second textured surface structure. Vertex angles of the second textured surface structure are greater than those of the first textured surface structure. According to the present application, it is ensured that the passivation performance of each position of the solar cell satisfies actual passivation requirements, and the anti-reflection performance of each position satisfies actual anti-reflection requirements, thereby improving the performance of the solar cell, achieving a more uniform black appearance and a more attractive appearance, and reducing material waste.

Description

A solar cell and its preparation method and photovoltaic module

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and benefits of Chinese patent application No. 202410382634.1, filed on March 29, 2024, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present application relates to the field of photovoltaic technology, and in particular to a solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0004] Solar cells can convert solar energy into electrical energy. They utilize clean energy and therefore have broad application prospects.

[0005] In solar cells, functional film layers such as passivation and anti-reflection layers are usually set on the light-facing side and the backlight side. On the one hand, this is for the passivation effect, and on the other hand, it is also necessary to obtain a better anti-reflection effect to increase the short-circuit current, etc.

[0006] However, existing solar cells do not take into account the different passivation and anti-reflection effects required by velvet structures at different locations, resulting in either a thicker passivation film affecting light absorption, or a thinner passivation film affecting the passivation effect and thus affecting cell performance. Summary of the Invention

[0007] The present application provides a solar cell and a preparation method thereof, and a photovoltaic module, aiming to solve the problem that, in a solar cell, it is difficult to achieve both passivation effect and anti-reflection effect while taking into account a suede structure.

[0008] In a first aspect of the present application, a solar cell is provided, comprising:

[0009] A silicon substrate, a front passivation anti-reflection layer on the light-facing side of the silicon substrate, and a back passivation anti-reflection layer on the backlight-reflection side of the silicon substrate;

[0010] The silicon substrate includes: a light-facing surface and a backlight surface; the light-facing surface of the silicon substrate has a first velvet structure, and at least part of the backlight surface of the silicon substrate has a second velvet structure; the apex angle of the second velvet structure is greater than the apex angle of the first velvet structure.

[0011] In the present application, the anti-reflection requirement of the light-facing surface of the solar cell is greater than the anti-reflection requirement of the backlight surface. The top angle of the first velvet structure of the light-facing surface of the silicon substrate is smaller than the top angle of the second velvet structure of at least part of the backlight surface of the silicon substrate. That is, the first velvet structure is more pointed, so that the first velvet structure has a larger specific surface area, that is, the reflectivity of the light-facing surface of the silicon substrate is lower and the light trapping effect is better, which can increase the short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. The appearance of the solar cell is uniformly black and more beautiful. The passivation requirement of the light-facing surface of the solar cell is smaller than the passivation requirement of the backlight surface. Therefore, the top angle of the second velvet structure of the backlight surface of the silicon substrate is larger, that is, the second velvet structure of the backlight surface of the silicon substrate is relatively flat, which is conducive to the preparation of a thicker back passivation anti-reflection layer, thereby achieving a good passivation effect. Therefore, the solar cell in the present application, on the one hand, can ensure that the passivation performance of each position is consistent with the actual passivation requirements, and the anti-reflection performance of each position is consistent with the actual anti-reflection requirements, which not only has a better passivation and anti-reflection effect, but also can reduce material waste; on the other hand, the first velvet structure and the second velvet structure can increase the absorption of light, and the light trapping effect is better, which can further improve the short-circuit current and further improve the photoelectric conversion efficiency of the solar cell, and the appearance of the solar cell is uniform black, which is more beautiful. In summary, the present application not only ensures that the passivation performance of each part of the solar cell is consistent with the actual passivation requirements, and the anti-reflection performance of each part is consistent with the actual anti-reflection requirements, improves the performance of the battery, and has a more uniform black appearance, which is more beautiful, and can also reduce material waste.

[0012] Optionally, the top angle of the second velvet structure is greater than or equal to 79°, and the top angle of the first velvet structure is less than 79°.

[0013] Optionally, the average vertex angle of the second velvet structure is greater than or equal to 85°, and the average vertex angle of the first velvet structure is less than 75°.

[0014] Optionally, the absolute value of the maximum difference between the vertex angles of adjacent first velvet structures on the light-facing surface of the silicon substrate is greater than the absolute value of the maximum difference between the vertex angles of adjacent second velvet structures on the backlight surface of the silicon substrate. The smaller the difference between the vertex angles of adjacent second velvet structures on the backlight surface of the silicon substrate, the more uniform the distribution of the velvet structures in that area, the more conducive it is to film deposition, and the better the passivation effect.

[0015] Optionally, the first velvet structure includes: a plurality of first-type pyramid structures; the first-type pyramid structures include: a cone surface and a cone top; the second velvet structure includes: a plurality of second-type pyramid structures; the second-type pyramid structures include: a cone surface and a cone top.

[0016] Optionally, the undulation of the conical surface of the first type of pyramid structure is greater than the undulation of the conical surface of the second type of pyramid structure;

[0017] Alternatively, the roughness of the conical surface of the first-type pyramid structure is greater than the roughness of the conical surface of the second-type pyramid structure. The greater the undulation / roughness of the conical surface of the pyramid-like structure, the better its light-trapping effect, but it is not conducive to the uniformity of the deposition of the passivation anti-reflection layer, which has an adverse effect on the passivation effect. Therefore, by providing the first-type pyramid structure with a larger undulation / roughness on the light-facing side, the requirements of light trapping and anti-reflection on the light-facing side are met, and the front passivation anti-reflection layer on the light-facing side mainly carries the anti-reflection function. Therefore, the front passivation anti-reflection layer on the light-facing side does not need to be as thick as the back passivation anti-reflection layer on the back-facing side. The second pyramid structure has a smaller undulation / roughness, the deposited back passivation anti-reflection layer is more uniform, and the back passivation film layer obtained with the same film preparation process time is thicker, meeting the back passivation requirements.

[0018] Optionally, the undulation of a first sub-cone surface close to the apex of the cone surface of the first type of pyramid structure is greater than the undulation of a second sub-cone surface close to the apex of the cone surface of the second type of pyramid structure;

[0019] Alternatively, the roughness of the first sub-conical surface is greater than the roughness of the second sub-conical surface.

[0020] Optionally, the first type of pyramid structure consists of a lower part and an upper part, the lower part is a part of the first type of pyramid structure away from the top, the height of the lower part is at least 1 / 10 of the height of the first type of pyramid structure, and the first sub-cone surface is: the area of ​​the cone surface of the first type of pyramid structure corresponding to the upper part;

[0021] The second type of pyramid structure consists of a lower part and an upper part, the lower part is the part of the second type of pyramid structure away from the top of the cone, the height of the lower part is at least 1 / 10 of the height of the second type of pyramid structure, and the second sub-cone surface is: the area corresponding to the upper part in the cone surface of the second type of pyramid structure. For a single pyramid-like structure, the part of the silicon substrate adjacent to the pyramid-like structure is more complicated and usually has more defects. The position of the adjacent pyramid-like structures is also more complicated and usually has more defects. Therefore, these positions require a thicker passivation anti-reflection layer to achieve a better passivation effect; while the defects at the top of the cone are usually fewer, and only a thinner passivation anti-reflection layer is required to achieve a better passivation effect. The undulation / roughness of the part of the pyramid-like structure near the top of the cone is greater, and the thickness of the deposited passivation anti-reflection layer is different. After the light enters the passivation anti-reflection layer with different thicknesses, the optical path of the light will change more times, which can increase the optical path. Combined with the velvet structure of the present application, the absorption of light can be further increased, and the light trapping effect is better. The light-facing side and the backlight side have different passivation and anti-reflection requirements, so the undulation / roughness requirements of the part near the top of the cone of the single pyramid-like structure are different. The undulation / roughness of the part near the top of the cone of the single pyramid-like structure on the light-facing side is greater.

[0022] Optionally, the first type of pyramid structure further includes: a bottom contour line away from the top of the pyramid, and the width of the first type of pyramid structure is the maximum inner dimension of the bottom contour line of the first type of pyramid structure;

[0023] The second type of pyramid structure further includes: a bottom contour line away from the top of the pyramid, and the width of the second type of pyramid structure is the maximum inner dimension of the bottom contour line of the second type of pyramid structure;

[0024] A ratio of the height of the first type of pyramid structure divided by the width of the first type of pyramid structure is greater than a ratio of the height of the second type of pyramid structure divided by the width of the second type of pyramid structure.

[0025] Optionally, the conical surface of the first type of pyramid structure and the conical surface of the second type of pyramid structure both have a branched texture, and the number of the branched textures on the conical surface of the first type of pyramid structure is greater than the number of the branched textures on the conical surface of the second type of pyramid structure;

[0026] Alternatively, the first type of pyramid structure has a branched texture on its surface, while the second type of pyramid structure has no branched texture on its surface. The more textures on the pyramid surface, the more uneven its surface is, and the better the light trapping and anti-reflection effects are.

[0027] Optionally, the front passivation anti-reflection layer includes: a first portion located on the first suede structure, and the back passivation anti-reflection layer includes: a second portion located on the second suede structure;

[0028] The thickness of the first portion is smaller than the thickness of the second portion.

[0029] Optionally, the backlight surface of the silicon substrate has a non-texture structure, and the back passivation anti-reflection layer includes: a second portion located on the second velvet structure, and a third portion located on the non-texture structure;

[0030] The thickness of the second part is smaller than the thickness of the third part.

[0031] Optionally, the front passivation anti-reflection layer includes: a first portion located on the first velvet structure, the backlight surface of the silicon substrate has a non-velvet structure, and the back passivation anti-reflection layer includes: a second portion located on the second velvet structure, and a third portion located on the non-velvet structure;

[0032] Among the first part, the second part and the third part, the thickness of the first part is the smallest, the thickness of the third part is the largest, and the thickness of the second part is in between.

[0033] Optionally, the front passivation anti-reflection layer includes: a first portion located on the first suede structure, and the back passivation anti-reflection layer includes: a second portion located on the second suede structure;

[0034] The thickness unevenness of the first portion is greater than the thickness unevenness of the second portion;

[0035] The thickness non-uniformity of the first portion is: the absolute value of the difference between two thicknesses at two positions along the same direction toward the pyramid top in the portion of the front passivation anti-reflection layer located on the same first-type pyramid structure, divided by the sum of the two thicknesses;

[0036] The second portion's thickness nonuniformity is calculated as the absolute value of the difference between two thicknesses at two locations along the same direction toward the apex of the back-surface passivation anti-reflection layer, located on the same second-type pyramid structure, divided by the sum of the two thicknesses. The greater the thickness nonuniformity of the passivation anti-reflection layer, the more changes in the light path will occur after light enters the passivation anti-reflection layer of varying thickness, increasing the optical path. This, combined with the suede structure, further increases light absorption and enhances the light trapping effect.

[0037] Optionally, at two opposite positions in the thickness direction of the silicon substrate, the difference between the thickness of the portion of the back passivation anti-reflection layer located on the second velvet structure and the thickness of the front passivation anti-reflection layer is greater than or equal to 15 nm and less than or equal to 50 nm.

[0038] Optionally, the backlight surface of the silicon substrate includes: first areas and second areas that are alternately distributed, and an isolation area is provided between adjacent first areas and second areas;

[0039] The solar cell further comprises: a first conductive layer located on the first region, and a second conductive layer located on the second region; the first conductive layer and the second conductive layer have different conductivity types;

[0040] In the backlight surface of the silicon substrate, at least one region among the first region, the second region and the isolation region has the second textured structure.

[0041] Optionally, the width of the isolation region is 50 um to 350 um; the width of the isolation region is parallel to the direction of alternating distribution of the first region and the second region.

[0042] Optionally, the backlight surface of the silicon substrate includes: a first area and a second area alternately distributed, and the solar cell also includes: a first conductive layer located on the first area, the first conductive layer is doped with a first conductive element, and at least part of the second area is doped with a second conductive element; the first conductive element and the second conductive element have different conductivity types; the part where the second area and the first area intersect has the second velvet structure.

[0043] Optionally, the solar cell further comprises: a first conductive layer located between the silicon substrate and the front passivation anti-reflection layer, and a second conductive layer located between the silicon substrate and the back passivation anti-reflection layer; the first conductive layer and the second conductive layer have different conductivity types;

[0044] The entire backlight surface of the silicon substrate has the second textured structure.

[0045] In a second aspect of the present application, a photovoltaic assembly is provided, comprising: a plurality of any of the aforementioned solar cells.

[0046] A third aspect of the present application provides a method for preparing a solar cell, comprising:

[0047] Providing a silicon substrate; the silicon substrate comprises: a light-facing surface and a backlight surface;

[0048] Texturing the silicon substrate to form a first textured surface structure on the light-facing surface of the silicon substrate and a second textured surface structure on at least a portion of the backlight surface of the silicon substrate; the second textured surface structure has a greater top angle than the first textured surface structure;

[0049] A front passivation anti-reflection layer is prepared on the light-facing side of the silicon substrate, and a back passivation anti-reflection layer is prepared on the backlight-reflection side of the silicon substrate.

[0050] Optionally, texturing the silicon substrate includes:

[0051] The light-facing surface and the backlight surface of the silicon substrate are textured separately, so that the texture time of at least a part of the backlight surface of the silicon substrate is shorter than the texture time of the light-facing surface of the silicon substrate; and / or,

[0052] A texturing protective layer is provided on at least a portion of the backlight surface of the silicon substrate, and the silicon substrate is texturized. Under the blocking effect of the texturing protective layer, the texturing time of at least a portion of the backlight surface of the silicon substrate is shorter than the texturing time of the light-facing surface of the silicon substrate; and / or,

[0053] The silicon substrate is placed obliquely in the texturing liquid, and in the thickness direction of the silicon substrate, the light-facing surface of the silicon substrate is closer to the liquid surface of the texturing liquid than the backlight surface at two opposite positions, and the silicon substrate is texturized.

[0054] Optionally, the difference between the texturing time of the light-facing surface of the silicon substrate and the texturing time of at least a portion of the backlight surface of the silicon substrate is 30 seconds to 200 seconds.

[0055] Optionally, the backlight surface of the silicon substrate includes: first areas and second areas that are alternately distributed, with an isolation area between adjacent first areas and second areas; before providing the texturing protective layer on at least a portion of the backlight surface of the silicon substrate, the method further includes:

[0056] performing a polishing process on the silicon substrate;

[0057] forming a first conductive layer on the backlight side of the silicon substrate;

[0058] Performing patterning on a portion of the first conductive layer located on the second region and the isolation region, so that the second region and the isolation region are exposed;

[0059] forming a second conductive layer on the second region, the isolation region, and the remaining first conductive layer; the first conductive layer and the second conductive layer have different conductivity types;

[0060] The step of providing a texturing protective layer on at least a portion of the backlight surface of the silicon substrate comprises:

[0061] performing laser processing on a portion of the second conductive layer located on the first region and the isolation region, so that the portion of the second conductive layer located on the first region and the isolation region is oxidized into the texturing protective layer;

[0062] The texturing of the silicon substrate, under the blocking effect of the texturing protective layer, is performed for a shorter time on at least a portion of the backlight surface of the silicon substrate than on the light-facing surface of the silicon substrate, so as to form a first textured surface structure on the light-facing surface of the silicon substrate and a second textured surface structure on at least a portion of the backlight surface of the silicon substrate, including:

[0063] The silicon substrate is textured to form the first textured structure on the light-facing surface of the silicon substrate. At the same time, the textured liquid removes the textured protective layer to expose the isolation area and the first conductive layer. The isolation area is then textured with the textured liquid to form the second textured structure in the isolation area on the backlight side of the silicon substrate.

[0064] Optionally, during the laser treatment:

[0065] Laser includes one of the following: nanosecond laser, picosecond laser and femtosecond laser;

[0066] and / or, the laser power is 10W to 100W;

[0067] And / or, the laser spot diameter is 50um to 350um.

[0068] Optionally, the silicon substrate is placed obliquely in the texturing liquid, and the angle between the thickness direction of the silicon substrate and the liquid surface of the texturing liquid is 3° to 7°.

[0069] This application not only ensures that the passivation performance of each part of the solar cell is consistent with the actual passivation requirements, but also that the anti-reflection performance of each part is consistent with the actual anti-reflection requirements, thereby improving the performance of the cell, and having a more uniform black appearance, which is more beautiful, while also reducing material waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0071] FIG1 shows a schematic structural diagram of a solar cell in an embodiment of the present application;

[0072] FIG2 shows a front view scanning electron microscope image of the light-facing surface of the first silicon substrate in an embodiment of the present application;

[0073] FIG3 shows a front view scanning electron microscope image of the light-facing surface of the second silicon substrate in an embodiment of the present application;

[0074] FIG4 shows a front view scanning electron microscope image of the light-facing surface of the third silicon substrate in an embodiment of the present application;

[0075] FIG5 shows a front view scanning electron microscope image of the light-facing surface of the fourth silicon substrate in an embodiment of the present application;

[0076] FIG6 shows a top-view scanning electron microscope image of the light-facing surface of a silicon substrate in an embodiment of the present application;

[0077] FIG7 shows a front view scanning electron microscope image of the backlight surface of the first silicon substrate in an embodiment of the present application;

[0078] FIG8 shows a front view scanning electron microscope image of the backlight surface of the second silicon substrate in an embodiment of the present application;

[0079] FIG9 shows a front view scanning electron microscope image of the backlight surface of the third silicon substrate in an embodiment of the present application;

[0080] FIG10 shows a bottom-up scanning electron microscope image of the backlight surface of a silicon substrate in an embodiment of the present application;

[0081] 11 to 16 are schematic diagrams showing a partial process of preparing a solar cell according to an embodiment of the present application.

[0082] Explanation of the accompanying figures: 1-silicon substrate, 11-cone top, 12-branched texture, 13-bottom contour line, 2-front passivation anti-reflection layer, 3-back passivation anti-reflection layer, 4-first conductive layer, 5-second conductive layer, 6-first electrode, 7-second electrode, 8-tunneling oxide layer, 9-laser action area, 10-textured protective layer, 14-plated polysilicon. DETAILED DESCRIPTION

[0083] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0084] In existing solar cells, it is difficult to take both the passivation effect and the anti-reflection effect into consideration, which affects the battery performance. The main reason is that as the thickness of the passivation anti-reflection layer increases, its passivation effect is better, but the anti-reflection effect will be appropriately reduced. Therefore, it is difficult to take both the passivation effect and the anti-reflection effect into consideration. More specifically, in existing solar cells, the front and back sides usually have velvet structures of the same size, and passivation anti-reflection layers of approximately equal thickness will be formed on the velvet structures of the same size, that is, the front and back sides have approximately the same passivation anti-reflection performance. However, the anti-reflection requirements of the light-facing side of the solar cell are obviously different from the anti-reflection requirements of the backlight side. The passivation requirements of the light-facing side of the solar cell are obviously different from the passivation requirements of the backlight side. That is, in existing solar cells, the passivation anti-reflection performance of the front and back sides does not meet their actual passivation anti-reflection requirements, which affects the battery performance. In response to the above technical problems, the main concept of the present application is to reasonably set the velvet structure according to the requirements of the solar cell's light-facing surface for passivation and anti-reflection, and the requirements of the solar cell's backlight surface for passivation and anti-reflection, so that the passivation and anti-reflection performance of the front and back sides of the solar cell are consistent with its actual passivation and anti-reflection requirements, thereby improving the cell performance. More specifically, in the present application, the solar cell's light-facing surface anti-reflection requirement is greater than the backlight surface anti-reflection requirement, and the top angle of the first velvet structure of the light-facing surface of the silicon substrate is smaller than the top angle of the second velvet structure of at least part of the backlight surface of the silicon substrate, that is, the first velvet structure is sharper, so that the first velvet structure has a larger specific surface area, that is, the reflectivity of the light-facing surface of the silicon substrate is lower and the light trapping effect is better, which can increase the short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell, and the appearance of the solar cell is uniform black, which is more beautiful. The requirement for passivation on the light-facing side of the solar cell is less than the requirement for passivation on the backlight side. Therefore, the top angle of the second velvet structure on the backlight side of the silicon substrate is larger, that is, the second velvet structure on the backlight side of the silicon substrate is relatively flat, which is conducive to the preparation of a thicker back passivation anti-reflection layer, thereby achieving a good passivation effect. Therefore, the solar cell in the present application, on the one hand, can ensure that the passivation performance of each position is consistent with the actual passivation requirements, and the anti-reflection performance of each position is consistent with the actual anti-reflection requirements, not only has a better passivation and anti-reflection effect, but also can reduce material waste; on the other hand, the first velvet structure and the second velvet structure can increase the absorption of light, have a better light trapping effect, can further improve the short-circuit current, further improve the photoelectric conversion efficiency of the solar cell, and the appearance of the solar cell is uniform black, which is more beautiful. In summary, the present application not only ensures that the passivation performance of each part of the solar cell is consistent with the actual passivation requirements, and the anti-reflection performance of each part is consistent with the actual anti-reflection requirements, improves the performance of the cell, and has a more uniform black appearance, which is more beautiful, while also reducing material waste.

[0085] The present application provides a solar cell. Referring to FIG1 , the solar cell may include: a silicon substrate 1; a front-side passivation anti-reflection layer 2 located on the light-facing side of the silicon substrate 1; and a back-side passivation anti-reflection layer 3 located on the backlight side of the silicon substrate. In FIG1 , the upper side of the silicon substrate 1 may be its light-facing side, and the lower side may be its backlight side. The upper surface of the silicon substrate 1 may be its light-facing surface, and the lower surface may be its backlight side. The silicon substrate 1 may be doped or intrinsic, and this is not specifically limited. The silicon substrate 1 may be a single crystal silicon substrate, and this is not specifically limited. The passivation anti-reflection layer may perform both passivation and anti-reflection functions. The material of the passivation anti-reflection layer may be selected from silicon oxide and / or silicon oxynitride, and the specific material of the passivation anti-reflection layer is not limited. The passivation anti-reflection layer may be prepared using methods such as PECVD (Plasma Enhanced Chemical Vapor Deposition), and the specific preparation method of the passivation anti-reflection layer is not specifically limited.

[0086] Among them, Figures 2 to 5 are mainly scanning electron microscope images obtained by scanning the first velvet structure from the front or side. Figure 6 is mainly scanning electron microscope images obtained by scanning the first velvet structure in the direction from the top of the cone to the bottom contour line. Figures 7 to 9 are mainly scanning electron microscope images obtained by scanning the second velvet structure from the front or side. Figure 10 is mainly scanning electron microscope images obtained by scanning the second velvet structure in the direction from the top of the cone to the bottom contour line. Figures 1 and 11 to 16 only represent the relative position relationship of each layer structure in the solar cell, and do not represent the relative size relationship of its actual size.

[0087] Referring to Figures 2 to 6 and 16, the light-facing surface of the silicon substrate 1 has a first velvet structure. Referring to Figures 7 to 10 and 16, at least a portion of the backlight surface of the silicon substrate 1 has a second velvet structure. Referring to Figures 2 to 10, the apex angle of the second velvet structure is greater than the apex angle of the first velvet structure. The apex angle of the first velvet structure is: the apex angle of the cross section of the first velvet structure, which can be measured by a scanning electron microscope SEM, as shown in Figures 2, 3, and 4. The apex angle of the second velvet structure is: the apex angle of the cross section of the second velvet structure, which can be measured by a scanning electron microscope SEM, as shown in Figures 7, 8, and 9. The apex 11 is the highest point in the first type of pyramid structure or the second type of pyramid structure. In the case where the highest part of the first type of pyramid structure or the second type of pyramid structure is a plane formed by multiple points of equal height, the apex here can be the geometric center of the plane. The side edges of a pyramid-like structure are the common edges of adjacent side surfaces in the pyramid-like structure. The first velvet structure has a smaller apex angle, that is, the first velvet structure is more pointed, which gives the first velvet structure a larger specific surface area, that is, the reflectivity of the light-facing surface of the silicon substrate 1 is lower and the light-trapping effect is better, which can increase the short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. The appearance of the solar cell is uniformly black and more beautiful. The requirement for passivation on the light-facing side of the solar cell is less than the requirement for passivation on the backlight side. Therefore, the apex angle of the second velvet structure on the backlight side of the silicon substrate 1 is larger, that is, the second velvet structure on the backlight side of the silicon substrate 1 is relatively flat, which is conducive to the preparation of a thicker back passivation anti-reflection layer, thereby achieving a good passivation effect. Therefore, the solar cell in the present application can, on the one hand, ensure that the passivation performance at each position is consistent with the actual passivation requirements, and the anti-reflection performance at each position is consistent with the actual anti-reflection requirements, not only improving the passivation and anti-reflection effects, but also reducing material waste. On the other hand, the first velvet structure and the second velvet structure can increase light absorption and have a better light-trapping effect, which can further increase the short-circuit current and further improve the photoelectric conversion efficiency of the solar cell. The appearance of the solar cell is uniformly black and more beautiful. In summary, this application not only ensures that the passivation performance of each part of the solar cell is consistent with the actual passivation requirements, but also that the anti-reflection performance of each part is consistent with the actual anti-reflection requirements, thereby improving the performance of the cell, and having a more uniform black appearance, which is more beautiful, while also reducing material waste.

[0088] It should be noted that, on the basis that the vertex angle of the second velvet structure is greater than the vertex angle of the first velvet structure, the difference between the two is not specifically limited. In the present application, the vertex angle of the second velvet structure is greater than the vertex angle of the first velvet structure, which can be understood as: each vertex angle of all the vertex angles of the second velvet structure is greater than each vertex angle of all the vertex angles of the first velvet structure. Alternatively, the vertex angle of the second velvet structure is greater than the vertex angle of the first velvet structure, which can be understood as: each vertex angle of the first preset proportion of the total number of all the vertex angles of the second velvet structure is greater than each vertex angle of the second preset proportion of the total number of all the vertex angles of the first velvet structure. The first preset proportion and the second preset proportion here can both be greater than or equal to 50%, and the first preset proportion and the second preset proportion can be equal or different, and there is no specific limitation on this. For example, each vertex angle of 50% of the total number of all the vertex angles of the second velvet structure is greater than each vertex angle of 50% of the total number of all the vertex angles of the first velvet structure. For example, each of 55% of the total number of all vertex angles of the second velvet structure is greater than each of 55% of the total number of all vertex angles of the first velvet structure. For another example, each of 60% of the total number of all vertex angles of the second velvet structure is greater than each of 60% of the total number of all vertex angles of the first velvet structure. For another example, each of 65% of the total number of all vertex angles of the second velvet structure is greater than each of 65% of the total number of all vertex angles of the first velvet structure. For another example, each of 70% of the total number of all vertex angles of the second velvet structure is greater than each of 70% of the total number of all vertex angles of the first velvet structure. For another example, each of 75% of the total number of all vertex angles of the second velvet structure is greater than each of 75% of the total number of all vertex angles of the first velvet structure. For another example, each of 80% of the total number of all vertex angles of the second velvet structure is greater than each of 80% of the total number of all vertex angles of the first velvet structure. For another example, each of 85% of the total number of all vertex angles of the second velvet structure is greater than each of 85% of the total number of all vertex angles of the first velvet structure. For another example, each of 90% of the total number of all vertex angles of the second velvet structure is greater than each of 90% of the total number of all vertex angles of the first velvet structure. For another example, each of 95% of the total number of all vertex angles of the second velvet structure is greater than each of 95% of the total number of all vertex angles of the first velvet structure.For another example, each of 99.3% of the total number of all vertex angles of the second velvet structure is greater than each of 99% of the total number of all vertex angles of the first velvet structure. For another example, each of 50% of the total number of all vertex angles of the second velvet structure is greater than each of 53% of the total number of all vertex angles of the first velvet structure. For another example, each of 60% of the total number of all vertex angles of the second velvet structure is greater than each of 55% of the total number of all vertex angles of the first velvet structure. For another example, each of 83% of the total number of all vertex angles of the second velvet structure is greater than each of 85% of the total number of all vertex angles of the first velvet structure. For another example, each of 97% of the total number of all vertex angles of the second velvet structure is greater than each of 96.2% of the total number of all vertex angles of the first velvet structure.

[0089] It should be noted that the total number of all vertex angles in the first velvet structure may be equal to or unequal to the total number of all vertex angles in the second velvet structure, and there is no specific limitation on this. The two may be equal or unequal. Whether the number of vertex angles in the first preset ratio of the total number of all vertex angles in the second velvet structure is equal to the number of vertex angles in the second preset ratio of the total number of all vertex angles in the first velvet structure is not specifically limited, and the two may be equal or unequal. Here, the entire light-facing surface of the silicon substrate 1 has the first velvet structure, or only a part of the light-facing surface of the silicon substrate has the first velvet structure, and there is no specific limitation on this. The entire backlight surface of the silicon substrate 1 has the second velvet structure, or only a part of the backlight surface of the silicon substrate 1 has the second velvet structure, and there is no specific limitation on this.

[0090] Optionally, referring to Figures 2 to 4, the vertex angle of the first velvet structure is less than 79°. The vertex angle of the first velvet structure is smaller, and the first velvet structure is sharper, so that the first velvet structure has a larger specific surface area, that is, the reflectivity of the light-facing surface of the silicon substrate 1 is lower and the light trapping effect is better, which can increase the short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. The appearance of the solar cell is uniformly black and more beautiful. At the same time, the thickness of the front passivation anti-reflection layer prepared on the first velvet structure is also relatively appropriate, which can meet the passivation requirements of the light-facing surface of the silicon substrate 1 and avoid material waste. In the accompanying drawings, No is an abbreviation for the number. For example, in Figure 2, the vertex angles of the first velvet structures marked with numbers 2 to 8 are 70.741°, 73.603°, 64.495°, 72.972°, 72.873°, 67.236°, and 76.121°, respectively. These 7 vertex angles are all less than 79°. For another example, in Figure 3, the vertex angles of the first velvet structure marked with numbers 3 to 7 are 78.208°, 78.415°, 71.499°, 75.904°, and 72.448°, respectively. These five vertex angles are all less than 79°. For another example, in Figure 4, the vertex angles of the first velvet structure marked with numbers 3 to 6 are 76.251°, 72.822°, 70.902°, and 71.456°, respectively. These four vertex angles are all less than 79°.

[0091] Here, the top angle of the first velvet structure is less than 79°, which may be that each of all the top angles of the first velvet structure is less than 79°, or each of the top angles of a third preset proportion of the total number of all the top angles of the first velvet structure is less than 79°, and the third preset proportion here may be greater than or equal to 50%.

[0092] Optionally, referring to Figures 7 to 9, the vertex angle of the second velvet structure is greater than or equal to 79°, and the vertex angle of the second velvet structure on the backlight side of the silicon substrate 1 is larger, that is, the second velvet structure on the backlight side of the silicon substrate 1 is relatively flat, which is conducive to preparing a thicker back passivation anti-reflection layer, thereby achieving a good passivation effect. For example, in Figure 7, the vertex angles of the second velvet structures marked with numbers 3 to 9 are 83.461°, 85.538°, 88.602°, 86.730°, 93.875°, 87.562°, and 90.991°, respectively. These seven vertex angles are all greater than 79°. For another example, in Figure 8, the vertex angles of the second velvet structures marked with numbers 3 to 6 are 92.291°, 87.538°, 94.880°, and 95.383°, respectively. These four vertex angles are all greater than 79°. For another example, in FIG9 , the vertex angles numbered 2 to 9 of the second velvet structure are 85.327°, 87.167°, 79.948°, 90.780°, 81.148°, 83.600°, 84.806°, and 87.975°, respectively. These eight vertex angles are all greater than 79°.

[0093] Here, the vertex angle of the second velvet structure is greater than or equal to 79°, and each of the vertex angles of all the vertex angles of the second velvet structure may be greater than or equal to 79°, or each of the vertex angles of the fourth preset proportion of the total number of all the vertex angles of the second velvet structure may be greater than or equal to 79°, and the fourth preset proportion here may be greater than or equal to 50%.

[0094] Optionally, referring to Figures 7 to 9, the average vertex angle of the second velvet structure is greater than or equal to 85°. The vertex angles of the second velvet structure on the backlight side of the silicon substrate 1 are all relatively large, that is, the second velvet structure on the backlight side of the silicon substrate 1 is relatively flat, which is conducive to preparing a thicker back passivation anti-reflection layer, thereby achieving a good passivation effect. The average vertex angle of the second velvet structure refers to: the arithmetic mean of all vertex angles of the second velvet structure, or can refer to the arithmetic mean of the vertex angles of the fifth preset proportion of the total number of all vertex angles of the second velvet structure. Here, the fifth preset proportion can be greater than or equal to 50%.

[0095] For example, the average apex angle of the second pile structure may be 85°, or 85.53°, or 88.6°, or 86.73°, or 87.875°, or 87.61°, or 93.875°, or 87.22°, or 90.9°, or 94.275°.

[0096] Optionally, referring to Figures 2 to 5, the average vertex angle of the first velvet structure is less than 75°, the vertex angles of the first velvet structure are all small, and the first velvet structure is sharper, so that the first velvet structure has a larger specific surface area, that is, the reflectivity of the light-facing surface of the silicon substrate 1 is lower and the light trapping effect is better, which can increase the short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. The appearance of the solar cell is uniformly black and more beautiful. At the same time, the thickness of the front passivation anti-reflection layer prepared on the first velvet structure is also relatively appropriate, which can meet the passivation requirements of the light-facing surface of the silicon substrate 1 and avoid material waste. The average vertex angle of the first velvet structure refers to: the arithmetic mean of all vertex angles of the first velvet structure, or it can refer to the arithmetic mean of the sixth preset proportion of the total number of vertex angles of all vertex angles of the first velvet structure. The sixth preset proportion here can be greater than or equal to 50%.

[0097] For example, the average apex angle of the first pile structure may be 74.99°, 74.5°, 74.02°, 73.59°, 73.11°, 72.5°, 72.01°, 71.49°, 71.23°, 70.69°, or 70.04°.

[0098] Optionally, the absolute value of the maximum difference between the vertex angles of adjacent first velvet structures on the light-facing surface of the silicon substrate 1 is greater than the absolute value of the maximum difference between the vertex angles of adjacent second velvet structures on the backlight surface of the silicon substrate 1. The uniformity of the vertex angles of the first velvet structure is less than that of the vertex angles of the second velvet structure. The vertex angles of the first velvet structure are more uneven. The difference in the vertex angles of the first velvet structure is greater, so that the first velvet structure has a larger specific surface area, that is, the reflectivity of the light-facing surface of the silicon substrate 1 is lower and the light trapping effect is better, which can increase the short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. The appearance of the solar cell is uniformly black and more beautiful. At the same time, the thickness of the front passivation anti-reflection layer prepared on the first velvet structure is also relatively appropriate, which can meet the passivation requirements of the light-facing surface of the silicon substrate 1 and avoid material waste. The vertex angles of the second velvet structure are more uniform, which is conducive to preparing a thicker and more uniform back passivation anti-reflection layer, thereby achieving a good passivation effect. On the light-facing surface of the silicon substrate 1, the vertex angles of adjacent first velvet structures refer to the two vertex angles of the first velvet structures that are closest to each other on the light-facing surface of the silicon substrate 1. The absolute value of the maximum difference between the vertex angles of adjacent first velvet structures on the light-facing surface of the silicon substrate 1 refers to: selecting a first preset number of pairs of vertex angles of two adjacent first velvet structures on the light-facing surface of the silicon substrate 1, subtracting the vertex angles of the two adjacent first velvet structures from the vertex angles of the first preset number of pairs of adjacent first velvet structures, and then selecting the maximum absolute value from the absolute values ​​of the first preset number of differences. On the backlight surface of the silicon substrate 1, the vertex angles of adjacent second velvet structures refer to the two vertex angles of the second velvet structures that are closest to each other on the backlight surface of the silicon substrate 1. The absolute value of the maximum difference between the vertex angles of adjacent second velvet structures on the backlight surface of the silicon substrate 1 refers to: from the backlight surface of the silicon substrate 1, a second preset number of pairs of vertex angles of adjacent second velvet structures are selected, and among the second preset number of pairs of vertex angles of adjacent second velvet structures, the vertex angles of the adjacent two second velvet structures are subtracted to obtain a second preset number of differences, and then the largest absolute value is selected from the absolute values ​​of the second preset number of differences.

[0099] It should be noted that there is no limitation on whether the first preset number and the second preset number are equal; they may be equal or unequal. The first preset number and the second preset number may be selected based on actual needs. For example, the first preset number and the second preset number may both be greater than or equal to 3. For another example, the first preset number and the second preset number may both be greater than or equal to 5. The absolute value of the maximum difference between the vertex angles of adjacent first textured structures on the light-facing surface of the silicon substrate 1 and the absolute value of the maximum difference between the vertex angles of adjacent second textured structures on the backlight surface of the silicon substrate 1 are not specifically limited.

[0100] Optionally, referring to Figures 2 to 6, the first velvet structure includes: a number of first-class pyramid structures, for example, in Figure 2, a first-class pyramid structure outlined by red lines, the first-class pyramid structure includes: a cone surface and a cone top 11. Optionally, referring to Figures 7 to 9, the second velvet structure includes: a number of second-class pyramid structures, for example, in Figure 7, a second-class pyramid structure outlined by red lines, the second-class pyramid structure includes: a cone surface and a cone top 11. The definition of the cone top 11 refers to the above description and will not be repeated here. In the first-class pyramid structure, the cone surface of the first-class pyramid structure is the set of all side surfaces of the first-class pyramid structure, that is, all surfaces of the first-class pyramid structure except the bottom surface and the cone top 11. The cone surface of the first-class pyramid structure connects its cone top 11 and the bottom contour line, and the bottom contour line is the bottommost contour line of the first-class pyramid structure. In the second type of pyramid structure, the cone surface of the second type of pyramid structure is the collection of all side surfaces of the second type of pyramid structure, that is, all surfaces of the second type of pyramid structure except the base surface and the cone apex 11. The cone surface of the second type of pyramid structure connects its cone apex 11 and the bottom contour line, and the bottom contour line is the bottommost contour line of the second type of pyramid structure.

[0101] Undulation primarily refers to the degree of undulation caused by relatively large surface elevations and depressions, while roughness refers to the degree of unevenness caused by micro-protrusions and micro-depressions on the surface. Optionally, the undulation of the first-type pyramidal structure is greater than that of the second-type pyramidal structure, or the roughness of the first-type pyramidal structure is greater than that of the second-type pyramidal structure. In one case, the number of protrusions and / or depressions on the conical surface of the first type of pyramidal structure may be greater than the number of protrusions and / or depressions on the conical surface of the second type of pyramidal structure; in another case, the degree of protrusions and / or depressions on the conical surface of the first type of pyramidal structure may be greater than the degree of protrusions and / or depressions on the conical surface of the second type of pyramidal structure; in another case, the arrangement of protrusions and / or depressions on the conical surface of the first type of pyramidal structure may be more disorderly than the arrangement of protrusions and / or depressions on the conical surface of the second type of pyramidal structure; in another case, the height of the protrusions and / or the depth of the depressions on the conical surface of the first type of pyramidal structure may be greater than the height of the protrusions and / or the depth of the depressions on the conical surface of the second type of pyramidal structure; furthermore, the conical surface morphology of the first type of pyramidal structure is more irregular, so that the first velvet structure has a larger specific surface area, lower reflectivity, better light trapping effect, can increase short-circuit current, and ultimately improve the photoelectric conversion efficiency of the solar cell, and the appearance of the solar cell is uniform black, which is more beautiful.

[0102] Optionally, the undulation of the first sub-cone surface near the top 11 of the cone surface of the first type of pyramidal structure is greater than the undulation of the second sub-cone surface near the top 11 of the cone surface of the second type of pyramidal structure, or the roughness of the first sub-cone surface is greater than the roughness of the second sub-cone surface. That is to say, the morphology of the upper sub-cone surface near the top 11 of the cone surface of the first type of pyramidal structure is more irregular than the morphology of the sub-cone surface near the top 11 of the cone surface of the second type of pyramidal structure. Specifically, the anti-reflection performance of the part of the light-facing surface of the silicon substrate 1 near the top 11 of the cone has better, and contributes more to the improvement of the photoelectric conversion efficiency of the solar cell. Therefore, in the present application, through the above adjustment, the first velvet structure has a larger specific surface area, lower reflectivity, and better light trapping effect, which can increase the short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. The appearance of the solar cell is uniform black, which is more beautiful. In one case, the number of protrusions and / or depressions on the first sub-cone surface near the top of the cone in the cone surface of the first type of pyramid structure may be greater than the number of protrusions and / or depressions on the second sub-cone surface near the top of the cone in the cone surface of the second type of pyramid structure; in another case, the degree of protrusions and / or depressions on the first sub-cone surface near the top of the cone in the cone surface of the first type of pyramid structure may be greater than the degree of protrusions and / or depressions on the second sub-cone surface near the top of the cone in the cone surface of the second type of pyramid structure; in another case, the arrangement of protrusions and / or depressions on the first sub-cone surface near the top of the cone in the cone surface of the first type of pyramid structure may be more disorderly than the arrangement of protrusions and / or depressions on the second sub-cone surface near the top of the cone in the cone surface of the second type of pyramid structure; in another case, the height of the protrusions and / or the depth of the depressions on the first sub-cone surface near the top of the cone in the cone surface of the first type of pyramid structure may be greater than the height of the protrusions and / or the depth of the depressions on the second sub-cone surface near the top of the cone in the cone surface of the second type of pyramid structure.

[0103] Optionally, referring to Figures 2 to 6, the first type of pyramid structure is composed of a lower portion and an upper portion, the lower portion being the portion of the first type of pyramid structure away from the apex 11, the upper portion being the portion of the first type of pyramid structure close to the apex 11 and the apex, or being the portion of the first type of pyramid structure excluding the lower portion, the height of the lower portion being at least 1 / 10 of the height of the first type of pyramid structure, the first sub-cone surface close to the apex of the first type of pyramid structure is: the area corresponding to the upper portion in the conical surface of the first type of pyramid structure. Optionally, referring to Figures 7 to 10, the second type of pyramid structure is composed of a lower portion and an upper portion, the lower portion being the portion of the second type of pyramid structure away from the apex 11, the upper portion being the portion of the second type of pyramid structure close to the apex 11 and the apex, or being the portion of the second type of pyramid structure excluding the lower portion, the height of the lower portion being at least 1 / 10 of the height of the second type of pyramid structure, and the second sub-cone surface is: the area corresponding to the upper portion in the conical surface of the second type of pyramid structure. Specifically, the second sub-cone surface and the first sub-cone surface are divided more accurately here, which is beneficial to the first velvet structure and the second velvet structure to ensure that the lower part of the pyramid-like structure accounts for a certain proportion during the preparation process, thereby ensuring the passivation requirements of the lower part of the pyramid-like structure. By having the upper and lower parts of the pyramid-like structure each occupy a certain proportion and having different morphology settings, a better light trapping effect in the upper part and a better passivation effect in the lower part are achieved. The cone surface morphology fluctuation / roughness of the upper part of the first type pyramid structure and the second type pyramid structure is larger, so that the reflectivity of the upper part of the first type pyramid structure and the second type pyramid structure is lower and the light trapping effect is better, which can increase the short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell, and the appearance of the solar cell is uniformly black, which is more beautiful, and the cone surface morphology of the lower part of the first type pyramid structure and the second type pyramid structure is relatively flat, which is conducive to the preparation of a thicker back passivation anti-reflection layer, thereby achieving a good passivation effect. In this article, regarding the proportion of the height of the lower part of the pyramid-like structure, it should be understood that as long as the height of the lower part of most of the pyramid-like structures in the velvet structure meets the above-mentioned proportion, the above-mentioned effect can be achieved. For a single pyramid-like structure, the situation of the part adjacent to the pyramid-like structure in the silicon substrate is relatively complicated, and usually has more defects (such as holes, surface recombination centers, etc.). The situation of the position adjacent to adjacent pyramid-like structures is also relatively complicated, and usually has more defects (such as holes, surface recombination centers, etc.). Therefore, these positions away from the top of the cone (such as the bottom of the pyramid-like structure) require a thicker passivation anti-reflection layer to achieve a better passivation effect, but these positions have a lower demand for anti-reflection; while the positions at or near the top of the cone (such as the top of the pyramid-like structure) usually have fewer defects. Therefore, these positions only require a thinner passivation anti-reflection layer to achieve a better passivation effect, but these positions have a greater demand for anti-reflection.The undulation / roughness of the pyramid-like structure near the top of the cone is greater. On the one hand, the greater undulation / roughness near the top of the cone can achieve lower reflectivity and better light trapping effect of this part of the structure; on the other hand, the thickness of the passivation anti-reflection layer deposited on this part is different, so after the light enters the passivation anti-reflection layer of different thicknesses, the optical path of the light will change more times, which can increase the optical path. In combination with the velvet structure of the present application, the absorption of light can be further increased, and the light trapping effect is better. The pyramid-like structure is relatively flat away from the top of the cone, which is conducive to the preparation of a thicker back passivation anti-reflection layer, thereby achieving a good passivation effect. In addition, the light-facing side and the backlight side have different requirements for passivation and anti-reflection, so the undulation / roughness requirements of the single pyramid-like structure near the top of the cone are different. The undulation / roughness of the single pyramid-like structure near the top of the cone on the light-facing side is greater.

[0104] For example, the portion of the first-type pyramid structure away from the apex 11 is the lower portion of the first-type pyramid structure, and the height of the lower portion is 1 / 10, 2 / 15, 3 / 20, 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5, or 1 / 4 of the height of the first-type pyramid structure. The first-type pyramid structure consists of an upper portion and a lower portion. The first sub-cone surface of the first-type pyramid structure, near its apex 11, is the area corresponding to the upper portion of the first-type pyramid structure.

[0105] For example, the portion of the second-type pyramid structure away from the apex 11 is the lower portion of the second-type pyramid structure, and the height of the lower portion is 1 / 10, 2 / 15, 3 / 20, 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5, or 1 / 4 of the height of the second-type pyramid structure. The second-type pyramid structure consists of an upper portion and a lower portion. The second sub-cone surface of the second-type pyramid structure, near its apex 11, is the area corresponding to the upper portion of the second-type pyramid structure.

[0106] Optionally, the first type of pyramid structure consists of a lower part and an upper part, and the part of the first type of pyramid structure away from the apex 11 is the lower part of the first type of pyramid structure, and the height of the lower part is at least 1 / 5 of the height of the first type of pyramid structure. In the cone surface of the first type of pyramid structure, the first sub-cone surface close to the apex 11 is the area corresponding to the upper part of the cone surface of the first type of pyramid structure. The second type of pyramid structure consists of a lower part and an upper part, and the part of the second type of pyramid structure away from the apex 11 is the lower part of the second type of pyramid structure, and the height of the lower part is at least 1 / 5 of the height of the second type of pyramid structure. In the cone surface of the second type of pyramid structure, the second sub-cone surface close to the apex 11 is the area corresponding to the upper part of the cone surface of the second type of pyramid structure. The technical effects that can be achieved by more accurately dividing the first sub-cone surface and the second sub-cone surface are as described above.

[0107] For example, the first type of pyramid structure consists of a lower part and an upper part. The part of the first type of pyramid structure away from the top 11 is the lower part of the first type of pyramid structure, and the height of the lower part is 1 / 5, or 1 / 4, or 3 / 10, or 2 / 5, or 1 / 3, or 1 / 2, or 3 / 5 of the height of the first type of pyramid structure.

[0108] For example, the second-type pyramid structure consists of a lower part and an upper part. The part of the second-type pyramid structure away from the top 11 is the lower part of the second-type pyramid structure, and the height of the lower part is 1 / 5, or 1 / 4, or 3 / 10, or 2 / 5, or 1 / 3, or 1 / 2, or 3 / 5 of the height of the second-type pyramid structure.

[0109] Optionally, referring to Figure 6, the first type of pyramid structure also includes: a bottom contour line 13 away from the top of the cone. Referring to Figures 2 to 4, and Figure 6, the width of the first type of pyramid structure is the maximum internal dimension of the bottom contour line 13 of the first type of pyramid structure. Referring to Figure 10, the second type of pyramid structure also includes: a bottom contour line 13 away from the top of the cone. Referring to Figures 7 to 10, the width of the second type of pyramid structure is the maximum internal dimension of the bottom contour line 13 of the second type of pyramid structure. The ratio of the height of the first type of pyramid structure to the width of the first type of pyramid structure is greater than the ratio of the height of the second type of pyramid structure to the width of the second type of pyramid structure. That is, the first type of pyramid structure has a larger aspect ratio, and the first velvet structure is sharper, which makes the first velvet structure have a larger specific surface area, that is, the reflectivity of the light-facing surface of the silicon substrate 1 is lower and the light trapping effect is better, which can increase the short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. The appearance of the solar cell is uniform black and more beautiful. At the same time, the thickness of the front passivation anti-reflection layer prepared on the first velvet structure is also relatively appropriate, which can meet the passivation requirements of the light-facing surface of the silicon substrate 1 and avoid material waste. The second type of pyramid structure has a smaller aspect ratio, and the second velvet structure is flatter, which is conducive to the preparation of a thicker back passivation anti-reflection layer, thereby achieving a good passivation effect.

[0110] The ratio of the height of the first-type pyramid structure to the width of the first-type pyramid structure is greater than the ratio of the height of the second-type pyramid structure to the width of the second-type pyramid structure. This may mean that the ratio of the height of all first-type pyramid structures in the first velvet structure to the width of each corresponding first-type pyramid structure is greater than the ratio of the height of all second-type pyramid structures in the second velvet structure to the width of each corresponding second-type pyramid structure. Alternatively, this may mean that the ratio of the height of the first-type pyramid structures in a seventh predetermined proportion of the total number of all first-type pyramid structures in the first velvet structure to the width of each corresponding first-type pyramid structure is greater than the ratio of the height of the second-type pyramid structures in an eighth predetermined proportion of the total number of second-type pyramid structures in the second velvet structure to the width of each corresponding second-type pyramid structure. The seventh and eighth predetermined proportions herein may be greater than or equal to 50%, and may be equal to or unequal to each other.

[0111] Referring to Figure 5 , the surface of the first-type pyramid structure has a branched texture 12. Optionally, both the first-type pyramid structure and the second-type pyramid structure have branched textures, with the number of branched textures on the first-type pyramid structure being greater than the number of branched textures on the second-type pyramid structure. Alternatively, the first-type pyramid structure has a branched texture, while the second-type pyramid structure does not. The shape of the branched texture 12 resembles a branch, i.e., a forked pattern on a main trunk. There is a corresponding relationship between the branched texture 12 and the protrusions or depressions on the cone surface of the pyramid-like structure. The branched texture 12 is usually located at the junction of the protrusions and depressions on the cone surface of the pyramid-like structure, that is, the more branched textures 12 there are, the more protrusions and depressions there are on the cone surface of the pyramid-like structure. Therefore, the more textures of the first-type pyramid structure, the larger the specific surface area of ​​the first velvet structure, and the more irregular the distribution position of the above-mentioned branched texture, so that the first velvet structure can have a larger specific surface area, lower reflectivity, better light trapping effect, can increase short-circuit current, and ultimately improve the photoelectric conversion efficiency of the solar cell, and the appearance of the solar cell is uniform black, which is more beautiful.

[0112] Optionally, the front passivation anti-reflection layer 2 includes: a first part located on the first velvet structure, and the back passivation anti-reflection layer includes: a second part located on the second velvet structure, the thickness of the first part is less than the thickness of the second part, the light-facing surface of the solar cell has a greater demand for anti-reflection and a relatively smaller demand for passivation, and the first velvet structure is sharper, so the thickness of the first part of the front passivation anti-reflection layer 2 located on the first velvet structure is smaller, the light-facing surface of the solar cell has better anti-reflection performance and relatively weak passivation performance, which is more consistent with the light-facing surface anti-reflection and passivation requirements of the solar cell, can increase the short-circuit current, and ultimately improve the photoelectric conversion efficiency of the solar cell, and the appearance of the solar cell is uniformly black, more beautiful, and can avoid waste. The backlight side of the solar cell has a relatively small demand for anti-reflection, but a greater demand for passivation. The second velvet structure is flatter, so the thickness of the second portion of the back passivation anti-reflection layer 3 located on the second velvet structure is larger, the backlight side of the solar cell has better passivation performance, and the anti-reflection performance is relatively weak, which is more consistent with the backlight side anti-reflection and passivation requirements of the solar cell. It can increase the short-circuit current, and ultimately improve the photoelectric conversion efficiency of the solar cell. The appearance of the solar cell is uniform black, which is more beautiful and can avoid waste. At the same time, in the present application, after light enters the passivation anti-reflection layer of different thicknesses, the optical path of the light will change more times, which can increase the optical path. In combination with the velvet structure of the present application, the absorption of light can be further increased, the light trapping effect is better, the short-circuit current can be further increased, and the photoelectric conversion efficiency of the solar cell can be further improved. The appearance of the solar cell is uniform black, which is more beautiful. The direction of the thickness here is perpendicular to the tangent at the corresponding position on the outer surface of the passivation anti-reflection layer.

[0113] Optionally, the backlight surface of the silicon substrate 1 has a non-velvet structure, and the back passivation anti-reflection layer 3 includes: a second portion located on the second velvet structure, and a third portion located on the non-velvet structure, the thickness of the second portion is less than the thickness of the third portion. Specifically, the non-velvet structure is smoother than the second velvet structure, making it easier to prepare a thicker back passivation anti-reflection layer 3. At the same time, in the present application, after light enters the passivation anti-reflection layers of different thicknesses, the optical path of the light will change more times, which can increase the optical path. Combined with the velvet structure of the present application, the absorption of light can be further increased, the light trapping effect is better, the short-circuit current can be further increased, and the photoelectric conversion efficiency of the solar cell can be further improved. The appearance of the solar cell is uniform black, which is more beautiful.

[0114] Optionally, the thickness of the first part, the thickness of the second part, and the thickness of the third part are in a relationship such that the thickness of the third part is the largest, the thickness of the second part is the second largest, or is between the thickness of the first part and the thickness of the second part, and the thickness of the first part is the smallest. On the one hand, it can ensure that each position has an excellent passivation effect, and the present application sets the thickness of the passivation anti-reflection layer according to the passivation requirements, which can reduce material waste. At the same time, in the present application, after the light enters the passivation anti-reflection layer of different thicknesses, the light path of the light will change more times, which can increase the optical path. In combination with the velvet structure of the present application, the absorption of light can be further increased, the light trapping effect is better, the short-circuit current can be further increased, and the photoelectric conversion efficiency of the solar cell can be further improved. The appearance of the solar cell is uniformly black, which is more beautiful. In summary, the present application not only ensures the excellent passivation effect of each part of the solar cell, but also greatly improves the anti-reflection effect, while also reducing material waste.

[0115] The front passivation anti-reflection layer 2 includes a first portion located on a first velvet structure, and the back passivation anti-reflection layer 3 includes a second portion located on a second velvet structure. The thickness unevenness of the first portion is calculated as follows: the absolute value of the difference between two thicknesses at two locations along the same direction toward the apex of the first-class pyramid structure in the front passivation anti-reflection layer, divided by the sum of the two thicknesses. The two locations are defined as any two locations along the same direction toward the apex 11 of the pyramid structure. For example, the three first-class pyramid structures in the first velvet structure are the left first-class pyramid structure, the middle first-class pyramid structure, and the right first-class pyramid structure. In the three first-class pyramid structures in the first velvet structure, the thickness unevenness of the first portion can be calculated as follows: the absolute value of the difference between two thicknesses at two locations along the same direction toward the apex of the first-class pyramid structure on the left side of the front passivation anti-reflection layer 2, divided by the sum of the two thicknesses. For another example, in the three first-type pyramid structures in the first velvet structure, the thickness unevenness of the first portion may be: the absolute value of the difference between two thicknesses at two positions along the same direction toward the apex of the first-type pyramid structure on the left side in the front passivation anti-reflection layer 2, divided by the sum of the two thicknesses. For another example, in the three first-type pyramid structures in the first velvet structure, the thickness unevenness of the first portion may be: the absolute value of the difference between two thicknesses at two positions along the same direction toward the apex of the first-type pyramid structure on the left side in the front passivation anti-reflection layer 2, divided by the sum of the two thicknesses. For another example, in the three first-type pyramid structures in the first velvet structure, the thickness unevenness of the first portion may be: the absolute value of the difference between two thicknesses at two positions along the same direction toward the apex of the first-type pyramid structure on the right side in the middle side in the front passivation anti-reflection layer 2, divided by the sum of the two thicknesses. For another example, in the three first-type pyramid structures in the first velvet structure, the thickness unevenness of the first portion may be: the absolute value of the difference between two thicknesses at two positions along the same direction toward the pyramid apex in the left portion of the first-type pyramid structure on the right side of the front passivation anti-reflection layer 2, divided by the sum of the two thicknesses. For another example, in the three first-type pyramid structures in the first velvet structure, the thickness unevenness of the first portion may be: the absolute value of the difference between two thicknesses at two positions along the same direction toward the pyramid apex in the right portion of the first-type pyramid structure on the right side of the front passivation anti-reflection layer 2, divided by the sum of the two thicknesses.

[0116] The thickness nonuniformity of the second portion is: the absolute value of the difference between two thicknesses at two locations along the same direction toward the apex of the second-type pyramid structure in the back-surface passivation anti-reflection layer 3, divided by the sum of the two thicknesses. The two locations here are defined as any two locations along the same direction toward the apex 11. The thickness nonuniformity of the second portion corresponds to the example described above for the thickness nonuniformity of the first portion of the three first-type pyramid structures in the first textured structure.

[0117] Optionally, the thickness unevenness of the first part is greater than the thickness unevenness of the second part, that is, in the back passivation anti-reflection layer 3, the thickness of the part located on the second velvet structure on the backlight side of the silicon substrate 1 is more uniform, which can ensure that all positions on the backlight side of the silicon substrate 1 have excellent passivation effect, and the present application sets the thickness of the passivation anti-reflection layer according to the passivation requirements, which can reduce material waste.

[0118] It should be noted that, when the thickness unevenness of the first portion is greater than the thickness unevenness of the second portion, the difference between the two is not specifically limited.

[0119] Optionally, at two relative positions in the thickness direction of the silicon substrate 1, the difference between the thickness of the back passivation anti-reflection layer 3 and the thickness of the front passivation anti-reflection layer 2 is greater than or equal to 15 nm (nanometers) and less than or equal to 50 nm. The difference between the two is appropriately set to fully ensure excellent passivation performance on the backlight side, and simultaneously obtain good passivation performance and anti-reflection effect on the light-facing side, and avoid waste.

[0120] For example, the thickness of the back passivation anti-reflection layer 3 can be 85 nm to 100 nm, or about 95 nm, and the thickness of the front passivation anti-reflection layer 2 can be 60 nm to 70 nm, or about 65 nm. Here, at two opposite locations in the thickness direction of the silicon substrate 1, the difference between the thickness of the back passivation anti-reflection layer 3 and the thickness of the front passivation anti-reflection layer 2 can be: 15 nm, or 16.3 nm, or 17.9 nm, or 19.4 nm, or 20.94 nm, or 22.6 nm, or 24.92 nm, or 27.5 nm, or 30.3 nm, or 32.6 nm, or 33.9 nm, or 35.7 nm, or 36.9 nm, or 18.34 nm, or 40 nm, or 41.3 nm, or 50 nm.

[0121] Optionally, referring to FIG1 , the backlight surface of the silicon substrate 1 includes: alternating first and second regions, with an isolation region between adjacent first and second regions, that is, a first region, an isolation region, followed by a second region, and then a first region, an isolation region, and a second region, and so on. For example, in FIG1 , in the backlight surface of the silicon substrate 1, the region between the dotted line L1 and the dotted line L2 is the first region, and the region between the dotted line L3 and the dotted line L4 is the second region, and the first region between the dotted line L1 and the dotted line L2 and the second region between the dotted line L3 and the dotted line L4 are adjacent, and the isolation region between the two is the region between the dotted line L2 and the dotted line L3 in the backlight surface of the silicon substrate 1. In FIG1 , the portion outlined by the oval frame contains an isolation region. It should be noted that in FIG1 , the dotted lines L1 to L4 do not actually exist in the solar cell, but are merely schematic diagrams for distinguishing the first region, the second region, and the isolation region. The solar cell also includes: a first conductive layer 4 located on the first area, and a second conductive layer 5 located on the second area. The first conductive layer 4 and the second conductive layer 5 have different conductivity types. One of the first conductive layer 4 and the second conductive layer 5 is p-type and the other is n-type. The solar cell is a back-contact solar cell.

[0122] Optionally, on the backlight surface of the silicon substrate 1, at least one of the first region, the second region, and the isolation region has the aforementioned second velvet structure. Providing the second velvet structure on the backlight surface of the silicon substrate 1 can lower the reflectivity, improve the light trapping effect, and improve the electrical performance of the back-contact solar cell. Furthermore, the location of the second velvet structure is more flexible and diverse. For example, only the first region has the aforementioned second velvet structure. For another example, only the second region has the aforementioned second velvet structure. For another example, only the isolation region has the aforementioned second velvet structure. Then, both the first and second regions are relatively flat, and the formed first conductive layer 4, second conductive layer 5, and back passivation anti-reflection layer 3 are of good quality. No conductive layer is required in the isolation region. Providing the second velvet structure can lower the reflectivity, improve the light trapping effect, and improve the electrical performance of the back-contact solar cell. For another example, both the first and second regions have the aforementioned second velvet structure. For another example, both the second region and the isolation region have the aforementioned second velvet structure. Both the first region and the isolation region have the aforementioned second velvet structure. For another example, the first region, the second region, and the isolation region all have the aforementioned second velvet structure.

[0123] Optionally, referring to Figure 1, the width d1 of the isolation area is 50um (micrometer) to 350um, and the width d1 of the isolation area is parallel to the alternating distribution direction of the first area and the second area. The width d1 of the isolation area is set more reasonably, which not only makes the insulation isolation effect of the first conductive layer 4 and the second conductive layer 5 better, but also avoids wasting space in the back contact solar cell.

[0124] For example, the width d1 of the isolation region may be 50um, or 52um, or 60um, or 63um, or 65.4um, or 77um, or 100um, or 128um, or 176.2um, or 150um, or 183um, or 200um, or 221um, or 250um, or 273.1um, or 286.4um, or 300um, or 307um, or 334um, or 350um.

[0125] Optionally, referring to Figure 1 , the solar cell further comprises: a first electrode 6 located on the first conductive layer 4, and a second electrode 7 located on the second conductive layer 5. Here, the first electrode 6 and the second electrode 7 are both used to collect and conduct carriers.

[0126] Optionally, the backlight surface of the silicon substrate 1 includes alternating first and second regions, i.e., a first region, an isolation region, followed by a second region, and then a first region, an isolation region, and a second region, repeating in this manner. The solar cell also includes a first conductive layer located on the first region, the first conductive layer being doped with a first conductive element, and at least a portion of the second region being doped with a second conductive element, the first conductive element and the second conductive element having different conductivity types, one being p-type and the other being n-type. The solar cell is a back-contact solar cell. The junction of the second and first regions, i.e., the isolation region, has the aforementioned second textured structure. Providing the second textured structure can reduce backside reflectivity, enhance light trapping, and improve the electrical performance of the back-contact solar cell. The junction of the second and first regions, i.e., the isolation region, can provide a certain degree of insulation or isolation. The second conductive element can be doped throughout the second region, or only partially within a portion of the second region, without specific limitation. For example, the first conductive layer can be an n-type conductive layer, the second conductive element can be a p-type conductive element, and an aluminum back field can be formed by aluminum grid lines.

[0127] Optionally, the solar cell is a back-contact solar cell, and the backlight surface of the silicon substrate 1 includes: alternating first and second regions, wherein a first conductive layer is formed on the first region, and a second conductive layer is formed on the second region, wherein the first and second conductive layers have different conductivity types, and the first and second conductive layers at least partially overlap, and an insulating structure is provided between the overlapping portions of the first and second conductive layers, and at least one of the first and second regions may have any of the aforementioned second velvet structures. The above-mentioned different conductivity types may, in some cases, have p-type doping and n-type doping, respectively.

[0128] Optionally, the solar cell is a back-contact solar cell, wherein the backlight surface of the silicon substrate 1 includes alternating n-type and p-type regions, wherein the n-type regions are used to collect and conduct electrons, and an isolation region is provided between adjacent n-type and p-type regions. The isolation region has any of the aforementioned second velvet structures. Optionally, the backlight surface of the silicon substrate 1 includes alternating n-type and p-type regions, wherein the p-type regions have any of the aforementioned second velvet structures, and the light-facing surface of the silicon substrate 1 has any of the aforementioned first velvet structures.

[0129] Optionally, the solar cell may further include: a first conductive layer located between the silicon substrate 1 and the front-side passivation anti-reflection layer; and a second conductive layer located between the silicon substrate 1 and the back-side passivation anti-reflection layer; the first conductive layer and the second conductive layer having different conductivity types, one being n-type and the other being p-type. The entire backlight side of the silicon substrate 1 has the aforementioned second textured structure, and the solar cell is a bifacial cell.

[0130] The present application also provides a photovoltaic module, which includes: a number of any of the aforementioned solar cells. There is no specific limitation on the number of solar cells in the photovoltaic module. The photovoltaic module may also include an encapsulation film located on both sides of the solar cell, etc. There is no specific limitation on other structures of the photovoltaic module.

[0131] The present application also provides a method for preparing a solar cell, which is used to prepare any of the aforementioned solar cells. The method comprises:

[0132] Step 101: Provide a silicon substrate; the silicon substrate includes a light-facing surface and a backlight surface.

[0133] Step 102: Texturing the silicon substrate to form a first textured surface structure on the light-facing surface of the silicon substrate and a second textured surface structure on at least a portion of the backlight surface of the silicon substrate; the apex angle of the second textured surface structure is greater than the apex angle of the first textured surface structure.

[0134] Here, the light-facing side and the backlight side of the silicon substrate can be textured separately, and the first texture structure and the second texture structure can be obtained by different texture times of the light-facing side and the backlight side, or the first texture structure and the second texture structure can be obtained by adjusting the composition and / or concentration of the texture liquid for the separate texture. The texture result can also be controlled by combining the adjustment of the time and the adjustment of the composition and / or concentration of the texture liquid. Here, the texture time, the composition and concentration of the texture liquid can also be regulated, etc., and there is no specific limitation on this. Alternatively, the light-facing side and the backlight side of the silicon substrate can be obtained in the same texture process, and the first texture structure and the second texture structure can be obtained by setting a texture protection layer and / or controlling the placement of the silicon substrate in the texture liquid.

[0135] Optionally, the aforementioned step 102 may include: separately texturing the light-facing surface and the backlight surface of the silicon substrate, so that the texturing time of at least a part of the backlight surface of the silicon substrate is shorter than the texturing time of the light-facing surface of the silicon substrate; and / or, providing a texturing protective layer on at least a part of the backlight surface of the silicon substrate, and texturing the silicon substrate, so that under the blocking effect of the texturing protective layer, the texturing time of at least a part of the backlight surface of the silicon substrate is shorter than the texturing time of the light-facing surface of the silicon substrate; and / or, placing the silicon substrate at an angle in the texturing liquid, so that at two relative positions in the thickness direction of the silicon substrate, the light-facing surface of the silicon substrate is closer to the liquid surface of the texturing liquid than the backlight surface, and texturing the silicon substrate.

[0136] Specifically, texturing, providing a texturing protective layer, and tilting the silicon substrate can be performed one by one, two by two, or all three, without specific limitation.

[0137] Differentiation in the preparation of the front and back velvet surfaces can be achieved by controlling the velvet preparation time of the light-facing side of the silicon substrate and making a difference between the velvet preparation time of at least part of the backlight side of the silicon substrate. For example, this can be achieved through the following different preparation methods: for example, the velvet surfaces of the light-facing side and the backlight side can be prepared separately; for example, a velvet preparation protective layer that can be etched by the velvet preparation liquid can be set on the backlight side, and the velvet preparation protective layer must be corroded on the backlight side before it can contact the silicon substrate for velvet preparation, so the actual velvet preparation time of the backlight side is shorter than that of the light-facing side; for example, the silicon substrate can be tilted and placed in the velvet preparation tank with the light-facing side facing up and the backlight side facing down. In the thickness direction of the silicon substrate, the light-facing side of the silicon substrate at two relative positions is closer to the liquid surface of the velvet preparation liquid than the backlight side. Therefore, the light-facing side exhausts faster than the backlight side, and the velvet preparation liquid reacts with the silicon substrate earlier and faster to achieve a difference in velvet preparation time; a combination of one or more of the above methods can also be used.

[0138] In the separate texturing method, on the basis that the texturing time of at least a portion of the backlight surface of the silicon substrate is shorter than the texturing time of the light-facing surface of the silicon substrate, other texturing factors are not limited. For example, whether the texturing liquid of at least a portion of the backlight surface of the silicon substrate is the same as the texturing liquid of the light-facing surface of the silicon substrate in terms of composition and concentration is not specifically limited, and the composition and concentration of the two texturing liquids here can be the same or different. For another example, in the process of texturing a surface, the angle between the direction of the thickness of the silicon substrate and the liquid surface of the texturing liquid is not limited. The difference between the two texturing times, the top angle of the first texturing structure, the top angle of the second texturing structure, etc. can be adjusted by adjusting the texturing factors such as the composition and concentration of the two texturing liquids and the angle between the direction of the thickness of the silicon substrate and the liquid surface of the texturing liquid, and there is no specific limitation on this. In the separate texturing method, in the process of texturing one of the two surfaces, the light-facing surface and the backlight surface, the other surface can be provided with a mask layer, etc.

[0139] Regarding the method of setting up a texturing protective layer, the texturing protective layer here refers to: a protective layer that can be etched by a texturing liquid. On the backlight side of the silicon substrate, the texturing liquid first etches the texturing protective layer to expose at least a portion of the backlight surface of the silicon substrate, and then texturing can be performed on at least a portion of the exposed backlight surface of the silicon substrate. On the light-facing side of the silicon substrate, the light-facing surface of the silicon substrate is exposed, and the texturing liquid directly texturings the light-facing surface of the silicon substrate. Therefore, the texturing time of at least a portion of the backlight surface of the silicon substrate will be shorter than the texturing time of the light-facing surface of the silicon substrate, so as to form a first texturing structure on the light-facing surface of the silicon substrate, and form a second texturing structure on at least a portion of the backlight surface of the silicon substrate. The top angle of the second texturing structure is greater than the top angle of the first texturing structure.

[0140] Regarding the method of setting the texturing protective layer, the material and thickness of the texturing protective layer are not specifically limited. As long as it can react with the texturing liquid and dissolve in the texturing liquid, the materials that can be selected can be silicon dioxide, phosphosilicate glass, borosilicate glass, silicon nitride, etc.; and for the selection of thickness, it is necessary to comprehensively consider the rate at which the texturing protective layer and the texturing liquid disappear, so as to achieve the required time difference. Texturing factors such as the composition and concentration of the texturing liquid, the angle between the direction of the thickness of the silicon substrate and the liquid surface of the texturing liquid, etc. are not specifically limited. The difference between the two texturing time lengths, the top angle of the first velvet structure, the top angle of the second velvet structure, etc. can be adjusted by adjusting the composition and concentration of the texturing liquid, the angle between the direction of the thickness of the silicon substrate and the liquid surface of the texturing liquid, the material and thickness of the texturing protective layer, etc. There is no specific limitation on this.

[0141] Regarding the method of placing the silicon substrate obliquely in the texturing liquid, since at two relative positions in the thickness direction of the silicon substrate, the light-facing surface of the silicon substrate is closer to the liquid surface of the texturing liquid than the backlight surface, on the one hand, gas will be produced in the texturing process. At two relative positions in the thickness direction of the silicon substrate, the distance between the light-facing surface of the silicon substrate and the texturing liquid surface is closer than the distance between the backlight surface of the silicon substrate and the texturing liquid surface. The gas produced by the texturing of the light-facing surface of the silicon substrate overflows from the texturing liquid surface faster, and the texturing reaction proceeds faster, so it is easy to The aforementioned first velvet structure and second velvet structure are obtained. On the other hand, when the silicon substrate enters the texturing liquid, it will carry air. At two relative positions in the thickness direction of the silicon substrate, the distance between the light-facing surface of the silicon substrate and the texturing liquid surface is closer than the distance between the backlight surface of the silicon substrate and the texturing liquid surface. The air on the backlight surface of the silicon substrate is less likely to be discharged, so the start time of the texturing reaction on the backlight surface of the silicon substrate will be later than the start time of the texturing reaction on the light-facing surface of the silicon substrate. Therefore, it is also easy to obtain the aforementioned first velvet structure and second velvet structure. The difference is particularly significant when the surface of the silicon substrate is uneven. For example, for back-contact solar cells, the backlight side of the silicon substrate may have certain grooves on the backlight side before texturing due to doping. The presence of this groove structure causes more air to be carried in the groove structure when the silicon substrate enters the texturing liquid, and the gas generated during the reaction is more likely to remain in the groove position. The narrower and deeper the groove is, the longer it may take for the air carried and the gas generated by the reaction to be discharged from the texturing liquid surface, so it is also easier to prepare the aforementioned first and second texturing structures. For example, for HPBC (composite passivated back-contact solar cell) and TBC (polycrystalline silicon back-contact solar cell), the grooves on the backlight side of the silicon substrate in TBC may be narrower. Therefore, when the silicon substrate enters the texturing liquid, the air carried in the groove structure of TBC and the gas generated by the reaction may take longer to be discharged from the texturing liquid, so it is easier to obtain a texturing surface with differentiation between the front and back sides.

[0142] There are no specific restrictions on whether the silicon substrate is placed obliquely in the texturing liquid, whether a texturing protective layer is provided, or the material and thickness of the texturing protective layer. There are no specific restrictions on texturing factors such as the composition and concentration of the texturing liquid, the angle between the thickness of the silicon substrate and the liquid surface of the texturing liquid, etc. The difference between the two texturing times, the top angle of the first and second texturing structures, etc. can be adjusted by adjusting the composition and concentration of the texturing liquid, the angle between the thickness of the silicon substrate and the liquid surface of the texturing liquid, the material and thickness of the texturing protective layer, etc. There are no specific restrictions on this.

[0143] Step 103 : preparing a front passivation anti-reflection layer on the light-facing side of the silicon substrate, and preparing a back passivation anti-reflection layer on the backlight-facing side of the silicon substrate.

[0144] The front passivation anti-reflection layer and the back passivation anti-reflection layer can be prepared by deposition or other methods, which are not specifically limited.

[0145] Optionally, on the basis that the texturing time of at least a part of the backlight surface of the silicon substrate is shorter than the texturing time of the light-facing surface of the silicon substrate, the difference between the texturing time of the light-facing surface of the silicon substrate and the texturing time of at least a part of the backlight surface of the silicon substrate is 30 seconds to 200 seconds. Within the range of the time difference, the morphologies of the first velvet structure and the second velvet structure obtained meet the corresponding passivation and anti-reflection requirements. The difference in texturing time is applicable to the above-mentioned three methods of texturing separately, setting a texturing protective layer, and tilting the silicon substrate. For example, for the two methods of texturing separately and setting a texturing protective layer, the difference between the texturing time of the light-facing surface of the silicon substrate and the texturing time of at least a part of the backlight surface of the silicon substrate can be 50 seconds to 200 seconds. With respect to the method of placing the silicon substrate at an angle, due to this placement of the silicon substrate, it is easier to obtain the aforementioned first velvet structure and second velvet structure. Therefore, in the case of a method including placing the silicon substrate at an angle, the difference between the texturing time of the light-facing surface of the silicon substrate and the texturing time of at least a portion of the backlight surface of the silicon substrate can be slightly smaller within the range of 30 seconds to 200 seconds. However, in the case of a method including placing the silicon substrate at an angle, due to differences in texturing factors such as whether a texturing protective layer is provided, the material and thickness of the texturing protective layer, the composition and concentration of the texturing liquid, and the angle between the direction of the thickness of the silicon substrate and the liquid surface of the texturing liquid, the difference between the texturing time of the light-facing surface of the silicon substrate and the texturing time of at least a portion of the backlight surface of the silicon substrate varies within the range of 30 seconds to 200 seconds.

[0146] For example, for at least one of the above-mentioned separate texturing, setting of texturing protective layer, and tilted placement of silicon substrate, on the basis that the texturing time of at least part of the backlight surface of the silicon substrate is shorter than the texturing time of the light-facing surface of the silicon substrate, the difference between the texturing time of the light-facing surface of the silicon substrate and the texturing time of at least part of the backlight surface of the silicon substrate can be 30 seconds, 33 seconds, 40 seconds, 46 seconds, 50 seconds, or 55 seconds, or 60 seconds, or 72 seconds, or 89 seconds, or 100 seconds, or 111 seconds, or 126 seconds, or 125 seconds, or 150 seconds, or 175 seconds, or 187 seconds, or 200 seconds.

[0147] It should be noted that, for a method involving placing the silicon substrate at an angle, the difference between the texturing time of the light-facing surface of the silicon substrate and the texturing time of at least a portion of the backlight surface of the silicon substrate may include the following two components: one is the difference in discharge time between the air on the light-facing surface of the silicon substrate and the air on at least a portion of the backlight surface of the silicon substrate, which will be carried with the air when the silicon substrate enters the texturing liquid; the other is the difference in texturing time caused by the different discharge rates of the reaction gas in the texturing reaction between the light-facing surface of the silicon substrate and at least a portion of the backlight surface of the silicon substrate.

[0148] Optionally, for the method of tilting the silicon substrate, the angle between the thickness direction of the silicon substrate and the liquid surface of the texturing liquid is 3° to 7°, and the vertex angle of the first texturing structure in the aforementioned angle range and the vertex angle of the second texturing structure in the aforementioned angle range are easily formed within this angle range. Under the same conditions, the larger the tilt angle, the greater the impact on the texturing of the front and back sides, and the greater the difference in the texturing of the front and back sides. For example, for the method of tilting the silicon substrate, the angle between the thickness direction of the silicon substrate and the liquid surface of the texturing liquid can be 3°, or 3.1°, or 3.7°, or 3.92°, or 4°, or 4.2°, or 4.5°, or 5°, or 5.6°, or 5.9°, or 6.3°, or 6.5°, or 6.9°, or 7°. The method of forming a certain angle between the thickness direction of the silicon substrate and the liquid surface of the texturing liquid can be achieved by tilting a single silicon substrate, or by tilting the entire tooling that carries the silicon substrate, such as a large flower basket.

[0149] It should be noted that for both the separate texturing and protective texturing layer methods described above, there is no specific limitation on the angle between the thickness of the silicon substrate and the surface of the texturing liquid during texturing. For example, the angle between the thickness of the silicon substrate and the surface of the texturing liquid can be less than 3°, or can be between 3° and 7°.

[0150] Optionally, before the aforementioned step 102, the method may further include: polishing the silicon substrate to form a smooth and clean surface, which may be achieved by alkali polishing or the like, and the specific polishing method is not limited. After polishing, referring to FIG11 , a whole layer of the first conductive layer 4 is prepared on the backlight surface of the silicon substrate. Referring to FIG13 , the portion of the first conductive layer 4 located on the second region and the isolation region is patterned so that the second region and the isolation region are exposed. Referring to FIG14 , a second conductive layer is prepared on the second region and the isolation region, as well as on the remaining first conductive layer 4, where the first conductive layer and the second conductive layer have different conductivity types, one being an n-type conductivity type and the other being a p-type conductivity type. Referring to FIG14 , the aforementioned step 102 may include: laser processing the portion of the second conductive layer located on the first region and the isolation region, so that the portion of the second conductive layer located on the first region and the isolation region is oxidized into a texturing protective layer 10, and the texturing protective layer 10 formed by laser oxidation can be etched away by the texturing liquid. Referring to Figure 16, the aforementioned step 102 may include: texturing the silicon substrate 1 to form the aforementioned first textured structure on the light-facing surface of the silicon substrate 1, and at the same time, removing the textured protective layer 10 with a textured liquid, so that the isolation area and the first conductive layer are exposed, and then texturing the isolation area with the textured liquid to form the aforementioned second textured structure in the isolation area on the backlight side of the silicon substrate 1. By etching the textured protective layer 10, the textured time of the isolation area on the backlight side of the silicon substrate 1 can be reduced, thereby simply obtaining the aforementioned first textured structure and second textured structure. The textured liquid will basically not etch the exposed first conductive layer.

[0151] Optionally, in the aforementioned laser processing: the laser includes: one of: nanosecond laser, picosecond laser and femtosecond laser. The above laser is easy to obtain, and the textured protective layer 10 obtained by oxidizing the part of the second conductive layer located on the first area and the isolation area is more suitable for reducing the textured time of the isolation area on the backlight surface of the silicon substrate 1, and it is easy to obtain any of the aforementioned first textured structure and second textured structure.

[0152] Optionally, in the aforementioned laser processing: the laser power is 10W (watts) to 100W, and the laser power is relatively appropriate, which not only makes the texturing time of the isolation area of ​​the backlight surface of the silicon substrate 1 of the oxidized texturing protective layer 10 reduced more appropriately, and is easy to obtain any of the aforementioned first texturing structure and second texturing structure, but also the laser power is relatively appropriate, and almost no laser damage is introduced into the solar cell.

[0153] For example, in the aforementioned laser processing: the laser power can be 10W, or 13W, or 18.2W, or 20W, or 25W, or 30W, or 34.2W, or 40W, or 50W, or 55W, or 63W, or 77W, or 89W, or 100W.

[0154] Optionally, in the aforementioned laser processing: the laser spot diameter is 50um to 350um, the laser spot diameter is relatively appropriate, and the width of the isolation area formed is also roughly 50um to 350um, which not only makes the insulation isolation effect of the first conductive layer 4 and the second conductive layer 5 better, but also avoids wasting space in the back contact solar cell.

[0155] For example, in the aforementioned laser processing: the laser spot diameter can be 50um, or 54um, or 63um, or 77um, or 89um, or 100um, or 144um, or 200um, or 231um, or 250um, or 272um, or 281um, or 300um, or 322um, or 350um.

[0156] The present application is further explained below with reference to specific embodiments.

[0157] Example

[0158] In the first step, a single crystal silicon substrate 1 is subjected to an alkaline polishing treatment using an alkaline solution to form a smooth and clean silicon surface. The backlight surface of the single crystal silicon substrate 1 includes alternating first and second regions, with an isolation region between adjacent first and second regions. The specific type of alkaline solution is not specifically limited; for example, it can be selected from at least one of a sodium hydroxide (NaOH) solution and a potassium hydroxide (KOH) solution.

[0159] In the second step, referring to FIG. 11 , a whole layer of tunnel oxide layer 8 and a whole layer of polysilicon layer are deposited on the surface of the single crystal silicon substrate 1 after alkali polishing.

[0160] In the third step, the deposited polysilicon layer is doped with acceptor impurities such as boron and phosphorus, and donor impurities to form a first conductive layer 4 .

[0161] In the fourth step, referring to FIG12 , the doped single crystal silicon substrate 1 is opened by laser. The laser opening mainly involves irradiating the second region and the isolation region with laser. The first conductive layer 4 at the irradiated region will be broken up.

[0162] In the fifth step, referring to Figure 13, the silicon substrate 1 that has been laser-opened is subjected to surface corrosion treatment, wherein the position irradiated by the laser is corroded, while the position not irradiated by the laser is not corroded, and the area irradiated by the laser is corroded out of the silicon substrate, that is, the part of the first conductive layer 4 located on the second area and the isolation area will be etched away, so that the second area and the isolation area are exposed, and the part of the first conductive layer 4 located on the first area is retained.

[0163] 14, a second conductive layer is formed on the backlight side of the etched silicon substrate 1. The first conductive layer and the second conductive layer have different conductivity types.

[0164] In the seventh step, referring to FIG14 , the silicon substrate 1 after the second conductive layer is formed is subjected to laser patterning. The locations where the P and N isolation regions are to be formed, as well as the first region, are laser patterned to form a weak, textured protective layer 10 that has a certain barrier effect against alkaline corrosion. The laser can be a nanosecond, picosecond, or femtosecond laser, with a laser power of 10-100W and a laser spot diameter of 50-350μm.

[0165] In the eighth step, referring to FIG. 15 , the light-facing surface of the silicon substrate 1 is cleaned by removing the coated polysilicon 14 using a chain acid etching or alkaline etching method, so that the light-facing surface of the silicon substrate 1 becomes the silicon substrate surface.

[0166] In the ninth step, referring to Figure 16 , the light-facing surface of the silicon substrate 1 treated in the eighth step is textured and then etched from the back surface. The angle between the thickness of the silicon substrate and the surface of the texturing solution is less than 3°. The entire light-facing surface of the silicon substrate 1 is textured to form a first textured structure. The back-facing surface, where the laser scan was performed in the seventh step, is first protected by a textured protective layer 10 to avoid alkaline corrosion for a certain period of time. This results in different etching times for the light-facing and back-facing surfaces under the same texturing process. The blocking time of the back-facing surface can be controlled within a certain range through the laser process, achieving an etching time difference of 50-200 seconds. While the light-facing surface utilizes a distributed texturing method and auxiliary additives to adjust the morphology of the first textured structure to achieve a low-reflectivity textured structure, the isolation area on the back-facing surface, protected by the textured protective layer 10, avoids forming a high-specific-surface textured structure and instead forms a second textured structure, thereby preserving the overall passivation performance of the back-facing surface. In the ninth step, the portion of the second conductive layer located above the first region is also etched away.

[0167] In the tenth step, a back passivation anti-reflection layer is formed on the first conductive layer and the second conductive layer, and a front passivation anti-reflection layer is formed on the light-facing side of the silicon substrate.

[0168] Comparative Example

[0169] The comparative example does not include step 7 of the aforementioned embodiment. In step 9 of the comparative example, since there is no protection of the textured protective layer, the textured structures formed in the isolated areas of the light-facing surface and the backlight surface are the same. The remaining steps of the comparative example are the same as those of the embodiment.

[0170] Under the same test environment, the electrical properties of the solar cells of the embodiment and the comparative example were tested. The test results are shown in the table below.

[0171] Comparison table of electrical performance of solar cells of test examples and comparative examples

[0172] In the above table, Eta refers to the photoelectric conversion efficiency, Voc refers to the open circuit voltage, Isc refers to the short circuit current, and FF refers to the conversion factor. It can be concluded from the above table that the photoelectric conversion efficiency, open circuit voltage, short circuit current and conversion factor of the solar cell of the embodiment are all higher than those of the solar cell of the comparative example. The main reason is that, in the embodiment, by adjusting the morphology of the first velvet structure on the light-facing side of the silicon substrate 1 and the second velvet structure on the isolation area of ​​the backlight side, the first velvet structure is made sharper and has a larger specific surface area, that is, the reflectivity of the light-facing side of the silicon substrate is lower and the light trapping effect is better, which can increase the short circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. At the same time, the top angle of the second velvet structure on the backlight side of the silicon substrate is larger, that is, the second velvet structure on the backlight side of the silicon substrate is relatively flat, which is conducive to the preparation of a thicker back passivation anti-reflection layer, thereby achieving a good passivation effect.

[0173] It should be noted that, for the sake of simplicity, the method embodiments are described as a series of action combinations, but those skilled in the art should be aware that the embodiments of the present application are not limited by the order of the actions described, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all optional embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0174] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0175] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus the necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for enabling a terminal (which can be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in each embodiment of the present application.

[0176] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are protected by this application.

Claims

1. A solar cell, characterized in that: include: A silicon substrate, a front passivation anti-reflection layer on the light-facing side of the silicon substrate, and a back passivation anti-reflection layer on the backlight-reflection side of the silicon substrate; The silicon substrate includes: a light-facing surface and a backlight surface; the light-facing surface of the silicon substrate has a first velvet structure, and at least part of the backlight surface of the silicon substrate has a second velvet structure; the apex angle of the second velvet structure is greater than the apex angle of the first velvet structure.

2. The solar cell according to claim 1, wherein The vertex angle of the second velvet structure is greater than or equal to 79°, and the vertex angle of the first velvet structure is less than 79°.

3. The solar cell according to claim 1, wherein The average vertex angle of the second velvet structure is greater than or equal to 85°, and the average vertex angle of the first velvet structure is less than 75°.

4. The solar cell according to claim 1, wherein The absolute value of the maximum difference between the vertex angles of adjacent first veneer structures on the light-facing surface of the silicon substrate is greater than the absolute value of the maximum difference between the vertex angles of adjacent second veneer structures on the backlight surface of the silicon substrate.

5. The solar cell according to claim 1, wherein The first velvet structure includes: a plurality of first-type pyramid structures; the first-type pyramid structures include: a cone surface and a cone top; the second velvet structure includes: a plurality of second-type pyramid structures; the second-type pyramid structures include: a cone surface and a cone top.

6. The solar cell according to claim 5, characterized in that The undulation of the conical surface of the first type of pyramid structure is greater than the undulation of the conical surface of the second type of pyramid structure; Alternatively, the roughness of the cone surface of the first type of pyramid structure is greater than the roughness of the cone surface of the second type of pyramid structure.

7. The solar cell according to claim 5, characterized in that The undulation of the first sub-cone surface close to the apex of the first type of pyramid structure is greater than the undulation of the second sub-cone surface close to the apex of the second type of pyramid structure; Alternatively, the roughness of the first sub-conical surface is greater than the roughness of the second sub-conical surface.

8. The solar cell according to claim 7, characterized in that The first type of pyramid structure consists of a lower part and an upper part, the lower part is a part of the first type of pyramid structure away from the top of the pyramid, and the height of the lower part is at least 1 / 10 of the height of the first type of pyramid structure. The first sub-cone surface is: the area of ​​the cone surface of the first type of pyramid structure corresponding to the upper part; The second type of pyramid structure consists of a lower part and an upper part, the lower part is the part of the second type of pyramid structure away from the top of the cone, the height of the lower part is at least 1 / 10 of the height of the second type of pyramid structure, and the second sub-cone surface is: the area corresponding to the upper part in the cone surface of the second type of pyramid structure.

9. The solar cell according to claim 5, characterized in that The first type of pyramid structure further includes: a bottom contour line away from the top of the pyramid, and the width of the first type of pyramid structure is the maximum inner dimension of the bottom contour line of the first type of pyramid structure; The second type of pyramid structure further includes: a bottom contour line away from the top of the pyramid, and the width of the second type of pyramid structure is the maximum inner dimension of the bottom contour line of the second type of pyramid structure; A ratio of the height of the first type of pyramid structure divided by the width of the first type of pyramid structure is greater than a ratio of the height of the second type of pyramid structure divided by the width of the second type of pyramid structure.

10. The solar cell according to claim 5, characterized in that The conical surface of the first type of pyramid structure and the conical surface of the second type of pyramid structure both have a branched texture, and the number of the branched textures on the conical surface of the first type of pyramid structure is greater than the number of the branched textures on the conical surface of the second type of pyramid structure; Alternatively, the cone surface of the first type of pyramid structure has a branched texture, and the cone surface of the second type of pyramid structure does not have a branched texture.

11. The solar cell according to any one of claims 1 to 10, characterized in that: The front passivation anti-reflection layer includes: a first portion located on the first suede structure; the back passivation anti-reflection layer includes: a second portion located on the second suede structure; The thickness of the first portion is smaller than the thickness of the second portion.

12. The solar cell according to any one of claims 1 to 10, characterized in that: The backlight surface of the silicon substrate has a non-texture structure, and the back passivation anti-reflection layer includes: a second portion located on the second velvet structure, and a third portion located on the non-texture structure; The thickness of the second part is smaller than the thickness of the third part.

13. The solar cell according to any one of claims 1 to 10, characterized in that: The front passivation anti-reflection layer includes: a first portion located on the first velvet structure; the backlight surface of the silicon substrate has a non-velvet structure; the back passivation anti-reflection layer includes: a second portion located on the second velvet structure; and a third portion located on the non-velvet structure. Among the first part, the second part and the third part, the thickness of the first part is the smallest, the thickness of the third part is the largest, and the thickness of the second part is in between.

14. The solar cell according to any one of claims 5 to 10, characterized in that: The front passivation anti-reflection layer includes: a first portion located on the first suede structure; the back passivation anti-reflection layer includes: a second portion located on the second suede structure; The thickness unevenness of the first portion is greater than the thickness unevenness of the second portion; The thickness non-uniformity of the first portion is: the absolute value of the difference between two thicknesses at two positions along the same direction toward the pyramid top in the portion of the front passivation anti-reflection layer located on the same first-type pyramid structure, divided by the sum of the two thicknesses; The thickness non-uniformity of the second portion is: the absolute value of the difference between two thicknesses at two positions along the same direction toward the top of the pyramid in the portion of the back passivation anti-reflection layer located on the same second-type pyramid structure, divided by the sum of the two thicknesses.

15. The solar cell according to any one of claims 1 to 10, characterized in that: In the thickness direction of the silicon substrate, at two opposite positions, the difference between the thickness of the portion of the back passivation anti-reflection layer located on the second velvet structure and the thickness of the front passivation anti-reflection layer is greater than or equal to 15nm and less than or equal to 50nm.

16. The solar cell according to any one of claims 1 to 10, characterized in that: The backlight surface of the silicon substrate comprises: first regions and second regions that are alternately distributed, with an isolation region between adjacent first regions and second regions; The solar cell further comprises: a first conductive layer located on the first region, and a second conductive layer located on the second region; the first conductive layer and the second conductive layer have different conductivity types; In the backlight surface of the silicon substrate, at least one region among the first region, the second region and the isolation region has the second textured structure.

17. The solar cell according to any one of claims 1 to 10, characterized in that: The backlight surface of the silicon substrate includes: a first area and a second area distributed alternately, and the solar cell also includes: a first conductive layer located on the first area, the first conductive layer is doped with a first conductive element, and at least part of the second area is doped with a second conductive element; the first conductive element and the second conductive element have different conductivity types; the part where the second area and the first area intersect has the second velvet structure.

18. The solar cell according to any one of claims 1 to 10, characterized in that: Also includes: a first conductive layer located between the silicon substrate and the front passivation anti-reflection layer, and a second conductive layer located between the silicon substrate and the back passivation anti-reflection layer; The first conductive layer and the second conductive layer have different conductivity types; The entire backlight surface of the silicon substrate has the second textured structure.

19. A photovoltaic module, characterized in that: include: The solar cell according to any one of claims 1 to 18.

20. A method for preparing a solar cell, characterized in that: include: providing a silicon substrate; The silicon substrate comprises: a light-facing surface and a backlight surface; Texturing the silicon substrate to form a first textured surface structure on the light-facing surface of the silicon substrate and a second textured surface structure on at least a portion of the backlight surface of the silicon substrate; the second textured surface structure has a greater top angle than the first textured surface structure; A front passivation anti-reflection layer is prepared on the light-facing side of the silicon substrate, and a back passivation anti-reflection layer is prepared on the backlight-reflection side of the silicon substrate.

21. The method for preparing a solar cell according to claim 20, wherein: Texturing the silicon substrate comprises: The light-facing surface and the backlight surface of the silicon substrate are textured separately, so that the texture time of at least a part of the backlight surface of the silicon substrate is shorter than the texture time of the light-facing surface of the silicon substrate; and / or, A texturing protective layer is provided on at least a portion of the backlight surface of the silicon substrate, and the silicon substrate is texturized. Under the blocking effect of the texturing protective layer, the texturing time of at least a portion of the backlight surface of the silicon substrate is shorter than the texturing time of the light-facing surface of the silicon substrate; and / or, The silicon substrate is placed obliquely in the texturing liquid, and in the thickness direction of the silicon substrate, the light-facing surface of the silicon substrate is closer to the liquid surface of the texturing liquid than the backlight surface at two opposite positions, and the silicon substrate is texturized.

22. The method for preparing a solar cell according to claim 21, wherein: The difference between the texturing time of the light-facing surface of the silicon substrate and the texturing time of at least a portion of the backlight surface of the silicon substrate is 30 seconds to 200 seconds.

23. The method for preparing a solar cell according to claim 21 or 22, characterized in that: The backlight surface of the silicon substrate includes: first areas and second areas that are alternately distributed, and an isolation area is provided between adjacent first areas and second areas; before providing the texturing protective layer on at least a portion of the backlight surface of the silicon substrate, the method further includes: performing a polishing process on the silicon substrate; forming a first conductive layer on the backlight side of the silicon substrate; Performing patterning on a portion of the first conductive layer located on the second region and the isolation region, so that the second region and the isolation region are exposed; forming a second conductive layer on the second region, the isolation region, and the remaining first conductive layer; the first conductive layer and the second conductive layer have different conductivity types; The step of providing a texturing protective layer on at least a portion of the backlight surface of the silicon substrate comprises: performing laser processing on a portion of the second conductive layer located on the first region and the isolation region, so that the portion of the second conductive layer located on the first region and the isolation region is oxidized into the texturing protective layer; The texturing of the silicon substrate, under the blocking effect of the texturing protective layer, is performed for a shorter time on at least a portion of the backlight surface of the silicon substrate than on the light-facing surface of the silicon substrate, so as to form a first textured surface structure on the light-facing surface of the silicon substrate and a second textured surface structure on at least a portion of the backlight surface of the silicon substrate, including: The silicon substrate is textured to form the first textured structure on the light-facing surface of the silicon substrate. At the same time, the textured liquid removes the textured protective layer to expose the isolation area and the first conductive layer. The isolation area is then textured with the textured liquid to form the second textured structure in the isolation area on the backlight side of the silicon substrate.

24. The method for preparing a solar cell according to claim 21 or 22, characterized in that: The silicon substrate is placed obliquely in the texturing liquid, and the angle between the thickness direction of the silicon substrate and the liquid surface of the texturing liquid is 3° to 7°.

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