Solar cell and photovoltaic module

Abstract

The present application relates to the technical field of photovoltaics. Provided are a solar cell and a photovoltaic module. The solar cell comprises a silicon substrate and a passivation and anti-reflection layer located on the silicon substrate, wherein a textured structure is provided on a surface of the silicon substrate, and the textured structure comprises a plurality of pyramid-like structures; each pyramid-like structure comprises a conical surface and a conical top, the conical surface of each pyramid-like structure comprises a first conical sub-surface, which is far away from the conical top, and a second conical sub-surface, and in the conical surface of each pyramid-like structure, the first conical sub-surface and the second conical sub-surface have different surface morphologies; and the passivation and anti-reflection layer comprises a first part located on the first conical sub-surface and a second part located on the second conical sub-surface, and in the passivation and anti-reflection layer, the thickness of the first part is greater than the thickness of the second part in the same direction close to the conical top. The present application can ensure that an excellent passivation effect is achieved at each position, and reduces waste, increases the absorption of light, and has a good light-trapping effect, thereby increasing a short-circuit current and improving the photoelectric conversion efficiency.

Description

Solar cell and photovoltaic module

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on February 7, 2024, with application number 202410175427.9 and titled “A Solar Cell and Photovoltaic Module,” the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] Solar cells use the photovoltaic effect to convert light energy into electrical energy. Since they use clean energy, they have broad application prospects.

[0005] In solar cells, especially on the front side of the cell, functional film layers such as passivation and anti-reflection layers are set. On the one hand, this is to passivate defects, and on the other hand, it is also necessary to obtain a better anti-reflection effect to increase short-circuit current, etc. However, in existing solar cells, the different passivation and anti-reflection effects required at different positions of the suede structure are not taken into account. As a result, either the passivation film is too thick, affecting light absorption, or the passivation film is too thin, affecting the passivation effect, and thus affecting the cell performance.

[0006] Summary of the Invention

[0007] The present application provides a solar cell and a photovoltaic module, aiming to solve the problem that, in solar cells, it is difficult to achieve both passivation and anti-reflection effects while taking into account the suede structure. In a first aspect, the present application provides a solar cell, comprising:

[0008] A silicon substrate and a passivation anti-reflection layer located on the silicon substrate;

[0009] The surface of the silicon substrate has a velvet structure, which includes: a plurality of pyramid-like structures; the pyramid-like structures include: a cone surface and a cone top; the cone surface of the pyramid-like structure includes: a first sub-cone surface away from the cone top, and a second sub-cone surface, the second sub-cone surface being the remaining portion of the cone surface of the pyramid-like structure except the first sub-cone surface; in the cone surface of the pyramid-like structure, the surface morphology of the first sub-cone surface and the second sub-cone surface are different;

[0010] The passivation anti-reflection layer includes: a first portion located on the first sub-conical surface, and a second portion located on the second sub-conical surface; in the passivation anti-reflection layer, the thickness of the first portion along the same direction close to the cone top is greater than the thickness of the second portion.

[0011] In the present application, in the cone surface of the pyramid-like structure, the surface morphology of the first sub-cone surface is different from that of the second sub-cone surface. The cone surface shape of this pyramid-like structure is more irregular, so that the 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 the silicon substrate, the situation of the part adjacent to the pyramid-like structure is more complicated, and usually there are more gaps; the situation of the position adjacent to the adjacent pyramid-like structures is also more complicated, and usually there are more gaps; therefore, these positions require a thicker passivation anti-reflection layer to achieve a better passivation effect, so the first sub-cone surface adjacent to these positions also requires a thicker passivation anti-reflection layer to achieve a better passivation effect, and the gaps at the top of the cone are usually smaller, and only a thinner passivation anti-reflection layer is required to achieve a better passivation effect, so the second sub-cone surface adjacent to the top of the cone also requires a relatively thin passivation anti-reflection layer to achieve a better passivation effect. Therefore, in the present application, the thickness of the first part along the same direction close to the top of the cone is greater than the thickness of the second part. 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 waste. At the same time, in this application, 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 distance. Combined with the suede structure of this application, it can further increase the absorption of light, and the light trapping effect is better, 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 uniform black, which is more beautiful. In summary, this application not only ensures the excellent passivation effect of all parts of the solar cell, but also greatly improves the anti-reflection effect, while also reducing waste.

[0012] Optionally, the undulation of the first sub-conical surface is smaller than the undulation of the second sub-conical surface;

[0013] Alternatively, the roughness of the first sub-conical surface is smaller than the roughness of the second sub-conical surface.

[0014] Optionally, the thickness of the first portion is greater than the thickness of the portion of the passivation anti-reflection layer located at the cone top;

[0015] and / or, the thickness of the portion of the passivation anti-reflection layer located at a position adjacent to adjacent pyramid-like structures is greater than the thickness of the portion of the passivation anti-reflection layer located at the pyramid top;

[0016] And / or, in the passivation anti-reflection layer, the thickness of the portion located at a position adjacent to adjacent pyramid-like structures is greater than the thickness of the second portion.

[0017] Optionally, in the passivation anti-reflection layer, the thickness non-uniformity between the first part and the second part is greater than 4%; the thickness non-uniformity is: the absolute value of the difference between the first thickness at the first position in the first part and the second thickness at the second position in the second part along the same direction close to the top of the cone, divided by the sum of the first thickness and the second thickness.

[0018] Optionally, the solar cell further comprises: an aluminum oxide layer located between the silicon substrate and the passivation anti-reflection layer;

[0019] The aluminum oxide layer includes: a third portion located on the first sub-conical surface, and a fourth portion located on the second sub-conical surface;

[0020] The thickness non-uniformity between the first portion and the second portion of the passivation anti-reflection layer is greater than the thickness non-uniformity between the third portion and the fourth portion of the aluminum oxide layer;

[0021] The thickness non-uniformity between the first portion and the second portion of the passivation anti-reflection layer is: the absolute value of the difference between the first thickness at a first position in the first portion and the second thickness at a second position in the second portion along the same direction close to the cone top, divided by the sum of the first thickness and the second thickness;

[0022] The thickness unevenness between the third portion and the fourth portion in the aluminum oxide layer is: the absolute value of the difference between the third thickness at the third position in the third portion and the fourth thickness at the fourth position in the fourth portion along the same direction close to the top of the cone, divided by the sum of the third thickness and the fourth thickness.

[0023] Optionally, the passivation anti-reflection layer includes: a front passivation anti-reflection layer located on the light-facing side of the silicon substrate, and a back passivation anti-reflection layer located on the backlight side of the silicon substrate;

[0024] In the thickness direction of the silicon substrate, at two opposite positions, the thickness of the back passivation anti-reflection layer is greater than the thickness of the front passivation anti-reflection layer.

[0025] Optionally, in the thickness direction of the silicon substrate, at two opposite positions, the difference between the thickness of the back passivation anti-reflection layer and the thickness of the front passivation anti-reflection layer is greater than or equal to 15 nm and less than or equal to 40 nm.

[0026] Optionally, the pyramid-like surface has a branched texture, and the number of the branched textures in the second sub-cone surface is greater than the number of the branched textures in the first sub-cone surface.

[0027] Optionally, the cone top of the pyramid-like structure and the second sub-cone surface of the cone surface of the pyramid-like structure have a cluster of nested ring-like textures.

[0028] Optionally, in a cluster of quasi-annular textures, along the height direction of the quasi-pyramid structure, the closer to the top of the pyramid, the smaller the outline of the quasi-annular texture.

[0029] Optionally, the portion of the pyramid-like structure away from the top of the pyramid is the lower portion of the pyramid-like structure, and the height of the lower portion accounts for at least 1 / 10 of the height of the pyramid-like structure;

[0030] The first sub-cone surface is: the area corresponding to the lower part of the cone surface of the pyramid-like structure;

[0031] The second sub-cone surface is an area of ​​the cone surface of the pyramid-like structure that is closer to the cone top than the first sub-cone surface.

[0032] Optionally, the pyramid-like structure further includes: a bottom contour line away from the top of the cone, wherein, in the same bottom contour line, there are at least two points with a height difference.

[0033] Optionally, the top angle of the suede structure is 55° to 90°.

[0034] Optionally, the height of the pyramid-like structure is 0.2 μm to 3 μm.

[0035] Optionally, the light-facing surface and / or the backlight surface of the silicon substrate has a suede structure.

[0036] In a second aspect of the present application, a photovoltaic assembly is provided, comprising: a plurality of any of the aforementioned solar cells.

[0037] The above-mentioned solar cells and photovoltaic modules have the same or similar beneficial effects, and to avoid repetition, they are not described here. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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 any creative work.

[0039] FIG1 shows a scanning electron microscope image of a first silicon substrate in an embodiment of the present application;

[0040] FIG2 shows a scanning electron microscope image of a second silicon substrate in an embodiment of the present application;

[0041] FIG3 shows a schematic diagram of a partial structure of a solar cell in an embodiment of the present application;

[0042] FIG4 shows a scanning electron microscope image of a third silicon substrate in an embodiment of the present application;

[0043] FIG5 shows a scanning electron microscope image of a fourth silicon substrate in an embodiment of the present application;

[0044] FIG6 shows a comparison of the reflectivity of the solar cell in the embodiment of the present application and the solar cell in the comparative example.

[0045] Description of reference numerals:

[0046] 1-silicon substrate, 2-passivation anti-reflection layer, 11-cone top, 12-branched texture, 13-annular texture, 131-spikes, 14-bottom contour line, 15-integrated pyramid-like structures. DETAILED DESCRIPTION

[0047] 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.

[0048] In existing solar cells, it is difficult to take both the passivation effect and the anti-reflection effect into account, which affects the performance of the cell. 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 account. The main idea of ​​the present application is to provide a more irregular cone shape of a pyramid-like structure so that the velvet structure has a larger specific surface area and improves the anti-reflection effect. On the basis of the velvet structure, according to the passivation requirements of different positions, the thickness of the passivation anti-reflection layer at the corresponding position is set to ensure that each position has an excellent passivation effect and reduce the waste of materials used in the passivation anti-reflection layer 2. Furthermore, 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 can be improved. In other words, the present application improves the anti-reflection effect and the passivation effect at the same time through the combination of the velvet structure and the passivation anti-reflection layer.

[0049] Figures 1, 2, and 5 are all SEM images obtained by scanning from the front of the velvet structure. Figure 4 is a SEM image obtained by scanning from the top of the pyramid-like structure of the velvet structure to the bottom contour line.

[0050] 1 to 5 , the present application provides a solar cell comprising: a silicon substrate 1, and a passivation anti-reflection layer 2 located on the silicon substrate 1. The silicon substrate 1 may have doped elements or be intrinsic, which is not specifically limited. The silicon substrate 1 may be a single crystal silicon substrate, etc., which is not specifically limited. The passivation anti-reflection layer 2 here can play a passivation role and can also play an anti-reflection role. The material of the passivation anti-reflection layer 2 can be selected from: silicon oxide, and / or silicon oxynitride, and the specific material of the passivation anti-reflection layer 2 is not limited. The passivation anti-reflection layer 2 can be prepared by PECVD (Plasma Enhanced Chemical Vapor Deposition) and other methods, and the specific preparation method of the passivation anti-reflection layer 2 is not specifically limited.

[0051] Referring to Figures 1 to 5, the surface of the silicon substrate 1 has a velvet structure, which includes multiple pyramid-like structures. For example, in Figure 1, the black lines outline the three pyramid-like structures in the velvet structure. The pyramid-like structures include a cone surface and a cone apex 11. The cone apex 11 is the highest point in the pyramid-like structure. In the case where the highest part of the pyramid-like structure is a plane formed by multiple points of equal height, the cone apex here can be the geometric center of the plane. In the pyramid-like structure, the cone surface of the pyramid-like structure is the collection of all side surfaces of the pyramid-like structure, that is, all surfaces of the pyramid-like structure except the bottom surface and the cone apex. The cone surface of the pyramid-like structure connects the cone apex and the bottom contour line, and the bottom contour line is the lowest contour line of the pyramid-like structure. The cone surface of the pyramid-like structure includes a first sub-cone surface away from the cone apex, and a second sub-cone surface. In other words, the first sub-cone surface is the portion of the cone surface farthest from the cone apex 11, that is, the portion of the cone surface close to the silicon substrate, and the second sub-cone surface is the portion of the cone surface other than the first sub-cone surface. In Figure 3, the dotted lines L1 to L6 do not actually exist in the solar cell; they are merely used to distinguish the first sub-cone surface from the second sub-cone surface, or to distinguish the lower section from the first section described below. For example, in Figure 3, for the leftmost pyramid-like structure, the portion of the cone surface between the right side of dotted line L1 and the left side of the apex of the leftmost pyramid-like structure, and the portion between the left side of dotted line L2 and the right side of the apex of the leftmost pyramid-like structure are the second sub-cone surface, while the portion to the left of L1 and the portion to the right of L2 are the first sub-cone surface. For the middle pyramid-like structure, the portion of the cone surface between the right side of dotted line L3 and the left side of the apex of the middle pyramid-like structure, and the portion between the left side of dotted line L4 and the right side of the apex of the middle pyramid-like structure are the second sub-cone surface, while the portion to the left of L3 and the portion to the right of L4 are the first sub-cone surface. For the rightmost pyramid-like structure, the part of the cone surface between the right side of the dotted line L5 and the left side of the cone top of the rightmost pyramid-like structure, and the part between the left side of the dotted line L6 and the right side of the cone top of the rightmost pyramid-like structure are the second sub-cone surface, and the part on the left side of L5 and the part on the right side of L6 are the first sub-cone surface.

[0052] The surface morphology of the sub-cone surface may include: the undulation of the sub-cone surface, or the roughness of the sub-cone surface, etc. The undulation mainly refers to the degree of undulation caused by the relatively large high and low structures on the surface, and the roughness refers to the degree of unevenness caused by the micro-protrusions / micro-depressions on the surface. Referring to Figures 1 to 5, in the cone surface of the pyramid-like structure, the surface morphology of the first sub-cone surface away from the cone top 11 is different from that of the second sub-cone surface, that is, the undulation or roughness of the first sub-cone surface is different from that of the second sub-cone surface; in one case, the number of protrusions and / or depressions on the second sub-cone surface may be greater than the number of protrusions and / or depressions on the first sub-cone surface; in another case, the degree of protrusions and / or depressions on the second sub-cone surface may be greater than the degree of protrusions and / or depressions on the first sub-cone surface; in another case, the first sub-cone surface may be greater than the first sub-cone surface; in another case, the second sub-cone surface may be greater than the first sub-cone surface; in another case, the second sub-cone surface may be greater than the first sub-cone surface; in another case, the second sub-cone surface may be greater than the first sub-cone surface. The arrangement of the protrusions and / or depressions of the second sub-cone surface is more disorderly than that of the first sub-cone surface; in another case, the height of the protrusions and / or the depth of the depressions of the second sub-cone surface may be greater than the height of the protrusions and / or the depth of the depressions of the first sub-cone surface; in this way, the shape of the cone surface of the pyramid-like structure is more irregular, so that the 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, and the appearance of the solar cell is uniform black, which is more beautiful.

[0053] Referring to Figure 3 , the passivation anti-reflection layer 2 includes a first portion located on the first sub-cone surface and a second portion located on the second sub-cone surface. In the passivation anti-reflection layer 2, the thickness of the first portion along the same direction near the cone apex 11 is greater than the thickness of the second portion. That is, when comparing the thickness of the first portion and the thickness of the second portion, the first portion and the second portion are defined as being located in the same direction near the cone apex 11. Throughout this document, the first portion and the second portion along the same direction near the cone apex 11 can be understood as being arranged sequentially in a direction from the bottom or bottom contour line of the pyramid-like structure toward the cone apex 11. Here, the thickness direction is perpendicular to the tangent line at the corresponding position on the outer surface of the passivation anti-reflection layer 2. Specifically, in the silicon substrate 1, the situation of the part adjacent to the pyramid-like structure is more complicated, and usually there are more gaps; the situation of the position adjacent to the adjacent pyramid-like structures is also more complicated, and usually there are more gaps; therefore, these positions require a thicker passivation anti-reflection layer to achieve a better passivation effect, so the first sub-cone surface adjacent to these positions also requires a thicker passivation anti-reflection layer to achieve a better passivation effect, and the gaps at the top of the cone are usually smaller, and only a thinner passivation anti-reflection layer is required to achieve a better passivation effect, so the second sub-cone surface adjacent to the top of the cone also requires a relatively thin passivation anti-reflection layer to achieve a better passivation effect. Therefore, in the present application, the thickness of the first part along the same direction close to the top of the cone is greater than the thickness of the second part. 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 waste. At the same time, in this application, 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 distance. Combined with the suede structure of this application, it can further increase the absorption of light, and the light trapping effect is better, 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 uniform black, which is more beautiful. In summary, this application not only ensures the excellent passivation effect of all parts of the solar cell, but also greatly improves the anti-reflection effect, while also reducing waste.

[0054] As shown in Figure 3, for the leftmost pyramid-like structure, the portion of the passivation anti-reflection layer 2 between dashed lines L1 and L2, excluding the apex 11, is the second portion, while the portion to the left of L1 and the portion to the right of L2 are the first portion. For the first and second portions along the same direction L7 near the apex 11, the thickness of the first portion is greater than the thickness of the second portion. For the first and second portions along the same direction L8 near the apex 11, the thickness of the first portion is greater than the thickness of the second portion. For the middle pyramid-like structure, the portion of the passivation anti-reflection layer 2 between dashed lines L3 and L4, excluding the apex 11, is the second portion, while the portion to the left of L3 and the portion to the right of L4 are the first portion. For the first and second portions along the same direction L9 near the apex, the thickness of the first portion is greater than the thickness of the second portion. For the first and second portions along the same direction L10 near the apex, the thickness of the first portion is greater than the thickness of the second portion. For the pyramid-like structure on the far right, in the passivation anti-reflection layer 2, the portion excluding the cone top and located between the dotted line L5 and the dotted line L6 is the second portion, and the portion located to the left of L5 and the portion located to the right of L6 are the first portion; for the first portion and the second portion along the same direction L11 close to the cone top, the thickness of the first portion is greater than the thickness of the second portion; for the first portion and the second portion along the same direction L12 close to the cone top, the thickness of the first portion is greater than the thickness of the second portion.

[0055] It should be noted that the thickness of a certain part of the passivation anti-reflection layer 2 can be measured by an instrument such as a transmission electron microscope. The thickness of a certain part can be the thickness of the part measured directly, or the thickness of a certain part can be the average thickness obtained by measuring multiple points selected in the part, etc. The measurement method is selected according to the measurability of the actual measurement target and is not specifically limited to this.

[0056] Optionally, referring to Figures 1 to 3 and Figure 5, in the cone surface of the pyramid-like structure, the undulation of the first sub-cone surface is smaller than the undulation of the second sub-cone surface, or the roughness of the first sub-cone surface is smaller than the roughness of the second sub-cone surface. The definitions of undulation and roughness here can refer to the corresponding records mentioned above. The cone surface shape of the pyramid-like structure is more irregular, so that the 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. As shown in Figure 3, for the leftmost pyramid-like structure, in the cone surface, the undulation of the first sub-cone surface located on the left side of the dotted line L1 and the first sub-cone surface located on the right side of the dotted line L2 is smaller than the undulation of the second sub-cone surface located between the right side of the dotted line L1 and the left side of the cone top of the leftmost pyramid-like structure, and the undulation of the second sub-cone surface between the left side of the dotted line L2 and the right side of the cone top of the leftmost pyramid-like structure; or, the roughness of the first sub-cone surface located on the left side of the dotted line L1 and the first sub-cone surface located on the right side of the dotted line L2 is smaller than the roughness of the second sub-cone surface located between the right side of the dotted line L1 and the left side of the cone top of the leftmost pyramid-like structure, and the second sub-cone surface between the left side of the dotted line L2 and the right side of the cone top of the leftmost pyramid-like structure. For the middle pyramid-like structure, in the cone surface, the undulation of the first sub-cone surface located on the left side of the dotted line L3 and the first sub-cone surface located on the right side of the dotted line L4 is smaller than the undulation of the second sub-cone surface located between the right side of the dotted line L3 and the left side of the cone top of the middle pyramid-like structure, and the undulation of the second sub-cone surface between the left side of the dotted line L4 and the right side of the cone top of the middle pyramid-like structure; or, the roughness of the first sub-cone surface located on the left side of the dotted line L3 and the first sub-cone surface located on the right side of the dotted line L4 is smaller than the roughness of the second sub-cone surface located between the right side of the dotted line L3 and the left side of the cone top of the middle pyramid-like structure, and the second sub-cone surface between the left side of the dotted line L4 and the right side of the cone top of the middle pyramid-like structure. For the rightmost pyramid-like structure, in the cone surface, the undulation of the first sub-cone surface located on the left side of the dotted line L5 and the first sub-cone surface located on the right side of the dotted line L6 is smaller than the undulation of the second sub-cone surface located between the right side of the dotted line L5 and the left side of the cone top of the rightmost pyramid-like structure, and the undulation of the second sub-cone surface between the left side of the dotted line L6 and the right side of the cone top of the rightmost pyramid-like structure; or, the roughness of the first sub-cone surface located on the left side of the dotted line L5 and the first sub-cone surface located on the right side of the dotted line L6 is smaller than the roughness of the second sub-cone surface located between the right side of the dotted line L5 and the left side of the cone top of the rightmost pyramid-like structure, and the second sub-cone surface between the left side of the dotted line L6 and the right side of the cone top of the rightmost pyramid-like structure.

[0057] Optionally, referring to Figure 3, in the passivation anti-reflection layer 2, the thickness of the first part is greater than the thickness of the passivation anti-reflection layer 2 located at the cone top 11; specifically, in the silicon substrate 1, the situation of the part adjacent to the pyramid-like structure is more complicated, and usually there are more gaps; the situation of the position adjacent to the adjacent pyramid-like structures is also more complicated, and usually there are more gaps; therefore, these positions require a thicker passivation anti-reflection layer to achieve a better passivation effect, so the first sub-cone surface adjacent to these positions also requires a thicker passivation anti-reflection layer to achieve a better passivation effect, and the gaps at the cone top are usually less, and only a thinner passivation anti-reflection layer is required to achieve a better passivation effect. Therefore, in the present application, the thickness of the first part of the passivation anti-reflection layer 2 is greater than the thickness of the part of the passivation anti-reflection layer 2 located at the cone top 11. 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 waste. At the same time, in the present application, 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 distance. 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 uniformly black, which is more beautiful.

[0058] For example, as shown in FIG3 , for the leftmost pyramid-like structure, the thickness of the first portion of the passivation anti-reflection layer 2 located to the left of the dotted line L1 and the first portion to the right of the dotted line L2 is greater than the thickness of the apex 11 of the leftmost pyramid-like structure in the passivation anti-reflection layer 2. For the middle pyramid-like structure, the thickness of the first portion of the passivation anti-reflection layer 2 located to the left of the dotted line L3 and the first portion to the right of the dotted line L4 is greater than the thickness of the apex 11 of the middle pyramid-like structure in the passivation anti-reflection layer 2. For the rightmost pyramid-like structure, the thickness of the first portion of the passivation anti-reflection layer 2 located to the left of the dotted line L5 and the first portion to the right of the dotted line L6 is greater than the thickness of the apex 11 of the rightmost pyramid-like structure in the passivation anti-reflection layer 2.

[0059] 3 , the portion between the dotted line L2 and the dotted line L3 is where the leftmost pyramid-like structure and the middle pyramid-like structure are adjacent, and the portion between the dotted line L4 and the dotted line L5 is where the rightmost pyramid-like structure and the middle pyramid-like structure are adjacent. Optionally, referring to Figure 3, the thickness of the portion of the passivation anti-reflection layer 2 located at the position adjacent to the adjacent pyramid-like structures is greater than the thickness of the portion of the passivation anti-reflection layer 2 located at the cone top 11; specifically, in the silicon substrate 1, the position where the adjacent pyramid-like structures are adjacent is relatively complicated, and usually has more gaps. Therefore, these positions require a thicker passivation anti-reflection layer to achieve a better passivation effect, while the gaps at the cone top are usually smaller, and only a thinner passivation anti-reflection layer is required to achieve a better passivation effect. Therefore, in the present application, the thickness of the portion of the passivation anti-reflection layer 2 located at the position adjacent to the adjacent pyramid-like structures is greater than the thickness of the portion of the passivation anti-reflection layer 2 located at the cone top 11. 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 waste. At the same time, in the present application, after light enters the passivation anti-reflection layer of different thicknesses, the light's optical path undergoes more changes, which can increase the optical path. Combined with the velvet structure of the present application, this can further increase light absorption, resulting in a better light trapping effect, further increasing the short-circuit current, and further improving the photoelectric conversion efficiency of the solar cell. Furthermore, the solar cell has a uniform black appearance, which is more aesthetically pleasing. As shown in FIG3 , the thickness of the portion of the passivation anti-reflection layer 2 between the dotted lines L2 and L3 is greater than the thickness of the pyramid-like structure apex 11 located on the leftmost side of the passivation anti-reflection layer 2, and is also greater than the thickness of the pyramid-like structure apex 11 located in the middle of the passivation anti-reflection layer 2. In FIG3 , the thickness of the portion of the passivation anti-reflection layer 2 between the dotted lines L4 and L5 is greater than the thickness of the pyramid-like structure apex located on the rightmost side of the passivation anti-reflection layer 2, and is also greater than the thickness of the pyramid-like structure apex located in the middle of the passivation anti-reflection layer 2.

[0060] Optionally, referring to Figure 3, the thickness of the portion of the passivation anti-reflection layer 2 located at the position adjacent to the adjacent pyramid-like structures is greater than the thickness of the second portion of the passivation anti-reflection layer 2; specifically, in the silicon substrate 1, the position where the adjacent pyramid-like structures are adjacent is relatively complicated, and usually has more gaps. Therefore, these positions require a thicker passivation anti-reflection layer to achieve a better passivation effect, while the gaps 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. Therefore, the second sub-cone surface adjacent to the top of the cone also requires a relatively thin passivation anti-reflection layer to achieve a better passivation effect. Therefore, in the present application, the thickness of the portion of the passivation anti-reflection layer 2 located at the position adjacent to the adjacent pyramid-like structures is greater than the thickness of the second portion of the passivation anti-reflection layer 2. 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 waste. At the same time, in the present application, 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 distance. 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 uniformly black, which is more beautiful.

[0061] As shown in Figure 3 , the thickness of the portion of the passivation anti-reflection layer 2 between the dotted lines L2 and L3 is greater than the thickness of the second portion of the passivation anti-reflection layer 2 between the dotted lines L1 and L2, excluding the cone apex, and is also greater than the thickness of the second portion of the passivation anti-reflection layer 2 between the dotted lines L3 and L4, excluding the cone apex. In Figure 3 , the thickness of the portion of the passivation anti-reflection layer 2 between the dotted lines L4 and L5 is greater than the thickness of the second portion of the passivation anti-reflection layer 2 between the dotted lines L5 and L6, excluding the cone apex, and is also greater than the thickness of the second portion of the passivation anti-reflection layer 2 between the dotted lines L3 and L4, excluding the cone apex.

[0062] Optionally, in the passivation anti-reflection layer 2, the thickness non-uniformity between the first part and the second part is greater than 4%; the thickness non-uniformity is: the absolute value of the difference between the first thickness at the first position in the first part and the second thickness at the second position in the second part along the same direction close to the top of the cone, divided by the sum of the first thickness and the second thickness, wherein the first position in the first part is any position in the first part, and the second position in the second part is any position in the second part. That is to say, here, the first part and the second part are limited to the same direction along the top of the cone 11, and the thickness non-uniformity of the first part and the second part in the passivation anti-reflection layer 2 is greater than 4%; specifically, in the silicon substrate 1, the adjacent positions of the adjacent pyramid-like structures are more complicated, and usually have more gaps. Therefore, these positions require a thicker passivation anti-reflection layer to achieve a better passivation effect, while the gaps at the top of the cone are usually less, and only a thinner passivation anti-reflection layer is required to achieve a better passivation effect. Therefore, the second sub-cone surface adjacent to the top of the cone also requires a relatively thin passivation anti-reflection layer to achieve a better passivation effect. Therefore, in the present application, the thickness non-uniformity of the first part and the second part in the passivation anti-reflection layer 2 is greater than 4%. 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 waste. At the same time, in the present application, 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 distance. 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 uniformly black, which is more beautiful.

[0063] For example, in the passivation anti-reflection layer 2, the thickness unevenness of the first part and the second part along the same direction close to the top of the cone can be: 4.001%, or 4.03%, or 4.09%, or 4.2%, or 4.31%, or 4.5%, or 4.9%, or 5%, or 5.2%, or 6%, or 7.23%, or 8%, or 9.2%, or 10.3%, or 11.2%, or 13.46%, or 15%, or 18%, or 20%, or 22%, or 25%.

[0064] Optionally, the solar cell may further include: an aluminum oxide layer (not shown in the figure) located between the silicon substrate 1 and the passivation anti-reflection layer 2. The thickness fluctuation of the aluminum oxide layer is less than the thickness fluctuation of the passivation anti-reflection layer 2; wherein the thickness fluctuation refers to the degree of thickness change; the thickness fluctuation of the aluminum oxide layer can specifically be the absolute value of the difference between the thickness of the aluminum oxide layer at the fifth position and the thickness of the aluminum oxide layer at the sixth position; the thickness fluctuation of the passivation anti-reflection layer 2 can specifically be the absolute value of the difference between the thickness of the passivation anti-reflection layer 2 at the seventh position and the thickness of the passivation anti-reflection layer 2 at the eighth position. In the thickness direction of the silicon substrate, the projections of the fifth position and the seventh position coincide, and the projections of the sixth position and the eighth position coincide. The fifth position and the sixth position are any two different positions in the aluminum oxide layer. Specifically, the aluminum oxide layer is usually obtained by atomic layer deposition, the surface morphology has little effect on atomic layer deposition, the thickness of the aluminum oxide layer is relatively uniform, and the aluminum oxide layer has better passivation performance.

[0065] It should be noted that the thickness of the aluminum oxide layer can be 3 nm (nanometers) to 7 nm, and the thickness of the aluminum oxide layer can also be measured by a transmission electron microscope, etc., and is not specifically limited to this. For example, the thickness fluctuation of the aluminum oxide layer can be 0.0001 nm-3 nm, for example, it can be 0.001 nm, 0.005 nm, 0.008 nm, 0.01 nm, 0.02 nm, 0.03 nm, 0.04 nm, 0.05 nm, 0.06 nm, 0.07 nm, 0.08 nm, 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 1nm, 2nm, 2.3nm, 3nm, the thickness fluctuation of the passivation anti-reflection layer 2 can be 3.5nm-50nm, for example, it can be 3.5nm, 4nm, 4.8nm, 6nm, 7nm, 8nm, 9nm, 10nm, 12nm, 12.5nm, 13nm14nm, 15nm, 16nm, 17nm, 18nm, 20nm, 25nm, 30nm, 36nm, 40nm, 45nm, 50nm.

[0066] Optionally, the aluminum oxide layer includes: a third portion located on the first sub-cone surface, and a fourth portion located on the second sub-cone surface. The thickness non-uniformity between the first portion and the second portion in the passivation anti-reflection layer 2 is greater than the thickness non-uniformity between the third portion and the fourth portion in the aluminum oxide layer. The thickness non-uniformity between the first portion and the second portion in the passivation anti-reflection layer 2 refers to the above description and will not be repeated here. The thickness non-uniformity between the third portion and the fourth portion in the aluminum oxide layer is: the absolute value of the difference between the third thickness at the third position in the third portion and the fourth thickness at the fourth position in the fourth portion in the same direction close to the top of the cone, divided by the sum of the third thickness and the fourth thickness. Here, the third portion and the fourth portion are both limited to the same direction close to the top of the cone. Here, the third position in the third portion is: any position in the third portion, and the fourth position in the fourth portion is: any position in the fourth portion. The thickness unevenness between the first and second parts of the passivation anti-reflection layer 2 is greater than the thickness unevenness between the third and fourth parts of the aluminum oxide layer, that is, the thickness unevenness of the passivation anti-reflection layer 2 is greater. The thickness of the passivation anti-reflection layer 2 matches the passivation requirements, which can ensure that each position has an excellent passivation effect. In addition, the thickness of the passivation anti-reflection layer is set according to the passivation requirements, which can reduce waste. At the same time, in the present application, 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, 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. It should be noted that the specific difference between the two thickness unevennesses is not specifically limited.

[0067] Optionally, the passivation anti-reflection layer 2 includes: a front passivation anti-reflection layer located on the light-facing side of the silicon substrate 1, and a back passivation anti-reflection layer located on the backlight side of the silicon substrate 1. At two opposing locations along the thickness direction of the silicon substrate 1, the back passivation anti-reflection layer has a greater thickness than the front passivation anti-reflection layer. Specifically, as the thickness of the passivation anti-reflection layer increases, its passivation effect improves, while its anti-reflection effect decreases appropriately. For the passivation anti-reflection layer, the anti-reflection requirement on the backlight side is lower than that on the light-facing side. Therefore, appropriately increasing the thickness of the back passivation anti-reflection layer ensures excellent passivation performance on the backlight side, while appropriately reducing the thickness of the front passivation anti-reflection layer can achieve a balanced passivation performance and anti-reflection effect.

[0068] Optionally, 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 and the thickness of the front passivation anti-reflection layer is greater than or equal to 15 nm and less than or equal to 40 nm. The appropriate setting of the difference between the two fully ensures excellent passivation performance on the backlight side, while simultaneously achieving good passivation performance and anti-reflection effects on the light-facing side, and avoids waste. For example, the thickness of the back passivation anti-reflection layer can be 85 nm to 100 nm, or approximately 95 nm, and the thickness of the front passivation anti-reflection layer can be 60 nm to 70 nm, or approximately 65 nm. Here, in the thickness direction of the silicon substrate 1, at two relative positions, the difference between the thickness of the back passivation anti-reflection layer and the thickness of the front passivation anti-reflection layer can be: 15nm, or 16.3nm, or 17.9nm, or 19.4nm, or 20.94nm, or 22.6nm, or 24.92nm, or 27.5nm, or 30.3nm, or 32.6nm, or 33.9nm, or 35.7nm, or 36.9nm, or 18.34nm, or 40nm.

[0069] Optionally, referring to FIG2 , the pyramid-like surface has a branched texture 12. The shape of the branched texture 12 is similar to that of a tree branch, i.e., a forked pattern on the main trunk. The number of branched textures 12 on the second sub-surface of the pyramid-like surface is greater than the number of branched textures 12 on the first sub-surface, farther from the apex. There is a correspondence between the branched textures 12 and the protrusions or depressions on the pyramid-like surface: the branched textures 12 are typically located at the intersection of the protrusions and depressions on the pyramid-like surface. That is, the greater the number of branched textures 12, the greater the number of protrusions and depressions on the pyramid-like surface. Therefore, the more textures there are, the larger the specific surface area of ​​the velvet structure. The more irregular the distribution of the branched textures, the larger the specific surface area of ​​the velvet structure, lower reflectivity, and better light trapping, thereby increasing the short-circuit current and ultimately improving the photoelectric conversion efficiency of the solar cell. Furthermore, the solar cell has a uniform black appearance, which is more aesthetically pleasing. For example, in FIG2 , in the cone surface of the pyramid-like structure on the far right, there is basically no branched texture in the first sub-cone surface away from the cone top, and there are more branched textures in the second sub-cone surface.

[0070] Optionally, referring to FIG4 , the cone top 11 of the pyramid-like structure and the second sub-cone surface of the pyramid-like structure have a cluster of nested ring-like textures 13. Here, the ring-like texture 13 can be an open-shaped, ring-like pattern, and / or the ring-like texture 13 can be a closed-shaped, ring-like pattern. For example, in FIG4 , in the cluster of nested ring-like textures 13 marked 13 in the middle position, both open-shaped patterns and closed-shaped patterns exist. In a cluster of nested ring-like textures 13, the number of ring-like textures 13 is not specifically limited, and the ring-like textures 13 are nested with each other. There is basically no ring-like texture in the first sub-cone surface of the pyramid-like structure. There is a corresponding relationship between the above-mentioned annular texture 13 and the protrusions or depressions on the cone surface of the pyramid-like structure: the annular texture 13 is usually located at the junction of the protrusions and depressions on the cone surface of the pyramid-like structure, that is, the more annular textures 13 there are, the more protrusions and depressions there are on the cone surface of the pyramid-like structure. Therefore, the more textures there are, the larger the specific surface area of ​​the velvet structure can be increased. The more irregular the distribution position of the above-mentioned annular texture is, the velvet structure can have a larger specific surface area, lower reflectivity, 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.

[0071] Referring to FIG. 4 , the quasi-annular texture 13 herein can be a skirt-like texture, i.e., an irregularly stacked texture similar to a skirt-like texture visible under electron microscopy, and / or a rose-like texture, i.e., an irregularly stacked texture similar to the stacked layers of rose petals within a rose flower visible under electron microscopy. In this manner, the quasi-annular texture 13 has an aesthetically pleasing shape, lower reflectivity, and better light trapping. The quasi-annular texture 13 is located on the conical surface and the apex, or, further, is located within the second sub-conical surface of the conical surface and on the apex.

[0072] Optionally, referring to Figure 4, in a cluster of annular textures 13, along the height direction of the pyramid-like structure, the closer to the top of the cone 11, the smaller the outline of the annular texture 13, and the farther away from the top of the cone 11, the larger the outline of the annular texture 13. The distribution position of the above-mentioned annular textures 13 is irregular. At the same time, the annular texture 13 can increase the specific surface area, so that the 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.

[0073] Optionally, referring to Figures 1 to 5, the portion of the pyramid-like structure that is away from the apex 11 is the lower portion of the pyramid-like structure, and the height of the lower portion accounts for at least 1 / 10 of the height of the pyramid-like structure; in the cone surface of the pyramid-like structure, the first sub-cone surface away from the apex 11 is: the area corresponding to the lower portion of the cone surface of the pyramid-like structure, and the second sub-cone surface is: the area of ​​the cone surface of the pyramid-like structure that is closer to the apex 11 than the first sub-cone surface. Specifically, the division of the second sub-cone surface and the first sub-cone surface here is more accurate, which is not only conducive to the preparation of the velvet structure, but also has 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, and the appearance of the solar cell is uniform black and more beautiful. In this article, with respect to the proportion of the height of the lower portion of the pyramid-like structure, it should be understood that as long as the height of the lower portion of most of the pyramid-like structures in the velvet structure meets the aforementioned proportion, the aforementioned effect can be achieved.

[0074] For example, the portion of the pyramid-like structure away from the apex 11 is the lower portion of the pyramid-like structure, and the height of the lower portion accounts for 1 / 10, 2 / 15, 3 / 20, 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5, or 1 / 4 of the height of the pyramid-like structure. In the conical surface of the pyramid-like structure, the first sub-conical surface away from the apex 11 is the area corresponding to the lower portion of the conical surface of the pyramid-like structure, and the second sub-conical surface is the area of ​​the conical surface of the pyramid-like structure that is closer to the apex 11 than the first sub-conical surface.

[0075] Optionally, the portion of the pyramid-like structure away from the apex 11 is the lower portion of the pyramid-like structure, and the height of the lower portion accounts for at least 1 / 5 of the height of the pyramid-like structure; the portion of the pyramid-like structure adjacent to the apex 11 is the upper portion of the pyramid-like structure, and the height of the upper portion accounts for at most 1 / 5 of the height of the pyramid-like structure; the portion of the pyramid-like structure located between the lower portion and the upper portion is the middle portion, and the height of the middle portion accounts for at least 2 / 5 of the height of the pyramid-like structure. In the cone surface of the pyramid-like structure, the first sub-cone surface away from the apex 11 is: the area corresponding to the lower portion of the cone surface of the pyramid-like structure. The second sub-cone surface is further divided into an upper sub-cone surface and a middle sub-cone surface. In the cone surface of the pyramid-like structure, the upper sub-cone surface is: the area corresponding to the upper portion of the cone surface of the pyramid-like structure. In the cone surface of the pyramid-like structure, the middle sub-cone surface is: the area corresponding to the middle portion of the cone surface of the pyramid-like structure. The division of the three sub-cones is more accurate, which is not only conducive to the preparation of the velvet structure, but also has 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. In addition, the appearance of the solar cell is uniformly black and more beautiful. In this article, with respect to the proportion of the height of the upper part of the pyramid-like structure, it should be understood that as long as the height of the upper part of the most pyramid-like structures in the velvet structure meets the aforementioned proportion, the aforementioned effect can be achieved. Similarly, in this article, with respect to the proportion of the height of the middle part of the pyramid-like structure, it should be understood that as long as the height of the middle part of the most pyramid-like structures in the velvet structure meets the aforementioned proportion, the aforementioned effect can be achieved.

[0076] For example, the portion of the pyramid-like structure adjacent to the apex 11 is the upper portion of the pyramid-like structure, and the height of the upper portion accounts for 1 / 10, 2 / 15, 3 / 20, 1 / 9, 1 / 8, 1 / 7, 1 / 6, or 1 / 5 of the height of the pyramid-like structure. For another example, the portion of the pyramid-like structure between the upper portion and the lower portion is the middle portion, and the height of the middle portion accounts for 2 / 5, 13 / 30, 7 / 15, 1 / 2, 8 / 15, 17 / 30, or 3 / 5 of the height of the pyramid-like structure.

[0077] Optionally, referring to Figures 3 and 4, the pyramid-like structure further includes: a bottom contour line 14 away from the cone top 11, wherein at least two points in the same bottom contour line 14 have a height difference. As shown in Figure 3, for the leftmost pyramid-like structure, the middle pyramid-like structure, and the rightmost pyramid-like structure, the bottom contour lines of the three have a height difference between the left and right endpoints. The shapes of these pyramid-like structures are more irregular, resulting in a velvet structure with a larger specific surface area, lower reflectivity, and better light trapping effect, which can increase short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. The solar cell also has a uniform black appearance and is more aesthetically pleasing.

[0078] Optionally, referring to Figure 1, the suede structure has a vertex angle a of 55° to 90°. The vertex angle of the suede structure is the angle between two opposing side edges passing through the apex of a pyramid-like structure. A suede structure with a vertex angle a of 55° to 90° provides a larger specific surface area, lower reflectivity, and better light trapping, thereby increasing short-circuit current and ultimately improving the photovoltaic conversion efficiency of the solar cell. Furthermore, the solar cell has a uniform black appearance, which is more aesthetically pleasing.

[0079] For example, the top angle a of the velvet structure may be 55°, or 56°, or 59.3°, or 62°, or 70°, or 73.5°, or 78.6°, or 80.2°, or 84°, or 89.3°, or 90°.

[0080] Optionally, the height of the pyramid-like structure is 0.2μm (micrometer) to 3μm. The height of the pyramid-like structure is more appropriate, so that the 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.

[0081] For example, the height of the pyramid-like structure can be 0.5μm to 3μm, or the height of the pyramid-like structure can be 0.2μm, or 0.31μm, or 0.37μm, or 0.42μm, or 0.6μm, or 0.73μm, or 0.88μm, or 0.95μm, or 1.2μm, or 1.24μm, or 1.7μm, or 1.99μm, or 2.21μm, or 2.7μm, or 2.79μm, or 3μm.

[0082] Optionally, the pyramid-like structure includes: a cone top 11, a cone surface, and at least two side edges. The side edges of the pyramid-like structure are the common edges of adjacent side surfaces in the pyramid-like structure. The side edges include: a lower segment away from the cone top 11, and a first segment, wherein the bending degree of the lower segment is less than the bending degree of the first segment. The bending degree of a sub-segment of a side edge refers to the degree of bending of the sub-segment. The irregular shape of each side edge gives the velvet structure a larger specific surface area, lower reflectivity, and better light trapping effect, which can increase 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. For example, in Figure 3, in the leftmost side edge of the leftmost pyramid-like structure: the bending degree of the lower segment located to the left of L1 is less than the bending degree of the first segment located to the right of L1. In the rightmost side edge of the leftmost pyramid-like structure: the bending degree of the lower segment located to the right of L2 is less than the bending degree of the first segment located to the left of L2.

[0083] Optionally, referring to FIG4 , in the velvet structure, at least the lower portions of at least two pyramid-like structures away from the apex 11 are fused together, and the apex of each fused pyramid-like structure 15 is separated, making the shape of the velvet structure flexible and diverse, and easy to prepare. The apex of each fused pyramid-like structure 15 is separated, so that the 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 and more beautiful. For example, in FIG4 , in the velvet structure, at least the lower portions of the two pyramid-like structures enclosed in the curly brackets on the left, away from the apex 11, are fused together, and the apex of each fused pyramid-like structure 15 is separated.

[0084] Optionally, in the direction perpendicular to the height of the pyramid-like structure, the distance between the apexes of adjacent integrated pyramid-like structures 15 is greater than 0.2 μm, and can also be greater than 0.5 μm. For example, it can be: 0.21 μm, or 0.31 μm, or 0.47 μm, or 0.5 μm, or 0.61 μm, or 0.77 μm, or 0.8 μm, or 0.88 μm, or 0.91 μm, or 1 μm, or 1.23 μm, or 1.34 μm, or 1.5 μm, or 1.6 μm.

[0085] Optionally, referring to FIG4 , in the velvet structure, at least the lower portions of at least two pyramid-like structures away from the apex 11 are fused into one, and the apex of each fused pyramid-like structure 15 has a height difference or is evenly distributed, making the shape of the velvet structure flexible and diverse, easy to prepare, and the 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, and the appearance of the solar cell is uniform black, which is more beautiful. For example, in FIG4 , in the velvet structure, at least the lower portions of the two pyramid-like structures enclosed in the left curly brackets away from the apex 11 are fused into one, and the apex of each fused pyramid-like structure 15 has a height difference. For another example, in FIG4 , in the velvet structure, at least the lower portions of the two pyramid-like structures enclosed in the right curly brackets away from the apex 11 are fused into one, and the apex of each fused pyramid-like structure 15 is roughly even.

[0086] Optionally, referring to Figure 4, in the velvet structure, at least the lower parts of at least two pyramid-like structures away from the cone top 11 are fused into one, and the cone tops of each integrated pyramid-like structure 15 have a height difference, which is greater than 0 and less than or equal to 1.6 microns; the height difference is set more reasonably, so that the velvet structure has a more reasonable specific surface area. On the one hand, the reflectivity is lower and the light trapping effect is better. On the other hand, the passivation anti-reflection layer formed in different parts has a thickness difference, which makes the incident light have a longer optical path and increases the absorption of light.

[0087] For example, in the velvet structure, at least the lower parts of at least two pyramid-like structures away from the cone top 11 are fused into one, and the cone tops of each integrated pyramid-like structure 15 have a height difference, and the height difference can be: 0.1μm, or 0.17μm, or 0.2μm, or 0.31μm, or 0.47μm, or 0.5μm, or 0.61μm, or 0.77μm, or 0.8μm, or 0.88μm, or 0.91μm, or 1μm, or 1.21μm, or 1.34μm, or 1.5μm, or 1.6μm.

[0088] Optionally, referring to Figure 4, in the velvet structure, at least the lower parts of at least two pyramid-like structures away from the cone top 11 are fused into one, and the cone tops of each integrated pyramid-like structure 15 have a height difference, which is greater than 0 and less than or equal to 0.8 microns; the height difference is smaller, so that the velvet structure has a more reasonable specific surface area. On the one hand, the reflectivity is lower and the light trapping effect is better. On the other hand, the passivation anti-reflection layer formed in different parts has a thickness difference, which makes the incident light have a longer optical path and increases the absorption of light.

[0089] For example, in the velvet structure, at least the lower parts of at least two pyramid-like structures away from the cone top 11 are fused into one, and the cone tops of each integrated pyramid-like structure 15 have a height difference, which can be: 0.1μm, or 0.13μm, or 0.2μm, or 0.33μm, or 0.4μm, or 0.47μm, or 0.5μm, or 0.61μm, or 0.77μm, or 0.8μm.

[0090] Optionally, in a velvet structure, at least the first sub-cone surfaces of at least two pyramid-like structures are fused together, and the apexes of the fused pyramid-like structures are separated. This allows the velvet structure to have a larger specific surface area, lower reflectivity, and better light trapping, thereby increasing short-circuit current and ultimately improving the photovoltaic conversion efficiency of the solar cell. Furthermore, the solar cell has a uniform black appearance, which is more aesthetically pleasing. For example, in FIG4 , in the velvet structure, at least the first sub-cone surfaces of the two pyramid-like structures enclosed in curly brackets, which are distal to the apex 11, are fused together, and the apexes of the fused pyramid-like structures 15 are separated.

[0091] Optionally, in the integrated pyramid-like structures, the annular textures in the cone surfaces of different pyramid-like structures are separated, so that the 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, and the appearance of the solar cell is uniform black, which is more beautiful. For example, in Figure 4, in the velvet structure, at least the lower part of the two pyramid-like structures enclosed in the curly brackets on the left, away from the cone top 11, is fused into one, and the cone tops of the integrated pyramid-like structures 15 are separated. Alternatively, in the integrated pyramid-like structures, the annular textures in the cone surfaces of different pyramid-like structures partially overlap, making the velvet structure flexible and diverse, and the 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, and the appearance of the solar cell is uniform black, which is more beautiful. For example, in Figure 4, in the velvet structure, at least the lower part away from the cone top 11 of the two pyramid-like structures enclosed in the right brackets are fused into one, and the annular texture parts in the cone surfaces of different pyramid-like structures of the integrated pyramid-like structures 15 overlap. Here, the outermost annular texture parts in the cone surfaces of different pyramid-like structures of the integrated pyramid-like structures 15 can be overlapped.

[0092] Optionally, within a cluster of quasi-annular textures, the quasi-annular textures at different locations along the height direction of the quasi-pyramid structure overlap, making the velvet structure flexible and diverse. The velvet structure also has a larger specific surface area, lower reflectivity, and better light trapping, which can increase short-circuit current and ultimately improve the photovoltaic conversion efficiency of the solar cell. Furthermore, the solar cell has a uniform black appearance, which is more aesthetically pleasing. For example, in Figure 4, within the cluster of quasi-annular textures labeled 13 at the bottom, the quasi-annular textures 13 at different locations along the height direction of the quasi-pyramid structure overlap.

[0093] Optionally, in the conical surface of the pyramid-like structure, the annular texture 13 extends from a position adjacent to the top of the cone 11 at most to a conical surface position corresponding to a portion of the pyramid-like structure whose height difference from the top of the cone 11 is 2 / 3, or, the annular texture 13 can also extend from a position adjacent to the top of the cone 11 at most to a side position (i.e., a conical surface position) corresponding to a portion of the pyramid-like structure whose height difference from the top of the cone 11 is 1 / 2; by adjusting the distribution position of the annular texture 13, the position where the side protrusions and depressions are concentrated can be adjusted, so that the velvet structure, especially the upper half of the 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, and the appearance of the solar cell is uniformly black, which is more beautiful.

[0094] Optionally, the maximum dimension d1 inside the quasi-annular texture 13 is 0.5 μm to 2 μm. The maximum dimension d1 inside the quasi-annular texture 13 is set more reasonably. It is not only easy to prepare, but also the 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.

[0095] For example, the maximum dimension d1 within the ring-like texture 13 may be 0.5 μm, 0.56 μm, 0.61 μm, 0.72 μm, 0.93 μm, 1 μm, 1.12 μm, 1.25 μm, 1.31 μm, 1.42 μm, 1.53 μm, 1.61 μm, 1.77 μm, 1.83 μm, 1.92 μm, or 2 μm. For another example, the maximum dimension d1 within the ring-like texture 13 may be 0.55 μm to 1.8 μm, or the maximum dimension d1 within the ring-like texture 13 may be 0.6 μm to 1.6 μm.

[0096] Optionally, referring to Figure 4, in the same type of annular texture, the maximum dimensions inside the annular texture are not equal in at least two directions perpendicular to each other, that is, in the same type of annular texture, the maximum dimension inside the annular texture in a first direction is not equal to the maximum dimension inside the annular texture in a second direction perpendicular to the first direction, which makes the shape of the velvet structure more irregular, the reflectivity 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.

[0097] Optionally, referring to Figure 4, in the same cluster of annular textures, at least one annular texture 13 has spikes 131 facing the outside of the annular texture 13. The spikes 131 can increase the specific surface area, so that the 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.

[0098] Optionally, referring to Figures 1 to 5, in the same type of pyramid structure, among the two side edges located on both sides of the cone top 11, the size of one side edge is larger than the size of the other side edge along the direction of the thickness of the silicon substrate, so that the shape of the pyramid-like structure is more irregular, the 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, and the appearance of the solar cell is uniform black, which is more beautiful.

[0099] Optionally, referring to Figures 1 to 4, for two adjacent pyramid-like structures, the smaller side edges of one pyramid-like structure are closely distributed with the smaller side edges of the other pyramid-like structure, so that the shape of the velvet structure is more irregular. The 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.

[0100] Optionally, referring to Figures 1 to 4, in a side edge, the lower segment away from the cone top 11 is a straight segment, or a segment with at most two inflection points. Specifically, for example, the lower segment is a straight segment with only one slope, in which case the lower segment has no inflection point; or, the lower segment is composed of two types of segments, which can be a straight segment and a curved segment, and the intersection of the straight segment and the curved segment has an inflection point, or the two types of segments can be two straight segments, the slopes of the two straight segments are different, and the intersection of the two straight segments has an inflection point; or, the lower segment is composed of three types of segments, which can be a straight segment, another straight segment, and a curved segment, the slopes of the two straight segments are different, and the intersection of the three has an inflection point; or, the lower segment can be composed of three straight segments, the slopes of the three straight segments are different, and the intersection of two adjacent straight lines has an inflection point. The lower segment here can be prepared using existing velveting methods and parameters, and has better process compatibility.

[0101] Optionally, referring to Figures 1 to 4, in a side edge, the first segment other than the lower segment is a broken line segment and / or a curved line segment. The number of broken line segments and the number of curved line segments contained in the first segment are not specifically limited. In this way, the shape of the velvet structure is more irregular, the 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.

[0102] For example, in Figure 3, in the left side edge of the leftmost pyramid-like structure, the lower segment to the left of L1 consists of two straight line segments with one inflection point, while the first segment to the right of L1 consists of multiple broken line segments and multiple curved line segments. In the right side edge of the leftmost pyramid-like structure, the lower segment to the right of L2 consists of one straight line segment with no inflection point, while the first segment to the left of L2 consists of multiple broken line segments and multiple curved line segments. In the left side edge of the middle pyramid-like structure, the lower segment to the left of L3 consists of two straight line segments with one inflection point, while the first segment to the right of L3 consists of multiple broken line segments and multiple curved line segments. In the right side edge of the middle pyramid-like structure, the lower segment to the right of L4 consists of three straight line segments with two inflection points, while the first segment to the left of L4 consists of multiple broken line segments and multiple curved line segments. In the left side edge of the rightmost pyramid-like structure: the lower segment located on the left side of L5 is two straight line segments with an inflection point, while the first segment located on the right side of L5 is composed of multiple broken line segments and multiple curved line segments; in the right side edge of the rightmost pyramid-like structure: the lower segment located on the right side of L6 is composed of a straight line segment without an inflection point, while the first segment located on the left side of L6 is composed of multiple broken line segments and multiple curved line segments.

[0103] Optionally, the length of the lower section of a side edge is at least 1 / 10 of the length of the side edge. Here, the division between the lower section and the first section of a side edge is more accurate, which is not only conducive to the preparation of the velvet structure, but also has 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.

[0104] For example, the length of the lower section of a side edge is 1 / 10, or 2 / 15, or 3 / 20, or 1 / 9, or 1 / 8, or 1 / 7, or 1 / 6, or 1 / 5, or 1 / 4 of the length of the side edge.

[0105] The first plane perpendicular to the thickness direction of the silicon substrate 1 refers to a plane defined by the length and width directions of the silicon substrate 1. In other words, when a solar cell is placed on a horizontal plane, with the light-facing or light-backward side of the silicon substrate 1 facing away from the horizontal plane, the first plane is parallel to the horizontal plane. For example, in FIG3 , the horizontal dashed lines extending left and right are schematic representations of the first plane. For another example, in FIG5 , the horizontal dashed lines extending left and right are schematic representations of the first plane. Optionally, the angle between the lower segment of a side edge and the first plane perpendicular to the thickness direction of the silicon substrate 1 is smaller than the angle between the first segment of the side edge and the first plane. Specifically, by using a corrosive additive to adjust the etching rate of the chemical solution on each crystal orientation of the silicon substrate, the side edges are subjected to irregular etching, resulting in a more irregular shape of the velvet structure. The 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 solar cell also has a uniform black appearance and is more aesthetically pleasing.

[0106] Optionally, the first section of a side edge is composed of an upper section and a middle section, wherein the upper section is adjacent to the cone top 11, and the middle section is located between the lower section and the upper section. The length of the upper section accounts for at least 1 / 10 of the length of the side edge, and the length of the middle section accounts for at least 2 / 5 of the length of the side edge. Specifically, the lower section is the portion of the side edge farthest from the cone top 11, or the lower section is the lowermost portion of the side edge; the upper section is the portion of the side edge closest to the cone top 11, or the upper section is the uppermost portion of the side edge; and the middle section is the portion located in the middle of the side edge. The aforementioned accurate division of the positions of the lower section, upper section, and middle section is not only conducive to the preparation of the velvet structure, but also has 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. In addition, the appearance of the solar cell is uniformly black, which is more beautiful.

[0107] For example, the length of the upper section of a side edge is 1 / 10, 2 / 15, 3 / 20, 1 / 9, 1 / 8, 1 / 7, 1 / 6, 1 / 5, or 1 / 4 of the length of the side edge. The portion of a side edge excluding the lower section and the upper section is the middle section. For example, the length of the middle section of a side edge is 2 / 5, 13 / 30, 7 / 15, 1 / 2, 8 / 15, 17 / 30, or 3 / 5 of the length of the side edge.

[0108] Optionally, referring to FIG3 , the angle b between the lower segment of a side edge and the first plane is 50° to 55°. Referring to FIG5 , the angle c between the upper segment and the first plane is 55° to 80°, and the angle between the middle segment and the first plane is 55° to 85°. In FIG5 , the white solid line is the reverse extension of the upper segment. The angles between the three sub-segments and the first plane are reasonably set, making fabrication easier. Furthermore, the portion of the pyramid-like structure near the apex 11 is sharper, resulting in lower reflectivity and better light trapping, which can increase short-circuit current and ultimately improve the photovoltaic conversion efficiency of the solar cell. Furthermore, the solar cell has a uniform black appearance, making it more aesthetically pleasing. If the lower segment of a side edge is a single straight segment, the angle b between the lower segment of the side edge and the first plane can be the angle between the straight segment and the first plane. For example, in FIG3 , if the lower segment of the right side edge of the leftmost pyramid-like structure, located to the right of L2, is a single straight segment, then the angle b between the lower segment of the right side edge and the first plane can be the angle between the straight segment and the first plane. If the lower segment of a side edge is not a single straight line segment, the angle b between the lower segment of the side edge and the first plane can be the angle between the straight line segment to which the lower endpoint of the lower segment belongs and the first plane. For example, in Figure 3, the lower segment of the left side edge of the leftmost pyramid-like structure, located to the left of L1, is composed of two straight lines and has a single inflection point. In other words, the lower segment of the side edge is composed of a first straight line segment and a second straight line segment connected from top to bottom. In this case, the angle b between the lower segment of the side edge and the first plane can be the angle between the straight line segment to which the lower endpoint of the lower segment belongs, i.e., the second straight line segment, i.e., the line connecting the lower endpoint of the lower segment and the inflection point closest to the lower endpoint of the lower segment, and the first plane. If the upper segment of a side edge is a single straight line segment, the angle c between the upper segment of the side edge and the first plane can be the angle between the straight line segment and the first plane. If the upper segment of a lateral edge is not a single straight segment, the angle c between the upper segment of the lateral edge and the first plane may be the angle between the line connecting the upper and lower endpoints of the upper segment and the first plane. Similarly, the angle between the middle segment of a lateral edge and the first plane may be the angle between the line connecting the upper and lower endpoints of the middle segment and the first plane.

[0109] Optionally, the light-facing surface and / or backlight surface of the silicon substrate 1 have any of the aforementioned velvet structures. This allows for flexible placement of the velvet structure of the silicon substrate 1, and the velvet structure has a larger specific surface area, lower reflectivity, and better light trapping, which can increase short-circuit current and ultimately improve the photoelectric conversion efficiency of the solar cell. Furthermore, the solar cell has a uniform black appearance, making it more aesthetically pleasing. For example, at least the light-facing surface of the solar cell has any of the aforementioned velvet structures. For another example, the solar cell is a bifacial solar cell, and the light-facing surface of the silicon substrate 1 has any of the aforementioned velvet structures, or the backlight surface of the silicon substrate 1 has any of the aforementioned velvet structures, or both the light-facing and backlight surfaces of the silicon substrate 1 have any of the aforementioned velvet structures. For another example, the solar cell is a back-contact solar cell, and the light-facing surface of the silicon substrate 1 has any of the aforementioned velvet structures. For another example, the solar cell is a back-contact solar cell, and the backlight surface of the silicon substrate 1 has any of the aforementioned velvet structures. For another example, the solar cell is a back-contact solar cell, and both the light-facing and backlight surfaces of the silicon substrate 1 have any of the aforementioned velvet structures. For another example, the solar cell is a back-contact solar cell. Whether the light-facing surface of the silicon substrate 1 has the aforementioned velvet structure is not limited. The back-light surface of the silicon substrate 1 includes: alternating first and second regions, wherein the first region is doped with a first conductive element, or a first conductive layer is provided on the first region and doped with the first conductive element, and at least a portion of the second region is doped with the second conductive element, or a second conductive layer is provided on at least a portion of the second region and doped with the second conductive element. Here, the first conductive element corresponds to a first conductivity type, and the second conductive element corresponds to a second conductivity type, and the first and second conductivity types are different. The first region has any of the aforementioned velvet structures, or both the second region have any of the aforementioned velvet structures, or both the first and second regions have any of the aforementioned velvet structures. Alternatively, the portion of the second region other than the portion doped with the second conductive element is provided with any of the aforementioned velvet structures. Alternatively, the portion of the second region other than the portion provided with the second conductive layer is provided with any of the aforementioned velvet structures. For another example, the solar cell is a back-contact solar cell, and whether the light-facing surface of the silicon substrate 1 has the aforementioned velvet structure is not limited. The backlight surface of the silicon substrate 1 includes: alternating first areas and second areas, where a first conductive layer is prepared on the first area, and a second conductive layer is prepared on the second area. The conductivity types of the first conductive layer and the second conductive layer are different, and there may be an isolation area between the first area and the second area, wherein the isolation area may have any of the aforementioned velvet structures, or at least one of the first area, the second area, and the isolation area may have any of the aforementioned velvet structures.For another example, the solar cell is a back-contact solar cell. Whether the light-facing surface of the silicon substrate 1 has the aforementioned textured structure is not limited. The back-facing surface of the silicon substrate 1 includes alternating first and second regions. A first conductive layer is formed on the first region, and a second conductive layer is formed on the second region. The first and second conductive layers have different conductivity types and at least partially overlap. An insulating structure is provided between the overlapping portions of the first and second conductive layers. At least one of the first and second regions may have any of the aforementioned textured structures. The different conductivity types may, in some cases, be p-type doped or n-type doped, respectively. For another example, the solar cell is a back-contact solar cell. The back-facing surface of the silicon substrate 1 includes alternating n-type and p-type regions. The p-type regions are used to collect and conduct holes, and the n-type regions are used to collect and conduct electrons. An isolation region is provided between adjacent n-type and p-type regions. The light-facing surface of the silicon substrate 1 has any of the aforementioned textured structures, and / or the isolation region has any of the aforementioned textured structures. Both the n-type and p-type regions are relatively flat, resulting in high-quality conductive and passivation layers. No conductive layer is required in the isolation region. Providing a velvet structure can lower reflectivity, enhance light trapping, and improve the electrical performance of the back-contact solar cell. For another example, the solar cell is a back-contact solar cell, where the backlight surface of the silicon substrate 1 includes alternating n-type and p-type regions, the p-type regions having any of the aforementioned velvet structures, and the light-facing surface of the silicon substrate 1 also having any of the aforementioned velvet structures.

[0110] This application also provides a photovoltaic module, comprising: a plurality of any of the aforementioned solar cells; the number of solar cells in the photovoltaic module is not specifically limited. The photovoltaic module may also include an encapsulating film located on both sides of the solar cells. Other structures of the photovoltaic module are not specifically limited.

[0111] The present application also provides a method for preparing a solar cell, which is used to prepare any of the aforementioned solar cells. The preparation method includes: performing a first texturing on the silicon substrate 1, cleaning the silicon substrate 1 after the first texturing, and performing a second texturing on the cleaned silicon substrate 1. The second texturing here is to perform irregular corrosion on the velvet structure obtained by the first texturing. The second texturing can reduce the internal size of the bottom contour line of the pyramid-like structure away from the top of the cone, making the cone surface rougher, etc., to form a sharper pyramid-like structure. The velvet structure of the present application can be obtained by adjusting the process conditions of the second texturing, or by selecting different additives for the second texturing than for the first texturing.

[0112] Optionally, during the second texturing process: the components of the additives in the texturing liquid may include: sodium benzoate, defoaming agent, surfactant; and / or, the mass content of the additives in the texturing liquid is 0.01% to 5%; and / or, the temperature of the texturing liquid is 50°C to 85°C; and / or, the duration of the second texturing is 30s (seconds) to 400s, and the process parameters for the second texturing are relatively suitable, and it is easy to prepare any of the aforementioned velvet structures. The velvet structure of the present application can be obtained by adjusting the process conditions of the second texturing, or by selecting different additives for the second texturing than for the first texturing. The aforementioned texturing method can also be referred to as wet texturing. The actual structure of the velvet structure obtained by wet texturing is relatively complex, and it is difficult to ensure the consistency of the morphology of each pyramid-like structure in the velvet structure. It should be understood that as long as the morphology of most of the pyramid-like structures in the velvet structure meets the characteristics of the morphological structure described above, the effect described in the present application can be achieved.

[0113] The present application is further explained below with reference to specific embodiments.

[0114] Example

[0115] In the first step, the single crystal silicon wafer is subjected to preliminary alkali texturing to form a pyramid structure on the surface. The specific type of alkaline solution is not specifically limited, and can be selected from at least one of sodium hydroxide (NaOH) solution and potassium hydroxide (KOH) solution, and the height of the pyramid formed is 0.5μm to 3μm. More specifically, the texturing solution in the first step can be: NaOH solution or KOH solution with a mass concentration of 1% to 9% is mixed with additive A to form a first reaction liquid; the first texturing is completed within a temperature range of 60°C to 85°C and for 150s to 600s. Specifically, the cleaned single crystal silicon wafer is placed in the above-mentioned first reaction liquid, and the first texturing is carried out within the aforementioned temperature range and time range to form a pyramid structure. The height of the pyramid structure is between 0.5μm and 3μm. The main components of additive A include surfactants, dispersants, and emulsifiers. In the first texturing process, the added mass ratio of additive A is 0.01% to 5%.

[0116] In the second step, the single crystal silicon wafer that has been texturized with alkali in the first step is washed with DI (deionized water) to remove the residual chemical solution.

[0117] In a third step, the pyramid surface after the DI water wash is subjected to auxiliary polishing and a second texturing etching using a polishing and texturing solution. An additive is used to adjust the etching rate of the solution on various crystal directions of the crystalline silicon. Irregular etching is performed on the conical surface of the pyramid surface, and the pyramid is further etched inward, gradually reducing the width of the pyramid and increasing the angle between the side edges and the first plane, thereby forming a suede structure with a pyramid-like structure having a lower reflectivity. During the second texturing process, the additives in the texturing solution may include sodium benzoate, a defoaming agent, and a surfactant. The weight content of the additives in the texturing solution is 0.01% to 5%. The texturing solution in the second step may be a mixture of a 1% to 15% NaOH solution or a KOH solution with sodium benzoate, a defoaming agent, and a surfactant. The temperature of the texturing solution is 50° C. to 85° C., such as 60° C. to 85° C., and the duration of the second texturing process is 30 seconds to 400 seconds, such as 30 seconds to 240 seconds. The NaOH solution or KOH solution here can also be replaced by an organic base, and the organic base can be one of tetramethylammonium hydroxide, ethylenediamine, ethylenetriamine, methylenediamine and tetrabutylammonium hydroxide.

[0118] In the fourth step, the single crystal silicon wafers treated in the third step are washed with DI water, alkali and hydrogen peroxide mixture to remove surface chemical residues. In the fourth step, the total cleaning time is 60s to 150s, and the cleaning temperature is 50℃ to 70℃.

[0119] In the fifth step, the structure obtained in the fourth step is subjected to ozone washing, acid washing, etc. to form a hydrophobic surface to facilitate subsequent production processes.

[0120] In the fifth step, in the final pyramid-like structure, the angle between the side edge and the first surface ranges from 50° to 85°. More specifically, the side edge is divided into an upper section adjacent to the top of the cone, a lower section farthest from the top of the cone, and a middle section located between the lower section and the upper section. The length of the lower section accounts for 1 / 4 of the length of the side edge, the length of the middle section accounts for 1 / 2 of the length of the side edge, and the length of the upper section accounts for 1 / 4 of the length of the side edge. In other words, the portion of the pyramid-like structure that is away from the top of the cone is the lower portion of the pyramid-like structure, the height of the lower portion is 1 / 4 of the height of the pyramid-like structure, and the lower section is the portion of the side edge that corresponds to the lower portion. The portion of the pyramid-like structure that is adjacent to the top of the cone is the upper portion of the pyramid-like structure, the height of the upper portion accounts for 1 / 4 of the height of the pyramid-like structure, and the upper section is the portion of the side edge that corresponds to the upper portion. The portion of the pyramid-like structure located between the upper and lower portions is the middle portion, and its height accounts for half the height of the pyramid-like structure. The middle section is the portion of the side edge corresponding to the middle portion. The angle between the lower section and the first plane is 50° to 55°, the angle c between the upper section and the first plane is 55° to 80°, and the angle between the middle section and the first plane is 55° to 85°. The velvet structure of the silicon substrate of the solar cell finally prepared in this embodiment is shown in Figures 1 to 3 and 5. The maximum internal dimension of the bottom contour line of the pyramid-like structure is 10nm to 200nm.

[0121] The sixth step is to continue preparing a passivation anti-reflection layer and other structures on the single crystal silicon wafer obtained in the fifth step to obtain a solar cell.

[0122] Comparative Example

[0123] The comparative example only includes the first step, fourth step, fifth step and sixth step in the aforementioned embodiment, and the first step, fourth step, fifth step and sixth step are performed in sequence, and the first step, fourth step, fifth step and sixth step correspond to the first step, fourth step, fifth step and sixth step in the embodiment respectively.

[0124] Under the same test environment, the reflectivity of the side with the suede structure in the solar cells of the embodiment and the comparative example was tested. The test results are shown in Figure 6. In Figure 6, the horizontal axis is the wavelength (Wavelength) of the light irradiating the solar cell, in nm, and the vertical axis is the reflectivity (Reflectance). The blue curve (the curve at the bottom) in Figure 6 is used to characterize the corresponding reflectivity in the embodiment, and the red curve (the curve at the top) is used to characterize the corresponding reflectivity in the comparative example. It can be concluded that within most of the wavelength range that can be used by the solar cell, the reflectivity of the suede structure in the solar cell of the embodiment is lower.

[0125] 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.

[0126] Comparative table of electrical properties of solar cells of test examples and comparative examples

[0127] In the table above, 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. As can be seen from the table above, the photoelectric conversion efficiency, open-circuit voltage, short-circuit current, and conversion factor of the solar cells of the embodiment are all higher than those of the solar cells of the comparative example. This is primarily due to the improvements to the suede structure in the embodiment, which reduce reflectivity and enhance light trapping, thereby increasing short-circuit current and ultimately improving the photoelectric conversion efficiency of the solar cell.

[0128] It should be noted that throughout the text, contents with the same name can refer to each other. In order to avoid repetition, the relevant parts will not be repeated.

[0129] 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 preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0130] 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.

[0131] 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 multiple 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.

[0132] 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 comprising: A silicon substrate, and a passivation anti-reflection layer located on the silicon substrate; The surface of the silicon substrate has a velvet structure, and the velvet structure includes: a plurality of pyramid-like structures; the pyramid-like structures include: a cone surface and a cone top; the cone surface of the pyramid-like structure includes: a first sub-cone surface away from the cone top, and a second sub-cone surface, and the second sub-cone surface is the remaining part of the cone surface of the pyramid-like structure except the first sub-cone surface; in the cone surface of the pyramid-like structure, the surface morphology of the first sub-cone surface and the second sub-cone surface are different; The passivation anti-reflection layer includes: a first part located on the first sub-conical surface, and a second part located on the second sub-conical surface; in the passivation anti-reflection layer, the thickness of the first part along the same direction close to the cone top is greater than the thickness of the second part.

2. The solar cell according to claim 1, wherein the undulation of the first sub-conical surface is smaller than the undulation of the second sub-conical surface; Alternatively, the roughness of the first sub-conical surface is smaller than the roughness of the second sub-conical surface.

3. The solar cell according to claim 1, wherein the thickness of the first portion is greater than the thickness of the passivation anti-reflection layer at the cone top portion; And / or, the thickness of the portion of the passivation anti-reflection layer located at the position adjacent to the adjacent pyramid-like structures is greater than the thickness of the portion of the passivation anti-reflection layer located at the pyramid top; And / or, in the passivation anti-reflection layer, the thickness of a portion located at a position adjacent to the adjacent pyramid-like structures is greater than the thickness of the second portion.

4. The solar cell according to claim 1, wherein in the passivation anti-reflection layer, the thickness non-uniformity between the first part and the second part is greater than 4%; the thickness non-uniformity is: the absolute value of the difference between a first thickness at a first position in the first part and a second thickness at a second position in the second part along the same direction close to the top of the cone, divided by the sum of the first thickness and the second thickness.

5. The solar cell according to claim 1, further comprising: an aluminum oxide layer located between the silicon substrate and the passivation anti-reflection layer; The aluminum oxide layer includes: a third portion located on the first sub-conical surface, and a fourth portion located on the second sub-conical surface; The thickness non-uniformity between the first part and the second part of the passivation anti-reflection layer is greater than the thickness non-uniformity between the third part and the fourth part of the aluminum oxide layer; The thickness non-uniformity between the first portion and the second portion of the passivation anti-reflection layer is: the absolute value of the difference between the first thickness at a first position in the first portion and the second thickness at a second position in the second portion along the same direction close to the cone top, divided by the sum of the first thickness and the second thickness; The thickness non-uniformity between the third part and the fourth part in the aluminum oxide layer is: the absolute value of the difference between the third thickness at the third position in the third part and the fourth thickness at the fourth position in the fourth part along the same direction close to the top of the cone, divided by the sum of the third thickness and the fourth thickness.

6. The solar cell according to claim 1, wherein the passivation anti-reflection layer comprises: A front passivation anti-reflection layer located on the light-facing side of the silicon substrate, and a back passivation anti-reflection layer located on the backlight-facing side of the silicon substrate; In the thickness direction of the silicon substrate, at two opposite positions, the thickness of the back passivation anti-reflection layer is greater than the thickness of the front passivation anti-reflection layer.

7. According to the solar cell of claim 6, in the thickness direction of the silicon substrate, at two relative positions, the difference between the thickness of the back passivation anti-reflection layer and the thickness of the front passivation anti-reflection layer is greater than or equal to 15 nm and less than or equal to 40 nm. 8 . The solar cell according to claim 1 , wherein the conical surface of the pyramid-like structure has a branched texture, and the number of the branched textures in the second sub-conical surface is greater than the number of the branched textures in the first sub-conical surface. 9 . The solar cell according to claim 1 , wherein the cone top of the pyramid-like structure and the second sub-cone surface of the cone surface of the pyramid-like structure have a cluster of nested ring-like textures. 10 . The solar cell according to claim 9 , wherein in a cluster of the quasi-annular textures, along the height direction of the quasi-pyramid structure, the closer to the cone top, the smaller the outline of the quasi-annular texture.

11. The solar cell according to any one of claims 1 to 10, wherein the portion of the pyramid-like structure away from the cone top is the lower portion of the pyramid-like structure, and the height of the lower portion accounts for at least 1 / 10 of the height of the pyramid-like structure; The first sub-conical surface is: an area corresponding to the lower part of the conical surface of the pyramid-like structure; The second sub-conical surface is: a region of the conical surface of the pyramid-like structure that is closer to the cone top than the first sub-conical surface.

12. The solar cell according to any one of claims 1 to 10, wherein the pyramid-like structure further comprises: A bottom contour line away from the cone top, wherein at least two points in the same bottom contour line have a height difference. 13 . The solar cell according to claim 1 , wherein a top angle of the textured structure is 55° to 90°. 14 . The solar cell according to claim 1 , wherein the pyramid-like structure has a height of 0.2 μm to 3 μm. 15 . The solar cell according to claim 1 , wherein the light-facing surface and / or the backlight surface of the silicon substrate has the suede structure.

16. A photovoltaic module, comprising: A plurality of solar cells as claimed in any one of claims 1 to 15.

Images