Method for manufacturing a solar cell, solar cell and photovoltaic module

Abstract

The embodiment of the present application relates to the photovoltaic field, and provides a preparation method of a solar cell, the solar cell and a photovoltaic module, the method comprises the following steps: obtaining a preliminary substrate with a first preliminary surface, the first preliminary surface has a plurality of initial texturing structures including a first texturing structure and a second texturing structure, the size of the first texturing structure is greater than the size of the second texturing structure; performing full-surface laser scanning on the first preliminary surface; using a first alkaline texturing solution, performing secondary texturing on the first preliminary surface after full-surface laser scanning, etching the second texturing structure, so that the preliminary substrate after secondary texturing forms a cell substrate, the first preliminary surface after secondary texturing forms a first surface, and the plurality of initial texturing structures after secondary texturing form a plurality of texturing structures. The preparation method of the solar cell provided by the embodiment of the present application can at least improve the problem that the conversion efficiency of the cell is low due to the poor uniformity of the texturing after texturing in the prior art.

Description

Technical Field

[0001] This application relates to the photovoltaic field, and in particular to a method for preparing a solar cell, a solar cell, and a photovoltaic module. Background Technology

[0002] A well-textured surface structure can not only reduce solar reflectivity and increase light absorption, but also improve surface passivation and electrode contact properties, thereby increasing carrier collection efficiency. Therefore, innovative research on texturing processes has always been a key focus in crystalline silicon solar cells. However, in existing technologies, the textured surface generally has poor uniformity, resulting in lower cell conversion efficiency. Summary of the Invention

[0003] This application provides a method for preparing a solar cell, a solar cell, and a photovoltaic module, which at least helps to improve the problem of low cell conversion efficiency caused by poor uniformity of the texturing surface after texturing in the prior art.

[0004] According to some embodiments of this application, one aspect of this application provides a method for fabricating a solar cell, comprising: obtaining a pre-substrate having a first pre-substrate surface, the first pre-substrate surface having a plurality of initial textured structures, the plurality of initial textured structures including a first textured structure and a second textured structure, the size of the first textured structure being larger than the size of the second textured structure; performing a full-surface laser scan on the first pre-substrate; using a first alkaline texturing solution to perform a secondary texturing on the first pre-substrate after the full-surface laser scan to etch the second textured structure, so that the pre-substrate after the secondary texturing forms a battery substrate, wherein the first pre-substrate after the secondary texturing forms a first surface, and the plurality of initial textured structures after the secondary texturing form a plurality of textured structures; and forming a functional layer on the first surface of the battery substrate to cover the plurality of textured structures.

[0005] In some embodiments, the first suede structure includes a first pyramid structure, the second suede structure includes a second pyramid structure, the bottom width of the first pyramid structure ranges from 1.1 μm to 1.7 μm, and the bottom width of the second pyramid structure ranges from 0.05 μm to 0.2 μm.

[0006] In some embodiments, performing a full-surface laser scan on the first preparatory surface includes: using a pulsed laser to perform a full-surface scan on the first preparatory surface, wherein the pulse width of the pulsed laser is in the range of 20ns-60ns, the scanning speed of the pulsed laser is in the range of 23000mm / s-27000mm / s, and the laser power of the pulsed laser is in the range of 30W-50W.

[0007] In some embodiments, a secondary texturing process is performed on the first prepared surface after laser scanning, including: performing a secondary texturing process on the first prepared surface for 60s-100s at a temperature of 50℃-70℃.

[0008] In some embodiments, the solute in the first alkaline texturing solution includes a first alkaline solute and a surfactant.

[0009] In some embodiments, the mass fraction of the first alkaline solute in the first alkaline texturing solution is 10%-60%, and the mass fraction of the surfactant in the first alkaline texturing solution is 2%-5%.

[0010] In some embodiments, after performing a full-surface laser scan on the first preparatory surface and before performing a secondary texturing on the first preparatory surface after the full-surface laser scan, the method further includes: pickling the preparatory substrate; cleaning the pickled preparatory substrate using an RCA cleaning solution; washing the cleaned preparatory substrate with water; and / or obtaining a preparatory substrate having a first preparatory surface, including: obtaining an initial preparatory substrate having a first initial preparatory surface; texturing the first initial preparatory surface using a second alkaline texturing solution to obtain the plurality of initial texturing structures, wherein the texturized first initial preparatory surface forms the first preparatory surface, and the texturized initial preparatory substrate forms the preparatory substrate, wherein the second alkaline texturing solution includes a second alkaline solute.

[0011] According to some embodiments of this application, another aspect of this application provides a solar cell, which is prepared using any of the solar cell preparation methods described above.

[0012] In some embodiments, the solar cell is at least one of a tunneling oxide passivated contact cell, an emitter and back passivated cell, a passivated emitter back surface fully diffused cell, a back contact cell, and a heterojunction cell.

[0013] In some embodiments, the dimensional deviation of the multiple velvet structures is less than 25%.

[0014] According to some embodiments of this application, another aspect of this application provides a photovoltaic module, including: a battery string, formed by connecting a plurality of the aforementioned solar cells; an encapsulating film for covering the surface of the battery string; and a cover plate for covering the surface of the encapsulating film facing away from the battery string.

[0015] The technical solution provided in this application has at least the following advantages:

[0016] First, a pre-substrate with a first pre-prepared surface is obtained. Then, the first pre-substrate, including a first initial textured surface structure and a second initial textured surface structure, is subjected to full-surface laser scanning. Next, a first alkaline texturing solution is used to perform secondary texturing on the first pre-substrate after full-surface laser scanning to etch a second textured surface structure with a size smaller than the first textured surface structure. This results in the pre-substrate after secondary texturing, the first pre-substrate, and the multiple initial textured surface structures forming a battery substrate, a first surface, and multiple textured surface structures, respectively. Finally, a functional layer covering the multiple textured surface structures is formed on the first surface of the battery substrate. To address the problem of poor uniformity of the texturized surface in existing technologies, which leads to low cell conversion efficiency, this application processes the initial texturized structure (first texturized structure and second texturized structure) with size differences through full-surface laser scanning. A second texturizing process is performed using a first alkaline texturizing solution to selectively etch the smaller second texturized structure. This process, while preserving the larger first texturized structure, achieves uniform modification and defect elimination of the texturized structure through chemical etching. The resulting cell substrate surface has a more uniform texturized morphology, thus providing a structural basis for the formation of subsequent functional layers, optimizing the optical light trapping performance and passivation effect of the solar cell, and improving the photoelectric conversion efficiency of the solar cell. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the drawings in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of a method for fabricating a solar cell according to an embodiment of this application;

[0019] Figure 2 This is a schematic diagram of a solar cell fabricated using a traditional solar cell textured surface preparation method, obtained via SEM (Scanning Electron Microscopy).

[0020] Figure 3 This is a SEM schematic diagram of a solar cell according to an embodiment of this application;

[0021] Figure 4The image shows a comparison of the QE (Quantum Efficiency) spectra of solar cells prepared using the conventional solar cell textured surface preparation method and the solar cell preparation method of this application, respectively. Detailed Implementation

[0022] As is known from the background art, the poor uniformity of the texturing surface after texturing in the prior art leads to low conversion efficiency of the battery. In order to solve the above problems, this application provides a method for preparing a solar cell, a solar cell, and a photovoltaic module.

[0023] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0026] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0027] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0028] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0029] In the accompanying drawings corresponding to the embodiments of this application, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be a third component between the two components. Conversely, when describing a component on the surface of another component, or when another component is formed or disposed on the surface of a component, it indicates that there is no third component between the two components. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0030] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may be present therein. Moreover, when a component such as a layer, film, region, or plate is "directly located" on another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it indicates that no other components are located therein.

[0031] The terminology used in the description of the various embodiments described herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "foreword" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0032] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0033] Figure 1 This is a flowchart of a method for fabricating a solar cell according to an embodiment of this application. Figure 1 As shown, the method includes the following steps:

[0034] Step S101: Obtain a pre-prepared substrate having a first pre-prepared surface. The first pre-prepared surface has a plurality of initial textured structures, including a first textured structure and a second textured structure. The size of the first textured structure is larger than the size of the second textured structure.

[0035] It should be noted that the first velvet structure and the second velvet structure mentioned above can be independent pyramid structures.

[0036] It should be noted that the dimension of the velvet structure refers to the width of the bottom surface, and the direction of the width is perpendicular to the thickness direction of the prepared substrate. In one embodiment, the bottom surface width of the first velvet structure is not less than 1.1 μm, and the bottom surface width of the second velvet structure is less than 1.1 μm.

[0037] In one embodiment, the prepared substrate is an N-type substrate, and the material of the prepared substrate includes silicon. The first prepared surface may be the front side of the prepared substrate, the back side of the prepared substrate, or both the front and back sides of the prepared substrate; this application does not impose specific limitations in this regard.

[0038] Step S102: Perform a full-surface laser scan on the first prepared surface.

[0039] It should be noted that the introduction of laser full-area scanning can eliminate nucleated small pyramids and uneven defects (i.e., the second textured surface structure) in the line-marked area, while retaining some independent and complete pyramid structures (i.e., the first textured surface structure). Laser scanning is a full-area scan, producing an ablation effect on both effective pyramids (i.e., the first textured surface structure) and ineffective pyramids (i.e., the second textured surface structure). Ineffective pyramids are small and irregular, achieving an ablation effect of >70%~90% after laser scanning; while effective pyramids are large, uniform, and regular, causing only slight ablation to the surface layer after laser scanning, with minimal overall impact. The line-marked area refers to the grooves and their edges on the surface of the solar cell silicon wafer left by the diamond wire cutting process, characterized by high-density dislocations and damage leading to incomplete or uneven pyramid textured surface growth.

[0040] Step S103: Using a first alkaline texturing solution, the first prepared surface after laser scanning is subjected to secondary texturing to etch the second textured surface structure so that the prepared substrate after secondary texturing forms a battery substrate. The first prepared surface after secondary texturing forms a first surface, and the multiple initial textured surface structures after secondary texturing form multiple textured surface structures.

[0041] It should be noted that a second texturing process is performed on the basis of full-surface laser scanning. On the one hand, the alkali is used to effectively corrode the incompletely ablated invalid pyramids (i.e., the second texturing structure), and on the other hand, the effective pyramids (i.e., the first texturing structure) that are damaged after full-surface laser scanning are modified.

[0042] Step S104: A functional layer is formed on the first surface of the battery substrate to cover the plurality of textured structures.

[0043] In this embodiment, a pre-substrate having a first pre-prepared surface is first obtained. Then, the first pre-substrate, including a first initial textured surface structure and a second initial textured surface structure, is subjected to full-surface laser scanning. Then, a first alkaline texturing solution is used to perform secondary texturing on the first pre-substrate after full-surface laser scanning to etch a second textured surface structure with a size smaller than the first textured surface structure. This allows the pre-substrate after secondary texturing, the first pre-substrate, and the multiple initial textured surface structures to form a battery substrate, a first surface, and multiple textured surface structures, respectively. Finally, a functional layer covering the multiple textured surface structures is formed on the first surface of the battery substrate. To address the problem of poor uniformity of the texturized surface in existing technologies, which leads to low cell conversion efficiency, this application processes the initial texturized structure (first texturized structure and second texturized structure) with size differences through full-surface laser scanning. A second texturizing process is performed using a first alkaline texturizing solution to selectively etch the smaller second texturized structure. This process, while preserving the larger first texturized structure, achieves uniform modification and defect elimination of the texturized structure through chemical etching. The resulting cell substrate surface has a more uniform texturized morphology, thus providing a structural basis for the formation of subsequent functional layers, optimizing the optical light trapping performance and passivation effect of the solar cell, and improving the photoelectric conversion efficiency of the solar cell.

[0044] It should be noted that in current manufacturing processes, the common texturing process for monocrystalline or quasi-monocrystalline silicon wafers uses alkaline pyramid etching, forming a random pyramid structure on the silicon surface that can reflect sunlight twice, typically with a reflectivity of around 10%. However, within and around the edges of the line grooves, due to the high density of dislocations and damage, the etching rate differs from that of intact areas. This results in pyramids on the line grooves being too large, too small, or even failing to form regular pyramids, instead becoming flat or over-etched scarred areas. The entire silicon wafer surface is no longer a uniformly and randomly distributed pyramid, but rather divided by line grooves, creating variations in texture quality. Existing texturing processes, influenced by factors such as thinning, variations in diamond line grooves, and low unit consumption, result in uneven pyramid distribution and size, as well as incomplete texture growth in the line groove areas, leading to enhanced recombination and poor light absorption. To address this, this application utilizes laser-assisted ablation to perform a comprehensive laser scan on the textured battery surface, ablating invalid pyramids with incomplete or uneven nucleation in the line mark area, and then performing a secondary texturing process to eliminate and modify the damaged structure, improve the uniformity of the pyramid textured surface, reduce surface recombination, enhance the light-trapping structure, and improve the cell conversion efficiency.

[0045] In some embodiments, the solar cell may be at least one of PERC cell (Passivated Emitter and Rear Cell), PERT cell (Passivated Emitter and Rear Totally Diffused Cell), TOPCon cell (Tunnel Oxide Passivated Contact), HIT / HJT cell (Heterojunction Technology), or BC cell (Back Contact). This application does not impose any specific limitations on this.

[0046] In one embodiment, taking a TOPCon battery as an example, the prepared substrate is N-type, and the first prepared surface is the front side of the prepared substrate. A functional layer is formed on the first surface of the battery substrate to cover the plurality of textured structures, including: forming a P+ emitter on the first surface of the battery substrate to cover the plurality of textured structures; forming a passivation layer on the surface of the P+ emitter facing away from the battery substrate; forming a first antireflection film on the surface of the passivation layer facing away from the battery substrate; and forming a plurality of spaced-apart first metal electrodes on the surface of the first antireflection film facing away from the battery substrate. The method further includes: forming a tunneling oxide layer on the surface of the battery substrate facing away from the P+ emitter; forming an n+poly layer on the surface of the tunneling oxide layer facing away from the battery substrate; forming a second antireflection film on the surface of the n+poly layer facing away from the battery substrate; and forming a plurality of spaced-apart second metal electrodes on the surface of the second antireflection film facing away from the battery substrate.

[0047] In one embodiment, the battery substrate can be at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. The passivation layer can be one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, titanium oxide, hafnium oxide, or aluminum oxide. The passivation layer can be a single-layer structure or a stacked structure. For example, the single-layer structure can be a single-layer aluminum oxide film, a single-layer silicon oxide film, a single-layer silicon nitride film, or a single-layer silicon oxynitride film. The stacked structure can be formed by stacking at least two of the following films: aluminum oxide film, silicon oxide film, silicon nitride film, or silicon oxynitride film. The battery substrate can be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type dopant element, which can be at least one of group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type dopant element, which can be at least one of group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In). The material of the tunneling oxide layer can be at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or magnesium fluoride.

[0048] In one alternative embodiment, the first velvet structure includes a first pyramid structure, the second velvet structure includes a second pyramid structure, the bottom width of the first pyramid structure ranges from 1.1μm to 1.7μm, and the bottom width of the second pyramid structure ranges from 0.05μm to 0.2μm. In this embodiment, by limiting the size of the first textured structure (first pyramid structure) to 1.1μm-1.7μm, it is ensured that the retained effective pyramid has sufficient sidewall area to provide excellent light-trapping effect and maintain the mechanical stability of the structure, avoiding structural fragility or insufficient light-trapping ability caused by pyramids that are too small. At the same time, the size of the second textured structure (second pyramid structure) is limited to 0.05μm-0.2μm, which precisely defines the range of tiny, invalid pyramids formed by line marks or uneven nucleation, providing a clear target for the subsequent laser scanning ablation process. This allows the laser energy to efficiently and selectively remove these sub-micron defect structures, thereby achieving the transformation of the textured surface from mixed sizes to uniform size after secondary texturing, significantly improving the uniformity of the textured surface, reducing the density of surface composite centers, and ultimately improving the photoelectric conversion efficiency of the battery.

[0049] It should be noted that invalid pyramids (i.e., second pyramid structures) appear as incompletely grown structures under SEM conditions, with a base width of 0.05μm~0.2μm, while normal pyramids (i.e., first pyramid structures) have a base width of 1.1μm~1.7μm. They can be distinguished by SEM measurement or by visual inspection.

[0050] In another alternative, the first preparatory surface is subjected to a full-surface laser scan, which includes: using a pulsed laser to scan the first preparatory surface, wherein the pulse width of the pulsed laser is in the range of 20ns-60ns, the scanning speed of the pulsed laser is in the range of 23000mm / s-27000mm / s, and the laser power of the pulsed laser is in the range of 30W-50W. In this embodiment, by limiting the pulse width of the pulsed laser to 20ns-60ns, cold processing is achieved using the high peak power of ultrashort pulses. While ablating the ineffective small pyramids in the line mark area, the heat-affected zone is minimized, and thermal damage or melting of the retained effective large pyramid structure is reduced as much as possible. The scanning speed is controlled at 23000mm / s-27000mm / s to ensure the uniformity of laser energy distribution and processing efficiency on the silicon wafer surface. This prevents excessive ablation due to excessively slow speed or incomplete ablation due to excessively fast speed. With a laser power of 30W-50W, the energy threshold sufficient to destroy the integrity of the small pyramid structure is guaranteed, while avoiding excessive power that could damage the silicon matrix or generate too many microcracks, thus providing an ideal substrate condition for subsequent secondary texturing.

[0051] In one embodiment, the scanning speed of the pulsed laser can be 23000 mm / s, 25000 mm / s, or 27000 mm / s, and this application does not impose a specific limitation thereon. The laser power of the pulsed laser can be 30W, 40W, or 50W, and this application does not impose a specific limitation thereon.

[0052] In one embodiment, the wavelength of the pulsed laser is 532 nm.

[0053] According to some exemplary embodiments of this application, a secondary texturing process is performed on the first prepared surface after laser scanning, including: performing a secondary texturing process on the first prepared surface at a temperature of 50℃-70℃ for 60s-100s. In this embodiment, the temperature of the secondary texturing is limited to 50℃-70℃ and the duration is controlled to 60s-100s. This aims to accurately remove the second textured surface structure (i.e., the smaller ineffective pyramid) and microstructural defects caused by laser damage after laser scanning through mild and moderate alkaline corrosion conditions. At the same time, it avoids excessive dissolution or morphological collapse of the retained first textured surface structure (large effective pyramid) due to high temperature or long-term corrosion. This combination of process parameters achieves a better balance between corrosion rate and structural integrity, ensuring the uniformity and regularity of the textured surface structure after secondary texturing, thereby effectively improving the textured surface defects in the line mark area and improving the light trapping effect and passivation quality of the battery surface.

[0054] According to some exemplary embodiments of this application, the solute in the first alkaline texturing solution includes a first alkaline solute and a surfactant. In this embodiment, introducing a surfactant into the first alkaline texturing solution can reduce the surface tension of the solution, enhance its wettability and permeability to the silicon wafer surface, and ensure that the alkaline solution uniformly covers and fully contacts the silicon surface, thereby effectively avoiding uneven texturing or spot defects caused by poor local wetting. At the same time, the surfactant helps to promote the dispersion and detachment of byproducts during the etching reaction, preventing them from accumulating in the pyramid gaps and hindering the reaction process. This ensures that the textured surface structure formed after secondary texturing (especially the retained large-size first textured surface structure) has higher morphological regularity and dimensional consistency, significantly improving textured surface uniformity and optical light trapping efficiency, and providing a high-quality interface foundation for subsequent functional layer deposition.

[0055] It should be noted that the first alkaline solute, surfactant and silicon participate in the reaction and will be adsorbed on the silicon wafer surface. During the effective reaction time (60s~100s), the small pyramids (i.e. the second textured structure) will be corroded or polished due to their small size under high alkaline concentration. The large and independent pyramids (i.e. the first textured structure) will not be completely corroded or polished, thus effectively performing surface modification.

[0056] According to some other exemplary embodiments of this application, the mass fraction of the first alkaline solute in the first alkaline texturing solution is 10%-60%, and the mass fraction of the surfactant in the first alkaline texturing solution is 2%-5%. In this embodiment, limiting the mass fraction of the first alkaline solute to 10%-60% ensures that the solution has sufficient corrosive activity to effectively remove the second texturing structure (defective pyramid) remaining after laser scanning during the secondary texturing process. At the same time, it avoids excessive corrosion or collapse of the retained first texturing structure (complete pyramid) due to excessive concentration. Combined with a surfactant mass fraction of 2%-5%, it ensures that the solution has sufficient surface tension reduction ability to enhance wettability and by-product removal effect, while preventing excessive surfactant introduction that leads to excessive foaming, cleaning difficulties, or residual pollution. This concentration ratio achieves a better balance between corrosion rate and surface uniformity, thereby effectively eliminating texturing defects in the line mark area while better preserving and modifying the effective pyramid structure, significantly improving texturing uniformity and battery conversion efficiency.

[0057] It should be noted that the mass fractions of the first alkaline solute and the surfactant mentioned above are merely illustrative examples. Those skilled in the art can flexibly adjust the mass fractions of the first alkaline solute and the surfactant according to actual needs, and this application does not impose specific limitations on them. In some embodiments, the mass fraction of the first alkaline solute is not in the range of 10%-60% (e.g., set to 5%, 70%, 80%, 90%, etc.), and / or the mass fraction of the surfactant is not in the range of 2%-5% (e.g., set to 1%, 6%, 10%, etc.), which can also achieve the technical effect of making the final battery substrate surface have a more uniform textured morphology, thereby solving the problem of poor uniformity of the textured surface after texturing in the prior art, which leads to low battery conversion efficiency. Of course, this technical effect is slightly worse than the technical effect of the first alkaline solute mass fraction being 10%-60% and the surfactant mass fraction being 2%-5%.

[0058] In one embodiment, the solvent of the first alkaline texturing solution includes water, and the first alkaline solute includes sodium hydroxide. In practical applications, those skilled in the art can flexibly select suitable first alkaline solute and surfactant according to actual needs, and this application does not impose specific limitations in this regard.

[0059] In one embodiment, the volume of the first alkaline texturing solution ranges from 680L to 720L.

[0060] According to some other exemplary embodiments of this application, after performing a full-surface laser scan on the first prepared surface and before performing a secondary texturing on the first prepared surface after the full-surface laser scan, the method further includes: pickling the prepared substrate; cleaning the pickled prepared substrate with RCA cleaning solution; washing the cleaned prepared substrate with water; and / or obtaining a prepared substrate having a first prepared surface, including: obtaining an initial prepared substrate having a first initial prepared surface; texturing the first initial prepared surface with a second alkaline texturing solution to obtain the plurality of initial texturing structures, wherein the texturized first initial prepared surface forms the first prepared surface, and the texturized initial prepared substrate forms the prepared substrate, wherein the second alkaline texturing solution includes a second alkaline solute. In this embodiment, acid washing and RCA cleaning processes are introduced after laser scanning and before secondary texturing. This removes metallic impurities, carbon contamination, and micro-debris generated on the silicon wafer surface during laser ablation, ensuring the purity and uniformity of the secondary texturing reaction and preventing surface defects or poor subsequent passivation caused by impurity adhesion. The initial texturing uses a solution containing a second alkaline solute to form first and second textured surface structures with significant size differences, laying a good microscopic morphological foundation for subsequent precise laser identification and selective ablation, thereby ensuring high uniformity, low surface recombination rate, and excellent photoelectric conversion efficiency of the final textured surface.

[0061] The prepared substrate after pickling is cleaned using RCA cleaning solution. Specifically, the prepared substrate after pickling is cleaned using the RCA standard cleaning method.

[0062] It should be noted that after obtaining the prepared substrate through the first texturing process, the invalid small pyramidal texturing structure (i.e., the second texturing structure) in the line mark area is ablated using a laser ablation process (i.e., laser full-surface scanning). Then, a second texturing process is used to improve the defects of the small pyramidal structure remaining in the laser-damaged area, effectively ensuring the uniformity of the texturing surface and the light-trapping effect. In one embodiment, after obtaining the prepared substrate through the first texturing process, the substrate is sequentially washed with water, acid-washed, washed with water, and then subjected to the laser ablation process to avoid the residual alkaline solution from the first texturing process affecting the laser effect. After the laser ablation process, the substrate is sequentially acid-washed, cleaned, and washed with water, and then subjected to the second texturing process. After the second texturing process, the substrate is sequentially cleaned, acid-washed, washed with water, slowly lifted, and dried to form the functional layer.

[0063] To verify the technical effect of this application, both the traditional solar cell textured surface preparation method and the solar cell preparation method of this application were used to prepare solar cells (textured front surface of the cell) using silicon raw materials with the same process parameters. The SEM images, QE spectrum curves, and key performance index comparison data of the actual solar cells prepared by the traditional solar cell textured surface preparation method and the solar cell preparation method of this application are shown below. Figure 2 , Figure 3 , Figure 4 As shown in Table 1, the performance indicators in Table 1 include reflectivity, open-circuit voltage (VOC), short-circuit current density (ISC), fill factor (FF), photoelectric conversion efficiency (ETA), antireflection film reflection loss, and blue light loss, in order to objectively quantify the significant advantages of this application.

[0064] Table 1

[0065]

[0066] Specifically, Figure 2 This is a SEM image of a solar cell fabricated using a traditional solar cell textured surface preparation method. Figure 2 In the image, the white circle indicates the invalid pyramid area marked by the lines. As you can see... Figure 2 The size of the pyramids varies greatly, and the uniformity of the velvet surface is poor. Figure 3 The SEM image of the solar cell prepared by the method of this application shows that... Figure 3 The size difference of the middle pyramid is small, and the uniformity of the velvet surface is good.

[0067] Specifically, Figure 4 In the diagram, the blue curve BSL represents the QE front response spectrum of a solar cell fabricated using a conventional solar cell textured surface preparation method, and the red curve SY represents the QE front response spectrum of a solar cell fabricated using the method described in this application. The horizontal axis represents the wavelength of the incident wave incident on the front of the cell, in nm, and the vertical axis represents the quantum efficiency, in %. Figure 4 As can be seen, when the incident wave is a short wavelength of 300nm-500nm, the cell exhibits a positive response in quantum efficiency. Within this range, compared to solar cells prepared using traditional solar cell textured surface preparation methods, solar cells prepared using the method described in this application have higher quantum efficiency and better light absorption.

[0068] The solar cell of this application, after laser ablation and secondary texturing, has an overall improved uniformity of the textured surface, a significant effective pyramid structure in the line mark area, and a 0.1-0.2% decrease in reflectivity; the QE spectral response is a front response, and the loss of the front antireflectivity film and blue light loss are reduced; under Zeta / SEM testing, the integrity and independence of the micro pyramid morphology are improved; it can improve the cell conversion efficiency by 0.02% without reducing the product yield.

[0069] This application also provides a solar cell, which is prepared using any of the above-described methods for preparing solar cells.

[0070] In the above embodiments, the solar cell is prepared using the above-described solar cell preparation method. In the solar cell preparation method, a preparation substrate having a first preparation surface is first obtained. Then, the first preparation surface, including a first initial textured surface and a second initial textured surface, is subjected to full-surface laser scanning. Then, a first alkaline texturing solution is used to perform secondary texturing on the first preparation surface after full-surface laser scanning to etch a second textured surface with a size smaller than the first textured surface. This results in the preparation substrate after secondary texturing, the first preparation surface, and the multiple initial textured surfaces forming a battery substrate, a first surface, and multiple textured surfaces, respectively. Finally, a functional layer covering the multiple textured surfaces is formed on the first surface of the battery substrate. To address the problem of poor uniformity of the texturized surface in existing technologies, which leads to low cell conversion efficiency, this application processes the initial texturized structure (first texturized structure and second texturized structure) with size differences through full-surface laser scanning. A second texturizing process is performed using a first alkaline texturizing solution to selectively etch the smaller second texturized structure. This process, while preserving the larger first texturized structure, achieves uniform modification and defect elimination of the texturized structure through chemical etching. The resulting cell substrate surface has a more uniform texturized morphology, thus providing a structural basis for the formation of subsequent functional layers, optimizing the optical light trapping performance and passivation effect of the solar cell, and improving the photoelectric conversion efficiency of the solar cell.

[0071] In one embodiment, the solar cell is at least one of a tunneling oxide passivated contact cell, an emitter and back passivated cell, a passivated emitter back surface fully diffused cell, a back contact cell, and a heterojunction cell.

[0072] In one alternative, the dimensional deviation of multiple textured structures is less than 25%. In this embodiment, the dimensional deviation of multiple textured structures is less than 25%, which means that after laser scanning and secondary texturing, the pyramid structure on the silicon wafer surface has high dimensional consistency and uniform distribution. This highly uniform textured structure can significantly reduce light scattering unevenness and surface passivation quality fluctuations caused by excessive pyramid size differences, thereby effectively reducing nonradiative recombination of charge carriers on the surface, improving the absorption rate and light trapping effect of front light, and ultimately resulting in a comprehensive improvement in the open-circuit voltage, short-circuit current, and fill factor of the solar cell, thereby achieving higher photoelectric conversion efficiency.

[0073] In one embodiment, the method for calculating the dimensional deviation of multiple velvet structures is as follows: 1) First, the microscopic morphology of multiple velvet structures is characterized by scanning electron microscopy (SEM), and the bottom width of multiple velvet structures is identified and extracted as the dimensional feature value; then, the dimensional data of all velvet structures are statistically analyzed, their average value is calculated, and the range between the maximum and minimum dimensions is calculated. Finally, the percentage of the range to the average value is calculated to obtain the dimensional dispersion between multiple velvet structures, thereby quantifying the uniformity of the velvet surface; or, 2) The dimensional data (bottom width) of all velvet structures are statistically analyzed, their standard deviation and arithmetic mean are calculated, and the ratio of the standard deviation to the arithmetic mean is determined as the dimensional deviation.

[0074] This application also provides a photovoltaic module, including: a battery string, which is formed by connecting multiple solar cells as described above; an encapsulating film for covering the surface of the battery string; and a cover plate for covering the surface of the encapsulating film away from the battery string.

[0075] It should be noted that the connection between photovoltaic cells can be achieved through techniques such as welding, with the aim of converging the current generated by the photovoltaic cells to form a greater output power; the encapsulating film is an important component inside the photovoltaic module, playing a role in sealing and bonding. The encapsulating film can be EVA (ethylene vinyl acetate copolymer), POE (polyolefin elastomer), or other special materials, which can effectively block the influence of external factors such as moisture and dust on the photovoltaic cells, while maintaining the physical stability of the photovoltaic cells; the cover plate is usually transparent tempered glass, located on the outermost layer of the photovoltaic module, directly exposed to the external environment. It not only needs to have good light transmittance and mechanical strength, but also needs to have properties such as UV protection, high temperature resistance, and impact resistance to protect the internal photovoltaic cells from damage.

[0076] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A method for preparing a solar cell, characterized in that, include: A pre-substrate having a first pre-prepared surface is obtained, the first pre-prepared surface having a plurality of initial textured structures, the plurality of initial textured structures including a first textured structure and a second textured structure, wherein the size of the first textured structure is larger than the size of the second textured structure; Perform a full-surface laser scan on the first prepared surface; Using a first alkaline texturing solution, the first prepared surface after laser scanning is subjected to secondary texturing to etch the second texturing structure, so that the prepared substrate after secondary texturing forms a battery substrate. The first prepared surface after secondary texturing forms a first surface, and the multiple initial texturing structures after secondary texturing form multiple texturing structures. The solute in the first alkaline texturing solution includes a first alkaline solute and a surfactant. A functional layer is formed on the first surface of the battery substrate to cover the plurality of textured structures.

2. The method for preparing a solar cell according to claim 1, characterized in that, The first velvet structure includes a first pyramid structure, and the second velvet structure includes a second pyramid structure. The bottom width of the first pyramid structure ranges from 1.1 μm to 1.7 μm, and the bottom width of the second pyramid structure ranges from 0.05 μm to 0.2 μm.

3. The method for preparing a solar cell according to claim 1, characterized in that, Performing a full-surface laser scan on the first prepared surface includes: The first prepared surface is scanned using a pulsed laser, wherein the pulse width of the pulsed laser is in the range of 20ns-60ns, the scanning speed of the pulsed laser is in the range of 23000mm / s-27000mm / s, and the laser power of the pulsed laser is in the range of 30W-50W.

4. The method for preparing a solar cell according to claim 1, characterized in that, A secondary texturing process is performed on the first prepared surface after laser scanning, including: At a temperature of 50℃-70℃, the first prepared surface is subjected to a secondary texturing process for 60s-100s.

5. The method for preparing a solar cell according to claim 1, characterized in that, The mass fraction of the first alkaline solute in the first alkaline texturing solution is 10%-60%, and the mass fraction of the surfactant in the first alkaline texturing solution is 2%-5%.

6. The method for preparing a solar cell according to claim 1, characterized in that, After performing a full-surface laser scan on the first prepared surface, and before performing a secondary texturing on the first prepared surface after the full-surface laser scan, the method further includes: pickling the prepared substrate; cleaning the pickled prepared substrate with RCA cleaning solution; and washing the cleaned prepared substrate with water. And / or, Obtaining a pre-prepared substrate having a first pre-prepared surface includes: obtaining an initial pre-prepared substrate having a first initial pre-prepared surface; texturing the first initial pre-prepared surface using a second alkaline texturing solution to obtain the plurality of initial texturized structures, wherein the texturized first initial pre-prepared surface forms the first pre-prepared surface, and the texturized initial pre-prepared substrate forms the pre-prepared substrate, wherein the second alkaline texturing solution includes a second alkaline solute.

7. A solar cell, characterized in that, The solar cell is prepared using the solar cell preparation method described in any one of claims 1 to 6.

8. The solar cell according to claim 7, characterized in that, The solar cell is at least one of the following: tunneling oxide passivated contact cell, emitter and back passivated cell, passivated emitter back surface fully diffused cell, back contact cell, and heterojunction cell.

9. The solar cell according to claim 7, characterized in that, The dimensional deviation of multiple velvet structures is less than 25%.

10. A photovoltaic module, characterized in that, include: A battery string, comprising multiple solar cells connected together as described in any one of claims 7-9; An encapsulating film is used to cover the surface of the battery string; A cover plate is used to cover the surface of the encapsulating film that faces away from the battery string.

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