Method for manufacturing 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 substrate, performing first texturing treatment on at least one side surface of the substrate to obtain a plurality of pyramid structures; performing laser treatment on the plurality of pyramid structures to melt at least part of the tip of the pyramid structure to obtain a plurality of first-type pyramid structures, and the tip of the first-type pyramid structure comprises a first curved surface; performing second texturing treatment on the plurality of first-type pyramid structures to obtain a plurality of second-type pyramid structures, and the tip of the second-type pyramid structure comprises a second curved surface, and the curvature radius of the first curved surface is smaller than the curvature radius of the second curved surface. The solar cell provided by the embodiment of the present application can at least improve the photoelectric conversion efficiency of the solar cell.

Description

Technical Field

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

[0002] In the manufacturing process of solar cells, texturing is one of the key steps affecting cell performance. Anisotropic etching of the silicon wafer surface using alkaline solutions (such as sodium hydroxide and potassium hydroxide) can create a pyramidal textured structure. This textured structure significantly reduces the reflectivity of the silicon wafer surface, causing incident light to undergo multiple reflections, thereby increasing the light absorption path and improving short-wavelength response and overall cell conversion efficiency. However, the pyramidal structure formed by traditional alkaline texturing processes typically has sharp edges and vertices, limiting the surface passivation effect. Furthermore, in the screen-printed electrode process, the sharp pyramidal valleys can lead to discontinuous metal paste filling, significantly impacting photoelectric conversion efficiency.

[0003] Therefore, there is an urgent need for a method for fabricating solar cells that can solve the above problems. Summary of the Invention

[0004] This application provides a method for preparing a solar cell, a solar cell, and a photovoltaic module, which at least helps to improve the photoelectric conversion efficiency of the solar cell.

[0005] According to some embodiments of this application, one aspect of this application provides a method for fabricating a solar cell, including obtaining a substrate; performing a first texturing process on at least one side surface of the substrate to obtain a plurality of pyramid structures; performing laser processing on the plurality of pyramid structures to melt at least a portion of the apex of the pyramid structures to obtain a plurality of first-type pyramid structures, the apex of the first-type pyramid structures including a first arc surface; performing a second texturing process on the plurality of first-type pyramid structures to obtain a plurality of second-type pyramid structures, the apex of the second-type pyramid structures including a second arc surface, the radius of curvature of the first arc surface being smaller than the radius of curvature of the second arc surface.

[0006] In some embodiments, at least one of the etching solution type, etching solution concentration, texturing time, and temperature is different between the first texturing process and the second texturing process.

[0007] In some embodiments, the texturing time of the first texturing process is longer than the texturing time of the second texturing process.

[0008] In some embodiments, a first texturing process is performed on at least one side surface of the substrate to obtain multiple pyramid structures, including: performing a first texturing process on at least one side surface of the substrate using a first texturing solution, the first texturing solution comprising an alkaline solution, the first texturing process lasting for 350s to 400s, and the first texturing process lasting for 75°C to 85°C.

[0009] In some embodiments, laser processing is performed on the plurality of pyramid structures to melt at least a portion of the apex of the pyramid structures to obtain a plurality of first-type pyramid structures, including: laser processing the plurality of pyramid structures with a target laser to make the apex of the pyramid structures molten, and cooling to obtain the plurality of first-type pyramid structures, wherein the apex of the first-type pyramid structure is hemispherical.

[0010] In some embodiments, the target laser is a picosecond laser, the wavelength of the target laser ranges from 500nm to 532nm, the scanning speed of the target laser ranges from 20000mm / s to 25000mm / s, and the power of the target laser ranges from 30W to 40W.

[0011] In some embodiments, the plurality of first-type pyramid structures are subjected to a second texturing process to obtain a plurality of second-type pyramid structures, including: performing a second texturing process on the plurality of first-type pyramid structures using a second texturing solution, the second texturing solution comprising an alkaline solution, the concentration of the second texturing solution being 40%~45%, the second texturing process being 50s~60s, and the second texturing process being 50℃~60℃.

[0012] In some embodiments, after laser processing of the plurality of pyramid structures and before performing a second texturing process on the plurality of first-type pyramid structures, the method further includes: sequentially cleaning the plurality of first-type pyramid structures with a first cleaning solution and a second cleaning solution to remove impurities and damaged parts from the surface of the first-type pyramid structures. The first cleaning solution comprises an acidic solution with a concentration of 40%–50%, a cleaning temperature of 15°C–25°C, and a cleaning time of 100–120 seconds. The second cleaning solution comprises an alkaline solution and an oxidizing solution with a concentration of 40%–50% and a concentration of 30%–35%, a cleaning time of 50–60 seconds, and a cleaning temperature of 50–60°C.

[0013] 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.

[0014] According to some embodiments of this application, another aspect of this application provides a photovoltaic module, including: a battery string, which is formed by connecting a plurality of solar cells prepared by any of the preparation methods 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 facing away from the battery string.

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

[0016] After the first texturing process, laser processing alters the original pointed shape of the pyramid's apex, resulting in a first-type pyramid structure including a first arc surface. Then, a second texturing process further refines this first-type pyramid structure, yielding a second arc surface with a larger radius of curvature than the first, resulting in a more rounded pyramid structure, i.e., a rounded pyramid structure. On one hand, the rounded pyramid apex allows for continuous and uniform coverage of the subsequently formed passivation layer, preventing thinning or breakage at the sharp corners. Furthermore, as the density of the passivation layer increases, the number of surface recombination centers decreases, extending carrier lifetime and thus improving the open-circuit voltage of the solar cell. On the other hand, during subsequent screen printing, the rounded pyramid apex facilitates the flow and spread of the metal paste, allowing it to flow more smoothly into the valleys and adhere tightly to the silicon surface, reducing the formation of bubbles and voids. This results in more continuous and dense paste filling, lowering contact resistance and series resistance, thereby improving the fill factor. The combined improvement in open-circuit voltage and fill factor enhances 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 2This is a three-dimensional structural diagram of a first type of pyramid structure according to an embodiment of this application;

[0020] Figure 3 This is a cross-sectional schematic diagram of a second type of pyramid structure according to an embodiment of this application;

[0021] Figure 4 This is a magnified view of a portion of a solar cell in the prior art;

[0022] Figure 5 This is a partially enlarged view of a solar cell according to an embodiment of this application.

[0023] The above figures include the following reference numerals:

[0024] 1. First type of pyramid structure; 11. Hemispherical structure; 12. First arc surface; 2. Second type of pyramid structure; 21. Second arc surface. Detailed Implementation

[0025] As the background technology shows, the pyramid structure formed by the traditional alkaline texturing process usually has sharp edges and apexes, which limits the surface passivation effect. Furthermore, in the screen printing electrode process, the sharp pyramid valleys can lead to discontinuous filling of the metal paste, significantly affecting its photoelectric conversion efficiency.

[0026] To address the above problems and improve the photoelectric conversion efficiency of solar cells, this application provides a method for fabricating a solar cell, a solar cell, and a photovoltaic module. The method for fabricating a solar cell includes: obtaining a substrate; performing a first texturing process on at least one surface of the substrate to obtain multiple pyramid structures; performing laser processing on the multiple pyramid structures to melt at least a portion of the apex of the pyramid structures to obtain multiple first-type pyramid structures, wherein the apex of the pyramid-like structures includes a first arc surface; performing a second texturing process on the multiple first-type pyramid structures to obtain multiple second-type pyramid structures, wherein the apex of the second-type pyramid structures includes a second arc surface, and the radius of curvature of the first arc surface is smaller than the radius of curvature of the second arc surface.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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).

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The terminology used in the description of the various embodiments 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 "part" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0036] 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.

[0037] This application provides an exemplary method for preparing a solar cell, such as... Figure 1 As shown, the method for preparing the above-mentioned solar cell includes:

[0038] Step S101: Obtain a substrate, and perform a first texturing process on at least one surface of the substrate to obtain multiple pyramid structures;

[0039] The substrate can be a monocrystalline silicon wafer, such as an n-type monocrystalline silicon wafer or a p-type monocrystalline silicon wafer, and its crystal orientation can be selected as (100) crystal orientation. The first texturing process described above can utilize the anisotropic etching characteristics of alkaline solution on silicon wafers to form multiple pyramid-shaped texturing structures on the surface of silicon wafers.

[0040] Step S102: Laser processing is performed on the above-mentioned multiple pyramid structures to melt at least a portion of the apex of the pyramid structures to obtain multiple first-type pyramid structures, wherein the apex of the first-type pyramid structure includes a first arc surface;

[0041] The aforementioned laser processing is used to scan the apex of multiple pyramid structures, rapidly heating the apex to a molten state. Upon cooling, the sharp edges of the apex transform into a smooth structure containing a first curved surface, forming a first type of pyramid structure. This laser processing can employ high-energy lasers, such as picosecond, nanosecond, or femtosecond lasers. Furthermore, the first curved surface can be approximately hemispherical or hemispherical, representing a transitional morphology formed by laser melting followed by solidification.

[0042] Step S103: Perform a second texturing process on the above-mentioned multiple first-type pyramid structures to obtain multiple second-type pyramid structures. The apex of the above-mentioned second-type pyramid structure includes a second arc surface, and the radius of curvature of the above-mentioned first arc surface is smaller than the radius of curvature of the above-mentioned second arc surface.

[0043] The second texturing process described above can also employ an alkaline solution to anisotropically etch the aforementioned multiple first-type pyramid structures. While preserving the main pyramid structure, the molten silicon region at the pyramid apex is further modified to form a second-type pyramid structure with a second curved surface. The alkaline solution can be at least one of potassium hydroxide, sodium hydroxide, and tetramethylammonium hydroxide. Because the second texturing process involves regrowth and re-etching based on laser pre-melting, the radius of curvature of the second curved surface is greater than that of the first curved surface, resulting in a more rounded and gentler pyramid apex.

[0044] Through the above embodiments, firstly, a substrate is obtained, and at least one surface of the substrate is subjected to a first texturing process to obtain multiple pyramid structures. Then, the multiple pyramid structures are subjected to laser processing to melt at least a portion of the pyramid apex, resulting in multiple first-type pyramid structures, where the apex of each pyramid structure includes a first arc surface. Finally, the multiple first-type pyramid structures are subjected to a second texturing process to obtain multiple second-type pyramid structures, where the apex of each second-type pyramid structure includes a second arc surface, and the radius of curvature of the first arc surface is smaller than that of the second arc surface. Performing laser processing after the first texturing process alters the original apex shape of the pyramid, resulting in a first-type pyramid structure including the first arc surface. Further modification of the first-type pyramid structure through the second texturing process yields a second arc surface with a larger radius of curvature than the first arc surface, thus obtaining a more rounded pyramid structure, i.e., a rounded pyramid structure. On the one hand, the rounded pyramid apex allows for a continuous and uniform coverage of the subsequently formed passivation layer, preventing thinning or breakage at the sharp corners. Furthermore, as the density of the passivation layer increases, the number of surface recombination centers decreases, extending carrier lifetime and thus improving the open-circuit voltage of the solar cell. On the other hand, during subsequent screen printing, the rounded pyramid apex facilitates the flow and spread of the metal paste, allowing it to flow more smoothly into the valleys and adhere tightly to the silicon surface. This reduces the formation of bubbles and voids, resulting in more continuous and dense paste filling, lowering contact resistance and series resistance, and thus improving the fill factor. Combining these improvements in open-circuit voltage and fill factor enhances the photoelectric conversion efficiency of the solar cell.

[0045] In some embodiments, at least one of the etching solution type, etching solution concentration, texturing time, and temperature differs between the first and second texturing processes. By differentiating at least one parameter between the two texturing processes, the process windows for the two stages of forming multiple pyramid structures and forming a second type of pyramid structure can be optimized respectively. The first texturing process can focus more on rapidly forming a uniform and complete pyramid structure, thereby ensuring light absorption capacity. The second texturing process can focus more on slowly and uniformly modifying the pyramid tips, avoiding excessive etching that would flatten the pyramid and cause light trapping failure, and also avoiding insufficient etching that would result in poor rounding effect. In other words, the parameter differentiation settings of the first and second texturing processes can make the overall process more repeatable.

[0046] In some specific implementations, the first and second texturing processes have different purposes. The purpose of the first texturing process is to form a pyramid structure, while the purpose of the second texturing process is to further process the first type of pyramid structure obtained by laser processing to obtain a second type of pyramid structure with a rounded apex. The first texturing process can use a relatively high concentration of potassium hydroxide or sodium hydroxide solution to form pyramids of uniform size and sufficient height in a short time. The second texturing process can use a slightly lower concentration of alkaline solution, or add appropriate amounts of surfactants such as isopropanol or ethanol to slow down the corrosion rate and improve the rounding accuracy. In addition, the temperatures of the first and second texturing processes can also be different. For example, the first texturing process can be carried out between 60°C and 80°C to ensure a sufficient reaction rate and pyramid growth kinetics; the second texturing process can be carried out at a slightly lower temperature, such as 50°C to 70°C, to more precisely control the morphology of the pyramid apex.

[0047] In other embodiments, the texturing time of the first texturing process is longer than that of the second texturing process. The longer first texturing time helps to form a pyramid of sufficient height and complete morphology, providing a good foundation for subsequent laser processing and secondary texturing; simultaneously, the shorter second texturing time ensures that corrosion is mainly concentrated in the apex region without significantly reducing the overall height of the pyramid. In other words, a longer texturing time for the first process than for the second process can achieve optimized surface passivation while maintaining good light-trapping effects, further improving both optical and electrical properties.

[0048] In practical applications, the first texturing process described above requires a sufficiently long time, such as 60s to 90s, to allow sufficient nucleation and growth on the silicon wafer surface, forming a pyramid array with uniform size and distribution. The second texturing process described above has a relatively short time, such as 40s to 60s, and its main purpose is not to regrow the pyramids, but to locally modify the tips of the pyramids after laser melting.

[0049] In some embodiments, step S101 can be implemented by the following steps, for example: step S1011, performing a first texturing treatment on at least one side surface of the substrate using a first texturing solution, wherein the first texturing solution includes an alkaline solution, the first texturing treatment time is 350s~400s, and the first texturing treatment temperature is 75℃~85℃. The above scheme further provides a specific implementation of the first texturing treatment, and the above parameter range can quickly form a high-quality pyramidal textured surface. Appropriate temperature and treatment time ensure sufficient corrosion reaction and allow the pyramid to grow to a suitable height, providing a structural basis for subsequent laser melting and secondary texturing. Simultaneously, the formed pyramid has low surface reflectivity and good light-trapping ability, which helps to further improve the short-circuit current.

[0050] The aforementioned first texturing solution includes an alkaline solution, which may be at least one selected from potassium hydroxide solution, sodium hydroxide solution, and tetramethylammonium hydroxide solution. The concentration of the alkaline solution is 40%–45% (mass fraction), a concentration range that allows for a relatively fast corrosion rate while obtaining pyramidal structures of moderate size and uniform distribution. The duration of the first texturing process, within the aforementioned temperature and time range, is beneficial for forming complete, regular square pyramidal or random pyramidal structures. In some embodiments, a small amount of isopropanol or ethanol may be added to the first texturing solution as a surfactant to improve the uniformity and reflectivity of the pyramids.

[0051] In other embodiments, step S102 can be implemented through the following steps, such as: step S1021, using a target laser to laser process the plurality of pyramid structures to make the tips of the pyramid structures molten, and after cooling, the plurality of first-type pyramid structures are obtained, wherein the tips of the first-type pyramid structures are hemispherical. Transforming the sharp tips into hemispherical structures reduces the curvature at the tips, reducing the density of dangling bonds and defect states on the surface. The hemispherical tips serve as the reaction substrate for secondary texturing, and their smooth contours can guide the subsequent second texturing process to proceed more uniformly in all directions, avoiding local over-corrosion or under-corrosion, and ultimately obtaining pyramid structures with higher roundness and better consistency.

[0052] When a target laser scans the pyramid apex, the laser energy is absorbed by the apex region, causing the local silicon to rapidly heat above its melting point and enter a molten state. Due to surface tension, the molten silicon tends to form a sphere or hemisphere with the lowest energy. Upon cooling, the apex solidifies into a hemispherical structure. This hemispherical structure is the apex morphology of the first type of pyramid structure, with a relatively small radius of curvature. The laser type can be a picosecond laser, nanosecond laser, or femtosecond laser. In some embodiments, an ultrashort pulse laser can be used to reduce the heat-affected zone. In practical applications, the laser scanning method described above can be area scanning or point scanning, and the scanning path can be set according to the pyramid distribution density and the size of the solar cells.

[0053] In other embodiments, the target laser is a nanosecond laser with a wavelength ranging from 500 nm to 532 nm, a scanning speed ranging from 20,000 mm / s to 25,000 mm / s, and a power ranging from 30 W to 40 W. The nanosecond laser, combined with the aforementioned wavelength, scanning speed, and power range, can precisely target energy to a tiny area at the tip of the pyramid, achieving selective melting of the tip without ablating the pyramid body or causing overall overheating and deformation of the silicon wafer. Appropriate heat input can also control the flow and resolidification process of the molten silicon, resulting in a uniform hemispherical tip with a smooth surface after cooling, providing favorable conditions for subsequent secondary texturing and passivation deposition.

[0054] The aforementioned target laser is a nanosecond laser, capable of injecting energy into a tiny area at the pyramid's apex in an extremely short time, resulting in a small heat-affected zone and effectively preventing damage to the pyramid's main body and the silicon substrate. The laser wavelength is 500nm~532nm, for example, any value from 500nm, 510nm, 520nm, and 532nm, or any two of these values. This wavelength band has a high absorption coefficient for silicon, which is beneficial for concentrating energy at the pyramid's apex. The scanning speed is 20000mm / s~25000mm / s, for example, any value from 20000mm / s, 21000mm / s, 22000mm / s, 23000mm / s, 24000mm / s, and 25000mm / s, or any two of these values. The power is 30W~40W, for example, any value from 30W, 32W, 34W, 36W, 38W, and 40W, or any two of these values.

[0055] In some embodiments, step S103 can be implemented through the following steps, for example: step S1031, using a second texturing solution to perform a second texturing treatment on the plurality of first-type pyramid structures, wherein the second texturing solution includes an alkaline solution, the concentration of the second texturing solution is 40%~45%, the second texturing treatment time is 50s~60s, and the second texturing treatment temperature is 50℃~60℃. The above scheme further provides a specific implementation of the second texturing treatment. The above second texturing parameters can effectively remove the laser-induced damage layer while ensuring significant rounding of the pyramid tip while minimizing the overall height loss of the pyramid. Compared to a simple chemical rounding process, since the laser pretreatment has already changed the pyramid tip morphology, the second texturing no longer requires prolonged strong corrosion to achieve good rounding, thereby maintaining the optical light-trapping performance of the pyramid and further improving the surface passivation effect and metal contact performance.

[0056] The second texturing solution includes an alkaline solution, such as potassium hydroxide, sodium hydroxide, or tetramethylammonium hydroxide, with a concentration of 40% to 45%. Compared to the first texturing treatment, the second texturing treatment involves a slightly lower temperature and a slightly shorter time to achieve gentle and controllable corrosion of the pyramid tip region. During the second texturing treatment, the alkaline solution preferentially corrodes the amorphous silicon layer, damaged layer, and melt-resolidified area at the laser-treated pyramid tip, while further refining the original pyramid structure to create a smoother pyramid tip. In other embodiments, isopropanol, ethanol, or a small amount of hydrogen peroxide may also be added to the second texturing solution to adjust the corrosion selectivity and surface cleanliness.

[0057] In other embodiments, after step S102 and before step S103, the method further includes step S104, sequentially cleaning the plurality of first-type pyramid structures with a first cleaning solution and a second cleaning solution to remove impurities and damaged parts from the surface of the first-type pyramid structures. The first cleaning solution comprises an acidic solution with a concentration of 40%–50%, a cleaning temperature of 15°C–25°C, and a cleaning time of 100–120 seconds. The second cleaning solution comprises an alkaline solution and an oxidizing solution with a concentration of 40%–50% and a concentration of 30%–35%, a cleaning time of 50–60 seconds, and a cleaning temperature of 50–60°C. This scheme further specifies that a cleaning step is added after laser treatment and before the second texturing process to repair laser-induced surface damage and remove contaminants. In practical applications, while laser processing can achieve tip rounding, it may introduce microcracks, amorphous silicon layers, metal contamination, or oxides onto the surface. A two-step cleaning process—acid pickling and alkali-oxidation cleaning—can effectively remove these impurities and damaged layers, repair laser-induced surface defects, and provide a clean, active reaction interface. This process helps prevent secondary contamination, improves the uniformity and repeatability of subsequent texturing processes, and allows for better interfacial contact between the passivation film and the silicon surface, further reducing interfacial recombination.

[0058] The first cleaning solution includes an acidic solution, such as hydrochloric acid, hydrofluoric acid, or nitric acid, with a concentration of 40%–50%. The cleaning temperature is 15°C–25°C, and the time is 100–120 seconds. It is mainly used to remove metallic impurities, oxides, and loose surface layers generated during laser processing. The second cleaning solution includes an alkaline solution and an oxidizing solution. The alkaline solution can be potassium hydroxide or sodium hydroxide, and the oxidizing solution can be hydrogen peroxide or ozone water. The concentration of the oxidizing solution is 30%–35%, the cleaning time is 50–60 seconds, and the temperature is 50°C–60°C. This cleaning step further removes organic contaminants, particles, and shallow damage caused by the laser, and forms a hydrophilic clean interface on the surface.

[0059] To enable those skilled in the art to better understand the technical solution of this application, the implementation process of the photovoltaic module repair method of this application will be described in detail below with reference to specific embodiments.

[0060] This embodiment relates to a specific method for fabricating a solar cell, including the following steps:

[0061] Step S1: Obtain a substrate, and perform a first texturing treatment on at least one side surface of the substrate using a sodium hydroxide solution. The first texturing treatment takes 400 seconds and is performed at a temperature of 82°C to obtain a pyramid structure.

[0062] Step S2: The multiple pyramid structures are laser-treated using a target laser to melt the apex of each pyramid. After cooling, the first type of pyramid structure is obtained. The wavelength of the target laser is 532 nm, the scanning speed is 25000 mm / s, the power is 40 W, and the pulse width is 40 ns. Figure 2 The structure shown above, the apex of the first type of pyramid structure 1 is a hemispherical structure 11, and the apex of the first type of pyramid structure 1 includes a first arc surface 12.

[0063] Step S3: The first cleaning solution and the second cleaning solution are used sequentially to clean the above-mentioned multiple first-type pyramid structures to remove impurities and damaged parts on the surface of the first-type pyramid structures. The first cleaning solution includes 49% hydrofluoric acid, the cleaning temperature of the first cleaning solution is 20°C, and the cleaning time of the first cleaning solution is 120s. The second cleaning solution includes 45% potassium hydroxide and 35% hydrogen peroxide, the cleaning time of the second cleaning solution is 60s, and the cleaning temperature of the second cleaning solution is 60°C.

[0064] Step S4: The above-mentioned multiple first-type pyramid structures are subjected to a second texturing treatment using 45% sodium hydroxide. The second texturing treatment time is 60 seconds, and the temperature is 60°C, to obtain the following... Figure 3 The structure shown above, the apex of the second type of pyramid structure 2 includes a second arc surface 21, as... Figure 2 and Figure 3 As shown, the radius of curvature of the first arc surface 12 is smaller than the radius of curvature of the second arc surface 21.

[0065] This application also provides a solar cell, which can be formed by all or some of the above steps. It should be noted that the parts that are the same as or corresponding to the foregoing embodiments can be referred to the corresponding descriptions of the foregoing embodiments, and will not be repeated here.

[0066] Figure 4 This is a magnified view of a portion of a solar cell in the prior art. Figure 5 This is a partial enlarged view of the solar cell in this application, such as... Figure 5 As shown, the surface of the solar cell in this application has a pyramid-like structure, compared to Figure 4 The pyramid structure in this application features a more rounded apex. On one hand, the rounded pyramid apex allows for continuous and uniform coverage of the subsequently formed passivation layer, preventing thinning or breakage at the sharp corners. Furthermore, as the density of the passivation layer increases, the number of surface recombination centers decreases, extending carrier lifetime and thus improving the open-circuit voltage of the solar cell. On the other hand, during subsequent screen printing, the rounded pyramid apex facilitates the flow and spread of the metal paste, allowing it to flow more smoothly into the valleys and adhere tightly to the silicon surface. This reduces the formation of bubbles and voids, resulting in more continuous and dense paste filling, lowering contact resistance and series resistance, and thus improving the fill factor. The combined improvement in open-circuit voltage and fill factor enhances the photoelectric conversion efficiency of the solar cell.

[0067] Embodiments of this application also provide a photovoltaic module, comprising:

[0068] The battery string is formed by connecting multiple solar cells of any one of the above embodiments;

[0069] Specifically, adjacent cell strings can be electrically connected by soldering strips. In some embodiments, the electrodes of the same polarity of the solar cells face the same direction, and the conductive strips connect the electrodes of different polarities of two adjacent solar cells. In other embodiments, the solar cells can also be arranged according to electrodes of different polarities, that is, the electrodes of multiple adjacent cells are arranged in the order of first polarity, second polarity, and first polarity, respectively, and the conductive strips connect two adjacent cells on the same side. In some embodiments, there is no gap between the cells, that is, the cells overlap each other.

[0070] An encapsulating film is used to cover the surface of the aforementioned battery string;

[0071] Specifically, the encapsulating film includes a first encapsulating layer and a second encapsulating layer. The first encapsulating layer covers either the front or back of the stacked battery string, and the second encapsulating layer covers the other side of the front or back of the battery string. Specifically, the encapsulating film material can be at least one of organic encapsulating films such as polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), polyvinyl octene coelastomer (POE), or polyethylene terephthalate (PET). In practical applications, there is a gap between the first and second encapsulating layers during lamination, but after lamination, the first and second encapsulating layers together form the aforementioned encapsulating film.

[0072] A cover plate is used to cover the surface of the encapsulating film away from the battery string.

[0073] Specifically, the cover plate can be made of light-transmitting materials such as glass or plastic. Furthermore, the surface of the cover plate facing the encapsulating film can be uneven, thereby increasing the utilization rate of incident light. The cover plate includes a first cover plate and a second cover plate, the first cover plate being disposed opposite to a first encapsulation layer, and the second cover plate being disposed opposite to a second encapsulation layer.

[0074] It should be understood that, unless otherwise stated, "substantially identical" within the measurement tolerance or manufacturing error range is equivalent to "identical" or "equal" in the description of the embodiments of this application.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0077] This application first obtains a substrate, and performs a first texturing process on at least one surface of the substrate to obtain multiple pyramid structures. Then, it performs laser processing on the multiple pyramid structures to melt at least a portion of the pyramid apex, obtaining multiple first-type pyramid structures, where the apex of each pyramid structure includes a first arc surface. Finally, it performs a second texturing process on the multiple first-type pyramid structures to obtain multiple second-type pyramid structures, where the apex of each second-type pyramid structure includes a second arc surface, and the radius of curvature of the first arc surface is smaller than that of the second arc surface. Performing laser processing after the first texturing process alters the original apex shape of the pyramid, resulting in a first-type pyramid structure including the first arc surface. Further modification of the first-type pyramid structure through the second texturing process yields a second arc surface with a larger radius of curvature than the first arc surface, thus obtaining a more rounded pyramid structure, i.e., a rounded pyramid structure. On the one hand, the rounded pyramid apex allows for a continuous and uniform coverage of the subsequently formed passivation layer, preventing thinning or breakage at the sharp corners. Furthermore, as the density of the passivation layer increases, the number of surface recombination centers decreases, extending carrier lifetime and thus improving the open-circuit voltage of the solar cell. On the other hand, during subsequent screen printing, the rounded pyramid apex facilitates the flow and spread of the metal paste, allowing it to flow more smoothly into the valleys and adhere tightly to the silicon surface. This reduces the formation of bubbles and voids, resulting in more continuous and dense paste filling, lowering contact resistance and series resistance, and thus improving the fill factor. Combining these improvements in open-circuit voltage and fill factor enhances the photoelectric conversion efficiency of the solar cell.

[0078] 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 substrate is obtained, and at least one surface of the substrate is subjected to a first texturing process to obtain multiple pyramid structures; The plurality of pyramid structures are subjected to laser processing to melt at least a portion of the apex of the pyramid structure, thereby obtaining a plurality of first-type pyramid structures, wherein the apex of the first-type pyramid structure includes a first arc surface; The plurality of first-type pyramid structures are subjected to a second texturing process to obtain a plurality of second-type pyramid structures. The apex of the second-type pyramid structure includes a second arc surface, and the radius of curvature of the first arc surface is smaller than the radius of curvature of the second arc surface.

2. The method for preparing a solar cell according to claim 1, characterized in that, The first texturing process and the second texturing process differ in at least one of the following: the type of etching solution, the concentration of the etching solution, the texturing time, and the temperature.

3. The method for preparing a solar cell according to claim 1, characterized in that, The texturing time of the first texturing process is longer than that of the second texturing process.

4. The method for preparing a solar cell according to claim 1, characterized in that, A first texturing process is performed on at least one surface of the substrate to obtain multiple pyramid structures, including: The substrate is subjected to a first texturing treatment on at least one side surface using a first texturing solution, the first texturing solution comprising an alkaline solution, the first texturing treatment time being 350s~400s, and the first texturing treatment temperature being 75℃~85℃.

5. The method for preparing a solar cell according to claim 1, characterized in that, Laser processing is applied to the plurality of pyramid structures to melt at least a portion of the apex of the pyramid structures, resulting in a plurality of first-type pyramid structures, including: The multiple pyramid structures are laser-processed using a target laser to melt the apex of the pyramid structure. After cooling, the multiple first-type pyramid structures are obtained, wherein the apex of the first-type pyramid structure is hemispherical.

6. The method for preparing a solar cell according to claim 5, characterized in that, The target laser is a picosecond laser, the wavelength of the target laser ranges from 500nm to 532nm, the scanning speed of the target laser ranges from 20000mm / s to 25000mm / s, and the power of the target laser ranges from 30W to 40W.

7. The method for preparing a solar cell according to claim 1, characterized in that, The plurality of first-type pyramid structures are subjected to a second texturing process to obtain a plurality of second-type pyramid structures, including: The plurality of first-type pyramid structures are subjected to a second texturing process using a second texturing solution, the second texturing solution comprising an alkaline solution, the concentration of the second texturing solution being 40%~45%, the second texturing process being 50s~60s, and the second texturing process being 50℃~60℃.

8. The method for preparing a solar cell according to claim 1, characterized in that, After laser processing of the plurality of pyramid structures and before performing a second texturing process on the plurality of first-type pyramid structures, the method further includes: The plurality of first-type pyramid structures are sequentially cleaned using a first cleaning solution and a second cleaning solution to remove impurities and damaged parts from the surface of the first-type pyramid structures. The first cleaning solution includes an acidic solution with a concentration of 40% to 50%, a cleaning temperature of 15°C to 25°C, and a cleaning time of 100 to 120 seconds. The second cleaning solution includes an alkaline solution and an oxidizing solution with a concentration of 40% to 50% and a concentration of 30% to 35%, a cleaning time of 50 to 60 seconds, and a cleaning temperature of 50 to 60°C.

9. A solar cell, characterized in that, The solar cell is prepared by the method for preparing a solar cell according to any one of claims 1 to 8.

10. A photovoltaic module, characterized in that, include: A battery string is formed by connecting multiple solar cells prepared by any one of the preparation methods as described in claims 1 to 8 or solar cells as described in claim 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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