Solar cell and method of manufacturing the same, photovoltaic module

Abstract

The application discloses a solar cell and a preparation method and a photovoltaic module thereof; the preparation method comprises the steps of texturing, first polishing and second polishing; the first polishing is performed on one side surface of a silicon substrate after texturing at a first temperature by using a first alkaline polishing solution to preliminarily flatten the one side surface of the silicon substrate and form a primary tower base structure; the second polishing is performed on the one side surface after the first polishing at a second temperature by using a second alkaline polishing solution to secondarily flatten the one side surface and make the primary tower base structure form a secondary tower base structure. The solar cell preparation method can improve the flatness of the surface of the silicon substrate, improve the morphology of the tower base structure after polishing, make the back surface of the silicon substrate more flat, provide better surface conditions for subsequent passivation treatment, is favorable for improving the subsequent passivation effect, and can improve the surface flatness while maintaining good reflection performance.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a solar cell, its preparation method, and a photovoltaic module. Background Technology

[0002] The back side of solar cells is typically polished to create a flat substrate, achieving better passivation conditions and utilizing the smooth surface to reflect incident light, thereby increasing sunlight absorption. Existing polishing techniques include two wet etching processes: alkaline etching and acid etching. Acid etching, using HF and HNO3, suffers from uneven etched surfaces and high wastewater treatment costs. Alkaline etching, using NaOH, polishes the back side, resulting in a smoother surface compared to acid etching. However, after conventional alkaline etching forms the substrate structure, a height difference may still exist at the substrate-base interface, exposing steeper sides that are difficult to passivate effectively. Therefore, how to further reduce the height difference at the substrate-base interface, improve the flatness of the silicon substrate's back surface and subsequent passivation effect, while also considering the reflective properties of the silicon substrate's back surface, remains a key technical challenge. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned problems and provide a solar cell and its preparation method, as well as a photovoltaic module. The solar cell preparation method can reduce the height difference at the junction of the tower and the substrate, improve the flatness of the silicon substrate surface and the subsequent passivation effect, and take into account the reflectivity of the silicon substrate surface.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a solar cell, comprising the steps of: Texturing: Providing a silicon substrate and texturing the silicon substrate to form a pyramid structure on the surface of the silicon substrate; First polishing: At a first temperature, a first alkaline polishing solution is used to polish one side of the textured silicon substrate for the first time, so as to initially level one side of the silicon substrate and form a primary tower base structure; Second polishing: At a second temperature, a second alkaline polishing solution is used to polish the side that has been polished for the first time, and the side is leveled for the second time, so that the primary tower base structure forms a secondary tower base structure.

[0005] Optionally, the width of the secondary tower base structure is 6 to 25 μm; the secondary tower base structure is recessed on the other side facing the silicon substrate, the secondary tower base structure includes a substrate disposed near the other side, and the height difference between the substrate and the surface of the other side is 0.3 to 0.5 μm; the secondary tower base structure also includes a sidewall disposed between the substrate and the surface of the other side, the sidewall being inclined.

[0006] Optionally, after the second polishing, the roughness Ra of one side is 0.05~0.13μm.

[0007] Optionally, the first alkaline polishing solution includes a first alkaline solution, a first additive, and deionized water, wherein the volume ratio of the first alkaline solution, the first additive, and the deionized water is 5~10:5~10:400~550; and the first additive includes, by mass percentage, 1.0%~2.0% potassium sorbate, 1.0%~5.0% dispersant, 1.0%~5.0% emulsifier, and 2.0%~10.0% surfactant.

[0008] Optionally, the second alkaline polishing solution includes a second alkaline solution, a second additive, and deionized water, wherein the volume ratio of the second alkaline solution, the second additive, and deionized water is 10~15:0.5~5:400~550; the second additive includes sodium benzoate, a surfactant, a catalyst, and deionized water.

[0009] Optionally, the first temperature is 80~90℃, and the second temperature is 60~65℃.

[0010] Optionally, the process may also include a passivation layer and a tunneling oxide layer preparation step, wherein the passivation layer and the tunneling oxide layer are prepared sequentially on one side surface that has undergone a second polishing.

[0011] Secondly, the present invention provides a solar cell, which is prepared by the solar cell preparation method described above; The solar cell includes a silicon substrate, one side of which has a polished surface. The polished surface has a secondary tower base structure with a width of 6–25 μm. The secondary tower base structure is recessed towards the other side of the silicon substrate. The secondary tower base structure includes a substrate disposed near the other side, and the height difference between the substrate and the surface of the first side is 0.3–0.5 μm. The secondary tower base structure also includes a sidewall disposed between the substrate and the surface of the first side, and the sidewall is inclined.

[0012] Optionally, the roughness Ra of the polished surface is 0.05~0.13μm.

[0013] Thirdly, the present invention provides a photovoltaic module comprising: A battery string is composed of multiple solar cells connected as described above; 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.

[0014] The beneficial effects of this invention include at least the following: This invention provides a method for fabricating a solar cell, comprising a first polishing step and a second polishing step. First, the first polishing process is used to pre-treat one side of the silicon substrate to form a primary pyramid base structure that coexists with the pyramid structure formed by texturing. Then, the second polishing process is used to further polish one side of the silicon substrate based on the first polishing process, flattening the pyramid structure and optimizing the pyramid base structure to improve the flatness of the silicon substrate surface, which is beneficial to improving the subsequent passivation effect and maintaining good reflectivity. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of the method for preparing the solar cell of the present invention.

[0016] Figure 2 This is a scanning electron microscope (SEM) image of the silicon substrate surface after the first polishing.

[0017] Figure 3 This is a scanning electron microscope (SEM) image of the silicon substrate surface after the second polishing.

[0018] Figure 4 This is a scanning electron microscope (SEM) image of the cross-section of the secondary tower base structure formed after the second polishing.

[0019] Among them, 1-pyramid structure, 2-primary base structure, 3-secondary base structure, 31-base, 32-side wall. Detailed Implementation

[0020] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0021] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0022] In this invention, the use of terms such as "first" and "second" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0023] Unless otherwise stated, the chemical raw materials, reagents, intermediates, and auxiliary materials involved in this invention may be commercially available products purchased from the market, or they may be prepared by those skilled in the art using conventional preparation methods described in existing technical literature known in the field.

[0024] In a first aspect, embodiments of the present invention provide a method for preparing a solar cell, see below. Figure 1 As shown, it includes the following steps: Texturing: A silicon substrate is provided, and the silicon substrate is texturized to form a pyramid structure 1 on the surface of the silicon substrate; First polishing: At a first temperature, a first alkaline polishing solution is used to polish one side of the textured silicon substrate, initially leveling one side of the silicon substrate to form a primary pyramid base structure 2; at this time, the primary pyramid base structure 2 coexists with at least a portion of the pyramid structure 1, and the resulting structure is described in [reference needed]. Figure 2 As shown; Second polishing: At a second temperature, a second alkaline polishing solution is used to polish the side that was polished in the first polishing, performing a second leveling of the side and causing the primary tower base structure 2 to form a secondary tower base structure 3. See the diagram for the resulting structure. Figure 3 As shown.

[0025] This invention provides a method for fabricating a solar cell, which includes a first polishing step and a second polishing step. First, the first polishing process is used to pre-treat one side of the silicon substrate to form a primary pyramid base structure 2 that coexists with the pyramid structure 1 formed by texturing. Then, the second polishing process is used to polish one side of the silicon substrate again based on the first polishing process, flattening the pyramid structure and optimizing the pyramid base structure to improve the flatness of the silicon substrate surface, which is beneficial to improving the subsequent passivation effect and maintaining good reflection performance.

[0026] See Figure 4As shown, the width of the secondary tower base structure 3 is 6–25 μm, where the width is the distance between the contact points of the opposite two side walls 32 of the secondary tower base structure 3 and the surface of the side surface. The secondary tower base structure 3 is recessed towards the other side of the silicon substrate. The secondary tower base structure 3 includes a base 31 disposed near the other side, and the height difference between the base 31 and the surface of the side surface is 0.3–0.5 μm. The secondary tower base structure 3 also includes a side wall 32 disposed between the base 31 and the surface of the side surface, and the side wall 32 is inclined. By processing one side of the silicon substrate through the first polishing and the second polishing, the height difference between the base 31 and the surface of the side surface can be controlled within the range of 0.3–0.5 μm within the tower base width of 6–25 μm, improving the flatness of one side of the silicon substrate, which is beneficial to improving the subsequent passivation effect and maintaining good reflectivity.

[0027] After the second polishing, the surface roughness Ra of one side is 0.05~0.13μm.

[0028] The first alkaline polishing solution comprises a first alkaline solution, a first additive, and deionized water, wherein the volume ratio of the first alkaline solution, the first additive, and the deionized water is 5~10:5~10:400~550; and the first additive comprises, by mass percentage, 1.0%~2.0% potassium sorbate, 1.0%~5.0% dispersant, 1.0%~5.0% emulsifier, and 2.0%~10.0% surfactant.

[0029] The first additive is a compound of potassium sorbate, dispersant, emulsifier, and surfactant. Potassium sorbate can stabilize the system in an alkaline polishing environment, inhibit the agglomeration and sedimentation of silicon particles inside the polishing solution, and reduce the problem of uneven local corrosion caused by silicon powder adhering to the pyramid surface. The dispersant can uniformly disperse the silicon debris generated by corrosion, avoiding the accumulation of silicon debris that blocks the pyramid gaps and causes local over-etching or under-etching. The emulsifier can improve the compatibility of various additives in the polishing solution, reduce additive stratification, and maintain the uniformity and stability of each component of the polishing solution. The surfactant can reduce the surface tension of the polishing solution, allowing the polishing solution to fully wet the tiny gaps of the pyramid tip, sidewalls 32, and base, uniformly weakening the sharp apex of the pyramid and smoothing the surface morphology. Through the compounding of the above components, one side of the silicon substrate is initially leveled while retaining the primary pyramid base structure, taking into account both the uniformity of the first polishing and the preservation of the textured structure, providing a morphological basis for the subsequent second polishing.

[0030] The second alkaline polishing solution includes a second alkaline solution, a second additive, and deionized water, wherein the volume ratio of the second alkaline solution, the second additive, and deionized water is 10~15:0.5~5:400~550; the second additive includes sodium benzoate, surfactant, catalyst, and deionized water.

[0031] The sodium benzoate helps maintain the stability of the second alkaline polishing slurry and reduces impurity adhesion; the surfactant helps improve the wetting ability of the second alkaline polishing slurry on the silicon substrate surface, allowing the second alkaline polishing slurry to act more uniformly on the pyramid structure remaining after the first polishing; the catalyst helps regulate the alkaline corrosion reaction rate, allowing the second polishing to further flatten the pyramid structure and regularize the primary pyramid base structure. Thus, through the combination of the sodium benzoate, the surfactant, and the catalyst, the second alkaline polishing slurry can further flatten one side of the silicon substrate while reducing excessive corrosion of the primary pyramid base structure.

[0032] In some embodiments, the second additive, by weight percentage, comprises 0.5% to 1.5% sodium benzoate, 1% to 5% surfactant, 5% to 10% catalyst, 0.1% to 10% sodium polystyrene sulfonate, and the balance being deionized water. Preferably, the content of sodium polystyrene sulfonate is 2% to 3%. In this embodiment, the surfactant may include sodium dodecyl sulfonate, and the catalyst may include polyethylene glycol.

[0033] In the above embodiments, sodium dodecyl sulfonate helps reduce the surface tension of the second alkaline polishing solution, improving its wetting ability on the silicon substrate surface and the fine areas between the pyramid structures; polyethylene glycol helps regulate the reaction process between the second alkaline polishing solution and the silicon substrate surface; sodium polystyrene sulfonate helps disperse and suspend silicon debris generated during the etching process, reducing the redeposition of silicon debris on the silicon substrate surface. The combination of these components helps reduce localized over-etching, under-etching, and silicon debris deposition on the silicon substrate surface, improving the smoothness of the silicon substrate surface and the pyramid structure profile after the second polishing.

[0034] In other embodiments, the second additive, by weight percentage, comprises 0.5%–1.5% sodium benzoate, 1%–5% lauryl glucoside, 5%–15% glucose, 5%–10% sodium diacetate, and the balance being deionized water. Preferably, by weight percentage, the second additive comprises 1% sodium benzoate, 4% lauryl glucoside, 11% glucose, 7% sodium diacetate, and 77% deionized water. Wherein, the lauryl glucoside serves as the surfactant, and the sodium diacetate serves as the catalyst.

[0035] In the above embodiments, lauryl glucoside helps improve the wettability of the second alkaline polishing solution on the silicon substrate surface, allowing the second alkaline polishing solution to contact the pyramid structure remaining after the first polishing more uniformly; sodium diacetate helps regulate the alkaline corrosion reaction rate during the second polishing process; glucose, as an auxiliary component, helps maintain the uniformity and stability of the second additive formulation system. Through the compounding of the above components, it is beneficial to make the pyramid structure more uniformly flattened during the second polishing process and to further regularize the primary pyramid base structure.

[0036] It should be noted that the above two formulations of the second additive are different specific embodiments of the second additive. In both embodiments, the second additive is based on sodium benzoate, surfactant, catalyst, and deionized water. The specific types and contents of the surfactant, catalyst, and auxiliary components can be selected according to the process conditions of the second polishing. All of the above formulations can be combined with the second alkaline solution to perform a second polishing on the side that has undergone the first polishing, further smoothing the pyramid structure remaining after the first polishing, causing the primary pyramid base structure to form a secondary pyramid base structure, reducing the height difference at the pyramid base interface, and improving the flatness of the silicon substrate surface, thereby facilitating the uniform preparation of the subsequent passivation layer and tunneling oxide layer.

[0037] Both the first alkaline solution and the second alkaline solution comprise sodium hydroxide solution or potassium hydroxide solution.

[0038] The first temperature is 80~90℃, such as 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, or 90℃; in some embodiments, the first polishing time is 350~500s; for example, it can be 350s, 400s, 450s, or 500s. The second temperature is 60~65℃, such as 60℃, 61℃, 62℃, 63℃, 64℃, or 65℃; in some embodiments, the second polishing time is 150~250s; for example, it can be 150s, 200s, or 250s. The first temperature is higher than the second temperature. The higher first temperature enhances the basic corrosive activity of the alkaline solution, enabling rapid and gentle modification of the sharp peaks of the pyramid, in conjunction with the first additive. At high temperatures, the wetting and dispersion efficiency of surfactants and dispersants is significantly improved, allowing the polishing solution to quickly penetrate the tiny gaps in the pyramid, uniformly dissolving the sharp silicon tips and simultaneously stripping away residual silicon powder and surface lattice damage layers from texturing. This achieves peak rounding in a short time. Simultaneously, the higher temperature allows the corrosion reaction to preferentially concentrate in the protruding tip area, resulting in controllable and minimal corrosion of the underlying pyramid base structure, preserving the primary pyramid base framework and preventing premature over-erosion. This efficiently completes the initial morphology modification and shortens the initial polishing time. The lower second temperature precisely slows down the overall alkaline corrosion rate. The catalyst in the second additive enables controllable and differentiated corrosion. The corrosion reaction is more selective at low temperatures, which can directionally and continuously smooth out the pyramid-shaped protrusions remaining after the initial polishing. At the same time, it significantly reduces the corrosion intensity on the bottom tower base, avoiding excessive expansion of the tower base width and blurring and deformation of the tower base outline caused by excessive corrosion at high temperatures. The complexation and suspension effect of sodium polystyrene sulfonate is more stable at low temperatures, which can continuously encapsulate the silicon debris generated by corrosion to prevent secondary deposition. It smoothly completes the tower base regularization and overall surface leveling, effectively controlling the amount of silicon wafer thinning, preventing silicon wafer thickness loss and fragmentation risk caused by excessive corrosion, and finally obtaining a tower base structure with regular outline and excellent flatness. This improves the surface reflectivity and ensures uniform and dense film coverage during the subsequent deposition of alumina passivation layer and tunnel oxide layer, optimizing the interface passivation quality.

[0039] The method also includes a passivation layer and a tunneling oxide layer preparation step: a passivation layer and a tunneling oxide layer are sequentially prepared on one side surface that has undergone a second polishing. In some embodiments, the tunneling oxide layer is deposited on the side of the passivation layer opposite to the other side using a thermal oxidation process; the oxidation temperature of the thermal oxidation process is 590~600℃, the oxygen flow rate is 36000 sccm, and the oxidation time is 400~500 s. Optionally, the passivation layer includes an alumina passivation layer.

[0040] Secondly, embodiments of the present invention provide a solar cell, which is prepared using the preparation method described above; The solar cell includes a silicon substrate, one side of which has a polished surface. The polished surface has a secondary tower base structure 3 with a width of 6-25 μm. The secondary tower base structure 3 is recessed towards the other side of the silicon substrate. The secondary tower base structure 3 includes a substrate disposed near the other side. The height difference between the substrate and the surface of the first side is 0.3-0.5 μm. The secondary tower base structure 3 also includes a sidewall 32 disposed between the substrate and the surface of the first side. The sidewall 32 is inclined.

[0041] Optionally, the roughness Ra of the polished surface is 0.05~0.13μm.

[0042] Thirdly, embodiments of the present invention provide a photovoltaic module, comprising: The battery string is composed of the aforementioned solar cells connected together; 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.

[0043] Example 1: Taking TOPCon solar cells as an example, a method for fabricating solar cells is provided, including the following steps: Step 1, N-type silicon wafer texturing: The N-type monocrystalline silicon wafer is cleaned and texturing. In an alkaline solution at 82°C for 420 seconds, a pyramid-shaped textured surface is formed on the surface of the N-type monocrystalline silicon wafer. Step 2, Diffusion Junction Formation: Diffusion junction formation is performed on the texturized pyramid using BCl3 as the boron source at a flow rate of 240 sccm, and N2 and O2 as protective gases at flow rates of 2000 sccm and 800 sccm, respectively. The temperature is 850~900℃ and the time is 1300~2000s to prepare the PN junction. Step 3, First Polishing: At a temperature of 82°C, a first alkaline polishing solution is used to polish one side of the texturized silicon substrate, initially leveling one side of the silicon substrate to form the primary tower base structure 2; the resulting structure is shown in [reference needed]. Figure 2 As shown; wherein, the first alkaline polishing solution comprises a first alkaline solution, a first additive, and deionized water, wherein the amounts of the first alkaline solution, the first additive, and the deionized water added are 5.7L, 8.6L, and 480L, respectively. By mass percentage, the first additive comprises 1.0%–2.0% potassium sorbate, 1.0%–5.0% dispersant, 1.0%–5.0% emulsifier, and 2.0%–10.0% surfactant, and also includes water. The first polishing treatment time is 400s; Step 4, Second Polishing: At 60°C, a second alkaline polishing solution is used to polish the side that was polished in the first polishing stage, leveling the side a second time and causing the primary tower base structure 2 to form a secondary tower base structure 3. See the attached diagram for the resulting structure. Figure 3 As shown; the processing time is 200s; wherein, the second alkaline polishing solution comprises 12L of second alkaline solution, 2L of second additive, and 480L of deionized water. By mass percentage, the second additive comprises 1% sodium benzoate, 4% lauryl glucoside, 11% glucose, 7% sodium diacetate, and 77% deionized water. The lauryl glucoside serves as the surfactant, and the sodium diacetate serves as the catalyst. The width of the secondary tower base structure 3 formed after the second polishing is 10–12 μm, and the height difference between the base of the secondary tower base structure 3 and the surface of one side is 0.3–0.5 μm.

[0044] Step 5: Tunneling oxide layer preparation: A thermal oxidation process is used to form a passivation layer on the side facing away from the silicon substrate. Tunneling oxide layer: Oxidation temperature controlled at 590~600℃, oxygen flow rate at 36000 sccm, oxidation time at 400~500 s, forming a layer with a thickness of 1.5~2.5 nm. Tunneling through the oxide layer; Step 6: Deposition and doping of doped polycrystalline silicon layers: Using low-pressure chemical vapor deposition (LPCVD) with silane (… Intrinsic silicon is first deposited as the silicon source, with the deposition temperature controlled at 590~600℃ and the time at 1500s. Silane ( ) Flow rate 1880 sccm, deposition thickness 100~120 nm.

[0045] Then, using phosphorus oxychloride as the doping source, phosphorus (P) was doped into intrinsic silicon. + Formation of polycrystalline silicon layer: diffusion temperature 800~1000℃, phosphorus oxychloride (POCl3) flow rate 1400sccm, time 1000s, propagation depth 100~200nm, reaching the tunnel oxide layer.

[0046] Step 7: Subsequent Processes: In Backside passivation film deposited on the surface of doped polycrystalline silicon layer The TOPCon battery is fabricated by stacking layers and preparing metal electrodes through screen printing.

[0047] Example 2: Compared with Example 1, the difference is that the width of the secondary tower base structure formed after the second polishing in Example 2 is 6μm, and the height difference between the base of the secondary tower base structure and the surface of one side is 0.3 to 0.5μm.

[0048] Example 3: Compared with Example 1, the difference is that the width of the secondary tower base structure formed after the second polishing in Example 3 is 25 μm, and the height difference between the base of the secondary tower base structure and the surface of one side is 0.3 to 0.5 μm.

[0049] Comparative Example 1: Compared with Example 1, the difference is that the polishing step of Comparative Example 1 only includes a second polishing step.

[0050] Comparative Example 2: Compared with Example 2, the difference is that the polishing step of Comparative Example 2 only includes a second polishing step.

[0051] Comparative Example 3: Compared with Example 3, the difference is that the polishing step of Comparative Example 3 only includes a second polishing step.

[0052] The reflectivity and surface roughness of one side of the polished silicon substrates of Examples 1-3 and Comparative Examples 1-3 were tested respectively. The width of the tower base structure formed in Example 1 and Comparative Example 1 was 10-12 μm, the width of the tower base structure formed in Example 2 and Comparative Example 2 was 6 μm, and the width of the tower base structure formed in Example 3 and Comparative Example 3 was 25 μm. The test results are shown in Table 1.

[0053] Table 1. Comparison of reflectivity and surface roughness of one side of the silicon substrate after polishing in Examples 1-3 and Comparative Examples 1-3.

[0054] As shown in Table 1, when the tower base widths are 6μm, 10-12μm and 25μm respectively, the Ra and Rq of one side of the silicon substrate obtained after two polishings in Examples 1-3 are all lower than the Ra and Rq of the corresponding proportions after only one polishing. This indicates that the two polishing treatments of the present invention can improve the flatness of the silicon substrate surface under different tower base width conditions.

[0055] Furthermore, the reflectivity test values ​​of Examples 1 to 3 are all higher than those of the corresponding comparative examples. Specifically, when the base width is 10–12 μm, the reflectivity of Example 1 is increased by approximately 2 percentage points compared to Comparative Example 1. When the base width is 6 μm and 25 μm, the reflectivity test values ​​of Examples 2 and 3 are not reduced due to the addition of the first polishing treatment. This indicates that the present invention can maintain good reflectivity while improving the surface flatness of the silicon substrate.

[0056] 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.

[0057] The above embodiments merely illustrate preferred implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing a solar cell, characterized in that, Including the following steps: Texturing: Providing a silicon substrate and texturing the silicon substrate to form a pyramid structure on the surface of the silicon substrate; First polishing: At a first temperature, a first alkaline polishing solution is used to polish one side of the textured silicon substrate for the first time, so as to initially level one side of the silicon substrate and form a primary tower base structure; Second polishing: At a second temperature, a second alkaline polishing solution is used to polish the side that has been polished for the first time, and the side is leveled for the second time, so that the primary tower base structure forms a secondary tower base structure.

2. The method for preparing a solar cell according to claim 1, characterized in that, The width of the secondary tower base structure is 6 to 25 μm. The secondary tower base structure is recessed towards the other side of the silicon substrate. The secondary tower base structure includes a base disposed near the other side. The height difference between the base and the surface of the other side is 0.3 to 0.5 μm. The secondary tower base structure also includes a sidewall disposed between the base and the surface of the other side. The sidewall is inclined.

3. The method for preparing a solar cell according to claim 1, characterized in that, After the second polishing, the surface roughness Ra of one side is 0.05~0.13μm.

4. The method for preparing a solar cell according to claim 1, characterized in that, The first alkaline polishing solution comprises a first alkaline solution, a first additive, and deionized water, wherein the volume ratio of the first alkaline solution, the first additive, and the deionized water is 5~10:5~10:400~550; and the first additive comprises, by mass percentage, 1.0%~2.0% potassium sorbate, 1.0%~5.0% dispersant, 1.0%~5.0% emulsifier, and 2.0%~10.0% surfactant.

5. The method for preparing a solar cell according to claim 1, characterized in that, The second alkaline polishing solution includes a second alkaline solution, a second additive, and deionized water, wherein the volume ratio of the second alkaline solution, the second additive, and deionized water is 10~15:0.5~5:400~550; the second additive includes sodium benzoate, surfactant, catalyst, and deionized water.

6. The method for preparing a solar cell according to claim 1, characterized in that, The first temperature is 80~90℃, and the second temperature is 60~65℃.

7. The method for preparing a solar cell according to claim 1, characterized in that, It also includes the preparation steps of passivation layer and tunneling oxide layer: the passivation layer and tunneling oxide layer are prepared sequentially on one side surface after the second polishing.

8. A solar cell, characterized in that, The solar cell is prepared using the solar cell preparation method according to any one of claims 1 to 7; The solar cell includes a silicon substrate, one side of which has a polished surface. The polished surface has a secondary tower base structure with a width of 6–25 μm. The secondary tower base structure is recessed towards the other side of the silicon substrate. The secondary tower base structure includes a substrate disposed near the other side, and the height difference between the substrate and the surface of the first side is 0.3–0.5 μm. The secondary tower base structure also includes a sidewall disposed between the substrate and the surface of the first side, and the sidewall is inclined.

9. The solar cell according to claim 8, characterized in that, The roughness Ra of the polished surface is 0.05~0.13μm.

10. A photovoltaic module, characterized in that, include: A battery string, consisting of multiple solar cells as described in claim 9 connected together; 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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