Texturing method of silicon substrate, solar cell and preparation method of solar cell

Abstract

The invention belongs to the technical field of solar cells, and provides a texturing method of a silicon substrate, a solar cell and a preparation method of the solar cell, and the texturing method comprises the following steps: providing the silicon substrate; a main pyramid suede structure is formed; cleaning with a cleaning solution containing a texturing additive; an attached pyramid suede structure is formed at the edge surface and / or the corner angle of the main pyramid; and performing post-treatment to obtain the silicon substrate with the clustered pyramid suede structure. According to the texturing method, the cleaning liquid containing the texturing additive is adopted to clean the silicon substrate after the main pyramid textured structure is formed, then the attached pyramid textured structure is formed, the cluster pyramid textured structure can be obtained, pyramid gaps are effectively utilized, the density and the compact degree of the pyramid textured structure are increased, and the texturing efficiency is improved. The reflectivity of the silicon substrate is reduced, passivation and current increase of the solar cell are facilitated, and the effect of improving the photoelectric performance of the solar cell is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and relates to a method for texturing a silicon substrate, a solar cell, and a method for manufacturing a solar cell. Background Art

[0002] During the preparation process of a solar cell, first, the silicon wafer is textured to obtain a uniform and dense pyramid-shaped textured surface structure. The textured surface structure plays a crucial role in the conversion efficiency of the silicon wafer. Therefore, the silicon wafer texturing process is a crucial step in the preparation process of a solar cell.

[0003] However, in the current texturing process, the coverage of the formed pyramid-shaped textured surface is low, and there are gaps between the pyramids. Therefore, it is necessary to optimize the texturing process to optimize the textured surface structure on the silicon wafer surface and reduce the reflectivity of the silicon wafer. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for texturing a silicon substrate, a solar cell, and a method for manufacturing a solar cell. The texturing method can obtain a cluster-shaped pyramid-shaped textured surface structure by cleaning the silicon substrate after the first texturing with a cleaning solution containing a texturing additive, effectively utilizes the gaps between the pyramids, increases the density and compactness of the pyramid-shaped textured surface, reduces the reflectivity of the silicon substrate, is more conducive to the passivation and current improvement of the battery, and achieves the effect of improving the optoelectronic performance of the battery.

[0005] To achieve the purpose of this invention, the following technical solutions are adopted:

[0006] In a first aspect, the present invention provides a method for texturing a silicon substrate, and the texturing method includes the following steps:

[0007] Provide a silicon substrate.

[0008] Form a main pyramid-shaped textured surface structure.

[0009] Clean, and perform the cleaning with a cleaning solution containing a texturing additive.

[0010] Form an attached pyramid-shaped textured surface structure at the edges and / or corners of the main pyramid.

[0011] Perform post-treatment to obtain a silicon substrate with a cluster-shaped pyramid-shaped textured surface structure.

[0012] In some embodiments, the surface tension of the texturing additive is 45 mN / m - 65 mN / m.

[0013] In some embodiments, in the texturing solution for forming the attached pyramid-shaped textured surface structure, the mass concentration ratio of the alkali solution is W 1 , and in the texturing solution for forming the main pyramid-shaped textured surface structure, the mass concentration ratio of the alkali solution is W2 , the said W 1 <W 2 .

[0014] In some embodiments, the cleaning includes the following steps:

[0015] First, clean with a cleaning solution containing a texturing additive.

[0016] Then, clean with a cleaning solution containing an oxidant.

[0017] Alternatively, first clean with a cleaning solution containing an oxidant.

[0018] Then, clean with a cleaning solution containing a texturing additive.

[0019] In some embodiments, the steps of cleaning and forming an attached pyramid texture structure are repeated more than once.

[0020] In some embodiments, the texturing method includes the following steps:

[0021] Provide a silicon substrate.

[0022] Texture the silicon substrate once to form a main pyramid texture structure.

[0023] Clean, and perform the cleaning with a cleaning solution containing a texturing additive.

[0024] Texture for the second time to form an attached pyramid texture structure at the edges and / or corners of the main pyramid.

[0025] Clean, and perform the cleaning with a cleaning solution containing a texturing additive.

[0026] Texture for the third time to continuously grow attached pyramids at the edges and / or corners of the main pyramid and the attached pyramids.

[0027] Perform post-treatment to obtain a silicon substrate with a cluster-like pyramid texture structure.

[0028] In some embodiments, the texturing solution for forming the main pyramid texture structure includes a texturing additive, an alkali, and water.

[0029] In some embodiments, the cleaning solution used for cleaning includes a texturing additive and water.

[0030] In some embodiments, the texturing solution for forming the attached pyramid texture structure includes a texturing additive, an alkali, and water.

[0031] In some embodiments, before forming the main pyramid texture structure, the silicon substrate is also subjected to the steps of pre-cleaning, rough polishing, and primary cleaning.

[0032] In some embodiments, the post-treatment includes steps of pure water cleaning, rounding, pickling, slow lifting, and drying.

[0033] In a second aspect, the present invention provides a method for manufacturing a solar cell, the method for manufacturing the solar cell comprising the following steps:

[0034] Providing a silicon substrate.

[0035] Forming a main pyramid texture structure.

[0036] Cleaning, and performing the cleaning using a cleaning solution containing a texturing additive.

[0037] Forming an attached pyramid texture structure at the edges and / or corners of the main pyramid.

[0038] Performing post-treatment to obtain a silicon substrate having a cluster-like pyramid texture structure.

[0039] Preparing an amorphous or microcrystalline film layer.

[0040] Preparing a conductive film layer.

[0041] Preparing electrodes to obtain the solar cell.

[0042] In a third aspect, the present invention provides a solar cell, comprising a silicon substrate, the silicon substrate having a cluster-like pyramid texture structure, the cluster-like pyramid texture structure including main pyramids and attached pyramids, and the attached pyramids being located on the edges and / or corners of the main pyramids.

[0043] In some embodiments, the tips of the attached pyramids are lower than the tips of the main pyramids.

[0044] In some embodiments, the height of the main pyramids is 1.3 - 1.6 μm.

[0045] In some embodiments, the main pyramids grow from the surface of the silicon substrate in a direction away from the silicon substrate, and the attached pyramids grow along the edges and / or ridges of the main pyramids.

[0046] In some embodiments, in the unit area of the silicon substrate, the proportion of the main pyramids is ≥ 50%.

[0047] In some embodiments, the solar cell further includes an amorphous or microcrystalline film layer, a conductive film layer, and electrodes located on the surface of the cluster-like pyramid texture structure of the silicon substrate.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] By cleaning with a texturing additive solution between two texturing processes, the present invention enables the pyramids to continue growing at the edges or corners of the main pyramids, thereby growing attached pyramids around the surface of the main pyramids to obtain a cluster-like pyramid surface structure. Compared with the conventional surface, the height difference of the cluster-like pyramid surface is smaller, which is more conducive to the contact of the film layer and electrode printing. Moreover, the cluster-like pyramids make more effective use of the gaps between the pyramids, increasing the density and compactness of the pyramid surface, reducing the reflectivity of the silicon wafer, being more conducive to the passivation of the battery and the improvement of current, and achieving the effect of enhancing the optoelectronic performance of the battery. Description of the Drawings

[0050] Figure 1 It is a top-view SEM image of the silicon wafer obtained in Example 1 of the present invention under an 8-μm scale.

[0051] Figure 2 It is a side-view SEM image of the silicon wafer obtained in Example 1 of the present invention under an 8-μm scale.

[0052] Figure 3 It is a top-view SEM image of the silicon wafer obtained in Comparative Example 1 of the present invention under an 8-μm scale.

[0053] Figure 4 It is a side-view SEM image of the silicon wafer obtained in Comparative Example 1 of the present invention under an 8-μm scale.

[0054] Figure 5 It is a top-view SEM image of the silicon wafer obtained in Comparative Example 2 of the present invention under an 8-μm scale.

[0055] Figure 6 It is a side-view SEM image of the silicon wafer obtained in Comparative Example 2 of the present invention under an 8-μm scale.

[0056] Figure 7 It is a top-view SEM image of the silicon wafer obtained in Comparative Example 3 of the present invention under an 8-μm scale.

[0057] Figure 8 It is a side-view SEM image of the silicon wafer obtained in Comparative Example 3 of the present invention under an 8-μm scale.

[0058] Figure 9 It is a schematic structural diagram of the cluster-like pyramid surface structure obtained by the present invention.

[0059] Figure 10 It is a schematic cross-sectional structural diagram of the cluster-like pyramid surface structure described in the present invention.

[0060] Figure 11 It is a schematic structural diagram of the pyramids on the surface of the silicon wafer obtained by the conventional method of Comparative Example 3 of the present invention.

[0061] Figure 12 It is a schematic cross-sectional structural diagram of the pyramids on the surface of the silicon wafer obtained by the conventional method of Comparative Example 3 of the present invention.

[0062] Figure 13 This is the flowchart of the texturing method of the present invention.

[0063] Among them, 1 - main pyramid, 2 - attached pyramid, 3 - large pyramid of primary texturing, 4 - small pyramid of secondary texturing. Specific embodiments

[0064] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0065] In a first aspect, the present invention provides a texturing method for a silicon substrate. The flowchart of the texturing method is as Figure 13 shown, including the following steps:

[0066] S1: Provide a silicon substrate.

[0067] S2: Form a main pyramid texture structure.

[0068] S3: Clean, and perform the cleaning with a cleaning solution containing a texturing additive.

[0069] S4: Form an attached pyramid texture structure at the edges and / or corners of the main pyramid.

[0070] S5: Post - treatment to obtain a silicon substrate with a cluster - like pyramid texture structure.

[0071] After the primary texturing of the silicon substrate in the present invention, a main body main pyramid is formed. Then, it is cleaned with a cleaning solution containing a texturing additive to clean and protect the surface of the main pyramid. Subsequently, secondary texturing is carried out. The pyramids of the secondary texturing will continue to grow at the edges or corners of the partial circumference of the main pyramid, thereby growing attached pyramids with a rectangular or irregular quadrilateral base, and obtaining a cluster - like pyramid texture structure. Compared with the conventional texture, the height difference of the cluster - like pyramid texture is smaller, which is more conducive to film layer contact and electrode printing. Moreover, the cluster - like pyramids make more effective use of the gaps between the pyramids, increasing the density and compactness of the pyramid texture, reducing the reflectivity of the silicon substrate, being more conducive to the passivation of the battery and current improvement, and achieving the effect of improving the optoelectronic performance of the battery.

[0072] As Figure 9 shown, the attached pyramid 2 of the present invention attaches to the main pyramid 1, grows at the edges and / or corners of the partial circumference of the main pyramid 1, and after some attached pyramids 2 grow out on the circumference of the main pyramid 1, the continuously growing attached pyramids can also attach to the circumference of the already grown attached pyramids; from Figure 10It can be seen that the height difference between the dependent pyramid 2 and the main pyramid 1 of the present invention is relatively small.

[0073] In addition, the base of the main pyramid 1 of the present invention is a regular square, while the base of the dependent pyramid 2 is incomplete compared to the square base of the main pyramid. Therefore, the dependent pyramid 2 is incomplete compared to the main pyramid 1, and its base is a rectangle or an irregular quadrilateral. That is, the side of the dependent pyramid 2 of the present invention will be attached or attached to at least one edge of the main pyramid 1, forming an attached relationship, and not existing independently. The pyramid velvet structure obtained by the conventional method of secondary velveting is as follows: Figure 11 and Figure 12 It can be known that the small pyramid 4 of the secondary textured material grows independently between the gaps of the large pyramid 3 of the primary textured material, exists independently, and has a small base size, which is different from the dependent pyramid of the present invention.

[0074] The present invention uses a cleaning solution containing a texturing additive to clean after a texturing process, and the principle of obtaining a clustered pyramid is as follows: a silicon substrate forms a main pyramid velvet surface after a texturing process, and then is cleaned by a cleaning solution containing a texturing additive. The velvet additive (such as a polymer ether substance) in the cleaning process has a strong adsorption capacity on the surface of the silicon substrate after texturing, which can enhance the hydrophobicity of the silicon substrate surface, thereby reducing the contact between the silicon substrate surface and the reaction substances in the solution, thereby achieving the effect of protecting the formed pyramid velvet surface during the secondary texturing process, and at the same time, a new pyramid is continuously corroded around the formed main pyramid. Since the new pyramid is a newly corroded interface, less protective substances are adsorbed, and a new interface will be quickly corroded. In summary, since the surface of the original main pyramid is protected by the additive, combined with the newly corroded interface around the main pyramid, a clustered pyramid velvet surface state is prepared as a whole.

[0075] After the post-processing described in the present invention, the top of the pyramid is corroded; specifically, the rounding step in the post-processing will corrode the top of the pyramid. If the rounding treatment is not performed, the passivation effect will be weakened, so the rounding treatment is performed.

[0076] In a specific embodiment, the surface tension of the texturing additive is 45mN / m-65mN / m, for example, 45mN / m, 50mN / m, 55mN / m, 60mN / m or 65mN / m, and is a hydrophobic texturing additive.

[0077] The texturing additives used in the present invention include any one of Xiaochen H13C hydrophobic additives, H16 hydrophilic additives or Shichuang HJ21v02 hydrophobic additives, or a combination of at least two of them. Among them, the texturing additives used for cleaning are preferably texturing additives with a surface tension within a specific range. As hydrophobic texturing additives, the components contain polymer components and can be adsorbed on the surface of the velvet surface to form a protective layer.

[0078] In a specific embodiment, in the etching solution for forming the adherent pyramid texture, the mass concentration ratio of the alkali solution is W 1 , and in the etching solution for forming the main pyramid texture, the mass concentration ratio of the alkali solution is W 2 , and the W 1 <W 2 .

[0079] In the present invention, it is preferred that the mass concentration ratio of the alkali solution in the secondary etching solution < the mass concentration ratio of the alkali solution in the primary etching solution, which can facilitate the formation of the adherent pyramid while protecting the main pyramid.

[0080] In a specific embodiment, the cleaning includes the following steps:

[0081] First, clean with a cleaning solution containing an etching additive.

[0082] Then, clean with a cleaning solution containing an oxidant.

[0083] Alternatively, first clean with a cleaning solution containing an oxidant.

[0084] Then, clean with a cleaning solution containing an etching additive.

[0085] Before or after cleaning with the cleaning solution containing an etching additive, the present invention can also clean with a cleaning solution containing an oxidant, which can increase the size of the cluster pyramids, thereby improving the coverage rate of the cluster pyramids and reducing the gaps between the pyramids.

[0086] Moreover, the present invention preferably uses the cleaning solution containing an oxidant for the first cleaning and then uses the cleaning solution containing an etching additive for the second cleaning. After the first cleaning with the oxidant, the surface cleanliness is higher. On this basis, the second cleaning with the cleaning solution containing an etching additive provides stronger protection for the already formed texture surface. After secondary etching, it is possible to fully utilize the gaps between the textures to grow cluster pyramids, achieving the effects of reducing the reflectivity and improving the battery efficiency.

[0087] In a specific embodiment, the temperature of the cleaning is 55°C - 70°C. For example, it can be 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0088] The temperature of the cleaning in the present invention will have a certain impact on the cluster pyramid structure. If the cleaning temperature is too low, the surface may not be thoroughly cleaned, and the residual reaction solution will continue to corrode the surface of the silicon substrate, weakening the protection of the cleaning solution for the texture surface of the silicon substrate. If the temperature of the second cleaning is too high, the surface of the silicon substrate may be oxidized, resulting in insufficient adsorption capacity of the additive and weakening the protection effect of the additive, increasing the reflectivity of the silicon substrate.

[0089] In a specific embodiment, the cleaning time is 100 s - 150 s. For example, it can be 100 s, 110 s, 120 s, 130 s, 140 s or 150 s, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0090] In a specific embodiment, the steps of cleaning and forming the attached pyramid velvet surface structure are repeated more than once. For example, it can be 1 time, 2 times, 3 times or 4 times, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0091] After the attached pyramid velvet surface structure is formed by secondary texturing in the present invention, the cleaning and secondary texturing steps can be carried out again to achieve multiple texturing.

[0092] In a specific embodiment, the texturing method includes the following steps:

[0093] Provide a silicon substrate.

[0094] Perform primary texturing on the silicon substrate to form a main pyramid velvet surface structure.

[0095] Clean, and use a cleaning solution containing a texturing additive for the cleaning.

[0096] Perform secondary texturing to form an attached pyramid velvet surface structure at the edges and / or corners of the main pyramid.

[0097] Clean, and use a cleaning solution containing a texturing additive for the cleaning.

[0098] Perform tertiary texturing to continuously grow attached pyramids at the edges and / or corners of the main pyramid and the attached pyramid.

[0099] Perform post-treatment to obtain a silicon substrate with a cluster-like pyramid velvet surface structure.

[0100] The present invention can perform multiple texturing steps. For example, in the above texturing method, after secondary texturing, cleaning and texturing can be carried out again to continuously grow pyramids, thereby effectively utilizing the gaps between the main pyramids and reducing the reflectivity.

[0101] In a specific embodiment, the primary texturing solution for forming the main pyramid velvet surface structure includes a texturing additive, an alkali and water.

[0102] In a specific embodiment, the cleaning solution used for cleaning includes a texturing additive and water. Among them, the content of the texturing additive is 0.1 wt% - 1 wt%. For example, it can be 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 0.9 wt% or 1 wt%, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0103] In a specific embodiment, the secondary texturing solution for forming the adherent pyramid texture structure includes a texturing additive, an alkali, and water.

[0104] In a specific embodiment, before forming the main pyramid texture structure, the silicon substrate is also subjected to pre-cleaning, rough polishing, and primary cleaning steps.

[0105] In a specific embodiment, the cleaning solution for the pre-cleaning includes an oxidant, an alkali, and water.

[0106] The silicon substrate of the present invention is pre-cleaned, for example, by cleaning with hydrogen peroxide and sodium hydroxide solution to remove surface oil stains.

[0107] In a specific embodiment, the cleaning solution used for the primary cleaning includes an oxidant and water.

[0108] The rough polishing in the present invention removes the oxide layer and mechanical damage layer of the silicon substrate. After rough polishing, the silicon substrate is subjected to primary cleaning to obtain a clean surface of the silicon substrate.

[0109] The oxidant used in the present invention is hydrogen peroxide, and the alkali used includes sodium hydroxide.

[0110] In a specific embodiment, the post-treatment includes pure water cleaning, rounding, pickling, slow lifting, and drying steps.

[0111] The rounding treatment in the present invention can corrode the tips of the pyramids in the cluster-like pyramid texture structure. If the rounding treatment is not performed, the passivation effect of the silicon substrate is weakened. Therefore, the rounding treatment needs to be performed during the post-treatment.

[0112] In a specific embodiment, the rounding solution used for the rounding includes ozone, HF, and water.

[0113] In a specific embodiment, after rounding, pure water cleaning is performed, and then the pickling is carried out.

[0114] In a second aspect, the present invention provides a method for manufacturing a solar cell, and the method for manufacturing the solar cell includes the following steps:

[0115] Provide a silicon substrate.

[0116] Form a main pyramid texture structure.

[0117] Clean, and perform the cleaning with a cleaning solution containing a texturing additive.

[0118] Form an adherent pyramid texture structure at the edges and / or corners of the main pyramid.

[0119] Perform post-treatment to obtain a silicon substrate with a cluster-like pyramid texture structure.

[0120] Prepare an amorphous or microcrystalline film layer.

[0121] Prepare a conductive film layer.

[0122] Prepare an electrode to obtain the solar cell.

[0123] In a specific embodiment, an amorphous / microcrystalline silicon film is grown and deposited on the front and back surfaces of the silicon substrate that has completed the texturing process.

[0124] Subsequently, a PN junction is formed on one side, and a high-low junction is formed on the other side.

[0125] PVD coating: Coat both sides of the coated silicon substrate with a conductive film.

[0126] Screen printing: The grid line electrodes are prepared through screen printing and curing to obtain the solar cell.

[0127] In a third aspect, the present invention provides a solar cell, which includes a silicon substrate having a cluster-like pyramid texture structure. The cluster-like pyramid texture structure includes main pyramids and attached pyramids, and the attached pyramids are located on the facets and / or edges of the main pyramids.

[0128] In a specific embodiment, the tip of the attached pyramid is lower than the tip of the main pyramid.

[0129] The tip of the main pyramid of the present invention is higher, and the attached pyramids are formed in the gaps between the main pyramids. Therefore, the reflectivity of the main pyramids is higher.

[0130] In a specific embodiment, in the unit area of the silicon substrate, the proportion of the main pyramids ≥ 50%, for example, it can be 50%, 55%, 60%, 65%, 70%, 75% or 80%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0131] Due to the high reflectivity of the main pyramids, in order to reduce the reflectivity, it is preferred that the proportion of the main pyramids in the unit area of the silicon substrate (in terms of quantity or base area) ≥ 50%.

[0132] In a specific embodiment, the main pyramids grow away from the surface of the silicon substrate, and the attached pyramids grow along the facets and / or edges of the main pyramids.

[0133] In the present invention, the attached pyramids grow along the facets and / or edges of the main pyramids and do not exist independently, while the pyramids prepared by conventional methods exist independently.

[0134] In a specific embodiment, the height of the main pyramid is 1.3 - 1.6 μm, for example, it can be 1.3 μm, 1.4 μm, 1.5 μm or 1.6 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0135] The technical solution of the present invention will be further described below through specific embodiments.

[0136] Example 1

[0137] This example provides a method for texturing a silicon wafer, and the texturing method includes the following steps:

[0138] (1) Take a single crystal silicon wafer that has been cleaned, gettered, and PSG-removed as the texturing silicon wafer for standby.

[0139] (2) Pre-cleaning: Immerse the single crystal silicon wafer in a pre-cleaning mixed solution at 65 °C for 240 s for cleaning.

[0140] The pre-cleaning solution is initially prepared with 280 L of pure water, 4 L of 45 wt% sodium hydroxide solution, and 20 L of 45 wt% hydrogen peroxide solution; the replenishment for each batch is 5 L of pure water, 100 mL of 45 wt% sodium hydroxide solution, and 1 L of 45 wt% hydrogen peroxide solution.

[0141] (3) Water washing: Immerse the single crystal silicon wafer obtained in step (2) in pure water for 120 s for cleaning.

[0142] (4) Coarse polishing: Immerse the single crystal silicon wafer obtained in step (3) in an alkaline solution at 80 °C for 60 s for alkaline polishing treatment.

[0143] The formula of the coarse polishing solution is: initially prepared with 280 L of pure water and 30 L of 45 wt% sodium hydroxide solution; the replenishment for each batch is 8 L of pure water and 500 mL of 45 wt% sodium hydroxide solution.

[0144] (5) First cleaning: Immerse the single crystal silicon wafer obtained in step (4) in a cleaning solution at 65 °C for 400 s for cleaning.

[0145] The cleaning solution is a solution of 5 wt% hydrogen peroxide and pure water. After cleaning, the single crystal silicon wafer is immersed in pure water for 120 s for cleaning.

[0146] (6) First texturing: Immerse the single crystal silicon wafer in a first texturing solution at 80 °C for 350 s for cleaning.

[0147] The formula of the first texturing solution is: initially prepared from 280 L of pure water, 3 L of 45 wt% sodium hydroxide, and 1 L of H13C texturing additive; the replenishment for each batch is 10 L of pure water, 350 mL of 45 wt% sodium hydroxide solution, and 280 mL of H13C texturing additive.

[0148] (7) Secondary cleaning: At 60 °C, immerse the single-crystalline silicon wafer obtained in step (6) in the H13C texturing additive for 120 s for cleaning.

[0149] The formula of the secondary cleaning solution is 2 L of H13C texturing additive and 280 L of pure water. The replenishment for each batch is 1 L of pure water and 100 mL of H13C texturing additive.

[0150] (8) Secondary texturing: Immerse the single-crystalline silicon wafer obtained in step (7) in the second texturing solution at 80 °C for 350 s for cleaning.

[0151] The formula of the second texturing solution is the same as that of the first texturing solution in step (6). After texturing is completed, immerse it in pure water for 120 s for cleaning.

[0152] (9) Rounding: Immerse the textured single-crystalline silicon wafer obtained in step (8) in the rounding cleaning solution for 350 s for cleaning.

[0153] The formula of the rounding cleaning solution is: 45 ppm of ozone and 2% HF solution; the process replenishment is 30 mL of HF solution and 4 L of pure water for each batch.

[0154] After rounding, immerse the silicon wafer in pure water for 120 s for cleaning.

[0155] (10) Pickling: Immerse the single-crystalline silicon wafer obtained in step (9) in a 5 wt% hydrofluoric acid solution for 300 s for cleaning. After pickling, immerse the silicon wafer in pure water for 120 s for cleaning.

[0156] (11) Slow lifting and drying: Clean the single-crystalline silicon wafer obtained in step (10) in pure water, slowly lift the single-crystalline silicon wafer at a speed of 3 mm / s, and dry it at 80 °C in clean air for 15 min to obtain the silicon wafer. The silicon wafer has a cluster-like pyramid texture structure. The cluster-like pyramid texture structure includes main pyramids and attached pyramids. The attached pyramids are located on the prism faces and edges of the main pyramids. The tips of the attached pyramids are lower than the tips of the main pyramids. The proportion of the main pyramids in the cluster-like pyramid texture structure is 55%, and the height of the main pyramids is 1.5 μm.

[0157] The top-view SEM image of the silicon wafer obtained in this embodiment is as Figure 1 shown ( Figure 1 the base dimensions are marked), and the side-view SEM image is as Figure 2 shown. The schematic diagram of the cluster-like pyramid structure on the silicon wafer surface is as Figure 9 shown, and the schematic diagram of the cross-sectional structure is as Figure 10 shown.

[0158] Example 2

[0159] This embodiment provides a method for texturing silicon wafers. Except for step (7) which is different from that in Embodiment 1, the rest are the same as those in Embodiment 1. Step (7) is specifically as follows:

[0160] (7) Secondary cleaning: At 60 °C, immerse the once-textured silicon wafer in step (6) in the H13C texturing additive solution for 120 s for soaking and cleaning. Among them, the formulation of the secondary cleaning solution is 2 L of H13C texturing additive and 280 L of pure water, and the replenishment for each batch is 1 L of pure water and 100 mL of H13C texturing additive.

[0161] After cleaning with the texturing additive solution, at 60 °C, immerse it in hydrogen peroxide for 120 s for soaking and cleaning. The formulation of the cleaning solution is the same as that of the primary cleaning solution.

[0162] The silicon wafer after texturing in this embodiment has a cluster-like pyramid texture structure. The cluster-like pyramid texture structure includes main pyramids and attached pyramids. The attached pyramids are located on the prism faces and edges of the main pyramids. The tips of the attached pyramids are lower than the tips of the main pyramids. The proportion of the main pyramids in the cluster-like pyramid texture structure is 50%, and the height of the main pyramids is 1.5 μm.

[0163] Embodiment 3

[0164] This embodiment provides a method for texturing silicon wafers. Except for step (7) which is different from that in Embodiment 1, the rest are the same as those in Embodiment 1. Step (7) is specifically as follows:

[0165] (7) Secondary cleaning: At 60 °C, immerse the once-textured silicon wafer in step (6) in hydrogen peroxide for 120 s for soaking and cleaning. The formulation of the cleaning solution is the same as that of the primary cleaning solution.

[0166] After cleaning with hydrogen peroxide, at 60 °C, immerse it in the H13C texturing additive solution for 120 s for soaking and cleaning. Among them, the formulation of the cleaning solution is 2 L of H13C texturing additive and 280 L of pure water, and the replenishment for each batch is 1 L of pure water and 100 mL of H13C texturing additive.

[0167] The silicon wafer after texturing in this embodiment has a cluster-like pyramid texture structure. The cluster-like pyramid texture structure includes main pyramids and attached pyramids. The attached pyramids are located on the prism faces and edges of the main pyramids. The tips of the attached pyramids are lower than the tips of the main pyramids. The proportion of the main pyramids in the cluster-like pyramid texture structure is 60%, and the height of the main pyramids is 1.5 μm.

[0168] Embodiment 4

[0169] This embodiment provides a method for texturing silicon wafers. Except for the secondary cleaning in the H16 hydrophilic texturing additive solution in step (7), the rest are the same as those in Embodiment 1.

[0170] Embodiment 5

[0171] This embodiment provides a method for texturing silicon wafers. Except for the secondary texturing in step (8), three cleaning steps and three texturing steps are sequentially carried out. Among them, the three cleaning steps are the same as the secondary cleaning step, and the three texturing steps are the same as the secondary texturing step. The rest are the same as those in Embodiment 1.

[0172] Embodiment 6

[0173] This embodiment provides a method for texturing silicon wafers. Except that the temperature of the secondary cleaning in step (7) is 55 °C, the rest are the same as those in Embodiment 1.

[0174] Embodiment 7

[0175] This embodiment provides a method for texturing silicon wafers. Except that the temperature of the secondary cleaning in step (7) is 70 °C, the rest are the same as those in Embodiment 1.

[0176] Embodiment 8

[0177] This embodiment provides a method for texturing silicon wafers. Except that the temperature of the secondary cleaning in step (7) is 40 °C, the rest are the same as those in Embodiment 1.

[0178] Embodiment 9

[0179] This embodiment provides a method for texturing silicon wafers. Except that the temperature of the secondary cleaning in step (7) is 80 °C, the rest are the same as those in Embodiment 1.

[0180] Comparative Example 1

[0181] This comparative example provides a method for texturing silicon wafers. Except for the secondary cleaning in pure water in step (7), the rest are the same as those in Embodiment 1.

[0182] The top-view SEM image of the silicon wafer obtained in this comparative example is as Figure 3 shown ( Figure 3 the base size is marked), and the side-view SEM image is as Figure 4 shown.

[0183] Comparative Example 2

[0184] This comparative example provides a method for texturing silicon wafers. Except that in step (7), the silicon wafers are washed twice with hydrogen peroxide, and the cleaning solution formulation is the same as that used in the first washing, the rest are the same as in Example 1.

[0185] The top-view SEM image of the silicon wafer obtained in this example is as Figure 5 shown ( Figure 5 the tower base size is marked in Figure 6 ), and the side-view SEM image is as

[0186] Comparative Example 3

[0187] This comparative example provides a method for texturing silicon wafers, and the method includes the following steps:

[0188] (1) Take the monocrystalline silicon wafers that have been cleaned, gettered, and PSG-removed as the silicon wafers for texturing and set aside.

[0189] (2) Pre-washing: Immerse the monocrystalline silicon wafers in the pre-washing mixed solution at 65 °C for 240 s for cleaning.

[0190] The pre-washing solution is initially prepared with 280 L of pure water, 4 L of 45 wt% sodium hydroxide solution, and 20 L of 45 wt% hydrogen peroxide solution; the replenishment solution for each batch is 5 L of pure water, 100 mL of 45 wt% sodium hydroxide solution, and 1 L of 45 wt% hydrogen peroxide solution.

[0191] (3) Water washing: Immerse the monocrystalline silicon wafers obtained in step (2) in pure water for 120 s for cleaning.

[0192] (4) Coarse polishing: Immerse the monocrystalline silicon wafers obtained in step (3) in the lye at 80 °C for 60 s for alkaline polishing treatment.

[0193] The formulation of the coarse polishing solution is: initially prepared with 280 L of pure water and 30 L of 45 wt% sodium hydroxide solution; the replenishment solution for each batch is 8 L of pure water and 500 mL of 45 wt% sodium hydroxide solution.

[0194] (5) Cleaning: Immerse the monocrystalline silicon wafers in the cleaning solution at 65 °C for 400 s for cleaning.

[0195] The cleaning solution is a solution of 5 wt% hydrogen peroxide and pure water. After cleaning, the monocrystalline silicon wafers are immersed in pure water for 120 s for cleaning.

[0196] (6) Texturing: Immerse the monocrystalline silicon wafers obtained in step (5) in the first texturing solution at 80 °C for 700 s for cleaning. After texturing, enter pure water for 120 s for cleaning.

[0197] The formulation of the first texturing solution is as follows: initially prepare it by mixing 280 L of pure water, 3 L of 45 wt% sodium hydroxide, and 1 L of H13C texturing additive; the replenishment solution for each batch is 10 L of pure water, 350 mL of 45 wt% sodium hydroxide solution, and 280 mL of texturing additive.

[0198] The top-view SEM image of the silicon wafer obtained in this comparative example is as shown in Figure 7 ( Figure 7 the tower base size is marked), and the side-view SEM image is as shown in Figure 8 ( Figure 11 the schematic diagram of the pyramid structure on the silicon wafer surface is as shown in Figure 12 ), and the schematic diagram of the cross-sectional structure is as shown in

[0199] After the completion of each batch of monocrystalline silicon wafers in the above examples and comparative examples, replenishment is carried out accordingly, and then texturing of the silicon wafers in the next batch is carried out to complete the texturing of the silicon wafers.

[0200] For the silicon wafers obtained in the above examples and comparative examples, cell preparation is carried out. The cell preparation includes the following steps:

[0201] Deposit and grow microcrystalline silicon layers on the front and back sides of the silicon wafers obtained in the above examples and comparative examples, and then form a PN junction on one side and a high-low junction on the other side.

[0202] PVD coating: Coat conductive films on both sides of the coated silicon wafers.

[0203] Screen printing: Prepare the grid line electrodes through screen printing and curing to obtain a solar cell, and perform performance testing on the solar cell. The test results are shown in Table 1:

[0204] Table 1

[0205]

[0206] From Figures 1 - 12 and Table 1, it can be seen that:

[0207] (1) From Figures 1 - 8 it can be known that after the first texturing and before the second texturing in the present invention, cleaning with a texturing additive solution can obtain a high proportion of cluster-like pyramid textured surfaces. From Figure 1 it can be obtained that the bottom size of the tower base of the main pyramid obtained in Example 1 is about 2.8 μm. From Figure 3 it can be obtained that the bottom size of the main tower base of the textured surface obtained in Comparative Example 1 is about 2.5 μm. From Figure 5 it can be obtained that the bottom size of the main tower base of the textured surface obtained in Comparative Example 2 is about 4 μm. From Figure 7 it can be obtained that the bottom size of the main tower base of the textured surface obtained in Comparative Example 3 is about 3.2 μm, and the proportion of the cluster-like pyramid textured surface obtained in Example 1 is higher, and the height difference of the cluster-like textured surface is smaller. FromFigures 9 - 12 It can be seen that in the present invention Figures 9 - 10 compared with the ordinary suede surface Figures 11 - 12 the attached pyramid suede surface grows attached to the periphery or edges of the main pyramid. The height difference between the attached pyramid and the main pyramid is smaller. The clustered pyramid suede makes full use of the gaps between the pyramids to grow more attached pyramids, effectively enhancing the light absorption effect of the suede surface.

[0208] (2) It can be seen from Example 1 and Comparative Examples 1-3 that the battery performance of Example 1 is better, the reflectivity is lower, and the short-circuit current Isc and fill factor FF are higher, indicating that the clustered pyramid is beneficial to the absorption of light waves by the battery chip and the passivation contact of the film layer. The higher reflectivity of Comparative Example 2 compared to Comparative Example 3 indicates that after surface oxidation and hydrophilic treatment followed by secondary texturing, the suede surface is enlarged and there is some loss in reflectivity, but the fill factor is improved; it can be seen from Example 1 and Examples 2-3 that before or after cleaning with the texturing additive solution, the present invention can also use an oxidant solution for cleaning, which can increase the size of the clustered pyramid, thereby increasing the coverage rate of the clustered pyramid, reducing the gaps between the pyramids, and improving the performance of the battery; it can be seen from Example 1 and Example 4 that the present invention preferably uses a hydrophobic texturing additive solution for secondary cleaning, which can further improve the performance of the battery; it can be seen from Example 1 and Example 5 that the present invention can perform secondary texturing or multiple texturing, and use the texturing additive for cleaning between the two texturings; it can be seen from Example 1 and Examples 6-9 that the temperature of the secondary cleaning in the present invention will affect the cleaning effect and thus affect the battery performance.

[0209] In summary, the present invention provides a method for texturing a silicon substrate, a solar cell, and a method for preparing a solar cell. By cleaning the silicon wafer after primary texturing with a cleaning solution containing a texturing additive, the method can obtain a clustered pyramid suede surface structure, effectively utilize the gaps between the pyramids, increase the density and compactness of the pyramid suede surface, reduce the reflectivity of the silicon wafer, and is more conducive to the passivation and current increase of the battery, achieving the effect of improving the optoelectronic performance of the battery.

[0210] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of within the technical scope disclosed by the present invention fall within the protection scope and public scope of the present invention.

Claims

1. A method for texturing a silicon substrate, characterized in that: The texturing method comprises the following steps: providing a silicon substrate; Forming the main pyramid velvet structure; Cleaning, using a cleaning solution containing a texturing additive to perform the cleaning; An attached pyramid velvet structure is formed at the edge faces and / or corners of the main pyramid; After post-treatment, a silicon substrate with a clustered pyramid velvet structure is obtained.

2. The method for texturing a silicon substrate according to claim 1, characterized in that: The surface tension of the texturing additive is 45mN / m-65mN / m.

3. The method for texturing a silicon substrate according to claim 1 or 2, characterized in that: In the texturing liquid forming the attached pyramid velvet structure, the mass concentration of the alkali solution accounts for W1, and in the texturing liquid forming the main pyramid velvet structure, the mass concentration of the alkali solution accounts for W2. <W2。 4. The method for texturing a silicon substrate according to claim 1 or 2, characterized in that: The cleaning comprises the following steps: First, use a cleaning solution containing a velveting additive to clean; Then use a cleaning solution containing an oxidant to clean; Alternatively, first use a cleaning solution containing an oxidant to clean; Then use a cleaning solution containing a velveting additive to clean it.

5. The method for texturing a silicon substrate according to claim 1 or 2, characterized in that: The steps of cleaning and forming the attached pyramid velvet structure are repeated more than once; And / or, the texturing method comprises the following steps: providing a silicon substrate; The silicon substrate is textured once to form a main pyramid texture structure; Cleaning, using a cleaning solution containing a texturing additive to perform the cleaning; Secondary velveting, forming an attached pyramid velvet structure on the edges and / or corners of the main pyramid; Cleaning, using a cleaning solution containing a texturing additive to perform the cleaning; The dependent pyramids are continuously grown on the edges and / or corners of the main pyramid and the dependent pyramids through three-step texturing. After post-treatment, a silicon substrate with a clustered pyramid velvet structure is obtained.

6. The method for texturing a silicon substrate according to claim 1 or 2, characterized in that: The texturing liquid for forming the main pyramid texture structure comprises a texturing additive, alkali and water; And / or, the cleaning liquid used for cleaning comprises a texturing additive and water; And / or, the texturing liquid for forming the dependent pyramid texture structure comprises a texturing additive, alkali and water.

7. The method for texturing a silicon substrate according to claim 1 or 2, characterized in that: Before forming the main pyramid velvet structure, the silicon substrate is pre-cleaned, roughly polished and cleaned once; And / or, the post-treatment includes pure water cleaning, rounding, pickling, slow pulling and drying steps.

8. A method for preparing a solar cell, characterized in that: The method for preparing the solar cell comprises the following steps: providing a silicon substrate; Forming the main pyramid velvet structure; Cleaning, using a cleaning solution containing a texturing additive to perform the cleaning; An attached pyramid velvet structure is formed at the edge faces and / or corners of the main pyramid; After post-treatment, a silicon substrate with a clustered pyramid velvet structure is obtained; Preparation of amorphous or microcrystalline film layers; preparing a conductive film layer; The electrodes are prepared to obtain the solar cell.

9. A solar cell, characterized in that: It comprises a silicon substrate having a clustered pyramid velvet structure. The clustered pyramid velvet structure comprises a main pyramid and dependent pyramids. The dependent pyramids are located on the edge faces and / or edges of the main pyramid.

10. The solar cell according to claim 9, characterized in that: The spire of the dependent pyramid is lower than the spire of the main pyramid; And / or, the proportion of the main pyramids per unit area of ​​the silicon substrate is ≥50%; And / or, the main pyramid grows from the surface of the silicon substrate in a direction away from the silicon substrate, and the dependent pyramid grows along the edge faces and / or edge lines of the main pyramid; And / or, the height of the main pyramid is 1.3-1.6 μm.

11. The solar cell according to claim 9 or 10, characterized in that: The solar cell further comprises an amorphous or microcrystalline film layer, a conductive film layer and an electrode located on the surface of the clustered pyramid velvet structure of the silicon substrate.

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