Process for manufacturing bc cell
By simplifying the TBC cell fabrication process through masking and laser modification, the problems of instability and complexity in laser film removal in existing technologies have been solved, enabling efficient and low-cost cell production and improving yield and light utilization.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- CHANGZHOU SHICHUANG ENERGY CO LTD
- Filing Date
- 2025-12-02
- Publication Date
- 2026-07-23
AI Technical Summary
Existing TBC battery manufacturing processes suffer from problems such as unstable backlight film layer structure due to laser removal, high cost, complex process flow and low yield. In particular, the laser removal of BSG and PSG processes has stringent requirements for lasers, and the alkaline texturing process has a small window and high reflectivity.
The masking method is adopted, which involves coating the back surface of the silicon substrate with HF-resistant and alkali-resistant masking materials and using laser thermal effects for local modification. This is simplified into a three-step wet process, including one alkaline etching, one deposition, boron diffusion, phosphorus diffusion and electrode fabrication. This reduces the number of chain HF process steps and uses a continuous laser to reduce equipment requirements.
It improved the yield of finished products, reduced manufacturing costs, increased the texturing process window, reduced silicon wafer reflectivity, and improved process stability and production capacity.
Smart Images
Figure CN2025139191_23072026_PF_FP_ABST
Abstract
Description
A fabrication process for BC batteries Technical Field
[0001] This invention relates to the field of photovoltaic technology, specifically a novel process for preparing BC cells using a mask method. Background Technology
[0002] Interdigitated back contact (IBC) solar cells emerged in the 1970s. In these cells, both the positive and negative electrodes are located on the back side of the cell, with no metal obstructing the front, significantly improving optical absorption. The fabrication process involves localized phosphorus and boron diffusion on the back side of the cell, forming finger-like, interlocking P-regions and N-regions, which in turn form the finger-like, interlocking positive and negative electrode regions. TOPCon (Tunnel Oxide Passivated Contact) solar cells are a novel type of silicon solar cell proposed in 2013 by the Fraunhofer Institute in Germany. TOPCon cells form a 1-2 nm tunneling oxide layer on a silicon substrate, then superimpose a doped polycrystalline silicon layer to create a passivated contact structure, effectively reducing the recombination rate between the silicon wafer surface and the metal. The TOPCon structure has now become the mainstream cell structure, achieving a mass production efficiency of 25.5%.
[0003] The development of more efficient novel battery structures (TBCs) by combining TOPCon and IBC technologies has become a hot topic, and is expected to achieve battery efficiencies greater than 27%. Currently, the industry's production process for TBCs includes the following steps: alkaline polishing -> LPVCD (tunneling oxide layer + Polysi deposition) -> boron diffusion -> laser local removal of backlight BSG -> chain HF removal of frontlight BSG -> alkaline polishing -> LPVCD (tunneling oxide layer + Polysi deposition) -> phosphorus diffusion -> laser local removal of backlight PSG -> chain HF removal of frontlight PSG -> alkaline texturing -> surface passivation -> printing and sintering. However, current processes have issues with stability, cost, and efficiency in the following steps: 1) Laser removal of BSG from the backlight: BSG is difficult to remove, and the requirements for the laser are very demanding, generally requiring high-power picosecond or femtosecond lasers, which are expensive, have low production capacity, are unstable, and the laser can easily damage the silicon substrate; 2) Laser removal of PSG from the backlight: The backlight film layer structure is P-polysi / BSG / n-Polysi / PSG. The laser must remove PSG precisely without damaging BSG, which places high demands on the laser process; 3) Alkali texturing process: PSG has weak alkali resistance to texturing, and existing battery processes require PSG to block alkali texturing to protect n-Polysi, resulting in a small process window, poor texturing effect, and high reflectivity; 4) The process flow is complex, with a total of 5 wet processes, resulting in low yield.
[0004] Therefore, developing stable and reliable processes, simplifying process flows, and reducing manufacturing costs are issues that the photovoltaic industry needs to work together to solve. Summary of the Invention
[0005] The purpose of this invention is to provide a stable and reliable manufacturing process suitable for the industrial production of high-efficiency TBC batteries, thereby meeting current industry needs.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] In a first aspect, the present invention proposes a process for manufacturing a BC battery, the process comprising the following steps:
[0008] S1, First alkaline etching: A flat base is formed on the back surface of the silicon substrate through alkaline etching.
[0009] S2, First deposition: Deposit a tunneling oxide layer and a polycrystalline silicon layer on the back surface of the silicon substrate after alkaline etching;
[0010] S3, Boron diffusion: Boron diffusion is performed on the deposited polycrystalline silicon layer to form P-type polycrystalline silicon, and BSG is formed on the surface of the P-type polycrystalline silicon at the same time;
[0011] S4. First coating: A first mask material is coated on the BSG formed on the backlight side during boron diffusion, wherein the first mask material is formed after a modification operation to form a first mask, and the first mask is resistant to HF, while the unmodified first mask material is not resistant to HF.
[0012] S5. Primary modification: The coated first mask material is locally modified, wherein in the modified area, the coated area of the modified first mask material forms an HF-resistant first mask;
[0013] S6. Secondary alkaline etching: First, use HF to remove the first mask material and the BSG below the unmodified region. Then, use alkaline etching to remove the P-type polysilicon in the unmodified region and the first mask in the modified region, while retaining the P-type polysilicon and BSG in the modified region.
[0014] S7. Secondary deposition: Deposit the tunneling oxide layer and polysilicon layer again on the backlight side;
[0015] S8. Phosphorus diffusion: Phosphorus diffusion is performed on the polycrystalline silicon layer deposited on the backlight to form N-type polycrystalline silicon, and PSG is formed on the surface of the N-type polycrystalline silicon.
[0016] S9. Secondary coating: A second mask material is coated onto the PSG formed on the backlight side during phosphorus diffusion. The second mask material is formed after a modification operation. The second mask is alkali resistant, while the unmodified second mask material is not alkali resistant.
[0017] S10, Secondary Modification: The coated second mask material is locally modified, wherein in the modified area, the coated area of the modified second mask material forms an alkali-resistant second mask, and the modified areas of the primary modification and the modified areas of the secondary modification intersect with each other.
[0018] S11, Three-stage alkaline etching: The second mask material, PSG and N-type polysilicon in the non-modified area are removed by alkaline etching, while the BSG and P-type polysilicon in the area are retained. The modified area retains the PSG and N-type polysilicon under the second mask under the protection of the second mask. Then, the BSG, second mask and PSG on the backlight surface are removed by HF treatment.
[0019] S12. Electrode fabrication: Deposit functional layers on the surface after three alkaline etchings, and fabricate electrodes in the P-type polysilicon region and the N-type polysilicon region, respectively.
[0020] Preferably, the first mask material is a nano-silicon suspension.
[0021] Preferably, the second mask material is a nano-silica suspension.
[0022] Preferably, the mass concentration of the suspensions of the first mask material and the second mask material is 10-20%.
[0023] Furthermore, the modification process involves patterned sintering of the mask material coating.
[0024] Furthermore, the patterned sintering is accomplished using the heat generated by laser scanning.
[0025] More preferably, the power of laser scanning is 500W~1000W.
[0026] Preferably, the coating method for the mask material includes spin coating, roller coating, spray coating, or blade coating.
[0027] Preferably, the tertiary alkaline etching includes texturing the silicon wafer surface while simultaneously etching with an alkaline agent.
[0028] Preferably, the functional layer is a passivation layer, an antireflection layer, or a passivation and antireflection layer, and the material of the functional layer can be alumina, silicon nitride, silicon oxynitride, silicon oxide, etc.
[0029] In a second aspect, the present invention provides a solar cell comprising a cell manufactured using the process described above.
[0030] Compared with the prior art, the beneficial effects of the present invention are:
[0031] 1. The method of this invention has only three wet processes, which eliminates two chain HF processes compared to existing processes, thus improving the yield of finished products;
[0032] 2. The modified second mask can achieve strong alkali resistance during texturing, which increases the texturing process window, improves the front texturing effect, and reduces the reflectivity of the silicon wafer compared to existing technologies.
[0033] 3. The laser modification mask of the present invention mainly utilizes the thermal effect of laser for modification, which greatly reduces the demand for laser, can be a continuous laser, has low price, large production capacity, stable process, and will not damage the silicon substrate.
[0034] 4. Compared with the prior art, the process of the present invention is simple and stable in terms of overall effect, and reduces the requirements for laser equipment and chain HF equipment, thereby reducing manufacturing costs. Attached Figure Description
[0035] Figure 1 shows the test results of the reflectivity of the silicon wafers after texturing in Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation
[0036] This invention develops an optimized process for fabricating BC batteries using a mask method, thereby solving several problems existing in the prior art. The method of this invention can be summarized as follows: alkaline polishing -> primary deposition (tunneling oxide layer + Polysi deposition) -> boron diffusion -> coating of the first mask -> laser local modification -> alkaline polishing -> secondary deposition (tunneling oxide layer + Polysi deposition) -> phosphorus diffusion -> coating of the second mask -> laser local modification -> alkaline texturing -> surface passivation -> printing and sintering.
[0037] In one exemplary embodiment, the technical solution of the present invention includes the following steps:
[0038] Step 1: Alkali polishing, cleaning the silicon wafer and forming a flat base on the silicon wafer surface;
[0039] Step 2: Deposit a tunneling oxide layer and a Polysi layer on the back side using LPCVD;
[0040] Step 3: Boron diffusion is carried out in a tubular device to form P-Polysi;
[0041] Step 4: Apply a layer of first mask material to the back BSG using methods such as spin coating, roller coating, spraying, or scraping.
[0042] Step 5: Locally modify the first mask material with laser. The modified first mask is resistant to HF, while the unmodified first mask material is not resistant to HF.
[0043] Step 6: Alkali polishing. First, use an HF bath to remove the first mask material and BSG from the non-laser areas on the front, edge, and back sides. Then, use a NaOH bath to remove P-Polysi and a small amount of silicon substrate from the non-laser areas on the front, edge, and back sides. After alkali polishing, P-Polysi and BSG are retained in the laser area on the back side.
[0044] Step 7: Deposit a tunneling oxide layer and a Polysi layer on the back side using LPCVD;
[0045] Step 8: Phosphorus diffusion occurs to form n-Polysi;
[0046] Step 9: Apply a second mask material to the back PSG using spin coating, roller coating, spray coating, or scraping coating methods;
[0047] Step 10: The area where n-Polysi needs to be preserved is treated with a laser-modified second mask material. The modified second mask is alkali-resistant, while the unmodified second mask material is not alkali-resistant.
[0048] Step 11: Alkali texturing. The front and edges only contain PSG and n-Polysi, and alkali texturing forms a textured surface. In the P-Polysi area on the back, alkali texturing removes PSG and n-Polysi, but retains BSG and P-Polysi. The n-Polysi area of the second mask on the back is laser modified and preserved intact. Finally, the BSG, modified second mask, and PSG are cleaned in an HF bath.
[0049] Step 12: ALD deposits aluminum oxide on both sides, and PECVD deposits silicon nitride on both sides;
[0050] Step 13: Print paste onto P-Polysi and n-Polysi, and sinter to form electrodes.
[0051] In the method of this invention, a first mask material is coated on the back side of the boron-expanded silicon wafer. This mask material is locally modified under the thermal effect of a laser. The modified first mask is resistant to HF, while the first mask material without laser treatment is not resistant to HF. The first mask material is preferably a suspension of nano-silicon. After being coated on the silicon wafer, it forms a silicon film coating. When this silicon film coating is irradiated by a laser, the heat of the laser causes the nano-silicon particles in the film layer to solidify and sinter, forming a dense silicon film. This dense silicon film has stronger resistance to HF than the unsintered silicon film, thereby protecting the underlying polycrystalline silicon layer for a certain period of time.
[0052] In the etching process following the formation of the first mask, the first mask material and BSG in the non-laser areas of the front, edge, and back sides are first removed using an HF bath. Then, the P-Polysi and a small amount of silicon substrate in the non-laser areas of the front, edge, and back sides are removed using a NaOH bath. After alkaline polishing, the P-Polysi and BSG are retained in the laser area on the back side.
[0053] Furthermore, a second mask material is coated on the back side of the phosphorus-expanded silicon wafer. This mask material undergoes localized modification under the thermal effect of a laser. The modified second mask is alkali-resistant, while the mask without laser treatment is not alkali-resistant. The second mask material is preferably a suspension of nano-silica. After being coated on the silicon wafer, it forms a silicon oxide film coating. When this silicon oxide film coating is irradiated by a laser, the heat from the laser causes the nano-silica particles in the film to solidify and sinter, forming a dense silicon oxide film. This dense silicon oxide film has stronger alkali resistance than the unsintered silicon oxide film, thereby protecting the underlying polycrystalline silicon layer for a certain period of time.
[0054] In the alkaline etching process following the formation of the second mask, the front and edges, containing only PSG and n-Polysi, develop a textured surface after alkaline texturing. In the P-Polysi region on the back side, alkaline texturing removes PSG and n-Polysi, while retaining BSG and P-Polysi. The n-Polysi region on the back side with the laser-modified second mask remains intact. Finally, the BSG, modified second mask, and PSG are cleaned in an HF bath.
[0055] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0056] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0057] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example 1
[0058] Alkali polishing -> LPVCD (tunneling oxide layer + Polysi deposition) -> Boron diffusion -> Mask coating 1 -> Laser local modification -> Alkali polishing -> LPVCD (tunneling oxide layer + Polysi deposition) -> Phosphorus diffusion -> Mask coating 2 -> Laser local modification -> Alkali texturing -> Surface passivation -> Printing and sintering
[0059] Step 1: Select an N-type silicon wafer with a resistivity range of 1~5Ωcm and a diameter of 182mm*94mm. Etch the wafer in a solution of NaOH and polishing additives to remove surface damage and form a flat base on the wafer surface. The base size is 10~20µm.
[0060] Step 2: Deposit a tunneling oxide layer and a Polysi layer on the back side using LPCVD, with the Polysi layer thickness controlled at 200~300nm.
[0061] Step 3: Boron diffusion is carried out in a tubular device to crystallize and dope Polysi, ultimately forming P-Polysi and BSG.
[0062] Step 4: Apply a layer of nano-silica suspension with a mass concentration of 10-20% to the back side of the BSG using a roller coating method. The weight of the nano-silica suspension should be controlled at 5-10 mg / tablet.
[0063] Step 5: Use a continuous infrared laser to locally act on mask 1, causing the mask to absorb heat and be modified. The modified mask is resistant to HF, while the unmodified mask is not resistant to HF.
[0064] Step 6: After laser modification, the silicon wafer is first subjected to an HF bath to remove mask 1 and BSG from the non-laser areas on the front, edge, and back sides. The HF volume concentration is 20%, and the reaction time is 240 seconds. Then, in a NaOH and polishing additive bath, the P-Polysi and a small amount of silicon substrate from the non-laser areas on the front, edge, and back sides are removed. The reaction temperature is 60℃, and the reaction time is 480 seconds. After alkaline etching, the P-Polysi and BSG are retained in the laser-treated area on the back side.
[0065] Step 7: Deposit a tunneling oxide layer and a Polysi layer on the back side using LPCVD, with the Polysi layer thickness controlled at 200~300nm.
[0066] Step 8: Phosphorus diffusion is carried out in a tubular device to crystallize and dope Polysi, ultimately forming n-Polysi and PSG.
[0067] Step 9: Apply a layer of nano-silica suspension with a mass concentration of 10-20% to the back PSG using a roller coating method. The weight of the nano-silica suspension should be controlled at 10-20 mg / tablet.
[0068] Step 10: Use a continuous infrared laser to act on the mask area where n-Polysi needs to be preserved. The laser irradiation power is 500W~1000W. After the mask absorbs heat, it is modified. The modified mask is alkali resistant, while the unmodified mask is not alkali resistant.
[0069] Step 11: The laser-modified wafer is first placed in a NaOH and texturing additive bath at 80°C for 480 seconds. The front and edges are etched to form a pyramidal textured surface; in the P-Polysi region on the back side, PSG and n-Polysi are removed, while BSG and P-Polysi are retained; in the laser-modified mask 2 region on the back side, n-Polysi and PSG are preserved intact. Then, the surface BSG, modified mask 2, and PSG are cleaned in an HF bath with a volume concentration of 20% for 240 seconds.
[0070] Step 12: After cleaning, aluminum oxide is deposited on both sides of the wafer in an ALD device, with an aluminum oxide thickness of 4-6 nm. Silicon nitride is then deposited on both sides in a PECVD device, with a silicon nitride thickness of 80 nm.
[0071] Step 13: Print paste onto P-Polysi and n-Polysi, and sinter to form electrodes.
[0072] Comparative Example 1:
[0073] Alkali polishing -> LPVCD (tunneling oxide layer + Polysi deposition) -> Boron diffusion -> Laser local removal of backside BSG -> Chain HF removal of frontside BSG -> Alkali polishing -> LPVCD (tunneling oxide layer + Polysi deposition) -> Phosphorus diffusion -> Laser local removal of backside PSG -> Chain HF removal of frontside PSG -> Alkali texturing -> Surface passivation -> Printing and sintering
[0074] Step 1: Select an N-type silicon wafer with a resistivity range of 1~5Ωcm and a diameter of 182mm*94mm. Etch the wafer in a solution of NaOH and polishing additives to remove surface damage and form a flat base on the wafer surface. The base size is 10~20µm.
[0075] Step 2: Deposit a tunneling oxide layer and a Polysi layer on the back side using LPCVD, with the Polysi layer thickness controlled at 200~300nm.
[0076] Step 3: Boron diffusion is carried out in a tubular device to crystallize and dope Polysi, ultimately forming P-Polysi and BSG.
[0077] Step 4: Use a UV femtosecond laser to locally remove the BSG on the back side.
[0078] Step 5: Use a chain-type wet process to remove BSG from the front and edges, with an HF volume concentration of 40-50%.
[0079] Step 6: Then, in a bath of NaOH and polishing additives, remove P-Polysi and a small amount of silicon substrate from the front, edge, and back laser areas. The reaction temperature is 60℃, and the reaction time is 480 seconds. After alkaline etching, P-Polysi and BSG are retained in the back laser area.
[0080] Step 7: Deposit a tunneling oxide layer and a Polysi layer on the back side using LPCVD, with the Polysi layer thickness controlled at 200~300nm.
[0081] Step 8: Phosphorus diffusion is carried out in a tubular device to crystallize and dope Polysi, ultimately forming n-Polysi and PSG.
[0082] Step 9: Use a green picosecond laser to remove the PSG layer on top of the P-Polsyi / BSG layer from step 6.
[0083] Step 10: Remove PSG from the front and edges using a chain wet process, with an HF volume concentration of 10-20%.
[0084] Step 11: In a bath containing NaOH and texturing additives, texturing is performed on the front and edges. The laser-etched area from Step 9 is then used to etch n-Polysi at a reaction temperature of 70°C for 480 seconds. After alkaline etching, a pyramidal texturized surface is formed on the front, while the P-Polysi / BSG and n-Polysi / PSG regions are retained on the back. Finally, the surface is cleaned in an HF bath to remove PSG and BSG; the HF volume concentration is 20-30%.
[0085] Step 12: After cleaning, aluminum oxide is deposited on both sides of the wafer in an ALD device, with an aluminum oxide thickness of 4-6 nm. Silicon nitride is then deposited on both sides in a PECVD device, with a silicon nitride thickness of 80 nm.
[0086] Step 13: Print paste onto P-Polysi and n-Polysi, and sinter to form electrodes. Test Implementation Examples
[0087] According to industry practice, the reflectivity of the texturized silicon wafer was tested using a reflectivity meter. The incident wavelength ranged from 300nm to 1080nm, with a test point every 10nm. The test results are shown in Figure 1. As shown in the figure, at wavelengths below 1050nm, the surface reflectivity of the silicon wafer in Example 1 was lower than that in Comparative Example 1. This indicates that the method of the present invention improves the front-side texturing effect, resulting in silicon wafer cells prepared according to the method of the present invention having lower surface reflectivity and improving light utilization.
[0088] Any aspects of this invention not described in detail are well-known to those skilled in the art.
[0089] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications and equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A manufacturing process for a BC battery, characterized in that, The process includes the following steps: S1, First alkaline etching: A flat base is formed on the back surface of the silicon substrate through alkaline etching. S2, First deposition: Deposit a tunneling oxide layer and a polycrystalline silicon layer on the back surface of the silicon substrate after alkaline etching; S3, Boron diffusion: Boron diffusion is performed on the deposited polycrystalline silicon layer to form P-type polycrystalline silicon, and BSG is formed on the surface of the P-type polycrystalline silicon at the same time; S4. First coating: A first mask material is coated on the BSG formed on the backlight side during boron diffusion, wherein the first mask material is formed after a modification operation to form a first mask, and the first mask is resistant to HF, while the unmodified first mask material is not resistant to HF. S5. Primary modification: The coated first mask material is locally modified, wherein in the modified area, the coated area of the modified first mask material forms an HF-resistant first mask; S6. Secondary alkaline etching: First, use HF to remove the first mask material and the BSG below the unmodified region. Then, use alkaline etching to remove the P-type polysilicon in the unmodified region and the first mask in the modified region, while retaining the P-type polysilicon and BSG in the modified region. S7. Secondary deposition: Deposit the tunneling oxide layer and polysilicon layer again on the backlight side; S8. Phosphorus diffusion: Phosphorus diffusion is performed on the polycrystalline silicon layer deposited on the backlight to form N-type polycrystalline silicon, and PSG is formed on the surface of the N-type polycrystalline silicon. S9. Secondary coating: A second mask material is coated onto the PSG formed on the backlight side during phosphorus diffusion. The second mask material is modified to form a second mask. The second mask is alkali resistant, while the unmodified second mask material is not alkali resistant. S10, Secondary Modification: The coated second mask material is locally modified, wherein in the modified area, the coated area of the modified second mask material forms an alkali-resistant second mask, and the modified areas of the primary modification and the modified areas of the secondary modification intersect with each other. S11, Three-stage alkaline etching: The second mask material, PSG and N-type polysilicon in the non-modified area are removed by alkaline etching, while the BSG and P-type polysilicon in the area are retained. The modified area retains the PSG and N-type polysilicon under the second mask under the protection of the second mask. Then, the BSG, second mask and PSG on the backlight surface are removed by HF treatment. S12. Electrode fabrication: Deposit functional layers on the surface after three alkaline etchings, and fabricate electrodes in the P-type polysilicon region and the N-type polysilicon region, respectively.
2. The fabrication process of the BC battery as described in claim 1, characterized in that, The first mask material is a nano-silicon suspension.
3. The fabrication process of the BC battery as described in claim 1, characterized in that, The second mask material is a nano-silica suspension.
4. The manufacturing process of the BC battery as described in claim 2 or 3, characterized in that, The modification process involves patterned sintering of the mask material coating.
5. The fabrication process of the BC battery as described in claim 4, characterized in that, The patterned sintering is accomplished using the heat generated by laser scanning.
6. The fabrication process of the BC battery as described in claim 1, characterized in that, The coating method for the mask material includes spin coating, roller coating, spray coating, or scraping coating.
7. The manufacturing process of the BC battery as described in claim 1, characterized in that, The three alkaline etching processes include texturing the silicon wafer surface while simultaneously etching it with an alkaline agent.
8. The fabrication process of the BC battery as described in claim 1, characterized in that, The functional layer is a passivation layer, an antireflection layer, or a passivation and antireflection layer.
9. A solar cell, characterized in that, The solar cell comprises a cell manufactured using the process described in any one of claims 1 to 9.