Etching slurry, etching method of solar cell and preparation method of solar cell

Abstract

The invention provides etching slurry, an etching method of a solar cell and a preparation method of the solar cell, and particularly relates to the technical field of solar cell preparation. The etching slurry comprises 10-40 wt% of waterborne epoxy resin, 10-40 wt% of a filler, 20-40 wt% of strong phosphoric acid, 1-5 wt% of a surfactant and the balance of pure water. According to the etching slurry provided by the invention, the strong phosphoric acid is used as an etching agent, so that the etching reaction can be stably carried out. And through the synergistic effect of the filler and the water-borne epoxy resin, the slurry is convenient to uniformly coat, so that the consistency of the etching depth and width is ensured. Besides, the application of the surfactant reduces the surface energy between the etching slurry and the substrate, enhances the miscibility of various components in the etching slurry, and effectively ensures the storage stability of the etching slurry. The etching slurry does not damage a substrate material, can maintain the original performance of the substrate material, and improves the quality and stability of a product.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell preparation, in particular to an etching slurry, a solar cell etching method and a solar cell preparation method. Background Art

[0002] BC (Back-Contact) cells are photovoltaic cells based on organic semiconductor materials. They boast high conversion efficiency and low manufacturing costs, and are considered a key development direction for the future photovoltaic industry. They have no grid lines on the front, but are located on the back, minimizing the need for light shielding. However, BC cells typically have wide grid lines, resulting in high silver paste consumption. Data indicates silver consumption is approximately 14mg / W, and the silver paste sintering temperature is as high as over 700°C, resulting in high energy consumption. To reduce costs, some researchers have proposed using electroplating to produce metal electrodes.

[0003] Currently, when preparing the metal electrodes for the P and N regions on the back of BC electroplated cells, laser ablation is required to first open the silicon nitride membrane to expose the silicon substrate, followed by nickel, copper, and tin electroplating. However, laser ablation damages the silicon substrate of the BC cell. The heat generated by laser ablation can oxidize the silicon substrate surface and make it difficult to clean. This results in a reduced opening voltage and poor gate line bonding in the prepared BC electroplated cell. Therefore, developing a method for preparing BC cells with excellent electrical performance and strong bonding is of great significance.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The object of the present invention is to provide an etching slurry, an etching method for a solar cell, and a preparation method for a solar cell, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: A first aspect of the present invention provides an etching slurry comprising 10-40 wt % of a waterborne epoxy resin, 10-40 wt % of a filler, 20-40 wt % of concentrated phosphoric acid, 1-5 wt % of a surfactant, and the balance being pure water.

[0007] Furthermore, the filler includes at least one of silicon dioxide, calcium carbonate, aluminum hydroxide, kaolin and titanium dioxide.

[0008] Preferably, the surfactant includes at least one of fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether and polyethylene glycol stearate.

[0009] Preferably, the volume concentration of the concentrated phosphoric acid is 80-90%.

[0010] Furthermore, the etching slurry has a viscosity of 600-1000 Pa.s.

[0011] The second aspect of the present invention provides a method for etching a solar cell, wherein a silicon nitride film layer is formed on a silicon substrate, and then the etching slurry described in the first aspect is used for screen printing to etch and form patterned grooves to complete the etching step.

[0012] Furthermore, the solar cell includes a BC cell.

[0013] Preferably, the thickness of the silicon nitride film layer is 70-120 nm.

[0014] Preferably, in the screen printing process, the mesh number of the screen is 200-500 meshes, the wire diameter is 15-30 μm, the yarn thickness is 20-50 μm, and the film thickness is 5-20 μm.

[0015] Preferably, the screen printing pressure is 0.2-1.0 MPa, and the printing speed is 100-500 mm / s.

[0016] Preferably, the etching temperature is 300-400° C., and the etching time is 1-5 minutes.

[0017] Preferably, the depth of the patterned groove is 80-140 nm; the width of the main groove is 100-500 μm, and the width of the fine groove is 50-200 μm.

[0018] Furthermore, the etching method also includes soaking, cleaning and drying processes after forming the patterned grooves.

[0019] Preferably, the medium used for soaking is water.

[0020] Preferably, the temperature of the water is 70-100° C., and the time is 3-10 minutes.

[0021] Preferably, the cleaning method is spraying, and the time is 2 to 5 minutes.

[0022] Preferably, nitrogen gas is used for the drying.

[0023] Preferably, the drying temperature is 30-60° C., and the drying time is 30-90 seconds.

[0024] A third aspect of the present invention provides a method for preparing a solar cell, wherein a silicon substrate with patterned grooves is electroplated with nickel to form a nickel seed layer, then electroplated with copper, and finally subjected to an anti-oxidation treatment to obtain a solar cell; wherein the silicon substrate with patterned grooves is etched according to the etching method.

[0025] Furthermore, the solar cell is a BC cell.

[0026] Preferably, the nickel electroplating process is: first, the BC battery silicon substrate with patterned grooves is placed in the nickel electroplating equipment at a uniform speed to ensure that its back is in full contact with the nickel electroplating solution and the cathode roller, and the anode is placed in the nickel electroplating solution; then, the light-induced light source is turned on to irradiate the back of the BC battery silicon substrate, and then the DC power supply is turned on to prepare nickel metal on the surface of the N region; then, the light source is turned off to place the equipment in a dark environment, and nickel metal is prepared on the surface of the P region, and finally a nickel seed layer is formed on the back of the BC battery silicon substrate.

[0027] Preferably, the nickel electroplating solution comprises 100-300 g / L of nickel salt, 30-60 g / L of boric acid, 0.5-2 g / L of wetting agent, and the remainder is pure water.

[0028] Preferably, the nickel salt includes at least one of nickel sulfate, nickel chloride, nickel bromide and nickel sulfamate.

[0029] Preferably, the anode is an insoluble anode.

[0030] Preferably, the anode is made of titanium / iridium alloy, titanium / iridium / ruthenium anode, titanium / lead dioxide anode or titanium / manganese dioxide anode.

[0031] Preferably, the wetting agent includes at least one of sodium lauryl sulfate, sodium benzenesulfinate, sodium diester sulfosuccinate and sodium diethyl phosphate.

[0032] Preferably, the temperature of the nickel electroplating solution is 25-60° C., and the pH is 2.5-4.5.

[0033] Preferably, the wavelength of the light-induced light source is 300-600 nm, and the light intensity is 50-200 mW / cm 2 .

[0034] Preferably, the current density provided by the DC power supply is 5-20A / dm 2 , the DC power supply is turned on for 15~60s.

[0035] Preferably, the nickel seed layer has a thickness of 0.2-1.0 μm.

[0036] Furthermore, the copper electroplating process is as follows: placing a silicon substrate with a nickel seed layer into a copper electroplating device, ensuring that its back side is in full contact with the copper electroplating solution and the cathode roller, placing the anode in the copper electroplating solution, turning on a DC power supply, and preparing copper metal on the surfaces of the N-region and the P-region at the same time to obtain a copper layer.

[0037] Preferably, the copper layer has a thickness of 5 to 15 μm.

[0038] Furthermore, the copper-plated silicon substrate is immersed in an antioxidant solution to perform the antioxidant treatment, and finally washed and dried to obtain a solar cell.

[0039] Preferably, the antioxidant solution comprises 2-10 wt % of benzimidazole, 0.5-2 wt % of benzotriazole, 20-40 wt % of mixed acid, 0.1-0.5 wt % of copper sulfate, and the balance is pure water.

[0040] Preferably, the mixed acid is formic acid, acetic acid and salicylic acid in a mass ratio of (1-3):(1-3):(1-3).

[0041] Preferably, the pH of the antioxidant solution is 3.0-6.0.

[0042] Preferably, the temperature of the anti-oxidation treatment is 20-50° C., and the time is 2-10 minutes.

[0043] Preferably, the drying temperature is 60-90° C. and the drying time is 5-10 minutes.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects: The etching slurry provided by the present invention uses concentrated phosphoric acid as an etchant, which can ensure the stable progress of the etching reaction. The synergistic effect of the filler and the water-based epoxy resin makes the slurry easy to apply evenly, thereby ensuring the consistency of the etching depth and width. In addition, the use of a surfactant reduces the surface energy between the etching slurry and the substrate, thereby allowing the etching process to proceed smoothly. At the same time, the surfactant also enhances the miscibility of the various components in the etching slurry, effectively ensuring the storage stability of the etching slurry. The etching slurry does not damage the substrate material, can maintain the original properties of the substrate material, and improves the quality and stability of the product.

[0045] The present invention provides a method for etching a solar cell. Using an etching slurry, the method can accurately and thoroughly open the silicon nitride layer on the silicon substrate, achieving efficient exposure of the silicon substrate and laying a solid foundation for subsequent process flows. Crucially, the etching process causes almost no damage to the PN junction, effectively avoiding the structural damage and performance degradation of the PN junction that may be caused by laser film opening. This contributes to a significant increase in the open-circuit voltage of the solar cell, thereby enhancing the overall performance of the cell and making it more competitive in terms of energy conversion efficiency. At the same time, etching and grooving also significantly improves the bonding force between the metal electrode and the silicon substrate, providing a strong guarantee for the stable operation of the cell, extending the battery life, reducing production costs, and promoting technological advancement in the photovoltaic industry.

[0046] The method for preparing solar cells provided by the present invention, in view of the advantages of the above-mentioned etching, combines it with the nickel-copper electroplating process to prepare metal electrodes, which not only reduces the production cost of solar cells, but also significantly improves the electrical performance of the cells, enhances the stability and reliability of the process, provides a strong guarantee for the efficient and stable production of solar cells, and promotes the sustainable development of the photovoltaic industry. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0048] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present invention, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0049] A first aspect of the present invention provides an etching slurry comprising 10-40 wt % of a waterborne epoxy resin, 10-40 wt % of a filler, 20-40 wt % of concentrated phosphoric acid, 1-5 wt % of a surfactant, and the balance being pure water.

[0050] The etching slurry provided by the present invention uses concentrated phosphoric acid as an etchant, which can ensure the stable progress of the etching reaction. The synergistic effect of the filler and the water-based epoxy resin makes the slurry easy to apply evenly, thereby ensuring the consistency of the etching depth and width. In addition, the use of a surfactant reduces the surface energy between the etching slurry and the substrate, thereby allowing the etching process to proceed smoothly. At the same time, the surfactant also enhances the miscibility of the various components in the etching slurry, effectively ensuring the storage stability of the etching slurry. The etching slurry does not damage the substrate material, can maintain the original properties of the substrate material, and improves the quality and stability of the product.

[0051] Typically but not limitatively, the content of the water-based epoxy resin in the etching slurry can be, for example, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt% or 40wt%, or any value within the range of 10wt% to 40wt%; the content of the filler can be, for example, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt% or 40wt%, or any value within the range of 10wt% to 40wt%; the content of concentrated phosphoric acid can be, for example, 20wt%, 25wt%, 30wt%, 35wt% or 40wt%, or any value within the range of 20wt% to 40wt%; the content of the surfactant can be, for example, 1wt%, 2wt%, 3wt%, 4wt% or 5wt%, or any value within the range of 1wt% to 5wt%, and the balance is pure water.

[0052] It should be noted that, in the present invention, “the balance is pure water” means that the weight of the entire formula is made up with pure water so that the sum of all raw materials is 100 wt %.

[0053] Furthermore, the filler includes at least one of silicon dioxide, calcium carbonate, aluminum hydroxide, kaolin and titanium dioxide.

[0054] Preferably, the surfactant includes at least one of fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether and polyethylene glycol stearate.

[0055] Preferably, the volume concentration of the concentrated phosphoric acid is 80-90%.

[0056] Typically but not limitatively, the volume concentration of the concentrated phosphoric acid may be, for example, 80%, 82%, 84%, 86%, 88% or 90%, or any value within the range of 80% to 90%.

[0057] Furthermore, the etching slurry has a viscosity of 600-1000 Pa.s.

[0058] Typically but not limitatively, the viscosity of the etching slurry may be, for example, 600 Pa.s, 650 Pa.s, 700 Pa.s, 750 Pa.s, 800 Pa.s, 850 Pa.s, 900 Pa.s, 950 Pa.s or 1000 Pa.s, or any value within the range of 600 Pa.s to 1000 Pa.s.

[0059] The second aspect of the present invention provides a method for etching a solar cell, wherein a silicon nitride film layer is formed on a silicon substrate, and then the etching slurry described in the first aspect is used for screen printing to etch and form patterned grooves to complete the etching step.

[0060] The present invention provides a method for etching a solar cell. Using an etching slurry, the method can accurately and thoroughly open the silicon nitride layer on the silicon substrate, achieving efficient exposure of the silicon substrate and laying a solid foundation for subsequent process flows. Crucially, the etching process causes almost no damage to the PN junction, effectively avoiding the structural damage and performance degradation of the PN junction that may be caused by laser film opening. This contributes to a significant increase in the open-circuit voltage of the solar cell, thereby enhancing the overall performance of the cell and making it more competitive in terms of energy conversion efficiency. At the same time, etching and grooving also significantly improves the bonding force between the metal electrode and the silicon substrate, providing a strong guarantee for the stable operation of the cell, extending the battery life, reducing production costs, and promoting technological advancement in the photovoltaic industry.

[0061] Furthermore, the solar cell includes a BC cell.

[0062] Preferably, the thickness of the silicon nitride film layer is 70-120 nm.

[0063] Typically but not limitatively, the thickness of the silicon nitride film layer may be, for example, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm or 120 nm, or any value within the range of 70 nm to 120 nm.

[0064] Preferably, in the screen printing process, the mesh number of the screen is 200-500 meshes, the wire diameter is 15-30 μm, the yarn thickness is 20-50 μm, and the film thickness is 5-20 μm.

[0065] Typically but not limitatively, in the screen printing process, the mesh number of the screen can be, for example, 200 mesh, 250 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh or 500 mesh, or any value within the range of 200 mesh to 500 mesh; the wire diameter can be, for example, 15 μm, 20 μm, 25 μm, 30 μm, or any value within the range of 15 μm to 30 μm; the yarn thickness can be, for example, 20 μm, 30 μm, 40 μm, 50 μm, or any value within the range of 20 μm to 50 μm; the film thickness can be, for example, 5 μm, 10 μm, 15 μm, 20 μm, or any value within the range of 5 μm to 20 μm.

[0066] Preferably, the screen printing pressure is 0.2-1.0 MPa, and the printing speed is 100-500 mm / s.

[0067] Typically but not limitatively, the screen printing pressure can be, for example, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1.0 MPa, or any value within the range of 0.2 MPa to 1.0 MPa; the printing speed can be, for example, 100 mm / s, 200 mm / s, 300 mm / s, 400 mm / s, 500 mm / s, or any value within the range of 100 mm / s to 500 mm / s.

[0068] Preferably, the etching temperature is 300-400° C., and the etching time is 1-5 minutes.

[0069] Typically but not limitatively, the etching temperature can be, for example, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, or any value within the range of 300°C to 400°C; the etching time can be, for example, 1 min, 2 min, 3 min, 4 min, 5 min, or any value within the range of 1 min to 5 min.

[0070] Preferably, the depth of the patterned groove is 80-140 nm; the width of the main groove is 100-500 μm, and the width of the fine groove is 50-200 μm.

[0071] Typically but not limitatively, the depth of the patterned groove can be, for example, 80nm, 100nm, 120nm, 140nm, or any value within the range of 80nm~140nm; the main groove width can be, for example, 100μm, 200μm, 300μm, 400μm, 500μm, or any value within the range of 100μm~500μm; the fine groove width can be, for example, 50μm, 100μm, 150μm, 200μm, or any value within the range of 50μm~200μm.

[0072] Furthermore, the etching method also includes soaking, cleaning and drying processes after forming the patterned grooves.

[0073] Preferably, the medium used for soaking is water.

[0074] Preferably, the temperature of the water is 70-100° C., and the time is 3-10 minutes.

[0075] Typically but not limitatively, the temperature of the water can be, for example, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, or any value within the range of 70°C to 100°C; the time is 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, or any value within the range of 3 min to 10 min.

[0076] Preferably, the cleaning method is spraying, and the time is 2 to 5 minutes.

[0077] Typically but not limitatively, the spraying time is 2 min, 3 min, 4 min or 5 min, and can also be any value within the range of 2 min to 5 min.

[0078] Preferably, nitrogen gas is used for the drying.

[0079] Preferably, the drying temperature is 30-60° C., and the drying time is 30-90 seconds.

[0080] Typically but not limitatively, the drying temperature can be, for example, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, or any value within the range of 30°C to 60°C; the drying time can be 30s, 45s, 60s, 75s or 90s, or any value within the range of 30s to 90s.

[0081] A third aspect of the present invention provides a method for preparing a solar cell, wherein a silicon substrate with patterned grooves is electroplated with nickel to form a nickel seed layer, then electroplated with copper, and finally subjected to an anti-oxidation treatment to obtain a solar cell; wherein the silicon substrate with patterned grooves is etched according to the etching method.

[0082] The method for preparing solar cells provided by the present invention, in view of the advantages of the above-mentioned etching, combines it with the nickel-copper electroplating process to prepare metal electrodes, which not only reduces the production cost of solar cells, but also significantly improves the electrical performance of the cells, enhances the stability and reliability of the process, provides a strong guarantee for the efficient and stable production of solar cells, and promotes the sustainable development of the photovoltaic industry.

[0083] Furthermore, the solar cell is a BC cell.

[0084] Preferably, the nickel electroplating process is: first, the BC battery silicon substrate with patterned grooves is placed in the nickel electroplating equipment at a uniform speed to ensure that its back is in full contact with the nickel electroplating solution and the cathode roller, and the anode is placed in the nickel electroplating solution; then, the light-induced light source is turned on to irradiate the back of the BC battery silicon substrate, and then the DC power supply is turned on to prepare nickel metal on the surface of the N region; then, the light source is turned off to place the equipment in a dark environment, and nickel metal is prepared on the surface of the P region, and finally a nickel seed layer is formed on the back of the BC battery silicon substrate.

[0085] Preferably, the nickel electroplating solution comprises 100-300 g / L of nickel salt, 30-60 g / L of boric acid, 0.5-2 g / L of wetting agent, and the remainder is pure water.

[0086] Typically but not limitatively, the content of nickel salt in the nickel electroplating solution can be, for example, 100 g / L, 150 g / L, 200 g / L, 250 g / L, 300 g / L, or any value within the range of 100 g / L to 300 g / L; the content of boric acid can be, for example, 30 g / L, 40 g / L, 50 g / L, 60 g / L, or any value within the range of 30 g / L to 60 g / L; the content of the wetting agent can be, for example, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, or any value within the range of 0.5 g / L to 2 g / L, and the rest is pure water.

[0087] Preferably, the nickel salt includes at least one of nickel sulfate, nickel chloride, nickel bromide and nickel sulfamate.

[0088] Preferably, the anode is an insoluble anode.

[0089] Preferably, the anode is made of titanium / iridium alloy, titanium / iridium / ruthenium anode, titanium / lead dioxide anode or titanium / manganese dioxide anode.

[0090] There are multiple materials on the anode, and different material layers are separated by “ / ”.

[0091] Preferably, the wetting agent includes at least one of sodium lauryl sulfate, sodium benzenesulfinate, sodium diester sulfosuccinate and sodium diethyl phosphate.

[0092] Preferably, the temperature of the nickel electroplating solution is 25-60° C., and the pH is 2.5-4.5.

[0093] Typically but not limitatively, the temperature of the nickel electroplating solution can be, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, or any value within the range of 25°C to 60°C; the pH value can be, for example, 2.5, 3.0, 3.5, 4.0, 4.5, or any value within the range of 2.5 to 4.5.

[0094] Preferably, the wavelength of the light-induced light source is 300-600 nm, and the light intensity is 50-200 mW / cm 2 .

[0095] Typically but not limitatively, the wavelength of the light-inducing light source can be, for example, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, or any value within the range of 300 nm to 600 nm; the light intensity can be, for example, 50 mW / cm², 100 mW / cm², 150 mW / cm², 200 mW / cm², or any value within the range of 50 mW / cm² to 200 mW / cm².

[0096] Preferably, the current density provided by the DC power supply is 5-20A / dm 2 , the DC power supply is turned on for 15~60s.

[0097] Typically but not limitatively, the current density provided by the DC power supply can be, for example, 5A / dm², 10A / dm², 15A / dm², 20A / dm², or any value within the range of 5A / dm² to 20A / dm²; the DC power supply on time can be, for example, 15s, 30s, 45s, 60s, or any value within the range of 15s to 60s.

[0098] Preferably, the nickel seed layer has a thickness of 0.2-1.0 μm.

[0099] Typically but not limitatively, the thickness of the nickel seed layer may be, for example, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, or 1.0 μm, or any value within the range of 0.2 μm to 1.0 μm.

[0100] Furthermore, the copper electroplating process is as follows: placing a silicon substrate with a nickel seed layer into a copper electroplating device, ensuring that its back side is in full contact with the copper electroplating solution and the cathode roller, placing the anode in the copper electroplating solution, turning on a DC power supply, and preparing copper metal on the surfaces of the N-region and the P-region at the same time to obtain a copper layer.

[0101] Preferably, the copper layer has a thickness of 5 to 15 μm.

[0102] Typically but not limitatively, the thickness of the copper layer may be, for example, 5 μm, 7 μm, 10 μm, 12 μm, or 15 μm, or any value within the range of 5 μm to 15 μm.

[0103] Furthermore, the copper-plated silicon substrate is immersed in an antioxidant solution to perform the antioxidant treatment, and finally washed and dried to obtain a solar cell.

[0104] Preferably, the antioxidant solution comprises 2-10 wt % of benzimidazole, 0.5-2 wt % of benzotriazole, 20-40 wt % of mixed acid, 0.1-0.5 wt % of copper sulfate, and the balance is pure water.

[0105] Typically but not limitatively, the content of benzimidazole in the antioxidant solution can be, for example, 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, or any value within the range of 2wt% to 10wt%; the content of benzotriazole can be, for example, 0.5wt%, 1wt%, 1.5wt%, 2wt%, or any value within the range of 0.5wt% to 2wt%; the content of mixed acid can be, for example, 20wt%, 30wt%, 40wt%, or any value within the range of 20wt% to 40wt%; the content of copper sulfate can be, for example, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, or any value within the range of 0.1wt% to 0.5wt%, and the balance is pure water.

[0106] Preferably, the mixed acid is formic acid, acetic acid and salicylic acid in a mass ratio of (1-3):(1-3):(1-3).

[0107] Typically, but not limiting, the mixed acid is formic acid, acetic acid and salicylic acid in a mass ratio of (1-3):(1-3):(1-3), for example, the mass ratio of formic acid, acetic acid and salicylic acid can be 1:1:1, 2:2:2, 3:3:3, 1:2:3, 3:2:1, etc.

[0108] Preferably, the pH of the antioxidant solution is 3.0-6.0.

[0109] Typically but not limitatively, the pH value of the antioxidant solution may be, for example, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, or 6.0, or any value within the range of 3.0 to 6.0.

[0110] Preferably, the temperature of the anti-oxidation treatment is 20-50° C., and the time is 2-10 minutes.

[0111] Typically but not limitatively, the temperature of the antioxidant treatment can be, for example, 20°C, 30°C, 40°C, 50°C, or any value within the range of 20°C to 50°C; the time can be 2 min, 4 min, 6 min, 8 min, 10 min, or any value within the range of 2 min to 10 min.

[0112] Preferably, the drying temperature is 60-90° C. and the drying time is 5-10 minutes.

[0113] Typically but not limitatively, the drying temperature can be, for example, 60°C, 70°C, 80°C, 90°C, or any value within the range of 60°C to 90°C; the drying time can be 5 min, 7 min, 10 min, or any value within the range of 5 min to 10 min.

[0114] The present invention is further illustrated below by specific examples and comparative examples. However, it should be understood that these examples are merely for the purpose of further explanation and should not be construed as limiting the present invention in any form. The raw materials used in the examples and comparative examples of the present invention, unless otherwise specified, were prepared under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without manufacturer's indication are all commercially available conventional products.

[0115] Example 1 This embodiment provides an etching slurry, including 26g of water-based epoxy resin (ZW-2895, Zhongke Zhiyuan), 27g of silicon dioxide, 30g of concentrated phosphoric acid (volume concentration of 83%), 3g of fatty alcohol polyoxyethylene ether, and pure water to make up to 100g.

[0116] Example 2 This embodiment provides an etching slurry, including 30g of water-based epoxy resin (ZW-2895, Zhongke Zhiyuan), 20g of aluminum hydroxide, 35g of concentrated phosphoric acid (volume concentration of 83%), 2g of fatty alcohol polyoxyethylene ether, and pure water to make up to 100g.

[0117] Example 3 This embodiment provides an etching slurry, including 35g of water-based epoxy resin (ZW-2895, Zhongke Zhiyuan), 12g of kaolin, 12g of titanium dioxide, 30g of concentrated phosphoric acid (volume concentration of 83%), 3g of fatty alcohol polyoxyethylene ether, and pure water to make up to 100g.

[0118] Example 4 This embodiment provides an etching slurry. The difference from Example 1 is that the amount of water-based epoxy resin is adjusted to 10g, the amount of silicon dioxide is adjusted to 40g, and pure water is used to make up 100g. The amounts of other raw materials are the same as those in Example 1 and are not repeated here.

[0119] Example 5 This embodiment provides an etching slurry. The difference from Example 1 is that the amount of water-based epoxy resin is adjusted to 40g, the amount of silicon dioxide is adjusted to 10g, and pure water is used to make up 100g. The amounts of other raw materials are the same as those in Example 1 and are not repeated here.

[0120] Example 6 This embodiment provides an etching slurry. The difference from Example 1 is that the amount of concentrated phosphoric acid is adjusted to 20 g, and pure water is used to make up 100 g. The amounts of other raw materials are the same as those in Example 1 and are not repeated here.

[0121] Example 7 This embodiment provides an etching slurry. The difference from Example 1 is that the amount of concentrated phosphoric acid is adjusted to 40 g, and pure water is used to make up 100 g. The amounts of other raw materials are the same as those in Example 1 and are not repeated here.

[0122] Comparative Example 1 This comparative example provides an etching slurry. The difference from Example 1 is that silicon dioxide is omitted and the amount of silicon dioxide is supplemented by aqueous epoxy resin. The amounts of other raw materials are the same as those in Example 1 and are not repeated here.

[0123] Comparative Example 2 This comparative example provides an etching slurry. The difference from Example 1 is that fatty alcohol polyoxyethylene ether is omitted and the amount of fatty alcohol polyoxyethylene ether is made up with pure water. The amounts of other raw materials are the same as those in Example 1 and are not repeated here.

[0124] Test Example 1 The etching slurries obtained in the examples and comparative examples were subjected to viscosity tests, and then placed in the dark for 1 month before being subjected to viscosity tests again. The obtained data are shown in Table 1 below.

[0125] Table 1

[0126] As can be seen from Table 1, the viscosity of the etching slurry increases to varying degrees after being stored for a period of time, which may cause the board to stick during printing. The viscosity of the etching slurry prepared in Example 1 changed little after being stored for one month. This result indicates that the etching slurry has good viscosity stability and is not easily affected by internal and external environmental factors.

[0127] Example 8 This embodiment provides a BC battery, and the preparation method is as follows: 1. After stirring the etching slurry of Example 1 evenly, pour it into the screen. The mesh number of the screen is 300 mesh, the wire diameter is 15μm, the yarn thickness is 30μm, and the film thickness is 7μm. Under 0.8MPa, adjust the printing speed to 300mm / s, and screen print on the BC battery silicon substrate with a silicon nitride film layer on the back. After printing, keep the slurry at 356℃ for etching for 3min. Then soak it in hot water at 85℃ for 6min, take it out and spray clean it for 3min, and then blow it dry with nitrogen at 44℃. A BC battery silicon substrate with patterned grooves on the back is obtained.

[0128] The depth of the patterned grooves was measured to be 80 nm; the width of the main grooves was 200 μm, and the width of the fine grooves was 70 μm.

[0129] 2. Place the BC battery silicon substrate with patterned grooves on the back into the nickel electroplating equipment at a uniform speed. The back is in full contact with the nickel electroplating solution and the cathode roller. The anode is a titanium / iridium alloy and is placed in the nickel electroplating solution. First, turn on the light-induced light source, adjust the wavelength to 400nm, and the light intensity to 100 mW / cm 2 , so that it irradiates the back of the BC battery silicon substrate, and then turns on the DC power supply to control the current density to 10A / dm 2 , the electroplating time is turned on for 30 seconds, nickel metal is prepared on the surface of the N area, and finally the light source is turned off to put the equipment in a dark environment, nickel metal is prepared on the surface of the P area, thereby forming a nickel seed of 0.8μm on the back of the BC battery silicon substrate.

[0130] Among them, the formula of the nickel electroplating solution is 200g / L nickel chloride, 45g / L boric acid, 1g / L sodium lauryl sulfate, and the remainder is pure water, the temperature is 40°C, and the pH is 3.0.

[0131] 3. Place the BC battery silicon substrate with the nickel seed layer horizontally into the copper electroplating equipment, with the back side in full contact with the copper electroplating solution and the cathode roller, and the anode placed in the copper electroplating solution. Turn on the DC power supply with a current density of 25A / dm 2 , the electroplating time is 5 minutes, and copper metal is prepared on the surface of the N area and the P area at the same time, thereby forming a 10μm copper layer.

[0132] Among them, the formula of the copper electroplating solution is 150g / L copper sulfate, 30mL / L concentrated sulfuric acid, 0.05g / L concentrated hydrochloric acid, 0.1g / L fatty alcohol polyoxyethylene ether, 0.2g / L sodium phenyl disulfide propane sulfonate, and the remainder is pure water. The temperature is 40°C and the pH is 3.0.

[0133] 4. Immerse the copper-plated BC battery silicon substrate in an antioxidant solution at 36°C for 7 minutes, then take it out and wash it with water. First, blow away the water droplets on the surface with cold air, and finally dry it at 70°C for 8 minutes to obtain a BC electroplated battery.

[0134] The antioxidant liquid includes 8wt% benzimidazole, 1wt% benzotriazole, 30wt% mixed acid, 0.3w% copper sulfate, and the balance is pure water. The mixed acid is a mixture of formic acid, acetic acid and salicylic acid in a mass ratio of 1:1:1.

[0135] Examples 9-14 These embodiments provide a BC battery, which is different from Example 8 in that the etching slurries of Examples 2 to 7 are used to replace the etching slurry of Example 1. The other steps are the same as those of Example 8 and will not be repeated here.

[0136] Example 15 This embodiment provides a BC battery. Unlike the embodiment 8, step 4 is performed according to the following process: The copper-plated BC battery silicon substrate is placed in a tin electroplating solution (current density 5A / dm 2 , electroplating time 2 min) to obtain a BC electroplating cell.

[0137] Comparative Examples 3-4 These comparative examples provide a BC battery. The difference from Example 8 is that the etching slurries of Comparative Examples 1 to 2 are used to replace the etching slurry of Example 1. The other steps are the same as those of Example 8 and will not be repeated here.

[0138] Comparative Example 5 This comparative example provides a BC battery. Unlike Example 8, step 1 is carried out according to the following process: a 432nm ultraviolet picosecond laser is used to groove the BC battery silicon substrate with a silicon nitride film layer according to a designed pattern. The laser frequency is 3MHz, the average laser power is 2.5W, and the laser spot size is 10μm to obtain a BC battery silicon substrate with patterned grooves on the back.

[0139] The depth of the patterned grooves was measured to be 80 nm; the width of the main grooves was 200 μm, and the width of the fine grooves was 70 μm.

[0140] The other steps are the same as those in Example 8 and will not be repeated here.

[0141] Comparative Example 6 This comparative example provides a BC battery. Unlike Example 8, step 4 is omitted. The other steps are the same as those in Example 8 and will not be repeated here.

[0142] Test Example 2 The BC batteries obtained in Examples 8-15 and Comparative Examples 3-4 were made into the same specifications and subjected to electrical performance testing using IV testing at a temperature of 25° C. and an AM of 1.5G. The data obtained are shown in Table 2 below.

[0143] Table 2

[0144] As can be seen from Table 2, the patterned grooves are formed by etching silicon nitride with an etching slurry, which causes almost no damage to the PN junction. Compared with the laser film opening method, the opening voltage of the BC electroplating battery is increased by about 20mV, and the photoelectric conversion efficiency is also improved to a certain extent.

[0145] Test Example 3 The BC batteries obtained in Examples 8-15 and Comparative Examples 3-4 were subjected to a tensile test between the metal electrode and the silicon substrate.

[0146] 1. Bonding strength between metal electrode and silicon substrate: 3M tape test; 2. Welding tensile force: Weld at 300℃, keep it still horizontally at room temperature for 5 minutes, and then use a tensile tester to test the welding tensile force. Normally, the average welding tensile force of 24 consecutive PAD points on each piece is taken. A value of ≥0.8N is qualified.

[0147] The results are shown in Table 3 below.

[0148] Table 3

[0149] As can be seen from Table 3, etching and grooving avoids the oxide layer produced during laser film opening. The nickel seed layer is easy to plate and has strong adhesion to the silicon substrate, which is beneficial to improving the bonding strength between the entire metal electrode and the silicon substrate.

[0150] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An etching slurry, characterized in that: The invention comprises 10-40 wt% of a waterborne epoxy resin, 10-40 wt% of a filler, 20-40 wt% of concentrated phosphoric acid, 1-5 wt% of a surfactant, and the balance being pure water.

2. The etching slurry according to claim 1, characterized in that The filler comprises at least one of silicon dioxide, calcium carbonate, aluminum hydroxide, kaolin and titanium dioxide; Preferably, the surfactant includes at least one of fatty alcohol polyoxyethylene ether, nonylphenol polyoxyethylene ether and polyethylene glycol stearate; Preferably, the volume concentration of the concentrated phosphoric acid is 80-90%.

3. The etching slurry according to claim 1, characterized in that The viscosity is 600~1000pa.s.

4. A method for etching a solar cell, characterized in that: A silicon nitride film layer is formed on a silicon substrate, and then the etching slurry according to any one of claims 1 to 3 is used for screen printing to etch and form patterned grooves to complete the etching step.

5. The etching method according to claim 4, characterized in that: The solar cell comprises a BC cell; Preferably, the thickness of the silicon nitride film layer is 70-120 nm; Preferably, in the screen printing process, the mesh size of the screen is 200-500 mesh; the wire diameter is 15-30 μm; the yarn thickness is 20-50 μm; and the film thickness is 5-20 μm. Preferably, the screen printing pressure is 0.2-1.0 MPa; the printing speed is 100-500 mm / s; Preferably, the etching temperature is 300-400° C. and the etching time is 1-5 minutes; Preferably, the depth of the patterned groove is 80-140 nm; the width of the main groove is 100-500 μm; and the width of the fine groove is 50-200 μm.

6. The etching method according to claim 4 or 5, characterized in that: It also includes the soaking, washing and drying processes after forming the patterned grooves; Preferably, the medium used for soaking is water; Preferably, the temperature of the water is 70-100°C and the time is 3-10 minutes; Preferably, the cleaning method is spraying, and the time is 2 to 5 minutes; Preferably, nitrogen is used for the drying; Preferably, the drying temperature is 30-60° C. and the drying time is 30-90 seconds.

7. A method for preparing a solar cell, characterized in that: The silicon substrate with the patterned grooves is electroplated with nickel to form a nickel seed layer, then electroplated with copper, and finally subjected to an anti-oxidation treatment to obtain a solar cell; Wherein, the silicon substrate with the patterned grooves is obtained by etching according to the etching method according to any one of claims 4 to 6.

8. The preparation method according to claim 7, characterized in that The solar cell is a BC cell; Preferably, the nickel electroplating process is as follows: first, the BC battery silicon substrate with patterned grooves is placed in the nickel electroplating equipment at a uniform speed to ensure that its back side is in full contact with the nickel electroplating solution and the cathode roller, and the anode is placed in the nickel electroplating solution; then, a light-induced light source is turned on to irradiate the back side of the BC battery silicon substrate, and then a DC power supply is turned on to prepare nickel metal on the surface of the N region; then, the light source is turned off to place the equipment in a dark environment, and nickel metal is prepared on the surface of the P region, thereby finally forming a nickel seed layer on the back side of the BC battery silicon substrate; Preferably, the nickel electroplating solution comprises 100-300 g / L of nickel salt, 30-60 g / L of boric acid, 0.5-2 g / L of wetting agent, and the remainder is pure water; Preferably, the nickel salt comprises at least one of nickel sulfate, nickel chloride, nickel bromide and nickel sulfamate; Preferably, the anode is an insoluble anode; Preferably, the anode is made of titanium / iridium alloy, titanium / iridium / ruthenium anode, titanium / lead dioxide anode or titanium / manganese dioxide anode; Preferably, the wetting agent comprises at least one of sodium lauryl sulfate, sodium benzenesulfinate, sodium diester sulfosuccinate and sodium diethyl phosphate; Preferably, the temperature of the nickel electroplating solution is 25-60° C.; the pH is 2.5-4.5; Preferably, the wavelength of the light-induced light source is 300-600 nm; the light intensity is 50-200 mW / cm 2 ; Preferably, the current density provided by the DC power supply is 5-20A / dm 2 ; The DC power supply is turned on for 15~60s; Preferably, the nickel seed layer has a thickness of 0.2-1.0 μm.

9. The preparation method according to claim 7, characterized in that The copper electroplating process is as follows: placing a silicon substrate with a nickel seed layer into a copper electroplating device, ensuring that its back surface is in full contact with the copper electroplating solution and the cathode roller, placing the anode in the copper electroplating solution, turning on a DC power supply, and simultaneously preparing copper metal on the surfaces of the N-region and the P-region to obtain a copper layer; Preferably, the copper layer has a thickness of 5 to 15 μm.

10. The preparation method according to claim 7, characterized in that Immersing the copper-plated silicon substrate in an antioxidant solution to perform the antioxidant treatment, and finally washing and drying to obtain a solar cell; Preferably, the antioxidant solution comprises 2-10 wt % benzimidazole, 0.5-2 wt % benzotriazole, 20-40 wt % mixed acid, 0.1-0.5 wt % copper sulfate, and the balance is pure water; Preferably, the mixed acid is formic acid, acetic acid and salicylic acid in a mass ratio of (1-3):(1-3):(1-3); Preferably, the pH of the antioxidant solution is 3.0-6.0; Preferably, the temperature of the antioxidant treatment is 20-50°C and the time is 2-10 minutes; Preferably, the drying temperature is 60-90° C. and the drying time is 5-10 minutes.

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