Tin electroplating solution, preparation method thereof and preparation method of crystalline silicon solar cell

Abstract

The invention provides a tin electroplating solution, a preparation method thereof and a preparation method of a crystalline silicon solar cell, and particularly relates to the technical field of solar cell preparation. The tin electroplating liquid comprises tin methanesulfonate, methanesulfonic acid, a brightener, a stabilizer, a grain refiner, a defoaming agent and water. In the tin electroplating solution, the stabilizer ensures the chemical stability of the tin electroplating solution in long-term use and storage; the microstructure of the coating is further optimized through the synergistic effect of the grain refiner and the defoaming agent; tin methanesulfonate is used as a main salt to provide a high-purity tin source, and the high efficiency and controllability of electroplating reaction are ensured by combining with a strong acid environment of methanesulfonic acid; and the metallic luster and the surface flatness of the plating layer are further enhanced by introducing the brightening agent. The tin electroplating liquid system shows remarkable advantages in the aspects of stability, plating quality and process applicability through cooperation of the raw materials, and the electroplating quality of a tin layer is improved.

Description

Technical Field

[0001] The invention relates to the technical field of solar cell preparation, and in particular to a tin electroplating solution and a preparation method thereof, and a preparation method of a crystalline silicon solar cell sheet. Background Art

[0002] Metallization is the core process for the preparation of silicon solar cells. It forms ohmic contact electrodes at both ends of the PN junction to achieve efficient current output. In the current industry, screen printing has become the most mainstream metallization technology due to its mature process advantages. However, the reliance on high-priced silver paste has led to high production costs, which has seriously restricted the large-scale promotion and application of solar cells. In order to break through this cost bottleneck and continuously improve battery performance, the industry is actively exploring the mass production path of preparing metal electrodes by electroplating. This method is expected to achieve significant cost optimization by replacing silver with low-cost metals such as nickel, copper, and tin.

[0003] In the electroplating process, electrotinning technology deposits a tin or tin alloy layer on the surface of the copper grid line through an electrochemical reduction reaction. This process can not only effectively prevent the oxidation corrosion of the copper grid line, but also significantly improve the welding performance of the electrode. As a key material in this process, the formulation system of the tin electroplating solution directly determines the final coating quality and battery performance. However, the current commercially available electroplating solutions generally face technical bottlenecks such as poor stability, insufficient high temperature tolerance, and poor defoaming performance. These problems often lead to the coating uniformity and density not meeting the ideal standards, which in turn causes the series resistance of solar cells to increase and the conversion efficiency to decrease, ultimately having a negative impact on product quality and performance.

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

[0005] One of the purposes of the present invention is to provide a tin electroplating solution, aiming to solve at least one of the above-mentioned technical problems in the prior art.

[0006] A second object of the present invention is to provide a method for preparing a tin electroplating solution.

[0007] A third object of the present invention is to provide a method for preparing a crystalline silicon solar cell.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] A first aspect of the present invention provides a tin electroplating solution comprising tin methanesulfonate, methanesulfonic acid, a brightener, a stabilizer, a grain refiner, a defoamer and water.

[0010] Further, by weight parts, each unit volume of the tin electroplating solution comprises 50-150 parts of stannous methylsulfonate, 70-140 parts of methylsulfonic acid, 4-10 parts of brightener, 20-60 parts of stabilizer, 0.5-5 parts of grain refiner, 0.5-3 parts of defoamer, and the balance is water.

[0011] Further, the brightener comprises at least one of Schiff base, benzalacetone, acetophenone, chlorobenzaldehyde, glutaraldehyde, salicylaldehyde, 4-tetradecylaniline, and 1,2,3-benzotriazole.

[0012] Preferably, the grain refiner comprises at least one of 3,4,5-trihydroxybenzoic acid, 4-hydroxybenzoic acid, p-cresol, m-cresol, o-cresol, and benzyl alcohol.

[0013] Preferably, the defoamer comprises at least one of polydimethylsiloxane, ethylene glycol siloxane, polyoxyethylene alcohol, polyethylene glycol, polypropylene glycol, bisphenol A polyoxyethylene ether, and polyoxypropylene oxyethylene glycerol ether.

[0014] Further, the preparation method of the stabilizer is as follows: dissolve tartaric acid and sodium potassium tartrate in pure water, and then slowly add concentrated sulfuric acid until the solution is clear; after the solution temperature drops to 50-60 °C, add p-dihydroxybenzene and ascorbic acid, and stir until completely dissolved to obtain the stabilizer.

[0015] Preferably, the concentration of the tartaric acid is 50-100 g / L.

[0016] Preferably, the mass ratio of the sodium potassium tartrate to the tartaric acid is 0.8-3.2:1.

[0017] Preferably, the mass of the concentrated sulfuric acid is 0.3-3 times the sum of the masses of the tartaric acid and the sodium potassium tartrate.

[0018] Preferably, the mass percentage concentration of the p-dihydroxybenzene is 6-16 wt%.

[0019] Preferably, the mass percentage concentration of the ascorbic acid is 3-8 wt%.

[0020] The second aspect of the present invention provides a preparation method of the tin electroplating solution. After adding methylsulfonic acid to part of the water and stirring evenly, after cooling to room temperature, continue to add stannous methylsulfonate and stir evenly, and finally add the brightener, stabilizer, grain refiner, defoamer, and the remaining water and stir evenly to obtain the tin electroplating solution.

[0021] The third aspect of the present invention provides a preparation method of a crystalline silicon solar cell. Activate the crystalline silicon solar cell with double-sided copper plating; then place it in a double-sided horizontal tin plating device for electroplating, and after electroplating, wash and dry to obtain a crystalline silicon solar cell with double-sided tin plating;

[0022] Among them, the tin electroplating solution in the double-sided horizontal tin electroplating equipment is the above-mentioned tin electroplating solution.

[0023] Furthermore, during the electroplating process, a pure tin bar is used as the anode, and the battery wafer to be electroplated is used as the cathode for electroplating.

[0024] Preferably, the temperature of the tin electroplating solution is 25 - 40°C.

[0025] Preferably, the current density of the electroplating is 5 - 20 A / dm 2 , and the electroplating time is 5 - 25 s.

[0026] Preferably, the thickness of the tin layer after tin plating is 0.5 - 1.0 μm.

[0027] Furthermore, in the crystalline silicon solar cell with double-sided copper plating, the thickness of the copper layer is 8 - 12 μm.

[0028] Furthermore, the activation solution used for activation is an acidic solution.

[0029] Preferably, the acidic solution is a methylsulfonic acid solution.

[0030] Furthermore, the volume concentration of the methylsulfonic acid solution is 5 - 20 mL / L.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] In the tin electroplating solution provided by the present invention, the stabilizer can effectively inhibit the hydrolysis reaction of stannous ions, greatly delay the appearance of the turbidity of the tin electroplating solution, ensure the chemical stability of the tin electroplating solution during long-term use and storage by blocking the generation path of stannic ions, thereby prolonging the life of the tin electroplating solution and reducing the maintenance cost. The synergistic effect of the grain refiner and the defoamer further optimizes the microstructure of the coating: the grain refiner significantly improves the uniformity and compactness of the coating by regulating the nucleation and growth process of tin crystals; the defoamer effectively inhibits the generation and residue of bubbles during electroplating, avoids defects such as pinholes and pockmarks on the surface of the coating, and at the same time improves the smoothness and flatness of the coating appearance. In addition, stannous methylsulfonate provides a high-purity tin source as the main salt, and combined with the strong acidic environment of methylsulfonic acid, it ensures the high efficiency and controllability of the electroplating reaction; the introduction of the brightener further enhances the metallic luster and surface flatness of the coating. This tin electroplating solution system shows significant advantages in terms of stability, coating quality and process applicability through the synergistic cooperation of raw materials, and improves the electroplating quality of the tin layer.

[0033] The preparation method of the tin electroplating solution provided by the present invention optimizes the feeding sequence and process conditions to ensure that each component is fully dissolved and plays a synergistic role, thereby improving the stability of the electroplating solution and the quality of the coating. This preparation method is simple to operate and easy to industrialize.

[0034] Due to the advantages of the above-mentioned tin electroplating solution, the preparation method of the crystalline silicon solar cell provided by the present invention makes the grain size of the tin layer in the crystalline silicon solar cell uniform and fine, reduces the contact resistance, and improves the quality, conversion efficiency and long-term reliability of the crystalline silicon solar cell. Specific embodiments

[0035] To make the objectives, 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 conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0036] In the following text, the terms "include", "have" and their cognates that can be used in various embodiments of the present invention are only intended to represent specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be construed as first excluding the existence or increasing the possibility of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0037] The first aspect of the present invention provides a tin electroplating solution, which includes stannous methyl sulfonate, methyl sulfonic acid, brightener, stabilizer, grain refiner, defoamer and water.

[0038] In the tin electroplating solution provided by the present invention, the stabilizer can effectively inhibit the hydrolysis reaction of stannous ions, greatly delay the appearance of the turbidity phenomenon of the tin electroplating solution, and ensure the chemical stability of the tin electroplating solution during long-term use and storage by blocking the generation path of tetravalent tin, thereby prolonging the life of the tin electroplating solution and reducing the maintenance cost. The synergistic effect of the grain refiner and the defoamer further optimizes the microstructure of the coating: the grain refiner significantly improves the uniformity and compactness of the coating by regulating the nucleation and growth process of tin crystals; the defoamer effectively inhibits the generation and residue of bubbles during the electroplating process, avoids defects such as pinholes and pockmarks on the surface of the coating, and improves the smoothness and flatness of the appearance of the coating. In addition, stannous methyl sulfonate provides a high-purity tin source as the main salt, and combined with the strong acidic environment of methyl sulfonic acid, it ensures the high efficiency and controllability of the electroplating reaction; the introduction of the brightener further enhances the metallic luster and surface flatness of the coating. This tin electroplating solution system shows significant advantages in terms of stability, coating quality and process applicability through the synergistic cooperation of raw materials, and improves the electroplating quality of the tin layer.

[0039] Further, by weight parts, each unit volume of the tin electroplating solution comprises 50 - 150 parts of stannous methylsulfonate, 70 - 140 parts of methylsulfonic acid, 4 - 10 parts of brightener, 20 - 60 parts of stabilizer, 0.5 - 5 parts of grain refiner, 0.5 - 3 parts of defoamer, and the balance is water.

[0040] Typically but not limitedly, in each unit volume of the tin electroplating solution, stannous methylsulfonate can be, for example, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, 100 parts, 110 parts, 120 parts, 130 parts, 140 parts or 150 parts, or any value within the range of 50 - 150 parts; methylsulfonic acid can be, for example, 70 parts, 80 parts, 90 parts, 100 parts, 110 parts, 120 parts, 130 parts or 140 parts, or any value within the range of 70 - 140 parts; the brightener can be, for example, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, or any value within the range of 4 - 10 parts; the stabilizer can be, for example, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts or 60 parts, or any value within the range of 20 - 60 parts; the grain refiner can be, for example, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts, or any value within the range of 0.5 - 5 parts; the defoamer can be, for example, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts or 3 parts, or any value within the range of 0.5 - 3 parts; the balance is water to make up the total amount of the electroplating solution per unit volume to the required amount.

[0041] In the implementation process of the present invention, the concentration unit of the tin electroplating solution raw materials can be g / L, mg / mL, kg / m 3 , and can also be enlarged or reduced according to the above - mentioned ratio.

[0042] Further, the brightener includes at least one of Schiff base, benzalacetone, acetophenone, chlorobenzaldehyde, glutaraldehyde, salicylaldehyde, 4 - tetradecylaniline and 1,2,3 - benzotriazole.

[0043] Preferably, the grain refiner includes at least one of 3,4,5 - trihydroxybenzoic acid, 4 - hydroxybenzoic acid, p - hydroxytoluene, m - hydroxytoluene, o - hydroxytoluene and benzyl alcohol.

[0044] Preferably, the defoamer includes at least one of polydimethylsiloxane, ethylene glycol siloxane, polyoxyethylene alcohol, polyethylene glycol, polypropylene glycol, bisphenol A polyoxyethylene ether and polyoxypropylene oxyethylene glycerol ether.

[0045] Further, the preparation method of the stabilizer is as follows: Dissolve tartaric acid and sodium potassium tartrate in pure water, and then slowly add concentrated sulfuric acid until the solution becomes clear; after the solution temperature drops to 50 - 60 °C, add p-diphenol and ascorbic acid, and stir until completely dissolved to obtain the stabilizer.

[0046] Preferably, the concentration of the tartaric acid is 50 - 100 g / L.

[0047] Typically but not restrictively, the concentration of the tartaric acid can be, for example, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L or 100 g / L, or any value within the range of 50 - 100 g / L.

[0048] Preferably, the mass ratio of sodium potassium tartrate to tartaric acid is 0.8 - 3.2:1.

[0049] Typically but not restrictively, the mass ratio of sodium potassium tartrate to tartaric acid can be, for example, 0.8:1, 1.0:1, 1.2:1, 1.5:1, 1.8:1, 2.0:1, 2.5:1, 3.0:1 or 3.2:1, or any ratio within the range of 0.8 - 3.2:1.

[0050] Preferably, the mass of the concentrated sulfuric acid is 0.3 - 3 times the sum of the masses of tartaric acid and sodium potassium tartrate.

[0051] Typically but not restrictively, the ratio of the mass of the concentrated sulfuric acid to the sum of the masses of tartaric acid and sodium potassium tartrate can be, for example, 0.3 times, 0.5 times, 0.8 times, 1.0 times, 1.5 times, 2.0 times, 2.5 times or 3.0 times, or any value within the range of 0.3 - 3 times.

[0052] Preferably, the mass percentage concentration of p-diphenol is 6 - 16 wt%.

[0053] Typically but not restrictively, the mass percentage concentration of p-diphenol can be, for example, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 14 wt% or 16 wt%, or any value within the range of 6 - 16 wt%.

[0054] Preferably, the mass percentage concentration of ascorbic acid is 3 - 8 wt%.

[0055] Typically but not restrictively, the mass percentage concentration of ascorbic acid can be, for example, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt% or 8 wt%, or any value within the range of 3 - 8 wt%.

[0056] In the second aspect of the present invention, there is provided a method for preparing the tin electroplating solution. After adding methanesulfonic acid to a part of water and stirring evenly, it is cooled to room temperature and then stannous methanesulfonate is added and stirred evenly. Finally, a brightening agent, a stabilizer, a grain refiner, an antifoaming agent and the remaining water are added and stirred evenly to obtain the tin electroplating solution.

[0057] The method for preparing the tin electroplating solution provided by the present invention optimizes the feeding sequence and process conditions to ensure that each component is fully dissolved and plays a synergistic role, thereby improving the stability of the electroplating solution and the quality of the coating. This preparation method is simple to operate and easy to industrialize.

[0058] During the preparation process, methanesulfonic acid is first added to a part of water and stirred evenly to ensure that a stable acidic environment is formed in the system, avoiding hydrolysis or precipitation when the subsequent tin salt is directly added. After the system is cooled to room temperature, stannous methanesulfonate is added to prevent oxidation or decomposition of tin ions at high temperatures, ensuring the solubility of the main salt and the long-term stability of the electroplating solution. Finally, a brightening agent, a stabilizer, a grain refiner, an antifoaming agent and the remaining water are added, enabling each additive to play a role while being evenly dispersed: the stabilizer inhibits the hydrolysis of stannous tin, reduces the generation of stannic tin, and extends the service life of the plating solution; the grain refiner optimizes the tin deposition process, improving the compactness and uniformity of the coating; the antifoaming agent reduces the bubble residue during electroplating and improves the surface smoothness of the coating; the brightening agent further improves the flatness and metallic luster of the coating.

[0059] By adding materials in stages and stirring at room temperature, complex temperature control or special equipment requirements are avoided. The operation is simple and easy to scale up industrially. The obtained electroplating solution has high stability and excellent coating quality, which can significantly reduce the series resistance of solar cells and improve the photoelectric conversion efficiency.

[0060] In the third aspect of the present invention, there is provided a method for preparing a crystalline silicon solar cell wafer. The crystalline silicon solar cell wafer with double-sided copper plating is activated; then it is placed in a double-sided horizontal tin electroplating device for electroplating, and after electroplating, it is cleaned and dried to obtain a crystalline silicon solar cell wafer with double-sided tin plating;

[0061] Among them, the tin electroplating solution in the double-sided horizontal tin electroplating device is the tin electroplating solution described above.

[0062] The method for preparing a crystalline silicon solar cell wafer provided by the present invention, due to the advantages of the above-mentioned tin electroplating solution, makes the grain size of the tin layer in the crystalline silicon solar cell wafer uniform and fine, reduces the contact resistance, and improves the quality, conversion efficiency and long-term reliability of the crystalline silicon solar cell wafer.

[0063] Further, during the electroplating process, a pure tin bar is used as the anode and the wafer to be plated is used as the cathode for electroplating.

[0064] Preferably, the temperature of the tin electroplating solution is 25 - 40 °C.

[0065] Typically but not limited thereto, the temperature of the tin plating solution may be, for example, 25°C, 28°C, 30°C, 32°C, 35°C, 38°C or 40°C, or may also be any value within the range of 25 to 40°C.

[0066] Preferably, the current density of the electroplating is 5 to 20 A / dm 2 , and the electroplating time is 5 to 25 s.

[0067] Typically but not limited thereto, the current density of the electroplating may be, for example, 5 A / dm 2 , 8 A / dm 2 , 10 A / dm 2 , 12 A / dm 2 , 15 A / dm 2 , 18 A / dm 2 or 20 A / dm 2 , or may also be any value within the range of 5 to 20 A / dm2; the electroplating time may be, for example, 5 s, 8 s, 10 s, 12 s, 15 s, 18 s, 20 s, 22 s or 25 s, or may also be any value within the range of 5 to 25 s.

[0068] Preferably, the thickness of the tin layer after tin plating is 0.5 to 1.0 μm.

[0069] Typically but not limited thereto, the thickness of the tin layer after tin plating may be, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm, or may also be any value within the range of 0.5 to 1.0 μm.

[0070] Further, in the double-sided copper-plated crystalline silicon solar cell, the thickness of the copper layer is 8 to 12 μm.

[0071] Typically but not limited thereto, in the double-sided copper-plated crystalline silicon solar cell, the thickness of the copper layer may be, for example, 8 μm, 9 μm, 10 μm, 11 μm or 12 μm, or may also be any value within the range of 8 to 12 μm.

[0072] Further, the activation solution used for activation is an acidic solution.

[0073] Preferably, the acidic solution is a methylsulfonic acid solution, which can undergo a slight chemical reaction with the copper layer oxide on the surface, remove the copper oxide without excessively eroding the substrate, and lay a foundation for subsequent tin plating.

[0074] Further, the volume concentration of the methylsulfonic acid solution is 5 to 20 mL / L.

[0075] Typically but not limited thereto, the volume concentration of the methanesulfonic acid solution may, for example, be 5 mL / L, 8 mL / L, 10 mL / L, 12 mL / L, 15 mL / L, 18 mL / L, or 20 mL / L, or may also be any value within the range of 5 to 20 mL / L.

[0076] The present invention will be further illustrated below by specific examples and comparative examples. However, it should be understood that these examples are only for more detailed illustration and should not be construed as limiting the present invention in any way. For the raw materials used in the examples and comparative examples of the present invention, where no specific conditions are indicated, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not indicated, they are all conventional products that can be obtained by purchasing in the market.

[0077] Example 1

[0078] This example provides a tin electroplating solution, wherein stannous methanesulfonate is 100 g / L, methanesulfonic acid is 100 g / L, Schiff base is 8 g / L, stabilizer is 40 g / L, 3,4,5-trihydroxybenzoic acid is 2 g / L, and polydimethylsiloxane is 1.5 g / L, and the rest is pure water.

[0079] The preparation method of the stabilizer is as follows: Take 70 g of tartaric acid and 120 g of sodium potassium tartrate and dissolve them in 1 L of pure water. Slowly add 100 mL of concentrated sulfuric acid until the solution is clear. After the temperature drops to 50 - 60 °C, then add 14 g of p-diphenol and 7 g of ascorbic acid, and stir until completely dissolved to obtain it.

[0080] The preparation method of the above tin electroplating solution is as follows:

[0081] Add 0.5 L of water into a container, and then start circulating stirring. Then add methanesulfonic acid and wait until the temperature drops to room temperature; add stannous methanesulfonate and stir evenly; then successively add brightener, grain refiner, stabilizer, and defoamer, and finally make up the volume to 1 L with pure water.

[0082] Example 2

[0083] This example provides a tin electroplating solution, wherein stannous methanesulfonate is 80 g / L, methanesulfonic acid is 100 g / L, benzalacetone is 5 g / L, stabilizer is 40 g / L, 4-hydroxybenzoic acid is 3 g / L, and polyethylene glycol is 0.8 g / L, and the rest is pure water.

[0084] The preparation method of the stabilizer is as follows: Take 50 g of tartaric acid and 150 g of sodium potassium tartrate and dissolve them in 1 L of pure water. Slowly add 150 mL of concentrated sulfuric acid until the solution is clear. After the temperature drops to 50 - 60 °C, then add 8 g of p-diphenol and 4 g of ascorbic acid, and stir until completely dissolved to obtain it.

[0085] The preparation method of the above tin electroplating solution is the same as that in Example 1 and will not be elaborated here.

[0086] Example 3

[0087] This example provides a tin electroplating solution, in which stannous methylsulfonate is 120 g / L, methylsulfonic acid is 90 g / L, chlorobenzaldehyde is 6 g / L, stabilizer is 50 g / L, p - hydroxytoluene is 4 g / L, ethylene glycol siloxane is 2 g / L, and the balance is water.

[0088] The preparation method of the stabilizer is as follows: Take 90 g of tartaric acid and 100 g of potassium sodium tartrate and dissolve them in 1 L of pure water. Slowly add 120 mL of concentrated sulfuric acid until the solution is clear. After cooling to 55 °C, add 12 g of p - dihydroxybenzene and 6 g of ascorbic acid, and stir to dissolve.

[0089] The preparation method of the above tin electroplating solution is the same as that in Example 1 and will not be elaborated here.

[0090] Example 4

[0091] This example provides a tin electroplating solution, in which stannous methylsulfonate is 60 g / L, methylsulfonic acid is 130 g / L, glutaraldehyde is 9 g / L, stabilizer is 30 g / L, benzyl alcohol is 1 g / L, polypropylene glycol is 2.5 g / L, and the balance is water.

[0092] The preparation method of the stabilizer is as follows: Take 60 g of tartaric acid and 180 g of potassium sodium tartrate and dissolve them in 1 L of pure water. Slowly add 80 mL of concentrated sulfuric acid until it is clear. After cooling to 60 °C, add 10 g of p - dihydroxybenzene and 5 g of ascorbic acid, and stir to dissolve.

[0093] The preparation method of the above tin electroplating solution is the same as that in Example 1 and will not be elaborated here.

[0094] Example 5

[0095] This example provides a tin electroplating solution, in which stannous methylsulfonate is 150 g / L, methylsulfonic acid is 70 g / L, salicylaldehyde is 7 g / L, stabilizer is 60 g / L, o - hydroxytoluene is 3 g / L, bisphenol A polyoxyethylene ether is 1 g / L, and the balance is water.

[0096] The preparation method of the stabilizer is as follows: Take 100 g of tartaric acid and 80 g of potassium sodium tartrate and dissolve them in 1 L of pure water. Slowly add 200 mL of concentrated sulfuric acid until it is clear. After cooling to 50 °C, add 16 g of p - dihydroxybenzene and 8 g of ascorbic acid, and stir to dissolve.

[0097] The preparation method of the above tin electroplating solution is the same as that in Example 1 and will not be elaborated here.

[0098] Example 6

[0099] This embodiment provides a tin plating solution, which contains 80 g / L of stannous methylsulfonate, 110 g / L of methylsulfonic acid, 5 g / L of 4-tetradecylaniline, 45 g / L of stabilizer, 2.5 g / L of m-cresol, 1.2 g / L of polyoxypropylene oxyethylene glycerol ether, and the balance is water.

[0100] The preparation method of the stabilizer is as follows: Dissolve 75 g of tartaric acid and 150 g of sodium potassium tartrate in 1 L of pure water, slowly add 100 mL of concentrated sulfuric acid until it becomes clear, add 9 g of p-diphenol and 4.5 g of ascorbic acid after cooling to 58 °C, and stir to dissolve.

[0101] The preparation method of the above tin plating solution is the same as that of Example 1, and will not be elaborated here.

[0102] Example 7

[0103] This embodiment provides a tin plating solution, which contains 140 g / L of stannous methylsulfonate, 85 g / L of methylsulfonic acid, 10 g / L of 1,2,3-benzotriazole, 55 g / L of stabilizer, 3 g / L of benzyl alcohol, 1.8 g / L of polyoxyethylene alcohol, and the balance is water.

[0104] The preparation method of the stabilizer is as follows: Dissolve 80 g of tartaric acid and 200 g of sodium potassium tartrate in 1 L of pure water, slowly add 180 mL of concentrated sulfuric acid until it becomes clear, add 14 g of p-diphenol and 7 g of ascorbic acid after cooling to 52 °C, and stir to dissolve.

[0105] The preparation method of the above tin plating solution is the same as that of Example 1, and will not be elaborated here.

[0106] Example 8

[0107] This embodiment provides a tin plating solution, which contains 70 g / L of stannous methylsulfonate, 120 g / L of methylsulfonic acid, 8 g / L of acetophenone, 25 g / L of stabilizer, 4.5 g / L of 3,4,5-trihydroxybenzoic acid, 0.8 g / L of polydimethylsiloxane, and the balance is water.

[0108] The preparation method of the stabilizer is as follows: Dissolve 55 g of tartaric acid and 130 g of sodium potassium tartrate in 1 L of pure water, slowly add 90 mL of concentrated sulfuric acid until it becomes clear, add 7 g of p-diphenol and 3.5 g of ascorbic acid after cooling to 56 °C, and stir to dissolve.

[0109] The preparation method of the above tin plating solution is the same as that of Example 1, and will not be elaborated here.

[0110] Example 9

[0111] This embodiment provides a tin plating solution, which contains 130 g / L of stannous methylsulfonate, 75 g / L of methylsulfonic acid, 7 g / L of chlorobenzaldehyde, 58 g / L of stabilizer, 4.2 g / L of 4-hydroxybenzoic acid, 1.5 g / L of polyethylene glycol, and the balance is water.

[0112] The preparation method of the stabilizer is as follows: Dissolve 95 g of tartaric acid and 110 g of sodium potassium tartrate in 1 L of pure water, slowly add 150 mL of concentrated sulfuric acid until it becomes clear, add 15 g of p-diphenol and 7.5 g of ascorbic acid after cooling to 54 °C, and stir until dissolved.

[0113] The preparation method of the above tin plating solution is the same as that of Example 1, and will not be elaborated here.

[0114] Examples 10 - 18

[0115] These examples provide tin plating solutions, whose formulation compositions are the same as those of Example 1. Different from Example 1, the formulation of the stabilizer is the same as that in Examples 2 - 9, and the remaining methods are the same as those of Example 1, and will not be elaborated here.

[0116] Comparative Example 1

[0117] This comparative example provides a tin plating solution. Different from Example 4, the stabilizer is not added to the plating solution, and the remaining raw materials and preparation methods are the same as those of Example 4, and will not be elaborated here.

[0118] Comparative Example 2

[0119] This comparative example provides a tin plating solution. Different from Example 4, the grain refiner 3,4,5-trihydroxybenzoic acid is not added to the plating solution, and the remaining raw materials and preparation methods are the same as those of Example 4, and will not be elaborated here.

[0120] Comparative Example 3

[0121] This comparative example provides a tin plating solution. Different from Example 4, the defoamer polydimethylsiloxane is not added to the plating solution, and the remaining raw materials and preparation methods are the same as those of Example 4, and will not be elaborated here.

[0122] Comparative Example 4

[0123] This comparative example provides a tin plating solution. Different from Example 4, the brightener Schiff base is not added to the plating solution, and the remaining raw materials and preparation methods are the same as those of Example 4, and will not be elaborated here.

[0124] Test Example 1

[0125] The tin electroplating solutions of the examples and comparative examples were subjected to a stability test. Specifically, the tin electroplating solution was heated to 50 °C, and air was pumped into the plating solution using an air pump (hot air at 40 °C, flow rate 10 L / min), and the time when the plating solution became turbid was recorded. The data is recorded in Table 1.

[0126] Table 1

[0127] Turbidity change time h Turbidity change time h Example 1 60 Example 12 55 Example 2 58 Example 13 53 Example 3 58 Example 14 57 Example 4 57 Example 15 54 Example 5 59 Example 16 54 Example 6 59 Example 17 56 Example 7 57 Example 18 58 Example 8 56 Comparative Example 1 20 Example 9 54 Comparative Example 2 45 Example 10 56 Comparative Example 3 48 Example 11 54 Comparative Example 4 24

[0128] As can be seen from Table 1, the tin electroplating solution of Example 1 had the longest time to become turbid in the 50 °C environment, indicating the best stability.

[0129] Examples 19 - 36

[0130] These examples provide crystalline silicon solar cell wafers. The silicon substrate was electroplated on both sides, and the current density of electroplating was controlled at 20 A / dm 2 , and the electroplating time was 3 min to obtain a crystalline silicon solar cell wafer with copper electroplated on both sides. The thickness of the copper layer was measured, and the photoelectric conversion efficiency and series resistance of the cell wafer at this time were measured and recorded in Tables 2 and 3.

[0131] The crystalline silicon solar cell wafer with copper electroplated on both sides was placed in a methanesulfonic acid solution with a concentration of 10 mL / L for activation for 30 s, and then placed in a double-sided horizontal tin electroplating device. The tin electroplating solution in the device corresponded to that provided in Examples 1 - 18. Using a pure tin bar as the anode, the rectifier and drive were turned on, and the cell wafer advanced at a constant speed for electroplating. The current density of electroplating was 3 A / dm 2 , and the electroplating time was 60 s. Finally, the cell wafer was washed with pure water and dried to obtain a crystalline silicon solar cell wafer with tin electroplated on both sides.

[0132] The thickness of the tin layer on the front side of the cell wafer (theoretical thickness 1 μm) was measured, and the photoelectric conversion efficiency and series resistance of the cell wafer at this time were measured and recorded in Tables 2 and 3.

[0133] Nine points were marked on the front side of the cell wafer according to the nine-square method. First, the thickness of the copper layer was measured, and then the thickness after tin electroplating was measured. The latter minus the former was the thickness of the tin layer. First, the average value of the tin layer thickness was calculated, and then

[0134] Comparative Examples 5 - 8

[0135] The crystalline silicon solar cell wafers with tin electroplated on both sides were prepared in the same manner as in Examples 19 - 36. The tin electroplating solutions used corresponded to those provided in Comparative Examples 1 - 4, and the data obtained was recorded in Tables 2 and 3.

[0136] Table 2

[0137]

[0138] Table 3

[0139]

[0140]

[0141] As can be seen from Table 2, the average thickness of the tin layer in Example 1 is closest to the theoretical thickness, and the thickness variance is the smallest, indicating that the thickness stability of the tin layer is better and the thickness is more uniform.

[0142] As can be seen from Table 3, the photoelectric conversion efficiency of the solar cell after tin plating in Example 1 has increased by 0.03%, and the series resistance has become lower, indicating that the tin plating solution helps to improve the conductivity of the solar cell.

[0143] Finally, it should be noted that the above-described embodiments are only specific embodiments of the present invention, used to illustrate the technical solutions of the present invention, rather than limiting it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: any person skilled in the art within the technical scope disclosed by the present invention can still modify the technical solutions recorded in the foregoing embodiments or can easily think of changes, or perform equivalent replacements for some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A tin electroplating solution, characterized in that, It includes stannous methylsulfonate, methylsulfonic acid, brightener, stabilizer, grain refiner, defoamer and water.

2. The tin electroplating solution according to claim 1, wherein, By weight, per unit volume of the tin electroplating solution includes 50 - 150 parts of stannous methylsulfonate, 70 - 140 parts of methylsulfonic acid, 4 - 10 parts of brightener, 20 - 60 parts of stabilizer, 0.5 - 5 parts of grain refiner, 0.5 - 3 parts of defoamer, and the balance is water.

3. The tin electroplating solution according to claim 1 or 2, characterized in that, The brightener includes at least one of Schiff base, benzalacetone, acetophenone, chlorobenzaldehyde, glutaraldehyde, salicylaldehyde, 4 - tetradecylaniline and 1,2,3 - benzotriazole; Preferably, the grain refiner includes at least one of 3,4,5 - trihydroxybenzoic acid, 4 - hydroxybenzoic acid, p - hydroxytoluene, m - hydroxytoluene, o - hydroxytoluene and benzyl alcohol; Preferably, the defoamer includes at least one of polydimethylsiloxane, ethylene glycol siloxane, polyoxyethylene alcohol, polyethylene glycol, polypropylene glycol, bisphenol A polyoxyethylene ether and polyoxypropylene oxyethylene glycerol ether; 4. The tin electroplating solution according to claim 1 or 2, characterized in that, The preparation method of the stabilizer is: dissolve tartaric acid and sodium potassium tartrate in pure water, then slowly add concentrated sulfuric acid until the solution is clear; after the solution temperature drops to 50 - 60 °C, add hydroquinone and ascorbic acid, and stir until completely dissolved to obtain the stabilizer; Preferably, the concentration of the tartaric acid is 50 - 100 g / L; Preferably, the mass ratio of sodium potassium tartrate to tartaric acid is 0.8 - 3.2:1; Preferably, the mass of the concentrated sulfuric acid is 0.3 - 3 times the sum of the masses of tartaric acid and sodium potassium tartrate; Preferably, the mass percentage concentration of hydroquinone is 6 - 16 wt%; Preferably, the mass percentage concentration of ascorbic acid is 3 - 8 wt%.

5. A method for preparing the tin electroplating solution according to any one of claims 1 to 4, characterized in that, After adding methylsulfonic acid to part of the water and stirring evenly, after cooling to room temperature, continue to add stannous methylsulfonate and stir evenly, and finally add brightener, stabilizer, grain refiner, defoamer and the remaining water and stir evenly to obtain the tin electroplating solution.

6. A preparation method of a crystalline silicon solar cell, characterized in that, Activate the double - sided copper - plated crystalline silicon solar cell wafer; then place it in a double - sided horizontal tin - plating device for electroplating, and after electroplating, wash and dry to obtain a double - sided tin - plated crystalline silicon solar cell wafer; Among them, the tin electroplating solution in the double - sided horizontal tin - plating device is the tin electroplating solution according to any one of claims 1 - 4.

7. The preparation method according to claim 6, wherein During the electroplating process, use a pure tin bar as the anode and the wafer to be plated as the cathode for electroplating; Preferably, the temperature of the tin electroplating solution is 25 - 40 °C; Preferably, the current density of the electroplating is 5 to 20 A / dm 2 , and the electroplating time is 5 to 25 s; Preferably, the thickness of the tin layer after tin plating is 0.5 - 1.0 μm.

8. The preparation method according to claim 6, characterized in that, In the double - sided copper - plated crystalline silicon solar cell wafer, the thickness of the copper layer is 8 - 12 μm.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The activation solution used for activation is an acidic solution; Preferably, the acidic solution is a methylsulfonic acid solution.

10. The preparation method according to claim 9, characterized in that, The volume concentration of the methylsulfonic acid solution is 5 - 20 mL / L.

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