Nickel-tungsten alloy electroplating solution, preparation method thereof and preparation method of solar cell metal electrode

Abstract

The invention provides a nickel-tungsten alloy electroplating solution, a preparation method thereof and a preparation method of a solar cell metal electrode, and particularly relates to the technical field of solar cell preparation. The nickel-tungsten alloy electroplating solution provided by the invention comprises nickel salt, tungstate, a complexing agent, a wetting agent and water. In the nickel-tungsten alloy electroplating solution provided by the invention, on the basis of nickel salt and tungstate, a uniform and compact nickel-tungsten alloy layer can be formed on the surface of a plated part, and the layer of alloy combines the electrical conductivity of nickel and the corrosion resistance and high hardness characteristics of tungsten, so that the comprehensive performance of the plated part is remarkably improved. And the complexing agent is added, so that the activity of nickel ions and tungsten ions and the electrodeposition process are effectively controlled, and the quality and the production efficiency of a plating layer are optimized. And the wetting agent is used, so that the wettability of the plating solution on the surface of a plating piece is improved, uniform deposition of an alloy layer is promoted, pores and defects are reduced, and the binding force and durability of a plating layer are enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of solar cell preparation, and in particular to a nickel-tungsten alloy electroplating solution and a preparation method thereof, and a preparation method for a solar cell metal electrode. Background Art

[0002] Diffusion barrier plays an important role in the manufacture of solar cells. Its main function is to prevent the diffusion of conductive layer metal to the silicon substrate. Currently, commonly used materials include metals such as nickel, tungsten, and cobalt. Although nickel has good conductivity, its conductivity is not as good as tungsten and it is easily oxidized in the air. The presence of the oxide layer will weaken the bonding between the conductive layer and the diffusion barrier layer, so pickling is required to remove the oxide layer before electroplating the conductive layer. However, if the oxide layer is not completely removed, it will affect the firmness of the interlayer bonding.

[0003] As a metal with a negative standard electrode potential, tungsten faces challenges when electrodeposited alone in aqueous solution, and usually needs to be co-deposited with other metals to form alloys. The preparation methods of tungsten alloy coatings mainly include magnetron sputtering and molten salt electroplating. Magnetron sputtering will deposit tungsten alloys on the entire surface of the substrate, but photovoltaic cells only need to deposit tungsten in specific areas, which requires additional mask protection and cleaning steps, increasing process complexity and cost. Molten salt electroplating requires high temperatures and has high requirements for equipment and operating conditions.

[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 nickel-tungsten alloy electroplating solution to improve the performance of the 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 nickel-tungsten alloy electroplating solution.

[0007] A third object of the present invention is to provide a metal electrode for a 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 nickel-tungsten alloy electroplating solution comprising a nickel salt, a tungstate, a complexing agent, a wetting agent and water.

[0010] Furthermore, the nickel-tungsten alloy electroplating solution comprises, by weight, 20 to 100 parts of nickel salt, 100 to 200 parts of tungstate, 20 to 80 parts of complexing agent, 0.2 to 1 part of wetting agent, and the balance is water per unit volume of the nickel-tungsten alloy electroplating solution.

[0011] Furthermore, the nickel salt includes at least one of nickel sulfate, nickel chloride and nickel sulfamate.

[0012] Preferably, the tungstate comprises sodium tungstate and / or potassium tungstate.

[0013] Preferably, the complexing agent comprises at least one of citric acid, tartaric acid, pyrophosphoric acid, tartrate, citrate and pyrophosphate.

[0014] Preferably, the wetting agent includes at least one of sodium diethylhexyl sulfate, sodium n-octyl sulfate, sodium isethionate and sodium succinate.

[0015] Preferably, the water comprises pure water.

[0016] The second aspect of the present invention provides a method for preparing the nickel-tungsten alloy electroplating solution, comprising adding the nickel salt, the complexing agent and the wetting agent into water and stirring evenly, and finally adding the tungstate and stirring evenly to obtain the nickel-tungsten alloy electroplating solution.

[0017] Furthermore, the pH of the nickel-tungsten alloy electroplating solution is 5.0-8.0.

[0018] The third aspect of the present invention provides a method for preparing a metal electrode of a solar cell, wherein a silicon substrate of the solar cell is placed in a nickel-tungsten alloy electroplating solution for direct current electroplating to obtain a nickel-tungsten alloy coating;

[0019] Then, copper plating and tin plating are performed on the nickel-tungsten alloy plating layer to obtain a solar cell metal electrode;

[0020] Wherein, the nickel-tungsten alloy electroplating solution is the nickel-tungsten alloy electroplating solution described in the first aspect.

[0021] Furthermore, in the direct current electroplating, the solar cell silicon substrate is used as the cathode and the titanium mesh is used as the anode.

[0022] Preferably, the temperature of the DC electroplating is 50-70°C, and the current density is 4-10A / dm 2 .

[0023] Preferably, the DC electroplating time is 30 to 150 seconds.

[0024] Furthermore, the solar cell silicon substrate is subjected to double-sided direct current electroplating to obtain a double-sided nickel-tungsten alloy coating.

[0025] Preferably, the copper plating is double-sided copper plating.

[0026] Preferably, the tinning is double-sided tinning.

[0027] Furthermore, the solar cell is an N-type TOPCon cell.

[0028] Preferably, the surface of the solar cell silicon substrate is provided with crisscross patterned grooves.

[0029] Preferably, the patterned groove has a width of 10-40 μm and a depth of 80-100 nm.

[0030] Preferably, the nickel-tungsten alloy coating has a thickness of 1.0-1.5 μm.

[0031] Preferably, the copper layer obtained after the copper plating has a thickness of 8 to 12 μm.

[0032] Preferably, the thickness of the tin layer obtained after the tin plating is 1 to 2 μm.

[0033] Furthermore, the method for preparing the metal electrode of a solar cell also includes a process of acid washing the silicon substrate of the solar cell before direct current electroplating.

[0034] Preferably, the pickling is performed using a hydrofluoric acid solution.

[0035] Preferably, the concentration of the hydrofluoric acid solution is 10-40 mL / L.

[0036] Preferably, the pickling time is 10 to 40 seconds.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] The nickel-tungsten alloy electroplating solution provided by the present invention is based on nickel salt and tungstate, and can form a uniform and dense nickel-tungsten alloy layer on the surface of the plated part. This alloy combines the electrical conductivity of nickel with the corrosion resistance and high hardness characteristics of tungsten, and significantly improves the comprehensive performance of the plated part. The addition of the complexing agent effectively controls the activity and electrodeposition process of nickel ions and tungsten ions, and optimizes the quality and production efficiency of the coating. The use of the wetting agent improves the wettability of the plating solution on the surface of the plated part, promotes the uniform deposition of the alloy layer, reduces pores and defects, and thus enhances the bonding strength and durability of the coating. The entire electroplating solution system uses water as a solvent, reduces the use of harmful chemicals, and meets modern environmental protection requirements. The electroplating solution provides convenience for the industrial application of nickel-tungsten alloy coatings, simplifies the process flow, and reduces production costs.

[0039] The preparation method provided by the present invention firstly stirs the nickel salt, the complexing agent and the wetting agent to form a uniform basic solution, then adds the tungstate to the basic solution and continues to stir until it is completely uniform, and finally obtains the desired nickel-tungsten alloy electroplating solution. This method not only ensures the uniform dispersion and effective fusion of each component, but also simplifies the preparation process, reduces the difficulty of operation, and improves the preparation efficiency.

[0040] The method for preparing the metal electrode of a solar cell provided by the present invention, in view of the advantages of the above-mentioned nickel-tungsten alloy electroplating solution, enables the prepared metal electrode of the solar cell to have better conductivity, corrosion resistance and wear resistance, thereby improving the overall performance and reliability of the solar cell in a high temperature or corrosive environment. DETAILED DESCRIPTION

[0041] 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.

[0042] 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 adding the possibility of one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0043] A first aspect of the present invention provides a nickel-tungsten alloy electroplating solution comprising a nickel salt, a tungstate, a complexing agent, a wetting agent and water.

[0044] The nickel-tungsten alloy electroplating solution provided by the present invention is based on nickel salt and tungstate, and can form a uniform and dense nickel-tungsten alloy layer on the surface of the plated part. This alloy combines the electrical conductivity of nickel with the corrosion resistance and high hardness characteristics of tungsten, and significantly improves the comprehensive performance of the plated part. The addition of the complexing agent effectively controls the activity and electrodeposition process of nickel ions and tungsten ions, and optimizes the quality and production efficiency of the coating. The use of the wetting agent improves the wettability of the plating solution on the surface of the plated part, promotes the uniform deposition of the alloy layer, reduces pores and defects, and thus enhances the bonding strength and durability of the coating. The entire electroplating solution system uses water as a solvent, reduces the use of harmful chemicals, and meets modern environmental protection requirements. The electroplating solution provides convenience for the industrial application of nickel-tungsten alloy coatings, simplifies the process flow, and reduces production costs.

[0045] Furthermore, the nickel-tungsten alloy electroplating solution comprises, by weight, 20 to 100 parts of nickel salt, 100 to 200 parts of tungstate, 20 to 80 parts of complexing agent, 0.2 to 1 part of wetting agent, and the balance is water per unit volume of the nickel-tungsten alloy electroplating solution.

[0046] In the nickel-tungsten alloy layer obtained in the nickel-tungsten alloy electroplating solution of the above ratio, the tungsten content is 40% to 50%. The plating layer with high tungsten content is beneficial to improving the barrier to the metallic copper of the conductive layer. The melting point is greater than 3000°C, ensuring that the barrier layer will not react with the conductive layer.

[0047] Typically but not limiting, the composition ratio of the nickel-tungsten alloy electroplating solution, in terms of weight parts, can include the following components and their corresponding ranges of parts per unit volume of the electroplating solution: the nickel salt can be 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts or 100 parts, or any value between 20 and 100 parts; the tungstate can be 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, 160 parts, 170 parts, 180 parts, 190 parts, 200 parts, 210 parts, 220 parts, 230 parts, 240 parts, 250 parts, 260 parts, 270 parts, 280 parts, 290 parts, 300 parts, 310 parts, 320 parts, 330 parts, 340 parts, 350 parts, 360 parts, 370 parts, 380 parts, 390 parts, 400 parts, 410 parts, 420 parts, 430 parts, 440 parts, 450 parts, 460 parts, 470 parts, 480 parts, 490 parts, 500 parts, 510 parts, 520 parts, 530 parts, 540 parts, 550 parts, 560 parts, 570 parts, 580 parts, 590 parts, 600 parts, 610 parts, 620 parts, 630 parts, 640 parts, 650 parts, 660 parts, 670 parts, 680 parts, 690 parts, 700 parts, 710 parts, 720 parts, 730 parts, 740 parts The proportion of the complexing agent can be 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 or 80, or any value between 20 and 80. The proportion of the wetting agent can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 1, or any value between 0.2 and 1. The balance is water to make up the required total amount of the electroplating solution per unit volume.

[0048] Furthermore, the nickel salt includes at least one of nickel sulfate, nickel chloride and nickel sulfamate.

[0049] Preferably, the tungstate comprises sodium tungstate and / or potassium tungstate.

[0050] Preferably, the complexing agent comprises at least one of citric acid, tartaric acid, pyrophosphoric acid, tartrate, citrate and pyrophosphate.

[0051] Preferably, the wetting agent includes at least one of sodium diethylhexyl sulfate, sodium n-octyl sulfate, sodium isethionate and sodium succinate.

[0052] Preferably, the water comprises pure water.

[0053] The second aspect of the present invention provides a method for preparing the nickel-tungsten alloy electroplating solution, comprising adding the nickel salt, the complexing agent and the wetting agent into water and stirring evenly, and finally adding the tungstate and stirring evenly to obtain the nickel-tungsten alloy electroplating solution.

[0054] The preparation method provided by the present invention firstly stirs the nickel salt, the complexing agent and the wetting agent to form a uniform basic solution, then adds the tungstate to the basic solution and continues to stir until it is completely uniform, and finally obtains the desired nickel-tungsten alloy electroplating solution. This method not only ensures the uniform dispersion and effective fusion of each component, but also simplifies the preparation process, reduces the difficulty of operation, and improves the preparation efficiency.

[0055] Furthermore, the pH of the nickel-tungsten alloy electroplating solution is 5.0-8.0.

[0056] The pH value of the nickel-tungsten alloy electroplating solution is controlled within the range of 5.0 to 8.0, ensuring the stability and solubility of the nickel salt and tungstate in the electroplating solution in the electrochemical reaction, thereby promoting the effective release and uniform deposition of metal ions during the electroplating process. Secondly, maintaining this pH value range helps to reduce the occurrence of hydrolysis and side reactions, which not only improves the service life of the electroplating solution, but also reduces the generation of impurities, ensuring the purity and quality of the coating. In addition, strict control of the pH value also helps to optimize the conductivity of the electroplating solution, ensuring the effective transfer of current and the uniformity of the electrodeposition rate, which is crucial for forming a uniform, dense and defect-free nickel-tungsten alloy coating.

[0057] Typically but not limiting, the pH value of the nickel-tungsten alloy electroplating solution can be precisely controlled at 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8 or 8.0, or any value within the range of 5.0 to 8.0.

[0058] The third aspect of the present invention provides a method for preparing a metal electrode of a solar cell, wherein a silicon substrate of the solar cell is placed in a nickel-tungsten alloy electroplating solution for direct current electroplating to obtain a nickel-tungsten alloy coating;

[0059] Then, copper plating and tin plating are performed on the nickel-tungsten alloy plating layer to obtain a solar cell metal electrode;

[0060] Wherein, the nickel-tungsten alloy electroplating solution is the nickel-tungsten alloy electroplating solution described in the first aspect.

[0061] The method for preparing the metal electrode of a solar cell provided by the present invention, in view of the advantages of the above-mentioned nickel-tungsten alloy electroplating solution, enables the prepared metal electrode of the solar cell to have better conductivity, corrosion resistance and wear resistance, thereby improving the overall performance and reliability of the solar cell in a high temperature or corrosive environment.

[0062] Furthermore, in the DC electroplating, the solar cell silicon substrate is used as the cathode, the titanium mesh is used as the anode, the surface to be plated contacts the nickel-tungsten alloy electroplating solution, the DC power supply is turned on to start electroplating, and after the electroplating is completed, the plated surface is cleaned or dried to proceed to the next process.

[0063] In some embodiments of the present invention, the other side is flipped over for electroplating to obtain a double-sided electroplated nickel-tungsten alloy layer.

[0064] Preferably, the temperature of the DC electroplating is 50-70°C, and the current density is 4-10A / dm 2 .

[0065] Typically, but not limiting, the temperature setting during DC plating can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C or 70°C, or any temperature value within the range of 50°C to 70°C; the current density setting can be 4A / dm 2 , 5A / dm 2 、6A / dm 2 , 7A / dm 2 , 8A / dm 2 、9A / dm 2 or 10A / dm 2 , or 4A / dm 2 Up to 10A / dm 2 Any current density value within the range.

[0066] Preferably, the DC electroplating time is 30 to 150 seconds.

[0067] Typically but not limiting, the time setting for the DC plating process can be 30s, 35s, 40s, 45s, 50s, 55s, 60s, 70s, 80s, 90s, 100s, 110s, 120s, 130s, 140s or 150s, or any time value within the range of 30 to 150s.

[0068] Furthermore, the solar cell silicon substrate is subjected to double-sided direct current electroplating to obtain a double-sided nickel-tungsten alloy coating.

[0069] Preferably, the copper plating is double-sided copper plating.

[0070] Preferably, the tinning is double-sided tinning.

[0071] Furthermore, the solar cell is an N-type TOPCon cell.

[0072] Preferably, the surface of the solar cell silicon substrate is provided with crisscross patterned grooves.

[0073] Preferably, the patterned groove has a width of 10-40 μm and a depth of 80-100 nm.

[0074] Typically but not restrictively, the width of the patterned groove can be set to 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 30μm, 35μm, 38μm or 40μm, or any width value in the range of 10μm to 40μm; the depth of the groove can be set to 80nm, 82nm, 84nm, 86nm, 88nm, 90nm, 92nm, 94nm, 96nm, 98nm or 100nm, or any depth value in the range of 80nm to 100nm.

[0075] Preferably, the nickel-tungsten alloy coating has a thickness of 1.0-1.5 μm.

[0076] Preferably, the copper layer obtained after the copper plating has a thickness of 8 to 12 μm.

[0077] Preferably, the thickness of the tin layer obtained after the tin plating is 1 to 2 μm.

[0078] Typically but not limiting, the thickness of the nickel-tungsten alloy coating can be 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm, or any thickness value within the range of 1.0 to 1.5 μm. Similarly, the thickness of the copper layer obtained after copper plating can be 8 μm, 9 μm, 10 μm, 11 μm or 12 μm, or any thickness value within the range of 8 μm to 12 μm. As for the tin layer obtained after tin plating, its thickness can be 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, or any thickness value within the range of 1 μm to 2 μm.

[0079] Furthermore, the method for preparing the metal electrode of a solar cell also includes a process of pickling the silicon substrate of the solar cell before direct current electroplating. In the process of preparing the metal electrode of the solar cell, the purpose of pickling the silicon substrate of the solar cell is to remove the oxide layer and other contaminants on the surface of the silicon substrate. The pickling process uses the chemical action of the acidic solution to effectively remove silicon oxide and other impurities on the silicon surface that may affect metal deposition, thereby ensuring that good electrical contact and mechanical bonding can be formed between the metal electrode and the silicon substrate. This step is crucial to improving the adhesion and conductivity of the electrode, and also helps to improve the performance and reliability of the final solar cell. Through pickling, the surface of the silicon substrate becomes cleaner and more active, providing a clean and more reactive surface for the subsequent metal electroplating process, thereby obtaining a better quality metal electrode layer.

[0080] Preferably, the pickling is performed using a hydrofluoric acid solution.

[0081] Preferably, the concentration of the hydrofluoric acid solution is 10-40 mL / L.

[0082] Preferably, the pickling time is 10 to 40 seconds.

[0083] Typically but not limiting, the concentration of the hydrofluoric acid solution can be 10 mL / L, 12 mL / L, 14 mL / L, 16 mL / L, 18 mL / L, 20 mL / L, 30 mL / L, 35 mL / L, 38 mL / L or 40 mL / L, or any concentration value within the range of 10 mL / L to 40 mL / L. Similarly, the time of the pickling process can be 10 s, 12 s, 14 s, 16 s, 18 s, 20 s, 30 s, 35 s, 38 s or 40 s, or any time value within the range of 10 s to 40 s.

[0084] The present invention is further described below by specific examples and comparative examples, but it should be understood that these examples are only used for more detailed description and should not be understood as limiting the present invention in any form. The raw materials used in the examples and comparative examples of the present invention, if no specific conditions are specified, are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0085] Example 1

[0086] The present embodiment provides a nickel-tungsten alloy electroplating solution, wherein the concentration of nickel sulfamate is 100 g / L, the concentration of sodium tungstate is 100 g / L, the concentration of citric acid is 40 g / L, and the concentration of diethylhexyl sodium sulfate is 0.5 g / L.

[0087] The preparation method of the above nickel-tungsten alloy electroplating solution is as follows:

[0088] First, weigh 100g of nickel sulfamate and dissolve it in pure water, then add 40g of citric acid and 0.5g of diethylhexyl sodium sulfate in turn, stir evenly to form a basic electroplating solution without tungstate, then add 100g of sodium tungstate, stir until completely dissolved, and then adjust the volume of the nickel-tungsten alloy electroplating solution to 1L, and detect the pH of the electroplating solution to be 6.0.

[0089] Example 2

[0090] The present embodiment provides a nickel-tungsten alloy electroplating solution, wherein the concentration of nickel sulfamate is 80 g / L, the concentration of sodium tungstate is 120 g / L, the concentration of citric acid is 40 g / L, and the concentration of diethylhexyl sodium sulfate is 0.5 g / L.

[0091] The preparation method of the above nickel-tungsten alloy electroplating solution is as follows:

[0092] First, weigh 80g of nickel sulfamate and dissolve it in pure water, then add 40g of citric acid and 0.5g of diethylhexyl sodium sulfate in turn, stir evenly to form a basic electroplating solution without tungstate, then add 120g of sodium tungstate, stir until completely dissolved, and then adjust the volume of the nickel-tungsten alloy electroplating solution to 1L, and detect the pH of the electroplating solution to be 6.0.

[0093] Example 3

[0094] The present embodiment provides a nickel-tungsten alloy electroplating solution, wherein the concentration of nickel sulfate is 60 g / L, the concentration of sodium tungstate is 200 g / L, the concentration of citric acid is 60 g / L, and the concentration of sodium n-octyl sulfate is 2 g / L.

[0095] The preparation method of the above nickel-tungsten alloy electroplating solution is as follows:

[0096] First, weigh 60g of nickel sulfate and dissolve it in pure water. Then add 60g of citric acid and 2g of sodium n-octyl sulfate in turn, stir evenly to form a basic electroplating solution without tungstate, then add 200g of sodium tungstate and stir until completely dissolved. Then adjust the volume of the nickel-tungsten alloy electroplating solution to 1L, and detect the pH of the electroplating solution to be 5.8.

[0097] Example 4

[0098] This embodiment provides a nickel-tungsten alloy electroplating solution, wherein the concentration of nickel chloride is 80 g / L, the concentration of sodium tungstate is 150 g / L, the concentration of tartaric acid is 50 g / L, and the concentration of sodium hydroxyethyl sulfonate is 1 g / L.

[0099] The preparation method of the above nickel-tungsten alloy electroplating solution is as follows:

[0100] First, weigh 80g of nickel chloride and dissolve it in pure water. Then add 50g of tartaric acid and 1g of sodium hydroxyethyl sulfonate in turn, stir evenly to form a basic electroplating solution without tungstate, then add 150g of sodium tungstate and stir until completely dissolved. Then adjust the volume of the nickel-tungsten alloy electroplating solution to 1L, and detect the pH of the electroplating solution to be 6.2.

[0101] Example 5

[0102] This embodiment provides a nickel-tungsten alloy electroplating solution. The difference from Embodiment 1 is that the concentration of nickel sulfamate is 20 g / L and the concentration of sodium tungstate is 200 g / L. The remaining raw materials and preparation steps are the same as those in Embodiment 1 and will not be repeated here.

[0103] Example 6

[0104] This embodiment provides a nickel-tungsten alloy electroplating solution. The difference from Embodiment 1 is that the concentration of nickel sulfamate is 20 g / L. The remaining raw materials and preparation steps are the same as those in Embodiment 1 and will not be repeated here.

[0105] Example 7

[0106] This embodiment provides a nickel-tungsten alloy electroplating solution. The difference from Embodiment 1 is that the concentration of nickel sulfamate is 10 g / L. The remaining raw materials and preparation steps are the same as those in Embodiment 1 and will not be repeated here.

[0107] Comparative Example 1

[0108] This comparative example provides a nickel electroplating solution, wherein the concentration of nickel sulfamate is 200 g / L, the concentration of citric acid is 40 g / L, and the concentration of diethylhexyl sodium sulfate is 0.5 g / L.

[0109] The preparation method of the above nickel-tungsten alloy electroplating solution is as follows:

[0110] First, weigh 200g of nickel sulfamate and dissolve it in pure water, then add 40g of citric acid and 0.5g of diethylhexyl sodium sulfate in sequence, stir until completely dissolved, then adjust the volume of the nickel electroplating solution to 1L, and detect the pH of the electroplating solution to be 5.0.

[0111] Comparative Example 2

[0112] This comparative example provides a nickel-tungsten alloy electroplating solution. The difference from Example 1 is that citric acid is not added, and the remaining raw materials are the same as those in Example 1, which will not be repeated here.

[0113] Comparative Example 3

[0114] This comparative example provides a tungsten electroplating solution, which is different from Example 1 in that nickel sulfamate is not added, and the concentration of sodium tungstate is 200 g / L. The remaining raw materials are the same as those in Example 1 and will not be repeated here.

[0115] Comparative Example 4

[0116] This comparative example provides a nickel-tungsten alloy electroplating solution. The difference from Example 1 is that no diethylhexyl sodium sulfate is added, and the remaining raw materials are the same as those in Example 1, which will not be repeated here.

[0117] Test Example 1

[0118] The solar cell silicon substrate after laser film opening was placed in the electroplating solution obtained in the embodiment and the comparative example for direct current electroplating at a current density of 5A / dm 2 The electroplating time was 2 min, and a solar cell silicon substrate (thickness of about 1.0 μm) with double-sided nickel-tungsten alloy was obtained. It was then placed in a high-temperature furnace (600-800°C) and baked for 1 h. The coating was observed to see if there was any discoloration or shedding of the grid lines, and the results were recorded in Table 1.

[0119] Table 1

[0120] Surface grid status Example 1 No discoloration, no shedding Example 2 No discoloration, no shedding Example 3 No discoloration, no shedding Example 4 No discoloration, no shedding Example 5 No discoloration, no shedding Example 6 No discoloration, some peeling Example 7 The grid line turns yellow and some of it falls off Comparative Example 1 The grid line turns yellow and some of it falls off Comparative Example 2 The grid line turns yellow and some of it falls off Comparative Example 3 Tungsten is difficult to plate Comparative Example 4 No discoloration, some peeling

[0121] It can be seen from Table 1 that with the increase of the mass fraction of tungsten in the nickel-tungsten alloy coating, the density and continuity of the nickel oxide film are destroyed, the protective ability of the inside of the coating is weakened, the internal stress becomes larger, and the oxide film formed under high temperature conditions has a loose layered structure, and the gate line is easy to fall off; this shows that the nickel-tungsten alloy coating with a suitable proportion has good high temperature resistance and oxidation resistance, is not easily oxidized in the air, and is suitable for long-term storage.

[0122] Test Example 2

[0123] The solar cell silicon substrate obtained in Test Example 1 was placed in a copper electroplating solution (current density 25 A / dm 2 , plating time 4min) and tin plating solution (current density 5A / dm 2 The solar cell was obtained by direct current electroplating in 200 μm (200 μm) for 2 min and electroplating time for 2 min, and then the electrical performance was tested, including photoelectric conversion efficiency, open circuit voltage, series resistance, etc. Specifically, IV test was adopted, and the test was conducted at a temperature of 25° C. and an AM of 1.5 G. The obtained data are shown in Table 2 below.

[0124] In Table 2, Eta (%) refers to the efficiency of the solar cell, which refers to the efficiency of the solar cell in converting the received solar radiation energy into electrical energy, usually expressed as a percentage. Uoc (V) is the open-circuit voltage. This refers to the voltage when there is no current flowing through the two ends of the solar cell (that is, when the circuit is disconnected). The open-circuit voltage is the voltage value that the battery can provide without a load, and the unit is V. Isc (A) refers to the short-circuit current, which refers to the current flowing through the battery when the two ends of the solar cell are directly short-circuited. The short-circuit current is the current value that the battery can provide when there is no external load, and the unit is A. FF (%) is the fill factor, which refers to the product of the ratio of the current and voltage of the solar cell under the actual working state to the current and voltage under the ideal condition (that is, the current and voltage at the maximum power point), usually expressed as a percentage.

[0125] Table 2

[0126] Eta(%) Uoc(V) Isc(A) FF(%) Rs(Ω) Example 1 26.47 0.7223 18.63 86.77 0.00057 Example 2 26.41 0.7217 18.58 86.85 0.00055 Example 3 26.35 0.7208 18.54 86.54 0.00060 Example 4 26.31 0.7197 18.51 86.34 0.00068 Example 5 26.26 0.7215 18.48 86.80 0.00072 Example 6 26.20 0.7195 18.48 86.96 0.00075 Example 7 26.13 0.7192 18.47 86.70 0.00076 Comparative Example 1 25.92 0.7223 18.59 85.17 0.00096 Comparative Example 2 26.08 0.7176 18.55 86.53 0.00084 Comparative Example 3 23.88 0.7045 18.18 83.71 0.00367 Comparative Example 4 25.96 0.7167 18.45 86.62 0.00078

[0127] It can be seen from Table 2 that the use of nickel-tungsten alloy as the diffusion barrier layer of electroplated solar cells has a good barrier effect on the conductive layer metal, which can increase the conductivity of solar cells, reduce series resistance, and improve the photoelectric conversion efficiency of solar cells.

[0128] 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 protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; 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 be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A nickel-tungsten alloy electroplating solution, It is characterized in that Includes nickel salt, tungstate, complexing agent, wetting agent and water.

2. The nickel-tungsten alloy electroplating solution according to claim 1, It is characterized in that Calculated by weight, each unit volume of the nickel-tungsten alloy electroplating solution includes 20 to 100 parts of nickel salt, 100 to 200 parts of tungstate, 20 to 80 parts of complexing agent, 0.2 to 1 part of wetting agent, and the balance is water.

3. The nickel-tungsten alloy electroplating solution according to claim 1 or 2, It is characterized in that The nickel salt comprises at least one of nickel sulfate, nickel chloride and nickel sulfamate; Preferably, the tungstate comprises sodium tungstate and / or potassium tungstate; Preferably, the complexing agent comprises at least one of citric acid, tartaric acid, pyrophosphoric acid, tartrate, citrate and pyrophosphate; Preferably, the wetting agent comprises at least one of sodium diethylhexyl sulfate, sodium n-octyl sulfate, sodium isethionate and sodium succinate; Preferably, the water comprises pure water.

4. A method for preparing the nickel-tungsten alloy electroplating solution according to any one of claims 1 to 3, It is characterized in that The nickel salt, the complexing agent and the wetting agent are added into water and stirred evenly, and finally the tungstate is added and stirred evenly to obtain the nickel-tungsten alloy electroplating solution.

5. The preparation method according to claim 4, It is characterized in that The pH value of the nickel-tungsten alloy electroplating solution is 5.0-8.

0.

6. A method for preparing a metal electrode for a solar cell, It is characterized in that Placing the solar cell silicon substrate in a nickel-tungsten alloy electroplating solution for direct current electroplating to obtain a nickel-tungsten alloy coating; Then, copper plating and tin plating are performed on the nickel-tungsten alloy plating layer to obtain a solar cell metal electrode; Wherein, the nickel-tungsten alloy electroplating solution is the nickel-tungsten alloy electroplating solution according to any one of claims 1 to 3.

7. The preparation method according to claim 6, It is characterized in that In the direct current electroplating, the solar cell silicon substrate is used as the cathode and the titanium mesh is used as the anode; Preferably, the temperature of the DC electroplating is 50-70°C, and the current density is 4-10A / dm 2 ; Preferably, the DC electroplating time is 30 to 150 seconds.

8. The preparation method according to claim 6, It is characterized in that Performing double-sided direct current electroplating on the solar cell silicon substrate to obtain double-sided nickel-tungsten alloy coatings; Preferably, the copper plating is double-sided copper plating; Preferably, the tinning is double-sided tinning.

9. The preparation method according to claim 6, It is characterized in that The solar cell is an N-type TOPCon cell; Preferably, the surface of the solar cell silicon substrate is provided with crisscross patterned grooves; Preferably, the width of the patterned groove is 10-40 μm and the depth is 80-100 nm; Preferably, the thickness of the nickel-tungsten alloy coating is 1.0 to 1.5 μm; Preferably, the thickness of the copper layer obtained after the copper plating is 8 to 12 μm; Preferably, the thickness of the tin layer obtained after the tin plating is 1 to 2 μm.

10. The preparation method according to any one of claims 6 to 9, It is characterized in that It also includes a process of pickling the solar cell silicon substrate before direct current electroplating; Preferably, the pickling is carried out using a hydrofluoric acid solution; Preferably, the concentration of the hydrofluoric acid solution is 10 to 40 mL / L; Preferably, the pickling time is 10 to 40 seconds.