Chemical tinning agent, preparation method thereof and application of chemical tinning agent in preparation of solar cell

Abstract

The invention provides a chemical tinning agent, a preparation method thereof and application of the chemical tinning agent in preparation of solar cells, and relates to the technical field of photovoltaic cell manufacturing, and the chemical tinning agent comprises the following components: main salt, a second reducing agent and a second composite complexing agent; the main salt comprises stannous mono-sulphate, copper sulfate and sodium persulfate; the second composite complexing agent comprises one or more of sodium gluconate, citric acid and glutamic acid. The invention solves the problems of high energy consumption, noble metal dependence, poor uniformity, poor adhesive force and the like in the traditional chemical plating process, realizes low energy consumption and high productivity, ensures that the grid line has good adhesive force and uniformity, prolongs the service life of the plating solution, and reduces the maintenance cost.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cell manufacturing, in particular to a chemical tin plating agent, a preparation method thereof and application in the preparation of solar cells. Background Art

[0002] Metallization is a key process in the manufacture of silicon solar cells. It's primarily used to create electrodes, forming ohmic contacts between the two ends of the PN junction and enabling current output. Screen printing is currently the most mature and common metallization process, but the high cost of the silver paste used has become a significant constraint on industry adoption. To reduce solar cell costs and improve cell efficiency, copper electroplating technology offers the greatest potential for cost reduction, as it eliminates the need for silver paste.

[0003] In the current photovoltaic cell copper manufacturing process, conductive copper grid lines are mainly formed on the silicon substrate surface by electroplating or chemical copper plating. The commonly used plating solution formula in the prior art usually contains copper sulfate (CuSO4), acidic additives (such as sulfuric acid), wetting agents (such as polyethylene glycol) and a small amount of chloride ions (Cl - The process steps include substrate pretreatment, preparation of a seed layer to prevent copper diffusion, electroplating of copper as a conductive layer, and finally electroplating of a protective layer and post-cleaning.

[0004] In order to reduce costs, some researchers have used screen-printed thin silver layers as seed layers and then electroplated copper as the main conductive layer, but this method does not have a significant advantage in reducing silver costs. It was further proposed to use electroplating technology to prepare front and back electrodes. Usually, nickel layers are first prepared on both sides as seed layers, and then copper is electroplated on both sides as a conductive layer. Finally, tin is electroplated on both sides as a protective layer, and finally a double-sided electroplated solar cell is obtained. Although this method completely replaces the use of silver, it may cause uneven coating thickness due to the purity of the plating solution and uneven current distribution, thereby affecting the conductive efficiency. At the same time, the internal stress of the coating is large, and there is a problem of poor bonding between the coating and the silicon substrate. In addition, the stability of the plating solution is low, the additives in the traditional formula are easy to decompose, and the accumulation of by-products leads to a short life of the plating solution, which requires frequent replacement and high cost.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] One of the purposes of the present invention is to provide a chemical tin plating agent to at least solve one of the technical problems existing in the prior art.

[0007] A second object of the present invention is to provide a method for preparing a chemical tin plating agent.

[0008] The third object of the present invention is to provide a chemical tin plating agent or the use of the chemical tin plating agent prepared by the preparation method in the preparation of solar cells.

[0009] A fourth object of the present invention is to provide a solar cell.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0011] In a first aspect, the present invention provides a chemical tin plating agent comprising the following components: a main salt, a second reducing agent, and a second complexing agent;

[0012] The main salts include stannous sulfate, copper sulfate and sodium persulfate;

[0013] The second complexing agent includes one or more of sodium gluconate, citric acid and glutamic acid.

[0014] Furthermore, the second reducing agent includes dimethylaminoborane and / or ascorbic acid.

[0015] Furthermore, the chemical tin plating agent further comprises a pH buffer, a second stabilizer and a surfactant;

[0016] Preferably, the pH buffer comprises one or more of boric acid, acetic acid-sodium acetate, sodium dihydrogen phosphate / disodium hydrogen phosphate;

[0017] Preferably, the second stabilizer includes one or more of polyethylene glycol and thiourea;

[0018] Preferably, the surfactant includes one or more of sodium dodecylbenzenesulfonate, polyethylene glycol octylphenyl ether, and perfluoroalkyl sulfonate.

[0019] Furthermore, the chemical tin plating agent includes the following components: 10-20 g / L stannous sulfate, 1-2 g / L copper sulfate, 30-50 g / L sodium persulfate, 5-10 g / L dimethylamino borane, 5-10 g / L ascorbic acid, 20-30 g / L sodium gluconate, 5-10 g / L citric acid, 5-10 g / L glutamic acid, 5-8 g / L pH buffer, 0.1-0.5 g / L stabilizer and 0.1-0.3 g / L surfactant, and the balance is water.

[0020] Furthermore, the pH of the chemical tin plating agent is 4.0-5.5.

[0021] In a second aspect, the present invention provides a method for preparing a chemical tin plating agent, comprising mixing a main salt, a second reducing agent, and a second composite complexing agent in a prescribed amount to obtain the chemical tin plating agent.

[0022] In a third aspect, the present invention provides a chemical tin plating agent or the use of the chemical tin plating agent prepared by the preparation method in the preparation of solar cells.

[0023] In a fourth aspect, the present invention provides a solar cell, wherein the preparation method comprises: forming patterned grooves on the front and back surfaces of a silicon substrate, and then sequentially forming a nickel layer, a copper layer, and a tin layer in the patterned grooves;

[0024] Wherein, the tin layer is prepared by using the chemical tin plating agent or the chemical tin plating agent prepared by the preparation method.

[0025] Furthermore, during the preparation of the tin layer, the tin plating temperature is 25-40° C. and the tin plating time is 1-4 minutes;

[0026] Preferably, an ultrasonic device is provided during chemical tin plating, and the ultrasonic frequency is 20-40 KHz.

[0027] Furthermore, the thickness of the nickel layer is 0.1-2 um; the thickness of the copper layer is 9-12 um; and the thickness of the tin layer is 1-2 um.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The chemical tin plating agent provided by the present invention comprises stannous sulfate, copper sulfate and sodium persulfate in the main salt system; stannous sulfate is used as the tin ion source; copper sulfate is used to catalyze the reduction reaction; 2 + with Sn 2 + replacement reaction accelerates Sn deposition while inhibiting Sn 2 + oxidation; sodium persulfate is used to oxidize and clean the surface of the substrate, remove oxides and activate the metal, enhance the adhesion of the coating, and form a dynamic balance with the second reducing agent to avoid excessive corrosion. The present invention also achieves Sn by adding a second composite complexing agent 2 + high stability, while preventing the plating layer from generating pores and improving the density. In addition, the chemical tin plating agent provided by the present invention realizes Sn 2 + high stability, while improving the stability of the plating solution. DETAILED DESCRIPTION

[0030] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear; however, in the event of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, the use of "or" means "and / or" unless otherwise stated. In addition, the use of the term "including" and other forms is non-limiting.

[0031] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] The first aspect of the present invention provides a chemical tin plating agent, comprising the following components: a main salt, a second reducing agent, and a second composite complexing agent;

[0033] The main salts include stannous sulfate, copper sulfate, and sodium persulfate. Stannous sulfate (SnSO) provides a source of tin ions. A high concentration can easily lead to turbidity in the plating solution and requires a complexing agent for stabilization. Copper sulfate acts as a catalyst. Sodium persulfate is used to clean and activate the metal surface, improving the adhesion and uniformity of the electroplated layer.

[0034] The second composite complexing agent includes one or more of sodium gluconate, citric acid and glutamic acid, which can improve the stability of the plating solution at room temperature.

[0035] In some preferred embodiments, the chemical tin plating agent further comprises a pH buffer, a second stabilizer and a surfactant;

[0036] Preferably, the second reducing agent comprises dimethylaminoborane and / or ascorbic acid, thereby achieving environmentally friendly reduction and improving reduction efficiency.

[0037] Preferably, the chemical tin plating agent comprises the following components: 10-20 g / L stannous sulfate, 1-2 g / L copper sulfate; 30-50 g / L sodium persulfate, 5-10 g / L dimethylaminoborane, 5-10 g / L ascorbic acid; 20-30 g / L sodium gluconate, 5-10 g / L citric acid, 5-10 g / L glutamic acid, 5-8 g / L pH buffer, 0.1-0.5 g / L stabilizer and 0.1-0.3 g / L surfactant, with the balance being water.

[0038] In the chemical tin plating agent, the concentration of stannous sulfate is 10-20 g / L, for example, 10 g / L, 15 g / L, 20 g / L, etc.;

[0039] In the chemical tin plating agent, the concentration of copper sulfate is 1-2 g / L, for example, 1 g / L, 1.5 g / L, 2 g / L, etc.;

[0040] In the chemical tin plating agent, the concentration of sodium persulfate is 30-50 g / L, for example, 30 g / L, 40 g / L, 50 g / L, etc.;

[0041] In the chemical tin plating agent, the concentration of dimethylaminoborane is 5-10 g / L, for example, 5 g / L, 7.5 g / L, 10 g / L, etc.;

[0042] In the chemical tin plating agent, the concentration of ascorbic acid is 5-10 g / L, for example, 5 g / L, 7.5 g / L, 10 g / L, etc.;

[0043] In the chemical tin plating agent, the concentration of sodium gluconate is 20-30 g / L; for example, it can be 20 g / L, 25 g / L, 30 g / L, etc.;

[0044] In the chemical tin plating agent, the concentration of citric acid is 5-10 g / L, for example, 5 g / L, 7.5 g / L, 10 g / L, etc.;

[0045] In the chemical tin plating agent, the concentration of glutamic acid is 5-10 g / L, for example, 5 g / L, 7.5 g / L, 10 g / L, etc.;

[0046] In the chemical tin plating agent, the concentration of the pH buffer is 5-8 g / L, for example, 5 g / L, 7.5 g / L, 10 g / L, etc.;

[0047] In the chemical tin plating agent, the concentration of the stabilizer is 0.1-0.5 g / L, for example, 0.1 g / L, 0.3 g / L, 0.5 g / L, etc.;

[0048] In the chemical tin plating agent, the concentration of the surfactant is 0.1-0.3 g / L, for example, 0.1 g / L, 0.2 g / L, 0.3 g / L, etc.

[0049] Preferably, the pH buffer includes one or more of boric acid (H3BO3), acetic acid-sodium acetate, sodium dihydrogen phosphate / disodium hydrogen phosphate; and is used to stabilize the pH value, reduce the need for sulfuric acid adjustment, and alleviate damage to the silicon wafer.

[0050] Preferably, the stabilizer includes one or more of polyethylene glycol (PEG-600) and thiourea;

[0051] Preferably, the surfactant includes one or more of sodium dodecylbenzenesulfonate (SDBS), polyethylene glycol octylphenyl ether, and perfluoroalkyl sulfonate, which are used to reduce surface tension and improve coating uniformity.

[0052] In the present invention, when a chemical tin plating agent is used, the tin plating conditions are room temperature (temperature 25-40°C), and the pH value of the chemical tin plating agent is 4.0-5.5. Using the chemical tin plating agent for tin plating can effectively avoid the problems of high energy consumption and low production capacity of the conventional low-temperature (5-10°C) electroplating tin process and excessive bubbles in the traditional electroplating solution circulation process.

[0053] The chemical tin plating agent provided by the present invention realizes an efficient and stable tin plating process at room temperature through the synergistic effect of various components, wherein the components have the following coordination relationship:

[0054] 1. Synergistic effect of the main salt system:

[0055] (1) Stannous sulfate: As a tin ion source, the concentration is controlled at 10-20g / L to avoid turbidity in the plating solution. It is necessary to rely on complexing agents to stabilize Sn. 2+ ;

[0056] (2) Copper sulfate (CuSO4): catalyzes the reduction reaction, through trace amounts of Cu 2+ With Sn 2+ The replacement reaction accelerates Sn deposition while inhibiting Sn 2+ oxidation;

[0057] (3) Sodium persulfate (Na2S2O8): Oxidatively cleans the substrate surface, removes oxides, activates the metal, enhances coating adhesion, and forms a dynamic equilibrium with the reducing agent to prevent excessive corrosion. Copper salt catalysis replaces traditional Pd activation, reducing costs. The oxidizing properties of sodium persulfate work synergistically with the reducing agent to achieve simultaneous surface activation and reduction deposition.

[0058] 2. Environmentally friendly reducing agent combination, dimethylaminoborane + ascorbic acid:

[0059] Dimethylaminoborane provides strong reducing properties (efficiently reducing Sn at room temperature 2+ ), ascorbic acid inhibits the rapid decomposition of dimethylaminoborane and prolongs the life of the plating solution; ascorbic acid acts as an antioxidant to reduce Sn 2+ Oxidized to Sn 4+ , avoiding turbidity in the plating solution. Compared to traditional formaldehyde or hypophosphite, dimethylaminoborane is non-toxic and ascorbic acid is biodegradable, meeting environmental requirements. The two work together to improve reduction efficiency, increasing the deposition rate by 20%-30% at room temperature.

[0060] 3. Stabilizing effect of complex complexing agent, sodium gluconate + citric acid + glutamic acid:

[0061] (1) Sodium gluconate: preferentially complexes Sn 2+ , to prevent Sn(OH)2 precipitation under alkaline conditions;

[0062] (2) Citric acid: broadens the pH buffer range (4.0-5.5) and synergistically stabilizes pH with boric acid;

[0063] (3) Glutamate: inhibits Cu 2+ Over-catalysis can prevent local deposition from being too rapid.

[0064] The ternary complexing agent system realizes Sn 2+The introduction of glutamic acid reduces pinholes in the coating and improves density.

[0065] 4. Synergy of pH buffer and stabilizer

[0066] (1) Boric acid: forms a B(OH)4-buffer pair under weak acidic conditions, reducing the effect of pH fluctuations on deposition;

[0067] (2) Polyethylene glycol: adsorbed on the surface of the substrate, inhibiting dendrite growth and improving the flatness of the coating;

[0068] Boric acid and citric acid form a double buffer, reducing the frequency of sulfuric acid addition and the risk of acid corrosion on silicon wafers;

[0069] 5. PEG-600 and SDBS jointly reduce surface tension, synergistically enhance the wettability of the plating solution, avoid the retention of hydrogen bubbles, and reduce the thickness deviation of the tin layer.

[0070] Therefore, the chemical tin plating agent provided by the present invention has the following advantages:

[0071] 1. High-speed chemical tin plating at room temperature: Optimize the complexing agent in the acidic tin plating solution to achieve tin plating at room temperature, reduce energy consumption, and eliminate the problem of bath decomposition caused by heating. At the same time, through the catalysis-complexation-reduction ternary system, a high deposition rate is achieved at 25-40°C, and energy consumption is reduced by 60% compared to low-temperature electroplating.

[0072] 2. Environmental protection: No cyanide or formaldehyde, and the difficulty of wastewater treatment is significantly reduced.

[0073] 3. Coating quality: The composite additives prevent the coating from generating pores, and the welding performance is better than that of traditional processes.

[0074] 4. Process stability: The life of the plating solution is extended, suitable for continuous production.

[0075] The present invention adopts a room-temperature chemical tin plating method, avoiding the commonly used low-temperature tin plating, accelerating the tin plating speed, and effectively avoiding the high energy consumption, low production capacity and insufficient production capacity of the conventional low-temperature electrotin plating process; the chemical nickel plating agent provided by the present invention realizes copper-based self-activated tin plating, and selectively enhances the surface reactivity of the copper substrate to initiate the reaction by adding sodium persulfate and sodium dodecylbenzenesulfonate surfactants, without the need for an additional activation step, and the plating uniformity and bonding strength are better.

[0076] In summary, the chemical nickel plating agent and chemical tin plating agent provided by the present invention solve the pain points of traditional chemical plating processes such as high energy consumption, dependence on precious metals, uniformity, and poor adhesion through the four-dimensional innovation of "low-temperature deposition + palladium-free catalysis + high speed at room temperature + self-activation", achieving low energy consumption and high production capacity. The gate lines have good adhesion and uniformity, extending the service life of the plating solution and reducing maintenance costs.

[0077] The second aspect of the present invention provides a method for preparing a chemical tin plating agent, which comprises mixing a main salt, a second reducing agent and a second composite complexing agent in a prescribed amount to obtain the chemical tin plating agent.

[0078] A third aspect of the present invention provides a chemical tin plating agent or use of the chemical tin plating agent prepared by the preparation method in preparing solar cells.

[0079] The fourth aspect of the present invention provides a chemical nickel plating agent, comprising the following components: a nickel salt, a first reducing agent, a first complexing agent, and an activator;

[0080] The first composite complexing agent includes one or more of ethylenediaminetetraacetic acid, sodium citrate (C6H5Na3O7), glycine (C2H5NO2) and potassium sodium tartrate; the composite complexing agent system can improve the stability and uniformity of the plating solution and enhance the anti-pollution ability of the plating solution.

[0081] The activator includes sodium borohydride, which cooperates with the composite complexing agent system to promote the self-catalyzed growth of nickel plating.

[0082] The chemical nickel plating agent provided by the present invention realizes low temperature, low consumption and high quality metal deposition. By developing the plating solution formula, a composite organic complexing agent is used to replace the traditional high temperature process. The composite organic complexing agent combination stabilizes Ni through multidentate coordination. 2+ , to prevent nickel ions from hydrolyzing or forming hydroxide precipitation at low temperatures (the solubility decreases at low temperatures and easily causes precipitation); different complexing agents have different effects on Ni 2 + complex strength gradient, regulating the free Ni 2+ The release rate can avoid the roughness or pores caused by too fast deposition at low temperature, and the complex complex can mask Fe 2+ 、Cu 2+ Impurity ions such as ions are removed, reducing the negative impact of impurities on the coating at low temperatures. Nickel layer deposition can be achieved at 20-40°C, with significantly improved bonding strength, good coating thickness uniformity, and prolonged plating solution stability. Palladium-free autocatalytic nickel plating: By introducing a nickel ion-reducing agent and sodium borohydride synergistic activation mechanism, nano-nickel catalytic cores are generated in situ on the substrate surface, completely eliminating the dependence on precious metal palladium.

[0083] In some preferred embodiments, the chemical nickel plating agent further comprises one or more of a buffer, a first stabilizer, an accelerator, and a wetting agent;

[0084] Preferably, the chemical nickel plating agent includes the following components: 20-30 g / L nickel salt, 3-6 g / L first reducing agent, 3-5 g / L ethylenediaminetetraacetic acid, 15-25 g / L sodium citrate, 5-10 g / L glycine, 0.5-1 g / L potassium sodium tartrate, 1-3 g / L activator, 8-12 g / L buffer, 1-2 mg / L first stabilizer, 0.1-0.3 g / L accelerator and 0.2-0.5 g / L wetting agent, with the balance being water.

[0085] In the chemical nickel plating agent, the concentration of nickel salt is 20-30 g / L, for example, 20 g / L, 25 g / L, 30 g / L, etc.;

[0086] In the chemical nickel plating agent, the concentration of the first reducing agent is 3-6 g / L, for example, 3 g / L, 4 g / L, 5 g / L, 6 g / L, etc.;

[0087] In the chemical nickel plating agent, the concentration of EDTA is 3-5 g / L, for example, 3 g / L, 4 g / L, 5 g / L, etc.

[0088] In the chemical nickel plating agent, the concentration of sodium citrate is 15-25 g / L, for example, 15 g / L, 20 g / L, 25 g / L, etc.;

[0089] In the chemical nickel plating agent, the concentration of glycine is 5-10 g / L, for example, 5 g / L, 7.5 g / L, 10 g / L, etc.;

[0090] In the chemical nickel plating agent, the concentration of potassium sodium tartrate is 0.5-1 g / L, for example, 0.5 g / L, 0.75 g / L, 1 g / L, etc.;

[0091] In the chemical nickel plating agent, the concentration of the activator is 1-3 g / L, for example, 1 g / L, 2 g / L, 3 g / L, etc.;

[0092] In the chemical nickel plating agent, the concentration of the buffer is 8-12 g / L, for example, 8 g / L, 10 g / L, 12 g / L, etc.;

[0093] In the chemical nickel plating agent, the concentration of the first stabilizer is 1-2 mg / L, for example, 1 mg / L, 1.5 mg / L, 2 mg / L, etc.;

[0094] In the chemical nickel plating agent, the concentration of the accelerator is 0.1-0.3 g / L, for example, 0.1 g / L, 0.2 g / L, 0.3 g / L, etc.;

[0095] In the chemical nickel plating agent, the concentration of the wetting agent is 0.2-0.5 g / L, for example, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, etc.;

[0096] Preferably, the nickel salt includes one or more of nickel sulfate (NiSO4·6H2O), nickel chloride, and nickel sulfamate; its function is to provide a nickel ion source. A too low concentration leads to a low deposition rate, and a too high concentration easily causes decomposition of the plating solution.

[0097] Preferably, the first reducing agent comprises one or more of dimethylamine borane (DMAB), sodium hypophosphite (NaH2PO2), and sodium borohydride; preferably dimethylamine borane.

[0098] Preferably, the buffer comprises one or more of boric acid (H3BO3) and sodium acetate, and is used to maintain pH stability.

[0099] Preferably, the first stabilizer includes one or more of thiourea (CH4N2S), 2-mercaptobenzothiazole (MBT), potassium iodate, and lead acetate; and can ensure the coating quality of the plating solution at low temperatures.

[0100] Preferably, the accelerator includes one or more of sodium fluoride (NaF) and ammonium fluoride to accelerate the deposition rate;

[0101] Preferably, the wetting agent includes one or more of polyethylene glycol (PEG-600) and sodium lauryl sulfate, which can reduce surface tension and reduce the porosity of the coating.

[0102] In the present invention, the pH of the chemical nickel plating agent is 8.5-9.5, and the nickel plating temperature is 20-40° C. The chemical nickel plating agent provided by the present invention has advantages in terms of plating solution stability, deposition rate, coating adhesion, etc. The components in the chemical nickel plating agent have the following coordination relationship:

[0103] 1. Main salt and reducing agent synergistic system:

[0104] (1) Nickel sulfate and dimethylamine borane form a "nickel source-organoboron reduction" binuclear system: DMAB decomposes under weak alkaline conditions to release active [H], which preferentially reacts with the complexed Ni 2+ Combine to form Ni-H intermediate;

[0105] (2) Sodium borohydride generates H- and BH4- through hydrolysis, inducing the formation of Ni-B nanocrystal nuclei on the substrate surface (sodium borohydride acts as an activator and works together with DMAB to generate nano-nickel nuclei, thus eliminating the need for a palladium catalyst), achieving palladium-free activation;

[0106] (3) The dual reduction pathway (DMAB+NaBH4) significantly improves the nickel ion reduction efficiency at low temperatures and significantly increases the deposition rate.

[0107] 2. Dynamic balance of complex complexing agent:

[0108] (1) EDTA: Strong chelation effect stabilizes free Ni 2+ , inhibiting nickel hydroxide precipitation;

[0109] (2) Sodium citrate: weak complexing properties regulate ion release rate and improve coating uniformity;

[0110] (3) Glycine: adsorbed on the substrate surface to form an oriented molecular film, reducing the interfacial energy difference and enhancing the binding force;

[0111] The above three form a gradient complex network, making Ni 2+ The concentration is always in a metastable state, and the life of the plating solution is extended.

[0112] 3. Combined effect of stabilizer and accelerator

[0113] (1) Thiourea is selectively adsorbed on the catalytic sites with high activity, inhibiting the self-decomposition of the plating solution;

[0114] (2) Sodium fluoride through F - Etch the oxide layer on the substrate surface, synchronously with H + Combined with accelerated H escape, it reduces the porosity of the coating.

[0115] At the same time, the present invention introduces a complexing agent, potassium sodium tartrate, which can preferentially complex impurity ions and improve the anti-pollution ability of the plating solution; polyethylene glycol (PEG-600) is used as a wetting agent to reduce surface tension and cooperate with the composite complexing agent to improve deep hole coverage and enhance uniformity, thereby ensuring bonding strength;

[0116] Furthermore, electroless nickel plating on silicon substrates for solar cells is inherently difficult and, unlike traditional metals, often requires palladium activation. Therefore, a NiSO4-DMAB-NaBH4 ternary system is used to directly generate a Ni-B catalytic layer on the surface of the ABS / FR4 substrate, replacing the traditional palladium activation process and reducing costs. Thiourea / EDTA / sodium citrate form a three-dimensional stable network, raising the decomposition trigger temperature of the plating solution to 55°C (compared to the industry average of 45°C).

[0117] Therefore, the chemical nickel plating agent provided by the present invention avoids the high temperature conditions during conventional nickel plating, improves adhesion and uniformity, and increases production efficiency; the chemical nickel plating agent does not require palladium catalysis, and promotes the self-catalyzed growth of nickel plating through the synergistic design of components; the composite complexing agent enhances the stability and service life of the plating solution; the chemical nickel plating agent provided by the present invention improves low-temperature adaptability, palladium-free catalysis and plating solution stability through the synergistic design of components.

[0118] A fifth aspect of the present invention provides a method for preparing a chemical nickel plating agent, comprising mixing a nickel salt, a first reducing agent, a first complexing agent and an activator in a prescribed amount to obtain the chemical nickel plating agent.

[0119] The chemical nickel plating agent provided by the present invention, the first composite complexing agent avoids excessive local deposition by stabilizing the nickel ion concentration and improves uniformity; the activator and the first reducing agent promote the uniform reduction deposition of nickel, enhance the density of the coating, and significantly improve the bonding force; the buffer maintains the pH stability of the plating solution, and the wetting agent improves the wettability of the substrate surface, jointly optimizing the bonding force and the covering effect; the nickel ions are stabilized by the first composite complexing agent, and by introducing the nickel ion-first reducing agent, sodium borohydride is used as the activator, and the sodium borohydride synergistic activation mechanism is adopted to generate nano nickel catalytic cores in situ on the substrate surface, completely getting rid of the dependence on precious metal palladium, thereby eliminating the need for a palladium catalyst, and sodium borohydride and the first composite complexing agent can further promote autocatalysis. The chemical nickel plating agent provided by the present invention realizes palladium-free catalysis while improving the stability of the plating solution.

[0120] A sixth aspect of the present invention provides a chemical nickel plating agent or use of the chemical nickel plating agent prepared by the preparation method in the preparation of solar cells.

[0121] A seventh aspect of the present invention provides a solar cell, wherein the preparation method comprises: forming patterned grooves on the front and back surfaces of a silicon substrate, and then sequentially forming a nickel layer, a copper layer, and a tin layer in the patterned grooves;

[0122] Wherein, the nickel layer is prepared by using the chemical nickel plating agent; the tin layer is prepared by using the chemical tin plating agent.

[0123] In some preferred embodiments, during the preparation of the nickel layer, the nickel plating temperature is 20-40° C., for example, 20° C., 30° C., 40° C., etc.; the nickel plating time is 2-8 min, for example, 2 min, 4 min, 6 min, 8 min, etc.; the pH of the chemical nickel plating agent is 8.5-9.5;

[0124] Preferably, an ultrasonic device is provided during the electroless nickel plating process; the ultrasonic frequency is 20-40 KHz, for example, 20 KHz, 30 KHz, 40 KHz, etc.;

[0125] Preferably, the nickel-plated battery cell is pickled; the pickling time is 70-90 seconds, for example, 70 seconds, 80 seconds, 90 seconds, etc.; the pickling solution includes a 15-20% sulfuric acid solution, for example, 15%, 16%, 17%, 18%, 19%, 20%, etc.;

[0126] Preferably, during the preparation of the tin layer, the tin plating temperature is 25-40° C., for example, 25° C., 30° C., 35° C., 40° C., etc.; the tin plating time is 1-4 minutes, for example, 1 minute, 2 minutes, 3 minutes, 4 minutes, etc.; the pH of the chemical tin plating agent is 4.0-5.5;

[0127] Preferably, an ultrasonic device is provided during chemical tin plating, and the ultrasonic frequency is 20-40 KHz, for example, 20 KHz, 30 KHz, 40 KHz, etc.;

[0128] Preferably, the thickness of the nickel layer is 0.1-2 um; the thickness of the copper layer is 9-12 um; and the thickness of the tin layer is 1-2 um.

[0129] Preferably, the width of the patterned groove is 10-50 μm; the depth of the patterned groove is 80-100 nm.

[0130] Preferably, after patterned grooves are formed on the front and back sides of the silicon substrate, acid washing is performed before forming the metal layer;

[0131] Preferably, the pickling solution used for pickling includes hydrofluoric acid; the concentration of the hydrofluoric acid is 10-20 mL / L; the temperature of the hydrofluoric acid is 25-38° C.; and the pickling time is 5-50 s.

[0132] Preferably, the double-sided copper layer is electroplated by constant current plating or pulse plating or constant current light induced plating or pulse light induced plating.

[0133] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0134] Preparation Example 1

[0135] This preparation example provides a chemical nickel plating agent, comprising the following components: 25 g / L nickel salt (specifically nickel sulfate), 4.5 g / L first reducing agent (specifically dimethylamine borane), 4.5 g / L ethylenediaminetetraacetic acid, 20 g / L sodium citrate, 7.5 g / L glycine, 0.75 g / L potassium sodium tartrate, 2 g / L activator (specifically sodium borohydride), 10 g / L buffer (specifically boric acid), 1.5 mg / L first stabilizer (specifically thiourea), 0.2 g / L accelerator (specifically sodium fluoride) and 0.35 g / L wetting agent (specifically polyethylene glycol), with the balance being water.

[0136] Preparation Example 2

[0137] This preparation example provides an electroless nickel plating agent comprising the following components: 20 g / L nickel salt, 6 g / L first reducing agent, 3 g / L ethylenediaminetetraacetic acid, 25 g / L sodium citrate, 5 g / L glycine, 1 g / L potassium sodium tartrate, 1 g / L activator, 12 g / L buffer, 1 mg / L first stabilizer, 0.3 g / L accelerator, and 0.2 g / L wetting agent, with the balance being water.

[0138] The specific selection of components is consistent with that in Preparation Example 1.

[0139] Preparation Example 3

[0140] This preparation example provides an electroless nickel plating agent comprising the following components: 30 g / L nickel salt, 3 g / L first reducing agent, 5 g / L ethylenediaminetetraacetic acid, 15 g / L sodium citrate, 10 g / L glycine, 0.5 g / L potassium sodium tartrate, 3 g / L activator, 8 g / L buffer, 1 mg / L first stabilizer, 0.1 g / L accelerator, and 0.5 g / L wetting agent, with the balance being water.

[0141] The specific selection of components is consistent with that in Preparation Example 1.

[0142] Preparation Example 4

[0143] This preparation example provides a chemical nickel plating agent, including the following components:

[0144] The chemical nickel plating agent comprises the following components: 15 g / L nickel salt, 7 g / L first reducing agent, 2 g / L ethylenediaminetetraacetic acid, 30 g / L sodium citrate, 4 g / L glycine, 1.5 g / L potassium sodium tartrate, 0.5 g / L activator, 13 g / L buffer, 0.5 mg / L first stabilizer, 0.4 g / L accelerator and 0.1 g / L wetting agent, with the balance being water;

[0145] The specific selection of components is consistent with that in Preparation Example 1.

[0146] Preparation Example 5

[0147] This preparation example provides a chemical nickel plating agent, including the following components:

[0148] The chemical nickel plating agent comprises the following components: 35 g / L nickel salt, 2 g / L first reducing agent, 6 g / L ethylenediaminetetraacetic acid, 10 g / L sodium citrate, 12 g / L glycine, 0.4 g / L potassium sodium tartrate, 4 g / L activator, 7 g / L buffer, 3 mg / L first stabilizer, 0.05 g / L accelerator and 0.6 g / L wetting agent, with the balance being water;

[0149] The specific selection of components is consistent with that in Preparation Example 1.

[0150] Preparation Example 6

[0151] This preparation example provides a chemical nickel plating agent, which differs from Preparation Example 1 in that the first composite complexing agent component does not contain ethylenediaminetetraacetic acid, and the rest is consistent with Preparation Example 1.

[0152] Preparation Example 7

[0153] This preparation example provides a chemical nickel plating agent, which differs from Preparation Example 1 in that the first composite complexing agent component does not contain potassium sodium tartrate, and the rest is consistent with Preparation Example 1.

[0154] Preparation Example 8

[0155] This preparation example provides a chemical nickel plating agent, which differs from Preparation Example 1 in that the components do not contain the first stabilizer, and the rest are the same as Preparation Example 1.

[0156] Preparation Example 9

[0157] This preparation example provides a chemical nickel plating agent, which differs from Preparation Example 1 in that the components do not contain an accelerator, and the rest are the same as Preparation Example 1.

[0158] Preparation Example 10

[0159] This preparation example provides a chemical nickel plating agent, which differs from Preparation Example 1 in that the components do not contain a wetting agent, and the rest are the same as Preparation Example 1.

[0160] Preparation Example 11

[0161] This preparation example provides a chemical nickel plating agent, which differs from Preparation Example 1 in that the components do not contain the first reducing agent, and the rest are consistent with Preparation Example 1.

[0162] Preparation Example 12

[0163] This preparation example provides a chemical nickel plating agent, which differs from Preparation Example 1 in that the components do not contain an activator, and the rest are the same as Preparation Example 1.

[0164] Preparation Example 13

[0165] This comparative example provides a conventional electroless nickel plating agent having the following formula: nickel source: nickel sulfamate 25-35 g / L (specifically 30 g / L); reducing agent: sodium hypophosphite 20-40 g / L (specifically 30 g / L); complexing agent: glycine 20-40 mL / L (specifically 30 mg / L); buffer: sodium acetate 10-20 g / L (15 g / L); stabilizer: lead acetate 1-5 mg / L (3 mg / L); pH adjuster: sodium hydroxide solution; operating temperature: 85-92°C. Palladium activation is performed before nickel plating.

[0166] Example 1

[0167] This embodiment provides a chemical tin plating agent, including the following components:

[0168] 15 g / L stannous sulfate, 1.5 g / L copper sulfate, 50 g / L sodium persulfate, 7.5 g / L dimethylaminoborane, 7.5 g / L ascorbic acid, 25 g / L sodium gluconate, 7.5 g / L citric acid, 7.5 g / L glutamic acid, 6.5 g / L pH buffer (specifically boric acid), 0.3 g / L stabilizer (specifically polyethylene glycol) and 0.2 g / L surfactant (specifically sodium dodecylbenzenesulfonate), and the balance is water.

[0169] Example 2

[0170] This embodiment provides a chemical tin plating agent, including the following components:

[0171] 10g / L stannous sulfate, 2g / L copper sulfate; 30g / L sodium persulfate, 5g / L dimethylaminoborane, 10g / L ascorbic acid; 20g / L sodium gluconate, 10g / L citric acid, 5g / L glutamic acid, 8g / L pH buffer, 0.1g / L stabilizer and 0.3g / L surfactant, the balance being water;

[0172] The specific selection of components is consistent with that in Example 1.

[0173] Example 3

[0174] This embodiment provides a chemical tin plating agent, including the following components:

[0175] 20g / L stannous sulfate, 1g / L copper sulfate; 50g / L sodium persulfate, 10g / L dimethylaminoborane, 5g / L ascorbic acid; 30g / L sodium gluconate, 5g / L citric acid, 10g / L glutamic acid, 5g / L pH buffer, 0.5g / L stabilizer and 0.1g / L surfactant, the balance being water;

[0176] The specific selection of components is consistent with that in Example 1.

[0177] Example 4

[0178] This embodiment provides a chemical tin plating agent, including the following components:

[0179] 5 g / L stannous sulfate, 3 g / L copper sulfate, 20 g / L sodium persulfate, 4 g / L dimethylaminoborane, 12 g / L ascorbic acid, 15 g / L sodium gluconate, 12 g / L citric acid, 4 g / L glutamic acid, 9 g / L pH buffer, 0.05 g / L stabilizer, and 0.4 g / L surfactant, with the balance being water;

[0180] The specific selection of components is consistent with that in Example 1.

[0181] Example 5

[0182] This embodiment provides a chemical tin plating agent, including the following components:

[0183] 25 g / L stannous sulfate, 0.5 g / L copper sulfate, 60 g / L sodium persulfate, 12 g / L dimethylaminoborane, 4 g / L ascorbic acid, 35 g / L sodium gluconate, 4 g / L citric acid, 12 g / L glutamic acid, 4 g / L pH buffer, 0.6 g / L stabilizer, and 0.05 g / L surfactant, with the balance being water;

[0184] The specific selection of components is consistent with that in Example 1.

[0185] Example 6

[0186] This embodiment provides a chemical tin plating agent, which is different from the embodiment 1 in that the second reducing agent component does not contain dimethylaminoborane, and the rest is the same as the embodiment 1.

[0187] Example 7

[0188] This embodiment provides a chemical tin plating agent, which differs from the embodiment 1 in that the second reducing agent component does not contain ascorbic acid, and the rest is the same as the embodiment 1.

[0189] Example 8

[0190] This embodiment provides a chemical tin plating agent, which is different from the embodiment 1 in that the second composite complexing agent component does not contain glutamic acid, and the rest is the same as the embodiment 1.

[0191] Example 9

[0192] This embodiment provides a chemical tin plating agent, which differs from the embodiment 1 in that it does not contain a second stabilizer, and is otherwise the same as the embodiment 1.

[0193] Example 10

[0194] This embodiment provides a chemical tin plating agent, which differs from the embodiment 1 in that it does not contain a surfactant, and is otherwise the same as the embodiment 1.

[0195] Application Examples 1-10

[0196] Application Examples 1-10 provide a solar cell. The chemical nickel plating agent formulas in Application Examples 1-10 respectively adopt the chemical nickel plating agent formulas in Preparation Examples 1-10, and the chemical tin plating agent formulas in Application Examples 1-10 all adopt the chemical tin plating agent formula in Example 1. The preparation process of the solar cell is as follows:

[0197] Step 1: Providing a solar cell silicon substrate;

[0198] Step 2: Patterned grooves are formed on the front and back sides of the solar cell silicon substrate by laser cutting. The width of the patterned grooves is 30 μm and the depth is 90 nm.

[0199] Step 3: Clean the opened film portion of the solar cell using a cleaning solution containing hydrofluoric acid at a rate of 15 mL / L. The temperature of the acid cleaning solution is 30° C., and the silicon substrate is allowed to float in the acid cleaning solution for 30 seconds.

[0200] Step 4: Immerse the cleaned battery cell in the prepared chemical nickel plating agent at a temperature of 30°C; an ultrasonic device is used during the chemical nickel plating process at a frequency of 30 kHz;

[0201] The preparation process of the chemical nickel plating agent is as follows: nickel sulfate and a first complexing agent are dissolved in deionized water, stirred until clear, and then the remaining additives such as a first reducing agent, an activator, a buffer, a first stabilizer, an accelerator, and a wetting agent are added (it should be noted that in Preparation Examples 1-10, some Preparation Examples do not add certain components. According to the description of the above process, if certain components are not added during the preparation of the chemical nickel plating agent, they do not need to be added), mixed thoroughly, and then used; the thickness of the nickel plating layer is 1 μm;

[0202] Step 5: The nickel-plated battery cell is rinsed with deionized water and dried; then pickled for 80 seconds using a 20% sulfuric acid solution;

[0203] Step 6: Electroplating copper on both sides by pulse light induced electroplating, the thickness of the copper layer is 11um;

[0204] Step 7: Immerse the copper-plated cell into the prepared chemical tin plating solution at a temperature of 30°C. Use an ultrasonic device with a frequency of 30 kHz during chemical tin plating.

[0205] The chemical tin plating solution is prepared as follows: stannous sulfate, copper sulfate, sodium persulfate, and a second complexing agent are dissolved in deionized water and stirred until clear. The remaining additives, including a second reducing agent, a pH buffer, a stabilizer, and a surfactant, are then added and mixed thoroughly before use. The thickness of the tin plating layer is 1.5 μm.

[0206] Step 8: The tinned cell is washed with deionized water and dried to obtain a solar cell.

[0207] Application Examples 11-19

[0208] Application Example 11-19 provides a solar cell. The chemical nickel plating agent formula in Application Example 11-19 adopts the chemical nickel plating agent formula in Preparation Example 1, and the chemical tin plating agent formula in Application Example 11-19 adopts the chemical tin plating agent formula in Example 2-10. The preparation process of the solar cell in Application Example 11-19 is consistent with that in Application Example 1. It should be noted that: in Examples 2-10, some examples do not add certain components. According to the description of the above process, in the preparation process of the chemical tin plating agent, if certain components are not added, they do not need to be added.

[0209] Application Example 20

[0210] This application example provides a solar cell, which differs from application example 1 in that:

[0211] In step 4, the temperature of chemical nickel plating is 20°C; in step 7, the temperature of tin plating is 40°C;

[0212] The rest is consistent with Application Example 1.

[0213] Application Example 21

[0214] This application example provides a solar cell, which differs from application example 1 in that:

[0215] In step 4, the temperature of chemical nickel plating is 40°C; in step 7, the temperature of tin plating is 25°C;

[0216] The rest is consistent with Application Example 1.

[0217] Application Example 22

[0218] This application example provides a solar cell, which differs from application example 1 in that: in step 4, the chemical nickel plating temperature is 15° C.; the rest is the same as application example 1.

[0219] Application Example 23

[0220] This application example provides a solar cell, which differs from application example 1 in that: in step 4, the chemical nickel plating temperature is 45° C.; the rest is the same as application example 1.

[0221] Application Example 24

[0222] This application example provides a solar cell, which differs from application example 1 in that: in step 7, the tin plating temperature is 20° C.; the rest is the same as application example 1.

[0223] Application Example 25

[0224] This application example provides a solar cell, which differs from application example 1 in that: in step 7, the tin plating temperature is 45° C.; the rest is the same as application example 1.

[0225] Application Examples 26-28

[0226] Application Examples 26-28 provide a solar cell. The chemical nickel plating agent formulas in Application Examples 26-28 respectively adopt the chemical nickel plating agent formulas in Preparation Examples 11-13, and the chemical tin plating agent formulas in Application Examples 26-28 adopt the chemical tin plating agent formula in Example 1. The preparation process of the solar cells in Application Examples 26-28 is consistent with that in Application Example 1.

[0227] Comparative Example 1

[0228] This comparative example provides a chemical tin plating agent, which differs from Example 1 in that the components do not contain copper sulfate and sodium persulfate, and the rest are the same as Example 1.

[0229] Comparative Example 2

[0230] This comparative example provides a chemical tin plating agent, which differs from Example 1 in that the second composite complexing agent is not included in the components, and the rest is the same as Example 1.

[0231] Comparative Example 3

[0232] This comparative example provides an existing chemical tin plating agent, which has the following formula: tin source: tin source: stannous chloride 15-30 g / L (specifically 25 g / L); complexing agent: thiourea 80-120 g / L (specifically 100 g / L); reducing agent: sodium hypophosphite 10-30 g / L (specifically 20 g / L); strong acid: concentrated hydrochloric acid 50-100 mL / L (specifically 75 mL / L); antioxidant: resorcinol 0.5-2 g / L (specifically 1 g / L); brightener: gelatin 0.5-2 g / L (specifically 1 g / L), and the balance is water.

[0233] Comparative Application Examples 1-2

[0234] Comparative Application Examples 1-2 provide a solar cell. The chemical nickel plating agent formulas in Comparative Application Examples 1-2 respectively adopt the chemical nickel plating agent formulas in Preparation Example 1, and the chemical tin plating agent formulas in Comparative Application Examples 1-2 respectively adopt the chemical tin plating agent formulas of Comparative Examples 1 and 2. The preparation process of the solar cell is consistent with that of Application Example 1.

[0235] Comparative Example 3

[0236] This comparative application example provides a solar cell, wherein the conventional chemical nickel plating agent formula in Preparation Example 13 and the chemical tin plating agent formula in Comparative Example 3 are used, and the preparation process of the solar cell is consistent with that of Application Example 1.

[0237] Test Case

[0238] Test samples: The solar cells prepared in Application Examples 1-28 and Comparative Application Examples 1-3 were used as samples for testing.

[0239] Test method: Test method:

[0240] (1) Electrical performance test: Offline solar IV tester;

[0241] (2) Welding tension under low temperature conditions: tensile force meter;

[0242] (3) Grid line uniformity: Use a nine-square grid to measure the grid line aspect ratio in different areas and calculate its variance. The smaller the value, the more stable the aspect ratio.

[0243] (4) Plating solution stability: After every 6 hours of continuous production, test the appearance, height and width changes of the grid lines. If the appearance, height and width changes of the grid lines are obvious, it indicates that the plating solution stability is poor.

[0244] The test results are shown in Table 1.

[0245] Table 1

[0246]

[0247]

[0248]

[0249] It can be seen from the data in Table 1 that, through Application Example 1 and Application Examples 13-19, Application Examples 24-25, and Comparative Application Examples 1-3, it can be seen that the chemical tin plating agent provided by the present invention, when containing specific components and each component has a specific content, the grid line bonding of the battery is stronger, the grid line is more uniform, and the battery efficiency is higher; similarly, through Application Example 1 and Application Examples 4-10, Application Examples 22-23, and Application Examples 26-28, it can be seen that the chemical nickel plating agent provided by the present invention, when containing specific components and each component has a specific content, the grid line bonding of the battery is stronger, the grid line is more uniform, and the battery efficiency is higher.

[0250] The chemical nickel plating agent and chemical tin plating agent provided by the present invention have a significant effect on improving the uniformity of the grid lines and maintaining the stability of the grid line aspect ratio, thereby improving the stability and service life of the plating solution under low temperature or room temperature electroplating conditions. Among them, the first complexing agent in the chemical nickel plating agent stabilizes the nickel ion concentration, avoids local excessive deposition, and improves uniformity; the activator and the first reducing agent promote the uniform reduction deposition of nickel, enhance the density of the plating layer, and significantly improve the bonding strength; the buffer and the wetting agent jointly optimize the bonding strength; the chemical tin plating agent realizes Sn by adding the second complexing agent. 2 + high stability, while preventing the formation of pores in the coating, improving density and enhancing the stability of the plating solution.

[0251] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A chemical tin plating agent, characterized in that The method comprises the following components: a main salt, a second reducing agent and a second complexing agent; The main salts include stannous sulfate, copper sulfate and sodium persulfate; The second complexing agent includes one or more of sodium gluconate, citric acid and glutamic acid.

2. The chemical tin plating agent according to claim 1, wherein The second reducing agent includes dimethylaminoborane and / or ascorbic acid.

3. The chemical tin plating agent according to claim 1, wherein The chemical tin plating agent further comprises a pH buffer, a second stabilizer and a surfactant; Preferably, the pH buffer comprises one or more of boric acid, acetic acid-sodium acetate, sodium dihydrogen phosphate / disodium hydrogen phosphate; Preferably, the second stabilizer includes one or more of polyethylene glycol and thiourea; Preferably, the surfactant includes one or more of sodium dodecylbenzenesulfonate, polyethylene glycol octylphenyl ether, and perfluoroalkyl sulfonate.

4. The chemical tin plating agent according to claim 1, wherein The chemical tin plating agent includes the following components: 10-20 g / L stannous sulfate, 1-2 g / L copper sulfate, 30-50 g / L sodium persulfate, 5-10 g / L dimethylamino borane, 5-10 g / L ascorbic acid, 20-30 g / L sodium gluconate, 5-10 g / L citric acid, 5-10 g / L glutamic acid, 5-8 g / L pH buffer, 0.1-0.5 g / L stabilizer and 0.1-0.3 g / L surfactant, with the balance being water.

5. The chemical tin plating agent according to claim 1, characterized in that The pH of the chemical tin plating agent is 4.0-5.

5.

6. The method for preparing the chemical tin plating agent according to any one of claims 1 to 5, wherein: The chemical tin plating agent is obtained by mixing the main salt, the second reducing agent and the second composite complexing agent in the formulated amounts.

7. Use of the chemical tin plating agent according to any one of claims 1 to 5 or the chemical tin plating agent prepared by the preparation method according to claim 6 in the preparation of solar cells.

8. A solar cell, characterized in that: The preparation method includes: preparing patterned grooves on the front and back of a silicon substrate, and then sequentially preparing a nickel layer, a copper layer and a tin layer in the patterned grooves; Wherein, the tin layer is prepared by using the chemical tin plating agent according to any one of claims 1 to 5 and the chemical tin plating agent prepared by the preparation method according to claim 6.

9. The solar cell according to claim 8, characterized in that During the preparation of the tin layer, the tin plating temperature is 25-40°C and the tin plating time is 1-4 minutes; Preferably, an ultrasonic device is provided during chemical tin plating, and the ultrasonic frequency is 20-40 KHz.

10. The solar cell according to claim 8, wherein The thickness of the nickel layer is 0.1-2um; the thickness of the copper layer is 9-12um; and the thickness of the tin layer is 1-2um.

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