CN120818869A

CN120818869A - Copper-tin alloy electroplating solution and preparation method thereof, and preparation method of solar cell metal electrode

Info

Publication number: CN120818869A
Application number: CN202411141224.4A
Authority: CN
Inventors: 唐义武; 李苏强; 薛怀军; 宋楠
Original assignee: Huansheng Photovoltaic Jiangsu Co Ltd
Current assignee: Huansheng Photovoltaic Jiangsu Co Ltd
Priority date: 2024-08-19
Filing date: 2024-08-19
Publication date: 2025-10-21

Abstract

The invention provides copper-tin alloy electroplating solution and a preparation method thereof, and a preparation method of a metal electrode of a solar cell, and particularly relates to the technical field of solar cell preparation. The copper-tin alloy electroplating solution provided by the invention comprises copper salt, tin salt, complexing agent, antioxidant, surfactant and water. Wherein, complexing agent and copper salt function, and the combination surfactant reduces the charge density of the interface of the electrode, increases the cathode polarization, reduces the balance potential difference between copper and tin, thereby being beneficial to improving the reduction and deposition efficiency of metal ions in the electroplating process, reducing the porosity, roughness and defects of the plating layer, and leading the plating layer to be more uniform and compact. The structure of the antioxidant serving as a coating can also prevent the oxidation of the coating and improve the service life of the copper-tin alloy. The electroplating solution can realize copper and tin codeposition, simplifies the working procedures, reduces the wastewater discharge in the production process, and reduces the manufacturing cost, so that the electroplating solution has more competitive power in industrial production.

Description

Copper-tin alloy electroplating solution and preparation method thereof, and preparation method of solar cell metal electrode

Technical Field

The invention relates to the technical field of solar cell preparation, in particular to copper-tin alloy electroplating solution and a preparation method thereof as well as a preparation method of a metal electrode of a solar cell.

Background

Electroplating solar cells are a process for forming a metal layer on the surface of a solar cell using an electroplating technique to improve the conductivity and protection properties thereof. Typically, the electrodes are of nickel copper tin construction, which is composed of multiple layers of metal, each layer having a specific function. The nickel layer serves as a barrier layer to prevent other metals from directly contacting the silicon substrate of the solar cell, thereby protecting the silicon substrate from corrosion. The copper layer serves as a conductive layer, contributing to the improvement of the efficiency of the battery due to its excellent conductive properties. The tin layer is used as a protective layer to cover the copper layer so as to prevent the copper layer from oxidizing and prolong the service life of the battery.

However, the conventional electroplating solar cell has disadvantages in terms of corrosion resistance and heat resistance. These performance defects may lead to reduced performance of the cell under severe environmental conditions, even during prolonged use, thereby affecting the overall performance and service life of the solar cell. In addition, the conventional electroplating method needs to be performed step by step, and the step by step process not only increases the complexity in the production process, but also leads to the reduction of the production efficiency. The plating of each layer of metal requires specific conditions and time, which undoubtedly increases production costs and time.

More seriously, the plating solution used in the plating process needs to be washed away after the plating is completed, which generates a large amount of waste water. These waste waters contain heavy metals and other harmful chemicals which, if not properly treated, can cause serious environmental pollution. Therefore, the existing electroplating method not only increases the production cost, but also creates a burden on the environment.

In view of this, the present invention has been made.

Disclosure of Invention

One of the objectives of the present invention is to provide an improved copper-nickel alloy plating solution, which aims to solve at least one of the above technical problems in the prior art.

The second purpose of the invention is to provide a preparation method of the copper-nickel alloy electroplating solution.

The third object of the present invention is to provide a solar cell metal electrode.

In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

In a first aspect, the present invention provides a copper-tin alloy plating solution comprising a copper salt, a tin salt, a complexing agent, an antioxidant, a surfactant, and water.

Further, the copper-tin alloy electroplating solution comprises, by weight, 100-200 parts of copper salt, 10-40 parts of tin salt, 5-30 parts of complexing agent, 0.5-2 parts of antioxidant, 0.2-1 part of surfactant and the balance of water.

Further, the copper salt includes at least one of copper sulfate, copper chloride, copper acetate, and copper methylsulfonate.

Preferably, the tin salt includes at least one of stannous sulfate, stannous chloride and stannous methylsulfonate.

Preferably, the complexing agent comprises at least one of citric acid, gluconic acid, glycine, tartaric acid and phenylalanine.

Further, the antioxidant includes at least one of phenol, phenolsulfonic acid, cresol sulfonic acid, resorcinol, hydroquinone, and catechol.

Preferably, the surfactant includes at least one of polyethylene glycol, polypropylene glycol, octylphenol polyethylene glycol ether and polyethylene glycol formal.

Preferably, the water comprises pure water.

The second aspect of the invention provides a preparation method of the copper-tin alloy electroplating solution, which comprises the following steps:

A. adding copper salt and complexing agent into water for reaction to obtain copper salt after complexing;

B. And dissolving the copper salt after complexing in water, adding tin salt, a surfactant and an antioxidant, and uniformly mixing to obtain the copper-tin alloy electroplating solution.

Further, in the step A, the reaction temperature is 40-50 ℃ and the reaction time is 15-45 min.

Preferably, the pH of the copper-tin alloy electroplating solution is 2.0-4.0.

The third aspect of the invention provides a method for preparing a solar cell metal electrode, which comprises the steps of placing a double-sided nickel-plated solar cell silicon substrate into copper-tin alloy electroplating solution for direct current electroplating to obtain the solar cell metal electrode;

wherein the copper-tin alloy plating solution is the copper-tin alloy plating solution according to the first aspect.

Further, the solar cell is an N-type TOPCon cell.

Preferably, the solar cell metal electrode comprises a nickel layer and a copper-nickel alloy layer arranged on the nickel layer.

Preferably, the thickness of the nickel layer is 0.5-1.0 μm.

Further, the thickness of the copper-nickel alloy layer is 8-10 mu m.

Further, the temperature of the direct current plating is 30-50 ℃ and the time is 6-12 min.

Preferably, the current density of the direct current plating is 4-8A/dm ².

Compared with the prior art, the invention has at least the following beneficial effects:

In the copper-tin alloy electroplating solution provided by the invention, the complexing agent acts with the copper salt, and the surfactant is combined to reduce the charge density of the interface of the electrode, increase the cathode polarization and reduce the balance potential difference between copper and tin, so that the reduction and deposition efficiency of metal ions in the electroplating process can be improved, the porosity, roughness and defects of a plating layer can be reduced, and the plating layer is more uniform and compact. The structure of the antioxidant serving as a coating can also prevent the oxidation of the coating and improve the service life of the copper-tin alloy. The electroplating solution can realize copper and tin codeposition, simplifies the procedures which need to be carried out step by step in the traditional electroplating process, and reduces the wastewater discharge in the production process. The simplification not only improves the production efficiency, but also reduces the manufacturing cost, so that the electroplating solution of the invention has more competitive power in industrial production.

According to the preparation method provided by the invention, firstly, copper salt is complexed, so that the stability of the copper salt is improved, the balance potential difference between the copper salt and tin salt is reduced, and a foundation is laid for forming a uniform copper-tin alloy layer. The preparation method disclosed by the invention is simple in process, reduces the production cost and is suitable for industrial mass production.

According to the preparation method of the metal electrode of the solar cell, provided by the invention, in view of the advantages of the copper-tin alloy electroplating solution, the preparation steps of the metal electrode are simplified, the waste water discharge in the production process is reduced, the production efficiency is improved, the preparation cost is reduced, and the prepared solar cell has better market competitiveness.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments.

The terms "comprises," "comprising," "including," or any other variation thereof, are intended to cover a specific feature, number, step, operation, element, component, or combination of the foregoing, which may be used in various embodiments of the present invention, and are not intended to first exclude the presence of or increase the likelihood of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.

Specifically, the complexing agent in the copper-tin alloy electroplating solution and the copper salt carry out complexation reaction, so that the stability of the electroplating solution is enhanced, and a foundation is laid for the subsequent electroplating process. Meanwhile, the addition of the surfactant obviously improves the cathode polarization, and the synergistic effect of the surfactant and the complexing agent effectively reduces the balance potential difference between copper and tin. This reduction in potential difference is critical to achieving copper-tin co-deposition and allows the two metals to be deposited more uniformly on the substrate during the electroplating process, thereby achieving a dense and uniform coating. The compact and uniform coating has obviously enhanced binding force with the substrate, is not easy to oxidize and discolor in the air, and keeps the lasting stability of the appearance. When facing weak acid or weak base environment, the coating shows strong corrosion resistance, which greatly expands the application range, especially in the occasion with special requirement on corrosion resistance.

In addition, the coating has good heat resistance, so that the performance of the coating is not affected even in a high-temperature environment. The characteristics lead the copper-tin alloy electroplating solution to have wide application prospect in the industrial fields of electronics, automobiles, aviation and the like.

Because the components of the electroplating solution are not easy to volatilize and have good stability, the material waste and the environmental problems caused by the volatilization of the components can be reduced in the actual production process. Meanwhile, the electroplating solution can realize copper and tin codeposition, so that the procedures needed to be carried out step by step in the traditional electroplating process are simplified, and the wastewater discharge in the production process is reduced. The simplification not only improves the production efficiency, but also reduces the manufacturing cost, so that the electroplating solution of the invention has more competitive power in industrial production.

Typically, but not limited to, the copper salt may be used in an amount of, for example, 100 parts, 120 parts, 140 parts, 160 parts, 180 parts or 200 parts, or any value in the range of 100 parts to 200 parts, the tin salt may be used in an amount of, for example, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts or 40 parts, or any value in the range of 10 parts to 40 parts, the complexing agent may be used in an amount of, for example, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts or 30 parts, or any value in the range of 5 parts to 30 parts, the antioxidant may be used in an amount of, for example, 0.5 parts, 1 part, 1.5 parts, or 2 parts, or any value in the range of 0.5 parts to 2 parts, and the surfactant may be used in an amount of, for example, 0.4 parts, 0.6 parts, 0.8 parts, or 1 part, or any value in the range of 0.2 parts to 1 part, or any value in the range of 0.2 parts. The balance is supplemented by water to the total volume of the plating solution required.

Further, the antioxidant includes at least one of phenol, phenolsulfonic acid, cresol sulfonic acid resorcinol, hydroquinone, and catechol.

Preferably, the water comprises pure water.

Specifically, the step A realizes copper salt complexation by adding copper salt and complexing agent into water, and is important because the step A not only provides necessary chemical basis for the subsequent electroplating process, but also improves the solubility and stability of copper salt through complexation reaction, thereby laying a solid foundation for forming uniform copper-tin alloy plating. Then, in the step B, the copper salt after complexing is dissolved in water, and tin salt, surfactant and antioxidant are added and uniformly mixed to obtain the final copper-tin alloy electroplating solution. The mixing process in this step ensures uniform distribution among the components, and provides a guarantee for the stability of the plating solution and uniform deposition during the plating process. The addition of the surfactant, as described above, helps to increase the cathodic polarization and improve the coating quality, while the presence of the antioxidant effectively prevents oxidation of the coating, extending the useful life of the metal electrode.

The copper-tin alloy electroplating solution obtained by the preparation method has good stability, uniform plating layer forming capability, excellent corrosion resistance and heat resistance and excellent electric conductivity. In addition, the method simplifies the preparation flow of the electroplating solution, reduces the production cost, reduces the influence on the environment, and is beneficial to promoting the sustainable development of the electroplating technology.

In the complexing reaction, at least one of citric acid, gluconic acid, glycine, tartaric acid and phenylalanine is combined with copper ions in copper salt through coordination bonds to form a stable copper complex, so that the free concentration of copper ions in the electroplating solution is reduced, and the subsequent plating performance difference caused by different copper-tin deposition speeds is prevented. The copper ion and the complexing agent form a stable complex, so that the solubility of copper is improved, the stable copper ion concentration is maintained in the electroplating process, and the uniformity of electroplating solution and the quality of an electroplated layer are ensured. The formation of copper complexes reduces the hydrolysis of copper ions, thereby improving the chemical stability of the plating solution and extending the service life of the plating solution.

Typically, but not by way of limitation, the temperature setting during the reaction may be 40 ℃, 42 ℃, 44 ℃, 46 ℃, 48 ℃ or 50 ℃ or any temperature value in the range of 40 ℃ to 50 ℃, and the duration of the reaction may be 15min, 20min, 25min, 30min, 35min, 40min or 45min or any time value in the range of 15min to 45 min.

Preferably, the pH of the copper-tin alloy electroplating solution is 2.0-4.0.

The pH value of the copper-tin alloy plating solution is controlled within the range of 2.0 to 4.0, so that the stability of copper salt and tin salt in the plating solution can be ensured, and unnecessary chemical reaction or precipitation of the copper salt and the tin salt is prevented, thereby maintaining the long-term stability and the service life of the plating solution. At the same time, the pH value range is favorable for promoting the uniform deposition of the copper-tin alloy, because the reduction potential and the deposition rate of metal ions can be well matched under the pH value condition, and the risk of uneven or defective plating layers is reduced. Meanwhile, the moderate acid environment is favorable for improving the bonding force between the plating layer and the substrate, because the acid condition can slightly etch the surface of the nickel layer, and the surface roughness is increased, so that the adhesive force of the plating layer is enhanced.

Typically, but not by way of limitation, the pH of the copper-tin alloy plating solution may be precisely set to 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8 or 4.0, but may also be any pH in the range of 2.0 to 4.0.

Further, the solar cell is an N-type TOPCon cell.

Preferably, the thickness of the nickel layer is 0.5-1.0 μm.

The thickness of the nickel layer is controlled within the range of 0.5-1 micrometers, and the nickel layer with the thickness is used as an effective barrier layer, so that the silicon substrate is prevented from being in direct contact with the copper-nickel alloy layer, the battery is protected from corrosion and chemical erosion, and the stability of the battery is enhanced. Meanwhile, the moderate thickness of the nickel layer ensures good conductivity, is beneficial to effective transmission of current and improves the conversion efficiency of the battery.

Typically, but not by way of limitation, the nickel layer may have a thickness of exactly 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm, but may also have any value in the range of 0.5 μm to 1.0 μm.

Further, the thickness of the copper-nickel alloy layer is 8-10 mu m.

The thickness of the copper-nickel alloy layer is controlled within the range of 8-10 microns, so that good conductivity is provided, effective transmission of current is ensured, and the mechanical strength and wear resistance of the electrode are improved, thereby improving the durability and reliability of the battery. In addition, the thickness range of the copper-nickel alloy layer is also beneficial to improving the production efficiency, because the electroplating process can be completed in a shorter time, the uniformity of the plating layer is easy to realize, the production cost is reduced, and the requirement of industrialized mass production is met.

Typically, but not by way of limitation, the thickness of the copper nickel alloy layer may be 8 μm, 8.5 μm,9 μm, 9.5 μm or 10 μm, or any value in the range of 8 μm to 10 μm.

The electroplating temperature is controlled to be 30-50 ℃, and the electroplating time is set to be 6-12 minutes, so that the electroplating effect and the production efficiency can be comprehensively optimized. The temperature range is favorable for accelerating electrochemical reaction and improving the reduction rate of metal ions on the electrode, thereby accelerating the deposition rate, shortening the production period and improving the production efficiency. Meanwhile, moderate temperature is helpful for reducing thermal stress and thermal deformation possibly occurring in the electroplating process, and keeping the uniformity and adhesive force of the plating layer.

The temperature range is also beneficial to reducing the decomposition of functional substances in the electrolyte, maintaining the stability of the electroplating solution and prolonging the service life of the electroplating solution. The shorter electroplating time combined with moderate temperature can reduce the porosity and roughness of the plating layer and improve the compactness and smoothness of the plating layer, thereby obtaining a copper-nickel alloy layer with higher quality. The high-quality coating can not only improve the conductivity of the solar cell, but also enhance the corrosion resistance and abrasion resistance of the solar cell, and prolong the service life of the solar cell.

Typically, but not by way of limitation, the temperature during the direct current plating process may be set at 30 ℃, 35 ℃,40 ℃, 45 ℃, or 50 ℃ and may be any value in the range of 30 ℃ to 50 ℃. The plating time may be set to 6min, 7min, 8min, 9min, 10min or 12min, or any value within a range of 6min to 12 min.

Preferably, the current density of the direct current plating is 4-8A/dm ².

The current density is controlled within the range of 4-8A/dm ², so that the high efficiency of the electroplating process and the superiority of the coating quality can be ensured. The current density interval is beneficial to realizing a faster deposition rate, thereby shortening the production period and improving the production efficiency. Meanwhile, the current density of 4-8A/dm ² can promote the uniform reduction of metal ions on the electrode, reduce the porosity and roughness of the coating and improve the compactness and smoothness of the coating.

Typically, but not by way of limitation, the current density during the DC plating process may be 4A/dm²、4.5A/dm²、5A/dm²、5.5A/dm²、6A/dm²、6.5A/dm²、7A/dm² or 8A/dm ², or any value in the range of 4A/dm ² to 8A/dm ².

The invention is further illustrated by the following specific examples and comparative examples, but it should be understood that these examples are for the purpose of illustration only and are not to be construed as limiting the invention in any way. The raw materials used in the examples and comparative examples of the present invention were conducted under conventional conditions or conditions recommended by the manufacturer, without specifying the specific conditions. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1

The embodiment provides a copper-tin alloy electroplating solution, wherein copper chloride is 150g/L, stannous chloride is 25g/L, citric acid is 20g/L, phenol is 1g/L, octyl phenol polyethylene glycol ether is 0.3g/L, polyethylene glycol is 0.3g/L, and the balance is pure water.

The preparation method of the copper-tin alloy electroplating solution comprises the following steps:

1. and (3) adding 150g of copper chloride and 20g of citric acid into a proper amount of water, uniformly mixing, reacting for 30min at 40 ℃, and evaporating to remove water after the reaction is finished to obtain the complexed copper chloride.

2. Adding the complexed copper chloride into 800mL of pure water, dissolving stannous chloride, continuously adding phenol, octylphenol polyethylene glycol ether and polyethylene glycol, stirring uniformly, detecting the pH value to be 2.0-4.0, and fixing the volume of the solution to 1L by using the pure water to obtain the copper-tin alloy electroplating solution.

Example 2

The embodiment provides a copper-tin alloy electroplating solution, wherein copper sulfate is 120g/L, stannous sulfate is 20g/L, tartaric acid is 10g/L, hydroquinone is 2g/L, octyl phenol polyethylene glycol ether is 0.3g/L, polyethylene glycol is 0.3g/L, and the balance is pure water.

The preparation method of the copper-tin alloy electroplating solution is the same as that of the embodiment 1.

Example 3

This example provides a copper-tin alloy plating solution in which 180g/L of copper acetate, 35g/L of stannous methylsulfonate, 8g/L of phenylalanine, 1g/L of resorcinol cresol sulfonate, 0.6g/L of octylphenol polyglycol ether, and the balance of pure water.

Example 4

The embodiment provides a copper-tin alloy plating solution, which is different from embodiment 1 in that copper chloride is 100g/L and stannous chloride is 10g/L, and the other raw materials are the same as embodiment 1, and are not described herein.

Example 5

The embodiment provides a copper-tin alloy plating solution, which is different from embodiment 1 in that copper chloride is 200g/L and stannous chloride is 40g/L, and the other raw materials are the same as embodiment 1, and are not described herein.

Example 6

The embodiment provides a copper-tin alloy electroplating solution, which is different from embodiment 1 in that citric acid is 30g/L, and the rest raw materials are the same as embodiment 1, and are not described herein.

Example 7

The embodiment provides a copper-tin alloy electroplating solution, which is different from embodiment 1 in that citric acid is 5g/L, and the rest raw materials are the same as embodiment 1, and are not described herein.

Example 8

The present example provides a copper-tin alloy plating solution, which is different from example 1 in that phenol is 0.5g/L, and the other raw materials are the same as example 1, and are not described here again.

Example 9

The embodiment provides a copper-tin alloy electroplating solution, which is different from embodiment 1 in that phenol is 2g/L, and the rest raw materials are the same as embodiment 1, and are not described herein.

Example 10

The embodiment provides a copper-tin alloy electroplating solution, which is different from embodiment 1 in that octyl phenol polyethylene glycol ether is 0.1g/L, polyethylene glycol is 0.1g/L, and the rest raw materials are the same as embodiment 1, and are not described herein.

Example 11

The embodiment provides a copper-tin alloy electroplating solution, which is different from embodiment 1 in that octyl phenol polyethylene glycol ether is 0.5g/L, polyethylene glycol is 0.5g/L, and the rest raw materials are the same as embodiment 1, and are not described herein.

Comparative example 1

This comparative example provides a copper-tin alloy plating solution, which is different from example 1 in that citric acid is eliminated, the other raw materials and steps are the same as those of example 1, step 1 is eliminated correspondingly, and the plating solution is directly prepared in pure water without treating copper chloride.

Comparative example 2

This comparative example provides a copper-tin alloy plating solution, which differs from example 1 in that phenol is eliminated, and the remaining raw materials and preparation method are the same as those of example 1, and are not described here again.

Comparative example 3

This comparative example provides a copper-tin alloy plating solution, which is different from example 1 in that octylphenol polyethylene glycol ether and polyethylene glycol are eliminated, and the other raw materials and preparation methods are the same as those of example 1, and are not described here again.

Test example 1

The copper-tin alloy plating solutions obtained in examples and comparative examples were placed in a thermostatic water bath at 75 ℃ and heated for 1 hour, and the changes thereof were observed and recorded in table 1.

The stability of the copper-tin alloy plating solution was judged by observing whether the plating solution was changed during the reaction. The stable copper-tin alloy plating solution maintains its clarity and transparency throughout the plating process.

If the bath remained clear in the plating tank and no metal deposited at the bottom, this indicates good stability of the bath. Conversely, if metal deposition is found at the bottom of the plating tank, this means that the plating solution is unstable.

Test example 2

Immersing a double-sided nickel-plated solar cell silicon substrate into the copper-tin alloy electroplating liquid obtained in the examples and the comparative examples, controlling the temperature at 40 ℃ for direct current electroplating for 9min, and measuring the height of a thin grid line on the front side of the solar cell by a 3D microscope according to nine Gong Gefa to obtain a copper-tin alloy layer, wherein the current density of the direct current electroplating is 6A/dm ², and taking an average value.

TABLE 1

As can be seen from Table 1, the copper ions and the complexing agent form a stable complex, the solubility of copper is improved, and the uniformity of the electroplating solution is ensured. Meanwhile, the hydrolysis of copper ions is reduced, and the existence of the antioxidant prevents tin ions from being oxidized, so that the chemical stability of the electroplating solution is improved, and the service life of the copper-tin alloy electroplating solution is prolonged.

Test example 3

The solar cell with the copper-tin alloy layer obtained in test example 2 was subjected to plating bonding force test, the main grid and PAD points of the front and back copper-tin alloy grid lines of the crystalline silicon solar cell were covered with a low-temperature solder strip, a small amount of flux was assisted in soldering at 180 ℃, soldering tension at 12 PAD points was tested with a tension meter, and the average value was taken (all points were not less than 0.8N as qualified), and the obtained data were recorded in table 2.

TABLE 2

As can be seen from table 2, the use of the complexing agent and the antioxidant helps to improve the quality of the copper-tin alloy plating layer, if the additives of the copper-tin alloy plating solution are not reasonably matched, copper-tin alloy is not co-deposited, copper is only deposited on the surface of the solar cell, and is easily oxidized in the air, so that the corrosion resistance of the cell is also deteriorated, and the welding tension is also reduced.

It should be noted that the foregoing embodiments are merely illustrative embodiments of the present invention, and not restrictive, and the scope of the invention is not limited to the embodiments, and although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that any modification, variation or substitution of some of the technical features of the embodiments described in the foregoing embodiments may be easily contemplated within the scope of the present invention, and the spirit and scope of the technical solutions of the embodiments do not depart from the spirit and scope of the embodiments of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A copper-tin alloy electroplating solution, characterized in that it comprises a copper salt, a tin salt, a complexing agent, an antioxidant, a surfactant and water.

2. The copper-tin alloy electroplating solution according to claim 1 is characterized in that, in parts by weight, per unit volume of the copper-tin alloy electroplating solution comprises 100-200 parts of copper salt, 10-40 parts of tin salt, 5-30 parts of complexing agent, 0.5-2 parts of antioxidant, 0.2-1 parts of surfactant, and the balance is water.

3. The copper-tin alloy electroplating solution according to claim 1 or 2, wherein the copper salt comprises at least one of copper sulfate, copper chloride, copper acetate and copper methanesulfonate;

Preferably, the tin salt comprises at least one of stannous sulfate, stannous chloride and stannous methanesulfonate;

Preferably, the complexing agent comprises at least one of citric acid, gluconic acid, aminoacetic acid, tartaric acid and phenylalanine.

4. The copper-tin alloy electroplating solution according to claim 1 or 2, wherein the antioxidant comprises at least one of phenol, phenolsulfonic acid, cresolsulfonic acid resorcinol, hydroquinone and catechol;

Preferably, the surfactant comprises at least one of polyethylene glycol, polypropylene glycol, octylphenol polyglycol ether and polyethylene glycol formal;

Preferably, the water comprises pure water.

5. A method for preparing the copper-tin alloy electroplating solution according to any one of claims 1 to 4, characterized in that it comprises the following steps:

A. Add copper salt and complexing agent into water to react and obtain complexed copper salt;

B. dissolving the complexed copper salt in water, adding tin salt, surfactant and antioxidant and mixing evenly to obtain the copper-tin alloy electroplating solution.

6. The preparation method according to claim 5, characterized in that in step A, the reaction temperature is 40-50°C and the reaction time is 15-45 minutes;

Preferably, the pH of the copper-tin alloy electroplating solution is 2.0-4.0.

7. A method for preparing a metal electrode for a solar cell, characterized in that a solar cell silicon substrate with nickel plating on both sides is placed in a copper-tin alloy electroplating solution for direct current electroplating to obtain a metal electrode for the solar cell;

Wherein, the copper-tin alloy electroplating solution is the copper-tin alloy electroplating solution according to any one of claims 1 to 4.

8. The preparation method according to claim 7, wherein the solar cell is an N-type TOPCon cell;

Preferably, the solar cell metal electrode comprises a nickel layer and a copper-nickel alloy layer disposed on the nickel layer;

Preferably, the thickness of the nickel layer is 0.5-1.0 μm.

9 . The preparation method according to claim 8 , wherein the copper-nickel alloy layer has a thickness of 8 to 10 μm.

10. The preparation method according to claim 7, characterized in that the temperature of the direct current electroplating is 30-50°C and the time is 6-12 minutes;

Preferably, the current density of the direct current electroplating is 4 to 8 A/dm ² .