A composite electroplating solution, a plating method of a photovoltaic cell, and a photovoltaic cell

Abstract

The application belongs to the technical field of photovoltaic cells, and provides a composite electroplating solution, an electroplating method of a photovoltaic cell and the photovoltaic cell. The composite electroplating solution contains not only metal salt and other components, but also fluoride complexing agent and silicon nitride corrosion inhibitor. The oxide layer can be selectively removed in the electroplating process without damaging the silicon nitride layer, and metal grid lines are deposited synchronously, which is beneficial to omit the pre-cleaning process before electroplating in the traditional electroplating process, can significantly simplify the production process, reduce the manufacturing cost, and is beneficial to improve the cell efficiency and reliability.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic cell technology, and relates to a composite electroplating solution, an electroplating method for photovoltaic cells, and photovoltaic cells. Background Technology

[0002] TOPCon (Tunnel Oxide Passivated Contact) cells, as a high-efficiency n-type solar cell technology, have attracted widespread attention due to their excellent passivation effect and conversion efficiency. In the manufacturing process of TOPCon cells, the electrode metallization process is particularly critical, significantly impacting the cell's conversion efficiency and production cost.

[0003] Traditional crystalline silicon solar cells commonly employ screen-printed silver paste to fabricate electrode grid lines. However, with the continuous rise in silver paste costs and the increasing demands for electrode precision in high-efficiency cells, this technology is facing severe challenges. Silver paste, as a precious metal material, is expensive and highly volatile, accounting for 25% to 40% of the non-silicon cost of solar cells, becoming one of the main bottlenecks for cost reduction and efficiency improvement in the photovoltaic industry. Furthermore, the width of silver grid lines fabricated using screen printing technology is typically greater than 30 μm, with a low aspect ratio, resulting in large shading areas and high series resistance, thus limiting further improvements in cell conversion efficiency.

[0004] Electroplating technology, as a revolutionary alternative to traditional silver paste processes, uses electroplated nickel and copper instead of precious silver to fabricate electrodes, offering the dual advantages of reduced costs and increased efficiency. Currently, mainstream TOPCon electroplating processes all require rigorous cleaning steps before electroplating to remove the native oxide layer (such as silicon oxide) and contaminants from the silicon wafer surface. For example, one existing technology requires two acid washes after laser grooving: the first to remove residual silicon nitride, and the second to remove the metal film layer from areas without grooves. Other existing technologies perform poly-plating removal and cleaning on the back of the silicon wafer before electrode deposition, or perform poly-plating removal on the front of N-type TOPCon cells, highlighting the necessity of pre-cleaning in traditional processes.

[0005] While these pre-cleaning steps can remove the oxide layer to some extent, they significantly increase the complexity of the production process and the cost of equipment investment. They also consume large amounts of chemical reagents, increasing production costs and the burden of wastewater treatment and environmental pressure. Furthermore, they may cause excessive surface corrosion and defects. Therefore, there is an urgent need in the field for a novel electroplating technology that can eliminate the pre-cleaning step while ensuring electrode quality. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a composite electroplating solution, an electroplating method for photovoltaic cells, and a photovoltaic cell. The composite electroplating solution not only contains metal salts and other components, but also contains fluoride complexing agents and silicon nitride corrosion inhibitors. It can selectively remove the oxide layer without damaging the silicon nitride layer during the electroplating process, and simultaneously deposit metal grid lines. This is beneficial to omitting the pre-cleaning process before electroplating in traditional electroplating processes, which can significantly simplify the production process, reduce manufacturing costs, and improve battery efficiency and reliability.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a composite electroplating solution, the composite electroplating solution comprising a metal salt containing electroplating metal ions and a solvent, and further comprising a fluoride complexing agent and a silicon nitride corrosion inhibitor.

[0009] The composite electroplating solution of this invention contains specific fluoride complexing agents and silicon nitride corrosion inhibitors. The fluoride complexing agents can selectively corrode and remove the native oxide layer (such as silicon oxide) during the electroplating process without damaging the silicon nitride layer. For example, based on the significant difference in the thermodynamic reaction free energies of silicon oxide and silicon nitride in fluoride solutions, ammonium fluoride can be used, which reacts with silicon oxide to form soluble hexafluorosilicates, while exhibiting an extremely low corrosion rate on silicon nitride. Simultaneously, the silicon nitride corrosion inhibitor used can form a protective film on the surface of the silicon nitride layer through an adsorption mechanism, further preventing fluoride attack without affecting the corrosion rate of silicon oxide. Therefore, while removing the oxide layer without damaging the silicon nitride layer, metal ions from the deposited metal salt can be electroplated simultaneously to form metal grid lines. Thus, using the aforementioned composite electroplating solution to electroplat battery cells that have been slotted but are not yet metallized can eliminate the pre-cleaning step required in traditional electroplating processes, significantly simplifying the production process, reducing manufacturing costs, and improving battery efficiency and reliability.

[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0011] As a preferred embodiment of the present invention, the fluoride complexing agent includes ammonium fluoride.

[0012] Preferably, the fluoride complexing agent accounts for 0.1% to 5% of the total mass of the composite electroplating solution. Exemplarily, it can be 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, etc.

[0013] Preferably, the silicon nitride corrosion inhibitor includes copper-based corrosion inhibitors and / or nitrogen-containing organic compounds.

[0014] Preferably, the silicon nitride corrosion inhibitor includes at least one of benzotriazole (BTA), 1,2,4-triazole (TAZ), glycine, or arginine.

[0015] Preferably, the silicon nitride corrosion inhibitor accounts for 0.05% to 3% of the composite electroplating solution by mass (100%). For example, it may be 0.05%, 0.08%, 0.1%, 0.13%, 0.15%, 0.18%, 0.2%, 0.23%, 0.25%, 0.28%, or 0.3%, etc.

[0016] Preferably, the mass ratio of the fluoride complexing agent to the silicon nitride corrosion inhibitor is (1~5):1. For example, it can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, or 5:1, etc. Therefore, the fluoride complexing agent and the silicon nitride corrosion inhibitor can exert a better synergistic effect, achieving the best selective corrosion effect.

[0017] As a preferred embodiment of the present invention, the composite electroplating solution further includes a reducing agent, which is mainly used to reduce electroplated metal ions.

[0018] Preferably, the reducing agent comprises sodium hypophosphite.

[0019] Preferably, the reducing agent accounts for 5% to 25% of the composite electroplating solution by mass, which is 100%. For example, it can be 5%, 6%, 7%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, or 25%, etc.

[0020] As a preferred embodiment of the present invention, the composite electroplating solution further includes a buffer, which is mainly used to maintain pH stability.

[0021] Preferably, the buffer comprises trisodium citrate and / or ammonium bifluoride.

[0022] Preferably, the buffer accounts for 1% to 25% of the composite electroplating solution by mass, which is 100%. For example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, or 25%, etc.

[0023] Preferably, based on the mass of the composite electroplating solution as 100%, the trisodium citrate accounts for 1% to 10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%; the ammonium bifluoride accounts for 3% to 12%, for example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11% or 12%.

[0024] As a preferred embodiment of the present invention, the composite electroplating solution further includes a surfactant, which is mainly used to improve the uniformity of the plating layer.

[0025] Preferably, the surfactant comprises sodium dodecyl sulfate.

[0026] Preferably, the surfactant accounts for 0.001% to 0.1% of the composite electroplating solution by mass, which is 100%. For example, it can be 0.001%, 0.003%, 0.005%, 0.008%, 0.01%, 0.03%, 0.05%, 0.08%, or 0.1%, etc.

[0027] As a preferred embodiment of the present invention, the electroplated metal ions include nickel ions and / or copper ions.

[0028] Preferably, the metal salt includes sulfates of electroplated metal ions, such as nickel sulfate and copper sulfate.

[0029] Preferably, the metal salt accounts for 10% to 30% of the composite electroplating solution by mass. For example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 23%, 25%, 28%, or 30%, etc.

[0030] As a preferred embodiment of the present invention, the solvent includes water. It is understood that the solvent is primarily used to disperse and dissolve other components, and therefore its proportion in the composite electroplating solution is the balance.

[0031] Preferably, the pH of the composite electroplating solution is 2.5 to 5.5. Exemplarily, it can be 2.5, 2.8, 3, 3.3, 3.5, 3.8, 4, 4.3, 4.5, 4.8, 5, 5.2, or 5.5, etc.

[0032] Preferably, the pH of the composite electroplating solution is controlled using a pH adjuster, which includes hydrochloric acid and / or ammonia.

[0033] Secondly, the present invention provides an electroplating method for photovoltaic cells, the electroplating method comprising the following steps:

[0034] Provides solar cells with a silicon nitride layer on the surface and grooves formed by slotting;

[0035] After the groove is cut, without cleaning, the battery cell is directly placed in the composite electroplating solution described in the first aspect for electroplating, so that the original oxide layer in the groove is removed and electrode grid lines are formed, thus completing metallization and obtaining a photovoltaic cell.

[0036] As a preferred embodiment of the present invention, the electroplating temperature is 75℃~85℃, the time is 1min~3min, and the current density is 1A / dm². 2 ~5A / dm 2 For example, the temperature can be 75°C, 78°C, 80°C, 82°C, or 85°C, etc.; the time can be 1 min, 1.5 min, 2 min, 2.5 min, or 3 min, etc.

[0037] Preferably, the electroplating method further includes, after the electroplating is completed, removing the battery cell and sequentially performing post-cleaning and annealing to complete the metallization;

[0038] Preferably, the electroplating process also includes stirring at a speed of 100 rpm to 300 rpm. For example, the stirring speed could be 100 rpm, 150 rpm, 200 rpm, 250 rpm, or 300 rpm.

[0039] Thirdly, the present invention provides a photovoltaic cell, which is obtained by metallization according to the electroplating method described in the second aspect.

[0040] It should be noted that, due to space limitations and to avoid redundancy, this invention does not exhaustively list all point values ​​within the above numerical range, but it is not limited to the listed values ​​either; other unlisted values ​​within the above numerical range are also applicable.

[0041] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0042] The composite electroplating solution provided by this invention not only contains metal salts and other components, but also contains specific fluoride complexing agents and silicon nitride corrosion inhibitors. It can selectively remove the oxide layer without damaging the silicon nitride layer during the electroplating process, and simultaneously deposit metal grid lines. This is beneficial to omit the pre-cleaning process before electroplating in traditional electroplating processes, which can significantly simplify the production process, reduce manufacturing costs, and improve battery efficiency and reliability. Attached Figure Description

[0043] Figure 1 This is a schematic flowchart of the electroplating method for photovoltaic cells in Example 1.

[0044] Figure 2 This is a schematic diagram of the structure of the battery cell in Example 1, which has grooves but is not metallized.

[0045] Figure 3 This is a schematic diagram illustrating the principle of the electroplating process in the photovoltaic cell electroplating method of Example 1.

[0046] Figure 2 as well as Figure 3In the middle: 1-front silicon nitride layer, 2-polycrystalline silicon layer, 3-silicon oxide layer, 4-N-type silicon substrate, 5-P-type emitter layer, 6-alumina layer, 7-back silicon nitride layer, 8-back metal finger electrode. Detailed Implementation

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0048] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0049] Example 1

[0050] This embodiment provides a composite electroplating solution, which includes a metal salt containing electroplating metal ions and a solvent, as well as a fluoride complexing agent, a silicon nitride corrosion inhibitor, and other components. Based on the mass of the composite electroplating solution as 100%, the specific components and their mass percentages are shown in Table 1 below:

[0051] Table 1

[0052]

[0053] Furthermore, the composite electroplating solution uses pH-adjusting hydrochloric acid and ammonia to adjust the pH to 3.5.

[0054] This embodiment also provides an electroplating method for photovoltaic cells, such as... Figure 1 As shown, it includes the following steps:

[0055] S1. A TOPCon solar cell with a pre-prepared silicon nitride passivation layer is provided, the surface of which has grooves formed by laser grooving; specifically, such as... Figure 2 As shown, the solar cell includes an N-type silicon substrate 4, which has a front side and a back side. The back side includes a stacked P-type emitter layer 5, an aluminum oxide layer 6, a back silicon nitride layer 7, and a back metal finger electrode 8. The front side includes a stacked silicon oxide layer 3, a polycrystalline silicon layer 2, and a front silicon nitride layer 1. The front silicon nitride layer is laser-grooved to form the groove.

[0056] S2. After the grooving is completed, the battery cells are directly immersed in the composite electroplating solution without any pre-cleaning treatment, and electroplated at 80°C for 2 minutes with a current density of 2A / dm³. 2 The solution is continuously stirred at 200 rpm. During the electroplating process, the fluoride complexing agent component in the electroplating solution simultaneously removes the original oxide layer at the groove, and the metal ions provided by the metal salt are deposited on the silicon surface in the clean groove to form a strong electrode grid line.

[0057] S3. Remove the solar cells, clean them, and then anneal them to form an electrode structure with low contact resistance, thus completing the metallization process and obtaining a photovoltaic cell.

[0058] Example 2

[0059] This embodiment provides a composite electroplating solution, the specific components of which and their mass percentages are shown in Table 2 below:

[0060] Table 2

[0061]

[0062] Furthermore, the composite electroplating solution uses pH-adjusting hydrochloric acid and ammonia to adjust the pH to 4.

[0063] This embodiment also provides an electroplating method for photovoltaic cells, wherein the electroplating method in step S2 is replaced by the composite electroplating solution of this embodiment, and the electroplating temperature is 78°C, the time is 3 min, and the current density is 3 A / dm³. 2 The stirring was continued at 280 rpm, and all other conditions were exactly the same as in Example 1.

[0064] Comparative Example 1, Example 3, and Example 4

[0065] The difference from Example 1 is that the content of the fluoride complexing agent was adjusted, and the mass percentage of ammonium fluoride was adjusted from 2.5% to 0% (Comparative Example 1), 1% (Example 3), and 5% (Example 4), respectively. This changed the mass ratio of fluoride complexing agent to silicon nitride corrosion inhibitor in the composite electroplating solution from 2.08:1 to 0:1, 0.83:1, and 4.17:1, respectively. In other words, no fluoride complexing agent was used in Comparative Example 1. Apart from the above, the other conditions were exactly the same as in Example 1.

[0066] Comparative Example 2 and Examples 5 and 6

[0067] The difference from Example 1 is that the content of silicon nitride corrosion inhibitor was adjusted. The mass percentage of copper corrosion inhibitor was adjusted from 1.2% to 0% (Comparative Example 2), 0.5% (Example 5), and 3% (Example 6), respectively. This changed the mass ratio of fluoride complexing agent to silicon nitride corrosion inhibitor in the composite electroplating solution from 2.08:1 to 1:0, 5:1, and 0.83:1, respectively. In other words, silicon nitride corrosion inhibitor was not used in Comparative Example 2. Apart from the above, the other conditions were exactly the same as in Example 1.

[0068] Examples 7 and 8

[0069] The difference from Example 1 is that the content of the fluoride complexing agent was adjusted, and the mass percentage of ammonium fluoride was adjusted from 2.5% to 1% (Example 7) and 5% (Example 8). At the same time, the content of the silicon nitride corrosion inhibitor was adjusted, and the mass percentage of the copper corrosion inhibitor was adjusted from 1.2% to 0.48% and 2.4% respectively, so that the mass ratio of fluoride complexing agent to silicon nitride corrosion inhibitor in the composite electroplating solution remained unchanged at 2.08:1. Except for the above, the other conditions were exactly the same as in Example 1.

[0070] Comparative Example 3

[0071] This comparative example provides an electroplating method for photovoltaic cells, the electroplating method comprising:

[0072] The TOPCon solar cell with a pre-prepared silicon nitride passivation layer provided in Example 1 has grooves formed by laser grooving on its surface.

[0073] After the groove is opened, the remaining silicon nitride is removed by a first acid pickling. Then, a metal film is deposited in the groove by physical vapor deposition. After annealing to form an alloy layer, a second acid pickling is performed to remove the metal film in other locations except the groove. Finally, conductive metal grid lines are prepared by electroplating to complete the metallization. The electrolyte used for electroplating includes 22% by mass of nickel sulfate, 18% by mass of sodium hypophosphite, 8% by mass of ammonium bifluoride buffer, 5% by mass of trisodium citrate, and 0.02% by mass of sodium dodecyl sulfate surfactant. The remainder is deionized water solvent.

[0074] Characterization and testing:

[0075] I. The oxide layer removal effect and silicon nitride damage degree of the photovoltaic cells obtained in the examples and comparative examples were tested by combining X-ray photoelectron spectroscopy (XPS) depth analysis with scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) area scanning analysis.

[0076] II. Electrode contact resistance of the photovoltaic cells obtained in the examples and comparative examples was tested using the transmission line model (TLM) method.

[0077] III. The photovoltaic cells obtained in the examples and comparative examples were subjected to cell efficiency testing, i.e., standard current-voltage (IV) characteristic testing, in accordance with the international standard IEC 60904-1.

[0078] The test results are shown in Table 3.

[0079] Table 3

[0080]

[0081] As can be seen from Table 1:

[0082] In Examples 1 and 2, by using a composite electroplating solution containing a fluoride complexing agent and a silicon nitride corrosion inhibitor, the oxide layer can be selectively removed during the electroplating process with almost no damage to the silicon nitride layer. In Example 2, the ammonium fluoride content is increased while the ammonium hydrogen fluoride and corrosion inhibitor content are reduced. Although the oxide layer can be completely removed, the balance between corrosion and protection is slightly lost, which has a very small impact on the passivation layer. As a result, the efficiency is slightly lower than that of the optimal example, but it is still significantly better than the conventional process.

[0083] Ammonium fluoride primarily provides fluoride ions (F) to corrode the oxide layer. - The concentration of fluoride directly determines the corrosion rate and completeness. In Comparative Example 1 and Example 3 (1.0%), insufficient corrosion ability resulted in residual oxide layer, increased contact resistance, and reduced efficiency. Example 4 (5.0%) had sufficient corrosion ability, but due to the high concentration of fluoride ions, the potential risk of attack on silicon nitride was slightly increased (very slight damage). Example 8 increased the amount of ammonium fluoride and the corrosion inhibitor, respectively, and protected silicon nitride while completely removing the oxide layer, achieving a high efficiency similar to that of the baseline Example 1.

[0084] Silicon nitride corrosion inhibitors form an adsorption protective film on the silicon nitride surface. The concentration of this film affects its integrity and strength. In Comparative Example 2 and Example 5 (0.5%), insufficient protection resulted in localized damage to the silicon nitride; in Example 6 (3.0%), excessive protection may have slightly affected the wettability of the plating solution in the tank or the metal deposition process, leading to slightly slower oxide layer removal and higher contact resistance.

[0085] Compared to Example 3, Example 7 showed a reduced amount of corrosion inhibitor, resulting in weaker protection and more significant damage under already low corrosion resistance, leading to a performance decline. Example 8, compared to Example 4, demonstrated enhanced protection, successfully suppressing potential damage under high fluoride concentrations and exhibiting superior performance. This proves that maintaining the optimal mass ratio of fluoride to corrosion inhibitor (approximately 2.08:1) is crucial. Experimental results show that when the ammonium fluoride content is 2%–4%, the silicon nitride corrosion inhibitor content is 1%–2.5%, and the mass ratio is maintained within the range of (2.0–2.2):1, a comprehensive effect of thorough oxide layer removal, zero damage to silicon nitride, lowest contact resistance, and optimal battery efficiency can be achieved.

[0086] As can be seen, this invention provides and uses a multifunctional composite electroplating solution, and further, by precisely balancing the proportions of each component, enables the selective etching of the oxide layer to be completed simultaneously during the electroplating process while protecting the silicon nitride layer from damage, and simultaneously forming metal deposition, thus completely eliminating the need for a separate pre-cleaning step. Therefore, the process is adjusted to laser grooving to form grooves, omitting the separate pre-cleaning step and directly performing electroplating (electroplating and oxide layer etching are simultaneous), followed by annealing, to obtain the finished solar cell. Thus, comparing Example 1 with Comparative Example 3 shows that the electroplating method of this invention has an oxide layer removal effect comparable to the traditional pre-cleaning process, achieving complete removal, and a significantly better silicon nitride protection effect than the traditional pre-cleaning process. In Comparative Example 3, excessive etching during the cleaning step may have resulted in severe damage to the silicon nitride layer. Simultaneously, in the photovoltaic cell of this invention, the electrode contact resistance is lower than that of the traditional process, which helps to improve the fill factor, ultimately increasing the cell conversion efficiency by 0.4% compared to the traditional process, demonstrating the technological advantages.

[0087] In summary, the electroplating process for photovoltaic cells provided by this invention can completely eliminate the independent pre-cleaning step, shorten the production process, and reduce equipment investment by approximately 20%. Production costs are reduced by more than 30% in chemical reagent consumption and wastewater treatment costs, resulting in less acidic wastewater discharge. Furthermore, the selective corrosion mechanism helps to better protect the silicon nitride passivation layer, improves the cell's open-circuit voltage, and enhances cell performance. This electroplating method has high process compatibility, is suitable for existing TOPCon cell production lines, requires no major equipment modifications, and is environmentally friendly, aligning with green manufacturing trends.

[0088] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0089] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0090] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A composite electroplating solution, characterized in that, The composite electroplating solution includes a metal salt containing electroplating metal ions and a solvent, and also includes ammonium fluoride and a silicon nitride corrosion inhibitor; the silicon nitride corrosion inhibitor includes at least one of benzotriazole or 1,2,4-triazole; the electroplating metal ions include nickel ions and / or copper ions.

2. The composite electroplating solution according to claim 1, characterized in that, Based on the mass of the composite electroplating solution as 100%, the ammonium fluoride accounts for 0.1% to 5%.

3. The composite electroplating solution according to claim 1, characterized in that, Based on the mass of the composite electroplating solution as 100%, the silicon nitride corrosion inhibitor accounts for 0.05% to 3%.

4. The composite electroplating solution according to claim 1, characterized in that, The mass ratio of ammonium fluoride to silicon nitride corrosion inhibitor is (1~5):

1.

5. The composite electroplating solution according to claim 1, characterized in that, The composite electroplating solution also includes a reducing agent.

6. The composite electroplating solution according to claim 5, characterized in that, The reducing agent includes sodium hypophosphite.

7. The composite electroplating solution according to claim 5, characterized in that, Based on the mass of the composite electroplating solution being 100%, the reducing agent accounts for 5% to 25%.

8. The composite electroplating solution according to claim 1, characterized in that, The composite electroplating solution also includes a buffer.

9. The composite electroplating solution according to claim 8, characterized in that, The buffer includes trisodium citrate and / or ammonium bifluoride.

10. The composite electroplating solution according to claim 8, characterized in that, Based on the mass of the composite electroplating solution being 100%, the buffer accounts for 1% to 25%.

11. The composite electroplating solution according to claim 9, characterized in that, Based on the mass of the composite electroplating solution as 100%, the trisodium citrate accounts for 1% to 10%, and the ammonium bifluoride accounts for 3% to 12%.

12. The composite electroplating solution according to claim 1, characterized in that, The composite electroplating solution also includes surfactants.

13. The composite electroplating solution according to claim 12, characterized in that, The surfactant includes sodium dodecyl sulfate.

14. The composite electroplating solution according to claim 12, characterized in that, Based on the mass of the composite electroplating solution being 100%, the surfactant accounts for 0.001% to 0.1%.

15. The composite electroplating solution according to claim 1, characterized in that, The metal salt includes sulfates of electroplated metal ions.

16. The composite electroplating solution according to claim 1, characterized in that, Based on the mass of the composite electroplating solution as 100%, the metal salt accounts for 10% to 30%.

17. The composite electroplating solution according to claim 1, characterized in that, The solvent includes water.

18. The composite electroplating solution according to claim 1, characterized in that, The pH of the composite electroplating solution is 2.5~5.

5.

19. The composite electroplating solution according to claim 18, characterized in that, The pH of the composite electroplating solution is controlled using a pH adjuster, which includes hydrochloric acid and / or ammonia.

20. A method for electroplating photovoltaic cells, characterized in that, Includes the following steps: Provides solar cells with a silicon nitride layer on the surface and grooves formed by slotting; After the groove is cut, without cleaning, the battery cell is directly placed in the composite electroplating solution described in any one of claims 1-19 for electroplating, so that the original oxide layer in the groove is removed and electrode grid lines are formed, thus completing metallization and obtaining a photovoltaic cell.

21. The electroplating method for photovoltaic cells according to claim 20, characterized in that, The electroplating temperature is 75℃~85℃, the time is 1min~3min, and the current density is 1A / dm. 2 ~5A / dm 2 .

22. The electroplating method for photovoltaic cells according to claim 20, characterized in that, The electroplating method further includes, after the electroplating is completed, removing the battery cells and sequentially performing post-cleaning and annealing to complete the metallization.

23. The electroplating method for photovoltaic cells according to claim 20, characterized in that, The electroplating process also involves stirring at a speed of 100 rpm to 300 rpm.

24. A photovoltaic cell, characterized in that, The metallization is completed by the electroplating method according to any one of claims 20-23.

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