Preparation method of BC solar cell and BC solar cell prepared by same

Abstract

The invention provides a preparation method of a BC solar cell and the BC solar cell prepared by the preparation method, and relates to the technical field of solar cells. The preparation method comprises the following steps: forming a patterned groove in the surface of a back coating layer of a BC battery silicon substrate; and sequentially carrying out oxide layer removal treatment, activation treatment, chemical nickel plating, copper electroplating and chemical tin plating on the patterned groove of the BC cell silicon substrate to obtain the BC solar cell. According to the preparation method of the BC solar cell, the conversion efficiency of the BC cell can be effectively improved, the production cost is reduced, and the reliability, the adhesive force and the weldability of a plating layer are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a preparation method of a BC solar cell and a BC solar cell prepared thereby. Background Art

[0002] A BC (Back Contact) cell is a photovoltaic cell based on an organic semiconductor material, which has characteristics such as high conversion efficiency and low manufacturing cost, and is regarded as one of the important development directions of the future photovoltaic industry. There are no grid lines on the front of the BC cell, and all grid lines are on the back, with low requirements for light shielding. Usually, the grid lines are relatively wide, and the consumption of silver paste is relatively large. There is data showing that its silver consumption is about 14 mg / W; at the same time, the sintering temperature of the silver paste is as high as over 700 °C, and the energy consumption is also relatively large.

[0003] In order to reduce costs, some researchers have further proposed to prepare metal electrodes by electroplating processes. Currently, when preparing the seed layer metal of the back P region and N region of the BC cell, the method of magnetron sputtering is usually required to improve the performance of the cell, and acidic chemicals are also required to remove the metal outside the pattern, which not only increases the preparation cost and complexity of the cell, but also may introduce additional pollution and defects, affecting the performance and lifespan of the cell.

[0004] Therefore, it is of great significance to research and obtain a preparation method of a BC cell with a simple process flow and reduced costs.

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

[0006] The purpose of the present invention is to provide a preparation method of a BC solar cell and a BC solar cell prepared thereby. The preparation method of the present invention prepares a metal electrode by using electroless nickel plating + electroplating copper + electroless tin plating processes to replace the original silver electrode, which not only reduces the production cost of the cell, but also improves the electrical performance of the cell.

[0007] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0008] In the first aspect, the present invention provides a preparation method of a BC solar cell, and the preparation method includes:

[0009] Forming a patterned groove on the surface of the coating layer on the back of the BC cell silicon substrate;

[0010] Performing an oxide layer removal treatment, an activation treatment, electroless nickel plating, electroplating copper, and electroless tin plating in sequence at the patterned groove of the BC cell silicon substrate to obtain the BC solar cell.

[0011] Further, the coating layer on the back of the BC cell silicon substrate includes a silicon nitride layer.

[0012] Further, the thickness of the silicon nitride layer is 50 to 100 nm.

[0013] Further, the patterned groove is formed by laser grooving.

[0014] Further, the power of the laser grooving is 4 to 10 W.

[0015] Further, the frequency of the laser grooving is 500 to 2000 kHz.

[0016] Further, the speed of the laser grooving is 10 to 50 m / s.

[0017] Further, the width of the patterned groove is 30 to 100 μm.

[0018] Further, the depth of the patterned groove is 70 to 120 nm.

[0019] Further, the deoxidation layer treatment includes:

[0020] Immersing the BC cell silicon substrate in a deoxidation working solution, followed by washing and drying.

[0021] Further, the deoxidation working solution includes: 10 to 50 mL / L of hydrofluoric acid, with the balance being water.

[0022] Further, the concentration of the hydrofluoric acid is 48 to 50 vol%.

[0023] Further, the temperature of the deoxidation layer treatment is 20 to 30 °C.

[0024] Further, the time of the deoxidation layer treatment is 10 to 60 s.

[0025] Further, the activation treatment includes:

[0026] Immersing the BC cell silicon substrate after the deoxidation layer treatment in an activator working solution, followed by washing and drying.

[0027] Further, the activator working solution includes: 0.1 to 1 g / L of palladium chloride, 0.5 to 5 g / L of ammonium chloride, 0.05 to 0.5 g / L of 2-aminopyridine, with the balance being water.

[0028] Further, the temperature of the activation treatment is 20 to 30 °C.

[0029] Further, the time of the activation treatment is 20 to 80 s.

[0030] Further, the electroless nickel plating includes:

[0031] Immerse the activated BC cell silicon substrate in the electroless nickel plating working solution for electroless nickel plating to form a nickel layer, and then wash and dry it.

[0032] Furthermore, the electroless nickel plating working solution includes: nickel sulfate 5 - 30 g / L, sodium hypophosphite 10 - 40 g / L, sodium citrate 5 - 20 g / L, thiourea 0.5 - 5 g / L, and the balance is water.

[0033] Furthermore, the pH of the electroless nickel plating working solution is 5.0 - 7.0.

[0034] Furthermore, the electroless nickel plating is carried out in a dark environment.

[0035] Furthermore, the temperature of the electroless nickel plating is 70 - 90 °C.

[0036] Furthermore, the time of the electroless nickel plating is 1 - 5 min.

[0037] Furthermore, the thickness of the nickel layer is 0.2 - 1.0 μm.

[0038] Furthermore, the electroplating of copper includes:

[0039] Immerse the BC cell silicon substrate after electroless nickel plating in the activation solution for activation, and then immerse it in the copper electroplating working solution for electroplating copper to form a copper layer, and then wash and dry it.

[0040] Furthermore, the activation solution includes concentrated sulfuric acid 10 - 100 mL / L, and the balance is water.

[0041] Furthermore, the temperature of the activation is 20 - 30 °C.

[0042] Furthermore, the time of the activation is 30 - 120 s.

[0043] Furthermore, the copper electroplating working solution includes: copper sulfate 180 - 250 g / L, concentrated sulfuric acid 50 - 70 mL / L, concentrated hydrochloric acid 3 - 8 mL / L, 2-ethylhexyl sodium sulfate 0.5 - 5 mL / L, benzylideneacetone 1 - 10 mL / L, and the balance is water.

[0044] Furthermore, the concentration of the concentrated sulfuric acid is 97 - 99 vol%.

[0045] Furthermore, the concentration of the concentrated hydrochloric acid is 35 - 40 vol%.

[0046] Furthermore, the current density of the electroplating of copper is 10 - 30 A / dm 2 .

[0047] Furthermore, the temperature of the electroplating of copper is 25 - 50 °C.

[0048] Furthermore, the time for electroplating copper is 2 to 10 minutes.

[0049] Furthermore, the thickness of the copper layer is 6 to 12 μm.

[0050] Furthermore, the electroless tin plating includes:

[0051] Immerse the BC cell silicon substrate after electroplating copper in the electroless tin plating working solution for electroless tin plating to form a tin layer, and then wash and dry it.

[0052] Furthermore, the electroless tin plating working solution includes: 5 to 30 g / L of stannous chloride, 5 to 20 g / L of sodium hypophosphite, 10 to 40 mL / L of concentrated hydrochloric acid, 5 to 30 mL / L of hydrazine hydrate, 5 to 20 g / L of sodium citrate, and the balance is water.

[0053] Furthermore, the concentration of the concentrated hydrochloric acid is 35 to 40 vol%. <9000130>

[0054] Furthermore, the pH of the electroless tin plating working solution is 1.0 to 4.0.

[0055] Furthermore, the temperature of the electroless tin plating is 30 to 60 °C.

[0056] Furthermore, the time for electroless nickel plating is 30 to 120 s.

[0057] Furthermore, the thickness of the tin layer is 0.2 to 1.0 μm.

[0058] In a second aspect, the present invention provides a BC solar cell, which is prepared by the preparation method of the BC solar cell as described in the first aspect.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) The present invention proposes a preparation method for a BC cell. By using the electroless nickel plating + electroplating copper + electroless tin plating process to prepare the metal electrode, replacing the original silver electrode, not only reduces the production cost of the cell, but also improves the electrical performance of the cell.

[0061] (2) In the present invention, the nickel layer obtained by electroless nickel plating has a uniform thickness and small internal stress. After continuing to plate copper and tin, the obtained metal electrode has a good bonding force with the silicon substrate; in addition, the tin layer obtained by the electroless tin plating method has good compactness, low porosity, strong corrosion resistance, and good solderability. Specific Embodiments

[0062] Unless otherwise defined herein, scientific and technical terms used in connection with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meanings and scopes of the terms should be clear. However, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or extrinsic definition. In this application, unless otherwise specified, the use of "or" means "and / or". In addition, the use of the term "comprising" and other forms is non-restrictive.

[0063] It should be noted that specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0064] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0065] In a first aspect, the present invention provides a method for preparing a BC solar cell, the preparation method comprising:

[0066] Forming a patterned groove on the surface of the coating layer on the back of the BC cell silicon substrate;

[0067] Performing a deoxidation layer treatment, an activation treatment, electroless nickel plating, electroplating copper, and electroless tin plating in sequence at the patterned groove of the BC cell silicon substrate to obtain the BC solar cell.

[0068] In the present invention, first, before electroless nickel plating, the patterned grooves are subjected to deoxidation treatment and activation treatment. The synergy of the deoxidation treatment and the activation treatment improves the surface cleanliness and activity. The deoxidation treatment can expose the silicon surface, significantly enhance the adsorption ability of subsequent noble metal ions, and provide a highly active substrate for the activation treatment. In the activation treatment, noble metal ions form stable complexes through complexation, are evenly adsorbed on the silicon surface, and form noble metal nanoparticles through chemical reduction. These particles serve as catalytic sites, providing uniform nucleation centers for subsequent electroless nickel plating and ensuring the density and adhesion of the nickel plating layer. Further, a nickel layer is formed at the patterned grooves by electroless nickel plating, which is suitable for the high-precision patterned electrode structure on the back of the BC cell. The plating layer is dense and has strong corrosion resistance, can maintain stability in harsh environments such as sulfides, and improve the long-term reliability of the battery. Moreover, the electroless nickel plating layer provides good adhesion for subsequent electroplating of copper, avoiding diffusion problems caused by direct contact between copper and silicon and reducing the interface resistance. Finally, after the nickel layer is formed at the patterned grooves, a copper layer and a tin layer are sequentially formed on the surface of the nickel layer by electroplating copper and electroless tin plating. Electroplated copper has high conductivity and can greatly improve the conversion efficiency of the BC cell. The tin layer can effectively prevent the oxidation of the copper electrode and maintain the long-term conductive stability of the BC cell. In summary, the preparation method of the BC solar cell of the present invention can effectively improve the conversion efficiency of the BC cell, reduce production costs, enhance the reliability and adhesion of the plating layer, and optimize the production process compatibility.

[0069] As an alternative embodiment, the back coating layer of the BC cell silicon substrate includes a silicon nitride layer.

[0070] As an alternative embodiment, the thickness of the silicon nitride layer is 50 - 100 nm, for example, it can be 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc.

[0071] As an alternative embodiment, the patterned grooves are formed by laser grooving.

[0072] As an alternative embodiment, the back coating layer of the BC cell silicon substrate is removed by laser grooving technology to form patterned grooves on the surface of the coating layer.

[0073] As an alternative embodiment, the power of the laser grooving is 4 - 10 W, for example, it can be 4 W, 5 W, 6 W, 7 W, 8 W, 9 W, 10 W, etc.

[0074] As an alternative embodiment, the frequency of the laser grooving is 500 - 2000 kHz, for example, it can be 400 kHz, 500 kHz, 600 kHz, 700 kHz, 800 kHz, 900 kHz, 1000 kHz, 1100 kHz, 1200 kHz, 1300 kHz, 1400 kHz, 1500 kHz, 1600 kHz, 1700 kHz, 1800 kHz, 1900 kHz, 2000 kHz, etc.

[0075] As an alternative embodiment, the speed of the laser grooving is 10 - 50 m / s, for example, it can be 10 m / s, 15 m / s, 20 m / s, 25 m / s, 30 m / s, 35 m / s, 40 m / s, 45 m / s, 50 m / s, etc.

[0076] As an alternative embodiment, the width of the patterned groove is 30 - 100 μm, for example, it can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc.

[0077] As an alternative embodiment, the depth of the patterned groove is 70 - 120 nm, for example, it can be 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, etc.

[0078] As an alternative embodiment, the deoxidation layer treatment includes:

[0079] Immerse the BC cell silicon substrate in the deoxidation working solution to remove the oxide layer at the patterned groove, and then wash and dry it to obtain the BC cell silicon substrate after the deoxidation layer treatment.

[0080] As an alternative embodiment, the deoxidation working solution includes: hydrofluoric acid 10 - 50 mL / L (for example, it can be 10 mL / L, 15 mL / L, 20 mL / L, 25 mL / L, 30 mL / L, 35 mL / L, 40 mL / L, 45 mL / L, 50 mL / L, etc.), and the balance is water.

[0081] As an alternative embodiment, the preparation method of the deoxidation working solution includes: mixing hydrofluoric acid and water to obtain the deoxidation working solution.

[0082] As an alternative embodiment, the concentration of hydrofluoric acid is 48 - 50 vol%, for example, it can be 48 vol%, 48.5 vol%, 49 vol%, 49.5 vol%, 50 vol%, etc.

[0083] It should be noted that the concentration of hydrofluoric acid here refers to the concentration of hydrofluoric acid itself before mixing with water (i.e., the concentration of HF therein).

[0084] As an optional embodiment, the temperature of the deoxidized layer treatment is 20-30 °C, for example, it can be 20 °C, 22 °C, 24 °C, 25 °C, 26 °C, 28 °C, 30 °C, etc.

[0085] As an optional embodiment, the time of the deoxidized layer treatment is 10-60 s, for example, it can be 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, etc.

[0086] As an optional embodiment, the washing in the deoxidized layer treatment includes washing with pure water.

[0087] As an optional embodiment, the drying in the deoxidized layer treatment includes drying with nitrogen.

[0088] As an optional embodiment, the activation treatment includes:

[0089] Immersing the BC cell silicon substrate after the deoxidized layer treatment in the activator working solution to activate the silicon layer at the patterned grooves, and then through washing and drying, obtaining the BC cell silicon substrate after the activation treatment.

[0090] As an optional embodiment, the activator working solution includes: palladium chloride 0.1-1 g / L, ammonium chloride 0.5-5 g / L, 2-aminopyridine 0.05-0.5 g / L, and the balance is water.

[0091] In the present invention, the activator working solution includes palladium chloride, ammonium chloride and 2-aminopyridine with specific concentrations. The synergistic effect of the three activates the silicon layer, stabilizes the complexed palladium ions, is beneficial to enhancing surface adsorption, increases the loading amount of palladium on the silicon surface, provides more dense catalytic sites, significantly improves the activation effect on the silicon surface, so that the electroless nickel plating reaction starts uniformly on the silicon surface, accelerates the nickel deposition rate, reduces the porosity of the coating at the same time, forms a denser nickel coating, and ensures the tight combination of the nickel coating and the silicon substrate, reducing the risk of peeling.

[0092] As an optional embodiment, the concentration of palladium chloride in the activator working solution is 0.1-1 g / L, for example, it can be 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, 1 g / L, etc.

[0093] As an alternative embodiment, the concentration of ammonium chloride in the activator working solution is 0.5 to 5 g / L, for example, it can be 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, etc.

[0094] As an alternative embodiment, the concentration of 2-aminopyridine in the activator working solution is 0.05 to 0.5 g / L, for example, it can be 0.05 g / L, 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.45 g / L, 0.5 g / L, etc.

[0095] As an alternative embodiment, the temperature of the activation treatment is 20 to 30 °C, for example, it can be 20 °C, 22 °C, 24 °C, 25 °C, 26 °C, 28 °C, 30 °C, etc.

[0096] As an alternative embodiment, the time of the activation treatment is 20 to 80 s, for example, it can be 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, etc.

[0097] As an alternative embodiment, the washing in the activation treatment includes washing with pure water.

[0098] As an alternative embodiment, the drying in the activation treatment includes drying with nitrogen.

[0099] As an alternative embodiment, the electroless nickel plating includes:

[0100] Immerse the BC cell silicon substrate after the activation treatment in the electroless nickel plating working solution for electroless nickel plating to form a nickel layer at the patterned groove, and then wash and dry.

[0101] As an alternative embodiment, the electroless nickel plating working solution includes: nickel sulfate 5 to 30 g / L, sodium hypophosphite 10 to 40 g / L, sodium citrate 5 to 20 g / L, thiourea 0.5 to 5 g / L, and the balance is water.

[0102] In the present invention, the electroless nickel plating working solution includes nickel sulfate, sodium hypophosphite, sodium citrate, and thiourea at specific concentrations, which can form a nickel layer with low internal stress, high density, and high bonding strength. Among them, the reason for the low internal stress is that the synergistic effect of the four components can regulate the reduction rate of Ni2+ uniformly through complexation regulation and adsorption regulation, avoiding lattice distortion caused by local rapid deposition. At the same time, fine grains disperse stress through grain boundaries, reducing macroscopic internal stress. The reason for the high density is that the synergistic effect of the four components can achieve complexation-reduction balance, ensure the controllability of the deposition process, and make the grains closely arranged, reducing the porosity of the coating and avoiding layered defects caused by intermittent growth of the coating. The reason for the high bonding strength is that after the silicon surface is activated by Pd, high-active sites are formed, and nickel preferentially nucleates at these sites to form chemical bonding. Moreover, sodium citrate prevents impurity adsorption, and thiourea inhibits oxidation, ensuring direct contact between the nickel layer and the silicon substrate.

[0103] As an alternative embodiment, the concentration of nickel sulfate in the electroless nickel plating working solution is 5 - 30 g / L, for example, it can be 5 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 14 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, 22 g / L, 24 g / L, 25 g / L, 26 g / L, 28 g / L, 30 g / L, etc.

[0104] As an alternative embodiment, the concentration of sodium hypophosphite in the electroless nickel plating working solution is 10 - 40 g / L, for example, it can be 10 g / L, 12 g / L, 14 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, 22 g / L, 24 g / L, 25 g / L, 26 g / L, 28 g / L, 30 g / L, 32 g / L, 34 g / L, 35 g / L, 36 g / L, 38 g / L, 40 g / L, etc.

[0105] As an alternative embodiment, the concentration of sodium citrate in the electroless nickel plating working solution is 5 - 20 g / L, for example, it can be 5 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 14 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, etc.

[0106] As an alternative embodiment, the concentration of thiourea in the electroless nickel plating working solution is 0.5 - 5 g / L, for example, it can be 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, etc.

[0107] As an alternative embodiment, the pH of the electroless nickel plating working solution is 5.0 - 7.0, for example, it can be 5.0, 5.2, 5.4, 5.5, 5.6, 5.8, 6.0, 6.2, 6.4, 6.5, 6.6, 6.8, 7, etc.

[0108] As an optional embodiment, the electroless nickel plating is carried out in a dark environment.

[0109] As an optional embodiment, the temperature of the electroless nickel plating is 70-90 °C, for example, it can be 70 °C, 72 °C, 74 °C, 75 °C, 76 °C, 78 °C, 80 °C, 82 °C, 84 °C, 85 °C, 86 °C, 88 °C, 90 °C, etc.

[0110] As an optional embodiment, the time of the electroless nickel plating is 1-5 min, for example, it can be 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, etc.

[0111] As an optional embodiment, the thickness of the nickel layer is 0.2-1.0 μm, for example, it can be 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, etc.

[0112] As an optional embodiment, the washing in the electroless nickel plating includes washing with pure water.

[0113] As an optional embodiment, the drying in the electroless nickel plating includes drying with nitrogen.

[0114] As an optional embodiment, the electroplating of copper includes:

[0115] Immersing the BC cell silicon substrate after electroless nickel plating in an activation solution for activation, then immersing it in a copper electroplating working solution for electroplating copper to form a copper layer, and then washing and drying.

[0116] As an optional embodiment, the activation solution includes 10-100 mL / L of concentrated sulfuric acid (for example, it can be 10 mL / L, 20 mL / L, 30 mL / L, 40 mL / L, 50 mL / L, 60 mL / L, 70 mL / L, 80 mL / L, 90 mL / L, 100 mL / L, etc.), and the balance is water.

[0117] As an optional embodiment, the preparation method of the activation solution includes: mixing concentrated sulfuric acid and water to obtain the activation solution.

[0118] As an optional embodiment, the concentration of the concentrated sulfuric acid is 97-99 vol%, for example, it can be 97 vol%, 97.5 vol%, 98 vol%, 98.5 vol%, 99 vol%, etc.

[0119] It should be noted that the concentration of the concentrated sulfuric acid here refers to the concentration of the concentrated sulfuric acid itself (i.e., the concentration of H2SO4 in it) before mixing with water.

[0120] As an alternative embodiment, before the copper electroplating, the activation temperature is 20 to 30 °C, for example, it can be 20 °C, 22 °C, 24 °C, 25 °C, 26 °C, 28 °C, 30 °C, etc.

[0121] As an alternative embodiment, before the copper electroplating, the activation time is 30 to 120 s, for example, it can be 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s, 120 s, etc.

[0122] As an alternative embodiment, the copper electroplating working solution comprises: 180 to 250 g / L of copper sulfate, 50 to 70 mL / L of concentrated sulfuric acid, 3 to 8 mL / L of concentrated hydrochloric acid, 0.5 to 5 mL / L of 2-ethylhexyl sodium sulfate, 1 to 10 mL / L of benzylideneacetone, and the balance is water.

[0123] In the present invention, the copper electroplating working solution includes copper sulfate, concentrated sulfuric acid, concentrated hydrochloric acid, 2-ethylhexyl sodium sulfate, and benzylideneacetone at specific concentrations. Each component cooperates with each other and synergistically enhances the effect. Through ion supply, conductivity enhancement, grain refinement, wetting optimization, and reduction of side reactions, an efficient and high-quality copper electroplating process is achieved, promoting the refinement of copper layer grains, significantly improving the denseness of the coating, achieving micro-leveling, reducing interfacial impurities, and enhancing the adhesion between the copper layer and the nickel layer.

[0124] As an alternative embodiment, the concentration of copper sulfate in the copper electroplating working solution is 180 to 250 g / L, for example, it can be 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, etc.

[0125] As an alternative embodiment, the concentration of concentrated sulfuric acid in the copper electroplating working solution is 50 to 70 mL / L, for example, it can be 50 mL / L, 52 mL / L, 54 mL / L, 56 mL / L, 58 mL / L, 60 mL / L, 62 mL / L, 64 mL / L, 66 mL / L, 68 mL / L, 70 mL / L, etc.

[0126] As an alternative embodiment, the concentration of concentrated hydrochloric acid in the copper electroplating working solution is 3 to 8 mL / L, for example, it can be 3 mL / L, 3.5 mL / L, 4 mL / L, 4.5 mL / L, 5 mL / L, 5.5 mL / L, 6 mL / L, 6.5 mL / L, 7 mL / L, 7.5 mL / L, 8 mL / L, etc.

[0127] As an optional embodiment, the concentration of sodium 2-ethylhexyl sulfate in the copper electroplating working solution is 0.5 to 5 mL / L, for example, it can be 0.5 mL / L, 1 mL / L, 1.5 mL / L, 2 mL / L, 2.5 mL / L, 3 mL / L, 3.5 mL / L, 4 mL / L, 4.5 mL / L, 5 mL / L, etc.

[0128] As an optional embodiment, the concentration of benzalacetone in the copper electroplating working solution is 1 to 10 mL / L, for example, it can be 1 mL / L, 1.5 mL / L, 2 mL / L, 2.5 mL / L, 3 mL / L, 3.5 mL / L, 4 mL / L, 4.5 mL / L, 5 mL / L, 6 mL / L, 7 mL / L, 8 mL / L, 9 mL / L, 10 mL / L, etc.

[0129] As an optional embodiment, the preparation method of the copper electroplating working solution includes: mixing copper sulfate, concentrated sulfuric acid, concentrated hydrochloric acid, sodium 2-ethylhexyl sulfate, benzalacetone and water to obtain the copper electroplating working solution.

[0130] As an optional embodiment, the concentration of the concentrated sulfuric acid is 97 to 99 vol%, for example, it can be 97 vol%, 97.5 vol%, 98 vol%, 98.5 vol%, 99 vol%, etc.

[0131] It should be noted that the concentration of the concentrated sulfuric acid here refers to the concentration of the concentrated sulfuric acid itself (i.e., the concentration of H2SO4 in it) before mixing with water.

[0132] As an optional embodiment, the concentration of the concentrated hydrochloric acid is 35 to 40 vol%, for example, it can be 35 vol%, 35.5 vol%, 36 vol%, 36.5 vol%, 37 vol%, 37.5 vol%, 38 vol%, 38.5 vol%, 39 vol%, 39.5 vol%, etc.

[0133] It should be noted that the concentration of the concentrated hydrochloric acid here refers to the concentration of the concentrated hydrochloric acid itself (i.e., the concentration of HCl in it) before mixing with water.

[0134] As an optional embodiment, the current density of the electroplated copper is 10 to 30 A / dm 2 , for example, it can be 10 A / dm 2 , 12 A / dm 2 , 14 A / dm 2 , 15 A / dm 2 , 16 A / dm 2 , 18 A / dm 2 , 20 A / dm 2 , 22 A / dm 2, 24 A / dm 2 , 25 A / dm 2 , 26 A / dm 2 , 28 A / dm 2 , 30 A / dm 2 etc.

[0135] As an alternative embodiment, the temperature of the copper electroplating is 25 - 50 °C, for example, it can be 25 °C, 26 °C, 28 °C, 30 °C, 32 °C, 34 °C, 35 °C, 36 °C, 38 °C, 40 °C, 42 °C, 44 °C, 45 °C, 46 °C, 48 °C, 50 °C, etc.

[0136] As an alternative embodiment, the time of the copper electroplating is 2 - 10 min, for example, it can be 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min, 10 min, etc.

[0137] As an alternative embodiment, the thickness of the copper layer is 6 - 12 μm, for example, it can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc.

[0138] As an alternative embodiment, the washing in the copper electroplating includes cleaning with pure water.

[0139] As an alternative embodiment, the drying in the copper electroplating includes drying with nitrogen.

[0140] As an alternative embodiment, the chemical tin plating includes:

[0141] Immersing the BC cell silicon substrate after copper electroplating in the chemical tin plating working solution for chemical tin plating to form a tin layer, and then washing and drying.

[0142] As an alternative embodiment, the chemical tin plating working solution includes: stannous chloride 5 - 30 g / L, sodium hypophosphite 5 - 20 g / L, concentrated hydrochloric acid 10 - 40 mL / L, hydrazine hydrate 5 - 30 mL / L, sodium citrate 5 - 20 g / L, and the balance is water.

[0143] In the present invention, the electroless tin plating working solution includes stannous chloride, sodium hypophosphite, concentrated hydrochloric acid, hydrazine hydrate, and sodium citrate at specific concentrations. Each component cooperates with each other, synergistically enhancing the effect, reducing the evolution of hydrogen, expelling impurities through gas disturbance, forming a pore-free structure, and the dense structure blocking the penetration of corrosive media; the surface of the coating is smooth, with a low oxide content (due to the strongly reducing environment), and tin itself is an excellent welding material, ensuring good bonding with the solder, and finally forming a tin coating with fine grains, a dense structure, strong corrosion resistance, and a clean surface.

[0144] As an optional embodiment, the concentration of stannous chloride in the electroless tin plating working solution is 5 - 30 g / L, for example, it can be 5 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 14 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, 22 g / L, 24 g / L, 25 g / L, 26 g / L, 28 g / L, 30 g / L, etc.

[0145] As an optional embodiment, the concentration of sodium hypophosphite in the electroless tin plating working solution is 5 - 20 g / L, for example, it can be 5 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 14 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, etc.

[0146] As an optional embodiment, the concentration of concentrated hydrochloric acid in the electroless tin plating working solution is 10 - 40 mL / L, for example, it can be 10 mL / L, 12 mL / L, 14 mL / L, 16 mL / L, 18 mL / L, 20 mL / L, 22 mL / L, 24 mL / L, 26 mL / L, 28 mL / L, 30 mL / L, 32 mL / L, 34 mL / L, 36 mL / L, 38 mL / L, 40 mL / L, etc.

[0147] As an optional embodiment, the concentration of hydrazine hydrate in the electroless tin plating working solution is 5 - 30 mL / L, for example, it can be 5 mL / L, 6 mL / L, 8 mL / L, 10 mL / L, 12 mL / L, 14 mL / L, 15 mL / L, 16 mL / L, 18 mL / L, 20 mL / L, 22 mL / L, 24 mL / L, 25 mL / L, 26 mL / L, 28 mL / L, 30 mL / , etc.

[0148] As an optional embodiment, the concentration of sodium citrate in the electroless tin plating working solution is 5 - 20 g / L, for example, it can be 5 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 14 g / L, 15 g / L, 16 g / L, 18 g / L, 20 g / L, etc.

[0149] As an alternative embodiment, the method for preparing the electroless tin plating working solution comprises: mixing stannous chloride, sodium hypophosphite, concentrated hydrochloric acid, hydrazine hydrate, sodium citrate and water to obtain the electroless tin plating working solution.

[0150] As an alternative embodiment, the concentration of the concentrated hydrochloric acid is 35 - 40 vol%, for example, it can be 35 vol%, 35.5 vol%, 36 vol%, 36.5 vol%, 37 vol%, 37.5 vol%, 38 vol%, 38.5 vol%, 39 vol%, 39.5 vol%, etc.

[0151] It should be noted that the concentration of the concentrated hydrochloric acid here refers to the concentration of the concentrated hydrochloric acid itself (i.e., the concentration of HCl in it) before mixing with water.

[0152] As an alternative embodiment, the pH of the electroless tin plating working solution is 1.0 - 4.0, for example, it can be 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, etc.

[0153] As an alternative embodiment, the temperature of the electroless tin plating is 30 - 60 °C, for example, it can be 30 °C, 32 °C, 34 °C, 35 °C, 36 °C, 38 °C, 40 °C, 42 °C, 44 °C, 45 °C, 46 °C, 48 °C, 50 °C, 52 °C, 54 °C, 55 °C, 56 °C, 58 °C, 60 °C, etc.

[0154] As an alternative embodiment, the time for electroless nickel plating is 30 - 120 s, for example, it can be 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s, 120 s, etc.

[0155] As an alternative embodiment, the thickness of the tin layer is 0.2 - 1.0 μm, for example, it can be 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, etc.

[0156] In a second aspect, the present invention provides a BC solar cell, which is prepared by the method for preparing a BC solar cell as described in the first aspect.

[0157] The present invention will be further described below through examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0158] Example 1

[0159] This example provides a method for preparing a BC solar cell, and the method for preparing the BC solar cell comprises the following steps:

[0160] S1. Laser grooving:

[0161] Provide a BC cell silicon substrate with a back coating layer (the back coating layer of the substrate has a silicon nitride layer with a thickness of 80 nm); use the laser grooving method (power of 6 W, frequency of 2000 kHz, speed of 30 m / s) to remove the coating layer on the back of the BC cell silicon substrate, and form a patterned groove (the width of the patterned groove is 65 μm and the depth is 95 nm) on the surface of the coating layer to obtain a BC cell silicon substrate with a patterned groove.

[0162] S2. De-oxidation layer treatment:

[0163] Immerse the BC cell silicon substrate with a patterned groove in the de-oxidation working solution at 25 °C for 35 s, then wash it clean with pure water and dry it with nitrogen to obtain a de-oxidized BC cell silicon substrate; wherein, the de-oxidation working solution includes: 25 mL / L of hydrofluoric acid, and the balance is water; the concentration of the hydrofluoric acid is 49%.

[0164] S3. Activation treatment:

[0165] Immerse the de-oxidized BC cell silicon substrate in the activator working solution at 25 °C for 50 s to uniformly activate it, then wash it three times with pure water and dry it with nitrogen to obtain an activated BC cell silicon substrate; wherein, the activator working solution includes: 0.5 g / L of palladium chloride, 2.2 g / L of ammonium chloride, 0.3 g / L of 2-aminopyridine, and the balance is water.

[0166] S4. Electroless nickel plating:

[0167] Immerse the activated BC cell silicon substrate in the electroless nickel plating working solution, turn off all light sources to make the reaction in a dark environment, carry out plating at 80 °C for 2.5 min, then wash it clean with pure water and dry it. A nickel layer with a thickness of 0.6 μm is formed at the patterned groove to obtain a nickel-plated BC cell silicon substrate; wherein, the electroless nickel plating working solution includes: 15 g / L of nickel sulfate, 25 g / L of sodium hypophosphite, 10 g / L of sodium citrate, 2 g / L of thiourea, and the balance is water.

[0168] S5. Electroplating copper:

[0169] Place the nickel-plated BC cell silicon substrate horizontally in the electroplating copper equipment with the back facing down, immerse it in the activation solution at 25 °C for activation for 75 s, and then immerse it in the copper electroplating working solution at 40 °C at 20 A / dm 2Electroplate copper at a current density of [value] for 6 minutes. After electroplating, wash it clean with pure water, then dry it to form a copper layer with a thickness of 9 μm on the nickel layer, obtaining a BC cell silicon substrate after copper plating; wherein, the activation solution includes 50 mL / L of concentrated sulfuric acid, and the balance is water, and the concentration of the concentrated sulfuric acid is 98%; the copper electroplating working solution includes: 215 g / L of copper sulfate, 60 mL / L of concentrated sulfuric acid, 5 mL / L of concentrated hydrochloric acid, 3 mL / L of 2-ethylhexyl sodium sulfate, 5 mL / L of benzalacetone, and the balance is water, the concentration of the concentrated sulfuric acid is 98%, and the concentration of the concentrated hydrochloric acid is 37%.

[0170] S6. Electroless tin plating:

[0171] Immerse the BC cell silicon substrate after copper plating in the electroless tin plating working solution, carry out plating at 45 °C for 75 s, then wash it clean with pure water, and then dry it to form a tin layer with a thickness of 0.6 μm on the copper layer, obtaining a BC cell after tin plating; wherein, the electroless tin plating working solution includes: 15 g / L of stannous chloride, 12 g / L of sodium hypophosphite, 20 mL / L of concentrated hydrochloric acid, 20 mL / L of hydrazine hydrate, 12 g / L of sodium citrate, and the balance is water, and the concentration of the concentrated hydrochloric acid is 37%.

[0172] Example 2

[0173] This example provides a method for preparing a BC solar cell, and the method for preparing the BC solar cell includes the following steps:

[0174] S1. Laser grooving:

[0175] Provide a BC cell silicon substrate with a back coating layer (the back coating layer of the substrate has a silicon nitride layer with a thickness of 80 nm); use the laser grooving method (power is 6 W, frequency is 2000 kHz, speed is 30 m / s) to remove the coating layer on the back of the BC cell silicon substrate, and form a patterned groove (the width of the patterned groove is 80 μm and the depth is 100 nm) on the surface of the coating layer, obtaining a BC cell silicon substrate with a patterned groove.

[0176] S2. Deoxidation layer treatment:

[0177] Immerse the BC cell silicon substrate with a patterned groove in the deoxidation working solution at 25 °C for 60 s, then wash it clean with pure water, and blow it dry with nitrogen to obtain a BC cell silicon substrate after deoxidation; wherein, the deoxidation working solution includes: 20 mL / L of hydrofluoric acid, and the balance is water; the concentration of the hydrofluoric acid is 49%.

[0178] S3. Activation treatment:

[0179] The deoxidized BC cell silicon substrate is immersed in the activator working solution at 25°C for 60 s to be uniformly activated, then washed three times with pure water and dried with nitrogen to obtain the activated BC cell silicon substrate; wherein, the activator working solution includes: palladium chloride 0.3 g / L, ammonium chloride 1.2 g / L, 2-aminopyridine 0.3 g / L, and the balance is water.

[0180] S4. Electroless nickel plating:

[0181] The activated BC cell silicon substrate is immersed in the electroless nickel plating working solution, all light sources are turned off to make the reaction in a dark environment, plated at 70°C for 5 min, then washed clean with pure water and dried, and a nickel layer with a thickness of 0.8 μm is formed at the patterned groove to obtain the nickel-plated BC cell silicon substrate; wherein, the electroless nickel plating working solution includes: nickel sulfate 20 g / L, sodium hypophosphite 20 g / L, sodium citrate 5 g / L, thiourea 5 g / L, and the balance is water.

[0182] S5. Electroplating copper:

[0183] The nickel-plated BC cell silicon substrate is horizontally placed in the electroplating copper equipment with the back facing down, immersed in the activation solution at 25°C for activation for 100 s, and then immersed in the copper electroplating working solution at 30°C for electroplating copper at a current density of 15 A / dm 2 for 10 min. After electroplating, it is washed clean with pure water and dried, and a copper layer with a thickness of 10 μm is formed on the nickel layer to obtain the copper-plated BC cell silicon substrate; wherein, the activation solution includes concentrated sulfuric acid 40 mL / L, and the balance is water, and the concentration of the concentrated sulfuric acid is 98%; the copper electroplating working solution includes: copper sulfate 200 g / L, concentrated sulfuric acid 70 mL / L, concentrated hydrochloric acid 3 mL / L, 2-ethylhexyl sodium sulfate 2 mL / L, benzylideneacetone 8 mL / L, and the balance is water, the concentration of the concentrated sulfuric acid is 98%, and the concentration of the concentrated hydrochloric acid is 37%.

[0184] S6. Electroless tin plating:

[0185] The copper-plated BC cell silicon substrate is immersed in the electroless tin plating working solution, plated at 40°C for 100 s, then washed clean with pure water and dried, and a tin layer with a thickness of 0.9 μm is formed on the copper layer to obtain the tin-plated BC cell; wherein, the electroless tin plating working solution includes: stannous chloride 10 g / L, sodium hypophosphite 10 g / L, concentrated hydrochloric acid 25 mL / L, hydrazine hydrate 15 mL / L, sodium citrate 10 g / L, and the balance is water, and the concentration of the concentrated hydrochloric acid is 37%.

[0186] Example 3

[0187] This embodiment provides a method for fabricating a BC solar cell, and the method for fabricating the BC solar cell includes the following steps:

[0188] S1. Laser grooving:

[0189] Provide a BC cell silicon substrate with a back coating layer (the back coating layer of the substrate has a silicon nitride layer with a thickness of 80 nm); use a laser grooving method (power of 6 W, frequency of 2000 kHz, speed of 30 m / s) to remove the coating layer on the back of the BC cell silicon substrate, and form a patterned groove (the width of the patterned groove is 50 μm and the depth is 80 nm) on the surface of the coating layer to obtain a BC cell silicon substrate with a patterned groove.

[0190] S2. De-oxidation layer treatment:

[0191] Immerse the BC cell silicon substrate with a patterned groove in a de-oxidation working solution at 25 °C for 20 s, then clean it with pure water and dry it with nitrogen to obtain a de-oxidized BC cell silicon substrate; wherein, the de-oxidation working solution includes: 40 mL / L of hydrofluoric acid, and the balance is water; the concentration of the hydrofluoric acid is 49%.

[0192] S3. Activation treatment:

[0193] Immerse the de-oxidized BC cell silicon substrate in an activator working solution at 25 °C for 40 s to uniformly activate it, then wash it three times with pure water and dry it with nitrogen to obtain an activated BC cell silicon substrate; wherein, the activator working solution includes: 1 g / L of palladium chloride, 0.5 g / L of ammonium chloride, 0.4 g / L of 2-aminopyridine, and the balance is water.

[0194] S4. Electroless nickel plating:

[0195] Immerse the activated BC cell silicon substrate in an electroless nickel plating working solution, turn off all light sources to make the reaction in a dark environment, carry out plating at 90 °C for 1 min, then clean it with pure water and dry it, and form a nickel layer with a thickness of 0.3 μm at the patterned groove to obtain a nickel-plated BC cell silicon substrate; wherein, the electroless nickel plating working solution includes: 5 g / L of nickel sulfate, 15 g / L of sodium hypophosphite, 5 g / L of sodium citrate, 1 g / L of thiourea, and the balance is water.

[0196] S5. Electroplating copper:

[0197] Place the nickel-plated BC cell silicon substrate horizontally in an electroplating copper device with the back facing down, immerse it in an activation solution at 25 °C for 50 s for activation, and then immerse it in a copper electroplating working solution at 50 °C at 25 A / dm 2Electroplate copper at a current density of [current density value] for 2 minutes. After electroplating, wash it thoroughly with pure water and then dry it to form a copper layer with a thickness of 6 μm on the nickel layer, obtaining a BC cell silicon substrate after copper plating; wherein, the activation solution includes 60 mL / L of concentrated sulfuric acid, and the balance is water, and the concentration of the concentrated sulfuric acid is 98%; the copper electroplating working solution includes: 220 g / L of copper sulfate, 50 mL / L of concentrated sulfuric acid, 8 mL / L of concentrated hydrochloric acid, 4 mL / L of 2-ethylhexyl sodium sulfate, 6 mL / L of benzylideneacetone, and the balance is water, the concentration of the concentrated sulfuric acid is 98%, and the concentration of the concentrated hydrochloric acid is 37%.

[0198] S6. Electroless tin plating:

[0199] Immerse the BC cell silicon substrate after copper plating in the electroless tin plating working solution, carry out plating at 50 °C for 30 s, then wash it thoroughly with pure water and then dry it to form a tin layer with a thickness of 0.3 μm on the copper layer, obtaining a BC cell after tin plating; wherein, the electroless tin plating working solution includes: 20 g / L of stannous chloride, 15 g / L of sodium hypophosphite, 15 mL / L of concentrated hydrochloric acid, 5 mL / L of hydrazine hydrate, 15 g / L of sodium citrate, and the balance is water, and the concentration of the concentrated hydrochloric acid is 37%.

[0200] Example 4

[0201] This example provides a method for preparing a BC solar cell. The difference from Example 1 is that in S3, ammonium chloride is no longer added, and the concentration of 2-aminopyridine is increased to 2.5 g / L, and other steps are exactly the same as those in Example 1.

[0202] Example 5

[0203] This example provides a method for preparing a BC solar cell. The difference from Example 1 is that in S3, 2-aminopyridine is no longer added, and the concentration of ammonium chloride is increased to 2.5 g / L, and other steps are exactly the same as those in Example 1.

[0204] Example 6

[0205] This example provides a method for preparing a BC solar cell. The difference from Example 1 is that in S3, soak it in the activator working solution at 25 °C for 5 minutes, and other steps are exactly the same as those in Example 1.

[0206] Example 7

[0207] This example provides a method for preparing a BC solar cell. The difference from Example 1 is that in S3, soak it in the activator working solution at 40 °C for 10 s, and other steps are exactly the same as those in Example 1.

[0208] Example 8

[0209] This embodiment provides a method for preparing a BC solar cell. The difference from Example 1 is that in S4, the chemical nickel plating working solution includes: the chemical nickel plating working solution includes: 15 g / L nickel sulfate, 25 g / L sodium borohydride, 10 g / L sodium citrate, 2 g / L ammonia water, and the balance is water. The other steps are exactly the same as in Example 1.

[0210] Example 9

[0211] This embodiment provides a method for preparing a BC solar cell. The difference from Example 1 is that, in S4, plating is performed at 95° C. for 50 seconds. The other steps are completely consistent with Example 1.

[0212] Example 10

[0213] This embodiment provides a method for preparing a BC solar cell. The difference from Example 1 is that, in S4, plating is performed at 65° C. for 6 minutes. The other steps are completely consistent with Example 1.

[0214] Example 11

[0215] This embodiment provides a method for preparing a BC solar cell. The difference from Example 1 is that in S5, the nickel-plated BC cell silicon substrate is no longer placed in an activation solution for activation before copper electroplating, but copper electroplating is performed directly. The other steps are exactly the same as in Example 1.

[0216] Example 12

[0217] This embodiment provides a method for preparing a BC solar cell. The difference from Example 1 is that in S5, the copper electroplating working solution includes: 215 g / L copper sulfate, 65 mL / L concentrated sulfuric acid, 8 mL / L 2-ethylhexyl sodium sulfate, and the balance is water. The other steps are exactly the same as in Example 1.

[0218] Example 13

[0219] This embodiment provides a method for preparing a BC solar cell. The difference from Example 1 is that in S5, the copper electroplating working solution includes: 215 g / L copper sulfate, 65 mL / L concentrated hydrochloric acid, 8 mL / L benzyl acetone, and the balance is water. The other steps are exactly the same as in Example 1.

[0220] Example 14

[0221] This embodiment provides a method for preparing a BC solar cell. The difference from embodiment 1 is that in step S5, the solar cell is immersed in a copper electroplating working solution at 25°C and a current of 8A / dm 2 Copper electroplating was carried out for 12 min at a current density of , and other steps were exactly the same as in Example 1.

[0222] Example 15

[0223] This embodiment provides a method for preparing a BC solar cell. The difference from Embodiment 1 is that in S5, it is immersed in a copper electroplating working solution at 55°C and electroplated with copper for 1 minute at a current density of 32 A / dm 2 . The other steps are exactly the same as those in Embodiment 1.

[0224] Embodiment 16

[0225] This embodiment provides a method for preparing a BC solar cell. The difference from Embodiment 1 is that in S6, the electroless tin plating working solution includes: 15 g / L of stannous chloride, 12 g / L of sodium borohydride, 20 mL / L of concentrated sulfuric acid, 20 mL / L of ammonia water, 12 g / L of sodium acetate, and the balance is water. The other steps are exactly the same as those in Embodiment 1.

[0226] Embodiment 17

[0227] This embodiment provides a method for preparing a BC solar cell. The difference from Embodiment 1 is that in S6, plating is carried out at 25°C for 150 s. The other steps are exactly the same as those in Embodiment 1.

[0228] Embodiment 18

[0229] This embodiment provides a method for preparing a BC solar cell. The difference from Embodiment 1 is that in S6, plating is carried out at 65°C for 25 s. The other steps are exactly the same as those in Embodiment 1.

[0230] Comparative Example 1

[0231] This comparative example provides a method for preparing a BC solar cell. The difference from Embodiment 1 is that the step of S2 removing the oxide layer is not carried out, and the other steps are exactly the same as those in Embodiment 1.

[0232] Comparative Example 2

[0233] This comparative example provides a method for preparing a BC solar cell. The difference from Embodiment 1 is that the step of S3 activation treatment is not carried out, and the other steps are exactly the same as those in Embodiment 1.

[0234] Comparative Example 3

[0235] This comparative example provides a method for preparing a BC solar cell. The difference from Embodiment 1 is that the step of S4 electroless nickel plating is not carried out, and the other steps are exactly the same as those in Embodiment 1.

[0236] Comparative Example 4

[0237] This comparative example provides a method for preparing a BC solar cell. The difference from Embodiment 1 is that the step of S5 electroplating copper is not carried out, and the other steps are exactly the same as those in Embodiment 1.

[0238] Comparative Example 5

[0239] This comparative example provides a method for preparing a BC solar cell, which is different from Example 1 in that the step of electroless tin plating in S6 is not carried out, and the other steps are exactly the same as those in Example 1.

[0240] Test Example 1

[0241] Test samples: BC solar cells provided in Examples 1 to 18, and BC solar cells provided in Comparative Examples 1 to 5.

[0242] Test methods:

[0243] (1) Electrical performance detection (photovoltaic conversion efficiency, open circuit voltage, short circuit current); specifically, IV testing is adopted, and the test is carried out at a temperature of 25 °C and AM of 1.5G;

[0244] (2) Adhesion between the metal electrode of the BC cell and the silicon substrate: 3M tape test (qualified if the metal grid line is not peeled off);

[0245] (3) Welding tensile force: Welding tensile force test (300 - 350 °C) is carried out on the PAD points on the metal electrode (the average tensile force on the back of the BC cell for testing 24 PAD points ≥ 0.8N is qualified).

[0246] The test results are shown in Table 1 below (" / " indicates unable to weld):

[0247] Table 1

[0248]

[0249]

[0250] As shown in Table 1, the present invention proposes a method for preparing a BC cell. By using the electroless nickel plating + electroplating copper + electroless tin plating process to prepare the metal electrode, replacing the original silver electrode, not only the production cost of the cell is reduced, but also the electrical performance of the cell is improved. In the present invention, the nickel layer obtained by electroless nickel plating has a uniform thickness and small internal stress. After continuing to plate copper and tin, the obtained metal electrode has a good adhesion to the silicon substrate; in addition, the tin layer obtained by the electroless tin plating method has good denseness, low porosity, strong corrosion resistance, and good solderability.

[0251] From the comparison between Example 1 and Examples 4 - 5, it can be seen that the activator working solution includes specific concentrations of palladium chloride, ammonium chloride, and 2-aminopyridine. The synergistic effect of the three activates the silicon layer, which can significantly improve the activation effect on the silicon surface, making the subsequent electroless nickel plating form a denser nickel coating, so as to further improve the photovoltaic conversion efficiency and welding tensile force.

[0252] From the comparison between Example 1 and Examples 6 - 7, it can be seen that the temperature of the activation treatment is preferably 20 - 30 °C, and the time of the activation treatment is limited to 20 - 80 s. Activating within this temperature and time range can better activate the silicon layer and avoid damaging the silicon layer; otherwise, too long activation time will instead damage the silicon surface, resulting in a decrease in the photoelectric conversion efficiency, open-circuit voltage, and short-circuit current. Or increasing the activation temperature and reducing the activation time will also damage the silicon surface, leading to a decrease in the photoelectric conversion efficiency, open-circuit voltage, and short-circuit current.

[0253] From the comparison between Example 1 and Example 8, it can be seen that the electroless nickel plating working solution includes nickel sulfate, sodium hypophosphite, sodium citrate, and thiourea at specific concentrations. The synergistic effect of the four components can form a nickel layer with low internal stress, high density, and high bonding strength, achieving the purpose of further improving the bonding strength, welding tensile strength, photoelectric conversion efficiency, open-circuit voltage, and short-circuit current between the metal electrode and the silicon substrate.

[0254] From the comparison between Example 1 and Examples 9 - 10, it can be seen that the temperature of the electroless nickel plating is preferably 70 - 90 °C, and the time of the electroless nickel plating is 1 - 5 min. Conducting electroless nickel plating within this parameter range can significantly improve the bonding strength, welding tensile strength, photoelectric conversion efficiency, open-circuit voltage, and short-circuit current between the metal electrode and the silicon substrate.

[0255] From the comparison between Example 1 and Example 11, it can be seen that if the nickel-plated BC cell silicon substrate is not placed in the activation solution for activation before electroplating copper, the copper-tin layer is likely to peel off.

[0256] From the comparison between Example 1 and Examples 12 - 13, it can be seen that the copper electroplating working solution includes copper sulfate, concentrated sulfuric acid, concentrated hydrochloric acid, 2-ethylhexyl sodium sulfate, and benzylideneacetone at specific concentrations. Each component cooperates with each other and synergistically enhances the effect, promoting the refinement of copper layer grains and significantly improving the compactness of the coating, achieving the purpose of significantly improving the bonding strength, welding tensile strength, photoelectric conversion efficiency, open-circuit voltage, and short-circuit current between the metal electrode and the silicon substrate.

[0257] From the comparison between Example 1 and Examples 14 - 15, it can be seen that the current density of the electroplating copper is preferably 10 - 30 A / dm 2 , the temperature of the electroplating copper is preferably 25 - 50 °C, and the time of the electroplating copper is preferably 2 - 10 min. Conducting electroplating copper within this parameter range can significantly improve the bonding strength, welding tensile strength, photoelectric conversion efficiency, open-circuit voltage, and short-circuit current between the metal electrode and the silicon substrate.

[0258] From the comparison between Example 1 and Example 16, it can be seen that the electroless tin plating working solution includes stannous chloride, sodium hypophosphite, concentrated hydrochloric acid, hydrazine hydrate, and sodium citrate at specific concentrations. Each component cooperates with each other and synergistically enhances the effect, ultimately forming a tin coating with fine grains, dense structure, strong corrosion resistance, and a clean surface, achieving the purpose of further improving the bonding force, welding tensile strength between the metal electrode and the silicon substrate, as well as the photoelectric conversion efficiency, open circuit voltage, and short circuit current.

[0259] From the comparison between Example 1 and Examples 17 - 18, it can be seen that the temperature of the electroless tin plating is preferably 30 - 60 °C, and the time of the electroless nickel plating is preferably 30 - 120 s. Conducting electroless tin plating within this parameter range can significantly improve the bonding force, welding tensile strength between the metal electrode and the silicon substrate, as well as the photoelectric conversion efficiency, open circuit voltage, and short circuit current.

[0260] From the comparison between Example 1 and Comparative Example 1, it can be seen that without the deoxidation layer treatment, the nickel - copper - tin layer peels off. This is because without the deoxidation layer treatment, it is difficult for precious metal ions to be adsorbed during the subsequent activation process, and the activation treatment effect is poor. During the subsequent process of plating the metal electrode, the nickel - copper - tin layer is extremely easy to peel off.

[0261] From the comparison between Example 1 and Comparative Example 2, it can be seen that without the activation treatment, there are no catalytic sites and no nucleation centers during the subsequent plating of the metal electrode, resulting in no plating of nickel, copper, or tin.

[0262] From the comparison between Example 1 and Comparative Example 3, it can be seen that without the step of S4 electroless nickel plating, copper and tin cannot be plated subsequently.

[0263] From the comparison between Example 1 and Comparative Examples 4 - 5, it can be seen that without either electroplating copper or electroless tin plating, the purpose of achieving welding cannot be realized.

[0264] Finally, it should be noted that: the above - mentioned embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the corresponding technical solutions...

Claims

1. A method for preparing a BC solar cell, characterized in that, The preparation method includes: Forming a patterned groove on the surface of the back coating layer of the BC cell silicon substrate; Successively performing deoxidation treatment, activation treatment, electroless nickel plating, electroplating copper, and electroless tin plating at the patterned groove of the BC cell silicon substrate to obtain the BC solar cell.

2. The manufacturing method of the BC solar cell according to claim 1, characterized in that, The back coating layer of the BC cell silicon substrate includes a silicon nitride layer; Preferably, the thickness of the silicon nitride layer is 50 - 100 nm; Preferably, the patterned groove is formed by laser grooving; Preferably, the power of the laser grooving is 4 - 10 W; the frequency of the laser grooving is 500 - 2000 kHz; the speed of the laser grooving is 10 - 50 m / s; Preferably, the width of the patterned groove is 30 - 100 μm; Preferably, the depth of the patterned groove is 70 - 120 nm.

3. The manufacturing method of the BC solar cell according to claim 1, characterized in that, The deoxidation treatment includes: Immersing the BC cell silicon substrate in a deoxidation working solution, followed by washing and drying; Preferably, the deoxidation working solution includes: 10 - 50 mL / L of hydrofluoric acid, with the balance being water; Preferably, the concentration of the hydrofluoric acid is 48 - 50 vol%; Preferably, the temperature of the deoxidation treatment is 20 - 30 °C; the time of the deoxidation treatment is 10 - 60 s.

4. The manufacturing method of the BC solar cell according to claim 1, wherein, The activation treatment includes: Immersing the BC cell silicon substrate after deoxidation treatment in an activator working solution, followed by washing and drying; Preferably, the activator working solution includes: 0.1 - 1 g / L of palladium chloride, 0.5 - 5 g / L of ammonium chloride, 0.05 - 0.5 g / L of 2-aminopyridine, with the balance being water; Preferably, the temperature of the activation treatment is 20 - 30 °C; the time of the activation treatment is 20 - 80 s.

5. The preparation method of the BC solar cell according to claim 1, wherein The electroless nickel plating includes: Immersing the BC cell silicon substrate after activation treatment in an electroless nickel plating working solution to perform electroless nickel plating to form a nickel layer, followed by washing and drying; Preferably, the electroless nickel plating working solution includes: 5 - 30 g / L of nickel sulfate, 10 - 40 g / L of sodium hypophosphite, 5 - 20 g / L of sodium citrate, 0.5 - 5 g / L of thiourea, with the balance being water; Preferably, the pH of the electroless nickel plating working solution is 5.0 - 7.0; Preferably, the electroless nickel plating is carried out in a dark environment; Preferably, the temperature of the electroless nickel plating is 70 - 90 °C; the time of the electroless nickel plating is 1 - 5 min; Preferably, the thickness of the nickel layer is 0.2 - 1.0 μm.

6. The manufacturing method of the BC solar cell according to claim 1, characterized in that, The electroplating copper includes: Immersing the BC cell silicon substrate after electroless nickel plating in an activation solution for activation, and then immersing it in a copper electroplating working solution for electroplating copper to form a copper layer, followed by washing and drying.

7. The method for preparing a BC solar cell according to claim 6, wherein, The activation solution includes 10 - 100 mL / L of concentrated sulfuric acid, with the balance being water; Preferably, the temperature of the activation is 20 - 30 °C; the time of the activation is 30 - 120 s; Preferably, the copper electroplating working solution includes: 180 - 250 g / L of copper sulfate, 50 - 70 mL / L of concentrated sulfuric acid, 3 - 8 mL / L of concentrated hydrochloric acid, 0.5 - 5 mL / L of 2-ethylhexyl sodium sulfate, 1 - 10 mL / L of benzylideneacetone, with the balance being water; Preferably, the concentration of the concentrated sulfuric acid is 97-99 vol%; Preferably, the concentration of the concentrated hydrochloric acid is 35-40 vol%; Preferably, the current density of the copper electroplating is 10-30 A / dm 2 ; the temperature of the copper electroplating is 25-50 °C; the time of the copper electroplating is 2-10 min; Preferably, the thickness of the copper layer is 6-12 μm.

8. The manufacturing method of the BC solar cell according to claim 1, characterized in that, The electroless tin plating includes: Immersing the BC cell silicon substrate after electroplating copper in an electroless tin plating working solution for electroless tin plating to form a tin layer, followed by washing and drying.

9. The preparation method of the BC solar cell according to claim 8, wherein, The electroless tin plating working solution includes: stannous chloride 5-30 g / L, sodium hypophosphite 5-20 g / L, concentrated hydrochloric acid 10-40 mL / L, hydrazine hydrate 5-30 mL / L, sodium citrate 5-20 g / L, and the balance is water; Preferably, the concentration of the concentrated hydrochloric acid is 35-40 vol%; Preferably, the pH of the electroless tin plating working solution is 1.0-4.0; Preferably, the temperature of the electroless tin plating is 30-60 °C; the time of the electroless nickel plating is 30-120 s; Preferably, the thickness of the tin layer is 0.2-1.0 μm.

10. A BC solar cell, characterized in that, The BC solar cell is prepared by the preparation method of the BC solar cell according to any one of claims 1-9.

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