BC solar cell electroplating method and application thereof

Abstract

The invention provides a BC solar cell electroplating method and application thereof, and relates to the technical field of solar cells, the BC solar cell electroplating method comprises the following steps: (a) slotting on a front silicon nitride layer and a back silicon nitride layer of a to-be-electroplated cell; (b) a metal coating is prepared in the slotting area of the back face of the to-be-electroplated battery piece, and the front face of the to-be-electroplated battery piece is connected with a power source cathode; and (c) carrying out oxidation treatment on the front surface of the to-be-electroplated battery piece. The front silicon nitride film is selectively slotted, and the electrode is in contact with the front surface of the silicon wafer, so that the conductive problem is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a BC solar cell electroplating method and application thereof. BACKGROUND

[0002] With the continuous breakthrough of BC (back contact) cell process flow and its key manufacturing technology, its application in the photovoltaic field is increasingly widespread. In particular, the XBC cell structure formed by combining BC cell with other cell technologies exhibits significant conversion efficiency advantage and good appearance consistency.

[0003] The common TBC electroplating process currently adopts a horizontal single-sided electroplating mode (roller transmission), in which the conduction of current is mainly concentrated on the back surface of the silicon wafer, and the front surface does not participate in conduction. In this process, the current usually needs to be transmitted along the grid lines through the silicon area after laser grooving or the conductive seed layer to realize local electroplating.

[0004] However, the existing BC cell electroplating technology still has deficiencies in actual application, mainly in the following aspects:

[0005] (1) The existing electroplating mode excessively relies on the back surface grid line conduction. Due to the height difference between the P region and the N region of the BC cell, it is easy to cause poor contact between the electrode and the P region or the N region, thereby affecting the uniformity of current transmission. To solve this problem, a flexible electrode is often used, which puts higher requirements on the electrode material and structure;

[0006] (2) The current needs to be conducted along the grid lines, so the grid line pattern is required to have a certain continuity and density, which not only increases the complexity of pattern design, but also limits the flexibility of design; at the same time, once defects such as broken grid and thick grid occur, it will directly affect the electroplating quality and cell performance.

[0007] In view of this, the present application is proposed. SUMMARY

[0008] One of the purposes of the present application is to provide a BC solar cell electroplating method to at least solve one of the technical problems existing in the prior art. The present application solves the conduction problem by selectively grooving the front surface silicon nitride film and contacting the electrode with the front surface of the silicon wafer.

[0009] The second purpose of the present application is to provide an application of the BC solar cell electroplating method in the preparation of a BC solar cell.

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

[0011] In a first aspect, the present application provides a BC solar cell electroplating method, comprising:

[0012] (a) grooving the front side and the back side of the silicon nitride layer of the cell to be plated;

[0013] (b) preparing a metal plating layer on the grooved area of the back side of the cell to be plated, wherein the front side of the cell to be plated is connected to the cathode of the power supply;

[0014] (c) performing an oxidation treatment on the front side of the cell to be plated.

[0015] Further, the grooving method comprises laser grooving.

[0016] Preferably, the laser grooving adopts ultraviolet picosecond laser; the single pulse energy of the ultraviolet picosecond laser is 0.2-1uJ.

[0017] Further, the grooving method comprises etching slurry grooving.

[0018] Preferably, the etching slurry grooving process comprises: applying silicon nitride etching slurry to the preset grid line area on the silicon nitride, etching the silicon nitride of the preset grid line area at a temperature of 300-400℃ to form a groove, and then performing a cleaning treatment.

[0019] Preferably, the silicon nitride etching slurry is applied to the preset grooving area on the silicon nitride by screen printing.

[0020] Preferably, the cleaning treatment is performed by using water at a temperature of 90-100℃.

[0021] Further, the grooving method comprises chemical etching.

[0022] Preferably, the chemical etching process comprises: preparing a mask on the non-grid line area, and then removing the silicon nitride of the preset grid line area by using an acid agent.

[0023] Preferably, the material of the mask comprises a corrosion-resistant material.

[0024] Further, between step (a) and step (b), annealing is further included.

[0025] Preferably, the annealing temperature is 750-850℃.

[0026] Further, the metal plating layer comprises a seed layer, a conductive layer and a protective layer arranged in a stack.

[0027] Preferably, the seed layer comprises a nickel layer; the conductive layer comprises a copper layer; and the protective layer comprises a tin layer.

[0028] Further, the oxidation treatment process comprises: connecting the metal plating layer of the back side of the cell to be plated to the anode of the power supply, immersing the front side of the cell to be plated into an electrolyte, and performing an oxidation treatment on the front side of the cell to be plated.

[0029] Preferably, the current is 0.1-3A during the oxidation process; the oxidation time is 30-300s.

[0030] Preferably, the electrolyte comprises 5%-10% of sulfuric acid solution in volume fraction.

[0031] Further, after the annealing, before the step (b), the edge of the cell to be plated is coated with glue;

[0032] Preferably, the glue comprises UV curing glue or heat curing glue.

[0033] Further, after the step (b), before the step (c), the cell to be plated is cleaned on the front side;

[0034] Preferably, the reagent used for cleaning comprises hydrofluoric acid; the concentration of the hydrofluoric acid is 2%-5%; the cleaning time is 30-120s.

[0035] Preferably, the thickness of the silicon nitride layer on the cell to be plated is 80-100nm; the refractive index is 2.0-2.5; the silicon nitride layer is prepared by PECVD method; the radio frequency power used for preparing the silicon nitride layer is 100-300W; the reaction temperature for preparing the silicon nitride layer is 300-500℃; the reaction gas used for preparing the silicon nitride layer comprises NH3 and SH4; the flow ratio of NH3 to SH4 is 6-10:1-2; the total gas flow of NH3 and SH4 is 3000-5000sccm; the pressure is 150-200Pa; the deposition time is 600-900s.

[0036] In the second aspect, the application provides a BC solar cell plating method for preparing a BC solar cell.

[0037] Compared with the prior art, the application has the following beneficial effects:

[0038] The application provides a BC solar cell electroplating method, which comprises the following steps: slotting a silicon nitride layer on a front surface of a BC cell, and conducting electricity by contacting the silicon nitride layer with the front surface of the silicon wafer through an electrode. After the front surface is slotted, the electroplating cathode can realize large-area and uniform contact with the front surface of the silicon wafer. Since the texture structure is consistent in height, the problem of poor contact caused by the height difference between the P / N zones in the traditional back surface conduction mode can be effectively avoided. Moreover, the conduction stability between the electrode and the silicon wafer is improved, the current distribution is uniform, the problems of broken grid and thick grid caused by poor conduction are avoided, the uniformity and consistency of the electroplating grid lines are improved, and thus the overall performance of the cell is improved. In addition, after the back surface electroplating process is completed, the slotted area on the front surface is subjected to oxidation treatment. The oxidation can form a high-quality silicon oxide layer on the surface of the silicon (the silicon in the slotted area is oxidized to form silicon oxide; both the silicon oxide and the silicon nitride are good passivation layers, and thus the passivation performance can be improved), compensate for the loss of the passivation layer caused by the front surface slotting, repair the surface defects of the silicon that may be exposed in the electroplating process, restore the passivation performance of the front surface, reduce the carrier recombination loss, improve the open-circuit voltage and the overall efficiency of the cell, and enhance the long-term stability and reliability of the cell. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0040] Figure 1 The structural schematic diagram of the cell wafer to be electroplated provided by the present application is shown in the figure.

[0041] Figure 2 The structural schematic diagram of the cell wafer to be electroplated after the back surface is opened is shown in the figure.

[0042] Figure 3 The structural schematic diagram of the cell wafer to be electroplated after the front surface is opened is shown in the figure.

[0043] Figure 4 The diagram of the cell wafer to be electroplated after the back surface is electroplated is shown in the figure.

[0044] Figure 5 The diagram of the cell wafer to be electroplated after the front surface is oxidized is shown in the figure.

[0045] Figure legend: 100-cell wafer to be electroplated. DETAILED DESCRIPTION

[0046] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0047] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] The first aspect of this invention provides a method for electroplating BC solar cells, comprising:

[0049] (a) such as Figures 1-3 As shown, grooves are cut on the front and back silicon nitride layers of the cell to be electroplated 100.

[0050] (b) such as Figure 4 As shown, a metal coating is prepared in the grooved area on the back of the cell to be electroplated, wherein the front of the cell to be electroplated is connected to the power cathode.

[0051] (c) such as Figure 5 As shown, the front side of the electroplated battery cell undergoes an oxidation treatment.

[0052] In this invention, the battery cell to be electroplated is a semi-finished coated battery cell, such as a blue film cell. The semi-finished coated battery cell can be any type of BC, such as TBC, HBC, or PBC.

[0053] In this invention, by selectively slotting the silicon nitride film on the front side of the battery cell to be electroplated (the slotting area ratio is 1%-100%, which can be adjusted as needed), and then contacting the electroplated negative electrode with the front side of the silicon wafer, a good and uniform conductivity effect is formed, thus solving the conductivity problem; after the back electrode is electroplated, the silicon after the front slotting is passivated and repaired by anodic electro-oxidation.

[0054] In some preferred embodiments, the film on the surface of the battery cell to be electroplated (BC coating semi-finished battery cell) is mainly composed of silicon nitride, with a thickness of 80-100 nm, more preferably 90 nm, and a refractive index of 2.0-2.5, more preferably 2.25.

[0055] In some preferred embodiments, the silicon nitride layer of the battery piece to be plated is prepared by PECVD method, and the process parameters are as follows: radio frequency power is 100-300 W, reaction temperature is 300-500 ℃, reaction gas flow ratio is NH3 / SH4=(6-10):(1-2), total gas flow is 3000-5000 sccm, pressure is 150-200 Pa, and deposition time is 600-900 s.

[0056] Further preferred parameters are as follows: radio frequency power is 200 W, reaction temperature is 400 ℃, reaction gas flow ratio is NH3 / SH4=8:1, total gas flow is 4300 sccm, pressure is 1750 Pa, and deposition time is 720 s.

[0057] In some preferred embodiments, the slotting method comprises laser slotting.

[0058] Preferably, the laser slotting adopts ultraviolet picosecond laser (wavelength 355 nm) to irradiate the silicon nitride and directly ablate the silicon nitride.

[0059] Preferably, the single pulse energy of the ultraviolet picosecond laser is 0.2-1 uJ, for example, it can be 0.2 uJ, 0.3 uJ, 0.4 uJ, 0.5 uJ, 0.6 uJ, 0.7 uJ, 0.8 uJ, 0.9 uJ, 1 uJ, etc.

[0060] As an alternative embodiment, the slotting method comprises etching slurry slotting.

[0061] Preferably, the etching slurry slotting process comprises: applying a silicon nitride etching slurry containing phosphoric acid components to the preset gate line area on the silicon nitride, reacting with the silicon nitride at a temperature of 300-400 ℃, for example, it can be 300 ℃, 350 ℃, 400 ℃, etc., to etch the silicon nitride in the preset gate line area to form a groove, and after completion, cleaning treatment is performed with hot water at about 95 ℃ to remove residues.

[0062] Preferably, the silicon nitride etching slurry is transferred to the preset slotting area on the silicon nitride by screen printing.

[0063] Preferably, the cleaning treatment is performed with water at 90-100 ℃, for example, it can be 90 ℃, 95 ℃, 100 ℃, etc.

[0064] As an alternative embodiment, the slotting method comprises chemical etching.

[0065] Preferably, the chemical etching process comprises: preparing a mask on the non-gate line area, and then removing the silicon nitride in the preset gate line area with an acid agent; preferably, the material of the mask comprises a corrosion-resistant material.

[0066] Specifically, the process of chemical etching is as follows: a photoresist or other corrosion-resistant material is printed as a mask, then patterned, so that the silicon nitride at the position of the grid line is exposed, and the silicon nitride at the position other than the grid line is protected, then the silicon nitride at the position of the grid line is etched by HF acid to achieve the purpose of slotting.

[0067] In some preferred embodiments, between step (a) and step (b), annealing is further included; the temperature of the annealing is 750-850℃, for example, it can be 750℃, 800℃, 850℃, etc. The purpose of the annealing is to activate H in the silicon nitride to passivate the silicon wafer, which is generally performed by a chain sintering furnace, with a peak temperature of 750-850℃, and nitrogen protection is also provided to the furnace chamber to prevent the oxidation of the silicon wafer at the slot.

[0068] In some preferred embodiments, the metal plating layer comprises a seed layer, a conductive layer and a protective layer arranged in a stack; preferably, the seed layer comprises a nickel layer; the conductive layer comprises a copper layer; and the protective layer comprises a tin layer. During plating, the silicon wafer needs to be shaded to reduce the difference between the P region and the N region.

[0069] In some preferred embodiments, the process of the oxidation treatment comprises: connecting the metal plating layer on the back surface of the to-be-plated battery piece to the positive pole of the power supply, immersing the front surface of the to-be-plated battery piece into an electrolyte (the front surface of the to-be-plated battery piece is in full contact with the electrolyte), and performing oxidation on the front surface of the to-be-plated battery piece; preferably, during the oxidation process, the current is 0.1-3A, for example, it can be 0.1A, 0.5A, 1A, 1.5A, 2A, 2.5A, 3A, etc.; and the oxidation time is 30-300s, for example, it can be 30s, 50s, 100s, 150s, 200s, 250s, 300s, etc. Preferably, the electrolyte comprises a sulfuric acid solution with a volume fraction of 5%-10%.

[0070] Specifically, during the front surface oxidation process, the silicon wafer is used as an anode and connected to the positive pole of the power supply, after power-on, the silicon reacts with the oxygen in the electrolyte to produce silicon oxide; the cathode (generally an inert electrode) is connected to the negative pole of the power supply and mainly produces hydrogen; the current is set to 0.1-3A, and the time is 30-300s, with the appearance after oxidation being similar to the color of the silicon nitride film as the criterion.

[0071] In some preferred embodiments, after the annealing, before step (b), the edge of the to-be-plated battery piece is coated with glue; preferably, the glue comprises UV-curable glue or heat-curable glue. The main purpose of the glue coating is to shield the edge to prevent the edge from being plated with metal during the plating process, which may cause electric leakage. Generally, acid- and alkali-resistant UV-curable glue or heat-curable glue is used and applied on the edge of the silicon wafer by a special device.

[0072] In some preferred embodiments, after step (b) and before step (c), the front side of the to-be-plated cell sheet is cleaned;

[0073] Preferably, the cleaning agent comprises hydrofluoric acid; the concentration of the hydrofluoric acid is 2%-5%, for example, it can be 2%, 3%, 4%, 5%, etc.

[0074] Preferably, the cleaning time is 30-120s, for example, it can be 30s, 75s, 120s, etc.

[0075] The BC solar cell plating method provided by the present application has the following advantages:

[0076] (1) The front side opening film solves the problem of conductive stability and uniformity. After the front side opening film, the cathode can be in large-area contact with the surface of the silicon sheet. Since the surface height is uniform, good contact can be ensured, thereby ensuring the uniformity of the current and the uniformity of the back side plating grid lines. The grid line conductive may appear broken grid, thick grid, etc.

[0077] (2) The front side opening film conductive is adopted. The current passes through the silicon sheet and the plating solution, and the back side only needs to be locally grooved to realize plating without pattern restriction.

[0078] (3) After the back side grid line plating is completed, reverse anode oxidation is performed. Not only can the passivation layer after the front side opening film be compensated, but also the silicon points leaked during the plating process can be passivated, thereby improving the passivation effect.

[0079] (4) The back side adopts electrochemical oxidation, which does not have high temperature and chemical corrosion process, has fast oxidation rate, and will not affect the back side grid line.

[0080] The second aspect of the present application provides an application of the BC solar cell plating method in the preparation of a BC solar cell.

[0081] The present application will be further described by examples. Unless otherwise specified, the materials in the examples are prepared according to the existing method or directly purchased from the market.

[0082] In the following examples and comparative examples, the surface film of the to-be-plated cell sheet (i.e. the BC plating film semi-finished cell sheet) mainly comprises silicon nitride, the thickness is 90nm, and the refractive index is 2.25. It is prepared by PECVD method, and the process parameters are as follows: radio frequency power is 200W, reaction temperature is 400℃, reaction gas flow ratio is NH3 / SH4=8:1, total gas flow is 4300sccm, pressure is 1750Pa, and deposition time is 720s.

[0083] Example 1

[0084] The embodiment provides a BC solar cell plating method, which comprises the following steps:

[0085] Step 1, providing a to-be-plated cell piece (i.e. a BC plating film semi-finished cell piece); slotting (slotting area ratio 10%) is performed on the front surface silicon nitride layer and the back surface silicon nitride layer of the to-be-plated cell piece (i.e. the BC plating film semi-finished cell piece):

[0086] The slotting mode is laser slotting, generally using ultraviolet picosecond laser (wavelength 355 nm) with single pulse energy 0.5uJ.

[0087] Step 2, annealing: the annealing temperature is 800 DEG C.

[0088] Step 3, gluing: using acid and alkali resistant UV curing glue, the edge of the silicon wafer is coated through a special device;

[0089] Step 4, back surface plating: the front surface of the to-be-plated cell piece is connected with the cathode of a power supply, the back surface of the to-be-plated cell piece is immersed in a plating solution, the plating solution is provided with a plating anode, the plating anode is connected with the anode of the power supply, a metal plating layer is prepared in the slotting area of the back surface of the to-be-plated cell piece, and a nickel layer, a copper layer and a tin layer are sequentially deposited in the slotting area of the back surface;

[0090] Then, the cell piece is cleaned and dried.

[0091] Step 5, front surface cleaning: the cell piece is cleaned on the front surface for 80s by using HF with a concentration of 5%.

[0092] Step 6, front surface oxidation, the metal plating layer of the back surface of the to-be-plated cell piece is connected with the anode of the power supply (i.e. the silicon wafer is connected with the anode of the power supply as an anode), the front surface of the to-be-plated cell piece is immersed in an electrolyte (the plating solution is a sulfuric acid solution with a volume fraction of 5% to 10%), the front surface of the to-be-plated cell piece is in full contact with the electrolyte, the electrolyte is provided with a plating cathode, the plating cathode is connected with the cathode of the power supply, the silicon wafer is used as an anode, the current is set to 2A, and the time is 200s.

[0093] Then, the cell piece is cleaned and dried, and a BC solar cell is obtained.

[0094] Embodiment 2

[0095] The embodiment provides a BC solar cell plating method, which is different from the embodiment 1.

[0096] In step 1, the slotting mode is etching slurry slotting, special silicon nitride etching slurry containing phosphoric acid component is adopted, the special silicon nitride etching slurry is transferred to the silicon nitride through screen printing, the silicon nitride is reacted at a temperature of 350 DEG C, after the reaction is completed, hot water at about 95 DEG C is used for cleaning, and residues are removed.

[0097] Embodiment 3

[0098] The embodiment provides a BC solar cell plating method, which is different from the embodiment 1 in that:

[0099] In step 1, the slotting mode is as follows: chemical etching, printing a photosensitive glue as a mask, then performing patterning to expose the silicon nitride at the position of the grid line pattern and protect the silicon nitride at the position of the non-grid line, and then etching the silicon nitride at the position of the grid line with HF acid to achieve the purpose of slotting.

[0100] Embodiment 4

[0101] The embodiment provides a BC solar cell plating method, which is different from the embodiment 1 in that:

[0102] In step 2, the annealing temperature is 750 DEG C.

[0103] Embodiment 5

[0104] The embodiment provides a BC solar cell plating method, which is different from the embodiment 1 in that:

[0105] In step 2, the annealing temperature is 850 DEG C.

[0106] Embodiment 6

[0107] The embodiment provides a BC solar cell plating method, which is different from the embodiment 1 in that: step 3 is not performed.

[0108] Embodiment 7

[0109] The embodiment provides a BC solar cell plating method, which is different from the embodiment 1 in that: step 5 is not performed.

[0110] Comparative example 1

[0111] The comparative example provides a BC solar cell plating method, which is different from the embodiment 1 in that: step 6 is not performed.

[0112] Comparative example 2

[0113] The comparative example provides a BC solar cell plating method, which adopts a conventional plating mode, and the specific process is as follows:

[0114] Step 1, slotting is performed on the silicon nitride layer on the back of a to-be-plated cell (that is, a BC plating film semi-finished cell), and the slotting area ratio is 10%.

[0115] The slotting mode is as follows: laser slotting, generally using ultraviolet picosecond laser (wavelength 355 nm), and the single pulse energy is 0.5uJ.

[0116] Step 2, annealing: the annealing temperature is 800 DEG C.

[0117] Step 3, gluing: using acid and alkali resistant UV curing glue, the edge of the silicon wafer is coated by special equipment;

[0118] Step 4, back plating: the back of the plated battery piece is placed in a horizontal plating equipment, the equipment is provided with a plurality of plating sub-baths, the sub-baths are filled with plating liquid, the plating liquid is provided with a plating anode, each sub-bath is provided with a plating cathode, the plating cathodes and the plating sub-baths are alternately arranged, the equipment transmission and current are turned on, and the nickel layer, the copper layer and the tin layer are sequentially deposited, and then the battery piece is cleaned and dried.

[0119] Test example

[0120] Test sample: the BC solar cell prepared by using examples 1-7 and comparative examples 1-2 as samples is tested.

[0121] Test method: IV test is performed on the 210mm BC solar cell under the condition that the temperature is 25℃ and AM is 1.5G.

[0122] The test results are shown in Table 1.

[0123] Table 1

[0124]

[0125]

[0126] From the data in Table 1, it can be seen that, compared with examples 1 and 6-7, and comparative examples 1, the lack of gluing step, the lack of front cleaning or the lack of front oxidation will affect the performance of the battery product. The BC solar cell plating method provided by the application can compensate for the passivation layer after the front film opening, improve the passivation effect, reduce the surface defects and dangling bonds, reduce the recombination rate of photo-generated carriers, prolong the minority carrier lifetime, improve the open circuit voltage and the fill factor, and finally improve the photoelectric conversion efficiency.

[0127] Finally, it should be pointed out that: the above embodiments are only used to illustrate the technical solutions of the application, but not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A method for electroplating BC solar cells, characterized in that, include: (a) Grooves are cut on the front and back silicon nitride layers of the cell to be electroplated; (b) A metal coating is prepared in the grooved area on the back of the cell to be electroplated, wherein the front of the cell to be electroplated is connected to the power cathode. (c) Oxidize the front side of the electroplated battery cell.

2. The BC solar cell electroplating method according to claim 1, characterized in that, The grooving method includes laser grooving; Preferably, the laser grooving uses an ultraviolet picosecond laser; the single-pulse energy of the ultraviolet picosecond laser is approximately 0.2-1 μJ.

3. The BC solar cell electroplating method according to claim 1, characterized in that, The grooving method includes grooving with corrosive slurry; Preferably, the process of etching grooves with the etching slurry includes: applying silicon nitride etching slurry to a preset gate area on silicon nitride, etching the silicon nitride in the preset gate area at a temperature of 300-400°C to form a groove, and then performing a cleaning process. Preferably, a silicon nitride etching paste is applied to a pre-defined grooved area on the silicon nitride using screen printing; Preferably, the cleaning process is carried out using water at 90-100℃.

4. The BC solar cell electroplating method according to claim 1, characterized in that, The grooving method includes chemical etching; Preferably, the chemical etching process includes: preparing a mask in the non-gate line region, and then using an acid to remove the silicon nitride in the preset gate line region; Preferably, the material of the mask includes a corrosion-resistant material.

5. The BC solar cell electroplating method according to claim 1, characterized in that, Annealing is also included between step (a) and step (b); Preferably, the annealing temperature is 750-850℃.

6. The BC solar cell electroplating method according to claim 1, characterized in that, The metal plating layer includes a seed layer, a conductive layer, and a protective layer stacked together. Preferably, the seed layer comprises a nickel layer; the conductive layer comprises a copper layer; and the protective layer comprises a tin layer.

7. The BC solar cell electroplating method according to claim 1, characterized in that, The oxidation process includes: connecting the metal plating layer on the back of the battery cell to be electroplated to the positive terminal of the power supply, immersing the front of the battery cell to be electroplated in an electrolyte, and oxidizing the front of the battery cell to be electroplated. Preferably, during the oxidation process, the current is 0.1-3A; the oxidation time is 30-300s; Preferably, the electrolyte comprises a sulfuric acid solution with a volume fraction of 5% to 10%.

8. The BC solar cell electroplating method according to claim 5, characterized in that, After annealing and before step (b), apply adhesive to the edges of the battery cell to be electroplated; Preferably, the adhesive includes a UV-curable adhesive or a thermosetting adhesive.

9. The BC solar cell electroplating method according to claim 1, characterized in that, After step (b) and before step (c), the front of the battery cell to be electroplated is cleaned. Preferably, the cleaning reagent includes hydrofluoric acid; the concentration of hydrofluoric acid is 2%-5%; and the cleaning time is 30-120 seconds. Preferably, the thickness of the silicon nitride layer on the battery cell to be electroplated is 80–100 nm; the refractive index is 2.0–2.5; the silicon nitride layer is prepared by PECVD; the radio frequency power used to prepare the silicon nitride layer is 100–300 W; the reaction temperature for preparing the silicon nitride layer is 300–500 °C; the reaction gases used to prepare the silicon nitride layer include NH3 and SH4; the flow ratio of NH3 to SH4 is 6–10:1–2; the total gas flow rate of NH3 and SH4 is 3000–5000 sccm; the pressure is 150–200 Pa; and the deposition time is 600–900 s.

10. The application of the BC solar cell electroplating method according to any one of claims 1-9 in the preparation of BC solar cells.

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