Heterojunction solar cell edge passivation integration method based on copper electroplating process

Abstract

This invention belongs to the field of photovoltaic solar cell technology, specifically relating to an integrated method for edge passivation of heterojunction solar cells based on copper electroplating. The method includes: Step S1 providing a cell substrate that has undergone copper electroplating but has not had its mask removed; Step S2 laser scribing under the protection of the mask layer; Step S3 placing the diced cell in an alkaline treatment solution, simultaneously removing the mask and chemically etching the damaged edge layer to expose a fresh silicon surface; Step S4 applying a passivation solution in a wet environment, where the active molecules of the passivating agent selectively bond with dangling bonds on the fresh silicon surface to form a passivation layer; and Step S5 cleaning and drying. This invention highly integrates scribing, mask removal, edge cleaning, and edge passivation into a low-temperature wet process, avoiding damage to the heterojunction cell from high temperatures, achieving self-aligned selective passivation, effectively suppressing edge recombination, improving cell efficiency, and without significantly increasing equipment investment and process costs.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic solar cell technology, and specifically to a method for edge passivation integration of heterojunction solar cells based on copper electroplating process. Background Technology

[0002] Heterojunction (HJT) solar cells possess advantages such as high open-circuit voltage, low temperature coefficient, and bifacial power generation, making them one of the mainstream technologies for high-efficiency photovoltaic cells. To reduce manufacturing costs and eliminate reliance on silver paste, copper electroplating technology has become an ideal solution for metallizing HJT cells. This involves depositing copper metal on the cell surface using electrochemical methods to form conductive grid lines, and it is gradually being applied in industry.

[0003] In the manufacturing process of HJT cells and modules, large-area cells are typically cut into sub-cells to reduce module internal losses and hot spot risk, and improve module output voltage. However, both laser cutting and mechanical scribing cause mechanical and thermal damage to the crystalline silicon substrate at the cell edges, generating numerous dangling bonds, dislocations, and microcracks. These areas form severe carrier recombination centers, known as "edge recombination," leading to a significant decrease in the cell's fill factor, open-circuit voltage, and photoelectric conversion efficiency. This has become one of the key bottlenecks restricting the efficiency improvement of HJT cell modules.

[0004] To address the aforementioned problems, existing technologies attempt to introduce an edge passivation process after cutting. A search reveals that the existing technologies related to this application mainly fall into the following categories: The first category is vacuum coating edge passivation technology. This type of technology attempts to deposit alumina or silicon nitride passivation films on the cut edges using plasma-enhanced chemical vapor deposition (PECVD) or atomic layer deposition (ALD). Some solutions also use low-temperature PECVD equipment to deposit intrinsic amorphous silicon films at the cut surface, with deposition temperatures around 80-120°C. However, this type of technology has significant drawbacks: even at relatively low deposition temperatures, thermal stress matching issues still exist, and the process temperature may still adversely affect the temperature-sensitive layer of the HJT battery; vacuum coating equipment is expensive, adding a separate step for edge passivation, disrupting the continuity and efficiency of the copper electroplating process, and significantly increasing production costs and line complexity; furthermore, selective deposition on irregular edges after cutting is expensive and extremely difficult to control.

[0005] The second category is laser-assisted wet passivation technology. One proposed approach involves slicing the entire battery cell, spraying ultrapure water onto the cut surfaces to form a water film, and then scanning the water film with a laser to ionize it. The oxygen ions then form a silicon oxide layer on the cut surfaces. While this approach introduces a wet environment, its core remains a laser-assisted process, requiring an additional laser scanning step. Furthermore, the quality of the resulting silicon oxide passivation layer is significantly affected by the uniformity of the water film. More importantly, this approach does not involve integration with copper electroplating processes.

[0006] The third category involves edge isolation techniques during the electroplating process. Existing technologies include a method for fabricating solar cells with electroplated grid lines. This method involves depositing an edge separation layer, such as indium tin oxide or vanadium-doped titanium oxide, before electroplating the grid lines. After electroplating, this separation layer is peeled off to prevent edge plating. The purpose of this approach is to achieve edge isolation rather than edge passivation, and it requires additional deposition and peeling of the edge separation layer. After peeling, no passivation treatment is applied to the exposed silicon edges, and the edge recombination problem caused by cutting still exists.

[0007] The fourth category involves organic solution edge passivation technology after cutting. Some studies have proposed a scheme combining low-temperature annealing with organic solution edge passivation. This scheme utilizes organic solutions such as sodium dodecyl sulfate, achieving passivation through the reaction of its sulfonate groups with silicon dangling bonds. However, this scheme is a separate passivation process after cutting, not integrated with the copper electroplating process, requiring a separate coating or immersion step after cutting. Furthermore, this scheme does not address the removal of the laser-damaged layer, and the passivation effect is limited by the quality of the damaged layer itself.

[0008] The fifth category involves etching to remove conductive material from the edges. Another approach involves adding a protective layer and then using an etching solution to etch the conductive material on the battery side. The purpose of this approach is to remove the conductive material at the edges to achieve edge isolation, rather than to passivate and repair cutting damage. It also does not involve the integration of the copper plating process or the repair of the damaged layer.

[0009] In summary, existing technologies generally follow a linear process approach of "cutting → separate passivation," and have the following common problems: lack of effective integration with the copper electroplating process, which increases process and equipment costs; failure to effectively remove the laser-damaged layer itself, resulting in limited passivation effect when applied directly to the damaged layer; and the contradiction between the low-temperature process requirements of HJT batteries and the high-temperature or high-cost characteristics of existing passivation technologies has not been properly resolved. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and provide an integrated method for edge passivation of heterojunction solar cells based on copper electroplating process. This method integrates dicing, film removal, edge cleaning and edge passivation into a low-temperature wet process, avoiding damage to heterojunction cells caused by high temperature, realizing self-aligned selective passivation, effectively suppressing edge recombination, improving cell efficiency, and without significantly increasing equipment investment and process cost.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for edge passivation integration of heterojunction solar cells based on copper electroplating process, characterized by comprising the following steps: Step S1: Provide a heterojunction solar cell substrate that has undergone copper electroplating but whose mask layer has not been removed; Step S2: Under the protection of the mask layer, the battery substrate is laser-scribbed to cut it into multiple sub-battery pieces; Step S3: The cut battery cells are placed in an alkaline treatment solution for treatment. The alkaline treatment solution simultaneously dissolves and removes the mask layer and chemically etches the edge damage layer formed by laser cutting, thereby exposing the fresh silicon surface. Step S4: In a wet environment, a passivation solution is applied to the alkaline-treated battery cell, so that the active molecules in the passivation solution selectively chemically bond with the dangling bonds on the fresh silicon surface to form a passivation layer. Step S5: Clean and dry the passivated solar cells. By placing the laser scribing process before the mask removal step, and using an alkaline treatment solution to etch away the edge damage layer generated by laser cutting while removing the mask layer, the exposed fresh silicon surface is immediately subjected to selective chemical passivation in a wet environment. This ensures that the entire process is conducted in a low-temperature wet environment, with a maximum temperature not exceeding 80°C. This fundamentally avoids damage to the amorphous silicon layer of heterojunction solar cells caused by high temperatures, achieving true low-temperature process compatibility. Simultaneously, through the sequential coupling of "first thoroughly removing the damage layer, then directly chemically saturating," the source of edge defects is effectively eliminated, significantly reducing the carrier edge recombination rate and resulting in excellent passivation quality. This method also cleverly utilizes copper... The essential film removal step in the electroplating process completes edge cleaning, eliminating the need for an additional independent damage layer removal process and expensive vacuum coating equipment. This achieves a high degree of integration of dicing, film removal, cleaning, and passivation, significantly simplifying the process flow and reducing manufacturing costs. Furthermore, the passivation process utilizes the difference in chemical reactivity between silicon, copper grid lines, and transparent conductive oxide to achieve self-aligned selective passivation only at the silicon cutting edge, without any additional mask, resulting in a wide process window and high yield. Laser dicing is performed under the physical protection of the mask layer, effectively preventing spatter from contaminating the copper grid lines and transparent conductive oxide layer on the front of the battery, ensuring the front performance and appearance quality of the battery.

[0012] In some embodiments, the alkaline treatment solution in step S3 is an aqueous solution of potassium hydroxide or sodium hydroxide, with a concentration of 1% to 10%, a treatment temperature of 25 to 80°C, and a treatment time of 2 to 6 minutes. Within the range of a concentration of 1% to 10%, a temperature of 25 to 80°C, and a treatment time of 2 to 6 minutes, the aqueous solution of potassium hydroxide or sodium hydroxide can efficiently and thoroughly dissolve and remove photosensitive adhesive films or dry film-type mask layers, while also performing sufficient and uniform isotropic chemical etching on the several-micrometer-thick damage layer generated by laser cutting. Simultaneously, it avoids excessive corrosion of the intact crystalline silicon substrate, ensuring the accuracy of edge geometry and the mechanical strength of the battery.

[0013] In some embodiments, steps S3 and S4 are performed sequentially in the same reaction tank. After the alkaline treatment in step S3 is completed, a concentrated passivating agent is injected into the tank to perform step S4, without the need to transfer the solar cell. The alkaline treatment and passivation steps are performed sequentially in the same reaction tank, eliminating the need to transfer the solar cell. This minimizes the time interval between etching and passivation treatment of the fresh silicon surface, preventing air exposure and natural oxidation caused by inter-process transfer. It ensures that the passivating agent can directly chemically bond on the atomically clean fresh silicon surface, thereby achieving optimal passivation quality and the lowest edge recombination rate. Simultaneously, this integrated operation further simplifies the process flow and improves production efficiency.

[0014] In some embodiments, the passivation solution in step S4 is a fluorine-containing solution with a concentration of 0.5% to 5%, achieving passivation through the formation of Si-F bonds. Using a fluorine-containing solution as the passivation solution allows hydrofluoric acid and other fluorine-containing solutions to react rapidly with dangling bonds on the silicon surface at room temperature, forming stable and dense Si-F bonds. This effectively saturates the active sites on the silicon surface and significantly reduces the interface state density. Si-F bonds exhibit high chemical and thermal stability, continuously suppressing edge recombination. Simultaneously, the dilute fluorine-containing solution has an extremely low corrosion rate on the copper gate wires and transparent conductive oxide layers, exhibiting good selectivity, resulting in a self-aligned passivation process that requires no additional mask.

[0015] In some embodiments, the passivation solution in step S4 contains organic molecules with one or more organic functional groups selected from thiol, carboxyl, and amino groups, which achieve passivation by forming covalent bonds with the silicon surface. Passivation using an organic molecule solution containing organic functional groups such as thiol, carboxyl, and amino groups allows these organic functional groups to form strong covalent bonds with dangling bonds on the silicon surface, such as Si-C and Si-OC, achieving chemical saturation of the active sites on the silicon surface. The organic molecular passivation layer has a flexible molecular structure and good coverage, capable of adapting to irregular morphologies such as microcracks and trenches at cutting edges, achieving full coverage. Simultaneously, organic passivation can control the thickness, hydrophobicity, and stability of the passivation layer through molecular structure design, providing better interface compatibility for subsequent component packaging.

[0016] In some embodiments, the passivation solution in step S4 is a solution capable of forming a self-assembled monolayer, wherein the self-assembled monolayer is selected from long-chain alkylsilanes or phosphoric acid derivatives. Passivation using a solution capable of forming a self-assembled monolayer, such as a long-chain alkylsilane or phosphoric acid derivative, allows the self-assembled monolayer to spontaneously form a highly ordered, densely packed monolayer on the silicon surface, exhibiting extremely high coverage uniformity and structural density, effectively blocking the diffusion of charge carriers to edge defects. The monolayer thickness is only at the nanometer level, without affecting the battery's geometry. Furthermore, the self-assembled monolayer of the long-chain alkyl group also possesses good hydrophobicity and chemical stability, providing long-term passivation protection for the cut edges.

[0017] In some embodiments, the passivation solution in step S4 is an iodine-ethanol solution, which achieves passivation by forming Si-I bonds. Using an iodine-ethanol solution for passivation allows the solution to react with silicon dangling bonds at room temperature, forming stable Si-I bonds and effectively saturating the active sites on the silicon surface. This solution system is simple, readily available, inexpensive, has a wide process window, and a fast passivation reaction rate. The ethanol solvent has good wettability and penetrability, enabling it to carry iodine molecules deep into microcracks and trenches, achieving sufficient passivation coverage of complex edge morphologies.

[0018] In some embodiments, the passivation solution in step S4 contains quinoline or a derivative thereof, and passivation is achieved by coordinating the lone pair electrons of the nitrogen atom in quinoline with the dangling bonds of silicon. Using a passivation solution containing quinoline or a derivative thereof, the nitrogen atom in the quinoline molecule has a lone pair electron, which can coordinate with the dangling bonds on the silicon surface, achieving chemical saturation of the dangling bonds through electron donor-acceptor interactions. This coordination passivation mechanism differs from covalent bond passivation, providing a new chemical pathway for edge passivation. Quinoline compounds have an aromatic ring structure, good molecular rigidity and thermal stability, and the resulting passivation layer exhibits excellent long-term stability.

[0019] In some embodiments, the passivation solution in step S4 is a composite solution containing an oxidant and a passivating agent, which forms a thin oxide layer while being covered by the passivating agent. Passivation using a composite solution containing an oxidant and a passivating agent involves the oxidant first growing an extremely thin, high-quality oxide layer in situ on the fresh silicon surface, followed immediately by chemical bonding with the active sites on the oxide layer surface, forming a bilayer passivation structure of oxide and organic matter. This composite passivation method combines the physical barrier effect of the silicon oxide layer with the chemical saturation effect of the organic passivation layer, achieving a lower interface state density and better long-term stability than a single passivation method.

[0020] In some embodiments, ultrasonic or megasonic assistance is used during the application of the passivation solution in step S4. Ultrasonic or megasonic assistance during the application of the passivation solution can generate cavitation effects or micro-acoustic flow in the passivation solution, significantly enhancing the mass transfer efficiency and penetration depth of passivation molecules within narrow structures such as microcracks, microgrooves, and deep holes at the cutting edge. This allows the passivating agent to fully contact and passivate the dangling bonds in these hard-to-reach areas, eliminating passivation dead zones and achieving comprehensive, dead-zone-free passivation, further improving the uniformity and effectiveness of edge passivation.

[0021] The beneficial effects of this invention are: First, the entire process is wet, with a maximum temperature not exceeding 80°C, completely eliminating the damage of high temperatures to the intrinsic amorphous silicon layer of the HJT battery, and is fully compatible with the low-temperature manufacturing process of the HJT battery.

[0022] Second, by using the time-series coupling of "alkali removal of the damage layer - immediate chemical passivation", the laser damage layer is completely removed first, exposing an atomically flat silicon surface. Then, chemical passivation is completed in the shortest possible time, which minimizes the interface state density and edge saturation dark current density. The passivation quality is significantly better than the solution of directly coating the damage layer.

[0023] Third, the laser scribing, film removal, edge cleaning and edge passivation are integrated into a continuous wet process. The damaged layer is removed by using the film removal step that is essential in the existing copper electroplating process. There is no need to add expensive vacuum coating equipment, which greatly simplifies the production line and significantly reduces manufacturing costs.

[0024] Fourth, by utilizing the differences in reactivity of silicon, copper gate lines, and transparent conductive oxides in specific chemical solutions, maskless, self-aligned selective passivation of the cutting edges is achieved, resulting in a wide process window and high yield.

[0025] Fifth, the laser scribing is performed under the protection of a mask layer, which effectively prevents splatter from contaminating the copper grid lines and transparent conductive oxide layer on the front of the battery.

[0026] Sixth, it effectively suppresses edge recombination, which can effectively improve the open-circuit voltage and fill factor of sub-cells, thereby improving the power output of the module and the efficiency of the cell and module. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0028] Figure 1 This is a schematic diagram of the process flow of an embodiment of the present invention; Figure 2 This is a schematic diagram of the HJT battery substrate structure after copper electroplating and before mask removal, according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the structure after laser scribing under mask protection according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure after simultaneous film removal and edge damage etching using alkaline solution according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure after selective edge passivation by solution method according to an embodiment of the present invention. Detailed Implementation

[0029] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings, are intended to cover non-exclusive inclusion.

[0031] The directional and positional terms used in this invention, such as up, down, front, back, left, right, inside, outside, top, bottom, side, etc., are merely for reference to the accompanying drawings. Therefore, the directional and positional terms used are for illustrating and understanding this invention, and not for limiting the scope of protection of this invention.

[0032] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments: like Figure 1As shown, this embodiment of the invention provides an overall process flow for a heterojunction solar cell edge passivation integration method based on copper electroplating, which includes steps S1 to S5 in sequence.

[0033] Example 1 This embodiment employs an integrated method of potassium hydroxide film removal and hydrofluoric acid passivation, the specific steps of which are as follows: Step S1: Provide an HJT battery substrate that has undergone copper plating but whose mask layer has not been removed. For example... Figure 2 As shown, the substrate has an amorphous silicon and TCO composite layer 2, a copper seed layer 3, a mask layer 4, and electroplated copper grid lines 5 sequentially formed on a silicon wafer substrate 1. The mask layer 4 is a photosensitive film that completely covers the area except for the copper grid lines 5.

[0034] Step S2: Under the protection of the mask layer 4, the battery substrate is cut into multiple sub-cells according to a preset size using a laser scribing device. (Refer to...) Figure 3 During the cutting process, the laser penetrates the mask layer 4, creating a damage layer containing heat-affected zones, slag, and microcracks at the newly exposed silicon wafer cutting edge. The mask layer 4 effectively prevents laser spatter from contaminating the front copper grid lines 5 and the TCO composite layer 2 during this process.

[0035] Step S3: Place the cut solar cell in a 5% (w / w) potassium hydroxide (KOH) aqueous solution at 50°C for 3 minutes. This alkaline solution serves two purposes: firstly, it rapidly dissolves and peels off the mask layer 4; secondly, it performs isotropic chemical etching on the damaged layer at the laser-cut edge. Due to the high chemical potential and numerous defects in the damaged silicon area, its etching rate is much higher than that of perfect single-crystal silicon, thus effectively removing the damaged silicon and exposing a clean, fresh silicon surface, the structure of which is as follows. Figure 4 As shown.

[0036] Step S4: After film removal and etching, without transferring the solar cells, a concentrated hydrofluoric acid (HF) solution is directly injected into the same processing tank to achieve a HF mass concentration of 2%, and the process is carried out at room temperature for 2 minutes. In a wet environment, HF molecules selectively react with the dangling bonds of the highly reactive fresh silicon edges to form stable Si-F bonds, thereby forming a passivation layer on the diced sidewalls of the silicon wafer. Figure 5 The passivation group 6 is shown in the diagram. Due to the extremely low reaction rate between the copper grid line 5 and the TCO composite layer 2 and the dilute HF solution, the passivation process exhibits self-aligned selectivity.

[0037] Step S5: Thoroughly clean the passivated solar cells with deionized water and dry them with dry nitrogen gas to obtain a high-efficiency heterojunction solar cell with effective suppression of edge recombination.

[0038] Example 2 The difference between this embodiment and Embodiment 1 is that sodium hydroxide is used as the alkaline treatment solution, and an organic molecule solution containing thiol functional groups is used for passivation.

[0039] Execution steps S1 and S2: Same as in Example 1, yielding the following result. Figure 2 and Figure 3 The image shows a battery cell after laser scribing with a mask.

[0040] Step S3: Place the cut solar cell in a 3% (w / w) sodium hydroxide (NaOH) aqueous solution at 60°C for 4 minutes. Simultaneously remove the mask layer 4 and chemically etch the edge damage layer to expose the fresh silicon surface. Figure 4 ).

[0041] Step S4: Subsequently, a concentrated organic molecule solution containing thiol (-SH) functional groups is injected into the same treatment tank to achieve a mass concentration of active molecules of 0.5% in the solution, and the treatment is carried out at 40°C for 3 minutes. The thiol functional groups chemically passivate the silicon wafer by forming Si-C covalent bonds with the dangling bonds of the fresh silicon edge. Passivation groups 6 cover the sidewalls of the silicon wafer. Figure 5 ).

[0042] Perform step S5: Clean with deionized water and dry with nitrogen.

[0043] Example 3 In this embodiment, potassium hydroxide is used for film removal, and a long-chain alkylsilane solution that forms a self-assembled monolayer is used for passivation.

[0044] Steps S1 and S2 are performed in the same manner as in Example 1.

[0045] Step S3: Place the cut battery cell in an 8% KOH aqueous solution and treat at 30°C for 5 minutes to complete the film removal and damage layer etching. Figure 4 ).

[0046] Step S4: The solar cells are then transferred to a passivation solution containing long-chain alkylsilanes (1% by mass) and treated at 50°C for 4 minutes. The long-chain alkylsilanes self-assemble on the fresh silicon edge surface to form a dense monolayer, serving as the passivation group 6 ( Figure 5 ).

[0047] Perform step S5: Clean with deionized water and dry with nitrogen.

[0048] Example 4 In this embodiment, a low-concentration sodium hydroxide solution is used for rapid membrane removal, and an iodine-ethanol solution is used for passivation.

[0049] Steps S1 and S2 are performed in the same manner as in Example 1.

[0050] Step S3: Place the cut battery cell in a 1% (w / w) NaOH aqueous solution and treat at 80°C for 2 minutes to quickly complete film removal and edge damage etching. Figure 4 ).

[0051] Step S4: Transfer the solar cell to an iodine-ethanol solution (I₂ mass concentration 0.1%) and treat at room temperature for 5 minutes. Iodine molecules react with the dangling bonds at the fresh silicon edges to form stable Si-I bonds, achieving passivation. Figure 5 ).

[0052] Perform step S5: Clean with deionized water and dry with nitrogen.

[0053] Example 5 In this embodiment, high-concentration potassium hydroxide is used for low-temperature, long-term membrane removal, and a passivation solution containing quinoline is used, supplemented by megasonic assisted passivation.

[0054] Steps S1 and S2 are performed in the same manner as in Example 1.

[0055] Step S3: Place the cut battery cells in a 10% KOH aqueous solution and treat at 25°C for 6 minutes to simultaneously complete film removal and damage etching. Figure 4 ).

[0056] Step S4: Inject a passivation solution containing quinoline (0.3% by mass) into the same treatment tank and treat at 30°C for 3 minutes. Megasonography is used throughout the passivation process to enhance the penetration efficiency of passivation molecules within microcracks and microtrenches. The lone pair electrons on the nitrogen atom of quinoline undergo coordination saturation with the silicon dangling bond, forming a passivation layer 6 ( Figure 5 ).

[0057] Perform step S5: Clean with deionized water and dry with nitrogen.

[0058] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this invention; the scope of protection of this invention is defined by the claims in the claims, and all equivalent changes and modifications made in accordance with this invention are within the scope of protection of this patent.

Claims

1. A method for edge passivation integration of heterojunction solar cells based on copper electroplating process, characterized in that: Includes the following steps: Step S1: Provide a heterojunction solar cell substrate that has undergone copper electroplating but whose mask layer has not been removed; Step S2: Under the protection of the mask layer, the battery substrate is laser scribing to cut it into multiple sub-battery pieces; Step S3: The cut battery cells are placed in an alkaline treatment solution for treatment. The alkaline treatment solution simultaneously dissolves and removes the mask layer and chemically etches the edge damage layer formed by laser cutting, thereby exposing the fresh silicon surface. Step S4: In a wet environment, a passivation solution is applied to the alkaline-treated battery cell, so that the active molecules in the passivation solution selectively chemically bond with the dangling bonds on the fresh silicon surface to form a passivation layer. Step S5: Clean and dry the passivated battery cells.

2. The method for edge passivation integration of heterojunction solar cells based on copper electroplating process according to claim 1, characterized in that: The alkaline treatment solution in step S3 is an aqueous solution of potassium hydroxide or sodium hydroxide, with a concentration of 1% to 10%, a treatment temperature of 25 to 80°C, and a treatment time of 2 to 6 minutes.

3. The method for edge passivation integration of heterojunction solar cells based on copper electroplating process according to claim 1, characterized in that: Steps S3 and S4 are performed sequentially in the same reaction tank. After the alkaline treatment in step S3 is completed, a concentrated passivating agent is injected into the tank to perform step S4, without the need to transfer the battery cells.

4. The method for edge passivation integration of heterojunction solar cells based on copper electroplating process according to claim 1, characterized in that: The passivation solution in step S4 is a fluorine-containing solution with a concentration of 0.5% to 5%, and passivation is achieved by forming Si-F bonds.

5. The method for edge passivation integration of heterojunction solar cells based on copper electroplating process according to claim 1, characterized in that: The passivation solution in step S4 contains organic molecules with one or more organic functional groups selected from thiol, carboxyl, and amino groups, which achieve passivation by forming covalent bonds with the silicon surface.

6. The method for edge passivation integration of heterojunction solar cells based on copper electroplating process according to claim 1, characterized in that: The passivation solution in step S4 is a solution capable of forming a self-assembled monolayer, wherein the self-assembled monolayer is selected from long-chain alkylsilanes or phosphoric acid derivatives.

7. The method for edge passivation integration of heterojunction solar cells based on copper electroplating process according to claim 1, characterized in that: The passivation solution in step S4 is an iodine-ethanol solution, which achieves passivation by forming Si-I bonds.

8. The method for edge passivation integration of heterojunction solar cells based on copper electroplating process according to claim 1, characterized in that: The passivation solution in step S4 contains quinoline or its derivatives, and passivation is achieved by coordinating the lone pair electrons of the nitrogen atom of quinoline with the dangling bond of silicon.

9. The method for edge passivation integration of heterojunction solar cells based on copper electroplating process according to claim 1, characterized in that: The passivation solution mentioned in step S4 is a composite solution containing an oxidant and a passivating agent, which is covered by the passivating agent while forming a thin oxide layer.

10. The method for edge passivation integration of heterojunction solar cells based on copper electroplating process according to any one of claims 1 to 9, characterized in that: The application of the passivation solution in step S4 is assisted by ultrasound or megaphony.

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