Back contact solar cell, method of manufacturing the same, and photovoltaic module

Abstract

The application discloses a back contact solar cell, a preparation method thereof and a photovoltaic module, and relates to the technical field of photovoltaics. The application uses a gradient structure of an adhesion barrier layer, a composite barrier layer and an electroplating nucleation layer as a composite seed layer, adopts a double-barrier mechanism: the adhesion barrier layer (such as Ni-X) forms an amorphous / nanocrystalline structure, and eliminates a grain boundary diffusion channel; the composite barrier layer (such as Ti / TiN) is a dense ceramic phase, has extremely high copper ion migration activation energy, and effectively inhibits the diffusion of copper to a silicon substrate. Through the structural optimization of the composite seed layer, the problem of PN junction leakage failure caused by the high-temperature diffusion of copper ions can be effectively solved. In addition, the adhesion barrier layer (such as Ni-X) reacts with silicon after annealing to generate a Ni-Si compound, converts physical adsorption into chemical bonding, greatly improves soldering tension, and completely solves the problems of poor bonding force of a traditional Cu or Ti composite seed layer with silicon and easy peeling after electroplating.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and more specifically, to back-contact solar cells, their fabrication methods, and photovoltaic modules. Background Technology

[0002] Back-contact solar cells place both positive and negative electrodes on the back of the cell, with no grid lines obstructing the front, significantly improving short-circuit current and photoelectric conversion efficiency. This is currently one of the important technological directions for crystalline silicon photovoltaic cells. To achieve low-cost, highly conductive metallized electrodes, the industry widely adopts a "composite seed layer + electroplated copper" solution to replace the high-cost silver paste screen printing process.

[0003] However, existing composite seed layer technologies have the following prominent problems in practical applications: (1) Insufficient adhesion: The bonding force between copper and silicon or passivation layer is poor, and the film layer is prone to peeling after electroplating, which affects the reliability of component packaging; (2) Copper diffusion leads to leakage failure: Copper is a fast-diffusion impurity in silicon. Under high temperature or long-term working conditions, copper ions can easily penetrate the barrier layer and enter the silicon substrate, resulting in a sharp increase in PN junction leakage current and a decrease in battery efficiency. (3) Stress mismatch causes warping: The difference in thermal expansion coefficient between a single metal layer (such as pure Cu) and the silicon substrate is large, and large internal stress is generated after deposition or annealing, which can easily cause the cell to warp. (4) Uneven electroplating nucleation: Some high-resistivity layers (such as TiN and TaN) have poor conductivity. When used directly as the electroplating underlayer, the initial current distribution is uneven, resulting in some areas not being plated or the plating thickness being uneven. (5) Low process integration: In traditional methods, each functional layer is often deposited in stages and vacuum is broken multiple times. The interlayer interface is easily contaminated by oxidation, and the production efficiency is low and the cost is high.

[0004] Therefore, there is an urgent need to develop new composite seed layer solutions with reasonable structural design, optimized materials, and high process integration to solve the problems of copper diffusion and poor adhesion.

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

[0006] The purpose of this invention is to provide a back-contact solar cell, its preparation method, and a photovoltaic module, aiming to solve the problems of copper diffusion and poor adhesion.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a back-contact solar cell, comprising: A silicon substrate having a front side and a back side, wherein a silicon doped region and a passivation layer are disposed on the back side, and a contact window is disposed on the passivation layer; The composite seed layer forms an electrical contact with the silicon doped region through a contact window; and from the direction near the silicon doped region to the direction away from the silicon doped region, it includes, in sequence, an adhesion barrier layer, a composite barrier layer and an electroplating nucleation layer.

[0008] In an optional embodiment, the material of the adhesion barrier layer is a nickel-containing metal, the material of the composite barrier layer is a titanium-containing barrier material, and the material of the electroplated nucleation layer is a copper-containing conductive material. Preferably, the material of the adhesion barrier layer is a nickel-based alloy Ni-X, where X is selected from at least one of P, W, V and Cr; More preferably, the nickel-based alloy Ni-X is a Ni-P alloy, and the atomic percentage of P is 5 at%-10 at%; More preferably, the thickness of the adhesion barrier layer is 10nm-120nm.

[0009] In optional embodiments, the composite barrier layer is a Ti layer, a TiN layer, or a Ti / TiN composite layer; Preferably, the thickness of the composite barrier layer is 5nm-50nm; Preferably, the material of the electroplated nucleation layer is pure copper or a copper alloy; Preferably, the thickness of the electroplated nucleation layer is 5nm-30nm.

[0010] In an optional embodiment, the thickness ratio of the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer is (2~8):(1~5):1; Preferably, the total thickness of the composite seed layer is 20nm-200nm; Preferably, the silicon doped region includes alternating P-type and N-type doped regions, and the composite seed layer is disposed in the contact window and electrode region to achieve electrical isolation between the P-region and the N-region; Preferably, the surface of the composite seed layer is further electroplated with a conductive layer, which is a pure copper layer, a copper-tin alloy layer, or a copper-silver alloy layer; the thickness of the conductive layer is 5μm-15μm.

[0011] Secondly, the present invention provides a method for preparing a back-contact solar cell according to any of the foregoing embodiments, comprising: Providing a silicon substrate: Forming a contact window pattern on the back side of the battery intermediate where doping and passivation layer deposition have been completed, exposing the silicon doped region; Composite seed layer deposition: An adhesion barrier layer, a composite barrier layer, and an electroplated nucleation layer are sequentially deposited on a silicon substrate.

[0012] In an optional embodiment, during the composite seed layer deposition step, the silicon substrate is placed in a multi-target magnetron sputtering apparatus and evacuated to a base vacuum ≤ 5 × 10⁻⁶. -4Pa; sequentially sputtering the adhesion barrier layer, composite barrier layer, and electroplated nucleation layer; the entire deposition process does not break the vacuum; Preferably, in the step of depositing the adhesion barrier layer, a nickel-based alloy target is used; the power density is 2 W / cm². 2 -5W / cm 2 The working gas pressure is 0.3 Pa - 0.8 Pa; the deposition rate is 0.2 nm / s - 0.5 nm / s. Preferably, the process of depositing the composite barrier layer includes: first sputtering a Ti layer with a thickness of 5 nm-15 nm, and then sputtering a TiN layer with a thickness of 5 nm-25 nm; more preferably, the sputtering of the Ti layer is carried out in an argon atmosphere, and the power density is controlled at 3 W / cm². 2 -6W / cm 2 More preferably, during the sputtering of the TiN layer, the flow rate ratio of the introduced nitrogen gas to argon gas is controlled to be 1:(1-3), and the power density is controlled to be 3W / cm³. 2 -6W / cm 2 ; Preferably, a copper target or a copper alloy target is used to deposit the electroplated nucleation layer, and the power density is controlled to be 1 W / cm². 2 -5W / cm 2 Deposition was carried out under an argon atmosphere.

[0013] In an optional implementation, the method further includes: after the composite seed layer deposition is completed, laser patterning, annealing and electroplating of a conductive layer are performed sequentially. Laser patterning uses pulsed laser to scan along the electrode gap to remove the composite seed layer metal in the non-electrode region, forming P-region electrode patterns and N-region electrode patterns that are electrically isolated from each other. Preferably, the laser scanning parameters for the laser patterning process are as follows: wavelength of 355nm or 532nm, and energy density of 0.1J / cm². 2 -1.0J / cm 2 The laser beam width is 10μm-30μm, and the scanning speed is 100mm / s-500mm / s.

[0014] In an optional implementation, during the annealing process, the annealing temperature is controlled at 200℃-350℃ and the time is 5min-15min; Preferably, during the annealing process, the annealing atmosphere is selected from nitrogen or a mixture of hydrogen and nitrogen, wherein the volume fraction of nitrogen in the mixture is 93%-98%, and the gas flow rate is controlled at 1L / min-10L / min. Preferably, the electroplating process for the conductive layer includes: using the patterned composite seed layer as the cathode, electroplating is performed using an acidic copper sulfate plating solution to deposit a conductive layer on the surface of the composite seed layer; more preferably, in the acidic copper sulfate plating solution, the copper ion concentration is 20 g / L-80 g / L, the sulfuric acid concentration is 100 g / L-200 g / L, and the chloride ion concentration is 40 mg / L-80 mg / L; even more preferably, the electroplating current density is controlled to be 1 A / dm³. 2 -10A / dm 2 .

[0015] In an optional implementation, the contact window pattern is formed by laser perforation; Preferably, the process of preparing the silicon substrate further includes: after laser drilling, performing RCA cleaning and dilute hydrofluoric acid treatment to remove the surface oxide layer; Preferably, the parameters for laser aperture are as follows: wavelength of 355nm or 532nm, pulse width in the nanosecond range, and aperture depth of 80nm-120nm; Preferably, the HF mass fraction in the dilute hydrofluoric acid used in the dilute hydrofluoric acid treatment process is 1%-5%, the treatment time is 30s-120s, and the treated silicon substrate is put into the magnetron sputtering equipment within 0.5h-2h.

[0016] Thirdly, the present invention provides a photovoltaic module, including any of the back-contact solar cells in the foregoing embodiments or back-contact solar cells prepared by any of the preparation methods described in the foregoing embodiments.

[0017] This invention offers the following advantages: It utilizes a gradient structure of an adhesion barrier layer, a composite barrier layer, and an electroplated nucleation layer as a composite seed layer, employing a dual barrier mechanism: the adhesion barrier layer (e.g., Ni-X) forms an amorphous / nanocrystalline structure, eliminating grain boundary diffusion channels; the composite barrier layer (e.g., Ti / TiN) is a dense ceramic phase with extremely high copper ion migration activation energy, effectively suppressing copper diffusion into the silicon substrate. Through structural optimization of the composite seed layer, the problem of PN junction leakage failure caused by high-temperature copper ion diffusion can be effectively solved.

[0018] In addition, after annealing, the adhesion barrier layer (such as Ni-X) reacts with silicon to form Ni-Si compound, which transforms physical adsorption into chemical bonding, greatly improving the welding pull force and completely solving the problem of poor bonding between traditional Cu or Ti composite seed layers and silicon, and easy peeling after electroplating. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the cross-section of the back electrode of a back-contact solar cell. Figure 2 This is a schematic diagram of the composite seed layer structure of a back-contact solar cell.

[0021] Explanation of key component symbols: 001-Silicon substrate; 002-Passivation layer; 003-Contact window; 004-Composite seed layer; 005-Adhesion barrier layer; 006-Composite barrier layer; 007-Electroplated nucleation layer; 008-Conductive layer; 009-Silicon doped region. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] To address issues such as copper diffusion and poor adhesion, this invention optimizes the structure of the composite seed layer 004, as follows: Figure 1 and Figure 2 As shown, this embodiment of the invention provides a back-contact solar cell, including a silicon substrate 001 and a composite seed layer 004. The silicon substrate 001 has a front side and a back side. A silicon doped region 009 and a passivation layer 002 are disposed on the back side. A contact window 003 is disposed on the passivation layer 002, exposing the underlying silicon doped region 009. The composite seed layer 004 forms an electrical contact with the silicon doped region 009 through the contact window 003. From the direction near the silicon doped region 009 to the direction away from the silicon doped region 009, the composite seed layer 004 includes an adhesion barrier layer 005, a composite barrier layer 006, and an electroplated nucleation layer 007 disposed sequentially.

[0024] The adhesion barrier layer 005 on the silicon surface is made of nickel-containing metal, the composite barrier layer 006 above the adhesion barrier layer 005 is made of titanium-containing barrier material, and the electroplated nucleation layer 007 above the composite barrier layer 006 is made of copper-containing conductive material. By optimizing the materials of the three layers, the bonding force with silicon can be improved, and the diffusion of copper into the silicon substrate can be suppressed.

[0025] In some embodiments, the material of the adhesion barrier layer 005 is a nickel-based alloy Ni-X, where X is selected from at least one of P, W, V, and Cr, and X can be any one or more of the above. More preferably, the nickel-based alloy Ni-X can be a Ni-P alloy, and the atomic percentage of P is 5at%-10at%, such as 5at%, 6at%, 7at%, 8at%, 9at%, 10at%, etc. Ni-P alloys have excellent amorphous forming ability and low cost. The thickness of the adhesion barrier layer 005 is 10nm-120nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, etc., preferably 70nm-90nm.

[0026] It should be noted that the present invention uses Ni-X alloy as an adhesion barrier layer, which reacts with silicon after annealing to generate Ni-Si compound, transforming physical adsorption into chemical bonding, greatly improving welding pull strength, and completely solving the problems of poor bonding between traditional Cu or Ti seed layers and silicon, and easy peeling after electroplating.

[0027] In some embodiments, the composite barrier layer 006 is a Ti layer, a TiN layer, or a Ti / TiN composite layer. The composite barrier layer 006 can be a Ti layer, a TiN layer, or a Ti / TiN composite layer, preferably a Ti / TiN composite layer. The thickness of the composite barrier layer 006 is 5nm-50nm, such as 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, etc., preferably 15nm-25nm.

[0028] It should be noted that, in response to the problem of PN junction leakage failure caused by high-temperature diffusion of copper ions, this invention adopts a dual blocking mechanism: the bottom Ni-X layer forms an amorphous / nanocrystalline structure to eliminate grain boundary diffusion channels; the middle Ti / TiN layer is a dense ceramic phase with extremely high copper ion migration activation energy, which effectively inhibits copper diffusion into the silicon substrate.

[0029] In some embodiments, the material of the electroplated nucleation layer 007 is pure copper or a copper alloy. The thickness of the electroplated nucleation layer 007 is 5nm-30nm, such as 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, etc., preferably 10nm-20nm. The surface Cu provides a low-resistance electroplating nucleation layer, ensuring uniform distribution of the initial electroplating current and excellent uniformity of the plating thickness.

[0030] Furthermore, the thickness ratio of the adhesion barrier layer 005, the composite barrier layer 006, and the electroplating nucleation layer 007 is (2~8):(1~5):1, such as 2:1:1, 3:2:1, 4:3:1, 5:3.5:1, 6:4:1, 7:4.5:1, 8:5:1, etc. The total thickness of the composite seed layer 004 is 20nm-200nm, such as 20nm, 50nm, 80nm, 100nm, 130nm, 150nm, 180nm, 200nm, etc.

[0031] It should be noted that the present invention effectively matches the difference in thermal expansion coefficients between each layer and the silicon substrate 001 through gradient structure design and stress buffering effect of Ti layer in composite barrier layer 006. The total thickness of composite seed layer 004 is ≤200 nm, and the cumulative stress is small, which solves the problem of cell warping and cracking caused by stress mismatch in traditional single metal layer.

[0032] Furthermore, the adhesion barrier layer 005, the composite barrier layer 006, and the electroplating nucleation layer 007 can be continuously deposited using the same multi-target magnetron sputtering equipment, without breaking the vacuum throughout the process. The silicon doped region 009 includes alternating P-type and N-type doped regions. The specific parameters and fabrication processes of the P-type and N-type doped regions are not limited, and the existing P-type and N-type doped region structures of back contact batteries are all within the scope of protection of this invention. The composite seed layer 004 is disposed in the contact window 003 and the electrode region to achieve electrical isolation between the P-region and the N-region. In actual operation, after the composite seed layer 004 is deposited, a laser lift-off process is used to remove the metal outside the gate lines, leaving only the seed layer in the contact window 003 and the electrode region to achieve electrical isolation between the P-region and the N-region.

[0033] In some embodiments, the surface of the composite seed layer 004 is further electroplated with a conductive layer 008, which is a pure copper layer, a copper-tin alloy layer, or a copper-silver alloy layer. The thickness of the conductive layer 008 is 5μm-15μm, such as 5μm, 8μm, 10μm, 13μm, 15μm, etc.

[0034] This invention also provides a method for fabricating a back-contact solar cell, comprising the following steps: S1, Providing a silicon substrate A contact window pattern is formed on the back side of the battery intermediate after the doping and passivation layers have been deposited, exposing the silicon surface of the P and N doped regions.

[0035] In some embodiments, the contact window pattern can be formed by laser aperture. The parameters of the laser aperture are as follows: wavelength is 355nm or 532nm, pulse width is in the nanosecond range, and aperture depth is 80nm-120nm, such as 80nm, 90nm, 100nm, 110nm, 120nm, etc.

[0036] In some embodiments, the process of preparing the silicon substrate further includes: after laser drilling, performing standard RCA cleaning and dilute hydrofluoric acid treatment to remove the natural oxide layer on the surface. The specific steps of standard RCA cleaning are as follows: sequentially cleaning with SC-1 solution (NH4OH:H2O2:H2O=1:1:5) at 80°C for 10 minutes to remove particulate matter, and cleaning with SC-2 solution (HCl:H2O2:H2O=1:1:6) at 80°C for 10 minutes to remove metal ions, and rinsing with deionized water after each step. The HF mass fraction in the dilute hydrofluoric acid used in the dilute hydrofluoric acid treatment is 1%-5%, such as 1%, 2%, 3%, 4%, 5%, etc.; the dilute hydrofluoric acid treatment time is 30s-120s, such as 30s, 50s, 80s, 100s, 120s, etc. The silicon substrate after dilute hydrofluoric acid treatment is placed in a magnetron sputtering device within 0.5h~2h to deposit a composite seed layer.

[0037] S2, composite seed layer deposition An adhesion barrier layer, a composite barrier layer, and an electroplated nucleation layer are sequentially deposited on a silicon substrate. The materials and thicknesses of the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer are as described above in the specification.

[0038] In some embodiments, the silicon substrate is placed in a multi-target magnetron sputtering apparatus and evacuated to a base vacuum ≤ 5 × 10⁻⁶. - 4 Pa, sequentially sputtering an adhesion barrier layer, a composite barrier layer, and an electroplating nucleation layer, without breaking the vacuum throughout the deposition process. The aforementioned "background vacuum" refers to a vacuum without the introduction of process gas. This invention employs a three-layer, vacuum-breaking continuous deposition process, eliminating interlayer oxidation contamination, achieving high process integration and superior production efficiency, and solving the problems of interface contamination and low efficiency associated with step-by-step deposition.

[0039] In some embodiments, a nickel-based alloy target can be used during the deposition of the adhesion barrier layer; the power density is controlled at 2 W / cm². 2 -5W / cm 2 For example, it can be 2W / cm 2 3W / cm 2 4W / cm 2 5W / cm 2 The working gas pressure is controlled at 0.3Pa-0.8Pa, such as 0.3Pa, 0.4Pa, 0.5Pa, 0.6Pa, 0.7Pa, 0.8Pa, etc.; the deposition rate is controlled at 0.2nm / s-0.5nm / s, such as 0.2nm / s, 0.3nm / s, 0.4nm / s, 0.5nm / s, etc.

[0040] In some embodiments, the process of depositing the composite barrier layer includes: first sputtering a Ti layer with a thickness of 5nm-15nm, and then sputtering a TiN layer with a thickness of 5nm-25nm. The Ti / TiN composite structure balances barrier performance and mechanical reliability, which is superior to a single Ti or a single TiN layer. Specifically, the thickness of the Ti layer can be 5nm, 8nm, 10nm, 13nm, 15nm, etc.; the thickness of the TiN layer can be 5nm, 10nm, 15nm, 20nm, 25nm, etc.

[0041] Furthermore, the sputtering of the Ti layer was carried out in a pure argon atmosphere, with a power density controlled at 3 W / cm². 2 -6W / cm 2 For example, it can be 3W / cm 2 4W / cm 2 5W / cm 2 6W / cm 2 After sputtering the Ti layer, nitrogen gas is introduced, and the flow ratio of nitrogen to argon is controlled to be 1:(1-3), such as 1:1, 1:2, 1:3, etc. TiN is then formed by sputtering in a mixed atmosphere of nitrogen and argon, maintaining a power density of 3 W / cm³. 2 -6W / cm 2 .

[0042] In some embodiments, a copper target or a copper alloy target is used to deposit an electroplated nucleation layer, controlling the power density to 1 W / cm². 2 -5W / cm 2 For example, it can be 1W / cm 2 2W / cm 2 3W / cm 2 4W / cm 2 5W / cm 2 Etc. When depositing the electroplating nucleation layer, deposition can be carried out in a pure argon atmosphere, but it is not limited to this.

[0043] S3, Laser Graphics A pulsed laser is used to scan along the electrode gap to remove the composite seed layer metal in the non-electrode region, forming P+ and N+ electrode patterns that are electrically isolated from each other.

[0044] In some embodiments, the laser scanning parameters for the laser patterning process are as follows: wavelength of 355nm or 532nm (either wavelength can be 355nm or 532nm); energy density of 0.1J / cm². 2 -1.0J / cm 2 For example, it can be 0.1 J / cm 2 0.3J / cm 2 0.5J / cm 2 0.8J / cm2 1.0 J / cm 2 The laser beam width is 10μm-30μm, such as 10μm, 15μm, 20μm, 25μm, 30μm, etc.; the scanning speed is 100mm / s-500mm / s, such as 100mm / s, 200mm / s, 300mm / s, 400mm / s, 500mm / s, etc. After laser treatment, the surface resistance of the non-electrode area is >10MΩ / □, and there is no visible damage to the underlying passivation layer.

[0045] S4, Annealing treatment After laser patterning is completed, the solar cells are placed in an annealing furnace for heat treatment.

[0046] In some embodiments, the annealing temperature is controlled to be 200℃-350℃, such as 200℃, 230℃, 250℃, 280℃, 300℃, 330℃, 350℃, etc.; the annealing time is 5min-15min, such as 5min, 8min, 10min, 13min, 15min, etc.

[0047] Furthermore, the annealing atmosphere used is selected from nitrogen or a mixture of hydrogen and nitrogen, wherein the volume fraction of nitrogen in the mixture is 93%-98%, such as 93%, 94%, 95%, 96%, 97%, 98%, etc.; the volume fraction of nitrogen is 2%-7%, such as 2%, 3%, 4%, 5%, 6%, 7%, etc. The flow rate of the mixture is controlled at 1L / min-10L / min, such as 1L / min, 3L / min, 5L / min, 8L / min, 10L / min, etc.

[0048] S5, Electroplated conductive layer Using the patterned composite seed layer as the cathode, an acidic copper sulfate plating solution is used for electroplating to deposit a conductive layer on the surface of the composite seed layer.

[0049] In some embodiments, the concentration of copper ions in the acidic copper sulfate plating solution is 20 g / L-80 g / L, such as 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, etc.; the concentration of sulfuric acid is 100 g / L-200 g / L, such as 100 g / L, 130 g / L, 150 g / L, 180 g / L, 200 g / L, etc.; and the concentration of chloride ions is 40 mg / L-80 mg / L, such as 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L, etc.

[0050] In some embodiments, during the electroplating process, the current density of the electroplating is controlled to be 1 A / dm². 2 -10A / dm2 For example, it can be 1A / dm 2 3A / dm 2 5A / dm 2 8A / dm 2 10A / dm 2 The electroplating time is not limited, as long as the thickness of the conductive layer reaches 5μm-15μm.

[0051] This invention provides a photovoltaic module, including a back-contact solar cell. By optimizing the composite seed layer, the problems of copper diffusion and poor adhesion can be solved. At the same time, the three-layer vacuum-breaking continuous deposition process solves the problems of interface contamination and low efficiency caused by step-by-step deposition. Therefore, assembling a photovoltaic module using the back-contact solar cell provided by this invention is beneficial to improving the module's lifespan and efficiency.

[0052] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0053] Example 1 This embodiment provides a back-contact solar cell, the fabrication process of which is as follows: (1) Provide silicon substrate Pretreatment: Take an N-type silicon wafer with a thickness of 150μm, clean it with standard RCA and set it aside.

[0054] Texturing: Using KOH alkaline solution, anisotropic etching is performed at 80℃ to form a pyramidal textured surface with a reflectivity ≤10%.

[0055] Oxide layer growth: A SiO2 layer with a thickness of 50 nm was thermally grown at 1000℃.

[0056] Boron diffusion: Using BBr3 as the boron source, diffusion is carried out at 1000℃ to form a P-type doped region, and BSG is removed after diffusion.

[0057] Phosphorus diffusion: Using POCl3 as the phosphorus source, N-type doped regions are formed by diffusion at 900℃, and PSG is removed after diffusion.

[0058] Annealing: Anneal at 950℃ for 20 min to activate doped atoms.

[0059] Back junction removal: Laser or plasma etching is used to remove the doped layers on the front side and edges.

[0060] P / N isolation: A laser device is used to scan along the electrode gap to achieve electrical isolation between the P and N regions.

[0061] Passivation layer deposition: A SiNx stacked passivation film with a thickness of 100 nm was deposited using the PECVD method.

[0062] Laser-guided aperture: On the back side of the back contact solar cell where doping and passivation layers have been deposited, a contact window pattern is created using laser-guided aperture to expose the P- and N-doped silicon surface. The laser-guided aperture parameters are as follows: wavelength 355nm, pulse width in the nanosecond range (50ns), and aperture depth 100nm; Standard RCA cleaning and dilute hydrofluoric acid treatment: After drilling, standard RCA cleaning and dilute hydrofluoric acid treatment are performed to remove the natural oxide layer on the surface. The dilute hydrofluoric acid treatment uses HF with a mass fraction of 3% for 80 seconds. The treated silicon substrate must be placed in a magnetron sputtering system within 1 hour.

[0063] (2) Deposition of composite seed layer The drilled solar cell is placed in a multi-target magnetron sputtering apparatus, and the vacuum is evacuated to a background vacuum of ≤5×10⁻⁶. -4 Pa, sequentially sputtering an adhesion barrier layer, a composite barrier layer, and an electroplated nucleation layer, the specific steps of which are as follows: Adhesion barrier layer deposition: Ni-P alloy target material with P content of 8 at%, at a power density of 3 W / cm³. 2 Under working pressure of 0.5 Pa, a Ni-P layer with a thickness of 80 nm was deposited at a deposition rate of 0.3 nm / s. Composite barrier layer deposition: First, sputter a Ti layer, controlling the power at 4W / cm. 2 A pure Ar atmosphere with a thickness of 10 nm was then introduced, followed by nitrogen gas, maintaining a power of 4 W / cm². 2 TiN with a thickness of 10 nm was formed by reaction sputtering under a nitrogen to argon flow rate ratio of 1:2.

[0064] Electroplating nucleation layer deposition: using a copper target, at a power density of 3W / cm² 2 A copper layer with a thickness of 15 nm was deposited under a pure Ar atmosphere.

[0065] The entire process is carried out without breaking the vacuum, with continuous deposition between layers and no oxidation contamination at the interlayer interfaces.

[0066] In this embodiment, the thickness ratio of the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer is 5.3:1.3:1, and the total thickness of the composite seed layer is 115nm.

[0067] (3) Laser patterning A pulsed laser is used to scan along the electrode gap to remove the seed layer metal in the non-electrode region, forming P+ and N+ electrode patterns that are electrically isolated from each other.

[0068] The laser scanning parameters are as follows: wavelength 355nm, energy density 0.5J / cm². 2 The laser beam width is 20μm and the scanning speed is 300mm / s.

[0069] (4) Annealing treatment After laser patterning is completed, the solar cells are placed in an annealing furnace for heat treatment.

[0070] The annealing atmosphere was 5% H2 + 95% N2, and the total gas flow rate was 5 L / min; the annealing temperature was 260℃, and the time was 10 min.

[0071] (5) Electroplated conductive layer Using the patterned composite seed layer as the cathode, electroplating was performed using an acidic copper sulfate plating solution to deposit a conductive layer on the surface of the seed layer. The concentration of copper ions in the plating solution was 60 g / L, the concentration of sulfuric acid was 150 g / L, and the concentration of chloride ions was 60 mg / L; the electroplating current density was 6 A / dm², and the electroplating reached a conductive layer thickness of 10 μm.

[0072] Example 2 This embodiment provides a back-contact solar cell, the fabrication process of which is as follows: (1) Provide silicon substrate The steps for doping and passivation layer deposition are as described in Example 1.

[0073] Laser-guided aperture: On the back side of the back contact solar cell where doping and passivation layers have been deposited, a contact window pattern is created by laser-guided aperture to expose the silicon surface of the P- and N-doped regions. The laser-guided aperture parameters are as follows: wavelength is 532 nm, pulse width is in the nanosecond range (specifically the same as in Example 1), and aperture depth is 80 nm. Standard RCA cleaning and dilute hydrofluoric acid treatment: After drilling, standard RCA cleaning and dilute hydrofluoric acid treatment are performed to remove the natural oxide layer on the surface. The dilute hydrofluoric acid treatment uses 1% HF by mass and lasts for 120 seconds. The treated silicon substrate must be placed in a magnetron sputtering system within 0.5 hours.

[0074] (2) Deposition of composite seed layer The drilled solar cell is placed in a multi-target magnetron sputtering apparatus, and the vacuum is evacuated to a background vacuum of ≤5×10⁻⁶. -4 Pa, sequentially sputtering an adhesion barrier layer, a composite barrier layer, and an electroplated nucleation layer, the specific steps of which are as follows: Adhesion barrier layer deposition: Ni-P alloy target material with P content of 5 at%, at a power density of 2 W / cm². 2 Under working pressure of 0.3 Pa, a Ni-P layer with a thickness of 10 nm was deposited at a deposition rate of 0.2 nm / s. Composite barrier layer deposition: First, a Ti layer is sputtered, with a controlled power of 3W / cm. 2 A pure Ar atmosphere with a thickness of 5 nm was then introduced, followed by nitrogen gas, maintaining a power of 3 W / cm². 2TiN with a thickness of 5 nm was formed by reaction sputtering under a nitrogen to argon flow rate ratio of 1:1.

[0075] Electroplating nucleation layer deposition: using a copper target, at a power density of 1 W / cm² 2 A copper layer with a thickness of 5 nm was deposited under a pure Ar atmosphere.

[0076] The entire process is carried out without breaking the vacuum, with continuous deposition between layers and no oxidation contamination at the interlayer interfaces.

[0077] In this embodiment, the thickness ratio of the adhesion barrier layer, the composite barrier layer, and the electroplating nucleation layer is 2:2:1, and the total thickness of the composite seed layer is 25nm.

[0078] (3) Laser patterning A pulsed laser is used to scan along the electrode gap to remove the seed layer metal in the non-electrode region, forming P+ and N+ electrode patterns that are electrically isolated from each other.

[0079] The laser scanning parameters are as follows: wavelength 532nm, energy density 0.1J / cm². 2 The laser beam width is 10μm and the scanning speed is 100mm / s.

[0080] (4) Annealing treatment After laser patterning is completed, the solar cells are placed in an annealing furnace for heat treatment.

[0081] The annealing atmosphere was N2, the gas flow rate was 1 L / min, the annealing temperature was 200℃, and the time was 15 min.

[0082] (5) Electroplated conductive layer Using the patterned composite seed layer as the cathode, electroplating was performed using an acidic copper sulfate plating solution to deposit a conductive layer on the surface of the seed layer. The concentration of copper ions in the plating solution was 20 g / L, the concentration of sulfuric acid was 100 g / L, and the concentration of chloride ions was 40 mg / L; the electroplating current density was 1 A / dm², and the electroplating reached a conductive layer thickness of 5 μm.

[0083] Example 3 This embodiment provides a back-contact solar cell, the fabrication process of which is as follows: (1) Provide silicon substrate The steps for doping and passivation layer deposition are as described in Example 1.

[0084] Laser-guided aperture: On the back side of the back contact solar cell where doping and passivation layers have been deposited, a contact window pattern is created by laser-guided aperture to expose the silicon surface of the P- and N-doped regions. The laser-guided aperture parameters are as follows: wavelength of 355 nm, pulse width in the nanosecond range (same as in Example 1), and aperture depth of 120 nm; Standard RCA cleaning and dilute hydrofluoric acid treatment: After drilling, standard RCA cleaning and dilute hydrofluoric acid treatment are performed to remove the natural oxide layer on the surface. The dilute hydrofluoric acid treatment uses 5% HF by mass and lasts for 30 seconds. The treated silicon substrate must be placed in a magnetron sputtering system within 2 hours.

[0085] (2) Deposition of composite seed layer The drilled solar cell is placed in a multi-target magnetron sputtering apparatus, and the vacuum is evacuated to a background vacuum of ≤5×10⁻⁶. -4 Pa, sequentially sputtering an adhesion barrier layer, a composite barrier layer, and an electroplated nucleation layer, the specific steps of which are as follows: Adhesion barrier layer deposition: Ni-P alloy target material with P content of 10 at%, at a power density of 5 W / cm². 2 Under working pressure of 0.8 Pa, a Ni-P layer with a thickness of 120 nm was deposited at a deposition rate of 0.5 nm / s. Composite barrier layer deposition: First, sputter a Ti layer, controlling the power at 6W / cm. 2 A pure Ar atmosphere was used, with a thickness of 15 nm; then nitrogen was introduced, maintaining a power of 6 W / cm. 2 TiN with a thickness of 25 nm was formed by reactive sputtering under a nitrogen to argon flow rate ratio of 1:3.

[0086] Electroplating nucleation layer deposition: using a copper target, at a power density of 5 W / cm² 2 A copper layer with a thickness of 30 nm was deposited under a pure Ar atmosphere.

[0087] The entire process is carried out without breaking the vacuum, with continuous deposition between layers and no oxidation contamination at the interlayer interfaces.

[0088] In this embodiment, the thickness ratio of the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer is 4:1.33:1, and the total thickness of the composite seed layer is 190nm.

[0089] (3) Laser patterning A pulsed laser is used to scan along the electrode gap to remove the seed layer metal in the non-electrode region, forming P+ and N+ electrode patterns that are electrically isolated from each other.

[0090] The laser scanning parameters are as follows: wavelength 355nm, energy density 1.0J / cm². 2 The laser beam width is 30μm and the scanning speed is 500mm / s.

[0091] (4) Annealing treatment After laser patterning is completed, the solar cells are placed in an annealing furnace for heat treatment.

[0092] The annealing atmosphere was 7% H2 + 93% N2, and the total gas flow rate was 10 L / min; the annealing temperature was 350℃, and the time was 5 min.

[0093] (5) Electroplated conductive layer Using the patterned composite seed layer as the cathode, electroplating was performed using an acidic copper sulfate plating solution to deposit a conductive layer on the surface of the seed layer. The concentration of copper ions in the plating solution was 80 g / L, the concentration of sulfuric acid was 200 g / L, and the concentration of chloride ions was 80 mg / L; the electroplating current density was 10 A / dm², and the electroplating reached a conductive layer thickness of 15 μm.

[0094] Example 4 The only difference from Example 1 is the change in the thickness of each layer: the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer, as detailed below: Adhesion barrier layer deposition: Deposit a Ni-P layer with a thickness of 60 nm. Composite barrier layer deposition: First, a Ti layer with a thickness of 15 nm is sputtered; then, a TiN layer with a thickness of 22.5 nm is sputtered.

[0095] Electroplating nucleation layer deposition: Deposit a copper layer with a thickness of 7.5 nm.

[0096] In this embodiment, the thickness ratio of the adhesion barrier layer, the composite barrier layer, and the electroplating nucleation layer is 8:5:1, and the total thickness of the composite seed layer is 105 nm.

[0097] Example 5 The only difference from Example 1 is the change in the thickness of each layer: the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer, as detailed below: Adhesion barrier layer deposition: Deposit a Ni-P layer with a thickness of 60 nm. Composite barrier layer deposition: First, a Ti layer with a thickness of 15 nm is sputtered; then, a TiN layer with a thickness of 15 nm is sputtered.

[0098] Electroplating nucleation layer deposition: Deposit a copper layer with a thickness of 30 nm.

[0099] In this embodiment, the thickness ratio of the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer is 2:1:1, and the total thickness of the composite seed layer is 120nm.

[0100] Example 6 The only difference from Example 1 is the change in the thickness of each layer: the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer, as detailed below: Adhesion barrier layer deposition: Deposit a Ni-P layer with a thickness of 60 nm. Composite barrier layer deposition: First, a Ti layer with a thickness of 15 nm is sputtered; then, a TiN layer with a thickness of 15 nm is sputtered.

[0101] Electroplating nucleation layer deposition: Deposit a copper layer with a thickness of 60 nm.

[0102] In this embodiment, the thickness ratio of the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer is 1:0.5:1, and the total thickness of the composite seed layer is 150nm.

[0103] Example 7 The only difference from Example 1 is the change in the thickness of each layer: the adhesion barrier layer, the composite barrier layer, and the electroplated nucleation layer, as detailed below: Adhesion barrier layer deposition: Deposit a Ni-P layer with a thickness of 60 nm. Composite barrier layer deposition: First, a Ti layer with a thickness of 17 nm is sputtered; then, a TiN layer with a thickness of 25 nm is sputtered.

[0104] Electroplating nucleation layer deposition: Deposit a copper layer with a thickness of 6 nm.

[0105] In this embodiment, the thickness ratio of the adhesion barrier layer, the composite barrier layer, and the electroplating nucleation layer is 10:7:1, and the total thickness of the composite seed layer is 108 nm.

[0106] Example 8 The only difference from Example 1 is that the material of the adhesion barrier layer is a Ni-W alloy (W content 8 at%).

[0107] Example 9 The only difference from Example 1 is that the composite barrier layer is a single Ti layer with the same thickness as the total thickness of the composite barrier layer in Example 1.

[0108] Example 10 The only difference from Example 1 is that the composite barrier layer is a single TiN layer with the same thickness as the total thickness of the composite barrier layer in Example 1.

[0109] Comparative Example 1 The only difference from Example 1 is that in step (2), only the Ni-P layer (80 nm) and the Cu layer (15 nm) are deposited, and the Ti / TiN composite barrier layer is not deposited; Comparative Example 2 The only difference from Example 1 is that in step (2), only the Ni-P layer (80 nm), Ti layer (10 nm) and TiN layer (10 nm) are deposited, and the Cu surface layer is not deposited; electroplating is performed directly. Comparative Example 3 The only difference from Example 1 is that in step (2), only the Ti / TiN composite barrier layer (20 nm) and Cu surface layer (15 nm) are deposited, and the Ni-P layer is not deposited; electroplating is performed directly. Test case The performance of the back-contact solar cells prepared in the test examples and comparative examples is shown in Table 1.

[0110] Test method: (1) Seed layer contact resistivity test: The contact resistivity of the seed layer was measured using the transmission line method. Parallel linear electrodes with unequal spacing of seed layers were fabricated on a silicon substrate. The total resistance corresponding to each spacing was measured using a semiconductor parameter analyzer. The contact resistivity was calculated after linear fitting. At least five sets of data were measured for each sample, and the average value (mΩ·cm) was taken. 2 ).

[0111] (2) Welding tensile test: After depositing a tin layer on the copper grid line, the tin-plated solder strip is soldered to the main grid at a temperature of 300~350℃ using a soldering station. A tensile testing machine is used to peel the strip vertically at 90° or 180°, and the tensile force value during the peeling process of each solder joint is recorded. At least 12 sets of data are measured for each sample and the average value (N / mm) is taken. (The higher the tensile force value, the better the weld bonding strength, and the better the seed layer adhesion and solderability).

[0112] (3) Reliability testing: The electroplated battery cells were aged at 250℃ in a N2 atmosphere for 100 hours. The leakage current density (I) under reverse bias (e.g., -12V) was measured before and after aging. Record the change in leakage current ΔI before and after aging. =[I (Back)-I (former)] / I (before) × 100% (ΔI) ≤10% is considered acceptable.

[0113] (4) Test for uniformity of copper plating thickness: On the back of the electroplated battery cell, nine points are selected using the nine-square grid method. The copper layer thickness at each point is measured using an X-ray fluorescence spectrometer, and the thickness non-uniformity is calculated: Non-uniformity = (maximum thickness - minimum thickness) / average thickness × 100% (non-uniformity < 5% is acceptable).

[0114] Table 1. Performance comparison of back-contact solar cells prepared in the examples and comparative examples.

[0115] As shown in Table 1, Examples 1-10 significantly reduced contact resistance, increased weld pull, suppressed leakage current increase, and improved electroplating uniformity compared to Comparative Examples 1-3. Specifically, the contact resistivity of each example was as low as 0.44~0.85 mΩ·cm. 2The welding tensile strength is as high as 1.24~1.97 N / mm, the increase in leakage current after aging is controlled within 18.3%, and the electroplating unevenness is less than 4.8%; while the contact resistivity of comparative examples 1-3 is as high as 0.58~2.45 mΩ·cm. 2 The welding tensile strength is as low as 0.65~1.99 N / mm, the leakage current increases by as much as 15.5%~320% after aging, and the electroplating unevenness is as high as 3.6%~18.4%.

[0116] Comparing Examples 1-7, it can be seen that if the thickness ratio of the adhesion barrier layer, composite barrier layer, and electroplated nucleation layer exceeds the specified range, it will lead to a significant decrease in performance. In Example 2, due to the excessively thin total thickness of the seed layer (25nm), the leakage current increased by 18.3% after aging; in Example 6, due to the excessively thick electroplated nucleation layer (60nm), the leakage current increased by 12.4% after aging, both exceeding the 10% acceptable threshold.

[0117] Comparing Examples 1 and 8-10, it can be seen that the material selection of the Ni-P adhesion barrier layer and the Ti / TiN composite barrier layer in Example 1 is more conducive to reducing contact resistance, increasing welding pull force and suppressing copper diffusion. Its comprehensive performance is better than Ni-W, single Ti layer and single TiN layer.

[0118] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A back-contact solar cell, characterized in that, include: A silicon substrate having opposing front and back sides, wherein a silicon doped region and a passivation layer are disposed on the back side, and a contact window is disposed on the passivation layer; A composite seed layer is formed in electrical contact with the silicon doped region through the contact window; and from the direction near the silicon doped region to the direction away from the silicon doped region, it sequentially includes an adhesion barrier layer, a composite barrier layer and an electroplating nucleation layer.

2. The back-contact solar cell according to claim 1, characterized in that, The material of the adhesion barrier layer is a nickel-containing metal, the material of the composite barrier layer is a titanium-containing barrier material, and the material of the electroplated nucleation layer is a copper-containing conductive material; Preferably, the material of the adhesion barrier layer is a nickel-based alloy Ni-X, where X is selected from at least one of P, W, V and Cr; More preferably, the nickel-based alloy Ni-X is a Ni-P alloy, and the atomic percentage of P is 5 at%-10 at%; More preferably, the thickness of the adhesion barrier layer is 10nm-120nm.

3. The back-contact solar cell according to claim 2, characterized in that, The composite barrier layer is a Ti layer, a TiN layer, or a Ti / TiN composite layer; Preferably, the thickness of the composite barrier layer is 5nm-50nm; Preferably, the material of the electroplated nucleation layer is pure copper or a copper alloy; Preferably, the thickness of the electroplated nucleation layer is 5nm-30nm.

4. The back-contact solar cell according to any one of claims 2-3, characterized in that, The thickness ratio of the adhesion barrier layer, the composite barrier layer, and the electroplating nucleation layer is (2~8):(1~5):1; Preferably, the total thickness of the composite seed layer is 20nm-200nm; Preferably, the silicon doped region includes alternating P-type and N-type doped regions, and the composite seed layer is disposed in the contact window and electrode region to achieve electrical isolation between the P-region and the N-region; Preferably, the surface of the composite seed layer is further electroplated with a conductive layer, which is a pure copper layer, a copper-tin alloy layer, or a copper-silver alloy layer; the thickness of the conductive layer is 5μm-15μm.

5. A method for preparing a back-contact solar cell according to any one of claims 1-4, characterized in that, include: Providing a silicon substrate: Forming a contact window pattern on the back side of the battery intermediate where doping and passivation layer deposition have been completed, exposing the silicon doped region; Composite seed layer deposition: The adhesion barrier layer, the composite barrier layer and the electroplating nucleation layer are sequentially deposited on the silicon substrate.

6. The preparation method according to claim 5, characterized in that, In the composite seed layer deposition step, the silicon substrate is placed in a multi-target magnetron sputtering apparatus and evacuated to a base vacuum ≤ 5 × 10⁻⁶. -4 Pa; the adhesion barrier layer, the composite barrier layer, and the electroplating nucleation layer are sputtered sequentially; the entire deposition process does not break the vacuum; Preferably, in the step of depositing the adhesion barrier layer, a nickel-based alloy target is used; wherein the power density is 2 W / cm². 2 -5W / cm 2 The working gas pressure is 0.3 Pa - 0.8 Pa; the deposition rate is 0.2 nm / s - 0.5 nm / s. Preferably, the process of depositing the composite barrier layer includes: first sputtering a Ti layer with a thickness of 5 nm-15 nm, and then sputtering a TiN layer with a thickness of 5 nm-25 nm; more preferably, the sputtering of the Ti layer is carried out in an argon atmosphere, and the power density is controlled at 3 W / cm². 2 -6W / cm 2 More preferably, during the sputtering of the TiN layer, the flow rate ratio of nitrogen to argon is controlled to be 1:(1-3), and the power density is controlled to be 3W / cm³. 2 -6W / cm 2 ; Preferably, the electroplated nucleation layer is deposited using a copper target or a copper alloy target, with the power density controlled at 1 W / cm². 2 -5W / cm 2 Deposition was carried out under an argon atmosphere.

7. The preparation method according to claim 5, characterized in that, Also includes: After the composite seed layer deposition is completed, laser patterning, annealing and electroplating of conductive layer are performed in sequence. The laser patterning process involves scanning along the electrode gap with a pulsed laser to remove the composite seed layer metal in the non-electrode region, forming electrically isolated P-region electrode patterns and N-region electrode patterns. Preferably, the laser scanning parameters for the laser patterning process are as follows: wavelength of 355nm or 532nm, and energy density of 0.1J / cm². 2 -1.0J / cm 2 The laser beam width is 10μm-30μm, and the scanning speed is 100mm / s-500mm / s.

8. The preparation method according to claim 7, characterized in that, During the annealing process, the annealing temperature is controlled at 200℃-350℃ and the time is 5min-15min. Preferably, during the annealing process, the annealing atmosphere is selected from nitrogen or a mixture of hydrogen and nitrogen, wherein the volume fraction of nitrogen in the mixture is 93%-98%, and the gas flow rate is controlled at 1L / min-10L / min. Preferably, the electroplating process for the conductive layer includes: using the patterned composite seed layer as the cathode, electroplating is performed using an acidic copper sulfate plating solution to deposit a conductive layer on the surface of the composite seed layer; more preferably, in the acidic copper sulfate plating solution, the copper ion concentration is 20 g / L-80 g / L, the sulfuric acid concentration is 100 g / L-200 g / L, and the chloride ion concentration is 40 mg / L-80 mg / L; even more preferably, the electroplating current density is controlled to be 1 A / dm³. 2 -10A / dm 2 .

9. The preparation method according to claim 5, characterized in that, The contact window pattern is formed by laser drilling; Preferably, the process of preparing the silicon substrate further includes: after laser drilling, performing RCA cleaning and dilute hydrofluoric acid treatment to remove the surface oxide layer; Preferably, the parameters for laser aperture are as follows: wavelength of 355nm or 532nm, pulse width in the nanosecond range, and aperture depth of 80nm-120nm; Preferably, the HF mass fraction in the dilute hydrofluoric acid used in the dilute hydrofluoric acid treatment process is 1%-5%, the treatment time is 30s-120s, and the treated silicon substrate is put into the magnetron sputtering equipment within 0.5h-2h.

10. A photovoltaic module, characterized in that, This includes the back-contact solar cell according to any one of claims 1-4 or the back-contact solar cell prepared by the preparation method according to any one of claims 5-9.

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