A solar cell and a method of manufacturing the same

Abstract

The application relates to a solar cell and a preparation method thereof, and belongs to the technical field of solar cells. The solar cell comprises a doped polysilicon passivation contact layer, a composite metal contact layer and a metal main and auxiliary grid electrode which are arranged in sequence in a stacking mode; wherein the composite metal contact layer comprises a nickel metal layer, a titanium metal layer and a silver metal layer which are arranged in sequence in a stacking mode, and the nickel metal layer is combined with the doped polysilicon passivation contact layer. The solar cell of the application sets the composite metal contact layer between the doped polysilicon passivation contact layer and the metal main and auxiliary grid electrode, the composite metal contact layer can form a metallurgical contact with the doped polysilicon passivation contact layer, the interface defect density is greatly reduced, the open-circuit voltage and the fill factor of the cell are simultaneously improved, the photoelectric conversion efficiency is improved, meanwhile, the interlayer bonding force of the multilayer metal structure of the composite metal contact layer is strong, the electrode adhesion is significantly improved, so that the efficiency decay rate of the cell under a long-term humid heat and cold heat cycle environment is reduced.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a solar cell and a method for its fabrication. Background Technology

[0002] N-type TOPCon (tunneling oxide passivated contact) solar cells have become the mainstream high-efficiency cell technology for mass production of photovoltaics due to their advantages such as ultra-low interfacial recombination, high open-circuit voltage, low degradation, and excellent process stability. The core structure of TOPCon cells is a silicon substrate-ultra-thin tunneling oxide layer-doped polycrystalline silicon (Poly) passivated contact layer. This structure can effectively passivate defects on the silicon wafer surface, block carrier recombination, and significantly improve the photoelectric conversion efficiency of the cell.

[0003] Currently, the main method for metal contact in mass-produced TOPCon batteries is to directly screen-print silver paste onto the Poly layer surface, followed by high-temperature sintering to achieve metal-Poly layer contact. This traditional process has several inherent drawbacks: First, during high-temperature sintering, silver paste metal particles easily penetrate the Poly layer and tunnel through the oxide layer, directly contacting the silicon substrate, damaging the passivation structure, causing severe carrier recombination losses, and reducing the battery's open-circuit voltage. Second, the physical contact between the metal paste and the Poly layer results in numerous voids, cavities, and defects at the interface, leading to high contact resistance and making it difficult to further improve the battery's fill factor. Third, the weak bonding between the metal paste and the Poly layer makes the battery prone to electrode detachment, interface oxidation, and contact resistance drift during long-term use, resulting in accelerated efficiency degradation and shortened lifespan. Fourth, the high density of interface defects after paste sintering makes it difficult to fully utilize the high efficiency advantages of the TOPCon passivation contact structure, becoming a core bottleneck restricting breakthroughs in TOPCon battery efficiency.

[0004] Existing improvement technologies mostly focus on optimizing slurry formulations, adjusting sintering process parameters, and modifying the poly layer through doping. These can only slightly improve contact performance and cannot fundamentally solve the problems of numerous defects and poor stability at the physical contact interface. Therefore, developing a novel structure and fabrication process that can achieve low-resistance, high-stability, and low-composite contact between the poly layer and the metal electrode has significant engineering value for improving the efficiency and reliability of TOPCon cells. Summary of the Invention

[0005] Based on this, this application provides a solar cell and a method for preparing the same, which can improve the photoelectric conversion efficiency of the solar cell.

[0006] In a first aspect, this application provides a solar cell comprising a doped polycrystalline silicon passivation contact layer, a composite metal contact layer, and metal main and secondary grid electrodes arranged in sequence; wherein the composite metal contact layer comprises a nickel metal layer, a titanium metal layer, and a silver metal layer arranged in sequence, and the nickel metal layer is bonded to the doped polycrystalline silicon passivation contact layer.

[0007] In some embodiments, the thickness of the nickel metal layer is 5 nm to 15 nm; and / or, the thickness of the titanium metal layer is 3 nm to 8 nm; and / or, the thickness of the silver metal layer is 20 nm to 50 nm.

[0008] In some embodiments, the solar cell further includes a nickel-silicon alloy transition layer disposed between the doped polycrystalline silicon passivation contact layer and the composite metal contact layer.

[0009] In some embodiments, the surface of the doped polysilicon passivation contact layer includes a blank area and an electrode area for setting metal main and secondary gate electrodes, and a composite metal contact layer is disposed in the electrode area.

[0010] In some embodiments, the doped polysilicon passivation contact layer comprises a boron-doped P-type polysilicon layer; and / or, the thickness of the doped polysilicon passivation contact layer is 80 nm to 150 nm; and / or, the doping concentration of the doped polysilicon passivation contact layer is 1 × 10⁻⁶. 20 atoms / cm 3 ~5×10 20 atoms / cm 3 .

[0011] Secondly, this application provides a method for preparing a solar cell as described in the above embodiments, comprising: obtaining a preform including a doped polycrystalline silicon passivation contact layer; sequentially depositing a nickel metal layer, a titanium metal layer and a silver metal layer on the surface of the doped polycrystalline silicon passivation contact layer using a low-temperature magnetron sputtering vapor deposition process to form a composite metal contact layer in situ.

[0012] In some embodiments, the deposition temperature of the composite metal contact layer is 150°C to 220°C.

[0013] In some embodiments, the deposition power of the nickel metal layer is 80W~120W and the deposition rate is 0.2nm / s~0.5nm / s; and / or, the deposition power of the titanium metal layer is 60W~90W and the deposition rate is 0.15nm / s~0.3nm / s; and / or, the deposition power of the silver metal layer is 100W~150W and the deposition rate is 0.4nm / s~0.8nm / s.

[0014] In some embodiments, after the composite metal contact layer is formed in situ, the method for preparing the solar cell further includes performing a low-temperature annealing treatment on the composite metal contact layer, wherein the annealing temperature of the low-temperature annealing treatment is 250°C to 300°C and the holding time is 30s to 60s.

[0015] In some embodiments, before forming the composite metal contact layer in situ, the method for preparing the solar cell further includes plasma etching cleaning of the surface of the doped polycrystalline silicon passivation contact layer. The plasma etching cleaning includes argon plasma treatment for a treatment time of 10s to 20s and a treatment power of 50W to 80W.

[0016] Compared with the prior art, this application has the following beneficial effects: The solar cell of this application incorporates a composite metal contact layer between a doped polycrystalline silicon passivation contact layer and metal main and secondary grid electrodes. This composite metal contact layer forms a metallurgical contact with the doped polycrystalline silicon passivation contact layer, significantly reducing interface defect density, simultaneously improving the cell's open-circuit voltage and fill factor, and enhancing photoelectric conversion efficiency. Furthermore, the multilayer metal structure of the composite metal contact layer exhibits strong interlayer bonding, significantly improving electrode adhesion and reducing efficiency degradation under long-term humid and hot / cold cycling conditions. Specifically, the nickel metal layer of the composite metal contact layer forms a stable nickel-silicon alloy interface with the doped polycrystalline silicon passivation contact layer, eliminating voids and defects in traditional physical contacts, reducing contact resistance, and decreasing carrier transport losses. The titanium metal layer forms a dense protective barrier, effectively blocking the diffusion of water vapor, oxygen, and metal ions, preventing interface oxidation failure. The silver metal layer improves the conductivity of the composite metal contact layer.

[0017] The solar cell fabrication method of this application adopts a low-temperature magnetron sputtering vapor deposition process, which does not require high-temperature sintering, avoids metal penetration and damage to the passivation structure of the solar cell, fully preserves the excellent passivation performance of the doped polycrystalline silicon passivation contact layer, and significantly reduces the interface carrier recombination loss. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the structure of a solar cell according to some embodiments; Figure 2 This is a surface region division diagram of the doped polysilicon passivation contact layer in some embodiments.

[0019] The reference numerals in the detailed embodiments are as follows: 10 - Solar cell; 100 - Doped polycrystalline silicon passivation contact layer; 110 - Blank area; 120 - Electrode area; 200 - Composite metal contact layer; 210 - Nickel metal layer; 220 - Titanium metal layer; 230 - Silver metal layer; 300 - Metal main and secondary grid electrodes; 400 - N-type silicon substrate; 500 - Tunneling oxide layer; 600 - P-type emitter; 700 - Front passivation and antireflection layer; 800 - Front metal electrode. Detailed Implementation

[0020] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0021] In the description of this application, it should be understood that, where they appear, the terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0022] Furthermore, where applicable, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0023] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," "fixing," etc., shall be interpreted broadly. For example, they may refer to a fixed connection, a detachable connection, or an integral part; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; they may refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0024] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0025] It should be noted that, if an element is described as "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is described as "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0026] Please see Figure 1 The solar cell 10 includes a doped polycrystalline silicon passivation contact layer 100, a composite metal contact layer 200, and metal main and secondary grid electrodes 300 arranged in sequence.

[0027] Among them, the doped polycrystalline silicon passivation contact layer 100 refers to the upper heavily doped polycrystalline silicon thin film structure in the passivation contact structure of the backlight surface of the TOPCon battery.

[0028] In some embodiments, the doped polysilicon passivation contact layer 100 includes a boron-doped P-type polysilicon layer.

[0029] In some embodiments, the thickness of the doped polysilicon passivation contact layer 100 is 80 nm to 150 nm.

[0030] For example, the thickness of the doped polysilicon passivation contact layer 100 can be 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm or 150nm.

[0031] In some embodiments, the doping concentration of the doped polysilicon passivation contact layer 100 is 1×10⁻⁶. 20 atoms / cm 3 ~5×10 20 atoms / cm 3 The solar cell 10 of this application ensures hole transport efficiency through high-concentration boron doping.

[0032] For example, the doping concentration of the doped polysilicon passivation contact layer 100 can be 1×10⁻⁶. 20 atoms / cm 3 2×10 20 atoms / cm 3 3×10 20 atoms / cm 3 4×10 20 atoms / cm 3 Or 5×10 20 atoms / cm 3 .

[0033] The composite metal contact layer 200 refers to an ultra-thin, dense composite structure made of metal located between the doped polysilicon passivation contact layer 100 and the metal main and secondary gate electrodes 300. The composite metal contact layer 200 includes a nickel metal layer 210, a titanium metal layer 220, and a silver metal layer 230 arranged in sequence. The nickel metal layer 210 is bonded to the doped polysilicon passivation contact layer 100, and the silver metal layer 230 is bonded to the metal main and secondary gate electrodes 300.

[0034] In some embodiments, the thickness of the nickel metal layer 210 is 5 nm to 15 nm.

[0035] For example, the thickness of the nickel metal layer 210 can be 5nm, 8nm, 10nm, 12nm or 15nm.

[0036] The nickel metal layer 210 is used to directly bond the doped polycrystalline silicon passivation contact layer 100, forming a nickel-silicon alloy transition interface through low-temperature bonding, which greatly reduces the contact resistance.

[0037] In some embodiments, the thickness of the titanium metal layer 220 is 3 nm to 8 nm.

[0038] For example, the thickness of the titanium metal layer 220 can be 3nm, 4nm, 5nm, 6nm, 7nm or 8nm.

[0039] The titanium metal layer 220 has excellent oxygen barrier, moisture protection and anti-diffusion properties, which can isolate it from external environmental corrosion, while buffering interlayer stress, preventing metal layer detachment, and improving the structural thermal stability of the composite metal contact layer 200.

[0040] In some embodiments, the thickness of the silver metal layer 230 is 20 nm to 50 nm.

[0041] For example, the thickness of the silver metal layer 230 can be 20nm, 30nm, 40nm or 50nm.

[0042] The silver metal layer 230 is used to improve the carrier transport rate and ensure the conductivity of the electrodes.

[0043] Optionally, the solar cell 10 further includes a nickel-silicon alloy transition layer disposed between the doped polycrystalline silicon passivated contact layer 100 and the composite metal contact layer 200.

[0044] The nickel-silicon alloy transition layer is used to eliminate dangling bonds on the surface of the doped polycrystalline silicon passivation contact layer 100, reduce the interfacial contact resistance, and form a metallurgical bonding interface with the doped polycrystalline silicon passivation contact layer 100 that is free of voids, cracks, and penetration defects.

[0045] The metal main and secondary grid electrodes 300 are the structure of the solar cell 10 used to capture and conduct photogenerated carriers excited by the silicon wafer after being illuminated.

[0046] Please see Figure 2 The surface of the polysilicon-doped passivation contact layer 100 includes a blank region 110 and an electrode region 120. Only the electrode region 120 is used to house the metal main and secondary gate electrodes 300, and the composite metal contact layer 200 is also only disposed in the electrode region 120. This ensures that the metal contact layer only covers the electrode contact area, and the blank region 110 of the polysilicon-doped passivation contact layer 100 fully retains the original passivation structure, achieving the optimal match of "low resistance conductivity in the contact area and efficient passivation in the non-contact area," maximizing the potential of battery performance.

[0047] Please continue reading. Figure 1 The solar cell 10 also includes an N-type silicon substrate 400 and a tunneling oxide layer 500, wherein the back surface of the N-type silicon substrate 400 is bonded to one side of the tunneling oxide layer 500, and the other side of the tunneling oxide layer 500 is bonded to a doped polycrystalline silicon passivation contact layer 100.

[0048] Optionally, the solar cell 10 further includes a P-type emitter 600, a front passivation and antireflection layer 700, and a front metal electrode 800. One side of the P-type emitter 600 is bonded to the front side of the N-type silicon substrate 400, and the other side of the P-type emitter 600 is bonded to one side of the front passivation and antireflection layer 700. The front metal electrode 800 is disposed on the other side of the front passivation and antireflection layer 700.

[0049] The solar cell 10 of this application incorporates a composite metal contact layer 200 between a doped polycrystalline silicon passivated contact layer 100 and metal main and secondary grid electrodes 300. The composite metal contact layer 200 forms a metallurgical contact with the doped polycrystalline silicon passivated contact layer 100, significantly reducing interface defect density, simultaneously increasing the cell's open-circuit voltage and fill factor, and improving photoelectric conversion efficiency. Furthermore, the multilayer metal structure of the composite metal contact layer 200 exhibits strong interlayer bonding, significantly enhancing electrode adhesion and reducing efficiency degradation under long-term humid and hot / cold cycling conditions. Specifically, the nickel metal layer 210 of the composite metal contact layer 200 forms a stable nickel-silicon alloy interface with the doped polycrystalline silicon passivated contact layer 100, eliminating void defects inherent in traditional physical contacts, reducing contact resistance, and decreasing carrier transport losses. The titanium metal layer 220 forms a dense protective barrier, effectively blocking the diffusion of water vapor, oxygen, and metal ions, preventing interface oxidation failure. The silver metal layer 230 improves the conductivity of the composite metal contact layer 200.

[0050] It should be noted that the composite metal contact layer 200 of this application is applicable not only to TOPCon solar cells 10, but also to sensitive structure cells such as HJT, TBC, ABC, HPBC, and perovskite cells. When the composite metal contact layer 200 is applicable to sensitive structure cells such as HJT, TBC, ABC, HPBC, and perovskite cells, the composite metal contact layer 200 is located between the metal main and secondary grid electrodes 300 and the layered structure originally bonded to the metal main and secondary grid electrodes 300.

[0051] This application also provides a method for preparing a solar cell as described above, comprising: obtaining a preform including a doped polycrystalline silicon passivation contact layer; sequentially depositing a nickel metal layer, a titanium metal layer and a silver metal layer on the surface of the doped polycrystalline silicon passivation contact layer using a low-temperature magnetron sputtering vapor deposition process to form a composite metal contact layer in situ.

[0052] In some embodiments, the deposition temperature of the composite metal contact layer is 150°C to 220°C.

[0053] For example, the deposition temperature of the composite metal contact layer can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C or 220°C.

[0054] This application enables the deposition temperature of the composite metal contact layer to be within the aforementioned range, which facilitates the in-situ growth of the composite metal contact layer on the surface of the doped polycrystalline silicon passivation contact layer under low-temperature conditions. The low-temperature process can avoid damage to the passivation structure, fully preserve the passivation performance of the tunneling oxide layer and the doped polycrystalline silicon passivation contact layer, fundamentally balance the passivation effect and metal conductive contact performance of the TOPCon cell, and break through the performance bottleneck of traditional processes.

[0055] In some embodiments, the deposition power of the nickel metal layer is 80W~120W, and the deposition rate is 0.2nm / s~0.5nm / s.

[0056] For example, the deposition power of the nickel metal layer can be 80W, 90W, 100W, 110W or 120W, and the deposition rate can be 0.2nm / s, 0.3nm / s, 0.4nm / s or 0.5nm / s.

[0057] In some embodiments, the deposition power of the deposited titanium metal layer is 60W~90W, and the deposition rate is 0.15nm / s~0.3nm / s.

[0058] For example, the deposition power of the deposited titanium metal layer can be 60W, 70W, 80W or 90W, and the deposition rate can be 0.15nm / s, 0.2nm / s, 0.25nm / s or 0.3nm / s.

[0059] In some embodiments, the deposition power of the silver metal layer is 100W~150W, and the deposition rate is 0.4nm / s~0.8nm / s.

[0060] For example, the deposition power of the silver metal layer can be 100W, 110W, 120W, 130W, 140W or 150W, and the deposition rate can be 0.4nm / s, 0.5nm / s, 0.6nm / s, 0.7nm / s or 0.8nm / s.

[0061] In some embodiments, after the composite metal contact layer is formed in situ, the method for preparing the solar cell further includes performing a low-temperature annealing treatment on the composite metal contact layer, wherein the annealing temperature of the low-temperature annealing treatment is 250°C to 300°C and the holding time is 30s to 60s.

[0062] For example, the annealing temperature for low-temperature annealing can be 250℃, 260℃, 270℃, 280℃, 290℃ or 300℃, and the holding time can be 30s, 40s, 50s or 60s.

[0063] Low-temperature annealing can promote the bonding of doped atoms in the metal atom-doped polycrystalline silicon passivation contact layer, stabilize the metallurgical contact interface, and the annealing temperature is lower than the high-temperature failure temperature of the doped polycrystalline silicon passivation contact layer, so it will not damage the passivation performance.

[0064] In some embodiments, before forming the composite metal contact layer in situ, the method for preparing the solar cell further includes plasma etching cleaning of the surface of the doped polycrystalline silicon passivation contact layer. The plasma etching cleaning includes argon plasma treatment for a treatment time of 10s to 20s and a treatment power of 50W to 80W.

[0065] For example, the processing time using argon plasma can be 15s, 16s, 17s, 18s, 19s or 20s, and the processing power can be 50W, 60W, 70W or 80W.

[0066] The plasma etching cleaning method in this application is only used to remove the weak oxide layer on the surface and will not damage the bulk structure and doping characteristics of the doped polysilicon passivation contact layer.

[0067] The specific methods for preparing solar cells are as follows: S1, Substrate Pretreatment N-type monocrystalline silicon wafers are selected and subjected to texturing, acid washing, deionized water cleaning, and drying to remove surface impurities and damaged layers. S2, Preparation of tunneling oxide layer An ultrathin tunneling silicon oxide layer with a thickness of 1.5nm~2.5nm was grown on the back surface of an N-type silicon substrate using a high-temperature thermal oxidation process. S3. Preparation of doped polycrystalline silicon passivation contact layer An intrinsic polycrystalline silicon layer is deposited on the surface of the tunneling oxide layer using a low-pressure chemical vapor deposition process, followed by boron doping via ion implantation and activation by annealing to form a doped polycrystalline silicon passivation contact layer. S4, Surface passivation cleaning Remove the oxide layer and particulate impurities on the surface of the doped polysilicon passivation contact layer while preserving the complete passivation structure of the doped polysilicon passivation contact layer; S5, In-situ grown composite metal contact layer A low-temperature magnetron sputtering vapor deposition process is used to sequentially deposit nickel, titanium and silver metal layers in all areas or electrode areas of the doped polycrystalline silicon passivation contact layer to form a composite metal contact layer in situ. The temperature is controlled at 150-220℃ throughout the deposition process. After the deposition is completed, the composite metal contact layer is subjected to low-temperature annealing treatment. S6, Electrode Preparation Metal main gate and sub-gate electrodes are prepared on the surface of the metal contact layer by screen printing or laser grooving coating process, and then cured at low temperature. S7, Subsequent Processes The battery fabrication process involves sequentially applying a textured pyramid surface, a boron diffusion passivation layer, a front alumina passivation layer, a front passivation antireflection film, edge isolation, and testing and sorting.

[0068] The solar cell fabrication method of this application employs a low-temperature magnetron sputtering vapor deposition process, eliminating the need for high-temperature sintering. This method fully preserves the excellent passivation performance of the doped polycrystalline silicon passivation contact layer, significantly reducing interfacial carrier recombination losses. Furthermore, the fabrication method is directly adaptable to existing TOPCon mass production lines without requiring major equipment modifications. The process is simple, highly controllable, highly efficient, and has low incremental costs, making it suitable for large-scale industrial deployment.

[0069] The technical solution of this application will be described below with reference to specific embodiments.

[0070] Example 1 This application provides a method for preparing a solar cell, which includes the following steps: S1, Substrate Pretreatment N-type single-crystal silicon wafers with a thickness of 180μm are selected and subjected to alkaline texturing, acid washing to remove impurities, multi-stage cleaning with deionized water, and drying at 120℃ to remove surface oil, metal impurities, and surface damage layers.

[0071] S2, Preparation of tunneling oxide layer An ultrathin tunneling silicon oxide layer with a thickness of 2nm was grown on the back surface of an N-type silicon substrate using a high-temperature thermal oxidation process. The oxidation temperature of the high-temperature thermal oxidation process was 900℃, and the holding time was 15min.

[0072] S3. Preparation of boron-doped p-type polycrystalline silicon layer An intrinsic polycrystalline silicon layer with a thickness of 100 nm was deposited on the surface of the tunneling oxide layer using a low-pressure chemical vapor deposition process, followed by boron ion implantation doping at a doping concentration of 2 × 10⁻⁶. 20 atoms / cm 3 Finally, the impurities are activated by rapid annealing at 950℃ to form a boron-doped P-type polycrystalline silicon layer.

[0073] S4, Surface passivation cleaning Argon plasma was used to treat the surface of boron-doped P-type polycrystalline silicon to remove trace amounts of weak oxide layer and particulate impurities. The treatment power was 60W and the treatment time was 15s, while preserving the complete passivation structure of the boron-doped P-type polycrystalline silicon layer.

[0074] S5, In-situ grown composite metal contact layer A low-temperature magnetron sputtering vapor deposition process was used to sequentially deposit nickel, titanium, and silver metal layers in the electrode region of a boron-doped p-type polycrystalline silicon layer at a deposition temperature of 180℃. First, a 10nm nickel metal layer was deposited at a deposition power of 100W and a deposition rate of 0.3nm / s; then a 5nm titanium metal layer was deposited at a deposition power of 75W and a deposition rate of 0.2nm / s; finally, a 30nm silver metal layer was deposited at a deposition power of 120W and a deposition rate of 0.6nm / s. After deposition, the metallurgical interface was rapidly annealed at 280℃ for 45s. The composite metal contact layer consists of sequentially stacked nickel, titanium, and silver metal layers, with the nickel metal layer bonded to the boron-doped p-type polycrystalline silicon layer.

[0075] S6, Electrode Preparation Silver paste gates are screen-printed on the surface of the metal contact layer, sintered at 850°C, and then cured at 180°C to form the main gate and fine gate electrodes.

[0076] S7, Subsequent Processes The battery fabrication process involves sequentially applying a textured pyramid surface, a boron diffusion passivation layer, a front alumina passivation layer, a front passivation antireflection film, edge isolation, and testing and sorting.

[0077] Example 2 This application embodiment changes the thickness of the nickel metal layer to 5nm, the thickness of the titanium metal layer to 3nm, and the thickness of the silver metal layer to 50nm, based on Embodiment 1, while keeping other aspects unchanged.

[0078] Example 3 This application embodiment changes the thickness of the nickel metal layer to 15nm, the thickness of the titanium metal layer to 8nm, and the thickness of the silver metal layer to 20nm, based on Embodiment 1, while keeping other aspects unchanged.

[0079] Example 4 This application embodiment changes the deposition temperature of the composite metal contact layer to 150°C based on Embodiment 1, while keeping other aspects unchanged.

[0080] Example 5 This application embodiment modifies the deposition temperature in step S5, the in-situ growth of the composite metal contact layer, to 220°C, based on embodiment 1, while keeping the others unchanged.

[0081] Example 6 This embodiment of the application is based on Embodiment 1, except for the low-temperature annealing treatment, while all other aspects remain unchanged. S5, the steps for in-situ growth of the composite metal contact layer are as follows: Using a low-temperature magnetron sputtering vapor deposition process, a nickel metal layer, a titanium metal layer, and a silver metal layer are sequentially deposited in the electrode region of the boron-doped P-type polycrystalline silicon layer. The deposition temperature is 180℃. First, a 10nm nickel metal layer is deposited with a deposition power of 100W and a deposition rate of 0.3nm / s; then, a 5nm titanium metal layer is deposited with a deposition power of 75W and a deposition rate of 0.2nm / s; finally, a 30nm silver metal layer is deposited with a deposition power of 120W and a deposition rate of 0.6nm / s.

[0082] Example 7 This application embodiment removes step S4 and surface passivation cleaning from embodiment 1, while keeping everything else unchanged.

[0083] Comparative Example 1 This application provides a comparative example of a method for preparing a solar cell, which includes the following steps: S1, Substrate Pretreatment N-type single-crystal silicon wafers with a thickness of 180μm are selected and subjected to alkaline texturing, acid washing to remove impurities, multi-stage cleaning with deionized water, and drying at 120℃ to remove surface oil, metal impurities, and surface damage layers.

[0084] S2, Preparation of tunneling oxide layer An ultrathin tunneling silicon oxide layer with a thickness of 2nm was grown on the back surface of an N-type silicon substrate using a high-temperature thermal oxidation process. The oxidation temperature of the high-temperature thermal oxidation process was 900℃, and the holding time was 15min.

[0085] S3. Preparation of boron-doped p-type polycrystalline silicon layer An intrinsic polycrystalline silicon layer with a thickness of 100 nm was deposited on the surface of the tunneling oxide layer using a low-pressure chemical vapor deposition process, followed by boron ion implantation doping at a doping concentration of 2 × 10⁻⁶. 20 atoms / cm 3 Finally, the impurities are activated by rapid annealing at 950℃ to form a boron-doped P-type polycrystalline silicon layer.

[0086] S4, Surface passivation cleaning Argon plasma was used to treat the surface of boron-doped P-type polycrystalline silicon to remove trace amounts of weak oxide layer and particulate impurities. The treatment power was 60W and the treatment time was 15s, while preserving the complete passivation structure of the boron-doped P-type polycrystalline silicon layer.

[0087] S5, Electrode Preparation Silver paste gates were fabricated on the surface of a boron-doped P-type polycrystalline silicon layer by screen printing, followed by high-temperature sintering at 850℃ and then low-temperature curing at 180℃ to prepare the main gate and fine gate electrodes.

[0088] S6, Subsequent Processes The battery fabrication process involves sequentially performing front passivation, antireflection film deposition, edge isolation, and testing and sorting.

[0089] Comparative Example 2 The comparative example in this application differs from Example 1 by only including a nickel metal layer and a silver metal layer in the composite metal contact layer, while keeping everything else unchanged. S5, the in-situ growth steps of the composite metal contact layer are as follows: A low-temperature magnetron sputtering vapor deposition process is used to sequentially deposit a nickel metal layer and a silver metal layer in the electrode region of a boron-doped P-type polycrystalline silicon layer. The deposition temperature is 180°C. First, a 10nm nickel metal layer is deposited at a deposition power of 100W and a deposition rate of 0.3nm / s; then, a 30nm silver metal layer is deposited at a deposition power of 120W and a deposition rate of 0.6nm / s. After deposition, the metallurgical interface is rapidly annealed at 280°C for 45s.

[0090] Comparative Example 3 The comparative example in this application differs from Example 1 by only including a titanium metal layer and a silver metal layer in the composite metal contact layer, while keeping everything else unchanged. S5, the in-situ growth steps of the composite metal contact layer are as follows: A low-temperature magnetron sputtering vapor deposition process is used to sequentially deposit a titanium metal layer and a silver metal layer in the electrode region of a boron-doped P-type polycrystalline silicon layer. The deposition temperature is 180°C. First, a 5nm titanium metal layer is deposited at a deposition power of 75W and a deposition rate of 0.2nm / s; then, a 30nm silver metal layer is deposited at a deposition power of 120W and a deposition rate of 0.6nm / s. After deposition, the metallurgical interface is rapidly annealed at 280°C for 45s.

[0091] Comparative Example 4 This comparative example modifies the structure of the composite metal contact layer based on Example 1. The composite metal contact layer includes a titanium metal layer, a nickel metal layer, and a silver metal layer stacked sequentially, while other aspects remain unchanged. S5. The in-situ growth steps of the composite metal contact layer are as follows: A low-temperature magnetron sputtering vapor deposition process is used to sequentially deposit a titanium metal layer, a nickel metal layer, and a silver metal layer in the electrode region of a boron-doped P-type polycrystalline silicon layer. The deposition temperature is 180°C. First, a 5nm titanium metal layer is deposited at a deposition power of 75W and a deposition rate of 0.2nm / s; then, a 10nm nickel metal layer is deposited at a deposition power of 100W and a deposition rate of 0.3nm / s; finally, a 30nm silver metal layer is deposited at a deposition power of 120W and a deposition rate of 0.6nm / s. After deposition, the layer is rapidly annealed at 280°C for 45s to stabilize the metallurgical interface. The composite metal contact layer includes a nickel metal layer, a titanium metal layer, and a silver metal layer stacked sequentially, with the nickel metal layer bonded to the boron-doped P-type polycrystalline silicon layer.

[0092] The photoelectric performance and reliability of the solar cells obtained in Examples 1-7 and Comparative Examples 1-4 were measured. The photoelectric performance included photoelectric conversion efficiency (ETA), open circuit voltage (VOC), short circuit current (ISC), fill factor (FF), and contact resistance. The results are shown in Table 1. The reliability test included the maximum power (Pmax), maximum power point voltage (Vmpp), maximum power point current (Impp), open circuit voltage (Voc), short circuit current (Isc), fill factor (FF), and power decay rate after 1000h damp heat aging test and 200 cold and hot cycle test. The results are shown in Tables 2-3.

[0093] Using Keithley 2400SMU, AM 1.5G solar irradiation at 100mW / cm 2 Under the light source, the battery performance was tested, and the photoelectric conversion efficiency was calculated as follows: ETA = Pout / Popt =Voc×Jsc×(Vmpp×Jmpp) / (Voc×Jsc) =Voc×Jsc×FF Where Pout, Popp, Vmpp, Jmpp, Voc, Jsc, and FF are the battery's operating output power, incident light power, battery's maximum power point voltage, battery's maximum power point current, open circuit voltage, short circuit current, and fill factor, respectively.

[0094] Contact resistance was measured using the transmission line model method.

[0095] The 1000-hour damp heat aging test includes sample preparation, initial performance testing (pretreatment), equipment calibration, sample entry into the test chamber, start of the test procedure, process monitoring, sample removal, condition restoration, and post-testing and evaluation.

[0096] The 200-cycle thermal cycling test includes sample preparation, initial performance testing (pretreatment), equipment calibration, sample entry into the test chamber, setting test parameters, single cycle procedure, process monitoring, intermediate testing, sample removal, state recovery, and post-testing and evaluation.

[0097] Attenuation ratio = (Pmax_initial - Pmax_current) / Pmax_initial × 100%.

[0098] Table 1. Photoelectric performance of solar cells in Examples 1-7 and Comparative Examples 1-4 Table 2. Results of 1000h damp heat aging test of solar cells of Example 1 and Comparative Examples 1-4 Table 3 Results of 200 thermal cycling tests on solar cells of Example 1 and Comparative Examples 1-4 As shown in Table 1, the photoelectric conversion efficiency of the solar cells prepared in Examples 1 to 7 of this application is 26.324% to 26.546%, the open-circuit voltage is 735.2V to 736.2V, the short-circuit current is 16.033A to 16.093A, and the contact resistance is 1.65mΩ to 2.07mΩ.

[0099] A comparison between Example 6 and Example 1 shows that Example 6 did not undergo low-temperature annealing treatment. The photoelectric conversion efficiency, open-circuit voltage, and short-circuit current of the solar cell prepared in Example 6 were all lower than those in Example 1. The contact resistance of the solar cell prepared in Example 6 was higher than that in Example 1. This indicates that low-temperature annealing treatment can promote the bonding of doped atoms in the metal atom-doped polycrystalline silicon passivation contact layer, stabilize the metallurgical contact interface, and the annealing temperature is lower than the high-temperature failure temperature of the doped polycrystalline silicon passivation contact layer, which will not damage the passivation performance and is beneficial to improving the performance of the solar cell.

[0100] A comparison between Example 7 and Example 1 shows that Example 7 omits steps S4 and surface passivation cleaning. The photoelectric conversion efficiency, open-circuit voltage, and short-circuit current of the solar cell prepared in Example 7 are all lower than those in Example 1. The contact resistance of the solar cell prepared in Example 7 is higher than that in Example 1. This indicates that surface passivation cleaning can be used to remove the weak oxide layer on the surface without damaging the bulk structure and doping characteristics of the doped polycrystalline silicon passivation contact layer, which is beneficial to improving the performance of the solar cell.

[0101] Comparing Comparative Example 1 and Example 1, it can be seen that the solar cell prepared in Comparative Example 1 has no composite metal contact layer. The photoelectric conversion efficiency, open-circuit voltage, and short-circuit current of the solar cell prepared in Comparative Example 1 are all lower than those of Example 1. The contact resistance of the solar cell prepared in Comparative Example 1 is higher than that of Example 1. This indicates that the composite metal contact layer can form a metallurgical contact with the doped polycrystalline silicon passivation contact layer, which greatly reduces the interface defect density, and simultaneously improves the cell open-circuit voltage and fill factor, thereby improving the photoelectric conversion efficiency.

[0102] As can be seen from the comparison between Comparative Example 2 and Example 1, the composite metal contact layer of Comparative Example 2 only includes a nickel metal layer and a silver metal layer, without a titanium metal layer. The photoelectric conversion efficiency, open circuit voltage, and short circuit current of the solar cell prepared in Comparative Example 2 are all lower than those of Example 1. The contact resistance of the solar cell prepared in Comparative Example 2 is higher than that of Example 1. This indicates that the titanium metal layer has excellent oxygen barrier, moisture protection, and anti-diffusion properties, which can isolate it from external environmental corrosion, buffer interlayer stress, prevent metal layer detachment, improve the structural thermal stability of the composite metal contact layer, and help improve the performance of the solar cell.

[0103] As can be seen from the comparison between Comparative Example 3 and Example 1, the composite metal contact layer of Comparative Example 3 only includes a titanium metal layer and a silver metal layer, without a nickel metal layer. The photoelectric conversion efficiency, open-circuit voltage, and short-circuit current of the solar cell prepared in Comparative Example 3 are all lower than those of Example 1. The contact resistance of the solar cell prepared in Comparative Example 3 is higher than that of Example 1. This indicates that the nickel metal layer is used to directly bond the doped polycrystalline silicon passivation contact layer, and a nickel-silicon alloy transition interface is formed through low-temperature bonding, which greatly reduces the contact resistance and is beneficial to improving the performance of the solar cell.

[0104] As can be seen from the comparison between Comparative Example 3 and Example 1, when the positions of the titanium metal layer and the nickel metal layer are swapped in Comparative Example 4, the photoelectric conversion efficiency, open circuit voltage, and short circuit current of the solar cell prepared in Comparative Example 4 are all lower than those of Example 1, and the contact resistance of the solar cell prepared in Comparative Example 4 is higher than that of Example 1.

[0105] As shown in Tables 2-3, the solar cells prepared in Example 1 outperformed Comparative Examples 1-4 in the 1000h damp heat aging test and 200 cycles of hot and cold cycling test.

[0106] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A solar cell, characterized in that, The solar cell includes a doped polycrystalline silicon passivation contact layer, a composite metal contact layer, and metal main and secondary grid electrodes arranged in sequence. The composite metal contact layer includes a nickel metal layer, a titanium metal layer, and a silver metal layer stacked sequentially, wherein the nickel metal layer is bonded to the doped polycrystalline silicon passivation contact layer.

2. The solar cell according to claim 1, characterized in that, The thickness of the nickel metal layer is 5nm~15nm; And / or, the thickness of the titanium metal layer is 3nm~8nm; And / or, the thickness of the silver metal layer is 20nm~50nm.

3. The solar cell according to claim 1, characterized in that, The solar cell further includes a nickel-silicon alloy transition layer, which is disposed between the doped polycrystalline silicon passivated contact layer and the composite metal contact layer.

4. The solar cell according to claim 1, characterized in that, The surface of the doped polysilicon passivation contact layer includes a blank area and an electrode area for setting the metal main and secondary gate electrodes, and the composite metal contact layer is disposed in the electrode area.

5. The solar cell according to any one of claims 1 to 4, characterized in that, The doped polycrystalline silicon passivation contact layer includes a boron-doped P-type polycrystalline silicon layer; And / or, the thickness of the doped polycrystalline silicon passivation contact layer is 80nm~150nm; And / or, the doping concentration of the doped polysilicon passivation contact layer is 1×10⁻⁶. 20 atoms / cm 3 ~5×10 20 atoms / cm 3 .

6. A method for preparing a solar cell according to any one of claims 1 to 5, characterized in that, The method for preparing the solar cell includes: obtaining a preform including a doped polycrystalline silicon passivation contact layer, and sequentially depositing a nickel metal layer, a titanium metal layer and a silver metal layer on the surface of the doped polycrystalline silicon passivation contact layer using a low-temperature magnetron sputtering vapor deposition process to form a composite metal contact layer in situ.

7. The method for preparing a solar cell according to claim 6, characterized in that, The deposition temperature of the composite metal contact layer is 150℃~220℃.

8. The method for preparing a solar cell according to claim 6, characterized in that, The deposition power for depositing the nickel metal layer is 80W~120W, and the deposition rate is 0.2nm / s~0.5nm / s; And / or, the deposition power of the titanium metal layer is 60W~90W, and the deposition rate is 0.15nm / s~0.3nm / s; And / or, the deposition power for depositing the silver metal layer is 100W~150W, and the deposition rate is 0.4nm / s~0.8nm / s.

9. The method for preparing a solar cell according to any one of claims 6 to 8, characterized in that, After the composite metal contact layer is formed in situ, the method for preparing the solar cell further includes performing a low-temperature annealing treatment on the composite metal contact layer. The annealing temperature of the low-temperature annealing treatment is 250℃~300℃, and the holding time is 30s~60s.

10. The method for preparing a solar cell according to any one of claims 6 to 8, characterized in that, Before forming the composite metal contact layer in situ, the method for preparing the solar cell further includes plasma etching cleaning of the surface of the doped polycrystalline silicon passivation contact layer. The plasma etching cleaning includes argon plasma treatment for a time of 10s to 20s and a power of 50W to 80W.

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