Composite material for solar cells and use thereof

Abstract

The application relates to a composite material for solar cells and application thereof. The composite material for solar cells comprises composite particles with a core-shell structure, and the composite particles comprise an inner core, an intermediate layer and a shell layer. The inner core contains boron-doped aluminum; the intermediate layer is coated on the outer surface of the inner core and contains silicon dioxide; and the shell is coated on the outer surface of the intermediate layer and contains phosphorus-doped tin oxide. The composite material can simplify the preparation process steps of the solar cells, reduce the process complexity and production cost, and improve the performance of the solar cells.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, specifically to a composite material for solar cells and its application. Background Technology

[0002] A solar cell is a thin-film photovoltaic semiconductor that directly generates electricity using sunlight. Also known as a "solar chip" or "photovoltaic cell," its core advantage lies in its ability to instantly output voltage and generate current when exposed to sufficient illumination. It is a core device with immense development potential in the clean energy field. The performance of a solar cell directly depends on the rationality and advancement of its manufacturing process; therefore, the manufacturing process is a key factor determining the photoelectric conversion efficiency, stability, and production cost of a solar cell.

[0003] However, current solar cell fabrication processes have significant shortcomings, involving cumbersome steps and complex procedures. The fabrication of the PN junction is particularly prominent—it typically requires depositing a polycrystalline silicon layer using LPCVD (low-pressure chemical vapor deposition) technology, followed by a tubular high-temperature diffusion process to create the PN junction. This process not only requires separate diffusion treatment of dopants such as boron and phosphorus, but also necessitates repeated post-processing steps. This not only prolongs the fabrication cycle but also significantly increases equipment investment, raw material consumption, and labor costs, resulting in a persistently high overall cost for solar cell fabrication.

[0004] Therefore, how to simplify the manufacturing process of solar cells, reduce process complexity and production costs, while ensuring or even improving cell performance has become a key technical challenge that urgently needs to be solved in the current solar cell field. Summary of the Invention

[0005] The purpose of this application is to provide a composite material for solar cells and its application, thereby solving the problems of multiple steps and high manufacturing costs in existing solar cell manufacturing processes.

[0006] To achieve the objectives of this application, the following technical solution is provided: In a first aspect, the present invention provides a composite material for solar cells, characterized in that it comprises composite particles having a core-shell structure, the composite particles comprising a core, an intermediate layer and an outer shell; wherein the core comprises boron-doped aluminum; the intermediate layer covers the outer surface of the core and comprises silicon dioxide; and the outer shell covers the outer surface of the intermediate layer and comprises phosphorus-doped tin oxide.

[0007] In some embodiments, the core comprises 35% to 45% of the composite particles by mass percentage, the intermediate layer comprises 5% to 15% of the composite particles, and the outer shell comprises 40% to 60% of the composite particles.

[0008] In some embodiments, the composite material for solar cells further includes an organic carrier, in which the composite particles are dispersed.

[0009] In some embodiments, the viscosity of the composite material is 10000 mPa. s~40000 mPa s.

[0010] In some embodiments, the composite particles account for 40% to 60% by mass percentage in the composite material for solar cells, and the organic carrier accounts for 40% to 60%.

[0011] In some embodiments, the organic carrier includes terpineol, acrylic resin, fumed silica, and a first additive.

[0012] In some embodiments, the organic carrier contains, by mass percentage, 50% to 70% terpineol, 10% to 30% acrylic resin, 5% to 15% fumed silica, and 5% to 15% of the first additive.

[0013] In some embodiments, the first additive includes a polycarboxylate dispersant, a silicone leveling agent, and a polyether defoamer.

[0014] In some embodiments, the polycarboxylate dispersant accounts for 20% to 40% by mass percentage in the first additive, the silicone leveling agent accounts for 30% to 50%, and the polyether defoamer accounts for 20% to 40%.

[0015] In a second aspect, the present invention provides a method for fabricating a solar cell, the method employing the composite material for solar cells described in the first aspect, comprising: fabricating an isolation trench on a first silicon wafer using a first laser to obtain a second silicon wafer; processing a pyramidal textured surface on the second silicon wafer using a second laser to obtain a third silicon wafer; screen printing the third silicon wafer using the composite material for solar cells, wherein the composite material is bonded to the third silicon wafer; and performing in-situ doping and oxidation on the third silicon wafer having the composite material using a third laser to obtain a fourth silicon wafer, the fourth silicon wafer having a PN contact region and SiO2. x layer.

[0016] In some embodiments, the first laser is an infrared laser with a wavelength of 1064 nm and an energy density of 1.5 J / cm². 2 ~2.5 J / cm 2The scanning speed is 3 m / s to 5 m / s, and the spot diameter is 6 μm to 10 μm; the depth of the isolation groove is 6 μm to 10 μm, and the width is 8 μm to 12 μm.

[0017] In some embodiments, the second laser is a green laser with a wavelength of 532 nm and an energy density of 0.8 J / cm². 2 ~1.5 J / cm 2 The scanning speed is 5 m / s to 8 m / s, and the spot diameter is 3 μm to 5 μm; the depth of the pyramid textured surface is 1.2 μm to 1.8 μm, the coverage is ≥85%, and the surface roughness Ra is 0.2 μm to 0.6 μm.

[0018] In some embodiments, the third laser is a 355 nm ultraviolet laser, and when the ultraviolet laser performs in-situ doping, the energy density in the phosphorus-doped region is 0.8 J / cm². 2 ~1.8 J / cm 2 The activation depth is 0.8 μm ~ 1.2 μm, and the sheet resistance is 80 Ω / □ ~ 120 Ω / □; the energy density in the boron-doped region is 1.8 J / cm². 2 ~ 2.2 J / cm 2 The activation depth is 0.5 μm ~ 0.8 μm, and the sheet resistance is 60 Ω / □ ~ 100 Ω / □.

[0019] In some embodiments, the energy density of the ultraviolet laser for in-situ oxidation is 0.6 J / cm². 2 ~1.2 J / cm 2 The scanning speed is 8 m / s to 16 m / s, and the spot diameter is 3 μm to 8 μm; the SiO x The layer thickness is 2 nm to 3 nm.

[0020] In some embodiments, the preparation method further includes: depositing a passivation layer and an antireflection layer on the fourth silicon wafer using a PECVD process to obtain a fifth silicon wafer; and using the third laser to process the fifth silicon wafer to remove the passivation layer and antireflection layer of the PN contact area.

[0021] In some embodiments, the third laser is an ultraviolet laser with a wavelength of 355 nm, a repetition frequency of 300 kHz to 500 kHz, and an energy density of 0.4 J / cm². 2 ~1 J / cm 2 The scanning speed is 5 m / s to 15 m / s, and the spot diameter is 2 μm to 5 μm.

[0022] In some embodiments, the antireflection layer includes a first antireflection layer and a second antireflection layer, one side of the fifth silicon wafer has the passivation layer and the first antireflection layer, and the other side has the second antireflection layer; wherein the thickness of the passivation layer is 8 mm to 15 mm, the thickness of the first antireflection layer is 50 mm to 80 mm, and the thickness of the second antireflection layer is 60 mm to 90 mm.

[0023] In some embodiments, the preparation method further includes: screen printing the fifth silicon wafer with a conductive paste; the conductive paste includes copper nanoparticles, polyimide resin, boron / phosphorus doped zinc oxide, and a second additive; and sintering the fifth silicon wafer with the conductive paste using the second laser to obtain a solar cell, wherein copper grid lines are formed on the solar cell.

[0024] In some embodiments, the conductive paste contains, by mass percentage, 30% to 50% copper nanoparticles, 20% to 40% polyimide resin, 10% to 20% boron / phosphorus doped zinc oxide, and 10% to 20% the second additive.

[0025] In some embodiments, the viscosity of the conductive paste is 15000 mPa. s~25000 mPa s; the second adjuvant includes one or more of dispersants, antioxidants, and homogenizing agents.

[0026] Thirdly, the present invention provides a solar cell comprising a composite material for solar cells as described in the first aspect, or the solar cell being manufactured using the preparation method described in the second aspect.

[0027] This invention designs composite particles with a core-shell structure, pre-integrating boron and phosphorus dopants into the same composite particle. This eliminates the need for separate diffusion treatment of the dopants and the need to use LPCVD to deposit polycrystalline silicon layers and tubular high-temperature diffusion processes to prepare the PN contact region, greatly simplifying the fabrication steps of solar cells and shortening the fabrication cycle. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1This is a schematic cross-sectional view of a composite material according to one embodiment; Figure 2 Figure A shows the fabrication process of a solar cell according to one implementation method. Figure 3 Schematic B shows the fabrication process of a solar cell according to one implementation method; Figure 4 This is Flowchart C, which illustrates the fabrication process of a solar cell according to one implementation method. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] It should be noted that when a component is said to be "fixed" to another component, it can be directly on the other component or it can be in a middle component. When a component is said to be "connected" to another component, it can be directly connected to the other component or it may be in a middle component.

[0032] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0033] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0034] The following is an explanation of the English abbreviations used in the text: (1) BC (Back Contact): Back contact; (2) PECVD (Plasma Enhanced Chemical Vapor Deposition): Plasma-enhanced chemical vapor deposition; (3) LPCVD (Low Pressure Chemical Vapor Deposition): Low-pressure chemical vapor deposition; (4) All-Si (All Silicon): All silicon; (5) Voc (Open Circuit Voltage): Open-circuit voltage, the terminal voltage of the battery when it is open-circuited, reflecting the height of the PN junction barrier; (6) Jsc (Short-Circuit Current Density): Short-circuit current density; (7) RoHS (Restriction of Hazardous Substances): Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment; (8) SEMI (Semiconductor Equipment and Materials International): International Semiconductor Equipment and Materials Association; (9) IEC (International Electrotechnical Commission); (10) TMA (Trimethyl Aluminum): Trimethylaluminum.

[0035] This invention provides a composite material for solar cells; please refer to [the relevant documentation]. Figure 1 The composite material comprises core-shell structured particles, including a core 10, an intermediate layer 20, and a shell. The core 10 contains boron-doped aluminum. The intermediate layer 20 covers the outer surface of the core 10 and contains silicon dioxide. The shell 30 covers the outer surface of the intermediate layer 20 and contains phosphorus-doped tin oxide. Specifically, this composite material can be used to fabricate the PN contact region in solar cells. Furthermore, using this composite material to fabricate solar cells can reduce the boron and phosphorus diffusion processes in the fabrication method, thereby reducing the number of steps in the solar cell fabrication process.

[0036] In a specific embodiment, the composite particles are divided into a core 10, an intermediate layer 20, and a shell layer from the inside out. The boron element in the core 10 can directly provide a boron doping source for the solar cell, which helps to form the P-region inside the cell; the phosphorus element doped in the shell layer can serve as a phosphorus doping source for the solar cell, providing support for the formation of the N-region inside the cell, and working together with the boron element provided by the core 10 to help to efficiently form the PN contact area.

[0037] This invention designs composite particles with a core-shell structure, pre-integrating boron and phosphorus dopants into the same particle. This eliminates the need for separate diffusion treatment of the dopants and the use of LPCVD deposition of polycrystalline silicon layers and tubular high-temperature diffusion processes to prepare the PN contact region, significantly simplifying the solar cell fabrication process and shortening the production cycle. Furthermore, this composite material can directly achieve PN contact region preparation in a single step through screen printing combined with laser in-situ doping and oxidation processes, eliminating repeated post-processing steps and effectively reducing equipment investment, raw material consumption, and labor costs. This fundamentally solves the problem of high costs associated with existing processes.

[0038] In some embodiments, the core comprises 35% to 45% of the composite particle by mass percentage, the intermediate layer comprises 5% to 15%, and the outer shell comprises 40% to 60%. Optionally, the mass percentage of the core in the composite particle can be 35%, 37%, 39%, 41%, 43%, or 45%; or, the mass percentage of the intermediate layer in the composite particle can be 5%, 7%, 9%, 11%, 13%, or 15%; or, the mass percentage of the outer shell in the composite particle can be 40%, 45%, 50%, 55%, or 60%.

[0039] Meeting the above-mentioned mass ratio range ensures optimal synergy between the core, intermediate layer, and shell, guaranteeing sufficient boron doping source for the core to form the P-region and sufficient phosphorus doping source for the shell to form the N-region. It also achieves good isolation and buffering effects through the reasonable proportion of the intermediate layer, further improving the overall performance of the composite material and meeting the preparation requirements of the PN contact region of solar cells.

[0040] In some embodiments, the composite material for solar cells further includes an organic carrier, in which the composite particles are dispersed. Specifically, the composite material can be a slurry with fluid dynamics, and the organic carrier can be an organic solvent for the composite particles. The introduction of the organic carrier can effectively improve the dispersibility of the composite particles, prevent particle agglomeration, ensure that the composite material can be uniformly distributed in subsequent coating, printing and other preparation processes, and at the same time give the composite material good flowability, facilitating subsequent processing and molding, and further adapting to the large-scale preparation requirements of the PN contact area of ​​solar cells.

[0041] In some embodiments, the composite particles account for 40% to 60% of the composite material for solar cells, and the organic carrier accounts for 40% to 60% by mass percentage. Optionally, the mass percentage of the composite particles in the composite material can be 40%, 45%, 50%, 55%, or 60%; or, the mass percentage of the organic carrier in the composite material can be 40%, 45%, 50%, 55%, or 60%.

[0042] Meeting the above-mentioned mass ratio range ensures that there are sufficient composite particles in the composite material to provide adequate boron and phosphorus doping sources, guaranteeing the molding quality and electrical properties of the PN contact area. At the same time, the reasonable proportion of organic carriers ensures that the composite particles are uniformly dispersed, maintaining the fluid dynamic slurry characteristics of the composite material. This facilitates the smooth implementation of subsequent large-scale processing technologies such as coating and printing, balancing material performance and processing convenience.

[0043] In some embodiments, the organic carrier includes terpineol, acrylic resin, fumed silica, and a first additive. Terpineol, as the main solvent, can effectively dissolve and disperse the composite particles, ensuring the fluidity of the slurry; acrylic resin can improve the film-forming properties and adhesion of the composite material, ensuring the structural stability of the contact area after subsequent processing; fumed silica can further optimize the dispersion effect of the composite particles and prevent particle agglomeration.

[0044] In some embodiments, the organic carrier comprises, by mass percentage, 50%–70% terpineol, 10%–30% acrylic resin, 5%–15% fumed silica, and 5%–15% of the first additive. Optionally, the mass percentage of terpineol in the organic carrier can be 50%, 60%, or 70%; or the mass percentage of acrylic resin in the organic carrier can be 10%, 20%, or 30%; or the mass percentage of fumed silica in the organic carrier can be 5%, 10%, or 15%; or the mass percentage of the first additive in the organic carrier can be 5%, 10%, or 15%. By combining the components in this proportion, the organic carrier can achieve optimal performance and better cooperate with the composite particles.

[0045] In some embodiments, the first additive includes a polycarboxylate dispersant, a silicone leveling agent, and a polyether defoamer. The polycarboxylate dispersant further improves the uniformity of dispersion of the composite particles in the organic carrier, effectively inhibits particle agglomeration, and ensures the stability of the slurry system. The silicone leveling agent improves the coating smoothness of the composite material, reduces defects such as pinholes and edge shrinkage during coating, and improves the surface quality of the contact area. The polyether defoamer effectively eliminates bubbles generated during slurry preparation and coating, preventing residual bubbles from affecting the structural integrity and electrical properties of the contact area. The synergistic effect of these three additives further optimizes the performance of the organic carrier, helping the composite material achieve better processing and performance characteristics.

[0046] In some embodiments, the polycarboxylate dispersant accounts for 20% to 40% of the first additive by mass percentage, the silicone leveling agent accounts for 30% to 50%, and the polyether defoamer accounts for 20% to 40%. Optionally, the polycarboxylate dispersant may account for 20%, 30%, or 40% of the first additive by mass; or, the silicone leveling agent may account for 30%, 40%, or 50% of the first additive by mass; or, the polyether defoamer may account for 20%, 30%, or 40% of the first additive by mass.

[0047] In some embodiments, the first additive may further include one or more of the following: thickener, leveling agent, viscosity modifier, anti-leakage agent, and wetting agent. Specifically, the first additive may include thickeners (such as polyamide wax, hydrogenated castor oil, etc.), leveling agents (such as polyether-modified silicone, acrylate leveling agents), viscosity modifiers (such as high-boiling-point solvents, cellulose-based thickeners, etc.), anti-leakage agents (such as micronized wax, special silicone control agents, etc.), and wetting agents (such as acetylenic diol wetting agents, nonionic surfactants, etc.).

[0048] The present invention also provides a method for preparing a composite material for solar cells. This method is used to prepare the composite material as described in the above embodiments. It includes the following steps: A100, prepare the organic carrier, and stir the organic carrier; A200 is prepared by sequentially adding boron-doped aluminum, silicon dioxide, and phosphorus-doped tin oxide to an organic carrier and stirring to obtain a composite material.

[0049] In a specific embodiment, the organic carrier configured in step A100 can refer to the composition provided in the above embodiments, and will not be repeated here. Then, a homogenizer can be used to stir the organic carrier, and the stirring speed can be 2000 r / min to 4000 r / min, and the stirring time can be 20 min to 40 min.

[0050] In a specific embodiment, in step A200, boron-doped aluminum can be added to the organic carrier and stirred for 10-30 minutes, followed by three-roll milling to ensure the particle size in the slurry is less than or equal to 1 μm. Then, silica is added to the organic carrier and stirred for 10-20 minutes. Finally, phosphorus-doped tin oxide is added to the organic carrier and stirred for 10-30 minutes. Optionally, the prepared composite material can also be degassed using vacuum degassing.

[0051] This invention also provides a method for preparing a solar cell; please refer to [the relevant documentation]. Figure 2This preparation method can be used to prepare solar cells using the composite materials provided in the above embodiments. Optionally, the prepared solar cell can be a BC solar cell. The preparation method specifically includes the following steps: S310 uses a first laser to create an isolation trench on a first silicon wafer to obtain a second silicon wafer; S320 uses a second laser to process the pyramidal textured surface on the second silicon wafer to obtain the third silicon wafer; S330 uses a composite material for solar cells to screen print onto a third silicon wafer, and the composite material is bonded onto the third silicon wafer. S340 uses a third laser to perform in-situ doping and oxidation on a third silicon wafer with composite materials to obtain a fourth silicon wafer. The fourth silicon wafer has a PN contact region and SiO2. x layer.

[0052] In a specific embodiment, the first, second, and third lasers have different wavelengths (colors), so the effects produced by the first, second, and third lasers irradiating the silicon wafer are different. Optionally, the repetition frequency of the first, second, and third lasers can all be from 100 kHz to 500 kHz, for example, 100 kHz, 200 kHz, 300 kHz, 400 kHz, and 500 kHz.

[0053] In a specific embodiment, a first laser can etch isolation trenches on a first silicon wafer to provide space for the formation of PN contact areas on the silicon wafer. A second laser is used to process the pyramidal textured surface on a second silicon wafer to refine the structure of the pyramidal textured surface, improve the absorption efficiency of sunlight by the silicon wafer, and reduce light reflection loss.

[0054] In a specific embodiment, the third laser is used to activate the composite material, causing phosphorus and boron elements in the composite material to dope and oxidize the third silicon wafer in situ, thereby forming P-regions and N-regions on the fourth silicon wafer and forming a PN junction between them. Specifically, the energy of the third laser can break the core-shell structure of the composite particles in the composite material, causing boron in the core and phosphorus in the shell to be released and rapidly diffuse to the surface of the silicon wafer, achieving in-situ doping. At the same time, the energy of the third laser can promote the oxidation reaction of the silicon wafer surface and the doped elements, forming a stable oxide layer that protects the doped region and ensures the connection between the P-region and the N-region, ultimately forming the PN contact region (PN junction).

[0055] It should be noted that the first, second, third, and fourth silicon wafers mentioned above all refer to the same silicon wafer material used in the fabrication of solar cells. The difference between the four lies in the different physical structures they form after being processed through different techniques.

[0056] In some embodiments, the first laser is an infrared laser with a wavelength of 1064 nm and an energy density of 1.5 J / cm². 2 ~2.5 J / cm 2 The scanning speed is 3 m / s to 5 m / s, and the spot diameter is 6 μm to 10 μm; the depth of the isolation groove is 6 μm to 10 μm, and the width is 8 μm to 12 μm.

[0057] In a specific embodiment, the energy density of the infrared laser can be 1.5 J / cm². 2 1.7 J / cm 2 1.9 J / cm 2 2.1 J / cm 2 2.3 J / cm 2 2.5 J / cm 2 .

[0058] In specific embodiments, the scanning speed of the infrared laser can be 3 m / s, 4 m / s, or 5 m / s.

[0059] In specific embodiments, the spot diameter of the infrared laser can be 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0060] In a specific embodiment, the depth of the isolation trench formed on the second silicon wafer can be 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, and the width can be 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm.

[0061] In some embodiments, the second laser is a green laser with a wavelength of 532 nm and an energy density of 0.8 J / cm². 2 ~1.5 J / cm 2 The scanning speed is 5 m / s to 8 m / s, the spot diameter is 3 μm to 5 μm, the depth of the pyramid textured surface is 1.2 μm to 1.8 μm, the coverage is ≥85%, and the surface roughness Ra is 0.2 μm to 0.6 μm.

[0062] In a specific embodiment, the energy density of the green laser can be 0.8 J / cm². 2 0.9 J / cm 2 1 J / cm 2 1.1 J / cm 2 1.2 J / cm 2 1.3 J / cm 2 1.4 J / cm 2 1.5 J / cm 2 .

[0063] In specific embodiments, the scanning speed of the green laser can be 5 m / s, 6 m / s, 7 m / s, or 8 m / s.

[0064] In specific embodiments, the spot diameter of the green laser can be 3 μm, 4 μm, or 5 μm.

[0065] In a specific embodiment, the depth of the pyramid textured surface on the third silicon wafer can be 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, or 1.8 μm.

[0066] In specific embodiments, the roughness Ra of the pyramid textured surface can be 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, or 0.6 μm.

[0067] In some embodiments, the third laser is a 355 nm ultraviolet laser, and when performing in-situ doping with ultraviolet laser, the energy density in the phosphorus-doped region is 0.8 J / cm². 2 ~1.8 J / cm 2 The activation depth ranges from 0.8 μm to 1.2 μm, and the sheet resistance ranges from 80 Ω / □ to 120 Ω / □; the energy density in the boron-doped region is 1.8 J / cm². 2 ~2.2 J / cm 2 The activation depth is 0.5 μm to 0.8 μm, and the sheet resistance is 60 Ω / □ to 100 Ω / □.

[0068] In a specific embodiment, the energy density of the ultraviolet laser in the phosphorus-doped region can be 0.8 J / cm². 2 1 J / cm 2 1.2J / cm 2 1.3 J / cm 2 1.4 J / cm 2 1.5 J / cm 2 1.6 J / cm 2 1.7 J / cm 2 1.8 J / cm 2 .

[0069] In specific embodiments, the activation depth of the ultraviolet laser in the phosphorus-doped region can be 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, or 1.2 μm.

[0070] In specific embodiments, the sheet resistance of the phosphorus-doped region can be 80 Ω / □, 90 Ω / □, 100 Ω / □, or 120 Ω / □.

[0071] In a specific embodiment, the energy density of the ultraviolet laser in the boron-doped region can be 1.8 J / cm². 2 1.9 J / cm 2 2J / cm 2 2.1 J / cm 2 2.2 J / cm 2 .

[0072] In specific embodiments, the activation depth of the ultraviolet laser in the boron-doped region can be 0.5 μm, 0.6 μm, 0.7 μm, or 0.8 μm.

[0073] In specific embodiments, the sheet resistance of the boron-doped region can be 60 Ω / □, 70 Ω / □, 80 Ω / □, 90 Ω / □, 100 Ω / □, or 120 Ω / □.

[0074] In some implementations, the energy density of in-situ oxidation using ultraviolet laser is 0.6 J / cm². 2 ~1.2 J / cm 2 The scanning speed is 8 m / s to 16 m / s, and the spot diameter is 3 μm to 8 μm; SiO x The layer thickness is 2 nm to 3 nm.

[0075] In a specific embodiment, the energy density of the ultraviolet laser is 0.6 J / cm². 2 0.7 J / cm 2 0.8 J / cm 2 0.9J / cm 2 1 J / cm 2 1.1 J / cm 2 1.2 J / cm 2 .

[0076] In specific embodiments, the spot diameter of the ultraviolet laser can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm.

[0077] In a specific embodiment, the SiO on the fourth silicon wafer x The layer thickness can be 2 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm, or 3 nm.

[0078] For some implementation methods, please refer to Figure 3 The preparation method also includes: S500 uses PECVD process to deposit a passivation layer and an anti-reflection layer on the fourth silicon wafer to obtain the fifth silicon wafer; The S600 uses a third laser to process the fifth silicon wafer to remove the passivation layer and antireflection layer in the PN contact area.

[0079] In a specific embodiment, in step S500, a passivation layer and a first antireflection layer are fabricated on the back side of the fourth silicon wafer using a PECVD process, and a second antireflection layer is fabricated on the front side of the fourth silicon wafer. After stabilization through post-processing, a fifth silicon wafer is obtained. The passivation layer on the back side is AlO₂. x The first antireflective layer is SiN. x The first layer, the second antireflective layer is another SiN layer. x layer.

[0080] In some embodiments, the settings for fabricating the passivation layer include a TMA to oxygen volume ratio of 1:(10~30), a deposition temperature of 180 ℃~260 ℃, an ambient pressure of 150 Pa~250 Pa, and a radio frequency power of 80 W~160 W. The passivation layer thickness is 8 mm~15 mm, and the negative charge density is ≥1×10⁻⁶. 12 cm -2 .

[0081] In specific embodiments, the volume ratio of TMA to oxygen can be 1:10, 1:20, or 1:30.

[0082] In specific embodiments, the deposition temperature can be 180 ℃, 200 ℃, 220 ℃, 240 ℃, or 260 ℃.

[0083] In specific embodiments, the ambient pressure can be 150 Pa, 160 Pa, 180 Pa, 200 Pa, 220 Pa, 240 Pa, or 250 Pa.

[0084] In specific embodiments, the radio frequency power can be 80 W, 100 W, 120 W, 140 W, or 160 W.

[0085] In specific embodiments, the thickness of the passivation layer can be 8mm, 10mm, 12mm, 14mm, or 15mm.

[0086] In some embodiments, the setup for fabricating the first antireflective layer includes a volume ratio of silane (SiH4) to ammonia of 1:(5~10), a deposition temperature of 280 ℃~360 ℃, an ambient pressure of 250 Pa~350 Pa, and a radio frequency power of 180 W~260 W. The thickness of the first antireflective layer is 50 mm~80 mm, and the refractive index of the first antireflective layer is 2.05.

[0087] In specific embodiments, the volume ratio of silane to ammonia can be 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0088] In specific embodiments, the deposition temperature can be 280 ℃, 300 ℃, 320 ℃, 340 ℃, or 360 ℃.

[0089] In specific embodiments, the ambient pressure can be 250 Pa, 260 Pa, 280 Pa, 300 Pa, 320 Pa, 340 Pa, or 350 Pa.

[0090] In specific embodiments, the radio frequency power can be 180 W, 200 W, 220 W, 240 W, or 260 W.

[0091] In a specific embodiment, the thickness of the first antireflective layer can be 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, or 80mm.

[0092] In some embodiments, the setup for fabricating the second antireflective layer includes a volume ratio of silane (SiH4), ammonia, and nitrogen of 1:(4~8):(5~10), a deposition temperature of 280 ℃~360 ℃, an ambient pressure of 250 Pa~350 Pa, and a radio frequency power of 250 W~300 W. The thickness of the second antireflective layer is 60 mm~90 mm, and the refractive index of the second antireflective layer is 2.15.

[0093] In specific embodiments, the volume ratio of silane to ammonia can be 1:4:(5~10), 1:6:(5~10), 1:8:(5~10), 1:(4~8):5, 1:(4~8):8, or 1:(4~8):10.

[0094] In specific embodiments, the deposition temperature can be 280 ℃, 300 ℃, 320 ℃, 340 ℃, or 360 ℃.

[0095] In specific embodiments, the ambient pressure can be 250 Pa, 260 Pa, 280 Pa, 300 Pa, 320 Pa, 340 Pa, or 350 Pa.

[0096] In specific embodiments, the radio frequency power can be 250 W, 260 W, 270 W, 280 W, 290 W, or 300 W.

[0097] In a specific embodiment, the thickness of the second antireflection layer can be 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, or 90mm.

[0098] In some embodiments, in step S600, the third laser is an ultraviolet laser with a wavelength of 355 nm, a repetition frequency of 300 kHz to 500 kHz, and an energy density of 0.4 J / cm².2 ~1 J / cm 2 The scanning speed is 5 m / s to 15 m / s, and the spot diameter is 2 μm to 5 μm.

[0099] In a specific embodiment, the energy density of the ultraviolet laser is 0.4 J / cm². 2 0.5 J / cm 2 0.6 J / cm 2 0.7J / cm 2 0.8 J / cm 2 1 J / cm 2 .

[0100] In specific embodiments, the scanning speed of the ultraviolet laser can be 5 m / s, 7 m / s, 9 m / s, 11 m / s, 13 m / s, or 15 m / s.

[0101] In specific embodiments, the spot diameter of the ultraviolet laser can be 2 μm, 3 μm, 4 μm, or 5 μm.

[0102] For some implementation methods, please refer to Figure 4 The preparation method also includes: S700 uses conductive paste to screen print on the fifth silicon wafer; the conductive paste includes copper nanoparticles, polyimide resin, boron / phosphorus doped zinc oxide, and a second additive. S800 uses a second laser to sinter a fifth silicon wafer containing conductive paste to obtain a solar cell, on which copper grid lines are formed.

[0103] In a specific embodiment, the conductive paste is a conductive paste without added silver. The conductive paste is screen-printed to create gate lines on the fifth silicon wafer; therefore, the paste on the fifth silicon wafer is laser-sintered to form gate lines. The sintered nanoparticles form a dense conductive network on the silicon wafer and form Cu-Si alloy contacts with the boron / phosphorus doped regions on the silicon wafer.

[0104] In some embodiments, the conductive paste contains, by mass percentage, 30%–50% copper nanoparticles, 20%–40% polyimide resin, 10%–20% boron / phosphorus-doped zinc oxide, and 10%–20% a second additive. Optionally, the mass percentage of copper nanoparticles in the conductive paste can be 30%, 35%, 40%, 45%, or 50%; or, the mass percentage of polyimide resin in the conductive paste can be 20%, 25%, 30%, 35%, or 40%; or, the mass percentage of boron / phosphorus-doped zinc oxide in the conductive paste can be 10%, 15%, or 20%; or, the mass percentage of the second additive in the conductive paste can be 10%, 15%, or 20%.

[0105] In some embodiments, the viscosity of the conductive paste is 15000 mPa. s~25000 mPa s. Optionally, the viscosity of the conductive paste can be 15000 mPa. s, 17000 mPa s, 19000 mPa s, 21000 mPa s, 23000 mPa s, 25000mPa s.

[0106] In some embodiments, the second adjuvant includes one or more of dispersants, antioxidants, and homogenizing agents. Specifically, the second adjuvant may include dispersants (such as polyacrylate dispersants, polyvinylpyrrolidone, etc.), antioxidants (such as benzotriazole and its derivatives, thiazole antioxidants, triazole antioxidants, etc.), homogenizing agents (such as fumed silica, organobentonite, etc.), and solvents (such as N-methylpyrrolidone, propylene glycol methyl ether acetate, etc.).

[0107] In some embodiments, in step S800, the second laser is a green laser with a wavelength of 532 nm and an energy density of 0.6 J / cm². 2 ~1.2 J / cm 2 The scanning speed is 6 m / s to 10 m / s, and the spot diameter is 4 μm to 8 μm.

[0108] In a specific embodiment, the energy density of the green laser can be 0.6 J / cm². 2 0.7 J / cm 2 0.8 J / cm 2 0.9 J / cm 2 1 J / cm 2 1.1 J / cm 21.2 J / cm 2 .

[0109] In specific embodiments, the scanning speed of the green laser can be 6 m / s, 7 m / s, 8 m / s, 9 m / s, or 10 m / s.

[0110] In specific embodiments, the spot diameter of the green laser can be 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm.

[0111] In a specific embodiment, green laser light is used for segmented sintering. The sintering temperature of the first segment can be 300 ℃~400 ℃, and the sintering temperature of the second segment can be 350 ℃~450 ℃, with the first segment sintering temperature being lower than the second segment sintering temperature. Optionally, the sintering temperature of the first segment can be 300 ℃, 350 ℃, or 400 ℃; or, the sintering temperature of the second segment can be 350 ℃, 400 ℃, or 450 ℃.

[0112] In some embodiments, the solar cell comprises the composite material for solar cells provided in the above embodiments, or the solar cell is fabricated using the preparation method provided in the above embodiments.

[0113] The technical solution of the present invention will be described in detail below through specific embodiments.

[0114] Example 1 This embodiment provides a BC solar cell and its fabrication method. This embodiment uses an N-type silicon wafer with a diameter of 182 mm as the substrate. The resistivity of the silicon wafer is 1 Ω·cm to 3 Ω·cm, the thickness is 135 μm, the flatness is less than or equal to 5 μm, and it is free of cracks and missing corners. The specific steps of the fabrication method include the following: (1) Substrate pretreatment: The silicon wafer is cleaned with a first cleaning solution to obtain the first silicon wafer. The cleaning environment is set at 30°C, the cleaning time is 4 min, and the spray pressure is 0.18 MPa. The first cleaning solution is prepared by mixing hydrofluoric acid and hydrochloric acid in a volume ratio of 1:3. The concentration of the first cleaning solution is 0.15 mol / L. The first cleaning solution is required to be free of bubbles and heavy metal residues. The particulate matter on the surface of the cleaned silicon wafer is required to be less than or equal to 10 particles / cm. 2 (Particle size ≥ 0.5μm). The cleaned silicon wafers are then rinsed and dried using ultrapure water (purity ≥ 18MΩ). The silicon wafer was rinsed with overflow for 3 minutes (cm); the drying temperature was 90℃, and the drying time was 5 minutes; the surface resistivity of the first silicon wafer after drying was greater than or equal to 1×10⁻⁶. 10 Ω·cm, the breakage rate of the first silicon wafer is 0.08%.

[0115] (2) Preparation of composite materials: An organic carrier was prepared and stirred. Boron-doped aluminum, silica, and phosphorus-doped tin oxide were added to the organic carrier in sequence and stirred to obtain the composite material. The composite material consists of a core (boron-doped aluminum), an intermediate layer (silica), an outer shell layer (phosphorus-doped tin oxide), and an organic carrier, with a mass ratio of 25:5:30:40. The organic carrier consists of terpineol, acrylic resin, fumed silica, and additives, with a mass ratio of 60:20:10:10. The additives consist of polycarboxylate dispersant, silicone leveling agent, and polyether defoamer, with a mass ratio of 3:4:3. The organic carrier was stirred at a speed of 3000 r / min. Boron-doped aluminum was stirred in the organic carrier for 20 min, silica for 15 min, and phosphorus-doped tin oxide for 20 min. Then, the mixture was degassed under vacuum at -0.09 mPa for 15 min. The slurry viscosity of the composite material was 5000 mPa. Viscosity stability ≤ ±5% (24h) at 25℃.

[0116] (3) Laser processing and first screen printing: (3-1) An isolation trench is formed on the first silicon wafer by etching with an infrared laser with a wavelength of 1064 nm, and a second silicon wafer is obtained; wherein, the energy density of the infrared laser is 2.0 J / cm 2 The scanning speed was 4 m / s, the spot size was 8 μm, and the depth and width of the etched isolation trench were 8 μm and 10 μm, respectively. (3-2) The pyramid textured surface on the second silicon wafer was treated with a green laser with a wavelength of 532 nm to obtain the third silicon wafer; wherein, the energy density of the green laser was 1.1 J / cm². 2 The scanning speed was 6 m / s, the spot size was 4 μm, and a 1.5 μm pyramidal textured surface was formed. The coverage of the pyramidal textured surface was greater than or equal to 90%, and the surface roughness Ra of the pyramidal textured surface was 0.3 μm to 0.5 μm. (3-3) The composite material was printed onto the third silicon wafer using screen printing technology. The screen printing machine was set to a 350 mesh screen, a squeegee pressure of 0.25 mPa, a printing speed of 65 mm / s, a printing thickness of 15 μm, and a registration deviation of less than or equal to 2 μm. At the same time, the printed third silicon wafer was dried in three stages: 150 ℃ / 3 min, 200 ℃ / 4 min, and 250 ℃ / 3 min, respectively, so that the adhesion of the composite material on the third silicon wafer was greater than or equal to 5 N / cm. 2 (3-4) In-situ doping of the third silicon wafer was performed using a 355 nm ultraviolet laser. The energy density of the ultraviolet laser in the phosphorus-doped region was 1.5 J / cm². 2 The activation depth is 1 μm, the sheet resistance is 100 Ω / □, and the energy density of the ultraviolet laser in the boron-doped region is 2.0 J / cm².2 The activation depth was 0.7 μm, and the sheet resistance was 80 Ω / □; subsequent in-situ oxidation yielded an energy density of 0.8 J / cm³. 2 The scanning speed was 12 m / s, the spot size was 5 μm, and a 2.5 nm thick SiO₂ layer was formed. x The fourth silicon wafer is obtained by processing the laser-processed silicon wafer. The laser-processed silicon wafer undergoes post-processing, with nitrogen gas used to blow away the surface silicon powder.

[0117] (4) Cleaning: The fourth silicon wafer was cleaned using a second cleaning solution. The cleaning environment was set at 45°C, the cleaning time was 1.5 min, and the spray pressure was 0.12 mPa. The second cleaning solution was a 0.8 mol / L sodium hydroxide solution. The alkaline-cleaned fourth silicon wafer was then rinsed with ultrapure water for 2.5 min and dried at 90°C for 4 min. The surface resistivity of the cleaned fourth silicon wafer was greater than or equal to 1×10⁻⁶. 10 Ω·cm.

[0118] (5) Passivation and anti-reflection treatment: AlO is first deposited on the back side of the fourth silicon wafer using PECVD process. x The deposition conditions were: trimethylaluminum to oxygen ratio of 1:20, deposition temperature of 220 °C, pressure of 199 Pa, and radio frequency power of 120 W. AlO₂ x The layer is 12 nm thick and has a negative charge density ≥1×10⁻⁶. 12 cm -2 SiN is then deposited on the back side of the silicon wafer. x The deposition conditions were as follows: silane and ammonia ratio of 1:8, deposition temperature of 320 °C, pressure of 299 Pa, and radio frequency power of 220 W for SiN. x The layer is 65 nm thick and has a refractive index of 2.05. SiN is deposited on the front side of the silicon wafer. x The deposition conditions were as follows: silane, ammonia, and nitrogen in a ratio of 1:6:10; deposition temperature of 320 °C; pressure of 299 Pa; and radio frequency power of 280 W. (SiN) x The layer has a thickness of 75 nm and a refractive index of 2.15, resulting in the fifth silicon wafer. The deposited fifth silicon wafer is then kept in the chamber for 10 min until the temperature drops below 100 °C before being removed.

[0119] (6) Laser mold opening: The fifth silicon wafer is processed using a 355 nm ultraviolet laser with a repetition frequency of 300 kHz to 500 kHz. The energy density of the ultraviolet laser is 0.6 J / cm². 2 The scanning speed was 9 m / s, the spot size was 2.5 μm, and the SiN on the back of the silicon wafer in the contact area was removed. x Layers and AlO x layer.

[0120] (7) Metallization: The fifth silicon wafer was screen-printed using a conductive paste. The conductive paste consisted of copper nanoparticles, polyimide resin, boron / phosphorus-doped zinc oxide, and additives, with a mass ratio of 40:30:15:15. The copper nanoparticles had a particle size of 50 nm, and the zinc oxide had a particle size of 30 nm to 50 nm. The printing thickness of the back contact area of ​​the fifth silicon wafer was 12 μm, and the gate line width was 25 μm; the front gate line thickness was 10 μm, and the width was 20 μm. The printed fifth silicon wafer was then dried for 6 min at a drying temperature of 130 ℃.

[0121] (8) Low-temperature laser sintering: The fifth silicon wafer was sintered using a 532 nm green laser. The energy density of the green laser was 0.9 J / cm². 2 The scanning speed was 8 m / s, the spot size was 6 μm, and segmented sintering was performed. The first segment was sintered at 350 ℃ for 3 min, and the second segment was sintered at 400 ℃ for 2 min. After sintering, copper nanoparticles formed a dense conductive network in the silicon wafer, forming Cu-Si alloy contacts with the doped regions, with a contact resistance of 8 × 10⁻⁶. -7 Ω cm 2 The resistivity of the conductive network is less than or equal to 2 × 10⁻⁶. -6 Ω cm.

[0122] Example 2 This embodiment provides a BC solar cell and its fabrication method. This embodiment uses a 210mm N-type silicon wafer as the substrate. The resistivity of the silicon wafer is 1Ω·cm to 3Ω·cm, the thickness is 135μm, the flatness is less than or equal to 5μm, and it is free of cracks and missing corners. The difference between this fabrication method and the fabrication method in Example 1 is: (1) The cleaning environment was set at 25°C, the cleaning time was 5 min, and the cleaning spray pressure was 0.15 MPa. The concentration of the first cleaning solution was 0.1 mol / L. The drying temperature was 80°C, and the fragmentation rate of the first silicon wafer was 0.1%.

[0123] (2) The slurry viscosity of the composite material is 20000 mPa. s (25℃).

[0124] (3) The energy density of the infrared laser is 1.8 J / cm². 2 The scanning speed was 5 m / s, the isolation groove depth was 5 μm, and the width was 8 μm. The energy density of the green laser was 1 J / cm². 2The scanning speed was 5 m / s, forming a 1 μm pyramidal textured surface. A slit coater was used to coat the composite material, achieving a coating thickness of 10 μm. The sheet resistance of the ultraviolet laser was 120 Ω / □ in the phosphorus-doped region and 60 Ω / □ in the boron-doped region, forming a 2 nm thick SiO₂ layer. x layer.

[0125] (4) The ambient temperature for cleaning is set at 40 ℃, the cleaning time is 2 min, and the concentration for the second cleaning is 0.5 mol / L. The drying temperature is 80 ℃.

[0126] (5) Backside AlO x The deposition conditions of the layer were 200 °C, 133 Pa, 100 W, and AlO₂. x The layer thickness is 10 nm. Backside SiN x The deposition conditions for the SiN layer were 300 °C, 266 Pa, and 200 W. x The layer thickness is 60 nm. Front-side SiN x The deposition conditions for the SiN layer were 300 °C, 266 Pa, and 250 W. x The layer thickness is 70 nm, and the surface recombination rate is ≤9×10 cm / s.

[0127] (6) The energy density of the ultraviolet laser is 0.5 J / cm². 2 The scanning speed is 8 m / s and the spot size is 2 μm.

[0128] (7) The printing thickness of the conductive paste is 8 μm, and the width of the front grid line is 25 μm. The drying temperature is 120 ℃.

[0129] (8) The energy density of the green laser is 0.8 J / cm². 2 The scanning speed was 5 m / s, the spot size was 5 μm, and the contact resistance was 9 × 10⁻⁶. -7 Ω cm 2 .

[0130] Comparative Example 1 This comparative example provides a BC solar cell and its fabrication method. The comparative example uses an 182mm N-type silicon wafer as the substrate. The resistivity of the silicon wafer is 1Ω·cm to 3Ω·cm, the thickness is 135μm, the flatness is less than or equal to 5μm, and it is free of cracks and missing corners. The BC solar cell is fabricated using a conventional method, specifically including: silicon wafer pretreatment, pre-tunneling oxide layer growth, LPCVD polycrystalline silicon deposition, tubular boron diffusion, first laser processing, polylite removal cleaning, tubular phosphorus diffusion, second laser processing, surface texturing, passivation treatment, third laser processing for mold opening, metallization, and high-temperature sintering.

[0131] The solar cells prepared in Examples 1-2 and Comparative Example 1 were tested and sorted. The results are shown in Table 1. The tests included: appearance inspection (no cracks, missing corners, or overflowing), electrical performance testing (Voc, FF, Jsc, conversion efficiency, leakage current), bifaciality testing, and reliability sampling testing (1000h of damp heat aging at 85℃ / 85% RH, followed by 200 thermal cycles at -40℃ to 85℃). The sorting criteria were: Grade A (conversion efficiency ≥ 26.8%), Grade B (conversion efficiency 26.5%~26.7%), and Grade C (conversion efficiency < 26.5%). The qualified finished products required Voc ≥ 730mV, FF ≥ 84%, and Jsc ≥ 42.5mA / cm². 2 Leakage current <10 -7 A / cm 2 The double-sided rate is 85-90%.

[0132] Table 1

[0133] The test results from Example 1 and Comparative Example 1 show that the yield of the solar cell provided in Example 1 can reach 95.8%, and the proportion of Grade A solar cells reaches 82%. The advantage of this preparation method lies in the use of steps (3-4), (5), and (6) to achieve SiO₂… x AlO x SiN x A three-layer passivation system, achieving a synergistic effect of chemical passivation and field passivation, can reduce the surface recombination rate of solar cells to 1×10⁻⁶. 2 The speed is below cm / s, which is more than 60% lower than the process of Comparative Example 1.

[0134] Meanwhile, the antireflective layer fabricated by this method reduces the front reflectivity of the solar cell to below 1.5%, and the textured back surface increases the bifaciality to 85%~90%, an improvement of 13%~18% compared to the process in Comparative Example 1. This results in the solar cell of Example 1 achieving a Voc exceeding 730 mV, an FF exceeding 84%, and a Jsc exceeding 42.8 mA / cm². 2 The conversion efficiency exceeds 26.5%, representing a 0.7% to 1.0% performance improvement compared to the solar cell provided in Comparative Example 1. Furthermore, the efficiency degradation after reliability testing does not exceed 2%, meeting the international standard IEC60904.

[0135] The advantage of the preparation method provided in Example 1 lies in the use of a composite material to replace the two-stage diffusion process in the traditional method, and the combination of three-laser processing to form the PN contact region. This results in the resistance of the PN contact region being no less than 1 × 10⁻⁶. 6 Ω, leakage current less than 10-7 A / cm 2 Compared to the process in Comparative Example 1, this process reduces costs by more than 80%. Furthermore, precise laser doping ensures sheet resistance fluctuations do not exceed 2%, significantly improving doping uniformity; the entire process utilizes low-temperature conditions (≤400℃) to prevent thermal damage to the silicon wafer, with a breakage rate not exceeding 0.2%. This represents a 75% reduction compared to the process in Comparative Example 1.

[0136] Furthermore, this invention employs a composite paste and a conductive paste for two separate printing processes on the silicon wafer. Neither the composite paste nor the conductive paste contains metallic silver or glass phase materials, thus replacing traditional silver-based pastes. This reduces paste costs by over 80% compared to the antireflective layer. The simplified cleaning process eliminates the need for a fluorine-containing mixture, reducing reagent costs by over 70% compared to the antireflective layer. Simultaneously, the sintering temperature can be controlled to not exceed 400°C during the conductive paste sintering process. This also enables densification of the copper-based paste and achieves low-resistance ohmic contact, while protecting the passivation layer from cracking, further reducing process costs.

[0137] Furthermore, the fabrication method provided by this invention, compared to traditional methods, reduces redundant processes such as pre-tunneling oxide layer growth, LPCVD polycrystalline silicon deposition, two-stage tubular high-temperature diffusion, multiple laser processing steps, and complex depolylation cleaning, reducing the process steps by 5 steps (a reduction rate of over 60%). This ensures that the complete solar cell process takes no more than 70 minutes, with a mass production cycle of no less than 600 cells / hour, improving production efficiency by over 40%, and meeting the core requirements of large-scale mass production in the photovoltaic industry.

[0138] Therefore, it is demonstrated that the preparation method provided by this invention can be applied in industrial production with a high yield. Furthermore, compared to traditional preparation methods, the solar cells prepared by the method provided by this invention exhibit significantly improved performance and reduced per-watt manufacturing cost. Thus, the preparation method of this invention achieves multiple optimizations in terms of superior performance and cost-effectiveness compared to conventional methods.

[0139] The test results of Examples 1 and 2 show that the yield rate of the solar cell provided in Example 2 can reach 95.2%, and the proportion of Grade A solar cells reaches 78%. The cell performance is also similar to that of the cell in Example 1, and is comparable to that of Comparative Example 1. Therefore, it can be seen that the preparation method provided by the present invention can be used for substrates of different specifications (182mm / 210mm large-size silicon wafers), has strong industrial applicability, and can quickly achieve pilot-scale and mass production worldwide.

[0140] In the description of the embodiments of this application, it should be noted that the orientation or positional relationship of the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and other indicators are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0141] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art will understand that all or part of the processes for implementing the above embodiments and equivalent variations made in accordance with the claims of this application are still within the scope of this application.

Claims

1. A composite material for solar cells, characterized in that, The composite particles include a core-shell structure, the composite particles comprising: The core contains boron-doped aluminum; An intermediate layer, covering the outer surface of the core, the intermediate layer comprising silicon dioxide; The outer casing covers the outer surface of the intermediate layer and contains phosphorus-doped tin oxide.

2. The composite material for solar cells according to claim 1, characterized in that, In the composite particles, the core accounts for 35% to 45% by mass percentage, the intermediate layer accounts for 5% to 15%, and the outer shell accounts for 40% to 60%.

3. The composite material for solar cells according to claim 1, characterized in that, The composite material for solar cells also includes an organic carrier, in which the composite particles are dispersed. The viscosity of the composite material is 10000 mPa. s~40000 mPa s.

4. The composite material for solar cells according to claim 3, characterized in that, In the composite material for solar cells, the proportion of composite particles is 40% to 60% by mass percentage, and the proportion of organic carrier is 40% to 60%.

5. A method for preparing a solar cell, characterized in that, The preparation method uses the composite material for solar cells as described in any one of claims 1-4, comprising: An isolation trench is fabricated on a first silicon wafer using a first laser to obtain a second silicon wafer; The pyramidal textured surface on the second silicon wafer is processed using a second laser to obtain a third silicon wafer; The third silicon wafer is screen-printed using a composite material for solar cells, and the composite material is bonded to the third silicon wafer. A third silicon wafer containing the aforementioned composite material is in-situ doped and oxidized using a third laser to obtain a fourth silicon wafer, the fourth silicon wafer having a PN contact region and SiO₂. x layer.

6. The preparation method according to claim 5, characterized in that, The first laser is an infrared laser with a wavelength of 1064 nm and an energy density of 1.5 J / cm². 2 ~2.5 J / cm 2 The scanning speed is 3 m / s to 5 m / s, and the spot diameter is 6 μm to 10 μm; the depth of the isolation groove is 6 μm to 10 μm, and the width is 8 μm to 12 μm.

7. The preparation method according to claim 5, characterized in that, The second laser is a green laser with a wavelength of 532 nm and an energy density of 0.8 J / cm². 2 ~1.5 J / cm 2 The scanning speed is 5 m / s to 8 m / s, and the spot diameter is 3 μm to 5 μm; the depth of the pyramid textured surface is 1.2 μm to 1.8 μm, the coverage is ≥85%, and the surface roughness Ra is 0.2 μm to 0.6 μm.

8. The preparation method according to claim 5, characterized in that, The third laser is a 355 nm ultraviolet laser, and when the ultraviolet laser is used for in-situ doping, the energy density in the phosphorus-doped region is 0.8 J / cm². 2 ~1.8 J / cm 2 The activation depth ranges from 0.8 μm to 1.2 μm, and the sheet resistance ranges from 80 Ω / □ to 120 Ω / □; the energy density in the boron-doped region is 1.8 J / cm². 2 ~2.2 J / cm 2 The activation depth is 0.5 μm to 0.8 μm, and the sheet resistance is 60 Ω / □ to 100 Ω / □.

9. The preparation method according to claim 8, characterized in that, The energy density of the ultraviolet laser for in-situ oxidation is 0.6 J / cm². 2 ~1.2 J / cm 2 The scanning speed is 8 m / s to 16 m / s, and the spot diameter is 3 μm to 8 μm; the SiO x The layer thickness is 2 nm to 3 nm.

10. The preparation method according to claim 5, characterized in that, The preparation method further includes: A passivation layer and an anti-reflection layer were deposited on the fourth silicon wafer using the PECVD process to obtain the fifth silicon wafer. The third laser is used to process the fifth silicon wafer to remove the passivation layer and antireflection layer in the PN contact area.

11. The preparation method according to claim 10, characterized in that, The third laser is an ultraviolet laser with a wavelength of 355 nm, a repetition frequency of 300 kHz to 500 kHz, and an energy density of 0.4 J / cm². 2 ~1 J / cm 2 The scanning speed is 5 m / s to 15 m / s, and the spot diameter is 2 μm to 5 μm.

12. The preparation method according to claim 10, characterized in that, The antireflection layer includes a first antireflection layer and a second antireflection layer. One side of the fifth silicon wafer has the passivation layer and the first antireflection layer, and the other side has the second antireflection layer. The passivation layer has a thickness of 8 mm to 15 mm, the first antireflection layer has a thickness of 50 mm to 80 mm, and the second antireflection layer has a thickness of 60 mm to 90 mm.

13. The preparation method according to claim 10, characterized in that, The preparation method further includes: The fifth silicon wafer is screen-printed using a conductive paste; the conductive paste comprises copper nanoparticles, polyimide resin, boron / phosphorus doped zinc oxide, and a second additive. The fifth silicon wafer containing the conductive paste is sintered using the second laser to obtain a solar cell, on which copper grid lines are formed.

14. A solar cell, characterized in that, The solar cell comprises a composite material for solar cells as described in any one of claims 1-4, or the solar cell is manufactured using a preparation method as described in any one of claims 5-13.

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