TOPCon photovoltaic solar cell and preparation method thereof

Abstract

The invention relates to the technical field of TOPCon solar cells, in particular to a TOPCon photovoltaic solar cell and a preparation method thereof.The preparation method comprises the steps that an N-type polycrystalline silicon substrate is pretreated and then subjected to carbon / nitrogen doping treatment, high-temperature annealing is carried out, an ultrathin tunneling oxide layer, a phosphorus-doped polycrystalline silicon thin film and a transparent conducting layer are deposited, and a transparent conducting layer is formed; and preparing a metal electrode on the transparent conductive layer to form a complete cell structure, and packaging to obtain the TOPCon photovoltaic solar cell. Carbon / nitrogen atoms are doped into the polycrystalline silicon and are subjected to high-temperature annealing, so that the atoms are diffused into the crystalline silicon and are enriched on an interface, the passivation effect is enhanced by utilizing the hydrogen trapping characteristic of the atoms, and defects are reduced; meanwhile, the work function is reduced, and the field passivation and carrier collection efficiency is enhanced; and because the bond length is shortened, the band gap is improved, optical parasitic absorption is reduced, and the solar cell performance is comprehensively improved.

Description

Technical Field

[0001] The invention relates to the technical field of TOPCon solar cells, and in particular to a TOPCon photovoltaic solar cell and a preparation method thereof. Background Art

[0002] TOPCon (Tunneling Oxide Passivation Contact) technology is an important development direction for high-efficiency solar cells. By introducing ultra-thin tunneling oxide layers and passivation contact layers, the photoelectric conversion efficiency and stability of the cell are significantly improved. The core of this technology is to achieve comprehensive passivation of the cell surface, reduce carrier recombination losses, and optimize interface characteristics to improve carrier collection efficiency.

[0003] Nevertheless, in order to improve cell efficiency, the preparation process of TOPCon photovoltaic solar cells still faces many problems. The existing polysilicon passivation contact structure has insufficient passivation performance and serious optical parasitic absorption, which limits the further improvement of cell efficiency. In addition, the realization of low film thickness and low parasitic absorption technology requires precise control of the composition and structure of the polysilicon thin film, which also puts higher requirements on the preparation process. Therefore, the present invention provides a TOPCon photovoltaic solar cell and a preparation method thereof to solve the above problems. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide a TOPCon photovoltaic solar cell and a method for preparing the same.

[0005] A method for preparing a TOPCon photovoltaic solar cell comprises the following steps:

[0006] (1) Silicon wafer pretreatment: N-type polysilicon substrate is selected, the surface is cleaned, and potassium hydroxide is used to remove damage;

[0007] (2) Carbon / nitrogen doping and high temperature annealing: Carbon / nitrogen doping is performed on the surface of the silicon wafer by ion implantation or gas phase doping, with a doping concentration of 1E15-1E16 ions / cm 2 , high temperature annealing treatment after doping, annealing temperature 900-1100℃;

[0008] (3) Preparation of tunneling oxide layer: A layer of ultra-thin tunneling oxide layer (tunneling silicon oxide) with a thickness of 1-2 nm is deposited on the doped silicon wafer using atomic layer deposition technology;

[0009] (4) Preparation of doped polysilicon film: A phosphorus-doped polysilicon film with a thickness of 10-50 nm is deposited on the tunneling oxide layer by plasma enhanced chemical vapor deposition;

[0010] (5) Deposition of transparent conductive layer: depositing a transparent conductive layer on the doped polysilicon film, the material is ITO or AZO, with a thickness of 100-200 nm;

[0011] (6) Preparation of metal electrodes: Metal electrodes are prepared on the transparent conductive layer by screen printing technology or laser etching to form a silver grid line structure to form a complete battery structure;

[0012] (7) Battery packaging: The battery is packaged using a transparent packaging material to obtain a TOPCon photovoltaic solar cell.

[0013] Preferably, in the (2) carbon / nitrogen doping and high temperature annealing step, the carbon source used is methane, graphite powder or silicon carbide powder with a purity > 99.99%; the nitrogen source is nitrogen or silicon nitride target with a nitrogen purity > 99.999%.

[0014] Preferably, in the (2) carbon / nitrogen doping and high temperature annealing step, ion implantation uses a high-precision ion implanter to implant carbon / nitrogen ions into the polysilicon substrate at a predetermined energy of 20-50 keV and a predetermined dose.

[0015] Preferably, in the (2) carbon / nitrogen doping and high temperature annealing step, the vapor phase doping is achieved by placing the polycrystalline silicon substrate in a mixed atmosphere containing a carbon source and a nitrogen source at a high temperature of 800-1000° C., and doping is achieved by chemical vapor deposition or thermal diffusion.

[0016] Preferably, in the (2) carbon / nitrogen doping and high temperature annealing step, the high temperature annealing is performed by placing the doped polycrystalline silicon substrate in a tube furnace in an inert gas or reducing gas atmosphere for a high temperature annealing treatment, and the annealing duration is 10-60 minutes.

[0017] Preferably, interface treatment is also included, utilizing the strong hydrogen-capturing ability of carbon / nitrogen atoms to introduce hydrogen during the high-temperature annealing process, that is, passing high-purity hydrogen into the reaction chamber so that hydrogen atoms combine with carbon / nitrogen atoms at the interface to form stable hydrogen bonds, thereby passivating interface defects.

[0018] Preferably, in the (6) metal electrode preparation step, the silver electrode conductive paste used for the metal electrode comprises, by mass, 60-70 parts of high-purity spherical silver powder, 30-40 parts of an organic carrier, 2-5 parts of a low-melting point lead-free glass powder, 0.5-1.5 parts of nano-silicon dioxide or nano-alumina, and 0.5-2 parts of polyethylene glycol; wherein the particle size of the high-purity spherical silver powder is 1-3 μm, the organic carrier is a mixture of a resin and a solvent in a mass ratio of 1:2.5-3, the resin comprises, by mass percentage, 50% of a polyurethane resin, 30% of an epoxy resin, and 20% of other additives, and the solvent comprises, by mass percentage, 30% of N-methylpyrrolidone, and 70% of ethylene glycol monobutyl ether or propylene glycol methyl ether acetate.

[0019] Preferably, in the (6) metal electrode preparation step, after the transparent conductive layer is deposited, a PECVD anti-reflection coating treatment is performed, and then a fine grid and a copper wire composite film are directly laid on the anti-reflection coating. Through a lamination process, a stable electrical connection is formed between the copper wire composite film and the fine grid under high temperature and high pressure, and a plurality of battery cells are connected in series to form a battery string.

[0020] Preferably, in the (7) battery packaging step, the packaging materials used include one or more of aesthetic tempered glazed glass, high-reflective backboard, high-reflective solder tape and polyolefin elastomer film, the battery string is overlapped with the packaging material, and during the heating and lamination process, the solder tape and the fine grid are formed into a stable electrical connection, and the copper wire composite film is laminated on the surface of adjacent battery cells to form a series connection.

[0021] A TOPCon photovoltaic solar cell is prepared by the above-mentioned method for preparing a TOPCon photovoltaic solar cell.

[0022] The beneficial effects achieved by the present invention are as follows: 1. The present invention, by doping carbon / nitrogen atoms into polycrystalline silicon and subjecting it to high-temperature annealing treatment, allows carbon / nitrogen atoms to diffuse through the silicon oxide interface, penetrate into the crystalline silicon substrate, and form enrichment at the interface, and utilizes its hydrogen capture ability to increase the H concentration at the interface and in the crystalline silicon body, effectively passivating more defect states, thereby improving the passivation performance of the battery; at the same time, the introduction of C / N atoms can also reduce the work function of the material, increase the curvature of the TOPCon interface energy band, enhance the field passivation ability, and improve the selective collection efficiency of carriers. In addition, since the C / N atomic radius is small, the bond length formed by them and the Si atom is shorter, which helps to increase the energy of the material absorbing photons, that is, increase the band gap, thereby effectively reducing optical parasitic absorption.

[0023] 2. The present invention optimizes the crystal structure of the film, widens the optical band gap, and effectively reduces the free carrier concentration by precisely controlling the carbon / nitrogen atoms and active atom content in the novel polysilicon film, thereby not only maintaining the passivation performance but also achieving the low thickness and low parasitic absorption characteristics of the film, thereby significantly improving the photoelectric conversion efficiency of the battery; by finely controlling the polysilicon preparation process, the precise construction of the localized passivation contact structure is achieved, ensuring that the surface of the solar cell obtains a comprehensive and efficient passivation effect, thereby greatly reducing carrier recombination losses.

[0024] 3. The present invention does not screen-print the main grid on the front of the battery, but laminates the copper wire composite film (organic film with embedded copper welding tape) on the surface of adjacent battery cells to form a series connection of battery cells. During the heating and lamination process, the welding tape and the fine grid form a stable electrical connection, which reduces the optical shielding area of ​​the component, improves the interface characteristics between the metal electrode and the silicon wafer surface, and improves the efficiency of the component. In addition, aesthetic tempered glazed glass, high-reflective backplane, high-reflective welding tape, POE film and other packaging materials are used to achieve no CTM loss in the component, reaching more than 100%, thereby improving the conversion efficiency of the component. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the process of preparing the TOPCon photovoltaic solar cell adopted in the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with specific embodiments.

[0027] Some step details of the embodiments and comparative examples are supplemented in advance:

[0028] 1. Silicon wafer pretreatment: Select polysilicon substrates with a purity of 6N or above as the starting material, and the surface flatness RMS does not exceed 1nm; the cleaning steps include preliminary rinsing with deionized water, soaking the silicon wafer in acetone, rinsing with deionized water again, using a diluted hydrofluoric acid solution to remove metal ions and oxides, and rinsing with deionized water;

[0029] Potassium hydroxide damage removal treatment: use a 5% potassium hydroxide solution, immerse the silicon wafer in the potassium hydroxide solution, soak at room temperature for 15 minutes, rinse thoroughly with deionized water and dry.

[0030] 2. Ion implantation parameters: The ion implantation angle is set to 3°, and the beam density is set to 5x10^14ions / cm 2 ·s, helium protective atmosphere, the injection process was carried out at room temperature.

[0031] 3. High temperature annealing process: heating rate 10℃ / min, cooling rate 15℃ / min.

[0032] 4. Preparation of tunneling oxide layer: Aluminum oxide or silicon oxide material is selected. The aluminum oxide precursor uses trimethylaluminum and water vapor, and the silicon oxide precursor uses tetraethyl orthosilicate and ozone. The atomic layer deposition temperature is 250° C. The following examples use aluminum oxide material.

[0033] 5. Preparation of doped polysilicon thin film:

[0034] The plasma enhanced chemical vapor deposition temperature is 600°C, the silicon source gas is silane SiH4, and the doping gas is phosphine PH3.

[0035] 6. Transparent conductive layer deposition: using sputtering method in physical vapor deposition.

[0036] 7. Metal electrode preparation: screen printing pressure 100N / cm 2 , printing speed 150mm / s.

[0037] 8. Packaging process: The front cover material is made of aesthetic tempered glazed glass, the packaging film is made of polyolefin elastomer film, the back panel material is made of high reflectivity back panel material, and the welding tape is made of high reflective welding tape; the battery assembly to be packaged (including the front cover, battery cell, packaging film, and back panel) is placed in a laminator for preheating at 80°C for 5 minutes. The battery assembly is quickly sent into the heating chamber of the laminator, a pressure of 0.5MPa is applied, the lamination temperature is 150°C, the time is 10 minutes, and it is taken out and cooled naturally after curing.

[0038] Example 1: A method for preparing a TOPCon photovoltaic solar cell, such as Figure 1 As shown, the following steps are included:

[0039] (1) Silicon wafer pretreatment: N-type polysilicon substrate is selected, the surface is cleaned, and potassium hydroxide is used to remove damage;

[0040] (2) Carbon / nitrogen doping and high temperature annealing:

[0041] A high-precision ion implanter was used to implant carbon / nitrogen ions at a predetermined energy of 30keV and a dose of 1E15ions / cm2 using methane with a purity of >99.99% as the carbon source and nitrogen with a purity of >99.999% as the nitrogen source. 2 Injected into an N-type polysilicon substrate;

[0042] The doped silicon wafer was placed in a tube furnace in an argon atmosphere for high temperature annealing at a temperature of 1000°C for 30 minutes.

[0043] (3) Preparation of tunneling oxide layer: A layer of ultra-thin tunneling oxide layer (tunneling silicon oxide) with a thickness of 1.5 nm is deposited on the doped silicon wafer using atomic layer deposition technology;

[0044] (4) Preparation of doped polysilicon film: A phosphorus-doped polysilicon film with a thickness of 30 nm is deposited on the tunnel oxide layer by plasma enhanced chemical vapor deposition;

[0045] (5) Deposition of transparent conductive layer: depositing a transparent conductive layer of ITO with a thickness of 150 nm on the doped polysilicon film;

[0046] (6) Preparation of metal electrodes: After the transparent conductive layer is deposited, a PECVD anti-reflective coating treatment is performed, i.e., an anti-reflective coating is formed on the transparent conductive layer; a fine grid is directly laid on the anti-reflective coating by screen printing, and a copper wire composite film is laid above the fine grid to form a conductive path; through a lamination process, the copper wire composite film and the fine grid are formed into a stable electrical connection under high temperature and high pressure to form a complete battery structure, i.e., a TOPCon photovoltaic solar cell is obtained.

[0047] A plurality of battery cells processed through the above steps are connected in series to form a battery string, and the series connection process is achieved by applying welding strips on the copper wire composite films of adjacent battery cells.

[0048] The silver electrode conductive paste used for the metal electrode comprises, by mass, 65 parts of high-purity spherical silver powder with a particle size of 2 μm, 35 parts of an organic carrier, 3.5 parts of low-melting-point lead-free glass powder, 1 part of nano-silicon dioxide, and 1.2 parts of polyethylene glycol;

[0049] The organic carrier is a mixture of resin and solvent in a mass ratio of 1:3. The resin contains 50% polyurethane resin, 30% epoxy resin and 20% other additives by mass. The solvent contains 30% N-methylpyrrolidone and 70% ethylene glycol monobutyl ether by mass.

[0050] (7) Battery packaging: Overlap the battery string with the selected packaging material and place it in a heated laminator. During the heating and lamination process, a stable electrical connection will be formed between the welding ribbon and the fine grid, and the copper wire composite film will also be laminated on the surface of the adjacent battery cells, thereby completing the series connection and packaging of the battery string.

[0051] Example 2: A method for preparing a TOPCon photovoltaic solar cell, such as Figure 1 As shown, the following steps are included:

[0052] (1) Silicon wafer pretreatment: N-type polysilicon substrate is selected, the surface is cleaned, and potassium hydroxide is used to remove damage;

[0053] (2) Carbon / nitrogen doping and high temperature annealing:

[0054] At 850℃, methane with a purity of >99.99% was used as a carbon source and nitrogen with a purity of >99.999% was used as a nitrogen source. Carbon / nitrogen was doped into the N-type polysilicon substrate by chemical vapor deposition, with a doping concentration of 1E16ions / cm 2 ;

[0055] The doped silicon wafer is annealed at high temperature in a nitrogen atmosphere containing high-purity hydrogen at a temperature of 1050°C for 45 minutes. The strong hydrogen-capturing ability of carbon / nitrogen atoms is utilized to form stable hydrogen bonds at high temperatures to passivate interface defects.

[0056] (3) Preparation of tunneling oxide layer: A layer of ultra-thin tunneling oxide layer (tunneling silicon oxide) with a thickness of 1.5 nm is deposited on the doped silicon wafer using atomic layer deposition technology;

[0057] (4) Preparation of doped polysilicon film: A phosphorus-doped polysilicon film with a thickness of 30 nm is deposited on the tunnel oxide layer by plasma enhanced chemical vapor deposition;

[0058] (5) Deposition of transparent conductive layer: depositing a transparent conductive layer of AZO on the doped polysilicon film with a thickness of 150 nm;

[0059] (6) Preparation of metal electrodes: After the transparent conductive layer is deposited, a PECVD anti-reflective coating treatment is performed, i.e., an anti-reflective coating is formed on the transparent conductive layer; a fine grid is directly laid on the anti-reflective coating by screen printing, and a copper wire composite film is laid above the fine grid to form a conductive path; through a lamination process, the copper wire composite film and the fine grid are formed into a stable electrical connection under high temperature and high pressure to form a complete battery structure, i.e., a TOPCon photovoltaic solar cell is obtained.

[0060] A plurality of battery cells processed through the above steps are connected in series to form a battery string, and the series connection process is achieved by applying welding strips on the copper wire composite films of adjacent battery cells.

[0061] The silver electrode conductive paste used for the metal electrode comprises, by mass, 65 parts of high-purity spherical silver powder with a particle size of 2 μm, 35 parts of an organic carrier, 3.5 parts of low-melting-point lead-free glass powder, 1 part of nano-alumina, and 1.2 parts of polyethylene glycol;

[0062] The organic carrier is a mixture of resin and solvent in a mass ratio of 1:3. The resin contains 50% polyurethane resin, 30% epoxy resin and 20% other additives by mass. The solvent contains 30% N-methylpyrrolidone and 70% propylene glycol methyl ether acetate by mass.

[0063] (7) Battery packaging: Overlap the battery string with the selected packaging material and place it in a heated laminator. During the heating and lamination process, a stable electrical connection will be formed between the welding ribbon and the fine grid, and the copper wire composite film will also be laminated on the surface of the adjacent battery cells, thereby completing the series connection and packaging of the battery string.

[0064] Example 3: A method for preparing a TOPCon photovoltaic solar cell, such as Figure 1 As shown, the following steps are included:

[0065] (1) Silicon wafer pretreatment: N-type polysilicon substrate is selected, the surface is cleaned, and potassium hydroxide is used to remove damage;

[0066] (2) Carbon / nitrogen doping and high temperature annealing:

[0067] Using gas phase doping, carbon / nitrogen was deposited at 1E15.5 ions / cm by chemical vapor deposition at 950°C. 2 The concentration of is doped into the polycrystalline silicon substrate, the carbon source is silicon carbide powder, and the nitrogen source is nitrogen gas;

[0068] The doped silicon wafer was annealed at high temperature in a tube furnace in a hydrogen atmosphere at a temperature of 1100°C for 20 minutes.

[0069] (3) Preparation of tunneling oxide layer: A layer of ultra-thin tunneling oxide layer (tunneling silicon oxide) with a thickness of 1.5 nm is deposited on the doped silicon wafer using atomic layer deposition technology;

[0070] (4) Preparation of doped polysilicon film: A phosphorus-doped polysilicon film with a thickness of 30 nm is deposited on the tunnel oxide layer by plasma enhanced chemical vapor deposition;

[0071] (5) Deposition of transparent conductive layer: depositing a transparent conductive layer of ITO with a thickness of 150 nm on the doped polysilicon film;

[0072] (6) Preparation of metal electrodes: After the transparent conductive layer is deposited, a PECVD anti-reflective coating treatment is performed, i.e., an anti-reflective coating is formed on the transparent conductive layer; a fine grid is directly laid on the anti-reflective coating by laser etching, and a copper wire composite film is laid above the fine grid to form a conductive path; through a lamination process, the copper wire composite film and the fine grid are formed into a stable electrical connection under high temperature and high pressure to form a complete battery structure, i.e., a TOPCon photovoltaic solar cell is obtained.

[0073] A plurality of battery cells processed through the above steps are connected in series to form a battery string, and the series connection process is achieved by applying welding strips on the copper wire composite films of adjacent battery cells.

[0074] The silver electrode conductive paste used for the metal electrode comprises, by mass, 62 parts of high-purity spherical silver powder with a particle size of 3 μm, 40 parts of an organic carrier, 4.5 parts of low-melting-point lead-free glass powder, 0.7 parts of nano-silicon dioxide, and 2 parts of polyethylene glycol;

[0075] The organic carrier is a mixture of resin and solvent in a mass ratio of 1:2.8, the resin comprises 50% polyurethane resin, 30% epoxy resin and 20% other additives by mass percentage, and the solvent comprises 30% N-methylpyrrolidone and 70% ethylene glycol monobutyl ether by mass percentage.

[0076] (7) Battery packaging: Overlap the battery string with the selected packaging material and place it in a heated laminator. During the heating and lamination process, a stable electrical connection will be formed between the welding ribbon and the fine grid, and the copper wire composite film will also be laminated on the surface of the adjacent battery cells, thereby completing the series connection and packaging of the battery string.

[0077] Comparative Example: A method for preparing a conventional TOPCon photovoltaic solar cell comprises the following steps:

[0078] (1) Select an N-type polysilicon substrate, clean the surface, and use potassium hydroxide to remove damage;

[0079] (2) Doping using conventional phosphorus diffusion process;

[0080] The doped silicon wafer was placed in a tube furnace in a nitrogen atmosphere for high temperature annealing at a temperature of 950°C.

[0081] (3) using atomic layer deposition technology to deposit an ultra-thin tunneling oxide layer with a thickness of 1.5 nm on the doped silicon wafer;

[0082] (4) using plasma enhanced chemical vapor deposition to deposit a phosphorus-doped polysilicon film with a thickness of 30 nm on the tunnel oxide layer;

[0083] (5) depositing a transparent conductive layer with a thickness of 150 nm on the doped polysilicon film;

[0084] (6) using a conventional silver-aluminum paste to prepare a metal electrode on the transparent conductive layer by screen printing technology to form a silver grid line structure;

[0085] The silver-aluminum paste includes, by mass percentage, 65% silver powder, 20% aluminum powder, 5% glass powder, and 10% organic vehicle (same as in the embodiment);

[0086] (7) Use transparent packaging material (EVA film) to encapsulate the battery.

[0087] Performance test: The TOPCon photovoltaic solar cells obtained in Examples 1 to 3 and the comparative example were subjected to relevant performance tests, and the results are shown in the following table;

[0088]

[0089] It can be seen from the table that the open circuit voltage in the embodiment is increased by about 0.04 V on average compared with the comparative example, and the short circuit current density is increased by about 1.7 mA / cm 2The fill factor increased by about 1.4% on average, while the most critical conversion efficiency increased by about 1.3% on average, indicating that the method of the present invention has a significant effect on improving the passivation performance of solar cells, enhancing the carrier collection efficiency and reducing optical parasitic absorption, so that the open circuit voltage (Voc), short circuit current density (Isc), fill factor (FF) and conversion efficiency (η) of solar cells are all improved, effectively improving the performance of polycrystalline silicon solar cells.

[0090] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing a TOPCon photovoltaic solar cell, characterized in that: The following steps are involved: (1) Silicon wafer pretreatment: Select N-type polysilicon substrate and use potassium hydroxide to remove damage after cleaning; (2) Carbon / nitrogen doping and high temperature annealing: Carbon / nitrogen doping is performed on the surface of the silicon wafer by ion implantation or gas phase doping, with a doping concentration of 1E15-1E16 ions / cm 2 , high temperature annealing treatment after doping, annealing temperature 900-1100℃; (3) Preparation of tunneling oxide layer: A layer of ultra-thin tunneling oxide layer with a thickness of 1-2 nm is deposited on the doped silicon wafer using atomic layer deposition technology; (4) Preparation of doped polysilicon film: A phosphorus-doped polysilicon film with a thickness of 10-50 nm is deposited on the tunneling oxide layer by plasma enhanced chemical vapor deposition; (5) Deposition of transparent conductive layer: depositing a transparent conductive layer on the doped polysilicon film, the material is ITO or AZO, with a thickness of 100-200 nm; (6) Preparation of metal electrodes: Metal electrodes are prepared on the transparent conductive layer by screen printing technology or laser etching to form a silver grid line structure to form a complete battery structure; (7) Cell packaging: Use transparent packaging materials to encapsulate and obtain TOPCon photovoltaic solar cells.

2. The method for preparing a TOPCon photovoltaic solar cell according to claim 1, characterized in that: In the (2) carbon / nitrogen doping and high temperature annealing step, the carbon source used is methane, graphite powder or silicon carbide powder with a purity of >99.99%; the nitrogen source is nitrogen gas or silicon nitride target material, and the nitrogen purity is >99.999%.

3. The method for preparing a TOPCon photovoltaic solar cell according to claim 1, characterized in that: In the (2) carbon / nitrogen doping and high temperature annealing step, ion implantation uses a high-precision ion implanter to implant carbon / nitrogen ions into the polysilicon substrate at a predetermined energy of 20-50 keV and a predetermined dose.

4. The method for preparing a TOPCon photovoltaic solar cell according to claim 1, characterized in that: In the (2) carbon / nitrogen doping and high temperature annealing step, the gas phase doping is achieved by placing the polycrystalline silicon substrate in a mixed atmosphere containing a carbon source and a nitrogen source at a high temperature of 800-1000° C., and doping is achieved by chemical vapor deposition or thermal diffusion.

5. The method for preparing a TOPCon photovoltaic solar cell according to claim 1, characterized in that: In the (2) carbon / nitrogen doping and high temperature annealing step, the high temperature annealing is to place the doped polysilicon substrate in a tubular furnace with an inert gas or reducing gas atmosphere for high temperature annealing treatment, and the annealing duration is 10-60 minutes.

6. The method for preparing a TOPCon photovoltaic solar cell according to claim 5, characterized in that: It also includes interface treatment, using the strong hydrogen-capturing ability of carbon / nitrogen atoms to introduce hydrogen during the high-temperature annealing process, that is, to pass high-purity hydrogen into the reaction chamber.

7. The method for preparing a TOPCon photovoltaic solar cell according to claim 1, characterized in that: In the (6) metal electrode preparation step, the silver electrode conductive paste used for the metal electrode comprises, by mass, 60-70 parts of high-purity spherical silver powder, 30-40 parts of an organic carrier, 2-5 parts of a low-melting-point lead-free glass powder, 0.5-1.5 parts of nano-silicon dioxide or nano-alumina, and 0.5-2 parts of polyethylene glycol; wherein the particle size of the high-purity spherical silver powder is 1-3 μm, the organic carrier is a mixture of a resin and a solvent in a mass ratio of 1:2.5-3, the resin comprises, by mass percentage, 50% of a polyurethane resin, 30% of an epoxy resin, and 20% of other additives, and the solvent comprises, by mass percentage, 30% of N-methylpyrrolidone, and 70% of ethylene glycol monobutyl ether or propylene glycol methyl ether acetate.

8. The method for preparing a TOPCon photovoltaic solar cell according to claim 1, characterized in that: In the (6) metal electrode preparation step, after the transparent conductive layer is deposited, a PECVD anti-reflection coating treatment is performed, and then a fine grid and a copper wire composite film are directly laid on the anti-reflection coating. Through a lamination process, the copper wire composite film and the fine grid are stably electrically connected under high temperature and high pressure, and a plurality of battery cells are connected in series to form a battery string.

9. The method for preparing a TOPCon photovoltaic solar cell according to claim 1, characterized in that: In the (7) battery packaging step, the packaging materials used include one or more of aesthetic tempered glazed glass, high-reflective backplane, high-reflective solder tape and polyolefin elastomer film. The battery string is overlapped with the packaging material. During the heating and lamination process, the solder tape and the fine grid form a stable electrical connection, and the copper wire composite film is laminated on the surface of adjacent battery cells to form a series connection.

10. A TOPCon photovoltaic solar cell, characterized in that: The TOPCon photovoltaic solar cell is prepared by the preparation method of any one of claims 1-9.

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