Doping method for passivation layer of TOPCon solar cell and TOPCon cell

Abstract

The invention relates to a doping method for a passivation layer of a TOPCon solar cell and the TOPCon solar cell, and aims to effectively improve the energy conversion efficiency of the solar cell. According to the doping method, the SiOdoped buffer layer is introduced in the doping process of the polycrystalline silicon passivation layer of the TOPCon solar cell, the layer can effectively inhibit the diffusion depth of a dopant in the polycrystalline silicon passivation layer, the Auger recombination effect on the surface of the cell is reduced, and then the open-circuit voltage and the cell efficiency are improved. By depositing the SiO doped buffer layer on the surface of the polycrystalline silicon passivation layer, the diffusion of a dopant can be controlled within a shallow gradient range, so that the interface recombination and photoelectric conversion efficiency of the cell are improved. The method not only improves the overall performance of the solar cell, but also has high industrial application potential. A test result shows that the photoelectric conversion efficiency of the prepared TOPCon solar cell is improved by more than 0.1%, and the prepared TOPCon solar cell has a good application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of TOPCon solar energy, and in particular to a doping method for a passivation layer of a TOPCon solar cell and a TOPCon cell. Background Art

[0002] TOPCon (Tunnel Oxide Passivated Contact) solar cells are an emerging high-efficiency photovoltaic technology that aims to significantly improve the efficiency of light energy conversion. Its structural feature is that an ultra-thin tunnel oxide layer (SiO x ) and doped polysilicon layer to form a selective transmission interface. This design greatly reduces the recombination of carriers at the interface, thereby effectively improving the open circuit voltage (Voc) and overall battery efficiency.

[0003] In the TOPCon structure, the tunneling oxide layer not only plays the role of isolation and passivation, preventing the metal electrode from directly contacting the silicon substrate and reducing the non-radiative recombination caused by interface defects, but also the doped polysilicon layer is responsible for selective conductivity, further improving the surface passivation effect. This innovative structure makes TOPCon solar cells perform well in terms of photoelectric conversion performance and has become an important direction for the development of photovoltaic technology today.

[0004] However, existing technologies still face a series of challenges in practical applications, especially in the control of dopant diffusion in the doped polysilicon layer and the resulting Auger recombination effect. Dopants (such as boron or phosphorus) are usually diffused into the polysilicon layer and the silicon substrate through high-temperature heat treatment. However, excessive dopant diffusion may lead to the formation of deep diffusion regions in the silicon substrate, thereby exacerbating the Auger recombination effect. This multi-carrier recombination mechanism is more significant at high doping concentrations, significantly increasing carrier losses and reducing the open circuit voltage and overall efficiency of the battery.

[0005] In addition, the trade-off between the thickness of the doped polysilicon layer and its light absorption characteristics is also a key issue. Although thicker polysilicon layers can provide better doping control and surface passivation effects, they will also increase the material's light absorption and reduce the number of photons entering the silicon substrate, thereby affecting the short-circuit current (Jsc) and overall cell efficiency. Therefore, how to control the dopant diffusion depth and reduce light absorption losses while maintaining excellent passivation effects has become a key technical challenge in improving the performance of TOPCon solar cells. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a doping method for a passivation layer of a TOPCon solar cell, so as to solve the problems of excessive diffusion of dopants, poor passivation effect and significant Auger recombination effect existing in the conventional preparation method in the prior art. The above problems in traditional TOPCon solar cells lead to limited improvement in open circuit voltage (Voc) and overall cell efficiency, thus affecting the performance of the cell and large-scale industrial application.

[0007] The present invention provides a doping method for a TOPCon solar cell passivation layer, comprising the following steps: S1: placing the silicon wafer after texturing in a diffusion furnace for boron diffusion, preparing a boron-doped emitter region on the front surface of the silicon wafer, so that a PN junction is formed on the front surface of the silicon wafer; S2: growing a layer of SiO on the front and back surfaces of the silicon wafer processed in step S1 x Tunneling oxide layer; S3: The SiO x Depositing an undoped amorphous intrinsic polysilicon passivation layer on the tunnel oxide layer; S4: A 30-100 nm thick silicon dioxide film is further deposited on the polysilicon passivation layer before and after the silicon wafer in step S3 by plasma enhanced chemical vapor deposition or low pressure chemical vapor deposition as a doping buffer layer; the buffer layer can effectively limit the diffusion distance of the dopant in the polysilicon passivation layer during the subsequent heat treatment process.

[0008] S5: performing boron diffusion on the doped buffer layer on the front side of the silicon wafer to complete P-type doping and crystallization of the front polysilicon passivation layer; S6: Phosphorus diffusion is performed on the silicon dioxide buffer layer on the back of the silicon wafer to complete N-type doping and crystallization of the back polysilicon passivation layer; S7: removing the silicon dioxide doped buffer layer on the surface of the silicon wafer after the treatment in step S6, so that the doped polysilicon passivation layer is exposed on the surface for subsequent battery preparation. An aluminum oxide passivation layer is deposited on the front of the silicon wafer, and a silicon nitride anti-reflection layer is deposited on the surface of the aluminum oxide passivation layer and the surface of the N-type doped polysilicon passivation layer;

[0009] S8: Perform subsequent preparation to obtain a TOPCon solar cell having a doping layer and a passivation layer.

[0010] Compared with the prior art, the doping method of the TOPCon solar cell passivation layer in the present application has the following advantages: 1. Precise control of doping diffusion: The traditional doping process in the prior art is changed to a structural design of a silicon dioxide doped buffer layer, which effectively inhibits excessive diffusion of dopants and avoids the Auger recombination effect caused by the diffusion of dopants into the silicon matrix in the traditional technology. By precisely controlling the diffusion depth of dopants in the polysilicon passivation layer, excessive diffusion of doping elements into the silicon matrix is ​​avoided. The doping method of the present invention significantly reduces the recombination loss of carriers and increases the open circuit voltage (Voc), thereby improving the overall efficiency of the battery.

[0011] Improvement of overall efficiency: The doped buffer layer structure design enables gradient passivation of the polysilicon passivation layer, avoids Auger recombination on the surface of the silicon substrate, and improves the open circuit voltage, short circuit current and ultimate photoelectric conversion efficiency of the solar cell. The doping method of the present invention can increase the photoelectric conversion efficiency (PCE) of the cell by more than 0.1%, and show better stability and cost-effectiveness in industrial production.

[0012] In general, the present invention proposes a method for introducing a silicon dioxide diffusion buffer layer on a polysilicon passivation layer. The silicon dioxide (SiO2) buffer layer can effectively limit the diffusion depth of dopants under high temperature conditions, thereby reducing the Auger recombination effect on the surface of the battery while maintaining a good interface passivation effect. The doping method of the present invention deposits a certain thickness of SiO2 doped buffer layer on the surface of the polysilicon passivation layer, and the diffusion of dopants in the polysilicon passivation layer can be controlled within a certain gradient range, thereby avoiding excessive diffusion of dopants in the polysilicon passivation layer into the silicon substrate and reducing interface recombination. This method can not only significantly increase the open circuit voltage, but also reduce the light absorption loss of the material, thereby improving the overall efficiency of solar cells.

[0013] In a possible implementation, in the step S3, the amorphous intrinsic polysilicon passivation layer is prepared by low pressure chemical vapor deposition or plasma enhanced chemical vapor deposition, and the thickness of the amorphous intrinsic polysilicon passivation layer is 50-120 nm.

[0014] Compared with the existing technology, the above technical solution can enhance the passivation effect on the silicon wafer surface. The amorphous intrinsic polysilicon passivation layer can effectively isolate the physical contact between the silicon wafer and the outside world and reduce the recombination of carriers on the surface; at the same time, through low-pressure chemical vapor deposition (LPCVD) or plasma enhanced chemical vapor deposition (PECVD), the thickness of the passivation layer is controlled at 50-120 nm, which effectively balances the passivation effect and light absorption performance; the passivation layer reduces interface recombination and controls light absorption, significantly improving the photoelectric conversion efficiency of the battery.

[0015] In a possible implementation, in the step S4, the silicon dioxide film is prepared by plasma enhanced chemical vapor deposition or low pressure chemical vapor deposition, and in the step S4, the thickness of the silicon dioxide film is 30-100 nm.

[0016] Compared with the existing technology, the deposition using the above technical solution can effectively control the diffusion depth of the dopant; the silicon dioxide film serves as a doping buffer layer with a thickness in the range of 50-100 nm, which can limit the diffusion depth of the dopant during the high-temperature diffusion process and prevent it from excessively diffusing into the silicon substrate; by limiting the diffusion depth, the Auger recombination effect is avoided, the carrier recombination loss is reduced, the open circuit voltage is significantly improved, and the overall conversion efficiency of the battery is improved.

[0017] In a possible implementation, in the step S5, the temperature of the boron diffusion is 900-1000° C., and the diffusion time is 10-60 minutes; in the step S6, the temperature of the phosphorus diffusion is 800-900° C., and the diffusion time is 10-60 minutes.

[0018] Compared with the existing technology, the temperature of boron diffusion can control the depth and uniformity of boron diffusion by optimizing the temperature, which can not only complete the doping of the polysilicon passivation layer and ensure that the doped layer has a good passivation effect, but also avoid excessive diffusion of dopants into the silicon substrate, thereby reducing carrier recombination on the surface of the silicon substrate; by precisely controlling the diffusion temperature, the diffusion process is more controllable, the Auger recombination effect is reduced, the electrical performance of the battery is improved, and the output performance and efficiency of the battery are significantly enhanced.

[0019] In a possible implementation, in the step S7, the silicon dioxide doped buffer layer is removed by using an HF solution.

[0020] Compared with the prior art, the above technical solution can remove the doped buffer layer cleanly through chemical treatment, ensuring effective contact between the passivation layer and the electrode. The doped buffer layer is effectively removed by HF solution to avoid affecting the subsequent deposition layer.

[0021] The technical problem to be solved by the present invention is to provide a TOPCon solar cell with a doping layer and a passivation layer to solve the problems of excessive diffusion of dopants, significant Auger recombination effect and insufficient passivation effect in the passivation layer of conventional TOPCon solar cells in the prior art.

[0022] In order to solve the above technical problems, the present invention provides a TOPCon solar cell having a doping layer and a passivation layer, wherein the TOPCon solar cell is prepared by the above doping method, and the TOPCon solar cell comprises: N-type silicon wafer, as substrate; A boron emitter, a tunneling oxide layer, and a boron-doped polysilicon passivation layer are arranged on the upper surface of the N-type silicon wafer, and a tunneling oxide layer and a phosphorus-doped polysilicon passivation layer are arranged on the lower surface; On one side of the boron-doped polysilicon passivation layer, an aluminum oxide passivation layer and a silicon nitride anti-reflection layer are deposited in sequence; A silicon nitride anti-reflection layer is deposited on one side of the phosphorus-doped polysilicon passivation layer; Metal electrodes are also arranged on the front and back of the solar cell respectively for connecting to an external circuit.

[0023] Compared with the prior art, the present invention discloses a doping method for a TOPCon solar cell passivation layer and a TOPCon cell, which have the following advantages: the TOPCo cell with a doping layer and a passivation layer of the present invention changes the traditional doping diffusion method in the prior art to a precisely controlled doping buffer layer design, which effectively solves the Auger recombination effect and improves the open circuit voltage and short circuit current; through the optimized passivation structure design, the interface passivation effect is enhanced, the recombination loss of carriers is reduced, and the overall performance of the cell is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the process of doping the polysilicon passivation layer with the silicon dioxide buffer layer in the present invention; Figure 2 A schematic diagram of removing the doped buffer layer after doping in the present invention; Figure 3 This is a schematic diagram of the final TOPCon battery structure in the present invention. DETAILED DESCRIPTION

[0025] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0026] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0027] In the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0028] The present invention provides a doping method for a TOPCon solar cell passivation layer, comprising the following steps: S1: The silicon wafer after texturing is placed in a diffusion furnace for boron diffusion, and a boron-doped emitter region is prepared on the front surface of the silicon wafer to form a PN junction on the front surface of the silicon wafer; specifically, the preparation of the silicon substrate: an N-type single crystal silicon wafer grown by the Czochralski method is used as a substrate, with a thickness of about 100-200 µm and a resistivity of 0.5-1.5Ω·cm. It is placed in a tank cleaning machine for alkaline corrosion, and a pyramid-shaped velvet texture is formed on the surface of the silicon wafer by alkaline texturing. The silicon wafer after texturing is placed in a diffusion furnace for boron diffusion, and a boron-doped emitter region is prepared on the front surface of the silicon wafer to form a PN junction on the front surface of the silicon wafer.

[0029] S2: growing a layer of SiO on the front and back surfaces of the silicon wafer processed in step S1 x Tunneling oxide layer; S3: The SiO x Depositing an undoped amorphous intrinsic polysilicon passivation layer on the tunnel oxide layer; S4: further depositing a 30-100 nm thick silicon dioxide film as a doping buffer layer on the front and rear polysilicon passivation layers of the silicon wafer in step S3 by plasma enhanced chemical vapor deposition or low pressure chemical vapor deposition; S5: performing boron diffusion on the doped buffer layer on the front side of the silicon wafer to complete P-type doping and crystallization of the front polysilicon passivation layer; S6: Phosphorus diffusion is performed on the silicon dioxide buffer layer on the back of the silicon wafer to complete the N-type doping and crystallization of the back polysilicon passivation layer, such as Figure 1 As shown; S7: removing the silicon dioxide doped buffer layer on the surface of the silicon wafer after the treatment in step S6, so that the doped polysilicon passivation layer is exposed on the surface. Figure 2 As shown, an aluminum oxide passivation layer is deposited on the front side of the silicon wafer, and a silicon nitride anti-reflection layer is deposited on the surface of the aluminum oxide passivation layer and the surface of the N-type doped polysilicon passivation layer; S8: Perform subsequent preparation, such as Figure 3 As shown, a TOPCon solar cell with a doping layer and a passivation layer is obtained.

[0030] In summary, the above technical solution includes the following steps: The present invention proposes a method for introducing a silicon dioxide diffusion buffer layer on a polysilicon passivation layer. Silicon dioxide (SiO2), as a widely used insulating material, can effectively limit the diffusion depth of dopants under high temperature conditions, thereby reducing the Auger recombination effect while maintaining a good interface passivation effect. By depositing a certain thickness of SiO2 doped buffer layer on the surface of the polysilicon passivation layer, the diffusion of dopants in the polysilicon passivation layer can be controlled within a certain gradient range, thereby avoiding excessive penetration of dopants in the polysilicon passivation layer into the silicon substrate and reducing interface recombination. This method can not only significantly increase the open circuit voltage, but also reduce the light absorption loss of the material, thereby improving the overall efficiency of the solar cell.

[0031] Prepare the silicon substrate: Use N-type single crystal silicon wafer as the substrate and form a pyramid-shaped velvet texture through alkaline corrosion to improve the light absorption rate and anti-reflection effect of the silicon wafer.

[0032] Growth of tunnel oxide layer: a layer of SiO is grown on the front and back surfaces of the processed silicon wafer. x Tunneling oxide layer, which effectively isolates the silicon substrate and the electrode, reduces non-radiative recombination caused by interface defects and enhances the passivation effect of the battery.

[0033] Deposition of amorphous polysilicon passivation layer: Deposit an undoped amorphous intrinsic polysilicon passivation layer on the tunneling oxide layer to enhance interface passivation and carrier selective transport and reduce carrier recombination losses.

[0034] Introduction of doped buffer layer: A 30-100 nm thick silicon dioxide (SiO2) film is further deposited on the intrinsic polysilicon passivation layer on the front and back surfaces by plasma enhanced chemical vapor deposition (PECVD) or low pressure chemical vapor deposition (LPCVD) process as a doped buffer layer. This buffer layer can effectively limit the diffusion distance of dopants in the polysilicon passivation layer during the subsequent heat treatment process.

[0035] Doping of polysilicon passivation layer: Boron is diffused on the silicon dioxide buffer layer on the front side of the silicon wafer at a temperature of 900-1000°C and a diffusion time of 10-60 minutes, so that the front polysilicon passivation layer completes P-type doping and achieves crystallization. Similarly, phosphorus is diffused on the silicon dioxide buffer layer on the back side of the silicon wafer at a temperature of 800-900°C and a diffusion time of 10-60 minutes, so that the back polysilicon passivation layer completes N-type doping and achieves crystallization.

[0036] Post-doping treatment: Use HF solution to remove the silicon dioxide buffer layer on the surface, so that the doped polysilicon passivation layer is exposed on the surface for subsequent battery preparation.

[0037] Subsequent preparation of the battery: Aluminum oxide passivation layer is deposited on the surface of the front doped polysilicon passivation layer using ALD technology, and silicon nitride layer is deposited on the front aluminum oxide layer surface and the back doped polysilicon surface using PECVD technology. Finally, the positive electrode and back electrode are screen printed, and sintering annealing and light injection are performed to obtain the TOPCon solar cell.

[0038] As a preferred solution, the N-type single crystal silicon wafer is grown by a Czochralski method, and the thickness of the N-type single crystal silicon wafer is 100-200 µm, and the resistivity is 0.5-1.5Ω•cm.

[0039] As a preferred solution, in step S2, the SiO x The tunnel oxide layer is prepared by thermal oxidation or chemical vapor deposition, and the SiO x The thickness of the tunnel oxide layer is 1.2-2nm.

[0040] As a preferred solution, in the step S3, the amorphous intrinsic polysilicon passivation layer is prepared by low pressure chemical vapor deposition or plasma enhanced chemical vapor deposition, and the thickness of the amorphous intrinsic polysilicon passivation layer is 50-120 nm.

[0041] As a preferred solution, in step S4, the silicon dioxide film is prepared by plasma enhanced chemical vapor deposition or low pressure chemical vapor deposition, and the thickness of the silicon dioxide film is 30-100 nm.

[0042] As a preferred solution, in step S5, the temperature of the boron diffusion is 900-1000° C., and the diffusion time is 10-60 minutes; in step S6, the temperature of the phosphorus diffusion is 800-900° C., and the diffusion time is 10-60 minutes.

[0043] As a preferred solution, in step S7, the aluminum oxide passivation layer is prepared by atomic layer deposition, and the silicon nitride anti-reflection layer is prepared by plasma enhanced chemical vapor deposition.

[0044] As a preferred solution, in the step S7, the doped buffer layer is removed by HF solution after the doping is completed.

[0045] As a preferred solution, in step S8, the subsequent preparation includes: screen printing of the positive electrode and the back electrode, sintering annealing and light injection.

[0046] The present invention also provides a TOPCon solar cell having a doping layer and a passivation layer. The TOPCon solar cell is prepared by the above-mentioned doping method, and its structural schematic diagram is shown as follows: Figure 3 As shown, the TOPCon solar cell comprises: N-type silicon wafer, as substrate; A boron emitter, a tunneling oxide layer, and a boron-doped polysilicon passivation layer are arranged on the upper surface of the N-type silicon wafer, and a tunneling oxide layer and a phosphorus-doped polysilicon passivation layer are arranged on the lower surface; On one side of the boron-doped polysilicon passivation layer, an aluminum oxide passivation layer and a silicon nitride anti-reflection layer are deposited in sequence; A silicon nitride anti-reflection layer is deposited on one side of the phosphorus-doped polysilicon passivation layer; Metal electrodes are also provided on the front and back sides respectively for connecting to an external circuit.

[0047] The following is further expanded in combination with the above data range to illustrate the feasibility of the technical solution of the present invention, as well as the expansion of the scope of the technical solution of the present invention, and provides comparative examples and embodiments of the present invention to further illustrate the technical effects of the present invention: Comparative Example The comparative example provides a TOPCon solar cell having a doping layer and a passivation layer and a doping method thereof. The structure of the TOPCon solar cell includes: An N-type silicon wafer is used as a substrate; a boron emitter, a tunneling oxide layer, a boron-doped polysilicon passivation layer, an aluminum oxide passivation layer and a silicon nitride anti-reflection layer are sequentially arranged on the upper surface of the N-type silicon wafer, and a tunneling oxide layer is sequentially arranged on the lower surface; a phosphorus-doped polysilicon passivation layer and a silicon nitride anti-reflection layer are also respectively provided with metal electrodes on the front and back sides for connecting to an external circuit.

[0048] The doping method comprises: S1: Preparation of silicon substrate An N-type single crystal silicon wafer with a thickness of 150 µm and a resistivity of 1.0 Ω·cm was selected and grown using the Czochralski method. The surface of the silicon wafer was treated by alkaline corrosion to form a pyramid-shaped velvet texture to enhance light absorption. The velvet-made silicon wafer was placed in a diffusion furnace for boron diffusion, and a boron-doped emitter region was prepared on the front surface of the silicon wafer to form a PN junction on the front surface of the silicon wafer.

[0049] S2: Formation of tunnel oxide layer On both sides of the silicon wafer, 1.5nm thick SiO2 was grown by dry oxygen oxidation. x Tunneling through the oxide layer.

[0050] S3: Deposition of polysilicon passivation layer Using low pressure chemical vapor deposition (LPCVD) method, SiO x A non-doped amorphous intrinsic polysilicon passivation layer with a thickness of 120 nm is deposited on the tunnel oxide layer.

[0051] S4: P-type doping: Front doping: Boron is diffused into the front polysilicon passivation layer at 900°C for 10 minutes to crystallize the polysilicon passivation layer and complete P-type doping.

[0052] S5: N-type doping: Back side doping: Phosphorus is diffused into the back side polysilicon passivation layer at 800°C for 10 minutes to form an N-type doped polysilicon passivation layer.

[0053] S6: Deposition of passivation and anti-reflection layers The aluminum oxide layer is deposited on the front side by atomic layer deposition (ALD). The silicon nitride anti-reflection layer is deposited on the surface of the front aluminum oxide layer and the surface of the back N-type polysilicon passivation layer by PECVD.

[0054] S7: Subsequent preparation The positive electrode and the back electrode were screen printed, sintered and annealed, and the final preparation of the battery was completed by light injection. The photoelectric conversion efficiency of the battery was tested and the efficiency was measured to be 25.12%.

[0055] Example 1 This embodiment provides a TOPCon solar cell having a doping layer and a passivation layer and a doping method thereof. The structure of the TOPCon solar cell includes: An N-type silicon wafer is used as a substrate; a boron emitter, a tunneling oxide layer, a boron-doped polysilicon passivation layer, an aluminum oxide passivation layer and a silicon nitride anti-reflection layer are sequentially arranged on the upper surface of the N-type silicon wafer, and a tunneling oxide layer is sequentially arranged on the lower surface; a phosphorus-doped polysilicon passivation layer and a silicon nitride anti-reflection layer are also respectively provided with metal electrodes on the front and back sides for connecting to an external circuit.

[0056] The doping method comprises: S1: Preparation of silicon substrate An N-type single crystal silicon wafer with a thickness of 120 µm and a resistivity of 1.0 Ω·cm was selected and grown using the Czochralski method. The surface of the silicon wafer was treated by alkaline corrosion to form a pyramid-shaped velvet texture to enhance light absorption. The velvet-made silicon wafer was placed in a diffusion furnace for boron diffusion, and a boron-doped emitter region was prepared on the front surface of the silicon wafer to form a PN junction on the front surface of the silicon wafer.

[0057] S2: Formation of tunnel oxide layer On both sides of the silicon wafer, 1.2nm thick SiO2 was grown by dry oxygen oxidation. x Tunneling through the oxide layer.

[0058] S3: Deposition of polysilicon passivation layer Using low pressure chemical vapor deposition (LPCVD) method, SiO x A non-doped amorphous intrinsic polysilicon passivation layer with a thickness of 50 nm is deposited on the tunneling oxide layer.

[0059] S4: Introduction of doped buffer layer On the polysilicon passivation layer, a 30nm thick silicon dioxide (SiO2) film is deposited by plasma enhanced chemical vapor deposition (PECVD) technology as a doping buffer layer.

[0060] S5: P-type doping: Front doping: Boron is diffused into the front SiO2 buffer layer at 900°C for 10 minutes to crystallize the polysilicon passivation layer and complete P-type doping.

[0061] S6: N-type doping: Reverse doping: Phosphorus is diffused into the SiO2 buffer layer on the back side at 800°C for 10 minutes to form an N-type doped polysilicon passivation layer.

[0062] S6: Surface treatment and passivation layer deposition After removing the SiO2-doped buffer layer on the surface, an aluminum oxide layer is deposited on the front side by atomic layer deposition (ALD). On the surface of the aluminum oxide layer and the surface of the N-type polysilicon passivation layer, a silicon nitride anti-reflection layer is deposited by PECVD.

[0063] S7: Subsequent preparation The positive electrode and the back electrode were screen printed, sintered and annealed, and the final preparation of the battery was completed by light injection. The photoelectric conversion efficiency of the battery was tested and the efficiency was measured to be 25.35%, which was 0.23% higher than the control ratio.

[0064] Example 2 This embodiment provides a TOPCon solar cell having a doping layer and a passivation layer and a doping method thereof. The structure of the TOPCon solar cell includes: N-type silicon wafer, as substrate; A boron emitter, a tunneling oxide layer, a boron-doped polysilicon passivation layer, an aluminum oxide passivation layer and a silicon nitride anti-reflection layer are sequentially arranged on the upper surface of the N-type silicon wafer, and a tunneling oxide layer is sequentially arranged on the lower surface; the phosphorus-doped polysilicon passivation layer and the silicon nitride anti-reflection layer are also provided with metal electrodes on the front and back sides respectively for connecting to an external circuit.

[0065] The doping method comprises: S1: Preparation of silicon substrate An N-type single crystal silicon wafer with a thickness of 150 µm and a resistivity of 1.2 Ω·cm was selected and grown by the Czochralski method. Alkaline etching was performed to form a pyramid-shaped velvet texture. The velvet-made silicon wafer was placed in a diffusion furnace for boron diffusion, and a boron-doped emitter region was prepared on the front surface of the silicon wafer, so that a PN junction was formed on the front surface of the silicon wafer.

[0066] S2: Formation of tunnel oxide layer Using wet oxygen oxidation method, SiO2 with a thickness of 1.6nm is grown on both sides of the silicon wafer. x Tunneling through the oxide layer.

[0067] S3: Deposition of polysilicon passivation layer Plasma enhanced chemical vapor deposition (PECVD) was used to deposit SiO x An undoped amorphous intrinsic polysilicon passivation layer with a thickness of 85 nm is deposited on the tunnel oxide layer.

[0068] S4: Introduction of doped buffer layer A SiO2 film with a thickness of 65 nm is deposited on the polysilicon passivation layer using a low pressure chemical vapor deposition (LPCVD) method as a doped buffer layer.

[0069] S5: P-type doping: Front doping: Boron is diffused into the front SiO2 buffer layer at 950°C for 35 minutes to complete P-type doping.

[0070] S6: N-type doping: Reverse doping: Phosphorus is diffused into the SiO2 buffer layer on the back side at 850°C for 35 minutes to form an N-type doped polysilicon passivation layer.

[0071] S7: Surface treatment and passivation layer deposition After removing the SiO2-doped buffer layer on the surface, an aluminum oxide passivation layer is deposited on the front side by atomic layer deposition (ALD). A silicon nitride anti-reflection layer is deposited on the surface of the aluminum oxide passivation layer and the surface of the N-type polysilicon passivation layer by PECVD.

[0072] S8: Subsequent preparation The cell is prepared by screen printing the positive electrode and the back electrode, performing sintering annealing, and light injection.

[0073] The photoelectric conversion efficiency of the battery was tested and the efficiency was measured to be 25.38%, which is 0.26% higher than the control ratio.

[0074] Example 3 This embodiment provides a TOPCon solar cell having a doping layer and a passivation layer and a doping method thereof. The structure of the TOPCon solar cell includes: N-type silicon wafer, as substrate; A boron emitter, a tunneling oxide layer, a boron-doped polysilicon passivation layer, an aluminum oxide passivation layer and a silicon nitride anti-reflection layer are sequentially arranged on the upper surface of the N-type silicon wafer, and a tunneling oxide layer is sequentially arranged on the lower surface; the phosphorus-doped polysilicon passivation layer and the silicon nitride anti-reflection layer are also provided with metal electrodes on the front and back sides respectively for connecting to an external circuit.

[0075] The doping method comprises: S1: Preparation of silicon substrate An N-type single crystal silicon wafer with a thickness of 200 µm and a resistivity of 0.5 Ω·cm was selected and grown by a Czochralski method. Alkaline etching was performed to form a pyramid-shaped velvet texture. The velvet-made silicon wafer was placed in a diffusion furnace for boron diffusion, and a boron-doped emitter region was prepared on the front surface of the silicon wafer, so that a PN junction was formed on the front surface of the silicon wafer.

[0076] S2: Formation of tunnel oxide layer Using chemical vapor deposition (CVD) method, 2nm thick SiO2 is grown on both sides of the silicon wafer. x Tunneling through the oxide layer.

[0077] S3: Deposition of polysilicon passivation layer Using low pressure chemical vapor deposition (LPCVD) method, SiO x A non-doped amorphous intrinsic polysilicon passivation layer with a thickness of 120 nm is deposited on the tunnel oxide layer.

[0078] S4: Introduction of doped buffer layer Plasma enhanced chemical vapor deposition (PECVD) technology is used to deposit a 100nm thick silicon dioxide film on the polysilicon passivation layer as a doping buffer layer.

[0079] S5: P-type doping: Front doping: Boron is diffused into the front SiO2 buffer layer at 1000°C for 60 minutes to complete P-type doping.

[0080] S6: N-type doping: Reverse doping: Phosphorus is diffused into the SiO2 buffer layer on the back side at 900°C for 60 minutes to form an N-type doped polysilicon passivation layer.

[0081] S7: Surface treatment and passivation layer deposition After removing the SiO2-doped buffer layer on the surface, an aluminum oxide layer is deposited on the front side by atomic layer deposition (ALD). A silicon nitride anti-reflection layer is deposited on the surface of the aluminum oxide layer and the surface of the N-type doped polysilicon passivation layer by PECVD.

[0082] S8: Subsequent preparation The positive electrode and back electrode were screen printed, sintered and annealed, and the final preparation of the battery was completed by light injection. The photoelectric conversion efficiency of the battery was tested and the efficiency was measured to be 25.28%, which was 0.16% higher than the control ratio.

[0083] The above-mentioned doping method of the present application, by introducing a SiO2 doped buffer layer, effectively controls the diffusion of dopants, reduces the Auger recombination effect, significantly improves the open circuit voltage (Voc), reduces carrier recombination losses, and prolongs the carrier life, thereby improving the overall performance of the battery. In addition, the use of a thinner polysilicon layer optimizes the light absorption characteristics, improves the short-circuit current (Jsc) and the photoelectric conversion efficiency. Compared with the comparative example, the above-mentioned embodiments of the present invention all improve the photoelectric conversion efficiency of the battery by introducing a doped buffer layer, improve the doping uniformity and passivation effect, and ultimately make the battery efficiency significantly improved compared with the comparative example. At the same time, the improved passivation effect reduces the interface recombination, maintains a high carrier concentration, and further improves the output power of the battery. The entire process simplifies the manufacturing process and reduces the production cost, making the technical solution very suitable for large-scale production, significantly improving the overall efficiency and economy of TOPCon solar cells, and through testing, the photoelectric conversion efficiency (PCE) of the TOPCon crystalline silicon solar cell prepared by the above-mentioned doping method of the present invention is increased by more than 0.1%, which has made great technical progress compared with the prior art and solved the problems existing in the background technology.

[0084] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description, and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0085] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0086] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A doping method for a TOPCon solar cell passivation layer, characterized in that: The following steps are involved: S1: placing the silicon wafer after texturing in a diffusion furnace for boron diffusion, preparing a boron-doped emitter region on the front surface of the silicon wafer, so that a PN junction is formed on the front surface of the silicon wafer; placing the silicon wafer after texturing in a diffusion furnace for boron diffusion, preparing a boron-doped emitter region on the front surface of the silicon wafer, so that a PN junction is formed on the front surface of the silicon wafer; S2: growing a layer of SiO on the front and back surfaces of the silicon wafer processed in step S1 x Tunneling oxide layer; S3: The SiO x Depositing an undoped amorphous intrinsic polysilicon passivation layer on the tunnel oxide layer; S4: further depositing a 30-100 nm thick silicon dioxide film as a doping buffer layer on the front and rear polysilicon passivation layers of the silicon wafer in step S3 by plasma enhanced chemical vapor deposition or low pressure chemical vapor deposition; S5: performing boron diffusion on the doped buffer layer on the front side of the silicon wafer to complete P-type doping and crystallization of the front polysilicon passivation layer; S6: Phosphorus diffusion is performed on the doped buffer layer on the back side of the silicon wafer to complete N-type doping and crystallization of the back polysilicon passivation layer; S7: removing the doped buffer layer on the surface of the silicon wafer after the treatment in step S6, exposing the doped polysilicon passivation layer on the surface, depositing an aluminum oxide passivation layer on the front side of the silicon wafer, and depositing a silicon nitride anti-reflection layer on the surface of the aluminum oxide passivation layer and the surface of the N-type doped polysilicon passivation layer; S8: Perform subsequent preparation to obtain a TOPCon solar cell having a doping layer and a passivation layer.

2. The doping method for the passivation layer of a TOPCon solar cell according to claim 1, characterized in that: The silicon wafer is grown by a Czochralski method, and the thickness of the N-type single crystal silicon wafer is 100-200 µm, and the resistivity is 0.5-1.5Ω•cm.

3. The doping method for the passivation layer of a TOPCon solar cell according to claim 1, characterized in that: In the step S2, the SiO x The tunnel oxide layer is prepared by thermal oxidation or chemical vapor deposition, and the SiO x The thickness of the tunnel oxide layer is 1.2-2nm.

4. The doping method for the passivation layer of a TOPCon solar cell according to claim 1, characterized in that: In the step S3, the amorphous intrinsic polysilicon passivation layer is prepared by low pressure chemical vapor deposition or plasma enhanced chemical vapor deposition, and the thickness of the amorphous intrinsic polysilicon passivation layer is 50-120 nm.

5. The doping method for the passivation layer of a TOPCon solar cell according to claim 1, characterized in that: In the step S4, the thickness of the silicon dioxide film is 30-100 nm.

6. The doping method for the passivation layer of a TOPCon solar cell according to claim 1, characterized in that: In the step S5, the temperature of the boron diffusion is 900-1000° C., and the diffusion time is 10-60 minutes; in the step S6, the temperature of the phosphorus diffusion is 800-900° C., and the diffusion time is 10-60 minutes.

7. The doping method for the passivation layer of a TOPCon solar cell according to claim 1, characterized in that: In the step S7, the aluminum oxide passivation layer is prepared by atomic layer deposition, and the silicon nitride anti-reflection layer is prepared by plasma enhanced chemical vapor deposition.

8. The doping method for the passivation layer of a TOPCon solar cell according to claim 1, characterized in that: In the step S7, the doped buffer layer is removed by using an HF solution.

9. The doping method for the passivation layer of a TOPCon solar cell according to claim 1, characterized in that: In the step S8, the subsequent preparation includes: screen printing of the positive electrode and the back electrode, sintering annealing and light injection.

10. A TOPCon battery, characterized in that: The TOPCon solar cell is obtained by processing by any one of the doping methods of claims 1 to 9, and the TOPCon solar cell comprises: N-type silicon wafer, as substrate; A boron emitter, a tunneling oxide layer, and a boron-doped polysilicon passivation layer are sequentially arranged on the upper surface of the N-type silicon wafer, and a tunneling oxide layer and a phosphorus-doped polysilicon passivation layer are sequentially arranged on the lower surface; On one side of the boron-doped polysilicon passivation layer, an aluminum oxide passivation layer and a silicon nitride anti-reflection layer are deposited in sequence; A silicon nitride anti-reflection layer is deposited on one side of the phosphorus-doped polysilicon passivation layer; Metal electrodes are also provided on the front and back of the solar cell for connecting to an external circuit.

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