Solar cell and preparation method thereof

Abstract

The invention provides a solar cell and a preparation method thereof. The method for preparing the solar cell comprises the following steps: forming a tin dioxide thin film on one side of the front surface of a silicon substrate; performing hydrogen plasma treatment on the tin dioxide thin film; and after the hydrogen plasma treatment, annealing treatment is carried out on the silicon substrate on which the tin dioxide thin film is formed, and the annealing treatment is carried out in a nitrogen trifluoride-containing gas environment. Therefore, the conductivity of the tin dioxide thin film on one side of the front surface of the silicon substrate can be improved, and the performance of the solar cell can be improved.

Description

Technical Field

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

[0002] In recent years, silicon HJT (heterojunction) solar cell technology has developed rapidly, attracting great attention from the industry. At present, the conversion efficiency of heterojunction solar cells has reached a world efficiency record of 26.81%. Compared with PERC and TOPCon cells, HJT cells have higher conversion efficiency, but also higher costs. High cost is one of the important reasons hindering the industrialization of HJT cells. The TCO of high-efficiency HJT cells is usually based on In 2 O 3 Developed for the substrate, In, as a rare metal element, has unstable production and its price is greatly affected by the international rare metal price. Indium-free TCO can avoid these factors and provide a basic guarantee for the industrialization of HJT batteries. In order to reduce the cost of HJT batteries, developing indium-free TCO (transparent conductive oxide) is one of the necessary routes.

[0003] However, the current indium-free TCO has poor conductivity and still needs to be improved. Summary of the invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0005] Currently, the available indium-free TCO is mostly SnO 2 , ZnO as the matrix, these indium-free TCOs all have poor electrical properties. Their conductivity is worse than that of indium-containing TCOs, and they cannot achieve a state of optical and electrical performance balance. Specifically, ZnO-based TCOs face both reliability issues and poor electrical performance; SnO 2 The TCO of the substrate has poor electrical properties. At the same time, due to the low carrier concentration, the contact between TCO and the gate line is poor, which will increase the contact resistance. 2 When used as a transparent conductive oxide layer in HJT cells, the FF (fill factor) of the cell is low, resulting in reduced conversion efficiency. 2 The properties of the material itself, SnO 2 It grows in the form of columnar crystals, and the deposition temperature of HJT battery thin films is usually not higher than 200 degrees. These factors lead to SnO 2 The film has small grains and many grain boundary defects, which affect the mobility of carriers. SnO is deposited at a lower temperature 2 At the same time, some SnO may also be generated, and the presence of SnO will reduce the upper limit of carrier concentration, making the contact between the TCO film layer and the gate line worse.

[0006] The inventors found that by subjecting the tin dioxide film to hydrogen plasma treatment, the conductivity of the tin dioxide film can be improved to a certain extent. After that, annealing in an environment containing nitrogen trifluoride gas can make the grains on the surface of the tin dioxide film larger, reduce grain boundary defects, and increase the mobility of carriers, thereby further improving the conductivity of the tin dioxide film.

[0007] The present invention aims to alleviate or solve at least one of the above-mentioned problems to at least some extent.

[0008] In one aspect of the present invention, a method for preparing a solar cell is provided. In some embodiments of the present invention, the method for preparing a solar cell includes: forming a tin dioxide film on the front side of a silicon substrate; subjecting the tin dioxide film to a hydrogen plasma treatment; after the hydrogen plasma treatment, subjecting the silicon substrate on which the tin dioxide film is formed to an annealing treatment, wherein the annealing treatment is performed in a gas environment containing nitrogen trifluoride. Thus, the conductivity of the tin dioxide film on the front side of the silicon substrate can be improved, thereby facilitating the improvement of the performance of the solar cell.

[0009] In some embodiments of the present invention, the temperature of the annealing treatment is 200° C.-250° C. and / or the time of the annealing treatment is 30 min-45 min. This is beneficial to further improve the conductivity of the tin dioxide film.

[0010] In some embodiments of the present invention, the annealing process is performed in a gas environment containing nitrogen trifluoride and nitrogen, so that the nitrogen trifluoride gas can be diluted with nitrogen to reduce the concentration of nitrogen trifluoride, thereby preventing adverse effects on operators and / or equipment.

[0011] In some embodiments of the present invention, during the annealing process, the flow ratio of nitrogen to nitrogen trifluoride is (5-15): 1. Thus, the safety of personnel during the operation can be better guaranteed, and adverse effects on equipment or the operating environment can be better avoided.

[0012] In some embodiments of the present invention, the tin dioxide film is formed by a magnetron sputtering method. During the deposition of the tin dioxide film, the power of the magnetron sputtering is 4kW-8kW, the deposition temperature is 0-200°C, and the chamber pressure is 0.3Pa-0.8Pa. This is conducive to forming a uniform film layer, thereby facilitating the improvement of the performance of the tin dioxide film.

[0013] In some embodiments of the present invention, the hydrogen plasma treatment satisfies at least one of the following conditions: the power is 500W-1000W; 2The flow rate is 1000sccm-4000sccm; the treatment time is 3min-10min. Therefore, by subjecting the tin dioxide film to hydrogen plasma treatment under the above conditions, the doping concentration on the surface of the tin dioxide film can be increased, thereby increasing the carrier concentration.

[0014] In some embodiments of the present invention, before forming the tin dioxide thin film, the method for preparing a solar cell also includes: forming a front amorphous silicon intrinsic layer and a back amorphous silicon intrinsic layer on the front side and the back side of the silicon substrate, respectively; forming an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer on the side of the front amorphous silicon intrinsic layer away from the silicon substrate, and forming a P-type amorphous silicon doped layer or a P-type microcrystalline silicon doped layer on the side of the back amorphous silicon intrinsic layer away from the silicon substrate; wherein the tin dioxide thin film is formed on the side of the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer away from the silicon substrate.

[0015] In some embodiments of the present invention, after or before the tin dioxide thin film is formed on the side of the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer away from the silicon substrate, a transparent oxide thin film is formed on the side of the P-type amorphous silicon doped layer or the P-type microcrystalline silicon doped layer away from the silicon substrate, and the material of the transparent oxide thin film includes at least one of tin dioxide and zinc oxide.

[0016] In some embodiments of the present invention, before the annealing treatment, the method for preparing a solar cell further includes subjecting the transparent oxide film to a hydrogen plasma treatment, thereby facilitating further improving the performance of the solar cell.

[0017] In another aspect of the present invention, the present invention provides a solar cell. In some embodiments of the present invention, the solar cell is prepared using the method described above. As a result, the tin dioxide film on the front side of the solar cell has good conductivity and is in good contact with the grid line on the front side, which is beneficial to improving the photoelectric conversion efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0019] Figure 1 A flow chart of a method for preparing a solar cell according to one embodiment of the present invention is shown;

[0020] Figure 2 A schematic structural diagram of a solar cell according to an embodiment of the present invention is shown.

[0021] Description of reference numerals:

[0022] 1: Silicon substrate; 2: Front amorphous silicon intrinsic layer; 3: Back amorphous silicon intrinsic layer; 4: N-type microcrystalline silicon doped layer; 5: P-type microcrystalline silicon doped layer; 6: Tin dioxide film; 7: Transparent oxide film; 8: Front gate line; 9: Back gate line. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0024] In one aspect of the present invention, the present invention provides a method for preparing a solar cell. In some embodiments of the present invention, reference is made to Figure 1 , the method for preparing a solar cell may include the following steps:

[0025] S100: forming a tin dioxide thin film on the front side of the silicon substrate.

[0026] In some embodiments of the present invention, the silicon substrate may be an N-type single crystal silicon wafer, wherein the thickness of the silicon substrate may be 100 μm-150 μm, and the resistivity of the silicon substrate may be 0.5 Ω·cm-3 Ω·cm.

[0027] Before forming a film layer on the silicon substrate, the silicon substrate may be cleaned and textured to form a textured surface, such as Figure 2 As shown, both the front and back sides of the silicon substrate 1 have pyramid structures.

[0028] It should be noted that the front and back sides of the silicon substrate are two opposite surfaces, wherein the front side refers to the side facing the solar cell for receiving light, and the back side refers to the side facing away from the solar cell for receiving light.

[0029] In some embodiments of the present invention, the tin dioxide thin film can be prepared by physical vapor deposition (PVD).

[0030] In some specific embodiments of the present invention, the tin dioxide film can be formed by magnetron sputtering. During the deposition of the tin dioxide film, the power used by the magnetron sputtering can be 4kW-8kW, the deposition temperature can be 0-200°C, and the chamber pressure can be 0.3Pa-0.8Pa. For example, the power used by the magnetron sputtering can be 4kW, 5kW, 6kW, 7kW, 8kW, etc., the deposition temperature can be 0°C, 20°C, 50°C, 100°C, 150°C, 200°C, etc., and the chamber pressure can be 0.3Pa, 0.5Pa, 0.6Pa, 0.7Pa, 0.8Pa, etc. This is conducive to forming a tin dioxide film with uniform thickness, uniform composition, compactness and strong adhesion, thereby further improving the performance of solar cells.

[0031] S200: performing hydrogen plasma treatment on the tin dioxide film.

[0032] After forming the tin dioxide film on the front side of the silicon substrate, the tin dioxide film can be treated with hydrogen plasma. By treating the tin dioxide film with hydrogen plasma, the Sn-O bonds on the surface of the tin dioxide film can be broken, so that Sn-OH is formed on the surface, thereby increasing the surface doping concentration and further increasing the carrier concentration.

[0033] In some embodiments of the present invention, when a tin dioxide film is prepared by a magnetron sputtering method, Ar can be used as a glow discharge working gas. In other embodiments of the present invention, in addition to Ar gas, O 2 , H 2 , H 2 One or more gases such as O.

[0034] In some embodiments of the present invention, the power used in the hydrogen plasma treatment may be 500W-1000W. For example, the power used in the hydrogen plasma treatment may be 500W, 600W, 700W, 800W, 900W, 1000W, etc.

[0035] In some embodiments of the present invention, during the hydrogen plasma treatment, H 2 The flow rate can be 1000sccm-4000sccm, for example, H 2 The flow rate can be 1000sccm, 1500sccm, 2000sccm, 2500sccm, 3000sccm, 3500sccm, 4000sccm, etc.

[0036] In some embodiments of the present invention, the hydrogen plasma treatment time may be 3 min-10 min, for example, the hydrogen plasma treatment time may be 3 min, 5 min, 7 min, 8 min, 10 min, etc. Within the above time, not only the doping concentration on the surface of the tin dioxide film can be increased, but also excessive Sn-O bond breakage to form Sn-Sn bonds can be avoided, thereby better avoiding adverse effects on the optical properties of the tin dioxide film.

[0037] Under the above conditions, hydrogen plasma treatment of the tin dioxide film is beneficial to increasing the doping concentration on the surface of the tin dioxide film, increasing the carrier concentration, and further improving the conductivity of the tin dioxide film.

[0038] In some embodiments of the present invention, the thickness of the tin dioxide film may be 90 nm-120 nm. For example, the thickness of the tin dioxide film may be 90 nm, 95 nm, 100 nm, 110 nm, 120 nm, etc.

[0039] S300: performing annealing treatment in a gas environment containing nitrogen trifluoride.

[0040] After the tin dioxide film is subjected to hydrogen plasma treatment, the silicon substrate on which the tin dioxide film is formed may be subjected to annealing treatment, wherein the annealing treatment is performed in a nitrogen trifluoride (NF 3 ) gas environment. As a result, the radius of fluorine ions is small and the electronegativity is strong. 3 Annealing treatment in a gas environment can allow fluorine ions to replace SnO 2 The oxygen ions on the surface of the film can further increase the doping concentration on the surface of the tin dioxide film, increase the surface carrier concentration, and thus reduce the contact resistance between the tin dioxide film and the front gate line; in addition, the bond length of the Sn-F bond is smaller than the bond length of the Sn-O bond. Under the action of the annealing temperature, the grain boundary will become smaller, the surface grain regrowth will be promoted, the surface grains will become larger, the grain boundary will be optimized, and the grain boundary defects will be reduced, thereby increasing the carrier mobility and improving the conductivity of the film.

[0041] In some embodiments of the present invention, the annealing temperature may be 200°C-250°C, for example, the annealing temperature may be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc. Annealing at the above temperature may more effectively promote the regrowth of grains on the surface of the tin dioxide film, optimize the grain boundaries, enlarge the grains, reduce the grain boundary defects, thereby increasing the carrier mobility, and further improving the conductive properties of the tin dioxide film.

[0042] In some embodiments of the present invention, the annealing time may be 30 min-45 min, for example, the annealing time may be 30 min, 32 min, 35 min, 37 min, 40 min, 45 min, etc. Thus, the grain growth on the surface of the tin dioxide film can be effectively promoted, and the grain boundary defects can be reduced, which is more conducive to improving the conductive properties of the tin dioxide film.

[0043] In some embodiments of the present invention, the annealing process is performed in a gas environment containing nitrogen trifluoride and nitrogen. Therefore, nitrogen trifluoride has a certain toxicity and the nitrogen trifluoride gas can be diluted by nitrogen to better ensure the safety of operators and the operating environment (including equipment).

[0044] In some specific embodiments of the present invention, during the annealing process, the flow ratio of nitrogen to nitrogen trifluoride may be (5-15):1, for example, the flow ratio of nitrogen to nitrogen trifluoride may be 5:1, 8:1, 10:1, 13:1, 15:1, etc. Thus, the nitrogen trifluoride can be better diluted and the toxicity of the mixed gas can be reduced, which is more conducive to ensuring the safety of personnel and the environment during the operation.

[0045] In some embodiments of the present invention, before forming the tin dioxide film, the method for preparing a solar cell may further include: forming a front amorphous silicon intrinsic layer and a back amorphous silicon intrinsic layer on the front side and the back side of the silicon substrate, respectively; forming an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer on the side of the front amorphous silicon intrinsic layer away from the silicon substrate, and forming a P-type amorphous silicon doped layer or a P-type microcrystalline silicon doped layer on the side of the back amorphous silicon intrinsic layer away from the silicon substrate; wherein the tin dioxide film is formed on the side of the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer away from the silicon substrate.

[0046] In some embodiments of the present invention, reference Figure 2 , a front amorphous silicon intrinsic layer 2 can be formed on the front side of the silicon substrate 1 , and a back amorphous silicon intrinsic layer 3 can be formed on the back side of the silicon substrate 1 .

[0047] In some embodiments of the present invention, the front amorphous silicon intrinsic layer 2 and the back amorphous silicon intrinsic layer 3 may be deposited by PECVD (plasma enhanced chemical vapor deposition), wherein the required process gas may include SiH 4 In addition, H can also be added according to process requirements 2 , CO 2 , CH 4 、N 2 One or more gases such as O.

[0048] In some embodiments of the present invention, the front amorphous silicon intrinsic layer 2 and the back amorphous silicon intrinsic layer 3 are deposited by PECVD, the deposition temperature can be 160°C-200°C, and the deposition pressure can be 0.2mbar-2mbar. For example, the deposition temperature can be 160°C, 170°C, 180°C, 190°C, 200°C, etc., and the deposition pressure can be 0.2mbar, 0.5mbar, 1mbar, 1.5mbar, 2mbar, etc.

[0049] In some embodiments of the present invention, the thickness of the front amorphous silicon intrinsic layer 2 and the thickness of the back amorphous silicon intrinsic layer 3 can be 5nm-10nm independently. For example, the thickness of the amorphous silicon intrinsic layer on the front side or the back side of the silicon substrate can be 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, etc.

[0050] In some embodiments of the present invention, reference Figure 2 An N-type microcrystalline silicon doping layer 4 can be formed on the side of the front amorphous silicon intrinsic layer 2 away from the silicon substrate 1, and a P-type microcrystalline silicon doping layer 5 can be formed on the side of the back amorphous silicon intrinsic layer 3 away from the silicon substrate 1. Afterwards, a tin dioxide film 6 can be formed on the side of the N-type microcrystalline silicon doping layer 4 away from the silicon substrate 1.

[0051] In some embodiments of the present invention, an N-type microcrystalline silicon doping layer 4 can be deposited on the front side of the silicon substrate 1 by PECVD, and the required process gas includes SiH 4 and PH 3 In addition, H can be added as needed. 2 , CO 2 , CH 4 、N 2 One or more gases such as O.

[0052] In some embodiments of the present invention, an N-type microcrystalline silicon doping layer 4 is deposited on the front side of the silicon substrate 1 by PECVD, the deposition temperature may be 160°C-200°C, and the deposition pressure may be 0.5mbar-5mbar. For example, the deposition temperature may be 160°C, 170°C, 180°C, 190°C, 200°C, etc., and the deposition pressure may be 0.5mbar, 1mbar, 3mbar, 5mbar, etc.

[0053] In some embodiments of the present invention, the thickness of the N-type microcrystalline silicon doping layer 4 may be 5nm-20nm. For example, the thickness of the N-type microcrystalline silicon doping layer 4 may be 5nm, 8nm, 12nm, 15nm, 17nm, 20nm, etc.

[0054] In some embodiments of the present invention, a P-type microcrystalline silicon doping layer 5 may be deposited on the back side of the silicon substrate 1 by PECVD. The required process gases include B 2 H 6 , TMB (trimethylboron) or both and SiH 4 In addition, H can also be added according to process requirements 2 , CO 2 , CH 4 、N 2 One or more gases such as O.

[0055] In some embodiments of the present invention, a P-type microcrystalline silicon doping layer 5 is deposited on the back side of the silicon substrate 1 by PECVD, and the deposition temperature can be 160°C-200°C, and the deposition pressure can be 0.5mbar-5mbar. For example, the deposition temperature can be 160°C, 170°C, 180°C, 190°C, 200°C, etc., and the deposition pressure can be 0.5mbar, 1mbar, 1.5mbar, 3mbar, 3.5mbar, 5mbar, etc.

[0056] In some embodiments of the present invention, the thickness of the P-type microcrystalline silicon doping layer 5 may be 5 nm-30 nm. For example, the thickness of the P-type microcrystalline silicon doping layer 5 may be 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, etc.

[0057] In some embodiments of the present invention, after or before a tin dioxide film is formed on a side of an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer away from a silicon substrate, a transparent oxide film may be formed on a side of a P-type amorphous silicon doped layer or a P-type microcrystalline silicon doped layer away from a silicon substrate, wherein the material of the transparent oxide film may include at least one of tin dioxide and zinc oxide. In some embodiments, the material of the transparent oxide film may be tin dioxide or zinc oxide.

[0058] In some embodiments of the present invention, reference Figure 2 , a transparent oxide film 7 may be formed on the side of the P-type microcrystalline silicon doping layer 5 away from the silicon substrate 1 .

[0059] In some embodiments of the present invention, the transparent oxide film 7 may be made of tin dioxide and may be formed by a magnetron sputtering method, using Ar as a glow discharge working gas. In addition, O may be added according to process requirements. 2 , H 2 , H 2 O and other gases. In some embodiments, the transparent oxide film 7 is formed by a magnetron sputtering method, the power may be 4kW-8kW, the deposition temperature may be 0-200°C, and the chamber pressure may be 0.3Pa-0.8Pa.

[0060] In some embodiments of the present invention, the thickness of the transparent oxide film 7 may be 90 nm-120 nm. For example, the thickness of the transparent oxide film 7 may be 90 nm, 100 nm, 110 nm, 120 nm, etc.

[0061] In some embodiments of the present invention, before the annealing treatment, the method for preparing a solar cell may further include performing a hydrogen plasma treatment on the transparent oxide film 7. The hydrogen plasma treatment can increase the carrier concentration of the transparent oxide film. Combined with the subsequent annealing treatment, it is more conducive to improving the conductive properties of the transparent oxide film on the back side, thereby helping to further improve the performance of the solar cell.

[0062] In some embodiments of the present invention, the material of the transparent oxide film 7 can be tin dioxide. Before the annealing treatment, the transparent oxide film 7 is subjected to hydrogen plasma treatment to increase the carrier concentration. The subsequent annealing treatment can also reduce the grain boundary defects of the transparent oxide film 7 to a certain extent, thereby further improving the conductivity of the transparent oxide film.

[0063] In other embodiments, since there are many back-side grid lines, the overall conductivity can be improved by using the back-side grid lines. Therefore, the transparent oxide film 7 may not be subjected to hydrogen plasma treatment.

[0064] In some embodiments of the present invention, after the annealing treatment, the method for preparing a solar cell may further include the step of preparing a metal grid line. Figure 2 A front gate line 8 can be formed on the side of the tin dioxide film 6 away from the silicon substrate 1 , and a back gate line 9 can be formed on the side of the transparent oxide film 7 away from the silicon substrate 1 .

[0065] In some embodiments of the present invention, the metal gate lines on the front side and the back side of the silicon substrate may be prepared by screen printing, laser transfer or electroplating.

[0066] In some embodiments of the present invention, the material of the front gate line 8 and the back gate line 9 can independently include at least one of metal silver and metal copper. In some specific embodiments, the front gate line 8 and the back gate line 9 can both be silver electrodes or copper electrodes.

[0067] In general, hydrogen plasma treatment of the tin dioxide film on the front side of the silicon substrate can break the Sn-O bond on the surface of the tin dioxide, forming Sn-OH on the surface, thereby increasing the surface doping concentration and the carrier concentration; annealing in an environment containing nitrogen trifluoride gas can make fluorine ions replace SnO 2The oxygen ions on the surface of the film further increase the surface doping concentration and the surface carrier concentration, thereby reducing the contact resistance between the tin dioxide film and the front gate line. In addition, the bond length of the Sn-F bond is smaller than the bond length of the Sn-O bond. Under the action of the annealing temperature, the grain boundary can be reduced, the surface grains can be enlarged, and the grain boundary defects can be reduced, thereby increasing the carrier mobility and improving the conductive properties of the tin dioxide film.

[0068] In another aspect of the present invention, a solar cell is provided. In some embodiments of the present invention, the solar cell is prepared by the method described above. Thus, in the solar cell, the tin dioxide film on the front side of the silicon substrate has good conductivity, and the contact resistance between the film layer and the front grid line is small, which is conducive to improving the photoelectric conversion efficiency of the solar cell.

[0069] In some embodiments of the present invention, a solar cell may include a silicon substrate, a front amorphous silicon intrinsic layer, a back amorphous silicon intrinsic layer, an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer, a P-type amorphous silicon doped layer or a P-type microcrystalline silicon doped layer, a tin dioxide film, a transparent oxide film, a front gate line and a back gate line. Among them, the front and back sides of the silicon substrate can both be velvet surfaces, the front amorphous silicon intrinsic layer is located on the front side of the silicon substrate, the back amorphous silicon intrinsic layer is located on the back side of the silicon substrate, the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer is located on the side of the front amorphous silicon intrinsic layer away from the silicon substrate, the P-type amorphous silicon doped layer or the P-type microcrystalline silicon doped layer is located on the side of the back amorphous silicon intrinsic layer away from the silicon substrate, the tin dioxide film is located on the side of the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer away from the silicon substrate, the transparent oxide film is located on the side of the P-type amorphous silicon doped layer or the P-type microcrystalline silicon doped layer away from the silicon substrate, the front gate line is located on the side of the tin dioxide film away from the silicon substrate, and the back gate line is located on the side of the transparent oxide film away from the silicon substrate.

[0070] In some specific embodiments of the present invention, reference Figure 2 The solar cell may include a silicon substrate 1, a front amorphous silicon intrinsic layer 2, a back amorphous silicon intrinsic layer 3, an N-type microcrystalline silicon doping layer 4, a P-type microcrystalline silicon doping layer 5, a tin dioxide film 6, a transparent oxide film 7, a front gate line 8, and a back gate line 9. The material and thickness of each film layer in the solar cell have been described in detail above and will not be repeated here.

[0071] The present invention will be described below by specific examples, and it will be appreciated by those skilled in the art that the following specific examples are only for illustrative purposes, and do not limit the scope of the present invention in any way. In addition, in the following examples, unless otherwise specified, the materials and equipment used are all commercially available. If in the following examples, specific processing conditions and processing methods are not clearly described, then conditions and methods known in the art can be used to process.

[0072] Example 1

[0073] (1) An N-type single crystal silicon wafer is selected as a silicon substrate, and the N-type single crystal silicon wafer is cleaned and textured to obtain a silicon substrate with textured surfaces on both sides.

[0074] (2) PECVD is used to deposit amorphous silicon intrinsic layers on the front and back of the silicon substrate, with the process gas being SiH 4 The deposition temperature is 180°C, the deposition pressure is 1 mbar, and the thickness of the front amorphous silicon intrinsic layer and the back amorphous silicon intrinsic layer are both 10 nm.

[0075] (3) PECVD is used to deposit an N-type microcrystalline silicon doping layer on the side of the front amorphous silicon intrinsic layer away from the silicon substrate. The process gas is SiH 4 and PH 3 The deposition temperature is 190°C, the deposition pressure is 2 mbar, and the thickness of the N-type microcrystalline silicon doped layer is 15 nm.

[0076] (4) PECVD is used to deposit a P-type microcrystalline silicon doping layer on the side of the back amorphous silicon intrinsic layer away from the silicon substrate. The process gas is SiH 4 and B 2 H 6 The deposition temperature is 190°C, the deposition pressure is 2 mbar, and the thickness of the P-type microcrystalline silicon doped layer is 15 nm.

[0077] (5) A tin dioxide film is formed on the side of the N-type microcrystalline silicon doped layer away from the silicon substrate and a tin dioxide film is formed on the side of the P-type microcrystalline silicon doped layer away from the silicon substrate by a magnetron sputtering method. Ar is used as the glow discharge working gas, the power is 6 kW, the deposition temperature is 50°C, the chamber pressure is 0.5 Pa, and the thickness of the tin dioxide film on the front side of the silicon substrate and the tin dioxide film on the back side of the silicon substrate are both 100 nm.

[0078] (6) The tin dioxide film on the front side of the silicon substrate and the tin dioxide film on the back side of the silicon substrate were treated with hydrogen plasma at a power of 800 W. 2The flow rate is 3000 sccm, and the time for hydrogen plasma treatment of the tin dioxide film on the front side of the silicon substrate and the time for hydrogen plasma treatment of the tin dioxide film on the back side of the silicon substrate are both 5 minutes.

[0079] (7) Anneal the silicon wafer and introduce N 2 and NF 3 Gas, total gas flow rate is 350sccm, N 2 and NF 3 The gas flow ratio is 10:1, the annealing temperature is 200°C, and the annealing time is 30 min.

[0080] (8) The front metal grid lines and the back metal grid lines are prepared by screen printing method.

[0081] Example 2

[0082] The difference from Example 1 is that in step (7) of Example 2, the temperature for annealing the silicon wafer is 220° C. The remaining steps and parameters are the same as those of Example 1.

[0083] Example 3

[0084] The difference from Example 1 is that in step (7) of Example 3, the temperature of annealing the silicon wafer is 250° C. The remaining steps and parameters are the same as those of Example 1.

[0085] Comparative Example 1

[0086] In Comparative Example 1, the silicon wafer was not annealed, and the remaining steps and parameters were the same as those in Example 1.

[0087] Comparative Example 2

[0088] The difference from Example 1 is that in step (7) of Comparative Example 2, annealing is performed in an atmospheric environment, the annealing temperature is 200° C., and the annealing time is 30 min. The remaining steps and parameters are the same as those of Example 1.

[0089] The square resistance of the 100 nm thick tin dioxide film in each embodiment and comparative example was tested, and the test results are recorded in Table 1.

[0090] Table 1 Sheet resistance test results of 100 nm thick tin dioxide films in various embodiments and comparative examples

[0091] Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Square resistance(omh / sq) 652 220 182 179 172

[0092] It can be seen from Table 1 that compared with the tin dioxide film that has not been annealed and that has been annealed in an atmospheric environment, the method proposed in the present invention has a significant improvement in the tin dioxide film containing NF 3Annealing in a gas environment can significantly reduce the square resistance of the tin dioxide film and improve the conductive properties of the tin dioxide film.

[0093] In the description of the present invention, the orientation or position relationship indicated by the terms "front" and "back" is based on the orientation or position relationship shown in the drawings and is only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the present invention.

[0094] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "some specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0095] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a solar cell, characterized in that: include: forming a tin dioxide thin film on the front side of the silicon substrate; performing hydrogen plasma treatment on the tin dioxide film; After the hydrogen plasma treatment, the silicon substrate on which the tin dioxide thin film is formed is subjected to an annealing treatment in a gas environment containing nitrogen trifluoride.

2. The method according to claim 1, characterized in that The annealing temperature is 200°C-250°C; And / or, the annealing treatment time is 30min-45min.

3. The method according to claim 1, characterized in that The annealing process is performed in a gas environment containing nitrogen trifluoride and nitrogen.

4. The method according to claim 3, characterized in that During the annealing process, the flow ratio of nitrogen and nitrogen trifluoride is (5-15):

1.

5. The method according to claim 1, characterized in that The tin dioxide film is formed by a magnetron sputtering method. During the deposition of the tin dioxide film, the power of the magnetron sputtering is 4kW-8kW, the deposition temperature is 0-200°C, and the chamber pressure is 0.3Pa-0.8Pa.

6. The method according to claim 1, characterized in that The hydrogen plasma treatment satisfies at least one of the following conditions: Power is 500W-1000W; The flow rate of H2 is 1000sccm-4000sccm; The processing time is 3min-10min.

7. The method according to any one of claims 1 to 6, characterized in that Before forming the tin dioxide film, the method further comprises: Forming a front amorphous silicon intrinsic layer and a back amorphous silicon intrinsic layer on the front side and the back side of the silicon substrate respectively; Forming an N-type amorphous silicon doping layer or an N-type microcrystalline silicon doping layer on a side of the front amorphous silicon intrinsic layer away from the silicon substrate, and forming a P-type amorphous silicon doping layer or a P-type microcrystalline silicon doping layer on a side of the back amorphous silicon intrinsic layer away from the silicon substrate; Wherein, the tin dioxide film is formed on a side of the N-type amorphous silicon doping layer or the N-type microcrystalline silicon doping layer away from the silicon substrate.

8. The method according to claim 7, characterized in that After or before the tin dioxide film is formed on the side of the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer away from the silicon substrate, a transparent oxide film is formed on the side of the P-type amorphous silicon doped layer or the P-type microcrystalline silicon doped layer away from the silicon substrate, and the material of the transparent oxide film includes at least one of tin dioxide and zinc oxide.

9. The method according to claim 8, characterized in that Before the annealing treatment, the method further includes performing a hydrogen plasma treatment on the transparent oxide film.

10. A solar cell, characterized in that: The solar cell is prepared by the method according to any one of claims 1 to 9.

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