Silicon-based heterojunction solar cell, preparation method, electrical equipment and application

Abstract

The present application relates to a silicon-based heterojunction solar cell, a preparation method, an electrical device and an application. The silicon-based heterojunction solar cell comprises a silicon substrate, a first passivation layer, an N-type doped layer and a first transparent electrode arranged in sequence along a first direction, wherein the first direction is the direction from the silicon substrate to the first transparent electrode in the thickness direction of the silicon substrate; the N-type doped layer comprises the following multiple sublayers arranged in sequence along the first direction: an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer. Through the optimized design of the N-type doped layer, the conductivity of the N-type doped layer is not affected and no additional carrier recombination is brought about. The overall process is simple, and the prepared solar cell can increase the current density while maintaining the fill factor, thereby achieving an improvement in the cell efficiency. The silicon-based heterojunction solar cell can utilize light energy more efficiently in photovoltaic applications.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a silicon-based heterojunction solar cell, a preparation method, electrical equipment and applications. Background Art

[0002] With the development of photovoltaic technology and the continuous increase in market demand, various types of solar cells have been widely studied. Silicon-based heterojunction cells have attracted much attention in the scientific research field and industry due to their advantages of good weak light response, high efficiency, simple process and high bifaciality. However, the efficiency of mass-produced silicon-based heterojunction cells is still low and cannot meet the market's expectations. Summary of the invention

[0003] Based on this, the purpose of this application includes providing a silicon-based heterojunction solar cell using an N-type doped layer, which has a high fill factor and a high current density, which is beneficial to improving the efficiency of light utilization; and also provides a preparation method, electrical equipment and application.

[0004] In a first aspect of the present application, a silicon-based heterojunction solar cell is provided, comprising a silicon substrate, a first passivation layer, an N-type doping layer and a first transparent electrode arranged in sequence along a first direction, wherein the first direction is a direction from the silicon substrate to the first transparent electrode in the thickness direction of the silicon substrate;

[0005] The N-type doped layer includes the following multiple sub-layers sequentially arranged along the first direction: an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer, and an oxygen-free contact layer.

[0006] In one embodiment, in the silicon-based heterojunction solar cell, the oxygen-silicon ratio in the oxygen-containing seed layer is ≥0.6, and the silicon-oxygen ratio in the oxygen-containing main layer is ≥0.6.

[0007] In one embodiment, in the silicon-based heterojunction solar cell, the energy band of the oxygen-free seed layer is 1.3 eV to 1.4 eV, and the energy band of the oxygen-containing seed layer is 1.6 eV to 2 eV.

[0008] In one embodiment, the silicon-based heterojunction solar cell satisfies one or more of the following conditions:

[0009] Along the first direction, the crystallization rates of the respective layers in the N-type doped layers increase successively;

[0010] The doping activation concentration of the P element in the oxygen-containing main layer is greater than 1×10 17 / cm 3 ;

[0011] The doping activation concentration of the P element in the oxygen-free contact layer is greater than 1×1017 / cm 3 .

[0012] In one embodiment, the silicon-based heterojunction solar cell satisfies one or more of the following conditions:

[0013] The thickness of the oxygen-free seed layer is ≤0.5 nm;

[0014] The thickness of the oxygen-containing seed layer is ≤0.5 nm;

[0015] The thickness of the oxygen-containing main layer is 13nm to 14nm;

[0016] The thickness of the oxygen-free contact layer is 1.5 nm to 2.5 nm.

[0017] In one embodiment, in the silicon-based heterojunction solar cell, a second passivation layer, a P-type doping layer and a second transparent electrode are sequentially arranged on a side of the silicon substrate away from the first passivation layer along a direction opposite to the first direction.

[0018] In one embodiment, in the silicon-based heterojunction solar cell, the first passivation layer and the second passivation layer are each independently an intrinsic hydrogenated amorphous silicon layer; and the silicon substrate is a microcrystalline silicon substrate or a nanocrystalline silicon substrate.

[0019] A second aspect of the present application provides a method for preparing a silicon-based heterojunction solar cell, comprising the following steps:

[0020] A first passivation layer, an N-type doping layer and a first transparent electrode are sequentially formed on a surface of one side of the silicon substrate;

[0021] Wherein, forming the N-doped layer on the first passivation layer includes: forming the following sub-layers in sequence on a side of the first passivation layer away from the silicon substrate: an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer.

[0022] In one embodiment, the preparation method satisfies one or more of the following conditions:

[0023] The molar ratio of the reaction gas raw materials H2, SiH4 and PH3 for forming the oxygen-free seed layer is 400:1:0.2 to 400:1:0.4, and the pressure of the reaction gas is 2 to 3 mbar;

[0024] The molar ratio of the reaction gas raw materials H2, SiH4, CO2 and PH3 for forming the oxygen-containing seed layer is 400:1:0.4:0.3 to 400:1:0.8:0.6, and the pressure of the reaction gas is 2 mbar to 3 mbar.

[0025] In one embodiment, the preparation method satisfies one or more of the following conditions:

[0026] The reaction gas raw materials H2, SiH4, CO2 and PH3 for forming the oxygen-containing main layer are 160:1:0.6:0.4 to 200:1:0.8:0.8, and the pressure of the reaction gas is 2mbar to 3mbar;

[0027] The reaction gas raw materials H2, SiH4 and PH3 for forming the oxygen-free contact layer are 160:1:0.6-200:1:0.8, and the pressure of the reaction gas is 2mbar-3mbar.

[0028] A third aspect of the present application provides an electrical device, comprising the silicon-based heterojunction solar cell described in the first aspect or the silicon-based heterojunction solar cell prepared by the preparation method described in the second aspect.

[0029] The fourth aspect of the present application provides an application of the silicon-based heterojunction solar cell described in the first aspect, the silicon-based heterojunction solar cell prepared by the preparation method described in the second aspect, or the electrical equipment described in the third aspect in photovoltaic power generation.

[0030] The silicon-based heterojunction solar cell provided in the present application, the N-type doped layer includes an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer stacked in sequence; wherein, the oxygen-free seed layer is conducive to improving the crystallization rate of the N main layer (i.e., the oxygen-containing main layer), the oxygen-containing seed layer can improve the overall band gap of the seed layer, reduce the additional carrier recombination caused by the sharp contraction of the band gap due to the high crystallization of the oxygen-free seed layer, the oxygen-containing main layer can improve the conductivity while ensuring the transmittance, and the oxygen-free contact layer can reduce the contact resistance between the silicon thin film layer and the transparent conductive oxide layer. Through the optimized design of the N-type doped layer, the current can be increased while ensuring the FF, thereby improving the battery efficiency.

[0031] The preparation method provided in the present application can realize the stacking of an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer on the oxygen-free seed layer, without affecting the conductivity of the N-type doped layer and without causing additional carrier recombination. The overall process is simple, and the prepared solar cell can increase the current density while maintaining the fill factor.

[0032] The electrical equipment provided in this application has a high utilization rate of light energy, which is beneficial to reducing costs and increasing battery life.

[0033] The silicon-based heterojunction solar cell provided in the present application can improve the current density while maintaining the fill factor, and can utilize light energy more efficiently in photovoltaic applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0035] Figure 1 This is a schematic diagram of an N-type doped layer of a silicon-based heterojunction solar cell according to an embodiment of the present application; wherein the meanings of the markings are as follows: oxygen-free seed (201), oxygen-containing seed layer (202), oxygen-containing main layer (203), oxygen-free contact layer (204).

[0036] Figure 2 The present invention is a schematic diagram of a silicon-based heterojunction solar cell according to an embodiment of the present application; wherein the meanings of the symbols are as follows: first transparent electrode (1), N-type doped layer (2), oxygen-free seed (201), oxygen-containing seed layer (202), oxygen-containing main layer (203), oxygen-free contact layer (204), i-α-Si:H (3), nc-Si silicon wafer (4), i-α-Si:H (5), P-type doped layer (6), second transparent electrode (7), gate electrode (8) and gate electrode (9). DETAILED DESCRIPTION

[0037] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are provided. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0038] The implementation of the present invention is described in detail below in conjunction with the accompanying drawings. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0040] the term

[0041] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0042] In the present invention, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0043] In the present invention, the terms “further”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present invention.

[0044] In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0045] In the present invention, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers in the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0046] In the present invention, the term "room temperature" generally refers to 4°C to 35°C, preferably 20°C ± 5°C. In some embodiments of the present invention, room temperature refers to 20°C to 30°C.

[0047] In the present invention, unless otherwise specified, the temperature parameter is allowed to be either a constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0048] In the present invention, when it comes to the unit of the data range, if there is a unit only after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 2-5h means that the units of the left endpoint "2" and the right endpoint "5" are both h (hours).

[0049] With the development of photovoltaic technology and the continuous increase in market demand, various types of solar cells have been widely studied. Silicon-based heterojunction cells have attracted much attention in the scientific research field and industry due to their advantages of good weak light response, high efficiency, simple process and high bifaciality. However, the efficiency of mass-produced silicon-based heterojunction cells is still low and cannot meet the market's expectations.

[0050] Compared with traditional solar cell technology, silicon-based heterojunction cells (Heterojunction with Intrinsic Thin-layer, referred to as "HJT") are a high-efficiency solar cell structure. HJT cells mainly include N-type crystalline silicon substrates and amorphous silicon thin films. The back of the cell includes a transparent conductive oxide film (transparent conductive oxide, referred to as "TCO", also referred to as TCO film), a P-type amorphous silicon film and a hydrogenated amorphous silicon film; the front of the cell includes a TCO transparent conductive oxide film, an N-type amorphous silicon film and an intrinsic amorphous silicon film. The introduction of amorphous silicon film enables heterojunction solar cells to have the advantages of both crystalline silicon and thin-film solar energy, with good surface passivation effect, and avoid direct contact between metal electrodes and silicon materials, further reducing carrier recombination losses, which is conducive to improving the conversion efficiency of the cell. In addition, HJT cells also have technical advantages such as low process temperature, fewer preparation processes and high bifaciality, and have received extensive attention from the research and development and industry circles.

[0051] Amorphous silicon optimization is one of the ways to improve the efficiency of HJT cells. With the development of technology, the performance requirements for the N-type doped layer in the single-sided or double-sided microcrystalline cell structure are getting higher and higher. The N-type doped layer should at least have good optical transmittance, good carrier transport, and good contact with the TCO layer. In fact, the industry generally believes that the optimization of the N-type doped layer (close to the light-facing side) has reached a bottleneck, and the current mainstream research direction is focused on the optimization of the P-type doped layer (close to the backlight side).

[0052] The inventors of the present application, after a lot of creative work, provide an N-type doping layer that can further increase the open circuit voltage of the battery, thereby facilitating the improvement of the battery efficiency.

[0053] In a first aspect of the present application, a silicon-based heterojunction solar cell is provided, comprising a silicon substrate, a first passivation layer, an N-type doping layer and a first transparent electrode arranged in sequence along a first direction, wherein the first direction is a direction from the silicon substrate to the first transparent electrode in the thickness direction of the silicon substrate;

[0054] The N-type doped layer includes the following multiple sub-layers sequentially arranged along the first direction: an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer, and an oxygen-free contact layer.

[0055] The silicon-based heterojunction solar cell provided in the present application, the N-type doped layer includes an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer stacked in sequence. The N-type doped layer provided in the present application is functionally designed for different functional requirements, and the N layer is divided into multiple sublayers, namely, an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer. Among them, the set oxygen-free seed layer is conducive to improving the crystallization rate of the N main layer (i.e., the oxygen-containing main layer), the oxygen-containing seed layer can increase the overall band gap of the seed layer, and reduce the additional carrier recombination caused by the sharp contraction of the band gap due to the high crystallization of the oxygen-free seed layer. The oxygen-containing main layer with high oxygen content and high phosphorus doping can improve the conductivity while ensuring the transmittance, and the oxygen-free high-phosphorus doped oxygen-free contact layer can reduce the contact resistance between the silicon thin film layer and the transparent conductive oxide layer. Through the optimized design of the N-type doped layer, the current can be increased while ensuring the FF, thereby achieving an improvement in the battery efficiency.

[0056] Figure 1 Schematic diagram of an N-type doping layer of a silicon-based heterojunction solar cell according to an embodiment of the present application, wherein 201 is an oxygen-free seed layer, 202 is an oxygen-containing seed layer, 203 is an oxygen-containing main layer, and 204 is an oxygen-free contact layer.

[0057] In one embodiment, in the silicon-based heterojunction solar cell, the oxygen-to-silicon ratio in the oxygen-containing seed layer is ≥ 0.6, and can further be 0.6 to 0.8. If the oxygen-to-silicon ratio in the oxygen-containing seed layer is too low, the seed layer energy band may be narrow, which may easily cause carrier recombination. The composition of the oxygen-containing seed layer can be P-doped microcrystalline silicon oxygen (P depedμc-SiO x ).

[0058] It can be understood that, unless otherwise specified, the oxygen-to-silicon ratio of the oxygen-containing seed layer in the present application refers to the ratio of oxygen atoms to silicon atoms inside the film.

[0059] In one embodiment, in the silicon-based heterojunction solar cell, the silicon-oxygen ratio in the oxygen-containing main layer is ≥ 0.6, and can further be 0.6 to 0.9. If the oxygen-silicon ratio of the oxygen-containing main layer is too low, the transmittance of the film may decrease, resulting in additional optical loss.

[0060] It can be understood that, unless otherwise specified, the silicon-oxygen ratio of the oxygen-containing main layer in the present application refers to the ratio of oxygen atoms to silicon atoms inside the film.

[0061] In one embodiment, in the silicon-based heterojunction solar cell, the energy band of the oxygen-free seed layer is 1.3eV to 1.4eV, and can also be selected from any one of the following band gaps or an interval consisting of any two band gaps: 1.3eV, 1.31eV, 1.32eV, 1.33eV, 1.34eV, 1.35eV, 1.36eV, 1.37eV, 1.38eV, 1.39eV, and 1.4eV.

[0062] In one embodiment, in the silicon-based heterojunction solar cell, the energy band of the oxygen-containing seed layer is 1.6eV to 2eV, and can further be 1.6eV to 1.8eV, and can also be selected from any one of the following band gaps or an interval consisting of any two of the following band gaps: 1.3eV, 1.4eV, 1.5eV, 1.6eV, 1.7eV, 1.8eV, 1.9eV, and 2eV.

[0063] In one embodiment, in the silicon-based heterojunction solar cell, the energy band of the oxygen-containing main layer is 1.6eV to 1.9eV, and can also be selected from any one of the following band gaps or an interval consisting of any two band gaps: 1.3eV, 1.4eV, 1.5eV, 1.6eV, 1.7eV, 1.8eV, 1.9eV, and 2eV.

[0064] In one embodiment, in the silicon-based heterojunction solar cell, the energy band of the oxygen-free contact layer is 1.3eV to 1.5eV, and can also be selected from any one of the following band gaps or an interval consisting of any two band gaps: 1.3eV, 1.31eV, 1.32eV, 1.33eV, 1.34eV, 1.35eV, 1.36eV, 1.37eV, 1.38eV, 1.39eV, 1.4eV, 1.41eV, 1.42eV, 1.43eV, 1.44eV, 1.45eV, 1.46eV, 1.47eV, 1.48eV, 1.49eV, 1.5eV, etc.

[0065] In one embodiment, in the silicon-based heterojunction solar cell, along the first direction, the crystallization rate of each layer in the N-type doped layer increases in sequence. If the crystallization rate of the N-type doped layer is too high, the degree of recombination of electrons and holes in the valence band is high, resulting in additional FF losses; if the crystallization rate of the N-type doped layer is too low, it may be unfavorable for carrier transmission, and also cause a decrease in the fill factor FF.

[0066] In one embodiment, in the silicon-based heterojunction solar cell, the crystallization rate of the oxygen-free seed layer is 40% to 60%, and can also be selected from any one of the following crystallization rates or an interval consisting of any two of the following crystallization rates: 40%, 45%, 50%, 55%, 60%, etc.

[0067] In one embodiment, in the silicon-based heterojunction solar cell, the crystallization rate of the oxygen-containing seed layer is 30% to 40%, and can also be selected from any one of the following crystallization rates or an interval consisting of any two of the following crystallization rates: 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc.

[0068] In one embodiment, in the silicon-based heterojunction solar cell, the crystallization rate of the oxygen-containing main layer is 30% to 45%, and can also be selected from any one of the following crystallization rates or an interval consisting of any two crystallization rates: 30%, 35%, 40%, 45%, etc.

[0069] In one embodiment, in the silicon-based heterojunction solar cell, the crystallization rate of the oxygen-free contact layer is 40% to 60%, and can also be selected from any one of the following crystallization rates or an interval consisting of any two of the following crystallization rates: 40%, 45%, 50%, 55%, 60%, etc.

[0070] In one embodiment, in the silicon-based heterojunction solar cell, the doping activation concentration of the P element in the oxygen-containing main layer is greater than or equal to 1×10 17 cm 3 , which can be further 1×10 17 cm 3 ~1.5×10 21 cm 3 , can also be selected from the following intervals consisting of any one or two doping activation concentrations: 1×10 17 / cm 3 , 5×10 17 / cm 3 , 1×10 18 / cm 3 , 5×10 18 / cm 3 , 1×10 19 / cm 3 , 5×10 19 / cm 3 , 1×10 20 / cm 3 , 5×10 20 / cm 3 , 1×10 21 / cm 3 , 1.5×10 21 / cm 3 wait.

[0071] In one embodiment, in the silicon-based heterojunction solar cell, the doping activation concentration of the P element in the oxygen-free contact layer is greater than 1×10 17 / cm 3 , which can be further 1×1017 cm 3 ~1.5×10 21 cm 3 , can also be selected from the following intervals consisting of any one or two doping activation concentrations: 1×10 17 / cm 3 , 5×10 17 / cm 3 , 1×10 18 / cm 3 , 5×10 18 / cm 3 , 1×10 19 / cm 3 , 5×10 19 / cm 3 , 1×10 20 / cm 3 , 5×10 20 / cm 3 , 1×10 21 / cm 3 , 1.5×10 21 / cm 3 wait.

[0072] In one embodiment, in the silicon-based heterojunction solar cell, the thickness of the oxygen-free seed layer is less than 0.5 nm, and can further be 0.3 nm to 0.5 nm, and can also be selected from the interval consisting of any one or any two of the following thicknesses: 0.3 nm, 0.35 nm, 0.4 nm, 0.45 nm, 0.5 nm, etc.

[0073] In one embodiment, in the silicon-based heterojunction solar cell, the thickness of the oxygen-containing seed layer is less than 0.5 nm, and can further be 0.3 nm to 0.5 nm, and can also be selected from the interval consisting of any one or any two of the following thicknesses: 0.3 nm, 0.35 nm, 0.4 nm, 0.45 nm, 0.5 nm, etc.

[0074] In one embodiment, in the silicon-based heterojunction solar cell, the thickness of the oxygen-containing main layer is 13nm to 14nm, and can also be selected from any one or two of the following thicknesses: 13nm, 13.1nm, 13.2nm, 13.3nm, 13.4nm, 13.5nm, 13.6nm, 13.7nm, 13.8nm, 13.9nm and 14nm.

[0075] In one embodiment, in the silicon-based heterojunction solar cell, the thickness of the oxygen-free contact layer is 1.5nm to 2.5nm, and can also be selected from any one or two of the following thicknesses: 1.5nm, 1.6nm, 1.7nm, 1.8nm, 1.9nm, 2.0nm, 2.1nm, 2.2nm, 2.3nm, 2.4nm and 2.5nm.

[0076] In one embodiment, in the silicon-based heterojunction solar cell, a second passivation layer, a P-type doping layer and a second transparent electrode are sequentially arranged on a side of the silicon substrate away from the first passivation layer along a direction opposite to the first direction.

[0077] In one embodiment, in the silicon-based heterojunction solar cell, the first passivation layer and the second passivation layer are each independently an intrinsic hydrogenated amorphous silicon layer; and the silicon substrate is a microcrystalline silicon substrate or a nanocrystalline silicon substrate.

[0078] In one embodiment, reference Figure 2 , the solar cell has the following structure:

[0079] A gate line electrode 8, a first transparent electrode 1, an N-type doped layer 2, the N-type doped layer 2 including an oxygen-free seed 201, an oxygen-containing seed layer 202, an oxygen-containing main layer 203 and an oxygen-free contact layer 204, i-α-Si:H (equivalent to a first passivation layer) 3, a nc-Si silicon wafer (equivalent to a silicon substrate) 4, i-α-Si:H (equivalent to a second passivation layer) 5, a P-type doped layer 6, a second transparent electrode 7 and a gate line electrode 9.

[0080] A second aspect of the present application provides a method for preparing a silicon-based heterojunction solar cell, comprising the following steps:

[0081] A first passivation layer, an N-type doping layer and a first transparent electrode are sequentially formed on a surface of one side of the silicon substrate;

[0082] Wherein, forming the N-doped layer on the first passivation layer includes: forming the following sub-layers in sequence on a side of the first passivation layer away from the silicon substrate: an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer.

[0083] A second aspect of the present application provides a method for preparing a silicon-based heterojunction solar cell, comprising the following steps:

[0084] S200: forming a first passivation layer on the front side of a silicon substrate; the substrate has two opposite sides, which are respectively referred to as a front side and a back side;

[0085] S500: forming an N-type doping layer on a side of the first passivation layer formed on the front side of the substrate away from the substrate;

[0086] Wherein, an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer are sequentially formed on the N-type doped layer in a direction away from the hydrogenated polysilicon layer.

[0087] The preparation method provided in the present application can realize the stacking of an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer on the oxygen-free seed layer, without affecting the conductivity of the N-type doped layer and without causing additional carrier recombination. The overall process is simple, and the prepared solar cell can increase the current density while maintaining the fill factor.

[0088] In one embodiment, the method for preparing a solar cell comprises the following steps:

[0089] S100: forming a silicon wafer, wherein the silicon wafer is an N-type single crystal silicon wafer; the substrate has two opposite surfaces, which are respectively called a front surface and a back surface;

[0090] S200: cleaning and texturing the front and back sides of the silicon wafer to obtain a substrate having a pyramid texture structure on the surface;

[0091] S300: forming a first passivation layer on the front surface of the substrate;

[0092] S400: forming a second passivation layer on the back side of the substrate;

[0093] S500: forming an N-type doping layer on a side of the first passivation layer formed on the front side of the substrate away from the substrate; wherein an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer are sequentially formed on the N-type doping layer in a direction away from the hydrogenated polysilicon layer;

[0094] S600: forming a p-type doping layer on a side of the second passivation layer formed on the back side of the substrate away from the substrate;

[0095] S700: forming TCO film layers on surfaces of the oxygen-free contact layer of the N-type doping layer and the p-type doping layer respectively;

[0096] S800: forming a gate line electrode on the surface of the TCO film layer.

[0097] It is understandable that in the step S200, the purpose of the cleaning treatment is to clean and remove the surface organic matter and metal ions so as to better form the functional layer of the solar cell on the surface of the N-type single crystal silicon. The present application does not limit the method of the cleaning treatment, which can be the RCA industry standard wet cleaning process, that is, using SPM (H2SO4 / H2O2), HF (DHF), APM (NH4OH / H2O2 / H2O), HPM (HCl / H2O2 / H2O)

[0098] It can be understood that in the step S200, the purpose of the texturing treatment is to form an uneven structure with uniform size on the surface of the silicon wafer. This uneven structure presents a pyramid structure in microscopic morphology, and millions of four-sided pyramids can be formed on each square centimeter of the silicon surface. This treatment can increase the absorption of light through the pyramid structure on its surface when the incident light enters the surface of the silicon wafer from different angles, thereby achieving the short-circuit current and conversion efficiency of the battery. The texturing treatment of single crystal silicon utilizes the anisotropic corrosion of silicon. The specific method used for the texturing treatment is not limited in the present application. The process can be achieved by using hot alkaline solutions such as sodium hydroxide, potassium hydroxide, lithium hydroxide and ethylenediamine solution. According to needs, after a silicon wafer with a plurality of tetrahedral pyramids on its surface is obtained by texturing with a hot alkaline solution, a suitable method such as a mechanical grinding method can be used to grind the tetrahedral pyramids that constitute the pyramid velvet surface on the silicon wafer surface, so that the sharp square cones on the surface of the tetrahedral pyramid structure are transformed into a smooth square cone-like structure; an acidic solution such as HF can also be used to remove the oxide layer on the surface of the pyramid velvet surface.

[0099] It is understandable that in the step S200, the cleaning and texturing treatment of the silicon wafer can be performed multiple times as needed. For example, after the texturing treatment is performed using a hot alkaline solution, the cleaning treatment can be performed again according to design and process requirements.

[0100] It can be understood that in the steps S300 and S400, the first passivation layer and the second passivation layer can be selected from hydrogenated amorphous silicon or hydrogenated amorphous silicon oxide, respectively.

[0101] It can be understood that in the step S700, the purpose of forming TCO film layers on the surfaces of the oxygen-free contact layer of the N-type doped layer and the p-type doped layer includes the following aspects: first, by utilizing its light transmittance, under the irradiation of sunlight, light can penetrate the TCO film into the interior of the solar cell and form a pn junction on its surface; second, by utilizing the conductive properties of the TCO film, it allows carriers in the n-type doped layer and the p-type doped layer to pass through and connect with external devices to achieve directional migration of carriers, thereby completing power conversion. The composition of the TCO film is not limited in this application, and can be composed of oxides composed of typical elements such as In, Sb, Zn and Cd, as well as composite multi-element oxide materials thereof. The present application does not limit the process method and equipment for preparing the TCO film. The TCO film can be prepared by physical vapor deposition (PVD), CVD (CVD), reactive plasma deposition (RPD) and other methods and their corresponding equipment.

[0102] It is understandable that in the step S800, the function of the gate electrode is to serve as a bridge between light absorption and charge transfer. The electrode is the current output end of the solar cell, and it can transfer the charge from the light absorption layer to the external circuit to complete the conversion and output of electric energy. Similarly, the method for preparing the gate electrode is not limited in this application, and the gate electrode can be prepared by screen printing, laser transfer technology, electroplating and other methods.

[0103] It is understandable that in the steps S100 to S800 , the silicon wafer of the solar cell or the solar cell precursor including multiple functional layers may be turned over (or reversed) according to process requirements.

[0104] In one embodiment, in the preparation method, the molar ratio of the reaction gas raw materials H2, SiH4 and PH3 for forming the oxygen-free seed layer is 400:1:0.2 to 400:1:0.4, and the pressure of the reaction gas is 2 mbar to 3 mbar.

[0105] In one embodiment, in the preparation method, the molar ratio of the reaction gas raw materials H2, SiH4, CO2 and PH3 for forming the oxygen-containing seed layer is 400:1:0.4:0.3 to 400:1:0.8:0.6, and the pressure of the reaction gas is 2 mbar to 3 mbar.

[0106] In one embodiment, in the preparation method, the reaction gas raw materials H2, SiH4, CO2 and PH3 for forming the oxygen-containing main layer are 160:1:0.6:0.4~200:1:0.8:0.8, and the pressure of the reaction gas is 2mbar~3mbar.

[0107] In one embodiment, in the preparation method, the reaction gas raw materials H2, SiH4 and PH3 for forming the oxygen-free contact layer are 160:1:0.6 to 200:1:0.8, and the pressure of the reaction gas is 2 mbar to 3 mbar.

[0108] In one embodiment, in the method for preparing the solar cell, the order of step S400 and step S500 can be interchanged.

[0109] In one embodiment, the method for preparing the solar cell (referred to as solar cell (A)) comprises the following steps:

[0110] S101: providing a nc-Si silicon wafer 4; the nc-Si silicon wafer has a front side and a back side that are opposite to each other;

[0111] S201: Clean and remove damage and texture the front and back sides of the nc-Si silicon wafer, forming a pyramid texture structure of uniform size on the front and back surfaces of the nc-Si silicon wafer, then remove surface organic matter and metal ions through RCA cleaning, then round the surface pyramids through the Rounding process, and finally remove the oxide layer with HF solution;

[0112] S301: i-α-Si:H3 is sequentially prepared on one side (equivalent to the front side) of the silicon wafer by VHF-PECVD equipment, with a thickness of 9.5 nm;

[0113] S401: After turning over, i-α-Si:H5 is prepared on the other surface (equivalent to the back side) with a thickness of 10 nm;

[0114] S501: After turning over, prepare an N-type doped layer 2 with a thickness of 15 nm. The doping activation concentration of the P element in the N-type doped layer (oxygen-containing main layer and oxygen-free contact layer) is 5×10 17 / cm 3; Wherein, according to the preparation sequence, the N-type doped layer 2 includes an oxygen-free seed 201, an oxygen-containing seed layer 202, an oxygen-containing main layer 203 and an oxygen-free contact layer 204; wherein, the thickness of the oxygen-free seed 201 in the N-type doped layer 2 is 0.5 nm, the preparation conditions are H2:SiH4:PH3 is 400:1:0.2-400:1:0.4, the reaction gas pressure is 3 mbar, the band gap of the obtained oxygen-free seed 201 is 1.3 eV, the crystallization rate is 55%, and the oxygen-free seed layer helps The thickness of the oxygen-containing seed layer 202 in the N-type doping layer 2 is 0.5 nm, and the preparation conditions are H2:SiH4:CO2:PH3 is 400:1:0.8:0.3, and the reaction gas pressure is 3 mbar. The oxygen-silicon ratio of the oxygen-containing seed layer 202 is 0.7, the band gap is 1.7 eV, and the crystallization rate is 40%, which is beneficial to improve the overall band gap including the oxygen-free seed layer and the oxygen-containing seed layer, and reduce the oxygen-free seed layer 20 1 The extra carrier recombination caused by the sharp contraction of the band gap due to high crystallization; the thickness of the oxygen-containing main layer 203 in the N-type doped layer 2 is 13.5nm, the preparation conditions are H2:SiH4:CO2:PH3 is 166:1:0.6:0.4, the reaction gas pressure is 3mbar, the silicon-oxygen ratio of the prepared oxygen-containing main layer 203 is 0.8, the band gap is 1.9eV, and the crystallization rate is 43%. The oxygen-containing main layer (also called N main layer) prepared by high oxygen content and high phosphorus doping layer), while ensuring transmittance, the conductivity is improved; the thickness of the oxygen-free contact layer 204 in the N-type doped layer 2 is 3nm, the preparation conditions are H2:SiH4:PH3 166:1:0.6, the reaction gas pressure is 3mbar, the obtained oxygen-free contact layer 204 has a band gap of 1.4eV, and a crystallization rate of 55%. The oxygen-free contact layer prepared by the oxygen-free high-phosphorus doping method can reduce the contact resistance between the silicon thin film layer and the transparent conductive oxide (TCO) layer, thereby improving the FF of the battery;

[0115] S601: Turn over again and prepare a P-type doped layer 6 with a thickness of 20 nm; the silicon-based thin film preparation stage is completed;

[0116] S701: TCO1 and TCO7 are prepared on the front and back sides of the silicon wafer using PVD equipment, with a thickness of 90 nm.

[0117] S801: preparing gate line electrodes 8 and 9 on the front and back sides respectively by screen printing, wherein the density of the P-side gate line electrodes 9 is greater than the density of the N-side gate line electrodes 8; and then performing curing and / or annealing treatment on the gate lines.

[0118] It can be understood that the P surface is the side where the dopant of the doped layer is the B element, and the N surface is the side where the dopant of the doped layer is the P element; the N surface is the relatively front side, i.e. the light incident side, and the P surface is the relatively back side.

[0119] In one embodiment, the preparation method of the solar cell (denoted as solar cell (B)) is basically the same as the preparation method of the aforementioned solar cell (A), except that in step S501, the preparation raw materials H2:SiH4:CO2:PH3 of the N-type doping layer 2 are 400:1:1:0.3.

[0120] In one embodiment, the preparation method of the solar cell (denoted as solar cell (C)) is basically the same as the preparation method of the aforementioned solar cell (A), except that in step S501, the preparation raw materials H2:SiH4:CO2:PH3 of the N-type doping layer 2 are 400:1:0.6:0.3.

[0121] In one embodiment, the preparation method of the solar cell (referred to as solar cell (D)) is basically the same as the preparation method of the aforementioned solar cell (A), the difference being that in step S501, the prepared N-type doped layer 2 includes an oxygen-free seed 201, an oxygen-containing main layer 203 and an oxygen-free contact layer 204, and does not include an oxygen-containing seed layer 202.

[0122] GB 11009-1989 was used to test the spectral response of solar cells, GB 12632-1990 was used to test single crystal cells, and GBT 6495.1-1996 was used to test the photovoltaic current and voltage characteristics of solar cells. The specific conditions were 25°C, AM1.5G spectrum, 1000W / cm 2 Light intensity polarity test. The measured performance is shown in Table 1. It should be noted that the performance of the solar cell in Table 1 are all relative values.

[0123] Table 1 Performance comparison of solar cells (A) to (D)

[0124]

[0125] The inventors of the present application also discovered that if the crystallization rates of the oxygen-free seed layer, oxygen-containing seed layer, oxygen-containing main layer and oxygen-free contact layer of the N-type doped layer sequentially arranged along the first direction are not set to increase in sequence, or the crystallization rate of the seed layer is low, then there will be no positive effect on the improvement of the crystallization rate of the subsequent oxygen-containing main layer; if the crystallization rate of the oxygen-containing main layer is too high, it will lead to serious parasitic absorption, which will seriously affect the optical performance.

[0126] A third aspect of the present application provides an electrical device, comprising the solar cell described in the first aspect or the solar cell prepared by the preparation method described in the second aspect.

[0127] It can be understood that the electrical equipment may be electric transportation equipment (such as ships, spacecraft, electric vehicles and battery vehicles, etc.), lighting equipment (lamps and auxiliary lighting elements, etc.), photovoltaic power generation equipment, and other equipment that requires electrical energy.

[0128] The electrical equipment provided in this application has a high utilization rate of light energy, which is beneficial to reducing costs and increasing battery life.

[0129] The fourth aspect of the present application provides an application of the solar cell described in the first aspect, the solar cell prepared by the preparation method described in the second aspect, or the electrical equipment described in the third aspect in photovoltaic power generation.

[0130] The silicon-based heterojunction solar cell provided in the present application can improve the current density while maintaining the fill factor (FF), and can utilize light energy more efficiently in photovoltaic applications.

[0131] In order to make it easier to understand and implement the present invention, the following more specific and detailed embodiments and comparative examples which are easier to implement are provided as references.

[0132] The following will further illustrate the concept, specific examples and technical effects of the present invention in conjunction with the accompanying drawings to fully understand the present invention. The purpose of providing these descriptions is only to help explain the present invention and should not be used to limit the scope of the claims of the present invention.

[0133] Unless otherwise specified, the raw materials used in the following experiments can be purchased from the market.

[0134] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0135] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims, and the description and drawings may be used to explain the contents of the claims.

Claims

1. A silicon-based heterojunction solar cell, characterized in that: It comprises a silicon substrate, a first passivation layer, an N-type doping layer and a first transparent electrode arranged in sequence along a first direction, wherein the first direction is a direction from the silicon substrate to the first transparent electrode in the thickness direction of the silicon substrate; The N-type doped layer includes the following multiple sub-layers arranged in sequence along the first direction: an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer; The energy band of the oxygen-free seed layer is 1.3eV to 1.4eV, the thickness of the oxygen-free seed layer is ≤0.5nm, the molar ratio of the reaction gas raw materials H2, SiH4 and PH3 to form the oxygen-free seed layer is 400:1:0.2 to 400:1:0.4, and the pressure of the reaction gas is 2mbar to 3mbar; The oxygen-silicon ratio of the oxygen-containing seed layer is ≥0.6, the thickness of the oxygen-containing seed layer is ≤0.5 nm, and the oxygen-containing seed layer is P-doped microcrystalline silicon oxygen; The silicon-oxygen ratio in the oxygen-containing main layer is ≥0.

6.

2. The silicon-based heterojunction solar cell according to claim 1, characterized in that: The energy band of the oxygen-containing seed layer is 1.6 eV to 2 eV.

3. The silicon-based heterojunction solar cell according to claim 1, characterized in that: One or more of the following conditions are met: Along the first direction, the crystallization rate of each sublayer in the N-type doped layer increases successively; The doping activation concentration of the P element in the oxygen-containing main layer is greater than 1×10 17 / cm 3 ; The doping activation concentration of the P element in the oxygen-free contact layer is greater than 1×10 17 / cm 3 .

4. The silicon-based heterojunction solar cell according to claim 1, characterized in that: One or more of the following conditions are met: The thickness of the oxygen-containing main layer is 13nm to 14nm; The thickness of the oxygen-free contact layer is 1.5 nm to 2.5 nm.

5. The silicon-based heterojunction solar cell according to any one of claims 1 to 4, characterized in that: Along the direction opposite to the first direction, a second passivation layer, a P-type doping layer and a second transparent electrode are sequentially arranged on a side of the silicon substrate away from the first passivation layer.

6. The silicon-based heterojunction solar cell according to claim 5, characterized in that: The first passivation layer and the second passivation layer are each independently an intrinsic hydrogenated amorphous silicon layer; and the silicon substrate is a microcrystalline silicon substrate or a nanocrystalline silicon substrate.

7. A method for preparing a silicon-based heterojunction solar cell, characterized in that: The following steps are involved: A first passivation layer, an N-type doping layer and a first transparent electrode are sequentially formed on a surface of one side of the silicon substrate; Wherein, forming the N-type doped layer on the first passivation layer comprises: forming the following sub-layers in sequence on a side of the first passivation layer away from the silicon substrate: an oxygen-free seed layer, an oxygen-containing seed layer, an oxygen-containing main layer and an oxygen-free contact layer; The molar ratio of the reaction gas raw materials H2, SiH4 and PH3 for forming the oxygen-free seed layer is 400:1:0.2-400:1:0.4, and the pressure of the reaction gas is 2 mbar-3 mbar; the thickness of the oxygen-free seed layer is ≤0.5 nm; The oxygen-silicon ratio of the oxygen-containing seed layer is ≥0.6, the thickness of the oxygen-containing seed layer is ≤0.5 nm, and the oxygen-containing seed layer is P-doped microcrystalline silicon oxygen; The silicon-oxygen ratio in the oxygen-containing main layer is ≥0.

6.

8. The preparation method according to claim 7, characterized in that: The molar ratio of the reaction gas raw materials H2, SiH4, CO2 and PH3 for forming the oxygen-containing seed layer is 400:1:0.4:0.3 to 400:1:0.8:0.6, and the pressure of the reaction gas is 2 mbar to 3 mbar.

9. The preparation method according to claim 7, characterized in that: One or more of the following conditions are met: The reaction gas raw materials H2, SiH4, CO2 and PH3 for forming the oxygen-containing main layer are 160:1:0.6:0.4 to 200:1:0.8:0.8, and the pressure of the reaction gas is 2 mbar to 3 mbar; The reaction gas raw materials H2, SiH4 and PH3 for forming the oxygen-free contact layer are 160:1:0.6-200:1:0.8, and the pressure of the reaction gas is 2 mbar-3 mbar.

10. An electrical device, characterized in that: The invention comprises the silicon-based heterojunction solar cell described in any one of claims 1 to 6 or the silicon-based heterojunction solar cell prepared by the preparation method described in any one of claims 7 to 9.

11. Use of the silicon-based heterojunction solar cell described in any one of claims 1 to 6 or the silicon-based heterojunction solar cell prepared by the preparation method described in any one of claims 7 to 9 or the electrical equipment described in claim 10 in photovoltaic power generation.

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