Preparation method of solar cell, solar cell and photovoltaic module

Abstract

The invention discloses a preparation method of a solar cell, the solar cell and a photovoltaic module. The preparation method of the solar cell comprises the following steps: forming an emitter on one surface of a silicon substrate; preparing a tunneling layer and an intrinsic amorphous silicon layer on the other surface of the silicon substrate; sequentially and alternately preparing a plurality of ultrathin oxide layers and intrinsic amorphous silicon layers on the surface of the intrinsic polycrystalline silicon layer; diffusing the intrinsic amorphous silicon layer to form a doped amorphous silicon layer; and annealing treatment is carried out on the doped amorphous silicon layer, so that amorphous silicon is converted into polycrystalline silicon, oxygen atoms and silicon atoms in the polycrystalline silicon layer are combined to form Si-O bonds, and the doped polycrystalline silicon layer containing the oxygen element is formed. Part of Si-O bonds in the ultrathin oxide layer are broken through the annealing process, oxygen is diffused into the doped amorphous silicon layer, the doped polycrystalline silicon layer containing the oxygen is formed, an oxygen source does not need to be additionally introduced, and the preparation process of the polycrystalline silicon layer containing the oxygen is simplified.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaics, and particularly relates to a preparation method of a solar cell, a solar cell, and a photovoltaic module. Background Art

[0002] The tunneling oxide passivated contact cell, abbreviated as TOPCon cell, is a kind of high-efficiency solar cell that uses an N-type silicon substrate and sequentially sets a tunneling oxide layer and a doped polysilicon layer on the back of the cell. A Chinese patent application with the application number 201610271978.0 discloses a controllable etching stacked passivation structure, its preparation method and application, and discloses the following technical solutions: including a double-layer passivation structure stacked on a crystalline silicon substrate in multiple layers, each of the double-layer passivation structures is composed of a layer of nano-silicon oxide film and a layer of doped polysilicon film, and the number of the double-layer passivation structures is 3 to 10 layers; at least one of the doped polysilicon films in the double-layer passivation structure contains one or more of carbon, nitrogen, and oxygen elements, and adding carbon, nitrogen, and oxygen elements to the doped polysilicon film is beneficial to improving the passivation performance. At the same time, it discloses the following preparation method: preparing an n-type silicon wafer, placing it in a PECVD chamber after standard RCA cleaning; using N 2 O plasma to prepare a 1nm nano-silicon oxide film on the surface of the crystalline silicon substrate, and then depositing a 25nm doped amorphous silicon film, and additionally introducing methane to dope C atoms; the above steps are repeated 4 times. The sample is put into a tube furnace and annealed at 900°C for 30 minutes, and the doped amorphous silicon film is converted into a doped polysilicon film, obtaining a 4-layer double-layer passivation structure composed of a nano-silicon oxide film and a C-doped polysilicon film, and the nano-silicon oxide also contains C atoms. An alumina film is deposited on the surface of the sample by ALD, and then a silicon nitride film is deposited by PECVD to obtain a passivation and antireflection layer. The sample is transferred to a tube furnace and post-treated by hydrogenation in a mixed atmosphere of nitrogen and hydrogen, and annealed at 420°C for 30 minutes to obtain a passivated wafer. However, this technical solution requires an additional oxygen source when preparing a polysilicon layer doped with oxygen elements, and the preparation process is complex. Summary of the Invention

[0003] One of the purposes of the present invention is to provide a preparation method of a solar cell, which solves the problems proposed in the above background art.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is: a preparation method of a solar cell, including the following steps:

[0005] S1: Texturing the surface of the silicon substrate and forming an emitter on one side of the silicon substrate;

[0006] S2: Sequentially preparing a tunneling layer and an intrinsic amorphous silicon layer on the other side of the silicon substrate;

[0007] S3: Prepare multiple layers of ultrathin oxide layers and intrinsic amorphous silicon layers alternately on the surface of the intrinsic polysilicon layer;

[0008] S4: Diffuse the intrinsic amorphous silicon layer to form a doped amorphous silicon layer;

[0009] S5: Anneal the doped amorphous silicon layer to convert the amorphous silicon into polysilicon, and at the same time combine oxygen atoms with silicon atoms in the polysilicon layer to form Si - O bonds, forming a doped polysilicon layer containing oxygen elements;

[0010] S6: Prepare a passivation and antireflection layer on the front side and a passivation layer on the back side respectively;

[0011] S7: Prepare a front electrode and a back electrode respectively.

[0012] Based on the above - mentioned solution and as a preferred solution of the above - mentioned solution, the thickness of each ultrathin oxide layer is 0.1 nm to 1 nm.

[0013] Based on the above - mentioned solution and as a preferred solution of the above - mentioned solution, the thickness of each doped polysilicon layer is 5 nm to 80 nm.

[0014] Based on the above - mentioned solution and as a preferred solution of the above - mentioned solution, the total thickness of each doped polysilicon layer is 40 nm to 250 nm.

[0015] Based on the above - mentioned solution and as a preferred solution of the above - mentioned solution, the tunneling layer, the intrinsic amorphous silicon layer and the ultrathin oxide layer are prepared by LPCVD process.

[0016] Based on the above - mentioned solution and as a preferred solution of the above - mentioned solution, the doping element in the doped polysilicon layer is phosphorus element or boron element, and the doping concentration of phosphorus element or boron element in each doped polysilicon layer increases sequentially from inside to outside.

[0017] Based on the above - mentioned solution and as a preferred solution of the above - mentioned solution, the silicon substrate is an N - type silicon substrate, the emitter is arranged on the front side of the silicon substrate, and the tunneling layer is arranged on the back side of the silicon substrate.

[0018] Based on the above - mentioned solution and as a preferred solution of the above - mentioned solution, the ultrathin oxide layer is a silicon oxide layer.

[0019] The second object of the present invention is to provide a solar cell prepared by the above - mentioned preparation method.

[0020] The third object of the present invention is to provide a photovoltaic module, and the photovoltaic module includes the solar cell as described above.

[0021] The beneficial effects of the present invention are:

[0022] 1. When preparing a solar cell with a stacked structure of a multi-layer tunneling layer and a doped polysilicon layer containing oxygen element, the preparation method of this solar cell simultaneously combines oxygen atoms with silicon atoms in the polysilicon layer to form Si-O bonds, thereby forming a doped polysilicon layer containing oxygen element. There is no need to additionally introduce an oxygen source, which will not introduce other impurity interferences, and only one diffusion process is required subsequently to complete, simplifying the preparation process of the polysilicon layer containing oxygen element.

[0023] 2. The doped polysilicon layer contains oxygen element, which helps to improve the passivation effect of the doped polysilicon layer and can also reduce the parasitic absorption in the medium and long wavelength bands; at the same time, it increases the band gap of the doped polysilicon layer, thereby reducing the absorption ability of incident light, increasing the short-circuit current of the doped polysilicon layer, and further improving the photoelectric conversion efficiency of the solar cell.

[0024] 3. The multi-layer ultra-thin oxide layer can enhance the multiple reflections of incident light in the battery, enhance light absorption, reduce the external reflection loss and back surface absorption loss at the back of the battery, and increase Jsc; the multi-layer ultra-thin oxide layer can also block the diffusion of P or B impurities to the silicon substrate, reduce the Auger recombination loss caused by impurity diffusion in the silicon substrate, improve the passivation effect, and increase Voc; and due to the blocking of the multi-layer ultra-thin oxide layer, a part of the impurities are blocked and then flow back to the surface layer, reducing the contact resistance between the electrode and the doped polysilicon layer. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for describing the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 It is a schematic structural diagram after step S1 of the present invention.

[0027] Figure 2 It is a schematic structural diagram after step S2 of the present invention.

[0028] Figure 3 It is a schematic structural diagram after step S3 of the present invention.

[0029] Figure 4 It is a schematic structural diagram after step S4 of the present invention.

[0030] Figure 5 It is a schematic structural diagram after step S5 of the present invention.

[0031] Figure 6 It is a schematic structural diagram after step S6 of the present invention.

[0032] Figure 7 This is the structural schematic diagram after step S7 of the present invention.

[0033] The reference numerals are as follows:

[0034] 1. Silicon substrate; 2. Emitter; 3. Tunneling layer; 4. Intrinsic amorphous silicon layer; 5. Ultra-thin oxide layer; 6. Doped amorphous silicon layer; 7. Doped polysilicon layer; 8. Passivation and antireflection layer; 9. Passivation layer; 10. Front electrode; 11. Back electrode. Specific embodiments

[0035] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0037] As shown in the attached Figure 1 to the attached Figure 7 A method for preparing a solar cell includes the following steps:

[0038] S1: Texturize the surface of the silicon substrate 1 and form an emitter 2 on one side of the silicon substrate 1;

[0039] S2: Sequentially prepare a tunneling layer 3 and an intrinsic amorphous silicon layer 4 on the other side of the silicon substrate 1;

[0040] S3: Sequentially and alternately prepare multiple layers of ultra-thin oxide layers 5 and intrinsic amorphous silicon layers 4 on the surface of the intrinsic polysilicon layer;

[0041] S4: Diffuse the intrinsic amorphous silicon layer 4 to form a doped amorphous silicon layer 6;

[0042] S5: Anneal the doped amorphous silicon layer 6 to convert amorphous silicon into polysilicon, and at the same time combine oxygen atoms with silicon atoms in the polysilicon layer to form Si-O bonds, thereby forming a doped polysilicon layer 7 containing oxygen elements;

[0043] S6: Prepare a passivation and antireflection layer 8 on the front and a passivation layer 9 on the back respectively;

[0044] S7: Prepare the front electrode 10 and the back electrode 11 respectively.

[0045] This solar cell preparation method combines oxygen atoms and silicon atoms in the polysilicon layer into Si-O bonds when preparing a solar cell with multiple layers of ultra-thin oxide layers and doped polysilicon layers containing oxygen elements, thereby forming a doped polysilicon layer containing oxygen elements. No additional oxygen source is required, and no interference from other impurities is introduced. Only one diffusion process is required to complete the process, thereby simplifying the preparation process of the polysilicon layer containing oxygen elements. The provision of multiple layers of ultra-thin oxide layers can enhance the multiple reflections of incident light in the battery, enhance light absorption, reduce external reflection losses and back absorption losses on the back of the battery, and improve Jsc; the multiple layers of ultra-thin oxide layers can also block the diffusion of P or B impurities into the silicon substrate, reduce Auger recombination losses caused by impurity diffusion in the silicon substrate, improve the passivation effect, and improve Voc; and due to the blocking of the multiple layers of ultra-thin oxide layers, a portion of the impurities are blocked and then flow back to the surface layer, thereby reducing the contact resistance between the electrode and the doped polysilicon layer.

[0046] The thickness of each ultra-thin oxide layer 5 is 0.1 nm to 1 nm. When multiple ultra-thin oxide layers and semiconductor layers are stacked, the diffusion barrier effect of each ultra-thin oxide layer is weak, which is conducive to the entry of doped elements into the silicon substrate to form a field passivation effect.

[0047] The thickness of each doped polysilicon layer 7 is 5 nm to 80 nm.

[0048] The total thickness of each doped polysilicon layer 7 is 40 nm to 250 nm.

[0049] The tunneling layer 3, the intrinsic amorphous silicon layer 4 and the ultra-thin oxide layer 5 are prepared by using the LPCVD process.

[0050] The doping element in the doped polysilicon layer 7 is phosphorus or boron, and the doping concentration of phosphorus or boron in each layer of the doped polysilicon layer 7 increases from the inside to the outside. The doped polysilicon layer located in the outer layer is directly in contact with the electrode, has a high doping concentration, and has better conductivity, which can reduce the contact resistance between the electrode and the doped polysilicon layer; the doped polysilicon layer located in the inner layer is close to the silicon substrate, has a low doping concentration, and has better passivation performance, which can reduce the recombination with the silicon substrate.

[0051] Since the doping concentration of phosphorus or boron in the doped polysilicon layer increases successively from the inside to the outside, the diffusion of oxygen into the polysilicon layer doped with a high concentration of phosphorus or boron is restricted. Therefore, the oxygen content in each of the doped polysilicon layers 6 decreases successively from the inside to the outside. The semiconductor layer located on the outer layer is in direct contact with the electrode, has a high doping concentration and better conductivity, which can reduce the contact resistance between the electrode and the semiconductor layer; the semiconductor layer located on the inner layer is close to the silicon substrate, has a low doping concentration and better passivation performance, which can reduce the recombination with the silicon substrate.

[0052] The silicon substrate 1 is an N-type silicon substrate 1, the emitter 2 is disposed on the front surface of the silicon substrate 1, and the tunneling layer 3 is disposed on the back surface of the silicon substrate 1. The ultra-thin oxide layer 5 is a silicon oxide layer.

[0053] A solar cell is prepared by using the above-mentioned preparation method.

[0054] A photovoltaic module, the photovoltaic module includes the solar cell as described above.

[0055] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments described herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a solar cell, characterized in that: The following steps are involved: S1: performing a texturing process on the surface of a silicon substrate (1), and forming an emitter (2) on one side of the silicon substrate (1); S2: sequentially preparing a tunneling layer (3) and an intrinsic amorphous silicon layer (4) on the other side of the silicon substrate (1); S3: alternately preparing multiple layers of ultra-thin oxide layers (5) and intrinsic amorphous silicon layers (4) on the surface of the intrinsic polycrystalline silicon layer; S4: diffusing the intrinsic amorphous silicon layer (4) to form a doped amorphous silicon layer (6); S5: performing annealing treatment on the doped amorphous silicon layer (6) to convert the amorphous silicon into polycrystalline silicon, and at the same time combining oxygen atoms with silicon atoms in the polycrystalline silicon layer to form Si-O bonds, thereby forming a doped polycrystalline silicon layer (7) containing oxygen elements; S6: preparing a front passivation anti-reflection layer (8) and a back passivation layer (9) respectively; S7: Prepare the front electrode (10) and the back electrode (11) respectively.

2. A method for preparing a solar cell according to claim 1, characterized in that: The thickness of each ultra-thin oxide layer (5) is 0.1 nm to 1 nm.

3. A method for preparing a solar cell according to claim 2, characterized in that: The thickness of each doped polysilicon layer (7) is 5 nm to 80 nm.

4. A method for preparing a solar cell according to claim 3, characterized in that: The total thickness of each doped polysilicon layer (7) is 40 nm to 250 nm.

5. The method for preparing a solar cell according to claim 1, characterized in that: The tunneling layer (3), the intrinsic amorphous silicon layer (4) and the ultra-thin oxide layer (5) are prepared by adopting the LPCVD process.

6. The method for preparing a solar cell according to claim 1, characterized in that: The doping element in the doped polysilicon layer (7) is phosphorus or boron, and the doping concentration of the phosphorus or boron in each layer of the doped polysilicon layer (7) increases from the inside to the outside.

7. The method for preparing a solar cell according to claim 1, characterized in that: The silicon substrate (1) is an N-type silicon substrate (1), the emitter (2) is arranged on the front side of the silicon substrate (1), and the tunneling layer (3) is arranged on the back side of the silicon substrate (1).

8. The method for preparing a solar cell according to claim 1, characterized in that: The ultra-thin oxide layer (5) is a silicon oxide layer.

9. A solar cell, characterized in that: The method is prepared by any one of claims 1 to 8.

10. A photovoltaic module, characterized in that: The photovoltaic module comprises the solar cell according to claim 9.

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