Solar cell and method for manufacturing the same

Abstract

The present invention provides a solar cell, comprising: a silicon substrate, wherein the second surface of the silicon substrate has alternately arranged gate line areas and non-gate line areas; a first doping layer arranged on the second surface of the gate line area; a first passivation layer covering the second surface of the non-gate line area and the first doping layer; and a first electrode, wherein the first electrode passes through the first passivation layer and contacts the first doping layer; the parasitic absorption on the back side of the solar cell of the present invention is reduced, current loss is avoided, and the conversion efficiency of the solar cell is improved.

Description

Technical Field

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

[0002] Solar cells are devices that convert solar energy directly into electrical energy, and their working principle is based on the photovoltaic effect. Among them, TOPCon solar cells are highly efficient solar cells that sequentially form an extremely thin tunnel SiOx layer and a highly doped polysilicon layer on the back of the silicon wafer, which makes TOPCon solar cells have excellent surface passivation and chemical passivation effects, and can effectively reduce the carrier recombination loss at the metal contact on the back of the solar cell while maintaining good contact performance, thereby improving the conversion efficiency of the cell. It has become the mainstream product of industrial solar cell manufacturers.

[0003] However, although the highly doped polysilicon layer used in the back structure of TOPCon solar cells can reduce the metal contact resistance, it also brings about the problem of near-infrared parasitic absorption, resulting in current loss. Summary of the invention

[0004] The object of the present invention is to provide a solar cell and a method for preparing the same.

[0005] To achieve the above-mentioned object of the invention, the present invention provides a solar cell, comprising:

[0006] A silicon substrate, wherein the silicon substrate has a first surface and a second surface opposite to each other, wherein the second surface has gate line regions and non-gate line regions arranged alternately;

[0007] A first doped layer, wherein the first doped layer is located on the second surface of the silicon substrate in the gate line region;

[0008] A first passivation layer, the first passivation layer covers the non-gate line region of the silicon substrate and the first doped layer;

[0009] A first electrode is provided, wherein the first electrode passes through the first passivation layer and contacts the first doping layer.

[0010] As a further improvement of the present invention, the first doping layer has the same doping type as the silicon substrate; and / or the doping concentration of the first doping layer is: 3E20-8E20.

[0011] As a further improvement of the present invention, one side surface of the first doping layer is in contact with the second surface of the silicon substrate, and the other side surface of the first doping layer is away from the second surface of the silicon substrate.

[0012] As a further improvement of the present invention, the doping concentration of the first doping layer is greater than the doping concentration of the silicon substrate.

[0013] As a further improvement of the present invention, the thickness of the first doping layer is 50 nm to 200 nm; and / or the width of the first doping layer is 180 nm to 230 nm.

[0014] As a further improvement of the present invention, the width of the gate line region is greater than or equal to the width of the first electrode; and / or the width of the gate line region is 180 nm to 230 nm.

[0015] As a further improvement of the present invention, the first passivation layer is in direct contact with the second surface of the silicon substrate in the non-gate line region.

[0016] As a further improvement of the present invention, the first passivation layer is an aluminum oxide layer; and / or the thickness of the first passivation layer is 2 nm to 7 nm.

[0017] As a further improvement of the present invention, the solar cell also includes a first anti-reflection layer arranged on the surface of the first passivation layer on the side away from the silicon substrate; the first anti-reflection layer is composed of at least one of a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer; and / or the thickness of the first anti-reflection layer is 60nm to 130nm.

[0018] As a further improvement of the present invention, the solar cell also includes a second doped layer, a second passivation layer, a second anti-reflection layer, and a second electrode, which are sequentially arranged on the first surface of the silicon substrate, and the second electrode passes through the second anti-reflection layer and the second passivation layer to contact the second doped layer.

[0019] As a further improvement of the present invention, the solar cell further includes a second doping layer disposed on the first surface of the silicon substrate and a second electrode in contact with the second doping layer, and both the first electrode and the second electrode are electrodes processed by laser assisted sintering.

[0020] To achieve the above object of the invention, the present invention further provides a method for preparing a solar cell, comprising:

[0021] Providing a silicon substrate, wherein the silicon substrate has a first surface and a second surface opposite to each other, wherein the second surface includes gate line regions and non-gate line regions arranged alternately;

[0022] forming a doping structure on the second surface of the silicon substrate;

[0023] Removing the doping structure in the non-gate line area on the second surface of the silicon substrate, and retaining the doping structure in the gate line area as the first doping layer;

[0024] forming a first passivation layer on the second surface of the silicon substrate;

[0025] forming a second doped layer at the first surface of the silicon substrate;

[0026] A first electrode electrically contacting the first doped layer and a second electrode electrically contacting the second doped layer are formed.

[0027] As a further improvement of the present invention, the first passivation layer contacts the second surface of the silicon substrate in the non-gate line region, and the first passivation layer contacts the surface of the first doped layer in the gate line region.

[0028] As a further improvement of the present invention, the step of “removing the doping structure in the non-gate line region on the second surface of the silicon substrate and retaining the doping structure in the gate line region as the first doping layer” includes:

[0029] forming a first mask layer on the doping structure;

[0030] The laser grooving process removes the first mask layer in the non-gate line area;

[0031] Removing the doped structure in the non-gate line area by an alkali polishing process;

[0032] The first mask layer in the gate line region is removed, and the doping structure in the gate line region is retained as the first doping layer.

[0033] As a further improvement of the present invention, the preparation method further includes: forming a second passivation layer and / or a second anti-reflection layer on the surface of the second doping layer; and / or forming a first anti-reflection layer on the surface of the first passivation layer.

[0034] As a further improvement of the present invention, “forming a first electrode electrically contacting the first doped layer and a second electrode electrically contacting the second doped layer” specifically includes the following steps:

[0035] forming the first electrode and the second electrode by screen printing process;

[0036] The laser-assisted sintering technology is used to perform auxiliary sintering on the first electrode and / or the second electrode.

[0037] As a further improvement of the present invention, the thickness of the first doping layer is 50nm~200nm; and / or, the width of the first doping layer is 180nm~230nm; and / or, the first passivation layer is an aluminum oxide layer; and / or, the thickness of the first passivation layer is 2nm~7nm.

[0038] The beneficial effects of the present invention are as follows: the solar cell of the present invention directly sets a first doping layer in the gate line region of the second surface of the silicon substrate, which can reduce the doping concentration of the polysilicon layer compared to the existing TOPCon solar cell, solve the problem of near-infrared parasitic absorption on the back of the existing TOPCon solar cell, reduce the parasitic absorption of the second surface of the solar cell of the present invention, avoid current loss, and improve the conversion efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic structural diagram of a solar cell of the present invention;

[0040] Figure 2(a) to Figure 2(i) is a flow chart for preparing the solar cell of the present invention;

[0041] Among them, 10, solar cell; 1, silicon substrate; 11, gate line area; 12, non-gate line area; 21, first doping layer; 21a, doping structure; 22, first passivation layer; 23, first anti-reflection layer; 24, first electrode; 31, second doping layer; 32, second passivation layer; 33, second anti-reflection layer; 34, second electrode; 4, first mask layer; 5, second mask layer. DETAILED DESCRIPTION

[0042] The present invention will be described in detail below in conjunction with the embodiments shown in the accompanying drawings. However, the embodiments do not limit the present invention, and any structural, methodological, or functional changes made by a person skilled in the art based on the embodiments are all within the protection scope of the present invention.

[0043] Please refer to Figure 1 As shown in FIG. 2 , the present invention provides a solar cell 10 , which includes a silicon substrate 1 , wherein the silicon substrate 1 has a first surface and a second surface opposite to each other, and the second surface has gate line regions 11 and non-gate line regions 12 arranged alternately.

[0044] In a specific embodiment, the silicon substrate 1 is an N-type silicon substrate, and the resistivity of the silicon substrate 1 is 0.3 Ω·cm to 7 Ω·cm. That is, the doping elements in the silicon substrate 1 are N-type doping elements such as phosphorus (P) and antimony (Sb). Of course, this is not limited to this.

[0045] Specifically, the first surface of the silicon substrate 1 is a pyramid velvet surface, and the width of the pyramids in the pyramid velvet surface is 0.5 μm to 3 μm.

[0046] In the present invention, the width dimension of the pyramid refers to the width dimension of the pyramid base. The base is a square, and the side length of the square is called the base width or base dimension in the industry.

[0047] Below, the structure and preparation method of the solar cell in the present invention are specifically described with the first surface being the front side of the silicon substrate 1 and the second surface being the back side of the silicon substrate 1. Of course, it can be understood that this is not limited to this. In other embodiments, the first surface can also be the back side of the silicon substrate 1. In this case, the second surface is the front side of the silicon substrate 1.

[0048] The solar cell 10 further includes a first doping layer 21 located on the second surface of the silicon substrate 1 in the gate line area 11, a first passivation layer 22 covering the second surface and the non-gate line area 12 and the first doping layer 21, and a first electrode 24 passing through the first passivation layer 22 and contacting the first doping layer 21.

[0049] Specifically, one side surface of the first doped layer 21 is in contact with the second surface of the silicon substrate 1, and the other side surface of the first doped layer 21 is away from the second surface of the silicon substrate 1. The first passivation layer 22 is in direct contact with the second surface of the silicon substrate 1 in the non-gate line area 12, and covers the first doped layer 21 in the gate line area 11.

[0050] The solar cell 10 in the present invention improves the back structure of the existing TOPCon solar cell. By directly setting the first doping layer 21 in the gate line area 11 and setting the first passivation layer 22 on the first doping layer 21 and the non-gate line area 12, compared with the existing TOPCon solar cell, the doping concentration of the polysilicon layer can be reduced, the problem of near-infrared parasitic absorption on the back of the existing TOPCon solar cell is solved, the parasitic absorption of the second surface of the solar cell 10 is reduced, the current loss is avoided, and the conversion efficiency of the solar cell 10 is improved.

[0051] Specifically, the first doping layer 21 has the same doping type as the silicon substrate 1. That is, in an embodiment where the silicon substrate 1 is an N-type silicon substrate, the doping element in the first doping layer 21 is an N-type doping element. In a specific embodiment, the N-type doping element is phosphorus, that is, the first doping layer 21 is a phosphorus-doped polysilicon layer. Of course, this is not limited to this. In other embodiments, other N-type doping elements such as arsenic, antimony, bismuth, etc. may also be selected.

[0052] Specifically, the doping concentration of the first doping layer 21 is 3E20-8E20. In a preferred embodiment, the optimal doping concentration of the first doping layer 21 is 4E20. Compared with the existing TOPCon solar cell, the doping concentration of the first doping layer 21 is reduced, and further the back structure of the solar cell 10 in the present invention does not have the problem of near-infrared parasitic absorption, thus avoiding current loss and improving the conversion efficiency of the solar cell 10.

[0053] Specifically, the doping concentration of the first doping layer 21 is greater than the doping concentration of the silicon substrate 1 .

[0054] In some optional implementations, the thickness of the first doping layer 21 is 50 nm to 200 nm. In a specific implementation, the thickness of the first doping layer 21 is 80 nm to 100 nm, but of course, it is not limited thereto.

[0055] In some optional implementations, the width of the gate line region 11 is greater than or equal to the width of the first electrode 24 , so as to improve the electrical connection effect between the first electrode 24 and the gate line region 11 .

[0056] In a specific implementation, the width of the gate line region 11 is 180 nm to 230 nm, and correspondingly, the width of the first doping layer 21 is 180 nm to 230 nm.

[0057] In some optional implementations, the first passivation layer 22 is an aluminum oxide layer to enhance the interface passivation effect.

[0058] Specifically, the thickness of the first passivation layer 22 is 2 nm to 7 nm, and preferably 3 nm to 6 nm.

[0059] In some optional embodiments, the solar cell 10 further includes a first anti-reflection layer 23 disposed on a surface of the first passivation layer 22 away from the silicon substrate 1. The first anti-reflection layer 23 is composed of at least one of a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer. That is, the first anti-reflection layer 23 may be a single-layer structure, such as a single-layer silicon nitride layer, a silicon oxynitride layer, or a silicon oxide layer; the first anti-reflection layer 23 may also be a stacked structure, such as a layer of silicon nitride layer and a layer of silicon oxynitride layer stacked together, or a layer of silicon nitride layer and a layer of silicon oxide layer stacked together, or a layer of silicon oxide layer and a layer of silicon oxynitride layer, or a layer of silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer stacked together.

[0060] Specifically, the thickness of the first anti-reflection layer 23 is 60 nm to 130 nm.

[0061] Furthermore, the solar cell 10 also includes a second doping layer 31, a second passivation layer 32, a second anti-reflection layer 33, and a second electrode 34, which are sequentially arranged on the first surface of the silicon substrate 1, and the second electrode 34 passes through the second anti-reflection layer 33 and the second passivation layer 32 and contacts the second doping layer 31.

[0062] In a specific embodiment, the second doped layer 31 is a boron-doped emitter, that is, the doping element of the second doped layer is boron. Of course, this is not limited to this.

[0063] Specifically, the doping concentration of the second doping layer 31 is 3e18-3e19cm -3 The thickness of the second doping layer 31 is 1-1.5 μm. The square resistance of the second doping layer 31 is 250-300 Ω / sq, preferably 250-280 Ω / sq.

[0064] In a preferred embodiment, the optimal thickness of the second doping layer 31 is 1.2 μm. The second passivation layer 32 is an aluminum oxide layer to enhance the interface passivation effect.

[0065] Specifically, the thickness of the second passivation layer 32 is 2 nm to 7 nm, and preferably 3 nm to 6 nm.

[0066] In a specific embodiment, the second passivation layer 32 and the first passivation layer 22 are formed simultaneously, which simplifies the manufacturing process of the solar cell 10 .

[0067] The second anti-reflection layer 33 is composed of at least one of a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer. That is, the second anti-reflection layer 33 may be a single-layer structure, such as a single-layer silicon nitride layer, a silicon oxynitride layer, or a silicon oxide layer; the second anti-reflection layer 33 may also be a stacked structure, such as a layer of silicon nitride layer and a layer of silicon oxynitride layer stacked together, or a layer of silicon nitride layer and a layer of silicon oxide layer stacked together, or a layer of silicon oxide layer and a layer of silicon oxynitride layer, or a layer of silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer stacked together.

[0068] In a specific embodiment, the second anti-reflection layer 33 has the same structure as the first anti-reflection layer 23 , so that when preparing the solar cell 10 , the second anti-reflection layer 33 and the first anti-reflection layer 23 can be prepared simultaneously, thereby simplifying the preparation process of the solar cell 10 .

[0069] Specifically, the second anti-reflection layer 33 has a thickness of 60 nm to 130 nm.

[0070] In this embodiment, the first electrode 24 is a laser-assisted sintering electrode, which can reduce the contact area recombination between the first electrode 24 and the first doping layer 21, reduce the contact area resistance, form effective contact, and improve the conversion efficiency and reliability of the solar cell 10.

[0071] In some optional embodiments, the second electrode 34 is an electrode processed by laser assisted sintering, which can greatly reduce the recombination of the contact area on the first surface of the solar cell 10 and further improve the conversion efficiency and reliability of the solar cell 10.

[0072] Specifically, the laser-assisted sintering process refers to irradiating the solar cell 10 with a laser of a preset high intensity while applying a deflection voltage of 10V or more.

[0073] Furthermore, the present invention also provides a method for preparing the above-mentioned solar cell 10, comprising the following steps:

[0074] Providing a silicon substrate 1, wherein the silicon substrate 1 has a first surface and a second surface opposite to each other, wherein the second surface includes gate line regions 11 and non-gate line regions 12 arranged alternately;

[0075] A doping structure 21a is formed on the second surface of the silicon substrate 1.

[0076] The doping structure 21 a in the non-gate line region 12 on the second surface of the silicon substrate 1 is removed, and the doping structure 21 a in the gate line region 11 is retained as the first doping layer 21 ;

[0077] forming a first passivation layer on the second surface of the silicon substrate 1;

[0078] forming a second doping layer 31 on the first surface of the silicon substrate 1;

[0079] A first electrode 24 electrically contacting the first doping layer 21 and a second electrode 34 electrically contacting the second doping layer 31 are formed.

[0080] In a specific embodiment, the silicon substrate 1 is an N-type silicon substrate, that is, the doping elements in the silicon substrate 1 are N-type doping elements such as phosphorus (P) and antimony (Sb). Of course, this is not limited to this.

[0081] Specifically, the first surface of the silicon substrate 1 is a pyramid velvet surface, and the width of the pyramids in the pyramid velvet surface is 0.5 μm to 3 μm.

[0082] In the present invention, the width dimension of the pyramid refers to the width dimension of the pyramid base. The base is a square, and the side length of the square is called the base width or base dimension in the industry.

[0083] Below, the method for preparing the solar cell in the present invention is specifically described with the first surface being the front side of the silicon substrate 1 and the second surface being the back side of the silicon substrate 1. Of course, it can be understood that this is not limited to this. In other embodiments, the first surface can also be the front side of the silicon substrate 1. In this case, the second surface is the back side of the silicon substrate 1.

[0084] In the method for preparing a solar cell of the present invention, a first doping layer is directly prepared on the gate line region 11 on the second surface / back side of the silicon substrate 1, thereby improving the back side structure of the existing TOPCon solar cell, eliminating the tunnel SiOx layer on the back side of the existing TOPCon solar cell, solving the problem of near-infrared parasitic absorption on the back side of the existing TOPCon solar cell, reducing the parasitic absorption on the back side of the solar cell, avoiding current loss, and improving the conversion efficiency of the solar cell.

[0085] Specifically, the doping type of the doping structure 21a is the same as that of the silicon substrate 1. That is, in an embodiment where the silicon substrate 1 is an N-type silicon substrate, the doping element in the doping structure 21a is an N-type doping element. In a specific embodiment, the N-type doping element is phosphorus, that is, the doping structure 21a is a phosphorus-doped polysilicon layer. Of course, this is not limited to this. In other embodiments, other N-type doping elements such as arsenic, antimony, bismuth, etc. may also be selected.

[0086] In a specific embodiment, "forming a doping structure 21a on the second surface of the silicon substrate 1" specifically means: performing amorphous silicon deposition and doping element diffusion treatment on the second surface of the silicon substrate 1, such as first depositing a layer of amorphous silicon and then using a doping element diffusion device to deposit a doping source layer on the second surface of the silicon substrate 1, and annealing and diffusion to form the doping structure 21a. Of course, this is not limited to this. In other embodiments, amorphous silicon and microcrystalline silicon may be deposited in a mixed state on the second surface and then doping element diffusion treatment may be performed to form the doping structure 21a; or amorphous silicon and polycrystalline silicon may be deposited in a mixed state on the second surface and then doping element diffusion treatment may be performed to form the doping structure 21a; or amorphous silicon, microcrystalline silicon and polycrystalline silicon may be deposited in a mixed state on the second surface and then doping element diffusion treatment may be performed to form the doping structure 21a; or phosphorus-doped amorphous silicon may be deposited on the second surface first and then annealed to form the doping structure 21a.

[0087] Specifically, the amorphous silicon deposition and doping element diffusion treatment on the second surface of the silicon substrate 1 include sequentially depositing amorphous silicon and a doping source layer, high temperature advancement and oxidation annealing, wherein, when depositing amorphous silicon, the corresponding process parameters are: deposition time 1650s, temperature 610°C, pressure 200mTorr, SiH4 flow rate 500-930sccm; when the doping element is phosphorus, the corresponding process parameters for depositing a doping source layer are: deposition time 1500s, temperature 830°C, pressure 150mbar, N2 flow rate 2200sccm, O2 flow rate 700sccm; high temperature advancement time is 550s, temperature is 910°C, pressure is 150mbar, N2 flow rate is 1000sccm; oxidation annealing time is 300s, temperature is 850°C, pressure is 300mbar, N2 flow rate is 2000sccm, O2 flow rate is 1500sccm.

[0088] In a specific embodiment, the thickness of the doping structure 21 a is 50-200 nm, and the doping depth is also 50 nm to 200 nm, preferably 80 nm to 100 nm. It can be seen that the thickness of the doping structure 21 a is the thickness of the subsequent first doping layer 21 .

[0089] In some optional embodiments, the step of “removing the doping structure 21a in the non-gate line region 12 on the second surface of the silicon substrate 1 and retaining the doping structure 21a in the gate line region 11 as the first doping layer 21” includes:

[0090] forming a first mask layer 4 on the doping structure 21a;

[0091] The laser grooving process removes the first mask layer 4 of the non-gate line area 12;

[0092] The doping structure 21a of the non-gate line region 12 is removed by an alkali polishing process;

[0093] The first mask layer 4 in the gate line region 11 is removed, and the doping structure 21 a in the gate line region 11 is retained as the first doping layer 21 .

[0094] In a specific embodiment, the doping structure 21a is the same as the doping element in the first mask layer 4. For example, when the doping element is phosphorus, the first mask layer 4 is a phosphorus-doped silicon oxide mask layer.

[0095] In a specific embodiment, during the final oxidation annealing process of the doping element diffusion treatment in the process of preparing the doping structure 21 a , the surface of the doping structure 21 a can be oxidized to form the first mask layer 4 .

[0096] Specifically, the thickness of the first mask layer 4 is 20 nm to 50 nm.

[0097] Specifically, during the "laser grooving process to remove the first mask layer 4 of the non-gate line area 12", the laser power is 40-60%, of which the optimal laser power is 50%, the laser wavelength is 3-8μm, the frequency is 700kHz, and the scanning speed is 75000-80000mm / s.

[0098] After laser grooving to remove the first mask layer 4 in the non-gate line area 12, the remaining width of the first mask layer 4 in the gate line area 11 is 180nm-230nm, and correspondingly, the width of the first doped layer 21 finally formed is 180nm-230nm.

[0099] In a specific embodiment, when the doping element is phosphorus, that is, the first mask layer 4 is a phosphorus-doped silicon oxide mask layer, “removing the first mask layer 4 in the gate line region 11 ” specifically includes the following steps: removing the first mask layer 4 using hydrofluoric acid.

[0100] In some optional embodiments, "forming a first passivation layer 22 on the second surface of the silicon substrate 1" specifically includes: depositing a layer of aluminum oxide on the second surface of the silicon substrate 1 using ALD, wherein the aluminum oxide layer covers the non-gate line area 12 and the first doped layer 21 of the second surface, that is, the aluminum oxide layer contacts the second surface in the non-gate line area 12, and contacts the surface of the first doped layer 21 in the gate line area 11.

[0101] Specifically, the deposition time of the aluminum oxide layer is 6-8 seconds, wherein the optimal deposition time is 7 seconds, and the temperature is 300° C. The thickness of the first passivation layer 22 is 2-7 nm, preferably 3-6 nm.

[0102] Furthermore, after forming the first passivation layer 22 on the second surface of the silicon substrate 1 , the preparation method further comprises the following step: forming a first anti-reflection layer 23 on the surface of the first passivation layer 22 .

[0103] Specifically, a first anti-reflection layer 23 is deposited on the back of the aluminum oxide layer by PECVD, and the thickness of the first anti-reflection layer is 60-130 nm.

[0104] The deposition time of the first anti-reflection layer 23 is 650-700 s, the temperature is 510-530° C., and the pressure is 1750 Pa.

[0105] In a specific embodiment, the first anti-reflection layer is a silicon nitride layer. Of course, this is not limiting, in other embodiments, the first anti-reflection layer may also be a silicon oxynitride layer or a silicon oxide layer, or a stacked structure formed by at least two of the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer.

[0106] In a specific embodiment, “forming a first electrode 24 electrically contacting the first doping layer 21” specifically includes the following steps:

[0107] The first electrode 24 is formed on the surface of the first anti-reflection layer 23 by screen printing. Specifically, conductive paste is firstly screen printed on the surface of the first anti-reflection layer 23, and then sintered at high temperature to form the first electrode 24 that passes through the first anti-reflection layer 23 and the first passivation layer 33 and contacts the first doping layer 21.

[0108] In some optional implementations, after the first electrode 24 is formed by a screen printing process, the preparation method further includes the following step: performing auxiliary sintering on the first electrode 24 by using a laser assisted sintering technique.

[0109] After the first electrode 24 is sintered by laser assisted sintering technology, the silver silicon in the first doping layer 21 and the first electrode 24 diffuses into each other, and a laser sintered silver silicon interdiffusion layer is formed in the metal contact area, which can reduce the contact area recombination between the first electrode 24 and the first doping layer 21, reduce the contact area resistance, and improve the conversion efficiency and reliability of the solar cell 10.

[0110] Specifically, during laser-assisted sintering, the laser power is 10%-20%, the frequency is 15%, the bias voltage is 40-50V, wherein the optimal bias voltage is 45V, and the scanning speed is 55m / s.

[0111] In some optional implementations, before forming the doping structure 21 a on the second surface of the silicon substrate 1 , a second doping layer 31 is first formed on the first surface of the silicon substrate 1 .

[0112] In a specific embodiment, the second doped layer 31 is a boron-doped emitter, that is, the doping element of the second doped layer is boron. Of course, this is not limited to this.

[0113] Specifically, “forming a second doping layer 31 on the first surface of the silicon substrate 1” specifically includes the following steps:

[0114] Performing double-sided texturing on the silicon substrate 1;

[0115] Boron diffusion is performed on the double-sided textured silicon substrate 1 to form a second doping layer and a second mask layer 5 located on the second doping layer.

[0116] Specifically, "double-sided texturing of the silicon substrate 1" is as follows: double-sided alkaline texturing of the silicon substrate 1 is performed using an aqueous solution of KOH, NaOH or TMAH to form pyramid texturing surfaces on both the first and second surfaces of the silicon substrate 1 to remove cutting damage on the surface of the N-type substrate.

[0117] “Diffusion of boron on the double-sided textured silicon substrate 1 to form a second doping layer and a second mask layer 5 located on the second doping layer” specifically refers to performing boron diffusion treatment on the first surface of the silicon substrate 1, such as using Huachuang’s high-temperature equipment to deposit a boron doping source layer on the first surface of the silicon substrate 1, and annealing and diffusion to form a second doping layer 31 and a second mask layer 5 located on the second doping layer 31, wherein the second doping layer 31 is a boron-doped emitter, and the second mask layer 5 is a boron-doped silicon oxide mask layer. The doping concentration in the second doping layer is 3e18~3e19cm -3 The square resistance of the second doped layer is 250 to 300 Ω / sq, preferably 250 to 280 Ω / sq.

[0118] Specifically, the boron diffusion treatment on the first surface of the silicon substrate 1 includes deposition, high temperature driving and oxidation annealing in sequence. In a specific embodiment, the deposition time is 400-700s, wherein the optimal deposition time is 600s; the deposition temperature is 835°C, the oxidation time is 3000-3600s, the oxidation temperature is 1045°C, the oxygen amount is 18000-22000sccm, and the pump pressure is 600-800mbar.

[0119] After forming the second doping layer 31 on the first surface of the silicon substrate 1 and before forming the doping structure 21a on the second surface of the silicon substrate 1, the preparation method further includes the following steps:

[0120] The second surface of the silicon substrate 1 is polished to remove the second mask layer 5 and the second doping layer 31 on the second surface.

[0121] It can be understood that after the second surface of the silicon substrate 1 is polished to form a polished surface, the polished surface is the second surface of the silicon substrate 1, and the doping structure 21a and the like are subsequently prepared on the second surface to form a structure in the solar cell 10 corresponding to the second surface.

[0122] “Polishing the second surface of the silicon substrate 1 to remove the second mask layer 5 and the second doping layer 31 on the second surface” specifically includes: first using a single-sided chain device to remove the second mask layer 5 on the second surface using hydrofluoric acid, then performing alkaline polishing on the second surface to remove the edge junctions and the second surface plating to remove the second doping layer 31 on the second surface, and finally performing a cleaning process.

[0123] In some optional embodiments, after removing the doping structure 21a of the non-gate line area 12 on the second surface of the silicon substrate 1, the first mask layer 4 of the second surface gate line area 11, and removing the second mask layer 5 on the first surface, a first passivation layer 22 and a first anti-reflection layer 23 are sequentially formed on the first doped layer 21 on the second surface of the silicon substrate 1 and the surface of the non-gate line area 12, and a second passivation layer 32 and a second anti-reflection layer 33 are synchronously formed on the second doped layer 31 on the first surface; when preparing the first electrode 24, a second electrode 34 is synchronously prepared on the second anti-reflection layer.

[0124] It can be known that the preparation method of the second electrode 34 in the present invention is consistent with the preparation method of the first electrode 24, which is also first screen-printed on the second anti-reflection layer 33, and then sintered at high temperature to form the second electrode 34 that passes through the second anti-reflection layer 33 and the second passivation layer 32 and contacts the second doping layer 31, and then the second electrode 34 is laser-assisted sintered using laser-assisted sintering technology.

[0125] Specifically, the above-mentioned “removing the doping structure 21a of the non-gate line area 12 on the second surface of the silicon substrate 1, the first mask layer 4 of the second surface gate line area 11, and removing the second mask layer 5 on the first surface” is performed after removing the first mask layer 4 of the non-gate line area 12 on the second surface of the silicon substrate 1. They include the following steps:

[0126] Pass the first surface of the silicon substrate 1 through a chain hydrofluoric acid bath to remove the edge of the first surface and the first mask layer 4 formed by coating the first surface;

[0127] Alkaline polishing process, using NaOH and H2O2 at 65°C to alkali etch and remove the doping structure 21a on the first surface, the edge plating and the non-gate line area 12 on the second surface;

[0128] Finally, hydrofluoric acid is used to remove the second mask layer 5 on the first surface and the first mask layer 4 on the second surface gate line region 11 .

[0129] The specific steps of “removing the doping structure 21a of the non-gate line region 12 on the second surface of the silicon substrate 1, the first mask layer 4 of the second surface gate line region 11, and removing the second mask layer 5 on the first surface” are as follows:

[0130] S1, chain HF: remove the edge after N2 annealing and the first mask layer 4 of the first surface, and keep the second surface PSG to protect the doping structure 21a of the second surface;

[0131] S2, alkaline polishing: using NaOH and additives to remove the redundant doping structures 21a on the first surface and the edge and the doping structures 21a on the non-gate line area 12 of the second surface of the silicon substrate 1, so as to avoid problems such as poor battery appearance and poor passivation effect;

[0132] S3, alkali washing: remove the residual additives in the alkali polishing and the impurities on the surface of the solar cell;

[0133] S4, pickling: neutralizing the residual alkali solution in the previous step with oxygen to remove metal impurity ions, and at the same time, removing the second mask layer 5 on the first surface and the first mask layer 4 on the second surface gate line area 11;

[0134] S5, slow lifting: Use room temperature deionized water, and the robot slowly lifts the flower basket to prevent water marks on the surface. Using hot water can easily introduce other impurities.

[0135] S6. Drying: Dry the prepared solar cells and flower baskets at a high temperature of 90°C to prevent liquid residue from remaining in the solar cells and flower baskets during unloading, which would affect subsequent processes.

[0136] Combination Figure 2(a) to Figure 2(i) FIG. 1 is a flow chart of a method for preparing the solar cell 10 in a specific embodiment of the present invention, wherein the first doping layer 21 is a phosphorus-doped polysilicon layer. Specifically, the method for preparing the solar cell 10 includes the following steps:

[0137] As shown in FIG. 2( a ), the silicon substrate 1 is subjected to double-sided texturing treatment, that is, the silicon substrate 1 is subjected to double-sided alkali texturing using an aqueous solution of KOH, NaOH or TMAH, and pyramid velvet surfaces are formed on both the first surface and the second surface of the silicon substrate 1, wherein the size of the pyramid base in the pyramid velvet surface is 0.5 μm to 3 μm;

[0138] As shown in FIG. 2( b ), the silicon substrate 1 after double-sided texturing is subjected to boron diffusion to form a second doping layer 31 and a second mask layer 5 located on the second doping layer 31 ;

[0139] As shown in FIG. 2( c ), the second surface of the silicon substrate 1 is polished to remove the second doping layer 31 and the second mask layer 5 on the second surface;

[0140] As shown in FIG. 2( d ), amorphous silicon is first deposited on the polished surface of the second surface of the silicon substrate 1 and then phosphorus diffusion treatment is performed to form a doping structure 21 a and a first mask layer 4 ;

[0141] As shown in FIG. 2( e ), the first mask layer 4 of the non-gate line region 12 of the second surface of the silicon substrate 1 is removed by laser grooving, and the retained width of the phosphorus first mask layer 4 of the gate line region 11 is 180 nm to 230 nm;

[0142] As shown in FIG. 2( f), the first surface of the silicon substrate 1 is subjected to a chain hydrofluoric acid bath to remove the first mask layer 4 on the first surface and the edge coating on one side, and then the first surface, the edge coating and the doping structure 21a of the non-gate line region 12 on the second surface of the silicon substrate 1 are removed by alkaline etching, and then the second mask layer 5 on the first surface and the first mask layer 4 on the gate line region 11 on the second surface are removed by hydrofluoric acid;

[0143] As shown in FIG. 2( g ), an aluminum oxide layer is deposited on the first surface and the second surface by ALD, with a thickness of 2 nm to 7 nm, preferably 3 nm to 6 nm, that is, a second passivation layer 32 is deposited on the surface of the second doped layer 31, and a first passivation layer 22 is deposited on the first doped layer 21 and the non-gate line region 12 of the second surface;

[0144] As shown in FIG. 2( h ), an anti-reflection layer is deposited on the surface of the aluminum oxide layer on the first surface and the second surface by PECVD, and the thickness of the anti-reflection layer is 60 to 130 nm, that is, the second anti-reflection layer 33 is deposited on the surface of the second passivation layer 32, and the first anti-reflection layer 23 is deposited on the surface of the first passivation layer 22;

[0145] As shown in FIG2(i), the electrode paste is printed on the second anti-reflection layer 33 and the first anti-reflection layer 23 by screen printing and then sintered and cured at high temperature to form the second electrode 34 and the first electrode 24, and then the second electrode 34 and the first electrode 24 are subjected to laser-assisted sintering.

[0146] The solar cell 10 in the present invention only directly sets the first doping layer 21 on the gate line area 11 of the second surface of the silicon substrate 1. Compared with the existing TOPCon solar cell, it can reduce the doping concentration of the polysilicon layer, solve the problem of near-infrared parasitic absorption on the back of the existing TOPCon solar cell, reduce the parasitic absorption on the back of the solar cell 10, avoid current loss, and improve the conversion efficiency of the solar cell 10.

[0147] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0148] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A solar cell, characterized in that: include: A silicon substrate, wherein the silicon substrate has a first surface and a second surface opposite to each other, wherein the second surface has gate line regions and non-gate line regions arranged alternately; A first doped layer, wherein the first doped layer is located on the second surface of the silicon substrate in the gate line region; A first passivation layer, the first passivation layer covers the non-gate line region of the silicon substrate and the first doped layer; A first electrode is provided, wherein the first electrode passes through the first passivation layer and contacts the first doping layer.

2. The solar cell according to claim 1, characterized in that: The first doping layer has the same doping type as the silicon substrate; and / or the doping concentration of the first doping layer is: 3E20-8E20.

3. The solar cell according to claim 1, characterized in that: One side surface of the first doping layer is in contact with the second surface of the silicon substrate, and the other side surface of the first doping layer is away from the second surface of the silicon substrate.

4. The solar cell according to claim 1, characterized in that: The doping concentration of the first doping layer is greater than the doping concentration of the silicon substrate.

5. The solar cell according to claim 1, characterized in that: The thickness of the first doping layer is 50 nm to 200 nm; and / or the width of the first doping layer is 180 nm to 230 nm.

6. The solar cell according to claim 1, characterized in that: The width of the gate line region is greater than or equal to the width of the first electrode; and / or the width of the gate line region is 180 nm to 230 nm.

7. The solar cell according to claim 1, characterized in that: The first passivation layer directly contacts the second surface of the silicon substrate in the non-gate line region.

8. The solar cell according to claim 1, characterized in that: The first passivation layer is an aluminum oxide layer; and / or the first passivation layer has a thickness of 2 nm to 7 nm.

9. The solar cell according to claim 1, characterized in that: The solar cell also includes a first anti-reflection layer arranged on a surface of the first passivation layer away from the silicon substrate; the first anti-reflection layer is composed of at least one of a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer; and / or the thickness of the first anti-reflection layer is 60nm to 130nm.

10. The solar cell according to claim 1, characterized in that: The solar cell further includes a second doping layer, a second passivation layer, a second anti-reflection layer, and a second electrode which are sequentially arranged on the first surface of the silicon substrate. The second electrode passes through the second anti-reflection layer and the second passivation layer and contacts the second doping layer.

11. The solar cell according to claim 1, characterized in that: The solar cell further includes a second doping layer disposed on the first surface of the silicon substrate and a second electrode in contact with the second doping layer. Both the first electrode and the second electrode are electrodes processed by laser assisted sintering.

12. A method for preparing a solar cell, characterized in that: include: Providing a silicon substrate, wherein the silicon substrate has a first surface and a second surface opposite to each other, wherein the second surface includes gate line regions and non-gate line regions arranged alternately; forming a doping structure on the second surface of the silicon substrate; Removing the doping structure in the non-gate line area on the second surface of the silicon substrate, and retaining the doping structure in the gate line area as the first doping layer; forming a first passivation layer on the second surface of the silicon substrate; forming a second doped layer at the first surface of the silicon substrate; A first electrode electrically contacting the first doped layer and a second electrode electrically contacting the second doped layer are formed.

13. The method for preparing a solar cell according to claim 12, characterized in that: The first passivation layer contacts the second surface of the silicon substrate in the non-gate line region, and the first passivation layer contacts the surface of the first doped layer in the gate line region.

14. The method for preparing a solar cell according to claim 12, characterized in that: The step of "removing the doping structure in the non-gate line area on the second surface of the silicon substrate and retaining the doping structure in the gate line area as the first doping layer" includes: forming a first mask layer on the doping structure; The laser grooving process removes the first mask layer in the non-gate line area; Removing the doped structure in the non-gate line area by an alkali polishing process; The first mask layer in the gate line region is removed, and the doping structure in the gate line region is retained as the first doping layer.

15. The method for preparing a solar cell according to claim 12, characterized in that: The preparation method further includes: forming a second passivation layer and / or a second anti-reflection layer on the surface of the second doping layer; and / or forming a first anti-reflection layer on the surface of the first passivation layer.

16. The method for preparing a solar cell according to claim 12, characterized in that: “Forming a first electrode electrically contacting the first doped layer and a second electrode electrically contacting the second doped layer” specifically includes the following steps: forming the first electrode and the second electrode by screen printing process; The laser-assisted sintering technology is used to perform auxiliary sintering on the first electrode and / or the second electrode.

17. The method for preparing a solar cell according to claim 12, characterized in that: The thickness of the first doping layer is 50nm to 200nm; and / or, the width of the first doping layer is 180nm to 230nm; and / or, the first passivation layer is an aluminum oxide layer; and / or, the thickness of the first passivation layer is 2nm to 7nm.

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