TOPCon solar cell front structure, back structure, TOPCon solar cell and its preparation

Abstract

The present invention discloses a front structure and a back structure of a TOPCon solar cell, a TOPCon solar cell and preparation thereof, and belongs to the technical field of solar cells. The front structure of the TOPCon solar cell provided by the present invention is provided with a first element diffusion layer only in the electrode region, and polysilicon doped with a first element is laminated on the first element diffusion layer, and the first electrode is in contact with the polysilicon doped with the first element, and such a structural design reduces the recombination current and contact resistance of the battery. In the front structure, whether it is N-type or P-type, the surface or the contact region of the electrode, extremely low recombination can be achieved, which significantly improves the open circuit voltage (Voc) of the battery.

Description

Technical Field

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

[0002] With the development of the photovoltaic industry, the conversion efficiency of crystalline silicon solar cells has been continuously improved, gradually approaching the theoretical limit. In the future, if the battery efficiency is to be further improved, better contact area passivation needs to be achieved. Conventional means to improve the passivation level of the contact area include selective emitters or surface fields, which can achieve lower contact recombination by increasing the local doping concentration or reducing the contact area. However, such means cannot fundamentally improve the problems of contact area recombination and resistance loss. Reducing the contact area will increase the contact resistance, which will lead to a loss of fill factor (FF), and will also reduce the battery efficiency.

[0003] Tunneling oxide passivation contact (TOPCon) technology is an effective means to achieve passivation of the contact area of ​​solar cells. In the existing TOPCon cell structure, the back side is passivated by tunneling oxide and doped polysilicon stacking, which can achieve extremely low surface and contact area recombination rates. Due to the parasitic absorption of polysilicon, the front side of the cell is generally passivated by boron diffused PN junction and aluminum oxide / silicon nitride stacking, and the recombination rate is relatively large, which has a certain impact on the open circuit voltage (Voc) of the cell; at the same time, the lateral resistance loss caused by the high square resistance emitter also limits the fill factor of the cell, affecting the photoelectric conversion efficiency of the solar cell. Summary of the invention

[0004] 1. Problem to be solved

[0005] The main purpose of the present invention is to provide a front structure of a TOPCon solar cell, aiming to improve the conversion efficiency of the solar cell; at the same time, the present invention also provides a TOPCon solar cell having the front structure and a preparation process.

[0006] 2. Technical solution

[0007] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] According to the purpose of the present invention, the first aspect of the present invention provides a front structure of a TOPCon solar cell, the front structure comprising a first electrode structure, and a passivation layer and an anti-reflection layer arranged on the front of a silicon wafer;

[0009] The first electrode structure includes a first electrode, which passes through a passivation layer and an anti-reflection layer, is disposed on the front side of the silicon wafer, and forms an electrode region;

[0010] Wherein, in the electrode region, the front side of the silicon wafer has a first element diffusion layer and first element doped polysilicon, and the first electrode is in contact with the first element doped polysilicon.

[0011] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, in the electrode region, the front side of the silicon wafer has a first element diffusion layer and a first element doped polysilicon layer, and the first electrode is in contact with the first element doped polysilicon layer.

[0012] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, in the electrode region, a polysilicon layer doped with a first element is formed, and the first electrode is in contact with the polysilicon layer doped with the first element.

[0013] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the first element-doped polysilicon layer is stacked on the first element diffusion layer, and the first electrode is in contact with the first element-doped polysilicon layer.

[0014] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the thickness of the polycrystalline silicon layer doped with the first element is 20-500 nm.

[0015] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the doping concentration of the polycrystalline silicon doped with the first element is 1e18-1e20cm -3 ;

[0016] Alternatively, the doping concentration of the polysilicon layer doped with the first element is 1e18-1e20cm -3 .

[0017] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, in the electrode region, silicon dioxide is further provided between the first element diffusion layer and the polysilicon doped with the first element;

[0018] Alternatively, in the electrode region, silicon dioxide is further provided between the first element diffusion layer and the first element-doped polysilicon layer.

[0019] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, in the electrode region, between the first element diffusion layer and the first element doped polysilicon, there is further: a layer containing silicon dioxide;

[0020] Alternatively, in the electrode region, a layer containing silicon dioxide is further provided between the first element diffusion layer and the first element-doped polysilicon layer.

[0021] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the silicon dioxide forms a tunneling oxide layer.

[0022] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, in the electrode region, a tunneling oxide layer is further provided between the first element diffusion layer and the first element doped polysilicon;

[0023] Alternatively, in the electrode region, a tunneling oxide layer is provided between the first element diffusion layer and the first element-doped polysilicon layer.

[0024] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the thickness of the layer containing silicon dioxide is 1 to 5 nm;

[0025] Alternatively, the thickness of the tunnel oxide layer is 1-5 nm.

[0026] The front structure of the TOPCon solar cell according to any embodiment of the first aspect of the present invention comprises an electrode region and a non-electrode region on the front side of the silicon wafer;

[0027] The polysilicon doped with the first element exists only in the electrode region; and / or,

[0028] The polysilicon layer doped with the first element exists only in the electrode region; and / or,

[0029] The silicon dioxide is present only in the electrode region; and / or,

[0030] The silicon dioxide-containing layer is present only in the electrode region; and / or,

[0031] The tunnel oxide layer only exists in the electrode region.

[0032] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the thickness of the first element diffusion layer is 10-10000 nm; further, the thickness of the first element diffusion layer is 100-2000 nm;

[0033] The element doping concentration of the first element diffusion layer is 1e15~1e20cm -3 ;

[0034] The element doping depth (junction depth) of the first element diffusion layer is 10-10000 nm; further, the thickness of the first element diffusion layer is 100-2000 nm.

[0035] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the first element is boron or phosphorus.

[0036] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, on the front side of the silicon wafer, a distance H between two adjacent first electrodes is 500-2000 μm, and the distance H is calculated based on the central axis of the electrode.

[0037] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the coverage width of the first element diffusion layer and / or the first element doped polysilicon layer does not exceed 80 μm; and / or the coverage width of the first tunneling oxide layer does not exceed 80 μm; and / or the coverage width of the silicon dioxide does not exceed 80 μm.

[0038] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the thickness of the passivation layer is 1-10 nm.

[0039] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the thickness of the anti-reflection layer is 20-200 nm.

[0040] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the passivation layer includes any one or two or more of oxide (such as aluminum oxide) and silicide (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0041] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0042] According to the front structure of the TOPCon solar cell of any embodiment of the first aspect of the present invention, the first electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0043] The second aspect of the present invention provides a method for preparing a front structure of a TOPCon solar cell according to any embodiment of the first aspect of the present invention, comprising:

[0044] Step S1: texturing and cleaning the front side of the silicon wafer;

[0045] Step S2: depositing a silicon glass layer containing a first element on the front side of the silicon wafer;

[0046] Step S3: using laser to locally process the front side of the silicon wafer to form an electrode region after the processing, wherein the silicon glass containing the first element in the electrode region is converted into polysilicon doped with the first element;

[0047] At the same time, the first element contained in the silicon glass layer diffuses on the substrate surface on the front side of the silicon wafer to form a first element diffusion layer;

[0048] Step S4: removing the silicon glass containing the first element from the non-electrode area on the front side of the silicon wafer;

[0049] Step S5: depositing a passivation layer and an anti-reflection layer on the front side of the silicon wafer;

[0050] Step S6: Printing and sintering on the front side of the silicon wafer to form a first electrode.

[0051] In the method for preparing the front structure of a TOPCon solar cell according to any embodiment of the second aspect of the present invention, in step S2, a tunneling oxide layer is first deposited on the front side of the silicon wafer, and then a silicon glass layer containing the first element is deposited;

[0052] Based on this, in step S3: when the front side of the silicon wafer is locally processed by laser, the first element contained in the silicon glass layer passes through the tunneling oxide layer to form a first element diffusion layer on the substrate surface of the front side of the silicon wafer.

[0053] According to the method for preparing the front structure of a TOPCon solar cell according to any embodiment of the second aspect of the present invention, in step S2, the thickness of the silicon glass layer containing the first element is 20-500 nm.

[0054] According to the method for preparing the front structure of a TOPCon solar cell of any embodiment of the second aspect of the present invention, in step S2, the doping concentration of the silicon glass layer containing the first element is 1e19-1e21cm -3 .

[0055] According to the method for preparing the front structure of a TOPCon solar cell according to any embodiment of the second aspect of the present invention, in step S2, the thickness of the tunneling oxide layer is 1-5 nm.

[0056] According to the method for preparing the front structure of a TOPCon solar cell of any embodiment of the second aspect of the present invention, in step S3, the thickness of the first element diffusion layer is 10-10000 nm; further, the thickness of the first element diffusion layer is 100-2000 nm;

[0057] The element doping concentration of the first element diffusion layer is 1e15~1e20cm -3 ;

[0058] The element doping depth (junction depth) of the first element diffusion layer is 10-10000 nm; further, the element doping depth (junction depth) of the first element diffusion layer is 100-2000 nm.

[0059] According to the method for preparing the front structure of a TOPCon solar cell in any embodiment of the second aspect of the present invention, in step S3, the process parameters of the laser treatment are:

[0060] The wavelength of the laser is: 300~1100 nm;

[0061] The frequency of the laser is: 10~100000 kHz;

[0062] Action time: 0.01~2min.

[0063] According to the method for preparing the front structure of a TOPCon solar cell in any embodiment of the second aspect of the present invention, in step S3, the process parameters of the laser treatment are:

[0064] The wavelength of the laser is: 500~1100 nm;

[0065] The frequency of the laser is: 500~10000 kHz;

[0066] Action time: 0.01~1min.

[0067] According to the method for preparing the front structure of a TOPCon solar cell in any embodiment of the second aspect of the present invention, in step S4, the process parameters of the sintering treatment are:

[0068] Sintering temperature: 600~900℃;

[0069] Sintering time: 0.5~5min.

[0070] In the method for preparing the front structure of a TOPCon solar cell according to any embodiment of the second aspect of the present invention, the first element is boron or phosphorus.

[0071] According to the purpose of the present invention, the third aspect of the present invention provides a back structure of a TOPCon solar cell, the back structure comprising a layer structure, and a second electrode;

[0072] The layer structure includes a second element diffusion layer, a tunneling oxide layer, a second element doped polysilicon layer, a passivation layer, and an anti-reflection layer;

[0073] The second electrode passes through the passivation layer and the anti-reflection layer and contacts the polysilicon layer doped with the second element.

[0074] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the thickness of the second element diffusion layer is 10-5000 nm;

[0075] The element doping concentration of the second element diffusion layer is 1e15~1e21cm -3 ;

[0076] The element doping depth (junction depth) of the second element diffusion layer is 10-5000 nm.

[0077] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the thickness of the second element diffusion layer is 100-2000 nm;

[0078] The element doping concentration of the second element diffusion layer is 1e15~1e21cm -3 ;

[0079] The element doping depth (junction depth) of the second element diffusion layer is 100-2000 nm.

[0080] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the thickness of the tunneling oxide layer is 1-5 nm.

[0081] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the thickness of the polysilicon layer doped with the second element is 20-500 nm;

[0082] The doping concentration of the second element is 1e19~1e21cm -3 .

[0083] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the thickness of the passivation layer is 1-10 nm.

[0084] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the thickness of the anti-reflection layer is 20-200 nm.

[0085] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the passivation layer includes any one or two or more of oxide (such as aluminum oxide) and silicide (such as silicon dioxide, silicon nitride, silicon carbide); for example, the passivation layer is an aluminum oxide layer.

[0086] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the anti-reflection layer includes any one or two or more of oxides (such as aluminum oxide) and silicides (such as silicon dioxide, silicon nitride, silicon carbide); for example, the anti-reflection layer is a silicon nitride layer.

[0087] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the second electrode is a metal electrode, and the metal electrode includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-clad copper electrode, and a silver-clad copper electrode.

[0088] According to the back structure of the TOPCon solar cell of any embodiment of the third aspect of the present invention, the second element is boron or phosphorus.

[0089] The fourth aspect of the present invention provides a method for preparing a back structure of a TOPCon solar cell according to any embodiment of the third aspect of the present invention, comprising:

[0090] Step S1: texturing and cleaning the back side of the silicon wafer;

[0091] Step S2: depositing a tunneling oxide layer and an undoped polysilicon layer on the back side of the silicon wafer;

[0092] Step S3: performing a doping treatment of the undoped polysilicon with a second element to convert the undoped polysilicon into polysilicon doped with the second element;

[0093] At the same time, the second element passes through the tunnel oxide layer and diffuses on the substrate surface at the back of the silicon wafer to form a second element diffusion layer;

[0094] Step S4: removing the silicon glass containing the second element from the back of the silicon wafer;

[0095] Step S5: depositing a passivation layer and an anti-reflection layer on the back of the silicon wafer;

[0096] Step S6: Printing and sintering to form a second electrode on the back side of the silicon wafer.

[0097] According to the method for preparing the back structure of a TOPCon solar cell according to any embodiment of the fourth aspect of the present invention, in step S2, the thickness of the tunneling oxide layer is 1-5 nm.

[0098] According to the method for preparing the back structure of a TOPCon solar cell of any embodiment of the fourth aspect of the present invention, in step S2, the thickness of the polysilicon layer doped with the second element is 20-500 nm;

[0099] The doping concentration of the second element is 1e19~1e21cm -3 .

[0100] According to the method for preparing the back structure of a TOPCon solar cell according to any embodiment of the fourth aspect of the present invention, in step S2, the thickness of the passivation layer is 1-10 nm.

[0101] According to the method for preparing the back structure of a TOPCon solar cell according to any embodiment of the fourth aspect of the present invention, in step S2, the thickness of the anti-reflection layer is 20-200 nm.

[0102] According to the method for preparing the back structure of a TOPCon solar cell in any embodiment of the fourth aspect of the present invention, in step S3, the process parameters for doping the second element are:

[0103] Temperature: 750~950℃;

[0104] Time: 60~180min;

[0105] The flow rate of the second element: 100~10000sccm.

[0106] According to the method for preparing the back structure of a TOPCon solar cell in any embodiment of the fourth aspect of the present invention, in step S4, the process parameters of the sintering treatment are:

[0107] Sintering temperature: 600~900℃;

[0108] Sintering time: 0.5~5min.

[0109] In the method for preparing the back structure of a TOPCon solar cell according to any embodiment of the fourth aspect of the present invention, the second element is boron or phosphorus.

[0110] A fifth aspect of the present invention provides a TOPCon solar cell, wherein the TOPCon solar cell has:

[0111] The front structure of a TOPCon solar cell according to any embodiment of the first aspect of the present invention;

[0112] Alternatively, the front structure of a TOPCon solar cell prepared by the method of any embodiment of the second aspect of the present invention;

[0113] and a back structure, the back structure comprising:

[0114] A tunneling oxide layer, a polysilicon layer doped with a second element, a passivation layer, an anti-reflection layer, and a second electrode in contact with the polysilicon layer doped with the second element are arranged on the back of the silicon wafer.

[0115] A sixth aspect of the present invention provides a method for preparing a TOPCon solar cell as described in any embodiment of the fifth aspect of the present invention, comprising:

[0116] Step A1: texturing and cleaning both sides of the silicon wafer;

[0117] Step A2: depositing a tunnel oxide layer and an undoped polysilicon layer on the back side of the silicon wafer;

[0118] Step A3: performing a doping treatment on the undoped polysilicon with a second element, so that the undoped polysilicon is converted into polysilicon doped with the second element;

[0119] Step A4: removing, texturing, and cleaning the silicon glass containing the second element from the front side of the silicon wafer;

[0120] Step A5: first depositing a tunneling oxide layer on the front side of the silicon wafer, and then depositing a silicon glass layer containing the first element;

[0121] Step A6: When the front side of the silicon wafer is locally processed by laser, the first element contained in the silicon glass layer passes through the tunneling oxide layer to form a first element diffusion layer on the substrate surface of the front side of the silicon wafer;

[0122] Step A7: removing the silicon glass containing the first element from the non-electrode area on the front side of the silicon wafer; and at the same time, removing the silicon glass containing the second element from the back side of the silicon wafer;

[0123] Step A8: depositing a passivation layer and an anti-reflection layer on both sides of the silicon wafer;

[0124] Step A9: Printing and sintering on both sides of the silicon wafer to form a first electrode and a second electrode.

[0125] A seventh aspect of the present invention provides a TOPCon solar cell, wherein the TOPCon solar cell has a back structure and a front structure:

[0126] The back structure is the back structure of the TOPCon solar cell according to any embodiment of the third aspect of the present invention;

[0127] Alternatively, the back structure of a TOPCon solar cell prepared by the method of any embodiment of the fourth aspect of the present invention;

[0128] The front structure comprises:

[0129] A first element diffusion layer, a tunneling oxide layer, a passivation layer, an anti-reflection layer, and a first electrode in contact with the first element diffusion layer are arranged on the front side of the silicon wafer.

[0130] An eighth aspect of the present invention provides a method for preparing a TOPCon solar cell according to any embodiment of the seventh aspect of the present invention, comprising:

[0131] Step A1: texturing and cleaning both sides of the silicon wafer;

[0132] Step A2: depositing a tunneling oxide layer on both sides of the silicon wafer;

[0133] Step A3: depositing an undoped polysilicon layer on the back side of the silicon wafer;

[0134] Step A4: performing a doping treatment on the undoped polysilicon with a second element, so that the undoped polysilicon is converted into polysilicon doped with the second element;

[0135] At the same time, the second element passes through the tunnel oxide layer and diffuses on the substrate surface at the back of the silicon wafer to form a second element diffusion layer;

[0136] Step A5: removing, texturing, and cleaning the silicon glass containing the second element from the front side of the silicon wafer;

[0137] Step A6: performing diffusion treatment of the first element on the front side of the silicon wafer to form a first element diffusion layer;

[0138] Step A7: removing the silicon glass containing the first element from the non-electrode area on the front side of the silicon wafer; and at the same time, removing the silicon glass containing the second element from the back side of the silicon wafer;

[0139] Step A8: depositing a passivation layer and an anti-reflection layer on both sides of the silicon wafer;

[0140] Step A9: Printing and sintering on both sides of the silicon wafer to form a first electrode and a second electrode.

[0141] A ninth aspect of the present invention provides a TOPCon solar cell, wherein the TOPCon solar cell has:

[0142] The front structure of a TOPCon solar cell according to any embodiment of the first aspect of the present invention;

[0143] Alternatively, the front structure of a TOPCon solar cell prepared by the method of any embodiment of the second aspect of the present invention;

[0144] Also has:

[0145] The back structure of a TOPCon solar cell as described in any embodiment of the third aspect of the present invention;

[0146] Alternatively, the back structure of a TOPCon solar cell prepared by the method of any embodiment of the fourth aspect of the present invention.

[0147] A tenth aspect of the present invention provides a method for preparing a TOPCon solar cell, comprising:

[0148] Step A1: texturing and cleaning both sides of the silicon wafer;

[0149] Step A2: depositing a tunneling oxide layer and an undoped polysilicon layer on the back side of the silicon wafer;

[0150] Step A3: performing a doping treatment on the undoped polysilicon with a second element, so that the undoped polysilicon is converted into polysilicon doped with the second element;

[0151] At the same time, the second element passes through the tunnel oxide layer and diffuses on the substrate surface at the back of the silicon wafer to form a second element diffusion layer;

[0152] Step A4: removing, texturing, and cleaning the silicon glass containing the second element from the front side of the silicon wafer;

[0153] Step A5: first depositing a tunneling oxide layer on the front side of the silicon wafer, and then depositing a silicon glass layer containing the first element;

[0154] Step A6: When the front side of the silicon wafer is locally processed by laser, the first element contained in the silicon glass layer passes through the tunneling oxide layer to form a first element diffusion layer on the substrate surface of the front side of the silicon wafer;

[0155] Step A7: removing the silicon glass containing the first element from the non-electrode area on the front side of the silicon wafer; and at the same time, removing the silicon glass containing the second element from the back side of the silicon wafer;

[0156] Step A8: depositing a passivation layer and an anti-reflection layer on both sides of the silicon wafer;

[0157] Step A9: Printing and sintering on both sides of the silicon wafer to form a first electrode and a second electrode.

[0158] According to the TOPCon solar cell of any embodiment of the fifth aspect of the present invention, or the TOPCon solar cell prepared by the method of any embodiment of the sixth aspect of the present invention, or the TOPCon solar cell of any embodiment of the seventh aspect of the present invention, or the TOPCon solar cell prepared by the method of any embodiment of the eighth aspect of the present invention, or the TOPCon solar cell of any embodiment of the ninth aspect of the present invention, or the TOPCon solar cell prepared by the method of any embodiment of the tenth aspect of the present invention, the first element is boron element or phosphorus element, the second element is boron element or boron element, and the first element and the second element are of different types.

[0159] Beneficial Effects

[0160] (1) The front structure of existing TOPCon solar cells generally uses a boron diffusion layer and an aluminum oxide and silicon nitride stack for passivation. The recombination rate is relatively large, which affects the open circuit voltage (Voc) and fill factor (FF) of the cell, and ultimately reduces the cell efficiency.

[0161] The front structure of the TOPCon solar cell provided by the present invention has a first element diffusion layer only in the electrode region, and polysilicon doped with the first element is stacked on the first element diffusion layer. The first electrode is in contact with the polysilicon doped with the first element. Such a structural design reduces the recombination current and contact resistance of the battery. In the front structure, whether it is N-type or P-type, the surface or the contact area of ​​the electrode, extremely low recombination can be achieved, which significantly improves the open circuit voltage (Voc) of the battery.

[0162] (2) The front structure of the TOPCon solar cell provided by the present invention has polysilicon doped with the first element only in the electrode region, which has a very small coverage area on the front of the silicon wafer, and can effectively avoid the adverse effects of parasitic absorption on the cell.

[0163] (3) The method for preparing the front structure of the TOPCon solar cell provided by the present invention can use a low-temperature process (such as PECVD low-temperature deposition and laser doping) to complete the deposition of the first element diffusion layer and the first element-doped polysilicon layer on the front of the silicon wafer; thereby avoiding the adverse effects of the traditional high-temperature element diffusion method on the life of the silicon wafer.

[0164] (4) The present invention provides a back structure of a TOPCon solar cell, which uses an N-type TOPCon structure as an emitter, thereby reducing the square resistance and recombination of the back structure of the cell and improving the fill factor (FF) of the cell.

[0165] (5) The front structure of the TOPCon solar cell provided by the present invention is that a first element diffusion layer is provided only in the electrode region, and polycrystalline silicon doped with the first element is stacked on the first element diffusion layer. The first electrode is in contact with the polycrystalline silicon doped with the first element. Such a structural design reduces the recombination current and contact resistance of the cell;

[0166] Its back structure uses an N-type TOPCon structure as the emitter, which can simultaneously reduce the square resistance and recombination of the back structure of the battery and improve the fill factor (FF) of the battery.

[0167] The battery with the above-mentioned front structure and back structure, whether N-type or P-type, the surface or the contact area of ​​the electrode can achieve extremely low recombination, significantly improve the open circuit voltage (Voc) and fill factor (FF) of the battery, and ultimately improve the battery efficiency.

[0168] (6) The index method of the TOPCon solar cell provided by the present invention is that the processes of the front and back structures of the cell are carried out independently, and the overall process is simple, which is conducive to reducing manufacturing costs. Specifically, after the TOPCon structure on the back of the cell is completed, the polysilicon layer coated on the front side is removed by texturing, which can solve the leakage problem at the edge of the cell without introducing additional process steps; then, single-sided processes such as PECVD and laser are used to complete the preparation of the front structure of the cell while avoiding affecting the back side. BRIEF DESCRIPTION OF THE DRAWINGS

[0169] Figure 1 A schematic diagram of the front structure of a TOPCon solar cell provided in Example 1 of the present invention;

[0170] Figure 2 A schematic diagram of the back structure of a TOPCon solar cell provided in Example 2 of the present invention;

[0171] Figure 3 A schematic diagram of the front structure of a TOPCon solar cell provided in Comparative Example 1 of the present invention;

[0172] Figure 4 A schematic diagram of the back structure of a TOPCon solar cell provided in Comparative Example 2 of the present invention;

[0173] Figure 5 A schematic structural diagram of a TOPCon solar cell (TOPCon-1) provided in Example 3 of the present invention;

[0174] Figure 6 A schematic structural diagram of a TOPCon solar cell (TOPCon-4) provided in Example 3 of the present invention;

[0175] In the figure: 100, silicon wafer;

[0176] 110, second tunneling oxide layer; 121, second passivation layer; 122, second anti-reflection layer; 130, second electrode; 141, second element diffusion layer; 142, second element doped polysilicon layer;

[0177] 150, first element diffusion layer; 161, first passivation layer; 162, first anti-reflection layer; 170, first electrode; 181, first tunneling oxide layer; 182, first element doped polysilicon layer;

[0178] 200, electrode area;

[0179] H, the distance between two adjacent first electrodes; h, the coverage width; C, the central axis. DETAILED DESCRIPTION

[0180] The present disclosure may be more easily understood by reference to the following description in conjunction with the accompanying drawings and examples, all of which constitute a part of the present disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions or parameters described and / or shown herein. Further, the terms used herein are only used for the purpose of describing specific embodiments by way of example and are not intended to be limiting unless otherwise stated.

[0181] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically not included, each separate embodiment is considered to be combinable with any other embodiment, and the combination is considered to represent another different embodiment. Conversely, for the sake of simplicity, the various features of the present disclosure described in the context of a single embodiment may also be provided individually or in any sub-combination. Finally, although a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or sub-structure itself may also be considered to be an independent embodiment.

[0182] Unless otherwise indicated, it should be understood that each individual element in a list and each combination of individual elements in the list will be interpreted as a different embodiment. For example, a list of embodiments expressed as "A, B, or C" should be interpreted to include embodiments "A", "B", "C", "A or B", "A or C", "B or C", or "A, B, or C".

[0183] In the present disclosure, the singular forms of the articles "a", "an", and "the" also include the corresponding plural references, and references to a specific value include at least that specific value unless the context clearly indicates otherwise. Thus, for example, reference to "a substance" is a reference to at least one of that substance and its equivalents.

[0184] When items are described by using conjunction terms such as “… and / or…”, the description should be understood to include any one of the associated listed items and all combinations of one or more thereof; for example, A and / or B should be interpreted as an embodiment including “A” but not including “B”, an embodiment including “B” but not including “A”, and an embodiment including “A” and “B”.

[0185] In general, the use of the term "about" indicates an approximate value that may vary depending on the desired properties obtained by the disclosed subject matter, and will be interpreted in a context-dependent manner based on function. Therefore, one of ordinary skill in the art will be able to interpret a certain degree of difference on a case-by-case basis. In some cases, the number of significant figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about". In other cases, a gradient in a range of values ​​can be used to determine the range of differences allowed by the term "about". Further, all ranges in this disclosure are inclusive and combinable, and reference to the values ​​stated in the range includes each value within the range.

[0186] Throughout the specification of this application document, when a certain part is described as “including” a certain constituent element, unless otherwise clearly described to the contrary, it does not mean that other constituent elements are excluded but that other constituent elements may also be included.

[0187] Throughout the specification of the present invention, when a certain step is recorded as being "above" or "before" other steps, it not only includes the case where a certain step has a direct time series relationship with other steps, but also includes the same rights as the case where a certain step has an indirect time series relationship where the time series of the order of two steps is changed, such as a mixing step after each step.

[0188] Throughout the specification of the present invention, when it is recorded as "according to any embodiment of the ... aspect of the ... object of the present invention...", unless otherwise clearly stated to the contrary, it does not mean that the constituent elements of the described scheme that appear before and after it are excluded, but that other constituent elements may also be included.

[0189] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs; the terms used herein and / or include any and all combinations of one or more of the listed items. In order to make the technical solutions and advantages of the present invention clear, the technical solutions in the embodiments of the present invention will be fully described below.

[0190] Example 1

[0191] The embodiment of the present invention provides a front structure of a TOPCon solar cell (labeled as Front-1). For the convenience of description, only the part related to the embodiment of the present invention is shown. Figure 1 shown.

[0192] The front structure of the solar cell provided in this embodiment includes:

[0193] A first element diffusion layer 150, a first tunneling oxide layer 181, a first element doped polysilicon layer 182, a first passivation layer 161, a first anti-reflection layer 162 and a first electrode 170 are arranged on the front side of the silicon wafer 100;

[0194] The first electrode 170 passes through the first passivation layer 161 and the first anti-reflection layer 162 to contact the first element-doped polysilicon layer 182 .

[0195] Regarding the "silicon wafer 100", it has a front side facing the sun during normal operation and a back side opposite to the front side, wherein the front side is a light-receiving side, and the back side is arranged on the other side of the silicon wafer 100 relative to the front side; wherein, the silicon wafer 100 can be a P-type or N-type silicon wafer, and can be a polycrystalline silicon wafer or a quasi-single-crystalline silicon wafer, and the corresponding type of silicon wafer 100 can be selected according to actual use needs.

[0196] It should be pointed out that the surface of the silicon wafer 100 can be made into a velvet structure (referred to as velvet) by using surface texturing technology, based on which the reflection loss of surface light can be further reduced, the utilization rate of incident light by the silicon wafer 100 can be improved, and the short-circuit current of the battery can be increased. The surface texturing method can generally adopt mechanical grooving, chemical corrosion, plasma etching, etc., and finally obtain a velvet structure, which includes but is not limited to alkali polishing surface, mechanical polishing surface, random pyramid, inverted pyramid, spherical crown, V-shaped groove, and morphology between the above morphologies. In addition, it can usually form an irregular hemispherical velvet texture by acid velvet, form a pyramid velvet texture by alkali velvet, or first form a pyramid velvet texture by alkali velvet and then smooth the pyramid tip by acid velvet. At this time, the surface morphology formed at the groove on the back of the silicon wafer 100 is conducive to increasing the absorption and reuse of light by the silicon wafer 100, so as to increase the short-circuit current density, thereby improving the conversion efficiency of solar cells.

[0197] Specifically in this embodiment, the silicon wafer 100 is a phosphorus-doped N-type single crystal silicon wafer, and the surface of the phosphorus-doped N-type single crystal silicon wafer is textured and cleaned by an alkali texturing method. More specifically, the resistivity of the silicon wafer 100 in this embodiment is 1 ohm·cm, the thickness is 130 um, and the reflectivity is 9%.

[0198] The "first element diffusion layer 150" needs to have the same polarity as the silicon wafer 100. For example, if the silicon wafer 100 is a phosphorus-doped N-type silicon wafer, the first element diffusion layer 150 is an N-type doping region containing diffused N-type dopants. If the silicon wafer 100 is a boron-doped P-type silicon wafer, the first element diffusion layer 150 is a P-type doping region containing diffused P-type dopants. Furthermore, the thickness of the first element diffusion layer 150 is 10~10000nm, and the element doping concentration of the first element diffusion layer 150 is 1e15~1e20cm -3 , the element doping depth (junction depth) of the first element diffusion layer 150 is 10~10000nm.

[0199] Specifically in this embodiment, the silicon wafer 100 is a boron-doped P-type silicon wafer, and the first element diffusion layer 150 is correspondingly a boron diffusion layer; the first element diffusion layer 150 is only located in a local area on the front side of the silicon wafer 100, but not in the entire area, that is, the first element diffusion layer 150 is only present in the following areas: Figure 1 The electrode region 200 shown in FIG. 1 is a schematic diagram of an electrode region 200; the thickness of the first element diffusion layer 150 is 1000 nm, and the element doping concentration of the first element diffusion layer 150 is 5e18 cm -3 , the element doping depth (junction depth) of the first element diffusion layer 150 is 1000nm.

[0200] The "first tunneling oxide layer 181" is mainly an ultra-thin oxide layer, which has an important influence on the properties of the passivation contact, and good contact comes from the defect-assisted tunneling mechanism or the micropores on the oxide layer. Preferably, the ultra-thin oxide layer is an ultra-thin silicon dioxide layer. Regarding the formation of the ultra-thin silicon dioxide layer, there are currently mainly thermal oxidation methods (including dry oxygen oxidation, wet oxygen oxidation), chemical vapor deposition (CVD) methods (including plasma chemical vapor deposition (PECVD) method, low pressure chemical vapor deposition (LPCVD) method), room temperature wet oxidation method, etc., preferably plasma chemical vapor deposition (PECVD) method. Furthermore, the thickness of the "first tunneling oxide layer 181" is 1~5nm. Specifically in this embodiment, the "first tunneling oxide layer 181" is a silicon oxide layer with a thickness of 2nm, and the first tunneling oxide layer 181 also only exists in Figure 1 The electrode region 200 is shown and is superimposed on the first element diffusion layer 150 .

[0201] The “polysilicon doped with the first element” is located between the first tunneling oxide layer 181 and the first passivation layer 161. The “polysilicon doped with the first element” is preferably present in the solar cell in the form of a layer to form the “polysilicon layer 182 doped with the first element”. The thickness of the “polysilicon layer 182 doped with the first element” is 20-500 nm, and the doping concentration of the polysilicon doped with the first element is 1e18-1e20 cm -3 Specifically in this embodiment, the “first element” is boron, the thickness of the polysilicon layer 182 doped with the first element is 100 nm, and the first element doping concentration of the polysilicon layer 182 doped with the first element is 5e18 cm -3 , and the first element doped polysilicon layer 182 also only exists in Figure 1 The electrode region 200 is shown and is superimposed on the first tunnel oxide layer 181;

[0202] Regarding the "first passivation layer 161", it can be an oxide layer of a single material with a thickness of 1 to 10 nm, or a combination of oxide layers of multiple materials and amorphous silicon layers, or a combination of multiple layers of amorphous silicon with different refractive indices of a single material; it is understandable that the specific structure of the first passivation layer 161 includes but is not limited to the several methods listed above, and the first passivation anti-reflection layer 160 can be set accordingly according to actual use needs, and no specific limitation is made here. Regarding the "first anti-reflection layer 162", it can be a silicon oxynitride layer, a silicon nitride layer, etc. with a thickness of 20 to 200 nm. It is understandable that the specific structure of the first anti-reflection layer 162 includes but is not limited to the several methods listed above, and the first passivation anti-reflection layer 160 can be set accordingly according to actual use needs, and no specific limitation is made here.

[0203] Furthermore, in some other preferred embodiments of the present invention, the first passivation layer 161 is preferably an oxide layer with a thickness of 1 to 10 nm, and the first anti-reflection layer 162 is preferably a silicon nitride layer with a thickness of 20 to 200 nm. At this time, the oxide layer and the silicon nitride layer are arranged in sequence from the silicon wafer 100 to the outside, and the oxide layer is in contact with the first element diffusion layer 150 on the inside, and the silicon nitride layer is in contact with the oxide layer. Furthermore, the oxide layer is preferably composed of one or more layers of a silicon oxide layer (also abbreviated as SiO2 layer) and an aluminum oxide layer (also abbreviated as Al2O3 layer). Therefore, the first passivation layer 161 can also be a combination of a silicon oxide layer and an aluminum oxide layer in the oxide layer. Among them, the silicon nitride layer (also abbreviated as SiN x The layer) is essentially a hydrogenated silicon nitride layer.

[0204] Regarding the “formation method” of the first passivation layer 161 or the first anti-reflection layer 162, the silicon oxide layer therein can be prepared by thermal oxidation (including dry oxygen oxidation, wet oxygen oxidation), chemical vapor deposition (CVD) (including plasma chemical vapor deposition (PECVD) method, low pressure chemical vapor deposition (LPCVD) method), room temperature wet oxidation method, etc., which are prepared according to actual use needs and are not specifically limited here; the silicon nitride layer can be prepared by chemical vapor deposition (CVD) (including plasma chemical vapor deposition (PECVD) method, low pressure chemical vapor deposition (LPCVD) method) The silicon nitride layer can be prepared by methods such as atomic layer deposition (ALD), plasma assisted ALD, pyrolysis deposition, delocalized PECVD, molecular beam epitaxy, deposition A1 plus oxidation, etc. It is prepared according to the actual use needs and is not specifically limited here. Aluminum oxide and silicon nitride will produce a large amount of hydrogen during the deposition of thin films, which can form good hydrogen passivation.

[0205] Specifically in this embodiment, Figure 1 As shown, an aluminum oxide (Al2O3) layer with a thickness of 5 nm is used as the first passivation layer 161, and a hydrogenated silicon nitride (SiN X ) layer as the first anti-reflection layer 162, at this time, the first passivation layer 161 and the first anti-reflection layer 162 are arranged in sequence from the silicon wafer 100 to the outside.

[0206] The “first electrode 170” mentioned above includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-coated copper electrode, and a silver-coated copper electrode. Figure 1 As shown, the first electrode 170 passes through the first passivation layer 161, passes through the first anti-reflection layer 162 and contacts the first element doped polysilicon layer 182. The distance H between two adjacent first electrodes is 500-2000 μm, and the distance H is calculated based on the distance between the central axes C of the two adjacent first electrodes 170. On this basis, Figure 1 As shown, the coverage width of the first element diffusion layer 150 is h, which does not exceed 80 μm, preferably 60-80 μm; the coverage width of the first element doped polysilicon layer 182 is also h, which does not exceed 80 μm, preferably 60-80 μm; the coverage width of the first tunneling oxide layer 181 is also h, which also does not exceed 80 μm, preferably 60-80 μm.

[0207] Specifically in this embodiment, the first electrode 170 is a silver electrode, the distance H between two adjacent first electrodes 170 is 1000 μm, the coverage width h of the first element diffusion layer 150 is 70 μm, the coverage width h of the first element doped polysilicon layer 182 is 70 μm, and the coverage width h of the first tunneling oxide layer 181 is 70 μm.

[0208] With respect to the front structure (labeled as Front-1) of the TOPCon solar cell provided in this embodiment, a specific preparation method is provided below, including:

[0209] Step S1: texturing and cleaning the front side of the silicon wafer 100, and controlling the thinning amount of a single side to be 1-5 μm;

[0210] Step S2: using plasma enhanced chemical vapor deposition (PECVD) to sequentially deposit a first tunneling oxide layer 181 and a silicon glass layer containing a first element (in this embodiment, borosilicate glass (BSG)) on the front surface of the silicon wafer 100 ;

[0211] The thickness of the silicon glass layer containing the first element is 120 nm and the doping concentration is 5e20 cm -3 ;

[0212] The thickness of the first tunnel oxide layer 181 is 2 nm;

[0213] Step S3: using laser to perform local processing on the front side of the silicon wafer 100, so that the BSG is crystallized and becomes the polysilicon layer 182 doped with the first element, and the first element is transmitted through the first tunneling oxide layer 181 to form an inner expansion layer (i.e., the first element diffusion layer 150) of the silicon wafer 100; finally, after the local laser processing, an electrode region 200 is formed, and the electrode region 200 contains the first element diffusion layer 150, the first tunneling oxide layer 181, and the polysilicon layer 182 doped with the first element;

[0214] Wherein, the process parameters of the laser treatment are:

[0215] The wavelength of the laser is: 1064 nm;

[0216] The frequency of the laser is: 5000kHz;

[0217] Action time: 0.05min.

[0218] Step S4: performing a process of removing the silicon glass containing the first element from the non-electrode area on the front side of the silicon wafer 100; specifically, hydrofluoric acid may be used to remove the BSG from the non-electrode area on the front side of the silicon wafer 100, and performing RCA cleaning;

[0219] Step S5: depositing a first passivation layer 161 and a first anti-reflection layer 162 in sequence on the front side of the silicon wafer 100;

[0220] Step S6: Printing and sintering to form a first electrode 170 on the front side of the silicon wafer;

[0221] Wherein, the process parameters of the sintering treatment are:

[0222] Sintering temperature: 750℃;

[0223] Sintering time: 2min.

[0224] Example 2

[0225] like Figure 2 As shown, an embodiment of the present invention provides a back structure of a TOPCon solar cell (labeled: Back-1).

[0226] The back structure of the solar cell provided in this embodiment includes:

[0227] A second element diffusion layer 141, a second tunneling oxide layer 110, a second element doped polysilicon layer 142, a second passivation layer 121, a second anti-reflection layer 122 and a second electrode 130 are arranged on the back side of the silicon wafer 100;

[0228] The second electrode 130 passes through the second passivation layer 121 and the second anti-reflection layer 122 to contact the second element-doped polysilicon layer 142 .

[0229] Regarding the "silicon wafer 100", it is the same as in Example 1, so the second element can also be selected from phosphorus or boron. Specifically in this embodiment, the second element is phosphorus.

[0230] Regarding the “second element diffusion layer 141”, its thickness can be 10-5000 nm, and the doping concentration of the second element can be 1e15-1e21 cm -3 , the element doping depth (junction depth) of the second element diffusion layer 141 can be 10~5000nm. Specifically in this embodiment, the silicon wafer 100 is a boron-doped P-type silicon wafer, and the second element diffusion layer 141 is correspondingly a phosphorus diffusion layer; the second element diffusion layer 141 is located on the back of the silicon wafer 100, and the thickness of the second element diffusion layer 141 is 200nm, and the doping concentration of the second element is 2e20cm -3 , the element doping depth (junction depth) of the second element diffusion layer 141 is 200 nm.

[0231] The “second tunneling oxide layer 110” is basically the same as the “first tunneling oxide layer 181” described in Example 1. Furthermore, the thickness of the “second tunneling oxide layer 110” is 1-5 nm. Specifically in this embodiment, the “second tunneling oxide layer 110” is a silicon oxide layer with a thickness of 2 nm, and the second tunneling oxide layer 110 is superimposed on the second element diffusion layer 141.

[0232] The second element doped polysilicon layer is located between the second tunnel oxide layer 110 and the second passivation layer 121. The second element doped polysilicon layer 142 has a thickness of 20-500 nm and a doping concentration of 1e19-1e21 cm -3 Specifically in this embodiment, the thickness of the second element doped polysilicon layer 142 is 150 nm, and the doping concentration of the second element doped polysilicon layer 142 is 2e20 cm -3 ;

[0233] The “second passivation layer 121” is basically the same as the “first passivation layer 161” described in Example 1. The “second anti-reflection layer 122” is basically the same as the “first anti-reflection layer 162” described in Example 1. Figure 2 As shown, an aluminum oxide (Al2O3) layer with a thickness of 5 nm is used as the second passivation layer 121, and a hydrogenated silicon nitride (SiN X ) layer as the second anti-reflection layer 122, at this time, the second passivation layer 121 and the second anti-reflection layer 122 are arranged in sequence from the silicon wafer 100 to the outside.

[0234] The “second electrode 130” mentioned above includes any one or two or more of a silver electrode, a copper electrode, an aluminum electrode, a tin-coated copper electrode, and a silver-coated copper electrode. Figure 2 As shown, the second electrode 130 passes through the second passivation layer 121, the second anti-reflection layer 122, and contacts the second element-doped polysilicon layer 142. Specifically in this embodiment, the second electrode 130 is a silver electrode.

[0235] For the back structure (labeled as Back-1) of the TOPCon solar cell provided in this embodiment, a specific preparation method is provided below, including:

[0236] Step S1: texturing and cleaning the back side of the silicon wafer 100, and controlling the thinning amount of a single side to be 1-5 μm;

[0237] Step S2: using low pressure chemical vapor deposition (LPCVD) to sequentially deposit a second tunnel oxide layer 110 and intrinsic polysilicon on the back side of the battery;

[0238] Wherein, the thickness of the second tunneling oxide layer 110 is 2 nm;

[0239] The thickness of the intrinsic polysilicon is 200 nm.

[0240] Step S3: doping the intrinsic polysilicon layer deposited on the back side of the silicon wafer 100 by high temperature diffusion of phosphorus, so that the intrinsic polysilicon is converted into a polysilicon layer doped with a second element (phosphorus);

[0241] At the same time, the second element passes through the second tunneling oxide layer 110 and diffuses on the substrate surface at the back of the silicon wafer 100 to form a second element diffusion layer 141;

[0242] Wherein, the process parameters of the phosphorus high temperature diffusion are:

[0243] Temperature: 880℃;

[0244] Time: 120 minutes;

[0245] Phosphorus source flow rate: 1500 sccm.

[0246] Step S4: performing a process of removing the silicon glass containing the second element from the back of the silicon wafer; specifically, hydrofluoric acid may be used to remove the PSG on the back of the silicon wafer 100, and then performing RCA cleaning;

[0247] Step S5: depositing a second passivation layer 121 and a second anti-reflection layer 122 in sequence on the back side of the silicon wafer;

[0248] Step S6: Printing and sintering to form a second electrode 130 on the back side of the silicon wafer 100;

[0249] Wherein, the process parameters of the sintering treatment are:

[0250] Sintering temperature: 750℃;

[0251] Sintering time: 2min.

[0252] Comparative Example 1

[0253] This comparative example provides a front structure of a TOPCon solar cell (labeled as Front-D1). The front structure of the solar cell provided in this comparative example is as follows: Figure 3 As shown, including:

[0254] A first element diffusion layer 150, a first passivation layer 161, and a first anti-reflection layer 162 are sequentially stacked on the front side of the silicon wafer 100, and further include a first electrode 170;

[0255] The first electrode 170 passes through the first passivation layer 161 and the first anti-reflection layer 162 to contact the first element diffusion layer 150 .

[0256] That is, as described above, the front structure of the TOPCon solar cell provided in this comparative example 1 is only different from the front structure of the TOPCon solar cell provided in Example 1 in structure, while the components, contents and other parameters of the first element diffusion layer 150, the first passivation layer 161, the first anti-reflection layer 162 and the first electrode 170 are the same as those in Example 1.

[0257] The front structure of the solar cell provided in this comparative example can be prepared according to the existing method.

[0258] Comparative Example 2

[0259] This comparative example provides a back structure of a TOPCon solar cell (labeled as Back-D1). The back structure of the solar cell provided in this comparative example is as follows: Figure 4 As shown, including:

[0260] A second tunneling oxide layer 110, a second element-doped polysilicon layer 142, a second passivation layer 121, and a second anti-reflection layer 122 are sequentially stacked on the back of the silicon wafer 100, and also include a second electrode 130;

[0261] The second electrode 130 passes through the second passivation layer 121 and the second anti-reflection layer 122 to contact the second element-doped polysilicon layer 142 .

[0262] That is, as described above, the back structure of the TOPCon solar cell provided in this comparative example 2 is only different from the back structure of the TOPCon solar cell provided in Example 2 in structure, while the components, contents and other parameters of the second tunneling oxide layer 110, the second element-doped polysilicon layer 142, the second passivation layer 121, the second anti-reflection layer 122 and the second electrode 130 are the same as those in Example 2.

[0263] The back structure of the solar cell provided in this comparative example can be prepared according to the existing method.

[0264] Example 3

[0265] The embodiments of the present invention provide the following different TOPCon solar cells:

[0266] The first TOPCon solar cell (labeled as TOPCon-1) has the front structure Front-1 of the TOPCon solar cell provided in Example 1 and the back structure Back-1 of the TOPCon solar cell provided in Example 2. The cell structure is as follows: Figure 5 As shown;

[0267] The second TOPCon solar cell (labeled as TOPCon-2) has the front structure Front-1 of the TOPCon solar cell provided in Example 1 and the back structure Back-D1 of the TOPCon solar cell provided in Comparative Example 2;

[0268] The third TOPCon solar cell (labeled as TOPCon-3) has the front structure Front-D1 of the TOPCon solar cell provided in Comparative Example 1 and the back structure Back-1 of the TOPCon solar cell provided in Example 2;

[0269] The fourth TOPCon solar cell (labeled as TOPCon-4) has the front structure Front-D1 of the TOPCon solar cell provided in Comparative Example 1 and the back structure Back-D1 of the TOPCon solar cell provided in Comparative Example 2. The cell structure is as follows: Figure 6 shown.

[0270] For the TOPCon solar cell (labeled: TOPCon-1) provided in this embodiment, a specific preparation method is provided below, including:

[0271] Step A1: texturing and cleaning the front and back sides of the silicon wafer 100, with the thinning amount on a single side controlled within 1-5 μm;

[0272] Step A2: using low pressure chemical vapor deposition (LPCVD) to sequentially deposit a second tunnel oxide layer 110 and intrinsic polysilicon on the back side of the battery (specific parameters are the same as those in Example 2);

[0273] Step A3: doping the intrinsic polysilicon layer deposited on the back side of the silicon wafer 100 by high temperature diffusion of phosphorus, so that the intrinsic polysilicon is converted into a polysilicon layer doped with a second element (phosphorus);

[0274] At the same time, the second element passes through the second tunneling oxide layer 110 and diffuses on the substrate surface at the back of the silicon wafer 100 to form a second element diffusion layer 141 (specific parameters are the same as those in Example 2);

[0275] Step A4: The front side of the silicon wafer 100 is treated to remove the silicon glass (PSG) containing the second element (phosphorus), and then subjected to alkali texturing. The back side of the silicon wafer 100 is protected from being etched by the alkali solution by PSG, and the thinning amount of a single side is 1-5 μm.

[0276] Step A5: using plasma enhanced chemical vapor deposition (PECVD) to sequentially deposit a first tunneling oxide layer 181 and a silicon glass layer containing a first element (in this embodiment, borosilicate glass (BSG), with specific parameters being the same as those in Embodiment 1) on the front surface of the silicon wafer 100 ;

[0277] Step A6: using laser to perform local processing on the front side of the silicon wafer 100, so that the BSG is crystallized and converted into the polysilicon layer 182 doped with the first element, and the first element is transmitted through the first tunneling oxide layer 181 to form an inner expansion layer (i.e., the first element diffusion layer 150) of the silicon wafer 100; finally, after the local laser processing, an electrode region 200 is formed, and the electrode region 200 contains the first element diffusion layer 150, the first tunneling oxide layer 181, and the polysilicon layer 182 doped with the first element (the specific parameters are the same as those in Example 1);

[0278] Step A7: performing a process of removing the silicon glass containing the first element from the non-electrode area on the front side of the silicon wafer 100; specifically, hydrofluoric acid may be used to remove the BSG from the non-electrode area on the front side of the silicon wafer 100, and performing RCA cleaning;

[0279] The back side of the silicon wafer is treated to remove the silicon glass containing the second element; specifically, hydrofluoric acid can be used to remove the PSG on the back side of the silicon wafer 100, and RCA cleaning can be performed;

[0280] Step A8: depositing a second passivation layer 121 and a second anti-reflection layer 122 on the front and back sides of the silicon wafer 100 in sequence;

[0281] Step A9: Printing and sintering the front and back sides of the silicon wafer 100 to form the first electrode 170 and the second electrode 130;

[0282] Wherein, the process parameters of the sintering treatment are the same as those in Example 1 or 2.

[0283] In this embodiment, the properties of the four TOPCon solar cells are also tested as shown in Table 1.

[0284] Table 1. Performance comparison parameters of various solar cells

[0285]

[0286] It can be seen from Table 1 that the final cell conversion efficiency of the solar cell TOPCon-1 provided in Example 3 of the present invention is improved by 0.38% compared with TOPCon-4.

[0287] The solar cell TOPCon-2 provided in Example 3 of the present invention has a final cell conversion efficiency increased by 0.27% compared to TOPCon-4.

[0288] The solar cell TOPCon-3 provided in Example 3 of the present invention has a final cell conversion efficiency increased by 0.06% compared to TOPCon-4.

[0289] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a TOPCon solar cell, characterized in that: include: Step A1: texturing and cleaning both sides of the silicon wafer; Step A2: depositing a tunnel oxide layer and an undoped polysilicon layer on the back side of the silicon wafer; Step A3: performing a doping treatment on the undoped polysilicon with a second element, so as to convert the undoped polysilicon into polysilicon doped with the second element; Step A4: removing, texturing, and cleaning the silicon glass containing the second element from the front side of the silicon wafer; Step A5: first depositing a tunneling oxide layer on the front side of the silicon wafer, and then depositing a silicon glass layer containing the first element by using a PECVD method; Step A6: locally processing the front side of the silicon wafer by using a laser to form an electrode region after the processing, wherein the silicon glass containing the first element in the electrode region is converted into polysilicon doped with the first element; At the same time, the first element contained in the silicon glass layer passes through the tunneling oxide layer to form a first element diffusion layer on the substrate surface corresponding to the electrode area on the front side of the silicon wafer; Step A7: removing the silicon glass containing the first element from the non-electrode area on the front side of the silicon wafer; and at the same time, removing the silicon glass containing the second element from the back side of the silicon wafer; Step A8: depositing a passivation layer and an anti-reflection layer on both sides of the silicon wafer; Step A9: Printing and sintering on both sides of the silicon wafer to form a first electrode and a second electrode; The first element is boron, the second element is phosphorus, and the silicon wafer is a boron-doped P-type silicon wafer.

2. The method for preparing a TOPCon solar cell according to claim 1, characterized in that: In step A5, the thickness of the silicon glass layer containing the first element is 20-500 nm; And / or, the doping concentration of the silicon glass layer containing the first element is 1e19~1e21cm -3 .

3. The method for preparing a TOPCon solar cell according to any one of claims 1 to 2, characterized in that: In step A5, the thickness of the tunnel oxide layer is 1-5 nm.

4. The method for preparing a TOPCon solar cell according to claim 3, characterized in that: In step A6, the thickness of the first element diffusion layer is 10-10000 nm.

5. The method for preparing a TOPCon solar cell according to claim 3, characterized in that: In step A6, the thickness of the first element diffusion layer is 100-2000 nm.

6. The method for preparing a TOPCon solar cell according to any one of claims 4 to 5, characterized in that: In step A6, the element doping concentration of the first element diffusion layer is 1e15~1e20cm -3 .

7. The method for preparing a TOPCon solar cell according to claim 6, characterized in that: In step A6, the process parameters of the laser treatment are: The wavelength of the laser is: 300~1100 nm; The frequency of the laser is: 10~100000 kHz; Action time: 0.01~2min.

8. The method for preparing a TOPCon solar cell according to claim 6, characterized in that: In step A6, the process parameters of the laser treatment are: The wavelength of the laser is: 500~1100 nm; The frequency of the laser is: 500~10000 kHz; Action time: 0.01~1min.

9. The method for preparing a TOPCon solar cell according to any one of claims 7 to 8, characterized in that: In step A9, the process parameters of the sintering treatment are: Sintering temperature: 600~900℃; Sintering time: 0.5~5min. 10.TOPCon solar cell, characterized in that The TOPCon solar cell has: a front structure and a back structure; The front structure is prepared by any method according to claims 1 to 9; The front structure includes a first electrode structure, and a passivation layer and an anti-reflection layer arranged on the front side of the silicon wafer; The first electrode structure includes a first electrode, which passes through a passivation layer and an anti-reflection layer, is disposed on the front side of the silicon wafer, and forms an electrode region; Wherein, in the electrode region, the front side of the silicon wafer has a first element diffusion layer, first element doped polysilicon, and silicon dioxide between the first element diffusion layer and the first element doped polysilicon, and the first electrode is in contact with the first element doped polysilicon; The doping concentration of the polysilicon doped with the first element is 1e18~1e20cm-3; The front side of the silicon wafer also includes a non-electrode area; The polysilicon doped with the first element exists only in the electrode region; The silicon dioxide is only present in the electrode region; The back structure comprises: A tunneling oxide layer, a polysilicon layer doped with a second element, a passivation layer, an anti-reflection layer, and a second electrode in contact with the polysilicon layer doped with the second element, arranged on the back side of the silicon wafer; The first element has the same polarity as the silicon wafer, the first element is boron, the second element is phosphorus, and the silicon wafer is a boron-doped P-type silicon wafer.

11. The TOPCon solar cell according to claim 10, characterized in that: In the electrode region, a polysilicon layer doped with a first element is formed, and the first electrode is in contact with the polysilicon layer doped with the first element.

12. The TOPCon solar cell according to claim 11, characterized in that: The thickness of the polysilicon layer doped with the first element is 20-500 nm.

13. The TOPCon solar cell according to any one of claims 10 to 12, characterized in that: In the electrode region, the silicon dioxide forms a tunneling oxide layer.

14. The TOPCon solar cell according to claim 13, characterized in that: In the electrode region, the thickness of the tunnel oxide layer is 1-5 nm.

15. The TOPCon solar cell according to any one of claims 10 to 12 and 14, characterized in that: The element doping depth of the first element diffusion layer is 10-10000nm; The element doping concentration of the first element diffusion layer is 1e15~1e20cm -3 .

16. The TOPCon solar cell according to any one of claims 10 to 12 and 14, characterized in that: On the front side of the silicon wafer, a distance H between two adjacent first electrodes is 500-2000 μm, and the distance H is calculated based on the central axis of the electrode.

17. The TOPCon solar cell according to claim 16, characterized in that: The coverage width of the first element diffusion layer does not exceed 80 μm; and / or, the coverage width of the polysilicon doped with the first element does not exceed 80 μm; and / or, the coverage width of the tunnel oxide layer on the front side of the silicon wafer does not exceed 80 μm; And / or, the coverage width of the silicon dioxide does not exceed 80 μm.

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