CN-116435385-B - TOPCon battery and preparation method thereof

Abstract

The invention provides a TOPCon battery which comprises a monocrystalline silicon piece, an inner expansion layer arranged on the back surface of the monocrystalline silicon piece, and a doped polysilicon layer arranged below the inner expansion layer, wherein the doped polysilicon layer comprises a first doped polysilicon region and a second doped polysilicon region, the doping concentration of the first doped polysilicon region is higher than that of the second doped polysilicon region, the inner layer comprises a first inner expansion region and a second inner expansion region, the position of the first inner expansion region corresponds to that of the first doped polysilicon region, and the junction depth of the first inner expansion region is larger than that of the second inner expansion region. The TOPCon battery provided by the invention has a specific structure, can ensure the thickness and the concentration of doped polysilicon of a metal contact region, avoid the tunnel oxide layer from being damaged in the slurry sintering process, reduce the composite current and the contact resistance, and simultaneously reduce the light parasitic absorption of a non-metal region, in particular reduce the free carrier absorption.

Inventors

• MAO WEIPING
• JIN ZHU
• ZHANG MINGMING
• GUO SHICHENG
• FAN XUAN
• FU SHAOJIAN
• YANG YANG
• YE FENG
• PAN LIMIN

Assignees

• 滁州捷泰新能源科技有限公司

Dates

Publication Date

20260512

Application Date

20230427

Claims (7)

1. 1. A method of making TOPCon battery comprising: preparing a doped amorphous silicon film on the surface of the tunneling layer, and then annealing; preparing a silicon oxide layer on the lower surface of the annealed film to serve as a diffusion barrier layer; grooving on the surface of the diffusion barrier layer; Performing POCl 3 diffusion, performing heavy doping at the slotting position, forming a first doped polysilicon region with higher doping concentration at the slotting position, and further forming a first inner diffusion region at the position of an inner diffusion layer corresponding to the first doped polysilicon region; forming a second doped polysilicon region with lower doping concentration at the ungrooved position, and forming a second inner expansion region at the position of the inner expansion layer corresponding to the second doped polysilicon region; the junction depth of the first inner expansion region is larger than that of the second inner expansion region.
2. 2. The method of claim 1, wherein the first doped polysilicon region has a doping concentration selected from the group consisting of 2e20 to 1e21cm -3 .
3. 3. The method of claim 1, wherein the second doped polysilicon region has a doping concentration selected from the group consisting of 5e 19-2 e20cm -3 .
4. 4. The method of claim 1, wherein the first polysilicon doped region and the first inward-expansion region are disposed in a TOPCon cell at positions corresponding to the metal electrodes.
5. 5. The method of claim 1, wherein the doped amorphous silicon film is selected from the group consisting of phosphorus doped amorphous silicon films; The phosphorus-doped amorphous silicon film is prepared by a PECVD method; the thickness of the phosphorus doped amorphous silicon film is selected from 100-200 nm.
6. 6. The method of claim 1, wherein the diffusion barrier layer has a thickness selected from 50-100 nm.
7. 7. The method of claim 1, wherein the slotting is performed by slotting a back metal electrode of the monocrystalline silicon piece at a position corresponding to the diffusion barrier layer.

Description

TOPCon battery and preparation method thereof Technical Field The invention belongs to the technical field of batteries, and particularly relates to a TOPCon battery and a preparation method thereof. Background In the prior art, a TOPCon (tunneling oxidation passivation contact) battery is generally used for preparing a 1-2 nm ultrathin tunneling oxide layer on the back surface of a silicon wafer, then depositing a doped polysilicon layer with the thickness of 80-200 nm on the surface of the oxide layer, and finally depositing silicon nitride on the doped polysilicon layer. TOPCon the back side of the cell typically uses Ag paste to burn through the dielectric film to form an ohmic contact with the doped polysilicon. In the slurry sintering process, metal Ag crystal grains possibly penetrate through the doped polysilicon film layer to damage the passivation effect of the interface oxide layer, the thickness of the doped polysilicon cannot be too thin, usually 100-150 nm, in order to reduce the composite current density of a metal contact area, the doping concentration of the doped polysilicon needs to be enough, usually >1e20cm -3, in order to ensure good field passivation effect and low ohmic contact, but the polysilicon film layer in the passivation structure is too thick and has too high doping concentration, free Carrier Absorption (FCA) of the doped polysilicon on long-wave light can cause the loss of TOPCon battery short-circuit current, and meanwhile parasitic absorption of the doped polysilicon on incident light on the back surface can cause the reduction of the double-sided rate of the battery. At present, the thickness and doping concentration of the polycrystalline silicon film layer are reduced as much as possible on the premise of ensuring that the metal electrode slurry does not burn through the tunneling oxide layer and the metal electrode and the polycrystalline silicon film layer form good ohmic contact, so that current loss is reduced, or a passivation structure is only adopted in a metal electrode area of the battery, and the light absorption and passivation effects of the battery are difficult to be achieved. Disclosure of Invention In view of the above, the present invention aims to provide a TOPCon battery and a preparation method thereof, and the TOPCon battery provided by the present invention can reduce the parasitic light absorption of a non-metal region while ensuring the thickness and concentration of doped polysilicon in a metal contact region. The invention provides a TOPCon battery, comprising: Monocrystalline silicon piece; an inner expansion layer arranged on the back surface of the monocrystalline silicon piece; a doped polysilicon layer disposed below the inner diffusion layer; The doped polysilicon layer comprises a first doped polysilicon region and a second doped polysilicon region, wherein the doping concentration of the first doped polysilicon region is higher than that of the second doped polysilicon region; The inner layer comprises a first inner expansion region and a second inner expansion region, the position of the first inner expansion region corresponds to that of the first doped polysilicon region, and the junction depth of the first inner expansion region is larger than that of the second inner expansion region. In the embodiment of the invention, other layer structures of the TOPCon battery can be arranged according to structures of TOPCon batteries which are well known to those skilled in the art, for example, a diffusion layer, a passivation layer, a front antireflection layer and a front metal electrode can be sequentially arranged on the front surface of monocrystalline silicon, a tunneling layer can be arranged between an inner diffusion layer and a doped polycrystalline silicon layer, and a back antireflection layer and a back metal electrode can be sequentially arranged below the doped polycrystalline silicon layer, namely, an inner diffusion layer, a tunneling layer, a doped polycrystalline silicon layer, a back antireflection layer and a back metal electrode are sequentially arranged on the back surface of the monocrystalline silicon. In the embodiment of the invention, the monocrystalline silicon wafer can be a phosphorus doped N-type monocrystalline silicon wafer, the resistivity can be 0.1-10 ohm cm, such as 0.5 ohm cm, 1 ohm cm, 2 ohm cm, 4 ohm cm, 6 ohm cm and 8 ohm cm, and the thickness can be 100-200 micrometers, such as 120 micrometers, 140 micrometers, 160 micrometers and 180 micrometers. In the embodiment of the invention, the diffusion layer may be a P-type doped layer formed by boron doping, and the sheet resistance may be selected from 100 to 300 Ω, such as 150Ω,200Ω, 250Ω. In the embodiment of the invention, the passivation layer can be selected from an alumina layer, and the thickness of the passivation layer can be selected from 2-6 nm, such as 3nm, 4nm and 5nm. In the embodiment of the invention, the front side anti-reflection laye