Diffusion process of solar cell, preparation method of solar cell and silicon wafer

Abstract

The invention discloses a diffusion process of a solar cell, a preparation method of the solar cell and a silicon wafer, and the diffusion process comprises the steps: introducing small nitrogen carrying phosphorus oxychloride into the textured silicon wafer in a diffusion furnace tube, depositing a phosphorus source at a first temperature, and introducing oxygen and large nitrogen at a second temperature for high-temperature propulsion to obtain a PN junction; introducing small nitrogen carrying phosphorus oxychloride, secondarily depositing a phosphorus source, and further forming a phosphorosilicate glass layer containing a low-concentration phosphorus source on the surface of the silicon wafer; and introducing atmospheric nitrogen to purge, ending diffusion, and obtaining an emitter containing the low-concentration phosphorus source on the surface of the silicon wafer. According to the method, a two-step source deposition mode is adopted, phosphorus oxychloride is deposited in a low-temperature environment, the surface concentration of a silicon wafer can be fully reduced, meanwhile, the uniformity of PN junctions is guaranteed by controlling the gas flow ratio of large nitrogen, oxygen and small nitrogen deposited by a phosphorus source, and the conversion efficiency of a solar cell can be effectively improved.

Description

technical field [0001] The invention relates to the technical field of solar cells, in particular to a diffusion process, a preparation method and a silicon wafer of a solar cell. Background technique [0002] At present, the photovoltaic field is developing rapidly, and photovoltaic products that meet various needs are constantly refreshing the outside world's perception of photovoltaics. How to achieve photovoltaic grid parity is still a topic that is constantly being explored in the photovoltaic field. High-efficiency and low-cost solar cells will gradually become the mainstream of the market. With the continuous update of solar technology, the conversion efficiency of solar cells is also rising. Among emerging technologies, PERC (Passivated Emitter and Rear Cell) batteries with superimposed selective emitter (SE) technology are undoubtedly one of the hottest fields. SE cells can be doped by laser, and have two main features: 1) The contact area between the metal grid l...

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Problems solved by technology

[0003] SE technology mainly uses phosphosilicate glass (PSG) as the phosphorus source, and injects the phosphorus source outside the PN junction into the surface layer of the silicon wafer by laser ablation, thereby forming a highly doped region locally, so the diffusion process is used as a laser doping process. The pre-process also provides the necessary phosphorus source for selective doping, but the current diffusion process prepares PN junctions with many redistribution processes of phosphorus sources, which makes the surface concentration of silicon wafers too high and the phosphorus source is unevenly distributed. , to increase carrier recombination, which affects the improvement of solar cell conversion efficiency

[0004] Although the prior art proposes a variety of methods in order to improve the conversion efficiency of solar cells, there are certain defects in these methods.

For example, the prepared PN junction is relatively shallow, and the current paste is generally highly corrosive, so it is easy to be burned through during silk printing and sintering, which affects the performance of the cell; or the residual phosphorus source causes damage to the silicon wafer surface during operation. Damage, and too many oxidation times cause the phosphosilicate glass layer to be too thick, and the concentration difference between the heavily doped region and the lightly doped region is too large to increase the carrier recombination, which is not conducive to improving the open circuit voltage

Or the phosphorus source is deposited too many times, which redistributes the phosphorus source on the surface of the silicon wafer many times, and then makes the overall silicon wafer doping concentration higher, which affects the doping effect and is not conducive to a significant increase in the conversion efficiency of the cell.

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