A variable temperature variable pressure diffusion process for improving photoelectric conversion efficiency

Abstract

The invention discloses a variable temperature and variable pressure diffusion process for improving photoelectric conversion efficiency, comprising the following steps: step one of high temperature oxidation; step two of variable temperature and variable pressure diffusion: S1 of constant temperature and variable pressure diffusion: raising the temperature inside the furnace to 790 degrees centigrade, maintaining the temperature constant, controlling the pressure to increase from 100mbar to 800mbar in 160s; S2 of constant temperature and constant pressure maintaining: keeping the pressure inside the furnace constant, and controlling the temperature in the furnace to rise from 790 to 835 degrees centigrade in 450s; and S3 of constant temperature and constant pressure diffusion: adjusting the temperature in the furnace to 800 degrees centigrade within 30s, adjusting the pressure in the furnace to 200mbar, and diffusing for 500s - 650s under this condition; and step three of annealing and cooling. The invention variably controls the temperature and pressure during the diffusion process, thereby reducing the requirement of the silicon wafer spacing, reducing the phosphorus source dosage of the diffusion process by 20%, reducing the total diffusion process time by more than 10 minutes, and improving the battery yield and battery photoelectric conversion efficiency. Thus, the invention is very worth promoting.

Description

technical field [0001] The invention relates to the technical field of solar cell diffusion technology, in particular to a temperature-variable-voltage diffusion technology for improving photoelectric conversion efficiency. Background technique [0002] The PN junction is the core of crystalline silicon cells. The preparation of a uniform high-resistance emitter is an important way to improve the conversion efficiency of crystalline silicon cells. It can not only reduce the front surface recombination to increase the open circuit voltage, but also greatly improve the short-wave spectral response to enhance the short circuit current. Continuous breakthroughs have been made in the development of high square resistance silver paste, which has solved the problems of excessive series resistance and emitter burn-through due to high square resistance. Improving the square resistance and uniformity of the emitter has become an important means to improve battery efficiency. [0003]...

AI Technical Summary

Problems solved by technology

Atmospheric pressure and high temperature diffusion tubes are usually selected at the nozzle or the end of the tube, and the gas is taken to the other end through a large nitrogen flow, which is easy to cause the phenomenon of high concentration at one end and low concentration at the other end, and the free path of gas molecules is small under normal pressure. There is a large difference in the probability of silicon wafers being exposed to phosphorus sources in different regions, and the sheet resistance can only be controlled by adjusting the temperature, but the uniformity within and between wafers cannot be guaranteed.

[0004] Atmospheric pressure diffusion will reduce the consistency of the doping concentration in the vertical direction of the diffused PN junction, thereby affecting the consistency of the depth of the PN junction and electrical properties. Preparation of electrodes under the same screen printing and sintering conditions will increase the number of defective chips due to large leakage currents. Ratio, while reducing the consistency of battery performance, increasing the proportion of low-grade (B-piece) cells, greatly affecting the reduction of battery manufacturing costs

[0005] In the prior art, the application number is "201410582186.6", a low-voltage diffusion process for high-resistivity crystalline silicon cells. By adjusting the pressure in the furnace, diffusion is carried out in a low-pressure manner, which can effectively reduce the total flow and total time of small nitrogen. , can better control the longitudinal distribution of diffusion doping concentration, and can effectively improve the uniformity of the diffusion resistance in the chip and between the chips. However, for the growing photovoltaic industry, the silicon The improvement of the photoelectric conversion efficiency of the chip can no longer meet the demand, so a new diffusion process is needed

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