Cooling and annealing process of solar cell

Abstract

The invention discloses a cooling and annealing process of a solar cell. The cooling and annealing process comprises the following steps of (1) diffusing to enter a boat; (2) oxidizing; (3) diffusing and introducing a source in a low-temperature state; (4) diffusing and pushing a junction in a high-temperature state; (5) taking out a silicon wafer out of a furnace, cooling the silicon wafer, and stabilizing the temperature of a furnace tube; (6) throwing the silicon wafer into the furnace for second times, and carrying out low-temperature annealing; and (7) diffusing to get out of the boat. By the cooling and annealing process, a diffusion dead layer is reduced, thermal defect caused by high-temperature reaction is reduced, and thus, the conversion efficiency of the solar cell is improved; particularly, the open-circuit voltage is obviously increased and is higher than that of a traditional process by 2mV, a filling factor is also improved, and thus, the conversion efficiency of the battery cell is obviously improved; and the thickness of a PN-junction dead layer of the silicon wafer surface after diffusion is reduced, lattice damage brought by high-temperature diffusion is reduced, and minority carrier lifetime is prolonged.

Description

technical field [0001] The invention relates to a temperature-lowering annealing process for solar cells. Background technique [0002] At present, the process of polycrystalline silicon solar cells has become increasingly mature and standardized production has been achieved. The main process steps are as follows: acid corrosion texturing→diffusion junction→wet etching trimming→PECVD anti-reflection coating→screen printing→sintering→testing and sorting . Among them, diffusion is the core step. The conventional diffusion junction process uses nitrogen to carry phosphorus oxychloride, and at the same time, large nitrogen and dry oxygen are introduced to react with silicon wafers at high temperatures. In this way, the phosphorus concentration on the surface of the silicon wafer after diffusion is too high, which is prone to thermal defects, and the life of the minority carriers will be reduced due to the high phosphorus concentration on the surface, and the diffusion "dead lay...

AI Technical Summary

Problems solved by technology

Among them, diffusion is the core step. The conventional diffusion junction process uses nitrogen to carry phosphorus oxychloride, and at the same time, large nitrogen and dry oxygen are introduced to react with silicon wafers at high temperatures. In this way, the phosphorus concentration on the surface of the silicon wafer after diffusion is too high, which is prone to thermal defects, and the life of the minority carriers will be reduced due to the high phosphorus concentration on the surface, and the diffusion "dead layer" is thicker, resulting in a corresponding deterioration of the short wave of the battery sheet. Affect the conversion efficiency of the cell