Annealing method for improving white points of crystalline silicon double-sided battery

Abstract

The invention provides an annealing method for improving white points of a crystalline silicon double-sided battery. The annealing method comprises the following steps of (1) feeding into a boat; (2)vacuumizing for the first time; (3) purging; (4) vacuumizing for the second time; (5) heating and oxidizing; (6) carrying out constant-temperature oxidation; (7) returning pressure; (8) discharging from the boat, wherein the stage from primary vacuumizing in the step (2) to constant-temperature oxidation in the step (6) is a continuous heating stage. According to the annealing method, an annealingprocess is optimized, the whole process is in the continuous heating stage from the step (2) to the step (6), heating and then cooling are not needed, the process time is saved, and the productivityis improved; meanwhile, the white dot proportion of the double-sided battery is obviously reduced, the industrial large-scale production is facilitated, and the annealing method has better industrialapplication prospect.

Description

technical field [0001] The invention belongs to the technical field of crystalline silicon solar cells, and in particular relates to an annealing method for improving white spots of crystalline silicon double-sided cells. Background technique [0002] In recent years, with the development of crystalline silicon cell technology, bifacial solar cells have begun to replace single-sided solar cells and gradually become mainstream products in the market because they can also generate electricity on the back side, which can greatly reduce costs. Both double-sided batteries and single-sided batteries have to undergo thermal oxidation treatment during the preparation process. The difference is that the back of the single-sided battery is covered by the aluminum back field, even if there are small white spots on the back, it will be completely covered by the aluminum back field, so There will be no defects in appearance; when producing double-sided batteries, the back of the battery ...

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Problems solved by technology

This method uses variable temperature and variable pressure to reduce PE white spots, but there are the following problems: 1) In this method, the temperature in the furnace tube is raised to 850-980° C. in step (3). If the temperature is too high, most impurities will enter the silicon wafer. It cannot be effectively eliminated, but instead increases the defect rate of EL; and the high temperature state greatly changes the distribution of phosphorus sources, which seriously affects the electrical properties of the silicon wafer; The pressure is controlled at 100-300mbar, the pressure is too low, the gas flow rate is too small, resulting in limited "purging" effect, and the reduction of white spots is limited; 3) The process of this method is too long in the process of heating and cooling, which seriously affects the production capacity

In this method, the temperature rise oxidation is performed first, and then the operation of purging and vacuuming is carried out, which will result in more impurities and seriously affect the electrical properties of the cell.

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