Polycrystalline silicon and preparation method thereof

Abstract

The invention discloses a preparation method of polycrystalline silicon. According to the method, the twin crystal growth control technology is adopted, the ordinary polycrystalline process is optimized, a heat insulation cage is quickly opened, and the opening of the heat insulation cage is adjusted to be 6-8cm; at the initial stage of growth of the crystal, the temperature of a heater is adjusted to be 1425-1440 DEG C, the heat insulation cage is slowly lifted, a layer of uniform dendritic crystal grows vertically on a nucleation source layer along the bottom of a crucible, then dendritic crystal is taken as the seed crystal, and vertically upward directionally grows to form the polycrystalline silicon. The polycrystalline silicon prepared by the invention contains a great quantity of twin crystals, as the twin crystals have the advantages that the interfacial energy of the twin crystals is low, the twin crystals are relatively more stable, and the like, and the polycrystalline silicon prepared by the method has the advantage of few dislocation defects, the battery efficiency of the polycrystalline silicon is higher than that of the ordinary polycrystalline silicon for 0.2-0.4%, the average battery efficiency of a whole silicon wafer reaches 17.5%, and the highest efficiency reaches 18.0%.

Description

technical field [0001] The invention belongs to the technical field of solar cells, and in particular relates to a method for preparing polysilicon. Background technique [0002] Crystalline silicon is the most commonly used semiconductor material in the manufacture of solar cells. At present, the crystalline silicon used in the manufacture of solar cells is mainly monocrystalline silicon by Czochralski method and polycrystalline silicon by ingot casting technology. Polysilicon ingot casting has a large amount of feeding, simple operation, and low process cost, but low conversion efficiency and short life of the battery; Czochralski monocrystalline silicon has high conversion efficiency, but less single feeding, complicated operation, and high cost, so it is basically eliminated. [0003] High-efficiency polysilicon ingot preparation technology can be said to be the development of the second-generation ingot technology. The nucleation and growth of silicon crystals are con...

AI Technical Summary

Problems solved by technology

[0005] However, the input cost of the above-mentioned first method is relatively high, and it is basically not used in large-scale production.

The second method is widely used at present, but the operation of this method is complicated, and the operator needs to have skilled operation experience to ensure that the seed crystal at the bottom of the crucible is not completely melted, and the yield is not high.

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