Production technology for polycrystalline silicon

Abstract

The invention discloses a production technology for polycrystalline silicon. The production technology includes the following steps: 1, a first coating, a second coating and a third coating are sequentially arranged on the surface of a crucible from inside to outside, and a crystalline silicone leftover material layer is laid; 2, a small quantity of raw polycrystalline silicon materials in the melted state is contained in the crucible, and the temperature of the crucible is controlled to be lower than the melting point of the crystalline silicone leftover material layer to enable the small quantity of melted raw polycrystalline silicon materials to form a crystallization protection layer; 3, in the vacuum environment, to-be-processed raw polycrystalline silicon materials are contained in the crucible, placed in a melting furnace with an electron beam generating device and processed through laser irradiation; 4, high-frequency induction heating is carried out in the vacuum environment, a slag forming constituent is added, plasma heating is carried out, steam-and-hydrogen-mixed argon is introduced, and directional solidification is carried out to obtain the polycrystalline silicon serving as the target product. By means of the production technology, the boron content, the phosphorous content and the metal impurity content can be effectively reduced, the complete polycrystalline silicon is prepared, long crystal dislocation is less, grain boundaries are proper, and the conversion rate of a polycrystalline silicon battery is increased.

Description

technical field

[0001] The invention relates to a production process of polysilicon, in particular to a production process of polysilicon in which boron, phosphorus and metal impurities are removed by metallurgy. Background technique

[0002] The photovoltaic industry is one of the fastest growing high-tech industries in the world in the 21st century. Polysilicon is the cornerstone of the global electronics industry and photovoltaic industry. Solar cells made of silicon materials have stable performance, long life, and lower cost than other solar cells. In order to produce solar cells with lower cost and better performance, industrial silicon (MG-Si) is used as raw material and refined by metallurgical methods to produce solar-grade silicon (SOG-Si). Solar-grade silicon contains a variety of impurities, among which phosphorus, boron, and metal impurities seriously affect the conversion efficiency and stability of silicon solar cells. At present, the metallurgical method us...