Method for producing solar grade polycrystalline silicon by molten salt electrolysis and directional solidification combination technique

Abstract

The invention relates to a method for producing solar grade polycrystalline silicon by molten salt electrolysis and directional solidification combination technique. The method is characterized by adopting the following processing steps: (1) preparing an aluminium-silicon alloy through eutectoid molten salt electrolysis; (2) separating aluminium from silicon through directional solidification; and (3) carrying out vacuum distillation and directional solidification on high-purity silicon. The phosphorus content of high-purity polycrystalline silicon obtained by the method is reduced to 0.08*10<-6>, the boron content is less than 0.1*10<-6> and the purity is more than 99.99995%, thus meeting the impurity content requirements (less than 0.5*10<-6>) of solar grade silicon.

Description

technical field [0001] The invention relates to a method for producing solar-grade polysilicon, in particular to a method for producing solar-grade polysilicon by the combined technology of molten salt electrolysis and directional solidification, and belongs to the field of metallurgy. Background technique [0002] Solar energy is an inexhaustible pollution-free green energy. The large-scale development and utilization of photovoltaic solar power generation is an effective way to solve the problems of global energy shortage and ecological environment deterioration, and has been valued by the energy strategies of various countries. At present, the most widely used solar cells are silicon cells, which account for more than 95% of the solar cell usage. In order to ensure its photoelectric conversion efficiency, the purity of the polysilicon material is required to be above 6N. Large-scale production of polysilicon materials for low-cost solar cells has become an urgent need fo...

AI Technical Summary

Problems solved by technology

Plasma beam oxidation refining can effectively remove impurities, but the equipment is complicated and the conditions are harsh, and it is currently limited to a small scale; The coagulation method adopts eutectic alloying metal and industrial silicon, so that impurities enter the alloying metal, and the silicon and alloying metal are separated after cooling or the alloying elements and impurities are removed by pickling. There are problems such as large amount of alloy usage and high energy consumption. , and the impurity content still cannot reach the standard when purifying industrial silicon