Boron Removal Method, Technology and Process for Producing Solar Grade Silicon by Metallurgical Method

As a kind of green renewable energy, solar energy has attracted wide attention, and impurity removal is a necessary purification process to obtain solar grade silicon from metallurgical grade silicon, which is very important for the preparation of silicon-based solar cells. The new technology for preparing solar grade polysilicon by the metallurgical method has become the focus of research and development because of its advantages such as low energy consumption, low cost and less pollution. However, the effective removal of boron is one of the most severe challenges we face. In this paper, the thermodynamic and kinetic properties of boron ( solubility, diffusivity, diffusion coefficient, mass transfer coefficients and activity coefficient) and the research topics of boron removal in recent years ( gas blowing, slag treatment, plasma treatment, acid leaching and solvent refining) are reviewed. It is found that solvent refining is a promising method to obtain high purity silicon. The enrichment rate of silicon and the removal rate of boron can reach more than 90%. Additives can strengthen the formation and precipitation of borides to improve the boron removal process, and the subsequent almost can be completely eliminated, which will not cause pollution to the refined silicon, which will be more effective in boron removal and increase the practicability of the process. At the end of the paper, several deboration processes are compared and analyzed, and the application prospect of metallurgical process is forecasted.