Boron removal for solar-grade silicon production by metallurgical route:A review

Solar energy has received considerable attention over the past few decades, due to its importance as a green and renewable energy. Low-cost solar-grade silicon production is critical for the widespread use of solar cells. Conventional routes (e.g., modified Siemens process: chlorosilane and hot filament) have still dominated the production of solar-grade silicon. The metallurgical route offers benefits in the productivity and cost, but efficient removal of boron is one of the most daunting challenges in front of us. This paper reviews thermodynamic and kinetic properties (solubility, diffusivity, diffusion coefficients, mass transfer rate, and activity coefficient) of boron and recent research topics (slag treatment, solvent refining, gas injection, plasma treatment, and acid leaching) for boron removal.