Application of Si-Based Solvents to the Purification of Metallurgical Grade-Silicon

Applying Si-based alloy solvents to Si purification is considered an emerging technology for the production of solar-grade Si (SOG-Si). This study reviews the principle of solvent refining. Alloy systems such as Si–Al, Si–Sn, and Si–Fe are reviewed along with the Si separation method. The effects of solvent refining processing parameters, such as the solvent metal, cooling rate, heating method, and processing time, on boron and phosphorus segregation behaviors and Si purification efficiency are discussed. Experimental and theoretical investigations have shown that removal efficiencies greater than 90% can be achieved for B and P from metallurgical-grade Si using a Si–Al alloy. Meanwhile, separation methods, namely, flotation, filtration, acid leaching, and directional solidification, are used to separate the refined Si from the alloy. Finally, a method for the potential industrial production of SOG-Si is proposed.