An Evolving Method for Solar-Grade Silicon Production: Solvent Refining

Use of photovoltaic (PV) power generation has recently been increasing rapidly because it provides clean, renewable energy. While production of solar-grade silicon (SOG-Si) has been dominated recently by the modified Siemens process and a fluidized bed reactor process, obtaining a stable supply of SOG-Si at lower cost is essential to further increases in PV installation. Metallurgical production offers benefits in productivity and possibly also in process cost. Several metallurgical processes, such as directional solidification, vacuum melting, and plasma melting, have been developed, but significant cost reductions or dramatic improvements in productivity are required to enable metallurgical refining to become the major route for SOG-Si production. The solvent refining process offers the possibility of cost reduction due to its high purification efficiency and low processing temperature. This paper reviews solvent refining processes for SOG-Si purification, emphasizing their advantages and identifying the problems that must be solved for process development.