Si growth by directional solidification of Si–Sn alloys to produce solar-grade Si

• Bulk silicon was grown from Si–Sn alloy by directional solidification.
• We investigated the growth mechanism and kinetics of silicon.
• The purification efficiency of grown silicon was examined.
• An overall solar grade silicon process was proposed.

Solidification refining of Si using Si–Sn solvent was investigated with the aim of developing a new Si refining process to produce solar grade silicon (SOG-Si). Bulk Si crystals were grown by directional solidification of Sn–Si alloys containing 50, 70, and 95.8 mol% Si. The conditions to grow bulk Si crystals from Si–Sn melts were consistent with the constitutional supercooling criterion, and the growth process was confirmed to be controlled by the diffusion of Si for the present growth conditions. Purification testing of the refined Si showed that more than 98% of metallic impurities, over 60% of B and over 70% of P are removed.