Effect of solidification conditions on the silicon growth and refining using Si–Sn melt

•Effect of different solidification conditions were experimentally compared.•Refined Si crystals were highly recovered with high purification efficiency.•The separation mechanism of refined Si was clarified.•Slow cooling under electromagnetic stirring benefits industrial application.

The solidification refining of Si using a Si–Sn solvent was investigated under various cooling conditions: (1) slow cooling, (2) slow cooling with electromagnetic stirring, and (3) directional solidification with the aim of developing a novel low-cost route for solar-grade Si production. The separation efficiency of refined Si achieved by combining slow cooling and electromagnetic stirring was much higher than that achieved using directional solidification; in addition, the purification efficiency of the refined Si in both methods was similar. The separation mechanism of refined Si from a Si–Sn melt is also discussed. Purification testing of the refined Si revealed that more than 96% of the metallic impurities, approximately 60% B, and over 70% P were removed.