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.