Efficient separation of bulk Si and enhanced B removal by Si–Sn–Cu ternary solvent refining with Zr addition

Abstract

• A novel Si–Sn–Cu ternary solvent with Zr-assisted refining method was proposed. • The activity coefficients of B in Si–Sn–Cu ternary solvent were firstly measured. • Large-area bulk Si was obtained from ternary solvent by precise temperature control. • B-removal fraction was further improved compared with Si-based binary solvent. • Effective separation and purification of primary Si were achieved simultaneously. Si recycling from Si powder waste is of great significance to the production profits and alleviate hazardous effects on the ecological environment. Solvent refining is an effective way to reproduce solar-grade silicon (SoG–Si) by recycling and reusing the Si powder waste. Herein, a Si–Sn–Cu ternary solvent with Zr-assisted refining method was proposed to make full use of the high activity coefficients of B and the strong B affinity of Zr. The activity coefficients of B at the different compositions of the Si–Sn–Cu ternary solvent were firstly measured, which provided guidance on the solvent optimization to improve the B removal efficiency. The precise temperature control enabled the obtainment of large-area bulk Si from Si–Sn–Cu solvent, and the enrichment percentage of the obtained bulk Si from ternary Si–Sn–Cu solvent was 99.2%. Moreover, compared to the binary solvents, the absolute B content in primary Si further decreased to 4.7 ppmw after directional solidification, showing a better B removal fraction (95.3%). It provides a new scientific insight and an experimental evidence for the effective separation and purification of primary Si crystals from Si-based multicomponent solvents.