Aditya Moudgal¹, Sarat Buasai¹, Alexander Joseph McMahon¹, Yi Jie Wu¹, Adam C. Powell¹, Uday Pal², Yu Zhong¹; ¹Worcester Polytechnic Institute, ²Boston University

Polysilicon production for photovoltaics (PV) via the dominant Siemens process is costly due to numerous unit operations, energy-intensity, and inherent safety problems. Molten salt electrolysis reduction of silica could potentially achieve similar energy use and cost to the Hall-Héroult process which produces the world’s aluminum, i.e. 90% lower energy use and 80% lower cost vs. the Siemens process. Recently a new molten salt was engineered for this purpose comprised of CaF₂-MgF₂-YF₃-CaO-SiO₂ with low volatility 4 S/cm and SiO₂ solubility >5 wt%, and inert anode compatibility – an order of magnitude better on all metrics than prior work. This presentation will describe experimental and modeling work to engineer a silicon reduction process using this molten salt. The process produces solid silicon using periodic current reversal to suppress cathodic instabilities.