Purity and minority carrier lifetime in silicon produced by direct electrolytic reduction of SiO₂ in molten CaCl₂

Si powder was produced by direct electrolytic reduction of SiO₂ in molten CaCl₂ at 1123 K. From the Si powder, Si ingots were obtained by a floating zone method. The concentrations of most metallic elements and of P in the Si ingots were lower than the acceptable levels for solar grade Si. The minority carrier lifetimes in the Si ingots were measured using a microwave photo conductivity decay method. The obtained values of ca. 1.0 μs were two orders of magnitude shorter than those observed in an Si ingot prepared from 10N purity Si.