Electrochemical Behavior of Silicon in Eutectic Calcium Chloride and Calcium Fluoride Molten Salt

It is suggested that solar grade silicon can be produced by electrorefining of metallurgical grade silicon in a three-electrode cell. This study focuses on the electrochemical behavior of silicon in eutectic calcium chloride and calcium fluoride molten salt. The mixture of calcium chloride and calcium fluoride was heated to 750˚C as the electrolyte. Tungsten was used as the reference electrode and as the cathode, while silicon cut from a boron-doped silicon wafer with ~0.5 ohm-cm resistivity was used as the anode and cathode. Cyclic voltammetry was performed to reveal the voltages for silicon dissolution and deposition. It also illustrates the removal of dissolved silicon from the electrolyte. In addition, in-situ purification of the electrolyte is demonstrated.