The use of Silicon Wafer Barriers in the Electrochemical Reduction of Solid Silica to Form Silicon in Molten Salts

摘要

Nowadays, silicon is the most critical element in solar cells and/or solar chips. Silicon having 98 to 99% Si as being metallurgical grade, requires further refinement/purification processes such as zone refining [1,2] and/or Siemens process [3] to upgrade it for solar applications. A promising method, based on straightforward electrochemical reduction of oxides by FFC Cambridge Process [4], was adopted to form silicon from porous SiO_2 pellets in molten CaCl_2 and CaCl_2-NaCl salt mixture [5]. It was reported that silicon powder contaminated by iron and nickel emanated from stainless steel cathode, consequently disqualified the product from solar applications. SiO_2 pellets sintered at 1300°C for 4 hours, were placed in between pure silicon wafer plates to defeat the contamination problem. Encouraging results indicated a reliable alternative method of direct solar grade silicon production for expanding solar energy field.