Metallurgical Grade and Metallurgically Refined Silicon for Photovoltaics

The chapter intends to give a summary on the production of metallurgical grade silicon and the status of research and development on solar silicon, which is obtained by the metallurgical route. In a first section, the carbothermic reduction of SiO2 in the submerged arc furnace is explained briefly. Metallurgical processes to refine silicon for photovoltaics are explained and summarized in the second section. Details for the following approaches are given:–Acid leaching–Slag treatment of the silicon melt–Vacuum degassing of the silicon melt–Purification of liquid silicon using gases or water vapor–Plasma treatment of the silicon melt–Segregation during solidification–Refining silicon from Si–Al melt solutions–Particle removal from liquid silicon Finally, the characteristics of the obtained solar silicon are discussed and summarized.