The continued rapid growth of the photovoltaic (PV) industry (43.5% growth in 2002) is limited by the availability of low-cost solar-grade (SoG) silicon feedstock in large quantities. It is estimated that current sources of SoG silicon (scraps and surplus capacity from the semiconductor industry) will not meet the demand by 2005. This project will develop low-cost technology for SoG silicon production by upgrading metallurgical-grade (MG) silicon, which is commercially produced in large quantities worldwide. Additives to the MG silicon will remove B, P, and Al impurities, and other impurities will be removed by directional solidification. The technology will be integrated with MG silicon production for commercialization. In Phase I, additions will be made to the low-purity MG silicon, which will be melted and directionally solidified. The additives will form compounds with high segregation coefficient impurities, which will be separated, volatilized, or segregated, leaving behind the higher purity silicon that can be used as SoG silicon feedstock.
Commercial Applications and Other Benefits as described by the awardee: The technology should provide SoG silicon for the PV community, thereby addressing the shortage that is expected by 2005. This feedstock could also be used for some devices in the semiconductor industry
