Development of Solar Grade (SoG) Silicon

76307S The continued rapid growth of the photovoltaic (PV) industry (over 60% growth in 2004) is limited by the availability of low-cost solar-grade (SoG) silicon feedstock in large quantities. The use of scraps and surplus silicon from the semiconductor industry is no longer adequate. While the timing is ripe to push photovoltaics as a reliable renewable energy source, further expansion must overcome this materials-availability issue. This project will develop low-cost technology for SoG silicon production by upgrading metallurgical-grade silicon, which is commercially produced in large quantities worldwide. In Phase I, a crucible was developed for the removal of impurities under vacuum processing. Starting with commercially available metallurgical-grade silicon, significant reductions in the difficult-to-remove impurities, B, P and Al, were demonstrated ¿ impurities were reduced from 12, 15 and 370 ppmw to 5.8, 0.23 and 0.065 ppmw, respectively. Phase II will develop techniques to improve the vacuum processing. This step will be followed by directional solidification in order to provide even further reductions in these impurities. Commercial Applications and Other Benefits as described by the awardee: There is currently no commercial source of solar-grade (SoG) silicon feedstock. By reducing the impurities in metallurgical-grade silicon, this technology should provide a low-cost solution to the materials shortage problem.