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ECN publication
Solar-grade silicon by a direct route based on carbothermic reduction of silica: requirements and production technology
Geerligs, L.J.; Wyers, G.P.; Jensen, R.; Raaness, O.S.; Waernes, A.N.; Santén, S.; Reinink, A.; Wiersma, B.
Published by: Publication date:
ECN Solar Energy 1-9-2002
ECN report number: Document type:
ECN-RX--02-042 Conference Paper
Number of pages: Full text:
4 Download PDF  

Presented at: 12th Workshop on Crystalline Silicon Solar Cell Materials and Processes, Breckenridge CO, USA, 11-14 augustus 2002.

In the European projects SOLSILC and SPURT, a process is developed forthe production of solar grade silicon (SOG-Si) by carbothermic reduction of silica, based on very pure raw materials. The purity of the raw materials greatly reduces the requirements on purification of the silicon, from dopants and other impurities. This paper reports the technology used for the Si production, which is suitable for the available high purity silica and carbon materials. It also reports results from the carbon removal process, which brings the carbon content of the silicon from several hundred ppmw to below 5 ppmw. Finally, it discusses experiments on the allowable impurity concentrations in SOG-Si feedstock for directional solidification. Segregation observed during directional solidification is better than previously published, and allowable concentrations of Fe and Ti are similar to what was previously published for monocrystalline material by Westinghouse Corp.

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