Refining of Silicon During its Solidification from a Cu-Si Melt

Current methods of solar-grade silicon (SG-Si) production are energy intensive and costly. The possibility of using metallurgical techniques for refining metallurgical-grade Si (MG-Si) to SG-Si has been investigated. The main steps in the metallurgical refining route include alloying with copper to produce a 50-50wt% Cu-Si alloy, controlled solidification, crushing, and acid leaching. The controlled solidification process involved 5 variations to determine the best process to maximize Si dendrite agglomeration in the sample and produce the purest Si. This was determined by using various techniques, such as: optical imaging, dendrite analysis, EPMA and SEM analysis and ICP analysis. The crushing and acid leaching steps were carried out to remove the unwanted Cu3Si eutectic from the pure Si dendrite phase. Upon completion of the analysis techniques, the optimal cooling method was determined to be the top cooled, 0.5°C/min sample.MAS