Low-cost solar grade silicon purification process with Al-Si system using a powder metallurgy technique

摘要

Silicon solar cell is one of the cleanest and most potential renewable resources. However, the high cost of raw material is impeding the development of silicon solar cell. In this paper, we have investigated a purification process designed for low-cost solar grade silicon with Al-Si system, using a powder metallurgy technique. It is found that by modulating the external pressure and/or protection ambient, the alloying of Al-Si powder mixture is easily accomplished at a relatively lower temperature. The mechanism of Si products purified from the Al-Si melt has been discussed based on their morphological characterizations. The impurity contents of the purified Si products can be controlled at a very low level (～3 ppmw).Mean-while, the yield of the purified Si products using the powder metallurgy technique is clarified to be higher than that of the conventional Al-Si purification technique without external pressure or protecting ambient. The process is quite potential of providing low-cost solar grade silicon feedstock for photovoltaic industry.