Thermodynamics of phosphorus removal from silicon in solvent refining of silicon

Abstract

Refining of silicon for solar applications using metallurgical approaches has attracted a considerable attention in the recent years. The present study involves employing solvent refining as a purification technique in which silicon recrystallization takes place from an iron-silicon alloy melt. It is believed that iron will perform as the impurity "getter" and purified silicon crystals grow from the alloy melt, while the impurities are segregated to the liquid alloy. The focus of this article is on removal of phosphorus, as a critical impurity in solar silicon. In order to assess the feasibility and efficiency of phosphorus removal through solvent refining, the distribution of phosphorus between solid Si and Fe-Si melt at 1483-1583 K (1210-1310 °C) was measured. Interaction parameter between phosphorus and iron was calculated by varying the concentration of phosphorus at each temperature.