Influence of iron, aluminum, calcium, titanium and vanadium impurities removal from silicon based on Cu-catalyzed chemical leaching

Abstract

In this work, silicon purifying process based on the novel Cu-catalyzed chemical leaching (CuCCL) treatment has been investigated as a function of different silicon particle size, HF concentration, leaching time, H2O2 concentration, Cu(NO3)2 concentration and leaching temperature. Typical impurity precipitate in silicon was analyzed, which revealed that the main impurities of Fe, Al, Ca, Ti, and V mainly exist as Si2Fe, Si–Fe–Al, Si–Fe–Al–Ca, and Si–Fe–Al–Ti–V phases in the MG-Si feedstock. The results showed that the main impurities Fe, Al, Ca, Ti, and V can be effectively eliminated by the CuCCL treatment, especially for Ca, Ti and V. In the appropriate experiment conditions, the removal of main impurities Fe, Al, Ca, Ti, and V from MG-Si significantly reached to 99.38%, 98.64, 100%, 100%, and 100%, respectively. It was found that the impurities on the silicon facilitated the formation of porous structures during the CuCCL process, and the generated porous structures further exposed more impurities to the acid etchants, which promote the impurity removal from silicon. Furthermore, the leaching behaviors of impurity precipitates in the CuCCL process were obtained through revealing their evolution during deposition and etching steps. The high-efficient silicon purification effect of this study may bring some new strategy for achieving the low-cost solar grade silicon.