SILICON PURIFICATION THROUGH MAGNESIUM ADDITION AND ACID LEACHING

Abstract

Silicon is the dominant material in photovoltaic devices and with regard to the PV market growth, the demand for solar grade silicon feedstock is expected to be high in the future. Although solar silicon is currently produced through both chemical and metallurgical routes, the chemical route is still the main production method, which is expensive and have environmental challenges. Acid leaching of silicon, which is a metallurgical refining process is applied for silicon purification in the present research work. In this case, magnesium in different portions is added to liquid silicon containing B, P, Fe, Al, and other trace impurities. The Si-Mg melts are solidified under a controlled cooling rate and then they are treated by acid leaching through using dilute HCl solutions. The effect of magnesium concentration on the segregation and removal of the impurities, in particular P and B, is studied by electron microscopy and chemical analysis techniques. It is indicated that the process is effective for removing the impurities, and the purification is depending on the amount of Mg added into the silicon.