Thermodynamic Properties of Impurity Components in Silicon-based Solutions: Influence of Interactions among Components on Impurity Removal from Silicon

ABSTRACT The thermodynamic properties of impurities in silicon-based solutions are the theoretical basis of silicon purification technology. These properties represent valuable information in regards to impurity removal for solar-grade silicon production by metallurgical methods. The thermodynamic properties of impurity components in silicon solutions obtained by both model calculations and experimental measurements are reviewed in detail in this paper with special focus on the infinite dilute activity coefficient and activity interaction coefficient of impurity components in binary Si-i and ternary Si-i-j systems. A positive or negative activity interaction coefficient value can be used to predict a mutually reinforcing or mutually restrictive relationship among impurity components during silicon purification. This review may provide workable guidance to researchers in selecting suitable refining systems and optimized refining conditions for silicon purification according to the thermodynamic properties of the impurity components therein; further, they may be used to establish a silicon solution thermodynamics database to support silicon purification technology.