Migration Behavior of Impurity Iron in Silicon Melt Under Pulsed Electric Current

Abstract

The impurity iron in silicon material will seriously affect the photoelectric conversion efficiency of silicon solar cells. However, the traditional silicon purification method has the disadvantages of long cycle, high energy consumption and serious pollution. In this study, an efficient and green pulsed electric current purification technology is proposed. The electromigration effect of iron elements, the current density gradient driving of iron phase, and the gravity of iron phase all affect the migration behavior of iron phase in silicon melt under pulsed electric current. Regardless of the depth of electrode insertion into the silicon melt, the solubility of iron in silicon decreases under the pulsed electric current, which helps to form the iron phase. At the same time, the iron phase tends to sink toward the bottom under the influence of gravity. When the electrode is shallowly inserted, a non-uniform electric field is formed in the silicon melt, and the iron phase is mainly driven by the current density gradient to accelerate sink toward the bottom. When the electrode is fully inserted, an approximately uniform electric field is formed in the silicon melt, and iron elements are preferentially migrated to the cathode by electromigration, forming iron phase sinking at the cathode. The study of impurity iron migration behavior in silicon melt under pulsed electric current provides a new approach for the purification of polycrystalline silicon.