Applications of directional solidification process in preparation of solar grade silicon by metallurgical route

In recent years, directional solidification technics is widely used in preparing the solar grade silicon (SOG-Si) by metallurgical route. It plays an important role to remove metallic impurities from metallurgical grade silicon (MG-Si) during purification of metallurgical route. While, in casting process, it is used mainly for the growth of large size columnar crystals in silicon ingot. And good crystal quality and the excellent electrical properties can be obtained in this process. In this paper, the latest research progresses of metallic impurities purification by directional solidification in metallurgical route, the improvement of crystal quality and the excellent electrical properties by ingot cast have been detailed introduced. On the basis of former studies, we proposed a new directional solidification technics for preparing SOG-Si by metallurgical route in this paper. Compared with present directional solidification for purification and ingot casting process, the new directional solidification technics is optimized, which combines with removal of impurities and ingot casting process. The growth of columnar crystal and the removal of metallic impurities can be carried out in the new directional solidification process at the same time. Therefore, the new directional solidification technics is different from the present directional solidification of purification and ingot casting process. It does not need the remelting process and can cut down the amount of quartz ceramics crucible. And the cost of preparing SOG-Si by metallurgical route is reduced simultaneously. This is beneficial to technology progresses and large-scale application for SOG-Si by metallurgical route.