METHOD OF PREPARING CAST SILICON BY DIRECTIONAL SOLIDIFICATION

摘要

A method of preparing a cast silicon crystalline ingot is provided. The method comprises charging a silicon spacer to the bottom surface of the crucible; arranging a monocrystalline silicon seed crystal on the silicon spacer such that no surface of the monocrystalline silicon material is in contact with the bottom surface of the crucible; charging polycrystalline silicon feedstock to the crucible; and applying heat through at least one of the opening and the at least one sidewall in order to form a partially melted charge of silicon in the crucible. The cast silicon crystalline ingot has no transverse dimension less than about five centimeters, and the cast silicon crystalline ingot has a dislocation density of less than 1000 dislocations/cm2. Wafers sliced from the cast silicon crystalline ingot have solar cell efficiency of at least 17.5% and light induced degradation no greater than 0.2%.