Process for casting silicon blocks of columnar structure

摘要

By means of the process and by means of the apparatus, fused silicon is produced continuously, or in phases, and zonally cast into a mold in which it is caused to solidify zonally. The temperature conditions in the solidification zone are controlled with the aid of a movable heating zone, by means of which the crystallization front is adjusted to the rising level that fills up the mold, this level being in turn controlled by the fusion rate of the silicon. Polycrystalline silicon blocks can be obtained in which, because of the flat shape of the crystallization front, the columnar single-crystal domains within the blocks extend almost vertically and which represent an excellent solar cell base material having high diffusion lengths and lifetimes of the minority charge carriers, from which solar cells of correspondingly high efficiencies can be produced.