COLUMNAR-GRAINED POLYCRYSTALLINE SOLAR CELL SUBSTRATE AND IMPROVED METHOD OF MANUFACTURE

摘要

The invention relates to improved techniques for manufacturing columnar-grained polycrystalline sheets which have particular utility as substrates or wafers for solar cells. The sheet is made from silicon on a setter material which supports the silicon material. The setter material and silicon are subjected to a thermal profile all of which promote columnar growth. The thermal profile sequentially creates a melt region where a thin-film capping layer grows at the top of the silicon, a nucleation region where preferential nucleation occurs at the capping-layer/molten-silicon interface, and then a growth region where both liquid and a growing polycrystalline sheet layer coexist. An annealing region is created where the temperature of the grown polycrystalline silicon sheet layer is controllably reduced to effect stress relief.