Growth of structure-controlled polycrystalline silicon ingots for solar cells by casting

We propose a new concept of growing a polycrystalline Si ingot suitable for solar cells by casting based on the directional growth behavior of polycrystalline Si investigated using an in situ observation system. The cooling conditions for the Si melt were crucial for controlling growth in the initial stage. At a high cooling rate, dendrite growth occurred along the crucible wall. This growth mechanism was found to be useful for obtaining a polycrystalline structure with large oriented grains. In fact, using the dendrites grown in the initial stage of casting, a polycrystalline Si ingot with large oriented grains was obtained. The solar cell properties of such structure-controlled polycrystalline Si were as good as those of single-crystalline Si.