Low Cost Silicon for Solar Energy Conversion Applications

Economically viable means of producing silicon solar cells for the conversion of solar energy into electric power are discussed. Emphasis is given to the discussion of crystal growth techniques capable of growing single-crystal silicon ribbons directly and inexpensively from molten silicon. The capillary action shaping technique (CAST) recently developed by IBM has a good potential for producing low cost silicon sheets suitable for solar cells. This technique has produced ribbon 100 mm wide and 0.3 mm thick. Problems that CAST must overcome in order to supply material for low cost solar cells are discussed. Economic and technological computer-modeled comparisons indicate that continuously grown CAST ribbons of these dimensions can meet a cost objective below $50/m
²
of sheet material. The results require that it be possible to fabricate a twelve-percent-efficient solar cell from CAST ribbon 100 mm wide and 0.3 mm thick at a polycrystalline silicon cost of $10/kg.