Patent ID: 7883680

Claim:
A method for purifying silicon to solar-grade purity, the method comprising: (a) forming a first molten liquid from silicon and a solvent metal selected from the group of copper, tin, zinc, antimony, silver, bismuth, aluminum, cadmium, gallium, indium, magnesium, lead, an alloy thereof, and combinations thereof; (b) contacting the first molten liquid with a first gas, to provide a second molten liquid; (c) cooling the second molten liquid to form first silicon crystals and a first mother liquid; (d) separating the first silicon crystals and the first mother liquid; (e) heating the first silicon crystals to form a first molten bath; (f) directionally solidifying the first molten bath to form second silicon crystals and a second mother liquor; (g) separating the second silicon crystals and the second mother liquor; (h) heating the second silicon crystals to provide a second molten bath; (i) directionally solidifying the second molten bath below the melting point, thereby forming a third silicon crystals, and separating the upper portion and the lower portion; wherein the upper portion comprises a third mother liquor and the lower portion comprises a third silicon.