METHOD FOR PURIFYING SILICON

1 . 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; and,

(g) separating the second silicon crystals and the second mother liquor.

2 . The method of claim 1 , wherein in step (a), the first molten liquid is formed by heating above the liquidus temperature.

3 . The method of claim 1 , wherein in step (b), a rotary degasser creates a vortex.

4 . The method of claim 1 , wherein at least one of steps (a)-(d) is carried out multiple times.

5 . The method of claim 1 , wherein the sequence of steps (a)-(d) is carried out multiple times prior to carrying out step (e).

6 . The method of claim 1 , wherein the sequence of steps (a)-(d) is carried out multiple times prior to carrying out the sequence of steps (e)-(g), and the first mother liquid obtained in step (d) comprises the solvent metal in step (a) of a prior sequence of steps (a)-(d).

7 . The method of claim 1 , wherein the sequence of steps (a)-(d) is carried out multiple times prior to carrying out the sequence of steps (e)-(g), and the first silicon crystals obtained in step (d) comprise the silicon in step (a) of a subsequent sequence of steps (a)-(d).

8 . A method of manufacturing solar cells, the method comprising making solar cells that comprise the second silicon of claim 1 .

9 . 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 and a vortex is created;

(c) cooling the second molten liquid to form first silicon crystals and a first mother liquid; and,

(d) separating the first silicon crystals and the first mother liquid.

10 . The method of claim 9 , wherein in step (a), the first molten liquid is formed by heating above the liquidus temperature.

11 . The method of claim 9 , wherein in step (b), the vortex contacts oxygen (O 2 ).

12 . The method of claim 11 , wherein the oxygen is from the atmosphere.

13 . The method of claim 9 , wherein in step (b), the vortex contacts at least one of chlorine (Cl 2 ), nitrogen (N 2 ), oxygen (O 2 ), or argon (Ar).

14 . The method of claim 9 , wherein step (b) is carried out twice, with chlorine (Cl 2 ) and nitrogen (N 2 ); and with oxygen (O 2 ) and argon (Ar), respectively.

15 . The method of claim 9 , wherein the vortex created is a vortex of the first molten liquid.

16 . The method of claim 9 , wherein the vortex created is a vortex of the second molten liquid.

17 . The method of claim 9 , wherein the vortex created is a vortex of both the first and second molten liquids.

18 . The method of claim 9 , wherein the vortex is created with a rotary degasser.

19 . The method of claim 9 , wherein a rotary degasser is used to add the gas.

20 . The method of claim 9 , wherein at least one of steps (a)-(d) is carried out multiple times.

21 . A method of manufacturing solar cells, the method comprising making solar cells that comprise the first silicon crystals of claim 9 .