METHOD FOR PURIFYING SILICON
The present invention provides for methods of purifying silicon, methods for obtaining purified silicon, as well as methods for obtaining purified silicon crystals, purified granulized silicon and/or purified silicon ingots.
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.