Methods and devices for forming thermoelectric elements
The present disclosure provides a thermoelectric element comprising a flexible semiconductor substrate having exposed surfaces with a metal content that is less than about 1% as measured by x-ray photoelectron spectroscopy (XPS) and a figure of merit (ZT) that is at least about 0.25, wherein the flexible semiconductor substrate has a Young's Modulus that is less than or equal to about 1×10 6 pounds per square inch (psi) at 25° C.
1. A method for forming a thermoelectric element having a figure of merit (ZT) that is at least 0.25 at 25° C., comprising:
(a) providing a reaction space comprising a semiconductor substrate in electrical communication with a plurality of electrodes, wherein said semiconductor substrate is substantially free of a metallic coating; and
(b) using said plurality of electrodes to direct electrical current through said semiconductor substrate at a current density of at least 0.1 mA/cm 2 and an electrical potential of at least 1 volt (V), to form a thermoelectric element comprising a pattern of holes, wherein said thermoelectric element has said ZT that is at least 0.25 at 25° C.
2. The method of claim 1 , wherein said plurality of electrodes comprises a working electrode and a counter electrode that are each in electrical communication with said semiconductor substrate.
3. The method of claim 1 , further comprising providing an etching solution in said reaction space, wherein during (b), said etching solution is in contact with said semiconductor substrate.
4. The method of claim 3 , wherein said etching solution comprises an acid.
5. The method of claim 1 , wherein said pattern of holes comprises a disordered pattern of holes.
6. The method of claim 1 , wherein said pattern of holes is polydisperse.
7. The method of claim 1 , wherein said thermoelectric element has a metal content of less than 1% as measured by x-ray photoelectron spectroscopy (XPS).
8. The method of claim 7 , wherein said metal content is less than or equal to 0.1% as measured by XPS.
9. The method of claim 8 , wherein said metal content is less than or equal to 0.01% as measured by XPS.
10. The method of claim 9 , wherein said metal content is less than or equal to 0.001% as measured by XPS.
11. The method of claim 1 , wherein said ZT is at least 0.3 at 25° C.
12. The method of claim 11 , wherein said ZT is at least 0.6 at 25° C.
13. The method of claim 12 , wherein said ZT is at least 0.8 at 25° C.
14. The method of claim 13 , wherein said ZT is at least 1.0 at 25° C.
15. The method of claim 14 , wherein said ZT is at least 1.3 at 25° C.
16. The method of claim 1 , wherein said current density is at least 1 mA/cm 2 .
17. The method of claim 16 , wherein said current density is at least 10 mA/cm 2 .
18. The method of claim 17 , wherein said current density is less than or equal to 50 mA/cm 2 .
19. The method of claim 1 , wherein a hole of said pattern of holes has a surface roughness from 0.1 nanometers (nm) to 50 nm as measured by transmission electron microscopy (TEM).