Methods for group V doping of photovoltaic devices
According to the embodiments provided herein, a method for doping an absorber layer can include contacting the absorber layer with an annealing compound. The annealing compound can include cadmium chloride and a group V salt comprising an anion and a cation. The anion, the cation, or both can include a group V element. The method can include annealing the absorber layer, whereby the absorber layer is doped with at least a portion of the group V element of the annealing compound.
1. A method for doping an absorber layer, comprising:
contacting the absorber layer with an annealing compound, wherein:
the absorber layer comprises cadmium, and tellurium;
the annealing compound comprises cadmium chloride and a group V salt comprising an anion and a cation;
the anion, the cation, or both comprise a group V element;
a ratio of cadmium chloride to group V salt within the annealing compound, on a weight per volume basis, is at least 30 to 1; and
annealing the absorber layer, whereby the absorber layer is doped with at least a portion of the group V element of the annealing compound.
2. The method of claim 1 , wherein the annealing compound is a solution, and a proportion of the group V salt to a total amount of the annealing compound is less than 100 grams per liter.
3. The method of claim 2 , wherein the proportion of the group V salt to the total amount of the annealing compound is between 1/25 grams per liter and 20 grams per liter.
4. The method of claim 1 , wherein a grain size of the absorber layer is increased during annealing of the absorber layer.
5. The method of claim 1 , wherein the group V salt is ammonium dihydrogen arsenate.
6. The method of claim 1 , wherein the group V salt is diammonium hydrogen phosphate.
7. The method of claim 1 , wherein the group V element is nitrogen.
8. The method of claim 1 , wherein the group V element is phosphorous.
9. The method of claim 1 , wherein the group V element is arsenic.
10. The method of claim 1 , wherein the group V element is antimony.
11. The method of claim 1 , wherein the group V element is bismuth.
12. The method of claim 1 , comprising exposing an absorber layer to a reducing environment, while the absorber layer is annealed.
13. The method of claim 12 , wherein the reducing environment comprises a forming gas configured to mitigate formation of group V oxides, the forming gas comprising hydrogen, nitrogen, carbon, or combinations thereof.
14. The method of claim 1 , wherein the absorber layer is annealed at a temperature between 350° C. and 500° C. for between 5 minutes and 60 minutes.
15. The method of claim 1 , wherein:
the annealing compound comprises an alkali metal chloride; and
at least a portion of the group V dopant is activated during annealing of the absorber layer.
16. The method of claim 1 , wherein, after the absorber layer is annealed, an atomic concentration of the group V dopant in a central region of the absorber layer is greater than 1×10 16 cm −3 .
17. The method of claim 1 , wherein the absorber layer comprises selenium.
18. The method of claim 1 , wherein a grain size of the absorber layer is increased during annealing of the absorber layer.
19. The method of claim 1 , wherein the group V salt is ammonium dihydrogen arsenate.
20. The method of claim 1 , wherein the group V salt is diammonium hydrogen phosphate.
21. The method of claim 1 , wherein the group V element is nitrogen.
22. The method of claim 1 , wherein the group V element is phosphorous.
23. The method of claim 1 , wherein the group V element is arsenic.
24. The method of claim 1 , wherein the group V element is antimony.
25. The method of claim 1 , wherein the group V element is bismuth.
26. The method of claim 1 , comprising exposing an absorber layer to a reducing environment, while the absorber layer is annealed.
27. The method of claim 26 , wherein the reducing environment comprises a forming gas configured to mitigate formation of group V oxides, the forming gas comprising hydrogen, nitrogen, carbon, or combinations thereof.