Method for forming silver-copper mixed kesterite semiconductor film

1. A method of forming a film comprising a Ag—Cu mixed kesterite compound having the formula Ag x Cu 2-x ZnSn(S y Se 1-y ) 4 , wherein 0<x<2, and 0≦y≦1, the method comprising:

forming a layer consisting of a Cu-deficient kesterite compound on a substrate, the Cu-deficient kesterite compound having the formula Cu 2-x Zn 1+x Sn(S y Se 1-y ) 4 , wherein 0<x<1, and 0≦y≦1;

forming a Ag layer consisting of elemental Ag on the layer consisting of the Cu-deficient kesterite compound; and

annealing the layer consisting of the Cu-deficient kesterite compound and the Ag layer.

2. The method of claim 1 , wherein the annealing is performed at a temperature ranging from 400° C. to 600° C.

3. The method of claim 1 , wherein the annealing is performed from 2 minutes to 10 minutes.

4. The method of claim 1 , wherein the annealing is performed using rapid thermal annealing.

5. The method of claim 1 , wherein the annealing is performed in a S-rich and/or Se-rich atmosphere.

6. The method of claim 5 , wherein the S- and/or Se-rich atmosphere is provided by supplying a S- and/or Se-containing gas into an annealing chamber where the annealing is performed.

7. The method of claim 6 , wherein the S- and/or Se-containing gas comprises H 2 Se, H 2 S, elemental Se or elemental S.

8. The method of claim 5 , wherein the S- and/or Se-rich atmosphere is provided by forming a capping layer comprising at least one of S and Se.

9. The method of claim 8 , wherein the capping layer is formed between the Cu-deficient kesterite compound and the Ag layer.

10. The method of claim 8 , wherein the capping layer is formed on the Ag layer before the annealing.

11. The method of claim 8 , wherein the capping layer comprises SnS, SnSe, SnS 2 , SnSe 2 or combinations thereof.

12. A method of forming a photovoltaic device comprising

forming a back contact layer on a substrate;

forming an absorber layer on the back contact layer, the absorber layer comprising a Ag—Cu mixed kesterite compound having the formula Ag x Cu 2-x ZnSn(S y Se 1-y ) 4 , wherein 0<x<2, and 0≦y≦1, wherein the forming the absorber layer comprises:

forming a layer consisting of a Cu-deficient kesterite compound on the substrate, the Cu-deficient kesterite compound having the formula Cu 2-x Zn 1+x Sn(S y Se 1-y ) 4 , wherein 0<x<1, and 0≦y≦1,

forming a Ag layer consisting of elemental Ag on the layer consisting of the Cu-deficient kesterite compound, and

annealing the layer consisting of the Cu-deficient kesterite compound and the Ag layer;

forming a buffer layer on the absorber layer; and

forming a transparent front contact layer on the buffer layer.

13. The method of claim 12 , wherein the annealing is performed in an S-rich and/or Se-rich atmosphere.

14. The method of claim 13 , wherein the S- and/or Se-rich atmosphere is provided by supplying a S- and/or Se-containing gas into an annealing chamber where the annealing is performed.

15. The method of claim 12 , wherein the S- and/or Se-rich atmosphere is provided by forming a capping layer comprising at least one of S and Se.

16. The method of claim 15 , wherein the capping layer is formed between the Cu-deficient kesterite compound and the Ag layer.

17. The method of claim 15 , wherein the capping layer is formed on the Ag layer before the annealing.

18. The method of claim 12 , further comprising forming metal contacts on the transparent front contact layer.

19. The method of claim 18 , further comprising forming an antireflective coating layer on the transparent contact layer.

20. The method of claim 1 , wherein the Ag layer is no longer present once the film comprising the Ag—Cu mixed kesterite compound is formed.