Metal plating composition and method for the deposition of copper—zinc—tin suitable for manufacturing thin film solar cell

1. A metal plating composition for the deposition of a copper-zinc-tin alloy, said alloy additionally containing at least one chalcogen, the metal plating composition comprising at least one copper plating species, at least one zinc plating species, at least one tin plating species, at least one complexing agent and at least one chalcogen plating species,

wherein the metal plating composition additionally comprises at least one additive, selected from the group consisting of disubstituted benzene compounds having general chemical formula I:

wherein R 1 and R 2 are the same or different, are selected independently from the group consisting of OH, SH, NR 3 R 4 , CO—R 5 , COOR 5 , CONR 3 R 4 , COSR 5 , SO 2 OR 5 , SO 2 R 5 , SO 2 NR 3 R 4 and the salts thereof or have the aforementioned meanings and form a common condensation chain;

with R 3 and R 4 being the same or different, being selected independently from the group consisting of H and alkyl; and

with R 5 being selected from the group consisting of H, alkyl and hydroxyalkyl, and wherein the metal plating composition has a pH in the range of greater than 10.5 to about 12.

2. The metal plating composition of claim 1 , wherein R 1 and R 2 are selected from the group consisting of COOH, COOCH 2 CH 2 OH, COOCH 2 CH 3 , COOCH 3 , NH 2 , CHO or together form a moiety CO—NH—SO 2 , said moiety being bonded to positions in ortho-orientation to the benzene ring.

3. The metal plating composition of claim 1 , wherein the copper-zinc-tin alloy is a Cu x Zn y Sn z Ch1 a Ch2 b alloy, with Ch1 being a first chalcogen, Ch2 being a second chalcogen and wherein x is from 1.5 to 2.5, y is from 0.9 to 1.5, z is from 0.5 to 1.1, a is from 0 to 4.2 and b is from 0 to 4.2.

4. The metal plating composition of claim 1 , wherein the copper, zinc and tin plating species are present in the composition at a molar ratio of copper:zinc:tin=1:0.1-10:0.1-4.

5. The metal plating composition of claim 1 , wherein the copper, zinc and tin plating species are present in the composition at a molar ratio of copper:zinc:tin=1:2-8:0.4-1.

6. The metal plating composition of claim 1 , wherein the copper plating species are copper phosphates or copper pyrophosphates and wherein the zinc plating species are zinc phosphates or zinc pyrophosphates.

7. The metal plating composition of claim 1 , wherein the tin plating species are tin stannates.

8. The metal plating composition of claim 1 , wherein at least one complexing agent is selected from the group consisting of oxalate, citrate and gluconate compounds.

9. The metal plating composition of claim 1 , wherein the composition further comprises a buffer system.

10. The metal plating composition of claim 9 , wherein the buffer system comprises hydrogenphosphate/phosphate.

11. The metal plating composition of claim 3 , wherein a>0, Ch1 is S and at least one chalcogen plating species is a sulfur plating species, said sulfur plating species being selected from the group consisting of thiosulfates, thiosulfonic acids, di(thiosulfonic) acids, sulfur sulfides, thiourea and the derivatives thereof, organic disulfides, organic polysulfides, colloidal elemental sulfur and compounds forming colloidal elemental sulfur.

12. The metal plating composition of claim 3 , wherein b>0, Ch2 is Se and at least one chalcogen plating species is a selenium plating species, said selenium plating species being selected from the group consisting of selenates, selenosulfites, diselenides and polyselenides.

13. A method of depositing of a copper-zinc-tin alloy, said alloy additionally containing at least one chalcogen, said method comprising contacting a substrate and an anode with the metal plating composition of claim 1 and flowing an electric current between said substrate and the anode.

14. The method of claim 13 , further comprising sulfurizing the copper-zinc-tin alloy by contacting same with a sulfur plating species.

15. The method of claim 14 , wherein the sulfur plating species is selected from the group consisting of elemental sulfur and a reducing atmosphere containing a sulfur compound.

16. The method of claim 13 , further comprising depositing a selenium monolayer onto the alloy.

17. The method of claim 13 , further comprising selenizing the copper-zinc-tin alloy by contacting same with a reducing atmosphere containing a selenium compound.

18. The metal plating composition of claim 1 , wherein the metal plating composition has a pH in the range of from about 11.2 to about 12.

19. The metal plating composition of claim 1 , wherein the metal plating composition does not contain a noble metal from the group consisting of silver, gold, palladium, iridium, ruthenium, rhodium, and platinum.