Electroplating additive for the deposition of metal, a binary, ternary, quaternary or pentanary alloy of elements of group 11 (IB)—group 13 (IIIA)—Group 16 (VIA)
The invention relates to electroplating additives for the deposition of a group IB metal/binary or ternary group IB-group IIIA/ternary, quaternary or pentanary group IB-group IIIA-group VIA alloy on substrates useful for thin film solar cells. The additives are thiourea compounds or derivatives which have the general formula (A): wherein X 1 and X 2 may be the same or different and are selected from the group consisting of arylene and heteroarylene; FG 1 and FG 2 may be the same or different or are selected from the group consisting of —S(O) 2 OH, —S(O)OH, —COOH, —P(O) 2 OH and primary, secondary and tertiary amino groups and salts and esters thereof; R is selected from the group consisting of alkylene, arylene or heteroarylene and n and m are integers from 1 to 5.
1. A process for coating a substrate with a binary or ternary group IB-group IIIA/ternary, quaternary or pentanary group IB-group IIIA-group VIA alloy comprising the following steps:
(i) pre-cleaning the substrate to be coated and
(ii) contacting the pre-cleaned substrate with a metal plating composition comprising an additive of the general formula (A) in a concentration range from 1 to 500 ppm:
wherein X 1 and X 2 may be the same or different and are selected from the group consisting of arylene and heteroarylene;
FG 1 and FG 2 may be the same or different and are selected from the group consisting of —S(O) 2 OH, —S(O)OH, —COOH, —P(O) 2 OH and primary, secondary and tertiary amino groups and salts and esters thereof;
R is selected from the group consisting of alkylene, arylene or heteroarylene and
n and m are integers from 1 to 5; and
further comprising a group IB plating species and a group IIIA plating species, and a buffer system in an amount such that the composition has a pH value from about 1 to about 6,
at a temperature from about 15° C. to about 80° C. to obtain a substrate coated with a binary or ternary group IB-group IIIA/ternary, quaternary or pentanary group IB-group IIIA-group VIA alloy.
2. The process according to claim 1 wherein the additive is selected from the group consisting of compounds having the general formula (I) to (III):
wherein Ar 1 and Ar 2 are the same or different and independently denote an arylene group;
wherein Het 1 and Het 2 are the same or different and denote a heteroarylene group and
wherein FG 1 , FG 2 , m and n are defined as in claim 1 .
3. The process according to claim 2 wherein Ar 1 and Ar 2 denote a phenylene or naphthylene group.
4. The process according to claim 2 wherein Het 1 and Het 2 denote a pyridylene or quinolinylene group.
5. The process according to claim 2 wherein the additive has the formula
wherein n′ is 2 to 12.
6. The process according to claim 1 wherein the metal plating composition further comprises a group VIA plating species.
7. The process according to claim 1 wherein the group IB plating species comprises copper, wherein the group IIIA plating species comprises gallium and/or indium and wherein the VIA plating species comprises selenium and/or sulfur.
8. The process according to claim 7 wherein the metal plating composition comprises plating species selected from:
(i) copper plating species,
(ii) copper and indium plating species,
(iii) copper, indium and gallium plating species,
(iv) copper, indium and selenium plating species,
(v) copper, indium and sulfur plating species,
(vi) copper, indium, gallium and selenium plating species,
(vii) copper, indium, gallium and sulfur plating species and
(viii) copper, indium, gallium, selenium and sulfur plating species.
9. The process according to claim 8 wherein the copper and indium plating species are comprised in the composition in a molar ratio of copper:indium of 1:0.1-50 and wherein the copper and selenium plating species are comprised in the composition in a molar ratio of copper:selenium of 1:0.01-40.
10. The process according to claim 9 wherein the copper and indium plating species are comprised in the composition in a molar ratio of copper:indium of 1:1-5 and wherein the copper and selenium plating species are comprised in the composition in a molar ratio of copper:selenium of 1:0.05-2.
11. The process according to claim 7 wherein the copper plating species are selected from copper sulphate, copper sulfamates and copper methane sulfonates and wherein the indium plating species are selected from indium sulfamates and indium methane sulfamates.
12. The process according to claim 1 wherein the composition has a pH value from about 1.8 to about 5.
13. The process according to claim 1 wherein the composition has a pH value from about 2.5 to about 4.
14. The process according to claim 1 wherein the additive is present in a concentration range of 5 to 100 ppm.
15. The process according to claim 1 wherein the additive is present in a concentration range of 10 to 50 ppm.
16. The process according to claim 1 wherein the composition further comprises a complexing agent in an amount of 0.001 to 2 mol/l.
17. The process according to claim 16 wherein the complexing agent is present in an amount of 0.005 to 1 mol/l.
18. The process according to claim 16 wherein the complexing agent is present in an amount of 0.02 to 0.5 mol/l.