Copper-nickel codeposition as a model for mass-transfer characterization in copper-indium-selenium thin-film production

The use of binary copper-nickel (Cu-Ni) codeposition from a complexing citrate electrolyte is proposed as a convenient model system for simple, rapid and inexpensive characterization of local mass-transfer limitations arising in the production of ternary copper-indium-selenium (CIS) thin films. Both the Cu-Ni and the CIS systems have been investigated in a small pilot cell and deposit thickness and composition distributions on a 5 x 5 cm(2) cathode have been compared. The experimental comparison confirms that the mass-transfer characteristics measured for copper deposition in the binary Cu-Ni codeposition system offer an excellent representation of the mass-transfer-limited deposition of copper and selenium in the ternary CIS system. The binary Cu-Ni system presents a number of advantages for process development, among which the possibility of operating at neutral pH and being much easier to handle, less expensive and less toxic than the CIS system. The results of the study presented here, although targeted to CIS production, may also be of use for the development of other electrodeposition processes in which one or more electro-active species are reduced under mass-transfer control.