Pulsed electrodeposition of CuSCN for superfilling of ZnO nanowire array electrodes

Pulsed electrodeposition at room temperature is shown to be a facile, simple and fast method for super-filling of CuSCN onto ZnO nanowire arrays for applications in transparent diodes and optoelectronic devices. Compared to previously suggested methods for CuSCN superfilling, it offers the advantages of low cost, room temperature deposition in a one-pot process, combined with fast deposition rates, making it highly accessible for lab-scale deposition as well as scale up for industrial processes. Each pulse consisted of a working time t_on, at which the potential was -500 mV vs. Ag/AgCl, and an off period t_off, at which zero potential vs. Ag/AgCl was applied. The t_off interval discharged the charged layer and regenerated the ion concentration near the cathode surface, resulting in denser nucleation and a more uniform coating. The pulse sequence controlled the deposition rate and the S/Cu ratio in the deposited CuSCN films, which was larger than in corresponding electrostatic depositions, due to higher SCN^- concentration near the ZnO surface accomplished during the t_off interval. Current-voltage characteristics showed excellent diode properties, significantly better than those of potentiostatic deposited CuSCN/ZnO diodes. We conclude that when high currents in transparent diodes are desirable, as in photovoltaic applications, pulsed electrodeposition and super-filling have significant advantages, with the pulse sequence t_on = 2 sec, t_off = 1 sec resulting in high deposition rates and optimized diode parameters.