Pulsed Electrodeposition for Copper Nanowires

Copper nanowires (Cu NWs) are a promising alternative to indium tin oxide (ITO), for use as transparent conductors that exhibit comparable performance at a lower cost. Furthermore, Cu NWs are flexible, a property not possessed by ITO. However, the Cu NW-based transparent electrode has a reddish color and tends to deteriorate in ambient conditions due to the oxidation of Cu. In this paper, we propose a pulsed-current (PC) plating method to deposit nickel onto the Cu NWs in order to reduce oxidation over a 30-day period, and to minimize the sheet resistance. Additionally, the effects of the pulse current, duty cycle, and pulse frequency on the performance of the Cu−Ni (copper−nickel) NW films have also been investigated. As a result, the reddish color of the electrode was eliminated, as oxidation was completely suppressed, and the sheet resistance was reduced from 35 Ω/sq to 27 Ω/sq. However, the transmittance decreased slightly from 86% to 76% at a wavelength of 550 nm. The Cu−Ni NW electrodes also exhibited excellent long-term cycling stability after 6000 bending cycles. Our fabricated Cu−Ni electrodes were successfully applied in flexible polymer-dispersed liquid crystal smart windows.