Work-function decrease of transparent conducting films composed of hydrazine-reduced graphene oxide and silver nanowire stacked layers by electrochemical treatment

Equilibrium potentials (EP) of various carbon materials on a glassy-carbon or a gold electrode have been investigated. Among them, hydrazine-reduced graphene oxide (h-rGO) was found to be notable for a marked decrease in EP after cyclic voltammetry (CV) in a negative potential region between −0.3 and −1.6 V vs. Ag/AgCl. The resulting h-rGOs indicated work-function (WF) values as small as 3.4–3.8 eV. Transparent conducting films composed of h-rGO/silver nanowire (AgNW)/polymer stacked layers were treated with similar CV using the AgNW layer as an electrode. The WF values of the films decreased from 4.4 to 3.6–4.1 eV, which values are suitable for negative electrodes. X-ray photoelectron spectra showed small oxygen-to-carbon ratios (O/C) for the small-WF samples. The counter cation was also observed, indicating electron doping. Sodium borohydride, whose reduction potential is −1.44 V vs. Ag/AgCl, also decreased the WF of the films.