•Reduced GO/Ag nanowire/polymer stacked layers gave transparent conducting films.•The stacked layers compensate for the weak points of the components.•Sheet resistance and transmittance of the film ...were similar to those of ITO glass.•The film using a fluorinated polymer was transparent from near-UV to near-IR.•Reduced GO made the entire surface conductive and prevented the corrosion of Ag.
Transparent conducting films composed of stacked layers (reduced graphene oxide (rGO)/silver nanowire (AgNW)/polymer) were prepared by low-cost wet processes. The arithmetic mean roughness value (Ra) of the rGO surface was about 3–4nm. One of the films using poly (perfluoro-4-vinyloxy-1-butene) (Cytop)) showed a 4.0Ω/sq sheet resistance and a 75% diffuse transmittance at 550nm, values similar to those of commercial indium-tin-oxide (ITO) glass. The film possessed a much wider transparent wavelength region (65% at 300nm and 80% at 2000nm) than ITO. Scanning electron microscope (SEM) images of the films using poly(methyl methacrylate) (PMMA) indicated that the rGO top layer made all the surface conductive, and prohibited the corrosion of AgNW. The protective function was confirmed by sulfur vapor treatment and the mechanism was discussed.
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•h-rGO films prepared by spin-coating are more homogeneous than those by dip-coating.•Large-sized h-rGO(NiSiNa) films prepared with a rotation number of 2000rpm had wrinkles.•Larger ...ratio of pyrrolic nitrogen to oxygen-bound nitrogen gave smaller WF values.•Mechanical pressing at 100°C made the thickness of AgNW films small.•The arithmetic average roughness of h-rGO/AgNW/Cytop film was 1.2nm.
Photomicroscope observation of hydrazine-reduced graphene oxide (h-rGO) films indicates that the films prepared by spin-coating are more homogeneous than those prepared by dip-coating. Graphene oxide (GO) is apt to aggregate during the dipping process. Increasing rotation speed of the spin-coating decreased film thickness and increased surface resistant (Rs). Rs of small-sized h-rGO(BF1A) was smaller than that of large-sized h-rGO(NiSiNa). The h-rGO(NiSiNa) films prepared with a rotation number smaller than 2000rpm had wrinkles about 5nm in height and particles with about 15nm height. The rotation number of 3000rpm decreased the wrinkles and particles resulting in smaller Rs. Increasing the hydrazine-treatment temperature from 90 to 140°C caused the Rs values to decrease. Work-function values of h-rGO(NiSiNa) were 3.6–3.8eV; smaller than those of other h-rGOs. Larger ratio of pyrrolic nitrogen to oxygen-bound nitrogen gave smaller WF values. Silver nanowire (AgNW) films prepared by multiple spin-coating processes showed small Rs vales and small Rs deviations. Mechanical pressing at 100°C made the thickness of AgNW films equal to the AgNW diameter and decreased the Rs values. Polymer (Cytop) was coated on the AgNW films and the h-rGO/AgNW/Cytop transparent conducting film was peeled off. The arithmetic average roughness of the h-rGO surface was 1.2nm.
•Work-function of hydrazine-reduced graphene oxide (h-rGO) is decreased by electrochemical treatment.•Transparent conducting films composed of h-rGO/silver nanowire/polymer were applied.•The ...work-function of the films decreased from 4.4 to 3.6–4.1eV.•Small oxygen-to-carbon ratios were observed for the small-work-function samples.•Sodium borohydride also decreased the work function of the films.
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 −1.6V vs. Ag/AgCl. The resulting h-rGOs indicated work-function (WF) values as small as 3.4–3.8eV. 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 3.6–4.1eV, 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 −1.44V vs. Ag/AgCl, also decreased the WF of the films.
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