Material- and process-effects on homogeneity and electric properties of transparent conducting films composed of hydrazine-reduced graphene oxide and/or silver nanowire

Abstract

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.