Electrical transport phenomenon and variable range hopping conduction in reduced graphene oxide/polystyrene composites

In this work, we investigate the temperature dependence of the electrical conductivity of a reduced graphene oxide (RGO)/polystyrene (PS) composites. We re-analysed, in our investigation, the experimental measurements of RGO/PS composites with different RGO concentrations obtained by W. Park et al. We show using two different methods: the Zabrodskii method and a numerical method based on the calculation of the percentage deviation; that the electrical conductivity follows, at the beginning, the Efros-Shklovskii Variable Range Hopping regime (ES VRH) with T−1/2. This behavior showed that long range electron-electron interaction reduces the Density Of State of carriers (DOS) at the Fermi level and creates the Coulomb gap (CG). When the RGO concentration increases, we noticed that the temperature dependence of the electrical conductivity tends toward T−1/3, which may suggest a possible crossover from ES VRH regime to the Mott VRH regime for high RGO concentration values. We also, calculated and represented the Density Of State (DOS) per energy and per area function g(E) for each sample. We noted that the width of parameter Δ representing the half of CG width decreases by increasing the RGO concentration and the function g(E) tends toward the constant g0 corresponding to the Mott VRH