Tribodiffusion-driven triboelectric nanogenerators based on MoS2

Recently, dynamic Schottky diode or p-n junction-based triboelectric nanogenerators (TENGs) which generate direct current were reported. However, most of them exhibited low output voltage because their semiconducting friction layers were directly constructed on an electrode. In this study, we report a "tribodiffusion-driven" TENG, the working mechanism of which differs from previously reported ones. When n-type MoS2 and p-type polypyrrole (PPy) are in contact, electrons and holes diffuse into PPy and MoS2, respectively, contributing to generating output voltages and currents. To increase the number of charges diffusing across the p-n junction, Ag nanoparticles (NPs) and a piezoelectric poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) layer were placed below MoS2. Additionally, PPy was p-doped using Pt NPs. These MoS2-based TENGs exhibited an instantaneous power density of 14.4 mW cm(-2) with an external load resistor of 1 M omega and a transferred charge density of 0.047 mu C cm(-2) in a single cycle when charging a capacitor. These values are higher than the previously reported values, demonstrating that tribodiffusion-based TENGs can be regarded as another type of TENG.