Highly Effective Energy Redistribution and Vertical Electron Transfer in Reduced Graphene Oxide/Au Composite Ultrathin Electrodes.

Among low-cost graphene-based electrodes, the reduced graphene oxide (rGO)/Au composite ultrathin electrode is a prototype in integrated optoelectronic devices based on flexible electrodes. However, fundamental research on the interfacial charge transfer behaviors in such rGO/Au composite ultrathin electrodes for practical film devices is still elusive. Here, the anisotropic decay kinetics of quantum-confined sp2 states are unraveled in pristine rGO films and rGO/Au composite ultrathin electrodes. It demonstrates that under 500 nm excitation, quantum-confined sp2 states in pristine rGO films undergo a highly effective excitation energy migration process within the first ∼100 fs, followed by a vertical energy diffusion with a rate of 1/0.49 ps-1. For rGO/Au composite ultrathin electrodes under 600 nm excitation, an averaged vertical electron transfer rate of 1/1.1 ps-1 from band-edge sp2 states in rGO to nearby Au interfaces is revealed. Our findings renew the understanding of energy transport and charge transfer mechanisms in rGO-based composite electrodes.