Signatures of Plexcitonic States in Molecular Electroluminescence

We investigate the electroluminescence (EL) of molecules confined between metallic electrodes and coupled to quantum plasmonic modes using a multi-particle quantum master equation (QME) approach. Within our general state-based framework, we describe electronic tunneling, vibrational damping, environmental dephasing, and the quantum coherent dynamics of coupled quantum electromagnetic field modes. As an example, we calculate the STM-induced spontaneous emission of a tetraphenylporphyrin (TPP) molecule coupled to a nanocavity plasmon. In the weak molecular exciton-plasmon coupling regime we find excellent agreement with experiments, including above-threshold hot luminescence, an effect not described by previous semiclassical calculations. In the strong coupling regime, we analyze the spectral features indicative of the formation of plexcitonic states, and the time-dependent quantum statistics of the emitted light.