Signatures of Plexcitonic States in Molecular Electroluminescence

TL;DR

This paper introduces a quantum master equation approach to study molecular electroluminescence, revealing signatures of plexcitonic states and matching experimental results in different coupling regimes.

Contribution

It develops a comprehensive quantum framework to analyze electroluminescence in molecules coupled to plasmonic modes, capturing phenomena beyond semiclassical models.

Findings

Excellent agreement with experimental electroluminescence data in weak coupling regime.

Identification of spectral features indicating plexcitonic state formation in strong coupling.

Observation of above-threshold hot luminescence not explained by previous models.

Abstract

We develop a quantum master equation (QME) approach to investigate the electroluminesence (EL) of molecules confined between metallic electrodes and coupled to quantum plasmonic modes. 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.