Manipulating Molecules with Strong Coupling: Polariton-Enhanced Triplet Harvesting*

A major focus in the study of organic exciton-polaritons has been the search for polariton condensation and lasing. However, their room-temperature stability and the large oscillator strengths of organic semiconductors offer the possibility for a wide range of further polaritonic effects. Indeed, within the strong coupling regime the upper and lower polariton states can be tuneably separated by as much as 100’s of meV from the parent exciton in these materials, enabling radical alteration of the energetic landscape. The effects of strong coupling can be profound, with reports of long-range energy transfer, altered chemical reactivity and work function modification. Theoretical work is now increasingly focused on the potential of strong coupling to manipulate electronic dynamics in the excited state. Here, we demonstrate for the first time the ability to manipulate the dynamics of singlet exciton fission using strong coupling. Within microcavities, we dramatically enhance the emission lifetime and increase delayed fluorescence by >75%, which we explain through a shift in the thermodynamic equilibrium between dark states in the exciton reservoir and the bright polaritons.