Dynamics of strongly coupled singlet fission molecules in optical microcavity

We have experimentally studied the dynamics of a singlet-fission molecule-metal microcavity system under strong coupling by using pump-probe transient absorption technique. Under one-photon pump, where the system is selectively pumped by wavelengths which are resonant with exciton, upper, and lower polariton, the dynamics of polariton states is found to be determined by that of the exciton, which has long-time character. Moreover, comparing to the neat film without cavity, the kinetics of the molecular triplet state is not significantly modified by strong singlet molecular exciton-photon coupling within the cavity. Under two-photon pump, short-time (sub-picosecond) dynamics is observed from both the polariton cavity system and solid-state neat film, indicating this results from the ultrafast optical response of the nonlinear organic molecules.