Photophysics and photochemistry of functionalized anthradithiophene in microcavities

We present a study of photodegradation in functionalized anthraditiophene (diF TES-ADT)-based films in hybrid cavities composed of distributed Bragg reflector (DBR) bottom mirror and top silver (Ag) mirror, depending on two different DBR reflectivity stopbands. The concentration of diF TES-ADT was chosen such that the films contain molecules in "amorphous" and "aggregate" phases characterized by different optical absorption spectra. We demonstrate that the cavity photon preferentially couples to the molecules in the "amorphous" phase and observe different photodegradation, attributed to photodimerization, dynamics for cavity photon-coupled and uncoupled states. The presence of the longer lived emissive states, such as entangled triplet pair (TT) states formed in the process of singlet fission, was correlated with a faster photodimerization dynamics. The observed cavity-dependent photodimerization dynamics offers an opportunity to manipulate the reaction rates and yield with cavity characteristics.