Efficient transfer of metallophosphor excitons via confined polaritons in organic nanocrystals

Abstract

We investigate the transfer of phosphorescent energy between co-assembled metallophosphors in crystalline nanostructures [Angew. Chem. Int. Ed. 57 7820 (2018) and J. Am. Chem. Soc. 140 4269 (2018)]. Neither Dexter’s nor Förster’s mechanism of resonance energy transfer (RET) could account fully for the observed rates, which exceed 85% with significant temperature dependence. But there exists an alternative pathway on RET mediated by intermediate states of resonantly confined exciton–polaritons. Such a mechanism was used to analyze artificial photosynthesis in organic fluorescents [Phys. Rev. Lett. 122 257402 (2019)]. For metallophosphors, the confined modes act as extended states lying between the molecular S1 and T1 states, offering a bridge for the long-lived T1 excitons to migrate from donors to acceptors. Population dynamics with parameters taken entirely based on experiments fits the observed lifetimes of phosphorescence across a broad range of doping and temperature.