Efficient transfer of metallophosphor excitons via confined polaritons in organic nanocrystals

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.