Switching on/off phosphorescent or non-radiative channels by aggregation-induced quantum interference

Pure organic materials with persistent and efficient room-temperature phosphorescence have recently aroused great research interest due to their vast potential in applications. One crucial design principle for such materials is to suppress as much as possible the non-radiative decay of the triplet exciton while maintaining a moderate phosphorescent radiative rate. However, molecular engineering often exhibits similar regulation trends for the two processes. Here, we propose that the quantum interference caused by aggregation can be utilized to control the phosphorescent and non-radiative decay channels. We systematically analyze various constructive and destructive transition pathways in aggregates with different molecular packing types and establish clear relationships between the luminescence characters and the signs of the singlet and triplet excitonic couplings. It is shown that the decay channels can be flexibly switched on or off by regulating the packing type and excitonic couplings. Most importantly, an enhanced phosphorescent decay and a completely suppressed non-radiative decay can be simultaneously realized in the aggregate packed with inversion symmetry. This work lays the theoretical foundation for future experimental realization of quantum interference effects in phosphorescence.