Harvesting Triplet Excitons in Lead-Halide Perovskites for Room-Temperature Phosphorescence

Room-temperature phosphorescence (RTP) has a much longer lifetime than fluorescence as it involves triplet excitons. This extended lifetime enables the design of advanced optoelectronics and biological sensing technologies. Despite the omnipresence of triplet states, harnessing these triplet excitons remains challenging for most organic materials due to the forbidden transitions between singlet and tri-plet states. Here we report novel organic-inorganic hybrid perovskites based on conjugated organic cations with low-lying triplet energy levels to extract triplet excitons from the inorganic component, thereby generating RTP with long lifetime in millisecond range. Dexter type energy transfer was confirmed to occur in this type of hybrid perovskites with transfer efficiency of up to 80%. More impressively, multiple-colored phosphorescence was achieved by facile design of the system using organic cations with different triplet exciton energies. These results are expected to greatly expand the prospects of hy...