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 because of forbidden transitions between singlet and triplet states. Here, we report novel organicinorganic 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 a long lifetime in the 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 a facile design of the system using organic cations with different triplet exciton energies. These results are expected to greatly expand the prospects of hybrid perovskites with functional organic cations for versatile display applications.