Boosting Phosphorescence Efficiency of Microstructures by Forming a Triplet Exciplex System

Abstract Low‐dimensional crystal structures with long lifetime phosphorescence hold great potential in biological imaging, sensors, and micro/nanophotonics. However, the high‐efficient phosphorescence is still scarce on the micro/nanoscale due to the strong nonradiative transitions and quenching of long‐lifetime triplet state caused by the large specific surface area. Herein, a one doped microstructure with high quantum yield phosphorescence is reported by doping an electron‐acceptor (guest) into an electron‐donor (host). The formation of a triplet exciplex between the donor and acceptor enables the doped microcrystals to display highly efficient long‐lived emission with 63.1% quantum yield, while the phosphorescence emissions of microstructures from a neat donor and acceptor are negligible. The emission mechanism in relation to the exciplex is elaborated from temperature‐dependent luminescence behavior and theoretical calculation. This work provides an effective strategy for achieving efficient long‐lived emissions at the micro‐scale, which will accelerate the research and development of advanced miniaturized functional devices.