Boosting Phosphorescence Efficiency of Microstructures by Forming a Triplet Exciplex System

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. One organic microstructure with high-efficiency (63.1%) room-temperature phosphorescence is achieved through forming a triplet exciplex in a host-guest doping system. Along with the increase in temperature, the emission intensity of the doped microstructures decreases at the phosphorescent peak of the donor first and then increases at a red-shift exciplex emission, confirming the formation of triplet exciplex between donor and acceptor.image