A red thermally activated delayed fluorescence material as a triplet sensitizer for triplet–triplet annihilation up-conversion with high efficiency and low energy loss

Taking advantage of the active and low-lying triplet state, a red thermally activated delayed fluorecence (TADF) molecule has been employed as a sensitizer to realize green-to-blue up-conversion (UC) emission with a large anti-Stokes shift of 97 nm and high ΦUC′ of 1.9%. Noteworthily, the UC emission is obviously observed even in air, which provided an opportunity for biological imaging and energy applications of triplet–triplet annihilation up-conversion (TTA-UC) materials in oxygenic environments.