Organic Thermally Activated Delayed Fluorescence Materials for Time‐Resolved Luminescence Imaging and Sensing

As one of the most attractive purely organic luminescent materials, thermally activated delayed fluorescence (TADF) luminophores have drawn wide attention in the last decade. The long-lived delayed fluorescence resulting from the reverse intersystem crossing from excited triplet state (T1) to excited singlet state (S1) in the TADF luminophores gives rise to long lifetimes ranging from nanoseconds to milliseconds, which offers a new strategy for time-resolved luminescence imaging (TRLI) and sensing. However, the sensitivity of the T1 state in TADF luminophores to triplet oxygen remains a significant challenge for their application. This progress report summarizes the recent developments of efficient purely organic TADF luminophores and novel aggregation-induced delayed fluorescence (AIDF) luminophores for TRLI and sensing in vitro and in vivo. The molecular design strategies, photophysical properties of the luminophores, and their application in specific imaging and sensing within the time domain are presented. Newly emerged organic materials with AIDF behavior open a new door for developing long-lived emitters for high signal-to-noise ratio (SNR) imaging and sensing in the oxygenic atmosphere.