Photoexcitation‐Induced Chiral Self‐Assembly for Phosphorescence‐to‐Thermally Activated Delayed Fluorescence Transformation

Abstract Phosphorescence and thermally activated delayed fluorescence are currently two important photophysical pathways that have greatly promoted the development of display, sensing, and bioimaging. However, achieving in situ conversion of these two photophysical pathways within the same molecule is extremely challenging. In this study, we covalently bond chiral donor–acceptor–donor' structures into a photoexcitation‐induced aggregated molecule, specifically hexathiobenzene, to achieve this goal through light irradiation. Initially, the target molecules predominantly exhibit phosphorescent properties. Upon photoirradiation, chiral self‐assembly occurs within the target molecules, which gives rise to a thermally activated delayed fluorescence (TADF)‐dominant emission behavior. This TADF emission relies on a self‐assembly structure that can effectively prevent oxygen from quenching triplet excitons, resulting in stronger signal intensity and longer photoluminescence lifetime. Consequently, a real time improvement of time‐resolved bioimaging can be achieved with the utilization of our strategy, rendering selectively dynamic control of imaging parameters at the desired time‐ and spatial resolution.