Achieving High‐Temperature Resistant Afterglow by Modulating Dual‐Mode Emission of Organic Emitters through Defects Engineering

Dual-mode afterglow, integrating ultralong phosphorescence and delayed fluorescence, offers promising opportunities for developing high-temperature resistant luminescent materials. However, there is an obvious gap between the emission lifetime of delayed fluorescence and phosphorescence. In this work, a dehydration-induced doping strategy is proposed to achieve high-temperature resistant afterglow by balancing phosphorescence and delayed fluorescence lifetime. The critical role of structural defects is demonstrated in the afterglow mechanism, where energy transferred between the defect states and guest molecules determines the lifetime of afterglow. In addition, efficient reverse intersystem crossing processes are achieved between the defect states and singlet states, facilitating the long-lived fluorescence. These synergistic effects result in the prolonged lifetime of delayed fluorescence to approach that of phosphorescence, which produced high-temperature resistant afterglow materials, even up to 125 °C. These results provide a clue for modulating the emission dynamics of afterglow materials for applications in information security, biomedical diagnosis, and chemical sensing.