Hierarchical Dual‐Mode Efficient Tunable Afterglow via J‐Aggregates in Single‐Phosphor‐Doped Polymer

The development of polymer‐based persistent luminescence materials with color‐tunable organic afterglow and multiple responses is highly desirable for the applications in anti‐counterfeiting, flexible displays and data‐storage. However, achieving efficient persistent luminescence from a single‐phosphor system with multiple responses remains a challenging task. Herein, a hierarchical dual‐mode emission system is developed by doping 9H‐pyrido[3,4‐b]indole (PI2) into an amorphous polyacrylamide matrix, which exhibits color‐tunable afterglow due to excitation‐, temperature‐ and humidity‐dependence. Notably, the coexistence of isolated state and J‐aggregate state of the guest molecule not only provides excitation‐dependent afterglow color, but also leads to hierarchical temperature‐dependent afterglow color resulting from different thermally activated delayed fluorescence (TADF) and ultralong organic phosphorescence (UOP) behaviors of the isolated and aggregated states. The complex responsiveness based on the hierarchical dual‐mode emission can serve for security features through inkjet printing and ink‐writing. These findings may provide further insight into the regulated persistent luminescence by isolated and aggregated phosphors in doped polymer systems and expand the scope of stimuli‐responsive organic afterglow materials for broader applications.