Host‐Programmed Operating Windows for Guest‐Encoded Dynamic Afterglow in PAH Composites

Dynamic organic afterglow materials can produce temporally tunable optical signals. However, their spectral dynamics, thermal stability, and processability are strongly coupled to specific emitter‐host structures, hindering the transfer of dynamic afterglow performance across diverse material forms and working conditions. This work reports a synthesis‐free, host‐tunable composite strategy using commercial single‐component polycyclic aromatic hydrocarbons (PAHs), where guest and host undertake separate core roles. The PAH guest determines emission spectra and time‐dependent color evolution via delayed‐emissive species with varied packing states and decay kinetics. Spectroscopic experiments and theoretical calculations verify that guest aggregation strengthens low‐energy delayed emission, and disparate decay rates of emissive species induce time‐resolved phosphorescence color change. The rigid host modulates confinement, emission duration, thermal tolerance, working‐temperature scope, and processability to realize guest‐encoded photoresponses. Validated across multiple matrix systems, this design preserves temporal spectral evolution and achieves phosphorescence up to 413 K. Via rational host selection, the same photophysical principle enables dynamic afterglow films, time‐temperature encoding and high‐temperature optical alarms. This framework delivers adaptable organic afterglow materials without heavy molecular modification.