A Facile Strategy for Achieving Polymeric Afterglow Materials with Wide Color-Tunability and Persistent Near-infrared Luminescence

Polymeric afterglow materials with wide color-tunability, efficient near-infrared (NIR) luminescence, and good water solubility are highly desired in various applications but are rarely reported. Herein, a facile but efficient approach is presented to achieve tunable multicolor afterglow and persistent NIR luminescence based on the direct phosphorescence resonance energy transfer (PRET) or sequential resonance energy transfer from the energy donor with ultralong room-temperature phosphorescence to the energy acceptors with red to NIR fluorescence. By simply regulating the doping compositions and concentrations of energy donor/acceptor pairs doped into the poly(vinyl alcohol) (PVA) matrix, the resulting PVA films exhibit persistent multicolor afterglow covering from visible to NIR regions. Notably, compared to the single-step PRET, the two-step sequential resonance energy transfer has the unique advantages of higher transfer efficiency of triplet excitons from the initial donor, a wider range of color-tunability mediated by the intermediary acceptor, and enhanced delayed fluorescence efficiency of the final acceptor. By preparing water-soluble PVA films with different doping compositions and concentrations, we demonstrate their great potential applications in advanced anti-counterfeiting and information encryption. This work provides a facile strategy for the exploration of polymeric afterglow materials with excellent color-tunability and efficient NIR delayed fluorescence, which can further help to expand the practical applications of organic afterglow materials.