Tunable Thermally Activated Delayed Fluorescence and Room-Temperature Phosphorescence Emissions, White and Red Long Afterglow Driven by Host–Guest Doping and Substituent Electronic Effects

Long afterglow luminogens with thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) emissions have important value in achieving a dynamic afterglow and exploring the intrinsic mechanism of phosphorescence. Therefore, based on different electron substitution effects, we designed and successfully prepared six host and guest materials and constructed and studied their host-guest doping systems. The doping systems present doping concentration and host-dependent TADF and RTP. Noteworthy, the host-guest doping system with an electron donating substituent group shows the longest RTP lifetime (1270 ms) and afterglow durations (11 s). Subsequently, four ternary doping systems were constructed based on Förster resonance energy transfer (FRET), with long-lived red and white afterglows, lasting for 6 and 11 s, respectively. In poly(methyl methacrylate) (PMMA), three guests give obvious TADF and RTP emissions. The maximum TADF and RTP lifetimes can reach 514 and 843 ms, respectively, corresponding to fluorescence, TADF, and RTP quantum yields of 0.17, 0.10, and 0.22, respectively, as well as afterglow durations of over 10 s in turn. Based on crystal analysis and theoretical calculations, the internal mechanisms of TADF and RTP are revealed. This work not only achieves long-lived red, white, and dynamic afterglows, high-level anticounterfeiting, and digital information encryption but also offers important theoretical insights into TADF and RTP emission mechanisms. It holds significant implications for advancing the applications of long afterglow materials in fields such as visual temperature detection, illumination, and encryption.