Organic afterglow materials, developed recently by breaking through the difficulties in modulating ultrafast-decayed excited states, exhibit ultralong-lived emission for persistent luminescence with lifetimes of several orders of magnitude longer than traditional fluorescent and phosphorescent emissions at room temperature. Their exceptional properties, namely ultralong luminescent lifetime, large Stokes shifts, facile excited state transformation, and environmentally sensitive emission, have led to a diverse range of advanced optoelectronic applications. Here, the organic afterglow is reviewed from the perspective of fundamental concepts on both phenomenon and mechanism, examining the technical challenges in relation to excited state tuning and lifetime elongation. In particular, the advances in material design strategies that afford a large variety of organic afterglow materials for a broad utility in optoelectronics including lighting and displays, anti-counterfeiting, optical recording, chemical sensors and bio-imaging are highlighted.

Blue/deep-blue emission is crucial for organic optoelectronics but remains a formidable challenge in organic afterglow due to the difficulties in populating and stabilizing the high-energy triplet excited states. Here, a facile strategy to realize the efficient deep-blue organic afterglow is proposed via host molecules to sensitize the triplet exciton population of guest and water implement to suppress the non-radiative decays by matrices rigidification. A series of highly luminescent deep-blue (405–428 nm) organic afterglow materials with lifetimes up to 1.67 s and quantum yields of 46.1% are developed. With these high-performance water-responsive materials, lifetime-encrypted rewritable paper has been constructed for water-jet printing of high-resolution anti-counterfeiting patterns that can retain for a long time (>1 month) and be erased by dimethyl sulfoxide vapor in 15 min with high reversibility for many write/erase cycles. These results provide a foundation for the design of high-efficient blue/deep-blue organic afterglow and stimuli-responsive materials with remarkable applications.

Organic ultralong room temperature phosphorescence (OURTP) materials with photophysical properties sensitive to external stimulus are highly attractive for advanced applications.H owever,m ost OURTPm olecules are in crystal and OURTP materials with good practicability and stimulusresponsive character are hard to be achieved. Here,wereport, for the first time,the highly efficient, ultralong-lived and deepblue OURTPmaterials by simply doping boron phosphor into cyanuric acid host. Host-guest OURTP composites with abundant and tunable H-bond network are highly stable in air with ultralong lifetime of 5.08 satroom temperature.They are sensitive to water,which can strength the H-bond network to significantly enhance OURTP quantum yield from 16.1 %to 37.6 %. Anti-counterfeiting paper was easily prepared for water-jet printing;t he jet-printed high-resolution OURTP patterns can be easily erased by solvent fuming for another printing/erasing cycle with high reversibility.

Direct population of triplet states via singlet-to-triplet absorption red-shifts the excitation wavelength and improves the organic afterglow efficiency under ambient conditions.

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Among five methods in predicting intersystem crossing of TADF molecules, NTO similarity and n-orbital analyses based on the T1 structure were found to be efficient with low computational costs and high accuracy.

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