Persistent luminescence from triplet excitons in organic molecules is rare, as fast non‐radiative deactivation typically dominates over radiative transitions. This work demonstrates that the substitution of a hydrogen atom in a derivative of phenanthroimidazole with an N‐phenyl ring can substantially stabilize the excited state. This stabilization converts an organic material without phosphorescence emission into a molecular system exhibiting efficient and ultralong afterglow phosphorescence at room temperature. Results from systematic photophysical investigations, kinetic modeling, excited‐state dynamic modeling, and single‐crystal structure analysis identify that the long‐lived triplets originate from a reduction of intrinsic non‐radiative molecular relaxations. Further modification of the N‐phenyl ring with halogen atoms affects the afterglow lifetime and quantum yield. As a proof‐of‐concept, an anticounterfeiting device is demonstrated with a time‐dependent Morse code feature for data encryption based on these emitters. A fundamental design principle is outlined to achieve long‐lived and emissive triplet states by suppressing intrinsic non‐radiative relaxations in the form of molecular vibrations or rotations.

Herein, a new “Y-series” non-fullerene acceptor, Y21, bearing an asymmetric electron-deficient-core (DA′D) and fluorinated dicyanomethylene derivatives as flanking groups, was designed and synthesized for organic solar cell applications. Rather than being a perfect C₂ symmetric traditional “Y-series” acceptor, Y21 possesses an electron-withdrawing unit (A′) shifted from the center of DA′D, turning into an asymmetric molecular geometry. Photovoltaic devices based on PM6:Y21 can realize a high J_sc of 24.9 mA cm⁻² and a PCE of 15.4%. Our work demonstrates a new way to tune the photoelectronic properties of the “Y-series” NFAs.

By increasing the fluorination sites of polymer donors, the J_SC, V_OC and FF are enhanced for solar cells, because of fine-tuned energy levels, reduced trap-assisted or bimolecular recombination, and improved charge carrier mobility.

Non-fullerene acceptors have been utilized to construct efficient organic solar cells (OSCs). In this work, two new acceptors, TPQx-4F and TPQx-6F, with quinoxaline (Qx)-fused rings, were designed and synthesized. The single-junction inverted OSC devices based on two NFAs, blended with PM6 as the polymer donor were systemically investigated. The introduction of fluorine atoms into the Qx-containing fused central framework not only downshifted the energy levels, but also greatly optimized the morphology of PM6:TPQx-6F blend films. The power conversion efficiency (PCE) of the PM6:TPQx-4F based devices improved from 6.78% to 7.72% through thermal annealing (TA) treatment. Meanwhile, the PM6:TPQx-6F based devices showed a PCE of 12.10%, in which a remarkable PCE of 14.30% was obtained after TA treatment. The different performances of the devices based on PM6:TPQx-4F and PM6:TPQx-6F were mainly attributed to the variation of the short-circuit current density (J_sc) and fill factor (FF). Further investigations indicated that the PM6:TPQx-6F blend films presented higher mobilities, and more efficient charge dissociation and uniform nanophase separation than those of the TPQx-4F-based devices, leading to higher J_sc and FF. In addition, enhanced J_sc and FF were simultaneously realized by simple TA treatment for the TPQx-4F- and TPQx-6F-based devices. This work provides more insight into the underlying reasons behind fine-tuning the energy levels and optimizing the active layer morphology in high-performance OSCs.

Cardiovascular diseases, including stroke driven by atherosclerosis, remain a leading global health concern. Current diagnostic imaging modalities such as magnetic resonance imaging fail to characterize oxidative stress within atherosclerotic plaques. Here, we introduce difuranfluoreno-dithiophen–based polymers designed for afterglow imaging, offering ultrabright luminescence, ultralow-power excitation (0.087 milliwatts per square centimeter), and ultrashort acquisition times (0.01 seconds). Through a molecular engineering strategy, we have optimized polymers for enhanced reactive oxygen species (ROS) generation capability, ROS capturing capability, and fluorescence quantum yield, resulting in an increase in afterglow intensity (~130-fold) compared to commonly used 2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene polymer (MEHPPV). Additionally, we have developed ratiometric afterglow nanoparticles doped with oxidative stress–responsive molecules, enabling imaging of oxidative stress markers in atherosclerotic plaque. This approach provides a tool for cardiovascular imaging and diagnostics, which is conducive to the auxiliary diagnosis and risk stratification of atherosclerosis.