Ultrabright and narrowband organic afterglow achieved by molecular engineering of coronene

Achieving simultaneously ultrabright and narrowband organic afterglow emission remains a formidable challenge because enhancing one property often compromises the other. Herein, we report a low-frequency vibronic coupling strategy to design intrinsic narrowband organic afterglow materials that combine high brightness with long lifetimes. Through molecular engineering of coronene, introduction of aroyl and ethoxy substituents breaks molecular symmetry, enhances intersystem crossing, and preserves a localized triplet state with a small radiative rate constant. The optimized coronene derivative doped into dimethyl isophthalate (DMI) exhibits a phosphorescence efficiency of 17.5%, a lifetime of 3.19 s, and a narrow full width at half maximum (FWHM) of 24.2 nm under ambient conditions. Deuteration further increases the lifetime to 5.11 s and phosphorescence efficiency to 20.2%, achieving one of the brightest (73 cd m^-2 at ∼0.2 s) and narrowband organic afterglow emissions to date. Theoretical simulations attribute the narrowband emission to dominant low-frequency vibronic coupling in the coronene derivative system, offering mechanistic insights into spectral narrowing. This work establishes a new paradigm for molecular design of ultrabright narrowband afterglow materials, paving the way for their applications in illumination, anticounterfeiting, and information encryption.