Organic Host-Guest Doped Red Room-Temperature Ultralong Afterglow Materials Based on Benzo[a]Carbazole Derivatives

Room-temperature afterglow materials with emission wavelengths over 650 nm are rarely reported due to the fact that low-energy excitons are extremely susceptible to nonradiative transitions caused by the environment. This work designs green emissions with ultralong phosphorescence lifetimes and strong quantum efficiencies as the internal excitation light sources. Through the Förster-resonance energy transfer (FRET) mechanism, phosphorescence emission is transferred to the fluorescence emission of commercial fluorescent molecules, successfully achieving the maximum delayed emission wavelengths of 646 nm-702 nm for red afterglow. The organic two-component doped room-temperature phosphorescence material using diphenyl sulfoxide as host molecule and rigid benzo[a]carbazole derivative as guest molecule emits strong green phosphorescence with the afterglow time of 20 s and the phosphorescence quantum efficiency of 27%, which is proven to be an excellent internal phosphorescence excitation light. Three-component ultralong red afterglow materials are acquired with common red fluorescence dyes such as Eosin B, Erythritol B sodium salt, Rhodamine B, and Rhodamine 6G as energy receptors. The results indicate that red ultralong afterglow materials with long emission wavelengths and high luminescence efficiencies can be easily constructed based on the FRET mechanism through appropriate molecular design.