Circularly Polarized Ultralong Room‐Temperature Phosphorescence and Multi‐Color Afterglow via the Stepwise Energy Transfer

Abstract Although circular polarized room‐temperature phosphorescence (CP‐RTP) materials have exhibited great prospects in optical multiplexing applications, realizing the ultralong lifetime, large circularly polarized luminescence (CPL) intensity, and multi‐color afterglow effect simultaneously is challenging. This work designs a kind of chiral phosphorescent material by doping the chromophores into the co‐assembly of the cellulose nanocrystals (CNCs) and poly(vinyl alcohol) (PVA). PVA provides the rigid surroundings and is inclined to form hydrogen bond networks with the chromophores, which favors the ultralong phosphorescent lifetime (1.713 s). The chiral space provided by the CNC nanofilm induces the lights with circularly polarized characteristics. By regulating the photonic bandgap structure, the film presents superior CPL and a large dissymmetry factor ( g lum : −0.2541). Besides, it presents the reversible humidity‐stimulus optical responses through the structural swelling and recovery. Next, this work applies a stepwise energy transfer rule to resolve the shortage of spectral overlap of the host matrix and dye guests by importing an intermediate to bridge the two components, thus realizing the multi‐color and tunable afterglow. This stepwise design enhances both lifetime and CPL effects of the terminal guests. Finally, this CP‐RTP nanofilm, with multimodal and convertible optics, shows practical applications in the anti‐counterfeiting areas.