Circularly Polarized Ultralong Room-Temperature Phosphorescence Bilayer Film with High Dissymmetry Factor and...

Although circularly polarized room-temperature phosphorescence (CP-RTP) materials have attracted great attention for applications in optical areas, simultaneously meeting the ultralong lifetime and large dissymmetry factor (g_lum) is challenging. This work first synthesizes RTP film by doping the self-designed phosphorescent chromophores into the poly(vinyl alcohol) (PVA), then realizes tunable luminescent colors under the guidance of the resonance energy transfer strategy. Next, the phosphorescent system is imported into the cellulose nanocrystal (CNC) film to produce the CP-RTP. However, incorporating the PVA into the CNC matrix inevitably weakens the chiral arrangement of CNC film and reduces the circularly polarized luminescence (CPL). Therefore, this work designs a unique bilayer film structure by combining the RTP film with the CNC film to optimize the CPL. This bilayer film presents direction-dependent chiral luminescent performance. The g_lum values of the bilayer film vary from -0.8563 to 0.1752 when the UV light illuminates in two directions. The construction of a bilayer film can not only realize the superior chiral optical intensity, but also resolve the issue of the single luminescent direction derived from the intrinsic chirality of the CNC film. Finally, the bilayer film with multimodal and convertible optics is applied in the construction of anti-counterfeiting materials.