Chiral Afterglow Materials for Imaging: High Dissymmetry Factor and Long Visualization Time via Cholesteric Liquid Crystal Polymers and Inorganic Phosphors
Circularly polarized afterglow (CPA) materials provide an advanced optical signature to light emission, offering great potential for advanced photonic technologies. However, practical implementation remains challenging due to the lack of satisfactory performance, that is, high luminescence dissymmetry factor (g_CPA), long visualization time, and good processability. Here, we develop processable, full-color CPA materials composed of cholesteric liquid crystal polymers (CLCPs) and inorganic phosphors embedded in polymers, achieving a high g_CPA value of up to 0.74 and a long visualization time of 7 min. The materials are constructed with a bilayer structure comprising CLCPs and inorganic luminophors such as Y2O2S:Eu,Mg,Ti, SrAl2O4:Eu,Dy, and Sr2MgSi2O7:Eu. The CLCPs are synthesized from polymerizable liquid crystal monomer RM257, chiral dopants R/S5011, dipropylamine, photoinitiator Irgacure 651, cross-linker PETMP, and chain extender. The resulting materials exhibit excellent circularly polarized optics, enabling the implementation of circular polarization differential imaging (CPDI), where images are generated by subtracting two images captured through left- and right-handed circularly polarized filters. This work demonstrates the unique application of CPA in imaging, opening a new pathway for the use of purely inorganic solid-state luminophors in chiral functional materials.