Circularly Polarized Luminescent Liquid Crystal Copolymers Constructed by Triplet–Singlet Förster‐Resonance Energy Transfer: Achieving Large Glum Values, Long Lifetime, and High Photoluminescence Quantum Yield

Abstract

AbstractCircularly polarized luminesce (CPL) materials are crucial for various applications, including display devices and bionics. However, existing CPL materials face difficulties in simultaneously meeting large luminescence asymmetry factors (glum), high photoluminescence quantum yields (PQY), and long lifetime. Here, a simple strategy to prepare a series of high‐performance CPL liquid crystal copolymers is constructed by triplet–singlet Förster‐resonance energy transfer (TS‐FRET). A series of chiral liquid crystal copolymers are successfully synthesized by copolymerizing phosphorescent donor bearing chiral cholesterol mesogen with fluorescence acceptor bearing naphthalimide chromophore. The introduction of the naphthalimide component promotes the formation of twist grain boundary smectic‐A phase (TGBA*) and behaves distinctive selective reflective effect. An effective TS‐FRET process occurs in the two components of copolymers, and dual emission characteristics of thermally activated delayed fluorescence and room‐temperature phosphorescence are observed in the copolymer films. When the naphthalimide content of copolymer is 10%, the luminescence lifetime can achieve 83.0 ms. As the naphthalimide content increases, the glum initially increases and subsequently decreases, reaching a maximum of −1.15. In addition, the copolymer films possess enhanced photoluminescence quantum yield by TS‐FRET with a maximum value of 68%. The application of copolymers in information security is also explored.