Alignment-Controlled Circularly Polarized Thermally Activated Delayed Fluorescence in Chiral Nematic Liquid Crystals

Abstract

Despite significant advances, simultaneously achieving a high emission dissymmetry factor (glum) and high luminescence efficiency remains a major challenge in the field of circularly polarized luminescent (CPL) materials. Here, we report a dual strategy that combines liquid crystal doping with naphthalimide-based thermally activated delayed fluorescence (TADF) emitters and controlled surface alignment to amplify CPL in chiral nematic liquid crystal (N*LC) systems. Two emitters were investigated: 1, bearing a conventional octyl chain, and 2, functionalized with cyanobiphenyl mesogenic units to enhance compatibility with the nematic host. Both compounds show TADF behavior within the LC matrix. Controlled homogeneous and homeotropic alignment of the N* phase enabled the systematic investigation of boundary-induced effects on CPL performance. Homogeneous alignment proved particularly effective, delivering high glum values of up to 0.14 even at low dopant loading (0.5 wt%), maintaining stable chiroptical responses over 30 days. These findings highlight macroscopic LC alignment as a critical, yet underexplored, parameter governing CPL performance and establish practical design principles for next-generation CP-TADF/LC materials targeting photonic and display device applications.