Fast and Reversible Circularly Polarized Luminescence Switching in Planar Chirality‐Induced Chiral Nematic Liquid Crystals in a DC Electric Field

Chiral liquid crystal (LC) materials are indispensable functional components of advanced optoelectronic devices. In this study, we fabricated chiral nematic liquid crystal (N*‐LC) devices by introducing perylene and its N,N ‐di‐ n ‐octyl‐3,4,9,10‐perylenetetracarboxylic diimide (OPDI) derivative, as achiral luminophores, into an N*‐LC host composed of the achiral 4'‐pentyl‐4‐cyanobiphenyl (5CB) LC and the planar‐chiral 4,12‐dihydroxy[2.2]paracyclophane ([2.2]‐PCP) dopant. Remarkably, both perylene and OPDI exhibited pronounced circularly polarized luminescence (CPL) within the planar‐chiral‐dopant‐induced N*‐LC environment, despite the use of achiral luminophores. Furthermore, the handedness of the CPL can be controlled by the planar chirality of the [2.2]‐PCP dopant. In addition, the resulting N*‐LC materials exhibited rapid and reversible inversion of CPL handedness when a direct‐current (DC) electric field was applied and then removed. This reversible behavior is ascribable to the electric‐field‐induced phase transition between the helical N*‐LC structure of 5CB and another ordered phase. These findings provide a new material design principle in which a planar‐chiral dopant induces the N*‐LC phase in 5CB, thereby enabling high‐speed, reversible CPL modulation based on the application of an electric field.