Tuning the circularly polarized luminescence of polymer-stabilized cholesteric liquid crystal films using chiral dopants

Abstract

In this work, a tetraphenylethene and imidazo[1,2-a]pyridine-attached difluoroboron β-diketonate triad TPE-BF₂acac-MeIP has been synthesized. TPE-BF₂acac-MeIP exhibits significant aggregation-induced emission and mechanofluochromism properties and can be utilized for latent fingerprint visualization. Due to its strong emission and high quantum efficiency, dye TPE-BF₂acac-MeIP is embedded into polymer-stabilized cholesteric liquid crystals (PSCLCs). Circularly polarized luminescence (CPL) with large dissymmetry factors (|g_lum| up to 0.61) and high emission quantum yields (Φ_F up to 64.2%) were obtained. Circular dichroism results indicated that the dye preferred to form conformations in one handedness (M- or P-) under chiral surroundings. CPL performance was dominated by the matching extent of emission of the dye with chiral conformations/stackings and selective Bragg reflection of the PSCLC film. In addition, via changing the dye concentration and film thickness, it was found that the inner filter effect also played a role in the |g_lum| value. This work not only gives us a better understanding of the origin of the CPL behaviour, but also lays foundations for the applications of CPL materials in three-dimensional optical displays, photoelectric devices, and information storage and processing.