Electric field, temperature and light-triggered triple dynamic circularly polarized luminescence switching in fluorescent cholesteric liquid crystals with a large dissymmetry factor

Abstract

Circularly polarized luminescent (CPL) materials with large luminescence dissymmetry factors (g_lum) are highly desirable for practical applications. In addition, stimuli-responsive CPL materials are quite attractive from both theoretical and application perspectives. Herein, a series of luminescent cholesteric liquid crystals were fabricated by doping a photoresponsive chiral fluorescent guest into a nematic liquid crystal host. The aim of this study is to amplify the chirality of the guest molecules by a helical assembly of cholesteric liquid crystals and realize the dynamic switching of CPL properties through the sensitivity of cholesteric liquid crystals to temperature, electricity and light. The results show that the obtained fluorescent cholesteric liquid crystals featuring a helical assembly structure present gratifying g_lum values and the maximum value is up to −0.39. Under the stimulation of external electric field or temperature, the assembly structure of the cholesteric liquid crystals can reversibly switch between helical and non-helical states, giving rise to the “on” and “off” conversion of CPL signals. In addition, the CPL intensity can also be regulated by UV light irradiation based on the photoinduced trans–cis isomerization of the chiral fluorescent guest. As a consequence, a triple stimuli-responsive CPL switching device derived from the luminescent cholesteric liquid crystals with a large g_lum and a high fluorescence quantum yield (up to 20.6%) was successfully constructed.