A photoswitchable circularly polarized luminescent cholesteric superstructure: direct visualization and dynamic modulation of the amplified luminescence dissymmetry factor

Abstract

The development of circularly polarized luminescence (CPL) materials with high luminescence dissymmetry factor (g_em) and stimuli-responsive characteristics is of great importance for various applications. Herein, a photoswitchable CPL-active cholesteric liquid crystal (CLC) device is developed using a new α-cyanodiarylethene-based chiral fluorescent photoswitch and another chiral dopant with the same handedness, in which amplifying and reversibly photoswitching g_em of the CPL signal can be realized by adjusting the relative position of selective reflection and fluorescence emission. More specifically, the g_em value of the CPL signal can reach an extremely large value of 1.25 when the reflection band and fluorescence emission band fully overlap. Meanwhile, the g_em value of the CPL signal is dynamically switched between 1.25 and 0.11 upon 520 nm and 405 nm light irradiation. On the basis of these results, high-contrast circularly polarized fluorescent patterns in the CLC cell can be directly visualized when observed by a circular polarizer, in which the recorded patterns can be erased and rewritten reversibly upon light irradiation. The ultrahigh g_em and dynamic phototuning behaviors in luminescent CLC present a significant improvement and provide a new strategy for the fabrication and application of CLC-based CPL materials.