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

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 alpha-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.

Automated summary

A photoswitchable CPL-active cholesteric liquid crystal (CLC) device has been developed, which can amplify and reversibly photoswitch the CPL signal by adjusting the relative position of selective reflection and fluorescence emission. The device exhibits high-contrast circularly polarized fluorescent patterns that can be erased and rewritten upon light irradiation.