Electrically Tunable Reflection Color of Chiral Ferroelectric Nematic Liquid Crystals

The recently discovered ferroelectric nematic (N-F) liquid crystals (LCs) with over 0.04 C m(-2) ferroelectric polarization and 10(4) relative dielectric constants, coupled with sub-millisecond switching, offer potential applications in high-power super capacitors and low voltage driven fast electro-optical devices. This paper presents electrical, optical, and electro-optical studies of a ferroelectric nematic LC material doped with commercially available chiral dopants. While the N-F phase of the undoped LC is only monotropic, the chiral N-F phase is enantiotropic, indicating a chirality induced stabilization of the polar nematic order. Compared to undoped N-F material, a remarkable improvement of the electro-optical switching time is demonstrated in the chiral doped materials. The color of the chiral mixtures that exhibit a selective reflection of visible light in the chiral N-F phase, can be reversibly tuned by 0.02-0.1 V mu m(-1) in-plane electric fields, which are much smaller than typically required in full-color cholesteric LC displays and do not require complicated driving scheme. The fast switchable reflection color at low fields has potential applications for LC displays without backlight, smart windows, shutters, and e-papers.