Low-voltage polymer-stabilised liquid crystal windows with highly polar molecules for privacy and thermal comfort

Smart windows that switch between transparent and opaque states are crucial for privacy and thermal comfort in buildings. Conventional polymer stabilised liquid crystal (PSLC) windows often require high operating voltages and lack efficient infrared (IR) control. Here, we investigate the effect of a ferroelectric nematic mesogen and chiral dopants on the switching voltage between transparent and opaque states of a PSLC using a high dielectric anisotropy nematic host. We find that the addition of 15wt% of ferroelectric mesogen lowers the switching voltage from ∼4V to 2V. We also show that the PSLC with 0.5wt% high helical twisting power chiral dopant requires 4 V to switch between 10% and 90% light blocking efficiencies, representing great potential for low voltage, high contrast privacy window applications. Finally, by increasing the concentration of the chiral dopant to ≈1.6% and stacking films with equal amount of left- and right-handed chiral dopants, we achieve films that were reflecting ∼90% of unpolarised light in the 720–820 nm range. We demonstrate that these materials may be used for smart windows that provide thermal comfort in buildings, enabling sunny rooms to stay cool without compromising natural light.