Versatile Energy-Saving Smart Glass Based on Tristable Cholesteric Liquid Crystals

Smart glass offers dynamic control over the transmission of light to address various needs in energy conservation, privacy, and information display; yet, most of the existing technologies still require continuous power for operation and are limited to single functions (usually either tint or haze control). In this work, we have developed a versatile tristable smart glass based on cholesteric liquid crystal (CLC). The smart glass is voltage-switchable among three field-free stable states of different optical transmission properties, and each corresponds to one of the following cholesteric textures: planar, focal conic, and lying helix. With a six-terminal electrode configuration, such tristable switching can be achieved in CLCs with Bragg reflections from near-ultraviolet to visible and near-infrared. By incorporating a dichroic dye into the CLC, we demonstrate a smart daylighting-privacy window based on the tristable optical switch, and both the tint and haze levels of the window are electrically switchable. We also make use of the Bragg reflection of planar-state CLC and explore the applicability of the tristable optical switch to full-color see-through displays. With the demonstrated versatility in design and outstanding field-off stability, it is anticipated that the CLC smart glass can find widespread use, from intelligent control of lighting, building climate, and privacy to semistatic window displays for advertisement use and artistic design.