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 nearultraviolet 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.

The image quality of the transparent AMOLED, which is the most potential candidate of next generation technology, is highly dependent on the surroundings. In this work, the concept of highimage-quality transparent display based on AMOLED with a desirable liquid crystal shutter back-panel is demonstrated.

An electrically activated bistable light shutter that exploits polymer-stabilized cholesteric liquid crystal film was developed. Under double-sided three-terminal electrode driving, the device can be bistable and switched between focal conic and homeotropic textures with a uniform in-plane and vertical electrical field. The transparent state with a transmittance of 80% and the opaque/scattering state with a transmittance of 13% can be realized without any optical compensation film, and each can be simply switched to the other by applying a pulse voltage. Also, gray-scale selection can be performed by varying the applied voltage. The designed energy-saving bistable light shutter can be utilized to preserve privacy and control illumination and the flow of energy.

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Dimming and scattering control are two of the major features of smart windows, which provide adjustable sunlight intensity and protect the privacy of people in a building. A hybrid photo- and electrical-controllable smart window that exploits salt and photochromic dichroic dye-doped cholesteric liquid crystal was developed. The photochromic dichroic dye causes a change in transmittance from high to low upon exposure to sunlight. When the light source is removed, the smart window returns from colored to colorless. The salt-doped cholesteric liquid crystal can be bi-stably switched from transparent into the scattering state by a low-frequency voltage pulse and switched back to its transparent state by a high-frequency voltage pulse. In its operating mode, an LC smart window can be passively dimmed by sunlight and the haze can be actively controlled by applying an electrical field to it; it therefore exhibits four optical states—transparent, scattering, dark clear, and dark opaque. Each state is stable in the absence of an applied voltage. This smart window can automatically dim when the sunlight gets stronger, and according to user needs, actively adjust the haze to achieve privacy protection.