Smart Switchable Window with Bistability and Tunability of Transmission

Abstract

Windows are used everywhere, from buildings to vehicles. Smart switchable windows are highly sought‐after in order to reduce energy consumption. An ideal smart window should have two functions. First, it should be able to control privacy. Second, it should be able to control radiant energy flow. Here, a smart window is reported that possesses the two functions. The smart window is based on a dichroic dye‐doped cholesteric liquid crystal. It exhibits two stable states in the absence of applied voltage. One of them is the planar state that is optically absorbing without haze and can control radiant energy flow. The other state is the focal conic state that is optically scattering and can control privacy. Furthermore, when voltage is applied, the liquid crystal is switched to a heliconical state, where the transmittance can be tuned continuously. Thanks to its superior performance, this smart window has a big potential for applications in architectural and vehicle windows.

Sunlight-Driven Smart Windows with a Wide Temperature Range of Optical Switching Based on Chiral Nematic Liquid Crystals

“…Defects and domain boundaries in LC systems lead to the scattering of incident light. For example, polymer/LC composites, such as polymer-dispersed LCs (PDLCs), have long been studied as transparent–scattering switching materials. − Chiral nematic (cholesteric) liquid crystals have also been applied to induce transparent–scattering switching. − In addition, absorption switching in LC systems can be achieved by doping dichroic dyes such as azobenzenes and anthraquinones. − Furthermore, selective reflection in chiral nematic LCs can also be applied to control transmission of light . With the aid of LC systems, functions and performance of smart windows could be customized to the diversity of specific needs, which depend on purposes and places.…”