Abstract
An electric field drives most dye-doped liquid crystal devices. Here, we demonstrate a new photo-responsive dye-doped self-organized cholesteric liquid crystal device. Upon UV or blue light exposure, the helical twisting power of the chiral azobenzene changes because of the trans-cis isomerization. As a result, the initially vertically aligned liquid crystal directors and dye molecules will change from transparent state to dark state. Such a polarizer-free photo-activated dimmer can be used for wide range of applications, such as diffractive photonic devices, portable information system, vehicular head-up displays, and as a smart window for energy-saving buildings.
Highlights
Guest-host liquid crystal (LC) devices [1,2,3,4], developed in late 1960s, have found renewed interest as dimmer for see-through displays [5], diffractive photonic devices [6], portable information system [7], and smart windows for energy-saving buildings [8]
A guest-host LC usually contains 2-3% absorptive dichroic dyes in a nematic host. These dichroic dye molecules follow the orientation of the LC directors
Unlike conventional voltage-driven guest-host displays, in this paper, we demonstrate a photo-sensitive dye-doped cholesteric liquid crystal (CLC) dimmer which is operated by low intensity light
Summary
Guest-host liquid crystal (LC) devices [1,2,3,4], developed in late 1960s, have found renewed interest as dimmer for see-through displays [5], diffractive photonic devices [6], portable information system [7], and smart windows for energy-saving buildings [8]. Unlike conventional voltage-driven guest-host displays, in this paper, we demonstrate a photo-sensitive dye-doped cholesteric liquid crystal (CLC) dimmer which is operated by low intensity light. Right- or left-handedness can be chosen based on the nature of chiral dopant and interaction with the LC host, while the helical twisting power can be controlled by electromagnetic fields, temperature, and chirality of the doping materials [14]. When a photosensitive chiral azobenzene compound is doped into a CLC host, it undergoes trans-cis photoisomerization upon UV-blue light exposure [15,16,17]. The LC directors and dye molecules are both aligned vertical to the glass substrates Under such condition, the absorption is minimum, i.e. the transmittance is maximum. One major advantage of our device is lower manufacturing cost in comparison with photochromic glass
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