[Paper] High Concentration Photochromic Dye-doped Liquid Crystals for Fast Switching Tunable Coloration

Abstract

Photochromic dye-doped liquid crystal devices change their properties in response to both optical and electrical stimuli, thereby enabling intelligent smart windows that can adapt to the environment. However, most devices investigated to date suffer from small absorbance that originates from the low solubility of dyes and thus requires a large cell-gap that hinders the electro-optic response. Here, we report the electro-optic properties of high concentration photochromic dye-doped nematic liquid crystals containing up to 30 wt% of diarylethene dye and their electro-optic and photochemical properties. In this system, a cell gap as thin as 2 μm was sufficient to achieve an absorbance exceeding 1, which facilitates a faster electro-optic response. We also observed a change in the response time in the activated and deactivated states, suggesting a change in the intrinsic material parameters by photoisomerization.