Energy saving, transparency changing thermochromism in dye-doped cholesteric liquid crystals for smart windows

[Display omitted] •Short pitch CLC films have been studied for use in smart windows.•With voltage, the CLC films switched between P, FC, and H states.•%T of the dye-doped CLC lowered in the FC state and increased in H & P states than pure.•The device showed good stability even after repeated cycles.•It is useful for privacy windows, smart windows all seasons, & QR code authentication. An electrically switchable smart window is made from a dye-doped Cholesteric liquid crystal (CLC). In this work, the impact of coumarin dye (0.3 and 1 wt%) on the structural and electro-optical properties of CLCs that reflect IR and blue light (Blue) was explored. The results suggest that high transmittance in Visible and NIR useful to preserve interior transmittance as well as heat suited for all seasons. Temperature-dependent microscopic studies confirmed the homogenous solubility of the dye in CLCs. The fabricated smart window was observed to show three switchable modes, comprising planar (P), focal-conic (FC), and homeotropic (H) states, depending on the applied voltages (1 kHz). The structural observations from microscopic studies and the transmission spectra of pure and dye-doped composites with and without the application of voltage are consistent. The visual transmittance of dye doped CLC increased from 84% in the planar state (OFF state) to 18% in the focal conic state (3 V/µm) and 92% in the homeotropic state (5 V/µm) with a short response time (