Design of chiral guest-host liquid crystals for a transmittance-tunable smart window

Abstract

Dichroic absorption dye-doped liquid crystal switching is preferred for transmittance control with maintaining visual clarity. In this paper, we present a parametric analysis of chiral guest-host liquid crystal (C-GHLC) switching for an enhanced transmittance-tunable smart window. Further analysis of the chiral twist power resulted in the proposal of a new modified transmittance governing formula for C-GHLC. The optimal C-GHLC cell design was determined through a comprehensive examination of the electro-optic transmittance change between transparent and opaque states by optimizing the chiral twist power in terms of ‘d/p’. Along with the theoretical parametric design of the C-GHLC cell, an optimal condition for the C-GHLC cell which can use commercial display driving environments was experimentally demonstrated for the first time. Consequently, an improved transmittance control (ΔT ≈ 40.5%) with a low voltage (V on ≈ 18 V) and with a sufficiently fast response time (τ ≈ 12 ms) suitable for 60 Hz (< 16.7 ms) was confirmed.