Cell thickness dependence of electrically tunable infrared reflectors based on polymer stabilized cholesteric liquid crystals

Abstract

We reported here the fabrication of the electrically tunable infrared (IR) reflectors based on the polymer stabilized cholesteric liquid crystal (PSCLC) with negative dielectric anisotropy. A systematic study of the influence of cell gap on the electrically tunable reflection bandwidth was performed. When a direct current (DC) electric field was applied, the reflection bandwidth red shifted in the cells with small cell gap, whereas the bandwidth broadening was observed in the cells with large cell gap. It is therefore reasonable to deduct that the reflection is dictated by the pitch gradient steepness which strongly relies on the cell thickness. The results reveal that for making PSCLC based IR reflector windows with electrically induced bandwidth broadening, a minimal cell gap thickness is required. The resulted IR reflectors possess a short native switching time and long-term operation stability, and are potentially applicable as smart energy saving windows in buildings and automobiles.