Energy-saving windows with broad photonic bandgap in infrared region based on enantiomorphic cholesteric liquid crystal templates

Abstract

Infrared (IR) light from the sun spans from 780 nm to ~1 mm and more than 85% of its energy lies between 800 nm to 1500 nm IR reflectors or absorbers are very important as smart windows in eco-friendly buildings because these devices can filter out IR light and control access of solar energy to regulate indoor temperature and maintain interior illumination In this study cholesteric liquid crystal (CLC) template technique was employed to fabricate a high-quality polymeric IR re?ector The IR photonic bandgap (PBG) re?ector was fabricated through the CLC polymer template (washing out/refilling) technique The fabrication involved four stages namely the before-curing after-curing after-washing-out and after-refilling stages A CLC template cell with a broadband re?ection was fabricated using weak UV light-induced longitudinal pitch gradient which leads to the broadening of PBG In addition a highly reflective IR mirror was achieved by adopting a single-layer CLC template film with a double-spiral photonic structure Finally an IR reflector of CLC polymer was successfully produced The device reflected more than 80% of the incoming IR light from 800 nm to 1500 nm and retained acceptable transmittance in the visible region The thermal insulation test shows that a considerable amount of incident and unwanted heat could be reflected Therefore a significant amount of energy could be saved on cooling temperature up to 2–3 °C and maintain interior illumination The structure proposed in this study might be written on windows by 3D printing technique in the future as eco-friendly building materials

Date of Award	2017 Feb 14
Original language	English
Supervisor	Chia-Rong Lee (Supervisor)