Transparent heat reflecting PVA/Cu/PVA photonic structures for energy saving smart windows

Abstract

Development of transparent heat reflecting, hence energy-saving windows using cost-effective materials has a pivotal role in interior temperature control of buildings, especially considering the regular growth in ambient temperature globally. The present article focuses on developing polymer/metal/polymer transparent heat reflection (THR) multilayer coatings on glass substrates. We have used polyvinyl alcohol as the polymer and copper films as metal coatings in the three-layer stack that was fabricated. We investigate the structure, uniformity, continuity, and optical properties of PVA/Cu/PVA multilayers using Field Emission Scanning Electron Microscope, ellipsometry, stylus profilometer, and UV-VIS-NIR spectrophotometer. The optical modeling using COMSOL Multiphysics software optimizes individual layer thickness. Annealing at 70 °C enhances the THR property and improves crystallinity. Samples annealed at 70 °C for 30 min with 95 nm thick PVA (2w/v %) and Cu of 15 nm thickness show maximum optical transmittance of 76.6 % in the visible band centered at 605 nm while transmitting only ≈ 9.2 % at 2000 nm in the infrared region. The high visible transmittance and low infrared transmittance of the PVA/Cu/PVA multilayer have the potential for energy-saving smart window applications.