Bi-layered energy efficient coatings as transparent heat mirrors based on vanadium oxide thin films

Abstract

Energy-efficient coatings based on two-layer-structured transparent heat mirrors were fabricated by depositing a vanadium oxide thin film on a silver thin film by thermal evaporation. Transparent heat mirrors are energy efficient coatings designed to save energy in hot climates by allowing only the visible part of solar radiation to pass through them and reflecting the infrared heat. These transparent heat mirrors can be used as energy-saving windows in energy-efficient buildings and green house agriculture. First, the optical, structural, and chemical properties of individual vanadium oxide thin films were investigated related to their application in transparent heat mirrors. Then, in order to realize their potential as energy efficient coating, optical characterization was performed on a two-layer structure. The performance of these coatings was calculated through integrated spectral transmittance and reflectance in the range of visible and infrared radiations. In addition, chemical depth profiling was performed to probe the diffusion of elements along the deposited layers. The fabricated coatings were found to show the expected behavior as transparent heat mirrors of high visible transparency and high infrared reflection.