Design and engineering of IZO/Ag/glass solar filters for low-emissivity window performance

Abstract. The electricity consumption in houses and commercial buildings generates about 18% of greenhouse gas emission. A critical issue of building energy consumption is heat and cooling loss through the window. Low-emissivity windows control thermal radiation through glass without decreasing the intensity of visible light. They are made up of optical filter coatings grown on a flat glass surface. Solar filters based on Ag/IZO multilayer films are grown and simulated on glass substrate. The targeted structure designs are grown by a sputtering system and characterized by scanning electron microscopy and x-ray diffraction techniques. To accurately simulate transmission spectrum, silver (Ag) and IZO optical constants were estimated by fitting ellipsometric data at different thicknesses. Transmission spectrum shows a good agreement among experiment and simulation. In addition, optical constant curves strongly show layer thickness dependence in both materials. In particular, the ultrathin Ag layer displays a percolation threshold in the vicinity of 15 nm, which leads to surface plasmon resonance with absorption at about 450 nm. These types of optical filter coatings would have potential applications as low-emission windows.