Transparent-conductive and infrared-shielding WO₃/Ag/WO₃ multilayer heterostructures

Multilayer thin films are used as functional coatings in a variety of applications. In optoelectronics, they are used as transparent conducting electrodes that possess high electrical conductivity and visible transmittance. Another application is infrared-blocking energy-saving coatings. These two applications are usually explored separately. In this work, multilayers based on thermally evaporated tungsten oxide/silver/tungsten oxide (WO₃/Ag/WO₃) coatings were investigated for both applications. The properties of these multilayers were optimized to fulfill the requirements of both applications simultaneously. First, the properties of single-layer Ag and WO₃ were investigated. Then, the properties of the multilayers were examined as a function of the thicknesses of the metallic and dielectric layers. The optimum structure consisted of a WO₃/Ag/WO₃ multilayer with thicknesses of 25/16/25 nm characterized by an electrical resistivity of 67 μΩ cm, a sheet resistance of 10.2 Ω/□, and a mean visible transmittance of 75 %. Such properties were suitable for transparent conductive applications. The infrared-blocking performance was manifested by a temperature reduction of 14 °C for solar radiation passing through a glass window.