Optical performance and solar control of wide-bandgap dielectric/Ag/ dielectric multilayers for energy-efficient window coatings

Windows remain one of the spectrally weakest elements in the thermal envelope of buildings, creating strong demand for transparent heat mirrors (THMs) with high visible transmittance and effective infrared blocking. In this study, the performance of a broad family of wide-bandgap oxides (HfO2, Ta2O5, ZrO2, Ga2O3, and Er2O3) is tested as the dielectric (D) layer in D/Ag/D multilayer THMs fabricated by physical vapor deposition. By varying the Ag thickness while keeping the dielectric thickness constant, the influence of the oxide environment on interfacial quality and optical performance is identified. Distinct interface widths and Ag–oxide interaction behaviors are observed, governed by the oxide type and Ag thickness. HfO2 and ZrO2 promote smoother surfaces and well-confined interfaces, whereas Ta2O5 leads to broader interfacial regions. These interfacial characteristics lead to pronounced performance hierarchies: HfO2/Ag/HfO2 and ZrO2/Ag/ZrO2 coatings provide the most balanced optical response, achieving visible transmittance above 80% and near-infrared reflectance approaching 80%. Er2O3/Ag/Er2O3 structures show superior thermal management, while Ga2O3/Ag/Ga2O3 exhibits intermediate thermal performance with good transparency. In contrast, Ta2O5/Ag/Ta2O5 multilayers exhibit reduced optical selectivity and weakest thermal blocking, due to increased roughness and interdiffusion. These findings highlight dielectric selection and interface quality as decisive parameters for high-performance THM coatings.