Optical properties in the near ultraviolet of low-emissivity coatings

Abstract Low-emissivity (low-E) coatings are widely used in architectural glazing to improve building energy performance and reduce environmental impact. Although their optical behavior is generally studied in the visible and infrared regions, this work investigates the ultraviolet optical properties of visually equivalent low-E multilayer coatings fabricated by magnetron sputtering, in order to enable the fabrication of bird-friendly coatings that prevent bird collisions with building glazing. The coatings were prepared with a silver layer and two different dielectric materials, tin oxide (SnO₂) and aluminum-doped zinc oxide (AZO). Visually equivalent samples with the different dielectric materials were designed and their optical properties characterized, showing the expected similar behavior in the visible and infrared regions, while revealing clear differences in the transmission of the samples, with over a 40% higher transmittance in the case of SnO₂ samples and similar reflectance in both types. Furthermore, from 13 to 40% lower emissivity was found for samples deposited with AZO, depending on the amount of silver. Finally, a remarkable increase in ultraviolet reflectance was observed with increasing silver thickness, from approximately 0.20 for the 10 nm Ag sample to around 0.45 for the 20 nm one. Graphical abstract Observation and comparison of the samples designed with different dielectrics (tin oxide and aluminum-doped zinc oxide) and same thickness of metal layer (silver). Similar behavior in the visible range but distinct in the ultraviolet.