Silica-Based Thin Films for Self-Cleaning Applications in Solar Energy Converters

Abstract

Solar glass with high transmittance and low reflectance is used as glazing in solar-thermal collectors or photovoltaic modules; however, in field conditions the glazed surface can be the subject of fouling; therefore, additional prerequisites are targeting self-cleaning features while preserving or enhancing the glass optical properties. This study presents the results obtained by applying silica-based layers to the solar glass surfaces; the surface properties are tailored by controlling the roughness to modify the optical properties and improve surface wettability, supporting self-cleaning mechanisms. The sol-gel silica nanoparticles are deposited in optimized conditions, with and without titanium dioxide and gold nanoparticles; the thin layers are analyzed by X-ray diffraction, contact angle, optical measurements, and atomic force microscopy. The roughness values are influenced by the chemical composition, with lower values for the layers containing only silica and increased values when TiO2 and Au nanoparticles are added. The layers have a predominant polar component of surface tension (>95%), supporting good wettability, up to enhanced superhydrophilic features as compared with the uncoated solar glass. Additionally, the investigations under simulated solar radiation outline self-cleaning features in methylene blue removal, as a combined effect of photocatalysis and superhydrophilicity.