Development of Sol–Gel Derived SiO2-TiO2 Double-Layer Antireflective Coatings for Solar Glass Covers

Solar glass covers play a critical role in determining the energy conversion efficiency of photovoltaic modules and solar thermal systems.However, significant reflection losses at the glass interface remain a barrier to maximizing sunlight collection.In this study, we fabricated highly transparent double-layer TiO2-SiO2 antireflective coatings via a simple, scalable base-catalyzed sol-gel method combined with dip-coating.Methyltriethoxysilane (MTES) was used to introduce a nanoporous structural network in the top silica layer to effectively lower its refractive index, while titanium (IV) isopropoxide (TTIP) served as the precursor for a dense underlying titania layer.Fourier transform infrared spectroscopy (FTIR) confirmed the successful chemical integration of the two metal oxides through the distinct formation of interfacial Si-O-Ti heterolinkages, alongside the preservation of hydrophobic methyl Si-CH3 functional groups from the chemical modifier.Scanning electron microscopy (SEM) micrographs revealed that sequentially depositing the low-index SiO2 outer layer successfully filled in microscopic valley regions and localized thermal stress cracks present on the underlying titania base layer, creating an exceptionally smooth and continuous bilayer surface.This optimized microstructural stack significantly suppressed surface light-scattering defects.Consequently, UV-Vis transmittance spectra demonstrated excellent broadband antireflective performance, achieving a peak transmittance of ~98.8% around 530 nm compared to the single-layer configurations.These findings highlight a practical, cost-effective path toward developing durable, highefficiency optical coatings for long-term outdoor solar energy harvesting applications.