Abstract
Windows are essential for advancing energy efficiency, yet fabricating window materials that simultaneously achieve high visible light transmission, exceptional and ultrabroadband near-infrared (NIR) shielding, neutral color appearance, excellent stability, and cost-effective, sustainable production remains a significant challenge. This study introduces ferrous ion-doped phosphosilicate glass (Fe2+-PSG), a material that meets all these criteria, establishing itself as a promising candidate for energy-efficient windows. Comprehensive characterization using Raman spectroscopy, synchrotron X-ray absorption near edge spectroscopy (XANES), UV–Vis-NIR transmission spectroscopy, and structural analysis reveals that the glass achieves superior visible light transmission performance (Tlum = 84.1 ± 0.3 %) and a neutral color temperature of 6753 ± 45 K. These remarkable properties are primarily attributed to the formation of colorless ferrous [FeO6] units, whose unique coordination environment is precisely controlled through phosphorus incorporation. Superior ultrabroadband NIR-shielding (750–2500 nm), with a high NIR-shielding figure of merit of 1.8 ± 0.1, is enabled by the incorporation of larger alkali ions such as K+ and Cs+. Additionally, Fe2+-PSG demonstrates exceptional stability, maintaining its performance after 12 months under ambient conditions and 24 h in hot water at 80 °C and 120 °C. These high-performance characteristics are attributed to structural modifications that alter the splitting energy of ferrous ions, enabling precise control over optical properties across the visible and NIR spectrum. Manufactured using the scalable and cost-effective melt-quench method, Fe2+-PSG offers a practical solution for sustainable window production, addressing limitations of current technologies and paving the way for real-world applications.
