Full solar spectrum optical and photothermal characterization of antimony tin oxide (ATO) films with tunable NIR absorptivity for energy-efficient building envelope applications

This work investigates the full-spectrum optical and photothermal properties of Antimony Tin Oxide (ATO)-coated glass for application in energy-efficient building glazing. A simple, scalable dip-coating method was employed to deposit ATO films, and their spectral optical performance was characterized across a broad wavelength range of 250 nm–20 µm [UV–Vis–near-infrared (NIR)–mid-infrared (MIR)]. In this study, for the first time, comprehensive optical data, including spectral transmittance, reflectance, absorptance, visible light transmittance, haze, and spectral and total mid-infrared emissivity (5–20 µm), are reported together for the full solar spectrum, along with the photothermal performance. UV–Vis–NIR spectroscopy and Fourier transform infrared analysis were performed for optical characterization, and surface morphology and nanoparticle dispersion were examined using scanning electron microscopy. The results reveal that ATO-coated glass exhibits high photothermal performance with light-to-heat efficiency greater than 65%, while deposition parameters can significantly affect this efficiency. ATO-coated glass shows high transparency in the visible region with strong and tunable spectral absorptance in the near- and mid-infrared regions, which is a critical feature for thermal control in building applications. The ability to fine-tune near-infrared (NIR) absorption through deposition parameters allows for tailored performance suited to specific environmental conditions. In addition, the coated glass shows low reflectance and high total emissivity in the MIR region (>0.9), specifically in the atmospheric window, enabling efficient radiative heat dissipation. By combining the tunable NIR-selective absorption for solar-heat shielding with controllable MIR radiative dissipation, this study identifies ATO as a promising photothermal material for energy-efficient glazed façade technologies. The comprehensive optical data provided in this study are essential for architectural applications and establish a foundation for future research on photothermal materials in building envelope systems.