Multilayer ITO/VO2/TiO2 thin films for control of solar and thermal spectra

• VO2/TiO2 films were reactively sputtered on ITO and common glass substrates.
• Multilayer structure combines thermochromism, low emissivity and anti-reflectance.
• Multilayer properties control both solar and thermal spectra for windows.
• Transition temperature of VO2 layer reduced to 52 °C by restricting grain to 92 nm.

In this study, a multilayer thin film of ITO/VO2/TiO2 was investigated for simultaneous control of the solar and thermal spectra with potential application as an energy-efficient coating for windows in built environments. The functions for these layers were: low emissivity, thermochromism, and anti-reflectance in the visible region. Films were deposited using reactive magnetron sputtering and characterized with scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis–NIR spectrophotometry, and Fourier transform infrared spectroscopy. The results demonstrate that relatively high luminous transmittance, low emissivity, and favorable thermochromism can be achieved for a film with a transition temperature centered at 52 °C with a hysteresis width of 18 °C. This shows that an advancement of the previous state of the art can be made by restricting the Scherrer grain size of the VO2 layer to 92 nm.