Elemental doping of VO2 thin films for smart window applications

Vanadium oxide (VO₂) thin films are among the most promising materials for smart, energy-efficient windows due to their ability to reversibly undergo a metal-insulator transition (MIT) in response to temperature. This transition results in distinct optical properties that are highly attractive for energy-saving applications. However, the practical use of VO₂ is limited by its relatively high transition temperature (68 °C), which is above ambient conditions. Elemental doping is a widely used approach to reduce the transition temperature of VO₂ thin films. However, the incorporation of dopants not only modifies the transition behavior but also affects the optical and thermochromic properties. This thesis investigates the effects of doping elements on the structural transition and optical performance of VO₂ thin films, obtained via a sol-gel approach. The effect of the different doping elements were expressed by comparing the optical and thermochromic properties of the thin films. These were evaluated by UV–Vis spectroscopy, along with the structural and morphological analyses, which were performed using XRD and SEM. In addition, the film thickness was determined by ellipsometry.