Long-Term Stability and Efficiency of VO₂ Nanostructure-Based Thermochromic Smart Windows

Buildings, accounting for approximately 40% of global energy consumption, heavily rely on windows for maintaining indoor comfort. However, conventional windows are known for their inefficiency due to high optical transmittance and thermal conductivity. In recent decades, efforts have focused on enhancing sustainability through the development of low-emissivity coatings and smart windows. Despite advancements, the commercialization of a vanadium dioxide (VO 2 ) nanostructure-based thermochromic film has been limited by stability issues. This study addresses the critical need for long-term stability and efficiency in VO 2 -based smart windows, showcasing a composite film that is highly resilient to heat, ultraviolet (UV) light, and humidity. The proposed films exhibit exceptional solar energy regulation capability (Δ T sol = 20.11%) alongside a visible light transmittance of 54.94%. Moreover, they exhibit strong stability even under conditions of high relative humidity (90%) and temperature (60 °C), maintaining consistent phase-transition performance over 40 days─equivalent to approximately 1777 days of real-world exposure. Impressively, even without encapsulation, the composite film retains 96.4% of its initial Δ T sol after continuous 60-day illumination. This research offers promising technical solutions for advancing the commercial viability of traditional VO 2 smart windows, contributing significantly to global efforts toward carbon neutrality and sustainable development.