Fully Discrete VO2 Particulate Film with Ultra-High Transmittance and Excellent Thermochromic Performance

Vanadium dioxide (VO2) has attracted widespread attention due to its extraordinary thermochromic properties. Visually transparent VO2 films hold great promise for applying in smart windows, smart radiative coolers, solar cells, and microwave absorbing windows. However, it remains a huge challenge to simultaneously achieve ultra-high luminous transmittance (T-lum) and excellent thermochromic performance due to their contradictory relationship. Here, a fully discrete VO2 particulate (FDVP) film is developed. It shows an ultra-high T-lum of 92.7% due to the reflectance being significantly reduced. Below the phase transition temperature (T-c, 69.1 degrees C), it is highly transparent to near-infrared (NIR) light, while above T-c, it blocks NIR light through the strong localized surface plasmon resonance (LSPR) effect, resulting in an excellent solar energy modulation (Delta T-sol) of 10.5% for smart windows. In addition, a 3.5 at.%W-doped FDVP film exhibits a desired T-c of 25.8 degrees C, an extremely narrow hysteresis width (Delta T) of 4.6 degrees C, and good optical properties (T-lum = 92.0%, Delta T-sol = 8.2%). The performance represents a new milestone for thermochromic VO2 films. This work will shed light on the structural design for high-performance VO2 films.