Design and Scalable Synthesis of Thermochromic VO-Based Coatings for Energy-Saving Smart Windows with Exceptional Optical Performance.

We report strongly thermochromic YSZ/VWSrO/SiO coatings, where YSZ is Y-stabilized ZrO, prepared by using a scalable deposition technique on standard glass at a low substrate temperature of 320 °C and without any substrate bias voltage. The coatings exhibit a transition temperature of 22 °C with an integral luminous transmittance of 63.7% (low-temperature state) and 60.7% (high-temperature state) and a modulation of the solar energy transmittance of 11.2%. Such a combination of properties, together with the low deposition temperature, fulfills the requirements for large-scale implementation on building glass and has not been reported yet. Reactive high-power impulse magnetron sputtering with a pulsed O flow feedback control allows us to prepare crystalline W and Sr codoped VO of the correct stoichiometry. The W doping of VO decreases the transition temperature, while the Sr doping of VO increases the luminous transmittance significantly. A coating design utilizing second-order interference in two antireflection layers is used to maximize both the integral luminous transmittance and the modulation of the solar energy transmittance. A compact crystalline structure of the bottom YSZ antireflection layer further improves the VO crystallinity, while the top SiO antireflection layer provides also the mechanical and environmental protection for the VWSrO layer.