Design and Scalable Synthesis of Thermochromic VO<sub>2</sub>-Based Coatings for Energy-Saving Smart Windows with Exceptional Optical Performance
Michal Kaufman, J. Vlček, Jiří Houška, Sadoon Farrukh, Stanislav Haviar
Abstract
High Resolution Image Download MS PowerPoint Slide We report strongly thermochromic YSZ/V 0.855 W 0.018 Sr 0.127 O 2 /SiO 2 coatings, where YSZ is Y-stabilized ZrO 2, 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 2 flow feedback control allows us to prepare crystalline W and Sr codoped VO 2 of the correct stoichiometry. The W doping of VO 2 decreases the transition temperature, while the Sr doping of VO 2 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 2 crystallinity, while the top SiO 2 antireflection layer provides also the mechanical and environmental protection for the V 0.855 W 0.018 Sr 0.127 O 2 layer.