Unveiling the NIR modulation performance enhancement of VO2 endowed by oxygen vacancy elimination

Vanadium dioxide has emerged as a promising material for smart windows owing to the temperature-responsive variable near-infrared (NIR) transmittance. Yet, the poor NIR modulation ability challenges its efficiency in thermal management. In this study, by meticulously controlling the oxygen vacancy content at a low level, VO₂ nanoparticles with excellent NIR modulation performance are achieved. Oxygen vacancy (V_O) defects elimination leads to a remarkable decrease of reflectance in the monoclinic (M) phase, dramatically enhancing the near-infrared contrast of VO₂ by 154 %. Density functional theory (DFT) calculations reveal that V_O elimination favors low refractive index in the NIR region. The optimized experiment is carried out to prepare VO₂ nanoparticles with low defects and high crystallinity. It shows the best NIR transmittance contrast at 1500 nm (ΔT_{1500 nm}) of 24.4 %, simultaneously keeping a high luminous transmittance (T_lum) of 79.7 %. This study is believed to provide valuable guidance for the current defect and thermochromic performance study of VO₂.