Moderating oxygen deficiency induced better thermochromic properties of monoclinic vanadium dioxide thin films

Monoclinic vanadium dioxide (M-VO2) is a kind of typical thermal phase change materials, but its relatively high phase transition temperature (68 degrees C) and low solar modulation efficiency greatly hinder the applications as energy materials. In this work, well-crystalline M-VO2 were prepared by pulsed laser deposition (PLD) under the adjustable oxygen pressure range. By fine adjusting the low oxygen pressure (0.1-0.9 Pa), VO2 maintain the monoclinic crystal and excellent photoelectrical properties, even if oxygen deficiency and other defects exist. Results indicate that the phase-transition temperature (T-c) decreases with the decrease of oxygen pressures while the solar modulation efficiency (Delta T-sol) increases with the decrease of oxygen pressures. Moreover, the M-VO2 thin films prepared with 0.3 Pa oxygen pressure showed the best photoelectric performance, in which the sheet resistance changes up to three orders of magnitude, the phase-transition temperature is 61 degrees C and the Delta T-sol is as high as 8.3%. This work has demonstrated the role of moderate oxygen defects in optimizing the photoelectric properties of M-VO2, also provided a feasibility study on how to deposit pure M-VO2 by PLD.