Shape-dependent thermochromic phenomenon in porous nano-structured VO2 films

In this paper, we report the preparation of thermochromic porous nano-structured VO2 films. The films with sphere-shaped, stone-shaped, and rod-shaped particles were derived from a sol–gel process with inorganic precursor and polyethylene glycol (PEG). The obtained porous nano-structured VO2 films show tiny particles (about 20 nm), excellent optical property (light switching efficiency of 67%), and controlled hysteresis loop features (width and slope). The films can be obtained by simply controlling the N2 flow rate during annealing process, providing an effective process for growing high quality thermochromic porous nano-structured VO2 films with controllable hysteresis features, which is of great importance in achieving practical application.