The valence conversion mechanism for Mo-doped VO2 films with enhanced thermochromic properties

Reducing the phase transition temperature ( T c ) of VO 2 films to achieve the application in the field of Smart Home is still a challenge. Thus, in the work, the ultra-thin VO 2 films with different Mo doping amounts were successfully prepared by an economic sol-gel method and atmosphere annealing, aiming to further investigate the mechanism of the decrease of T c . The results show that the VO 2 films with 3 at % Mo doping possess the T c of 29.5 °C. Notedly, in the as-prepared films, the maximum transmittance in the visible region ( T vis ) is 46.3 % and the solar direct transmittance ( T sol ) is 45.8 %. According to the XPS spectra, it is confirmed that the Mo doping prominently induces the valence change of V ions from +4 to +3, inhibiting the strain in the phase transition process of VO 2 films, and leading to the decrease of T c . Our work will provide a feasible solution for reducing the T c of the ultra-thin VO 2 films.