Enhancing the Thermochromic Properties of VO2 Thin Films by W-Ti Co-doping

Vanadium dioxide (VO 2 ) is a promising thermochromic material for smart windows; however, its practical application is limited by a relatively high phase transition temperature ( T c ) and insufficient modulation capability in both luminous transmittance ( ) and solar energy ( ). Cation co-doping serves as an effective strategy for optimizing its thermochromic performance near room temperature. W-Ti co-doped VO 2 films were fabricated via a two-step rapid thermal processing (RTP) annealing method using vanadyl acetylacetonate as the precursor. The co-doping of W and Ti leads to an enhancement in the thermochromic performance of the VO 2 thin films. The phase transition temperature ( T c ) was reduced from 69.75 °C to 52.35 °C. By adjusting the Ti doping content, the co-doped films maintained a low Tc while improving the luminous transmittance modulation ( ) from 39.8% to 46.1% and the solar energy modulation ability ( ) from 6.3% to 9.3%. These improvements are attributed to modifications in the band structure induced by W-Ti co-doping. The enhanced thermochromic performance, compared with that of undoped VO 2 , demonstrates that W-Ti co-doping provides a promising strategy for advancing VO 2 -based smart window applications.