Enhancing the thermochromic properties of VO₂ thin films by W-Ti Co-doping

Vanadium dioxide (VO₂) 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 ((Formula presented) ) and solar energy ((Formula presented) ). Cation co-doping serves as an effective strategy for optimizing its thermochromic performance near room temperature. W-Ti co-doped VO₂ 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 VO₂ 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 ((Formula presented) ) from 39.8% to 46.1% and the solar energy modulation ability ((Formula presented) ) 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 VO₂, demonstrates that W-Ti co-doping provides a promising strategy for advancing VO₂-based smart window applications.