Facile Preparation of VO₂ Films with Enhanced Luminous Transmittance and Infrared Modulation Ability

The facile preparation of cost-effective VO2 thin films with high luminous transmittance and outstanding infrared modulation ability is highly desirable but still challenging since the optimization of one aspect often comes at the expense of deterioration in another. Furthermore, the complexity of the doping process or design of composite films often increases the preparation cost and complicates the operation. In this work, the film thickness was adjusted by controlling the vanadium ion concentration of the sol and spin-coating parameters. The influence of the annealing time at various film thicknesses on the optical performance was examined. The results revealed that the thin film thicknesses of VO2 ranging from 100 to 120 nm showed outstanding optical performances with Tlum,av = 36.9%, ΔTsol = 11.1%, and ΔT2500 nm ≈ 70% (Tlum,av is the average of luminous transmittance in the low/high-temperature phase). Short suitable annealing times were beneficial for expanding the optical band gap of the films, as well as increasing the porosity, thereby effectively enhancing the average luminous transmittance (Tlum,av = 43.1%) and maintaining relatively high modulation ability (ΔTsol = 11.5%, ΔT2500 nm = 65.1%). Overall, the proposed preparation method of highly compatible VO2 films simplifies the operation process and appears to be promising for a wide range of future applications, namely in visible-infrared zoom detection systems.