Sputtering Flexible VO2 Films for Effective Thermal Modulation.

Flexible vanadium dioxide (VO2) thermochromic films show great potential for large-scale fabrication and possess broader applications compared with VO2 coatings on rigid substrates. However, the fabrication of flexible VO2 films remains a challenge so far, leading to the scarcity of research on flexible VO2 films for smart windows. With the aim to obtain a flexible VO2-based films with excellent optical properties and a long service life, we designed and successfully fabricated a flexible ITO/VO2/ITO (IVI) film on the colorless transparent polyimide substrate, which could be directly attached to glasses for indoor temperature modulation. This flexible IVI film effectively enhances the luminous transmittance (Tlum) and solar modulation ability (ΔTsol) (15 and 68% increase relative to a VO2 single layer), reduces the thermal emissivity (εT) (50.7% decrease relative to a VO2 single layer), and exhibits better durability than previously reported structures. Such excellent comprehensive performance offers it great potential in practical applications on smart windows. This work is supposed to provide a new strategy for facile direct fabrication of flexible VO2 films and broaden the applications of flexible VO2 in more coatings and devices.