Sputtering Flexible VO 2 Films for Effective Thermal Modulation.

Flexible vanadium dioxide (VO 2 ) thermochromic films show great potential for large-scale fabrication and possess broader applications compared with VO 2 coatings on rigid substrates. However, the fabrication of flexible VO 2 films remains a challenge so far, leading to the scarcity of research on flexible VO 2 films for smart windows. With the aim to obtain a flexible VO 2 -based films with excellent optical properties and a long service life, we designed and successfully fabricated a flexible ITO/VO 2 /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 ( T lum ) and solar modulation ability (Δ T sol ) (15 and 68% increase relative to a VO 2 single layer), reduces the thermal emissivity (ε T ) (50.7% decrease relative to a VO 2 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 VO 2 films and broaden the applications of flexible VO 2 in more coatings and devices.