Flexible VO2 thermochromic films with narrow hysteresis loops

Fabricating flexible vanadium dioxide (VO2) films is a serious challenge towards commercial applications. In this work, we proposed a new strategy to directly deposit VO2 thermochromic films on flexible substrates by using Cr2O3 structural template layer, which can serve as growth template for low temperature (~300 °C) deposition of VO2 films. The obtained crystalline VO2 films on flexible substrates show significant phase transition properties with narrow hysteresis loops. Optical and electrical characterizations have indicated phase transition features of the flexible VO2 films, with an excellent solar modulation ability (~60% at 2500 nm) and a resistivity change over 2 orders of magnitude. Meanwhile, the flexible VO2 film exhibits narrow hysteresis loops during the phase transition process, and the hysteresis loop widths are less than 1 °C. Flexibility and stability of VO2 film in this work has been demonstrated by a designed bending test, which can maintain stable thermochromic performance after over 5000 bending cycles. This work provided a facile strategy to fabricate VO2 films on flexible substrates as flexible electronic devices.