Thermochromic properties of BN/VO2/BN trilayer films with low phase transition temperature and high hysteresis width

A novel thermochromic BN/VO2/BN trilayer thin film was deliberately designed and deposited using pulsed laser deposition combined with rapid thermal annealing. The structure, surface morphology, surface roughness, and thermochromic properties of the as-prepared sandwich structure film were analyzed. A BN buffer layer did not significantly reduce the phase transition temperature Tt, but rather played a role in modifying the surface morphology of VO2 thin film. Covering the BN/VO2 bilayer film with a second BN layer greatly reduced Tt with large hysteresis width, and luminous transmittance (Tlum) was also enhanced, whereas solar modulation efficiency (ΔTsol) was reduced. In particular, when the thickness of BN was 70 nm, the resulting BN/VO2/BN trilayer film reached a low Tt value of 36 °C with large hysteresis width (25 °C) and a high Tlum (∼40%), but with a very low ΔTsol. The properties revealed by this first attempt to use BN thin film in the fabrication of VO2-based multilayer sandwich structures open up a new path for the design of advanced thermochromic heterostructures with tunable functionalities for smart windows and optical storage devices. [Display omitted]