Preparation and characterization of VO2/Cu-Zr NPs/VO2 composite films with enhanced thermochromic properties

The contradiction between luminous transmittance (Tlum) and solar modulation ability (& UDelta;Tsol) of vanadium dioxide (VO2) smart windows can be reconciled through the regulation of surface morphology. In this study, Cu-Zr bimetallic nanoparticles (Cu-Zr NPs) were embedded into VO2/VO2 bilayer films by pulsed laser deposition to tailor the VO2 surface morphology. XRD characterization revealed that the introduction of Cu-Zr NPs can significantly improve the crystallinity of VO2 films. FESEM characterization illustrated that the grain size and morphology of top-VO2 layer were sensitive to the density of Cu-Zr NPs. From the transmission spectrum, evident localized surface plasmon resonance (LSPR) phenomena could be observed in the range of 1300-1500 nm. When the pulse number for depositing Cu-Zr NPs is 35, the composite film exhibits both high Tlum of 62.4% and excellent & UDelta;Tsol of 10.6% simultaneously. In addition, the finite difference time domain (FDTD) simulation suggested that the improvement of thermochromic properties could be attributed to the LSPR effect induced by the unevenly distributed VO2 grains on the surface. This work confirmed the existence of non-noble Cu-Zr NPs could both improve the crystallinity and regulate the surface morphology of VO2 film, which simplified the fabricating process of VO2 thermochromic smart windows and was cost-effective.