Improving the thermochromic performance of VO 2 films by embedding Cu-Al nanoparticles as heterogeneous nucleation cores in the VO 2 /VO 2 bilayer structure

VO 2 -based films show great potential applications in thermochromic smart windows. However, enhancing luminous transmittance ( Tlum ) while maintaining high solar modulation ability ( ΔTsol ) remains a formidable challenge. Here, we present a novel VO 2 /Cu-Al nanoparticles (NPs)/VO 2 composite film structure, seamlessly integrating Cu-Al bimetallic NPs within VO 2 films by pulsed laser deposition on alkali-free glass substrates. The content of Cu-Al NPs in the composite films is controlled by the pulse number ( Np ) applied to the Cu-Al alloy target. X-ray diffraction results indicate that the crystallinity of VO 2 films is significantly enhanced by the incorporation of an appropriate amount of Cu-Al NPs. The SEM characterization results revealed that the particle size of VO 2 composite films initially increases to approximately 131 nm and subsequently decreases to around 120 nm as Np increases, with a concurrent transition in particle shape from quasi-circular to elongated. The Tlum and ΔTsol of the resulting composite films were dramatically improved to 71.6 % and 9.5 %, respectively, when Np was 300. These enhanced thermochromic properties are attributed to the localized surface plasmon resonance (LSPR) of the VO 2 particles. This research opens up a promising avenue for the convenient production of customized high-quality VO 2 films tailored for smart window applications.