Regulating the surface morphology and improving the thermochromic properties of VO films by introducing Cu-Ag and Cu-Zr nanoparticles into the VO/VO/VO structure

In this work, Cu-Ag and Cu-Zr bimetallic nanoparticles (NPs) were embedded into VO/VO/VO tri-layer films by using pulsed laser deposition. The results showed that Cu-Ag and Cu-Zr NPs have a significant regulating effect on the crystallinity and surface morphology of VO films. In comparison to Cu-Ag NPs, Cu-Zr NPs exhibit a much milder degree of surface morphology regulating influence on VO films. The introduction of Cu-Ag and Cu-Zr nanoparticles leads to a completely different surface morphology of VO films. Owing to the ability to adjust the surface of the VO film to be granular, the resulting local surface plasmon resonance effect effectively modulates the spectral curve, thereby enhancing the thermochromic properties of the composite films. Both Cu-Ag and Cu-Zr NPs can significantly improve the thermochromic properties of VO films. And high luminous transmittance (T = 74.6%) and high solar modulation ability (ΔT = 8.4%) were simultaneously achieved when the pulse number for depositing Cu-Zr NPs was 100. Additionally, the transmission spectrum of the composite films was simulated by using the finite-difference-time-domain method, and the growth mechanism of the composite films was explored. This work provides a guidance on controlling the morphology of VO films by Cu-based bimetallic NPs, which will promote the application of VO films in smart windows.