Optical properties of periodic micropatterned VO2 thermochromic films prepared by thermal and intense pulsed light sintering

Abstract

Vanadium dioxide (VO2) has garnered considerable attention in recent years as a promising material for thermochromic window applications because of its reversible metal-insulator transition (MIT) near room temperature and corresponding significant changes in its optical properties. However, the trade-off between improving luminous transmittance (Tlum) and maintaining the near-infrared modulation ability (ΔTNIR) limits the commercialization of VO2-based smart windows. To overcome these restrictions, we manufactured nanoinks based on VO2 nanoparticles and fabricated films via spin-coating these inks on quartz substrates. In this study, a simple photolithography method is employed to produce micropatterned VO2 films with different periodicities. The dried VO2 films were sintered by thermal and intense pulsed light (IPL) sintering processes. These micropatterned structures could favorably transmit visible light without sacrificing high ΔTNIR, and the patterned films showed improved Tlum compared to continuous films. The patterned VO2 films thermally sintered at 400 °C have Tlum of 51.5%–58.8%, ΔTNIR of 19.5%–27.6%, and ΔTsol of 5.7%–8.0%. The patterned VO2 films IPL-sintered at 2000 V have Tlum of 42.7%–50.7%, ΔTNIR of 21.7%–26.9%, and ΔTsol of 6.1%–7.6%. This facile fabrication method offers a new and promising direction for the use of VO2 thermochromic materials in smart window applications. Keywords: Vanadium dioxide, Metal-insulator transition, Thermochromic smart window, Photolithography, Intense pulsed light