Synchronized improvements of luminous transmittance and solar modulation ability of VO2 films by employing SnO2 buffer layers.

• High quality SnO 2 /VO 2 bi-layer films are prepared by pulsed laser deposition. • The grain size and roughness of VO 2 can be regulated by SnO 2 buffer layer. • Balance between luminous transmittance and solar modulation ability is achieved. For decades, the practical application of VO 2 -based smart windows is limited by its low luminous transmittance (T lum) and solar modulation ability (ΔT sol). In this study, SnO 2 /VO 2 thermochromic thin films were produced on amorphous glass substrates via pulsed laser deposition and were characterized by x-ray diffraction, scanning electron microscopy, atomic force microscopy, spectrophotometry, and resistance measurements. By adjusting the thickness of SnO 2 buffer layer, not only the semiconductor-to-metal transition temperature of VO 2 films can be effectively tuned, but also the T lum and ΔT sol of VO 2 films can be increased synchronously to 54.9% and 8.3%, respectively. It is shown that the grain size of VO 2 films increases from ~15 nm to ~90 nm with the SnO 2 buffer layer thicknesses increase from 25 nm to 125 nm, and consequently the electrical and optical properties of VO 2 films are effectively improved. These can be attributed to the fact that SnO 2 buffer layer can effectively control the grain size, surface roughness and optical band gap of VO 2.The results suggest that the SnO 2 buffer layer is very beneficial for the growth of high-quality VO 2 films on glass substrates, which is of importance for the application of VO 2 in energy-efficient smart windows. [ABSTRACT FROM AUTHOR]