Thermal studies on chemical bath deposited thermochromic VO2 thin film for energy efficient glass windows

Abstract

Thermochromic materials have been studied extensively for their thermal switching properties for smart window application, among this vanadium dioxide (VO2) is extensively researched. In this study, acidic Chemical Bath Deposition (CBD) method has been used to deposit thermochromic vanadium dioxide (VO2) thin film on microscope glass substrate modified by PVP K-30 surfactant and using NH4VO3 as a source of vanadium. The thin films are synthesized by varying the deposition time (15 min, 30 min and 80 min.) and annealing temperature (450 °C, 500 °C, and 570 °C) under nitrogen gas atmosphere. Thermal studies done by DSC shows that 68 °C is the critical transition temperature of VO2 thin film synthesized, an alternative route to identify the thermochromic characteristic other than the routine UV–Vis-near IR absorption spectroscopy. The DSC curve have also been used to notify crystallinity and purity of phases from Full Width Half Maxima (FWHM) and enthalpy of transition studies. The crystalline phases of the thin film were studied using XRD, which shows dominant peaks at 27.6° and 39.5° with their respective index of (011) and (020). The XRD characterization show that crystalline size and FWHM are directly proportional to the annealing temperature. In the present studies, it is clearly shown, the future potential of CBD synthesized VO2 thin films for smart window applications compared to other synthesis techniques.