Influence of applied voltage on optimal performance and durability of tungsten and vanadium oxide co-sputtered thin films for electrochromic applications

摘要

In this research, tungsten and vanadium oxide co-sputtered thin films are evaluated for electrochromic properties based on the effects of applied cyclic voltages of -0.7 V, -1.0 V and -1.3 V for 9600 s. XRD patterns reveal the appearance of new peaks after completion of -1.3 V cycles, these peaks are not seen after lower voltage scans. SEM images also verify severely damaged morphologies. Chronoamperometry (CA) scan of -1.3 V shows a drastic reduction in current density value to as low as 32% for bleaching and 26% for coloring respectively. This is because of the lesser intercalation and de-intercalation as a result of damaged and disturbed orientation. Whereas the films with -1.0 V testing cycles shows the current density drop to 93% and 88% for bleaching and coloring respectively. A remarkable discovery in switching times of WO3-V2O5 co-sputtered thin films is also achieved. Coloring and bleaching times are drastically reduced to 5.5 s and 1.3 s as compared to only WO3 films having these values as 13.4 and 4.1 s respectively. We further investigates electrochromic films for different states and concentrations by XPS, electrochemical impedance spectroscopy (EIS) for electronic/ionic conductivity comparison and visible spectroscopy to verify optical modulation and calculation of some optical constants.