Real-Time Analysis and Characterization of Dynamic Performances for Coloration-Bleaching Processes in Electrochromic Devices Based on WO3 Layers Prepared by Sol-Gel Synthesis

Abstract

A comparative characterization of multiple coloration-bleaching cycles under various modes of power (voltage and current supply) is performed for electrochromic devices (ECDs) based on WO3 layers prepared from metal tungsten or tungsten carbide and annealed at different temperatures from 150 to 350° C. The results indicate that optimal voltage/current values and exposure time strongly depend on WO3 synthesis and annealing conditions. Particularly, a sustainable functioning of ECD involving WO3 prepared from metal tungsten and annealed at 150° C is achieved upon a stepwise change of coloration and bleaching voltage from 1.5 to 2.5 V at the current 1 mA within 600 s, while for the sample prepared from tungsten carbide and annealed at 350° C a similar mode within 300 s is effective, probably due to certain differences in the electrochromic material structure. Deviations from optimal power supply conditions result in the destabilization of ECD performances and significant efficiency decrease after several coloration-bleaching cycles, particularly due to an incomplete bleaching.