Electrochemical investigation of electrochromic device based on WO3 and Ti doped V2O5 films by using electrolyte containing ferrocene

Electrochromic devices (ECDs) based on WO 3 and Ti doped V 2 O 5 films are fabricated by using lithium (LiClO 4 ) liquid electrolyte containing ferrocene redox couple . The addition of ferrocene in electrolyte enhances electrochromic properties of device. The device based on LiClO 4 -Ferrocene electrolyte has larger charge density than that based on LiClO 4 electrolyte. In the 600–1500   nm wavelength range, the transmittance of colored device is under 2% and it has faster coloring response. At 680   nm wavelength, it shows larger changes in transmittance from 68% to 1.8% while device based on LiClO 4 electrolyte changes transmittance from 68.3% to 11.5%. The cycling data reveal that device based on LiClO 4 -Ferrocene electrolyte can yield more stable electrochromic properties at 65   °C than room temperature. In order to deeper understand the effect of electrolyte on films and devices, electrochemical impedance spectroscopy (EIS) and the voltage distribution of films based on an analog cell are separately measured and analyzed in LiClO 4 and LiClO 4 -Ferrocene electrolytes. Results indicate that compared with LiClO 4 electrolyte, films have lower charge-transfer resistance and the distributed voltage on Ti doped V 2 O 5 film is larger in LiClO 4 -Ferrocene electrolyte, which can enhance optical properties of ECD by improving charge density of Ti doped V 2 O 5 film.