Photoelectric Characteristics and Equivalent Circuit Analysis of Flexible Tungsten Oxide Electrochromic Thin Film

The tungsten oxide (WO_1-x) was deposited by cyclic voltammery on indium tin oxide (ITO)/polyethylene terephthalate (PET) substrate in different deposition cycles. The different deposition cycles were analyzed for energy dispersive spectrum (EDS), optical characteristic, surface morphology, life time, cyclic voltammery, and electrochemical impedance spectroscopy (EIS). The optical characteristic was measured for transmittance variation and coloration efficiency, the surface morphologies were measured for the WO_1-x thin-film thickness and roughness, and EIS was measured for the transfer impedance. The electrochromic behaviors of the WO_1-x thin film were performed in a 0.1 M lithium perchlorate/propylene carbonate (LiClO₄/PC) electrolyte. When the deposition cycles were 50 cycles, the WO_1-x thin film had the highest transmittance variation (ΔT_{650 nm}=79.54%), the thickness was 318.26 nm, the transfer impedance was 70.51 Ω, and the thin film can cycle for 124 times.