Optical, electrical, and electrochemical properties of indium tin oxide thin films studied in different layer-structures and their corresponding inorganic all-thin-film solid-state electrochromic devices

In this investigation, the indium tin oxide (ITO) film layers were prepared by reactive direct current magnetron sputtering at room temperature with different deposition parameters on six different substrates: glass, polyethylene terephthalate (PET), NiOx/ITO/glass, NiOx/ITO/PET, WO3/ITO/glass, and WO3/ITO/PET. The ITO deposited on WO3/ITO/glass showed great advantage than others having a resistance as low as 9.2 Ω/◻ and a high average optical transmittance of 77.1% and reaching the balance between the optical and electrical properties of ITO thin films. Meanwhile, the WO3 film as electrochromism layer on ITO (under different deposited parameters)/glass shows nearly perfect reversibility, charge density of 20 mC/cm2, and fast response time of about 2–6 s. With the outer ITO thin film layer optimized, the electrochromic devices (ECDs) with typical five-layer structure were deposited. ECDs show the reversible dark-blue-coloration and bleaching cycles, large optical contrast, fast response time, and good stability. The device with glass/ITO/NiOx/electrolyte/WO3/ITO structure represents a transmittance variation from 20% (colored state) to 90% (bleached state).