Plasma assisted atomic layer deposition NiO nanofilms for improved hybrid solid state electrochromic device

Abstract

Alternate methods for deposition of electrochromic metal oxide thin films need to be explored to obtain an optimized one while designing solid state hybrid or all-inorganic electrochromic device. To continue this quest, electrochromic performance from a hybrid electrochromic device obtaining using plasma assisted atomic layer deposition (ALD) grown nickel oxide (NiO) thin film and viologen has been studied. A few tens of nanometers thick films of NiO were deposited first on silicon to optimize the deposition parameters prior to depositing on Fluorine-doped Tin Oxide (FTO)/glass substrates for fabricating the device. The structural and morphological properties of as-prepared films were analyzed by scanning electron spectroscopy (SEM), x-ray diffraction (XRD), Raman spectroscopy and x-ray photo electron spectroscopy (XPS) techniques. Thereafter, a solid state organic-inorganic hybrid electrochromic device was fabricated using Nickel oxide (NiO) and ethyl viologen (EV). The device changes its color between transparent and blue states under the potential window of ±1.7 V while taking less than 2s for toggling between the two-colored states. The device also exhibits an impressive electrochromic behavior with coloration efficiency of 118cm2/C, contrast ratio of 21% and a good cycle life/stability. The ALD grown films appeared to have advantage over other methods as it yields an atomically smooth and crack-less nano film so that proper power utilization take place for color switching. All these results open a new way to the fabrication of inorganic component to fabricate high-performance hybrid solid state electrochromic devices.