Electrochromic performance of reactive plasma-sputtered NiOx thin films on flexible PET/ITO substrates for flexible electrochromic devices

Electrochromic properties of NiOx (nickel oxide) thin films sputtered on 40 Ω/□ flexible PET (polyethylene terephthalate)/ITO (indium tin oxide) substrates were investigated. Metallic Ni target, sputtered by radio frequency (r.f.) power with argon gases and reacted with oxygen gases at room temperature (23 °C), was proven to provide significant electrochromic properties. Cyclic voltammetry switching measurements found that only low driving voltages from −0.6 V to 1 V were needed to provide reversible Li+ ion intercalation and deintercalation. Light modulation with up to 40% of transmittance variation, optical density change of 0.354 and color efficiency of 67 cm2/C at a wavelength of 550 nm were obtained for 1100 cycles of Li+ intercalation and deintercalation in a 1 M LiClO4-PC (propylene carbonate) electrolyte.