An investigation was conducted on the electrochromic properties of plasma sputtered-nickel-vanadium oxide thin films on 40 Omega/square flexible polyethylene terephthalate/indium tin oxide substrates. Metallic Ni0.93V0.07 target, sputtered by radio frequency power with argon gases and reacted with oxygen gases at room temperature (23 degrees C), was proven to provide extraordinary electrochromic performance. Cyclic voltammetry switching measurements found that only low driving voltages from -1 V to 1 V were needed to provide reversible Li+ ion intercalation and deintercalation. The light modulation with up to 52% of transmittance variation, optical density change of 0.446 and color efficiency of 63.8 cm(2)/C at a wavelength of 550 nm was obtained for 200 cycles of Li+ intercalation and deintercalation in a 1 M LiClO4-propylene carbonate electrolyte. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.