Electrochromic Iridium-Containing Nickel Oxide Films with Excellent Electrochemical Cycling Performance

Electrochromic Ni oxide thin films attract much interest because of their large potential for applications as optically active layers in energy-saving and comfort enhancing smart windows in buildings. However Ni oxide, typically being the anodic counter electrode in a W-oxide-based device, may suffer severe charge capacity degradation upon extended electrochemical cycling. It is therefore important to identify improved Ni-oxide-based thin films for electrochromics. Here we describe a new class of such films wherein an addition of a small amount of Ir to Ni oxide is found to provide strongly improved electrochemical cycling durability. Best properties were achieved with Ir/(Ir + Ni) = 7.6%, and such films displayed charge capacity and optical modulation that, remarkably, were still increasing after 10,000 cycles. (C) 2015 The Electrochemical Society.