Effect of cobalt on the electrochromic properties of NiO films deposited by spray pyrolysis

In this work, the morphological, optical and electrochromic properties of NiO and Ni–Co oxides films are reported. Those films were deposited on FTO glass substrates using a simple spray pyrolysis method. SEM images indicated that the size of particles that formed the Ni–Co oxide films decreased from 18 to 6 nm as the content of Co increases. In addition, the thickness of the films decreased from 378 to 310 nm as the content of cobalt augments from 0 to 10 mol%. This reduction of thickness also produced a diminution of the band gap of the films, which benefited the electrochromic properties. Electrochemical measurements were carried out and found that the diffusion coefficient, reversibility and coloration efficiency were enhanced in samples with cobalt with respect to the sample with pure NiO. Thus, the results suggest that our films could be useful for electrochromic applications.