Preparation of Co doped NiO thin films with excellent switching time and coloring efficiency through sol-gel spin coating

This paper fabricates novel electrochromic films through the sol-gel spin coating of nickel (Ni) and tunable cobalt (Co) atoms. The particle size, band gap, conductivity, and response time of the electrochromic films were improved by accurately adjusting the doping ratio of Co atoms from cobalt acetate. According to the results of scanning electron microscope and X-ray diffraction, the particles size of the Ni-Co oxide film decreased from 9 nm to 25 nm, with the increase in Co content. The reduction of the band gap enhanced the film conductivity, resulting in better electrochromic properties. The electrochemical and optical measurements show the excellence of the film in switching time and coloring efficiency: thanks to incorporating Co atoms, the switching time was shortened from 15.2 s to 10.2 s, and the coloring efficiency was increased from 35.57 to 42.5 cm2 C−1. Overall, the proposed film has a promising future for electrochromic applications.