Tailoring the physical properties and electrochromic performance of nebulizer spray coated Co3O4 films through copper doping

Pristine and copper (Cu)-doped Co3O4 thin films on glass substrates by nebulized spray pyrolysis method. X-ray diffraction patterns revealed that a decline in crystalline quality and reduction in crystallite size was observed for the films with the increase in Cu doping concentration. The morphology of Co3O4 and Cu-doped Co3O4 thin films was analyzed using scanning electron microscopy. The optical parameters such as band gap, refractive index extinction coefficient and optical dielectric constants of the deposited films were evaluated by UV transmission spectra. Cyclic voltammetry (CV) studies in NaOH solution suggested that integral area of CV curves increased upon Cu inclusion in Co3O4 which suggests that more ion pathways/channels created for efficient ion insertion and extraction. The optimum level of Cu dopant concentration was found to be 6 at. % in Co3O4 which exhibited a maximum coloration efficiency (CE) of 42 cm2/C which is approximately three times larger than pristine Co3O4 film (CE = 15 cm2/C).