Electrochromic Properties of Sol-Gel NiO Films

Electrochromic films of NiO & NiO-TiO2 (with Ti concentrations 5, 10, 15, 20, 25 & 30%) have been prepared bythe sol-gel route using dip coating technique onto fluorine-doped tin oxide-coated glass substrates (FTO/glass).Ethanolic sols from nickel acetate tetrahydrate (Ni(CH3COO)2•4H2O) and titanium isopropoxide precursors wereused in the preparationsd. The nano-sized films were sintered in air between 250 and 300°C. Characteristics ofdifferent films were studied in a comparative manner. Photoluminescence spectra, UV/Visible spectra,electrochromic behavior, cyclic voltammetry, XRD and SEM have been investigated.Typically, as the TiO2 content was increased, film characteristics were enhanced. Then mechanisms of colorationand morphology transformation of the layer during cycling in 0.05 M KOH electrolyte are discussed in terms of anactivation and degradation period. Finally, a used type of electrolyte based on KOH mixed with starch has been alsotested with complete windows.