Characterization and electrochromic properties of NiO thin films prepared using a green aqueous solution by pulsed spray pyrolysis technique

Nickel acetylacetonate of 0.2 M aqueous solution is used to synthesize (NiO) thin films by pulsed spray pyrolysis method onto glass substrates. Structural and morphological properties of the deposited films were examined using (XRD) and (FESEM) techniques. The results revealed that at low substrate temperatures and short spray time, the obtained films were amorphous, whereas the films deposited at higher temperatures and long spray time has a cubic phase. Cross-sectional FESEM is used to properly estimate films thicknesses. The energy band gap is calculated to be 3.52–3.89 eV using optical spectrum measurements. Electrochromic properties of NiO films deposited on FTO working electrode substrates are measured in a three-electrode cell containing KOH with Ag/AgCl reference electrode at a scan rate of 20 mV/s. The charge density increases with the thickness, and it is 98.0 mC/cm 2 at the thickness of 360 nm after 30-min deposition time at 400 °C and for most of the samples the film stability increases after cycling. Graphical abstract