Spray-pyrolysis derived molybdenum-doped zinc oxide films: Insightful studies of multifaceted properties

The current study explores the deposition of thin films of pure zinc oxide (ZnO) and molybdenum-doped zinc oxide (Mo:ZnO) using spray pyrolysis, with Mo doping concentrations of 3 %, 5 %, and 7 %. A comprehensive characterization was conducted employing Raman spectroscopy, energy dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, and electrochemical measurements. This multi-faceted approach aimed to investigate the structural, morphological, optical, and chemical composition of the films. Raman spectra were utilized to assess the structural properties, while EDX and XPS analyses confirmed the presence of Zn, O, and Mo in the synthesized samples, with XPS revealing Mo in the +6 oxidation state in Mo-doped ZnO films. Furthermore, UV–Vis absorption spectroscopy, analyzed via Tauc’s relationship, indicated an increase in the band gap from 3.28 eV to 3.35 eV with increasing Mo content. Photocurrent and Mott–Schottky measurements confirm the n-type character of all deposited films and were in good agreement. Analysis by means of cyclic voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and galvanostatic charge–discharge (GCD) reveal an enhancement in specific capacity (SC) for Mo-doped ZnO compered to undoped ZnO with an increase with Mo concentrations. The highest SCs are obtained for 3 % Mo-ZnO film and were found equal to 37.02 and 113 F/g for v: 10 mV/s and I_GCD: 0.6 A/g respectively.