Insights on the Effect of Applied Potential on the Properties of Electrodeposited p-Type Cuprous Oxide (Cu₂O) Thin Films

In this work, the effect of the applied cathodic potential on properties of electrodeposited p-type Cu₂O thin films was investigated. Electrochemical deposition was carried out on indium tin oxide (ITO) substrate from alkaline Cu(II) lactate-based solution at different cathodic potentials (− 0.60 to − 0.80 V vs. Ag/AgCl) without subsequent annealing. It was shown that changing the electrodeposition applied potential could tune both the phase structure and band gap energy of the Cu₂O thin films. The morphological, optical, and structural characterizations of the deposits were carried out using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and UV-VIS spectroscopy, respectively. FESEM observations of the as-prepared deposits revealed uniform, rough and desert rose-like crystallites composed of square or triangular pyramidal and truncated polyhedral morphologies. The XRD investigation showed that the films were crystalline and revealed the presence of two other sub-stoichiometric copper oxide phases (Cu₄O₃ and Cu₆₄O), depending on the applied potential. The crystallite size, evaluated using the Scherer formula, varied tightly with the cathode potential and increased in the − 0.65 to − 0.75 V potential range, indicating that the films are of better crystallization. The optical band gaps, deduced from experimental Tauc plots, were found to be 2.33, 1.98, 2.25, 2.27 and 2.50 eV for thin films deposited at − 0.60, − 0.65, − 0.70, − 0.75 and − 0.8 V vs Ag/AgCl, respectively. A mechanism of the phase formation is proposed and discussed.