Deposition Time-Dependent Electrochemical Evolution of p-Type Cu₂O Thin Films: Probing Cu²⁺ Ion Diffusion, Nucleation Kinetics, Electrochemical Impedance, and Photo-Response

Abstract This study investigates the electrodeposition of Cu₂O thin films on fluorine-doped tin oxide substrates, focusing on the effects of deposition time on their structural, optical, and electrochemical properties. The electrochemical characterization led to insights into the nucleation and growth mechanisms of Cu₂O, as identified through cyclic voltammetry and chronoamperometry. X-ray diffraction analysis confirmed the formation of cubic Cu₂O, revealing a preferential (111) orientation, particularly prominent at longer deposition times. Optical studies indicated a decrease in the bandgap energy from 2.33 to 2.21 eV with increasing deposition time, attributed to improved crystallinity and the introduction of defect states. Atomic force microscopy showed that surface roughness increased from 17.23 to 26.025 nm as deposition time extended from 300 to 1200 s. Furthermore, electrochemical impedance spectroscopy demonstrated enhanced charge transfer capabilities, with a reduction in charge transfer resistance (Rct) from 2.96 to 1.14 × 10³ Ω·cm², highlighting the impact of deposition time on the electrochemical performance of the thin films.