Understanding and Unveiling the Role of Chlorine Potassium Concentration in Electrochemical Nucleation, Growth, and Properties of p-Type Cu₂O Thin Films

The electrodeposition of Cu₂O thin films was systematically investigated by varying the chloride ion (Cl⁻) concentration in the electrolyte. Current-time transient analysis revealed an increase in the diffusion coefficient (D₀) from 2.09 × 10⁻⁷ cm² s⁻¹ at low Cl⁻ concentration to 3.72 × 10⁻⁶ cm² s⁻¹ at higher Cl⁻ levels, indicating enhanced mass transport and faster growth kinetics. Dimensionless current-time transients compared with the Scharifker-Hills model confirmed progressive nucleation across all conditions, with a decreasing nucleation rate (AN₀) from 21.685 × 10⁶ cm⁻² s⁻¹ to 4.790 × 10⁶ cm⁻² s⁻¹ as Cl⁻ concentration increased. Similarly, the saturation nucleation density (N_sat) declined from 16.980 × 10⁶ cm⁻² to 4.847 × 10⁶ cm⁻², suggesting that higher Cl⁻ concentrations favor larger grain formation by reducing the density of active nucleation sites. X-ray diffraction analysis confirmed the formation of single-phase cubic Cu₂O with a dominant (111) orientation across all samples, with crystallite sizes increasing from 62 nm to 94 nm as Cl⁻ concentration increased. These findings highlight the crucial role of electrolyte composition in controlling the nucleation and growth mechanisms of Cu₂O films, offering valuable insights for optimizing deposition parameters in optoelectronic and energy applications.