Role of solution chemistry in determining the morphology and photoconductivity of electrodeposited cuprous oxide films

Electrodeposition of single-phase, crystalline Cu₂O thin films is demonstrated using acidic lactate/Cu²⁺ solutions. Relative speciation distributions of the various metal complex ions present under different growth conditions are calculated using reported equilibrium association constants and supported experimentally by UV-vis absorption spectroscopy. Cu₂O films grown from acidic lactate solutions can exhibit a distinctive flowerlike, dendritic morphology in contrast to the faceted, dense films obtained using alkaline lactate solutions. Dependence of thin film morphology on the lactate/Cu²⁺ molar ratio and the applied potential is described. Hot point probe measurements have been used to determine the p-type conductivity of these Cu₂O films. A short circuit current density of 23 μA/cm² under 0.583 mW/cm² monochromatic green light emitting diode (LED) illumination was measured for a Cu₂O film grown at pH = 5.27, which was substantially larger than that of a Cu ₂O film deposited under basic conditions.