(615c) Solution Speciation Effects On Electrodeposited Cuprous Oxide Films for Solution-Processed Photovoltaics

Electrodeposited cuprous oxide (Cu₂O) is a p-type semiconductor that holds promise for constructing future photovoltaic devices using solution-based processes that require low energy input, feature benign chemistry, and contain earth abundant materials. Recently, we have successfully demonstrated the electrodeposition of single-phase, polycrystalline Cu₂O thin films from acidic lactate/Cu²⁺ solutions. A distinctive dendritic, flowerlike Cu₂O morphology is observed when films are grown from acidic lactate-based deposition baths; this stands in stark contrast to the faceted, dense films obtained from traditionally used alkaline solutions. Numerical simulation and UV-Vis absorption spectroscopy have been employed to demonstrate key differences in the relative distributions of various metal complex ions present under different growth conditions. Hot point probe measurements confirm the p-type conductivity of all Cu₂O films obtained in this work. Importantly, a short circuit current density of 23 uA/cm² under monochromatic green LED illumination (0.583 mW/cm²) was measured for a Cu₂O film grown at pH 5.3, which was substantially larger than that of a Cu₂O film deposited from basic lactate solution. These findings suggest that gaining a deeper understanding of the effects of metal complex ion speciation on the ultimate optoelectronic properties of electrodeposited Cu₂O films can lead to improved performance for realizing efficient photovoltaic devices with this material.