Electrodeposited p-type Cu2O thin films at high pH for all-oxide solar cells with improved performance

Highlights: • Cu₂O electrodeposited at pH 13.5 has poorly-defined grains with mixed orientations. • Chemical dissolution becomes significant at high electrodeposition pH. • Solar cell performance is improved with partially merged grains. • Optimal power conversion efficiency of ~1.55% is obtained. • Cu₂O with poorly-defined grains has high electron mobility. -- Abstract: We report the electrodeposition of cuprous oxide (Cu₂O) films from cupric sulfate-lactate electrolytes at high pH 13.5 and their performance in all-oxide fluorine-doped tin oxide/Cu₂O/aluminium-doped zinc oxide solar cells. The deposit grains are found to grow with rather randomly distributed < 111> and < 100> crystal orientations and have a poorly-definded morphology with evidence of chemical dissolution that takes place during the deposition process. Significant improvements in the solar cell performance with high power conversion efficiencies of up to 1.55% is achieved, which is much better that those ( < 0.2%) of solar cells with Cu₂O layer electrodeposited at lower pH. The performance enhancement is primarily attributed to the improved electron transport in the Cu₂O thin film due to partial merging of grains.