Effect of alkaline-doping on photoelectrochemical activity of electrodeposited cuprous oxide films

P-type Cu2O films with alkaline ions (Li+, Na+ and K+) of unintentional dopants on indium tin oxide coated glass substrate are successfully fabricated via a simple electrodeposition method for photoelectrochemical (PEC) hydrogen generation. The SEM and XRD analysis show the as-grown films with the pyramid-like morphology and cubic structure, and the composition of alkaline-doped Cu2O films are examined using XPS spectroscopy to demonstrate the substitution of alkaline ions in the Cu2O lattice. The optical analyses, including the absorbance and low-temperature photoluminescence spectra, confirm a bandgap of 2.3 eV and the presence of structural defects in alkaline-doped Cu2O films. The Mott-Schottky plot shows the flat band potentials of the alkaline-doped Cu2O films to be approximately −0.1 V and the hole concentrations in the order of 1017 cm−3. Significantly, the Cu2O:Li film photocathode exhibits a higher photocurrent of −2.2 mA cm−2 at a potential of −0.6 V vs Ag/AgCl which are greater than those of Cu2O:K and Cu2O:Na films due to greater preferred orientation degrees along (111) and less structural defects, because the ionic radii of Cu and Li is similar. These results demonstrate the great potential of alkaline doped Cu2O films in solar-related applications.