Band Gap Reduction of ZnO for Photoelectrochemical Splitting of Water

We combine first-principles density functional theory, material synthesis and characterization, and photoelectrochemical (PEC) measurements to explore methods to effectively reduce the band gap of ZnO for the application of PEC water splitting. We find that the band gap reduction of ZnO can be achieved by N and Cu incorporation into ZnO. We have successfully synthesized ZnO:N thin films with various reduced band gaps by reactive RF magnetron sputtering. We further demonstrate that heavy Cu-incorporation lead to both p-type doping and band gap significantly reduced ZnO thin films. The p-type conductivity in our ZnO:Cu films is clearly revealed by Mott-Schottky plots. The band gap reduction and photoresponse with visible light for N- and Cu-incorporated ZnO thin films are demonstrated.