Ab initio study of the electronic, optical, and water-splitting properties of Fe-doped ZnO monolayer

In this paper, we present the electronic, optical, and water-splitting properties of the Fe-doped ZnO monolayer by the first-principles method. The acquired results demonstrate that the Fe doping induces band level and decreases the band gap of the ZnO monolayer whereas the intrinsic vacancies also induce band levels and enrich the optoelectronic properties. The results of the formation energy validate the Fe doping in ZnO. We observed that the zinc vacancy can be created easily in an oxygen-rich condition, whereas oxygen vacancy is easy to be created when oxygen is poor. The optical properties of Fe-doped ZnO were calculated and the change in optical properties versus incident photons is presented. The relation between the obtained band and density of states (DOS) and the relation between the optical properties and DOS are discussed in detail. We found that the induced band level from Fe and intrinsic vacancies can enhance the optical properties under the visible and near-ultraviolet region. The Zn15FeO16 and Zn14Fe2O16 were taken as an example to demonstrate a water-splitting property of the Fe-doped ZnO monolayer. This work demonstrates that Fe doping and the corresponding intrinsic vacancies can improve the performance of ZnO monolayer-based optoelectronic devices and photocatalysts. This research will advance the practical applications of Fe-doped ZnO monolayer into new territory. •Hubbard U was used in the studies of Fe-doped ZnO monolayer.•Fe improves the absorption in solar energy region.•Intrinsic vacancy improves the absorption in solar energy region.•Fe-doped ZnO monolayer is a promising water-splitting photocatalyst.•We provide the basis for Fe-doped ZnO monolayer applications.