First-principles study of the electronic structure and optical properties of Ce-doped ZnO

Density functional theory calculations by using both generalized gradient approximation (GGA) method and the GGA with considering strong correlation effect (GGA+U) were performed to elucidate the effect of Ce-4f orbit on the electronic structure of ZnO. It is found that after the cerium incorporation, a new localized band appears between the valence and conduction bands, which corresponds to the majority spin of Ce-4f states. It is this localized band that constructs a bridge between the valence and conduction states, which will improve the optical performance of ZnO. ZnO:Ce is a degenerate semiconductor. The strong correlation effect is very important for the 4f orbit of the Ce atom in ZnO:Ce. The mismatch of the majority and minority spin for the Ce-4f, Ce-5d states and the spin-polarized holes in O-2p states induced by Ce doping leads to the presence of the magnetic order for ZnO:Ce. We also studied the band structure and optical properties of ZnO:Ce with lacking one electron and two electrons, respectively. With the deficiency of the electrons, the Fermi level moves downward. The magnetism disappears when the system lacks two electrons. The analysis of optical properties shows that ZnO:Ce is a promising dielectric material and has potential applications in optoelectric devices.