Theoretical and experimental studies on electronic structure and optical properties of Cu-doped ZnO

In this work, first-principles plane-wave ultrasoft pseudopotential method is employed to investigate band structures, density of states and absorption spectra in pure and Cu-doped ZnO theoretically. In experiment, Cu-doped ZnO crystalline film is synthesized by hydrothermal method. Compared with pure ZnO, the photoluminescence spectrum in Cu-doped ZnO shows that the UV emission peak shifts to lower energy and its intensity decreases. Moreover, there are two more emission peaks centered in blue and green regions. The calculated results show that there is an energy shift both in conduction and valence band which lead to the band gap become narrower in Cu-doped ZnO than that of pure ZnO. Moreover, some impurity levels are calculated near the valence band maximum in theory, which causes two emission peaks centered at about 469 nm and 535 nm observed in PL spectra.