LAUSR

We used the CASTEP program with a GGA+U method to study the effects of Cu doping on the formation energy, electronic and optical properties of V-doped ZnO. The calculated enthalpies show that Cu inclines stay near V. The formation energy shows Cu and V codoping is easy to form in an oxygen atmosphere. Vanadium introduces an impurity band level and Cu widen the level. The relation between the band and density of states (DOS) has been discussed. The calculated absorption coefficient (α(ω)) shifts to lower energy (red shift). The absorption coefficient also has a broad increased peak in the green energy region (around 530 nm). We also calculated the other optical constants of Cu and V codoped ZnO. The relation between the optical properties and DOS has been discussed. Our calculations not only can explain the experiment and but also clarify the mechanism and role of Cu on the optical properties of V-doped ZnO. Our study provides a reference and method for improving codoping content and absorption in the visible region of V-doped ZnO. We also provide a reference in designing optical devices base on V-doped ZnO.