Microstructure and optoelectronic properties of Cu–Li codoped ZnO film: Role of CuZn and Lii defects

Abstract Wurtzite Cu–Li codoped ZnO (Cu–Li:ZnO) films with Cu concentrations of 0–3 at.% were grown by sol–gel method. The conductivity, band gap and transparency of the Cu–Li:ZnO films decrease with increasing the Cu concentration due to the substitution of Cu for the Zn sites (Cu Zn ) and the interstitial Li atoms (Li i ). The Cu Zn defects generate a fully occupied impurity band above the valance band maximum (VBM), resulting in an upward shift of the VBM and a decrease of the band gap. The Cu Zn acceptors can compensate for the Li i donors and further form complex self-compensation defects [Cu Zn  + Zn i ]. The carrier mobility of the Cu–Li:ZnO film is about 2–5 orders of magnitude lower than that of the intrinsic one due to the grain boundary and surface scattering.