Effect of strontium (Sr) doping on the structural, electronic and optical properties of ZnO, by first-principles calculations

We apply the first principles approach using the GGA-PBE + U approximation to study the effect of Sr doping on the structural, electronic and optical properties of ZnO. The computed results show that the optimized lattice parameters as well as the calculated band gaps of pure ZnO and Sr-doped ZnO (SZO) at low and high concentrations are in good agreement with the experimental data. Electronic investigations show that for low Sr concentrations, the appearance of Sr 5s states at a lower energy level than the Zn 4s states at the bottom of the conduction band, causes a reduction of the band gap. However, by increasing further the Sr content, the band gap increases because the Sr 5s states shift to higher energies. The calculated optical properties improve the optical performance of the SZO systems. Hence these findings provide a theoretical reference for future research on Sr-doped ZnO.