Optical and structural analysis of rare earth and Li co-doped ZnO nanoparticles

ZnO nanoparticles co-doped with rare earths (RE) and Li were synthesized by the chemical method. The structural properties of the samples were investigated by the X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicated that RE3+ and Li+ ions were incorporated into the lattice of ZnO and nanoparticles formed. Photoluminescence (PL) measurements of RE and Li co-doped ZnO showed two characteristic green emissions that caused by Er3+ inner shell transitions of 2H11/2→4I15/2 and 4S3/2→4I15/2. A schematic of transitions exhibited the transfer of excited energy and the PL enhancement mechanism of co-doped ZnO, in which Gd as a sensibilizer could effectively enhance the luminescence intensity. Moreover, we analyzed the band structures of pure and co-doped ZnO by the full-potential linearized augmented plane wave (FP-LAPW) method, which showed that the Fermi level shifted upward into the conduction band and obtained n-type conductive properties after RE doping.

► We use chemical method to prepare ZnO nanoparticles co-doped with Er, Gd and Li. ► We investigate morphology and luminescence properties of co-doped ZnO samples. ► We illustrate Gd3+ and Li+ play the different roles in the process of photoluminescence enhancement. ► We use first principle method to study the variation of the band gap and Fermi level of rare earth doped ZnO structure.