New insights on the luminescence properties and Judd–Ofelt analysis of Er-doped ZnO semiconductor quantum dots

Abstract

In this study, Er³⁺ doped ZnO semiconductor quantum dots (QDs) were synthesized using a wet chemical method. The successful doping of Er³⁺ ions into the ZnO host lattice and the elemental composition was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The ZnO and Er³⁺ doped ZnO QDs with a hexagonal structure, spherical shape, and particle size of approximately 5 nm were revealed by XRD and transmission electron microscopy (TEM). The absorption, luminescence properties, and fluorescence lifetimes of the samples were studied as the concentration of Er³⁺ ions varied. The intensity parameters, emission transition probabilities, branching ratios, and emission lifetimes of the excited levels of Er³⁺ ions in the ZnO host were determined using the Judd–Ofelt theory, which provided insight into the covalent relationship between the ions and ligands as well as the nature of the ZnO host lattice. Moreover, the energy transfer process from the ZnO host to Er³⁺ ions and the yield of this process are explained in detail along with specific calculations. The Er³⁺ doped ZnO QDs displayed a significantly longer lifetime than undoped ZnO, which opens up many potential applications in fields such as photocatalysis, optoelectronics, photovoltaics, and biosensing.