Effect of Eu doping on the photoluminescence properties of ZnO nanophosphors for red emission applications

A simple and efficient combustion method was used to synthesize undoped ZnO and europium (Eu ³⁺ ) doped ZnO or ZnO:Eu ³⁺ nanophosphors (NPr). The X-ray diffraction pattern shows that the ZnO:Eu ³⁺ consists of a single phase wurtzite structure. The X-ray photoelectron spectra suggest that there were Eu ³⁺ ions present in the matrix of the sample at the lower concentration of Eu ³⁺ and confirmed the formation of Eu ₂ O ₃ at higher doping concentrations. ZnO native defect and Eu ³⁺ f-f transition related emissions were observed under excitation by a 325 nm He-Cd laser. The Judd-Ofelt intensity parameters (Ω _t (t = 2, 4)) were estimated from the photoluminescence data. The value of Ω ₂ at higher doping concentration (5 and 6 mol% of Eu ³⁺ ) was found to be higher than Ω ₄ , pointing to more covalency and asymmetricity of Eu ³⁺ ions with ligands in the ZnO host. These ZnO:Eu ³⁺ NPrs have the potential for applications as source of red light in light emitting devices.