Influence of local structure on luminescence dynamics of red emitting ZnO:Eu3+ nanostructures and its Judd-Ofelt analysis

Abstract

Red emitting ZnO:Eu3+ nanostructures were synthesized by co-precipitation method. X-ray diffraction and Raman spectra indicated the formation of hexagonal wurtzite structure with preferential growth along (101) crystal plane. It is found that Eu3+ incorporation alter the morphology of the ZnO:Eu3+ nanostructures from rod to flower-like structures. The existence of trivalent europium ions in the ZnO lattice was confirmed by X-ray photoelectron spectroscopy. A defect-mediated energy transfer pathway from the ZnO host to the Eu3+ ions was identified in ZnO:Eu3+ nanoparticles, when excited with He-Cd laser of wavelength 442 nm. The observed intense red emission was due to intra 4f-4f transitions of Eu3+ ions. The emission intensity of ZnO:Eu3+ nanostructures was found to increase with europium content up to 2 at%, beyond that quenching was observed and is attributed to the multipole-multipole interactions. Life time measurements of all samples revealed the single exponential behaviour of luminescence decay profiles. Higher value of Judd-Ofelt intensity parameter (Ω2) and asymmetric ratio obtained indicated the reduction in symmetry around Eu3+ ions in these phosphors. CIE chromaticity and correlated color temperature analysis of these ZnO:Eu3+ nanoparticles have shown that the emission is in the red region with high color purity.