Nanocrystalline SrS:Ce³⁺ system for the generation of white light-emitting diodes

Nanocrystalline SrS phosphors doped with Ce³⁺ ions at different concentrations (0.5, 1, 1.5 and 2 mol%) are synthesized via the solid-state diffusion method (SSDM), which is suitable for the large-scale production of phosphors in industrial applications. The as-prepared samples are characterized using an X-ray diffraction (XRD) technique, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray (EDX) analysis. The optical properties of these phosphors are analyzed using reflectance spectra, photoluminescence spectra and afterglow decay curves. The cubic structure of the SrS phosphor is confirmed by XRD analysis and the crystallite size calculated by Scherer's formula using XRD data shows the nanocrystalline nature of the phosphors. No phase change is observed with increasing concentrations of Ce³⁺ ions. The surface morphology of the prepared phosphors is determined by FESEM, which shows a sphere-like structure and good connectivity of the grains. The authenticity of the formation of nanocrystalline phosphors is examined by HRTEM analysis. Elemental compositional information for the prepared phosphors is gathered by EDX analysis. Photoluminescence studies reveal that the emission spectra of the prepared phosphor shows broad band emission centered at 458 and 550 nm due to the transition of electrons from the 5d → 4f energy levels. The afterglow decay characteristics of different as-synthesized SrS:Ce³⁺ nanophosphors are conceptually described. Copyright © 2016 John Wiley & Sons, Ltd.