Red Emission Stimulated by Electric-Dipole Transition of Eu³⁺–Co-Doped MgAl₂O₄:Sm³⁺ Nanophosphors Synthesized via Sol–Gel Method: A Promising Colour Purity for w-LEDs Applications

Among the many notable features that have attracted attention to white light-emitting diodes (w-LEDs) are their exceptionally high energy conversion efficiency, long operational life and compliance with sustainable development principles. Herein, we report a promising colour purity for w-LED applications that was derived from MgAl₂O₄:Sm³⁺,Eu³⁺ red-emitting phosphors. x-ray powder diffraction confirmed the face-centred cubic crystal structure of MgAl₂O₄:Sm³⁺,Eu³⁺ with crystallite sizes ranging from 7 to 11 nm. Scanning electron microscopy, transmission electron microscopy and energy-dispersive x-ray spectroscopy confirmed the agglomerated nanoparticles and elemental composition of the phosphor material, respectively. Diffuse reflectance spectra, with the aid of the Kubelka–Munk function, approximated the bandgap, and the concept of the Burstein–Moss effect was unpacked. Photoluminescence studies confirmed the emissions from europium and samarium. Moreover, a Gaussian fit was performed on host emission spectra to verify the existence of defects. Dipole-quadrupole interactions were accountable for concentration quenching in the luminosity intensity. A relatively high colour purity (~99.7%) and relatively low correlated colour temperature (CCT) values were calculated from the nanophosphors. Thus, the fabricated red-emitting phosphors are appropriate for w-LEDs because of their appropriate colour rendering qualities, lower CCT values and good colour purity. In addition, a promising quantum efficiency, lifetimes and relatively good thermal stability enables these phosphors for practical applications in light-emitting materials.