Linking Macro- And Micro-structural Analysis with Luminescence Control in Oxynitride Phosphors for Light-Emitting Diodes

Eu2+-doped UCr4C4-type oxynitride phosphors are emerging innovative materials to replace oxide and nitride phosphors for high-end light-emitting devices. However, the synthesis of high-purity phosphors and controlling the O/N ratio remain challenging. Here, we synthesized a series of Sr0.98Li2.5 + zAl1.5 - zO3 + 2zN1 - 2z:0.02Eu phosphors by precursor engineering, and these products showed an unexpected redshift from 583 to 620 nm. Joint refinement combining synchrotron X-ray diffraction and neutron powder diffraction was conducted to determine macro-structural properties. Extended X-ray absorption fine structure spectra revealed the micro-structural properties around the luminescent centers. The effects on photoluminescence from the first-shelled O/N ligands and the second-shelled Li/Al ions were demonstrated in detail. Finally, the light-emitting diode packages constructed using our phosphor revealed higher luminous efficiency of radiation and luminous efficacy than the SrLiAl3N4:Eu comparator. This study provided the basis for developing novel oxynitride phosphors and insights into the structural analysis from the macro and micro perspectives.