Insight Into Cr 3+ ‐Activated Oxynitride Near‐Infrared Phosphors

ABSTRACT Oxynitride‐based phosphor have many advantages, such as a wide range of excitation spectrum, high luminous efficiency, good thermal and chemical stability, and no toxicity. In the present work, we successfully synthesized Cr 3+ ‐activated Mg 0.695 Si 0.695 Al 1.39 O 3.65 N 0.35 oxynitride‐based NIR phosphors by a solid‐state reaction method. Under 400 nm excitation, phosphors with increasing Cr 3+ ‐activating contents exhibited a redshift from 685 to 897 nm cause by deceacing crystal strong and the Cr 3+ ‐Cr 3+ pair effect, with an optimal PLQY of ∼76.12%, higher than that of MgAl 2 O 4 :Cr 3+ , but shows poorer thermal stability. Experimental analysis and numerical simulation showed that the mechanism of this unique emission of this phosphor is primarily due to the hybrid Cr─O/N bonding relative to the Cr─O bonding in the oxide and, together with the creation of new occupied states within the bandgap by N incorporation, leads to a highly PLQY; the more polar covalent bonding and weaker bonding strength in the oxynitride octahedra also result in poorer thermal stability of the luminescence compared with the oxide phosphor. We also demonstrated an oxynitride‐based NIR pc‐LED device for potential applications in night‐vision, non‐visual imaging, and lighting agriculture. Our study is the insight on the Cr 3+ ‐activated oxynitride‐based phosphors, and it shows clear implications for potential applications in promising fields.