Considerable improved near-infrared luminescence in ionic-free doped ZnAl2O4 by oxygen defects engineering

Recently, the phosphor for near-infrared LED is of importance, and a lot of the researches have been attracted on the synthesis and composition design. However, the large number of researches for near-infrared luminescent materials mainly focus on activator ions doped inorganic materials, including rare earth ions and transition metal ions. Here, an ionic-free doped NIR phosphor of ZnAl 2 O 4 is proposed for NIR LED through oxygen defects engineering. The spinel-structured ZnAl 2 O 4 phosphors with deficiency of zinc were synthesized by high temperature solid state reaction, which were characterized by a series of techniques, including XRD, UV–Vis, XPS, EPR, DFT calculation, PLE/PL spectroscopy, and temperature-dependent PL spectra analysis. The deficiency of zinc results in the appearance of zinc vacancy (V Zn ) and oxygen vacancy (V O ). Most of the oxygen vacancy is V O + , along with a small content of V O ++ in ZnAl 2 O 4 . Under the excitation of ultraviolet light at 302 nm, the phosphor outputs a broad near-infrared emission band with the maximum at 715 nm. Higher concentration of zinc deficiency leads to stronger near-infrared luminescence, because of the increased oxygen vacancy. The phosphors exhibited a good thermal stability, and they were successfully packaged on the 285-nm UV LED chip, which outputted bright and intense near-infrared light, indicating that the NIR phosphors synthesized in this work have the prospect application in NIR LED. • Spinel-structured ZnAl 2 O 4 phosphors with zinc deficiency were synthesized. • The zinc deficiency results in the appearance of zinc vacancy and oxygen vacancy. • The phosphor outputs a near-infrared emission and has a good thermal stability. • The phosphors have the prospect application in NIR LED.