Near-Infrared Emission of Sm²⁺ in Oxynitrides

Near-infrared (NIR) luminescent materials hold promising applications in NIR spectroscopy technologies, but the NIR emitters are largely limited to some transition metals with spin-forbidden transitions that lead to low absorption efficiency of the pumping light. Exploring novel efficient NIR emitters is thus an urgent and challenging task for developing high-efficiency NIR luminescent materials. Here, an interesting NIR emission of Sm2+ is reported in BaAlSi5O2N7, which exhibits both a line spectrum at 682 nm and a broadband centered at 778 nm with a full-width at half maximum (FWHM) of 141 nm. Temperature-dependent photoluminescence spectra and decay curves evidence that the thermally assisted electrons crossover (TAEC) process contributes to the enhancement of the broadband NIR emission. The fabricated NIR phosphor-converted light-emitting diode (pc-LED) shows promising potential as a NIR lighting source and proves robust thermal stability under high-temperature aging test. The present surprising NIR emission from Sm2+ in highly stable oxynitrides opens a way to explore efficient and reliable NIR phosphors that are suitable for commercial LED chips.