Luminescent properties and LED Application of Broadband Near-Infrared Emitting NaInGe2O6: Cr3+ phosphors

A NIR-emitting Cr3+-activated phosphors (NaInGe2O6: Cr3+) covering whole NIR-I region (700–1200 nm) were successfully designed and prepared via solid-state reaction. XRD and Rietveld refinement verified that the octahedral In3+ site is the preferred site of Cr3+ substitution in NaInGe2O6 structure. The synthesized NaInGe2O6: Cr3+ phosphors exhibit two strong absorption bands at 480 and 700 nm, and show a mountain-like single-band emission at 900 nm with FWHM = 175 nm. The crystal field parameters are calculated using steady-state spectral data, in which a low Dq/B value of 1.89 is obtained and results in this broadband NIR emission. NaInGe2O6: Cr3+ exhibits good emission thermal stability, i.e. 55 % of room temperature intensity at 373 K. Besides, an efficient NIR pc-LED is fabricated and shows NIR output of 25.2 mW@120 mA. This broadband NaInGe2O6: Cr3+ NIR phosphor could be merged into pc-LED package for hand-held spectrometers, security cameras and vivo biomarkers.