Achieving Flat Ultra‐Broadband NIR Emission in Cr 3+ Doped Garnet‐Type Phosphors Enabled by Structural Regulation Toward Multi‐Functional Spectroscopy Applications

Abstract Cr 3+ ‐activated near‐infrared (NIR) emitting phosphors are considered as one of the most potential light‐conversion materials for NIR phosphor converted light‐emitting diodes (NIR pc‐LEDs). However, it is still a challenge for a single Cr 3+ ion to achieve a flat ultra‐broadband emission toward multi‐functional spectroscopy applications. Herein, a chemical unit co‐substituting strategy is utilized to regulate the crystallographic occupancy of Cr 3+ ions, and a flat ultra‐broadband NIR emission is successfully realized with a record emission wavelength of 915 nm in garnet‐type phosphors Ca 3 Sc 2‐ x Hf x Al x Si 3‐ x O 12 : y Cr 3+ (0 ≤ x ≤ 1, 0.02 ≤ y ≤ 0.06), together with a large full width at half maximum (FWHM) regulation from 130 to 250 nm. The relation between the site occupation of Cr 3+ ions in disordered [CaO 8 ], [(Sc, Hf)O 6 ] and [(Si, Al)O 4 ] polyhedrons and the corresponding NIR emission are clarified by carefully evaluating the structural evolution, Raman spectra, electron paramagnetic resonance and time‐resolved emission lifetime spectra of Cr 3+ ions. The corresponding crystal field strength of Cr 3+ ions is investigated to further clarify the multi‐sites induced flat broadband NIR emission. Finally, a blue light pumped NIR pc‐LED is fabricated with a total output power of 37.58 mW and photoelectric conversion efficiency (PCE) of 13.67%@100 mA, which realizes the multi‐functional applications in night vision imaging, non‐destructive detection and palmprint vein recognition for assistant medical treatment.