Achieving Flat Ultra‐Broadband NIR Emission in Cr <sup>3+</sup> Doped Garnet‐Type Phosphors Enabled by Structural Regulation Toward Multi‐Functional Spectroscopy Applications
Dongpeng Wang, Liqing Yan, Ge Zhu, Song Ma, N. Zhou, Shanshan Li, Zhuowei Li, Cong Yan, Xue Bai, Xiaoguang Han, Bin Dong
Abstract
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.