Regulating Near-infrared Luminescence of ZnGa2O4:Cr3+ via F/O Anion Substitution

The ZnGa2O4:xCr3+, yMgF2 phosphors were synthesized using the high-temperature solid-state reaction method, and their phase structure and luminescence properties were investigated. The results show that F ions play a crucial role in MgF2 doping, which substitute for O anions to form multiple Cr3+ centers of [CrO6] and [Cr(O, F)6] with different local environments, thereby significantly broadening the emission spectra of ZnGa2O4:Cr3+. Furthermore, tunable emission bands peaking from 689 nm to 900 nm are achieved by increasing the Cr3+ concentration. Steady-state and transient-state spectroscopic analysis shows that the energy transfer between multiple Cr3+ centers accounts for the significant red-shift of emission bands with increasing the Cr3+ concentration. The optimized sample ZnGa2O4: 0.1Cr3+, 0.2MgF2 (ZMGOF:0.1Cr3+) exhibits a broadband near-infrared (NIR) emission ranging from 700 nm to 1 200 nm under the blue light excitation, with a maximum emission wavelength of 885 nm and a full width at half maximum(FWHM)of 215 nm. Meanwhile, the ZMGOF:0.1Cr3+ phosphor shows high luminescent efficiency and good thermal stability, for which an internal (external) quantum efficiency of 92.3% (48.1%) is achieved and 89.6% of the initial intensity can be maintained at 100 ℃. By combining the ZMGOF:0.1Cr3+ phosphor with the blue chip, a pc-LED device was fabricated with a NIR output power of 34.5 mW and an energy conversion efficiency of 12.3% at 100 mA driving current. © 2024 Editorial Office of Chinese Optics. All rights reserved.