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.
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