Blue-Light-Excitable Broadband Ca3Ga2Ge3O12:Cr3+,Ni2+ Phosphor for the Applications in NIR-II Window
Near-infrared (NIR) phosphor-converted light-emitting diode (pc-LED) light sources in the second NIR window (NIR-II, 1000–1700 nm) have sparked great interest for their emerging applications in non-destructive detection and medical diagnostics fields. However, the development of efficient NIR-II phosphors that can be excited by commercial blue LED chips remains a significant challenge, and thus impeding the applications of NIR pc-LED. Herein, a blue-light-excitable broadband NIR-II luminescence of Ni 2+ is achieved upon incorporating Cr 3+ and Ni 2+ into the Ca 3 Ga 2 Ge 3 O 12 (CGGO) host simultaneously. Through the energy transfer from Cr 3+ to Ni 2+ , CGGO:Cr 3+ ,Ni 2+ phosphor presents the improved NIR-II emission peaking at 1470 nm under 460 nm blue light excitation. The internal/external quantum efficiency values are significantly improved from 13.8%/3.3% to 24.6%/13.3% along with the enhanced luminescence thermal stability. Finally, a NIR pc-LED is fabricated by combining CGGO:Cr 3+ ,Ni 2+ phosphor with 450 nm blue chip, and its potential applications in non-destructive examination and biomedical imaging fields have been demonstrated. The strategy of Cr 3+ and Ni 2+ co-doping solves the problem that Ni 2+ luminescence cannot be effectively excited by blue light and provides the design insights to exploit more ultra-broadband NIR pc-LEDs based on blue LED chips.
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