Blue‐Light‐Excitable Broadband Ca₃Ga₂Ge₃O₁₂:Cr³⁺,Ni²⁺ Phosphor for the Applications in NIR‐II Window

Abstract

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 Ni2+ is achieved upon incorporating Cr3+ and Ni2+ into the Ca3Ga2Ge3O12 (CGGO) host simultaneously. Through the energy transfer from Cr3+ to Ni2+, CGGO:Cr3+,Ni2+ 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:Cr3+,Ni2+ phosphor with 450 nm blue chip, and its potential applications in non‐destructive examination and biomedical imaging fields have been demonstrated. The strategy of Cr3+ and Ni2+ co‐doping solves the problem that Ni2+ 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.