A high-efficiency blue-LED-excitable broadband Cr3+/Ni2+ co-doped garnet phosphor toward next-generation spectroscopy applications

Abstract

The performance of near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) mainly depend on NIR phosphors. The energy transfer (ET) from Cr³⁺ to Ni²⁺ is considered an effective method to improve the luminous efficiency of Ni²⁺-activated phosphors. However, most phosphors usually introduce a low concentration of Cr³⁺ ions as a sensitizer, resulting in a limited absorption efficiency. Herein, a Cr³⁺/Ni²⁺ co-doped Ca₃Al₂Ge₃O₁₂ garnet host was designed, which increased the absorption efficiency by heavily doping with Cr³⁺, resulting in a high external quantum efficiency (EQE) of 45.7%. The heavily doped Cr³⁺ ions (15%) acted as a light harvester, selectively transferring the absorbed energy to the Ni²⁺ ions (1%) instead of quenching between Cr³⁺, whereby Ni²⁺ ions effectively extracted the excitation energy to generate NIR-II luminescence. The NIR-II emission intensity of the optimized CAGG:Cr³⁺, Ni²⁺ was enhanced by 17.4 times compared with that of CAGG:Ni²⁺, achieving excellent luminescent thermal stability (73.9%@373 K). Finally, an NIR pc-LED was fabricated by combining the CAGG:Cr³⁺, Ni²⁺ phosphor with a 460 nm commercial blue chip, demonstrating its application potential in the identification and analysis of organic compounds. This study not only provides an efficient broadband NIR-II phosphor but also provides a novel idea to improve the luminescence performance of NIR-II phosphors.