Broadband\nShortwave Infrared-Emitting Cr<sup>3+</sup>- and Ni<sup>2+</sup>-Codoped\nY<sub>3</sub>Al<sub>2</sub>Ga<sub>3</sub>O<sub>12</sub> Phosphor with\nExcellent Thermal Stab

Shortwave infrared (SWIR)-emitting\nmaterials have emerged as superior\nlight sources with increasing demand for potential applications in\nnoninvasive analysis, night vision illumination, and medical diagnosis.\nFor developing next-generation SWIR phosphor-converted light-emitting\ndiodes (pc-LEDs), the scarcity of intense blue-light-pumped broadband\nSWIR luminescent materials and poor thermal stability of current Ni<sup>2+</sup>-activated phosphors are the ongoing challenges. Here, a\nblue-light-excitable (440 nm) Y<sub>3</sub>Al<sub>2</sub>Ga<sub>3</sub>O<sub>12</sub>:Cr<sup>3+</sup>,Ni<sup>2+</sup> phosphor with ultrawide\nSWIR emission centered at ∼1430 nm (FWHM ∼264 nm) is\nreported. The efficient Cr<sup>3+</sup> → Ni<sup>2+</sup> energy\ntransfer is exploited for a remarkable enhancement of 18-fold in SWIR\nemission under blue-light excitation. Significantly, the excellent\nthermal stability (90% at 440 K) of the SWIR band is obtained in the\ncodoped phosphor which is the best among reported SWIR phosphors.\nBesides, the experimental techniques (XANES and EXAFS) and density\nfunctional theory calculations are employed to investigate the local\nstructure and propose [GaO<sub>6</sub>] octahedrons as favorable occupation\nsites for Ni<sup>2+</sup>/Cr<sup>3+</sup> ions. A SWIR pc-LED is fabricated\nusing a blue chip as a proof of concept for invisible illumination\ntechnology, nondestructive spectroscopic analysis, anticounterfeiting,\nand imaging applications. This work offers effective insights into\nenergy transfer-assisted SWIR enhancement and presents a thermally\nrobust Cr<sup>3+</sup>–Ni<sup>2+</sup>-codoped phosphor for\ndesigning future mini-SWIR pc-LEDs for spectroscopy applications.