Broadband Shortwave Infrared-Emitting Cr- and Ni-Codoped YAlGaO Phosphor with Excellent Thermal Stability for Multifunctional Applications.

Shortwave infrared (SWIR)-emitting materials have emerged as superior light sources with increasing demand for potential applications in noninvasive analysis, night vision illumination, and medical diagnosis. For developing next-generation SWIR phosphor-converted light-emitting diodes (pc-LEDs), the scarcity of intense blue-light-pumped broadband SWIR luminescent materials and poor thermal stability of current Ni-activated phosphors are the ongoing challenges. Here, a blue-light-excitable (440 nm) YAlGaO:Cr,Ni phosphor with ultrawide SWIR emission centered at ∼1430 nm (FWHM ∼264 nm) is reported. The efficient Cr → Ni energy transfer is exploited for a remarkable enhancement of 18-fold in SWIR emission under blue-light excitation. Significantly, the excellent thermal stability (90% at 440 K) of the SWIR band is obtained in the codoped phosphor which is the best among reported SWIR phosphors. Besides, the experimental techniques (XANES and EXAFS) and density functional theory calculations are employed to investigate the local structure and propose [GaO] octahedrons as favorable occupation sites for Ni/Cr ions. A SWIR pc-LED is fabricated using a blue chip as a proof of concept for invisible illumination technology, nondestructive spectroscopic analysis, anticounterfeiting, and imaging applications. This work offers effective insights into energy transfer-assisted SWIR enhancement and presents a thermally robust Cr-Ni-codoped phosphor for designing future mini-SWIR pc-LEDs for spectroscopy applications.