Near-Infrared Phosphors with Significantly Improved Luminescence Intensity and Zero-Thermal-Quenching for Light-Emitting Diodes.

The development of near-infrared (NIR) phosphors with augmented luminous efficiency and robust thermal stability holds pivotal importance for high-performance NIR lighting sources. Herein, LnCaGaGeO:Cr (Ln = Lu, Y, and Gd) compounds are successfully synthesized, and the one with Ln = Lu shows the most intense emission. Subsequently, the luminescence properties of LuCaGaGeO:Cr, which are contingent upon the Cr concentration, are meticulously examined. It is found that replacing Ga with Al can remarkably boost the emission intensity of LuCaGaGeO:Cr. Specifically, the emission intensity of LuCaAlGeO:Cr is 3.69-fold that of LuCaGaGeO:Cr. Nevertheless, despite the high emission intensity of LuCaAlGeO:Cr, its thermal stability is rather poor ( = 21.18%). To address this thermal stability issue, a series of LuCaAlGeO:Cr solid solutions are ingeniously designed through the cosubstitution of Ca-Ge by Lu-Al. This innovative design effectively optimizes the electron population and endows the material with thermal quenching characteristics. Significantly, the sample with = 0.3 maintains nearly 100% of its emission intensity at 423 K when compared with that at room temperature, manifesting a rare zero-thermal quenching performance. Finally, NIR LEDs fabricated by using these optimized phosphors display substantial potential for applications in fields such as nondestructive detection and night vision.