Broadband, Enhanced, and Antithermally Quenched Near-Infrared Phosphors via a Cosubstitution Approach

Abstract

Wearable biosensing and food safety inspection devices with high thermal stability, high brightness, and broad near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) could accelerate the next-generation NIR light applications. In this work, NIR La_3-xGd_xGa₅GeO₁₄:Cr³⁺ (x = 0 to 1.5) phosphors were successfully fabricated by a high-temperature solid-state method. Here, by doping Gd³⁺ ions into the La³⁺ sites in the La₃Ga₅GeO₁₄ matrix, a 7.9-fold increase in the photoluminescence (PL) intensity of the Cr³⁺ ions, as well as a remarkably broadened full width at half-maximum (FWHM) of the corresponding PL spectra, is achieved. The enhancements in the PL, PLE intensity, and FWHM are attributed to the suppression of the nonradiative transition process of Cr³⁺ when Gd³⁺ ions are doped into the host, which can be demonstrated by the decay curves. Moreover, the La_1.5Gd_1.5Ga₅GeO₁₄:Cr³⁺ phosphor displays an abnormally negative thermal phenomenon that the integral PL intensity reaches 131% of the initial intensity when the ambient temperature increases to 160 °C. Finally, the broadband NIR pc-LED was fabricated based on the as-explored La_1.5Gd_1.5Ga₅GeO₁₄:Cr³⁺ phosphors combined with a 460 nm chip, and the potential applications for the broadband NIR pc-LEDs were discussed in detail.