Thermally Stable Broadband Cr³⁺-Doped RbAl₃P₆O₂₀ Phosphor for Near-Infrared Spectroscopy Applications

The research on near-infrared (NIR) phosphors has become a trending topic, as their optical properties directly impact the performance of the NIR phosphor-converted light-emitting diode (pc-LED). NIR pc-LED has emerged as a multifunctional light source across various fields due to its unique advantages of high penetration and invisibility. Herein, a peculiar broadband NIR-emitting phosphor is presented, RbAl₃P₆O₂₀: Cr³⁺ (RAPO: Cr³⁺), with an NIR emission range from 650 to 1000 nm and peaking at ∼785 nm with a full-width at half-maximum (fwhm) of ∼1900 cm^-1. Gaussian fitting analysis reveals that broadband emission originates from Cr³⁺, occupying two different octahedral sites in the host. The optimized phosphor RAPO: 0.08Cr³⁺ exhibits an internal quantum efficiency of 60% and excellent thermal stability (90% at 423 K). The application of pc-LED devices was evaluated by assembling a RAPO: 0.08Cr³⁺ phosphor with an InGaN-based LED (450 nm), achieving a remarkable NIR output power of 27.9 mW at 120 mA. The results demonstrate that RAPO: Cr³⁺ is an optimistic phosphor for NIR photoelectron (pc-LED) light sources.