Single‐Site Occupancy of Eu²⁺ in Multiple Cations Enables Efficient Ultra‐Broadband Visible to Near‐Infrared Luminescence

Abstract An important challenge in the research and development of compact near‐infrared (NIR) light sources is the discovery of new efficient ultra‐broadband NIR luminescent materials to replace the conventional Cr 3+ ‐doped compounds. Herein, this work reports a divalent europium‐doped Ba 3 GeO 4 Br 2 phosphor that exhibits a high photoluminescence quantum yield of 48.8% and an ultra‐broad emission band ranging continuously from 500 to 1100 nm (full width at half maximum = 202 nm) under near‐ultraviolet or blue light excitation. A strategy of embedding alumina crucible in high purity graphite crucible is devised and deployed during solid‐state sintering to facilitate the conversion of Eu 3+ into Eu 2+ . Theoretical calculations, structural refinement, and spectral analysis demonstrate that the visible to NIR emission in Ba 3 GeO 4 Br 2 :Eu 2+ originates from the Eu 2+ ions occupying the distorted Ba3O 3 Br 4 polyhedra in the lattice. The as‐prepared phosphor‐converted light‐emitting diode device achieves an optical output power of 30.1 mW@100 mA (520–1100 nm) and a photoelectric efficiency of 22%@100 mA (350–1100 nm). Experiments on tissue penetration and NIR imaging illustrate its application in spectral detection and food quality testing appears promising.