Polyhedral Symmetry Breaking Strategy Enabled High‐Performance Broadband Near‐Infrared Emission in Cr 3+ ‐Doped Garnet Phosphors

ABSTRACT Conventional understanding holds that structural rigidity is crucial for maintaining thermal stability, while reduced local symmetry is generally believed to compromise structural integrity and thus hinder high quantum efficiency. Challenging this view, we introduced a novel polyhedral symmetry‐breaking strategy in a garnet‐type Lu 3 Al 5 O 12 host via charge‐compensated dual‐site substitution. This tailored symmetry reduction not only preserves thermal robustness but also synergistically enhances the luminescence performance of Cr 3+ , yielding a broad emission with a full width at half maximum (FWHM) exceeding 112 nm, an exceptional external quantum efficiency (EQE) of 37%, and excellent thermal stability retaining 76% of the initial intensity at 423 K. The fabricated phosphor‐converted light‐emitting diode (pc‐LED) exhibits outstanding optoelectronic performance: under a driving current of 350 mA, it delivers an output power of 106.7 mW and a power conversion efficiency ranging from 9.4% to 22.3% at currents of 10–350 mA, significantly surpassing commercial near‐infrared (NIR) LEDs such as the Osram SFH 4737 and Lumileds ONYX. With exceptional performance in night vision and vein imaging applications, this work provides a new material platform and design strategy for developing highly efficient and stable NIR light sources.