A Thermally Robust Beryl‐Structure Be 3 Al 2 Si 6 O 18 :Cr 3+ Phosphor for Broadband NIR pc‐LEDs

ABSTRACT Cr 3+ ‐activated near‐infrared (NIR) phosphors, featuring tunable emission wavelengths and broadband characteristics, are highly promising for constructing compact phosphor‐converted NIR light sources based on blue light‐emitting diode (LED). However, unlike mature visible emission, blue‐to‐NIR conversion generally suffers from large Stokes losses and significant thermal loading, imposing stringent requirements on the thermal stability of NIR phosphors for long‐term device reliability. Herein, we report a rigid silicate beryl‐structured Be 3 Al 2 Si 6 O 18 :Cr 3+ (BASO:Cr 3+ ) phosphor, in which Cr 3+ ions occupy weak‐crystal‐field [AlO 6 ] octahedral sites, enabling broadband NIR emission peaking at 744 nm. More importantly, the BASO:0.005Cr 3+ phosphor exhibits exceptional thermal stability, retaining over 90% of its integrated emission intensity even at 210°C, outperforming most reported Cr 3+ ‐activated broadband NIR phosphors. The calculated Huang–Rhys factor (S), markedly smaller than those of analogous NIR phosphors, reveals weakened electron–phonon coupling in the rigid lattice, which effectively suppresses thermally activated nonradiative relaxation. Benefiting from the superior luminescence and thermal robustness, the fabricated NIR pc‐LED achieves an excellent photoelectric efficiency of 17% at 10 mA and a maximum NIR output power of 59.5 mW at 150 mA. Proof‐of‐concept demonstrations further reveal the multifunctional potential of this device in plant growth lighting, night vision, nondestructive testing, and qualitative analysis of unknown components.