High‐Temperature Stable Narrowband Near‐Infrared Phosphor‐Converted Light‐Emitting Diode Based on Melt‐Grown CsPbCl ₃ : Yb ³⁺ Crystal

ABSTRACT Narrowband near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) featuring low full‐width at half maximum (FWHM) and high conversion efficiency are crucial for chemical content evaluation, light therapy, and bioimaging. Recently, Yb 3+ doped CsPbCl 3 nanocrystals (NCs) have emerged as promising phosphors for NIR pc‐LEDs, delivering narrowband 980 nm emission with an FWHM below 50 nm and a photoluminescence quantum yield (PLQY) exceeding 100%. However, the practical employment of CsPbCl 3 : Yb 3+ NCs is limited by their poor thermal stability. In this work, we present a high‐temperature stable, melt‐grown CsPbCl 3 : Yb 3+ single crystal (SC) and narrowband NIR pc‐LEDs fabricated from CsPbCl 3 : Yb 3+ powder and violet LED chips. Our pc‐LEDs achieve a low FWHM of 46.81 nm and a high conversion efficiency of 2.44% at a drive current of 20 mA. More importantly, our pc‐LEDs exhibit exceptional thermal stability, retaining 98.2% of their PL emission intensity at 360 K. Finally, these NIR pc‐LEDs successfully demonstrate applications in night vision, vein imaging, non‐destructive testing, and the detection of early fruit bruises. This work underscores the significant potential of narrowband 980 nm pc‐LEDs based on CsPbCl 3 : Yb 3+ crystal for diverse applications.