Unlocking Chlorine Oxide‐Based Ultra‐Wideband Near‐Infrared Phosphor and Advancing Spectral Performance via Lattice Engineering

Abstract

Near‐infrared (NIR) phosphor‐converted light–emitting diodes (pc‐LEDs) are increasingly used in night vision, surveillance, and biomedicine. A major challenge is to identify a phosphor that efficiently converts blue light into wideband NIR emission. In this paper, a rare‐earth divalent europium (Eu2+)‐activated halogen oxide (Sr3GeO4Cl2) phosphor is unlocked via a high‐temperature solid‐state reaction. The Sr3GeO4Cl2:Eu2+ phosphor emits a wide spectrum (500–950 nm) with a peak at 700 nm when excited by 450 nm blue light. Extended X‐ray absorption fine structure (EXAFS) analysis reveals that the NIR emission primarily originates from Eu2+ ions, and the Eu─O bond length closely resembles the Sr─O bond length. Lattice engineering, specifically Ge/Si cation substitution, increased Eu2+ incorporation into the crystal lattice, boosting luminescence intensity by 75%–122% and quantum efficiency from 15% to 26%. This is related to the combined effect of reduced non‐radiative energy transfer and changes in the local lattice structure of Eu2+. A NIR pc‐LED device using the optimized phosphor showed a photoelectric efficiency of 16.5% and an optical output of 25.07 mW at 100 mA. This study not only explores new Eu2+‐activated NIR phosphors but also highlights the importance of crystal engineering to enhance luminescence properties, guiding future research for efficient NIR pc‐LED development.