Multi-sites energy transfer in Fe³⁺-doped KAl₁₁O₁₇ phosphor toward zero thermal quenching near-infrared luminescence

Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) have demonstrated great potential for optoelectronic and biomedical applications, while the exploration of NIR phosphors with high thermal stability remains a challenge. Herein, we report an NIR phosphor KAl11O17:Fe3+ with zero thermal quenching (TQ) behavior up to 200°C. The asymmetrical broadband NIR emission with three sub-bands centered at 700, 770, and 800 nm is related to the superposition of different Fe3+ emission centers located in Al2O4, Al3O6, and Al4O6 sites of the KAl11O17 host, respectively. Temperature- and Fe3+ concentration-dependent emission spectra verify that the energy transfer (ET) between multiple Fe3+ emitters and the weak electron–phonon coupling (EPC) effect contribute to the thermally stable broadband NIR emission. The fabricated NIR pc-LED using optimized KAl11O17:Fe3+ phosphor exhibits great potential in information encryption applications.