Highly efficient and thermally stable broadband near-infrared emitting fluoride Cs2KGaF6:Cr3+ for multiple LED applications

Abstract

Near-infrared (NIR) phosphor-converted light-emitting diode (pc-LED) is a prospective next-generation light source for smart and broadband NIR spectroscopy. However, the improvement of photoluminescence quantum yield and thermal quenching stability is still a crucial challenge for the pc-LED related broadband NIR phosphors. Herein, a highly efficient and thermally stable broadband NIR emitting fluoride phosphor Cs₂KGaF₆:Cr³⁺ is fabricated, which exhibits a full width at half-maximum (FWHM) of 110 nm centered at 782 nm. Notably, the phosphor exhibits an ultra-high internal quantum efficiency (IQE) of 90.2% and excellent thermal stability (I_150 °C = 88.7%). The excellent anti-thermal quenching behavior is attributed to the relatively weak electron–phonon coupling effect in Cs₂KGaF₆:Cr³⁺ with a small Huang–Rhys factor of 2.17. Based on the prominent luminescent properties of the phosphor, a NIR pc-LED with a high photoelectric conversion efficiency of 22.05% is fabricated by combining the phosphor with a commercial blue LED chip. Moreover, the NIR pc-LED manifests distinguished performances in night vision security inspection, non-destructive testing, intelligent identification and biomedical imaging, indicating extensive application prospects for the as-prepared Cs₂KGaF₆:Cr³⁺ phosphor.