A General Ammonium Salt Assisted Synthesis Strategy for Cr3+‐Doped Hexafluorides with Highly Efficient Near Infrared Emissions

Abstract The discovery of highly efficient broadband near infrared (NIR) emission material is urgent and crucial for constructing NIR lighting sources and emerging applications. Herein, a series of NIR emission hexafluorides A 2 BMF 6 :Cr 3+ (A = Na, K, Rb, Cs; B = Li, Na, K, Cs; M = Al, Ga, Sc, In) peaking at ≈733–801 nm with a full width at half maximum (FWHM) of ≈98–115 nm are synthesized by a general ammonium salt assisted synthesis strategy. Benefiting from the pre‐ammoniation of the trivalent metal sources, the Cr 3+ can be more efficiently doped into the A 2 BMF 6 and simultaneously prevent the generation of the competitive phase. Particularly, Na 3 ScF 6 :Cr 3+ (λ em = 774 nm, FWHM ≈ 108 nm) with optimal Cr 3+ ‐doping concentration of 35.96% shows a high internal quantum efficiency of 91.5% and an external quantum efficiency of ≈40.82%. A lighting emitting diode (LED) device with a NIR output power of ≈291.05 mW at 100 mA driven current and high photoelectric conversion efficiency of 20.94% is fabricated. The general synthesis strategy opens up new avenues for the exploration of Cr 3+ ‐doped high efficiency phosphors, and the as‐obtained record NIR output power demonstrates for NIR LED lighting sources applications.