Mn⁴⁺ non-equivalent doped fluoride phosphors with a short fluorescence decay time for backlighting

The non-equivalent doping of Mn⁴⁺ in red-emitting fluoride phosphors effectively shortens the fluorescence lifetime. Herein, we successfully synthesized Rb₂NaInF₆:Mn⁴⁺ phosphors by an ion-exchange method. The compensation mechanism of Mn⁴⁺ local symmetry and charge balance in the phosphor were studied in detail by theoretical calculations based on density functional theory. The phosphor Rb₂NaInF₆:Mn⁴⁺ (5.59 mol%) exhibits intense red emission with a short fluorescence lifetime (1.45 ms). Meanwhile, it has excellent colour stability and thermal quenching stability at elevated temperatures. Using Rb₂NaInF₆:Mn⁴⁺, β-SiAlON:Eu²⁺ and a blue-emitting GaN chip as red, green, and blue components, the white light-emitting diode (w-LED) exhibits a wide colour gamut of 94.1% of the National Television System Committee (NTSC) standard value. So, this work provides valuable information to investigate novel red-emitting fluoride phosphors for LED backlighting.