A K₃HF₂WO₂F₄: Mn⁴⁺ oxyfluoride red phosphor with high quantum efficiency for backlight display

The light source of backlight display combined with green/yellow phosphors and K₂SiF₆: Mn⁴⁺ red phosphor is extensively utilized. However, the poor water stability and long fluorescence lifetime (>8 ms) of K₂SiF₆: Mn⁴⁺ restrict its further application. Herein, we prepared a novel oxyfluoride phosphor K 3 HF 2 WO 2 F 4 : Mn 4 + with a short lifetime and excellent luminescent properties via a coprecipitation method. The new crystal structure was investigated by single-crystal X-ray diffraction and theoretical calculations. The theoretical calculations reveal that the Mn⁴⁺ was preferentially incorporated via [MnF₆]²⁻ anionic group substitution, with a lower formation energy than that of the single-atom substitution. The optimized phosphor K 3 HF 2 WO 2 F 4 : Mn 4+ achieves 80.5 % of the commercial K₂SiF₆: Mn⁴⁺ emission intensity. Its internal and external quantum efficiencies are measured to be 93.24 % and 49.15 %, respectively. Its fluorescence lifetime and thermal quenching temperature are 3.98 ms and 383 K. In addition, the phosphor exhibits better water stability, with a luminescence intensity of 86.7 % of the initial intensity maintained after soaking for 6 h after surface modification with oleic acid. The WLED fabricated by using the as-prepared K 3 HF 2 WO 2 F 4 : Mn 4+ red phosphor, the β-SiAlON: Eu 2+ green phosphors and a blue chip achieves a wide color gamut of 110 % NTSC value. All of the results confirm the promising application prospects of the material in backlight display technologies.