Cs2MnF6 Red Phosphor with Ultrahigh Absorption Efficiency

To improve absorption efficiency (AE) and subsequently improve external quantum efficiency (EQE) remains one of the significant challenges for Mn4+-doped red-emitting fluoride phosphors. In this study, we propose to use Mn4+ as a part of matrix to enhance the AE of fluoride phosphors. Red-emission phosphors Cs2MnF6, Cs2MnF6:Sc3+, and Cs2MnF6:Si4+ were synthesized successfully by a coprecipitation method. The Rietveld refinement of X-ray diffraction reveals that this red phosphor exhibits a cubic structure in Fm3̅m space group. Owing to Mn4+ being a part of matrix, this kind of red phosphor possesses an extremely high AE, which can be promoted to 88%. The doping of Sc3+ and Si4+ ions into Cs2MnF6 can effectively increase the luminescence intensity to 253 and 232%, respectively, relative to that of Cs2MnF6. The relative emission intensity of Cs2MnF6:5%Si4+ red phosphor preserves about 115% when temperature rises to 175 °C. By employing Cs2MnF6:5%Si4+ as a red-emitting component, high-performance LED-1 with Ra = 86.2, R9 = 82.1 and CCT = 3297 K, and LED-2 with an ultrawide color gamut (NTSC value of 122.3% and rec. 2020 value of 91.3%) are obtained. This work may provide a new idea to explore a new type of fluoride phosphor with high EQE for high-performance white-light-emitting diodes.