Highly Efficient and Stable Narrow-Band Red Phosphor Cs2SiF6:Mn4+ for High-Power Warm White LED Applications

Due to the unique narrow-band red emission and broadband blue light excitation, as well as milder synthesis conditions, Mn4+ ion activated fluoride red phosphors show great promise for white light emitting diode (W-LED) applications. However, as the Mn4+ emission belongs to a spin-forbidden transition (E-2(g) -> (4)A(2)), it is a fundamental challenge to synthesize these phosphors with a high external quantum efficiency (EQE) above 60%. Herein, a highly efficient and thermally stable red fluoride phosphor, Cs2SiF6:Mn4+, with a high internal quantum efficiency (IQE) of 89% and ultrahigh EQE of 71% is demonstrated. Furthermore, nearly 95% of the room-temperature IQE and EQE are maintained at 150 degrees C. The static and dynamic spectral measurements, as well as density functional theory (DFT) calculations, show that the excellent performance of Cs2SiF6:Mn4+ is due to the Mn4+ ions being evenly distributed in the host lattice Cs2SiF6. By employing Cs2SiF6:Mn4+ as a red light component, stable 10 W high-power warm W-LEDs with a luminous efficiency of similar to 110 lm/W could be obtained. These findings indicate that red phosphor Cs2SiF6:Mn4+ may be a highly suitable candidate for fabricating high-performance high-power warm white LEDs.