A novel Cs2NbOF5:Mn4+ oxyfluoride red phosphor for light-emitting diode devices

The addition of a red-emitting phosphor to YAG:Ce3+-based white light-emitting diodes (WLEDs) greatly facilitates their applications in the field of high-color-rendering-index warm solid-state lighting. It is highly desirable to develop a red phosphor with satisfactory spectral features and low synthesis cost. In this study, a novel non-rare-earth and nonequivalent doping type of Cs2NbOF5:Mn4+ oxyfluoride red-emitting phosphor with high luminous efficiency was obtained via a facile room-temperature co-precipitation method, and its morphology and luminescent properties were investigated in detail. The Cs2NbOF5:Mn4+ phosphor with micro-rod-like morphology exhibited broad band absorption at blue light region (similar to 474 nm) and narrow bandwidth emissions at red region (similar to 633 nm). The color purity of the Cs2NbOF5:Mn4+ phosphor was calculated to be about 99%, and the internal quantum yield (QY) under 474 nm excitation was 63.4%. The concentration quenching of Mn4+ in Cs2NbOF5 matrix was mainly due to dipole-dipole interactions, and the activation energy of temperature quenching was calculated to be similar to 0.2610 eV. The demonstration of a blue InGaN LED chip in combination with a blend of newly developed Cs2NbOF5:Mn4+ red phosphor and YAG:Ce3+ yellow phosphor greatly decreased the correlated color temperature (CCT) from 6255 to 3517 K while significantly improving the color rendering index (CRI) from 72.5 to 87.5. It deserves to be mentioned that the brand-new matrix to phosphor in the present study can be extended to various niobium/tantalum oxyfluoride series, which is very helpful for developing and designing new red phosphors.