Mn4+-activated red phosphors have attracted considerable attention as promising red components in the spectra of white light emitting diodes (WLEDs) to achieve warm white light with superior performance.

A novel red fluoride phosphor NKSF:Mn was obtained at room temperature by controlling the ratio of NaF to KF. The chromaticity coordinates of phosphor NKSF:Mn are very close to the CIE coordinates of ideal red ascribed to the contribution of particularly strong zero-phonon lines.

In most Eu activated phosphors, only red luminescence from the D is obtainable, and efficiency is limited by concentration quenching. Herein we report a new phosphor of CaLaO(BO):Eu (CLBO:Eu) with advanced photoluminescence properties. The yellow luminescence emitted from the D states is not thermally quenched at room temperature. The relative intensities of the yellow and red emission bands depend strongly on the Eu doping concentration. More importantly, concentration quenching of Eu photoluminescence is absent in this phosphor, and the stoichiometric compound of CaEuO(BO) emits stronger luminescence than the Eu doped compounds of CLBO:Eu; it is three times stronger than that of a commercial red phosphor of YO:Eu. Another beneficial phenomenon is that ligand-to-metal charge transfer (CT) transitions occur in the long UV region with the lowest charge transfer band (CTB) stretched down to about 3.67 eV (∼330 nm). The CT transitions significantly enhance Eu excitation, and thus result in stronger photoluminescence and promote trapping of excitons for persistent afterglow emission. Along with structure characterization, optical spectra and luminescence dynamics measured under various conditions as a function of Eu doping, temperature, and excitation wavelength are analyzed for a fundamental understanding of electronic interactions and for potential applications.

Two red micro-crystal phosphors: (NH4)2TiF6:Mn4+and (NH4)2SiF6:Mn4+have been obtained through ion exchange at room temperature for a few hours. The reaction mechanism and luminescence properties of them have been comprehensively invested.