Fast response Sc3+-sensitized K2NbF7:Mn4+ phosphors with high luminescence intensity and moisture resistance selected by DFT calculations

Mn4+-activated fluoride phosphors exhibiting broadband excitation and sharp line emission within the sensitivity range of the human eye are extensively utilized as supplementary red phosphors for white light-emitting diodes (WLEDs), and the K2SiF6:Mn4+ phosphor has achieved considerable commercial success. However, the K2SiF6:Mn4+ phosphor has defects in long fluorescence decay life and poor moisture resistance owing to its Mn-doped fluoride composition, which severely restricts its application in fast response commercialized backlight LEDs. Hence, we selected the monoclinic crystal K2NbF7:Mn4+ phosphor with higher zero phonon line (ZPL) emission. Using density functional theory (DFT) calculations, we identified the optimal sensitizer Sc3+ and improved the original synthesis method to develop a new K2NbF7:0.06Mn4+-0.02Sc3+ (KNFMSc) phosphor successfully. The KNFMSc phosphor has an integral luminescence intensity 2.63 times that of K2SiF6:Mn4+, superior moisture resistance performance, which is characterized by maintaining 60.78 % of its initial luminescence intensity after a 12 h water immersion, and a faster fluorescence decay lifetime of 3.79 ms. After being assembled into LEDs, the KNFMSc phosphor emits warm white light with a color rendering index of 93.5 and a correlated color temperature of 3924 K, representing enhanced luminous stability under varying driving currents. Therefore, the prepared KNFMSc phosphor holds considerable potential for application in WLEDs and backlighting LEDs, offering a new alternative to commercial phosphors.