Double Sites Occupancy of Mn4+ in Cs2NaAlF6 with Enhanced Photoluminescence for White Light-Emitting Diodes

In this work, we present a novel single-phase red phosphor of Cs2NaAlF6:Mn4+ with two Al3+ lattice sites, which shows two groups of vibrational phonon sidebands and ultra-intense zero phonon line (ZPL) under blue light illumination. The evidences have shown that the interesting spectral features originate from the non-equivalent occupation of Mn4+ for both Al3+ sites, which induces the neighboring cation vacancies surrounding Mn4+ and highly distorted [MnF6] octahedral in the Cs2NaAlF6 host. The luminescent behavior of double sites occupied by Mn4+ can absorb researchers’ interest on novel red-emitting phosphors. Profiting from the photoluminescence (PL) features, superior color rendering index of Ra = 90.3, R9 = 81, and low correlated color temperature of Tc = 3967 K are achieved from white light-emitting diode (LED) by using yellow Y3Al5O12:Ce3+ (YAG) and red Cs2NaAlF6:Mn4+ phosphors as blue light converters. These results suggest that Cs2NaAlF6:Mn4+ for phosphor has a stupendous potential for LED lighting.