An ultra-intense zero phonon line of Mn4+with the low 2E level energy in Rb2LiAlF6

Herein, Rb 2 LiMF 6 :Mn 4+ (M= Al, In) phosphors were prepared by the non-equivalent doping of Mn 4+ . Mn 4+ in Rb 2 LiAlF 6 exhibits an ultra-intense zero phonon line (ZPL) detected at 627 nm, due to the highly-distorted symmetry. In contrast, the ZPL at 625 nm for Rb 2 LiInF 6 :Mn 4+ is very weak. The 2 E energy of Mn 4+ in Rb 2 LiAlF 6 (15,949 cm −1 ) is lower than that in all reported fluoride phosphors, which may be ascribed to the stronger polarization effect of Li + . Compared with Rb 2 LiInF 6 :Mn 4+ (5.07 %), Rb 2 LiAlF 6 :Mn 4+ (6.33 %) has a high internal quantum efficiency (IQE) values of 69.8 % and excellent thermal stability. The white LED packaged with Rb 2 LiAlF 6 :Mn 4+ (6.33 %) exhibits perfect performances with a high color render index (CRI = 92.3) and low color temperature (CCT =3875 K) as well as a high luminous efficiency (LE = 97.1 lm/W). Therefore, this work provides a promising red-emitting phosphor for high-quality white LEDs.