Mn⁴⁺-activated Li₃Mg₂SbO₆ as an ultrabright fluoride-free red-emitting phosphor for warm white light-emitting diodes

In this paper, we report on highly efficient Mn⁴⁺-activated double perovskite Li₃Mg₂SbO₆ (LMS) red-emitting phosphors. These LMS:Mn⁴⁺ phosphors can be efficiently excited over a broad wavelength band from 235 nm to 600 nm peaking at 344 nm and 469 nm, and exhibited an intense red emission band with a range from 600 nm to 800 nm centered around 651 nm. The optimal Mn⁴⁺ doping concentration of LMS:Mn⁴⁺ was 0.6 mol% and its internal quantum efficiency can reach as high as 83%. Besides, the thermal quenching effect on the optical property was also analyzed. Finally, a warm white light-emitting diode (WLED) lamp was fabricated by using a 454 nm InGaN blue LED chip combined with a blend of YAG:Ce³⁺ yellow phosphors and the as-prepared LMS:0.6% Mn⁴⁺ red phosphors, which showed bright white light with CIE chromaticity coordinates (0.4093, 0.3725), correlated color temperature (CCT = 3254 K), color rendering index (CRI = 81) and luminous efficacy (LE = 87 lm/W).