Be2+‐Induced Red Emission Enhancement in CaAl12O19:Mn4+ for Wide Color Gamut Display: Suppressing Self‐Reduction of Mn4+ to Mn2+

Abstract

AbstractMn4+‐activated CaAl12O19 (CAO: Mn4+) is recognized as a promising candidate for red phosphor used in wide color gamut displays. However, the spontaneous self‐reduction of Mn4+ to Mn2+ occurs for charge compensation through Mn2+‐Mn4+ substitution for Al3+‐Al3+, lowering the quantum efficiency of Mn4+. To suppress the self‐reduction, some divalent metal ions, including Ba2+, Sr2+, Cd2+, Zn2+, and Mg2+, are added for charge compensation instead of Mn2+, but only small luminescence enhancement is observed. In this paper, remarkable luminescence enhancement in CAO: Mn4+ via co‐doping Be2+ is reported. The photoluminescence properties are studied as a function of Be2+ doping concentration, and the optimal Be2+ concentration of 0.01 is found. The internal quantum efficiency of 74.9% and external quantum efficiency of 56.3% are achieved under UV excitation, higher than those via co‐doping other divalent metal ions. This study indicates that the addition of Be2+ dominates the charge compensation because Be2+ is closer to Al3+ in size than Mn2+ and other divalent metal ions. The backlight light‐emitting diodes using CAO: Mn4+, Be2+ are fabricated, exhibiting a 110.1% Nation Television Standards Committee (NTSC) color gamut, wider than both the current commercial backlight using K2SiF6: Mn4+ (KSF) red phosphor and the conventional one using YAG yellow phosphor.