Heavy Mn2+ Doped MgAl2O4 Phosphor for High‐Efficient Near‐Infrared Light‐Emitting Diode and the Night‐Vision Application

Abstract

Photoluminescence originated from doped activators in the solid state materials usually faces the challenge of concentration quenching, restricting the further increase of photoluminescence intensity. Herein, a new strategy is demonstrated by the heavy doping Mn 2+ into MgAl 2 O 4, leading to the broad‐band near‐infrared (NIR) emission peaking at ≈825 nm with a full width at half maximum of ≈125 nm, as well as high internal quantum efficiency of ≈53% upon 450 nm laser excitation. Density functional theory calculation and extend X‐ray absorption fine structure provide a understanding of Al 3+/Mn 2+ disorder and Mn 2+–Mn 2+ aggregation in spinel Mg 1–x Al 2 O 4:x Mn 2+ with high Mn 2+ content, which enables the formation of superexchange coupled IV Mn 2+–VI Mn 2+ pair. The NIR light‐emitting diodes fabricated by the 450 nm blue chip and Mg 0.50 Al 2 O 4:0.50Mn 2+ phosphor gives a high NIR output power of ≈78.41 mW under a driven current of 120 mA, and night‐vision application as light source in the dark is demonstrated. This work opens new paths for rational design of efficient broad‐band NIR emitting phosphor, and also provides new insights into the Mn 2+ luminescence and the applications.