Unlocking Controllable Multi‐Band Emission from a Mn‐Doped Spinel: Ranging from Narrow‐Band Green to Efficient NIR

ABSTRACT Achieving controllable multiple emissions within a single phosphor system remains a challenge due to the divergent host lattice requirements for different luminescent behaviors. In this study, we demonstrate a tunable multimode emission strategy in a MgAlGaO 4 spinel host through regulating the manganese valence state and modulating interionic interactions, with nearly all observed emission originating from Mn 2+ . Under low doping levels, the material can exhibit either narrow‐band green emission with a full width at half maximum of only 27 nm or red emission, depending on the synthesis atmosphere. At high doping levels, significant exchange interactions between Mn 2+ ions lead to effective broadband near‐infrared (NIR) emission, with an impressive external quantum efficiency of 56.8%. This new type of luminescent material has a lot of potential for use in advanced technologies, including displays with a wide color range, night vision, NIR bioimaging, and encrypting information.