Pentavalent Manganese Luminescence: Designing Narrow-Band Near-Infrared Light-Emitting Diodes as Next-Generation Compact Light Sources

Manganese in the pentavalent state (Mn5+) is both rare and central in materials exhibiting narrow-band near-infrared (NIR) emission and is highly sought after for phosphor-converted light-emitting diodes as promising candidates for future miniature solid-state NIR light source. We develop the Ca14Zn6Ga10–xMnxO35 (x = 0.3, 0.5, 1.0, 1.25, 1.5, and 3.0) series that exhibit simultaneous Mn4+ (650–750 nm) and Mn5+ (1100–1250 nm) luminescence. We reveal a preferential occupancy of Mn in regular octahedral and tetrahedral environments, with the short bond length between these responsible for luminescence. We present a theoretical spin–orbital interaction model in which breaking the spin selection rule permits the luminescence of Mn4+ and Mn5+. A total photon flux of 87.5 mW under a 7 mA driving current demonstrates its potential for real-time application. This work pushes our understanding of achieving Mn5+ luminescence and opens the way for the design of Mn5+-based narrow-band NIR phosphors.