Double Organic‐Ligand Enabled Narrow‐Band Manganese Halides Toward Wide Gamut Displays, Flexible X‐Ray Detection, and 3D Printing Applications

Abstract Hybrid manganese halides, as a novel class of lead‐free family, have been extensively explored. However, achieving a green emission line‐width of less than 40 nm, along with high efficiency and stability, remains rare. Herein, a dual organic cations strategy is demonstrated to reduce emission line‐width and boost stability of A 2 MnBr 4 by employing tetramethylammonium (TMA) and tetramethylammonium (TEA) cations. The [(TMA)(TEA)]MnBr 4 microcrystals, synthesized via mechanochemical method, have an extremely narrow emission line‐width of 39.83 nm, a high photoluminescence quantum yield of 87.57% under 455 nm excitation, a high light yield of 37860 photons MeV −1 under X‐ray irradiation and excellent thermal stability (maintaining 76.56% of the initial emission intensity at 140 °C). The impressive properties are primarily attributed to the low distortion of [MnBr 4 ] tetrahedron, small electron–phonon coupling, and high exciton confinement. The assembled white light‐emitting diode demonstrates an ultra‐wide gamut of 117.9% of the NTSC 1931 standard. The [(TMA)(TEA)]MnBr 4 scintillator films exhibit a high spatial resolution of 14.65 lp mm −1 , and 3D‐printed green‐emitting structures achieve complex information encryption. This work not only introduces the way for obtaining narrow‐band manganese halides but also authenticates its potential applications in wide gamut displays, X‐ray detection, and 3D printing fields.