Highly Efficient and Tunable Emission of Lead-Free Manganese Halides toward White Light-Emitting Diode and X-Ray Scintillation Applications

Environmental friendly metal halides have become emerging candidates as energy downconverting emitters for lighting and X-ray imaging applications. Herein, luminescent single crystals of tetramethylammonium manganese chloride (C4H12NMnCl3) and tetraethylammonium bromide ((C8H20N)(2)MnBr4) are synthesized via a facile room-temperature evaporation method. C4H12NMnCl3 and (C8H20N)(2)MnBr4 with octahedrally and tetrahedrally coordinated Mn2+ have correspondingly exhibited red and green emission peaking at 635 and 515 nm both originating from T-4(1)-(6)A(1) transition of Mn2+ with high photoluminescence quantum yield (PLQY) of 91.8% and 85.1% benefiting from their specific crystal structures. Thanks to their strong photoexcitation under blue light, high PLQY, tunable emission spectra, good environmental stability, the white light-emitting diode based on blending of C4H12NMnCl3 and (C8H20N)(2)MnBr4 delivers an outstanding luminous efficacy of 96 lm W-1, approaching commercial level, and shows no obvious photoluminescence intensity degradation after 3000 h under operation. In addition, manganese halides also demonstrate interesting characteristics under X-ray excitation, C4H12NMnCl3 and (C8H20N)(2)MnBr4 exhibit steady-state X-ray light yields of 50 500 and 24 400 photons MeV-1, low detectable limits of 36.9 and 24.2 nGy(air) s(-1), good radiation hardness, and X-ray imaging demonstration with high-resolution of 5 lp mm(-1). This work presents a new avenue for luminescent Mn-based metal halides toward multifunctional light-emitting applications.