Unraveling the Near-Unity Narrow-Band Green Emissionin Zero-Dimensional Mn 2+ -Based Metal Halides: A Case Studyof (C 10 H 16 N) 2 Zn 1– x Mn x Br 4 SolidSolutions

Zero-dimensional (0D) Mn2+-based metal halides are potential candidates as narrow-band green emitters, and thus it is critical to provide a structural understanding of the photo-physical process. Herein, we propose that a sufficiently long Mn-Mn distance in 0D metal halides enables the all Mn2+ centers emit spontaneously, thereby leading to near-unity photoluminescence quantum yield. Taking lead-free (C10H16N)2Zn1-xMnxBr4 (x = 0-1) solid solution as an example, the Zn/Mn alloying inhibits the concentration quenching that is caused by the energy transfer of Mn2+. (C10H16N)2MnBr4 exhibits highly thermal stable luminescence even up to 150 °C with a narrow-band green emission at 518 nm and a FWHM of 46 nm. The fabricated white LED device shows a high luminous efficacy of 120 lm/W and a wide color gamut of 104% NTSC, suggesting its potential for liquid crystal displays back-lighting. These results provide a guidance for designing new narrow-band green emitters in Mn2+-based metal halides.