Coordination units of Mn 2+ modulation toward tunable emission in zero-dimensional bromides for white light-emitting diodes

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 10; no. 6; pp. 2095 - 2102
• Main Authors: Zhou, Guojun, Ding, Jialiang, Jiang, Xingxing, Zhang, Jian, Molokeev, Maxim S., Ren, Qiqiong, Zhou, Jun, Li, Shili, Zhang, Xian-Ming
• Format: Journal Article
• Language: English
• Published: 10.02.2022
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/D1TC05680H

Organic–inorganic metal halides have become a multifunctional platform for manipulating photoluminescence due to highly efficient and tunable emissions, especially for lead-free Mn 2+ -based halides. Herein, the zero-dimensional (0D) bromides of (C 5 H 14 N 3 ) 2 MnBr 4 and (CH 6 N 3 ) 2 MnBr 4 with different coordination environments were designed and synthesized by a solvent evaporation method. They exhibit green and red broadband emission peaks at 528 nm and 627 nm with high photoluminescence quantum yields of 86.83% and 61.91%, respectively, which are attributed to the d–d transition ( 4 T 1 (G) → 6 A 1 (S)) of [MnBr 4 ] 2− tetrahedral and [Mn 3 Br 12 ] 6− octahedral units. The cases emphasize the effect of organic ligands on the intrinsic emissions of Mn 2+ ions, thereby revealing the luminescence mechanism of Mn 2+ ions in 0D isolated structures through the Tanabe–Sugano (TS) energy diagram. Thanks to their bright and stable emissions, the fabricated white light-emitting diode (LED) based on (C 5 H 14 N 3 ) 2 MnBr 4 and (CH 6 N 3 ) 2 MnBr 4 provides an outstanding color rendering index ( R a ) of 90.8 at a correlated color temperature (CCT) of 3709 K, along with the CIE chromaticity coordinates of (0.3985, 0.3979) and a luminous efficacy of 51.2 lm W −1 . This work aims at clarifying the relationship between the coordination units of Mn 2+ and tunable emissions, and in particular, proposes a new strategy to explore phosphors excited by blue light for white LEDs.