Enhanced Photoluminescence in Hybrid Manganese Halides via Halogen Regulation for LED Applications

Organic–inorganic Mn(II)-based halides have aroused a great deal of attention due to their unique optoelectronic properties. Selecting the appropriate valence and size of organic groups and adopting halogen regulation of inorganic genes are two effective strategies to enhance the luminescence properties of Mn(II)-based halides. Herein, two new zero-dimensional (C 8 H 18 N) 2 MnX 4 (X = Cl and Br) compounds were synthesized by choosing monovalent and large N -ethylcyclohexylaminium (C 8 H 17 N + ) to combine [MnCl 4 ] 2– and [MnBr 4 ] 2– tetrahedra, respectively. They exhibit bright green-light emission with maximum peaks centered at 530 and 525 nm and lifetimes of 3.0 ms and 294 μs for (C 8 H 18 N) 2 MnCl 4 and (C 8 H 18 N) 2 MnBr 4, respectively. Amazingly, the photoluminescence quantum yield (PLQY) was significantly enhanced from 33.87% to 81.12% when Cl – was replaced with Br – . Moreover, both crystals exhibit high thermal, environmental, and optical stability. Theoretical calculations reveal that the photoluminescence of both (C 8 H 18 N) 2 MnX 4 (X = Cl and Br) compounds originated from [MnX 4 ] 2– tetrahedra, namely, the radiative recombination of the 4 T 1 → 6 A 1 spin-forbidden transition of Mn 2+ . To demonstrate practical optoelectronic applications, LED devices were assembled by using (C 8 H 18 N) 2 MnX 4 (X = Cl and Br) crystals, exhibiting remarkable color stability. This work not only presents promising applications of (C 8 H 18 N) 2 MnX 4 in solid-state lighting but also provides an effective strategy to design novel Mn(II)-based halides with outstanding photoluminescence.