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 (C8H18N)2MnX4 (X = Cl and Br) compounds were synthesized by choosing monovalent and large N-ethylcyclohexylaminium (C8H17N+) to combine MnCl42- and MnBr42- 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 (C8H18N)2MnCl4 and (C8H18N)2MnBr4, 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 (C8H18N)2MnX4 (X = Cl and Br) compounds originated from MnX42- tetrahedra, namely, the radiative recombination of the 4T1 → 6A1 spin-forbidden transition of Mn2+. To demonstrate practical optoelectronic applications, LED devices were assembled by using (C8H18N)2MnX4 (X = Cl and Br) crystals, exhibiting remarkable color stability. This work not only presents promising applications of (C8H18N)2MnX4 in solid-state lighting but also provides an effective strategy to design novel Mn(II)-based halides with outstanding photoluminescence.
Shen et al. (2025) studied this question.