Luminescence tuning in a zero-dimensional organic–inorganic hybrid metal halide family of (C7H18N2)MBr4 (M = Cd, Zn, and Mn)

Abstract

The increasing demands in optoelectronic applications have driven the advancement of organic–inorganic hybrid metal halides (OIHMHs), owing to their exceptional optical transparency and high luminescence performance. In this work, three zero-dimensional OIMH single crystals of (C₇H₁₈N₂)MBr₄ (C₇H₁₈N₂ = 1-propylpiperazine, M = Cd, Zn, and Mn) were prepared via a facile saturated crystallization method with adjustable luminescence properties. (C₇H₁₈N₂)MnBr₄ displays intensive green light emission with the highest photoluminescence yield (PLQY) of 54.93% originating from the d–d transition of Mn²⁺. Due to filled d orbital configurations of Zn²⁺ and Cd²⁺, (C₇H₁₈N₂)CdBr₄ and (C₇H₁₈N₂)ZnBr₄ exhibited blue light owing to their stronger self-trapped excitons (STEs) recombination. Furthermore, (C₇H₁₈N₂)CdBr₄ and (C₇H₁₈N₂)ZnBr₄ exhibited another red luminescence band after grinding, originating from defect-induced STEs. In addition, due to their excellent PL performance, the white LED fabricated based on (C₇H₁₈N₂)MnBr₄ and (C₇H₁₈N₂)ZnBr₄ has demonstrated a high color rendering index (CRI) of 88.2. This work not only provides a strategy for optimizing the photoluminescence performance by modulating metal ions within the same crystal structure of OIHMHs, but also provides insights into both intrinsic STE emission and the design of high-performance luminescent materials.