Tunable Dimensionality and Emission of Organic Metal Halides by Denser Stacking of Pb–Br Polyhedra

Organic metal halides (OMHs) have attracted extensive research interests due to their interesting photoluminescent properties. However, to date, most OMHs have been synthesized through the trial-and-error method, and it remains a big challenge to control the molecular-level structures through directed synthetic approaches to rationally optimize luminescence properties. In this work, we proposed a crystal structure modulation strategy to control the dimensionality and optical properties of OMHs by increasing the packing density of Pb–Br octahedra via altering the precursor stoichiometry. By precisely adjusting the ratio of 3-aminomethylpyridine to PbBr2 in the initial reactants, (C6N2H10)2PbBr6 (0D-J1) with a 0D structure, (C6N2H10)­PbBr6 (2D-J2) with a 2D structure, and C3NH5PbBr (3D-J3) with a 3D structure were successfully synthesized. 0D-J1 exhibits a bright broadband yellow emission with a photoluminescence quantum yield (PLQY) of 35.40%. 2D-J2 shows a free exciton narrowband emission at room temperature and self-trapped excitons (STEs) emission at low temperatures. 3D-J3 displays a permanent defect state broad emission at room temperature. Additionally, the synthesis of compounds from the T series and P series with different dimensionalities further verifies the general applicability of this strategy. This strategy enables the directed control of the structure and optical properties of LD-OMHs while preserving the functionality of organic cations, and paves an avenue for designing and synthesizing LD-OMHs with functional coordination between organic cations and inorganic polyhedra. Together with the efficient emission and outstanding stability of 0D-J1, a high-performance white-light emitting diode (WLED) with a high color rendering index (CRI) of 92 is demonstrated.