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.