Room‐temperature phosphorescence (RTP) has attracted considerable attention due to its potential applications in light‐emitting, bioimaging, and chemical sensing devices, but it is full of challenges to achieve new molecular systems for efficient RTP. Herein, three imidazole derivatives involving triplet excitons as organic cations are employed to synthesize three isostructural 1D lead halides with distinct emission characteristics, in which (2‐MBI)PbBr3 and (2‐PI)PbBr3 show the blue and broadband white fluorescence, respectively, while (5‐MBI)PbBr3 (5‐MBI = 5‐methylbenzimidazole) exhibits efficient green RTP peaking at 520 nm under UV excitation. The underlying photophysical regulatory mechanism is unveiled that extra‐molecular “heavy atomic effects” and the spin–orbit coupling from [PbBr3−]∞ units enhance the intersystem crossing and Dexter‐type electron transfer of excitons from inorganic units to triplet states (Tn) in 5‐MBI cations. An information encryption pattern is also realized by combining the different photoluminescence of these 1D organic and inorganic hybrid lead halides. This study suggests a feasible strategy to modulate the photoluminescence to achieve efficient RTP in low‐dimensional hybrid metal halides.

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Low-dimensional organic–inorganic metal halides (LOMHs) recently have attracted much attention due to their tunable crystal structures and excellent photoelectric properties. The configuration and arrangement of organic cations in LOMHs have significant effect on the structure of inorganic frameworks and luminescence properties. In this work, we systematically explored the "spatial effect" and "hydrogen bonding effect" of organic cations on the structure and properties of LOMHs, by synthesizing three LOMHs including (N-AD)­PbCl4, (N-AD)2Pb2Br7, and (N-AD)4Pb3I12 (N-AD: N-acetylethylenediamine, C4H10N2O). Specifically, (110)-oriented two-dimensional (N-AD)­PbCl4 and (N-AD)2Pb2Br7 with manifest blue-white emissions, originating from the free excitons (FEs) and self-trapped excitons (STEs), respectively. The UV-pumped light-emitting diode (LED)-based on (N-AD)2Pb2Br7 was prepared, and the highest color rendering index (CRI) and correlated color temperature (CCT) were up to 80 and 4484 K, respectively. This proves its potential application in solid-state lighting.

Organic−inorganic hybrid metal halides have attracted widespread attention due to their excellent tunability and versatility. Here, we have selected pyridinium derivatives with different substituent groups or substitution positions as the organic templating cations and obtained six 1D chain-like structures. They are divided into three types: type I (single chain), type II (double chain), and type III (triple chain), with tunable optical band gaps and emission properties. Among them, only (2,4-LD)PbBr 3 (2,4-LD = 2,4-lutidine) shows an exciton-dependent emission phenomenon, ranging from strong yellow-white to weak redwhite light. By comparing its photoluminescence spectrum with that of its bromate (2,4-LD)Br, it is found that the strong yellow-white emission at 534 nm mainly came from the organic component. Furthermore, through a comparison of the fluorescence spectra and lifetimes of (2,4-LD)PbBr 3 and (2-MP)PbBr 3 (2-MP = 2-methylpyridine) with similar structures at different temperatures, we confirm that the tunable emission of (2,4-LD)PbBr 3 comes from different photoluminescent sources corresponding to organic cations and self-trapped excitons. Density functional theory calculations further reveal that (2,4-LD)PbBr 3 has a stronger interaction between organic and inorganic components compared to (2-MP)PbBr 3 . This work highlights the importance of organic templating cations in hybrid metal halides and the new functionalities associated with them.

Lead-free low-dimensional organic-inorganic hybrid metal halides (OIMHs) have been widely concerned in solid-state lighting (SSL) on account of their excellent photoluminescent properties and stability. Herein, we synthesized a new zero-dimensional...