Efficient Room‐Temperature Phosphorescence of 1D Organic–Inorganic Hybrid Metal Halides

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 (T_n) 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.