Aggregation‐Induced Dual Phosphorescence from ( o ‐Bromophenyl)‐Bis(2,6‐Dimethylphenyl)Borane at Room Temperature

Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non‐radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers ( o , m , p ‐bromophenyl)‐bis(2,6‐dimethylphenyl)boranes. Among the 3 isomers ( o ‐, m ‐ and p ‐ BrTAB ) synthesized, the ortho ‐one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o ‐ BrTAB , the short lifetime component is ascribed to the T 1 M state of the monomer which emits the higher energy phosphorescence. The long‐lived, lower energy phosphorescence emission is attributed to the T 1 A state of an aggregate, with multiple intermolecular interactions existing in crystalline o ‐ BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.