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.