Aromatic carbonyl-mediated excited-state engineering enables aggregation-induced phosphorescence

Conventional organic luminophores generally exhibit fluorescence, while triplet excitons are often difficult to utilize for emission due to spin-forbidden transitions. Herein, we develop an aromatic carbonyl incor-poration strategy to enable aggrega-tion-induced phosphorescence (AIP) by introducing electron-withdrawing carbonyl motifs into fluorophores. The designed aromatic carbonyl-substituted molecule (TPO-PM) ex-hibits efficient phosphorescence emission with a phosphorescence quantum yield of 17.19% and a life-time of 36.94 ms. Theoretical and experimental investigations reveal that aromatic carbonyl incorporation transforms the S1 state from a locally excited (LE) state in TPO into a hy-bridized local and charge-transfer (HLCT) state in TPO-PM. This excit-ed-state transformation reduces the singlet-triplet energy gap (ΔEST) from 1.48 to 0.31 eV and enhances spin-orbit coupling (SOC) from 0.327 to 2.426 cm-1, thereby accelerating intersystem crossing (ISC). Meanwhile, the reduced oscillator strength suppresses the radiative decay of S1 state, weakening the competition between fluorescence and ISC pathways. Extension of aromatic carbonyl modification to diverse fluorophores and further demonstrates the generality of this strategy for constructing organic phosphorescent materials.