Excited-State Modulation of Aggregation-Induced Emission Molecules for High-Efficiency Triplet Exciton Generation

Restriction of intramolecular motion (RIM) is commonly adopted to achieve high luminescence for aggregation-induced emission (AIE) materials. However, recent studies found that RIM cannot fully explain the behavior of some new systems because of the existence of extra nonradiative excited state channels. In this work, two D-pi-A type molecules, TPA-P-C and CBZ-P-C with AIE properties, were prepared via the Suzuki-Miyaura reaction. CBZ-P-C showed an unusual solvent effect, being nonemissive in low-polar solvents but highly emissive in polar solvents. Theoretical calculations and time-resolved spectroscopic experiments demonstrated for CBZ-P-C a quantitative intersystem crossing (ISC) in low-polar solvents, resulting in low emission quantum yield but high singlet oxygen generation. In addition, a rigid matrix (triphenylphosphine (TPP)) was selected as host for the stabilization of the triplet excitons. Both doping materials showed high room-temperature phosphorescence (RTP) as a consequence of the highly efficient triplet exciton generation. The present study provides a new insight for understanding AIE materials and paves an easy yet efficient way for the excited-state modulation of AIE molecules.