Aggregation-Dependent Thermally Activated Delayed Fluorescence Emitters: AIE or ACQ?

The understanding of the excited state dynamics of thermally activated delayed fluorescence (TADF) materials is crucial. In this study, two donor-acceptor-type TADF emitters with highly twisted conformation are synthesized. The emitters with subtle chemical modification of donor unit exhibit opposite aggregation luminescent behaviors: aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ). Through the photophysical properties study, crystallographic analysis, and theory simulations, it is discovered that X-aggregation supports AIE behavior by restricting the intramolecular motions and preserving TADF emission via an efficient reverse intersystem crossing (RISC) process, but on the other hand, H-aggregation leads to ACQ behavior due to inhibited RISC, disabled TADF channel, and weak phosphorescence from radiative low-lying triplet state. The findings shed light on the excited-state dynamic behaviors of TADF emitters, which are dependent on aggregation.

Automated summary

In this study, two donor-acceptor-type TADF emitters with highly twisted conformation are synthesized. Through various experiments and analysis, it is discovered that X-aggregation supports aggregation-induced emission behavior, while H-aggregation leads to aggregation-caused quenching.