Quinoline-based aggregation-induced delayed fluorescence materials for highly efficient non-doped organic light-emitting diodes

Abstract

Three new emitters, namely 10,10'-(quinoline-2,8-diyl)bis(10H-phenoxazine) (Fene), 10,10'-(quinoline-2,8-diyl)bis(10H-phenothiazine) (Fens) and 10,10'-(quinoline-2,8-diyl)bis(9,9-dimethyl-9,10-dihydroacridine) (Yad), featuring quinoline as a new electron acceptor have been designed and conveniently synthesized. These emitters possessed small singlet–triplet splitting energy (ΔEst) and twisted structures, which not only endowed them show thermally activated delayed fluorescence (TADF) properties but also afforded a remarkable aggregation-induced emission (AIE) feature. Moreover, they also showed aggregation-induced delayed fluorescence (AIDF) property and good photoluminescence (PL) property, which are the ideal emitters for non-doped organic light-emitting diodes (OLEDs). Furthermore, high-performance non-doped OLEDs based on Fene, Fens and Yad were achieved, and excellent maximum external quantum efficiencies (EQEmax) of 14.9%, 13.1% and 17.4%, respectively, were obtained. It was also found that all devices exhibited relatively low turn-on voltages ranging from 3.0 V to 3.2 V probably due to their twisted conformation and the AIDF properties. These results demonstrated the quinoline-based emitters could have a promising application in non-doped OLEDs.