Quinoline-based TADF emitters exhibiting aggregation-induced emission for efficient non-doped organic light-emitting diodes

Abstract

The thermally activated delayed fluorescence (TADF) materials with aggregation-induced emission (AIE) properties have attracted increasing interest for their applications as the emitters in non-doped organic light-emitting diodes (OLEDs). In this work, three quinoline-based TADF molecules 9,9-dimethyl-10-(quinolin-2-yl)-9,10-dihydroacridine (DMAC-QL), 10-(quinolin-2-yl)-10H-phenoxazine (PXZ-QL) and 10-(quinolin-2-yl)-10H-phenothiazine (PTZ-QL) were conveniently synthesized by a one-step reaction starting from commercially available materials. The twisted conformation was confirmed by single crystal analysis, and all the compounds exhibited high thermal stability. Moreover, the ΔE_ST values of DMAC-QL, PXZ-QL and PTZ-QL were 0.06, 0.10 and 0.04 eV, and their delay lifetimes were 2.15, 1.86 and 15.76 μs, respectively, indicating their excellent TADF properties. They also exhibited typical AIE and aggregation-induced delayed fluorescence (AIDF) properties in THF/H₂O solution. The non-doped OLEDs based on the emitters DMAC-QL, PXZ-QL and PTZ-QL were fabricated, and the maximal EQEs of the devices were 7.7, 17.3 and 14.8%, respectively, along with turn-on voltages of 3.2, 2.6 and 2.8 eV. It was further found that the efficiency roll-off of the non-doped device based on PXZ-QL was very small due to its short delay lifetime and excellent AIE and AIDF properties.