Asymmetric donor-acceptor-host red thermally activated delayed fluorescent emitter for high-efficiency organic light emitting diodes

Efficient red emitters are crucial to the widespread use of organic light-emitting diodes (OLEDs) in future display and lighting technologies. However, the highly planar configurations of red TADF emitters lead to intermolecular-interaction-induced quenching. To obtain highly efficient doping-insensitive red emitters, a novel asymmetric red thermally activated delayed fluorescence (TADF) emitter, TPA-AQ-DCP, was developed using an asymmetric donor-acceptor-host (D-A-H) structure. The material consists of anthraquinone as the acceptor, triphenylamine as the donor, and 1,4-di(9H-carbazol-9-yl)benzene (DCP) serving as part of the emitter with host material properties. It is demonstrated that incorporating the host group into the TADF emitter with asymmetrical structure improves electron and hole transport within the emitter, effectively reducing concentration quenching. As a consequence, the asymmetric D-A-H structured TPA-AQ-DCP exhibited a relatively high photoluminescent quantum yield (PLQY) of 79.2% and fast radiative rate constant (k_r) of 6.60 × 10⁷ s⁻¹, and thus better EL performance. Consequently, an efficient external quantum efficiency (EQE) of 11.76-17.60% with an emission peak of 610-620 nm was achieved for the TPA-AQ-DCP-based devices with doping ratios ranging from 5 wt% to 25 wt%.