Near-infrared cyclometalated iridium( iii ) complexes with bipolar features for efficient OLEDs via solution-processing

A novel bipolar NIR iridium( iii ) complex (CH 3 OTPA-BTz-Iq) 2 Ir(pic-OXD) with both a hole transporting (HT) triphenylamine (TPA) group and an electron transporting (ET) oxadiazole (OXD) group was designed and synthesized. It was observed that the incorporation of OXD and TPA into the ligand (CH 3 OTPA-BTz-Iq) 2 Ir(pic-OXD) improved the optophysical and electroluminescence performance in comparison with the parent iridium( iii ) complex (CH 3 OTPA-BTz-Iq) 2 Irpic. In (CH 3 OTPA-BTz-Iq) 2 Ir(pic-OXD)-based OLEDs, a maximum external quantum efficiency (EQE max ) of 1.15% at 716 nm was obtained, which is much superior than that of the (CH 3 OTPA-BTz-Iq) 2 Irpic-based OLEDs (0.41% at 723 nm).