DCz-BTP is an asymmetric bipolar TADF host designed for high-performance organic light-emitting diodes (OLEDs). DCz-BTP has a benzo[4,5]thieno[2,3-b]pyridine core skeleton with two electron-rich carbazole units attached. The incorporation of a pyridine fragment instead of dibenzothiophene enables strong intermolecular interactions, leading to satisfactory bipolar transporting properties. Comparing with the commonly used host materials such as mCP and DPEPO, pseudo-symmetric bipolar host DCz-BTP delivers lower driving voltage and enhanced electroluminescence performance. HF-OLEDs based on DCz-BTP host demonstrate a low turn-on voltage of 2.8 V and a maximum EQE of 20.5% using the 4TCzBN sensitizer and TBPe emitter.
Blue thermally activated delayed fluorescent OLEDs (TADF-OLEDs) based on 4TCzBN as the guest DCz-BTP as the bipolar host exhibit a low turn-on voltage of 2.8 V and a high maximum external quantum efficiency (EQEmax) of 29.0 %.