Highly Efficient Solution-Processed TADF Bluish-Green and Hybrid White Organic Light-Emitting Diodes Using Novel Bipolar Host Materials

Two pyridine containing bipolar host materials with high triplet energy, 9,10-dihydro-9,9-dimethyl-10-(3-(6-(3-(9,9-dimethylacridin-10(9H)-yl)phenyl)pyridin-2-yl)phenyl acridin (DDMACPy) and N-(3-(6-(3-(diphenyl amino)phenyl)pyridin-2-yl)phenyl)-N-phenylbenzenamine (DTPAPy), are synthesized from modifying the commonly adapted host material 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (DCzPPy). The HOMO levels of DDMACPy (5.50 eV) and DTPAPy (5.60 eV) are found to be shallower than that of DCzPPy (5.90 eV) that leads to the improvement in hole injection from the hole transport layer PEDOT:PSS (WF = 5.10 eV). These host materials are used in the emitting layer of blue organic light-emitting diode (OLED) with the sky-blue TADF emitter, 9,9-dimethyl-9,10-dihydroacridine-2,4,6-triphenyl-1,3,5-triazine (DAMC-TRZ), as the guest. The DDMACPy-based device shows the highest performance among them with the maximum external quantum efficiency (EQEmax), current efficiency (CEmax) and power efficiency (PEmax) of 21.0%, ...