Simplified thermally activated delayed fluorescence organic light-emitting diodes

Recently, after the first demonstration of efficient, thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs), these devices have been widely investigated, and several new materials (hole and electron transport materials) have been reported. In this work, we demonstrate highly efficient TADF OLEDs with a simplified structure, and systematically characterize these partially evaluated reported materials; (4s,6s)-2,4,5,6,-tetra(9H-carbazol-9-ypisophthalonitrile (4CzIPN) has been used as a TADF emissive dopant; the exciton blocking and carrier transport characteristics of 9,9'-Diphenyl-6-(9-phenyl-9H-carbazol-3-yl)-9H,9'H-3,3'-bicarbazole (Tris-PCz) and 2,7-bis(2,2'-bipyridin-5-yl)triphenylene (BPy-TP2) have been characterized and compared with those of other widely used wellknown organic materials. The demonstrated simplified TADF OLEDs with a 4CzIPN doped single emissive layer showed a high peak external quantum efficiency and power efficiency of 18.6% and 31.5 lm/W, respectively.