High-triplet-energy host materials containing saturated carbon atom for blue and green phosphorescent OLEDs

Two novel bipolar host materials containing saturated sp(3)-hybridized carbon atom, namely 4-(4-(bis(9-ethyl-9H-carbazol-3-yl)ethyl)pheny1)-1H-1,2,4-triazole (p-TzCCz) and 3-(4-(bis(9-ethy1-9H-carbazol-3yl)ethyl)pheny1)-1H-1,2,4-triazole (m-TzCCz), are designed and synthesized for blue and green phosphorescence organic light-emitting diodes (PHOLEDs). Carbazole and triazole are selected as the p- and n-type units to construct the bipolar hosts. The presence of the saturated sp(3)-hybridized carbon atom successfully blocks 7r-conjugation, leading to extremely high triplet energies of 2.95 eV for both p-TzCCz and m-TzCCz, and the distorted molecular configuration endows them high glass transition temperatures of above 100 degrees C. p-TzCCz and m-TzCCz are used as hosts to fabricate PHOLEDs with iridium phosphors as doped emitters. m-TzCCz-hosted blue and green devices exhibited external quantum efficiency as high as 11.89% and 16.09% with color coordinates of (0.14, 0.34) and (0.29, 0.63), respectively. This work may provide an effective strategy to design high triplet energy bipolar host materials for OLEDs application. (C) 2017 Elsevier B.V. All rights reserved.