Mixed-host engineering of blue thermally activated delayed fluorescence devices for enhanced efficiency and suppressed efficiency roll-off

Abstract

Blue thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) with enhanced efficiency and suppressed efficiency roll-offs were fabricated using a mixed host consisting of 3,3-di(9H-carbazol-9-yl)-biphenyl (mCBP) and bis[2-(diphenyl-phosphino)phenyl]ether oxide (DPEPO). Notably, mCBP and DPEPO, which are generally used as hosts in blue TADF OLEDs, exhibit material stability and efficiency as their trade-off characteristics. The mixed-host structure, when applied to 10,10′-(4,4′-sulfonylbis(4,1-phenylene))bis(9,9-dimethyl-9,10-dihydroacridine), which is a blue TADF dopant, facilitated a maximum efficiency of 18.1%. Furthermore, the critical current density (J0), at which the external quantum efficiency decreases by half of its maximum value, was observed to be 3.9 times that of the DPEPO device. © 2021 Elsevier B.V.