Control of Singlet Emission Energy in a DiphenyloxadiazoleContaining Fluorophore Leading To Thermally Activated DelayedFluorescence

摘要

2-(4-(9,9-Dimethylacridin-10(9H)-yl)phenyl)-5-phenyl-1,3,4-oxadiazole has an energy difference betweenthe lowest excited singlet and triplet states (ΔEST) of ca. 0.24eV. Introduction of two electronegative fluorine atoms ontothe acceptor portion of the molecule to give 2-(4-(9,9-dimethylacridin-10(9H)-yl)-3,5-difluorophenyl)-5-phenyl-1,3,4-oxadiazole lowers the energy of the singlet emission witha negligible effect on the corresponding triplet energy, leadingto a donor?acceptor compound with decreased ΔEST of ca.0.13 eV that displays thermally activated delayed fluorescence.Organic light-emitting diodes fabricated using the lattercompound display high EQEmax of 21.9% at a luminance of 10 cd/m2 and sky-blue emission, however, they suffer from alarge efficiency roll-off at increased luminance.