Thermally activated delayed fluorescence of Bis(9,9-dimethyl-9,10-dihydroacridine) dibenzo[b,d]thiophene 5,5-dioxide derivatives for organic light-emitting diodes

Two luminescent dibenzo[b,d]thiophene 5,5-dioxide derivatives combined with 9,9-dimethyl-9,10-dihydroacridine were synthesized and the appearance of thermally activated delayed fluorescence was confirmed. Both 3,7- and 2,8-bis(9,9-dimethyl-9,10-dihydroacridine)dibenzo[b,d]thiophene 5,5-dioxide (3ASOA) and (4ASOA) showed prompt and delayed fluorescence with high total photoluminescence (PL) quantum efficiencies of 72% and 88% in their doped films, respectively. The maximum external electroluminescence (EL) efficiencies of 13.8% in 4ASOA and 10.4% in 3ASOA were obtained. Further, 4ASOA showed slightly relaxed rolloff behavior, indicating that 2,8-substitution of the donors appreciably improved both PL and EL characteristics.