Effective host materials for blue/white organic light-emitting diodes by utilizing the twisted conjugation structure in 10-phenyl-9,10-dihydroacridine block

Two new 10-phenyl-9,10-dihydroacridine derivatives attached by dibenzothiophene (DBT) and dibenzofuran (DBF) were synthesized. The influence of the substituents of these materials was studied by theoretical calculations (DFT calculation) and experimental measurements. Owing to the twisted N-phenyl ring, both molecules possess sufficiently high triplet energies and are suitable as hosts for phosphorescent organic light-emitting diodes. To evaluate the electroluminescent (EL) performance of these materials, FIrpic-based blue PHOLEDs and two-color white PHOLEDs (FIrpic and PO-01 as the dopants) were fabricated using the common device structures. High external quantum efficiencies (EQE) of 21.1 % and 20.9 % for FIrpic-based blue PHOLEDs were achieved by FPhAc and TPhAc, respectively. The white device based on the host FPhAc achieved a higher performance, with a maximum EQE of 24.7 % than the device with TPhAc as host material.