Highly efficient thermally activated delayed fluorescence devices using a phosphorescent dye as host

In this work, we further researched the influence of heavy atom on the electroluminescent (EL) performances of organic light-emitting diodes (OLEDs) containing thermally activated delayed fluorescence (TADF) materials as emitters by utilizing iridium(III)bis(4',6'-difluorophenylpyridinato)tet-rakis(1-pyrazolyl)borate (Ir(mppy)(3)) as the host of the assistant light-emitting layer (EML) and 2-[4-(diphenylamino)phenyl]-10,10-dioxide-9H-thioxanthen-9-one (TXO-TPA) as emitter. Though optimizing the doping concentration of TXO-TPA and the thickness of assistant EML, we have successfully improved the EL performances of TXO-TPA based device by analyzing energy transfer, exciton quenching progresses and carrier distribution within EMLs. Finally, the optimal device obtained high current efficiency and external quantum efficiency of 38.92 cd/A and 12.41% at 2000 cd/m(2) (3.2 V). Meanwhile, the optimal device has a slower efficiency roll-off with maximum current efficiency of 42.43 cd/A (EQE=12.95%) with a long LT50 (the time for brightness decay to 50% of the initial brightness) lifetime of 6700 h at 2000 cd/m(2).

Automated summary

By investigating the influence of heavy atoms on the EL performance of OLEDs containing TADF materials, the study successfully enhanced device performance through optimization of doping concentration and thickness, resulting in a device with high current efficiency and external quantum efficiency at high brightness.