Utilization of double-sensitized structure toward achieving high performance green and red phosphorescent organic light-emitting diodes

In this work, iridium(III)bis(4-(tert-butyl)-2,6-diuoro-2,3-bipyridinne)acetylacetonate (FK306) was utilized as sensitizer and incorporated into both light-emitting and electron transport layers to constitute a double-sensitized system because of its low-lying energy levels and well matched triplet energy. Experimental results confirmed that the incorporated FK306 molecules were helpful in effectively modulating the transportation of electrons due to sensitizing effect, which caused decreased electron accumulation, improved carrier balance and thus enhanced carrier recombination probability. Furthermore, the presence of FK306 molecules within light-emitting and electron transport layers helped to broaden the recombination zone and suppress exciton quenching, thus leading to higher efficiency and slower efficiency roll-off. Finally, high performance green OLED with a double-sensitized structure obtained the maximum current efficiency of 95.86 cd A−1, external quantum efficiency of 28.6%, power efficiency of 94.06 lm W−1 and brightness of 102 924 cd m−2. And, our experimental results demonstrated that this device design strategy was also efficient in enhancing the performance of red OLEDs.