Highly efficient yellow phosphorescent organic light-emitting diodes for two-peak tandem white organic light-emitting diode applications

Reported herein are highly efficient yellow phosphorescent organic light-emitting diodes for tandem white organic light-emitting diode (WOLED) applications. The fabricated device structure was ITO/di-[4-(N, N-ditolyl- amino)-phenyl] cyclohexane(TAPC)(50 nm)/bis[2-(2-hydroxyphenyl)-pyridine] beryllium(Bepp2): iridium(III) bis(4( 4-t-butylphenyl) thieno [3,2-c] pyridinato-N, C-2') acetylacetonate)(Ir(tptpy) 2(acac))(10 nm)/(1,3,5-tri[(3-pyridyl)-phen-3yl] benzene(TmPyPB)(40 nm)/LiF (1.5 nm)/Al(100 nm). The extremely high 25.0% external quantum efficiency (EQE), the 84.4 cd/Acurrent efficiency, and the 90.7 lm/Wpower efficiency are reported, with Commission Internationale de L'Eclairage (CIE) coordinates of (0.49, 0.50). Such good performances are attributed to the good exciton confinement structure fabricated herein, and the highly efficient yellow dopant. The white tandem device was fabricated by utilizing this yellow device with the authors' phosphorescent blue-OLED unit. An excellent 67.2 lm/Wpower efficiency and a 48.6% EQE with CIE coordinates of (0.39, 0.49) were obtained.