High-efficiency white phosphorescent organic light-emitting devices with greenish-blue and red-emitting layers

We demonstrate high-efficiency white light emission from a phosphorescent organic light-emitting device with greenish-blue and red emissive layers. $\mathrm{Bis}\text{{2-[3,5-}\mathrm{bis(trifluoromethyl)phenyl}\mathrm{]-}{\mathrm{pyridinato-N,C}}^{2^{\prime }}\}\mathrm{iridium(III)picolinate}$ $\mathrm{[(}{\mathrm{CF}}_3\mathrm{ppy}{)}_2\mathrm{Ir(pic)}]$ and $\mathrm{bis}{\text{{2-[2}}^{\prime }-\mathrm{benzo}\text{(4,5-}\mathrm{a})\mathrm{thienyl}]{\mathrm{pyridinato-N,C}}^{3^{\prime }}\}\mathrm{iridium(III)acetylacetonate}$ were employed for the greenish-blue and red phosphorescent materials for the emissive layers. To enhance the emission efficiency of $({\mathrm{CF}}_3\mathrm{ppy}{)}_2\mathrm{Ir(pic)},$ ${\text{4,4}}^{\prime }-\mathrm{bis}\text{(9-}\mathrm{carbazolyl}{\text{)-2,2}}^{\prime }-\mathrm{dimethyl-biphenyl}$ was used as the charge-transporting host. White light emission was obtained by controlling the layer thickness and the concentration of each phosphorescent material in the emissive layers. A maximum external quantum efficiency of 12%, a luminance efficiency of 18 cd/A, and a maximum power efficiency of 10 lm/W were achieved at a current density of $\text{0.01\hspace{0.17em}}{\mathrm{mA/cm}}^2.$ This high efficiency is primarily attributed to the improvement of greenish-blue emission efficiency due to the strong confinement of triplet excitons on the $({\mathrm{CF}}_3\mathrm{ppy}{)}_2\mathrm{Ir(pic)}$ molecules.