Efficient iridium(III) based, true-blue emitting phosphorescent OLEDS employing both double emission and double buffer layers

New device architectures and efficient iridium based phosphors were simultaneously developed for fabrication of true-blue phosphorescent organic light-emitting devices (OLEDs). To fully explore the potential of these true-blue-emitting phosphors, we employed a device architecture that incorporates both double-emitting layers (one with hole-transport and the second with electron-transport materials) and double buffer layers for efficient exciton confinement. In addition, the parent, true-blue emitting heteroleptic Ir^III complex Ir1 was synthesized by incorporating one 4,6-difluorophenyl-2-pyridyl cyclometalate (dfppy) together with two 3-(trifluoromethyl)-5-pyridyl pyrazolates (fppz), while others derivatives Ir2-Ir4 were prepared by addition of alkyl substituent at the pyridyl sites. Electrophosphorescence with efficiencies up to 13.7% photon/electron and 20.4 cd/A, and with adequate CIE_x,y color coordinates of (0.157, 0.189) were successfully achieved.