New Bipolar Host Materials for Realizing Blue Phosphorescent Organic Light-Emitting Diodes with High Efficiency at 1000 cd/m(2)

Abstract

New host molecules such as 9-(6-(9H-carbazol-9-yl)pyridin-3-yl)-6-(9H-carbazol-9-yl)-9H-pyrido[2,3-b]indole (pPCB2CZ) and 9-(6-(9H-carbazol-9-yl)pyridin-2-yl)-6-(9H-carbazol-9-yl)-9H-pyrido[2,3-b]indole (mPCB2CZ) were designed and synthesized for blue phosphorescent organic light-emitting diodes (PhOLEDs). The glass transition temperatures of two host molecules were measured higher than 120 degrees C, and the identical triplet energies were determined to be 2.92 eV for both molecules. The bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(III) (FIrpic)-doped mPCB2CZ-based PhOLED exhibited practically useful driving voltage of 4.8 V in a simple organic three layer device configuration which has a smaller number of interfaces in conventional multilayer PhOLEDs. Also, the high quantum efficiency of 23.7% is reported at the practically useful brightness value of 1000 cd/m(2).