Reduction of Self-Quenching Effect in Organic Electrophosphorescence Emitting Devices via the Use of Sterically Hindered Spacers in Phosphorescence Molecules

The incorporation of a sterically demanding pinene moietyinto the ligand of a phosphorescent iridium complex prevents self-quenching by neighboring molecules, raising its photoluminescence quantum yield to 0.71 in solution. The compound is highly interesting as a dopant in electroluminescent devices, as shown for various concentrations of the complex in 4,4′-bis-(carbazolyl)-biphenyl (CBP) (see Figure).