Novel high Tg hole-transport molecules based on indolo[3,2-b]carbazoles for organic light-emitting devices

A variety of 5,11-diaryl-5,11-dihydroindolo[3,2-b]carbazole derivatives have been synthesized for use as hole-transport layers in organic light-emitting devices (OLED). The new hole-transport molecules (HTM) possess several salient features: (i) exceptionally high glass transition temperatures; (ii) ready evaporation to form uniform thin films; and (iii) ideal ionization potentials matched to indium–tin oxide (ITO) anode. Cyclic voltammetry (CV) of these molecules exhibits reversible redox behavior. OLEDs utilizing this type of molecules in their hole-transport layers have demonstrated low threshold voltages and excellent current–voltage (J–V) characteristics.