Thermally Stable Hole-Transporting Material for Organic Light-Emitting Diode: an Isoindole Derivative

A new hole-transporting material, 1,3,4,5,6,7-hexaphenyl-2-{3‘-(9-ethylcarbazolyl)}-isoindole (HPCzI), has been synthesized. The new compound is a highly phenylated isoindole with good thermal and chemical stabilities. Thermal analysis using scanning calorimetry shows the compound to have a high melting point at 311.5 °C. Its bulky structure leads to good film-forming properties of the compound via thermal evaporation. Aside from the high hole mobility, the compound possesses other important attributes required for a good hole-transporting host material for applications in organic electroluminescence. The photophysical property of HPCzI and its performance as a hole-transporting material in a double-layered electroluminescent device were investigated. At a drive voltage of 8.8 V and a current density of 20 mA/cm 2, the device with a configuration of ITO/HPCzI/AlQ 3 /MgAg (30 Ω/□:700 Å:700 Å:2000 Å) showed a green AlQ 3 emission with a current efficiency of 3.5 cd/A.