A Simple Carbazole/Oxadiazole Hybrid Molecule: An Excellent Bipolar Host for Green and Red Phosphorescent OLEDs

摘要

Phosphorescent organic light-emitting diodes (PHOLEDs) continue to attract intense interest because they can, in theory, approach a 100% internal quantum efficiency by utilizing both singlet and triplet excitons. To achieve highly efficient electrophosphorescence by reducing competitive factors such as concentration quenching and triplet-triplet annihilation, phosphorescent emitters of heavy-metal complexes are usually doped into a suitable host material. Thus the synthesis of host materials and dopants are equally important for the formation of efficient PHOLEDs. It is desirable that the host materials have a large enough bandgap for effective energy transfer to the guest, good carrier transport properties for a balanced recombination of carriers in the emitting layer, and energy-level matching with neighboring layers for effective charge injection.