Combining carbazole electron donors with a high triplet energy and a pyridine electron acceptor with a high electron affinity, 2,6-bis(3-(carbazol-9-yl)phenyl)pyridine (26DCzPPy) is one of the most popular bipolar host materials used in organic light-emitting diodes.
Bipolar host materials are molecules composed of an electron-donating moiety capable of mediating hole injection and transportation, and an electron-withdrawing moiety capable of mediating electron injection and transportation.