mCBP-CN, or 3,3′-di(carbazol-9-yl)-5-cyano-1,1′-biphenyl, has a structure of two carbazole units attached to a biphenyl linker. The only difference that it has to the well known host mCBP is that a polar cyano (CN) group is attached to one of the phenyls. The asymmetrically attached CN group can both increase the ground-state dipole moment and greatly improve film morphology and device thermal stabilities.
The strong electron withdrawing CN group can also effectively alter the electron densities of the orbitals, making mCBP-CN an electron transporting host with deep HOMO/LUMO energy levels (while mCBP is a hole transport host material).