n-type organic semiconductors have a pyromellitic diimide structure and electronic or electro-optic devices include pyromellitic diimide compounds as organic semiconductors. Specific semiconductors include pyromellitic diimide compounds have sidechains comprising fluorine substituted aliphatic or aromatic moieties linked to the pyromellitic diimide structure by an alkylene or heteroalkylene linking group. An electronic or electro-optic device includes a first electrode, a second electrode space apart from the first electrode, and an organic semiconductor layer arranged between the first and second electrodes. The organic semiconductor layer comprises a pyromellitic diimide compound.