One order of magnitude: Naphthalene‐ and acenaphthene‐fused phosphole P‐oxides (see figure) are shown to have reasonably high thermal and electrochemical stabilities and electron‐accepting ability. The electron mobility of the naphthalene‐fused phosphole P‐oxide is about one order higher than that of tris(8‐hydroxyquinoline)aluminium(III) Alq3 at any given electric field.