ted alkoxy group, or a substituted or unsubstituted aryl group; Ar1, Ar2, Ar3, and Ar4 are each a substituted or unsubstituted aryl or heterocyclic group, which may be the same or different from each other; both Ar1 and Ar3 are fused aromatic rings; and at least one of R1 and R2 is a hydrogen, a halogen, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group; an