A novel electron acceptor was synthesized from one-step functionalization of the readily available indigo dye. The resulting bay-annulated indigo (BAI) was utilized for the preparation of a series of novel donoracceptor small molecules and polymers. As revealed experimentally and by theoretical calculations, substituted BAIs have stronger electron accepting characteristics when compared to several premier electron deficient building blocks. As a result, the donoracceptor materials incorporating BAI acceptor possess low-lying LUMO energy levels and small HOMOLUMO gaps. In situ grazing incidence wide-angle X-ray scattering studies of the thin films of BAI donoracceptor polymers indicated improved crystallinity upon thermal treatment. Field effect transistors based on these polymers show excellent ambipolar transporting behavior, with the hole and electron mobilities reaching 1.5 and 0.41 cm(2) V-1 s(1), respectively, affirming BAI as a potent electron accepting unit for high performance organic electronic materials.