Structural design, synthesis, and characterization of a series of organic semiconductors consisting exclusively of dithienylcyclopentadienone subunits within a polythiophene backbone are described as the first example for organic electronic devices. The donor (thiophene)-alt-acceptor (cyclopentadienone) copolymers exhibit a substantial p-carrier mobility in OFET but an unexpected noncorrelation between absorption and photoconductivity.