Cyclopentadithiophene based polymers-a comparison of optical, electrochemical and organic field-effect transistor characteristics

A series of cyclopentadithiophene based polymers have been synthesized by oxidative polymerisation or palladium-catalyzed coupling reactions. Polymers have been prepared with backbones containing benzothiadiazole, benzoxadiazole, 2,2'-bithiophene, phenyl and fluorene units. The backbone structure is shown to have a large effect on the film morphology, and the optical and electrochemical properties in solution and the solid state. We show that the polymer composition can be used to tune the band gap over the entire visible spectrum. Spin-coated films of these polymers have been used as the active layer of organic field effect transistors and hole mobilities up to 3.7 x 10(-3) cm(2) V(-1) s(-1) have been measured under ambient conditions.