Novel copolymers incorporating dithieno[3,2-b : 2 ',3 '-d]thiophene moieties for air-stable and high performance organic field-effect transistors

A series of semiconducting copolymers incorporating dithieno[3,2-b:2',3'-d] thiophene moieties in the polythiophene backbone were synthesized. The resulting four copolymers are found to have large band gap (similar to 2.5 eV) and large ionization potential (-5.1 eV). Organic field-effect transistors were fabricated by spin-coating polymer solutions onto OTS-modified SiO(2)/Si substrates with top-contact configuration. The best resulting hole mobility afforded was 0.028 cm(2) V(-1) s(-1) with an on/off ratio of 2 x 10(4) and a threshold voltage of about -18.9 V in the saturation regime. Furthermore, all the devices exhibited high environmental stability against oxygen doping and relatively high ambient humidity (similar to 30%).