A series of benzothiadiazole oligothiophene and oligo(thienylenevinylene) donor–acceptor (D–A) copolymers were synthesizedand characterized. These low optical band gap materials (∼1.5eV) are capable of absorbing photons in the range of 400–800nm and exhibit good thermal stability. Their hole mobilities, determinedusing an organic field-effect transistor (OFET) architecture, varyover a range of 3 orders of magnitude and strongly correlate withthe molecular ordering and morphology of the respective thin films.Spin-coated films of the poly(benzothiadiazole-sexithiophene) PBT6, which exhibits a highly crystalline lamellar π–πstacked edge-on orientation on the OFET substrate, possesses a holemobility of ca. 0.2 cm2/V·s. Vinylene-containing analogs PBT6V2and PBT6V2′are amorphous andexhibit very low mobilities. The molecular weight of PBT6has a strong influence on the electronic properties: a sample witha lower molecular weight exhibits a mobility approximately 1 orderof magnitude lower than the high molecular weight homologue, and theabsorption maximum is appreciably blue-shifted. The hole mobilityof PBT6is further enhanced by a factor of ca. 3 throughfabrication of the OFET by drop casting. OFETs fabricated by thisprocess exhibit mobilities of up to 0.75 cm2/V·s and ION/OFFratios in the range of 106–107. These results demonstrate the potential ofincorporating benzothiadiazole units into polythiophene derivativesto develop high-mobility semiconducting polymers. [ABSTRACT FROM AUTHOR]