Thieno[3,2- b ]pyrrole and Benzo[ c ][1,2,5]thiadiazole Donor-Acceptor Semiconductors for Organic Field-Effect Transistors.

Two p-type donor-acceptor (D-A) semiconducting small molecules were synthesized to investigate the effect of the backbone curvature on the organic field-effect transistor performance. The backbone curvature of the donor-acceptor small molecules was modified by changing the spacer group from bithiophene to thienothiophene. Bithiophene to thienothiophene spacer groups were placed between 4-thieno[3,2-]pyrrole (donor) and benzo[][1,2,5]thiadiazole (acceptor) to generate and donor-acceptor molecules. A good charge carrier mobility of 2.59 × 10 cm V s was measured for the curved molecule (), while the linear molecule analog () only gave a low mobility of 5.41 × 10 cm V s after annealing at 120 °C in bottom-contact bottom-gate devices. Out-of-plane grazing-incidence X-ray diffraction analysis revealed more drastic thermally induced crystallinity for as compared to , explaining the difference observed in the performance of devices fabricated from each molecule.