Bis(2-oxo-7-azaindolin-3-ylidene)benzodifuran-dione-based donor–acceptor polymers for high-performance n-type field-effect transistors

Two donor–acceptor (D–A) conjugated polymers, PBABDF-DT and PBABDF-TVT, were synthesized using a strongly electron-deficient unit, (3E,7E)-3,7-bis(6-bromo-1-(4-decyltetradecyl)-2-oxo-7-azaindolin-3-ylidene)benzo[1,2-b:4,5-b′]difuran-2,6(3H,7H)-dione (BABDF) as the acceptor, and dithiophene and (E)-2-(2-(thiophen-2-yl)vinyl)thiophene as the donor units. Both polymers exhibited low LUMO energy levels (∼−4.0 eV) for marching with electron transport and displayed excellent n-type charge transport characteristics. The organic field-effect transistors exhibited the highest electron mobilities of 1.86 cm2 V−1 s−1 and 1.56 cm2 V−1 s−1 with high Ion/Ioff ratios of 1.6 × 106 and 1.0 × 106 for PBABDF-DT and PBABDF-TVT, respectively. Both polymers had highly uniform polymer nanofibers, orderly lamellar crystalline structures, and close π–π stacking distances which all contributed to the high charge carrier mobility.