Vinylene and benzo[ c ][1,2,5]thiadiazole: effect of the π-spacer unit on the properties of bis(2-oxoindolin-3-ylidene)-benzodifuran-dione containing polymers for n-channel organic field-effect transistors.

Two polymers based on (3 E ,7 E )-3,7-bis(2-oxoindolin-3-ylidene)benzo[1,2- b :4,5- b ']difuran-2,6(3 H ,7 H )-dione (BIBDF) coupled with ( E )-2-(2-(thiophen-2-yl)vinyl)thiophene (TVT) or dithienylbenzothiadiazole (TBT), namely PBIBDF-TVT and PBIBDF-TBT were synthesized via the Stille coupling reaction. The effect of benzothiadiazole or vinylene-π spacer of the copolymers on optical properties, energy levels, electronic device performance and microstructure were studied. It was found that PBIBDF-TBT based OFET devices, annealed at 180 °C, showed better performance with the highest electron mobility of 2.9 × 10 -2 cm 2 V s -1 whereas PBIBDF-TVT polymer exhibited 5.0 × 10 -4 cm 2 V s -1 . The two orders of magnitude higher electron mobility of PBIBDF-TBT over PBIBDT-TVT is a clear indicator of the better charge transport ability of this polymer semiconductor arising from its higher crystallinity and better donor-acceptor interaction.