Vinylene and benzo[][1,2,5]thiadiazole: effect of the -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- 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 donoracceptor interaction. Bottom-gate-top-contact OFET device structure using PBIBDF-TVT and PBIBDF-TBT based polymer semiconductors.