[Abstract]

Two copolymers containing alternating electron-donating and electron-accepting units, based on naphthalene diimide and bithiophene vinylene bithiophene with different pendant groups, i.e., C24 (P(NDI-T2VT2)-24) and C28 (P(NDI-T2VT2)-28) are synthesized via Stille-coupling polymerization reaction to study the effect of length of the alkyl side chain on the performance of n-type organic field-effect transistors (OFETs). The thermal stability, optical absorption, thin-film crystallinity, and electronic properties of the OFETs with the copolymers are investigated. Both polymers showed reliable n-type transistor characteristics with electron mobility of 0.015 cm2/Vs (C24) and 0.019 cm2/Vs (C28) with a standard deviation of 0.01 from 36 devices. Furthermore, (P(NDI-T2VT2))-C28 OFETs showed slightly better device mobility than C24 because of their better solubility and crystallinity. Mobilities up to 0.019 cm2/Vs are recorded for (P(NDI-T2VT2))-C28 are analyzed.