Converting a Semiconducting Polymer from Ambipolar into n-Type Dominant by Amine End-Capping

A donor-acceptor polymer of (3E,7E)-3,7-bis(2-oxoindolin-3-ylidene)benzo[1,2-b : 4,5-b′]difuran-2,6(3H,7H)-dione (IBDF) and bithiophene (BT) exhibits typical ambipolar charge transport behaviour in organic thin film transistors. Using the electron rich triphenylamine as an end capping group, a notable suppression of hole transport is observed. This interesting phenomenon is accounted for by the hole trapping effect of the triphenylamine end-capper. Thus, this study provides a novel and facile approach to tuning the charge carrier polarity of a polymer semiconductor from ambipolar to n-type dominant.