Chlorinated Isoindigo-based Conjugated Polymers: Effect of Rotational Freedom of Conjugated Segment on Crystallinity and Charge-Transport Characteristics

Abstract

The chlorinated isoindigo (CI) is promising building block for organic semiconducting materials because the favourable properties, such as ready availability, lower price, and higher capability to hold the electron density than fluorine atoms, make them advantageous for use in semiconducting materials. In this study, we systematically investigate the effect of the structural property – flexibility vs rigidity – of the donor unit on the crystallinity and charge transport characteristics of chlorinated isoindigo acceptor-based D-A type conjugated polymers. Interestingly, in GIXRD analysis, although TV unit is more planar structure than BT unit, PCIBT had more improved molecular ordering than PCITV. This may be associated with the BT unit having higher rotational freedom compared to that of the TV unit. This property of the BT unit can facilitate thermal-assisted polymer chain packing in film state that results in an enhanced molecular ordering of PCIBT after thermal annealing process.