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

The chlorinated isoindigo (CI) is a promising building block for organic semiconducting materials because the favorable 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. It was reported that CI can be more readily synthesized than fluorinated isoindigo (FI), and the CI-based conjugated polymer exhibited comparable device performance with the FI-based conjugated polymer. Chorine-substituted conjugated molecules, however, have been less investigated than that of the fluorine atom, presumably, due to the large size of the chlorine atom, which induces steric hindrance effects in the conjugated backbone. 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 to understanding the str...