Dynamics-induced charge transfer in semiconducting conjugated polymers

The mechanism of charge transport in semiconducting conjugated polymers is of fundamental importance. The role of polymer dynamics therein is considered crucial but is not yet fully explored. In the present work, we combine density functional theory (DFT) and ab intio molecular dynamics (AIMD) simulations to study the dynamics-induced charge transfer (CT) in ordered bi-molecular systems of the widely investigated polymers PCPDTBT and P3HT, respectively. Our AIMD simulations capture interchain and intrachain CT providing valuable insights into polaron energetics during the CT processes. We show that interchain CT in the bi-molecular systems is induced by the vibrational dynamics and significant coupling of electrons to specific vibrational modes. We find that the polaron shared by the two neighboring molecules is energetically stabilized with respect to the single oligomer polaron; in a film environment this stabilization could make the polaron transfer to the surrounding polymer matrix less favourable. This could be an important parameter in designing efficient organic semiconductor materials. Our results provide detailed insights into charge transport mechanisms at the molecular level and illustrate the role of polaron energetics in dynamical charge transfer.