Study on charge-transfer state in a donor–acceptor polymer heterojunction

Charge-transfer (CT) state in a donor–acceptor polymer heterojunction is theoretically investigated. The simulations are performed within the framework of an extended version of the one-dimensional Su–Schrieffer–Heeger tight-binding model combined with a nonadiabatic evolution method. We firstly focus on the formation and stability of a CT state in a static picture, in which case the effect of the energy offset is mainly concerned. Subsequently, dynamic process for the CT state formation and recombination is addressed. It is found that there exists a critical energy offset for the charge transfer and recombination, which is determined by both the exciton binding energy and the CT state one. The investigation may give a light to the optoelectronic and magnetic applications for organic polymers.

Graphical ahstractDependence of the driving potential P on the energy offset ΔE. P > 0 means that the initially generated CT state at the D–A interface should be inclined to recombine into an exciton. P < 0 implies that the initially generated CT state can not recombine into an exciton, however, the reverse process, that is, the dissociation of an exciton into a CT state will take place.Figure optionsDownload as PowerPoint slideHighlights
► We model a D–A polymer heterojunction, and investigate the CT state.
► We analyze the stability of a CT state by calculating its energy.
► The dynamic process of the charge transfer and recombination is presented.
► There exists a critical energy offset for the charge transfer and recombination.
► We aim to give a light to choose the optimalizing energy offset in applications.