Abstract
The key process in organic photovoltaic cells is the charge separation at organic donor-acceptor interfaces. However, exactly how the charges separate into free charge carriers still remains a puzzle. We present here simulations of the electron dynamics of this process using a nonadiabatic Ehrenfest method. From these simulations, we give a direct illustration of the charge separation process. The results show that the delocalization of the electronic states involved plays a critical role in order to overcome the Coulomb attraction of the charge transfer (CT) exciton. Charge separation only occurs for sufficiently strong intermolecular interactions. Alternatively, the CT exciton relaxes into a bound polaron pair. The results also show that the “excess energy” of the hot CT exciton facilitates the charge separation process to a certain degree.
- Received 5 December 2013
- Revised 15 August 2014
DOI:https://doi.org/10.1103/PhysRevB.90.115420
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