Zhigang SHUAI
Tsinghua University

We have implemented the nonadiabatic Ehrenfest dynamics within the density functional tight binding (DFTB) framework to investigate the carrier transport in the donor-acceptor type photovoltaic polymers. The equations of motion for the electrons are evolved under the fixed subspace spanned by the active molecular orbitals during each nuclear time step and the feedback from charge to the nuclei motions, namely, the polaronic effect is considered. We investigated the charge transport dynamics for the ladder-type poly(p-phenylenes) (LPPP) and poly(diketopyrrolo-pyrrole (DPP)) series with ~2×10³ atoms. It was found that the diffusion abilities are determined by the magnitude of transfer integrals and localization length for frontier orbital which caused by the self-trapping effects (polaron) arising from the double bond stretching and twisting motions. This method can be useful in exploring the underlying charge transport behavior and improving the structure design of materials in organic electronics.