To describe nonadiabatic electron dynamics in large organic systems, we use the mixed quantum-classical CPA-FSSH method in conjunction with DFTB, which has been shown to give accurate electronic structures for model organic photovoltaic systems . The electronic structure calculations are performed at the DFTB3 level of theory with the 3ob-3-1 Slater-Koster parameter set as implemented in the DFTB+ package . Dispersion interactions between the atoms are incorporated using the Lennard-Jones potential with UFF parameters . The initialized wavefunction, |Ψ(r, 0) , is the LUMO of the donor moiety, |Φ D LUMO , which is a widely used approximation for simulating photoinduced charge transfer dynamics. Here, the LUMO of the donor moiety is obtained from a separate DFTB calculation performed for the isolated donor. From the set of eigenvectors (MOs) of the entire system at the zeroth timestep, {|Φ i (r; R(0)) }, an MO maximizing the overlap Φ D LUMO |Φ i (r; R) is selected.