To understand charge transfer dynamics in large organic photovoltaic systems, we use the CPA-FSSH method in the DFTB+ software package (version 17.1). In particular, we use the DFTB3 variant 72 as our electronic structure method to obtain the adiabatic eigenvectors and eigenvalues at each nuclear time step. For this implementation, we assume that the photoinduced excited state dynamics can be well described with a single-electron wavefunction. Hence, we adapt the single particle version of the time-dependent Kohn-Sham (TDKS) approximation, which assumes the time-dependent excited state wavefunction |Ψ(r, t) can be represented as a linear combination of the ground state KS orbitals |Φ i (r, R(t)) , as given in Eq. ( ). This definition of |Ψ(r, t) has been shown to provide reasonable photoinduced charge transfer dynamics. Using the above definition, Eq. ( ) can be numerically integrated using the fourth-order Runge-Kutta (RK4) method to obtain the expansion coefficients, a i (t), at each time step. During the integration, to compute the non-adiabatic coupling elements (Eq. ( )), we use the following well-established approximation 64