Quantum Dynamics of Electron–Hole Separation in Stacked Perylene Diimide-Based Self-Assembled Nanostructures

We report on high-dimensional quantum dynamical simulations of electron-hole separation in self-assembled mesomorphic nanostructures composed of donor-acceptor conjugated co-oligomers. The latter are based on perylene diimide (PDI) acceptor units combined with fluorene-thiophene-benzothiadiazole donor units, which form highly ordered, stacked structural motifs upon self-assembly. Simulations are shown for a first-principles parametrized model lattice of 25 stacked PDI units under the effects of an applied external field and temperature. The simulations are carried out with the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method with nearly 900 vibrational degrees of freedom and 25 electronic states. Temperature effects are included using the thermofield dynamics approach. A transition between a short-time coherent dynamics and a kinetic regime is highlighted. From a flux-over-population analysis, electron-hole dissociation rates are obtained in the range of 5-20 ns-1 in the absence of static disorder, exhibiting a moderate field and temperature dependence. These results for electron-hole separation rates can be employed as a benchmark to calibrate the parametrization of kinetic Monte Carlo simulations applied to much larger lattice sizes.