We report on quantum dynamical studies of ultrafast photo-induced energy and charge transfer in organic semiconductor materials, complementing time-resolved spectroscopic observations that underscore the coherent nature of the ultrafast elementary transfer events in these molecular aggregate systems. Our approach combines first-principles parametrized Hamiltonians with accurate quantum dynamics simulations using multiconfigurational methods, along with semiclassical approaches. This paper focuses on the elementary mechanism of coherent exciton migration and creation of charge-transfer excitons in polythiophene type materials, representative of the poly(3-hexylthiophene) (P3HT) polymer. Special emphasis is placed on the interplay of trapping due to high-frequency phonon modes, and thermal activation due to low-frequency ”soft” modes which drive a diffusive dynamics.
We present theoretical studies of elementary exciton and charge transfer processes in functional organic materials, in view of understanding the key microscopic factors that lead to efficient charge generation in photovoltaics applications. As highlighted by recent experiments, these processes can be guided by quantum coherence, despite the presence of static and dynamic disorder. Our approach combines first-principles parametrized Hamiltonians, based on Time-Dependent Density Functional Theory (TDDFT) and/or high-level electronic structure calculations, with accurate quantum dynamics simulations using the Multi-Configuration Time-Dependent Hartree (MCTDH) method. This contribution specifically addresses charge generation in a novel class of highly ordered oligothiophene-perylene diimide type co-oligomer assemblies, highlighting that chemical design of donor/acceptor combinations needs to be combined with a detailed understanding of the effects of molecular packing.