Ab inito study on morphology of donor-acceptor polymers

Donor-acceptor (DA) polymers have been found to be good materials for organic electronics since they provide interesting features like mechanical flexibility and high impact resistance.
Moreover, they offer the possibility to produce devises by low cost roll-to-roll printing techniques. Thus, they are highly promising candidates for organic thin-film transistors and solar cells. For applications, however, these materials should fulfill several demands such as ambient stability, good solubility, and good film-forming properties. The charge carrier mobility is one of the most important quantities.
In order to analyze the influence of the molecular structure on these properties, we investigate DA polymers using first-principals methods as density functional theory (DFT). In particular, density functional based tight binding (DFTB) is used to study large systems.
Starting from isolated monomers being the building blocks of the DA polymers the total energy, the atomic charges, the difference between highest occupied and lowest unoccupied molecular orbitals, and the reorganization energies are calculated.
Furthermore, oligomers up to a length of 100 conjugated units as well as infinite long polymers are considered. Finally, the morphological properties are investigated by studying systems of several polymer chains with different crossing angles and relative shifts.