 |
Center for Nonlinear Studies |
Conjugated polymers are well-known for their use in materials for organic electronics. In these materials, useful optoelectronic properties arise from the conjugation of pi-orbitals along the polymer backbone. In aggregate structures, such as thin films or polymer nanoparticles, optical properties can be affected by internal (polymer chain) morphology and intermolecular packing. Internal effects are due to torsional disorder between units in the polymer backbone, resulting in 'twisted' intramolecular morphologies, while intermolecular disorder arises due to variation in the packing of polymer chains and interactions between polymer pi-systems. Many of these materials are semicrystalline, so important structural variation on the aggregate scale is found in ordered/disordered domain structures. The presence of these structural effects make computational studies of excited states in these materials extremely difficult. This talk will present models using combinations of molecular dynamics, Density-Functional Theory, and kinetic Monte-Carlo methods that probe the effects of chain morphology and packing on the spectral, structural, and transport properties of singlet excitons in isolated polymer chains and aggregate structures. Applying these methods to poly(3-hexylthiophene), a polymer frequently used in organic photovoltaics, results have suggested deleterious effects of structural disorder on properties related to photovoltaic performance, e.g. absorption cross section and exciton diffusion length.
Host: Sergei Tretiak