title: Influence of molecular designs on polaronic and vibrational transitions in a conjugated push-pull copolymer.
abstract: Electron-phonon interactions of free charge-carriers in doped pi-conjugated polymers are conceptually described by 1-dimensional (1D) delocalization. Thereby, polaronic transitions fit the 1D-Froehlich model in quasi-confined chains. However, recent developments in conjugated polymers have diversified the backbones to become elaborate heterocylcic macromolecules. Their complexity makes it difficult to investigate the electron-phonon coupling. In this work we resolve the electron-phonon interactions in the ground and doped state in a complex push-pull polymer. We focus on the polaronic transitions using in-situ spectroscopy to work out the differences between single-unit and push-pull systems to obtain the desired structural- electronic correlations in the doped state. We apply the classic 1D-Froehlich model to generate optical model fits. Interestingly, we find the 1D-approach in push-pull polarons in agreement to the model, pointing at the strong 1D-character and plain electronic structure of the push-pull structure. In contrast, polarons in the single-unit polymer emerge to a multi- dimensional problem difficult to resolve due to their anisotropy. Thus, we report an enhancement of the 1D-character by the push-pull concept in the doped state - an important view in light of the main purpose of push-pull polymers for photovoltaic devices.
authors.affiliation: Center for Surface- and Nanoanalytics, Johannes Kepler University of Linz, A-4040 Linz, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Cobet
authors.affiliation: Physics Department, Technical University of Chemnitz, 09107 Chemnitz, Germany.
authors.forename: Jacek
authors.initials: J
authors.lastname: Gasiorowski
authors.affiliation: Department of Physics, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Reghu
authors.initials: R
authors.lastname: Menon
authors.affiliation: Center for Surface- and Nanoanalytics, Johannes Kepler University of Linz, A-4040 Linz, Austria.
authors.forename: Kurt
authors.initials: K
authors.lastname: Hingerl
authors.affiliation: Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz, Austria.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Schlager
authors.affiliation: Department of Physics, University of Vermont, Cook Building, 82 University Place, University of Vermont Burlington, VT 05405-0125, USA.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: White
authors.affiliation: Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz, Austria.
authors.forename: Helmut
authors.initials: H
authors.lastname: Neugebauer
authors.affiliation: Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz, Austria.
authors.forename: N Serdar
authors.initials: NS
authors.lastname: Sariciftci
authors.affiliation: Institute of Physical Chemistry, Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Stadler