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"Macroscopic & nanoscale charge transport in poly(3-alkylthiophene)s: from single nanofiber to semi-crystalline thin films."

A key parameter influencing strongly the performance of devices based on organic semiconductors (solar cells, transistors, organic LEDs) is the easiness with which an electric charge (hole or electron) can be transported by an electric field through the polymer. Physicists quantify this material property by the charge carrier mobility, µ. The aim of this work is to explore charge transport (in term of performance, mechanism and influencing morphological factors) in poly(3-alkylthiophene)s (P3AT)s, a family of conjugated polymers which is frequently used as model system. We will investigate charge transport for two kinds of P3AT layers: those obtained from nanofiber dispersions (model system 1) and those obtained from molecularly dissolved solution (model system 2).

We will see that both systems have their own advantages and that the comparison of the two systems will allow us to conclude on which morphological factors influence in-plane charge transport in P3ATs layers. Another key point of this thesis lies in the fact that we will perform a multi length scales study: a nanoscale approach on one isolated nanofiber and a macroscopic approach on semi-crystalline thin films. Considering isolated nanofibers as nanoscopic basic building blocks of macroscopic thin films, we will propose qualitative models for charge transport in organic field-effect transistors.