Relation of Structure and Charge Transport in 'Single-Stack' Organic Nanowires
Organic nanowires may provide insights into the fundamental processes of charge generation and transport in organic semiconductors under nanoscopic confinement. Here, we demonstrate how a simple molecular design results in nanowires with defined lateral dimensions that comprised a single stack of tightly π–π stacked chromophores at their core. Moreover, we prepared well-defined microfibers that exhibited hierarchical structure formation with a remarkably high degree of internal order and enabled us to obtain detailed structural information on all length scales with molecular level precision. The nanowires and microfibers nanowires showed light-induced formation of radical cations that behaved like positive polaron charge carriers. The nanofibrils were semiconducting, showed space-charge injection-limited conductivity behavior, and exhibited photo-current generation, relating their macroscopic electric properties to the spectroscopically characterized charge carriers. Our results, thus, provide an example of a universal organic nanowire model system that successfully links molecular design, well-defined supramolecular structure formation, charge carrier generation, and finally macroscopic charge transport.
About Holger Frauenrath
Holger Frauenrath studied chemistry at RWTH Aachen, Germany from 1992 to 1997, with a focus on synthetic organic chemistry. He performed his PhD thesis from 1998 to 2001 in the research group of Prof Hartwig Höcker at RWTH Aachen, working on a project related to the stereospecific polymerization of methacrylates as well as their copolymerization with olefins using zirconocene catalysts. Afterwards, he joined the group of Prof. Sam Stupp at Northwestern University, Evanston, IL, USA, as a postdoctoral fellow supported by a Feodor Lynen fellowship of the Alexander von Humboldt Foundation. His postdoctoral research projects were centered around the supramolecular self-assembly of rod-coil molecules. After his return to Germany in 2003, he started to build his own research group at FU Berlin, funded with an Emmy Noether Grant from the German Science Foundation. In 2005, the research group moved to the Department of Materials at ETH Zurich, Switzerland, where Holger Frauenrath obtained his Habilitation in 2009. In the same year, he was appointed as a tenure-track assistant professor at the Institute of Materials (IMX) of the Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, building the new Laboratory of Macromolecular and Organic Materials (LMOM). Holger Frauenrath has won several awards, including the Raimund Stadler Award of the Germany Chemical Society (GdCh), and a European Research Council (ERC) grant.