AVS 58th Annual International Symposium and Exhibition
    Energy Frontiers Focus Topic Tuesday Sessions
       Session EN+NS-TuM

Paper EN+NS-TuM2
Orbital-dependent Charge Transfer Dynamics in Potential Molecular Wires

Tuesday, November 1, 2011, 8:20 am, Room 103

Session: Ultrafast Charge and Energy Transfer in Nanomaterials
Presenter: Michael Zharnikov, Universität Heidelberg, Germany
Authors: H. Hamoudi, Universität Heidelberg, Germany
S. Neppl, Technische Universität München, Germany
P. Kao, Penn State University
B. Schüpbach, Universität Frankfurt, Germany
P. Feulner, Technische Universität München, Germany
A. Terfort, Universität Frankfurt, Germany
D.L. Allara, Penn State University
M. Zharnikov, Universität Heidelberg, Germany
Correspondent: Click to Email
Continued progress in technologically important fields such as molecular and organic electronics as well as organic photovoltaics depends on reliable information about the charge transport (CT) through individual molecular groups, above all so-called molecular wires, since these represent important building blocks of a variety of devices. In this context, femtosecond CT dynamics in a series of self-assembled monolayers with oligo(phenylenethynylene) and oligo(phenyl) backbone, which are prototypes of potential molecule wires, was addressed by resonant Auger spectroscopy using the core hole clock method. The length of the molecular backbone was varied to monitor the respective dependence of the CT time. The CT pathway was unambiguously defined by resonant excitation of the nitrile tailgroup attached to the backbone. Due to the conjugation of the electronic systems of this group and the adjacent terminal phenyl ring of the backbone, a splitting of the degenerated unoccupied molecular orbital (MO) of nitrile occurred, resulting in two different MOs which could be selectively addressed by X-rays and used as the starting points for CT. The characteristic CT times were found to depend strongly on the character of the MO which mediates the CT process. This demonstrates that the efficiency and rate of CT in molecular wires can be controlled by resonant injection of the charge carriers into specific MOs.