Electronic properties of interfaces with conjugated oligo- and polymers

• Applicant: Professorin Dr. Petra Tegeder
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2008 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 66250412

The project focuses on polymer interfaces that are of direct relevance for organic photo-voltaic cells (OPVCs), their function and efficiency. Our goal is to provide a complete under-standing of the energy levels and charge carrier dynamics at all interfaces that occur in polymer/polymer heterojunction photovoltaic cells (i.e., donor polymer/anode, donor/acceptor and acceptor polymer/cathode interfaces) and how these energy levels influence the OPVC energy conversion efficiency. These interfaces comprise new polythiophene-based donor polymers, and in this second project phase also imide-substituted acceptor copolymers, available through collaboration with the Scherf group (Uni Wuppertal) within this priority program. Using one- and two-photon photoemission (2PPE) spectroscopy all relevant properties that determine the open circuit voltage (i.e., polymer/electrode work function, energy offset between polymer valence and conduction bands, offset between donor valence and acceptor conduction band) will be will determined. In addition time-resolved 2PPE provides access to the charge carrier dynamics at polymer/electrode interfaces. These values will be used, in combination with OPVC characterization, to test existing device models, and to provide a reliable parameter base for improved understanding of device function. This work is performed in close cooperation with the project of Neher/Scherf (Uni Potsdam/Uni Wuppertal) which employs the same semiconducting polymers for OPVC fabrication and characterization. These concerted efforts will provide elementary physical properties of polymer interfaces and full characterization of OPVCs and will thus lead to a significant advance in the understanding of elementary processes of organic photovoltaics.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1355: Elementary Processes of Organic Photovoltaics