Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 38: [DS] Organic electronics and photovoltaics: electronic properties I (jointly with CPP, HL, O)
O 38.3: Vortrag
Mittwoch, 28. März 2012, 10:00–10:15, H 2032
Effect of molecular p-doping on hole density and mobility in P3HT and MEH-PPV — •Patrick Pingel and Dieter Neher — Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam
Molecularly doped semiconducting polymers can exhibit exceptionally high electrical conductivity, making them suitable for use in solution-processed organic circuitry. Recently, p-doping of conjugated polymers with the strong molecular acceptor tetrafluorotetracyanoquinodimethane, F4TCNQ, has been introduced.
Here, we present a detailed study of the doping efficiency and carrier mobility in thin layers of poly(3-hexylthiophene), P3HT, and poly(2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene vinylene), MEH-PPV, doped with F4TCNQ over a wide range of concentrations. Investigation of these layers with impedance spectroscopy in a metal-insulator-semiconductor (MIS) geometry allowed us to determine both charge carrier density and mobility as a function of doping ratio.
We show that the density of mobile holes increases strictly linearly with increasing F4TCNQ concentration, but the mobilities in P3HT and MEH-PPV exhibit non-monotonic dependencies on doping concentration. This behavior can be fully explained by a model originally developed by Arkhipov et al. [Phys. Rev. B 72, 235202 (2005)], which predicts that the Coulomb potential of a doping-induced negative counterion acts as a trapping center for holes. Thus, energetical disorder in the polymer layer is effectively increased upon chemical doping.