Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 8: Poster: Organic Semiconductors
CPP 8.45: Poster
Montag, 14. März 2011, 17:30–19:30, P2
Impedance spectroscopic investigations of molecularly doped conjugated polymers — •Patrick Pingel and Dieter Neher — Soft Matter Physics, University of Potsdam, Germany
Molecularly doped semiconducting polymers can exhibit exceptionally high electrical conductivity, making them suitable for use in solution-processed organic circuitry. Recently, doping of conjugated polymers with the strong molecular acceptor tetrafluorotetracyanoquinodimethane, F4TCNQ, has been introduced [1]. It has been proposed that F4TCNQ-doping leads to the formation of charge transfer complexes with hybrid supramolecular orbitals and a reduced band gap, and that free holes are generated via thermally-induced dissociation of these complexes. Here, thin layers of poly(2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene vinylene), MEH-PPV, have been doped at various doping ratios. Investigation of these samples with impedance spectroscopy in a metal-insulator-semiconductor (MIS) geometry allowed us to determine both charge carrier density and mobility of the doped polymer layers. The free carrier density is found to be well below the dopant concentration, which is in full agreement to our model that free carrier formation proceeds via a charge transfer complex. Moreover, we observed the formation of an inversion layer upon depletion bias, which is absent in non-doped samples.
[1] E.F. Aziz et al., Adv. Funct. Mater. 2007, 19, 3257.