title: Dielectric Function of Undoped and Doped Poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene] by Ellipsometry in a Wide Spectral Range.
abstract: Ellipsometric measurements in a wide spectral range (from 0.05 to 6.5 eV) have been carried out on the organic semiconducting polymer, poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene] (MDMO-PPV), in both undoped and doped states. The real and imaginary parts of the dielectric function and the refractive index are determined accurately, provided that the layer thickness is measured independently. After doping, the optical properties show the presence of new peaks, which could be well-resolved by spectroscopic ellipsometry. Also for the doped material, the complex refractive index, with respect to the dielectric function, has been determined. The broadening of the optical transitions is due to the delocalization of polarons at higher doping level. The detailed information about the dielectric function as well as refractive index function obtained by spectroscopic ellipsometry allows not only qualitative but also quantitative description of the optical properties of the undoped/doped polymer. For the direct characterization of the optical properties of MDMO-PPV, ellipsometry turns out to be advantageous compared to conventional reflection and transmission measurements.
authors.affiliation: Linz Institute for Organic Solar Cells (LIOS), Physical Chemistry, and Center for Surface and Nanoanalytics, Johannes Kepler University of Linz , Altenberger Strasse 69, 4040 Linz, Austria.
authors.forename: Jacek
authors.initials: J
authors.lastname: Gasiorowski
authors.forename: Kurt
authors.initials: K
authors.lastname: Hingerl
authors.forename: Reghu
authors.initials: R
authors.lastname: Menon
authors.forename: Thomas
authors.initials: T
authors.lastname: Plach
authors.forename: Helmut
authors.initials: H
authors.lastname: Neugebauer
authors.forename: Karin
authors.initials: K
authors.lastname: Wiesauer
authors.forename: Cigdem
authors.initials: C
authors.lastname: Yumusak
authors.forename: Niyazi S
authors.initials: NS
authors.lastname: Sariciftci