Dresden 2011 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: Poster: Organic Semiconductors

CPP 8.44: Poster

Monday, March 14, 2011, 17:30–19:30, P2

Correlation between sheet resistance and NIR-VIS absorption of PEDOT:PSS — •Felix Herrmann, Sebastian Engmann, Sviatoslav Shokhovets, Harald Hoppe, and Gerhard Gobsch — TU-Ilmenau, Ilmenau, Germany

PEDOT:PSS is a widely used buffer and hole-collecting layer in organic photovoltaics. In the past years a constant improvement of the PEDOT:PSS conductivity has been shown. This make PEDOT:PSS a potential candidate to replace ITO electrodes. Although this material is widely used in optoelectronic devices like solar cells and light emitting diodes, only little is known about the optical properties. Especially the absorption in the NIR and VIS region contains some information about free carriers and trap states in the gap. Therefore a relation between the absorption of PEDOT:PSS and the conductivity can be expected. Typically the absorption coefficient in this region is below 10⁴ per cm and the film thickness reaches about 40 nm. For these small absorptions the sensitivity of standard measurement methods like transmission/reflection and ellipsometry is rather poor. Therefore ellipsometric measurements were complemented by photothermal deflection spectroscopy. The charge carrier density calculations on the basis of the absorption and dielectric function were compared with the experimentally determined sheet resistance of different films to prove that relation.