Berlin 2008 – wissenschaftliches Programm

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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 5: Poster Session SYSA

SYSA 5.22: Poster

Dienstag, 26. Februar 2008, 14:30–20:00, Poster A

Effect of blending ratio and internal order on the optical properties of P3HT:PCBM bulk heterojunction films — •Thomas Madena, Martin Knipper, Ingo Riedel, and Jürgen Parisi — Energy- and Semiconductor Research Laboratory, Department of Physics, University of Oldenburg, Carl-von-Ossietzky-Strasse 9-11, D-26111 Oldenburg

Organic solar cells represent thin film devices comprising a multilayer system of planar semiconductor films finished with a metal electrode. Internal reflections of the incident light and the resulting coherent superposition of electromagnetic waves travelling in opposite directions cause a spatially nonuniform light intensity distribution. Calculation of the intensity pattern along the cross section of the device is an essential step for optimizing the photocurrent in single junction and in particular multispectral tandem devices. Provided that thickness and optical constants of individual layers of the device are known optical simulation of the light propagation can be carried out via the transfer matrix formalism. In this work we investigated the absorber of solution-processed organic solar cells based on conjugated polymer-fullerene (P3HT: PCBM) bulk heterojunctions. Variation of the blending ratio and thermal annealing of the films have strong impact on the device performance. Ellipsometry was applied together with structural analysis of P3HT: PCBM films in order to relate their optical response to the film composition and thermally induced internal ordering. The results are correlated with the measured photocurrent and spectral response of solar cells with respective active layer composition.