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Nanomorphology of P3HT:PCBM-Based Absorber Layers of Organic Solar Cells after Different Processing Conditions Analyzed by Low-Energy Scanning Transmission Electron Microscopy

Published online by Cambridge University Press:  20 November 2012

Marina Pfaff ,
Michael F.G. Klein ,
Erich Müller ,
Philipp Müller ,
Alexander Colsmann ,
Uli Lemmer  and
Dagmar Gerthsen
Marina Pfaff*
Affiliation:
Laboratory for Electron Microscopy (LEM), Karlsruhe Institute of Technology (KIT), Engesserstraße 7, 76131 Karlsruhe, Germany Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Straße 1a, 76131 Karlsruhe, Germany
Michael F.G. Klein
Affiliation:
Light Technology Institute, Karlsruhe Institute of Technology (KIT), Engesserstraße 13, 76131 Karlsruhe, Germany
Erich Müller
Affiliation:
Laboratory for Electron Microscopy (LEM), Karlsruhe Institute of Technology (KIT), Engesserstraße 7, 76131 Karlsruhe, Germany Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Straße 1a, 76131 Karlsruhe, Germany
Philipp Müller
Affiliation:
Laboratory for Electron Microscopy (LEM), Karlsruhe Institute of Technology (KIT), Engesserstraße 7, 76131 Karlsruhe, Germany Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Straße 1a, 76131 Karlsruhe, Germany
Alexander Colsmann
Affiliation:
Light Technology Institute, Karlsruhe Institute of Technology (KIT), Engesserstraße 13, 76131 Karlsruhe, Germany
Uli Lemmer
Affiliation:
Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Straße 1a, 76131 Karlsruhe, Germany Light Technology Institute, Karlsruhe Institute of Technology (KIT), Engesserstraße 13, 76131 Karlsruhe, Germany
Dagmar Gerthsen
Affiliation:
Laboratory for Electron Microscopy (LEM), Karlsruhe Institute of Technology (KIT), Engesserstraße 7, 76131 Karlsruhe, Germany Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Straße 1a, 76131 Karlsruhe, Germany
*
*Corresponding author. E-mail: marina.pfaff@kit.edu
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Abstract

In this study the nanomorphology of P3HT:PC61BM absorber layers of organic solar cells was studied as a function of the processing parameters and for P3HT with different molecular weight. For this purpose we apply scanning transmission electron microscopy (STEM) at low electron energies in a scanning electron microscope. This method exhibits sensitive material contrast in the high-angle annular dark-field (HAADF) mode, which is well suited to distinguish materials with similar densities and mean atomic numbers. The images taken with low-energy HAADF STEM are compared with conventional transmission electron microscopy and atomic force microscopy images to illustrate the capabilities of the different techniques. For the interpretation of the low-energy HAADF STEM images, a semiempirical equation is used to calculate the image intensities. The experiments show that the nanomorphology of the P3HT:PC61BM blends depends strongly on the molecular weight of the P3HT. Low-molecular-weight P3HT forms rod-like domains during annealing. In contrast, only small globular features are visible in samples containing high-molecular-weight P3HT, which do not change significantly after annealing at 150°C up to 30 min.

Keywords

scanning transmission electron microscopylow electron energyHAADForganic solar cellP3HTPCBMnanomorphology
Type
Materials Applications
Information
Microscopy and Microanalysis , Volume 18 , Issue 6 , December 2012 , pp. 1380 - 1388
Copyright
Copyright © Microscopy Society of America 2012

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