Polymer Solar Cells - Phase Separation and Morphology Formation

This project is part of the DFG priority programm "Elementary Processes of Organic Photovoltaics" and is conducted in collaboration with the following partners:

Homepage of the TRAPOS research group: www.trapos.eu

Project description

Organic polymer solar cells (PSCs) offer a promising alternative to their inorganic counterparts due to their potential for low cost and light weight photovoltaic devices. Their development is connected to the rapid advances in the field of organic light emitting diodes (OLEDs). Semiconducting polymers exhibit electrical and optical properties similar to inorganic semiconductors while having attractive mechanical properties and processing advantages. In contrast to inorganic solar cells PSCs are considered for processing with established coating methods, e.g., knife coating, gravure coating and slot die coating for roll-to-roll production.

Figure 1: Layer structure of the polymer solar cell with approximate film thicknesses. Electron donor (P3HT) and acceptor (PCBM) are blended together to maximize the interface where exciton dissociation into electrons and holes takes place. For an effcient photocurrent, each material must provide a continuous path for electron and hole transport to the respective contact. Isolated domains can collect charges and cause recombination.

The upscaling of these processes is a big challenge, since typical cell thicknesses are in the order of a few hundred nanometer. The structure and nano morphology of the photoactive blend is crucial for solar cell performance and depends strongly on drying kinetics and solvent properties. This project focuses on the drying characteristics of organic semiconducting materials and the influence of drying kinetics on the morphology.


Publications on thin film drying kinetics:

  • B. Schmidt-Hansberg, M. Baunach, J. Krenn, S. Walheim, U. Lemmer, P. Scharfer, W. Schabel
    Spatially resolved drying kinetics of multi-component solution cast films for organic electronics
    Chemical Engineering and Processing 50, 509-515 (2001)
  • B. Schmidt-Hansberg, M. F. G. Klein, K. Peters, F. Buss, J. Pfeifer, S. Walheim, A. Colsmann, U. Lemmer, P. Scharfer, W. Schabel
    In-situ monitoring the drying kinetics of knife coated polymer-fullerene films for organic solar cells
    Journal of Applied Physics 106, 124501 (2009)

    Feature article in Virtual Journal of Nanoscale Science & Technology 21, 1 (2010)


Publications on structure formation during film drying:

  • M. Sanyal, B. Schmidt-Hansberg, M.F.G. Klein, C. Munuera, A. Vorobiev, A. Colsmann, P. Scharfer, U. Lemmer, W. Schabel, H. Dosch, E. Barrena
    Effect of Photovoltaic Polymer/Fullerene Blend Composition Ratio on Microstructure Evolution during Film Solidification Investigated in Real Time by X-ray Diffraction
    Macromolecules 44, 3795–3800 (2011)
  • M. Sanyal, B. Schmidt-Hansberg, M.F.G. Klein, A. Colsmann, C. Munuera, A. Vorobiev, U. Lemmer, W. Schabel, H. Dosch, E. Barrena
    In Situ X-Ray Study of Drying-Temperature Influence on the Structural Evolution of Bulk-Heterojunction Polymer–Fullerene Solar Cells Processed by Doctor-Blading
    Advanced Energy Materials 1, 363-367 (2011)