Prof. Ullrich Steiner "Kinetic evolution of structure formation in polymer films for organic photovoltaics"
Adolphe Merkle Institute, Fribourg, Switzerland
What |
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When |
Apr 22, 2015 from 02:15 PM to 03:15 PM |
Where | Seminarraum A, FMF, Stefan-Meier-Str. 21, Freiburg |
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In contrast to low molecular weight materials, long macromolecular chains entangle, trapping them in morphologies that are far from thermodynamic equilibrium. While complex in term of their physical description, this opens a rich play field in terms of structures and related physical effects that can be achieved, as demonstrated by biology, where the control of non-equilibrium structures is one of the pillars of life. Rather than determined by equilibrium thermodynamics, structure formation is determined by kinetic aspects and the trajectory the system takes across phase space.
Here, I will address two aspects of non-equillibrium structure formation in polymer melts. The first part will discuss the seemingly simple case of polymer film formation. Preparation procedures and the presence of interfaces often prevents the equilibration of the polymers within the film with interesting consequences for all its macroscopic properties, including the stability of the film itself.
The second part investigates the structure formation in polymer based solar cells. In these systems, the interplay of crystallisation and phase separation gives rise to structure formation on a hierarchy of length scales the details of which determine the photovoltaic performance of these devices.
invited by Dr. Michael Sommer