Shafigh Mehraeen, Massachusetts Institute of Technology
February 11, 2015
810 S. Clinton Street, Chicago, IL 60612
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Self-Assembly, Complex Fluids, and Charge Transport in Nanoscience
Molecular structure of many polymers including biopolymers creates elastic rigidity that impacts polymers behavior. Understanding this impact is critical to address the physics describing variety of single-molecule experiments and biological processes including self-assembly. In the first part of my talk, utilizing analytical theories and numerical simulations, I illustrate the effect of molecular elasticity on the behavior of single molecules employed in tethered-bead single-molecule experiments as well as the morphology of assemblages in protein self-assembly processes. In the context of self-assembly, I will also discuss directed self-assembly and dewetting of nanoparticles within channels. I show that nanoparticles transit through a more diverse set of self-assembled configurations than observed for compressed systems. In the second part of my talk, I will discuss the impact of active layer morphology on charge transport properties of organic solar cells. The morphology of the active layer in polymer:fullerene solar cells is a key parameter in determining their performance. Transmission electron microscopy images show that while not-annealed polymer/fullerene bilayers possess a sharp interface, intermixing proceeds upon annealing. Transient absorption studies also indicate that the not-annealed bilayer yields fewer, but longer lived, charge carriers compared to the bulk heterojunction solar cells. Our computer simulations suggest that the difference in bimolecular recombination dynamics observed for the bulk heterojunction and bilayer cells could be related to the confinement of charge carriers to the interface, leading to lower recombination in the bilayer cells.
Jun 17, 2019
Jun 17, 2019