PLEASE NOTE TIME CHANGE to 2:45 PM
Please post and forward to your groups (Poster attached), thank you.
Center for Excitonics presents:
Polymer-Acceptor Bulk Heterojunction Solar Cells: From Chemical Structure to Packing and
Efficiency
April 17, 2018 at 2:45 PM/36-428
Jean-Luc Bredas
Department of Chemistry and Biochemistry, Georgia Tech
[
http://www.rle.mit.edu/excitonics/wp-content/uploads/2017/08/Jean-luc-Breda…]
The morphology of the active layer of a bulk heterojunction (BHJ) solar cell, made of a
blend of an electron-donating polymer and an electron-accepting fullerene or nonfullerene
derivative, is known to play a determining role in device performance. Here, based on the
results of molecular dynamics simulations and long-range corrected density functional
theory calculations, we first describe the nature of the binding interactions at the
donor�Cacceptor interfaces, the molecular-level packing in the pure phases as well as at
these interfaces, and the impact of the system dynamics on the interfacial electronic
structure.
We then discuss how even minor changes in the chemical structure of the polymer backbone
have been shown experimentally to change substantially the blend morphology and the
resulting solar-cell efficiency. Taking a series of representative systems based on
benzothiadiazole-quaterthiophene polymers and PC71BM, we elucidate the impact of the
chemical changes on the ��local�� morphology. We focus on the extent of polymer-fullerene
mixing, on their packing, and on the characteristics of the fullerene-fullerene connecting
network in the mixed regions, which are all aspects that are difficult to access
experimentally. We are able to rationalize the evolutions in power conversion efficiencies
within the polymer series. Finally, we address the peculiarities observed in the
PIPCP-fullerene blends. This work is supported by the Office of Naval Research, namely in
the framework of the MURI Center on Advanced Organic Photovoltaics.
Jean-Luc Br��das is a Belgian chemist and currently at Georgia Tech. He was a
Distinguished Professor of Material Science and Engineering in the Physical Science and
Engineering Division at KAUST, and at the Universit�� de Mons-Hainaut Belgium. He studied
Chemistry (B.S. 1976) and obtained a PhD in 1979 at the Facult��s Universitaires
Notre-Dame de la Paix (University of Namur), Belgium. His research deals with the
structural, electronic, and optical properties of novel organic and nanomaterials with
promising characteristics in the field of electronics, photonics, and information
technology. Br��das is among the top 100 most cited chemists in the world, and is
included in the list of the Highly Cited Researchers for Chemistry [2]. He is the Director
of International Programs at the Center for Organic Photonics and Electronics at Georgia
Tech. He is a member of the International Academy of Quantum Molecular Science (2011).[1]
He is a Fellow of the American Association for the Advancement of Science, the American
Chemical Society, the American Physical Society, and the Optical Society of America.
Light refreshments will be served.
The Center For Excitonics Is An Energy Frontier Research Center Funded By The U.S.
Department Of Energy,
Office Of Science And Office Of Basic Energy Sciences