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Conjugated Block Copolymer Photovoltaics with near 3% Efficiency through Microphase Separation
journal contribution
posted on 2013-06-12, 00:00 authored by Changhe Guo, Yen-Hao Lin, Matthew D. Witman, Kendall
A. Smith, Cheng Wang, Alexander Hexemer, Joseph Strzalka, Enrique D. Gomez, Rafael VerduzcoOrganic
electronic materials have the potential to impact almost
every aspect of modern life including how we access information, light
our homes, and power personal electronics. Nevertheless, weak intermolecular
interactions and disorder at junctions of different organic materials
limit the performance and stability of organic interfaces and hence
the applicability of organic semiconductors to electronic devices.
Here, we demonstrate control of donor–acceptor heterojunctions
through microphase-separated conjugated block copolymers. When utilized
as the active layer of photovoltaic cells, block copolymer-based devices
demonstrate efficient photoconversion well beyond devices composed
of homopolymer blends. The 3% block copolymer device efficiencies
are achieved without the use of a fullerene acceptor. X-ray scattering
results reveal that the remarkable performance of block copolymer
solar cells is due to self-assembly into mesoscale lamellar morphologies
with primarily face-on crystallite orientations. Conjugated block
copolymers thus provide a pathway to enhance performance in excitonic
solar cells through control of donor–acceptor interfaces.