Electronic Structure of Organic Semiconductors by GW Methods

Friday, April 17, 2015 4:30 p.m. to 6 p.m.
Dr. Noa Marom of Tulane University
Organic photovoltaics are attractive for large area, low cost
applications and for flexible, lightweight modules. However, their relatively
low efficiency leaves much to be desired. Insight from computation may help
improve device performance by designing new organic semiconductors and ordered
nanostructured interfaces. It is important to obtain an accurate description of
the electronic structure of organic semiconductors, including the fundamental gaps and absolute
positions of the donor HOMO and the acceptor LUMO at the interface. This
requires going beyond ground state density functional theory (DFT). 0Many-body perturbation theory is often used for this
purpose within the GW approximation, where G is the one particle Green function
and W is the dynamically screened Coulomb interaction. Typically, GW
calculations are performed as a non-self-consistent perturbative correction to
DFT eigenvalues, known as G0W0. The predictive power of G0W0 is limited by
a strong dependence of the results on the DFT starting point. Self-interaction
errors (SIE), spurious charge transfer, and incorrect ordering and
hybridization of molecular orbitals may propagate from the DFT level to G0W0. These issues
may be addressed by judiciously choosing a hybrid DFT starting point or by
going beyond G0W0 to a higher level of self-consistency. Here, this is
demonstrated for prototypical organic semiconductors and interfaces. Read More

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Physical Sciences Building: 161


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physics colloquium