Accurate Description of the Electronic Structure of Organic Semiconductors by GW Methods

TYPECondensed Matter Seminar
Speaker:Noa Marom
Affiliation:Tulane University, New Orleans
Location:Lidow Nathan Rosen (300)

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).

Many-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.


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