Berlin 2015 – scientific programme
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DF: Fachverband Dielektrische Festkörper
DF 3: Photovoltaics: Kesterites and Less Widely used Materials (HL with DF)
DF 3.1: Talk
Monday, March 16, 2015, 11:15–11:30, ER 164
Optical properties of Cu-chalcogenide photovoltaic absorbers from self-consistent GW and the Bethe-Salpeter equation — •Sabine Körbel1,2, David Kammerlander2, Rafael Alejandro Sarmiento Pérez2,3, Miguel Alexandre Lopes Marques1, and Silvana Botti3 — 1Martin-Luther-Universität Halle-Wittenberg, Germany — 2Université Claude Bernard Lyon 1, France — 3Friedrich-Schiller-Universität Jena, Germany
Self-consistent GW and the solution of the Bethe-Salpeter equation are currently the best approaches to accurately simulate electronic excitations in a vast class of materials, ranging from molecules to solids. However, numerical instabilities, caused by a vanishing band gap in density-functional theory, make it impossible to use the common implementations of these techniques to calculate optical absorption spectra of the best-known thin-film absorbers for solar cells: Cu(In,Ga)(S,Se)2 chalcopyrites and Cu2ZnSn(S,Se)4 kesterites/stannites. Here we solve this problem by using a finite-difference method in k-space to evaluate the otherwise diverging dipole matrix elements, obtaining excellent agreement with experiment. Having established the validity of this approach, we use it then to calculate the optical response of the less-studied, but promising, Cu2ZnGe(S,Se)4 compounds, opening the way to predictive calculations of still unknown materials.