Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 101: Molecular Films: Electronics, Photovoltaics and Structure

O 101.1: Vortrag

Freitag, 4. April 2014, 10:30–10:45, WIL A317

Towards computational solar cell design: Calculating ab initio charge-transfer coupling elements for large systems — •Christoph Schober, Harald Oberhofer, and Karsten Reuter — Technische Universität München, Germany

Organic solar cells promise outstanding application possibilities, but current systems lack the efficiency to be economically viable. Improvements are often the result of experimental intuition or empirical knowledge, rather than strategic design. Towards a computer-aided design we need to understand, amongst others, the complex mechanism of charge propagation in (possibly amorphous) materials. To this end, Hamiltonian charge-transfer coupling elements are a key ingredient linking microscopic structure and the charge mobilities that determine the device efficiency. To make the calculation of these coupling elements numerically tractable for complex systems we implement a fragment molecular orbital scheme in FHIaims, a highly parallelized all-electron ab initio code that due to its atom-centered basis sets is ideally suited to tackle the non-periodicity of organic solar cell materials. We use the self-consistent density of the fragments to construct the system Hamiltonian with correct number of electrons, and additionally implement an embedding scheme that allows to consider the generally neglected second fragment and therewith take polarization effects into account. We present charge-transfer coupling elements for a number of systems previously used for benchmarking and for larger molecules used as hole transport material for organic solar cells.