As Project Coordinator within Prof. Kremer's ERC Advanced Grant "MOLPROCOMP" at the Max Planck Institute for Polymer Research in Mainz, my general interest is in the development and application of computer simulation methods for a molecular understanding of non-equilibrium processes in soft-matter systems. Such an endeavor requires the combined efforts of quantum-chemical, atomistic, and coarse-grained simulation techniques.

Quantum chemistry based on Many-body Green's functions theory (GW-BSE)

My scientific expertise is on ab-inito techniques for the calculation of structural and electronic properties of materials. Method development currently focuses on the evaluation and development of many-body Green’s functions theory (GW-BSE) for use in typical quantum-chemical applications. An efficient localized-orbital based implementation of this beyond-DFT method coupled to standard packages of quantum chemistry allows to treat excited states of molecular structures containing >100 atoms with a high level of accuracy [JCTC 8, 997 (2012)]. Notably, it is possible to describe local and charge-transfer excitations, e.g. in donor-acceptor complexes, equally well with a single approach [JCTC 8, 1790 (2012)]. The current challenge is to account for environment effects when the complex is embedded in a molecular aggregate, e.g., formed by vapor-deposition or solution processing of the material. We found in a recent study that mesoscale methods (polarizable continuum and/or lattice models) are inadequate to quantitatively account for local crystal fields and the related polarization induced effects [PRL 109, 136401 (2012)]. We therefore presently focus on the development of a hybrid QM/MM approach that couples the efficient GW-BSE calculations to a classical environment represented by atomic partial charges and polarizabilities [JCTC 10, 3104 (2014)].

Structure-processing-property relationships in organic electronics

The specific research focus in the context of the ERC "MOLPROCOMP" is on charge and energy dynamics in nanostructured soft-matter systems. In close collaboration with the group of Denis Andrienko, we develop a multiscale simulation ansatz that combines first-principles electronic structure theory with molecular mechanics and kinetic Monte-Carlo methods [JCTC 7, 3335 (2011)]. This approach allows to address the key design challenges in organic electronics such as the optimization of charge photogeneration and reduction of charge carrier recombination for organic photovoltaic cells, by systematically analyzing the interplay between molecular electronic structure and material morphology. Being able to follow the link from microscopic light-energy conversion processes to macroscopic properties facilitates device-scale modeling and subsequently the formulation of structure-property relationships for optimizing device performance.

This highly interdisciplinary research relies on collaborations with theoreticians and experimentalists from physics and chemistry, as well as industrial partners such as BASF or InnovationLab Heidelberg. To this end, I was heavily involved in multiple third party funded projects from planning and application to execution. Examples are the studies of photogeneration of free charge carriers in donor-acceptor nanostructures (DFG SPP 1355, BMBF Project MEDOS) as well as the development of efficient emission layers for deep-blue OLEDs (BMBF Project MESOMERIE).