Today’s technological innovation is driven by a deep understanding of the fundamental properties of matter at the nanoscale and below, where the quantum character of the electrons and the many-body effects of their correlated dynamics determine the properties of a material. This understanding is twofold: On the one hand, modern spectroscopy techniques probe these many-body quantum excitations. On the other hand, theoretical ab-initio methods, that rely solely on the basic laws of quantum physics and do not make model assumptions, predict the micro- and macroscopic properties of a material and explain experimental findings.
In particular, the electronic and optical properties of a material are most relevant both for a better understanding of the fundamental materials physics with applications in state-of-the-art characterization techniques (e.g. ellipsometry and photoluminescence) and the design of new materials systems and devices for photovoltaics (as photovoltaic absorber or transparent conducting semiconductor in photovoltaic cells) or optoelectronics (such as light-emitting diodes, semiconductor lasers or novel display technologies). An accurate theoretical description of the optical properties requires to take the lattice degrees of freedom of a material (e.g. static lattice strain, lattice deformation by defects, lattice dynamics due to phonons) and its coupling to the electronic motion into account, without relying on models that necessitate empirical input parameters. Up to now, the available theoretical ab-initio tools largely disregarded the impact of the atomic lattice.
The present project aimed at developing theoretical methods and ab-initio numerical simulation tools for a quantitatively correct prediction of optical materials properties focusing in particular on the impact of electron-lattice coupling. Further, the optical properties of a number of simple semiconductors and some more complex materials of interest for technological applications should be calculated with these new tools to benchmark the developed methods with known data, to make predictions for future experiments, and to identify novel materials that are of potential technological interest.
In addition to advancing fundamental science, the project contributes to the EU Societal Challenges for “secure, clean, and efficient energy”, “smart, green, and integrated transport”, and “climate action, environment, resource efficiency and raw materials” by its direct impact in photovoltaics and optoelectronics and its utility in the search for novel materials with technologically interesting properties.
