Our research group at the Institute of Solid State Physics at Leibniz Universität Hannover, headed by Prof. Dr.-Ing. Rolf Brendel, works theoretically and deals with simulations and calculations of phenomena that are significant for the analysis, characterisation and optimisation of solar cells and solar modules. Through our cooperation with the Institute for Solar Energy Research Hameln (ISFH), we also have access to excellent experimental equipment, which we use, for example, to determine the material data we need for our simulations. In addition, we are researching the integration of photovoltaics into the energy system, from the building level to countries and continents.