The field of Theoretical Spectroscopy in chemistry is researching materials of various types from single molecules to large semiconductor crystals or nanostructures. The focus group clustered around Rudolf Mößbauer Tenure Track Professor Frank Ortmann investigates their properties by means of simulations with the ultimate goal to predict the characteristic features only based on their atomic or molecular structure. Typical examples include questions such as how do novel materials react upon illumination by light (like in a solar cell) or upon application of a voltage. A central research topic is electronic transport in organic semiconductors that are used for organic solar cells or organic LEDs. We investigate, for example, why some semiconductor materials bind the electrons relatively strongly while others conduct them well. The spatial orientation of the molecules within the semiconductor material is one important aspect. Interestingly, even the smallest chemical modifications can alter the arrangement of the molecules and thus improve charge transport. The prediction of these properties often involve simulations with supercomputers, because only they provide the necessary computational power to perform complex simulations.