The research in my computational condensed matter physics group ranges from molecules to solids and nano devices. I will give a broad overview our recent work and highlight selected examples. An example of our research at the molecule level uses density functional theory calculations to analyze single molecule force experiments on a N-heterocyclic carbene isothiocyanate adduct. Our calculations show rupture at the desired, catalytically active site in agreement with the atomic force single molecule experiments. The main focus of our research are semiconductors for photovoltaics and transparent electronics. In these materials the most important properties concern the charge carrier generation through either optical excitation and intrinsic or intentional doping. Using computational methods based on density functional theory we have studied the optical and electronic properties various layered mixed anion compounds and copperchalcogenides. I will focus on the optical properties of Cu3PSe4, a potential solar absorber, and the electronic properties of BaCuChF, Ch=(S,Se,Te), which are hole conducting transparent conductors.