The development of a new generation of photovoltaic technologies is an important task in order to increase the production
of clean energy. Perovskite solar cells, with an exceptionally rapid development over the last decade, have transformed
into perhaps the most promising candidate to provide a low-cost alternative to conventional cells. While having excellent
efficiency, the most successful category of photovoltaic perovskites, the class of hybrid lead-halide perovskites, suffers
from poor stability in ambient conditions and gives rise to potential health concerns due to lead toxicity. Because of these
issues, studies yielding a better understanding of lead-based perovskites and investigations of new, lead-free materials are
likely meaningful steps towards better and more competitive solar cells. This thesis contains studies about established leadbased
perovskites, CH3NH3PbI3 and CH(NH2)2PbI3, as well as the lead-free alternatives AgBi2I7 and Cs2AgBiI6. The main
method employed is electronic structure calculations through density functional theory under periodic boundary conditions
including band structure calculations and projected density of states. A particular focus is given to systems with mixed
anion and related effects on the electronic structure.