Tuning interfacial properties in perovskite solar cells through defined molecular assemblies In the frame of a world fighting a dramatic global warming caused by human related activities research towards the development of renewable energies plays a crucial role. Solar energy is one of the most important clean energy sources and its role in the satisfaction of the global energy demand is set to increase. In this context a particular class of materials captured the attention of the scientific community for its attractive properties: halide perovskites. Devices with perovskite as light absorber saw an impressive development within the last decade reaching nowadays efficiencies comparable to mature photovoltaic technologies like silicon solar cells. Yet there are still several roadblocks to overcome before a wide spread commercialization of this kind of devices is enabled. One of the critical points lies at the interfaces: perovskite solar cells (PSCs) are made of several layers with different chemical and physical features. In order for the device to function properly these properties have to be well matched. This dissertation deals with some of the challenges related to interfaces in PSCs with a focus on the interface between the perovskite material itself and the subsequent charge transport layer. [...]