Advancing charge selective contacts for efficient monolithic Perovskite silicon tandem solar cells Hybrid organic inorganic perovskites are one of the most promising material classes for photovoltaic energy conversion. In solar cells the perovskite absorber is sandwiched between n and p type contact layers which selectively transport electrons and holes to the cell’s cathode and anode respectively. This thesis aims to advance contact layers in perovskite solar cells and unravel the impact of interface and contact properties on the device performance. Further the contact materials are applied in monolithic perovskite silicon heterojunction (SHJ) tandem solar cells which can overcome the single junction efficiency limits and attract increasing attention. Therefore all contact layers must be highly transparent to foster light harvesting in the tandem solar cell design. Besides the SHJ device restricts processing temperatures for the selective contacts to below 200°C. A comparative study of various electron selective contact materials all processed below 180°C in n i p type perovskite solar cells highlights that selective contacts and their interfaces to the absorber govern the overall device performance. ...