Abstract
Perovskite and silicon solar cells have recently been shown to be perfect partners for tandem devices with potentially very high efficiency at low additional costs over standard silicon cells. Here, we present the development of efficient perovskite top cells suitable for 4-terminal and monolithic tandem integration on silicon heterojunction bottom cells. We show a 4-terminal tandem measurement with 25.6% efficiency on small cells and 23.2% on a 1 cm(2) fully integrated device. Monolithic tandems with > 20% efficiencies were developed on several types of silicon wafers, allowing for a direct optical comparison. We identify parasitic absorption to be the limiting factor for high performance and discuss several practical solutions to reduce them.