A research collaboration between Fraunhofer ISE, Fraunhofer CSP, and KAUST has developed an advanced method for perovskite/PV tandem solar cells. The study investigates the use of self-assembled monolayers (SAMs) as hole-selective contacts to enhance PV cell efficiency. SAMs provide passivation, simple processing, and low parasitic absorption, but achieving optimal thickness and packing density has been challenging. The research identifies annealing temperature as a crucial factor in SAM formation. Through in situ angle-resolved X-ray photoelectron spectroscopy, the study demonstrates that raising the temperature from 100°C to 150°C reduces SAM layer thickness to a single monolayer, thereby improving adsorption density. This modification results in enhanced interfacial passivation, leading to a 1.3% increase in power conversion efficiency. The champion device developed through this approach is approaching 30% PCE, indicatingsignificant progress in the efficiency of perovskite/silicon tandem solar cells.