Fischer, OliverBett, Alexander J.Zhu, YanMessmer, ChristophBui, Anh DinhSchygulla, PatrickFell, AndreasEr-Raji, OussamaKore, Bhushan P.Schindler, FlorianMacdonald, DanielHameiri, ZivGlunz, Stefan W.Schubert, Martin C.2026-07-032026-07-032590-2393ORCID:/0000-0001-5792-7630/work/219174058ORCID:/0000-0002-9660-6132/work/219174833https://hdl.handle.net/1885/733812859Monolithic perovskite silicon tandem solar cells reach efficiencies beyond the theoretical efficiency limit of silicon single-junction solar cells. However, the metastability of perovskite materials and the increasing number of functional layers with increasing number of junctions undermines their stability. This poses a significant challenge for industrialization. To enable fast progress in performance and stability, advanced characterization methods tailored for metastable perovskite-based tandem solar cells are essential. This work discusses the Suns open-circuit voltage ( Suns - V OC) and intensity-dependent photoluminescence ( Suns -PL) imaging methods, which are specifically adapted to perovskite silicon tandem solar cells. Spatially resolved implied open-circuit voltage and implied fill factor images facilitate the localization of losses in large-area solar cells, supporting root-cause analysis of electrical limitations. Furthermore, subcell-resolved Suns - V OC measurements of the tandem solar cells allow charge carrier transport losses to be quantified. Combining both methods allows selectivity losses to be identified. Challenges of the methods are thoroughly analyzed, ensuring reliable measurements with the appropriate measurement routine.This work was funded by the German Federal Ministry for Economic Affairs and Climate Action ( BMWK ) under contract numbers 03EE1087A and 03EE1087B ( KATANA ) and 03EE1182A and 03EE1182B ( PERLE ) and by the Australian Renewable Energy Agency ( ARENA ) through a research grant 2022/TRAC001 .enPublisher Copyright: © 2025 The Author(s).fill factor lossesperovskite-silicon tandem solar cellsselectivity lossesSuns-PL imagingSuns-V measurementsvoltage losses2025-12-0310.1016/j.matt.2025.102404105016847204