High‐Performance Flexible All‐Perovskite Tandem Solar Cells with Reduced <i>V</i> _OC ‐Deficit in Wide‐Bandgap Subcell

Among various types of perovskite-based tandem solar cells (TSCs), all-perovskite TSCs are particular attractiveness for building- and vehicle-integrated photovoltaics, or space energy areas as they can be fabricated on flexible lightweight substrates with a very high power-to-weight ratio. However, the efficiency tandems is lagging far behind their rigid counterparts primarily due to challenges in developing efficient wide-bandgap (WBG) perovskite well low open-circuit voltage (VOC). Here, it reported that use self-assembled monolayers hole-selective contact effectively suppresses interfacial recombination allows subsequent uniform growth 1.77 eV WBG superior optoelectronic quality. In addition, postdeposition treatment 2-thiopheneethylammonium chloride employed further suppress bulk recombination, boosting VOC top cell 1.29 V. Based this, first proof-of-concept four-terminal TSC power conversion 22.6% presented. When integrating into two-terminal tandems, 23.8% 2.1 V achieved, which par 28% grown substrate.