Defect passivated wide-bandgap perovskite films for high performance four-terminal perovskite/silicon tandem solar cells

Wide-bandgap (WBG) perovskite solar cells (PSCs) have garnered significant attention due to their potential to form high-quality, stable films, which can significantly enhance the efficiency of silicon-based tandem solar cells (TSCs). However, the performance of these devices is hindered by poor crystallization, a high intrinsic trap density in the WBG perovskite film, and nonradiative recombination, primarily due to bulk defects. In response to these challenges, we introduce 3-pyridinylmethylammonium iodide (3-PyAI) as an additive to passivate intrinsic defects within the bulk of the perovskite film. The addition of 3-PyAI significantly lowers defect induced nonradiative recombination by developing interactions with uncoordinated Pb2+ ions and FA+ cations. The resulting 3-PyAI-modified perovskite film significantly improves crystallinity, enlarges grain size, enhances bulk quality, and minimizes nonradiative recombination defects. Consequently, the methylammonium-free Cs0.22FA0.78Pb(I0.85Br0.15)3 PSCs demonstrate power conversion efficiency (PCE) of 21.75%, much higher than that of the control device at 19.60%. Building on this advance, we integrated a silicon bottom solar cell, developing a four-terminal (4T) TSC that achieved a champion PCE of 30.52%. This work addresses the critical performance bottlenecks in WBG-PSCs and establishes a robust framework for realizing high-efficiency TSCs, representing a significant step toward the practical implementation of next-generation photovoltaic technologies.