Molecular‐Extrusion‐Driven Halogen Homogenization for Efficient Perovskite‐Silicon Tandem Solar Cells

ABSTRACT Phase segregation is an inevitable phenomenon in wide‐bandgap perovskites, triggering nonradiative recombination and degrading device performance. Herein, we propose a molecular‐extrusion‐driven passivation strategy by introducing bromomethyl‐triphenylphosphonium bromide (TPB‐Br) into perovskite precursors to achieve halogen homogenization. This approach simultaneously passivates bulk and interfacial defects, significantly mitigates phase segregation, and suppresses nonradiative recombination in wide‐bandgap perovskites. As a result, we realize high‐quality wide‐bandgap perovskite films with high crystallinity, low defect density and released residual strain. Champion devices based on these films deliver impressive power conversion efficiencies (PCEs) of 23.63% in the 1.68 eV perovskite sub‐cell and 32.03% (1.05 cm 2 ) in the perovskite/silicon tandem solar cell. More importantly, the unencapsulated devices maintained 90.1%, 81.2%, and 93.4% of their initial PCEs under long‐term storage, thermal‐aging, and light‐soaking for 1200 h, respectively. Our work demonstrates the advantage and feasibility of the synergistic passivation strategy in preparing high‐quality wide‐bandgap perovskite films and tandem solar cells.