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

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 cm²) 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.