Macroporous PbI₂ template and dual-mode coordination enable efficient perovskite solar cells

Sequential deposition is widely used in perovskite/silicon tandem solar cells and perovskite PV modules for its flexibility in composition tuning and film quality control. However, owing to its CdI₂-type layered structure, PbI₂ easily forms dense films, which impede organic cation infiltration and reaction, resulting in poor perovskite film quality. Herein, the dual-modal molecule 4Cl-PA was introduced into the PbI₂ precursor solution. It was found that the unique conformation of the two adjacent amide groups enables dual-mode synergistic coordination to PbI₂, thereby effectively suppressing the tight stacking of PbI₂. Moreover, the Cl atom enhances the molecular dipole moment, facilitating anchoring at polar sites on PbI₂ nuclei, while π-π stacking of the benzene rings improves film moisture resistance. This dual-mode coordination induces a loose PbI₂ template with macroporous structure, optimizes the subsequent reaction with organic cations, and then affords high-quality perovskite films. TRPL measurements showed that the carrier lifetime increased to 161 ns, which indicates improved charge transport and suppressed non-radiative recombination within the perovskite films. As a result, the perovskite solar cells regulated by 4Cl-PA achieved a champion PCE of 22.73% and a J_sc of 25.75 mA cm^-2. This work provides a practical strategy for tailoring the pore structure of PbI₂ films to facilitate complete organic cation infiltration in sequential deposition.