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 Jsc 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.