Dual-functional phthalamide modulation of aging-resistant PbI₂ for efficient perovskite solar cells

The sequential preparation of perovskite solar cells (PSCs) has received widespread concern for its use in large-scale perovskite modules and perovskite/silicon tandem solar cells. However, the instability of the PbI₂ precursor solution and the incomplete reaction of ammonium salts hinder the industrialization of PSCs. Here, by introducing phthalamide (PA) into PbI₂ solution, the carbonyl oxygen of PA molecules undergoes a bidentate coordination reaction with Pb²⁺ to form an octahedral coordination structure, and the nitrogen atom in the -NH₂ group exhibits weakly acidic properties due to the conjugation effect. These dual mechanisms synergistically suppress the hydrolysis of PbI₂. This dual-functional modulation strategy not only inhibits aging of the PbI₂ precursor solution, but also promotes thorough reaction between PbI₂ and organic ammonium salts. Moreover, carbonyl (C=O) and amino (-NH₂) groups generate van der Waals forces through dipole-dipole interactions, promoting intermolecular interactions within the precursor solution, which facilitates the formation and growth of crystal nuclei. π-electrons in benzene ring further contribute to van der Waals forces via π-π stacking, improving the smoothness and coverage of the perovskite film. Notably, the fabricated PSCs achieved a current density (J_SC) of 26.70 mA cm^-2, and devices retained 95 % of its initial PCE after 1000 h of nitrogen exposure. Aging-resistant PbI₂ precursor tactic enable reproducible, high-efficiency, and low-cost perovskite solar cells.