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 (JSC) 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.