A dual-molecular interface engineering strategy for highly efficient and stable perovskite solar cells

Defects and interfacial stress at the SnO₂/perovskite buried interface severely hinder further improvements in the performance and scalable manufacturing of perovskite solar cells (PSCs). Herein, we propose a dual-molecular co-modification strategy composed of l-citrulline and l-malic acid (CM) to construct a multifunctional interfacial layer with a bridging effect. CM chemically reacts with undercoordinated Sn⁴⁺ in SnO₂via its hydroxyl (–OH) groups, while its urea group (–NH–CO–NH₂) simultaneously passivate undercoordinated Pb²⁺ and I⁻ defects on the perovskite side. This strategy yields a multilayer configuration that improves the crystallinity of the perovskite film and alleviates its residual stress, thereby reducing non-radiative recombination at the buried interface and optimizing the interfacial energy barrier. As a result, rigid devices achieve an impressive champion power conversion efficiency (PCE) of 26.25%, and unencapsulated devices retain 88.31% of their initial efficiency after 1800 h of storage in air. This study provides an effective dual-molecular interface engineering approach for constructing highly efficient and stable perovskite photovoltaic devices.