Dual-molecular strategy with ODADI and PDADI for inverted perovskite solar cells: surface defect passivation and hydrophobic barrier construction

Inverted (p–i–n) perovskite solar cells (PSCs) have attracted considerable attention owing to their low-temperature fabrication and excellent operational stability. Nevertheless, defect-induced non-radiative recombination and environmental degradation at the perovskite surface and interfaces remain major obstacles to further improvements in device efficiency and stability. Herein, a synergistic dual-molecular passivation strategy employing 1,3-diaminopropane dihydroiodide (PDADI) and 1,8-octanediamine dihydriodide (ODADI) is developed to precisely engineer the perovskite/electron-transport-layer interface. PDADI effectively passivates surface and interfacial defects by coordinating its terminal amino groups with undercoordinated Pb²⁺, thereby suppressing non-radiative recombination. In contrast, ODADI not only further passivates residual defects but also forms a compact hydrophobic barrier on the perovskite surface through its long alkyl chain, significantly enhancing environmental stability. Comprehensive characterizations reveal that the dual-passivation treatment substantially reduces defect-state density, prolongs carrier lifetime, improves interfacial charge transport, and mitigates non-radiative voltage losses. As a result, inverted PSCs based on this strategy deliver a champion power-conversion efficiency of 24.7% with negligible hysteresis and maintain 91% of their initial efficiency after 1000 h of aging in a nitrogen atmosphere. Moreover, the dual-passivated films exhibit markedly enhanced structural and optical stability under humid air conditions. This work demonstrates an effective interfacial engineering strategy for achieving highly efficient and stable inverted perovskite solar cells through synergistic molecular passivation.