Nanoscopic Parylene Layer: Enhancing Perovskite Solar Cells Through Parylene‐D Passivation

Abstract The development of eco‐friendly energy sources has advanced photovoltaic technologies, with perovskite solar cells (PSCs) emerging as promising alternatives owing to their high efficiency, low fabrication costs, and excellent optical and electronic properties. However, their commercialization is hindered by stability issues, such as ion migration, defect‐induced degradation, and nonuniformity of the solution process over large areas, particularly at the perovskite/hole‐transporting layer (HTL) interface. To address these challenges, chemical vapor deposition (CVD) is employed to introduce an ultrathin, uniform parylene‐D layer at the perovskite/HTL interface. Parylene‐D, containing additional chlorine functional groups compared to parylene‐C, supports bidentate chelation, enabling effective interaction with uncoordinated Pb 2 ⁺ and perovskite surface defects. This passivation layer significantly reduces nonradiative recombination and suppresses ion migration without affecting the morphology or electrical properties of large‐area perovskites. The optimized parylene‐D treatment yields PSCs with 23.75% efficiency and enhanced open‐circuit voltage and fill factor. Stability tests demonstrate that the parylene‐D‐treated devices retain their initial efficiency after 1500 h under 10% relative humidity at room temperature and maintain 80% efficiency after 1200 h at 65 °C in a nitrogen environment. Furthermore, the scalability of this approach is validated by fabricating a large‐area module (25 cm 2 aperture area), achieving module and active area efficiencies of 19.44% and 20.59%, respectively. These results highlight the potential of parylene‐D passivation via CVD as a practical and scalable strategy to enhance PSC performance and stability.