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