The preparation of traditional organic-inorganic lead-halogen hybrid perovskite solar cells often requires strict nitrogen glove box conditions, thus hindering their industrial scalability. This study develops a large-area perovskite film formation process and designs a novel device structure to achieve a dual enhancement of module device efficiency and stability in a high humidity air environment (55%). High-quality perovskite thin films are successfully prepared by vacuum extraction in ambient air, followed by a double-end low-temperature photopolymerization process utilizing acrylate monomer molecules for inner encapsulation modification of the freshly formed perovskite thin films. The influences of these techniques on the photoelectric characteristics of perovskite thin films and devices are investigated. The results indicate that uniform and dense perovskite films can be achieved in ambient air with a pumping time of 60 s. By adjusting the concentration of ethylene glycol dimethacrylate monomer molecules used in the low-temperature photopolymerization process, the surface defects on the perovskite film can be effectively controlled. The optimal concentration of 1 mg/mL results in perovskite film with optimal morphology and fluorescence intensity. Furthermore, rigid module device and flexible module device (effective area: 18 cm²), based on the polymer inner encapsulation, demonstrate outstanding outdoor photoelectric conversion efficiencies of 19.51% and 18.17%, respectively (with the highest indoor low-light conversion efficiencies of 34.5% and 30.2%, respectively). Notably, the untreated flexible device exhibits a significant decline in photoelectric conversion efficiency, falling below 50% of the initial value after one month of exposure to air. In contrast, device incorporating the polymer inner encapsulation layer maintains over 90% of their original efficiency, highlighting their excellent humidity resistance stability. Moreover, the polymer encapsulation layer also greatly improves the bending stability of the flexible device. This research paves the way for industrial-scale producing perovskite solar cells and addressing the challenges associated with humidity and large-area fabrication. The findings contribute to advancing perovskite solar cell technology and offering a pathway for high-efficiency and stable devices suitable for practical applications.