Closed‐Loop Slit‐Flushing Antisolvent Strategy Enables Controlled Three‐Dimensional Mass Transfer for Large‐Area Perovskite Solar Cells

The antisolvent process remains the dominant fabrication route for high‐efficiency perovskite solar cells (PSCs), but its scalability is constrained by intrinsic mass transfer characteristics and the requirements of green manufacturing. To address these challenges, we develop a closed‐loop slit‐flushing antisolvent (SFA) strategy that offers ambient‐air processability, antisolvent recyclability, and a three‐dimensional controllable mass transfer regime. By creating a pressure‐driven forced flow within a parallel‐plate slit, we transform the mass transfer mechanism from a purely vertical diffusion‐dominated regime of static bathing to a synergistic combination of horizontal forced convection and vertical diffusion, which ensures uniform and controllable nucleation over large‐area films. With an optimized slit height of 0.5 mm, the SFA method yields highly uniform, compact, and pinhole‐free perovskite films in ambient air on a 100 × 100 mm substrate, with reduced defect density and a homogenized distribution. Small‐area PSCs achieve a champion power conversion efficiency (PCE) of 24.59%, while the champion large‐area flexible module with an aperture area of 61.2 cm 2 delivers a laboratory PCE of 18.69% and a certified PCE of 17.35%. This study presents a straightforward, low‐cost, and practical solution to the scaling bottleneck of antisolvent methods, enabling the fabrication of efficient and stable large‐area perovskite photovoltaics.