Scaling perovskite solar cells (PSCs) to large-area, durable modules requires buried interfaces that form uniformly under manufacturing-relevant coating conditions, yet this remains difficult to achieve. Here we report a microflow-driven strategy that enables a bilayer NiOₓ/self-assembled monolayer (SAM) contact in perovskite films processed entirely in ambient air. Evaporation-driven Marangoni recirculation transports π-conjugated SAM molecules to the NiOₓ surface, where strong anchoring promotes dense and uniform coverage. A porous matrix stabilizer homogenizes the solvent vapour flux above the wet film, equalizing the flow field and enabling uniform SAM transport and interfacial assembly over large areas. The resulting inverted rigid PSCs achieve a power conversion efficiency (PCE) of 26.2% (blade-coated, 0.113 cm²), rigid mini-modules achieve a certified PCE of 24.1% (blade-coated, aperture area 20.41 cm²), and flexible large-area modules achieve a certified PCE of 21.13% (slot-die-coated, aperture area 617.4 cm²), placing their performance among the highest reported at these respective scales. Encapsulated modules retain 91% of their initial PCE after 1,000 h of one-sun maximum power point tracking and 93.7% after 1,128 h under damp heat (85 °C/85% relative humidity). These results establish solvent microflow as a controllable lever for scalable, efficient and stable perovskite photovoltaics.