Formamidinium lead iodide (FAPbI₃) has emerged as one of the most promising perovskite semiconductors for perovskite solar cells (PSCs), demonstrating high power conversion efficiency (PCE) and good stability. However, only a few reports address the scalable processing and fabrication of FAPbI₃ perovskite solar modules. Here, we report a void-free perovskite-buried interface in p-i-n-based PSCs, which enables us to upscale lab-scale solar cells (<1 cm²) to mini-module dimensions (>10 cm²). An innovative combination of a moderate N₂ flow during vacuum-assisted growth (VAG) control of the perovskite thin films as well as the employment of MACl as an additive eliminates interfacial voids in blade-coated large-area FAPbI₃ layers, enabling respective PCEs of 20.0% and 18.3% in blade-coated PSCs (0.105 cm²) and fully scalable modules (aperture area of 12.25 cm² and geometric fill factor of 96.3%). This is a remarkable advance in upscaling FAPbI₃-based perovskite photovoltaics.