Operationally Stable Perovskite Solar Modules Enabled by MA‐Free Perovskite Crystallization and Passivation via Scalable Coating

Perovskite solar modules (PSMs) must deliver not only high-power conversion efficiency (PCE) but also long-term operational stability to approach commercialization. Yet efficiency and stability are both compromised when translating laboratory spin-coated perovskite solar cells (PSCs) into scalable PSMs, owing to mismatched crystallization dynamics, ineffective defect passivation, and compositional degradation. Here we resolve these challenges through a three-pronged strategy. First, we deconstruct the compositional origins of operational stability, identifying MA (methylammonium)-free Cs-FA (formamidinium) composition as intrinsically robust against continuous operation. Second, we tailor the phase-transition and crystallization pathways of air-processed scalable-coating by controlled Br incorporation in CsPbX₃, which reconciles precursor solubility, nucleation kinetics, and α-phase stability, yielding dense and defect-suppressed films. Finally, we analyze the root cause of scalable passivation inefficacy and developed cyclohexanecarboxamidinium (CHCA) as a blade-coating-compatible passivator enabling uniform and durable defect suppression. The optimized devices exhibited improved PCEs up to 26.1% (0.646 cm²) and 22.8% (20.8 cm²). Meanwhile, we documented exceptional operational stability with ∼3200 h T₉₆ for PSC and ∼2000 h T₈₄ for PSM. Our findings establish a mechanistic framework for achieving operationally stable perovskite solar modules under industrially relevant conditions.