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

ABSTRACT 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 CsPbX 3 , 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 cm 2 ) and 22.8% (20.8 cm 2 ). Meanwhile, we documented exceptional operational stability with ∼3200 h T 96 for PSC and ∼2000 h T 84 for PSM. Our findings establish a mechanistic framework for achieving operationally stable perovskite solar modules under industrially relevant conditions.