Insight‐Guided Optimization of the Individual Steps in Ambient Slot‐Die‐Coated Perovskite Solar Cells

Scalable fabrication of perovskite solar cells (PSCs) under ambient conditions remains a key challenge for transferring technology from the lab to industry. Herein, an insight‐guided optimization framework is presented that integrates ink rheology control, interfacial engineering, and crystallization management to achieve reproducible, high‐quality perovskite films via doctor‐blade and slot‐die coating. Hydroxypropyl cellulose is employed as a rheological additive to stabilize meniscus formation, suppress pinholes, and enhance film crystallinity. Charge extraction and interface uniformity are improved by introducing a mesoporous Al 2 O 3 scaffold on top of NiO x , which promotes perovskite infiltration and reduces interfacial defects. Finally, an air‐knife quenching step homogenizes solvent evaporation, yielding compact, large‐grained films with superior optoelectronic properties. Together, these strategies enable reproducible PSCs with uniform thickness (210–230 nm), improve fill factor and current density, and achieve efficiencies up to 17% on flexible substrates—all processed in ambient air. Beyond device improvements, the study establishes a methodology that couples rheological mapping with coating dynamics, offering transferable insights into the deposition–crystallization interplay essential for roll‐to‐roll scalable photovoltaics. This work demonstrates that combining polymer additives, mesoporous scaffolds, and quenching‐assisted drying provides a robust route toward ambient, manufacturable PSC technologies.