Outdoor Stability of 518 cm ² Active Area Screen‐Printed Mesoscopic Carbon‐Based Perovskite Solar Modules Over 12 Months

Abstract Mesoscopic carbon‐based perovskite solar cells (C‐PSCs) composed of screen‐printed TiO ₂ , ZrO ₂ , and carbon layers offer a pathway to stable, scalable, low‐cost photovoltaics via commercially mature fabrication methods. While their potential lifespan has been demonstrated under standardized conditions, few studies examine the behavior of large‐area modules exposed to real‐world environments. Here, 12 months of outdoor weathering data are presented for 518 cm ² active area MAPbI ₃ modules with over 80% geometric fill factor, fabricated using low‐cost mechanical scribing. Modules exhibited power conversion efficiencies (PCEs) up to 9.4% under 1 sun, with PCE increasing at lower light intensities. Following outdoor continuous intermittent power point tracking for over 12 months, an encapsulated module retained 68% of its initial PCE. Performance remained stable during cooler months, only falling when temperatures rose during summer months. Similar temperature‐dependent trends are observed in repeated trials. Weathering trials identified key degradation pathways linked to fabrication—namely, non‐uniform heating during perovskite annealing, encapsulation, and infiltration‐related failures. Controlling heat exposure and conformity during module manufacture and operation is therefore critical to extending lifetime. These results highlight the importance of real‐condition assessments in optimizing the scale‐up of novel perovskite technologies, providing key insights into the steps required to achieve commercially viable lifetimes.