Coring Technique Development and Failure Analysis of Perovskite Solar Modules

ABSTRACT Understanding degradation in perovskite solar modules (PSMs) is crucial for improving long‐term stability, yet accessing internal layers without introducing artifacts remains difficult. We present a controlled coring method tailored for PSMs that enables mechanical extraction of intact device sections while preserving their structural, chemical, and optoelectronic properties. Comprehensive characterizations confirm that the cored devices remain representative of the original module, with no detectable artifacts introduced during extraction. Applying this technique to field‐aged modules operated outdoors for 10 months reveals nonuniform photoluminescence, bandgap shifts, Ag oxidation, and the α‐to‐δ phase transition of formamidinium lead iodide (FAPbI 3 ), which are clear evidence of moisture‐driven Ag corrosion and ion migration at the perovskite/Ag interface. This work establishes a reliable approach for accessing encapsulated perovskite modules and provides direct insight into real‐world degradation pathways, offering guidance for improving the durability of perovskite photovoltaic technologies.