Insights Into Degradation Pathways of Perovskite Thin Films under Outdoor and Indoor Conditions: A Comparative Analysis

ABSTRACT Metal halide perovskite materials exhibit high power conversion efficiencies (PCEs), reaching up to 27% under standard solar illumination and exceeding 40% under indoor low‐light conditions. Despite extensive outdoor stability studies, the degradation of perovskites under indoor low‐light conditions, particularly in oxygen‐rich environments, has not been investigated. This study systematically investigates the degradation pathways of perovskite thin films under low‐light (1000 lux [N 2 /O 2 ]) and low Rh∼40%(dark) conditions, comparing them with an outdoor high‐light intensity (1 sun [N 2 /O 2 ]) environment. Structural, morphological, and chemical changes are monitored using X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The films show excellent stability under 1000 lux [N 2 ], with no phase transitions, PbI 2 formation, or significant electronic changes. Under 1000 lux [O 2 ], no phase transformation or morphological degradation occurs, but XRD indicates strain formation. XPS confirms photo‐oxidative degradation, and PL reveals reduced carrier lifetimes due to defect formation. A pronounced PbI 2 phase emerges only under high‐light conditions (1 sun [N 2 /O 2 ]), highlighting the role of illumination in decomposition. These findings provide important direction for future research on indoor photovoltaics, demonstrating that perovskite thin films are susceptible to photo‐oxidative degradation not only under high light illumination but also under low indoor illumination.