Outdoor Performance and Thermally Accelerated Degradation of Inverted Perovskite Solar Cells

In this article, the long‐term outdoor performance of inverted perovskite solar cells (PSCs) with glass–glass encapsulation is investigated over a 3‐year period. Despite achieving initial power conversion efficiencies of >20%, the devices show significant degradation during summer months, particularly when surface temperatures exceed 50°C, with their internal cell temperatures increasing to ~90°C. Optical and scanning electron microscopy imaging reveal the formation of a high‐resistance phase within the perovskite layer, particularly near the NiO x interface, as the major degradation pathway. Indoor accelerated tests, conducted under heat and light conditions, replicate these effects, indicating the occurrence of thermally induced phase transitions. The measurement methodology also influences the degradation; devices measured with maximum power point tracking show slightly less deterioration than do those assessed via current–voltage curve tracing. Additionally, UV‐cut filters show minimal benefits, likely owing to the inherent UV blocking feature of NiO x . These findings underscore the critical role of thermal management and operational conditions in ensuring the stability of PSCs. Further improving the material design, encapsulation, and measurement protocols is essential for enhancing the outdoor reliability and commercial viability of PSCs.