Outdoor Performance and Degradation Analysis of Inverted Perovskite Solar Cells

Perovskite solar cells were evaluated under two installation conditions: fixed at a south-facing tilt of 35° and mounted on a 2-axis tracking system. Significant performance degradation was observed during the high-temperature periods of July and August, with conversion efficiencies declining from 20–22% to 8–10%. Comparison between fixed-angle and tracking installations indicated that cells on the 2-axis system began to degrade one to two months earlier. Both J-V curve tracing and maximum power point tracking (MPPT) methods were employed, and although the sample size was limited, MPPT measurements appeared to induce slightly less degradation than J-V tracing. Three years of outdoor measurements revealed that the most critical degradation factor was elevated cell temperature during summer, accompanied by structural changes in the perovskite layer. Post-degradation analyses were conducted using optical microscopy, X-ray diffraction (XRD), and cross-sectional scanning electron microscopy (SEM). Severely degraded cells exhibited high-resistance layers in the cross-sections. Accelerated indoor degradation tests using a solar simulator with heating reproduced similar degradation phenomena, confirming the key role of temperature in device deterioration.