Researchers from The European Commission's ISPRA (Istituto Superiore per la Protezione e la Ricerca Ambientale) Joint Research Center have reported the results of a one-year outdoor monitoring campaign of two full-size single-junction perovskite solar modules at the European Solar Test Installation (ESTI) in northern Italy. The study, conducted between June 2024 and June 2025 under a humid subtropical climate, provides valuable long-term performance data for perovskite PV technology, which is largely assessed under controlled indoor conditions.
The two glass–glass modules, designated YZ517 and YZ518, each with an active area of 0.7164 m², were mounted on fixed, south-facing racks tilted at 45°. Before deployment, the researchers developed a stable indoor measurement protocol using simulated sunlight, establishing an optimal I–V sweep time of 10 s to ensure reproducible baseline data.
While both modules showed initial efficiencies around 14–15%, their field performance diverged over the course of the year. Module YZ517 demonstrated relatively stable behavior, with an efficiency decrease of about 3 percentage points - from 15% to roughly 12% - after 12 months outdoors. Module YZ518, however, degraded significantly faster, with its efficiency dropping below 7%, and was thus excluded from deeper analysis.
Temperature-dependent analysis of YZ517 revealed coefficients of −0.054 %/°C for maximum power (Pmax), −0.09 %/°C for open-circuit voltage (VOC) and +0.089 %/°C for short-circuit current (ISC). These values are broadly consistent with reported literature and highlight moderate thermal sensitivity, with voltage and power decreasing while current increases at higher temperatures - behavior somewhat analogous to crystalline silicon PV but not always expected for PSCs.
Seasonal performance trends were also documented. On warm summer days, peak efficiency was observed in the cooler morning hours, preceding the irradiance maximum, while in winter, when module temperatures stayed below ~35 °C, efficiency followed irradiance more closely. Variations between morning and afternoon performance, especially after cloudy periods, point to light-soaking and metastability effects typical of perovskite devices.
Overall, this long-term field dataset provides a meaningful benchmark for the outdoor behavior of large-area perovskite modules. The results confirm encouraging stability for well-behaved devices such as YZ517 but emphasize the need for improved consistency and reliability before perovskite photovoltaics can become a fully competitive commercial technology.
