Since the emergence of the Perovskite Solar Cells (PSC) in 2009[1], significant progresses have been made, with high-efficiency devices reaching up to an outstanding 27% [2] in just 16 years. However, despite this quick development in a relatively short time frame, one of the main limiting factors hindering the industrialization of these photovoltaic technologies is their limited operational stability.

To mitigate the fast degradation of these photovoltaic devices, several strategies has been explored, with encapsulation emerging as one of the most effective[3]. These methods play a vital role in delaying the rapid degradation of the perovskite photovoltaic devices protecting them from environmental factors as heat, moisture and oxygen. However, ensuring the long-term reliability of these devices not only require of stable materials and hermetic encapsulations, but also robust testing protocols to evaluate the inner stability of the device and the effectiveness of the encapsulation protocols of the devices.

In this context, standardized stressing tests -performed both in outdoor and indoor conditions- are key[4,5]. Outdoor tests track devices under real operation conditions, while during indoor tests the degradation processes are accelerated by exposing devices to controlled stressing factors, such as elevated temperatures, continuous illumination or light and dark cycles[5]. However, reliable stability data remains scarce in the literature. This is, in part due to the lack of well-equipped testing facilities with the infrastructure needed to perform these tests.

One notable location for outdoor tests is Valencia, which offers extreme climatic conditions- high humidity, high temperatures and a large number of sunny days, particularly during the summer time- making it ideal for outdoor stress testing. Moreover, the University of Valencia and in particular the MOED group has become an established group in this regard, having experience in vacuum-processed perovskite solar cells, in encapsulation of PSC, and in conducting indoor and outdoor tests.

Beyond infrastructure, several technical issues must be addressed to ensure reliable stability data. These include the right measurement of the light, the correct calculation of the active area of the devices, and the gathering of representative and consistent data from each pixel or device over time. Post-treatment of the data is also essential, not only to condense the information but also to reveal correlations between the stability data with variables that would otherwise remain hidden.

This presentation will highlight the results and the insights gained over the past year by the MOED group on encapsulation methods, stability testing under various conditions, and advanced data post-processing methods for analysing stability data.