Ferroelectricity and stability measurements in perovskite solar cells

With the ferroelectric nature of modern perovskite solar cells being more and more accepted by the community, new questions arise. How do the microscopic electric fields within the polar domains affect the device performance, and how must measurement routines be adapted to account for the ferroelectric effect within the light-harvesting layer? This becomes particularly important, if devices are measured constantly for a long time as commonly performed in solar cell ageing tests. In this perspective article, we discuss which effects may arise from creeping poling even under low driving voltages or under illumination, as well as effects from phase transitions when crossing the Curie temperature for accelerated ageing at elevated temperatures. We elucidate why ferroelectric effects must be carefully considered when assessing the lifetime of perovskite solar cells and where comparability comes to its limits.