In Situ Metrology for Degradation Studies of Perovskite Solar Cells

Perovskite solar cells (PSC) have attracted considerable attention in recent years due to the high efficiencies achieved, their scalability potential and the introduction of record efficiency tandem devices with a perovskite layer on top of silicon. Although the reported efficiencies and scalability approaches demonstrated show great potential for this technology, stability issues are a significant obstacle for PSC before they can compete with established PV technologies. Although efficient encapsulation offers some protection from environmental factors, encapsulation will never be perfect and through the years some permeation of oxygen and humidity into PV modules is inevitable. There are a number of critical factors for PSC degradation, and tests require accurate conditions and measurements in order to distinguish different degradation mechanisms. In situ metrology for ageing tests of perovskite PV devices has been developed at NPL that involves accurately controlled environments that can simulate realistic encapsulation conditions, while applying electrical measurements and spatial characterisation techniques. Environmental conditions including atmospheric composition, spectrum and intensity of illumination, and temperature can be accurately controlled. At the same time, current-voltage measurements, luminescence imaging, and photocurrent mapping of PSC can be performed during degradation. This allows the collection of a significant amount of data, in order to record the failure processes of samples and reveal the degradation mechanisms.