Photo-stability of perovskite solar cells with Cu electrode

Towards higher stability of perovskite solar cells, Cu has been observed to be more suitable electrode material compared to conventional Al and Ag electrodes. The photo-stability of such devices has not been explored much in the literature, therefore we present here the investigation carried out towards the photo-stability of PSCs based on top Cu electrodes. The PSCs were prepared in normal geometry and stored in dark, under continuous illumination of a white LED lamp inside the laboratory and under direct sunlight outside the laboratory and tested as per the international summit on organic photovoltaics stability protocols. In dark storage the encapsulated solar cells exhibited highest stability but under illumination they exhibited degradation in their performance and the degradation was fastest in the direct sunlight. Degradation under illumination has been attributed to the photo-oxidation of the perovskite film. Cu has been observed to diffuse into and react with the underlying perovskite film and the ultraviolet and infrared contents in direct sunlight accelerated the photo-oxidation and chemical reactions between Cu and perovskite film. The chemical reactions of Cu electrode with perovskite constituents made it disappear after some time. These investigations suggest that Cu too is not a very stable electrode material for PSCs under natural operating conditions.