Analysis of light-induced degradation in inverted perovskite solar cells under short-circuited conditions

We present a study at both the device level and the interfacial analytic level on the light-induced degradation in the inverted CH3NH3PbI3 (MAPbI3) perovskite solar cells (PSCs) with an optimized structure, which is based on the Cu electrode and the charge transport layers of PTAA and Bphen. To accelerate the degradation process, the PSCs are exposed to concentrated sunlight of 2 suns with different illumination duration under the short-circuited condition. Compared to under the open-circuited condition, the PSCs presented here show a slightly more obvious decrease of power conversion efficiency (PCE) and a more distinct hysteresis with the time of light exposure. We infer that, under the short-circuited condition, the more dramatic migration of ions induced by photocurrents should result in greater ohmic dissipation and more trap states. But the weak degradation effects indicate that the devices still exhibit an unexpected photochemical stability against light exposure. Most importantly, there is a self-healing behavior to partly recover the degradation with the light exposure time of more than 8 h, which can be ascribed to the modification from the Cu electrode and the charge transport layers of PTAA and Bphen. Being wrapped tightly in these coverlayers, the possible volatile decomposition products are restrained inside of the MAPbI3 layers and converted back to MAPbI3 with a great probability.