Degradation analysis of perovskite solar cells doped with MABr3 via electrochemical impedance

Abstract

In this study, perovskite solar cells with a structure CsyFA1-xMAxCS0.05Pb(I1.05-xBrx)3, with X = 0 (no doping was added to the base structure CsFAPbI3) and X = 0.085 (CsFAPbI3 was doped with 8.5% MABr3) were prepared and were subjected to a 60 days ageing process (15 days under vacuum conditions followed by 45 days under room conditions) to study their stability. J-V curves showed that after the 60 days, the cells with no MABr3 only had 50.32% of the original efficiency remaining, while the samples with 8.5% MABr3 had 92.89% of the original efficiency, being the Jsc the main parameter that was affected during the ageing period. IPCE measurements suggest the formation of Cs segregates, that maintain or even increase the Jsc. According to electrochemical impedance studies, these segregates could be promoted by the lower ionic movement resistance in the 8.5% MABr3 samples, which may allow to re-arrange the atoms of the crystalline structure in a benefic way. This work is of great importance because it helps to understand how the doping affects the degradation processes, while showing how Impedance Spectroscopy can be used to characterize the changes in the electrical and ionic dynamics of the solar cells.