Enhanced stability of FA-based perovskite: Rare-earth metal compound EuBr₂ doping

It is highly desirable to enhance the long-term stability of perovskite solar cells (PSCs) so that this class of photovoltaic cells can be effectively used for the commercialization purposes. In this contribution, attempts have been made to use the two-step sequential method to dope EuBr₂ into FAMAPbI₃ perovskite to promote the stability. It is shown that the device durability at 85 °C in air with RH of 20%–40% is improved substantially, and simultaneously the champion device efficiency of 23.04% is achieved. The enhancement in stability is attributed to two points: (i) EuBr₂ doping effectively inhibits the decomposition and α–δ phase transition of perovskite under ambient environment, and (ii) EuBr₂ aggregates in the oxidized format of Eu(BrO₃)₃ at perovskite grain boundaries and surface, hampering humidity erosion and mitigates degradation through coordination with H₂O.