Improving Stability of Lead Halide Perovskite via PbF₂ Layer Covering

The stability of perovskites is an urgent problem to be solved before commercialization. An ultrathin PbF₂ layer covering the perovskite can be an effective strategy to improve the stability of the perovskite greatly. The perovskite/PbF₂ interface (XPbI₃/PbF₂, X = Cs and MA) is constructed, and the structural and chemical properties are studied by first-principles calculations. The results show that PbF₂ has better structural stability than the perovskites and can stabilize the octahedral frame of perovskite in the perovskite/PbF₂ interface. The PbF₂ layer reconstructs the XPbI₃ surface, resulting in the perovskite PbI interface transforming into a more stable XI interface in the perovskite/PbF₂ interface. Meanwhile, the tiny stress compression in the perovskite/PbF₂ interface can enhance the stability of perovskite. The large affinity of F atoms can adsorb free Pb atoms and suppress deleterious ion migration. In addition, the XPbI₃/PbF₂ interfaces have good dynamic stability at room temperature (300 K). Therefore, the PbF₂ layer covering provides new ideas for the stability study of perovskites.