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.