RESUMEN
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.
RESUMEN
Interfacial electronic properties are greatly significant to study the photoelectric properties of semiconductor heterostructures. The novel heterostructures are constructed using perovskite 3D CsPbX3 (X = Cl, Br, I) and 2D PtSe2, and the structural and photoelectrical properties are studied by density functional theory. The band levels transform and interfacial charge transfer have serious differences at the interface of the CsPbX3-PtSe2 heterostructures. The CsPbCl3-PtSe2 and CsPbBr3-PtSe2 heterostructures show the type-I band arrangement, however, the CsPbI3-PtSe2 heterostructure demonstrate the type-II band arrangement. The difference in work function of the two semiconductors causes electrons to flow spontaneously at the interface. Moreover, the monolayer PtSe2 can broaden the absorption spectrum of the CsPbX3-PtSe2 heterostructures, that effectively enhance absorption capability of the heterostructures, especially the CsPbI3-PtSe2 heterostructure. These results demonstrate PtSe2 semiconductor materials can effectively improve the photoelectric performance of all-inorganic metal halide perovskite.