Ferroelectric Polarization in CsPbI3/CsSnI3 Perovskite Heterostructure

Ferroelectricity is believed to be an important origin for the excellent performance of halide perovskite optoelectronic devices, and building halide perovskite heterostructure is an excellent strategy to enhance performance of interfacial ferroelectric polarization. Herein, all-inorganic perovskite CsPbI3/CsSnI3 heterostructures are constructed for disclosing the interfacial electrical contacts and the ferroelectricity via first-principles calculations. In CsPbI3/CsSnI3 heterostructure, there are four kinds of electrical contacts, i.e., PbI2-SnI2, CsI-CsI, PbI2-CsI, and CsI-SnI2 interfaces. Large-cation anion displacements along z-direction are observed for all interface compositions, which indicate a strong ferroelectric field effect in the CsPbI3/CsSnI3 heterostructure. The net polarization displacements of PbI2 SnI2 and CsI-CsI interfaces are smaller than the values of PbI2-CsI and CsI-SnI2 interfaces. The interfacial ferroelectricity drives electron extraction from the perovskite and hinders electron-hole recombination by keeping the electrons and holes separated. The intrinsically interfacial ferroelectric polarization results from of diverse interfaces and the interface charge transfer. This work suggests that such an all-inorganic perovskite heterostructure has significant potential for future optoelectronic applications.