Layer Edge States Stabilized by Internal Electric Fields in Two-Dimensional Hybrid Perovskites

Two-dimensional (2D) organic–inorganic
hybrid perovskites
have been intensively explored in recent years due to their tunable
band gaps and exciton binding energies and increased stability with
respect to three-dimensional (3D) hybrid perovskites. Experimental
observations suggest the existence of localized edge states in 2D
hybrid perovskites which facilitate extremely efficient electron–hole
dissociation and long carrier lifetimes, while multiple origins for
their formation have been proposed. Using first-principles calculations,
we demonstrate that layer edge states are stabilized by internal electric
fields created by polarized molecular alignment of organic cations
in 2D hybrid perovskites when they are two layers or thicker. Our
study gives a simple physical explanation of the edge state formation,
and facilitating the design and manipulation of layer edge states
for optoelectronic applications.