Flexoelectric effect induced p-n homojunction in monolayer GeSe

Recently, two-dimensional in-plane ferroelectric materials group-IV monochalcogenides MX (M = Ge, Sn; X = S, Se) have attracted much attention due to their rich physical properties. Here, we study the flexoelectric effect on the electronic, optical and transport properties in the monolayer germanium selenide (GeSe). We found that bending along the armchair (polarization) direction can separate the highest occupied molecular orbital and the lowest unoccupied molecular orbital in the real space and form the type-II band alignment, which can be used to fabricate p-n homojunctions. This outstanding property hints the potential applications of the bending monolayer GeSe for the exciton transport and solar cell, and provides new routines for advanced two-dimensional semiconductor devices.