Comparative study of the exciton binding energies of thin and ultrathin organic-inorganic perovskites due to dielectric mismatch effects

Abstract

The multi-quantum well (MQW) organic-inorganic perovskite offer an approach of tuning the exciton binding energy based on the well-barrier dielectric mismatch effect, which called the image charge effect. The exfoliation from MQW organic-inorganic perovskite forms a twodimensional (2D) nano-sheet. As with other 2D materials, like graphene or transition metal dichalcogenides (TMDs), the ultra-thin perovskites layers are highly sensitive to the dielectric environment. We investigate the ultrathin crystalline 2D van-der-Waals (vdW) layers of organic-inorganic perovskite crystals close to a surface of the substrate. We show that binding exciton energy is strongly influenced by the surrounding dielectric environment. We find that the Keldysh model somehow estimates the strong dependence of the exciton binding energies on environmental screening. We compare our binding energies results with experimental results in the (C 6 H 13 NH 3 ) 2 PbI 4 perovskite, and we estimate the binding energy values of (C 4 H 9 NH 3 ) 2 PbBr 4 . I-IntroductionFor about a decade, 2D materials have represented one of the hottest directions in solid-state research. Much attention has been paid to 2D layered compounds such as graphene or TMDs.Due to weak vdW bonding, it is easy to cleave neighboring layers and form ultra-thin samples. [1][2][3][4][5] In these materials, new optical and electronic properties emerge for mono-or fewlayer regions, providing new avenues for material applications. Here, we explore a recent addition to this library, ultrathin crystalline layers of organic-inorganic perovskite crystals.These materials differ from the previous types of 2D vdW layers in being a hybrid material with an organic compound intrinsically integrated into an inorganic crystal structure.