  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 (C6H13NH3)2PbI4 perovskite, and we estimate the
binding energy values of (C4H9NH3)2PbBr4.
