Influence of the image charge effect on excitonic energy structure in organic-inorganic multiple quantum well crystals

We have experimentally compared the excitonic properties of hybrid multiple quantum wells, (C₆H₅-C₂H₄NH₃)₂PbBr₄ and (C₄H₉NH₃)₂PbBr₄, using photoluminescence, reflection, and photoluminescence excitation measurements. We focused on the contribution of the image charge effect (ICE) to the excitonic energy structure in these materials which have different dielectric constants of the barrier layers. We have found that the binding energies of the $2s$ and $3s$ excitons are considerably enhanced by ICE, while the contribution of ICE to the $1s$ excitons is smaller because of the small Bohr radius, which is comparable to the well width.