The exciton eigenstates and biexciton interaction energies in a spherical core-shell hetero-nano structure in the type II and the quasi-type II carrier localization regimes have been analyzed. For the analysis, we have evaluated the electron-hole overlap integral, the binding energy of exciton ground state, and the interaction energy of bi-exciton ground state in the structure. In the evaluation, the first order perturbation approach has been employed, where the direct Coulomb interaction energy, the surface polarization energy and the dielectric solvation energy are included. Our results show that the exciton eigenenergies and exciton-exciton interaction energy strongly depend on the choice of materials on which both the dielectric constants and the electron and hole effective masses rely. (C) 2014 Elsevier B.V. All rights reserved.