Core-Shell Heterostructures for Photovoltaic Energy Conversion Igor Vasiliev, Department of Physics, New Mexico State University, Las Cruces, NM 88003 Our research focuses on theoretical prediction of the structural, electronic, and optical properties of core-shell semiconductor nanoparticles. The goal of this project is to expand the knowledge of chemistry and physics of semiconductor heterostructures and accelerate the development of composite materials for efficient conversion of solar energy. Inverted (a) and traditional (b) core-shell nanoparticles Ab initio density functional study of core-shell semiconductor nanoparticles Two types of core-shell nanoparticles were considered in our study: traditional, in which a core of a narrow gap semi-conductor is covered with a shell of a wide gap material, and inverted, in which a wide-gap core is enclosed in a narrow-gap shell. The structures, electronic densities of states, and energy gaps of core-shell nanoparticles were analyzed using ab initio density functional and time-dependent density functional computational methods. The surfaces of nanoparticles were passivated with partially charged hydrogen atoms. This approach removed the electronic states associated with the surface hydrogen atoms from the gap. Structures and densities of states of CdSe/ZnSe and CdTe/ZnTe nanoparticles