Independent Control of Electron and Hole Localization in Core/Barrier/Shell Nanostructures

By use of a two-band effective mass model and first-order perturbation theory, we demonstrate the capacity for complete spatial control over excitonic wave functions in core/barrier/shell nanostructures. By exploring parameter space with core size and barrier width as variables, we show that each exciton can be in a core-localized or shell-localized state (Type-I localization) and as well in a charge-separated state (Type-II localization). Furthermore, the width of each localization region in parameter space can be tuned by controlling material properties, providing design principles for nanostructures with desirable features for key applications. Depending on the localization regime of excitons, both radiative and nonradiative decay rates can be significantly enhanced or suppressed in these nanostructures, making them suitable for dual-color emission and for producing low threshold and broad bandwidth of optical gain.