Multicolor Luminescence from Semiconductor Nanocrystal Composites Tunable in an Electric Field

Semiconductor nanostructures have interesting electro-optic properties due to quantum confinement of electrons, strong exciton binding energies, and the possibility to tailor the bandgap and radiative emission rates. An electric field normal to the quantum well, for example, shifts the absorption edge to lower energies (red-shift) and increases the refractive index below the absorption edge allowing to control the intensity of a light beam through electroabsorption. Such nanostructures can be conveniently used for the direct modulation of light, since they show much larger electro-optic effects than bulk semiconductors. Moreover, the optical properties of semiconductor nanostructures can be controlled by an electric field due to different emission rates from radiative centers in different charge states.