Optical properties of tetrapod-shaped CdTe nanocrystals

We studied the carrier confinement in tetrapod-shaped colloidal CdTe nanocrystals by means of absorption, photoluminescence, and photoluminescence excitation spectroscopy at room and cryogenic temperatures. The spectra show features characteristic of the tetrapod shape together with a clear dependence on the dominant confinement parameter, i.e., the diameter of the tetrapod arm. Theoretical calculations based on an envelope-function approximation and using the exact tetrapod shape have been performed to assign the observed spectral features. Oscillator strength and size dependence of the transitions energy have been calculated showing a direct correlation between the oscillator strength and the nanocrystal shape.