CONFINEMENT AND SHAPE EFFECTS ON THE OPTICAL-SPECTRA OF SMALL CDSE NANOCRYSTALS

A tight-binding model is used to investigate confinement and shape eff ects on the optical absorption spectrum of CdSe nanocrystals up to 5 n m diam. The effects of size dispersion are studied and we show that to simulate the spectrum of a collection of nanocrystals it is not alway s sufficient to broaden inhomogeneously the mean diameter cluster spec trum. Our results are compared with calculations based on other method s and show good agreement with experimental data. We have also calcula ted the absorption spectra of CdSe crystallites with different morphol ogies: spherical clusters and oblate and prolate elliptic nanocrystals . We have performed a comparison of the energies and absorption bands as a function of the morphological changes and we present a detailed s tudy of the modifications in the features of the optical spectra.