The electronic structure of semiconductor nanocrystals

We review the rapid progress made in our understanding of the crystal prope rties of semiconductors and nanocrystals focussing on theoretical results o btained within the multiband effective mass approximation. A comparison wit h experiment shows these results are valid for nanocrystals down 22-26 Angs trom in diameter. The effect of the electron-hole Coulomb interaction on th e optical spectra is analyzed. A theory of the quantum-size levels in wide gap (CdSe) and narrow gap semiconductors (InAs) is presented that describes the absorption spectra of these semiconductors well. A great enhancement o f the electron-hole exchange interaction leads to the formation of the opti cally forbidden Dark Exciton in nanocrystals, which strongly affects their photoluminescence. A theory of the band-edge exciton fine structure is pres ented and applied to the study of the PL in CdSe nanocrystals. The effect o f doping on nanocrystal spectra is considered. The enhancement of the short -range spin-spin interaction in Mn-doped nanocrystals leads to a giant spli tting of the electron and hole spin sublevels.