Optical properties of dense and diluted ensembles of semiconductor quantumdots

We examine collective effects in an ensemble of close-packed ultrasmall CdS e quantum dots by comparison of optical properties of dense and diluted thi n film composites. Studies of absorption spectra, photoluminescence excitat ion spectra and electroabsorption of diluted and condensed structures along with numerical simulation confirmed that in a dense ensemble extended elec tron states occur by analogy with Anderson transitions in disordered solids . Therefore evolution from isolated quantum dots to quantum dot solids in c ase of strong confinement results in a drastic modification of optical and electronic properties.