Optical Properties of Dense and Diluted Ensembles of Semiconductor Quantum Dots

We examine collective effects in an ensemble of close-packed ultrasmall CdSe quantum dots by comparison of optical properties of dense and diluted thin film composites. Studies of absorption spectra, photoluminescence excitation spectra and electroabsorption of diluted and condensed structures along with numerical simulation confirmed that in a dense ensemble extended electron states occur by analogy with Anderson transitions in disordered solids. Therefore evolution from isolated quantum dots to quantum dot solids in case of strong confinement results in a drastic modification of optical and electronic properties.