EPITAXIAL-GROWTH OF HIGHLY LUMINESCENT CDSE CDS CORE/SHELL NANOCRYSTALS WITH PHOTOSTABILITY AND ELECTRONIC ACCESSIBILITY/

The synthesis of epitaxially grown, wurtzite CdSe/CdS core/shell nanoc rystals is reported. Shells of up to three monolayers in thickness wer e grown on cores ranging in diameter from 23 to 39 Angstrom. Shell gro wth was controllable to within a tenth of a monolayer and was consiste ntly accompanied by a red shift of the absorption spectrum, an increas e of the room temperature photoluminescence quantum yield (up to at le ast 50%), and an increase in the photostability. Shell growth was show n to be uniform and epitaxial by the use of X-ray photoelectron spectr oscopy (XPS), X-ray diffraction (XRD), high resolution transmission el ectron microscopy (HRTEM), and optical spectroscopy. The experimental results indicate that in the excited state the hole is confined to the core and the electron is delocalized throughout the entire structure. The photostability can be explained by the confinement of the hole, w hile the delocalization of the electron results in a degree of electro nic accessibility that makes these nanocrystals attractive for use in optoelectronic devices.