Graded Shells in Semiconductor Nanocrystals

The current state-of-the-art of the fabrication and photophysics of graded shells in quantum dots is reviewed. Graded shells, i.e. partially alloyed interfaces between core and shell or between two shells of semi-conductor -nanoheterostructures, have been demonstrated to improve fluorescence -properties and suppress non-radiative pathways of exciton dynamics. By simply looking at linear optics on the level of single excitons this is reflected in increased -photoluminescence quantum yields. However, it is shown that graded shells have further beneficial implications for band structure engineering and multiexciton dynamics such as optical gain and charge carrier multiplication.