  We argue that the experimentally easily accessible optical absorption
spectrum can often be used to distinguish between a random alloy phase and a
stoichiometrically equivalent core/shell realization of ensembles of
monodisperse colloidal semiconductor quantum dots without the need for more
advanced structural characterization tools. Our proof-of-concept is performed
by conceptually straightforward exact-disorder tight-binding calculations. The
underlying stochastical tight-binding scheme only parametrizes bulk band
structure properties and does not employ additional free parameters to
calculate the optical absorption spectrum, which is an easily accessible
experimental property. The method is applied to selected realizations of type-I
Cd(Se,S) and type-II (Zn,Cd)(Se,S) alloyed quantum dots with an underlying
zincblende crystal structure and the corresponding core/shell counterparts.
