  Colloidal semiconductor nanoplatelets, in which carriers are strongly
confined only along one dimension, present fundamentally different excitonic
properties than quantum dots, which support strong confinement in all three
dimensions. In particular, multiple excitons strongly confined in just one
dimension are free to re-arrange in the lateral plane, reducing the probability
for multi-body collisions. Thus, while simultaneous multiple photon emission is
typically quenched in quantum dots, in nanoplatelets its probability can be
tuned according to size and shape. Here, we focus on analyzing multi-exciton
dynamics in individual CdSe/CdS nanoplatelets of various sizes through the
measurement of second-, third-, and fourth-order photon correlations. Thus, for
the first time, we can directly probe the dynamics of the two, three and four
exciton states in the single nanocrystal level. Remarkably, although higher
orders of correlation vary substantially among the synthesis products, they
strongly correlate with the value of second order antibunching. The scaling of
the higher order moments with the degree of antibunching presents a small yet
clear deviation from the accepted model of Auger recombination through binary
collisions. Such a deviation suggests that many-body contributions are present
already at the level of triexcitons. These findings highlight the benefit of
high-order photon correlation spectroscopy as a technique to study
multi-exciton dynamics in colloidal semiconductor nanocrystals.
