Stochastic models of charge carrier dynamics in semiconducting nanosystems

We discuss recent experiments on photoexcited charge carrier relaxation dynamics in semiconducting nanotubes and nanoparticles within the framework of the stochastic model. We conclude that the elementary excitations in these nanosystems are excitons. Since the average number of excitons per nanosystem is typically small and comparable to a fluctuation, the quantized character of the number of excitons in nanosystems turns out to be essential, with no sufficient evidence to reduce the stochastic model to a bulk description.