  We present a diffusion-based simulation and theoretical models for
explanation of photoluminescence (PL) emission intensity in semiconductor
nanoplatelets. It is shown that the shape of PL intensity curves can be
reproduced by the interplay of recombination, diffusion and trapping of
excitons. The emission intensity at short times is purely exponential and is
defined by recombination. At long times it is governed by the release of
excitons from surface traps and is characterized by a power-law tail. We show
that the crossover from one limit to another is controlled by diffusion
properties. This intermediate region exhibits a rich behaviour depending on the
value of diffusivity. Proposed approach reproduces all the features of
experimental curves measured for different nanoplatelet systems.
