  Thermal quenching is one of the essential factors in reducing the efficiency
of radiative processes in luminophores of various nature. The emission activity
of low dimensional structures is influenced also by multiplicity of parameters
that are related to synthesis processes, treatment regimes, etc. In the present
work, we have investigated the temperature dependence of photoluminescence
caused by exciton and defect-related transitions in ensembles of biocompatible
InP/ZnS core/shell nanocrystals with an average size of 2.1 and 2.3 nm. The
spread in the positions of energy levels is shown to be due to size
distribution of quantum dots in the ensembles under study. For a quantitative
analysis of the experimental data, we have proposed a band model accounting for
the Gaussian distribution of the thermally activated barriers in the
photoluminescence quenching processes. The model offers the thermal escape of
an electrons from the core into the shell as the main mechanism for
non-radiative decay of excitons. In turn, the quenching of defect-related
emission is predominantly brought about through the emptying of the hole
capture centers based on dangling phosphorus bonds. We have revealed the
correlation between size distributions of quantum dots and scatter of the
activation energy of exciton luminescence quenching. The developed approach
will give further the possibility to optimize technological regimes and methods
for band engineering of indium phosphide-based type-I quantum dots.
