Temperature dependence of the optical absorption spectra of InP/ZnS quantum dots

The optical-absorption spectra of InP/ZnS (core/shell) quantum dots have been studied in a broad temperature range of $T$ = 6.5–296 K. Using the second-order derivative spectrophotometry technique, the energies of optical transitions at room temperature were found to be $E_1$ = 2.60 $\pm$ 0.02 eV (for the first peak of excitonic absorption in the InP core) and $E_2$ = 4.70 $\pm$ 0.02 eV (for processes in the ZnS shell). The experimental curve of $E_1(T)$ has been approximated for the first time in the framework of a linear model and in terms of the Fan’s formula. It is established that the temperature dependence of $E_1$ is determined by the interaction of excitons and longitudinal acoustic phonons with $\hbar\omega$ = 15 meV.