AB-INITIO CALCULATION OF THE EXCITON LIFETIME OF INP AND CDSE QUANTUM DOTS

Abstract

We calculate the exciton radiative lifetime of spherical Indium Phosphide (InP) and Cadmium Selenide (CdSe) colloidal quantum dots. In experiments, InP and CdSe quantum dots can be coated by another semiconductor shell, organic ligands, or inorganic molecules. In our calculation, the quantum dots are terminated by pseudo-hydrogen to remove surface states, which are introduced by dangling bonds. The single-particle energies and wavefunctions are obtained using the Atomic effective pseudopotentials (AEPs) method. The Configuration Interaction (CI) theory was used for the electronic excitation calculations. In this work, the radiative lifetime is calculated in the framework of the standard time-dependence perturbation theory. The dangling bonds of anion atoms (P and Se) at the surface are invoked to explain the finite dark exciton lifetime, which is expected to be infinitely long in nanocrystals. Our results are in good agreement with experimental measurements for core-shell nanoparticles but significantly different from the quantum dots coated by organic ligands or by more complex shells.