Emission behaviour of CdTe/SiO2 core/shell quantum dots in external electric field

Abstract

Optical properties of CdTe/SiO2 core/shell colloidal quantum dots were investigated in external electric field in the range of 0–140 kV/cm. Maximum of photoluminescence intensity was centered at 2.39 eV with the full width at half maximum of 0.26 eV. It was found that the photoluminescence intensity of quantum dots tends to decrease by 22% and the integrated luminescence intensity tends to decrease by 23% with increasing electric field to the maximum value. However, an increase in the integrated luminescence intensity in the region of 60 kV/cm was observed. We show that both interband and trap-state luminescence is affected by an external electric field with no Stark shift observed. Based on these results, we propose that relaxation of the excited states in CdTe/SiO2 core/shell colloidal quantum dots exposed to an external electric field is affected by two field-dependent mechanisms, i.e. field-induced quenching of luminescence and blocking of charge carrier trapping. The obtained results can be useful to gain better understanding of the electric field effect on the optical properties of CdTe/SiO2 colloidal semiconductor quantum dots and, in particular, on the operation of hybrid organic-inorganic LEDs with emitting layers based on the studied nanocrystals.