Control the shallow trap states concentration during the formation of luminescent Ag2S and Ag2S/SiO2 core/shell quantum dots

Abstract

The paper presents the results of a study of shallow non-radiative trap states in colloidal Ag2S QDs and Ag2S/SiO2 core/shell QDs, passivated with 2-mercaptopropionic acid in ethylene glycol carried out the thermally stimulated luminescence technique. For Ag2S QDs, the presence of thermoluminescence peaks in the region of 150–330 K was established. The formation of the SiO2 shells leads to the disappearance of the thermoluminescence peak at 250 K. It is interpreted as a “healing” of defects, localized on Ag2S QD surface. The depths of the detected trap states were estimated using a kinetic model. They showed that the observed thermoluminescence bands are due to the presence of shallow holes trap states in Ag2S QDs with depths of 0.117 eV and 0.135 eV for the thermoluminescence peaks at 190 K and 250 K, respectively.