Reversible and Irreversible Degradation of CdS/ZnSe Nanocrystals Capped with Oleic Acid

Single-photon processes of optically induced degradation of the photoluminescence intensity in CdS/ZnSe nanocrystals (NCs) are investigated, and the mechanisms of this degradation are established. It is demonstrated that three processes contribute to the photodegradation of the NCs. The corresponding characteristic times are of about 9.9 s, 260 s, and 2 h. In these experiments, it is found that the short-term process in the degradation is caused by the activation of Auger recombination when a photoinduced hole is captured in a surface trap, and the long-term process can be associated with the temperature-induced detachment of the ligand (oleic acid) from the NC surface and activation of the non-radiative relaxation channel. The hole detrapping time is calculated to be 135 s.