Hot excitons are responsible for increasing photoluminescence blinking activity in single lead sulfide/cadmium sulfide nanocrystals

Abstract

The kinetics of photoluminescence blinking for isolated PbS/CdS nanocrystals changes with the photon excitation energy, with PL blinking increasing in frequency and changing from a two-state to a multistate on/off switching when the excitation energy changes from 1S_h–1S_e (≈1.4 eV) to 1P_h–1P_e (≈2.4 eV). This increase in PL blinking activity with increased photon excitation energy is reasoned in terms of the formation of hot excitons leading to emission from both the band edge state and defect states, with defect states connected to traps that are otherwise inaccessible following low photon energy excitation at the band edge.