Photoluminescence Enhancement of a CdSe/ZnS Nanocrystal Thin Film

Abstract

Here we report that the closely packed CdSe/ZnS core/shell nanocrystal (NC) film and the isolated NC show different behaviors of the photoluminescence (PL) intensity with continuous irradiation. The PL intensity of the bilayer of closely packed NC film was enhanced by continuous irradiation of Ar laser (wavelength 488nm) under ambient air. On the other hand, fluorescence intermittency was observed by continuous irradiation for the isolated NCs. The result suggests that the photo-induced fluorescence enhancement (PFE) is attributed to the closely packed structure of NCs. It was supported the hypothesis that electrostatic potential produced by photoionization of a certain fraction of the NCs decrease the ionization probability of the adjacent NCs, and it leads to the enhancement of total emission efficiency.