Absorption cross-section spectrum of single CdSe/ZnS nanocrystals revealed through photoluminescence excitation spectroscopy

Abstract

The absorption spectrum represents an important aspect of single semiconductor nanocrystals (NCs), revealing the morphology and orientation of the NCs. By conducting quantitative photoluminescence excitation spectroscopy based on a single-photon counting method, we succeed in clarifying the absorption cross-section spectrum of neutral excitons in single CdSe/ZnS NCs. With the values of the absorption cross section, we reveal that the intensity saturation of the neutral-exciton emission can be explained by considering the Poisson statistics for incident photons and by the small quantum yield of the biexciton emission. We also evaluated quantitatively the biexciton emission contribution and the ionization rate of NCs that appear at increased incident photon fluxes.