Size Dependent Optical Properties of CdSe Nanocrystals at Low Temperature

In this work, we demonstrate that the optical properties of CdSe nanocrystals (NCs) show a strong size dependence at low temperature (similar to 10 K). The photoluminescence (PL) peak is shifted to higher energies as the growth time of synthesized CdSe NCs decreases, which can be attributed to size differences of CdSe NCs. The power-dependent PL measurements, where the PL intensities are linearly increased as a function of laser excitation powers were performed. These linearly increased PL intensities support the excitonic properties of confined states in CdSe NCs. In addition, the carrier dynamics of CdSe NCs are observed using time-resolved PL measurements. The carrier decay times are increased as the sizes of CdSe NCs are increased.