Spectroscopy and femtosecond dynamics of type-II CdTe/CdSe core-shell quantum dots

Abstract

Syntheses of CdTe/CdSe type-II quantum dots (QDs) using CdO and CdCl 2 as precursors for core-and shell, respectively, are reported. Characterization was made via near-IR interband emission, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDX), and X-ray diffraction (XRD). Femtosecond fluorescence upconversion measurements on the relaxation dynamics of the CdTe core (in CdTe/CdSe) emission and CdTe/CdSe interband emission reveal that as the size of the core increases from 5.3, 6.1 to 6.9 nm, the rate of photoinduced electron separation decreases from 1.96, 1.44 to 1.07 × 1012 s-1. The finite rates of the initial charge separation are tentatively rationalized by the small electron-phonon coupling, causing weak coupling between the initial and charge-separated states. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.