Spectroscopy and Femtosecond Dynamics of Type-II CdTe/CdSe Core-Shell Quantum Dots

摘要

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(JEM),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 x 10~(12)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.