Upconversion luminescent characteristics and peak shift of CdSeS nanocrystals under different wavelength laser excitation |
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Authors: | Wenzhi Wu Yachen Gao Qing Chang Hongan Ye Zhiren Zheng Weilong Liu Aihua Li Yanqiang Yang |
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Institution: | (1) School of Electronic Engineering, Heilongjiang University, Harbin, 150080, China;(2) Department of Physics, Center for Condensed Matter Science and Technology, Harbin Institute of Technology, Harbin, 150001, China |
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Abstract: | Upconversion luminescence was obtained from CdSeS nanocrystals (NCs) under 800 nm femtosecond laser excitation. The structural
and optical characteristics of the CdSeS NCs were investigated experimentally by use of UV–visible absorption spectroscopy,
transmission electron microscopy, X-ray diffractometry, and time-resolved luminescence dynamics. Peak shift of luminescence
in CdSeS NCs can be readily observed under different wavelength femtosecond excitation. The pump power dependence of the luminescence
intensity and time-resolved decay revealed that one, two, and three-photon absorption occur. It was found that upconversion
luminescence is composed of photoinduced trapping and a band-edge excitonic state, and two types of species are involved in
the biexponential luminescence decay kinetics. With increasing Se-doped composition, luminescence lifetimes of CdSeS NCs with
similar sizes become shorter. This is not consistent with the changes of undoped CdS NCs and is ascribed to impurity level
increased doping in the energy gap, which is favorable for trapping luminescence. A simple energy level of doping NCs is used
to interpret upconversion luminescence and the peak shift of steady-state emission. |
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