Open AccessUp-conversion luminescence of CdTe and CdTe/CdS quantum dots excited by femtosecond laser of low intensity
Author(s) -
Li Min An,
Yanqiang Yang,
Woo-Seuk Song,
W H Su,
Qinghui Zeng,
Kang-Ju Chao,
Xianggui Kong
Publication year - 2009
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.58.7914
Subject(s) - luminescence , femtosecond , materials science , quantum dot , excited state , cadmium telluride photovoltaics , photon upconversion , laser , excitation , absorption (acoustics) , optoelectronics , exciton , atomic physics , molecular physics , optics , physics , condensed matter physics , quantum mechanics , composite material
We studied the steady-state and time-resolved luminescence properties of CdTe and CdTe/CdS core/shell quantum dots by one-and two-photon excitation with a femtosecond laser of low intensity. The 800 nm excitation causes a blue shift of the emission peak compared with 400 nm laser excitation. Near-quadratic laser power dependence of the up-conversion intensity and biexponential decay kinetics are observed. It is found that upconversion luminescence is composed of a photoinduced trapping and a band edge excitonic state. The blue shift of the emission peak is caused by the relative change in luminescence intensity between excitonic and trapping states. Two-step two-photon absorption involving the surface as intermediate states has been proposed for the mechanism of up-conversion luminescence of CdTe/CdS quantum dots.