Radiative emission from multiphoton-excited semiconductor quantum dots

被引:0
作者
Han, T.-T. [1 ]
Fu, Y. [1 ]
Ågren, H. [1 ]
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[1] Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, AlbaNova, 5-706 91 Stockholm, Sweden
来源
Journal of Applied Physics | 2007年 / 101卷 / 06期
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Optical transitions in CdS semiconductor quantum dots (QDs) have been studied by the Monte Carlo method based on probability calculations of the time-dependent Schrödinger equation. It has been demonstrated that excited by a continuous-wave laser; an assembly of CdS QDs; whose radii range from 2 to 5 nm centered at 3.7 nm; shows an emission peak around 2.65 eV in the optical emission spectrum; which corresponds to optical transitions among degenerate sublevels close to the ground sublevels in the conduction and valence bands of a CdS QD having a radius of 3.7 nm. For resonant one-photon excitation; the emission peak is very sharp; while for resonant two-photon excitation; the emission peak becomes blueshifted and broadened. The inclusion of the nonradiative electron-phonon processes makes the two-photon excitation peak significantly sharper and shows a better agreement with experimental work; thus demonstrating the upconversion luminescence of the QDs required for many applications including bioimaging. © 2007 American Institute of Physics;
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