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Size and composition dependent multiple exciton generation efficiency in PbS, PbSe, and PbS(x)Se(1-x) alloyed quantum dots.
- Source :
-
Nano letters [Nano Lett] 2013 Jul 10; Vol. 13 (7), pp. 3078-85. Date of Electronic Publication: 2013 Jun 20. - Publication Year :
- 2013
-
Abstract
- Using ultrafast transient absorption and time-resolved photoluminescence spectroscopies, we studied multiple exciton generation (MEG) in quantum dots (QDs) consisting of either PbSe, PbS, or a PbSxSe1-x alloy for various QD diameters with corresponding bandgaps (Eg) ranging from 0.6 to 1 eV. For each QD sample, we determine the MEG efficiency, ηMEG, defined in terms of the electron-hole pair creation energy (εeh) such that ηMEG = Eg/εeh. In previous reports, we found that ηMEG is about two times greater in PbSe QDs compared to bulk PbSe, however, little could be said about the QD-size dependence of MEG. In this study, we find for both PbS and PbSxSe1-x alloyed QDs that ηMEG decreases lineally with increasing QD diameter within the strong confinement regime. When the QD radius is normalized by a material-dependent characteristic radius, defined as the radius at which the electron-hole Coulomb and confinement energies are equivalent, PbSe, PbS, and PbSxSe1-x exhibit similar MEG behaviors. Our results suggest that MEG increases with quantum confinement, and we discuss the interplay between a size-dependent MEG rate versus hot exciton cooling.
Details
- Language :
- English
- ISSN :
- 1530-6992
- Volume :
- 13
- Issue :
- 7
- Database :
- MEDLINE
- Journal :
- Nano letters
- Publication Type :
- Academic Journal
- Accession number :
- 23750998
- Full Text :
- https://doi.org/10.1021/nl4009748