Blinking, Flickering, and Correlation in Fluorescence of Single Colloidal CdSe Quantum Dots with Different Shells under Different Excitations
2013 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 9, 4844-4851 p.Article in journal (Refereed) Published
We studied the fluorescence spectra from single CdSe core-CdS/ZnS and CdS/CdZnS/ZnS shell colloidal quantum dots (QDs) (different shell thicknesses and different surface ligands) under different optical excitations. It was found that the single QD blinks (on and off) at low excitation and flickers (without distinguishable on and off) under high excitation. Theoretical analysis suggests that under low excitation the single QD blinks due to transfer of the photogenerated electron and hole between QD core states and surface states, and the transfer rate is inversely proportional to the shell thickness, as demonstrated experimentally. Under high excitation, the photogenerated electron and hole via interband excitation are further excited via intraband excitation, which will keep the electron and hole from relaxing to the ground exciton state, therefore significantly suppressing the radiative interband recombination, resulting in QD flickering. It was further observed experimentally that the fluorescence events from two neighboring QDs under high excitation are correlated. The correlation can be most possibly understood that one QD, which is kept at the excited state by the high excitation, radiatively recombines under the stimulation of the emission from its neighboring QD.
Place, publisher, year, edition, pages
2013. Vol. 117, no 9, 4844-4851 p.
Semiconductor Nanocrystals, Thickness, Photoluminescence, Cells
IdentifiersURN: urn:nbn:se:kth:diva-120287DOI: 10.1021/jp311975hISI: 000315707600056ScopusID: 2-s2.0-84874838216OAI: oai:DiVA.org:kth-120287DiVA: diva2:614548
FunderSwedish Research Council
QC 201304052013-04-052013-04-042015-03-06Bibliographically approved