Delayed Exciton Emission and Its Relation to Blinking in CdSe Quantum Dots.
The efficiency and stability of emission from semiconductor nanocrystal quantum dots (QDs) is negatively affected by "blinking" on the single-nanocrystal level, that is, random alternation of bright and dark periods. The time scales of these fluctuations can be as long as many seconds, orders of magnitude longer than typical lifetimes of exciton states in QDs. In this work, we investigate photoluminescence from QDs delayed over microseconds to milliseconds. Our results prove the existence of long-lived charge-separated states in QDs. We study the properties of delayed emission as a direct way to learn about charge carrier separation and recovery of the exciton state. A new microscopic model is developed to connect delayed emission to exciton recombination and blinking from which we conclude that bright periods in blinking are in fact not characterized by uninterrupted optical cycling as often assumed.
Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science , Princetonplein 1, 3584 CC Utrecht, The Netherlands.
Freddy T
FT
Rabouw
Center for Nanophotonics, FOM Institute AMOLF , Science Park 104, 1098 XG Amsterdam, The Netherlands.
Marko
M
Kamp
Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science , Princetonplein 1, 3584 CC Utrecht, The Netherlands.
Relinde J A
RJ
van Dijk-Moes
Department of Chemistry, University of Washington , Seattle, Washington 98195-1700, United States.
Daniel R
DR
Gamelin
Center for Nanophotonics, FOM Institute AMOLF , Science Park 104, 1098 XG Amsterdam, The Netherlands.
A Femius
AF
Koenderink
Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science , Princetonplein 1, 3584 CC Utrecht, The Netherlands.
Andries
A
Meijerink
Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science , Princetonplein 1, 3584 CC Utrecht, The Netherlands.
Daniël
D
Vanmaekelbergh
Nanocrystal; blinking; charge carrier trapping; colloidal quantum dot; excited state dynamics