Spin Blockades to Relaxation of Hot Multiexcitons in Nanocrystals

Tufan Ghosh, Joanna Dehnel, Marcel Fabian, Efrat Lifshitz*, Roi Baer, Sanford Ruhman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


The conjecture that, as in bulk semiconductors, hot multiexcitons in nanocrystals cool rapidly to the lowest available energy levels is tested here by recording the effects of a single cold "spectator" exciton on the relaxation dynamics of a subsequently deposited hot counterpart. Results in CdSe/CdS nanodots show that a preexisting cold "spectator exciton" allows only half of the photoexcited electrons to relax directly to the band-edge. The rest are blocked in an excited quantum state due to conflicts in spin orientation. The latter fully relax in this sample only after ∼25 ps as the blocked electrons spins flip, prolonging the temporal window of opportunity for harvesting the retained energy more than 100 fold! Common to all quantum-confined nanocrystals, this process will delay cooling and impact the spectroscopic signatures of hot multiexcitons in all envisioned generation scenarios. How the spin-flipping rate scales with particle size and temperature remains to be determined.

Original languageAmerican English
Pages (from-to)2341-2348
Number of pages8
JournalJournal of Physical Chemistry Letters
Issue number10
StatePublished - 16 May 2019

Bibliographical note

Funding Information:
S.R. holds the Lester Aronberg Chair in Chemistry. S.R. acknowledges financial support from the Israel Science Foundation (Grant # 163/16). R.B. gratefully acknowledges support of the Israel Science Foundation (ISF Grant No. 189-14) and the binational US−Israel Science Foundation (BSF Grant No. 2015687). T.G. thanks the Lady Davis Fellowship Trust and the Raymond and Janine Bollag Post-Doctoral Fellowship Fund for a fellowship. S.R. and T.G. thank Dr. O. Liubashevski and Dr. J. Dana for technical help. E.L. acknowledges financial support from the Israel Science Foundation Projects 914/15 and 1508/14. J.D. acknowledges the Marie-Sklodowska Curie action H2020-MSCA-ITN-642656 (PHONSI) for fellowship support.

Publisher Copyright:
© 2019 American Chemical Society.


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