Two Biexciton Types Coexisting in Coupled Quantum Dot Molecules

Nadav Frenkel, Einav Scharf, Gur Lubin, Adar Levi, Yossef E. Panfil, Yonatan Ossia, Josep Planelles, Juan I. Climente*, Uri Banin*, Dan Oron*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Coupled colloidal quantum dot molecules (CQDMs) are an emerging class of nanomaterials, manifesting two coupled emission centers and thus introducing additional degrees of freedom for designing quantum-dot-based technologies. The properties of multiply excited states in these CQDMs are crucial to their performance as quantum light emitters, but they cannot be fully resolved by existing spectroscopic techniques. Here we study the characteristics of biexcitonic species, which represent a rich landscape of different configurations essentially categorized as either segregated or localized biexciton states. To this end, we introduce an extension of Heralded Spectroscopy to resolve the different biexciton species in the prototypical CdSe/CdS CQDM system. By comparing CQDMs with single quantum dots and with nonfused quantum dot pairs, we uncover the coexistence and interplay of two distinct biexciton species: A fast-decaying, strongly interacting biexciton species, analogous to biexcitons in single quantum dots, and a long-lived, weakly interacting species corresponding to two nearly independent excitons. The two biexciton types are consistent with numerical simulations, assigning the strongly interacting species to two excitons localized at one side of the quantum dot molecule and the weakly interacting species to excitons segregated to the two quantum dot molecule sides. This deeper understanding of multiply excited states in coupled quantum dot molecules can support the rational design of tunable single- or multiple-photon quantum emitters.

Original languageAmerican English
Pages (from-to)14990-15000
Number of pages11
JournalACS Nano
Volume17
Issue number15
DOIs
StatePublished - 8 Aug 2023

Bibliographical note

Publisher Copyright:
© 2023 American Chemical Society.

Keywords

  • Biexcitons
  • Binding energy
  • Hybridization
  • Quantum dots
  • SPAD arrays
  • Single-particle spectroscopy

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