Optically Detected Magnetic Resonance Spectroscopy of Cu-Doped CdSe/CdS and CuInS2Colloidal Quantum Dots

Adi Harchol, Yahel Barak, Kira E. Hughes, Kimberly H. Hartstein, Huygen J. Jöbsis, P. Tim Prins, Celso De Mello Donegá, Daniel R. Gamelin, Efrat Lifshitz*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Copper-doped II-VI and copper-based I-III-VI2colloidal quantum dots (CQDs) have been at the forefront of interest in nanocrystals over the past decade, attributable to their optically activated copper states. However, the related recombination mechanisms are still unclear. The current work elaborates on recombination processes in such materials by following the spin properties of copper-doped CdSe/CdS (Cu@CdSe/CdS) and of CuInS2and CuInS2/(CdS, ZnS) core/shell CQDs using continuous-wave and time-resolved optically detected magnetic resonance (ODMR) spectroscopy. The Cu@CdSe/CdS ODMR showed two distinct resonances with different g factors and spin relaxation times. The best fit by a spin Hamiltonian simulation suggests that emission comes from recombination of a delocalized electron at the conduction band edge with a hole trapped in a Cu2+site with a weak exchange coupling between the two spins. The ODMR spectra of CuInS2CQDs (with and without shells) differ significantly from those of the copper-doped II-VI CQDs. They are comprised of a primary resonance accompanied by another resonance at half-field, with a strong correlation between the two, indicating the involvement of a triplet exciton and hence stronger electron-hole exchange coupling than in the doped core/shell CQDs. The spin Hamiltonian simulation shows that the hole is again associated with a photogenerated Cu2+site. The electron resides near this Cu2+site, and its ODMR spectrum shows contributions from superhyperfine coupling to neighboring indium atoms. These observations are consistent with the occurrence of a self-trapped exciton associated with the copper site. The results presented here support models under debate for over a decade and help define the magneto-optical properties of these important materials.

Original languageEnglish
Pages (from-to)12866-12877
Number of pages12
JournalACS Nano
Volume16
Issue number8
DOIs
Publication statusPublished - 1 Aug 2022

Bibliographical note

Funding Information:
E.L. and D.R.G. acknowledge the USA/Israel Binational Science Foundation (No. 2016156 and No. 2020076). E.L. acknowledges partial support from the joint USA National Science Foundation– USA/Israel Binational Science Foundation (NSF-BSF, No. 2017637) and from the Israel Science Foundation (No. 2528/19 and No. 1045/17). D.R.G. acknowledges partial support of this research from the UW Molecular Engineering Materials Center (DMR-1719797), an NSF Materials Research Science and Engineering Center. Additional support from the NSF (DMR-1807394 to D.R.G.) is gratefully acknowledged. C.d.M.D. acknowledges support by The Netherlands Organization for Scientific Research (NWO; grant 14614 “Q-Lumicon”). The authors are grateful to Dr. Kusha Sharma and Dr. Faris Horani for their assistance in editing.

Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.

Funding

E.L. and D.R.G. acknowledge the USA/Israel Binational Science Foundation (No. 2016156 and No. 2020076). E.L. acknowledges partial support from the joint USA National Science Foundation– USA/Israel Binational Science Foundation (NSF-BSF, No. 2017637) and from the Israel Science Foundation (No. 2528/19 and No. 1045/17). D.R.G. acknowledges partial support of this research from the UW Molecular Engineering Materials Center (DMR-1719797), an NSF Materials Research Science and Engineering Center. Additional support from the NSF (DMR-1807394 to D.R.G.) is gratefully acknowledged. C.d.M.D. acknowledges support by The Netherlands Organization for Scientific Research (NWO; grant 14614 “Q-Lumicon”). The authors are grateful to Dr. Kusha Sharma and Dr. Faris Horani for their assistance in editing.

Keywords

  • Colloidal Quantum Dots
  • Continuous-Wave Optically Detected Magnetic Resonance
  • Copper-Doped
  • Core/Shell
  • Photoluminescence
  • Semiconductors

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