Charge Trapping Defects in CdSe Nanocrystal Quantum Dots

António J. Almeida, Ayaskanta Sahu, Andreas Riedinger, David J. Norris, Martin S. Brandt, Martin Stutzmann, Rui N. Pereira

Research output: Contribution to journalArticle

Abstract

Charge trapping due to defects in semiconductor quantum dots (QDs) is expected to challenge the applicability of QDs in future technologies. The efficient elimination of defects from QDs demands an understanding of their origin and of their impact on (photo)electronic properties. Here, we identify the presence of two charge states of a defect in CdSe QDs using electron paramagnetic resonance (EPR), combined with electronic tuning of QDs via chemically induced Ag doping. From light-induced EPR, we show that these defects have a central role in Fermi level pinning in ensembles of intrinsic QDs. By analyzing the dependence of the EPR signal of the defects on the concentration of Ag dopants, we further demonstrate that the defects act as effective electron traps in the QDs. Our study also provides support to the proposed behavior of Ag dopants in CdSe QDs, according to which Ag atoms are n-type dopants at concentrations below 2 Ag atoms per QD and become p-type dopants for higher Ag concentrations. From temperature-dependent EPR, we estimate a lower limit for the ionization energy of the studied defects. Based on the characteristics of the EPR spectrum, we propose that these defects are associated with Se vacancies with the paramagnetic state being the positively charged state of the defect.

Original languageEnglish (US)
Pages (from-to)13763-13770
Number of pages8
JournalJournal of Physical Chemistry C
Volume120
Issue number25
DOIs
StatePublished - Jun 30 2016

Fingerprint

Charge trapping
Nanocrystals
Semiconductor quantum dots
nanocrystals
trapping
quantum dots
Defects
defects
Paramagnetic resonance
electron paramagnetic resonance
Doping (additives)
Atoms
Electron traps
Ionization potential
Fermi level
electronics
Electronic properties
Vacancies
atoms
elimination

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry

Cite this

Almeida, A. J., Sahu, A., Riedinger, A., Norris, D. J., Brandt, M. S., Stutzmann, M., & Pereira, R. N. (2016). Charge Trapping Defects in CdSe Nanocrystal Quantum Dots. Journal of Physical Chemistry C, 120(25), 13763-13770. https://doi.org/10.1021/acs.jpcc.6b00910

Charge Trapping Defects in CdSe Nanocrystal Quantum Dots. / Almeida, António J.; Sahu, Ayaskanta; Riedinger, Andreas; Norris, David J.; Brandt, Martin S.; Stutzmann, Martin; Pereira, Rui N.

In: Journal of Physical Chemistry C, Vol. 120, No. 25, 30.06.2016, p. 13763-13770.

Research output: Contribution to journalArticle

Almeida, AJ, Sahu, A, Riedinger, A, Norris, DJ, Brandt, MS, Stutzmann, M & Pereira, RN 2016, 'Charge Trapping Defects in CdSe Nanocrystal Quantum Dots', Journal of Physical Chemistry C, vol. 120, no. 25, pp. 13763-13770. https://doi.org/10.1021/acs.jpcc.6b00910
Almeida AJ, Sahu A, Riedinger A, Norris DJ, Brandt MS, Stutzmann M et al. Charge Trapping Defects in CdSe Nanocrystal Quantum Dots. Journal of Physical Chemistry C. 2016 Jun 30;120(25):13763-13770. https://doi.org/10.1021/acs.jpcc.6b00910
Almeida, António J. ; Sahu, Ayaskanta ; Riedinger, Andreas ; Norris, David J. ; Brandt, Martin S. ; Stutzmann, Martin ; Pereira, Rui N. / Charge Trapping Defects in CdSe Nanocrystal Quantum Dots. In: Journal of Physical Chemistry C. 2016 ; Vol. 120, No. 25. pp. 13763-13770.
@article{57348239c0494d17bccd8b71e1f08fd2,
title = "Charge Trapping Defects in CdSe Nanocrystal Quantum Dots",
abstract = "Charge trapping due to defects in semiconductor quantum dots (QDs) is expected to challenge the applicability of QDs in future technologies. The efficient elimination of defects from QDs demands an understanding of their origin and of their impact on (photo)electronic properties. Here, we identify the presence of two charge states of a defect in CdSe QDs using electron paramagnetic resonance (EPR), combined with electronic tuning of QDs via chemically induced Ag doping. From light-induced EPR, we show that these defects have a central role in Fermi level pinning in ensembles of intrinsic QDs. By analyzing the dependence of the EPR signal of the defects on the concentration of Ag dopants, we further demonstrate that the defects act as effective electron traps in the QDs. Our study also provides support to the proposed behavior of Ag dopants in CdSe QDs, according to which Ag atoms are n-type dopants at concentrations below 2 Ag atoms per QD and become p-type dopants for higher Ag concentrations. From temperature-dependent EPR, we estimate a lower limit for the ionization energy of the studied defects. Based on the characteristics of the EPR spectrum, we propose that these defects are associated with Se vacancies with the paramagnetic state being the positively charged state of the defect.",
author = "Almeida, {Ant{\'o}nio J.} and Ayaskanta Sahu and Andreas Riedinger and Norris, {David J.} and Brandt, {Martin S.} and Martin Stutzmann and Pereira, {Rui N.}",
year = "2016",
month = "6",
day = "30",
doi = "10.1021/acs.jpcc.6b00910",
language = "English (US)",
volume = "120",
pages = "13763--13770",
journal = "Journal of Physical Chemistry C",
issn = "1932-7447",
publisher = "American Chemical Society",
number = "25",

}

TY - JOUR

T1 - Charge Trapping Defects in CdSe Nanocrystal Quantum Dots

AU - Almeida, António J.

AU - Sahu, Ayaskanta

AU - Riedinger, Andreas

AU - Norris, David J.

AU - Brandt, Martin S.

AU - Stutzmann, Martin

AU - Pereira, Rui N.

PY - 2016/6/30

Y1 - 2016/6/30

N2 - Charge trapping due to defects in semiconductor quantum dots (QDs) is expected to challenge the applicability of QDs in future technologies. The efficient elimination of defects from QDs demands an understanding of their origin and of their impact on (photo)electronic properties. Here, we identify the presence of two charge states of a defect in CdSe QDs using electron paramagnetic resonance (EPR), combined with electronic tuning of QDs via chemically induced Ag doping. From light-induced EPR, we show that these defects have a central role in Fermi level pinning in ensembles of intrinsic QDs. By analyzing the dependence of the EPR signal of the defects on the concentration of Ag dopants, we further demonstrate that the defects act as effective electron traps in the QDs. Our study also provides support to the proposed behavior of Ag dopants in CdSe QDs, according to which Ag atoms are n-type dopants at concentrations below 2 Ag atoms per QD and become p-type dopants for higher Ag concentrations. From temperature-dependent EPR, we estimate a lower limit for the ionization energy of the studied defects. Based on the characteristics of the EPR spectrum, we propose that these defects are associated with Se vacancies with the paramagnetic state being the positively charged state of the defect.

AB - Charge trapping due to defects in semiconductor quantum dots (QDs) is expected to challenge the applicability of QDs in future technologies. The efficient elimination of defects from QDs demands an understanding of their origin and of their impact on (photo)electronic properties. Here, we identify the presence of two charge states of a defect in CdSe QDs using electron paramagnetic resonance (EPR), combined with electronic tuning of QDs via chemically induced Ag doping. From light-induced EPR, we show that these defects have a central role in Fermi level pinning in ensembles of intrinsic QDs. By analyzing the dependence of the EPR signal of the defects on the concentration of Ag dopants, we further demonstrate that the defects act as effective electron traps in the QDs. Our study also provides support to the proposed behavior of Ag dopants in CdSe QDs, according to which Ag atoms are n-type dopants at concentrations below 2 Ag atoms per QD and become p-type dopants for higher Ag concentrations. From temperature-dependent EPR, we estimate a lower limit for the ionization energy of the studied defects. Based on the characteristics of the EPR spectrum, we propose that these defects are associated with Se vacancies with the paramagnetic state being the positively charged state of the defect.

UR - http://www.scopus.com/inward/record.url?scp=84976888715&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84976888715&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcc.6b00910

DO - 10.1021/acs.jpcc.6b00910

M3 - Article

VL - 120

SP - 13763

EP - 13770

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 25

ER -