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Nano Research 2019, 12(7): 1595-1603 https://doi.org/10.1007/s12274-019-2398-4
Research Article | Issue | Published: 22 April 2019

Photoluminescence of Ag–In–S/ZnS quantum dots: Excitation energy dependence and low-energy electronic structure

Show Author's Information Irina V. Martynenko1( ),  Anvar S. Baimuratov2,  Florian Weigert1,  José X. Soares3,  Lorena Dhamo1,  Philip Nickl1,  Ilona Doerfel1,  Jutta Pauli1,  Ivan D. Rukhlenko2,4,  Alexander V. Baranov2( ),  Ute Resch-Genger1( )
Federal Institute for Materials Research and Testing (BAM),Unter den Eichen 87,12205,Berlin, Germany;
ITMO University,49 Kronverksky Pr., St. Petersburg,,197101,Russia;
,University of Porto,Rua de Jorge Viterbo Ferreira, 228,4050-313,Porto, Portugal;
Institute of Photonics and Optical Sciences (IPOS), School of Physics,The University of Sydney,Camperdown,2006,NSW, Australia;
Keywords:
core/shell quantum dot, silver indium sulfide, defect photoluminescence, photoluminescence quantum yield, single-dot spectroscopy
Topics:
Absorption spectrumCopper compoundsElectronic structureElectronsEnergy gapIndium sulfideNanocrystalsPhotoluminescenceQuantum yieldSemiconducting indium compounds Semiconducting silver compoundsSilver compoundsSulfur compounds
Cite this article:
Martynenko IV, Baimuratov AS, Weigert F, et al. Photoluminescence of Ag–In–S/ZnS quantum dots: Excitation energy dependence and low-energy electronic structure. Nano Research, 2019, 12(7): 1595-1603. https://doi.org/10.1007/s12274-019-2398-4
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Abstract Full text Electronic supplementary material About this article

Cd-free I-III-VI group semiconductor quantum dots (QDs) like Ag-In-S and Cu-In-S show unstructured absorption spectra with a pronounced Urbach tail, rendering the determination of their band gap energy (Eg) and the energy structure of the exciton difficult. Additionally, the origin of the broad photoluminescence (PL) band with lifetimes of several hundred nanoseconds is still debated. This encouraged us to study the excitation energy dependence (EED) of the PL maxima, PL spectral band widths, quantum yields (QYs), and decay kinetics of AIS/ZnS QDs of different size, composition, and surface capping ligands. These results were then correlated with the second derivatives of the corresponding absorption spectra. The excellent match between the onset of changes in PL band position and spectral width with the minima found for the second derivatives of the absorption spectra underlines the potential of the EED approach for deriving Eg values of these ternary QDs from PL data. The PL QY is, however, independent of excitation energy in the energy range studied. From the EED of the PL features of the AIS/ZnS QDs we could also derive a mechanism of the formation of the low-energy electronic structure. This was additionally confirmed by a comparison of the EED of PL data of as-synthesized and size-selected QD ensembles and the comparison of these PL data with PL spectra of single QDs. These results indicate a strong contribution of intrinsic inhomogeneous PL broadening to the overall emission features of AIS/ZnS QDs originating from radiative transitions from a set of energy states of defects localized at different positions within the quantum dot volume, in addition to contributions from dimensional and chemical broadening. This mechanism was confirmed by numerically modelling the absorption and PL energies with a simple mass approximation for spherical QDs and a modified donor-acceptor model, thereby utilizing the advantages of previously proposed PL mechanisms of ternary QDs. These findings will pave the road to a deeper understanding of the nature of PL in quantum confined I-III-VI group semiconductor nanomaterials.


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Electronic supplementary material
About this article

Photoluminescence of Ag–In–S/ZnS quantum dots: Excitation energy dependence and low-energy electronic structure

Show Author's information Irina V. Martynenko1( ), Anvar S. Baimuratov2, Florian Weigert1, José X. Soares3, Lorena Dhamo1, Philip Nickl1, Ilona Doerfel1, Jutta Pauli1, Ivan D. Rukhlenko2,4, Alexander V. Baranov2( ), Ute Resch-Genger1( )
Federal Institute for Materials Research and Testing (BAM),Unter den Eichen 87,12205,Berlin, Germany;
ITMO University,49 Kronverksky Pr., St. Petersburg,,197101,Russia;
,University of Porto,Rua de Jorge Viterbo Ferreira, 228,4050-313,Porto, Portugal;
Institute of Photonics and Optical Sciences (IPOS), School of Physics,The University of Sydney,Camperdown,2006,NSW, Australia;

Abstract

Cd-free I-III-VI group semiconductor quantum dots (QDs) like Ag-In-S and Cu-In-S show unstructured absorption spectra with a pronounced Urbach tail, rendering the determination of their band gap energy (Eg) and the energy structure of the exciton difficult. Additionally, the origin of the broad photoluminescence (PL) band with lifetimes of several hundred nanoseconds is still debated. This encouraged us to study the excitation energy dependence (EED) of the PL maxima, PL spectral band widths, quantum yields (QYs), and decay kinetics of AIS/ZnS QDs of different size, composition, and surface capping ligands. These results were then correlated with the second derivatives of the corresponding absorption spectra. The excellent match between the onset of changes in PL band position and spectral width with the minima found for the second derivatives of the absorption spectra underlines the potential of the EED approach for deriving Eg values of these ternary QDs from PL data. The PL QY is, however, independent of excitation energy in the energy range studied. From the EED of the PL features of the AIS/ZnS QDs we could also derive a mechanism of the formation of the low-energy electronic structure. This was additionally confirmed by a comparison of the EED of PL data of as-synthesized and size-selected QD ensembles and the comparison of these PL data with PL spectra of single QDs. These results indicate a strong contribution of intrinsic inhomogeneous PL broadening to the overall emission features of AIS/ZnS QDs originating from radiative transitions from a set of energy states of defects localized at different positions within the quantum dot volume, in addition to contributions from dimensional and chemical broadening. This mechanism was confirmed by numerically modelling the absorption and PL energies with a simple mass approximation for spherical QDs and a modified donor-acceptor model, thereby utilizing the advantages of previously proposed PL mechanisms of ternary QDs. These findings will pave the road to a deeper understanding of the nature of PL in quantum confined I-III-VI group semiconductor nanomaterials.

Keywords: core/shell quantum dot, silver indium sulfide, defect photoluminescence, photoluminescence quantum yield, single-dot spectroscopy

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Acknowledgements

Publication history

Received: 17 February 2019
Revised: 29 March 2019
Accepted: 01 April 2019
Published: 22 April 2019
Issue date: July 2019

Copyright

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Acknowledgements

Acknowledgements

U. Resch-Genger gratefully acknowledges financial support from the grants RE1203/17-1 (M-Eranet project ICENAP; financial support of F. Weigert) and RE1203/12-3 (financial support of L. Dhamo) from the German Research Council (DFG). A. Baimuratov, I. Rukhlenko and A. Baranov gratefully acknowledge support from the Federal Target Program for Research and Development of the Ministry of Science and Higher Education of the Russian Federation (No. 14.587.21.0047, project identifier RFMEFI58718X0047). I. Martynenko acknowledges support from an Adolf-Martens fellowship granted by BAM. The authors gratefully acknowledge fruitful discussions with J. Santos, University of Porto and performance of first DMA measurements by A. Schmidt, BAM (Division 4.2).

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