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Li Y, Wang L, Xiang D, Zhu J, Wu K. Dielectric and Wavefunction Engineering of Electron Spin Lifetime in Colloidal Nanoplatelet Heterostructures. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2306518. [PMID: 38234238 DOI: 10.1002/advs.202306518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Revised: 11/23/2023] [Indexed: 01/19/2024]
Abstract
Colloidal semiconductor nanoplatelets (NPLs) have emerged as low-cost and free-standing alternates of traditional quantum wells. The giant heavy- and light-hole splitting in NPLs allows for efficient optical spin injection. However, the electron spin lifetimes for prototypical CdSe NPLs are within a few picoseconds, likely limited by strong electron-hole exchange in these quantum- and dielectric-confined materials. Here how this hurdle can be overcome with engineered NPL-heterostructures is demonstrated. By constructing type-I CdSe/ZnS core/shell NPLs, dielectric screening inside the core is strongly enhanced, prolonging the electron spin polarization time (τesp) to over 30 ps (or 60 ps electron spin-flip time). Alternatively, by growing type-II CdSe/CdTe core/crown NPLs to spatially separate electron and hole wavefunctions, the electron-hole exchange is strongly suppressed, resulting in τesp as long as 300 ps at room temperature. This study not only exemplifies how the well-established synthetic chemistry of colloidal heterostructures can aid in spin dynamics control but also establishes the feasibility of room-temperature coherent spin manipulation in colloidal NPLs.
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Affiliation(s)
- Yulu Li
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Lifeng Wang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
- University of the Chinese Academy of Sciences, Beijing, Hebei, 100049, China
| | - Dongmei Xiang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Jingyi Zhu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Kaifeng Wu
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
- University of the Chinese Academy of Sciences, Beijing, Hebei, 100049, China
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2
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Smirnova OO, Kalitukha IV, Rodina AV, Dimitriev GS, Sapega VF, Ken OS, Korenev VL, Kozyrev NV, Nekrasov SV, Kusrayev YG, Yakovlev DR, Dubertret B, Bayer M. Optical Alignment and Optical Orientation of Excitons in CdSe/CdS Colloidal Nanoplatelets. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2402. [PMID: 37686910 PMCID: PMC10489814 DOI: 10.3390/nano13172402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 08/21/2023] [Accepted: 08/22/2023] [Indexed: 09/10/2023]
Abstract
Optical alignment and optical orientation of excitons are studied experimentally on an ensemble of core/shell CdSe/CdS colloidal nanoplatelets. Linear and circular polarization of photoluminescence during resonant excitation of excitons is measured at cryogenic temperatures and with magnetic fields applied in the Faraday geometry. The developed theory addresses the optical alignment and optical orientation of excitons in colloidal nanocrystals, taking into account both bright and dark exciton states in the presence of strong electron-hole exchange interaction and the random in-plane orientation of nanoplatelets within the ensemble. Our theoretical analysis of the obtained experimental data allows us to evaluate the exciton fine structure parameters, the g-factors, and the spin lifetimes of the bright and dark excitons. The optical alignment effect enables the identification of the exciton and trion contributions to the emission spectrum, even in the absence of their clear separation in the spectra.
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Affiliation(s)
- Olga O. Smirnova
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Ina V. Kalitukha
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - Anna V. Rodina
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | | | - Victor F. Sapega
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Olga S. Ken
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | | | - Nikolai V. Kozyrev
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Sergey V. Nekrasov
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Yuri G. Kusrayev
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Dmitri R. Yakovlev
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - Benoit Dubertret
- Laboratoire de Physique et d’Étude des Matériaux, ESPCI, CNRS, 75231 Paris, France
| | - Manfred Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany
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3
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Harkort C, Kudlacik D, Kopteva NE, Yakovlev DR, Karzel M, Kirstein E, Hordiichuk O, Kovalenko MV, Bayer M. Spin-Flip Raman Scattering on Electrons and Holes in Two-Dimensional (PEA) 2 PbI 4 Perovskites. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2300988. [PMID: 37066731 DOI: 10.1002/smll.202300988] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 03/14/2023] [Indexed: 06/19/2023]
Abstract
The class of Ruddlesden-Popper type (PEA)2 PbI4 perovskites comprises 2D structures whose optical properties are determined by excitons with a large binding energy of about 260 meV. It complements the family of other 2D semiconductor materials by having the band structure typical for lead halide perovskites, that can be considered as inverted compared to conventional III-V and II-VI semiconductors. Accordingly, novel spin phenomena can be expected for them. Spin-flip Raman scattering is used here to measure the Zeeman splitting of electrons and holes in a magnetic field up to 10 T. From the recorded data, the electron and hole Landé factors (g-factors) are evaluated, their signs are determined, and their anisotropies are measured. The electron g-factor value changes from +2.11 out-of-plane to +2.50 in-plane, while the hole g-factor ranges between -0.13 and -0.51. The spin flips of the resident carriers are arranged via their interaction with photogenerated excitons. Also the double spin-flip process, where a resident electron and a resident hole interact with the same exciton, is observed showing a cumulative Raman shift. Dynamic nuclear spin polarization induced by spin-polarized holes is detected in corresponding changes of the hole Zeeman splitting. An Overhauser field of the polarized nuclei acting on the holes as large as 0.6 T can be achieved.
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Affiliation(s)
- Carolin Harkort
- Experimentelle Physik 2, Technische Universität Dortmund, D-44227, Dortmund, Germany
| | - Dennis Kudlacik
- Experimentelle Physik 2, Technische Universität Dortmund, D-44227, Dortmund, Germany
| | - Natalia E Kopteva
- Experimentelle Physik 2, Technische Universität Dortmund, D-44227, Dortmund, Germany
| | - Dmitri R Yakovlev
- Experimentelle Physik 2, Technische Universität Dortmund, D-44227, Dortmund, Germany
| | - Marek Karzel
- Experimentelle Physik 2, Technische Universität Dortmund, D-44227, Dortmund, Germany
| | - Erik Kirstein
- Experimentelle Physik 2, Technische Universität Dortmund, D-44227, Dortmund, Germany
| | - Oleh Hordiichuk
- Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093, Zürich, Switzerland
- Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, CH-8600, Dübendorf, Switzerland
| | - Maksym V Kovalenko
- Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093, Zürich, Switzerland
- Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, CH-8600, Dübendorf, Switzerland
| | - Manfred Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, D-44227, Dortmund, Germany
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Diroll BT, Guzelturk B, Po H, Dabard C, Fu N, Makke L, Lhuillier E, Ithurria S. 2D II-VI Semiconductor Nanoplatelets: From Material Synthesis to Optoelectronic Integration. Chem Rev 2023; 123:3543-3624. [PMID: 36724544 DOI: 10.1021/acs.chemrev.2c00436] [Citation(s) in RCA: 32] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The field of colloidal synthesis of semiconductors emerged 40 years ago and has reached a certain level of maturity thanks to the use of nanocrystals as phosphors in commercial displays. In particular, II-VI semiconductors based on cadmium, zinc, or mercury chalcogenides can now be synthesized with tailored shapes, composition by alloying, and even as nanocrystal heterostructures. Fifteen years ago, II-VI semiconductor nanoplatelets injected new ideas into this field. Indeed, despite the emergence of other promising semiconductors such as halide perovskites or 2D transition metal dichalcogenides, colloidal II-VI semiconductor nanoplatelets remain among the narrowest room-temperature emitters that can be synthesized over a wide spectral range, and they exhibit good material stability over time. Such nanoplatelets are scientifically and technologically interesting because they exhibit optical features and production advantages at the intersection of those expected from colloidal quantum dots and epitaxial quantum wells. In organic solvents, gram-scale syntheses can produce nanoparticles with the same thicknesses and optical properties without inhomogeneous broadening. In such nanoplatelets, quantum confinement is limited to one dimension, defined at the atomic scale, which allows them to be treated as quantum wells. In this review, we discuss the synthetic developments, spectroscopic properties, and applications of such nanoplatelets. Covering growth mechanisms, we explain how a thorough understanding of nanoplatelet growth has enabled the development of nanoplatelets and heterostructured nanoplatelets with multiple emission colors, spatially localized excitations, narrow emission, and high quantum yields over a wide spectral range. Moreover, nanoplatelets, with their large lateral extension and their thin short axis and low dielectric surroundings, can support one or several electron-hole pairs with large exciton binding energies. Thus, we also discuss how the relaxation processes and lifetime of the carriers and excitons are modified in nanoplatelets compared to both spherical quantum dots and epitaxial quantum wells. Finally, we explore how nanoplatelets, with their strong and narrow emission, can be considered as ideal candidates for pure-color light emitting diodes (LEDs), strong gain media for lasers, or for use in luminescent light concentrators.
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Affiliation(s)
- Benjamin T Diroll
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States
| | - Burak Guzelturk
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States
| | - Hong Po
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Corentin Dabard
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Ningyuan Fu
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Lina Makke
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Emmanuel Lhuillier
- Sorbonne Université, CNRS, Institut des NanoSciences de Paris, INSP, 75005 Paris, France
| | - Sandrine Ithurria
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
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5
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Shornikova EV, Yakovlev DR, Gippius NA, Qiang G, Dubertret B, Khan AH, Di Giacomo A, Moreels I, Bayer M. Exciton Binding Energy in CdSe Nanoplatelets Measured by One- and Two-Photon Absorption. NANO LETTERS 2021; 21:10525-10531. [PMID: 34874734 PMCID: PMC8886564 DOI: 10.1021/acs.nanolett.1c04159] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 11/24/2021] [Indexed: 05/22/2023]
Abstract
Colloidal semiconductor nanoplatelets exhibit strong quantum confinement for electrons and holes as well as excitons in one dimension, while their in-plane motion is free. Because of the large dielectric contrast between the semiconductor and its ligand environment, the Coulomb interaction between electrons and holes is strongly enhanced. By means of one- and two-photon photoluminescence excitation spectroscopy, we measure the energies of the 1S and 1P exciton states in CdSe nanoplatelets with thicknesses varied from 3 up to 7 monolayers. By comparison with calculations, performed in the effective mass approximation with account of the dielectric enhancement, we evaluate exciton binding energies of 195-315 meV, which is about 20 times greater than that in bulk CdSe. Our calculations of the effective Coulomb potential for very thin nanoplatelets are close to the Rytova-Keldysh model, and the exciton binding energies are comparable with the values reported for monolayer-thick transition metal dichalcogenides.
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Affiliation(s)
- Elena V. Shornikova
- Experimentelle
Physik 2, Technische Universität
Dortmund, 44221 Dortmund, Germany
| | - Dmitri R. Yakovlev
- Experimentelle
Physik 2, Technische Universität
Dortmund, 44221 Dortmund, Germany
- Ioffe
Institute, Russian Academy of Sciences, 194 021 St. Petersburg, Russia
| | | | - Gang Qiang
- Experimentelle
Physik 2, Technische Universität
Dortmund, 44221 Dortmund, Germany
| | - Benoit Dubertret
- Laboratoire
de Physique et d’Etude des Matériaux, ESPCI, CNRS, 75231 Paris, France
| | | | | | - Iwan Moreels
- Department
of Chemistry, Ghent University, 9000 Ghent, Belgium
| | - Manfred Bayer
- Experimentelle
Physik 2, Technische Universität
Dortmund, 44221 Dortmund, Germany
- Ioffe
Institute, Russian Academy of Sciences, 194 021 St. Petersburg, Russia
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6
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Xiang D, Li Y, Wang L, Ding T, Wang J, Wu K. Electron and Hole Spin Relaxation in CdSe Colloidal Nanoplatelets. J Phys Chem Lett 2021; 12:86-93. [PMID: 33306386 DOI: 10.1021/acs.jpclett.0c03257] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Solution-processed quantum-confined nanocrystals are important building blocks for scalable implementation of quantum information science. Extensive studies on colloidal quantum dots (QDs) have revealed subpicosecond hole spin relaxation, whereas the electron spin dynamics remains difficult to probe. Here we study electron and hole spin dynamics in CdSe colloidal nanoplatelets (also called quantum wells) of varying thicknesses using circularly polarized transient absorption spectroscopy at room temperature. The clear spectroscopic features of transition bands associated with heavy, light, and spin-orbit split-off holes enabled separate probes of electron and hole dynamics. The hole spin-flip occurred within ∼200 fs, arising from strong spin-orbit coupling in the valence band. The electron spin lifetime decreased from 6.2 to 2.2 ps as the platelet thickness is reduced from 6 to 4 monolayers, reflecting an exchange interaction between the electron and the hole and/or surface dangling bond spins enhanced by quantum confinement.
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Affiliation(s)
- Dongmei Xiang
- State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - Yulu Li
- State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - Lifeng Wang
- State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
- University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Tao Ding
- State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - Junhui Wang
- State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
| | - Kaifeng Wu
- State Key Laboratory of Molecular Reaction Dynamics and Dynamics Research Center for Energy and Environmental Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China
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7
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Tolmachev DO, Ivanov VY, Yakovlev DR, Shornikova EV, Witkowski B, Shendre S, Isik F, Delikani S, Demir HV, Bayer M. Optically detected magnetic resonance in CdSe/CdMnS nanoplatelets. NANOSCALE 2020; 12:21932-21939. [PMID: 33112343 DOI: 10.1039/d0nr05633b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Core/shell CdSe/(Cd,Mn)S colloidal nanoplatelets containing magnetic Mn2+ ions are investigated by the optically detected magnetic resonance technique, combining 60 GHz microwave excitation and photoluminescence detection. Resonant heating of the Mn spin system is observed. We identify two mechanisms of optical detection, via variation of either the photoluminescence polarization or its intensity in an external magnetic field. The spin-lattice relaxation dynamics of the Mn spin system is measured and used for evaluation of the Mn concentration. In CdSe/(Cd,Zn,Mn)S nanoplatelets the addition of Zn in the shells significantly broadens the magnetic resonance, evidencing local strain.
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Affiliation(s)
- Danil O Tolmachev
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany.
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8
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Shornikova EV, Yakovlev DR, Tolmachev DO, Ivanov VY, Kalitukha IV, Sapega VF, Kudlacik D, Kusrayev YG, Golovatenko AA, Shendre S, Delikanli S, Demir HV, Bayer M. Magneto-Optics of Excitons Interacting with Magnetic Ions in CdSe/CdMnS Colloidal Nanoplatelets. ACS NANO 2020; 14:9032-9041. [PMID: 32585089 DOI: 10.1021/acsnano.0c04048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Excitons in diluted magnetic semiconductors represent excellent probes for studying the magnetic properties of these materials. Various magneto-optical effects, which depend sensitively on the exchange interaction of the excitons with the localized spins of the magnetic ions can be used for probing. Here, we study core/shell CdSe/(Cd,Mn)S colloidal nanoplatelets hosting diluted magnetic semiconductor layers. The inclusion of the magnetic Mn2+ ions is evidenced by three magneto-optical techniques using high magnetic fields up to 15 T: polarized photoluminescence, optically detected magnetic resonance, and spin-flip Raman scattering. We show that the holes in the excitons play the dominant role in exchange interaction with magnetic ions. We suggest and test an approach for evaluation of the Mn2+ concentration based on the spin-lattice relaxation dynamics of the Mn2+ spin system.
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Affiliation(s)
- Elena V Shornikova
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
| | - Dmitri R Yakovlev
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Danil O Tolmachev
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Vitalii Yu Ivanov
- Institute of Physics, Polish Academy of Sciences, PL-02-668 Warsaw, Poland
| | - Ina V Kalitukha
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Victor F Sapega
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Dennis Kudlacik
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
| | - Yuri G Kusrayev
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | | | - Sushant Shendre
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Materials Sciences, Nanyang Technological University, 639798 Singapore
| | - Savas Delikanli
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Materials Sciences, Nanyang Technological University, 639798 Singapore
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
| | - Hilmi Volkan Demir
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Materials Sciences, Nanyang Technological University, 639798 Singapore
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
| | - Manfred Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
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9
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Ayari S, Quick MT, Owschimikow N, Christodoulou S, Bertrand GHV, Artemyev M, Moreels I, Woggon U, Jaziri S, Achtstein AW. Tuning trion binding energy and oscillator strength in a laterally finite 2D system: CdSe nanoplatelets as a model system for trion properties. NANOSCALE 2020; 12:14448-14458. [PMID: 32618327 DOI: 10.1039/d0nr03170d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We present a theoretical study combined with experimental validations demonstrating that CdSe nanoplatelets are a model system to investigate the tunability of trions and excitons in laterally finite 2D semiconductors. Our results show that the trion binding energy can be tuned from 36 meV to 18 meV with the lateral size and decreasing aspect ratio, while the oscillator strength ratio of trions to excitons decreases. In contrast to conventional quantum dots, the trion oscillator strength in a nanoplatelet at low temperature is smaller than that of the exciton. The trion and exciton Bohr radii become lateral size tunable, e.g. from ∼3.5 to 4.8 nm for the trion. We show that dielectric screening has strong impact on these properties. By theoretical modeling of transition energies, binding energies and oscillator strength of trions and excitons and comparison with experimental findings, we demonstrate that these properties are lateral size and aspect ratio tunable and can be engineered by dielectric confinement, allowing to suppress e.g. detrimental trion emission in devices. Our results strongly impact further in-depth studies, as the demonstrated lateral size tunable trion and exciton manifold is expected to influence properties like gain mechanisms, lasing, quantum efficiency and transport even at room temperature due to the high and tunable trion binding energies.
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Affiliation(s)
- Sabrine Ayari
- Laboratoire de Physique des Materiaux, Faculte des Sciences de Bizerte, Universite de Carthage, Jarzouna 7021, Tunisia
| | - Michael T Quick
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
| | - Nina Owschimikow
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
| | | | | | - Mikhail Artemyev
- Research Institute for Physical Chemical Problems of Belarusian State University, 220006 Minsk, Belarus
| | - Iwan Moreels
- Department of Chemistry, Ghent University, Krijgslaan 281 - S3, 9000 Gent, Belgium
| | - Ulrike Woggon
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
| | - Sihem Jaziri
- Laboratoire de Physique des Materiaux, Faculte des Sciences de Bizerte, Universite de Carthage, Jarzouna 7021, Tunisia and Laboratoire de Physique de la Matiere Condensee, Departement de Physique, Faculte des Sciences de Tunis, Campus Universitaire, 1060 Tunis, Tunisia
| | - Alexander W Achtstein
- Institute of Optics and Atomic Physics, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
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10
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Feng D, Yakovlev DR, Dubertret B, Bayer M. Charge Separation Dynamics in CdSe/CdS Core/Shell Nanoplatelets Addressed by Coherent Electron Spin Precession. ACS NANO 2020; 14:7237-7244. [PMID: 32453553 DOI: 10.1021/acsnano.0c02402] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We investigate the charge separation dynamics provided by carrier surface trapping in CdSe/CdS core/shell nanoplatelets by means of a three-laser-beam pump-orientation-probe technique, detecting the electron spin coherence at room temperature. Signals with two Larmor precession frequencies are found, which strongly differ in their dynamical characteristics and dependencies on pump power and shell thickness. The electron trapping process occurs on a time scale of about 10 ns, and the charge separation induced thereby has a long lifetime of up to hundreds of microseconds. On the other hand, the hole trapping requires times from subpicoseconds to hundreds of picoseconds, and the induced charge separation has a lifetime of a few nanoseconds. With increasing CdS shell thickness the hole trapping vanishes, while the electron trapping is still detectable. These findings have important implications for understanding the photophysical processes of nanoplatelets and other colloidal nanostructures.
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Affiliation(s)
- Donghai Feng
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
| | - Dmitri R Yakovlev
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Benoit Dubertret
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI, CNRS, 75231 Paris, France
| | - Manfred Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
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11
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Shornikova EV, Golovatenko AA, Yakovlev DR, Rodina AV, Biadala L, Qiang G, Kuntzmann A, Nasilowski M, Dubertret B, Polovitsyn A, Moreels I, Bayer M. Surface spin magnetism controls the polarized exciton emission from CdSe nanoplatelets. NATURE NANOTECHNOLOGY 2020; 15:277-282. [PMID: 31988504 DOI: 10.1038/s41565-019-0631-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 12/18/2019] [Indexed: 06/10/2023]
Abstract
The surface of nominally diamagnetic colloidal CdSe nanoplatelets can demonstrate paramagnetic behaviour owing to the uncompensated spins of dangling bonds, as we reveal here by optical spectroscopy in high magnetic fields up to 15 T using the exciton spin as a probe of the surface magnetism. The strongly nonlinear magnetic field dependence of the circular polarization of the exciton emission is determined by the magnetization of the dangling-bond spins (DBSs), the exciton spin polarization as well as the spin-dependent recombination of dark excitons. The sign of the exciton-DBS exchange interaction depends on the nanoplatelet growth conditions.
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Affiliation(s)
- Elena V Shornikova
- Experimentelle Physik 2, Technische Universität Dortmund, Dortmund, Germany.
| | | | - Dmitri R Yakovlev
- Experimentelle Physik 2, Technische Universität Dortmund, Dortmund, Germany.
- Ioffe Institute, Russian Academy of Sciences, St. Petersburg, Russia.
| | - Anna V Rodina
- Ioffe Institute, Russian Academy of Sciences, St. Petersburg, Russia.
| | - Louis Biadala
- Institut d'Electronique, de Microélectronique et de Nanotechnologie, CNRS, Villeneuve-d'Ascq, France
| | - Gang Qiang
- Experimentelle Physik 2, Technische Universität Dortmund, Dortmund, Germany
| | - Alexis Kuntzmann
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI, CNRS, Paris, France
| | - Michel Nasilowski
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI, CNRS, Paris, France
| | - Benoit Dubertret
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI, CNRS, Paris, France
| | - Anatolii Polovitsyn
- Department of Chemistry, Ghent University, Ghent, Belgium
- Istituto Italiano di Tecnologia, Genova, Italy
| | - Iwan Moreels
- Department of Chemistry, Ghent University, Ghent, Belgium
- Istituto Italiano di Tecnologia, Genova, Italy
| | - Manfred Bayer
- Experimentelle Physik 2, Technische Universität Dortmund, Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, St. Petersburg, Russia
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Shornikova EV, Yakovlev DR, Biadala L, Crooker SA, Belykh VV, Kochiev MV, Kuntzmann A, Nasilowski M, Dubertret B, Bayer M. Negatively Charged Excitons in CdSe Nanoplatelets. NANO LETTERS 2020; 20:1370-1377. [PMID: 31960677 DOI: 10.1021/acs.nanolett.9b04907] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The low-temperature emission spectrum of CdSe colloidal nanoplatelets (NPLs) consists of two narrow lines. The high-energy line stems from the recombination of neutral excitons. The origin of the low-energy line is currently debated. We experimentally study the spectral shift, emission dynamics, and spin polarization of both lines at low temperatures down to 1.5 K and in high magnetic fields up to 60 T and show that the low-energy line originates from the recombination of negatively charged excitons (trions). This assignment is confirmed by the NPL photocharging dynamics and associated variations in the spectrum. We show that the negatively charged excitons are considerably less sensitive to the presence of surface spins than the neutral excitons. The trion binding energy in three-monolayer-thick NPLs is as large as 30 meV, which is 4 times larger than its value in the two-dimensional limit of a conventional CdSe quantum well confined between semiconductor barriers. A considerable part of this enhancement is gained by the dielectric enhancement effect, which is due to the small dielectric constant of the environment surrounding the NPLs.
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Affiliation(s)
- Elena V Shornikova
- Experimentelle Physik 2 , Technische Universität Dortmund , 44221 Dortmund , Germany
| | - Dmitri R Yakovlev
- Experimentelle Physik 2 , Technische Universität Dortmund , 44221 Dortmund , Germany
- Ioffe Institute, Russian Academy of Sciences , 194021 St. Petersburg , Russia
| | - Louis Biadala
- Institut d'Electronique, de Microélectronique et de Nanotechnologie, CNRS , 59652 Villeneuve-d'Ascq , France
| | - Scott A Crooker
- National High Magnetic Field Laboratory , Los Alamos National Laboratory , Los Alamos , 87545 New Mexico , United States
| | - Vasilii V Belykh
- P. N. Lebedev Physical Institute, Russian Academy of Sciences , 119991 Moscow , Russia
| | - Mikhail V Kochiev
- P. N. Lebedev Physical Institute, Russian Academy of Sciences , 119991 Moscow , Russia
| | - Alexis Kuntzmann
- Laboratoire de Physique et d'Etude des Matériaux , ESPCI, CNRS , 75231 Paris , France
| | - Michel Nasilowski
- Laboratoire de Physique et d'Etude des Matériaux , ESPCI, CNRS , 75231 Paris , France
| | - Benoit Dubertret
- Laboratoire de Physique et d'Etude des Matériaux , ESPCI, CNRS , 75231 Paris , France
| | - Manfred Bayer
- Experimentelle Physik 2 , Technische Universität Dortmund , 44221 Dortmund , Germany
- Ioffe Institute, Russian Academy of Sciences , 194021 St. Petersburg , Russia
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