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Kumar P, Huang SH, Hsu CY, Chung SY, Cha HC, Chuang CM, Chen KL, Huang YC. Enhancing Power Conversion Efficiency of Organic Solar Cells with Magnetoplasmonic Fe 3O 4@Au@m-ABS Nanoparticles. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:1175. [PMID: 39057852 PMCID: PMC11279951 DOI: 10.3390/nano14141175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2024] [Revised: 07/04/2024] [Accepted: 07/08/2024] [Indexed: 07/28/2024]
Abstract
Organic-inorganic nanocomposites have the potential to be used in photovoltaic materials due to their eco-friendliness, suitable band gaps, and high stability. In this work, we integrated gold and Fe3O4 magnetic nanoparticles with poly-m-amino benzene sulfonic (m-ABS) to synthesize Fe3O4@Au@poly-(m-aminobenzenesulfonic acid) (Fe3O4@Au@m-ABS) magneto-plasmonic nanoparticles (MPNPs) to enhance the performance of the organic photovoltaic (OPV). These MPNPs exhibit broad UV-Vis absorption and a low band gap of 2.878 eV, enhancing their suitability for photovoltaic applications. The MPNPs were introduced into the ZnO electron transporting layer (ETL) and active layer to investigate the influence of MPNPs on the power conversion efficiency (PCE) of the OPVs. When 0.1 vol% MPNPs were incorporated in the ETL, the OPVs achieved a PCE of 14.24% and a fill factor (FF) of 69.10%. On the other hand, when 0.1 vol% MPNPs were incorporated in the active layer, the OPVs showed a PCE of 14.11% and an FF of 68.83%. However, the OPVs without MPNPs only possessed a PCE of 13.15% and an FF of 63.69%. The incorporation of MPNPs increased the PCE by 8.3% in the OPV device. These findings suggest that Fe3O4@Au@m-ABS MPNPs are promising nanocomposite materials for enhancing the performance of OPVs.
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Affiliation(s)
- Pradeep Kumar
- Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 243303, Taiwan; (P.K.); (S.-Y.C.); (H.-C.C.)
| | - Shih-Han Huang
- Organic Electronics Research Center, Ming Chi University of Technology, New Taipei City 24301, Taiwan;
- Center for Sustainability and Energy Technologies, Chang Gung University, Taoyuan 33302, Taiwan
| | - Chia-Yi Hsu
- Institute of Nanoscience, National Chung Hsing University, Taichung 40227, Taiwan;
| | - Ssu-Yung Chung
- Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 243303, Taiwan; (P.K.); (S.-Y.C.); (H.-C.C.)
| | - Hou-Chin Cha
- Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 243303, Taiwan; (P.K.); (S.-Y.C.); (H.-C.C.)
- Organic Electronics Research Center, Ming Chi University of Technology, New Taipei City 24301, Taiwan;
| | - Chih-Min Chuang
- Department of Physics, National Atomic Research Institute, Taoyuan 325207, Taiwan;
| | - Kuen-Lin Chen
- Institute of Nanoscience, National Chung Hsing University, Taichung 40227, Taiwan;
- Department of Physics, National Chung Hsing University, Taichung 40227, Taiwan
| | - Yu-Ching Huang
- Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 243303, Taiwan; (P.K.); (S.-Y.C.); (H.-C.C.)
- Organic Electronics Research Center, Ming Chi University of Technology, New Taipei City 24301, Taiwan;
- Center for Sustainability and Energy Technologies, Chang Gung University, Taoyuan 33302, Taiwan
- Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan 33302, Taiwan
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2
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Freire-Fernández F, Sinai NG, Hui Tan MJ, Park SM, Koessler ER, Krauss T, Huo P, Odom TW. Room-Temperature Polariton Lasing from CdSe Core-Only Nanoplatelets. ACS NANO 2024; 18:15177-15184. [PMID: 38808728 DOI: 10.1021/acsnano.4c03164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
This paper reports how CdSe core-only nanoplatelets (NPLs) coupled with plasmonic Al nanoparticle lattices can exhibit exciton-polariton lasing. By improving a procedure to synthesize monodisperse 4-monolayer CdSe NPLs, we could resolve polariton decay dynamics and pathways. Experiment and theory confirmed that the system is in the strong coupling regime based on anticrossings in the dispersion diagrams and magnitude of the Rabi-splitting values. Notably, polariton lasing is observed only for cavity lattice periodicities that exhibit specific dispersive characteristics that enable polariton accumulation. The threshold of polariton lasing is 25-fold lower than the reported photon lasing values from CdSe NPLs in similar cavity designs. This open-cavity platform offers a simple approach to control exciton polaritons anticipated to benefit quantum information processing, optoelectronics, and chemical reactions.
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Affiliation(s)
| | - Nathan G Sinai
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Max Jin Hui Tan
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Sang-Min Park
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Eric Rodolfo Koessler
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Todd Krauss
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
- Institute of Optics, University of Rochester, Rochester, New York 14627, United States
| | - Pengfei Huo
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
- Institute of Optics, University of Rochester, Rochester, New York 14627, United States
| | - Teri W Odom
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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3
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Watkins NE, Diroll BT, Williams KR, Liu Y, Greene CL, Wasielewski MR, Schaller RD. Amplified Spontaneous Emission from Electron-Hole Quantum Droplets in Colloidal CdSe Nanoplatelets. ACS NANO 2024; 18:9605-9612. [PMID: 38497777 DOI: 10.1021/acsnano.3c13170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
Two-dimensional cadmium selenide nanoplatelets (NPLs) exhibit large absorption cross sections and homogeneously broadened band-edge transitions that offer utility in wide-ranging optoelectronic applications. Here, we examine the temperature-dependence of amplified spontaneous emission (ASE) in 4- and 5-monolayer thick NPLs and show that the threshold for close-packed (neat) films decreases with decreasing temperature by a factor of 2-10 relative to ambient temperature owing to extrinsic (trapping) and intrinsic (phonon-derived line width) factors. Interestingly, for pump intensities that exceed the ASE threshold, we find development of intense emission to lower energy in particular provided that the film temperature is ≤200 K. For NPLs diluted in an inert polymer, both biexcitonic ASE and low-energy emission are suppressed, suggesting that described neat-film observables rely upon high chromophore density and rapid, collective processes. Transient emission spectra reveal ultrafast red-shifting with the time of the lower energy emission. Taken together, these findings indicate a previously unreported process of amplified stimulated emission from polyexciton states that is consistent with quantum droplets and constitutes a form of exciton condensate. For studied samples, quantum droplets form provided that roughly 17 meV or less of thermal energy is available, which we hypothesize relates to polyexciton binding energy. Polyexciton ASE can produce pump-fluence-tunable red-shifted ASE even 120 meV lower in energy than biexciton ASE. Our findings convey the importance of biexciton and polyexciton populations in nanoplatelets and show that quantum droplets can exhibit light amplification at significantly lower photon energies than biexcitonic ASE.
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Affiliation(s)
- Nicolas E Watkins
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Benjamin T Diroll
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Kali R Williams
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Yuzi Liu
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Chelsie L Greene
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Michael R Wasielewski
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- International Institute for Nanotechnology, Paula Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208, United States
| | - Richard D Schaller
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, United States
- International Institute for Nanotechnology, Paula Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208, United States
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4
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Raja A, Brus LE. Non-local dielectric effects in nanoscience. J Chem Phys 2023; 159:020901. [PMID: 37449580 DOI: 10.1063/5.0150293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 06/19/2023] [Indexed: 07/18/2023] Open
Abstract
The physical properties of charges and excitations in nanoscale materials are influenced both by the dielectric properties of the material itself and the surrounding environment. This non-local dielectric effect was first discussed in the context of molecules in solvents over a century ago. In this perspective, we discuss non-local dielectric effects in zero-dimensional, one-dimensional, and two-dimensional nanoscale systems.
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Affiliation(s)
- Archana Raja
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Louis E Brus
- Department of Chemistry, Columbia University, New York, New York 10027, USA
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5
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Abstract
Lasers and optical amplifiers based on solution-processable materials have been long-desired devices for their compatibility with virtually any substrate, scalability, and ease of integration with on-chip photonics and electronics. These devices have been pursued across a wide range of materials including polymers, small molecules, perovskites, and chemically prepared colloidal semiconductor nanocrystals, also commonly referred to as colloidal quantum dots. The latter materials are especially attractive for implementing optical-gain media as in addition to being compatible with inexpensive and easily scalable chemical techniques, they offer multiple advantages derived from a zero-dimensional character of their electronic states. These include a size-tunable emission wavelength, low optical gain thresholds, and weak sensitivity of lasing characteristics to variations in temperature. Here we review the status of colloidal nanocrystal lasing devices, most recent advances in this field, outstanding challenges, and the ongoing progress toward technological viable devices including colloidal quantum dot laser diodes.
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Affiliation(s)
- Namyoung Ahn
- Nanotechnology and Advanced Spectroscopy Team, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Clément Livache
- Nanotechnology and Advanced Spectroscopy Team, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Valerio Pinchetti
- Nanotechnology and Advanced Spectroscopy Team, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Victor I Klimov
- Nanotechnology and Advanced Spectroscopy Team, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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6
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Martin PI, Panuganti S, Portner JC, Watkins NE, Kanatzidis MG, Talapin DV, Schaller RD. Excitonic Spin-Coherence Lifetimes in CdSe Nanoplatelets Increase Significantly with Core/Shell Morphology. NANO LETTERS 2023; 23:1467-1473. [PMID: 36753635 DOI: 10.1021/acs.nanolett.2c04845] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
We report spin-polarized transient absorption for colloidal CdSe nanoplatelets as functions of thickness (2-6 monolayer thickness) and core/shell motif. Using electro-optical modulation of co- and cross-polarization pump-probe combinations, we sensitively observe spin-polarized transitions. Core-only nanoplatelets exhibit few-picosecond spin lifetimes that weakly increase with layer thickness. The spectral content of differenced spin-polarized signals indicate biexciton binding energies that decrease with increasing thickness and smaller values than previously reported. Shell growth of CdS with controlled thicknesses, which partially delocalize the electron from the hole, significantly increases the spin lifetime to ∼49 ps at room temperature. Implementation of ZnS shells, which do not alter delocalization but do alter surface termination, increased spin lifetimes up to ∼100 ps, bolstering the interpretation that surface termination heavily influences spin coherence, likely due to passivation of dangling bonds. Spin precession in magnetic fields both confirms long coherence lifetime at room temperature and yields the excitonic g factor.
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Affiliation(s)
- Phillip I Martin
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Shobhana Panuganti
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Joshua C Portner
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Nicolas E Watkins
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Mercouri G Kanatzidis
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Dmitri V Talapin
- Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Richard D Schaller
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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7
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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: 27] [Impact Index Per Article: 27.0] [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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8
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Rodà C, Geiregat P, Di Giacomo A, Moreels I, Hens Z. Area-Independence of the Biexciton Oscillator Strength in CdSe Colloidal Nanoplatelets. NANO LETTERS 2022; 22:9537-9543. [PMID: 36409988 DOI: 10.1021/acs.nanolett.2c03683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Colloidal CdSe nanoplatelets (NPLs) are unique systems to study two-dimensional excitons and excitonic complexes. However, while absorption and emission of photons through exciton formation and recombination have been extensively quantified, few studies have addressed the exciton-biexciton transition. Here, we use cross-polarized pump-probe spectroscopy to measure the absorption coefficient spectrum of this transition and determine the biexciton oscillator strength (fBX). We show that fBX is independent of the NPL area and that the concomitant biexciton area (SBX) agrees with predictions of a short-range interaction model. Moreover, we show that fBX is comparable to the oscillator strength of forming localized excitons at room temperature while being unaffected itself by center-of-mass localization. These results confirm the relevance of biexcitons for light-matter interaction in NPLs. Moreover, the quantification of the exciton-biexciton transition introduced here will enable researchers to rank 2D materials by the strength of this transition and to compare experimental results with theoretical predictions.
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Affiliation(s)
- Carmelita Rodà
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
| | - Pieter Geiregat
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
| | - Alessio Di Giacomo
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
| | - Iwan Moreels
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
| | - Zeger Hens
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, 9000Gent, Belgium
- NB-Photonics, Center for Nano- and Biophotonics, Ghent University, 9000Gent, Belgium
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9
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Kumar P, Kumar U, Huang YC, Tsai PY, Liu CH, Wu CH, Huang WM, Chen KL. Photocatalytic activity of a hydrothermally synthesized γ-Fe2O3@Au/MoS2 heterostructure for organic dye degradation under green light. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.114186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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10
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Nguyen KA, Pachter R, Day PN. Theoretical Investigation of the Electronic Spectra of Cadmium Chalcogenide 2D Nanoplatelets. J Phys Chem A 2022; 126:8818-8825. [DOI: 10.1021/acs.jpca.2c05253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Kiet A. Nguyen
- Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio45433, United States
- UES, Inc., Dayton, Ohio45432, United States
| | - Ruth Pachter
- Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio45433, United States
| | - Paul N. Day
- Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio45433, United States
- UES, Inc., Dayton, Ohio45432, United States
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11
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Wang S, Dyksik M, Lampe C, Gramlich M, Maude DK, Baranowski M, Urban AS, Plochocka P, Surrente A. Thickness-Dependent Dark-Bright Exciton Splitting and Phonon Bottleneck in CsPbBr 3-Based Nanoplatelets Revealed via Magneto-Optical Spectroscopy. NANO LETTERS 2022; 22:7011-7019. [PMID: 36036573 PMCID: PMC9479212 DOI: 10.1021/acs.nanolett.2c01826] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The optimized exploitation of perovskite nanocrystals and nanoplatelets as highly efficient light sources requires a detailed understanding of the energy spacing within the exciton manifold. Dark exciton states are particularly relevant because they represent a channel that reduces radiative efficiency. Here, we apply large in-plane magnetic fields to brighten optically inactive states of CsPbBr3-based nanoplatelets for the first time. This approach allows us to access the dark states and directly determine the dark-bright splitting, which reaches 22 meV for the thinnest nanoplatelets. The splitting is significantly less for thicker nanoplatelets due to reduced exciton confinement. Additionally, the form of the magneto-PL spectrum suggests that dark and bright state populations are nonthermalized, which is indicative of a phonon bottleneck in the exciton relaxation process.
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Affiliation(s)
- Shuli Wang
- Laboratoire
National des Champs Magnétiques Intenses, EMFL, CNRS UPR 3228,
Université Grenoble Alpes, Université
Toulouse, Université Toulouse 3, INSA-T, 38042 Grenoble
and 31400 Toulouse, France
| | - Mateusz Dyksik
- Department
of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland
| | - Carola Lampe
- Nanospectroscopy
Group and Center for Nanoscience (CeNS), Nano-Institute Munich, Department
of Physics, Ludwig-Maximilians-Universität
München (LMU), Munich 80539 Germany
| | - Moritz Gramlich
- Nanospectroscopy
Group and Center for Nanoscience (CeNS), Nano-Institute Munich, Department
of Physics, Ludwig-Maximilians-Universität
München (LMU), Munich 80539 Germany
| | - Duncan K. Maude
- Laboratoire
National des Champs Magnétiques Intenses, EMFL, CNRS UPR 3228,
Université Grenoble Alpes, Université
Toulouse, Université Toulouse 3, INSA-T, 38042 Grenoble
and 31400 Toulouse, France
| | - Michał Baranowski
- Department
of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland
| | - Alexander S. Urban
- Nanospectroscopy
Group and Center for Nanoscience (CeNS), Nano-Institute Munich, Department
of Physics, Ludwig-Maximilians-Universität
München (LMU), Munich 80539 Germany
| | - Paulina Plochocka
- Laboratoire
National des Champs Magnétiques Intenses, EMFL, CNRS UPR 3228,
Université Grenoble Alpes, Université
Toulouse, Université Toulouse 3, INSA-T, 38042 Grenoble
and 31400 Toulouse, France
- Department
of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland
| | - Alessandro Surrente
- Department
of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, 50-370 Wroclaw, Poland
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12
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Gramlich M, Swift MW, Lampe C, Lyons JL, Döblinger M, Efros AL, Sercel PC, Urban AS. Dark and Bright Excitons in Halide Perovskite Nanoplatelets. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2103013. [PMID: 34939751 PMCID: PMC8844578 DOI: 10.1002/advs.202103013] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 10/13/2021] [Indexed: 05/22/2023]
Abstract
Semiconductor nanoplatelets (NPLs), with their large exciton binding energy, narrow photoluminescence (PL), and absence of dielectric screening for photons emitted normal to the NPL surface, could be expected to become the fastest luminophores amongst all colloidal nanostructures. However, super-fast emission is suppressed by a dark (optically passive) exciton ground state, substantially split from a higher-lying bright (optically active) state. Here, the exciton fine structure in 2-8 monolayer (ML) thick Csn - 1 Pbn Br3n + 1 NPLs is revealed by merging temperature-resolved PL spectra and time-resolved PL decay with an effective mass model taking quantum confinement and dielectric confinement anisotropy into account. This approach exposes a thickness-dependent bright-dark exciton splitting reaching 32.3 meV for the 2 ML NPLs. The model also reveals a 5-16 meV splitting of the bright exciton states with transition dipoles polarized parallel and perpendicular to the NPL surfaces, the order of which is reversed for the thinnest NPLs, as confirmed by TR-PL measurements. Accordingly, the individual bright states must be taken into account, while the dark exciton state strongly affects the optical properties of the thinnest NPLs even at room temperature. Significantly, the derived model can be generalized for any isotropically or anisotropically confined nanostructure.
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Affiliation(s)
- Moritz Gramlich
- Nanospectroscopy GroupNano‐Institute MunichDepartment of PhysicsLudwig‐Maximilians‐Universität München (LMU)Munich80539Germany
| | - Michael W. Swift
- Center for Computational Materials ScienceU.S. Naval Research LaboratoryWashington D.C.20375USA
| | - Carola Lampe
- Nanospectroscopy GroupNano‐Institute MunichDepartment of PhysicsLudwig‐Maximilians‐Universität München (LMU)Munich80539Germany
| | - John L. Lyons
- Center for Computational Materials ScienceU.S. Naval Research LaboratoryWashington D.C.20375USA
| | - Markus Döblinger
- Department of ChemistryLudwig‐Maximilians‐Universität München (LMU) & Center for NanoScience (CeNS)Munich81377Germany
| | - Alexander L. Efros
- Center for Computational Materials ScienceU.S. Naval Research LaboratoryWashington D.C.20375USA
| | - Peter C. Sercel
- Center for Hybrid Organic Inorganic Semiconductors for EnergyGoldenCO80401USA
| | - Alexander S. Urban
- Nanospectroscopy GroupNano‐Institute MunichDepartment of PhysicsLudwig‐Maximilians‐Universität München (LMU)Munich80539Germany
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13
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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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14
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Rodà C, Salzmann BBV, Wagner I, Ussembayev Y, Chen K, Hodgkiss JM, Neyts K, Moreels I, Vanmaekelbergh D, Geiregat P. Stimulated Emission through an Electron-Hole Plasma in Colloidal CdSe Quantum Rings. NANO LETTERS 2021; 21:10062-10069. [PMID: 34842440 PMCID: PMC9113625 DOI: 10.1021/acs.nanolett.1c03501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Colloidal CdSe quantum rings (QRs) are a recently developed class of nanomaterials with a unique topology. In nanocrystals with more common shapes, such as dots and platelets, the photophysics is consistently dominated by strongly bound electron-hole pairs, so-called excitons, regardless of the charge carrier density. Here, we show that charge carriers in QRs condense into a hot uncorrelated plasma state at high density. Through strong band gap renormalization, this plasma state is able to produce broadband and sizable optical gain. The gain is limited by a second-order, yet radiative, recombination process, and the buildup is counteracted by a charge-cooling bottleneck. Our results show that weakly confined QRs offer a unique system to study uncorrelated electron-hole dynamics in nanoscale materials.
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Affiliation(s)
- Carmelita Rodà
- Physics
and Chemistry of Nanostructures, Department of Chemistry, Center for Nano and
Biophotonics, Liquid Crystals and Photonics Research Group, Department of Information
Technology, and Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, B-9000 Gent, Belgium
| | - Bastiaan B. V. Salzmann
- Debye
Institute for Nanomaterials Science, Utrecht
University, 3508 TA Utrecht, The Netherlands
| | - Isabella Wagner
- School of Chemical and Physical Sciences, Robinson Research Institute,
and MacDiarmid Institute
for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Yera Ussembayev
- Physics
and Chemistry of Nanostructures, Department of Chemistry, Center for Nano and
Biophotonics, Liquid Crystals and Photonics Research Group, Department of Information
Technology, and Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, B-9000 Gent, Belgium
| | - Kai Chen
- School of Chemical and Physical Sciences, Robinson Research Institute,
and MacDiarmid Institute
for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6012, New Zealand
- The
Dodd-Walls Centre for Photonic and Quantum Technologies, University of Otago, Dunedin 9010, New Zealand
| | - Justin M. Hodgkiss
- School of Chemical and Physical Sciences, Robinson Research Institute,
and MacDiarmid Institute
for Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Kristiaan Neyts
- Physics
and Chemistry of Nanostructures, Department of Chemistry, Center for Nano and
Biophotonics, Liquid Crystals and Photonics Research Group, Department of Information
Technology, and Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, B-9000 Gent, Belgium
| | - Iwan Moreels
- Physics
and Chemistry of Nanostructures, Department of Chemistry, Center for Nano and
Biophotonics, Liquid Crystals and Photonics Research Group, Department of Information
Technology, and Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, B-9000 Gent, Belgium
| | - Daniel Vanmaekelbergh
- Debye
Institute for Nanomaterials Science, Utrecht
University, 3508 TA Utrecht, The Netherlands
| | - Pieter Geiregat
- Physics
and Chemistry of Nanostructures, Department of Chemistry, Center for Nano and
Biophotonics, Liquid Crystals and Photonics Research Group, Department of Information
Technology, and Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, B-9000 Gent, Belgium
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15
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Zhang Z, Thung YT, Wang L, Chen X, Ding L, Fan W, Sun H. Surface Depletion Effects in Bromide-Ligated Colloidal Cadmium Selenide Nanoplatelets: Toward Efficient Emission at High Temperature. J Phys Chem Lett 2021; 12:9086-9093. [PMID: 34519516 DOI: 10.1021/acs.jpclett.1c02623] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The colloidal semiconductor nanoplatelet (NPL) with broad ligand-semiconductor interface is an ideal system for surface science investigation, but the study regarding depletion effects in NPLs remains lacking. Herein we explore such effects in colloidal CdSe NPLs through Br ligation. Apart from improved brightness and red-shifted optical features, we also experimentally observed abnormal negative thermal quenching phenomena in bromide-ligated CdSe NPLs over 200 K under a cryogenic environment and up to 383 K under an ambient environment, which was absent in pristine NPLs. We speculate that the surface depletion effect shall account for these anomalous phenomena due to the susceptibility of the surface depletion region on photoexcited carrier concentration and surface condition. The existence of the depletion layer in NPLs is also validated quantitatively with k·p simulation. Besides offering an alternative explanation on the red-shifted optical properties of CdSe NPLs by Br-ligation, our findings pave the new route toward solution-processed NPLs-based optoelectronics with boosted thermal resistance.
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Affiliation(s)
- Zitong Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Yi Tian Thung
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Lin Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai 200072, China
| | - Xiaoxuan Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Lu Ding
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Singapore 138634, Singapore
| | - Weijun Fan
- School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Handong Sun
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
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16
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Zhang Y, Zhang H, Chen D, Sun CJ, Ren Y, Jiang J, Wang L, Li Z, Peng X. Engineering of Exciton Spatial Distribution in CdS Nanoplatelets. NANO LETTERS 2021; 21:5201-5208. [PMID: 34114464 DOI: 10.1021/acs.nanolett.1c01278] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Zinc-blende CdS nanoplatelets with atomically flat and very large {100} basal planes terminated solely by one type of element (either Cd or S atoms) are synthesized. Optical spectroscopy, X-ray diffraction, X-ray absorption, and transmission electron microscopy confirm that the surface structures of newly developed S-terminated CdS nanoplatelets are at least as well-defined as the original Cd-terminated nanoplatelets. Band gaps of the nanoplatelets are found to depend on not only the quantum-confined dimension (thickness) but also the nature of the surface termination. The facet structure dictates the packing of the ligands (carboxylate for Cd-terminated nanoplatelets and alkyl for S-terminated nanoplatelets), which causes a difference in the lattice strain and significantly affects the optical spectral width. Experimental and theoretical results reveal that engineering the exciton spatial distribution by the tailored synthesis of semiconductor nanocrystals with a precisely controlled surface structure is fully possible, which should open a new door for delivering the long-promised potential of semiconductor nanocrystals.
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Affiliation(s)
- Yan Zhang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Haibing Zhang
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Dongdong Chen
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Cheng-Jun Sun
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Yang Ren
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Jianhui Jiang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Linjun Wang
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Zheng Li
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
| | - Xiaogang Peng
- Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
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17
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Sui X, Gao X, Wu X, Li C, Yang X, Du W, Ding Z, Jin S, Wu K, Sum TC, Gao P, Liu J, Wei X, Zhang J, Zhang Q, Tang Z, Liu X. Zone-Folded Longitudinal Acoustic Phonons Driving Self-Trapped State Emission in Colloidal CdSe Nanoplatelet Superlattices. NANO LETTERS 2021; 21:4137-4144. [PMID: 33913710 DOI: 10.1021/acs.nanolett.0c04169] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Colloidal CdSe nanoplatelets (NPLs) have substantial potential in light-emitting applications because of their quantum-well-like characteristics. The self-trapped state (STS), originating from strong electron-phonon coupling (EPC), is promising in white light luminance because of its broadband emission. However, achieving STS in CdSe NPLs is extremely challenging because of their intrinsic weak EPC nature. Herein, we developed a strong STS emission in the spectral range of 450-600 nm by building superlattice (SL) structures with colloidal CdSe NPLs. We demonstrated that STS is generated via strong coupling of excitons and zone-folded longitudinal acoustic phonons with formation time of ∼450 fs and localization length of ∼0.56 nm. The Huang-Rhys factor, describing the EPC strength in SL structure, is estimated to be ∼19.9, which is much larger than that (∼0.1) of monodispersed CdSe NPLs. Our results provide an in-depth understanding of STS and a platform for generating and manipulating STS by designing SL structures.
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Affiliation(s)
- Xinyu Sui
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P.R. China
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Xiaoqing Gao
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, People's Republic of China
| | - Xianxin Wu
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P.R. China
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
| | - Chun Li
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P.R. China
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
- Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, P.R. China
| | - Xuekang Yang
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P.R. China
| | - Wenna Du
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P.R. China
- Key Laboratory of Semiconductor Materials Science, Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
| | - Zhengping Ding
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Shengye Jin
- State Key Laboratory of Molecular Reaction Dynamics and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Kaifeng Wu
- State Key Laboratory of Molecular Reaction Dynamics and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Tze Chien Sum
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Peng Gao
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Junjie Liu
- State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, P.R. China
- Beijing Innovation Center for Engineering Science and Advanced Technology, Peking University, Beijing 100871, P.R. China
| | - Xiaoding Wei
- State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, P.R. China
- Beijing Innovation Center for Engineering Science and Advanced Technology, Peking University, Beijing 100871, P.R. China
| | - Jun Zhang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, and Center of Materials Science and Optoelectronics Engineering, Chinese Academy of Sciences, Beijing 100083, China
| | - Qing Zhang
- Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, P.R. China
| | - Zhiyong Tang
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
- Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325000, People's Republic of China
| | - Xinfeng Liu
- CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, P.R. China
- University of Chinese Academy of Sciences, Beijing 100049, P.R. China
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18
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Greenwood AR, Mazzotti S, Norris DJ, Galli G. Determining the Structure-Property Relationships of Quasi-Two-Dimensional Semiconductor Nanoplatelets. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:4820-4827. [PMID: 38230251 PMCID: PMC10788900 DOI: 10.1021/acs.jpcc.0c10559] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/18/2024]
Abstract
We report a theoretical study of CdSe nanoplatelets aimed at identifying the main factors determining their photophysical properties. Using atomic configurations optimized with density functional theory calculations, we computed quasiparticle and exciton binding energies of nanoplatelets with two to seven monolayers. We employed many body perturbation theory at the GW level and solved the Bethe-Salpeter equation to obtain absorption spectra and excitonic properties. Our results, which agree well with recent experiments, were then used to design a model that allows us to disentangle the effects of quantum confinement, strain induced by passivating ligands, and dielectric environment on the electronic properties of nanoplatelets. We found that, for the model to accurately reproduce our first principle results, it is critical to account for surface stress and consider a finite potential barrier and energy-dependent effective masses when describing quantum confinement. Our findings call into question previous assumptions on the validity of an infinite barrier to describe carrier confinement in nanoplatelets, suggesting that it may be possible to optimize interfacial charge transfer and extraction by appropriately choosing passivating ligands. The model developed here is generalizable to core-shell platelets and enables the description of system sizes not yet directly treatable by first-principles calculations.
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Affiliation(s)
- Arin R. Greenwood
- Pritzker
School of Molecular Engineering, University
of Chicago, Chicago, Illinois 60637, United States
| | - Sergio Mazzotti
- Optical
Materials Engineering Laboratory, Department of Mechanical and Process
Engineering, ETH Zurich, Zurich 8092, Switzerland
| | - David J. Norris
- Optical
Materials Engineering Laboratory, Department of Mechanical and Process
Engineering, ETH Zurich, Zurich 8092, Switzerland
| | - Giulia Galli
- Pritzker
School of Molecular Engineering, University
of Chicago, Chicago, Illinois 60637, United States
- Department
of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
- Argonne
National Laboratory, Argonne, Illinois 60439, United States
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19
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Peric N, Lambert Y, Singh S, Khan AH, Franchina Vergel NA, Deresmes D, Berthe M, Hens Z, Moreels I, Delerue C, Grandidier B, Biadala L. Van Hove Singularities and Trap States in Two-Dimensional CdSe Nanoplatelets. NANO LETTERS 2021; 21:1702-1708. [PMID: 33544602 DOI: 10.1021/acs.nanolett.0c04509] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Semiconductor nanoplatelets, which offer a compelling combination of the flatness of two-dimensional semiconductors and the inherent richness brought about by colloidal nanostructure synthesis, form an ideal and general testbed to investigate fundamental physical effects related to the dimensionality of semiconductors. With low temperature scanning tunnelling spectroscopy and tight binding calculations, we investigate the conduction band density of states of individual CdSe nanoplatelets. We find an occurrence of peaks instead of the typical steplike function associated with a quantum well, that rule out a free in-plane electron motion, in agreement with the theoretical density of states. This finding, along with the detection of deep trap states located on the edge facets, which also restrict the electron motion, provides a detailed picture of the actual lateral confinement in quantum wells with finite length and width.
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Affiliation(s)
- Nemanja Peric
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Yannick Lambert
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Shalini Singh
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Ghent, Belgium
| | - Ali Hossain Khan
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Ghent, Belgium
| | - Nathali Alexandra Franchina Vergel
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Dominique Deresmes
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Maxime Berthe
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Zeger Hens
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Ghent, Belgium
| | - Iwan Moreels
- Physics and Chemistry of Nanostructures, Ghent University, 9000 Ghent, Belgium
| | - Christophe Delerue
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Bruno Grandidier
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
| | - Louis Biadala
- Université de Lille, CNRS, Centrale Lille, Université Polytechnique Hauts-de-France, Junia-ISEN, Centrale Lille, UMR 8520 - IEMN, F-59000 Lille, France
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20
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Zhang Z, Thung YT, Chen X, Wang L, Fan W, Ding L, Sun H. Study of Complex Optical Constants of Neat Cadmium Selenide Nanoplatelets Thin Films by Spectroscopic Ellipsometry. J Phys Chem Lett 2021; 12:191-198. [PMID: 33325711 DOI: 10.1021/acs.jpclett.0c03304] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Knowledge of tunability of complex optical constants of colloidal CdSe nanoplatelets (NPLs) thin films is essential for accurate modeling and design of NPL-containing optoelectronic devices. Here, dielectric functions, complex optical conductivities, and absorption coefficients of a series of CdSe NPL films with a varying number of atomic layers were investigated in a combination of spectroscopic ellipsometry techniques and transmittance measurements over a broad spectral range. Fine electronic structures were deciphered from the dielectric functions. Oscillator strengths at the lowest exciton resonance up to 0.62 for a series of CdSe NPL films were also determined. From our results, increasing the number of monolayers was found to boost the complex optical constants and the amplitude of the coupling strength of the fundamental exciton state mainly due to higher inorganic volume filling factors and pronounced surface passivation. Our work gives insights into both the interpretation and improvements of performance of CdSe NPL-based photoelectronic applications.
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Affiliation(s)
- Zitong Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Yi Tian Thung
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Xiaoxuan Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Lin Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai 200072, China
| | - Weijun Fan
- School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Lu Ding
- A*STAR (Agency for Science, Technology and Research), Institute of Materials Research and Engineering, Singapore 138634, Singapore
| | - Handong Sun
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
- Centre for Disruptive Photonic Technologies (CDPT), School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
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21
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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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