1
|
Swift MW, Efros AL, Erwin SC. Controlling light emission from semiconductor nanoplatelets using surface chemistry. Nat Commun 2024; 15:7737. [PMID: 39231939 PMCID: PMC11374790 DOI: 10.1038/s41467-024-51842-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 08/15/2024] [Indexed: 09/06/2024] Open
Abstract
Semiconductor nanoplatelets are atomically flat nanocrystals which emit light with high spectral purity at wavelengths controlled by their thickness. Despite their technological potential, efforts to further sharpen the emission lines of nanoplatelets have generally failed for unknown reasons. Here, we demonstrate theoretically that the linewidth is controlled by surface chemistry-specifically, inhomogeneities in the ligand layer on the nanoplatelet surface lead to a spatially fluctuating potential that localizes excitons. This localization leads to increased scattering and optical broadening. Importantly, localization also reduces the rate of radiative emission. Our model explains the observed linewidth and predicts that a more uniform ligand layer will sharpen the lines and increase the emission rates. These findings demonstrate that light emission from nanoplatelets can be controlled by optimizing their surface chemistry, an important advantage for their eventual use in optical technologies.
Collapse
Affiliation(s)
- Michael W Swift
- Center for Computational Materials Science, Naval Research Laboratory, Washington, DC, USA.
| | - Alexander L Efros
- Center for Computational Materials Science, Naval Research Laboratory, Washington, DC, USA.
| | - Steven C Erwin
- Center for Computational Materials Science, Naval Research Laboratory, Washington, DC, USA.
| |
Collapse
|
2
|
Morshed O, Amin M, Cogan NMB, Koessler ER, Collison R, Tumiel TM, Girten W, Awan F, Mathis L, Huo P, Vamivakas AN, Odom TW, Krauss TD. Room-temperature strong coupling between CdSe nanoplatelets and a metal-DBR Fabry-Pérot cavity. J Chem Phys 2024; 161:014710. [PMID: 38953450 DOI: 10.1063/5.0210700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Accepted: 05/27/2024] [Indexed: 07/04/2024] Open
Abstract
The generation of exciton-polaritons through strong light-matter interactions represents an emerging platform for exploring quantum phenomena. A significant challenge in colloidal nanocrystal-based polaritonic systems is the ability to operate at room temperature with high fidelity. Here, we demonstrate the generation of room-temperature exciton-polaritons through the coupling of CdSe nanoplatelets (NPLs) with a Fabry-Pérot optical cavity, leading to a Rabi splitting of 74.6 meV. Quantum-classical calculations accurately predict the complex dynamics between the many dark state excitons and the optically allowed polariton states, including the experimentally observed lower polariton photoluminescence emission, and the concentration of photoluminescence intensities at higher in-plane momenta as the cavity becomes more negatively detuned. The Rabi splitting measured at 5 K is similar to that at 300 K, validating the feasibility of the temperature-independent operation of this polaritonic system. Overall, these results show that CdSe NPLs are an excellent material to facilitate the development of room-temperature quantum technologies.
Collapse
Affiliation(s)
- Ovishek Morshed
- The Institute of Optics, University of Rochester, Rochester, New York 14627, USA
| | - Mitesh Amin
- The Institute of Optics, University of Rochester, Rochester, New York 14627, USA
| | - Nicole M B Cogan
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Eric R Koessler
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Robert Collison
- The Institute of Optics, University of Rochester, Rochester, New York 14627, USA
| | - Trevor M Tumiel
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - William Girten
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Farwa Awan
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Lele Mathis
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Pengfei Huo
- The Institute of Optics, University of Rochester, Rochester, New York 14627, USA
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - A Nickolas Vamivakas
- The Institute of Optics, University of Rochester, Rochester, New York 14627, USA
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Teri W Odom
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
| | - Todd D Krauss
- The Institute of Optics, University of Rochester, Rochester, New York 14627, USA
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Chen S, Al-Hilfi SH, Chen G, Zhang H, Zheng W, Virgilio LD, Geuchies JJ, Wang J, Feng X, Riedinger A, Bonn M, Wang HI. Tuning the Inter-Nanoplatelet Distance and Coupling Strength by Thermally Induced Ligand Decomposition. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2308951. [PMID: 38010120 DOI: 10.1002/smll.202308951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Indexed: 11/29/2023]
Abstract
CdSe nanoplatelets (NPLs) are promising 2D semiconductors for optoelectronic applications, in which efficient charge transport properties are desirable. It is reported that thermal annealing constitutes an effective strategy to control the optical absorption and electrical properties of CdSe NPLs by tuning the inter-NPL distance. Combining optical absorption, transmission electron microscopy, and thermogravimetric analysis, it is revealed that the thermal decomposition of ligands (e.g., cadmium myristate) governs the inter-NPL distance and thus the inter-NPL electronic coupling strength. Employing ultrafast terahertz spectroscopy, it is shown that this enhanced electronic coupling increases both the free carrier generation efficiency and the short-range mobility in NPL solids. The results show a straightforward method of controlling the interfacial electronic coupling strength for developing functional optoelectronic devices through thermal treatments.
Collapse
Affiliation(s)
- Shuai Chen
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Samir H Al-Hilfi
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Guangbo Chen
- Center for Advancing Electronics Dresden (cfaed) and Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Mommsenstr. 4, 01062, Dresden, Germany
| | - Heng Zhang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Wenhao Zheng
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Lucia Di Virgilio
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Jaco J Geuchies
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Junren Wang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Xinliang Feng
- Center for Advancing Electronics Dresden (cfaed) and Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Mommsenstr. 4, 01062, Dresden, Germany
- Max Planck Institute of Microstructure Physics, D-06120, Halle (Saale), Germany
| | - Andreas Riedinger
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Hai I Wang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
- Nanophotonics, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 1, Utrecht, 3584 CC, The Netherlands
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
Movilla JL, Planelles J, Climente JI. Excitons in metal halide perovskite nanoplatelets: an effective mass description of polaronic, dielectric and quantum confinement effects. NANOSCALE ADVANCES 2023; 5:6093-6101. [PMID: 37941960 PMCID: PMC10628976 DOI: 10.1039/d3na00592e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 10/05/2023] [Indexed: 11/10/2023]
Abstract
A theoretical model for excitons confined in metal halide perovskite nanoplatelets is presented. The model accounts for quantum confinement, dielectric confinement, short and long range polaron interactions by means of effective mass theory, image charges and Haken potentials. We use it to describe the band edge exciton of MAPbI3 structures surrounded by organic ligands. It is shown that the quasi-2D quantum and dielectric confinement squeezes the exciton radius, and this in turn enhances short-range polaron effects as compared to 3D structures. Dielectric screening is then weaker than expected from the static dielectric constant. This boosts the binding energies and radiative recombination probabilities, which is a requisite to match experimental data in related systems. The thickness dependence of Coulomb polarization and self-energy potentials is in fair agreement with sophisticated atomistic models.
Collapse
Affiliation(s)
- Jose L Movilla
- Departament d'Educació i Didàctiques Específiques, Universitat Jaume I Av. Sos Baynat, s/n 12071 Castelló Spain
| | - Josep Planelles
- Departament de Química Física i Analítica, Universitat Jaume I Av. Sos Baynat, s/n 12071 Castelló Spain
| | - Juan I Climente
- Departament de Química Física i Analítica, Universitat Jaume I Av. Sos Baynat, s/n 12071 Castelló Spain
| |
Collapse
|
7
|
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.
Collapse
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
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Rodà C, Di Giacomo A, Tasende Rodríguez LC, M CS, Leemans J, Hens Z, Geiregat P, Moreels I. Colloidal CdSe/CdS Core/Crown Nanoplatelets for Efficient Blue Light Emission and Optical Amplification. NANO LETTERS 2023; 23:3224-3230. [PMID: 37125440 DOI: 10.1021/acs.nanolett.2c05061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The application of CdSe nanoplatelets (NPLs) in the ultraviolet/blue region remains an open challenge due to charge trapping typically leading to limited photoluminescence quantum efficiency (PL QE) and sub-bandgap emission in core-only NPLs. Here, we synthesized 3.5 monolayer core/crown CdSe/CdS NPLs with various crown dimensions, exhibiting saturated blue emission and PL QE up to 55%. Compared to core-only NPLs, the PL intensity decays monoexponentially over two decades due to suppressed deep trapping and delayed emission. In both core-only and core/crown NPLs we observe biexciton-mediated optical gain between 470 and 510 nm, with material gain coefficients up to 7900 cm-1 and consistently lower gain thresholds in crowned NPLs. Gain lifetimes are limited to 40 ps, due to residual ultrafast trapping and higher exciton densities at threshold. Our results provide guidelines for rational optimization of thin CdSe NPLs toward lighting and light-amplification applications.
Collapse
Affiliation(s)
- Carmelita Rodà
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Technologiepark, Zwijnaarde 15, 9052 Gent, Belgium
| | - Alessio Di Giacomo
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Technologiepark, Zwijnaarde 15, 9052 Gent, Belgium
| | - Lucía Camila Tasende Rodríguez
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Technologiepark, Zwijnaarde 15, 9052 Gent, Belgium
| | - Chandra Sekhar M
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Technologiepark, Zwijnaarde 15, 9052 Gent, Belgium
| | - Jari Leemans
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Technologiepark, Zwijnaarde 15, 9052 Gent, Belgium
| | - Zeger Hens
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Technologiepark, Zwijnaarde 15, 9052 Gent, Belgium
| | - Pieter Geiregat
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Technologiepark, Zwijnaarde 15, 9052 Gent, Belgium
| | - Iwan Moreels
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Krijgslaan 281-S3, 9000 Gent, Belgium
| |
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
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.
Collapse
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
| |
Collapse
|
12
|
Kirstein E, Zhukov EA, Yakovlev DR, Kopteva NE, Harkort C, Kudlacik D, Hordiichuk O, Kovalenko MV, Bayer M. Coherent Spin Dynamics of Electrons in Two-Dimensional (PEA) 2PbI 4 Perovskites. NANO LETTERS 2023; 23:205-212. [PMID: 36574606 DOI: 10.1021/acs.nanolett.2c03975] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The versatile potential of lead halide perovskites and two-dimensional materials is merged in the Ruddlesden-Popper perovskites having outstanding optical properties. Here, the coherent spin dynamics in Ruddlesden-Popper (PEA)2PbI4 perovskites is investigated by picosecond pump-probe Kerr rotation in an external magnetic field. The Larmor spin precession of resident electrons with a spin dephasing time of 190 ps is identified. The longitudinal spin relaxation time in weak magnetic fields measured by the spin inertia method is as long as 25 μs. A significant anisotropy of the electron g-factor with the in-plane value of +2.45 and out-of-plane value of +2.05 is found. The exciton out-of-plane g-factor of +1.6 is measured by magneto-reflectivity. This work contributes to the understanding of the spin-dependent properties of two-dimensional perovskites and their spin dynamics.
Collapse
Affiliation(s)
- Erik Kirstein
- Experimental Physics 2, Department of Physics, TU Dortmund, 44227 Dortmund, Germany
| | - Evgeny A Zhukov
- Experimental Physics 2, Department of Physics, TU Dortmund, 44227 Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Dmitri R Yakovlev
- Experimental Physics 2, Department of Physics, TU Dortmund, 44227 Dortmund, Germany
- Ioffe Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia
| | - Nataliia E Kopteva
- Experimental Physics 2, Department of Physics, TU Dortmund, 44227 Dortmund, Germany
| | - Carolin Harkort
- Experimental Physics 2, Department of Physics, TU Dortmund, 44227 Dortmund, Germany
| | - Dennis Kudlacik
- Experimental Physics 2, Department of Physics, TU Dortmund, 44227 Dortmund, Germany
| | - Oleh Hordiichuk
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
- EMPA-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf CH-8600, Switzerland
| | - Maksym V Kovalenko
- Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland
- EMPA-Swiss Federal Laboratories for Materials Science and Technology, Dübendorf CH-8600, Switzerland
| | - Manfred Bayer
- Experimental Physics 2, Department of Physics, TU Dortmund, 44227 Dortmund, Germany
| |
Collapse
|
13
|
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.
Collapse
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
| |
Collapse
|
14
|
Anand A, Zaffalon ML, Cova F, Pinchetti V, Khan AH, Carulli F, Brescia R, Meinardi F, Moreels I, Brovelli S. Optical and Scintillation Properties of Record-Efficiency CdTe Nanoplatelets toward Radiation Detection Applications. NANO LETTERS 2022; 22:8900-8907. [PMID: 36331389 PMCID: PMC9706671 DOI: 10.1021/acs.nanolett.2c02975] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 10/26/2022] [Indexed: 06/16/2023]
Abstract
Colloidal CdTe nanoplatelets featuring a large absorption coefficient and ultrafast tunable luminescence coupled with heavy-metal-based composition present themselves as highly desirable candidates for radiation detection technologies. Historically, however, these nanoplatelets have suffered from poor emission efficiency, hindering progress in exploring their technological potential. Here, we report the synthesis of CdTe nanoplatelets possessing a record emission efficiency of 9%. This enables us to investigate their fundamental photophysics using ultrafast transient absorption, temperature-controlled photoluminescence, and radioluminescence measurements, elucidating the origins of exciton- and defect-related phenomena under both optical and ionizing excitation. For the first time in CdTe nanoplatelets, we report the cumulative effects of a giant oscillator strength transition and exciton fine structure. Simultaneously, thermally stimulated luminescence measurements reveal the presence of both shallow and deep trap states and allow us to disclose the trapping and detrapping dynamics and their influence on the scintillation properties.
Collapse
Affiliation(s)
- Abhinav Anand
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via R. Cozzi 55, 20125Milano, Italy
| | - Matteo L. Zaffalon
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via R. Cozzi 55, 20125Milano, Italy
| | - Francesca Cova
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via R. Cozzi 55, 20125Milano, Italy
| | - Valerio Pinchetti
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via R. Cozzi 55, 20125Milano, Italy
| | | | - Francesco Carulli
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via R. Cozzi 55, 20125Milano, Italy
| | - Rosaria Brescia
- Electron
Microscopy Facility, Istituto Italiano di
Tecnologia, Via Morego 30, 16163Genova, Italy
| | - Francesco Meinardi
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via R. Cozzi 55, 20125Milano, Italy
| | - Iwan Moreels
- Department
of Chemistry, Ghent University, 9000Ghent, Belgium
- Electron
Microscopy Facility, Istituto Italiano di
Tecnologia, Via Morego 30, 16163Genova, Italy
| | - Sergio Brovelli
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via R. Cozzi 55, 20125Milano, Italy
- Electron
Microscopy Facility, Istituto Italiano di
Tecnologia, Via Morego 30, 16163Genova, Italy
| |
Collapse
|
15
|
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
| |
Collapse
|
16
|
Baghdasaryan DA, Harutyunyan VA, Hayrapetyan DB, Kazaryan EM, Baskoutas S, Sarkisyan HA. Exciton States and Optical Absorption in CdSe and PbS Nanoplatelets. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12203690. [PMID: 36296880 PMCID: PMC9611409 DOI: 10.3390/nano12203690] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 10/11/2022] [Accepted: 10/13/2022] [Indexed: 06/12/2023]
Abstract
The exciton states and their influence on the optical absorption spectrum of CdSe and PbS nanoplatelets (NPLs) are considered theoretically in this paper. The problem is discussed in cases of strong, intermediate, and weak size quantization regimes of charge carrier motion in NPLs. For each size quantization regime, the corresponding potential that adequately describes the electron-hole interaction in this mode of space quantization of charge carriers is chosen. The single-particle energy spectra and corresponding wave functions for strong intermediate and weak size quantization regimes have been revealed. The dependence of material parameters on the number of monolayers in the sample has been considered. The related selection rules and the dependence of the absorption coefficient on the frequency and polarization direction of the incident light wave were obtained. The interband transition threshold energy dependencies were obtained for each size quantization regime. The effect of dielectric coefficient mismatch and different models of electron-hole interaction potentials have been studied in CdSe and PbS NPLs. It is also shown that with an increase in the linear dimensions of the structure, the threshold frequency of absorption decreases. The binding energies and absorption coefficient results for NPL with different thicknesses agree with the experimental data. The values of the absorption exciton peaks measured experimentally are close to our calculated values for CdSe and PbS samples.
Collapse
Affiliation(s)
- Davit A. Baghdasaryan
- Institute of Engineering and Physics, Russian-Armenian University, H. Emin 123, Yerevan 0051, Armenia
| | - Volodya A. Harutyunyan
- Institute of Engineering and Physics, Russian-Armenian University, H. Emin 123, Yerevan 0051, Armenia
| | - David B. Hayrapetyan
- Institute of Engineering and Physics, Russian-Armenian University, H. Emin 123, Yerevan 0051, Armenia
| | - Eduard M. Kazaryan
- Institute of Engineering and Physics, Russian-Armenian University, H. Emin 123, Yerevan 0051, Armenia
| | - Sotirios Baskoutas
- Department of Materials Science, University of Patras, 26504 Patras, Greece
| | - Hayk A. Sarkisyan
- Institute of Engineering and Physics, Russian-Armenian University, H. Emin 123, Yerevan 0051, Armenia
- Institute of Electronics and Telecommunications, Peter the Great St. Petersburg Polytechnic University, 195251 Saint Petersburg, Russia
| |
Collapse
|
17
|
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] [Received: 05/05/2022] [Revised: 08/20/2022] [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.
Collapse
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
| |
Collapse
|
18
|
Macias-Pinilla DF, Planelles J, Climente JI. Biexcitons in CdSe nanoplatelets: geometry, binding energy and radiative rate. NANOSCALE 2022; 14:8493-8500. [PMID: 35662303 DOI: 10.1039/d2nr01354a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Biexciton properties in semiconductor nanostructures are highly sensitive to quantum confinement, relative electron-hole masses, dielectric environment and Coulomb correlations. Here we present a variational Quantum Monte Carlo model which, coupled to effective mass Hamiltonians, takes into account all of the above effects. The model is used to provide theoretical assessment on the biexciton ground state properties in colloidal CdSe nanoplatelets. A number of characteristic features is observed: (i) the finite thickness of these systems makes the biexciton geometry depart from the planar square expected in the two-dimensional (2D) limit, and form a distorted tetrahedron instead; (ii) the strong dielectric confinement enhances not only Coulomb attractions but also repulsions, which lowers the ratio of the biexciton-to-exciton binding energy down to EXXb/EXb = 0.07. (iii) EXXb is less sensitive than EXb to lateral confinement, and yet it can reach values above 30 meV, thus granting room temperature stability; (iv) the ratio of biexciton-to-exciton radiative rates, kradXX/kradX, decreases from 3.5 to ∼1 as the platelet area increases. These results pave the way for the rational design of biexciton properties in metal chalcogenide nanoplatelets.
Collapse
Affiliation(s)
- David F Macias-Pinilla
- Institute of Advanced Materials (INAM), Universitat Jaume I, Av. Sos Baynat, s/n, 12071 Castelló, Spain
- Departament de Química Física i Analítica, Universitat Jaume I, Av. Sos Baynat, s/n, 12071 Castelló, Spain.
| | - Josep Planelles
- Departament de Química Física i Analítica, Universitat Jaume I, Av. Sos Baynat, s/n, 12071 Castelló, Spain.
| | - Juan I Climente
- Departament de Química Física i Analítica, Universitat Jaume I, Av. Sos Baynat, s/n, 12071 Castelló, Spain.
| |
Collapse
|