1
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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.
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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.
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2
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Kambhampati P. Unraveling the excitonics of light emission from metal-halide perovskite quantum dots. NANOSCALE 2024; 16:15033-15058. [PMID: 39052235 DOI: 10.1039/d4nr01481b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/27/2024]
Abstract
Metal halide semicondictor perovskites have been under intense investigation for their promise in light absorptive applications like photovoltaics. They have more recently experienced interest for their promise in light emissive applications. A key aspect of perovskites is their glassy, ionic lattice that exhibits dynamical disorder. One possible result of this dynamical disorder is their strong coupling between electronic and lattice degrees of freedom which may confer remarkable properties for light emission such as defect tolerance. How does the system, comprised of excitons, couple to the bath, comprised of lattice modes? How does this system-bath interaction give rise to novel light emissive properties and how do these properties give insight into the nature of these materials? We review recent work from this group in which time-resolved photoluminescence spectroscopy is used to reveal such insights. Based upon a fast time resolution of 3 ps, energy resolution, and temperature dependence, a wide variety of insights are gleaned. These insights include: lattice contributions to the emission linewidths, multiexciton formation, hot carrier cooling, excitonic fine structure, single dot superradiance, and a breakdown of the Condon approximation, all due to complex structural dynamics in these materials.
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3
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Sukkabot W. Observation of spin-splitting energies on sp-d exchange interactions tailored in colloidal CdSe/CdMnS core/shell nanoplatelets: an atomistic tight-binding model. Phys Chem Chem Phys 2024; 26:11807-11814. [PMID: 38566596 DOI: 10.1039/d4cp00353e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Using the atomistic tight-binding model plus sp-d exchange term, the embedding of magnetic ions into CdSe/CdMnS core/shell nanoplatelets (NPLs) at different effective temperatures resulted in sp-d exchange interactions, which in turn cause modifications in electronic and magnetic characteristics. The influence of CdMnS monolayers on single-particle spectra, optical band gaps, wave function overlaps and exciton binding energies is more pronounced than that of the effective temperature. Due to the electron, hole and Zeeman splitting energies, with the growth of CdMnS shell monolayers, electron g-factor values are unchanged, but hole and exciton g-factor values are enhanced. Additionally, all g values decrease with increasing temperature, thus representing decreased magnetization of the paramagnetic system. By changing nanoplatelet architectures and temperatures, manipulation of s-d and p-d exchange interactions is accomplished. Overall, studied materials combine the merits of NPLs and magnetic ions, hence leading to alternate possibilities for active applications in spin-based devices.
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Affiliation(s)
- Worasak Sukkabot
- Department of Physics, Faculty of Science, Ubon Ratchathani University, 85 Sathollmark Rd. Warinchamrab, Ubon Ratchathani 34190, Thailand.
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4
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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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5
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Strandell D, Mora Perez C, Wu Y, Prezhdo OV, Kambhampati P. Excitonic Quantum Coherence in Light Emission from CsPbBr 3 Metal-Halide Perovskite Nanocrystals. NANO LETTERS 2024; 24:61-66. [PMID: 38113396 DOI: 10.1021/acs.nanolett.3c03180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
The decay of excited states via radiative and nonradiative paths is well understood in molecules and bulk semiconductors but less so in nanocrystals. Here, we perform time-resolved photoluminescence (t-PL) experiments on CsPbBr3 metal-halide perovskite nanocrystals, with a time resolution of 3 ps, sufficient to observe the decay of both excitons and biexcitons as a function of temperature. The striking result is that the radiative rate constant of the single exciton increases at low temperatures with an exponential functional form, suggesting quantum coherent effects with dephasing at high temperatures. The opposing directions of the radiative and nonradiative decay rate constants enable enhanced brightening of PL from excitons to biexcitons due to quantum effects, promoting a faster approach to the quantum theoretical limits of light emission. Ab initio quantum dynamics simulations reproduce the experimental observations of radiation controlled by quantum spatial coherence enhanced at low temperatures.
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Affiliation(s)
- Dallas Strandell
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Carlos Mora Perez
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Yifan Wu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Oleg V Prezhdo
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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6
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Tanghe I, Samoli M, Wagner I, Cayan SA, Khan AH, Chen K, Hodgkiss J, Moreels I, Thourhout DV, Hens Z, Geiregat P. Optical gain and lasing from bulk cadmium sulfide nanocrystals through bandgap renormalization. NATURE NANOTECHNOLOGY 2023; 18:1423-1429. [PMID: 37798564 DOI: 10.1038/s41565-023-01521-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 09/06/2023] [Indexed: 10/07/2023]
Abstract
Strongly confined colloidal quantum dots have been investigated for low-cost light emission and lasing for nearly two decades. However, known materials struggle to combine technologically relevant metrics of low-threshold and long inverted-state lifetime with a material gain coefficient fit to match cavity losses, particularly under electrical excitation. Here we show that bulk nanocrystals of CdS combine an exceptionally large material gain of 50,000 cm-1 with best-in-class gain thresholds below a single exciton per nanocrystal and 3 ns gain lifetimes not limited by non-radiative Auger processes. We quantitatively account for these findings by invoking a strong bandgap renormalization effect, unobserved in nanocrystals to date, to the best of our knowledge. Next, we demonstrate broadband amplified spontaneous emission and lasing under quasi-continuous-wave conditions. Our results highlight the prospects of bulk nanocrystals for lasing from solution-processable materials.
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Affiliation(s)
- Ivo Tanghe
- Photonics Research Group, Ghent University, Gent, Belgium
- NoLIMITS Center For Non-Linear Microscopy and Spectroscopy, Ghent University, Gent, Belgium
- Physics and Chemistry of Nanostructures, Ghent University, Gent, Belgium
| | - Margarita Samoli
- Physics and Chemistry of Nanostructures, Ghent University, Gent, Belgium
| | - Isabella Wagner
- School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand
| | - Servet Ataberk Cayan
- NoLIMITS Center For Non-Linear Microscopy and Spectroscopy, Ghent University, Gent, Belgium
- Physics and Chemistry of Nanostructures, Ghent University, Gent, Belgium
| | - Ali Hossain Khan
- Department of Chemical and Biological Sciences, S. N. Bose National Centre for Basic Sciences, Kolkata, India
- Ghent University, Physics and Chemistry of Nanostructures, Gent, Belgium
| | - Kai Chen
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand
- Robinson Research Institute, Victoria University of Wellington, Wellington, New Zealand
- The Dodd-Walls Centre for Photonic and Quantum Technologies, University of Otago, Dunedin, New Zealand
| | - Justin Hodgkiss
- School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand
| | - Iwan Moreels
- Physics and Chemistry of Nanostructures, Ghent University, Gent, Belgium
| | - Dries Van Thourhout
- Photonics Research Group, Ghent University, Gent, Belgium
- NoLIMITS Center For Non-Linear Microscopy and Spectroscopy, Ghent University, Gent, Belgium
| | - Zeger Hens
- NoLIMITS Center For Non-Linear Microscopy and Spectroscopy, Ghent University, Gent, Belgium
- Physics and Chemistry of Nanostructures, Ghent University, Gent, Belgium
| | - Pieter Geiregat
- NoLIMITS Center For Non-Linear Microscopy and Spectroscopy, Ghent University, Gent, Belgium.
- Physics and Chemistry of Nanostructures, Ghent University, Gent, Belgium.
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7
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Liu H, Chen P, Zhang X, Wang X, He T, Chen R. Lateral surface passivation of CdSe nanoplatelets through crown management. NANOSCALE 2023; 15:14140-14145. [PMID: 37584662 DOI: 10.1039/d3nr03133k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/17/2023]
Abstract
Two-dimensional colloidal CdSe nanoplatelets (NPLs) have been considered as ideal emitting materials for high performance light-emitting devices due to their excellent optical properties. However, the understanding of defect related radiative and nonradiative recombination centers in CdSe NPLs is still far from sufficient, especially their physical distribution locations. In this work, CdSe core and CdSe/CdS core/crown NPLs have been successfully synthesized and their optical properties have been characterized by laser spectroscopies. It is found that the photoluminescence quantum yield of CdSe NPLs is improved by a factor of 4 after the growth of the CdS crown. At low temperatures, the change in the ratio of low and high energy emission intensities from NPLs suggests that the radiative recombination centers are mainly located on the lateral surface of the samples. This finding is further confirmed by the surface passivation experiment. Meanwhile, the nonradiative recombination centers of NPLs located on the lateral surface are also confirmed by ligand exchange. These results demonstrate the importance of understanding the optical properties of the lateral surface of NPLs, which are important for the design of material structures for optoelectronic applications.
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Affiliation(s)
- Huan Liu
- Harbin Institute of Technology, Harbin 150001, China
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
| | - Peixian Chen
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Xuanyu Zhang
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
| | - Xiongbin Wang
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
| | - Tingchao He
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
| | - Rui Chen
- Department of Electrical and Electronic Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
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8
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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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9
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Durmusoglu EG, Hu S, Hernandez-Martinez PL, Izmir M, Shabani F, Guo M, Gao H, Isik F, Delikanli S, Sharma VK, Liu B, Demir HV. High External Quantum Efficiency Light-Emitting Diodes Enabled by Advanced Heterostructures of Type-II Nanoplatelets. ACS NANO 2023; 17:7636-7644. [PMID: 36912794 PMCID: PMC10134493 DOI: 10.1021/acsnano.3c00046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 03/09/2023] [Indexed: 06/18/2023]
Abstract
Colloidal quantum wells (CQWs), also known as nanoplatelets (NPLs), are exciting material systems for numerous photonic applications, including lasers and light-emitting diodes (LEDs). Although many successful type-I NPL-LEDs with high device performance have been demonstrated, type-II NPLs are not fully exploited for LED applications, even with alloyed type-II NPLs with enhanced optical properties. Here, we present the development of CdSe/CdTe/CdSe core/crown/crown (multi-crowned) type-II NPLs and systematic investigation of their optical properties, including their comparison with the traditional core/crown counterparts. Unlike traditional type-II NPLs such as CdSe/CdTe, CdTe/CdSe, and CdSe/CdSexTe1-x core/crown heterostructures, here the proposed advanced heterostructure reaps the benefits of having two type-II transition channels, resulting in a high quantum yield (QY) of 83% and a long fluorescence lifetime of 73.3 ns. These type-II transitions were confirmed experimentally by optical measurements and theoretically using electron and hole wave function modeling. Computational study shows that the multi-crowned NPLs provide a better-distributed hole wave function along the CdTe crown, while the electron wave function is delocalized in the CdSe core and CdSe crown layers. As a proof-of-concept demonstration, NPL-LEDs based on these multi-crowned NPLs were designed and fabricated with a record high external quantum efficiency (EQE) of 7.83% among type-II NPL-LEDs. These findings are expected to induce advanced designs of NPL heterostructures to reach a fascinating level of performance, especially in LEDs and lasers.
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Affiliation(s)
- Emek G. Durmusoglu
- LUMINOUS!
Centre of Excellence for Semiconductor Lighting and Displays, The
Photonics Institute, School of Electrical and Electronic Engineering,
School of Physical and Mathematical Sciences, School of Materials
Science and Engineering, Nanyang Technological
University, Singapore 639798
| | - Sujuan Hu
- State
Key Laboratory of Optoelectronic Materials and Technologies, School
of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Pedro Ludwig Hernandez-Martinez
- LUMINOUS!
Centre of Excellence for Semiconductor Lighting and Displays, The
Photonics Institute, School of Electrical and Electronic Engineering,
School of Physical and Mathematical Sciences, School of Materials
Science and Engineering, Nanyang Technological
University, Singapore 639798
| | - Merve Izmir
- LUMINOUS!
Centre of Excellence for Semiconductor Lighting and Displays, The
Photonics Institute, School of Electrical and Electronic Engineering,
School of Physical and Mathematical Sciences, School of Materials
Science and Engineering, Nanyang Technological
University, Singapore 639798
| | - Farzan Shabani
- Department
of Electrical and Electronics Engineering, Department of Physics,
UNAM—Institute of Materials Science and Nanotechnology and
National Nanotechnology Research Center, Bilkent University, Ankara 06800, Turkey
| | - Min Guo
- State
Key Laboratory of Optoelectronic Materials and Technologies, School
of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Huayu Gao
- State
Key Laboratory of Optoelectronic Materials and Technologies, School
of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Furkan Isik
- Department
of Electrical and Electronics Engineering, Department of Physics,
UNAM—Institute of Materials Science and Nanotechnology and
National Nanotechnology Research Center, Bilkent University, Ankara 06800, Turkey
| | - Savas Delikanli
- Department
of Electrical and Electronics Engineering, Department of Physics,
UNAM—Institute of Materials Science and Nanotechnology and
National Nanotechnology Research Center, Bilkent University, Ankara 06800, Turkey
| | - Vijay Kumar Sharma
- LUMINOUS!
Centre of Excellence for Semiconductor Lighting and Displays, The
Photonics Institute, School of Electrical and Electronic Engineering,
School of Physical and Mathematical Sciences, School of Materials
Science and Engineering, Nanyang Technological
University, Singapore 639798
| | - Baiquan Liu
- State
Key Laboratory of Optoelectronic Materials and Technologies, School
of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Hilmi Volkan Demir
- LUMINOUS!
Centre of Excellence for Semiconductor Lighting and Displays, The
Photonics Institute, School of Electrical and Electronic Engineering,
School of Physical and Mathematical Sciences, School of Materials
Science and Engineering, Nanyang Technological
University, Singapore 639798
- Department
of Electrical and Electronics Engineering, Department of Physics,
UNAM—Institute of Materials Science and Nanotechnology and
National Nanotechnology Research Center, Bilkent University, Ankara 06800, Turkey
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10
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Shulenberger KE, Jilek MR, Sherman SJ, Hohman BT, Dukovic G. Electronic Structure and Excited State Dynamics of Cadmium Chalcogenide Nanorods. Chem Rev 2023; 123:3852-3903. [PMID: 36881852 DOI: 10.1021/acs.chemrev.2c00676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
The cylindrical quasi-one-dimensional shape of colloidal semiconductor nanorods (NRs) gives them unique electronic structure and optical properties. In addition to the band gap tunability common to nanocrystals, NRs have polarized light absorption and emission and high molar absorptivities. NR-shaped heterostructures feature control of electron and hole locations as well as light emission energy and efficiency. We comprehensively review the electronic structure and optical properties of Cd-chalcogenide NRs and NR heterostructures (e.g., CdSe/CdS dot-in-rods, CdSe/ZnS rod-in-rods), which have been widely investigated over the last two decades due in part to promising optoelectronic applications. We start by describing methods for synthesizing these colloidal NRs. We then detail the electronic structure of single-component and heterostructure NRs and follow with a discussion of light absorption and emission in these materials. Next, we describe the excited state dynamics of these NRs, including carrier cooling, carrier and exciton migration, radiative and nonradiative recombination, multiexciton generation and dynamics, and processes that involve trapped carriers. Finally, we describe charge transfer from photoexcited NRs and connect the dynamics of these processes with light-driven chemistry. We end with an outlook that highlights some of the outstanding questions about the excited state properties of Cd-chalcogenide NRs.
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Affiliation(s)
| | - Madison R Jilek
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Skylar J Sherman
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Benjamin T Hohman
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Gordana Dukovic
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States.,Renewable and Sustainable Energy Institute (RASEI), University of Colorado Boulder, Boulder, Colorado 80309, United States.,Materials Science and Engineering, University of Colorado Boulder, Boulder, Colorado 80303, United States
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11
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Diroll BT, Guzelturk B, Po H, Dabard C, Fu N, Makke L, Lhuillier E, Ithurria S. 2D II-VI Semiconductor Nanoplatelets: From Material Synthesis to Optoelectronic Integration. Chem Rev 2023; 123:3543-3624. [PMID: 36724544 DOI: 10.1021/acs.chemrev.2c00436] [Citation(s) in RCA: 32] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The field of colloidal synthesis of semiconductors emerged 40 years ago and has reached a certain level of maturity thanks to the use of nanocrystals as phosphors in commercial displays. In particular, II-VI semiconductors based on cadmium, zinc, or mercury chalcogenides can now be synthesized with tailored shapes, composition by alloying, and even as nanocrystal heterostructures. Fifteen years ago, II-VI semiconductor nanoplatelets injected new ideas into this field. Indeed, despite the emergence of other promising semiconductors such as halide perovskites or 2D transition metal dichalcogenides, colloidal II-VI semiconductor nanoplatelets remain among the narrowest room-temperature emitters that can be synthesized over a wide spectral range, and they exhibit good material stability over time. Such nanoplatelets are scientifically and technologically interesting because they exhibit optical features and production advantages at the intersection of those expected from colloidal quantum dots and epitaxial quantum wells. In organic solvents, gram-scale syntheses can produce nanoparticles with the same thicknesses and optical properties without inhomogeneous broadening. In such nanoplatelets, quantum confinement is limited to one dimension, defined at the atomic scale, which allows them to be treated as quantum wells. In this review, we discuss the synthetic developments, spectroscopic properties, and applications of such nanoplatelets. Covering growth mechanisms, we explain how a thorough understanding of nanoplatelet growth has enabled the development of nanoplatelets and heterostructured nanoplatelets with multiple emission colors, spatially localized excitations, narrow emission, and high quantum yields over a wide spectral range. Moreover, nanoplatelets, with their large lateral extension and their thin short axis and low dielectric surroundings, can support one or several electron-hole pairs with large exciton binding energies. Thus, we also discuss how the relaxation processes and lifetime of the carriers and excitons are modified in nanoplatelets compared to both spherical quantum dots and epitaxial quantum wells. Finally, we explore how nanoplatelets, with their strong and narrow emission, can be considered as ideal candidates for pure-color light emitting diodes (LEDs), strong gain media for lasers, or for use in luminescent light concentrators.
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Affiliation(s)
- Benjamin T Diroll
- Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States
| | - Burak Guzelturk
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States
| | - Hong Po
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Corentin Dabard
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Ningyuan Fu
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Lina Makke
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
| | - Emmanuel Lhuillier
- Sorbonne Université, CNRS, Institut des NanoSciences de Paris, INSP, 75005 Paris, France
| | - Sandrine Ithurria
- Laboratoire de Physique et d'Etude des Matériaux, ESPCI-Paris, PSL Research University, Sorbonne Université Univ Paris 06, CNRS UMR 8213, 10 rue Vauquelin 75005 Paris, France
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12
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Bai B, Zhang C, Dou Y, Kong L, Wang L, Wang S, Li J, Zhou Y, Liu L, Liu B, Zhang X, Hadar I, Bekenstein Y, Wang A, Yin Z, Turyanska L, Feldmann J, Yang X, Jia G. Atomically flat semiconductor nanoplatelets for light-emitting applications. Chem Soc Rev 2023; 52:318-360. [PMID: 36533300 DOI: 10.1039/d2cs00130f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The last decade has witnessed extensive breakthroughs and significant progress in atomically flat two-dimensional (2D) semiconductor nanoplatelets (NPLs) in terms of synthesis, growth mechanisms, optical and electronic properties and practical applications. Such NPLs have electronic structures similar to those of quantum wells in which excitons are predominantly confined along the vertical direction, while electrons are free to move in the lateral directions, resulting in unique optical properties, such as extremely narrow emission line width, short photoluminescence (PL) lifetime, high gain coefficient, and giant oscillator strength transition (GOST). These unique optical properties make NPLs favorable for high color purity light-emitting applications, in particular in light-emitting diodes (LEDs), backlights for liquid crystal displays (LCDs) and lasers. This review article first introduces the intrinsic characteristics of 2D semiconductor NPLs with atomic flatness. Subsequently, the approaches and mechanisms for the controlled synthesis of atomically flat NPLs are summarized followed by an insight on recent progress in the mediation of core/shell, core/crown and core/crown@shell structures by selective epitaxial growth of passivation layers on different planes of NPLs. Moreover, an overview of the unique optical properties and the associated light-emitting applications is elaborated. Despite great progress in this research field, there are some issues relating to heavy metal elements such as Cd2+ in NPLs, and the ambiguous gain mechanisms of NPLs and others are the main obstacles that prevent NPLs from widespread applications. Therefore, a perspective is included at the end of this review article, in which the current challenges in this stimulating research field are discussed and possible solutions to tackle these challenges are proposed.
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Affiliation(s)
- Bing Bai
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henaon University, Kaifeng 475004, China
| | - Chengxi Zhang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, China.
| | - Yongjiang Dou
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, China.
| | - Lingmei Kong
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, China.
| | - Lin Wang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, China.
| | - Sheng Wang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, China.
| | - Jun Li
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henaon University, Kaifeng 475004, China
| | - Yi Zhou
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henaon University, Kaifeng 475004, China
| | - Long Liu
- Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, School of Materials Science and Engineering, and Collaborative Innovation Center of Nano Functional Materials and Applications, Henaon University, Kaifeng 475004, China
| | - Baiquan Liu
- School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Xiaoyu Zhang
- Key Laboratory of Automobile Materials, Ministry of Education, College of Materials Science and Engineering, Jilin Provincial International Cooperation Key Laboratory of High-Efficiency Clean Energy Materials, Electron Microscopy Center, Jilin University, Changchun 130012, China
| | - Ido Hadar
- Institute of Chemistry, and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Yehonadav Bekenstein
- Department of Materials Science and Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Aixiang Wang
- School of Chemistry and Chemical Engineering, Linyi University, Linyi 276005, P. R. China
| | - Zongyou Yin
- Research School of Chemistry, The Australian National University, ACT 2601, Australia
| | - Lyudmila Turyanska
- Faculty of Engineering, The University of Nottingham, Additive Manufacturing Building, Jubilee Campus, University Park, Nottingham NG7 2RD, UK
| | - Jochen Feldmann
- Chair for Photonics and Optoelectronics, Nano-Institute Munich and Department of Physics, Ludwig-Maximilians-Universität (LMU), Königinstr. 10, Munich 80539, Germany
| | - Xuyong Yang
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, China.
| | - Guohua Jia
- School of Molecular and Life Sciences, Curtin University, Perth, WA 6102, Australia.
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13
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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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14
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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.
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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
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15
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Diroll BT, Brumberg A, Schaller RD. Gain roll-off in cadmium selenide colloidal quantum wells under intense optical excitation. Sci Rep 2022; 12:8016. [PMID: 35577869 PMCID: PMC9110332 DOI: 10.1038/s41598-022-11882-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 02/24/2022] [Indexed: 12/04/2022] Open
Abstract
Colloidal quantum wells, or nanoplatelets, show among the lowest thresholds for amplified spontaneous emission and lasing among solution-cast materials and among the highest modal gains of any known materials. Using solution measurements of colloidal quantum wells, this work shows that under photoexcitation, optical gain increases with pump fluence before rolling off due to broad photoinduced absorption at energies lower than the band gap. Despite the common occurrence of gain induced by an electron–hole plasma found in bulk materials and epitaxial quantum wells, under no measurement conditions was the excitonic absorption of the colloidal quantum wells extinguished and gain arising from a plasma observed. Instead, like gain, excitonic absorption reaches a minimum intensity near a photoinduced carrier sheet density of 2 × 1013 cm−2 above which the absorption peak begins to recover. To understand the origins of these saturation and reversal effects, measurements were performed with different excitation energies, which deposit differing amounts of excess energy above the band gap. Across many samples, it was consistently observed that less energetic excitation results in stronger excitonic bleaching and gain for a given carrier density. Transient and static optical measurements at elevated temperatures, as well as transient X-ray diffraction of the samples, suggest that the origin of gain saturation and reversal is a heating and disordering of the colloidal quantum wells which produces sub-gap photoinduced absorption.
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16
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Diroll BT, Banerjee T. Transient reshaping of intraband transitions by hot electrons. NANOSCALE 2022; 14:1340-1346. [PMID: 35015024 DOI: 10.1039/d1nr06203d] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Hot electrons, far above the lattice temperature of a material, present opportunities for enhanced solar energy harvesting or performance of otherwise unfavorable chemistry. The spectroscopic signatures and dynamics of hot carrier absorption and emission have been extensively studied in bulk and nanoscopic semiconductors, but the effects on intraband transitions are largely unexplored. Here, the effect of hot electrons on the properties of colloidal quantum wells made of cadmium selenide is examined using ultrafast spectroscopy. Similar to expitaxial quantum wells, these atomically precise materials support intersubband transitions (a class of intraband transitions in 1D and 2D materials) in the near-infrared spectral window. Using energy-dependent photoexcitation, it is shown that electrons reach effective temperatures of 2000 K or greater. This results in a substantial transient shift in the oscillator strength of the instersubband transition to lower energies on a sub-picosecond time-scale. Similar heating of electrons is achieved under mid-infrared re-excitation, which permits ultrafast transmittance modulation throughout the near-infrared.
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Affiliation(s)
| | - Tathagata Banerjee
- Center for Nanoscale Materials, Argonne National Laboratory, USA.
- Department of Physics, University of Illinois Urbana-Champaign, USA
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17
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Vong AF, Irgen-Gioro S, Wu Y, Weiss EA. Origin of Low Temperature Trion Emission in CdSe Nanoplatelets. NANO LETTERS 2021; 21:10040-10046. [PMID: 34843260 DOI: 10.1021/acs.nanolett.1c03726] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Colloidal semiconductor nanoplatelets (NPLs) are a scalable materials platform for optoelectronic applications requiring fast and narrow emission, including spin-to-photon transduction within quantum information networks. In particular, three-particle negative trions of NPLs are appealing emitters since, unlike excitons, they do not have an optically "dark" sublevel. In CdSe NPLs, trion emission dominates the photoluminescence (PL) spectrum at low temperature but using them as single photon-emitting states requires more knowledge about their preparation, since trions in these materials are not directly optically accessible from the ground state. This work demonstrates, using power-dependent time-resolved transient absorptions (TA) of CdSe NPLs, that trions form via biexciton decay in 1.6 ps. The scaling of the trion population and formation lifetime with excitation power indicates that they do not form through collisional mechanisms typical for 2D materials, but rather by a unimolecular hole transfer. This work is a step toward deterministic single photon emission from trions.
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Affiliation(s)
- Albert F Vong
- Department of Materials Science and Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Shawn Irgen-Gioro
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Yue Wu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Emily A Weiss
- Department of Materials Science and Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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18
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Keitel RC, Aellen M, Feber BL, Rossinelli AA, Meyer SA, Cui J, Norris DJ. Active Mode Switching in Plasmonic Microlasers by Spatial Control of Optical Gain. NANO LETTERS 2021; 21:8952-8959. [PMID: 34723554 DOI: 10.1021/acs.nanolett.1c01957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The pursuit of miniaturized optical sources for on-chip applications has led to the development of surface plasmon polariton lasers (plasmonic lasers). While applications in spectroscopy and information technology would greatly benefit from the facile and active tuning of the output wavelength from such devices, this topic remains underexplored. Here, we demonstrate optically controlled switching between predefined wavelengths within a plasmonic microlaser. After fabricating Fabry-Pérot plasmonic cavities that consist of two curved block reflectors on an ultrasmooth flat Ag surface, we deposit a thin film of CdSe/CdxZn1-xS/ZnS colloidal core/shell/shell nanoplatelets (NPLs) as the gain medium. Our cavity geometry allows the spatial and energetic separation of transverse modes. By spatially modulating the gain profile within this device, we demonstrate active selection and switching between four transverse modes within a single plasmonic laser. The fast buildup and decay of the plasmonic modes promises picosecond switching times, given sufficiently rapid changes in the structured illumination.
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Affiliation(s)
- Robert C Keitel
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - Marianne Aellen
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - Boris le Feber
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - Aurelio A Rossinelli
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - Stefan A Meyer
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - Jian Cui
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
- Helmholtz Pioneer Campus, Helmholtz Zentrum München, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - David J Norris
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland
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19
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Geiregat P, Rodá C, Tanghe I, Singh S, Di Giacomo A, Lebrun D, Grimaldi G, Maes J, Van Thourhout D, Moreels I, Houtepen AJ, Hens Z. Localization-limited exciton oscillator strength in colloidal CdSe nanoplatelets revealed by the optically induced stark effect. LIGHT, SCIENCE & APPLICATIONS 2021; 10:112. [PMID: 34054127 PMCID: PMC8165098 DOI: 10.1038/s41377-021-00548-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 04/21/2021] [Accepted: 04/28/2021] [Indexed: 05/04/2023]
Abstract
2D materials are considered for applications that require strong light-matter interaction because of the apparently giant oscillator strength of the exciton transitions in the absorbance spectrum. Nevertheless, the effective oscillator strengths of these transitions have been scarcely reported, nor is there a consistent interpretation of the obtained values. Here, we analyse the transition dipole moment and the ensuing oscillator strength of the exciton transition in 2D CdSe nanoplatelets by means of the optically induced Stark effect (OSE). Intriguingly, we find that the exciton absorption line reacts to a high intensity optical field as a transition with an oscillator strength FStark that is 50 times smaller than expected based on the linear absorption coefficient. We propose that the pronounced exciton absorption line should be seen as the sum of multiple, low oscillator strength transitions, rather than a single high oscillator strength one, a feat we assign to strong exciton center-of-mass localization. Within the quantum mechanical description of excitons, this 50-fold difference between both oscillator strengths corresponds to the ratio between the coherence area of the exciton's center of mass and the total area, which yields a coherence area of a mere 6.1 nm2. Since we find that the coherence area increases with reducing temperature, we conclude that thermal effects, related to lattice vibrations, contribute to exciton localization. In further support of this localization model, we show that FStark is independent of the nanoplatelet area, correctly predicts the radiative lifetime, and lines up for strongly confined quantum dot systems.
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Affiliation(s)
- Pieter Geiregat
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium.
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium.
| | - Carmelita Rodá
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
| | - Ivo Tanghe
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
- Photonics Research Group, Ghent University, Gent, Belgium
| | - Shalini Singh
- Department of Chemical Sciences and Bernal Institute, University of Limerick, Limerick, Ireland
| | - Alessio Di Giacomo
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
| | - Delphine Lebrun
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
| | - Gianluca Grimaldi
- Center for Nanophotonics, NWO-Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands
| | - Jorick Maes
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
| | - Dries Van Thourhout
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
- Photonics Research Group, Ghent University, Gent, Belgium
| | - Iwan Moreels
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
| | - Arjan J Houtepen
- Opto-Electronic Materials Section, Department of Chemical Engineering, Delft University, Delft, The Netherlands
| | - Zeger Hens
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent, Belgium
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20
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Weiss EA. Influence of Shape Anisotropy on the Emission of Low-Dimensional Semiconductors. ACS NANO 2021; 15:3568-3577. [PMID: 33691063 DOI: 10.1021/acsnano.1c01337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The emergence of precise and scalable synthetic methods for producing anisotropic semiconductor nanostructures provides opportunities to tune the photophysical properties of these particles beyond their band gaps, and to incorporate them into higher-order structures with macroscopic anisotropic responses to electric and optical fields. This perspective article discusses some of these opportunities in the context of colloidal semiconductor nanoplatelets, with a focus on the influence of confinement anisotropy on processes that dictate the emission.
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Affiliation(s)
- Emily A Weiss
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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21
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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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22
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Di Giacomo A, Rodà C, Khan AH, Moreels I. Colloidal Synthesis of Laterally Confined Blue-Emitting 3.5 Monolayer CdSe Nanoplatelets. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2020; 32:9260-9267. [PMID: 33191978 PMCID: PMC7659369 DOI: 10.1021/acs.chemmater.0c03066] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/09/2020] [Indexed: 05/03/2023]
Abstract
The typical synthesis protocol for blue-emitting CdSe nanoplatelets (NPLs) yields particles with extended lateral dimensions and large surface areas, resulting in NPLs with poor photoluminescence quantum efficiency. We have developed a synthesis protocol that achieves an improved control over the lateral size, by exploiting a series of long-chained carboxylate precursors that vary from cadmium octanoate (C8) to cadmium stearate (C18). The length of this metallic precursor is key to tune the width and aspect ratio of the final NPLs, and for the shorter chain lengths, the synthesis yield is improved. NPLs prepared with our procedure possess significantly enhanced photoluminescence quantum efficiencies, up to 30%. This is likely due to their reduced lateral dimensions, which also grant them good colloidal stability. As the NPL width can be tuned below the bulk exciton Bohr radius, the band edge blue-shifts, and we constructed a sizing curve relating the NPL absorption position and width. Further adjusting the synthesis protocol, we were able to obtain even thinner NPLs, emitting in the near-UV region, with a band-edge quantum efficiency of up to 11%. Results pave the way to stable and efficient light sources for applications such as blue and UV light-emitting devices and lasers.
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23
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Erdem O, Foroutan S, Gheshlaghi N, Guzelturk B, Altintas Y, Demir HV. Thickness-Tunable Self-Assembled Colloidal Nanoplatelet Films Enable Ultrathin Optical Gain Media. NANO LETTERS 2020; 20:6459-6465. [PMID: 32787166 DOI: 10.1021/acs.nanolett.0c02153] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We propose and demonstrate construction of highly uniform, multilayered superstructures of CdSe/CdZnS core/shell colloidal nanoplatelets (NPLs) using liquid interface self-assembly. These NPLs are sequentially deposited onto a solid substrate into slabs having monolayer-precise thickness across tens of cm2 areas. Because of near-unity surface coverage and excellent uniformity, amplified spontaneous emission (ASE) is observed from an uncharacteristically thin film having 6 NPL layers, corresponding to a mere 42 nm thickness. Furthermore, systematic studies on optical gain of these NPL superstructures having thicknesses ranging from 6 to 15 layers revealed the gradual reduction in gain threshold with increasing number of layers, along with a continuous spectral shift of the ASE peak (∼18 nm). These observations can be explained by the change in the optical mode confinement factor with the NPL waveguide thickness and propagation wavelength. This bottom-up construction technique for thickness-tunable, three-dimensional NPL superstructures can be used for large-area device fabrication.
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Affiliation(s)
- Onur Erdem
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey
| | - Sina Foroutan
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey
| | - Negar Gheshlaghi
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey
| | - Burak Guzelturk
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Yemliha Altintas
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey
- Department of Materials Science and Nanotechnology, Abdullah Gul University, Kayseri 38080, Turkey
| | - Hilmi Volkan Demir
- Department of Electrical and Electronics Engineering, Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey
- LUMINOUS! Centre of Excellence for Semiconductor Lighting and Displays, The Photonics Institute, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
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24
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Benjamin E, Yallapragada VJ, Amgar D, Yang G, Tenne R, Oron D. Temperature Dependence of Excitonic and Biexcitonic Decay Rates in Colloidal Nanoplatelets by Time-Gated Photon Correlation. J Phys Chem Lett 2020; 11:6513-6518. [PMID: 32693606 PMCID: PMC7458474 DOI: 10.1021/acs.jpclett.0c01628] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/22/2020] [Indexed: 05/20/2023]
Abstract
Excitons in colloidal semiconductor nanoplatelets (NPLs) are weakly confined in the lateral dimensions. This results in significantly smaller Auger rates and, consequently, larger biexciton quantum yields, when compared to spherical quantum dots (QDs). Here we report a study of the temperature dependence of the biexciton Auger rate in individual CdSe/CdS core-shell NPLs, through the measurement of time-gated second-order photon correlations in the photoluminescence. We also utilize this method to directly estimate the single-exciton radiative rate. We find that whereas the radiative lifetime of NPLs increases with temperature, the Auger lifetime is almost temperature-independent. Our findings suggest that Auger recombination in NPLs is qualitatively similar to that of semiconductor quantum wells. Time-gated photon correlation measurements offer the unique ability to study multiphoton emission events, while excluding effects of competing fast processes, and can provide significant insight into the photophysics of a variety of nanocrystal multiphoton emitters.
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Li Q, He S, Lian T. How Exciton and Single Carriers Block the Excitonic Transition in Two-Dimensional Cadmium Chalcogenide Nanoplatelets. NANO LETTERS 2020; 20:6162-6169. [PMID: 32697589 DOI: 10.1021/acs.nanolett.0c02461] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Cadmium chalcogenide nanoplatelets (NPLs) possess unique properties and have shown great potential in lasing, light-emitting diodes, and photocatalytic applications. However, the exact natures of the band-edge exciton and single carrier (electron and hole) states remain unclear, even though they affect the key properties and applications of these materials. Herein, we study the contribution of a single carrier (electron or hole) state to phase space filling of single exciton states of cadmium chalcogenide NPLs. With pump fluence dependent TA study and selective electron removal, we determine that a single electron and hole states contribute 85% and 12%, respectively, to the blocking of the excitonic transition in CdSe/ZnS core/shell NPLs. These observations can be rationalized by a model of band-edge exciton and single carrier states of 2D NPLs that differs significantly from that of quantum dots.
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Affiliation(s)
- Qiuyang Li
- Department of Chemistry, Emory University, 1515 Dickey Drive, NE, Atlanta, Georgia 30322, United States
| | - Sheng He
- Department of Chemistry, Emory University, 1515 Dickey Drive, NE, Atlanta, Georgia 30322, United States
| | - Tianquan Lian
- Department of Chemistry, Emory University, 1515 Dickey Drive, NE, Atlanta, Georgia 30322, United States
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Antolinez FV, Rabouw FT, Rossinelli AA, Cui J, Norris DJ. Observation of Electron Shakeup in CdSe/CdS Core/Shell Nanoplatelets. NANO LETTERS 2019; 19:8495-8502. [PMID: 31686517 DOI: 10.1021/acs.nanolett.9b02856] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
While ensembles of CdSe nanoplatelets (NPLs) show remarkably narrow photoluminescence line widths at room temperature, adding a CdS shell to increase their fluorescence efficiency and photostability causes line width broadening. Moreover, ensemble emission spectra of CdSe/CdS core/shell NPLs become strongly asymmetric at cryogenic temperatures. If the origin of these effects were understood, this could potentially lead to stable core/shell NPLs with narrower emission, which would be advantageous for applications. To move in this direction, we report time-resolved emission spectra of individual CdSe/CdS core/shell NPLs at 4 K. We observe surprisingly complex emission spectra that contain multiple spectrally narrow emission features that change during the experiment. With machine-learning algorithms, we can extract characteristic peak energy differences in these spectra. We show that they are consistent with electron "shakeup lines" from negatively charged trions. In this process, an electron-hole pair recombines radiatively but gives part of its energy to the remaining electron by exciting it into a higher single-electron level. This "shakeup" mechanism is enabled in our NPLs due to strong exciton binding and weak lateral confinement of the charge carriers. Time-resolved single-photon-counting measurements and numerical calculations suggest that spectral jumps in the emission features originate from fluctuations in the confinement potential caused by microscopic structural changes on the NPL surface (e.g., due to mobile surface charges). Our results provide valuable insights into line width broadening mechanisms in colloidal NPLs.
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Affiliation(s)
- Felipe V Antolinez
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering , ETH Zurich , 8092 Zurich , Switzerland
| | - Freddy T Rabouw
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering , ETH Zurich , 8092 Zurich , Switzerland
| | - Aurelio A Rossinelli
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering , ETH Zurich , 8092 Zurich , Switzerland
| | - Jian Cui
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering , ETH Zurich , 8092 Zurich , Switzerland
| | - David J Norris
- Optical Materials Engineering Laboratory, Department of Mechanical and Process Engineering , ETH Zurich , 8092 Zurich , Switzerland
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Li Q, Lian T. Exciton Spatial Coherence and Optical Gain in Colloidal Two-Dimensional Cadmium Chalcogenide Nanoplatelets. Acc Chem Res 2019; 52:2684-2693. [PMID: 31433164 DOI: 10.1021/acs.accounts.9b00252] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Two-dimensional (2D) cadmium chalcogenide (CdX, X = Se, S, Te) colloidal nanoplatelets (NPLs) make up an emerging class of quantum well materials that exhibit many unique properties including uniform quantum confinement, narrow thickness distribution, large exciton binding energy, giant oscillator strength, long Auger lifetime, and high photoluminescence quantum yield. These properties have led to their great performances in optoelectrical applications such as lasing materials with a low threshold and large gain coefficient. Many of these properties are determined by the structure and dynamics of band-edge excitons in these 2D materials. Motivated by fundamental understanding of both 2D nanomaterials and their applications, the properties of 2D excitons have received intense recent interest. This Account provides an overview of three key properties of 2D excitons: how big is the 2D exciton (i.e., exciton center-of-mass coherent area); how the exciton moves in 2D NPLs (i.e., exciton in-plane transport mechanism); how multiple excitons interact with each other (i.e., biexciton Auger recombination); and their effects on the optical gain mechanism and threshold of colloidal NPLs. After a brief introduction in Section 1, the current understandings of 2D electronic structures of cadmium chalcogenide NPLs, and type-I CdSe/CdS and type-II CdSe/CdTe core/crown NPL heterostructures are summarized in Section 2. Section 3 discusses the direct measurement of exciton center-of-mass coherent area in 2D CdSe NPLs, its dependence on NPL parameters (thickness, lateral area, dielectric environment, and temperature), and the resulting giant oscillator strength transition (GOST) effect in 2D NPLs. 2D exciton diffusive in-plane transport in CdX NPLs and the comparison of exciton transport mechanisms in 2D NPLs and 1D nanorods are reviewed in Section 4. How Auger recombination lifetime depends on nanocrystal dimensions in NPLs, quantum dots, and nanorods is discussed in Section 5. The lateral area and thickness dependent Auger recombination rates of NPLs are shown to be well described by a model that accounts for the different dependence of the Auger recombination rates on the quantum confined and nonconfined dimensions. It is shown that Auger recombination rates do not follow the "universal volume scaling" law in 1D and 2D nanocrystals. Section 6 describes optical gain mechanisms in CdSe NPLs and the dependence of optical gain threshold on NPL lateral size, optical density, and temperature. The differences of optical gain properties in 0D-2D and the bulk materials are also discussed, highlighting the unique gain properties of 2D NPLs. At last, the Account ends with a summary and perspective of key remaining challenges in this field in Section 7.
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Affiliation(s)
- Qiuyang Li
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
| | - Tianquan Lian
- Department of Chemistry, Emory University, 1515 Dickey Drive Northeast, Atlanta, Georgia 30322, United States
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Li Q, Yang Y, Que W, Lian T. Size- and Morphology-Dependent Auger Recombination in CsPbBr 3 Perovskite Two-Dimensional Nanoplatelets and One-Dimensional Nanorods. NANO LETTERS 2019; 19:5620-5627. [PMID: 31244208 DOI: 10.1021/acs.nanolett.9b02145] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (NCs), including zero-dimensional (0D) quantum dots (QDs), one-dimensional (1D) nanorods (NRs), and two-dimensional (2D) nanoplatelets (NPLs), have shown promising performances in light-emitting diode (LED) and lasing applications. However, Auger recombination, one of the key processes that limit their performance, remains poorly understood in CsPbX3 2D NPLs and 1D NRs. We show that the biexciton Auger lifetimes of CsPbBr3 NPLs (NRs) scale linearly with the NPL lateral area (NR length) and deviates from the "universal volume scale law" that has been observed for QDs. These results are consistent with a model in which the Auger recombination rate for 1D NRs and 2D NPLs is a product of binary collision frequency in the nonquantum confined dimension and Auger probability per collision. Comparisons of Auger recombination in CsPbBr3 NCs of different dimensionalities and similar band gaps suggest that Auger probability increases in NCs with a higher number of confined dimensions. Compared to CdSe and PbSe NCs with the same dimensionalities and similar sizes, Auger recombination rates in 0D-2D CsPbBr3 NCs are over 10-fold faster. Fast Auger recombination in CsPbBr3 NCs shows their potentials for Auger-assisted up-conversion and single photon source, while suppressing Auger recombination may further enhance their performances in LED and lasing applications.
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Affiliation(s)
- Qiuyang Li
- Department of Chemistry , Emory University , 1515 Dickey Drive, NE , Atlanta , Georgia 30322 , United States
| | - Yawei Yang
- Department of Chemistry , Emory University , 1515 Dickey Drive, NE , Atlanta , Georgia 30322 , United States
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, International Center for Dielectric Research, and Shaanxi Engineering Research Center of Advanced Energy Materials and Devices, School of Electronic and Information Engineering , Xi'an Jiaotong University , Xi'an 710049 , Shaanxi People's Republic of China
| | - Wenxiu Que
- Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, International Center for Dielectric Research, and Shaanxi Engineering Research Center of Advanced Energy Materials and Devices, School of Electronic and Information Engineering , Xi'an Jiaotong University , Xi'an 710049 , Shaanxi People's Republic of China
| | - Tianquan Lian
- Department of Chemistry , Emory University , 1515 Dickey Drive, NE , Atlanta , Georgia 30322 , United States
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