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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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2
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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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3
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Li F, Klepzig LF, Keppler N, Behrens P, Bigall NC, Menzel H, Lauth J. Layer-by-Layer Deposition of 2D CdSe/CdS Nanoplatelets and Polymers for Photoluminescent Composite Materials. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:11149-11159. [PMID: 36067458 DOI: 10.1021/acs.langmuir.2c00455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Two-dimensional (2D) semiconductor nanoplatelets (NPLs) are strongly photoluminescent materials with interesting properties for optoelectronics. Especially their narrow photoluminescence paired with a high quantum yield is promising for light emission applications with high color purity. However, retaining these features in solid-state thin films together with an efficient encapsulation of the NPLs is a challenge, especially when trying to achieve high-quality films with a defined optical density and low surface roughness. Here, we show photoluminescent polymer-encapsulated inorganic-organic nanocomposite coatings of 2D CdSe/CdS NPLs in poly(diallyldimethylammonium chloride) (PDDA) and poly(ethylenimine) (PEI), which are prepared by sequential layer-by-layer (LbL) deposition. The electrostatic interaction between the positively charged polyelectrolytes and aqueous phase-transferred NPLs with negatively charged surface ligands is used as a driving force to achieve self-assembled nanocomposite coatings with a well-controlled layer thickness and surface roughness. Increasing the repulsive forces between the NPLs by increasing the pH value of the dispersion leads to the formation of nanocomposites with all NPLs arranging flat on the substrate, while the surface roughness of the 165 nm (50 bilayers) thick coating decreases to Ra = 14 nm. The photoluminescence properties of the nanocomposites are determined by the atomic layer thickness of the NPLs and the 11-mercaptoundecanoic acid ligand used for their phase transfer. Both the full width at half-maximum (20.5 nm) and the position (548 nm) of the nanocomposite photoluminescence are retained in comparison to the colloidal CdSe/CdS NPLs in aqueous dispersion, while the measured photoluminescence quantum yield of 5% is competitive to state-of-the-art nanomaterial coatings. Our approach yields stable polymer-encapsulated CdSe/CdS NPLs in smooth coatings with controllable film thickness, rendering the LbL deposition technique a powerful tool for the fabrication of solid-state photoluminescent nanocomposites.
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Affiliation(s)
- Fuzhao Li
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering─Innovation Across Disciplines), 30167 Hannover, Germany
- Institute for Technical Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany
| | - Lars F Klepzig
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering─Innovation Across Disciplines), 30167 Hannover, Germany
- Institute of Physical Chemistry and Electrochemistry, Leibniz Universität Hannover, Callinstraße 3A, 30167 Hannover, Germany
| | - Nils Keppler
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering─Innovation Across Disciplines), 30167 Hannover, Germany
- Institute of Inorganic Chemistry, Leibniz Universität Hannover, Callinstraße 9, 30167 Hannover, Germany
| | - Peter Behrens
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering─Innovation Across Disciplines), 30167 Hannover, Germany
- Institute of Inorganic Chemistry, Leibniz Universität Hannover, Callinstraße 9, 30167 Hannover, Germany
- Laboratory of Nano and Quantum Engineering, Schneiderberg 39, 30167 Hannover, Germany
| | - Nadja C Bigall
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering─Innovation Across Disciplines), 30167 Hannover, Germany
- Institute of Physical Chemistry and Electrochemistry, Leibniz Universität Hannover, Callinstraße 3A, 30167 Hannover, Germany
- Laboratory of Nano and Quantum Engineering, Schneiderberg 39, 30167 Hannover, Germany
| | - Henning Menzel
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering─Innovation Across Disciplines), 30167 Hannover, Germany
- Institute for Technical Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany
| | - Jannika Lauth
- Cluster of Excellence PhoenixD (Photonics, Optics, and Engineering─Innovation Across Disciplines), 30167 Hannover, Germany
- Institute of Physical Chemistry and Electrochemistry, Leibniz Universität Hannover, Callinstraße 3A, 30167 Hannover, Germany
- Laboratory of Nano and Quantum Engineering, Schneiderberg 39, 30167 Hannover, Germany
- Institute of Physical and Theoretical Chemistry, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany
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4
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Duan R, Zhang Z, Xiao L, Zhao X, Thung YT, Ding L, Liu Z, Yang J, Ta VD, Sun H. Ultralow-Threshold and High-Quality Whispering-Gallery-Mode Lasing from Colloidal Core/Hybrid-Shell Quantum Wells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2108884. [PMID: 34997633 DOI: 10.1002/adma.202108884] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 12/22/2021] [Indexed: 06/14/2023]
Abstract
The realization of efficient on-chip microlasers with scalable fabrication, ultralow threshold, and stable single-frequency operation is always desired for a wide range of miniaturized photonic systems. Herein, an effective way to fabricate nanostructures- whispering-gallery-mode (WGM) lasers by drop-casting CdSe/CdS@Cd1- x Znx S core/buffer-shell@graded-shell nanoplatelets (NPLs) dispersion onto silica microspheres is presented. Benefiting from the excellent gain properties from the interface engineered core/hybrid shell NPLs and high-quality factor WGM resonator from excellent optical field confinement, the proposed room-temperature NPLs-WGM microlasers show a record-low lasing threshold of 3.26 µJ cm-2 under nanosecond laser pumping among all colloidal NPLs-based lasing demonstrations. The presence of sharp discrete transverse electric- and magnetic-mode spikes, the inversely proportional dependence of the free spectra range on microsphere sizes and the polarization anisotropy of laser output represent the first direct experimental evidence for NPLs-WGM lasing nature, which is verified theoretically by the computed electric-field distribution inside the microcavity. Remarkably, a stable single-mode lasing output with an ultralow lasing threshold of 3.84 µJ cm-2 is achieved by the Vernier effect through evanescent field coupling. The results highlight the significance of interface engineering on the optimization of gain properties of heterostructured nanomaterials and shed light on developing future miniaturized tunable coherent light sources.
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Affiliation(s)
- Rui Duan
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
- College of Physics and Optoelectronic Engineering, Harbin Engineering University, Harbin, 150001, China
| | - Zitong Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Lian Xiao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Xiaoxu Zhao
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Yi Tian Thung
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Lu Ding
- Institute of Materials Research and Engineering, A*STAR (Agency for Science Technology and Research), Singapore, 138634, Singapore
| | - Zheng Liu
- School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798, Singapore
- School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore
- CINTRA CNRS/NTU/THALES, UMI 3288, Singapore, 637553, Singapore
| | - Jun Yang
- Guangdong Provincial Key Laboratory of Information Photonics Technology, College of Information Engineering, Guangdong University of Technology, Guangzhou, 510006, China
| | - Van Duong Ta
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
- Department of Optical Devices, Le Quy Don Technical University, Hanoi, 100000, Vietnam
| | - Handong Sun
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
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5
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Chehaibou B, Izquierdo E, Chu A, Abadie C, Cavallo M, Khalili A, Dang TH, Gréboval C, Xu XZ, Ithurria S, Vincent G, Gallas B, Mugny G, Arnaud A, Lhuillier E, Delerue C. The complex optical index of PbS nanocrystal thin films and their use for short wave infrared sensor design. NANOSCALE 2022; 14:2711-2721. [PMID: 35112698 DOI: 10.1039/d1nr07770h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
As nanocrystals (NCs) gain maturity, they become central building blocks for optoelectronics in devices such as solar cells and, more recently, infrared focal plane arrays. Now that the proof of concept of these devices has been established, their optimization requires a deeper understanding of their electronic and optical features to engineer their optoelectronic properties accurately. Though PbS NCs have been extensively investigated, the complex optical index of PbS NC thin films remains mostly unknown. Some previous works have unveiled the optical index for this type of material optimized for solar cells (excitonic peak at 940 nm), but longer wavelengths remain scarce and surface chemistry effects, which are known to be of central importance for layer doping, are simply unexplored. Here, we conduct a systematic investigation of the complex optical index of PbS NC thin films using broadband spectrally resolved ellipsometry. The obtained results are then compared with simulations combining tight-binding (TB) modeling at the NC level and the Bruggeman model to expand the results to the film scale. While TB calculation gives the NC optical indices, we extract the key NC film parameters such as the NC volume fraction and ligand indices by fitting the Bruggeman formula to ellipsometry measurements. We also bring evidence that this joint modeling method can be conducted without the need for ellipsometry data while preserving the main feature of the experimental results. Finally, the unveiled optical indices are used to model the absorption of short-wave infrared diode stacks based on PbS NCs and are relevant for state-of-the-art devices. Our electromagnetic modeling shows that the absorption within the contact is now a major limitation of the current device operated at the telecom wavelength.
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Affiliation(s)
- Bilal Chehaibou
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia, UMR 8520 - IEMN, F-59000 Lille, France.
| | - Eva Izquierdo
- Sorbonne Université, CNRS - UMR 7588, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
| | - Audrey Chu
- Sorbonne Université, CNRS - UMR 7588, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
| | - Claire Abadie
- ONERA - The French Aerospace Lab, 6, chemin de la Vauve aux Granges, BP 80100, 91123 Palaiseau, France
| | - Mariarosa Cavallo
- Sorbonne Université, CNRS - UMR 7588, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
| | - Adrien Khalili
- Sorbonne Université, CNRS - UMR 7588, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
| | - Tung Huu Dang
- Sorbonne Université, CNRS - UMR 7588, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
| | - Charlie Gréboval
- Sorbonne Université, CNRS - UMR 7588, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
| | - Xiang Zhen Xu
- 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
| | - 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
| | - Grégory Vincent
- ONERA - The French Aerospace Lab, 6, chemin de la Vauve aux Granges, BP 80100, 91123 Palaiseau, France
| | - Bruno Gallas
- Sorbonne Université, CNRS - UMR 7588, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
| | - Gabriel Mugny
- STMicroelectronics, 12 rue Jules Horowitz, 38019 Grenoble, France
| | - Arthur Arnaud
- STMicroelectronics, 850 rue J. Monnet, 38926 Crolles, France
| | - Emmanuel Lhuillier
- Sorbonne Université, CNRS - UMR 7588, Institut des NanoSciences de Paris, INSP, F-75005 Paris, France.
| | - Christophe Delerue
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, Junia, UMR 8520 - IEMN, F-59000 Lille, France.
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6
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Tanghe I, Butkus J, Chen K, Tamming RR, Singh S, Ussembayev Y, Neyts K, van Thourhout D, Hodgkiss JM, Geiregat P. Broadband Optical Phase Modulation by Colloidal CdSe Quantum Wells. NANO LETTERS 2022; 22:58-64. [PMID: 34965360 DOI: 10.1021/acs.nanolett.1c03181] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Two-dimensional (2D) semiconductors are primed to realize a variety of photonic devices that rely on the transient properties of photogenerated charges, yet little is known on the change of the refractive index. The associated optical phase changes can be beneficial or undesired depending on the application, but require proper quantification. Measuring optical phase modulation of dilute 2D materials is, however, not trivial with common methods. Here, we demonstrate that 2D colloidal CdSe quantum wells, a useful model system, can modulate the phase of light across a broad spectrum using a femtosecond interferometry method. Next, we develop a toolbox to calculate the time-dependent refractive index of colloidal 2D materials from widely available transient absorption experiments using a modified effective medium algorithm. Our results show that the excitonic features of 2D materials result in broadband, ultrafast, and sizable phase modulation, even extending to the near infrared because of intraband transitions.
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Affiliation(s)
- Ivo Tanghe
- Photonics Research Group, Ghent University, Gent 9000, Belgium
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent 9000, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent 9000, Belgium
| | - Justinas Butkus
- School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6012, New Zealand
- The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin 9016, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6012, New Zealand
| | - Kai Chen
- The Dodd-Walls Centre for Photonic and Quantum Technologies, Dunedin 9016, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6012, New Zealand
- Robinson Research Institute, Faculty of Engineering, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Ronnie R Tamming
- School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6012, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6012, New Zealand
- Robinson Research Institute, Faculty of Engineering, Victoria University of Wellington, Wellington 6012, New Zealand
| | - Shalini Singh
- Department of Chemical Sciences and Bernal Institute, University of Limerick, Limerick V94 T9PX, Ireland
| | - Yera Ussembayev
- Liquid Crystals and Photonics Research Group, Department of Electronics and Information Systems, Ghent University, Gent 9000, Belgium
| | - Kristiaan Neyts
- Liquid Crystals and Photonics Research Group, Department of Electronics and Information Systems, Ghent University, Gent 9000, Belgium
| | - Dries van Thourhout
- Photonics Research Group, Ghent University, Gent 9000, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent 9000, Belgium
| | - Justin M Hodgkiss
- School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6012, New Zealand
- MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6012, New Zealand
| | - Pieter Geiregat
- Physics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Gent 9000, Belgium
- Center for Nano and Biophotonics, Ghent University, Gent 9000, Belgium
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7
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Clark PCJ, Lewis NK, Ke JCR, Ahumada-Lazo R, Chen Q, Neo DCJ, Gaulding EA, Pach GF, Pis I, Silly MG, Flavell WR. Surface band bending and carrier dynamics in colloidal quantum dot solids. NANOSCALE 2021; 13:17793-17806. [PMID: 34668501 DOI: 10.1039/d1nr05436h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Band bending in colloidal quantum dot (CQD) solids has become important in driving charge carriers through devices. This is typically a result of band alignments at junctions in the device. Whether band bending is intrinsic to CQD solids, i.e. is band bending present at the surface-vacuum interface, has previously been unanswered. Here we use photoemission surface photovoltage measurements to show that depletion regions are present at the surface of n and p-type CQD solids with various ligand treatments (EDT, MPA, PbI2, MAI/PbI2). Using laser-pump photoemission-probe time-resolved measurements, we show that the timescale of carrier dynamics in the surface of CQD solids can vary over at least 6 orders of magnitude, with the fastest dynamics on the order of microseconds in PbS-MAI/PbI2 solids and on the order of seconds for PbS-MPA and PbS-PbI2. By investigating the surface chemistry of the solids, we find a correlation between the carrier dynamics timescales and the presence of oxygen contaminants, which we suggest are responsible for the slower dynamics due to deep trap formation.
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Affiliation(s)
- Pip C J Clark
- Department of Physics and Astronomy and the Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK.
| | - Nathan K Lewis
- Department of Physics and Astronomy and the Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK.
| | - Jack Chun-Ren Ke
- Department of Physics and Astronomy and the Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK.
| | - Ruben Ahumada-Lazo
- Department of Physics and Astronomy and the Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK.
| | - Qian Chen
- Department of Materials, The University of Manchester, Manchester M13 9PL, UK
| | - Darren C J Neo
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, USA
| | | | - Gregory F Pach
- National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Igor Pis
- Laboratorio TASC, IOM CNR, S.S. 14 km 163.5, 34149 Basovizza, Trieste, Italy
- Elettra-Sincrotrone Trieste S.C.p.A., S. S. 14 Km 163.5, 34149 Basovizza, Trieste, Italy
| | - Mathieu G Silly
- Synchrotron SOLEIL, BP 48, Saint-Aubin, F91192 Gif sur Yvette CEDEX, France
| | - Wendy R Flavell
- Department of Physics and Astronomy and the Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK.
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8
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Zhang Z, Thung YT, Wang L, Chen X, Ding L, Fan W, Sun H. Surface Depletion Effects in Bromide-Ligated Colloidal Cadmium Selenide Nanoplatelets: Toward Efficient Emission at High Temperature. J Phys Chem Lett 2021; 12:9086-9093. [PMID: 34519516 DOI: 10.1021/acs.jpclett.1c02623] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The colloidal semiconductor nanoplatelet (NPL) with broad ligand-semiconductor interface is an ideal system for surface science investigation, but the study regarding depletion effects in NPLs remains lacking. Herein we explore such effects in colloidal CdSe NPLs through Br ligation. Apart from improved brightness and red-shifted optical features, we also experimentally observed abnormal negative thermal quenching phenomena in bromide-ligated CdSe NPLs over 200 K under a cryogenic environment and up to 383 K under an ambient environment, which was absent in pristine NPLs. We speculate that the surface depletion effect shall account for these anomalous phenomena due to the susceptibility of the surface depletion region on photoexcited carrier concentration and surface condition. The existence of the depletion layer in NPLs is also validated quantitatively with k·p simulation. Besides offering an alternative explanation on the red-shifted optical properties of CdSe NPLs by Br-ligation, our findings pave the new route toward solution-processed NPLs-based optoelectronics with boosted thermal resistance.
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Affiliation(s)
- Zitong Zhang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Yi Tian Thung
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Lin Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
- Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, 149 Yanchang Road, Shanghai 200072, China
| | - Xiaoxuan Chen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
| | - Lu Ding
- Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Singapore 138634, Singapore
| | - Weijun Fan
- School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Handong Sun
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
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Inbanathan FPN, Kumar P, Dasari K, Katiyar RS, Chen J, Jadwisienczak WM. Ellipsometry Study of CdSe Thin Films Deposited by PLD on ITO Coated Glass Substrates. MATERIALS 2021; 14:ma14123307. [PMID: 34203798 PMCID: PMC8232614 DOI: 10.3390/ma14123307] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 06/07/2021] [Accepted: 06/10/2021] [Indexed: 11/17/2022]
Abstract
Cadmium selenide (CdSe) thin films were deposited on indium tin oxide (ITO) coated glass substrates using pulsed laser deposition (PLD) technique under different growth temperatures. Samples were investigated for their structural, morphological, and optical properties through X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-Vis-NIR spectroscopy. AFM analysis revealed that the surface roughness of the as-grown CdSe thin films increased with the increase in deposition temperature. The optical constants and film thickness were obtained from spectroscopic ellipsometry analysis and are discussed in detail. The optical band gap of the as-grown CdSe thin films, calculated from the Tauc plot analysis, matched with the ellipsometry measurements, with a band gap of ~1.71 eV for a growth temperature range of 150 °C to 400 °C. The CdSe thin films were found to have a refractive index of ~3.0 and extinction coefficient of ~1.0, making it a suitable candidate for photovoltaics.
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Affiliation(s)
- Flavia P. N. Inbanathan
- School of Electrical Engineering and Computer Science, Ohio University, Athens, OH 45701, USA;
- Correspondence: (F.P.N.I.); (K.D.)
| | - Pawan Kumar
- Department of Physics, Gurukula Kangri Vishwavidyalaya, Haridwar, Uttarakand 249404, India;
| | - Kiran Dasari
- Department of Physics, University of Puerto Rico, San Juan, PR 00936, USA;
- Correspondence: (F.P.N.I.); (K.D.)
| | - Ram S. Katiyar
- Department of Physics, University of Puerto Rico, San Juan, PR 00936, USA;
| | - Jixin Chen
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, USA;
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