1
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Chen GH, Chen PH, Lin CT, Jang TW, Yang P, Chen HS. Enhanced Photostability of Core/Shell Quantum Dots under Intense Blue Light Irradiation through Positive Photoaging Mechanism. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37927092 DOI: 10.1021/acsami.3c13236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
Photostability of semiconductor core/shell quantum dots (QDs) has historically been perceived as intricate and unpredictable. Notably, the long-term luminescence stability of QDs under light exposure does not seem to consistently correspond with their characteristics in the absence of light. In this study, we propose a positive photoaging mechanism of QDs, integrating both ligand/shell-induced photobrightening and surface photo-oxidation, to deal with the photostability nuances. When QDs are subjected to higher energy light, their photobrightening and photodarkening conjointly determine the photostability. Enhanced photostability may not be simply attributed to a thicker shell or the presence of ligands. When adjusted with an optimal shell thickness and supplemented with negatively charged ligands, QDs exhibit enhanced photostability in both solvents and polymers.
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Affiliation(s)
- Guan-Hong Chen
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Po-Hsun Chen
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Chen-Te Lin
- Ph.D. Program in Prospective Functional Materials Industry, College of Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Tyng-Woei Jang
- Ph.D. Program in Prospective Functional Materials Industry, College of Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Ping Yang
- School of Material Science and Engineering, University of Jinan, Jinan 250022, P. R. China
| | - Hsueh-Shih Chen
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
- College of Semiconductor Research, National Tsing Hua University, Hsinchu 30013, Taiwan
- Department of Chemical Engineering & Materials Science, College of Engineering, Yuan Ze University, Taoyuan 32003, Taiwan
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2
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Zhu D, Bahmani Jalali H, Saleh G, Di Stasio F, Prato M, Polykarpou N, Othonos A, Christodoulou S, Ivanov YP, Divitini G, Infante I, De Trizio L, Manna L. Boosting the Photoluminescence Efficiency of InAs Nanocrystals Synthesized with Aminoarsine via a ZnSe Thick-Shell Overgrowth. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2303621. [PMID: 37243572 DOI: 10.1002/adma.202303621] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 05/18/2023] [Indexed: 05/29/2023]
Abstract
InAs-based nanocrystals can enable restriction of hazardous substances (RoHS) compliant optoelectronic devices, but their photoluminescence efficiency needs improvement. We report an optimized synthesis of InAs@ZnSe core@shell nanocrystals allowing to tune the ZnSe shell thickness up to seven mono-layers (ML) and to boost the emission, reaching a quantum yield of ≈70% at ≈900 nm. It is demonstrated that a high quantum yield can be attained when the shell thickness is at least ≈3ML. Notably, the photoluminescence lifetimeshows only a minor variation as a function of shell thickness, whereas the Auger recombination time (a limiting aspect in technological applications when fast) slows down from 11 to 38 ps when increasing the shell thickness from 1.5 to 7MLs. Chemical and structural analyses evidence that InAs@ZnSe nanocrystals do not exhibit any strain at the core-shell interface, likely due to the formation of an InZnSe interlayer. This is supported by atomistic modeling, which indicates the interlayer as being composed of In, Zn, Se and cation vacancies, alike to the In2 ZnSe4 crystal structure. The simulations reveal an electronic structure consistent with that of type-I heterostructures, in which localized trap states can be passivated by a thick shell (>3ML) and excitons are confined in the core.
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Affiliation(s)
- Dongxu Zhu
- Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
| | - Houman Bahmani Jalali
- Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
- Photonic Nanomaterials, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
| | - Gabriele Saleh
- Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
| | - Francesco Di Stasio
- Photonic Nanomaterials, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
| | - Mirko Prato
- Materials Characterization, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
| | - Nefeli Polykarpou
- Inorganic Nanocrystals Laboratory, Department of Chemistry, University of Cyprus, Nicosia, 1678, Cyprus
| | - Andreas Othonos
- Laboratory of Ultrafast Science, Department of Physics, University of Cyprus, Nicosia, 1678, Cyprus
| | - Sotirios Christodoulou
- Inorganic Nanocrystals Laboratory, Department of Chemistry, University of Cyprus, Nicosia, 1678, Cyprus
| | - Yurii P Ivanov
- Electron Spectroscopy and Nanoscopy, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
| | - Giorgio Divitini
- Electron Spectroscopy and Nanoscopy, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
| | - Ivan Infante
- BCMaterials, Basque Center for Materials, Applications, and Nanostructures, UPV/EHU Science Park, Leioa, 48940, Spain
- Ikerbasque Basque Foundation for Science, Bilbao, 48009, Spain
| | - Luca De Trizio
- Chemistry Facility, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
| | - Liberato Manna
- Nanochemistry, Istituto Italiano di Tecnologia, Via Morego 30, Genova, 16163, Italy
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3
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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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4
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Neuhaus SJ, Marino E, Murray CB, Kagan CR. Frequency Stabilization and Optically Tunable Lasing in Colloidal Quantum Dot Superparticles. NANO LETTERS 2023; 23:645-651. [PMID: 36602545 DOI: 10.1021/acs.nanolett.2c04498] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Self-assembled superparticles composed of colloidal quantum dots establish microsphere cavities that support optically pumped lasing from whispering gallery modes. Here, we report on the time- and excitation fluence-dependent lasing properties of CdSe/CdS quantum dot superparticles. Spectra collected under constant photoexcitation reveal that the lasing modes are not temporally stable but instead blue-shift by more than 30 meV over 15 min. To counter this effect, we establish a high-fluence light-soaking protocol that reduces this blue-shift by more than an order of magnitude to 1.7 ± 0.5 meV, with champion superparticles displaying mode blue-shifts of <0.5 meV. Increasing the pump fluence allows for optically controlled, reversible, color-tunable red-to-green lasing. Combining these two paradigms suggests that quantum dot superparticles could serve in applications as low-cost, robust, solution-processable, tunable microlasers.
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Affiliation(s)
- Steven J Neuhaus
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania19104, United States
| | - Emanuele Marino
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania19104, United States
- Dipartimento di Fisica e Chimica, Università degli Studi di Palermo, Via Archirafi 36, 90123Palermo, Italy
| | - Christopher B Murray
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania19104, United States
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania19104, United States
| | - Cherie R Kagan
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania19104, United States
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania19104, United States
- Department of Electrical and System Engineering, University of Pennsylvania, Philadelphia, Pennsylvania19104, United States
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5
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Brumberg A, Watkins NE, Diroll BT, Schaller RD. Acceleration of Biexciton Radiative Recombination at Low Temperature in CdSe Nanoplatelets. NANO LETTERS 2022; 22:6997-7004. [PMID: 36018835 DOI: 10.1021/acs.nanolett.2c01791] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Colloidal semiconductor nanocrystals offer bandgap tunability, high photoluminescence quantum yield, and colloidal processing of benefit to optoelectronics, however rapid nonradiative Auger recombination (AR) deleteriously affects device efficiencies at elevated excitation intensities. AR is understood to transition from temperature-dependent behavior in bulk semiconductors to temperature-independent behavior in zero-dimensional quantum dots (QDs) as a result of discretized band structure that facilitates satisfaction of linear momentum conservation. For nanoplatelets (NPLs), two-dimensional morphology renders prediction of photophysical behaviors challenging. Here, we investigate and compare the temperature dependence of excited-stated lifetime and fluence-dependent emission of CdSe NPLs and QDs. For NPLs, upon temperature reduction, biexciton lifetime surprisingly decreases (even becoming shorter lived than trion emission) and emission intensity increases nearly linearly with fluence rather than saturating, consistent with dominance of radiative recombination rather than AR. CdSe NPLs thus differ fundamentally from core-only QDs and foster increased utility of photogenerated excitons and multiexcitons at low temperatures.
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Affiliation(s)
- Alexandra Brumberg
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - 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
| | - 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
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6
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Yang H, Li S, Zhang L, Xiang W, Zhang Y, Wang X, Xiao M, Cui Y, Zhang J. Observation of high-density multi-excitons in medium-size CdSe/CdZnS/ZnS colloidal quantum dots through transient spectroscopy and their optical gain properties. NANOSCALE 2022; 14:5369-5376. [PMID: 35311884 DOI: 10.1039/d2nr00761d] [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
Semiconductor quantum dots have extremely significant advantages in terms of optoelectronic devices. However, it is unfeasible to avoid the generation of charged exciton states during operation. Such states can change the radiation recombination rate and bring additional non-radiative Auger recombination channels. Herein, we synthesize high photoluminescence quantum yield medium-size CdSe/CdZnS/ZnS core/alloy shell/shell QDs. Their multiexciton spectra and dynamics were systematically studied by pump-power-dependent fluorescence blinking and time-correlated spectroscopy. The lifetimes of positively/negatively charged trions and biexcitons are estimated to be 0.74/6.1 and 0.16 ns, respectively. It demonstrated that the band-edge biexciton is influenced by the Coulomb interaction and Stark effect. The amplified spontaneous emission threshold is only 81 μJ cm-2 and can retain a long operation lifetime under continuous pumping. A vertical microcavity surface-emitting laser device is fabricated using these QDs. The coupling factor between the spontaneous emission and cavity mode is 0.81, which benefits the low stimulated emission threshold. This work provides a new perspective of the charged states in the multiexciton AR process in the QDs, implying a promising application prospect of such QDs as optical gain materials in "zero-threshold" laser fabrication.
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Affiliation(s)
- Hongyu Yang
- Advanced Photonic Center, School of Electronic science and Engineering, Southeast University, Nanjing 210096, China.
| | - Si Li
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, and School of Physics, Nanjing University, Nanjing 210093, China.
| | - Lei Zhang
- Advanced Photonic Center, School of Electronic science and Engineering, Southeast University, Nanjing 210096, China.
| | - Wenbin Xiang
- Advanced Photonic Center, School of Electronic science and Engineering, Southeast University, Nanjing 210096, China.
| | - Yi Zhang
- College of Energy and Electrical Engineering, Hohai University, Nanjing, 210098, China.
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, and School of Physics, Nanjing University, Nanjing 210093, China.
| | - Min Xiao
- National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, and School of Physics, Nanjing University, Nanjing 210093, China.
- University of Arkansas, Fayetteville, Arkansas 72701, USA
| | - Yiping Cui
- Advanced Photonic Center, School of Electronic science and Engineering, Southeast University, Nanjing 210096, China.
| | - Jiayu Zhang
- Advanced Photonic Center, School of Electronic science and Engineering, Southeast University, Nanjing 210096, China.
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7
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Sun H, Cavanaugh P, Jen-La Plante I, Ippen C, Bautista M, Ma R, Kelley DF. Biexciton and trion dynamics in InP/ZnSe/ZnS quantum dots. J Chem Phys 2022; 156:054703. [DOI: 10.1063/5.0082223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Haochen Sun
- Chemistry and Biochemistry, University of California Merced, 5200 North Lake Road, Merced, California 95343, USA
| | - Paul Cavanaugh
- Chemistry and Biochemistry, University of California Merced, 5200 North Lake Road, Merced, California 95343, USA
| | | | - Christian Ippen
- Nanosys, Inc., 233 S. Hillview Dr., Milpitas, California 95035, USA
| | - Maria Bautista
- Nanosys, Inc., 233 S. Hillview Dr., Milpitas, California 95035, USA
| | - Ruiqing Ma
- Nanosys, Inc., 233 S. Hillview Dr., Milpitas, California 95035, USA
| | - David F. Kelley
- Chemistry and Biochemistry, University of California Merced, 5200 North Lake Road, Merced, California 95343, USA
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8
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Cheng Y, Wan H, Liang T, Liu C, Wu M, Hong H, Liu K, Shen H. Continuously Graded Quantum Dots: Synthesis, Applications in Quantum Dot Light-Emitting Diodes, and Perspectives. J Phys Chem Lett 2021; 12:5967-5978. [PMID: 34160222 DOI: 10.1021/acs.jpclett.1c01554] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Colloidal quantum dot (QD) light-emitting diodes (QLEDs) hold the promise of next-generation displays and illumination owing to their excellent color saturation, high efficiency, and solution processability. For achieving high-performance light-emitting diodes (LEDs), engineering the fine compositions and structures of QDs is of paramount importance and attracts tremendous research interest. The recently developed continuously graded QDs (cg-QDs) with gradually altered nanocompositions and electronic band structures present the most advanced example in this area. In this Perspective, we summarize the current progress in LEDs based on cg-QDs, mainly concentrating on their synthesis and advantages in addressing the great challenges in QLEDs, like efficiency roll-off at high current densities, short operation lifetimes at high brightness, and low brightness near the voltage around the bandgap. In addition, we propose accessible approaches exploiting the cutting-edge mechanisms and techniques to further optimize and improve the performance of QLEDs.
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Affiliation(s)
- Yang Cheng
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- Key Laboratory for Special Functional Materials, Ministry of Education, School of Materials Science and Engineering, Henan University, Kaifeng 475004, China
| | - Haoyue Wan
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Tianyu Liang
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Can Liu
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Muhong Wu
- International Center for Quantum Materials, Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
- Songshan Lake Laboratory for Materials Science, Dongguan 523808, China
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing 100871, China
| | - Hao Hong
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
| | - Kaihui Liu
- State Key Laboratory for Mesoscopic Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing 100871, China
- International Center for Quantum Materials, Collaborative Innovation Center of Quantum Matter, Peking University, Beijing 100871, China
| | - Huaibin Shen
- Key Laboratory for Special Functional Materials, Ministry of Education, School of Materials Science and Engineering, Henan University, Kaifeng 475004, China
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9
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Wang L, Pan J, Liu C, Zhao Z, Fang F, Wang Y, Wang G, Lei W, Chen J, Zhao D. Tailoring Nanostructures of Quantum Dots toward Efficient and Stable All-Solution Processed Quantum Dot Light-Emitting Diodes. ACS APPLIED MATERIALS & INTERFACES 2021; 13:17861-17868. [PMID: 33832222 DOI: 10.1021/acsami.1c02515] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Quantum dots (QDs) light-emitting diodes (QLEDs) are considered the most promising candidate for application in displays. While the efficiency of QLEDs has been greatly developed in recent years and is comparable to that of organic light-emitting diodes (OLEDs), it still remains challenging to realize both high efficiency and long lifetimes. In this work, we report efficient and stable red QLEDs with the maximum current efficiency of 13.48 cd A-1, external quantum efficiency of 18.65%, and low efficiency roll-off at high luminance with a long lifetime exceeding ∼2.9 × 105 h, representing a 3-fold increase in stability. Tailoring the composition of QDs suppresses nonradiative Förster resonant energy transfer and Auger recombination and provides favorable valence band alignment to boost the hole injection. Our work suggests that tailoring the nanostructures of QDs offers an effective means to simultaneously achieve high efficiency and high stability, accelerating QLED technology for practical applications in displays and lighting.
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Affiliation(s)
- Lixi Wang
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Jiangyong Pan
- School of Electronic and Information Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, P. R. China
| | - Chengjun Liu
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Zihan Zhao
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Fan Fang
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Ye Wang
- Key Laboratory of Material Physics, Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, P. R. China
| | - Guangzhao Wang
- Key Laboratory of Extraordinary Bond Engineering and Advanced Materials Technology of Chongqing, School of Electronic Information Engineering, Yangtze Normal University, Chongqing 408100, P. R. China
| | - Wei Lei
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Jing Chen
- Joint International Research Laboratory of Information Display and Visualization, School of Electronic Science and Engineering, Southeast University, Nanjing 210096, P. R. China
| | - Dewei Zhao
- College of Materials Science and Engineering, Sichuan University, Chengdu 610065, P. R. China
- Engineering Research Center of Alternative Energy Materials & Devices, Ministry of Education, Sichuan University, Chengdu 610065, P. R. China
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10
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Guo W, Tang J, Zhang G, Li B, Yang C, Chen R, Qin C, Hu J, Zhong H, Xiao L, Jia S. Photoluminescence Blinking and Biexciton Auger Recombination in Single Colloidal Quantum Dots with Sharp and Smooth Core/Shell Interfaces. J Phys Chem Lett 2021; 12:405-412. [PMID: 33356280 DOI: 10.1021/acs.jpclett.0c03065] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
There is an inconsistence on whether a smooth core/shell interface can reduce Auger recombination and suppress photoluminescence (PL) blinking in single colloidal quantum dots (QDs). Here, we investigate the influence of a core/shell interface on PL blinking and biexciton Auger recombination by comparing the single-dot PL spectra of CdxZn1-xSeyS1-y/ZnS core/shell QDs with sharp and smooth interfaces. The inconsistence can be clarified when considering different PL blinking mechanisms. For the single QDs showing Auger blinking, a smooth core/shell interface potential can suppress PL blinking through reducing the Auger recombination. In contrast, we find slightly reduced biexciton Auger recombination rates but increased PL blinking activities in the band-edge carrier (BC)-blinking QDs with the smooth core/shell interface. This is because the smooth interface potential cannot reduce the PL blinking caused by the transfer of electrons to the surface states; however, there is potential to increase electron wave function delocalization for reducing the biexciton Auger recombination rate.
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Affiliation(s)
- Wenli Guo
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Jialun Tang
- Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Guofeng Zhang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Bin Li
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
- Key Laboratory of Spectral Measurement and Analysis of Shanxi Province, College of Physics and Information Engineering, Shanxi Normal University, Linfen 041004, China
| | - Changgang Yang
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Ruiyun Chen
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Chengbing Qin
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Jianyong Hu
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Haizheng Zhong
- Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Liantuan Xiao
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
| | - Suotang Jia
- State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
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11
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Affiliation(s)
- Christopher Melnychuk
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
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12
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Ying X, Liu Y, Liu Z, Zhang M, Wang C, Wang W, Gu H, Huang R, Luo D, Liu X. Exploring different photocatalytic behaviors of Cd xZn 1−xSe yS 1−y gradient-alloyed quantum dots via composition regulation. Catal Sci Technol 2021. [DOI: 10.1039/d1cy01142a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Different photocatalytic behaviors of CdxZn1−xSeyS1−y gradient alloyed quantum dots via composition regulation.
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Affiliation(s)
- Xiangjing Ying
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P.R. China
| | - Yuxin Liu
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P.R. China
| | - Zheng Liu
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P.R. China
| | - Menglong Zhang
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P.R. China
| | - Chuanglei Wang
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P.R. China
| | - Weizhe Wang
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P.R. China
| | - Huaimin Gu
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P.R. China
| | - Runda Huang
- School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, P.R. China
| | - Dongxiang Luo
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P.R. China
- School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, P.R. China
| | - Xiao Liu
- Institute of Semiconductor Science and Technology, South China Normal University, Guangzhou 510631, P.R. China
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13
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Smirnov AM, Ezhova KV, Mantsevich VN, Dneprovskii VS. Dynamic photonic crystal in a colloidal quantum-dot solution: formation, structure analysis, and dimensionality switching. OPTICS LETTERS 2020; 45:2415-2418. [PMID: 32287247 DOI: 10.1364/ol.389127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 03/10/2020] [Indexed: 06/11/2023]
Abstract
We demonstrated, for the first time, to the best of our knowledge, a simple method to create three-dimensional (3D) dynamic photonic crystal (PhC) with controllable lattice symmetry through the interference of four non-coplanar laser beams in a non-linear optical medium [colloidal solution of CdSe/ZnS quantum dots (QDs)]. 3D dynamic PhC was formed due to the periodically changing refraction and absorption of resonantly excited excitons in the colloidal solution of QDs. The formation of dynamic PhC was confirmed by the observed self-diffraction of the laser beams on the dynamic structure which they have created. Tuning of the PhC dimensionality to the two-dimensional (2D) and one-dimensional (1D) was done through the reduction of the number of interfering beams to three and two, respectively, and by controlling the polarization of interacting beams. Physical processes responsible for the observed self-action effects that arise in CdSe/ZnS QDs are discussed in detail.
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14
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Boldt K, Bartlett S, Kirkwood N, Johannessen B. Quantification of Material Gradients in Core/Shell Nanocrystals Using EXAFS Spectroscopy. NANO LETTERS 2020; 20:1009-1017. [PMID: 31960678 DOI: 10.1021/acs.nanolett.9b04143] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Core/shell nanocrystals with a graded interface between core and shell exhibit improved optoelectronic properties compared with particles with an abrupt, sharp interface. Material gradients mitigate interfacial defects and define the shape of the confinement potential. So far, few works exist that allow to quantify the width of the gradient. In this study, ZnSe/CdS nanocrystals with graded shells made at different temperatures are characterized using extended X-ray absorption fine structure (EXAFS) and Raman spectroscopies. The average coordination number of the probed element with respect to the two possible counterions is fit to a simple, geometric model. It is shown that at the lower temperature limit for shell growth (260 °C), substantial interfacial alloying can be attributed mainly to cation migration. At higher temperature (290 °C), strain minimization leads to atomic ordering of the metal ions and an anomalously low degree of phase mixing.
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Affiliation(s)
- Klaus Boldt
- Department of Chemistry & Zukunftskolleg, Box 710 , University of Konstanz , 78457 Konstanz , Germany
| | - Stuart Bartlett
- Diamond Light Source , Diamond House, Harwell Science and Innovation Campus , Didcot , Oxfordshire OX11 0DE , United Kingdom
| | - Nicholas Kirkwood
- ARC Centre in Exciton Science, School of Chemistry , The University of Melbourne , Parkville , Victoria 3010 , Australia
| | - Bernt Johannessen
- ANSTO Australian Synchrotron , 800 Blackburn Rd , Clayton , Victoria 3168 , Australia
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15
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Altintas Y, Gungor K, Gao Y, Sak M, Quliyeva U, Bappi G, Mutlugun E, Sargent EH, Demir HV. Giant Alloyed Hot Injection Shells Enable Ultralow Optical Gain Threshold in Colloidal Quantum Wells. ACS NANO 2019; 13:10662-10670. [PMID: 31436957 DOI: 10.1021/acsnano.9b04967] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
As an attractive materials system for high-performance optoelectronics, colloidal nanoplatelets (NPLs) benefit from atomic-level precision in thickness, minimizing emission inhomogeneous broadening. Much progress has been made to enhance their photoluminescence quantum yield (PLQY) and photostability. However, to date, layer-by-layer growth of shells at room temperature has resulted in defects that limit PLQY and thus curtail the performance of NPLs as an optical gain medium. Here, we introduce a hot-injection method growing giant alloyed shells using an approach that reduces core/shell lattice mismatch and suppresses Auger recombination. Near-unity PLQY is achieved with a narrow full-width-at-half-maximum (20 nm), accompanied by emission tunability (from 610 to 650 nm). The biexciton lifetime exceeds 1 ns, an order of magnitude longer than in conventional colloidal quantum dots (CQDs). Reduced Auger recombination enables record-low amplified spontaneous emission threshold of 2.4 μJ cm-2 under one-photon pumping. This is lower by a factor of 2.5 than the best previously reported value in nanocrystals (6 μJ cm-2 for CdSe/CdS NPLs). Here, we also report single-mode lasing operation with a 0.55 mJ cm-2 threshold under two-photoexcitation, which is also the best among nanocrystals (compared to 0.76 mJ cm-2 from CdSe/CdS CQDs in the Fabry-Pérot cavity). These findings indicate that hot-injection growth of thick alloyed shells makes ultrahigh performance NPLs.
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Affiliation(s)
- Yemliha Altintas
- Department of Electrical and Electronics Engineering and Department of Physics UNAM - Institute of Materials Science and Nanotechnology , Bilkent University Ankara 06800 , Turkey
- Department of Materials Science and Nanotechnology and Department of Electrical-Electronics Engineering , Abdullah Gül University , Kayseri TR-38080 , Turkey
| | - Kivanc Gungor
- Department of Electrical and Electronics Engineering and Department of Physics UNAM - Institute of Materials Science and Nanotechnology , Bilkent University Ankara 06800 , Turkey
| | - Yuan Gao
- Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , ON M5S 3G4 , Canada
| | - Mustafa Sak
- Department of Electrical and Electronics Engineering and Department of Physics UNAM - Institute of Materials Science and Nanotechnology , Bilkent University Ankara 06800 , Turkey
| | - Ulviyya Quliyeva
- Department of Electrical and Electronics Engineering and Department of Physics UNAM - Institute of Materials Science and Nanotechnology , Bilkent University Ankara 06800 , Turkey
| | - Golam Bappi
- Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , ON M5S 3G4 , Canada
| | - Evren Mutlugun
- Department of Electrical and Electronics Engineering and Department of Physics UNAM - Institute of Materials Science and Nanotechnology , Bilkent University Ankara 06800 , Turkey
- Department of Materials Science and Nanotechnology and Department of Electrical-Electronics Engineering , Abdullah Gül University , Kayseri TR-38080 , Turkey
| | - Edward H Sargent
- Department of Electrical and Computer Engineering , University of Toronto , 10 King's College Road , Toronto , ON M5S 3G4 , Canada
| | - Hilmi Volkan Demir
- Department of Electrical and Electronics Engineering and Department of Physics UNAM - Institute of Materials Science and Nanotechnology , Bilkent University Ankara 06800 , Turkey
- Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, School of Materials Science and Nanotechnology , Nanyang Technological University , Singapore 639798 , Singapore
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16
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Zhang L, Lv B, Yang H, Xu R, Wang X, Xiao M, Cui Y, Zhang J. Quantum-confined stark effect in the ensemble of phase-pure CdSe/CdS quantum dots. NANOSCALE 2019; 11:12619-12625. [PMID: 31233067 DOI: 10.1039/c9nr03061a] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Colloidal semiconductor quantum dots (QDs) have recently attracted great attention in electric field sensing via the quantum-confined Stark effect (QCSE), but they suffer from the random local electric field around the charged QDs through the Auger process or defect traps. Here, QCSE in the ensemble of phase-pure wurtzite CdSe/CdS QDs was studied by applying a uniform external electric field. We observed clear field-dependent photoluminescence (PL) and absorption characteristics in thick-shell CdSe/CdS QDs with 11 CdS monolayers (11 MLs) including a pronounced spectral redshift in PL of ∼2.3 nm and absorption of ∼2.1 nm. The time-dependent PL intensity traces implied that the thick-shell QDs were conducive to realize the Stark shift in QD ensembles due to the effective suppression of the main sources of the local field. These findings were in stark contrast to those of moderate-shell (5 MLs) and ultrathick-shell (15 MLs) CdSe/CdS QDs. The measurement value of exciton polarizability was smaller than the theoretical value, which may be influenced by very few exciton traps. Moreover, the amplified stimulated emission also exhibited obvious optical modulations under the electric field with decreased emission intensity and an increased ultrafast lifetime. Finally, the temporal evolution of the multiexciton process in thick-shell CdSe/CdS QDs indicated that the multiexciton state induced a higher energy state near the band edge, which may weaken the QCSE of a single exciton. Therefore, it was demonstrated that efficient field control over the optical properties of these nanomaterials is feasible and this can open up potential applications in field-controlled electro-optic modulators.
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Affiliation(s)
- Lei Zhang
- Advanced Photonics Center, Southeast University, Nanjing 210096, China.
| | - Bihu Lv
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
| | - Hongyu Yang
- Advanced Photonics Center, Southeast University, Nanjing 210096, China.
| | - Ruilin Xu
- Advanced Photonics Center, Southeast University, Nanjing 210096, China.
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
| | - Yiping Cui
- Advanced Photonics Center, Southeast University, Nanjing 210096, China.
| | - Jiayu Zhang
- Advanced Photonics Center, Southeast University, Nanjing 210096, China.
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17
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He Y, Hu S, Han T, Chen X, Yu Y, Li T, Zhu W, Ouyang G. Suppression of the Auger Recombination Process in CdSe/CdS Core/Shell Nanocrystals. ACS OMEGA 2019; 4:9198-9203. [PMID: 31460008 PMCID: PMC6648246 DOI: 10.1021/acsomega.9b00926] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 05/15/2019] [Indexed: 05/24/2023]
Abstract
We investigate the Auger recombination (AR) rate in CdSe/CdS core/shell nanocrystals (NCs) under different interface confinements in terms of the interface bond relaxation mechanism and Fermi's golden rule. We find that the epitaxial layer of CdS can not only depress the influence of the Coulomb interaction between electrons and holes, but can also change the wave function and quantum confinement, resulting in the reduction of the AR rate. Moreover, the AR lifetime of CdSe/CdS core/shell NCs at a fixed entire dimension is lower than that of bare CdSe because of interface confinement of the wave function. A great drop of the AR rate can be achieved by adding an alloying layer that depresses the interface effect. Our predictions are in agreement with the available evidence, suggesting that the proposed approach could provide a general method to explore the AR process in core/shell NCs.
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Affiliation(s)
- Yan He
- College
of Science, Guangdong University of Petrochemical
Technology, Maoming, 525000 Guangdong, China
- Key
Laboratory of Low-Dimensional Quantum Structures and Quantum Control
of Ministry of Education, Synergetic Innovation Center for Quantum
Effects and Applications (SICQEA), Hunan
Normal University, Changsha 410081, China
| | - Sumei Hu
- College
of Science, Guangdong University of Petrochemical
Technology, Maoming, 525000 Guangdong, China
| | - Taikun Han
- College
of Science, Guangdong University of Petrochemical
Technology, Maoming, 525000 Guangdong, China
| | - Xingyuan Chen
- College
of Science, Guangdong University of Petrochemical
Technology, Maoming, 525000 Guangdong, China
| | - Yanxia Yu
- College
of Science, Guangdong University of Petrochemical
Technology, Maoming, 525000 Guangdong, China
| | - Tianle Li
- College
of Science, Guangdong University of Petrochemical
Technology, Maoming, 525000 Guangdong, China
| | - Weiling Zhu
- College
of Science, Guangdong University of Petrochemical
Technology, Maoming, 525000 Guangdong, China
| | - Gang Ouyang
- Key
Laboratory of Low-Dimensional Quantum Structures and Quantum Control
of Ministry of Education, Synergetic Innovation Center for Quantum
Effects and Applications (SICQEA), Hunan
Normal University, Changsha 410081, China
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18
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Enders F, Budweg A, Zeng P, Lauth J, Smith TA, Brida D, Boldt K. Switchable dissociation of excitons bound at strained CdTe/CdS interfaces. NANOSCALE 2018; 10:22362-22373. [PMID: 30474672 DOI: 10.1039/c8nr07973k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Charge carrier dynamics of semiconductor nano-heterostructures are determined by band alignment and lattice mismatch of the adjacent materials. However, quantum efficiencies for the separation of excited charge carriers at such an interface are hard to predict and cannot yet be easily controlled. In this work we examine nanorods with a severely strained, axial CdTe/CdS interface using femtosecond transient absorption spectroscopy. We show that charge separation is mitigated by equal contributions of valence band distortion and formation of coulomb pairs across the interface. Left undisturbed such localised excitons relax rapidly via non-radiative recombination channels. By adding a competitive hole acceptor that disrupts the coulomb interaction we overcome the synergetic co-localisation of the carriers and realise charge separation. The thus created long-lived state can be exploited for a broad range of applications such as photocatalysis, water splitting, and switchable nanodevices.
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Affiliation(s)
- Florian Enders
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany.
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19
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Righetto M, Bolzonello L, Volpato A, Amoruso G, Panniello A, Fanizza E, Striccoli M, Collini E. Deciphering hot- and multi-exciton dynamics in core-shell QDs by 2D electronic spectroscopies. Phys Chem Chem Phys 2018; 20:18176-18183. [PMID: 29961782 PMCID: PMC6044327 DOI: 10.1039/c8cp02574f] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
2D electronic spectroscopy maps acquired in different configurations unveil intraband hot carrier cooling and interband multi-exciton recombination dynamics.
Although the harnessing of multiple and hot excitons is a prerequisite for many of the groundbreaking applications of semiconductor quantum dots (QDs), the characterization of their dynamics through conventional spectroscopic techniques is cumbersome. Here, we show how a careful analysis of 2DES maps acquired in different configurations (BOXCARS and pump–probe geometry) allows the tracking and visualization of intraband Auger relaxation mechanisms, driving the hot carrier cooling, and interband bi- and tri-exciton recombination dynamics. The results obtained on archetypal core–shell CdSe/ZnS QDs suggest that, given the global analysis of the resulting datasets, 2D electronic spectroscopy techniques can successfully and efficiently dispel the intertwined dynamics of fast and ultrafast recombination processes in nanomaterials. Hence, we propose this analysis scheme to be used in future research on novel quantum confined systems.
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Affiliation(s)
- Marcello Righetto
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, I-35131 Padova, Italy.
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20
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Li Q, Lian T. Area- and Thickness-Dependent Biexciton Auger Recombination in Colloidal CdSe Nanoplatelets: Breaking the "Universal Volume Scaling Law". NANO LETTERS 2017; 17:3152-3158. [PMID: 28418671 DOI: 10.1021/acs.nanolett.7b00587] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Colloidal nanoplatelets (NPLs) have shown great potentials for lasing applications due to their sharp absorption and emission peaks, large absorption cross sections, large radiative decay rates, and long multiexciton lifetimes. How multiexciton lifetimes depend on material dimensions remains unknown in two-dimensional (2D) materials, despite being a key parameter affecting optical gain threshold and many other properties. Herein, we report a study of room-temperature biexciton Auger recombination time of CdSe NPLs as a function of thickness and lateral area. Comparison of all NPLs shows that the biexciton lifetime does not increase linearly with volume, unlike previously reported "universal volume scaling law" for quantum dots. For NPLs of the same thickness (∼1.8 nm), the biexciton lifetime increase linearly with their lateral area (from 143.7 ± 12.6 to 320.1 ± 17.1 ps when the area increases from 90.5 ± 21.4 to 234.2 ± 41.9 nm2). The biexciton lifetime depends linearly on (1/Ek(e))7/2 (Ek(e) is the electron confinement energy) or nearly linearly on d7 (d is NPL thickness). The observed dependence is consistent with a model in which biexciton Auger recombination rate scales with the product of exciton binary collision frequency and Auger recombination probability in biexciton complexes. The linear increase of Auger lifetimes with NPL lateral areas reflects a 1/area dependence of the binary collision frequency for 2D excitons and the thickness-dependent biexciton Auger recombination time is attributed to its strong dependence on the degree of quantum confinement. This model may be generally applicable to exciton Auger recombination in quantum confined 1D and 2D nanomaterials.
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Affiliation(s)
- Qiuyang Li
- 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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21
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Gong K, Kelley DF, Kelley AM. Nonuniform Excitonic Charge Distribution Enhances Exciton-Phonon Coupling in ZnSe/CdSe Alloyed Quantum Dots. J Phys Chem Lett 2017; 8:626-630. [PMID: 28107015 DOI: 10.1021/acs.jpclett.6b02944] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Zinc to cadmium cation exchange of ZnSe quantum dots has been used to produce a series of alloyed Zn1-xCdxSe quantum dots. As x increases and the lowest-energy exciton shifts to the red, the peak initially broadens and then sharpens as x approaches 1. Resonance Raman spectra obtained with excitation near the lowest excitonic absorption peak show a gradual shift of the longitudinal optical phonon peak from 251 cm-1 in pure ZnSe to 210 cm-1 in nearly pure CdSe with strong broadening at intermediate compositions. The LO overtone to fundamental intensity ratio, a rough gauge of exciton-phonon coupling strength, increases considerably for intermediate compositions compared with those of either pure ZnSe or pure CdSe. The results indicate that partial localization of the hole in locally Cd-rich regions of the alloyed particles increases the strengths of local internal electric fields, increasing the coupling between the exciton and polar optical phonons.
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Affiliation(s)
- Ke Gong
- Chemistry & Chemical Biology, University of California, Merced , 5200 North Lake Road, Merced, California 95343, United States
| | - David F Kelley
- Chemistry & Chemical Biology, University of California, Merced , 5200 North Lake Road, Merced, California 95343, United States
| | - Anne Myers Kelley
- Chemistry & Chemical Biology, University of California, Merced , 5200 North Lake Road, Merced, California 95343, United States
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22
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Liao C, Xu R, Xu Y, Zhang C, Xiao M, Zhang L, Lu C, Cui Y, Zhang J. Ultralow-Threshold Single-Mode Lasing from Phase-Pure CdSe/CdS Core/Shell Quantum Dots. J Phys Chem Lett 2016; 7:4968-4976. [PMID: 27973873 DOI: 10.1021/acs.jpclett.6b02465] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The development of colloidal quantum dot (QD) lasers is blocked by Auger recombination (AR). Here, phase-pure wurtzite CdSe/CdS core/shell QDs with controlled shell thickness are reported, which possess nearly defect-free core/shell interfaces. Benefiting from increased volume, electron-hole partial spatial separation, and nearly defect-free alloyed interface, this series of QDs exhibit a greater than 3 orders of magnitude decrease in AR rates with increasing shell thickness. Consequently, the amplified spontaneous emission threshold of the QDs with an 11 monolayer CdS shell is found to reach a minimum of 16 μJ cm-2. A record long lifetime (>1000 ps) and extraordinarily large bandwidth (>170 nm) of optical gain are observed by employing ultrafast transient absorption spectroscopy. We leverage the low-threshold gain of the QDs to fabricate microlasers that display single-mode operation and an ultralow threshold of ∼2 μJ cm-2. Our results represent a valuable step toward practical QD lasers.
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Affiliation(s)
- Chen Liao
- Advanced Photonic Center, Southeast University , Nanjing 210096, China
| | - Ruilin Xu
- Advanced Photonic Center, Southeast University , Nanjing 210096, China
| | - Yanqing Xu
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University , Nanjing 210093, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University , Nanjing 210093, China
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University , Nanjing 210093, China
| | - Lei Zhang
- Advanced Photonic Center, Southeast University , Nanjing 210096, China
| | - Changgui Lu
- Advanced Photonic Center, Southeast University , Nanjing 210096, China
| | - Yiping Cui
- Advanced Photonic Center, Southeast University , Nanjing 210096, China
| | - Jiayu Zhang
- Advanced Photonic Center, Southeast University , Nanjing 210096, China
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23
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Abstract
Abstract
The current state-of-the-art of the fabrication and photophysics of graded shells in quantum dots is reviewed. Graded shells, i.e. partially alloyed interfaces between core and shell or between two shells of semiconductor nanoheterostructures, have been demonstrated to improve fluorescence properties and suppress non-radiative pathways of exciton dynamics. By simply looking at linear optics on the level of single excitons this is reflected in increased photoluminescence quantum yields. However, it is shown that graded shells have further beneficial implications for band structure engineering and multiexciton dynamics such as optical gain and charge carrier multiplication.
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Affiliation(s)
- Klaus Boldt
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
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