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Yang W, Yang Y, Kaledin AL, He S, Jin T, McBride JR, Lian T. Surface passivation extends single and biexciton lifetimes of InP quantum dots. Chem Sci 2020; 11:5779-5789. [PMID: 32832054 PMCID: PMC7416692 DOI: 10.1039/d0sc01039a] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 05/15/2020] [Indexed: 01/18/2023] Open
Abstract
Indium phosphide quantum dots (InP QDs) are nontoxic nanomaterials with potential applications in photocatalytic and optoelectronic fields. Post-synthetic treatments of InP QDs are known to be essential for improving their photoluminescence quantum efficiencies (PLQEs) and device performances, but the mechanisms remain poorly understood. Herein, by applying ultrafast transient absorption and photoluminescence spectroscopies, we systematically investigate the dynamics of photogenerated carriers in InP QDs and how they are affected by two common passivation methods: HF treatment and the growth of a heterostructure shell (ZnS in this study). The HF treatment is found to improve the PLQE up to 16-20% by removing an intrinsic fast hole trapping channel (τ h,non = 3.4 ± 1 ns) in the untreated InP QDs while having little effect on the band-edge electron decay dynamics (τ e = 26-32 ns). The growth of the ZnS shell, on the other hand, is shown to improve the PLQE up to 35-40% by passivating both electron and hole traps in InP QDs, resulting in both a long-lived band-edge electron (τ e > 120 ns) and slower hole trapping lifetime (τ h,non > 45 ns). Furthermore, both the untreated and the HF-treated InP QDs have short biexciton lifetimes (τ xx ∼ 1.2 ± 0.2 ps). The growth of an ultra-thin ZnS shell (∼0.2 nm), on the other hand, can significantly extend the biexciton lifetime of InP QDs to 20 ± 2 ps, making it a passivation scheme that can improve both the single and multiple exciton lifetimes. Based on these results, we discuss the possible trap-assisted Auger processes in InP QDs, highlighting the particular importance of trap passivation for reducing the Auger recombination loss in InP QDs.
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Affiliation(s)
- Wenxing Yang
- Department of Chemistry , Emory University , 1515 Dickey Drive Northeast , Atlanta , Georgia 30322 , USA . ;
- Department of Chemistry - Ångström Laboratory , Physical Chemistry , Uppsala University , SE-75120 Uppsala , Sweden
| | - Yawei Yang
- Department of Chemistry , Emory University , 1515 Dickey Drive Northeast , Atlanta , Georgia 30322 , USA . ;
- Electronic Materials Research Laboratory , Key Laboratory of the Ministry of Education , International Center for Dielectric Research , Shaanxi Engineering Research Center of Advanced Energy Materials and Devices , School of Electronic Science and Engineering , Xi'an Jiaotong University , Xi'an 710049 , Shaanxi , P. R. China
| | - Alexey L Kaledin
- Cherry L. Emerson Center for Scientific Computation , Emory University , 1515 Dickey Drive , Atlanta , GA 30322 , USA
| | - Sheng He
- Department of Chemistry , Emory University , 1515 Dickey Drive Northeast , Atlanta , Georgia 30322 , USA . ;
| | - Tao Jin
- Department of Chemistry , Emory University , 1515 Dickey Drive Northeast , Atlanta , Georgia 30322 , USA . ;
| | - James R McBride
- Department of Chemistry , The Vanderbilt Institute of Nanoscale Science and Engineering , Vanderbilt University , Nashville , TN 37235 , USA
| | - Tianquan Lian
- Department of Chemistry , Emory University , 1515 Dickey Drive Northeast , Atlanta , Georgia 30322 , USA . ;
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52
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Freymeyer NJ, Click SM, Reid KR, Chisholm MF, Bradsher CE, McBride JR, Rosenthal SJ. Effect of indium alloying on the charge carrier dynamics of thick-shell InP/ZnSe quantum dots. J Chem Phys 2020; 152:161104. [PMID: 32357779 DOI: 10.1063/1.5145189] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Thick-shell InP/ZnSe III-V/II-VI quantum dots (QDs) were synthesized with two distinct interfaces between the InP core and ZnSe shell: alloy and core/shell. Despite sharing similar optical properties in the spectral domain, these two QD systems have differing amounts of indium incorporation in the shell as determined by high-resolution energy-dispersive x-ray spectroscopy scanning transmission electron microscopy. Ultrafast fluorescence upconversion spectroscopy was used to probe the charge carrier dynamics of these two systems and shows substantial charge carrier trapping in both systems that prevents radiative recombination and reduces the photoluminescence quantum yield. The alloy and core/shell QDs show slight differences in the extent of charge carrier localization with more extensive trapping observed in the alloy nanocrystals. Despite the ability to grow a thick shell, structural defects caused by III-V/II-VI charge carrier imbalances still need to be mitigated to further improve InP QDs.
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Affiliation(s)
| | - Sophia M Click
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Kemar R Reid
- Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Matthew F Chisholm
- Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - Cara E Bradsher
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - James R McBride
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Sandra J Rosenthal
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA
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53
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Lee S. Design Principle of Reactive Components for Dimethacrylate‐Terminated Quantum Dots: Preserved Photoluminescent Quantum Yield, Excellent Pattern Uniformity, and Suppression of Aggregation in the Matrix. MACROMOL CHEM PHYS 2020. [DOI: 10.1002/macp.201900488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Seonwoo Lee
- Department of Electrical and Computer EngineeringInter‐university Semiconductor Research CenterSeoul National University 1 Gwanakro, Gwanak‐gu Seoul 08826 Republic of Korea
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54
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Hughes KE, Stein JL, Friedfeld MR, Cossairt BM, Gamelin DR. Effects of Surface Chemistry on the Photophysics of Colloidal InP Nanocrystals. ACS NANO 2019; 13:14198-14207. [PMID: 31730352 DOI: 10.1021/acsnano.9b07027] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Indium phosphide (InP) semiconductor nanocrystals (NCs) provide a promising alternative to traditional heavy-metal-based luminescent materials for lighting and display technologies, and implementation of InP NCs in consumer products is rapidly increasing. As-synthesized InP NCs typically have very low photoluminescence quantum yields (PLQY), however. Although empirical methods have led to NCs with near-unity PLQYs, a fundamental understanding of how specific synthetic and post-synthetic protocols can alter the electronic landscape of InP NCs is still lacking. Here, we have studied a series of homologous InP NCs prepared from InP clusters using a combination of room-temperature and low-temperature time-resolved spectroscopies to elucidate how specific charge-carrier trapping processes are affected when various surface modifications are performed. The data allow identification of large PLQY increases that occur specifically through elimination of surface electron traps and provide a rationale for understanding the microscopic origins of this trap suppression in terms of elimination of undercoordinated surface In3+ ions. Despite essentially complete elimination of surface electron trapping when surface In3+ is addressed, hole trapping still exists. This hole trapping is shown to be partially suppressed by even very thin shell growth, attributable to elimination of undercoordinated surface phosphides. We also observe signatures of bright-dark excitonic splitting in InP NCs with only submonolayer surface coverage of select additives (divalent Lewis acids or fluoride anions)-signatures that have only been previously observed in thick-shelled InP NCs. Together, these synthetic and spectroscopic results improve our understanding of relationships between specific InP NC surface chemistries and the resulting NC photophysics.
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Affiliation(s)
- Kira E Hughes
- Department of Chemistry , University of Washington , Seattle , Washington 98195-1700 , United States
| | - Jennifer L Stein
- Department of Chemistry , University of Washington , Seattle , Washington 98195-1700 , United States
| | - Max R Friedfeld
- Department of Chemistry , University of Washington , Seattle , Washington 98195-1700 , United States
| | - Brandi M Cossairt
- Department of Chemistry , University of Washington , Seattle , Washington 98195-1700 , United States
| | - Daniel R Gamelin
- Department of Chemistry , University of Washington , Seattle , Washington 98195-1700 , United States
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55
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Kim Y, Chang JH, Choi H, Kim YH, Bae WK, Jeong S. III-V colloidal nanocrystals: control of covalent surfaces. Chem Sci 2019; 11:913-922. [PMID: 34084346 PMCID: PMC8145357 DOI: 10.1039/c9sc04290c] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Accepted: 11/25/2019] [Indexed: 01/15/2023] Open
Abstract
Colloidal quantum dots (QDs) are nanosized semiconductors whose electronic features are dictated by the quantum confinement effect. The optical, electrical, and chemical properties of QDs are influenced by their dimensions and surface landscape. The surface of II-VI and IV-VI QDs has been extensively explored; however, in-depth investigations on the surface of III-V QDs are still lagging behind. This Perspective discusses the current understanding of the surface of III-V QDs, outlines deep trap states presented by surface defects, and suggests strategies to overcome challenges associated with deep traps. Lastly, we discuss a route to create well-defined facets in III-V QDs by providing a platform for surface studies and a recently reported approach in atomistic understanding of covalent III-V QD surfaces using the electron counting model with fractional dangling bonds.
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Affiliation(s)
- Youngsik Kim
- Department of Energy Science, Center for Artificial Atoms, Sungkyunkwan University Suwon-si Gyeonggi-do 16419 Republic of Korea
| | - Jun Hyuk Chang
- School of Chemical and Biological Engineering, Seoul National University Seoul Republic of Korea
| | - Hyekyoung Choi
- Department of Energy Science, Center for Artificial Atoms, Sungkyunkwan University Suwon-si Gyeonggi-do 16419 Republic of Korea
| | - Yong-Hyun Kim
- Graduate School of Nanoscience and Technology, Department of Physics, Korea Advanced Institute of Science and Technology Daejeon 34141 Republic of Korea
| | - Wan Ki Bae
- SKKU Advanced Institute of Nanotechnology (SAINT), Center for Artificial Atoms, Sungkyunkwan University Suwon-si Gyeonggi-do 16419 Republic of Korea
| | - Sohee Jeong
- Department of Energy Science, Center for Artificial Atoms, Sungkyunkwan University Suwon-si Gyeonggi-do 16419 Republic of Korea
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McVey BFP, Swain RA, Lagarde D, Tison Y, Martinez H, Chaudret B, Nayral C, Delpech F. Unraveling the role of zinc complexes on indium phosphide nanocrystal chemistry. J Chem Phys 2019; 151:191102. [PMID: 31757128 DOI: 10.1063/1.5128234] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The addition of zinc complexes to the syntheses of indium phosphide nanocrystals (InP NCs) has become commonplace, due to their ability to alter and significantly improve observed optical properties. In this paper, the role of zinc complexes on the synthesis and observed properties of InP is carefully examined. Produced InP and InP:Zn2+ NCs are thoroughly characterized from both structural (core and surface) and optical perspectives over a wide range of Zn2+ compositions (0%-43% atomic content). We find no differences in the physical (NC size and polydispersity) and structural properties (crystallographic phase) of InP and InP:Zn2+ NCs. Optically, significant changes are observed when zinc is added to InP syntheses, including blueshifted absorption edges and maxima, increased quantum yields, and the near elimination of surface state emission. These improved optical properties result from surface passivation by zinc carboxylate moieties. Changes to the optical properties begin at zinc concentrations as low as 5%, demonstrating the high sensitivity of InP optical properties to exogenous species.
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Affiliation(s)
- B F P McVey
- LPCNO, Université de Toulouse, CNRS, INSA, UPS, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - R A Swain
- LPCNO, Université de Toulouse, CNRS, INSA, UPS, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - D Lagarde
- LPCNO, Université de Toulouse, CNRS, INSA, UPS, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - Y Tison
- Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (IPREM-ECP), Université de Pau et des Pays de l'Adour, Hélioparc, 2 Ave. Président Angot, F-64053 Pau, France
| | - H Martinez
- Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (IPREM-ECP), Université de Pau et des Pays de l'Adour, Hélioparc, 2 Ave. Président Angot, F-64053 Pau, France
| | - B Chaudret
- LPCNO, Université de Toulouse, CNRS, INSA, UPS, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - C Nayral
- LPCNO, Université de Toulouse, CNRS, INSA, UPS, 135 Avenue de Rangueil, 31077 Toulouse, France
| | - F Delpech
- LPCNO, Université de Toulouse, CNRS, INSA, UPS, 135 Avenue de Rangueil, 31077 Toulouse, France
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De CK, Roy D, Mandal S, Mandal PK. Suppressed Blinking under Normal Air Atmosphere in Toxic-Metal-Free, Small Sized, InP-Based Core/Alloy-Shell/Shell Quantum Dots. J Phys Chem Lett 2019; 10:4330-4338. [PMID: 31294573 DOI: 10.1021/acs.jpclett.9b01157] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Suppressed blinking has been reported in large (diameter ∼14.1 nm) core/shell InP quantum dots (QDs) under reduced air environment. We report here suppressed blinking with approximately four times smaller (diameter ∼3.6 nm) core/alloy-shell/shell InP QDs under ambient air atmosphere. The ⟨ON fraction⟩ has been obtained to be 0.65. Approximately 26% of the single QDs exhibit ON fraction >80%. The smaller ON exponent (1.19) magnitude in comparison to the OFF exponent (1.45) indicates longer ON events are interrupted by smaller OFF events. ON event truncation time is ∼1.5 times that of the OFF event, signifying the detrapping rate is much higher than the trapping rate. Interestingly, the detrapping rate/trapping rate (single-particle level property) could be directly correlated to the photoluminescence quantum yield (ensemble level property). An additional exponential term required to fit the probability density distribution of the ON event duration could be correlated with hole trapping, leading to extended ON times (>60 s).
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58
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Kamysbayev V, Srivastava V, Ludwig NB, Borkiewicz OJ, Zhang H, Ilavsky J, Lee B, Chapman KW, Vaikuntanathan S, Talapin DV. Nanocrystals in Molten Salts and Ionic Liquids: Experimental Observation of Ionic Correlations Extending beyond the Debye Length. ACS NANO 2019; 13:5760-5770. [PMID: 30964280 DOI: 10.1021/acsnano.9b01292] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The nature of the interface between the solute and the solvent in a colloidal solution has attracted attention for a long time. For example, the surface of colloidal nanocrystals (NCs) is specially designed to impart colloidal stability in a variety of polar and nonpolar solvents. This work focuses on a special type of colloids where the solvent is a molten inorganic salt or organic ionic liquid. The stability of such colloids is hard to rationalize because solvents with high density of mobile charges efficiently screen the electrostatic double-layer repulsion, and purely ionic molten salts represent an extreme case where the Debye length is only ∼1 Å. We present a detailed investigation of NC dispersions in molten salts and ionic liquids using small-angle X-ray scattering (SAXS), atomic pair distribution function (PDF) analysis and molecular dynamics (MD) simulations. Our SAXS analysis confirms that a wide variety of NCs (Pt, CdSe/CdS, InP, InAs, ZrO2) can be uniformly dispersed in molten salts like AlCl3/NaCl/KCl (AlCl3/AlCl4-) and NaSCN/KSCN and in ionic liquids like 1-butyl-3-methylimidazolium halides (BMIM+X-, where X = Cl, Br, I). By using a combination of PDF analysis and molecular modeling, we demonstrate that the NC surface induces a solvent restructuring with electrostatic correlations extending an order of magnitude beyond the Debye screening length. These strong oscillatory ion-ion correlations, which are not accounted by the traditional mechanisms of steric and electrostatic stabilization of colloids, offer additional insight into solvent-solute interactions and enable apparently "impossible" colloidal stabilization in highly ionized media.
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Affiliation(s)
- Vladislav Kamysbayev
- Department of Chemistry and James Franck Institute , University of Chicago , Chicago , Illinois 60637 , United States
| | - Vishwas Srivastava
- Department of Chemistry and James Franck Institute , University of Chicago , Chicago , Illinois 60637 , United States
| | - Nicholas B Ludwig
- Department of Chemistry and James Franck Institute , University of Chicago , Chicago , Illinois 60637 , United States
| | - Olaf J Borkiewicz
- X-ray Science Division, Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Hao Zhang
- Department of Chemistry and James Franck Institute , University of Chicago , Chicago , Illinois 60637 , United States
| | - Jan Ilavsky
- X-ray Science Division, Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Byeongdu Lee
- X-ray Science Division, Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - Karena W Chapman
- X-ray Science Division, Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | | | - Dmitri V Talapin
- Department of Chemistry and James Franck Institute , University of Chicago , Chicago , Illinois 60637 , United States
- Center for Nanoscale Materials , Argonne National Laboratory , Argonne , Illinois 60439 , United States
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