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Kambhampati P. Unraveling the excitonics of light emission from metal-halide perovskite quantum dots. NANOSCALE 2024; 16:15033-15058. [PMID: 39052235 DOI: 10.1039/d4nr01481b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/27/2024]
Abstract
Metal halide semicondictor perovskites have been under intense investigation for their promise in light absorptive applications like photovoltaics. They have more recently experienced interest for their promise in light emissive applications. A key aspect of perovskites is their glassy, ionic lattice that exhibits dynamical disorder. One possible result of this dynamical disorder is their strong coupling between electronic and lattice degrees of freedom which may confer remarkable properties for light emission such as defect tolerance. How does the system, comprised of excitons, couple to the bath, comprised of lattice modes? How does this system-bath interaction give rise to novel light emissive properties and how do these properties give insight into the nature of these materials? We review recent work from this group in which time-resolved photoluminescence spectroscopy is used to reveal such insights. Based upon a fast time resolution of 3 ps, energy resolution, and temperature dependence, a wide variety of insights are gleaned. These insights include: lattice contributions to the emission linewidths, multiexciton formation, hot carrier cooling, excitonic fine structure, single dot superradiance, and a breakdown of the Condon approximation, all due to complex structural dynamics in these materials.
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2
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Yue L, Li J, Yao C, Chen J, Yan C, Wang X, Cao J. Nonequilibrium Lattice Dynamics of Individual and Attached PbSe Quantum Dots under Photoexcitation. J Phys Chem Lett 2024; 15:7667-7673. [PMID: 39037601 DOI: 10.1021/acs.jpclett.4c01541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
Quantum dot (QD) solids are emerging materials for many optoelectronic applications. To enhance interdot coupling and charge transport, surface ligands can be removed, allowing individual QDs to be attached along specific crystal orientations (termed "oriented attachment"). Optimizing the electronic and optical properties of QD solids demands a comprehensive understanding of the nanoscale energy flow in individual and attached QDs under photoexcitation. In this work, we employed ultrafast electron diffraction to directly measure how oriented attachment along ⟨100⟩ directions affects the nonequilibrium lattice dynamics of lead selenide QDs. The oriented attachment anisotropically alters the ultrafast energy relaxation along specific crystal axes. Along the ⟨100⟩ directions, both the lattice deformation and atomistic random motions are suppressed in comparison with those of individual QDs. Conversely, the effects are enhanced along the unattached ⟨111⟩ directions due to ligand removal. The oriented attachment switches the major lattice thermalization pathways from ⟨100⟩ to ⟨111⟩ directions.
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Affiliation(s)
- Luye Yue
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jingjun Li
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Changyuan Yao
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jie Chen
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Chang Yan
- Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
- Zhangjiang Institute for Advanced Study, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xuan Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Jianming Cao
- Center for Ultrafast Science and Technology, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
- Physics Department and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
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3
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Strandell DP, Ghosh A, Zenatti D, Nagpal P, Kambhampati P. Direct Observation of Higher Multiexciton Formation and Annihilation in CdSe Quantum Dots. J Phys Chem Lett 2023:6904-6911. [PMID: 37498205 DOI: 10.1021/acs.jpclett.3c01627] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
Most experiments on multiexcitons (MX) in quantum dots focused on the biexciton (XX), which is now well-understood. In contrast, there is little understanding of higher MX in quantum dots as a result of their difficulty to observe. Here, we apply time-resolved photoluminescence (t-PL) spectroscopy with 3 ps time resolution, sufficient to directly resolve previously unobserved spectral dynamics of a higher MX in CdSe quantum dots. These experiments resolve the controversy of the sequence of MX emissions, revealing that the higher channels sequentially populate the lower channels. There is a strong dependence of MX recombination kinetics upon a higher MX state, following a universal volume scaling law for Auger recombination for larger dots. Smaller dots show deviations for higher MX. In addition to triexcitons (3X), these experiments reveal MX up to the tetraexciton (4X). These experiments provide a direct observation of MX formation and annihilation in quantum dots. The impact of this observation is a step toward designing quantum dots to exploit higher MX processes.
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Affiliation(s)
- Dallas P Strandell
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Arnab Ghosh
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Davide Zenatti
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Priya Nagpal
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
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4
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Jasrasaria D, Weinberg D, Philbin JP, Rabani E. Simulations of nonradiative processes in semiconductor nanocrystals. J Chem Phys 2022; 157:020901. [PMID: 35840368 DOI: 10.1063/5.0095897] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The description of carrier dynamics in spatially confined semiconductor nanocrystals (NCs), which have enhanced electron-hole and exciton-phonon interactions, is a great challenge for modern computational science. These NCs typically contain thousands of atoms and tens of thousands of valence electrons with discrete spectra at low excitation energies, similar to atoms and molecules, that converge to the continuum bulk limit at higher energies. Computational methods developed for molecules are limited to very small nanoclusters, and methods for bulk systems with periodic boundary conditions are not suitable due to the lack of translational symmetry in NCs. This perspective focuses on our recent efforts in developing a unified atomistic model based on the semiempirical pseudopotential approach, which is parameterized by first-principle calculations and validated against experimental measurements, to describe two of the main nonradiative relaxation processes of quantum confined excitons: exciton cooling and Auger recombination. We focus on the description of both electron-hole and exciton-phonon interactions in our approach and discuss the role of size, shape, and interfacing on the electronic properties and dynamics for II-VI and III-V semiconductor NCs.
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Affiliation(s)
- Dipti Jasrasaria
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Daniel Weinberg
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - John P Philbin
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Eran Rabani
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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5
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Kambhampati P. Nanoparticles, Nanocrystals, and Quantum Dots: What are the Implications of Size in Colloidal Nanoscale Materials? J Phys Chem Lett 2021; 12:4769-4779. [PMID: 33984241 DOI: 10.1021/acs.jpclett.1c00754] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Semiconductor nanoparticles (NP) or nanocrystals (NC) have been investigated for many decades, with particular acceleration in interest upon the discovery of quantum confinement effects thereby yielding quantum dots (QD) from certain well-grown NC. The term NP is commonly used in the case of metal and wide gap semiconductor nanocrystals. The term NC is commonly used in semiconductor nanocrystals, whether covalent II-VI or ionic perovskites, that are colloidally grown. The term QD applies to select semiconductor nanocrystals for whom their size is on the order of the excitonic Bohr radius. In the case of colloidal particles on the nanometer length scale, these terms are often used carelessly and interchangeably. The words have specific meaning in relationship to specific physical effects which give rise to specific key processes that can be measured. Here, we provide a Perspective on the ways in which size confers function across different families of NP. In this way, we aim to find ways to identify their similarities and differences by providing the correct semantics for discussion of the salient processes.
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6
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Lei H, Wang Y, Liu S, Zhu M, Pu C, Lin S, Qin H, Peng X. Delocalized Surface Electronic States on Polar Facets of Semiconductor Nanocrystals. ACS NANO 2020; 14:16614-16623. [PMID: 33095559 DOI: 10.1021/acsnano.0c07176] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Wurtzite CdSe@CdS dot@platelet nanocrystals with (001) and (00-1) polar facets as the basal planes and (100) family of nonpolar facets as the side planes are applied for studying surface defects on semiconductor nanocrystals. When they are terminated with cadmium ions coordinated with carboxylate ligands, a single set of absorption features and band-edge photoluminescence (PL) with near unity PL quantum yield and monoexponential PL decay dynamics (lifetime ∼28 ns) are observed. In addition to these spectral signatures, when the surface is converted to sulfur-terminated, a second set of sharp absorption features with decent extinction coefficients and a secondary band-edge PL with low PL quantum yield and long-lifetime (>78 ns) PL decay dynamics are reproducibly recorded. Photochemical analysis confirms that the secondary UV-vis and PL spectral features are quantitatively correlated with each other. Chemical analysis and X-ray photoelectron spectroscopy measurements confirm that such secondary spectral features are well correlated with the sulfide (such as -SH) and disulfide (such as -S-S-) surface sites of a basal plane, which likely form surface hole electronic states delocalized on the entire basal plane. Results suggest that, for studying surface defects on semiconductor nanocrystals, it is essential to prepare a nearly monodisperse surface structure in terms of facets and surface chemical bonding.
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Affiliation(s)
- Hairui Lei
- Center for Chemistry of Novel and High-Performance Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Yonghong Wang
- Center for Chemistry of Novel and High-Performance Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Shaojie Liu
- Center for Chemistry of Novel and High-Performance Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Meiyi Zhu
- Center for Chemistry of Novel and High-Performance Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Chaodan Pu
- Center for Chemistry of Novel and High-Performance Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Shangxin Lin
- Center for Chemistry of Novel and High-Performance Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Haiyan Qin
- Center for Chemistry of Novel and High-Performance Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
| | - Xiaogang Peng
- Center for Chemistry of Novel and High-Performance Materials, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
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7
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Xiao J, Liu Y, Steinmetz V, Çaǧlar M, Mc Hugh J, Baikie T, Gauriot N, Nguyen M, Ruggeri E, Andaji-Garmaroudi Z, Stranks SD, Legrand L, Barisien T, Friend RH, Greenham NC, Rao A, Pandya R. Optical and Electronic Properties of Colloidal CdSe Quantum Rings. ACS NANO 2020; 14:14740-14760. [PMID: 33044058 DOI: 10.1021/acsnano.0c01752] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Luminescent colloidal CdSe nanorings are a recently developed type of semiconductor structure that have attracted interest due to the potential for rich physics arising from their nontrivial toroidal shape. However, the exciton properties and dynamics of these materials with complex topology are not yet well understood. Here, we use a combination of femtosecond vibrational spectroscopy, temperature-resolved photoluminescence (PL), and single-particle measurements to study these materials. We find that on transformation of CdSe nanoplatelets to nanorings, by perforating the center of platelets, the emission lifetime decreases and the emission spectrum broadens due to ensemble variations in the ring size and thickness. The reduced PL quantum yield of nanorings (∼10%) compared to platelets (∼30%) is attributed to an enhanced coupling between (i) excitons and CdSe LO-phonons at 200 cm-1 and (ii) negatively charged selenium-rich traps, which give nanorings a high surface charge (∼-50 mV). Population of these weakly emissive trap sites dominates the emission properties with an increased trap emission at low temperatures relative to excitonic emission. Our results provide a detailed picture of the nature of excitons in nanorings and the influence of phonons and surface charge in explaining the broad shape of the PL spectrum and the origin of PL quantum yield losses. Furthermore, they suggest that the excitonic properties of nanorings are not solely a consequence of the toroidal shape but also a result of traps introduced by puncturing the platelet center.
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Affiliation(s)
- James Xiao
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Yun Liu
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Violette Steinmetz
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Mustafa Çaǧlar
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Jeffrey Mc Hugh
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Tomi Baikie
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Nicolas Gauriot
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Malgorzata Nguyen
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Edoardo Ruggeri
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Zahra Andaji-Garmaroudi
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
- Department of Chemical Engineering & Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB3 0AS, Cambridge, United Kingdom
| | - Samuel D Stranks
- Sorbonne Université, CNRS-UMR 7588, Institut des NanoSciences de Paris, INSP, 4 Place Jussieu, F-75005 Paris, France
| | - Laurent Legrand
- Sorbonne Université, CNRS-UMR 7588, Institut des NanoSciences de Paris, INSP, 4 Place Jussieu, F-75005 Paris, France
| | - Thierry Barisien
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Richard H Friend
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Neil C Greenham
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
| | - Akshay Rao
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, CB3 0HE, Cambridge, United Kingdom
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8
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Utterback JK, Cline RP, Shulenberger KE, Eaves JD, Dukovic G. The Motion of Trapped Holes on Nanocrystal Surfaces. J Phys Chem Lett 2020; 11:9876-9885. [PMID: 33170725 DOI: 10.1021/acs.jpclett.0c02618] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This Perspective discusses the phenomenon of trapped-hole diffusion in colloidal semiconductor nanocrystals. Surface charge-carrier traps are ubiquitous in nanocrystals and often dictate the fate of photoexcited carriers. New measurements and calculations are unveiling the nature of the nanocrystal surface, but many challenges to understanding the dynamics of trapped carriers remain. In contrast to the view that trapped holes are stationary, we have put forward a series of reports demonstrating that trapped holes on the surfaces of CdS and CdSe nanocrystals are mobile and move between traps in a sequence of hops. We summarize how these findings advance the understanding of carrier dynamics in colloidal nanocrystals and how they may impact a broad set of excited-state behaviors in these materials.
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Affiliation(s)
- James K Utterback
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - R Peyton Cline
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | | | - Joel D Eaves
- 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
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9
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Mrad R, Poggi M, Ben Chaâbane R, Negrerie M. Role of surface defects in colloidal cadmium selenide (CdSe) nanocrystals in the specificity of fluorescence quenching by metal cations. J Colloid Interface Sci 2020; 571:368-377. [DOI: 10.1016/j.jcis.2020.03.058] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/11/2020] [Accepted: 03/16/2020] [Indexed: 12/27/2022]
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10
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Yonemoto DT, Papa CM, Mongin C, Castellano FN. Thermally Activated Delayed Photoluminescence: Deterministic Control of Excited-State Decay. J Am Chem Soc 2020; 142:10883-10893. [PMID: 32497428 DOI: 10.1021/jacs.0c03331] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Thermally activated photophysical processes are ubiquitous in numerous organic and metal-organic molecules, leading to chromophores with excited-state properties that can be considered an equilibrium mixture of the available low-lying states. Relative populations of the equilibrated states are governed by temperature. Such molecules have been devised as high quantum yield emitters in modern organic light-emitting diode technology and for deterministic excited-state lifetime control to enhance chemical reactivity in solar energy conversion and photocatalytic schemes. The recent discovery of thermally activated photophysics at CdSe nanocrystal-molecule interfaces enables a new paradigm wherein molecule-quantum dot constructs are used to systematically generate material with predetermined photophysical response and excited-state properties. Semiconductor nanomaterials feature size-tunable energy level engineering, which considerably expands the purview of thermally activated photophysics beyond what is possible using only molecules. This Perspective is intended to provide a nonexhaustive overview of the advances that led to the integration of semiconductor quantum dots in thermally activated delayed photoluminescence (TADPL) schemes and to identify important challenges moving into the future. The initial establishment of excited-state lifetime extension utilizing triplet-triplet excited-state equilibria is detailed. Next, advances involving the rational design of molecules composed of both metal-containing and organic-based chromophores that produce the desired TADPL are described. Finally, the recent introduction of semiconductor nanomaterials into hybrid TADPL constructs is discussed, paving the way toward the realization of fine-tuned deterministic control of excited-state decay. It is envisioned that libraries of synthetically facile composites will be broadly deployed as photosensitizers and light emitters for numerous synthetic and optoelectronic applications in the near future.
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Affiliation(s)
- Daniel T Yonemoto
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Christopher M Papa
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Cedric Mongin
- Laboratoire PPSM, ENS Paris-Saclay, 61 Avenue du Président Wilson, 94235 Cachan CEDEX, France
| | - Felix N Castellano
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
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11
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Papa CM, Garakyaraghi S, Granger DB, Anthony JE, Castellano FN. TIPS-pentacene triplet exciton generation on PbS quantum dots results from indirect sensitization. Chem Sci 2020; 11:5690-5696. [PMID: 32864083 PMCID: PMC7425078 DOI: 10.1039/d0sc00310g] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 05/18/2020] [Indexed: 01/06/2023] Open
Abstract
Many fundamental questions remain in the elucidation of energy migration mechanisms across the interface between semiconductor nanomaterials and molecular chromophores.
Many fundamental questions remain in the elucidation of energy migration mechanisms across the interface between semiconductor nanomaterials and molecular chromophores. The present transient absorption study focuses on PbS quantum dots (QDs) of variable size and band-edge exciton energy (ranging from 1.15 to 1.54 eV) post-synthetically modified with a carboxylic acid-functionalized TIPS-pentacene derivative (TPn) serving as the molecular triplet acceptor. In all instances, selective excitation of the PbS NCs at 743 nm leads to QD size-dependent formation of an intermediate with time constants ranging from 2–13 ps, uncorrelated to the PbS QD valence band potential. However, the rate constant for the delayed formation of the TPn triplet excited state markedly increases with increasing PbS conduction band energy, featuring a parabolic Marcus free energy dependence in the normal region. These observations provide evidence of an indirect triplet sensitization process being inconsistent with a concerted Dexter-like energy transfer process. The collective data are consistent with the generation of an intermediate resulting from hole trapping of the initial PbS excited state by midgap states, followed by formation of the TPn triplet excited state whose rate constant and yield increases with decreasing quantum dot size.
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Affiliation(s)
- Christopher M Papa
- Department of Chemistry , North Carolina State University , Raleigh , North Carolina 27695-8204 , USA .
| | - Sofia Garakyaraghi
- Department of Chemistry , North Carolina State University , Raleigh , North Carolina 27695-8204 , USA .
| | - Devin B Granger
- Department of Chemistry , University of Kentucky , Lexington , Kentucky 40506-0055 , USA
| | - John E Anthony
- Department of Chemistry , University of Kentucky , Lexington , Kentucky 40506-0055 , USA
| | - Felix N Castellano
- Department of Chemistry , North Carolina State University , Raleigh , North Carolina 27695-8204 , USA .
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12
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Sanderson WM, Hoy J, Morrison C, Wang F, Wang Y, Morrison PJ, Buhro WE, Loomis RA. Excitation Energy Dependence of Photoluminescence Quantum Yields in Semiconductor Nanomaterials with Varying Dimensionalities. J Phys Chem Lett 2020; 11:3249-3256. [PMID: 32255643 DOI: 10.1021/acs.jpclett.0c00489] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The excitation energy dependence (EED) of the photoluminescence quantum yield (ΦPL) of semiconductor nanoparticles with varying dimensionalities is reported. Specifically, the EEDs of CdSe quantum dots, CdSe quantum platelets, CdSe quantum belts, and CdTe quantum wires were determined via measurements of individual ΦPL values and photoluminescence efficiency (PLEff(E)) spectra. There is a general trend of overall decreasing efficiency for radiative recombination with increasing excitation energy. In addition, there are often local minima in the PLEff(E) spectra that are most often at energies between quantum-confinement transitions. The average PL lifetimes of the samples do not depend on the excitation energy, suggesting that the EED of ΦPL arises from charge carrier trapping that competes efficiently with intraband carrier relaxation to the band edge. The local minima in the PLEff(E) spectra are attributed to excitation into optically coupled states that results in the loss of carriers in the semiconductor. The EED data suggest that the PLEff(E) spectra depend on the sample synthesis, preparation, surface passivation, and environment.
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Affiliation(s)
- William M Sanderson
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University in St. Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - Jessica Hoy
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University in St. Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - Calynn Morrison
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University in St. Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - Fudong Wang
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University in St. Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - Yuanyuan Wang
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University in St. Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - Paul J Morrison
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University in St. Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - William E Buhro
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University in St. Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
| | - Richard A Loomis
- Department of Chemistry and Institute of Materials Science and Engineering, Washington University in St. Louis, One Brookings Drive, CB 1134, Saint Louis, Missouri 63130, United States
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13
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14
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Huang Z, Lee Tang M. Semiconductor Nanocrystal Light Absorbers for Photon Upconversion. J Phys Chem Lett 2018; 9:6198-6206. [PMID: 30380890 DOI: 10.1021/acs.jpclett.8b02154] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Semiconductor nanocrystals (NCs) can initiate energy and charge transfer in multiple applications with their unique optical and electronic properties. In particular, NCs are excellent light absorbers for initiating triplet energy transfer (TET) to organic molecules, a key step in triplet-fusion-based photon upconversion. Triplet energy transfer across this inorganic-organic interface is one of the bottlenecks that currently limits the overall photon upconversion quantum yield. In this Perspective, we summarize the progress made in the past three years on this hybrid photon upconversion platform. We discuss the effects of NC size, composition, and surface states on TET. Nanocrystal surface engineering may address the loss mechanisms arising from defect states and exciton-phonon coupling. Alternative materials for NC triplet photosensitizers that do not contain toxic heavy metals will be especially useful for various biological applications.
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Affiliation(s)
- Zhiyuan Huang
- Department of Chemistry , University of California, Riverside , Riverside , California 92521 , United States
| | - Ming Lee Tang
- Department of Chemistry , University of California, Riverside , Riverside , California 92521 , United States
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15
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Banski M, Chrzanowski M, Zatryb G, Misiewicz J, Podhorodecki A. Enhanced photoluminescence stability of CdS nanocrystals through a zinc acetate reagent. RSC Adv 2018; 8:25417-25422. [PMID: 35539763 PMCID: PMC9082552 DOI: 10.1039/c8ra03504k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 06/16/2018] [Indexed: 11/21/2022] Open
Abstract
In this study, the role of a zinc acetate precursor in improving the luminescence stability of purple-emitting CdS nanocrystals is investigated. The oleate-capped core of CdS nanocrystals exhibits intense photodarkening under prolonged UV excitation. From the results of photoluminescence experiments, we can observe that photobleaching is responsible for the degradation of temporal stability, i.e., decline in photoluminescence intensity. Herein, we demonstrate that by adding zinc acetate to the synthesis solution, one can enhance the photoluminescence stability by the complete suppression of the bleaching processes of nanocrystals. We can distinguish between the effects caused by zinc ions and those caused by acetate ligands. Acetate ligands improve the photoluminescence stability of the core of CdS nanocrystals. However, only when zinc acetate is used, the PL stability can be conserved at high excitation power. Simultaneously, we have studied the influence of zinc cations and acetate ligands on the kinetics of nanocrystal growth. The presented results underline the importance of short surface capping ligands and zinc cations in CdS nanocrystal synthesis. This study exhibits a new advantage of exploiting zinc acetate reagents in one-pot nanocrystal synthesis.
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Affiliation(s)
- M Banski
- Department of Experimental Physics, Wroclaw University of Science and Technology Wybrzeze Wyspianskiego 27 50-370 Wroclaw Poland
| | - M Chrzanowski
- Department of Experimental Physics, Wroclaw University of Science and Technology Wybrzeze Wyspianskiego 27 50-370 Wroclaw Poland
| | - G Zatryb
- Department of Experimental Physics, Wroclaw University of Science and Technology Wybrzeze Wyspianskiego 27 50-370 Wroclaw Poland
| | - J Misiewicz
- Department of Experimental Physics, Wroclaw University of Science and Technology Wybrzeze Wyspianskiego 27 50-370 Wroclaw Poland
| | - A Podhorodecki
- Department of Experimental Physics, Wroclaw University of Science and Technology Wybrzeze Wyspianskiego 27 50-370 Wroclaw Poland
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16
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Orfield NJ, Majumder S, McBride JR, Yik-Ching Koh F, Singh A, Bouquin SJ, Casson JL, Johnson AD, Sun L, Li X, Shih CK, Rosenthal SJ, Hollingsworth JA, Htoon H. Photophysics of Thermally-Assisted Photobleaching in "Giant" Quantum Dots Revealed in Single Nanocrystals. ACS NANO 2018; 12:4206-4217. [PMID: 29709173 DOI: 10.1021/acsnano.7b07450] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Quantum dots (QDs) are steadily being implemented as down-conversion phosphors in market-ready display products to enhance color rendering, brightness, and energy efficiency. However, for adequate longevity, QDs must be encased in a protective barrier that separates them from ambient oxygen and humidity, and device architectures are designed to avoid significant heating of the QDs as well as direct contact between the QDs and the excitation source. In order to increase the utility of QDs in display technologies and to extend their usefulness to more demanding applications as, for example, alternative phosphors for solid-state lighting (SSL), QDs must retain their photoluminescence emission properties over extended periods of time under conditions of high temperature and high light flux. Doing so would simplify the fabrication costs for QD display technologies and enable QDs to be used as down-conversion materials in light-emitting diodes for SSL, where direct-on-chip configurations expose the emitters to temperatures approaching 100 °C and to photon fluxes from 0.1 W/mm2 to potentially 10 W/mm2. Here, we investigate the photobleaching processes of single QDs exposed to controlled temperature and photon flux. In particular, we investigate two types of room-temperature-stable core/thick-shell QDs, known as "giant" QDs for which shell growth is conducted using either a standard layer-by-layer technique or by a continuous injection method. We determine the mechanistic pathways responsible for thermally-assisted photodegradation, distinguishing effects of hot-carrier trapping and QD charging. The findings presented here will assist in the further development of advanced QD heterostructures for maximum device lifetime stability.
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Affiliation(s)
- Noah J Orfield
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Somak Majumder
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - James R McBride
- Department of Chemistry , Vanderbilt University , Nashville , Tennessee 37235 , United States
| | - Faith Yik-Ching Koh
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Ajay Singh
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Sarah J Bouquin
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Joanna L Casson
- Chemistry Division , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Alex D Johnson
- Physics Department and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Liuyang Sun
- Physics Department and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Xiaoqin Li
- Physics Department and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Chih-Kang Shih
- Physics Department and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712 , United States
| | - Sandra J Rosenthal
- Department of Chemistry , Vanderbilt University , Nashville , Tennessee 37235 , United States
| | - Jennifer A Hollingsworth
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
| | - Han Htoon
- Materials Physics and Applications Division: Center for Integrated Nanotechnologies , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
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17
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Xiao L, Wang Y, Huang Y, Wong T, Sun H. Self-trapped exciton emission from carbon dots investigated by polarization anisotropy of photoluminescence and photoexcitation. NANOSCALE 2017; 9:12637-12646. [PMID: 28825435 DOI: 10.1039/c7nr03913a] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Carbon dots have attracted tremendous attention because of their intrinsic advantages that open up opportunities to replace traditional fluorescent materials in various application fields. However, until now, the emission mechanism from carbon dots has been controversial, substantially hindering the extensive exploitation of these materials. Here, we explore systematically the essential emission behavior of carbon dots by using polarization anisotropy spectroscopy, electric-field modulation spectroscopy, and time-resolved photoluminescence measurements. We probe the momentum evolution dynamics and evaluate the decay process of the photoexcited hot carriers, which manifest characteristics that are distinct from band edge emission. We provide clear evidence that carbon dot emission originates from radiative recombination of self-trapped excitons, where the mobilization of the carriers is largely impeded due to the existence of a strong local potential field and thus the relaxation of the hot carriers is strongly suppressed. Based on the self-trapped exciton model, all the optical properties of carbon dots inferred from both steady-state and time-resolved optical spectroscopy can be interpreted consistently. Our investigation provides an alternative insight into the emission mechanisms of carbon dots, which may improve our understanding of these novel materials.
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Affiliation(s)
- Lian Xiao
- 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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18
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Arora V, Soni U, Mittal M, Yadav S, Sapra S. Synthesis of trap emission free cadmium sulfide quantum dots: Role of phosphonic acids and halide ions. J Colloid Interface Sci 2017; 491:329-335. [DOI: 10.1016/j.jcis.2016.12.049] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 12/01/2016] [Accepted: 12/17/2016] [Indexed: 10/20/2022]
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19
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Park SD, Baranov D, Ryu J, Cho B, Halder A, Seifert S, Vajda S, Jonas DM. Bandgap Inhomogeneity of a PbSe Quantum Dot Ensemble from Two-Dimensional Spectroscopy and Comparison to Size Inhomogeneity from Electron Microscopy. NANO LETTERS 2017; 17:762-771. [PMID: 28045274 DOI: 10.1021/acs.nanolett.6b03874] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Femtosecond two-dimensional Fourier transform spectroscopy is used to determine the static bandgap inhomogeneity of a colloidal quantum dot ensemble. The excited states of quantum dots absorb light, so their absorptive two-dimensional (2D) spectra will typically have positive and negative peaks. It is shown that the absorption bandgap inhomogeneity is robustly determined by the slope of the nodal line separating positive and negative peaks in the 2D spectrum around the bandgap transition; this nodal line slope is independent of excited state parameters not known from the absorption and emission spectra. The absorption bandgap inhomogeneity is compared to a size and shape distribution determined by electron microscopy. The electron microscopy images are analyzed using new 2D histograms that correlate major and minor image projections to reveal elongated nanocrystals, a conclusion supported by grazing incidence small-angle X-ray scattering and high-resolution transmission electron microscopy. The absorption bandgap inhomogeneity quantitatively agrees with the bandgap variations calculated from the size and shape distribution, placing upper bounds on any surface contributions.
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Affiliation(s)
- Samuel D Park
- Department of Chemistry and Biochemistry and Renewable and Sustainable Energy Institute, University of Colorado , Boulder, Colorado 80309, United States
| | - Dmitry Baranov
- Department of Chemistry and Biochemistry and Renewable and Sustainable Energy Institute, University of Colorado , Boulder, Colorado 80309, United States
| | - Jisu Ryu
- Department of Chemistry and Biochemistry and Renewable and Sustainable Energy Institute, University of Colorado , Boulder, Colorado 80309, United States
| | - Byungmoon Cho
- Department of Chemistry and Biochemistry and Renewable and Sustainable Energy Institute, University of Colorado , Boulder, Colorado 80309, United States
| | | | | | | | - David M Jonas
- Department of Chemistry and Biochemistry and Renewable and Sustainable Energy Institute, University of Colorado , Boulder, Colorado 80309, United States
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20
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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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21
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Arvani M, Virkki K, Abou-Chahine F, Efimov A, Schramm A, Tkachenko NV, Lupo D. Photoinduced hole transfer in QD-phthalocyanine hybrids. Phys Chem Chem Phys 2016; 18:27414-27421. [PMID: 27722635 DOI: 10.1039/c6cp04374g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A series of CdSe quantum dot (QD)-phthalocyanine (Pc) hybrids were synthesized and their photophysics was studied using steady state and time-resolved spectroscopic methods. Emission of QDs was progressively quenched upon increasing the concentration of Pc in the hybrids. A detailed transient absorption study of the hybrids revealed that the mechanism of quenching is charge separation, resulting in the formation of hybrids with negatively charged QDs and the Pc cation. Direct photo-excitation of Pc did not show any detectable interaction between the excited state of Pc and the QD to which it is attached. An explanation is proposed, based on the suggestion that the energy of the lowest unoccupied molecular orbital (LUMO) of Pc is lower than the lower edge of the QD conduction band, while the energy of the highest occupied molecular orbital (HOMO) of Pc is sufficiently higher than the high energy edge of the QD valence band (VB), thus permitting hole transfer from the QD VB to the Pc HOMO after photo-excitation of QDs.
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Affiliation(s)
- M Arvani
- Department of Electronics and Communications Engineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - K Virkki
- Department of Chemistry and Bioengineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - F Abou-Chahine
- Department of Chemistry and Bioengineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - A Efimov
- Department of Chemistry and Bioengineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - A Schramm
- Department of Electronics and Communications Engineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - N V Tkachenko
- Department of Chemistry and Bioengineering, Tampere University of Technology, 33720 Tampere, Finland.
| | - D Lupo
- Department of Electronics and Communications Engineering, Tampere University of Technology, 33720 Tampere, Finland.
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22
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Gao Y, Yu G, Wang Y, Dang C, Sum TC, Sun H, Demir HV. Green Stimulated Emission Boosted by Nonradiative Resonant Energy Transfer from Blue Quantum Dots. J Phys Chem Lett 2016; 7:2772-2778. [PMID: 27388758 DOI: 10.1021/acs.jpclett.6b01122] [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
Thanks to their tunability and versatility, the colloidal quantum dots (CQDs) made of II-VI semiconductor compound offer the potential to bridge the "green gap" in conventional semiconductors. However, when the CQDs are pumped to much higher initial excitonic states compared to their bandgap, multiexciton interaction is enhanced, leading to a much higher stimulated emission threshold. Here, to circumvent this drawback, for the first time, we show a fully colloidal gain in green enabled by a partially indirect pumping approach assisted by Förster resonance energy transfer process. By introducing the blue CQDs as exciton donors, the lasing threshold of the green CQDs, is reduced dramatically. The blue CQDs thus serve as an energy-transferring buffer medium to reduce excitation energy from pumping photons in a controlled way by injecting photoinduced excitons into green CQDs. Our newly developed colloidal pumping scheme could enable efficient CQD lasers of full visible colors by a single pump source and cascaded exciton transfer. This would potentially pave the way for an efficient multicolor laser for lighting and display applications.
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Affiliation(s)
- Yuan Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and The Photonics Institute, Nanyang Technological University , 50 Nanyang Avenue, 639798, Singapore
| | - Guannan Yu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
| | - Yue Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
| | - Cuong Dang
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and The Photonics Institute, Nanyang Technological University , 50 Nanyang Avenue, 639798, Singapore
| | - Tze Chien Sum
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
| | - Handong Sun
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and The Photonics Institute, Nanyang Technological University , 50 Nanyang Avenue, 639798, Singapore
| | - Hilmi Volkan Demir
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, 637371, Singapore
- LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering and The Photonics Institute, Nanyang Technological University , 50 Nanyang Avenue, 639798, Singapore
- Department of Electrical and Electronics Engineering and Department of Physics, UNAM - Institute of Materials Science and Nanotechnology, Bilkent University , 06800 Bilkent, Ankara, Turkey
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23
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Woodall DL, Tobias AK, Jones M. Resolving carrier recombination in CdS quantum dots: A time-resolved fluorescence study. Chem Phys 2016. [DOI: 10.1016/j.chemphys.2015.10.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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24
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Debnath T, Maiti S, Ghosh HN. Unusually Slow Electron Cooling to Charge-Transfer State in Gradient CdTeSe Alloy Nanocrystals Mediated through Mn Atom. J Phys Chem Lett 2016; 7:1359-1367. [PMID: 27003582 DOI: 10.1021/acs.jpclett.6b00348] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We have synthesized Mn-doped CdTeSe gradient alloy nanocrystals (NCs) by a colloidal synthetic method, and charge carrier dynamics have been revealed through ultrafast transient absorption (TA) spectroscopy. Due to the reactivity difference between Te and Se, a CdTe-rich core and CdSe-rich shell have been formed in the CdTeSe alloy with the formation of a gradient type II core-shell structure. Electron paramagnetic resonance studies suggest Mn atoms are located in the surface of the alloy NCs. Steady-state optical absorption and emission studies suggest formation of a charge-transfer (CT) state in which electrons are localized in a CdSe-rich shell and holes are localized in a CdTe-rich core which appears in the red region of the spectra. Electron transfer in the CT state is found to take place in the Marcus inverted region. To understand charge-transfer dynamics in the CdTeSe alloy NCs and to determine the effect of Mn doping on the alloy, ultrafast transient absorption studies have been carried out. In the case of the undoped alloy, formation of the CT state is found to take place through electron relaxation to the conduction band of the CT state with a time of 600 fs and through hole relaxation (from the CdSe-rich state to the CdTe-rich state) to the valence band of the CT state with a time scale of 1 ps. However, electron relaxation in the presence of Mn dopants takes place initially via an electron transfer to the Mn 3d state (d(5)) followed by transfer from the Mn 3d state (d(6)) to the CT state, which has been found to take place with a >700 ps time scale in addition to the hole relaxation time of 2 ps. Charge recombination time of the CT state is found to be extremely slow in the Mn-doped CdTeSe alloy NCs as compared to the undoped one, where the Mn atom acts as an electron storage center.
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Affiliation(s)
- Tushar Debnath
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India
| | - Sourav Maiti
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India
- Department of Chemistry, Savitribai Phule Pune University , Ganeshkhind, Pune 411007, India
| | - Hirendra N Ghosh
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India
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25
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Coropceanu I, Rossinelli A, Caram JR, Freyria FS, Bawendi MG. Slow-Injection Growth of Seeded CdSe/CdS Nanorods with Unity Fluorescence Quantum Yield and Complete Shell to Core Energy Transfer. ACS NANO 2016; 10:3295-301. [PMID: 26885562 DOI: 10.1021/acsnano.5b06772] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
A two-step process has been developed for growing the shell of CdSe/CdS core/shell nanorods. The method combines an established fast-injection-based step to create the initial elongated shell with a second slow-injection growth that allows for a systematic variation of the shell thickness while maintaining a high degree of monodispersity at the batch level and enhancing the uniformity at the single-nanorod level. The second growth step resulted in nanorods exhibiting a fluorescence quantum yield up to 100% as well as effectively complete energy transfer from the shell to the core. This improvement suggests that the second step is associated with a strong suppression of the nonradiative channels operating both before and after the thermalization of the exciton. This hypothesis is supported by the suppression of a defect band, ubiquitous to CdSe-based nanocrystals after the second growth.
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Affiliation(s)
- Igor Coropceanu
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Aurelio Rossinelli
- Optical Materials Engineering Laboratory, ETH Zurich , 8092 Zurich, Switzerland
| | - Justin R Caram
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Francesca S Freyria
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Moungi G Bawendi
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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26
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Bozyigit D, Yazdani N, Yarema M, Yarema O, Lin WMM, Volk S, Vuttivorakulchai K, Luisier M, Juranyi F, Wood V. Soft surfaces of nanomaterials enable strong phonon interactions. Nature 2016; 531:618-22. [PMID: 26958836 DOI: 10.1038/nature16977] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 01/04/2016] [Indexed: 12/23/2022]
Abstract
Phonons and their interactions with other phonons, electrons or photons drive energy gain, loss and transport in materials. Although the phonon density of states has been measured and calculated in bulk crystalline semiconductors, phonons remain poorly understood in nanomaterials, despite the increasing prevalence of bottom-up fabrication of semiconductors from nanomaterials and the integration of nanometre-sized components into devices. Here we quantify the phononic properties of bottom-up fabricated semiconductors as a function of crystallite size using inelastic neutron scattering measurements and ab initio molecular dynamics simulations. We show that, unlike in microcrystalline semiconductors, the phonon modes of semiconductors with nanocrystalline domains exhibit both reduced symmetry and low energy owing to mechanical softness at the surface of those domains. These properties become important when phonons couple to electrons in semiconductor devices. Although it was initially believed that the coupling between electrons and phonons is suppressed in nanocrystalline materials owing to the scarcity of electronic states and their large energy separation, it has since been shown that the electron-phonon coupling is large and allows high energy-dissipation rates exceeding one electronvolt per picosecond (refs 10-13). Despite detailed investigations into the role of phonons in exciton dynamics, leading to a variety of suggestions as to the origins of these fast transition rates and including attempts to numerically calculate them, fundamental questions surrounding electron-phonon interactions in nanomaterials remain unresolved. By combining the microscopic and thermodynamic theories of phonons and our findings on the phononic properties of nanomaterials, we are able to explain and then experimentally confirm the strong electron-phonon coupling and fast multi-phonon transition rates of charge carriers to trap states. This improved understanding of phonon processes permits the rational selection of nanomaterials, their surface treatments, and the design of devices incorporating them.
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Affiliation(s)
- Deniz Bozyigit
- Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
| | - Nuri Yazdani
- Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
| | - Maksym Yarema
- Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
| | - Olesya Yarema
- Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
| | - Weyde Matteo Mario Lin
- Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
| | - Sebastian Volk
- Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
| | - Kantawong Vuttivorakulchai
- Nano TCAD Group, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
| | - Mathieu Luisier
- Nano TCAD Group, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
| | - Fanni Juranyi
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Vanessa Wood
- Laboratory for Nanoelectronics, Department of Information Technology and Electrical Engineering, ETH Zurich, CH-8092 Zurich, Switzerland
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27
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Jethi L, Mack TG, Krause MM, Drake S, Kambhampati P. The Effect of Exciton-Delocalizing Thiols on Intrinsic Dual Emitting Semiconductor Nanocrystals. Chemphyschem 2016; 17:665-9. [PMID: 26752223 DOI: 10.1002/cphc.201501049] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Indexed: 11/07/2022]
Affiliation(s)
- Lakshay Jethi
- Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, QC, H3A0B8, Canada
| | - Timothy G Mack
- Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, QC, H3A0B8, Canada
| | - Michael M Krause
- Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, QC, H3A0B8, Canada
| | - Sebastian Drake
- Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, QC, H3A0B8, Canada
| | - Patanjali Kambhampati
- Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, QC, H3A0B8, Canada.
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28
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Yang C, Faust A, Amit Y, Gdor I, Banin U, Ruhman S. Impurity Sub-Band in Heavily Cu-Doped InAs Nanocrystal Quantum Dots Detected by Ultrafast Transient Absorption. J Phys Chem A 2016; 120:3088-97. [DOI: 10.1021/acs.jpca.5b10682] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chunfan Yang
- The Institute of Chemistry and ‡The Institute of Chemistry and the Center
for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Adam Faust
- The Institute of Chemistry and ‡The Institute of Chemistry and the Center
for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Yorai Amit
- The Institute of Chemistry and ‡The Institute of Chemistry and the Center
for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Itay Gdor
- The Institute of Chemistry and ‡The Institute of Chemistry and the Center
for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Uri Banin
- The Institute of Chemistry and ‡The Institute of Chemistry and the Center
for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Sanford Ruhman
- The Institute of Chemistry and ‡The Institute of Chemistry and the Center
for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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29
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Chauhan S, Watson DF. Photoinduced electron transfer from quantum dots to TiO2: elucidating the involvement of excitonic and surface states. Phys Chem Chem Phys 2016; 18:20466-75. [DOI: 10.1039/c6cp03813a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
CdSe QDs transfer electrons from band-edge and surface states to TiO2; core/shell CdSe/ZnS QDs transfer electrons exclusively from band-edge states.
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Affiliation(s)
- Saurabh Chauhan
- Department of Chemistry
- University at Buffalo
- The State University of New York
- Buffalo
- USA
| | - David F. Watson
- Department of Chemistry
- University at Buffalo
- The State University of New York
- Buffalo
- USA
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30
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Lenngren N, Abdellah MA, Zheng K, Al-Marri MJ, Zigmantas D, Žídek K, Pullerits T. Hot electron and hole dynamics in thiol-capped CdSe quantum dots revealed by 2D electronic spectroscopy. Phys Chem Chem Phys 2016; 18:26199-26204. [DOI: 10.1039/c6cp04190f] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
State-specific relaxation and trapping of excitations in thiol-capped CdSe QDs is followed by 2D electronic spectroscopy.
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Affiliation(s)
- Nils Lenngren
- Department of Chemical Physics
- Lund University
- 221 00 Lund
- Sweden
| | - Mohamed A. Abdellah
- Department of Chemical Physics
- Lund University
- 221 00 Lund
- Sweden
- Department of Chemistry
| | - Kaibo Zheng
- Department of Chemical Physics
- Lund University
- 221 00 Lund
- Sweden
- Gas Processing Center
| | | | | | - Karel Žídek
- Department of Chemical Physics
- Lund University
- 221 00 Lund
- Sweden
- Regional Centre for Special Optics and Optoelectronic Systems (TOPTEC)
| | - Tõnu Pullerits
- Department of Chemical Physics
- Lund University
- 221 00 Lund
- Sweden
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31
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Lifshitz E. Evidence in Support of Exciton to Ligand Vibrational Coupling in Colloidal Quantum Dots. J Phys Chem Lett 2015; 6:4336-4347. [PMID: 26538048 DOI: 10.1021/acs.jpclett.5b01567] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The Perspective focuses on the investigation of an unresolved conflict in semiconductor colloidal quantum dots (CQDs) research, concerning the influence of the immediate surrounding on the optical properties of the materials. Today's advanced synthetic colloidal procedures offer formation of a high-quality inorganic crystallite, capped with various organic/inorganic molecular ligands. The Perspective aims to clarify whether exciton recombination processes in CQDs are influenced by the type of crystallite-ligand bonding and, moreover, whether these excitonic processes experience direct coupling to the ligands' vibrational modes. Most ligands used have redox characteristics whose functional groups are added on to the CQDs' surface via coordination, covalent or ionic bonding. The surface-ligand bonding introduces electronic states either above or below the intraband/interband energy gap, resulting in electronic passivation or in creation of trapping states that affect intraband and interband relaxation processes. Furthermore, crystalline electronic states may have a direct coupling to molecular vibrational states via direct overlap of electronic wave functions or through a long-range energy-transfer process. Also, photoejected carriers resulting from an Auger process or ionization processes may diffuse temporarily onto a ligand site. These scenarios are discussed in the current publication with supporting theoretical and experimental observations.
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Affiliation(s)
- Efrat Lifshitz
- Schulich Faculty of Chemistry, Russell Berrie Nanotechnology Institute, Solid State Institute, Technion, Israel Institute of Technology , Haifa 32000, Israel
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32
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Krause MM, Jethi L, Mack TG, Kambhampati P. Ligand Surface Chemistry Dictates Light Emission from Nanocrystals. J Phys Chem Lett 2015; 6:4292-4296. [PMID: 26538044 DOI: 10.1021/acs.jpclett.5b02015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
There are several contradictory accounts of the changes to the emissive behavior of semiconductor nanocrystal upon a ligand exchange from trioctylphosphine/cadmium-phosphonates passivation to N-butylamine. This communication explains the contradictory accounts of this reaction using new insights into ligand chemistry. Also, a previously unknown link between surface emission and cadmium-phosphonate (Z-type) ligands is shown.
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Affiliation(s)
- Michael M Krause
- Department of Chemistry, McGill University , 801 Sherbrooke Street West, Montréal, Québec H3A 0B8, Canada
| | - Lakshay Jethi
- Department of Chemistry, McGill University , 801 Sherbrooke Street West, Montréal, Québec H3A 0B8, Canada
| | - Timothy G Mack
- Department of Chemistry, McGill University , 801 Sherbrooke Street West, Montréal, Québec H3A 0B8, Canada
| | - Patanjali Kambhampati
- Department of Chemistry, McGill University , 801 Sherbrooke Street West, Montréal, Québec H3A 0B8, Canada
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33
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Rosen EL, Gilmore K, Sawvel AM, Hammack AT, Doris SE, Aloni S, Altoe V, Nordlund D, Weng TC, Sokaras D, Cohen BE, Urban JJ, Ogletree DF, Milliron DJ, Prendergast D, Helms BA. Chemically directing d-block heterometallics to nanocrystal surfaces as molecular beacons of surface structure. Chem Sci 2015; 6:6295-6304. [PMID: 30090247 PMCID: PMC6054122 DOI: 10.1039/c5sc01474c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 07/28/2015] [Indexed: 02/04/2023] Open
Abstract
Our understanding of structure and bonding in nanoscale materials is incomplete without knowledge of their surface structure. Needed are better surveying capabilities responsive not only to different atoms at the surface, but also their respective coordination environments. We report here that d-block organometallics, when placed at nanocrystal surfaces through heterometallic bonds, serve as molecular beacons broadcasting local surface structure in atomic detail. This unique ability stems from their elemental specificity and the sensitivity of their d-orbital level alignment to local coordination environment, which can be assessed spectroscopically. Re-surfacing cadmium and lead chalcogenide nanocrystals with iron- or ruthenium-based molecular beacons is readily accomplished with trimethylsilylated cyclopentadienyl metal carbonyls. For PbSe nanocrystals with iron-based beacons, we show how core-level X-ray spectroscopies and DFT calculations enrich our understanding of both charge and atomic reorganization at the surface when beacons are bound.
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Affiliation(s)
- Evelyn L Rosen
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - Keith Gilmore
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - April M Sawvel
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - Aaron T Hammack
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - Sean E Doris
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
- Department of Chemistry , University of California , Berkeley , CA 94720 , USA
| | - Shaul Aloni
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - Virginia Altoe
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - Dennis Nordlund
- Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Menlo Park , CA 94025 , USA
| | - Tsu-Chien Weng
- Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Menlo Park , CA 94025 , USA
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource , SLAC National Accelerator Laboratory , Menlo Park , CA 94025 , USA
| | - Bruce E Cohen
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - Jeffrey J Urban
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - D Frank Ogletree
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - Delia J Milliron
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
- McKetta Department of Chemical Engineering , The University of Texas at Austin , Austin , Texas 78712 , USA
| | - David Prendergast
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
| | - Brett A Helms
- The Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , CA 94720 , USA .
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34
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Debnath T, Maiti S, Maity P, Ghosh HN. Subpicosecond Exciton Dynamics and Biexcitonic Feature in Colloidal CuInS2 Nanocrystals: Role of In-Cu Antisite Defects. J Phys Chem Lett 2015; 6:3458-65. [PMID: 26273721 DOI: 10.1021/acs.jpclett.5b01767] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Charge carrier dynamics of multinary quantum dots like CuInS2 (CIS) nanocrystals (NCs) is not clearly understood, especially in ultrafast time scales. Herein we have synthesized colloidal CIS NCs that show defect-induced emission between donor (antisite) and acceptor (internal/surface) states as indicated from steady-state and time-resolved photoluminescence (PL) measurements. Subpicosecond transient absorption (TA) spectra of CIS NCs reveal a gradient of electronic states that exists above the conduction band edge. The electron cooling rate has been determined to be ∼0.1-0.15 eV/ps. The cascade of electron cooling dynamics was monitored after following the TA kinetics at different electronic states. Interestingly, the kinetics at the antisite state unveil a biexcitonic feature, which has been enlightened through a probe-induced biexciton mechanism. With progressively higher fluence (⟨N⟩), the biexciton binding energy increases, and the electron cooling to the antisite state considerably slows down. Extra energy released during Auger recombination of bi/multiexcitons are used to re-excite the electron to a further high energy level, resulting in longer electron cooling time to the antisite states.
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Affiliation(s)
- Tushar Debnath
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India
| | - Sourav Maiti
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India
| | - Partha Maity
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India
| | - Hirendra N Ghosh
- Radiation & Photochemistry Division, Bhabha Atomic Research Centre , Mumbai 400085, India
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35
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Bhandari S, Khandelia R, Pan UN, Chattopadhyay A. Surface Complexation-Based Biocompatible Magnetofluorescent Nanoprobe for Targeted Cellular Imaging. ACS APPLIED MATERIALS & INTERFACES 2015; 7:17552-17557. [PMID: 26226317 DOI: 10.1021/acsami.5b04022] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report the synthesis of a magnetofluorescent biocompatible nanoprobe-following room temperature complexation reaction between Fe3O4-ZnS nanocomposite and 8-hydroxyquinoline (HQ). The composite nanoprobe exhibited high luminescence quantum yield, low rate of photobleaching, reasonable excited-state lifetime, luminescence stability especially in human blood serum, superparamagnetism and no apparent cytotoxicity. Moreover, the nanoprobe could be used for spatio-controlled cell labeling in the presence of an external magnetic field. The ease of synthesis and cell labeling in vitro make it a suitable candidate for targeted bioimaging applications.
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Affiliation(s)
- Satyapriya Bhandari
- †Department of Chemistry and ‡Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Rumi Khandelia
- †Department of Chemistry and ‡Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Uday Narayan Pan
- †Department of Chemistry and ‡Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Arun Chattopadhyay
- †Department of Chemistry and ‡Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
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36
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Carey GH, Levina L, Comin R, Voznyy O, Sargent EH. Record Charge Carrier Diffusion Length in Colloidal Quantum Dot Solids via Mutual Dot-To-Dot Surface Passivation. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:3325-3330. [PMID: 25899173 DOI: 10.1002/adma.201405782] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 03/11/2015] [Indexed: 06/04/2023]
Abstract
Through a combination of chemical and mutual dot-to-dot surface passivation, high-quality colloidal quantum dot solids are fabricated. The joint passivation techniques lead to a record diffusion length for colloidal quantum dots of 230 ± 20 nm. The technique is applied to create thick photovoltaic devices that exhibit high current density without losing fill factor.
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Affiliation(s)
- Graham H Carey
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Larissa Levina
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Riccardo Comin
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Oleksandr Voznyy
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
| | - Edward H Sargent
- Department of Electrical and Computer Engineering, University of Toronto, 10 King's College Road, Toronto, Ontario, M5S 3G4, Canada
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37
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Olutas M, Guzelturk B, Kelestemur Y, Yeltik A, Delikanli S, Demir HV. Lateral Size-Dependent Spontaneous and Stimulated Emission Properties in Colloidal CdSe Nanoplatelets. ACS NANO 2015; 9:5041-50. [PMID: 25950419 DOI: 10.1021/acsnano.5b01927] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Here, we systematically investigated the spontaneous and stimulated emission performances of solution-processed atomically flat quasi-2D nanoplatelets (NPLs) as a function of their lateral size using colloidal CdSe core NPLs. We found that the photoluminescence quantum efficiency of these NPLs decreases with increasing lateral size while their photoluminescence decay rate accelerates. This strongly suggests that nonradiative channels prevail in the NPL ensembles having extended lateral size, which is well-explained by the increasing number of the defected NPL subpopulation. In the case of stimulated emission the role of lateral size in NPLs influentially emerges both in the single- and two-photon absorption (1PA and 2PA) pumping. In the amplified spontaneous emission measurements, we uncovered that the stimulated emission thresholds of 1PA and 2PA exhibit completely opposite behavior with increasing lateral size. The NPLs with larger lateral sizes exhibited higher stimulated emission thresholds under 1PA pumping due to the dominating defected subpopulation in larger NPLs. On the other hand, surprisingly, larger NPLs remarkably revealed lower 2PA-pumped amplified spontaneous emission thresholds. This is attributed to the observation of a "giant" 2PA cross-section overwhelmingly growing with increasing lateral size and reaching record levels higher than 10(6) GM, at least an order of magnitude stronger than colloidal quantum dots and rods. These findings suggest that the lateral size control in the NPLs, which is commonly neglected, is essential to high-performance colloidal NPL optoelectronic devices in addition to the vertical monolayer control.
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Affiliation(s)
- Murat Olutas
- †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey
- ‡Department of Physics, Abant Izzet Baysal University, Bolu 14280, Turkey
| | - Burak Guzelturk
- †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey
| | - Yusuf Kelestemur
- †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey
| | - Aydan Yeltik
- †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey
| | - Savas Delikanli
- †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey
| | - Hilmi Volkan Demir
- †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey
- §Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore
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38
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Califano M. Origins of photoluminescence decay kinetics in CdTe colloidal quantum dots. ACS NANO 2015; 9:2960-2967. [PMID: 25716138 DOI: 10.1021/nn5070327] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Recent experimental studies have identified at least two nonradiative components in the fluorescence decay of solutions of CdTe colloidal quantum dots (CQDs). The lifetimes reported by different groups, however, differed by orders of magnitude, raising the question of whether different types of traps were at play in the different samples and experimental conditions and even whether different types of charge carriers were involved in the different trapping processes. Considering that the use of these nanomaterials in biology, optoelectronics, photonics, and photovoltaics is becoming widespread, such a gap in our understanding of carrier dynamics in these systems needs addressing. This is what we do here. Using the state-of-the-art atomistic semiempirical pseudopotential method, we calculate trapping times and nonradiative population decay curves for different CQD sizes considering up to 268 surface traps. We show that the seemingly discrepant experimental results are consistent with the trapping of the hole at unsaturated Te bonds on the dot surface in the presence of different dielectric environments. In particular, the observed increase in the trapping times following air exposure is attributed to the formation of an oxide shell on the dot surface, which increases the dielectric constant of the dot environment. Two types of traps are identified, depending on whether the unsaturated bond is single (type I) or part of a pair of dangling bonds on the same Te atom (type II). The energy landscape relative to transitions to these traps is found to be markedly different in the two cases. As a consequence, the trapping times associated with the different types of traps exhibit a strikingly contrasting sensitivity to variations in the dot environment. Based on these characteristics, we predict the presence of a sub-nanosecond component in all photoluminescence decay curves of CdTe CQDs in the size range considered here if both trap types are present. The absence of such a component is attributed to the suppression of type I traps.
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Affiliation(s)
- Marco Califano
- Institute of Microwaves and Photonics, School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
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39
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Ellis JL, Hickstein DD, Schnitzenbaumer KJ, Wilker MB, Palm BB, Jimenez JL, Dukovic G, Kapteyn HC, Murnane MM, Xiong W. Solvents effects on charge transfer from quantum dots. J Am Chem Soc 2015; 137:3759-62. [PMID: 25751367 DOI: 10.1021/jacs.5b00463] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
To predict and understand the performance of nanodevices in different environments, the influence of the solvent must be explicitly understood. In this Communication, this important but largely unexplored question is addressed through a comparison of quantum dot charge transfer processes occurring in both liquid phase and in vacuum. By comparing solution phase transient absorption spectroscopy and gas-phase photoelectron spectroscopy, we show that hexane, a common nonpolar solvent for quantum dots, has negligible influence on charge transfer dynamics. Our experimental results, supported by insights from theory, indicate that the reorganization energy of nonpolar solvents plays a minimal role in the energy landscape of charge transfer in quantum dot devices. Thus, this study demonstrates that measurements conducted in nonpolar solvents can indeed provide insight into nanodevice performance in a wide variety of environments.
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Affiliation(s)
- Jennifer L Ellis
- †Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
| | - Daniel D Hickstein
- †Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
| | - Kyle J Schnitzenbaumer
- ‡Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - Molly B Wilker
- ‡Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - Brett B Palm
- §Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, Colorado 80309, United States
| | - Jose L Jimenez
- §Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, Colorado 80309, United States
| | - Gordana Dukovic
- ‡Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
| | - Henry C Kapteyn
- †Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
| | - Margaret M Murnane
- †Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
| | - Wei Xiong
- †Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, United States
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40
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Gdor I, Shapiro A, Yang C, Yanover D, Lifshitz E, Ruhman S. Three-pulse femtosecond spectroscopy of PbSe nanocrystals: 1S bleach nonlinearity and sub-band-edge excited-state absorption assignment. ACS NANO 2015; 9:2138-2147. [PMID: 25629237 DOI: 10.1021/nn5074868] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Above band-edge photoexcitation of PbSe nanocrystals induces strong below band gap absorption as well as a multiphased buildup of bleaching in the 1Se1Sh transition. The amplitudes and kinetics of these features deviate from expectations based on biexciton shifts and state filling, which are the mechanisms usually evoked to explain them. To clarify these discrepancies, the same transitions are investigated here by double-pump-probe spectroscopy. Re-exciting in the below band gap induced absorption characteristic of hot excitons is shown to produce additional excitons with high probability. In addition, pump-probe experiments on a sample saturated with single relaxed excitons prove that the resulting 1Se1Sh bleach is not linear with the number of excitons per nanocrystal. This finding holds for two samples differing significantly in size, demonstrating its generality. Analysis of the results suggests that below band edge induced absorption in hot exciton states is due to excited-state absorption and not to shifted absorption of cold carriers and that 1Se1Sh bleach signals are not an accurate counter of sample excitons when their distribution includes multiexciton states.
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Affiliation(s)
- Itay Gdor
- Institute of Chemistry, The Hebrew University , Jerusalem 91904, Israel
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41
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Jethi L, Krause MM, Kambhampati P. Toward Ratiometric Nanothermometry via Intrinsic Dual Emission from Semiconductor Nanocrystals. J Phys Chem Lett 2015; 6:718-721. [PMID: 26262492 DOI: 10.1021/acs.jpclett.5b00024] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Semiconductor nanocrystals have been synthesized that support intrinsic dual emission from the excitonic core as well as the surface. By virtue of chemical control of the thermodynamics of the core/surface equilibria, these nanocrystals support ratiometric temperature sensing over a broad temperature scale. This surface-chemistry-based approach for creating intrinsic dual emission enables a completely new strategy for application of these nanocrystals in optical nanothermometry.
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Affiliation(s)
- Lakshay Jethi
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Michael M Krause
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
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42
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Krause MM, Kambhampati P. Linking surface chemistry to optical properties of semiconductor nanocrystals. Phys Chem Chem Phys 2015; 17:18882-94. [DOI: 10.1039/c5cp02173a] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This perspective gives insight into how the chemistry occurring at the surface of semiconductor nanocrystals is crucial to tailoring their optical properties to a myriad of applications.
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