1
|
Roy D, Ghosh S, De CK, Mukherjee S, Mandal S, Mandal PK. Excitation-Energy-Dependent Photoluminescence Quantum Yield is Inherent to Optically Robust Core/Alloy-Shell Quantum Dots in a Vast Energy Landscape. J Phys Chem Lett 2022; 13:2404-2417. [PMID: 35257586 DOI: 10.1021/acs.jpclett.2c00157] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The importance of alloy-shelling in optically robust Core/Alloy-Shell (CAS) QDs has been described from structural and energetic aspects. Unlike fluorescent dyes, both Core/Shell (CS) and CAS QDs exhibit excitation-energy-dependent photoluminescence quantum yield (PLQY). For both CdSe and InP CAS QDs (with metal- and nonmetal-based alloy-shelling, respectively), with increasing excitation energy, (a) the ultrafast rise-time or relaxation-time to the band-edge increases and (b) the magnitude of the normalized bleach signal decreases. Ultrasensitive single-particle spectroscopic investigation results showed that with decreasing excitation energy, (a) the fraction of ON events increases, (b) the ratio of exciton-detrapping rate/trapping rate increases, and (c) the extent of beneficial hole trapping increases. A relative decrease in PLQY with increasing excitation energy is much less pronounced in CAS QDs than in CS QDs. Unless trap states are removed completely especially in the higher-energy landscape, PLQY will remain inherently dependent on excitation energy for QDs in the vast energy landscape. When reporting the PLQY of QDs, the magnitude of the excitation energy must be mentioned.
Collapse
Affiliation(s)
- Debjit Roy
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Swarnali Ghosh
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Chayan K De
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Soumen Mukherjee
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Saptarshi Mandal
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| | - Prasun K Mandal
- Department of Chemical Sciences & Centre for Advanced Functional Materials, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur, West Bengal, India 741246
| |
Collapse
|
2
|
Bang SY, Suh YH, Fan XB, Shin DW, Lee S, Choi HW, Lee TH, Yang J, Zhan S, Harden-Chaters W, Samarakoon C, Occhipinti LG, Han SD, Jung SM, Kim JM. Technology progress on quantum dot light-emitting diodes for next-generation displays. NANOSCALE HORIZONS 2021; 6:68-77. [PMID: 33400752 DOI: 10.1039/d0nh00556h] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Quantum dot light-emitting diodes (QD-LEDs) are widely recognised as great alternatives to organic light-emitting diodes (OLEDs) due to their enhanced performances. This focus article surveys the current progress on the state-of-the-art QD-LED technology including material synthesis, device optimization and innovative fabrication processes. A discussion on the material synthesis of core nanocrystals, shell layers and surface-binding ligands is presented for high photoluminescence quantum yield (PLQY) quantum dots (QDs) using heavy-metal free materials. The operational principles of several types of QD-LED device architectures are also covered, and the recent evolution of device engineering technologies is investigated. By exploring the fabrication process for pixel-patterning of QD-LEDs on an active-matrix backplane for full-colour display applications, we anticipate further improvement in device performance for the commercialisation of next-generation displays.
Collapse
Affiliation(s)
- Sang Yun Bang
- Electrical Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge, CB3 0FA, UK.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
3
|
Gupta SK, Mao Y. Recent advances, challenges, and opportunities of inorganic nanoscintillators. FRONTIERS OF OPTOELECTRONICS 2020; 13:156-187. [PMID: 36641550 PMCID: PMC9743955 DOI: 10.1007/s12200-020-1003-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 03/19/2020] [Indexed: 05/11/2023]
Abstract
This review article highlights the exploration of inorganic nanoscintillators for various scientific and technological applications in the fields of radiation detection, bioimaging, and medical theranostics. Various aspects of nanoscintillators pertaining to their fundamental principles, mechanism, structure, applications are briefly discussed. The mechanisms of inorganic nanoscintillators are explained based on the fundamental principles, instrumentation involved, and associated physical and chemical phenomena, etc. Subsequently, the promise of nanoscintillators over the existing single-crystal scintillators and other types of scintillators is presented, enabling their development for multifunctional applications. The processes governing the scintillation mechanisms in nanodomains, such as surface, structure, quantum, and dielectric confinement, are explained to reveal the underlying nanoscale scintillation phenomena. Additionally, suitable examples are provided to explain these processes based on the published data. Furthermore, we attempt to explain the different types of inorganic nanoscintillators in terms of the powder nanoparticles, thin films, nanoceramics, and glasses to ensure that the effect of nanoscience in different nanoscintillator domains can be appreciated. The limitations of nanoscintillators are also highlighted in this review article. The advantages of nanostructured scintillators, including their property-driven applications, are also explained. This review article presents the considerable application potential of nanostructured scintillators with respect to important aspects as well as their physical and application significance in a concise manner.
Collapse
Affiliation(s)
- Santosh K Gupta
- Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India
| | - Yuanbing Mao
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL, 60616, USA.
| |
Collapse
|
4
|
Bai T, Wang X, Dong Y, Xing S, Shi Z, Feng S. One-Pot Synthesis of High-Quality AgGaS 2/ZnS-based Photoluminescent Nanocrystals with Widely Tunable Band Gap. Inorg Chem 2020; 59:5975-5982. [PMID: 32286807 DOI: 10.1021/acs.inorgchem.9b03768] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Herein, we present a facile colloidal method to synthesize the high-quality AgGaS2 nanocrystals (NCs) within 2 min via exploiting the high-reactivity S precursor and then extend this synthetic strategy to the preparation of AgGaS2/ZnS core-shell NCs by a one-pot method without prior purification of AgGaS2 core. The as-synthesized samples were structurally characterized to confrim the formation of AgGaS2/ZnS core-shell NCs. The energy band gap of the AgGaS2/ZnS NCs can be effectively tunable from 2.98 to 2.83 eV by the control of their nonstoichiometry and further continuously decreases to 1.90 eV by the preparation of alloyed AgGaxIn1-xS2/ZnS NCs (1 ≤ x ≤ 0). Benefitting from the efficient band gap modulations, the photoluminescence (PL) colors of the AgGaS2-based NCs can cover almost the whole visible region from blue (460 nm) to red (671 nm). Our work demonstrates the one-pot synthesis of AgGaS2/ZnS core-shell NCs and their band gap engineering, which is of crucial in scalability toward industrial application and in tailoring optical characteristics of I-III-VI2 materials.
Collapse
Affiliation(s)
- Tianyu Bai
- College of Medical Laboratory, Dalian Medical University, No. 9 West Section Lvshun South Road, Dalian 116044, PR China
| | - Xuemin Wang
- College of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, PR China
| | - Yanyu Dong
- College of Medical Laboratory, Dalian Medical University, No. 9 West Section Lvshun South Road, Dalian 116044, PR China
| | - Shanghua Xing
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, PR China
| | - Zhan Shi
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, PR China
| | - Shouhua Feng
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, PR China
| |
Collapse
|
5
|
De CK, Roy D, Mandal S, Mandal PK. Suppressed Blinking under Normal Air Atmosphere in Toxic-Metal-Free, Small Sized, InP-Based Core/Alloy-Shell/Shell Quantum Dots. J Phys Chem Lett 2019; 10:4330-4338. [PMID: 31294573 DOI: 10.1021/acs.jpclett.9b01157] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Suppressed blinking has been reported in large (diameter ∼14.1 nm) core/shell InP quantum dots (QDs) under reduced air environment. We report here suppressed blinking with approximately four times smaller (diameter ∼3.6 nm) core/alloy-shell/shell InP QDs under ambient air atmosphere. The ⟨ON fraction⟩ has been obtained to be 0.65. Approximately 26% of the single QDs exhibit ON fraction >80%. The smaller ON exponent (1.19) magnitude in comparison to the OFF exponent (1.45) indicates longer ON events are interrupted by smaller OFF events. ON event truncation time is ∼1.5 times that of the OFF event, signifying the detrapping rate is much higher than the trapping rate. Interestingly, the detrapping rate/trapping rate (single-particle level property) could be directly correlated to the photoluminescence quantum yield (ensemble level property). An additional exponential term required to fit the probability density distribution of the ON event duration could be correlated with hole trapping, leading to extended ON times (>60 s).
Collapse
|
6
|
Paul S, Ghosh S, De SK. Efficient Charge Separation in Plasmonic ZnS@Sn:ZnO Nanoheterostructure: Nanoscale Kirkendall Effect and Enhanced Photophysical Properties. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:4324-4339. [PMID: 29571262 DOI: 10.1021/acs.langmuir.8b00442] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Tetravalent Sn doped ZnO nanocrystals show excellent plasmonic absorbance in the visible region. Plasmonic ZnS@Sn:ZnO core-shell heterostructures have been synthesized by the anion exchange process where the O2- is exchanged by S2- anion. An increase of sulfur concentration induces interior hollow structures arising from the different diffusion rates of O2- and S2- ions. Gradual transformation of wurtztie ZnO nanocrystals in the anion exchange process stabilizes the wurtzite crystalline phase of ZnS. Carrier concentration and various types of intrinsic defect states in both ZnO and ZnS result in ultraviolet, blue, and green emissions. The coexistence of exciton-plasmon coupling in the same nanoparticle and efficient electron-hole separation in type II heterostructure increases the photocatalytic activity and photo current gain.
Collapse
Affiliation(s)
- Sumana Paul
- Department of Materials Science , Indian Association for the Cultivation of Science , Kolkata 700032 , India
| | - Sirshendu Ghosh
- Department of Materials Science , Indian Association for the Cultivation of Science , Kolkata 700032 , India
| | - Subodh Kumar De
- Department of Materials Science , Indian Association for the Cultivation of Science , Kolkata 700032 , India
| |
Collapse
|
7
|
Roy D, Mandal S, De CK, Kumar K, Mandal PK. Nearly suppressed photoluminescence blinking of small-sized, blue–green–orange–red emitting single CdSe-based core/gradient alloy shell/shell quantum dots: correlation between truncation time and photoluminescence quantum yield. Phys Chem Chem Phys 2018; 20:10332-10344. [DOI: 10.1039/c8cp00952j] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nearly suppressed PL blinking of small sized CdSe based CGASS QDs.
Collapse
Affiliation(s)
- Debjit Roy
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
| | - Saptarshi Mandal
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
| | - Chayan K. De
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
| | - Kaushalendra Kumar
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
| | - Prasun K. Mandal
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Kolkata
- Mohanpur
- India
- Centre for Advanced Functional Materials
| |
Collapse
|
8
|
Fisher AAE, Osborne MA. Sizing Up Excitons in Core-Shell Quantum Dots via Shell-Dependent Photoluminescence Blinking. ACS NANO 2017; 11:7829-7840. [PMID: 28679040 DOI: 10.1021/acsnano.7b01978] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Semiconductor nanocrystals or quantum dots (QDs) are now widely used across solar cell, display, and bioimaging technologies. While advances in multishell, alloyed, and multinary core-shell QD structures have led to improved light-harvesting and photoluminescence (PL) properties of these nanomaterials, the effects that QD-capping have on the exciton dynamics that govern PL instabilities such as blinking in single-QDs is not well understood. We report experimental measurements of shell-size-dependent absorption and PL intermittency in CdSe-CdS QDs that are consistent with a modified charge-tunnelling, self-trapping (CTST) description of the exciton dynamics in these nanocrystals. By introducing an effective, core-exciton size, which accounts for delocalization of charge carriers across the QD core and shell, we show that the CTST models both the shell-depth-dependent red-shift of the QD band gap and changes in the on/off-state switching statistics that we observe in single-QD PL intensity trajectories. Further analysis of CdSe-ZnS QDs, shows how differences in shell structure and integrity affect the QD band gap and PL blinking within the CTST framework.
Collapse
Affiliation(s)
- Aidan A E Fisher
- Department of Chemistry, School of Life Sciences, University of Sussex , Falmer, Brighton BN1 9QJ, United Kingdom
| | - Mark A Osborne
- Department of Chemistry, School of Life Sciences, University of Sussex , Falmer, Brighton BN1 9QJ, United Kingdom
| |
Collapse
|
9
|
Osborne MA, Fisher AAE. Charge-tunnelling and self-trapping: common origins for blinking, grey-state emission and photoluminescence enhancement in semiconductor quantum dots. NANOSCALE 2016; 8:9272-9283. [PMID: 27088542 DOI: 10.1039/c6nr00529b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Understanding instabilities in the photoluminescence (PL) from light emitting materials is crucial to optimizing their performance for different applications. Semiconductor quantum dots (QDs) offer bright, size tunable emission, properties that are now being exploited in a broad range of developing technologies from displays and solar cells to biomaging and optical storage. However, instabilities such as photoluminescence intermittency, enhancement and bleaching of emission in these materials can be detrimental to their utility. Here, we report dielectric dependent blinking, intensity-"spikes" and low-level, "grey"-state emission, as well as PL enhancement in ZnS capped CdSe QDs; observations that we found consistent with a charge-tunnelling and self-trapping (CTST) description of exciton-dynamics on the QD-host system. In particular, modulation of PL in grey-states and PL enhancement are found to have a common origin in the equilibrium between exciton charge carrier core and surface-states within the CTST framework. Parameterized in terms of size and electrostatic properties of the QD and its nanoenvironment, the CTST offers predictive insight into exciton-dynamics in these nanomaterials.
Collapse
Affiliation(s)
- M A Osborne
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QJ, UK.
| | - A A E Fisher
- Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QJ, UK.
| |
Collapse
|
10
|
Davidowski SK, Lisowski CE, Yarger JL. Characterizing mixed phosphonic acid ligand capping on CdSe/ZnS quantum dots using ligand exchange and NMR spectroscopy. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2016; 54:234-238. [PMID: 26639792 DOI: 10.1002/mrc.4372] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 09/10/2015] [Accepted: 09/19/2015] [Indexed: 06/05/2023]
Abstract
The ligand capping of phosphonic acid functionalized CdSe/ZnS core-shell quantum dots (QDs) was investigated with a combination of solution and solid-state (31) P nuclear magnetic resonance (NMR) spectroscopy. Two phosphonic acid ligands were used in the synthesis of the QDs, tetradecylphosphonic acid and ethylphosphonic acid. Both alkyl phosphonic acids showed broad liquid and solid-state (31) P NMR resonances for the bound ligands, indicative of heterogeneous binding to the QD surface. In order to quantify the two ligand populations on the surface, ligand exchange facilitated by phenylphosphonic acid resulted in the displacement of the ethylphosphonic acid and tetradecylphosphonic acid and allowed for quantification of the free ligands using (31) P liquid-state NMR. After washing away the free ligand, two broad resonances were observed in the liquids' (31) P NMR corresponding to the alkyl and aromatic phosphonic acids. The washed samples were analyzed via solid-state (31) P NMR, which confirmed the ligand populations on the surface following the ligand exchange process. Copyright © 2015 John Wiley & Sons, Ltd.
Collapse
Affiliation(s)
| | | | - Jeffery L Yarger
- School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287, USA
| |
Collapse
|
11
|
Mangum BD, Wang F, Dennis AM, Gao Y, Ma X, Hollingsworth JA, Htoon H. Competition between auger recombination and hot-carrier trapping in PL intensity fluctuations of type II nanocrystals. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2014; 10:2892-2901. [PMID: 24715631 DOI: 10.1002/smll.201302896] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 02/18/2014] [Indexed: 06/03/2023]
Abstract
Performing time-tagged, time-correlated, single-photon-counting studies on individual colloidal nanocrystal quantum dots (NQDs), the evolution of photoluminescence (PL) intensity-fluctuation behaviors in near-infrared (NIR) emitting type II, InP/CdS core-shell NQDs is investigated as a function of shell thickness. It is observed that Auger recombination and hot-carrier trapping compete in defining the PL intensity-fluctuation behavior for NQDs with thin shells, whereas the role of hot-carrier trapping dominates for NQDs with thick shells. These studies further reveal the distinct ramifications of altering either the excitation fluence or repetition rate. Specifically, an increase in laser pump fluence results in the creation of additional hot-carrier traps. Alternately, higher repetition rates cause a saturation in hot-carrier traps, thus activating Auger-related PL fluctuations. Furthermore, it is shown that Auger recombination of negatively charged excitons is suppressed more strongly than that of positively charged excitons because of the asymmetry in the electron-hole confinement in type II NQDs. Thus, this study provides new understanding of how both NQD structure (shell thickness and carrier-separation characteristics) and excitation conditions can be used to tune the PL stability, with important implications for room-temperature single-photon generation. Specifically, the first non-blinking NQD capable of single-photon emission in the near-infrared spectral regime is described.
Collapse
Affiliation(s)
- Benjamin D Mangum
- Center for Integrated Nanotechnologies Materials Physics, & Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA
| | | | | | | | | | | | | |
Collapse
|
12
|
Schmidt R, Krasselt C, Göhler C, von Borczyskowski C. The fluorescence intermittency for quantum dots is not power-law distributed: a luminescence intensity resolved approach. ACS NANO 2014; 8:3506-3521. [PMID: 24580107 DOI: 10.1021/nn406562a] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The photoluminescence (PL) of single emitters like semiconductor quantum dots (QDs) shows PL intermittency, often called blinking. We explore the PL intensities of single CdSe/ZnS QDs in polystyrene (PS), on polyvenylalcohol (PVA), and on silicon oxide (SiOx) by the change-point analysis (CPA). By this, we relate results from the macrotime (sub-ms to 1000 s) and the microtime (0.1-100 ns) range to discrete PL intensities. We conclude that the intensity selected "on"-times in the ms range correspond to only a few (discrete) switching times, while the PL decays in the ns range are multiexponential even with respect to the same selected PL intensity. Both types of relaxation processes depend systematically on the PL intensity in course of a blinking time trace. The overall distribution of on-times does not follow a power law contrary to what has often been reported but can be compiled into 3-4 characteristic on-times. The results can be explained by the recently suggested multiple recombination centers model. Additionally, we can identify a well-defined QD state with a very low PL intensity above the noise level, which we assign to the strongly quenched exciton state. We describe our findings by a model of a hierarchical sequence of hole and electron trapping. Blinking events are the consequence of slow switching processes among these states and depend on the physicochemical properties of the heterogeneous nanointerface of the QDs.
Collapse
Affiliation(s)
- Robert Schmidt
- Institute of Physics, Optical Spectroscopy and Molecular Physics, Centre for Nanostructured Materials and Analytics (nanoMA), Technische Universität Chemnitz , 09107 Chemnitz, Germany
| | | | | | | |
Collapse
|
13
|
Dong C, Liu H, Zhang A, Ren J. Controllable Blinking-to-Nonblinking Behavior of Aqueous CdTeS Alloyed Quantum Dots. Chemistry 2014; 20:1940-6. [DOI: 10.1002/chem.201303605] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 11/21/2013] [Indexed: 11/06/2022]
|
14
|
Zhang H, Ye Y, Yang B, Shen L, Cui Y, Zhang J. Alloying Buffer Layers in Colloidal CdSe/ZnS Core/Shell Nanocrystals. Aust J Chem 2014. [DOI: 10.1071/ch13574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
When a ZnS shell is coated onto a CdSe core, some non-radiative defects are formed with the relaxation of the strain induced by the large lattice mismatch between CdSe and ZnS even though there are Zn0.5Cd0.5Se or ZnSe buffer layers, as indicated by the decrease of photoluminescent (PL) quantum yield and the reverse evolution of temperature-dependent time-resolved PL decay. X-Ray photoelectron spectroscopy analysis reveals that these defects are induced by the formation of an interfacial alloy during the epitaxy process. These defects could be significantly suppressed if the ZnxCd1–xSeyS1–y alloy buffer layer is artificially introduced.
Collapse
|
15
|
Cordones AA, Leone SR. Mechanisms for charge trapping in single semiconductor nanocrystals probed by fluorescence blinking. Chem Soc Rev 2013; 42:3209-21. [DOI: 10.1039/c2cs35452g] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
|
16
|
Cordones AA, Scheele M, Alivisatos AP, Leone SR. Probing the Interaction of Single Nanocrystals with Inorganic Capping Ligands: Time-Resolved Fluorescence from CdSe–CdS Quantum Dots Capped with Chalcogenidometalates. J Am Chem Soc 2012; 134:18366-73. [DOI: 10.1021/ja3071732] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Amy A. Cordones
- Department
of Chemistry, and ‡Department of Physics, University of California, Berkeley, California 94720, United States
- Material
Sciences Division and #Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720,
United States
| | - Marcus Scheele
- Department
of Chemistry, and ‡Department of Physics, University of California, Berkeley, California 94720, United States
- Material
Sciences Division and #Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720,
United States
| | - A. Paul Alivisatos
- Department
of Chemistry, and ‡Department of Physics, University of California, Berkeley, California 94720, United States
- Material
Sciences Division and #Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720,
United States
| | - Stephen R. Leone
- Department
of Chemistry, and ‡Department of Physics, University of California, Berkeley, California 94720, United States
- Material
Sciences Division and #Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720,
United States
| |
Collapse
|
17
|
Change point analysis of matrix dependent photoluminescence intermittency of single CdSe/ZnS quantum dots with intermediate intensity levels. Chem Phys 2012. [DOI: 10.1016/j.chemphys.2012.02.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
18
|
Gómez-Campos FM, Califano M. Hole surface trapping in CdSe nanocrystals: dynamics, rate fluctuations, and implications for blinking. NANO LETTERS 2012; 12:4508-4517. [PMID: 22849432 DOI: 10.1021/nl3016279] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Carrier trapping is one of the main sources of performance degradation in nanocrystal-based devices. Yet the dynamics of this process is still unclear. We present a comprehensive investigation into the efficiency of hole transfer to a variety of trap sites located on the surface of the core or the shell or at the core/shell interface in CdSe nanocrystals with both organic and inorganic passivation, using the atomistic semiempirical pseudopotential approach. We separate the contribution of coupling strength and energetics in different systems and trap configurations, obtaining useful general guidelines for trapping rate engineering. We find that trapping can be extremely efficient in core-only systems, with trapping times orders of magnitude faster than radiative recombination. The presence of an inorganic shell can instead bring the trapping rates well below the typical radiative recombination rates observed in these systems.
Collapse
Affiliation(s)
- Francisco M Gómez-Campos
- Departamento de Electrónica y Tecnología de Computadores, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain
| | | |
Collapse
|
19
|
Issac A, Krasselt C, Cichos F, von Borczyskowski C. Influence of the dielectric environment on the photoluminescence intermittency of CdSe quantum dots. Chemphyschem 2012; 13:3223-30. [PMID: 22753139 DOI: 10.1002/cphc.201101040] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 04/18/2012] [Indexed: 11/08/2022]
Abstract
We show experimentally that the photoluminescence intermittency (blinking) of single CdSe quantum dots (QDs) is influenced by the dielectric properties of the embedding environment (matrix), the type of ligands and the capping shell. For the on-times, we observe (and tentatively explain) a strong deviation from the commonly reported inverse power law behaviour, which can be taken into account by an exponential cut-off at long times. We assign this component to the photoejection of the electron, while the power law behaviour is a combination of hole- and electron-trapping processes. The cut-off times and their distributions depend strongly on the polarity of the environment. Also, the off-times show, though on a much longer timescale, deviations from the inverse power laws. We suggest a model including surface states and self-trapped states, which quantitatively explains the experimental observations.
Collapse
Affiliation(s)
- Abey Issac
- Optical Spectroscopy and Molecular Physics and nanoMA (Center for Nanostructured Materials and Analytics), Chemnitz University of Technology, Institute of Physics, 09107 Chemnitz, Germany
| | | | | | | |
Collapse
|
20
|
Krasselt C, Schuster J, von Borczyskowski C. Photoinduced hole trapping in single semiconductor quantum dots at specific sites at silicon oxide interfaces. Phys Chem Chem Phys 2011; 13:17084-92. [DOI: 10.1039/c1cp22040c] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|