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Wang Q, Zhu H, Tan Y, Hao J, Ye T, Tang H, Wang Z, Ma J, Sun J, Zhang T, Zheng F, Zhang W, Choi HW, Choy WCH, Wu D, Sun XW, Wang K. Spin Quantum Dot Light-Emitting Diodes Enabled by 2D Chiral Perovskite with Spin-Dependent Carrier Transport. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2305604. [PMID: 37789724 DOI: 10.1002/adma.202305604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Revised: 10/02/2023] [Indexed: 10/05/2023]
Abstract
Chiral-induced spin selectivity (CISS) effect provides innovative approach to spintronics and quantum-based devices for chiral materials. Different from the conventional ferromagnetic devices, the application of CISS effect is potential to operate under room temperature and zero applied magnetic field. Low dimensional chiral perovskites by introducing chiral amines are beginning to show significant CISS effect for spin injection, but research on chiral perovskites is still in its infancy, especially on spin-light emitting diode (spin-LED) construction. Here, the spin-QLEDs enabled by 2D chiral perovskites as CISS layer for spin-dependent carrier injection and CdSe/ZnS quantum dots (QDs) as light emitting layer are reported. The regulation pattern of the chirality and thickness of chiral perovskites, which affects the circularly polarized electroluminescence (CP-EL) emission of spin-QLED, is discovered. Notably, the spin injection polarization of 2D chiral perovskites is higher than 80% and the CP-EL asymmetric factor (gCP-EL ) achieves up to 1.6 × 10-2 . Consequently, this work opens up a new and effective approach for high-performance spin-LEDs.
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Affiliation(s)
- Qingqian Wang
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
- Institute of Physics, Henan Academy of Sciences, Zhengzhou, 450046, China
| | - Hongmei Zhu
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Yangzhi Tan
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Junjie Hao
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
- College of Integrated Circuits and Optoelectronic Chips, Shenzhen Technology University, Shenzhen, 518118, China
| | - Taikang Ye
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Haodong Tang
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
- College of Integrated Circuits and Optoelectronic Chips, Shenzhen Technology University, Shenzhen, 518118, China
| | - Zhaojin Wang
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Jingrui Ma
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Jiayun Sun
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Tianqi Zhang
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Fankai Zheng
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Wenda Zhang
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Hoi Wai Choi
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Wallace C H Choy
- Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, 999077, China
| | - Dan Wu
- College of New Materials and New Energies, Shenzhen Technology University, Shenzhen, 518118, China
| | - Xiao Wei Sun
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
| | - Kai Wang
- Institute of Nanoscience and Applications, Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
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Lubert-Perquel D, Acharya S, Johnson JC. Optically Addressing Exciton Spin and Pseudospin in Nanomaterials for Spintronics Applications. ACS APPLIED OPTICAL MATERIALS 2023; 1:1742-1760. [PMID: 38037653 PMCID: PMC10683369 DOI: 10.1021/acsaom.3c00299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 10/26/2023] [Accepted: 10/26/2023] [Indexed: 12/02/2023]
Abstract
Oriented exciton spins that can be generated and manipulated optically are of interest for a range of applications, including spintronics, quantum information science, and neuromorphic computing architectures. Although materials that host such excitons often lack practical coherence times for use on their own, strategic transduction of the magnetic information across interfaces can combine fast modulation with longer-term storage and readout. Several nanostructure systems have been put forward due to their interesting magneto-optical properties and their possible manipulation using circularly polarized light. These material systems are presented here, namely two-dimensional (2D) systems due to the unique spin-valley coupling properties and quantum dots for their exciton fine structure. 2D magnets are also discussed for their anisotropic spin behavior and extensive 2D magnetic states that are not yet fully understood but could pave the way for emergent techniques of magnetic control. This review also details the experimental and theoretical tools to measure and understand these systems along with a discussion on the progress of optical manipulation of spins and magnetic order transitions.
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Affiliation(s)
- Daphné Lubert-Perquel
- Materials, Chemical, and
Computational Science Directorate, National
Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Swagata Acharya
- Materials, Chemical, and
Computational Science Directorate, National
Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Justin C. Johnson
- Materials, Chemical, and
Computational Science Directorate, National
Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, United States
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3
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Shulenberger KE, Jilek MR, Sherman SJ, Hohman BT, Dukovic G. Electronic Structure and Excited State Dynamics of Cadmium Chalcogenide Nanorods. Chem Rev 2023; 123:3852-3903. [PMID: 36881852 DOI: 10.1021/acs.chemrev.2c00676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
The cylindrical quasi-one-dimensional shape of colloidal semiconductor nanorods (NRs) gives them unique electronic structure and optical properties. In addition to the band gap tunability common to nanocrystals, NRs have polarized light absorption and emission and high molar absorptivities. NR-shaped heterostructures feature control of electron and hole locations as well as light emission energy and efficiency. We comprehensively review the electronic structure and optical properties of Cd-chalcogenide NRs and NR heterostructures (e.g., CdSe/CdS dot-in-rods, CdSe/ZnS rod-in-rods), which have been widely investigated over the last two decades due in part to promising optoelectronic applications. We start by describing methods for synthesizing these colloidal NRs. We then detail the electronic structure of single-component and heterostructure NRs and follow with a discussion of light absorption and emission in these materials. Next, we describe the excited state dynamics of these NRs, including carrier cooling, carrier and exciton migration, radiative and nonradiative recombination, multiexciton generation and dynamics, and processes that involve trapped carriers. Finally, we describe charge transfer from photoexcited NRs and connect the dynamics of these processes with light-driven chemistry. We end with an outlook that highlights some of the outstanding questions about the excited state properties of Cd-chalcogenide NRs.
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Affiliation(s)
| | - Madison R Jilek
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Skylar J Sherman
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Benjamin T Hohman
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Gordana Dukovic
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States.,Renewable and Sustainable Energy Institute (RASEI), University of Colorado Boulder, Boulder, Colorado 80309, United States.,Materials Science and Engineering, University of Colorado Boulder, Boulder, Colorado 80303, United States
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Biswas S, Kim J, Zhang X, Scholes GD. Coherent Two-Dimensional and Broadband Electronic Spectroscopies. Chem Rev 2022; 122:4257-4321. [PMID: 35037757 DOI: 10.1021/acs.chemrev.1c00623] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Over the past few decades, coherent broadband spectroscopy has been widely used to improve our understanding of ultrafast processes (e.g., photoinduced electron transfer, proton transfer, and proton-coupled electron transfer reactions) at femtosecond resolution. The advances in femtosecond laser technology along with the development of nonlinear multidimensional spectroscopy enabled further insights into ultrafast energy transfer and carrier relaxation processes in complex biological and material systems. New discoveries and interpretations have led to improved design principles for optimizing the photophysical properties of various artificial systems. In this review, we first provide a detailed theoretical framework of both coherent broadband and two-dimensional electronic spectroscopy (2DES). We then discuss a selection of experimental approaches and considerations of 2DES along with best practices for data processing and analysis. Finally, we review several examples where coherent broadband and 2DES were employed to reveal mechanisms of photoinitiated ultrafast processes in molecular, biological, and material systems. We end the review with a brief perspective on the future of the experimental techniques themselves and their potential to answer an even greater range of scientific questions.
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Affiliation(s)
- Somnath Biswas
- Department of Chemistry, Princeton University, Princeton, New Jersey 08 544, United States
| | - JunWoo Kim
- Department of Chemistry, Princeton University, Princeton, New Jersey 08 544, United States
| | - Xinzi Zhang
- Department of Chemistry, Princeton University, Princeton, New Jersey 08 544, United States
| | - Gregory D Scholes
- Department of Chemistry, Princeton University, Princeton, New Jersey 08 544, United States
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Crisp RW, Schrauben JN, Beard MC, Luther JM, Johnson JC. Coherent exciton delocalization in strongly coupled quantum dot arrays. NANO LETTERS 2013; 13:4862-9. [PMID: 24041088 DOI: 10.1021/nl402725m] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Quantum dots (QDs) coupled into disordered arrays have exhibited the intriguing property of bulk-like transport while maintaining discrete excitonic optical transitions. We have utilized ultrafast cross-polarized transient grating (CPTG) spectroscopy to measure electron-hole wave function overlap in CdSe QD films with chemically modified surfaces for tuning inter-QD electronic coupling. By comparing the CPTG decays with those of isolated QDs, we find that excitons coherently delocalize to form excited states more than 200% larger than the QD diameter.
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Affiliation(s)
- Ryan W Crisp
- National Renewable Energy Laboratory , 15013 Denver West Pkwy, Golden, Colorado 80401, United States
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Ma H, Jin Z, Zhang Z, Li G, Ma G. Exciton Spin Relaxation in Colloidal CdSe Quantum Dots at Room Temperature. J Phys Chem A 2012; 116:2018-23. [DOI: 10.1021/jp2116643] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hong Ma
- Department of Physics, Shanghai University, 99 Shanghai Road, Shanghai 200444,
P. R. China
- College of
Physics and Electronics, Shandong Normal University, Jinan 250014, P. R. China
| | - Zuanming Jin
- Department of Physics, Shanghai University, 99 Shanghai Road, Shanghai 200444,
P. R. China
| | - Zhengbing Zhang
- Department of Physics, Shanghai University, 99 Shanghai Road, Shanghai 200444,
P. R. China
| | - Gaofang Li
- Department of Physics, Shanghai University, 99 Shanghai Road, Shanghai 200444,
P. R. China
| | - Guohong Ma
- Department of Physics, Shanghai University, 99 Shanghai Road, Shanghai 200444,
P. R. China
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7
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Turner DB, Hassan Y, Scholes GD. Exciton superposition states in CdSe nanocrystals measured using broadband two-dimensional electronic spectroscopy. NANO LETTERS 2012; 12:880-886. [PMID: 22201519 DOI: 10.1021/nl2039502] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Coherent superpositions among eigenstates are of interest in fields as diverse as photosynthesis and quantum computation. In this report, we used two-dimensional electronic spectroscopy (2D ES) to measure the decoherence time of a superposition of the two lowest-energy excitons in colloidal CdSe nanocrystals (cubic phase) in solution at room temperature. In the electron-hole representation, the quantum coherence is, remarkably, a twelve-particle correlation. By comparing the measured 2D ES to simulations, we also explored the effects of inhomogeneous broadening and examined the spectroscopic signatures of biexcitons.
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Affiliation(s)
- Daniel B Turner
- Department of Chemistry and Centre for Quantum Information and Quantum Control, University of Toronto, 80 Saint George Street, Toronto, Ontario, M5S 3H6 Canada
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8
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Wong CY, Scholes GD. Biexcitonic Fine Structure of CdSe Nanocrystals Probed by Polarization-Dependent Two-Dimensional Photon Echo Spectroscopy. J Phys Chem A 2010; 115:3797-806. [DOI: 10.1021/jp1079197] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Cathy Y. Wong
- Department of Chemistry, 80 St. George Street, Institute for Optical Sciences, and Centre for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario, M5S 3H6 Canada
| | - Gregory D. Scholes
- Department of Chemistry, 80 St. George Street, Institute for Optical Sciences, and Centre for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario, M5S 3H6 Canada
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Womick JM, Miller SA, Moran AM. Toward the origin of exciton electronic structure in phycobiliproteins. J Chem Phys 2010; 133:024507. [PMID: 20632763 DOI: 10.1063/1.3457378] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Femtosecond laser spectroscopies are used to examine the electronic structures of two proteins found in the phycobilisome antenna of cyanobacteria, allophycocyanin (APC) and C-phycocyanin (CPC). The wave function composition involving the pairs of phycocyanobilin pigments (i.e., dimers) found in both proteins is the primary focus of this investigation. Despite their similar geometries, earlier experimental studies conducted in our laboratory and elsewhere observe clear signatures of exciton electronic structure in APC but not CPC. This issue is further investigated here using new experiments. Transient grating (TG) experiments employing broadband quasicontinuum probe pulses find a redshift in the signal spectrum of APC, which is almost twice that of CPC. Dynamics in the TG signal spectra suggest that the sub-100 fs dynamics in APC and CPC are respectively dominated by internal conversion and nuclear relaxation. A specialized technique, intraband electronic coherence spectroscopy (IECS), photoexcites electronic and nuclear coherences with nearly full suppression of signals corresponding to electronic populations. The main conclusion drawn by IECS is that dephasing of intraband electronic coherences in APC occurs in less than 25 fs. This result rules out correlated pigment fluctuations as the mechanism enabling exciton formation in APC and leads us to propose that the large Franck-Condon factors of APC promote wave function delocalization in the vibronic basis. For illustration, we compute the Hamiltonian matrix elements involving the electronic origin of the alpha84 pigment and the first excited vibronic level of the beta84 pigment associated with a hydrogen out-of-plane wagging mode at 800 cm(-1). For this pair of vibronic states, the -51 cm(-1) coupling is larger than the 40 cm(-1) energy gap, thereby making wave function delocalization a feasible prospect. By contrast, CPC possesses no pair of vibronic levels for which the intermolecular coupling is larger than the energy gap between vibronic states. This study of APC and CPC may be important for understanding the photophysics of other phycobiliproteins, which generally possess large vibronic couplings.
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Affiliation(s)
- Jordan M Womick
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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11
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Huxter VM, Scholes GD. Acoustic phonon strain induced mixing of the fine structure levels in colloidal CdSe quantum dots observed by a polarization grating technique. J Chem Phys 2010; 132:104506. [DOI: 10.1063/1.3350871] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
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12
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Womick JM, Moran AM. Exciton Coherence and Energy Transport in the Light-Harvesting Dimers of Allophycocyanin. J Phys Chem B 2009; 113:15747-59. [DOI: 10.1021/jp907644h] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Jordan M. Womick
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Andrew M. Moran
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
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13
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Kim J, Wong CY, Scholes GD. Exciton fine structure and spin relaxation in semiconductor colloidal quantum dots. Acc Chem Res 2009; 42:1037-46. [PMID: 19425542 DOI: 10.1021/ar8002046] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Quantum dots (QDs) have discrete quantum states isolated from the environment, making QDs well suited for quantum information processing. In semiconductor QDs, the electron spins can be coherently oriented by photoexcitation using circularly polarized light, creating optical orientation. The optically induced spin orientation could serve as a unit for data storage and processing. Carrier spin orientation is also envisioned to be a key component in a related, though parallel, field of semiconductor spintronics. However, the oriented spin population rapidly loses its coherence by interaction with the environment, thereby erasing the prepared information. Since long-lasting spin orientation is desirable in both areas of investigation, spin relaxation is the central focus of investigation for optimization of device performance. In this Account, we discuss a topic peripherally related to these emerging areas of investigation: exciton fine structure relaxation (EFSR). The radiationless transition occurring in the exciton fine structure not only highlights a novel aspect of QD exciton relaxation but also has implications for carrier spin relaxation in QDs. We focus on examining the EFSR in connection with optical spin orientation and subsequent ultrafast relaxation of electron and hole spin densities in the framework of the exciton fine structure basis. Despite its significance, the study of exciton fine structure in colloidal QDs has been hampered by the experimental challenge arising from inhomogeneous line broadening that obscures the details of closely spaced fine structure states in the frequency domain. In this Account, we show that spin relaxation occurring in the fine structure of CdSe QDs can be probed by a time-domain nonlinear polarization spectroscopy, circumventing the obstacles confronted in the frequency-domain spectroscopy. In particular, by combining polarization sequences of multiple optical pulses with the unique optical selection rules of semiconductors, fast energy relaxation among the QD exciton fine structure states is selectively measured. The measured exciton fine structure relaxation, which is a nanoscale analogue of molecular radiationless transitions, contains direct information on the relaxation of spin densities of electron and hole carriers, that is, spin relaxation in QDs. From the exciton fine structure relaxation rates measured for CdSe nanorods and complex-shaped nanocrystals using nonlinear polarization spectroscopy, we elucidated the implications of QD size and shape on the QD exciton properties as well, for example, size- and shape-scaling laws governing exciton spin flips and how an exciton is delocalized in a QD. We envision that the experimental development and the discoveries of QD exciton properties presented in this Account will inspire further studies toward revealing the characteristics of QD excitons and spin relaxation therein, for example, spin relaxation in QDs made of various materials with different electronic structures, spin relaxation under an external perturbation of QD electronic states using magnetic fields, and spin relaxation of separated electrons and holes in type-II QD heterostructures.
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Affiliation(s)
- Jeongho Kim
- Department of Chemistry, 80 St. George Street, Institute for Optical Sciences, and Center for Quantum Information and Quantum Control, University of Toronto, Ontario, M5S 3H6 Canada
| | - Cathy Y. Wong
- Department of Chemistry, 80 St. George Street, Institute for Optical Sciences, and Center for Quantum Information and Quantum Control, University of Toronto, Ontario, M5S 3H6 Canada
| | - Gregory D. Scholes
- Department of Chemistry, 80 St. George Street, Institute for Optical Sciences, and Center for Quantum Information and Quantum Control, University of Toronto, Ontario, M5S 3H6 Canada
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Womick JM, Miller SA, Moran AM. Probing the Dynamics of Intraband Electronic Coherences in Cylindrical Molecular Aggregates. J Phys Chem A 2009; 113:6587-98. [DOI: 10.1021/jp811064z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Jordan M. Womick
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Stephen A. Miller
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
| | - Andrew M. Moran
- Department of Chemistry, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599
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Womick JM, Miller SA, Moran AM. Correlated Exciton Fluctuations in Cylindrical Molecular Aggregates. J Phys Chem B 2009; 113:6630-9. [DOI: 10.1021/jp810291d] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Jordan M. Womick
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Stephen A. Miller
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Andrew M. Moran
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599
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Collini E, Scholes GD. Electronic and Vibrational Coherences in Resonance Energy Transfer along MEH-PPV Chains at Room Temperature. J Phys Chem A 2009; 113:4223-41. [DOI: 10.1021/jp810757x] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Elisabetta Collini
- Lash-Miller Chemical Laboratories, Institute for Optical Sciences and Centre for Quantum Information and Quantum Control, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Gregory D. Scholes
- Lash-Miller Chemical Laboratories, Institute for Optical Sciences and Centre for Quantum Information and Quantum Control, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
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17
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He J, Lo SS, Kim J, Scholes GD. Control of exciton spin relaxation by electron-hole decoupling in type-II nanocrystal heterostructures. NANO LETTERS 2008; 8:4007-4013. [PMID: 18839999 DOI: 10.1021/nl802668s] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The electron spin flip relaxation dynamics in type II CdSe/CdTe nanorod heterostructures are investigated by an ultrafast polarization transient grating technique. Photoexcited charge separation in the heterostructures suppresses the electron-hole exchange interaction and their recombination, which reduces the electron spin relaxation rate in CdSe nanocrystals by 1 order of magnitude compared to exciton relaxation. The electron orientation is preserved during charge transfer from CdTe to CdSe, and its relaxation time constant is found to be approximately 5 ps at 293 K in the CdSe part of these nanorods. This finding suggests that hole spin relaxation determines the exciton fine structure relaxation rate and therefore control of exciton spin relaxation in semiconductor nanostructures is possible by delocalizing or translating the hole density relative to the electron.
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Affiliation(s)
- Jun He
- Department of Chemistry, Institute for Optical Sciences, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
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18
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Johnson JC, Gerth KA, Song Q, Murphy JE, Nozik AJ, Scholes GD. Ultrafast exciton fine structure relaxation dynamics in lead chalcogenide nanocrystals. NANO LETTERS 2008; 8:1374-1381. [PMID: 18376866 DOI: 10.1021/nl080126a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The rates of fine structure relaxation in PbS, PbSe, and PbTe nanocrystals were measured on a femtosecond time scale as a function of temperature with no applied magnetic field by cross-polarized transient grating spectroscopy (CPTG) and circularly polarized pump-probe spectroscopy. The relaxation rates among exciton fine structure states follow trends with nanocrystal composition and size that are consistent with the expected influence of material dependent spin-orbit coupling, confinement enhanced electron-hole exchange interaction, and splitting between L valleys that are degenerate in the bulk. The size dependence of the fine structure relaxation rate is considerably different from what is observed for small CdSe nanocrystals, which appears to result from the unique material properties of the highly confined lead chalcogenide quantum dots. Modeling and qualitative considerations lead to conclusions about the fine structure of the lowest exciton absorption band, which has a potentially significant bearing on photophysical processes that make these materials attractive for practical purposes.
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Affiliation(s)
- Justin C Johnson
- National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, USA.
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