1
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Tran TX, Jang YJ, Vu VT, Jung CW, Do VD, Jin Y, Lee J, Kim H, Kim JH. Augmented Extraction Efficiency of a Hot D Exciton in MoS 2 via Intervalley Scattering. NANO LETTERS 2024; 24:11163-11169. [PMID: 39225119 DOI: 10.1021/acs.nanolett.4c01837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
Prolonging hot carrier cooling, a crucial factor in optoelectronic applications, including hot carrier photovoltaics, presents a significant challenge. High-energy band-nesting excitons within parallel bands offer a promising and underexplored avenue for addressing this issue. Here, we exploit an exceptional D exciton cooling prolongation of 2 to 3 orders of magnitude compared to sub-picosecond in typical transition metal dichalcogenides (TMDs) owing to the complex Coulomb environment and the sequential and mismatch-valley relaxation. Simultaneously, the intervalley scattering upconversion of band-edge excitons with the slow D exciton formation in the metastable Γ valley/hill also reduces the cooling rate. We successfully extract D and C excitons as hot carriers through integrating with various thicknesses of TiOx, achieving the highest efficiency of 98% and 85% at a Ti thickness of 2 nm. Our findings highlight the potential of band-nesting excitons for extending hot carrier cooling time, paving the way for advancements in hot carrier-based optoelectronic devices.
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Affiliation(s)
- Thanh-Xuan Tran
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
- Center for Ultrafast Phase Transformation, Department of Physics, Sogang University, Seoul 04107, Republic of Korea
| | - Yu Jin Jang
- Solar Energy Research Institute of Singapore (SERIS), National University of Singapore (NUS), Singapore 117574
| | - Van-Tu Vu
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Chan-Woo Jung
- Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Van Dam Do
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Yeongrok Jin
- Department of Physics, Pusan National University, Busan 46241, Republic of Korea
| | - Jaekwang Lee
- Department of Physics, Pusan National University, Busan 46241, Republic of Korea
| | - Hyunjung Kim
- Center for Ultrafast Phase Transformation, Department of Physics, Sogang University, Seoul 04107, Republic of Korea
| | - Ji-Hee Kim
- Department of Physics, Pusan National University, Busan 46241, Republic of Korea
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2
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Fang J, Li P, Zhang L, Li X, Zhang J, Qin C, Debnath T, Huang W, Chen R. Stimulating Phonon Bottleneck Effect in Organic Semiconductors by Charge-Transfer-Mediated J-Aggregation. J Am Chem Soc 2024; 146:961-969. [PMID: 38157246 DOI: 10.1021/jacs.3c11262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Hot carriers rapidly lose kinetic energies on a subpicosecond time scale, posing significant limitations on semiconductors' photon-conversion efficiencies. To slow the hot carrier cooling, the phonon bottleneck effect is constructed prevalently in quantum-confined structures with discrete energy levels. However, the maximum energy separation (ΔEES) between the energy levels is in a range of several hundred meV, leading to unsatisfactory cooling time. To address this, we design a novel organic semiconductor capable of forming intermolecular charge transfer (CT) in J-aggregates, where the lowest singlet excited state (S1) splits into two states due to the significant interplay between the Coulomb interaction and intermolecular CT coupling. The ΔEES between the two states can be adjusted up to 1.02 eV, and an extremely slow carrier cooling process of ∼72.3 ps was observed by femtosecond transient absorption spectroscopy. Moreover, the phonon bottleneck effect was identified in organic materials for the first time, and CT-mediated J-aggregation with short-range interactions was found to be the key to achieving large ΔEES. The significantly prolonged carrier cooling time, compared to <100 fs in the isolated molecule (10-6 M), highlights the potential of organic molecules with diversified aggregation structures in achieving long-lived hot carriers. These findings provide valuable insights into the intrinsic photophysics of electron-phonon scattering in organic semiconductors.
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Affiliation(s)
- Jiawen Fang
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, China
| | - Ping Li
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, China
| | - Longyan Zhang
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, China
| | - Xiuzhi Li
- Henan Key Laboratory of Infrared Materials and Spectrum Measures and Applications, School of Physics, Henan Normal University, Xinxiang 453007, China
| | - Jingyu Zhang
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, China
| | - Chaochao Qin
- Henan Key Laboratory of Infrared Materials and Spectrum Measures and Applications, School of Physics, Henan Normal University, Xinxiang 453007, China
| | - Tushar Debnath
- Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Wei Huang
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, China
- Institute of Flexible Electronics (IFE), Northwestern Polytechnical University, Xi'an 710072, Shaanxi, China
| | - Runfeng Chen
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing 210023, China
- School of Materials Science and Engineering, Zhejiang Sci-Tech University, Hangzhou 310018, China
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3
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Zhou M, Higaki T, Hu G, Sfeir MY, Chen Y, Jiang DE, Jin R. Three-orders-of-magnitude variation of carrier lifetimes with crystal phase of gold nanoclusters. SCIENCE (NEW YORK, N.Y.) 2019; 364:279-282. [PMID: 31000661 DOI: 10.1126/science.aaw8007] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 03/22/2019] [Indexed: 11/02/2022]
Abstract
We report a three-orders-of-magnitude variation of carrier lifetimes in exotic crystalline phases of gold nanoclusters (NCs) in addition to the well-known face-centered cubic structure, including hexagonal close-packed (hcp) Au30 and body-centered cubic (bcc) Au38 NCs protected by the same type of capping ligand. The bcc Au38 NC had an exceptionally long carrier lifetime (4.7 microseconds) comparable to that of bulk silicon, whereas the hcp Au30 NC had a very short lifetime (1 nanosecond). Although the presence of ligands may, in general, affect carrier lifetimes, experimental and theoretical results showed that the drastically different recombination lifetimes originate in the different overlaps of wave functions between the tetrahedral Au4 building blocks in the hierarchical structures of these NCs.
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Affiliation(s)
- Meng Zhou
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Tatsuya Higaki
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Guoxiang Hu
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - Matthew Y Sfeir
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Yuxiang Chen
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - De-En Jiang
- Department of Chemistry, University of California, Riverside, CA 92521, USA.
| | - Rongchao Jin
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
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4
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Philbin JP, Rabani E. Electron-Hole Correlations Govern Auger Recombination in Nanostructures. NANO LETTERS 2018; 18:7889-7895. [PMID: 30403875 DOI: 10.1021/acs.nanolett.8b03715] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The fast nonradiative decay of multiexcitonic states via Auger recombination is a fundamental process affecting a variety of applications based on semiconductor nanostructures. From a theoretical perspective, the description of Auger recombination in confined semiconductor nanostructures is a challenging task due to the large number of valence electrons and exponentially growing number of excited excitonic and biexcitonic states that are coupled by the Coulomb interaction. These challenges have restricted the treatment of Auger recombination to simple, noninteracting electron-hole models. Herein we present a novel approach for calculating Auger recombination lifetimes in confined nanostructures having thousands to tens of thousands of electrons, explicitly including electron-hole interactions. We demonstrate that the inclusion of electron-hole correlations are imperative to capture the correct scaling of the Auger recombination lifetime with the size and shape of the nanostructure. In addition, correlation effects are required to obtain quantitatively accurate lifetimes even for systems smaller than the exciton Bohr radius. Neglecting such correlations can result in lifetimes that are two orders of magnitude too long. We establish the utility of the new approach for CdSe quantum dots of varying sizes and for CdSe nanorods of varying diameters and lengths. Our new approach is the first theoretical method to postdict the experimentally known "universal volume scaling law" for quantum dots and makes novel predictions for the scaling of the Auger recombination lifetimes in nanorods.
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Affiliation(s)
- John P Philbin
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
| | - Eran Rabani
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
- The Sackler Center for Computational Molecular and Materials Science , Tel Aviv University , Tel Aviv 69978 , Israel
- Materials Science Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
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5
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Stolle CJ, Lu X, Yu Y, Schaller RD, Korgel BA. Efficient Carrier Multiplication in Colloidal Silicon Nanorods. NANO LETTERS 2017; 17:5580-5586. [PMID: 28762274 DOI: 10.1021/acs.nanolett.7b02386] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Auger recombination lifetimes, absorption cross sections, and the quantum yields of carrier multiplication (CM), or multiexciton generation (MEG), were determined for solvent-dispersed silicon (Si) nanorods using transient absorption spectroscopy (TAS). Nanorods with an average diameter of 7.5 nm and aspect ratios of 6.1, 19.3, and 33.2 were examined. Colloidal Si nanocrystals of similar diameters were also studied for comparison. The nanocrystals and nanorods were passivated with organic ligands by hydrosilylation to prevent surface oxidation and limit the effects of surface trapping of photoexcited carriers. All samples used in the study exhibited relatively efficient photoluminescence. The Auger lifetimes increased with nanorod length, and the nanorods exhibited higher CM quantum yield and efficiency than the nanocrystals with a similar band gap energy Eg. Beyond a critical length, the CM quantum yield decreases. Nanorods with the aspect ratio of 19.3 had the highest CM quantum yield of 1.6 ± 0.2 at 2.9Eg, which corresponded to a multiexciton yield that was twice as high as observed for the spherical nanocrystals.
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Affiliation(s)
- Carl Jackson Stolle
- McKetta Department of Chemical Engineering, Texas Materials Institute, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Xiaotang Lu
- McKetta Department of Chemical Engineering, Texas Materials Institute, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Yixuan Yu
- McKetta Department of Chemical Engineering, Texas Materials Institute, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Richard D Schaller
- Department of Chemistry, Northwestern University , Evanston, Illinois 60439, United States
- Center for Nanoscale Materials, Argonne National Laboratories , Argonne, Illinois 60439, United States
| | - Brian A Korgel
- McKetta Department of Chemical Engineering, Texas Materials Institute, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin , Austin, Texas 78712, United States
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6
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Ponseca CS, Chábera P, Uhlig J, Persson P, Sundström V. Ultrafast Electron Dynamics in Solar Energy Conversion. Chem Rev 2017; 117:10940-11024. [DOI: 10.1021/acs.chemrev.6b00807] [Citation(s) in RCA: 211] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Carlito S. Ponseca
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Pavel Chábera
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Jens Uhlig
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Petter Persson
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Villy Sundström
- Division
of Chemical Physics, Chemical Center, and ‡Theoretical Chemistry Division,
Chemical Center, Lund University, Box 124, Lund SE-221 00, Sweden
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7
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Spoor FM, Tomić S, Houtepen AJ, Siebbeles LDA. Broadband Cooling Spectra of Hot Electrons and Holes in PbSe Quantum Dots. ACS NANO 2017; 11:6286-6294. [PMID: 28558190 PMCID: PMC5492216 DOI: 10.1021/acsnano.7b02506] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 05/30/2017] [Indexed: 05/22/2023]
Abstract
Understanding cooling of hot charge carriers in semiconductor quantum dots (QDs) is of fundamental interest and useful to enhance the performance of QDs in photovoltaics. We study electron and hole cooling dynamics in PbSe QDs up to high energies where carrier multiplication occurs. We characterize distinct cooling steps of hot electrons and holes and build up a broadband cooling spectrum for both charge carriers. Cooling of electrons is slower than of holes. At energies near the band gap we find cooling times between successive electronic energy levels in the order of 0.5 ps. We argue that here the large spacing between successive electronic energy levels requires cooling to occur by energy transfer to vibrational modes of ligand molecules or phonon modes associated with the QD surface. At high excess energy the energy loss rate of electrons is 1-5 eV/ps and exceeds 8 eV/ps for holes. Here charge carrier cooling can be understood in terms of emission of LO phonons with a higher density-of-states in the valence band than the conduction band. The complete mapping of the broadband cooling spectrum for both charge carriers in PbSe QDs is a big step toward understanding and controlling the cooling of hot charge carriers in colloidal QDs.
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Affiliation(s)
- Frank
C. M. Spoor
- Optoelectronic
Materials Section, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Stanko Tomić
- Joule
Physics Laboratory, School of Computing, Science and Engineering, University of Salford, Manchester M5 4WT, United Kingdom
| | - Arjan J. Houtepen
- Optoelectronic
Materials Section, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Laurens D. A. Siebbeles
- Optoelectronic
Materials Section, Department of Chemical Engineering, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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8
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Pietryga JM, Park YS, Lim J, Fidler AF, Bae WK, Brovelli S, Klimov VI. Spectroscopic and Device Aspects of Nanocrystal Quantum Dots. Chem Rev 2017; 116:10513-622. [PMID: 27677521 DOI: 10.1021/acs.chemrev.6b00169] [Citation(s) in RCA: 400] [Impact Index Per Article: 57.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The field of nanocrystal quantum dots (QDs) is already more than 30 years old, and yet continuing interest in these structures is driven by both the fascinating physics emerging from strong quantum confinement of electronic excitations, as well as a large number of prospective applications that could benefit from the tunable properties and amenability toward solution-based processing of these materials. The focus of this review is on recent advances in nanocrystal research related to applications of QD materials in lasing, light-emitting diodes (LEDs), and solar energy conversion. A specific underlying theme is innovative concepts for tuning the properties of QDs beyond what is possible via traditional size manipulation, particularly through heterostructuring. Examples of such advanced control of nanocrystal functionalities include the following: interface engineering for suppressing Auger recombination in the context of QD LEDs and lasers; Stokes-shift engineering for applications in large-area luminescent solar concentrators; and control of intraband relaxation for enhanced carrier multiplication in advanced QD photovoltaics. We examine the considerable recent progress on these multiple fronts of nanocrystal research, which has resulted in the first commercialized QD technologies. These successes explain the continuing appeal of this field to a broad community of scientists and engineers, which in turn ensures even more exciting results to come from future exploration of this fascinating class of materials.
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Affiliation(s)
- Jeffrey M Pietryga
- Nanotechnology and Advanced Spectroscopy Team, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Young-Shin Park
- Nanotechnology and Advanced Spectroscopy Team, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.,Center for High Technology Materials, University of New Mexico , Albuquerque, New Mexico 87131, United States
| | - Jaehoon Lim
- Nanotechnology and Advanced Spectroscopy Team, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Andrew F Fidler
- Nanotechnology and Advanced Spectroscopy Team, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
| | - Wan Ki Bae
- Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology , Seoul 02792, Korea
| | - Sergio Brovelli
- Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca , I-20125 Milano, Italy
| | - Victor I Klimov
- Nanotechnology and Advanced Spectroscopy Team, Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
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9
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Placencia D, Boercker JE, Foos EE, Tischler JG. Synthesis and Optical Properties of PbSe Nanorods with Controlled Diameter and Length. J Phys Chem Lett 2015; 6:3360-3364. [PMID: 26267558 DOI: 10.1021/acs.jpclett.5b01511] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The synthesis of PbSe nanorods with low branching (<1%), high aspect ratios (up to ∼16), and controlled lengths and diameters was demonstrated via the removal of water and oleic acid from the synthesis precursors. It was determined that the proper combination of reaction time and temperature allows for the control of PbSe nanorod length and diameter and therefore control over their electronic states, as probed through absorbance and photoluminescence measurements. Similar to PbSe nanowires, nanorods display higher Stokes shifts than for spherical nanocrystals due to intrananorod diameter fluctuations.
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Affiliation(s)
- Diogenes Placencia
- U.S. Naval Research Laboratory , 4555 Overlook Avenue, SW, Washington, DC 20375, United States
| | - Janice E Boercker
- U.S. Naval Research Laboratory , 4555 Overlook Avenue, SW, Washington, DC 20375, United States
| | - Edward E Foos
- Naval Surface Warfare Center, Indian Head Explosive Ordinance Disposal Technology Division , 2008 Stump Neck Road, Indian Head, Maryland 20640, United States
| | - Joseph G Tischler
- U.S. Naval Research Laboratory , 4555 Overlook Avenue, SW, Washington, DC 20375, United States
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10
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Sills A, Califano M. Origins of improved carrier multiplication efficiency in elongated semiconductor nanostructures. Phys Chem Chem Phys 2015; 17:2573-81. [DOI: 10.1039/c4cp03706e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Our calculations show that the origins of improved carrier multiplication efficiency in elongated semiconductor nanostructures can be attributed purely to electronic structure effects.
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Affiliation(s)
- Andrew Sills
- Institute of Microwaves and Photonics
- School of Electronic and Electrical Engineering
- University of Leeds
- UK
| | - Marco Califano
- Institute of Microwaves and Photonics
- School of Electronic and Electrical Engineering
- University of Leeds
- UK
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11
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Cunningham PD, Boercker JE, Placencia D, Tischler JG. Anisotropic absorption in PbSe nanorods. ACS NANO 2014; 8:581-590. [PMID: 24377267 DOI: 10.1021/nn405184j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We present absorption anisotropy measurements in PbSe nanostructures. This is accomplished via a new means of measuring absorption anisotropy in randomly oriented solution ensembles of nanostructures via pump-probe spectroscopy, which exploits the polarization memory effect. We observe isotropic absorption in nanocrystals and anisotropic absorption in nanorods, which increases upon elongation from aspect ratio 1 to 4 and is constant for longer nanorods. The measured volume-normalized absorption cross section is 1.8 ± 0.3 times larger for parallel pump and probe polarizations in randomly oriented nanorods as compared to nanocrystals. We show that this enhancement would be larger than an order of magnitude for aligned nanorods. Despite being in the strong quantum confinement regime, the aspect ratio dependence of the absorption anisotropy in PbSe nanorods is described classically by the effects of dielectric contrast on an anisotropic nanostructure. These results imply that the dielectric constant of the surrounding medium can be used to influence the optoelectronic properties of nanorods, including polarized absorption and emission, phonon modes, multiple exciton generation efficiency, and Auger recombination rate.
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Affiliation(s)
- Paul D Cunningham
- U.S. Naval Research Laboratory , 4555 Overlook Avenue SW, Washington, D.C. 20375, United States
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12
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Boercker JE, Foos EE, Placencia D, Tischler JG. Control of PbSe Nanorod Aspect Ratio by Limiting Phosphine Hydrolysis. J Am Chem Soc 2013; 135:15071-6. [DOI: 10.1021/ja404576j] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Janice E. Boercker
- United States Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Edward E. Foos
- United States Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Diogenes Placencia
- United States Naval Research Laboratory, Washington, D.C. 20375, United States
| | - Joseph G. Tischler
- United States Naval Research Laboratory, Washington, D.C. 20375, United States
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13
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Kramer IJ, Sargent EH. The Architecture of Colloidal Quantum Dot Solar Cells: Materials to Devices. Chem Rev 2013; 114:863-82. [DOI: 10.1021/cr400299t] [Citation(s) in RCA: 401] [Impact Index Per Article: 36.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Illan J. Kramer
- Edward S. Rogers Department of Electrical & Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario M5S 3G4, Canada
| | - Edward H. Sargent
- Edward S. Rogers Department of Electrical & Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario M5S 3G4, Canada
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14
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Aerts M, Spoor FCM, Grozema FC, Houtepen AJ, Schins JM, Siebbeles LDA. Cooling and Auger recombination of charges in PbSe nanorods: crossover from cubic to bimolecular decay. NANO LETTERS 2013; 13:4380-4386. [PMID: 23968451 DOI: 10.1021/nl402223q] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The cooling and Auger recombination of electron-hole pairs in PbSe quantum dots (QDs) and a series of nanorods (NRs) with similar diameter and varying length was studied by ultrafast pump-probe laser spectroscopy. Hot exciton cooling rates are found to be independent of nanocrystal shape. The energy relaxation rate decreases during cooling of charges, due to reduction of the density of electronic states. Auger recombination occurs via cubic third-order kinetics of uncorrelated charges in the QDs and NRs with length up to 29 nm. On increasing the NR length to 52 nm, a crossover to bimolecular exciton decay is found. This suggests a spatial extent of the one-dimensional exciton of 30-50 nm, which is significantly smaller than the value of 92 nm for the three-dimensional exciton diameter in bulk PbSe. The Auger decay time increases with NR length, which is beneficial for applications in nanocrystal lasers as well as for generation of free charges in photovoltaics.
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Affiliation(s)
- Michiel Aerts
- Optoelectronic Materials Section, Department of Chemical Engineering, Delft University of Technology , Julianalaan 136, 2628 BL Delft, The Netherlands
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15
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Midgett AG, Luther JM, Stewart JT, Smith DK, Padilha LA, Klimov VI, Nozik AJ, Beard MC. Size and composition dependent multiple exciton generation efficiency in PbS, PbSe, and PbS(x)Se(1-x) alloyed quantum dots. NANO LETTERS 2013; 13:3078-85. [PMID: 23750998 DOI: 10.1021/nl4009748] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Using ultrafast transient absorption and time-resolved photoluminescence spectroscopies, we studied multiple exciton generation (MEG) in quantum dots (QDs) consisting of either PbSe, PbS, or a PbSxSe1-x alloy for various QD diameters with corresponding bandgaps (Eg) ranging from 0.6 to 1 eV. For each QD sample, we determine the MEG efficiency, ηMEG, defined in terms of the electron-hole pair creation energy (εeh) such that ηMEG = Eg/εeh. In previous reports, we found that ηMEG is about two times greater in PbSe QDs compared to bulk PbSe, however, little could be said about the QD-size dependence of MEG. In this study, we find for both PbS and PbSxSe1-x alloyed QDs that ηMEG decreases lineally with increasing QD diameter within the strong confinement regime. When the QD radius is normalized by a material-dependent characteristic radius, defined as the radius at which the electron-hole Coulomb and confinement energies are equivalent, PbSe, PbS, and PbSxSe1-x exhibit similar MEG behaviors. Our results suggest that MEG increases with quantum confinement, and we discuss the interplay between a size-dependent MEG rate versus hot exciton cooling.
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Affiliation(s)
- Aaron G Midgett
- National Renewable Energy Laboratory , Golden, Colorado 80401, United States
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16
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Stewart JT, Padilha LA, Bae WK, Koh WK, Pietryga JM, Klimov VI. Carrier Multiplication in Quantum Dots within the Framework of Two Competing Energy Relaxation Mechanisms. J Phys Chem Lett 2013; 4:2061-8. [PMID: 26283253 DOI: 10.1021/jz4004334] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The realization of high-yield, low-threshold carrier multiplication (CM) in semiconductor quantum dots (QDs) is a promising step toward third-generation photovoltaics (PV). Recent studies of QD solar cells have shown that CM can indeed produce greater-than-unity quantum efficiencies in photon-to-charge-carrier conversion, establishing the relevance of this process to practical PV technologies. While being appreciable, the reported CM yields are still not high enough for a significant increase in the power conversion efficiency over traditional bulk materials. At present, the design of nanomaterials with improved CM is hindered by a poor understanding of the mechanism underlying this process. Here, we present a possible solution to this problem by introducing a model that treats CM as a competition between impact-ionization-like scattering and non-CM energy losses. Importantly, it allows for evaluation of expected CM yields from fairly straightforward measurements of Auger recombination (inverse of CM) and near-band-edge carrier cooling. The validation of this model via a comparative CM study of PbTe, PbSe, and PbS QDs suggests that it indeed represents a predictive capability, which might help in the development of nanomaterials with improved CM performance.
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Affiliation(s)
- John T Stewart
- Center for Advanced Solar Photophysics, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Lazaro A Padilha
- Center for Advanced Solar Photophysics, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Wan Ki Bae
- Center for Advanced Solar Photophysics, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Weon-Kyu Koh
- Center for Advanced Solar Photophysics, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Jeffrey M Pietryga
- Center for Advanced Solar Photophysics, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Victor I Klimov
- Center for Advanced Solar Photophysics, C-PCS, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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Padilha LA, Stewart JT, Sandberg RL, Bae WK, Koh WK, Pietryga JM, Klimov VI. Aspect ratio dependence of auger recombination and carrier multiplication in PbSe nanorods. NANO LETTERS 2013; 13:1092-9. [PMID: 23360573 DOI: 10.1021/nl304426y] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Nanomaterials with efficient carrier multiplication (CM), that is, generation of multiple electron-hole pairs by single photons, have been the object of intense scientific interest as potential enablers of high efficiency generation-III photovoltaics. In this work, we explore nanocrystal shape control as a means for enhancing CM. Specifically, we investigate the influence of aspect ratio (ρ) of PbSe nanorods (NRs) on both CM and the inverse of this process, Auger recombination. We observe that Auger lifetimes in NRs increase with increasing particle volume and for a fixed cross-sectional size follow a linear dependence on the NR length. For a given band gap energy, the CM efficiency in NRs shows a significant dependence on aspect ratio and exhibits a maximum at ρ ∼ 6-7 for which the multiexciton yields are a factor of ca. 2 higher than those in quantum dots with a similar bandgap energy. To rationalize our experimental observations, we analyze the influence of dimensionality on both CM and non-CM energy-loss mechanisms and offer possible explanations for the seemingly divergent effects the transition from zero- to one-dimensional confinement has on the closely related processes of Auger recombination and CM.
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Affiliation(s)
- Lazaro A Padilha
- Center for Advanced Solar Photophysics, Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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Hendricks MP, Cossairt BM, Owen JS. The importance of nanocrystal precursor conversion kinetics: mechanism of the reaction between cadmium carboxylate and cadmium bis(diphenyldithiophosphinate). ACS NANO 2012; 6:10054-10062. [PMID: 23043371 DOI: 10.1021/nn303769h] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We describe the synthesis of cadmium bis(diphenyldithiophosphinate) (Cd(S(2)PPh(2))(2)) from secondary phosphine sulfides and its conversion to cadmium sulfide nanocrystals. Heating Cd(S(2)PPh(2))(2) and cadmium tetradecanoate (≥4 equiv) to 240 °C results in complete conversion of Cd(S(2)PPh(2))(2) to cadmium sulfide nanocrystals with tetradecanoate surface termination. The nanocrystals have a narrow size distribution (d = 3.8-4.1 nm, σ < 10%) that is evident from the line width of the lowest energy absorption feature (λ = 412-422 nm, fwhm = 0.17 eV) and display bright photoluminescence (PLQY(band edge+trap) = 36%). Interestingly, the final diameter is insensitive to the reaction conditions, including the total concentration of precursors and initial cadmium to sulfur ratio. Monitoring the reaction with (31)P NMR, UV-visible, and infrared absorption spectroscopies shows that the production of cadmium diphenylphosphinate (Cd(O(2)PPh(2))(2)) and tetradecanoic anhydride co-products is coupled with the formation of cadmium sulfide. From these measurements we propose a balanced chemical equation for the conversion reaction and use it to optimize a synthesis that affords CdS nanocrystals in quantitative yield. In light of these results we discuss the importance of well-defined precursor reactivity to reproducible conversion kinetics and the synthesis of nanocrystals with unambiguous chemical composition.
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Affiliation(s)
- Mark P Hendricks
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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