1
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Wang K, Tao Y, Tang Z, Xu X, Benetti D, Vidal F, Zhao H, Rosei F, Sun X. Efficient Photoelectrochemical Hydrogen Generation Based on Core Size Effect of Heterostructured Quantum Dots. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2306453. [PMID: 38032174 DOI: 10.1002/smll.202306453] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 11/12/2023] [Indexed: 12/01/2023]
Abstract
Colloidal quantum dots (QDs) are shown to be effective as light-harvesting sensitizers of metal oxide semiconductor (MOS) photoelectrodes for photoelectrochemical (PEC) hydrogen (H2) generation. The CdSe/CdS core/shell architecture is widely studied due to their tunable absorption range and band alignment via engineering the size of each composition, leading to efficient carrier separation/transfer with proper core/shell band types. However, until now the effect of core size on the PEC performance along with tailoring the core/shell band alignment is not well understood. Here, by regulating four types of CdSe/CdS core/shell QDs with different core sizes (diameter of 2.8, 3.1, 3.5, and 4.8 nm) while the thickness of CdS shell remains the same (thickness of 2.0 ± 0.1 nm), the Type II, Quasi-Type II, and Type I core/shell architecture are successfully formed. Among these, the optimized CdSe/CdS/TiO2 photoelectrode with core size of 3.5 nm can achieve the saturated photocurrent density (Jph) of 17.4 mA cm-2 under standard one sun irradiation. When such cores are further optimized by capping alloyed shells, the Jph can reach values of 22 mA cm2 which is among the best-performed electrodes based on colloidal QDs.
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Affiliation(s)
- Kanghong Wang
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux et Télécommunications, 1650 Boul. Lionel Boulet, Varennes, Québec, J3×1P7, Canada
- Suzhou Institute for Advanced Research, University of Science and Technology China, Suzhou, Jiangsu, 215123, P. R. China
| | - Yi Tao
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Zikun Tang
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Xiaolan Xu
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Daniele Benetti
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux et Télécommunications, 1650 Boul. Lionel Boulet, Varennes, Québec, J3×1P7, Canada
| | - François Vidal
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux et Télécommunications, 1650 Boul. Lionel Boulet, Varennes, Québec, J3×1P7, Canada
| | - Haiguang Zhao
- State Key Laboratory of Bio-Fibers and Eco-Textiles & College of Physics, University-Industry Joint Center for Ocean Observation and Broadband Communication, Qingdao University, No. 308 Ningxia Road, Qingdao, 266071, P. R. China
| | - Federico Rosei
- Institut National de la Recherche Scientifique, Centre Énergie, Matériaux et Télécommunications, 1650 Boul. Lionel Boulet, Varennes, Québec, J3×1P7, Canada
| | - Xuhui Sun
- Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu, 215123, P. R. China
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2
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Li G, Lin K, Zhao K, Huang Y, Ji T, Shi L, Hao Y, Xiong Q, Zheng K, Pullerits T, Cui Y. Localized Bound Multiexcitons in Engineered Quasi-2D Perovskites Grains at Room Temperature for Efficient Lasers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2211591. [PMID: 36918401 DOI: 10.1002/adma.202211591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2022] [Revised: 03/03/2023] [Indexed: 05/19/2023]
Abstract
Reducing the excitation threshold to minimize the Joule heating is critical for the realization of perovskite laser diodes. Although bound excitons are promising for low threshold laser, how to generate them at room temperature for laser applications is still unclear in quasi-2D perovskite-based devices. In this work, via engineering quasi-2D perovskite PEA2 (CH3 NH3 )n -1 Pbn Br3 n +1 microscopic grains by the anti-solvent method, room-temperature multiexciton radiative recombination is successfully demonstrated at a remarkably low pump density of 0.97 µJ cm-2 , which is only one-fourth of that required in 2D CdSe nanosheets. In addition, the well-defined translational momentum in quasi-2D perovskite grains can restrict the Auger recombination which is detrimental to radiative emission. Furthermore, the quasi-2D perovskite grains are favorable for increasing binding energies of excitons and biexcitons and so as the related radiative recombination. Consequently, the prepared <n = 8> phase quasi-2D perovskite film renders a threshold of room-temperature stimulated emission as low as 13.7 µJ cm-2 , reduced by 58.6% relative to the amorphous counterpart with larger grains. The findings in this work are expected to facilitate the development of solution-processable perovskite multiexcitonic laser diodes.
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Affiliation(s)
- Guohui Li
- College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China
- Chemical physics division and NanoLund, Lund University, Box 124, Lund, 22100, Sweden
- Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering, Taiyuan, 030006, China
| | - Kai Lin
- College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Kefan Zhao
- College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Yang Huang
- College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Ting Ji
- College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Linlin Shi
- College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Yuying Hao
- College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China
| | - Qihua Xiong
- Department of Physics, Tsinghua University, Beijing, 100084, China
| | - Kaibo Zheng
- Chemical physics division and NanoLund, Lund University, Box 124, Lund, 22100, Sweden
| | - Tonu Pullerits
- Chemical physics division and NanoLund, Lund University, Box 124, Lund, 22100, Sweden
| | - Yanxia Cui
- College of Optoelectronics, Key Laboratory of Interface Science and Engineering in Advanced Materials, Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, China
- Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering, Taiyuan, 030006, China
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3
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Chung NTK, Nguyen PT, Tung HT, Phuc DH. Quantum Dot Sensitized Solar Cell: Photoanodes, Counter Electrodes, and Electrolytes. Molecules 2021; 26:2638. [PMID: 33946485 PMCID: PMC8125700 DOI: 10.3390/molecules26092638] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 04/25/2021] [Accepted: 04/27/2021] [Indexed: 11/16/2022] Open
Abstract
In this study, we provide the reader with an overview of quantum dot application in solar cells to replace dye molecules, where the quantum dots play a key role in photon absorption and excited charge generation in the device. The brief shows the types of quantum dot sensitized solar cells and presents the obtained results of them for each type of cell, and provides the advantages and disadvantages. Lastly, methods are proposed to improve the efficiency performance in the next researching.
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Affiliation(s)
- Nguyen Thi Kim Chung
- Thu Dau Mot University, Number 6, Tran Van on Street, Phu Hoa Ward, Thu Dau Mot 55000, Vietnam;
| | - Phat Tan Nguyen
- Department of Physics, Ho Chi Minh City University of Education, Ho Chi Minh City 70250, Vietnam;
| | - Ha Thanh Tung
- Faculty of Physics, Dong Thap University, Cao Lanh City 870000, Vietnam
| | - Dang Huu Phuc
- Laboratory of Applied Physics, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 70880, Vietnam
- Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 70880, Vietnam
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4
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Zhang Y, Wu G, Liu F, Ding C, Zou Z, Shen Q. Photoexcited carrier dynamics in colloidal quantum dot solar cells: insights into individual quantum dots, quantum dot solid films and devices. Chem Soc Rev 2020; 49:49-84. [PMID: 31825404 DOI: 10.1039/c9cs00560a] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The certified power conversion efficiency (PCE) record of colloidal quantum dot solar cells (QDSCs) has considerably improved from below 4% to 16.6% in the last few years. However, the record PCE value of QDSCs is still substantially lower than the theoretical efficiency. So far, there have been several reviews on recent and significant achievements in QDSCs, but reviews on photoexcited carrier dynamics in QDSCs are scarce. The photovoltaic performances of QDSCs are still limited by the photovoltage, photocurrent and fill factor that are mainly determined by the photoexcited carrier dynamics, including carrier (or exciton) generation, carrier extraction or transfer, and the carrier recombination process, in the devices. In this review, the photoexcited carrier dynamics in the whole QDSCs, originating from individual quantum dots (QDs) to the entire device as well as the characterization methods used for analyzing the photoexcited carrier dynamics are summarized and discussed. The recent research including photoexcited multiple exciton generation (MEG), hot electron extraction, and carrier transfer between adjacent QDs, as well as carrier injection and recombination at each interface of QDSCs are discussed in detail herein. The influence of photoexcited carrier dynamics on the physiochemical properties of QDs and photovoltaic performances of QDSC devices is also discussed.
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Affiliation(s)
- Yaohong Zhang
- Faculty of Informatics and Engineering, The University of Electro-Communications, Tokyo 182-8585, Japan.
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5
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Li XB, Xin ZK, Xia SG, Gao XY, Tung CH, Wu LZ. Semiconductor nanocrystals for small molecule activation via artificial photosynthesis. Chem Soc Rev 2020; 49:9028-9056. [DOI: 10.1039/d0cs00930j] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The protocol of artificial photosynthesis using semiconductor nanocrystals shines light on green, facile and low-cost small molecule activation to produce solar fuels and value-added chemicals.
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Affiliation(s)
- Xu-Bing Li
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials
- Technical Institute of Physics and Chemistry
- Chinese Academy of Sciences
- Beijing 100190
- P. R. China
| | - Zhi-Kun Xin
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials
- Technical Institute of Physics and Chemistry
- Chinese Academy of Sciences
- Beijing 100190
- P. R. China
| | - Shu-Guang Xia
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials
- Technical Institute of Physics and Chemistry
- Chinese Academy of Sciences
- Beijing 100190
- P. R. China
| | - Xiao-Ya Gao
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials
- Technical Institute of Physics and Chemistry
- Chinese Academy of Sciences
- Beijing 100190
- P. R. China
| | - Chen-Ho Tung
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials
- Technical Institute of Physics and Chemistry
- Chinese Academy of Sciences
- Beijing 100190
- P. R. China
| | - Li-Zhu Wu
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials
- Technical Institute of Physics and Chemistry
- Chinese Academy of Sciences
- Beijing 100190
- P. R. China
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6
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Abstract
Ab initio based study of organic molecular based quantum cutting with predicted efficiency of 1.2, and proposition of design criteria.
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Affiliation(s)
| | - Mark T. Lusk
- Department of Physics
- Colorado School of Mines
- Golden
- USA
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7
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Ramalingam G, Saravanan KV, Vizhi TK, Rajkumar M, Baskar K. Synthesis of water-soluble and bio-taggable CdSe@ZnS quantum dots. RSC Adv 2018; 8:8516-8527. [PMID: 35539869 PMCID: PMC9078530 DOI: 10.1039/c7ra13400b] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Accepted: 02/08/2018] [Indexed: 11/21/2022] Open
Abstract
Many synthesized semiconductor QDs materials are formed using trioctylphosphine oxide (TOPO) but it requires high temperature, is very expensive and is also hydrophobic. Our study deals with selective syntheses of CdSe and core–shell CdSe/ZnS quantum dots (QDs) in aqueous solution by a simple heating and refluxing method. It is more hydrophilic, needs less temperature, is economically viable and is eco-friendly. Bio-ligands, such as thioacetamide, itaconic acid and glutathione, were used as stabilizers for the biosynthesis of QDs. A simplified aqueous route was used to improve the quality of the colloidal nanocrystals. As a result, highly monodisperse, photoluminescent and biocompatible nanoparticles were obtained. The synthesized QDs were characterized by XRD, FTIR, confocal microscopy, ultraviolet (UV) absorption and photoluminescence (PL). The size of synthesized QDs was observed as 5.74 nm and the core–shell shape was confirmed by using XRD and confocal microscopy respectively. The QD nanoparticles showed antibacterial activity against pathogenic bacteria. The QDs could be applied for biological labelling, fluorescence bio-sensing and bio-imaging etc. Mystristic capped CdSe QDs with schematic diagram and formation mechanism of bio-taggable CdSe@ZnS QDs.![]()
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Affiliation(s)
- G. Ramalingam
- Department of Nanoscience and Technology
- Alagappa University
- India
| | | | - T. Kayal Vizhi
- Department of Physics
- Central University of Tamil Nadu
- India
| | - M. Rajkumar
- Department of Environmental Sciences
- Bharathiyar University
- Coimbatore
- India
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8
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Kaur H, Singh S, Aggarwal P, Sharma S, Yadav S, Hazra RK. Strongly Correlated Excitons of Regular/Irregular Planar Quantum Dots in Magnetic Field: Size-Extensive Bi- and Triexciton (e-h-e-h and e-e-h/e-h-h) Systems by Multipole Expansion. ACS OMEGA 2017; 2:7410-7423. [PMID: 31457308 PMCID: PMC6645354 DOI: 10.1021/acsomega.7b00886] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 09/26/2017] [Indexed: 06/10/2023]
Abstract
Excitons in parabolically confined planar quantum dots with a transverse magnetic field have been studied in various model systems. The correlations between e-h, e-e, and h-h have been incorporated in terms of exact, simply elegant, and absolutely terminating finite summed Lauricella functions which eliminate the secular divergence problem and pave way for a comprehensive understanding of certain exotic phenomena of various two-dimensional regular and irregular quantum dots. A simple yet highly accurate and exact variational wave function in terms of Whittaker-M function extensible to multiexcitonic systems has been propounded. We have also presented a formulation extending the size of the systems to triexcitonic (e-e-h/e-h-h), biexcitonic (e-h-e-h), and multiexcitonic ("N" e-h pair) planar dots by mono-, di-, quadru-, and octopole expansions. As a benchmark, we have examined the energy spectra, level-spacing statistics, heat capacities (C v at 1 K), and magnetization (T ≈ 0-1 K) of He/SiO2/BN/GaAs model systems for different lateral confinements, magnetic fields, mass ratios of e-h, and dielectric constants (ϵ).
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9
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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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10
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11
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Goldey MB, Brawand NP, Vörös M, Galli G. Charge Transport in Nanostructured Materials: Implementation and Verification of Constrained Density Functional Theory. J Chem Theory Comput 2017; 13:2581-2590. [DOI: 10.1021/acs.jctc.7b00088] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Matthew B. Goldey
- Institute
for Molecule Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Nicholas P. Brawand
- Institute
for Molecule Engineering, University of Chicago, Chicago, Illinois 60637, United States
| | - Márton Vörös
- Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Giulia Galli
- Institute
for Molecule Engineering, University of Chicago, Chicago, Illinois 60637, United States
- Argonne National Laboratory, Lemont, Illinois 60439, United States
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12
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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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13
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Eshet H, Baer R, Neuhauser D, Rabani E. Theory of highly efficient multiexciton generation in type-II nanorods. Nat Commun 2016; 7:13178. [PMID: 27725668 PMCID: PMC5062596 DOI: 10.1038/ncomms13178] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 09/09/2016] [Indexed: 12/20/2022] Open
Abstract
Multiexciton generation, by which more than a single electron–hole pair is generated on optical excitation, is a promising paradigm for pushing the efficiency of solar cells beyond the Shockley–Queisser limit of 31%. Utilizing this paradigm, however, requires the onset energy of multiexciton generation to be close to twice the band gap energy and the efficiency to increase rapidly above this onset. This challenge remains unattainable even using confined nanocrystals, nanorods or nanowires. Here, we show how both goals can be achieved in a nanorod heterostructure with type-II band offsets. Using pseudopotential atomistic calculation on a model type-II semiconductor heterostructure we predict the optimal conditions for controlling multiexciton generation efficiencies at twice the band gap energy. For a finite band offset, this requires a sharp interface along with a reduction of the exciton cooling and may enable a route for breaking the Shockley–Queisser limit. Multiple exciton generation could help limit thermalization losses in solar cells, but the efficiency of the process is still limited. Here, the authors show by atomistic calculations that type-II interfaces in nanostructures along with a change in exciton cooling rate favour multiple exciton generation.
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Affiliation(s)
- Hagai Eshet
- School of Chemistry, The Sackler Faculty of Exact Sciences, Tel Aviv University,Tel Aviv 69978, Israel.,The Raymond and Beverly Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 69978, Israel
| | - Roi Baer
- Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Daniel Neuhauser
- Department of Chemistry, University of California at Los Angeles, Los Angeles, California 90095 USA
| | - Eran Rabani
- The Raymond and Beverly Sackler Center for Computational Molecular and Materials Science, Tel Aviv University, Tel Aviv 69978, Israel.,Department of Chemistry, University of California and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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14
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Ka I, Le Borgne V, Fujisawa K, Hayashi T, Kim YA, Endo M, Ma D, El Khakani MA. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids. Sci Rep 2016; 6:20083. [PMID: 26830452 PMCID: PMC4735719 DOI: 10.1038/srep20083] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 12/01/2015] [Indexed: 11/15/2022] Open
Abstract
The pulsed laser deposition method was used to decorate appropriately single wall
carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a
novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand
engineering and/or surface functionalization. The number of laser ablation pulses
(NLp) was used to control the average size of the PbS-QDs and their
coverage on the SWCNTs’ surface. Photoconductive (PC) devices fabricated
from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse,
which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent
measurements revealed a strong photoconductivity of the NHs in the UV-visible
region, which is shown to be due to multiple exciton generation (MEG) in the
PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap
(Eg) = 0.86 eV), the MEG contribution of the NHs
based PC devices was shown to lead to a normalized internal quantum efficiency in
excess of 300% for photon energies ≥4.5Eg. While the lowest MEG
threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG
efficiency reaches values as high as
0.9 ± 0.1.
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Affiliation(s)
- Ibrahima Ka
- Institut National de la Recherche Scientifique, Centre-Énergie, Matériaux et Télécommunications, 1650, Blvd. Lionel-Boulet, Varennes, Qc, J3X-1S2, Canada
| | - Vincent Le Borgne
- Institut National de la Recherche Scientifique, Centre-Énergie, Matériaux et Télécommunications, 1650, Blvd. Lionel-Boulet, Varennes, Qc, J3X-1S2, Canada
| | - Kazunori Fujisawa
- Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano, 380-8553, Japan
| | - Takuya Hayashi
- Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano, 380-8553, Japan
| | - Yoong Ahm Kim
- Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano, 380-8553, Japan.,School of Polymer Science and Engineering, Chonnam National University, 77 Yonggong-ro, Buk-gu, Gwangju, 500-757, South Korea
| | - Morinobu Endo
- Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano, 380-8553, Japan
| | - Dongling Ma
- Institut National de la Recherche Scientifique, Centre-Énergie, Matériaux et Télécommunications, 1650, Blvd. Lionel-Boulet, Varennes, Qc, J3X-1S2, Canada
| | - My Ali El Khakani
- Institut National de la Recherche Scientifique, Centre-Énergie, Matériaux et Télécommunications, 1650, Blvd. Lionel-Boulet, Varennes, Qc, J3X-1S2, Canada
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15
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Li H, Zhitomirsky D, Dave S, Grossman JC. Toward the Ultimate Limit of Connectivity in Quantum Dots with High Mobility and Clean Gaps. ACS NANO 2016; 10:606-614. [PMID: 26743175 DOI: 10.1021/acsnano.5b05626] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Colloidal quantum dots (CQDs) are highly versatile nanoscale optoelectronic building blocks, but despite their materials engineering flexibility, there is a considerable lack of fundamental understanding of their electronic structure as they couple within thin films. By employing a joint experimental-theoretical study, we reveal the impact of connectivity in CQD assemblies, going beyond the single CQD picture. High-resolution transmission electron microscopy (HR-TEM) demonstrates connectivity motifs across different CQD sizes and length scales and provides the necessary perspective to build robust computational models to systematically study the achievable degree of connectivity in these materials. We focused on state-of-the-art surface ligand treatments, taking into account both the degree of connectivity and nanocrystal orientation, and performed ab initio simulations within the phonon-assisted hopping regime. Importantly, both the TEM studies and our simulation results revealed morphological and electronic defects that could dramatically reduce optoelectronic performance, and yet would not have been captured within a single CQD model that neglects connectivity. We calculate carrier mobility in the presence of such defect states and conclude that the best-achievable CQD assemblies for optoelectronics will require a modest degree of fusing via the {001} facet, followed by atomic ligand passivation to generate a clean band gap and unprecedentedly high charge transport.
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Affiliation(s)
- Huashan Li
- Department of Materials Science and Engineering and §Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - David Zhitomirsky
- Department of Materials Science and Engineering and §Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Shreya Dave
- Department of Materials Science and Engineering and §Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Jeffrey C Grossman
- Department of Materials Science and Engineering and §Department of Mechanical Engineering, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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16
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LaCount MD, Weingarten D, Hu N, Shaheen SE, van de Lagemaat J, Rumbles G, Walba DM, Lusk MT. Energy Pooling Upconversion in Organic Molecular Systems. J Phys Chem A 2015; 119:4009-16. [PMID: 25793313 DOI: 10.1021/acs.jpca.5b00509] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Michael D. LaCount
- Department
of Physics, Colorado School of Mines, Golden, Colorado 80401, United States
| | | | | | | | | | - Garry Rumbles
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | | | - Mark T. Lusk
- Department
of Physics, Colorado School of Mines, Golden, Colorado 80401, United States
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17
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Zhang X, Liu J, Johansson EMJ. Efficient charge-carrier extraction from Ag₂S quantum dots prepared by the SILAR method for utilization of multiple exciton generation. NANOSCALE 2015; 7:1454-1462. [PMID: 25504257 DOI: 10.1039/c4nr04463k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The utilization of electron-hole pairs (EHPs) generated from multiple excitons in quantum dots (QDs) is of great interest toward efficient photovoltaic devices and other optoelectronic devices; however, extraction of charge carriers remains difficult. Herein, we extract photocharges from Ag2S QDs and investigate the dependence of the electric field on the extraction of charges from multiple exciton generation (MEG). Low toxic Ag2S QDs are directly grown on TiO2 mesoporous substrates by employing the successive ionic layer adsorption and reaction (SILAR) method. The contact between QDs is important for the initial charge separation after MEG and for the carrier transport, and the space between neighbor QDs decreases with more SILAR cycles, resulting in better charge extraction. At the optimal electric field for extraction of photocharges, the results suggest that the threshold energy (hνth) for MEG is 2.41Eg. The results reveal that Ag2S QD is a promising material for efficient extraction of charges from MEG and that QDs prepared by SILAR have an advantageous electrical contact facilitating charge separation and extraction.
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Affiliation(s)
- Xiaoliang Zhang
- Department of Chemistry-Ångström Laboratory, Uppsala University, 75120 Uppsala, Sweden.
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18
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Stolle CJ, Schaller RD, Korgel BA. Efficient Carrier Multiplication in Colloidal CuInSe2 Nanocrystals. J Phys Chem Lett 2014; 5:3169-74. [PMID: 26276328 DOI: 10.1021/jz501640f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Transient absorption spectroscopy (TAS) was used to study carrier multiplication (CM) (also called multiexciton generation (MEG)) in solvent-dispersed colloidal CuInSe2 nanocrystals with diameters as small as 4.5 nm. Size-dependent carrier cooling rates, absorption cross sections, and Auger lifetimes were also determined. The energy threshold for CM in the CuInSe2 nanocrystals was found to be 2.4 ± 0.2 times the nanocrystal energy gap (Eg) and the CM efficiency was 36 ± 6% per unit Eg. This is similar to other types of nanocrystal quantum dot materials.
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Affiliation(s)
- C 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
| | - Richard D Schaller
- ‡Department of Chemistry, Northwestern University, Evanston, Illinois 60208, 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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19
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Eshet H, Baer R, Neuhauser D, Rabani E. Multiexciton Generation in Seeded Nanorods. J Phys Chem Lett 2014; 5:2580-2585. [PMID: 26277946 DOI: 10.1021/jz5010279] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The stochastic formulation of multiexciton generation (MEG) rates is extended to provide access to MEG efficiencies in nanostructures containing thousands of atoms. The formalism is applied to a series of CdSe/CdS seeded nanorod heterostructures with different core and shell dimensions. At energies above 3Eg (where Eg is the band gap), the MEG yield increases with decreasing core size, as expected for spherical nanocrystals. Surprisingly, this behavior is reversed for energies below this value, and is explained by the dependence of the density of states near the valence band edge, which increases with the core diameter. Our predictions indicate that the onset of MEG can be shifted to lower energies by manipulating the density of states in complex nanostructure geometries.
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Affiliation(s)
- Hagai Eshet
- †School of Chemistry, The Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Roi Baer
- ‡Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Daniel Neuhauser
- ¶Department of Chemistry, University of California at Los Angeles, Los Angeles, California 90095, United States
| | - Eran Rabani
- †School of Chemistry, The Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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20
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Dohnalová K, Gregorkiewicz T, Kůsová K. Silicon quantum dots: surface matters. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:173201. [PMID: 24713583 DOI: 10.1088/0953-8984/26/17/173201] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Silicon quantum dots (SiQDs) hold great promise for many future technologies. Silicon is already at the core of photovoltaics and microelectronics, and SiQDs are capable of efficient light emission and amplification. This is crucial for the development of the next technological frontiers-silicon photonics and optoelectronics. Unlike any other quantum dots (QDs), SiQDs are made of non-toxic and abundant material, offering one of the spectrally broadest emission tunabilities accessible with semiconductor QDs and allowing for tailored radiative rates over many orders of magnitude. This extraordinary flexibility of optical properties is achieved via a combination of the spatial confinement of carriers and the strong influence of surface chemistry. The complex physics of this material, which is still being unraveled, leads to new effects, opening up new opportunities for applications. In this review we summarize the latest progress in this fascinating research field, with special attention given to surface-induced effects, such as the emergence of direct bandgap transitions, and collective effects in densely packed QDs, such as space separated quantum cutting.
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Affiliation(s)
- K Dohnalová
- Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, NL-1098 XH Amsterdam, The Netherlands
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21
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Sun J, Yu W, Usman A, Isimjan TT, DGobbo S, Alarousu E, Takanabe K, Mohammed OF. Generation of Multiple Excitons in Ag2S Quantum Dots: Single High-Energy versus Multiple-Photon Excitation. J Phys Chem Lett 2014; 5:659-65. [PMID: 26270833 DOI: 10.1021/jz5000512] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We explored biexciton generation via carrier multiplication (or multiple-exciton generation) by high-energy photons and by multiple-photon absorption in Ag2S quantum dots (QDs) using femtosecond broad-band transient absorption spectroscopy. Irrespective of the size of the QDs and how the multiple excitons are generated in the Ag2S QDs, two distinct characteristic time constants of 9.6-10.2 and 135-175 ps are obtained for the nonradiative Auger recombination of the multiple excitons, indicating the existence of two binding excitons, namely, tightly bound and weakly bound excitons. More importantly, the lifetimes of multiple excitons in Ag2S QDs were about 1 and 2 orders of magnitude longer than those of comparable size PbS QDs and single-walled carbon nanotubes, respectively. This result is significant because it suggests that by utilizing an appropriate electron acceptor, there is a higher possibility to extract multiple electron-hole pairs in Ag2S QDs, which should improve the performance of QD-based solar cell devices.
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Affiliation(s)
- Jingya Sun
- †Solar and Photovoltaic Engineering Research Center and ‡KAUST Catalysis Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Weili Yu
- †Solar and Photovoltaic Engineering Research Center and ‡KAUST Catalysis Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Anwar Usman
- †Solar and Photovoltaic Engineering Research Center and ‡KAUST Catalysis Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Tayirjan T Isimjan
- †Solar and Photovoltaic Engineering Research Center and ‡KAUST Catalysis Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Silvano DGobbo
- †Solar and Photovoltaic Engineering Research Center and ‡KAUST Catalysis Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Erkki Alarousu
- †Solar and Photovoltaic Engineering Research Center and ‡KAUST Catalysis Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Kazuhiro Takanabe
- †Solar and Photovoltaic Engineering Research Center and ‡KAUST Catalysis Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Omar F Mohammed
- †Solar and Photovoltaic Engineering Research Center and ‡KAUST Catalysis Center, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
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22
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Stolle CJ, Harvey TB, Pernik DR, Hibbert JI, Du J, Rhee DJ, Akhavan VA, Schaller RD, Korgel BA. Multiexciton Solar Cells of CuInSe2 Nanocrystals. J Phys Chem Lett 2014; 5:304-309. [PMID: 26270704 DOI: 10.1021/jz402596v] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Peak external quantum efficiencies (EQEs) of just over 120% were observed in photovoltaic (PV) devices of CuInSe2 nanocrystals prepared with a photonic curing process. The extraction of more than one electron/hole pair as a result of the absorption of a single photon can occur if multiple excitons are generated and extracted. Multiexciton generation (MEG) in the nanocrystal films was substantiated by transient absorption spectroscopy. We propose that photonic curing leads to sufficient electronic coupling between nanocrystals to enable multiexciton extraction under typical solar illumination conditions. Under low light conditions, however, the EQE drops significantly, indicating that photonic curing-induced ligand desorption creates a significant amount of traps in the film that limit the overall power conversion efficiency of the device.
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Affiliation(s)
- C 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
| | - Taylor B Harvey
- †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
| | - Douglas R Pernik
- †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
| | - Jarett I Hibbert
- †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
| | - Jiang Du
- †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
| | - Dong Joon Rhee
- †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
| | - Vahid A Akhavan
- ‡NovaCentrix, 200-B Parker Drive, Suite 580, Austin, Texas 78728, United States
| | - Richard D Schaller
- §Center for Nanoscale Materials, Argonne National Laboratories, Argonne, Illinios 60439, United States
- ∥Department of Chemistry, Northwestern University, Evanston, Illinois 60208, 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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23
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Semiconductor quantum dot-doped glass as spectral converter for photovoltaic application. CHINESE SCIENCE BULLETIN-CHINESE 2013. [DOI: 10.1007/s11434-013-0017-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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24
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Elward JM, Chakraborty A. Effect of Dot Size on Exciton Binding Energy and Electron-Hole Recombination Probability in CdSe Quantum Dots. J Chem Theory Comput 2013; 9:4351-9. [PMID: 26589152 DOI: 10.1021/ct400485s] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Jennifer M Elward
- Department of Chemistry, Syracuse University , Syracuse, New York 13244, United States
| | - Arindam Chakraborty
- Department of Chemistry, Syracuse University , Syracuse, New York 13244, United States
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25
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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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26
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Beard MC, Luther JM, Semonin OE, Nozik AJ. Third generation photovoltaics based on multiple exciton generation in quantum confined semiconductors. Acc Chem Res 2013; 46:1252-60. [PMID: 23113604 DOI: 10.1021/ar3001958] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Improving the primary photoconversion process in a photovoltaiccell by utilizing the excess energy that is otherwise lost as heat can lead to an increase in the overall power conversion efficiency (PCE). Semiconductor nanocrystals (NCs) with at least one dimension small enough to produce quantum confinement effects provide new ways of controlling energy flow not achievable in thin film or bulk semiconductors. Researchers have developed various strategies to incorporate these novel structures into suitable solar conversion systems. Some of these methods could increase the PCE past the Shockley-Queisser (SQ) limit of ∼33%, making them viable "third generation photovoltaic" (TGPV) cell architectures. Surpassing the SQ limit for single junction solar cells presents both a scientific and a technological challenge, and the use of semiconductor NCs to enhance the primary photoconversion process offers a promising potential solution. The NCs are synthesized via solution phase chemical reactions producing stable colloidal solutions, where the reaction conditions can be modified to produce a variety of shapes, compositions, and structures. The confinement of the semiconductor NC in one dimension produces quantum films, wells, or discs. Two-dimensional confinement leads to quantum wires or rods (QRs), and quantum dots (QDs) are three-dimensionally confined NCs. The process of multiple exciton generation (MEG) converts a high-energy photon into multiple electron-hole pairs. Although many studies have demonstrated that MEG is enhanced in QDs compared with bulk semiconductors, these studies have either used ultrafast spectroscopy to measure the photon-to-exciton quantum yields (QYs) or theoretical calculations. Implementing MEG in a working solar cell has been an ongoing challenge. In this Account, we discuss the status of MEG research and strategies towards implementing MEG in working solar cells. Recently we showed an external quantum efficiency for photocurrent of greater than 100% (reaching 114%) at ∼4Eg in a PbSe QD solar cell. The internal quantum efficiency reached 130%. These results compare favorably with ultrafast transient spectroscopic measurements. Thus, we have shown that one of the tenets of the SQ limit, that photons only produce one electron-hole pair at the electrodes of a solar cell, can be overcome. Further challenges include increasing the MEG efficiency and improving the QD device structure and operation.
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Affiliation(s)
- Matthew C. Beard
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Joseph M. Luther
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Octavi E. Semonin
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Department of Physics, University of Colorado, Boulder, Colorado 80309, United States
| | - Arthur J. Nozik
- National Renewable Energy Laboratory, Golden, Colorado 80401, United States
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States
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27
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Baer R, Rabani E. Communication: Biexciton generation rates in CdSe nanorods are length independent. J Chem Phys 2013; 138:051102. [DOI: 10.1063/1.4790600] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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28
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Zohar G, Baer R, Rabani E. Multiexciton Generation in IV-VI Nanocrystals: The Role of Carrier Effective Mass, Band Mixing, and Phonon Emission. J Phys Chem Lett 2013; 4:317-322. [PMID: 26283441 DOI: 10.1021/jz301892z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We study the role of the effective mass, band mixing, and phonon emission on multiexciton generation in IV-VI nanocrystals. A four-band k · p effective mass model, which allows for an independent variation of these parameters, is adopted to describe the electronic structure of the nanocrystals. Multiexciton generation efficiencies are calculated using a Green's function formalism, providing results that are numerically similar to impact excitation. We find that multiexciton generation efficiencies are maximized when the effective mass of the electron and hole are small and similar. Contact with recent experimental results for multiexciton generation in PbS and PbSe is made.
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Affiliation(s)
| | - Roi Baer
- ‡Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, Hebrew University, Jerusalem 91904, Israel
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29
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Li H, Lusk MT, Collins RT, Wu Z. Optimal size regime for oxidation-resistant silicon quantum dots. ACS NANO 2012; 6:9690-9699. [PMID: 23061893 DOI: 10.1021/nn303109t] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
First-principles computations have been carried out to predict that appropriately terminated silicon quantum dots with diameters in the range of 1.2-2 nm will offer a superb resistance to oxidation. This is because surface treatments can produce dangling bond defect densities sufficiently low that dots of this size are unlikely to have any defect at all. On the other hand, these dots are large enough that the severe angles between facets do not expose bonds that are vulnerable to subsequent oxygen attack. The absence of both surface defects and geometry-related vulnerabilities allows even very short passivating ligands to generate an effective barrier, an important consideration for charge and exciton transport within quantum dot assemblies. Our computations, which employ many-body perturbation theory using Green functions, also indicate that dots within this size regime have optical and electronic properties that are robust to small amounts of inadvertent oxidation, and that any such oxygen incorporation is essentially frozen in place.
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Affiliation(s)
- Huashan Li
- Department of Physics, Colorado School of Mines, Golden, Colorado 80401, United States
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30
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Sandberg RL, Padilha LA, Qazilbash MM, Bae WK, Schaller RD, Pietryga JM, Stevens MJ, Baek B, Nam SW, Klimov VI. Multiexciton dynamics in infrared-emitting colloidal nanostructures probed by a superconducting nanowire single-photon detector. ACS NANO 2012; 6:9532-9540. [PMID: 23020520 DOI: 10.1021/nn3043226] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Carrier multiplication (CM) is the process in which absorption of a single photon produces multiple electron-hole pairs. Here, we evaluate the effect of particle shape on CM efficiency by conducting a comparative study of spherical nanocrystal quantum dots (NQDs) and elongated nanorods (NRs) of PbSe using a time-resolved technique that is based on photon counting in the infrared using a superconducting nanowire single-photon photodetector (SNSPD). Due to its high sensitivity and low noise levels, this technique allows for accurate determination of CM yields, even with the small excitation intensities required for quantitative measurements, and the fairly low emission quantum yields of elongated NR samples. Our measurements indicate an up to ∼60% increase in multiexciton yields in NRs versus NQDs, which is attributed primarily to a decrease in the electron-hole pair creation energy. These findings suggest that shape control is a promising approach for enhancing the CM process. Further, our work demonstrates the effectiveness of the SNSPD technique for the rapid screening of CM performance in infrared nanomaterials.
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Affiliation(s)
- Richard L Sandberg
- Center for Advanced Solar Photophysics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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31
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Hyeon-Deuk K, Prezhdo OV. Photoexcited electron and hole dynamics in semiconductor quantum dots: phonon-induced relaxation, dephasing, multiple exciton generation and recombination. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:363201. [PMID: 22906924 DOI: 10.1088/0953-8984/24/36/363201] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Photoexcited dynamics of electrons and holes in semiconductor quantum dots (QD), including phonon-induced relaxation, multiple exciton generation, fission and recombination (MEG, MEF and MER), were simulated by combining ab initio time-dependent density functional theory and non-adiabatic molecular dynamics. These nonequilibrium phenomena govern the optical properties and photoexcited dynamics of QDs, determining the branching between electronic processes and thermal energy losses. Our approach accounts for QD size and shape as well as defects, core-shell distribution, surface ligands and charge trapping, which significantly influence the properties of photoexcited QDs. The method creates an explicit time-domain representation of photoinduced processes and describes various kinetic regimes owing to the non-perturbative treatment of quantum dynamics. QDs of different sizes and materials, with and without ligands, are considered. The simulations provide direct evidence that the high-frequency ligand modes on the QD surface play a pivotal role in the electron-phonon relaxation, MEG, MEF and MER. The insights reported here suggest novel routes for controlling the photoinduced processes in semiconductor QDs and lead to new design principles for increasing the efficiencies of photovoltaic devices.
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Affiliation(s)
- Kim Hyeon-Deuk
- Department of Chemistry, Kyoto University, Kyoto, 606-8502, Japan.
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32
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Kilina S, Velizhanin KA, Ivanov S, Prezhdo OV, Tretiak S. Surface ligands increase photoexcitation relaxation rates in CdSe quantum dots. ACS NANO 2012; 6:6515-6524. [PMID: 22742432 DOI: 10.1021/nn302371q] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Understanding the pathways of hot exciton relaxation in photoexcited semiconductor nanocrystals, also called quantum dots (QDs), is of paramount importance in multiple energy, electronics and biological applications. An important nonradiative relaxation channel originates from the nonadiabatic (NA) coupling of electronic degrees of freedom to nuclear vibrations, which in QDs depend on the confinement effects and complicated surface chemistry. To elucidate the role of surface ligands in relaxation processes of nanocrystals, we study the dynamics of the NA exciton relaxation in Cd(33)Se(33) semiconductor quantum dots passivated by either trimethylphosphine oxide or methylamine ligands using explicit time-dependent modeling. The large extent of hybridization between electronic states of quantum dot and ligand molecules is found to strongly facilitate exciton relaxation. Our computational results for the ligand contributions to the exciton relaxation and electronic energy-loss in small clusters are further extrapolated to larger quantum dots.
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Affiliation(s)
- Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States.
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Lin Z, Li H, Franceschetti A, Lusk MT. Efficient exciton transport between strongly quantum-confined silicon quantum dots. ACS NANO 2012; 6:4029-4038. [PMID: 22468899 DOI: 10.1021/nn3003407] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Many-body Green function analysis and first-order perturbation theory are used to quantify the influence of size, surface reconstruction, and surface treatment on exciton transport between small silicon quantum dots. Competing radiative processes are also considered in order to determine how exciton transport efficiency is influenced. The analysis shows that quantum confinement causes small (~1 nm) Si quantum dots to exhibit exciton transport efficiencies far exceeding that of their larger counterparts for the same center-to-center separation. This surprising result offers the prospect of designing assemblies of quantum dots through which excitons can travel for long distances, a game-changing paradigm shift for next-generation solar energy harvesting. We also find that surface reconstruction significantly influences the absorption cross section and leads to a large reduction in both transport rate and efficiency. Further, exciton transport efficiency is higher for hydrogen-passivated dots as compared with those terminated with more electronegative ligands, a result not predicted by Förster theory.
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Affiliation(s)
- Zhibin Lin
- Department of Physics, Colorado School of Mines, Golden, Colorado 80401, USA.
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Baer R, Rabani E. Expeditious stochastic calculation of multiexciton generation rates in semiconductor nanocrystals. NANO LETTERS 2012; 12:2123-2128. [PMID: 22443374 DOI: 10.1021/nl300452c] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A stochastic method is developed to calculate the multiexciton generation (MEG) rates in semiconductor nanocrystals (NCs). The numerical effort scales near-linearly with system size allowing the study of MEG rates up to diameters and exciton energies previously unattainable using atomistic calculations. Illustrations are given for CdSe NCs of sizes and energies relevant to current experimental setups, where direct methods require treatment of over 10(11) states. The approach is not limited to the study of MEG and can be applied to calculate other correlated electronic processes.
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Affiliation(s)
- Roi Baer
- Fritz Haber Center for Molecular Dynamics, Chaim Weizmann Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904 Israel
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Hyeon-Deuk K, Prezhdo OV. Multiple exciton generation and recombination dynamics in small Si and CdSe quantum dots: an ab initio time-domain study. ACS NANO 2012; 6:1239-1250. [PMID: 22214339 DOI: 10.1021/nn2038884] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Multiple exciton generation and recombination (MEG and MER) dynamics in semiconductor quantum dots (QDs) are simulated using ab initio time-dependent density functional theory in combination with nonadiabatic molecular dynamics. The approach differs from other MEG and MER theories because it provides atomistic description, employs time-domain representation, allows for various dynamical regimes, and includes electron-phonon interactions. MEG rapidly accelerates with energy, reflecting strong energy dependence of double exciton (DE) density of states. At early times, MEG is Gaussian rather than exponential. Exponential dynamics, assumed in rate theories, starts at a later time and becomes more important in larger QDs. Phonon-assisted MEG is observed at energies below the purely electronic threshold, particularly in the presence of high-frequency ligand vibrations. Coupling to phonons is essential for MER since higher-energy DEs must relax to recombine into single excitons (SEs), and SEs formed during MERs must lose some of their energy to avoid recreating DEs. MER simulated starting from a DE is significantly slower than MER involving an optical excitation of a SE, followed by MEG and then MER. The latter time scale agrees with experiment, emphasizing the importance of quantum-mechanical superpositions of many DEs for efficient MER. The detailed description of the interplay between MEG and MER coupled to phonons provides important insights into the excited state dynamics of semiconductor QDs and nanoscale materials in general.
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Affiliation(s)
- Kim Hyeon-Deuk
- Department of Chemistry, Kyoto University, Kyoto 606-8502, Japan.
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