51
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Groves C. Simulating charge transport in organic semiconductors and devices: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:026502. [PMID: 27991440 DOI: 10.1088/1361-6633/80/2/026502] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Charge transport simulation can be a valuable tool to better understand, optimise and design organic transistors (OTFTs), photovoltaics (OPVs), and light-emitting diodes (OLEDs). This review presents an overview of common charge transport and device models; namely drift-diffusion, master equation, mesoscale kinetic Monte Carlo and quantum chemical Monte Carlo, and a discussion of the relative merits of each. This is followed by a review of the application of these models as applied to charge transport in organic semiconductors and devices, highlighting in particular the insights made possible by modelling. The review concludes with an outlook for charge transport modelling in organic electronics.
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Affiliation(s)
- C Groves
- Durham University, School of Engineering and Computing Sciences, South Road, Durham, DH1 3LE, UK
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52
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Li X, Tang ML. Triplet transport in thin films: fundamentals and applications. Chem Commun (Camb) 2017; 53:4429-4440. [DOI: 10.1039/c7cc00861a] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
An overview of experimental and theoretical work on triplet energy transfer, with a focus on triplet transport in thin films.
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Affiliation(s)
- Xin Li
- Chemistry Department
- University of California
- Riverside
- USA
| | - Ming Lee Tang
- Chemistry Department
- University of California
- Riverside
- USA
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53
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Zhao B, Abdi-Jalebi M, Tabachnyk M, Glass H, Kamboj VS, Nie W, Pearson AJ, Puttisong Y, Gödel KC, Beere HE, Ritchie DA, Mohite AD, Dutton SE, Friend RH, Sadhanala A. High Open-Circuit Voltages in Tin-Rich Low-Bandgap Perovskite-Based Planar Heterojunction Photovoltaics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29. [PMID: 28066989 DOI: 10.1002/adma.201604744] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Revised: 09/24/2016] [Indexed: 05/06/2023]
Abstract
Low-bandgap CH3 NH3 (Pbx Sn1-x )I3 (0 ≤ x ≤ 1) hybrid perovskites (e.g., ≈1.5-1.1 eV) demonstrating high surface coverage and superior optoelectronic properties are fabricated. State-of-the-art photovoltaic (PV) performance is reported with power conversion efficiencies approaching 10% in planar heterojunction architecture with small (<450 meV) energy loss compared to the bandgap and high (>100 cm2 V-1 s-1 ) intrinsic carrier mobilities.
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Affiliation(s)
- Baodan Zhao
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Mojtaba Abdi-Jalebi
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Maxim Tabachnyk
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Hugh Glass
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Varun S Kamboj
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Wanyi Nie
- Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Andrew J Pearson
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Yuttapoom Puttisong
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Karl C Gödel
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Harvey E Beere
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - David A Ritchie
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | | | - Siân E Dutton
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Richard H Friend
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Aditya Sadhanala
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
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54
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Tuning the role of charge-transfer states in intramolecular singlet exciton fission through side-group engineering. Nat Commun 2016; 7:13622. [PMID: 27924819 PMCID: PMC5150654 DOI: 10.1038/ncomms13622] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 10/17/2016] [Indexed: 12/23/2022] Open
Abstract
Understanding the mechanism of singlet exciton fission, in which a singlet exciton separates into a pair of triplet excitons, is crucial to the development of new chromophores for efficient fission-sensitized solar cells. The challenge of controlling molecular packing and energy levels in the solid state precludes clear determination of the singlet fission pathway. Here, we circumvent this difficulty by utilizing covalent dimers of pentacene with two types of side groups. We report rapid and efficient intramolecular singlet fission in both molecules, in one case via a virtual charge-transfer state and in the other via a distinct charge-transfer intermediate. The singlet fission pathway is governed by the energy gap between singlet and charge-transfer states, which change dynamically with molecular geometry but are primarily set by the side group. These results clearly establish the role of charge-transfer states in singlet fission and highlight the importance of solubilizing groups to optimize excited-state photophysics.
The understanding of how a singlet exciton separates into triplet states in organic semiconductors is crucial to the design of efficient organic solar cells. Here, Lukman et al. identify the role played by charge-transfer states during triplet formation through side-group engineering of pentacenes.
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55
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Zhu T, Wan Y, Guo Z, Johnson J, Huang L. Two Birds with One Stone: Tailoring Singlet Fission for Both Triplet Yield and Exciton Diffusion Length. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:7539-7547. [PMID: 27348847 DOI: 10.1002/adma.201600968] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 05/04/2016] [Indexed: 06/06/2023]
Abstract
By direct imaging of singlet and triplet populations with ultrafast microscopy, it is shown that the triplet diffusion length and singlet fission yield can be simultaneously optimized for tetracene and its derivatives, making them ideal structures for application in bilayer solar cells.
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Affiliation(s)
- Tong Zhu
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Yan Wan
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Zhi Guo
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Justin Johnson
- National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, CO, 80401, USA
| | - Libai Huang
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
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56
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Lefrancois D, Rehn DR, Dreuw A. Accurate adiabatic singlet-triplet gaps in atoms and molecules employing the third-order spin-flip algebraic diagrammatic construction scheme for the polarization propagator. J Chem Phys 2016; 145:084102. [DOI: 10.1063/1.4961298] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Daniel Lefrancois
- Interdisciplinary Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany
| | - Dirk R. Rehn
- Departments of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden
| | - Andreas Dreuw
- Interdisciplinary Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany
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57
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Kawata S, Pu YJ, Saito A, Kurashige Y, Beppu T, Katagiri H, Hada M, Kido J. Singlet Fission of Non-polycyclic Aromatic Molecules in Organic Photovoltaics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:1585-1590. [PMID: 26663207 DOI: 10.1002/adma.201504281] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 10/14/2015] [Indexed: 06/05/2023]
Abstract
Singlet fission of thienoquinoid compounds in organic photovoltaics is demonstrated. The escalation of the thienoquinoid length of the compounds realizes a suitable packing structure and energy levels for singlet fission. The magnetic-field dependence of the photocurrent and the external quantum efficiency of the devices reveal singlet fission of the compounds and dissociation of triplet excitons into charges.
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Affiliation(s)
- So Kawata
- Department of Organic Device Engineering, Yamagata University, Yonezawa, Yamagata, 992-8510, Japan
| | - Yong-Jin Pu
- Department of Organic Device Engineering, Yamagata University, Yonezawa, Yamagata, 992-8510, Japan
- JST-PRESTO, Kawaguchi, Saitama, 332-0012, Japan
| | - Ayaka Saito
- Department of Organic Device Engineering, Yamagata University, Yonezawa, Yamagata, 992-8510, Japan
| | - Yuki Kurashige
- JST-PRESTO, Kawaguchi, Saitama, 332-0012, Japan
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki, Aichi, 444-8585, Japan
| | - Teruo Beppu
- Department of Chemistry and Chemical Engineering, Yamagata University, Yonezawa, Yamagata, 992-8510, Japan
| | - Hiroshi Katagiri
- Department of Chemistry and Chemical Engineering, Yamagata University, Yonezawa, Yamagata, 992-8510, Japan
| | - Masaki Hada
- JST-PRESTO, Kawaguchi, Saitama, 332-0012, Japan
- Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa, 226-8503, Japan
| | - Junji Kido
- Department of Organic Device Engineering, Yamagata University, Yonezawa, Yamagata, 992-8510, Japan
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58
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Hartnett PE, Margulies EA, Mauck CM, Miller SA, Wu Y, Wu YL, Marks TJ, Wasielewski MR. Effects of Crystal Morphology on Singlet Exciton Fission in Diketopyrrolopyrrole Thin Films. J Phys Chem B 2016; 120:1357-66. [DOI: 10.1021/acs.jpcb.5b10565] [Citation(s) in RCA: 109] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Patrick E. Hartnett
- Department of Chemistry and the Argonne-Northwestern Solar Energy
Research Center, and ‡Department of Materials Science and Engineering and the Materials
Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Eric A. Margulies
- Department of Chemistry and the Argonne-Northwestern Solar Energy
Research Center, and ‡Department of Materials Science and Engineering and the Materials
Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Catherine M. Mauck
- Department of Chemistry and the Argonne-Northwestern Solar Energy
Research Center, and ‡Department of Materials Science and Engineering and the Materials
Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Stephen A. Miller
- Department of Chemistry and the Argonne-Northwestern Solar Energy
Research Center, and ‡Department of Materials Science and Engineering and the Materials
Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yilei Wu
- Department of Chemistry and the Argonne-Northwestern Solar Energy
Research Center, and ‡Department of Materials Science and Engineering and the Materials
Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yi-Lin Wu
- Department of Chemistry and the Argonne-Northwestern Solar Energy
Research Center, and ‡Department of Materials Science and Engineering and the Materials
Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Tobin J. Marks
- Department of Chemistry and the Argonne-Northwestern Solar Energy
Research Center, and ‡Department of Materials Science and Engineering and the Materials
Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Michael R. Wasielewski
- Department of Chemistry and the Argonne-Northwestern Solar Energy
Research Center, and ‡Department of Materials Science and Engineering and the Materials
Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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59
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Lu C, Tang Z. Advanced Inorganic Nanoarchitectures from Oriented Self-Assembly. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:1096-108. [PMID: 26488133 DOI: 10.1002/adma.201502869] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Revised: 07/20/2015] [Indexed: 05/28/2023]
Abstract
Complex and well-defined nanostructures are promising for emerging properties with broad applications. Self-assembly processes driven by diverse interactions generate varied nanostructures by using versatile nanocrystals as building blocks, while oriented attachment growth allows individual nanocrystals to be integrated and fused into highly anisotropic structures. By a combination of self-assembly technique and oriented attachment growth, many advanced nanostructures can be made. Such approaches can be viewed as an architecture of the nanoscale counterparts in the microworld, named as nanoarchitectures.
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Affiliation(s)
- Chenguang Lu
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
| | - Zhiyong Tang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China
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60
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Xie B, Liu L, Cui G, Fang WH, Cao J, Feng W, Li XQ. Ab initio implementation of quantum trajectory mean-field approach and dynamical simulation of the N2CO photodissociation. J Chem Phys 2015; 143:194107. [DOI: 10.1063/1.4935800] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Binbin Xie
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Lihong Liu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ganglong Cui
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Wei-Hai Fang
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Jun Cao
- Guizhou Provincial Key Laboratory of Computational Nano-material Science, Guizhou Normal College, Guiyang 550018, China
| | - Wei Feng
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Xin-qi Li
- Department of Physics, Beijing Normal University, Beijing 100875, China
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61
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Bakulin AA, Morgan SE, Kehoe TB, Wilson MWB, Chin AW, Zigmantas D, Egorova D, Rao A. Real-time observation of multiexcitonic states in ultrafast singlet fission using coherent 2D electronic spectroscopy. Nat Chem 2015; 8:16-23. [DOI: 10.1038/nchem.2371] [Citation(s) in RCA: 268] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 09/08/2015] [Indexed: 12/23/2022]
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62
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Castrucci JS, Josey DS, Thibau E, Lu ZH, Bender TP. Boron Subphthalocyanines as Triplet Harvesting Materials within Organic Photovoltaics. J Phys Chem Lett 2015; 6:3121-3125. [PMID: 26267212 DOI: 10.1021/acs.jpclett.5b01254] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Singlet fission, the generation of two excited triplet states from a single absorbed photon, is currently an area of significant interest to photovoltaic researchers. In this Letter, we outline how a polychlorinated boron subphthalocyanine, previously hypothesized to be an effective harvester of singlet fission derived triplets from pentacene, is relatively efficient at facilitating the process. As expected, we found a major increase in photocurrent generation at the expense of device voltage. For a direct point of comparison, we also have paired the same polychlorinated boron subphthalocyanine with α-sexithiophene to probe the alternative technique of complementary absorption engineering. The sum of these efforts have let us present new guidelines for the molecular design of boron subphthalocyanine for organic photovoltaic applications.
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Affiliation(s)
- Jeffrey S Castrucci
- ‡Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario M5S 3E4, Canada
| | | | - Emmanuel Thibau
- ‡Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario M5S 3E4, Canada
| | - Zheng-Hong Lu
- ‡Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario M5S 3E4, Canada
| | - Timothy P Bender
- ‡Department of Materials Science and Engineering, University of Toronto, 184 College Street, Toronto, Ontario M5S 3E4, Canada
- §Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
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63
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Peng W, Rupich SM, Shafiq N, Gartstein YN, Malko AV, Chabal YJ. Silicon Surface Modification and Characterization for Emergent Photovoltaic Applications Based on Energy Transfer. Chem Rev 2015; 115:12764-96. [DOI: 10.1021/acs.chemrev.5b00085] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Weina Peng
- Department of Materials
Science and Engineering and ‡Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Sara M. Rupich
- Department of Materials
Science and Engineering and ‡Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Natis Shafiq
- Department of Materials
Science and Engineering and ‡Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Yuri N. Gartstein
- Department of Materials
Science and Engineering and ‡Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Anton V. Malko
- Department of Materials
Science and Engineering and ‡Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Yves J. Chabal
- Department of Materials
Science and Engineering and ‡Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, United States
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64
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Thompson NJ, Hontz E, Chang W, Van Voorhis T, Baldo M. Magnetic field dependence of singlet fission in solutions of diphenyl tetracene. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2015; 373:rsta.2014.0323. [PMID: 25987573 PMCID: PMC4455722 DOI: 10.1098/rsta.2014.0323] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/18/2015] [Indexed: 06/04/2023]
Abstract
Magnetic field effects provide a convenient and specific probe of singlet exciton fission within optoelectronic devices. Here, we demonstrate that this tool may also be applied to screen potential fission material candidates in solution. We characterize the phenomenon in diphenyl tetracene (DPT), which shows strong fluorescence modulation and the expected field dependence in its transient decay as a function of concentration. Solution measurements may also be used to test for the presence of an intermediate charge transfer state, but we observe no changes to the field dependence of DPT singlet exciton fission in toluene relative to chloroform.
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Affiliation(s)
- Nicholas J Thompson
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Eric Hontz
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Wendi Chang
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Troy Van Voorhis
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Marc Baldo
- Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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65
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Tayebjee MJY, McCamey DR, Schmidt TW. Beyond Shockley-Queisser: Molecular Approaches to High-Efficiency Photovoltaics. J Phys Chem Lett 2015; 6:2367-78. [PMID: 26266619 DOI: 10.1021/acs.jpclett.5b00716] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Molecular materials afford abundant flexibility in the tunability of physical and electronic properties. As such, they are ideally suited to engineering low-cost, flexible, light-harvesting materials that break away from the single-threshold paradigm. Single-threshold solar cells are capable of harvesting a maximum of 33.7% of incident sunlight, whereas two-threshold cells are capable of energy harvesting efficiencies exceeding 45%. In this Perspective, we provide the theoretical background with which upper efficiency limits for various multiple-threshold solar cell architectures may be calculated and review and discuss various reports that employ processes such as triplet-triplet annihilation and singlet fission in multiple-threshold devices comprised of molecular materials.
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Affiliation(s)
- Murad J Y Tayebjee
- †School of Photovoltaic and Renewable Energy Engineering, ‡School of Physics, and ¶School of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Dane R McCamey
- †School of Photovoltaic and Renewable Energy Engineering, ‡School of Physics, and ¶School of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Timothy W Schmidt
- †School of Photovoltaic and Renewable Energy Engineering, ‡School of Physics, and ¶School of Chemistry, University of New South Wales, Sydney, New South Wales 2052, Australia
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66
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Identification of a triplet pair intermediate in singlet exciton fission in solution. Proc Natl Acad Sci U S A 2015; 112:7656-61. [PMID: 26060309 DOI: 10.1073/pnas.1503471112] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Singlet exciton fission is the spin-conserving transformation of one spin-singlet exciton into two spin-triplet excitons. This exciton multiplication mechanism offers an attractive route to solar cells that circumvent the single-junction Shockley-Queisser limit. Most theoretical descriptions of singlet fission invoke an intermediate state of a pair of spin-triplet excitons coupled into an overall spin-singlet configuration, but such a state has never been optically observed. In solution, we show that the dynamics of fission are diffusion limited and enable the isolation of an intermediate species. In concentrated solutions of bis(triisopropylsilylethynyl)[TIPS]--tetracene we find rapid (<100 ps) formation of excimers and a slower (∼ 10 ns) break up of the excimer to two triplet exciton-bearing free molecules. These excimers are spectroscopically distinct from singlet and triplet excitons, yet possess both singlet and triplet characteristics, enabling identification as a triplet pair state. We find that this triplet pair state is significantly stabilized relative to free triplet excitons, and that it plays a critical role in the efficient endothermic singlet fission process.
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67
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Pensack RD, Tilley AJ, Parkin SR, Lee TS, Payne MM, Gao D, Jahnke AA, Oblinsky DG, Li PF, Anthony JE, Seferos DS, Scholes GD. Exciton Delocalization Drives Rapid Singlet Fission in Nanoparticles of Acene Derivatives. J Am Chem Soc 2015; 137:6790-803. [DOI: 10.1021/ja512668r] [Citation(s) in RCA: 171] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Ryan D. Pensack
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Andrew J. Tilley
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Sean R. Parkin
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Tia S. Lee
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Marcia M. Payne
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Dong Gao
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Ashlee A. Jahnke
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Daniel G. Oblinsky
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Peng-Fei Li
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - John E. Anthony
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Dwight S. Seferos
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Gregory D. Scholes
- Department
of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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68
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Casanova D. Bright Fission: Singlet Fission into a Pair of Emitting States. J Chem Theory Comput 2015; 11:2642-50. [DOI: 10.1021/acs.jctc.5b00144] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- David Casanova
- Kimika Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU) and Donostia International Physics Center (DIPC), P.K. 1072, 20080 Donostia, Euskadi, Spain
- IKERBASQUE, Basque Foundation
for Science, 48013 Bilbao, Euskadi, Spain
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69
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Liang Y, Lu C, Ding D, Zhao M, Wang D, Hu C, Qiu J, Xie G, Tang Z. Capping nanoparticles with graphene quantum dots for enhanced thermoelectric performance. Chem Sci 2015; 6:4103-4108. [PMID: 28717467 PMCID: PMC5497257 DOI: 10.1039/c5sc00910c] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 04/13/2015] [Indexed: 11/21/2022] Open
Abstract
Graphene quantum dots (GQDs) are shown to serve as phase transfer agents to transfer various types of nanoparticles (NPs) from non-polar to polar solvents. Thorough characterization of the NPs proves complete native ligand exchange. Pellets of this GQD-NP composite show that the GQDs limit the crystal size during spark plasma sintering, yielding enhanced thermoelectric performance compared with NPs exchanged with inorganic ions. A photoluminescence study of the GQD-NP composite also suggests energy transfer from GQDs to NPs.
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Affiliation(s)
- Yuantong Liang
- CAS Key Lab for Nanosystem and Hierarchy Fabrication , National Center for Nanoscience and Technology , Beijing , 100190 , China . ; .,Key Laboratory of Synthesis and Natural Functional Molecular Chemistry of Ministry of Education , College of Chemistry & Materials Science , Northwest University , Xi'an , 710069 , China .
| | - Chenguang Lu
- CAS Key Lab for Nanosystem and Hierarchy Fabrication , National Center for Nanoscience and Technology , Beijing , 100190 , China . ;
| | - Defang Ding
- CAS Key Lab for Nanosystem and Hierarchy Fabrication , National Center for Nanoscience and Technology , Beijing , 100190 , China . ;
| | - Man Zhao
- CAS Key Lab for Nanosystem and Hierarchy Fabrication , National Center for Nanoscience and Technology , Beijing , 100190 , China . ;
| | - Dawei Wang
- CAS Key Lab for Nanosystem and Hierarchy Fabrication , National Center for Nanoscience and Technology , Beijing , 100190 , China . ;
| | - Chao Hu
- Carbon Research Laboratory , Center for Nano Materials and Science , State Key Laboratory of Fine Chemicals , School of Chemical Engineering and Key Laboratory for Micro/Nano Technology of Liaoning Province , Dalian University of Technology , Dalian 116024 , China
| | - Jieshan Qiu
- Carbon Research Laboratory , Center for Nano Materials and Science , State Key Laboratory of Fine Chemicals , School of Chemical Engineering and Key Laboratory for Micro/Nano Technology of Liaoning Province , Dalian University of Technology , Dalian 116024 , China
| | - Gang Xie
- Key Laboratory of Synthesis and Natural Functional Molecular Chemistry of Ministry of Education , College of Chemistry & Materials Science , Northwest University , Xi'an , 710069 , China .
| | - Zhiyong Tang
- CAS Key Lab for Nanosystem and Hierarchy Fabrication , National Center for Nanoscience and Technology , Beijing , 100190 , China . ;
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70
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Musser AJ, Maiuri M, Brida D, Cerullo G, Friend RH, Clark J. The nature of singlet exciton fission in carotenoid aggregates. J Am Chem Soc 2015; 137:5130-9. [PMID: 25825939 PMCID: PMC4440407 DOI: 10.1021/jacs.5b01130] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Singlet exciton fission allows the fast and efficient generation of two spin triplet states from one photoexcited singlet. It has the potential to improve organic photovoltaics, enabling efficient coupling to the blue to ultraviolet region of the solar spectrum to capture the energy generally lost as waste heat. However, many questions remain about the underlying fission mechanism. The relation between intermolecular geometry and singlet fission rate and yield is poorly understood and remains one of the most significant barriers to the design of new singlet fission sensitizers. Here we explore the structure-property relationship and examine the mechanism of singlet fission in aggregates of astaxanthin, a small polyene. We isolate five distinct supramolecular structures of astaxanthin generated through self-assembly in solution. Each is capable of undergoing intermolecular singlet fission, with rates of triplet generation and annihilation that can be correlated with intermolecular coupling strength. In contrast with the conventional model of singlet fission in linear molecules, we demonstrate that no intermediate states are involved in the triplet formation: instead, singlet fission occurs directly from the initial 1B(u) photoexcited state on ultrafast time scales. This result demands a re-evaluation of current theories of polyene photophysics and highlights the robustness of carotenoid singlet fission.
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Affiliation(s)
- Andrew J Musser
- †Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Margherita Maiuri
- ‡IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, I-20133 Milano, Italy
| | - Daniele Brida
- §Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz, Germany
| | - Giulio Cerullo
- ‡IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, I-20133 Milano, Italy
| | - Richard H Friend
- †Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Jenny Clark
- ∥Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom
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71
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Liu Y, Zhang C, Wang R, Zhang B, Tan Z, Wang X, Xiao M. Large Optical Nonlinearity Induced by Singlet Fission in Pentacene Films. Angew Chem Int Ed Engl 2015; 54:6222-6. [DOI: 10.1002/anie.201501396] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Indexed: 01/19/2023]
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72
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Liu Y, Zhang C, Wang R, Zhang B, Tan Z, Wang X, Xiao M. Large Optical Nonlinearity Induced by Singlet Fission in Pentacene Films. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201501396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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73
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Elward JM, Chakraborty A. Effect of Heterojunction on Exciton Binding Energy and Electron–Hole Recombination Probability in CdSe/ZnS Quantum Dots. J Chem Theory Comput 2015; 11:462-71. [DOI: 10.1021/ct500548x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Jennifer M. Elward
- Army Research
Laboratory, Aberdeen Proving Ground, Aberdeen, Maryland 21005, United States
| | - Arindam Chakraborty
- Department
of Chemistry, Syracuse University, Syracuse, New York 13244, United States
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74
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Yang L, Tabachnyk M, Bayliss SL, Böhm ML, Broch K, Greenham NC, Friend RH, Ehrler B. Solution-processable singlet fission photovoltaic devices. NANO LETTERS 2015; 15:354-8. [PMID: 25517654 DOI: 10.1021/nl503650a] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We demonstrate the successful incorporation of a solution-processable singlet fission material, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), into photovoltaic devices. TIPS-pentacene rapidly converts high-energy singlet excitons into pairs of triplet excitons via singlet fission, potentially doubling the photocurrent from high-energy photons. Low-energy photons are captured by small-bandgap electron-accepting lead chalcogenide nanocrystals. This is the first solution-processable singlet fission system that performs with substantial efficiency with maximum power conversion efficiencies exceeding 4.8%, and external quantum efficiencies of up to 60% in the TIPS-pentacene absorption range. With PbSe nanocrystal of suitable bandgap, its internal quantum efficiency reaches 170 ± 30%.
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Affiliation(s)
- Le Yang
- Cavendish Laboratory , J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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75
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Ando M, Kehoe TB, Yoneya M, Ishii H, Kawasaki M, Duffy CM, Minakata T, Phillips RT, Sirringhaus H. Evidence for charge-trapping inducing polymorphic structural-phase transition in pentacene. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:122-129. [PMID: 25382806 DOI: 10.1002/adma.201403556] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 09/30/2014] [Indexed: 06/04/2023]
Abstract
Trapped-charge-induced transformation of pentacene polymorphs is observed by using in situ Raman spectroscopy and molecular dynamics simulations reveal that the charge should be localized in pentacene molecules at the interface with static intermolecular disorder along the long axis. Quantum chemical calculations of the intermolecular transfer integrals suggest the disorder to be large enough to induce Anderson-type localization.
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Affiliation(s)
- Masahiko Ando
- Central Research Laboratory, Hitachi, Ltd., 7-1-1 Omika, Ibaraki, 319-1292, Japan
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76
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Zhang B, Zhang C, Xu Y, Wang R, He B, Liu Y, Zhang S, Wang X, Xiao M. Polarization-dependent exciton dynamics in tetracene single crystals. J Chem Phys 2014; 141:244303. [DOI: 10.1063/1.4904385] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Bo Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yanqing Xu
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Rui Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Bin He
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yunlong Liu
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Shimeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, USA
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77
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Affiliation(s)
- Francesco Ambrosio
- Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Alessandro Troisi
- Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry CV4 7AL, United Kingdom
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78
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Bardeen CJ. Triplet excitons: Bringing dark states to light. NATURE MATERIALS 2014; 13:1001-1003. [PMID: 25282506 DOI: 10.1038/nmat4112] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Affiliation(s)
- Christopher J Bardeen
- Department of Chemistry, University of California Riverside, Riverside, California 92521, USA
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79
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Wilson MWB, Rao A, Johnson K, Gélinas S, di Pietro R, Clark J, Friend RH. Temperature-independent singlet exciton fission in tetracene. J Am Chem Soc 2014; 135:16680-8. [PMID: 24148017 DOI: 10.1021/ja408854u] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We use transient absorption spectroscopy to demonstrate that the dynamics of singlet exciton fission in tetracene are independent of temperature (10–270 K). Low-intensity, broad-band measurements allow the identification of spectral features while minimizing bimolecular recombination. Hence, by directly observing both species, we find that the time constant for the conversion of singlets to triplet pairs is ~90 ps. However, in contrast to pentacene, where fission is effectively unidirectional, we confirm that the emissive singlet in tetracene is readily regenerated from spin-correlated "geminate" triplets following fission, leading to equilibrium dynamics. Although free triplets are efficiently generated at room temperature, the interplay of superradiance and frustrated triplet diffusion contributes to a nearly 20-fold increase in the steady-state fluorescence as the sample is cooled. Together, these results require that singlets and triplet pairs in tetracene are effectively degenerate in energy, and begin to reconcile the temperature dependence of many macroscopic observables with a fission process which does not require thermal activation.
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80
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Zhang B, Zhang C, Wang R, Tan Z, Liu Y, Guo W, Zhai X, Cao Y, Wang X, Xiao M. Nonlinear Density Dependence of Singlet Fission Rate in Tetracene Films. J Phys Chem Lett 2014; 5:3462-3467. [PMID: 26278594 DOI: 10.1021/jz501736y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Singlet fission holds the potential to dramatically improve the efficiency of solar energy conversion by creating two triplet excitons from one photoexcited singlet exciton in organic semiconductors. It is generally assumed that the singlet-fission rate is linearly dependent on the exciton density. Here we experimentally show that the rate of singlet fission has a nonlinear dependence on the density of photoexcited singlet excitons in tetracene films with small crystalline grains. We disentangle the spectrotemporal features of singlet and triplet dynamics from ultrafast spectroscopic data with the algorithm of singular value decomposition. The correlation between their temporal dynamics indicates a superlinear dependence of fission rate on the density of singlet excitons, which may arise from excitonic interactions.
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Affiliation(s)
| | | | | | - Zhanao Tan
- ‡New and Renewable Energy of Beijing Key Laboratory, School of Renewable Energy, North China Electric Power University, Beijing 102206, China
| | | | | | | | | | | | - Min Xiao
- §Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States
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81
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Jung J, Yoon YJ, He M, Lin Z. Organic-inorganic nanocomposites composed of conjugated polymers and semiconductor nanocrystals for photovoltaics. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/polb.23612] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Jaehan Jung
- School of Materials Science and Engineering; Georgia Institute of Technology; Atlanta Georgia 30332
| | - Young Jun Yoon
- School of Materials Science and Engineering; Georgia Institute of Technology; Atlanta Georgia 30332
| | - Ming He
- School of Materials Science and Engineering; Georgia Institute of Technology; Atlanta Georgia 30332
| | - Zhiqun Lin
- School of Materials Science and Engineering; Georgia Institute of Technology; Atlanta Georgia 30332
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82
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Piland GB, Burdett JJ, Dillon RJ, Bardeen CJ. Singlet Fission: From Coherences to Kinetics. J Phys Chem Lett 2014; 5:2312-9. [PMID: 26279552 DOI: 10.1021/jz500676c] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Singlet fission, in which an initially excited singlet state spontaneously splits into a pair of triplet excitons, is a process that can potentially boost the efficiency of solar energy conversion. The separate electronic bands in organic semiconductors make them especially useful for dividing a high-energy singlet exciton into a pair of lower-energy triplet excitons. Recent experiments illustrate the role of spin coherence in fission, while kinetic models are used to describe how triplet and singlet states interact on longer time scales. Despite insights gained from recent experiments, the detailed structure and dynamics of the electronic states involved in the initial step of singlet fission remain active areas of investigation. On longer time scales, finding ways to efficiently harvest the triplet excitons will be an important challenge for making devices based on this phenomenon. A full understanding of singlet fission requires consideration of a sequence of photophysical events (decoherence, relaxation, and diffusion) occurring on different time scales.
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Affiliation(s)
- Geoffrey B Piland
- Department of Chemistry, University of California, Riverside, Riverside, California 92506, United States
| | - Jonathan J Burdett
- Department of Chemistry, University of California, Riverside, Riverside, California 92506, United States
| | - Robert J Dillon
- Department of Chemistry, University of California, Riverside, Riverside, California 92506, United States
| | - Christopher J Bardeen
- Department of Chemistry, University of California, Riverside, Riverside, California 92506, United States
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83
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Bayliss SL, Chepelianskii AD, Sepe A, Walker BJ, Ehrler B, Bruzek MJ, Anthony JE, Greenham NC. Geminate and nongeminate recombination of triplet excitons formed by singlet fission. PHYSICAL REVIEW LETTERS 2014; 112:238701. [PMID: 24972236 DOI: 10.1103/physrevlett.112.238701] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Indexed: 06/03/2023]
Abstract
We report the simultaneous observation of geminate and nongeminate triplet-triplet annihilation in a solution-processable small molecule TIPS-tetracene undergoing singlet exciton fission. Using optically detected magnetic resonance, we identify recombination of triplet pairs directly following singlet fission, as well as recombination of triplet excitons undergoing bimolecular triplet-triplet annihilation. We show that the two processes give rise to distinct magnetic resonance spectra, and estimate the interaction between geminate triplet excitons to be 60 neV.
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Affiliation(s)
- Sam L Bayliss
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Alexei D Chepelianskii
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom and LPS, Université Paris-Sud, CNRS, UMR 8502, F-91405, Orsay, France
| | - Alessandro Sepe
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Brian J Walker
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Bruno Ehrler
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Matthew J Bruzek
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506, USA
| | - John E Anthony
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Neil C Greenham
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
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84
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Akimov AV, Long R, Prezhdo OV. Coherence penalty functional: A simple method for adding decoherence in Ehrenfest dynamics. J Chem Phys 2014; 140:194107. [DOI: 10.1063/1.4875702] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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85
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Harvesting singlet fission for solar energy conversion via triplet energy transfer. Nat Commun 2014; 4:2679. [PMID: 24145737 DOI: 10.1038/ncomms3679] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 09/26/2013] [Indexed: 11/09/2022] Open
Abstract
The efficiency of a conventional solar cell may be enhanced if one incorporates a molecular material capable of singlet fission, that is, the production of two triplet excitons from the absorption of a single photon. To implement this, we need to successfully harvest the two triplets from the singlet fission material. Here we show in the tetracene (Tc)/copper phthalocyanine (CuPc) model system that triplets produced from singlet fission in the former can transfer to the later on the timescale of 45±5 ps. However, the efficiency of triplet energy transfer is limited by a loss channel due to faster formation (400±100 fs) and recombination (2.6±0.5 ps) of charge transfer excitons at the interface. These findings suggest a design principle for efficient energy harvesting from singlet fission: one must reduce interfacial area between the two organic chromophores to minimize charge transfer/recombination while optimizing light absorption, singlet fission and triplet rather than singlet transfer.
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86
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Pensack RD, Song Y, McCormick TM, Jahnke AA, Hollinger J, Seferos DS, Scholes GD. Evidence for the Rapid Conversion of Primary Photoexcitations to Triplet States in Seleno- and Telluro- Analogues of Poly(3-hexylthiophene). J Phys Chem B 2014; 118:2589-97. [DOI: 10.1021/jp5013347] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Ryan D. Pensack
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Yin Song
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Theresa M. McCormick
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Ashlee A. Jahnke
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Jon Hollinger
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Dwight S. Seferos
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Gregory D. Scholes
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
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87
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Poletayev AD, Clark J, Wilson MWB, Rao A, Makino Y, Hotta S, Friend RH. Triplet dynamics in pentacene crystals: applications to fission-sensitized photovoltaics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:919-24. [PMID: 24375546 DOI: 10.1002/adma.201302427] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Indexed: 05/12/2023]
Abstract
The decay and transport of triplet excitons photogenerated via singlet exciton fission in polycrystalline and single-crystalline pentacene is reported. Using transient absorption spectroscopy, we find evidence for diffusion-mediated triplet-triplet annihilation. We estimate monomolecular lifetimes, bimolecular annihilation rate constants, and triplet exciton diffusion lengths. We discuss these results in the context of current solar cell device architectures.
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Affiliation(s)
- Andrey D Poletayev
- Cavendish Laboratory, University of Cambridge, J. J. Thompson Ave, Cambridge, CB30HE, UK
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88
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O'Connor GD, Bacskay GB, Woodhouse GVG, Troy TP, Nauta K, Schmidt TW. Excitation spectra of large jet-cooled polycyclic aromatic hydrocarbon radicals: 9-anthracenylmethyl (C15H11) and 1-pyrenylmethyl (C17H11). J Phys Chem A 2013; 117:13899-907. [PMID: 24079545 DOI: 10.1021/jp4088833] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The 9-anthracenylmethyl (C15H11) and 1-pyrenylmethyl (C17H11) radicals were identified by a combination of mass-resolved laser spectroscopy of a jet-cooled electrical discharge and quantum chemical methods. The 9-anthracenylmethyl radical was found to exhibit an origin band at 13757 cm(-1), with vibrational structure observed in a1 modes, and even quanta of b1 and a2 modes. The 1-pyrenylmethyl radical was found to exhibit an origin band at 13,417 cm(-1), with a more complex vibrational structure as compared to 9-anthracenylmethyl, on account of its lower symmetry and larger size. The origin bands of these species were predicted to within 250 cm(-1) by fitting a linear relationship between observed origin wavelengths of similar chromophores and the calculated TD-B3LYP transition energies. A refined fit including the title radicals provides estimated absorption energies for the larger 2-perylenylmethyl and 6-anthanthrenylmethyl species of 1.44 and 1.41 eV, respectively, with an estimated error of 30 meV.
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89
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Singlet exciton fission in solution. Nat Chem 2013; 5:1019-24. [DOI: 10.1038/nchem.1801] [Citation(s) in RCA: 392] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 10/16/2013] [Indexed: 12/23/2022]
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90
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91
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Eaton SW, Shoer LE, Karlen SD, Dyar SM, Margulies EA, Veldkamp BS, Ramanan C, Hartzler DA, Savikhin S, Marks TJ, Wasielewski MR. Singlet exciton fission in polycrystalline thin films of a slip-stacked perylenediimide. J Am Chem Soc 2013; 135:14701-12. [PMID: 24011336 DOI: 10.1021/ja4053174] [Citation(s) in RCA: 216] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The crystal structure of N,N-bis(n-octyl)-2,5,8,11-tetraphenylperylene-3,4:9,10-bis(dicarboximide), 1, obtained by X-ray diffraction reveals that 1 has a nearly planar perylene core and π-π stacks at a 3.5 Å interplanar distance in well-separated slip-stacked columns. Theory predicts that slip-stacked, π-π-stacked structures should enhance interchromophore electronic coupling and thus favor singlet exciton fission. Photoexcitation of vapor-deposited polycrystalline 188 nm thick films of 1 results in a 140 ± 20% yield of triplet excitons ((3*)1) in τ(SF) = 180 ± 10 ps. These results illustrate a design strategy for producing perylenediimide and related rylene derivatives that have the optimized interchromophore electronic interactions which promote high-yield singlet exciton fission for potentially enhancing organic solar cell performance and charge separation in systems for artificial photosynthesis.
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Affiliation(s)
- Samuel W Eaton
- Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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92
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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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93
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Miao C, Liu T, Zhu Y, Dai Q, Xu W, Xu L, Xu S, Zhao Y, Song H. Super-intense white upconversion emission of Yb2O3 polycrystals and its application on luminescence converter of dye-sensitized solar cells. OPTICS LETTERS 2013; 38:3340-3343. [PMID: 23988951 DOI: 10.1364/ol.38.003340] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In this Letter, we present the observation of super-intense upconversion (UC) white emission of Yb2O3 under 980 nm excitation, its evolution on excitation power density, the UC mechanism, and its application on the luminescence converter of dye-sensitized solar cells (DSSCs). It is significant to observe that Yb2O3 demonstrates at least one order more intense UC luminescence than β-phase NaYF4:Yb3+, Er3+ and Yb2O3/DSSCs exhibit much better photovoltaic performance than β-phase NaYF4:Yb3+, Er3+/DSSCs under strong excitation. This indicates that Yb2O3 would become a novel candidate of the solar energy converter, especially in the application of concentrator solar cells.
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Affiliation(s)
- Chuang Miao
- State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China
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94
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Ireland RM, Zhang L, Gopalan P, Katz HE. Tellurium thin films in hybrid organic electronics: morphology and mobility. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:4358-4364. [PMID: 23161744 DOI: 10.1002/adma.201203647] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Indexed: 06/01/2023]
Abstract
Elemental Te displays a wide variety of nanoscale morphologies of vapor-deposited films, depending on the substrate surface and temperature. These morphologies are correlated to field-effect mobilities in transistors made with Te as the lone semiconductor or from Te-organic multilayer semiconductors. Two examples of morphologies and transistor output characteristics, i.e., on a room temperature oxide and heated organic, are shown in the figure.
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Affiliation(s)
- Robert M Ireland
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, USA
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95
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Musser AJ, Al-Hashimi M, Maiuri M, Brida D, Heeney M, Cerullo G, Friend RH, Clark J. Activated singlet exciton fission in a semiconducting polymer. J Am Chem Soc 2013; 135:12747-54. [PMID: 23883167 DOI: 10.1021/ja405427j] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Singlet exciton fission is a spin-allowed process to generate two triplet excitons from a single absorbed photon. This phenomenon offers great potential in organic photovoltaics, but the mechanism remains poorly understood. Most reports to date have addressed intermolecular fission within small-molecular crystals. However, through appropriate chemical design chromophores capable of intramolecular fission can also be produced. Here we directly observe sub-100 fs activated singlet fission in a semiconducting poly(thienylenevinylene). We demonstrate that fission proceeds directly from the initial 1Bu exciton, contrary to current models that involve the lower-lying 2Ag exciton. In solution, the generated triplet pairs rapidly recombine and decay through the 2Ag state. In films, exciton diffusion breaks this symmetry and we observe long-lived triplets which form charge-transfer states in photovoltaic blends.
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Affiliation(s)
- Andrew J Musser
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom.
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96
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Nelson J, Emmott CJM. Can solar power deliver? PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20120372. [PMID: 23816915 DOI: 10.1098/rsta.2012.0372] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Solar power represents a vast resource which could, in principle, meet the world's needs for clean power generation. Recent growth in the use of photovoltaic (PV) technology has demonstrated the potential of solar power to deliver on a large scale. Whilst the dominant PV technology is based on crystalline silicon, a wide variety of alternative PV materials and device concepts have been explored in an attempt to decrease the cost of the photovoltaic electricity. This article explores the potential for such emerging technologies to deliver cost reductions, scalability of manufacture, rapid carbon mitigation and new science in order to accelerate the uptake of solar power technologies.
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Affiliation(s)
- Jenny Nelson
- Department of Physics, Imperial College London, London SW7 2AZ, UK.
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97
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Greenham NC. Polymer solar cells. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2013; 371:20110414. [PMID: 23816905 DOI: 10.1098/rsta.2011.0414] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
This article reviews the motivations for developing polymer-based photovoltaics and describes some of the material systems used. Current challenges are identified, and some recent developments in the field are outlined. In particular, recent work to image and control nanostructure in polymer-based solar cells is reviewed, and very recent progress is described using the unique properties of organic semiconductors to develop strategies that may allow the Shockley-Queisser limit to be broken in a simple photovoltaic cell.
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Affiliation(s)
- Neil C Greenham
- Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK.
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98
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Wilson MWB, Rao A, Ehrler B, Friend RH. Singlet exciton fission in polycrystalline pentacene: from photophysics toward devices. Acc Chem Res 2013; 46:1330-8. [PMID: 23656886 DOI: 10.1021/ar300345h] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Singlet exciton fission is the process in conjugated organic molecules bywhich a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers first reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These investigations used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest has been recently rekindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating additional photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chemistry, and small-molecule device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycrystalline thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, we review the results of our recent transient absorption and device-based studies of polycrystalline pentacene. We address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins our conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, we discuss our demonstration that triplet excitons generated via singlet fission in pentacene can be dissociated at an interface with a suitable electron acceptor, such as fullerenes and infrared-absorbing inorganic semiconducting quantum dots. We highlight our recent reports of a pentacene/PbSe hybrid solar cell with a power conversion efficiency of 4.7% and of a pentacene/PbSe/amorphous silicon photovoltaic device. Although substantive challenges remain, both to better our understanding of the mechanism of singlet exciton fission and to optimize device performance, this realization of a solar cell where photocurrent is simultaneously contributed from a blue-absorbing fission-capable material and an infrared-absorbing conventional cell is an important step towards a dual-bandgap, single-junction, fission-enhanced photovoltaic device, which could one day surpass the Shockley-Queisser limit.
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Affiliation(s)
- Mark W. B. Wilson
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Akshay Rao
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Bruno Ehrler
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
| | - Richard H. Friend
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, U.K
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99
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Lee J, Jadhav P, Reusswig PD, Yost SR, Thompson NJ, Congreve DN, Hontz E, Van Voorhis T, Baldo MA. Singlet exciton fission photovoltaics. Acc Chem Res 2013; 46:1300-11. [PMID: 23611026 DOI: 10.1021/ar300288e] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Singlet exciton fission, a process that generates two excitons from a single photon, is perhaps the most efficient of the various multiexciton-generation processes studied to date, offering the potential to increase the efficiency of solar devices. But its unique characteristic, splitting a photogenerated singlet exciton into two dark triplet states, means that the empty absorption region between the singlet and triplet excitons must be filled by adding another material that captures low-energy photons. This has required the development of specialized device architectures. In this Account, we review work to develop devices that harness the theoretical benefits of singlet exciton fission. First, we discuss singlet fission in the archetypal material, pentacene. Pentacene-based photovoltaic devices typically show high external and internal quantum efficiencies. They have enabled researchers to characterize fission, including yield and the impact of competing loss processes, within functional devices. We review in situ probes of singlet fission that modulate the photocurrent using a magnetic field. We also summarize studies of the dissociation of triplet excitons into charge at the pentacene-buckyball (C60) donor-acceptor interface. Multiple independent measurements confirm that pentacene triplet excitons can dissociate at the C60 interface despite their relatively low energy. Because triplet excitons produced by singlet fission each have no more than half the energy of the original photoexcitation, they limit the potential open circuit voltage within a solar cell. Thus, if singlet fission is to increase the overall efficiency of a solar cell and not just double the photocurrent at the cost of halving the voltage, it is necessary to also harvest photons in the absorption gap between the singlet and triplet energies of the singlet fission material. We review two device architectures that attempt this using long-wavelength materials: a three-layer structure that uses long- and short-wavelength donors and an acceptor and a simpler, two-layer combination of a singlet-fission donor and a long-wavelength acceptor. An example of the trilayer structure is singlet fission in tetracene with copper phthalocyanine inserted at the C60 interface. The bilayer approach includes pentacene photovoltaic cells with an acceptor of infrared-absorbing lead sulfide or lead selenide nanocrystals. Lead selenide nanocrystals appear to be the most promising acceptors, exhibiting efficient triplet exciton dissociation and high power conversion efficiency. Finally, we review architectures that use singlet fission materials to sensitize other absorbers, thereby effectively converting conventional donor materials to singlet fission dyes. In these devices, photoexcitation occurs in a particular molecule and then energy is transferred to a singlet fission dye where the fission occurs. For example, rubrene inserted between a donor and an acceptor decouples the ability to perform singlet fission from other major photovoltaic properties such as light absorption.
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Affiliation(s)
- Jiye Lee
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Priya Jadhav
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Philip D. Reusswig
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Shane R. Yost
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Nicholas J. Thompson
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel N. Congreve
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Eric Hontz
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Troy Van Voorhis
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Marc A. Baldo
- Energy Frontier Research Center for Excitonics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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100
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Ehrler B, Musselman KP, Böhm ML, Morgenstern FSF, Vaynzof Y, Walker BJ, Macmanus-Driscoll JL, Greenham NC. Preventing interfacial recombination in colloidal quantum dot solar cells by doping the metal oxide. ACS NANO 2013; 7:4210-20. [PMID: 23531107 DOI: 10.1021/nn400656n] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Recent research has pushed the efficiency of colloidal quantum dot solar cells toward a level that spurs commercial interest. Quantum dot/metal oxide bilayers form the most efficient colloidal quantum dot solar cells, and most studies have advanced the understanding of the quantum dot component. We study the interfacial recombination process in depleted heterojunction colloidal quantum dot (QD) solar cells formed with ZnO as the oxide by varying (i) the carrier concentration of the ZnO layer and (ii) the density of intragap recombination sites in the QD layer. We find that the open-circuit voltage and efficiency of PbS QD/ZnO devices can be improved by 50% upon doping of the ZnO with nitrogen to reduce its carrier concentration. In contrast, doping the ZnO did not change the performance of PbSe QD/ZnO solar cells. We use X-ray photoemission spectroscopy, ultraviolet photoemission spectroscopy, transient photovoltage decay measurements, transient absorption spectroscopy, and intensity-dependent photocurrent measurements to investigate the origin of this effect. We find a significant density of intragap states within the band gap of the PbS quantum dots. These states facilitate recombination at the PbS/ZnO interface, which can be suppressed by reducing the density of occupied states in the ZnO. For the PbSe QD/ZnO solar cells, where fewer intragap states are observed in the quantum dots, the interfacial recombination channel does not limit device performance. Our study sheds light on the mechanisms of interfacial recombination in colloidal quantum dot solar cells and emphasizes the influence of quantum dot intragap states and metal oxide properties on this loss pathway.
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Affiliation(s)
- Bruno Ehrler
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
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