1
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Banappanavar G, Saxena R, Bässler H, Köhler A, Kabra D. Impact of Photoluminescence Imaging Methodology on Transport Parameters in Semiconductors. J Phys Chem Lett 2024; 15:3109-3117. [PMID: 38470078 DOI: 10.1021/acs.jpclett.4c00169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Triplet-triplet annihilation-induced delayed emission provides a pathway for investigating triplets via emission spectroscopy. This bimolecular annihilation depends directly on the transport properties of triplet excitons in disordered organic semiconductors. Photoluminescence (PL) imaging is a direct method for studying exciton and charge-carrier diffusivity. However, most of these studies neglect dispersive transport. Early time scale measurements using this technique can lead to an overestimation of the diffusion coefficient (DT) or diffusion length (Ld). In this study, we investigated the time-dependent triplet DT using PL imaging. We observed an overestimation of Ld in classical delayed PL imaging, often 1 order of magnitude higher than the actual Ld value. We compared various thicknesses of polymeric thin films to study the dispersive nature of triplet excitons. Transient analysis of delayed PL imaging and steady state imaging reveals the importance of considering the time-dependent nature of DT for the triplet excitons in disordered electronic materials.
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Affiliation(s)
- Gangadhar Banappanavar
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Rishabh Saxena
- Soft Matter Optoelectronics and Bavarian Polymer Institute (BPS), University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany
| | - Heinz Bässler
- Bayreuth Institute of Macromolecular Research (BIMF), University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany
| | - Anna Köhler
- Soft Matter Optoelectronics and Bavarian Polymer Institute (BPS), University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany
- Bayreuth Institute of Macromolecular Research (BIMF), University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany
| | - Dinesh Kabra
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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2
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Ito S, Fukuyama M, Tanaka K, Chujo Y. Effects of Regioregularity of
π
‐Conjugated Polymers Composed of Boron
β
‐Diketiminate on Their Stimuli‐Responsive Luminescence. MACROMOL CHEM PHYS 2022. [DOI: 10.1002/macp.202100504] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Shunichiro Ito
- Department of Polymer Chemistry Graduate School of Engineering Kyoto University Katsura Nishikyo‐ku Kyoto 615–8510 Japan
| | - Misuzu Fukuyama
- Department of Polymer Chemistry Graduate School of Engineering Kyoto University Katsura Nishikyo‐ku Kyoto 615–8510 Japan
| | - Kazuo Tanaka
- Department of Polymer Chemistry Graduate School of Engineering Kyoto University Katsura Nishikyo‐ku Kyoto 615–8510 Japan
| | - Yoshiki Chujo
- Department of Polymer Chemistry Graduate School of Engineering Kyoto University Katsura Nishikyo‐ku Kyoto 615–8510 Japan
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3
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Zhang X, Yang Q, Fu Y, Zhang Y. Secondary Exciplex by Electromer Mediated Charge Transfer for Multiband Electroluminescence. ACS Macro Lett 2021; 10:1236-1242. [PMID: 35549035 DOI: 10.1021/acsmacrolett.1c00501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Charge-transfer states have been observed extensively in heterojunctions of organic semiconductors, which are also referred to as exciplexes in polymer blends. Such mechanisms have been well understood in the conventional material systems. However, electromer states may be produced only in some polymeric molecules with folded chains. We report here the interaction between exciplex and electromer states, which facilitates the formation of a new electrically excited state that we define as a secondary exciplex. This is an indirect process understood as an electromer-mediated heterojunction. We discovered such an optoelectronic mechanism in the blend film of poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-pheny-l,4-phenylene-diamine) (PFB) and poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT). Four emission bands can be resolved from the electroluminescence spectrum, including those based on the excitons, the electromers, and the primary and secondary exciplexes. The whole electroluminescence spectrum thus extends from the green (500 nm) to the near-infrared (900 nm) with a full bandwidth of 400 nm. These new discoveries with the conventional light-emitting polymers are important not only for polymeric optoelectronics, but also for the development of broadband light-emitting devices.
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Affiliation(s)
- Xinping Zhang
- Institute of Information Photonics Technology, Beijing University of Technology, Beijing 100124, People's Republic of China
| | - Qiaohui Yang
- Institute of Information Photonics Technology, Beijing University of Technology, Beijing 100124, People's Republic of China
| | - Yulan Fu
- Institute of Information Photonics Technology, Beijing University of Technology, Beijing 100124, People's Republic of China
| | - Yiwei Zhang
- Institute of Information Photonics Technology, Beijing University of Technology, Beijing 100124, People's Republic of China
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4
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Liu R, Tan KT, Gong Y, Chen Y, Li Z, Xie S, He T, Lu Z, Yang H, Jiang D. Covalent organic frameworks: an ideal platform for designing ordered materials and advanced applications. Chem Soc Rev 2021; 50:120-242. [DOI: 10.1039/d0cs00620c] [Citation(s) in RCA: 206] [Impact Index Per Article: 68.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Covalent organic frameworks offer a molecular platform for integrating organic units into periodically ordered yet extended 2D and 3D polymers to create topologically well-defined polygonal lattices and built-in discrete micropores and/or mesopores.
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5
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Charge-carrier photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrent nearby the regime of the space charge-limited current. Front Chem Sci Eng 2020. [DOI: 10.1007/s11705-020-1976-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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6
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Wang H, Jin S, Zhang X, Xie Y. Excitonic Effects in Polymeric Photocatalysts. Angew Chem Int Ed Engl 2020; 59:22828-22839. [DOI: 10.1002/anie.202002241] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Indexed: 12/31/2022]
Affiliation(s)
- Hui Wang
- Hefei National Laboratory for Physical Sciences at the Microscale CAS Centre for Excellence in Nanoscience University of Science and Technology of China Hefei Anhui 230026 P. R. China
- Institute of Energy Hefei Comprehensive National Science Center Hefei Anhui 230031 P. R. China
| | - Sen Jin
- Hefei National Laboratory for Physical Sciences at the Microscale CAS Centre for Excellence in Nanoscience University of Science and Technology of China Hefei Anhui 230026 P. R. China
| | - Xiaodong Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale CAS Centre for Excellence in Nanoscience University of Science and Technology of China Hefei Anhui 230026 P. R. China
- Institute of Energy Hefei Comprehensive National Science Center Hefei Anhui 230031 P. R. China
| | - Yi Xie
- Hefei National Laboratory for Physical Sciences at the Microscale CAS Centre for Excellence in Nanoscience University of Science and Technology of China Hefei Anhui 230026 P. R. China
- Institute of Energy Hefei Comprehensive National Science Center Hefei Anhui 230031 P. R. China
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7
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Affiliation(s)
- Hui Wang
- Hefei National Laboratory for Physical Sciences at the Microscale CAS Centre for Excellence in Nanoscience University of Science and Technology of China Hefei Anhui 230026 P. R. China
- Institute of Energy Hefei Comprehensive National Science Center Hefei Anhui 230031 P. R. China
| | - Sen Jin
- Hefei National Laboratory for Physical Sciences at the Microscale CAS Centre for Excellence in Nanoscience University of Science and Technology of China Hefei Anhui 230026 P. R. China
| | - Xiaodong Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale CAS Centre for Excellence in Nanoscience University of Science and Technology of China Hefei Anhui 230026 P. R. China
- Institute of Energy Hefei Comprehensive National Science Center Hefei Anhui 230031 P. R. China
| | - Yi Xie
- Hefei National Laboratory for Physical Sciences at the Microscale CAS Centre for Excellence in Nanoscience University of Science and Technology of China Hefei Anhui 230026 P. R. China
- Institute of Energy Hefei Comprehensive National Science Center Hefei Anhui 230031 P. R. China
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8
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Zhang X, Tang F, Wang M, Zhan W, Hu H, Li Y, Friend RH, Song X. Femtosecond visualization of oxygen vacancies in metal oxides. SCIENCE ADVANCES 2020; 6:eaax9427. [PMID: 32181341 PMCID: PMC7060066 DOI: 10.1126/sciadv.aax9427] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 12/12/2019] [Indexed: 06/09/2023]
Abstract
Oxygen vacancies often determine the electronic structure of metal oxides, but existing techniques cannot distinguish the oxygen-vacancy sites in the crystal structure. We report here that time-resolved optical spectroscopy can solve this challenge and determine the spatial locations of oxygen vacancies. Using tungsten oxides as examples, we identified the true oxygen-vacancy sites in WO2.9 and WO2.72, typical derivatives of WO3 and determined their fingerprint optoelectronic features. We find that a metastable band with a three-stage evolution dynamics of the excited states is present in WO2.9 but is absent in WO2.72. By comparison with model bandstructure calculations, this enables determination of the most closely neighbored oxygen-vacancy pairs in the crystal structure of WO2.72, for which two oxygen vacancies are ortho-positioned to a single W atom as a sole configuration among all O─W bonds. These findings verify the existence of preference rules of oxygen vacancies in metal oxides.
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Affiliation(s)
- Xinping Zhang
- Institute of Information Photonics Technology and College of Applied Sciences, Beijing University of Technology, Beijing 100124, China
| | - Fawei Tang
- College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Education Ministry of China, Beijing University of Technology, Beijing 100124, China
| | - Meng Wang
- Institute of Information Photonics Technology and College of Applied Sciences, Beijing University of Technology, Beijing 100124, China
| | - Wangbin Zhan
- College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Education Ministry of China, Beijing University of Technology, Beijing 100124, China
| | - Huaxin Hu
- College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Education Ministry of China, Beijing University of Technology, Beijing 100124, China
| | - Yurong Li
- College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Education Ministry of China, Beijing University of Technology, Beijing 100124, China
| | - Richard H. Friend
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Xiaoyan Song
- College of Materials Science and Engineering, Key Laboratory of Advanced Functional Materials, Education Ministry of China, Beijing University of Technology, Beijing 100124, China
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9
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Tegegne NA, Abdissa Z, Mammo W, Andersson MR, Schlettwein D, Schwoerer H. Ultrafast excited state dynamics of a bithiophene-isoindigo copolymer obtained by direct arylation polycondensation and its application in indium tin oxide-free solar cells. ACTA ACUST UNITED AC 2018. [DOI: 10.1002/polb.24743] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Newayemedhin A. Tegegne
- Physics Department, Laser Research Institute; Stellenbosch University; Stellenbosch South Africa
| | - Zelalem Abdissa
- Science Faculty, Department of Chemistry; Addis Ababa University; P.O. Box 33658, Addis Ababa Ethiopia
| | - Wendimagegn Mammo
- Science Faculty, Department of Chemistry; Addis Ababa University; P.O. Box 33658, Addis Ababa Ethiopia
| | - Mats R. Andersson
- Future Industries Institute, University of South Australia; Mawson Lakes Boulevard, Mawson Lakes South Australia 5095 Australia
| | - Derck Schlettwein
- Institute of Applied Physics, Justus-Liebig-University; Heinrich Buff Ring 16, 35392 Giessen Germany
| | - Heinrich Schwoerer
- Physics Department, Laser Research Institute; Stellenbosch University; Stellenbosch South Africa
- Max Planck Institute for the Structure and Dynamics of Matter; Luruper Chaussee 149, 22761 Hamburg Germany
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10
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Influence of excitons interaction with charge carriers on photovoltaic parameters in organic solar cells. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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11
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Wagenpfahl A. Mobility dependent recombination models for organic solar cells. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:373001. [PMID: 28612756 DOI: 10.1088/1361-648x/aa7952] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Modern solar cell technologies are driven by the effort to enhance power conversion efficiencies. A main mechanism limiting power conversion efficiencies is charge carrier recombination which is a direct function of the encounter probability of both recombination partners. In inorganic solar cells with rather high charge carrier mobilities, charge carrier recombination is often dominated by energetic states which subsequently trap both recombination partners for recombination. Free charge carriers move fast enough for Coulomb attraction to be irrelevant for the encounter probability. Thus, charge carrier recombination is independent of charge carrier mobilities. In organic semiconductors charge carrier mobilities are much lower. Therefore, electrons and holes have more time react to mutual Coulomb-forces. This results in the strong charge carrier mobility dependencies of the observed charge carrier recombination rates. In 1903 Paul Langevin published a fundamental model to describe the recombination of ions in gas-phase or aqueous solutions, known today as Langevin recombination. During the last decades this model was used to interpret and model recombination in organic semiconductors. However, certain experiments especially with bulk-heterojunction solar cells reveal much lower recombination rates than predicted by Langevin. In search of an explanation, many material and device properties such as morphology and energetic properties have been examined in order to extend the validity of the Langevin model. A key argument for most of these extended models is, that electron and hole must find each other at a mutual spatial location. This encounter may be limited for instance by trapping of charges in trap states, by selective electrodes separating electrons and holes, or simply by the morphology of the involved semiconductors, making it impossible for electrons and holes to recombine at high rates. In this review, we discuss the development of mobility limited recombination models from the early Langevin theory to state-of-the art models for charge carrier recombination in organic solar cells.
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12
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Zarrabi N, Burn PL, Meredith P, Shaw PE. Acceptor and Excitation Density Dependence of the Ultrafast Polaron Absorption Signal in Donor-Acceptor Organic Solar Cell Blends. J Phys Chem Lett 2016; 7:2640-2646. [PMID: 27355877 DOI: 10.1021/acs.jpclett.6b00806] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Transient absorption spectroscopy on organic semiconductor blends for solar cells typically shows efficient charge generation within ∼100 fs, accounting for the majority of the charge carriers. In this Letter, we show using transient absorption spectroscopy on blends containing a broad range of acceptor content (0.01-50% by weight) that the rise of the polaron signal is dependent on the acceptor concentration. For low acceptor content (<10% by weight), the polaron signal rises gradually over ∼1 ps with most polarons generated after 200 fs, while for higher acceptor concentrations (>10%) most polarons are generated within 200 fs. The rise time in blends with low acceptor content was also found to be sensitive to the pump fluence, decreasing with increasing excitation density. These results indicate that the sub-100 fs rise of the polaron signal is a natural consequence of both the high acceptor concentrations in many donor-acceptor blends and the high excitation densities needed for transient absorption spectroscopy, which results in a short average distance between the exciton and the donor-acceptor interface.
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Affiliation(s)
- Nasim Zarrabi
- Centre for Organic Photonics & Electronics, School of Mathematics & Physics, and School of Chemistry and Molecular Biosciences, The University of Queensland , Brisbane, Queensland 4072, Australia
| | - Paul L Burn
- Centre for Organic Photonics & Electronics, School of Mathematics & Physics, and School of Chemistry and Molecular Biosciences, The University of Queensland , Brisbane, Queensland 4072, Australia
| | - Paul Meredith
- Centre for Organic Photonics & Electronics, School of Mathematics & Physics, and School of Chemistry and Molecular Biosciences, The University of Queensland , Brisbane, Queensland 4072, Australia
| | - Paul E Shaw
- Centre for Organic Photonics & Electronics, School of Mathematics & Physics, and School of Chemistry and Molecular Biosciences, The University of Queensland , Brisbane, Queensland 4072, Australia
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13
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Kim IS, Kim IB, Kim DY, Kwon SH, Ko DK. Effect of Fluorine Substitution on the Charge Carrier Dynamics of Benzothiadiazole-Based Solar Cell Materials. Macromol Rapid Commun 2016; 37:1242-8. [PMID: 27226245 DOI: 10.1002/marc.201600197] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 05/04/2016] [Indexed: 11/08/2022]
Abstract
The femtosecond transient absorption (TA) characterization of a new benzothiadiazole (BT)-based donor-acceptor conjugated copolymer, poly[(2,6-dithieno[3,2-b:2',3'-d]thiophene)-alt-(4,7-di(4-octyldodecylthiopen-2-yl)-2,1,3-benzo[c][1,2,5]thiadiazole (PBT), as well as its fluorinated derivatives, PFBT and PDFBT, is carried out. Additionally, bulk heterojunction (BHJ) films consisting of the copolymers and [6,6]-phenyl-C71 -butylic acid methyl ester (PC70 BM) are examined using TA spectroscopy. Both the singlet excited state dynamics in the copolymers and the charge transfer state dynamics in the BHJs are investigated in terms of fluorination dependency; the fluorinated copolymers exhibit less singlet exciton recombination rate than the fluorine-free copolymer, and the BHJs including the fluorinated copolymers display slower monomolecular recombination than the fluorine-free analogue. Furthermore, the excitation-intensity-dependent TA dynamics of the copolymers and BHJs is investigated, revealing that, when sufficiently high excitation intensity is used to induce annihilation processes, the fluorinated copolymers and BHJs incorporating the fluorinated copolymers show more rapid TA decay ascribable to morphological enhancement. These TA spectroscopic findings are found to correlate with the device characteristics with respect to fluorinated content in the polymer solar cells. In particular, both the short-circuit current density and fill factor of BHJ solar cells correspond closely with the fast decay parameters of the BHJ films under high excitation intensity.
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Affiliation(s)
- In-Sik Kim
- School of Physics and Chemistry, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea
| | - In-Bok Kim
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea
| | - Dong-Yu Kim
- School of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea
| | - Seong-Hoon Kwon
- School of Physics and Chemistry, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea
| | - Do-Kyeong Ko
- Advanced Photonics Research Institute and School of Physics and Chemistry, Gwangju Institute of Science and Technology, Gwangju, 61005, South Korea
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14
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Kim IS, Jang SY, Park T, Jo C, Kim DY, Ko DK. Femtosecond transient absorption dynamics in low bandgap polymer solar cell materials including poly(thienylenevinylene) derivative and benzothiadiazole moiety. Chem Phys 2015. [DOI: 10.1016/j.chemphys.2015.08.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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15
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Wang X, Liao Q, Li H, Bai S, Wu Y, Lu X, Hu H, Shi Q, Fu H. Near-Infrared Lasing from Small-Molecule Organic Hemispheres. J Am Chem Soc 2015; 137:9289-95. [DOI: 10.1021/jacs.5b03051] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xuedong Wang
- Beijing
National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Qing Liao
- Beijing
Key Laboratory for Optical Materials and Photonic Devices, Department
of Chemistry, Capital Normal University, Beijing 100048, P. R. China
| | - Hui Li
- Beijing
National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Shuming Bai
- Beijing
National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Yishi Wu
- Beijing
National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Xiaomei Lu
- Beijing
Key Laboratory for Optical Materials and Photonic Devices, Department
of Chemistry, Capital Normal University, Beijing 100048, P. R. China
| | - Huaiyuan Hu
- Department
of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487, United States
| | - Qiang Shi
- Beijing
National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Hongbing Fu
- Beijing
National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Beijing
Key Laboratory for Optical Materials and Photonic Devices, Department
of Chemistry, Capital Normal University, Beijing 100048, P. R. China
- Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, P. R. China
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16
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Kim IS, Kwon S, Kim J, Kim DY, Ko DK. Excitation-intensity-dependent charge carrier dynamics in thienylenevinylene-phthalimide copolymer based thin polymer films. POLYMER 2015. [DOI: 10.1016/j.polymer.2015.03.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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17
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Zhang X, Li H, Wang Y, Liu F. Stimulated emission within the exciplex band by plasmonic-nanostructured polymeric heterojunctions. NANOSCALE 2015; 7:5624-5632. [PMID: 25757393 DOI: 10.1039/c5nr00140d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Organic heterojunctions have been extensively employed in the design of light-emitting diodes, photovoltaic devices, and thin-film field-effect transistors, which can be achieved by constructing a bilayer or a multi-layered thin-film deposition, or by blending two or more organic semiconductors with different charge-transport performances. Charge transfer excited states or exciplex may form on the heterointerfaces. Efficient light-emitting diodes have been demonstrated using exciplex emission. However, lasing or stimulated emission processes have not been observed with exciplex formation at organic heterojunctions. In this work, we demonstrate strong coherent interaction between photons and exciplex formation in the blends of poly-9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-l,4-phenylenediamine (PFB) and poly-9,9'-dioctylfluorene-co-benzothiadiazole (F8BT), leading to transient stimulated exciplex emission. The responsible mechanisms involve plasmonic local-field enhancement and plasmonic feedback in a three-dimensional gold-nanoparticle matrix.
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Affiliation(s)
- Xinping Zhang
- Institute of Information Photonics Technology and College of Applied Sciences, Beijing University of Technology, Beijing 100124, P. R. China.
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18
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Hedley GJ, Ward AJ, Alekseev A, Howells CT, Martins ER, Serrano LA, Cooke G, Ruseckas A, Samuel IDW. Determining the optimum morphology in high-performance polymer-fullerene organic photovoltaic cells. Nat Commun 2014; 4:2867. [PMID: 24343223 PMCID: PMC3905772 DOI: 10.1038/ncomms3867] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 11/05/2013] [Indexed: 11/17/2022] Open
Abstract
The morphology of bulk heterojunction organic photovoltaic cells controls many of the performance characteristics of devices. However, measuring this morphology is challenging because of the small length-scales and low contrast between organic materials. Here we use nanoscale photocurrent mapping, ultrafast fluorescence and exciton diffusion to observe the detailed morphology of a high-performance blend of PTB7:PC71BM. We show that optimized blends consist of elongated fullerene-rich and polymer-rich fibre-like domains, which are 10–50 nm wide and 200–400 nm long. These elongated domains provide a concentration gradient for directional charge diffusion that helps in the extraction of charge pairs with 80% efficiency. In contrast, blends with agglomerated fullerene domains show a much lower efficiency of charge extraction of ~45%, which is attributed to poor electron and hole transport. Our results show that the formation of narrow and elongated domains is desirable for efficient bulk heterojunction solar cells. The morphology of organic solar cells is crucial to their performance but is difficult to measure. Using a variety of probes, Hedley et al. map the morphology of polymer-fullerene solar cells and find that elongated fibre-like polymer- and fullerene-rich domains are desirable for high performance.
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Affiliation(s)
- Gordon J Hedley
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
| | - Alexander J Ward
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
| | - Alexander Alekseev
- Materials and Condensed Matter Physics, SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK
| | - Calvyn T Howells
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
| | - Emiliano R Martins
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
| | - Luis A Serrano
- Glasgow Centre for Physical Organic Chemistry, WestCHEM, School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
| | - Graeme Cooke
- Glasgow Centre for Physical Organic Chemistry, WestCHEM, School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
| | - Arvydas Ruseckas
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
| | - Ifor D W Samuel
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK
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19
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Chow PCY, Albert-Seifried S, Gélinas S, Friend RH. Nanosecond intersystem crossing times in fullerene acceptors: implications for organic photovoltaic diodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2014; 26:4851-4. [PMID: 24902831 PMCID: PMC4515088 DOI: 10.1002/adma.201400846] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 04/14/2014] [Indexed: 05/19/2023]
Abstract
Triplet-exciton formation through intersystem crossing of photogenerated singlet excitons in fullerene acceptors can compete with charge generation in organic photovoltaic diodes. This article reports the intersystem crossing timescale (τISC ) of the most commonly used fullerene acceptors, PC60 BM and PC70 BM, in solutions and in spin-coated films. These times are on the nanosecond timescale, and are longer than the characteristic times for charge generation (τd ).
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Affiliation(s)
- Philip C Y Chow
- Cavendish Laboratory, University of CambridgeCB3 0HE, United Kingdom
| | | | - Simon Gélinas
- Cavendish Laboratory, University of CambridgeCB3 0HE, United Kingdom
| | - Richard H Friend
- Cavendish Laboratory, University of CambridgeCB3 0HE, United Kingdom
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20
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Chow PCY, Gélinas S, Rao A, Friend RH. Quantitative Bimolecular Recombination in Organic Photovoltaics through Triplet Exciton Formation. J Am Chem Soc 2014; 136:3424-9. [DOI: 10.1021/ja410092n] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Philip C. Y. Chow
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Simon Gélinas
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Akshay Rao
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Richard H. Friend
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
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21
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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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22
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Zhang X, Li H. Laser-induced selective crosslinking for scaling the heterointerfacial domain in polymer blends. OPTICS EXPRESS 2013; 21:24620-24629. [PMID: 24150306 DOI: 10.1364/oe.21.024620] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Organic blends containing heterojunction structures at the interfacial phase have been applied extensively in organic optoelectronic devices to modify charge transfer, separation, and recombination processes. Scaling and controlling the transition domains at the hetero-interface are of crucial importance for deep insights into the involved physics and for architecturing the devices with improved performance. However, it is difficult to recognize and characterize these transition domains directly using the conventional microscopic techniques, in particular when different molecules are dissolved in the same solvent with equal solubility. In this work, we introduce a technique defined as laser-induced selective cross-linking to isolate the interfacial phase from other phases into a directly measurable practicity. Thus, the hetero-domains become visualized and directly measurable. Based on the insolubility of the selectively cross-linked molecules in organic solvents, a lift-off process may remove the uncross-linked or incompletely cross-linked molecules, so that the hetero-domain is more clearly visualized and more precisely measured. A transition domain in a scale of about 200 nm is resolved in the F8BT/PFB blend film between their respectively rich phases after the selective cross-linking of the F8BT molecules by a blue laser. Furthermore, hetero-crosslinking between F8BT and PFB molecules was also resolved by both microscopic and near-field spectroscopic investigations.
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Chen L, Zhang Q, Lei Y, Zhu F, Wu B, Zhang T, Niu G, Xiong Z, Song Q. Photocurrent generation through electron-exciton interaction at the organic semiconductor donor/acceptor interface. Phys Chem Chem Phys 2013; 15:16891-7. [PMID: 24002235 DOI: 10.1039/c3cp52974f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work, we report our effort to understand the photocurrent generation that is contributed via electron-exciton interaction at the donor/acceptor interface in organic solar cells (OSCs). Donor/acceptor bi-layer heterojunction OSCs, of the indium tin oxide/copper phthalocyanine (CuPc)/fullerene (C60)/molybdenum oxide/Al type, were employed to study the mechanism of photocurrent generation due to the electron-exciton interaction, where CuPc and C60 are the donor and the acceptor, respectively. It is shown that the electron-exciton interaction and the exciton dissociation processes co-exist at the CuPc/C60 interface in OSCs. Compared to conventional donor/acceptor bi-layer OSCs, the cells with the above configuration enable holes to be extracted at the C60 side while electrons can be collected at the CuPc side, resulting in a photocurrent in the reverse direction. The photocurrent thus observed is contributed to primarily by the charge carriers that are generated by the electron-exciton interaction at the CuPc/C60 interface, while charges derived from the exciton dissociation process also exist at the same interface. The mechanism of photocurrent generation due to electron-exciton interaction in the OSCs is further investigated, and it is manifested by the transient photovoltage characteristics and the external quantum efficiency measurements.
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Affiliation(s)
- Lijia Chen
- Chongqing Key Laboratory for Advanced Materials and Technologies of Clean Energy, Chongqing 400715, P. R. China.
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24
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Kaake L, Dang XD, Leong WL, Zhang Y, Heeger A, Nguyen TQ. Effects of impurities on operational mechanism of organic bulk heterojunction solar cells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:1706-1712. [PMID: 23281094 DOI: 10.1002/adma.201203786] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 11/05/2012] [Indexed: 06/01/2023]
Abstract
Photoconductive atomic force microscopy in conjunction with transient absorption spectroscopy and charge transport study were used to investigate the effect of impurities (TCNQ and PC84 BM) on the performance of low band gap conjugated polymer and fullerene solar cells to gain insight into whether differing impurity shapes may lead to different loss mechanisms.
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Affiliation(s)
- Loren Kaake
- Center for Polymers and Organic Solids, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
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25
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Kaake LG, Jasieniak JJ, Bakus RC, Welch GC, Moses D, Bazan GC, Heeger AJ. Photoinduced Charge Generation in a Molecular Bulk Heterojunction Material. J Am Chem Soc 2012; 134:19828-38. [DOI: 10.1021/ja308949m] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
| | | | | | - Gregory C. Welch
- Department of Chemistry, Dalhousie University, Halifax, NS, Canada
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Paraecattil AA, Beaupré S, Leclerc M, Moser JE, Banerji N. Intensity Dependent Femtosecond Dynamics in a PBDTTPD-Based Solar Cell Material. J Phys Chem Lett 2012; 3:2952-8. [PMID: 26292232 DOI: 10.1021/jz301110e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
PBDTTPD is a conjugated polymer with high power conversion efficiency if used in organic solar cells together with fullerene derivatives. We have investigated for the first time the excited state dynamics of pristine PBDTTPD thin film as well as the ultrafast evolution of charge carriers in PBDTTPD:PCBM bulk heterojunction blend using femtosecond transient absorption spectroscopy. In the latter, charges appear within the time resolution of the experiment (<100 fs), but clean spectral signatures allowed to directly follow slower ∼1 ps charge separation. Only the slower quenching component competes with exciton-exciton and exciton-charge annihilation, leading to a reduced yield of charge carriers at high laser fluence. Our excellent measuring sensitivity made it possible to reduce pump power to a point where annihilation is quasi suppressed. In this case >80% of charges survive after 1 ns; the rest recombines (most probably geminately) on the 200 ps time scale.
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Affiliation(s)
| | - Serge Beaupré
- ‡Department of Chemistry, Université Laval, G1K 7P4 Quebec City, Quebec, Canada
| | - Mario Leclerc
- ‡Department of Chemistry, Université Laval, G1K 7P4 Quebec City, Quebec, Canada
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27
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Bonon BMA, Atvars TDZ. Energy Transfer from Poly(Vinyl Carbazole) to a Fluorene-Vinylene Copolymer in Solution and in the Solid State†. Photochem Photobiol 2012; 88:801-9. [DOI: 10.1111/j.1751-1097.2012.01133.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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28
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Michinobu T, Seo C, Noguchi K, Mori T. Effects of click postfunctionalization on thermal stability and field effect transistor performances of aromatic polyamines. Polym Chem 2012. [DOI: 10.1039/c2py20079a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Herrmann D, Niesar S, Scharsich C, Köhler A, Stutzmann M, Riedle E. Role of structural order and excess energy on ultrafast free charge generation in hybrid polythiophene/Si photovoltaics probed in real time by near-infrared broadband transient absorption. J Am Chem Soc 2011; 133:18220-33. [PMID: 21942512 DOI: 10.1021/ja207887q] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Despite the central role of light absorption and the subsequent generation of free charge carriers in organic and hybrid organic-inorganic photovoltaics, the precise process of this initial photoconversion is still debated. We employ a novel broadband (UV-Vis-NIR) transient absorption spectroscopy setup to probe charge generation and recombination in the thin films of the recently suggested hybrid material combination poly(3-hexylthiophene)/silicon (P3HT/Si) with 40 fs time resolution. Our approach allows for monitoring the time evolution of the relevant transient species under various excitation intensities and excitation wavelengths. Both in regioregular (RR) and regiorandom (RRa) P3HT, we observe an instant (<40 fs) creation of singlet excitons, which subsequently dissociate to form polarons in 140 fs. The quantum yield of polaron formation through dissociation of delocalized excitons is significantly enhanced by adding Si as an electron acceptor, revealing ultrafast electron transfer from P3HT to Si. P3HT/Si films with aggregated RR-P3HT are found to provide free charge carriers in planar as well as in bulk heterojunctions, and losses are due to nongeminate recombination. In contrast for RRa-P3HT/Si, geminate recombination of bound carriers is observed as the dominant loss mechanism. Site-selective excitation by variation of pump wavelength uncovers an energy transfer from P3HT coils to aggregates with a 1/e transfer time of 3 ps and reveals a factor of 2 more efficient polaron formation using aggregated RR-P3HT compared to disordered RRa-P3HT. Therefore, we find that polymer structural order rather than excess energy is the key criterion for free charge generation in hybrid P3HT/Si solar cells.
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Affiliation(s)
- Daniel Herrmann
- Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität München, Oettingenstraße 67, 80538 München, Germany
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30
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Aguirre A, Botta C, Janssen RAJ, Meskers SCJ. Delayed Fluorescence in Perhydrotriphenylene–Oligothiophene Inclusion Compounds: Evidence for Molecular Oxygen-Related Excited States. J Phys Chem A 2011; 115:7966-71. [DOI: 10.1021/jp203762s] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Aranzazu Aguirre
- Molecular Materials and Nanosystems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | | | - René A. J. Janssen
- Molecular Materials and Nanosystems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Stefan C. J. Meskers
- Molecular Materials and Nanosystems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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31
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Howard IA, Mauer R, Meister M, Laquai F. Effect of morphology on ultrafast free carrier generation in polythiophene:fullerene organic solar cells. J Am Chem Soc 2011; 132:14866-76. [PMID: 20923187 DOI: 10.1021/ja105260d] [Citation(s) in RCA: 351] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Despite significant study, the precise mechanisms that dictate the efficiency of organic photovoltaic cells, such as charge separation and recombination, are still debated. Here, we directly observe efficient ultrafast free charge generation in the absence of field in annealed poly(3-hexylthiophene):methanofullerene (P3HT:PCBM). However, we find this process is much less efficient in unannealed and amorphous regiorandom blends, explaining the superior short-circuit current and fill-factor of annealed RR-P3HT:PCBM solar cells. We use transient optical spectroscopy in the visible and near-infrared spectral region covering, but not limited to, the previously unobserved and highly relevant time scale spanning 1 to 100 ns, to directly observe both geminate and nongeminate charge recombination. We find that exciton quenching leads directly (time scale less than 100 fs) to two populations: bound charges and free charges. The former do not lead to photocurrent in a photovoltaic cell; they recombine geminately within 2 ns and are a loss channel. However, the latter can be efficiently extracted in photovoltaic cells. Therefore, we find that the probability of ultrafast free charge formation after exciton quenching directly limits solar cell efficiency. This probability is low in disordered P3HT:PCBM blends but approaches unity in annealed blends.
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Affiliation(s)
- Ian A Howard
- Max Planck Research Group for Organic Optoelectronics, Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany.
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Schlenker CW, Thompson ME. Current Challenges in Organic Photovoltaic Solar Energy Conversion. UNIMOLECULAR AND SUPRAMOLECULAR ELECTRONICS I 2011; 312:175-212. [DOI: 10.1007/128_2011_219] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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33
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Howard IA, Laquai F. Optical Probes of Charge Generation and Recombination in Bulk Heterojunction Organic Solar Cells. MACROMOL CHEM PHYS 2010. [DOI: 10.1002/macp.201000353] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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