1
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Verma A, Jackson NE. Assessing molecular doping efficiency in organic semiconductors with reactive Monte Carlo. J Chem Phys 2024; 160:104106. [PMID: 38465678 DOI: 10.1063/5.0197816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Accepted: 02/22/2024] [Indexed: 03/12/2024] Open
Abstract
The addition of molecular dopants into organic semiconductors (OSCs) is a ubiquitous augmentation strategy to enhance the electrical conductivity of OSCs. Although the importance of optimizing OSC-dopant interactions is well-recognized, chemically generalizable structure-function relationships are difficult to extract due to the sensitivity and dependence of doping efficiency on chemistry, processing conditions, and morphology. Computational modeling for an integrated OSC-dopant design is an attractive approach to systematically isolate fundamental relationships, but requires the challenging simultaneous treatment of molecular reactivity and morphology evolution. We present the first computational study to couple molecular reactivity with morphology evolution in a molecularly doped OSC. Reactive Monte Carlo is employed to examine the evolution of OSC-dopant morphologies and doping efficiency with respect to dielectric, the thermodynamic driving for the doping reaction, and dopant aggregation. We observe that for well-mixed systems with experimentally relevant dielectric constants, doping efficiency is near unity with a very weak dependence on the ionization potential and electron affinity of OSC and dopant, respectively. At experimental dielectric constants, reaction-induced aggregation is observed, corresponding to the well-known insolubility of solution-doped materials. Simulations are qualitatively consistent with a number of experimental studies showing a decrease of doping efficiency with increasing dopant concentration. Finally, we observe that the aggregation of dopants lowers doping efficiency and thus presents a rational design strategy for maximizing doping efficiency in molecularly doped OSCs. This work represents an important first step toward the systematic integration of molecular reactivity and morphology evolution into the characterization of multi-scale structure-function relationships in molecularly doped OSCs.
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Affiliation(s)
- Archana Verma
- Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Nicholas E Jackson
- Department of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, USA
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2
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Hua Z, Wu B, Zhang Y, Wang C, Dong T, Song Y, Jiang Y, Wang C. Efficient Charge Separation and Transport in Fullerene-CuPcOC 8 Donor-Acceptor Nanorod Enhancing Photocatalytic Hydrogen Generation. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:256. [PMID: 38334527 PMCID: PMC10856716 DOI: 10.3390/nano14030256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 01/01/2024] [Accepted: 01/02/2024] [Indexed: 02/10/2024]
Abstract
Photocatalytic hydrogen generation via water decomposition is a promising avenue in the pursuit of large-scale, cost-effective renewable hydrogen energy generation. However, the design of an efficient photocatalyst plays a crucial role in achieving high yields in hydrogen generation. Herein, we have engineered a fullerene-2,3,9,10,16,17,23,24-octa(octyloxy)copper phthalocyanine (C60-CuPcOC8) photocatalyst, achieving both efficient hydrogen generation and high stability. The significant donor-acceptor (D-A) interactions facilitate the efficient electron transfer from CuPcOC8 to C60. The rate of photocatalytic hydrogen generation for C60-CuPcOC8 is 8.32 mmol·g-1·h-1, which is two orders of magnitude higher than the individual C60 and CuPcOC8. The remarkable increase in hydrogen generation activity can be attributed to the development of a robust internal electric field within the C60-CuPcOC8 assembly. It is 16.68 times higher than that of the pure CuPcOC8. The strong internal electric field facilitates the rapid separation within 0.6 ps, enabling photogenerated charge transfer efficiently. Notably, the hydrogen generation efficiency of C60-CuPcOC8 remains above 95%, even after 10 h, showing its exceptional photocatalytic stability. This study provides critical insight into advancing the field of photocatalysis.
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Affiliation(s)
- Zihui Hua
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; (Z.H.); (Y.Z.); (C.W.); (T.D.); (Y.J.)
- University of Chinese Academy of Sciences, Beijing 100049, China;
| | - Bo Wu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; (Z.H.); (Y.Z.); (C.W.); (T.D.); (Y.J.)
- University of Chinese Academy of Sciences, Beijing 100049, China;
| | - Yuhe Zhang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; (Z.H.); (Y.Z.); (C.W.); (T.D.); (Y.J.)
| | - Chong Wang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; (Z.H.); (Y.Z.); (C.W.); (T.D.); (Y.J.)
- University of Chinese Academy of Sciences, Beijing 100049, China;
| | - Tianyang Dong
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; (Z.H.); (Y.Z.); (C.W.); (T.D.); (Y.J.)
| | - Yupeng Song
- University of Chinese Academy of Sciences, Beijing 100049, China;
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials and CityU-CAS Joint Laboratory of Functional Materials and Devices, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Ying Jiang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; (Z.H.); (Y.Z.); (C.W.); (T.D.); (Y.J.)
- University of Chinese Academy of Sciences, Beijing 100049, China;
| | - Chunru Wang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; (Z.H.); (Y.Z.); (C.W.); (T.D.); (Y.J.)
- University of Chinese Academy of Sciences, Beijing 100049, China;
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3
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Lin C, O'Connor JP, Phelan BT, Young RM, Wasielewski MR. Ultrafast Charge Transfer Dynamics in a Slip-Stacked Donor-Acceptor-Acceptor System. J Phys Chem A 2024; 128:244-250. [PMID: 38153126 DOI: 10.1021/acs.jpca.3c07539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
Photoexcitation of molecular electron donor and/or acceptor chromophore aggregates can greatly affect their charge-transfer dynamics. Excitonic coupling not only alters the energy landscape in the excited state but may also open new photophysical pathways, such as symmetry-breaking charge separation (SB-CS). Here, we investigate the impact of excitonic coupling on a covalent donor-acceptor-acceptor system comprising a perylene donor (Per) and two perylenediimide (PDI) acceptor chromophores in which the three components are π-stacked in a geometry that is slipped along their long axes (Per-PDI2). Following selective photoexcitation of PDI, femtosecond transient absorption data for Per-PDI2 is compared to that for the single-donor, single-acceptor Per-PDI system, and the PDI2 dimer, which both have the same interchromophore geometry as Per-PDI2. The data show that electron transfer from Per to the lower exciton state of the PDI dimer is slower than that of the single PDI acceptor system. This is due to the lower free energy of the reaction for charge separation because of the electronic stabilization afforded by the excitonic coupling between the PDIs. While PDI2 was shown previously to undergo ultrafast SB-CS, the strong π-π electronic interaction of Per with the adjacent PDI in Per-PDI2 breaks the electronic symmetry of the PDI dimer, resulting in the oxidation of Per rather than SB-CS. These results show that the electronic coupling between molecules designed to accept charges produced by SB-CS in molecular dimers and the chromophores comprising the dimer must be balanced to favor SB-CS.
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Affiliation(s)
- Chenjian Lin
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - James P O'Connor
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Brian T Phelan
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Ryan M Young
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R Wasielewski
- Department of Chemistry and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
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4
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Maimaris M, Pettipher AJ, Azzouzi M, Walke DJ, Zheng X, Gorodetsky A, Dong Y, Tuladhar PS, Crespo H, Nelson J, Tisch JWG, Bakulin AA. Sub-10-fs observation of bound exciton formation in organic optoelectronic devices. Nat Commun 2022; 13:4949. [PMID: 35999214 PMCID: PMC9399228 DOI: 10.1038/s41467-022-32478-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 08/02/2022] [Indexed: 11/09/2022] Open
Abstract
Fundamental mechanisms underlying exciton formation in organic semiconductors are complex and elusive as it occurs on ultrashort sub-100-fs timescales. Some fundamental aspects of this process, such as the evolution of exciton binding energy, have not been resolved in time experimentally. Here, we apply a combination of sub-10-fs Pump-Push-Photocurrent, Pump-Push-Photoluminescence, and Pump-Probe spectroscopies to polyfluorene devices to track the ultrafast formation of excitons. While Pump-Probe is sensitive to the total concentration of excited states, Pump-Push-Photocurrent and Pump-Push-Photoluminescence are sensitive to bound states only, providing access to exciton binding dynamics. We find that excitons created by near-absorption-edge photons are intrinsically bound states, or become such within 10 fs after excitation. Meanwhile, excitons with a modest >0.3 eV excess energy can dissociate spontaneously within 50 fs before acquiring bound character. These conclusions are supported by excited-state molecular dynamics simulations and a global kinetic model which quantitatively reproduce experimental data. Ultrafast action spectroscopies of organic optoelectronic devices reveal that the formation of bound exciton state occurs as fast as 10 fs. Excitons having excess energy can dissociate spontaneously within 50-fs before acquiring bound character.
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Affiliation(s)
- Marios Maimaris
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
| | | | - Mohammed Azzouzi
- Department of Physics, Imperial College London, London, SW7 2AZ, UK
| | - Daniel J Walke
- Department of Physics, Imperial College London, London, SW7 2AZ, UK.,Helmholtz Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, Berlin, 14109, Germany
| | - Xijia Zheng
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
| | - Andrei Gorodetsky
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK.,School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT, UK
| | - Yifan Dong
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK.,National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Pabitra Shakya Tuladhar
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK
| | - Helder Crespo
- Department of Physics, Imperial College London, London, SW7 2AZ, UK.,IFIMUP and Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, R. do Campo Alegre 687, 4169-007, Porto, Portugal
| | - Jenny Nelson
- Department of Physics, Imperial College London, London, SW7 2AZ, UK
| | - John W G Tisch
- Department of Physics, Imperial College London, London, SW7 2AZ, UK
| | - Artem A Bakulin
- Department of Chemistry and Centre for Processable Electronics, Imperial College London, London, W12 0BZ, UK.
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5
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Peng WT, Brey D, Giannini S, Dell’Angelo D, Burghardt I, Blumberger J. Exciton Dissociation in a Model Organic Interface: Excitonic State-Based Surface Hopping versus Multiconfigurational Time-Dependent Hartree. J Phys Chem Lett 2022; 13:7105-7112. [PMID: 35900333 PMCID: PMC9376959 DOI: 10.1021/acs.jpclett.2c01928] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 07/19/2022] [Indexed: 05/20/2023]
Abstract
Quantum dynamical simulations are essential for a molecular-level understanding of light-induced processes in optoelectronic materials, but they tend to be computationally demanding. We introduce an efficient mixed quantum-classical nonadiabatic molecular dynamics method termed eXcitonic state-based Surface Hopping (X-SH), which propagates the electronic Schrödinger equation in the space of local excitonic and charge-transfer electronic states, coupled to the thermal motion of the nuclear degrees of freedom. The method is applied to exciton decay in a 1D model of a fullerene-oligothiophene junction, and the results are compared to the ones from a fully quantum dynamical treatment at the level of the Multilayer Multiconfigurational Time-Dependent Hartree (ML-MCTDH) approach. Both methods predict that charge-separated states are formed on the 10-100 fs time scale via multiple "hot-exciton dissociation" pathways. The results demonstrate that X-SH is a promising tool advancing the simulation of photoexcited processes from the molecular to the true nanomaterials scale.
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Affiliation(s)
- Wei-Tao Peng
- Department
of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
| | - Dominik Brey
- Institute
of Physical and Theoretical Chemistry, Goethe
University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Samuele Giannini
- Department
of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
| | - David Dell’Angelo
- Department
of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
| | - Irene Burghardt
- Institute
of Physical and Theoretical Chemistry, Goethe
University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | - Jochen Blumberger
- Department
of Physics and Astronomy and Thomas Young Centre, University College London, London WC1E 6BT, United Kingdom
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6
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Zhang G, Lin FR, Qi F, Heumüller T, Distler A, Egelhaaf HJ, Li N, Chow PCY, Brabec CJ, Jen AKY, Yip HL. Renewed Prospects for Organic Photovoltaics. Chem Rev 2022; 122:14180-14274. [PMID: 35929847 DOI: 10.1021/acs.chemrev.1c00955] [Citation(s) in RCA: 120] [Impact Index Per Article: 60.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Organic photovoltaics (OPVs) have progressed steadily through three stages of photoactive materials development: (i) use of poly(3-hexylthiophene) and fullerene-based acceptors (FAs) for optimizing bulk heterojunctions; (ii) development of new donors to better match with FAs; (iii) development of non-fullerene acceptors (NFAs). The development and application of NFAs with an A-D-A configuration (where A = acceptor and D = donor) has enabled devices to have efficient charge generation and small energy losses (Eloss < 0.6 eV), resulting in substantially higher power conversion efficiencies (PCEs) than FA-based devices. The discovery of Y6-type acceptors (Y6 = 2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]-thiadiazolo[3,4-e]-thieno[2″,3″:4',5']thieno-[2',3':4,5]pyrrolo-[3,2-g]thieno-[2',3':4,5]thieno-[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile) with an A-DA' D-A configuration has further propelled the PCEs to go beyond 15% due to smaller Eloss values (∼0.5 eV) and higher external quantum efficiencies. Subsequently, the PCEs of Y6-series single-junction devices have increased to >19% and may soon approach 20%. This review provides an update of recent progress of OPV in the following aspects: developments of novel NFAs and donors, understanding of the structure-property relationships and underlying mechanisms of state-of-the-art OPVs, and tasks underpinning the commercialization of OPVs, such as device stability, module development, potential applications, and high-throughput manufacturing. Finally, an outlook and prospects section summarizes the remaining challenges for the further development of OPV technology.
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Affiliation(s)
- Guichuan Zhang
- State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China.,School of Semiconductor Science and Technology, South China Normal University, Foshan 528225, China
| | - Francis R Lin
- Department of Materials Science and Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China.,Department of Chemistry, City University of Hong Kong, Kowloon 999077, Hong Kong, China
| | - Feng Qi
- Department of Materials Science and Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China.,Department of Chemistry, City University of Hong Kong, Kowloon 999077, Hong Kong, China
| | - Thomas Heumüller
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstrasse 7, 91058 Erlangen, Germany.,Helmholtz Institute Erlangen-Nürnberg (HI ERN), Immerwahrstrasse 2, 91058 Erlangen, Germany
| | - Andreas Distler
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstrasse 7, 91058 Erlangen, Germany
| | - Hans-Joachim Egelhaaf
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstrasse 7, 91058 Erlangen, Germany.,Helmholtz Institute Erlangen-Nürnberg (HI ERN), Immerwahrstrasse 2, 91058 Erlangen, Germany
| | - Ning Li
- State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
| | - Philip C Y Chow
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam 999077, Hong Kong, China
| | - Christoph J Brabec
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstrasse 7, 91058 Erlangen, Germany.,Helmholtz Institute Erlangen-Nürnberg (HI ERN), Immerwahrstrasse 2, 91058 Erlangen, Germany
| | - Alex K-Y Jen
- Department of Materials Science and Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China.,Department of Chemistry, City University of Hong Kong, Kowloon 999077, Hong Kong, China.,School of Energy and Environment, City University of Hong Kong, Kowloon 999077, Hong Kong, China.,Hong Kong Institute for Clean Energy, City University of Hong Kong, Kowloon 999077, Hong Kong, China
| | - Hin-Lap Yip
- State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China.,Department of Materials Science and Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China.,School of Energy and Environment, City University of Hong Kong, Kowloon 999077, Hong Kong, China.,Hong Kong Institute for Clean Energy, City University of Hong Kong, Kowloon 999077, Hong Kong, China
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7
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Yan Y, Zhang Y, Memon WA, Wang M, Zhang X, Wei Z. The role of entropy gains in the exciton separation in organic solar cells. Macromol Rapid Commun 2022; 43:e2100903. [PMID: 35338684 DOI: 10.1002/marc.202100903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 02/16/2022] [Indexed: 11/06/2022]
Abstract
In organic solar cell (OSC), the lower dielectric constant of organic semiconductor material induces a strong Coulomb attraction between electron-hole pairs, which leads to a low exciton separation efficiency, especially the charge transfer (CT) state. The CT state formed at the electron-donor (D) and electron-acceptor (A) interface is regarded as an unfavorable property of organic photovoltaic devices. Since the OSC works in a nonzero temperature condition, the entropy effect would be one of the main reasons to overcome the Coulomb energy barrier and must be taken into account. In this review, we review the present understanding of the entropy-driven charge separation and describe how factors such as the dimensionality of the organic semiconductor, energy disorder effect, the morphology of the active layer, and the nonequilibrium effect affect the entropy contribution in compensating the Coulomb dissociation barrier for CT exciton separation and charge generation process. We focus on the investigation of the entropy effect on exciton dissociation mechanism from both theoretical and experimental aspects, which provides pathways for understanding the underlying mechanisms of exciton separation and further enhancing the efficiency of OSCs. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Yangjun Yan
- School of Science, Beijing Jiaotong University, Beijing, 100044, China.,CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Yajie Zhang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Waqar Ali Memon
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Mengni Wang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Xinghua Zhang
- School of Science, Beijing Jiaotong University, Beijing, 100044, China
| | - Zhixiang Wei
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
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8
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Carr JM, Allen TG, Larson BW, Davydenko IG, Dasari RR, Barlow S, Marder SR, Reid OG, Rumbles G. Short and long-range electron transfer compete to determine free-charge yield in organic semiconductors. MATERIALS HORIZONS 2022; 9:312-324. [PMID: 34787147 DOI: 10.1039/d1mh01331a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Understanding how Frenkel excitons efficiently split to form free-charges in low-dielectric constant organic semiconductors has proven challenging, with many different models proposed in recent years to explain this phenomenon. Here, we present evidence that a simple model invoking a modest amount of charge delocalization, a sum over the available microstates, and the Marcus rate constant for electron transfer can explain many seemingly contradictory phenomena reported in the literature. We use an electron-accepting fullerene host matrix dilutely sensitized with a series of electron donor molecules to test this hypothesis. The donor series enables us to tune the driving force for photoinduced electron transfer over a range of 0.7 eV, mapping out normal, optimal, and inverted regimes for free-charge generation efficiency, as measured by time-resolved microwave conductivity. However, the photoluminescence of the donor is rapidly quenched as the driving force increases, with no evidence for inverted behavior, nor the linear relationship between photoluminescence quenching and charge-generation efficiency one would expect in the absence of additional competing loss pathways. This behavior is self-consistently explained by competitive formation of bound charge-transfer states and long-range or delocalized free-charge states, where both rate constants are described by the Marcus rate equation. Moreover, the model predicts a suppression of the inverted regime for high-concentration blends and efficient ultrafast free-charge generation, providing a mechanistic explanation for why Marcus-inverted-behavior is rarely observed in device studies.
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Affiliation(s)
- Joshua M Carr
- University of Colorado Boulder, Materials Science & Engineering Program, Boulder, CO, 80303, USA
| | - Taylor G Allen
- National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, CO, 80401, USA.
| | - Bryon W Larson
- National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, CO, 80401, USA.
| | - Iryna G Davydenko
- Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA, 30332, USA
| | - Raghunath R Dasari
- Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA, 30332, USA
| | - Stephen Barlow
- National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, CO, 80401, USA.
- Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA, 30332, USA
- University of Colorado Boulder, Renewable and Sustainable Energy Institute, Boulder, CO, 80303, USA
| | - Seth R Marder
- National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, CO, 80401, USA.
- Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA, 30332, USA
- University of Colorado Boulder, Renewable and Sustainable Energy Institute, Boulder, CO, 80303, USA
- University of Colorado Boulder, Department of Chemistry, Boulder, CO, 80303, USA
- University of Colorado Boulder, Department of Chemical and Biological Engineering, Boulder, CO, 80303, USA
| | - Obadiah G Reid
- National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, CO, 80401, USA.
- University of Colorado Boulder, Renewable and Sustainable Energy Institute, Boulder, CO, 80303, USA
| | - Garry Rumbles
- National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, CO, 80401, USA.
- University of Colorado Boulder, Renewable and Sustainable Energy Institute, Boulder, CO, 80303, USA
- University of Colorado Boulder, Department of Chemistry, Boulder, CO, 80303, USA
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9
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Krishnan S, Senthilkumar K. Modified fullerenes as acceptors in bulk heterojunction organic solar cells - a theoretical study. Phys Chem Chem Phys 2021; 23:27468-27476. [PMID: 34870653 DOI: 10.1039/d1cp04402h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the present study, electronic structure calculations were used to provide strategies for designing poly(3-hexylthiophene) (P3HT)-fullerene-derivative-based donor-acceptor materials for use in high-efficiency bulk heterojunction organic solar cells (BHJ OSCs). The work systematically analyses the impact of electron-donating and -withdrawing substituents on the opto-electronic properties of the fullerene structures. Parameters relating to the absorption spectra, orbital distributions, and energy ordering of the frontier molecular orbitals (FMO), the interactions between P3HT and the fullerene derivatives, and charge transfer across the interface were investigated. We found that substitution with the electron-withdrawing group NO2 enhances the electronic coupling between the fullerene and P3HT; however, it reduces the open-circuit voltage (VOC) of the OSC through lowering the LUMO energy level. Furthermore, the results show that substitution with an electron-withdrawing group (NO2) and electron-donating group (OCH3) can improve the power conversion efficiency (PCE) of the OSC, since this slightly improves the photon absorption abilities and charge transfer coupling at the interface without overly compromising VOC relative to PC61BM. Our study shows that alkyl chain modification in the PC61BM acceptor is a promising strategy for improving the performances of OSCs.
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Affiliation(s)
- S Krishnan
- Department of Physics, Bharathiar University, Coimbatore - 641 046, India.
| | - K Senthilkumar
- Department of Physics, Bharathiar University, Coimbatore - 641 046, India.
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10
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Łapkowski M. Perinone-New Life of an Old Molecule. MATERIALS 2021; 14:ma14226880. [PMID: 34832283 PMCID: PMC8620774 DOI: 10.3390/ma14226880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 11/09/2021] [Accepted: 11/10/2021] [Indexed: 11/16/2022]
Abstract
A review of publications on the synthesis and properties of a family of compounds called perinones was carried out. The basic molecule has been known for several decades mainly as a photostable pigment, and in recent years it has become increasingly used in organic electronics. This paper describes the methods of synthesis of low molecular weight compounds and polymers based on that molecule; the basic spectroscopic, photochemical, electrochemical and electronic properties important for the construction of organic electronics and optoelectronics devices are also discussed.
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Affiliation(s)
- Mieczysław Łapkowski
- Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice, Poland;
- Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 34 M. Curie-Sklodowska Street, 41-819 Zabrze, Poland
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11
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Huang Y, Zhang L, Hao Y. Why ultrafast charge separation occurs in bulk-heterojunction organic solar cells: a multichain tight binding model study. Phys Chem Chem Phys 2021; 23:22685-22691. [PMID: 34604887 DOI: 10.1039/d1cp03686f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Bulk-heterojunction (BHJ) organic solar cells (OSCs) exhibit ultrafast charge separation (UCS) which enables lower geminate charge recombination and high internal quantum efficiency. Unravelling why UCS occurs in BHJ-OSCs is important for the exploration of devices in future, however it is still far from clear. In this work, we build a multichain tight-binding model to study the conditions for realizing UCS. We propose that two conditions are important: (i) the BHJ-OSC has a morphology with donor and acceptor molecules being individually aggregated; (ii) the ratio of the donor/acceptor interfacial coupling to the internal donor/donor and acceptor/acceptor coupling should be smaller than a threshold. In addition, we suggest that increasing the donor/acceptor energetic offset will boost the UCS efficiency. As a fundamental theoretical analysis on the underlying mechanism of UCS, our work provides design rules for optimizing high-performance BHJ OSCs.
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Affiliation(s)
- Yujuan Huang
- College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan, 030024, China.
| | - Longlong Zhang
- College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan, 030024, China.
| | - Yuying Hao
- College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan, 030024, China.
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12
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Wanigasekara S, Kattel B, Rudayni F, Chan WL. Extracting Electrons from Delocalized Excitons by Flattening the Energetic Pathway for Charge Separation. J Phys Chem Lett 2021; 12:9047-9054. [PMID: 34516118 DOI: 10.1021/acs.jpclett.1c02228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
At organic donor-acceptor (D-A) interfaces, electron and hole are bound together to form charge transfer (CT) excitons. The electron and hole wave functions in these CT excitons can spatially delocalize. The electron delocalization opens up possibilities of extracting free charges from bound excitons by manipulating the potential energy landscape on the nanoscale. Using a prototype trilayer structure that has a cascade band structure, we show that the yield of charge separation can be doubled as compared to the bilayer counterpart when the thickness of the intermediate layer is around 3 nm. This thickness coincides with the electron delocalization size of CT excitons typically found in these organic films. Tight-binding calculation for the CT states in the trilayer structure further demonstrates that electron delocalization, together with the energy level cascade, can effectively flatten the energetic pathway for charge separation. Hence, it is possible to add nanometer-thick layers between the donor and the acceptor to significantly enhance the charge separation yield.
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Affiliation(s)
- Shanika Wanigasekara
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Bhupal Kattel
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Fatimah Rudayni
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
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13
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Díaz FR, Duan HG, Miller RJD, Thorwart M. Ultrafast Charge Transfer and Relaxation at a Donor-Acceptor Interface. J Phys Chem B 2021; 125:8869-8875. [PMID: 34319718 DOI: 10.1021/acs.jpcb.1c03595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The efficiency of charge separation in organic photovoltaic materials is crucially determined by the underlying dynamics of the charge transfer (CT) excitons and their dissociation into free electrons and holes. To unravel the main principles of the underlying mechanism on a molecular level, we construct a toy model of electronically coupled donors interacting with a manifold of CT exciton states. In particular, we set up a ladder of CT site energies to model the exciton dissociation. To mimic the complexity of the exciton dynamics at the donor-acceptor interface, the electronic CT manifold is designed to include two vibrational modes that are vibronically coupled to the excitons. We examine the impact of the electronic and vibrational coherences and the structure of the vibronic manifold on the transfer efficiency and charge recombination. Optimal configurations of the vibronic CT manifold are revealed. In particular, the rate of charge recombination can be minimized when the transient dynamics are carefully explored. Such a toy model can be used as a guide for the design of organic materials for efficient photovoltaic devices.
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Affiliation(s)
- Fernando Rodríguez Díaz
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2A, 12489 Berlin, Germany.,Nanosystems Institute, Universidad Nacional de San Martín, Av.ËIJ 25 de Mayo 1021, San Martín, Buenos Aires, Argentina
| | - Hong-Guang Duan
- I. Institut für Theoretische Physik, Universität Hamburg, Notkestraße 9, 22607 Hamburg, Germany.,The Hamburg Center for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - R J Dwayne Miller
- Departments of Chemistry and Physics, University of Toronto, 80 St. George Street, Toronto, ON, Canada M5S 3H6
| | - Michael Thorwart
- I. Institut für Theoretische Physik, Universität Hamburg, Notkestraße 9, 22607 Hamburg, Germany.,The Hamburg Center for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
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14
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Kaiser W, Janković V, Vukmirović N, Gagliardi A. Nonequilibrium Thermodynamics of Charge Separation in Organic Solar Cells. J Phys Chem Lett 2021; 12:6389-6397. [PMID: 34232672 DOI: 10.1021/acs.jpclett.1c01817] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
This work presents a novel theoretical description of the nonequilibrium thermodynamics of charge separation in organic solar cells (OSCs). Using stochastic thermodynamics, we take realistic state populations derived from the phonon-assisted dynamics of electron-hole pairs within photoexcited organic bilayers to connect the kinetics with the free energy profile of charge separation. Hereby, we quantify for the first time the difference between nonequilibrium and equilibrium free energy profile. We analyze the impact of energetic disorder and delocalization on free energy, average energy, and entropy. For a high disorder, the free energy profile is well-described as equilibrated. We observe significant deviations from equilibrium for delocalized electron-hole pairs at a small disorder, implying that charge separation in efficient OSCs proceeds via a cold but nonequilibrated pathway. Both a large Gibbs entropy and large initial electron-hole distance provide an efficient charge separation, while a decrease in the free energy barrier does not necessarily enhance charge separation.
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Affiliation(s)
- Waldemar Kaiser
- Department of Electrical and Computer Engineering, Technical University of Munich, Karlstraße 45, 80333 Munich, Germany
| | - Veljko Janković
- Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - Nenad Vukmirović
- Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
| | - Alessio Gagliardi
- Department of Electrical and Computer Engineering, Technical University of Munich, Karlstraße 45, 80333 Munich, Germany
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15
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Amsterdam SH, Marks TJ, Hersam MC. Leveraging Molecular Properties to Tailor Mixed-Dimensional Heterostructures beyond Energy Level Alignment. J Phys Chem Lett 2021; 12:4543-4557. [PMID: 33970639 DOI: 10.1021/acs.jpclett.1c00799] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The surface sensitivity and lack of dielectric screening in two-dimensional (2D) materials provide numerous intriguing opportunities to tailor their properties using adsorbed π-electron organic molecules. These organic-2D mixed-dimensional heterojunctions are often considered solely in terms of their energy level alignment, i.e., the relative energies of the frontier molecular orbitals versus the 2D material conduction and valence band edges. While this simple model is frequently adequate to describe doping and photoinduced charge transfer, the tools of molecular chemistry enable additional manipulation of properties in organic-2D heterojunctions that are not accessible in other solid-state systems. Fully exploiting these possibilities requires consideration of the details of the organic adlayer beyond its energy level alignment, including hybridization and electrostatics, molecular orientation and thin-film morphology, nonfrontier orbitals and defects, excitonic states, spin, and chirality. This Perspective explores how these relatively overlooked molecular properties offer unique opportunities for tuning optical and electronic characteristics, thereby guiding the rational design of organic-2D mixed-dimensional heterojunctions with emergent properties.
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Affiliation(s)
- Samuel H Amsterdam
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Tobin J Marks
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
- Department of Materials Science and Engineering and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
- Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Mark C Hersam
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
- Department of Materials Science and Engineering and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
- Applied Physics Program, Northwestern University, Evanston, Illinois 60208, United States
- Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois 60208, United States
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16
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Tsokkou D, Cheng CY, Krainova N, Mukhopadhyay S, Giebink NC, Banerji N. Ultrafast Charge Transfer Dynamics at the Origin of Photoconductivity in Doped Organic Solids. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:7086-7096. [PMID: 33859770 PMCID: PMC8040020 DOI: 10.1021/acs.jpcc.1c01990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 03/10/2021] [Indexed: 06/12/2023]
Abstract
In spite of their growing importance for optoelectronic devices, the fundamental properties and photophysics of molecularly doped organic solids remain poorly understood. Such doping typically leads to a small fraction of free conductive charges, with most electronic carriers remaining Coulombically bound to the ionized dopant. Recently, we have reported photocurrent for devices containing vacuum-deposited TAPC (1,1-bis(4-bis(4-methylphenyl)aminophenyl)cyclohexane) doped with MoO3, showing that photoexcitation of charged TAPC molecules increases the concentration of free holes that contribute to conduction. Here, we elucidate the excited-state dynamics of such doped TAPC films to unravel the key mechanisms responsible for this effect. We demonstrate that excitation of different electronic transitions in charged and neutral TAPC molecules allows bound holes to overcome the Coulombic attraction to their MoO3 counterions, resulting in an enhanced yield of long-lived free carriers. This is caused by ultrafast back-and-forth shuffling of charges and excitation energy between adjacent cations and neutral molecules, competing with relatively slow nonradiative decay from higher excited states of TAPC•+. The light-induced generation of conductive carriers requires the coexistence of cationic and neutral TAPC, a favorable energy level alignment, and intermolecular interactions in the solid state.
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Affiliation(s)
- Demetra Tsokkou
- Department
of Chemistry and Biochemistry, University
of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Chiao-Yu Cheng
- Department
of Electrical Engineering, The Pennsylvania
State University, University
Park, Pennsylvania 16802, United States
| | - Nina Krainova
- Department
of Electrical Engineering, The Pennsylvania
State University, University
Park, Pennsylvania 16802, United States
| | - Sukrit Mukhopadhyay
- The
Dow Chemical Company, 1776 Building, Midland, Michigan 48674, United
States
| | - Noel C. Giebink
- Department
of Electrical Engineering, The Pennsylvania
State University, University
Park, Pennsylvania 16802, United States
| | - Natalie Banerji
- Department
of Chemistry and Biochemistry, University
of Bern, Freiestrasse 3, 3012 Bern, Switzerland
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17
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Rijal K, Rudayni F, Kafle TR, Chan WL. Collective Effects of Band Offset and Wave Function Dimensionality on Impeding Electron Transfer from 2D to Organic Crystals. J Phys Chem Lett 2020; 11:7495-7501. [PMID: 32812767 DOI: 10.1021/acs.jpclett.0c01796] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Excited-state electron transfer (ET) across molecules/transition metal dichalcogenide crystal (TMDC) interfaces is a critical process for the functioning of various organic/TMDC hybrid optoelectronic devices. Therefore, it is important to understand the fundamental factors that can facilitate or limit the ET rate. Here it is found that an undesirable combination of the interfacial band offset and the spatial dimensionality of the delocalized electron wave function can significantly slow down the ET process. Specifically, it is found that whereas the ET rate from TMDCs (MoS2 and WSe2) to fullerenes is relative insensitive to the band offset, the ET rate from TMDCs to perylene molecules can be reduced by an order of magnitude when the band offset is large. For the perylene crystal, the sensitivity of the ET rate on the band offset is explained by the 1D nature of the electronic wave function, which limits the availability of states with the appropriate energy to accept the electron.
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Affiliation(s)
- Kushal Rijal
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Fatimah Rudayni
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Tika R Kafle
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
| | - Wai-Lun Chan
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, United States
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18
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Schlesinger I, Powers-Riggs NE, Logsdon JL, Qi Y, Miller SA, Tempelaar R, Young RM, Wasielewski MR. Charge-transfer biexciton annihilation in a donor-acceptor co-crystal yields high-energy long-lived charge carriers. Chem Sci 2020; 11:9532-9541. [PMID: 34094218 PMCID: PMC8162030 DOI: 10.1039/d0sc03301d] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Organic donor-acceptor (D-A) co-crystals have attracted much interest due to their important optical and electronic properties. Co-crystals having ⋯DADA⋯ π-stacked morphologies are especially interesting because photoexcitation produces a charge-transfer (CT) exciton, D˙+-A˙-, between adjacent D-A molecules. Although several studies have reported on the steady-state optical properties of this type of CT exciton, very few have measured the dynamics of its formation and decay in a single D-A co-crystal. We have co-crystallized a peri-xanthenoxanthene (PXX) donor with a N,N-bis(3-pentyl)-2,5,8,11-tetraphenylperylene-3,4:9,10-bis(dicarboximide) (Ph4PDI) acceptor to give an orthorhombic PXX-Ph4PDI ⋯DADA⋯ π-stacked co-crystal with a CT transition dipole moment that is perpendicular to the transition moments for S n ← S0 excitation of PXX and Ph4PDI. Using polarized, broadband, femtosecond pump-probe microscopy, we have determined that selective photoexcitation of Ph4PDI in the single co-crystal results in CT exciton formation within the 300 fs instrument response time. At early times (0.3 ≤ t ≤ 500 ps), the CT excitons decay with a t -1/2 dependence, which is attributed to CT biexciton annihilation within the one-dimensional ⋯DADA⋯ π-stacks producing high-energy, long-lived (>8 ns) electron-hole pairs in the crystal. These energetic charge carriers may prove useful in applications ranging from photovoltaics and opto-electronics to photocatalysis.
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Affiliation(s)
- Itai Schlesinger
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Natalia E Powers-Riggs
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Jenna L Logsdon
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Yue Qi
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Stephen A Miller
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Roel Tempelaar
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Ryan M Young
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
| | - Michael R Wasielewski
- Department of Chemistry and Institute for Sustainability and Energy at Northwestern, Northwestern University 2145 Sheridan Road Evanston Illinois 60208-3113 USA
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19
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Leonard AA, Mosquera MA, Jones LO, Cai Z, Fauvell TJ, Kirschner MS, Gosztola DJ, Schatz GC, Schaller RD, Yu L, Chen LX. Photophysical implications of ring fusion, linker length, and twisting angle in a series of perylenediimide-thienoacene dimers. Chem Sci 2020; 11:7133-7143. [PMID: 33209244 PMCID: PMC7654190 DOI: 10.1039/d0sc02862b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 06/17/2020] [Indexed: 01/05/2023] Open
Abstract
Perylenediimide (PDI) derivatives have been widely studied as electron acceptor alternatives to fullerenes in organic photovoltaics (OPVs) because of their tunable absorption in the visible range, inexpensive synthesis, and photochemical stability. A common motif for improving device efficiency involves joining multiple PDIs together through electron-rich linkers to form a twisted acceptor-donor-acceptor molecule. Molecular features such as ring fusion are further employed to modify the structure locally and in films. These synthetic efforts have greatly enhanced OPV device efficiencies, however it remains unclear how the increasingly elaborate structural modifications affect the photophysical processes integral to efficient photon-to-charge conversion. Here we carry out a systematic study of a series of PDI dimers with thienoacene linkers in which the twist angle, linker length, and degree of ring fusion are varied to investigate the effects of these structural features on the molecular excited states and exciton recombination dynamics. Spectroscopic characterization of the dimers suggest that ring fusion causes greater coupling between the donor and acceptor components and greatly enhances the lifetime of a thienoacene to PDI charge transfer state. The lifetime of this CT state also correlates well with the linker-PDI dihedral angle, with smaller dihedral angle resulting in longer lifetime. DFT and two-photon absorption TDDFT calculations were developed in-house to model the ground state and excited transitions, providing theoretical insight into the reasons for the observed photophysical properties and identifying the charge transfer state in the excited state absorption spectra. These results highlight how the longevity of the excited state species, important for the efficient conversion of excitons to free carriers in OPV devices, can be chemically tuned by controlling ring fusion and by using steric effects to control the relative orientations of the molecular fragments. The results provide a successful rationalization of the behavior of solar cells involving these acceptor molecules.
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Affiliation(s)
- Ariel A Leonard
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA .
| | - Martín A Mosquera
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA .
| | - Leighton O Jones
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA .
| | - Zhengxu Cai
- Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications , School of Materials Science & Engineering , Beijing Institute of Technology , Beijing 100081 , China
| | - Thomas J Fauvell
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA .
| | - Matthew S Kirschner
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA .
| | - David J Gosztola
- Center for Nanoscale Materials , Argonne National Laboratory , 9700 South Cass Avenue Lemont , Illinois 60439 , USA
| | - George C Schatz
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA .
| | - Richard D Schaller
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA .
- Center for Nanoscale Materials , Argonne National Laboratory , 9700 South Cass Avenue Lemont , Illinois 60439 , USA
| | - Luping Yu
- Department of Chemistry and James Frank Institute , The University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , USA
| | - Lin X Chen
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA .
- Chemical Sciences and Engineering Division , Argonne National Laboratory , 9700 South Cass Avenue, Lemont , Illinois 60439 , USA .
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20
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Wang R, Zhang C, Li Q, Zhang Z, Wang X, Xiao M. Charge Separation from an Intra-Moiety Intermediate State in the High-Performance PM6:Y6 Organic Photovoltaic Blend. J Am Chem Soc 2020; 142:12751-12759. [DOI: 10.1021/jacs.0c04890] [Citation(s) in RCA: 122] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Rui Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Qian Li
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Zhiguo Zhang
- College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Xiaoyong Wang
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Min Xiao
- National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center for Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701, United States
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21
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Diego Fernandes J, Maximino MD, Braunger ML, Pereira MS, de Almeida Olivati C, Constantino CJL, Alessio P. Supramolecular architecture and electrical conductivity in organic semiconducting thin films. Phys Chem Chem Phys 2020; 22:13554-13562. [PMID: 32510547 DOI: 10.1039/d0cp01293a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Organic thin films are an essential component of the structure of optical and electronic devices. However, the optical and electrical properties of these films depend on their supramolecular architecture, which may vary according to the techniques used to manufacture them. Here, the correlation between conductivity and supramolecular architecture was investigated. The supramolecular architecture was analyzed in terms of the molecular organization and J- or H-aggregation established during the fabrication of perylene tetracarboxylic diimide (PTCD) nanometric films. Three deposition techniques, Langmuir-Schaefer (LS), Langmuir-Blodgett (LB), and Physical Vapor Deposition (PVD), were evaluated. The UV-vis absorption spectra indicated that LS, LB, and PVD films grow homogeneously. Also, the presence of J and H aggregates was observed for all films, the H aggregates prevailing for the LB film. The FTIR measurements suggested that the molecular organization is similar for LS and LB films, with a tendency to form head-on organization onto a solid substrate. For the PVD film, the perylene macrocycles are inclined approximately 45° relative to the substrate. AFM measurements indicated a homogenous surface for all films. In terms of electrical conductivity, the highest conductivity was found for LS, followed by LB and PVD. The conductivity values were interpreted in terms of molecular organization and J- or H-aggregate formation.
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Affiliation(s)
- José Diego Fernandes
- School of Technology and Applied Sciences, São Paulo State University (UNESP), Presidente Prudente, 19060-900, SP, Brazil.
| | - Mateus D Maximino
- School of Technology and Applied Sciences, São Paulo State University (UNESP), Presidente Prudente, 19060-900, SP, Brazil.
| | - Maria Luisa Braunger
- Department of Applied Physics, "Gleb Wataghin" Institute of Physics, University of Campinas-UNICAMP, Campinas, SP 13083-859, Brazil
| | - Matheus S Pereira
- School of Technology and Applied Sciences, São Paulo State University (UNESP), Presidente Prudente, 19060-900, SP, Brazil.
| | - Clarissa de Almeida Olivati
- School of Technology and Applied Sciences, São Paulo State University (UNESP), Presidente Prudente, 19060-900, SP, Brazil.
| | - Carlos J L Constantino
- School of Technology and Applied Sciences, São Paulo State University (UNESP), Presidente Prudente, 19060-900, SP, Brazil.
| | - Priscila Alessio
- School of Technology and Applied Sciences, São Paulo State University (UNESP), Presidente Prudente, 19060-900, SP, Brazil.
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22
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Tu Z, Han G, Yi Y. Barrier-Free Charge Separation Enabled by Electronic Polarization in High-Efficiency Non-fullerene Organic Solar Cells. J Phys Chem Lett 2020; 11:2585-2591. [PMID: 32163716 DOI: 10.1021/acs.jpclett.0c00405] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The separation of charge-transfer states into free charges at the donor/acceptor (D/A) interfaces plays a central role in organic solar cells (OSCs). Because of strong Coulomb attraction, the separation mechanisms are elusive, particularly for the high-efficiency non-fullerene (NF) OSCs with low exciton-dissociation driving forces. Here, we demonstrate that the Coulomb barriers can be substantially overcome by electronic polarization for OSCs based on a series of A-D-A acceptors (ITIC, IT-4F, and Y6). In contrast to fullerene-based D/A heterojunctions, the polarization energies for both donor holes and acceptor electrons are remarkably increased from the interfaces to pure regions in the NF heterojunctions because of strong stabilization on electrons but destabilization on holes by electrostatic interactions in the A-D-A acceptors. In particular, upon incorporation of fluorine substituents and electron-poor cores into ITIC, the increased polarization energies can completely compensate for the Coulomb attraction in the IT-4F- and Y6-based heterojunctions, leading to barrierless charge separation.
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Affiliation(s)
- Zeyi Tu
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy Sciences, Beijing 100049, China
| | - Guangchao Han
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Yuanping Yi
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy Sciences, Beijing 100049, China
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23
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Alzola JM, Powers-Riggs NE, La Porte NT, Young RM, Marks TJ, Wasielewski MR. Photoinduced electron transfer from zinc meso-tetraphenylporphyrin to a one-dimensional perylenediimide aggregate: Probing anion delocalization effects. J PORPHYR PHTHALOCYA 2020. [DOI: 10.1142/s1088424619500858] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Organic photovoltaics incorporating non-fullerene acceptors based on perylenediimide (PDI) now rival fullerene acceptor-based devices in performance, although the mechanisms of charge generation in PDI-based devices are not yet fully understood. Fullerene-based systems are proposed to undergo electron transfer directly from the photoexcited donor into a band of delocalized acceptor states, thus increasing charge generation efficiency. Similarly, anion delocalization has been shown to enhance the rate of electron transfer from a photoexcited donor to two electronically coupled PDI acceptors. Here we investigate how additional electron acceptors may further increase the rate of electron transfer from the donor zinc meso-tetraphenylporphyrin (ZnTPP) to an aggregate of PDI acceptors (PDI[Formula: see text]. Femtosecond transient visible and mid-infrared absorption spectroscopies show that the rate of electron transfer from 1*ZnTPP to the PDI assembly ZnTPP2-PDI3 is statistically identical to that of the previously examined ZnTPP-PDI2. A Marcus theory analysis indicates that the parameters governing electron transfer are nearly identical for the two molecules, suggesting that the maximum electron transfer rate enhancement has been achieved in a cofacial PDI dimer because the ZnTPP directly couples to the first two PDI acceptors whereas the coupling to the third PDI is too weak.
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Affiliation(s)
- Joaquin M. Alzola
- Department of Chemistry, Center for Light Energy Activated Redox Processes (LEAP), and Institute for Sustainability and Energy at Northwestern (ISEN), Northwestern University, 2145 Sheridan Road, Evanston IL 60208-3113, USA
| | - Natalia E. Powers-Riggs
- Department of Chemistry, Center for Light Energy Activated Redox Processes (LEAP), and Institute for Sustainability and Energy at Northwestern (ISEN), Northwestern University, 2145 Sheridan Road, Evanston IL 60208-3113, USA
| | - Nathan T. La Porte
- Department of Chemistry, Center for Light Energy Activated Redox Processes (LEAP), and Institute for Sustainability and Energy at Northwestern (ISEN), Northwestern University, 2145 Sheridan Road, Evanston IL 60208-3113, USA
| | - Ryan M. Young
- Department of Chemistry, Center for Light Energy Activated Redox Processes (LEAP), and Institute for Sustainability and Energy at Northwestern (ISEN), Northwestern University, 2145 Sheridan Road, Evanston IL 60208-3113, USA
| | - Tobin J. Marks
- Department of Chemistry, Center for Light Energy Activated Redox Processes (LEAP), and Institute for Sustainability and Energy at Northwestern (ISEN), Northwestern University, 2145 Sheridan Road, Evanston IL 60208-3113, USA
| | - Michael R. Wasielewski
- Department of Chemistry, Center for Light Energy Activated Redox Processes (LEAP), and Institute for Sustainability and Energy at Northwestern (ISEN), Northwestern University, 2145 Sheridan Road, Evanston IL 60208-3113, USA
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24
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Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes. Nat Commun 2020; 11:617. [PMID: 32001688 PMCID: PMC6992633 DOI: 10.1038/s41467-020-14476-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 01/09/2020] [Indexed: 11/24/2022] Open
Abstract
Charge separation dynamics after the absorption of a photon is a fundamental process relevant both for photosynthetic reaction centers and artificial solar conversion devices. It has been proposed that quantum coherence plays a role in the formation of charge carriers in organic photovoltaics, but experimental proofs have been lacking. Here we report experimental evidence of coherence in the charge separation process in organic donor/acceptor heterojunctions, in the form of low frequency oscillatory signature in the kinetics of the transient absorption and nonlinear two-dimensional photocurrent spectroscopy. The coherence plays a decisive role in the initial ~200 femtoseconds as we observe distinct experimental signatures of coherent photocurrent generation. This coherent process breaks the energy barrier limitation for charge formation, thus competing with excitation energy transfer. The physics may inspire the design of new photovoltaic materials with high device performance, which explore the quantum effects in the next-generation optoelectronic applications. Although coherent vibrational motion in donor-acceptor blends may contribute to photogeneration generation in organic solar cells (OSCs), proof of a direct correlation is still lacking. Here, the authors report the role of vibrational coherence on photocurrent generation in ternary OSC blends.
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25
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Rana D, Jovanov V, Wagner V, Materny A, Donfack P. Insights into ultrafast charge-pair dynamics in P3HT:PCBM devices under the influence of static electric fields. RSC Adv 2020; 10:42754-42764. [PMID: 35514888 PMCID: PMC9058153 DOI: 10.1039/d0ra07935a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 11/16/2020] [Indexed: 12/16/2022] Open
Abstract
Polymer-fullerene blends based on poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric-acid methyl ester (PCBM) have been extensively studied as promising bulk heterojunction materials for organic semiconductor devices with improved performance. In these donor–acceptor systems where the bulk morphology plays a crucial role, the generation and subsequent decay mechanisms of photoexcitation species are still not completely understood. In this work, we use femtosecond transient absorption spectroscopy to investigate P3HT:PCBM diodes under the influence of applied static electric fields in comparison to P3HT:PCBM thin films. At the same time, we try to present a detailed overview about work already done on these donor–acceptor systems. The excited state dynamics obtained at 638 nm from P3HT:PCBM thin films are found to be similar to those observed earlier in neat P3HT films, while those obtained in the P3HT:PCBM devices are affected by field-induced exciton dissociation, resulting not only in comparatively slower decay dynamics, but also in bimolecular deactivation processes. External electric fields are expected to enhance charge generation in the investigated P3HT:PCBM devices by dissociating excitons and loosely bound intermediate species like polaron pairs (PPs) and charge transfer (CT) excitons, which can already dissociate only due to the intrinsic fields at the donor–acceptor interfaces. Our results clearly establish the formation of PP-like transient species different from CT excitons in the P3HT:PCBM devices as a result of a field-induced diffusion-controlled exciton dissociation process. We find that the loosely bound transient species formed in this way also are reduced in part via a bimolecular annihilation process resulting in charge loss in typical donor–acceptor P3HT:PCBM bulk heterojunction semiconductor devices, which is a rather interesting finding important for a better understanding of the performance of these devices. Electric field effects in P3HT:PCBM solar cell result in polaron-pair-like secondary photoexcitation species showing slower and bimolecular decay characteristics.![]()
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Affiliation(s)
- Debkumar Rana
- Physics and Earth Sciences
- Jacobs University Bremen
- 28759 Bremen
- Germany
| | - Vladislav Jovanov
- Physics and Earth Sciences
- Jacobs University Bremen
- 28759 Bremen
- Germany
| | - Veit Wagner
- Physics and Earth Sciences
- Jacobs University Bremen
- 28759 Bremen
- Germany
| | - Arnulf Materny
- Physics and Earth Sciences
- Jacobs University Bremen
- 28759 Bremen
- Germany
| | - Patrice Donfack
- Physics and Earth Sciences
- Jacobs University Bremen
- 28759 Bremen
- Germany
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26
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Ball ML, Zhang B, Fu T, Schattman AM, Paley DW, Ng F, Venkataraman L, Nuckolls C, Steigerwald ML. The importance of intramolecular conductivity in three dimensional molecular solids. Chem Sci 2019; 10:9339-9344. [PMID: 32110297 PMCID: PMC7006630 DOI: 10.1039/c9sc03144h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 08/20/2019] [Indexed: 12/26/2022] Open
Abstract
Recent years have seen tremendous progress towards understanding the relation between the molecular structure and function of organic field effect transistors. The metrics for organic field effect transistors, which are characterized by mobility and the on/off ratio, are known to be enhanced when the intermolecular interaction is strong and the intramolecular reorganization energy is low. While these requirements are adequate when describing organic field effect transistors with simple and planar aromatic molecular components, they are insufficient for complex building blocks, which have the potential to localize a carrier on the molecule. Here, we show that intramolecular conductivity can play a role in controlling device characteristics of organic field effect transistors made with macrocycle building blocks. We use two isomeric macrocyclic semiconductors that consist of perylene diimides linked with bithiophenes and find that the trans-linked macrocycle has a higher mobility than the cis-based device. Through a combination of single molecule junction conductance measurements of the components of the macrocycles, control experiments with acyclic counterparts to the macrocycles, and analyses of each of the materials using spectroscopy, electrochemistry, and density functional theory, we attribute the difference in electron mobility of the OFETs created with the two isomers to the difference in intramolecular conductivity of the two macrocycles.
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Affiliation(s)
- Melissa L Ball
- Department of Chemistry , Columbia University , New York , New York 10027 , USA . ; ;
| | - Boyuan Zhang
- Department of Chemistry , Columbia University , New York , New York 10027 , USA . ; ;
| | - Tianren Fu
- Department of Chemistry , Columbia University , New York , New York 10027 , USA . ; ;
- Department of Applied Physics and Applied Math , Columbia University , New York , New York 10027 , USA
| | - Ayden M Schattman
- Department of Chemistry , Columbia University , New York , New York 10027 , USA . ; ;
| | - Daniel W Paley
- Department of Chemistry , Columbia University , New York , New York 10027 , USA . ; ;
| | - Fay Ng
- Department of Chemistry , Columbia University , New York , New York 10027 , USA . ; ;
| | - Latha Venkataraman
- Department of Chemistry , Columbia University , New York , New York 10027 , USA . ; ;
- Department of Applied Physics and Applied Math , Columbia University , New York , New York 10027 , USA
| | - Colin Nuckolls
- Department of Chemistry , Columbia University , New York , New York 10027 , USA . ; ;
| | - Michael L Steigerwald
- Department of Chemistry , Columbia University , New York , New York 10027 , USA . ; ;
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27
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Swick SM, Gebraad T, Jones L, Fu B, Aldrich TJ, Kohlstedt KL, Schatz GC, Facchetti A, Marks TJ. Building Blocks for High‐Efficiency Organic Photovoltaics: Interplay of Molecular, Crystal, and Electronic Properties in Post‐Fullerene ITIC Ensembles. Chemphyschem 2019; 20:2608-2626. [DOI: 10.1002/cphc.201900793] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 09/13/2019] [Indexed: 12/31/2022]
Affiliation(s)
- Steven M. Swick
- Department of Chemistry Northwestern University Evanston Illinois 60208 United States
- Center for Light Energy Activated Redox Processes Evanston Illinois 60208 United States
| | - Tim Gebraad
- Department of Chemistry Northwestern University Evanston Illinois 60208 United States
- Center for Light Energy Activated Redox Processes Evanston Illinois 60208 United States
| | - Leighton Jones
- Department of Chemistry Northwestern University Evanston Illinois 60208 United States
- Center for Light Energy Activated Redox Processes Evanston Illinois 60208 United States
| | - Bo Fu
- Department of Chemistry Northwestern University Evanston Illinois 60208 United States
- Center for Light Energy Activated Redox Processes Evanston Illinois 60208 United States
| | - Thomas J. Aldrich
- Department of Chemistry Northwestern University Evanston Illinois 60208 United States
- Center for Light Energy Activated Redox Processes Evanston Illinois 60208 United States
| | - Kevin L. Kohlstedt
- Department of Chemistry Northwestern University Evanston Illinois 60208 United States
- Center for Light Energy Activated Redox Processes Evanston Illinois 60208 United States
| | - George C. Schatz
- Department of Chemistry Northwestern University Evanston Illinois 60208 United States
- Center for Light Energy Activated Redox Processes Evanston Illinois 60208 United States
| | - Antonio Facchetti
- Department of Chemistry Northwestern University Evanston Illinois 60208 United States
- Center for Light Energy Activated Redox Processes Evanston Illinois 60208 United States
| | - Tobin J. Marks
- Department of Chemistry Northwestern University Evanston Illinois 60208 United States
- Center for Light Energy Activated Redox Processes Evanston Illinois 60208 United States
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28
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Kawashima E, Fujii M, Yamashita K. Entropy promotes charge separation in bulk heterojunction organic photovoltaics. J Photochem Photobiol A Chem 2019. [DOI: 10.1016/j.jphotochem.2019.111875] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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29
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Guo Y, Ma Z, Niu X, Zhang W, Tao M, Guo Q, Wang Z, Xia A. Bridge-Mediated Charge Separation in Isomeric N-Annulated Perylene Diimide Dimers. J Am Chem Soc 2019; 141:12789-12796. [PMID: 31334641 DOI: 10.1021/jacs.9b05723] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The possibility and rate of charge separation (CS) in donor-bridge-acceptor molecules mainly depend on two factors: electronic coupling and solvent effects. The question of how CS occurred in two identical chromophores is fundamental, as it is particularly interesting for potential molecular electronics applications and the photosynthetic reaction centers (RCs). Conjugated bridge definitely plays a crucial role in electronic coupling. To determine the bridge-mediated charge separation dynamics between the two identical chromophores, the isomeric N-annulated perylene diimide dimers (para-BDNP and meta-BDNP) with different conjugated bridge structures have been comparatively investigated in different solvents using femtosecond transient absorption spectra (fs-TA). It is found that the charge separation is disfavored in weak polar solvent, whereas direct spectroscopic signatures of radicals are observed in polar solvents, and the rate of charge separation increases as the solvent polarity increasing. To our surprise, the rate of charge separation in m-BDNP is more than an order of magnitude slower than that in p-BDNP, although there is a larger negative ΔGCS in m-BDNP. The slow CS rate that occurred in m-BDNP mainly results from the intrinsic destructive interference of the wave function through the meta-substituted bridge. The roles of solvent effects in free energy and electronic coupling for charge separation are further identified with quantum calculations.
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Affiliation(s)
- Yuanyuan Guo
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Zetong Ma
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Xinmiao Niu
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Wei Zhang
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Min Tao
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Qianjin Guo
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Zhaohui Wang
- Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry , Tsinghua University , Beijing 100084 , China
| | - Andong Xia
- University of Chinese Academy of Sciences , Beijing 100049 , China
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30
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Ball M, Zhang B, Zhong Y, Fowler B, Xiao S, Ng F, Steigerwald M, Nuckolls C. Conjugated Macrocycles in Organic Electronics. Acc Chem Res 2019; 52:1068-1078. [PMID: 30869865 DOI: 10.1021/acs.accounts.9b00017] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This Account describes a body of research on the design, synthesis, and application of a new class of electronic materials made from conjugated macrocycles. Our macrocyclic design takes into consideration the useful attributes of fullerenes and what properties make fullerenes efficient n-type materials. We identified four electronic and structural elements: (1) a three-dimensional shape; (2) a conjugated and delocalized π-space; (3) the presence of an interior and exterior to the π-surface; and (4) low-energy unoccupied molecular orbitals allowing them to accept electrons. The macrocyclic design incorporates some of these properties, including a three-dimensional shape, an interior/exterior to the π-surface, and low-lying LUMOs maintaining the n-type semiconducting behavior, yet we also install synthetic flexibility in our approach in order to tune the properties further. Each of the macrocycles comprises perylenediimide cores wound together with linkers. The perylenediimide building block endows each macrocycle with the ability to accept electrons, while the synthetic flexibility to install different linkers allows us to create macrocycles with different electronic properties and sizes. We have created three macrocycles that all absorb well into the visible range of the solar spectrum and possess different shapes and sizes. We then use these materials in an array of applications that take advantage of their ability to function as n-type semiconductors, absorb in the visible range of the solar spectrum, and possess intramolecular cavities. This Account will discuss our progress in incorporating these new macrocycles in organic solar cells, organic photodetectors, organic field effect transistors, and sensors. The macrocycles outperform acyclic controls in organic solar cells. We find the more rigid macrocyclic structure results in less intrinsic charges and lower dark current in organic photodetectors. Our macrocyclic-based photodetector has the highest detectivity of non-fullerene acceptors. The macrocycles also function as sensors and are able to recognize nuanced differences in analytes. Perylenediimide-based fused oligomers are efficient materials in both organic solar cells and field effect transistors. We will use the oligomers to construct macrocycles for use in solar energy conversion. In addition, we will incorporate different electron-rich linkers in our cycles in an attempt to engineer the HOMO/LUMO gap further. Looking further into the future, we envision opportunities in applying these conjugated macrocycles as electronic host/guest materials, as concatenated electronic materials by threading the macrocycles with electroactive oligomers, and as a locus for catalysis that is driven by light and electric fields.
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Affiliation(s)
- Melissa Ball
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Boyuan Zhang
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Yu Zhong
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Brandon Fowler
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Shengxiong Xiao
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry, Shanghai Normal University, Shanghai 200234, China
| | - Fay Ng
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Michael Steigerwald
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, New York, New York 10027, United States
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Key Laboratory of Rare Earth Functional Materials, Optoelectronic Nano Materials and Devices Institute, Department of Chemistry, Shanghai Normal University, Shanghai 200234, China
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31
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Becker-Koch D, Rivkin B, Paulus F, Xiang H, Dong Y, Chen Z, Bakulin AA, Vaynzof Y. Probing charge transfer states at organic and hybrid internal interfaces by photothermal deflection spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:124001. [PMID: 30572317 DOI: 10.1088/1361-648x/aafa4e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In organic and hybrid photovoltaic devices, the asymmetry required for charge separation necessitates the use of a donor and an acceptor material, resulting in the formation of internal interfaces in the device active layer. While the core objective of these interfaces is to facilitate charge separation, bound states between electrons and holes may form across them, resulting in a loss mechanism that diminishes the performance of the solar cells. These interfacial transitions appear in organic systems as charge transfer (CT) states and as bound charge pairs (BCP) in hybrid systems. Despite being similar, the latter are far less investigated. Herein, we employ photothermal deflection spectroscopy and pump-push-probe experiments in order to determine the characteristics and dynamics of interfacial states in two model systems: an organic P3HT:PCBM and hybrid P3HT:ZnO photovoltaic layer. By controlling the area of the internal interface, we identify CT states between 1.4 eV and 1.8 eV in the organic bulk-heterojunction (BHJ) and BCP between 1.1 eV and 1.4 eV in the hybrid BHJ. The energetic distribution of these states suggests that they not only contribute to losses in photocurrent, but also significantly limit the possible maximum open circuit voltage obtainable from these devices.
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Affiliation(s)
- David Becker-Koch
- Kirchhoff Institut für Physik, Ruprecht-Karls-Universität, Heidelberg, Germany. Centre for Advanced Materials, Ruprecht-Karls-Universität, Heidelberg, Germany
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32
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Duan HG, Nalbach P, Miller RJD, Thorwart M. Ultrafast Energy Transfer in Excitonically Coupled Molecules Induced by a Nonlocal Peierls Phonon. J Phys Chem Lett 2019; 10:1206-1211. [PMID: 30802058 DOI: 10.1021/acs.jpclett.9b00242] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Molecular vibration can influence exciton transfer via either a local (intramolecular) Holstein or a nonlocal (intermolecular) Peierls mode. We show that a strong vibronic coupling to a nonlocal mode dramatically speeds up the transfer by opening an additional transfer channel. This Peierls channel is rooted in the formation of a conical intersection of the excitonic potential energy surfaces. For increasing Peierls coupling, the electronically coherent transfer for weak coupling turns into an incoherent transfer of a localized exciton through the intersection for strong coupling. The interpretation in terms of a conical intersection intuitively explains recent experiments of ultrafast energy transfer in photosynthetic and photovoltaic molecular systems.
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Affiliation(s)
- Hong-Guang Duan
- I. Institut für Theoretische Physik , Universität Hamburg , Jungiusstraße 9 , 20355 Hamburg , Germany
- Max Planck-Institute for the Structure and Dynamics of Matter , Luruper Chaussee 149 , 22761 Hamburg , Germany
| | - Peter Nalbach
- Westfälische Hochschule , Münsterstr. 265 , 46397 Bocholt , Germany
| | - R J Dwayne Miller
- Max Planck-Institute for the Structure and Dynamics of Matter , Luruper Chaussee 149 , 22761 Hamburg , Germany
- The Departments of Chemistry and Physics , University of Toronto , 80 St. George Street , Toronto , Canada M5S 3H6
| | - Michael Thorwart
- I. Institut für Theoretische Physik , Universität Hamburg , Jungiusstraße 9 , 20355 Hamburg , Germany
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33
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Zhou J, Wu Y, Roy I, Samanta A, Stoddart JF, Young RM, Wasielewski MR. Choosing sides: unusual ultrafast charge transfer pathways in an asymmetric electron-accepting cyclophane that binds an electron donor. Chem Sci 2019; 10:4282-4292. [PMID: 31057755 PMCID: PMC6471873 DOI: 10.1039/c8sc05514a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 03/06/2019] [Indexed: 12/20/2022] Open
Abstract
Photo-driven electron transfer is faster from an electron donor guest to the harder to reduce acceptor in an asymmetric cyclophane host.
Constructing functional molecular systems for solar energy conversion and quantum information science requires a fundamental understanding of electron transfer in donor–bridge–acceptor (D–B–A) systems as well as competitive reaction pathways in acceptor–donor–acceptor (A–D–A) and acceptor–donor–acceptor′ (A–D–A′) systems. Herein we present a supramolecular complex comprising a tetracationic cyclophane having both phenyl-extended viologen (ExV2+) and dipyridylthiazolothiazole (TTz2+) electron acceptors doubly-linked by means of two p-xylylene linkers (TTzExVBox4+), which readily incorporates a perylene (Per) guest in its cavity (Per ⊂ TTzExVBox4+) to establish an A–D–A′ system, in which the ExV2+ and TTz2+ units serve as competing electron acceptors with different reduction potentials. Photoexcitation of the Per guest yields both TTz+˙–Per+˙–ExV2+ and TTz2+–Per+˙–ExV+˙ in <1 ps, while back electron transfer in TTz2+–Per+˙–ExV+˙ proceeds via the unusual sequence TTz2+–Per+˙–ExV+˙ → TTz+˙–Per+˙–ExV2+ → TTz2+–Per–ExV2+. In addition, selective chemical reduction of TTz2+ gives Per ⊂ TTzExVBox3+˙, turning the complex into a D–B–A system in which photoexcitation of TTz+˙ results in the reaction sequence 2*TTz+˙–Per–ExV2+ → TTz2+–Per–ExV+˙ → TTz+˙–Per–ExV2+. Both reactions TTz2+–Per+˙–ExV+˙ → TTz+˙–Per+˙–ExV2+ and TTz2+–Per–ExV+˙ → TTz+˙–Per–ExV2+ occur with a (16 ± 1 ps)–1 rate constant irrespective of whether the bridge molecule is Per+˙ or Per. These results are explained using the superexchange mechanism in which the ionic states of the perylene guest serve as virtual states in each case and demonstrate a novel supramolecular platform for studying the effects of bridge energetics within D–B–A systems.
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Affiliation(s)
- Jiawang Zhou
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Sustainability and Energy at Northwestern , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA
| | - Yilei Wu
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Sustainability and Energy at Northwestern , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA
| | - Indranil Roy
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ;
| | - Avik Samanta
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ;
| | - J Fraser Stoddart
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Molecular Design and Synthesis , Tianjin University , Tianjin 300072 , China.,School of Chemistry , University of New South Wales , Sydney , New South Wales 2052 , Australia
| | - Ryan M Young
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Sustainability and Energy at Northwestern , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA
| | - Michael R Wasielewski
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA . ; .,Institute for Sustainability and Energy at Northwestern , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208-3113 , USA
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34
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Dimitrov SD, Azzouzi M, Wu J, Yao J, Dong Y, Tuladhar PS, Schroeder BC, Bittner ER, McCulloch I, Nelson J, Durrant JR. Spectroscopic Investigation of the Effect of Microstructure and Energetic Offset on the Nature of Interfacial Charge Transfer States in Polymer: Fullerene Blends. J Am Chem Soc 2019; 141:4634-4643. [PMID: 30807130 PMCID: PMC6429453 DOI: 10.1021/jacs.8b11484] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Despite
performance improvements of organic photovoltaics, the
mechanism of photoinduced electron–hole separation at organic
donor–acceptor interfaces remains poorly understood. Inconclusive
experimental and theoretical results have produced contradictory models
for electron–hole separation in which the role of interfacial
charge-transfer (CT) states is unclear, with one model identifying
them as limiting separation and another as readily dissociating. Here,
polymer–fullerene blends with contrasting photocurrent properties
and enthalpic offsets driving separation were studied. By modifying
composition, film structures were varied from consisting of molecularly
mixed polymer–fullerene domains to consisting of both molecularly
mixed and fullerene domains. Transient absorption spectroscopy revealed
that CT state dissociation generating separated electron–hole
pairs is only efficient in the high energy offset blend with fullerene
domains. In all other blends (with low offset or predominantly molecularly
mixed domains), nanosecond geminate electron–hole recombination
is observed revealing the importance of spatially localized electron–hole
pairs (bound CT states) in the electron–hole dynamics. A two-dimensional
lattice exciton model was used to simulate the excited state spectrum
of a model system as a function of microstructure and energy offset.
The results could reproduce the main features of experimental electroluminescence
spectra indicating that electron–hole pairs become less bound
and more spatially separated upon increasing energy offset and fullerene
domain density. Differences between electroluminescence and photoluminescence
spectra could be explained by CT photoluminescence being dominated
by more-bound states, reflecting geminate recombination processes,
while CT electroluminescence preferentially probes less-bound CT states
that escape geminate recombination. These results suggest that apparently
contradictory studies on electron–hole separation can be explained
by the presence of both bound and unbound CT states in the same film,
as a result of a range of interface structures.
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Affiliation(s)
- S D Dimitrov
- SPECIFIC, College of Engineering , Swansea University , Bay Campus , Swansea SA1 8EN , United Kingdom
| | | | | | | | | | | | - B C Schroeder
- Department of Chemistry , University College , London WC1H 0AJ , United Kingdom
| | - E R Bittner
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - I McCulloch
- Physical Sciences and Engineering Division, KAUST Solar Center (KSC) , King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | | | - J R Durrant
- SPECIFIC, College of Engineering , Swansea University , Bay Campus , Swansea SA1 8EN , United Kingdom
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35
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Collado-Fregoso E, Pugliese SN, Wojcik M, Benduhn J, Bar-Or E, Perdigón Toro L, Hörmann U, Spoltore D, Vandewal K, Hodgkiss JM, Neher D. Energy-Gap Law for Photocurrent Generation in Fullerene-Based Organic Solar Cells: The Case of Low-Donor-Content Blends. J Am Chem Soc 2019; 141:2329-2341. [PMID: 30620190 DOI: 10.1021/jacs.8b09820] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The involvement of charge-transfer (CT) states in the photogeneration and recombination of charge carriers has been an important focus of study within the organic photovoltaic community. In this work, we investigate the molecular factors determining the mechanism of photocurrent generation in low-donor-content organic solar cells, where the active layer is composed of vacuum-deposited C60 and small amounts of organic donor molecules. We find a pronounced decline of all photovoltaic parameters with decreasing CT state energy. Using a combination of steady-state photocurrent measurements and time-delayed collection field experiments, we demonstrate that the power conversion efficiency, and more specifically, the fill factor of these devices, is mainly determined by the bias dependence of photocurrent generation. By combining these findings with the results from ultrafast transient absorption spectroscopy, we show that blends with small CT energies perform poorly because of an increased nonradiative CT state decay rate and that this decay obeys an energy-gap law. Our work challenges the common view that a large energy offset at the heterojunction and/or the presence of fullerene clusters guarantee efficient CT dissociation and rather indicates that charge generation benefits from high CT state energies through a slower decay to the ground state.
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Affiliation(s)
- Elisa Collado-Fregoso
- Department of Physics and Astronomy , University of Potsdam , Karl-Liebknecht-Straße 24-25 , 14476 Potsdam-Golm , Germany
| | - Silvina N Pugliese
- School of Chemical and Physical Sciences , Victoria University of Wellington , Wellington 6040 , New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6040 , New Zealand
| | - Mariusz Wojcik
- Institute of Applied Radiation Chemistry , Lodz University of Technology , Wroblewskiego 15 , 93590 Lodz , Poland
| | - Johannes Benduhn
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics , Technische Universität Dresden , Nöthnitzer Straße 61 , 01187 Dresden , Germany
| | - Eyal Bar-Or
- Department of Physics and Astronomy , University of Potsdam , Karl-Liebknecht-Straße 24-25 , 14476 Potsdam-Golm , Germany
| | - Lorena Perdigón Toro
- Department of Physics and Astronomy , University of Potsdam , Karl-Liebknecht-Straße 24-25 , 14476 Potsdam-Golm , Germany
| | - Ulrich Hörmann
- Department of Physics and Astronomy , University of Potsdam , Karl-Liebknecht-Straße 24-25 , 14476 Potsdam-Golm , Germany
| | - Donato Spoltore
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics , Technische Universität Dresden , Nöthnitzer Straße 61 , 01187 Dresden , Germany
| | - Koen Vandewal
- Institute for Materials Research (IMO-IMOMEC) , Hasselt University , Wetenschapspark 1 , 3590 Diepenbeek , Belgium
| | - Justin M Hodgkiss
- School of Chemical and Physical Sciences , Victoria University of Wellington , Wellington 6040 , New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6040 , New Zealand
| | - Dieter Neher
- Department of Physics and Astronomy , University of Potsdam , Karl-Liebknecht-Straße 24-25 , 14476 Potsdam-Golm , Germany
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36
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Hou Y, Xie C, Radmilovic VV, Puscher B, Wu M, Heumüller T, Karl A, Li N, Tang X, Meng W, Chen S, Osvet A, Guldi D, Spiecker E, Radmilović VR, Brabec CJ. Assembling Mesoscale-Structured Organic Interfaces in Perovskite Photovoltaics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1806516. [PMID: 30633825 DOI: 10.1002/adma.201806516] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 12/16/2018] [Indexed: 06/09/2023]
Abstract
Mesoscale-structured materials offer broad opportunities in extremely diverse applications owing to their high surface areas, tunable surface energy, and large pore volume. These benefits may improve the performance of materials in terms of carrier density, charge transport, and stability. Although metal oxides-based mesoscale-structured materials, such as TiO2 , predominantly hold the record efficiency in perovskite solar cells, high temperatures (above 400 °C) and limited materials choices still challenge the community. A novel route to fabricate organic-based mesoscale-structured interfaces (OMI) for perovskite solar cells using a low-temperature and green solvent-based process is presented here. The efficient infiltration of organic porous structures based on crystalline nanoparticles allows engineering efficient "n-i-p" and "p-i-n" perovskite solar cells with enhanced thermal stability, good performance, and excellent lateral homogeneity. The results show that this method is universal for multiple organic electronic materials, which opens the door to transform a wide variety of organic-based semiconductors into scalable n- or p-type porous interfaces for diverse advanced applications.
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Affiliation(s)
- Yi Hou
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
| | - Chen Xie
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
| | - Vuk V Radmilovic
- Innovation Center, Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120, Belgrade, Serbia
| | - Bianka Puscher
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058, Erlangen, Germany
| | - Mingjian Wu
- Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 6, 91058, Erlangen, Germany
| | - Thomas Heumüller
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
| | - André Karl
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
| | - Ning Li
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
- Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou, 450002, China
| | - Xiaofeng Tang
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
| | - Wei Meng
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
| | - Shi Chen
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
| | - Andres Osvet
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
| | - Dirk Guldi
- Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058, Erlangen, Germany
| | - Erdmann Spiecker
- Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstr. 6, 91058, Erlangen, Germany
| | | | - Christoph J Brabec
- Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Martensstr. 7, 91058, Erlangen, Germany
- Bavarian Center for Applied Energy Research (ZAE Bayern), Immerwahrstr. 2, 91058, Erlangen, Germany
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37
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Lankevich V, Bittner ER. Relating free energy and open-circuit voltage to disorder in organic photovoltaic systems. J Chem Phys 2018; 149:244123. [DOI: 10.1063/1.5050506] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Affiliation(s)
- V. Lankevich
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA
| | - E. R. Bittner
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA
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38
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Yang W, Yao Y, Guo P, Sun H, Luo Y. Optimum driving energy for achieving balanced open-circuit voltage and short-circuit current density in organic bulk heterojunction solar cells. Phys Chem Chem Phys 2018; 20:29866-29875. [PMID: 30468215 DOI: 10.1039/c8cp05145c] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Organic bulk heterojunction solar cells generally suffer from a trade-off between the open circuit voltage (Voc) and the short circuit current density (Jsc) under a given donor/acceptor (D/A) interfacial energetic offset (or the so-called driving force). Here we theoretically investigate the optimum driving energy required for achieving the balanced Jsc and Voc simultaneously. To this end, the Jscversus the driving force ΔE curves are calculated under two different charge separation mechanisms by employing the drift-diffusion method. For the Marcus incoherent mechanism, the curve features a high plateau in a broad range of ΔE starting from 0.2 eV, which is due to the accumulation of undissociated excitons within their lifetime and signifies the possibility of obtaining a sizable Jsc under a ΔE value much smaller than the reorganization energy. After incorporating both the electron and hole transfer pathways into the device model, the calculated J-V curves are comparable to experimentally measured ones foractual blended systems of different driving forces. For the coherent mechanism, it is demonstrated that the maximum Jsc can also be achieved under the ΔE of 0.2 eV if a large proportion of the high-lying delocalized states are harvested through tuning the density of states for the charge transfer excitons to reduce the sub-gap states. This theoretical work revealed quantitatively the relationship between the interfacial energy offsets and device performance, and also provides some guidelines for identifying the macroscopic features of the actual charge separation mechanisms in bulk heterojunction solar cells.
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Affiliation(s)
- Wenchao Yang
- Key Laboratory of Microelectronics and Energy of Henan, School of Physics and Electronic Engineering, Xinyang Normal University, Xinyang, 464000, China.
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39
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Kafle TR, Kattel B, Wang T, Chan WL. The relationship between the coherent size, binding energy and dissociation dynamics of charge transfer excitons at organic interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:454001. [PMID: 30265252 DOI: 10.1088/1361-648x/aae50b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
At organic semiconductor interfaces, an electron and a hole can be bound Coulombically to form an interfacial charge transfer (CT) exciton. It is still under debate how a CT exciton can overcome its strong binding and dissociate into free carriers. Experimentally, capturing the evolution of the CT exciton on time (fs-ps) and length scales (nm) in which the dissociation process occurs is challenging. To overcome this challenge, time-resolved two photon photoemission spectroscopy is used to measure the binding energies and electronic coherent sizes of a series of CT states at organic interfaces, and capture the temporal dynamics of these CT excitons after their excitation. Using zinc phthalocyanine (ZnPc)/fullerene (C60) interface as a model system, it is shown that the interfacial CT process first populates a hot CT state with a coherent size of ~4 nm. Hot and delocalized CT excitons subsequently relax into CT excitons with lower energies and smaller coherent sizes. To correlate the CT exciton properties with the dissociation efficiency, we develop a method that exploits graphene field effect transistors to probe the rate and yield of free carrier generation at the interface. Our results show that exciton dissociation can be more efficient if one can extract electrons from the hot and delocalized CT state. We propose a cascade structure that would serve this purpose.
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Affiliation(s)
- Tika R Kafle
- Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, United States of America
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40
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Derr JB, Tamayo J, Espinoza EM, Clark JA, Vullev VI. Dipole-induced effects on charge transfer and charge transport. Why do molecular electrets matter? CAN J CHEM 2018. [DOI: 10.1139/cjc-2017-0389] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Charge transfer (CT) and charge transport (CTr) are at the core of life-sustaining biological processes and of processes that govern the performance of electronic and energy-conversion devices. Electric fields are invaluable for guiding charge movement. Therefore, as electrostatic analogues of magnets, electrets have unexplored potential for generating local electric fields for accelerating desired CT processes and suppressing undesired ones. The notion about dipole-generated local fields affecting CT has evolved since the middle of the 20th century. In the 1990s, the first reports demonstrating the dipole effects on the kinetics of long-range electron transfer appeared. Concurrently, the development of molecular-level designs of electric junctions has led the exploration of dipole effects on CTr. Biomimetic molecular electrets such as polypeptide helices are often the dipole sources in CT systems. Conversely, surface-charge electrets and self-assembled monolayers of small polar conjugates are the preferred sources for modifying interfacial electric fields for controlling CTr. The multifaceted complexity of such effects on CT and CTr testifies for the challenges and the wealth of this field that still remains largely unexplored. This review outlines the basic concepts about dipole effects on CT and CTr, discusses their evolution, and provides accounts for their future developments and impacts.
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Affiliation(s)
- James B. Derr
- Department of Biochemistry, University of California, Riverside, CA 92521, USA
| | - Jesse Tamayo
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - Eli M. Espinoza
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - John A. Clark
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
| | - Valentine I. Vullev
- Department of Biochemistry, University of California, Riverside, CA 92521, USA
- Department of Chemistry, University of California, Riverside, CA 92521, USA
- Department of Bioengineering, University of California, Riverside, CA 92521, USA
- Materials Science and Engineering Program, University of California, Riverside, CA 92521, USA
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41
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Closely packed, low reorganization energy π-extended postfullerene acceptors for efficient polymer solar cells. Proc Natl Acad Sci U S A 2018; 115:E8341-E8348. [PMID: 30127011 DOI: 10.1073/pnas.1807535115] [Citation(s) in RCA: 95] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
New organic semiconductors are essential for developing inexpensive, high-efficiency, solution-processable polymer solar cells (PSCs). PSC photoactive layers are typically fabricated by film-casting a donor polymer and a fullerene acceptor blend, with ensuing solvent evaporation and phase separation creating discrete conduits for photogenerated holes and electrons. Until recently, n-type fullerene acceptors dominated the PSC literature; however, indacenodithienothiophene (IDTT)-based acceptors have recently enabled remarkable PSC performance metrics, for reasons that are not entirely obvious. We report two isomeric IDTT-based acceptors 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz-(5, 6)indanone))-5,5,11,11-tetrakis(4-nonylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']di-thiophene (ITN-C9) and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-benz(6,7)indanone))-5,5,11,11-tetrakis(4-nonylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITzN-C9) that shed light on the exceptional IDTT properties vis-à-vis fullerenes. The neat acceptors and blends with fluoropolymer donor poly{[4,8-bis[5-(2- ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b']dithiophene2,6-diyl]-alt-[2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo4H,8H-benzo[1,2-c:4,5-c']dithiophene-1,3-diyl]]} (PBDB-TF) are investigated by optical spectroscopy, cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetry, single-crystal X-ray diffraction, photovoltaic response, space-charge-limited current transport, atomic force microscopy, grazing incidence wide-angle X-ray scattering, and density functional theory-level quantum chemical analysis. The data reveal that ITN-C9 and ITzN-C9 organize such that the lowest unoccupied molecular orbital-rich end groups have intermolecular π-π distances as close as 3.31(1) Å, with electronic coupling integrals as large as 38 meV, and internal reorganization energies as small as 0.133 eV, comparable to or superior to those in fullerenes. ITN-C9 and ITzN-C9 have broad solar-relevant optical absorption, and, when blended with PBDB-TF, afford devices with power conversion efficiencies near 10%. Performance differences between ITN-C9 and ITzN-C9 are understandable in terms of molecular and electronic structure distinctions via the influences on molecular packing and orientation with respect to the electrode.
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42
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Qian D, Zheng Z, Yao H, Tress W, Hopper TR, Chen S, Li S, Liu J, Chen S, Zhang J, Liu XK, Gao B, Ouyang L, Jin Y, Pozina G, Buyanova IA, Chen WM, Inganäs O, Coropceanu V, Bredas JL, Yan H, Hou J, Zhang F, Bakulin AA, Gao F. Design rules for minimizing voltage losses in high-efficiency organic solar cells. NATURE MATERIALS 2018; 17:703-709. [PMID: 30013057 DOI: 10.1038/s41563-018-0128-z] [Citation(s) in RCA: 284] [Impact Index Per Article: 47.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 06/08/2018] [Indexed: 06/08/2023]
Abstract
The open-circuit voltage of organic solar cells is usually lower than the values achieved in inorganic or perovskite photovoltaic devices with comparable bandgaps. Energy losses during charge separation at the donor-acceptor interface and non-radiative recombination are among the main causes of such voltage losses. Here we combine spectroscopic and quantum-chemistry approaches to identify key rules for minimizing voltage losses: (1) a low energy offset between donor and acceptor molecular states and (2) high photoluminescence yield of the low-gap material in the blend. Following these rules, we present a range of existing and new donor-acceptor systems that combine efficient photocurrent generation with electroluminescence yield up to 0.03%, leading to non-radiative voltage losses as small as 0.21 V. This study provides a rationale to explain and further improve the performance of recently demonstrated high-open-circuit-voltage organic solar cells.
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Affiliation(s)
- Deping Qian
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Zilong Zheng
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Huifeng Yao
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Wolfgang Tress
- Laboratory of Photonics and Interfaces (LPI), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Thomas R Hopper
- Department of Chemistry, Imperial College London, London, UK
| | - Shula Chen
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Sunsun Li
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Jing Liu
- Department of Chemistry and Energy Institute, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
| | - Shangshang Chen
- Department of Chemistry and Energy Institute, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
| | - Jiangbin Zhang
- Department of Chemistry, Imperial College London, London, UK
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Xiao-Ke Liu
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Bowei Gao
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Liangqi Ouyang
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Yingzhi Jin
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Galia Pozina
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Irina A Buyanova
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Weimin M Chen
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Olle Inganäs
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Veaceslav Coropceanu
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA.
| | - Jean-Luc Bredas
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - He Yan
- Department of Chemistry and Energy Institute, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
| | - Jianhui Hou
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
| | - Fengling Zhang
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden
| | - Artem A Bakulin
- Department of Chemistry, Imperial College London, London, UK.
| | - Feng Gao
- Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping, Sweden.
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43
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Causa' M, Ramirez I, Martinez Hardigree JF, Riede M, Banerji N. Femtosecond Dynamics of Photoexcited C 60 Films. J Phys Chem Lett 2018; 9:1885-1892. [PMID: 29569924 DOI: 10.1021/acs.jpclett.8b00520] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The well known organic semiconductor C60 is attracting renewed attention due to its centimeter-long electron diffusion length and high performance of solar cells containing 95% fullerene, yet its photophysical properties remain poorly understood. We elucidate the dynamics of Frenkel and intermolecular (inter-C60) charge-transfer (CT) excitons in neat and diluted C60 films from high-quality femtosecond transient absorption (TA) measurements performed at low fluences and free from oxygen or pump-induced photodimerization. We find from preferential excitation of either species that the CT excitons give rise to a strong electro-absorption (EA) signal but are extremely short-lived. The Frenkel exciton relaxation and triplet yield strongly depend on the C60 aggregation. Finally, TA measurements on full devices with applied electric field allow us to optically monitor the dissociation of CT excitons into free charges for the first time and to demonstrate the influence of cluster size on the spectral signature of the C60 anion.
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Affiliation(s)
- Martina Causa'
- Department of Chemistry and Biochemistry , University of Bern , Freiestrasse 3 , 3012 Bern , Switzerland
| | - Ivan Ramirez
- Clarendon Laboratory, Department of Physics , University of Oxford , Parks Road , OX1 3PU , Oxford , United Kingdom
| | - Josue F Martinez Hardigree
- Clarendon Laboratory, Department of Physics , University of Oxford , Parks Road , OX1 3PU , Oxford , United Kingdom
| | - Moritz Riede
- Clarendon Laboratory, Department of Physics , University of Oxford , Parks Road , OX1 3PU , Oxford , United Kingdom
| | - Natalie Banerji
- Department of Chemistry and Biochemistry , University of Bern , Freiestrasse 3 , 3012 Bern , Switzerland
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44
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Zhang G, Zhao J, Chow PCY, Jiang K, Zhang J, Zhu Z, Zhang J, Huang F, Yan H. Nonfullerene Acceptor Molecules for Bulk Heterojunction Organic Solar Cells. Chem Rev 2018; 118:3447-3507. [PMID: 29557657 DOI: 10.1021/acs.chemrev.7b00535] [Citation(s) in RCA: 570] [Impact Index Per Article: 95.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The bulk-heterojunction blend of an electron donor and an electron acceptor material is the key component in a solution-processed organic photovoltaic device. In the past decades, a p-type conjugated polymer and an n-type fullerene derivative have been the most commonly used electron donor and electron acceptor, respectively. While most advances of the device performance come from the design of new polymer donors, fullerene derivatives have almost been exclusively used as electron acceptors in organic photovoltaics. Recently, nonfullerene acceptor materials, particularly small molecules and oligomers, have emerged as a promising alternative to replace fullerene derivatives. Compared to fullerenes, these new acceptors are generally synthesized from diversified, low-cost routes based on building block materials with extraordinary chemical, thermal, and photostability. The facile functionalization of these molecules affords excellent tunability to their optoelectronic and electrochemical properties. Within the past five years, there have been over 100 nonfullerene acceptor molecules synthesized, and the power conversion efficiency of nonfullerene organic solar cells has increased dramatically, from ∼2% in 2012 to >13% in 2017. This review summarizes this progress, aiming to describe the molecular design strategy, to provide insight into the structure-property relationship, and to highlight the challenges the field is facing, with emphasis placed on most recent nonfullerene acceptors that demonstrated top-of-the-line photovoltaic performances. We also provide perspectives from a device point of view, wherein topics including ternary blend device, multijunction device, device stability, active layer morphology, and device physics are discussed.
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Affiliation(s)
- Guangye Zhang
- Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction , Hong Kong University of Science and Technology (HKUST) , Clear Water Bay , Kowloon, Hong Kong , China.,HKUST-Shenzhen Research Institute , No. 9 Yuexing first RD, Hi-tech Park , Nanshan, Shenzhen 518057 , China
| | - Jingbo Zhao
- Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction , Hong Kong University of Science and Technology (HKUST) , Clear Water Bay , Kowloon, Hong Kong , China
| | - Philip C Y Chow
- Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction , Hong Kong University of Science and Technology (HKUST) , Clear Water Bay , Kowloon, Hong Kong , China.,HKUST-Shenzhen Research Institute , No. 9 Yuexing first RD, Hi-tech Park , Nanshan, Shenzhen 518057 , China
| | - Kui Jiang
- Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction , Hong Kong University of Science and Technology (HKUST) , Clear Water Bay , Kowloon, Hong Kong , China.,HKUST-Shenzhen Research Institute , No. 9 Yuexing first RD, Hi-tech Park , Nanshan, Shenzhen 518057 , China
| | - Jianquan Zhang
- Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction , Hong Kong University of Science and Technology (HKUST) , Clear Water Bay , Kowloon, Hong Kong , China.,HKUST-Shenzhen Research Institute , No. 9 Yuexing first RD, Hi-tech Park , Nanshan, Shenzhen 518057 , China
| | - Zonglong Zhu
- Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction , Hong Kong University of Science and Technology (HKUST) , Clear Water Bay , Kowloon, Hong Kong , China
| | - Jie Zhang
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices , South China University of Technology , Guangzhou 510640 , P. R. China
| | - Fei Huang
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices , South China University of Technology , Guangzhou 510640 , P. R. China
| | - He Yan
- Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration & Reconstruction , Hong Kong University of Science and Technology (HKUST) , Clear Water Bay , Kowloon, Hong Kong , China.,HKUST-Shenzhen Research Institute , No. 9 Yuexing first RD, Hi-tech Park , Nanshan, Shenzhen 518057 , China.,Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices , South China University of Technology , Guangzhou 510640 , P. R. China
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45
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Thanh Phuc N, Ishizaki A. Control of Excitation Energy Transfer in Condensed Phase Molecular Systems by Floquet Engineering. J Phys Chem Lett 2018; 9:1243-1248. [PMID: 29469574 DOI: 10.1021/acs.jpclett.8b00067] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Excitation energy transfer (EET) is one of the most important processes in both natural and artificial chemical systems including, for example, photosynthetic complexes and organic solar cells. The EET rate, however, is strongly suppressed when there is a large difference in the excitation energy between the donor and acceptor molecules. Here, we demonstrate both analytically and numerically that the EET rate can be greatly enhanced by periodically modulating the excitation energy difference. The enhancement of EET by using this Floquet engineering, in which the system's Hamiltonian is made periodically time-dependent, turns out to be efficient even in the presence of strong fluctuations and dissipations induced by the coupling with a huge number of dynamic degrees of freedom in the surrounding molecular environments. As an effect of the environment on the Floquet engineering of EET, the optimal driving frequency is found to depend on the relative magnitudes of the system and environment's characteristic time scales with an observed frequency shift when moving from the limit of slow environmental fluctuations (inhomogeneous broadening limit) to that of fast fluctuations (homogeneous broadening limit).
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Affiliation(s)
- Nguyen Thanh Phuc
- Department of Theoretical and Computational Molecular Science , Institute for Molecular Science , Okazaki 444-8585 , Japan
- Department of Structural Molecular Science , The Graduate University for Advanced Studies , Okazaki 444-8585 , Japan
| | - Akihito Ishizaki
- Department of Theoretical and Computational Molecular Science , Institute for Molecular Science , Okazaki 444-8585 , Japan
- Department of Structural Molecular Science , The Graduate University for Advanced Studies , Okazaki 444-8585 , Japan
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46
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Yan Y, Song L, Shi Q. Understanding the free energy barrier and multiple timescale dynamics of charge separation in organic photovoltaic cells. J Chem Phys 2018; 148:084109. [DOI: 10.1063/1.5017866] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Yaming Yan
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China and University of Chinese Academy of Sciences, Beijing 100049, China
| | - Linze Song
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China and University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qiang Shi
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China and University of Chinese Academy of Sciences, Beijing 100049, China
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47
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Acocella A, Höfinger S, Haunschmid E, Pop SC, Narumi T, Yasuoka K, Yasui M, Zerbetto F. Structural determinants in the bulk heterojunction. Phys Chem Chem Phys 2018; 20:5708-5720. [PMID: 29410990 DOI: 10.1039/c7cp08435h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Photovoltaics is one of the key areas in renewable energy research with remarkable progress made every year. Here we consider the case of a photoactive material and study its structural composition and the resulting consequences for the fundamental processes driving solar energy conversion. A multiscale approach is used to characterize essential molecular properties of the light-absorbing layer. A selection of bulk-representative pairs of donor/acceptor molecules is extracted from the molecular dynamics simulation of the bulk heterojunction and analyzed at increasing levels of detail. Significantly increased ground state energies together with an array of additional structural characteristics are identified that all point towards an auxiliary role of the material's structural organization in mediating charge-transfer and -separation. Mechanistic studies of the type presented here can provide important insights into fundamental principles governing solar energy conversion in next-generation photovoltaic devices.
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Affiliation(s)
- Angela Acocella
- Department of Chemistry "G. Ciamician", University of Bologna, via F. Selmi 2, 40126 Bologna, Italy.
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48
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Boström EV, Mikkelsen A, Verdozzi C, Perfetto E, Stefanucci G. Charge Separation in Donor-C 60 Complexes with Real-Time Green Functions: The Importance of Nonlocal Correlations. NANO LETTERS 2018; 18:785-792. [PMID: 29266952 DOI: 10.1021/acs.nanolett.7b03995] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We use the nonequilibrium Green function (NEGF) method to perform real-time simulations of the ultrafast electron dynamics of photoexcited donor-C60 complexes modeled by a Pariser-Parr-Pople Hamiltonian. The NEGF results are compared to mean-field Hartree-Fock (HF) calculations to disentangle the role of correlations. Initial benchmarking against numerically highly accurate time-dependent density matrix renormalization group calculations verifies the accuracy of NEGF. We then find that charge-transfer (CT) excitons partially decay into charge separated (CS) states if dynamical nonlocal correlation corrections are included. This CS process occurs in ∼10 fs after photoexcitation. In contrast, the probability of exciton recombination is almost 100% in HF simulations. These results are largely unaffected by nuclear vibrations; the latter become however essential whenever level misalignment hinders the CT process. The robust nature of our findings indicates that ultrafast CS driven by correlation-induced decoherence may occur in many organic nanoscale systems, but it will only be correctly predicted by theoretical treatments that include time-nonlocal correlations.
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Affiliation(s)
- Emil Viñas Boström
- Lund University , Department of Physics and European Theoretical Spectroscopy Facility (ETSF), P.O. Box 118, 221 00 Lund, Sweden
| | - Anders Mikkelsen
- Lund University , Department of Physics and NanoLund, P.O. Box 118, 221 00 Lund, Sweden
| | - Claudio Verdozzi
- Lund University , Department of Physics and European Theoretical Spectroscopy Facility (ETSF), P.O. Box 118, 221 00 Lund, Sweden
| | - Enrico Perfetto
- CNR-ISM , Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma 1, Via Salaria Km 29.3, I-00016 Monterotondo Scalo, Italy
- Dipartimento di Fisica and European Theoretical Spectroscopy Facility (ETSF), Università di Roma Tor Vergata , Via della Ricerca Scientifica 1, 00133 Rome, Italy
| | - Gianluca Stefanucci
- Dipartimento di Fisica and European Theoretical Spectroscopy Facility (ETSF), Università di Roma Tor Vergata , Via della Ricerca Scientifica 1, 00133 Rome, Italy
- INFN, Sezione di Roma Tor Vergata , Via della Ricerca Scientifica 1, 00133 Rome, Italy
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49
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Few S, Chia C, Teo D, Kirkpatrick J, Nelson J. The impact of chemical structure and molecular packing on the electronic polarisation of fullerene arrays. Phys Chem Chem Phys 2018; 19:18709-18720. [PMID: 28696470 DOI: 10.1039/c7cp00317j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electronic polarisation contributes to the electronic landscape as seen by separating charges in organic materials. The nature of electronic polarisation depends on the polarisability, density, and arrangement of polarisable molecules. In this paper, we introduce a microscopic, coarse-grained model in which we treat each molecule as a polarisable site, and use an array of such polarisable dipoles to calculate the electric field and associated energy of any arrangement of charges in the medium. The model incorporates chemical structure via the molecular polarisability and molecular packing patterns via the structure of the array. We use this model to calculate energies of charge pairs undergoing separation in finite fullerene lattices of different chemical and crystal structures. The effective dielectric constants that we estimate from this approach are in good quantitative agreement with those measured experimentally in C60 and phenyl-C61-butyric acid methyl ester (PCBM) films, but we find significant differences in dielectric constant depending on packing and on direction of separation, which we rationalise in terms of density of polarisable fullerene cages in regions of high field. In general, we find lattices containing molecules of more isotropic polarisability tensors exhibit higher dielectric constants. By exploring several model systems we conclude that differences in molecular polarisability (and therefore, chemical structure) appear to be less important than differences in molecular packing and separation direction in determining the energetic landscape for charge separation. We note that the results are relevant for finite lattices, but not necessarily for infinite systems. We propose that the model could be used to design molecular systems for effective electronic screening.
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Affiliation(s)
- Sheridan Few
- Centre for Plastic Electronics, Department of Physics, Imperial College London, London SW7 2AZ, UK.
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50
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Steyrleuthner R, Zhang Y, Zhang L, Kraffert F, Cherniawski BP, Bittl R, Briseno AL, Bredas JL, Behrends J. Impact of morphology on polaron delocalization in a semicrystalline conjugated polymer. Phys Chem Chem Phys 2018; 19:3627-3639. [PMID: 28094360 DOI: 10.1039/c6cp07485e] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We investigate the delocalization of holes in the semicrystalline conjugated polymer poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (PBTTT) by directly measuring the hyperfine coupling between photogenerated polarons and bound nuclear spins using electron nuclear double resonance spectroscopy. An extrapolation of the corresponding oligomer spectra reveals that charges tend to delocalize over 4.0-4.8 nm with delocalization strongly dependent on molecular order and crystallinity of the PBTTT polymer thin films. Density functional theory calculations of hyperfine couplings confirm that long-range corrected functionals appropriately describe the change in coupling strength with increasing oligomer size and agree well with the experimentally measured polymer limit. Our discussion presents general guidelines illustrating the various pitfalls and opportunities when deducing polaron localization lengths from hyperfine coupling spectra of conjugated polymers.
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Affiliation(s)
- Robert Steyrleuthner
- Freie Universität Berlin, Berlin Joint EPR Lab, Institut für Experimentalphysik, Berlin, Germany.
| | - Yuexing Zhang
- King Abdullah University of Science & Technology, Solar & Photovoltaics Engineering Research Center, Thuwal 23955-6900, Saudi Arabia and Department of Chemistry, Hubei University, Wuhan 430062, China
| | - Lei Zhang
- Department of Polymer Science and Engineering, Conte Research Center, University of Massachusetts, 120 Governors Drive, Amherst, MA 01003, USA
| | - Felix Kraffert
- Freie Universität Berlin, Berlin Joint EPR Lab, Institut für Experimentalphysik, Berlin, Germany.
| | - Benjamin P Cherniawski
- Department of Polymer Science and Engineering, Conte Research Center, University of Massachusetts, 120 Governors Drive, Amherst, MA 01003, USA
| | - Robert Bittl
- Freie Universität Berlin, Berlin Joint EPR Lab, Institut für Experimentalphysik, Berlin, Germany.
| | - Alejandro L Briseno
- Department of Polymer Science and Engineering, Conte Research Center, University of Massachusetts, 120 Governors Drive, Amherst, MA 01003, USA
| | - Jean-Luc Bredas
- King Abdullah University of Science & Technology, Solar & Photovoltaics Engineering Research Center, Thuwal 23955-6900, Saudi Arabia
| | - Jan Behrends
- Freie Universität Berlin, Berlin Joint EPR Lab, Institut für Experimentalphysik, Berlin, Germany.
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