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Huang M, Hu T, Han G, Li C, Zhu L, Zhou J, Xie Z, Sun Y, Yi Y. Toward Quantifying the Relation between Exciton Binding Energies and Molecular Packing. J Phys Chem Lett 2022; 13:11065-11070. [PMID: 36416780 DOI: 10.1021/acs.jpclett.2c03043] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Reducing the exciton binding energy Eb of organic photoactive materials is critical to minimize the energy loss and improve the photovoltaic efficiency of organic solar cells. However, the relation between the Eb and molecular packing is not well understood. Herein, the Eb in the crystals of a series of A-D-A type nonfullerene acceptors with different lengths of alkyl side chains has been examined by self-consistent quantum mechanics/embedded charge calculations. The variation of molecular packing induced by the different alkyl chains can have an important impact on the polarization effect of charge carriers and thereby the Eb. More interestingly, the Eb values are found to be linearly increased with the ratio of the void fraction vs the packing coefficient of molecular backbones in the solid crystals. Owing to the smallest ratio, a remarkable low Eb of several tens of meV is achieved for the acceptor with an optimal length of alkyl chains.
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Affiliation(s)
- Miaofei Huang
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy Sciences, Beijing 100049, China
| | - Taiping Hu
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
| | - Guangchao Han
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
| | - Chao Li
- School of Chemistry, Beihang University, Beijing 100191, China
| | - Lingyun Zhu
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, China
| | - Jiadong Zhou
- State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, 510640 Guangzhou, China
| | - Zengqi Xie
- State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, 510640 Guangzhou, China
| | - Yanming Sun
- School of Chemistry, Beihang University, Beijing 100191, China
| | - Yuanping Yi
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy Sciences, Beijing 100049, China
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Stadtmüller B, Emmerich S, Jungkenn D, Haag N, Rollinger M, Eich S, Maniraj M, Aeschlimann M, Cinchetti M, Mathias S. Strong modification of the transport level alignment in organic materials after optical excitation. Nat Commun 2019; 10:1470. [PMID: 30931921 PMCID: PMC6443800 DOI: 10.1038/s41467-019-09136-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 02/25/2019] [Indexed: 11/20/2022] Open
Abstract
Organic photovoltaic devices operate by absorbing light and generating current. These two processes are governed by the optical and transport properties of the organic semiconductor. Despite their common microscopic origin-the electronic structure-disclosing their dynamical interplay is far from trivial. Here we address this issue by time-resolved photoemission to directly investigate the correlation between the optical and transport response in organic materials. We reveal that optical generation of non-interacting excitons in a fullerene film results in a substantial redistribution of all transport levels (within 0.4 eV) of the non-excited molecules. As all observed dynamics evolve on identical timescales, we conclude that optical and transport properties are completely interlinked. This finding paves the way for developing novel concepts for transport level engineering on ultrafast time scales that could lead to novel functional optoelectronic devices.
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Affiliation(s)
- Benjamin Stadtmüller
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany.
- Graduate School of Excellence Materials Science in Mainz, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany.
| | - Sebastian Emmerich
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
- Graduate School of Excellence Materials Science in Mainz, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Dominik Jungkenn
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Norman Haag
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Markus Rollinger
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Steffen Eich
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Mahalingam Maniraj
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Martin Aeschlimann
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663, Kaiserslautern, Germany
| | - Mirko Cinchetti
- Experimentelle Physik VI, Technische Universität Dortmund, 44221, Dortmund, Germany
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077, Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), Georg-August-Universität Göttingen, 37077, Göttingen, Germany
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Sami S, Haase PAB, Alessandri R, Broer R, Havenith RWA. Can the Dielectric Constant of Fullerene Derivatives Be Enhanced by Side-Chain Manipulation? A Predictive First-Principles Computational Study. J Phys Chem A 2018; 122:3919-3926. [PMID: 29561616 PMCID: PMC5911807 DOI: 10.1021/acs.jpca.8b01348] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
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The
low efficiency of organic photovoltaic (OPV) devices has often
been attributed to the strong Coulombic interactions between the electron
and hole, impeding the charge separation process. Recently, it has
been argued that by increasing the dielectric constant of materials
used in OPVs, this strong interaction could be screened. In this work,
we report the application of periodic density functional theory together
with the coupled perturbed Kohn–Sham method to calculate the
electronic contribution to the dielectric constant for fullerene C60 derivatives, a ubiquitous class of molecules in the field
of OPVs. The results show good agreement with experimental data when
available and also reveal an important undesirable outcome when manipulating
the side chain to maximize the static dielectric constant: in all
cases, the electronic contribution to the dielectric constant decreases
as the side chain increases in size. This information should encourage
both theoreticians and experimentalists to further investigate the
relevance of contributions to the dielectric constant from slower
processes like vibrations and dipolar reorientations for facilitating
the charge separation, because electronically, enlarging the side
chain of conventional fullerene derivatives only lowers the dielectric
constant, and consequently, their electronic dielectric constant is
upper bound by the one of C60.
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Affiliation(s)
| | | | | | | | - Remco W A Havenith
- Department of Inorganic and Physical Chemistry , Ghent University , Krijgslaan 281-(S3) , B-9000 Ghent , Belgium
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