1
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Hubenko K, Kusber A, Naumann M, Büchner B, Knupfer M. Evolution of the pentacene exciton band width in pentacene-tetracene blends. J Chem Phys 2024; 160:144708. [PMID: 38597316 DOI: 10.1063/5.0188846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 03/25/2024] [Indexed: 04/11/2024] Open
Abstract
Pentacene is one of the most investigated organic semiconductors. It is well known that the motion of excitons in pentacene and other organic semiconductors is determined by inter-molecular exciton coupling based on charge-transfer processes. In the present study, we demonstrate the impact of the admixture of tetracene, which has a larger band gap and interrupts the pentacene-pentacene interaction, on the exciton behavior in pentacene. Using a combination of optical absorption and electron energy-loss spectroscopy, we show that both the Davydov splitting and the exciton band width in pentacene strongly decrease with increasing tetracene concentration, while the decrease of the exciton band width is substantially larger.
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Affiliation(s)
- Kateryna Hubenko
- Leibniz Institute for Solid State and Materials Research, Helmholtz Str. 20, D-01069 Dresden, Germany
- Institute for Scintillation Materials National Academy of Sciences of Ukraine, 60 Nauky ave., 61072 Kharkiv, Ukraine
| | - Anncharlott Kusber
- Leibniz Institute for Solid State and Materials Research, Helmholtz Str. 20, D-01069 Dresden, Germany
| | - Marco Naumann
- Leibniz Institute for Solid State and Materials Research, Helmholtz Str. 20, D-01069 Dresden, Germany
| | - Bernd Büchner
- Leibniz Institute for Solid State and Materials Research, Helmholtz Str. 20, D-01069 Dresden, Germany
| | - Martin Knupfer
- Leibniz Institute for Solid State and Materials Research, Helmholtz Str. 20, D-01069 Dresden, Germany
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2
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Sivanesan V, Broch K, Tegeder P. Excited States Dynamics at Pentacene/Perfluoropentacene Interfaces: A Femtosecond Time-Resolved Second Harmonic Generation Study. Chemphyschem 2024; 25:e202300904. [PMID: 38305504 DOI: 10.1002/cphc.202300904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 01/31/2024] [Accepted: 01/31/2024] [Indexed: 02/03/2024]
Abstract
Understanding the dynamics of excited states after optical excitation at donor-acceptor (D/A) interfaces is of paramount importance for improving the efficiency and performance of optoelectronic devices. Here, we studied the ultrafast excited state dynamics after optical excitation at interfaces between the electron donor (D) pentacene (PEN) and the electron acceptor (A) perfuoropentacene (PFP) as well as within the single compounds (PEN and PFP) using femtosecond (fs) time-resolved second harmonic generation (SHG). In the single compounds singlet fission is observed on a time scale of around 200 fs. In the bilayer systems a huge SHG intensity rise is observed due to the creation of charge transfer states at the interface and accordingly to formation of a local electric field within tens of picoseconds. The local electric field and therefore the SHG signal intensity from the interface of PEN/PFP bilayer is much more intense compared to the PFP/PEN system because the PFP and PEN intermixing at the PEN/PFP interface is higher. Accordingly a population of defect states on a time scale of 55±12 ps has been proposed for PEN/PFP. Our study provides important insights into D/A charge transfer properties, which is needed for the understanding of the interfacial photophysics of pentacene-based organic compounds.
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Affiliation(s)
- Vipilan Sivanesan
- Physikalisch-Chemisches Institut, Universität Heidelberg, 69120, Heidelberg, Germany
| | - Katharina Broch
- Institut für Angewandte Physik, Universität Tübingen, 72076, Tübingen, Germany
| | - Petra Tegeder
- Physikalisch-Chemisches Institut, Universität Heidelberg, 69120, Heidelberg, Germany
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3
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Wagner T, Antczak G, Ghanbari E, Navarro-Quezada A, Györök M, Volokitina A, Marschner F, Zeppenfeld P. Standard deviation of microscopy images used as indicator for growth stages. Ultramicroscopy 2022; 233:113427. [PMID: 34990906 DOI: 10.1016/j.ultramic.2021.113427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 10/18/2021] [Accepted: 11/12/2021] [Indexed: 11/29/2022]
Abstract
Photoelectron emission microscopy (PEEM) and low energy electron microscopy (LEEM) can easily distinguish between organic molecules adsorbed in crystallites or in the wetting layers as well as the bare metal substrate due to their different electronic properties. Already before (and during) the condensation of such solid phases (2D islands or 3D crystallites), there is a dilute 2D gas phase. Such a 2D gas phase consists of molecules, which are highly mobile and diffuse across the surface. The individual molecules are too small to be resolved in PEEM/LEEM images. Here, we discuss, how image features below and above the resolution limit of a PEEM/LEEM affect the mean electron yield and its (normalized) standard deviation. We support our findings with two experimental examples: the deposition of cobalt phthalocyanine (CoPc) on Ag(100) and of perfluoro-pentacene on Ag(110). Our results demonstrate, how a spatial and temporal analysis of image series can be used to obtain information about molecular phases, which cannot be directly resolved in microscopy images.
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Affiliation(s)
- Thorsten Wagner
- Johannes Kepler University, Institute of Experimental Physics, Surface Science Division, Altenberger Str. 69, 4040 Linz, Austria.
| | - Grażyna Antczak
- University of Wrocław, Institute of Experimental Physics, Pl. M. Borna 9, 50-204 Wrocław, Poland.
| | - Ebrahim Ghanbari
- Johannes Kepler University, Institute of Experimental Physics, Surface Science Division, Altenberger Str. 69, 4040 Linz, Austria
| | - Andrea Navarro-Quezada
- Johannes Kepler University, Institute of Experimental Physics, Surface Science Division, Altenberger Str. 69, 4040 Linz, Austria; Johannes Kepler University, Institute of Semiconductor and Solid State Physics, Quantum Materials Group, Altenberger Str. 69, 4040 Linz, Austria.
| | - Michael Györök
- Johannes Kepler University, Institute of Experimental Physics, Surface Science Division, Altenberger Str. 69, 4040 Linz, Austria.
| | - Anna Volokitina
- Johannes Kepler University, Institute of Experimental Physics, Surface Science Division, Altenberger Str. 69, 4040 Linz, Austria
| | - Felix Marschner
- Johannes Kepler University, Institute of Experimental Physics, Surface Science Division, Altenberger Str. 69, 4040 Linz, Austria
| | - Peter Zeppenfeld
- Johannes Kepler University, Institute of Experimental Physics, Surface Science Division, Altenberger Str. 69, 4040 Linz, Austria.
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4
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Günder D, Valencia AM, Guerrini M, Breuer T, Cocchi C, Witte G. Polarization Resolved Optical Excitation of Charge-Transfer Excitons in PEN:PFP Cocrystalline Films: Limits of Nonperiodic Modeling. J Phys Chem Lett 2021; 12:9899-9905. [PMID: 34610238 DOI: 10.1021/acs.jpclett.1c02761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Charge-transfer excitons (CTXs) at organic donor/acceptor interfaces are considered important intermediates for charge separation in photovoltaic devices. Crystalline model systems provide microscopic insights into the nature of such states as they enable microscopic structure-property investigations. Here, we use angular-resolved UV/vis absorption spectroscopy to characterize the CTXs of crystalline pentacene:perfluoro-pentacene (PEN:PFP) films allowing determination of the polarization of this state. This analysis is complemented by first-principles many-body calculations, performed on the three-dimensional PEN:PFP cocrystal, which confirm that the lowest-energy excitation is a CTX. Analogous simulations performed on bimolecular clusters are unable to reproduce this state. We ascribe this failure to the lack of long-range interactions and wave function periodicity in these cluster calculations, which appear to remain a valid tool for modeling properties of organic materials ruled by local intermolecular couplings.
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Affiliation(s)
- Darius Günder
- Philipps-Universität Marburg, Molekulare Festkörperphysik, 35032 Marburg, Germany
| | - Ana M Valencia
- Carl von Ossietzky Universität Oldenburg, Institute of Physics, Carl-von-Ossietzky-Straße 9, 26129 Oldenburg, Germany
| | - Michele Guerrini
- Carl von Ossietzky Universität Oldenburg, Institute of Physics, Carl-von-Ossietzky-Straße 9, 26129 Oldenburg, Germany
| | - Tobias Breuer
- Philipps-Universität Marburg, Molekulare Festkörperphysik, 35032 Marburg, Germany
| | - Caterina Cocchi
- Carl von Ossietzky Universität Oldenburg, Institute of Physics, Carl-von-Ossietzky-Straße 9, 26129 Oldenburg, Germany
- Humboldt-Universität zu Berlin, Physics Department and IRIS Adlershof, Zum Großen Windkanal 2, 12489 Berlin, Germany
| | - Gregor Witte
- Philipps-Universität Marburg, Molekulare Festkörperphysik, 35032 Marburg, Germany
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5
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Wang Q, Yang J, Franco-Cañellas A, Bürker C, Niederhausen J, Dombrowski P, Widdascheck F, Breuer T, Witte G, Gerlach A, Duhm S, Schreiber F. Pentacene/perfluoropentacene bilayers on Au(111) and Cu(111): impact of organic-metal coupling strength on molecular structure formation. NANOSCALE ADVANCES 2021; 3:2598-2606. [PMID: 36134152 PMCID: PMC9419101 DOI: 10.1039/d1na00040c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Accepted: 03/08/2021] [Indexed: 05/12/2023]
Abstract
As crucial element in organic opto-electronic devices, heterostructures are of pivotal importance. In this context, a comprehensive study of the properties on a simplified model system of a donor-acceptor (D-A) bilayer structure is presented, using ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED) and normal-incidence X-ray standing wave (NIXSW) measurements. Pentacene (PEN) as donor and perfluoropentacene (PFP) as acceptor material are chosen to produce bilayer structures on Au(111) and Cu(111) by sequential monolayer deposition of the two materials. By comparing the adsorption behavior of PEN/PFP bilayers on such weakly and strongly interacting substrates, it is found that: (i) the adsorption distance of the first layer (PEN or PFP) indicates physisorption on Au(111), (ii) the characteristics of the bilayer structure on Au(111) are (almost) independent of the deposition sequence, and hence, (iii) in both cases a mixed bilayer is formed on the Au substrate. This is in striking contrast to PFP/PEN bilayers on Cu(111), where strong chemisorption pins PEN molecules to the metal surface and no intermixing is induced by subsequent PFP deposition. The results illustrate the strong tendency of PEN and PFP molecules to mix, which has important implications for the fabrication of PEN/PFP heterojunctions.
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Affiliation(s)
- Qi Wang
- Institut für Angewandte Physik, Universität Tübingen 72076 Tübingen Germany
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices and Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University Suzhou 215123 People's Republic of China
| | - Jiacheng Yang
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices and Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University Suzhou 215123 People's Republic of China
| | | | - Christoph Bürker
- Institut für Angewandte Physik, Universität Tübingen 72076 Tübingen Germany
| | - Jens Niederhausen
- Helmholtz Zentrum Berlin für Materialien und Energie GmbH 14109 Berlin Germany
| | - Pierre Dombrowski
- Fachbereich Physik, Philipps-Universität Marburg 35032 Marburg Germany
| | - Felix Widdascheck
- Fachbereich Physik, Philipps-Universität Marburg 35032 Marburg Germany
| | - Tobias Breuer
- Fachbereich Physik, Philipps-Universität Marburg 35032 Marburg Germany
| | - Gregor Witte
- Fachbereich Physik, Philipps-Universität Marburg 35032 Marburg Germany
| | - Alexander Gerlach
- Institut für Angewandte Physik, Universität Tübingen 72076 Tübingen Germany
| | - Steffen Duhm
- Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices and Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University Suzhou 215123 People's Republic of China
| | - Frank Schreiber
- Institut für Angewandte Physik, Universität Tübingen 72076 Tübingen Germany
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6
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Abstract
Singlet fission (SF) is a photophysical downconversion pathway, in which a singlet excitation transforms into two triplet excited states. As such, it constitutes an exciton multiplication generation process, which is currently at the focal point for future integration into solar energy conversion devices. Beyond this, various other exciting applications were proposed, including quantum cryptography or organic light emitting diodes. Also, the mechanistic understanding evolved rapidly during the last year. Unfortunately, the number of suitable SF-chromophores is still limited. This is per se problematic, considering the wide range of envisaged applicability. With that in mind, we emphasize uncommon SF-scaffolds and outline requirements as well as strategies to expand the chromophore pool of SF-materials.
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Affiliation(s)
- Tobias Ullrich
- Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Department für Chemie und Pharmazie, Egerlandstr. 1-3, 91058 Erlangen, Germany.
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7
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Wei YC, Shen SW, Wu CH, Ho SY, Zhang Z, Wu CI, Chou PT. Through-Space Exciton Delocalization in Segregated HJ-Crystalline Molecular Aggregates. J Phys Chem A 2021; 125:943-953. [DOI: 10.1021/acs.jpca.0c09075] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yu-Chen Wei
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, ROC
| | - Shin-Wei Shen
- Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, 10617 Taiwan, ROC
| | - Cheng-Ham Wu
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, ROC
| | - Ssu-Yu Ho
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, ROC
| | - Zhiyun Zhang
- Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology, Shanghai 200237, P. R. China
| | - Chih-I Wu
- Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, 10617 Taiwan, ROC
| | - Pi-Tai Chou
- Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, ROC
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8
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Amsterdam SH, LaMountain T, Stanev TK, Sangwan VK, López-Arteaga R, Padgaonkar S, Watanabe K, Taniguchi T, Weiss EA, Marks TJ, Hersam MC, Stern NP. Tailoring the Optical Response of Pentacene Thin Films via Templated Growth on Hexagonal Boron Nitride. J Phys Chem Lett 2021; 12:26-31. [PMID: 33296212 DOI: 10.1021/acs.jpclett.0c03132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The optoelectronic properties of organic thin films are strongly dependent on their molecular orientation and packing, which in turn is sensitive to the underlying substrate. Hexagonal boron nitride (hBN) and other van der Waals (vdW) materials are known to template different organic thin film growth modalities from conventional inorganic substrates such as SiO2. Here, the morphology and temperature-dependent optical properties of pentacene films grown on hBN are reported. Pentacene deposited on hBN forms large-grain films with a molecular π-face-on orientation unlike the dendritic edge-on thin-film phase on SiO2. Pentacene/hBN films exhibit a 40 meV lower free exciton emission than pentacene/SiO2 and an unconventional emission energy temperature dependence. Time-resolved photoluminescence (PL) decay measurements show a long-lived signal in the π-face-on phase related to delayed emission from triplet-triplet fusion. This work demonstrates that growth on vdW materials provides a pathway for controlling optoelectronic functionality in molecular thin films.
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Affiliation(s)
- Samuel H Amsterdam
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Trevor LaMountain
- Applied Physics Program, Northwestern University, Evanston, Illinois 60208, United States
| | - Teodor K Stanev
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, United States
| | - Vinod K Sangwan
- Department of Materials Science and Engineering and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Rafael López-Arteaga
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Suyog Padgaonkar
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Emily A Weiss
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
- Applied Physics Program, 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
| | - 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
| | - Mark C Hersam
- Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
- Applied Physics Program, 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 Engineering and Computer Science and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States
| | - Nathaniel P Stern
- Applied Physics Program, Northwestern University, Evanston, Illinois 60208, United States
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, United States
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9
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Bossanyi DG, Matthiesen M, Wang S, Smith JA, Kilbride RC, Shipp JD, Chekulaev D, Holland E, Anthony JE, Zaumseil J, Musser AJ, Clark J. Emissive spin-0 triplet-pairs are a direct product of triplet-triplet annihilation in pentacene single crystals and anthradithiophene films. Nat Chem 2020; 13:163-171. [PMID: 33288892 DOI: 10.1038/s41557-020-00593-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 10/27/2020] [Indexed: 02/01/2023]
Abstract
Singlet fission and triplet-triplet annihilation represent two highly promising ways of increasing the efficiency of photovoltaic devices. Both processes are believed to be mediated by a biexcitonic triplet-pair state, 1(TT). Recently however, there has been debate over the role of 1(TT) in triplet-triplet annihilation. Here we use intensity-dependent, low-temperature photoluminescence measurements, combined with kinetic modelling, to show that distinct 1(TT) emission arises directly from triplet-triplet annihilation in high-quality pentacene single crystals and anthradithiophene (diF-TES-ADT) thin films. This work demonstrates that a real, emissive triplet-pair state acts as an intermediate in both singlet fission and triplet-triplet annihilation and that this is true for both endo- and exothermic singlet fission materials.
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Affiliation(s)
- David G Bossanyi
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, UK.
| | - Maik Matthiesen
- Institute for Physical Chemistry, Heidelberg University, Heidelberg, Germany
| | - Shuangqing Wang
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, UK
| | - Joel A Smith
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, UK
| | - Rachel C Kilbride
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, UK
| | - James D Shipp
- Department of Chemistry, The University of Sheffield, Sheffield, UK
| | | | - Emma Holland
- Department of Chemistry, University of Kentucky, Lexington, KY, USA
| | - John E Anthony
- Department of Chemistry, University of Kentucky, Lexington, KY, USA
| | - Jana Zaumseil
- Institute for Physical Chemistry, Heidelberg University, Heidelberg, Germany
| | - Andrew J Musser
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, UK.,Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA
| | - Jenny Clark
- Department of Physics and Astronomy, The University of Sheffield, Sheffield, UK.
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10
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Hammer S, Zeiser C, Deutsch M, Engels B, Broch K, Pflaum J. Spatial Anisotropy of Charge Transfer at Perfluoropentacene-Pentacene (001) Single-Crystal Interfaces and its Relevance for Thin Film Devices. ACS APPLIED MATERIALS & INTERFACES 2020; 12:53547-53556. [PMID: 33167608 DOI: 10.1021/acsami.0c17152] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Archetypal donor-acceptor (D-A) interfaces composed of perfluoropentacene (PFP) and pentacene (PEN) are examined for charge transfer (CT) state formation and energetics as a function of their respective molecular configuration. To exclude morphological interference, our structural as well as highly sensitive differential reflectance spectroscopy studies were carried out on PFP thin films epitaxially grown on PEN(001) single-crystal facets. Whereas the experimental data supported by complementary theoretical calculations confirm the formation of a strong CT state in the case of a cofacial PFP-PEN stacking, CT formation is energetically less favorable and thus absent for the corresponding head-to-tail configuration as disclosed for the first time. In view of technological implementations, the knowledge gained on the single-crystal references is transferred to thin-film diodes composed of either stacked PFP/PEN bilayers or mixed PFP:PEN heterojunction interfaces. As demonstrated, their electronic and electroluminescent behavior can be consistently described by the absence or presence of interfacial CT states. Thus, our results hint at the thorough design of D-A interfaces to achieve the highest device performances.
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Affiliation(s)
- Sebastian Hammer
- Experimental Physics VI, Julius Maximilians University Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Clemens Zeiser
- Institute for Applied Physics, Eberhard Karls University Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Marian Deutsch
- Institute for Physical and Theoretical Chemistry, Julius Maximilians University Würzburg, Emil-Fischer-Straße 42, 97074 Würzburg, Germany
| | - Bernd Engels
- Institute for Physical and Theoretical Chemistry, Julius Maximilians University Würzburg, Emil-Fischer-Straße 42, 97074 Würzburg, Germany
| | - Katharina Broch
- Institute for Applied Physics, Eberhard Karls University Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Jens Pflaum
- Experimental Physics VI, Julius Maximilians University Würzburg, Am Hubland, 97074 Würzburg, Germany
- Bavarian Center for Applied Energy Research, Magdalene-Schoch-Straße 3, 97074 Würzburg, Germany
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11
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Huang YE, Wang XZ, Hu P, Qi XH, Huang XY, Kloc C, Wu X, Du KZ. Single-photon upconversion in 6-pentaceneone crystal from bulk to ultrathin flakes. NANOSCALE 2020; 12:6227-6232. [PMID: 32129396 DOI: 10.1039/d0nr00306a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Phonon-assisted single-photon upconversion, which was not previously reported in organic materials, has been demonstrated in the 6-pentaceneone crystal through the linear pumping power dependent anti-Stokes photoluminescence (ASPL), nanoseconds PL lifetime and quenched ASPL at low temperature. Furthermore, the 6-pentaceneone crystal can be mechanically exfoliated to ultrathin flakes and it exhibits thickness-dependent photoluminescence.
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Affiliation(s)
- Yue-E Huang
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, 32 Shangsan Road, Fuzhou 350007, China.
| | - Xing-Zhi Wang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore
| | - Peng Hu
- School of Physics, Northwest University, Xi'an 710069, China
| | - Xing-Hui Qi
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China
| | - Xiao-Ying Huang
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China
| | - Christian Kloc
- School of Materials Science & Engineering, Nanyang Technological University, 639798, Singapore
| | - Xiaohui Wu
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, 32 Shangsan Road, Fuzhou 350007, China.
| | - Ke-Zhao Du
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, 32 Shangsan Road, Fuzhou 350007, China.
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12
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Sarkar A, Pyne DK, Biswas T, Das R, Kar GK, Halder A. Tunable luminescence of a synthesized furophenanthraquinone derivative: interactions with different solvents. LUMINESCENCE 2020; 35:709-720. [PMID: 32000298 DOI: 10.1002/bio.3776] [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: 07/16/2019] [Revised: 11/21/2019] [Accepted: 01/02/2020] [Indexed: 11/07/2022]
Abstract
The synthesis is described of a luminescent furophenanthraquinone derivative, 9-methoxyphenanthro[4,3-b]furan-4,5-dione (MPFD). The biological importance of tetracyclic furophenanthraquinones was considered and the tunable luminescence of MPFD in different solvents was studied to explore the nature of the specific interactions between MPFD and solvents. Observation of dual emission bands and identical nature of the fluorescence excitation spectra of MPFD monitored at the emission wavelength in polar solvents indicated the formation of two different types of species in the excited state, probably due to proton transfer from the solvent to MPFD. Luminescence intensity due to anionic species was found to be increased and the corresponding peak was red shifted with increase in the proton-donating ability of the solvents, acting as an acid with respect to MPFD. Availability of more acidic protons in the solvent facilitated this phenomenon occurring in the excited state. MPFD also interacted with halogen-containing solvents by forming electron donor-acceptor charge transfer (CT) complexes. This CT complex formation was dependent on the number of chlorine atoms; the position of the corresponding luminescence band varied with the polarity of the solvent. Extent of the CT increased with increase in the number of chlorine atoms in the dichloro, trichloro and tetrachloro solvents, whereas the luminescence peak due to the CT complex was found to be blue shifted with decrease in solvent polarity. Interaction of the synthesized bioactive MPFD with different solvents deserves biological importance as proton transfer and CT play pivotal roles in biology.
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Affiliation(s)
- Aparna Sarkar
- Department of Chemistry, Presidency University, 86/1 College Street, Kolkata, India
| | - Dinesh Kumar Pyne
- Department of Chemistry, Presidency University, 86/1 College Street, Kolkata, India
| | - Tuyan Biswas
- Department of Chemistry, Presidency University, 86/1 College Street, Kolkata, India
| | - Rumpa Das
- Department of Chemistry, Presidency University, 86/1 College Street, Kolkata, India
| | - Gandhi K Kar
- Department of Chemistry, Presidency University, 86/1 College Street, Kolkata, India
| | - Arnab Halder
- Department of Chemistry, Presidency University, 86/1 College Street, Kolkata, India
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13
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Kim VO, Broch K, Belova V, Chen YS, Gerlach A, Schreiber F, Tamura H, Della Valle RG, D'Avino G, Salzmann I, Beljonne D, Rao A, Friend R. Singlet exciton fission via an intermolecular charge transfer state in coevaporated pentacene-perfluoropentacene thin films. J Chem Phys 2019; 151:164706. [PMID: 31675857 DOI: 10.1063/1.5130400] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Singlet exciton fission is a spin-allowed process in organic semiconductors by which one absorbed photon generates two triplet excitons. Theory predicts that singlet fission is mediated by intermolecular charge-transfer states in solid-state materials with appropriate singlet-triplet energy spacing, but direct evidence for the involvement of such states in the process has not been provided yet. Here, we report on the observation of subpicosecond singlet fission in mixed films of pentacene and perfluoropentacene. By combining transient spectroscopy measurements to nonadiabatic quantum-dynamics simulations, we show that direct excitation in the charge-transfer absorption band of the mixed films leads to the formation of triplet excitons, unambiguously proving that they act as intermediate states in the fission process.
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Affiliation(s)
- Vincent O Kim
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Katharina Broch
- Fritz Haber Institute of the Max Planck Society, Department of Physical Chemistry, Faradayweg, 4-614195 Berlin, Germany
| | - Valentina Belova
- Eberhard-Karls Universität Tübingen, Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Y S Chen
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Alexander Gerlach
- Eberhard-Karls Universität Tübingen, Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Frank Schreiber
- Eberhard-Karls Universität Tübingen, Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076 Tübingen, Germany
| | - Hiroyuki Tamura
- Department of Chemical System Engineering, The University of Tokyo, Tokyo 113-8656, Japan
| | - Raffaele Guido Della Valle
- Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna and INSTM-UdR Bologna, Viale Risorgimento 4, 40136 Bologna, Italy
| | - Gabriele D'Avino
- Institut Néel, CNRS and Grenoble Alpes University, F-38042 Grenoble, France
| | - Ingo Salzmann
- Department of Physics, Department of Chemistry and Biochemistry, Centre for Research in Molecular Modeling (CERMM), Centre for NanoScience Research (CeNSR), Concordia University, 7141 Sherbrooke St. West, Montreal, Quebec H4B 1R6, Canada
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, Department of Chemistry, Université de Mons, Place du Parc 20, 7000 Mons, Belgium
| | - Akshay Rao
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Richard Friend
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
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14
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Abstract
Entanglement of states is one of the most surprising and counterintuitive consequences of quantum mechanics, with potent applications in cryptography and computing. In organic semiconductor materials, one particularly significant manifestation is the spin-entangled triplet-pair state, which consists of a pair of localized triplet excitons coupled into an overall spin-0, -1, or -2 configuration. The most widely analyzed of these is the spin-0 pair, denoted 1(TT), which was initially invoked in the 1960s to explain delayed fluorescence in acene films. It is considered an essential gateway state for triplet-triplet annihilation and the reverse process, singlet fission, enabling interconversion between one singlet and two triplet excitons without any change in overall spin. This state has returned to the forefront of organic materials research in recent years, thanks both to its central role in the resurgent field of singlet fission and to its implication in a host of exotic new photophysical behaviors. Here we review the properties of triplet-pair states, from first principles to recent experimental results.
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Affiliation(s)
- Andrew J Musser
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom; ,
| | - Jenny Clark
- Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, United Kingdom; ,
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15
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Döring RC, Rosemann NW, Huttner A, Breuer T, Witte G, Chatterjee S. Charge-transfer processes and carrier dynamics at the pentacene-C 60 interface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:134001. [PMID: 30645985 DOI: 10.1088/1361-648x/aafea7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Heterostructures of pentacene (PEN) and buckminsterfullerene (C60) are frequently attracting scientific interest as a well-defined small-molecule model system for the study of internal interfaces between two organic semiconductors. They are prototypical representatives forming a donor-acceptor combination for studies of fundamental optoelectronic processes in organic photovoltaics. Despite their importance in exciton dissociation, the energetics of their interfacial charge-transfer (CT) states and their microscopic excitation dynamics are not yet clarified and still being discussed. Here, we present steady-state and time-resolved photoluminescence measurements on stacked heterostructures composed of these two materials. All experiments are performed in the visible and near-infrared spectral regions as CT states are expected at energies below the fundamental electronic transitions of the respective bulk materials. A characteristic, interface-specific emission at around 1.13-1.17 eV is found, which we attribute to an interfacial CT state. Its excitation energy dependence reveals the intricate relaxation dynamics of excitons formed in both constituent materials. Moreover, the analysis of the dynamics of the C60 excitons shows that the lifetime of this state is reduced in the presence of an interface with PEN. This quenching is attributed to a long-range interaction, i.e. the relaxation of excitations into the interfacial CT state.
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Affiliation(s)
- Robin C Döring
- Institute of Experimental Physics I, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
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16
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Navarro-Quezada A, Ghanbari E, Wagner T, Zeppenfeld P. Molecular Reorientation during the Initial Growth of Perfluoropentacene on Ag(110). THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2018; 122:12704-12711. [PMID: 29963216 PMCID: PMC6018566 DOI: 10.1021/acs.jpcc.8b00869] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 05/28/2018] [Indexed: 05/09/2023]
Abstract
Perfluoropentacene (PFP) is an organic material that has been widely studied over the last years and has already found applications in organic electronics. However, fundamental physical questions, such as the structural formation and the preferential orientation of the molecules during deposition on metal surfaces, are still not fully understood. In this work, we report on a unique in-plane molecular reorientation during the completion of the first monolayer of PFP on the Ag(110) surface. To characterize the molecular alignment, we have monitored the deposition process in real time using polarization-dependent differential reflectance spectroscopy and reflectance anisotropy spectroscopy. Abrupt changes in the optical signals reveal an intricate sequence of reorientation transitions of the PFP molecules upon monolayer completion and during the formation of the second monolayer, eventually leading to a full alignment of the long molecular axis along the [001] direction of the substrate and an enhanced structural ordering. Scanning tunneling microscopy and low-energy electron diffraction confirm the observed molecular reorientation upon monolayer compression and provide further details on the structural and orientational ordering of the PFP monolayer before and after compression.
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Affiliation(s)
- Andrea Navarro-Quezada
- Institute of Experimental Physics and Institute of Semiconductor and
Solid State Physics, Johannes Kepler University, Altenberger Street 69, 4040 Linz, Austria
- E-mail: (A.N.-Q)
| | - Ebrahim Ghanbari
- Institute of Experimental Physics and Institute of Semiconductor and
Solid State Physics, Johannes Kepler University, Altenberger Street 69, 4040 Linz, Austria
| | - Thorsten Wagner
- Institute of Experimental Physics and Institute of Semiconductor and
Solid State Physics, Johannes Kepler University, Altenberger Street 69, 4040 Linz, Austria
- E-mail: (T.W.)
| | - Peter Zeppenfeld
- Institute of Experimental Physics and Institute of Semiconductor and
Solid State Physics, Johannes Kepler University, Altenberger Street 69, 4040 Linz, Austria
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17
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Tempelaar R, Reichman DR. Vibronic exciton theory of singlet fission. I. Linear absorption and the anatomy of the correlated triplet pair state. J Chem Phys 2018; 146:174703. [PMID: 28477613 DOI: 10.1063/1.4982362] [Citation(s) in RCA: 67] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Recent time-resolved spectroscopic experiments have indicated that vibronic coupling plays a vital role in facilitating the process of singlet fission. In this work, which forms the first article of a series, we set out to unravel the mechanisms underlying singlet fission through a vibronic exciton theory. We formulate a model in which both electronic and vibrational degrees of freedom are treated microscopically and non-perturbatively. Using pentacene as a prototypical material for singlet fission, we subject our theory to comparison with measurements on polarization-resolved absorption of single crystals, and employ our model to characterize the excited states underlying the absorption band. Special attention is given to the convergence of photophysical observables with respect to the basis size employed, through which we determine the optimal basis for more expensive calculations to be presented in subsequent work. We furthermore evaluate the energetic separation between the optically prepared singlet excited state and the correlated triplet pair state, as well as provide a real-space characterization of the latter, both of which are of key importance in the discussion of fission dynamics. We discuss our results in the context of recent experimental studies.
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Affiliation(s)
- Roel Tempelaar
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA
| | - David R Reichman
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA
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18
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Hestand NJ, Spano FC. Expanded Theory of H- and J-Molecular Aggregates: The Effects of Vibronic Coupling and Intermolecular Charge Transfer. Chem Rev 2018; 118:7069-7163. [PMID: 29664617 DOI: 10.1021/acs.chemrev.7b00581] [Citation(s) in RCA: 690] [Impact Index Per Article: 115.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The electronic excited states of molecular aggregates and their photophysical signatures have long fascinated spectroscopists and theoreticians alike since the advent of Frenkel exciton theory almost 90 years ago. The influence of molecular packing on basic optical probes like absorption and photoluminescence was originally worked out by Kasha for aggregates dominated by Coulombic intermolecular interactions, eventually leading to the classification of J- and H-aggregates. This review outlines advances made in understanding the relationship between aggregate structure and photophysics when vibronic coupling and intermolecular charge transfer are incorporated. An assortment of packing geometries is considered from the humble molecular dimer to more exotic structures including linear and bent aggregates, two-dimensional herringbone and "HJ" aggregates, and chiral aggregates. The interplay between long-range Coulomb coupling and short-range charge-transfer-mediated coupling strongly depends on the aggregate architecture leading to a wide array of photophysical behaviors.
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Affiliation(s)
- Nicholas J Hestand
- Department of Chemistry , Temple University , Philadelphia , Pennsylvania 19122 , United States
| | - Frank C Spano
- Department of Chemistry , Temple University , Philadelphia , Pennsylvania 19122 , United States
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19
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Rinn A, Breuer T, Wiegand J, Beck M, Hübner J, Döring RC, Oestreich M, Heimbrodt W, Witte G, Chatterjee S. Interfacial Molecular Packing Determines Exciton Dynamics in Molecular Heterostructures: The Case of Pentacene-Perfluoropentacene. ACS APPLIED MATERIALS & INTERFACES 2017; 9:42020-42028. [PMID: 29135216 DOI: 10.1021/acsami.7b11118] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The great majority of electronic and optoelectronic devices depend on interfaces between p-type and n-type semiconductors. Finding matching donor-acceptor systems in molecular semiconductors remains a challenging endeavor because structurally compatible molecules may not necessarily be suitable with respect to their optical and electronic properties, and the large exciton binding energy in these materials may favor bound electron-hole pairs rather than free carriers or charge transfer at an interface. Regardless, interfacial charge-transfer exciton states are commonly considered as an intermediate step to achieve exciton dissociation. The formation efficiency and decay dynamics of such states will strongly depend on the molecular makeup of the interface, especially the relative alignment of donor and acceptor molecules. Structurally well-defined pentacene-perfluoropentacene heterostructures of different molecular orientations are virtually ideal model systems to study the interrelation between molecular packing motifs at the interface and their electronic properties. Comparing the emission dynamics of the heterosystems and the corresponding unitary films enables accurate assignment of every observable emission signal in the heterosystems. These heterosystems feature two characteristic interface-specific luminescence channels at around 1.4 and 1.5 eV that are not observed in the unitary samples. Their emission strength strongly depends on the molecular alignment of the respective donor and acceptor molecules, emphasizing the importance of structural control for device construction.
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Affiliation(s)
- Andre Rinn
- Faculty of Physics & Materials Sciences Centre, Philipps-Universität Marburg , Renthof 5, 35032 Marburg, Germany
| | - Tobias Breuer
- Faculty of Physics & Materials Sciences Centre, Philipps-Universität Marburg , Renthof 5, 35032 Marburg, Germany
| | - Julia Wiegand
- Institut für Festkörperphysik, Leibniz Universität Hannover , Appelstrasse 2, D-30167 Hannover, Germany
| | - Michael Beck
- Institut für Festkörperphysik, Leibniz Universität Hannover , Appelstrasse 2, D-30167 Hannover, Germany
| | - Jens Hübner
- Institut für Festkörperphysik, Leibniz Universität Hannover , Appelstrasse 2, D-30167 Hannover, Germany
| | - Robin C Döring
- Faculty of Physics & Materials Sciences Centre, Philipps-Universität Marburg , Renthof 5, 35032 Marburg, Germany
| | - Michael Oestreich
- Institut für Festkörperphysik, Leibniz Universität Hannover , Appelstrasse 2, D-30167 Hannover, Germany
| | - Wolfram Heimbrodt
- Faculty of Physics & Materials Sciences Centre, Philipps-Universität Marburg , Renthof 5, 35032 Marburg, Germany
| | - Gregor Witte
- Faculty of Physics & Materials Sciences Centre, Philipps-Universität Marburg , Renthof 5, 35032 Marburg, Germany
| | - Sangam Chatterjee
- Faculty of Physics & Materials Sciences Centre, Philipps-Universität Marburg , Renthof 5, 35032 Marburg, Germany
- Institute of Experimental Physics I, Justus-Liebig-University Giessen , Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
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20
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Yong CK, Musser AJ, Bayliss SL, Lukman S, Tamura H, Bubnova O, Hallani RK, Meneau A, Resel R, Maruyama M, Hotta S, Herz LM, Beljonne D, Anthony JE, Clark J, Sirringhaus H. The entangled triplet pair state in acene and heteroacene materials. Nat Commun 2017; 8:15953. [PMID: 28699637 PMCID: PMC5510179 DOI: 10.1038/ncomms15953] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 05/17/2017] [Indexed: 12/18/2022] Open
Abstract
Entanglement of states is one of the most surprising and counter-intuitive consequences of quantum mechanics, with potent applications in cryptography and computing. In organic materials, one particularly significant manifestation is the spin-entangled triplet-pair state, which mediates the spin-conserving fission of one spin-0 singlet exciton into two spin-1 triplet excitons. Despite long theoretical and experimental exploration, the nature of the triplet-pair state and inter-triplet interactions have proved elusive. Here we use a range of organic semiconductors that undergo singlet exciton fission to reveal the photophysical properties of entangled triplet-pair states. We find that the triplet pair is bound with respect to free triplets with an energy that is largely material independent (∼30 meV). During its lifetime, the component triplets behave cooperatively as a singlet and emit light through a Herzberg-Teller-type mechanism, resulting in vibronically structured photoluminescence. In photovoltaic blends, charge transfer can occur from the bound triplet pairs with >100% photon-to-charge conversion efficiency.
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Affiliation(s)
- Chaw Keong Yong
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.,Department of Physics, University of California, Berkeley, California 94720, USA
| | - Andrew J Musser
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.,Department of Physics and Astronomy, The University of Sheffield, Hicks Buildling, Hounsfield Road, Sheffield S3 7RH, UK
| | - Sam L Bayliss
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Steven Lukman
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Hiroyuki Tamura
- Department of Chemical System Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Olga Bubnova
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Rawad K Hallani
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA
| | - Aurélie Meneau
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - Roland Resel
- Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria
| | - Munetaka Maruyama
- Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
| | - Shu Hotta
- Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan
| | - Laura M Herz
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium
| | - John E Anthony
- Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA
| | - Jenny Clark
- Department of Physics and Astronomy, The University of Sheffield, Hicks Buildling, Hounsfield Road, Sheffield S3 7RH, UK
| | - Henning Sirringhaus
- Cavendish Laboratory, Optoelectronics Group, University of Cambridge, Madingley Road, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
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21
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Belova V, Beyer P, Meister E, Linderl T, Halbich MU, Gerhard M, Schmidt S, Zechel T, Meisel T, Generalov AV, Anselmo AS, Scholz R, Konovalov O, Gerlach A, Koch M, Hinderhofer A, Opitz A, Brütting W, Schreiber F. Evidence for Anisotropic Electronic Coupling of Charge Transfer States in Weakly Interacting Organic Semiconductor Mixtures. J Am Chem Soc 2017; 139:8474-8486. [PMID: 28570061 DOI: 10.1021/jacs.7b01622] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We present a comprehensive investigation of the charge-transfer (CT) effect in weakly interacting organic semiconductor mixtures. The donor-acceptor pair diindenoperylene (DIP) and N,N'-bis(2-ethylhexyl)-1,7-dicyanoperylene-3,4/9,10-bis(dicarboxyimide) (PDIR-CN2) has been chosen as a model system. A wide range of experimental methods was used in order to characterize the structural, optical, electronic, and device properties of the intermolecular interactions. By detailed analysis, we demonstrate that the partial CT in this weakly interacting mixture does not have a strong effect on the ground state and does not generate a hybrid orbital. We also find a strong CT transition in light absorption as well as in photo- and electroluminescence. By using different layer sequences and compositions, we are able to distinguish electronic coupling in-plane vs out-of-plane and, thus, characterize the anisotropy of the CT state. Finally, we discuss the impact of CT exciton generation on charge-carrier transport and on the efficiency of photovoltaic devices.
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Affiliation(s)
- Valentina Belova
- Institut für Angewandte Physik, Universität Tübingen , Tübingen 72076, Germany
| | - Paul Beyer
- Department of Physics, Humboldt-Universität zu Berlin , Berlin 10099, Germany
| | - Eduard Meister
- Institute of Physics, Experimental Physics IV, University of Augsburg , Augsburg 86135, Germany
| | - Theresa Linderl
- Institute of Physics, Experimental Physics IV, University of Augsburg , Augsburg 86135, Germany
| | - Marc-Uwe Halbich
- Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg , Marburg 35037, Germany
| | - Marina Gerhard
- Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg , Marburg 35037, Germany
| | - Stefan Schmidt
- Institute of Physics, Experimental Physics IV, University of Augsburg , Augsburg 86135, Germany
| | - Thomas Zechel
- Institute of Physics, Experimental Physics IV, University of Augsburg , Augsburg 86135, Germany
| | - Tino Meisel
- Department of Physics, Humboldt-Universität zu Berlin , Berlin 10099, Germany
| | | | - Ana Sofia Anselmo
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH , Berlin 14109, Germany
| | - Reinhard Scholz
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP), Technische Universität Dresden , Dresden 01062, Germany
| | - Oleg Konovalov
- European Synchrotron Radiation Facility, Grenoble 38000, France
| | - Alexander Gerlach
- Institut für Angewandte Physik, Universität Tübingen , Tübingen 72076, Germany
| | - Martin Koch
- Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg , Marburg 35037, Germany
| | | | - Andreas Opitz
- Department of Physics, Humboldt-Universität zu Berlin , Berlin 10099, Germany
| | - Wolfgang Brütting
- Institute of Physics, Experimental Physics IV, University of Augsburg , Augsburg 86135, Germany
| | - Frank Schreiber
- Institut für Angewandte Physik, Universität Tübingen , Tübingen 72076, Germany
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22
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Tempelaar R, Reichman DR. Vibronic exciton theory of singlet fission. II. Two-dimensional spectroscopic detection of the correlated triplet pair state. J Chem Phys 2017; 146:174704. [DOI: 10.1063/1.4982359] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Roel Tempelaar
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA
| | - David R. Reichman
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, USA
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23
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Bettis Homan S, Sangwan VK, Balla I, Bergeron H, Weiss EA, Hersam MC. Ultrafast Exciton Dissociation and Long-Lived Charge Separation in a Photovoltaic Pentacene-MoS 2 van der Waals Heterojunction. NANO LETTERS 2017; 17:164-169. [PMID: 28073273 DOI: 10.1021/acs.nanolett.6b03704] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
van der Waals heterojunctions between two-dimensional (2D) layered materials and nanomaterials of different dimensions present unique opportunities for gate-tunable optoelectronic devices. Mixed-dimensional p-n heterojunction diodes, such as p-type pentacene (0D) and n-type monolayer MoS2 (2D), are especially interesting for photovoltaic applications where the absorption cross-section and charge transfer processes can be tailored by rational selection from the vast library of organic molecules and 2D materials. Here, we study the kinetics of excited carriers in pentacene-MoS2 p-n type-II heterojunctions by transient absorption spectroscopy. These measurements show that the dissociation of MoS2 excitons occurs by hole transfer to pentacene on the time scale of 6.7 ps. In addition, the charge-separated state lives for 5.1 ns, up to an order of magnitude longer than the recombination lifetimes from previously reported 2D material heterojunctions. By studying the fractional amplitudes of the MoS2 decay processes, the hole transfer yield from MoS2 to pentacene is found to be ∼50%, with the remaining holes undergoing trapping due to surface defects. Overall, the ultrafast charge transfer and long-lived charge-separated state in pentacene-MoS2 p-n heterojunctions suggest significant promise for mixed-dimensional van der Waals heterostructures in photovoltaics, photodetectors, and related optoelectronic technologies.
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Affiliation(s)
- Stephanie Bettis Homan
- Department of Chemistry and ‡Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Vinod K Sangwan
- Department of Chemistry and ‡Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Itamar Balla
- Department of Chemistry and ‡Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Hadallia Bergeron
- Department of Chemistry and ‡Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Emily A Weiss
- Department of Chemistry and ‡Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Mark C Hersam
- Department of Chemistry and ‡Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
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24
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McDonough TJ, Zhang L, Roy SS, Kearns NM, Arnold MS, Zanni MT, Andrew TL. Triplet exciton dissociation and electron extraction in graphene-templated pentacene observed with ultrafast spectroscopy. Phys Chem Chem Phys 2017; 19:4809-4820. [DOI: 10.1039/c6cp06454j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Transient absorption measurements of pentacene, controlling molecular orientation (via graphene templating), fluence, and polarization, provide new evidence for charge generation.
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Affiliation(s)
| | - Lushuai Zhang
- Department of Materials Science and Engineering
- University of Wisconsin–Madison
- Madison
- USA
| | - Susmit Singha Roy
- Department of Materials Science and Engineering
- University of Wisconsin–Madison
- Madison
- USA
| | | | - Michael S. Arnold
- Department of Materials Science and Engineering
- University of Wisconsin–Madison
- Madison
- USA
| | - Martin T. Zanni
- Department of Chemistry
- University of Wisconsin–Madison
- Madison
- USA
| | - Trisha L. Andrew
- Department of Chemistry
- University of Wisconsin–Madison
- Madison
- USA
- Department of Materials Science and Engineering
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25
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Nishidate K, Yoshimoto N, Chantngarm P, Saito H, Hasegawa M. Tuning the work function of graphene with the adsorbed organic molecules: first-principles calculations. Mol Phys 2016. [DOI: 10.1080/00268976.2016.1213437] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Kazume Nishidate
- Department of Electrical and Electronic Engineering, Faculty of Engineering, Iwate University, Morioka, Japan
| | - Noriyuki Yoshimoto
- Department of Materials Science, Faculty of Engineering, Iwate University, Morioka, Japan
| | - Peerasak Chantngarm
- Department of Electronics and Telecommunication Engineering, Faculty of Engineering, Rajamangala University of Technology Krungthep, Thailand
| | | | - Masayuki Hasegawa
- Soft-Path Engineering Research Center, Faculty of Engineering, Iwate University, Morioka, Japan
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Schwarze M, Tress W, Beyer B, Gao F, Scholz R, Poelking C, Ortstein K, Günther AA, Kasemann D, Andrienko D, Leo K. Band structure engineering in organic semiconductors. Science 2016; 352:1446-9. [PMID: 27313043 DOI: 10.1126/science.aaf0590] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 04/13/2016] [Indexed: 01/25/2023]
Abstract
A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials. We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors.
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Affiliation(s)
- Martin Schwarze
- Institut für Angewandte Photophysik, Technische Universität Dresden, 01069 Dresden, Germany
| | - Wolfgang Tress
- Biomolecular and Organic Electronics, IFM, Linköping University, 58183 Linköping, Sweden
| | - Beatrice Beyer
- Fraunhofer Institute for Electron Beam, Plasma Technology and COMEDD, 01109 Dresden, Germany
| | - Feng Gao
- Biomolecular and Organic Electronics, IFM, Linköping University, 58183 Linköping, Sweden
| | - Reinhard Scholz
- Institut für Angewandte Photophysik, Technische Universität Dresden, 01069 Dresden, Germany. Dresden Center for Computational Materials Science, Technische Universität Dresden, 01062 Dresden, Germany
| | - Carl Poelking
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Katrin Ortstein
- Institut für Angewandte Photophysik, Technische Universität Dresden, 01069 Dresden, Germany
| | - Alrun A Günther
- Institut für Angewandte Photophysik, Technische Universität Dresden, 01069 Dresden, Germany
| | - Daniel Kasemann
- Institut für Angewandte Photophysik, Technische Universität Dresden, 01069 Dresden, Germany
| | - Denis Andrienko
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Karl Leo
- Institut für Angewandte Photophysik, Technische Universität Dresden, 01069 Dresden, Germany.
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27
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Organic heterojunctions: Contact-induced molecular reorientation, interface states, and charge re-distribution. Sci Rep 2016; 6:21291. [PMID: 26887445 PMCID: PMC4758050 DOI: 10.1038/srep21291] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 01/21/2016] [Indexed: 11/08/2022] Open
Abstract
We reveal the rather complex interplay of contact-induced re-orientation and interfacial electronic structure - in the presence of Fermi-level pinning - at prototypical molecular heterojunctions comprising copper phthalocyanine (H16CuPc) and its perfluorinated analogue (F16CuPc), by employing ultraviolet photoelectron and X-ray absorption spectroscopy. For both layer sequences, we find that Fermi-level (EF) pinning of the first layer on the conductive polymer substrate modifies the work function encountered by the second layer such that it also becomes EF-pinned, however, at the interface towards the first molecular layer. This results in a charge transfer accompanied by a sheet charge density at the organic/organic interface. While molecules in the bulk of the films exhibit upright orientation, contact formation at the heterojunction results in an interfacial bilayer with lying and co-facial orientation. This interfacial layer is not EF-pinned, but provides for an additional density of states at the interface that is not present in the bulk. With reliable knowledge of the organic heterojunction's electronic structure we can explain the poor performance of these in photovoltaic cells as well as their valuable function as charge generation layer in electronic devices.
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28
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Wang X, Broch K, Schreiber F, Meixner AJ, Zhang D. Revealing nanoscale optical properties and morphology in perfluoropentacene films by confocal and tip-enhanced near-field optical microscopy and spectroscopy. Phys Chem Chem Phys 2016; 18:15919-26. [DOI: 10.1039/c6cp01153e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Combining confocal and high resolution near-field optical microscopy and spectroscopy, we propose a sensitive method for determining the local morphology in organic semiconductor thin films.
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Affiliation(s)
- Xiao Wang
- Institute of Physical and Theoretical Chemistry and LISA+
- University of Tübingen
- 72076 Tübingen
- Germany
| | - Katharina Broch
- Institute of Applied Physics
- University of Tübingen
- 72076 Tübingen
- Germany
- Cavendish Laboratory
| | - Frank Schreiber
- Institute of Applied Physics
- University of Tübingen
- 72076 Tübingen
- Germany
| | - Alfred J. Meixner
- Institute of Physical and Theoretical Chemistry and LISA+
- University of Tübingen
- 72076 Tübingen
- Germany
| | - Dai Zhang
- Institute of Physical and Theoretical Chemistry and LISA+
- University of Tübingen
- 72076 Tübingen
- Germany
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29
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Jo SB, Kim HH, Lee H, Kang B, Lee S, Sim M, Kim M, Lee WH, Cho K. Boosting Photon Harvesting in Organic Solar Cells with Highly Oriented Molecular Crystals via Graphene-Organic Heterointerface. ACS NANO 2015; 9:8206-19. [PMID: 26166186 DOI: 10.1021/acsnano.5b03929] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Photon harvesting in organic solar cells is highly dependent on the anisotropic nature of the optoelectronic properties of photoactive materials. Here, we demonstrate an efficient approach to dramatically enhance photon harvesting in planar heterojunction solar cells by using a graphene-organic heterointerface. A large area, residue-free monolayer graphene is inserted at anode interface to serve as an atomically thin epitaxial template for growing highly orientated pentacene crystals with lying-down orientation. This anisotropic orientation enhances the overall optoelectronic properties, including light absorption, charge carrier lifetime, interfacial energetics, and especially the exciton diffusion length. Spectroscopic and crystallographic analysis reveal that the lying-down orientation persists until a thickness of 110 nm, which, along with increased exciton diffusion length up to nearly 100 nm, allows the device optimum thickness to be doubled to yield significantly enhanced light absorption within the photoactive layers. The resultant photovoltaic performance shows simultaneous increment in Voc, Jsc, and FF, and consequently a 5 times increment in the maximum power conversion efficiency than the equivalent devices without a graphene layer. The present findings indicate that controlling organic-graphene heterointerface could provide a design strategy of organic solar cell architecture for boosting photon harvesting.
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Affiliation(s)
- Sae Byeok Jo
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Hyun Ho Kim
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Hansol Lee
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Boseok Kang
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Seongkyu Lee
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Myungsun Sim
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Min Kim
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
| | - Wi Hyoung Lee
- Department of Organic and Nano System Engineering, Konkuk University , Seoul 143-701, Korea
| | - Kilwon Cho
- Department of Chemical Engineering, Pohang University of Science and Technology , Pohang 790-784, Korea
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30
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Chakraborty H, Shukla A. Theory of triplet optical absorption in oligoacenes: From naphthalene to heptacene. J Chem Phys 2014; 141:164301. [DOI: 10.1063/1.4897955] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Himanshu Chakraborty
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Alok Shukla
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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31
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Kolata K, Breuer T, Witte G, Chatterjee S. Molecular packing determines singlet exciton fission in organic semiconductors. ACS NANO 2014; 8:7377-83. [PMID: 24957197 DOI: 10.1021/nn502544d] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Carrier multiplication by singlet exciton fission enhances photovoltaic conversion efficiencies in organic solids. This decay of one singlet exciton into two triplet states allows the extraction of up to two electrons per harvested photon and, hence, promises to overcome the Shockley–Queisser limit. However, the microscopic mechanism of singlet exciton fission, especially the relation between molecular packing and electronic response, remains unclear, which therefore hampers the systematic improvement of organic photovoltaic devices. For the model system perfluoropentacene, we experimentally show that singlet exciton fission is greatly enhanced for a slip-stacked molecular arrangement by addressing different crystal axes featuring different packing schemes. This reveals that the fission process strongly depends on the intermolecular coupling: slip-stacking favors delocalization of excitations and allows for efficient exciton fission, while face-to-edge molecular orientations commonly found in the prevailing herringbone molecular stacking patterns even suppress it. Furthermore, we clarify the controversially debated role of excimer states as intermediary rather than competitive or precursory. Our detailed findings serve as a guideline for the design of next-generation molecular materials for application in future organic light-harvesting devices exploiting singlet exciton fission.
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32
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Scholz R, Luschtinetz R, Seifert G, Jägeler-Hoheisel T, Körner C, Leo K, Rapacioli M. Quantifying charge transfer energies at donor-acceptor interfaces in small-molecule solar cells with constrained DFTB and spectroscopic methods. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:473201. [PMID: 24135026 DOI: 10.1088/0953-8984/25/47/473201] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Charge transfer states around the donor-acceptor interface in an organic solar cell determine the device performance in terms of the open circuit voltage. In the present work, we propose a computational scheme based on constrained density functional tight binding theory (c-DFTB) to assess the energy of the lowest charge transfer (CT) state in such systems. A comparison of the c-DFTB scheme with Hartree-Fock based configuration interaction of singles (CIS) and with time-dependent density functional theory (TD-DFT) using the hybrid functional B3LYP reveals that CIS and c-DFTB reproduce the correct Coulomb asymptotics between cationic donor and anionic acceptor configurations, whereas TD-DFT gives a qualitatively wrong excitation energy. Together with an embedding scheme accounting for the polarizable medium, this c-DFTB scheme is applied to several donor-acceptor combinations used in molecular solar cells. The external quantum efficiency of photovoltaic cells based on zinc phthalocyanine-C60 blends reveals a CT band remaining much narrower than the density of states of acceptor HOMO and donor LUMO, an observation which can be interpreted in a natural way in terms of Marcus transfer theory. A detailed comparison with c-DFTB calculations reveals an energy difference of 0.32 eV between calculated and observed absorption from the electronic ground state into the CT state. In a blend of a functionalized thiophene and C60, the photoluminescence spectra differ significantly from neat films, allowing again an assignment to CT states. The proposed computational scheme reproduces the observed trends of the observed open circuit voltages in photovoltaic devices relying on several donor-acceptor blends, finding an offset of 1.16 eV on average. This value is similar as in polymer-fullerene photovoltaic systems where it amounts to about 0.9 eV, indicating that the photophysics of CT states in molecular donor-acceptor blends and in polymer-fullerene blends are governed by the same mechanisms.
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Affiliation(s)
- Reinhard Scholz
- Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden, Germany
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33
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Broch K, Gerlach A, Lorch C, Dieterle J, Novák J, Hinderhofer A, Schreiber F. Structure formation in perfluoropentacene:diindenoperylene blends and its impact on transient effects in the optical properties studied in real-time during growth. J Chem Phys 2013; 139:174709. [PMID: 24206324 DOI: 10.1063/1.4827868] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- K Broch
- Universität Tübingen, Institut für Angewandte Physik and LISA+, Auf der Morgenstelle 10, 72076 Tübingen, Germany
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34
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Beljonne D, Yamagata H, Brédas JL, Spano FC, Olivier Y. Charge-transfer excitations steer the Davydov splitting and mediate singlet exciton fission in pentacene. PHYSICAL REVIEW LETTERS 2013; 110:226402. [PMID: 23767738 DOI: 10.1103/physrevlett.110.226402] [Citation(s) in RCA: 183] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Indexed: 05/21/2023]
Abstract
Quantum-chemical calculations are combined to a model Frenkel-Holstein Hamiltonian to assess the nature of the lowest electronic excitations in the pentacene crystal. We show that an admixture of charge-transfer excitations into the lowest singlet excited states form the origin of the Davydov splitting and mediate instantaneous singlet exciton fission by direct optical excitation of coherently coupled single and double exciton states, in agreement with recent experiments.
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Affiliation(s)
- D Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, 7000 Mons, Belgium
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35
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Breuer T, Witte G. Thermally activated intermixture in pentacene-perfluoropentacene heterostructures. J Chem Phys 2013; 138:114901. [DOI: 10.1063/1.4795004] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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