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Etherington MK, Kukhta NA, Higginbotham HF, Danos A, Bismillah AN, Graves DR, McGonigal PR, Haase N, Morherr A, Batsanov AS, Pflumm C, Bhalla V, Bryce MR, Monkman AP. Persistent Dimer Emission in Thermally Activated Delayed Fluorescence Materials. J Phys Chem C Nanomater Interfaces 2019; 123:11109-11117. [PMID: 31080540 PMCID: PMC6501699 DOI: 10.1021/acs.jpcc.9b01458] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Indexed: 05/22/2023]
Abstract
We expose significant changes in the emission color of carbazole-based thermally activated delayed fluorescence (TADF) emitters that arise from the presence of persistent dimer states in thin films and organic light-emitting diodes (OLEDs). Direct photoexcitation of this dimer state in 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) reveals the significant influence of dimer species on the color purity of its photoluminescence and electroluminescence. The dimer species is sensitive to the sample preparation method, and its enduring presence contributes to the widely reported concentration-mediated red shift in the photoluminescence and electroluminescence of evaporated thin films. This discovery has implications on the usability of these, and similar, molecules for OLEDs and explains disparate electroluminescence spectra presented in the literature for these compounds. The dimerization-controlled changes observed in the TADF process and photoluminescence efficiency mean that careful consideration of dimer states is imperative in the design of future TADF emitters and the interpretation of previously reported studies of carbazole-based TADF materials.
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Affiliation(s)
- Marc K. Etherington
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
- E-mail:
| | - Nadzeya A. Kukhta
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
| | - Heather F. Higginbotham
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
| | - Andrew Danos
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
| | - Aisha N. Bismillah
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
| | - David R. Graves
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
| | - Paul R. McGonigal
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
| | - Nils Haase
- Merck
KGaA, Performance Materials—Display Solutions, Frankfurter Straße 250, 64293 Darmstadt, Germany
- Institute
of Physics, Experimental Physics IV, University
of Augsburg, Universitätsstr.
1, 86135 Augsburg, Germany
| | - Antonia Morherr
- Merck
KGaA, Performance Materials—Display Solutions, Frankfurter Straße 250, 64293 Darmstadt, Germany
| | - Andrei S. Batsanov
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
| | - Christof Pflumm
- Merck
KGaA, Performance Materials—Display Solutions, Frankfurter Straße 250, 64293 Darmstadt, Germany
| | - Vandana Bhalla
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
- Department
of Chemistry, Guru Nanak Dev University, Grand Trunk Road, Off NH 1, Amritsar, Punjab 143005, India
| | - Martin R. Bryce
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
| | - Andrew P. Monkman
- Department
of Physics and Department of Chemistry, Durham University, South Road, Durham DH1
3LE, U.K.
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Chernenkaya A, Morherr A, Backes S, Popp W, Witt S, Kozina X, Nepijko SA, Bolte M, Medjanik K, Öhrwall G, Krellner C, Baumgarten M, Elmers HJ, Schönhense G, Jeschke HO, Valentí R. Microscopic origin of the charge transfer in single crystals based on thiophene derivatives: A combined NEXAFS and density functional theory approach. J Chem Phys 2016; 145:034702. [PMID: 27448899 DOI: 10.1063/1.4958659] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Affiliation(s)
- A. Chernenkaya
- Graduate School Materials Science in Mainz, 55128 Mainz, Germany
- Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| | - A. Morherr
- Physikalisches Institut, Goethe-Universität, 60438 Frankfurt am Main, Germany
| | - S. Backes
- Institut für Theoretische Physik, Goethe-Universität, 60438 Frankfurt am Main, Germany
| | - W. Popp
- Institut für Theoretische Physik, Goethe-Universität, 60438 Frankfurt am Main, Germany
| | - S. Witt
- Physikalisches Institut, Goethe-Universität, 60438 Frankfurt am Main, Germany
| | - X. Kozina
- Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| | - S. A. Nepijko
- Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| | - M. Bolte
- Institut für Anorganische Chemie, Goethe-Universität, 60438 Frankfurt am Main, Germany
| | - K. Medjanik
- MAX-IV Laboratory, Lund University, 22100 Lund, Sweden
| | - G. Öhrwall
- MAX-IV Laboratory, Lund University, 22100 Lund, Sweden
| | - C. Krellner
- Physikalisches Institut, Goethe-Universität, 60438 Frankfurt am Main, Germany
| | - M. Baumgarten
- Max-Planck-Institut für Polymerforschung, 55021 Mainz, Germany
| | - H. J. Elmers
- Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| | - G. Schönhense
- Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany
| | - H. O. Jeschke
- Institut für Theoretische Physik, Goethe-Universität, 60438 Frankfurt am Main, Germany
| | - R. Valentí
- Institut für Theoretische Physik, Goethe-Universität, 60438 Frankfurt am Main, Germany
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Rotter P, Lechner BAJ, Morherr A, Chisnall DM, Ward DJ, Jardine AP, Ellis J, Allison W, Eckhardt B, Witte G. Coupling between diffusion and orientation of pentacene molecules on an organic surface. Nat Mater 2016; 15:397-400. [PMID: 26901514 DOI: 10.1038/nmat4575] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 01/20/2016] [Indexed: 06/05/2023]
Abstract
The realization of efficient organic electronic devices requires the controlled preparation of molecular thin films and heterostructures. As top-down structuring methods such as lithography cannot be applied to van der Waals bound materials, surface diffusion becomes a structure-determining factor that requires microscopic understanding. Scanning probe techniques provide atomic resolution, but are limited to observations of slow movements, and therefore constrained to low temperatures. In contrast, the helium-3 spin-echo (HeSE) technique achieves spatial and time resolution on the nm and ps scale, respectively, thus enabling measurements at elevated temperatures. Here we use HeSE to unveil the intricate motion of pentacene admolecules diffusing on a chemisorbed monolayer of pentacene on Cu(110) that serves as a stable, well-ordered organic model surface. We find that pentacene moves along rails parallel and perpendicular to the surface molecules. The experimental data are explained by admolecule rotation that enables a switching between diffusion directions, which extends our molecular level understanding of diffusion in complex organic systems.
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Affiliation(s)
- Paul Rotter
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Barbara A J Lechner
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - Antonia Morherr
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - David M Chisnall
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - David J Ward
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - Andrew P Jardine
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - John Ellis
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - William Allison
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
| | - Bruno Eckhardt
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Gregor Witte
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
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