1
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Cakaj A, Schmid M, Hofmann A, Brütting W. Controlling Spontaneous Orientation Polarization in Organic Semiconductors─The Case of Phosphine Oxides. ACS Appl Mater Interfaces 2023; 15:54721-54731. [PMID: 37970727 DOI: 10.1021/acsami.3c13049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2023]
Abstract
Upon film growth by physical vapor deposition, the preferential orientation of polar organic molecules can result in a nonzero permanent dipole moment (PDM) alignment, causing a macroscopic film polarization. This effect, known as spontaneous orientation polarization (SOP), was studied in the case of different phosphine oxides (POs). We investigate the control of SOP by molecular design and film-growth conditions. Our results show that using less polar POs with just one phosphor-oxygen bond yields an exceptionally high degree of SOP with the so-called giant surface potential (slope), reaching more than 150 mV nm-1 in a neat bis-4-(N-carbazol(yl)phenyl)phenyl phosphine oxide (BCPO) film grown at room temperature. Additionally, by altering the evaporation rate and substrate temperature, we are able to control the SOP magnitude over a broad range from 0 to almost 300 mV nm-1. Diluting BCPO in a nonpolar host enhances the PDM alignment only marginally, but combining temperature control with dipolar doping can result in highly aligned molecules with more than 80% of their PDMs standing upright on the substrate on average.
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Affiliation(s)
- Albin Cakaj
- Institute of Physics, University of Augsburg, Augsburg 86135, Germany
| | - Markus Schmid
- Institute of Physics, University of Augsburg, Augsburg 86135, Germany
| | - Alexander Hofmann
- Institute of Physics, University of Augsburg, Augsburg 86135, Germany
| | - Wolfgang Brütting
- Institute of Physics, University of Augsburg, Augsburg 86135, Germany
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2
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Kirsch C, Naujoks T, Haizmann P, Frech P, Peisert H, Chassé T, Brütting W, Scheele M. Zwitterionic Carbazole Ligands Enhance the Stability and Performance of Perovskite Nanocrystals in Light-Emitting Diodes. ACS Appl Mater Interfaces 2023. [PMID: 37367642 DOI: 10.1021/acsami.3c05756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
We introduce a new carbazole-based zwitterionic ligand (DCzGPC) synthesized via Yamaguchi esterification which enhances the efficiency of lead halide perovskite (LHP) nanocrystals (NCs) in light-emitting diodes (LED). A facile ligand exchange of the native ligand shell, monitored by nuclear magnetic resonance (NMR), ultraviolet-visible (UV-vis), and photoluminescence (PL) spectroscopy, enables more stable and efficient LHP NCs. The improved stability is demonstrated in solution and solid-state LEDs, where the NCs exhibit prolonged luminescence lifetimes and improved luminance, respectively. These results represent a promising strategy to enhance the stability of LHP NCs and to tune their optoelectronic properties for further application in LEDs or solar cells.
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Affiliation(s)
- Christopher Kirsch
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076 Tübingen, Germany
| | - Tassilo Naujoks
- Institut für Physik, Universität Augsburg, Augsburg 86135, Germany
| | - Philipp Haizmann
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076 Tübingen, Germany
| | - Philipp Frech
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076 Tübingen, Germany
| | - Heiko Peisert
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076 Tübingen, Germany
| | - Thomas Chassé
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076 Tübingen, Germany
| | | | - Marcus Scheele
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076 Tübingen, Germany
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3
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Hammer S, Linderl T, Tvingstedt K, Brütting W, Pflaum J. Spectroscopic analysis of vibrational coupling in multi-molecular excited states. Mater Horiz 2023; 10:221-234. [PMID: 36367085 DOI: 10.1039/d2mh00829g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Multi-molecular excited states accompanied by intra- and inter-molecular geometric relaxation are commonly encountered in optical and electrooptical studies and applications of organic semiconductors as, for example, excimers or charge transfer states. Understanding the dynamics of these states is crucial to improve organic devices such as light emitting diodes and solar cells. Their full microscopic description, however, demands sophisticated tools such as ab initio quantum chemical calculations which come at the expense of high computational costs and are prone to errors by assumptions as well as iterative algorithmic procedures. Hence, the analysis of spectroscopic data is often conducted at a phenomenological level only. Here, we present a toolkit to analyze temperature dependent luminescence data and gain first insights into the relevant microscopic parameters of the molecular system at hand. By means of a Franck-Condon based approach considering a single effective inter-molecular vibrational mode and different potentials for the ground and excited state we are able to explain the luminescence spectra of such multi-molecular states. We demonstrate that by applying certain reasonable simplifications the luminescence of charge transfer states as well as excimers can be satisfactorily reproduced for temperatures ranging from cryogenics to above room temperature. We present a semi-classical and a quantum-mechanical description of our model and, for both cases, demonstrate its applicability by analyzing the temperature dependent luminescence of the amorphous donor-acceptor heterojunction tetraphenyldibenzoperiflanthene:C60 as well as polycrystalline zinc-phthalocyanine to reproduce the luminescence spectra and extract relevant system parameters such as the excimer binding energy.
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Affiliation(s)
- Sebastian Hammer
- Experimental Physics VI, Julius Maximilian University Würzburg, 97074 Würzburg, Germany.
| | - Theresa Linderl
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - Kristofer Tvingstedt
- Experimental Physics VI, Julius Maximilian University Würzburg, 97074 Würzburg, Germany.
| | - Wolfgang Brütting
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - Jens Pflaum
- Experimental Physics VI, Julius Maximilian University Würzburg, 97074 Würzburg, Germany.
- Bavarian Center for Applied Energy Research, 97074 Würzburg, Germany
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4
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Naujoks T, Jayabalan R, Kirsch C, Zu F, Mandal M, Wahl J, Waibel M, Opitz A, Koch N, Andrienko D, Scheele M, Brütting W. Quantum Efficiency Enhancement of Lead-Halide Perovskite Nanocrystal LEDs by Organic Lithium Salt Treatment. ACS Appl Mater Interfaces 2022; 14:28985-28996. [PMID: 35695840 DOI: 10.1021/acsami.2c04018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Surface-defect passivation is key to achieving a high photoluminescence quantum yield in lead halide perovskite nanocrystals. However, in perovskite light-emitting diodes, these surface ligands also have to enable balanced charge injection into the nanocrystals to yield high efficiency and operational lifetime. In this respect, alkaline halides have been reported to passivate surface trap states and increase the overall stability of perovskite light emitters. On the one side, the incorporation of alkaline ions into the lead halide perovskite crystal structure is considered to counterbalance cation vacancies, whereas on the other side, the excess halides are believed to stabilize the colloids. Here, we report an organic lithium salt, viz. LiTFSI, as a halide-free surface passivation on perovskite nanocrystals. We show that treatment with LiTFSI has multiple beneficial effects on lead halide perovskite nanocrystals and LEDs derived from them. We obtain a higher photoluminescence quantum yield and a longer exciton lifetime and a radiation pattern that is more favorable for light outcoupling. The ligand-induced dipoles on the nanocrystal surface shift their energy levels toward a lower hole-injection barrier. Overall, these effects add up to a 4- to 7-fold boost of the external quantum efficiency in proof-of-concept LED structures, depending on the color of the used lead halide perovskite nanocrystal emitters.
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Affiliation(s)
- Tassilo Naujoks
- Institut für Physik, Universität Augsburg, Augsburg 86135, Germany
| | | | - Christopher Kirsch
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, Tübingen 72076, Germany
| | - Fengshuo Zu
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 12489, Germany
| | - Mukunda Mandal
- Max Planck Institute für Polymerforschung, Ackermannweg 10, Mainz 55128, Germany
| | - Jan Wahl
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, Tübingen 72076, Germany
| | - Martin Waibel
- Institut für Physik, Universität Augsburg, Augsburg 86135, Germany
| | - Andreas Opitz
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 12489, Germany
| | - Norbert Koch
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin 12489, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin 12489, Germany
| | - Denis Andrienko
- Max Planck Institute für Polymerforschung, Ackermannweg 10, Mainz 55128, Germany
| | - Marcus Scheele
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, Tübingen 72076, Germany
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5
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Crovini E, Zhang Z, Kusakabe Y, Ren Y, Wada Y, Naqvi BA, Sahay P, Matulaitis T, Diesing S, Samuel IDW, Brütting W, Suzuki K, Kaji H, Bräse S, Zysman-Colman E. Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode. Beilstein J Org Chem 2021; 17:2894-2905. [PMID: 34956408 PMCID: PMC8685574 DOI: 10.3762/bjoc.17.197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 11/19/2021] [Indexed: 12/02/2022] Open
Abstract
In this work we showcase the emitter DICzTRZ in which we employed a twin-emitter design of our previously reported material, ICzTRZ. This new system presented a red-shifted emission at 488 nm compared to that of ICzTRZ at 475 nm and showed a comparable photoluminescence quantum yield of 57.1% in a 20 wt % CzSi film versus 63.3% for ICzTRZ. The emitter was then incorporated within a solution-processed organic light-emitting diode that showed a maximum external quantum efficiency of 8.4%, with Commission Internationale de l'Éclairage coordinate of (0.22, 0.47), at 1 mA cm-2.
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Affiliation(s)
- Ettore Crovini
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
| | - Zhen Zhang
- Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany
| | - Yu Kusakabe
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Yongxia Ren
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Yoshimasa Wada
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Bilal A Naqvi
- Experimental Physics IV, Institute of Physics, University of Augsburg, Universitätstrasse. 1, 86159 Augsburg, Germany
| | - Prakhar Sahay
- Experimental Physics IV, Institute of Physics, University of Augsburg, Universitätstrasse. 1, 86159 Augsburg, Germany
| | - Tomas Matulaitis
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
| | - Stefan Diesing
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK
| | - Ifor D W Samuel
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK
| | - Wolfgang Brütting
- Experimental Physics IV, Institute of Physics, University of Augsburg, Universitätstrasse. 1, 86159 Augsburg, Germany
| | - Katsuaki Suzuki
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Hironori Kaji
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Stefan Bräse
- Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany
- Institute of Biological and Chemical Systems – Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany
| | - Eli Zysman-Colman
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
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6
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Grassl F, Ullrich A, Mansour AE, Abdalbaqi SM, Koch N, Opitz A, Scheele M, Brütting W. Coupled Organic-Inorganic Nanostructures with Mixed Organic Linker Molecules. ACS Appl Mater Interfaces 2021; 13:37483-37493. [PMID: 34328310 DOI: 10.1021/acsami.1c08614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The electronic properties of semiconducting inorganic lead sulfide (PbS) nanocrystals (NCs) and organic linker molecules are dependent on the size of NCs as well as the used ligands. Here, we demonstrate that a weakly binding ligand can be successfully attached to PbS NCs to form a coupled organic-inorganic nanostructure (COIN) by mixing with a strong binding partner. We use the weakly binding zinc β-tetraaminophthalocyanine (Zn4APc) in combination with the strongly binding 1,2-ethanedithiol (EDT) as a mixed ligand system and compare its structural, electronic, and (photo-)electrical properties with both single-ligand COINs. It is found that binding of Zn4APc is assisted by the presence of EDT leading to improved film homogeneity, lower trap density, and enhanced photocurrent of the derived devices. Thus, the mixing of ligands is a versatile tool to achieve COINs with improved performance.
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Affiliation(s)
- Florian Grassl
- Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany
| | - Aladin Ullrich
- Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany
| | - Ahmed E Mansour
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
| | | | - Norbert Koch
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
| | - Andreas Opitz
- Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Marcus Scheele
- Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076 Tübingen, Germany
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7
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Haase N, Danos A, Pflumm C, Stachelek P, Brütting W, Monkman AP. Are the rates of dexter transfer in TADF hyperfluorescence systems optically accessible? Mater Horiz 2021; 8:1805-1815. [PMID: 34846509 DOI: 10.1039/d0mh01666g] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Seemingly not, but for unexpected reasons. Combining the triplet harvesting properties of TADF materials with the fast emission rates and colour purity of fluorescent emitters is attractive for developing high performance OLEDs. In this "hyperfluorescence" approach, triplet excitons are converted to singlets on the TADF material and transferred to the fluorescent material by long range Förster energy transfer. The primary loss mechanism is assumed to be Dexter energy transfer from the TADF triplet to the non-emissive triplet of the fluorescent emitter. Here we use optical spectroscopy to investigate energy transfer in representative emissive layers. Despite observing kinetics that at first appear consistent with Dexter quenching of the TADF triplet state, transient absorption, photoluminescence quantum yields, and comparison to phosphor-sensitised "hyperphosphorescent" systems reveal that this is not the case. While Dexter quenching by the fluorescent emitter is likely still a key loss mechanism in devices, we demonstrate that - despite initial appearances - it is inoperative under optical excitation. These results reveal a deep limitation of optical spectroscopy in characterizing hyperfluorescent systems.
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Affiliation(s)
- Nils Haase
- Institute of Physics, Experimental Physics IV, University of Augsburg, Universitätsstr. 1, 86135 Augsburg, Germany
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8
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Naqvi BA, Schmid M, Crovini E, Sahay P, Naujoks T, Rodella F, Zhang Z, Strohriegl P, Bräse S, Zysman-Colman E, Brütting W. Corrigendum: What Controls the Orientation of TADF Emitters? Front Chem 2021; 9:632639. [PMID: 33681148 PMCID: PMC7927789 DOI: 10.3389/fchem.2021.632639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 01/07/2021] [Indexed: 11/13/2022] Open
Affiliation(s)
- Bilal A Naqvi
- Institute of Physics, University of Augsburg, Augsburg, Germany
| | - Markus Schmid
- Institute of Physics, University of Augsburg, Augsburg, Germany
| | - Ettore Crovini
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom
| | - Prakhar Sahay
- Institute of Physics, University of Augsburg, Augsburg, Germany
| | - Tassilo Naujoks
- Institute of Physics, University of Augsburg, Augsburg, Germany
| | | | - Zhen Zhang
- Institute of Organic Chemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Peter Strohriegl
- Macromolecular Chemistry, University of Bayreuth, Bayreuth, Germany
| | - Stefan Bräse
- Institute of Organic Chemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany.,Institute of Biological and Chemical Systems - Functional Molecular Systems, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| | - Eli Zysman-Colman
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom
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9
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Schmid M, Harms K, Degitz C, Morgenstern T, Hofmann A, Friederich P, Johannes HH, Wenzel W, Kowalsky W, Brütting W. Optical and Electrical Measurements Reveal the Orientation Mechanism of Homoleptic Iridium-Carbene Complexes. ACS Appl Mater Interfaces 2020; 12:51709-51718. [PMID: 33164497 DOI: 10.1021/acsami.0c14613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Understanding and controlling the driving forces for molecular alignment in optoelectronic thin-film devices is of crucial importance for improving their performance. In this context, the preferential orientation of organometallic iridium complexes is in the focus of research to benefit from their improved light-outcoupling efficiencies in organic light-emitting diodes (OLEDs). Although there has been great progress concerning the orientation behavior for heteroleptic Ir complexes, the mechanism behind the alignment of homoleptic complexes is still unclear yet. In this work, we present a sky-blue phosphorescent dye that shows variable alignment depending on systematic modifications of the ligands bound to the central iridium atom. From an optical study of the transition dipole moment orientation and the electrically accessible alignment of the permanent dipole moment, we conclude that the film morphology is related to both the aspect ratio of the dye and the local electrostatic interaction of the ligands with the film surface during growth. These results indicate a potential strategy to actively control the orientation of iridium-based emitters for the application in OLEDs.
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Affiliation(s)
- Markus Schmid
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - Kristoffer Harms
- Applied Organic Materials, Institute for High Frequency Technology, Technical University of Braunschweig, 38106 Braunschweig, Germany
| | - Carl Degitz
- Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
- Merck KGaA, Performance Materials - Display Solutions, Frankfurter Straße 250, 64293 Darmstadt, Germany
| | | | - Alexander Hofmann
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - Pascal Friederich
- Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
- Institute of Theoretical Informatics, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Hans-Hermann Johannes
- Applied Organic Materials, Institute for High Frequency Technology, Technical University of Braunschweig, 38106 Braunschweig, Germany
| | - Wolfgang Wenzel
- Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Wolfgang Kowalsky
- Applied Organic Materials, Institute for High Frequency Technology, Technical University of Braunschweig, 38106 Braunschweig, Germany
| | - Wolfgang Brütting
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
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10
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Naqvi BA, Schmid M, Crovini E, Sahay P, Naujoks T, Rodella F, Zhang Z, Strohriegl P, Bräse S, Zysman-Colman E, Brütting W. What Controls the Orientation of TADF Emitters? Front Chem 2020; 8:750. [PMID: 33102430 PMCID: PMC7500207 DOI: 10.3389/fchem.2020.00750] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 07/21/2020] [Indexed: 11/13/2022] Open
Abstract
Thermally-activated delayed fluorescence (TADF) emitters—just like phosphorescent ones—can in principle allow for 100% internal quantum efficiency of organic light-emitting diodes (OLEDs), because the initially formed electron-hole pairs in the non-emissive triplet state can be efficiently converted into emissive singlets by reverse intersystem crossing. However, as compared to phosphorescent emitter complexes with their bulky—often close to spherical—molecular structures, TADF emitters offer the advantage to align them such that their optical transition dipole moments (TDMs) lie preferentially in the film plane. In this report, we address the question which factors control the orientation of TADF emitters. Specifically, we discuss how guest-host interactions may be used to influence this parameter and propose an interplay of different factors being responsible. We infer that emitter orientation is mainly governed by the molecular shape of the TADF molecule itself and by the physical properties of the host—foremost, its glass transition temperature Tg and its tendency for alignment being expressed, e.g., as birefringence or the formation of a giant surface potential of the host. Electrostatic dipole-dipole interactions between host and emitter are not found to play an important role.
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Affiliation(s)
- Bilal A Naqvi
- Institute of Physics, University of Augsburg, Augsburg, Germany
| | - Markus Schmid
- Institute of Physics, University of Augsburg, Augsburg, Germany
| | - Ettore Crovini
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom
| | - Prakhar Sahay
- Institute of Physics, University of Augsburg, Augsburg, Germany
| | - Tassilo Naujoks
- Institute of Physics, University of Augsburg, Augsburg, Germany
| | | | - Zhen Zhang
- Institute of Organic Chemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Peter Strohriegl
- Macromolecular Chemistry, University of Bayreuth, Bayreuth, Germany
| | - Stefan Bräse
- Institute of Organic Chemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany.,Institute of Biological and Chemical Systems - Functional Molecular Systems, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| | - Eli Zysman-Colman
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom
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11
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12
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Jurow MJ, Morgenstern T, Eisler C, Kang J, Penzo E, Do M, Engelmayer M, Osowiecki WT, Bekenstein Y, Tassone C, Wang LW, Alivisatos AP, Brütting W, Liu Y. Manipulating the Transition Dipole Moment of CsPbBr 3 Perovskite Nanocrystals for Superior Optical Properties. Nano Lett 2019; 19:2489-2496. [PMID: 30848600 DOI: 10.1021/acs.nanolett.9b00122] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Colloidal cesium lead halide perovskite nanocrystals exhibit unique photophysical properties including high quantum yields, tunable emission colors, and narrow photoluminescence spectra that have marked them as promising light emitters for applications in diverse photonic devices. Randomly oriented transition dipole moments have limited the light outcoupling efficiency of all isotropic light sources, including perovskites. In this report we design and synthesize deep blue emitting, quantum confined, perovskite nanoplates and analyze their optical properties by combining angular emission measurements with back focal plane imaging and correlating the results with physical characterization. By reducing the dimensions of the nanocrystals and depositing them face down onto a substrate by spin coating, we orient the average transition dipole moment of films into the plane of the substrate and improve the emission properties for light emitting applications. We then exploit the sensitivity of the perovskite electronic transitions to the dielectric environment at the interface between the crystal and their surroundings to reduce the angle between the average transition dipole moment and the surface to only 14° and maximize potential light emission efficiency. This tunability of the electronic transition that governs light emission in perovskites is unique and, coupled with their excellent photophysical properties, introduces a valuable method to extend the efficiencies and applications of perovskite based photonic devices beyond those based on current materials.
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Affiliation(s)
- Matthew J Jurow
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Thomas Morgenstern
- Institute of Physics , University of Augsburg , 86135 Augsburg , Germany
| | - Carissa Eisler
- Department of Chemistry and Materials Science and Engineering , University of California , Berkeley , California 94720 , United States
| | - Jun Kang
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Erika Penzo
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Mai Do
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Manuel Engelmayer
- Institute of Physics , University of Augsburg , 86135 Augsburg , Germany
| | - Wojciech T Osowiecki
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Department of Chemistry and Materials Science and Engineering , University of California , Berkeley , California 94720 , United States
| | - Yehonadav Bekenstein
- Department of Chemistry and Materials Science and Engineering , University of California , Berkeley , California 94720 , United States
| | - Christopher Tassone
- SSRL Materials Science Division , SLAC National Accelerator Laboratory , 2575 Sand Hill Rd MS 69 , Menlo Park , California 94025 , United States
| | - Lin-Wang Wang
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - A Paul Alivisatos
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Department of Chemistry and Materials Science and Engineering , University of California , Berkeley , California 94720 , United States
- Kavli Energy NanoScience Institute , Berkeley , California 94720 , United States
| | - Wolfgang Brütting
- Institute of Physics , University of Augsburg , 86135 Augsburg , Germany
| | - Yi Liu
- Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
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13
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Morgenstern T, Schmid M, Hofmann A, Bierling M, Jäger L, Brütting W. Correlating Optical and Electrical Dipole Moments To Pinpoint Phosphorescent Dye Alignment in Organic Light-Emitting Diodes. ACS Appl Mater Interfaces 2018; 10:31541-31551. [PMID: 30136569 DOI: 10.1021/acsami.8b08963] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Understanding the morphology of organic materials within optoelectronic thin film devices is of crucial importance for the development of state-of-the-art organic light emitting diodes (OLEDs). In this context, the preferential alignment of organometallic Ir complexes has been in the focus of research to benefit from the improved light-outcoupling efficiencies. Although the emissive dipole orientation has been identified from an optical point of view and molecular dynamic simulations give first insights into film morphologies, new experimental techniques are necessary to pinpoint the exact alignment of phosphorescent dye molecules. In this work, optical characterization of luminescent thin films was combined with electrical measurements on bilayer devices to elucidate the orientation distribution of both, electrical and optical dipole moments of phosphorescent guest-host systems. The results not only confirm previous suggestions for the alignment mechanism of organometallic dyes but also disclose a direct correlation between the degree of electrical and optical dipole alignment, thus opening a roadway for achieving higher light-outcoupling efficiency in OLEDs.
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Affiliation(s)
- Thomas Morgenstern
- Institute of Physics , University of Augsburg , 86135 Augsburg , Germany
| | - Markus Schmid
- Institute of Physics , University of Augsburg , 86135 Augsburg , Germany
| | - Alexander Hofmann
- Institute of Physics , University of Augsburg , 86135 Augsburg , Germany
| | - Markus Bierling
- Institute of Physics , University of Augsburg , 86135 Augsburg , Germany
| | - Lars Jäger
- Institute of Physics , University of Augsburg , 86135 Augsburg , Germany
| | - Wolfgang Brütting
- Institute of Physics , University of Augsburg , 86135 Augsburg , Germany
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14
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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15
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Preinfalk JB, Schackmar FR, Lampe T, Egel A, Schmidt TD, Brütting W, Gomard G, Lemmer U. Tuning the Microcavity of Organic Light Emitting Diodes by Solution Processable Polymer-Nanoparticle Composite Layers. ACS Appl Mater Interfaces 2016; 8:2666-2672. [PMID: 26744904 DOI: 10.1021/acsami.5b10717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In this study, we present a simple method to tune and take advantage of microcavity effects for an increased fraction of outcoupled light in solution-processed organic light emitting diodes. This is achieved by incorporating nonscattering polymer-nanoparticle composite layers. These tunable layers allow the optimization of the device architecture even for high film thicknesses on a single substrate by gradually altering the film thickness using a horizontal dipping technique. Moreover, it is shown that the optoelectronic device parameters are in good agreement with transfer matrix simulations of the corresponding layer stack, which offers the possibility to numerically design devices based on such composite layers. Lastly, it could be shown that the introduction of nanoparticles leads to an improved charge injection, which combined with an optimized microcavity resulted in a maximum luminous efficacy increase of 85% compared to a nanoparticle-free reference device.
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Affiliation(s)
- Jan B Preinfalk
- Light Technology Institute, Karlsruhe Institute of Technology (KIT) , Engesserstr. 13, 76131 Karlsruhe, Germany
| | - Fabian R Schackmar
- Light Technology Institute, Karlsruhe Institute of Technology (KIT) , Engesserstr. 13, 76131 Karlsruhe, Germany
| | - Thomas Lampe
- Institute of Physics, University of Augsburg , Universitätsstr. 1, 86135 Augsburg, Germany
| | - Amos Egel
- Light Technology Institute, Karlsruhe Institute of Technology (KIT) , Engesserstr. 13, 76131 Karlsruhe, Germany
| | - Tobias D Schmidt
- Institute of Physics, University of Augsburg , Universitätsstr. 1, 86135 Augsburg, Germany
| | - Wolfgang Brütting
- Institute of Physics, University of Augsburg , Universitätsstr. 1, 86135 Augsburg, Germany
| | - Guillaume Gomard
- Light Technology Institute, Karlsruhe Institute of Technology (KIT) , Engesserstr. 13, 76131 Karlsruhe, Germany
- Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Uli Lemmer
- Light Technology Institute, Karlsruhe Institute of Technology (KIT) , Engesserstr. 13, 76131 Karlsruhe, Germany
- Institute of Microstructure Technology, Karlsruhe Institute of Technology (KIT) , Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
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16
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Jurow MJ, Mayr C, Schmidt TD, Lampe T, Djurovich PI, Brütting W, Thompson ME. Understanding and predicting the orientation of heteroleptic phosphors in organic light-emitting materials. Nat Mater 2016; 15:85-91. [PMID: 26436340 DOI: 10.1038/nmat4428] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 08/21/2015] [Indexed: 06/05/2023]
Abstract
Controlling the alignment of the emitting molecules used as dopants in organic light-emitting diodes is an effective strategy to improve the outcoupling efficiency of these devices. To explore the mechanism behind the orientation of dopants in films of organic host materials, we synthesized a coumarin-based ligand that was cyclometalated onto an iridium core to form three phosphorescent heteroleptic molecules, (bppo)2Ir(acac), (bppo)2Ir(ppy) and (ppy)2Ir(bppo) (bppo represents benzopyranopyridinone, ppy represents 2-phenylpyridinate, and acac represents acetylacetonate). Each emitter was doped into a 4,4'-bis(N-carbazolyl)-1,1'-biphenyl host layer, and the resultant orientation of their transition dipole moment vectors was measured by angle-dependent p-polarized photoluminescent emission spectroscopy. In solid films, (bppo)2Ir(acac) is found to have a largely horizontal transition dipole vector orientation relative to the substrate, whereas (ppy)2Ir(bppo) and (bppo)2Ir(ppy) are isotropic. We propose that the inherent asymmetry at the surface of the growing film promotes dopant alignment in these otherwise amorphous films. Modelling the net orientation of the transition dipole moments of these materials yields general design rules for further improving horizontal orientation.
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Affiliation(s)
- Matthew J Jurow
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Christian Mayr
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - Tobias D Schmidt
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - Thomas Lampe
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - Peter I Djurovich
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
| | - Wolfgang Brütting
- Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - Mark E Thompson
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA
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17
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Pithan L, Meister E, Jin C, Weber C, Zykov A, Sauer K, Brütting W, Riegler H, Opitz A, Kowarik S. Thermally driven smoothening of molecular thin films: Structural transitions in n-alkane layers studied in real-time. J Chem Phys 2015; 143:164707. [PMID: 26520543 DOI: 10.1063/1.4934501] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We use thermal annealing to improve smoothness and to increase the lateral size of crystalline islands of n-tetratetracontane (TTC, C44H90) films. With in situ x-ray diffraction, we find an optimum temperature range leading to improved texture and crystallinity while avoiding an irreversible phase transition that reduces crystallinity again. We employ real-time optical phase contrast microscopy with sub-nm height resolution to track the diffusion of TTC across monomolecular step edges which causes the unusual smoothing of a molecular thin film during annealing. We show that the lateral island sizes increase by more than one order of magnitude from 0.5 μm to 10 μm. This desirable behavior of 2d-Ostwald ripening and smoothing is in contrast to many other organic molecular films where annealing leads to dewetting, roughening, and a pronounced 3d morphology. We rationalize the smoothing behavior with the highly anisotropic attachment energies and low surface energies for TTC. The results are technically relevant for the use of TTC as passivation layer and as gate dielectric in organic field effect transistors.
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Affiliation(s)
- Linus Pithan
- Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Eduard Meister
- Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany
| | - Chenyu Jin
- Max-Planck-Institut für Kolloid- und Grenzflächenforschung, 14476 Potsdam-Golm, Germany
| | - Christopher Weber
- Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Anton Zykov
- Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Katrein Sauer
- Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | | | - Hans Riegler
- Max-Planck-Institut für Kolloid- und Grenzflächenforschung, 14476 Potsdam-Golm, Germany
| | - Andreas Opitz
- Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Stefan Kowarik
- Institut für Physik, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
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18
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Wagner T, Pöthig A, Augenstein HMS, Schmidt TD, Kaposi M, Herdtweck E, Brütting W, Herrmann WA, Kühn FE. From Simple Ligands to Complex Structures: Structural Diversity of Silver(I) Complexes Bearing Tetradentate (alkylenebimpy) NHC Ligands. Organometallics 2015. [DOI: 10.1021/om5013067] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Thomas Wagner
- Chair
of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry
and Catalysis Research Center, Technische Universität München, 85748 Garching b. München, Germany
| | - Alexander Pöthig
- Chair
of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry
and Catalysis Research Center, Technische Universität München, 85748 Garching b. München, Germany
| | - Hannah M. S. Augenstein
- Chair
of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry
and Catalysis Research Center, Technische Universität München, 85748 Garching b. München, Germany
| | - Tobias D. Schmidt
- Institute
of Physics, University of Augsburg, 86159 Augsburg, Germany
| | - Marlene Kaposi
- Chair
of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry
and Catalysis Research Center, Technische Universität München, 85748 Garching b. München, Germany
| | - Eberhard Herdtweck
- Chair
of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry
and Catalysis Research Center, Technische Universität München, 85748 Garching b. München, Germany
| | - Wolfgang Brütting
- Institute
of Physics, University of Augsburg, 86159 Augsburg, Germany
| | - Wolfgang A. Herrmann
- Chair
of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry
and Catalysis Research Center, Technische Universität München, 85748 Garching b. München, Germany
| | - Fritz E. Kühn
- Chair
of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry
and Catalysis Research Center, Technische Universität München, 85748 Garching b. München, Germany
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19
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Abstract
Materials to devices: coupled organic–inorganic nanostructures provide versatile perspectives for quantum dot-based optoelectronic devices.
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Affiliation(s)
- M Scheele
- Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany.
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20
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Scholz BJ, Frischeisen J, Jaeger A, Setz DS, Reusch TCG, Brütting W. Extraction of surface plasmons in organic light-emitting diodes via high-index coupling. Opt Express 2012; 20 Suppl 2:A205-A212. [PMID: 22418669 DOI: 10.1364/oe.20.00a205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The efficiency of organic light-emitting diodes (OLEDs) is still limited by poor light outcoupling. In particular, the excitation of surface plasmon polaritons (SPPs) at metal-organic interfaces represents a major loss channel. By combining optical simulations and experiments on simplified luminescent thin-film structures we elaborate the conditions for the extraction of SPPs via coupling to high-index media. As a proof-of-concept, we demonstrate the possibility to extract light from wave-guided modes and surface plasmons in a top-emitting white OLED by a high-index prism.
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Affiliation(s)
- Bert J Scholz
- Institute of Physics, University of Augsburg, Universit¨atsstrasse 1, 86159 Augsburg, Germany
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22
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Frischeisen J, Niu Q, Abdellah A, Kinzel JB, Gehlhaar R, Scarpa G, Adachi C, Lugli P, Brütting W. Light extraction from surface plasmons and waveguide modes in an organic light-emitting layer by nanoimprinted gratings. Opt Express 2011; 19 Suppl 1:A7-A19. [PMID: 21263715 DOI: 10.1364/oe.19.0000a7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Organic light-emitting diodes (OLEDs) usually exhibit a low light outcoupling efficiency because a large fraction of power is lost to surface plasmons (SPs) and waveguide modes. In this paper it is demonstrated that periodic grating structures with almost µm-scale can be used to extract SPs as well as waveguide modes and therefore enhance the outcoupling efficiency in light-emitting thin film structures. The gratings are fabricated by nanoimprint lithography using a commercially available diffraction grating as a mold which is pressed into a polymer resist. The outcoupling of SPs and waveguide modes is detected in fluorescent organic films adjacent to a thin metal layer in angular dependent photoluminescence measurements. Scattering up to 5th-order is observed and the extracted modes are identified by comparison to the SP and waveguide dispersion obtained from optical simulations. In order to demonstrate the low-cost, high quality and large area applicability of grating structures in optoelectronic devices, we also present SP extraction using a grating structure fabricated by a common DVD stamp.
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Affiliation(s)
- Jörg Frischeisen
- Institute of Physics, University of Augsburg, Universitätsstrasse 1, 86159 Augsburg, Germany.
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23
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Frischeisen J, Mayr C, Reinke NA, Nowy S, Brütting W. Surface plasmon resonance sensor utilizing an integrated organic light emitting diode. Opt Express 2008; 16:18426-18436. [PMID: 18958121 DOI: 10.1364/oe.16.018426] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
A novel surface plasmon resonance (SPR) sensor based on an integrated planar and polychromatic light source is presented. The sensor comprises an organic light emitting diode (OLED) and a metallic sensing layer located on opposite sides of a glass prism. We successfully fabricated and tested prototype sensors based on this approach by the use of different prism geometries and OLEDs with blue, green and red emission color. We investigated the angular and wavelength dependent SPR dispersion relation for sensing layers consisting of silver and gold in contact with air. Further on we demonstrated the sensor function by real time monitoring of temperature changes inside an adjacent water reservoir as well as by recording the dissolving process of sodium chloride in water. The presented technique offers the advantage that there is no necessity to couple light from external bulky sources such as lasers or halogen lamps into the sensing device which makes it particularly interesting for miniaturization.
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Affiliation(s)
- Jörg Frischeisen
- University of Augsburg, Institute of Physics, Augsburg, Germany.
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24
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Brütting W, Bronner M, Götzenbrugger M, Opitz A. Ambipolar Blends of Cu-Phthalocyanine and Fullerene: Charge Carrier Mobility, Electronic Structure and their Implications for Solar Cell Applications. ACTA ACUST UNITED AC 2008. [DOI: 10.1002/masy.200850808] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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29
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Cölle M, Forero-Lenger S, Gmeiner J, Brütting W. Vibrational analysis of different crystalline phases of the organic electroluminescent material aluminium tris(quinoline-8-olate) (Alq3). Phys Chem Chem Phys 2003. [DOI: 10.1039/b303689h] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Berleb S, Brütting W. Dispersive electron transport in tris(8-hydroxyquinoline) aluminum (Alq3) probed by impedance spectroscopy. Phys Rev Lett 2002; 89:286601. [PMID: 12513168 DOI: 10.1103/physrevlett.89.286601] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2002] [Indexed: 05/24/2023]
Abstract
Electron transport in tris(8-hydroxyquinoline) aluminum (Alq3) is investigated by impedance spectroscopy under conditions of space-charge limited conduction (SCLC). Existing SCLC models are extended to include the field dependence of the charge carrier mobility and energetically distributed trap states. The dispersive nature of electron transport is revealed by a frequency-dependent mobility with a dispersion parameter alpha in the range 0.4-0.5, independent of temperature. This indicates that positional rather than energetic disorder is the dominant mechanism for the dispersive transport of electrons in Alq3.
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Affiliation(s)
- Stefan Berleb
- Experimental Physics II, University of Bayreuth, 95440 Bayreuth, Germany
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31
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Cölle M, Dinnebier RE, Brütting W. The structure of the blue luminescent delta-phase of tris(8-hydroxyquinoline)aluminium(III) (Alq3). Chem Commun (Camb) 2002:2908-9. [PMID: 12478807 DOI: 10.1039/b209164j] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The existence of the facial isomer in the delta-phase of Alq3 is proven by X-ray structural analysis, revealing that both the different molecular structure and the weaker overlap of the pi-orbitals of hydroxyquinoline ligands belonging to neighboring Alq3 molecules as compared to other phases (alpha, beta) are likely to be the origin of the significantly different optical properties of delta-Alq3.
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Affiliation(s)
- Michael Cölle
- Universität Bayreuth, Experimentalphysik II, Universitätsstr. 30, 95440 Bayreuth, Germany.
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32
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Braun M, Gmeiner J, Tzolov M, Coelle M, Meyer FD, Milius W, Hillebrecht H, Wendland O, von Schütz JU, Brütting W. A new crystalline phase of the electroluminescent material tris(8-hydroxyquinoline) aluminum exhibiting blueshifted fluorescence. J Chem Phys 2001. [DOI: 10.1063/1.1369157] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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33
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Riechel S, Lemmer U, Feldmann J, Berleb S, Mückl AG, Brütting W, Gombert A, Wittwer V. Very compact tunable solid-state laser utilizing a thin-film organic semiconductor. Opt Lett 2001; 26:593-595. [PMID: 18040393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Optically pumped organic semiconductor lasers are fabricated by evaporation of a thin film of tris(8-hydroxyquinoline) aluminum (Alq(3)) molecularly doped with a laser dye on top of a polyester substrate with an embossed grating structure. We achieve low-threshold, longitudinally monomode distributed-feedback laser operation. By varying the film thickness of the organic semiconductor film, we can tune the wavelength of the surface-emitting laser over 44 nm. The low laser threshold allows the use of a very compact all-solid-state pump laser ( approximately 10 cm long). This concept opens up a way to obtain inexpensive lasers that are tunable over the whole visible range.
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34
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Forero S, Nguyen PH, Brütting W, Schwoerer M. Charge carrier transport in poly(p-phenylenevinylene) light-emitting devices. Phys Chem Chem Phys 1999. [DOI: 10.1039/a808614a] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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35
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Jandke M, Strohriegl P, Berleb S, Werner E, Brütting W. Phenylquinoxaline Polymers and Low Molar Mass Glasses as Electron-Transport Materials in Organic Light-Emitting Diodes. Macromolecules 1998. [DOI: 10.1021/ma9806054] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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36
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37
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Greczmiel M, Strohriegl P, Meier M, Brütting W. Polymethacrylates with Pendant Oxadiazole Units Synthesis and Application in Organic LEDs. Macromolecules 1997. [DOI: 10.1021/ma970226v] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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38
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Brütting R, Pösch P, Strohriegl P, Buchwald E, Brütting W, Schwoerer M. Aromatic polyethers with oxadiazole units – synthesis and application in organic light emitting diodes. MACROMOL CHEM PHYS 1997. [DOI: 10.1002/macp.1997.021980907] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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39
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Brütting W, Nguyen PH, Paasch G. dc-conduction mechanism and Peierls gap in organic and inorganic charge-density-wave conductors. Phys Rev B Condens Matter 1995; 51:9533-9543. [PMID: 9977615 DOI: 10.1103/physrevb.51.9533] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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40
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Kuhs WF, Mattern G, Brütting W, Dragan H, Burggraf M, Pilawa B, Dormann E. Electrocrystallization, crystal structure and physical properties of hexaperylene hexafluorophosphate, (C20H12)6
.+.PF6
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41
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Nguyen PH, Paasch G, Brütting W, Riess W. Analysis of the dc conductivity of the quasi-one-dimensional charge-density-wave conductor (fluoranthene)2X. Phys Rev B Condens Matter 1994; 49:5172-5181. [PMID: 10011468 DOI: 10.1103/physrevb.49.5172] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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