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Han GR, Kwon O, Kim S, Choi J, Son JB, Min KS, Lee JW, Choi B, Kim SK. Investigation of the Relationship between Quantum Yield, Charge-Transfer State, and Structure of the Ligands in Red-Emitting Heteroleptic Iridium(III) Complexes. J Phys Chem A 2024; 128:6124-6131. [PMID: 39042856 DOI: 10.1021/acs.jpca.4c00914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
Iridium(III) organometallic complexes have been a key component in commercialization of organic light-emitting diodes, but the direct relationship between their structural features and photophysical properties has not yet been fully established. Here, combined experimental and theoretical studies are carried out to elucidate the main factors governing the quantum efficiency of red phosphorescent emitters by using two heteroleptic iridium(III) complexes with high geometrical similarity. It is found that two red-emitting heteroleptic iridium complexes differing only in the steric direction of phenylquinoline (pq) and phenylisoquinoline (piq) ligands, annotated Red-pq and Red-piq, show clearly different degrees of distortion of the ligand geometry in the excited state, which leads to the higher quantum yield of Red-piq than that of Red-pq. This larger distortion of the piq ligand causes more suppressed nonradiative decay of Red-piq than that of Red-pq which is the important factor governing the higher quantum yield of Red-piq.
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Affiliation(s)
- Gi Rim Han
- Department of Chemistry, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Ohyun Kwon
- Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co., Ltd., Samsung-ro 130, Youngtong-gu, Suwon-si, Gyeonggi-do 16678, Republic of Korea
| | - Sungmin Kim
- Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co., Ltd., Samsung-ro 130, Youngtong-gu, Suwon-si, Gyeonggi-do 16678, Republic of Korea
| | - Jongwon Choi
- Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co., Ltd., Samsung-ro 130, Youngtong-gu, Suwon-si, Gyeonggi-do 16678, Republic of Korea
| | - Jung Bae Son
- Department of Chemistry, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Kyung Suk Min
- Department of Chemistry, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Jong Woo Lee
- Department of Applied Chemistry, University of Seoul, Seoulsiripdae-ro 163, Dongdaemun-gu, Seoul 02504, Republic of Korea
| | - Byoungki Choi
- Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co., Ltd., Samsung-ro 130, Youngtong-gu, Suwon-si, Gyeonggi-do 16678, Republic of Korea
| | - Seong Keun Kim
- Department of Chemistry, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 08826, Republic of Korea
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2
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Tenopala-Carmona F, Lee OS, Crovini E, Neferu AM, Murawski C, Olivier Y, Zysman-Colman E, Gather MC. Identification of the Key Parameters for Horizontal Transition Dipole Orientation in Fluorescent and TADF Organic Light-Emitting Diodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2100677. [PMID: 34338351 DOI: 10.1002/adma.202100677] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 04/21/2021] [Indexed: 06/13/2023]
Abstract
In organic light-emitting diodes (OLEDs), horizontal orientation of the emissive transition dipole moment (TDM) can improve light outcoupling efficiency by up to 50% relative to random orientation. Therefore, there have been extensive efforts to identify drivers of horizontal orientation. The aspect ratio of the emitter molecule and the glass-transition temperature (Tg ) of the films are currently regarded as particularly important. However, there remains a paucity of systematic studies that establish the extent to which these and other parameters control orientation in the wide range of emitter systems relevant for state-of-the-art OLEDs. Here, recent work on molecular orientation of fluorescent and thermally activated delayed fluorescent emitters in vacuum-processed OLEDs is reviewed. Additionally, to identify parameters linked to TDM orientation, a meta-analysis of 203 published emitter systems is conducted and combined with density-functional theory calculations. Molecular weight (MW) and linearity are identified as key parameters in neat systems. In host-guest systems with low-MW emitters, orientation is mostly influenced by the host Tg , whereas the length and MW of the emitter become more relevant for systems involving higher-MW emitters. To close, a perspective of where the field must advance to establish a comprehensive model of molecular orientation is given.
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Affiliation(s)
- Francisco Tenopala-Carmona
- Organic Semiconductor Centre, SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
- Humboldt Centre for Nano- and Biophotonics, Department of Chemistry, University of Cologne, Greinstr. 4-6, 50939, Köln, Germany
| | - Oliver S Lee
- Organic Semiconductor Centre, SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK
| | - Ettore Crovini
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK
| | - Ana M Neferu
- Organic Semiconductor Centre, SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK
| | - Caroline Murawski
- Organic Semiconductor Centre, SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
| | - Yoann Olivier
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solide, Namur Institute of Structured Matter, Université de Namur, Rue de Bruxelles, 61, Namur, 5000, Belgium
| | - Eli Zysman-Colman
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK
| | - Malte C Gather
- Organic Semiconductor Centre, SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK
- Humboldt Centre for Nano- and Biophotonics, Department of Chemistry, University of Cologne, Greinstr. 4-6, 50939, Köln, Germany
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3
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Camacho R, Täuber D, Scheblykin IG. Fluorescence Anisotropy Reloaded-Emerging Polarization Microscopy Methods for Assessing Chromophores' Organization and Excitation Energy Transfer in Single Molecules, Particles, Films, and Beyond. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1805671. [PMID: 30721532 DOI: 10.1002/adma.201805671] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 11/12/2018] [Indexed: 06/09/2023]
Abstract
Fluorescence polarization is widely used to assess the orientation/rotation of molecules, and the excitation energy transfer between closely located chromophores. Emerging since the 1990s, single molecule fluorescence spectroscopy and imaging stimulate the application of light polarization for studying molecular organization and energy transfer beyond ensemble averaging. Here, traditional fluorescence polarization and linear dichroism methods used for bulk samples are compared with techniques specially developed for, or inspired by, single molecule fluorescence spectroscopy. Techniques for assessing energy transfer in anisotropic samples, where the traditional fluorescence anisotropy framework is not readily applicable, are discussed in depth. It is shown that the concept of a polarization portrait and the single funnel approximation can lay the foundation for alternative energy transfer metrics. Examples ranging from fundamental studies of photoactive materials (conjugated polymers, light-harvesting aggregates, and perovskite semiconductors) to Förster resonant energy transfer (FRET)-based biomedical imaging are presented. Furthermore, novel uses of light polarization for super-resolution optical imaging are mentioned as well as strategies for avoiding artifacts in polarization microscopy.
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Affiliation(s)
- Rafael Camacho
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, B-3001, Leuven, Belgium
| | - Daniela Täuber
- Chemical Physics and NanoLund, Lund University, P.O. Box 124, SE-22100, Lund, Sweden
- Biopolarisation, Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, D-07745, Jena, Germany
- Institute of Solid State Physics, FSU Jena, Helmholtzweg 3, D-07743, Jena, Germany
| | - Ivan G Scheblykin
- Chemical Physics and NanoLund, Lund University, P.O. Box 124, SE-22100, Lund, Sweden
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4
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Babazadeh M, Burn PL, Huang DM. Calculating transition dipole moments of phosphorescent emitters for efficient organic light-emitting diodes. Phys Chem Chem Phys 2019; 21:9740-9746. [DOI: 10.1039/c9cp01045a] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Quantum-chemical calculations show that the direction of the transition dipole moment of organometallic phosphorescent emitters is sensitive to molecular geometry.
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Affiliation(s)
- Mohammad Babazadeh
- Centre for Organic Photonics & Electronics
- School of Chemistry and Molecular Biosciences
- The University of Queensland
- Australia
| | - Paul L. Burn
- Centre for Organic Photonics & Electronics
- School of Chemistry and Molecular Biosciences
- The University of Queensland
- Australia
| | - David M. Huang
- Department of Chemistry
- School of Physical Sciences
- The University of Adelaide
- Adelaide 5005
- Australia
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5
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Hedley GJ, Steiner F, Vogelsang J, Lupton JM. Fluctuations in the Emission Polarization and Spectrum in Single Chains of a Common Conjugated Polymer for Organic Photovoltaics. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2018; 14:e1804312. [PMID: 30444577 DOI: 10.1002/smll.201804312] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Indexed: 06/09/2023]
Abstract
Measuring the nanoscale organization of conjugated polymer chains used in organic photovoltaic (OPV) blends is vital if one wants to understand the materials. This is made very difficult with high efficiency OPV polymers such as PTB7 that form aggregates, as a lack of periodicity and a high degree of disorder make understanding of the nanoscale organization challenging. Here, single molecule spectroscopy is used to observe single chains and aggregates of PTB7. Using four detectors the photoluminescence intensity, wavelength, polarization, and lifetime are simultaneously monitored. Fast (milliseconds) and slow (seconds) fluctuations are observed over a time window of 30 s in all of these observables from single aggregates and chains as individual chromophores activate and deactivate, leading to dynamical changes in the emission spectrum and dipole orientation. This information can be used to help reconstruct the spatial and spectral organization of disordered aggregates of PTB7, thereby adding valuable new information on how the chains are arranged in space.
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Affiliation(s)
- Gordon J Hedley
- WestCHEM, School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040, Regensburg, Germany
| | - Florian Steiner
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040, Regensburg, Germany
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, D-81377, München, Germany
| | - Jan Vogelsang
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, D-81377, München, Germany
| | - John M Lupton
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040, Regensburg, Germany
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6
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Guo L, Wang X, Feng L. Synthesis, photophysical and electrochemical properties of a blue emitter with binaphthalene and carbazole units. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2018; 201:376-381. [PMID: 29775930 DOI: 10.1016/j.saa.2018.04.067] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 04/17/2018] [Accepted: 04/29/2018] [Indexed: 06/08/2023]
Abstract
A blue emitter, 3,3'-(2,2'-dimethoxy-[1,1'-binaphthalene]-6,6'-diyl)bis(9-benzyl-9H-carbazole), was synthesized by Suzuki coupling reaction. The photophysical properties of the emitter in solution were firstly investigated by UV-Vis absorption and fluorescence emission techniques. The results indicate that the emitter has excellent optical and electron transfer properties. The maximum absorption and emission peaks of the emitter are 302 nm and 406 nm with 67.4% fluorescence quantum yield in chloroform, respectively. Thermal stability study reveals that the emitter has a good thermal stability (Td > 330 °C, Tg > 160 °C). Electrochemical Redox properties of the emitters were measured by cyclic voltammetry, and the energy gaps of highest occupied molecular orbital and the lowest unoccupied molecular orbital levels are in good agreement with the results of theoretical calculation. Furthermore, the multilayer electrochemcial device with the emitter was fabricated and its properties were explored. The wavelength of electroluminescence for the device with this emitter locates at 428 nm. These results indicate the emitter as a deep blue-emitting material has promising application in organic light-emitting diode devices.
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Affiliation(s)
- Lixia Guo
- School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan, 030006, PR China
| | - Xiaoju Wang
- Institute of Molecular Science, Chemical Biology and Molecular Engineering, Laboratory of Education Ministry, Shanxi University, Taiyuan 030006, PR China
| | - Liheng Feng
- School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan, 030006, PR China.
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7
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Abstract
The breaking of molecular symmetry through photoexcitation is a ubiquitous but rather elusive process, which, for example, controls the microscopic efficiency of light harvesting in molecular aggregates. A molecular excitation within a π-conjugated segment will self-localize due to strong coupling to molecular vibrations, locally changing bond alternation in a process which is fundamentally nondeterministic. Probing such symmetry breaking usually relies on polarization-resolved fluorescence, which is most powerful on the level of single molecules. Here, we explore symmetry breaking by designing a large, asymmetric acceptor-donor-acceptor (A1-D-A2) complex 10 nm in length, where excitation energy can flow from the donor, a π-conjugated oligomer, to either one of the two boron-dipyrromethene (bodipy) dye acceptors of different color. Fluorescence correlation spectroscopy (FCS) reveals a nondeterministic switching between the energy-transfer pathways from the oligomer to the two acceptor groups on the submillisecond timescale. We conclude that excitation energy transfer, and light harvesting in general, are fundamentally nondeterministic processes, which can be strongly perturbed by external stimuli. A simple demonstration of the relation between exciton localization within the extended π-system and energy transfer to the endcap is given by considering the selectivity of endcap emission through the polarization of the excitation light in triads with bent oligomer backbones. Bending leads to increased localization so that the molecule acquires bichromophoric characteristics in terms of its fluorescence photon statistics.
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Plasmonic Purcell effect reveals obliquely ordered phosphorescent emitters in Organic LEDs. Sci Rep 2017; 7:1826. [PMID: 28500306 PMCID: PMC5431857 DOI: 10.1038/s41598-017-01701-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 04/03/2017] [Indexed: 11/11/2022] Open
Abstract
The non-isotropic alignment of molecules can increase the interaction efficiency with propagating light fields. This applies to both emissive and absorptive systems and can be exploited for achieving unprecedented efficiencies of organic opto-electronic devices such as organic light-emitting diodes. Optical analysis has revealed certain phosphorescent emitters to align spontaneously in an advantageous orientation. Unfortunately, established approaches only determine an average orientation because emission patterns solely depend on the second moments of the transition dipole vector distribution. In order to resolve further details of such a distribution, additional differences in the emission characteristics of parallel and perpendicularly oriented emitters need to be introduced. A thin metal layer near the emitters introduces plasmon mediated losses mostly for perpendicular emitters. Then, analyzing the emission at different polarizations allows one to measure emission lifetimes of mostly parallel or mostly perpendicular oriented emitters. This should alter the transient emission when observing the temporal phosphorescence decay under different directions and/or polarizations. The angular width of the orientation distribution can be derived from the degree of such lifetime splitting. Our results suggest a narrow but obliquely oriented molecular ensemble of Ir(MDQ)2(acac) doped into the α-NPD host inside an Organic LED stack.
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Wilhelm P, Vogelsang J, Poluektov G, Schönfelder N, Keller TJ, Jester S, Höger S, Lupton JM. Molecular Polygons Probe the Role of Intramolecular Strain in the Photophysics of π‐Conjugated Chromophores. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201610723] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Philipp Wilhelm
- Institut für Angewandte und Experimentelle Physik Universität Regensburg Universitätsstrasse 31 93053 Regensburg Germany
| | - Jan Vogelsang
- Institut für Angewandte und Experimentelle Physik Universität Regensburg Universitätsstrasse 31 93053 Regensburg Germany
| | - Georgiy Poluektov
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - Nina Schönfelder
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - Tristan J. Keller
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - Stefan‐Sven Jester
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - Sigurd Höger
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - John M. Lupton
- Institut für Angewandte und Experimentelle Physik Universität Regensburg Universitätsstrasse 31 93053 Regensburg Germany
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10
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Wilhelm P, Vogelsang J, Poluektov G, Schönfelder N, Keller TJ, Jester S, Höger S, Lupton JM. Molecular Polygons Probe the Role of Intramolecular Strain in the Photophysics of π‐Conjugated Chromophores. Angew Chem Int Ed Engl 2017; 56:1234-1238. [DOI: 10.1002/anie.201610723] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Philipp Wilhelm
- Institut für Angewandte und Experimentelle Physik Universität Regensburg Universitätsstrasse 31 93053 Regensburg Germany
| | - Jan Vogelsang
- Institut für Angewandte und Experimentelle Physik Universität Regensburg Universitätsstrasse 31 93053 Regensburg Germany
| | - Georgiy Poluektov
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - Nina Schönfelder
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - Tristan J. Keller
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - Stefan‐Sven Jester
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - Sigurd Höger
- Kekulé-Institut für Organische Chemie und Biochemie der Universität Bonn Gerhard-Domagk-Strasse 1 53121 Bonn Germany
| | - John M. Lupton
- Institut für Angewandte und Experimentelle Physik Universität Regensburg Universitätsstrasse 31 93053 Regensburg Germany
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Abstract
Organic (opto)electronic materials have received considerable attention due to their applications in thin-film-transistors, light-emitting diodes, solar cells, sensors, photorefractive devices, and many others. The technological promises include low cost of these materials and the possibility of their room-temperature deposition from solution on large-area and/or flexible substrates. The article reviews the current understanding of the physical mechanisms that determine the (opto)electronic properties of high-performance organic materials. The focus of the review is on photoinduced processes and on electronic properties important for optoelectronic applications relying on charge carrier photogeneration. Additionally, it highlights the capabilities of various experimental techniques for characterization of these materials, summarizes top-of-the-line device performance, and outlines recent trends in the further development of the field. The properties of materials based both on small molecules and on conjugated polymers are considered, and their applications in organic solar cells, photodetectors, and photorefractive devices are discussed.
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Affiliation(s)
- Oksana Ostroverkhova
- Department of Physics, Oregon State University , Corvallis, Oregon 97331, United States
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12
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Kumar GR, Sarkar SK, Thilagar P. Aggregation-Induced Emission and Sensing Characteristics of Triarylborane-Oligothiophene-Dicyanovinyl Triads. Chemistry 2016; 22:17215-17225. [DOI: 10.1002/chem.201603349] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Indexed: 02/05/2023]
Affiliation(s)
- George Rajendra Kumar
- Inorganic and Physical Chemistry Department (IPC); Indian Institute of Science (IISc); Bangalore 560012 India
| | - Samir Kumar Sarkar
- Inorganic and Physical Chemistry Department (IPC); Indian Institute of Science (IISc); Bangalore 560012 India
| | - Pakkirisamy Thilagar
- Inorganic and Physical Chemistry Department (IPC); Indian Institute of Science (IISc); Bangalore 560012 India
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13
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Park KH, Cho JW, Kim TW, Shimizu H, Nakao K, Iyoda M, Kim D. Defining Cyclic-Acyclic Exciton Transition at the Single-Molecule Level: Size-Dependent Conformational Heterogeneity and Exciton Delocalization in Ethynylene-Bridged Cyclic Oligothiophenes. J Phys Chem Lett 2016; 7:1260-1266. [PMID: 26983838 DOI: 10.1021/acs.jpclett.6b00360] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Conformational disorder in π-conjugated cyclic systems plays a crucial role in controlling the extent of exciton delocalization in much the same way as that in linear counterparts. However, to date, there have been no detailed spectroscopic investigations on the nature of excitons in π-conjugated cyclic systems at the single-molecule level. Herein, we studied the effect of conformational disorder on the excitonic behaviors of cyclic oligothiophenes composed of 6, 8, 10, and 12 subunits (C-6T, C-8T, C-10T, and C-12T, respectively) by employing single-molecule fluorescence spectroscopy. We found that, due to the cyclic symmetry constraint which suppresses S1-S0 transition, small and rigid C-6T and C-8T exhibit extremely long fluorescence lifetimes, while short lifetimes typical of linear systems are dominant in large, flexible C-10T and C-12T. Two-dimensional correlation maps between fluorescence lifetimes and spectral positions show that, by torsional defects created through continued photoexcitation, fully delocalized cyclic excitons shrink to form acyclic excitons in the case of C-10T, while localized acyclic excitons from initial states are maintained in the case of C-12T. The distribution of linear dichroism values from C-6T to C-10T gradually broadens but narrows in C-12T, suggesting a cyclic-to-acyclic transition in excitonic nature between C-10T and C-12T.
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Affiliation(s)
- Kyu Hyung Park
- Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University , Seoul 03722, Korea
| | - Jae-Won Cho
- Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University , Seoul 03722, Korea
| | - Tae-Woo Kim
- Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University , Seoul 03722, Korea
| | - Hideyuki Shimizu
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University , Hachioji, Tokyo 192-0397, Japan
| | - Kazumi Nakao
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University , Hachioji, Tokyo 192-0397, Japan
| | - Masahiko Iyoda
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University , Hachioji, Tokyo 192-0397, Japan
| | - Dongho Kim
- Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University , Seoul 03722, Korea
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14
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Wang Y, Cabry CP, Xiao M, Male L, Cowling SJ, Bruce DW, Shi J, Zhu W, Baranoff E. Blue and Green Phosphorescent Liquid-Crystalline Iridium Complexes with High Hole Mobility. Chemistry 2015; 22:1618-21. [DOI: 10.1002/chem.201504669] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Yafei Wang
- School of Chemistry; University of Birmingham; Birmingham B15 2TT (UK
- Department of Chemistry; Key Lab of Environment-Friendly Chemistry and Application in the Ministry of Education, Xiangtan University; Xiangtan 411105 (P.R. China
| | | | - ManJun Xiao
- Department of Chemistry; Key Lab of Environment-Friendly Chemistry and Application in the Ministry of Education, Xiangtan University; Xiangtan 411105 (P.R. China
| | - Louise Male
- School of Chemistry; University of Birmingham; Birmingham B15 2TT (UK
| | - Stephen J. Cowling
- Department of Chemistry; University of York; Heslington, York YO10 5DD (UK
| | - Duncan W. Bruce
- Department of Chemistry; University of York; Heslington, York YO10 5DD (UK
| | - Junwei Shi
- Department of Chemistry; Key Lab of Environment-Friendly Chemistry and Application in the Ministry of Education, Xiangtan University; Xiangtan 411105 (P.R. China
| | - Weiguo Zhu
- Department of Chemistry; Key Lab of Environment-Friendly Chemistry and Application in the Ministry of Education, Xiangtan University; Xiangtan 411105 (P.R. China
| | - Etienne Baranoff
- School of Chemistry; University of Birmingham; Birmingham B15 2TT (UK
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