1
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Gu Q, Gorgon S, Romanov AS, Li F, Friend RH, Evans EW. Fast Transfer of Triplet to Doublet Excitons from Organometallic Host to Organic Radical Semiconductors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2402790. [PMID: 38819637 DOI: 10.1002/adma.202402790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 05/09/2024] [Indexed: 06/01/2024]
Abstract
Spin triplet exciton formation sets limits on technologies using organic semiconductors that are confined to singlet-triplet photophysics. In contrast, excitations in the spin doublet manifold in organic radical semiconductors can show efficient luminescence. Here the dynamics of the spin allowed process of intermolecular energy transfer from triplet to doublet excitons are explored. A carbene-metal-amide (CMA-CF3) is employed as a model triplet donor host, since following photoexcitation it undergoes extremely fast intersystem crossing to generate a population of triplet excitons within 4 ps. This enables a foundational study for tracking energy transfer from triplets to a model radical semiconductor, TTM-3PCz. Over 74% of all radical luminescence originates from the triplet channel in this system under photoexcitation. It is found that intermolecular triplet-to-doublet energy transfer can occur directly and rapidly, with 12% of triplet excitons transferring already on sub-ns timescales. This enhanced triplet harvesting mechanism is utilized in efficient near-infrared organic light-emitting diodes, which can be extended to other opto-electronic and -spintronic technologies by radical-based spin control in molecular semiconductors.
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Affiliation(s)
- Qinying Gu
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
- Shanghai Artificial Intelligence Laboratory, Shanghai, 200232, P. R. China
| | - Sebastian Gorgon
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Alexander S Romanov
- Department of Chemistry, University of Manchester, Oxford Rd., Manchester, M13 9PL, UK
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun, 130012, P. R. China
| | - Richard H Friend
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Emrys W Evans
- Department of Chemistry, Swansea University, Singleton Park, Swansea, SA2 8PP, UK
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2
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Cho HH, Gorgon S, Londi G, Giannini S, Cho C, Ghosh P, Tonnelé C, Casanova D, Olivier Y, Baikie TK, Li F, Beljonne D, Greenham NC, Friend RH, Evans EW. Efficient near-infrared organic light-emitting diodes with emission from spin doublet excitons. NATURE PHOTONICS 2024; 18:905-912. [PMID: 39247521 PMCID: PMC11374703 DOI: 10.1038/s41566-024-01458-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2023] [Accepted: 05/07/2024] [Indexed: 09/10/2024]
Abstract
The development of luminescent organic radicals has resulted in materials with excellent optical properties for near-infrared emission. Applications of light generation in this range span from bioimaging to surveillance. Although the unpaired electron arrangements of radicals enable efficient radiative transitions within the doublet-spin manifold in organic light-emitting diodes, their performance is limited by non-radiative pathways introduced in electroluminescence. Here we present a host-guest design for organic light-emitting diodes that exploits energy transfer with up to 9.6% external quantum efficiency for 800 nm emission. The tris(2,4,6-trichlorophenyl)methyl-triphenyl-amine radical guest is energy-matched to the triplet state in a charge-transporting anthracene-derivative host. We show from optical spectroscopy and quantum-chemical modelling that reversible host-guest triplet-doublet energy transfer allows efficient harvesting of host triplet excitons.
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Affiliation(s)
- Hwan-Hee Cho
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | | | - Giacomo Londi
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
- Present Address: Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy
| | - Samuele Giannini
- Laboratory for Chemistry of Novel Materials, University of Mons, Mons, Belgium
- Present Address: Institute of Chemistry of OrganoMetallic Compounds, National Research Council (ICCOM-CNR), Pisa, Italy
| | - Changsoon Cho
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- Institute for Convergence Research and Education in Advanced Technology, Yonsei University, Seoul, Republic of Korea
| | - Pratyush Ghosh
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Claire Tonnelé
- Donostia International Physics Centre, Donostia, Spain
- Ikerbasque Foundation for Science, Bilbao, Spain
| | - David Casanova
- Donostia International Physics Centre, Donostia, Spain
- Ikerbasque Foundation for Science, Bilbao, Spain
| | - Yoann Olivier
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
| | - Tomi K Baikie
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Mons, Belgium
| | - Neil C Greenham
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | | | - Emrys W Evans
- Department of Chemistry, Swansea University, Swansea, UK
- Centre for Integrative Semiconductor Materials, Swansea University, Swansea, UK
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3
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Li P, Bai F. A Thorough Examination of the Variables Affecting the Quantum Efficiency of Radiative Decay of Trichlorotriphenylmethyl Radicals. J Phys Chem A 2024; 128:4279-4287. [PMID: 38752807 DOI: 10.1021/acs.jpca.4c01779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2024]
Abstract
Fluorescence quantum efficiency is determined by the competition between radiation and nonradiation processes of the excited states. Understanding the factors affecting the radiation and nonradiative decay rates is of great significance for the design of luminescent materials. The excitation state deactivation mechanisms of singlet and triplet states have been extensively studied, providing a comprehensive understanding of the processes involved in the relaxation of these states. However, research on free radical systems involving doublet states is relatively scarce. Therefore, in this study, radiation and nonradiative decay rates and the mechanism of a series of trichlorotriphenylmethyl-based radicals were investigated theoretically. The results indicate that the relative rotations of electron donor and acceptor, as well as the internal rotations of trichlorotriphenylmethyl moiety, play important roles in energy dissipation through nonradiative channels. The effect of a solid-state environment on the radiation and nonradiative decay rates of radicals was investigated using a combination of quantum mechanics and molecular mechanics methods. The results indicate that the solid-state environment restricts the expansion of the conjugated system in the excited state of radicals, leading to a slight decrease in radiative decay rate. In addition, the solid-state environment reduces the reorganization energy and also affects the adiabatic excitation energy of radicals. The reduction in reorganization energy results in a decrease in nonradiative rate, while the opposite effect is observed for adiabatic excitation energy. The nonradiative rate of radicals in a solid-state environment is thus inflected by a combination of molecular geometric structure relaxation and ground-excited state energy gap.
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Affiliation(s)
- Pengyuan Li
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Institute of Theoretical Chemistry and College of Chemistry, Jilin University, Changchun 130021, P. R. China
| | - Fuquan Bai
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Institute of Theoretical Chemistry and College of Chemistry, Jilin University, Changchun 130021, P. R. China
- State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China
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Ju CW, Shen Y, French EJ, Yi J, Bi H, Tian A, Lin Z. Accurate Electronic and Optical Properties of Organic Doublet Radicals Using Machine Learned Range-Separated Functionals. J Phys Chem A 2024. [PMID: 38382058 DOI: 10.1021/acs.jpca.3c07437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Luminescent organic semiconducting doublet-spin radicals are unique and emergent optical materials because their fluorescent quantum yields (Φfl) are not compromised by the spin-flipping intersystem crossing (ISC) into a dark high-spin state. The multiconfigurational nature of these radicals challenges their electronic structure calculations in the framework of single-reference density functional theory (DFT) and introduces room for method improvement. In the present study, we extended our earlier development of ML-ωPBE [J. Phys. Chem. Lett., 2021, 12, 9516-9524], a range-separated hybrid (RSH) exchange-correlation (XC) functional constructed using the stacked ensemble machine learning (SEML) algorithm, from closed-shell organic semiconducting molecules to doublet-spin organic semiconducting radicals. We assessed its performance for a new test set of 64 doublet-spin radicals from five categories while placing all previously compiled 3926 closed-shell molecules in the new training set. Interestingly, ML-ωPBE agrees with the nonempirical OT-ωPBE functional regarding the prediction of the molecule-dependent range-separation parameter (ω), with a small mean absolute error (MAE) of 0.0197 a0-1, but saves the computational cost by 2.46 orders of magnitude. This result demonstrates an outstanding domain adaptation capacity of ML-ωPBE for diverse organic semiconducting species. To further assess the predictive power of ML-ωPBE in experimental observables, we also applied it to evaluate absorption and fluorescence energies (Eabs and Efl) using linear-response time-dependent DFT (TDDFT), and we compared its behavior with nine popular XC functionals. For most radicals, ML-ωPBE reproduces experimental measurements of Eabs and Efl with small MAEs of 0.299 and 0.254 eV, only marginally different from those of OT-ωPBE. Our work illustrates a successful extension of the SEML framework from closed-shell molecules to doublet-spin radicals and will open the venue for calculating optical properties for organic semiconductors using single-reference TDDFT.
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Affiliation(s)
- Cheng-Wei Ju
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States
| | - Yili Shen
- Manning College of Information and Computer Sciences, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Ethan J French
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, United States
| | - Jun Yi
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Department of Chemistry, Wake Forest University, Winston-Salem, North Carolina 27109, United States
| | - Hongshan Bi
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Aaron Tian
- Manning College of Information and Computer Sciences, University of Massachusetts, Amherst, Massachusetts 01003, United States
- Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Zhou Lin
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
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5
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Mizuno A, Matsuoka R, Mibu T, Kusamoto T. Luminescent Radicals. Chem Rev 2024; 124:1034-1121. [PMID: 38230673 DOI: 10.1021/acs.chemrev.3c00613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2024]
Abstract
Organic radicals are attracting increasing interest as a new class of molecular emitters. They demonstrate electronic excitation and relaxation dynamics based on their doublet or higher multiplet spin states, which are different from those based on singlet-triplet manifolds of conventional closed-shell molecules. Recent studies have disclosed luminescence properties and excited state dynamics unique to radicals, such as highly efficient electron-photon conversion in OLEDs, NIR emission, magnetoluminescence, an absence of heavy atom effect, and spin-dependent and spin-selective dynamics. These are difficult or sometimes impossible to achieve with closed-shell luminophores. This review focuses on luminescent organic radicals as an emerging photofunctional molecular system, and introduces the material developments, fundamental properties including luminescence, and photofunctions. Materials covered in this review range from monoradicals, radical oligomers, and radical polymers to metal complexes with radical ligands demonstrating radical-involved emission. In addition to stable radicals, transiently formed radicals generated in situ by external stimuli are introduced. This review shows that luminescent organic radicals have great potential to expand the chemical and spin spaces of luminescent molecular materials and thus broaden their applicability to photofunctional systems.
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Affiliation(s)
- Asato Mizuno
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan
| | - Ryota Matsuoka
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Shonan Village, HayamaKanagawa 240-0193, Japan
| | - Takuto Mibu
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan
| | - Tetsuro Kusamoto
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan
- SOKENDAI (The Graduate University for Advanced Studies), Shonan Village, HayamaKanagawa 240-0193, Japan
- JST-PRESTO, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012, Japan
- Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
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6
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Cho HH, Gorgon S, Hung HC, Huang JY, Wu YR, Li F, Greenham NC, Evans EW, Friend RH. Efficient and Bright Organic Radical Light-Emitting Diodes with Low Efficiency Roll-Off. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2303666. [PMID: 37684741 DOI: 10.1002/adma.202303666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 08/08/2023] [Indexed: 09/10/2023]
Abstract
Organic radicals have been of interest due to their potential to replace nonradical-based organic emitters, especially for deep-red/near-infrared (NIR) electroluminescence (EL), based on the spin-allowed doublet fluorescence. However, the performance of the radical-based EL devices is limited by low carrier mobility which causes a large efficiency roll-off at high current densities. Here, highly efficient and bright doublet EL devices are reported by combining a thermally activated delayed fluorescence (TADF) host that supports both electron and hole transport and a tris(2,4,6-trichlorophenyl)methyl-based radical emitter. Steady-state and transient photophysical studies reveal the optical signatures of doublet luminescence mechanisms arising from both host and guest photoexcitation. The host system presented here allows balanced hole and electron currents, and a high maximum external quantum efficiency (EQE) of 17.4% at 707 nm peak emission with substantially improved efficiency roll-off is reported: over 70% of the maximum EQE (12.2%) is recorded at 10 mA cm-2 , and even at 100 mA cm-2 , nearly 50% of the maximum EQE (8.4%) is maintained. This is an important step in the practical application of organic radicals to NIR light-emitting devices.
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Affiliation(s)
- Hwan-Hee Cho
- Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Sebastian Gorgon
- Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Hsiao-Chun Hung
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, 10617, Taipei, Taiwan
| | - Jun-Yu Huang
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, 10617, Taipei, Taiwan
| | - Yuh-Renn Wu
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, 10617, Taipei, Taiwan
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun, 130012, P. R. China
| | - Neil C Greenham
- Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Emrys W Evans
- Department of Chemistry, Swansea University, Singleton Park, Swansea, SA2 8PP, UK
| | - Richard H Friend
- Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
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7
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Ding J, Zhang M, Gao Y, Lu C, Zhang M, Li F. A Simple Molecular Design Strategy for Luminescent Radicals to Achieve Near-Infrared Emission. J Phys Chem Lett 2023; 14:8244-8250. [PMID: 37676025 DOI: 10.1021/acs.jpclett.3c01820] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/08/2023]
Abstract
The spin-allowed doublet emission of luminescent radicals has recently attracted significant attention. However, the spectral range of most reported luminescent radical emitters and their corresponding organic light-emitting diodes (OLEDs) is confined to the red and deep red regions, with only a few extending to the near-infrared region, specifically in the context of an emission peak exceeding 800 nm. Herein, a luminescent radical, 2-(4-(bis(2,4,6-trichlorophenyl)methyl radical)-3,5-dichlorophenyl)-4-phenyl-4H-thieno[3,2-b]indole (TTM-2PTI), with NIR emission peaking at 830 nm in toluene, was obtained through attaching a 4-phenyl-4H-thieno[3,2-b]indole group to the TTM radical core. An organic light-emitting diode (OLED) utilizing TTM-2PTI as the emitter exhibits electroluminescence (EL) emission peaking at 870 nm, which is the longest EL wavelength among the doublet-emissive near-infrared (NIR) OLEDs. This work provides a simple molecular design strategy to achieve NIR emission of radicals by leveraging the lower steric hindrance and electron-donating ability of thiophene.
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Affiliation(s)
- Junshuai Ding
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun 130012, P. R. China
| | - Minzhe Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun 130012, P. R. China
| | - Yuhang Gao
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun 130012, P. R. China
| | - Chen Lu
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun 130012, P. R. China
| | - Ming Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun 130012, P. R. China
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun 130012, P. R. China
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8
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Gao S, Cui Z, Li F. Doublet-emissive materials for organic light-emitting diodes: exciton formation and emission processes. Chem Soc Rev 2023; 52:2875-2885. [PMID: 37052349 DOI: 10.1039/d2cs00772j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
Doublet-emission is mainly discovered in stable radicals, lanthanide-metal complexes with an f1 electron configuration and transition-metal complexes with a low-spin d5 electron configuration, and has a distinct radiation mechanism from closed-shell luminescent molecules and thus technology opportunities. There exists an unpaired electron in the frontier molecular orbitals which enables efficient nanosecond-scale luminescence in these materials due to the spin-allowed transitions between doublet-spin states. In this review, we summarize recent advances in these materials and their application in organic light emitting diodes (OLEDs). The photoluminescence and electroluminescence mechanisms of different doublet-emissive molecular systems are discussed, in addition to the photophysical phenomena arising from doublet states. We also outline the current challenges faced by each molecular system, and the potential outlook on the future research trends in this field.
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Affiliation(s)
- Shengxiang Gao
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, P. R. China.
| | - Zhiyuan Cui
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, P. R. China.
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, P. R. China.
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9
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Lu C, Cho E, Cui Z, Gao Y, Cao W, Brédas JL, Coropceanu V, Li F. Towards Efficient and Stable Donor-Acceptor Luminescent Radicals. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2208190. [PMID: 36417767 DOI: 10.1002/adma.202208190] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 11/01/2022] [Indexed: 06/16/2023]
Abstract
In contrast to closed-shell luminescent molecules, the electronic ground state and lowest excited state in organic luminescent radicals are both spin doublet, which results in spin-allowed radiative transitions. Most reported luminescent radicals with high photoluminescent quantum efficiency (PLQE) have a donor-acceptor (D-A•) chemical structure where an electron-donating group is covalently attached to an electron-withdrawing radical core (A•). Understanding the main factors that define the efficiency and stability of D-A• type luminescent radicals remains challenging. Here, we designed and synthesized a series of tri(2,4,6-trichlorophenyl)methyl (TTM) radical derivatives with donor substituents varying by their extent of conjugation and their number of imine-type nitrogen atoms. The experimental results suggest that the luminescence efficiency and stability of the radicals are proportional to the degree of conjugation but inversely proportional to the number of imine nitrogen atoms in the substituents. These experimental trends are very well reproduced by density functional theory calculations. The theoretical results indicate that both the luminescence efficiency and radical stability are related to the energy difference between the charge transfer (CT) and local-excitation (LE) states, which decreases as either the number of imine nitrogen atoms in the substituent increases or its conjugation length decreases.
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Affiliation(s)
- Chen Lu
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Eunkyung Cho
- Department of Chemistry and Biochemistry, University of Arizona College of Science, Tucson, AZ, 85721-0088, USA
| | - Zhiyuan Cui
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Yuhang Gao
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Wenjuan Cao
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Jean-Luc Brédas
- Department of Chemistry and Biochemistry, University of Arizona College of Science, Tucson, AZ, 85721-0088, USA
| | - Veaceslav Coropceanu
- Department of Chemistry and Biochemistry, University of Arizona College of Science, Tucson, AZ, 85721-0088, USA
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, P. R. China
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11
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Abroshan H, Winget P, Kwak HS, Brown CT, Halls MD. Organic radical emitters: nature of doublet excitons in emissive layers. Phys Chem Chem Phys 2022; 24:16891-16899. [PMID: 35788234 DOI: 10.1039/d2cp00592a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Organic radical emitters have received significant attention as a new route to efficient organic light-emitting diodes (OLEDs). The electronic structure of radical emitters allows bypassing the triplet harvesting issue in current OLED devices. However, the nature of doublet excited states remains elusive due to the complex nature of emissive layers. To date, the computational efforts have treated radical carrying materials as isolated entities in the gas phase. However, OLED materials are applied as thin solid films where intermolecular interactions significantly impact optoelectronic properties of the devices. Here, we combine molecular dynamics simulations and quantum chemical calculations to evaluate the effect of emitter-host interactions on the performance of radical-based emissive layers. Results demonstrate that intermolecular interactions remarkably modulate the electronic properties of the radicals in the thin solid films. The doublet excitons of isolated emitters demonstrate a hybrid character of charge-transfer (CT) and local-excitation (LE), while the emitter-host clusters present a significant CT character. Further, the impact of static and dynamic disorders on the hole-electron recombination is studied. Although the host-emitter interactions simultaneously decrease radiative rates and increase non-radiative rates, the latter rates are 100 times smaller than the former rates, allowing internal quantum efficiency to reach 100% for the doublet-based emission process. The results of this study highlight the significant impact of host-emitter interactions on radiative and non-radiative recombination processes and offer guidelines to tune these interactions for advancing radical-based OLEDs.
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12
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Fluorescent Organic π‐Radicals Stabilized with Boron: Featuring a SOMO–LUMO Electronic Transition. Angew Chem Int Ed Engl 2022; 61:e202201965. [DOI: 10.1002/anie.202201965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Indexed: 11/07/2022]
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13
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Ito M, Shirai S, Xie Y, Kushida T, Ando N, Soutome H, Fujimoto KJ, Yanai T, Tabata K, Miyata Y, Kita H, Yamaguchi S. Fluorescent Organic π‐Radicals Stabilized with Boron: Featuring a SOMO–LUMO Electronic Transition. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202201965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Masato Ito
- Nagoya University: Nagoya Daigaku Graduate School of Science JAPAN
| | - Shusuke Shirai
- Nagoya University: Nagoya Daigaku Graduate School of Science JAPAN
| | - Yongfa Xie
- Nagoya University: Nagoya Daigaku Graduate School of Science JAPAN
| | | | - Naoki Ando
- Nagoya University: Nagoya Daigaku Graduate School of Science JAPAN
| | - Hiroki Soutome
- Nagoya University: Nagoya Daigaku Graduate School of Science JAPAN
| | - Kazuhiro J. Fujimoto
- Nagoya University: Nagoya Daigaku Institute of Transformative Bio-Molecules JAPAN
| | - Takeshi Yanai
- Nagoya University: Nagoya Daigaku Institute of Transformative Bio-Molecules JAPAN
| | | | | | | | - Shigehiro Yamaguchi
- Nagoya University Department of Chemistry Graduate School of Science Furo, Chikusa 464-8602 Nagoya JAPAN
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14
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Proton-induced Conversion from Non-Aufbau to Aufbau Electronic Structure of an Organic Radical with Turn-on Fluorescence. Chem Res Chin Univ 2022. [DOI: 10.1007/s40242-022-2015-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Luo J, Rong XF, Ye YY, Li WZ, Wang XQ, Wang W. Research Progress on Triarylmethyl Radical-Based High-Efficiency OLED. Molecules 2022; 27:1632. [PMID: 35268732 PMCID: PMC8911689 DOI: 10.3390/molecules27051632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 02/24/2022] [Accepted: 02/25/2022] [Indexed: 11/17/2022] Open
Abstract
Perchlorotrityl radical (PTM), tris (2,4,6-trichlorophenyl) methyl radical (TTM), (3,5-dichloro-4-pyridyl) bis (2,4,6 trichlorophenyl) methyl radical (PyBTM), (N-carbazolyl) bis (2,4,6-trichlorophenyl) methyl radical (CzBTM), and their derivatives are stable organic radicals that exhibit light emissions at room temperature. Since these triarylmethyl radicals have an unpaired electron, their electron spins at the lowest excited state and ground state are both doublets, and the transition from the lowest excited state to the ground state does not pose the problem of a spin-forbidden reaction. When used as OLED layers, these triarylmethyl radicals exhibit unique light-emitting properties, which can increase the theoretical upper limit of the OLED's internal quantum efficiency (IQE) to 100%. In recent years, research on the luminescent properties of triarylmethyl radicals has attracted increasing attention. In this review, recent developments in these triarylmethyl radicals and their derivatives in OLED devices are introduced.
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Affiliation(s)
| | | | | | | | - Xiao-Qiang Wang
- College of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan 430081, China; (J.L.); (X.-F.R.); (Y.-Y.Y.); (W.-Z.L.)
| | - Wenjing Wang
- College of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan 430081, China; (J.L.); (X.-F.R.); (Y.-Y.Y.); (W.-Z.L.)
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Tan Y, Hsu SN, Tahir H, Dou L, Savoie BM, Boudouris BW. Electronic and Spintronic Open-Shell Macromolecules, Quo Vadis? J Am Chem Soc 2022; 144:626-647. [PMID: 34982552 DOI: 10.1021/jacs.1c09815] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Open-shell macromolecules (i.e., polymers containing radical sites either along their backbones or at the pendant sites of repeat units) have attracted significant attention owing to their intriguing chemical and physical (e.g., redox, optoelectronic, and magnetic) properties, and they have been proposed and/or implemented in a wide range of potential applications (e.g., energy storage devices, electronic systems, and spintronic modules). These successes span multiple disciplines that range from advanced macromolecular chemistry through nanoscale structural characterization and on to next-generation solid-state physics and the associated devices. In turn, this has allowed different scientific communities to expand the palette of radical-containing polymers relatively quickly. However, critical gaps remain on many fronts, especially regarding the elucidation of key structure-property-function relationships that govern the underlying electrochemical, optoelectronic, and spin phenomena in these materials systems. Here, we highlight vital developments in the history of open-shell macromolecules to explain the current state of the art in the field. Moreover, we provide a critical review of the successes and bring forward open opportunities that, if solved, could propel this class of materials in a meaningful manner. Finally, we provide an outlook to address where it seems most likely that open-shell macromolecules will go in the coming years. Our considered view is that the future of radical-containing polymers is extremely bright and the addition of talented researchers with diverse skills to the field will allow these materials and their end-use devices to have a positive impact on the global science and technology enterprise in a relatively rapid manner.
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Affiliation(s)
- Ying Tan
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Sheng-Ning Hsu
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Hamas Tahir
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Letian Dou
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States.,Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907, United States
| | - Brett M Savoie
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Bryan W Boudouris
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States.,Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
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Zhou HP, Wu SX, Duan YC, Gao FW, Pan QQ, Kan YH, Su ZM. The combination of skeleton-engineering and periphery-engineering: a design strategy for organic doublet emitters. Phys Chem Chem Phys 2022; 24:26853-26862. [DOI: 10.1039/d2cp03948f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A series of radicals based on tris(2,4,6-trichlorophenyl)methyl (TTM) were theoretically designed and evaluated by combining skeleton-engineering and periphery-engineering strategies.
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Affiliation(s)
- Hai-Ping Zhou
- School of Chemistry and Environmental Engineering, Jilin Provincial Science and Technology Innovation Center of Optical Materials and Chemistry, Changchun University of Science and Technology, Changchun 130012, China
| | - Shui-Xing Wu
- Key Laboratory of Electrochemical Energy Storage and Energy Conversion of Hainan Province, School of Chemistry & Chemical Engineering, Hainan Normal University, Haikou 571158, China
| | - Ying-Chen Duan
- School of Chemistry and Environmental Engineering, Jilin Provincial Science and Technology Innovation Center of Optical Materials and Chemistry, Changchun University of Science and Technology, Changchun 130012, China
| | - Feng-Wei Gao
- School of Chemistry and Environmental Engineering, Jilin Provincial Science and Technology Innovation Center of Optical Materials and Chemistry, Changchun University of Science and Technology, Changchun 130012, China
| | - Qing-Qing Pan
- School of Chemistry and Environmental Engineering, Jilin Provincial Science and Technology Innovation Center of Optical Materials and Chemistry, Changchun University of Science and Technology, Changchun 130012, China
| | - Yu-He Kan
- Jiangsu Province Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huai’an 223300, China
| | - Zhong-Min Su
- School of Chemistry and Environmental Engineering, Jilin Provincial Science and Technology Innovation Center of Optical Materials and Chemistry, Changchun University of Science and Technology, Changchun 130012, China
- State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130021, China
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Ji L, Shi J, Wei J, Yu T, Huang W. Air-Stable Organic Radicals: New-Generation Materials for Flexible Electronics? ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1908015. [PMID: 32583945 DOI: 10.1002/adma.201908015] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Revised: 03/05/2020] [Accepted: 03/08/2020] [Indexed: 05/28/2023]
Abstract
In the last few years, air-stable organic radicals and radical polymers have attracted tremendous attention due to their outstanding performance in flexible electronic devices, including transistors, batteries, light-emitting diodes, thermoelectric and photothermal conversion devices, and among many others. The main issue of radicals from laboratory studies to real-world applications is that the number of known air-stable radicals is very limited, and the radicals that have been used as materials are even less. Here, the known and newly developed air-stable organic radicals are summarized, generalizing the way of observing air-stable radicals. The special electric and photophysical properties of organic radicals and radical polymers are interpreted, which give radicals a wide scope for various of potential applications. Finally, the exciting applications of radicals that have been achieved in flexible electronic devices are summarized. The aim herein is to highlight the recent achievements in radicals in chemistry, materials science, and flexible electronics, and further bridge the gap between these three disciplines.
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Affiliation(s)
- Lei Ji
- Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE) & Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University, Xi'an, Shaanxi, 710072, China
| | - Junqing Shi
- Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE) & Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University, Xi'an, Shaanxi, 710072, China
| | - Juan Wei
- Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE) & Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University, Xi'an, Shaanxi, 710072, China
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore
| | - Tao Yu
- Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE) & Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University, Xi'an, Shaanxi, 710072, China
| | - Wei Huang
- Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE) & Shaanxi Institute of Biomedical Materials and Engineering (SIBME), Northwestern Polytechnical University, Xi'an, Shaanxi, 710072, China
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Zhao T, Han J, Duan P, Liu M. New Perspectives to Trigger and Modulate Circularly Polarized Luminescence of Complex and Aggregated Systems: Energy Transfer, Photon Upconversion, Charge Transfer, and Organic Radical. Acc Chem Res 2020; 53:1279-1292. [PMID: 32649172 DOI: 10.1021/acs.accounts.0c00112] [Citation(s) in RCA: 152] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Chiral functional materials with circularly polarized luminescence (CPL) have risen rapidly in recent years because of their fascinating characteristics and potential applications in various research fields. CPL refers to the differential spontaneous emission of left (L)- and right (R)-handed circularly polarized light upon photon or electron excitation. Generally, an outstanding CPL-active material needs to possess a high luminescence dissymmetry factor (glum) (defined as 2(IL - IR)/(IL + IR) where I is the emission intensity), which is between -2 and +2. Although the exciting development in CPL-active materials was achieved, the modulation of CPL signs is still a challenge. For small organic systems, a relatively small glum value, one of the key parameters of CPL, limits their practical applications. Searching for efficient approaches for amplifying glum is important. Therefore, over the past decades, besides optimizing the structure of small molecules, many other strategies to obtain efficient CPL-active materials have been developed. For instance, self-assembly has been well demonstrated as an effective approach to amplify the supramolecular chirality as well as the glum values. On the other hand, chiral liquid crystals (CLCs), which are capable of selective reflection of left- and right-handed circularly polarized light, also to serve as a host matrix for endowing guest emitters with CPL activity and high glum values. However, self-assembly focuses on modulating the conformation and spatial arrangement of chiral emitters. And the CPL of a luminophore-doped CLC matrix depends on the helix pitch and band gap positions. Lately, novel photophysical approaches to modulate CPL signs have gradually emerged.In this Account, we discuss the recent progress of excited-state-regulation involved CPL-active materials. The emergence, amplification, and inversion of CPL can be adjusted through regulation of the excited state of chiral emitters. For example, Förster resonance energy transfer (FRET) can amplify the glum values of chiral energy acceptors in chiral supramolecular assemblies. By combining the concepts of photon upconversion and CPL, high-energy upconverted circularly polarized emission was achieved under excitation of low-energy light, accompanied by an amplified glum. In addition, the organic systems with unpaired electrons, i.e., charge transfer (CT) system and open-shell π-radical, show favorable CPL properties, which can be flexibly tuned with an applied magnetic field. It should be noted that these photophysical process are associated with the excited state of chiral emitters. So far, while the main focus is on the regulation of the molecular and supramolecular nanostructures, direct regulation of the excited state of the chiral system will serve as a new platform to understand and regulate the CPL activity and will be helpful to develop smart chiroptical materials.
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Affiliation(s)
- Tonghan Zhao
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology (NCNST), No.11, ZhongGuanCun BeiYiTiao, Beijing 100190, P.R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Jianlei Han
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology (NCNST), No.11, ZhongGuanCun BeiYiTiao, Beijing 100190, P.R. China
| | - Pengfei Duan
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology (NCNST), No.11, ZhongGuanCun BeiYiTiao, Beijing 100190, P.R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Minghua Liu
- CAS Center for Excellence in Nanoscience, CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology (NCNST), No.11, ZhongGuanCun BeiYiTiao, Beijing 100190, P.R. China
- Beijing National Laboratory for Molecular Science, CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, No.2, ZhongGuanCun BeiYiJie, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
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An K, Xie G, Gong S, Chen Z, Zhou X, Ni F, Yang C. Monoradically luminescent polymers by a super acid-catalyzed polymerization and deep-red electroluminescence. Sci China Chem 2020. [DOI: 10.1007/s11426-020-9778-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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21
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Recent progress in phosphorescent Ir(III) complexes for nondoped organic light-emitting diodes. Coord Chem Rev 2020. [DOI: 10.1016/j.ccr.2020.213283] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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Jin Q, Chen S, Sang Y, Guo H, Dong S, Han J, Chen W, Yang X, Li F, Duan P. Circularly polarized luminescence of achiral open-shell π-radicals. Chem Commun (Camb) 2019; 55:6583-6586. [DOI: 10.1039/c9cc03281a] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Doublet emission-based circularly polarized luminescence was successfully realized in luminescent π-radicals by applying three kinds of approaches, namely, induction by a longitudinal magnetic field, supramolecular chiral co-assembly, and doping into chiral liquid crystals.
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