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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. Adv Mater 2023; 35:e2303666. [PMID: 37684741 DOI: 10.1002/adma.202303666] [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] [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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Gorgon S, Lv K, Grüne J, Drummond BH, Myers WK, Londi G, Ricci G, Valverde D, Tonnelé C, Murto P, Romanov AS, Casanova D, Dyakonov V, Sperlich A, Beljonne D, Olivier Y, Li F, Friend RH, Evans EW. Reversible spin-optical interface in luminescent organic radicals. Nature 2023; 620:538-544. [PMID: 37587296 PMCID: PMC10432275 DOI: 10.1038/s41586-023-06222-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 05/16/2023] [Indexed: 08/18/2023]
Abstract
Molecules present a versatile platform for quantum information science1,2 and are candidates for sensing and computation applications3,4. Robust spin-optical interfaces are key to harnessing the quantum resources of materials5. To date, carbon-based candidates have been non-luminescent6,7, which prevents optical readout via emission. Here we report organic molecules showing both efficient luminescence and near-unity generation yield of excited states with spin multiplicity S > 1. This was achieved by designing an energy resonance between emissive doublet and triplet levels, here on covalently coupled tris(2,4,6-trichlorophenyl) methyl-carbazole radicals and anthracene. We observed that the doublet photoexcitation delocalized onto the linked acene within a few picoseconds and subsequently evolved to a pure high-spin state (quartet for monoradical, quintet for biradical) of mixed radical-triplet character near 1.8 eV. These high-spin states are coherently addressable with microwaves even at 295 K, with optical readout enabled by reverse intersystem crossing to emissive states. Furthermore, for the biradical, on return to the ground state the previously uncorrelated radical spins either side of the anthracene shows strong spin correlation. Our approach simultaneously supports a high efficiency of initialization, spin manipulations and light-based readout at room temperature. The integration of luminescence and high-spin states creates an organic materials platform for emerging quantum technologies.
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Affiliation(s)
- Sebastian Gorgon
- Cavendish Laboratory, University of Cambridge, Cambridge, UK.
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford, UK.
| | - Kuo Lv
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, P. R. China
| | - Jeannine Grüne
- Experimental Physics VI, Faculty of Physics and Astronomy, University of Würzburg, Würzburg, Germany
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | | | - William K Myers
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford, UK
| | - Giacomo Londi
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
| | - Gaetano Ricci
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
| | - Danillo Valverde
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
| | | | - Petri Murto
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
| | | | | | - Vladimir Dyakonov
- Experimental Physics VI, Faculty of Physics and Astronomy, University of Würzburg, Würzburg, Germany
| | - Andreas Sperlich
- Experimental Physics VI, Faculty of Physics and Astronomy, University of Würzburg, Würzburg, Germany
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Mons, Belgium
| | - Yoann Olivier
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, P. R. China
| | | | - Emrys W Evans
- Department of Chemistry, Swansea University, Swansea, UK.
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Murto P, Chowdhury R, Gorgon S, Guo E, Zeng W, Li B, Sun Y, Francis H, Friend RH, Bronstein H. Mesitylated trityl radicals, a platform for doublet emission: symmetry breaking, charge-transfer states and conjugated polymers. Nat Commun 2023; 14:4147. [PMID: 37438369 DOI: 10.1038/s41467-023-39834-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 06/29/2023] [Indexed: 07/14/2023] Open
Abstract
Neutral π-radicals have potential for use as light emitters in optoelectronic devices due to the absence of energetically low-lying non-emissive states. Here, we report a defect-free synthetic methodology via mesityl substitution at the para-positions of tris(2,4,6-trichlorophenyl)methyl radical. These materials reveal a number of novel optoelectronic properties. Firstly, mesityl substituted radicals show strongly enhanced photoluminescence arising from symmetry breaking in the excited state. Secondly, photoexcitation of thin films of 8 wt% radical in 4,4'-bis(carbazol-9-yl)-1,1'-biphenyl host matrix produces long lived (in the order of microseconds) intermolecular charge transfer states, following hole transfer to the host, that can show unexpectedly efficient red-shifted emission. Thirdly, covalent attachment of carbazole into the mesitylated radical gives very high photoluminescence yield of 93% in 4,4'-bis(carbazol-9-yl)-1,1'-biphenyl films and light-emitting diodes with maximum external quantum efficiency of 28% at a wavelength of 689 nm. Fourthly, a main-chain copolymer of the mesitylated radical and 9,9-dioctyl-9H-fluorene shows red-shifted emission beyond 800 nm.
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Affiliation(s)
- Petri Murto
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | | | - Sebastian Gorgon
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Erjuan Guo
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
- State Key Laboratory of Materials Processing and Die and Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, China
| | - Weixuan Zeng
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | - Biwen Li
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Yuqi Sun
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Haydn Francis
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK
| | - Richard H Friend
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
| | - Hugo Bronstein
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK.
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
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