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Gillett AJ, Tonnelé C, Londi G, Ricci G, Catherin M, Unson DML, Casanova D, Castet F, Olivier Y, Chen WM, Zaborova E, Evans EW, Drummond BH, Conaghan PJ, Cui LS, Greenham NC, Puttisong Y, Fages F, Beljonne D, Friend RH. Spontaneous exciton dissociation enables spin state interconversion in delayed fluorescence organic semiconductors. Nat Commun 2021; 12:6640. [PMID: 34789719 PMCID: PMC8599618 DOI: 10.1038/s41467-021-26689-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [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: 06/29/2021] [Accepted: 10/14/2021] [Indexed: 11/09/2022] Open
Abstract
Engineering a low singlet-triplet energy gap (ΔEST) is necessary for efficient reverse intersystem crossing (rISC) in delayed fluorescence (DF) organic semiconductors but results in a small radiative rate that limits performance in LEDs. Here, we study a model DF material, BF2, that exhibits a strong optical absorption (absorption coefficient = 3.8 × 105 cm-1) and a relatively large ΔEST of 0.2 eV. In isolated BF2 molecules, intramolecular rISC is slow (delayed lifetime = 260 μs), but in aggregated films, BF2 generates intermolecular charge transfer (inter-CT) states on picosecond timescales. In contrast to the microsecond intramolecular rISC that is promoted by spin-orbit interactions in most isolated DF molecules, photoluminescence-detected magnetic resonance shows that these inter-CT states undergo rISC mediated by hyperfine interactions on a ~24 ns timescale and have an average electron-hole separation of ≥1.5 nm. Transfer back to the emissive singlet exciton then enables efficient DF and LED operation. Thus, access to these inter-CT states, which is possible even at low BF2 doping concentrations of 4 wt%, resolves the conflicting requirements of fast radiative emission and low ΔEST in organic DF emitters.
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Affiliation(s)
- Alexander J Gillett
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK.
| | - Claire Tonnelé
- Donostia International Physics Centre (DIPC), Donostia, Euskadi, Spain
| | - Giacomo Londi
- Laboratory for Chemistry of Novel Materials, Université de Mons, Place du Parc 20, 7000, Mons, Belgium
| | - Gaetano Ricci
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solide, Namur Institute of Structured Matter, Université de Namur, B-5000, Namur, Belgium
| | - Manon Catherin
- Aix Marseille Univ, CNRS, CINaM UMR 7325, AMUtech, Campus de Luminy, 13288, Marseille, France
| | - Darcy M L Unson
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
| | - David Casanova
- Donostia International Physics Centre (DIPC), Donostia, Euskadi, Spain
| | - Frédéric Castet
- Institut des Sciences Moléculaires, Université de Bordeaux, 33405, Talence, France
| | - Yoann Olivier
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solide, Namur Institute of Structured Matter, Université de Namur, B-5000, Namur, Belgium
| | - Weimin M Chen
- Department of Physics, Chemistry and Biology (IFM) Linköping University, Linköping, Sweden
| | - Elena Zaborova
- Aix Marseille Univ, CNRS, CINaM UMR 7325, AMUtech, Campus de Luminy, 13288, Marseille, France
| | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
- Department of Chemistry, Swansea University, Singleton Park, Swansea, UK
| | - Bluebell H Drummond
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
| | - Patrick J Conaghan
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
- ARC Centre of Excellence in Exciton Science, School of Chemistry, University of Sydney, Sydney, NSW, 2006, Australia
| | - Lin-Song Cui
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
- Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Neil C Greenham
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
| | - Yuttapoom Puttisong
- Department of Physics, Chemistry and Biology (IFM) Linköping University, Linköping, Sweden.
| | - Frédéric Fages
- Aix Marseille Univ, CNRS, CINaM UMR 7325, AMUtech, Campus de Luminy, 13288, Marseille, France.
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, Université de Mons, Place du Parc 20, 7000, Mons, Belgium.
| | - Richard H Friend
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK.
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Hall JW, Unson DML, Brunel P, Collins LR, Cybulski MK, Mahon MF, Whittlesey MK. Copper-NHC-Mediated Semihydrogenation and Hydroboration of Alkynes: Enhanced Catalytic Activity Using Ring-Expanded Carbenes. Organometallics 2018. [DOI: 10.1021/acs.organomet.8b00467] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jonathan W. Hall
- Department of Chemistry, University of Bath, Claverton
Down, Bath BA2 7AY, United Kingdom
| | - Darcy M. L. Unson
- Department of Chemistry, University of Bath, Claverton
Down, Bath BA2 7AY, United Kingdom
| | - Paul Brunel
- Department of Chemistry, University of Bath, Claverton
Down, Bath BA2 7AY, United Kingdom
| | - Lee R. Collins
- Department of Chemistry, University of Bath, Claverton
Down, Bath BA2 7AY, United Kingdom
| | - Mateusz K. Cybulski
- Department of Chemistry, University of Bath, Claverton
Down, Bath BA2 7AY, United Kingdom
| | - Mary F. Mahon
- Department of Chemistry, University of Bath, Claverton
Down, Bath BA2 7AY, United Kingdom
| | - Michael K. Whittlesey
- Department of Chemistry, University of Bath, Claverton
Down, Bath BA2 7AY, United Kingdom
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