Projects per year
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 × 105cm−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.
Original language | English |
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Article number | 6640 |
Journal | Nature Communications |
Volume | 12 |
Issue number | 1 |
DOIs | |
Publication status | Published - Dec 2021 |
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Dive into the research topics of 'Spontaneous exciton dissociation enables spin state interconversion in delayed fluorescence organic semiconductors'. Together they form a unique fingerprint.Projects
- 1 Finished
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Equipment renewal for the Consortium des Equipements de Calcul Intensif (CECI)
Bontempi, G. (PI), CHAMPAGNE, B. (CoPI), Geuzaine , C. (CoPI), RIGNANESE, G. M. (CoPI) & Lazzaroni, R. (CoPI)
1/01/22 → 31/12/23
Project: Research
Equipment
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High Performance Computing Technology Platform
Champagne, B. (Manager)
Technological Platform High Performance ComputingFacility/equipment: Technological Platform