Are the rates of dexter transfer in TADF hyperfluorescence systems optically accessible?

Haase, Nils; Danos, Andrew; Pflumm, Christof; Stachelek, Patrycja; Brütting, Wolfgang; Monkman, Andrew P.

doi:10.1039/d0mh01666g

Cited by 43 publications

(57 citation statements)

References 60 publications

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“…These may include charge trapping or Dexter transfer to the slow-RISC MR-TADF dopant, although these processes have proven to be incredibly challenging to even quantify by traditional means. 70 Therefore while the improvement in colour coordinate offered by the MR-TADF hyperfluorescence strategy is welcomed, it is clear that a deeper understanding of the relevant in operando mechanism and processes is required to unlock their full potential.…”

Section: Devicesmentioning

confidence: 99%

Diindolocarbazole – achieving multiresonant thermally activated delayed fluorescence without the need for acceptor units

et al. 2022

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Section: Devicesmentioning

confidence: 99%

Diindolocarbazole – achieving multiresonant thermally activated delayed fluorescence without the need for acceptor units

et al. 2022

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“…These may include charge trapping or Dexter transfer to the slow-RISC MR-TADF dopant, although these processes have proven to be incredibly challenging to even quantify by traditional means. 69 Therefore while the improvement in colour coordinate offered by the MR-TADF hyperfluorescence strategy is welcomed, it is clear that a deeper understanding of the relevant in operando mechanism and processes is required to unlock their full potential.…”

Section: Devicesmentioning

confidence: 99%

Diindolocarbazole – Achieving Multiresonant Thermally Activated Delayed Fluorescence Without The Need for Acceptor Units

Hall

Stavrou

Du̅da

et al. 2021

Preprint

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In this work we present a new multi-resonance thermally activated delayed fluorescence (MR-TADF) emitter paradigm, demonstrating that the structure need not require the presence of acceptor atoms. Based on an in-silico design, the compound DiICzMes4 possesses a red-shifted emission, enhanced photoluminescence quantum yield, and smaller ΔEST than the parent indolocarbazole that induces MR-TADF properties. Coupled cluster calculations accurately predict the magnitude of the singlet-triplet energy gap, ΔEST, when the optimized singlet and triplet geometries are used. Slow yet optically detectable reverse intersystem crossing contributes to low efficiency in organic light-emitting diodes using DiICzMes4 as then emitter. However, when used as a terminal emitter in combination with a TADF assistant dopant within a hyperfluorescence device architecture, maximum external quantum efficiencies of up to 16.9% were achieved at CIE (0.15,0.11). This represents one of the bluest hyperfluorescent devices reported to date. Simultaneously, recognising that MR-TADF emitters do not require acceptor atoms reveals an unexplored frontier in materials design, where yet greater performance may yet be discovered.

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“…Indeed, truly ground-breaking device performances have been achieved when pairing a high-RISC D-A assistant dopant with narrowband MR-TADF terminal emitters. [22][23][24] This performance is in some cases supported by spontaneous alignment of the MR-TADF with the substrate, thus improving optical outcoupling of the device, 24 although the specific loss mechanisms that occur under electrical excitation, including charge trapping and Dexter transfer, 25 remain poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Emission and Absorption Tuning in MR-TADF B,N-Doped Hep-tacenes: Towards Ideal-Blue Hyperfluorescent OLEDs

Stavrou

Suresh

Hall

et al. 2022

Preprint

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Developing high-efficiency purely organic blue organic light-emitting diodes (OLEDs) that meet the stringent industry standards is a major current research challenge. Hyperfluorescent device approaches achieve in large measure the desired high performance by combining the advantages of a high-efficiency thermally activated delayed fluorescence (TADF) assistant dopant with a narrowband deep-blue multi-resonant TADF (MR-TADF) terminal emitter. However, this ap-proach requires suitable spectral overlap to support Förster resonance energy transfer (FRET) between the two. Here we demonstrate colour tuning of a recently reported MR-TADF B,N-heptacene core through control of the boron substituents. While there is little impact on the intrinsic TADF properties - as both singlet and triplet energies decrease in tandem - this approach improves the emission colour coordinate as well as the spectral overlap for blue hyperfluorescence OLEDs (HF OLEDs). Crucially, the red-shifted and more intense absorption allows us to pair this MR-TADF emitter with a high-performance TADF assistant dopant and achieve maximum external quantum efficiency (EQEmax) of 15% at colour coordinates of (0.15, 0.10). The efficiency values recorded for our device at a practical luminance of 100 cd m-2 are among the highest reported for HF TADF OLEDs with CIEy ≤ 0.1.

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Are the rates of dexter transfer in TADF hyperfluorescence systems optically accessible?

Abstract: Seemingly not, but for unexpected reasons. Combining the triplet harvesting properties of TADF materials with the fast emission rates and colour purity of fluorescent emitters is attractive for developing high...

Cited by 43 publications

References 60 publications

Diindolocarbazole – achieving multiresonant thermally activated delayed fluorescence without the need for acceptor units

Diindolocarbazole – achieving multiresonant thermally activated delayed fluorescence without the need for acceptor units

Diindolocarbazole – Achieving Multiresonant Thermally Activated Delayed Fluorescence Without The Need for Acceptor Units

Emission and Absorption Tuning in MR-TADF B,N-Doped Hep-tacenes: Towards Ideal-Blue Hyperfluorescent OLEDs

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