Molecular Design Realizing Very Fast Reverse Intersystem Crossing in Purely Organic Emitter

wada, yoshimasa; Nakagawa, Hirofumi; Matsumoto, Soma; Wakisaka, Yasuaki; Kaji, Hironori

doi:10.26434/chemrxiv.9745289

Cited by 6 publications

(4 citation statements)

References 9 publications

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“…To the best of our knowledge, k RISC of over 10 7 s -1 for Br-3-PXZ-XO is the highest value ever reported for an organic TADF material 28 . This high k RISC reflects its fast transient photoluminescence decay with a delayed fluorescence lifetime of 490 ns (Fig.…”

Section: Resultsmentioning

confidence: 66%

Kinetic prediction of reverse intersystem crossing in organic donor–acceptor molecules

et al. 2020

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Reverse intersystem crossing (RISC), the uphill spin-flip process from a triplet to a singlet excited state, plays a key role in a wide range of photochemical applications. Understanding and predicting the kinetics of such processes in vastly different molecular structures would facilitate the rational material design. Here, we demonstrate a theoretical expression that successfully reproduces experimental RISC rate constants ranging over five orders of magnitude in twenty different molecules. We show that the spin flip occurs across the singlet-triplet crossing seam involving a higher-lying triplet excited state where the semiclassical Marcus parabola is no longer valid. The present model explains the counterintuitive substitution effects of bromine on the RISC rate constants of previously unknown molecules, providing a predictive tool for material design.

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Section: Resultsmentioning

confidence: 66%

Kinetic prediction of reverse intersystem crossing in organic donor–acceptor molecules

et al. 2020

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“…Kaji and co-workers 49 recently reported a through-space CT molecule, TpAT-tFFO, by introducing face-to-face alignment of the donor and acceptor units (Fig. 7a).…”

Section: Discussionmentioning

confidence: 99%

Nanosecond-time-scale delayed fluorescence molecule for deep-blue OLEDs with small efficiency rolloff

et al. 2020

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Aromatic organic deep-blue emitters that exhibit thermally activated delayed fluorescence (TADF) can harvest all excitons in electrically generated singlets and triplets as light emission. However, blue TADF emitters generally have long exciton lifetimes, leading to severe efficiency decrease, i.e., rolloff, at high current density and luminance by exciton annihilations in organic light-emitting diodes (OLEDs). Here, we report a deep-blue TADF emitter employing simple molecular design, in which an activation energy as well as spin-orbit coupling between excited states with different spin multiplicities, were simultaneously controlled. An extremely fast exciton lifetime of 750 ns was realized in a donor-acceptor-type molecular structure without heavy metal elements. An OLED utilizing this TADF emitter displayed deep-blue electroluminescence (EL) with CIE chromaticity coordinates of (0.14, 0.18) and a high maximum EL quantum efficiency of 20.7%. Further, the high maximum efficiency were retained to be 20.2% and 17.4% even at high luminance.

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“…5). While the existing organic TADF molecules exhibit k RISC smaller than 10 8 s -1 , the theory predicts that even k RISC of 10 9 s -1 , corresponding to a time constant of 1.0 ns, can be achieved with H SO less than 10 cm -1 ; for example, H SO 10 of 7.7 cm -1 for E A of 0.10 eV and H SO of 2.9 cm -1 for E A of 0.05 eV at T of 300 K. These H SO are an order of magnitude smaller than those of iridium-containing phosphors and could be achieved by exploiting heavy atom effects of nonmetals in periods 3 and 4 30,31 . However, we have shown that such heuristic approaches sometimes lead to the retardation of H SO , in part because of their more pronounced effects on S1 S1-T2 difference T2 the excited-state electronic configurations at the S 1 -T 2 MESX geometries.…”

Section: Resultsmentioning

confidence: 99%

Kinetic Prediction of Reverse Intersystem Crossing in Organic Donor–Acceptor Molecules

Aizawa¹,

Harabuchi²,

Maeda³

et al. 2020

Preprint

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Reverse intersystem crossing (RISC), the uphill spin-flip process from a triplet to a singlet excited state, plays a key role in a wide range of photochemical applications. Understanding and predicting the kinetics of such processes in vastly different molecular structures would facilitate the rational design of new materials. Here, we demonstrate a theoretical expression that successfully reproduces experimental RISC rate constants ranging over five orders of magnitude in twenty different molecules. We show that the spin flip occurs across the singlet–triplet crossing seam involving a higher-lying triplet excited state where the semi-classical Marcus parabola is no longer valid. The present model explains the counterintuitive substitution effects of bromine on the RISC rate constants of newly synthesized molecules, providing a predictive tool for material design.<br>

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Molecular Design Realizing Very Fast Reverse Intersystem Crossing in Purely Organic Emitter

Cited by 6 publications

References 9 publications

Kinetic prediction of reverse intersystem crossing in organic donor–acceptor molecules

Kinetic prediction of reverse intersystem crossing in organic donor–acceptor molecules

Nanosecond-time-scale delayed fluorescence molecule for deep-blue OLEDs with small efficiency rolloff

Kinetic Prediction of Reverse Intersystem Crossing in Organic Donor–Acceptor Molecules

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