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Triplet decay-induced negative temperature dependence of the transient photoluminescence decay of thermally activated delayed fluorescence emitter

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Abstract

The photophysical properties of three TX-based D–A isomers (TXO-PhCz1, TXO-PhCz3, and TXO-PhCz4) with a PhCz donor at different substitution positions of phenyl group on a TXO unit were investigated. The substitution position of the PhCz unit significantly impacts the photophysical properties of these isomers. TXO-PhCz1 exhibits a very weak emission in both undoped and doped films, while TXO-PhCz3 and TXO-PhCz4 exhibit a strong emission with the requisite properties for TADF emitters, including a small ΔEST and transient PL decay curves with a prompt and delayed fluorescent component. TXO-PhCz4 exhibits a much stronger orbital coupling than TXO-PhCz3 and then the phosphorescent emission causes the inverse temperature dependence of the transient PL decay, which is contrary to that of TXO-PhCz3 and other TADF emitters. TXO-PhCz4 exhibits a small ΔEST of 23 meV and a short decay time of 14 μs at room temperature, which are much smaller and shorter than those of TXO-PhCz3. Multilayer OLEDs based on TXO-PhCz4 exhibit a very low-efficiency roll-off with a maximum current efficiency of 49.2 cd A−1, a maximum power efficiency of 47.7 lm W−1, and a maximum EQE of 16.3%.

Graphical abstract: Triplet decay-induced negative temperature dependence of the transient photoluminescence decay of thermally activated delayed fluorescence emitter

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Publication details

The article was received on 04 Sep 2017, accepted on 30 Oct 2017 and first published on 31 Oct 2017


Article type: Paper
DOI: 10.1039/C7TC04025C
Citation: J. Mater. Chem. C, 2017, Advance Article
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    Triplet decay-induced negative temperature dependence of the transient photoluminescence decay of thermally activated delayed fluorescence emitter

    X. Wei, Y. Chen, R. Duan, J. Liu, R. Wang, Y. Liu, Z. Li, Y. Yi, Y. Yamada-Takamura, P. Wang and Y. Wang, J. Mater. Chem. C, 2017, Advance Article , DOI: 10.1039/C7TC04025C

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