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Issue 19, 2017
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Towards highly efficient thermally activated delayed fluorescence devices through a trap-assisted recombination mechanism and reduced interfacial exciton annihilation

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Abstract

In this contribution, two bipolar materials, 3-(3-(9H-carbazol-9-yl)phenyl)-5-(4-(tert-butyl)phenyl)-1,2,4-thiadiazole (3-CzTHZ) and 5-(3-(9H-carbazol-9-yl)phenyl)-3-(4-(tert-butyl)phenyl)-1,2,4-thiadiazole (5-CzTHZ), were developed as host matrices for the TADF emitter 1,2,3,4-tetrakis(carbazol-9-yl)-5,6-dicyanobenzene (4CzPN). By adjusting the host–guest compatibility, two types of emission mechanisms were realized in varied devices according to their different charge-trapping characteristics within the emissive layer (EML). Based on a systematic investigation on both photoluminescence (PL) and electroluminescence (EL) performances, we found that the trap-assisted recombination method could contribute to realizing the full potential of TADF emitters since this mechanism was beneficial to minimizing the energy loss during the host → guest energy transfer (ET) processes. Moreover, the compatibilities between the electron transport layer (ETL) and EML were also fine-tuned to reduce the detriment of interfacial exciton annihilation. Consequently, an outstanding performance was achieved in a 3-CzTHZ-hosted device with the maximum external quantum efficiency (EQE) of 22.2% and power efficiency (PE) of 65.9 lm W−1.

Graphical abstract: Towards highly efficient thermally activated delayed fluorescence devices through a trap-assisted recombination mechanism and reduced interfacial exciton annihilation

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Publication details

The article was received on 11 Feb 2017, accepted on 09 Apr 2017 and first published on 10 Apr 2017


Article type: Paper
DOI: 10.1039/C7TC00653E
Citation: J. Mater. Chem. C, 2017,5, 4636-4644
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    Towards highly efficient thermally activated delayed fluorescence devices through a trap-assisted recombination mechanism and reduced interfacial exciton annihilation

    W. Zhang, J. Jin, Z. Huang, X. Lv, S. Zhuang and L. Wang, J. Mater. Chem. C, 2017, 5, 4636
    DOI: 10.1039/C7TC00653E

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