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Pyridine linked fluorene hybrid bipolar host for blue, green, and orange phosphorescent organic light-emitting diodes toward solution processing

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Abstract

Herein, a new series of ambipolar host materials is synthesized, which features a pyridine core and triphenylamine or carbazole arm combined in a non-conjugated configuration. Theoretical calculation results show that their HOMO/LUMO distribution is adjusted from an overlapped state to partially and thoroughly separated states, and their hole/electron transportation ability and energy levels are also tuned, in addition to their triplet energy level varying from 2.38 to 2.87 eV. Thermogravimetric analysis and DSC measurement results display a high thermal decomposition temperature of 420–490 °C and a wide glass transition temperature range of 160–173 °C, along with excellent reversible redox behavior in electrochemical processes. Utilizing the pure host of 4′,4′′′-(pyridine-2,6-diylbis(9H-fluorene-9,9-diyl))bis(N,N-diphenyl-[1,1′-biphenyl]-4-amine), blue organic light-emitting diodes (OLEDs) show a high efficiency of 18.5 cd A−1 and 13.6 lm W−1 compared with 16.3 cd A−1 and 11.6 lm W−1 for the cohost diodes, respectively. Additionally, orange phosphorescent device from the N,N′-((pyridine-2,6-diylbis(9H-fluorene-9,9-diyl))bis(4,1-phenylene))bis(N-phenylnaphthalen-1-amine) cohost shows higher efficiency than the single host devices with a maximum luminous efficiency of 37.3 cd A−1 in a high brightness region of around 12 680 cd m−2, which makes it one of the most efficient orange OLEDs containing a solution processed single emissive layer structure. Significantly, their efficiency roll-off is greatly suppressed at high luminance, particularly for the orange device with a 3.21% decrease in efficiency from the maximum to a high brightness of 10 000 cd m−2. This work provides a useful guide for molecular design toward solution processed OLEDs.

Graphical abstract: Pyridine linked fluorene hybrid bipolar host for blue, green, and orange phosphorescent organic light-emitting diodes toward solution processing

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Publication details

The article was received on 22 Sep 2017, accepted on 30 Oct 2017 and first published on 31 Oct 2017


Article type: Paper
DOI: 10.1039/C7TC04339B
Citation: J. Mater. Chem. C, 2017, Advance Article
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    Pyridine linked fluorene hybrid bipolar host for blue, green, and orange phosphorescent organic light-emitting diodes toward solution processing

    S. Ye, L. Li, M. Zhang, Z. Zhou, M. Quan, L. Guo, Y. Wang, M. Yang, W. Lai and W. Huang, J. Mater. Chem. C, 2017, Advance Article , DOI: 10.1039/C7TC04339B

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