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Issue 43, 2009
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1,3,5-Triazine derivatives as new electron transport–type host materials for highly efficient green phosphorescent OLEDs

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Abstract

We have synthesized three star-shaped 1,3,5-triazine derivatives—2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T), 2,4,6-tris(triphenyl-3-yl)-1,3,5-triazine (T3T), and 2,4,6-tris(9,9′-spirobifluorene-2-yl)-1,3,5-triazine (TST)—as new electron transport (ET)-type host materials for green phosphorescent organic light-emitting devices. The morphological, thermal, and photophysical properties and the electron mobilities of these ET-type host materials are influenced by the nature of the aryl substituents attached to the triazene core. The metameta linkage between the 1,3,5-triazine core and the peripheral aryl moieties in T2T and T3T limited the effective extension of their π conjugation, leading to high triplet energies of 2.80 and 2.69 eV, respectively. Time-of-flight mobility measurements revealed the good electron mobilities for these compounds (each > 10−4 cm2V−1 s−1), following the order T3T > TST > T2T. The device incorporating T2T as the host, doped with (PPy)2Ir(acac) and 1,3,5-tris(N-phenylbenzimidizol-2-yl)benzene (TBPI) as the ET layer, achieved a high external quantum efficiency (ηext) of 17.5% and a power efficiency (ηp) of 59.0 lm W−1. For the same device configuration, the T3T-based device provided values of ηext and ηp of 14.4% and 50.6 lm W−1, respectively; the TST-based device provided values of 5.1% and 12.3 lm W−1, respectively. We ascribe the superior performance of the T2T-based devices to balanced charge recombination; we ascribe the poor efficiencies of the TST-based devices to its relatively low triplet energy (2.54 eV), which did not allow efficient confinement of the triplet excitons on the green phosphorescent emitter (PPy)2Ir(acac).

Graphical abstract: 1,3,5-Triazine derivatives as new electron transport–type host materials for highly efficient green phosphorescent OLEDs

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Publication details

The article was received on 07 Jul 2009, accepted on 27 Aug 2009 and first published on 21 Sep 2009


Article type: Paper
DOI: 10.1039/B913423A
J. Mater. Chem., 2009,19, 8112-8118

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    1,3,5-Triazine derivatives as new electron transport–type host materials for highly efficient green phosphorescent OLEDs

    H. Chen, S. Yang, Z. Tsai, W. Hung, T. Wang and K. Wong, J. Mater. Chem., 2009, 19, 8112
    DOI: 10.1039/B913423A

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