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Proceedings Paper

Novel host materials for blue phosphorescent OLEDs
Author(s): Peter Strohriegl; Daniel Wagner; Pamela Schrögel; Sebastian T. Hoffmann; Anna Köhler; Ute Heinemeyer; Ingo Münster
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Paper Abstract

We present two classes of host materials for blue phosphors. The first are carbazole substituted biphenyls 1-9. In these CBP-type materials the triplets are confined to one half of the molecules by using either twisted biphenyls or by a metalinkage of the carbazoles to the biphenyl. We obtained high triplet energies of 2.95-2.98 eV and high glass transition temperatures in the range of 100-120 °C. OLEDs were fabricated using the host material 6 and the carbene emitter Ir(dbfmi) with pure blue emission at 450 nm. The devices achieved an external quantum efficiency of 8.7% at 100 cd/m2 and 6.1% at 1000 cd/m2. MBPTRZ with an electron transporting biscarbazolyltriazine that is separated from the hole transporting carbazole by a non-conjugated, meta-linked biphenyl unit is an example for a bipolar matrix material. The excellent glass forming properties and the high Tg of 132 °C ensure morphological stability in OLEDs. The meta-linkage and the additional twist at the biphenyl unit, which is achieved by two methyl groups in the 2- and 2’-position of the biphenyl in MBPTRZ leads to a decoupling of the electron accepting and electron donating part and therefore to a high triplet energy of 2.81 eV. DFT calculations show a clear separation of the electron and hole transporting moieties. A phosphorescent OLED with MBPTRZ as host and FIrpic as emitter reached a maximum external quantum efficiency of 7.0%, a current efficiency of 16.3 cd/A and a power efficiency of 6.3 lm/W.

Paper Details

Date Published: 27 September 2013
PDF: 12 pages
Proc. SPIE 8829, Organic Light Emitting Materials and Devices XVII, 882906 (27 September 2013); doi: 10.1117/12.2023305
Show Author Affiliations
Peter Strohriegl, Univ. Bayreuth (Germany)
Daniel Wagner, Univ. Bayreuth (Germany)
Pamela Schrögel, Univ. Bayreuth (Germany)
Sebastian T. Hoffmann, Univ. Bayreuth (Germany)
Anna Köhler, Univ. Bayreuth (Germany)
Ute Heinemeyer, BASF SE (Germany)
Ingo Münster, BASF SE (Germany)


Published in SPIE Proceedings Vol. 8829:
Organic Light Emitting Materials and Devices XVII
Franky So; Chihaya Adachi, Editor(s)

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