Host materials for blue phosphorescent OLEDs

PCTrz, a new bipolar host material containing a phenoxy-carbazole separated from a biscarbazolyl-triazine by a non-conjugated ether bond is presented. Computational calculations demonstrated the separation of PCTrz into an oxidation and a reduction site. A phosphorescent OLED with PCTrz as host and FIrpic as blue emitter yielded high current efficiencies of up to 16.2 cd/A. Additionally two electron transporting host materials DBFTaz and DBFTazC, both containing 1,2,4-triazole moieies, were synthesized and characterized. The triazole moiety in DBFTaz was formed by a classical ring closure reaction between a N-benzoylbenzimidate and a hydrazine. For DBFTazC we used another synthetical pathway which involves subsequent coupling of a carbazole and a triazole moiety to a dibenzofuran core. Both triazoles posses high triplet energies of 2.95 eV for DBFTaz and 2.97 eV for DBFTazC, which make the compounds interesting as matrix materials for blue phosphorescent OLEDs.

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