Well defined carbazol-3,9-diyl-based derivatives as host materials for electrophosphorescent devices have been synthesized by the modified Ullmann reaction as a key step. The full characterization. of their structure by mass spectrometry, infrared absorption and proton magnetic resonance spectroscopy is presented. The amorphous compounds with glass transition temperatures of 103-154 degrees C possess high thermal stability with onset decomposition temperatures exceeding 360 degrees C. Conjugation of the 3,9-linked systems is rather confined within one carbazole unit, retaining large triplet energies suitable for green. and red electro-phosphorescence. Using the new host material, efficient green phosphorescent organic light emitting diodes was demonstrated.