Electro-active oligomers containing pendent 3-phenylcarbazol-6-yl or 2-phenylfluoren-7-yl fragments as materials for OLEDs

Abstract Vinyl oligomers containing 3-phenyl-9-ethylcarbazol-6-yl or 2-phenyl-9,9-diethylfluoren-7-yl fragments were synthesized and characterized by NMR spectroscopy, elemental analysis and gel permeation chromatography. The derivatives represent materials of high thermal stability with initial thermal destruction temperatures of 348 °C and 332 °C. The glass transition temperatures of the amorphous materials were 150 °C and 139 °C, respectively. The electron photoemission spectra of layers of the synthesized oligomers showed ionization potentials in a range 5.6–5.9 eV. Hole-transporting properties of the materials were tested in the structures of organic light emitting diodes with Alq3 as the green emitter. The device containing hole transporting layers of oligomer with phenyl-9,9-diethylfluoren-7-yl fragments exhibited the best overall performance with a maximal photometric efficiency of about 1.9 cd/A and maximum brightness of about 2150 cd/m2. The efficiency was about 40% higher than that of a device containing hole transporting layers of poly(9-vinylcarbazole) (PVK).