Twin derivatives of fluorophenyl, difluorophenyl or trifluorophenyl substituted carbazoles as electroactive amorphous materials.

Twin derivatives containing two 4-fluorophenyl, 3,5-difluorophenyl or 2,4,6-trifluorophenyl substituted carbazole rings were synthesized by the multi-step synthetic routes. Thermal properties and hole injecting/transport properties of the materials were examined by thermogravimetric analysis, differential scanning calorimetry, electron photoemission and time of flight techniques, respectively. Hole-transporting properties of thin amorphous layers of the derivatives were also tested in the structures of organic light emitting diodes (OLEDs) with Alq 3 as the green emitter. The bilayer device based on a twin derivative composed of 3-(3,5-difluorophenyl) carbazol-9-yl blocks exhibited the best overall performance with a maximal photometric efficiency of about 2.1 cd/A and maximum brightness of 560 cd/m 2 . An analogous multilayer OLED with an additional PEDOT:PSS hole injecting layer demonstrated turn on voltage of 6.0 V, maximum brightness of about 6200 cd/m 2 and maximal photometric efficiency of 3.4 cd/A. [ABSTRACT FROM AUTHOR]